WorldWideScience

Sample records for fcc bcc hcp

  1. NiFe epitaxial films with hcp and fcc structures prepared on bcc-Cr underlayers

    Energy Technology Data Exchange (ETDEWEB)

    Higuchi, Jumpei, E-mail: higuchi@futamoto.elect.chuo-u.ac.jp [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Ohtake, Mitsuru; Sato, Yoichi [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan); Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)

    2011-09-30

    NiFe epitaxial films are prepared on Cr(211){sub bcc} and Cr(100){sub bcc} underlayers grown hetero-epitaxially on MgO single-crystal substrates by ultra-high vacuum rf magnetron sputtering. The film growth behavior and the crystallographic properties are studied by reflection high energy electron diffraction and pole figure X-ray diffraction. Metastable hcp-NiFe(11-bar 00) and hcp-NiFe(112-bar 0) crystals respectively nucleate on Cr(211){sub bcc} and Cr(100){sub bcc} underlayers, where the hcp-NiFe crystals are stabilized through hetero-epitaxial growth. The hcp-NiFe(11-bar 00) crystal is a single-crystal with the c-axis parallel to the substrate surface, whereas the hcp-NiFe(112-bar 0) crystal is a bi-crystal with the respective c-axes lying in plane and perpendicular each other. With increasing the film thickness, the hcp structure in the NiFe films starts to transform into more stable fcc structure by atomic displacement parallel to the hcp(0001) close packed plane. The resulting films consist of hcp and fcc crystals.

  2. NiFe epitaxial films with hcp and fcc structures prepared on bcc-Cr underlayers

    International Nuclear Information System (INIS)

    Higuchi, Jumpei; Ohtake, Mitsuru; Sato, Yoichi; Kirino, Fumiyoshi; Futamoto, Masaaki

    2011-01-01

    NiFe epitaxial films are prepared on Cr(211) bcc and Cr(100) bcc underlayers grown hetero-epitaxially on MgO single-crystal substrates by ultra-high vacuum rf magnetron sputtering. The film growth behavior and the crystallographic properties are studied by reflection high energy electron diffraction and pole figure X-ray diffraction. Metastable hcp-NiFe(11-bar 00) and hcp-NiFe(112-bar 0) crystals respectively nucleate on Cr(211) bcc and Cr(100) bcc underlayers, where the hcp-NiFe crystals are stabilized through hetero-epitaxial growth. The hcp-NiFe(11-bar 00) crystal is a single-crystal with the c-axis parallel to the substrate surface, whereas the hcp-NiFe(112-bar 0) crystal is a bi-crystal with the respective c-axes lying in plane and perpendicular each other. With increasing the film thickness, the hcp structure in the NiFe films starts to transform into more stable fcc structure by atomic displacement parallel to the hcp(0001) close packed plane. The resulting films consist of hcp and fcc crystals.

  3. The mechanism of bcc α′ nucleation in single hcp ε laths in the fcc γ → hcp ε → bcc α′ martensitic phase transformation

    International Nuclear Information System (INIS)

    Yang, Xu-Sheng; Sun, Sheng; Zhang, Tong-Yi

    2015-01-01

    High Resolution Transmission Electron Microscopy (HRTEM) and Molecular Dynamics (MD) simulations were conducted here to study the plastic deformation induced γ (fcc) → ε (hcp) → α′ (bcc) martensitic transformation in 304 stainless steels for the α′ nucleation from single hcp-ε laths. Results elucidate that the underlying microscopic mechanism for the α′ nucleation from single hcp-ε laths obeys the Bogers–Burgers–Olson–Cohen “3T/8–T/3” model. In particular, the atomic-scale observations clearly show the Kurdyumov–Sachs (K–S) lattice orientation relation (OR) and Pitsch OR at the γ/α′ interfaces, the lattice rotation inside an α′ martensitic inclusion, the transition lattice and the reverse shear-shuffling induced continuous lattice elastic deformation at the diffuse ε/α′ interface, which caters the 3T/8 and T/3 shears and sheds atomic process insight into the mechanism of the martensitic transformation

  4. Dose dependence of true stress parameters in irradiated bcc, fcc, and hcp metals

    Science.gov (United States)

    Byun, T. S.

    2007-04-01

    The dose dependence of true stress parameters has been investigated for nuclear structural materials: A533B pressure vessel steels, modified 9Cr-1Mo and 9Cr-2WVTa ferritic martensitic steels, 316 and 316LN stainless steels, and Zircaloy-4. After irradiation to significant doses, these alloys show radiation-induced strengthening and often experience prompt necking at yield followed by large necking deformation. In the present work, the critical true stresses for deformation and fracture events, such as yield stress (YS), plastic instability stress (PIS), and true fracture stress (FS), were obtained from uniaxial tensile tests or calculated using a linear strain-hardening model for necking deformation. At low dose levels where no significant embrittlement was detected, the true fracture stress was nearly independent of dose. The plastic instability stress was also independent of dose before the critical dose-to-prompt-necking at yield was reached. A few bcc alloys such as ferritic martensitic steels experienced significant embrittlement at doses above ∼1 dpa; and the true fracture stress decreased with dose. The materials fractured before yield at or above 10 dpa.

  5. A thermodynamic model for predicting surface melting and overheating of different crystal planes in BCC, FCC and HCP pure metallic thin films

    International Nuclear Information System (INIS)

    Jahangir, Vafa; Riahifar, Reza; Sahba Yaghmaee, Maziar

    2016-01-01

    In order to predict as well as study the surface melting phenomena in contradiction to surface overheating, a generalized thermodynamics model including the surface free energy of solid and the melt state along with the interfacial energy of solid–liquid (melt on substrate) has been introduced. In addition, the effect of different crystal structures of surfaces in fcc, bcc and hcp metals was included in surface energies as well as in the atomistic model. These considerations lead us to predict surface melting and overheating as two contradictory melting phenomena. The results of the calculation are demonstrated on the example of Pb and Al thin films in three groups of (100), (110) and (111) surface planes. Our conclusions show good agreement with experimental results and other theoretical investigations. Moreover, a computational algorithm has been developed which enables users to investigate the surface melt or overheating of single component metallic thin film with variable crystal structures and different crystalline planes. This model and developed software can be used for studying all related surface phenomena. - Highlights: • Investigating the surface melting and overheating phenomena • Effect of crystal orientations, surface energies, geometry and different atomic surface layers • Developing a computational algorithm and its related code (free-software SMSO-Ver1) • Thickness and orientation of surface plane dominate the surface melting or overheating. • Total excess surface energy as a function of thickness and temperature explains melting.

  6. A thermodynamic model for predicting surface melting and overheating of different crystal planes in BCC, FCC and HCP pure metallic thin films

    Energy Technology Data Exchange (ETDEWEB)

    Jahangir, Vafa, E-mail: vafa.jahangir@yahoo.com; Riahifar, Reza, E-mail: reza_rfr@yahoo.com; Sahba Yaghmaee, Maziar, E-mail: fkmsahba@uni-miskolc.hu

    2016-03-31

    In order to predict as well as study the surface melting phenomena in contradiction to surface overheating, a generalized thermodynamics model including the surface free energy of solid and the melt state along with the interfacial energy of solid–liquid (melt on substrate) has been introduced. In addition, the effect of different crystal structures of surfaces in fcc, bcc and hcp metals was included in surface energies as well as in the atomistic model. These considerations lead us to predict surface melting and overheating as two contradictory melting phenomena. The results of the calculation are demonstrated on the example of Pb and Al thin films in three groups of (100), (110) and (111) surface planes. Our conclusions show good agreement with experimental results and other theoretical investigations. Moreover, a computational algorithm has been developed which enables users to investigate the surface melt or overheating of single component metallic thin film with variable crystal structures and different crystalline planes. This model and developed software can be used for studying all related surface phenomena. - Highlights: • Investigating the surface melting and overheating phenomena • Effect of crystal orientations, surface energies, geometry and different atomic surface layers • Developing a computational algorithm and its related code (free-software SMSO-Ver1) • Thickness and orientation of surface plane dominate the surface melting or overheating. • Total excess surface energy as a function of thickness and temperature explains melting.

  7. First-principles calculations of the structural and thermodynamic properties of bcc, fcc and hcp solid solutions in the Al-TM (TM = Ti, Zr and Hf) systems: A comparison of cluster expansion and supercell methods

    International Nuclear Information System (INIS)

    Ghosh, G.; Walle, A. van de; Asta, M.

    2008-01-01

    The thermodynamic properties of solid solutions with body-centered cubic (bcc), face-centered cubic (fcc) and hexagonal close-packed (hcp) structures in the Al-TM (TM = Ti, Zr and Hf) systems are calculated from first-principles using cluster expansion (CE), Monte-Carlo simulation and supercell methods. The 32-atom special quasirandom structure (SQS) supercells are employed to compute properties at 25, 50 and 75 at.% TM compositions, and 64-atom supercells have been employed to compute properties of alloys in the dilute concentration limit (one solute and 63 solvent atoms). In general, the energy of mixing (Δ m E) calculated by CE and dilute supercells agree very well. In the concentrated region, the Δ m E values calculated by CE and SQS methods also agree well in many cases; however, noteworthy discrepancies are found in some cases, which we argue originate from inherent elastic and dynamic instabilities of the relevant parent lattice structures. The importance of short-range order on the calculated values of Δ m E for hcp Al-Ti alloys is demonstrated. We also present calculated results for the composition dependence of the atomic volumes in random solid solutions with bcc, fcc and hcp structures. The properties of solid solutions reported here may be integrated within the CALPHAD formalism to develop reliable thermodynamic databases in order to facilitate: (i) calculations of stable and metastable phase diagrams of binary and multicomponent systems, (ii) alloy design, and (iii) processing of Al-TM-based alloys

  8. Premelting hcp to bcc Transition in Beryllium

    Science.gov (United States)

    Lu, Y.; Sun, T.; Zhang, Ping; Zhang, P.; Zhang, D.-B.; Wentzcovitch, R. M.

    2017-04-01

    Beryllium (Be) is an important material with wide applications ranging from aerospace components to x-ray equipment. Yet a precise understanding of its phase diagram remains elusive. We have investigated the phase stability of Be using a recently developed hybrid free energy computation method that accounts for anharmonic effects by invoking phonon quasiparticles. We find that the hcpbcc transition occurs near the melting curve at 0 materials.

  9. Allotropic transformation bcc in equilibrium hcp in zirconium

    International Nuclear Information System (INIS)

    Akhtar, A.

    1976-01-01

    The allotropic transformation hcp(α) in equilibrium bcc(β) was examined in crystal bar zirconium. The β → α transformation is massive type in melt grown crystals of β--Zr. Upon thermal cycling through α → β → α the bcchcp transformation occurs frequently through a shear process and less frequently through a massive transformation. The presence of α → β transformation substructure may favor the operation of the shear mode. The hcpbcc phase change occurs through a massive transformation. A lack of transformation memory is associated with the process of thermal cycling. 11 fig., 3 tables

  10. Pre-melting hcp to bcc Transition in Beryllium

    OpenAIRE

    Lu, Y.; Sun, T.; Zhang, Ping.; Zhang, P.; Zhang, D. -B.; Wentzcovitch, R. M.

    2017-01-01

    Beryllium (Be) is an important material with wide applications ranging from aerospace components to X-ray equipments. Yet a precise understanding of its phase diagram remains elusive. We have investigated the phase stability of Be using a recently developed hybrid free energy computation method that accounts for anharmonic effects by invoking phonon quasiparticles. We find that the hcp to bcc transition occurs near the melting curve at 0

  11. Structural and magnetic properties of hcp and fcc Ni nanoparticles

    International Nuclear Information System (INIS)

    Gong, J.; Wang, L.L.; Liu, Y.; Yang, J.H.; Zong, Z.G.

    2008-01-01

    The face-centered-cubic (fcc) and hexagonal-close-packed (hcp) Ni nanoparticles were synthesized with citrate by sol-gel method and heat-treating technique. The structure, morphology and magnetic properties of the samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). Our XRD and TEM results suggested that hcp Ni nanoparticles were successfully synthesized when the heating temperature reaches 300 deg. C. With a further increase in temperature to 400 deg. C, a temperature-induced phase transformation of hcp to fcc was observed. Moreover, the VSM results demonstrated the existence of ferromagnetic behavior in the synthesized fcc and hcp Ni nanoparticles. Nevertheless, the magnetic measurement suggested that the magnetic properties in hcp nanoparticles is probably the sum of two contributions: superparamagnetic and ferromagnetic one. The unsaturated magnetization is much smaller than 47.6 emu/g for the fcc nanoparticles obtained at 400 deg. C and 55 emu/g for the bulk material. It was also found that changes of the stress, grain size and crystal structure during heat-treating have significant influences on the magnetic properties of the Ni nanoparticles

  12. Inherited textures in the bcc phase furnish information about the type of transformation from the fcc phase

    International Nuclear Information System (INIS)

    Jung, V.

    1982-07-01

    Drawing annealed cylindric 18/8 Cr Ni steels, which are originally free of textures, produces the transformed phases - hcp and bcc - both showing major texture contributions with increasing stretching of the cylindric specimens. After stretching the original fcc-phase shows two orientations: [100]fcc vertical stroke vertical stroke cylinder axis and [111]fcc vertical stroke vertical stroke cylinder axis, i.e. direction of stress. In both cases the martensitic phase is produced by gliding and shear in the sequence fcchcpbcc by Nishiyama-Wasserman (N-W) or Kurdjumov-Sachs (K-S) transformation in the (111)fcc planes, which enclose a small angle with direction of stress, i.e. cylinder axis. The calculated orientation distributions of the (110)bcc reflex are compared with the distribution measured by neutron diffraction to get information on the bulk material. The special K-S transformation with only 6 (110)bcc orientations shows relatively good agreement with the measured distribution, except at small angles ω between the cylinder axis and the scattering vector. This might be caused by the isotropic fraction of the fcc phase producing an anisotropic (110)bcc orientation distribution. (orig.) [de

  13. Epitaxial growth of Co(0 0 0 1)hcp/Fe(1 1 0)bcc magnetic bi-layer films on SrTiO3(1 1 1) substrates

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Shikada, Kouhei; Kirino, Fumiyoshi; Futamoto, Masaaki

    2008-01-01

    Co(0 0 0 1) hcp /Fe(1 1 0) bcc epitaxial magnetic bi-layer films were successfully prepared on SrTiO 3 (1 1 1) substrates. The crystallographic properties of Co/Fe epitaxial magnetic bi-layer films were investigated. Fe(1 1 0) bcc soft magnetic layer grew epitaxially on SrTiO 3 (1 1 1) substrate with two type variants, Nishiyama-Wasserman and Kurdjumov-Sachs relationships. An hcp-Co single-crystal layer is obtained on Ru(0 0 0 1) hcp interlayer, while hcp-Co layer formed on Au(1 1 1) fcc or Ag(1 1 1) fcc interlayer is strained and may involve fcc-Co phase. It has been shown possible to prepare Co/Fe epitaxial magnetic bi-layer films which can be usable for patterned media application

  14. Ab initio lattice stability of fcc and hcp Fe-Mn random alloys

    International Nuclear Information System (INIS)

    Gebhardt, T; Music, D; Hallstedt, B; Schneider, J M; Ekholm, M; Abrikosov, I A; Vitos, L

    2010-01-01

    We have studied the lattice stability of face centred cubic (fcc) versus hexagonal close packed (hcp) Fe-Mn random alloys using ab initio calculations. In the calculations we considered the antiferromagnetic order of local moments, which for fcc alloys models the magnetic configuration of this phase at room temperature (below its Neel temperature) as well as their complete disorder, corresponding to paramagnetic fcc and hcp alloys. For both cases, the results are consistent with our thermodynamic calculations, obtained within the Calphad approach. For the room temperature magnetic configuration, the cross-over of the total energies of the hcp phase and the fcc phase of Fe-Mn alloys is at the expected Mn content, whereas for the magnetic configuration above the fcc Neel temperature, the hcp lattice is more stable within the whole composition range studied. The increase of the total energy difference between hcp and antiferromagnetic fcc due to additions of Mn as well as the stabilizing effect of antiferromagnetic ordering on the fcc phase are well displayed. These results are of relevance for understanding the deformation mechanisms of these random alloys.

  15. Ab initio lattice stability of fcc and hcp Fe-Mn random alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gebhardt, T; Music, D; Hallstedt, B; Schneider, J M [Materials Chemistry, RWTH Aachen University, D-52056 Aachen (Germany); Ekholm, M; Abrikosov, I A [Department of Physics, Chemistry and Biology (IFM), Linkoeping University, SE-581 83 Linkoeping (Sweden); Vitos, L, E-mail: gebhardt@mch.rwth-aachen.d [Department of Materials Science and Engineering, Applied Materials Physics, oyal Institute of Technology, SE-10044 Stockholm (Sweden)

    2010-07-28

    We have studied the lattice stability of face centred cubic (fcc) versus hexagonal close packed (hcp) Fe-Mn random alloys using ab initio calculations. In the calculations we considered the antiferromagnetic order of local moments, which for fcc alloys models the magnetic configuration of this phase at room temperature (below its Neel temperature) as well as their complete disorder, corresponding to paramagnetic fcc and hcp alloys. For both cases, the results are consistent with our thermodynamic calculations, obtained within the Calphad approach. For the room temperature magnetic configuration, the cross-over of the total energies of the hcp phase and the fcc phase of Fe-Mn alloys is at the expected Mn content, whereas for the magnetic configuration above the fcc Neel temperature, the hcp lattice is more stable within the whole composition range studied. The increase of the total energy difference between hcp and antiferromagnetic fcc due to additions of Mn as well as the stabilizing effect of antiferromagnetic ordering on the fcc phase are well displayed. These results are of relevance for understanding the deformation mechanisms of these random alloys.

  16. Experimental observations elucidating the mechanisms of structural bcc-hcp transformations in ?-Ti alloys

    NARCIS (Netherlands)

    Van Bohemen, S.M.C.; Sietsma, J.; Van der Zwaag, S.

    2006-01-01

    The formation mechanisms of two hcp ? phase morphologies in Ti-4.5Fe-6.8Mo-1.5Al have been investigated by optical microscopy (OM), atomic force microscopy (AFM), electron probe microanalysis (EPMA) and dilatometry. At relatively high temperatures primary ? forms predominantly on prior bcc ? grain

  17. Calculated temperature dependence of elastic constants and phonon dispersion of hcp and bcc beryllium

    Science.gov (United States)

    Hahn, Steven; Arapan, Sergiu; Harmon, Bruce; Eriksson, Olle

    2011-03-01

    Conventional first principle methods for calculating lattice dynamics are unable to calculate high temperature thermophysical properties of materials containing modes that are entropically stabilized. In this presentation we use a relatively new approach called self-consistent ab initio lattice dynamics (SCAILD) to study the hcp to bcc transition (1530 K) in beryllium. The SCAILD method goes beyond the harmonic approximation to include phonon-phonon interactions and produces a temperature-dependent phonon dispersion. In the high temperature bcc structure, phonon-phonon interactions dynamically stabilize the N-point phonon. Fits to the calculated phonon dispersion were used to determine the temperature dependence of the elastic constants in the hcp and bcc phases. Work at the Ames Laboratory was supported by the Department of Energy-Basic Energy Sciences under Contract No. DE-AC02-07CH11358.

  18. NMR-ON on 60CoCo(fcc, hcp, thin film), 52MnCo(fcc), and 90NbCo(fcc)

    International Nuclear Information System (INIS)

    Zech, E.; Hagn, E.; Ernst, H.; Eska, G.

    1978-01-01

    With the NMR-ON method the magnetic hyperfine splitting constant of dilute impurities in a ferromagnetic host material (Fe, Ni, Co) can be determined with high accuracy (10 -3 ...10 -4 ). Only few NMR-ON experiments with Co as host lattice have been performed up to now. In constrast to Fe and Ni, two stable modifications exist for Co (fcc and hcp). In the hcp case the magnetic hyperfine field is expected to be anisotropic. Due to the electric field gradient, which is present in this case, a (small) guadrupole interaction is superimposed to the magnetic hyperfine interaction. For 60 CoCo measurements were done on a fcc foil, a hcp single crystal, and on thin films, which were prepared by evaporating Co into glass. For 52 MnCo and 90 NbCo measurements were performed for fcc Co. (Auth.)

  19. Hydrogen diffusion and trapping in bcc and fcc metals

    International Nuclear Information System (INIS)

    Richter, D.

    1979-01-01

    The fundamental aspects of the metal--hydrogen systems are described. The large number of anomalous properties are the reason for continuous scientific effort. The time scale of hydrogen motion is extremely short. The characteristic frequencies of the localized modes of hydrogen in Ta, Nb, or V are in the order of 10 -14 sec (energies between 0.1 to 0.2 eV); the jump frequencies for H-diffusion at elevated temperatures in those systems are between 10 +12 to 10 +13 sec -1 . They are comparable with the correlation times for diffusion in liquids and more than ten orders of magnitude larger than the jump times for nitrogen in Nb. Out of the large number of experimental data this paper will survey only some recent results on representative fcc and bcc metals for dilute H solutions. The nature of the elementary step in H-diffusion is described. Here the temperature and isotope dependence of the H-diffusion coefficient gives hints to the mechanism involved. The experimental results are discussed in terms of semiclassical and quantum mechanical diffusion theories

  20. Vacancy formation enthalpies in bcc and fcc FeCo by positron annihilation

    International Nuclear Information System (INIS)

    Jackman, J.A.; Kim, S.M.; Buyers, W.J.L.

    1982-01-01

    A long slit angular correlation apparatus was used to measure the peak coincidence count rate in stoichiometric FeCo from 290 K to 1510 K. The count rate did not change significantly at the order-disorder phase transition (1008 K), but decreased sharply by 3.2% at the bcc-fcc phase transition at 1258 K. The threshold temperatures for the trapping of positrons in vacancies are measured to be 1125 K for the bcc phase and 1260 K for the fcc phase. The vacancy formation enthalpies in the bcc and fcc phases are determined to be 1.45 +- 0.05 eV and 1.63 +- 0.05 eV. The activation energies for self-diffusion have been estimated from the threshold temperatures, and are found to be 2.45 eV and 2.74 eV for the bcc and fcc phases respectively. (Auth.)

  1. Cesium under pressure: First-principles calculation of the bcc-to-fcc phase transition

    Science.gov (United States)

    Carlesi, S.; Franchini, A.; Bortolani, V.; Martinelli, S.

    1999-05-01

    In this paper we present the ab initio calculation of the structural properties of cesium under pressure. The calculation of the total energy is done in the local-density approximation of density-functional theory, using a nonlocal pseudopotential including the nonlinear core corrections proposed by Louie et al. The calculation of the pressure-volume diagram for both bcc and fcc structures allows us to prove that the transition from bcc to fcc structure is a first-order transition.

  2. Effect of the fcc-hcp martensitic transition on the equation of state of solid krypton up to 140 GPa

    Science.gov (United States)

    Rosa, A. D.; Garbarino, G.; Briggs, R.; Svitlyk, V.; Morard, G.; Bouhifd, M. A.; Jacobs, J.; Irifune, T.; Mathon, O.; Pascarelli, S.

    2018-03-01

    Solid krypton (Kr) undergoes a pressure-induced martensitic phase transition from a face-centered cubic (fcc) to a hexagonal close-packed (hcp) structure. These two phases coexist in a very wide pressure domain inducing important modifications of the bulk properties of the resulting mixed phase system. Here, we report a detailed in situ x-ray diffraction and absorption study of the influence of the fcc-hcp phase transition on the compression behavior of solid krypton in an extended pressure domain up to 140 GPa. The onset of the hcp-fcc transformation was observed in this study at around 2.7 GPa and the coexistence of these two phases up to 140 GPa, the maximum investigated pressure. The appearance of the hcp phase is also evidenced by the pressure-induced broadening and splitting of the first peak in the XANES spectra. We demonstrate that the transition is driven by a continuous nucleation and intergrowth of nanometric hcp stacking faults that evolve in the fcc phase. These hcp stacking faults are unaffected by high-temperature annealing, suggesting that plastic deformation is not at their origin. The apparent small Gibbs free-energy differences between the two structures that decrease upon compression may explain the nucleation of hcp stacking faults and the large coexistence domain of fcc and hcp krypton. We observe a clear anomaly in the equation of state of the fcc solid at ˜20 GPa when the proportion of the hcp form reaches ˜20 % . We demonstrate that this anomaly is related to the difference in stiffness between the fcc and hcp phases and propose two distinct equation of states for the low and high-pressure regimes.

  3. Energy barrier of bcc-fcc phase transition via the Bain path in Yukawa system

    Science.gov (United States)

    Kiyokawa, Shuji

    2018-05-01

    In the Yukawa system with the dimensionless screening parameter κ>1.5 , when bcc-fcc transition occurs via Bain path, we show that spontaneous transitions do not occur even if the system temperature reaches the transition point of bcc-fcc because it is necessary to increase once the free energy in the process of transition from bcc to fcc through Bain deformation. Here, we refer the temporary increment of the free energy during Bain deformation as Bain barrier. Since there are the Bain barriers at the transitions between bcc and fcc phases, these phases may coexist as metastable state in the wide region (not a coexistence line) of κ and the coupling constant Γ. We study the excess energy of the system and the free energy difference between bcc and fcc phases by the Monte Carlo method, where the simulation box is divided into a large number of elements with small volume and a particle in the box is restricted be placed in one of these elements. By this method, we can tabulate the values of the interparticle potential and can calculate the internal energy fast and precisely.

  4. Magnetic properties of metastable bcc and fcc Fe-Cu alloys produced by vapor quenching

    International Nuclear Information System (INIS)

    Sumiyama, Kenji; Yoshitake, Tsutomu; Nakamura, Yoji

    1984-01-01

    High concentration Fesub(1-x)Cusub(x) alloys have been obtained by rf sputtering technique and investigated by X-ray diffraction and magnetization measurements. The bcc phase is extended over the region with x=0-0.4, while the fcc phase with x=0.6-1.0. For x=0.4-0.6, we have the mixed phase of bcc and fcc. The lattice constant of bcc phase increases slightly and that of fcc phase decreases with increasing x. In the bcc alloys, the average magnetic moment decreases with increasing x and deviates upwards from the simple dilution law. In the fcc alloys, the magnetic moment also decreases with increasing x but it deviates downwards from the simple dilution law. The Curie temperature, Tsub(c), of the Fesub(1-x)Cusub(x) alloys decreases abruptly with increasing x: Tsub(c) is higher than 750 K for the bcc alloys, while it is lower than 320 K for the fcc alloys and become 0 K at about x=0.92. (author)

  5. bcc-to-hcp transformation pathways for iron versus hydrostatic pressure: Coupled shuffle and shear modes

    Science.gov (United States)

    Liu, J. B.; Johnson, D. D.

    2009-04-01

    Using density-functional theory, we calculate the potential-energy surface (PES), minimum-energy pathway (MEP), and transition state (TS) versus hydrostatic pressure σhyd for the reconstructive transformation in Fe from body-centered cubic (bcc) to hexagonal closed-packed (hcp). At fixed σhyd , the PES is described by coupled shear (γ) and shuffle (η) modes and is determined from structurally minimized hcp-bcc energy differences at a set of (η,γ) . We fit the PES using symmetry-adapted polynomials, permitting the MEP to be found analytically. The MEP is continuous and fully explains the transformation and its associated magnetization and volume discontinuity at TS. We show that σhyd (while not able to induce shear) dramatically alters the MEP to drive reconstruction by a shuffle-only mode at ≤30GPa , as observed. Finally, we relate our polynomial-based results to Landau and nudge-elastic-band approaches and show they yield incorrect MEP in general.

  6. Kinetics of disorder-to-fcc phase transition via an intermediate bcc state

    International Nuclear Information System (INIS)

    Liu Yongsheng; Nie Huifen; Bansil, Rama; Steinhart, Milos; Bang, Joona; Lodge, Timothy P.

    2006-01-01

    Time-resolved small-angle x-ray scattering measurements reveal that a long-lived intermediate bcc state forms when a poly(styrene-b-isoprene) diblock copolymer solution in an isoprene selective solvent is rapidly cooled from the disordered micellar fluid at high temperature to an equilibrium fcc state. The kinetics of the epitaxial growth of the [111] fcc peak from the [110] bcc peak was obtained by fitting the scattering data to a simple model of the transformation. The growth of the [111] fcc peak agrees with the Avrami model of nucleation and growth kinetics with an exponent n=1.4, as does the initial decay of the [110] bcc peak, with an exponent n=1.3. The data were also found to be in good agreement with the Cahn model of grain boundary nucleation and growth

  7. Synthesis and characterization of branched fcc/hcp ruthenium nanostructures and their catalytic activity in ammonia borane hydrolysis

    KAUST Repository

    AlYami, Noktan

    2018-01-30

    Several systems have shown the ability to stabilize uncommon crystal structures during the synthesis of metallic nanoparticles. By tailoring the nanoparticle crystal structure, the physical and chemical properties of the particles can also be controlled. Herein, we first synthesized branched nanoparticles of mixed hcp/fcc ruthenium, which were formed using tungsten carbonyl [W(CO)6] as both a reducing agent and a source of carbon monoxide. The branched particles were formed from multiple particulates off a central core. High-resolution transmission electron microscopy (HRTEM) clearly showed that the branched structures consisted of aligned hcp crystal domains, a mixture of fcc and hcp crystal domains with several defects and misalignments, and particles that contained multiple cores and branches. Branched particles were also formed with molybdenum carbonyl [Mo(CO)6], and faceted particles of hcp and fcc particles were formed with Re2(CO)10 as a carbon monoxide source. Without metal carbonyls, small particles of spherical hcp ruthenium were produced, and their size could be controlled by the selection of the precursor. The ruthenium nanoparticles were tested for ammonia borane hydrolysis; the branched nanoparticles were more reactive for catalytic hydrogen evolution than the faceted hcp/fcc nanoparticles or the spherical hcp nanoparticles. This work showcases the potential of crystal phase engineering of transition metal nanoparticles by different carbon monoxide precursors for tailoring their catalytic reactivity.

  8. Towards an unbiased comparison of CC, BCC, and FCC lattices in terms of prealiasing

    KAUST Repository

    Vad, Viktor

    2014-06-01

    In the literature on optimal regular volume sampling, the Body-Centered Cubic (BCC) lattice has been proven to be optimal for sampling spherically band-limited signals above the Nyquist limit. On the other hand, if the sampling frequency is below the Nyquist limit, the Face-Centered Cubic (FCC) lattice was demonstrated to be optimal in reducing the prealiasing effect. In this paper, we confirm that the FCC lattice is indeed optimal in this sense in a certain interval of the sampling frequency. By theoretically estimating the prealiasing error in a realistic range of the sampling frequency, we show that in other frequency intervals, the BCC lattice and even the traditional Cartesian Cubic (CC) lattice are expected to minimize the prealiasing. The BCC lattice is superior over the FCC lattice if the sampling frequency is not significantly below the Nyquist limit. Interestingly, if the original signal is drastically undersampled, the CC lattice is expected to provide the lowest prealiasing error. Additionally, we give a comprehensible clarification that the sampling efficiency of the FCC lattice is lower than that of the BCC lattice. Although this is a well-known fact, the exact percentage has been erroneously reported in the literature. Furthermore, for the sake of an unbiased comparison, we propose to rotate the Marschner-Lobb test signal such that an undue advantage is not given to either lattice. © 2014 The Eurographics Association and John Wiley & Sons Ltd. Published by John Wiley & Sons Ltd.

  9. Towards an unbiased comparison of CC, BCC, and FCC lattices in terms of prealiasing

    KAUST Repository

    Vad, Viktor; Csé bfalvi, Balá zs; Rautek, Peter; Grö ller, Eduard M.

    2014-01-01

    In the literature on optimal regular volume sampling, the Body-Centered Cubic (BCC) lattice has been proven to be optimal for sampling spherically band-limited signals above the Nyquist limit. On the other hand, if the sampling frequency is below the Nyquist limit, the Face-Centered Cubic (FCC) lattice was demonstrated to be optimal in reducing the prealiasing effect. In this paper, we confirm that the FCC lattice is indeed optimal in this sense in a certain interval of the sampling frequency. By theoretically estimating the prealiasing error in a realistic range of the sampling frequency, we show that in other frequency intervals, the BCC lattice and even the traditional Cartesian Cubic (CC) lattice are expected to minimize the prealiasing. The BCC lattice is superior over the FCC lattice if the sampling frequency is not significantly below the Nyquist limit. Interestingly, if the original signal is drastically undersampled, the CC lattice is expected to provide the lowest prealiasing error. Additionally, we give a comprehensible clarification that the sampling efficiency of the FCC lattice is lower than that of the BCC lattice. Although this is a well-known fact, the exact percentage has been erroneously reported in the literature. Furthermore, for the sake of an unbiased comparison, we propose to rotate the Marschner-Lobb test signal such that an undue advantage is not given to either lattice. © 2014 The Eurographics Association and John Wiley & Sons Ltd. Published by John Wiley & Sons Ltd.

  10. Martensitic transformation, fcc and hcp relative phase stability, and thermal cycling effects in Fe-Mn and Fe-Mn-X Alloys (X = Si, Co)

    International Nuclear Information System (INIS)

    Baruj, Alberto

    1999-01-01

    In this Thesis we present a study of the fcc and hcp relative phase stability in the Fe-Mn and Fe-Mn-Co systems. In particular, we have investigated the effect of two main factors affecting the relative phase stability: changes in the chemical composition of the alloys and changes in the density of crystalline defects in the microstructure.In order to analyse the effect of chemical composition, we have performed an experimental study of the fcc/hcp martensitic transformation temperatures in Fe-Mn-Co alloys in the composition range lying between 15% and 34% Mn, and between 1% and 16% Co.We have measured the martensitic transformation temperatures by means of dilatometry and electrical resistivity.We have combined this information with measurements of the fcc/hcp martensitic transformation temperatures in Co-rich alloys to perform a modelling of the Gibbs energy function for the hcp phase in the Fe-Mn-Co and Fe-Co systems.We found that, for alloys in the Mn range between 17% and 25%, Co additions tend to stabilise slightly the fcc phase.In the alloys with Mn contents below that range, increasing the amount of Co stabilise the bcc phase. In alloys with Mn contents above 25% the Neel temperature is depressed by the addition of Co, which stabilise the hcp phase.In order to investigate the effect of changes in the density of crystalline defects, we have performed thermal cycling experiments through the fcc/hcp martensitic transformation in Fe-Mn, Fe-Mn-Co and Fe-Mn-Si alloys.We have applied the thermodynamic description obtained before in order to analyse these experiments.We found in the thermal cycling experiments a first stage where the martensitic transformation is promoted.This stage occurs in all the studied alloys during the first cycle or the two first cycles.Increasing the number of thermal cycles, the promotion stage is replaced by an inhibition of the transformation stage.We propose a possible microstructural interpretation of these phenomena where the plastic

  11. Stress induced martensitic transformation from bcc to fcc in Ag-Zn

    International Nuclear Information System (INIS)

    Takezawa, K.; Akamatsu, R.; Marukawa, K.

    1995-01-01

    The martensitic transformation in Ag-Zn alloys of low-Zn content has been studied by optical and electron microscopic observations and by tensile tests. The β 1 phase of B2 structure transforms to the thermo-elastic martensite having 9R structure similar to Cu-based alloys upon cooling to temperature below Ms. When the β 1 phase is stretched at room temperature, the slip deformation occurs at first and then the stress-induced martensite(SIM) of wedge-like morphology forms. The SIM has the ordered fcc structure containing micro-twins. This direct transformation from bcc to fcc is a unique feature in Ag-Zn alloys. In Cu alloys, martensites of fcc structure appear only after the second transformation from the first transformation product of 9R structure. The critical stress for the martensitic transformation and a degree of order of SIM decrease as the deformation temperature rises. In Ag-Zn alloys, the martensite of disordered fcc is thermally produced also by up-quenching to a higher temperature. In the present study, the relation between martensites of ordered and disordered fcc is discussed through thermodynamical calculations. The condition for the direct transformation from bcc to fcc is also examined. (orig.)

  12. Microstructure and mechanical properties of bulk highly faulted fcc/hcp nanostructured cobalt microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Barry, Aliou Hamady [Université Paris 13, Sorbonne Paris Cité, LSPM CNRS UPR 3407, 93430 Villetaneuse (France); Laboratoire Chimie des Matériaux, Département de Chimie, Faculté des Sciences et Technique, Université de Nouakchott (Mauritania, Islamic Republic of); Dirras, Guy, E-mail: dirras@unv-paris13.fr [Université Paris 13, Sorbonne Paris Cité, LSPM CNRS UPR 3407, 93430 Villetaneuse (France); Schoenstein, Frederic; Tétard, Florent; Jouini, Noureddine [Université Paris 13, Sorbonne Paris Cité, LSPM CNRS UPR 3407, 93430 Villetaneuse (France)

    2014-05-01

    Nanostructured cobalt powders with an average particle size of 50 nm were synthesized using a polyol method and subsequently consolidated by spark plasma sintering (SPS). SPS experiments performed at 650 °C with sintering times ranging from 5 to 45 min under a pressure of 100 MPa, yielded to dense bulk nanostructured cobalt (relative density greater than 97%). X-ray diffraction patterns of the as-prepared powders showed only a face centered cubic (fcc) crystalline phase, whereas the consolidated samples exhibited a mixture of both fcc and hexagonal close packed (hcp) phases. Transmission electron microscopy observations revealed a lamellar substructure with a high density of nanotwins and stacking faults in every grain of the sintered samples. Room temperature compression tests, carried out at a strain rate of 10{sup −3} s{sup −1}, yielded to highest strain to fracture values of up to 5% for sample of holding time of 15 min, which exhibited a yield strength of 1440 MPa, an ultimate strength as high as 1740 MPa and a Young's modulus of 205 GPa. The modulus of elasticity obtained from the nanoindentation tests, ranges from 181 to 218 GPa. The lowest modulus value of 181 GPa was obtained for the sample with the highest sintering time (45 min), which could be related to mass density loss as a consequence of trapped gases releasing. - Highlights: • Co nanopowder (50 nm) was prepared by reduction in polyol medium. • SPS was used to process bulk nanostructured Co specimens. • Microstructures were made of intricate fcc/hcp, along with nanotwins and SFs. • High strengths and moderate compressive ductility were obtained. • Deformation mechanisms related to complex interplay of different length scales.

  13. Curie temperatures of fcc and bcc Nickel and Permalloy: Supercell and Green's function methods

    Czech Academy of Sciences Publication Activity Database

    Yu, P.; Jin, X.F.; Kudrnovský, Josef; Wang, D. S.; Bruno, P.

    2008-01-01

    Roč. 77, č. 5 (2008), 054431/1-054431/8 ISSN 1098-0121 R&D Projects: GA MŠk OC 150; GA AV ČR IAA100100616 Institutional research plan: CEZ:AV0Z10100520 Keywords : fcc - and bcc-Ni * Permalloy * magnetic moments * Curie temperatures Subject RIV: BE - Theoretical Physics Impact factor: 3.322, year: 2008

  14. Pre-melting hcp to bcc Transition in Beryllium: A Study by First-Principles Phonon Quasiparticle Approach

    Science.gov (United States)

    Zhang, D. B., Sr.

    2017-12-01

    Beryllium (Be) is an important material with wide applications ranging from aerospace components to X-ray equipments. Yet a precise understanding of its phase diagram remains elusive. We have investigated the phase stability of Be using a recently developed hybrid free energy computation method that accounts for anharmonic effects by invoking phonon quasiparticles. We find that the hcp to bcc transition occurs near the melting curve at 0

  15. Kinetics of self-interstitial migration in bcc and fcc transition metals

    Science.gov (United States)

    Bukkuru, S.; Bhardwaj, U.; Srinivasa Rao, K.; Rao, A. D. P.; Warrier, M.; Valsakumar, M. C.

    2018-03-01

    Radiation damage is a multi-scale phenomenon. A thorough understanding of diffusivities and the migration energies of defects is a pre-requisite to quantify the after-effects of irradiation. We investigate the thermally activated mobility of self-interstitial atom (SIA) in bcc transition metals Fe, Mo, Nb and fcc transition metals Ag, Cu, Ni, Pt using molecular dynamics (MD) simulations. The self-interstitial diffusion involves various mechanisms such as interstitialcy, dumbbell or crowdion mechanisms. Max-Space Clustering (MSC) method has been employed to identify the interstitial and its configuration over a wide range of temperature. The self-interstitial diffusion is Arrhenius like, however, there is a slight deviation at high temperatures. The migration energies, pre-exponential factors of diffusion and jump-correlation factors, obtained from these simulations can be used as inputs to Monte Carlo simulations of defect transport. The jump-correlation factor shows the degree of preference of rectilinear or rotational jumps. We obtain the average jump-correlation factor of 1.4 for bcc metals and 0.44 for fcc metals. It indicates that rectilinear jumps are preferred in bcc metals and rotational jumps are preferred in fcc metals.

  16. Diffraction evidence for an FCC in equilibrium HCP transformation in ytterbium

    International Nuclear Information System (INIS)

    Kayser, F.X.

    1971-04-01

    X-ray powder patterns obtained from polycrystalline wires of high-purity Yb in several heat treated conditions have demonstrated (i) the existence of a martensitic transformation, β-Yb (fcc) reversible α-Yb(hcp) and (ii) that the hexagonal close-packed structure is the thermodynamically stable form of Yb at temperatures below approximately 270 0 K. Precision lattice parameters determined for both polymorphs at room temperature indicate the fractional volume change on the transformation to be 0.0091, a magnitude that is consistent with the belief that α-Yb is divalent. This can be regarded as a stacking fault transformation, and one wherein the preponderance of the volume change is accommodated by displacements normal to the habit plane

  17. Influence of the intermediate bcc phase on the evolution of superfluid inclusions in hcp matrix 3He-4He

    International Nuclear Information System (INIS)

    Birchenko, A.P.; Mikhin, N.P.; Neoneta, A.S.; Rudavskij, Eh.Ya.; Fisun, Ya.Yu.

    2016-01-01

    The evolution of liquid inclusions which are formed in the hcp matrix by rapid cooling of the 3 He- 4 He solution containing 1.05% 3 He was studied by pulse NMR. The diffusion coefficient of 3 He in the liquid was measured by two-pulses spin-echo method during evolution of the inclusions. Measurements were carried out at 1.67 K which corresponds to the bcc phase existence in the phase diagram, as well as at 1.38 K, where the bcc phase is absent. It is found that in the process of the evolution, in both cases the size of the liquid inclusions is less than diffusion length and so the diffusion is restricted. The measured restricted dif-fusion coefficient allowed to find the characteristic size of the inclusions. In the first case, during the evolution of liquid inclusions, dendrites of intermediate bcc phase is forming and the inclusions are separating into a lot of smaller droplets. Due to the rapid growth of the bcc dendrites, the droplet size decreases rapidly, and the process comes to disappearance of bcc phase and an amorphous state appearance. The results obtained by measuring the diffusion coefficient, correlated with the behavior of the spin-lattice relaxation time in such a system. In the second case at a lower temperature bcc phase is not formed, and the size of the liquid inclusions decreases very slow until the completion of their solidification.

  18. Atomic vibration amplitudes in fcc and hcp 4He through x-ray diffraction measurements

    International Nuclear Information System (INIS)

    Venkataraman, C.T.; Simmons, R.O.

    2003-01-01

    Atomic vibration amplitudes in dense fcc and hcp 4 He crystals have been measured using synchrotron x rays from the dependence of integrated Bragg intensities up to wave vectors of 91 nm -1 . Observed raw Bragg x-ray integrated intensities cover an extraordinary range, greater than 10 5 , due to the combined effect of the Debye-Waller factor and electronic form factor. From analysis of these intensities mean-square atomic vibration amplitudes Q 2 > and Lindemann ratios are determined. Path-integral Monte Carlo (PIMC) computations of Draeger and Ceperley, extrapolated to the thermodynamic limit, provide excellent agreement with these experimental results. For both present measurements and the PIMC results, one finds both a predominantly Gaussian distribution in Q 2 > and an extraordinarily large Lindemann ratio. In contrast, these directly measured x-ray values are significantly larger than published values inferred from Born-von Karman fitting to phonon dispersion measured by neutron scattering. Mildly anharmonic neon, which is fairly well described by self-consistent phonon theories, is contrasted with present results on fcc 4 He at corresponding densities

  19. Comparison of void strengthening in fcc and bcc metals: Large-scale atomic-level modelling

    International Nuclear Information System (INIS)

    Osetsky, Yu.N.; Bacon, D.J.

    2005-01-01

    Strengthening due to voids can be a significant radiation effect in metals. Treatment of this by elasticity theory of dislocations is difficult when atomic structure of the obstacle and dislocation is influential. In this paper, we report results of large-scale atomic-level modelling of edge dislocation-void interaction in fcc (copper) and bcc (iron) metals. Voids of up to 5 nm diameter were studied over the temperature range from 0 to 600 K. We demonstrate that atomistic modelling is able to reveal important effects, which are beyond the continuum approach. Some arise from features of the dislocation core and crystal structure, others involve dislocation climb and temperature effects

  20. Beyond chemical accuracy: The pseudopotential approximation in diffusion Monte Carlo calculations of the HCP to BCC phase transition in beryllium.

    Energy Technology Data Exchange (ETDEWEB)

    Shulenburger, Luke [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Mattsson, Thomas Kjell Rene [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Desjarlais, Michael Paul [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-01-01

    Motivated by the disagreement between recent diffusion Monte Carlo calculations of the phase transition pressure between the ambient and beta-Sn phases of silicon and experiments, we present a study of the HCP to BCC phase transition in beryllium. This lighter element provides an opportunity for directly testing many of the approximations required for calculations on silicon and may suggest a path towards increasing the practical accuracy of diffusion Monte Carlo calculations of solids in general. We demonstrate that the single largest approximation in these calculations is the pseudopotential approximation and after removing this we find excellent agreement with experiment for the ambient HCP phase and results similar to careful calculations using density functional theory for the phase transition pressure.

  1. Positron lifetime studies of the hcp to fcc transformation induced by mechanical attrition of elemental titanium

    International Nuclear Information System (INIS)

    Manna, I.; Chattopadhyay, P.P.; Nandi, P.; Nambissan, P.M.G.

    2004-01-01

    Nanocrystallisation by planetary ball-milling of high purity elemental titanium (Ti) revealed a polymorphic transformation from its normal hexagonal close packed (hcp) structure to a face-centered cubic (fcc) phase. Positron lifetime measurements were carried out on samples collected after different hours of milling to characterize the defect structures at grain surfaces. With increasing hours of milling, the nanocrystalline grain size decreased and the positron lifetimes--one related to the annihilation at the grain surfaces and the other to that at the intergranular open volume domains--increased significantly due to the increased free volume at the trapping vacancy sites. However, between 5 to 10 hours of milling, the two lifetimes decreased before resuming increasing once again. This marked deviation from an otherwise expected continuous increase of positron lifetime coincided with structural rearrangement within the system bringing in an enhancement in the density of electrons. The repacking of atoms along the [0001] crystallographic direction could be a possibility for this observation. Positron radiation effects on the migration and agglomeration of nanoparticles are also discussed

  2. About the choice of Gibbs' potential for modelling of FCCHCP transformation in FeMnSi-based shape memory alloys

    Science.gov (United States)

    Evard, Margarita E.; Volkov, Aleksandr E.; Belyaev, Fedor S.; Ignatova, Anna D.

    2018-05-01

    The choice of Gibbs' potential for microstructural modeling of FCCHCP martensitic transformation in FeMn-based shape memory alloys is discussed. Threefold symmetry of the HCP phase is taken into account on specifying internal variables characterizing volume fractions of martensite variants. Constraints imposed on model constants by thermodynamic equilibrium conditions are formulated.

  3. Indium-defect interactions in FCC and BCC metals studied using the modified embedded atom method

    Energy Technology Data Exchange (ETDEWEB)

    Zacate, M. O., E-mail: zacatem1@nku.edu [Northern Kentucky University, Department of Physics, Geology, and Engineering Technology (United States)

    2016-12-15

    With the aim of developing a transferable potential set capable of predicting defect formation, defect association, and diffusion properties in a wide range of intermetallic compounds, the present study was undertaken to test parameterization strategies for determining empirical pair-wise interaction parameters in the modified embedded atom method (MEAM) developed by Baskes and coworkers. This report focuses on indium-solute and indium-vacancy interactions in FCC and BCC metals, for which a large set of experimental data obtained from perturbed angular correlation measurements is available for comparison. Simulation results were found to be in good agreement with experimental values after model parameters had been adjusted to reproduce as best as possible the following two sets of quantities: (1) lattice parameters, formation enthalpies, and bulk moduli of hypothetical equiatomic compounds with the NaCl crystal structure determined using density functional theory and (2) dilute solution enthalpies in metals as predicted by Miedema’s semi-empirical model.

  4. Vacancy-mediated fcc/bcc phase separation in Fe1 -xNix ultrathin films

    Science.gov (United States)

    Menteş, T. O.; Stojić, N.; Vescovo, E.; Ablett, J. M.; Niño, M. A.; Locatelli, A.

    2016-08-01

    The phase separation occurring in Fe-Ni thin films near the Invar composition is studied by using high-resolution spectromicroscopy techniques and density functional theory calculations. Annealed at temperatures around 300 ∘C ,Fe0.70Ni0.30 films on W(110) break into micron-sized bcc and fcc domains with compositions in agreement with the bulk Fe-Ni phase diagram. Ni is found to be the diffusing species in forming the chemical heterogeneity. The experimentally determined energy barrier of 1.59 ±0.09 eV is identified as the vacancy formation energy via density functional theory calculations. Thus, the principal role of the surface in the phase separation process is attributed to vacancy creation without interstitials.

  5. Identifying self-interstitials of bcc and fcc crystals in molecular dynamics

    Science.gov (United States)

    Bukkuru, S.; Bhardwaj, U.; Warrier, M.; Rao, A. D. P.; Valsakumar, M. C.

    2017-02-01

    Identification of self-interstitials in molecular dynamics (MD) simulations is of critical importance. There exist several criteria for identifying the self-interstitial. Most of the existing methods use an assumed cut-off value for the displacement of an atom from its lattice position to identify the self-interstitial. The results obtained are affected by the chosen cut-off value. Moreover, these chosen cut-off values are independent of temperature. We have developed a novel unsupervised learning algorithm called Max-Space Clustering (MSC) to identify an appropriate cut-off value and its dependence on temperature. This method is compared with some widely used methods such as effective sphere (ES) method and nearest neighbor sphere (NNS) method. The cut-off radius obtained using our method shows a linear variation with temperature. The value of cut-off radius and its temperature dependence is derived for five bcc (Cr, Fe, Mo, Nb, W) and six fcc (Ag, Au, Cu, Ni, Pd, Pt) crystals. It is seen that the ratio of the cut-off values "r" to the lattice constant "a" lies between 0.23 and 0.3 at 300 K and this ratio is on an average smaller for the fcc crystals. Collision cascade simulations are carried out for Primary knock-on Atom (PKA) energies of 5 keV in Fe (at 300 K and 1000 K) and W (at 300 K and 2500 K) and the results are compared using the various methods.

  6. Size dependent hcp-to-fcc transition temperature in Co nanoclusters obtained by ion implantation in silica

    International Nuclear Information System (INIS)

    Mattei, G.; Maurizio, C.; Fernandez, C Julian de; Mazzoldi, P.; Battaglin, G.; Canton, P.; Cattaruzza, E.; Scian, C.

    2006-01-01

    In this work we present in situ investigations on the increase of the hcp-to-fcc transition temperature for Co with respect to the bulk value (420 deg. C) when nanoclusters are considered. Starting from Co:SiO 2 composites obtained by ion implantation with average Co cluster size of about 5 nm, a transition temperature between 800 deg. C and 900 deg. C is found upon thermal annealing in vacuum by in situ transmission electron microscopy. Preliminary results on electron irradiation to promote the transition at lower temperatures are presented

  7. Identifying self-interstitials of bcc and fcc crystals in molecular dynamics

    International Nuclear Information System (INIS)

    Bukkuru, S.; Bhardwaj, U.; Warrier, M.; Rao, A.D.P.; Valsakumar, M.C.

    2017-01-01

    Identification of self-interstitials in molecular dynamics (MD) simulations is of critical importance. There exist several criteria for identifying the self-interstitial. Most of the existing methods use an assumed cut-off value for the displacement of an atom from its lattice position to identify the self-interstitial. The results obtained are affected by the chosen cut-off value. Moreover, these chosen cut-off values are independent of temperature. We have developed a novel unsupervised learning algorithm called Max-Space Clustering (MSC) to identify an appropriate cut-off value and its dependence on temperature. This method is compared with some widely used methods such as effective sphere (ES) method and nearest neighbor sphere (NNS) method. The cut-off radius obtained using our method shows a linear variation with temperature. The value of cut-off radius and its temperature dependence is derived for five bcc (Cr, Fe, Mo, Nb, W) and six fcc (Ag, Au, Cu, Ni, Pd, Pt) crystals. It is seen that the ratio of the cut-off values “r” to the lattice constant “a” lies between 0.23 and 0.3 at 300 K and this ratio is on an average smaller for the fcc crystals. Collision cascade simulations are carried out for Primary knock-on Atom (PKA) energies of 5 keV in Fe (at 300 K and 1000 K) and W (at 300 K and 2500 K) and the results are compared using the various methods. - Highlights: • Max-Space Clustering (MSC) method is developed to identify interstitials in crystals. • MSC provides a structured way to identify the temperature dependent cut-off radius. • It is compared with widely used sphere methods and found to be better. • MSC coupled with graph tree optimization can be used to obtain diffusion trajectory. • Cascade simulations of Fe, W are carried out and results are compared with various methods.

  8. Identifying self-interstitials of bcc and fcc crystals in molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Bukkuru, S., E-mail: srinivasaraobukkuru@gmail.com [Dept. of Nuclear Physics, Andhra University, Visakhapatnam 530003 (India); Bhardwaj, U., E-mail: haptork@gmail.com [Computational Analysis Division, BARC, Visakhapatnam 530012, Andhra Pradesh (India); Warrier, M., E-mail: manoj.warrier@gmail.com [Computational Analysis Division, BARC, Visakhapatnam 530012, Andhra Pradesh (India); Rao, A.D.P., E-mail: adp_rao_99@yahoo.com [Dept. of Nuclear Physics, Andhra University, Visakhapatnam 530003 (India); Valsakumar, M.C., E-mail: mc.valsakumar@gmail.com [IIT Palakkad, Kozhippara P.O., Palakkad 678557, Kerala (India)

    2017-02-15

    Identification of self-interstitials in molecular dynamics (MD) simulations is of critical importance. There exist several criteria for identifying the self-interstitial. Most of the existing methods use an assumed cut-off value for the displacement of an atom from its lattice position to identify the self-interstitial. The results obtained are affected by the chosen cut-off value. Moreover, these chosen cut-off values are independent of temperature. We have developed a novel unsupervised learning algorithm called Max-Space Clustering (MSC) to identify an appropriate cut-off value and its dependence on temperature. This method is compared with some widely used methods such as effective sphere (ES) method and nearest neighbor sphere (NNS) method. The cut-off radius obtained using our method shows a linear variation with temperature. The value of cut-off radius and its temperature dependence is derived for five bcc (Cr, Fe, Mo, Nb, W) and six fcc (Ag, Au, Cu, Ni, Pd, Pt) crystals. It is seen that the ratio of the cut-off values “r” to the lattice constant “a” lies between 0.23 and 0.3 at 300 K and this ratio is on an average smaller for the fcc crystals. Collision cascade simulations are carried out for Primary knock-on Atom (PKA) energies of 5 keV in Fe (at 300 K and 1000 K) and W (at 300 K and 2500 K) and the results are compared using the various methods. - Highlights: • Max-Space Clustering (MSC) method is developed to identify interstitials in crystals. • MSC provides a structured way to identify the temperature dependent cut-off radius. • It is compared with widely used sphere methods and found to be better. • MSC coupled with graph tree optimization can be used to obtain diffusion trajectory. • Cascade simulations of Fe, W are carried out and results are compared with various methods.

  9. Gibbs energy modelling of the driving forces and calculation of the fcc/hcp martensitic transformation temperatures in Fe-Mn and Fe-Mn-Si alloys

    International Nuclear Information System (INIS)

    Cotes, S.; Fernandez Guillermet, A.; Sade, M.

    1999-01-01

    Very recent, accurate dilatometric measurements of the fcc hcp martensitic transformation (MT) temperatures are used to develop a new thermodynamic description of the fcc and hcp phases in the Fe-Mn-Si system, based on phenomenological models for the Gibbs energy function. The composition dependence of the driving forces for the fcc→hcp and the hcp→fcc MTs is established. Detailed calculations of the MT temperatures are reported, which are used to investigate the systematic effects of Si additions upon the MT temperatures of Fe-Mn alloys. A critical comparison with one of the most recent thermodynamic analyses of the Fe-Mn-Si system, which is due to Forsberg and Agren, is also presented. (orig.)

  10. A systematic study on the interfacial energy of O-line interfaces in fcc/bcc systems

    International Nuclear Information System (INIS)

    Dai, Fuzhi; Zhang, Wenzheng

    2013-01-01

    Habit planes between face-centered cubic (fcc)/body-centered cubic (bcc) phases usually exhibit irrational orientations, which often agree with the O-line criterion. Previously, energy calculation was made to test whether the habit planes were energetically favorable, but the values of the energy were found very sensitive to the initial atomic configuration in an irrationally orientated interface. In this paper, under the O-line condition, simple selection criteria are proposed to define and remove interfacial interstitials and vacancies in the initial atomic configuration. The criteria are proved to be effective in obtaining robust energy results. Interfacial energies of two types of O-line interfaces in fcc/bcc systems are calculated following the criteria. The observed transformation crystallography of precipitates in Ni–Cr and Cu–Cr systems can be explained consistently as the irrational habit plane in each system is associated with the lowest energy O-line interface. (paper)

  11. Interface Mediated Nucleation and Growth of Dislocations in fcc-bcc nanocomposite

    Science.gov (United States)

    Zhang, Ruifeng; Wang, Jian; Beyerlein, Irene J.; Germann, Timothy C.

    2011-03-01

    Heterophase interfaces play a crucial role in determining material strength for nanostructured materials because they can block, store, nucleate, and remove dislocations, the essential defects that enable plastic deformation. Much recent theoretical and experimental effort has been conducted on nanostructured Cu-Nb multilayer composites that exhibited extraordinarily high strength, ductility, and resistance to radiation and mechanical loading. In decreasing layer thicknesses to the order of a few tens of nanometers or less, the deformation behavior of such composites is mainly controlled by the Cu/Nb interface. In this work, we focus on the cooperative mechanisms of dislocation nucleation and growth from Cu/Nb interfaces, and their interaction with interface. Two types of experimentally observed Cu/Nb incoherent interfaces are comparatively studied. We found that the preferred dislocation nucleation sites are closely related to atomic interface structure, which in turn, depend on the orientation relationship. The activation stress and energies for an isolated Shockley dislocation loop of different sizes from specific interface sites depend strongly on dislocation size, atomic interface pattern, and loading conditions. Such findings provide important insight into the mechanical response of a wide range of fcc/bcc metallic nanocomposites via atomic interface design.

  12. Dynamics of the HCP/BCC phase transition and of the diffusion in zirconium: a model based on a tight-binding potential

    International Nuclear Information System (INIS)

    Willaime, F.

    1991-09-01

    We have developed an N-body interatomic potential, based on the second moment approximation of the tight-binding scheme, by fitting its four adjustable parameters to the cohesive energy, atomic volume, and elastic constants of hcp-Zr. We then showed that various properties of this potential compare favorably with those of zirconium in both the low temperatures hcp phase and the high temperature bcc phase. Such is the case in particular for the elastic constants, the phonon dispersion curves, the thermal expansion, and the melting temperature. We reproduced by molecular dynamics (MD) simulations on this potential the hcp/bcc phase transformation in both ways. It indeed occurs following the mechanism predicted by Burgers. We find a vibrational entropy of transformation equal to 0.13 k B . Our calculations suggest that in real zirconium the electronic contribution to the transformation entropy is important. We show that some interatomic potential lead to a higher value of the vibrational entropy in the hcp phase than in the bcc phase. We specified the dynamics of the vacancy migration in the bcc phase. The atomic jumps are almost exclusively nearest neighbour ones. The walk of the vacancy becomes strongly correlated at high temperatures. The vacancy jump frequency is very large and has a perfectly arrhenian behaviour. There is no evicence of a dynamical lowering of the vacancy migration barrier: the static and dynamic values of the vacancy migration energy are almost equal, both being unusually small (0.3 eV). The self diffusion coefficent of our model for the vacancy mechanism reproduces an anomalous fast diffusion close to that measured experimentally in bcc-Zr. In our model at high temperatures the time interval between successive jumps is almost equal to the time of flight. The migration events will therefore influence the formation of the vacancies [fr

  13. Neutron and PIMC determination of the longitudinal momentum distribution of HCP, BCC and normal liquid 4He

    International Nuclear Information System (INIS)

    Blasdell, R.C.; Ceperley, D.M.; Simmons, R.O.

    1993-07-01

    Deep inelastic neutron scattering has been used to measure the neutron Compton profile (NCP) of a series of condensed 4 He samples at densities from 28.8 atoms/nm 3 (essentially the minimum possible density in the solid phase) up to 39.8 atoms/nm 3 using a chopper spectrometer at the Argonne National Laboratory Intense Pulsed Neutron Source. At the lowest density, the NCP was measured along an isochore through the hcp, bcc, and normal liquid phases. Average atomic kinetic energies are extracted from each of the data sets and are compared to both published and new path integral Monte-Carlo (PIMC) calculations as well as other theoretical predictions. In this preliminary analysis of the data, account is taken of the effects of instrumental resolution, multiple scattering, and final-state interactions. Both our measurements and the PIMC theory show that there are only small differences in the kinetic energy and longitudinal momentum distribution of isochoric helium samples, regardless of their phase or crystal structure

  14. Dissolving, trapping and detrapping mechanisms of hydrogen in bcc and fcc transition metals

    Directory of Open Access Journals (Sweden)

    Yu-Wei You

    2013-01-01

    Full Text Available First-principles calculations are performed to investigate the dissolving, trapping and detrapping of H in six bcc (V, Nb, Ta, Cr, Mo, W and six fcc (Ni, Pd, Pt, Cu, Ag, Au metals. We find that the zero-point vibrations do not change the site-preference order of H at interstitial sites in these metals except Pt. One vacancy could trap a maximum of 4 H atoms in Au and Pt, 6 H atoms in V, Nb, Ta, Cr, Ni, Pd, Cu and Ag, and 12 H atoms in Mo and W. The zero-point vibrations never change the maximum number of H atoms trapped in a single vacancy in these metals. By calculating the formation energy of vacancy-H (Vac-Hn complex, the superabundant vacancy in V, Nb, Ta, Pd and Ni is demonstrated to be much more easily formed than in the other metals, which has been found in many metals including Pd, Ni and Nb experimentally. Besides, we find that it is most energetically favorable to form Vac-H1 complex in Pt, Cu, Ag and Au, Vac-H4 in Cr, Mo and W, and Vac-H6 in V, Nb, Ta, Pd and Ni. At last, we examine the detrapping behaviors of H atoms in a single vacancy and find that with the heating rate of 10 K/min a vacancy could accommodate 4, 5 and 6 H atoms in Cr, Mo and W at room temperature, respectively. The detrapping temperatures of all H atoms in a single vacancy in V, Nb, Ta, Ni, Pd, Cu and Ag are below room temperature.

  15. Anisotropy migration of self-point defects in dislocation stress fields in BCC Fe and FCC Cu

    International Nuclear Information System (INIS)

    Sivak, A.B.; Chernov, V.M.; Dubasova, N.A.; Romanov, V.A.

    2007-01-01

    Spatial dependence of the interaction energies of self-point defects (vacancies and self interstitial atoms in stable, metastable and saddle point configurations) with edge dislocations in slip systems {1 1 0} and {1 0 0} in BCC Fe and {1 1 1} in FCC Cu was calculated using the anisotropic theory of elasticity and molecular statics (hybrid method). The migration pathways of vacancies and SIA ( dumbbell in Fe and dumbbell in Cu) along which the migration of the defects with the lowest energy barriers were defined in the presence of the dislocation stress fields. These pathways are significantly different in the stress fields of dislocations

  16. Bcc and Fcc transition metals and alloys: a central role for the Jahn-Teller effect in explaining their ideal and distorted structures.

    Science.gov (United States)

    Lee, Stephen; Hoffmann, Roald

    2002-05-01

    Transition metal elements, alloys, and intermetallic compounds often adopt the body centered cubic (bcc) and face centered cubic (fcc) structures. By comparing quantitative density functional with qualitative tight-binding calculations, we analyze the electronic factors which make the bcc and fcc structures energetically favorable. To do so, we develop a tight-binding function, DeltaE(star), a function that measures the energetic effects of transferring electrons within wave vector stars. This function allows one to connect distortions in solids to the Jahn-Teller effect in molecules and to provide an orbital perspective on structure determining deformations in alloys. We illustrate its use by considering first a two-dimensional square net. We then turn to three-dimensional fcc and bcc structures, and distortions of these. Using DeltaE(star), we rationalize the differences in energy of these structures. We are able to deduce which orbitals are responsible for instabilities in seven to nine valence electron per atom (e(-)/a) bcc systems and five and six e(-)/a fcc structures. Finally we demonstrate that these results account for the bcc and fcc type structures found in both the elements and binary intermetallic compounds of group 4 through 9 transition metal atoms. The outline of a theory of metal structure deformations based on loss of point group operation rather than translational symmetry is presented.

  17. The influence of additions of Al and Si on the lattice stability of fcc and hcp Fe-Mn random alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gebhardt, T; Music, D; Schneider, J M [Materials Chemistry, RWTH Aachen University, D-52056 Aachen (Germany); Ekholm, M; Abrikosov, I A [Department of Physics, Chemistry and Biology (IFM), Linkoeping University, SE-58183 Linkoeping (Sweden); Vitos, L [Department of Materials and Engineering, Applied Materials Physics, Royal Institute of Technology (KTH), SE-10044 Stockholm (Sweden); Dick, A; Hickel, T; Neugebauer, J, E-mail: gebhardt@mch.rwth-aachen.de [Department of Computational Materials Design, Max-Planck-Institut fuer Eisenforschung GmbH, D-40237 Duesseldorf (Germany)

    2011-06-22

    We have studied the influence of additions of Al and Si on the lattice stability of face-centred-cubic (fcc) versus hexagonal-closed-packed (hcp) Fe-Mn random alloys, considering the influence of magnetism below and above the fcc Neel temperature. Employing two different ab initio approaches with respect to basis sets and treatment of magnetic and chemical disorder, we are able to quantify the predictive power of the ab initio methods. We find that the addition of Al strongly stabilizes the fcc lattice independent of the regarded magnetic states. For Si a much stronger dependence on magnetism is observed. Compared to Al, almost no volume change is observed as Si is added to Fe-Mn, indicating that the electronic contributions are responsible for stabilization/destabilization of the fcc phase.

  18. The influence of additions of Al and Si on the lattice stability of fcc and hcp Fe-Mn random alloys

    International Nuclear Information System (INIS)

    Gebhardt, T; Music, D; Schneider, J M; Ekholm, M; Abrikosov, I A; Vitos, L; Dick, A; Hickel, T; Neugebauer, J

    2011-01-01

    We have studied the influence of additions of Al and Si on the lattice stability of face-centred-cubic (fcc) versus hexagonal-closed-packed (hcp) Fe-Mn random alloys, considering the influence of magnetism below and above the fcc Neel temperature. Employing two different ab initio approaches with respect to basis sets and treatment of magnetic and chemical disorder, we are able to quantify the predictive power of the ab initio methods. We find that the addition of Al strongly stabilizes the fcc lattice independent of the regarded magnetic states. For Si a much stronger dependence on magnetism is observed. Compared to Al, almost no volume change is observed as Si is added to Fe-Mn, indicating that the electronic contributions are responsible for stabilization/destabilization of the fcc phase.

  19. A multi-scale homogenization model for fine-grained porous viscoplastic polycrystals: II - Applications to FCC and HCP materials

    Science.gov (United States)

    Song, Dawei; Ponte Castañeda, P.

    2018-06-01

    In Part I of this work (Song and Ponte Castañeda, 2018a), a new homogenization model was developed for the macroscopic behavior of three-scale porous polycrystals consisting of random distributions of large pores in a fine-grained polycrystalline matrix. In this second part, the model is used to investigate both the instantaneous effective behavior and the finite-strain macroscopic response of porous FCC and HCP polycrystals for axisymmetric loading conditions. The stress triaxiality and Lode parameter are found to have significant effects on the evolution of the substructure, which in turn have important implications for the overall hardening/softening behavior of the porous polycrystal. The intrinsic effect of the texture evolution of the polycrystalline matrix is inferred by appropriate comparisons with corresponding results for porous isotropic materials, and found to be significant, especially at low triaxialities. In particular, the predictions of the model identify, for the first time, two disparate regimes for the macroscopic response of porous polycrystals: a porosity-controlled regime at high triaxialities, and a texture-controlled regime at low triaxialities. The transition between these two regimes is found to be quite sharp, taking place between triaxialities of 1 and 2.

  20. Statistical study of defects caused by primary knock-on atoms in fcc Cu and bcc W using molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Warrier, M., E-mail: Manoj.Warrier@gmail.com [Computational Analysis Division, BARC, Visakhapatnam, Andhra Pradesh, 530012 (India); Bhardwaj, U.; Hemani, H. [Computational Analysis Division, BARC, Visakhapatnam, Andhra Pradesh, 530012 (India); Schneider, R. [Computational Science, Ernst-Moritz-Arndt University, D-17489 Greifswald (Germany); Mutzke, A. [Max-Planck-Institut für Plasmaphysik, D-17491 Greifswald (Germany); Valsakumar, M.C. [School for Engineering Sciences and Technology, University of Hyderabad, Gachibowli, Hyderabad, Telangana State, 500046 (India)

    2015-12-15

    We report on molecular Dynamics (MD) simulations carried out in fcc Cu and bcc W using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) code to study (i) the statistical variations in the number of interstitials and vacancies produced by energetic primary knock-on atoms (PKA) (0.1–5 keV) directed in random directions and (ii) the in-cascade cluster size distributions. It is seen that around 60–80 random directions have to be explored for the average number of displaced atoms to become steady in the case of fcc Cu, whereas for bcc W around 50–60 random directions need to be explored. The number of Frenkel pairs produced in the MD simulations are compared with that from the Binary Collision Approximation Monte Carlo (BCA-MC) code SDTRIM-SP and the results from the NRT model. It is seen that a proper choice of the damage energy, i.e. the energy required to create a stable interstitial, is essential for the BCA-MC results to match the MD results. On the computational front it is seen that in-situ processing saves the need to input/output (I/O) atomic position data of several tera-bytes when exploring a large number of random directions and there is no difference in run-time because the extra run-time in processing data is offset by the time saved in I/O. - Highlights: • MD simulations of collision cascades in 200 random directions explored in the energy range of 1–5 keV for fcc Cu and bcc W. • 60–80 random directions must be sampled for the number of displacements produced in a collision cascade to stabilize. • In-cascade clustering of interstitials and vacancies occur. • Direction averaged distribution of interstitials and vacancies around the origin of a PKA is presented. • Comparisons with MD indicate that the recoils produced in BCA-MC simulations be checked for recombination against all vacancies created.

  1. Geometric factors in f.c.c. and b.c.c. metal-on-metal epitaxy

    International Nuclear Information System (INIS)

    Bruce, L.A.; Jaeger, H.

    1978-01-01

    Deposits of Ni, Au and Ag formed by condensing metal vapour in U.H.V. onto (001)W, held at a temperature Tsub(s) in the range 300K< Tsub(s)<1200 K, always form epitaxial layers. However, while Au and Ag form (001) epitaxial layers of f.c.c. single crystals, (001)d parallel to (001)s with, say, [110]d parallel to [010]s, Ni and Cu occur in two orthogonal domains, each characterized by an exclusive set of fault (or twin) planes. Within a fault plane, atoms are hexagonally close-packed and, within a domain, fault planes are normal to either [1-1-0]s or [1-10]s and a close-packed direction in the planes is normal to the substrate. The lateral stacking of the fault planes may range from random at low values of Tsub(s) to that of, say, (11-1-) planes in heavily faulted and/or twinned (110) epitaxed f.c.c. material, or of basal planes in (110) epitaxed h.c.p. material at high values of Tsub(s). The results are readily explained on the basis of a growth model developed for deposits of Ni and Cu on (001) Ag. (author)

  2. Investigating effects of BCC and FCC arrangements on flow and heat transfer characteristics in pebbles through CFD methodology

    Energy Technology Data Exchange (ETDEWEB)

    Ferng, Yuh Ming, E-mail: ymferng@ess.nthu.edu.tw [Department of Engineering and System Science, Institute of Nuclear Engineering and Science, National Tsing Hua University, 101, Sec. 2. Kuang-Fu Rd., Hsingchu 30013, Taiwan, ROC (China); Lin, Kun-Yueh [Department of Engineering and System Science, Institute of Nuclear Engineering and Science, National Tsing Hua University, 101, Sec. 2. Kuang-Fu Rd., Hsingchu 30013, Taiwan, ROC (China)

    2013-05-15

    Highlights: ► An HTGR would be one of the possible energy generation sources. ► We propose a CFD model to study effects of pebble arrangements for a PRB core. ► The entrance effect on the Nu number can be reasonably captured. ► The present predicted Nu versus Re{sub p} shows good agreement with data and correlation. ► Using FCC lattice in a core, simulation results may be non-conservative. -- Abstract: A high temperature gas cooled reactor (HTGR) would be one of the possible energy generation sources due to its advantages of inherently safety performance and higher conversion efficiency, etc. However, safety is the most important issue for its commercialization in energy industry. It is very crucial for safety design and operation of an HTGR to investigate its thermal–hydraulic characteristics. In this article, a computational fluid dynamics (CFD) methodology is proposed to investigate effects of different arrangements on these characteristics for an HTGR with a pebble bed (PB) core. Two kinds of arrangement: body-centered cubic (BCC) and face-centered cubic (FCC) are studies herein. Based on the simulation results, higher heat transfer capability and lower pebble temperature are predicted in the pebbles with the FCC-arrangement. The thermally fully-developed flow condition may be reached, which is shown in the result that the predicted average Nussel (Nu) number decreases from the 1st layer and reaches to an asymptotic value as the gas passes through the 6th layer of pebbles. This entrance effect reveals that the system codes using the correlations developed from the fully-developed flow condition can be appropriately applied in the entire PBR core. In addition, the present predicted dependence of Nu number on the inlet Reynolds (Re) number shows good agreement with that obtained from the well-known KTA. Measured data of Nu number versus Re number are also used to validate the CFD model.

  3. ''Cube-on-hexagon'' orientation relationship for Fe on GaN(0001): The missing link in bcc/hcp epitaxy

    International Nuclear Information System (INIS)

    Gao Cunxu; Brandt, Oliver; Laehnemann, Jonas; Jahn, Uwe; Jenichen, Bernd; Schoenherr, Hans-Peter; Erwin, Steven C.

    2010-01-01

    We investigate, experimentally and theoretically, the epitaxy of body-centered-cubic Fe on hexagonal GaN. For growth on the Ga-polar GaN(0001) surface we find the well-known Pitsch-Schrader orientation relationship between Fe and GaN. On the N-polar GaN(0001) surface we observe coexistence between the familiar Burgers orientation and a new orientation in which the Fe(001) plane is parallel to GaN(0001). This 'cube-on-hexagon' orientation constitutes the high-symmetry link required for constructing a symmetry diagram for bcc/hcp systems in which all orientation relationships are connected by simple rotations.

  4. High temperature series expansions with a multiple-exchange Hamiltonian for the bcc and hcp phases of solid 3He

    International Nuclear Information System (INIS)

    Roger, M.; Suaudeau, E.; Bernier, M.E.R.

    1987-08-01

    High temperature series expansions with a multiple-exchange Hamiltonian are performed to fourth order in arbitrary magnetic field for both phases of solid 3 He. The susceptibility series are analysed with Pade approximants and compared with recent experimental results. For the hcp phase we estimate the ferromagnetic ordering temperature from susceptibility series and discuss the influence of four-particle exchange in lowering the transition

  5. Comparison between radiation effects in some fcc and bcc metals irradiated with energetic heavy ions - a review

    International Nuclear Information System (INIS)

    Iwase, A.; Ishino, S.

    2000-01-01

    It has been reported that there are substantial differences in radiation effects in fcc copper and bcc iron. Whether these differences are due to the difference in crystal structure or not is the subject of the present paper. These differences have been discussed in terms of microstructure and mechanical property changes, whereas in the present paper, results of electrical resistivity measurements are discussed in terms of damage production cross sections, defect annihilation cross sections, damage efficiency and so on during and after various ion irradiations with wide energy ranges from 1 MeV to more than 100 MeV. For crucial discussion on the effect of the difference in crystal structure, nickel and iron are compared. These metals are allotted closely in the periodic table, with similar melting points and fairly strong electron-lattice coupling, both ferromagnetic and yet with different crystal structure. It may be concluded that as far as the damage production and defect annihilation cross sections and survival ratio are concerned, the difference in crystal structure is not an essential factor. Electronic energy deposition may play an important role even for low energy ions as well as for high energies. The effect of electronic energy deposition on defect clustering is discussed

  6. Thermal-hydraulic study of fixed bed nuclear reactor (FBNR), in FCC, BCC and pseudo-random configurations of the core through CFD method

    International Nuclear Information System (INIS)

    Luna, M.; Chavez, I.; Cajas, D.; Santos, R.

    2015-01-01

    The study of thermal-hydraulic performance of a fixed bed nuclear reactor (FBNR) core and the effect of the porosity was studied by the CFD method with 'SolidWorks' software. The representative sections of three different packed beds arrangements were analyzed: face-centered cubic (FCC), body-centered cubic (BCC), and a pseudo-random, with values of porosity of 0.28, 0.33 and 0.53 respectively. The minimum coolant flow required to avoid the phase change for each one of the configurations was determined. The results show that the heat transfer rate increases when the porosity value decreases, and consequently the minimum coolant flow in each configuration. The results of minimum coolant flow were: 728.51 kg/s for the FCC structure, 372.72 kg/s for the BCC, and 304.96 kg/s for the pseudo-random. Meanwhile, the heat transfer coefficients in each packed bed were 6480 W/m 2 *K, 3718 W/m 2 *K and 3042 W/m 2 *K respectively. Finally the pressure drop was calculated, and the results were 0.588 MPa for FCC configuration, 0.033 MPa for BCC and 0.017 MPa for the pseudo-random one. This means that with a higher porosity, the fluid can circulate easier because there are fewer obstacles to cross, so there are fewer energy losses. (authors)

  7. In-situ transmission electron microscopy study of ion-irradiated copper : comparison of the temperature dependence of cascade collapse in FCC- and BCC- metals.

    Energy Technology Data Exchange (ETDEWEB)

    Daulton, T. L.

    1998-10-23

    The kinetics which drive cascade formation and subsequent collapse into point-defect clusters is investigated by analyzing the microstructure produced in situ by low fluence 100 keV Kr ion irradiations of fcc-Cu over a wide temperature range (18-873 K). The yield of collapsed point-defect clusters is demonstrated unequivocally to be temperature dependent, remaining approximately constant up to lattice temperatures of 573 K and then abruptly decreasing with increasing temperature. This drop in yield is not caused by defect loss during or following ion irradiation. This temperature dependence can be explained by a thermal spike effect. These in-situ yield measurements are compared to previous ex-situ yield measurements in fcc-Ni and bcc-Mo.

  8. In situ transmission electron microscopy study of ion-irradiated copper: comparison of the temperature dependence of cascade collapse in fcc- and bcc-metals

    International Nuclear Information System (INIS)

    Daulton, T.L.; Kirk, M.A.; Rehn, L.E.

    2000-01-01

    The kinetics which drive cascade formation and subsequent collapse into point-defect clusters are investigated by analyzing the microstructure produced in situ by low fluence 100 keV Kr ion irradiations of fcc-Cu over a wide temperature range (18-873 K). The yield of collapsed point-defect clusters is demonstrated unequivocally to be temperature dependent, remaining approximately constant up to lattice temperatures of 573 K and then abruptly decreasing with increasing temperature. This drop in yield is not caused by defect loss during or following ion irradiation. In addition, this temperature dependence can be explained by a thermal spike effect. These in situ yield measurements are compared to previous ex situ yield measurements in fcc-Ni and bcc-Mo

  9. Phonon dispersion curves of BCC Ba

    International Nuclear Information System (INIS)

    Mizuki, J.; Stassis, C.; Zarestky, J.

    1985-01-01

    Ba, as well as Sr and Ca, is a divalent alkaline earth metal. At room temperature and ambient pressure, the structure of Ba is bcc, whereas that of Sr and Ca is fcc. Under pressure, the bcc phase of Ba transforms to an hcp structure at 55 kbar. Also, at 37 kbar Ba becomes a superconductor with T/sub c/ = 0.06 K. These properties are highly dependent on the position of the d bands relative to the Fermi level. Experimental investigation of the elastic and lattice dynamical properties of these metals has been hindered by difficulties in growing single crystals. However, recently the authors were able to grow several single crystals of bcc Ba of sufficient volume for inelastic neutron scattering experiments. Some of the results are summarized here

  10. Impacts of Interface Energies and Transformation Strain from BCC to FCC on Massive-like δ-γ Transformation in Steel

    International Nuclear Information System (INIS)

    Yoshiya, M; Sato, M; Watanabe, M; Nakajima, K; Yokoi, T; Ueshima, N; Nagira, T; Yasuda, H

    2015-01-01

    Interface energies of δ/γ, γ/γ, δ/δ, L/δ, and L/γ interfaces, at first, as a function of misorientation were evaluated with an aid of atomistic simulations with embedded atom method. Then, under geometric constraints where grains or interfaces compete each other to minimize overall free energy, effective interface energies for those interfaces were quantified. It is found that neither the minimum nor effective δ/γ interface energies, 0.41 or 0.56 J/m 2 , respectively, is significantly higher than those of other interfaces including liquid/solid interfaces, but the δ/γ interface energy is significantly high for the small entropy change upon δ-γ massive-like transformation, resulting in significantly higher undercooling required for γ nucleation in the δ phase matrix than in solidification. Detachment of δ-phase dendrite tips away from γ-phase dendrite trunks can be explained only from a viewpoint of interface energy if small misorientationis introduced at the δ/γ interface from the perfect lattice matching between BCC and FCC crystal structures. Examining the BCC-to-FCC transformation strain on the γ nucleation in the massive-like transformation, the γ nucleation is prohibited 170 K or more undercooling is achieved unless any relaxation mechanism for the transformation strain is taken into account. (paper)

  11. A Study on Thermal Properties and α( hcp) → β( bcc) Phase Transformation Energetics in Ti-5 mass% Ta-1.8 mass% Nb Alloy Using Inverse Drop Calorimetry

    Science.gov (United States)

    Behera, Madhusmita; Raju, S.; Jeyaganesh, B.; Mythili, R.; Saroja, S.

    2010-12-01

    Accurate measurements of enthalpy increment ( H T - H 298.15) values have been made on a Ti-5 mass% Ta-1.8 mass% Nb alloy using the inverse drop calorimetry technique in the temperature range from 463 K to 1457 K. The measured enthalpy increment values show a steady increase with temperature in both α- hcp and β- bcc solid solution regions. It is found that both the onset as well the completion of the α → β phase change are demonstrated by a marked deviation of the enthalpy increment behavior from the otherwise smooth variation encountered in the respective low-temperature α- and high-temperature β-phase domains. The transformation start ( T s) and finish ( T f) temperatures of the α → β phase change are found to be (1072±10) K and (1156±10) K, respectively. In the actual α → β phase transformation region, the variation of the enthalpy with the progress of transformation is found to follow a sigmoidal shape which is in line with the diffusive nature of the phase transformation. An estimation of the total enthalpy change associated with the α → β phase transformation (Δ° H tr) has been made by assuming a simple diffusion limited kinetic model for the phase change. The net enthalpy change for the α → β transformation is found to be 76 J · g-1. The measured temperature variation of the enthalpy increment in both α- and β-phase regimes are fitted to simple analytical functional forms to obtain temperature-dependent estimates of the specific heat, C P . The total specific heat change associated with the α → β phase transformation {Δ^{circ}{CP^{α}}^{→{β}}} is estimated to be 904 J · kg-1 · K-1.

  12. Effects of PEO-PPO diblock impurities on the cubic structure of aqueous PEO-PPO-PEO pluronics micelles: fcc and bcc ordered structures in F127

    DEFF Research Database (Denmark)

    Mortensen, Kell; Pedersen, Walther Batsberg; Hvidt, S.

    2008-01-01

    We report on structural properties of PEO-PPO-PEO type of triblock block copolymers (Pluronics F127) with special emphasis on the effect of diblock PEO-PPO impurities on the ordered gel phase. Commercial F127 polymers contain as received roughly 20% PEO-PPO diblock and 80% PEO-PPO-PEO triblock...... copolymers. Aqueous solutions of F127 copolymers used as received form fee ordered micellar structure. Copolymers depleted with respect to the diblock impurity, resulting in a pure PEO-PPO-PEO triblock copolymer system, form bcc ordered micelles within the major parts of the gel phase. However, close...

  13. Converting hcp Mg-Al-Zn alloy into bcc Mg-Li-Al-Zn alloy by electrolytic deposition and diffusion of reduced lithium atoms in a molten salt electrolyte LiCl-KCl

    International Nuclear Information System (INIS)

    Lin, M.C.; Tsai, C.Y.; Uan, J.Y.

    2007-01-01

    A body-centered cubic (bcc) Mg-12Li-9Al-1Zn (wt.%) alloy was fabricated in air by electrolysis from LiCl-KCl molten salt at 500 deg. C. Electrolytic deposition of Li atoms on cathode (Mg-Al-Zn alloy) and diffusion of the Li atoms formed the bcc Mg-Li-Al-Zn alloy with 12 wt.% Li and only 0.264 wt.% K. Low K concentration in the bcc Mg alloy strip after the electrolysis process resulted from 47% atomic size misfit between K and Mg atoms and low solubility of K in Mg matrix

  14. Metastable bcc Fe-Mn alloys produced by rf sputtering

    International Nuclear Information System (INIS)

    Sumiyama, Kenji; Kadono, Masaru; Nakamura, Yoji

    1981-01-01

    Fe sub(1-x)Mn sub(x) alloy films obtained by rf sputtering technique have been investigated by X-ray diffraction, magnetization and Moessbauer effect measurements. The single bcc phase extends up to about x = 0.2, while a bcc-fcc mixed phase appears for x = 0.2 - 0.26. The lattice constants of the bcc phase are about 0.5% larger than those of the bulk specimens. The magnetization decreases monotonically with increasing x in the bcc phase, while it decreases sharply in the bcc-fcc mixed phase. These results are consistent with the Moessbauer spectra of these alloy films. The volume fraction of bcc and fcc phases has been estimated from Moessbauer analyses as well as magnetization measurements. (author)

  15. Insulating fcc YH

    International Nuclear Information System (INIS)

    Molen, S. J. van der; Nagengast, D. G.; Gogh, A. T. M. van; Kalkman, J.; Kooij, E. S.; Rector, J. H.; Griessen, R.

    2001-01-01

    We study the structural, optical, and electrical properties of Mg z Y 1-z switchable mirrors upon hydrogenation. It is found that the alloys disproportionate into essentially pure YH 3-δ and MgH 2 with the crystal structure of YH 3-δ dependent on the Mg concentration z. For 0 3-δ are observed, whereas for z≥0.1 only cubic YH 3-δ is present. Interestingly, cubic YH 3-δ is expanded compared to YH 2 , in disagreement with theoretical predictions. From optical and electrical measurements we conclude that cubic YH 3-δ is a transparent insulator with properties similar to hexagonal YH 3-δ . Our results are inconsistent with calculations predicting fcc YH 3-δ to be metallic, but they are in good agreement with recent GW calculations on both hcp and fcc YH 3 . Finally, we find an increase in the effective band gap of the hydrided Mg z Y 1-z alloys with increasing z. Possibly this is due to quantum confinement effects in the small YH 3 clusters

  16. Strength and strain rate sensitivity for hcp and fcc nanopolycrystal ...

    Indian Academy of Sciences (India)

    Abstract. While there is overwhelming evidence that strengthening from grain size refinement persists into the nanocrystalline grain size regime consistent with extrapolation of classical Hall–Petch (H–P) behaviour, there are indications of a transition to an inverse H–P dependence, i.e. grain boundary weakening behaviour,.

  17. Atomistic simulation of fcc—bcc phase transition in single crystal Al under uniform compression

    International Nuclear Information System (INIS)

    Li Li; Liang Jiu-Qing; Shao Jian-Li; Duan Su-Qing; Li Yan-Fang

    2012-01-01

    By molecular dynamics simulations employing an embedded atom model potential, we investigate the fcc-to-bcc phase transition in single crystal Al, caused by uniform compression. Results show that the fcc structure is unstable when the pressure is over 250 GPa, in reasonable agreement with the calculated value through the density functional theory. The morphology evolution of the structural transition and the corresponding transition mechanism are analysed in detail. The bcc (011) planes are transited from the fcc (111-bar) plane and the (11-bar1) plane. We suggest that the transition mechanism consists mainly of compression, shear, slid and rotation of the lattice. In addition, our radial distribution function analysis explicitly indicates the phase transition of Al from fcc phase to bcc structure. (condensed matter: structural, mechanical, and thermal properties)

  18. On hyper BCC-algebras

    OpenAIRE

    Borzooei, R. A.; Dudek, W. A.; Koohestani, N.

    2006-01-01

    We study hyper BCC-algebras which are a common generalization of BCC-algebras and hyper BCK-algebras. In particular, we investigate different types of hyper BCC-ideals and describe the relationship among them. Next, we calculate all nonisomorphic 22 hyper BCC-algebras of order 3 of which only three are not hyper BCK-algebras.

  19. On hyper BCC-algebras

    Directory of Open Access Journals (Sweden)

    R. A. Borzooei

    2006-01-01

    Full Text Available We study hyper BCC-algebras which are a common generalization of BCC-algebras and hyper BCK-algebras. In particular, we investigate different types of hyper BCC-ideals and describe the relationship among them. Next, we calculate all nonisomorphic 22 hyper BCC-algebras of order 3 of which only three are not hyper BCK-algebras.

  20. Quantitative analysis of thermal diffuse X-ray scattering on single crystals. Communication 2. FCC metals

    International Nuclear Information System (INIS)

    Najsh, V.E.; Novoselova, T.V.; Sagaradze, I.V.; Kvyatkovskij, B.E.; Fedorov, V.I.; Chernenkov, Yu.P.

    1994-01-01

    With the use of X-ray diffractometer a study was made into the intensity of diffuse scattering in Ni crystals with FCC lattice. Earlier accomplished quantitative analysis for BCC crystals was extended to FCC lattices. Comparative evaluation was made for cooperative thermal oscillation patterns and corresponding diffuse scattering in crystals of various structures. Measurements on FCC crystals were carried out at room temperature using AgK a lpha-radiation in 96 points of Ni crystal. 8 refs., 4 figs

  1. The development of BCC

    International Nuclear Information System (INIS)

    He Xiaoping; Yang Hailiang; Sun Jianfeng; Ren Shuqing; Zhang Jiasheng; Shi Lei; Peng Jianchang; Li Hongyu; Qiu Aici; Tang Junping; Xi'an Jiaotong Univ., Xi'an

    2004-01-01

    An analysis of principle of a BCC for measuring ion beam density and the main reasons related to the measuring accuracy were presented. An array of 13 biased charge collecrors was designed for the measurement of ion beam density of 'FLASH-II' high power ion beam source, and the data of experiments was analyzed. (authors)

  2. Smarandache hyper BCC-algebra

    OpenAIRE

    Ahadpanah, A.; Borumand Saeid, A.

    2011-01-01

    In this paper, we define the Smarandache hyper BCC-algebra, and Smarandache hyper BCC-ideals of type 1, 2, 3 and 4. We state and prove some theorems in Smarandache hyper BCC -algebras, and then we determine the relationships between these hyper ideals.

  3. FCC-ee Overview

    CERN Document Server

    Zimmermann, F; Benedikt, M; Burkhardt, H; Cerutti, F; Ferrari, A; Gutleber, J; Haerer, B; Holzer, B; Jensen, E; Kersevan, R; Lebrun, P; Martin, R; Mereghetti, A; Osborne, J; Papaphilippou, Y; Schulte, D; Tomas, R; Wenninger, J; Blondel, A; Koratzinos, M; Boscolo, M; Lari, L; Furukawa, K; Ohmi, K; Oide, K; White, S; Bogomyagkov, A; Koop, I; Levichev, E; Muchnoi, N; Nikitin, S; Shatilov, D; Wienands, U; Gianfelice, E; Medina, L

    2015-01-01

    The FCC-ee is a proposed circular e+e- collider installed in a new 100 km tunnel delivering high luminosity to four experiments at centre-of-mass energies ranging from 91 GeV (Z pole) over 160 GeV (W threshold) and 240 GeV (H production) to 350 GeV (t physics). The FCC-ee design is pursued as part of the global Future Circular Collider (FCC) study, which regards the FCC-ee as a potential intermediate step towards a 100-TeV hadron collider, called FCC-hh, sharing the same tunnel infrastructure. We here report the FCC-ee design status.

  4. Strong, Ductile, and Thermally Stable bcc-Mg Nanolaminates.

    Science.gov (United States)

    Pathak, Siddhartha; Velisavljevic, Nenad; Baldwin, J Kevin; Jain, Manish; Zheng, Shijian; Mara, Nathan A; Beyerlein, Irene J

    2017-08-15

    Magnesium has attracted attention worldwide because it is the lightest structural metal. However, a high strength-to-weight ratio remains its only attribute, since an intrinsic lack of strength, ductility and low melting temperature severely restricts practical applications of Mg. Through interface strains, the crystal structure of Mg can be transformed and stabilized from a simple hexagonal (hexagonal close packed hcp) to body center cubic (bcc) crystal structure at ambient pressures. We demonstrate that when introduced into a nanocomposite bcc Mg is far more ductile, 50% stronger, and retains its strength after extended exposure to 200 C, which is 0.5 times its homologous temperature. These findings reveal an alternative solution to obtaining lightweight metals critically needed for future energy efficiency and fuel savings.

  5. Preparation of hcp-Ni(112-bar 0) epitaxial thin films on Au(100) single-crystal underlayers

    Energy Technology Data Exchange (ETDEWEB)

    Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi, E-mail: ohtake@futamoto.elect.chuo-u.ac.j [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan)

    2010-01-01

    Ni epitaxial films with an hcp structure are successfully obtained on Au(100) single-crystal underlayers formed on MgO(100) substrates at temperatures lower than 300 {sup 0}C by molecular beam epitaxy. With increasing the substrate temperature, the volume ratio of more stable fcc phase inc{sub r}eases in the film. The Ni film prepared at 100 {sup 0}C consists primarily of hcp crystal with the (112-bar 0) plane parallel to the substrate surface coexisting with a small amount of fcc-Ni(100) crystal. The lattice constant of hcp-Ni crystal is determined as a = 0.249 nm, c = 0.398 nm, and c/a = 1.60.

  6. Preparation of hcp-Ni(112-bar 0) epitaxial thin films on Au(100) single-crystal underlayers

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    Ni epitaxial films with an hcp structure are successfully obtained on Au(100) single-crystal underlayers formed on MgO(100) substrates at temperatures lower than 300 0 C by molecular beam epitaxy. With increasing the substrate temperature, the volume ratio of more stable fcc phase inc r eases in the film. The Ni film prepared at 100 0 C consists primarily of hcp crystal with the (112-bar 0) plane parallel to the substrate surface coexisting with a small amount of fcc-Ni(100) crystal. The lattice constant of hcp-Ni crystal is determined as a = 0.249 nm, c = 0.398 nm, and c/a = 1.60.

  7. Spin-polarized scanning tunneling microscopy of magnetic nanostructures at the example of bcc-Co/Fe(110), Fe/Mo(110), and copper phthalocyanine/Fe(1110); Spinpolarisierte Rastertunnelmikroskopie magnetischer Nanostrukturen am Beispiel von bcc-Co/Fe(110), Fe/Mo(110) und Kupfer-Phthalocyanin/Fe(110)

    Energy Technology Data Exchange (ETDEWEB)

    Methfessel, Torsten

    2010-12-09

    This thesis provides an introduction into the technique of spin-polarized scanning tunnelling microscopy and spectroscopy as an experimental method for the investigation of magnetic nanostructures. Experimental results for the spin polarized electronic structure depending on the crystal structure of ultrathin Co layers, and depending on the direction of the magnetization for ultrathin Fe layers are presented. High-resolution measurements show the position-dependent spin polarization on a single copper-phthalocyanine molecule deposited on a ferromagnetic surface. Co was deposited by molecular beam epitaxy on the (110) surface of the bodycentered cubic metals Cr and Fe. In contrast to previous reports in the literature only two layers of Co can be stabilized in the body-centered cubic (bcc) structure. The bcc-Co films on the Fe(110) surface show no signs of epitaxial distortions. Thicker layers reconstruct into a closed-packed structure (hcp / fcc). The bcc structure increases the spin-polarization of Co to P=62 % in comparison to hcp-Co (P=45 %). The temperature-dependent spin-reorientation of ultrathin Fe/Mo(110) films was investigated by spin-polarized spectroscopy. A reorientation of the magnetic easy axis from the [110] direction along the surface normal to the in-plane [001] axis is observed at T (13.2{+-}0.5) K. This process can be identified as a discontinuous reorientation transition, revealing two simultaneous minima of the free energy in a certain temperature range. The electronic structure of mono- and double-layer Fe/Mo(110) shows a variation with the reorientation of the magnetic easy axis and with the direction of the magnetization. The investigation of the spin-polarized charge transport through a copper-phthalocyanine molecule on the Fe/Mo(110) surface provides an essential contribution to the understanding of spin-transport at the interface between metal and organic molecule. Due to the interaction with the surface of the metal the HOMO-LUMO energy

  8. An atomic-scale model of fcc crystal-growth

    Energy Technology Data Exchange (ETDEWEB)

    Waal, B.W. van de (Technische Hogeschool Twente, Enschede (Netherlands). Dept. of Physics)

    1991-01-01

    Nearly perfect fcc growth may be simulated by the application of a simple growth-algorithm - only sites that are at least 4-coordinated are occupied - to a selected seed. The seed is a 22-atom cluster, being the smallest close-packed structure with two crossing stacking-faults. The stacking-faults produce active surface-sites, that can not be exhausted by occupation; they are arranged in non-vanishing steps, similar to those produced by screw-dislocations. The algorithm prevents further stacking-faults, and ensures ABC-stacking of close-packed (111)-layers, characteristic of the fcc structure. The same algorithm would not produce further growth of perfect fcc clusters or of Mackay icosahedra. It is proposed that the ability to grow fast under near-equilibrium conditions is a better criterion to select clusters as precursors of the bulk-structure than their cohesive energy. The crystal structure problem of the rare gases - why fcc, not hcp - is discussed in connection with the apparent impossibility to simulate hcp growth by an analogous procedure. (orig.).

  9. Preparation of metastable bcc permalloy epitaxial thin films on GaAs(011){sub B3} single-crystal substrates

    Energy Technology Data Exchange (ETDEWEB)

    Ohtake, Mitsuru, E-mail: ohtake@futamoto.elect.chuo-u.ac.jp [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Higuchi, Jumpei; Yabuhara, Osamu [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan); Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)

    2011-09-30

    Permalloy (Py) single-crystal films with bcc structure were obtained on GaAs(011){sub B3} single-crystal substrates by ultra high vacuum rf magnetron sputtering. The film growth and the detailed film structures were investigated by refection high energy electron diffraction and pole figure X-ray diffraction. bcc-Py films epitaxially grow on the substrates in the orientation relationship of Py(011)[011-bar]{sub bcc} || GaAs(011)[011-bar]{sub B3}. The lattice constant of bcc-Py film is determined to be a = 0.291 nm. With increasing the film thickness, parts of the bcc crystal transform into more stable fcc structure by atomic displacement parallel to the bcc{l_brace}011{r_brace} close-packed planes. The resulting film thus consists of a mixture of bcc and fcc crystals. The phase transformation mechanism is discussed based on the experimental results. The in-plane magnetization properties reflecting the magnetocrystalline anisotropy of bcc-Py crystal are observed for the Py films grown on GaAs(011){sub B3} substrates.

  10. Preparation of metastable bcc permalloy epitaxial thin films on GaAs(011)B3 single-crystal substrates

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Higuchi, Jumpei; Yabuhara, Osamu; Kirino, Fumiyoshi; Futamoto, Masaaki

    2011-01-01

    Permalloy (Py) single-crystal films with bcc structure were obtained on GaAs(011) B3 single-crystal substrates by ultra high vacuum rf magnetron sputtering. The film growth and the detailed film structures were investigated by refection high energy electron diffraction and pole figure X-ray diffraction. bcc-Py films epitaxially grow on the substrates in the orientation relationship of Py(011)[011-bar] bcc || GaAs(011)[011-bar] B3 . The lattice constant of bcc-Py film is determined to be a = 0.291 nm. With increasing the film thickness, parts of the bcc crystal transform into more stable fcc structure by atomic displacement parallel to the bcc{011} close-packed planes. The resulting film thus consists of a mixture of bcc and fcc crystals. The phase transformation mechanism is discussed based on the experimental results. The in-plane magnetization properties reflecting the magnetocrystalline anisotropy of bcc-Py crystal are observed for the Py films grown on GaAs(011) B3 substrates.

  11. Electronic structure and superconductivity of fcc Cr

    International Nuclear Information System (INIS)

    Xu, J.; Freeman, A.J.; Jarlborg, T.; Brodsky, M.B.

    1984-01-01

    Results of self-consistent electronic structure calculations are reported for metastable fcc Cr metal. Unlike the case of bcc Cr which has E/sub F/ at a minimum in the density of states (DOS), the DOS at E/sub F/ in fcc Cr is at a peak making this one of the higher-DOS metals with the fcc structure (e.g., comparable with that of Ni and Pt). A calculated Stoner factor of 0.82 indicates that ferromagnetic ordering is not expected. Calculations of the electron-phonon coupling parameter lambda and superconducting transition temperature T/sub c/ were made using the rigid-ion approximation and strong-coupling theory with various estimates of the (unknown) phonon contribution. We conclude that T/sub c/'sroughly-equal2.5 K are reasonable, although they are substantially smaller than the T/sub c/roughly-equal10 K derived from measurements on Au-Cr-Au sandwiches

  12. Emergence of the bcc Phase and Phase Transition in Be through Phonon Quasiparticle Calculations

    Science.gov (United States)

    Zhang, D. B., Sr.; Wentzcovitch, R. M.

    2016-12-01

    Beryllium (Be) is an important material with applications in a number of areas ranging from aerospace components to X-ray equipment. Yet a precise understanding of the phase diagram of Be remains elusive. We have investigated the phase stability of Be using a recently developed hybrid free energy computation method that accounts for anharmonic effects by invoking phonon quasiparticle properties. We find that the hcp to bcc transition occurs near the melting curve at 0

  13. A metastable HCP intermetallic phase in Cu-Al bilayer films

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Limei

    2006-07-01

    For the present study, three kinds of layered Cu/Al films have been fabricated. The first kind of samples were multilayered Cu/Al films deposited by sputtering on (001)Si. The individual layer thicknesses were 100 nm, 200 nm and 400 nm, while the total film thickness of 800 nm was kept constant, thus leading to multilayer systems with 8, 4 and 2 layers, respectively. The second type of samples were Cu/Al bilayer films grown on (0001) sapphire by sputtering, with individual layer thicknesses of 400 nm. The third type of samples were bilayer films (100 nm Cu and 100 nm Al) deposited on (0001)sapphire by MBE at room temperature. Applying conventional transmission electron microscopy and X-ray diffraction, different epitaxial growth behaviors were found in these films. All multilayer films from the first type were polycrystalline. The second type of films show a (111) FCC texture and possess intermetallic phases at the interfaces. HRTEM investigations displayed that along [111]FCC, the atomic structure of the interlayer has an ABAB stacking sequence, which is identical with a hexagonal close-packed (HCP) structure in [0001] direction, but not with the ABCABC stacking sequence of Cu and Al in [111]FCC. The lattice parameters of the HCP structure at the interlayer were determined from a model which gave the best agreement between the experimental and simulated images. The parameters are: a=b=0.256 nm, c=0.419 nm, ?=120 , with the space group of P6m2. Furthermore, lattice distortion analysis revealed that the lattice parameters of the HCP phase are increasing from the near-Cu-side to the near-Al-side. The chemical composition of the interlayer was investigated by energy dispersive X-ray spectroscopy (EDS). EDS linescans were performed from pure Al to pure Cu layers. In order to examine the stability of this HCP phase, in-situ heating experiments were performed in the HRTEM at {proportional_to}600 C. Ex-situ heating experiments were performed at different temperatures to

  14. Inelastic neutron scattering from high-density fcc 4He

    International Nuclear Information System (INIS)

    Thomlinson, W.; Eckert, J.; Shirane, G.

    1978-01-01

    The phonon dispersion relations in high-density crystals of fcc 4 He have been measured along high-symmetry directions by the neutron-inelastic-scattering technique. A recent study of the lattice dynamics of fcc 4 He by Eckert et al. has been extended to cover the fcc phase diagram at pressures below 5 kbar. Molar volumes of 9.03, 9.43, and 9.97 cm 3 /mole have been studied in the temperature range from near the melting curve to near the fcc-hcp transition line. The phonon dispersion relations are in good agreement with a first-order self-consistent phonon theory calculation by Goldman. The observed phonon-group line shapes at large energy and momentum transfers show evidence for multiphonon scattering in agreement with calculations by Glyde. Eckert et al. reported extremely large anharmonic isochoric temperature shifts of the phonon energies. The present work studied the shifts as a function of molar volume and temperature. Mode-Grueneisen-parameter dispersion curves have been measured using the present data and earlier measurements at lower density in the fcc phase by Traylor et al. Macroscopic Grueneisen parameters have been calculated from the phonon density of states obtained from the data

  15. Magnetic properties of fcc (Co95Fe5)1-xAlx ribbons

    International Nuclear Information System (INIS)

    Makhlouf, Salah A.; Parker, F.T.; Benameur, T.

    1999-01-01

    Rapidly quenched (Co 95 Fe 5 ) 1-x Al x ribbons are investigated by X-ray diffraction, magnetization, and Moessbauer effect measurements. A single fcc phase is obtained for all ribbons x ≤ 10 at.%. The lattice constant increases linearly with x and is discussed in connection with magnetic moment. The influence of Al substitution on both magnetization and Fe-atom hyperfine field (H) is studied. At 296 K, the magnetization decreases linearly while H drops nonlinearly as x increases. Al substitution leads to substantial differences in iron hyperfine fields in bcc and fcc systems. Fe moment is perturbed differently by Al substitution in fcc (Co 95 Fe 5 ) 1-x Al x and bcc Fe-Al systems

  16. Ab initio study of the bcc-hcp transformation in iron

    Czech Academy of Sciences Publication Activity Database

    Friák, Martin; Šob, Mojmír

    2008-01-01

    Roč. 77, č. 17 (2008), 174117/1-174117/7 ISSN 1098-0121 R&D Projects: GA MŠk OC 147; GA AV ČR IAA1041302 Institutional research plan: CEZ:AV0Z20410507 Keywords : ab initio calculations * phase transformations * iron Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.322, year: 2008

  17. FCC Official Brochure - 2016

    CERN Multimedia

    Charitos, Panagiotis

    2016-01-01

    The FCC brochure describes the main scope of the study and give more information about the main scenarios explored under the study. It also highlights the R&D efforts under the study that will go into a Conceptual Design Report. Finally, it offers more information about the collaboration and a list of useful contact details.

  18. On Weak-BCC-Algebras

    Science.gov (United States)

    Thomys, Janus; Zhang, Xiaohong

    2013-01-01

    We describe weak-BCC-algebras (also called BZ-algebras) in which the condition (x∗y)∗z = (x∗z)∗y is satisfied only in the case when elements x, y belong to the same branch. We also characterize ideals, nilradicals, and nilpotent elements of such algebras. PMID:24311983

  19. Metastable phase transformation and hcp-ω transformation pathways in Ti and Zr under high hydrostatic pressures

    International Nuclear Information System (INIS)

    Gao, Lei; Ding, Xiangdong; Sun, Jun; Lookman, Turab; Salje, E. K. H.

    2016-01-01

    The energy landscape of Zr at high hydrostatic pressure suggests that its transformation behavior is strongly pressure dependent. This is in contrast to the known transition mechanism in Ti, which is essentially independent of hydrostatic pressure. Generalized solid-state nudged elastic band calculations at constant pressure shows that α-Zr transforms like Ti only at the lowest pressure inside the stability field of ω-phase. Different pathways apply at higher pressures where the energy landscape contains several high barriers so that metastable states are expected, including the appearance of a transient bcc phase at ca. 23 GPa. The global driving force for the hcp-ω transition increases strongly with increasing pressure and reaches 23.7 meV/atom at 23 GPa. Much of this energy relates to the excess volume of the hcp phase compared with its ω phase.

  20. Metastable phase transformation and hcp-ω transformation pathways in Ti and Zr under high hydrostatic pressures

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Lei; Ding, Xiangdong, E-mail: dingxd@mail.xjtu.edu.cn, E-mail: ekhard@esc.cam.ac.uk; Sun, Jun [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Lookman, Turab [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Salje, E. K. H., E-mail: dingxd@mail.xjtu.edu.cn, E-mail: ekhard@esc.cam.ac.uk [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ (United Kingdom)

    2016-07-18

    The energy landscape of Zr at high hydrostatic pressure suggests that its transformation behavior is strongly pressure dependent. This is in contrast to the known transition mechanism in Ti, which is essentially independent of hydrostatic pressure. Generalized solid-state nudged elastic band calculations at constant pressure shows that α-Zr transforms like Ti only at the lowest pressure inside the stability field of ω-phase. Different pathways apply at higher pressures where the energy landscape contains several high barriers so that metastable states are expected, including the appearance of a transient bcc phase at ca. 23 GPa. The global driving force for the hcp-ω transition increases strongly with increasing pressure and reaches 23.7 meV/atom at 23 GPa. Much of this energy relates to the excess volume of the hcp phase compared with its ω phase.

  1. FCC Official Brochure - Japanese Version

    CERN Multimedia

    AUTHOR|(CDS)2082248; Yamamoto, Akira; Uchibori, Yumemi.katsuki

    2017-01-01

    The FCC brochure describes the main scope of the study and give more information about the main scenarios explored under the study. It also highlights the ongoing R&D efforts launched by the FCC study. Finally, it offers more information about the collaboration and a list of useful contact details.

  2. FCC Official Brochure - French Version

    CERN Multimedia

    Charitos, Panagiotis

    2017-01-01

    The FCC brochure describes the main scope of the study and give more information about the main scenarios explored under the study. It also highlights the ongoing R&D efforts launched by the FCC study. Finally, it offers more information about the collaboration and a list of useful contact details.

  3. FCC Official Brochure - German version

    CERN Multimedia

    Charitos, Panagiotis

    2017-01-01

    The FCC brochure describes the main scope of the study and give more information about the main scenarios explored under the study. It also highlights the ongoing R&D efforts launched by the FCC study. Finally, it offers more information about the collaboration and a list of useful contact details.

  4. Spontaneous recombination volumes of Frenkel defects in neutron-irradiated non-fcc metals

    International Nuclear Information System (INIS)

    Nakagawa, M.; Mansel, W.; Boening, K.; Rosner, P.; Vogl, G.

    1979-01-01

    Production and production-rate curves for the non-fcc metals Fe, Mo, Ta, W, Zr, and Sn are obtained by electrical-resistivity measurements taken at 4.6 K during reactor neutron irradiations. The saturation concentration of Frenkel defects, c/sub s/, and the recombination volume v/sub o/ are evaluated. A parabolic relation between the spontaneous recombination volume v 0 and the compressibility kappa for a series of bcc metals is found

  5. Lattice distortion in hcp rare gas solids

    Science.gov (United States)

    Grechnev, A.; Tretyak, S. M.; Freiman, Yu. A.

    2010-04-01

    The lattice distortion parameter δ ≡c/a-√8/3 has been calculated as a function of molar volume for the hcp phases of He, Ar, Kr, and Xe. Results from both semi-empirical potentials and density functional theory are presented. Our study shows that δ is negative for helium in the entire pressure range. For Ar, Kr, and Xe δ changes sign from negative to positive as the pressure increases, growing rapidly in magnitude at higher pressures.

  6. Energetics of dislocation transformations in hcp metals

    International Nuclear Information System (INIS)

    Wu, Zhaoxuan; Yin, Binglun; Curtin, W.A.

    2016-01-01

    Dislocation core structures of hcp metals are highly complex and differ significantly among the hcp family. Some dislocations undergo unconventional transformations that have significant effects on the material plastic flow. Here, the energetics of dislocation dissociations are analyzed in a general anisotropic linear elastic theory framework for transformations in which changes in the partial Burgers vectors are small. Quantitative analyses on various transformations are made using DFT-computed stacking fault energies and partial Burgers vectors. Specifically, possible transformations of the mixed, edge, and screw 〈c+a〉 and screw 〈a〉 dislocations in 6 hcp metals (Mg, Ti, Zr, Re, Zn, Cd) are studied. Climb dissociation of mixed or edge 〈c+a〉 dislocations to the Basal plane is energetically favorable in all 6 metals and thus only limited by thermal activation. The 〈c+a〉 screw dislocation is energetically preferable on Pyramidal I for Ti, Zr, and Re, and on Pyramidal II for Zn and Cd. In Mg, the energy difference between screw 〈c+a〉 on Pyramidal I and II planes is small, suggesting relatively easy cross-slip. For the screw 〈a〉, Basal dissociation is energetically favorable in Mg, Re, Zn and Cd, while Prism dissociation is strongly favorable in Ti and Zr. Only Ti, Zr and Re show a metastable state for dissociation on the Prism plane, and the energy difference between screw 〈a〉 on the Prism and Pyramidal I planes is relatively small in all systems, suggesting relatively easy cross-slip of 〈a〉 in Ti and Zr. The elastic analysis thus provides a single framework able to capture the controlling energetics for different dissociations and slip systems in hcp metals. When the calculated energy differences are very small, the results point to the need for detailed modeling of the atomistic core structure. Moreover, the analyses rationalize broad experimental observations on dominant slip systems and dislocation behaviours, and provide

  7. Atomic displacements in bcc dilute alloys

    Indian Academy of Sciences (India)

    We present here a systematic investigation of the atomic displacements in bcc transition metal (TM) dilute alloys. We have calculated the atomic displacements in bcc (V, Cr, Fe, Nb, Mo, Ta and W) transition metals (TMs) due to 3d, 4d and 5d TMs at the substitutional site using the Kanzaki lattice static method. Wills and ...

  8. Nucleation and growth of a BCC Fe phase deposited on a single crystal (001) Cu film

    International Nuclear Information System (INIS)

    Koike, J.

    1991-01-01

    As a thin film overlayer grows on a substrate with a different structure, the overlayer initially adopts the substrate structure and subsequently transforms to an equilibrium bulk structure. such a growth characteristic has been extensively studied in Fe/Cu bicrystals. An Fe overlayer grown on a Cu substrate is known to have the fcc structure up to a thickness of 2 nm, whereas a thicker Fe overlayer consists of submicrometer grains of the bcc-Cu has been reported in a relatively thick Fe film and was found to consist of the Nishiyama (N), Kurdjumov-Sacks (KS), or Pitsch (P), depending on the orientation of the substrate surface. However, previous studies have not explained how the bcc structure nucleates or how the observed submicrometer polycrystalline grains form. The paper provides an understanding of these two points. Transmission electron microscopy (TEM) was used to study Fe/Cu bicrystals as the Fe thickness was varied systematically. Analysis of moire fringes, which are caused by superposition of different structures, enabled us to determine the orientation relationship between the very thin Fe layer and the Cu substrate. We show that a single variant of the P orientation relationship, which accompanies atomic rearrangement parallel to the interface, predominates at the nucleation stage of the bcc structure. Nucleation of other variants of P, N, and KS occurs with increasing Fe thickness and causes the formation of the submicrometer bcc grains

  9. FCC 5 and FCC 6 (3/4)

    CERN Multimedia

    CERN. Geneva; Schulte, Daniel

    2016-01-01

    Abstract: The electron-positron collider, FCC-ee, should provide collisions over a wide range of beam energies, ranging from roughly 35 GeV to almost 200 GeV. The physics goals of the FCC-ee collider call for luminosities around 1e36 cm-2s-1 per interaction point at the Z pole and several 1e34 cm-2s-1 at the ZH production peak. The beam energy should be pushed above 175 GeV, with a total synchrotron-radiation power not exceeding 100 MW. The extremely high luminosities and resulting short beam lifetime, due to radiative Bhabha scattering, can be sustained by top-up injection. The FCC-ee acce...

  10. Lattice Dynamics of fcc Ca

    DEFF Research Database (Denmark)

    Stassis, C.; Zaretsky, J.; Misemer, D. K.;

    1983-01-01

    A large single crystal of FCC Ca was grown and was used to study the lattice dynamics of this divalent metal by coherent inelastic neutron scattering. The phonon dispersion curves were measured, at room temperature, along the [ξ00], [ξξ0], [ξξξ], and [0ξ1] symmetry directions. The dispersion curves...... to the propagation of elastic waves. The frequencies of the T1[ξξ0] branch for ξ between approximately 0.5 and 0.8 are slightly above the velocity-of-sound line determined from the low-frequency measurements. Since a similar effect has been observed in FCC Yb, it is natural to assume that the anomalous dispersion...... bear a striking resemblance to those of FCC Yb, which is also a divalent metal with an electronic band structure similar to that of Ca. In particular, the shear moduli c44 and (c11-c 12)/2 differ by a factor of 3.4, which implies that FCC Ca (like FCC Yb) is very anisotropic with regard...

  11. Enabling microstructural changes of FCC/BCC alloys in 2D dislocation dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Ilker Topuz, Ahmet, E-mail: aitopuz@gmail.com

    2015-03-11

    Dimension reduction procedure is the recipe to represent defects in two dimensional dislocation dynamics according to the changes in the geometrical properties of the defects triggered by different conditions such as radiation, high temperature, or pressure. In the present study, this procedure is extended to incorporate further features related to the presence of defects with a special focus on face-centered cubic/body-centered cubic alloys used for diverse engineering purposes. In order to reflect the microstructural state of the alloy on the computational cell of two dimensional dislocation dynamics, the distribution of the multi-type defects over slip lines is implemented by using corresponding strength and line spacing for each type of defect. Additionally, a simple recursive incremental relation is set to count the loop accumulation on the precipitates. In the case of continuous resistance against the motion of edge dislocations on the slip lines, an expression of friction is introduced to see its contribution on the yield strength. Each new property is applied independently on a different material by using experimental information about defect properties and grain sizes under the condition of plain strain deformation: both constant and dynamically increasing obstacle strength for precipitate coarsening in prime-aged and heat-treated copper-chromium-zirconium, internal friction in tantalum-2.5tungsten, and mixed hardening due to the presence of precipitates and prismatic loops in irradiated oxide dispersion strengthened EUROFER with 0.3% yttria.

  12. Kinetics of disorder-to-fcc phase transition via an intermediate bcc state

    Czech Academy of Sciences Publication Activity Database

    Liu, Y.; Nie, H.; Bansil, R.; Steinhart, Miloš; Bang, J.; Lodge, T. P.

    2006-01-01

    Roč. 73, č. 6 (2006), 061803-1-061803-6 ISSN 1539-3755 Institutional research plan: CEZ:AV0Z40500505 Keywords : x-ray scattering * polymer blends * polymer solutions Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.438, year: 2006

  13. New developments in FCC catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Kelkar, C.P. [BASF Corporation, Iselin, NJ (United States)

    2011-07-01

    Fluid catalytic cracking (FCC) unit is one of the primary boiling point reduction units in the refinery that converts longer chain crude oil to useful products such as distillate, gasoline and LPG. As the quality of feedstock deteriorates, while specifications on the product side are becoming more and more stringent, the FCC unit is being severely challenged. Over the past few years BASF has introduced two new platform technologies that will assist in this challenge. This paper will present an overview of those platforms and also provide a brief update on the research underway to mitigate the current REO crisis. (orig.)

  14. FCC-ee: Energy Calibration

    Energy Technology Data Exchange (ETDEWEB)

    Koratzinos, M. [Univ. of Geneva (Switzerland); Blondel, A. [Univ. of Geneva (Switzerland); Gianfelice-Wendt, E. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Zimmermann, F. [European Organization for Nuclear Research (CERN), Geneva (Switzerland)

    2015-06-02

    The FCC-ee aims to improve on electroweak precision measurements, with goals of 100 ke V on the Z mass and width, and a fraction of MeV on the W mass. Compared to LEP, this implies a much improved knowledge of the center-of-mass energy when operating at the Z peak and WW threshold. This can be achieved by making systematic use of resonant depolarization. A number of issues have been identified, due in particular to the long polarization times. However the smaller emittance and energy spread of FCC-ee with respect to LEP should help achieve a much improved performance.

  15. FCC-ee: Energy calibration

    CERN Document Server

    Koratzinos, M.; Gianfelice-Wendt, E.; Zimmermann, F.

    The FCC-ee aims to improve on electroweak precision measurements, with goals of 100 keV on the Z mass and width, and a fraction of MeV on the W mass. Compared to LEP, this implies a much improved knowledge of the centre-of-mass energy when operating at the Z peak and WW threshold. This can be achieved by making systematic use of resonant depolarization. A number of issues have been identified, due in particular to the long polarization times. However the smaller emittance and energy spread of FCC-ee with respect to LEP should help achieve a much improved performance.

  16. FCC 3 and FCC 4 (2/4)

    CERN Multimedia

    CERN. Geneva; Dam, Mogens

    2016-01-01

    Abstract: Owing to its specific interaction region design, the FCC-ee will be able to deliver unprecedented luminosities at centre-of-mass energies ranging from below the Z pole to the ttbar threshold and above. Operation at four energy regimes - at the Z pole, at the WW threshold, at 240 GeV for Higgs production, and at the ttbar thre...

  17. Electronic structure of hcp transition metals

    DEFF Research Database (Denmark)

    Jepsen, O.; Andersen, O. Krogh; Mackintosh, A. R.

    1975-01-01

    Using the linear muffin-tin-orbital method described in the previous paper, we have calculated the electronic structures of the hcp transition metals, Zr, Hf, Ru, and Os. We show how the band structures of these metals may be synthesized from the sp and d bands, and illustrate the effects...... of hybridization, relativistic band shifts, and spin-orbit coupling by the example of Os. By making use of parameters derived from the muffin-tin potential, we discuss trends in the positions and widths of the energy bands, especially the d bands, as a function of the location in the periodic table. The densities...... of states of the four metals are presented, and the calculated heat capacities compared with experiment. The Fermi surfaces of both Ru and Os are found to be in excellent quantitative agreement with de Haas-van Alphen measurements, indicating that the calculated d-band position is misplaced by less than 10...

  18. Crystal structure of secretory protein Hcp3 from Pseudomonas aeruginosa.

    Science.gov (United States)

    Osipiuk, Jerzy; Xu, Xiaohui; Cui, Hong; Savchenko, Alexei; Edwards, Aled; Joachimiak, Andrzej

    2011-03-01

    The Type VI secretion pathway transports proteins across the cell envelope of Gram-negative bacteria. Pseudomonas aeruginosa, an opportunistic Gram-negative bacterial pathogen infecting humans, uses the type VI secretion pathway to export specific effector proteins crucial for its pathogenesis. The HSI-I virulence locus encodes for several proteins that has been proposed to participate in protein transport including the Hcp1 protein, which forms hexameric rings that assemble into nanotubes in vitro. Two Hcp1 paralogues have been identified in the P. aeruginosa genome, Hsp2 and Hcp3. Here, we present the structure of the Hcp3 protein from P. aeruginosa. The overall structure of the monomer resembles Hcp1 despite the lack of amino-acid sequence similarity between the two proteins. The monomers assemble into hexamers similar to Hcp1. However, instead of forming nanotubes in head-to-tail mode like Hcp1, Hcp3 stacks its rings in head-to-head mode forming double-ring structures.

  19. High Temperature Magneto-Elastic Instability of Dislocations in bcc Iron

    International Nuclear Information System (INIS)

    Dudarev, S.; Bullough, R.; Gilbert, M.; Derlet, P.

    2007-01-01

    Full text of publication follows: Density functional calculations show that the low temperature structure of self-interstitial defects in iron is fundamentally different from the structure of self-interstitial defects in all the other bcc metals. The origin of this anomaly is associated with the magnetic part of the cohesive energy of iron, where the Stoner exchange term stabilizes the body centred cubic phase, and where the magnetic part of energy is strongly affected by the large strain associated with the core region of an interstitial defect. At elevated temperatures magnetic excitations erode the stability of the bcc phase, giving rise to the gradual softening of the 110 transverse acoustic phonon modes and to the α-γ bcc-fcc martensitic phase transition occurring at 912 deg. C at normal pressure. Elastic moduli of bcc iron vary as a function of temperature with c' = (C 11 - c 12 )/2 vanishing at the α-γ transition point. This has significant effects on the magnitude of both the elastic interactions between dislocations and other defects in the material and on the intrinsic structural stability of the dislocations and other defects themselves. To evaluate structural stability of defects at elevated temperatures we investigate elastic self-energies of dislocations in the continuum anisotropic elasticity approximation. We also develop atomistic models of dislocations and point defects based on a generalised form of the magnetic potential. By varying the magnetic part of the potential we are able to reproduce the experimentally observed variation of elastic moduli as a function of temperature, and assess relative stability of various types of defect structures. Our analysis shows that, in complete contrast to other straight dislocations, the elastic self-energy of straight 100 edge dislocations actually sharply decreases as we approach the α-γ transition, indicating that this surprising fact is a probable explanation of the frequent observation of the 100

  20. Stacking faults and mechanisms strain-induced transformations of hcp metals (Ti, Mg) during mechanical activation in liquid hydrocarbons

    Science.gov (United States)

    Lubnin, A. N.; Dorofeev, G. A.; Nikonova, R. M.; Mukhgalin, V. V.; Lad'yanov, V. I.

    2017-11-01

    The evolution of the structure and substructure of metals Ti and Mg with hexagonal close-packed (hcp) lattice is studied during their mechanical activation in a planetary ball mill in liquid hydrocarbons (toluene, n-heptane) and with additions of carbon materials (graphite, fullerite, nanotubes) by X-ray diffraction, scanning electron microscopy, and chemical analysis. The temperature behavior and hydrogen-accumulating properties of mechanocomposites are studied. During mechanical activation of Ti and Mg, liquid hydrocarbons decay, metastable nanocrystalline titanium carbohydride Ti(C,H) x and magnesium hydride β-MgH2 are formed, respectively. The Ti(C,H) x and MgH2 formation mechanisms during mechanical activation are deformation ones and are associated with stacking faults accumulation, and the formation of face-centered cubic (fcc) packing of atoms. Metastable Ti(C,H)x decays at a temperature of 550°C, the partial reverse transformation fcchcp occurs. The crystalline defect accumulation (nanograin boundaries, stacking faults), hydrocarbon destruction, and mechanocomposite formation leads to the enhancement of subsequent magnesium hydrogenation in the Sieverts reactor.

  1. Realizing high magnetic moments in fcc Fe nanoparticles through atomic structure stretch

    International Nuclear Information System (INIS)

    Baker, S H; Roy, M; Thornton, S C; Binns, C

    2012-01-01

    We describe the realization of a high moment state in fcc Fe nanoparticles through a controlled change in their atomic structure. Embedding Fe nanoparticles in a Cu 1-x Au x matrix causes their atomic structure to switch from bcc to fcc. Extended x-ray absorption fine structure (EXAFS) measurements show that the structure in both the matrix and the Fe nanoparticles expands as the amount of Au in the matrix is increased, with the data indicating a tetragonal stretch in the Fe nanoparticles. The samples were prepared directly from the gas phase by co-deposition, using a gas aggregation source and MBE-type sources respectively for the nanoparticle and matrix materials. The structure change in the Fe nanoparticles is accompanied by a sharp increase in atomic magnetic moment, ultimately to values of ∼2.5 ± 0.3 μ B /atom. (paper)

  2. Measurements of electric quadrupole moments of neutron-deficient Au, Pt, and Ir nuclei with NMR-ON in hcp-Co

    CERN Multimedia

    Smolic, E; Hagn, E; Zech, E; Seewald, G

    2002-01-01

    The aim of the experiments is the measurement of $\\,$i) nuclear magnetic moments and electric quadrupole moments of neutron-deficient isotopes in the region Os-Ir-Pt-Au with the methods of quadrupole-interaction-resolved NMR on oriented nuclei " QI-NMR-ON " and modulated adiabatic passage on oriented nuclei " MAPON " and $\\,$ii) the magnetic hyperfine field, electric field gradient (EFG), and spin-lattice relaxation of 5d elements in ferromagnetic Fe, Ni, fcc-Co and hcp-Co.\\\\ The measurements on Au isotopes have been finished successfully. The quadrupole moments of $^{186}$Au, $^{193m}$Au, $^{195}$Au, $^{195m}$Au, $^{197m}$Au, $^{198}$Au and $^{199}$Au were determined with high precision.\\\\ For neutron-deficient Ir isotopes QI-NMR-ON measurements were performed after implantation of Hg precursors. The EFG of Ir in hcp-Co has been calibrated. Thus precise values for the spectroscopic quadrupole mo...

  3. Synthesis and characterization of branched fcc/hcp ruthenium nanostructures and their catalytic activity in ammonia borane hydrolysis

    KAUST Repository

    AlYami, Noktan; LaGrow, Alec P; Anjum, Dalaver H.; Guan, Chao; Miao, Xiaohe; Sinatra, Lutfan; Yuan, Ding-Jier; Mohammed, Omar F.; Huang, Kuo-Wei; Bakr, Osman

    2018-01-01

    Several systems have shown the ability to stabilize uncommon crystal structures during the synthesis of metallic nanoparticles. By tailoring the nanoparticle crystal structure, the physical and chemical properties of the particles can also

  4. Phonons in fcc binary alloys

    International Nuclear Information System (INIS)

    Sharma, Amita; Rathore, R.P.S.

    1992-01-01

    Born-Mayer potential has been modified to account for the unpaired (three body) forces among the common nearest neighbours of the ordered binary fcc alloys i.e. Ni 3 Fe 7 , Ni 5 Fe 5 and Ni 75 Fe 25 . The three body potential is added to the two body form of Morse to formalize the total interaction potential. Measured inverse ionic compressibility, cohesive energy, lattice constant and one measured phonon frequency are used to evaluate the defining parameters of the potential. The potential seeks to bring about the binding among 140 and 132 atoms though pair wise (two body) and non-pair wise (three body) forces respectively. The phonon-dispersion relations obtained by solving the secular equation are compared with the experimental findings on the aforesaid alloys. (author). 19 refs., 3 figs

  5. Vacancy behavior in a compressed fcc Lennard-Jones crystal

    International Nuclear Information System (INIS)

    Beeler, J.R. Jr.

    1981-12-01

    This computer experiment study concerns the determination of the stable vacancy configuration in a compressed fcc Lennard-Jones crystal and the migration of this defect in a compressed crystal. Isotropic and uniaxial compression stress conditions were studied. The isotropic and uniaxial compression magnitudes employed were 0.94 less than or equal to eta less than or equal to 1.5, and 1.0 less than or equal to eta less than or equal to 1.5, respectively. The site-centered vacancy (SCV) was the stable vacancy configuration whenever cubic symmetry was present. This includes all of the isotropic compression cases and the particular uniaxial compression case (eta = √2) that give a bcc structure. In addition, the SCV was the stable configuration for uniaxial compression eta 1.20, the SV-OP is an extended defect and, therefore, a saddle point for SV-OP migration could not be determined. The mechanism for the transformation from the SCV to the SV-OP as the stable form at eta = 1.29 appears to be an alternating sign [101] and/or [011] shear process

  6. Vibrational contribution to the thermodynamics of nanosized precipitates: vacancy-copper clusters in bcc-Fe

    International Nuclear Information System (INIS)

    Talati, Mina; Posselt, Matthias; Al-Motasem, Ahmed; Bergner, Frank; Bonny, Giovanni

    2012-01-01

    The effects of lattice vibration on the thermodynamics of nanosized coherent clusters in bcc-Fe consisting of vacancies and/or copper are investigated within the harmonic approximation. A combination of on-lattice simulated annealing based on Metropolis Monte Carlo simulations and off-lattice relaxation by molecular dynamics is applied to obtain the most stable cluster configurations at T = 0 K. The most recent interatomic potential built within the framework of the embedded-atom method for the Fe-Cu system is used. The total free energy of pure bcc-Fe and fcc-Cu as well as the total formation free energy and the total binding free energy of the vacancy-copper clusters are determined for finite temperatures. Our results are compared with the available data from previous investigations performed using many-body interatomic potentials and first-principles methods. For further applications in rate theory and object kinetic Monte Carlo simulations, the vibrational effects evaluated in the present study are included in the previously developed analytical fitting formulae. (paper)

  7. Co thin film with metastable bcc structure formed on GaAs(111 substrate

    Directory of Open Access Journals (Sweden)

    Minakawa Shigeyuki

    2014-07-01

    Full Text Available Co thin films are prepared on GaAs(111 substrates at temperatures ranging from room temperature to 600 ºC by radio-frequency magnetron sputtering. The growth behavior and the detailed resulting film structure are investigated by in-situ reflection high-energy electron diffraction and X-ray diffraction. In early stages of film growth at temperatures lower than 200 ºC, Co crystals with metastable A2 (bcc structure are formed, where the crystal structure is stabilized through hetero-epitaxial growth. With increasing the film thickness beyond 2 nm, the metastable structure starts to transform into more stable A1 (fcc structure through atomic displacements parallel to the A2{110} close-packed planes. The crystallographic orientation relationship between the A2 and the transformed A1 crystals is A1{111} || A2{110}. When the substrate temperature is higher than 400 ºC, Ga atoms of substrate diffuse into the Co films and a Co-Ga alloy with bcc-based ordered structure of B2 is formed.

  8. Spheroidization behavior of dendritic b.c.c. phase in Zr-based モ-phase composite

    Directory of Open Access Journals (Sweden)

    Sun Guoyuan

    2013-03-01

    Full Text Available The spheroidization behavior of the dendritic b.c.c. phase dispersed in a bulk metallic glass (BMG matrix was investigated through applying semi-solid isothermal processing and a subsequent rapid quenching procedure to a Zr-based モ-phase composite. The Zr-based composite with the composition of Zr56.2Ti13.8Nb5.0Cu6.9Ni5.6Be12.5 was prefabricated by a water-cooled copper mold-casting method and characterized by X-ray diffraction (XRD and scanning electron microscope (SEM. The results show that the composite consists of a glassy matrix and uniformly distributed fine dendrites of the モ-Zr solid solution with the body-centered-cubic (b.c.c. structure. Based on the differential scanning calorimeter (DSC examination results, and in view of the b.c.c. モ-Zr to h.c.p. メ-Zr phase transition temperature, a semi-solid holding temperature of 900 ìC was determined. After reheating the prefabricated composite to the semi-solid temperature, followed by an isothermal holding process at this temperature for 5 min, and then quenching the semi-solid mixture into iced-water; the two-phase microstructure composed of a BMG matrix and uniformly dispersed spherical b.c.c. モ-Zr particles with a high degree of sphericity was achieved. The present spheroidization transition is a thermodynamically autonomic behavior, and essentially a diffusion process controlled by kinetic factors; and the formation of the BMG matrix should be attributed to the rapid quenching of the semi-solid mixture as well as the large glass-forming ability of the remaining melt in the semi-solid mixture.

  9. 47 CFR 2.926 - FCC identifier.

    Science.gov (United States)

    2010-10-01

    ... representative may receive a grantee code electronically via the Internet at https://gullfoss2.fcc.gov/prod/oet... which has not been granted equipment authorization where such grant is required prior to marketing...

  10. HOM power in FCC-ee cavities

    CERN Document Server

    Karpov, Ivan; Chapochnikova, Elena

    2018-01-01

    This Note summarizes the results of the power loss calculations for FCC-ee machines with 400.79 MHz cavity options. The requirements for the single-cell cavity design and for the operation with beam are obtained from the results for the high-current FCC-ee machine (Z). For other machines the power loss is sufficiently low and can be absorbed and extracted by foreseen HOM couplers.

  11. High-pressure high-temperature stability of hcp-IrxOs1-x (x = 0.50 and 0.55) alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yusenko, Kirill V.; Bykova, Elena; Bykov, Maxim; Gromilov, Sergey A.; Kurnosov, Alexander V.; Prescher, Clemens; Prakapenka, Vitali B.; Crichton, Wilson A.; Hanfland, Michael; Margadonna, Serena; Dubrovinsky, Leonid S.

    2016-12-23

    Hcp-Ir0.55Os0.45 and hcp-Ir0.50Os0.50 alloys were synthesised by thermal decomposition of single-source precursors in hydrogen atmosphere. Both alloys correspond to a miscibility gap in the Ir–Os binary phase diagram and therefore are metastable at ambient conditions. An in situ powder X-ray diffraction has been used for a monitoring a formation of hcp-Ir0.55Os0.45 alloy from (NH4)2[Ir0.55Os0.45Cl6] precursor. A crystalline intermediate compound and nanodimentional metallic particles with a large concentration of defects has been found as key intermediates in the thermal decomposition process in hydrogen flow. High-temperature stability of titled hcp-structured alloys has been investigated upon compression up to 11 GPa using a multi-anvil press and up to 80 GPa using laser-heated diamond-anvil cells to obtain a phase separation into fcc + hcp mixture. Compressibility curves at room temperature as well as thermal expansion at ambient pressure and under compression up to 80 GPa were collected to obtain thermal expansion coefficients and bulk moduli. hcp-Ir0.55Os0.45 alloy shows bulk moduli B0 = 395 GPa. Thermal expansion coefficients were estimated as α = 1.6·10-5 K-1 at ambient pressure and α = 0.3·10-5 K-1 at 80 GPa. Obtained high-pressure high-temperature data allowed us to construct the first model for pressure-dependent Ir–Os phase diagram.

  12. Crystal structure of secretory protein Hcp3 from Pseudomonas aeruginosa

    OpenAIRE

    Osipiuk, Jerzy; Xu, Xiaohui; Cui, Hong; Savchenko, Alexei; Edwards, Aled; Joachimiak, Andrzej

    2011-01-01

    The Type VI secretion pathway transports proteins across the cell envelope of Gram-negative bacteria. Pseudomonas aeruginosa, an opportunistic Gram-negative bacterial pathogen infecting humans, uses the type VI secretion pathway to export specific effector proteins crucial for its pathogenesis. The HSI-I virulence locus encodes for several proteins that has been proposed to participate in protein transport including the Hcp1 protein, which forms hexameric rings that assemble into nanotubes in...

  13. Micromechanical modeling of the deformation of HCP metals

    Energy Technology Data Exchange (ETDEWEB)

    Graff, S. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Materialforschung

    2008-12-04

    Nowadays, intense research is conducted to understand the relation between microstructural features and mechanical properties of hexagonal close-packed (hcp) metals. Due to their hexagonal structure, hcp metals exhibit mechanical properties such as strong anisotropy, which is more pronounced than for construction metals with cubic crystal structure, and tension/compression asymmetry. Deformation mechanisms in hcp metals, dislocation motion on specific slip systems and activation of twinning, are not yet completely understood. The purpose of this work is to link the physical mechanisms developing during deformation of magnesium (Mg) on the microscale with the macroscopic yielding properties of texture Mg samples. It will be shown that the mechanical behavior of hcp metals may be understood and reproduced with the help of a visco-plastic model for crystal plasticity and a phenomenological yield criterion with appropriate hardening behavior. The study of single crystal specimens subjected to channel die compression tests reveals the active slip systems and twinning systems of the material considered. The material anisotropy at mesoscale is reproduced by using adequate critical resolved shear stresses (CRSS) for the considered deformation mechanisms. In order to describe the macroscopic behavior, texture is incorporated into polycrystalline Representative Volume Elements (RVEs) and various mechanical properties of extruded bars and rolled plates can be predicted. For RVEs exhibiting the texture of rolled plates the numerical results reveal the plate's anisotropic yielding and hardening behavior on a mesoscale. In order to extend the modeling possibilities to process simulations and to allow for time-saving simulations of structural behavior, a phenomenological yield surface accounting for anisotropy and tension/compression asymmetry has been established and implemented in a finite element code. Its numerous model parameters are calibrated by an optimization

  14. HCP to FCT + precipitate transformations in lamellar gamma-titanium aluminide alloys

    Science.gov (United States)

    Karadge, Mallikarjun Baburao

    Fully lamellar gamma-TiAl [alpha2(HCP) + gamma(FCT)] based alloys are potential structural materials for aerospace engine applications. Lamellar structure stabilization and additional strengthening mechanisms are major issues in the ongoing development of titanium aluminides due to the microstructural instability resulting from decomposition of the strengthening alpha 2 phase. This work addresses characterization of multi-component TiAl systems to identify the mechanism of lamellar structure refinement and assess the effects of light element additions (C and Si) on creep deformation behavior. Transmission electron microscopy studies directly confirmed for the first time that, fine lamellar structure is formed by the nucleation and growth of a large number of basal stacking faults on the 1/6 dislocations cross slipping repeatedly into and out of basal planes. This lamellar structure can be tailored by modifying jog heights through chemistry and thermal processing. alpha 2 → gamma transformation during heating (investigated by differential scanning calorimetry and X-ray diffraction) is a two step process involving the formation of a novel disordered FCC gamma' TiAl [with a(gamma') = c(gamma)] as an intermediate phase followed by ordering. Addition of carbon and silicon induced Ti2AlC H-type carbide precipitation inside the alpha2 lath and Ti 5(Al,Si)3 zeta-type silicide precipitation at the alpha 2/gamma interface. The H-carbides preserve alpha2/gamma type interfaces, while zeta-silicide precipitates restrict ledge growth and interfacial sliding enabling strong resistance to creep deformation.

  15. Genetic analysis of the spindle checkpoint genes san-1, mdf-2, bub-3 and the CENP-F homologues hcp-1 and hcp-2 in Caenorhabditis elegans

    Directory of Open Access Journals (Sweden)

    Moore Landon L

    2008-02-01

    Full Text Available Abstract Background The spindle checkpoint delays the onset of anaphase until all sister chromatids are aligned properly at the metaphase plate. To investigate the role san-1, the MAD3 homologue, has in Caenorhabditis elegans embryos we used RNA interference (RNAi to identify genes synthetic lethal with the viable san-1(ok1580 deletion mutant. Results The san-1(ok1580 animal has low penetrating phenotypes including an increased incidence of males, larvae arrest, slow growth, protruding vulva, and defects in vulva morphogenesis. We found that the viability of san-1(ok1580 embryos is significantly reduced when HCP-1 (CENP-F homologue, MDF-1 (MAD-1 homologue, MDF-2 (MAD-2 homologue or BUB-3 (predicted BUB-3 homologue are reduced by RNAi. Interestingly, the viability of san-1(ok1580 embryos is not significantly reduced when the paralog of HCP-1, HCP-2, is reduced. The phenotype of san-1(ok1580;hcp-1(RNAi embryos includes embryonic and larval lethality, abnormal organ development, and an increase in abnormal chromosome segregation (aberrant mitotic nuclei, anaphase bridging. Several of the san-1(ok1580;hcp-1(RNAi animals displayed abnormal kinetochore (detected by MPM-2 and microtubule structure. The survival of mdf-2(RNAi;hcp-1(RNAi embryos but not bub-3(RNAi;hcp-1(RNAi embryos was also compromised. Finally, we found that san-1(ok1580 and bub-3(RNAi, but not hcp-1(RNAi embryos, were sensitive to anoxia, suggesting that like SAN-1, BUB-3 has a functional role as a spindle checkpoint protein. Conclusion Together, these data suggest that in the C. elegans embryo, HCP-1 interacts with a subset of the spindle checkpoint pathway. Furthermore, the fact that san-1(ok1580;hcp-1(RNAi animals had a severe viability defect whereas in the san-1(ok1580;hcp-2(RNAi and san-1(ok1580;hcp-2(ok1757 animals the viability defect was not as severe suggesting that hcp-1 and hcp-2 are not completely redundant.

  16. Luminosity Targets for FCC-hh

    CERN Document Server

    Zimmermann, F.; Buffat, X.; Schulte, D.

    2016-01-01

    We discuss the choice of target values for the peak and integrated luminosity of a future high-energy frontier circular hadron collider (FCC-hh). We review the arguments on the physics reach of a hadron collider. Next we show that accelerator constraints will limit the beam current and the turnaround time. Taking these limits into account, we derive an expression for the ultimate integrated luminosity per year, depending on a possible pile-up limit imposed by the physics experiments. We finally benchmark our result against the planned two phases of FCC-hh [1, 2, 3

  17. Pore Scale Thermal Hydraulics Investigations of Molten Salt Cooled Pebble Bed High Temperature Reactor with BCC and FCC Configurations

    Directory of Open Access Journals (Sweden)

    Shixiong Song

    2014-01-01

    CFD results and empirical correlations’ predictions of pressure drop and local Nusselt numbers. Local pebble surface temperature distributions in several default conditions are investigated. Thermal removal capacities of molten salt are confirmed in the case of nominal condition; the pebble surface temperature under the condition of local power distortion shows the tolerance of pebble in extreme neutron dose exposure. The numerical experiments of local pebble insufficient cooling indicate that in the molten salt cooled pebble bed reactor, the pebble surface temperature is not very sensitive to loss of partial coolant. The methods and results of this paper would be useful for optimum designs and safety analysis of molten salt cooled pebble bed reactors.

  18. Ab initio calculation of phase boundaries in iron along the bcc-fcc transformation path and magnetism of iron overlayers

    Czech Academy of Sciences Publication Activity Database

    Friák, Martin; Šob, Mojmír; Vitek, V.

    2001-01-01

    Roč. 63, č. 5 (2001), s. čl. 052405 ISSN 0163-1829 R&D Projects: GA ČR GA106/99/1178; GA MŠk ME 264 Grant - others:-(US) INT9605232 Institutional research plan: CEZ:AV0Z2041904 Keywords : ultrathin fe films * generalized-gradient approximation * energy-electron-diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.070, year: 2001

  19. Stacking fault density as engineering criterion for resistance to radiation swelling of alloys' FCC- and BCC-lattice

    International Nuclear Information System (INIS)

    Zheltov, Yu.V.; Ageev, V.S.; Kolesnikov, Yu.G.

    1990-01-01

    The experimental data on influence of Mn, Cr, Ni, P, B, Ce alloying in austenitic and simultaneously Nb, V, B alloying in ferritic steels and also heat treatment on stacking fault density (SFD) are represented. In all cases besides influence of Cr in austenitic steel the increase of SFD is shown. The decrease of radiation swelling of industrial steels at the increase of their SFD, measured by X-rays, was studied. The tendency of increase of relative radiation swelling change at SFD increase at relative fluence rise is verified. It is shown that SFD may be a perspective proximate characteristics of choice of radiation-resistant steel melts within one steel quality. 14 refs.; 4 figs. (author)

  20. Link between structural and mechanical stability of fcc- and bcc-based ordered MgeLi alloys

    CSIR Research Space (South Africa)

    Phasha, MJ

    2010-06-01

    Full Text Available ) pseudopotential method, embodied in the CASTEP code [10]. The Hohenberg-Kohn-Sham density functional theory (DFT) [11] was used 5 within the GGA formalism [12] to describe the electronic exchange-correlation interactions. We used the recent PBE form..., Int. J. Quantum Chem. 77 (2000) 895. [11] P. Hohenberg and W. Kohn, Phys. Rev. 136, B 864 (1964), W. Kohn and L.J. Sham, Phys. Rev. 140 (1965) A 1133. [12] J.P. Perdew and Y. Wang, Phys. Rev. B 45 (1992) 13244. [13] J.P. Perdew, K. Burke and M...

  1. Electron microscopy and plastic deformation of HCP metals and alloys

    International Nuclear Information System (INIS)

    Poirier, J.-P.; Le Hazif, Roger

    1976-01-01

    The recent literature on the slip systems of the h.c.p. metals is reviewed and the contribution of transmission electron microscopy assessed. It is now clear that the stress-strain curves and the dislocation configurations in the slip plane are very similar, whether the principal slip system is basal or prismatic. The important problem of the relative ease of slip systems is linked to the ease of splitting of dislocations in the slip planes and to the electronic band structure of the metal [fr

  2. HCP, grid and data infrastructures for astrophysics: an integrated view

    International Nuclear Information System (INIS)

    Pasian, F.

    2009-01-01

    Also in the case of astrophysics, the capability of performing Big Science requires the availability of large Hcp facilities. But computational resources alone are far from being enough for the community: as a matter of fact, the whole set of e-infrastructures (network, computing nodes, data repositories, applications) need to work in an inter operable way. This implies the development of common (or at least compatible) user interfaces to computing resources, transparent access to observations and numerical simulations through the Virtual Observatory, integrated data processing pipelines, data mining and semantic web applications. Achieving this inter operability goal is a must to build a real Knowledge Infrastructure in the astrophysical domain.

  3. Analytic nearest neighbour model for FCC metals

    International Nuclear Information System (INIS)

    Idiodi, J.O.A.; Garba, E.J.D.; Akinlade, O.

    1991-06-01

    A recently proposed analytic nearest-neighbour model for fcc metals is criticised and two alternative nearest-neighbour models derived from the separable potential method (SPM) are recommended. Results for copper and aluminium illustrate the utility of the recommended models. (author). 20 refs, 5 tabs

  4. Academic Training Lectures | FCC | 2-5 February

    CERN Multimedia

    2016-01-01

    Please note that the next series of Academic Training Lectures will take place from 2 to 5 February 2016.   Tuesday, 2 February 2016 from 10.30 a.m. to 12.30 p.m. in the Filtration Plant (Building 222-R-001) FCC 1: Introduction to FCC by Michael Benedikt FCC 2: FCC Physics - Challenges and Potentials by Christophe Grojean, Michelangelo Mangano https://indico.cern.ch/event/472105/   Wednesday, 3 February 2016 from 10.30 a.m. to 12.30 p.m in the Filtration Plant (Building 222-R-001) FCC 3: FCC hh Detectors and Experiments by Werner Riegler FCC 4: Experimental Measurements and Detectors for the FCC-ee by Mogens Dam https://indico.cern.ch/event/472106/   Thursday, 4 February 2016 from 10.30 a.m. to 12.30 p.m in the Filtration Plant (Building 222-R-001) FCC 5: FCC Hadron Collider Design by Daniel Schulte FCC 6: FCC Lepton Collider Design by Frank Zimmermann https://indico...

  5. Phase diagram of power law and Lennard-Jones systems: Crystal phases

    International Nuclear Information System (INIS)

    Travesset, Alex

    2014-01-01

    An extensive characterization of the low temperature phase diagram of particles interacting with power law or Lennard-Jones potentials is provided from Lattice Dynamical Theory. For power law systems, only two lattice structures are stable for certain values of the exponent (or softness) (A15, body centered cube (bcc)) and two more (face centered cubic (fcc), hexagonal close packed (hcp)) are always stable. Among them, only the fcc and bcc are equilibrium states. For Lennard-Jones systems, the equilibrium states are either hcp or fcc, with a coexistence curve in pressure and temperature that shows reentrant behavior. The hcp solid never coexists with the liquid. In all cases analyzed, for both power law and Lennard-Jones potentials, the fcc crystal has higher entropy than the hcp. The role of anharmonic terms is thoroughly analyzed and a general thermodynamic integration to account for them is proposed

  6. Pivotal ERIVANCE basal cell carcinoma (BCC) study: 12-month update of efficacy and safety of vismodegib in advanced BCC.

    Science.gov (United States)

    Sekulic, Aleksandar; Migden, Michael R; Lewis, Karl; Hainsworth, John D; Solomon, James A; Yoo, Simon; Arron, Sarah T; Friedlander, Philip A; Marmur, Ellen; Rudin, Charles M; Chang, Anne Lynn S; Dirix, Luc; Hou, Jeannie; Yue, Huibin; Hauschild, Axel

    2015-06-01

    Primary analysis from the pivotal ERIVANCE BCC study resulted in approval of vismodegib, a Hedgehog pathway inhibitor indicated for treatment of adults with metastatic or locally advanced basal cell carcinoma (BCC) that has recurred after surgery or for patients who are not candidates for surgery or radiation. An efficacy and safety analysis was conducted 12 months after primary analysis. This was a multinational, multicenter, nonrandomized, 2-cohort study in patients with measurable and histologically confirmed locally advanced or metastatic BCC taking oral vismodegib (150 mg/d). Primary outcome measure was objective response rate (complete and partial responses) assessed by independent review facility. After 12 months of additional follow-up, median duration of exposure to vismodegib was 12.9 months. Objective response rate increased from 30.3% to 33.3% in patients with metastatic disease, and from 42.9% to 47.6% in patients with the locally advanced form. Median duration of response in patients with locally advanced BCC increased from 7.6 to 9.5 months. No new safety signals emerged with extended treatment duration. Limitations include low prevalence of advanced BCC and challenges of designing a study with heterogenous manifestations. The 12-month update of the study confirms the efficacy and safety of vismodegib in management of advanced BCC. Copyright © 2015 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.

  7. Regeneration of Hydrotreating and FCC Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    CM Wai; JG Frye; JL Fulton; LE Bowman; LJ Silva; MA Gerber

    1999-09-30

    Hydrotreating, hydrocracking, and fluid catalytic cracking (FCC) catalysts are important components of petroleum refining processes. Hydrotreating and hydrocracking catalysts are used to improve the yield of high-quality light oil fractions from heavier crude oil and petroleum feedstocks containing high levels of impurities. FCC catalysts improve the yield of higher octane gasoline from crude oil. Residuum hydrotreating and cracking catalysts are susceptible to irreversible deactivation caused by adsorption of sulfur and by metals impurities, such as vanadium and nickel. The gradual buildup of these impurities in a hydrotreating catalyst eventually plugs the pores and deactivates it. Nickel and vanadium adversely affect the behavior of cracking catalysts, reducing product yield and quality. Replacing deactivated catalysts represents a significant cost in petroleum refining. Equally important are the costs and potential liabilities associated with treating and disposing spent catalysts. For example, recent US Environmental Protection Agency rulings have listed spent hydrotreating and hydrorefining catalysts as hazardous wastes. FCC catalysts, though more easily disposed of as road-base or as filler in asphalt and cement, are still an economic concern mainly because of the large volumes of spent catalysts generated. New processes are being considered to increase the useful life of catalysts or for meeting more stringent disposal requirements for spent catalysts containing metals. This report discusses a collaborative effort between Pacific Northwest National Laboratory (PNNL) and Phillips Petroleum, Inc., to identify promising chemical processes for removing metals adhered to spent hydrodesulfurization (HDS, a type of hydrotreating catalyst) and FCC catalysts. This study, conducted by PNNL, was funded by the US Department of Energy's Bartlesville Project Office. Fresh and spent catalysts were provided by Phillips Petroleum. The FCC catalyst was a rare

  8. Physics case of FCC-ee

    CERN Document Server

    d'Enterria, David

    2016-01-01

    The physics case for electron-positron beams at the Future Circular Collider (FCC-ee) is succinctly summarized. The FCC-ee core program involves $e^+e^-$ collisions at $\\sqrt{s}$ = 90, 160, 240, and 350 GeV with multi-ab$^{-1}$ integrated luminosities, yielding about 10$^{12}$ Z bosons, 10$^{8}$ W$^+$W$^-$ pairs, 10$^{6}$ Higgs bosons and 4$\\cdot$10$^{5}$ $t\\bar{t}$ pairs per year. The huge luminosities combined with $\\cal{100}$ keV knowledge of the c.m. energy will allow for Standard Model studies at unrivaled precision. Indirect constraints on new physics can thereby be placed up to scales $\\Lambda_{_{\\rm NP}} \\approx$ 7 and 100 TeV for particles coupling respectively to the Higgs and electroweak bosons.

  9. Electrical Power Budget for FCC-ee

    CERN Document Server

    Aull, S.; Bozzini, D.; Brunner, O.; Burnet, J.-P.; Butterworth, A.; Calaga, R.; Jensen, E.; Mertens, V.; Milanese, A.; Nonis, M.; Oide, K.; Schwerg, N.; Tavian, L.; Wenninger, J.; Zimmermann, F.; Rinolfi, L; Blondel, A.; Koratzinos, M.; Gorgi Zadeh, S.

    2016-01-01

    We present a first rough estimate for the electrical power consumption of the FCC-ee lepton collider. This electrical power is dominated by the RF system, which provides the motivation for the ongoing R&D on highly efficient RF power sources. Other contributions come from the warm arc magnets, the cryogenics systems, cooling, ventilation, general services, the particle-physics detectors, and the injector complex.

  10. Defect accumulation behaviour in hcp metals and alloys

    International Nuclear Information System (INIS)

    Woo, C.H.

    2000-01-01

    The effects of displacement damage on the physical and mechanical properties of metals and alloys, caused by the bombardment of energetic particles, have been investigated for several decades. Besides the obvious technical and industrial implications, an important motive of such investigations is to understand the factors that differentiate the response of different metals under different irradiation conditions. Recently, much interest is shown in the possible effects of the crystal lattice structure on variations in the damage accumulation behaviour of metals and alloys. In this paper we focus on the case of metals and alloys that crystallize in the hexagonal close pack (hcp) structure, and describe recent understanding of the damage production, accumulation and its consequences in these metals

  11. Phonon dispersion curves of fcc La

    International Nuclear Information System (INIS)

    Stassis, C.; Loong, C.; Zarestky, J.

    1982-01-01

    Large single crystals of fcc La were grown in situ and were used to study the lattice dynamics of this phase of La by coherent inelastic neutron scattering. The phonon dispersion curves have been measured along the [xi00], [xixi0], [xixixi], and [0xi1] symmetry directions at 660 and 1100 K. The T[xixixi] branch exhibits anomalous dispersion for xi>0.25 and, in addition, close to the zone boundary, the phonon frequencies of this branch decrease with decreasing temperature. This soft-mode behavior may be related to the #betta→α# transformation in La, an assumption supported by recent band-theoretical calculations of the generalized susceptibility of fcc La. At X the frequencies of the L[xi00] branch are considerably lower than those of the corresponding branch of #betta#-Ce; a similar but not as pronounced effect is observed for the frequencies of the L[xixixi] branch close to the point L. Since the calculated generalized susceptibility of fcc La exhibits strong peaks at X and L, these anomalies may be due to the renormalization of the phonon frequencies by virtual fbold-arrow-left-rightd transitions to the unoccupied 4f level in La. The data were used to evaluate the elastic constants, the phonon density of states, and the lattice specific heat at constant pressure C/sub P//sup

  12. FCC riser quick separation system: a review

    Directory of Open Access Journals (Sweden)

    Zhi Li

    2016-10-01

    Full Text Available Abstract The riser reactor is the key unit in the fluid catalytic cracking (FCC process. As the FCC feedstocks become heavier, the product mixture of oil, gas and catalysts must be separated immediately at the outlet of the riser to avoid excessive coking. The quick separation system is the core equipment in the FCC unit. China University of Petroleum (Beijing has developed many kinds of separation system including the fender-stripping cyclone and circulating-stripping cyclone systems, which can increase the separation efficiency and reduce the pressure drop remarkably. For the inner riser system, a vortex quick separation system has been developed. It contains a vortex quick separator and an isolated shell. In order to reduce the separation time, a new type of separator called the short residence time separator system was developed. It can further reduce the separation time to less than 1 s. In this paper, the corresponding design principles, structure and industrial application of these different kinds of separation systems are reviewed. A system that can simultaneously realize quick oil gas separation, quick oil gas extraction and quick pre-stripping of catalysts at the end of the riser is the trend in the future.

  13. Beam Dynamics Challenges for FCC-ee

    CERN Document Server

    AUTHOR|(SzGeCERN)442987; Benedikt, Michael; Oide, Katsunobu; Bogomyagkov, Anton; Levichev, Evgeny; Migliorati, Mauro; Wienands, Uli

    2015-01-01

    The goals of FCC-ee include reaching luminosities of up to a few 1036 cm-2s-1 per interaction point at the Z pole or some 1034 cm-2s-1 at the ZH production peak, and pushing the beam energy up to ≥175 GeV, in a ring of 100 km circumference, with a total synchrotron-radiation power not exceeding 100 MW. A parameter baseline as well as high-luminosity crab-waist options were described in [1] and [2], respectively. The extremely high luminosity and resulting short beam lifetime (due to radiative Bhabha scattering) are sustained by top-up injection. The FCC-ee design status and typical beam parameters for different modes of operation are reported in [3]. One distinct feature of the FCC-ee design is its conception as a double ring, with separate beam pipes for the two counter-rotating (electron and positron) beams, resembling, in this aspect, the high-luminosity B factories PEP-II, KEKB and SuperKEKB as well as the LHC. The two separate rings do not only permit operation with a large number of bunches, up to a f...

  14. Volumes of virtual modifications and virtual polymorphous transformations in transition metals under pressure

    International Nuclear Information System (INIS)

    Zil'bershtejn, V.A.; Zaretskij, L.B.; Ehstrin, Eh.I.

    1975-01-01

    To find out what phases are likely to occur under pressure, it is necessary to know the relative density of various modifications, that is the ratio of the volumes of stable and virtual modifications and generally speaking the ratio of the phase compressibility. If the virtual phase volume is less than the volume of the stable phase, then such a phase is likely to appear under pressure. A method has been developed for computing the volumes of the virtual modifications from the data on the solid solutions lattice parameters. Testing the applicability of the method for a number of systems with a complete mutual solubility has shown, that the method proposed permits to estimate the volumes of the transition metals virtual modifications with the error probably not exceeding 1%. The analysis was made of the data available on the solid solutions of transition metals with fcc-, bcc- and hcp-lattices. The virtual volumes have been computed for hcp-iridium, hcp-rhodium, hcp-molybdenum, fcc-molybdenum, fcc-chromium, bcc-rhenium, bcc-ruthenium and bcc-technetium. The data obtained on the virtual modifications volumes permit to assume that the pressure increase is likely to result in the phase transformations of fcc-hcp in iridium and rhodium, and bcc-hcp in molybdenum, while evidently the transformations of bcc-fcc in molybdenum and chromium, hcp-bcc in technetium, rhenium and ruthenium are impossible. The pressure resulting in the transformations in the metals investigated equals approximately hundreds of kbar, or even approximately 1 Mbar for Ir

  15. Equation of state and thermodynamic properties of BCC metals

    Directory of Open Access Journals (Sweden)

    Vu Van Hung, N.T. Hoa

    2017-10-01

    Full Text Available The moment method in statistical dynamics is used to study the equation of state and thermodynamic properties of the bcc metals taking into account the anharmonicity effects of the lattice vibrations and hydrostatic pressures. The explicit expressions of the lattice constant, thermal expansion  oefficient, and the specific heats of the bcc metals are derived within the fourth order moment approximation. The termodynamic quantities of W, Nb, Fe,and Ta metals are calculated as a function of the pressure, and they are in good agreement with the corresponding results obtained from the first principles calculations and experimental results. The effective pair potentials work well for the calculations of bcc metals.

  16. Ultrahigh pressure deformation of polycrystaline hcp-cobalt

    Science.gov (United States)

    Merkel, S.; Antonangeli, D.; Fiquet, G.; Yagi, T.

    2003-12-01

    During the past few years, a novel set of methods has been developed allowing direct measurements on elasticity and rheology under static ultrahigh pressures using synchrotron x-ray diffraction and the diamond anvil cell. In particular, the analysis on the development of texture and uniaxial stress in a polycrystalline sample under ultrahigh pressure and non-hydrostatic conditions yielded to very interesting results on the microscopic deformation mechanisms and strength of MgO, silicate perovskite or ɛ -Fe [eg. Merkel et al. 2002, Merkel et al. 2003]. However, our understanding of the properties of the ɛ phase of iron remains poor. There are considerable uncertainties and disagreement on the results of various experiments or first-principles calculations. In particular, the results of the radial diffraction measurement on ɛ -Fe [Mao et al. 1998] have been highly controversial. In order to address this issue, we performed investigations on polycrystalline hcp-cobalt. Its properties such as the bulk modulus and thermal expansion are very close to those of ɛ -Fe and it is readily available under ambient conditions. Thus, it is a well known material and results from the high pressure radial diffraction experiments can be compared with those from well-established techniques. In the present analysis, we performed a new set a measurements between 0 and 20 GPa under ambient temperature conditions at the ESRF synchrotron source using amorphous boron gasket, monochromatic x-ray beam, and imaging plate techniques. From such an experiment, we are able to extract information on non-hydrostatic stress, elasticity, and preferred orientations of the sample in-situ under high pressure and compare them with results obtained previously on ɛ -Fe. Documenting the evolution of stress, elasticity and texture in hcp metals is of great interest for our understanding of the bulk properties and seismic anisotropy of the Earth's inner core. S. Merkel et al., J. Geophys. Res. 107 (2002

  17. Improving the Accuracy of a Heliocentric Potential (HCP Prediction Model for the Aviation Radiation Dose

    Directory of Open Access Journals (Sweden)

    Junga Hwang

    2016-12-01

    Full Text Available The space radiation dose over air routes including polar routes should be carefully considered, especially when space weather shows sudden disturbances such as coronal mass ejections (CMEs, flares, and accompanying solar energetic particle events. We recently established a heliocentric potential (HCP prediction model for real-time operation of the CARI-6 and CARI-6M programs. Specifically, the HCP value is used as a critical input value in the CARI-6/6M programs, which estimate the aviation route dose based on the effective dose rate. The CARI-6/6M approach is the most widely used technique, and the programs can be obtained from the U.S. Federal Aviation Administration (FAA. However, HCP values are given at a one month delay on the FAA official webpage, which makes it difficult to obtain real-time information on the aviation route dose. In order to overcome this critical limitation regarding the time delay for space weather customers, we developed a HCP prediction model based on sunspot number variations (Hwang et al. 2015. In this paper, we focus on improvements to our HCP prediction model and update it with neutron monitoring data. We found that the most accurate method to derive the HCP value involves (1 real-time daily sunspot assessments, (2 predictions of the daily HCP by our prediction algorithm, and (3 calculations of the resultant daily effective dose rate. Additionally, we also derived the HCP prediction algorithm in this paper by using ground neutron counts. With the compensation stemming from the use of ground neutron count data, the newly developed HCP prediction model was improved.

  18. Application of Zeolitic Additives in the Fluid Catalytic Cracking (FCC

    Directory of Open Access Journals (Sweden)

    A. Nemati Kharat

    2013-06-01

    Full Text Available Current article describes application of zeolites in fluid catalytic cracking (FCC. The use of several zeolitic additives for the production light olefins and reduction of pollutants is described. Application of zeolites as fluid catalytic cracking (FCC catalysts and additives due to the presence of active acid sites in the zeolite framework  increase the formation of desired cracking products (i.e., olefin and branched products  in the FCC unit.

  19. The FCC-ee study: Progress and challenges

    OpenAIRE

    Koratzinos, Michael; Aumon, Sandra; Bogomyagkov, Anton; Boscolo, Manuela; Cook, Charlie; Doblhammer, Andreas; Härer, Bastian; Tomás, Rogelio; Levichev, Evgeny; Medina Medrano, Luis; Shatilov, Dmitry; Wienands, Ulrich; Zimmermann, Frank

    2015-01-01

    The FCC (Future Circular Collider) study represents a vision for the next large project in high energy physics, comprising an 80-100 km tunnel that can house a future 100 TeV hadron collider. The study also includes a high luminosity e+e- collider operating in the centre-of-mass energy range of 90-350 GeV as a possible intermediate step, the FCC-ee. The FCC-ee aims at definitive electro-weak precision measurements of the Z, W, H and top particles, and search for rare phenomena. Although FCC-e...

  20. Study of Collective Effects in the FCC-ee Collider

    OpenAIRE

    Zobov, Mikhail; Belli, Eleonora; Castorina, Giovanni; Migliorati, Mauro; Persichelli, Serena; Rumolo, Giovanni; Spataro, Bruno

    2018-01-01

    The Future Circular Collider (FCC) study aims at designing different options of a post-LHC collider. The high luminosity electron-positron collider FCC-ee based on the crab waist concept is considered as an intermediate step on the way towards FCC-hh, a 100 TeV hadron collider using the same tunnel of about 100 km. Due to a high intensity of circulating beams the impact of collective effects on FCC-ee performance has to be carefully analyzed. In this paper we evaluate beam coupling impedance ...

  1. PURIFIED WASTE FCC CATALYST AS A CEMENT REPLACEMENT MATERIAL

    Directory of Open Access Journals (Sweden)

    Danute Vaiciukyniene

    2015-06-01

    Full Text Available Zeolites are commonly used in the fluid catalytic cracking process. Zeolite polluted with oil products and became waste after some time used. The quantity of this waste inevitably rises by expanding rapidly oil industry. The composition of these catalysts depends on the manufacturer and on the process that is going to be used. The main factors retarding hydration process of cement systems and modifying them strength are organic compounds impurities in the waste FCC catalyst. The present paper shows the results of using purified waste FCC catalyst (pFCC from Lithuania oil refinery, as Portland cement replacement material. For this purpose, the purification of waste FCC catalyst (FCC samples was treated with hydrogen peroxide. Hydrogen peroxide (H2O2 is one of the most powerful oxidizers known. By acting of waste with H2O2 it can eliminate the aforementioned waste deficiency, and the obtained product becomes one of the most promising ingredients, in new advanced building materials. Hardened cement paste samples with FCC or pFCC were formed. It was observed that the pFCC blended cements developed higher strength, after 28 days, compared to the samples with FCC or reference samples. Typical content of Portland cement substituting does not exceed 30 % of mass of Portland cement in samples. Reducing the consumption of Portland cement with utilizing waste materials is preferred for reasons of environmental protection.

  2. Shear instabilities in perfect bcc crystals during simulated tensile tests

    Czech Academy of Sciences Publication Activity Database

    Černý, M.; Šesták, P.; Pokluda, J.; Šob, Mojmír

    2013-01-01

    Roč. 87, č. 1 (2013), 014117/1-014117/4 ISSN 1098-0121 R&D Projects: GA ČR(CZ) GAP108/12/0311 Institutional support: RVO:68081723 Keywords : instabilities * tensile test * bcc metals * ab initio calculations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.664, year: 2013

  3. Ground state searches in fcc intermetallics

    International Nuclear Information System (INIS)

    Wolverton, C.; de Fontaine, D.; Ceder, G.; Dreysse, H.

    1991-12-01

    A cluster expansion is used to predict the fcc ground states, i.e., the stable phases at zero Kelvin as a function of composition, for alloy systems. The intermetallic structures are not assumed, but derived regorously by minimizing the configurational energy subject to linear constraints. This ground state search includes pair and multiplet interactions which spatially extend to fourth nearest neighbor. A large number of these concentration-independent interactions are computed by the method of direct configurational averaging using a linearized-muffin-tin orbital Hamiltonian cast into tight binding form (TB-LMTO). The interactions, derived without the use of any adjustable or experimentally obtained parameters, are compared to those calculated via the generalized perturbation method extention of the coherent potential approximation within the context of a KKR Hamiltonian (KKR-CPA-GPM). Agreement with the KKR-CPA-GPM results is quite excellent, as is the comparison of the ground state results with the fcc-based portions of the experimentally-determined phase diagrams under consideration

  4. Neutron Scattering from fcc Pr and Pr3Tl

    DEFF Research Database (Denmark)

    Birgeneau, R. J.; Als-Nielsen, Jens Aage; Bucher, E.

    1972-01-01

    Elastic-neutron-scattering measurements on the singlet-ground-state ferromagnets fcc Pr and Pr3 Tl are reported. Both exhibit magnetic phase transitions, possibly to a simple ferromagnetic state at 20 and 11.6 °K, respectively. The transitions appear to be of second order although that in fcc Pr...

  5. Dislocation Structure and Mobility in Hcp Rare-Gas Solids: Quantum versus Classical

    Directory of Open Access Journals (Sweden)

    Santiago Sempere

    2018-01-01

    Full Text Available We study the structural and mobility properties of edge dislocations in rare-gas crystals with the hexagonal close-packed (hcp structure by using classical simulation techniques. Our results are discussed in the light of recent experimental and theoretical studies on hcp 4 He, an archetypal quantum crystal. According to our simulations classical hcp rare-gas crystals present a strong tendency towards dislocation dissociation into Shockley partials in the basal plane, similarly to what is observed in solid helium. This is due to the presence of a low-energy metastable stacking fault, of the order of 0.1 mJ/m 2 , that can get further reduced by quantum nuclear effects. We compute the minimum shear stress that induces glide of dislocations within the hcp basal plane at zero temperature, namely, the Peierls stress, and find a characteristic value of the order of 1 MPa. This threshold value is similar to the Peierls stress reported for metallic hcp solids (Zr and Cd but orders of magnitude larger than the one estimated for solid helium. We find, however, that in contrast to classical hcp metals but in analogy to solid helium, glide of edge dislocations can be thermally activated at very low temperatures, T∼10 K, in the absence of any applied shear stress.

  6. Electronic structure of metastable bcc Cu–Cr alloy thin films: Comparison of electron energy-loss spectroscopy and first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Liebscher, C.H.; Freysoldt, C. [Max-Planck-Institut für Eisenforschung GmbH, 40237 Düsseldorf (Germany); Dennenwaldt, T. [Institute of Condensed Matter Physics and Interdisciplinary Center for Electron Microscopy, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne (Switzerland); Harzer, T.P.; Dehm, G. [Max-Planck-Institut für Eisenforschung GmbH, 40237 Düsseldorf (Germany)

    2017-07-15

    Metastable Cu–Cr alloy thin films with nominal thickness of 300 nm and composition of Cu{sub 67}Cr{sub 33} (at%) are obtained by co-evaporation using molecular beam epitaxy. The microstructure, chemical phase separation and electronic structure are investigated by transmission electron microscopy (TEM). The thin film adopts the body-centered cubic crystal structure and consists of columnar grains with ~50 nm diameter. Aberration-corrected scanning TEM in combination with energy dispersive X-ray spectroscopy confirms compositional fluctuations within the grains. Cu- and Cr-rich domains with composition of Cu{sub 85}Cr{sub 15} (at%) and Cu{sub 42}Cr{sub 58} (at%) and domain size of 1–5 nm are observed. The alignment of the interface between the Cu- and Cr-rich domains shows a preference for {110}-type habit plane. The electronic structure of the Cu–Cr thin films is investigated by electron energy loss spectroscopy (EELS) and is contrasted to an fcc-Cu reference sample. The experimental EEL spectra are compared to spectra computed by density functional theory. The main differences between bcc-and fcc-Cu are related to differences in van Hove singularities in the electron density of states. In Cu–Cr solid solutions with bcc crystal structure a single peak after the L{sub 3}-edge, corresponding to a van Hove singularity at the N-point of the first Brillouin zone is observed. Spectra computed for pure bcc-Cu and random Cu–Cr solid solutions with 10 at% Cr confirm the experimental observations. The calculated spectrum for a perfect Cu{sub 50}Cr{sub 50} (at%) random structure shows a shift in the van Hove singularity towards higher energy by developing a Cu–Cr d-band that lies between the delocalized d-bands of Cu and Cr. - Highlights: • Compositional fluctuations on the order of 1–5 nm in Cu- and Cr-rich domains are observed. • EELS determines a single van Hove singularity for bcc Cu–Cr solid solutions. • The electronic structure is dominated by d

  7. Recovery of Frenkel defects in fcc metals

    International Nuclear Information System (INIS)

    Chaplin, R.L.; Miller, M.G.

    1976-01-01

    Because of the production of Frenkel defects occurs most readily along specific crystallographic directions in fcc structures, the recovery mechanism by which annihilation occurs should also be related to the same crystallographic orientations. The recovery path of a diffusing interstitial requires the formation of a temporary metastable state as a close-pair Frenkel defect prior to annihilation. A theoretical treatment of this scheme for interstitial-vacancy recombination shows that during the Isub(D) diffusion there is an experimentally measurable difference if the recovery forms a Isub(B) or a Isub(C) close-pair configuration in aluminum. Experimental results are given which show a difference from the theoretical predictions, and it is concluded that the assumed analytical function describing the interstitial-vacancy distribution created by a 0.4 MeV electron irradiation should be modified. (author)

  8. Precision measurements of the top quark couplings at the FCC

    CERN Document Server

    AUTHOR|(CDS)2051271

    2015-01-01

    The design study of the Future Circular Colliders (FCC) in a 100-km ring in the Geneva area has started at CERN at the beginning of 2014, as an option for post-LHC particle accelerators. The study has an emphasis on proton-proton and electron-positron high-energy frontier machines. In the current plans, the first step of the FCC physics programme would exploit a high-luminosity e+e- collider called FCC-ee, with centre-of-mass energies ranging from below the Z pole to the t-tbar threshold and beyond, followed by 100\\,TeV proton-proton collisions as ultimate goal. When combined, these two steps offer a large palette of complementary measurements and sensitivity for new physics. In particular, the association of the FCC-ee and the FCC-hh allows measurements of the top-quark electroweak and Yukawa couplings to be performed with unrivaled precision.

  9. Magnetism of CrO overlayers on Fe(001)bcc surface: first principles calculations

    Science.gov (United States)

    Félix-Medina, Raúl Enrique; Leyva-Lucero, Manuel Andrés; Meza-Aguilar, Salvador; Demangeat, Claude

    2018-04-01

    Riva et al. [Surf. Sci. 621, 55 (2014)] as well as Calloni et al. [J. Phys.: Condens. Matter 26, 445001 (2014)] have studied the oxydation of Cr films deposited on Fe(001)bcc through low-energy electron diffraction, Auger electron spectroscopy and scanning tunneling microscopy. In the present work we perform a density functional approach within Quantum Expresso code in order to study structural and magnetic properties of CrO overlayers on Fe(001)bcc. The calculations are performed using DFT+U. The investigated systems include O/Cr/Fe(001)bcc, Cr/O/Fe(001)bcc, Cr0.25O0.75/Fe(001)bcc, as well as the O coverage Ox/Cr/Fe(001)bcc (x = 0.25; 0.50). We have found that the ordered CrO overlayer presents an antiferromagnetic coupling between Cr and Fe atoms. The O atoms are located closer to the Fe atoms of the surface than the Cr atoms. The ground state of the systems O/Cr/Fe(001)bcc and Cr/O/Fe(001)bcc corresponds to the O/Cr/Fe(001)bcc system with a magnetic coupling c(2 × 2). The effect of the O monolayer on Cr/Fe(001)bcc changes the ground state from p(1 × 1) ↓ to c(2 × 2) and produces an enhancement of the magnetic moments. The Ox overlayer on Cr/Fe(001)bcc produces an enhancement of the Cr magnetic moments.

  10. Agglomeration Versus Localization Of Hydrogen In BCC Fe Vacancies

    International Nuclear Information System (INIS)

    Simonetti, S.; Juan, A.; Brizuela, G.; Simonetti, S.

    2006-01-01

    Severe embrittlement can be produced in many metals by small amounts of hydrogen. The interactions of hydrogen with lattice imperfections are important and often dominant in determining the influence of this impurity on the properties of solids. The interaction between four-hydrogen atoms and a BCC Fe structure having a vacancy has been studied using a cluster model and a semiempirical method. For a study of sequential absorption, the hydrogen atoms were positioned in their energy minima configurations, near to the tetrahedral sites neighbouring the vacancy. VH 2 and VH 3 complexes are energetically the most stables in BCC Fe. The studies about the stability of the hydrogen agglomeration gave as a result that the accumulation is unfavourable in complex vacancy-hydrogen with more than three atoms of hydrogen. (authors)

  11. FCC-ee Physics workshop | 19-21 June 2014

    CERN Multimedia

    2014-01-01

    The 7th FCC-ee/TLEP workshop, the first after the FCC kick-off in February 2014, will be focused on physics and experiments.     It will take place on 19-21 June at CERN in the TH auditorium. The registration is open and the agenda is available on the indico web page: http://indico.cern.ch/event/313708/. You are all cordially invited to attend! This will be the first in a series of workshops that will lead us to the first FCC-ee physics milestone, a document defining the physics landscape and study plans, required for March 2015. More information can be found here. FCC-ee is a high-luminosity Z, W, Higgs and top factory, to be hosted in a 100km tunnel, possibly as the first step towards a 100 TeV pp collider FCC-hh. These two machines are being studied within the FCC design study. High precision, high statistics and a clean environment are the tools available in FCC-ee to shed light on the unknown physics that underlies present mysteries: dark matter, the baryon asymmetry of th...

  12. 9th FCC-ee (TLEP) Physics Workshop

    CERN Document Server

    2015-01-01

    This is the 9th in the series of FCCee/TLEP-related workshops. It follows on from the sucessful 8th TLEP workshop that took place in Paris on 27-29 October 2014, and the FCC kick-off meeting held on 12-15 February 2014 at University of Geneva. The workshop is open to all FCC-ee /TLEP design study members, and more generally to all interested in a precision Z, W, H, top factory. The focus will be on physics and experiments at the FCC-ee, but a more general session is organized the first day (Tuesday 3 February afternoon) with presentations about the FCC design study as a whole, and on machine and physics for the FCC-ee and the FCC-hh, with synergies and complementarities. This session is aimed at a larger audience, towards improving the project visibility in Italy. It will be followed by a social dinner in the evening. The workshop starts on Tuesday at 13:30 and ends on Thursday 16:00. Registration is now open, please proceed at your earliest convenience! Please visit the FCC-ee / TLEP web site, and subscrib...

  13. The Hexagonal Close-Packed (HCP) a double dagger dagger Face-Centered Cubic (FCC) Transition in Co-Re-Based Experimental Alloys Investigated by Neutron Scattering

    Czech Academy of Sciences Publication Activity Database

    Mukherji, D.; Strunz, Pavel; Piegert, S.; Gilles, R.; Hofmann, M.; Holzel, M.; Rösler, J.

    43A, č. 6 (2012), s. 1834-1844 ISSN 1073-5623 R&D Projects: GA MPO FR-TI1/378 Institutional research plan: CEZ:AV0Z10480505 Keywords : Co-base alloy * neutron diffraction * electron microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.627, year: 2012

  14. Vibration mitigation by the reversible fcc/hcp martensitic transformation during cyclic tension-compression loading of an Fe-Mn-Si-based shape memory alloy

    International Nuclear Information System (INIS)

    Sawaguchi, Takahiro; Sahu, Puspendu; Kikuchi, Takehiko; Ogawa, Kazuyuki; Kajiwara, Setsuo; Kushibe, Atsumichi; Higashino, Masahiko; Ogawa, Takatoshi

    2006-01-01

    The present work concerns the damping behavior of an Fe-28Mn-6Si-5Cr-0.5NbC (mass%) shape memory alloy determined by low cycle fatigue tests, and the corresponding deformation mechanism under cyclic tension-compression loading. The specific damping capacity increases with increasing strain amplitude and reaches saturation at ∼80%, above the strain amplitude of 0.4%. Quantitative X-ray diffraction analyses and microstructural observations using atomic force microscopy revealed that a significant amount of the tensile stress-induced ε martensite is reversely transformed into the austenite by subsequent compression; in other words, the stress-induced 'reverse' martensitic transformation takes place in the alloy

  15. IR Laser-induced Ablation of Ag in Dielectric Breakdown of Gaseous Hydrocarbons: Simultaneous Occurrence of Metastable HCP and Stable FCC Ag Nanostructures in C:H Shell

    Czech Academy of Sciences Publication Activity Database

    Urbanová, Markéta; Pokorná, Dana; Bakardjieva, Snejana; Šubrt, Jan; Bastl, Zdeněk; Bezdička, Petr; Pola, Josef

    2010-01-01

    Roč. 213, 2-3 (2010), s. 114-122 ISSN 1010-6030 R&D Projects: GA AV ČR IAA400720619; GA MŠk LC523 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z40320502; CEZ:AV0Z40400503 Keywords : ir laser * dielectric breakdown * ablation Subject RIV: CH - Nuclear ; Quantum Chemistry Impact factor: 2.243, year: 2010

  16. Ab initio calculations of mechanical properties of bcc W-Re-Os random alloys: effects of transmutation of W.

    Science.gov (United States)

    Li, Xiaojie; Schönecker, Stephan; Li, Ruihuan; Li, Xiaoqing; Wang, Yuanyuan; Zhao, Jijun; Johansson, Börje; Vitos, Levente

    2016-06-03

    To examine the effect of neutron transmutation on tungsten as the first wall material of fusion reactors, the elastic properties of W 1-x-y  Re x  Os y (0  ⩽  x, y  ⩽  6%) random alloys in body centered cubic (bcc) structure are investigated systematically using the all-electron exact muffin-tin orbitals (EMTO) method in combination with the coherent-potential approximation (CPA). The calculated lattice constant and elastic properties of pure W are consistent with available experiments. Both Os and Re additions reduce the lattice constant and increase the bulk modulus of W, with Os having the stronger effect. The polycrystalline shear modulus, Young's modulus and the Debye temperature increase (decrease) with the addition of Re (Os). Except for C 11 , the other elastic parameters including C 12 , C 44 , Cauchy pressure, Poisson ratio, B/G, increase as a function of Re and Os concentration. The variations of the latter three parameters and the trend in the ratio of cleavage energy to shear modulus for the most dominant slip system indicate that the ductility of the alloy enhances with increasing Re and Os content. The calculated elastic anisotropy of bcc W slightly increases with the concentration of both alloying elements. The estimated melting temperatures of the W-Re-Os alloy suggest that Re or Os addition will reduce the melting temperature of pure W solid. The classical Labusch-Nabarro model for solid-solution hardening predicts larger strengthening effects in W 1-y  Os y than in W 1-x  Re x . A strong correlation between C' and the fcc-bcc structural energy difference for W 1-x-y  Re x  Os y is revealed demonstrating that canonical band structure dictates the alloying effect on C'. The structural energy difference is exploited to estimate the alloying effect on the ideal tensile strength in the [0 0 1] direction.

  17. The FCC-ee study: Progress and challenges

    CERN Document Server

    Koratzinos, Michael; Bogomyagkov, Anton; Boscolo, Manuela; Cook, Charlie; Doblhammer, Andreas; Härer, Bastian; Tomás, Rogelio; Levichev, Evgeny; Medina Medrano, Luis; Shatilov, Dmitry; Wienands, Ulrich; Zimmermann, Frank

    The FCC (Future Circular Collider) study represents a vision for the next large project in high energy physics, comprising an 80-100 km tunnel that can house a future 100 TeV hadron collider. The study also includes a high luminosity e+e- collider operating in the centre-of-mass energy range of 90-350 GeV as a possible intermediate step, the FCC-ee. The FCC-ee aims at definitive electro-weak precision measurements of the Z, W, H and top particles, and search for rare phenomena. Although FCC-ee is based on known technology, the goal performance in luminosity and energy calibration make it quite challenging. During 2014 the study went through an exploration phase. The study has now entered its second year and the aim is to produce a conceptual design report during the next three to four years. We here report on progress since the last IPAC conference.

  18. Calculation of the electronic and magnetic structures of 3d impurities in the Hcp Fe matrix

    International Nuclear Information System (INIS)

    Franca, Fernando

    1995-01-01

    In this work we investigate the local magnetic properties and the electronic structure of HCP Fe, as well introducing transition metals atoms 3d (Cs, Ti, Cr, Mn, Co, Ni, Cu, Zn) in HCP iron matrix. We employed the discrete variational method (DVM), which is an orbital molecular method which incorporate the Hartree-Fock-Slater theory and the linear combination of atomic orbitals (LCAO), in the self-consistent charge approximation and the local density approximation of Von Barth and Hedin to the exchange-correlation potential. We used the embedded cluster model to investigate the electronic structure and the local magnetic properties for the central atom of a cluster of 27 atoms immersed in the microcrystal representing the HCP Fe. (author)

  19. Magnetic properties of cyclically deformed austenite

    Energy Technology Data Exchange (ETDEWEB)

    Das, Arpan, E-mail: dasarpan1@yahoo.co.in

    2014-06-01

    In meta-stable austenitic stainless steels, low cycle fatigue deformation is accompanied by a partial stress/strain-induced solid state phase transformation of paramagnetic γ(fcc) austenite phase to ferromagnetic α{sup /}(bcc) martensite. The measured characteristic of magnetic properties, which are the saturation magnetization, susceptibility, coercivity, retentivity, and the area under the magnetic hysteresis loop are sensitive to the total strain amplitude imposed and the corresponding material behaviour. The morphologies and nucleation characteristics of deformation induced martensites (i.e., ϵ(hcp), α{sup /}(bcc)) have been investigated through analytical transmission electron microscope. It has been observed that deformation induced martensites can nucleate at a number of sites (i.e., shear band intersections, isolated shear bands, shear band–grain boundary intersection, grain boundary triple points, etc.) through multiple transformation sequences: γ(fcc)→ϵ(hcp), γ(fcc)→ϵ(hcp)→α{sup /}(bcc), γ(fcc)→ deformation twin →α{sup /}(bcc) and γ(fcc)→α{sup /}(bcc). - Highlights: • LCF tests were done at various strain amplitudes of 304LNSS. • Quantification of martensite was done through ferritecope. • Magnetic properties were characterised through VSM. • Correlation of magnetic properties with the cyclic plastic response was done. • TEM was done to investigate the transformation micro-mechanisms.

  20. Mechanism and energetics of dislocation cross-slip in hcp metals

    Science.gov (United States)

    Wu, Zhaoxuan; Curtin, W. A.

    2016-10-01

    Hexagonal close-packed (hcp) metals such as Mg, Ti, and Zr are lightweight and/or durable metals with critical structural applications in the automotive (Mg), aerospace (Ti), and nuclear (Zr) industries. The hcp structure, however, brings significant complications in the mechanisms of plastic deformation, strengthening, and ductility, and these complications pose significant challenges in advancing the science and engineering of these metals. In hcp metals, generalized plasticity requires the activation of slip on pyramidal planes, but the structure, motion, and cross-slip of the associated dislocations are not well established even though they determine ductility and influence strengthening. Here, atomistic simulations in Mg reveal the unusual mechanism of dislocation cross-slip between pyramidal I and II planes, which occurs by cross-slip of the individual partial dislocations. The energy barrier is controlled by a fundamental step/jog energy and the near-core energy difference between pyramidal dislocations. The near-core energy difference can be changed by nonglide stresses, leading to tension-compression asymmetry and even a switch in absolute stability from one glide plane to the other, both features observed experimentally in Mg, Ti, and their alloys. The unique cross-slip mechanism is governed by common features of the generalized stacking fault energy surfaces of hcp pyramidal planes and is thus expected to be generic to all hcp metals. An analytical model is developed to predict the cross-slip barrier as a function of the near-core energy difference and applied stresses and quantifies the controlling features of cross-slip and pyramidal I/II stability across the family of hcp metals.

  1. Outline and Status of the FCC-ee Design Study

    CERN Document Server

    Zimmermann, Frank

    2015-01-01

    The Update of the European Strategy for Particle Physics in 2013 [1] declared as its second highest priority that “…to propose an ambitious post-LHC accelerator project….., CERN should undertake design studies for accelerator projects in a global context,…with emphasis on proton-proton and electron-positron high-energy frontier machines…”. In response to this request, the global Future Circular Collider (FCC) study is designing a 100-TeV proton collider (FCC-hh) in a new ~100 km tunnel near Geneva, a high-luminosity electron-positron collider (FCC-ee) as a potential intermediate step, and a lepton-hadron option (FCC-he). The FCC study comprises accelerators, technology, infrastructure, detector, physics, concepts for worldwide data services, international governance models, and implementation scenarios. The FCC study is mandated to deliver a Conceptual Design Report and preliminary cost estimate by the time of the next European Strategy Update expected for 2019. As of July 2015, 58 institutes from...

  2. Observation of mass flux through hcp 4He off the melting curve

    International Nuclear Information System (INIS)

    Ray, M W; Hallock, R B

    2009-01-01

    Solid hcp 4 He has been created off the melting curve using two growth techniques. In an effort to observe the flow of 4 He through the solid, rather than squeezing the solid directly, the experimental apparatus allows injection of 4 He atoms from superfluid in porous Vycor directly into the solid. We will describe the apparatus and our observations. Evidence for the transport of mass through a sample cell filled with hcp solid 4 He off the melting curve is found. The temperature and pressure dependence of this behavior will be presented.

  3. Importance of correlation effects in hcp iron revealed by a pressure-induced electronic topological transition.

    Science.gov (United States)

    Glazyrin, K; Pourovskii, L V; Dubrovinsky, L; Narygina, O; McCammon, C; Hewener, B; Schünemann, V; Wolny, J; Muffler, K; Chumakov, A I; Crichton, W; Hanfland, M; Prakapenka, V B; Tasnádi, F; Ekholm, M; Aichhorn, M; Vildosola, V; Ruban, A V; Katsnelson, M I; Abrikosov, I A

    2013-03-15

    We discover that hcp phases of Fe and Fe(0.9)Ni(0.1) undergo an electronic topological transition at pressures of about 40 GPa. This topological change of the Fermi surface manifests itself through anomalous behavior of the Debye sound velocity, c/a lattice parameter ratio, and Mössbauer center shift observed in our experiments. First-principles simulations within the dynamic mean field approach demonstrate that the transition is induced by many-electron effects. It is absent in one-electron calculations and represents a clear signature of correlation effects in hcp Fe.

  4. Electronic properties of iron impurity in hcp metals from Moessbauer studies

    International Nuclear Information System (INIS)

    Janot, C.; Delcroix, P.

    1975-01-01

    Moessbauer spectroscopy was used in quantitative investigating the electronic properties of iron impurities in hexagonal close-packed metals. Beryllium of the highest commercially obtainable purity containing about 300 ppm residual impurities was used as a host element. Experimental evidence is given for the existence of localized electronic states which have non-spherical distribution and obviously contribute especially to the electric field gradient. Iron impurity seems to retain the same electronic behaviour as long as the host hcp metal is a normal one (Mg, Cd, Zn), but the localized electronic states seem to disappear when the host is a transition hcp metal (Co, Ti, Sc, Zr, etc.). (Z.S.)

  5. Welding and joining of single crystals of BCC refractory metals

    International Nuclear Information System (INIS)

    Hiraoka, Yutaka; Fujii, Tadayuki

    1989-01-01

    Welding and joining is one of key technologies for the wider utilizations of a material. In the present work, the applicability of welding and joining for a single crystal of BCC refractory metal was investigated. Electron-beam welding and tungsten-inert-gas welding by a melt-run technique, and high-temperature brazing by using brazing metals such as Mo-40%Ru alloy, vanadium or platinum were conducted for molybdenum single crystal which had been prepared by means of secondary recrystallization. 12 refs.,12 figs., 2 tabs. (Author)

  6. Hydrogen storage in Ti-Mn-(FeV) BCC alloys

    International Nuclear Information System (INIS)

    Santos, S.F.; Huot, J.

    2009-01-01

    Recently, the replacement of vanadium by the less expensive (FeV) commercial alloy has been investigated in Ti-Cr-V BCC solid solutions and promising results were reported. In the present work, this approach of using (FeV) alloys is adopted to synthesize alloys of the Ti-Mn-V system. Compared to the V-containing alloys, the alloys containing (FeV) have a smaller hydrogen storage capacity but a larger reversible hydrogen storage capacity, which is caused by the increase of the plateau pressure of desorption. Correlations between the structure and the hydrogen storage properties of the alloys are also discussed.

  7. Strain ordering in BCC metals and the associated anelasticity

    International Nuclear Information System (INIS)

    Dattagupta, S.; Ranganathan, R.; Balakrishnan, R.

    1982-01-01

    The BCC to BCT transformation is thought to occur as a consequence of strain ordering due to the interaction between impurity interstitials. A Hamiltonian is given, which involves the interaction energies between the strain fields of the interstitials belonging to three distinct sublattices. In the BCT phase, one of the sublattices is preferentially occupied. The free energy of the system is calculated in the mean field approximation. In this, the BCC to BCT transformation is found to be a first-order transition at a temperature Tsub(p) that is proportional to the concentration of the interstitials and certain basic interaction parameters. The anelastic behaviour of the interacting interstitials is then studied in the region T > Tsub(p). From the anelastic strain, which is proportional to the order parameter associated with the phase transition, the static compliance is obtained. The latter obeys a Curie-Weiss type of law. The creep function, which determines the response to a constant applied stress, is found to exhibit viscous behaviour near Tsub(p). From the creep function, the frequency-dependent compliance and the internal friction are evaluated. The results predict a shift and a broadening of the internal friction peak as Tsub(p) is approached from above. The features show qualitative resemblance with the recent data on Ta-O. (author)

  8. Fission-neutron displacement cross sections in metals

    International Nuclear Information System (INIS)

    Takamura, Saburo; Aruga, Takeo; Nakata, Kiyotomo

    1985-01-01

    The sensitivity damage rates for 22 metals were measured after fission-spectrum neutron irradiation at low temperature and the experimental damage rates were compared with the theoretical calculation. The relation between the theoretical displacement cross section and the atomic weight of metals can be written by two curves; one is for fcc and hcp metals, and another is for bcc metals. On the other hand, the experimental displacement cross section versus atomic weight is shown approximately by a curve for both fcc and bcc metals, and the cross section for hcp metals deviates from the curve. The defect production efficiency is 0.3-0.4 for fcc metals and 0.6-0.8 for bcc metals. (orig.)

  9. Search for anisotropy in the Debye-Waller factor of HCP solid 4He

    Science.gov (United States)

    Barnes, Ashleigh L.; Hinde, Robert J.

    2016-02-01

    The properties of hexagonal close packed (hcp) solid 4He are dominated by large atomic zero point motions. An accurate description of these motions is therefore necessary in order to accurately calculate the properties of the system, such as the Debye-Waller (DW) factors. A recent neutron scattering experiment reported significant anisotropy in the in-plane and out-of-plane DW factors for hcp solid 4He at low temperatures, where thermal effects are negligible and only zero-point motions are expected to contribute. By contrast, no such anisotropy was observed either in earlier experiments or in path integral Monte Carlo (PIMC) simulations of solid hcp 4He. However, the earlier experiments and the PIMC simulations were both carried out at higher temperatures where thermal effects could be substantial. We seek to understand the cause of this discrepancy through variational quantum Monte Carlo simulations utilizing an accurate pair potential and a modified trial wavefunction which allows for anisotropy. Near the melting density, we find no anisotropy in an ideal hcp 4He crystal. A theoretical equation of state is derived from the calculated energies of the ideal crystal over a range of molar volumes from 7.88 to 21.3 cm3, and is found to be in good qualitative agreement with experimental data.

  10. Thermodynamics of dilute 3He-4He solid solutions with hcp structure

    Science.gov (United States)

    Chishko, K. A.

    2018-02-01

    To interpret the anomalies in heat capacity CV(T) and temperature-dependent pressure P(T) of solid hexagonal close-packed (hcp) 4He we exploit the model of hcp crystalline polytype with specific lattice degrees of freedom and describe the thermodynamics of impurity-free 4He solid as superposition of phononic and polytypic contributions. The hcp-based polytype is a stack of 2D basal atomic monolayers on triangular lattice packed with arbitrary long (up to infinity) spatial period along the hexagonal c axis perpendicular to the basal planes. It is a crystal with perfect ordering along the layers, but without microscopic translational symmetry in perpendicular direction (which remains, nevertheless, the rotational crystallographic axis of third order, so that the polytype can be considered as semidisordered system). Each atom of the hcp polytype has twelve crystallographic neighbors in both first and second coordination spheres at any arbitrary packing order. It is shown that the crystal of such structure behaves as anisotropic elastic medium with specific dispersion law of phonon excitations along c axis. The free energy and the heat capacity consist of two terms: one of them is a normal contribution [with CV(T) ˜ T3] from phonon excitations in an anisotropic lattice of hexagonal symmetry, and another term (an "excessive" heat) is a contribution resulted by packing entropy from quasi-one-dimensional system of 2D basal planes on triangular lattice stacked randomly along c axis without braking the closest pack between neighboring atomic layers. The excessive part of the free energy has been treated within 1D quasi-Ising (lattice gas) model using the transfer matrix approach. This model makes us possible to interpret successfully the thermodynamic anomaly (heat capacity peak in hcp 4He) observed experimentally.

  11. The role of edge dislocations in the deformation of BCC metals

    International Nuclear Information System (INIS)

    Lung, C.W.

    1994-08-01

    It was widely accepted that the screw dislocation is responsible for the strong temperature dependence of the yield stresses observed in bcc metals. In this paper, we show the role of edge dislocations in the deformation of bcc metals and point out that in some cases, its main contribution to the yield stress cannot be ignored. (author). 15 refs, 2 figs, 1 tab

  12. FCC catalyst technologies expand limits of process capability

    International Nuclear Information System (INIS)

    Leiby, S.

    1992-01-01

    This paper reports that over the past 30 or so years, many improvements in fluid catalytic cracking (FCC) operation have been achieved as the result of innovations in catalyst formulation. During the 1990s, new environmental regulations on issues such as reformulated gasoline will place new demands on both the refining industry and catalyst suppliers. An overview of cracking catalyst technology therefore seems in order. Today, high-technology innovations by catalyst manufacturers are rapid, but profit margins are slim. Catalyst formulations are shrouded in secrecy and probably depend almost as much on art as on science. Special formulations for specific cracking applications get the greatest emphasis today. To illustrate this point, OGJ's Worldwide Catalyst Report lists over 200 FCC catalyst designations. Catalysts containing components to enhance gasoline octane now account for about 70% of total U.S. FCC catalyst usage

  13. Nanosized f.c.c. thallium inclusions in aluminium

    International Nuclear Information System (INIS)

    Johnson, E.; Johansen, A.; Thoft, N.B.; Andersen, H.H.; Sarholt-Kristensen, L.

    1993-01-01

    Ion implantation of pure aluminium with thallium induces the formation of nanosized crystalline inclusions of thallium with a f.c.c. structure. The size of the inclusions depends on the implantation conditions and subsequent annealing treatments and is typically in the range from 1 to 10 nm. The inclusions are aligned topotactically with the aluminium matrix with a cube-cube orientation relationship and they have a truncated octahedral shape bounded by {111} and {001} planes. The lattice parameter of the f.c.c. thallium inclusions is 0.484 ± 0.002 nm, which is slightly but significantly larger than in the high-pressure f.c.c. thallium phase known to be stable above 3.8 GPa. (Author)

  14. Site occupation state of deuterium atoms in fcc Fe

    International Nuclear Information System (INIS)

    Aoki, Katsutoshi; Machida, Akihiko; Saitoh, Hiroyuki; Hattori, Takanori; Sano-Furukawa, Asami

    2015-01-01

    The deuterization process of fcc Fe to form solid-solution fcc FeD x was investigated by in situ neutron diffraction measurements at high temperature and high pressure. In a completely deuterized specimen at 988 K and 6.3 GPa, deuterium atoms occupy the octahedral and tetrahedral interstitial sites with an occupancy of 0.532(9) and 0.056(5), respectively, giving a deuterium composition x of 0.64(1). During deuterization, the metal-lattice expands approximately linearly with deuterium composition at a rate of 2.21 Å 3 per deuterium atom. The minor occupation of tetrahedral site is likely driven by the intersite movement of deuterium atoms along the <111> direction in the fcc metal lattice. These results provide implications for the light elements in the Earth's core and the mechanism of hydrogen embrittlement of ferrous metals. (author)

  15. Effects of temperature and void on the dynamics and microstructure of structural transition in single crystal iron

    Science.gov (United States)

    Shao, Jian-Li; Wang, Pei; Zhang, Feng-Guo; He, An-Min

    2018-06-01

    With classic molecular dynamics simulations, we investigate the effects of temperature and void on the bcc to hcp/fcc structural transition in single crystal iron driven by 1D ([0 0 1]) and 3D (uniform) compressions. The results show that the pressure threshold does not reduce monotonously with temperature. The pressure threshold firstly increases and then decreases in the range of 60–360 K under 1D compression, while the variation trend is just opposite under 3D compression. As expected, the initial defect may lower the pressure threshold via heterogenous nucleation. This effect is found to be more distinct at lower temperature, and the heterogenous nucleation mainly results in hcp structure. Under the condition of strain constraint, the products of structural transition will respectively form flaky hcp twin structure ((1 0 0) or (0 1 0)) and lamellar structure ({1 1 0}) of mixed phases under 1D and 3D compressions. During the structural transition, we find the shear stress (1D compression) of hcp phase is always lower than that of bcc phase. The cold energy calculations indicate that the hcp phase is the most stable under high pressure. However, we observe the evident metastable state of bcc phase, whose energy will be much higher than both hcp and fcc phases, and then provides the possibility for the occurrence of fcc nucleation.

  16. Impact of FCC regenerator design in the NOx emissions

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Hugo Borges; Sandes, Emanuel Freire; Gilbert, William Richard; Roncolatto, Rodolfo Eugenio; Gobbo, Rodrigo; Casavechia, Luiz Carlos; Candido, William Victor Carlos [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil); Bridi, Patricia Elaine [Possebon Engenharia, Sao Mateus do Sul, PR (Brazil)

    2012-07-01

    Fluid Catalytic Cracking (FCC) is the main point source of NOx in the refinery and it is responsible for at least 20% of the total NOx emissions from the refineries. The thermal NOx formation in the FCC regenerator is negligible. However, half of the feed nitrogen is converted to coke, and is burned in the regenerator. The majority of coke nitrogen is reduced to N2 and less than 10% is converted to NOx. This number may vary significantly with the oxygen excess in the flue gas and other operational conditions. With the purpose of evaluating the impact of different regenerator designs in NOx formation, several tests were carried out in the PETROBRAS FCC prototype unit. The test unit is equipped with adiabatic insulation and a CO boiler, allowing it to reproduce the heat balance of a commercial FCC and to operate either in full combustion or partial combustion. Two different designs of FCC regenerators were evaluated: single stage regenerator (the existing configuration) and two stage regenerator, with the catalyst bed divided into two sections by a structured packing baffle. It was observed in the tests that the combustion regime had a very strong effect on NOx formation. In full combustion, the effect of the FCC operating variables: excess oxygen, combustion promoter content in catalyst and regenerator design could be identified. The two stage configuration was capable of decreasing NOx emissions by 30%. In partial combustion, the effect of the CO-boiler variables on NOx emissions was overwhelming, but the use of the structured packing baffle was able to improve the catalyst regeneration.(author)

  17. Atomistic modeling of carbon Cottrell atmospheres in bcc iron

    Science.gov (United States)

    Veiga, R. G. A.; Perez, M.; Becquart, C. S.; Domain, C.

    2013-01-01

    Atomistic simulations with an EAM interatomic potential were used to evaluate carbon-dislocation binding energies in bcc iron. These binding energies were then used to calculate the occupation probability of interstitial sites in the vicinity of an edge and a screw dislocation. The saturation concentration due to carbon-carbon interactions was also estimated by atomistic simulations in the dislocation core and taken as an upper limit for carbon concentration in a Cottrell atmosphere. We obtained a maximum concentration of 10 ± 1 at.% C at T = 0 K within a radius of 1 nm from the dislocation lines. The spatial carbon distributions around the line defects revealed that the Cottrell atmosphere associated with an edge dislocation is denser than that around a screw dislocation, in contrast with the predictions of the classical model of Cochardt and colleagues. Moreover, the present Cottrell atmosphere model is in reasonable quantitative accord with the three-dimensional atom probe data available in the literature.

  18. An analytic n-body potential for bcc Iron

    Energy Technology Data Exchange (ETDEWEB)

    Pontikis, V. [Commissariat a l' Energie Atomique, DRECAM/LSI, CE de Saclay, Building 524, Room 40B, 91191 Gif-sur-Yvette Cedex (France)]. E-mail: Vassilis.Pontikis@cea.fr; Russier, V. [Centre d' Etudes de Chimie Metallurgique, CNRS UPR2801, 94407 Vitry-sur-Seine (France); Wallenius, J. [Royal Institute of Technology, Department of Nuclear and Reactor Physics, Stockholm (Sweden)

    2007-02-15

    We have developed an analytic n-body phenomenological potential for bcc iron made of two electron-density functionals representing repulsion via the Thomas-Fermi free-electron gas kinetic energy term and attraction via a square root functional similar to the second moment approximation of the tight-binding scheme. Electron-density is given by radial, hydrogen-like orbitals with effective charges taken as adjustable parameters fitted on experimental and ab-initio data. Although the set of adjustable parameters is small, prediction of static and dynamical properties of iron is in excellent agreement with the experiments. Advantages and shortcomings of this model are discussed with reference to published works.

  19. An analytic n-body potential for bcc Iron

    International Nuclear Information System (INIS)

    Pontikis, V.; Russier, V.; Wallenius, J.

    2007-01-01

    We have developed an analytic n-body phenomenological potential for bcc iron made of two electron-density functionals representing repulsion via the Thomas-Fermi free-electron gas kinetic energy term and attraction via a square root functional similar to the second moment approximation of the tight-binding scheme. Electron-density is given by radial, hydrogen-like orbitals with effective charges taken as adjustable parameters fitted on experimental and ab-initio data. Although the set of adjustable parameters is small, prediction of static and dynamical properties of iron is in excellent agreement with the experiments. Advantages and shortcomings of this model are discussed with reference to published works

  20. Neutron spectroscopy of fast hydrogen diffusion in BCC transition metals

    International Nuclear Information System (INIS)

    Richter, D.; Lottner, V.

    1979-01-01

    Quasielastic neutron scattering reveals microscopic details of both the time and space development of the H-diffusion process on an atomic scale. After outlining the method on the example of PdH/sub x/, new results on the jump geometry in bcc metals are surveyed. In particular, the anomalous diffusion behavior of H in Nb, Ta, and V at elevated temperature is emphasized, where correlated jump processes are important. The influence of impurities on the H-diffusion process is demonstrated by experiments performed on NbH/sub x/ doped with nitrogen impurities, which act as trapping centers for the diffusing hydrogen. The results are discussed in terms of a two-state random walk model which includes multiple trapping and detrapping processes. The concentration and temperature dependence of the capture and escape rates of traps are obtained

  1. Evolution of anisotropy in bcc Fe distorted by interstitial boron

    Science.gov (United States)

    Gölden, Dominik; Zhang, Hongbin; Radulov, Iliya; Dirba, Imants; Komissinskiy, Philipp; Hildebrandt, Erwin; Alff, Lambert

    2018-01-01

    The evolution of magnetic anisotropy in bcc Fe as a function of interstitial boron atoms was investigated in thin films grown by molecular beam epitaxy. The thermodynamic nonequilibrium conditions during film growth allowed one to stabilize an interstitial boron content of about 14 at .% accompanied by lattice tetragonalization. The c /a ratio scaled linearly with the boron content up to a maximum value of 1.05 at 300 °C substrate growth temperature, with a room-temperature magnetization of. In contrast to nitrogen interstitials, the magnetic easy axis remained in-plane with an anisotropy of approximately -5.1 ×106erg /cm3 . Density functional theory calculations using the measured lattice parameters confirm this value and show that boron local ordering indeed favors in-plane magnetization. Given the increased temperature stability of boron interstitials as compared to nitrogen interstitials, this study will help to find possible ways to manipulate boron interstitials into a more favorable local order.

  2. Nucleation of fcc Ta when heating thin films

    International Nuclear Information System (INIS)

    Janish, Matthew T.; Mook, William M.; Carter, C. Barry

    2015-01-01

    Thin tantalum films have been studied during in situ heating in a transmission electron microscope. Diffraction patterns from the as-deposited films were typical of amorphous materials. Crystalline grains were observed to form when the specimen was annealed in situ at 450 °C. Particular attention was addressed to the formation and growth of grains with the face-centered cubic (fcc) crystal structure. These observations are discussed in relation to prior work on the formation of fcc Ta by deformation and during thin film deposition

  3. Hierarchically-Driven Approach for Quantifying Fatigue Crack Initiation and Short Crack Growth Behavior in Aerospace Materials

    Science.gov (United States)

    2016-08-31

    structure-energy correlation in several FCC metals was investigated by Wolf [32] who established a linear relationship between GB energy and volume...which could change the pining strength of impeding dislocations. This has motivated several atomistic studies in BCC [59,60], FCC [61,62], and HCP...the indents were measured using AFM’s tapping mode on a scanning probe microscope. DISTRIBUTION A: Distribution approved for public release. Page

  4. Effect of stacking faults on the magnetocrystalline anisotropy of hcp Co: a first-principles study.

    Science.gov (United States)

    Aas, C J; Szunyogh, L; Evans, R F L; Chantrell, R W

    2013-07-24

    In terms of the fully relativistic screened Korringa-Kohn-Rostoker method we investigate the effect of stacking faults on the magnetic properties of hexagonal close-packed (hcp) cobalt. In particular, we consider the formation energy and the effect on the magnetocrystalline anisotropy energy (MAE) of four different stacking faults in hcp cobalt-an intrinsic growth fault, an intrinsic deformation fault, an extrinsic fault and a twin-like fault. We find that the intrinsic growth fault has the lowest formation energy, in good agreement with previous first-principles calculations. With the exception of the intrinsic deformation fault which has a positive impact on the MAE, we find that the presence of a stacking fault generally reduces the MAE of bulk Co. Finally, we consider a pair of intrinsic growth faults and find that their effect on the MAE is not additive, but synergic.

  5. A new f.c.c. phase in yttrium films

    International Nuclear Information System (INIS)

    Kaul, V.K.; Srivastava, O.N.

    1976-01-01

    A new polymorphic phase characterised by a face-centered cubic structure, with lattice parameter 5.83 +- 0.02A, has been identified in thin films of yttrium. Electron diffraction evidence and electrical resistivity measurements have been carried out in order to detect the new f.c.c. phase. (Auth.)

  6. A Guide to Federal Regulation; Understanding the FCC Rules.

    Science.gov (United States)

    Cable Television Information Center, Washington, DC.

    While it is apparent that the Federal Communications Commission (FCC) has given a great deal of thought to the regulation of cable systems, the basic success or failure of cable as a communications service will depend on local development. Relatively little guidance has been provided to local franchising authorities for selecting among applicants,…

  7. Cross-twinning model of fcc crystal growth

    NARCIS (Netherlands)

    van de Waal, B.W.

    1995-01-01

    The theory developed in 1960 by Wagner, Hamilton and Seidensticker (WHS-theory) to explain observed crystal growth phenomena in Ge is critically reviewed and shown to be capable of explaining preservation of ABC stacking order in two dimensions in fcc crystals of effectively spherical closed shell

  8. QCD and $\\gamma\\,\\gamma$ studies at FCC-ee

    CERN Document Server

    Skands, Peter

    2016-10-20

    The Future Circular Collider (FCC) is a post-LHC project aiming at searches for physics beyond the SM in a new 80--100~km tunnel at CERN. Running in its first phase as a very-high-luminosity electron-positron collider (FCC-ee), it will provide unique possibilities for indirect searches of new phenomena through high-precision tests of the SM. In addition, by collecting tens of ab$^{-1}$ integrated luminosity in the range of center-of-mass energies $\\sqrt{s}$~=90--350~GeV, the FCC-ee also offers unique physics opportunities for precise measurements of QCD phenomena and of photon-photon collisions through, literally, billions of hadronic final states as well as unprecedented large fluxes of quasireal $\\gamma$'s radiated from the $\\rm e^+e^-$ beams. We succinctly summarize the FCC-ee perspectives for high-precision extractions of the QCD coupling, for detailed analyses of parton radiation and fragmentation, and for SM and BSM studies through $\\gamma\\gamma$ collisions.

  9. FCC-hh Hadron Collider - Parameter Scenarios and Staging Options

    CERN Document Server

    Benedikt, Michael; Schulte, Daniel; Zimmermann, F; Syphers, M J

    2015-01-01

    FCC-hh is a proposed future energy-frontier hadron collider, based on dipole magnets with a field around 16 T installed in a new tunnel with a circumference of about 100 km, which would provide proton collisions at a centre-of-mass energy of 100 TeV, as well as heavy-ion collisions at the equivalent energy. The FCC-hh should deliver a high integrated proton-proton luminosity at the level of several 100 fb−1 per year, or more. The challenges for operating FCC-hh with high beam current and at high luminosity include the heat load from synchrotron radiation in a cold environment, the radiation from collision debris around the interaction region, and machine protection. In this paper, starting from the FCC-hh design baseline parameters we explore different approaches for increasing the integrated luminosity, and discuss the impact of key individual pa- rameters, such as the turnaround time. We also present some injector considerations and options for early hadron-collider operation.

  10. Quantitative comparison between simulated and experimental FCC rolling textures

    DEFF Research Database (Denmark)

    Wronski, M.; Wierzbanowski, K.; Leffers, Torben

    2015-01-01

    The degree of similarity between simulated and experimental fcc rolling textures is characterized by a single scalar parameter. The textures are simulated with a relatively simple and efficient 1-point model which allows us to vary the strength of the interaction between the grains and the surrou...

  11. Dynamic optimization of a FCC converter unit: numerical analysis

    Directory of Open Access Journals (Sweden)

    E. Almeida Nt

    2011-03-01

    Full Text Available Fluidized-bed Catalytic Cracking (FCC is a process subject to frequent variations in the operating conditions (including feed quality and feed rate. The production objectives usually are the maximization of LPG and gasoline production. This fact makes the FCC converter unit an excellent opportunity for real-time optimization. The present work aims to apply a dynamic optimization in an industrial FCC converter unit, using a mechanistic dynamic model, and to carry out a numerical analysis of the solution procedure. A simultaneous approach was used to discretize the system of differential-algebraic equations and the resulting large-scale NLP problem was solved using the IPOPT solver. This study also does a short comparison between the results obtained by a potential dynamic real-time optimization (DRTO against a possible steady-state real-time optimization (RTO application. The results demonstrate that the application of dynamic real-time optimization of a FCC converter unit can bring significant benefits in production.

  12. Atomistically-informed dislocation dynamics in FCC crystals

    International Nuclear Information System (INIS)

    Martinez, E.; Marian, J.; Arsenlis, A.; Victoria, M.; Martinez, E.; Victoria, M.; Perlado, J.M.

    2008-01-01

    Full text of publication follows. We will present a nodal dislocation dynamics (DD) model to simulate plastic processes in fcc crystals. The model explicitly accounts for all slip systems and Burgers vectors observed in fcc systems, including stacking faults and partial dislocations. We derive simple conservation rules that describe all partial dislocation interactions rigorously and allow us to model and quantify cross-slip processes, the structure and strength of dislocation junctions, and the formation of fcc-specific structures such as stacking fault tetrahedra. The DD framework is built upon isotropic non-singular linear elasticity, and supports itself on information transmitted from the atomistic scale. In this fashion, connection between the meso and micro scales is attained self-consistently with core parameters fitted to atomistic data. We perform a series of targeted simulations to demonstrate the capabilities of the model, including dislocation reactions and dissociations and dislocation junction strength. Additionally we map the four-dimensional stress space relevant for cross-slip and relate our fundings to the plastic behaviour of' monocrystalline fcc metals. (authors)

  13. Deformation microstructure and orientation of F.C.C. crystals

    DEFF Research Database (Denmark)

    Liu, Q.; Hansen, N.

    1995-01-01

    The effect of crystallographic orientation on the microstructural evolution in f.c.c. metals with medium to high stacking fault energy is analyzed. This analysis is based on a literature review of the behaviour of single crystals and polycrystals supplemented with an experimental study of cold...

  14. The incidence of metastatic basal cell carcinoma (mBCC) in Denmark, 1997-2010.

    Science.gov (United States)

    Nguyen-Nielsen, Mary; Wang, Lisa; Pedersen, Lars; Olesen, Anne Braae; Hou, Jeannie; Mackey, Howard; McCusker, Margaret; Basset-Seguin, Nicole; Fryzek, Jon; Vyberg, Mogens

    2015-01-01

    Few data exist on the occurrence of metastatic basal cell carcinoma (mBCC). To identify all cases of mBCC in Denmark over a 14-year period. We searched the Danish National Patient Registry covering all Danish hospitals, the Danish Cancer Registry, the National Pathology Registry and the Causes of Death Registry during the period 1997 to 2010 for potential cases of mBCC registered according to the International classification of diseases ICD-10 and the International Systemized Nomenclature of Medicine (SNOMED). We identified 126,627 patients with a history of primary basal cell carcinoma (BCC) in the registries during the 14-year study period. Using case identifications from the four registries, a total of 170 potential mBCC cases were identified. However, after a pathology review, only five cases could be confirmed, of which three were basosquamous carcinomas. The 14-year cumulative incidence proportion of mBCC was 0.0039% (95% CI 0.0016-0.0083) among individuals with a history of previous BCC (n = 126,627) and 0.0001% (95% CI 0.0000-0.0002) in the general population. MBCC is a rare disease and only a small proportion of potential cases identified in automated clinical databases or registries can be confirmed by pathology and medical record review.

  15. TRANSICIÓN DE FASE ENTRE FORMAS FCC Y BCC DEL ESTRONCIO Y SUS PROPIEDADES ESTRUCTURALES Y ELECTRONICAS MEDIANTE TEORÍA DEL FUNCIONAL DE LA DENSIDAD (DFT

    Directory of Open Access Journals (Sweden)

    María A. Puerto

    2012-01-01

    Full Text Available Se han realizado cálculos de primeros principios para de terminar las propiedades estructurales y electrónicas del estroncio en sus fases de cristalización Im-3m y Fm-3m dentro del formalismo de la Teoría del Funcional de la Densidad (DFT. Esto se hizo a partir del método de ondas planas aumentadas y linealizadas en la versión de potencial completo (FP-LAPW con la aproximación de gradiente generalizado (GGA. Se encontró que la configuración más estable es la Fm-3m , con una constante de red a 0 = 11,38 bohr , energía de cohesión E o = - 0,107 Ry y módulo de volumen B 0 = 113 GPa . A partir de la densidad de esta dos y la estructura de bandas de energía se evidenció el carácter metálico de este elemento para ambas estructuras cristalinas. Se predice una posible transición de fase estructural de la Fm-3m a la Im-3m bajo una presión de 178 GPa .

  16. Comprehensive first-principles study of stable stacking faults in hcp metals

    International Nuclear Information System (INIS)

    Yin, Binglun; Wu, Zhaoxuan; Curtin, W.A.

    2017-01-01

    The plastic deformation in hcp metals is complex, with the associated dislocation core structures and properties not well understood on many slip planes in most hcp metals. A first step in establishing the dislocation properties is to examine the stable stacking fault energy and its structure on relevant slip planes. However, this has been perplexing in the hcp structure due to additional in-plane displacements on both sides of the slip plane. Here, density functional theory guided by crystal symmetry analysis is used to study all relevant stable stacking faults in 6 hcp metals (Mg, Ti, Zr, Re, Zn, Cd). Specially, the stable stacking fault energy, position, and structure on the Basal, Prism I and II, Pyramidal I and II planes are determined using all-periodic supercells with full atomic relaxation. All metals show similar stacking fault position and structure as dictated by crystal symmetry, but the associated stacking fault energy, being governed by the atomic bonding, differs significantly among them. Stacking faults on all the slip planes except the Basal plane show substantial out-of-plane displacements while stacking faults on the Prism II, Pyramidal I and II planes show additional in-plane displacements, all extending to multiple atom layers. The in-plane displacements are not captured in the standard computational approach for stacking faults, and significant differences are shown in the energies of such stacking faults between the standard approach and fully-relaxed case. The existence of well-defined stable stacking fault on the Pyramidal planes suggests zonal dislocations are unlikely. Calculations on the equilibrium partial separation further suggests 〈c + a〉 dissociation into three partials on the Pyramidal I plane is unlikely and 〈c〉 dissociation on Prism planes is unlikely to be stable against climb-dissociation onto the Basal planes in these metals.

  17. Superparamagnetism and coercivity in HCP-Co nanoparticles dispersed in silica matrix

    Energy Technology Data Exchange (ETDEWEB)

    Julian Fernandez, C. de E-mail: dejulian@padova.infm.it; Mattei, G.; Sangregorio, C.; Battaglin, C.; Gatteschi, D.; Mazzoldi, P

    2004-05-01

    The magnetic properties of Co HCP nanoparticles dispersed in a silica matrix with sizes between 2{+-}0.7 and 5{+-}2.2 nm were investigated. The temperature dependence of zero-field cooled and field cooled magnetizations and of the coercive field were analyzed considering the thermal activated demagnetization process. Enhanced anisotropy was observed for the 2 nm nanoparticles, while the demagnetization process of the larger ones is dominated by interparticle interactions.

  18. Superparamagnetism and coercivity in HCP-Co nanoparticles dispersed in silica matrix

    International Nuclear Information System (INIS)

    Julian Fernandez, C. de; Mattei, G.; Sangregorio, C.; Battaglin, C.; Gatteschi, D.; Mazzoldi, P.

    2004-01-01

    The magnetic properties of Co HCP nanoparticles dispersed in a silica matrix with sizes between 2±0.7 and 5±2.2 nm were investigated. The temperature dependence of zero-field cooled and field cooled magnetizations and of the coercive field were analyzed considering the thermal activated demagnetization process. Enhanced anisotropy was observed for the 2 nm nanoparticles, while the demagnetization process of the larger ones is dominated by interparticle interactions

  19. Synthesis, multi-nonlinear dielectric resonance and electromagnetic absorption properties of hcp-cobalt particles

    International Nuclear Information System (INIS)

    Wen, Shulai; Liu, Ying; Zhao, Xiuchen; Cheng, Jingwei; Li, Hong

    2014-01-01

    Hcp-cobalt particles were successfully prepared by a liquid phase reduction method, and the microstructure, static magnetic properties, electromagnetic and microwave absorption properties of the cobalt particles with irregular shape were investigated in detail. The measured results indicate that the saturation magnetization was less than that of hcp-Co single crystals, and the coercivity was larger than that of bulk cobalt crystal. The permittivity presents multi-nonlinear dielectric resonance, which may result from the irregular shape containing parts of cutting angle of dodecahedron of cobalt particles. The real part of permeability decreases with the frequency, and the imaginary part has a wide resonant peak. The paraffin-based composite containing 70 wt% cobalt particles possessed strong absorption characteristics with a minimum RL of −38.97 dB at 10.81 GHz and an absorption band with RL under −10 dB from 8.72 to 13.26 GHz when the thickness is 1.8 mm, which exhibits excellent microwave absorption in middle and high frequency. The architectural design of material morphologies is important for improving microwave absorption properties toward future application. - Highlights: • Hcp-cobalt particles were prepared by a liquid phase reduction method. • The saturation magnetization was less than that of hcp-Co single crystals. • The permittivity presents multi-nonlinear dielectric resonance. • The real part of permeability decreases with frequency, and the imaginary part presents a wide resonant peak. • The paraffin-based composite possessed a minimum RL of −38.97 dB at 10.81 GHz

  20. 76 FR 69738 - Revised 2011 Annual Telecommunications Reporting Worksheet (FCC Form 499-A) and Accompanying...

    Science.gov (United States)

    2011-11-09

    ... Telecommunications Reporting Worksheet (FCC Form 499-A) and Accompanying Instructions AGENCY: Federal Communications... Telecommunications Reporting Worksheet (FCC Form 499-A) and accompanying instructions that have been approved by the... INFORMATION CONTACT: Ernesto Beckford, Wireline Competition Bureau, Telecommunications Access Policy Division...

  1. Crystal Structure of Hcp from Acinetobacter baumannii: A Component of the Type VI Secretion System.

    Directory of Open Access Journals (Sweden)

    Federico M Ruiz

    Full Text Available The type VI secretion system (T6SS is a bacterial macromolecular machine widely distributed in Gram-negative bacteria, which transports effector proteins into eukaryotic host cells or other bacteria. Membrane complexes and a central tubular structure, which resembles the tail of contractile bacteriophages, compose the T6SS. One of the proteins forming this tube is the hemolysin co-regulated protein (Hcp, which acts as virulence factor, as transporter of effectors and as a chaperone. In this study, we present the structure of Hcp from Acinetobacter baumannii, together with functional and oligomerization studies. The structure of this protein exhibits a tight β barrel formed by two β sheets and flanked at one side by a short α-helix. Six Hcp molecules associate to form a donut-shaped hexamer, as observed in both the crystal structure and solution. These results emphasize the importance of this oligomerization state in this family of proteins, despite the low similarity of sequence among them. The structure presented in this study is the first one for a protein forming part of a functional T6SS from A. baumannii. These results will help us to understand the mechanism and function of this secretion system in this opportunistic nosocomial pathogen.

  2. Ab initio study of stability and migration of H and He in hcp-Sc

    International Nuclear Information System (INIS)

    Yang, L; Zu, X T; Peng, S M; Long, X G; Gao, F; Heinisch, H L; Kurtz, R J

    2011-01-01

    Ab initio calculations based on density functional theory have been performed to determine the relative stabilities and migration of H and He atoms in hcp-Sc. The results show that the formation energy of an interstitial H or He atom is smaller than that of a corresponding substitutional atom. The tetrahedral (T) interstitial position is more stable than an octahedral (O) position for both He and H interstitials. The nudged elastic band method has been used to study the migration of interstitial H and He atoms in hcp-Sc. It is found that the migration energy barriers for H interstitials in hcp-Sc are significantly different from those for He interstitials, but their migration mechanisms are similar. In addition, the formation energies of five different configurations of a H-H pair were determined, revealing that the most stable configuration consists of two H atoms located at the second-neighbor tetrahedral interstitial sites along the hexagonal direction. The formation and relative stabilities of some small He clusters have also been investigated.

  3. Calculation of the surface energy of hcp-metals with the empirical electron theory

    International Nuclear Information System (INIS)

    Fu Baoqin; Liu Wei; Li Zhilin

    2009-01-01

    A brief introduction of the surface model based on the empirical electron theory (EET) and the dangling bond analysis method (DBAM) is presented in this paper. The anisotropy of spatial distribution of covalent bonds of hexagonal close-packed (hcp) metals such as Be, Mg, Sc, Ti, Co, Zn, Y, Zr, Tc, Cd, Hf, and Re, has been analyzed. And under the first-order approximation, the calculated surface energy values for low index surfaces of these hcp-metals are in agreement with experimental and other theoretical values. Correlated analysis showed that the anisotropy of surface energy of hcp-metals was related with the ratio of lattice constants (c/a). The calculation method for the research of surface energy provides a good basis for models of surface science phenomena, and the model may be extended to the surface energy estimation of more metals, alloys, ceramics, and so on, since abundant information about the valence electronic structure (VES) is generated from EET.

  4. Database implementation to fluidized cracking catalytic-FCC process

    Energy Technology Data Exchange (ETDEWEB)

    Santana, Antonio Otavio de; Dantas, Carlos Costa, E-mail: aos@ufpe.b [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear; Santos, Valdemir A. dos, E-mail: valdemir.alexandre@pq.cnpq.b [Universidade Catolica de Pernambuco, Recife, PE (Brazil). Centro de Ciencia e Tecnologia

    2009-07-01

    A process of Fluidized Cracking Catalytic (FCC) was developed by our research group. A cold model FCC unit, in laboratory scale, was used for obtaining of the data relative to the following parameters: air flow, system pressure, riser inlet pressure, rise outlet pressure, pressure drop in the riser, motor speed of catalyst injection and density. The measured of the density is made by gamma ray transmission. For the fact of the process of FCC not to have a database until then, the present work supplied this deficiency with the implementation of a database in connection with the Matlab software. The data from the FCC unit (laboratory model) are obtained as spreadsheet of the MS-Excel software. These spreadsheets were treated before importing them as database tables. The application of the process of normalization of database and the analysis done with the MS-Access in these spreadsheets treated revealed the need of an only relation (table) for to represent the database. The Database Manager System (DBMS) chosen has been the MS-Access by to satisfy our flow of data. The next step was the creation of the database, being built the table of data, the action query, selection query and the macro for to import data from the unit FCC in study. Also an interface between the application 'Database Toolbox' (Matlab2008a) and the database was created. This was obtained through the drivers ODBC (Open Data Base Connectivity). This interface allows the manipulation of the database by the users operating in the Matlab. (author)

  5. Database implementation to fluidized cracking catalytic-FCC process

    International Nuclear Information System (INIS)

    Santana, Antonio Otavio de; Dantas, Carlos Costa; Santos, Valdemir A. dos

    2009-01-01

    A process of Fluidized Cracking Catalytic (FCC) was developed by our research group. A cold model FCC unit, in laboratory scale, was used for obtaining of the data relative to the following parameters: air flow, system pressure, riser inlet pressure, rise outlet pressure, pressure drop in the riser, motor speed of catalyst injection and density. The measured of the density is made by gamma ray transmission. For the fact of the process of FCC not to have a database until then, the present work supplied this deficiency with the implementation of a database in connection with the Matlab software. The data from the FCC unit (laboratory model) are obtained as spreadsheet of the MS-Excel software. These spreadsheets were treated before importing them as database tables. The application of the process of normalization of database and the analysis done with the MS-Access in these spreadsheets treated revealed the need of an only relation (table) for to represent the database. The Database Manager System (DBMS) chosen has been the MS-Access by to satisfy our flow of data. The next step was the creation of the database, being built the table of data, the action query, selection query and the macro for to import data from the unit FCC in study. Also an interface between the application 'Database Toolbox' (Matlab2008a) and the database was created. This was obtained through the drivers ODBC (Open Data Base Connectivity). This interface allows the manipulation of the database by the users operating in the Matlab. (author)

  6. The role of equilibrium volume and magnetism on the stability of iron phases at high pressures.

    Science.gov (United States)

    Alnemrat, S; Hooper, J P; Vasiliev, I; Kiefer, B

    2014-01-29

    The present study provides new insights into the pressure dependence of magnetism by tracking the hybridization between crystal orbitals for pressures up to 600 GPa in the known hcp, bcc and fcc iron. The Birch-Murnaghan equation of state parameters are; bcc: V0 = 11.759 A(3)/atom, K0 = 177.72 GPa; hcp: V0 = 10.525 A(3)/atom, K0 = 295.16 GPa; and fcc: V0 = 10.682 A(3)/atom, K0 = 274.57 GPa. These parameters compare favorably with previous studies. Consistent with previous studies we find that the close-packed hcp and fcc phases are non-magnetic at pressures above 50 GPa and 60 GPa, respectively. The principal features of magnetism in iron are predicted to be invariant, at least up to ∼6% overextension of the equilibrium volume. Our results predict that magnetism for overextended fcc iron disappears via an intermediate spin state. This feature suggests that overextended lattices can be used to stabilize particular magnetic states. The analysis of the orbital hybridization shows that the magnetic bcc structure at high pressures is stabilized by splitting the majority and minority spin bands. The bcc phase is found to be magnetic at least up to 600 GPa; however, magnetism is insufficient to stabilize the bcc phase itself, at least at low temperatures. Finally, the analysis of the orbital contributions to the total energy provides evidence that non-magnetic hcp and fcc phases are likely more stable than bcc at core earth pressures.

  7. Helium bubbles in bcc Fe and their interactions with irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Gai, Xiao, E-mail: X.Gai@lboro.ac.uk; Lazauskas, Tomas; Smith, Roger; Kenny, Steven D.

    2015-07-15

    The properties of helium bubbles in a body-centred cubic (bcc) Fe lattice have been examined. The atomic configurations and formation energies of different He–vacancy complexes were determined. The 0 K results show that the most energetically favourable He to Fe vacancy ratio increases from about 1:1 for approximately 5 vacancies up to about 4:1 for 36 vacancies. The formation mechanisms for small He clusters have also been considered. Isolated interstitials and small clusters can diffuse quickly through the lattice. MD simulations of randomly placed interstitial He atoms at 500 K showed clustering over the time scale of nanoseconds with He clusters containing up to 4 atoms being mobile over this time scale. He clusters containing 4 or 5 atoms were shown to eject an Fe dumbbell interstitial which could then detach from the He cluster and diffuse with the remaining He–vacancy complex being effectively immobile. Collision cascades initiated near larger bubbles showed that Fe vacancies produced by the cascades readily become part of the He–vacancy complexes. Energy barriers for He to join an existing bubble as a function of the He–vacancy ratio are also calculated. These can be larger than the diffusion barrier in the pristine lattice, but are lower when the bubbles contain excess vacancies, thus indicating that bubble growth may be kinetically constrained.

  8. Solid-liquid interface free energies of pure bcc metals and B2 phases

    Science.gov (United States)

    Wilson, S. R.; Gunawardana, K. G. S. H.; Mendelev, M. I.

    2015-04-01

    The solid-liquid interface (SLI) free energy was determined from molecular dynamics (MD) simulation for several body centered cubic (bcc) metals and B2 metallic compounds (space group: P m 3 ¯ m ; prototype: CsCl). In order to include a bcc metal with a low melting temperature in our study, a semi-empirical potential was developed for Na. Two additional synthetic "Na" potentials were also developed to explore the effect of liquid structure and latent heat on the SLI free energy. The obtained MD data were compared with the empirical Turnbull, Laird, and Ewing relations. All three relations are found to predict the general trend observed in the MD data for bcc metals obtained within the present study. However, only the Laird and Ewing relations are able to predict the trend obtained within the sequence of "Na" potentials. The Laird relation provides the best prediction for our MD data and other MD data for bcc metals taken from the literature. Overall, the Laird relation also agrees well with our B2 data but requires a proportionality constant that is substantially different from the bcc case. It also fails to explain a considerable difference between the SLI free energies of some B2 phases which have nearly the same melting temperature. In contrast, this difference is satisfactorily described by the Ewing relation. Moreover, the Ewing relation obtained from the bcc dataset also provides a reasonable description of the B2 data.

  9. Sulfur and octane trade off in FCC naphta conventional hydrotreating

    Energy Technology Data Exchange (ETDEWEB)

    Badra, C. [INTEVEP S.A. Research and Technological Support Center of Petroleos de Venzuela, Caracas (Venezuela). Dept. de Refinacion; Perez, J.A. [INTEVEP S.A. Research and Technological Support Center of Petroleos de Venzuela, Caracas (Venezuela). Dept. de Refinacion; Salazar, J.A. [INTEVEP S.A. Research and Technological Support Center of Petroleos de Venzuela, Caracas (Venezuela). Dept. de Refinacion; Cabrera, L. [INTEVEP S.A. Research and Technological Support Center of Petroleos de Venzuela, Caracas (Venezuela). Dept. de Refinacion; Gracia, W. [INTEVEP S.A. Research and Technological Support Center of Petroleos de Venzuela, Caracas (Venezuela). Dept. de Refinacion

    1997-06-01

    A model to predict the change of octane numbers expected in an FCC naphtha hydrotreating process as a function of the hydroprocessing severity (degree of sulfur removal) and the type of naphtha (expressed as the sulfur content and bromine number in the feedstock) is presented. When considering hydrotreating as an option for processing their catalytic naphthas, refiners search for the proper balance between the desired reduction of sulfur and olefins and the resulting undesired reduction of octane (RON and MON). In doing so, refiners should study the possibility of performing the hydrotreating at mild severities and/or the possibility of fractionating FCC naphthas to just treat a specific cut. This paper provides simple tools to study and analyze these study cases and to assess the sulfur-octane trade offs. (orig.)

  10. Status of the FCC-ee Interaction Region Design

    CERN Document Server

    Roman Martin; Medina, L

    2015-01-01

    The FCC-ee project is a high-luminosity circular electron-positron collider envisioned to operate at center-of-mass energies from 90 to 350 GeV, allowing high-precision measurements of the properties of the Z, W and Higgs boson as well as the top quark. It is considered to be a predecessor of a new 100 TeV proton-proton collider hosted in the same 80 to 100 km tunnel in the Geneva area. Currently two interaction region designs are being developed by CERN and BINP using different approaches to the definition of baseline parameters. Both preliminary designs are presentedwith the aimof highlighting the challenges the FCC-ee is facing.

  11. Physics Perspectives for a Future Circular Collider: FCC-ee

    CERN Multimedia

    CERN. Geneva

    2017-01-01

    The lectures will briefly discuss the parameters of a Future Circular Collider, before addressing in detail the physics perspectives and the challenges for the experiments and detector systems. The main focus will be on ee and pp collisions, but opportunities for e—p physics will also be covered. The FCC physics perspectives will be presented with reference to the ongoing LHC programme, including the physics potential from future upgrades to the LHC in luminosity and possibly energy.  

  12. Description of hardening curves of fcc single- and polycrystals

    International Nuclear Information System (INIS)

    Mecking, H.

    1975-01-01

    Stress-strain curves are analyzed over their entire strain region and over a wide range of temperatures to arrive at a general analytic description of work-hardening curves. The data were obtained with fcc single and polycrystals, but there is experimental and theoretical evidence that the principles of the analysis are also applicable for other crystal structures and even for more complex technical materials. 9 figs, 1 table, 46 refs

  13. First results for a FCC-hh ring optics design

    CERN Document Server

    Chance, Antoine; Payet, Jacques; Alemany Fernandez, Reyes; Holzer, Bernhard; Schulte, Daniel

    2015-01-01

    The first order considerations of the optics for the FCC-hh ring are presented. The arc cell is generated taking into account some general considerations like the whole circumference, maximum gradients and lengths of the elements in the cell. The integration of the insertion regions started. Three types of Dispersion Suppressors (DIS) are studied. The sensitivity of the arc parameters to these layout considerations is studied in more detail. An alternative layout is shown as well.

  14. Dynamic Aperture Studies for the FCC-ee

    CERN Document Server

    Medina, L; Tomas, R; Zimmermann, F

    2015-01-01

    Dynamic aperture (DA) studies have been conducted on the latest Future Circular Collider – ee (FCC-ee) lattices as a function of momentum deviation.Two different schemes for the interaction region are used, which are connected to the main arcs: the crab waist approach, developed by BINP, and an update to the CERN design where the use of crab cavities is envisioned. The results presented show an improvement in the performance of both designs.

  15. Photonic bandgap structure of 3-D fcc silica nanospheres

    Energy Technology Data Exchange (ETDEWEB)

    Woo, Y. K.; Ha, N. Y.; Hwang, Ji Soo; Chang, H. J.; Wu, J. W. [Dept. of Physics, Ewha Womans University, Seoul (Korea, Republic of)

    2002-07-01

    Photonic crystal is an artificial optical material with a periodic dielectric potential, hence exhibiting a bandgap for a propagating electromagnetic wave. We fabricated crystal possessing 3-D fcc opal structure from silica nanospheres. The crystals are self-assembled on a flat glass by evaporating the solvent in the nanosphere suspension at the room temperature. The suspension consists of silica nanospheres with a diameter of 200 nm. The microscopic arrangement of nanospheres is identified by a scanning electron microscope, the resulting structure being fcc.Transmission spectrum of the fabricated photonic crystal in the visible and near-infrared regions is measured at different incident angles to find the distinct Bragg peaks, analysis of which further confirmed the fcc structure of the photonic crystal. From the optical microscopic image, we find that the opal domain varies from 30 μm to 125 μm in size. In order to relate the observed Bragg peaks with the microscopic arrangement of silica nanospheres, we introduced the scalar wave approximation, where the electric field in the medium is treated as a scalar rather than a vector quantity. It is found that the theoretical prediction of the position of bandgap is in a good agreement with the experimental measurement.

  16. Beam Optics for FCC-ee Collider Ring

    CERN Document Server

    Oide, Katsunobu; Aumon, S; Benedikt, M; Blondel, A; Bogomyagkov, A V; Boscolo, M; Burkhardt, H; Cai, Y; Doblhammer, A; Haerer, B; Holzer, B; Koop, I; Koratzinos, M; Jowett, John M; Levichev, E B; Medina, L; Ohmi, K; Papaphilippou, Y; Piminov, P A; Shatilov, D N; Sinyatkin, S V; Sullivan, M; Wenninger, J; Wienands, U; Zhou, D; Zimmermann, F

    2017-01-01

    A beam optics scheme has been designed [ 1 ] for the Future Circular Collider- e + e − (FCC-ee). The main characteristics of the design are: beam energy 45 to 175 GeV, 100 km circumference with two interaction points (IPs) per ring, horizontal crossing angle of 30 mrad at the IP and the crab-waist scheme [ 2 ] with local chromaticity correction. The crab-waist scheme is implemented within the local chromaticity correction system without additional sextupoles, by reducing the strength of one of the two sextupoles for vertical chromatic correction at each side of the IP. So- called “tapering" of the magnets is applied, which scales all fields of the magnets according to the local beam energy to compensate for the effect of synchrotron radiation (SR) loss along the ring. An asymmetric layout near the interaction region reduces the critical energy of SR photons on the incoming side of the IP to values below 100 keV, while matching the geometry to the beam line of the FCC proton collider (FCC-hh) [ 3 ] as clos...

  17. FCC-ee accelerator parameters, performance and limitations

    CERN Document Server

    Koratzinos, Mike

    2016-12-22

    CERN has recently launched the Future Circular Collider (FCC) study to deal with all aspects of an ambitious post-LHC possible programme. The emphasis of the study is on a 100 TeV proton collider to be housed in a 80-100 km new ring in the Geneva region. An electron machine will also be considered as a possible intermediate first step (FCC-ee). The study benefits from earlier work done in the context of TLEP and has already published a parameter table, to serve as the basis for the work to be done. The study aims to publish a conceptual design report at around 2018. The recent discovery of a light Higgs boson has opened up considerable interest in circular e+e- Higgs factories around the world. FCC-ee is capable of very high luminosities in a wide centre-of-mass (ECM) spectrum from 90 to 350 GeV. This allows the very precise study of the Z, W and H bosons as well as the top quark, allowing for meaningful precision tests of the closure of the Standard Model.

  18. Future Circular Collider Study FCC-he Baseline Parameters

    CERN Document Server

    Bruning, Oliver; Klein, Max; Pellegrini, Dario; Schulte, Daniel; Zimmermann, Frank

    2017-01-01

    Initial considerations are presented on the FCC-he, the electron-hadron collider con guration within the Future Circular Collider study. This note considers arguments for the choice of the electron beam energy based on physics, ep scattering kinematics and cost. The default con guration for the electron accelerator, as for the LHeC, is chosen to be a multi-turn energy recovery linac external to the proton beam tunnel. The main accelerator parameters of the FCC-he are discussed, assuming the concurrent operation of ep with the 100TeV cms energy pp collider. These are compared with the LHeC design concept, for increased performance as for a Higgs facility using the HL-LHC, and also the high energy HE-LHC ep collider configuration. Initial estimates are also provided for the luminosity performance of electron-ion colliders for the 60 GeV electron ERL when combined with the LHC, the HE-LHC and the FCC ion beams.

  19. Epitaxial growth of fcc Ti films on Al(001) surfaces

    International Nuclear Information System (INIS)

    Saleh, A.A.; Shutthanandan, V.; Shivaparan, N.R.; Smith, R.J.; Tran, T.T.; Chambers, S.A.

    1997-01-01

    High-energy ion scattering (HEIS), x-ray photoelectron spectroscopy, and x-ray photoelectron diffraction (XPD) were used to study the growth of thin Ti films on Al(001) surfaces. The Al surface peak area in the backscattered ion spectrum of MeV He + ions, incident along the [00 bar 1] direction, was used to monitor the atomic structure of the Ti films during growth. An initial decrease in the area was observed indicating epitaxial film growth. This decrease continued up to a critical film thickness of about 5.5 ML, after which point the structure of the film changed. Titanium films 3, 5, and 9 ML thick were characterized using XPD in the same chamber. Both the HEIS and XPD results show that the Ti films grow with an fcc structure on Al(001). A tetragonal distortion of 2.4% in the fcc Ti film was measured using ions incident along the [10 bar 1] direction. Although there is a general similarity of fcc Ti growth on both Al(001) and Al(110), the submonolayer growth regime does show differences for the two surfaces. copyright 1997 The American Physical Society

  20. Photonic bandgap structure of 3-D fcc silica nanospheres

    International Nuclear Information System (INIS)

    Woo, Y. K.; Ha, N. Y.; Hwang, Ji Soo; Chang, H. J.; Wu, J. W.

    2002-01-01

    Photonic crystal is an artificial optical material with a periodic dielectric potential, hence exhibiting a bandgap for a propagating electromagnetic wave. We fabricated crystal possessing 3-D fcc opal structure from silica nanospheres. The crystals are self-assembled on a flat glass by evaporating the solvent in the nanosphere suspension at the room temperature. The suspension consists of silica nanospheres with a diameter of 200 nm. The microscopic arrangement of nanospheres is identified by a scanning electron microscope, the resulting structure being fcc.Transmission spectrum of the fabricated photonic crystal in the visible and near-infrared regions is measured at different incident angles to find the distinct Bragg peaks, analysis of which further confirmed the fcc structure of the photonic crystal. From the optical microscopic image, we find that the opal domain varies from 30 μm to 125 μm in size. In order to relate the observed Bragg peaks with the microscopic arrangement of silica nanospheres, we introduced the scalar wave approximation, where the electric field in the medium is treated as a scalar rather than a vector quantity. It is found that the theoretical prediction of the position of bandgap is in a good agreement with the experimental measurement.

  1. Attrition Resistant Fischer-Tropsch Catalysts Based on FCC Supports

    Energy Technology Data Exchange (ETDEWEB)

    Adeyiga, Adeyinka

    2010-02-05

    Commercial spent fluid catalytic cracking (FCC) catalysts provided by Engelhard and Albemarle were used as supports for Fe-based catalysts with the goal of improving the attrition resistance of typical F-T catalysts. Catalysts with the Ruhrchemie composition (100 Fe/5 Cu/4.2 K/25 spent FCC on mass basis) were prepared by wet impregnation. XRD and XANES analysis showed the presence of Fe{sub 2}O{sub 3} in calcined catalysts. FeC{sub x} and Fe{sub 3}O{sub 4} were present in the activated catalysts. The metal composition of the catalysts was analyzed by ICP-MS. F-T activity of the catalysts activated in situ in CO at the same conditions as used prior to the attrition tests was measured using a fixed bed reactor at T = 573 K, P = 1.38 MPa and H{sub 2}:CO ratio of 0.67. Cu and K promoted Fe supported over Engelhard provided spent FCC catalyst shows relatively good attrition resistance (8.2 wt% fines lost), high CO conversion (81%) and C{sub 5}+ hydrocarbons selectivity (18.3%).

  2. Slip transmission in bcc FeCr polycrystal

    Energy Technology Data Exchange (ETDEWEB)

    Patriarca, Luca, E-mail: luca.patriarca@polimi.it [Politecnico di Milano, Department of Mechanical Engineering, Via La Masa 34, I-20156 Milano (Italy); Abuzaid, Wael; Sehitoglu, Huseyin [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206W. Green St., Urbana, IL 61801 (United States); Maier, Hans J. [Institut für Werkstoffkunde, Leibniz Universität Hannover, An der Universität 2, D-30823 Garbsen (Germany)

    2013-12-20

    Grain boundaries induce heterogeneities in the deformation response of polycrystals. Studying these local variations in response, measured through high resolution strain measurement techniques, is important and can improve our understanding of fatigue damage initiation in the vicinity of grain boundaries and material hardening. In this work, strain fields across grain boundaries were measured using advanced digital image correlation techniques. In conjunction with strain measurements, grain orientations from electron back-scattered diffraction were used to establish the dislocation reactions at each boundary, providing the corresponding residual Burgers vectors due to slip transmission across the interfaces. A close correlation was found between the magnitude of the residual Burgers vector and the local strain change across the boundary. When the residual Burgers vector magnitude (with respect to the lattice spacing) exceeds 1.0, the high strains on one side of the boundary are paired with low strains across the boundary, indicating the difficulties for slip dislocations to penetrate the grain interfaces. When the residual Burgers vector approaches zero, the strain fields vary smoothly across the boundary due to limited resistance to slip transmission. The results suggest that the residual Burgers vector magnitude, which relates to the GB (Grain Boundary) resistance to slip transmission, enables a quantitative analysis of the accumulation of strain at the microstructural level and the development of strain heterogeneities across grain boundaries. The results are presented for FeCr bcc alloy which exhibits single slip per grain making the measurements and dislocation reactions rather straightforward. The work points to the need to incorporate details of slip dislocation–grain boundary interaction (slip transmission) in modeling research.

  3. Pressure Profile in the experimental area of FCC-hh and FCC-ee calculated by an analytical code

    CERN Multimedia

    Aichinger, Ida

    2017-01-01

    Ultra high vacuum in the beam pipe is a basic requirement for the Future Circular Colliders (FCC). The dimension of the FCC and the high energy of the particles will make this requirement challenging. Simulations that predict the vacuum quality due to material and beam induced effects will allow to evaluate different designs and to choose an optimal solution. The mathematical model behind the simulations will be shown. Four coupled differential equations describe the mass conservation of the residual gas particles in the beam pipe. The sinks include all kind of distributed and local pumping. The sources are caused by synchrotron radiation, electron clouds, thermal outgassing and ion-induced desorption. The equation system is solved by an analytical method. This requires a transformation to first order equations for which a general valid solution exists. Adding a particular solution and the inclusion of appropriate boundary conditions define the solution function. The big advantage here is that an analytical...

  4. Axial ratio dependence of the stability of self-interstitials in HCP structures

    International Nuclear Information System (INIS)

    Peng, Qing; Ji, Wei; Huang, Hanchen; De, Suvranu

    2013-01-01

    We investigate the effect of the axial ratio (c/a) on the stability of self-interstitial atoms (SIAs) in hexagonal close-packed crystal structures, using hcp-zirconium as a prototype, through density functional theory based ab initio calculations. The axial ratio is found to dominate the relative stability of SIAs over volumetric strains. We observe that below the ideal value of 1.633, the basal octahedral configuration is the most stable. Above the ideal value, the off-plane SIAs are more stable than in-plane ones

  5. Self-interstitials structure in the hcp metals: A further perspective from first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Pasianot, Roberto C., E-mail: pasianot@cnea.gov.ar [Gerencia Materiales, CAC-CNEA, Avda. Gral. Paz 1499, 1650 San Martín (Argentina); CONICET, Godoy Cruz 2290, 1425 Buenos Aires (Argentina); Instituto Sabato, UNSAM/CNEA, Avda. Gral. Paz 1499, 1650 San Martín (Argentina)

    2016-12-01

    We study the structure of several standard and non-standard self-interstitial configurations in a series of hcp metals, by using Density Functional Theory as embodied in the computer codes SIESTA and WIEN2k. The considered metals include Be, Mg, Ti, Zr, Co, Zn, and Cd, thus spanning the whole range of experimental c/a ratios, different kinds of bonding, and even magnetism (Co). The results show the importance of low symmetry configurations, closely related to the non-basal crowdion, in order to rationalize the experimental data on self-interstitial structure and migration.

  6. Crystallographic phase transitions in actinide metals as a function of pressure

    International Nuclear Information System (INIS)

    Eriksson, O.; Soederlind, P.; Melsen, J.; Ahuja, R.; Johansson, B.

    1993-01-01

    We present first-principles calculations of the equilibrium volumes and crystal structures of the light actinides (Th--Pu). The calculated equilibrium volumes for fcc Th, bct Pu, α-U, and β-Np are found to agree reasonably well with the experimental data, and when comparing the total energies of the bcc, fcc, bct, α-U, and β-Np structures we obtain the correct crystal structures for all studied systems. Equilibrium volumes for Th--Pu, using a hypothetical fcc structure, have been calculated; although spin-orbit coupling is included in these calculations, the calculated equilibrium volume of Pu is smaller than for Np, in disagreement with experiment. Moreover, the calculated tetragonal elastic constant, C', is shown to be negative for bcc U, bcc Np, bcc Pu, and fcc Pu. Thus, our zero temperature calculations suggest that the bcc structure is unstable for these elements and that fcc Pu is also unstable. This is in conflict with experiment and we are led to the conclusion that temperature effects must be of crucial importance for stabilizing cubic structures in U, Np, and Pu. Further, as a function of decreasing volume we predict a crystal structure sequence fcc → bct → fcc in Th, a sequence α-U → bct → bcc in U, and a sequence β-Np → bct → bcc in Np. Also, a sequence of transitions in Sc as a function of decreasing volume have been calculated, namely hcpfcc → ω → β-Np → bcc

  7. In situ neutron diffraction study of grain-orientation-dependent phase transformation in 304L stainless steel at a cryogenic temperature

    International Nuclear Information System (INIS)

    Tao Kaixiang; Wall, James J.; Li, Hongqi; Brown, Donald W.; Vogel, Sven C.; Choo, Hahn

    2006-01-01

    In situ time-of-flight neutron diffraction was performed to investigate the martensitic phase transformation during quasistatic uniaxial compression testing of 304L stainless steel at 300 and 203 K. In situ neutron diffraction enabled the bulk measurement of intensity evolution for various hkl atomic planes during the austenite (fcc) to martensite (hcp and bcc) phase transformation. Based on the neutron diffraction patterns, the martensite phases were observed from the very beginning of the plastic deformation at 203 K. However, at 300 K, no newly formed martensite, except a small amount of preexisting hcp phase, was observed throughout the test. From the changes in the relative intensities of individual hkl atomic planes, the grain-orientation-dependent phase transformation was investigated. The preferred orientation of the newly formed martensite grains was also investigated for the sample deformed at 203 K using neutron diffraction. The results reveal the orientation relationships between the austenite and the newly formed martensites. The fcc grain family diffracting with (200) plane normal parallel to the loading axis is favored for the fcc to bcc transformation and the bcc (200) plane normals are primarily aligned along the loading direction. For the fcc to hcp transformation, the fcc grains with (111) plane normals at an angle in between about 10 deg. and 50 deg. to the loading direction are favored

  8. Calculation of the electronic and magnetic structures of 3d impurities in the Hcp Fe matrix; Calculo da estrutura eletronica e magnetica de impurezas 3d na matriz do Fe HCP

    Energy Technology Data Exchange (ETDEWEB)

    Franca, Fernando

    1995-12-31

    In this work we investigate the local magnetic properties and the electronic structure of HCP Fe, as well introducing transition metals atoms 3d (Cs, Ti, Cr, Mn, Co, Ni, Cu, Zn) in HCP iron matrix. We employed the discrete variational method (DVM), which is an orbital molecular method which incorporate the Hartree-Fock-Slater theory and the linear combination of atomic orbitals (LCAO), in the self-consistent charge approximation and the local density approximation of Von Barth and Hedin to the exchange-correlation potential. We used the embedded cluster model to investigate the electronic structure and the local magnetic properties for the central atom of a cluster of 27 atoms immersed in the microcrystal representing the HCP Fe. (author) 32 refs., 19 figs., 2 tabs.

  9. Atomistic properties of helium in hcp titanium: A first-principles study

    International Nuclear Information System (INIS)

    Wang Yongli; Liu, Shi; Rong Lijian; Wang Yuanming

    2010-01-01

    First-principles calculations based on density functional theory have been performed to investigate the behaviors of He in hcp-type Ti. The most favorable interstitial site for He is not an ordinary octahedral or tetrahedral site, but a novel interstitial site (called FC) with a formation energy as low as 2.67 eV, locating the center of the face shared by two adjacent octahedrons. The origin was further analyzed by composition of formation energy of interstitial He defects and charge density of defect-free hcp Ti. It has also been found that an interstitial He atom can easily migrate along direction with an activation energy of 0.34 eV and be trapped by another interstitial He atom with a high binding energy of 0.66 eV. In addition, the small He clusters with/without Ti vacancy have been compared in details and the formation energies of He n V clusters with a pre-existing Ti vacancy are even higher than those of He n clusters until n ≥ 3.

  10. Momentum density of hcp and liquid helium-4 by inelastic neutron scattering

    International Nuclear Information System (INIS)

    Hilleke, R.O.

    1983-01-01

    A measurement of the momentum density in hcp and liquid 4 He by inelastic neutron scattering is reported. Using the Low Resolution Medium Energy Chopper Spectrometer at the Intense Pulsed Neutron Source at Argonne National Laboratory, momentum transfers in the range 12 to 22.5 A -1 were attained. At these momentum transfers, the momentum density of the sample is related to the dynamic structure factor by the impulse approximation. The measured momentum distribution is Gaussian and the kinetic energy is larger than proposed by existing theories. Data were taken on two solid samples, the first was a 19.45 cm 3 /mole hcp solid, the second was 18.20 cm 3 /mole; both solid samples were maintained at 1.70 K during data collection. Data were also taken on a liquid sample with a molar volume of 18.20 cm 3 /mole at 4.00 K. At 1.70 K the two solid samples are essentially in their ground states so that the measurement is of the ground state momentum density. The liquid sample was included to see if the difference between the liquid and solid momentum density at the same molar volume was observable

  11. Ab-initio approach to the effect of Fe on the diffusion in hcp Zr

    International Nuclear Information System (INIS)

    Perez, Rodolfo Ariel; Weissmann, Mariana

    2008-01-01

    The role of Fe in the hcp Zr diffusion process is analyzed, given its ultra-fast diffusion (up to nine orders of magnitude higher than the self-diffusion in the temperature range 779-1128 K) and the enhancement observed in the self and substitutional diffusion induced by its unavoidable presence as impurity. Ab-initio calculations using SIESTA and WIEN2K codes were performed in order to find the actual Fe minimum energy configuration within the hcp Zr matrix and its interaction with vacancies. Several off-centre quasi-interstitial positions with energies similar to substitutional Fe were encountered. The comparison with diffusion coefficient measurements and Moessbauer experiments allows us to discard the substitutional position of the Fe atom as well as to affirm that its presence creates a considerable lattice distortion together with an increment in the number of vacancies. The above effects could be responsible for the enhancement in the self and substitutional diffusion, whereas the large amount of quasi-interstitial positions for Fe could be, at least partially, responsible for the ultra-fast Fe diffusion

  12. Extended solubility and martensitic hcp nickel formation in antimony implanted nickel

    International Nuclear Information System (INIS)

    Johnson, E.; Sarholt-Kristensen, L.; Johansen, A.

    1982-01-01

    Radiation damage microstructure and associated disorder have been investigated in antimony implanted nickel crystals using combined RBS and TEM analyses. In crystals implanted at and below room temperature with 80 keV Sb + ions to a fluence of 5x10 20 m -2 , the retained antimony concentration in the implantation zone is approaching 15 at.%, with nearly all the antimony located substitutionally. The associated disorder as seen in the RBS analysis is insignificant. Annealing up to 600 0 C has little influence on the antimony distribution, whilst the dechanneling level is reduced. TEM and diffraction analysis of room temperature implanted samples show that the radiation damage consists of dense distributions of dislocation clusters and tangles, superimposed on a rather homogeneous background of new phase particles, identified as hcp nickel. The particles have a size 0.1-0.2 μm. The high substitutional antimony concentration at and below room temperature, which exceeds the solubility limit, indicates that its formation is thermally diffusionless and rather an effect of radiation enhanced solubility. The diffusionless nature of the microstructure is also indicated from the presence of martensitic hcp nickel, believed to form due to relief of radiation induced internal stress. (Auth.)

  13. Modeling the effect of neighboring grains on twin growth in HCP polycrystals

    Science.gov (United States)

    Kumar, M. Arul; Beyerlein, I. J.; Lebensohn, R. A.; Tomé, C. N.

    2017-09-01

    In this paper, we study the dependence of neighboring grain orientation on the local stress state around a deformation twin in a hexagonal close packed (HCP) crystal and its effects on the resistance against twin thickening. We use a recently developed, full-field elasto-visco-plastic formulation based on fast Fourier transforms that account for the twinning shear transformation imposed by the twin lamella. The study is applied to Mg, Zr and Ti, since these HCP metals tend to deform by activation of different types of slip modes. The analysis shows that the local stress along the twin boundary are strongly controlled by the relative orientation of the easiest deformation modes in the neighboring grain with respect to the twin lamella in the parent grain. A geometric expression that captures this parent-neighbor relationship is proposed and incorporated into a larger scale, mean-field visco-plastic self-consistent model to simulate the role of neighboring grain orientation on twin thickening. We demonstrate that the approach improves the prediction of twin area fraction distribution when compared with experimental observations.

  14. Remanence coercivity of dot arrays of hcp-CoPt perpendicular films

    Energy Technology Data Exchange (ETDEWEB)

    Mitsuzuka, K; Shimatsu, T; Aoi, H [Research Institute of Electrical Communication, Tohoku University, Sendai, 980-8577 (Japan); Kikuchi, N; Okamoto, S; Kitakami, O, E-mail: shimatsu@riec.tohoku.ac.j [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, 980-8577 (Japan)

    2010-01-01

    The remanence coercivity, H{sub r}, of hcp-CoPt dot arrays with various dot thicknesses, {delta}, (3 and 10 nm) and Pt content (20-30at%) were experimentally investigated as a function of the dot diameter, D(30-400 nm). All dot arrays showed a single domain state, even after removal of an applied field equal to H{sub r}. The angular dependence of H{sub r} for the dot arrays indicated coherent rotation of the magnetization during nucleation. H{sub r} increased as Ddecreased in all series of dot arrays with various {delta} and Pt content. Assuming that the nucleation field of a dot is determined by the switching field of a grain having the smallest switching field, we calculated the value of nucleation field H{sub n}{sup cal} taking account of the c-axis distribution and the distribution of the demagnetizing field in the dot. The values of H{sub r} obtained experimentally are in good agreement with those of H{sub n}{sup cal}, taking account of thermal agitation of magnetization. This result suggested that the reversal process of hcp-CoPt dot arrays starts from a nucleation at the center of the dot followed by a propagation process.

  15. Symmetry-selected spin-split hybrid states in C-60/ferromagnetic interfaces

    DEFF Research Database (Denmark)

    Li, Dongzhe; Barreteau, Cyrille; Kawahara, Seiji Leo

    2016-01-01

    ferromagnetic surfaces: bcc-Cr(001), bcc-Fe(001), bcc-Co(001), fcc-Co(001), and hcp-Co(0001). We show that the adsorption geometry of the molecule with respect to the surface crystallographic orientation of the magnetic substrate as well as the strength of the interaction play a crucial role in the spin...... tunneling spectroscopy measurements on single C60 adsorbed on Cr(001) and Co/Pt(111) also confirm that the symmetry both of the substrate and of the molecular conformation has a strong influence on the induced spin polarization. Our finding may give valuable insights for further engineering of spin...

  16. Ab initio theory of noble gas atoms in bcc transition metals.

    Science.gov (United States)

    Jiang, Chao; Zhang, Yongfeng; Gao, Yipeng; Gan, Jian

    2018-06-18

    Systematic ab initio calculations based on density functional theory have been performed to gain fundamental understanding of the interactions between noble gas atoms (He, Ne, Ar and Kr) and bcc transition metals in groups 5B (V, Nb and Ta), 6B (Cr, Mo and W) and 8B (Fe). Our charge density analysis indicates that the strong polarization of nearest-neighbor metal atoms by noble gas interstitials is the electronic origin of their high formation energies. Such polarization becomes more significant with an increasing gas atom size and interstitial charge density in the host bcc metal, which explains the similar trend followed by the unrelaxed formation energies of noble gas interstitials. Upon allowing for local relaxation, nearby metal atoms move farther away from gas interstitials in order to decrease polarization, albeit at the expense of increasing the elastic strain energy. Such atomic relaxation is found to play an important role in governing both the energetics and site preference of noble gas atoms in bcc metals. Our most notable finding is that the fully relaxed formation energies of noble gas interstitials are strongly correlated with the elastic shear modulus of the bcc metal, and the physical origin of this unexpected correlation has been elucidated by our theoretical analysis based on the effective-medium theory. The kinetic behavior of noble gas atoms and their interaction with pre-existing vacancies in bcc transition metals have also been discussed in this work.

  17. Biological changes of APA-BCC analgesic microcapsule in cerebrospinal fluid of patients with carcinomatous pain

    International Nuclear Information System (INIS)

    Luo Yun; Li Yanling; Xue Yilong; Guo Shulong; Gao Yuhong; Cui Xin

    2005-01-01

    To explore the changes of alginate-polylysine-alginate microcapsulated bovine adrenal medullary chromaffin cells (APA-BCC microcapsules) in morphology, survival rate and leucine- enkephalin secretion after they were transplanted into CSF of cancerpain patients, the APA- BCC microcapsules were Implanted into cavitas subarachnoidealis of cancer-pain patients by conventional lumbar puncture. After 7 or 8 days, cerebrospinal fluid was collected and the morphology of the APA-BCC microcapsule, the survival rate of cells were observed and secretory volume of leucine-enkephalin was assayed by radioimmunity method. Seven days after trans- plantation, the mean VAS decreased from 8.8 to 2.4, the survival rate of cells averagely reduced from 91.2% to 89.1%, morphology of APA-BCC microcapsules did not change obviously and secretory volume of leucine-enkephalin went up 1.65 times compared with that at pretrans- plantation. In conclusion, APA-BCC can survive, secret leucine-enkephalin and produce analgesic effect after transplanted into CSF of cancer-patients. (authors)

  18. The study on binary Mg-Co hydrogen storage alloys with BCC phase

    International Nuclear Information System (INIS)

    Zhang Yao; Tsushio, Yoshinori; Enoki, Hirotoshi; Akiba, Etsuo

    2005-01-01

    Novel Mg-Co binary alloys were successfully synthesized by mechanical alloying. These alloys were studied by X-ray diffraction (XRD), transmission electron micrograph (TEM), pressure-composition-isotherms measurements (P-C-T) and differential scanning calorimetry (DSC). Both XRD Rietveld analysis and TEM observation confirmed that these binary alloys contain BCC phase and that the BCC phase existed in the range from 37 to 80 at.% Co. The lattice parameter of the BCC phase increased with the increase of the Co content from 37 to 50 at.%. When the Co content reached 50 at.%, the lattice parameter reached a maximum value, and then turned to decrease gradually with further increase of the Co content. Most of Mg-Co BCC alloys absorbed hydrogen at 373 K under 6 MPa of hydrogen pressure. The Mg 60 Co 40 alloy showed the highest hydrogen absorption capacity, about 2.7 mass% hydrogen. However, all the Mg-Co alloys studied did not desorb hydrogen at 373 K. By means of DSC measurements and in situ XRD analysis, it was found that under 4 MPa hydrogen atmosphere, Mg 50 Co 50 alloy transformed from BCC solid solution to Mg 2 CoH 5 tetragonal hydride at 413 K

  19. The hamster cheek pouch (HCP) as an experimental model of oral cancer for BNCT: biodistribution and pharmacokinetics of BPA

    International Nuclear Information System (INIS)

    Kreimann, E.; Itoiz, M.E.; Dagrosa, A.; Garavaglia, R.; Farias, S.; Batistoni, D.; Schwint, A.E.

    2000-01-01

    We propose and validate the HCP model of oral cancer for BNCT studies. This model serves to explore new applications of the technique, study the biology of BNCT and assess Boron uptake in clinically relevant oral tissues. Tumors are induced by a process that mimics spontaneous malignant transformation instead of by the growth of implanted tumor cells. Syrian hamsters were submitted to tumor induction with a chemical carcinogenesis protocol and then used for biodistribution and pharmacokinetic studies of BPA. The data reveal selective uptake by tumor and, to a lesser degree, by precancerous tissue. Boron concentration in oral tissues and skin was higher than in blood, an issue of clinical relevance given that these tissues may be dose-limiting. Absolute and relative values of Boron concentration would be potentially therapeutic. Boron concentration exhibited a linear relationship with percentage of viable tissue in HCP tumors. The HCP model would provide a novel, contributory approach to BNCT research. (author)

  20. First-principles study of ternary fcc solution phases from special quasirandom structures

    International Nuclear Information System (INIS)

    Shin Dongwon; Wang Yi; Liu Zikui; Walle, Axel van de

    2007-01-01

    In the present work, ternary special quasirandom structures (SQSs) for a fcc solid solution phase are generated at different compositions, x A =x B =x C =(1/3) and x A =(1/2), x B =x C =(1/4), whose correlation functions are satisfactorily close to those of a random fcc solution. The generated SQSs are used to calculate the mixing enthalpy of the fcc phase in the Ca-Sr-Yb system. It is observed that first-principles calculations of all the binary and ternary SQSs in the Ca-Sr-Yb system exhibit very small local relaxation. It is concluded that the fcc ternary SQSs can provide valuable information about the mixing behavior of the fcc ternary solid solution phase. The SQSs presented in this work can be widely used to study the behavior of ternary fcc solid solutions

  1. Constraining Phosphorus Chemistry in Carbon- and Oxygen-Rich Circumstellar Envelopes: Observations of PN, HCP, and CP

    Science.gov (United States)

    Milam, S. N.; Halfen, D. T.; Tenenbaum, E. D.; Apponi, A. J.; Woolf, N. J.; Ziurys, L. M.

    2008-09-01

    Millimeter-wave observations of PN, CP, and HCP have been carried out toward circumstellar envelopes of evolved stars using the Arizona Radio Observatory (ARO). HCP and PN have been identified in the carbon-rich source CRL 2688 via observations at 1 mm using the Submillimeter Telescope (SMT) and 2-3 mm with the Kitt Peak 12 m. An identical set of measurements were carried out toward IRC +10216, as well as observations of CP at 1 mm. PN was also observed toward VY Canis Majoris (VY CMa), an oxygen-rich supergiant star. The PN and HCP line profiles in CRL 2688 and IRC +10216 are roughly flat topped, indicating unresolved, optically thin emission; CP, in contrast, has a distinct "U" shape in IRC +10216. Modeling of the line profiles suggests abundances, relative to H2, of f(PN) ~ (3-5) × 10-9 and f(HCP) ~ 2 × 10-7 in CRL 2688, about an order of magnitude higher than in IRC +10216. In VY CMa, f(PN) is ~4 × 10-8. The data in CRL 2688 and IRC +10216 are consistent with LTE formation of HCP and PN in the inner envelope, as predicted by theoretical calculations, with CP a photodissociation product at larger radii. The observed abundance of PN in VY CMa is a factor of 100 higher than LTE predictions. In IRC +10216, the chemistry of HCP/CP mimics that of HCN/CN and suggests an N2 abundance of f ~ 1 × 10-7. The chemistry of phosphorus appears active in both carbon- and oxygen-rich envelopes of evolved stars.

  2. Beam-beam studies for FCC-hh

    CERN Document Server

    AUTHOR|(CDS)2068329; Pieloni, Tatiana; Buffat, Xavier; Furuseth, Sondre Vik

    2017-01-01

    The Future Circular Collider hadron-hadron (FCC-hh) design study is currently exploring different IR design possibilities including round and flat optics or different crossing schemes. The present study intends to evaluate each scenario from the beam-beam effects point of view. In particular the single particle long term stability to maximize beam lifetimes and luminosity reach is used to quantify the differences. The impact of strong head on interactions on the beam quality and lifetime is addressed by means of GPU accelerated simulations code featuring a weak-strong 6-dimensional beam-beam interaction.

  3. Phase transition of the FCC Ising ferromagnet with competing interactions

    International Nuclear Information System (INIS)

    Oh, J.H.; Lee, J.Y.; Kim, D.C.

    1984-01-01

    A molecular field theory with correlation and Monte Carlo simulations are utilized to determine the zero field phase diagram of a fcc Ising model with ferromagnetic nearest neighbor(-J) and antiferromagnetic next neighbor (*aJ) interactions. The correlated molecular field theory predicts a fluctuation induced first order phase transition for 0.87<*a<1.31. Monte Carlo analysis indicates that the first order transition occurs for a somewhat wider range of *a. The transition temperatures obtained by the two methods are in good agreement especially near *a=1 where the fluctuation effect is expected to be large. (Author)

  4. Enhanced propylene production in FCC by novel catalytic materials

    Energy Technology Data Exchange (ETDEWEB)

    Kelkar, C.P.; Harris, D.; Xu, M.; Fu, J. [BASF Catalyst LLC, Iselin, NJ (United States)

    2007-07-01

    Fluid catalytic cracking is expected to increasingly supply the additional incremental requirements for propylene. The most efficient route to increase propylene yield from an FCC unit is through the use of medium pore zeolites such as ZSM-5. ZSM-5 zeolite cracks near linear olefins in the gasoline range to LPG olefins such as propylene and butylenes. This paper will describe catalytic approaches to increase gasoline range olefins and the chemistry of ZSM-5 to crack those olefins. The paper will also describe novel catalytic materials designed to increase propylene. (orig.)

  5. Optimising A Read Out for A Possible FCC hh Collision

    CERN Document Server

    Alagaraisamy, Revathy

    2017-01-01

    The Future Circular Collider Study (FCC) aims to provide a conceptual design for an accelerator to possibly be constructed in the 2040s-2050s. The most ambitious design proposed is a 100 km-circumference proton-proton collider (FCChh), designed to achieve a centre-of-mass energy of 100 TeV and exceeding . Thus,along with this the precision of the detector is increased via many ways,e.g: calculation and reduction of electronic noise with PCB readout in detector.

  6. EFFECT OF VANADIUM ON THE DEACTIVATION OF FCC CATALYSTS

    Directory of Open Access Journals (Sweden)

    Roncolatto R.E

    1998-01-01

    Full Text Available This work provides concrete evidence that vanadium causes the destruction of the zeolite in the FCC catalysts by a mechanism of acid attack or solid-solid transformation, as well as additional dealumination of the zeolite framework in the presence of steam and at high temperature. While these effects resulted in the reduction in crystallinity (zeolite Y content, specific area and unit cell size of the Y zeolite as the amount of vanadium in the catalysts increased, the reduction in activity was the most pronounced. The differences in these behaviors were interpreted and the model can be used for better catalyst formulation or screening.

  7. Olefin recovery from FCC off-gas can pay off

    International Nuclear Information System (INIS)

    Brahn, M.G.

    1992-01-01

    This paper reports on olefins recovery from refinery FCC offgas streams which offers an attractive cash flow from olefins from a tail-gas stream that has typically been consumed as refinery fuel. Such recovery schemes can be employed in refineries or olefins plants, and can be tailored to fit individual requirements. Mobil Chemical Co. has operated such a dephlegmator-based off-gas recovery unit at its Beaumont, Tex., olefin plant since 1987. It reported that the project was paid out within 11 months of initial start-up

  8. Steady-State Crack Growth in Rate-Sensitive Single Crystals

    DEFF Research Database (Denmark)

    Juul, Kristian Jørgensen; Nielsen, Kim Lau; Niordson, Christian Frithiof

    2016-01-01

    The characteristics of the active plastic zone surrounding a crack growingin a single crystal (FCC, BCC, and HCP) at constant velocity is investigated for ModeI loading under plane strain assumptions. The framework builds upon a steady-state relation bringing the desired solution out in a frame...... translating with the crack tip. In the study, the shielding of the crack tip that follows from plastic slip is investigated by adopting the SSV-model. High resolution plots of the plastic zones are obtained and a detailed study confirms the existence of analytically determined velocity discontinuities from...... the literature. The plastic zone is found to be smallest for the FCC structure andlargest for the HCP structure, which is also reected in the shielding ratio, where FCC crystals show the smallest shielding and HCP the largest shielding....

  9. Structural characterization of metastable hcp-Ni thin films epitaxially grown on Au(100) single-crystal underlayers

    International Nuclear Information System (INIS)

    Ohtake, Mitsuru; Tanaka, Takahiro; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    Ni(1120) epitaxial thin films with hcp structure were prepared on Au(100) single-crystal underlayers at 100 deg. C by ultra high vacuum molecular beam epitaxy. The detailed film structure is studied by in situ reflection high energy electron diffraction, x-ray diffraction, and transmission electron microscopy. The hcp-Ni film consists of two types of variants whose c-axes are rotated around the film normal by 90 deg. each other. An atomically sharp boundary is recognized between the film and the underlayer, where misfit dislocations are introduced. Presence of such dislocations seems to relieve the strain caused by the lattice mismatch between the film and the underlayer.

  10. Stress and stability of sputter deposited A-15 and bcc crystal structure tungsten thin films

    Energy Technology Data Exchange (ETDEWEB)

    O' Keefe, M.J.; Stutz, C.E.

    1997-07-01

    Magnetron sputter deposition was used to fabricate body centered cubic (bcc) and A-15 crystal structure W thin films. Previous work demonstrated that the as-deposited crystal structure of the films was dependent on the deposition parameters and that the formation of a metastable A-15 structure was favored over the thermodynamically stable bcc phase when the films contained a few atomic percent oxygen. However, the A-15 phase was shown to irreversibly transform into the bcc phase between 500 C and 650 C and that a significant decrease in the resistivity of the metallic films was measured after the transformation. The current investigation of 150 nm thick, sputter deposited A-15 and bcc tungsten thin films on silicon wafers consisted of a series of experiments in which the stress, resistivity and crystal structure of the films was measured as a function of temperatures cycles in a Flexus 2900 thin film stress measurement system. The as-deposited film stress was found to be a function of the sputtering pressure and presputter time; under conditions in which the as-deposited stress of the film was {approximately}1.5 GPa compressive delamination of the W film from the substrate was observed. Data from the thermal studies indicated that bcc film stress was not affected by annealing but transformation of the A-15 structure resulted in a large tensile increase in the stress of the film, regardless of the as-deposited stress of the film. In several instances, complete transformation of the A-15 structure into the bcc phase resulted in {ge}1 GPa tensile increase in film stress.

  11. Stress and stability of sputter deposited A-15 and bcc crystal structure tungsten thin films

    International Nuclear Information System (INIS)

    O'Keefe, M.J.; Stutz, C.E.

    1997-01-01

    Magnetron sputter deposition was used to fabricate body centered cubic (bcc) and A-15 crystal structure W thin films. Previous work demonstrated that the as-deposited crystal structure of the films was dependent on the deposition parameters and that the formation of a metastable A-15 structure was favored over the thermodynamically stable bcc phase when the films contained a few atomic percent oxygen. However, the A-15 phase was shown to irreversibly transform into the bcc phase between 500 C and 650 C and that a significant decrease in the resistivity of the metallic films was measured after the transformation. The current investigation of 150 nm thick, sputter deposited A-15 and bcc tungsten thin films on silicon wafers consisted of a series of experiments in which the stress, resistivity and crystal structure of the films was measured as a function of temperatures cycles in a Flexus 2900 thin film stress measurement system. The as-deposited film stress was found to be a function of the sputtering pressure and presputter time; under conditions in which the as-deposited stress of the film was approximately1.5 GPa compressive delamination of the W film from the substrate was observed. Data from the thermal studies indicated that bcc film stress was not affected by annealing but transformation of the A-15 structure resulted in a large tensile increase in the stress of the film, regardless of the as-deposited stress of the film. In several instances, complete transformation of the A-15 structure into the bcc phase resulted in ge1 GPa tensile increase in film stress

  12. Dislocation cross-slip in fcc solid solution alloys

    International Nuclear Information System (INIS)

    Nöhring, Wolfram Georg; Curtin, W.A.

    2017-01-01

    Cross-slip is a fundamental process of screw dislocation motion and plays an important role in the evolution of work hardening and dislocation structuring in metals. Cross-slip has been widely studied in pure FCC metals but rarely in FCC solid solutions. Here, the cross-slip transition path in solid solutions is calculated using atomistic methods for three representative systems of Ni-Al, Cu-Ni and Al-Mg over a range of solute concentrations. Studies using both true random alloys and their corresponding average-alloy counterparts allow for the independent assessment of the roles of (i) fluctuations in the spatial solute distribution in the true random alloy randomness and (ii) average alloy properties such as stacking fault energy. The results show that the solute fluctuations dominate the activation energy barrier, i.e. there are large sample-to-sample variations around the average activation barrier. The variations in activation barrier correlate linearly with the energy difference between the initial and final states. The distribution of this energy difference can be computed analytically in terms of the solute/dislocation interaction energies. Thus, the distribution of cross-slip activation energies can be accurately determined from a parameter-free analytic model. The implications of the statistical distribution of activation energies on the rate of cross-slip in real alloys are then identified.

  13. Precision Electroweak measurements at the FCC-ee

    CERN Document Server

    Dam, Mogens

    2016-01-01

    Because of a luminosity of up to five orders of magnitude larger than at LEP, electroweak precision measurements at the FCC-ee -- the Future Circular Collider with electron-positron beams -- would provide improvements by orders of magnitude over the present status and constitute a broad search for the existence of new, weakly interacting particles up to very high energy scales. The FCC-ee will address centre-of-mass energies ranging from below the Z pole to the $\\mathrm{t\\bar{t}}$ threshold and above. At energies around the Z pole, the Z-boson mass and width can be measured to better than 100 keV each. Asymmetry measurements at the Z pole allow improvements in the determination of the weak mixing angle by at least a factor 30 to $\\delta\\sin^2\\theta\\mathrm{_W^{eff}}\\simeq 6\\times 10^{-6}$. A determination of the electromagnetic coupling constant at the Z energy scale, $\\alpha_\\mathrm{QED}(m_\\mathrm{Z}^2)$, to a relative precision of $3\\times 10^{-5}$ can be obtained via measurement of the forward-backward asym...

  14. Iron Contamination Mechanism and Reaction Performance Research on FCC Catalyst

    Directory of Open Access Journals (Sweden)

    Zhaoyong Liu

    2015-01-01

    Full Text Available FCC (Fluid Catalytic Cracking catalyst iron poisoning would not only influence units’ product slate; when the poisoning is serious, it could also jeopardize FCC catalysts’ fluidization in reaction-regeneration system and further cause bad influences on units’ stable operation. Under catalytic cracking reaction conditions, large amount of iron nanonodules is formed on the seriously iron contaminated catalyst due to exothermic reaction. These nodules intensify the attrition between catalyst particles and generate plenty of fines which severely influence units’ smooth running. A dense layer could be formed on the catalysts’ surface after iron contamination and the dense layer stops reactants to diffuse to inner structures of catalyst. This causes extremely negative effects on catalyst’s heavy oil conversion ability and could greatly cut down gasoline yield while increasing yields of dry gas, coke, and slurry largely. Research shows that catalyst’s reaction performance would be severely deteriorated when iron content in E-cat (equilibrium catalyst exceeds 8000 μg/g.

  15. Dielectric matrix, dynamical matrix and phonon dispersion in hcp transition metal scandium

    International Nuclear Information System (INIS)

    Singh, Joginder; Singh, Natthi; Prakash, S.

    1976-01-01

    Complete dielectric matrix is evaluated for hcp transition metal scandium using the non-interacting s- and d-band model. The local field corrections which are consequence of the non-diagonal part of the dielectric matrix are calculated explicitly. The free electron approximation is used for the s-electrons and the simple tight-binding approximation is used for the d-electrons. The theory developed by Singh and others is used to invert the dielectric matrix and the explicit expressions for the dynamical matrix are obtained. The phonon dispersion relations are investigated by using the renormalized Animalu transition metal model potential (TMMP) for bare ion potential. The contribution due to non-central forces which arise due to local fields is found to be 20%. The results are found in resonably good agreement with the experimental values. (author)

  16. Impact of polymorphisms in the HCP5 and HLA-C, and ZNRD1 genes on HIV viral load

    DEFF Research Database (Denmark)

    Thørner, Lise Wegner; Erikstrup, Christian; Harritshøj, Lene Holm

    2016-01-01

    AIMS: Single nucleotide polymorphisms (SNPs) in the human leucocyte antigen (HLA) complex P5 (HCP5), HLA-C, and near the zinc ribbon domain containing 1 (ZNRD1) have been shown to influence viral load (VL) set point in HIV-infected individuals with a known seroconversion onset. We aimed to determ...

  17. Observation of a New High-Pressure Solid Phase in Dynamically Compressed Aluminum

    Science.gov (United States)

    Polsin, D. N.

    2017-10-01

    Aluminum is ideal for testing theoretical first-principles calculations because of the relative simplicity of its atomic structure. Density functional theory (DFT) calculations predict that Al transforms from an ambient-pressure, face-centered-cubic (fcc) crystal to the hexagonal close-packed (hcp) and body-centered-cubic (bcc) structures as it is compressed. Laser-driven experiments performed at the University of Rochester's Laboratory for Laser Energetics and the National Ignition Facility (NIF) ramp compressed Al samples to pressures up to 540 GPa without melting. Nanosecond in-situ x-ray diffraction was used to directly measure the crystal structure at pressures where the solid-solid phase transformations of Al are predicted to occur. Laser velocimetry provided the pressure in the Al. Our results show clear evidence of the fcc-hcp and hpc-bcc transformations at 216 +/- 9 GPa and 321 +/- 12 GPa, respectively. This is the first experimental in-situ observation of the bcc phase in compressed Al and a confirmation of the fcc-hcp transition previously observed under static compression at 217 GPa. The observations indicate these solid-solid phase transitions occur on the order of tens of nanoseconds time scales. In the fcc-hcp transition we find the original texture of the sample is preserved; however, the hcp-bcc transition diminishes that texture producing a structure that is more polycrystalline. The importance of this dynamic is discussed. The NIF results are the first demonstration of x-ray diffraction measurements at two different pressures in a single laser shot. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  18. First Results for Fluid Dynamics, Neutronics and Fission Product Behaviour in HTR applying the HTR Code Package (HCP) Prototype

    International Nuclear Information System (INIS)

    Allelein, H.-J.; Kasselmann, S.; Xhonneux, A.; Lambertz, D.

    2014-01-01

    To simulate the different aspects of High Temperature Reactor (HTR) cores, a variety of specialized computer codes have been developed at Forschungszentrum Jülich (IEK-6) and Aachen University (LRST) in the last decades. In order to preserve knowledge, to overcome present limitations and to make these codes applicable to modern computer clusters, these individual programs are being integrated into a consistent code package. The so-called HTR code package (HCP) couples the related and recently applied physics models in a highly integrated manner and therefore allows to simulate phenomena with higher precision in space and time while at the same time applying state-of-the-art programming techniques and standards. This paper provides an overview of the status of the HCP and reports about first benchmark results for an HCP prototype which couples the fluid dynamics and time dependent neutronics code MGT-3D, the burn up code TNT and the fission product release code STACY. Due to the coupling of MGT-3D and TNT, a first step towards a new reactor operation and accident simulation code was made, where nuclide concentrations calculated by TNT are fed back into a new spectrum code of the HCP. Selected operation scenarios of the HTR-Module 200 concept plant and the HTTR were chosen to be simulated with the HCP prototype. The fission product release during normal operation conditions will be calculated with STACY based on a core status derived from SERPENT and MGT–3D. Comparisons will be shown against data generated by the legacy codes VSOP99/11, NAKURE and FRESCO-II. (author)

  19. 75 FR 62818 - Sunshine Act Meeting; FCC To Hold Open Commission Meeting Thursday, October 14, 2010

    Science.gov (United States)

    2010-10-13

    ... changes to the FCC's CableCARD rules to improve the consumer experience with the video navigation devices... Connection also will carry the meeting live via the Internet. To purchase these services call (703) 993-3100... purchased from the FCC's duplicating contractor, Best Copy and Printing, Inc. (202) 488-5300; Fax (202) 488...

  20. Determination of positions and curved transition pathways of screw dislocations in BCC crystals from atomic displacements

    Czech Academy of Sciences Publication Activity Database

    Gröger, Roman; Vítek, V.

    2015-01-01

    Roč. 643, SEP (2015), s. 203-210 ISSN 0921-5093 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : Screw dislocation * BCC metal * Dislocation pathway Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.647, year: 2015

  1. First-principles study of ternary bcc alloys using special quasi-random structures

    International Nuclear Information System (INIS)

    Jiang Chao

    2009-01-01

    Using a combination of exhaustive enumeration and Monte Carlo simulated annealing, we have developed special quasi-random structures (SQSs) for ternary body-centered cubic (bcc) alloys with compositions of A 1 B 1 C 1 , A 2 B 1 C 1 , A 6 B 1 C 1 and A 2 B 3 C 3 , respectively. The structures possess local pair and multisite correlation functions that closely mimic those of the random bcc alloy. We employed the SQSs to predict the mixing enthalpies, nearest neighbor bond length distributions and electronic density of states of bcc Mo-Nb-Ta and Mo-Nb-V solid solutions. Our convergence tests indicate that even small-sized SQSs can give reliable results. Based on the SQS energetics, the predicting powers of the existing empirical ternary extrapolation models were assessed. The present results suggest that it is important to take into account the ternary interaction parameter in order to accurately describe the thermodynamic behaviors of ternary alloys. The proposed SQSs are quite general and can be applied to other ternary bcc alloys.

  2. Direct Observation of the BCC (100) Plane in Thin Films of Sphere-forming Diblock Copolymers

    Science.gov (United States)

    Ji, Shengxiang; Nagpal, Umang; Liao, Wen; de Pablo, Juan; Nealey, Paul

    2010-03-01

    In sphere-forming diblock copolymers, periodic arrays of spheres are arranged in a body-centred cubic (BCC) lattice structure in bulk. However, in thin films different surface morphologies were observed as a function of the film thickness, and the transition from the hexagonal array to the BCC (110) arrangement of spheres on film surfaces was located with respect to the increase of the film thickness. Here we report the first direct observation of the BCC (100) plane in thin films of poly (styrene-b-methyl methacrylate) diblock copolymers on homogeneous substrates. By balancing the surface energies of both blocks, the lower energy BCC (100) plane corresponding to a square arrangement of half spheres, formed on film surfaces when the film thickness was commensurate with the spacing, L100, between (100) planes or greater than 2 L100. A hexagonal arrangement of spheres was only observed when the thickness was less than 2 L100 and incommensurate with 1 L100. Monte Carlo (MC) simulation confirmed our experimental observation and was used to investigate the transition of the arrangement of spheres as a function of the film thickness.

  3. Hirsutane Sesquiterpenes from Cultures of the Basidiomycete Marasmiellus sp. BCC 22389

    Directory of Open Access Journals (Sweden)

    Masahiko Isaka

    2016-08-01

    Full Text Available Abstract Two new hirsutane sesquiterpenes, marasmiellins A (1 and B (2, were isolated from cultures of the basidiomycete Marasmiellus sp. BCC 22389. The structures were elucidated on the basis of NMR spectroscopic and mass spectrometry data. The absolute configuration of marasmiellin B was determined by application of the modified Mosher’s method. Graphical Abstract

  4. Investigation of irradiation strengthening of bcc metals and their alloys. Progress report, January 1977--October 1977

    International Nuclear Information System (INIS)

    1977-01-01

    Progress is reported in the areas of (a) the effect of neutron damage on the dislocation kinetics in bcc metals and their alloys, and (b) the effect of 3 He on the deformation characteristics of body centered cubic metals and their alloys. Results obtained from these projects are discussed

  5. Solubility of hydrogen and deuterium in bcc-uranium-titanium alloys

    International Nuclear Information System (INIS)

    Powell, G.L.; Kirkpatrick, J.R.

    1996-01-01

    For the bcc-U-Ti alloy system, H and D solubility measurements have been made on 12 alloy specimens ranging in composition from pure U to pure Ti and temperature range bounded by 900 K to 1,500 K. The results are described by a model within a standard error of 3%

  6. Nucleation of recrystallization at selected sites in deformed fcc metals

    DEFF Research Database (Denmark)

    Xu, Chaoling

    The objective of this thesis is to explore nucleation of recrystallization at selected sites in selected face-centered-cubic (FCC) metals, namely cold rolled columnar-grained nickel and high purity aluminum further deformed by indenting. Various techniques, including, optical microscopy, electron...... backscattered diffraction (EBSD), electron channeling contrast (ECC) and synchrotron X-ray technique, differential-aperture X-ray microscopy (DAXM), were used to characterize the microstructures, to explore nucleation sites, orientation relationships between nuclei and deformed microstructures, and nucleation...... mechanisms. In the cold rolled nickel samples, the preference of triple junctions (TJs) and grain boundaries (GBs) as nucleation sites is observed. The majorities of the nuclei have the same orientations as the surrounding matrix or are twin-related to a surrounding deformed grain. Only a few nuclei...

  7. Calculation of the surface free energy of fcc copper nanoparticles

    International Nuclear Information System (INIS)

    Jia Ming; Lai Yanqing; Tian Zhongliang; Liu Yexiang

    2009-01-01

    Using molecular dynamics simulations with the modified analytic embedded-atom method we calculate the Gibbs free energy and surface free energy for fcc Cu bulk, and further obtain the Gibbs free energy of nanoparticles. Based on the Gibbs free energy of nanoparticles, we have investigated the heat capacity of copper nanoparticles. Calculation results indicate that the Gibbs free energy and the heat capacity of nanoparticles can be divided into two parts: bulk quantity and surface quantity. The molar heat capacity of the bulk sample is lower compared with the molar heat capacity of nanoparticles, and this difference increases with the decrease in the particle size. It is also observed that the size effect on the thermodynamic properties of Cu nanoparticles is not really significant until the particle is less than about 20 nm. It is the surface atoms that decide the size effect on the thermodynamic properties of nanoparticles

  8. The FCC-ee Interaction Region Magnet Design

    CERN Document Server

    Koratzinos, Michael; Blondel, Alain; Bogomyagkov, Anton; Holzer, Bernhard; Oide, Katsunobu; Sinyatkin, Sergey; Zimmermann, Frank; van Nugteren, Jeroen

    2016-01-01

    The design of the region close to the interaction point of the FCC-ee experiments is especially challenging. The beams collide at an angle (+-15 mrad) in the high-field region of the detector solenoid. Moreover, the very low vertical beta_y* of the machine necessitates that the final focusing quadrupoles have a distance from the IP (L*) of around 2 m and therefore are inside the main detector solenoid. The beams should be screened from the effect of the detector magnetic field, and the emittance blow-up due to vertical dispersion in the interaction region should be minimized, while leaving enough space for detector components. Crosstalk between the two final focus quadrupoles, only about 6 cm apart at the tip, should also be minimized.

  9. Lattice mechanical properties of some fcc f-shell metals

    International Nuclear Information System (INIS)

    Baria, J.K.; Jani, A.R.

    2003-01-01

    A pseudopotential depending on an effective core radius is proposed to study the binding energy, equation of state, ion-ion interaction, phonon dispersion curves (q-space and r-space analysis), mode Grueneisen parameters and dynamical elastic constants of some fcc f-shell metals La, Yb, Ce and Th. The contribution of the s-like electrons is calculated in the second-order perturbation theory for the potential while d- and f-like electron is taken into account by introducing repulsive short-range Born-Mayer term. The parameter of the potential is evaluated by zero pressure condition. An excellent agreement between theoretical investigations and experimental findings is achieved which confirms the present formalism. (author)

  10. Rayleigh oscillations localized near free surface of a fcc crystal

    International Nuclear Information System (INIS)

    Kosevich, A.M.; Matsokin, D.V.; Savotchenko, S.E.

    1997-01-01

    The waves, which are localized near the free (001) surface of a fcc crystal and propagate in the [110] direction, are described using the model of central interaction of the nearest neighbors. The frequencies of these waves come into the gaps within the frequency spectrum of bulk harmonic oscillations with a fixed wave vector k component along the surface. The long-wave limit and the case of wave vectors close to the Brillouin band boundary are studied analytically. These limit dependences are in agreement with other authors results which were obtained by numerical methods. Analytical calculations in the limit intervals of k are supplemented by numerical calculations for any values of the wave vector. It is essential that these waves have a displacement component which is perpendicular to the crystal surface and can, therefore, be studied by methods of He atoms inelastic scattering

  11. The FCC process as a producer of light olefins

    International Nuclear Information System (INIS)

    Yung, K.Y.; Yanik, S.; O'Connor, P.; Pouwels, C.

    1992-01-01

    To reduce emissions from the gasoline engine, aromatics content and vapor pressure of the motor gasoline pool will be reduced and a minimum amount of oxygen will be mandated. This reformulation will limit the application of high octane components like benzene, toluene and butanes and will require the use of oxygenates. To compensate for the loss in octane, the use of alkylate and, of course also oxygenates will grow. The Fluid Catalytic Cracking Unit is, as producer of (olefinic) propanes, butanes and pentanes, an important feedstock producer for alkylate and oxygenate producing process. Hence, process adjustments and FCC catalyst formations to increase the yield of above desirable light products are of prime importance and will be dealt with in this paper

  12. Lattice dynamics of fcc helium at high pressure

    International Nuclear Information System (INIS)

    Eckert, J.; Thomlinson, W.; Shirane, G.

    1977-01-01

    The neutron-inelastic-scattering technique was used to measure the phonon dispersion relations in a high-density crystal of fcc He at 38 K. The crystal was grown at a pressure of 4.93 kbar and a temperature of 38.5 K in a high-pressure sample holder. Its lattice parameter was determined to be 3.915 +- 0.002 A, equivalent to a molar volume of 9.03 cm 3 /mol. The measured dispersion curves were found to be in good agreement with a recent calculation by Goldman using the first-order self-consistent phonon theory without short-range correlation functions. The strong anharmonic effects observed in earlier measurements on the crystals of 21 cm 3 /mol were found to be much less prominent in this He crystal. The magnitude of the multiphonon interference effects on the one-phonon intensities is shown to be less than half of that observed in the low-density crystals. Thermodynamic analysis of the data yielded THETA/sup M//sub D/ = 154 K which indicates that the ratio of mean amplitude of vibration to the nearest-neighbor distance is 8.6%, as opposed to nearly 30% for the lowest-density He crystals. The dependence of the phonon energies on volume is discussed with reference to the earlier work of Traylor et al. on an fcc crystal at 11.7 cm 3 /mol. Limited measurements were also made at 22 K to determine the temperature dependence of the phonon energies. Unusually large isochoric temperature shifts of as much as 15% for some phonons close to the zone center were found over the range of 22--38 K

  13. In vivo assessment of optical properties of basal cell carcinoma and differentiation of BCC subtypes by high-definition optical coherence tomography

    DEFF Research Database (Denmark)

    Boone, Marc; Suppa, Mariano; Miyamoto, Makiko

    2016-01-01

    High-definition optical coherence tomography (HD-OCT) features of basal cell carcinoma (BCC) have recently been defined. We assessed in vivo optical properties (IV-OP) of BCC, by HD-OCT. Moreover their critical values for BCC subtype differentiation were determined. The technique of semi-log plot...

  14. Cellular Phone Towers, FCC registered communications towers. Points were generated from FCC data latlong. Originally created as a basis of comparison for Appraiser's cell tower points, bu comparison was inconclusive. Represented all registered FCC sites as of 6/26/2003. No, Published in 2003, 1:1200 (1in=100ft) scale, Sedgwick County Government.

    Data.gov (United States)

    NSGIC Local Govt | GIS Inventory — Cellular Phone Towers dataset current as of 2003. FCC registered communications towers. Points were generated from FCC data latlong. Originally created as a basis of...

  15. Influence of hydrostatic pressure on BCC-lattice parameter in molybdenum, niobium and vanadium with rhenium solid solutions

    International Nuclear Information System (INIS)

    Smol'yaninova, Eh.A.; Stribuk, E.K.; Tyavlovskij, V.I.

    1987-01-01

    Data on the effect of 1.8GPa hydrostatic pressure on bcc lattice parameters of solid solutions in Mo-Re, Nb-Re, V-re systems are presented. It is shown that after the application hydrostatic pressure a decrease in bcc lattice parameter is observed and the greatest change in the lattice parameter takes place in bcc of solid solutions in the Nb-Re system (DELTA A ∼ 0.0035 nm). Analysis of the experimental data obtained on the basis of calculations made for packing density change in the above-mentioned solid solutions under the pressure is carried out

  16. Atomistic simulations of dislocations in a model BCC multicomponent concentrated solid solution alloy

    International Nuclear Information System (INIS)

    Rao, S.I.; Varvenne, C.; Woodward, C.; Parthasarathy, T.A.; Miracle, D.; Senkov, O.N.; Curtin, W.A.

    2017-01-01

    Molecular statics and molecular dynamics simulations are presented for the structure and glide motion of a/2〈111〉 dislocations in a randomly-distributed model-BCC Co 16.67 Fe 36.67 Ni 16.67 Ti 30 alloy. Core structure variations along an individual dislocation line are found for a/2〈111〉 screw and edge dislocations. One reason for the core structure variations is the local variation in composition along the dislocation line. Calculated unstable stacking fault energies on the (110) plane as a function of composition vary significantly, consistent with this assessment. Molecular dynamics simulations of the critical glide stress as a function of temperature show significant strengthening, and much shallower temperature dependence of the strengthening, as compared to pure BCC Fe as well as a reference mean-field BCC alloy material of the same overall composition, lattice and elastic constants as the target alloy. Interpretation of the strength versus temperature in terms of an effective kink-pair activation model shows the random alloy to have a much larger activation energy than the mean-field alloy or BCC Fe. This is interpreted as due to the core structure variations along the dislocation line that are often unfavorable for glide in the direction of the load. The configuration of the gliding dislocation is wavy, and significant debris is left behind, demonstrating the role of local composition and core structure in creating kink pinning (super jogs) and/or deflection of the glide plane of the dislocation. - Graphical abstract: Measured critical resolved shear stress scaled by the (111) shear modulus (39 GPa) necessary to achieve on-going glide as a function of temperature, for the a/2[111] screw dislocation in the model BCC Co 16.67 Fe 36.67 Ni 16.67 Ti 30 alloy. The upper and lower bounds of the critical resolved shear stress is shown in the plot. Also shown in is the measured strength for the mean-field A-atom material and BCC Fe as a function of

  17. Threefold symmetric magnetic two-ion coupling in hcp rare-earth metals

    International Nuclear Information System (INIS)

    Jensen, J.

    1997-01-01

    The heavy rare earths crystallize in the hcp structure. Most of magnetic couplings between two ions in these metals are independent of the two different orientations of the hexagonal layers. However, trigonal anisotropy terms may occur, reflecting that c-axis is only threefold axis. In the presence of a trigonal coupling the symmetry is reduced, and the double-zone representation in the c-direction ceases to be valid. The strong interaction between the transverse optical phonons and the acoustic spin waves propagating in the c-direction of Yb detected more than twenty years ago, was the first example of a trigonal coupling found in these systems. A few years ago a careful neutron-diffraction study of the c-axis modulated magnetic structures in Er showed the presence of higher harmonics at positions along the c-axis translated by odd multiple of 2φ/c. This indicates distortions of the structures due to trigonal couplings, and the same characteristic phenomenon has now been also observed in Ho. Additionally, mean field calculations show that a trigonal coupling in Ho is required, in order to explain the increase in the commensurable effects observed for the 8 and 10 layered periodic structures, when a field is applied along the c-axis. (author)

  18. Modelling the motion of {112-bar 2} twinning dislocations in the HCP metals

    International Nuclear Information System (INIS)

    Serra, A.; Bacon, D.J.

    2005-01-01

    Deformation twinning is important for plasticity of the hcp metals, but little is known about the dynamics of the mechanisms that control twin boundary motion. With the exception of the {112-bar 1} twin, atomic shuffles are required for glide of twinning dislocations and hence boundary movement is temperature-dependent. A computer method has been developed to simulate a step with dislocation character in a boundary with full periodicity in the boundary plane, i.e. along both the direction of the line of the defect and its direction of motion. It may be used to investigate the properties of such interfaces as the defects in them move over large distances. We explain the nature of the method and apply it to study the motion of twinning dislocations in the {112-bar 2} boundary as a function of applied stress and temperature. A new reaction at the boundary leading to the creation of a (c+a) crystal dislocation and a {112-bar 1} micro-twin is described

  19. Nucleation size of hcp-CoPt dot arrays characterized by time dependence of coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, N; Kitakami, O [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, 980-8577 (Japan); Mitsuzuka, K; Shimatsu, T; Aoi, H, E-mail: kikuchin@tagen.tohoku.ac.j [Research Institute of Electrical Communication, Tohoku University, Sendai, 980-8577 (Japan)

    2010-01-01

    The magnetization reversal process for dot arrays is likely to start from a nucleation followed by propagation process. In this study, we estimated the nucleation diameter D{sub n} for dot arrays made from thin hcp-CoPt perpendicular films (thickness {delta}=3 nm) and Co/Pt multilayered films ({delta}=9 nm), respectively. The dot diameter, D, was varied from 30 to 200 nm for CoPt dot arrays, and from 40 to 80 nm for Co/Pt dot arrays. The remanence coercivity was measured at measurement times t' = 10{sup 3} s and 10{sup -5} s (pulse field), and defined as H{sub r} and H{sub r}{sup P}. The energy barrier {Delta}E was evaluated by fitting H{sub r} and H{sub r}{sup P} to Sharrock's equation. The value of D{sub n} was estimated from {Delta}E, {delta} and the effective magnetic anisotropy of dot arrays including the demagnetizing energy due to the dot shape K{sub u}{sup eff}. D{sub n} was independent of Din both series of dot arrays, and about 17 nm for CoPt dot arrays and about 11 nm for Co/Pt dot arrays. These values were close to both the grain size and the exchange length of these films.

  20. Diffusivities and atomic mobilities in disordered fcc and ordered L12 Ni–Al–W alloys

    International Nuclear Information System (INIS)

    Chen, Chong; Zhang, Lijun; Xin, Jinghua; Wang, Yaru; Du, Yong; Luo, Fenghua; Zhang, Zhongjian; Xu, Tao; Long, Jianzhan

    2015-01-01

    Highlights: • The atomic mobilities for fcc Al–W, fcc Ni–W, fcc Ni–Al–W and L1 2 Ni–Al–W alloys were critically assessed. • The impurity diffusivity of W in fcc-Al was obtained via first-principles calculations. • The calculated results agree well with the diffusivities available in the literature. • Two fcc/L1 2 -type diffusion couples were prepared and the concentration-distance profiles were measured. • The model-predicted concentration profiles agree well with the experimental data in the literature and in the present work. - Abstract: Based on various experimentally measured diffusivities available in the literature together with the reported thermodynamic parameters, the atomic mobilities for disordered fcc and ordered L1 2 Ni–Al–W alloys were assessed on the basis of a recently developed phenomenological model incorporated in the DICTRA software. In order to provide the missing impurity diffusion coefficients of W in fcc-Al, first-principles calculations were utilized in the present work. Comprehensive comparisons between the calculated and experimental diffusion coefficients show that all the experimental data can be well reproduced by the atomic mobilities obtained in the present work. In order to further verify the reliability of the presently obtained atomic mobilities, two fcc/L1 2 -type diffusion couples (i.e., Ni–5 at.% Al–5 at.% W/Ni–20 at.% Al–4 at.% W and Ni/Ni–22 at.% Al–2 at.% W) were prepared and the concentration-distance profiles after annealing at 1323 K for 86.4 ks were measured. The excellent agreement between the model-predicted concentration-distance profiles and the experimental data indicates that the presently obtained atomic mobilities in fcc/L1 2 Ni–Al–W alloys are reliable

  1. Reusing a residue of the oil industry (FCC) in the production of building elements

    OpenAIRE

    Caicedo Casso, Eduard Andrés; Universidad del Valle; Mejía de Gutiérrez, Ruby; Universidad del Valle; Gordillo Suárez, Marisol; Universidad Autónoma de Occidente; Torres Agredo, Janneth; Universidad Nacional de Colombia, sede Palmira

    2015-01-01

    This paper analyzes the feasibility of using a residue of spent catalyst (FCC) of the cracking process, from a Colombian oil company, in the production of building elements such as locks and pavers. To define the optimal mix of portland cement/FCC, Portland cement mortars with FCC ratios between 0 and 70% as replacement of cement were prepared and its compressive strength is evaluated at ages up to 28 days of curing. Using a statistical processing, applying the methodology of response, the pr...

  2. A constitutional investigation of the Mo-Pd-Rh ternary system at 1100deg C

    International Nuclear Information System (INIS)

    Guerler, R.; Pratt, J.N.

    1991-01-01

    Phase relations in the system Mo-Pd-Rh were studied at 1100deg C using conventionally melted and ultrarapidly solidified samples. Optical microscopy, X-ray diffraction, scanning electron microscopy and electron probe microanalysis were used for phase characterisation. The complete isothermal section at 1100deg C was established. The Mo bcc phase was found to have a very limited solid solution range whereas the ternary fcc solid solution originating on the Pd-Rh binary is the dominant phase in the system at this temperature. The centre of the isothermal is dominated by the ternary extension of the Mo-Rh hcp intermediate phase. The three phase (bcc+fcc+hcp) equilibrium region is located very near to the Mo-Pd binary system. No additional ternary intermediate phases were observed. The results are consistent with an isothermal section reported at higher temperatures. (orig.)

  3. First results for fluid dynamics, neutronics and fission product behavior in HTR applying the HTR code package (HCP) prototype

    Energy Technology Data Exchange (ETDEWEB)

    Allelein, H.-J., E-mail: h.j.allelein@fz-juelich.de [Forschungszentrum Jülich, 52425 Jülich (Germany); Institute for Reactor Safety and Reactor Technology, RWTH Aachen University, 52064 Aachen (Germany); Kasselmann, S.; Xhonneux, A.; Tantillo, F.; Trabadela, A.; Lambertz, D. [Forschungszentrum Jülich, 52425 Jülich (Germany)

    2016-09-15

    To simulate the different aspects of High Temperature Reactor (HTR) cores, a variety of specialized computer codes have been developed at Forschungszentrum Jülich (IEK-6) and Aachen University (LRST) in the last decades. In order to preserve knowledge, to overcome present limitations and to make these codes applicable to modern computer clusters, these individual programs are being integrated into a consistent code package. The so-called HTR code package (HCP) couples the related and recently applied physics models in a highly integrated manner and therefore allows to simulate phenomena with higher precision in space and time while at the same time applying state-of-the-art programming techniques and standards. This paper provides an overview of the status of the HCP and reports about first benchmark results for an HCP prototype which couples the fluid dynamics and time dependent neutronics code MGT-3D, the burn up code TNT and the fission product release code STACY. Due to the coupling of MGT-3D and TNT, a first step towards a new reactor operation and accident simulation code was made, where nuclide concentrations calculated by TNT lead to new cross sections, which are fed back into MGT-3D. Selected operation scenarios of the HTR-Module 200 concept plant and the HTTR were chosen to be simulated with the HCP prototype. The fission product release during normal operation conditions will be calculated with STACY based on a core status derived from SERPENT and MGT-3D. Comparisons will be shown against data generated by SERPENT and the legacy codes VSOP99/11, NAKURE and FRESCO-II.

  4. Lattice dynamics and thermophysical properties of h.c.p. Os and Ru from the quasi-harmonic approximation.

    Science.gov (United States)

    Palumbo, Mauro; Dal Corso, Andrea

    2017-10-04

    We report first-principles phonon frequencies and anharmonic thermodynamic properties of h.c.p. Os and Ru calculated within the quasi-harmonic approximation, including Grüneisen parameters, temperature-dependent lattice parameters, thermal expansion, and isobaric heat capacity. We discuss the differences between a full treatment of anisotropy and a simplified approach with a constant [Formula: see text] ratio. The results are systematically compared with the available theoretical and experimental data and an overall satisfactory agreement is obtained.

  5. Modelling irradiation-induced softening in BCC iron by crystal plasticity approach

    International Nuclear Information System (INIS)

    Xiao, Xiazi; Terentyev, Dmitry; Yu, Long; Song, Dingkun; Bakaev, A.; Duan, Huiling

    2015-01-01

    Crystal plasticity model (CPM) for BCC iron to account for radiation-induced strain softening is proposed. CPM is based on the plastically-driven and thermally-activated removal of dislocation loops. Atomistic simulations are applied to parameterize dislocation-defect interactions. Combining experimental microstructures, defect-hardening/absorption rules from atomistic simulations, and CPM fitted to properties of non-irradiated iron, the model achieves a good agreement with experimental data regarding radiation-induced strain softening and flow stress increase under neutron irradiation. - Highlights: • A stress- and thermal-activated defect absorption model is proposed for the dislocation-loop interaction. • A temperature-dependent plasticity theory is proposed for the irradiation-induced strain softening of irradiated BCC metals. • The numerical results of the model match with the corresponding experimental data.

  6. Simulation of He embrittlement at grain boundaries in bcc transition metals

    International Nuclear Information System (INIS)

    Suzudo, Tomoaki; Yamaguchi, Masatake

    2015-01-01

    To investigate what atomic properties largely determine vulnerability to He embrittlement at grain boundaries (GB) of bcc metals, we introduce a computational model composed of first principles density functional theory and a He segregation rate theory model. Predictive calculations of He embrittlement at the first wall of the future DEMO fusion concept reactor indicate that variation in the He embrittlement originated not only from He production rate related to neutron irradiation, but also from the He segregation energy at the GB that has a systematic trend in the periodic table. - Highlights: • We modeled He grain boundary (GB) segregation of bcc transition metals using first-principles-based rate theory. • We established the quantitative relation between He embrittlement and He segregation using GB cohesive energy. • He embrittlement was strongly dependent on He segregation energy at the GB that has a systematic trend in the periodic table.

  7. Simulation of He embrittlement at grain boundaries in bcc transition metals

    Energy Technology Data Exchange (ETDEWEB)

    Suzudo, Tomoaki, E-mail: suzudo.tomoaki@jaea.go.jp; Yamaguchi, Masatake

    2015-10-15

    To investigate what atomic properties largely determine vulnerability to He embrittlement at grain boundaries (GB) of bcc metals, we introduce a computational model composed of first principles density functional theory and a He segregation rate theory model. Predictive calculations of He embrittlement at the first wall of the future DEMO fusion concept reactor indicate that variation in the He embrittlement originated not only from He production rate related to neutron irradiation, but also from the He segregation energy at the GB that has a systematic trend in the periodic table. - Highlights: • We modeled He grain boundary (GB) segregation of bcc transition metals using first-principles-based rate theory. • We established the quantitative relation between He embrittlement and He segregation using GB cohesive energy. • He embrittlement was strongly dependent on He segregation energy at the GB that has a systematic trend in the periodic table.

  8. First-principles study of atomic ordering in bcc Cu-Al

    Science.gov (United States)

    Lanzini, F.; Gargano, P. H.; Alonso, P. R.; Rubiolo, G. H.

    2011-01-01

    The order-disorder transitions and phase stability in the body centered cubic structure of Cu-Al binary alloys are studied by means of theoretical methods. The total energy of different ordered compounds sharing a common bcc Bravais lattice was calculated within the framework of density functional theory. A set of effective cluster interactions was calculated through a cluster expansion (CE) of the total energies. The finite temperature phase diagram of bcc Cu-Al was obtained using the CE formalism coupled with the cluster variation method calculation of the configurational entropy. These results are confronted with a simpler semi-empirical approach based on effective pair interactions obtained from experiment. Both approaches predict a single first-order A2/DO3 transition for compositions close to Cu3Al, in agreement with the most recent experimental results.

  9. Modelling irradiation-induced softening in BCC iron by crystal plasticity approach

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Xiazi [State Key Laboratory for Turbulence and Complex System, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871 (China); CAPT, HEDPS and IFSA Collaborative Innovation Center of MoE, Peking University, Beijing 100871 (China); Terentyev, Dmitry, E-mail: dterenty@SCKCEN.BE [Structural Material Group, Institute of Nuclear Materials Science, SCK-CEN, Mol (Belgium); Yu, Long; Song, Dingkun [State Key Laboratory for Turbulence and Complex System, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871 (China); Bakaev, A. [Structural Material Group, Institute of Nuclear Materials Science, SCK-CEN, Mol (Belgium); Duan, Huiling, E-mail: hlduan@pku.edu.cn [State Key Laboratory for Turbulence and Complex System, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871 (China); CAPT, HEDPS and IFSA Collaborative Innovation Center of MoE, Peking University, Beijing 100871 (China)

    2015-11-15

    Crystal plasticity model (CPM) for BCC iron to account for radiation-induced strain softening is proposed. CPM is based on the plastically-driven and thermally-activated removal of dislocation loops. Atomistic simulations are applied to parameterize dislocation-defect interactions. Combining experimental microstructures, defect-hardening/absorption rules from atomistic simulations, and CPM fitted to properties of non-irradiated iron, the model achieves a good agreement with experimental data regarding radiation-induced strain softening and flow stress increase under neutron irradiation. - Highlights: • A stress- and thermal-activated defect absorption model is proposed for the dislocation-loop interaction. • A temperature-dependent plasticity theory is proposed for the irradiation-induced strain softening of irradiated BCC metals. • The numerical results of the model match with the corresponding experimental data.

  10. Precision natural SUSY at CEPC, FCC-ee, and ILC

    International Nuclear Information System (INIS)

    Fan, JiJi; Reece, Matthew; Wang, Lian-Tao

    2015-01-01

    Testing the idea of naturalness is and will continue to be one of the most important goals of high energy physics experiments. It will play a central role in the physics program of future colliders. In this paper, we present projections of the reach of natural SUSY at future lepton colliders: CEPC, FCC-ee and ILC. We focus on the observables which give the strongest reach, the electroweak precision observables (for left-handed stops), and Higgs to gluon and photon decay rates (for both left- and right-handed stops). There is a “blind spot” when the stop mixing parameter X t is approximately equal to the average stop mass. We argue that in natural scenarios, bounds on the heavy Higgs bosons from tree-level mixing effects that modify the hbb̄ coupling together with bounds from b→sγ play a complementary role in probing the blind spot region. For specific natural SUSY scenarios such as folded SUSY in which the top partners do not carry Standard Model color charges, electroweak precision observables could be the most sensitive probe. In all the scenarios discussed in this paper, the combined set of precision measurements will probe down to a few percent in fine-tuning.

  11. New theory for crack-tip twinning in fcc metals

    Science.gov (United States)

    Andric, Predrag; Curtin, W. A.

    2018-04-01

    Dislocation emission from a crack tip is a necessary mechanism for crack tip blunting and toughening. In fcc metals under Mode I loading, a first partial dislocation is emitted, followed either by a trailing partial dislocation ("ductile" behaviour) or a twinning partial dislocation ("quasi-brittle"). The twinning tendency is usually estimated using the Tadmor and Hai extension of the Rice theory. Extensive molecular statics simulations reveal that the predictions of the critical stress intensity factor for crack tip twinning are always systematically lower (20-35%) than observed. Analyses of the energy change during nucleation reveal that twin partial emission is not accompanied by creation of a surface step while emission of the trailing partial creates a step. The absence of the step during twinning motivates a modified model for twinning nucleation that accounts for the fact that nucleation does not occur directly at the crack tip. Predictions of the modified theory are in excellent agreement with all simulations that show twinning. Emission of the trailing partial dislocation, including the step creation, is predicted using a model recently introduced to accurately predict the first partial emission and shows why twinning is preferred. A second mode of twinning is found wherein the crack first advances by cleavage and then emits the twinning partial at the new crack tip; this mode dominates for emission beyond the first twinning partial. These new theories resolve all the discrepancies between the Tadmor twinning analysis and simulations, and have various implications for fracture behaviour and transitions.

  12. Scenario for Precision Beam Energy Calibration in FCC-ee

    CERN Document Server

    Koop, I A

    2015-01-01

    The resonance depolarization method was very successfully used in the experiments at LEP, where the mass of the Z-boson was determined with the relative uncertainty [1, 2]. In the future FCC-ee circular electron-positron collider the luminosity at Z-peak (beam energy 45.5 GeV) is expected be 4-5 orders of magnitude higher and one goal is to perform the same experiments as at LEP, but with much greater accuracy, approaching the level of [3]. Obviously this can be done only by measuring the spin precession frequency. But there are many problems which still need to be solved on the way towards a complete design. The first one: the self-polarization takes too long a time. The Sokolov-Ternov polarization time is about 250 hours at Z-peak. One approach is to install the special field-asymmetric polarizing wigglers to make the self-polarization time much shorter [4, 5] and to utilize only few percent of the polarization degree to measure the resonance spin precession frequency. But these very strong wigglers substan...

  13. Path-integral Monte Carlo study of phonons in the bcc phase of Helium-3

    OpenAIRE

    Sorkin, V.; Polturak, E.; Adler, Joan

    2006-01-01

    Using Path Integral Monte Carlo and the Maximum Entropy method, we calculate the dynamic structure factor of solid He-3 in the bcc phase at a finite temperature of T = 1.6 K and a molar volume of 21.5 cm^3. From the single phonon dynamic structure factor, we obtain both the longitudinal and transverse phonon branches along the main crystalline directions, [001], [011] and [111]. Our results are compared with other theoretical predictions and available experimental data.

  14. Atomistic model application to the problem of magnetite adhesion on iron BCC

    International Nuclear Information System (INIS)

    Forti; M; Alonso, P; Gargano, P; Rubiolo, G

    2012-01-01

    Oxide scale adhesion on a metal substrate has been investigated in the Magnetite - BCC Iron system. An Universal Binding Energy Relation (UBER) has been applied to obtain the interface energy from a fitting parameter. The interface energy thus calculated is in a reasonable order of magnitude when compared to experimental data for similar systems. This result allows this technique to be used to develop a comparative scale based on quantitative data which otherwise would require complex experiments to be obtained (author)

  15. 3D atomistic simulation of fatigue behavior of a ductile crack in bcc iron

    Czech Academy of Sciences Publication Activity Database

    Uhnáková, Alena; Machová, Anna; Hora, Petr

    2011-01-01

    Roč. 33, č. 9 (2011), s. 1182-1188 ISSN 0142-1123 R&D Projects: GA ČR(CZ) GAP108/10/0698 Institutional research plan: CEZ:AV0Z20760514 Keywords : 3D molecular dynamics * fatigue * bcc iron * mode I Subject RIV: JG - Metallurgy Impact factor: 1.546, year: 2011 http://www.sciencedirect.com/science/article/pii/S0142112311000600

  16. Crack-induced stress, dislocations and acoustic emission by 3-D atomistic simulation in bcc iron

    Czech Academy of Sciences Publication Activity Database

    Spielmannová, Alena; Machová, Anna; Hora, Petr

    2009-01-01

    Roč. 57, č. 14 (2009), s. 4065-4073 ISSN 1359-6454 R&D Projects: GA ČR GA101/09/1630; GA AV ČR KJB200760802; GA ČR(CZ) GA101/07/0789 Institutional research plan: CEZ:AV0Z20760514 Keywords : bcc iron * crack * dislocation emisision Subject RIV: JG - Metallurgy Impact factor: 3.760, year: 2009

  17. Short-range order clustering in BCC Fe-Mn alloys induced by severe plastic deformation

    Science.gov (United States)

    Shabashov, V. A.; Kozlov, K. A.; Sagaradze, V. V.; Nikolaev, A. L.; Lyashkov, K. A.; Semyonkin, V. A.; Voronin, V. I.

    2018-03-01

    The effect of severe plastic deformation, namely, high-pressure torsion (HPT) at different temperatures and ball milling (BM) at different time intervals, has been investigated by means of Mössbauer spectroscopy in Fe100-xMnx (x = 4.1, 6.8, 9) alloys. Deformation affects the short-range clustering (SRC) in BCC lattice. Two processes occur: destruction of SRC by moving dislocations and enhancement of the SRC by migration of non-equilibrium defects. Destruction of SRC prevails during HPT at 80-293 K; whereas enhancement of SRC dominates at 473-573 K. BM starts enhancing the SRC formation at as low as 293 K due to local heating at impacts. The efficiency of HPT in terms of enhancing SRC increases with increasing temperature. The authors suppose that at low temperatures, a significant fraction of vacancies are excluded from enhancing SRC because of formation of mobile bi- and tri-vacancies having low efficiency of enhancing SRC as compared to that of mono vacancies. Milling of BCC Fe100-xMnx alloys stabilises the BCC phase with respect to α → γ transition at subsequent isothermal annealing because of a high degree of work hardening and formation of composition inhomogeneity.

  18. Hydrogen storage performance of Ti-V-based BCC phase alloys with various Fe content

    International Nuclear Information System (INIS)

    Yu, X.B.; Feng, S.L.; Wu, Z.; Xia, B.J.; Xu, N.X.

    2005-01-01

    The effect of Fe content on hydrogen storage characteristics of Ti-10Cr-18Mn-(32-x)V-xFe (x = 0, 2, 3, 4, 5) alloys has been investigated at 353 K. The X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images of the alloys present BCC and C14 two-phase structures for all of the Fe-containing alloys. With the increasing Fe content, the lattice parameters of the BCC phase decrease, which results in an increase of the hydrogen desorption plateau pressure of the alloys. Among the studied alloys, Ti-10Cr-18Mn-27V-5Fe alloy exhibits the smallest PCT plateau slope and a more suitable plateau pressure (0.1 MPa equ <1 MPa). The maximum and effective capacities of the alloy are 3.32 wt.% and 2.26 wt.%, respectively, which are higher than other reported Fe-containing BCC phase alloys. In addition, the V/Fe ratio in this alloy is close to that of (VFe) alloy, whose cost is much lower than that of pure V

  19. Hydrogen storage in TiCr1.2(FeV)x BCC solid solutions

    International Nuclear Information System (INIS)

    Santos, Sydney F.; Huot, Jacques

    2009-01-01

    The Ti-V-based BCC solid solutions have been considered attractive candidates for hydrogen storage due to their relatively large hydrogen absorbing capacities near room temperature. In spite of this, improvements of some issues should be achieved to allow the technological applications of these alloys. Higher reversible hydrogen storage capacity, decreasing the hysteresis of PCI curves, and decrease in the cost of the raw materials are needed. In the case of vanadium-rich BCC solid solutions, which usually have large hydrogen storage capacities, the search for raw materials with lower cost is mandatory since pure vanadium is quite expensive. Recently, the substitutions of vanadium in these alloys have been tried and some interesting results were achieved by replacing vanadium by commercial ferrovanadium (FeV) alloy. In the present work, this approach was also adopted and TiCr 1.2 (FeV) x alloy series was investigated. The XRD patterns showed the co-existence of a BCC solid solution and a C14 Laves phase in these alloys. SEM analysis showed the alloys consisted of dendritic microstructure and C14 colonies. The amount of C14 phase increases when the amount of (FeV) decreases in these alloys. Concerning the hydrogen storage, the best results were obtained for the TiCr 1.2 (FeV) 0.4 alloy, which achieved 2.79 mass% of hydrogen storage capacity and 1.36 mass% of reversible hydrogen storage capacity

  20. Ab initio study of Cr interactions with point defects in bcc Fe

    International Nuclear Information System (INIS)

    Olsson, P.; Domain, Ch.; Wallenius, J.

    2008-01-01

    Full text of publication follows. Ferritic martensitic steels are candidate structural materials for fast neutron reactors, and in particular high-Cr reduced-activation steels. In Fe-Cr alloys, Cr plays a major role in the radiation-induced evolution of the mechanical properties. Using ab initio calculations based on density functional theory, the properties of Cr in α-Fe have been investigated. The intrinsic point defect formation energies were found to be larger in model bcc Cr as compared to those in ferromagnetic bcc Fe. The interactions of Cr with point defects (vacancy and self interstitials) have been characterised. Single Cr atoms interact weakly with vacancies but significantly with self-interstitial atoms. Mixed interstitials of any interstitial symmetry are bound. Configurations where two Cr atoms are in nearest neighbour position are generally unfavourable in bcc Fe except when they are a part of a interstitial complex. Mixed interstitials do not have as strong directional stability as pure Fe interstitials have. The effects on the results using the atom description scheme of either the ultrasoft pseudo-potential (USPP) or the projector augmented wave (PAW) formalisms are connected to the differences in local magnetic moments that the two methods predict. As expected for the Fe-Cr system, the results obtained using the PAW method are more reliable than the ones obtained with USPP. (authors)

  1. Microstructural characterization of EXCEL alloy

    International Nuclear Information System (INIS)

    Oroza Z E, Celiz; Saumell M, Lani; Versaci, R A; Bozzano, P B

    2012-01-01

    The microstructure of Excel alloy was studied by optical and scanning electron microscopy. X-ray diffraction was used to analyze the present phases. Characteristic peaks of α-Zr (HCP), β-Zr (BCC) and δhydride (FCC) were identified. The high relatives intensities of certain peaks suggest that samples are textured. Basal poles were dominant in radial-longitudinal planes and prismatic poles have the highest concentration in radial-tangential planes (author)

  2. Structural dependence of the 5d-metal surface energies as deduced from surface core-level shift measurements

    International Nuclear Information System (INIS)

    Mrartensson, N.; Saalfeld, H.B.; Kuhlenbeck, H.; Neumann, M.

    1989-01-01

    Surface core-level shift measurements performed at the BESSY storage ring yield -0.41(2) eV for Os(0001) and 0.00(10) eV for Re(0001). An analysis of the surface shifts in the 5d transition series shows that the surface energy as a function of Z has a maximum at lower Z for the bcc phase than for the fcc-hcp phases, at W and between Re and Os, respectively

  3. Workshop summary, future prospects and FCC-ee impact on $\\alpha_s$

    CERN Document Server

    d'Enterria, David

    2015-01-01

    The workshop on “High-precision α s measurements from LHC to FCC-ee” –organized in the con- text of the preparation of the Future Circular Collider (FCC) Conceptual Design Report, within the FCC-e + e − “QCD and photon-photon” physics working group activities– discussed the latest advances in the measurement of the strong interaction coupling α s . The meeting brought together leading experts in the field to explore in depth recent theoretical and experimental developments on the determination of α s , new ways to measure this coupling in lepton-lepton, lepton-hadron and hadron-hadron collisions, and in particular the improvements expected at the proposed Future Circular Collider e + e − (FCC-ee) facility.

  4. Tunneling anisotropic magnetoresistance in Co/AIOx/Al tunnel junctions with fcc Co (111) electrodes

    NARCIS (Netherlands)

    Wang, Kai; Tran, T. Lan Ahn; Brinks, Peter; Brinks, P.; Sanderink, Johannes G.M.; Bolhuis, Thijs; van der Wiel, Wilfred Gerard; de Jong, Machiel Pieter

    2013-01-01

    Tunneling anisotropic magnetoresistance (TAMR) has been characterized in junctions comprised of face-centered cubic (fcc) Co (111) ferromagnetic electrodes grown epitaxially on sapphire substrates, amorphous AlOx tunnel barriers, and nonmagnetic Al counterelectrodes. Large TAMR ratios have been

  5. Melting temperature and structural transformation of some rare-earth metals

    International Nuclear Information System (INIS)

    Vu Van Hung; Hoang Van Tich; Dang Thanh Hai

    2009-01-01

    the pressure dependence of the melting temperatures of rare-earth metals is studied using the equation of states derived from the statistical moment (SMM). SMM studies were carried out order to calculate the Helmholtz free energy of hcp, bcc Dy and fcc, bcc Ce metals at a wide range of temperatures. the stable phase of Dy and Ce metals can be determined by examining the Helmholtz free energy at a given temperature, i, e. the phase that gives the lowest free energy will be stable. For example, we found that at T lower than 1750 K the hcp Dy metal is stable. At T higher than 1750 K the bcc Dy metal is also stable. Thus 1750 K marks the phase transition temperature of Dy metal. These findings are in agreement with previous experiments. (author)

  6. Fabry-Perot magnonic ballistic coherent transport across ultrathin ferromagnetic lamellar bcc Ni nanostructures between Fe leads

    Science.gov (United States)

    Khater, A.; Saim, L.; Tigrine, R.; Ghader, D.

    2018-06-01

    We propose thermodynamically stable systems of ultrathin lamellar bcc Ni nanostructures between bcc Fe leads, sbnd Fe[Ni(n)]Fesbnd , based on the available literature for bcc Ni overlayers on Fe(001) surfaces, and establish the necessary criteria for their structural and ferromagnetic order, for thicknesses n ≤ 6 bcc Ni monatomic layers. The system is globally ferromagnetic. A theoretical model is presented to investigate and understand the ballistic coherent scattering of Fe spin-waves, incident from the leads, at the ferromagnetic bcc Ni nanostructure. The Nisbnd Ni and Nisbnd Fe exchange are computed using the Ising effective field theory (EFT), and the magnetic ground state of the system is constructed in the Heisenberg representation. We compute the spin-wave eigenmodes localized on the bcc Ni nanostructure, using the phase field matching theory (PFMT), illustrating the effects of symmetry breaking on the confinement of localized spin excitations. The reflection and transmission scattering properties of spin-waves incident from the Fe leads, across the embedded Ni nanostructures are investigated within the framework of the same PFMT methodology. A highly refined Fabry-Perot magnonic ballistic coherent transmission spectra is observed for these sbnd Fe[Ni(n)]Fesbnd systems.

  7. Limitations of BCC_CSM's ability to predict summer precipitation over East Asia and the Northwestern Pacific

    Science.gov (United States)

    Gong, Zhiqiang; Dogar, Muhammad Mubashar Ahmad; Qiao, Shaobo; Hu, Po; Feng, Guolin

    2017-09-01

    This study examines the ability of the Beijing Climate Center Climate System Model (BCC_CSM) to predict the meridional pattern of summer precipitation over East Asia-Northwest Pacific (EA-NWP) and its East Asia-Pacific (EAP) teleconnection. The differences of summer precipitation modes of the empirical orthogonal function and the bias of atmospheric circulations over EA-NWP are analyzed to determine the reason for the precipitation prediction errors. Results indicate that the BCC_CSM could not reproduce the positive-negative-positive meridional tripole pattern from south to north that differs markedly from that observed over the last 20 years. This failure can be attributed to the bias of the BCC_CSM hindcasts of the summer EAP teleconnection and the low predictability of 500 hPa at the mid-high latitude lobe of the EAP. Meanwhile, the BCC_CSM hindcasts' deficiencies of atmospheric responses to SST anomalies over the Indonesia maritime continent (IMC) resulted in opposite and geographically shifted geopotential anomalies at 500 hPa as well as wind and vorticity anomalies at 850 hPa, rendering the BCC_CSM unable to correctly reproduce the EAP teleconnection pattern. Understanding these two problems will help further improve BCC_CSM's summer precipitation forecasting ability over EA-NWP.

  8. Limitations of BCC_CSM's ability to predict summer precipitation over East Asia and the Northwestern Pacific

    KAUST Repository

    Gong, Zhiqiang

    2017-04-05

    This study examines the ability of the Beijing Climate Center Climate System Model (BCC_CSM) to predict the meridional pattern of summer precipitation over East Asia-Northwest Pacific (EA-NWP) and its East Asia-Pacific (EAP) teleconnection. The differences of summer precipitation modes of the empirical orthogonal function and the bias of atmospheric circulations over EA-NWP are analyzed to determine the reason for the precipitation prediction errors. Results indicate that the BCC_CSM could not reproduce the positive-negative-positive meridional tripole pattern from south to north that differs markedly from that observed over the last 20 years. This failure can be attributed to the bias of the BCC_CSM hindcasts of the summer EAP teleconnection and the low predictability of 500 hPa at the mid-high latitude lobe of the EAP. Meanwhile, the BCC_CSM hindcasts\\' deficiencies of atmospheric responses to SST anomalies over the Indonesia maritime continent (IMC) resulted in opposite and geographically shifted geopotential anomalies at 500 hPa as well as wind and vorticity anomalies at 850 hPa, rendering the BCC_CSM unable to correctly reproduce the EAP teleconnection pattern. Understanding these two problems will help further improve BCC_CSM\\'s summer precipitation forecasting ability over EA-NWP.

  9. Exploring the $Z' \\rightarrow t\\overline{t}$ heavy resonance at FCC-hh

    CERN Document Server

    Smith, Rachel Emma Clarke

    2017-01-01

    My summer student project explored the feasibility of detecting final states with boosted top quarks at 100 TeV with the baseline FCC-hh detector. I focused specifically on the $Z' \\rightarrow t\\overline{t}$ hadronic process. I determined the exclusion cross-section of $Z' \\rightarrow t\\overline{t}$ and the integrated luminosity required to make a discovery at the baseline FCC detector at 95% confidence level.

  10. Prediction of physicochemical properties of FCC feedstock by Chemometric analysis of their ultraviolet spectrum

    International Nuclear Information System (INIS)

    Baldrich Ferrer, Carlos A

    2008-01-01

    Chemometric analysis by Partial Least Squares (PLS) has been applied in this work to correlate the ultraviolet spectrum of combined Fluid Catalytic Cracking (FCC) feedstock with their physicochemical properties. The prediction errors obtained in the validation process using refinery samples demonstrate the accuracy of the predicted properties. This new analytical methodology allows obtaining in one analysis detailed information about the most important physicochemical properties of FCC feedstock and could be used as a valuable tool for operational analysis

  11. The crystal structure and stability of molybdenum at ultrahigh pressures

    International Nuclear Information System (INIS)

    Jona, F; Marcus, P M

    2005-01-01

    Crystal structures and their stabilities for molybdenum under increasing hydrostatic pressures are investigated by first-principles calculations of the Gibbs free energy. Three structures are considered: body-centred cubic (bcc, the ground state at zero pressure), hexagonal close-packed (hcp) and face-centred cubic (fcc). For each structure and each pressure (up to 8 Mbar) the equilibrium states are found from minima of the Gibbs free energy at zero temperature. The stability is tested by calculating the elastic constants and checking whether they satisfy the appropriate stability conditions. The bcc structure is confirmed to be stable at zero pressure and at 6 Mbar. At and above 6.2 M-bar the ground-state structure changes to hcp, which is found to be stable at 7 M-bar. At 7.7 Mbar another transition occurs, and the ground-state structure changes from hcp to fcc. The fcc structure, which is unstable at zero pressure, becomes metastable over the range from 3 to 7.7 M-bar and becomes the ground state at higher pressures (at least up to 8 Mbar). Direct confirmation of these calculated transition pressures with experiment is not now possible, as the maximum static pressure currently reached experimentally is 5.6 Mbar, where Mo is found to be still in the bcc phase

  12. Dislocation Line Tensions in the Noble Metals, the Alkali Metals and beta-Brass

    Energy Technology Data Exchange (ETDEWEB)

    Pettersson, B; Malen, K

    1971-06-15

    The line tension for a straight partial dislocation which can produce the necessary slip for a martensitic phase transformation of the bcc-fcc or bcc-hcp type has been calculated in ordered 6-brass and in Li, Na and K. Also the line tension for a Shockley partial dislocation in Cu, Ag and Au has been calculated. Negative line tension is found for certain dislocation directions, and the possible influence of this on the stability of a stacking fault bounded by these partials is discussed

  13. Bulk Nanostructured FCC Steels With Enhanced Radiation Tolerance

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xinghang; Hartwig, K. Ted; Allen, Todd; Yang, Yong

    2012-10-27

    The objective of this project is to increase radiation tolerance in austenitic steels through optimization of grain size and grain boundary (GB) characteristics. The focus will be on nanocrystalline austenitic Fe-Cr-Ni alloys with an fcc crystal structure. The long-term goal is to design and develop bulk nanostructured austenitic steels with enhanced void swelling resistance and substantial ductility, and to enhance their creep resistance at elevated temperatures via GB engineering. The combination of grain refinement and grain boundary engineering approaches allows us to tailor the material strength, ductility, and resistance to swelling by 1) changing the sink strength for point defects, 2) by increasing the nucleation barriers for bubble formation at GBs, and 3) by changing the precipitate distributions at boundaries. Compared to ferritic/martensitic steels, austenitic stainless steels (SS) possess good creep and fatigue resistance at elevated temperatures, and better toughness at low temperature. However, a major disadvantage of austenitic SS is that they are vulnerable to significant void swelling in nuclear reactors, especially at the temperatures and doses anticipated in the Advanced Burner Reactor. The lack of resistance to void swelling in austenitic alloys led to the switch to ferritic/martensitic steels as the preferred material for the fast reactor cladding application. Recently a type of austenitic stainless steel, HT-UPS, was developed at ORNL, and is expected to show enhanced void swelling resistance through the trapping of point defects at nanometersized carbides. Reducing the grain size and increasing the fraction of low energy grain boundaries should reduce the available radiation-produced point defects (due to the increased sink area of the grain boundaries), should make bubble nucleation at the boundaries less likely (by reducing the fraction of high-energy boundaries), and improve the strength and ductility under radiation by producing a higher

  14. Calculation of thermodynamic equilibrium between bcc disordered solid solutions U and Mo

    International Nuclear Information System (INIS)

    Alonso, Paula R.; Rubiolo, Gerardo H.

    2003-01-01

    There is actually an interest to develop a new fuel with higher density for research reactors. Fuel plates would be obtained by dispersion, a method that requires both a very dense fuel dispersant (>15.0 g U/cm 3 ) and a very high volume loading of the dispersant (>55%). Dispersants based in gamma (BCC) stabilized uranium alloys are being investigated, as they are able to reach uranium densities of 17.0 g U/cm 3 . Among them, we focus in U(Mo) bcc solid solutions with the addition of ternary elements to stabilize gamma phase. Transition metals, 4d and 5d, of groups VII and VIII are good candidates for the ternary alloy U - Mo - X. Their relative power to stabilize gamma phase seems to be in close relation with bonding energies between atoms in the alloy. A first approach to the calculation of these energies has been performed by the semi empiric method of Miedema where only bonds between pairs are considered, neglecting ternary and quaternary bonds. There is also a lack of information concerning solubilities of the ternary elements in the ternary cubic phase. In this work we aim to calculate bonding energies between atoms in the alloy using a cluster expansion of the formation energy (T=0 K) of a series of bcc ordered compounds in the systems U-Mo-X. Then the calculation of the equilibrium phase diagram by the Cluster Variation Method will be done (CVM). We show here the first part of the investigation devoted to calculation of phases equilibria in the U Mo system Formation energies of the ordered compounds were obtained by the first principles methods TB-LMTO-ASA and FP-LAPW. Another set of bonding energies was calculated in order to fit the known experimental diagram and new formation energies for the ordered compounds were derived from them. Discrepancies between both sets are discussed. (author)

  15. Ab initio study of vibronic transitions between x2π and 12Σ+ electronic states of HCP+ ion

    Directory of Open Access Journals (Sweden)

    Stojanović Ljiljana

    2013-01-01

    Full Text Available The ground and low-lying excited doublet electronic states of the HCP+ ion were studied by means of multireference configuration interaction method. Vibronic energy levels of the X2Π state of Σ, Π, Δ, and Φ symmetry, up to the 2500 cm-1, have been calculated variationally, employing previously developed ab initio methods which take into account vibronic and spin-orbit interactions. Obtained vibronic wave functions were used to estimate transition moments between vibronic energy levels of the X2Π and 12Σ+ electronic states. Results were compared to available experimental and theoretical data. [Projekat Ministarstva nauke Republike Srbije, br. 172040

  16. Effects of applied strain on nanoscale self-interstitial cluster formation in BCC iron

    Science.gov (United States)

    Gao, Ning; Setyawan, Wahyu; Kurtz, Richard J.; Wang, Zhiguang

    2017-09-01

    The effect of applied strains on the configurational evolution of self-interstitial clusters in BCC iron (Fe) is explored with atomistic simulations. A novel cluster configuration is discovered at low temperatures (family of 〈 hkl 〉 loops is calculated as a function of strain. The results show that loop anisotropy is governed by the angle between the stress direction and the orientation of the 〈 111 〉 crowdions in the loop, and directly linked to the stress induced preferred nucleation of self-interstitial atoms.

  17. A numerical study of crack initiation in a bcc iron system based on dynamic bifurcation theory

    International Nuclear Information System (INIS)

    Li, Xiantao

    2014-01-01

    Crack initiation under dynamic loading conditions is studied under the framework of dynamic bifurcation theory. An atomistic model for BCC iron is considered to explicitly take into account the detailed molecular interactions. To understand the strain-rate dependence of the crack initiation process, we first obtain the bifurcation diagram from a computational procedure using continuation methods. The stability transition associated with a crack initiation, as well as the connection to the bifurcation diagram, is studied by comparing direct numerical results to the dynamic bifurcation theory [R. Haberman, SIAM J. Appl. Math. 37, 69–106 (1979)].

  18. Abnormal Strain Rate Sensitivity Driven by a Unit Dislocation-Obstacle Interaction in bcc Fe

    Science.gov (United States)

    Bai, Zhitong; Fan, Yue

    2018-03-01

    The interaction between an edge dislocation and a sessile vacancy cluster in bcc Fe is investigated over a wide range of strain rates from 108 down to 103 s-1 , which is enabled by employing an energy landscape-based atomistic modeling algorithm. It is observed that, at low strain rates regime less than 105 s-1 , such interaction leads to a surprising negative strain rate sensitivity behavior because of the different intermediate microstructures emerged under the complex interplays between thermal activation and applied strain rate. Implications of our findings regarding the previously established global diffusion model are also discussed.

  19. Temperature dependent magnon-phonon coupling in bcc Fe from theory and experiment.

    Science.gov (United States)

    Körmann, F; Grabowski, B; Dutta, B; Hickel, T; Mauger, L; Fultz, B; Neugebauer, J

    2014-10-17

    An ab initio based framework for quantitatively assessing the phonon contribution due to magnon-phonon interactions and lattice expansion is developed. The theoretical results for bcc Fe are in very good agreement with high-quality phonon frequency measurements. For some phonon branches, the magnon-phonon interaction is an order of magnitude larger than the phonon shift due to lattice expansion, demonstrating the strong impact of magnetic short-range order even significantly above the Curie temperature. The framework closes the previous simulation gap between the ferro- and paramagnetic limits.

  20. Laser diffraction analysis of colloidal crystals

    Energy Technology Data Exchange (ETDEWEB)

    Sogami, Ikuo S.; Shinohara, Tadatomi; Yoshiyama, Tsuyoshi [Kyoto Sangyo Univ., Department of Physics, Kyoto (Japan)

    2001-10-01

    Laser diffraction analysis is made on crystallization in salt-free aqueous suspensions of highly-charged colloidal particles for semi-dilute specimens of concentration 0.1-10.0 vol%. Kossel diffraction patterns which represent faithfully accurate information on lattice symmetries in the suspensions enable us to investigate the time evolution of colloidal crystals. The results show that the crystallization proceeds by way of the following intermediate phase transitions: two-dimensional hcp structure {yields} random layer structure {yields} layer structure with one sliding degree of freedom {yields} stacking disorder structure {yields} stacking structure with multivariant periodicity {yields} fcc twin structure with twin plane (111) {yields} normal fcc structure {yields} bcc twin structure with twin plane (11-bar2) or (1-bar12) {yields} normal bcc structure. For concentrated suspensions (>2 vol %), the phase transition ceases to proceed at the normal fcc structure. (author)

  1. Laser diffraction analysis of colloidal crystals

    International Nuclear Information System (INIS)

    Sogami, Ikuo S.; Shinohara, Tadatomi; Yoshiyama, Tsuyoshi

    2001-01-01

    Laser diffraction analysis is made on crystallization in salt-free aqueous suspensions of highly-charged colloidal particles for semi-dilute specimens of concentration 0.1-10.0 vol%. Kossel diffraction patterns which represent faithfully accurate information on lattice symmetries in the suspensions enable us to investigate the time evolution of colloidal crystals. The results show that the crystallization proceeds by way of the following intermediate phase transitions: two-dimensional hcp structure → random layer structure → layer structure with one sliding degree of freedom → stacking disorder structure → stacking structure with multivariant periodicity → fcc twin structure with twin plane (111) → normal fcc structure → bcc twin structure with twin plane (11-bar2) or (1-bar12) → normal bcc structure. For concentrated suspensions (>2 vol %), the phase transition ceases to proceed at the normal fcc structure. (author)

  2. Classification of different kinds of pesticide residues on lettuce based on fluorescence spectra and WT-BCC-SVM algorithm

    Science.gov (United States)

    Zhou, Xin; Jun, Sun; Zhang, Bing; Jun, Wu

    2017-07-01

    In order to improve the reliability of the spectrum feature extracted by wavelet transform, a method combining wavelet transform (WT) with bacterial colony chemotaxis algorithm and support vector machine (BCC-SVM) algorithm (WT-BCC-SVM) was proposed in this paper. Besides, we aimed to identify different kinds of pesticide residues on lettuce leaves in a novel and rapid non-destructive way by using fluorescence spectra technology. The fluorescence spectral data of 150 lettuce leaf samples of five different kinds of pesticide residues on the surface of lettuce were obtained using Cary Eclipse fluorescence spectrometer. Standard normalized variable detrending (SNV detrending), Savitzky-Golay coupled with Standard normalized variable detrending (SG-SNV detrending) were used to preprocess the raw spectra, respectively. Bacterial colony chemotaxis combined with support vector machine (BCC-SVM) and support vector machine (SVM) classification models were established based on full spectra (FS) and wavelet transform characteristics (WTC), respectively. Moreover, WTC were selected by WT. The results showed that the accuracy of training set, calibration set and the prediction set of the best optimal classification model (SG-SNV detrending-WT-BCC-SVM) were 100%, 98% and 93.33%, respectively. In addition, the results indicated that it was feasible to use WT-BCC-SVM to establish diagnostic model of different kinds of pesticide residues on lettuce leaves.

  3. Enhanced moments in bcc Co{sub 1−x}Mn{sub x} on MgO(001)

    Energy Technology Data Exchange (ETDEWEB)

    Snow, R.J.; Bhatkar, H. [Department of Physics, Montana State University, Bozeman, MT 59715 (United States); N' Diaye, A.T.; Arenholz, E. [Advanced Light Source, Lawrence Berkeley Nat. Labs, Berkeley, CA 94720 (United States); Idzerda, Y.U., E-mail: Idzerda@montana.edu [Department of Physics, Montana State University, Bozeman, MT 59715 (United States)

    2016-12-01

    A 40% enhancement of the Co magnetic moment has been found for thin films of bcc Co{sub 1−x}Mn{sub x} grown by molecular beam epitaxy on a 2 nm bcc Fe buffer layer on MgO(001). Although the bcc phase cannot be stabilized in the bulk, we confirm that it is stable as an epitaxial film in the composition range x=0–0.7. Using X-ray absorption spectroscopy and X-ray magnetic circular dichroism, we show that the Co moment is a maximum of 2.38 μ{sub B} at x=0.24, while the net Mn moment remains roughly constant until x=0.24, then drops steadily. Mn is found to align parallel with Co for all ferromagnetic concentrations, up to x=0.7, where the total moment of the film abruptly collapses to zero, most likely due to the onset of the observed structural instability. - Highlights: • Stabilization of bcc Co{sub 1−x}Mn{sub x} films in the composition range of x=0 to 0.7. • Enhancement of Co moment by 40% from pure bcc Co. • Parallel alignment of Mn moment and Co moment. • Measured the elemental moment of Co and Mn as a function of composition.

  4. Interdiffusion and atomic mobility studies in Ni-rich fcc Ni−Al−Mn alloys

    International Nuclear Information System (INIS)

    Cheng, Kaiming; Liu, Dandan; Zhang, Lijun; Du, Yong; Liu, Shuhong; Tang, Chengying

    2013-01-01

    Highlights: •The interdiffusion coefficients of fcc Ni–Al–Mn alloys are experimentally determined. •The atomic mobilities of fcc Ni–Al–Mn alloys have been assessed. •The calculated results agree well with the present experimental diffusivities. •The mobility parameters obtained can be used to predict many diffusion phenomena. -- Abstract: By employing nine groups of bulk diffusion couples together with electron probe microanalysis technique, the composition dependence of ternary interdiffusion coefficients in Ni-rich fcc Ni−Al−Mn alloys at 1373 K was determined via the Matano–Kirkaldy method. The experimental interdiffusion coefficients were critically assessed to obtain the atomic mobilities of Ni, Al and Mn in fcc Ni−Al−Mn alloys by using the DICTRA (DIffusion-Controlled TRAnsformations) software package. The reliability of these mobilities was validated by comprehensive comparison between the model-predicted diffusion properties and the experimental data. The obtained atomic mobilities could be used to describe various diffusion phenomena in fcc Ni–Al–Mn alloys, such as the concentration profiles, interdiffusion flux and diffusion paths

  5. Stacking fault density and bond orientational order of fcc ruthenium nanoparticles

    Science.gov (United States)

    Seo, Okkyun; Sakata, Osami; Kim, Jae Myung; Hiroi, Satoshi; Song, Chulho; Kumara, Loku Singgappulige Rosantha; Ohara, Koji; Dekura, Shun; Kusada, Kohei; Kobayashi, Hirokazu; Kitagawa, Hiroshi

    2017-12-01

    We investigated crystal structure deviations of catalytic nanoparticles (NPs) using synchrotron powder X-ray diffraction. The samples were fcc ruthenium (Ru) NPs with diameters of 2.4, 3.5, 3.9, and 5.4 nm. We analyzed average crystal structures by applying the line profile method to a stacking fault model and local crystal structures using bond orientational order (BOO) parameters. The reflection peaks shifted depending on rules that apply to each stacking fault. We evaluated the quantitative stacking faults densities for fcc Ru NPs, and the stacking fault per number of layers was 2-4, which is quite large. Our analysis shows that the fcc Ru 2.4 nm-diameter NPs have a considerably high stacking fault density. The B factor tends to increase with the increasing stacking fault density. A structural parameter that we define from the BOO parameters exhibits a significant difference from the ideal value of the fcc structure. This indicates that the fcc Ru NPs are highly disordered.

  6. Deformation-induced crystallographic-preferred orientation of hcp-iron: An experimental study using a deformation-DIA apparatus

    Science.gov (United States)

    Nishihara, Yu; Ohuchi, Tomohiro; Kawazoe, Takaaki; Seto, Yusuke; Maruyama, Genta; Higo, Yuji; Funakoshi, Ken-ichi; Tange, Yoshinori; Irifune, Tetsuo

    2018-05-01

    Shear and uniaxial deformation experiments on hexagonal close-packed iron (hcp-Fe) was conducted using a deformation-DIA apparatus at a pressure of 13-17 GPa and a temperature of 723 K to determine its deformation-induced crystallographic-preferred orientation (CPO). Development of the CPO in the deforming sample is determined in-situ based on two-dimensional X-ray diffraction using monochromatic synchrotron X-rays. In the shear deformation geometry, the and axes gradually align to be sub-parallel to the shear plane normal and shear direction, respectively, from the initial random texture. In the uniaxial compression and tensile geometry, the and axes, respectively, gradually align along the direction of the uniaxial deformation axis. These results suggest that basal slip (0001) is the dominant slip system in hcp-Fe under the studied deformation conditions. The P-wave anisotropy for a shear deformed sample was calculated using elastic constants at the inner core condition by recent ab-initio calculations. Strength of the calculated anisotropy was comparable to or higher than axisymmetric anisotropy in Earth's inner core.

  7. Size effects of nano-spaced basal stacking faults on the strength and deformation mechanisms of nanocrystalline pure hcp metals

    Science.gov (United States)

    Wang, Wen; Jiang, Ping; Yuan, Fuping; Wu, Xiaolei

    2018-05-01

    The size effects of nano-spaced basal stacking faults (SFs) on the tensile strength and deformation mechanisms of nanocrystalline pure cobalt and magnesium have been investigated by a series of large-scale 2D columnar and 3D molecular dynamics simulations. Unlike the strengthening effect of basal SFs on Mg alloys, the nano-spaced basal SFs are observed to have no strengthening effect on the nanocrystalline pure cobalt and magnesium from MD simulations. These observations could be attributed to the following two reasons: (i) Lots of new basal SFs are formed before (for cobalt) or simultaneously with (for magnesium) the other deformation mechanisms (i.e. the formation of twins and the edge dislocations) during the tensile deformation; (ii) In hcp alloys, the segregation of alloy elements and impurities at typical interfaces, such as SFs, can stablilise them for enhancing the interactions with dislocation and thus elevating the strength. Without such segregation in pure hcp metals, the edge dislocations can cut through the basal SFs although the interactions between the dislocations and the pre-existing SFs/newly formed SFs are observed. The nano-spaced basal SFs are also found to have no restriction effect on the formation of deformation twins.

  8. High precision measurement of the hyperfine fields of substitutional and defect associated Cd in single crystalline hcp cobalt

    CERN Document Server

    Correia, J G; Melo, A A; Soares, J C

    1996-01-01

    The hyperfine fields of Cd in single crystalline hcp Co were measured after simultaneous implantation of 111mCd and 111In. High statistics measurements could be done separately for each parent isotope combining the e--g and g-g PAC techniques. The hyperfine coupling constants wL(CdCo)=422.8(1) Mrad/s and w0(CdCo)=6.14(11) Mrad/s are determined for Cd probes in undisturbed substitutional sites. Several defect associated sites in the hcp Co lattice are clearly seen in the data. Most of the radiation damage created by the ion implantation anneals out at temperatures below 503 K, with only one dominating component surviving at this temperature. This defect is assigned as a probe atom in an interstitial site, surrounded by a vacancy tetrahedron. The corresponding magnetic field and electric field gradient are collinear with the c-axis of the Co lattice, and the respective coupling constants are wL(defect)= 216.7(2) Mrad/s and w0(defect)= 45.3(6) Mrad/s.

  9. Elastic fields, dipole tensors, and interaction between self-interstitial atom defects in bcc transition metals

    Science.gov (United States)

    Dudarev, S. L.; Ma, Pui-Wai

    2018-03-01

    Density functional theory (DFT) calculations show that self-interstitial atom (SIA) defects in nonmagnetic body-centered-cubic (bcc) metals adopt strongly anisotropic configurations, elongated in the direction [S. Han et al., Phys. Rev. B 66, 220101 (2002), 10.1103/PhysRevB.66.220101; D. Nguyen-Manh et al., Phys. Rev. B 73, 020101 (2006), 10.1103/PhysRevB.73.020101; P. M. Derlet et al., Phys. Rev. B 76, 054107 (2007), 10.1103/PhysRevB.76.054107; S. L. Dudarev, Annu. Rev. Mater. Res. 43, 35 (2013), 10.1146/annurev-matsci-071312-121626]. Elastic distortions, associated with such anisotropic atomic structures, appear similar to distortions around small prismatic dislocation loops, although the extent of this similarity has never been quantified. We derive analytical formulas for the dipole tensors of SIA defects, which show that, in addition to the prismatic dislocation looplike character, the elastic field of a SIA defect also has a significant isotropic dilatation component. Using empirical potentials and DFT calculations, we parametrize dipole tensors of defects for all the nonmagnetic bcc transition metals. This enables a quantitative evaluation of the energy of elastic interaction between the defects, which also shows that in a periodic three-dimensional simple cubic arrangement of crowdions, long-range elastic interactions between a defect and all its images favor a orientation of the defect.

  10. Angular forces and melting in bcc transition metals: A case study of molybdenum

    International Nuclear Information System (INIS)

    Moriarty, J.A.

    1994-01-01

    Both the multi-ion and effective pair potentials also permit a large amount of supercooling of the liquid before the onset of freezing. With v 2 eff a bcc structure is nucleated at freezing, while with the multi-ion potentials an amorphous glasslike structure is obtained, which appears to be related to the energetically competitive A15 structure. In our second approach to melting, the multi-ion potentials have been used to obtain accurate solid and liquid free energies from quasiharmonic lattice dynamics and MD calculations of thermal energies and pressures. The resulting ion-thermal melting curve exactly overlaps the dynamically observed melting point, indicating that no superheating of the solid occurred in our MD simulations. To obtain a full melting curve, electron-thermal contributions to the solid and liquid free energies are added in terms of the density of electronic states at the Fermi level, ρ(E F ). Here the density of states for the solid has been calculated with the linear-muffin-tin-orbital method, while for the liquid tight-binding calculations have been used to justify a simple model. In the liquid ρ(E F ) is increased dramatically over the bcc solid, and the net effect of the electron-thermal contributions is to lower the calculated melting temperatures by about a factor of 2. A full melting curve to 2 Mbar has thereby been obtained and the calculated melting properties near zero pressure are in generally good agreement with experiment

  11. Multiscale modeling of dislocation processes in BCC tantalum: bridging atomistic and mesoscale simulations

    International Nuclear Information System (INIS)

    Yang, L H; Tang, M; Moriarty, J A

    2001-01-01

    Plastic deformation in bcc metals at low temperatures and high-strain rates is controlled by the motion of a/2 screw dislocations, and understanding the fundamental atomistic processes of this motion is essential to develop predictive multiscale models of crystal plasticity. The multiscale modeling approach presented here for bcc Ta is based on information passing, where results of simulations at the atomic scale are used in simulations of plastic deformation at mesoscopic length scales via dislocation dynamics (DD). The relevant core properties of a/2 screw dislocations in Ta have been obtained using quantum-based interatomic potentials derived from model generalized pseudopotential theory and an ab-initio data base together with an accurate Green's-function simulation method that implements flexible boundary conditions. In particular, the stress-dependent activation enthalpy for the lowest-energy kink-pair mechanism has been calculated and fitted to a revealing analytic form. This is the critical quantity determining dislocation mobility in the DD simulations, and the present activation enthalpy is found to be in good agreement with the previous empirical form used to explain the temperature dependence of the yield stress

  12. Structure and creep of Russian reactor steels with a BCC structure

    Science.gov (United States)

    Sagaradze, V. V.; Kochetkova, T. N.; Kataeva, N. V.; Kozlov, K. A.; Zavalishin, V. A.; Vil'danova, N. F.; Ageev, V. S.; Leont'eva-Smirnova, M. V.; Nikitina, A. A.

    2017-05-01

    The structural phase transformations have been revealed and the characteristics of the creep and long-term strength at 650, 670, and 700°C and 60-140 MPa have been determined in six Russian reactor steels with a bcc structure after quenching and high-temperature tempering. Creep tests were carried out using specially designed longitudinal and transverse microsamples, which were fabricated from the shells of the fuel elements used in the BN-600 fast neutron reactor. It has been found that the creep rate of the reactor bcc steels is determined by the stability of the lath martensitic and ferritic structures in relation to the diffusion processes of recovery and recrystallization. The highest-temperature oxide-free steel contains the maximum amount of the refractory elements and carbides. The steel strengthened by the thermally stable Y-Ti nanooxides has a record high-temperature strength. The creep rate at 700°C and 100 MPa in the samples of this steel is lower by an order of magnitude and the time to fracture is 100 times greater than that in the oxide-free reactor steels.

  13. Diffusion behavior and atomic mobilities for fcc Cu–Cr–Ni alloys

    International Nuclear Information System (INIS)

    Xu, Gaochi; Liu, Yajun; Lei, Fuyue; Sheng, Guang; Kang, Zhitao

    2015-01-01

    In this work, diffusion couples of fcc Cu–Cr–Ni alloys annealed at 1373 K for 80 h are investigated. The interdiffusion coefficients are retrieved from common compositions of two diffusion couples, which are then combined with thermodynamic descriptions to explore atomic mobilities of Cu, Cr and Ni in fcc Cu–Cr–Ni alloys within the CALPHAD framework. In order to confirm the quality of such kinetic characteristics, a comparison between calculated and experimentally measured concentration profiles of diffusion couples and diffusion paths in Gibbs triangle is made, where the agreement is excellent. The results of this study contribute to the establishment of a general Ni-based mobility database for alloy design. - Highlights: • Atomic mobilities of fcc Cu–Cr–Ni phases were determined. • Experimental interdiffusivities were critically evaluated. • Main and cross interdiffusivities show their peculiarities. • The profiles reveal kinetic importance for alloy microstructures

  14. Cross-talk studies between FCC-hh Experimental Interaction Regions

    CERN Document Server

    AUTHOR|(CDS)2081283; Seryi, Andrei; Appleby, Robert Barrie; Rafique, Haroon; Besana, Maria Ilaria

    2017-01-01

    Debris from 50 TeV proton-proton collisions at the main interaction point in the FCC-hh may contribute to the background in the subsequent detector. This cross-talk is of possible concern for the FCC-hh due to the high luminosity and energy of the collider. DPMJET-III is used as a collision debris generator in order to assess the muon cross-talk contribution. An analytical calculation of muon range in rock is performed. This is followed by a full Monte Carlo simulation using FLUKA, where the accelerator tunnel has been modelled. The muon cross talk between the adjacent interaction points is assessed and its implications for FCC-hh design are discussed.

  15. Interdiffusion coefficients and atomic mobilities in fcc Cu-Fe-Mn alloys

    Directory of Open Access Journals (Sweden)

    Li J.

    2014-01-01

    Full Text Available In the present work, the interdiffusion coefficients in fcc Cu-Fe-Mn alloys were experimentally determined via a combination of solid/solid diffusion couples, electron probe microanalysis (EPMA technique and Matano-Kirkaldy method. Based on the reliable thermodynamic description of fcc phase in the Cu-Fe-Mn system available in the literature as well as the ternary diffusion coefficients measured in the present work, the atomic mobilities in fcc Cu-Fe-Mn alloys were assessed by utilizing the DICTRA (Diffusion Controlled TRAnsformation software package. The calculated interdiffusion coefficients based on the assessed atomic mobilities agree well with most of the experimental data. The comprehensive comparison between various model-predicted diffusion properties and the measured data, including the concentration penetration profiles, interdiffusion flux profile, and diffusion paths, further verify the reliability of the presently obtained atomic mobilities.

  16. Measuring light-by-light scattering at the LHC and FCC

    CERN Document Server

    d'Enterria, David

    2016-01-01

    Elastic light-by-light scattering, $\\gamma\\gamma\\to\\gamma\\gamma$, can be measured in electromagnetic interactions of lead (Pb) ions at the Large Hadron Collider (LHC) and Future Circular Collider (FCC), using the large (quasi)real photon fluxes available in ultraperipheral collisions. The $\\gamma\\gamma\\to\\gamma\\gamma$ cross sections for diphoton masses m$_{\\gamma\\gamma}>$ 5 GeV in pp, pPb, and PbPb collisions at LHC ($\\sqrt{\\rm s_{_{NN}}}$ = 5.5, 8.8, 14 TeV) and FCC ($\\sqrt{\\rm s_{_{NN}}}$ = 39, 63, 100 TeV) center-of-mass energies are presented. The measurement has controllable backgrounds in PbPb collisions, and one expects about 70 and 2500 signal events per year at the LHC and FCC respectively, after typical detector acceptance and reconstruction efficiency selections.

  17. Towards a Monochromatization Scheme for Direct Higgs Production at FCC-ee

    CERN Document Server

    Valdivia Garcia, Marco Alan; Zimmermann, Frank

    2016-01-01

    Direct Higgs production in e+e− collisions at the FCC is of interest if the centre-of-mass energy spread can be reduced by at least an order of magnitude. A monochromatization scheme, to accomplish this, can be realized with horizontal dispersion of opposite sign for the two colliding beams at the interaction point (IP). We recall historical approaches to monochromatization, then derive a set of IP parameters which would provide the required performance in FCC e+e− collisions at 62.5 GeV beam energy, compare these with the baseline optics parameters at neighbouring energies (45.6 and 80 GeV), comment on the effect of beamstrahlung, and indicate the modifications of the FCC-ee final-focus optics needed to obtain the required parameters.

  18. Simulation of recrystallization textures in FCC materials based on a self consistent model

    International Nuclear Information System (INIS)

    Bolmaro, R.E; Roatta, A; Fourty, A.L; Signorelli, J.W; Bertinetti, M.A

    2004-01-01

    The development of re-crystallization textures in FCC polycrystalline materials has been a long lasting scientific problem. The appearance of the so-called cubic component in high stack fault energy laminated FCC materials is not an entirely understood phenomenon. This work approaches the problem using a self- consistent simulation technique of homogenization. The information on first preferential neighbors is used in the model to consider grain boundary energies and intra granular misorientations and to treat the growth of grains and the mobility of the grain boundary. The energies accumulated by deformations are taken as conducting energies of the nucleation and the later growth is statistically governed by the grain boundary energies. The model shows the correct trend for re-crystallization textures obtained from previously simulated deformation textures for high and low stack fault energy FCC materials. The model's topological representation is discussed (CW)

  19. Elastic-constant systematics in f.c.c. metals, including lanthanides-actinides

    Energy Technology Data Exchange (ETDEWEB)

    Ledbetter, Hassel [Mechanical Engineering Department, University of Colorado, Boulder, Colorado 80309 (United States); Migliori, Albert [Los Alamos National Laboratory (E536), Los Alamos, New Mexico 87545 (United States)

    2008-01-15

    For f.c.c. metals, using Blackman's diagram of dimensionless elastic-constant ratios, we consider the systematics of physical properties and interatomic bonding. We focus especially on the lanthanides-actinides La, Ce, Yb, Th, U, Pu, those for which we know some monocrystal elastic constants. Their behavior differs from the other f.c.c. metals, and all except La show a negative Cauchy pressure, contrary to most f.c.c. metals, which show a positive Cauchy pressure. Among the lanthanides-actinides, {delta}-Pu stands apart, consistent with its many odd physical properties. Based on elastic-constant correlations, we suggest that {delta}-Pu possesses a strong s-electron interatomic-bonding component together with a covalent component. Elastically, {delta}-Pu shows properties similar to Yb. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Precision measurement of the top quark mass at threshold with the FCC-ee

    CERN Document Server

    Foppiani, Nicolo

    2016-01-01

    The project concerns the study of the sensitivity in measuring the Top quark mass at threshold at the FCC-ee, using a Montecarlo analysis. In particular it has been developed within the FCC software framework, using a fast simulation. The work focused firstly on developing a b-tagging algorithm inside of the FCC fast simulation, managing to obtain results comparable with the ALEPH ones, and new results with a futuristic detector like ILD. Afterwards the selection of the tt events at energy close to the pair production threshold has been studied, obtaining a selection efficiency of 55 % and a background rejection at the level of 99.4 %. In the end, a list of points that can be achieved in the future, to complete the analysis, has been identified.

  1. Direct measurement of α_Q_E_D(m_Z"2) at the FCC-ee

    International Nuclear Information System (INIS)

    Janot, Patrick

    2016-01-01

    When the measurements from the FCC-ee become available, an improved determination of the standard-model “input' parameters will be needed to fully exploit the new precision data towards either constraining or fitting the parameters of beyond-the-standard-model theories. Among these input parameters is the electromagnetic coupling constant estimated at the Z mass scale, α_Q_E_D(m_Z"2). The measurement of the muon forward-backward asymmetry at the FCC-ee, just below and just above the Z pole, can be used to make a direct determination of α_Q_E_D(m_Z"2) with an accuracy deemed adequate for an optimal use of the FCC-ee precision data.

  2. Direct measurement of alpha_QED(mZ)at the FCC-ee

    CERN Document Server

    Janot, Patrick

    2016-02-08

    When the measurements from the FCC-ee become available, an improved determination of the standard-model "input" parameters will be needed to fully exploit the new precision data towards either constraining or fitting the parameters of beyond-the-standard-model theories. Among these input parameters is the electromagnetic coupling constant estimated at the Z mass scale, alpha_QED(mZ). The measurement of the muon forward- backward asymmetry at the FCC-ee, just below and just above the Z pole, can be used to make a direct determination of alpha_QED(mZ) with an accuracy deemed adequate for an optimal use of the FCC-ee precision data.

  3. Experimental study of the spin density of metastable fcc ferromagnetic Fe-Cu alloys

    International Nuclear Information System (INIS)

    Bove, L. E.; Petrillo, C.; Sacchetti, F.; Mazzone, G.

    2000-01-01

    Magnetization density measurements on metastable Fe x Cu 1-x alloys at four compositions (x=20, 40, 50, and 60 at. %) and at 5 K temperature were carried out by means of polarized neutron diffraction. The samples were produced by high-energy ball milling and characterized by x-ray diffraction and fluorescence measurements. Additional bulk magnetization measurements were carried out on the two samples at high Fe concentration. Over the present concentration region, the Fe-Cu system is ferromagnetic and the four samples were found to be in the fcc phase. Fe-Cu is therefore a very suitable system to investigate the magnetic state of Fe in an fcc environment. Other than confirming that the Fe-Cu system is not a simple dilution alloy, the present results were compatible with a two-state model for fcc Fe--that is, two different coexisting electronic states associated with different magnetic moments and form factors

  4. Pressure-induced structural change from hexagonal to fcc metal lattice in scandium trihydride

    International Nuclear Information System (INIS)

    Ohmura, A.; Machida, A.; Watanuki, T.; Aoki, K.; Nakano, S.; Takemura, K.

    2007-01-01

    We synthesized scandium hydrides by hydrogenation of a scandium foil with hydrogen fluid under high pressure at ambient temperature. Scandium dihydride (ScH 2 ) and trihydride (ScH 3 ) were prepared near 4 and 5 GPa, respectively. The hydrogenation process and pressure-induced structural changes in ScH 3 were investigated by synchrotron radiation X-ray diffraction measurements up to 54.7 GPa. A structural transition from hexagonal to the fcc lattice began at 30 GPa and was completed at 46 GPa via an intermediate state similar to those reported for other hexagonal trihydrides. The intermediate state was not interpreted in terms of a coexisting state for the low-pressure hexagonal and the high-pressure fcc structures. The onset transition pressure of ScH 3 supported the previously proposed relation that the hexagonal-fcc transition pressure is inversely proportional to the ionic radius of the trihydride

  5. First Design of a Proton Collimation System for 50 TeV FCC-hh

    CERN Document Server

    Fiascaris, Maria; Mirarchi, Daniele; Redaelli, Stefano

    2016-01-01

    We present studies aimed at defining a first conceptual solution for a collimation system for the hadron-hadron option for the Future Circular Collider (FCC-hh). The baseline collimation layout is based on the scaling of the present LHC collimation system to the FCC-hh energy. It currently includes a dedicated betatron cleaning insertion as well as collimators in the experimental insertions to protect the inner triplets. An aperture model for the FCC-hh is defined and the geometrical acceptance is calculated at top energy taking into account mechanical and optics imperfections. Based on these studies the collimator settings needed to protect the machine are defined. The performance of the collimation system is then assessed with particle tracking simulation tools assuming a perfect machine.

  6. On the mechanical stability of the body-centered cubic phase and the emergence of a metastable cI16 phase in classical hard sphere solids

    Science.gov (United States)

    Warshavsky, Vadim B.; Ford, David M.; Monson, Peter A.

    2018-01-01

    The stability of the body-centered cubic (bcc) solid phase of classical hard spheres is of intrinsic interest and is also relevant to the development of perturbation theories for bcc solids of other model systems. Using canonical ensemble Monte Carlo, we simulated systems initialized in a perfect bcc lattice at various densities in the solid region. We observed that the systems rapidly evolved into one of four structures that then persisted for the duration of the simulation. Remarkably, one of these structures was identified as cI16, a cubic crystalline structure with 16 particles in the unit cell, which has recently been observed experimentally in lithium and sodium solids at high pressures. The other three structures do not exhibit crystalline order but are characterized by common patterns in the radial distribution function and bond-orientational order parameter distribution; we refer to them as bcc-di, with i ranging from 1 to 3. We found similar outcomes when employing any of the three single occupancy cell (SOC) restrictions commonly used in the literature. We also ran long constant-pressure simulations with box shape fluctuations initiated from bcc and cI16 initial configurations. At lower pressures, all the systems evolved to defective face-centered cubic (fcc) or hexagonal close-packed (hcp) structures. At higher pressures, most of the systems initiated as bcc evolved to cI16 with some evolving to defective fcc/hcp. High pressure systems initiated from cI16 remained in that structure. We computed the chemical potential of cI16 using the Einstein crystal reference method and found that it is higher than that of fcc by ˜0.5kT-2.5kT over the pressure range studied, with the difference increasing with pressure. We find that the undistorted bcc solid, even with constant-volume and SOC restrictions applied, is so mechanically unstable that it is unsuitable for consideration as a metastable phase or as a reference system for studying bcc phases of other systems

  7. Assessment and correction of BCC_CSM's performance in capturing leading modes of summer precipitation over North Asia

    KAUST Repository

    Gong, Zhiqiang

    2017-11-07

    This article examines the ability of Beijing Climate Center Climate System Model (BCC_CSM) in demonstrating the prediction accuracy and the leading modes of the summer precipitation over North Asia (NA). A dynamic-statistic combined approach for improving the prediction accuracy and the prediction of the leading modes of the summer precipitation over NA is proposed. Our results show that the BCC_CSM can capture part of the spatial anomaly features of the first two leading modes of NA summer precipitation. Moreover, BCC_CSM regains relationships such that the first and second mode of the empirical orthogonal function (EOF1 and EOF2) of NA summer precipitation, respectively, corresponds to the development of the El Niño and La Niña conditions in the tropical East Pacific. Nevertheless, BCC_CSM exhibits limited prediction skill over most part of NA and presents a deficiency in reproducing the EOF1\\'s and EOF2\\'s spatial pattern over central NA and EOF2\\'s interannual variability. This can be attributed as the possible reasons why the model is unable to capture the correct relationships among the basic climate elements over the central NA, lacks in its ability to reproduce a consistent zonal atmospheric pattern over NA, and has bias in predicting the relevant Sea Surface Temperature (SST) modes over the tropical Pacific and Indian Ocean regions. Based on the proposed dynamic-statistic combined correction approach, compared with the leading modes of BCC_CSM\\'s original prediction, anomaly correlation coefficients of corrected EOF1/EOF2 with the tropical Indian Ocean SST are improved from 0.18/0.36 to 0.51/0.62. Hence, the proposed correction approach suggests that the BCC_CSM\\'s prediction skill for the summer precipitation prediction over NA and its ability to capture the dominant modes could be certainly improved by choosing proper historical analogue information.

  8. Increase of propylene production and recovery in a PETROBRAS FCC units; Aumento da producao e recuperacao de propeno em uma Unidade de FCC da PETROBRAS

    Energy Technology Data Exchange (ETDEWEB)

    Penna, Elisangela Melo; Pinho, Andrea de Rezende; Wolff, Marcelo Straubel [Petroleo Brasileiro S.A (PETROBRAS), Rio de Janeiro, RJ (Brazil)

    2012-07-01

    Propylene is one of the major petrochemical raw materials and its demand has been growing rapidly in recent years. Projections for future years indicate that the growth in propylene production via pyrolysis tends to be lower than the growth in the demand for ethylene, creating a supply deficit of this product. The FCC units are in a unique position to meet this increase in propylene demand due to its operational flexibility. Although their primary function in recent decades has been the gasoline production, FCC units are often operated for maximizing other products, such as LPG or distillates. At the FCC conversion section, the increase of propylene yield requires some increase in reaction severity, which can be obtained by increasing reactor riser temperature, and the use of catalyst additives based on ZSM-5. However, besides maximizing the propylene production in the reactor, a second objective should be pursued: the propylene recovery increase in the gas recovery section. In this section, the yield is affected by the gas compressor performance, the equipment design and process scheme. Eventually, new equipment may be installed, such as chillers, aimed at improving the absorption system. Predicting a real increase in propylene demand in the Brazilian market, this study aims to evaluate the adequacy of the gas recovery section of a PETROBRAS FCC unit, analyzing the impacts that a new products yields profile, which bend the propylene production compared to a conventional operation, would cause on this unit. In this paper, the main limitations and modifications that would be needed for an operation were identified, aiming at maximizing the propylene production, as well as proposed changes in the hardware of the unit. (author)

  9. Considerations on operation schedule and maintenance aspects of FCC-hh

    CERN Document Server

    Niemi, Arto; Foraz, Katy

    2018-01-01

    The Future Circular Hadron Collider (FCC-hh) has ambitious goals for integrated luminosity production. Reaching these goals requires reducing the time for planned technical stops and commissioning, compared to the LHC. This note describes potential options for an FCC-hh operation schedule. Special attention is given to considerations on how to accomplish the required maintenance activities in a limited time frame. The note recommends to study further the feasibility and cost-efficiency of operating without annual stops and longer intervals between long shutdowns.

  10. Updates on the optics of the future hadron-hadron collider FCC-hh

    CERN Document Server

    AUTHOR|(CDS)2093721; Boutin, David Jean Henri; Dalena, Barbara; Holzer, Bernhard; Langner, Andy Sven; Schulte, Daniel

    2017-01-01

    The FCC-hh (Future Hadron-Hadron Circular Collider) is one of the three options considered for the next generation accelerator in high-energy physics as recommended by the European Strategy Group. The layout of FCC-hh has been optimized to a more compact design following recommendations from civil engineering aspects. The updates on the first order and second order optics of the ring will be shown for collisions at the required centre-of-mass energy of 100 TeV. Special emphasis is put on the dispersion suppressors and general beam cleaning sections as well as first considerations of injection and extraction sections.

  11. Tapering Options and Emittance Fine Tuning for the FCC-ee Collider

    OpenAIRE

    Härer, Bastian; Doblhammer, Andreas; Holzer, Bernhard

    2016-01-01

    The lepton collider version of the FCC study describes a future electron-positron collider with a circumference in the order of 100 km, optimised for operation with collision energies in the range of 90 GeV to 350 GeV (FCC- ee). This paper presents the layout of the machine and the constraints on the design of the arc lattice in the context of the four different beam energies that are foreseen for beam operation. Special emphasis is put on the compensation of the effect of the strong synchrot...

  12. The phase diagram of molybdenum at extreme conditions and the role of local liquid structures

    Energy Technology Data Exchange (ETDEWEB)

    Ross, M

    2008-08-15

    Recent DAC measurements made of the Mo melting curve by the x-ray diffraction studies confirms that, up to at least 110 GPa (3300K) melting is directly from bcc to liquid, evidence that there is no basis for a speculated bcc-hcp or fcc transition. An examination of the Poisson Ratio, obtained from shock sound speed measurements, provides evidence that the 210 GPa (4100K) transition detected from shock experiments is a continuation of the bcc-liquid melting, but is from a bcc-to a solid-like mixed phase rather than to liquid. Calculations, modeled to include the free energy of liquid local structures, predict that the transition from the liquid to the mixed phase is near 150 GPa(3500K). The presence of local structures provides the simplest and most direct explanation for the Mo phase diagram, and the low melting slopes.

  13. Maximizing light olefins production in fluid catalytic cracking (FCC) units; Maximizacao de olefinas leves em unidades de craqueamento catalitico fluido

    Energy Technology Data Exchange (ETDEWEB)

    Pimenta, Ricardo D.M.; Pinho, Andrea de Rezende [PETROBRAS, Rio de Janeiro, RJ (Brazil)

    2004-07-01

    The Fluid Catalytic Cracking (FCC) process is widely spread over the ten PETROBRAS refineries in its thirteen industrial units. The importance of the FCC process resides on its high gasoline output, being the main supplier of this important product to the system. Additionally, FCC process is the main source of light hydrocarbons in the LPG range, including light olefins. The increasing demand for ethylene, propylene and butylenes was encouraging to concentrate the research efforts on studies about alternatives for the traditional FCC process. In the present work, the proposals from main licensors (UOP, KBR, Stone and Webster) for a light-olefins-driven FCC process (Petrochemical FCC) will be compared. Furthermore, the catalytic route for light olefins production in FCC units is also described. An additive based on ZSM- 5 zeolite, which is produced following a PETROBRAS proprietary technology, is being largely applied into the catalyst inventories of all FCC units. An analysis of different scenarios was performed to estimate the maximum potential of light olefins production from the highest possible ZSM-5 additive usage. More specifically for the case of ethylene, which production is also boosted by the same type of additive, studies are being conducted with the objective of recovering it from a C2 stream using specific units to do the splitting (UPGR). The search for increasing light olefins production in the refining processes is in line with PETROBRAS strategic plan which targeted for the company a more intense activity in the Brazilian petrochemical market (author)

  14. Quasi-static crack tip fields in rate-sensitive FCC single crystals

    Indian Academy of Sciences (India)

    In this work, the effects of loading rate, material rate sensitivity and constraint level on quasi-static crack tip fields in a FCC single crystal are studied. ... Global General Motors R&D, India Science Lab, GM Technical Centre (India), Bangalore 560 066, India; Department of Mechanical Engineering, Indian Institute of Science, ...

  15. 47 CFR 0.409 - Commission policy on private printing of FCC forms.

    Science.gov (United States)

    2010-10-01

    ... ORGANIZATION General Information General § 0.409 Commission policy on private printing of FCC forms. The... in quality to the original document, without change to the page size, image size, configuration of... Managing Director. [53 FR 27861, July 25, 1988] Printed Publications ...

  16. Stability and ordering properties of fcc alloys based on Rh, Ir, Pd, and Pt

    Czech Academy of Sciences Publication Activity Database

    Turchi, P. E. A.; Drchal, Václav; Kudrnovský, Josef

    2006-01-01

    Roč. 74, č. 6 (2006), 064202/1-064202/12 ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z1010914 Keywords : alloy phase stability * ordering in alloys * fcc alloys of Rh, Ir, Pd, Pt Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.107, year: 2006

  17. 75 FR 34450 - FCC to Hold Open Commission Meeting Thursday, June 17, 2010

    Science.gov (United States)

    2010-06-17

    ..., and bring the benefits of broadband to all Americans. The meeting site is fully accessible to people... www.capitolconnection.gmu.edu http://www.capitolconnection.gmu.edu/ >. Copies of materials adopted at this meeting can be purchased from the FCC's duplicating contractor, Best Copy and Printing, Inc. (202...

  18. Nitrogen Chemistry and Coke Transformation of FCC Coked Catalyst during the Regeneration Process

    Science.gov (United States)

    Shi, Junjun; Guan, Jianyu; Guo, Dawei; Zhang, Jiushun; France, Liam John; Wang, Lefu; Li, Xuehui

    2016-06-01

    Regeneration of the coked catalyst is an important process of fluid catalytic cracking (FCC) in petroleum refining, however, this process will emit environmentally harmful gases such as nitrogen and carbon oxides. Transformation of N and C containing compounds in industrial FCC coke under thermal decomposition was investigated via TPD and TPO to examine the evolved gaseous species and TGA, NMR and XPS to analyse the residual coke fraction. Two distinct regions of gas evolution are observed during TPD for the first time, and they arise from decomposition of aliphatic carbons and aromatic carbons. Three types of N species, pyrrolic N, pyridinic N and quaternary N are identified in the FCC coke, the former one is unstable and tends to be decomposed into pyridinic and quaternary N. Mechanisms of NO, CO and CO2 evolution during TPD are proposed and lattice oxygen is suggested to be an important oxygen resource. Regeneration process indicates that coke-C tends to preferentially oxidise compared with coke-N. Hence, new technology for promoting nitrogen-containing compounds conversion will benefit the in-situ reduction of NO by CO during FCC regeneration.

  19. Carbon flow analysis and Carbon emission reduction of FCC in Chinese oil refineries

    Science.gov (United States)

    Jia, Fengrui; Wei, Na; Ma, Danzhu; Liu, Guangxin; Wu, Ming; Yue, Qiang

    2017-08-01

    The major problem of the energy production in oil refineries is the high emission of CO2 in China. The fluid catalytic cracking unit (FCC) is the key source of carbon emission in the oil refineries. According to the statistical data, the carbon emission of FCC unit accounts for more than 31% for the typical oil refineries. The carbon flow of FCC in the typical Chinese oil refineries were evaluated and analysed, which aimed at the solution of CO2 emission reduction. The method of substances flow analysis (SFA) and the mathematical programming were used to evaluate the carbon metabolism and optimize the carbon emission. The results indicated that the combustion emission of the reaction-regeneration subsystem (RRS) was the major source of FCC. The quantity of CO2 emission of RSS was more than 90%. The combustion efficiency and the amount of residual oil affected the carbon emission of RRS most according to the optimized analysis of carbon emission reduction. Moreover, the fractionation subsystem (TFS) had the highest environmental efficiency and the absorption-stabilization subsystem (ASS) had the highest resource efficiency (approximately to 1) of carbon.

  20. Overview of design development of FCC-hh Experimental Interaction Regions

    CERN Document Server

    AUTHOR|(CDS)2082479; Abelleira, Jose; Cruz Alaniz, Emilia; Van Riesen-Haupt, Leon; Benedikt, Michael; Besana, Maria Ilaria; Buffat, Xavier; Burkhardt, Helmut; Cerutti, Francesco; Langner, Andy Sven; Martin, Roman; Riegler, Werner; Schulte, Daniel; Tomas Garcia, Rogelio; Appleby, Robert Barrie; Rafique, Haroon; Barranco Garcia, Javier; Pieloni, Tatiana; Boscolo, Manuela; Collamati, Francesco; Nevay, Laurence James; Hofer, Michael

    2017-01-01

    The experimental interaction region (EIR) is one of the key areas that define the performance of the Future Circular Collider. In this overview we will describe the status and the evolution of the design of EIR of FCC-hh, focusing on design of the optics, energy deposition in EIR elements, beam-beam effects and machine detector interface issues.

  1. Single-crystal FCC and DHCP phases in Ce/Pr superlattices

    International Nuclear Information System (INIS)

    Lee, S.; Goff, J.P.; Ward, R.C.C.; Wells, M.R.; McIntyre, G.J.

    2002-01-01

    Cerium usually comprises a mixture of polycrystalline FCC and DHCP allotropes. Single-crystal Ce has been stabilised in Ce/Pr superlattices grown using molecular beam epitaxy. It is found that FCC or DHCP phases can be obtained depending on superlattice composition and growth conditions. Low-temperature neutron scattering was performed on Ce/Pr samples using the triple-axis spectrometer D10 at the ILL. Such measurements revealed one sample, [Ce 20 Pr 20 ] 60 , to be a single crystal with a DHCP unit cell; while another, [Ce 30 Pr 10 ] 56 , was a mixture of FCC and DHCP phases. Antiferromagnetic ordering of magnetic moments was observed in the DHCP sample (T N =11.1 K) with a magnetic structure similar to that found in bulk β-Ce. Surprisingly, the magnetic ordering was found to be confined to single Ce blocks. Furthermore, it was found that, at low temperatures, the lattice contraction observed for bulk FCC Ce was suppressed in Ce/Pr superlattices. (orig.)

  2. Pseudomorphic-to-bulk fcc phase transition of thin Ni films on Pd(100)

    International Nuclear Information System (INIS)

    Rizzi, G.A.; Petukhov, M.; Sedona, F.; Granozzi, G.; Cossaro, A.; Bruno, F.; Cvetko, D.; Morgante, A.; Floreano, L.

    2004-01-01

    We have measured the transformation of pseudomorphic Ni films on Pd(100) into their bulk fcc phase as a function of the film thickness. We made use of x-ray diffraction and x-ray induced photoemission to study the evolution of the Ni film and its interface with the substrate. The growth of a film with tetragonally strained face centered symmetry (fct) has been observed by out-of-plane x-ray diffraction up to a limit thickness of 10 Ni pseudomorphic layers (some of them partially filled and intermixed with the substrate), where a new fcc bulklike phase is formed. After the formation of the bulklike Ni domains, we observed the pseudomorphic fct domains to disappear preserving the number of layers and their spacing. The phase transition thus proceeds via lateral growth of the bulklike phase within the pseudomorphic one, i.e., the bulklike fcc domains penetrate down to the substrate when formed. This large depth of the walls separating the domains of different phases is also indicated by the increase of the intermixing at the substrate-film interface, which starts at the onset of the transition and continues at even larger thickness. The bulklike fcc phase is also slightly strained; its relaxation towards the orthomorphic lattice structure proceeds slowly with the film thickness, being not yet completed at the maximum thickness presently studied of 30 A (∼17 layers)

  3. evaluation of commercial FCC catalysts for hydrocarbon conversion. I. Physicochemical characterization and n-hexane conversion.

    NARCIS (Netherlands)

    Brait, A.; Brait, A.; Seshan, Kulathuiyer; Lercher, J.A.

    1998-01-01

    The physicochemical properties of six steam-stabilized, commercial FCC catalysts were compared in respect of their catalytic activity for n-hexane conversion. The conversion of n-hexane over these catalysts could be fully explained by three reaction pathways: protolytic cracking, protolytic

  4. Interfacial morphologies and growth modes of F.C.C. metallic crystals from liquid alloys

    International Nuclear Information System (INIS)

    Camel, Denis

    1980-01-01

    Equilibrium and growth morphologies of f.c.c. metallic crystals in contact with liquid alloys have been observed in-situ using transmission electron microscopy. These morphologies have been discussed in terms of atomic interfacial structure and growth mechanisms with the help of a statistical thermodynamic model which takes into account the effects of chemical interactions and interfacial adsorption. (author) [fr

  5. Study of the multiple exchange frequencies in bcc 3He by thermodynamic measurements

    International Nuclear Information System (INIS)

    Bernier, M.; Suaudeau, E.; Roger, M.

    1987-08-01

    To study the multiple exchange hamiltonian of solid 3 He we measured the contribution of the spin exchange to the pressure of bcc solid in various magnetic fields (O≤ H≤ 7.5T). Due to the nature of the atomic exchange of a fermion system this contribution is a strong function of the spin polarization. The characteristic frequencies of the exchange hamiltonian are obtained by fitting the pressure measurements with the results of a statistical calculation using a high temperature series expansion of the hamiltonian in a temperature range where both the magnetic effect is significant and the expansion converges (7mK < T < 30mK). We discuss the results obtained for two molar volumes

  6. Atomistic studies of nucleation of He clusters and bubbles in bcc iron

    International Nuclear Information System (INIS)

    Yang, L.; Deng, H.Q.; Gao, F.; Heinisch, H.L.; Kurtz, R.J.; Hu, S.Y.; Li, Y.L.; Zu, X.T.

    2013-01-01

    Atomistic simulations of the nucleation of He clusters and bubbles in bcc iron at 800 K have been carried out using the newly developed Fe–Fe interatomic potential, along with Ackland potential for the Fe–Fe interactions. Microstructure changes were analyzed in detail. We found that a He cluster with four He atoms is able to push out an iron interstitial from the cluster, creating a Frenkel pair. Small He clusters and self-interstitial atom (SIA) can migrate in the matrix, but He-vacancy (He-V) clusters are immobile. Most SIAs form clusters, and only the dislocation loops with a Burgers vector of b = 1/2 appear in the simulations. SIA clusters (or loops) are attached to He-V clusters for He implantation up to 1372 appm, while the He-V cluster–loop complexes with more than one He-V cluster are formed at the He concentration of 2057 appm and larger

  7. Effects of applied strain on nanoscale self-interstitial cluster formation in BCC iron

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Ning; Setyawan, Wahyu; Kurtz, Richard J.; Wang, Zhiguang

    2017-09-01

    The effect of applied strains on the configurational evolution of self-interstitial clusters in BCC iron (Fe) is explored with atomistic simulations. A novel cluster configuration is discovered at low temperatures (<600 K), which consists of <110> dumbbells and <111> crowdions in a specific configuration, resulting in an immobile defect. The stability and diffusion of this cluster at higher temperatures is explored. In addition, an anisotropy distribution factor of a particular [hkl] interstitial loop within the family of loops is calculated as a function of strain. The results show that loop anisotropy is governed by the angle between the stress direction and the orientation of the <111> crowdions in the loop, and directly linked to the stress induced preferred nucleation of self-interstitial atoms.

  8. Properties of grain boundaries in BCC iron and iron-based alloys

    International Nuclear Information System (INIS)

    Terentyev, D.; He, Xinfu

    2010-01-01

    The report contains a summary of work done within the collaboration established between SCK-CEN and CIEA, performed during the internship of Xinfu He (CIAE) in the period of September 2009 to June 2010. In this work, we have carried out an atomistic study addressing the properties of grain boundaries in BCC Fe and Fe-Cr alloys. Throughout this work we report on the structural and cohesive properties of grain boundaries; thermal stability; interaction of grain boundaries with He and diffusivity of He in the core of the grain boundaries; equilibrium segregation of Cr near the grain boundary zone; cleavage fracture of grain boundaries; influence of the Cr precipitates, voids and He bubbles on the structure and strength of grain boundaries.

  9. Compositional Variation of the Phonon Dispersion Curves of bcc Fe-Ga Alloys

    International Nuclear Information System (INIS)

    Zarestky, Jerel L.; Garlea, Vasile O.; Lograsso, Tom; Schlagel, D.L.; Stassis, C.

    2005-01-01

    Inelastic neutron scattering techniques have been used to measure the phonon dispersion curves of bcc Fe1-xGax x=10.8, 13.3, 16.0, 22.5 alloys as a function of Ga concentration. The phonon frequencies of every branch were found to decrease significantly with increasing Ga concentration. The softening was most pronounced for the T2 0 branch and, to a lesser extent, the L branch in the vicinity of = 2 3. The concentration dependence of the shear elastic constant C =1/2 C11-C12 , calculated from the slope of the T2 0 branch, was found to agree with the results of sound velocity measurements. For the higher concentration sample measured, 22.5 at. % Ga, new branches appeared, an effect associated with the increase in the number of atoms per unit cell.

  10. Itinerant-electron antiferromagnetism and superconductivity in bcc Cr-Re alloys

    International Nuclear Information System (INIS)

    Nishihara, Y.; Yamaguchi, Y.; Kohara, T.; Tokumoto, M.

    1985-01-01

    The magnetic and superconducting properties of bcc Cr-Re alloys with up to 40 at. % Re were studied via measurements of the magnetic susceptibility, electrical resistivity, and nuclear magnetic resonance of the Re nuclei. Antiferromagnetic order coexists with superconductivity above 18 at. % Re. The results were analyzed with the coexistence model of spin-density waves and superconductivity. In the Re-concentration range greater than 18 at. %, about 10% of the Fermi surface satisfies the nesting condition and the rest of it contributes to form the superconducting gap. This model also explains the increase in the superconducting transition temperature and the decrease in the magnetic susceptibility by annealing as a competing effect between spin-density waves and superconductivity

  11. Calculation of elastic constants of BCC transition metals: tight-binding recursion method

    International Nuclear Information System (INIS)

    Masuda, K.; Hamada, N.; Terakura, K.

    1984-01-01

    The elastic constants of BCC transition metals (Fe, Nb, Mo and W) are calculated by using the tight-binding d band and the Born-Mayer repulsive potential. Introducing a small distortion characteristic to C 44 (or C') elastic deformation and calculating the energy change up to second order in the atomic displacement, the shear elastic constants C 44 and C' are determined. The elastic constants C 11 and C 12 are then calculated by using the relations B=1/3(C 11 + 2C 12 ) and C'=1/2(C 11 -C 12 ), where B is the bulk modulus. In general, the agreement between the present results and the experimental values is satisfactory. The characteristic elasticity behaviour, i.e. the strong Nsub(d) (number of d electrons) dependence of the observed anisotropy factor A=C 44 /C', will also be discussed. (author)

  12. Nuclear spin relaxation due to hydrogen diffusion in b.c.c. metals

    International Nuclear Information System (INIS)

    Faux, D.A.; Hall, C.K.

    1989-01-01

    We present Monte Carlo simulation results for the proton-proton contribution to the T 1 -1 relaxation rate for hydrogen spins diffusing on the tetrahedral sites of a b.c.c. metal. It is assumed that each hydrogen blocks all sites to the zeroth (no multiple-occupancy), second or third neighbour and that longer-range interactions may be neglected. Comparisons are made to the BPP and Torrey models. It is found that both the BPP and Torrey models give reasonable values for the peak height but that their predictions for the peak position and the high- and low-temperature limit are in error, particularly for large blocking distances. (orig.)

  13. Properties of grain boundaries in BCC iron and iron-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Terentyev, D.; He, Xinfu

    2010-08-15

    The report contains a summary of work done within the collaboration established between SCK-CEN and CIEA, performed during the internship of Xinfu He (CIAE) in the period of September 2009 to June 2010. In this work, we have carried out an atomistic study addressing the properties of grain boundaries in BCC Fe and Fe-Cr alloys. Throughout this work we report on the structural and cohesive properties of grain boundaries; thermal stability; interaction of grain boundaries with He and diffusivity of He in the core of the grain boundaries; equilibrium segregation of Cr near the grain boundary zone; cleavage fracture of grain boundaries; influence of the Cr precipitates, voids and He bubbles on the structure and strength of grain boundaries.

  14. Thermodynamic properties of bcc crystals at high temperatures: The transition metals

    International Nuclear Information System (INIS)

    MacDonald, R.A.; Shukla, R.C.

    1985-01-01

    The second-neighbor central-force model of a bcc crystal, previously used in lowest-order anharmonic perturbation theory to calculate the thermodynamic properties of the alkali metals, is here applied to the transition metals V, Nb, Ta, Mo, and W. The limitations of the model are apparent in the thermal-expansion results, which fall away from the experimental trend above about 1800 K. The specific heat similarly fails to exhibit the sharp rise that is observed at higher temperatures. A static treatment of vacancies cannot account for the difference between theory and experiment. The electrons have been taken into account by using a model that specifically includes d-band effects in the electron ground-state energy. The results thus obtained for the bulk moduli are quite satisfactory. In the light of these results, we discuss the prerequisites for a better treatment of metals when the electrons play an important role in determining the thermodynamic properties

  15. Microstructural studies of hydrogen and deuterium in bcc refractory metals. Final technical report

    International Nuclear Information System (INIS)

    Moss, S.C.

    1984-04-01

    Research was conducted on the microstructural atomic arrangements in alloys of hydrogen and deuterium with bcc refractory metals with emphasis on V and Nb. Because these are interstitial phases in which the host metal lattice is substantially deformed by the incorporation of the H(D) atoms, there are pronounced x-ray scattering effects. X-ray diffraction was used, with neutron scattering providing useful corollary data. One objective was to determine the phase relations, solid solution structures and phase transitions in metal-hydride alloys which depend upon the hydrogen-hydrogen interaction via the displacement field of the metal atoms. This has often included the elucidation of subtle thermodynamic properties (as in critical wetting) which are revealed in structural studies. Crystals were supplied for positron annihilation studies of the Fermi surface of H-Ta alloys which have revealed significant electronic trends. Work on alkali-graphite intercalates was initiated

  16. The glide of screw dislocations in bcc Fe: Atomistic static and dynamic simulations

    International Nuclear Information System (INIS)

    Chaussidon, Julien; Fivel, Marc; Rodney, David

    2006-01-01

    We present atomic-scale simulations of screw dislocation glide in bcc iron. Using two interatomic potentials that, respectively, predict degenerate and non-degenerate core structures, we compute the static 0 K dependence of the screw dislocation Peierls stress on crystal orientation and show strong boundary condition effects related to the generation of non-glide stress components. At finite temperatures we show that, with a non-degenerate core, glide by nucleation/propagation of kink-pairs in a {1 1 0} glide plane is obtained at low temperatures. A transition in the twinning region, towards an average {1 1 2} glide plane, with the formation of debris loops is observed at higher temperatures

  17. Interactions of foreign interstitial and substitutional atoms in bcc iron from ab initio calculations

    Science.gov (United States)

    You, Y.; Yan, M. F.

    2013-05-01

    C and N atoms are the most frequent foreign interstitial atoms (FIAs), and often incorporated into the surface layers of steels to enhance their properties by thermochemical treatments. Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Nb and Mo are the most common alloying elements in steels, also can be called foreign substitutional atoms (FSAs). The FIA and FSA interactions play an important role in the diffusion of C and N atoms, and the microstructures and mechanical properties of surface modified layers. Ab initio calculations based on the density functional theory are carried out to investigate FIA interactions with FSA in ferromagnetic bcc iron. The FIA-FSA interactions are analyzed systematically from five aspects, including interaction energies, density of states (DOS), bond populations, electron density difference maps and local magnetic moments.

  18. Comparison of interface structure of BCC metallic (Fe, V and Nb) films on MgO (100) substrate

    Energy Technology Data Exchange (ETDEWEB)

    Du, J.L. [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Zhang, L.Y. [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an, 710049 (China); Fu, E.G., E-mail: efu@pku.edu.cn [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Ding, X., E-mail: dingxd@mail.xjtu.edu.cn [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an, 710049 (China); Yu, K.Y., E-mail: kyyu@cup.edu.cn [Department of Materials Science and Engineering, China University of Petroleum, Beijing 102249 (China); Wang, Y.G. [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Wang, Y.Q.; Baldwin, J.K. [Experimental Physical Sciences Directorate, Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Wang, X.J. [State Key Laboratory of Advanced Optical Communication Systems and Networks, Peking University, Beijing 100871 (China); Xu, P. [Department of Chemistry, Harbin Institute of Technology, Harbin, Heilongjiang, 150001 (China)

    2017-07-15

    Highlights: • The difference of BCC metal/MgO(100) interface configuration with various lattice mismatches is identified by experiments and simulations in terms of dislocations and work of separation. • The strength of bonds along interface is found to be the fundamental factor to determine the interface configurations between BCC metal and MgO substrate. • The combination of experiments and simulations shows that the O-atop model is the actual match type between BCC metal and MgO substrate. - Abstract: This study systematically investigates the interface structure of three body-centered-cubic (BCC) metallic (Fe, V and Nb) films grown on MgO(100) substrates through experiments and simulations. Orientation relationships of their interfaces with the different lattice mismatches exhibit cube-on-cube configurations. The misfit dislocations at these three interfaces exhibit different characteristics. High resolution TEM (HRTEM), combined with first principle calculations, demonstrates the O-atop match type between metal atoms and MgO substrates for the first time. The fundamental mechanism in determining the interface configuration is discussed in terms of the work of separation and delocalization of atomic charge density.

  19. Assessment of the structural relations between the bcc and omega phases of Ti, Zr, Hf and other transition metals

    International Nuclear Information System (INIS)

    Aurelio, G.; Guillermet, A.F.

    2000-01-01

    The name omega (Ω) phase refers to a high-pressure structural modification of the transition metals (TMs) Ti, Zr, and Hf. In alloys of Ti, Zr and Hf with other TMs, the Ω phase can be formed and retained metastably at room temperature by quenching the bcc structure, which is usually the stable high-temperature phase in these alloy systems. As a part of a systematic investigation of the structural and bonding properties of the bcc and Ω phases, and of the bcc → Ω phase transformation in TMs and alloys, we present in this paper a detailed analysis of the structural relations between these phases in Ti, Zr, Hf and in other TMs. The approach is as follows. First, we establish the most general geometrical relations connecting the lattice parameters and interatomic distances (IDs) of the bcc and Ω structures. Next, we focus on the ratio between the relevant IDs of these phases, which are assessed on the basis of an extensive database with experimental and theoretical information. Both stable and metastable structures are considered, and various remarkable regularities in ID ratios are discussed. Finally, in the light of the systematics of ID ratios established in the present work, a discussion is made of the probable lattice parameters for the Ω phase of Hf, which are not yet accurately known from direct measurements. (orig.)

  20. Assessment and correction of BCC_CSM's performance in capturing leading modes of summer precipitation over North Asia

    KAUST Repository

    Gong, Zhiqiang; Dogar, Muhammad Mubashar; Qiao, Shaobo; Hu, Po; Feng, Guolin

    2017-01-01

    in the tropical East Pacific. Nevertheless, BCC_CSM exhibits limited prediction skill over most part of NA and presents a deficiency in reproducing the EOF1's and EOF2's spatial pattern over central NA and EOF2's interannual variability. This can be attributed

  1. Investigation of irradiation strengthening of b.c.c. metals and their alloys. Progress report, January 1976--October 1976

    International Nuclear Information System (INIS)

    1976-01-01

    Research on irradiation of bcc metals and alloys is reported. Data and information are presented in appendixes on low temperature neutron irradiation of Nb, effects of tritium on the yield stress of Nb, multiple dislocation motion, dislocation group motion, dislocation kinetics, and computer simulation of dislocation motion

  2. Limitations of BCC_CSM's ability to predict summer precipitation over East Asia and the Northwestern Pacific

    KAUST Repository

    Gong, Zhiqiang; Dogar, Muhammad Mubashar; Qiao, Shaobo; Hu, Po; Feng, Guolin

    2017-01-01

    This study examines the ability of the Beijing Climate Center Climate System Model (BCC_CSM) to predict the meridional pattern of summer precipitation over East Asia-Northwest Pacific (EA-NWP) and its East Asia-Pacific (EAP) teleconnection

  3. SCC, Bowen's disease and BCC arising on chronic radiation dermatitis due to radiation therapy for tinea pedis

    International Nuclear Information System (INIS)

    Aoki, Eri; Aoki, Mikako; Ikemura, Akiko; Igarashi, Tsukasa; Suzuki, Kayano; Kawana, Seiji

    2000-01-01

    We reported a case who developed three different types of skin cancers: SCC, BCC, and Bowen's disease, on the chronic radiation dermatitis. He had been treated for his tinea pedis et palmaris with radiotherapy in 1940's. It is very ratre that three different types of skin cancers arise in the same patient. This is a second case reported in Japan. (author)

  4. Ensemble averaged structure–function relationship for nanocrystals: effective superparamagnetic Fe clusters with catalytically active Pt skin [Ensemble averaged structure-function relationship for composite nanocrystals: magnetic bcc Fe clusters with catalytically active fcc Pt skin

    Energy Technology Data Exchange (ETDEWEB)

    Petkov, Valeri [Central Michigan University, Mt. Pleasant, MI (United States); Prasai, Binay [Central Michigan University, Mt. Pleasant, MI (United States); Shastri, Sarvjit [Argonne National Lab. (ANL), Argonne, IL (United States). X-ray Science Division; Park, Hyun-Uk [Sungkyunkwan University, Suwon (Korea). Department of Chemistry; Kwon, Young-Uk [Sungkyunkwan University, Suwon (Korea). Department of Chemistry; Skumryev, Vassil [Institucio Catalana de Recerca i Estudis Avançats (ICREA), Barcelona (Spain); Universitat Autònoma de Barcelona (Spain). Department of Physics

    2017-09-12

    Practical applications require the production and usage of metallic nanocrystals (NCs) in large ensembles. Besides, due to their cluster-bulk solid duality, metallic NCs exhibit a large degree of structural diversity. This poses the question as to what atomic-scale basis is to be used when the structure–function relationship for metallic NCs is to be quantified precisely. In this paper, we address the question by studying bi-functional Fe core-Pt skin type NCs optimized for practical applications. In particular, the cluster-like Fe core and skin-like Pt surface of the NCs exhibit superparamagnetic properties and a superb catalytic activity for the oxygen reduction reaction, respectively. We determine the atomic-scale structure of the NCs by non-traditional resonant high-energy X-ray diffraction coupled to atomic pair distribution function analysis. Using the experimental structure data we explain the observed magnetic and catalytic behavior of the NCs in a quantitative manner. Lastly, we demonstrate that NC ensemble-averaged 3D positions of atoms obtained by advanced X-ray scattering techniques are a very proper basis for not only establishing but also quantifying the structure–function relationship for the increasingly complex metallic NCs explored for practical applications.

  5. Communication government agencies: the case of FCC/ Organismos de regulación y control de las comunicaciones: el caso de la FCC

    Directory of Open Access Journals (Sweden)

    Dra. Ana I. Segovia Alonso; asegovia@ccinf.ucm.es

    2009-01-01

    Full Text Available The Federal Communications Commission (FCC is one of the pioneering regulatory agencies in relation to the communication system within the capitalist model. From a general perspective, beginning with its constitution, plan of action, and regulatory decisions, we carry out a research of the historical, political and economic conditions under which this commission operates and was created. The main objective is to outline the reasons for the failures and mistakes of the FCC, that has been accused –since its origins- of acting in defence of the industry interests it seemingly regulates, and not in the public interest; and of being a creature of Congress, with no real independence from the politic, economic, and judiciary power. The final purpose of this essay is to suggest the necessary democratization of the communicative space, which needs an agency transformation that could change the current defence of the existing status quo. La Comisión Federal de Comunicaciones (FCC es uno de los organismos pioneros en el control y regulación del sistema comunicativo en el modelo capitalista. Desde una mirada general a partir de su composición, formas de actuación, y decisiones normativas, se realiza un estudio de los condicionamientos históricos, políticos y económicos bajo los cuales se crea y desarrolla su labor esta Comisión. El objetivo fundamental es delinear las razones de los errores y negligencias de la FCC, acusada desde sus inicios de actuar en defensa de los intereses de la industria a la que pretende regular, y no en interés del público; y de ser una criatura del Congreso sin independencia del poder político, ni económico, ni judicial. El propósito final del presente artículo es plantear la necesaria democratización del espacio comunicativo, que pasa por una transformación de estos organismos y su defensa del status quo existente.

  6. Electronic structure and superconductivity of europium

    International Nuclear Information System (INIS)

    Nixon, Lane W.; Papaconstantopoulos, D.A.

    2010-01-01

    We have calculated the electronic structure of Eu for the bcc, hcp, and fcc crystal structures for volumes near equilibrium up to a calculated 90 GPa pressure using the augmented-plane-wave method in the local-density approximation. The frozen-core approximation was used with a semi-empirical shift of the f-states energies in the radial Schroedinger equation to move the occupied 4f valence states below the Γ 1 energy and into the core. This shift of the highly localized f-states yields the correct europium phase ordering with lattice parameters and bulk moduli in good agreement with experimental data. The calculated superconductivity properties under pressure for the bcc and hcp structures are also found to agree with and follow a T c trend similar to recent measurement by Debessai et al.

  7. Ion irradiation effects on high purity bcc Fe and model FeCr alloys

    International Nuclear Information System (INIS)

    Bhattacharya, Arunodaya

    2014-01-01

    FeCr binary alloys are a simple representative of the reduced activation ferritic/martensitic (F-M) steels, which are currently the most promising candidates as structural materials for the sodium cooled fast reactors (SFR) and future fusion systems. However, the impact of Cr on the evolution of the irradiated microstructure in these materials is not well understood in these materials. Moreover, particularly for fusion applications, the radiation damage scenario is expected to be complicated further by the presence of large quantities of He produced by the nuclear transmutation (∼ 10 appm He/dpa). Within this context, an elaborate ion irradiation study was performed at 500 C on a wide variety of high purity FeCr alloys (with Cr content ranging from ∼ 3 wt.% to 14 wt.%) and a bcc Fe, to probe in detail the influence of Cr and He on the evolution of microstructure. The irradiations were performed using Fe self-ions, in single beam mode and in dual beam mode (damage by Fe ions and co-implantation of He), to separate ballistic damage effect from the impact of simultaneous He injection. Three different dose ranges were studied: high dose (157 dpa, 17 appm He/dpa for the dual beam case), intermediate dose (45 dpa, 57 appm He/dpa for dual beam case) and in-situ low dose (0.33 dpa, 3030 appm He/dpa for the dual beam case). The experiments were performed at the JANNuS triple beam facility and dual beam in situ irradiation facility at CEA-Saclay and CSNSM, Orsay respectively. The microstructure was principally characterized by conventional TEM, APT and EDS in STEM mode. The main results are as follows: 1) A comparison of the cavity microstructure in high dose irradiated Fe revealed strong swelling reduction by the addition of He. It was achieved by a drastic reduction in cavity sizes and an increased number density. This behaviour was observed all along the damage depth, up to the damage peak. 2) Cavity microstructure was also studied in the dual beam high dose

  8. Segregation of sp-impurities at grain boundaries and surfaces: comparison of fcc cobalt and nickel

    Czech Academy of Sciences Publication Activity Database

    Všianská, Monika; Vémolová, H.; Šob, Mojmír

    2017-01-01

    Roč. 25, č. 8 (2017), č. článku 085004. ISSN 0965-0393 R&D Projects: GA ČR(CZ) GA16-24711S Institutional support: RVO:68081723 Keywords : local magnetic-moments * total-energy calculations * augmented-wave method * solute segregation * tilt boundaries * embrittling potency * alloying elements * hcp metals * basis-set * 1st-principles * grain boundary segregation * strengthening/embrittling energy * grain boundary magnetism * ab initio calculations * surface segregation Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.891, year: 2016

  9. A Novel FCC Catalyst Based on a Porous Composite Material Synthesized via an In Situ Technique

    Directory of Open Access Journals (Sweden)

    Shu-Qin Zheng

    2015-11-01

    Full Text Available To overcome diffusion limitations and improve transport in microporous zeolite, the materials with a wide-pore structure have been developed. In this paper, composite microspheres with hierarchical porous structure were synthesized by an in situ technique using sepiolite, kaolin and pseudoboehmite as raw material. A novel fluid catalytic cracking (FCC catalyst for maximizing light oil yield was prepared based on the composite materials. The catalyst was characterized by XRD, FT-IR, SEM, nitrogen adsorption-desorption techniques and tested in a bench FCC unit. The results indicated that the catalyst had more meso- and macropores and more acid sites than the reference catalyst, and thus can increase light oil yield by 1.31 %, while exhibiting better gasoline and coke selectivity.

  10. Ultraboosted Zt and γt production at the HL-LHC and FCC-hh

    Energy Technology Data Exchange (ETDEWEB)

    Aguilar-Saavedra, J.A. [Universidad de Granada, Departamento de Fisica Teorica y del Cosmos, Granada (Spain)

    2017-11-15

    Searches for anomalous Zt and γt production provide an excellent probe of flavour-changing top interactions when the energies considered are very large. In this note we estimate the sensitivity to these interactions at the high-luminosity phase of the LHC and a future 100 TeV pp collider (FCC-hh). For the LHC, the expected limits on t → uZ/uγ branching ratios from Zt and γt production will reach the 10{sup -5} level, one order of magnitude better than the existing projections for t → uZ from t anti t production. For the FCC-hh, the limits on t → uZ/uγ could reach an impressive sensitivity at the 10{sup -6} level, with limits on t → cZ/cγ at the 10{sup -5} level. (orig.)

  11. Two-Layer 16 Tesla Cosθ Dipole Design for the FCC

    Energy Technology Data Exchange (ETDEWEB)

    Holik, Eddie Frank [Fermilab; Ambrosio, Giorgio [Fermilab; Apollinari, G. [Fermilab

    2018-02-13

    The Future Circular Collider or FCC is a study aimed at exploring the possibility to reach 100 TeV total collision energy which would require 16 tesla dipoles. Upon the conclusion of the High Luminosity Upgrade, the US LHC Accelerator Upgrade Pro-ject in collaboration with CERN will have extensive Nb3Sn magnet fabrication experience. This experience includes robust Nb3Sn conductor and insulation scheming, 2-layer cos2θ coil fabrication, and bladder-and-key structure and assembly. By making im-provements and modification to existing technology the feasibility of a two-layer 16 tesla dipole is investigated. Preliminary designs indicate that fields up to 16.6 tesla are feasible with conductor grading while satisfying the HE-LHC and FCC specifications. Key challenges include accommodating high-aspect ratio conductor, narrow wedge design, Nb3Sn conductor grading, and especially quench protection of a 16 tesla device.

  12. Anisotropy in the inelastic neutron scattering from fcc NiH

    International Nuclear Information System (INIS)

    Antonov, V.E.; Fedotov, V.K.; Gnesin, B.A.; Kolesnikov, A.I.; Grosse, G.; Ivanov, A.S.; Wagner, F.E.

    2000-01-01

    A sample of nearly stoichiometric fcc nickel hydride in the form of polycrystalline plates with strong texture was studied by inelastic neutron scattering (INS) in two different orientations, with the [100] axis of the texture parallel and at an angle of 45 to the direction of neutron momentum transfer. The INS spectra were measured at 5 K with energy transfers ω ranging from 26 to 380 meV. In the region of the second and third band of optical hydrogen vibrations, they showed a significant directional dependence. A similar anisotropy was recently observed in the INS spectrum of fcc palladium hydride, and the now available data for NiH and PdH are discussed together. (orig.)

  13. The impact of the Family Communication Coordinator (FCC) Protocol on the role stress of hospital chaplains.

    Science.gov (United States)

    Dodd-McCue, Diane; Tartaglia, Alexander

    2005-01-01

    The Family Communication Coordinator (FCC) Protocol was implemented to provide early family intervention and to facilitate effective communications during potential organ donation cases. Previous studies found the Protocol associated with improved donor outcome measures and with reduced role stress for ICU nurses caring for potential donors. The present study examines the impact of the Protocol on the perceived role stress of hospital chaplains serving as FCCs. All hospital chaplains serving as FCCs at an academic teaching hospital were surveyed. Their perceptions of job dimensions, role stress, job satisfaction, and commitment were measured; interviews and secondary data supplemented the surveys. The findings demonstrate that the FCC Protocol is associated with improved role stress, specifically role ambiguity and role conflict, among hospital chaplains serving as FCCs. Additionally, the findings suggest that satisfaction with the Protocol may be associated with experience with the Protocol.

  14. FCC Rolling Textures Reviewed in the Light of Quantitative Comparisons between Simulated and Experimental Textures

    DEFF Research Database (Denmark)

    Wierzbanowski, Krzysztof; Wroński, Marcin; Leffers, Torben

    2014-01-01

    The crystallographic texture of metallic materials has a very strong effect on the properties of the materials. In the present article, we look at the rolling textures of fcc metals and alloys, where the classical problem is the existence of two different types of texture, the "copper-type texture......" and the "brass-type texture." The type of texture developed is determined by the stacking fault energy of the material, the rolling temperature and the strain rate of the rolling process. Recent texture simulations by the present authors provide the basis for a renewed discussion of the whole field of fcc......} slip without or with deformation twinning, but we also consider slip on other slip planes and slip by partial dislocations. We consistently make quantitative comparison of the simulation results and the experimental textures by means of a scalar correlation factor. We find that the development...

  15. Diffusivities and atomic mobilities in Cu-rich fcc Al-Cu-Mn alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Ming; Du, Yong; Cui, Senlin; Xu, Honghui; Liu, Shuhong [Central South Univ., Changsha (China). State Key Laboratory of Powder Metallurgy; Zhang, Lijun [Bochum Univ. (DE). Interdisciplinary Centre for Advanced Materials Simulation (ICAMS)

    2012-07-15

    Via solid-solid diffusion couples, electron probe microanalysis and the Whittle and Green method, interdiffusivities in fcc Al-Cu-Mn alloys at 1 123 K were measured. The reliability of the obtained diffusivities is validated by comparing the computed diffusivities with literature data plus constraints among the diffusivities. Through assessments of experimentally determined diffusion coefficients by means of a diffusion-controlled transformations simulation package, the atomic mobilities of Al, Cu, and Mn in fcc Al-Cu-Mn alloys are obtained. Comprehensive comparisons between the model-predicted and the experimental data indicate that the presently obtained atomic mobilities can reproduce most of the diffusivities, concentration profiles, and diffusion paths reasonably. (orig.)

  16. Effects of Dynamic Impact Loading on Microstructure of FCC (TWIP) Steel

    Science.gov (United States)

    2014-08-01

    the plate to the maximum bulge at the centre of the plate after a blast. Figure 2 shows the aluminium bulge depth measuring device in which the...is shown in Table 1. The most notable feature of the steel is the high level of manganese (18%) combined with significant levels of aluminium ...representatively in the current investigation. Figure 9(a) shows the typical rolling texture components in FCC alloys [12] as reference, consisting of ideal

  17. First-principles calculation of the magnetic properties of paramagnetic fcc iron

    International Nuclear Information System (INIS)

    Johnson, D.D.; Gyorffy, B.L.; Pinski, F.J.; Staunton, J.; Stocks, G.M.

    1985-01-01

    Using the disordered local moment picture of itinerant magnetism, we present calculations of the temperature and volume dependence of the magnetic moment and spin-spin correlations for fcc Fe in the paramagnetic state. These calculations are based on the parameter-free, first principles approach of local spin density functional theory and the coherent potential approximation is used to treat the disorder associated with the random orientation of the local moments

  18. Physics Perspectives for a Future Circular Collider: FCC-hh - Accelerator & Detectors

    CERN Multimedia

    CERN. Geneva

    2017-01-01

    The lectures will briefly discuss the parameters of a Future Circular Collider, before addressing in detail the physics perspectives and the challenges for the experiments and detector systems. The main focus will be on ee and pp collisions, but opportunities for e—p physics will also be covered. The FCC physics perspectives will be presented with reference to the ongoing LHC programme, including the physics potential from future upgrades to the LHC in luminosity and possibly energy.

  19. Physics perspectives for a Future Circular Collider: FCC-hh/eh - Physics-Perspectives

    CERN Multimedia

    CERN. Geneva

    2017-01-01

    The lectures will briefly discuss the parameters of a Future Circular Collider, before addressing in detail the physics perspectives and the challenges for the experiments and detector systems. The main focus will be on ee and pp collisions, but opportunities for e—p physics will also be covered. The FCC physics perspectives will be presented with reference to the ongoing LHC programme, including the physics potential from future upgrades to the LHC in luminosity and possibly energy.

  20. Strength of Dislocation Junctions in FCC-monocrystals with a [\\overline{1}11] Deformation Axis

    Science.gov (United States)

    Kurinnaya, R. I.; Zgolich, M. V.; Starenchenko, V. A.

    2017-07-01

    The paper examines all dislocation reactions implemented in FCC-monocrystals with axis deformation oriented in the [\\overline{1}11] direction. It identifies the fracture stresses of dislocation junctions depending on intersection geometry of the reacting dislocation loop segments. Estimates are produced for the full spectrum of reacting forest dislocations. The paper presents the statistical data of the research performed and identifies the share of long strong dislocation junctions capable of limiting the zone of dislocation shift.

  1. Catalytic cracking of vacuum gasoil overSVR, ITH, and MFI zeolites as FCC catalyst additives

    Czech Academy of Sciences Publication Activity Database

    Hussain, A. I.; Palani, A.; Aitani, A. M.; Čejka, Jiří; Shamzhy, Mariya; Kubů, Martin; Al-Khattaf, S. S.

    2017-01-01

    Roč. 161, JUN 2017 (2017), s. 23-32 ISSN 0378-3820 R&D Projects: GA ČR GBP106/12/G015; GA ČR(CZ) GP14-30898P Institutional support: RVO:61388955 Keywords : ith * mfi * Light olefins * FCC additives Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 3.752, year: 2016

  2. Stacking fault growth of FCC crystal: The Monte-Carlo simulation approach

    International Nuclear Information System (INIS)

    Jian Jianmin; Ming Naiben

    1988-03-01

    The Monte-Carlo method has been used to simulate the growth of the FCC (111) crystal surface, on which is presented the outcrop of a stacking fault. The comparison of the growth rates has been made between the stacking fault containing surface and the perfect surface. The successive growth stages have been simulated. It is concluded that the outcrop of stacking fault on the crystal surface can act as a self-perpetuating step generating source. (author). 7 refs, 3 figs

  3. Kaolin and commercial fcc catalysts in the cracking of loads of polypropylene under refinary conditions

    Directory of Open Access Journals (Sweden)

    A. M. Ribeiro

    2013-12-01

    Full Text Available The efficiency of Commercial FCC catalysts (low, medium and high activities was evaluated by the catalytic cracking process of combined feeds of polypropylene (PP and vaseline, using a microactivity test unit (M.A.T. for the production of fuel fractions (gasoline, diesel and residue. The PP/vaseline loads, at 2.0% and 4.0% wt, were processed under refinery conditions (load/catalyst ratio and temperature of process. For the PP/vaseline load (4.0% wt, the production of the gasoline fraction was favored by all catalysts, while the diesel fraction was favored by PP/vaseline load (2.0% wt, showing a preferential contact of the zeolite external surface with the end of the polymer chains for the occurrence of the catalytic cracking. All the loads produced a bigger quantity of the gaseous products in the presence of highly active commercial FCC catalyst. The improvement in the activity of the commercial FCC catalyst decreased the production of the liquid fractions and increased the quantity of the solid fractions, independent of the concentration of the loads. These results can be related to the difficulty of the polymer chains to access the catalyst acid sites, occurring preferentially end-chain scission at the external surface of the catalyst.

  4. submitter Prospects of Sterile Neutrino Search with the FCC-ee

    CERN Document Server

    Bay Nielsen, Sissel

    A proposed future circular e + e − collider, the FCC-ee, is suggested to search for sterile neutrinos. The Neutrino Minimal Standard Model, νMSM, is a model of sterile neutrinos, that accommodates explanations for several phenomena of physics beyond the Standard Model. This thesis presents an overview of the theoretical motivation for νMSM, an outline of the experimental conditions at the FCC-ee, and a review of previous accelerator bounds for sterile neutrinos. Two studies of sterile neutrinos with masses at the electroweak scale are introduced, an analysis of long lived sterile neutrinos, and an analysis of short lived sterile neutrinos. Both analyses include background studies and sensitivity estimates for the FCC-ee detector. The study of long lived sterile neutrinos is based on a search for detectable displaced vertices with 1012 Z decays, obtaining a search reach on the mixing angle |θ| 2 as small as 10−11. The study of short lived sterile neutrinos is a Monte Carlo study with a cut-based analysi...

  5. submitter Some Critical Collective Effects for the FCC-ee Collider

    CERN Document Server

    Belli, Eleonora; Migliorati, Mauro; Persichelli, Serena; Rumolo, Giovanni; Spataro, Bruno; Zobov, Mikhail

    2017-01-01

    In the framework of the Future Circular Collider (FCC) design studies at CERN [1], the high luminosity electron-positron collider FCC-ee is considered as a possible first step towards FCC-hh, a 100 TeV hadron collider in the same tunnel of about 100 km. Table 1 summarizes the main beam parameters at four different center-of-mass energies from 45.6 GeV (Z pole) to 175 GeV (top pair threshold). One of the major issues for such a kind of machine is represented by collective effects due to electromagnetic fields generated by the interaction of the beam with the vacuum chamber, which could produce instabilities, thus limiting the machine operation and performance. An impedance model is needed to study these instabilities, to predict their effects on the beam dynamics and to find a possible solution for their mitigation. Another critical aspect for the future lepton collider is represented by the electron cloud which will be discussed in the last section of this contribution, together with possible strategies to su...

  6. Design and performance studies of a hadronic calorimeter for a FCC-hh experiment

    Science.gov (United States)

    Faltova, J.

    2018-03-01

    The hadron-hadron Future Circular Collider (FCC-hh) project studies the physics reach of a proton-proton machine with a centre-of-mass-energy of 100 TeV and five times greater peak luminosities than at the High-Luminosity LHC (HL-LHC). The high-energy regime of the FCC-hh opens new opportunities for the discovery of physics beyond the standard model. At 100 TeV a large fraction of the W, Z, H bosons and top quarks are produced with a significant boost. It implies an efficient reconstruction of very high energetic objects decaying hadronically. The reconstruction of those boosted objects sets the calorimeter performance requirements in terms of energy resolution, containment of highly energetic hadron showers, and high transverse granularity. We present the current baseline technologies for the calorimeter system in the barrel region of the FCC-hh reference detector: a liquid argon electromagnetic and a scintillator-steel hadronic calorimeters. The focus of this paper is on the hadronic calorimeter and the performance studies for hadrons. The reconstruction of single particles and the achieved energy resolution for the combined system of the electromagnetic and hadronic calorimeters are discussed.

  7. Nature of nitrogen specie in coke and their role in NOx formation during FCC catalyst regeneration

    International Nuclear Information System (INIS)

    Babich, I.V.; Seshan, K.; Lefferts, L.

    2005-01-01

    NO x emission during the regeneration of coked fluid catalytic cracking (FCC) catalysts is an environmental problem. In order to follow the route to NO x formation and try to find ways to suppress it, a coked industrial FCC catalyst has been prepared using model N-containing compounds, e.g., pyridine, pyrrole, aniline and hexadecane-pyridine mixture. Nitrogen present in the FCC feed is incorporated as polyaromatic compounds in the coke deposited on the catalyst during cracking. Its functionality has been characterized using XPS. Nitrogen specie of different types, namely, pyridine, pyrrolic or quaternary-nitrogen (Q-N) have been discriminated. Decomposition of the coke during the catalyst regeneration (temperature programmed oxidation (TPO) and isothermal oxidation) has been monitored by GC and MS measurements of the gaseous products formed. The pyrrolic- and pyridinic-type N specie, present more in the outer coke layers, are oxidized under conditions when still large amount of C or CO is available from coke to reduced NO x formed to N 2 . ''Q-N'' type species are present in the inner layer, strongly adsorbed on the acid sites on the catalyst. They are combusted last during regeneration. As most of the coke is already combusted at this point, lack of reductants (C, CO, etc.) results in the presence of NO x in the tail gas

  8. FCC046: A CANDIDATE GASEOUS POLAR RING DWARF ELLIPTICAL GALAXY IN THE FORNAX CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    De Rijcke, S.; Buyle, P.; Koleva, M. [Department of Physics and Astronomy, Ghent University, Krijgslaan 281 S9, B-9000 Ghent (Belgium)

    2013-06-20

    FCC046 is a Fornax Cluster dwarf elliptical galaxy. Optical observations have shown that this galaxy, besides an old and metal-poor stellar population, also contains a very young centrally concentrated population and is actively forming stars, albeit at a very low level. Here, we report on 21 cm observations of FCC046 with the Australia Telescope Compact Array which we conducted in the course of a small survey of Fornax Cluster early-type dwarf galaxies. We have discovered a {approx}10{sup 7} M{sub Sun} H I cloud surrounding FCC046. We show that the presence of this significant gas reservoir offers a concise explanation for this galaxy's optical morphological and kinematical properties. Surprisingly, the H I gas, as evidenced by its morphology and its rotational motion around the galaxy's optical major axis, is kinematically decoupled from the galaxy's stellar body. This is the first time such a ring of gaseous material in minor-axis rotation is discovered around a dwarf galaxy.

  9. Development of OCDMA system based on Flexible Cross Correlation (FCC) code with OFDM modulation

    Science.gov (United States)

    Aldhaibani, A. O.; Aljunid, S. A.; Anuar, M. S.; Arief, A. R.; Rashidi, C. B. M.

    2015-03-01

    The performance of the OCDMA systems is governed by numerous quantitative parameters such as the data rate, simultaneous number of users, the powers of transmitter and receiver, and the type of codes. This paper analyzes the performance of the OCDMA system using OFDM technique to enhance the channel data rate, to save power and increase the number of user of OSCDMA systems compared with previous hybrid subcarrier multiplexing/optical spectrum code division multiplexing (SCM/OSCDM) system. The average received signal to noise ratio (SNR) with the nonlinearity of subcarriers is derived. The theoretical results have been evaluated based on BER and number of users as well as amount of power saved. The proposed system gave better performance and save around -6 dBm of the power as well as increase the number of users twice compare to SCM/OCDMA system. In addition it is robust against interference and much more spectrally efficient than SCM/OCDMA system. The system was designed based on Flexible Cross Correlation (FCC) code which is easier construction, less complexity of encoder/decoder design and flexible in-phase cross-correlation for uncomplicated to implement using Fiber Bragg Gratings (FBGs) for the OCDMA systems for any number of users and weights. The OCDMA-FCC_OFDM improves the number of users (cardinality) 108% compare to SCM/ODCMA-FCC system.

  10. Monitoring catalyst flow rate in a FCC cold pilot unity by gamma ray transmission measurements

    International Nuclear Information System (INIS)

    Brito, Marcio F.P.; Netto, Wilson F.S.; Miranda, Marcia V.F.E.S.; Junior, Isacc A.S.; Dantas, Carlos C.; Melo, Silvio B.; Lima, Emerson A.O.

    2013-01-01

    A model for monitoring catalyst mass flow in riser of Fluid Catalytic Cracking - FCC, pilot unity as a function of air flow and solid injection is proposed. The fluidized FCC- catalyst bed system is investigated in an experimental setup the Cold Pilot Unity - CPU by means of gamma ray transmission measurements. Riser in CPU simulates the reactor in FCC process. By automation control air flow is instrumentally measured in riser and the solid injection is manually controlled by valve adjusting. Keeping a constant solid injection, catalyst level at the return column was measured by gamma transmission for several air flow values in riser. The operational condition reached a steady state regime before given to setup a new air flow value. A calibration of catalyst level as a function of air flow in riser is calculated, therefore, a model for solid feed rate is derived. Recent published work evaluates solid concentration in riser of the CPU by means of gamma ray transmission, and a correlation with air velocity is obtained. In this work, the model for solid feed rate was further investigated by carrying out experiments to measure catalyst concentration at the same air flow values. These experiments lead to a model for monitoring catalyst flow in riser as function of solid feed rate and air flow. Simulation with random numbers produced with Matlab software allows to define validation criteria for the model parameters. (author)

  11. Ternary diffusion in Cu-rich fcc Cu–Al–Si alloys at 1073 K

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Dandan [School of Materials Science and Engineering, Central South University, Changsha, Hunan 410083 (China); State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Zhang, Lijun [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Du, Yong, E-mail: yongducalphad@gmail.com [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Xu, Honghui [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Jin, Zhanpeng [School of Materials Science and Engineering, Central South University, Changsha, Hunan 410083 (China)

    2013-07-25

    Highlights: •Interdiffusivities in Cu-rich fcc Cu–Al–Si alloys at 1073 K were determined. •The present results were compared with experimental data in boundary binary systems. •The present results were validated by thermodynamic constraints and Fick’s law. •The sign of ternary cross diffusivities was predicted in terms of thermodynamics. -- Abstract: Utilizing six groups of bulk diffusion couples and with electron probe microanalysis technique, the composition dependence of ternary interdiffusion coefficients in Cu-rich fcc Cu–Al–Si alloys at 1073 K were determined by the Matano-Kirkaldy method. Using a three-dimensional representation, the obtained main ternary diffusion coefficients were found to be consistent with the experimental data in boundary binaries available in the literature. The reliability of the obtained interdiffusivities was further validated by thermodynamic constraints as well as by Fick’s second law applied to numerical simulation. The sign of the ternary cross diffusivities in fcc Cu–Al–Si alloys, which shows a noticeable effect on microstructure, was also successfully predicted in terms of thermodynamics.

  12. Ternary diffusion in Cu-rich fcc Cu–Al–Si alloys at 1073 K

    International Nuclear Information System (INIS)

    Liu, Dandan; Zhang, Lijun; Du, Yong; Xu, Honghui; Jin, Zhanpeng

    2013-01-01

    Highlights: •Interdiffusivities in Cu-rich fcc Cu–Al–Si alloys at 1073 K were determined. •The present results were compared with experimental data in boundary binary systems. •The present results were validated by thermodynamic constraints and Fick’s law. •The sign of ternary cross diffusivities was predicted in terms of thermodynamics. -- Abstract: Utilizing six groups of bulk diffusion couples and with electron probe microanalysis technique, the composition dependence of ternary interdiffusion coefficients in Cu-rich fcc Cu–Al–Si alloys at 1073 K were determined by the Matano-Kirkaldy method. Using a three-dimensional representation, the obtained main ternary diffusion coefficients were found to be consistent with the experimental data in boundary binaries available in the literature. The reliability of the obtained interdiffusivities was further validated by thermodynamic constraints as well as by Fick’s second law applied to numerical simulation. The sign of the ternary cross diffusivities in fcc Cu–Al–Si alloys, which shows a noticeable effect on microstructure, was also successfully predicted in terms of thermodynamics

  13. Steady-state crack growth in single crystals under Mode I loading

    DEFF Research Database (Denmark)

    Juul, Kristian Jørgensen; Nielsen, Kim Lau; Niordson, Christian Frithiof

    2017-01-01

    The active plastic zone that surrounds the tip of a sharp crack growing under plane strain Mode I loading conditions at a constant velocity in a single crystal is studied. Both the characteristics of the plastic zone and its effect on the macroscopic toughness is investigated in terms of crack tip...... that the largest shielding effect develops in HCP crystals, while the lowest shielding exists for FCC crystals. Rate-sensitivity is found to affect the plastic zone size, but the characteristics overall remain similar for each individual crystal structure. An increasing rate-sensitivity at low crack velocities...... shielding due to plasticity (quantified by employing the Suo, Shih, and Varias set-up). Three single crystals (FCC, BCC, HCP) are modelled in a steady-state elastic visco-plastic framework, with emphasis on the influence of rate-sensitivity and crystal structures. Distinct velocity discontinuities...

  14. First-principles calculation for the effect of hydrogen atoms on the mobility of a screw dislocation in BCC iron

    International Nuclear Information System (INIS)

    Itakura, Mitsuhiro; Kaburaki, Hideo; Yamaguchi, Masatake; Endo, Tatsuro; Higuchi, Kenji; Ogata, Shigenobu; Kimizuka, Hajime

    2012-01-01

    Effect of hydrogen atoms on the mobility of a screw dislocation in BCC iron has been evaluated using the first-principles calculation. The stable position of a hydrogen atom is found to be near the screw dislocation core and inside the core respectively when the dislocation is at the easy-core or hard-core configuration in BCC iron. The intrinsically unstable hard-core configuration of the screw dislocation is stabilized when a hydrogen atom is trapped inside the core. On the basis of this first-principles result, an elastic string model of a dislocation is developed to predict the kink motion in the presence of a hydrogen atom. It is found that a double-kink formation is facilitated when a hydrogen atom is located near a dislocation line, however, a kink motion is retarded when a hydrogen atom is behind the kink. (author)

  15. Investigation of the structural and hydrogenation properties of disordered Ti-V-Cr-Mo BCC solid solutions

    International Nuclear Information System (INIS)

    Raufast, C.; Planté, D.; Miraglia, S.

    2014-01-01

    Highlights: • Materials synthesis and structural analysis of selected compositions of TiVCr(Mo) bcc samples. • Extraction of the thermodynamics relevant parameters for hydride formation and dissociation state of Ti 0.3 V 1.7 Cr 0.7 Mo 0.3 sample. • Discussion of the hydrides practicability. - Abstract: Selected compositions in the Ti-Cr-V-Mo system (with the BCC structure-type) have been synthesized and characterized for structural (crystalline structure, solidification microstructure) and thermodynamic properties (equilibrium and reversible hydrogen storage capacity). We present as well the effect of co-melting with a so-called activating phase that results in a secondary phase development and a subsequent enhancement of the hydrogen sorption kinetics. Ageing properties and applicability of such materials for hybrid hydrogen storage systems are also discussed

  16. Impact of Intragranular Substructure Parameters on the Forming Limit Diagrams of Single-Phase B.C.C. Steels

    Directory of Open Access Journals (Sweden)

    Gérald Franz

    2013-11-01

    Full Text Available An advanced elastic-plastic self-consistent polycrystalline model, accounting for intragranular microstructure development and evolution, is coupled with a bifurcation-based localization criterion and applied to the numerical investigation of the impact of microstructural patterns on ductility of single-phase steels. The proposed multiscale model, taking into account essential microstructural aspects, such as initial and induced textures, dislocation densities, and softening mechanisms, allows us to emphasize the relationship between intragranular microstructure of B.C.C. steels and their ductility. A qualitative study in terms of forming limit diagrams for various dislocation networks, during monotonic loading tests, is conducted in order to analyze the impact of intragranular substructure parameters on the formability of single-phase B.C.C. steels.

  17. Magnetic ordering of four particle exchange model in BCC 3He

    International Nuclear Information System (INIS)

    Ishikawa, Koji; Okada, Isamu

    1978-01-01

    The low temperature magnetic ordering of BCC 3 He within the mean field approximation was studied. A model including four particle exchange interactions was considered. Two types of cyclic quadrupole exchange process, planar and folded, were taken into account. Assuming four sublattices, it was considered to minimize the spin energy with respect to the classical spin vector and to find out four ordered states at the absolute zero point. They are antiferromagnetic (AF), weak ferromagnetic (WF) and two kinds of simple cubic antiferromagnetic states (SCAF). The condition for the existence of each ordered state is given, and the free energies of the ordered states are calculated in the mean field approximation. The transition between AF or SCAF and the paramagnetic states is of the first order. The phase diagram is drawn in the parameter space. The phase diagram was obtained numerically at Hetherington and Willard's value and at its neighbouring values. The difference between the present result and HW's is that of magnetic field direction in the perpendicular simple cubic antiferromagnetic states. The second order transition disappears, and the WF state changes gradually into AF state. With respect to the first order transition, the transition temperature increases with magnetic field. In this case, a critical magnetic field exists. (Kato, T

  18. Flow stress asymmetry and cyclic stress--strain response in a BCC Ti--V alloy

    International Nuclear Information System (INIS)

    Koss, D.A.; Wojcik, C.C.

    1976-01-01

    The cyclic stress-strain response of relatively stable bcc β-phase Ti--40 percent V alloy single crystals was studied. Flow stress asymmetry found in the alloy is attributed to the fact that screw dislocations, when gliding on a (211) plane, are more mobile in the twinning direction than in the antitwinning direction. Thus the flow stress of the crystal is greater when it is sheared in the antitwinning direction than in the twinning direction (the latter case results when crystals of the 100 orientation are stressed in tension and those of the 110 orientation are stressed in compression). Such behavior can be a result of the core of a screw dislocation being asymmetric under stress which causes the flow stress asymmetry observed. It should be noted that screw dislocations dominate the low temperature deformation structure of Ti-40V, which strongly suggests deformation is controlled by screw dislocation motion. The observation in Mo that the microyield stress is independent of crystal orientation could be a result of edge dislocation motion controlling microyield in that instance and this observation would not be inconsistent with screw dislocation motion controlling the macroscopic (epsilon/sub p/ greater than 0.05 percent) deformation measured here

  19. Effect of orientation of prismatic dislocation loops on interaction with free surfaces in BCC iron

    Science.gov (United States)

    Fikar, Jan; Gröger, Roman; Schäublin, Robin

    2017-12-01

    The prismatic loops appear in metals as a result of high-energy irradiation. Understanding their formation and interaction is important for quantification of irradiation-induced deterioration of mechanical properties. Characterization of dislocation loops in thin foils is commonly made using transmission electron microscopy (TEM), but the results are inevitably influenced by the proximity of free surfaces. The prismatic loops are attracted to free surfaces by image forces. Depending on the type, shape, size, orientation and depth of the loop in the foil, they can escape to the free surface creating denuded loop-free zones and thus invalidating TEM observations. In our previous studies we described a simple general method to determine the critical depth and the critical stress to move prismatic dislocation loops. The critical depths can be further used to correct measurements of the loop density by TEM. Here, we use this procedure to compare 〈100〉 loops and 1/2 〈111〉 loops in body-centered cubic (BCC) iron. The influences of the interatomic potential and the loop orientation are studied in detail. The difference between interstitial and vacancy type loop is also investigated.

  20. Diffusion of Y and Ti/Zr in bcc iron: A first principles study

    International Nuclear Information System (INIS)

    Murali, D.; Panigrahi, B.K.; Valsakumar, M.C.; Sundar, C.S.

    2011-01-01

    The diffusion of yttrium plays an important role in the kinetics of formation of oxide nanoclusters in oxide dispersion strengthened alloys. Also, the diffusivity of minor alloying elements like Ti and Zr are of special interest as they are crucial for fine dispersion of oxide nanoclusters in the ferritic matrix. These solute atoms occupy substitutional sites in bcc Fe. The diffusion coefficients of these solute atoms were calculated using Le Claire’s nine frequency model involving the vacancy mechanism. We have done detailed density functional theory calculation of the interaction of these solute atoms with vacancies (□) and estimated various migration energy barriers of the vacancies in the presence of these solute atoms using nudged elastic band method. Strikingly, compared with Zr and Ti, Y shows a very large relaxation towards first neighbor vacancy resulting in strong binding with the vacancy. The Y-□ binding energy of 1.45 eV is almost double that of Zr-□ binding energy of 0.78 eV. We have also compared the calculated diffusion coefficients of these solute atoms with the experimental values.

  1. Amylase Production from Thermophilic Bacillus sp. BCC 021-50 Isolated from a Marine Environment

    Directory of Open Access Journals (Sweden)

    Altaf Ahmed Simair

    2017-06-01

    Full Text Available The high cost of fermentation media is one of the technical barriers in amylase production from microbial sources. Amylase is used in several industrial processes or industries, for example, in the food industry, the saccharification of starchy materials, and in the detergent and textile industry. In this study, marine microorganisms were isolated to identify unique amylase-producing microbes in starch agar medium. More than 50 bacterial strains with positive amylase activity, isolated from marine water and soil, were screened for amylase production in starch agar medium. Bacillus sp. BCC 021-50 was found to be the best amylase-producing strain in starch agar medium and under submerged fermentation conditions. Next, fermentation conditions were optimized for bacterial growth and enzyme production. The highest amylase concentration of 5211 U/mL was obtained after 36 h of incubation at 50 °C, pH 8.0, using 20 g/L molasses as an energy source and 10 g/L peptone as a nitrogen source. From an application perspective, crude amylase was characterized in terms of temperature and pH. Maximum amylase activity was noted at 70 °C and pH 7.50. However, our results show clear advantages for enzyme stability in alkaline pH, high-temperature, and stability in the presence of surfactant, oxidizing, and bleaching agents. This research contributes towards the development of an economical amylase production process using agro-industrial residues.

  2. Strain Fields And Crystallographic Characteristics Of Interstitial Dislocation Loops of Various Geometry In BCC Iron

    International Nuclear Information System (INIS)

    Sivak, Alexander B.; Chernov, Viatcheslav M.; Romanov, Vladimir A.

    2008-01-01

    The formation energy, the relaxation volume, the dipole-force tensor, the self strain tensor and strain fields of interstitial dislocation loops in bcc iron (clusters of self interstitial atoms) have been calculated by molecular statics. Hexagonal and square dislocation loops of different types with different Burgers vectors, directions of dislocation segments and habit planes containing up to ∼2500 self-interstitials have been considered. Analytical expressions describing size dependence of the formation energy, the relaxation volume and the self strain tensor for the loops stated have been obtained. The most energetically favorable loops are hexagonal loops with Burgers vector a/2 and habit plane {11x}, where x takes values in the range from 0 to 1 depending on the loop size. The formation energy of a loops with and dislocation segments is ∼14% and 23% greater than that of hexagonal a/2 loops at N>500, respectively. The analysis of the formation energies of a/2 and a loops demonstrated that the nucleation of an a loop by joining of two a/2 loops is possible when the total number of constituent self-interstitials in these loops is larger than 13

  3. Investigation of point defects diffusion in bcc uranium and U–Mo alloys

    International Nuclear Information System (INIS)

    Smirnova, D.E.; Kuksin, A.Yu.; Starikov, S.V.

    2015-01-01

    We present results of investigation of point defects formation and diffusion in pure γ-U and γ-U–Mo fuel alloys. The study was performed using molecular dynamics simulation with the different interatomic potentials. The point defects formation and migration energies were estimated for bcc γ-U and U–9 wt.%Mo alloy. The calculated diffusivities of atoms via defects are provided for pure γ-U and for the alloy components. Analysis of simulation results shows that self-interstitial atoms play a leading role in the self-diffusion processes in the materials studied. This fact can explain a remarkably high self-diffusion mobility observed experimentally for γ-U. The self-diffusion coefficients in γ-U calculated in this assumption agree with the data measured experimentally. It is shown that alloying of γ-U with Mo increase formation energy for self-interstitial atoms and decelerate their mobility. These changes lead to decrease of self-diffusion coefficients in U–Mo alloy compared to pure U

  4. On the Secrecy Capacity Region of the Block-Fading BCC with Limited CSI Feedback

    KAUST Repository

    Hyadi, Amal

    2017-02-07

    In this work, we examine the secrecy capacity region of the block-fading broadcast channel with confidential messages (BCC) when the transmitter has limited knowledge of the channel. In particular, we consider a two-user communication system where the transmitter has one common message to be transmitted to both users and one confidential message intended to only one of them. The confidential message has to be kept secret from the other user to whom the information is not intended. The transmitter is not aware of the channel state information (CSI) of neither channel and is only provided by limited CSI feedback sent at the beginning of each fading block. Assuming an error-free feedback link, we characterize the secrecy capacity region of this channel and show that even with a 1-bit CSI feedback, a positive secrecy rate can still be achieved. Then, we look at the case where the feedback link is not error- free and is rather a binary erasure channel (BEC). In the latter case, we provide an achievable secrecy rate region and show that as long as the erasure event is not a probability 1 event, the transmitter can still transmit the confidential information with a positive secrecy rate.

  5. MD and BCA simulations of He and H bombardment of fuzz in bcc elements

    Science.gov (United States)

    Klaver, T. P. C.; Zhang, S.; Nordlund, K.

    2017-08-01

    We present results of MD simulations of low energy He ion bombardment of low density fuzz in bcc elements. He ions can penetrate several micrometers into sparse fuzz, which allows for a sufficient He flux through it to grow the fuzz further. He kinetic energy falls off exponentially with penetration depth. A BCA code was used to carry out the same ion bombardment on the same fuzz structures as in MD simulations, but with simpler, 10 million times faster calculations. Despite the poor theoretical basis of the BCA at low ion energies, and the use of somewhat different potentials in MD and BCA calculations, the ion penetration depths predicted by BCA are only ∼12% less than those predicted by MD. The MD-BCA differences are highly systematic and trends in the results of the two methods are very similar. We have carried out more than 200 BCA calculation runs of ion bombardment of fuzz, in which parameters in the ion bombardment process were varied. For most parameters, the results show that the ion bombardment process is quite generic. The ion species (He or H), ion mass, fuzz element (W, Ta, Mo, Fe) and fuzz element lattice parameter turned out to have a modest influence on ion penetration depths at most. An off-normal angle of incidence strongly reduces the ion penetration depth. Increasing the ion energy increases the ion penetration, but the rate by which ion energy drops off at high ion energies follows the same exponential pattern as at lower energies.

  6. Growth of a brittle crack (001) in 3D bcc iron crystal with a Cu nano-particle

    Czech Academy of Sciences Publication Activity Database

    Uhnáková, Alena; Machová, Anna; Hora, Petr; Červená, Olga

    2014-01-01

    Roč. 83, February (2014), s. 229-234 ISSN 0927-0256 R&D Projects: GA ČR GA101/09/1630 Institutional support: RVO:61388998 Keywords : brittle crack extension * 3D * mode I * bcc iron * Cu nano-particle * molecular dynamics * acoustic emission Subject RIV: JG - Metallurgy Impact factor: 2.131, year: 2014 http://www.sciencedirect.com/science/article/pii/S0927025613006575

  7. 3D atomistic simulation of fatigue behavior of a ductile crack in bcc iron loaded in mode II

    Czech Academy of Sciences Publication Activity Database

    Uhnáková, Alena; Pokluda, J.; Machová, Anna; Hora, Petr

    2012-01-01

    Roč. 61, AUG 2012 (2012), s. 12-19 ISSN 0927-0256 R&D Projects: GA ČR(CZ) GAP108/10/0698 Institutional research plan: CEZ:AV0Z20760514 Keywords : fatigue * mode II * bcc iron * molecular dynamic simulations Subject RIV: JG - Metallurgy Impact factor: 1.878, year: 2012 http://www.sciencedirect.com/science/article/pii/S0927025612001929

  8. Crystal plasticity model for BCC iron atomistically informed by kinetics of correlated kinkpair nucleation on screw dislocation

    Science.gov (United States)

    Narayanan, Sankar; McDowell, David L.; Zhu, Ting

    2014-04-01

    The mobility of dislocation in body-centered cubic (BCC) metals is controlled by the thermally activated nucleation of kinks along the dislocation core. By employing a recent interatomic potential and the Nudged Elastic Band method, we predict the atomistic saddle-point state of 1/2 screw dislocation motion in BCC iron that involves the nucleation of correlated kinkpairs and the resulting double superkinks. This unique process leads to a single-humped minimum energy path that governs the one-step activation of a screw dislocation to move into the adjacent {110} Peierls valley, which contrasts with the double-humped energy path and the two-step transition predicted by other interatomic potentials. Based on transition state theory, we use the atomistically computed, stress-dependent kinkpair activation parameters to inform a coarse-grained crystal plasticity flow rule. Our atomistically-informed crystal plasticity model quantitatively predicts the orientation dependent stress-strain behavior of BCC iron single crystals in a manner that is consistent with experimental results. The predicted temperature and strain-rate dependencies of the yield stress agree with experimental results in the 200-350 K temperature regime, and are rationalized by the small activation volumes associated with the kinkpair-mediated motion of screw dislocations.

  9. Structural changes and tribological behaviors of nitrogen ion-implanted tantalum

    International Nuclear Information System (INIS)

    Wang, W.J.; Wang, T.M.; Wang, X.J.

    1996-01-01

    Single-crystal tantalum sheets were implanted by 110 keV nitrogen ions to a dose of 5 x 10 17 ions/cm 2 at a temperature less than 100 C. The structural changes and the concentration depth profiles of the implanted layers were characterized by glancing-angle X-ray diffraction (GXRD), selected area diffraction (SAD) and Auger electron spectroscopy (AES), respectively. The microhardness, the friction coefficient and the wear rate of the specimens against hardened GCr15 steel balls were also determined before and after the implantation. Scanning electron microscopy (SEM) and electron probe micro-analyzer (EPMA) were used to analyze the wear tracks. The results showed that there exist deviations between the characterization results of AES and GXRD or SAD. The AES measurement suggests the formation of the tantalum nitrides with a maximum N/Ta ratio of 1/2, while the GXRD and SAD reveal the formation of bcc Ta(N), fcc TaN and a trace amount of hcp Ta 2 N. This can be explained by considering the inhomogeneous distribution of nitrogen atoms in micro-regions: the enrichment of nitrogen atoms in local micro-regions leads to the formation of fcc TaN; however, the unfavorable structural compatibility between bcc Ta and hcp Ta 2 N hinders the formation of hcp Ta 2 N in the regions where the N/Ta ratio reaches 1/2. The detected trace amount of the hcp Ta 2 N phase in the implanted layers can be considered as an after effect of nitrogen loss from the originally formed nitrides. The results also showed that the tribological properties of the Ta surfaces were improved due to the implantation. It is believed that the implantation-induced Ta(N), fcc TaN, and hcp Ta 2 N phases are responsible for this improvement. (orig.)

  10. The physical and mechanical metallurgy of advanced O+BCC titanium alloys

    Science.gov (United States)

    Cowen, Christopher John

    deformation mechanisms as a function of stress, temperature, and strain rate. Microstructure-creep relationships for Ti-Al-Nb-xB alloys were developed with the understanding gained. A rule-of-mixtures empirical model based on constituent phase volume fractions and strain rates was developed to predict the minimum creep rates of two-phase O+BCC microstructures. The most innovative results of this thesis were produced through the development of an in-situ creep testing methodology. The creep deformation evolution was chronicled in-situ during high temperature creep experiments, while creep displacement versus time data was simultaneously obtained. The in-situ experiments revealed that prior-BCC grain boundaries were the locus of damage accumulation during creep deformation. A methodology that allows in-situ observation of surface creep deformation as a function of creep displacement has yet to be presented in the literature.

  11. Determinants of adherence to therapies among Malaysian women with breast cancer: MyBCC Cohort

    Directory of Open Access Journals (Sweden)

    Mao Li Cheng

    2017-12-01

    Full Text Available Background: Breast cancer therapies have been progressively advancing to improve the breast cancer survival over the last few decades. However, non-adherence to cancer treatments has shown to be associated with reduced treatment effectiveness, increased mortality, and increased health care costs. The aim of the study is to understand the determinants of adherence to therapies among Malaysian breast cancer patients. Methods: This was a secondary analysis of all newly diagnosed Malaysian breast cancer patients recruited into a prospective cohort study in Universiti Malaya Medical Centre, MyBCC cohort, from 1st February 2012 to 31st December 2015. The MyBCC cohort study has ethics approval, MEC number 896.150. The treatment options (surgery, chemotherapy, radiotherapy, and overall therapies, surgical options, socio-demographic characteristics, clinical signs and symptoms, traditional and complementary medicine, and psychosocial assessments were measured using Hospital Anxiety and Depression Scale (HADS and Multidimensional Scale of Perceived Social Support (MSPSS. Results: In total, 467 patients were analysed. The adherence to surgery was 93.8%, chemotherapy 87.7%, radiotherapy 89.1%, and overall therapies 65.8% respectively. Breast conserving surgery was associated with adherence to surgery compared to mastectomy (adjusted OR 5.48 [95% CI 1.00, 30.09], p = 0.034, radiotherapy (adjusted OR 5.44 [95% CI 1.17, 25.16], p = 0.030 and overall therapies (adjusted OR 2.45 [95% CI 1.04, 5.78], p = 0.041. Time from diagnosis to surgery of less than 60 days was associated with adherence to surgery (adjusted OR 49.98 [95% CI 8.47, 289.05], p less than 0.0001 and overall therapies (adjusted OR 9.38 [95% CI 1.26, 69.73], p = 0.029. Adherence to chemotherapy associated with no surgery (adjusted OR 0.15 [95% CI 0.03, 0.70], p = 0.016. Adherence to radiotherapy was associated with financial reimbursement (adjusted OR 4.34 [95% CI 1.03, 18.26], p = 0.045 and

  12. Development of a new formulation of interferons (HEBERPAG for BCC treatment

    Directory of Open Access Journals (Sweden)

    Bello-Rivero I

    2013-12-01

    Full Text Available Purpose: This work is aimed to show briefly, the clinical development of a new pharmaceutical formulation of interferons for the treatment of basal cell carcinoma. Methods: A rationale design of the combination of IFN-α2b and -γ based in their anti-proliferative synergism on several tumors cell lines identified adequate proportions to be combined to obtain the best clinical results. The potential mechanism of antitumoral effect was studied by qPCR mRNA quantification. HEBERPAG (anti-proliferative synergistic combination of co-formulated recombinant interferons-α2b and –γ was used in clinical trials in adult patients with non-melanoma skin cancer. Trials were conducted after approval by the ethics review boards of the institutions participating in trials; and the patients gave their written informed consent to be enrolled in the studies and receive HEBERPAG. Results: HEBERPAG inhibits the proliferation of several tumor cell lines in vitro and in vivo. The combination has improved pharmacodinamic properties. Several clinical trials have demonstrated the efficacy of HEBERPAG in BCC, with excellent cosmetic effect and well tolerable, mild side effects. HEBERPAG was approved by State Control Center for Drug, Medical Equipment and Devises in Cuba, for the treatment of basal cell carcinoma of any subtype, size and localization, and adjuvant to other treatments, surgical or not. After 3-year follow-up, a recurrence rate of 0.03% was detected in treated patients. Conclusions: HEBERPAG is a novel formulation of IFNs, more potent than separated IFNs for the treatment of basal cell carcinoma, with more rapid and prolonged clinical effect and excellent cosmetic effect and safety profile.

  13. Structural transformation in mechanosynthesized bcc Fe-Al-Si(Ge) solid solutions during heating

    International Nuclear Information System (INIS)

    Kubalova, L.M.; Sviridov, I.A.; Vasilyeva, O.Ya.; Fadeeva, V.I.

    2007-01-01

    X-ray diffractometry and Moessbauer spectroscopy study of Fe 50 Al 25 Si 25 and Fe 50 Al 25 Ge 25 alloys obtained by mechanical alloying (MA) of elementary powders was carried out. Phase transformation during heating of synthesized products was studied using differential scanning calorimetry (DSC). After 2.5 h of MA monophase alloys containing bcc Fe(Al, Ge) solid solutions Fe(Al, Si) are formed. Fe(Al, Si) is partially ordered B2 type and Fe(Al, Ge) is completely disordered. DSC curves of synthesized alloys displayed the presence of exothermal peaks caused by phase transformation. The metastable Fe(Al, Si) solid solution transformed into FeAl 1-x Si x (B2) and FeSi 1-x Al x (B20) equilibrium phases. The Fe(Al, Ge) solid solution transformed into equilibrium phases through intermediate stage of Fe 6 Ge 3 Al 2 metastable phase formation. The Fe 6 Ge 3 Al 2 phase dissociated into three equilibrium phases: FeAl 1-x Ge x (B2), χ-Fe 6 Ge 5 and η-Fe 13 (Ge, Al) 8 (B8 2 ). The structure of Fe 6 Ge 3 Al 2 was calculated by Rietveld method, the distribution of Al and Ge in the elementary cell and its parameters were calculated. Moessbauer study showed that Fe(Al, Si) and Fe(Al, Ge) solid solutions are paramagnetic. In the equilibrium state the alloy containing Si is also paramagnetic while the alloy with Ge showed ferromagnetic properties

  14. Decrease Risk Behavior HIV Infected on Construction Laborers with Behavior Change Communication (BCC Approach

    Directory of Open Access Journals (Sweden)

    Purwaningsih Purwaningsih

    2016-09-01

    The purpose of this study was to determine the effectiveness of BCC approach to the reduction of contracting HIV risk behavior in the construction laborers. Method: This study used operational research design. In this study measures the effectiveness of behavior change of construction workers on the prevention of HIV transmission by comparing the behavior of the construction workers before and after the intervention. The subjects of this study were 150 people risk group of construction workers who work and are spread throughout the city of Surabaya. This research was carried out into three phases, namely, phase preintervention research, intervention research, and post-intervention phase of the study. Implemented in the first year and second year praintervensi stage implemented intervention and post-intervention phases. Result: The results of this study showed that 72% of construction workers is productive (18–35 years and visit his family more than once a month (38%. There is 20% of construction workers had sex with commercial sex workers and no one was using drugs. By 50% of construction workers never get information about HIV/AIDS and as many as 48% never use the services of HIV/AIDS. Discussion: External motivation construction workers associated with the utilization of behavioral HIV/AIDS services with sufficient correlation. Strong external motivation is influenced by risk behaviors of HIV/AIDS were conducted and the desire to get help. Weak external motivation is influenced by a lack of exposure to information related to HIV/AIDS services. The results of the FGD stakeholders have the perception is the same if a construction worker is a high risk group of contracting HIV. Most of the construction workers not have enough knowledge for the prevention of HIV transmission because they do not have access to HIV care and behavior are at risk of contracting HIV by construction workers. Keywords: construction workers, behavior change communication, behavior

  15. Elastic properties of Ti-24Nb-4Zr-8Sn single crystals with bcc crystal structure

    International Nuclear Information System (INIS)

    Zhang, Y.W.; Li, S.J.; Obbard, E.G.; Wang, H.; Wang, S.C.; Hao, Y.L.; Yang, R.

    2011-01-01

    Research highlights: → The single crystals of Ti2448 alloy with the bcc crystal structure were prepared. → The elastic moduli and constants were measured by several resonant methods. → The crystal shows significant elastic asymmetry in tension and compression. → The crystal exhibits weak nonlinear elasticity with large elastic strain ∼2.5%. → The crystal has weak atomic interactions against crystal distortion to low symmetry. - Abstract: Single crystals of Ti2448 alloy (Ti-24Nb-4Zr-8Sn in wt.%) were grown successfully using an optical floating-zone furnace. Several kinds of resonant methods gave consistent Young's moduli of 27.1, 56.3 and 88.1 GPa and shear moduli of 34.8, 11.0 and 14.6 GPa for the , and oriented single crystals, and C 11 , C 12 and C 44 of 57.2, 36.1 and 35.9 GPa respectively. Uniaxial testing revealed asymmetrical elastic behaviors of the crystals: tension caused elastic softening with a large reversible strain of ∼4% and a stress plateau of ∼250 MPa, whereas compression resulted in gradual elastic stiffening with much smaller reversible strain. The crystals exhibited weak nonlinear elasticity with a large elastic strain of ∼2.5% and a high strength, approaching ∼20% and ∼30% of its ideal shear and ideal tensile strength respectively. The crystals showed linear elasticity with a small elastic strain of ∼1%. These elastic deformation characteristics have been interpreted in terms of weakened atomic interactions against crystal distortion to low crystal symmetry under external applied stresses. These results are consistent with the properties of polycrystalline Ti2448, including high strength, low elastic modulus, large recoverable strain and weak strengthening effect due to grain refinement.

  16. bcc transition metals under pressure: results from ultrasonic interferometry and diamond-cell experiments

    International Nuclear Information System (INIS)

    Katahara, K.W.; Manghnani, M.H.; Ming, L.C.; Fisher, E.S.

    1976-01-01

    Hydrostatic pressure derivatives of the single-crystal elastic moduli, dC/sub ij//dP, have been measured ultrasonically for b.c.c. Nb--Mo and Ta--W solid solutions. The composition dependence of various electronic properties of these alloys is known to be reasonably well approximated by a rigid-electron-band filling model where e/a, the electron per atom ratio, is the primary parameter. The results indicate that the elastic moduli and their pressure derivatives may also be calculated in such a model. In particular, the dC/sub ij//dP show relatively sharp increases at e/a compositions of 5.4 for Nb--Mo and 5.7 for Ta--W. Both compositions correspond to changes in Fermi surface topology, as deduced from existing band calculations and the rigid band assumption. The results are discussed in the light of related electronic properties and possible geophysical applications. A comparison is also made between ultrasonic results and X-ray diffraction data for Nb. Using diamond-anvil pressure cell, compression of Nb was determined by X-ray diffraction up to 55 kbar in a liquid medium under purely hydrostatic conditions, and up to 175 kbar in a solid medium under nonhydrostatic conditions. The data obtained under hydrostatic conditions agree well with the ultrasonic equation of state and shock wave data, whereas the nonhydrostatic results tend to imply either a higher bulk modulus K/sub s/ or a higher (par. deltaK/sub s//par. deltaP)/sub T/

  17. Validation of a 15-item care-related regret coping scale for health-care professionals (RCS-HCP).

    Science.gov (United States)

    Courvoisier, Delphine Sophie; Cullati, Stephane; Ouchi, Rieko; Schmidt, Ralph Eric; Haller, Guy; Chopard, Pierre; Agoritsas, Thomas; Perneger, Thomas V

    2014-01-01

    Coping with difficult care-related situations is a common challenge for health-care professionals. How these professionals deal with the regrets they may experience following one of the many decisions and interventions they must make every day can have an impact on their own health and quality of life, and also on their patient care practices. To identify professionals most at need for extra support, development and validation of a tool measuring coping style are needed. We performed a survey of physicians and nurses of a French-speaking University hospital; 469 health-care professionals responded to the survey, and 175 responded to the same survey one-month later. Regret was assessed with the regret coping scale developed for this study, self-report questions on the frequency of regretted situations and the intensity of regret. Construct validity was assessed using measures of health-care professionals' quality of life (including job and life satisfaction, and self-reported health) as well as sleep problems and depression. Based on factor analysis and item response analysis, the initial 31-item scale was shortened to 15 items, which measured three types of strategies: problem-focused strategies (i.e., trying to find solutions, talking to colleagues) and two types of emotion-focused strategies, A (i.e., self-blame, rumination) and B (e.g., acceptance, emotional distance). All subscales showed high internal consistency (α >0.85). Overall, as expected, problem-focused and emotion-focused B strategies correlated with higher quality of life, fewer sleep problems and less depression, and emotion-focused A strategies showed the opposite pattern. The regret coping scale (RCS-HCP) is a valid and reliable measure of coping abilities of hospital-based health-care professionals.

  18. HCP track calculations in Lif:Mg,Ti: 3D modeling of the ''track – escape'' parameter

    International Nuclear Information System (INIS)

    Sattinger, D.; Sharon, A.; Horowitz, Y.S.

    2011-01-01

    The conceptual framework of the track interaction model (TIM) was conceived in the 1970s and mathematically formulated in the 1980s to describe heavy charged particle TL fluence response supralinearity. The extended track interaction model (ETIM) was developed to include saturation effects due to overlapping tracks and has been applied to both proton and alpha particle TL fluence response. One of the parameters of major importance in the TIM is the ''track – escape'' parameter, defined by N e /N w , where N e represents the number of electrons which escape the parent track during heating, and N w is the number of electrons which recombine within the parent track to produce a TL photon. Recently a first attempt was carried out to theoretically model escape parameters calculated in 2D geometry as a function of particle type and energy using trapping center (TC), luminescent center (LC) and competitive center (CC) occupation probabilities calculated from track segment radial dose distributions and optical absorption (OA) dose response. In this study, the calculations are extended to 3D geometry using a Monte Carlo approach which samples the point of creation of the charge carriers according to the TC occupation probabilities and then estimates N w by sampling the chord length to the track exterior. Charge carriers which escape the irradiated track volume contribute to N e . This more sophisticated 3D calculation of N e /N w is expected to increase the reliability of the modeling of heavy charged particle TL fluence response in the framework of the ETIM and enhance our understanding of “track effects” in Heavy Charged Particle (HCP) induced TL.

  19. Proceedings, High-Precision $\\alpha_s$ Measurements from LHC to FCC-ee

    Energy Technology Data Exchange (ETDEWEB)

    d' Enterria, David [CERN; Skands, Peter Z. [Monash U.

    2015-01-01

    This document provides a writeup of all contributions to the workshop on "High precision measurements of $\\alpha_s$: From LHC to FCC-ee" held at CERN, Oct. 12--13, 2015. The workshop explored in depth the latest developments on the determination of the QCD coupling $\\alpha_s$ from 15 methods where high precision measurements are (or will be) available. Those include low-energy observables: (i) lattice QCD, (ii) pion decay factor, (iii) quarkonia and (iv) $\\tau$ decays, (v) soft parton-to-hadron fragmentation functions, as well as high-energy observables: (vi) global fits of parton distribution functions, (vii) hard parton-to-hadron fragmentation functions, (viii) jets in $e^\\pm$p DIS and $\\gamma$-p photoproduction, (ix) photon structure function in $\\gamma$-$\\gamma$, (x) event shapes and (xi) jet cross sections in $e^+e^-$ collisions, (xii) W boson and (xiii) Z boson decays, and (xiv) jets and (xv) top-quark cross sections in proton-(anti)proton collisions. The current status of the theoretical and experimental uncertainties associated to each extraction method, the improvements expected from LHC data in the coming years, and future perspectives achievable in $e^+e^-$ collisions at the Future Circular Collider (FCC-ee) with $\\cal{O}$(1--100 ab$^{-1}$) integrated luminosities yielding 10$^{12}$ Z bosons and jets, and 10$^{8}$ W bosons and $\\tau$ leptons, are thoroughly reviewed. The current uncertainty of the (preliminary) 2015 strong coupling world-average value, $\\alpha_s(m_Z)$ = 0.1177 $\\pm$ 0.0013, is about 1\\%. Some participants believed this may be reduced by a factor of three in the near future by including novel high-precision observables, although this opinion was not universally shared. At the FCC-ee facility, a factor of ten reduction in the $\\alpha_s$ uncertainty should be possible, mostly thanks to the huge Z and W data samples available.

  20. Monitoring of mass flux of catalyst FCC in a Cold Pilot Unit by gamma radiation transmission

    International Nuclear Information System (INIS)

    Brito, Marcio Fernando Paixao de

    2014-01-01

    This paper proposes a model for monitoring the mass flow of catalyst FCC - Fluid Catalytic Cracking - in a CPU - Cold Pilot unit - due to the injection of air and solid by gamma radiation transmission. The CPU simplifies the process of FCC, which is represented by the catalyst cycle, and it was constructed of acrylic, so that the flow can be visualized. The CPU consists of riser separation chamber and return column, and simulates the riser reactor of the FCC process. The catalyst is injected into the column back to the base of the riser, an inclined tube, where the compressed air means that there fluidization along the riser. When the catalyst comes in the separation chamber, the solid phase is sent to the return column, and the gas phase exits the system through one of the four cyclones at the top of the separation chamber. The transmission gamma of measures will be made by means of three test sections that have source and detector shielded. Pressure drop in the riser measurements are made through three pressure gauges positioned on the riser. The source used was Am-241 gamma ray with energy of 60 keV, and detector used was a scintillator of NaI (Tl) of 2 x 2 . Measures the mass flow of catalyst are made by varying the seal of the catalyst, and density of solid in the riser because with the combination of these measures can determine the speed of the catalyst in the riser. The results show that the transmission gamma is a suitable technique for monitoring the flow of catalyst, flow model in CPU is annular, tomography third generation is more appropriate to study the CPU and the density variation in circulation in the CPU decreases linearly with increasing air flow. (author)

  1. Modelling of the intragranular back-stress and recovery in FCC single crystals and polycrystals

    International Nuclear Information System (INIS)

    Sauzay, M.

    2003-01-01

    High temperature mechanical tests including recovery times on FCC metals or alloys involve at least two mechanisms. First, the formation of a two phase dislocation microstructure (cells, walls/channels... ) induces intragranular back-stress and hardening. Second, if the recovery time and the temperature are large enough, the previously formed dislocation microstructure can disappear, even if no remote stress is applied. Simple models of these two mechanisms are proposed. They are based on TEM observations and are validated comparing with several measurements from the literature. These models do not use arty fitted parameter and could help to predict the macroscopic behavior during creep-fatigue tests. (author)

  2. Microstructure and Mechanical Strengths of Metastable FCC Solid Solutions in Al-Ce-Fe System

    OpenAIRE

    A., Inoue; H., Yamaguchi; M., Kikuchi; T., Masumoto; Institute for Materials Research; Institute for Materials Research; Institute for Materials Research; Institute for Materials Research

    1990-01-01

    A metastable fcc solid solution (SS) with high mechanical strengths and good bending ductility was found to be formed in rapidly solidified Al-Ce-Fe alloys containing the solute elements below about 6 at%. The SS consists of equiaxed grains with a size of about 2μm and contains a high density of internal defects. The highest hardness (H_v) and tensile fracture strengtn (σ_f) are 440 and 860 MPa in the as-quenched state and remain almost unchanged up to about 600 K for 1 h, though fine compoun...

  3. Study Of Boosted W-Jets And Higgs-Jets With the SiFCC Detector

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Shin-Shan [Taiwan, Natl. Central U.; Chekanov, Sergei [Argonne; Gray, Lindsey [Fermilab; Kotwal, Ashutosh [Duke U.; Sen, Sourav [Duke U.; Tran, Nhan Viet [Fermilab

    2016-11-04

    We study the detector performance in the reconstruction of hadronically-decaying W bosons and Higgs bosons at very high energy proton colliders using a full GEANT4 simulation of the SiFCC detector. The W and Higgs bosons carry transverse momentum in the multi-TeV range, which results in collimated decay products that are reconstructed as a single jet. We present a measurement of the energy response and resolution of boosted W-jets and Higgs-jets and show the separation of two sub-jets within the boosted boson jet.

  4. FCC-hh final-focus for flat-beams: parameters and energy deposition studies

    CERN Document Server

    AUTHOR|(CDS)2081283; Cruz Alaniz, Emilia; Seryi, Andrei; Van Riesen-Haupt, Leon; Besana, Maria Ilaria

    2017-01-01

    The international Future Circular Collider (FCC) study comprises the study of a new scientific structure in a tunnel of 100 km. This will allow the installation of two accelerators, a 45.6–175 GeV lepton collider and a 100-TeV hadron collider. An optimized design of a final-focus system for the hadron collider is presented here. The new design is more compact and enables unequal ${\\beta}$$^{∗}$ in both planes, whose choice is justified here. This is followed by energy deposition studies, where the total dose in the magnets as a consequence of the collision debris is evaluated.

  5. First Considerations on Beam Optics and Lattice Design for the Future Hadron-Hadron Collider FCC

    CERN Document Server

    Alemany Fernandez, R

    2014-01-01

    The present document explains the steps carried out in order to make the first design of the Future Hadron-Hadron Collider (FCC-hh) following the base line parameters that can be found in [1]. Two lattice layouts are presented, a ring collider with 12 arcs and 12 straight sections, four of them designed as interaction points, and a racetrack like collider with two arcs and two straight sections, each of them equipped with two interaction points. The lattice design presented in the paper is modular allowing the same modules be used for both layouts. The present document addresses as well the beta star reach at the interaction points.

  6. Simulation of short-term annealing of displacement cascades in FCC metals

    International Nuclear Information System (INIS)

    Heinisch, H.L.; Doran, D.G.; Schwartz, D.M.

    1980-01-01

    Computer models have been developed for the simulation of high energy displacement cascades. The objective is the generation of defect production functions for use in correlation analysis of radiation effects in fusion reactor materials. In particular, the stochastic cascade annealing simulation code SCAS has been developed and used to model the short-term annealing behavior of simulated cascades in FCC metals. The code is fast enough to make annealing of high energy cascades practical. Sets of cascades from 5 keV to 100 keV in copper were generated by the binary collision code MARLOWE

  7. Ab initio pair potentials for FCC metals: An application of the method of Moebius transform

    International Nuclear Information System (INIS)

    Mookerjee, A.; Chen Nanxian; Kumar, V.; Satter, M.A.

    1991-10-01

    We use the method of Moebius transform introduced by one of us (Chen, Phys. Rev. Lett. 64, 1193 (1990)) to obtain pair potentials for fcc metals from first principles total energy calculations. The derivation is exact for radial potentials and it converges much faster than the earlier reported method of Carlsson-Gelatt-Ehrenreich. We have tested this formulation for Cu using the tight binding representation of the linear muffin tin orbital method. Our results agree with those obtained by Carlsson et al. and qualitatively with the other Morse-type pair potentials derived from effective medium theories. (author). 18 refs, 3 figs, 3 tabs

  8. Development of local shear bands and orientation gradients in fcc polycrystals

    International Nuclear Information System (INIS)

    Beaudoin, A.J. Jr.; Mecking, H.; Kocks, U.F.

    1995-01-01

    A finite element formulation which derives constitutive response from crystal plasticity theory is used to examine localized deformation in fcc polycrystals. The polycrystals are simple, idealized arrangements of grains. Localized deformations within individual grains lead to the development of domains that are separated by boundaries of high misorientation. Shear banding is seen to occur on a microscopic scale of grain dimensions. The important consequences of these simulations are that the predicted local inhomogeneities are meeting various requirements which make them possible nucleation sites for recrystallization

  9. Modelling of the intragranular back-stress and recovery in FCC single crystals and polycrystals

    Energy Technology Data Exchange (ETDEWEB)

    Sauzay, M

    2003-07-01

    High temperature mechanical tests including recovery times on FCC metals or alloys involve at least two mechanisms. First, the formation of a two phase dislocation microstructure (cells, walls/channels... ) induces intragranular back-stress and hardening. Second, if the recovery time and the temperature are large enough, the previously formed dislocation microstructure can disappear, even if no remote stress is applied. Simple models of these two mechanisms are proposed. They are based on TEM observations and are validated comparing with several measurements from the literature. These models do not use arty fitted parameter and could help to predict the macroscopic behavior during creep-fatigue tests. (author)

  10. Exploring the triplet parameters space to optimise the final focus of the FCC-hh

    CERN Document Server

    AUTHOR|(CDS)2141109; Abelleira, Jose; Seryi, Andrei; Cruz Alaniz, Emilia

    2017-01-01

    One of the main challenges when designing final focus systems of particle accelerators is maximising the beam stay clear in the strong quadrupole magnets of the inner triplet. Moreover it is desirable to keep the quadrupoles in the triplet as short as possible for space and costs reasons but also to reduce chromaticity and simplify corrections schemes. An algorithm that explores the triplet parameter space to optimise both these aspects was written. It uses thin lenses as a first approximation and MADX for more precise calculations. In cooperation with radiation studies, this algorithm was then applied to design an alternative triplet for the final focus of the Future Circular Collider (FCC-hh).

  11. Mobile application MDDCS for modeling the expansion dynamics of a dislocation loop in FCC metals

    Science.gov (United States)

    Kirilyuk, Vasiliy; Petelin, Alexander; Eliseev, Andrey

    2017-11-01

    A mobile version of the software package Dynamic Dislocation of Crystallographic Slip (MDDCS) designed for modeling the expansion dynamics of dislocation loops and formation of a crystallographic slip zone in FCC-metals is examined. The paper describes the possibilities for using MDDCS, the application interface, and the database scheme. The software has a simple and intuitive interface and does not require special training. The user can set the initial parameters of the experiment, carry out computational experiments, export parameters and results of the experiment into separate text files, and display the experiment results on the device screen.

  12. Radiation Load Optimization in the Final Focus System of FCC-hh

    CERN Document Server

    Martin, Roman; Cerutti, Francesco; Tomás, Rogelio

    2016-01-01

    With a center-of-mass energy of up to 100 TeV, FCC-hh will produce highly energetic collision debris at the Interaction Point (IP). Protecting the final focus quadrupoles from this radiation is challenging, since the required amount of shielding placed inside the magnets will reduce the free aperture, thereby limiting the β^{*} reach and luminosity. Hence, radiation mitigation strategies that make best use of the available aperture are required. In this paper, we study the possibility to split the first quadrupole Q1 into two quadrupoles with individual apertures, in order to distribute the radiation load more evenly and reduce the peak dose.

  13. Ecuaciones constitutivas avanzadas para describir el comportamiento termoviscoplástico de metales FCC

    OpenAIRE

    Pereira Valadés, Daniel

    2011-01-01

    En este proyecto de fin de carrera se ha llevado a cabo el estudio y proposición de ecuaciones constitutivas avanzadas que permitan describir con exactitud el comportamiento termoviscoplástico de metales FCC. Este estudio es de vital importancia para entender el proceso que tiene lugar en estos metales bajo condiciones de carga dinámicas, siempre en deformación plástica. La utilidad del estudio reside en la gran cantidad de procesos industriales que se llevan a cabo con este tipo de solicitac...

  14. Anti-Invar properties and magnetic order in fcc Fe-Ni-C alloy

    International Nuclear Information System (INIS)

    Nadutov, V.M.; Kosintsev, S.G.; Svystunov, Ye.O.; Garamus, V.M.; Willumeit, R.; Eckerlebe, H.; Ericsson, T.; Annersten, H.

    2011-01-01

    Anti-Invar effect was revealed in the fcc Fe-25.3%Ni-0.73%C (wt%) alloy, which demonstrates high values of thermal expansion coefficient (TEC) (15-21)x10 -6 K -1 accompanied by almost temperature-insensitive behavior in temperature range of 122-525 K. Alloying with carbon considerably expanded the low temperature range of anti-Invar behavior in fcc Fe-Ni-based alloy. The Curie temperature of the alloy T C =195 K was determined on measurements of temperature dependences of magnetic susceptibility and saturation magnetization. The Moessbauer and small-angle neutron scattering (SANS) experiments on the fcc Fe-25.3%Ni-(0.73-0.78)%C alloys with the varying temperatures below and above the Curie point and in external magnetic field of 1.5-5 T were conducted. Low value of the Debye temperature Θ D =180 K was estimated using the temperature dependence of the integral intensity of Moessbauer spectra for specified temperature range. The inequality B eff =(0.7-0.9)B ext was obtained in external field Moessbauer measurement that points to antiferromagnetically coupled Fe atoms, which have a tendency to align their spins perpendicular to B ext . Nano length scale magnetic inhomogeneities nearby and far above T C were revealed, which assumed that it is caused by mixed antiferromagnetically and ferromagnetically coupled Fe atom spins. The anti-Invar behavior of Fe-Ni-C alloy is explained in terms of evolution of magnetic order with changing temperature resulting from thermally varied interspin interaction and decreasing stiffness of interatomic bond. - Highlights: → Anti-Invar effect was revealed in the fcc Fe-25.3%Ni-0.73%C (wt%) alloy. → Carbon expanded the temperature range of anti-Invar behavior in Fe-Ni-based alloy. → Moessbauer data point to mixed interspin interaction and low the Dedye temperature. → The SANS experiments reveal nano length scale magnetic inhomogeneities ≤6 nm. → Anti-Invar behavior of Fe-Ni-C alloy explained by thermally varied magnetic order.

  15. The effect of hydrogen on the superconducting and structural properties of b.c.c. Nb-Ru alloys

    International Nuclear Information System (INIS)

    Robbins, C.G.; Ishikawa, M.; Treyvaud, A.; Muller, J.

    1975-01-01

    The superconducting transition temperature (Tsub(c)) has been measured before and after the introduction of hydrogen into Nbsub((1-x))Rusub(x) (0.20<=x<=0.33). In all cases, the presence of appreciable amounts of this interstitial component led to a sharp increase in the Tsub(c). All the evidence suggests that conversion of the host metal lattice to f.c.c. is necessary for the appearance of the elevated Tsub(c). (author)

  16. A newly developed maneuver, field change conversion (FCC), improved evaluation of the left ventricular volume more accurately on quantitative gated SPECT (QGS) analysis

    International Nuclear Information System (INIS)

    Tajima, Osamu; Shibasaki, Masaki; Hoshi, Toshiko; Imai, Kamon

    2002-01-01

    The purpose of this study was to investigate whether a newly developed maneuver that reduces the reconstruction area by a half more accurately evaluates left ventricular (LV) volume on quantitative gated SPECT (QGS) analysis. The subjects were 38 patients who underwent left ventricular angiography (LVG) followed by G-SPECT within 2 weeks. Acquisition was performed with a general purpose collimator and a 64 x 64 matrix. On QGS analysis, the field magnification was 34 cm in original image (Original: ORI), and furthermore it was changed from 34 cm to 17 cm to enlarge the re-constructed image (Field Change Conversion: FCC). End-diastolic volume (EDV) and end-systolic volume (ESV) of the left ventricle were also obtained using LVG. EDV was 71±19 ml, 83±20 ml and 98±23 ml for ORI, FCC and LVG, respectively (p<0.001: ORI versus LVG, p<0.001: ORI versus FCC, p<0.001: FCC versus LVG). ESV was 28±12 ml, 34±13 ml and 41±14 ml for ORI, FCC and LVG, respectively (p<0.001: ORI versus LVG, p<0.001: ORI versus FCC, p<0.001: FCC versus LVG). FCC was better than ORI for calculating LV volume in clinical cases. Furthermore, FCC is a useful method for accurately measuring the LV volume on QGS analysis. (author)

  17. Growth of metastable fcc Mn thin film on GaAs(001) and its electronic structure studied by photoemission with synchrotron radiation

    International Nuclear Information System (INIS)

    Chen Yan; Dong Guosheng; Zhang Ming

    1995-01-01

    The epitaxial growth of metastable fcc Mn thin films on GaAs(001) surface has been achieved at a substrate temperature of 400 K. The development of the fcc Mn thin films as a function of coverage is studied by photoemission with synchrotron radiation. The electron density of states below the Fermi edge of the fcc Mn phase is measured. A significant difference of the electronic structures is observed between the metastable fcc Mn phase and the thermodynamically stable α-Mn phase. Possible mechanisms are proposed to interpret the experimental result

  18. Nanoclusters in bcc-Fe containing vacancies, copper and nickel: Structure and energetics

    International Nuclear Information System (INIS)

    Al-Motasem, A.T.; Posselt, M.; Bergner, F.

    2011-01-01

    Highlights: → Fe-Cu-Ni model alloys for RPV steels. → Atomistic simulation, mainly MMC and MD simulations. → Finding the most stable configurations of defect clusters. → Energetics of clusters, formation and binding energies. → Size dependence of monomer binding energy formula as input for OKMC methods. - Abstract: The most stable atomic configuration of coherent nanoclusters in bcc-Fe formed by vacancies, Cu and Ni as well as the corresponding energetics are determined by on-lattice simulated annealing and subsequent off-lattice relaxation. An interatomic potential recently designed for investigations of radiation-induced effects in the ternary Fe-Cu-Ni system is used in the atomistic simulations. Ternary v l Cu m Ni n clusters show a core-shell structure with vacancies in the core coated by a shell of Cu atoms, followed by a shell of Ni atoms. In binary Cu m Ni n clusters the Cu core is covered by a shell of Ni atoms. On the contrary, binary v l Ni n clusters consist of a pure vacancy cluster surrounded by an agglomeration of Ni atoms. The latter is similar to a pure Ni cluster (Ni n ) and consists of Ni atoms at the second nearest neighbor distance. Because of this special arrangement of atoms v l Ni n and Ni n are also called quasi-clusters. In all clusters investigated Ni atoms may be nearest neighbors of Cu atoms but never nearest neighbors of vacancies or other Ni atoms. The atomic configurations found can be understood by the peculiarities of the binding between vacancies, Cu, Ni and Fe atoms. The structure obtained for Cu m Ni n clusters is in agreement with previous theoretical results and with indications from measurements while for the other clusters reference data are not available. It is shown that the presence of Ni atoms promotes the nucleation of clusters containing vacancies and Cu. This is in agreement with experimental observations and with recent results of atomic kinetic Monte Carlo simulations. Based on the specific atomic structure

  19. Retraction of 'Composition design and mechanical properties of BCC Ti solid solution alloys with low Young's modulus'

    International Nuclear Information System (INIS)

    Tulugan, Keli Mu; Park, Cheol Hong; Park, Won Jo; Qing, Wang

    2012-01-01

    The article 'Composition design and mechanical properties of BCC Ti solid solution alloys with low Young's modulus' has been retracted upon the request of the third author (Prof. Wang Qing, the first author's former advisor during his internship at DaLian University of Technology). The article was published without the third author's knowledge and consent. The corresponding author (Prof. Wonjo Park) apologizes to the third author, to the readers, and to the editorial staff of the JMST. The JMST editorial board does not tolerate such actions from authors and we will take appropriate action to prevent this from happening in the future

  20. A new parameterization for ice cloud optical properties used in BCC-RAD and its radiative impact

    International Nuclear Information System (INIS)

    Zhang, Hua; Chen, Qi; Xie, Bing

    2015-01-01

    A new parameterization of the solar and infrared optical properties of ice clouds that considers the multiple habits of ice particles was developed on the basis of a prescribed dataset. First, the fitting formulae of the bulk extinction coefficient, single-scatter albedo, asymmetry factor, and δ-function forward-peak factor at the given 65 wavelengths as a function of effective radius were created for common scenarios, which consider a greater number of wavelengths and are more accurate than those used previously. Then, the band-averaged volume extinction and absorption coefficients, asymmetry factor and forward-peak factor of ice cloud were derived for the BCC-RAD (Beijing Climate Center radiative transfer model) using a parameter reference table. Finally, the newly developed and the original schemes in the BCC-RAD and the commonly used Fu Scheme of ice cloud were all applied to the BCC-RAD. Their influences on radiation calculations were compared using the mid-latitude summer atmospheric profile with ice clouds under no-aerosol conditions, and produced a maximum difference of approximately 30.0 W/m 2 for the radiative flux, and 4.0 K/d for the heating rate. Additionally, a sensitivity test was performed to investigate the impact of the ice crystal density on radiation calculations using the three schemes. The results showed that the maximum difference was 68.1 W/m 2 for the shortwave downward radiative flux (for the case of perpendicular solar insolation), and 4.2 K/d for the longwave heating rate, indicating that the ice crystal density exerts a significant effect on radiation calculations for a cloudy atmosphere. - Highlights: • A new parameterization of the radiative properties of ice cloud was obtained. • More accurate fitting formulae of them were created for common scenarios. • The band-averaged of them were derived for our radiation model of BCC-RAD. • We found that there exist large differences of results among different ice schemes. • We found

  1. Temperature dependence of enthalpies and entropies of formation and migration of mono-vacancy in BCC iron

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Haohua; Woo, C.H., E-mail: chungho@cityu.edu.hk

    2014-12-15

    Entropies and enthalpies of vacancy formation and diffusion in BCC iron are calculated for each temperature directly from free-energies using phase-space trajectories obtained from spin–lattice dynamics simulations. Magnon contributions are found to be particularly substantial in the temperature regime near the α−β (ferro/para-magnetic) transition. Strong temperature dependence and singular behavior can be seen in this temperature regime, reflecting magnon softening effects. Temperature dependence of the lattice component in this regime is also much more significant compared to previous estimations based on Arrhenius-type fitting. Similar effects on activation processes involving other irradiation-produced defects in magnetic materials are expected.

  2. Future Circular Collider Study (FCC) kick-off meeting | 12-15 February

    CERN Multimedia

    2014-01-01

    The kick-off meeting of the international "Future Circular Collider Study" (FCC) will take place in Geneva from 12 to 15 February 2014 at the University of Geneva, Unimail site. The programme and registration details can be found on the meeting's website. This meeting is the starting point of the five-year international "Future Circular Collider Study" (FCC). The main emphasis of the conceptual design study will be on a hadron collider with a centre-of-mass energy of the order of 100 TeV in a new tunnel with a 80-100 km circumference for the purposes of studying physics at the highest energies. The study will also include a lepton collider, as a potential intermediate step towards realisation of the hadron facility. Options for e-p scenarios will also be considered. The main purpose of this meeting is to discuss the study topics and to prepare international collaborations. The meeting is a public meeting with a registration deadline closing on Friday 31 Janua...

  3. High-Pressure Geophysical Properties of Fcc Phase FeHX

    Science.gov (United States)

    Thompson, E. C.; Davis, A. H.; Bi, W.; Zhao, J.; Alp, E. E.; Zhang, D.; Greenberg, E.; Prakapenka, V. B.; Campbell, A. J.

    2018-01-01

    Face centered cubic (fcc) FeHX was synthesized at pressures of 18-68 GPa and temperatures exceeding 1,500 K. Thermally quenched samples were evaluated using synchrotron X-ray diffraction (XRD) and nuclear resonant inelastic X-ray scattering (NRIXS) to determine sample composition and sound velocities to 82 GPa. To aid in the interpretation of nonideal (X ≠ 1) stoichiometries, two equations of state for fcc FeHX were developed, combining an empirical equation of state for iron with two distinct synthetic compression curves for interstitial hydrogen. Matching the density deficit of the Earth's core using these equations of state requires 0.8-1.1 wt % hydrogen at the core-mantle boundary and 0.2-0.3 wt % hydrogen at the interface of the inner and outer cores. Furthermore, a comparison of Preliminary Reference Earth Model (PREM) to a Birch's law extrapolation of our experimental results suggests that an iron alloy containing ˜0.8-1.3 wt % hydrogen could reproduce both the density and compressional velocity (VP) of the Earth's outer core.

  4. Design of an Inductive Adder for the FCC injection kicker pulse generator

    Science.gov (United States)

    Woog, D.; Barnes, M. J.; Ducimetière, L.; Holma, J.; Kramer, T.

    2017-07-01

    The injection system for a 100 TeV centre-of-mass collider is an important part of the Future Circular Collider (FCC) study. Due to issues with conventional kicker systems, such as self-triggering and long term availability of thyratrons and limitations of HV-cables, innovative design changes are planned for the FCC injection kicker pulse generator. An inductive adder (IA) based on semiconductor (SC) switches is a promising technology for kicker systems. Its modular design, and the possibility of an active ripple suppression are significant advantages. Since the IA is a complex device, with multiple components whose characteristics are important, a detailed design study and construction of a prototype is necessary. This paper summarizes the system requirements and constraints, and describes the main components and design challenges of the prototype IA. It outlines the results from simulations and measurements on different magnetic core materials as well as on SC switches. The paper concludes on the design choices and progress for the prototype to be built at CERN.

  5. Dynamic simulation of industrial Fluidized-bed Catalytic Cracking - FCC unit

    Energy Technology Data Exchange (ETDEWEB)

    Secchi, Argimiro R.; Neumann, Gustavo A.; Trierweiler, Jorge O. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Dept. de Engenharia Quimica]. E-mail: arge@enq.ufrgs.br; gneumann@enq.ufrgs.br; jorge@enq.ufrgs.br; Santos, Marlova G. [PETROBRAS S.A., Canoas, RS (Brazil). Refinaria Alberto Pasqualini]. E-mail: marlova@petrobras.com.br

    2000-07-01

    In this work a mathematical model for the dynamic simulation of the Fluidized-bed Catalytic Cracking (FCC) Reactor, to be used in the analysis, control, and optimization of this system is developed. Based on the full range of published data in FCC performance and kinetic rates, and adapted to the industrial unit of the PETROBRAS' Alberto Pasqualini Refinery (REFAP), an integrated dynamic model is build up. The model is sufficiently complex to capture the major dynamics effects that occur in this system. The regenerator is modeled as emulsion and bubble phases that exchange mass and heat. The riser is modeled as an adiabatic plug flow reactor. The fluid dynamic is taking into account for the catalyst circulation, and the dynamics of the gas phase and the riser are also considered into the model. The model, represented by a non-linear system of differential-algebraic equations, was written in language C and implemented in MATLAB/SIMULINK. The results are compared with the data obtained from the industrial plant of REFAP. (author)

  6. Design and performance of an electromagnetic calorimeter for a FCC-hh experiment

    Science.gov (United States)

    Zaborowska, A.

    2018-03-01

    The physics reach and feasibility of the Future Circular Collider are currently under investigation. The goal is to collide protons with centre-of-mass energies up to 100 TeV, extending the research carried out at the current HEP facilities. The detectors designed for the FCC experiments need to tackle harsh conditions of the unprecedented collision energy and luminosity. The baseline technology for the calorimeter system of the FCC-hh detector is described. The electromagnetic calorimeter in the barrel, as well as the electromagnetic and hadronic calorimeters in the endcaps and the forward regions, are based on the liquid argon as active material. The detector layout in the barrel region combines the concept of a high granularity calorimeter with precise energy measurements. The calorimeters have to meet the requirements of high radiation hardness and must be able to deal with a very high number of collisions per bunch crossings (pile-up). A very good energy and angular resolution for a wide range of electrons' and photons' momentum is needed in order to meet the demands based on the physics benchmarks. First results of the performance studies with the new liquid argon calorimeter are presented, meeting the energy resolution goal.

  7. Dislocation creation and void nucleation in FCC ductile metals under tensile loading: a general microscopic picture.

    Science.gov (United States)

    Pang, Wei-Wei; Zhang, Ping; Zhang, Guang-Cai; Xu, Ai-Guo; Zhao, Xian-Geng

    2014-11-10

    Numerous theoretical and experimental efforts have been paid to describe and understand the dislocation and void nucleation processes that are fundamental for dynamic fracture modeling of strained metals. To date an essential physical picture on the self-organized atomic collective motions during dislocation creation, as well as the essential mechanisms for the void nucleation obscured by the extreme diversity in structural configurations around the void nucleation core, is still severely lacking in literature. Here, we depict the origin of dislocation creation and void nucleation during uniaxial high strain rate tensile processes in face-centered-cubic (FCC) ductile metals. We find that the dislocations are created through three distinguished stages: (i) Flattened octahedral structures (FOSs) are randomly activated by thermal fluctuations; (ii) The double-layer defect clusters are formed by self-organized stacking of FOSs on the close-packed plane; (iii) The stacking faults are formed and the Shockley partial dislocations are created from the double-layer defect clusters. Whereas, the void nucleation is shown to follow a two-stage description. We demonstrate that our findings on the origin of dislocation creation and void nucleation are universal for a variety of FCC ductile metals with low stacking fault energies.

  8. Towards the conceptual design of the cryogenic system of the Future Circular Collider (FCC)

    Science.gov (United States)

    Chorowski, M.; Correia Rodrigues, H.; Delikaris, D.; Duda, P.; Haberstroh, C.; Holdener, F.; Klöppel, S.; Kotnig, C.; Millet, F.; Polinski, J.; Quack, H.; Tavian, L.

    2017-12-01

    Following the update of the European strategy in particle physics, CERN has undertaken an international study of possible future circular colliders beyond the LHC. The study considers several options for very high-energy hadron-hadron, electron-positron and hadron-electron colliders. From the cryogenics point of view, the most challenging option is the hadron-hadron collider (FCC-hh) for which the conceptual design of the cryogenic system is progressing. The FCC-hh cryogenic system will have to produce up to 120 kW at 1.8 K for the superconducting magnet cooling, 6 MW between 40 and 60 K for the beam-screen and thermal-shield cooling as well as 850 g/s between 40 and 290 K for the HTS current-lead cooling. The corresponding total entropic load represents about 1 MW equivalent at 4.5 K and this cryogenic system will be by far the largest ever designed. In addition, the total mass to be cooled down is about 250’000 t and an innovative cool-down process must be proposed. This paper will present the proposed cryogenic layout and architecture, the cooling principles of the main components, the corresponding cooling schemes, as well as the cryogenic plant arrangement and proposed process cycles. The corresponding required development plan for such challenging cryogenic system will be highlighted.

  9. Electronic Structure of the fcc Transition Metals Ir, Rh, Pt, and Pd

    DEFF Research Database (Denmark)

    Andersen, O. Krogh

    1970-01-01

    We give a complete description of a relativistic augmented-plane-wave calculation of the band structures of the paramagnetic fcc transition metals Ir, Rh, Pt, and Pd. The width and position of the d band decrease in the sequence Ir, Pt, Rh, Pd; and N(EF)=13.8,23.2,18.7, and 32.7 (states/atom)/Ry,......We give a complete description of a relativistic augmented-plane-wave calculation of the band structures of the paramagnetic fcc transition metals Ir, Rh, Pt, and Pd. The width and position of the d band decrease in the sequence Ir, Pt, Rh, Pd; and N(EF)=13.8,23.2,18.7, and 32.7 (states....../atom)/Ry, respectively. Spin-orbit coupling is important for all four metals and the coupling parameter varies by 30% over the d bandwidth. Detailed comparisons with de Haas—van Alphen Fermi-surface dimensions have previously been presented and the agreement was very good. Comparison with measured electronic specific...

  10. Determination of the catalyst circulation rate in a FCC cold flow pilot unit using nuclear techniques

    International Nuclear Information System (INIS)

    Santos, Valdemir A. dos; Lima, Emerson A.O.

    2013-01-01

    Nuclear techniques of gamma transmission and radioactive tracer were used to estimate the catalyst circulation rate in a cold flow pilot plant unit of Fluid Catalytic Cracking (FCC). Catalyst circulation rate in a FCC unit, allow to determine operating conditions of the exchange catalyst and inlet data for fluid dynamic simulation computational program. The pilot unit was fabricated obeying geometrical parameters provided by the Petrobras Research Center (CENPES), based on hot pilot units to existing in that center. The cold flow pilot unit has a transfer line, two separation vessels flash type, a return column, a riser and a regenerator. The vertical sections as riser, return column, regenerator column and transfer line are made of transparent material (glass). The two separation vessels have bases with tapered cylindrical shapes and are made of steel plates. The riser is divided into four sections of different diameters (0.005 m, 0.010 m, 0.018 m and 0.025 m) and rising upwards, to simulate the increasing flow rate caused by the increase of volume with the increase of the number of moles due to molecules breakage. The radioactive tracer used was the catalyst itself (intrinsic tracer) irradiated by neutron activation, yielding the radioisotope 59 Fe. The velocity measurements were also obtained with aid of an electronic clock triggered by certain radiation levels across the two detectors. Besides estimates for the catalyst circulation rate was possible to identify the type of flow relative to the catalyst in return column. (author)

  11. Observations of a fcc helium gas-bubble superlattice in copper, nickel, and stainless steel

    International Nuclear Information System (INIS)

    Johnson, P.B.; Mazey, D.J.

    1980-01-01

    Transmission electron microscopy is used to investigate the spatial arrangement of the small gas bubbles produced in several fcc metals by 30 keV helium ion irradiation to high dose at 300 K. In what is a new result for this important class of metals it is found that the helium gas bubbles lie on a superlattice having an fcc structure with principal axes aligned with those of the metal matrix. The bubble lattice constant asub(i), is measured for a helium fluence just below the critical dose for radiation blistering of the metal surface (approximately 4 x 10 17 He/cm 2 ). Implantation rates are typically approximately 10 14 He ions cm -2 sec -1 . The values of asub(i) obtained for copper, nickel and stainless steel are (7.6 +- 0.3)nm, (6.6 +- 0.5)nm and (6.4 +- 0.5)nm respectively. Above the critical dose the bubble lattice is seen to survive in some blister caps as well as in the region between blisters. Bubble alignment is also observed in the case of hydrogen bubbles produced in copper by low energy proton irradiation to high fluence at 300 K. The presentation of this data was accompanied by a cine film illustrating the behaviour of the gas bubble lattice in copper during post-irradiation annealing in the electron microscope. A summary of the film is given in the appendix. (author)

  12. Low-cycle fatigue-cracking mechanisms in fcc crystalline materials

    Science.gov (United States)

    Zhang, P.; Qu, S.; Duan, Q. Q.; Wu, S. D.; Li, S. X.; Wang, Z. G.; Zhang, Z. F.

    2011-01-01

    The low-cycle fatigue (LCF) cracking behavior in various face-centered-cubic (fcc) crystalline materials, including Cu single crystals, bicrystals and polycrystals, Cu-Al and Cu-Zn alloys, ultrafine-grained (UFG) Al-Cu and Cu-Zn alloys, was systematically investigated and reviewed. In Cu single crystals, fatigue cracking always nucleates along slip bands and deformation bands. The large-angle grain boundary (GB) becomes the preferential site in bicrystals and polycrystals. In addition, fatigue cracking can also nucleate along slip bands and twin boundaries (TBs) in polycrystalline materials. However, shear bands and coarse deformation bands are observed to the preferential sites for fatigue cracking in UFG materials with a large number of GBs. Based on numerous observations on fatigue-cracking behavior, the fatigue-cracking mechanisms along slip bands, GBs, TBs, shear bands and deformation bands were systematically compared and classified into two types, i.e. shear crack and impingement crack. Finally, these fatigue-cracking behaviors are discussed in depth for a better understanding of their physical nature and the transition from intergranular to transgranular cracking in various fcc crystalline materials. These comprehensive results for fatigue damage mechanisms should significantly aid in obtaining the optimum design to further strengthen and toughen metallic materials in practice.

  13. Ab initio random structure search for 13-atom clusters of fcc elements

    International Nuclear Information System (INIS)

    Chou, J P; Hsing, C R; Wei, C M; Cheng, C; Chang, C M

    2013-01-01

    The 13-atom metal clusters of fcc elements (Al, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au) were studied by density functional theory calculations. The global minima were searched for by the ab initio random structure searching method. In addition to some new lowest-energy structures for Pd 13 and Au 13 , we found that the effective coordination numbers of the lowest-energy clusters would increase with the ratio of the dimer-to-bulk bond length. This correlation, together with the electronic structures of the lowest-energy clusters, divides the 13-atom clusters of these fcc elements into two groups (except for Au 13 , which prefers a two-dimensional structure due to the relativistic effect). Compact-like clusters that are composed exclusively of triangular motifs are preferred for elements without d-electrons (Al) or with (nearly) filled d-band electrons (Ni, Pd, Cu, Ag). Non-compact clusters composed mainly of square motifs connected by some triangular motifs (Rh, Ir, Pt) are favored for elements with unfilled d-band electrons. (paper)

  14. Diffusion coefficients of rare earth elements in fcc Fe: A first-principles study

    Science.gov (United States)

    Wang, Haiyan; Gao, Xueyun; Ren, Huiping; Chen, Shuming; Yao, Zhaofeng

    2018-01-01

    The diffusion data and corresponding detailed insights are particularly important for the understanding of the related kinetic processes in Fe based alloys, e.g. solute strengthening, phase transition, solution treatment etc. We present a density function theory study of the diffusivity of self and solutes (La, Ce, Y and Nb) in fcc Fe. The five-frequency model was employed to calculate the microscopic parameters in the correlation factors of the solute diffusion. The interactions of the solutes with the first nearest-neighbor vacancy (1nn) are all attractive, and can be well understood on the basis of the combination of the strain-relief effects and the electronic effects. It is found that among the investigated species, Ce is the fastest diffusing solute in fcc Fe matrix followed by Nb, and the diffusion coefficients of these two solutes are about an order of magnitude higher than that of Fe self-diffusion. And the results show that the diffusion coefficient of La is slightly higher than that of Y, and both species are comparable to that of Fe self-diffusion.

  15. Axens new HyC 10 technology optimized with FCC while processing bitumen from Western Canada

    Energy Technology Data Exchange (ETDEWEB)

    Wisdom, L.; Sardar, H.; Nocca, J.L. [Axens North America Inc., Houston, TX (United States); Morel, F. [Axens SA, Salindres (France)

    2006-07-01

    A low pressure mild hydroconversion (MHC) method was described. HyC Technology has been recently commercialized as a cost-effective way of integrating fluid catalytic cracking (FCC) pretreating at moderate pressures, while still meeting the current and projected future requirements for ultra low sulfur diesel fuel. MHC has a low-medium conversion with sufficient FCC feed throughput to maintain gasoline production along with optimized hydrogen consumption. The process was recently tested using Canadian bitumen at a United States PADD II refinery. Details of production processes, feed quality and cracking potential for Canadian bitumen were presented. Partially hydrotreated straight run diesel (HDT) techniques were also compared with the MHC method. It was noted that MHC converted diesel is more refractory than HDT converted diesel, and that HDT techniques remain more appropriate for a variety of feeds and in situations where there is a hydrogen deficiency. Plans are now in place to adjust MHC HyC technology towards current diesel specifications, as well as to ensure constant MHC conversion. Yields, diesel, and residue product quality data for the first commercial plant using the technology were presented, as well as feedstock design bases. refs., tabs., figs.

  16. Microstructure-sensitive modelling of dislocation creep in polycrystalline FCC alloys: Orowan theory revisited

    Energy Technology Data Exchange (ETDEWEB)

    Galindo-Nava, E.I., E-mail: eg375@cam.ac.uk; Rae, C.M.F.

    2016-01-10

    A new approach for modelling dislocation creep during primary and secondary creep in FCC metals is proposed. The Orowan equation and dislocation behaviour at the grain scale are revisited to include the effects of different microstructures such as the grain size and solute atoms. Dislocation activity is proposed to follow a jog-diffusion law. It is shown that the activation energy for cross-slip E{sub cs} controls dislocation mobility and the strain increments during secondary creep. This is confirmed by successfully comparing E{sub cs} with the experimentally determined activation energy during secondary creep in 5 FCC metals. It is shown that the inverse relationship between the grain size and dislocation creep is attributed to the higher number of strain increments at the grain level dominating their magnitude as the grain size decreases. An alternative approach describing solid solution strengthening effects in nickel alloys is presented, where the dislocation mobility is reduced by dislocation pinning around solute atoms. An analysis on the solid solution strengthening effects of typical elements employed in Ni-base superalloys is also discussed. The model results are validated against measurements of Cu, Ni, Ti and 4 Ni-base alloys for wide deformation conditions and different grain sizes.

  17. Effect of spin-orbit interactions on the structural stability, thermodynamic properties, and transport properties of lead under pressure

    Science.gov (United States)

    Smirnov, N. A.

    2018-03-01

    The paper investigates the role of spin-orbit interaction in the prediction of structural stability, lattice dynamics, elasticity, thermodynamic and transport properties (electrical resistivity and thermal conductivity) of lead under pressure with the FP-LMTO (full-potential linear-muffin-tin orbital) method for the first-principles band structure calculations. Our calculations were carried out for three polymorphous lead modifications (fcc, hcp, and bcc) in generalized gradient approximation with the exchange-correlation functional PBEsol. They suggest that compared to the scalar-relativistic calculation, the account for the SO effects insignificantly influences the compressibility of Pb. At the same time, in the calculation of phonon spectra and transport properties, the role of SO interaction is important, at least, for P ≲150 GPa. At higher pressures, the contribution from SO interaction reduces but not vanishes. As for the relative structural stability, our studies show that SO effects influence weakly the pressure of the fcchcp transition and much higher the pressure of the hcpbcc transition.

  18. Low-temperature embrittlement and fracture of metals with different crystal lattices – Dislocation mechanisms

    Directory of Open Access Journals (Sweden)

    V.M. Chernov

    2016-12-01

    Full Text Available The state of a low-temperature embrittlement (cold brittleness and dislocation mechanisms for formation of the temperature of a ductile-brittle transition and brittle fracture of metals (mono- and polycrystals with various crystal lattices (BCC, FCC, HCP are considered. The conditions for their formation connected with a stress-deformed state and strength (low temperature yield strength as well as the fracture breaking stress and mobility of dislocations in the top of a crack of the fractured metal are determined. These conditions can be met for BCC and some HCP metals in the initial state (without irradiation and after a low-temperature damaging (neutron irradiation. These conditions are not met for FCC and many HCP metals. In the process of the damaging (neutron irradiation such conditions are not met also and the state of low-temperature embrittlement of metals is absent (suppressed due to arising various radiation dynamic processes, which increase the mobility of dislocations and worsen the strength characteristics.

  19. Study of the embedded atom method of atomistic calculations for metals and alloys: Progress report, March 1, 1987-February 28, 1988

    International Nuclear Information System (INIS)

    Johnson, R.A.

    1987-11-01

    The relationships between the physical input and output of the Embedded Atom Method (EAM) used in atomistic calculations for metals and alloys and the model functions and parameters are being investigated. An analytic fcc EAM model has been derived based on short range approximations to the input functions in EAM and has been studied both analytically and numerically for the fcc lattice. This model has been extended to longer ranges and applied to both fcc and hcp metals. The correspondence between models based on density functional theory (EAM), tight binding methods, and effective medium theory has been reported. The reasons for difficulty in applying EAM to bcc metals is under study and a new form of alloy potential which retains general properties of pure metal potentials has been developed. 8 refs

  20. NCTA v. FCC - Do Commercial Free Speech Justifications Trump Consumers' Personal Data Protection Rights? Answer To Shape Mobile Advertising Industry

    DEFF Research Database (Denmark)

    Cleff, Evelyne Beatrix; King, Nancy J.

    2010-01-01

    telecommunication carriers' personal data sharing practices in order to protect their customers' data privacy when the regulation restricts use of the data for marketing purposes. In this case National Cable and Telecommunications Association (NCTA) challenged a new Federal Communications Commission (FCC) rule...... requiring carriers to obtain customers' advance approval before releasing their telephone record information for marketing purposes. NCTA claimed the FCC's new opt-in rule violates companies' First Amendment right to engage in commercial speech. At stake in this appeal was the constitutionally required...... balance between protecting consumers' information privacy in an era of pervasive data processing and protecting the rights of marketers to engage in protected commercial free speech that involves using customers' personal information. A ruling against the FCC would have limited the use of government...