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4,825 Matching Results
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1 - 24 of
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Shock-induced alpha-omega structural phase transformation of titanium: A molecular-dynamics study
None
Date:
March 15, 2004
Creator:
Sadigh, B; Lenosky, T; Oppelstrup, T; Minich, R & Gilmer, G
Object Type:
Article
System:
The UNT Digital Library
[People converse at Mean Green Fling booth]
Photograph of people talking at a booth during the Mean Green Fling. One woman in the center of the photograph is looking at the woman in front of her, who has her back to the camera. They are both holding papers in their hands. The woman facing the camera seems to be talking. Behind her, a woman wearing a UNT branded shirt is standing, looking at the camera. A man is sitting down next to her, looking at the camera and smiling. He is wearing a shirt that says, "Alpha Phi Omega." Candy is scattered on the table in front of them, along with newspapers and a fraternity sweatshirt. People can be seen walking between other booths in the background.
Date:
August 26, 2007
Creator:
Ha, Khai
Object Type:
Photograph
System:
The UNT Digital Library
Measurement of the alpha asymmetry parameter for the Omega- ---> Lambda K- decay
None
Date:
February 1, 2005
Creator:
Chen, Y. C.; /Taiwan, Inst. Phys.; Burnstein, R. A.; Chakravorty, A.; Chan, A.; Choong, W. S. et al.
Object Type:
Article
System:
The UNT Digital Library
[Award winners gathered together]
A picture of a group of award winners at the 2004 Multicultural Center Awards ceremony. They are standing at the front of the room and have certificates in their hands with their organization names on them. Sorority and fraternity members are also wearing windbreakers and t-shirts from their organizations.
Date:
April 12, 2004
Creator:
University of North Texas. Multicultural Center.
Object Type:
Photograph
System:
The UNT Digital Library
[ΑΤΩ wearing paint at UNT vs. Navy game, 2007]
Photograph of four crowd-members with painted backs during the UNT vs. Navy football game. Together they spell out "ΑΤΩ" and the fourth has a painting of a shield and sword. Other people are wearing green T-shirts and have white and green accessories.
Date:
November 10, 2007
Creator:
Baugh, Brian
Object Type:
Photograph
System:
The UNT Digital Library
[Award winners holding certificates]
A picture of a group of award winners at the 2004 Multicultural Center Awards ceremony. They are standing in a row and have certificates in their hands with their organization names on them. They are (L-R) "University Program Council", "World Echoes", "Rho Delta Chapter; Zeta Phi Beta Sorority, Inc.", and "Gamma Rho Chapter; Alpha Phi Omega". The Greek life group members are wearing a windbreaker and t-shirt from their groups.
Date:
April 12, 2004
Creator:
University of North Texas. Multicultural Center.
Object Type:
Photograph
System:
The UNT Digital Library
[Funeral Program for Lenard Curtis Gaskin]
Funeral program for Reverend Lenard Curtis Gaskin, born July 19, 1923 and died December 25, 2007. The funeral was held at Friendship Baptist Church, officiated by Pastor Kevin L. Nelson. Funeral arrangements were made through Lewis Funeral Home and he was buried in Meadowlawn Memorial Park in San Antonio, Texas.
Date:
December 25, 2007
Creator:
unknown
Object Type:
Pamphlet
System:
The Portal to Texas History
Optics Performance at 1(omega), 2 (omega), and 3 (omega): Final Report on LDRD Project 03-ERD-071
The interaction of intense laser light with dielectric materials is a fundamental applied science problem that is becoming increasingly important with the rapid development of ever more powerful lasers. To better understand the behavior of optical components in large fusion-class laser systems, we are systematically studying the interaction of high-fluence, high-power laser light with high-quality optical components, with particular interest on polishing/finishing and stress-induced defects and surface contamination. We focus on obtaining comparable measurements at three different wavelengths, 1{omega} (1053 nm), 2{omega} (527 nm), and 3{omega} (351 nm).
Date:
February 8, 2006
Creator:
Honig, J.; Adams, J.; Carr, C.; Demos, S.; Feit, M.; Mehta, N. et al.
Object Type:
Report
System:
The UNT Digital Library
[Funeral Program for Theodore R. Edwards, Jr., December 18, 2009]
Funeral program for Theodore R. Edwards, Jr., born September 22, 1938 and died December 10, 2009. The funeral was held December 18, 2009 at Macedonia Missionary Baptist Church, officiated by Dr. Jerry Wm. Dailey. Funeral arrangements were made through Lewis Funeral Home and he was buried in Fort Sam Houston National Cemetery, near San Antonio, Texas
Date:
December 18, 2009
Creator:
unknown
Object Type:
Pamphlet
System:
The Portal to Texas History
Observation of parity violation in the Omega- ---> Lambda K- decay
The {alpha} decay parameter in the process {Omega}{sup -} {yields} {Lambda}K{sup -} has been measured from a sample of 4.50 million unpolarized {Omega}{sup -} decays recorded by the HyperCP (E871) experiment at Fermilab and found to be [1.78 {+-} 0.19(stat) {+-} 0.16(syst)] x 10{sup -2}. This is the first unambiguous evidence for a nonzero {alpha} decay parameter, and hence parity violation, in the {Omega}{sup -} {Lambda}K{sup -} decay.
Date:
May 1, 2005
Creator:
Lu, L. C.; U., /Virginia; Burnstein, R. A.; Chakravorty, A.; Chen, Y. C.; Choong, W.-S. et al.
Object Type:
Article
System:
The UNT Digital Library
Devloping High Energy Radiography for HED Experiments on NIF and Omega-EP
High energy radiography capabilities are essential for many future DNT/HED experiments on NIF. We have been developing bright, high-energy (15-100 keV), high resolution (< 20 {micro}m), 1-D and 2-D radiography solutions for DNT experiments on NIF. In this LDRD, we have made significant progress utilizing high-energy, high-intensity, short-pulse lasers to generate hard K-{alpha} photons. High energy K-{alpha} sources are created by hot electrons interacting in the target fluor material after irradiation by lasers with intensity I{sub L} > 10{sup 17} W/cm{sup 2}. High resolution point projection 1-D and 2-D radiography have been achieved using {mu}-foil and {mu}-wire targets attached to low-Z substrate materials. The {mu}-wire size was 10 x 10 x 300 {micro}m on a 300 x 300 x 5 {micro}m CH substrate creating the point source size equivalent to these micro targets. This unique technique will utilize the NIF short pulse laser (ARC) as a backlighter suitable for the full range of DNT science experiments on NIF.
Date:
February 14, 2008
Creator:
Maddox, B.; Tommasini, R.; Remington, B.; Key, M. & Town, R.
Object Type:
Report
System:
The UNT Digital Library
Charged Particle Spectroscopy on Omega (Final report)
Using the 2-MeV Van de Graaf Accelerator at SUNY Geneseo's Nuclear Structure Laboratory, a {sup 3}He-implanted tantalum target was bombarded by 450-keV deuterons to produce high energy protons via the {sup 3}He(d,p){sup 4}He reaction. A 1500-{micro}m surface barrier detector with a 3/16 inch diameter collimator was placed at 8.75 cm from the target and 135{sup o} from the incident beam. A movable arm was setup so that an array of aluminum filters of varying thicknesses could be rotated in front of the detector. A 6-{micro}m mylar filter was also mounted on the movable arm and was used to calibrate the detector as described in the CR-39 experiment report. Eight aluminum filters with thicknesses ranging from 250pm to 1100{micro}m were in turn rotated in front of the collimator and spectra were taken for each. The results are shown on the attached graphs. The theoretical curve for each graph was generated using TRIM The exact energy distribution of the proton beam incident on the target was not known; because no such spectrum could be taken due to the high count rate for elastically scattered deuterons. Instead, it was assumed that the incident beam had a distribution similar to that measured through the …
Date:
January 1, 2001
Creator:
Fletcher, K.; Padalino, S.; Schwartz, B.; Olsen, M.; Wakeman, T. & Petrasso, R.
Object Type:
Report
System:
The UNT Digital Library
Line-imaging velocimeter for shock diagnostics at the OMEGA laser facility
None
Date:
January 26, 2004
Creator:
Celliers, P M; Bradley, D K; Collins, G W; Hicks, D G; Boehly, T R & Armstrong, W J
Object Type:
Article
System:
The UNT Digital Library
Two Dimensional Simulations of Plastic-Shell, Direct-Drive Implosions on OMEGA
Multidimensional hydrodynamic properties of high-adiabat direct-drive plastic-shell implosions on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] are investigated using the multidimensional hydrodynamic code, DRACO. Multimode simulations including the effects of nonuniform illumination and target roughness indicate that shell stability during the acceleration phase plays a critical role in determining target performance. For thick shells that remain integral during the acceleration phase, target yields are significantly reduced by the combination of the long-wavelength ({ell} < 10) modes due to surface roughness and beam imbalance and the intermediate modes (20 {le} {ell} {le} 50) due to single-beam nonuniformities. The neutron-production rate for these thick shells truncates relative to one-dimensional (1-D) predictions. The yield degradation in the thin shells is mainly due to shell breakup at short wavelengths ({lambda} {approx} {Delta}, where {Delta} is the in-flight shell thickness). The neutron-rate curves for the thinner shells have significantly lower amplitudes and a fall-off that is less steep than 1-D rates. DRACO simulation results are consistent with experimental observations.
Date:
September 27, 2004
Creator:
Radha, P. B.; Goncharov, V. N.; Collins, T. B.; Delettrez, J. A.; Elbaz, Y.; Glebov, V. Y. et al.
Object Type:
Article
System:
The UNT Digital Library
Constraining |V(td)|/|V(ts)| Using Radiative Penguin B -> V(K*/rho/omega)gamma Decays
Exclusive radiative penguin B decays, B {yields} (K*{sup 0}/K*{sup +}) and B {yields} ({rho}/{omega}){gamma}, are flavor-changing neutral-current (FCNC) processes. Studies of these decays are of special interest in testing Standard Model (SM) predictions and searching for other beyond-the-SM FCNC interactions. Using 89 x 10{sup 6} B{bar B} pairs from BABAR, we measure the branching fraction ({Beta}), CP-asymmetry ({Alpha}), and isospin asymmetry ({Delta}{sub 0-}) of B {yields} (K*{sup 0}/K*{sup +}){gamma} as follows: {Beta}(B{sup 0} {yields} K*{sup 0}{gamma}) = 3.92 {+-} 0.20(stat.) {+-} 0.24(syst.); {Beta}(B{sup +} {yields} K*{sup +}{gamma}) = 3.87 {+-} 0.28(stat.) {+-} 0.26(syst.); {Alpha}(B {yields} K*{gamma}) = -0.013 {+-} 0.36(stat.) {+-} 0.10(syst.); {Delta}{sub 0-}(B {yields} K*{gamma}) = 0.050 {+-} 0.045(stat.) {+-} 0.028(syst.) {+-} 0.024(R{sup +/0}). The 90% confidence intervals for the CP-asymmetry and the isospin-asymmetry in the B {yields} K*{gamma} decay are given as: -0.074 < {Alpha}(B {yields} K*{gamma}) < 0.049, -0.046 < {Delta}{sub 0-} (B {yields} K*{gamma}) < 0.146. We also search for B {yields} ({rho}/{omega}){gamma} decays using 211 x 10{sup 6} B{bar B} pairs from BABAR. No evidence for these decays is found. We set the upper limits at 90% confidence level for these decays: {Beta}(B{sup 0} {yields} {rho}{sup 0}{gamma}) < 0.4 x 10{sup -6}; {Beta}(B{sup +}{yields} {rho}{sup …
Date:
March 8, 2006
Creator:
Tan, Ping
Object Type:
Report
System:
The UNT Digital Library
The Role of Ledge Nucleation/Migration in ''Omega'' Plate Thickening Behavior in Al-Cu-Mg-Ag Alloys
The thickening kinetics of {Omega} plates in an Al-4Cu-0.3Mg-0.2Ag (wt. %) alloy have been measured at 200 C, 250 C and 300 C using conventional transmission electron microscopy techniques. At all temperatures examined the thickening showed a linear dependence on time. At 200 C the plates remained less than 6nm in thickness after 1000h exposure. At temperatures above 200 C the thickening kinetics are greatly increased. Atomic resolution Z-contrast microscopy has been used to examine the structure and chemistry of the (001){sub {Omega}} {parallel} (111){sub {alpha}} interphase boundary in samples treated at each temperature. In all cases, two atomic layers of Ag and Mg segregation were found at the broad face of the plate. The risers of the growth ledges and the ends of the plates were free of segregation. No significant levels of Ag or Mg were detected inside the plate at any time. The necessary redistribution of Ag and Mg accompanying a migrating thickening ledge occurs at all temperatures and is not considered to play a decisive role in the excellent coarsening resistance exhibited by the {Omega} plates at temperatures up to 200 C. Plates transformed at 200 C rarely contained ledges and usually exhibited a strong vacancy …
Date:
March 16, 2001
Creator:
Hutchinson, C.R.
Object Type:
Article
System:
The UNT Digital Library
Measurement of the asymmetry in the decay Antiomega+ ---> Antilambda K+ ---> anti-p pi+ K+
The asymmetry in the {bar p} angular distribution in the sequential decay {bar {Omega}}{sup +} {yields} {bar {Lambda}}K{sup +} {yields} {bar p}{pi}{sup +}K{sup +} has been measured to be {bar {alpha}}{sub {Omega}}{bar {alpha}}{sub {Lambda}} = [+1.16{+-}0.18(stat){+-}0.17(syst)]x10{sup -2} using 1.89x10{sup 6} unpolarized {bar {Omega}}{sup +} decays recorded by the Hyper CP (E871) experiment at Fermilab. Using the known value of {alpha}{sub {Lambda}}, and assuming that {bar {alpha}}{sub {Lambda}} = -{alpha}{sub {Lambda}}, {bar {alpha}}{sub {Omega}} = [-1.81{+-}0.28(stat){+-}0.26(syst)]x10{sup -2}. A comparison between this measurement of {bar {alpha}}{sub {Omega}}{bar {alpha}}{sub {Lambda}} and recent measurements of {alpha}{sub {Omega}}{alpha}{sub {Lambda}} made by HyperCP shows no evidence of a violation of CP symmetry.
Date:
January 1, 2006
Creator:
Lu, L. C.; Burnstein, R. A.; Chakravorty, A.; Chen, Y. C.; Choong, W. S.; Clark, K. et al.
Object Type:
Article
System:
The UNT Digital Library
K-(alpha) Radiography at 20-100 keV Using Short-Pulse Lasers
X-ray radiography is an important tool for diagnosing and imaging planar and convergent hydrodynamics phenomena for laser experiments. Until now, hydrodynamics experiments at Omega and NIF utilize E{sub x-ray} < 9 keV backlighter x-rays emitted by thermal plasmas. However, future experiments will need to diagnose larger and denser targets and will require x-ray probes of energies from 20-100 keV and possibly up to 1 MeV. Hard K-{alpha} x-ray photons can be created through high-energy electron interactions in the target material after irradiation by petawatt-class high-intensity-short-pulse lasers with > 10{sup 17} W/cm{sup 2}. We have performed several experiments on the JanUSP, and the Vulcan 100TW, and Vulcan Petawatt lasers to understand K-{alpha} sources and to test radiography concepts. 1-D radiography using an edge-on foil and 2-D radiography using buried wires and cone-fiber targets were tested. We find that 1-D thin edge-on foils can have imaging resolution better than 10 {micro}m. Micro volume targets produce bright sources with measured conversion efficiency from laser energy to x-ray photons of {approx} 1 x 10{sup -5}. This level of conversion may not be enough for 2-D point projection radiography. A comparison of our experimental measurements of small volume sources with the LSP/PIC simulation show similar …
Date:
August 29, 2005
Creator:
Park, H. S.; Chambers, D.; Clarke, R.; Eagleton, R.; Giraldez, E.; Goldsack, T. et al.
Object Type:
Article
System:
The UNT Digital Library
Development of Lower Energy Neutron Spectroscopy for Areal Density Measurement in Implosion Experiment at NIF and Omega
Areal density ({rho}R) is a fundamental parameter that characterizes the performance of an ICF implosion. For high areal densities ({rho}R> 0.1 g/cm{sup 2}), which will be realized in implosion experiments at NIF and LMJ, the target areal density exceeds the stopping range of charged particles and measurements with charged particle spectroscopy will be difficult. In this region, an areal density measurement method using down shifted neutron counting is a promising alternative. The probability of neutron scattering in the imploded plasma is proportional to the areal density of the plasma. The spectrum of neutrons scattered by the specific target nucleus has a characteristic low energy cut off. This enables separate, simultaneous measurements of fuel and pusher {rho}Rs. To apply this concept in implosion experiments, the detector should have extremely large dynamic range. Sufficient signal output for low energy neutrons is also required. A lithium-glass scintillation-fiber plate (LG-SCIFI) is a promising candidate for this application. In this paper we propose a novel technique based on downshifted neutron measurements with a lithium-glass scintillation-fiber plate. The details of instrumentation and background estimation with Monte Carlo calculation are reported.
Date:
August 2, 2001
Creator:
Isumi, N; Lerche, R A; Phillips, T W; Schmid, G J; Moran, M J & Sangster, T C
Object Type:
Article
System:
The UNT Digital Library
Transitions of Dislocation Glide to Twinning and Shear Transformation in Shock-Deformed Tantalum
Recent TEM studies of deformation substructures developed in tantalum and tantalum-tungsten alloys shock-deformed at a peak pressure {approx}45 GPa have revealed the occurrence of shock-induced phase transformation [i.e., {alpha} (bcc) {yields} {omega} (hexagonal) transition] in addition to shock-induced deformation twinning. The volume fraction of twin and {omega} domains increases with increasing content of tungsten. A controversy arises since tantalum exhibits no clear equilibrium solid-state phase transformation under hydrostatic pressures up to 174 GPa. It is known that phase stability of a material system under different temperatures and pressures is determined by system free energy. That is, a structural phase that has the lowest free energy will be stable. For pressure-induced phase transformation under hydrostatic-pressure conditions, tantalum may undergo phase transition when the free energy of a competing phase {omega} becomes smaller than that of the parent phase {alpha} above a critical pressure (P{sub eq}), i.e., the equilibrium {alpha} {yields} {omega} transition occurs when the pressure increases above P{sub eq}. However, it is also known that material shocked under dynamic pressure can lead to a considerable increase in temperature, and the higher the applied pressure the higher the overheat temperature. This means a higher pressure is required to achieve an equivalent …
Date:
October 19, 2009
Creator:
Hsiung, L L; Campbell, G H & McNaney, J M
Object Type:
Article
System:
The UNT Digital Library
Alpha Radiolysis of Sorbed Water on Uranium Oxides and Uranium Oxyfluorides
The radiolysis of sorbed water and other impurities contained in actinide oxides has been the focus of a number of studies related to the establishment of criteria for the safe storage and transport of these materials. Gamma radiolysis studies have previously been performed on uranium oxides and oxyfluorides (UO{sub 3}, U{sub 3}O{sub 8}, and UO{sub 2}F{sub 2}) to evaluate the long-term storage characteristics of {sup 233}U. This report describes a similar study for alpha radiolysis. Uranium oxides and oxyfluorides (with {sup 238}U as the surrogate for {sup 233}U) were subjected to relatively high alpha radiation doses (235 to 634 MGy) by doping with {sup 244}Cm. The typical irradiation time for these samples was about 1.5 years, which would be equivalent to more than 50 years irradiation by a {sup 233}U sample. Both dry and wet (up to 10 wt % water) samples were examined in an effort to identify the gas pressure and composition changes that occurred as a result of radiolysis. This study shows that several competing reactions occur during radiolysis, with the net effect that only very low pressures of hydrogen, nitrogen, and carbon dioxide are generated from the water, nitrate, and carbon impurities, respectively, associated with the …
Date:
September 10, 2003
Creator:
Icenhour, A.S.
Object Type:
Report
System:
The UNT Digital Library
[38th Annual Greek Explosion]
Video of the 38th Annual Greek Explosion, a step show hosted by the University of North Texas in 2008.
Date:
March 1, 2008
Creator:
University of North Texas. Center for Media Production.
Object Type:
Video
System:
The UNT Digital Library
DIRECT OBSERVATION OF THE ALPHA-EPSILON TRANSITION IN SHOCKED SINGLE CRYSTAL IRON
In-situ x-ray diffraction was used to study the response of single crystal iron under shock conditions. Measurements of the response of [001] iron showed a uniaxial compression of the initially bcc lattice along the shock direction by up to 6% at 13 GPa. Above this pressure, the lattice responded with a further collapse of the lattice by 15-18% and a transformation to a hcp structure. The in-situ measurements are discussed and results summarized.
Date:
August 23, 2005
Creator:
Kalantar, D H; Collins, G W; Colvin, J D; Davies, H M; Eggert, J H; Hawreliak, J et al.
Object Type:
Article
System:
The UNT Digital Library
The Hexagon, Volume 97, Number 2, Summer 2006
Quarterly publication of the Alpha Chi Sigma chemistry fraternity containing articles related to chemistry research and the activities of the organization, including local chapters and groups.
Date:
Summer 2006
Creator:
Alpha Chi Sigma
Object Type:
Journal/Magazine/Newsletter
System:
The UNT Digital Library