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Sample records for 2cr 1molow cycle

  1. The Effect of Ballistic Impacts on the High Cycle Fatigue Properties of Ti-48Al-2Nb-2Cr (at.%)

    Draper, S. L.; Lerch, B. A.; Pereira, J. M.; Nathal, M. V.; Austin, C. M.; Erdman, O.

    2000-01-01

    The ability of gamma - TiAl to withstand potential foreign and/or domestic object damage is a technical risk to the implementation of gamma - TiAl in low pressure turbine (LPT) blade applications. The overall purpose of the present study was to determine the influence of ballistic impact damage on the high cycle fatigue strength of gamma - TiAl simulated LPT blades. Impact and specimen variables included ballistic impact energy, projectile hardness, impact temperature, impact location, and leading edge thickness. The level of damage induced by the ballistic impacting was studied and quantified on both the impact (front) and backside of the specimens. Multiple linear regression was used to model the cracking and fatigue response as a function of the impact variables. Of the impact variables studied, impact energy had the largest influence on the response of gamma - TiAl to ballistic impacting. Backside crack length was the best predictor of remnant fatigue strength for low energy impacts (fatigue strength. For the fatigue design stresses of a 6th stage LPT blade in a GE90 engine, a Ti-48Al-2Nb-2Cr LPT blade would survive an impact of normal service conditions.

  2. Penetration depth measurements of K2Cr3As3 and Rb2Cr3As3

    Pang, G. M.; Smidman, M.; Jiang, W. B.; Shi, Y. G.; Bao, J. K.; Tang, Z. T.; Weng, Z. F.; Wang, Y. F.; Jiao, L.; Zhang, J. L.; Luo, J. L.; Cao, G. H.; Yuan, H. Q.

    2016-02-01

    The newly discovered superconductors A2Cr3As3 (A=K, Rb, Cs), with a quasi-one-dimensional crystal structure have attracted considerable interest. The crystal structure consists of double-walled tubes of [Cr3As3]2- that extend along the c-axis. Previously we reported measurements of the change in London penetration depth of polycrystalline samples of K2Cr3As3 using a tunnel diode oscillator based technique, which show a linear temperature dependence at low temperatures, giving evidence for line nodes in the superconducting gap. Here we report similar measurements of the penetration depth for polycrystalline Rb2Cr3As3 and several single crystals of K2Cr3As3, prepared by two different research groups. The single crystal measurements show similar behavior to polycrystalline samples down to 0.9-1.2 K, where a downturn is observed in the frequency shift for all single crystal samples. These results give further evidence for nodal superconductivity in K2Cr3As3, which indicates that the superconducting pairing state is unconventional. The different low temperature behavior, observed in samples which have deteriorated after being exposed to air, emphasizes that it is necessary to properly handle the samples prior to being measured because the A2Cr3As3 compounds are extremely air sensitive and evidence for nodal superconductivity from penetration depth measurements is only observed in the samples which display a sharp superconducting transition. Therefore further work is required to improve the quality of single crystals and to identify the origin of the downturn.

  3. Deformation in 2CrMo-1/2CrMoV pressure vessel weldments at elevated temperature

    The elastic and creep deformation occurring in low alloy ferritic steel pipe to pipe weldments has been studied in pressure vessel experiments carried out at 838 K and a range of internal steam pressures. The welds were made in heavy section 1/2CrMoV parent pipe, using 2CrMo weld metal and tested in either the as-welded or stress relieved condition. The results obtained are analysed in terms of the deformations that occur in the hoop and axial direction of the parent pipe and weld metals. Elastically the parent pipe and weld metals behave identically, and both exhibit primary and steady state creep. The steady state behaviour of the parent pipe agrees with that expected from multi-axial creep deformation theory. The stress relieved welds behave similarly to the parent pipe in the hoop direction, but not in the axial direction. This is considered to be due to offloading of stress predominantly in the hoop direction. In the as-welded condition, the hoop and axial creep strains and strain rates are greater than in the parent pipe or stress relieved welds. The reasons for this are discussed in terms of welding residual stresses. (author)

  4. Type IIIa cracking at 2CrMo welds in 1/2CrMoV pipework

    Brett, S.J.; Smith, P.A. [National Power plc, Swindon (United Kingdom)

    1998-12-31

    The most common form of in-service defect found today on the welds of National Power`s 1/2CrMoV pipework systems is Type IV cracking which occurs in intercritically transformed material at the edge of the heat affected zone. However an alternate form of cracking, termed IIIa, which occurs close to the weld fusion line in fully grain refined heat affected zones, has also been observed. The incidence of Type IIIa cracking has increased in recent years and these defects now constitute a significant part of the total recorded crack population. This presentation describes Type IIIa cracking and compares and contrasts it with the better documented Type IV cracking. Particular reference is made to the role of carbon diffusion at the weld fusion line in promoting Type IIIa damage in preference to Type IV. (orig.) 5 refs.

  5. Optical properties of heusler alloys Co2FeSi, Co2FeAl, Co2CrAl, and Co2CrGa

    Shreder, E. I.; Svyazhin, A. D.; Belozerova, K. A.

    2013-11-01

    The results of an investigation of optical properties and the calculations of the electronic structure of Co2FeSi, Co2FeAl, Co2CrAl, and Co2CrGa Heusler alloys are presented. The main focus of our attention is the study of the spectral dependence of the real part (ɛ1) and imaginary part (ɛ2) of the dielectric constant in the range of wavelengths λ = 0.3-13 μm using the ellipsometric method. An anomalous behavior of the optical conductivity σ(ω) has been found in the infrared range in the Co2CrAl and Co2CrGa alloys, which differs substantially from that in the Co2FeSi and Co2FeAl alloys. The results obtained are discussed based on the calculations of the electronic structure.

  6. Epitaxial growth and transport properties of Sr$_2$CrWO$_6$ thin films

    Philipp, J. B.; Reisinger, D.; Schonecke, M.; Opel, M.; Marx, A.; Erb, A.; Alff, L.; Gross, R.

    2002-01-01

    We report on the preparation and characterization of epitaxial thin films of the double-perovskite Sr$_2$CrWO$_6$ by Pulsed Laser Deposition (PLD). On substrates with low lattice mismatch like SrTiO$_3$, epitaxial Sr$_2$CrWO$_6$ films with high crystalline quality can be grown in a molecular layer-by-layer growth mode. Due to the similar ionic radii of Cr and W, these elements show no sublattice order. Nevertheless, the measured Curie temperature is well above 400 K. Due to the reducing growt...

  7. Investigation on Crystal Structure, Magnetism and Colossal Magnetoresistance of Y_2CrS_4

    2011-01-01

    Ternary yttrium chromium sulfide, Y2CrS4, was well prepared by a solid state reaction of Y2S3, Cr, and S. In this year we investigated its crystal structure, magnetism and magnetotransport properties. The X-ray diffraction pattern at 300 K was refined with

  8. Half metallicity in Sr2CrOsO6 via Na doping

    Highlights: • Na-doped Sr2CrOsO6 is investigated by using the density functional theory. • Both NaSr5Cr3Os3O18 and NaSrCrOsO6 are half metals. • The Curie temperature of NaSr5Cr3Os3O18 and NaSrCrOsO6 is higher than room temperature. - Abstract: The insulating Sr2CrOsO6 has the highest Curie temperature of 725 K among the double perovskites so far. In this study, by doping with Na, NaSr5Cr3Os3O18 and NaSrCrOsO6 are investigated by using the density functional theory. The calculated results indicated that the hole generated by Na goes to Os 5d t2g orbitals. This makes one of the insulating spin channels in Sr2CrOsO6 to be metallic in the Na-doped compounds. Thus, they become half metals. The estimated magnetic ordering temperature is 579 K for NaSr5Cr3Os3O18 and 615 K for NaSrCrOsO6, which are higher than the room temperature. Therefore, we expect that the Na-doped Sr2CrOsO6 would be promising candidates as spintronic material

  9. The Cracking Analysis of 2Cr13 Steel Piston Rod While Quenching%2Cr13钢活塞杆淬火裂纹分析

    黄丽秋; 曹虹; 周预平; 赵林武; 张庆坤; 汤晶晶; 王明哲

    2006-01-01

    在生产2Cr13马氏体不锈钢活塞杆时发现,已锻成形的部分有一段被加热到锻造温度范围内,在后续锻造中变形很小甚至没有变形,且淬火时产生了裂纹.经试验分析是由于该段晶粒粗大,淬火时组织应力超过该段的材料强度所致.

  10. Magnetism in Sr2CrMoO6 : A combined ab initio and model study

    Sanyal, Prabuddha; Halder, Anita; Si, Liang; Wallerberger, Markus; Held, Karsten; Saha-Dasgupta, Tanusri

    2016-07-01

    Using a combination of first-principles density functional theory (DFT) calculations and exact diagonalization studies of a first-principles derived model, we carry out a microscopic analysis of the magnetic properties of the half-metallic double perovskite compound Sr2CrMoO6 , a sister compound of the much discussed material Sr2FeMoO6 . The electronic structure of Sr2CrMoO6 , though appearing similar to Sr2FeMoO6 at first glance, shows nontrivial differences with that of Sr2FeMoO6 on closer examination. In this context, our study highlights the importance of charge transfer energy between the two transition metal sites. The change in charge transfer energy due to a shift of Cr d states in Sr2CrMoO6 compared to Fe d in Sr2FeMoO6 suppresses the hybridization between Cr t2 g and Mo t2 g. This strongly weakens the hybridization-driven mechanism of magnetism discussed for Sr2FeMoO6 . Our study reveals that, nonetheless, the magnetic transition temperature of Sr2CrMoO6 remains high since an additional superexchange contribution to magnetism arises with a finite intrinsic moment developed at the Mo site. We further discuss the situation in comparison to another related double perovskite compound, Sr2CrWO6 . We also examine the effect of correlation beyond DFT, using dynamical mean field theory.

  11. Neutron diffraction studies of the Na-ion battery electrode materials NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3

    Yahia, H. Ben; Essehli, R.; Avdeev, M.; Park, J.-B.; Sun, Y.-K.; Al-Maadeed, M. A.; Belharouak, I.

    2016-06-01

    The new compounds NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 were synthesized by sol-gel method and their crystal structures were determined by using neutron powder diffraction data. These compounds were characterized by galvanometric cycling and cyclic voltammetry. NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 crystallize with a stuffed α-CrPO4-type structure. The structure consists of a 3D-framework made of octahedra and tetrahedra that are sharing corners and/or edges generating channels along [100] and [010], in which the sodium atoms are located. Of significance, in the structures of NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 a statistical disorder Ni2+/Cr3+ was observed on both the 8g and 4a atomic positions, whereas in NaCoCr2(PO4)3 the statistical disorder Co2+/Cr3+ was only observed on the 8g atomic position. When tested as negative electrode materials, NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 delivered specific capacities of 352, 385, and 368 mA h g-1, respectively, which attests to the electrochemical activity of sodium in these compounds.

  12. Strain-tunable extraordinary magnetocrystalline anisotropy in Sr2CrReO6 epitaxial films

    Lucy, J. M.; Ball, M. R.; Restrepo, O. D.; Hauser, A. J.; Soliz, J. R.; Freeland, J. W.; Woodward, P. M.; Windl, W.; Yang, F. Y.

    2014-11-01

    We report the discovery of extraordinarily large anisotropy fields and strain-tunable magnetocrystalline anisotropy in Sr2CrReO6 epitaxial films. We determine the strain-induced tetragonal distortions and octahedral rotations in Sr2CrReO6 epitaxial films grown on (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT), SrTiO3 (STO), and SrCr0.5Nb0.5O3/LSAT substrates using x-ray diffraction and density functional theory. The structural distortions drive dramatic changes in magnetocrystalline anisotropy. We use magnetometry measurements and first principles calculations to determine the atomic origins of the large anisotropy observed. These techniques elucidate the interplay between structural deformations and magnetic behavior and lay the groundwork for the study of other strongly correlated systems in this class of ferromagnetic oxides.

  13. Structure, magnetism, and electron-transport properties of Mn2CrGa-based nanomaterials

    Zhang, Wenyong; Kharel, Parashu; Skomski, Ralph; Valloppilly, Shah; Li, Xingzhong; Sellmyer, David J.

    2016-05-01

    Mn2CrGa in the disordered cubic structure has been synthesized using rapid quenching and subsequent annealing. The cubic phase transforms to a stable tetragonal phase when a fraction of Cr or Ga is replaced by Pt or Al, respectively. All samples are ferrimagnetic with high Curie temperatures (Tc); Mn2CrGa exhibits the highest Tc of about 813 K. The tetragonal samples have appreciable values of magnetocrystalline anisotropy energy, which leads to an increase in coercivity (Hc) that approaches about 10 kOe in the Pt-doped sample. The Hc linearly increases with a decrease of temperature, concomitant with the anisotropy change with temperature. All samples are metallic and show negative magnetoresistance with room-temperature resistivities on the order of 1 mΩcm. The magnetic properties including high Tc and low magnetic moment suggest that these tetragonal materials have potential for spin-transfer-torque-based devices.

  14. Orbital ordering in the two-dimensional ferromagnetic semiconductor Rb2CrCl4

    Schwingenschlögl, U.; Eyert, V.

    2007-05-01

    We present the results of electronic structure calculations for the two-dimensional ferromagnet Rb2CrCl4. They are obtained by the augmented spherical wave (ASW) method as based on density functional theory and the local density approximation. In agreement with experimental data, Rb2CrCl4 is found to be semiconducting and displays long-range ferromagnetic order of the localized Cr 3d moments. The magnetic properties are almost independent of the structural modifications arising from the Jahn-Teller instability, which leads from the parent body-centered tetragonal K2NiF4 structure to a side-centered orthorhombic lattice. In contrast, the insulating gap is observed only for the latter structure due to the reduced symmetry. Our results thus suggest to interpret the orbital ordering as a necessary prerequisite for the opening of the gap rather than for the ferromagnetic order.

  15. Electronic structure, magnetism, and transport properties of the Heusler alloy Fe2CrAl

    We report the electronic band structure, magnetism, and transport properties of the Heusler compound Fe2CrAl. The band-structure calculation for Fe2CrAl at the experimental lattice constant does not show the half-metallicity. The magnetism measurements show that the saturated moment at 5 K and the Curie temperature are 1.75 μB per formula unit and 234 K, respectively. The temperature dependence of the magnetization follows the spin-wave behavior at low temperature. The electrical resistivity shows a semiconducting-like behavior, which can be explained by the electronic band-structure calculations. The dependence of the magnetoresistance on the applied field is related to the competition between the effect of the Lorentz force and the extinction of inelastic s-d-s scattering

  16. Structure, magnetism, and electron-transport properties of Mn2CrGa-based nanomaterials

    Wenyong Zhang

    2016-05-01

    Full Text Available Mn2CrGa in the disordered cubic structure has been synthesized using rapid quenching and subsequent annealing. The cubic phase transforms to a stable tetragonal phase when a fraction of Cr or Ga is replaced by Pt or Al, respectively. All samples are ferrimagnetic with high Curie temperatures (Tc; Mn2CrGa exhibits the highest Tc of about 813 K. The tetragonal samples have appreciable values of magnetocrystalline anisotropy energy, which leads to an increase in coercivity (Hc that approaches about 10 kOe in the Pt-doped sample. The Hc linearly increases with a decrease of temperature, concomitant with the anisotropy change with temperature. All samples are metallic and show negative magnetoresistance with room-temperature resistivities on the order of 1 mΩcm. The magnetic properties including high Tc and low magnetic moment suggest that these tetragonal materials have potential for spin-transfer-torque-based devices.

  17. Long afterglow properties of Zn2GeO4:Mn2+, Cr3+ phosphor

    Cong, Yan; He, Yangyang; Dong, Bin; Xiao, Yu; Wang, Limei

    2015-04-01

    Zn2GeO4:Mn2+, Cr3+ phosphors were prepared by conventional solid state reaction and the photoluminescence properties were investigated. The Mn2+ activated Zn2GeO4 phosphors exhibited green emission at 533 nm due to the 4T1(4G) → 6A1(6S) transition of Mn2+ ions. With Cr3+ co-doping in Zn2GeO4 host, long afterglow characteristics were found from the same transition of Mn2+. The TL results revealed the presence of same traps in the phosphor, and the doping of Cr3+ ions deepened the VGe traps. The native defect VGe as a hole traps is responsible for the long afterglow emission in Zn2GeO4:Mn2+, Cr3+ phosphor. The possible mechanism of this phosphor has also been discussed.

  18. Epitaxial growth and magnetic properties of Sr2CrReO6 thin films

    The double perovskite Sr2CrReO6 is an interesting material for spintronics, showing ferrimagnetism up to 635 K with a predicted high spin polarization of ∼86%. We fabricated Sr2CrReO6 epitaxial films by pulsed laser deposition on (0 0 1)-oriented SrTiO3 substrates. Phase-pure films with optimum crystallographic and magnetic properties were obtained by growing at a substrate temperature of 7000C in pure O2 of 6.6x10-4mbar. The films are c-axis oriented, coherently strained, and show less than 20% anti-site defects. The magnetization curves reveal high saturation magnetization of 0.8μB/formula unit and high coercivity of 1.1 T, as well as a strong magnetic anisotropy.

  19. Towards half-metallic interfaces: Co2CrAl/InP contacts

    Although the interest in half-metallic Heusler alloys, likely to be usable in spintronic applications, has grown considerably, their interfaces with semiconductors show very low spin polarization. I identify mechanisms which can keep high spin polarization at the interface (more than 80% of the electrons at the Fermi level of majority spin) although the half-metallicity is lost. The large enhancement of the Cr moment at the interface between a CrAl-terminated Co2CrAl (001) spacer and the InP(001) semiconductor weakens the effect of the interface states, resulting in this high spin polarization. On the other hand, the Co2CrAl/InP interfaces made up by a Co layer and either an In or a P one show a severe decrease of the Co spin moment, but Cr in the subinterface layer is bulklike and the resulting spin polarization is similar to that of the CrAl-based interfaces

  20. Hexavalent hydrogen complex in hypothetical Y{sub 2}CrH{sub 6}

    Takagi, Shigeyuki, E-mail: shigeyuki.takagi@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Miwa, Kazutoshi [Toyota Central R and D Laboratories, Inc., Nagakute 480-1192 (Japan); Ikeshoji, Tamio; Sato, Ryutaro; Matsuo, Motoaki; Li, Guanqiao; Aoki, Katsutoshi [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Orimo, Shin-ichi [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2013-12-15

    Highlights: ► A possible synthesis of Y{sub 2}CrH{sub 6} was theoretically investigated. ► We found the thermodynamically stable structure with a hexavalent [CrH{sub 6}]{sup 6−}. ► The large charge state of [CrH{sub 6}]{sup 6−} brings diversity to the cation combinations. ► The large charge state would provide a chemical flexibility to the complex hydride. -- Abstract: The crystal, electronic and phonon structures, and thermodynamic stability of a hypothetical complex hydride Y{sub 2}CrH{sub 6} were investigated using first-principles calculations. We found that the hydride contains CrH{sub 6} octahedra in the K{sub 2}PtCl{sub 6}-type structure. The electronic structure illustrates that two yttrium atoms donate a total of six electrons to the octahedra, indicating the charge state Y{sub 2}{sup 3+}[CrH{sub 6}]{sup 6-} which abides by the 18-electron rule. The phonon dispersion curves demonstrate that the hydride is dynamically stable. The calculated enthalpy change of −11 kJ/mol for the reaction, 2YH{sub 2}+Cr + H{sub 2} → Y{sub 2}CrH{sub 6}, gives a possible route to synthesize the stable complex hydride containing [CrH{sub 6}]{sup 6−}. The large charge state of the hexavalent complex anion [CrH{sub 6}]{sup 6−} would be useful to explore new complex hydrides, providing the chemical flexibility through the multiple combinations of cations.

  1. Half metallicity in Sr{sub 2}CrOsO{sub 6} via Na doping

    Zu, Ningning [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Wang, Jing [Key Laboratory of Applied Chemistry, Yanshan University, Qinhuangdao 066004 (China); Wang, Ying, E-mail: ywang_2012@ciac.ac.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Wu, Zhijian, E-mail: zjwu@ciac.ac.cn [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

    2015-07-05

    Highlights: • Na-doped Sr{sub 2}CrOsO{sub 6} is investigated by using the density functional theory. • Both NaSr{sub 5}Cr{sub 3}Os{sub 3}O{sub 18} and NaSrCrOsO{sub 6} are half metals. • The Curie temperature of NaSr{sub 5}Cr{sub 3}Os{sub 3}O{sub 18} and NaSrCrOsO{sub 6} is higher than room temperature. - Abstract: The insulating Sr{sub 2}CrOsO{sub 6} has the highest Curie temperature of 725 K among the double perovskites so far. In this study, by doping with Na, NaSr{sub 5}Cr{sub 3}Os{sub 3}O{sub 18} and NaSrCrOsO{sub 6} are investigated by using the density functional theory. The calculated results indicated that the hole generated by Na goes to Os 5d t{sub 2g} orbitals. This makes one of the insulating spin channels in Sr{sub 2}CrOsO{sub 6} to be metallic in the Na-doped compounds. Thus, they become half metals. The estimated magnetic ordering temperature is 579 K for NaSr{sub 5}Cr{sub 3}Os{sub 3}O{sub 18} and 615 K for NaSrCrOsO{sub 6}, which are higher than the room temperature. Therefore, we expect that the Na-doped Sr{sub 2}CrOsO{sub 6} would be promising candidates as spintronic material.

  2. Strain-dependent, Extraordinary Magnetocrystalline Anisotropy in Sr2CrReO6 Epitaxial Films

    Lucy, Jeremy; Soliz, Jennifer; Ball, Molly; Restrepo, Oscar; Windl, Wolfgang; Woodward, Patrick; Yang, Fengyuan; Hauser, Adam; Freeland, John; CenterEmergent Materials Collaboration; Magnetic Materials Group Collaboration

    2014-03-01

    We have grown Sr2CrReO6 films that exhibit one of the largest anisotropy fields shown to date (18.1 T) and a large uniaxial magnetocrystalline anisotropy energy Ku = 9.05 × 106 erg/cm3. We investigate strain-controlled magnetocrystalline anisotropy for epitaxial Sr2CrReO6 films grown on (LaAlO3)0.3 (Sr2AlTaO6)0.7 , SrTiO3 and Sr2CrNbO6/LSAT substrates using high resolution X-ray diffraction, in-plane and out-of-plane superconducting quantum interference device magnetometry, and density functional theory calculations. The substrates impose tetragonal distortions of c/ a = 1.025, 1.007 and 0.991, respectively, which lead to dramatic changes in magnetocrystalline anisotropy of order tens of tesla and a switching of the magnetic easy axis from in-plane for compressive strain to out-of-plane for tensile strain, as observed via magnetometry measurements. Density functional theory calculations elucidate the dependence of oxygen octahedra tilting and rotation on tetragonal distortions, which affect both electronic and magnetic properties of the films. Finally, X-ray magnetic circular dichroism measurements reveal strong magnetic moment contributions at the oxygen sites, as evident in oxygen-specific X-ray absorption spectra.

  3. Microstructural and tribological characterization of plasma- and gas-nitrided 2Cr13 steel in vacuum

    Plasma- and gas-nitrided 2Cr13 samples were characterized using optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and microhardness testing techniques. Nitrogen concentration profiles in the cross-sections of the nitrided samples were obtained by glow discharge optical spectroscopy (GDOS). Residual stress profiles along depth of the nitrided samples were measured using an X-ray stress tester. The tribological behaviour of the plasma- and the gas-nitrided samples in vacuum was investigated in order to analyse the effect of nitriding on wear resistance of the 2Cr13 steel. The results show the tribological properties of the 2Cr13 steel in vacuum are improved considerably by plasma nitriding and gas nitriding resulted from microstructure modification and surface hardening during nitriding. The plasma-nitrided samples have better wear resistance than the gas-nitrided samples under 30 N, while the gas-nitrided samples have higher wear resistance under 90 N. With increasing normal load from 30 N to 90 N, the wear mechanism shows a transition from mild adhesive and abrasive wear to severe adhesive or even delamination wear. The plasma-nitrided sample has thicker compound layer than the gas-nitrided sample, resulting that it exhibits more intensive delamination under high load of 90 N.

  4. Observation of magnetic cluster phase above Curie temperature in Fe2CrAl Heusler alloy

    We present a detailed magnetic critical behavior study of Fe2CrAl Heusler alloy, for the first time, with rigorous analysis of high precision magnetization data obtained over the critical temperature region. Our studies confirm that B2 type site-disordered in Fe2CrAl alloy exhibits long-range ferromagnetic order below a well defined Curie temperature (T=208 K). Though the nature of this transition is found to be of second order, the estimated critical exponents β=0.42, γ=1.356 and δ=4.25, are in between the theoretically predicted values for three-dimensional Heisenberg and mean-field interaction models. However, it is noteworthy that the scaling relations are obeyed indicating renormalization of interactions around the Curie temperature (TC), where magnetization data collapse into two separate branches, above and below TC. This conclusively shows that calculated critical exponents as well as critical temperature are unambiguous and intrinsic to the system. However, magnetization vs temperature data shows another magnetic transition (at T=313 K) above the Curie temperature. It is shown that the short range magnetic correlation exist even beyond TC with cluster moment ∼102 μB. This is attributed to a site disorder which results in formation of Cr clusters with short range ferromagnetic order. - Highlights: ► Magnetization vs temperature data of Fe2CrAl alloy shows two transitions around 208 K and 313 K. ► We have established that first magnetic transition (208 K) to be a ferromagnetic transition. ► The estimated critical exponents are in between 3D Heisenberg and mean-field models. ► It is shown that the short range magnetic correlation exist even at 313 K with cluster moment ∼102 μB. ► This is attributed to site-disorder, results in formation of Cr clusters.

  5. COST 505 - project D 31. Evaluation of 2% CrMoWV steel (23 CrMoNiWV 8 8) for high temperature steam turbine rotor forgings

    The aim of the research work has been to examine the behaviour of the newly developed 2% CrMoWV (23 CrMoNiWV 8 8) HP and IP rotor steel in creep, low-cycle fatigue, toughness and long-time embrittlement tests. The results of the tests over a duration of about 20 000 h showed that in comparison with the traditional 1% CrMoV shaft steel the 2% CrMoWV shaft steel has a distinctly higher fracture toughness with equal creep and low-cicle fatigue strength. Exposures of notched-bar impact test specimens revealed in the temperature range of 400 bis 500deg C a time and temperature-dependent reduction in fracture toughness on account of P-segregations at the grain boundaries. However, the loss of toughness is within acceptable limits and can presumably be prevented or distinctly decreased by a further reduction of the P-contend during the steel melting process. (orig./MM)

  6. Perpendicular magnetic anisotropy in Fe2Cr1−xCoxSi Heusler alloy

    Perpendicular magnetic anisotropy (PMA) was achieved in annealed Fe2Cr1 − xCoxSi (FCCS) Heusler alloys with different Co compositions x. The Co composition is varied to tune the Fermi level in order to achieve both higher spin polarization and better thermal stability. The PMA is thermally stable up to 400 oC for FCCS with x = 0, 0.3, 0.5 and 350 oC for FCCS with x = 0.7, 0.9, 1. The thickness of FCCS films with PMA ranges from 0.6 to 1.2 nm. The annealing temperature and FCCS thickness are found to greatly affect the PMA. The magnetic anisotropy energy density KU is 2.8  ×  106 erg cm−3 for 0.8 nm Fe2CrSi, and decreases as the Co composition x increases, suggesting that the PMA induced at the FCCS/MgO interface is dominated by the contribution of Fe atoms. There is a trade-off between high spin polarization and strong PMA by adjusting the Co composition. (paper)

  7. Antioxidative role of selenium on some tissues of (Cd2+), Cr3+)-induced rainbow trout.

    Orun, Ibrahim; Talas, Zeliha Selamoglu; Ozdemir, Ilknur; Alkan, Aysel; Erdogan, Kenan

    2008-09-01

    Chemical toxic pollutants (especially heavy metals) are important sources of reactive oxygen species (ROS) in biological systems. Membrane phospholipids of aerobic organisms are continually subjected to oxidant challenges from endogenous and exogenous sources, while peroxidized membranes and lipid peroxidation products represent constant threats to aerobic cells. The primary antioxidant protection against free radical and ROS is provided by the enzymes glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT), respectively. The trace element selenium has been implicated in chemo-prevention and drug-resistance through reduction of oxidative stress. Selenium could prevent damage to the unsaturated fatty acid of subcellular membranes by lipid peroxidation induced by free radicals. The results reported here show that sodium selenite has an important contribution to antioxidative defense for the spleen and heart of rainbow trout. The ability of sodium selenite to prevent the oxidative stress induced by heavy metals (Cd(2+), Cr(3+)) in fish was rationalized. PMID:17920681

  8. Grain-size control in Ti-48Al-2Cr-2Nb with yttrium additions

    Trivedi, P. B.; Patankar, S. N.; (Sam) Froes, F. H.; Baburaj, E. G.; Genç, A.; Ovecoglu, L.

    2002-08-01

    A gas-atomized (GA) prealloyed powder of the Ti-48Al-2Cr-2Nb intermetallic and 1.6 wt pct Y were mechanically alloyed (MA) and hot isostatically pressed (hipped) to produce a fully dense nanocrystalline material. Mechanical alloying of the as-blended powder for 16 hours resulted in the formation of a disordered fcc phase. Hipping of the alloy powder produced a single-phase nanocrystalline TiAl intermetallic, containing a distribution of 20 to 35-nm-sized Al2Y4O9 particles. The formation of oxide particles occurred by the chemical combination of Al and Y with oxygen, which entered as a contaminant during milling. Oxide particles increased the hardness of the intermetallic compound and minimized grain growth even at 0.8 T m , where T m is the melting point of the compound.

  9. Sign reversal of transformation entropy change in Co2Cr(Ga,Si) shape memory alloys

    Xu, Xiao; Omori, Toshihiro; Nagasako, Makoto; Kanomata, Takeshi; Kainuma, Ryosuke

    2015-11-01

    In situ X-ray diffraction (XRD) measurements and compression tests were performed on Co2Cr(Ga,Si) shape memory alloys. The reentrant martensitic transformation behavior was directly observed during the in situ XRD measurements. The high-temperature parent phase and low-temperature reentrant parent phase were found to have a continuous temperature dependence of lattice parameter, therefore suggesting that they are the same phase in nature. Moreover, compression tests were performed on a parent-phase single crystal sample; an evolution from normal to inverse temperature dependence of critical stress for martensitic transformation was directly observed. Based on the Clausius-Clapeyron analysis, a sign reversal of entropy change can be expected on the same alloy.

  10. Sign reversal of transformation entropy change in Co2Cr(Ga,Si) shape memory alloys

    In situ X-ray diffraction (XRD) measurements and compression tests were performed on Co2Cr(Ga,Si) shape memory alloys. The reentrant martensitic transformation behavior was directly observed during the in situ XRD measurements. The high-temperature parent phase and low-temperature reentrant parent phase were found to have a continuous temperature dependence of lattice parameter, therefore suggesting that they are the same phase in nature. Moreover, compression tests were performed on a parent-phase single crystal sample; an evolution from normal to inverse temperature dependence of critical stress for martensitic transformation was directly observed. Based on the Clausius-Clapeyron analysis, a sign reversal of entropy change can be expected on the same alloy

  11. NMR investigation of the quasi-one-dimensional superconductor K(2)Cr(3)As(3).

    Zhi, H Z; Imai, T; Ning, F L; Bao, Jin-Ke; Cao, Guang-Han

    2015-04-10

    We report ^{75}As NMR measurements on the new quasi-one-dimensional superconductor K_{2}Cr_{3}As_{3} (T_{c}∼6.1  K) [J. K. Bao et al., Phys. Rev. X 5, 011013 (2015)]. We found evidence for strong enhancement of Cr spin fluctuations above T_{c} in the [Cr_{3}As_{3}]_{∞} double-walled subnanotubes based on the nuclear spin-lattice relaxation rate 1/T_{1}. The power-law temperature dependence, 1/T_{1}T∼T^{-γ} (γ∼0.25), is consistent with the Tomonaga-Luttinger liquid. Moreover, absence of the Hebel-Slichter coherence peak of 1/T_{1} just below T_{c} suggests an unconventional nature of superconductivity. PMID:25910155

  12. Study of energy bands and magnetic properties of Co2CrSi Heusler alloy

    Dibya Prakash Rai; Sandeep; M P Ghimire; R K Thapa

    2011-10-01

    The electronic and magnetic properties of Co2CrSi is calculated by using full-potential linearized augmented plane wave (FP–LAPW) method based on density functional theory (DFT). Density of states (DOS), magnetic moment and band structures of the system are presented. For the exchange and correlation energy, local spin density approximation (LSDA+U) with the inclusion of Hubbard potential U is used. Our calculation shows indirect bandgap of 0.91 eV in the minority channel of DOS. This is supported by band structures and hence favoured the half metallic ferromagnetic (HMF) nature of the system. The effective magnetic moment of 4.006 B also supported our conclusion with a near integral value. The DOS of Co and Cr were found to hybridize and was also responsible for the ferromagnetic nature of the system.

  13. Thermodynamic stabilities of Cs2CrO4(β), Cs3CrO4 and M2Cr2O7(l) (where M=Na, K or Cs) by solid electrolyte emf method

    The emf of the galvanic cells with Pt, Cs2CrO4 (α or β) vertical stroke Cr2O3 vertical stroke Cs3 CrO4 (cell I) and Pt, s2CrO4(β) vertical stroke Cr2O 3 vertical stroke Cs2Cr2O7(l) (cell II) against air vertical stroke Pt reference electrode using 15 mol% calcia stabilized zirconia as the electrolyte were measured to be EI(a)(mV)=(1345.88±3.68)-(0.5 3174±0.03376)T(K); (860-967 K) EI(b) (mV)=(1266.47±1.50)-(0.45345± 0.04351)T(K); (1052-1097 K) EII (mV)=(344.42±1.84)-(0.25715±0.0079)T(K); (1025-1189 K). Using the literature data for the standard Gibbs energies of formation of α-Cs2CrO4 and Cr2O3 together with the above numerical expressions for the emf values of cell I, the transition temperature and the standard enthalpy of α-to-β phase transformation in Cs2CrO4 were found to be 1014 K and 12.8 kJmol-1. In addition, the ΔGf0 (Cs3CrO4) was derived to be as follows: (ΔGf0 (Cs3CrO4)±2.0) (kJmol-1)=-1531.72+0.38044 T(K). The emf results from cell II led to the expression ΔGf0 (Cs2Cr2O7,l±3.35) (kJmol-1)=-2066.47+0.55062 T(K). By making emf measurements on galvanic cells with Pt, M2CrO4 (β) vertical stroke Cr2O3 vertical stroke M2 Cr2O7 (l) (where M=Na or K) against air vertical stroke Pt as the reference electrode in a cell configuration identical with cell II, the following expressions for ΔGf0 of M2Cr2O7(l) were derived. ΔGf0(Na2Cr2O7,l pm2.0) (kJmol-1)=-1942.68+0.51289 T(K), ΔGf0(K2Cr2O7,l±2.5) (kJmol-1)=-2037.35+0.5406 T(K). The third law treatment of the emf data on cells I and II yielded the values of -1549.8±1.4 kJmol-1 and -2108±4 kJmol-1 for the standard enthalpies of formation, ΔHf,2980 of Cs3CrO4(s) and Cs2Cr2O7(s). (orig.)

  14. High-pressure and high-temperature synthesis and physical properties of Ca2CrO4 solid

    Cao, L. P.; Jin, M. L.; Li, W. M.; Wang, X. C.; Liu, Q. Q.; Xu, Y. L.; Pan, L. Q.; Jin, C. Q.

    2016-05-01

    The bulk Ca2CrO4 samples were synthesized under high pressure and high temperature conditions using CaO and CrO2 as starting materials. The structure of the prepared Ca2CrO4 solid is characterized by X-ray diffraction with Rietveld refinement as tetragonal structure with the space group I41/acd. The CrO6 octahedrons elongate along c axis and rotate in ab plane. DC and AC magnetic susceptibility measurement results indicate spin glass behavior at low temperature. Temperature dependence of resistivity measurement results show Ca2CrO4 is an insulator at both ambient condition and high pressure.

  15. The effect of chemical pressure on the structure and properties of A2CrOsO6 (A=Sr, Ca) ferrimagnetic double perovskite

    Morrow, Ryan; Soliz, Jennifer R.; Hauser, Adam J.; Gallagher, James C.; Susner, Michael A.; Sumption, Michael D.; Aczel, Adam A.; Yan, Jiaqiang; Yang, Fengyuan; Woodward, Patrick M.

    2016-06-01

    The ordered double perovskites Sr2CrOsO6 and Ca2CrOsO6 have been synthesized and characterized with neutron powder diffraction, electrical transport measurements, and high field magnetization experiments. As reported previously Sr2CrOsO6 crystallizes with R 3 bar symmetry due to a-a-a- octahedral tilting. A decrease in the tolerance factor leads to a-a-b+ octahedral tilting and P21/n space group symmetry for Ca2CrOsO6. Both materials are found to be ferrimagnetic insulators with saturation magnetizations near 0.2 μB. Sr2CrOsO6 orders at 660 K while Ca2CrOsO6 orders at 490 K. Variable temperature magnetization measurements suggest that the magnetization of the Cr3+ and Os3+ sublattices have different temperature dependences in Sr2CrOsO6. This leads to a non-monotonic temperature evolution of the magnetic moment. Similar behavior is not seen in Ca2CrOsO6. Both compounds have similar levels of Os/Cr antisite disorder, with order parameters of η=80.2(4)% for Sr2CrOsO6 and η=76.2(5)% for Ca2CrOsO6, where η=2θ-1 and θ is the occupancy of the osmium ion on the osmium-rich Wyckoff site.

  16. Epitaxy of thin films of the Heusler compound Co2Cr0.6Fe0.4Al

    Conca, A.; Jourdan, M; Herbort, C.; Adrian, H.

    2006-01-01

    Epitaxial thin films of the highly spin polarized Heusler compound Co2Cr0.6Fe0.4Al are deposited by dc magnetron sputtering. It is shown by XRD and TEM investigations how the use of an Fe buffer layer on MgO(100) substrates supports the growth of highly ordered Co2Cr0.6Fe0.4Al at low deposition temperatures. The as grown samples show a relatively large ordered magnetic moment of mu = 3.0mu_B/f.u. providing evidence for a low level of disorder.

  17. 利用离子液体[BMIM]2[CR]萃取牛血清蛋白的研究%Study on the BSA extraction by ionic liquid of [BMIM]2 [CR

    娄本浊

    2012-01-01

    An environmental friendly ionic liquid [ BMIM]2[CR] with affinity is synthesized by ionic exchange and the bovine serum albumin ( BSA) is extracted by this new type of extracting agent. The results showed that the optimum conditions of BSA extraction are 10 mmol/L of ionic liquid concentration, 30 min of extraction time and in acidic solution, and the extraction efficiency can be above 90%. This studied providing certain feasibility conditions for protein extraction application.%利用离子交换过程将亲和性染料刚果红合成为[BMIM]2[CR],并进行牛血清蛋白萃取实验.研究结果表明,[BMIM]2[CR]离子液体的浓度为10mmol/L,萃取时间为30min以及溶液呈酸性时,对牛血清蛋白的萃取效果最佳,可达90%以上.该研究可为[BMIM]2[CR]实际蛋白质萃取应用中提供一定的可行性条件.

  18. Structural properties of the quaternary Heusler alloy Co2Cr1-xFexAl

    The quarternary substitutional series Co2Cr1-xFexAl was investigated by means of surface and bulk sensitive techniques in order to exploit its structural and compositional properties. Both bulk and powder samples of the alloy series were investigated to obtain specific information about this material. The long range order was determined by means of x-ray diffraction and neutron diffraction, while the site specific (short range) order was proved by extended x-ray absorption fine structure spectroscopy. The magnetic structure was investigated by Moessbauer spectroscopy in transmission and scattering modes in order to compare and separate powder and bulk properties. The chemical composition was analysed by means of x-ray photo emission spectroscopy combined with Auger electron spectroscopy depth profiling. The results from these methods are compared to get an insight into the differences between surface and bulk properties and the appearance of disorder in such alloys. The material shows an extremely high sensitivity to oxygen. In particular, powder materials show a high amount of oxygen contamination. Therefore, an additional oxide-mediated tunnel magneto-resistance may always contribute to measurements of magneto-resistive effects because the oxide layers will provide natural tunnelling barriers. In addition, the results suggest that thin films have to be produced under ultra-high vacuum conditions

  19. Structural properties of the quaternary Heusler alloy Co2Cr1-xFexAl

    Wurmehl, Sabine; Martins Alves, Maria C.; Morais, Jonder; Ksenofontov, Vadim; Teixeira, Sergio R.; Machado, Giovanna; Fecher, Gerhard H.; Felser, Claudia

    2007-03-01

    The quarternary substitutional series Co2Cr1-xFexAl was investigated by means of surface and bulk sensitive techniques in order to exploit its structural and compositional properties. Both bulk and powder samples of the alloy series were investigated to obtain specific information about this material. The long range order was determined by means of x-ray diffraction and neutron diffraction, while the site specific (short range) order was proved by extended x-ray absorption fine structure spectroscopy. The magnetic structure was investigated by Mössbauer spectroscopy in transmission and scattering modes in order to compare and separate powder and bulk properties. The chemical composition was analysed by means of x-ray photo emission spectroscopy combined with Auger electron spectroscopy depth profiling. The results from these methods are compared to get an insight into the differences between surface and bulk properties and the appearance of disorder in such alloys. The material shows an extremely high sensitivity to oxygen. In particular, powder materials show a high amount of oxygen contamination. Therefore, an additional oxide-mediated tunnel magneto-resistance may always contribute to measurements of magneto-resistive effects because the oxide layers will provide natural tunnelling barriers. In addition, the results suggest that thin films have to be produced under ultra-high vacuum conditions.

  20. Magnetic and structural properties of nanostructured Fe–20Al–2Cr powder mixtures

    Nanostructured Fe–20Al–2Cr (wt.%) powders have been prepared using high energy planetary ball-mill. Changes in structural, morphological and magnetic properties of the powders during mechanical alloying (MA) and during subsequent annealing have been examined by X-ray diffraction, scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The observed structural and microstructural changes have been related to several processes occurring during MA. After MA, the material becomes significantly disordered and refines to nanoscale grain sizes (~ 14 nm). The obtained bcc α-Fe(Al,Cr) solid solution shows a ferromagnetic behavior. Upon subsequent annealing at 400 °C, α-Fe2O3 and spinel oxides are formed at the surface of particles, while structural defects disappeared as Fe(Al,Cr) solid solution becomes more ordered and grain growth occurs. The saturation magnetization (Ms) shows lower values after annealing, attributed to the formation of metal oxides with low magnetic moment. - Graphical abstract: Display Omitted - Highlights: • Nanostructured Fe–Al–Cr powders were prepared by MA. • Careful analysis of the XRD patterns by using the Rietveld refinement • The lattice distortion is evidenced by the increase of both the lattice parameter and the static Debye Waller parameter. • Annealing at 400 °C stabilizes the microstructure at the nanometer range and leads to the formation of Fe3O4 and Fe2O3 oxides. • Both the milled and annealed samples are ferromagnetic

  1. Pitting Corrosion of Ni3(Si,Ti+2Cr Intermetallic Compound at Various Chloride Concentrations

    Gadang Priyotomo

    2014-05-01

    Full Text Available The pitting corrosion of Ni3(Si,Ti with 2 at% Cr containing two regions of a Ni3(Si,Ti single-phase of L12 structure and a mixture phase of of (L12 +Niss was investigated as function of chloride concentrations by using a polarization method, scanning electron microscope and energy dispersive X-Ray spectroscopy in neutral sodium chloride solutions at 293 K.  The pitting corrosion of Ni3(Si,Ti with and without the addition of aluminium and type C276 alloy were also studied under the same experimental condition for the comparison.  The pitting potential obtained for the Ni3(Si,Ti with 2 at% Cr decreased with increasing chloride concentration.  The specific pitting potentials and the pitting potentials were decreased in the order of C276 alloy > Ni3(Si,Ti > Ni3(Si,Ti + 2Cr > Ni3(Si,Ti + 4Al, which means that the pitting corrosion resistance of Ni3(Si,Ti with 2 at% Cr was higher than Ni3(Si,Ti with 4 at% Al, but lower than that of Ni3(Si,Ti.  A critical chloride concentration of Ni3(Si,Ti with 2 at% Cr was found to be higher than that of Ni3(Si,Ti with at% Al. In addition, the presence of high concentration for oxygen indicates the occurrence of pit formation.

  2. High-temperature deformation behavior of the gamma alloy Ti-48Al-2Cr-2Nb

    The hot-workability of a two-phase (gamma + alpha-2) alloy, Ti-48Al-2Cr-2Nb, has been studied by conducting isothermal compression tests to 0.8 true strain over the temperature range of 975-1200 C at strain rates between 0.1 and 0.003/S. A deformation map showing temperature, strain rate, soundness of deformation, and isostress contours was constructed. Good workability is found from the low temperature/low strain rate regime to combinations of high temperature and either high or low strain rate. The upper-limit flow stress for good workability is between 450 and 500 MPa. Deformation induced softening occurs at all conditions. SEM and TEM examinations of the deformed specimens reveal that nonuniform deformation takes place at all strain rates, but cracking occurs mostly at high strain rates (e.g. 0.1/s), especially combined with low temperatures. The cracking appears to progress primarily along gamma/alpha-2 interfaces. It is thought that nonuniform deformation develops channels of shear bands, which in turn promote localized recrystallization, thus accommodating higher strains. 9 refs

  3. Instant capture of recoil 51Cr(III) from neutron activated K2CrO4

    A new method of measuring the initial 51Cr(III) produced from nuclear recoil of K2CrO4 was developed. In this method K2CrO4 was mixed with MgO in the presence of a small amount of water, and the mixture was irradiated in a nuclear reactor. After irradiation, the mixture was dissolved in water, and MgO precipitate was separated from the solution. The yield of recoil 51Cr(III) could be calculated from the 51Cr activity in the precipitate measured. On the other hand, the yield of retention of 51Cr as chromate could be calculated from the activity found in the supernatant. The 51Cr(III) yield thus obtained is almost a factor of 2 higher than observed in pure K2CrO4 without mixing with MgO, irradiated under the same condition. Another important observation is that the 51Cr(III) yield is independent of irradiation time in presence of MgO. Without MgO the observed 51Cr(III) yield decreases with increasing irradiation time, suggesting possible oxidation of Cr(III) to chromate during irradiation. This variation is not observed in the system of K2CrO4 containing MgO, indicating that the initial Cr(III) is adsorbed immediately after nuclear recoil by MgO and is protected from oxidation by gamma radiation. (author) 4 refs.; 4 figs.; 2 tabs

  4. Antisite disorder study by Monte Carlo simulation of the double perovskite Sr2CrReO6

    El Rhazouani, O.; Benyoussef, A.; Zarhri, Z.; El Kenz, A.

    2016-03-01

    In the last few years there has been a growing interest in the double perovskite (DP) Sr2CrReO6, as a magnetic material used in spintronics, due to its high Curie temperature (TC=610 K). Antisite disorder is a defect that affects the spin polarization and the Curie temperature of all PDs. We conducted this work by Monte Carlo simulation to study the effect of the antisite disorder on this compound for two cases: Cr-excess expressed by Sr2Cr1+xRe1-xO6 and Re-excess expressed by Sr2Cr1-xRe1+xO6. This simulation has transformed the concept of the antisite conceived as defect, into a tool to explain the role of transition metals, namely Cr and Re, in the stability and the magnetic performance of the compound Sr2CrReO6. This simulation allows positioning the Cr as a key element in determining the high Curie temperature and the ferromagnetic stability. The effect of crystal field of Re in the disordered sublattice regarding the disorder rates was also explored.

  5. The Structure-Function Relationships of Complement Receptor Type 2 (CR2; CD21).

    Hannan, Jonathan Paul

    2016-01-01

    Human complement receptor type 2 (CR2; CD21) is a surface-associated glycoprotein which binds to a variety of endogenous ligands, including the complement component C3 fragments iC3b, C3dg and C3d, the low-affinity IgE receptor CD23, and the type I cytokine, interferon-alpha. CR2 links the innate complement-mediated immune response to pathogens and foreign antigens with the adaptive immune response by binding to C3d that is covalently attached to targets, and which results in a cell signalling phenomenon that lowers the threshold for B cell activation. Variations or deletions of the CR2 gene in humans, or the Cr2 gene in mice associate with a variety of autoimmune and inflammatory conditions. A number of infectious agents including Epstein-Barr virus (EBV), Human Immunodeficiency Virus (HIV) and prions also bind to CR2 either directly or indirectly by means of C3d-targeted immune complexes. In this review we discuss the interactions that CR2 undertakes with its best characterized ligands C3d, CD23 and the EBV gp350/220 envelope protein. To date only a single physiologically relevant complex of CR2 with one of its ligands, C3d, has been elucidated. By contrast, the interactions with CD23 and EBV gp350/220, while being important from physiologic and disease-associated standpoints, respectively, are only incompletely understood. A detailed knowledge of the structure-function relationships that CR2 undergoes with its ligands is necessary to understand the implications of using recombinant CR2 in therapeutic or imaging agents, or alternatively targeting CR2 to down-regulate the antibody mediated immune response in cases of autoimmunity. PMID:26916158

  6. Magnetic and structural properties of nanostructured Fe–20Al–2Cr powder mixtures

    Zerniz, N. [Laboratory of Inorganic Materials Chemistry, Chemistry Department, University Badji Mokhtar of Annaba, BP: 12, Annaba 23000 (Algeria); Azzaza, S., E-mail: s.azzaza@gmail.com [Laboratory of Magnetism and Spectroscopy of Solids, Department of Physics, University Badji Mokhtar of Annaba, BP: 12, Annaba 23000 (Algeria); Department of Technology, Faculty of Technology, University 20 Août 1955 of Skikda, B.P.26, Route d' El-Hadaiek, Skikda 21000 (Algeria); Chater, R. [Laboratory of Inorganic Materials Chemistry, Chemistry Department, University Badji Mokhtar of Annaba, BP: 12, Annaba 23000 (Algeria); Abbas, H. [Department of Biology, College of Science, University of Bahrain, PO Box 32038 (Bahrain); Bououdina, M. [Nanotechnology Centre, University of Bahrain, PO Box 32038 (Bahrain); Department of Physics, College of Science, University of Bahrain, PO Box 32038 (Bahrain); Bouchelaghem, W. [Laboratory of Inorganic Materials Chemistry, Chemistry Department, University Badji Mokhtar of Annaba, BP: 12, Annaba 23000 (Algeria)

    2015-02-15

    Nanostructured Fe–20Al–2Cr (wt.%) powders have been prepared using high energy planetary ball-mill. Changes in structural, morphological and magnetic properties of the powders during mechanical alloying (MA) and during subsequent annealing have been examined by X-ray diffraction, scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The observed structural and microstructural changes have been related to several processes occurring during MA. After MA, the material becomes significantly disordered and refines to nanoscale grain sizes (~ 14 nm). The obtained bcc α-Fe(Al,Cr) solid solution shows a ferromagnetic behavior. Upon subsequent annealing at 400 °C, α-Fe{sub 2}O{sub 3} and spinel oxides are formed at the surface of particles, while structural defects disappeared as Fe(Al,Cr) solid solution becomes more ordered and grain growth occurs. The saturation magnetization (Ms) shows lower values after annealing, attributed to the formation of metal oxides with low magnetic moment. - Graphical abstract: Display Omitted - Highlights: • Nanostructured Fe–Al–Cr powders were prepared by MA. • Careful analysis of the XRD patterns by using the Rietveld refinement • The lattice distortion is evidenced by the increase of both the lattice parameter and the static Debye Waller parameter. • Annealing at 400 °C stabilizes the microstructure at the nanometer range and leads to the formation of Fe{sub 3}O{sub 4} and Fe{sub 2}O{sub 3} oxides. • Both the milled and annealed samples are ferromagnetic.

  7. Tunnelkontakte mit Heusler-Elektrode: Spinpolarisation von Co 2Cr 0,6Fe 0,4Al und Einfluss der Barriere

    Herbort, Christian

    2010-01-01

    Ziel dieser Arbeit ist die Bestimmung der Spinpolarisation von der Heusler-Verbindung Co2Cr0,6Fe0,4Al. Dieses Ziel wurde durch die sorgfältige Präparation von Co2Cr0,6Fe0,4Al basierten Tunnelkontakten realisiert. Tunnelwiderstandsmessungen an Co2Cr0,6Fe0,4Al-basiertenrnTunnelkontakten ergaben einen Tunnelmagnetowiderstand von 101% bei 4 K. DieserrnTunnelmagnetowiderstand legt eine untere Grenze von 67% für die Spinpolarisation von Co2Cr0,6Fe0,4Al fest.rnrnCo2Cr0,6Fe0,4Al ist eine Heusler-Verb...

  8. Soft X-ray photoemission study of Co2(Cr1−xFex)Ga Heusler compounds

    We have performed soft X-ray photoemission spectroscopy (SXPES) and X-ray absorption spectroscopy (XAS) of the Co-based Heusler compounds Co2(Cr1−xFex)Ga (x = 0.0, 0.4, and 1.0) in order to study their electronic structures. Band-structure calculation was carried out and compared with the experimental results. SXPES spectra show hν-dependence, revealing the contributions of the Co, Cr, and Fe 3d electronic states in the valence band. The band width observed by the SXPES seems to be narrower than that predicted by the band-structure calculation. XAS spectra depend strongly on the value of x in Co2(Cr1−xFex)Ga. The electron correlation effects are found to be stronger as x changes from 0.0 to 1.0. (author)

  9. Electronic and magnetic tunability of Sr2CrReO6 films by growth-mediated oxygen modulation

    Highly ordered epitaxial films of ferrimagnetic semiconductor Sr2CrReO6 (SCRO) have been fabricated by off-axis magnetron sputtering, and characterized as a function of the oxygen partial pressure. In this Letter, we report 18 000% modulation in electrical resistivity at T = 7K (60% at room temperature) from a 1% modulation in the oxygen partial pressure during film growth. The growth window was centered at peak saturation magnetization, which drops due to both increasing and decreasing oxygen growth pressure. The results suggest that n-type doping due to oxygen vacancies plays a dominant role in the electrical properties and modulation of Sr2CrReO6 thin films.

  10. Reversal of the Upper Critical Field Anisotropy and Spin-Locked Superconductivity in K2Cr3As3

    Recently, superconductivity in K2Cr3As3 (Tc =6.1 K) was discovered. The crystalline lattice contains an array of weakly coupled, double well [(Cr3As3)2-]∞ linkages stretched along the c axis, suggesting the possibility of quasi-one-dimensional superconductivity. Moderately anisotropic upper critical field was revealed in single crystals, with very large initial slopes, dH||c2 /dT=12 T/K along the Cr chains and dHperpendicularc2 /dT =7 T/K perpendicular to the chains. Given the ambiguity of conclusions based on the extrapolations of Hc2(T) measured near Tc to low temperatures, we performed high-field measurements of Hc2(T) on K2Cr3As3 single crystals in pulsed magnetic fields which enabled us to reveal the full anisotropic Hc2(T) curves from Tc down to 600 mK.

  11. Effect of heat treatment on the microstructure of a 2CrMoNiWV rotor steel

    Li, Cheng

    1996-01-01

    A wide range of experiments have been carried out on a 2CrMoNiWV low alloy steel to investigate the effect of various heat treatment conditions on microstructural change, alloy carbide transformation mechanism and mechanical properties. Two complete continuous cooling transformation (CCT) diagrams were constructed for this steel on the basis of experimental dilatometry thermal analysis, metallographic examination and current phase transformation theory. The significance of these two ...

  12. Strong-coupling electron-phonon superconductivity in noncentrosymmetric quasi-one-dimensional K$_2$Cr$_3$As$_3$

    Subedi, Alaska

    2015-01-01

    I study the lattice dynamics and electron-phonon coupling in non-centrosymmetric quasi-one-dimensional K$_2$Cr$_3$As$_3$ using density functional theory based first principles calculations. The phonon dispersions show stable phonons without any soft-mode behavior. They also exhibit features that point to a strong interaction of K atoms with the lattice. I find that the calculated Eliashberg spectral function shows a large enhancement around 50 cm$^{-1}$. The phonon modes that show large coupl...

  13. ACUTE TOXICITIES OF CD2+, CR+6, HG2+, NI2+, AND ZN2+ TO ESTUARINE MACROFAUNA

    Static acute toxicity bioassays were conducted at 20 C and 20 o/oo salinity with CdCl2-2 and one half H2O, K2CrO4, HgCl2, NiCl2-6H2O, and ZnCl2 using adults of starfish, Asterias forbesi; sandworm, Nereis virens; hermit crab, Pagurus longicarpus; softshell clam, Mya arenaria; mud...

  14. Depth-resolved magnetic and structural analysis of relaxing epitaxial Sr2CrReO6

    Lucy, Jeremy; Yang, Fengyuan; Hauser, Adam; Liu, Yaohua; Zhou, Hua; Choi, Yongseong; Te Velthuis, Suzanne G. E.; Haskel, Daniel

    2015-03-01

    Structural relaxation in a Sr2CrReO6 epitaxial film, with strong spin-orbit coupling, leads to depth-dependent magnetism. We combine a couple of depth-resolved synchrotron x-ray techniques, including two-dimensional reciprocal space mapping and x-ray magnetic circular dichroism experiments, to demonstrate this effect. An 800 nm film of Sr2CrReO6, grown with tensile epitaxial strain on SrCr0.5Nb0.5O3(200 nm)/LSAT, relaxes away from the Sr2CrReO6/SrCr0.5Nb0.5O3 interface. Grazing incidence x-ray diffraction measurements of the film elucidate the in-plane strain relaxation while depth-resolved x-ray magnetic circular dichroism at the Re L edge reveals the magnetic contributions of the Re site. The smooth relaxation of the film correlates with a systematic change in the magnetism.This provides an interesting and powerful way to probe the depth-varying structural and magnetic properties of a complex oxide with synchrotron-source x-ray techniques. Work supported by the NSF, Grant No. DMR-1420451.

  15. Modeling the Constitutive Relationship of Powder Metallurgy Ti-47Al-2Nb-2Cr Alloy During Hot Deformation

    Sun, Yu; Hu, Lianxi; Ren, Junshuai

    2015-03-01

    In the present work, the isothermal compression tests of PM alloy Ti-47Al-2Nb-2Cr were carried out in the temperature range of 950-1200 °C. A Gleeble 1500D thermosimulation machine was used, and samples were tested at strain rates ranging from 10-3 to 10-1 s-1. Based on the obtained flow stress curves, the hot deformation behavior was presented. The constitutive relationship of powder metallurgy (PM) Ti-47Al-2Nb-2Cr alloy was developed using an Arrhenius-type constitutive model that involves strain compensation in addition to an artificial neural network model. The accuracy and reliability of the developed models were quantified in terms of statistical parameters such as correlation coefficient and absolute value of relative error. It was found that deformation temperature and strain rate have obvious effects on the flow characteristics, and the flow stress increases with the increasing strain rate and the decreasing temperature. Moreover, the proposed models possess excellent prediction capability of flow stresses for the present alloy during hot deformation. Compared with the traditional Arrhenius-type model, the backpropagation neural network model is more accurate when presenting the isothermal compressing deformation behavior at elevated temperatures for PM Ti-47Al-2Nb-2Cr alloy.

  16. Structural and magnetic properties of epitaxial Heusler alloy Fe2Cr0.5Co0.5Si

    This paper reports the study of structural and magnetic properties of Heusler alloy Fe2Cr0.5Co0.5Si (FCCS) thin film and its tunnel magnetoresistance (TMR) effect. The smooth quaternary Heusler alloy FCCS film with surface roughness of rms value of 0.25 nm measured by atomic force microscopy and partial L21 phase was obtained by magnetron sputtering at room temperature followed by in-situ annealing at 400 °C. The saturation magnetization and coercivity of FCCS are 410 emu/cm3 and 20 Oe, respectively. The magnetic tunnel junctions (MTJs) using FCCS as free layer were studied in detail as a function of post-annealing temperature. A TMR ratio of 15.6% has been achieved with 300 °C post-annealing. This is about twice the highest TMR ratio obtained in MTJs using Fe2CrSi. The enhancement of TMR ratio can be attributed to the successful tuning of the Fermi level of Fe2CrSi close to the center of the minority band gap by Co-doping

  17. Giant magnetic anisotropy changes in Sr2CrReO6 thin films on BaTiO3

    The integration of ferromagnetic and ferroelectric materials into hybrid heterostructures leads to systems with improved or even novel functionality. We here discuss the properties of the ferromagnetic double perovskite Sr2CrReO6, deposited as a thin film onto ferroelectric BaTiO3 single crystal substrates via pulsed laser deposition. High resolution X-ray diffraction evidences the high crystalline quality of the epitaxial Sr2CrReO6 layers. Temperature dependent electrical transport and SQUID measurements show abrupt changes both in resistivity and magnetization at the temperatures of the BaTiO3 phase transitions. Furthermore, the coercive field abruptly changes by more than 1.2 T at the BaTiO3 phase transitions. These observations reveal a giant change of the magnetic anisotropy in the Sr2CrReO6 thin film associated with the crystalline phase transitions of the substrate. We attribute these effects to the high sensitivity of the double perovskites to mechanical deformation.

  18. Morphology and magnetoresistance of Co2Cr0.6Fe0.4Al-based tunnelling junctions

    Some ferromagnetic Heusler compounds are theoretically predicted to be half metallic materials, i.e. to be characterized by a huge spin polarization at the Fermi energy. We investigate the correlations between junction preparation conditions, morphology and transport properties of planar MgO/Co2Cr0.6Fe0.4Al/AlOx/Co/CoOx/Pt tunnelling junctions. Epitaxial Co2Cr0.6Fe0.4Al thin films were deposited by dc and rf magnetron sputtering on different buffer layers (Cr, Fe, MgO) on MgO(1 0 0) substrates. By RHEED, LEED and in situ STM investigations different surface morphologies were observed. Atomically flat surfaces with Co2Cr0.6Fe0.4Al unit cell sized steps (B2 structure) were obtained by rf sputtering on MgO substrates with e-beam evaporated MgO buffer layers. However, this morphology results in AlOx tunnelling barriers with improper wetting properties.

  19. Investigation of the electronic, magnetic and optical properties of Co2CrZ (Z = Si, Ge) under pressure—a density functional theory study

    The structural, electronic, magnetic and optical properties of Co-based Heusler compounds, Co2CrZ (Z = Si, Ge), are studied using first-principle density functional theory. The calculations are performed within the generalized gradient approximation. Our calculated structural parameters at 0 GPa agree well with previous available results. The calculated magnetic moment agrees well with the Slater–Pauling (SP) rule. We have studied the effect of pressure on the electronic and magnetic properties of Co2CrSi and Co2CrGe. With an increase in applied pressure, a decrease in cell volume is observed. Under application of external pressure, the valence band and conduction band are shifted downward which leads to a modification of electronic structure. There exists an indirect band gap along Γ–X for both the alloys. Co2CrSi and Co2CrGe retain 100% spin polarization up to 60 and 50 GPa, respectively. The local magnetic moments of the Co and Si (Ge) atoms increase with an increase in pressure whereas the local magnetic moment of the Cr atom decreases. In addition, the optical properties such as dielectric function, absorption spectra, optical conductivity and energy loss function of these alloys have also been investigated. To our knowledge this is the first theoretical prediction of the pressure dependence of the structural, electronic, magnetic and optical properties of Co2CrSi and Co2CrGe. (paper)

  20. Microstructure and mechanical properties of cast Ti-47Al-2Cr-2Nb alloy melted in various crucibles

    Wang Ligang; Zheng Lijing; Cui Renjie

    2012-01-01

    The main factors limiting the mass production of TiAl-based components are the high reactivity of TiAl-based alloys with the crucible or mould at high temperature. In this work, various crucibles (e.g. CaO, Y2O3 ceramic crucibles and water-cooled copper crucible) were used to fabricate the Ti-47Al-2Cr-2Nb alloy in a vacuum induction furnace. The effects of crucible materials and melting parameters on the microstructure and mechanical properties of the alloy were analyzed by means of microstru...

  1. A new oxochromate: SrNi2Cr8O15 of the BaV10O15 type

    A new quaternary oxochromate(III) was prepared by solid state reaction. Single crystal X-ray investigations of SrNi2Cr8O15 show that this compound belongs to the BaV10O15type. [Space group D2h18-Ccmb, a = 10,042; b = 11,413; c = 9,260A; Z = 4.] Ni2+ and Cr3+ occupy the octahedrally coordinated point positions statistically. The surrounding of Sr2+ is similar to the iso- and heteropolyacids. (Author)

  2. X-ray magnetic circular dichroism study of Re 5d magnetism in Sr2CrReO6

    Majewski, P.; Gepraegs, S.; Sanganas, O.; Opel, M.; Gross, R.; Wilhelm, F; Rogalev, A.; Alff, L.

    2006-01-01

    We have measured Re 5d spin and orbital magnetic moments in the ferrimagnetic double perovskite Sr2CrReO6 by X-ray magnetic circular dichroism at the L_{2,3} edges. In fair agreement with recent band-structure calculations [Vaitheeswaran et. al., Ref 1], at the Re site a large 5d spin magnetic moment of -0.68 mu_B and a considerable orbital moment of +0.25 mu_B have been detected. We found that the Curie temperature of the double perovskites A2BB'O6 scales with the spin magnetic moment of the...

  3. Effects of processing variables on the creep behavior of investment cast Ti-48Al-2Nb-2Cr

    Intermetallics based on ordered γ-TiAl are being considered for the replacement of steels and nickel-based superalloys for high temperature aerospace and automotive applications. This study investigates the creep behavior of investment cast Ti-48Al-2Nb-2Cr with microstructures ranging from duplex to nearly lamellar. Constant load creep tests were conducted in air at temperatures of 650 C and 760 C and at stress levels of 104MPa, 155MPa, and 207MPa. The effects of cooling rates during casting, aluminum content, oxygen level, and microstructure on creep properties are discussed. The activation energy for creep and stress exponent are also reported

  4. Ag2CrO4 nanoparticles loaded on two-dimensional large surface area graphite-like carbon nitride sheets: simple synthesis and excellent photocatalytic performance.

    Shi, Lei; Liang, Lin; Wang, Fangxiao; Liu, Mengshuai; Sun, Jianmin

    2016-04-01

    Graphite-like carbon nitride (g-C3N4) with a large surface area was prepared through thermal condensation of guanidine hydrochloride at 650 °C. Various amounts of silver chromate (Ag2CrO4) nanoparticles with small size were highly loaded on the g-C3N4 by a simple co-precipitation method at room temperature. The chemical constituents, surface structure and optical properties of the resultant Ag2CrO4/g-C3N4 composites were thoroughly characterized. And the photocatalytic performances were evaluated by degradation of Rhodamine B (RhB) and phenol, the experimental results indicated that the as-prepared Ag2CrO4/g-C3N4 composites presented excellent photocatalytic activity under visible-light irradiation. With the mass ratio of Ag2CrO4 to g-C3N4 at 1 : 2, the Ag2CrO4/g-C3N4 composites exhibited optimal photocatalytic activity for degrading RhB, approximately 6.1 and 10.4 times higher than those on pure g-C3N4 and bare Ag2CrO4 particles. The improved photocatalytic activity was mainly attributed to the combined effect including the larger surface area, highly dispersed smaller Ag2CrO4 nanoparticles, stronger visible absorption and higher charge separation efficiency of the Ag2CrO4/g-C3N4 composites. Moreover, the possible mechanism for the photocatalytic activity was tentatively proposed. PMID:26937621

  5. Phase diagram of the double perovskite Sr2CrReO6: Effective-field theory

    The double perovskite Sr2CrReO6 has very important characteristics for spintronic applications. It is a ferrimagnetic material distinguished by its high Curie temperature Tc≈635 K. We made this statistical study to further reveal the different ways in which this compound can behave with respect to interaction couplings and crystal fields prevailing in the system. We used as approximation an effective field theory (EFT) without correlation in the context of the Ising model. Thus we report different phase diagrams, firstly in relation to the exchange couplings present in the model adopted, and secondly in relation to the crystal fields of Cr and Re. We compare the results found by this method with those found by other statistical methods. Several phase transitions are detected and reentrant phenomenon was observed. - Highlights: • Phase diagram of double perovskite Sr2CrReO6 has been investigated • The phase diagrams depend on the exchange couplings and the crystal fields • Reentrant phenomenon has been observed

  6. Electronic structure of quasi-one-dimensional superconductor K2Cr3As3 from first-principles calculations.

    Jiang, Hao; Cao, Guanghan; Cao, Chao

    2015-01-01

    The electronic structure of quasi-one-dimensional superconductor K2Cr3As3 is studied through systematic first-principles calculations. The ground state of K2Cr3As3 is paramagnetic. Close to the Fermi level, the Cr-3dz(2), dxy, and d(x(2)-y(2)) orbitals dominate the electronic states, and three bands cross EF to form one 3D Fermi surface sheet and two quasi-1D sheets. The electronic DOS at EF is less than 1/3 of the experimental value, indicating a large electron renormalization factor around EF. Despite of the relatively small atomic numbers, the antisymmetric spin-orbit coupling splitting is sizable (≈60 meV) on the 3D Fermi surface sheet as well as on one of the quasi-1D sheets. Finally, the imaginary part of bare electron susceptibility shows large peaks at Γ, suggesting the presence of large ferromagnetic spin fluctuation in the compound. PMID:26525099

  7. Phase diagram of the double perovskite Sr{sub 2}CrReO{sub 6}: Effective-field theory

    El Rhazouani, O. [LMPHE, URAC 12, Department of Physics, Faculté des Sciences, Université Mohammed V-Agdal, Rabat (Morocco); Benyoussef, A. [LMPHE, URAC 12, Department of Physics, Faculté des Sciences, Université Mohammed V-Agdal, Rabat (Morocco); Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Kenz, A. El, E-mail: elkenz@fsr.ac.ma [LMPHE, URAC 12, Department of Physics, Faculté des Sciences, Université Mohammed V-Agdal, Rabat (Morocco)

    2015-03-01

    The double perovskite Sr{sub 2}CrReO{sub 6} has very important characteristics for spintronic applications. It is a ferrimagnetic material distinguished by its high Curie temperature T{sub c}≈635 K. We made this statistical study to further reveal the different ways in which this compound can behave with respect to interaction couplings and crystal fields prevailing in the system. We used as approximation an effective field theory (EFT) without correlation in the context of the Ising model. Thus we report different phase diagrams, firstly in relation to the exchange couplings present in the model adopted, and secondly in relation to the crystal fields of Cr and Re. We compare the results found by this method with those found by other statistical methods. Several phase transitions are detected and reentrant phenomenon was observed. - Highlights: • Phase diagram of double perovskite Sr{sub 2}CrReO{sub 6} has been investigated • The phase diagrams depend on the exchange couplings and the crystal fields • Reentrant phenomenon has been observed.

  8. 金属切削加工中难加工材料2Cr13的本构模型%Constitutive Model of 2Cr13 for Finite Element Analysis of Chip Formation Process

    李琳; 解丽静; 王西彬; 张之敬

    2009-01-01

    使用准静态压缩实验和切削实验相结合的方法,拟合出2Cr13材料的Johnson-Cook模型.在低应变率范围内采用压缩实验的方法来获得材料模型的系数,使用切削实验来获得高应变率条件下的材料系数.由于压缩实验所能获得的最大应变率仍然比切削实验中所能达到的最低应变率低几个数量级,因此实验采用应变外推的方法来获得符合Johnson-Cook公式应用范围的材料参数.在切屑成形仿真模型中,使用新建立的Jonhson-Cook材料模型,将仿真结果同实验进行对比,验证了模型的准确性.%The prediction accuracy of cutting process simulation is related with the description of nonlinear behavior of material at extremely high strain, strain rate and temperature in machining. An integral Johnson-Cook model was presented herein to characterize the mechanical behavior of work materials in machining, and the parameters in the model were determined by fitting the data from both quasi -static compression and cutting tests. Then the material equation of 2Cr13 stainless steel was derived with this method and used in the finite element model of orthogonal cutting with carbide tools. At last, the simulation results were verified with experimental data.

  9. Tunnel magnetoresistance effect in magnetic tunnel junctions using Fermi-level-tuned epitaxial Fe2Cr1−xCoxSi Heusler alloy

    This paper reports a systematic investigation on the structural and magnetic properties of Fe2Cr1−xCoxSi Heusler alloys with various compositions of x by co-sputtering Fe2CrSi and Fe2CoSi targets and their applications in magnetic tunnel junctions (MTJs). Fe2Cr1−xCoxSi films of high crystalline quality have been epitaxially grown on MgO substrate using Cr as a buffer layer. The L21 phase can be obtained at x = 0.3 and 0.5, while B2 phase for the rest compositions. A tunnel magnetoresistance (TMR) ratio of 19.3% at room temperature is achieved for MTJs using Fe2Cr0.3Co0.7Si as the bottom electrode with 350 °C post-annealing. This suggests that the Fermi level in Fe2Cr1−xCoxSi has been successfully tuned close to the center of band gap of minority spin with x = 0.7 and therefore better thermal stability and higher spin polarization are achieved in Fe2Cr0.3Co0.7Si. The post-annealing effect for MTJs is also studied in details. The removal of the oxidized Fe2Cr0.3Co0.7Si at the interface with MgO barrier is found to be the key to improve the TMR ratio. When the thickness of the inserted Mg layer increases from 0.3 to 0.4 nm, the TMR ratio is greatly enhanced from 19.3% to 28%

  10. Incubation of cocaine cue reactivity associates with neuroadaptations in the cortical serotonin (5-HT) 5-HT2C receptor (5-HT2CR) system.

    Swinford-Jackson, S E; Anastasio, N C; Fox, R G; Stutz, S J; Cunningham, K A

    2016-06-01

    Intensification of craving elicited by drug-associated cues during abstinence occurs over time in human cocaine users while elevation of cue reactivity ("incubation") is observed in rats exposed to extended forced abstinence from cocaine self-administration. Incubation in rodents has been linked to time-dependent neuronal plasticity in the medial prefrontal cortex (mPFC). We tested the hypothesis that incubation of cue reactivity during abstinence from cocaine self-administration is accompanied by lower potency and/or efficacy of the selective serotonin (5-HT) 5-HT2C​ receptor (5-HT2CR) agonist WAY163909 to suppress cue reactivity and a shift in the subcellular localization profile of the mPFC 5-HT2CR protein. We observed incubation of cue reactivity (measured as lever presses reinforced by the discrete cue complex) between Day 1 and Day 30 of forced abstinence from cocaine relative to sucrose self-administration. Pharmacological and biochemical analyses revealed that the potency of the selective 5-HT2CR agonist WAY163909 to suppress cue reactivity, the expression of synaptosomal 5-HT2CR protein in the mPFC, and the membrane to cytoplasmic expression of the 5-HT2CR in mPFC were lower on Day 30 vs. Day 1 of forced abstinence from cocaine self-administration. Incubation of cue reactivity assessed during forced abstinence from sucrose self-administration did not associate with 5-HT2CR protein expression in the mPFC. Collectively, these outcomes are the first indication that neuroadaptations in the 5-HT2CR system may contribute to incubation of cocaine cue reactivity. PMID:26926963

  11. Mössbauer studies of hyperfine fields in disordered Fe2CrAl

    N Lakshmi; K Venugopalan; J Varma

    2002-09-01

    Heusler-like alloy Fe2CrAl was prepared and studied. Structure determination was done by X-ray. The structure was found to conform to the B2 type. Magnetic hyperfine fields in this sample were studied by the Mössbauer effect. The Mössbauer spectra were recorded over a range of temperature from 40 to 296 K. The Mössbauer spectra showed the co-existence of a paramagnetic part with a magnetic hyperfine portion at all recorded temperatures. Even with the distribution in the magnetic hyperfine field, the average hyperfine field follows the $(T=T_{c})^{3/2}$ law. The paramagnetic part of the hyperfine field is explained in terms of the clustering of Cr atoms.

  12. Microstructure of Co2Cr xFe1-xAl thin films for magneto-electronic applications

    Thin films of the Heusler alloy Co2Cr0.6Fe0.4Al have been prepared by means of magnetron sputtering under varying conditions (sputter power, sputter pressure and substrate temperature). All the films are polycrystalline with the cubic B2 structure. The extent of Co-Al antisite defects, lattice constants, internal stress states are influenced by the sputter conditions which is related to differences in the saturation magnetization. The magnetic moment can be increased by additional annealing up to an optimum temperature of 400 deg. C, but does not reach the theoretically predicted value. Above 600 deg. C the metastable B2 phase transforms into either (ε)-Co/Cr or (α)-Co/Cr

  13. Sign reversal of transformation entropy change in Co{sub 2}Cr(Ga,Si) shape memory alloys

    Xu, Xiao, E-mail: xu@material.tohoku.ac.jp; Omori, Toshihiro; Kainuma, Ryosuke [Department of Materials Science, Tohoku University, Sendai 980-8579 (Japan); Nagasako, Makoto [Department of Materials Science, Tohoku University, Sendai 980-8579 (Japan); Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Kanomata, Takeshi [Department of Materials Science, Tohoku University, Sendai 980-8579 (Japan); Research Institute for Engineering and Technology, Tohoku Gakuin University, Tagajo 985-8537 (Japan)

    2015-11-02

    In situ X-ray diffraction (XRD) measurements and compression tests were performed on Co{sub 2}Cr(Ga,Si) shape memory alloys. The reentrant martensitic transformation behavior was directly observed during the in situ XRD measurements. The high-temperature parent phase and low-temperature reentrant parent phase were found to have a continuous temperature dependence of lattice parameter, therefore suggesting that they are the same phase in nature. Moreover, compression tests were performed on a parent-phase single crystal sample; an evolution from normal to inverse temperature dependence of critical stress for martensitic transformation was directly observed. Based on the Clausius-Clapeyron analysis, a sign reversal of entropy change can be expected on the same alloy.

  14. Strong-coupling electron-phonon superconductivity in noncentrosymmetric quasi-one-dimensional K2Cr3As3

    Subedi, Alaska

    2015-11-01

    I study the lattice dynamics and electron-phonon coupling in noncentrosymmetric quasi-one-dimensional K2Cr3As3 using density functional theory based first principles calculations. The phonon dispersions show stable phonons without any soft-mode behavior. They also exhibit features that point to a strong interaction of K atoms with the lattice. I find that the calculated Eliashberg spectral function shows a large enhancement around 50 cm-1. The phonon modes that show large coupling involve in-plane motions of all three species of atoms. The q dependent electron-phonon coupling decreases strongly away from the qz=0 plane. The total electron-phonon coupling is large, with a value of λep=3.0 , which readily explains the experimentally observed large mass enhancement.

  15. Half-metallic behavior and electronic structure of Sr2CrMoO6 magnetic system

    Complex perovskite materials with the A2BB'O6 formula have been recently studied because of their peculiar magnetic and electronic properties. The origin of magnetism in the double perovskite Sr2FeMoO6 brought these properties again into discussion. Recently, a new interaction mechanism was proposed for cases in which the hybridization of 3d and 2p levels of Mo with the 3d Fe levels is responsible for the half-metallic behavior in the Sr2FeMoO6 material. We report on LAPW ab initio calculations within the generalized gradient approximation (GGA) to density functional theory (DFT) for another double perovskite, namely, Sr2CrMoO6. Our results show that this is also a half-metallic system. We correlate our results with an extension of the recent model proposed by Sarma to explain the conduction mechanism in this compound

  16. Conversion electron Moessbauer spectroscopy of epitaxial Co2Cr0.6Fe0.4Al thin films

    Heusler half-metals are promising for spintronic applications. Epitaxial thin films of the exemplar compound Co2Cr0.6Fe0.4Al (CCFA) were investigated using conversion electron Moessbauer spectroscopy to clarify the factors influencing the spin polarization. CCFA films were deposited by rf magnetron sputtering on MgO substrates with and without an Fe buffer layer. Annealing improves their crystallographic order, causes the diffusion of Fe atoms from the Fe buffer layer into the CCFA, and favors the Co-Fe disorder. The listed factors are possible reasons for the increase and subsequent reduction of the tunneling magnetoresistance in CCFA thin films observable across the annealing temperature range

  17. Structure and luminescent properties of Co2+/Cr3+ co-doped ZnGa2O4 nanoparticles

    Co2+/Cr3+ co-doped ZnGa2O4 nanoparticles were prepared by a citrate sol–gel method. Their structure and luminescent properties were studied by using X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and fluorescence spectrophotometer. The nanoparticles with the size of 18–50 nm were obtained when the precursor was annealed at 500 °C or above. Ga3+ ions occupied the octahedral sites as well as the tetrahedral sites, while Cr3+ ions only entered the octahedral sites by replacing Ga3+. The as-synthesized samples had partially inverted spinel structure and the inversion degree slightly decreased with increasing temperature. The Cr3+:ZnGa2O4 sample exhibited an intense emission at 695 nm, corresponding to the 2E→4A2 transition of octahedral Cr3+. The emission intensity of Cr3+ was largely reduced when the sample was co-doped with Co2+. However, the emission intensity of Co2+ in 2% Co/1% Cr co-doped ZnGa2O4 is improved approximately 2 times when compared with 2% co-doped sample. This enhanced emission could be attributed to an efficient energy transfer from Cr3+ to Co2+. The energy transfer mechanism is also discussed. - Highlights: • Co2+/Cr3+: ZnGa2O4 nanoparticles have been synthesized by a citrate sol–gel method. • The chemical environments of Ga3+ and Cr3+ as a function of annealing temperature were studied. • Ga3+ ions occupy both the tetrahedral and octahedral sites of spinel structure in the samples. • The emission intensity of Co2+ is improved by Cr3+ codoping in ZnGa2O4 with 550 nm excitation. • The possible energy transfer process was discussed

  18. Structural, electronic, and magnetic properties of double perovskite Pb2CrMO6 (M=Mo, W and Re) from first-principles investigation

    We use first-principles methods to study double perovskite Pb2CrMO6 (M: some 4d and 5d transition metals), and find that a magnetic I4/m structure is lowest in total energy per formula unit for M=Mo, W, and Re. Our electronic structure investigation shows that the three double perovskite compounds are half-metallic ferrimagnets with total magnetic moments of 2μB, 2μB and 1μB per formula unit, respectively. With the spin–orbit coupling included, our calculations show the high magnetocrystalline anisotropy (MCA) in Pb2CrReO6. Fortunately, the spin polarization of Pb2CrMO6 at the Fermi level remains 90% ∼99%. The orbital moments of 3d Cr and 4d Mo are small, but the 5d ions of W and Re have large unquenched orbital moments, which can be attributed stronger spin–orbit coupling in the 5d orbitals than in 3d/4d ones. In addition, these results are confirmed by using improved exchange–correlation functionals. Furthermore, we calculate the spin exchange constants of the three Pb2CrMO6, and our Monte Carlo simulated Curie temperatures for them are at least 480 K. These materials, when synthesized, should be useful in spintronics. - Highlights: • Our first-principles calculation show that a magnetic I4/m structure is lowest in total energy per formula unit for Pb2CrMO6 (M=Mo, W, and Re). • With spin–orbit coupling included, the spin polarization of Pb2CrMO6 at the Fermi level remains 90%–99%. • The simulated Curie temperature (Tc) values by Monte Carlo method are at least 480 K, which is favorable for potential spintronic applications

  19. Development of improved HP/IP rotor material 2% CrMoNiWV (23 CrMoNiWV 88)

    The new 2% CrMoNiWV steel has a sufficient strength level, a very good creep (rupture) behaviour and an excellent toughness behaviour for a creep resistant steel. Even after long time high temperature exposure the toughness degradation is so small that it is still better than this of best 1% CrMo(Ni)V steels. The fatigue behaviour is well comparable to this of 1% CrMo(Ni)V. The 2% CrMoNiWV steel has the capability to substitute the traditional 1% CrMo(Ni)V. (orig.) With 26 annexes

  20. Experimental determination of UO2(cr) dissolution kinetics: Effects of solution saturation state and pH

    To evaluate the release of uranium from natural ore deposits, spent nuclear fuel repositories, and REDOX permeable reactive barriers (PRB), knowledge of the fundamental reaction kinetics associated with the dissolution of uranium dioxide is necessary. Dissolution of crystalline uranium (IV) dioxide under environmental conditions has been studied for four decades but a cardinal gap in the published literature is the effect of pH and solution saturation state on UO2(cr) dissolution. To resolve inconsistencies, UO2 dissolution experiments have been conducted under oxic conditions using the single-pass flow-through system. Experiments were conducted as a function of total dissolved carbonate ([CO3-3]T) from 0.001 to 0.1M; pH from 7.5 to 11.1; ratio of flow-through rate (q) to specific surface area (S), constant ionic strength (I)=0.1M, and temperatures (T) from 23 to 60oC utilizing both powder and monolithic specimens. The results show that UO2 dissolution varies as a function of the ratio q/S and temperature. At values of log10q/S>-7.0, UO2 dissolution becomes invariant with respect to q/S, which can be interpreted as evidence for dissolution at the forward rate of reaction. The data collected in these experiments show the rate of UO2 dissolution increased by an order of magnitude with a 30oC increase in temperature. The results also show the overall dissolution rate increases with an increase in pH and decreases as the dissolved uranium concentration approaches saturation with respect to secondary reaction products. Thus, as the value of the reaction quotient, Q, approaches equilibrium, K (with respect to a potential secondary phase) the dissolution rate decreases. This decrease in dissolution rate (r) was also observed when comparing measured UO2 dissolution rates from static tests where r=1.7+/-0.14x10-8molm-2s-1 to the rate for flow-through reactors where r=3.1+/-1.2x10-7molm-2s-1. Thus, using traditional static test methods can result in an underestimation of the

  1. Stress and temperature change creep deformation in polycrystalline and polysynthetically twinned Ti-47Al-2Nb-2Cr

    Stress change and temperature change creep tests were conducted on investment cast and HIPed near-γ Ti-47Al-2Nb-2Cr alloy (in the duplex microstructure), and on polysynthetically twinned (PST) crystals prepared from the same alloy. Initial results of shear-compression creep on the PST crystal and polycrystals are compared with data from tensile creep tests. Specimens were deformed at 760--808 C (1,400--1,480 F) at strain rates near 10-7 s-1. The PST crystal was cut so that {111} lamellar planes were parallel to the 45 degree axis in a compression-shear fixture and with left-angle 110 right-angle directions parallel to the principle resolved shear stress. Both specimens exhibited normal transients. The PST crystal exhibited an activation energy of about 150 kJ/mol and a stress exponent of n∼5, with are different from values obtained from the polycrystal deformed under similar conditions (260 kJ/mol, n∼3). These data are discussed in terms of current understanding of creep deformation in the literature

  2. Manganese-mediated ferromagnetism in La2Fe1-Mn2Cr1-O6 perovskite oxides

    R M Tiwari; Mrudul Gadhvi; Abanti Nag; N Y Vasanthacharya; J Gopalakrishnan

    2010-07-01

    We have investigated the structure and magnetic properties of the perovskite oxides of the formula La2Fe1-Mn2Cr1-O6 (0 < < 1.0). For 0 < ≤ 0.5, the members adopt the orthorhombic (Pbnm) structure, where the transition metal atoms are disordered at the 4b sites and the MO6 (M = Fe, Mn, Cr) octahedra become increasingly distorted with increasing . For 0.65 ≤ < 1.0, the members adopt the rhombohedral (R-3c) structure that is similar to LaMnO3+ ( ≥ 0.1) where the MO6 octahedra are undistorted. While the magnetic properties of the latter series are largely similar to the parent LaMnO3+ arising from the double-exchange (DE) between mixed valent MnIII/MnIV, the magnetic properties of the orthorhombic members show a distinct (albeit weak) ferromagnetism (C ∼ 200 K) that seems to arise from a MnIII-mediated superexchange (SE) between FeIII/CrIII in the disordered perovskite structure containing FeIII, MnIII and CrIII.

  3. Coordinated XTE Observations of Coronal Structure and Flares on the Rs CVn Binary Sigma(sup 2) CrB

    Brown, Alexander

    1999-01-01

    This NASA grant supported my RXTE observing and data analysis during AO2. The research involved a 100 kilosecond observation of the active RS CVn binary sigma(sup 2) CrB obtained on 1997 March 11-13. This observation covered two orbits of the binary (2.5 days elapsed time) as part of a coordinated satellite and ground-based study of coronal structure and flaring within this system. Simultaneous data was obtained from the ASCA X-ray satellite and the Very Large Array radio telescope. The one month of effort funded for the PI was used to calibrate and analyze the RXTE data. Additional research effort on this project to lead to a final publication has been provided from LTSA and GSRP grants. An initial attempt was made to calibrate the RXTE data in May 1997 but the results were disappointing with poor background subtraction leading to a relatively noisy PCA light curve. Subsequently major improvements have been made in the calibration techniques for low count rate PCA data and we returned to Goddard Space Flight Center in February 1999 when we were able to produce vastly better calibrated data. The RXTE results are currently being integrated with the ASCA and VLA data and a paper should be submitted by the end of summer 1999.

  4. Dendritic Growth and Microstructure Evolution with Different Cooling Rates in Ti48Al2Cr2Nb Alloy

    Liu, Yi; Hu, Rui; Zhang, Tiebang; Kou, Hongchao; Wang, Jun; Yang, Guang; Li, Jinshan

    2016-01-01

    The influence of cooling rates on the dendritic growth and microstructure evolution of Ti48Al2Cr2Nb alloy is studied by electromagnetic levitation combined with copper mold casting. The different cooling rates of the conical as-cast sample with diameters from 4.7 to 0.8 mm were calculated by ANSYS software. The results show that primary dendrite arm spacing decreases with increase in cooling rate. Peritectic transformation (L + β → α) and the transformation of α → (α2 + γ) are restrained at cooling rate of 2.3 × 104 K s-1. With further increase in cooling rate (2.6 × 104 K s-1), a fine and homogeneous microstructure can be observed in the conical casting sample with the diameter of 0.8 mm. It consists of a large amount of massive γ phase, lath-like γ phase, and only few lamellar structures (α2 + γ). The formation of the microstructure in the alloy is attributed to the strong chilling, giving rise to the high undercooling and the high dislocation density during rapid solidification.

  5. A mixture of massive and feathery microstructures of Ti48Al2Cr2Nb alloy by high undercooled solidification

    A mixture of massive and feathery microstructures was observed in Ti48Al2Cr2Nb alloy subjected to the undercooled solidification rather than the heat treatments in most cases. Double recalescence events and primary β solidification confirmed that massive γ phase did not directly nucleate from the undercooled melt but formed during the solid-state transformations. It is believed that small white areas (aluminium-poor) along lamellar grain boundaries may be closely related to the formation of massive γ phase and feathery γ phase. High dislocation density and stacking faults were detected in massive γ phase by transmission electron microscopy. The high energy of defects and undercooling in the solid state phase transformation can provide sufficiently high driving force for the nucleation of massive γ phase. - Graphical abstract: Display Omitted - Highlights: • A mixture of massive and feathery microstructures was observed. • Massive γ formed during the solid-state transformations. • Defects and undercooling provide driving force for the nucleation of massive γ

  6. Electrochemical treatment of heavy metals (Cu2+, Cr6+, Ni2+) from industrial effluent and modeling of copper reduction.

    Hunsom, M; Pruksathorn, K; Damronglerd, S; Vergnes, H; Duverneuil, P

    2005-02-01

    An electrochemical technique was tested in a laboratory scale to treat heavy metals (Cu2+, Cr6+ and Ni2+) from plating industrial effluent. The experiments were performed in a membrane reactor having a capacity of 1 l. Stainless-steel sheets with surface area of 0.011 m2 and titanium coated with ruthenium oxide were used as cathode and anode, respectively. The electrolyte was circulated at a constant flow rate (0.42 l/min) and the pH was kept constant at 1. Applied current densities were 10 and 90 A/m2. According to the experiment, it was found that a membrane reactor with plane electrode was capable for treating plating wastewater with low energy consumption (42.30 kWh/kg metal) and low operating cost (5.43 US dollars/m3). More than 99% of metal reduction was achieved and the final concentrations of copper, chromium and nickel in treated water were 0.10-0.13, 0.19-0.20 and 0.05-0.13 ppm, respectively. The brightener had no effect on copper reduction whereas hexavalent chromium had strong effect. The kinetic of copper reduction in the presence of hexavalent chromium was modeled as a two-step process with respect to copper concentration. PMID:15707634

  7. Widmannstätten laths in Ti48Al2Cr2Nb alloy by undercooled solidification

    Liu, Yi; Hu, Rui, E-mail: rhu@nwpu.edu.cn; Yang, Guang; Kou, Hongchao; Zhang, Tiebang; Wang, Jun; Li, Jinshan

    2015-09-15

    Widmannstätten laths in Ti48Al2Cr2Nb alloy were obtained by containerless electromagnetic levitation during undercooled solidification rather than heat treatments in most cases. The nucleation of γ{sub Widmannstätten} is confirmed by the thermal history of the second recalescence behaviour. High dislocation density, stacking faults and dislocation slip are observed by transmission electron microscopy. By quantitative analysis of the transformation energy, the driving force for γ{sub Widmannstätten} in the solid state phase transformation is calculated, compared with that of heat treatments. Meanwhile, the proper undercoolings (ΔT = 257–300 K), post-solidification cooling rates (11.1–29.1 K/s), the fine lamellar colony sizes (306–467 μm) and proper undercoolings in the solid state phase transformation are in favour of promoting the formation of Widmannstätten laths at moderate undercoolings. - Graphical abstract: Display Omitted - Highlights: • Widmannstätten laths were observed in undercooled TiAl alloy. • The influencing factors were discussed in undercooled TiAl alloy. • An analysis of the nucleation of γ{sub Widmannstätten} is carried out.

  8. Moessbauer study of epitaxial Co2Cr0.6Fe0.4Al thin films

    Epitaxial thin films of the promising for spintronic applications Heusler half-metallic compound Co2Cr0.6Fe0.4Al (CCFA) were investigated using conversion electron Moessssbauer spectroscopy (CEMS) in order to get insight into the structural and magnetic properties. Thin films of 100 nm thickness were deposited by rf magnetron sputtering on MgO substrates without and with 10 nm Fe buffer layer. We discuss a correlation between the annealing temperature and the structural disorder and hyperfine fields on Fe atoms measured by Moessbauer spectroscopy. Samples prepared at the optimum annealing temperature as determined by tunneling magnetoresistance measurements show the optimum degree of order on the Fe sites as determined by CEMS. Additionally, we observed evidence for a diffusion of Cr atoms from the CCFA thin film into the Fe buffer layer and the related diffusion of Fe atoms from the buffer into the CCFA film. Thus the thermal treatment changes the Fe to Cr ratio of the Heusler compound additional to influencing the degree of disorder on the Fe/Cr sites

  9. Structural and optical properties of crystalline and nanocrystalline NaIn(WO4)2:Cr3+

    Highlights: • Optical properties are summarized for single crystals and nanopowders of NaIn(WO4)2:Cr. • EPR properties are compared in terms of different site occupation of Cr ion in the NaIn(WO4)2 matrix. • The changes in the PL and ESR properties of the nanopowders vs. their decreasing size are studied. • An increase of isolated ions with temperature at the expense of chromium complexes is observed. • Magnetic susceptibility and moment of the powders are discussed in terms of Cr substitution. -- Abstract: EPR and optical spectra of chromium doped NaIn(WO4)2 single crystals and nanopowders have been measured. The resonance EPR measurements have been performed for two crystal orientations in respect to the magnetic field and analyzed in terms of various Cr3+ ion site occupancies in the crystal lattice. They have been structurally and optically identified. The changes in the photoluminescence and electron spin resonance properties of the nanoparticles vs. their decreasing size have also been studied. Magnetic susceptibility and effective magnetic moment of the nanopowders were measured and discussed in terms of chromium substitution. Comparisons between chromium substitution in single crystals and nanopowders have been performed

  10. Analysis of cross-weld creep rupture data on the 1/2Cr1/2Mo1/4V type IV zone

    For the ferritic steel 1/2Cr1/2Mo1/4V, the operating experience of medium and long term creep failures in power station welds has been of cavitation and cracking in the heat affected zone (HAZ) adjacent to the parent material, in what is referred to as the Type IV zone. This experience has led to the generation of uniaxial cross-weld creep rupture data on 1/2CrMoV weldments and to the development of life assessment procedures such as R5 Volume 7, which uses the rupture strength of the Type IV zone to calculate the life of power station components. Recently, the ECCC Working Group 3A has conducted a collation of the UK and German cross-weld creep rupture data on 1/2CrMoV weldments. Creep failure in 1/2CrMoV cross-weld specimens occurs in a variety of weldment zones; typically in the parent, the Type IV zone or the weld metal. Post test examination of the specimens has enabled those tests that failed in the Type IV zone to be identified and a creep rupture data assessment has been performed to derive a new model for the rupture strength of the Type IV zone.

  11. Effect of Cr incorporation on the structural and optoelectronic properties of TiO{sub 2}:Cr deposited by means of a magnetron co-sputtering process

    Hajjaji, A. [Photovoltaic Laboratory Research and Technology Centre of Energy, Borj-Cedria Science and Technology Park, BP 95, 2050 Hammam-Lif (Tunisia); Institut National de la Recherche Scientifique, INRS-Energie, Materiaux et Telecommunications, 1650, Blvd. Lionel-Boulet, Varennes, Quebec J3X 1S2 (Canada); Gaidi, M., E-mail: mounir.gaidi@crten.rnrt.tn [Photovoltaic Laboratory Research and Technology Centre of Energy, Borj-Cedria Science and Technology Park, BP 95, 2050 Hammam-Lif (Tunisia); Bessais, B. [Photovoltaic Laboratory Research and Technology Centre of Energy, Borj-Cedria Science and Technology Park, BP 95, 2050 Hammam-Lif (Tunisia); El Khakani, M.A. El, E-mail: elkhakani@emt.inrs.ca [Institut National de la Recherche Scientifique, INRS-Energie, Materiaux et Telecommunications, 1650, Blvd. Lionel-Boulet, Varennes, Quebec J3X 1S2 (Canada)

    2011-10-01

    In this work, we report on the effect of Cr incorporation on the microstructural and optical properties of TiO{sub 2}:Cr thin films deposited by the RF-magnetron sputtering method. The structural, morphological, chemical bonding and optoelectronic properties of the sputter-deposited TiO{sub 2}:Cr films were systematically investigated, as a function the incorporated Cr content, by means of various techniques including X-ray diffraction (XRD), atomic force microscopy (AFM), Fourier-Transform Infra-Red (FTIR) absorption, X-ray Photoelectron Spectroscopy (XPS) and ellipsometry. The Cr incorporation into the TiO{sub 2} films was controlled by adjusting the RF power (P{sub Cr}) on the Cr target during the co-sputtering process of TiO{sub 2} and Cr. We were thus able to demonstrate that by varying P{sub Cr} from 8 W to 150 W, the Cr content of the TiO{sub 2}:Cr films can be fairly controlled from {approx}2 at.% to {approx}18 at.% and their associated bandgap engineered from 3.3 eV to 1.5 eV. The room-temperature deposited TiO{sub 2}:Cr are mainly amorphous with the presence of some TiO{sub 2} nanocrystallites, and their density increases as their Cr content is increased. The Cr inclusions were found to coexist under both metallic and oxidized forms in the films. By subjecting the TiO{sub 2}:Cr films to post-annealing treatment (at 550 deg. C), their crystalline structure was found to be sensitive to their Cr content. Indeed, an anatase-to-rutile phase transformation has been pointed out to occur at a Cr content of {approx}7 at.%. Likewise, the Cr-content dependence of the bandgap of annealed TiO{sub 2}:Cr films undergoes a transition around the 7 at.% of Cr. Our results demonstrate the ability to control the Cr-content of TiO{sub 2}:Cr films, which leads to tune their optoelectronic properties, such as bandgap or optical absorption edge.

  12. Effect of Cr incorporation on the structural and optoelectronic properties of TiO2:Cr deposited by means of a magnetron co-sputtering process

    In this work, we report on the effect of Cr incorporation on the microstructural and optical properties of TiO2:Cr thin films deposited by the RF-magnetron sputtering method. The structural, morphological, chemical bonding and optoelectronic properties of the sputter-deposited TiO2:Cr films were systematically investigated, as a function the incorporated Cr content, by means of various techniques including X-ray diffraction (XRD), atomic force microscopy (AFM), Fourier-Transform Infra-Red (FTIR) absorption, X-ray Photoelectron Spectroscopy (XPS) and ellipsometry. The Cr incorporation into the TiO2 films was controlled by adjusting the RF power (PCr) on the Cr target during the co-sputtering process of TiO2 and Cr. We were thus able to demonstrate that by varying PCr from 8 W to 150 W, the Cr content of the TiO2:Cr films can be fairly controlled from ∼2 at.% to ∼18 at.% and their associated bandgap engineered from 3.3 eV to 1.5 eV. The room-temperature deposited TiO2:Cr are mainly amorphous with the presence of some TiO2 nanocrystallites, and their density increases as their Cr content is increased. The Cr inclusions were found to coexist under both metallic and oxidized forms in the films. By subjecting the TiO2:Cr films to post-annealing treatment (at 550 deg. C), their crystalline structure was found to be sensitive to their Cr content. Indeed, an anatase-to-rutile phase transformation has been pointed out to occur at a Cr content of ∼7 at.%. Likewise, the Cr-content dependence of the bandgap of annealed TiO2:Cr films undergoes a transition around the 7 at.% of Cr. Our results demonstrate the ability to control the Cr-content of TiO2:Cr films, which leads to tune their optoelectronic properties, such as bandgap or optical absorption edge.

  13. {[Na1(μ-H2O)Na2]2[(C2O4)2Cr(μ-OH)2Cr(C2O4)2]·H2O} n , a novel hydrated form

    Bélombé, Michel M.; Nenwa, Justin; Ngoune, Jean; Álvarez, Eleuterio; Galindo, Agustín

    2010-01-01

    The unit cell of the title compound, poly[[μ-aqua-μ-hydroxido-di-μ-oxalato-chromium(III)disodium] monohydrate], {[CrNa2(C2O4)2(OH)(H2O)]·H2O} n , contains four [Na1(μ-H2O)Na2][(C2O4)2Cr(μ-OH)·H2O] formula units, each of which consists of two crystallographically independent Na+ sites (bridged by one aqua ligand), one half of a centrosymmetric di-μ-hydroxido-bis­[cis-bis­(oxalato)chromate(III)] dimer, [(C2O4)2Cr(μ-OH)2Cr(C2O4)2]4−, and one uncoordin­ated water mol­ecule. The structure is best ...

  14. Optical properties and electronic structure of alloys Co2Cr1- x Fe x Al ( x = 0, 0.4, 0.6, 1.0)

    Shreder, E. I.; Lukoyanov, A. V.; Marchenkov, V. V.

    2016-01-01

    The results of the investigation of the optical properties and calculations of the density of states N( E) of the Heusler alloys Co2Cr1- x Fe x Al ( x = 0, 0.4, 0.6, 1.0) have been presented. It has been found that the band spectrum substantially changes, especially in the vicinity of the Fermi level, due to the concentration transition from Co2FeAl to Co2CrAl. These changes are accompanied by significant changes in the optical properties. The optical properties of the Co2FeAl alloy are typical of metals. The anomalous behavior of the optical properties of the alloys with x = 0, 0.4, and 0.6 is determined by the electronic states at the Fermi level.

  15. High-pressure structural behavior of the double perovskite Sr2CrReO6: an experimental and theoretical study

    Olsen, J.S.; Gerward, Leif; Vaitheeswaran, G.;

    2009-01-01

    The high-pressure structural behavior of Sr2CrReO6 has been studied experimentally using synchrotron radiation and the diamond anvil cell and theoretically using density functional theory. The experimental zero-pressure bulk modulus is B0=1704GPa and the pressure derivative is B0'=4.71.0. These r......The high-pressure structural behavior of Sr2CrReO6 has been studied experimentally using synchrotron radiation and the diamond anvil cell and theoretically using density functional theory. The experimental zero-pressure bulk modulus is B0=1704GPa and the pressure derivative is B0......'=4.71.0. These results compare well with the calculated values 172.6GPa and 5.7. A pseudo-cubic unit cell can describe the crystal structure at low pressure, but the tetragonal structure becomes evident at high pressure....

  16. Microstructure and composition of cast Ti-47Al-2Cr-2Nb alloys produced by yttria crucibles

    Cui, R.J.; Tang, X.X.; Gao, M. [School of Materials Science and Engineering, Beihang University, No. 37, Xueyuan Road, Beijing 100191 (China); Zhang, H., E-mail: zhanghu@buaa.edu.cn [School of Materials Science and Engineering, Beihang University, No. 37, Xueyuan Road, Beijing 100191 (China); Gong, S.K. [School of Materials Science and Engineering, Beihang University, No. 37, Xueyuan Road, Beijing 100191 (China)

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer Second-generation {gamma}-TiAl alloys were melted and allowed to solidify in yttria crucibles. Black-Right-Pointing-Pointer The effects of processing parameters on the microstructure and composition of the cast alloys were investigated. Black-Right-Pointing-Pointer The cubic crystal structure of {beta} phase was the primary solidification phase and there were three microsegregations in the lamellar microstructure. Black-Right-Pointing-Pointer A kinetic view of the transport processes and interactions between the melt and the crucible was given. Black-Right-Pointing-Pointer The increase of oxygen concentration in TiAl melts was governed by a rate equation of dc{sub t}/d{tau}=-KA(c{sub 0}-c{sub s})/V. - Abstract: In this work, second-generation {gamma}-TiAl alloys with chemical compositions of Ti-47Al-2Cr-2Nb (at.%) with an initial oxygen concentration of 0.05 wt% were melted with different melting parameters (temperatures and times) and allowed to solidify in yttria crucibles. The microstructure and composition of the cast alloys were investigated, using back-scattered scanning electron microanalysis (BSE), transmission electron microscopy (TEM), energy dispersive spectrometry (EDS) and chemical composition analysis. The microstructure observations and composition analysis showed that {beta} phase was the primary solidification phase and there were three microsegregations in the metal matrix, i.e. single {gamma} phase, remaining {beta} phase and yttria inclusions. There was not a clear change in the morphology of {beta} phase and the lamellar spacing as melting parameters were changed, while the size and morphology of the yttria inclusions depend on melting parameters. Lower melt temperature and shorter interaction time result in the formation of near-equiaxed yttria particles. Higher melt temperature and longer interaction time lead to the formation of coarser and elongated ribbon-like particles. The oxygen content and the

  17. Magnetic tunneling junctions with the Heusler compound Co2Cr0.6Fe0.4Al

    Materials with large spin polarization are required for applications in spintronics devices. For this reason, major research efforts are directed to study the properties of compounds which are expected to be half metals, i.e. materials with 100% spin polarization. Half metals are expected to have a gap in the density of states at the Fermi energy for one spin band while the other spin band is metallic leading to a completely spin polarized current. The ferromagnetic full Heusler alloy Co2Cr0.6Fe0.4Al (CCFA) has attracted great interest in the field of spintronics. The high Tc (800 K) and the expected half metallicity make CCFA a good candidate for applications in spintronic devices such as magnetic tunneling junctions (MTJs). This thesis presents the results of the study of the electronic and structural properties of CCFA thin films. The films were implemented in magnetic tunneling junctions and the tunneling magnetoresistance effect (TMR) was investigated. The main objectives were the measurement of the spin polarisation of the CCFA alloy and to obtain information about its electronic structure. The influence of the deposition conditions on the thin film properties and on the surface crystalline order and their respective influence on the TMR ratio was investigated. Epitaxial CCFA thin films with two alternative growth orientations were deposited on different substrates and buffer layers. An annealing step was used to improve the crystalline properties of the thin films. In the tunneling junctions, Al2O3 was used as a barrier material and Co was chosen as counter electrode. The multilayer systems were patterned in Mesa structures using lithographic techniques. In the framework of the Julliere model, a maximum spin polarisation of 54% at 4K was measured in tunneling junctions with epitaxial CCFA electrodes. A strong influence of the annealing temperature on the TMR ratio was determined. The increase of the TMR ratio could be correlated to an improvement of the

  18. The Influence of Microalloying and Thermal Treatment on Mechanical Properties of Billets and Pipes Prepared from Microalloyed Steel C0.2Mn2Cr1

    The influence of doping with Ca, Ba and B on processing and mechanical properties of tubes prepared from steel C0.2Mn2Cr1 was investigated. Significant increase of plasticity and impact strength was observed. Optimal technological parameters of broaching and reducing processes for obtaining high strength was established and the critical reduction needed for cavity formation at the tip of mandrel was determined. Cavity formation parameters were established via hot-twisting and tapered sample rolling tests. (author)

  19. FP-LMTO investigation of the structural, electronic and agneticproperties of Heusler compounds Ru2CrZ (Ge, Sn, Si)

    Elchikh M.; Bahlouli S.; Aarizou Z.

    2013-01-01

    The electronic structure of the antiferomagnetic full Heusler alloys Ru2CrZ (Ge, Sn, Si) have been studied by first principal calculations using Full-Potential linearized Muffin Tin Orbital (FP-LMTO) method based on the generalized Gradient Approximation (GGA). It was shown that obtained equilibrium lattice parameters agree well with available experimental data. The influence of Z-elements on the electronic structure and magnetic properties of these compounds is analysed.

  20. FP-LMTO investigation of the structural, electronic and agneticproperties of Heusler compounds Ru2CrZ (Ge, Sn, Si

    Elchikh M.

    2013-03-01

    Full Text Available The electronic structure of the antiferomagnetic full Heusler alloys Ru2CrZ (Ge, Sn, Si have been studied by first principal calculations using Full-Potential linearized Muffin Tin Orbital (FP-LMTO method based on the generalized Gradient Approximation (GGA. It was shown that obtained equilibrium lattice parameters agree well with available experimental data. The influence of Z-elements on the electronic structure and magnetic properties of these compounds is analysed.

  1. Ab Initio Research on a New Type of Half-Metallic Double Perovskites, A2CrMO6 (A = IVA Group Elements; M = Mo, Re and W

    Yun-Ping Liu

    2014-03-01

    Full Text Available The research based on density functional theory was carried out using generalized gradient approximation (GGA for full-structural optimization and the addition of the correlation effect (GGA + U (Coulomb parameter in a double perovskite structure, A2BB’O6. According to the similar valance electrons between IIA(s2 and IVA(p2, IVA group elements instead of alkaline-earth elements settled on the A-site ion position with fixed BB' combinations as CrM (M = Mo, Re and W. The ferrimagnetic half-metallic (HM-FiM properties can be attributed to the p-d hybridization between the Crd-Mp and the double exchange. All the compounds can be half-metallic (HM materials, except Si2CrMoO6, Ge2CrMo and Ge2CrReO6, because the strong-correlation correction should be considered. For M = W, only A = Sn and Pb are possible candidates as HM materials. Nevertheless, an examination of the structural stability is needed, because Si, Ge, Sn and Pb are quite different from Sr. All compounds are stable, except for the Si-based double perovskite structure.

  2. Structural characterization and complex impedance studies on fast ion conducting mixed system (SbI3)–(Ag2CrO4)1−

    S Austin Suthanthiraraj; S Sarojini

    2013-12-01

    This paper deals with preparation and physico-chemical characterization of a new mixed system, (SbI3)–(Ag2CrO4)1− (0.1 ≤ ≤ 0.9), undertaken with a view to evaluate silver ion transport properties and identify those fast ion conducting compositions. Polycrystalline samples of various compositions were synthesized by rapid melt-quenching method. Powder X-ray diffraction (XRD) analysis in conjunction with differential scanning calorimetry (DSC) and electrical transport evaluation involving silver ionic transport number and temperaturedependent electrical complex impedance measurements were carried out in order to identify the different phases responsible for the conduction mechanism. Realization of a fast ionic conductivity value of 3.2 × 10-2 S cm-1 in the case of the composition, (SbI3)0.3–(Ag2CrO4)0.7, at room temperature due to silver ion transport has been discussed in terms of observed structural and thermal characteristics. A detailed analysis of conductivity spectra pertaining to the best conducting system, (SbI3)0.3–(Ag2CrO4)0.7, has also been presented.

  3. Vacancy-induced insulator - direct spin gapless semiconductor - half-metal transition in double perovskite La2CrFeO6: A first-principles study

    Wu, Haiping; Qian, Yan; Tan, Weishi; Kan, Erjun; Lu, Ruifeng; Deng, Kaiming

    2015-11-01

    Double perovskite oxide La2CrFeO6 with the characteristic of ferrimagnetic insulator has been reported by Chakraverty and Lee et al. Engineering the physical properties of materials, including obtaining unusual properties, can be achieved by some measures, and defect-tuning has been one of the most efficient measures. Here, by using density-functional calculations, La vacancy is introduced in La2CrFeO6 and special properties are obtained successfully. The results show that the magnetic phase of La2CrFeO6 would transfer from ferrimagnetic to ferromagnetic ordering as long as La vacancy is introduced. Furthermore, La1.75CrFeO6 shows direct spin gapless semiconductor, and La1.5CrFeO6 behaves as half-metal with the half-metallic gap of 0.42 eV. In the whole range of La vacancy, the electronic configurations of both Cr and Fe ions exhibit high-spin states, the magnetic moment of Fe remains 4.20 μB, while that of Cr ions decreases from 2.66 to 1.97 μB with increasing the amount of La vacancy. This work opens an alternative way to design spintronic materials, especially for direct spin gapless semiconductors which have never been reported in perovskite oxides.

  4. Morphology and magnetoresistance of Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al-based tunnelling junctions

    Herbort, C; Arbelo, E; Jourdan, M, E-mail: jourdan@uni-mainz.d [Institute of Physics, Johannes Gutenberg University, 55099 Mainz (Germany)

    2009-04-21

    Some ferromagnetic Heusler compounds are theoretically predicted to be half metallic materials, i.e. to be characterized by a huge spin polarization at the Fermi energy. We investigate the correlations between junction preparation conditions, morphology and transport properties of planar MgO/Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al/AlO{sub x}/Co/CoO{sub x}/Pt tunnelling junctions. Epitaxial Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al thin films were deposited by dc and rf magnetron sputtering on different buffer layers (Cr, Fe, MgO) on MgO(1 0 0) substrates. By RHEED, LEED and in situ STM investigations different surface morphologies were observed. Atomically flat surfaces with Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al unit cell sized steps (B2 structure) were obtained by rf sputtering on MgO substrates with e-beam evaporated MgO buffer layers. However, this morphology results in AlO{sub x} tunnelling barriers with improper wetting properties.

  5. 新型低碳马氏体弹簧钢35Si2CrVB的研究%Study on New Low Carbon Martensite Spring Steel

    黎业生; 饶克

    2001-01-01

    传统中、高碳弹簧钢在性能、生产和使用上存在许多缺点,为适应汽车工业发展的需要,研究了碳含量较低的新型低碳马氏体弹簧钢35Si2CrVB。经与传统弹簧钢60Si2MnA相比较,该钢不仅有高的强度、塑韧性,良好的综合力学性能,而且具有低的脱碳敏感性、高的淬透性和高的弹减抗力等。显微组织观察发现,由于35Si2CrVB钢的含碳量降低,其淬火组织发生了变化,几乎全是具有高位错密度的板条状马氏体,而只有极少量孪晶结构的片状马氏体。%The traditional middle and high carbon spring steels have some drawbacks in properties,production and application,in order to meet the demands of rapid development of automobile,therefore,a new low carbon spring steel 35Si2CrVB has been investigated.Comparing the new spring steel 35Si2CrVB with the traditional spring steel 60Si2MnA it is shown that the new spring steel has not only high strength,good ductility,good comprehensive mechanical properties,but also low decarbonization tendency,sufficient hardenability and high elastic sag resistance etc.The microstructure change in quenched steel,caused by the decreasing of carbon content,was detected through metallographic observation.The new low carbon spring steel 35Si2CrVB after quenching is composed of almost lath martensite with high dislocation density and only a little plaste martensite with twins structure.

  6. Biogeochemical Cycling

    Bebout, Brad; Fonda, Mark (Technical Monitor)

    2002-01-01

    This lecture will introduce the concept of biogeochemical cycling. The roles of microbes in the cycling of nutrients, production and consumption of trace gases, and mineralization will be briefly introduced.

  7. Sulfur cycle

    LokaBharathi, P.A.

    Microbes, especially bacteria, play an important role in oxidative and reductive cycle of sulfur. The oxidative part of the cycle is mediated by photosynthetic bacteria in the presence of light energy and chemosynthetic forms in the absence of light...

  8. The double perovskite oxide Sr2CrMoO(6-δ) as an efficient electrocatalyst for rechargeable lithium air batteries.

    Ma, Zhong; Yuan, Xianxia; Li, Lin; Ma, Zi-Feng

    2014-12-01

    A double perovskite oxide Sr2CrMoO6-δ (SCM), synthesized using the sol-gel and annealing method with the assistance of citric acid and ethylene diamine tetraacetic acid, was investigated for the first time as an efficient catalyst for rechargeable lithium air batteries. The SCM cathode enables higher specific capacity, lower overpotential and a much better cyclability compared to the pure Super P electrode owing to its excellent electrocatalytic activity towards the formation/decomposition of Li2O2. PMID:25325080

  9. Investigations on intercrystalline resistance of plasma arc-welded coating materials X 2 CrNiNb 19 9 and S-NiCr 20 Nb

    The resistance to intercrystalline corrosion (IC) has been tested on single and double layer plasma arc-weldings of austenite steel X2CrNiNb199 as well as the alloy inconel 82 (S-NiCr 20 Nb) using short-term testing methods. The austenite platings can be considered as IC resistant. The inconel alloy tends to selective corrosion in the potential range of -30 to +30 mVEsub(H), the areas of greater precipitation are particularly attacked. (GSCH)

  10. CYCLIC OXIDATION OF Ti-48%Al-2%Cr-2%Nb-(0~1%)W ALLOYS BETWEEN 800 AND 1000°C IN AIR

    SANG-HWAN BAK; DONG YI SEO; SEON-JIN KIM; JAE CHUN LEE; DONG BOK LEE

    2010-01-01

    Ti-48%Al-2%Cr-2%Nb-(0, 0.5, 1) at.%W alloys were synthesized via the powder metallurgical route, and cyclically oxidized at 800, 900, or 1000°C in air for up to 100 h in order to find the effects of W on their oxidation characteristics. At 800°C, they oxidized relatively slowly, and the scales were thin and adherent. At 900°C, the scales began to spall locally. At 1000°C, they spalled repetitively during oxidation. Cr, Nb, and W improved the cyclic oxidation resistance of TiAl alloys. The oxi...

  11. Brillouin light scattering study of Co$_{2}$Cr$_{0.6}$Fe$_{0.4}$Al and Co$_{2}$FeAl Heusler compounds

    Gaier, O.; Hamrle, J.; Trudel, S; Parra, A. Conca; Hillebrands, B.; Arbelo, E.; Herbort, C.; Jourdan, M

    2008-01-01

    The thermal magnonic spectra of Co$_{2}$Cr$_{0.6}$Fe$_{0.4}$Al (CCFA) and Co$_2$FeAl were investigated using Brillouin light scattering spectroscopy (BLS). For CCFA, the exchange constant A (exchange stiffness D) is found to be 0.48 $\\mu$erg/cm (203 meV A$^2$), while for Co$_2$FeAl the corresponding values of 1.55 $\\mu$erg/cm (370 meV A$^2$) were found. The observed asymmetry in the BLS spectra between the Stokes and anti-Stokes frequencies was assigned to an interplay between the asymmetrica...

  12. Corrosion characteristics of Zr-0.8Sn-0.4Fe-0.2Cr-xNb system with the variation of intermediate annealing temperature

    To investigate the effects of Nb content and annealing parameter on corrosion resistance in Zr-0.8Sn-0.4Fe-0.2Cr-xNb (x=0.1, 0.2, 0.4, 0.8%) alloys, corrosion tests have been carried out under the 400 degree C steam condition. The corrosion resistance of the alloys decreased with increasing the Nb content and the accumulated annealing parameter. But the Nb content in precipitates and the hydrogen pick-up fraction in matrix increased when the adding Nb content and the accumulated annealing parameter increased. The fraction of t-ZrO2 in oxide layers decreased with increasing the accumulated annealing parameter. It was concluded that the corrosion resistance of Zr-0.8Sn-0.4Fe-0.2Cr-xNb alloys could be controlled by the characteristics of (Zr, Nb)(Fe, Cr)2 type precipitates with the variation of the Nb content and the accumulated annealing parameter

  13. Antioxidative role of selenium against the toxic effect of heavy metals (Cd+2, Cr+3) on liver of rainbow trout (Oncorhynchus mykiss Walbaum 1792).

    Talas, Zeliha Selamoglu; Orun, Ibrahim; Ozdemir, Ilknur; Erdogan, Kenan; Alkan, Aysel; Yilmaz, Ismet

    2008-09-01

    The main purpose of this study is to discuss the effect of Cd+2, Cr+3 and Se metals on biochemical parameters in liver tissue of Oncorhynchus mykiss. The rainbow trout were exposed to heavy metal stress (Cd+2, Cr+3) at 2 ppm dosage. The present study was undertaken to determine the protective effect of selenium treatment at the same dosage (2 ppm) on some biochemical parameters. The activity of catalase (CAT), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and the changes in levels of malondialdehyde (MDA) from biochemical parameters were determined in liver tissue of the fish groups exposed to heavy metals, especially for the selenium-applied groups. Results of this study showed that the activities of CAT, GSH-Px and SOD in the tissues of fish exposed to the stress of Cd+2 and Cr+3 were significantly lower than the control groups (P metal stress, whereas significant decreases were obtained in selenium-applied groups. The result of the statistical evaluation showed that the negative effects occurring in the biochemical parameters of the applied groups exposed to the toxicity of heavy metal were significantly eliminated (P < 0.05) as a result of selenium treatment. PMID:18665459

  14. Effects of the preparation method on the structure and the visible-light photocatalytic activity of Ag2CrO4

    Difa Xu

    2014-05-01

    Full Text Available Silver chromate (Ag2CrO4 photocatalysts are prepared by microemulsion, precipitation, and hydrothermal methods, in order to investigate the effect of preparation methods on the structure and the visible-light photocatalytic activity. It is found that the photocatalytic activity of the prepared Ag2CrO4was highly dependent on the preparation methods. The sample prepared by microemulsion method exhibits the highest photocatalytic efficiency on the degradation of methylene blue (MB under visible-light irradiation. The enhanced photocatalytic activity could be ascribed to the smaller particle size, higher surface area, relatively stronger light absorption, and blue-shift absorption edge, which result in the adsorption of more MB molecules, a shorter diffusion process of more photogenerated excitons, and a stronger oxidation ability of the photogenerated holes. Considering the universalities of microemulsion, precipitation, and hydrothermal methods, this work may also provide a prototype for the comparative study of semiconductor based photocatalysis for water purification and environmental remediation.

  15. Delineating the roles of Cr and Mo during ordering transformations in stoichiometric Ni2(Cr1−x,Mox) alloys

    Commercial Ni−Cr−Mo based superalloys form ordered Ni2(Cr, Mo) precipitates at intermediate temperature, which deteriorates their mechanical and corrosion properties, and whose kinetics varies significantly with alloy compositions. The aim of the present study is to understand the roles of Cr and Mo solutes on ordering kinetics and transformation mechanisms in Ni−Cr−Mo alloys. On the basis of the present study, it has been concluded that the Ni2(Cr, Mo) phase evolves with a sluggish ordering kinetics when its formation is governed only by the lattice diffusion of Cr, but its kinetics increases beyond a certain Mo/Cr ratio when lattice diffusion of Mo also starts contributing to its formation. This change has been found to occur in alloys having Mo/Cr ratio = 1 and has been attributed to partial change in the nature of atomic bonding from covalent type to metallic type. This change in the nature of bonding also reduced the necessary undercooling required below the disorder/order phase boundary for the precipitation of the ordered phase. Micromechanisms of ordering transformations involved in the evolution of the ordered phase have been described by a qualitative transformation model

  16. Removal of Heavy Metals Fe3+, Cu2+, Zn2+, Pb2+, Cr3+ and Cd2+ from Aqueous Solutions by Using Eichhornia Crassipes

    S.A. Shama

    2010-01-01

    Full Text Available The adsorption capacity of Eichhornia Crassipes towards metal ions such as Fe3+, Cu2+, Zn2+, Pb2+, Cr3+ and Cd2+, was studied. The adsorption capacity was investigated by batch experiments. The results showed that the removal percentages increased as the weight of sorbent increased, except for Fe3+ and Zn2+. The effect of contact time was also studied and the results showed that the removal percentages increased as the contact time increased for Cr3+, Zn2+ and Pb2+, but for Fe3+, Cu2+ and Cd2+ the removal decreased. The effect of pH of the solution was also studied and the removal percentages increased as pH increased. Also the effect of the initial concentration of metal ions was studied at four different concentrations (5, 10, 30, 50 mg/L; in case of metal ions (Cu2+, Zn2+ and Cd2+ the removal percentages increased by increasing initial concentration. But, for the other metal ions it decreased by increasing initial concentration over 30 mg/L. The order of increasing removal percentages of metal ions at pH=4.86, initial concentration of metal ions 30 mg/L, and after four hours of shaking was: Cu2+< Cr3+

  17. Electronic structure and magnetic properties of quaternary Heusler alloy Co2CrGa1−xGex (x=0−1)

    The electronic structure of Co-based quaternary Heusler compounds Co2CrGa1−xGex (x=0.00, 0.25, 0.50, 0.75, 1.00) are calculated by first-principles density functional theory. The substitution of Ga by Ge leads to increase in the number of valence electrons. With increasing concentration of Ge, lattice constant decreases linearly whereas bulk modulus and total magnetic moment increases. This shows that the magnetic properties of the compound are dependent on electron concentration of main group element. The calculations show that the alloys with x=0.00, 0.25, 0.50 are not true half-metallic materials whereas alloy with x=0.75, 1.00 exhibit 100% spin polarization at the Fermi level. It shows that the Fermi level can be shifted within the energy-gap to achieve 100% spin polarization. The effect of volumetric and tetragonal strain on magnetic properties is also studied. - Highlights: • We present study of electronic and magnetic properties of Co2CrGa1−xGex (x=0−1). • The Fermi level shift with change in Ge concentration. • The compounds with x=0.00, 0.25 and 0.50 have spin-polarization less than 100%. • At x=0.75 and 1.00, 100% spin-polarization is achieved. • Effect of volumetric and tetragonal strain on magnetic properties has been studied

  18. The interface of tunnelling junctions with the Heusler electrode Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al

    Jourdan, Martin; Herbort, Christian; Arbelo Jorge, Elena; Kallmayer, Michael; Elmers, Hans Joachim [Institut fuer Physik, Johannes Gutenberg Universitaet, Mainz (Germany)

    2009-07-01

    The compound Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al was the first Heusler material for which half metallic properties and a magnetic ordering temperature well above room temperature were predicted. However, no Julliere spin polarisation larger than {approx_equal}60% could be observed up to now. The affinity of Cr for oxidation is considered to be the origin for this reduced value. We improved the vacuum condition of our preparation system to below 10{sup -9} mbar. This resulted in a pronounced change of the morphology of the rf sputter deposited Al layer which is deposited on top of the Heusler electrode in order to become the tunnelling barrier after oxidation. In situ STM investigation show the growth of Al islands on the Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al surface. This growth mode results in an increased roughness of the barrier, which limits the achievable tunnelling magnetoresistance (TMR). Alternative methods of barrier deposition are employed and investigated by in situ STM and RHEED. Additionally, the effect of the Al deposition method and oxidation process on the surface magnetisation of the Heusler electrode is investigated by XMCD-TEY experiments.

  19. Cr(III)-Cr(III) interactions in two alkoxo-bridged heterometallic Zn2Cr2 complexes self-assembled from zinc oxide, Reinecke's salt, and diethanolamine.

    Semenaka, Valentyna V; Nesterova, Oksana V; Kokozay, Volodymyr N; Dyakonenko, Viktoriya V; Zubatyuk, Roman I; Shishkin, Oleg V; Boca, Roman; Jezierska, Julia; Ozarowski, Andrew

    2010-06-21

    Two new tetranuclear complexes, [Zn(2)Cr(2)(NCS)(4)(Dea)(2)(HDea)(2)].4DMSO (1; DMSO = dimethyl sulfoxide) and [Zn(2)Cr(2)(NCS)(4)(Dea)(2)(HDea)(2)].2CH(3)CN (2), were prepared from zinc oxide, Reinecke's salt, NH(4)[Cr(NCS)(4)(NH(3))(2)].H(2)O, ammonium thiocyanate, and a nonaqueous solution of diethanolamine (H(2)Dea) in a reaction carried out under open air. Both compounds have similar centrosymmetric crystal structures based on a tetranuclear {Zn(2)Cr(2)(mu(3)-O)(2)(mu-O)(4)} core. Variable-temperature magnetic susceptibility measurements of 1 and 2 show weak antiferromagnetic coupling between chromium centers. The magnetic data and high-field, high-frequency electron paramagnetic resonance spectra were analyzed in terms of the spin Hamiltonian H = JS(1).S(2) - j(S(1).S(2) + mu(B)B{g(1)}S(1) + D(Cr){S(z1)(2) - S(1)(S(1) + 1)/3} + E(Cr)(S(x1)(2) - S(y1)(2)) + mu(B)B{g(2)}S(2) + D(Cr){S(z2)(2) - S(2)(S(2) + 1)/3} + E(Cr)(S(x2)(2) - S(y2)(2)) + D(12){S(z1)S(z2) - S(1).S(2)/3} + E(12)(S(x1)S(x2) - S(y1)S(y2)) with J = 13.7 cm(-1), j = 1.1 cm(-1), D(Cr) = 0.3864 cm(-1), E(Cr) = -0.1104 cm(-1), D(12) = -0.1873 cm(-1), and E(12) = -0.0155 cm(-1) for 1 and J = 9.4 cm(-1), j = 0.8 cm(-1), D(Cr) = 0.3564 cm(-1), E(Cr) = -0.0647 cm(-1), D(12) = -0.1850 cm(-1), and E(12) = -0.0112 cm(-1) for 2. Density functional theory (DFT) calculations were employed to calculate the zero-field splitting on Cr(3+) ions. Calculations of the exchange integrals J were attempted by using the "broken-symmetry" DFT method. PMID:20540565

  20. Cycling more for safer cycling

    VAN HOUT, Kurt

    2009-01-01

    Cycling presents a lot of benefits to the individual and to society. Health, environment, accessibility, local businesses, … all gain when more people cycle. Yet many governments are reluctant when it comes to promoting cycling, mainly because of (perceived) safety issues. Since studies have established a clear and consistent relationship between bicycle use and cyclist accident risk, this lack of bicycle promotion will influence the safety outcome of bicyclists. In this paper the relation be...

  1. Cycling injuries.

    Cohen, G. C.

    1993-01-01

    Bicycle-related injuries have increased as cycling has become more popular. Most injuries to recreational riders are associated with overuse or improper fit of the bicycle. Injuries to racers often result from high speeds, which predispose riders to muscle strains, collisions, and falls. Cyclists contact bicycles at the pedals, seat, and handlebars. Each is associated with particular cycling injuries.

  2. Current-voltage characteristics of double tunnel contacts Co2CrAl-I-Pb/Sn-I-Pb at spin-polarized tunnel injection

    Current-voltage characteristics and features of the existence of superconducting state under the action of tunnel injection of spin-polarized current Iinj with a high spin polarization degree (p approx 0,97) have been studied in double tunnel contacts ferromagnet-insulator-superconductor-insulator-superconductor Co2CrAl-I-Pb/Sn-I-Pb. An empiric formula for description of dependence of energy gap vs Iinj is proposed. A new spin-polarized inhomogeneous superconducting state, including superconductive and resistance areas, is found. It is found that there exists a of proximity effect between ferromagnetic and superconducting films through the tunnel barrier. The recombination effective time of spin-polarized quasiparticles for nonequilibrium Pb superconductor is estimated.

  3. Mechanistic study of β-hydroxy elimination from [tetrasulphophthalocyanine Co111-CR1R2CR3R4OH] in aqueous solutions

    The reactions of cobalt(II) tetrasulphophthalocyanine, [Co11(tspc)]4- with .CH3, .CH2Ch(2OH, .CH2C(CH3)2OH free radicals have been studied. The results indicate that the first product formed in these reactions has the form [Co11-(tspc-R)]4-, where R is the aliphatic free radical, the exact nature of the bonding of .R to tspc is not clear. The compled [Co11-(tspc-R)]4- rearranges into [(tspc)Co111-R]4- in a process obeying a first-order rate law. [(tspc)Co111-CH3]4- decomposes into [Co111(tspc)]3-+CH4, whereas the complexes [TSPC)Co111-CR,R2CR3R4OH]4- decompose into [Co111(tspc)]3-+R1R2 C=CR3R4+OH-. (Author)

  4. Interpretation of electron spectra of hexacyano-complexes of Fe(2), Co(3), V(2), Cr(3), Mn(2) by semi-empirical methods

    Semi-empirical interpretation of d-d-transitions of M(CN)sub(6)sup(n+) complexes (M=Fe(2), Co(3), V(2), Cr(3), Mn(2)) is made on the basis of the method of angular overlapping and the theory of ligand field and evaluation of transition with charge transfer using the modified Iorgensen method and parameters B, C, Δ, obtained from the analysis of d-d-transitions on the basis of angular overlapping method, is made. Parameters of Δ, B, C field, obtained according to the method of angular overlapping and the theory of ligand field, to prove the reliability of different interpretations, are compared. It is found that parameters of the angular overlapping method esub(σ), esub(π) are in a good correlation with overlapping integrals Ssub(σ), Ssub(π)

  5. The strain induced band gap modulation from narrow gap semiconductor to half-metal on Ti{sub 2}CrGe: A first principles study

    Li, Jia, E-mail: jiali@hebut.edu.cn [School of Science, Hebei University of Technology, Tianjin 300401 (China); Research Institute for Energy Equipment Materials, Hebei University of Technology, Tianjin 300401 (China); Zhang, Zhidong [School of Science, Hebei University of Technology, Tianjin 300401 (China); Lu, Zunming; Xie, Hongxian; Fang, Wei; Li, Shaomin; Liang, Chunyong; Yin, Fuxing [Research Institute for Energy Equipment Materials, Hebei University of Technology, Tianjin 300401 (China)

    2015-11-15

    The Heusler alloy Ti{sub 2}CrGe is a stable L2{sub 1} phase with antiferromagnetic ordering. With band-gap energy (∼ 0.18 eV) obtained from a first-principles calculation, it belongs to the group of narrow band gap semiconductor. The band-gap energy decreases with increasing lattice compression and disappears until a strain of −5%; moreover, gap contraction only occurs in the spin-down states, leading to half-metallic character at the −5% strain. The Ti{sub 1}, Ti{sub 2}, and Cr moments all exhibit linear changes in behavior within strains of −5%– +5%. Nevertheless, the total zero moment is robust for these strains. The imaginary part of the dielectric function for both up and down spin states shows a clear onset energy, indicating a corresponding electronic gap for the two spin channels.

  6. X-Ray Phase Analysis Of Nitrided Layers Of X2CrNiMo17-12-2 Austenitic Steel

    Frączek T.

    2015-09-01

    Full Text Available This work presents the results of diffraction analyses carried out using X-ray phase analyses (XRD and GIXRD of nitrided layers of X2CrNiMo17-12-2 austenitic steel. Plasma nitriding process was c arried out in the temperature range of 325 ÷ 400 °C and time of 2 ÷ 4 h. Hydrogen-nitrogen plasma was used as reactive atmosphere (H2 75% + N2 25% with pressure of 150 Pa. On the basis of the X-ray analyses it was stated that the obtained nitrided layers consisted of a subsurface layer of chromium nitrides and a zone of nitrogen saturated austenite.

  7. Interpretation of electron spectra of hexacyano-complexes of Fe(2), Co(3), V(2), Cr(3), Mn(2) by semi-empirical methods

    Zakharieva-Pencheva, O.; Nikolov, G.S. (Sofia Univ. (Bulgaria))

    1982-01-01

    Semi-empirical interpretation of d-d-transitions of M(CN)sub(6)sup(n+) complexes (M=Fe(2), Co(3), V(2), Cr(3), Mn(2)) is made on the basis of the method of angular overlapping and the theory of ligand field and evaluation of transition with charge transfer using the modified Iorgensen method and parameters B, C, ..delta.., obtained from the analysis of d-d-transitions on the basis of angular overlapping method, is made. Parameters of ..delta.., B, C field, obtained according to the method of angular overlapping and the theory of ligand field, to prove the reliability of different interpretations, are compared. It is found that parameters of the angular overlapping method esub(sigma), esub(..pi..) are in a good correlation with overlapping integrals Ssub(sigma), Ssub(..pi..).

  8. The strain induced band gap modulation from narrow gap semiconductor to half-metal on Ti2CrGe: A first principles study

    The Heusler alloy Ti2CrGe is a stable L21 phase with antiferromagnetic ordering. With band-gap energy (∼ 0.18 eV) obtained from a first-principles calculation, it belongs to the group of narrow band gap semiconductor. The band-gap energy decreases with increasing lattice compression and disappears until a strain of −5%; moreover, gap contraction only occurs in the spin-down states, leading to half-metallic character at the −5% strain. The Ti1, Ti2, and Cr moments all exhibit linear changes in behavior within strains of −5%– +5%. Nevertheless, the total zero moment is robust for these strains. The imaginary part of the dielectric function for both up and down spin states shows a clear onset energy, indicating a corresponding electronic gap for the two spin channels

  9. Brillouin light scattering study of Co2Cr0.6Fe0.4Al and Co2FeAl Heusler compounds

    The thermal magnonic spectra of Co2Cr0.6Fe0.4Al (CCFA) and Co2FeAl were investigated using Brillouin light scattering (BLS) spectroscopy. For CCFA, the exchange constant A (exchange stiffness D) is found to be 0.48 ± 0.04 μerg cm-1 (203 ± 16 meV A2), while for Co2FeAl the corresponding values of 1.55 ± 0.05 μerg cm-1 (370 ± 10 meV A2) were found. The observed asymmetry in the BLS spectra between the Stokes and anti-Stokes frequencies was assigned to an interplay between the asymmetrical profiles of hybridized Damon-Esbach and perpendicular standing spin-wave modes, combined with the optical sensitivity of the BLS signal to the upper side of the CCFA or Co2FeAl film.

  10. Tunneling junctions with the Heusler electrode Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al

    Herbort, Christian; Arbelo, Elena; Jourdan, Martin [Institute of Physics, Johannes Gutenberg University, Mainz (Germany)

    2008-07-01

    Some ferromagnetic Heusler compounds are theoretically predicted to be half metallic materials, i. e. to be characterized by a huge spin polarization at the Fermi energy. We investigate the correlations between junction preparation conditions, morphology and transport properties of planar MgO-Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al-AlO{sub x}-Co/CoO{sub x}-Pt tunnelling junctions. Epitaxial Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al (CCFA) thin films were deposited by dc- and rf-sputtering on different buffer layers (Cr,Fe,MgO) on MgO(1,0,0) substrates. By RHEED, LEED and in-situ STM investigations very different surface morphologies were observed for the different preparation processes. With dc-sputtered CCFA films (island morphology) on Fe buffer layers we determined a maximum spin polarization of the Heusler compound of 54% (Julliere model, T=4 K). Atomically flat surfaces with CCFA unit cell sized steps (B2 structure) were obtained by rf-sputtering on MgO substrates with e-beam evaporated MgO buffer layers. Considering that the TMR of the CCFA based junctions depends strongly on the interface at the tunneling barrier, the AlO{sub x} layer needs to be optimized separately for the different CCFA morphologies. The barrier optimization process on the new atomically flat CCFA surfaces (rf-sputtered on MgO buffer) is in progress and current results of spectroscopic and TMR measurements will be shown.

  11. Glacial cycles

    Kaufmann, R. K.; Juselius, Katarina

    We use a statistical model, the cointegrated vector autoregressive model, to assess the degree to which variations in Earth's orbit and endogenous climate dynamics can be used to simulate glacial cycles during the late Quaternary (390 kyr-present). To do so, we estimate models of varying complexity...... and compare the accuracy of their in-sample simulations. Results indicate that strong statistical associations between endogenous climate variables are not enough for statistical models to reproduce glacial cycles. Rather, changes in solar insolation associated with changes in Earth's orbit are needed...... to simulate glacial cycles accurately. Also, results suggest that non-linear 10 dynamics, threshold effects, and/or free oscillations may not play an overriding role in glacial cycles....

  12. Fuel cycles

    AECL publications, from the open literature, on fuels and fuel cycles used in CANDU reactors are listed in this bibliography. The accompanying index is by subject. The bibliography will be brought up to date periodically

  13. Fes cycling

    Berkelmans Rik

    2008-01-01

    Full Text Available Many research with functional electrical stimulation (FES has been done to regain mobility and for health benefits. Better results have been reported for FES-cycling than for FES-walking. The majority of the subjects during such research are people with a spinal cord injury (SCI, cause they often lost skin sensation. Besides using surface stimulation also implanted stimulators can be used. This solves the skin sensation problem, but needs a surgery. Many physiological effects of FES-cycling has been reported, e.g., increase of muscles, better blood flow, reduction of pressure ulcers, improved self-image and some reduction of bone mineral density (BMD loss. Also people with an incomplete SCI benefit by FES-cycling, e.g. cycling time without FES, muscle strength and also the walking abilities increased. Hybrid exercise gives an even better cardiovascular training. Presently 4 companies are involved in FES-cycling. They all have a stationary mobility trainer. Two of them also use an outdoor tricycle. One combined with voluntary arm cranking. By optimizing the stimulation parameters the power output and fatigue resistance will increase, but will still be less compared to voluntary cycling.

  14. 压缩机2Cr13活塞杆亚温淬火工艺及其弯曲问题的研究%Research of Subcritical Quenching Process of Compressor 2Cr13 Piston Rod and Its Bending Problems

    曲德毅; 朱国庆

    2011-01-01

    After the 2Crl3 piston rod passes through subcritical quenching and quenching & tempering,the stabilization process of adopting air cooling or furnace cooling of 3 ~ 4h under 580 t can basically eliminate the stress,and there is no obvious second tempering Brittle production. Thus it can ensure the amount of bending decreased when the 2Crl3 piston rod with high - frequency quenching and avoid the discharge phenomenon of sensor from melting piston rod.%2Cr13活塞杆经过亚温淬火、回火调质后,采用580℃保温3~4h空冷或炉冷的稳定化工艺,基本上可以消除应力,并且没有明显的第二类回火脆性的产生,从而保证了2Cr13活塞杆高频淬火时减小弯曲量,避免感应器放电现象熔化活塞杆.

  15. Structure and luminescent properties of Co{sup 2+}/Cr{sup 3+} co-doped ZnGa{sub 2}O{sub 4} nanoparticles

    Duan, Xiulan, E-mail: xlduan@sdu.edu.cn; Liu, Jian; Wu, Yuanchun; Yu, Fapeng; Wang, Xinqiang

    2014-09-15

    Co{sup 2+}/Cr{sup 3+} co-doped ZnGa{sub 2}O{sub 4} nanoparticles were prepared by a citrate sol–gel method. Their structure and luminescent properties were studied by using X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and fluorescence spectrophotometer. The nanoparticles with the size of 18–50 nm were obtained when the precursor was annealed at 500 °C or above. Ga{sup 3+} ions occupied the octahedral sites as well as the tetrahedral sites, while Cr{sup 3+} ions only entered the octahedral sites by replacing Ga{sup 3+}. The as-synthesized samples had partially inverted spinel structure and the inversion degree slightly decreased with increasing temperature. The Cr{sup 3+}:ZnGa{sub 2}O{sub 4} sample exhibited an intense emission at 695 nm, corresponding to the {sup 2}E→{sup 4}A{sub 2} transition of octahedral Cr{sup 3+}. The emission intensity of Cr{sup 3+} was largely reduced when the sample was co-doped with Co{sup 2+}. However, the emission intensity of Co{sup 2+} in 2% Co/1% Cr co-doped ZnGa{sub 2}O{sub 4} is improved approximately 2 times when compared with 2% co-doped sample. This enhanced emission could be attributed to an efficient energy transfer from Cr{sup 3+} to Co{sup 2+}. The energy transfer mechanism is also discussed. - Highlights: • Co{sup 2+}/Cr{sup 3+}: ZnGa{sub 2}O{sub 4} nanoparticles have been synthesized by a citrate sol–gel method. • The chemical environments of Ga{sup 3+} and Cr{sup 3+} as a function of annealing temperature were studied. • Ga{sup 3+} ions occupy both the tetrahedral and octahedral sites of spinel structure in the samples. • The emission intensity of Co{sup 2+} is improved by Cr{sup 3+} codoping in ZnGa{sub 2}O{sub 4} with 550 nm excitation. • The possible energy transfer process was discussed.

  16. Effect of the Heat Treatment on the Chromium Partition in CaO-MgO-SiO2-Cr2O3 Synthetic Slags

    Albertsson, Galina Jelkina; Teng, Lidong; Engström, Fredrik; Seetharaman, Seshadri

    2013-12-01

    Mg-spinel phase is known to be important for control of Cr leaching from Cr-containing slags. The objective of the present study is to get an understanding of the phase relationships in the CaO-MgO-SiO2-Cr2O3 system with a view to control the precipitation of Cr-spinel in the slag phase. The equilibrium phases in CaO-MgO-SiO2-Cr2O3 slag system in the range of 1673 K to 1873 K (1400 °C to 1600 °C) have been investigated experimentally and compared with the results from thermodynamic calculations. The slag compositions close to the industrial slag systems were chosen. The Cr2O3 and MgO contents in the slag were fixed to be 6 and 8 wt pct, respectively. The basicity (CaO/SiO2) of the slag was varied in the range of 1.0 to 2.0. The slags were synthesized at a pre-determined oxygen partial pressure (10-4) or air (2.13 × 104 Pa) at a temperature above the liquidus temperature. The samples were then soaked at targeted temperatures for 24 hours in controlled atmosphere in order to achieve the equilibrium state before quenching in water. Four different heat-treatment regimes (defined as Ia, Ib, II.a and II.b) in Section II-D) were used in the present experiments. The lower oxygen partial pressure was maintained by a suitable mixture of CO and CO2 gases. Phases present and their compositions in the quenched slags were studied using scanning electron microscopy coupled with energy-dispersive spectroscopy and X-ray diffraction techniques. The chromium content in the phases present was analyzed using wavelength-dispersive spectrometer. The experimental results obtained are compared with the calculation results from Factsage software. The size of spinel crystals increased drastically after slow-cooling from 1873 K (1600 °C) followed by annealing at 1673 K (1400 °C) for 24 hours (heating regimes II) compared to samples being quenched directly after soaking at 1873 K (1600 °C) (heating regime I.a). It was found that the amount of foreign elements in the spinel phase, and

  17. Koszul cycles

    Bruns, Winfreid; Römer, Tim

    2010-01-01

    We prove regularity bounds for Koszul cycles holding for every ideal of dimension at most 1 in a polynomial ring. We generalize the lower bound for the Green-Lazarsfeld index of Veronese rings we proved in arXiv:0902.2431 to the multihomogeneous setting.

  18. Happy Cycling

    Geert Jensen, Birgitte; Nielsen, Tom

    2013-01-01

    og Interaktions Design, Aarhus Universitet under opgave teamet: ”Happy Cycling City – Aarhus”. Udfordringen i studieopgaven var at vise nye attraktive løsningsmuligheder i forhold til cyklens og cyklismens integration i byrum samt at påpege relationen mellem design og overordnede diskussioner af...

  19. Structural and magnetic properties of nanocrystalline Nd4.5Fe72Co2Cr3Al1B17.5 ribbons

    In this work, it was made a study on structural and magnetic properties of nanocrystalline Nd4.5Fe72Co2Cr3Al1B17.5 ribbons obtained from crystallisation of amorphous precursors. A complex two-step crystallisation process, was found by differential scanning calorimetry (DSC): a first crystallisation peak at around T=570 deg. C exhibiting the precipitation of α-Fe and t-Fe3B phases and a diffusive stage ending in a second exothermic peak. Also, isothermal annealings of 10 min duration were performed at 605, 635, 650 and 685 deg. C . Hysteresis curves of isothermally annealed samples showed magnetic hardening, with coercive fields above 2 kOe and an optimised M R/M S ratio of around 0.6. Except for the highest treatment temperature used in this work, the demagnetizing curves of annealed ribbons exhibited a step near zero field. This fact suggests a low exchange coupling between hard and soft phases, which can be attributed to the grain border phases. Otherwise, Moessbauer effect spectroscopy allowed us to determine that the absence of step in the demagnetizing curve of ribbons annealed at 685 deg. C , may be attributed to the formation of a α-(Fe, Co) solid solution (with hyperfine parameters B HF=35.5 T and δ=-0.11 mm/s). The formation of this solid solution also explains the diffusive process in the second crystallisation stage observed by DSC experiment

  20. Forming Mechanism of Gaseous Defect in Ti-48A1-2Cr-2Nb Exhaust Valves Formed with Permanent Mold Centrifugal Casting Method

    2001-01-01

    A method combining theoretical analysis with experiment is adopted and the flowing process of Ti-48AI-2Cr-2Nb alloy melt poured in a permanent mould during the centrifugal casting process has been analyzed. A mathematical model of the filling process is established and the forming mechanism of internal gaseous defect is summarized. The results of calculation show that the melt fills the mould with varying cross-section area and inclined angle. The filling speed of the cross-section is a function of filling time. The cross-section area is directly proportional to the filling speed and the inclined angle is inversely proportional to the filling speed at a given rotating speed of the platform. Both of them changes more obvious near the mould entrance.The gaseous defect can be formed in several ways and the centrifugal field has an important influence on the formation of the defect. In addition, the filling process in centrifugal field has been verified by wax experiments and the theoretical analysis are consistent with experimental results.

  1. Laser stimulated kinetics effects on the phase transition of the ferromagnetic/superconducting MgB2/(CrO2) bilayer thin films

    Graphical abstract: Dependence of resistance versus temperature for different power densities. The nonzero value is generated from the bottom CrO2 resistive layer. The onset transition temperature is our reference for the enhancement value. - Highlights: • Photoinduced enhancement of critical temperature in MgB2–Cr2O3 films was found. • Crucail role of electron–phonon interacton was shown. • Optimal ratio fundamental/SHG intensities was varied within 4:1 and 6:1. - Abstract: Using bicolor laser treatment by Nd:YAG 20 ns laser (1064–532 nm) and 180 ns CO2 laser beams (10.6–5.3 μm) it was shown a possibility of critical temperature enhancement in ferromagnetic superconducting MgB2/CrO2 bilayer films. The role of the phonon sub-system effectively interacting with 3d Cr originating localized trapping levels is discussed. The pump–probe laser kinetics for the probing second harmonic generation at 1064 nm is explored in details to show principal role of the localized trapping levels. The relaxation of the processes after the switching off the photo inducing beams show the disappearance of the enhanced superconductivity after the 20–30 s. The temperature dependence of the resistance show nonlinear dependence versus the pumping power and different optimal fundamental to writing power density beams ratio

  2. Laser stimulated kinetics effects on the phase transition of the ferromagnetic/superconducting MgB{sub 2}/(CrO{sub 2}) bilayer thin films

    AlZayed, N.S. [Physics and Astronomy Department, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Kityk, I.V., E-mail: ikityk@el.pcz.czest.pl [Faculty of Electrical Engineering, Czestochowa University Technology, Armii Krajowej 17, PL-42201 Czestochowa (Poland); Soltan, S. [Max Planck Institute, Solid State Research, D-70569 Stuttgart (Germany); Physics Department, Faculty of Science, Helwan University, 11798 Helwan, Cairo (Egypt); Wojciechowski, A. [Faculty of Electrical Engineering, Czestochowa University Technology, Armii Krajowej 17, PL-42201 Czestochowa (Poland); Fedorchuk, A.O. [Department of Inorganic and Organic Chemistry, Lviv National University of Veterinary Medicine and Biotechnologies, Pekarska St., 50, 79010 Lviv (Ukraine); Lakshminarayana, G. [Materials Science and Technology Division (MST-7), Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Shahabuddin, M. [Physics and Astronomy Department, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia)

    2014-05-01

    Graphical abstract: Dependence of resistance versus temperature for different power densities. The nonzero value is generated from the bottom CrO{sub 2} resistive layer. The onset transition temperature is our reference for the enhancement value. - Highlights: • Photoinduced enhancement of critical temperature in MgB{sub 2}–Cr{sub 2}O{sub 3} films was found. • Crucail role of electron–phonon interacton was shown. • Optimal ratio fundamental/SHG intensities was varied within 4:1 and 6:1. - Abstract: Using bicolor laser treatment by Nd:YAG 20 ns laser (1064–532 nm) and 180 ns CO{sub 2} laser beams (10.6–5.3 μm) it was shown a possibility of critical temperature enhancement in ferromagnetic superconducting MgB{sub 2}/CrO{sub 2} bilayer films. The role of the phonon sub-system effectively interacting with 3d Cr originating localized trapping levels is discussed. The pump–probe laser kinetics for the probing second harmonic generation at 1064 nm is explored in details to show principal role of the localized trapping levels. The relaxation of the processes after the switching off the photo inducing beams show the disappearance of the enhanced superconductivity after the 20–30 s. The temperature dependence of the resistance show nonlinear dependence versus the pumping power and different optimal fundamental to writing power density beams ratio.

  3. Moessbauer study of epitaxial Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al thin films.

    Ksenofontov, Vadim; Felser, Claudia [Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg - University, 55099 Mainz (Germany); Herbort, Christian; Jourdan, Martin [Institute of Physics, Johannes Gutenberg - University, 55099 Mainz (Germany)

    2008-07-01

    Epitaxial thin films of the promising for spintronic applications Heusler half-metallic compound Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al (CCFA) were investigated using conversion electron Moessssbauer spectroscopy (CEMS) in order to get insight into the structural and magnetic properties. Thin films of 100 nm thickness were deposited by rf magnetron sputtering on MgO substrates without and with 10 nm Fe buffer layer. We discuss a correlation between the annealing temperature and the structural disorder and hyperfine fields on Fe atoms measured by Moessbauer spectroscopy. Samples prepared at the optimum annealing temperature as determined by tunneling magnetoresistance measurements show the optimum degree of order on the Fe sites as determined by CEMS. Additionally, we observed evidence for a diffusion of Cr atoms from the CCFA thin film into the Fe buffer layer and the related diffusion of Fe atoms from the buffer into the CCFA film. Thus the thermal treatment changes the Fe to Cr ratio of the Heusler compound additional to influencing the degree of disorder on the Fe/Cr sites.

  4. Epitaxial Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al thin films and magnetic tunneling junctions

    Conca, Andres; Jourdan, Martin; Herbort, Christian; Adrian, Hermann [Institut fuer Physik, Johannes Gutenberg University, Staudinger Weg 7, 55128 Mainz (Germany)

    2007-07-01

    The full-Heusler compound Co2Cr{sub 0.6}Fe{sub 0.4}Al (CCFA) is expected to be a half metal, i.e. to show a 100% spin polarization at the Fermi energy. This property, together with the relatively high Curie temperature (800 K) and the soft magnetic behaviour make CCFA a promising candidate for implementation in spinelectronic devices. Magnetic tunneling junctions were deposited using epitaxial CCFA thin films as ground electrode with AlOx as barrier and Co as counter electrode. The use of an Fe buffer layer on MgO(100) induces the growth of highly ordered CCFA films with smooth surface even at low deposition temperatures, as proved by XRD, TEM and in-situ STM investigations. The CCFA films were additionally annealed at different temperatures up to 600 C. The dependence of the TMR ratio on the annealing temperature was studied. A maximum TMR ratio of 40.5% was measured from which a spin polarization of 54% is deduced by the Julliere model. Possible correlations between the TMR ratio and the surface properties, as observed with STM and RHEED, are discussed. Alternatively, epitaxial CCFA films were also grown directly on MgAl{sub 2}O{sub 4}(100) and Al{sub 2}O{sub 3}(110). A comparison with the results on MgO substrates is shown.

  5. First-Principles Calculations of the Mechanical and Elastic Properties of 2Hc- and 2Ha-WS2/CrS2 Under Pressure

    Jiang, Hua-Long; Jia, Song-Hao; Zhou, Da-Wei; Pu, Chun-Ying; Zhang, Fei-Wu; Zhang, Shuai

    2016-06-01

    By utilizing the first-principles method, the pressure-induced effects on phase transition, mechanical stability, and elastic properties of WS2/CrS2 are investigated in the pressure range from 0 to 80 GPa. Transitions from 2Hc to 2Ha for WS2 and CrS2 are found to occur at 17.5 and 25 GPa, respectively. It is found that both 2Ha and 2Hc phases of WS2 and CrS2 meet the mechanical stability criteria up to 80 GPa, suggesting that those structures are mechanically stable. The bulk and shear modulus anisotropy of the two phases of WS2 and CrS2 decrease rapidly under pressure and, finally, trend to isotropy. With increasing pressure, the elastic moduli (Y, B, and G), sound velocities (vs, vp, vm), and Debye temperatures (Θ) of 2Ha and 2Hc of WS2 and CrS2 increase monotonously. Moreover, the Debye temperature (Θ) of 2Hc phase is higher than that of 2Ha phase for both WS2 and CrS2. The bulk, shear, and Young's modulus, Poisson coefficient, and brittle/ductile behaviour are estimated. The percentages of anisotropy in compressibility and shear and the ratio of bulk to shear modulus (B/G) are also studied.

  6. Magnetic properties of the fully spin-polarized Sr2CrOsO6 double perovskite: A Monte Carlo simulation

    El Rhazouani, O.; Zarhri, Z.; Benyoussef, A.; El Kenz, A.

    2016-03-01

    Sr2CrOsO6 double perovskite (DP) has been gaining importance in recent years thanks to its high ordering temperature (Tc = 725 K) that is the highest Tc measured among all DPs so far. Spin-polarized (5d t2g)-orbital of Os-atoms is completely filled, which allows the compound to be considered as fully spin-polarized exactly at the limit of the metal-insulator transition. This interesting property gives the compound exceptional properties and more ability to use in spintronic applications. In this paper, the energetic and the magnetic behavior of this material have been explored using Monte Carlo Simulation (MCS) within the framework of Ising model. Ground state phase diagram has been dressed and analyzed. Size effect on the magnetic properties has been analyzed. Effect of the crystal field of Osmium on the thermal behavior has been explored. Critical exponents have been calculated, discussed regarding the crystal field of Osmium and evaluated against the universality class.

  7. Simultaneous preconcentrations of Co(2+), Cr(6+), Hg(2+) and Pb(2+) ions by Bacillus altitudinis immobilized nanodiamond prior to their determinations in food samples by ICP-OES.

    Ozdemir, Sadin; Kilinc, Ersin; Celik, Kadir Serdar; Okumus, Veysi; Soylak, Mustafa

    2017-01-15

    A novel solid phase extraction method was developed for simultaneous preconcentration-separation of Co(2+), Cr(6+), Hg(2+) and Pb(2+) ions prior to their determinations in food samples by ICP-OES. Thermophilic Bacillus altitudinis immobilized nanodiamond was used as a new biosorbent. SEM and FT-IR analysis were studied to characterize the biosorbent. The optimum pH values of quantitative biosorption for Co(2+), Cr(6+), Hg(2+) and Pb(2+) were found to be 5.0, 6.0, 6.0 and 6.0, respectively. A flow rate of 3.0mLmin(-1) was selected as optimum for all metal ions. 5mL of 1mol/L HCl was used as eluent. Preconcentration factor was achieved as 80. LODs were calculated as 0.071, 0.023, 0.016 and 0.034ngmL(-1), respectively for Hg(2+), Co(2+), Cr(6+) and Pb(2+). The biosorption capacities were calculated for Co(2+), Cr(6+), Hg(2+) and Pb(2+) as 26.4, 30.4, 19.5, and 35.2mg/g, respectively. The developed method was successfully applied to food samples to determine analyte concentrations. PMID:27542497

  8. Ultrasonic-assisted preparation of novel ternary ZnO/Ag3VO4/Ag2CrO4 nanocomposites and their enhanced visible-light activities in degradation of different pollutants

    Pirhashemi, Mahsa; Habibi-Yangjeh, Aziz

    2016-05-01

    Novel ternary ZnO/Ag3VO4/Ag2CrO4 nanocomposites were successfully fabricated via preparation of ZnO/Ag3VO4 followed by coupling of it with Ag2CrO4 through facile ultrasonic-assisted method. The resultant samples were carefully characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive analysis of X-rays, UV-vis diffuse reflectance spectroscopy, Fourier transform-infrared spectroscopy, and photoluminescence techniques. Photocatalytic activity for degradation of organic dyes, including rhodamine B, methylene blue, and methyl orange was examined under visible-light irradiation. Among the prepared samples, the ternary nanocomposite with 20% of Ag2CrO4 demonstrated the superior activity. This nanocomposite showed 10.6, 2.9, and 3.0-folds greater activity compared to ZnO, ZnO/Ag2CrO4, and ZnO/Ag3VO4, respectively. The enhanced activity was attributed to more harvesting of the visible-light irradiation and efficiently separation of the photogenerated charge carriers in the ternary nanocomposites. To understand efficiently separation of the charge carriers, a plausible diagram was proposed based on formation of tandem n-n heterojunctions.

  9. Electronic, magnetic, and optical characteristics of half-semiconductor double perovskite oxide Sr2CrOsO6 governed by 3d (t2g3)-5d (t2g3) antiferromagnetic coupling

    H.-E., M. Musa Saad

    2016-07-01

    In this study, motivated by observations of the remarkable magnetic insulating nature and high Curie temperature (TC=725 K) of double perovskite oxide Sr2CrOsO6, the electronic, magnetic, and optical characteristics of Sr2CrOsO6 were determined using the full potential linear muffin-tin orbital method according to density functional theory. The spin-orbit coupling contribution was included in the local spin density approximation (LSDA) and generalized gradient approximation (GGA). In addition, the Coulomb repulsion (U) and Hund's exchange (J) energies were considered in both methods (LSDA+U and GGA+U). Full structural optimization confirmed that the ground state of Sr2CrOsO6 is face-centered cubic (Fm-3m symmetry). Calculations predicted that Sr2CrOsO6 is ferrimagnetic half-semiconductive (HSC) due to the vertical hopping of t2g electrons via antiferromagnetic coupling [Cr3+ (t2g3↑)-O (2pπ)-Os5+ (t2g3↓)], which agreed with the experimental results. The HSC energy-gaps originate from the splitting of three partially occupied Os5+ (5d) bands into two fully filled bands and one empty spin-down band. The real ε1 (ω) and imaginary ε2 (ω) parts of the dielectric function ε (ω) and energy-loss spectrum L (ω) were calculated, analyzed, and compared with the electronic results.

  10. Fuel cycle

    The situation of the nuclear fuel cycle for LWR type reactors in France and in the Federal Republic of Germany was presented in 14 lectures with the aim to compare the state-of-the-art in both countries. In addition to the momentarily changing fuilds of fuel element development and fueling strategies, the situation of reprocessing, made interesting by some recent developmnts, was portrayed and differences in ultimate waste disposal elucidated. (orig.)

  11. High-cycle Fatigue Fracture Behavior of Ultrahigh Strength Steels

    Weijun HUI; Yihong NIE; Han DONG; Yuqing WENG; Chunxu WANG

    2008-01-01

    The fatigue fracture behavior of four ultrahigh strength steels with different melting processes and therefore different inclusion sizes were studied by using a rotating bar two-point bending fatigue machine in the high-cycle regime up to 107 cycles of loading. The fracture surfaces were observed by field emission scanning electron microscopy (FESEM). It was found that the size of inclusion has significant effect on the fatigue behavior.For AISI 4340 steel in which the inclusion size is smaller than 5.5 μm, all the fatigue cracks except one did not initiated from inclusion but from specimen surface and conventional S-N curve exists. For 65Si2MnWE and Aermet 100 steels in which the average inclusion sizes are 12.2 and 14.9 μm, respectively, fatigue cracks initiated from inclusions at lower stress amplitudes and stepwise S-N curves were observed. The S-N curvedisplays a continuous decline and fatigue failures originated from large oxide inclusion for 60Si2CrVA steel in which the average inclusion size is 44.4 μm. In the case of internal inclusion-induced fractures at cycles beyond about 1×106 for 65Si2MnWE and 60Si2CrVA steels, inclusion was always found inside the fish-eye and a granular bright facet (GBF) was observed in the vicinity around the inclusion. The GBF sizes increasewith increasing the number of cycles to failure Nf in the long-life regime. The values of stress intensity factor range at crack initiation site for the GBF are almost constant with Nf, and are almost equal to that for the surface inclusion and the internal inclusion at cycles lower than about 1×106. Neither fish-eye nor GBF was observed for Aermet 100 steel in the present study.

  12. First principles study of the origin of Strain-tunable extraordinary magnetocrystalline anisotropy in Sr2CrReO6 epitaxial films

    Ball, M. R.; Lucy, J. M.; Restrepo, O. D.; Hauser, A. J.; Soliz, J. R.; Freeland, J. W.; Woodward, P. M.; Windl, W.; Yang, F. Y.

    2015-03-01

    Magnetocrystalline anisotropy (MCA) has significant implications in a range of applications such as power generation and magnetic data storage. We report the discovery of extraordinarily large anisotropy fields and strain-tunable MCA in Sr2CrReO6 epitaxial films. These films grown on (LaAlO3)0.3 (Sr2AlTaO6)0.7 (LSAT), SrTiO3, and SrCr0.5Nb0.5O3/LSAT substrates undergo dramatic changes in MCA shown by a shift in easy axis from in-plane to out-of plane. To find the origin of this, we determine the strain-induced distortions and octahedral rotations by performing density functional theory (DFT) calculations using VASP. Correlation effects were treated within GGA +U. In DFT, the change in easy axis under strain seen in experiment can be examined through the difference in total energies for magnetic orientation along different crystalline axes known as the magnetic anisotropy energy (MAE). The MAE is directly related to the moment anisotropy which is the difference between hard- and easy-axis orbital moments. When a sign change in the moment anisotropy is present, a change in easy axis is indicated. We indeed find this sign change with increasing c / a ratio which is in agreement with experiments. The origin of the MAE resides in the strain-induced changes in spin-orbit coupling on the Re-atoms. This interplay between structural deformations and magnetism leads to a giant MCA

  13. Isolating the Epstein-Barr virus gp350/220 binding site on complement receptor type 2 (CR2/CD21).

    Young, Kendra A; Chen, Xiaojiang S; Holers, V Michael; Hannan, Jonathan P

    2007-12-14

    Complement receptor type 2 (CR2/CD21) is essential for the attachment of Epstein-Barr virus (EBV) to the surface of B-lymphocytes in an interaction mediated by the viral envelope glycoprotein gp350. The heavily glycosylated structure of EBV gp350 has recently been elucidated by x-ray crystallography, and the CR2 binding site on this protein has been characterized. To identify the corresponding gp350 binding site on CR2, we have undertaken a site-directed mutagenesis study targeting regions of CR2 that have previously been implicated in the binding of CR2 to the C3d/C3dg fragments of complement component C3. Wild-type or mutant forms of CR2 were expressed on K562 cells, and the ability of these CR2-expressing cells to bind gp350 was measured using flow cytometry. Mutations directed toward the two N-terminal extracellular domains of CR2 (SCR1-2) reveal that a large contiguous surface of CR2 SCR1-2 is involved in gp350 binding, including a number of positively charged residues (Arg-13, (Arg-28, (Arg-36, Lys-41, Lys-57, Lys-67, and Arg-83). These data appear to complement the CR2 binding site on gp350, which is characterized by a preponderance of negative charge. In addition to identifying the importance of charge in the formation of a CR2-gp350 complex, we also provide evidence that both SCR1 and SCR2 make contact with gp350. Specifically, two anti-CR2 monoclonal antibodies, designated as monoclonal antibodies 171 and 1048 whose primary epitopes are located within SCR2, inhibit binding of wild-type CR2 to EBV gp350; with regard to SCR1, both K562 cells expressing an S15P mutation and recombinant S15P CR2 proteins exhibit diminished gp350 binding. PMID:17925391

  14. Modification of tribology and high-temperature behavior of Ti 48Al 2Cr 2Nb intermetallic alloy by laser cladding

    Liu, Xiu-Bo; Wang, Hua-Ming

    2006-06-01

    In order to improve the tribology and high-temperature oxidation properties of the Ti-48Al-2Cr-2Nb intermetallic alloy simultaneously, mixed NiCr-Cr 3C 2 precursor powders had been investigated for laser cladding treatment to modify wear and high-temperature oxidation resistance of the material. The alloy samples were pre-placed with NiCr-80, 50 and 20%Cr 3C 2 (wt.%), respectively, and laser treated at the same parameters, i.e., laser output power 2.8 kW, beam scanning speed 2.0 mm/s, beam dimension 1 mm × 18 mm. The treated samples underwent tests of microhardness, wear and high-temperature oxidation. The results showed that laser cladding with different constitution of mixed precursor NiCr-Cr 3C 2 powders improved surface hardness in all cases. Laser cladding with NiCr-50%Cr 3C 2 resulted in the best modification of tribology and high-temperature oxidation behavior. X-ray diffraction (XRD), optical microscope (OM), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS) analyses indicated that the formation of reinforced Cr 7C 3, TiC and both continuous and dense Al 2O 3, Cr 2O 3 oxide scales were supposed to be responsible for the modification of the relevant properties. As a result, the present work had laid beneficial surface engineering foundation for TiAl alloy applied as future light weight and high-temperature structural candidate materials.

  15. Microstructure and temperature coefficient of resistance of thin cermet resistor films deposited from CrSi2-Cr-SiC targets by S-gun magnetron

    Technological solutions for producing nanoscale cermet resistor films with sheet resistances above 1000 Ω/□ and low temperature coefficients of resistance (TCR) have been investigated. 2-40 nm thick cermet films were sputter deposited from CrSi2-Cr-SiC targets by a dual cathode dc S-gun magnetron. In addition to studying film resistance versus temperature, the nanofilm structural features and composition were analyzed using scanning electron microscopy, atomic force microscopy, high-resolution transmission electron microscopy, energy-dispersive x-ray spectroscopy, and electron energy loss spectroscopy. This study has revealed that all cermet resistor films deposited at ambient and elevated temperatures were amorphous. The atomic ratio of Si to Cr in these films was about 2 to 1. The film TCR displayed a significant increase when the deposited film thickness was reduced below 2.5 nm. An optimized sputter process consisting of wafer degassing, cermet film deposition at elevated temperature with rf substrate bias, and a double annealing in vacuum, consisting of in situ annealing following the film sputtering and an additional annealing following the exposure of the wafers to air, has been found to be very effective for the film thermal stabilization and for fine tuning the film TCR. Cermet films with thicknesses in the range of 2.5-4 nm deposited using this technique had sheet resistances ranging from 1800 to 1200 Ω/□ and TCR values from -50 ppm/ deg. C to near zero, respectively. A possible mechanism responsible for the high efficiency of annealing the cermet films in vacuum (after preliminary exposure to air), resulting in resistance stabilization and TCR reduction, is also discussed.

  16. Safe cycling!

    Anaïs Schaeffer

    2012-01-01

    The HSE Unit will be running a cycling safety campaign at the entrances to CERN's restaurants on 14, 15 and 16 May. Pop along to see if they can persuade you to get back in the saddle!   With summer on its way, you might feel like getting your bike out of winter storage. Well, the HSE Unit has come up with some original ideas to remind you of some of the most basic safety rules. This year, the prevention campaign will be focussing on three themes: "Cyclists and their equipment", "The bicycle on the road", and "Other road users". This is an opportunity to think about the condition of your bike as well as how you ride it. From 14 to 16 May, representatives of the Swiss Office of Accident Prevention and the Touring Club Suisse will join members of the HSE Unit at the entrances to CERN's restaurants to give you advice on safe cycling (see box). They will also be organising three activity stands where you can test your knowle...

  17. Numerical adiabatic potentials of orthorhombic Jahn-Teller effects retrieved from ultrasound attenuation experiments. Application to the SrF2:Cr crystal

    Zhevstovskikh, I. V.; Bersuker, I. B.; Gudkov, V. V.; Averkiev, N. S.; Sarychev, M. N.; Zherlitsyn, S.; Yasin, S.; Shakurov, G. S.; Ulanov, V. A.; Surikov, V. T.

    2016-06-01

    A methodology is worked out to retrieve the numerical values of all the main parameters of the six-dimensional adiabatic potential energy surface (APES) of a polyatomic system with a quadratic T-term Jahn-Teller effect (JTE) from the ultrasound experiments. The method is based on a verified assumption that ultrasound attenuation and speed encounter anomalies when the direction of propagation and polarization of its wave of strain coincides with the characteristic directions of symmetry breaking in the JTE. For the SrF2:Cr crystal, employed as a basic example, we observed anomaly peaks in the temperature dependence of attenuation of ultrasound at frequencies of 50-160 MHz in the temperature interval of 40-60 K for the wave propagating along the [110] direction, for both the longitudinal and the shear modes, the latter with two polarizations along the [001] and [1 1 ¯ 0 ] axes, respectively. We show that these anomalies are due to the ultrasound relaxation by the system of non-interacting Cr2+ JT centers with orthorhombic local distortions. The interpretation of the experimental findings is based on the T2 g⊗(eg+t2 g) JTE problem including the linear and the quadratic terms of vibronic interactions in the Hamiltonian and the same-symmetry modes reduced to one interaction mode. Combining the experimental results with a theoretical analysis, we show that on the complicated six-dimensional APES of this system with three tetragonal, four trigonal, and six orthorhombic extrema points, the latter are global minima, while the former are saddle points, and we estimate numerically all the main parameters of this surface, including the linear and quadratic vibronic coupling constants, the primary force constants, the coordinates of all the extrema points and their energies, the energy barrier between the orthorhombic minima, and the tunneling splitting of the ground vibrational states. To our knowledge, such a based-on-experimental-data numerical reconstruction of the APES

  18. Magnetic tunneling junctions with the Heusler compound Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al

    Conca Parra, A.

    2007-07-20

    Materials with large spin polarization are required for applications in spintronics devices. For this reason, major research efforts are directed to study the properties of compounds which are expected to be half metals, i.e. materials with 100% spin polarization. Half metals are expected to have a gap in the density of states at the Fermi energy for one spin band while the other spin band is metallic leading to a completely spin polarized current. The ferromagnetic full Heusler alloy Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al (CCFA) has attracted great interest in the field of spintronics. The high Tc (800 K) and the expected half metallicity make CCFA a good candidate for applications in spintronic devices such as magnetic tunneling junctions (MTJs). This thesis presents the results of the study of the electronic and structural properties of CCFA thin films. The films were implemented in magnetic tunneling junctions and the tunneling magnetoresistance effect (TMR) was investigated. The main objectives were the measurement of the spin polarisation of the CCFA alloy and to obtain information about its electronic structure. The influence of the deposition conditions on the thin film properties and on the surface crystalline order and their respective influence on the TMR ratio was investigated. Epitaxial CCFA thin films with two alternative growth orientations were deposited on different substrates and buffer layers. An annealing step was used to improve the crystalline properties of the thin films. In the tunneling junctions, Al{sub 2}O{sub 3} was used as a barrier material and Co was chosen as counter electrode. The multilayer systems were patterned in Mesa structures using lithographic techniques. In the framework of the Julliere model, a maximum spin polarisation of 54% at 4K was measured in tunneling junctions with epitaxial CCFA electrodes. A strong influence of the annealing temperature on the TMR ratio was determined. The increase of the TMR ratio could be correlated

  19. Deposition of La0.8Sr0.2Cr0.97V0.03O3 and MnCr2O4 thin films on ferritic alloy for solid oxide fuel cell application

    Mikkelsen, Lars; Chen, Ming; Hendriksen, Peter Vang;

    2007-01-01

    Single layer dense films of La0.8Sr0.2Cr0.97V0.03O3 (LSC) and MnCr2O4 with a thickness of 500 nm were deposited on a commercially available ferritic alloy (Crofer 22APU) by large-area Pulsed Laser Deposition. The deposited samples were subsequently oxidized at 1173 K for 500 h in humidified air...

  20. Nanostructured and Conventional Cr2O3, TiO2, and TiO2-Cr2O3 Thermal-Sprayed Coatings for Metal-Seated Ball Valve Applications in Hydrometallurgy

    Vernhes, Luc; Bekins, Craig; Lourdel, Nicolas; Poirier, Dominique; Lima, Rogerio S.; Li, Duanjie; Klemberg-Sapieha, Jolanta E.

    2016-06-01

    A detailed characterization project was undertaken by Velan, an international industrial valve designer and manufacturer, in collaboration with the National Research Council of Canada, Boucherville, and Polytechnique Montréal. The purpose was to assess the mechanical and tribological resistances of promising ceramic coatings for hydrometallurgy applications, including a novel n-TiO2-Cr2O3 blend. Hardness and shear strength were determined using microhardness indentation testers and universal tensile testing equipment. Wear resistance of the coatings under sliding wear, abrasion, and galling conditions were measured by standard pin-on-disk tests, abrasion tests, and custom-designed galling tests. The main result is that the synergy between Cr2O3 and n-TiO2 produced abrasion performance exceeding that of these materials alone. Also, an optimized balance between the hard and brittle Cr2O3 phases and the soft and ductile n-TiO2 phases resulted in higher abrasion, sliding, and galling resistance. The novel n-TiO2-Cr2O3 blend is therefore considered as a promising evolution of the current TiO2-Cr2O3 blend.

  1. Finite Element Analysis of Precision Forging Process for 2Cr18Ni8W2 Stainless Steel Bar%2Cr18Ni8W2不锈钢圆棒精锻过程的有限元模拟

    肖强

    2016-01-01

    采用DEFORM-3D有限元软件模拟了2Cr18Ni8W2不锈钢在两种精锻工艺下的温度和等效应变分布,分析了工艺条件对精锻过程中温度场和应变场的影响,并进行了试验验证.结果表明:采用优化工艺条件锻造时钢坯表面及内部温度均比现场工艺条件下的低,其内部应变分布也比现场工艺条件下的均匀;在精锻过程中增加倒数第二道次的变形量会导致锻造后的钢坯内部应变分布的不均匀性,造成晶粒大小不均,从而引起探伤误报警;采用优化工艺条件锻造后的圆棒经探伤完全合格,其组织均匀,在等轴晶的内部出现大量的形变孪晶.%The temperature and equivalent strain distribution of 2Cr18Ni8W2 stainless steel bar in two different precision forging processes were simulated by the DEFORM-3D finite element analysis software.The effects of forging process condition on the temperature field and strain field during precision forging process were analyzed and then verified by experimental results.The results show that the temperatures on the surface and inner of the billet in the optimized forging process were lower than those in the on-site process,and the strain distribution in the billet was also more homogeneous than that in on-site process.The deformation increase in the penultimate pass during the precision forging process would increase the uneven distribution of the strain in the billet after the last pass,initiating the grain size nonuniformity,and then resulted in ultrasonic test misinformation.The stainless steel bar forged with optimized process passed the ultrasonic test.The microstructure was uniform and the deformation twin was observed inside the isometric crystal.

  2. Study on HIx cycling techniques for thermo chemical hydrogen production process. R and D on refractory and corrosion resistant pressure sensor for hydrogen iodide cycling test loop

    High refractory and corrosion resistant pressure sensor with tantalum/SUS 316 welding type diaphragm has been developed for hydrogen iodide cycling test in thermo chemical hydrogen production process and tested its fatigue and corrosion properties. With these results, the following conclusions were derived. (1) New type of high refractory and corrosion resistant alloy was found in Ta/SUS 316 welding region and its elemental composition was identified as 83Ta-11Fe-2Ni-2Cr-2Mo [wt.%]. (2) This pressure sensor achieved a new record of the longest fatigue life over 107 cycles within 0.44%F.S./degC and (3) No degradation of its mechanical and sensitivity properties was found after 20000 hours hydrogen iodide cycling test. (author)

  3. Novel mode of 2-fold interpenetration observed in a primitive cubic network of formula [Ni(1,2-bis(4-pyridyl)acetylene)2(Cr2O7)]n.

    Scott, Hayley S; Bajpai, Alankriti; Chen, Kai-Jie; Pham, Tony; Space, Brian; Perry, John J; Zaworotko, Michael J

    2015-10-14

    A primitive cubic (pcu) network of formula [Ni(1,2-bis(4-pyridyl)acetylene)2(Cr2O7)]n, , has been synthesised and found to exhibit a novel type of inclined 2-fold interpenetration and an isosteric heat of adsorption (Q(st)) of 30.5 kJ mol(-1) towards CO2 at zero loading. Q(st) is relatively high in the broad context but less than that observed in related hybrid ultramicroporous materials, a feature that can be understood after studying pore structure and molecular simulations of CO2 adsorption. PMID:26307270

  4. Manufacturing, Microstructure and Corrosion Resistance of Electrophoretically Deposited SiO2 and Ni/SiO2 Coatings On X2CrNiMo17–12–2 Steel

    Ratajski T.

    2016-06-01

    Full Text Available The SiO2 and Ni/SiO2 coatings were electrophoretically deposited on X2CrNiMo17-12-2 steel using ethanol-based suspensions of the SiO2 and Ni powders. The influence of the zeta potential and concentration of the suspensions, the applied voltage and deposition time on the quality of the coatings was studied. Microstructure of the plan-view and cross sections of the coatings was investigated using scanning electron microscopy. The plan-view images revealed the uniform microstructure of the coatings with sporadically observed cracks, pores as well SiO2 and Ni agglomerates. On the cross-sections, the Cr2O3 layer, resulted from oxidation of the substrate during sintering of the coatings was observed. The polarization tests have shown that SiO2 and Ni/SiO2 coatings improve the corrosion resistance of the X2CrNiMo17-12-2 steel in 3.5% NaCl aqueous solution.

  5. Mixed-ligand coordination of the (UO2)2+ cation and apophyllite topology of uranyl chlorochromate layer in the structure of ((CH3)2CHNH3)[(UO2)(CrO4)Cl(H2O)

    Addition of the Cl- anions to the synthesis mixture stabilizes specific structures of uranyl complexes which results in new compounds with the unprecedented structural topologies. ((CH3)2CHNH3)[(UO2)(CrO4) . Cl(H2O)] is a new member of the small family of compounds based upon the Ur(XmOn)5 (X = Cl, Br, I) bipyramids. The structure is based upon uranyl chloride chromate layers that alternate with the layers of protonated amine molecules. The layers contain UrClO4 pentagonal bipyramids that share three of its equatorial corners with CrO4 tetrahedra. Topological analysis shows that the [(UO2)(CrO4)Cl(H2O)]- layer belongs to the same topology of interpolyhedral linkage as in α-UO2MoO4(H2O)2. This type of topology (linkage of 4-membered rings creating 8-membered rings) is known in silicate crystal chemistry as the topology of the [Si4O10] layers in the minerals of the apophyllite group. Their linkage via various intermediate units results in a large family of open-framework and pillared silicates. (orig.)

  6. The business cycle and the life cycle

    Paul Gomme; Richard Rogerson; Peter Rupert; Randall Wright

    2004-01-01

    The paper documents how cyclical fluctuations in market work vary over the life cycle and then assesses the predictions of a life-cycle version of the growth model for those observations. The analysis yields a simple but striking finding. The main discrepancy between the model and that data lies in the inability of the model to account for fluctuations in hours for individuals in the first half of their life cycle. The predictions for those in the latter half of the life cycle are quite close...

  7. Solar cycle 25: another moderate cycle?

    Cameron, Robert H; Schuessler, Manfred

    2016-01-01

    Surface flux transport simulations for the descending phase of cycle 24 using random sources (emerging bipolar magnetic regions) with empirically determined scatter of their properties provide a prediction of the axial dipole moment during the upcoming activity minimum together with a realistic uncertainty range. The expectation value for the dipole moment around 2020 $(2.5\\pm1.1\\,$G) is comparable to that observed at the end of cycle 23 (about $2\\,$G). The empirical correlation between the dipole moment during solar minimum and the strength of the subsequent cycle thus suggests that cycle 25 will be of moderate amplitude, not much higher than that of the current cycle. However, the intrinsic uncertainty of such predictions resulting from the random scatter of the source properties is considerable and fundamentally limits the reliability with which such predictions can be made before activity minimum is reached.

  8. Solar Cycle 25: Another Moderate Cycle?

    Cameron, R. H.; Jiang, J.; Schüssler, M.

    2016-06-01

    Surface flux transport simulations for the descending phase of Cycle 24 using random sources (emerging bipolar magnetic regions) with empirically determined scatter of their properties provide a prediction of the axial dipole moment during the upcoming activity minimum together with a realistic uncertainty range. The expectation value for the dipole moment around 2020 (2.5 ± 1.1 G) is comparable to that observed at the end of Cycle 23 (about 2 G). The empirical correlation between the dipole moment during solar minimum and the strength of the subsequent cycle thus suggests that Cycle 25 will be of moderate amplitude, not much higher than that of the current cycle. However, the intrinsic uncertainty of such predictions resulting from the random scatter of the source properties is considerable and fundamentally limits the reliability with which such predictions can be made before activity minimum is reached.

  9. In-situ observations on interphase boundary migration and grain growth during α/γ phase transformation in iron-4. 2%Cr alloy%Fe-4.2%Cr合金α/γ相变中相边界移动和晶粒长大的原位观察

    渡边忠雄

    2005-01-01

    In-situ observations on α/γ phase transformation were made to study the effects of grain boundary microstructures on the formation of a new phase and the migration of α/γ interphase boundary in an iron-4. 2%Cr alloy. It was found that triple junctions with more random boundaries could be the primary nucleation sites for a new phase, while triple junctions with low angle or low ∑ coincidence boundaries did not play any role as preferential sites. The migration of α/γ interphase boundary during heating over the transformation temperature range showed the two stage behaviour characterized by a stage with a migration velocity of 0. 33~0. 75 mm/s and secondly by a stage with 3. 7~7. 6 mm/s. It was also found that abnormal grain growth and a high density of ∑3 coincidence boundaries could occur in a phase with bcc structure after cycling of α/γ phase transformation. A new mechanism of nucleation and growth of a new phase in α/γ phase transformation is proposed on the basis of roles of plane-matching interphase boundaries, as previously discussed on the origin of anisotropy of grain growth due to the migration of {110} plane-matching boundaries in Fe-3%Si alloy. The most recent theoretical work on the distribution of plane-matching boundaries in solids with different crystal structures was found to be useful for the understanding of nucleation and growth during α/γ phase transformation.

  10. Chromium substitution in mullite type bismuth aluminate: Bi{sub 2}Cr{sub x}Al{sub 4−x}O{sub 9} with 0≤x≤2.0

    Debnath, Tapas, E-mail: debnath@du.ac.bd [Department of Chemistry, University of Dhaka, Dhaka (Bangladesh); Ullah, Ahamed [Department of Chemistry, University of Dhaka, Dhaka (Bangladesh); Rüscher, Claus H. [Institute of Mineralogy, Leibniz University of Hannover, Hannover (Germany); Hussain, Altaf [Department of Chemistry, University of Dhaka, Dhaka (Bangladesh)

    2014-12-15

    Nominal compositions Bi{sub 2}Cr{sub x}Al{sub 4−x}O{sub 9} with 0.0≤x≤2.0 (Δx=0.2) were prepared using appropriate amounts of nitrates dissolved in glycerine and heated at 800 °C for 24 h as we previously used for the preparation of solid solution series Bi{sub 2}M{sub x}/M′{sub 4−x}O{sub 9} (M/M′=Fe/Al, Ga/Al and Fe/Ga). The samples were characterized using XRD, FTIR and optical microscopic techniques. Analyses of XRD data show mullite type single phase can be prepared up to x=1.2. The lattice parameters (a, b and c) increases with increasing Cr content. Further increase in x (i.e., x≥1.4) show the presence of some additional phases indicating a limiting value for Cr doping is in the range of 1.2≤x<1.4. The effect of Cr incorporation could also be observed in the infrared absorption spectra via systematic hard mode shifts of certain lattice modes, e.g. the Bi–O related vibration changes from 96 cm{sup −1} to 93 cm{sup −1} with increasing x up to 1.2 and certain intensity changes together with shift in peak positions. Interestingly, the absence of any splitting and shift of the high energy IR absorption peak at 821 cm{sup −1} as assigned to the characteristic tetrahedral type dimer, Al{sub 2}O{sub 7}, indicate that the Cr thus partially substitutes only the octahedrally coordinated Al. This is confirmed by Rietveld structure refinements, too. - Graphical abstract: Structural model of Cr doped bismuth aluminate, Bi{sub 2}Cr{sub x}Al{sub 4−x}O{sub 9}. - Highlights: • Chromium doped bismuth aluminate, Bi{sub 2}Cr{sub x}Al{sub 4−x}O{sub 9} with mullite type structure are synthesized. • The samples are characterized by XRD and FTIR techniques. • Cr can replace only certain amount of octahedrally coordinated Al in Bi{sub 2}Al{sub 4}O{sub 9} under present experimental conditions.

  11. Estudo da remoção de Cd2+ , Cr3+ e Pb2+ de soluções aquosas empregando a zeólita natural escolecita: uma abordagem cinética e termodinâmica

    Karla Carolina Saqueto

    2010-12-01

    Full Text Available Devido às suas propriedades físicas favoráveis, associados à alta estabilidade física e química em condições normais, materiais naturais, como as zeólitas, têm sido amplamente aplicadas no tratamento de águas residuárias para remover poluentes. A capacidade de troca catiônica de uma zeólita natural brasileira, identificada como escolecita, tem sido avaliada para aplicação no controle de águas residuais. No presente trabalho o potencial da escolecita para remoção de metais tóxicos (Cd2+, Cr3+ e Pb2+ foi investigado. Os efeitos do pH, da temperatura e da concentração de metais em solução durante o processo de adsorção foram avaliados. Isotermas descrevendo o mecanismo de adsorção foram obtidas utilizando-se soluções contendo 50 mg.L-1 de cada metal. Foi observada a tendência de retenção de Cr3+ = Cd2+> Pb2+, entre 50 e 250 mg.L-1 e Cr3+ = Cd2+> Pb2+, e entre 200 mg.L-1 e 600 mg.L-1, a tendência é mais favorecida, é Cd2+> Cr3+> Pb2+. Acima de 600 mg.L-1, a tendência de adsorção observada é Cr3+>Cd2+>Pb2+. Adsorção de Cr3+ e Cd2+ é melhor descrita pela isoterma de Freundich enquanto que para o Pb2+ é pela isoterma de Langmuir. A ordem de dessorção é Cd2+> Pb2+> Cr3+. A adsorção dos metais estudados segue a cinética de primeira ordem e não foi observada uma expressiva influencia da temperatura na adsorção dos cátions.

  12. Cycling in Sydney, Australia

    Alexis Zander

    2013-01-01

    Full Text Available Introduction. Cycling can be an enjoyable way to meet physical activity recommendations and is suitable for older people; however cycling participation by older Australians is low. This qualitative study explored motivators, enablers, and barriers to cycling among older people through an age-targeted cycling promotion program. Methods. Seventeen adults who aged 50–75 years participated in a 12-week cycling promotion program which included a cycling skills course, mentor, and resource pack. Semistructured interviews at the beginning and end of the program explored motivators, enablers, and barriers to cycling. Results. Fitness and recreation were the primary motivators for cycling. The biggest barrier was fear of cars and traffic, and the cycling skills course was the most important enabler for improving participants’ confidence. Reported outcomes from cycling included improved quality of life (better mental health, social benefit, and empowerment and improved physical health. Conclusions. A simple cycling program increased cycling participation among older people. This work confirms the importance of improving confidence in this age group through a skills course, mentors, and maps and highlights additional strategies for promoting cycling, such as ongoing improvement to infrastructure and advertising.

  13. Initiation and growth of thermal fatigue crack networks in an AISI 304 L type austenitic stainless steel (X2 CrNi18-09)

    We studied the behaviour of a 304 L type austenitic stainless steel submitted to thermal fatigue. Using the SPLASH equipment of CEA/SRMA we tested parallelepipedal specimens on two sides: the specimens are continuously heated by Joule effect, while two opposites faces are cyclically. cooled by a mixed spray of distilled water and compressed air. This device allows the reproduction and the study of crack networks similar to those observed in nuclear power plants, on the inner side of circuits fatigued by mixed pressurized water flows at different temperatures. The crack initiation and the network constitution at the surface were observed under different thermal conditions (Tmax = 320 deg C, ΔT between 125 and 200 deg C). The experiment produced a stress gradient in the specimen, and due to this gradient, the in-depth growth of the cracks finally stopped. The obtained crack networks were studied quantitatively by image analysis, and different parameters were studied: at the surface during the cycling, and post mortem by step-by-step layer removal by grinding. The maximal depth obtained experimentally, 2.5 mm, is relatively coherent with the finite element modelling of the SPLASH test, in which compressive stresses appear at a depth of 2 mm. Some of the crack networks obtained by thermal fatigue were also tested in isothermal fatigue crack growth under 4-point bending, at imposed load. The mechanisms of the crack selection, and the appearance of the dominating crack are described. Compared to the propagation of a single crack, the crack networks delay the propagation, depending on the severity of the crack competition for domination. The dominating crack can be at the network periphery, in that case it is not as shielded by its neighbours as a crack located in the center of the network. It can also be a straight crack surrounded by more sinuous neighbours. Indeed, on sinuous cracks, the loading is not the same all along the crack path, leading to some morphological

  14. The role of complement receptors type 1 (CR1, CD35) and 2 (CR2, CD21) in promoting C3 fragment deposition and membrane attack complex formation on normal peripheral human B cells

    Nielsen, Claus Henrik; Pedersen, Morten Løbner; Marquart, Hanne Vibeke;

    2002-01-01

    Normal human B lymphocytes are known to activate the alternative pathway (AP) of complement, leading to C3-fragment deposition and membrane attack complex (MAC) formation. The process is mediated via complement receptor type 2 (CR2, CD21), with complement receptor type 1 (CR1, CD35) playing a...... subsidiary role. In this study, we examine the relative contributions of CR1 and CR2 to the deposition of C3 fragments and MAC on B lymphocytes under circumstances where all complement pathways are operational. C3-fragment deposition and MAC formation were assessed on human peripheral B lymphocytes in the......) bearing CR1, however, markedly reduced both C3-fragment deposition and MAC formation. Our data suggest that C3-fragment deposition and MAC formation on B lymphocytes in vivo may involve both AP and classical pathway activation, with CR1 contributing significantly to the latter. On the other hand, the...

  15. Effect of Post-Weld Heat Treatment on Mechanical and Electrochemical Properties of Gas Metal Arc-Welded 316L (X2CrNiMo 17-13-2) Stainless Steel

    Muhammad, F.; Ahmad, A.; Farooq, A.; Haider, W.

    2016-08-01

    In the present research work, corrosion behavior of post-weld heat-treated (PWHT) AISI 316L (X2CrNiMo 17-13-2) specimens joined by gas metal arc welding is compared with as-welded samples by using potentiodynamic polarization technique. Welded samples were PWHT at 1323 K for 480 s and quenched. Mechanical properties, corrosion behavior and microstructures of as-welded and PWHT specimens were investigated. Microstructural studies have shown grain size refinement after PWHT. Ultimate tensile strength and yield strength were found maximum for PWHT samples. Bend test have shown that PWHT imparted ductility in welded sample. Fractographic analysis has evidenced ductile behavior for samples. Potentiodynamic polarization test was carried out in a solution composed of 1 M H2SO4 and 1 N NaCl. Corrosion rate of weld region was 127.6 mpy, but after PWHT, it was decreased to 13.12 mpy.

  16. Selective corrosion of duplex stainless steel. Pt. 1 Corrosion behaviour of duplex stainless steel X2CrNiMoN22-5-3 with special consideration of the microstructure

    This paper is dealing with investigations on interrelations between microstructure and corrosion behaviour of duplex stainless steel X2CrNiMoN22-5-3. With the application of conventional methods like Strauss- and Huey-test it is not possible to describe correctly the corrosion behaviour. In contrary, by means of the development of the electrochemical potentiodynamic reactivation (EPR) method it is possible to give a reliable proof of corrosion susceptibility. The knowledge about the corrosion of duplex stainless steel was intensified by fundamental investigation of interrelations between precipitations and corrosion behaviour. By means of numerous investigations on the microstructure by means of SEM and TEM secondary phases were analysed and quantified and depletion areas created by precipitations were characterized. (orig.)

  17. Selective corrosion of duplex stainless steel. Pt. 2 Localized corrosion manifestations under exposure of chlorides on duplex stainless steel X2CrNiMoN22-5-3 and mechanical behavior in dependence of the microstructure

    In completion to part 1 of this paper this part deals with interrelations between localized corrosion manifestations, mechanical properties and the microstructure of duplex stainless steel X2CrNiMoN22-5-3. The pit formation on duplex stainless steels is substantially determined by the distribution of the alloying elements within single phases and by defects in the oxide layer. The positive properties of molybdenum become ineffective at thicker oxide layers due to the fact, that molybdate, which is responsible for inhibition of pitting, can not be formed. Depletion areas caused by precipitations are preferential attack places for corrosion. The influence of chlorides for duplex stainless steels in rolled and welded conditions is characterized by a logarithmic dependence. (orig.)

  18. Predicted behavior of technetium in a geological disposal vault for used nuclear fuel -- Ramifications of a recent determination of the enthalpy of formation of TcO2(cr)

    Recently, the authors reported a value of ΔfH degree(TcO2(cr)) = -(458 ± 6) kJ-mol based on heat of solution measurements. The implications of this value on the database used in the Canadian Nuclear Fuel Waste Management Program for the evaluation of the technetium released by congruent dissolution of used UO2 fuel have now been assessed. It is probable that the Tc(IV) oxides are more stable than previously predicted and, hence, they are less likely to be oxidized to TcO4-(aq) under moderately reducing conditions. The authors have revised earlier calculations done to predict the solution concentrations of technetium species in a vault as a function of the oxidation conditions in model groundwaters

  19. Thermodynamics of bis-(η6-diphenyl)chromium (I) fulleride [(η6-Ph2)2Cr]+[C60].- in the range from T->(0 to 360)K

    In the present work, the temperature dependence of heat capacity Cp,mo=f(T) of crystalline bis-(η6-diphenyl)chromium (I) fulleride [(η6-Ph2)2Cr]+[C60].- has been measured by precision adiabatic vacuum calorimetry between T=(6 and 360)K with an uncertainty of +/-0.2%. In this temperature interval, the transformations were detected and their thermodynamic characteristics were estimated. The experimental data were used for calculating standard (po=0.1MPa) thermodynamic functions Cp,mo/R, Δ0THmo/RT, Δ0TSmo/R and Φmo/R=Δ0TSmo/R-Δ0THmo/RT (where R is the universal gas constant) in the range T->(0 to 360)K

  20. The role of complement receptors type 1 (CR1, CD35) and 2 (CR2, CD21) in promoting C3 fragment deposition and membrane attack complex formation on normal peripheral human B cells

    Nielsen, Claus Henrik; Pedersen, Morten Løbner; Marquart, Hanne Vibeke Hansen;

    2002-01-01

    Normal human B lymphocytes are known to activate the alternative pathway (AP) of complement, leading to C3-fragment deposition and membrane attack complex (MAC) formation. The process is mediated via complement receptor type 2 (CR2, CD21), with complement receptor type 1 (CR1, CD35) playing a...... subsidiary role. In this study, we examine the relative contributions of CR1 and CR2 to the deposition of C3 fragments and MAC on B lymphocytes under circumstances where all complement pathways are operational. C3-fragment deposition and MAC formation were assessed on human peripheral B lymphocytes in the...... presence of 30% autologous serum. Blocking the CR2 ligand-binding site with monoclonal antibody (mAb) FE8 resulted in significant reduction (37.9+/-11.9%) in C3-fragment deposition, whereas MAC formation was only marginally affected (12.1+/-22.2% reduction). Blocking the CR1 binding-site resulted in...

  1. Estudo da remoção de Cd2+ , Cr3+ e Pb2+ de soluções aquosas empregando a zeólita natural escolecita: uma abordagem cinética e termodinâmica

    Karla Carolina Saqueto; Nemésio Neves Batista Salvador; Marcos Valério Battisti; Ana Marta Ribeiro Machado

    2010-01-01

    Devido às suas propriedades físicas favoráveis, associados à alta estabilidade física e química em condições normais, materiais naturais, como as zeólitas, têm sido amplamente aplicadas no tratamento de águas residuárias para remover poluentes. A capacidade de troca catiônica de uma zeólita natural brasileira, identificada como escolecita, tem sido avaliada para aplicação no controle de águas residuais. No presente trabalho o potencial da escolecita para remoção de metais tóxicos (Cd2+, Cr3+ ...

  2. Life cycle assessment (LCA)

    Thrane, Mikkel; Schmidt, Jannick Andresen

    2004-01-01

    The chapter introduces Life Cycle Assessment (LCA) and its application according to the ISO 1404043 standards.......The chapter introduces Life Cycle Assessment (LCA) and its application according to the ISO 1404043 standards....

  3. HIV Life Cycle

    HIV Overview The HIV Life Cycle (Last updated 9/22/2015; last reviewed 9/22/2015) Key Points HIV gradually destroys the immune ... life cycle. What is the connection between the HIV life cycle and HIV medicines? Antiretroviral therapy (ART) ...

  4. Cycling To Awareness.

    Kozak, Stan

    1999-01-01

    Encourages environmental and outdoor educators to promote bicycling. In the community and the curriculum, cycling connects environmental issues, health and fitness, law and citizenship, appropriate technology, and the joy of being outdoors. Describes the Ontario Cycling Association's cycling strategy and its four components: school cycling…

  5. Sucrose-aided combustion synthesis of nanosized LiMn{sub 1.99-y}Li{sub y}M{sub 0.01}O{sub 4} (M = Al{sup 3+}, Ni{sup 2+}, Cr{sup 3+}, Co{sup 3+}, y = 0.01 and 0.06) spinels. Characterization and electrochemical behavior at 25 and at 55 C in rechargeable lithium cells

    Amarilla, J.M.; Pico, F.; Rojo, J.M.; Rojas, R.M. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas (CSIC), Sor Juana Ines de la Cruz no. 3, Cantoblanco, 28049 Madrid (Spain); Petrov, K.; Avdeev, G. [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria)

    2009-06-15

    Doubly doped LiMn{sub 1.99-y}Li{sub y}M{sub 0.01}O{sub 4} (M = Al{sup 3+}, Ni{sup 2+}, Cr{sup 3+}, Co{sup 3+}; y = 0.01 and 0.06) spinels have been synthesized by the sucrose-aided combustion method. Combined TG/DTA and XRD studies have shown that stoichiometric single-phase spinels are formed after annealing of the samples at 700 C for 1 h. The samples obtained are nanocrystalline materials having a narrow size-distribution and a coherent domain size between 40 and 60 nm, depending on the amount of fuel (sucrose) used in the synthesis. The influence of the Li-excess, the type of M{sup n+}-dopant cation and the amount of fuel used in the synthesis on the electrochemical behavior of the spinels in a Li-cell at room and at elevated temperature (55 C) has been studied. At 25 C all the spinels synthesized have a good capacity retention after 100 cycles, QRt-100 > 92%. At 55 C the increase of the Li-excess improves the cycling performances. Rate capability studies show that the spinels retain >90% of their capacity even at 5C rate. The synergic effect of the Li-excess and the particle size on the electrochemical properties of the spinels as cathode material has been settled. The LiMn{sub 1.93}Li{sub 0.06}M{sub 0.01}O{sub 4}, (M = Al{sup 3+}, Ni{sup 2+}) spinels, with cyclabilities >99.9% by cycle at both 25 and 55 C, and high rate capabilities, are the ones that show the best electrochemical properties. (author)

  6. The Solar Cycle

    David H. Hathaway

    2015-09-01

    Full Text Available The solar cycle is reviewed. The 11-year cycle of solar activity is characterized by the rise and fall in the numbers and surface area of sunspots. A number of other solar activity indicators also vary in association with the sunspots including; the 10.7 cm radio flux, the total solar irradiance, the magnetic field, flares and coronal mass ejections, geomagnetic activity, galactic cosmic ray fluxes, and radioisotopes in tree rings and ice cores. Individual solar cycles are characterized by their maxima and minima, cycle periods and amplitudes, cycle shape, the equatorward drift of the active latitudes, hemispheric asymmetries, and active longitudes. Cycle-to-cycle variability includes the Maunder Minimum, the Gleissberg Cycle, and the Gnevyshev–Ohl (even-odd Rule. Short-term variability includes the 154-day periodicity, quasi-biennial variations, and double-peaked maxima. We conclude with an examination of prediction techniques for the solar cycle and a closer look at cycles 23 and 24.

  7. Euro area business cycles

    Atilim Seymen

    2012-01-01

    The role of global, euro area and country-specific shocks in business cycle dynamics of six euro area member countries is assessed with the aid of SVAR models. Output fluctuations are driven by global shocks to a large extent in the euro area, and no Europeanisation of business cycles due to, for example the European Monetary Union, could be established. Business cycle heterogeneity is driven mainly by (asymmetric) country-specific shocks in the euro area and not by heterogeneous responses to...

  8. Fast breeder fuel cycle

    Basic elements of the ex-reactor part of the fuel cycle (reprocessing, fabrication, waste handling and transportation) are described. Possible technical and proliferation measures are evaluated, including current methods of accountability, surveillance and protection. The reference oxide based cycle and advanced cycles based on carbide and metallic fuels are considered utilizing conventional processes; advanced nonaqueous reprocessing is also considered. This contribution provides a comprehensive data base for evaluation of proliferation risks

  9. Real business cycle realizations

    Smith, Gregor W.; Stanley E. Zin

    1997-01-01

    Much recent business cycle research focuses on moments of macroeconomic aggregates. We construct examples of real business cycle sample paths for output, consumption, and employment for the U.S. economy. Annual sample paths are generated from an initial condition in 1925, measured technology and government spending shocks since then, and a standard, calibrated, one-sector model of the business cycle. Quarterly sample paths are generated similarly, from an initial condition in 1955. The law of...

  10. Fictitious Supercontinent Cycles

    Herndon, J Marvin

    2013-01-01

    Descriptions of phenomena, events, or processes made on the basis of problematic paradigms can be unreasonably complex (e.g. epicycles) or simply wrong (e.g. ultraviolet catastrophe). Supercontinent cycles, also called Wilson cycles, are, I submit, artificial constructs, like epicycles. Here I provide the basis for that assertion and describe published considerations from a fundamentally different, new, indivisible geoscience paradigm which obviate the necessity for assuming supercontinent cycles.

  11. Alternative fuel cycles

    Uranium resource utilization and economic considerations provide incentives to study alternative fuel cycles as future options to the PHWR natural uranium cycle. Preliminary studies to define the most favourable alternatives and their possible introduction dates are discussed. The important and uncertain components which influence option selection are reviewed, including nuclear capacity growth, uranium availability and demand, economic potential, and required technological developments. Finally, a summary of Ontario Hydro's program to further assess cycle selection and define development needs is given. (auth)

  12. Friction Generated Limit Cycles

    Ohlsson, Henrik; Åström, Karl Johan

    2001-01-01

    This paper treats limit cycles caused by friction. The goal has been to explain phenomena that have been observed experimentally in mechatronic systems. Experiments have shown that oscillations of qualitatively different types can be obtained simply by changing controller specifications. Stiction is important in some cases but not in others. Necessary conditions for limit cycle are given for the case where stiction is important. Conditions for local stability of the limit cycles are also pres...

  13. [Cycling in Zagreb].

    Matos, Stipan; Krapac, Ladislav; Krapac, Josip

    2007-01-01

    Cycling in Zagreb, as means of urban transport inside and outside the city, has a bright past, hazy presence but a promising future. Every day, aggressive citizens who lack urban traffic culture mistreat many cyclists but also many pedestrians. Sedentary way of living, unhealthy eating habits and inadequate recreation would surely be reduced if Zagreb had a network of cycling tracks (190 cm) or lanes (80 cm). Main city roads were constructed at the beginning of the 20th century. Today, the lack of cycling tracks is particularly evident in terms of missing connections between northern and southern parts of the city. Transportation of bikes in public vehicles, parking of bikes as well as cycling along the foot of the mountains Medvednica and Zumberacko gorje is not adequately organized. Better organization is necessary not only because of the present young generation but also because of the young who will shortly become citizens of the EU, where cycling is enormously popular. Cycling tourism is not known in Zagreb, partly due to inadequate roads. The surroundings of Zagreb are more suitable for cycling tourism and attractive brochures and tourist guides offer information to tourists on bikes. Professional, acrobatic and sports cycling do not have a tradition in Zagreb and in Croatia. The same holds true for recreational cycling and indoor exercise cycling. The authors discuss the impact of popularization of cycling using print and electronic media. The role of district and local self-government in the construction and improvement of traffic roads in Zagreb is very important. It is also significant for the implementation of legal regulations that must be obeyed by all traffic participants in order to protect cyclists, the most vulnerable group of traffic participants besides passengers. Multidisciplinary action of all benevolent experts would surely increase safety and pleasure of cycling in the city and its surroundings. This would also help reduce daily stress and

  14. Historicising the Hydrosocial Cycle

    Jeremy J. Schmidt

    2014-01-01

    This paper examines the historical claims made in support of the hydrosocial cycle. In particular, it considers how arguments advancing the hydrosocial cycle make historical claims regarding modernist conceptions of what water is (i.e. H2O) and its fit with society. The paper gives special emphasis to the society/nature dualism and to the notion of agency as key sites of contest in arguments regarding the hydrosocial cycle. It finds that, while several versions of the hydrosocial cycle seek t...

  15. Edgeworth cycles revisited

    Doyle, Joseph [MIT Sloan School of Management, 50 Memorial Drive, E52-447, Cambridge MA 02142 (United States); Muehlegger, Erich [John F. Kennedy School of Government, Harvard University, Mailbox 25, 79 JFK Street, Cambridge, MA 02138 (United States); Samphantharak, Krislert [Graduate School of International Relations and Pacific Studies, University of California at San Diego, 9500 Gilman Drive 1519, La Jolla, CA 92093 (United States)

    2010-05-15

    Some gasoline markets exhibit remarkable price cycles, where price spikes are followed by a series of small price declines: a pattern consistent with a model of Edgeworth cycles described by Maskin and Tirole. We extend the model and empirically test its predictions with a new dataset of daily station-level prices in 115 US cities. Consistent with the theory, and often in contrast with previous empirical work, we find the least and most concentrated markets are much less likely to exhibit cycling behavior both within and across cities; areas with more independent convenience-store gas stations are also more likely to cycle. (author)

  16. Life cycle management (LCM)

    Remmen, Arne; Thrane, Mikkel

    2004-01-01

    The chapter gives an introduction to Life Cycle Management (LCM) and shows how LCM can be practiced in different contexts and at different ambition levels.......The chapter gives an introduction to Life Cycle Management (LCM) and shows how LCM can be practiced in different contexts and at different ambition levels....

  17. Seeing the Carbon Cycle

    Drouin, Pamela; Welty, David J.; Repeta, Daniel; Engle-Belknap, Cheryl A.; Cramer, Catherine; Frashure, Kim; Chen, Robert

    2006-01-01

    In this article, the authors present a classroom experiment that was developed to introduce middle school learners to the carbon cycle. The experiment deals with transfer of CO[subscript 2] between liquid reservoirs and the effect CO[subscript 2] has on algae growth. It allows students to observe the influence of the carbon cycle on algae growth,…

  18. The carbon cycle revisited

    Bolin, Bert; Fung, Inez

    1992-01-01

    Discussions during the Global Change Institute indicated a need to present, in some detail and as accurately as possible, our present knowledge about the carbon cycle, the uncertainties in this knowledge, and the reasons for these uncertainties. We discuss basic issues of internal consistency within the carbon cycle, and end by summarizing the key unknowns.

  19. Life Cycle Environmental Management

    Pedersen, Claus Stig; Jørgensen, Jørgen; Pedersen, Morten Als

    1996-01-01

    processes. The discipline of life cycle environmental management (LCEM) focuses on the incorporation of environmental criteria from the life cycles of products and other company activities into the company management processes. This paper introduces the concept of LCEM as an important element of the...

  20. Family Life Cycle: 1980.

    Norton, Arthur J.

    1983-01-01

    Used data from a 1980 national sample survey to show differences in the timing of major family life-cycle events according to age, social and economic characteristics, and marital history. Results suggest that age generational differences, more than any other factor, influence timing of life-cycle events. (Author/JAC)

  1. Power Plant Cycling Costs

    Kumar, N.; Besuner, P.; Lefton, S.; Agan, D.; Hilleman, D.

    2012-07-01

    This report provides a detailed review of the most up to date data available on power plant cycling costs. The primary objective of this report is to increase awareness of power plant cycling cost, the use of these costs in renewable integration studies and to stimulate debate between policymakers, system dispatchers, plant personnel and power utilities.

  2. Rock Cycle Roulette.

    Schmidt, Stan M.; Palmer, Courtney

    2000-01-01

    Introduces an activity on the rock cycle. Sets 11 stages representing the transitions of an earth material in the rock cycle. Builds six-sided die for each station, and students move to the stations depending on the rolling side of the die. Evaluates students by discussing several questions in the classroom. Provides instructional information for…

  3. Predicting the Sunspot Cycle

    Hathaway, David H.

    2009-01-01

    The 11-year sunspot cycle was discovered by an amateur astronomer in 1844. Visual and photographic observations of sunspots have been made by both amateurs and professionals over the last 400 years. These observations provide key statistical information about the sunspot cycle that do allow for predictions of future activity. However, sunspots and the sunspot cycle are magnetic in nature. For the last 100 years these magnetic measurements have been acquired and used exclusively by professional astronomers to gain new information about the nature of the solar activity cycle. Recently, magnetic dynamo models have evolved to the stage where they can assimilate past data and provide predictions. With the advent of the Internet and open data policies, amateurs now have equal access to the same data used by professionals and equal opportunities to contribute (but, alas, without pay). This talk will describe some of the more useful prediction techniques and reveal what they say about the intensity of the upcoming sunspot cycle.

  4. Nuclear fuel cycles

    The source of energy in the nuclear reactors in fission if a heavy nuclei by absorbing a neutron and giving fission products, few neutrons and gamma radiation. The Nuclear Fuel Cycle may be broadly defined as the set of process and operations needed to manufacture nuclear fuels, to irradiate them in nuclear reactors and to treat and store them, temporarily or permanently, after irradiation. Several nuclear fuel cycles may be considered, depending on the type of reactor and the type of fuel used and whether or not the irradiated fuel will be reprocessed. The nuclear fuel cycle starts with uranium exploration and ends with final disposal of the material used and generated during the cycle. For practical reasons the process has been further subdivided into the front-end and the back-end. The front-end of the cycle occurs before irradiation and the back-end begins with the discharge of spent fuel from the reactor

  5. Spectroscopy of the electronic states of the Heusler compounds Co2FeAl and Co2Cr0.6Fe0.4Al and the influence of oxidation

    Jourdan, Martin; Große-Schulte, Fabian; Hahn, Michaela; Schönhense, Gerd

    2011-04-01

    The band structures of the Heusler compounds Co2Cr0.6Fe0.4Al and Co2FeAl were investigated in situ by angle-resolved ultraviolet photoemission spectroscopy. The samples were prepared by a sputtering process optimized for tunnelling junction preparation, the photoemission process in the normal direction of the (0 0 1)-oriented thin films was excited by a helium gas discharge lamp (hν = 21.2 eV and hν = 40.8 eV). The spectra of clean samples are compared with calculations of the total and partial bulk density of states and are evaluated within the three-step model of photoemission. Basic agreement with theoretical predictions of the bulk band structure is concluded. At oxygen exposures of the thin films of only 1 Langmuir a chemisorption phase with significant changes in the valence-band spectrum near the Fermi energy is observed. At 10 L oxygen the spectra are indicative of an oxide within the UPS probing depth.

  6. T lymphocyte expression of complement receptor 2 (CR2/CD21): a role in adhesive cell-cell interactions and dysregulation in a patient with systemic lupus erythematosus (SLE).

    Levy, E; Ambrus, J; Kahl, L; Molina, H; Tung, K; Holers, V M

    1992-11-01

    Complement receptor 2 (CR2, CD21), the receptor for both the C3d,g portion of human complement component C3 and the Epstein-Barr virus, has been recently described on peripheral T cells. By using dual stain flow cytometric analysis, we have also observed that a peripheral T lymphocyte subpopulation of normal healthy donors bears CR2 in a range varying from 1.1 to 23.2% (mean 12.6%) of total CD3+ cells. T lymphocytes from nine patients with inactive SLE expressed CR2 in a similar range. Three patients with active SLE were also studied. One of them, having neuropathy and glomerulonephritis, displayed an expansion of the CR2 T cell subpopulation which reached as much as 89% of total CD3+ cells. To examine potential functional roles of T cell CR2, cells from a Jurkat-derived CR2 expressing T cell line were found to bind in vitro to human CR2-, complement-coated K562 cell targets in a CR2- and complement-dependent fashion. Based on these studies, we hypothesize that CR2 might act to increase adherence of T cells to nucleated target cells bearing C3d,g, a function which may be relevant to cytotoxicity or other T cell activities requiring cell-cell interaction. PMID:1424280

  7. Structural characterization and electron density distribution studies of (La0.8Ca0.2)(Cr0.9-xCo0.1Mnx)O3

    Saravanan, R.; Thenmozhi, N.; Fu, Yen-Pei

    2016-07-01

    The doped lanthanum chromite (La0.8Ca0.2)(Cr0.9-xCo0.1Mnx)O3 (x=0.03, 0.06, 0.09 and 0.12) were synthesized by solid state reaction technique. The samples have been characterized by X-ray diffraction for structural and charge density analysis. XRD data show that the grown samples are orthorhombic in structure with single phase. The spatial charge density distribution in the unit cell for the synthesized samples has been studied using maximum entropy method. Further, the samples were analyzed by UV-visible spectrometry for optical properties and scanning electron microscopy for surface morphology. From the optical data, it was found that the direct band gap of the samples range from 2.27 to 2.46 eV. The samples were also investigated by vibrating sample magnetometry for magnetic properties. From VSM data, it is inferred that all the samples in this series are found to be predominantly antiferromagnetic in nature. Since the doped lanthanum chromites have good mechanical properties and electrical conductivity at high temperature, these materials are used in solid oxide fuel cells (SOFC).

  8. Corrosion behaviors of a γ-toughened Cr13Ni5Si2/Cr3Ni5Si2 multi-phase ternary metal silicide alloy in NaCl solution

    Corrosion behaviors of a novel corrosion-resistant γ-toughened Cr13Ni5Si2/Cr3Ni5Si2 multi-phase ternary metal silicide alloy and properties of the passive film formed in NaCl solution were examined by anodic polarization, cyclic polarization and electrochemical impedance spectroscopy (EIS) experiments as well as X-ray photoelectron spectroscopy (XPS) and potentiostatic polarization measurements. Effects of immersion time and chloride ion concentration on corrosion behaviors of the alloy were also evaluated. Results indicated that the alloy exhibited excellent corrosion resistance in NaCl solution due to the spontaneous formation of a compact and protective passive film composed mainly of chromium (III) oxide as well as the high chemical stability and strong inter-atomic bonds inherent to Cr13Ni5Si2 and Cr3Ni5Si2 intermetallic phases. Moreover, corrosion resistance of the alloy was quite insensitive to the increase of chloride ion concentration and was improved noticeably with the increasing immersion time

  9. Study of vibrational and rapid local motions of hydrogen in the storage compound Ti0.8 Zr0.2 CrMnH3 by slow neutron scattering

    The vibrational and the rapid local motions of hydrogen in the storage compound Ti0,8 Zr0,2 CrMnH3 have been studied by slow neutron scattering with the beryllium-filter-time-of-flight spectrometer. The form of the density of states of the normal modes of vibrations in host metal does no appear to change on hydrogenation, but a shift of 25% towards lower frequencies has been observed. Debye temperatures for the metal and corresponding hydride have been estimated to be respectively (522 +- 15)K and (311 +- 10)K. An energy distribution consisting of three peeks ∼ 50mev (FWHM) wide corresponding to the energy transfer of 85, 115 and 141mev has been observed and were attributed to hydrogen local vibrations in three types of interstices wich differs in composition of Ti and Zr atoms. In the quasielastic scattering, a broadening of 15μev has been detected for the momentum transfer Q = 2,1(angstrom)-1 and for temperature T= 1250C. The broadening has been attributed to rapid local motions of hydrogen in a dumb-bell of lenght equal to the jump lenght for diffusion, l approx. 3(angstrom). (author)

  10. Spectroscopy of the electronic states of the Heusler compounds Co2FeAl and Co2Cr0.6Fe0.4Al and the influence of oxidation

    The band structures of the Heusler compounds Co2Cr0.6Fe0.4Al and Co2FeAl were investigated in situ by angle-resolved ultraviolet photoemission spectroscopy. The samples were prepared by a sputtering process optimized for tunnelling junction preparation, the photoemission process in the normal direction of the (0 0 1)-oriented thin films was excited by a helium gas discharge lamp (hν = 21.2 eV and hν = 40.8 eV). The spectra of clean samples are compared with calculations of the total and partial bulk density of states and are evaluated within the three-step model of photoemission. Basic agreement with theoretical predictions of the bulk band structure is concluded. At oxygen exposures of the thin films of only 1 Langmuir a chemisorption phase with significant changes in the valence-band spectrum near the Fermi energy is observed. At 10 L oxygen the spectra are indicative of an oxide within the UPS probing depth.

  11. Comparison between MgO and AlO{sub x} barriers in Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al-tunnel junctions

    Herbort, Christian; Conca, Andres; Jourdan, Martin; Adrian, Hermann [Institut fuer Physik, Johannes Gutenberg Universitaet, Staudinger Weg 7, 55128 Mainz (Germany)

    2007-07-01

    In magnetic tunnel junctions with conventional ferromagnetic electrodes MgO proved to be a superior barrier material concerning the achievable tunnel magnetoresistance effect (TMR). Alternatively, large TMR effects could be obtained by employing novel materials with high spin polarisation. On example for such a material is the Heusler compound Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al (CCFA). We compare the TMR effect of CCFA based tunnel junctions with amorphous AlO{sub x} and epitaxial MgO barriers. Whereas we have already optimized junctions with AlO{sub x} barriers and obtained TMR effects which can be associated to a spin polarization of the CCFA>50%, the process of MgO deposition requires further improvement. The interface at the barriers is characterized by in situ RHEED and LEED as well as by STM investigations. It is shown that epitaxial MgO can be grown by rf-magnetron sputtering on epitaxial (100) oriented CCFA thin films. The barrier morphology of AlO{sub x} and MgO is compared by transmission electron microscopy (TEM) and related to the TMR effect. The dependence of the TMR effect on the major preparation parameters is shown.

  12. Effects of post-growth annealing on structural and compositional properties of the Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al surface and its relevance for the surface electron spin polarization

    Wuestenberg, Jan-Peter; Fischer, Johannes; Aeschlimann, Martin; Cinchetti, Mirko [Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Erwin-Schroedingerstr. 46, D-67663 Kaiserslautern (Germany); Herbort, Christian; Jourdan, Martin, E-mail: jpwuest@physik.uni-kl.d [Institute of Physics, University of Mainz, Staudinger Weg 7, D-55099 Mainz (Germany)

    2009-04-21

    In this study we investigate the influence of post-growth annealing on different Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al samples. We find strong changes in the geometric surface structure as well as in the element specific concentrations during the annealing process. These irreversible changes go in hand with characteristic changes in the electron spin polarization (ESP) at the surface: as observed in Cinchetti et al (2007 J. Phys. D: Appl. Phys. 40 1544), the iron buffered sample shows the largest spin polarization at the Fermi level. The latter remains positive as a consequence of the reduced density of states for the minority carriers due to the predicted minority gap, which can be clearly seen for all samples above the proposed minimum annealing temperature of 400 {sup 0}C. Above this temperature we observe a characteristic dip in the ESP as a sign of increasing structure quality. It appears at 0.6 eV binding energy and is consistent with a peak in the minority electron density of states seen in both experiment and theory.

  13. Brillouin light scattering study of Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al and Co{sub 2}FeAl Heusler compounds

    Gaier, O; Hamrle, J; Trudel, S; Conca Parra, A; Hillebrands, B [Fachbereich Physik and Forschungszentrum OPTIMAS, Technische Universitaet Kaiserslautern, Erwin-Schroedinger-Strasse 56, D-67663 Kaiserslautern (Germany); Arbelo, E; Herbort, C; Jourdan, M, E-mail: gaier@physik.uni-kl.d [Institut fuer Physik, Johannes-Gutenberg-Universitaet Mainz, Staudinger Weg 7, D-55099 Mainz (Germany)

    2009-04-21

    The thermal magnonic spectra of Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al (CCFA) and Co{sub 2}FeAl were investigated using Brillouin light scattering (BLS) spectroscopy. For CCFA, the exchange constant A (exchange stiffness D) is found to be 0.48 {+-} 0.04 {mu}erg cm{sup -1} (203 {+-} 16 meV A{sup 2}), while for Co{sub 2}FeAl the corresponding values of 1.55 {+-} 0.05 {mu}erg cm{sup -1} (370 {+-} 10 meV A{sup 2}) were found. The observed asymmetry in the BLS spectra between the Stokes and anti-Stokes frequencies was assigned to an interplay between the asymmetrical profiles of hybridized Damon-Esbach and perpendicular standing spin-wave modes, combined with the optical sensitivity of the BLS signal to the upper side of the CCFA or Co{sub 2}FeAl film.

  14. Magnetism of the Heusler compound Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al at interfaces with Cr and AlO{sub x}

    Jourdan, Martin; Arbelo-Jorge, Elena; Herbort, Christian [Institut fuer Physik, Johannes Gutenberg Universitaet Mainz (Germany); Charlton, Timothy; Langridge, Sean [ISIS Facility, Rutherford Appleton Laboratory, Oxfordshire (United Kingdom)

    2008-07-01

    Co{sub 2}Cr{sub 0.6}Fe{sub 0.4}Al (CCFA) belongs to the Heusler compounds for which a huge spin polarization is theoretically predicted. However, for spintronics applications the electronic properties at the interface with insulating barriers (tunneling devices) or paramagnetic metals (spin valves) are of major importance. We investigate the ferromagnetic moment of CCFA at interfaces with Cr and AlO{sub x} by polarised neutron reflectometry (PNR). Fitting the reflectometry data to a model which allows layers of the CCFA with different magnetic moments compared to the bulk moment, evidence for a reduced moment in a 1-2nm interface layer of the CCFA was identified. However, the reduction is clearly smaller at the Cr interface compared to the AlO{sub x} interface. Additionally, at the Cr interface the best fits are obtained, if ferromagnetic order of the complete 6nm Cr layer is assumed (with {approx_equal}0.3 {mu}{sub B}/Cr-atom). This surprising observation is discussed in the framework of epitaxially induced stress of the Cr layer.

  15. Effects of post-growth annealing on structural and compositional properties of the Co2Cr0.6Fe0.4Al surface and its relevance for the surface electron spin polarization

    In this study we investigate the influence of post-growth annealing on different Co2Cr0.6Fe0.4Al samples. We find strong changes in the geometric surface structure as well as in the element specific concentrations during the annealing process. These irreversible changes go in hand with characteristic changes in the electron spin polarization (ESP) at the surface: as observed in Cinchetti et al (2007 J. Phys. D: Appl. Phys. 40 1544), the iron buffered sample shows the largest spin polarization at the Fermi level. The latter remains positive as a consequence of the reduced density of states for the minority carriers due to the predicted minority gap, which can be clearly seen for all samples above the proposed minimum annealing temperature of 400 0C. Above this temperature we observe a characteristic dip in the ESP as a sign of increasing structure quality. It appears at 0.6 eV binding energy and is consistent with a peak in the minority electron density of states seen in both experiment and theory.

  16. Interlinked Cycles for Index Coding: Generalizing Cycles and Cliques

    Thapa, Chandra; Ong, Lawrence; Johnson, Sarah J.

    2016-01-01

    We consider a graphical approach to index coding. While cycles have been shown to provide coding gain, only disjoint cycles and cliques (a specific type of overlapping cycles) have been exploited in existing literature. In this paper, we define a more general form of overlapping cycles, called the interlinked-cycle (IC) structure, that generalizes cycles and cliques. We propose a scheme, called the interlinked-cycle-cover (ICC) scheme, that leverages IC structures in digraphs to construct sca...

  17. Bimodality and the Hale cycle

    Wilson, Robert M.

    1988-01-01

    Evidence is provided of a modulation of between 20 and 24 yr for the Hale cycle, and comparison of consecutive pairs of cycles strongly suggests that even-numbered cycles are preferentially paired with odd-numbered following cycles. The results indicate that cycles 22 and 23 form a new cyle pair. The sum of monthly mean sunspot numbers over consecutively paired sunspot cycles for Hale cycle 12 is found to be about 19,100 + or - 3000.

  18. Assessing Cycling Participation in Australia

    Chris Rissel; Cameron Munro; Adrian Bauman

    2013-01-01

    Planning and evaluating cycling programs at a national or state level requires accurate measures of cycling participation. However, recent reports of cycling participation have produced very different estimates. This paper examines the reported rates of cycling in five recent population surveys of cycling. Three surveys (one national and two from Sydney) asking respondents when they last rode a bicycle generated cycling participation (cycled in the past year) estimates of 29.7%, 34.1% and 28....

  19. Future fuel cycles

    A fuel cycle must offer both financial and resource savings if it is to be considered for introduction into Ontario's nuclear system. The most promising alternative CANDU fuel cycles are examined in the context of both of these factors over a wide range of installed capacity growth rates and economic assumptions, in order to determine which fuel cycle, or cycles, should be introduced, and when. It is concluded that the optimum path for the long term begins with the prompt introduction of the low-enriched-uranium fuel cycle. For a wide range of conditions, this cycle remains the optimum throughout the very long term. Conditions of rapid nuclear growth and very high uranium price escalation rates warrant the supersedure of the low-enriched-uranium cycle by either a plutonium-topped thorium cycle or plutonium recycle, beginning between 2010 and 2025. It is also found that the uranium resource position is sound in terms of both known resources and production capability. Moreover, introduction of the low-enriched-uranium fuel cycle and 1250 MWe reactor units will assure the economic viability of nuclear power until at least 2020, even if uranium prices increase at a rate of 3.5% above inflation. The interrelationship between these two conclusions lies in the tremendous incentive for exploration which will occur if the real uranium price escalation rate is high. From a competitive viewpoint, nuclear power can withstand increases in the price of uranium. However, such increases will likely further expand the resource base, making nuclear an even more reliable energy source. (auth)

  20. Cycling across borders

    Jože Kos

    1999-01-01

    Full Text Available The article describes the intent and content of the international Velo-City conference 1999, Maribor–Graz and the organisation of this cycling development planning meeting. It focuses on the resolution of the conference concerning cycling traffic policies, the emerging network of European cycling connections and the traffic planning workshop about a difficult square in Maribor. The content framework of particular papers is shown, as well as other post-conference events. In the conclusion certain useful addresses for obtaining added data on sustainable traffic planning are given.

  1. Initiation and growth of thermal fatigue crack networks in an AISI 304 L type austenitic stainless steel (X2 CrNi18-09); Amorcage et propagation de reseaux de fissures de fatigue thermique dans un acier inoxydable austenitique de type X2 CrNi18-09 (AISI 304 L)

    Maillot, V

    2004-07-01

    We studied the behaviour of a 304 L type austenitic stainless steel submitted to thermal fatigue. Using the SPLASH equipment of CEA/SRMA we tested parallelepipedal specimens on two sides: the specimens are continuously heated by Joule effect, while two opposites faces are cyclically. cooled by a mixed spray of distilled water and compressed air. This device allows the reproduction and the study of crack networks similar to those observed in nuclear power plants, on the inner side of circuits fatigued by mixed pressurized water flows at different temperatures. The crack initiation and the network constitution at the surface were observed under different thermal conditions (Tmax = 320 deg C, {delta}T between 125 and 200 deg C). The experiment produced a stress gradient in the specimen, and due to this gradient, the in-depth growth of the cracks finally stopped. The obtained crack networks were studied quantitatively by image analysis, and different parameters were studied: at the surface during the cycling, and post mortem by step-by-step layer removal by grinding. The maximal depth obtained experimentally, 2.5 mm, is relatively coherent with the finite element modelling of the SPLASH test, in which compressive stresses appear at a depth of 2 mm. Some of the crack networks obtained by thermal fatigue were also tested in isothermal fatigue crack growth under 4-point bending, at imposed load. The mechanisms of the crack selection, and the appearance of the dominating crack are described. Compared to the propagation of a single crack, the crack networks delay the propagation, depending on the severity of the crack competition for domination. The dominating crack can be at the network periphery, in that case it is not as shielded by its neighbours as a crack located in the center of the network. It can also be a straight crack surrounded by more sinuous neighbours. Indeed, on sinuous cracks, the loading is not the same all along the crack path, leading to some

  2. The effect of cycling intensity on cycling economy during seated and standing cycling

    Arkesteijn, Marco; Simon A. Jobson; James G Hopker; Passfield, Louis

    2016-01-01

    BACKGROUND: Previous research has shown that cycling in a standing position reduces cycling economy compared with seated cycling. It is unknown whether the cycling intensity moderates the reduction in cycling economy while standing. PURPOSE: The aim was to determine whether the negative effect of standing on cycling economy would be decreased at a higher intensity. METHODS: Ten cyclists cycled in 8 different conditions. Each condition was either at an intensity of 50% or 70% ...

  3. Cycles in graphs

    Alspach, BR

    1985-01-01

    This volume deals with a variety of problems involving cycles in graphs and circuits in digraphs. Leading researchers in this area present here 3 survey papers and 42 papers containing new results. There is also a collection of unsolved problems.

  4. Fuel cycle data survey

    A survey of the fuel cycle cost data published during 1977 and 1978 is presented in tabular and graphical form. Cost trends for the period 1965 onwards are presented for yellow cake, conversion, uranium enrichment, fuel fabrication and reprocessing

  5. Fuel cycle studies

    Programs are being conducted in the following areas: advanced solvent extraction techniques, accident consequences, fuel cycles for nonproliferation, pyrochemical and dry processes, waste encapsulation, radionuclide transport in geologic media, hull treatment, and analytical support for LWBR

  6. The Pneumocystis life cycle

    Cécile-Marie Aliouat-Denis; Anna Martinez; El Moukhtar Aliouat; Muriel Pottier; Nausicaa Gantois; Eduardo Dei-Cas

    2009-01-01

    First recognised as "schizonts" of Trypanosoma cruzi, Pneumocystis organisms are now considered as part of an early-diverging lineage of Ascomycetes. As no robust long-term culture model is available, most data on the Pneumocystis cell cycle have stemmed from ultrastructural images of infected mammalian lungs. Although most fungi developing in animals do not complete a sexual cycle in vivo, Pneumocystis species constitute one of a few exceptions. Recently, the molecular identification of seve...

  7. Reviewing the Leverage Cycle

    Ana Fostel; John Geanakoplos

    2013-01-01

    We review the theory of leverage developed in collateral equilibrium models with incomplete markets. We explain how leverage tends to boost asset prices, and create bubbles. We show how leverage can be endogenously determined in equilibrium, and how it depends on volatility. We describe the dynamic feedback properties of leverage, volatility, and asset prices, in what we call the Leverage Cycle. We also describe some cross-sectional implications of multiple leverage cycles, including contagio...

  8. Offshore Rankine Cycles

    Brandsar, Jo

    2012-01-01

    The title of the thesis - "Offshore Rankine Cycles" - is very general and cover a large range of engineering fields, e.g. thermodynamic cycles (Rankine, ORC, Brayton, Kalina, etc.), mechanical equipment (gas/steam turbine, heat exchangers and additional equipment) and safety concerns (flammable and/or toxic fluids, high temperature and pressures), to name the most important.The thesis try to give a brief overview of all critical points and alternatives, concerning employment of a wa...

  9. Resuscitating Real Business Cycles

    Robert G. King; Sergio T. Rebelo

    2000-01-01

    The Real Business Cycle (RBC) research program has grown spectacularly over the last decade, as its concepts and methods have diffused into mainstream macroeconomics. Yet, there is increasing skepticism that technology shocks are a major source of business fluctuations. This chapter exposits the basic RBC model and shows that it requires large technology shocks to produce realistic business cycles. While Solow residuals are sufficiently volatile, these imply frequent technological regress. Pr...

  10. Solar Cycle Prediction

    Petrovay, K

    2010-01-01

    A review of solar cycle prediction methods and their performance is given, including forecasts for cycle 24 and focusing on aspects of the solar cycle prediction problem that have a bearing on dynamo theory. The scope of the review is further restricted to the issue of predicting the amplitude (and optionally the epoch) of an upcoming solar maximum no later than right after the start of the given cycle. Prediction methods form three main groups. Precursor methods rely on the value of some measure of solar activity or magnetism at a specified time to predict the amplitude of the following solar maximum. Their implicit assumption is that each numbered solar cycle is a consistent unit in itself, while solar activity seems to consist of a series of much less tightly intercorrelated individual cycles. Extrapolation methods, in contrast, are based on the premise that the physical process giving rise to the sunspot number record is statistically homogeneous, i.e., the mathematical regularities underlying its variati...

  11. Structural and magnetic properties of nanocrystalline Nd{sub 4.5}Fe{sub 72}Co{sub 2}Cr{sub 3}Al{sub 1}B{sub 17.5} ribbons

    Pampillo, L.G. [Laboratorio de Solidos Amorfos, Departamento de Fisica, Facultad de Ingenieria, Universidad de Buenos Aires, Av. Paseo Colon 850 (C1063ACV), Ciudad de, Buenos Aires (Argentina)]. E-mail: lpampillo@fi.uba.ar; Saccone, F.D. [Laboratorio de Solidos Amorfos, Departamento de Fisica, Facultad de Ingenieria, Universidad de Buenos Aires, Av. Paseo Colon 850 (C1063ACV), Ciudad de, Buenos Aires (Argentina); Sirkin, H.R.M. [Laboratorio de Solidos Amorfos, Departamento de Fisica, Facultad de Ingenieria, Universidad de Buenos Aires, Av. Paseo Colon 850 (C1063ACV), Ciudad de, Buenos Aires (Argentina)

    2007-02-01

    In this work, it was made a study on structural and magnetic properties of nanocrystalline Nd{sub 4.5}Fe{sub 72}Co{sub 2}Cr{sub 3}Al{sub 1}B{sub 17.5} ribbons obtained from crystallisation of amorphous precursors. A complex two-step crystallisation process, was found by differential scanning calorimetry (DSC): a first crystallisation peak at around T=570 deg. C exhibiting the precipitation of {alpha}-Fe and t-Fe{sub 3}B phases and a diffusive stage ending in a second exothermic peak. Also, isothermal annealings of 10 min duration were performed at 605, 635, 650 and 685 deg. C . Hysteresis curves of isothermally annealed samples showed magnetic hardening, with coercive fields above 2 kOe and an optimised M {sub R}/M {sub S} ratio of around 0.6. Except for the highest treatment temperature used in this work, the demagnetizing curves of annealed ribbons exhibited a step near zero field. This fact suggests a low exchange coupling between hard and soft phases, which can be attributed to the grain border phases. Otherwise, Moessbauer effect spectroscopy allowed us to determine that the absence of step in the demagnetizing curve of ribbons annealed at 685 deg. C , may be attributed to the formation of a {alpha}-(Fe, Co) solid solution (with hyperfine parameters B {sub HF}=35.5 T and {delta}=-0.11 mm/s). The formation of this solid solution also explains the diffusive process in the second crystallisation stage observed by DSC experiment.

  12. Helium process cycle

    Ganni, Venkatarao

    2007-10-09

    A unique process cycle and apparatus design separates the consumer (cryogenic) load return flow from most of the recycle return flow of a refrigerator and/or liquefier process cycle. The refrigerator and/or liquefier process recycle return flow is recompressed by a multi-stage compressor set and the consumer load return flow is recompressed by an independent consumer load compressor set that maintains a desirable constant suction pressure using a consumer load bypass control valve and the consumer load return pressure control valve that controls the consumer load compressor's suction pressure. The discharge pressure of this consumer load compressor is thereby allowed to float at the intermediate pressure in between the first and second stage recycle compressor sets. Utilizing the unique gas management valve regulation, the unique process cycle and apparatus design in which the consumer load return flow is separate from the recycle return flow, the pressure ratios of each recycle compressor stage and all main pressures associated with the recycle return flow are allowed to vary naturally, thus providing a naturally regulated and balanced floating pressure process cycle that maintains optimal efficiency at design and off-design process cycle capacity and conditions automatically.

  13. Helium process cycle

    Ganni, Venkatarao

    2008-08-12

    A unique process cycle and apparatus design separates the consumer (cryogenic) load return flow from most of the recycle return flow of a refrigerator and/or liquefier process cycle. The refrigerator and/or liquefier process recycle return flow is recompressed by a multi-stage compressor set and the consumer load return flow is recompressed by an independent consumer load compressor set that maintains a desirable constant suction pressure using a consumer load bypass control valve and the consumer load return pressure control valve that controls the consumer load compressor's suction pressure. The discharge pressure of this consumer load compressor is thereby allowed to float at the intermediate pressure in between the first and second stage recycle compressor sets. Utilizing the unique gas management valve regulation, the unique process cycle and apparatus design in which the consumer load return flow is separate from the recycle return flow, the pressure ratios of each recycle compressor stage and all main pressures associated with the recycle return flow are allowed to vary naturally, thus providing a naturally regulated and balanced floating pressure process cycle that maintains optimal efficiency at design and off-design process cycle capacity and conditions automatically.

  14. Life Cycle Sustainability Dashboard

    Traverso, Marzia; Finkbeiner, Matthias; Jørgensen, Andreas;

    2012-01-01

    One method to assess the sustainability performance of products is life cycle sustainability assessment (LCSA), which assesses product performance considering the environmental,economic, and social dimensions of the life cycle. The results of LCSA can be used to compare different products or to...... sustainability is the communicability of the results by means of a graphical representation (a cartogram), characterized by a suitable chromatic scale and ranking score. The integration of LCSA and the dashboard of sustainability into a so-called Life Cycle Sustainability Dashboard (LCSD) is described here. The...... support decision making toward sustainable production and consumption. In both cases, LCSA results could be too disaggregated and consequently too difficult to understand and interpret by decision makers. As non-experts are usually the target audience of experts and scientists, and are also involved in...

  15. Buoyancy organic Rankine cycle

    Schoenmaker, J.; Rey, J.F.Q. [Centro de Engenharia, Modelagem e Ciencias Sociais Aplicadas, Universidade Federal do ABC (CECS-UFABC), Rua Santa Adelia 166, Bairro Bangu, 09210-170 Santo Andre, SP (Brazil); Pirota, K.R. [Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas (UNICAMP), C.P. 6165, Campinas, SP (Brazil)

    2011-03-15

    In the scope of renewable energy, we draw attention to a little known technique to harness solar and geothermal energy. The design here proposed and analyzed is a conceptual hybrid of several patents. By means of a modified organic Rankine cycle, energy is obtained utilizing buoyancy force of a working fluid. Based on thermodynamic properties we propose and compare the performance of Pentane and Dichloromethane as working fluids. Theoretical efficiencies up to 0.26 are estimated for a 51 m (Pentane) and 71.5 m (Dichloromethane) high column of water in a regime below 100 C operation temperature. These findings are especially relevant in the scope of distributed energy systems, combined cycle plants, and low-temperature Rankine cycles. (author)

  16. Superfluid thermodynamic cycle refrigerator

    Swift, Gregory W.; Kotsubo, Vincent Y.

    1992-01-01

    A cryogenic refrigerator cools a heat source by cyclically concentrating and diluting the amount of .sup.3 He in a single phase .sup.3 He-.sup.4 He solution. The .sup.3 He in superfluid .sup.4 He acts in a manner of an ideal gas in a vacuum. Thus, refrigeration is obtained using any conventional thermal cycle, but preferably a Stirling or Carnot cycle. A single phase solution of liquid .sup.3 He at an initial concentration in superfluid .sup.4 He is contained in a first variable volume connected to a second variable volume through a superleak device that enables free passage of .sup.4 He while restricting passage of .sup.3 He. The .sup.3 He is compressed (concentrated) and expanded (diluted) in a phased manner to carry out the selected thermal cycle to remove heat from the heat load for cooling below 1 K.

  17. Superfluid thermodynamic cycle refrigerator

    A cryogenic refrigerator cools a heat source by cyclically concentrating and diluting the amount of 3He in a single phase 3He-4He solution. The 3He in superfluid 4He acts in a manner of an ideal gas in a vacuum. Thus, refrigeration is obtained using any conventional thermal cycle, but preferably a Stirling or Carnot cycle. A single phase solution of liquid 3He at an initial concentration in superfluid 4He is contained in a first variable volume connected to a second variable volume through a superleak device that enables free passage of 4He while restricting passage of 3He. The 3He is compressed (concentrated) and expanded (diluted) in a phased manner to carry out the selected thermal cycle to remove heat from the heat load for cooling below 1 K. 12 figs

  18. Cycles in fossil diversity

    Rohde, Robert A.; Muller, Richard A.

    2004-10-20

    It is well-known that the diversity of life appears to fluctuate during the course the Phanerozoic, the eon during which hard shells and skeletons left abundant fossils (0-542 Ma). Using Sepkoski's compendium of the first and last stratigraphic appearances of 36380 marine genera, we report a strong 62 {+-} 3 Myr cycle, which is particularly strong in the shorter-lived genera. The five great extinctions enumerated by Raup and Sepkoski may be an aspect of this cycle. Because of the high statistical significance, we also consider contributing environmental factors and possible causes.

  19. Global Carbon Cycle

    Probst, Jean-Luc; Faure, Hugues; Veizer, Jan

    1999-01-01

    The European Union of Geosciences held its 9th biannual meeting in Strasbourg, March 23–27, 1997. During this meeting, Symposium N8 18, Global carbon Cycle, was held under the sponsorship of the IGCP 1 n8404 on the «Terrestrial Carbon in the past 125 Ka», the INQUA 2 Carbon Commission and the ESCOBA-Biosphere 3 project of the EC Environment and Climate Programme. The «Global Carbon Cycle» Symposium attracted 28 oral and poster presentations and about one hundred par...

  20. Resurrecting Equilibria Through Cycles

    Barnett, Richard C.; Bhattacharya, Joydeep; Bunzel, Helle

    equilibria because they asymptotically violate some economic restriction of the model. The literature has always ruled out such paths. This paper studies a pure-exchange monetary overlapping generations economy in which real balances cycle forever between momentary equilibrium points. The novelty is to show...... that segments of the offer curve that have been previously ignored, can in fact be used to produce asymptotically valid cyclical paths. Indeed, a cycle can bestow dynamic validity on momentary equilibrium points that had erstwhile been classified as dynamically invalid....

  1. Global water cycle

    Robertson, Franklin; Goodman, Steven J.; Christy, John R.; Fitzjarrald, Daniel E.; Chou, Shi-Hung; Crosson, William; Wang, Shouping; Ramirez, Jorge

    1993-01-01

    This research is the MSFC component of a joint MSFC/Pennsylvania State University Eos Interdisciplinary Investigation on the global water cycle extension across the earth sciences. The primary long-term objective of this investigation is to determine the scope and interactions of the global water cycle with all components of the Earth system and to understand how it stimulates and regulates change on both global and regional scales. Significant accomplishments in the past year are presented and include the following: (1) water vapor variability; (2) multi-phase water analysis; (3) global modeling; and (4) optimal precipitation and stream flow analysis and hydrologic processes.

  2. Life Cycle Environmental Management

    Pedersen, Claus Stig; Jørgensen, Jørgen; Pedersen, Morten Als

    1996-01-01

    A precondition for environmentally conscious management is the awareness of the environmental impact potentials created by an industrial company. There is an obvious need for management tools to support the implementation of relevant environmental criteria into the industrial decision making...... processes. The discipline of life cycle environmental management (LCEM) focuses on the incorporation of environmental criteria from the life cycles of products and other company activities into the company management processes. This paper introduces the concept of LCEM as an important element...... of the complete set of environmental objects in an industrial manufacturing company....

  3. Carbon cycle makeover

    Canfield, Donald Eugene; Kump, Lee R.

    2013-01-01

    remaining in sediments after respiration leave a residual of oxygen in the atmosphere. The source of oxygen to the atmosphere represented by organic matter burial is balanced by oxygen sinks associated with rock weathering and chemical reaction with volcanic gases. This is the long-term carbon and oxygen...... geochemical cycle. But Earth is an old planet, and oxygen levels have changed through time (2). On page 540 of this issue, Schrag et al. (3) challenge the most commonly used geochemical approach to assess long-term changes in the coupled oxygen and carbon cycles....

  4. Menstrual cycle pattern and fertility

    Kolstad, Henrik A.; Bonde, Jens Peter; Hjøllund, Niels Henrik;

    1999-01-01

    To characterize how the menstrual cycle pattern relates to fertility regardless of potential biases caused by inappropriate coital timing during the menstrual cycle or early embryonal loss.......To characterize how the menstrual cycle pattern relates to fertility regardless of potential biases caused by inappropriate coital timing during the menstrual cycle or early embryonal loss....

  5. The Pneumocystis life cycle

    Cécile-Marie Aliouat-Denis

    2009-05-01

    Full Text Available First recognised as "schizonts" of Trypanosoma cruzi, Pneumocystis organisms are now considered as part of an early-diverging lineage of Ascomycetes. As no robust long-term culture model is available, most data on the Pneumocystis cell cycle have stemmed from ultrastructural images of infected mammalian lungs. Although most fungi developing in animals do not complete a sexual cycle in vivo, Pneumocystis species constitute one of a few exceptions. Recently, the molecular identification of several key players in the fungal mating pathway has provided further evidence for the existence of conjugation and meiosis in Pneumocystisorganisms. Dynamic follow-up of stage-to-stage transition as well as studies of stage-specific proteins and/or genes would provide a better understanding of the still hypothetical Pneumocystislife cycle. Although difficult to achieve, stage purification seems a reasonable way forward in the absence of efficient culture systems. This mini-review provides a comprehensive overview of the historical milestones leading to the current knowledge available on the Pneumocystis life cycle.

  6. Educational Business Cycles

    Tepe, Markus; Vanhuysse, Pieter

    2009-01-01

    teacher employment patterns at the state level in Germany and find strong evidence of cycling mechanisms, in the form of electioneering and honeymooning. Against a backdrop of a continuously shrinking total teachers' pool, German state-level incumbents accelerate the hiring of new teachers during election...

  7. Educational Business Cycles

    Tepe, Markus; Vanhuysse, Pieter

    teacher employment patterns at the state level in Germany and find strong evidence of cycling mechanisms, in the form of electioneering and honeymooning. Against a backdrop of a continuously shrinking total teachers' pool, German state-level incumbents accelerate the hiring of new teachers during election...

  8. 90-Day Cycle Handbook

    Park, Sandra; Takahashi, Sola

    2013-01-01

    90-Day Cycles are a disciplined and structured form of inquiry designed to produce and test knowledge syntheses, prototyped processes, or products in support of improvement work. With any type of activity, organizations inevitably encounter roadblocks to improving performance and outcomes. These barriers might include intractable problems at…

  9. ITER fuel cycle

    Resulting from the Conceptual Design Activities (1988-1990) by the parties involved in the International Thermonuclear Experimental Reactor (ITER) project, this document summarizes the design requirements and the Conceptual Design Descriptions for each of the principal subsystems and design options of the ITER Fuel Cycle conceptual design. The ITER Fuel Cycle system provides for the handling of all tritiated water and gas mixtures on ITER. The system is subdivided into subsystems for fuelling, primary (torus) vacuum pumping, fuel processing, blanket tritium recovery, and common processes (including isotopic separation, fuel management and storage, and processes for detritiation of solid, liquid, and gaseous wastes). After an introduction describing system function and conceptual design procedure, a summary of the design is presented including a discussion of scope and main parameters, and the fuel design options for fuelling, plasma chamber vacuum pumping, fuel cleanup, blanket tritium recovery, and auxiliary and common processes. Design requirements are defined and design descriptions are given for the various subsystems (fuelling, plasma vacuum pumping, fuel cleanup, blanket tritium recovery, and auxiliary/common processes). The document ends with sections on fuel cycle design integration, fuel cycle building layout, safety considerations, a summary of the research and development programme, costing, and conclusions. Refs, figs and tabs

  10. Re-Cycling

    Brown, Robert W.; Covault, Corbin E.

    2015-01-01

    An old comedy routine on Saturday Night Live by Father Guido Sarducci introduced a "Five-Minute University," because five minutes is all that's remembered after graduation anyway. In counterpoint, we discuss "cycling," a teaching method for memory enhancement. Our principal implementation consists of offering a simple version…

  11. Assisted Cycling Tours

    Hollingsworth, Jan Carter

    2008-01-01

    This article discusses Assisted Cycling Tours (ACT), a Westminster, Colorado based 501(c)3, non-profit that is offering the joy of bicycle tours in breathtaking, scenic locations to children and adults with developmental and physical disabilities and their families. ACT was founded by Bob Matter and his son David with a goal of opening up the…

  12. The Science of Cycling

    Crompton, Zoe; Daniels, Shelley

    2014-01-01

    Children are engaged by finding out about science in the real world (Harlen, 2010). Many children will be cyclists or will have seen or heard about the success of British cyclists in the Olympics and the Tour de France. This makes cycling a good hook to draw children into learning science. It is also a good cross-curricular topic, with strong…

  13. Boundedly rational credit cycles

    S??ez, Mar??a

    1996-01-01

    We propose an evolutionary model of a credit market. We show that the economy exhibits credit cycles. The model predicts dynamics which are consistent with some evidence about the Great Depression. Real shocks trigger episodes of credit--crunch which are observed in the process of adjustment towards the post shock equilibrium.

  14. Fuel cycle. Fuel reprocessing

    Reprocessing includes mechanical and chemical operations on spent fuel for extraction of valuable materials. These operations are a part of the fuel cycle. In this paper are given technical data on spent fuels, transport, storage, decladding, dissolution, Purex process, elaboration of U and Pu and reprocessing engineering. This article is completed by 106 references

  15. The Geologic Nitrogen Cycle

    Johnson, B. W.; Goldblatt, C.

    2013-12-01

    N2 is the dominant gas in Earth's atmosphere, and has been so through the majority of the planet's history. Originally thought to only be cycled in significant amounts through the biosphere, it is becoming increasingly clear that a large degree of geologic cycling can occur as well. N is present in crustal rocks at 10s to 100s of ppm and in the mantle at 1s to perhaps 10s of ppm. In light of new data, we present an Earth-system perspective of the modern N cycle, an updated N budget for the silicate Earth, and venture to explain the evolution of the N cycle over time. In an fashion similar to C, N has a fast, biologically mediated cycle and a slower cycle driven by plate tectonics. Bacteria fix N2 from the atmosphere into bioavailable forms. N is then cycled through the food chain, either by direct consumption of N-fixing bacteria, as NH4+ (the primary waste form), or NO3- (the most common inorganic species in the modern ocean). Some organic material settles as sediment on the ocean floor. In anoxic sediments, NH4+ dominates; due to similar ionic radii, it can readily substitute for K+ in mineral lattices, both in sedimentary rocks and in oceanic lithosphere. Once it enters a subduction zone, N may either be volatilized and returned to the atmosphere at arc volcanoes as N2 or N2O, sequestered into intrusive igneous rocks (as NH4+?), or subducted deep into the mantle, likely as NH4+. Mounting evidence indicates that a significant amount of N may be sequestered into the solid Earth, where it may remain for long periods (100s m.y.) before being returned to the atmosphere/biosphere by volcanism or weathering. The magnitude fluxes into the solid Earth and size of geologic N reservoirs are poorly constrained. The size of the N reservoirs contained in the solid Earth directly affects the evolution of Earth's atmosphere. It is possible that N now sequestered in the solid Earth was once in the atmosphere, which would have resulted in a higher atmospheric pressure, and

  16. Efficient Enumeration of Chordless Cycles

    Dias, Elisângela Silva; Castonguay, Diane; Longo, Humberto; Jradi, Walid Abdala Rfaei

    2013-01-01

    In a finite undirected simple graph, a {\\it chordless cycle} is an induced subgraph which is a cycle. We propose two algorithms to enumerate all chordless cycles of such a graph. Compared to other similar algorithms, the proposed algorithms have the advantage of finding each chordless cycle only once. To ensure this, we introduced the concepts of vertex labeling and initial valid vertex triplet. To guarantee that the expansion of a given chordless path will always lead to a chordless cycle, w...

  17. Stirling cycle cryogenic cooler

    Gasser, M. G.; Sherman, A.; Studer, P. A.; Daniels, A.; Goldowsky, M. P. (Inventor)

    1983-01-01

    A long lifetime Stirling cycle cryogenic cooler particularly adapted for space applications is described. It consists of a compressor section centrally aligned end to end with an expansion section, and respectively includes a reciprocating compressor piston and displacer radially suspended in interconnecting cylindrical housings by active magnetic bearings and has adjacent reduced clearance regions so as to be in noncontacting relationship therewith and wherein one or more of these regions operate as clearance seals. The piston and displacer are reciprocated in their housings by linear drive motors to vary the volume of respectively adjacent compression and expansion spaces which contain a gaseous working fluid and a thermal regenerator to effect Stirling cycle cryogenic cooling.

  18. Stirling cycle cryogenic cooler

    Gasser, M. G.; Sherman, A.; Studer, P. A.; Daniels, A.; Goldowsky, M. P.

    1983-06-01

    A long lifetime Stirling cycle cryogenic cooler particularly adapted for space applications is described. It consists of a compressor section centrally aligned end to end with an expansion section, and respectively includes a reciprocating compressor piston and displacer radially suspended in interconnecting cylindrical housings by active magnetic bearings and has adjacent reduced clearance regions so as to be in noncontacting relationship therewith and wherein one or more of these regions operate as clearance seals. The piston and displacer are reciprocated in their housings by linear drive motors to vary the volume of respectively adjacent compression and expansion spaces which contain a gaseous working fluid and a thermal regenerator to effect Stirling cycle cryogenic cooling.

  19. CANDU fuel cycle flexibility

    High neutron economy, on-power refuelling, and a simple bundle design provide a high degree of flexibility that enables CANDU (Canada Deuterium Uranium; registered trademark) reactors to be fuelled with a wide variety of fuel types. Near-term applications include the use of slightly enriched uranium (SEU), and recovered uranium (RU) from reprocessed spent Light Water Reactor (LWR) fuel. Plutonium and other actinides arising from various sources, including spent LWR fuel, can be accommodated, and weapons-origin plutonium could be destroyed by burning in CANDU. In the DUPIC fuel cycle, a dry processing method would convert spent Pressurized Water Reactor (PWR) fuel to CANDU fuel. The thorium cycle remains of strategic interest in CANDU to ensure long-term resource availability, and would be of specific interest to those countries possessing large thorium reserves, but limited uranium resources. (author). 21 refs

  20. Riding the cycle

    The current state of the Canadian oil and natural gas industry is reviewed as part of a discussion of economic cycles focusing in particular on the most recent cycle and the impact it has had on the industry. The review of the state of the industry includes discussion of production, exports, commodity prices, the stimulating effect of price increases on the number of oil and natural gas wells drilled, drilling rig operating days. Also discussed are the effect of foreign exchange rates, capital spending, industry financial performance in terms of return on capital employed, the impact of oil and gas prices on Alberta provincial revenues, estimates of Canada's ultimate crude oil and natural gas resources potential, pipelines and pipeline proposals for northern gas, and projection of crude oil and natural gas production in Canada to 2010

  1. A Kalina cycle with ejector

    A Kalina cycle with ejector (EKalina cycle) is proposed in this paper. In the EKalina cycle, an ejector is used to substitute for the throttle valve and the absorber in the Kalina cycle system 11 (KCS 11). The exhaust pressure of the expander is decreased by the ejector resulted in an increase of the working pressure difference of the expansion, and to increase the power output and the thermal efficiency of the cycle. The thermodynamic analyses and comparisons between the EKalina cycle and the KCS 11 are conducted on the cycle's power output, thermal efficiency with the low-grade heat source (LGHS). Water is chosen as the LGHS fluid, and the same temperature and mass flow rate of the water is the standard condition for the comparative analysis on the EKalina cycle and the KCS 11. Results show that the net power output and thermal efficiency of the EKalina cycle are higher than that of the KCS 11. - Highlights: • A Kalina cycle with ejector (EKalina cycle) based on Kalina cycle system 11 (KCS 11) is proposed. • Substituting ejector for the throttle valve to avoid throttling losses improves the cycle performance. • The net power output and thermal efficiency of EKalina cycle are higher than that of KCS 11

  2. Assessing Cycling Participation in Australia

    Chris Rissel

    2013-01-01

    Full Text Available Planning and evaluating cycling programs at a national or state level requires accurate measures of cycling participation. However, recent reports of cycling participation have produced very different estimates. This paper examines the reported rates of cycling in five recent population surveys of cycling. Three surveys (one national and two from Sydney asking respondents when they last rode a bicycle generated cycling participation (cycled in the past year estimates of 29.7%, 34.1% and 28.9%. Two other national surveys which asked participants to recall (unprompted any physical activity done for exercise, recreation or sport in the previous 12 months, estimated cycling in the past year as 11.1% and 6.5%. While unprompted recall of cycling as a type of physical activity generates lower estimates of cycling participation than specific recall questions, both assessment approaches produced similar patterns of cycling by age and sex with both approaches indicating fewer women and older adults cycling. The different question styles most likely explain the substantial discrepancies between the estimates of cycling participation. Some differences are to be expected due to sampling variability, question differences, and regional variation in cycling.

  3. HCl removal using cycled carbide slag from calcium looping cycles

    Highlights: • Cycled carbide slag from calcium looping cycles is used to remove HCl. • The optimum temperature for HCl removal of cycled carbide slag is 700 °C. • The presence of CO2 restrains HCl removal of cycled carbide slag. • CO2 capture conditions have important effects on HCl removal of cycled carbide slag. • HCl removal capacity of carbide slag drops with cycle number rising from 1 to 50. - Abstract: The carbide slag is an industrial waste from chlor-alkali plants, which can be used to capture CO2 in the calcium looping cycles, i.e. carbonation/calcination cycles. In this work, the cycled carbide slag from the calcium looping cycles for CO2 capture was proposed to remove HCl in the flue gas from the biomass-fired and RDFs-fired boilers. The effects of chlorination temperature, HCl concentration, particle size, presence of CO2, presence of O2, cycle number and CO2 capture conditions in calcium looping cycles on the HCl removal behavior of the carbide slag experienced carbonation/calcination cycles were investigated in a triple fixed-bed reactor. The chlorination product of the cycled carbide slag from the calcium looping after absorbing HCl is not CaCl2 but CaClOH. The optimum temperature for HCl removal of the cycled carbide slag from the carbonation/calcination cycles is 700 °C. The chlorination conversion of the cycled carbide slag increases with increasing the HCl concentration. The cycled carbide slag with larger particle size exhibits a lower chlorination conversion. The presence of CO2 decreases the chlorination conversions of the cycled carbide slag and the presence of O2 has a trifling impact. The chlorination conversion of the carbide slag experienced 1 carbonation/calcination cycle is higher than that of the uncycled calcined sorbent. As the number of carbonation/calcination cycles increases from 1 to 50, the chlorination conversion of carbide slag drops gradually. The high calcination temperature and high CO2 concentration in the

  4. Cycles in Nonlinear Macroeconomics

    Voronin, Anatoly V.; Chernyshov, Sergey I.

    2007-01-01

    The monograph is concerned with some key problems of the theory of nonlinear economic dynamics. The authors' concept consists in analyzing the problem of structural instability of economic systems within the framework of the synergetic paradigm. As examples, the classical models of macroeconomics are considered. The authors present the results of the study of the phenomenon of self-organization in open and nonequilibrium economic systems. The generation of limit cycles, as well as of more com...

  5. Pork Barrel Cycles

    Allan Drazen; Marcela Eslava

    2006-01-01

    We present a model of political budget cycles in which incumbents influence voters by targeting government spending to specific groups of voters at the expense of other voters or other expenditures. Each voter faces a signal extraction problem: being targeted with expenditure before the election may reflect opportunistic manipulation, but may also reflect a sincere preference of the incumbent for the types of spending that voter prefers. We show the existence of a political equilibrium in whi...

  6. The carbon dioxide cycle

    James, P.B.; Hansen, G.B.; Titus, T.N.

    2005-01-01

    The seasonal CO2 cycle on Mars refers to the exchange of carbon dioxide between dry ice in the seasonal polar caps and gaseous carbon dioxide in the atmosphere. This review focuses on breakthroughs in understanding the process involving seasonal carbon dioxide phase changes that have occurred as a result of observations by Mars Global Surveyor. ?? 2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

  7. Recycling and Endogenous Cycles

    Fodha, Mouez; Francesco MAGRIS

    2012-01-01

    This article investigates the conditions under which deterministic cycles can emerge in a discrete-time model with infinitely lived agents and when the economy is characterized by two sectors producing two perfectly substitutable goods: a virgin good and a recycled one. The occurrence of deterministic fluctuations rests upon the countercyclical behavior of the recycling industry: an increase in present consumption implies a lower future waste activity together with a lower agents' total incom...

  8. Concordance in Business Cycles

    C. John McDermott; Alasdair Scott

    2000-01-01

    We study the properties of a test that determines whether two time series comove. The test computes a simple nonparametric statistic for “concordance,” which describes the proportion of time that the cycles of two series spend in the same phase. We establish the size and power properties of this test. As an illustration, the procedures are applied to output series from selected major industrial countries. We find limited evidence of widespread concordance for these countries.

  9. Steps and cycles

    Chadwick, Andy

    2015-01-01

    Andy Chadwick* explains how interaction between continuous trend with natural climate cycles produces the observed stepped pattern of global warming Climate-change ‘sceptics’ have made great mileage out of the current hiatus in observed global warming. Atmospheric temperatures have not really increased since the turn of the 21st Century, a fact frequently cited as incompatible with, or even disproving, global warming. These same commentators draw a discreet veil over the fact that temper...

  10. Nuclear Fuel Cycle

    Dale, Deborah J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-10-28

    These slides will be presented at the training course “International Training Course on Implementing State Systems of Accounting for and Control (SSAC) of Nuclear Material for States with Small Quantity Protocols (SQP),” on November 3-7, 2014 in Santa Fe, New Mexico. The slides provide a basic overview of the Nuclear Fuel Cycle. This is a joint training course provided by NNSA and IAEA.

  11. FUZZY REASONING IN CYCLES

    曹立明

    1990-01-01

    By the similarity between the syllogism in logic and a path proposition in graph theory,a new concept,fuzzy reasoning graph G has been given in this paper. Transitive closure has been studied and used to do reasoning related to self-loop in G,and an algorithm has been designed to cope with reasoning in other cycles in G. Both approaches are applicable and efficient.

  12. The nuclear fuel cycle

    The papers presented at the International Conference on The Nuclear Fuel Cycle, held at Stockholm, 28 to 31 October 1975, are reviewed. The meeting, organised by the U.S. Atomic Industrial Forum, and the Swedish Nuclear Forum, was concerned more particularly with economic, political, social and commercial aspects than with tecnology. The papers discussed were considered under the subject heading of current status, uranium resources, enrichment, and reprocessing. (U.K.)

  13. International Business Cycle

    Marek Lubiński

    2007-06-01

    Full Text Available Prime stylized facts of international business cycle theory refer to positive correlation in the cyclical components of important macroeconomic variables across countries. However a number of indicators of business cycle synchronization do not point to clear trends. It can be ascribed to the fact that different forces influence level of business cycle correlation. When investigating into the forces behind the commonness in aggregate fluctuations economic research seems to have pointed in two directions. One strand of the literature examines the idea of common exogenous shocks that affect economies simultaneously. In addition to that economic interdependencies such as trade in goods and services or capital account transactions may serve as the channels through which disturbances spill over across countries.The observed degree of output co movement reflects both the nature of the shocks that have occurred and the degree of economic interdependence. In the periods when common shocks prevail level of synchronization is usually higher than in times of transmission dominance.

  14. Bifurcation of limit cycles near equivariant compound cycles

    2007-01-01

    In this paper we study some equivariant systems on the plane. We first give some criteria for the outer or inner stability of compound cycles of these systems. Then we investigate the number of limit cycles which appear near a compound cycle of a Hamiltonian equivariant system under equivariant perturbations. In the last part of the paper we present an application of our general theory to show that a Z3 equivariant system can have 13 limit cycles.

  15. Cycle-to-cycle variability as an optimal behavioral strategy

    Brezina, Vladimir; Proekt, Alex; Weiss, Klaudiusz R.

    2006-01-01

    Aplysia feeding behavior is highly variable from cycle to cycle. In some cycles, when the variability causes a mismatch between the animal's movements and the requirements of the feeding task, the variability makes the behavior unsuccessful. We propose that the behavior is variable nevertheless because the variability serves a higher-order functional purpose. When the animal is faced with a new and only imperfectly known feeding task in each cycle, the variability implements a trial-and-error...

  16. How well can business cycle accounting account for business cycles?

    Otsu, Keisuke

    2012-01-01

    The business cycle accounting method introduced by Chari, Kehoe and McGrattan (2007) is a useful tool to decompose business cycle fluctuations into their contributing factors. However, the model estimated by the maximum likelihood method cannot replicate business cycle moments computed from data. Moment-based estimation might be an attractive alternative if the purpose of the research is to study business cycle properties such as volatility, persistence and cross-correlation of variables inst...

  17. Menstrual cycle pattern and fertility

    Kolstad, Henrik A.; Bonde, Jens Peter; Hjøllund, Niels Henrik;

    1999-01-01

    OBJECTIVE: To characterize how the menstrual cycle pattern relates to fertility regardless of potential biases caused by inappropriate coital timing during the menstrual cycle or early embryonal loss. DESIGN: Prospective follow-up study. SETTING: Healthy couples recruited throughout Denmark...

  18. Fictitious Supercontinent Cycles

    Marvin Herndon, J.

    2014-05-01

    "Supercontinent cycles" or "Wilson cycles" is the idea that before Pangaea there were a series of supercontinents that each formed and then broke apart and separated before colliding again, re-aggregating, and suturing into a new supercontinent in a continuing sequence. I suggest that "supercontinent cycles" are artificial constructs, like planetary orbit epicycles, attempts to describe geological phenomena within the framework of problematic paradigms, namely, planetesimal Earth formation and plate tectonics' mantle convection. The so-called 'standard model of solar system formation' is problematic as it would lead to insufficiently massive planetary cores and necessitates additional ad hoc hypotheses such as the 'frost line' between Mars and Jupiter to explain planetary differences and whole-planet melting to explain core formation from essentially undifferentiated matter. The assumption of mantle convection is crucial for plate tectonics, not only for seafloor spreading, but also for continental movement; continent masses are assumed to ride atop convection cells. In plate tectonics, plate collisions are thought to be the sole mechanism for fold-mountain formation. Indeed, the occurrence of mountain chains characterized by folding which significantly predate the breakup of Pangaea is the primary basis for assuming the existence of supercontinent cycles with their respective periods of ancient mountain-forming plate collisions. Mantle convection is physically impossible. Rayleigh Number justification has been misapplied. The mantle bottom is too dense to float to the surface by thermal expansion. Sometimes attempts are made to obviate the 'bottom heavy' prohibition by adopting the tacit assumption that the mantle behaves as an ideal gas with no viscous losses, i.e., 'adiabatic'. But the mantle is a solid that does not behave as an ideal gas as evidenced by earthquakes occurring at depths as great as 660 km. Absent mantle convection, plate tectonics is not valid

  19. The world tourism exports cycle

    Gouveia, Pedro; Guerreiro, Raul Filipe; Paulo M.M. Rodrigues

    2013-01-01

    Considering that tourism is an important industry on a global scale, this study analyses and compares the deviations cycles from the long-term trend of tourism exports for all regions of the world with the cycle of the European Union with 27 member states (EU27). In this context, the approach followed allows us to analyse and determine the synchronization between tourism exports cycles of various regions of interest. In parallel, lagged concordance indices of cycles are id...

  20. GEOSS Water Cycle Integrator

    Koike, Toshio; Lawford, Richard; Cripe, Douglas

    2013-04-01

    It is critically important to recognize and co-manage the fundamental linkages across the water-dependent domains; land use, including deforestation; ecosystem services; and food-, energy- and health-securities. Sharing coordinated, comprehensive and sustained observations and information for sound decision-making is a first step; however, to take full advantage of these opportunities, we need to develop an effective collaboration mechanism for working together across different disciplines, sectors and agencies, and thereby gain a holistic view of the continuity between environmentally sustainable development, climate change adaptation and enhanced resilience. To promote effective multi-sectoral, interdisciplinary collaboration based on coordinated and integrated efforts, the intergovernmental Group on Earth Observations (GEO) is implementing the Global Earth Observation System of Systems (GEOSS). A component of GEOSS now under development is the "GEOSS Water Cycle Integrator (WCI)", which integrates Earth observations, modeling, data and information, management systems and education systems. GEOSS/WCI sets up "work benches" by which partners can share data, information and applications in an interoperable way, exchange knowledge and experiences, deepen mutual understanding and work together effectively to ultimately respond to issues of both mitigation and adaptation. (A work bench is a virtual geographical or phenomenological space where experts and managers collaborate to use information to address a problem within that space). GEOSS/WCI enhances the coordination of efforts to strengthen individual, institutional and infrastructure capacities, especially for effective interdisciplinary coordination and integration. GEO has established the GEOSS Asian Water Cycle Initiative (AWCI) and GEOSS African Water Cycle Coordination Initiative (AfWCCI). Through regional, inter-disciplinary, multi-sectoral integration and inter-agency coordination in Asia and Africa, GEOSS

  1. Liquid air cycle engines

    Rosevear, Jerry

    1992-01-01

    Given here is a definition of Liquid Air Cycle Engines (LACE) and existing relevant technologies. Heat exchanger design and fabrication techniques, the handling of liquid hydrogen to achieve the greatest heat sink capabilities, and air decontamination to prevent heat exchanger fouling are discussed. It was concluded that technology needs to be extended in the areas of design and fabrication of heat exchangers to improve reliability along with weight and volume reductions. Catalysts need to be improved so that conversion can be achieved with lower quantities and lower volumes. Packaging studies need to be investigated both analytically and experimentally. Recycling with slush hydrogen needs further evaluation with experimental testing.

  2. The nuclear fuel cycle

    After a short introduction about nuclear power in the world, fission physics and the French nuclear power plants, this brochure describes in a digest way the different steps of the nuclear fuel cycle: uranium prospecting, mining activity, processing of uranium ores and production of uranium concentrates (yellow cake), uranium chemistry (conversion of the yellow cake into uranium hexafluoride), fabrication of nuclear fuels, use of fuels, reprocessing of spent fuels (uranium, plutonium and fission products), recycling of energetic materials, and storage of radioactive wastes. (J.S.)

  3. The software life cycle

    Ince, Darrel

    1990-01-01

    The Software Life Cycle deals with the software lifecycle, that is, what exactly happens when software is developed. Topics covered include aspects of software engineering, structured techniques of software development, and software project management. The use of mathematics to design and develop computer systems is also discussed. This book is comprised of 20 chapters divided into four sections and begins with an overview of software engineering and software development, paying particular attention to the birth of software engineering and the introduction of formal methods of software develop

  4. Sometimes "Newton's Method" Always "Cycles"

    Latulippe, Joe; Switkes, Jennifer

    2012-01-01

    Are there functions for which Newton's method cycles for all non-trivial initial guesses? We construct and solve a differential equation whose solution is a real-valued function that two-cycles under Newton iteration. Higher-order cycles of Newton's method iterates are explored in the complex plane using complex powers of "x." We find a class of…

  5. Changing global carbon cycle

    Full text: The increase in atmospheric carbon dioxide (C02) is the single largest human perturbation on the earth's radiative balance contributing to climate change. Its rate of change reflects the balance between anthropogenic carbon emissions and the dynamics of a number of terrestrial and ocean processes that remove or emit C02. It is the long term evolution of this balance that will determine to large extent the speed and magnitude of the human induced climate change and the mitigation requirements to stabilise atmospheric C02 concentrations at any given level. In this talk, we show new trends in global carbon sources and sinks, with particularly focus on major shifts occurring since 2000 when the growth rate of atmospheric C02 has reached its highest level on record. The acceleration in the C02 growth results from the combination of several changes in properties of the carbon cycle, including: acceleration of anthropogenic carbon emissions; increased carbon intensity of the global economy, and decreased efficiency of natural carbon sinks. We discuss in more detail some of the possible causes of the reduced efficiency of natural carbon sinks on land and oceans, such as the decreased net sink in the Southern Ocean and on terrestrial mid-latitudes due to world-wide occurrence of drought. All these changes reported here characterise a carbon cycle that is generating stronger than expected climate forcing, and sooner than expected

  6. Velenje - Mislinja cycle track regulation

    Vidonja, Klemen

    2013-01-01

    In my graduation thesis, I am planning a cycle track from Velenje to Mislinja, where it will be connected to an existing bike track to Otiški vrh. The cycle track would be placed on a deserted railway route from Velenje to Dravograd. A short section of cycle track is already in use, but it has to be repared. I planned the rest of the cycle track and I regulated it in a turist – recreational manner, suitable for all types of riders. The cycle track is placed away from traffic, does not dema...

  7. Part 5. Fuel cycle options

    The results of the FBR fuel cycle study that supported US contributions to the INFCE are presented. Fuel cycle technology is reviewed from both generic and historical standpoints. Technology requirements are developed within the framework of three deployment scenarios: the reference international, the secured area, and the integral cycle. Reprocessing, fabrication, waste handling, transportation, and safeguards are discussed for each deployment scenario. Fuel cycle modifications designed to increase proliferation defenses are described and assessed for effectiveness and technology feasibility. The present status of fuel cycle technology is reviewed and key issues that require resolution are identified

  8. Open cycle thermoacoustics

    Reid, Robert Stowers

    2000-01-01

    A new type of thermodynamic device combining a thermodynamic cycle with the externally applied steady flow of an open thermodynamic process is discussed and experimentally demonstrated. The gas flowing through this device can be heated or cooled in a series of semi-open cyclic steps. The combination of open and cyclic flows makes possible the elimination of some or all of the heat exchangers (with their associated irreversibility). Heat is directly exchanged with the process fluid as it flows through the device when operating as a refrigerator, producing a staging effect that tends to increase First Law thermodynamic efficiency. An open-flow thermoacoustic refrigerator was built to demonstrate this concept. Several approaches are presented that describe the physical characteristics of this device. Tests have been conducted on this refrigerator with good agreement with a proposed theory.

  9. Nutrient Cycling Study

    Peter A. Pryfogle

    2005-09-01

    The particular goal of this study is to develop measurement techniques for understanding how consortia of organisms from geothermal facilities utilize sulfur and iron for metabolic activity; and in turn, what role that activity plays in initiating or promoting the development of a biofilm on plant substrates. Sulfur cycling is of interest because sulfur is produced in the resource. Iron is found in some of the steel formulations used in plant components and is also added as chemical treatment for reducing sulfide emissions from the plants. This report describes the set-up and operation of a bioreactor for evaluating the response of colonies of geothermal organisms to changes in nutrient and environmental conditions. Data from initial experiments are presented and plans for future testing is discussed.

  10. CANDU advanced fuel cycles

    This report is based on informal lectures and presentations made on CANDU Advanced Fuel Cycles over the past year or so, and discusses the future role of CANDU in the changing environment for the Canadian and international nuclear power industry. The changing perspectives of the past decade lead to the conclusion that a significant future market for a CANDU advanced thermal reactor will exist for many decades. Such a reactor could operate in a stand-alone strategy or integrate with a mixed CANDU-LWR or CANDU-FBR strategy. The consistent design focus of CANDU on enhanced efficiency of resource utilization combined with a simple technology to achieve economic targets, will provide sufficient flexibility to maintain CANDU as a viable power producer for both the medium- and long-term future

  11. HTGR fuel cycle

    In the spring of 1987, the HTGR fuel cycle project has been existing for ten years, and for this reason a status seminar has been held on May 12, 1987 in the Juelich Nuclear Research Center, that gathered the participants in this project for a discussion on the state of the art in HTGR fuel element development, graphite development, and waste management. The papers present an overview of work performed so far and an outlook on future tasks and goals, and on taking stock one can say that the project has been very successful so far: The HTGR fuel element now available meets highest requirements and forms the basis of today's HTGR safety philosophy; research work on graphite behaviour in a high-temperature reactor has led to complete knowledge of the temperature or neutron-induced effects, and with the concept of direct ultimate waste disposal, the waste management problem has found a feasible solution. (orig./GL)

  12. Coupled quantum Otto cycle.

    Thomas, George; Johal, Ramandeep S

    2011-03-01

    We study the one-dimensional isotropic Heisenberg model of two spin-1/2 systems as a quantum heat engine. The engine undergoes a four-step Otto cycle where the two adiabatic branches involve changing the external magnetic field at a fixed value of the coupling constant. We find conditions for the engine efficiency to be higher than in the uncoupled model; in particular, we find an upper bound which is tighter than the Carnot bound. A domain of parameter values is pointed out which was not feasible in the interaction-free model. Locally, each spin seems to cause a flow of heat in a direction opposite to the global temperature gradient. This feature is explained by an analysis of the local effective temperature of the spins. PMID:21517482

  13. The nuclear power cycle

    Fifty years after the first nuclear reactor come on-line, nuclear power is fourth among the world's primary energy sources, after oil, coal and gas. In 2002, there were 441 reactors in operation worldwide. The United States led the world with 104 reactors and an installed capacity of 100,000 MWe, or more than one fourth of global capacity. Electricity from nuclear energy represents 78% of the production in France, 57% in Belgium, 46% in Sweden, 40% in Switzerland, 39% in South Korea, 34% in Japan, 30% in Germany, 30% in Finland, 26% in Spain, 22% in Great Britain, 20% in the United States and 16% in Russia. Worldwide, 32 reactors are under construction, including 21 in Asia. This information document presents the Areva activities in the nuclear power cycle: the nuclear fuel, the nuclear reactors, the spent fuel reprocessing and recycling and nuclear cleanup and dismantling. (A.L.B.)

  14. The uranium cycle

    In identifying uranium provinces, and, more importantly, mineralized zones within these provinces, it is of paramount importance to attempt to trace the geochemical behaviour of an element through all stages of Earth's evolution. Aspects that need to be addressed in this regard include solar abundance levels and fractionation processes during accretion, changing patterns of crustal evolution, effects of an evolving atmosphere, and the weathering cycle. Abundance patterns and partition coefficients of some of the siderophile elements in mantle rocks lend support to a multistage accretionary process. Lack of a terrestrial record in the first 500 Ma necessitates that lunar models be invoked, which suggests that early fractionation of a mafic/ultramafic magma resulted in an anorthositic crust. Fractionation of the mantle and transfer of materials to the upper levels must be central to any model invoked for development of the crust. Given high heat flow conditions in the early Archaean it would seem inescapable that the process of sea floor spreading and plate tectonics was an ongoing process. If the plate tectonic model is taken back to 3500 Ma, and assuming current speading rates, then about half of the mantle has passed through the irreversible differentiation cycle. Arguments in support of recycled material must be balanced against mantle metasomatism effects. With the associated advent of partial melting of the mantle material a partitioning of minor and trace elements into the melt fraction would take place. The early primitive mafic and ultramafic komatiites exemplify this feature by concentrating U and Th by a factor of 5 compared to chondritic abundances. It is of tantamount importance to understand the generation of the magmas in order to predict which are the 'fertile' bodies in terms of radioelement concentrations. In that the granitoid magmas image their source compositions, the association of high radioelements will primarily be source-dependent. Uranium

  15. The Hamburg oceanic carbon cycle circulation model. Cycle 1

    The carbon cycle model calculates the prognostic fields of oceanic geochemical carbon cycle tracers making use of a 'frozen' velocity field provided by a run of the LSG oceanic circulation model (see the corresponding manual, LSG=Large Scale Geostrophic). The carbon cycle model includes a crude approximation of interactions between sediment and bottom layer water. A simple (meridionally diffusive) one layer atmosphere model allows to calculate the CO2 airborne fraction resulting from the oceanic biogeochemical interactions. (orig.)

  16. Money and Business Cycles: A Real Business Cycle Interpretation

    Charles I. Plosser

    1990-01-01

    This paper focuses on the role of money in economic fluctuations. While money may play an important role in market economies, its role as an important impulse to business cycles remains a highly controversial hypothesis. For years economists have attempted to construct monetary theories of the business cycle with only limited empirical success. Alternatively, recent real theories of the cycle have taken the view that to a first approximation independent variations in the nominal quantity of o...

  17. Removing Cycles in Esterel Programs

    Reinhard von Hanxleden

    2007-05-01

    Full Text Available Esterel belongs to the family of synchronous programming languages, which are affected by cyclic signal dependencies. This prohibits a static scheduling, limiting the choice of available compilation techniques for programs with such cycles. This work proposes an algorithm that, given a constructive synchronous Esterel program, performs a semantics-preserving source code level transformation that removes cyclic signal dependencies. The transformation is divided into two parts: detection of cycles and iterative resolution of these cycles. It is based on the replacement of cycle signals by a signal expression involving no other cycle signals, thereby breaking the cycle. This transformation of cyclic Esterel programs enables the use of efficient compilation techniques, which are only available for acyclic programs. Furthermore, experiments indicate that the code transformation can even improve code quality produced by compilers that can already handle cyclic programs.

  18. Reproductive cycles of buffalo.

    Perera, B M A O

    2011-04-01

    The domestic water buffalo (Bubalus bubalis) has an important role in the agricultural economy of many developing countries in Asia, providing milk, meat and draught power. It is also used in some Mediterranean and Latin American countries as a source of milk and meat for specialized markets. Although the buffalo can adapt to harsh environments and live on poor quality forage, reproductive efficiency is often compromised by such conditions, resulting in late sexual maturity, long postpartum anoestrus, poor expression of oestrus, poor conception rates and long calving intervals. The age at puberty is influenced by genotype, nutrition, management and climate, and under favourable conditions occurs at 15-18 months in river buffalo and 21-24 months in swamp buffalo. The ovaries are smaller than in cattle and contain fewer primordial follicles. Buffalo are capable of breeding throughout the year, but in many countries a seasonal pattern of ovarian activity occurs. This is attributed in tropical regions to changes in rainfall resulting in feed availability or to temperature stress resulting in elevated prolactin secretion, and in temperate regions to changes in photoperiod and melatonin secretion. The mean length of the oestrous cycle is 21 days, with greater variation than observed in cattle. The signs of oestrus in buffalo are less overt than in cattle and homosexual behaviour between females is rare. The duration of oestrus is 5-27 h, with ovulation occurring 24-48 h (mean 34 h) after the onset of oestrus. The hormonal changes occurring in peripheral circulation are similar to those observed in cattle, but the peak concentrations of progesterone and oestradiol-17β are less. The number of follicular waves during an oestrous cycle varies from one to three and influences the length of the luteal phase as well as the inter-ovulatory interval. Under optimal conditions, dairy types managed with limited or no suckling resume oestrus cyclicity by 30-60 days after calving

  19. Life cycle of mobile devices

    T.V. Rohal; S.I. Naumenko; G.О Peresadko

    2011-01-01

    Article is devoted features of life cycle of mobile devices. The article highlighted a number of disadvantages associated with managing the life cycle of the product. Disadvantages include the orientation is not on the quality of mobile devices and their design, the obsolescence of digital products. The article drew attention to the need for process improvement life cycle management of mobile devices. For since this type of product is now the most popular among the population, consumers are i...

  20. Entrepreneurship and the business cycle

    Thurik, Roy

    2014-01-01

    Entrepreneurship has a cyclical component, raising two questions. Is the entrepreneurship cycle related to the business cycle? And is there causality? A two-way relationship between entrepreneurship and the business cycle would be in line with the two faces of entrepreneurs: as agents of change creating upswings (opportunity entrepreneurship) and as rational actors escaping unemployment by setting up a business (necessity entrepreneurship). Nascent entrepreneurship can indeed be precyclical, ...

  1. Rethinking the Ancient Sulfur Cycle

    Fike, David A.; Bradley, Alexander S.; Rose, Catherine V.

    2015-05-01

    The sulfur biogeochemical cycle integrates the metabolic activity of multiple microbial pathways (e.g., sulfate reduction, disproportionation, and sulfide oxidation) along with abiotic reactions and geological processes that cycle sulfur through various reservoirs. The sulfur cycle impacts the global carbon cycle and climate primarily through the remineralization of organic carbon. Over geological timescales, cycling of sulfur is closely tied to the redox state of Earth's exosphere through the burial of oxidized (sulfate) and reduced (sulfide) sulfur species in marine sediments. Biological sulfur cycling is associated with isotopic fractionations that can be used to trace the fluxes through various metabolic pathways. The resulting isotopic data provide insights into sulfur cycling in both modern and ancient environments via isotopic signatures in sedimentary sulfate and sulfide phases. Here, we review the deep-time δ34S record of marine sulfates and sulfides in light of recent advances in understanding how isotopic signatures are generated by microbial activity, how these signatures are encoded in marine sediments, and how they may be altered following deposition. The resulting picture shows a sulfur cycle intimately coupled to ambient carbon cycling, where sulfur isotopic records preserved in sedimentary rocks are critically dependent on sedimentological and geochemical conditions (e.g., iron availability) during deposition.

  2. Regenerative superheated steam turbine cycles

    Fuller, L. C.; Stovall, T. K.

    1980-01-01

    PRESTO computer program was developed to analyze performance of wide range of steam turbine cycles with special attention given to regenerative superheated steam turbine cycles. It can be used to model standard turbine cycles, including such features as process steam extraction, induction and feedwater heating by external sources, peaking, and high back pressure. Expansion line efficiencies, exhaust loss, leakages, mechanical losses, and generator losses are used to calculate cycle heat rate and generator output. Program provides power engineer with flexible aid for design and analysis of steam turbine systems.

  3. Fast reactor fuel cycle facility

    An integrated fuel cycle facility named Fast Reactor Fuel Cycle Facility (FRFCF) is planned to be set up at Kalpakkam to close the fuel cycle of the Prototype Fast Breeder Reactor (PFBR) that is already under construction there. FRFCF is the first project of its kind in India. Closure of fuel cycle of PFBR will be a significant milestone of the second stage of nuclear power programme of the Department of Atomic Energy. The facility would be ready for operation in 2014. Design work and safety review of FRFCF are presently in progress. (author)

  4. The earth's hydrological cycle

    Bonnet, R-M; Calisto, M; Destouni, G; Gurney, R; Johannessen, J; Kerr, Y; Lahoz, WA; Rast, M

    2014-01-01

    This book gives a comprehensive presentation of our present understanding of the Earth's Hydrological cycle and the problems, consequences and impacts that go with this topic. Water is a central component in the Earth's system. It is indispensable for life on Earth in its present form and influences virtually every aspect of our planet's life support system. On relatively short time scales, atmospheric water vapor interacts with the atmospheric circulation and is crucial in forming the Earth's climate zones. Water vapor is the most powerful of the greenhouse gases and serves to enhance the tropospheric temperature. The dominant part of available water on Earth resides in the oceans. Parts are locked up in the land ice on Greenland and Antarctica and a smaller part is estimated to exist as groundwater. If all the ice over the land and all the glaciers were to melt, the sea level would rise by some 80 m. In comparison, the total amount of water vapor in the atmosphere is small; it amounts to ~ 25 kg/m2, or the ...

  5. Biomass Gasification Combined Cycle

    Judith A. Kieffer

    2000-07-01

    Gasification combined cycle continues to represent an important defining technology area for the forest products industry. The ''Forest Products Gasification Initiative'', organized under the Industry's Agenda 2020 technology vision and supported by the DOE ''Industries of the Future'' program, is well positioned to guide these technologies to commercial success within a five-to ten-year timeframe given supportive federal budgets and public policy. Commercial success will result in significant environmental and renewable energy goals that are shared by the Industry and the Nation. The Battelle/FERCO LIVG technology, which is the technology of choice for the application reported here, remains of high interest due to characteristics that make it well suited for integration with the infrastructure of a pulp production facility. The capital cost, operating economics and long-term demonstration of this technology area key input to future economically sustainable projects and must be verified by the 200 BDT/day demonstration facility currently operating in Burlington, Vermont. The New Bern application that was the initial objective of this project is not currently economically viable and will not be implemented at this time due to several changes at and around the mill which have occurred since the inception of the project in 1995. The analysis shows that for this technology, and likely other gasification technologies as well, the first few installations will require unique circumstances, or supportive public policies, or both to attract host sites and investors.

  6. The closed fuel cycle

    Available in abstract form only. Full text of publication follows: The fast growth of the world's economy coupled with the need for optimizing use of natural resources, for energy security and for climate change mitigation make energy supply one of the 21. century most daring challenges. The high reliability and efficiency of nuclear energy, its competitiveness in an energy market undergoing a new oil shock are as many factors in favor of the 'renaissance' of this greenhouse gas free energy. Over 160,000 tHM of LWR1 and AGR2 Used Nuclear Fuel (UNF) have already been unloaded from the reactor cores corresponding to 7,000 tons discharged per year worldwide. By 2030, this amount could exceed 400,000 tHM and annual unloading 14,000 tHM/year. AREVA believes that closing the nuclear fuel cycle through the treatment and recycling of Used Nuclear Fuel sustains the worldwide nuclear power expansion. It is an economically sound and environmentally responsible choice, based on the preservation of natural resources through the recycling of used fuel. It furthermore provides a safe and secure management of wastes while significantly minimizing the burden left to future generations. (authors)

  7. The nitrogen cycle.

    Stein, Lisa Y; Klotz, Martin G

    2016-02-01

    Nitrogen is the fourth most abundant element in cellular biomass, and it comprises the majority of Earth's atmosphere. The interchange between inert dinitrogen gas (N2) in the extant atmosphere and 'reactive nitrogen' (those nitrogen compounds that support, or are products of, cellular metabolism and growth) is entirely controlled by microbial activities. This was not the case, however, in the primordial atmosphere, when abiotic reactions likely played a significant role in the inter-transformation of nitrogen oxides. Although such abiotic reactions are still important, the extant nitrogen cycle is driven by reductive fixation of dinitrogen and an enzyme inventory that facilitates dinitrogen-producing reactions. Prior to the advent of the Haber-Bosch process (the industrial fixation of N2 into ammonia, NH3) in 1909, nearly all of the reactive nitrogen in the biosphere was generated and recycled by microorganisms. Although the Haber-Bosch process more than quadrupled the productivity of agricultural crops, chemical fertilizers and other anthropogenic sources of fixed nitrogen now far exceed natural contributions, leading to unprecedented environmental degradation. PMID:26859274

  8. Activity Cycle of Solar Filaments

    K. J. Li; Q. X. Li; P. X. Gao; J. Mu; H. D. Chen; T. W. Su

    2007-06-01

    Long-term variation in the distribution of the solar filaments observed at the Observatorie de Paris, Section de Meudon from March 1919 to December 1989 is presented to compare with sunspot cycle and to study the periodicity in the filament activity, namely the periods of the coronal activity with the Morlet wavelet used. It is inferred that the activity cycle of solar filaments should have the same cycle length as sunspot cycle, but the cycle behavior of solar filaments is globally similar in profile with, but different in detail from, that of sunspot cycles. The amplitude of solar magnetic activity should not keep in phase with the complexity of solar magnetic activity. The possible periods in the filament activity are about 10.44 and 19.20 years. The wavelet local power spectrum of the period 10.44 years is statistically significant during the whole consideration time. The wavelet local power spectrum of the period 19.20 years is under the 95% confidence spectrum during the whole consideration time, but over the mean red-noise spectrum of = 0.72 before approximate Carrington rotation number 1500, and after that the filament activity does not statistically show the period. Wavelet reconstruction indicates that the early data of the filament archive (in and before cycle 16) are more noiseful than the later (in and after cycle 17).

  9. Nuclear fuel cycle information workshop

    This overview of the nuclear fuel cycle is divided into three parts. First, is a brief discussion of the basic principles of how nuclear reactors work; second, is a look at the major types of nuclear reactors being used and world-wide nuclear capacity; and third, is an overview of the nuclear fuel cycle and the present industrial capability in the US

  10. Business Cycles Accounting for Paraguay

    Hnatkovska, Viktoria; Koehler-Geib, Friederike

    2015-01-01

    This study investigates the role of domestic and external shocks in business cycle fluctuations in Paraguay during 1991–2012. Time-series methods and a structural model-based approach are used to conduct an integrated analysis of business cycles. First, structural vector autoregression is used to assess the role played by external factors and domestic shocks in driving fluctuations in gros...

  11. Variations on the Zilch Cycle

    Binder, P.-M.; Tanoue, C. K. S.

    2013-01-01

    Thermo dynamic cycles in introductory physics courses are usually made up from a small number of permutations of isothermal, adiabatic, and constant-pressure and volume quasistatic strokes, with the working fluid usually being an ideal gas. Among them we find the Carnot, Stirling, Otto, Diesel, and Joule-Brayton cycles; in more advanced courses,…

  12. Analysis of Sunspot Activity Cycles

    Greenkorn, Robert A.

    2009-04-01

    A nonlinear analysis of the daily sunspot number for each of cycles 10 to 23 is used to indicate whether the convective turbulence is stochastic or chaotic. There is a short review of recent papers considering sunspot statistics and solar activity cycles. The differences in the three possible regimes - deterministic laminar flow, chaotic flow, and stochastic flow - are discussed. The length of data sets necessary to analyze the regimes is investigated. Chaos is described and a chronology of recent results that utilize chaos and fractals to analyze sunspot numbers follows. The parameters necessary to describe chaos - time lag, phase space, embedding dimension, local dimension, correlation dimension, and the Lyapunov exponents - are determined for the attractor for each cycle. Assuming the laminar regime is unlikely if chaos is not indicated in a cycle by the calculations, the regime must be stochastic. The sunspot numbers in each of cycles 10 to 19 indicate stochastic behavior. There is a transition from stochastic to chaotic behavior of the sunspot numbers in cycles 20, 21, 22, and 23. These changes in cycles 20 - 23 may indicate a change in the scale of turbulence in the convection zone that could result in a change in the convective heat transfer and a change in the size of the convection region for these four cycles.

  13. The LifeCycle model

    Krink, Thiemo; Løvbjerg, Morten

    2002-01-01

    Adaptive search heuristics are known to be valuable in approximating solutions to hard search problems. However, these techniques are problem dependent. Inspired by the idea of life cycle stages found in nature, we introduce a hybrid approach called the LifeCycle model that simultaneously applies...

  14. The water cycle for kids

    Neno, Stephanie; Morgan, Jim; Zonolli, Gabriele; Perlman, Howard; Gonthier, Gerard

    2013-01-01

    The U.S. Geological Survey (USGS) and the Food and Agriculture Organization of the United Nations (FAO) have created a water-cycle diagram for use in elementary and middle schools. The diagram is available in many languages. This diagram is part of the USGS's Water Science School, in which the water cycle is described in detail.

  15. Corporate governance cycles during transition

    Jones, Derek C.; Mygind, Niels

    2004-01-01

    We begin by identifying a typical governance life-cycle, defined as changes in ownership structure, and including both the identity of the major owner and ownership concentration. The cycle is marked by key events and phases including start-up, initial growth, mature growth, and possibly a crisis...

  16. Business Cycle Theory before Keynes

    Claude Diebolt

    2009-01-01

    This article is concerned with the development of the theory of business cycles before Keynes. It is impossible to treat fully all the theories or to mention all those who have contributed to the literature. Our main consideration will be the development of cycle theory, with maximum emphasis upon ideas.

  17. Prospects for Predicting Cycle 24

    Arnab Rai Choudhuri

    2008-03-01

    Although we have reliable data of solar polar fields only from the mid-1970s, it seems that the polar field at a minimum is well correlated with the next cycle, but the strength of the cycle is not correlated with the polar field produced at its end. We explain this by suggesting that the Babcock–Leighton mechanism of poloidal field generation from tilted active regions involves randomness, whereas the other aspects of the dynamo process are more ordered. To model actual cycles, we have to ‘correct’ our theoretical dynamo model by ‘feeding’ information about the polar field at the minima. Following this process, we find that our model fits the observed sunspot numbers of cycles 21–23 reasonably well and predicts that cycle 24 will be the weakest in a century.

  18. Reciprocating heat-engine cycles

    The performance of a generalized irreversible reciprocating heat-engine cycle model consisting of two heating branches, two cooling branches and two adiabatic branches with heat-transfer loss and friction-like term loss was analyzed using finite-time thermodynamics. The relations between the power output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relation between the power output and the efficiency of the cycle are derived. Moreover, analysis and optimization of the model were carried out in order to investigate the effect of the cycle process on the performances of the cycles using numerical examples. The results obtained herein include the performance characteristics of irreversible reciprocating Diesel, Otto, Atkinson, Brayton, Dual and Miller cycles

  19. Fuel cycle cost uncertainty from nuclear fuel cycle comparison

    This paper examined the uncertainty in fuel cycle cost (FCC) calculation by considering both model and parameter uncertainty. Four different fuel cycle options were compared in the analysis including the once-through cycle (OT), the DUPIC cycle, the MOX cycle and a closed fuel cycle with fast reactors (FR). The model uncertainty was addressed by using three different FCC modeling approaches with and without the time value of money consideration. The relative ratios of FCC in comparison to OT did not change much by using different modeling approaches. This observation was consistent with the results of the sensitivity study for the discount rate. Two different sets of data with uncertainty range of unit costs were used to address the parameter uncertainty of the FCC calculation. The sensitivity study showed that the dominating contributor to the total variance of FCC is the uranium price. In general, the FCC of OT was found to be the lowest followed by FR, MOX, and DUPIC. But depending on the uranium price, the FR cycle was found to have lower FCC over OT. The reprocessing cost was also found to have a major impact on FCC

  20. Limit cycles in quantum systems

    Niemann, Patrick

    2015-04-27

    In this thesis we investigate Limit Cycles in Quantum Systems. Limit cycles are a renormalization group (RG) topology. When degrees of freedom are integrated out, the coupling constants flow periodically in a closed curve. The presence of limit cycles is restricted by the necessary condition of discrete scale invariance. A signature of discrete scale invariance and limit cycles is log-periodic behavior. The first part of this thesis is concerned with the study of limit cycles with the similarity renormalization group (SRG). Limit cycles are mainly investigated within conventional renormalization group frameworks, where degrees of freedom, which are larger than a given cutoff, are integrated out. In contrast, in the SRG potentials are unitarily transformed and thereby obtain a band-diagonal structure. The width of the band structure can be regarded as an effective cutoff. We investigate the appearance of limit cycles in the SRG evolution. Our aim is to extract signatures as well as the scaling factor of the limit cycle. We consider the 1/R{sup 2}-potential in a two-body system and a three-body system with large scattering lengths. Both systems display a limit cycle. Besides the frequently used kinetic energy generator we apply the exponential and the inverse generator. In the second part of this thesis, Limit Cycles at Finite Density, we examine the pole structure of the scattering amplitude for distinguishable fermions at zero temperature in the medium. Unequal masses and a filled Fermi sphere for each fermion species are considered. We focus on negative scattering lengths and the unitary limit. The properties of the three-body spectrum in the medium and implications for the phase structure of ultracold Fermi gases are discussed.

  1. Limit cycles in quantum systems

    In this thesis we investigate Limit Cycles in Quantum Systems. Limit cycles are a renormalization group (RG) topology. When degrees of freedom are integrated out, the coupling constants flow periodically in a closed curve. The presence of limit cycles is restricted by the necessary condition of discrete scale invariance. A signature of discrete scale invariance and limit cycles is log-periodic behavior. The first part of this thesis is concerned with the study of limit cycles with the similarity renormalization group (SRG). Limit cycles are mainly investigated within conventional renormalization group frameworks, where degrees of freedom, which are larger than a given cutoff, are integrated out. In contrast, in the SRG potentials are unitarily transformed and thereby obtain a band-diagonal structure. The width of the band structure can be regarded as an effective cutoff. We investigate the appearance of limit cycles in the SRG evolution. Our aim is to extract signatures as well as the scaling factor of the limit cycle. We consider the 1/R2-potential in a two-body system and a three-body system with large scattering lengths. Both systems display a limit cycle. Besides the frequently used kinetic energy generator we apply the exponential and the inverse generator. In the second part of this thesis, Limit Cycles at Finite Density, we examine the pole structure of the scattering amplitude for distinguishable fermions at zero temperature in the medium. Unequal masses and a filled Fermi sphere for each fermion species are considered. We focus on negative scattering lengths and the unitary limit. The properties of the three-body spectrum in the medium and implications for the phase structure of ultracold Fermi gases are discussed.

  2. Digital daily cycles of individuals

    Aledavood, Talayeh; Jørgensen, Sune Lehmann; Saramäki, Jari

    2015-01-01

    Humans, like almost all animals, are phase-locked to the diurnal cycle. Most of us sleep at night and are active through the day. Because we have evolved to function with this cycle, the circadian rhythm is deeply ingrained and even detectable at the biochemical level. However, within the broader...... day-night pattern, there are individual differences: e.g., some of us are intrinsically morning-active, while others prefer evenings. In this article, we look at digital daily cycles: circadian patterns of activity viewed through the lens of auto-recorded data of communication and online activity. We...

  3. Introducing Life Cycle Impact Assessment

    Hauschild, Michael Zwicky; Huijbregts, Mark AJ

    2015-01-01

    methodology projects and presents the international scientific discussions and methodological consensus attempts in consecutive working groups under the auspices of the Society of Environmental Toxicology and Chemistry (SETAC) as well as the UNEP/ SETAC Life Cycle Initiative, and the (almost) parallel......This chapter serves as an introduction to the presentation of the many aspects of life cycle impact assessment (LCIA) in this volume of the book series ‘LCA Compendium’. It starts with a brief historical overview of the development of life cycle impact assessment driven by numerous national LCIA...

  4. Prospects for predicting cycle 24

    Choudhuri, Arnab Rai

    2008-01-01

    Although we have reliable data of solar polar fields only from the mid-1970s, it seems that the polar field at a minimum is well correlated with the next cycle, but the strength of the cycle is not correlated with the polar field produced at its end. We explain this by suggesting that the Babcock–Leighton mechanism of poloidal field generation from tilted active regions involves randomness, whereas the other aspects of the dynamo process are more ordered. To model actual cycles, we have to 'c...

  5. BWROPT: A multi-cycle BWR fuel cycle optimization code

    Ottinger, Keith E.; Maldonado, G. Ivan, E-mail: Ivan.Maldonado@utk.edu

    2015-09-15

    Highlights: • A multi-cycle BWR fuel cycle optimization algorithm is presented. • New fuel inventory and core loading pattern determination. • The parallel simulated annealing algorithm was used for the optimization. • Variable sampling probabilities were compared to constant sampling probabilities. - Abstract: A new computer code for performing BWR in-core and out-of-core fuel cycle optimization for multiple cycles simultaneously has been developed. Parallel simulated annealing (PSA) is used to optimize the new fuel inventory and placement of new and reload fuel for each cycle considered. Several algorithm improvements were implemented and evaluated. The most significant of these are variable sampling probabilities and sampling new fuel types from an ordered array. A heuristic control rod pattern (CRP) search algorithm was also implemented, which is useful for single CRP determinations, however, this feature requires significant computational resources and is currently not practical for use in a full multi-cycle optimization. The PSA algorithm was demonstrated to be capable of significant objective function reduction and finding candidate loading patterns without constraint violations. The use of variable sampling probabilities was shown to reduce runtime while producing better results compared to using constant sampling probabilities. Sampling new fuel types from an ordered array was shown to have a mixed effect compared to random new fuel type sampling, whereby using both random and ordered sampling produced better results but required longer runtimes.

  6. Life-cycle cost analysis of adsorption cycles for desalination

    Thu, Kyaw

    2010-08-01

    This paper presents the thermo-economic analysis of the adsorption desalination (AD) cycle that is driven by low-temperature waste heat from exhaust of industrial processes or renewable sources. The AD cycle uses an adsorbent such as the silica gel to desalt the sea or brackish water. Based on an experimental prototype AD plant, the life-cycle cost analysis of AD plants of assorted water production capacities has been simulated and these predictions are translated into unit cost of water production. Our results show that the specific energy consumption of the AD cycle is 1.38 kWh/m3 which is the lowest ever reported. For a plant capacity of 1000 m3/d, the AD cycle offers a unit cost of $0.457/m3 as compared to more than $0.9 for the average RO plants. Besides being cost-effective, the AD cycle is also environment-friendly as it emits less CO2 emission per m3 generated, typically 85% less, by comparison to an RO process. © 2010 Desalination Publications.

  7. BWROPT: A multi-cycle BWR fuel cycle optimization code

    Highlights: • A multi-cycle BWR fuel cycle optimization algorithm is presented. • New fuel inventory and core loading pattern determination. • The parallel simulated annealing algorithm was used for the optimization. • Variable sampling probabilities were compared to constant sampling probabilities. - Abstract: A new computer code for performing BWR in-core and out-of-core fuel cycle optimization for multiple cycles simultaneously has been developed. Parallel simulated annealing (PSA) is used to optimize the new fuel inventory and placement of new and reload fuel for each cycle considered. Several algorithm improvements were implemented and evaluated. The most significant of these are variable sampling probabilities and sampling new fuel types from an ordered array. A heuristic control rod pattern (CRP) search algorithm was also implemented, which is useful for single CRP determinations, however, this feature requires significant computational resources and is currently not practical for use in a full multi-cycle optimization. The PSA algorithm was demonstrated to be capable of significant objective function reduction and finding candidate loading patterns without constraint violations. The use of variable sampling probabilities was shown to reduce runtime while producing better results compared to using constant sampling probabilities. Sampling new fuel types from an ordered array was shown to have a mixed effect compared to random new fuel type sampling, whereby using both random and ordered sampling produced better results but required longer runtimes

  8. Ammonium generation during SRAT cycle

    During the IDMS noble-metal demonstration runs ammonium nitrate deposition was found in the vessel vent system of the feed preparation area. In the bench-scale experiments of studying the hydrogen generation during the sludge treatment cycle, ammonium ion production was also monitored. It was found that: During a simulation of the DWPF Cold Chemical Runs SRAT cycle no detectable amount of ammonium ions was generated when treating a non-noble-metal containing sludge simulant according to the nitric acid flowsheet. Ammonium ions were generated during the SRAT-SME cycle when treating the noble-metal containing sludge with either formic acid or nitric acid/late-washing PHA. This is due to the reaction between formic acid and nitrate catalyzed by the noble metals in the sludge simulant. Ammonium ion production closely followed the hydrogen evolution from the catalytic decomposition of formic acid. This report summarizes the results of the production of ammonia during the SRAT cycle

  9. Optimisation of the nominal cycle

    Redaelli, S

    2011-01-01

    The energy ramp and the betatron squeeze are critical phases of the LHC operation. During the squeeze, delicate optics manipulations take place when the stored energy is maximum. In 2010, ramp and squeeze were commissioned rapidly and smoothly became operational. On the other hand, during the first commissioning exercise, the focus was put on machine safety and on operational robustness rather then in efficiency for luminosity production. After having accumulated a full year of experience on the operational cycle and having gained important feedback on machine behaviour and operational procedures, it is now time to address the optimization of the LHC cycle, while still respecting safe boundaries. In this paper, the experience with the LHC operational cycle is reviewed, possible bottlenecks are identified and paths for improvements are addressed. Proposals for improvement are based on a critical look at the limiting factors encountered in the different phases of the cycle. More complex operation configurations...

  10. Towards Life Cycle Sustainability Assessment

    Marzia Traverso

    2010-10-01

    Full Text Available Sustainability is nowadays accepted by all stakeholders as a guiding principle for both public policy making and corporate strategies. However, the biggest challenge for most organizations remains in the real and substantial implementation of the sustainability concept. The core of the implementation challenge is the question, how sustainability performance can be measured, especially for products and processes. This paper explores the current status of Life Cycle Sustainability Assessment (LCSA for products and processes. For the environmental dimension well established tools like Life Cycle Assessment are available. For the economic and social dimension, there is still need for consistent and robust indicators and methods. In addition to measuring the individual sustainability dimensions, another challenge is a comprehensive, yet understandable presentation of the results. The “Life Cycle Sustainability Dashboard” and the “Life Cycle Sustainability Triangle” are presented as examples for communication tools for both experts and non expert stakeholders.

  11. Venus Altitude Cycling Balloon Project

    National Aeronautics and Space Administration — The ISTAR Group ( IG) and team mate Thin Red Line Aerospace (TRLA) propose a Venus altitude cycling balloon (Venus ACB), an innovative superpressure balloon...

  12. (Auto)Ethnographies and Cycling

    Larsen, Jonas

    2014-01-01

    This article discusses the formation, salience and reformation of everyday bodily routines and resources in relation to cycling; it also examines how we can study them ethnographically in different places. I discuss forms of embodied, sensuous and mobile ethnography that can illuminate how routines......, habits and affective capacities of cycling are cultivated and performed. The article argues that autoethnography is particularly apt at illuminating the embodied qualities of movement, and it sits within established ethnographies of ‘excising’ and ‘mobile bodies’. In the second part of the article, I...... draw upon ongoing autoethnographies of cycling in a familiar place (my hometown, Copenhagen) and by learning to cycle ‘out-of-place’ (in London) and ‘in-a-new–way’ (when commuting long distance on a racer bike). The study challenges static notions of the body by analysing how cyclists’ (and researchers...

  13. DIPS power conversion cycle selection

    This paper presents the results of the dynamic power conversion cycle selection process conducted by the Rocketdyne Division of Rockwell International as part of the Dynamic Isotope Power Subsystem (DIPS) Program, sponsored by the U.S. Department of Energy (DOE). Rocketdyne is under contract with DOE for the DIPS Program. The objective of the DIPS Program is to demonstrate the technology necessary to provide dynamic radioisotope space electrical power systems in the 1 to 10 kWe range to support evolving military and civilian missions in the early 1990s and beyond. Selecting the most appropriate DIPS power conversion cycle that would support this objective was an integral step in this process. The closed Brayton cycle was selected as the preferred power conversion cycle for the DIPS Program based on an evaluation of several key areas concerning spacecraft power systems performance

  14. Cell cycle control in Alphaproteobacteria.

    Collier, Justine

    2016-04-01

    Alphaproteobacteria include many medically and environmentally important organisms. Despite the diversity of their niches and lifestyles, from free-living to host-associated, they usually rely on very similar mechanisms to control their cell cycles. Studies on Caulobacter crescentus still lay the foundation for understanding the molecular details of pathways regulating DNA replication and cell division and coordinating these two processes with other events of the cell cycle. This review highlights recent discoveries on the regulation and the mode of action of conserved global regulators and small molecules like c-di-GMP and (p)ppGpp, which play key roles in cell cycle control. It also describes several newly identified mechanisms that modulate cell cycle progression in response to stresses or environmental conditions. PMID:26871482

  15. Total Product Life Cycle (TPLC)

    U.S. Department of Health & Human Services — The Total Product Life Cycle (TPLC) database integrates premarket and postmarket data about medical devices. It includes information pulled from CDRH databases...

  16. Mirador - Carbon Cycle and Ecosystems

    National Aeronautics and Space Administration — Earth Science data access made simple. This Focus Area deals with the cycling of carbon in reservoirs and ecosystems as it changes naturally, is changed by humans,...

  17. Mirador - Water and Energy Cycles

    National Aeronautics and Space Administration — Earth Science data access made simple. Through water and energy cycle research we can improve hurricane prediction, quantify tropical rainfall and eventually begin...

  18. Glacial Cycles and Milankovitch Forcing

    Raghuraman, Shiv Priyam

    2015-01-01

    Using a recent conceptual model of the glacial-interglacial cycles we present more evidence of Milankovitch cycles being the trigger for retreat and forming of ice sheets in the cycles. This model is based on a finite approximation of an infinite dimensional model which has three components: Budyko's energy balance model describing the annual mean temperatures at latitudes, Widiasih's ODE which describes the behavior of the edge of the ice sheet, and Walsh et al. who introduced a snow line to account for glacial accumulation and ablation zones. Certain variables in the model are made to depend on the Milankovitch cycles, in particular, the obliquity of the Earth's axis and the eccentricity of the Earth's orbit. We see as a result that deglaciation and glaciation do occur mostly due to obliquity and to some extent eccentricity.

  19. Grown-up business cycles

    Pugsley, Benjamin; Şahin, Ayşegül

    2014-01-01

    We document two striking facts about U.S. firm dynamics and interpret their significance for aggregate employment dynamics. The first observation is the steady decline in the firm entry rate over the last thirty years, and the second is the gradual shift of employment from younger to older firms over the same period. Both observations hold across industries and geographies. We show that, despite these trends, firms' life-cycle dynamics and business-cycle properties have remained virtually unc...

  20. Limit cycles of effective theories

    Glazek, Stanislaw D.

    2006-01-01

    A simple example is used to show that renormalization group limit cycles of effective quantum theories can be studied in a new way. The method is based on the similarity renormalization group procedure for Hamiltonians. The example contains a logarithmic ultraviolet divergence that is generated by both real and imaginary parts of the Hamiltonian matrix elements. Discussion of the example includes a connection between asymptotic freedom with one scale of bound states and the limit cycle with a...

  1. New Relationship in Carbon Cycle

    Aleksei Naumov

    2012-01-01

    The problem of carbon dioxide accumulation in the atmosphere is closely related to the biological carbon cycle processes insufficiently studied from the global viewpoint. Based on data obtained from the literature on net primary production (NPP) and soil respiration (SR) of world ecosystems, a quantitative analysis of the relationship between these basic parameters of the production/destruction phase of the carbon cycle is offered in this paper. A direct correspondence (equality in carbon equ...

  2. No News in Business Cycles

    Forni, Mario; Gambetti, Luca; Sala, Luca

    2011-01-01

    This paper uses a structural, large dimensional factor model to evaluate the role of 'news' shocks (shocks with a delayed effect on productivity) in generating the business cycle. We find that (i) existing small-scale VECM models are affected by 'non-fundamentalness' and therefore fail to recover the correct shock and impulse response functions; (ii) news shocks have a limited role in explaining the business cycle; (iii) their effects are in line with what predicted by standard neoclassical t...

  3. Business Cycle Theory and Econometrics

    Allan W. Gregory; Smith, Gregor W.

    1995-01-01

    We outline in turn criticisms made by econometricians of the methods used in empirical business-cycle research and then criticisms made by business-cycle researchers of some methods used by econometricians. The aim is to clarify and in some cases correct these criticisms. Overall there is no conflict in using rigourous statistical procedures to study modern dynamic stochastic general equilibrium models. We also provide a concise bibliography of recent research on statistical methods for busin...

  4. Social learning and innovation cycles

    Garfagnini, Umberto; Strulovici, Bruno

    2012-01-01

    We study social learning and innovation in an overlapping generations model, emphasizing the trade-off between marginal innovation (combining existing technologies) and radical innovation (breaking new ground). We characterize both short-term and long-term dynamics of innovation, and the intergenerational accumulation of knowledge. Innovation cycles emerge endogenously, but the number of cycles is finite almost surely, and radical innovation terminates in finite time. We identify a negative r...

  5. Muscular & mechanical efficiency in cycling

    Blake, Oliver Malcolm

    2011-01-01

    In cycling some muscle coordination patterns result in high power outputs whereas others are more efficient. This study examined mechanical factors that affect muscle activity to identify coordination patterns used for different power outputs, total muscle activation and muscle activation effectiveness to produce power in cycling. Electromyography, pedal forces, kinematics, power output, cadence and slope were measured and compared indoors and/or outdoors in competitive cyclists at a range of...

  6. Animal spirits and business cycles

    Bidder, Rhys

    2015-01-01

    Animal spirits are often suggested as a cause of business cycles, but they are very difficult to define. Recent research proposes a novel explanation based on the changing level of risk over time and people’s uncertainty about how the world works. The interaction of these two can lead to significant business cycle fluctuations in response to spikes in volatility. This finding gives researchers an alternative to irrational behavior as an explanation for why swings in consumer sentiment appear ...

  7. The NEWS Water Cycle Climatology

    Rodell, Matthew; Beaudoing, Hiroko Kato; L'Ecuyer, Tristan; William, Olson

    2012-01-01

    NASA's Energy and Water Cycle Study (NEWS) program fosters collaborative research towards improved quantification and prediction of water and energy cycle consequences of climate change. In order to measure change, it is first necessary to describe current conditions. The goal of the first phase of the NEWS Water and Energy Cycle Climatology project was to develop "state of the global water cycle" and "state of the global energy cycle" assessments based on data from modern ground and space based observing systems and data integrating models. The project was a multi-institutional collaboration with more than 20 active contributors. This presentation will describe the results of the water cycle component of the first phase of the project, which include seasonal (monthly) climatologies of water fluxes over land, ocean, and atmosphere at continental and ocean basin scales. The requirement of closure of the water budget (i.e., mass conservation) at various scales was exploited to constrain the flux estimates via an optimization approach that will also be described. Further, error assessments were included with the input datasets, and we examine these in relation to inferred uncertainty in the optimized flux estimates in order to gauge our current ability to close the water budget within an expected uncertainty range.

  8. Optimization of the fuel cycle

    The nuclear fuel cycle can be optimized subject to a wide range of criteria. Prime amongst these are economics, sustainability of resources, environmental aspects, and proliferation-resistance of the fuel cycle. Other specific national objectives will also be important. These criteria, and their relative importance, will vary from country to country, and with time. There is no single fuel cycle strategy that is optimal for all countries. Within the short term, the industry is attached to dominant thermal reactor technologies, which themselves have two main variants, a cycle closed by reprocessing of spent fuel and subsequent recycling and a once through one where spent fuel is stored in advance of geological disposal. However, even with current technologies, much can be done to optimize the fuel cycles to meet the relevant criteria. In the long term, resource sustainability can be assured for centuries through the use of fast breeder reactors, supporting high-conversion thermal reactors, possibly also utilizing the thorium cycle. These must, however, meet the other key criteria by being both economic and safe. (author)

  9. Thorium fuel cycles in CANDU

    In recent years, Atomic Energy of Canada Limited has been examining in detail the implications of using thorium-based fuels tn the CANDU reactor. Various cycles initiated and enriched either with fissile plutonium or with enriched uranium, and with effective conversion ratios ranging up to 1.0, have been evaluated. We have concluded that: 1. Substantial quantities of uranium can be saved by adoption of the thorium fuel cycle, and the long-term security of fissile supply both for the domestic and overseas market can be considerably enhanced. The amount saved will depend on the details of the fuel cycle and the anticipated growth of nuclear power in Canada. 2. The fuel cycle can be introduced into the basic CANDU design without major modifications and without compromising current safety standards. 3. The economic conditions that make thorium competitive with the once-through natural uranium cycle depend a the price of uranium and on the costs both to fabricate α and γ-emitting fuels and to either enrich uranium or to extract fissile material from spent fuel. While timing is difficult to predict, we believe that competitive economic conditions will prevail toward the end of this century. 4. A twenty-year technological development program will be required to establish commercial confidence in the fuel cycle. (author)

  10. Fuel cycles using adulterated plutonium

    Brooksbank, R. E.; Bigelow, J. E.; Campbell, D. O.; Kitts, F. G.; Lindauer, R. B.

    1978-01-01

    Adjustments in the U-Pu fuel cycle necessitated by decisions made to improve the nonproliferation objectives of the US are examined. The uranium-based fuel cycle, using bred plutonium to provide the fissile enrichment, is the fuel system with the highest degree of commercial development at the present time. However, because purified plutonium can be used in weapons, this fuel cycle is potentially vulnerable to diversion of that plutonium. It does appear that there are technologically sound ways in which the plutonium might be adulterated by admixture with /sup 238/U and/or radioisotopes, and maintained in that state throughout the fuel cycle, so that the likelihood of a successful diversion is small. Adulteration of the plutonium in this manner would have relatively little effect on the operations of existing or planned reactors. Studies now in progress should show within a year or two whether the less expensive coprocessing scheme would provide adequate protection (coupled perhaps with elaborate conventional safeguards procedures) or if the more expensive spiked fuel cycle is needed as in the proposed civex pocess. If the latter is the case, it will be further necessary to determine the optimum spiking level, which could vary as much as a factor of a billion. A very basic question hangs on these determinations: What is to be the nature of the recycle fuel fabrication facilities. If the hot, fully remote fuel fabrication is required, then a great deal of further development work will be required to make the full cycle fully commercial.

  11. Thermodynamic Cycles--One More Time.

    Nolan, Michael J.

    1995-01-01

    Discusses interesting aspects of the Carnot cycle and other thermodynamic cycles that are generally not dealt with in elementary physics texts. Presents examples that challenge the student to think about the extraction of net work from a cycle. (JRH)

  12. Binary Brayton cycle with two isothermal processes

    Highlights: • This paper presents binary Brayton cycle with two isothermal processes. • Different parameters affecting the cycle performance have been studied. • The present cycle is a promising cycle for future power generation. - Abstract: The literature introduced isothermal concept and binary Brayton cycle as two promising methods used to enhance the performance of the gas turbine. Consequently, this work presents a cycle based on the blending of the two methods. This cycle is composed of gas turbine topping cycle with isothermal combustion and air turbine bottoming cycle with isothermal heating. Different parameters affecting the cycle performance have been studied. Simulations demonstrate that the present cycle achieves drastic enhancement in performance. The cycle merits justify its potential utilization for future power generation

  13. The British cycling economy: 'gross cycling product' report

    Grous, Alexander

    2011-01-01

    We believe this is the first-ever attempt to chart the full extent of cycling’s contribution to the British economy. Previous studies have focused on particular sectors such as the bicycle retail trade, but never before has a study been conducted into the true ‘Gross Cycling Product’ (GCP) of UK plc – from bike sales to improved health. The GCP report was conceived by Sky and British Cycling and has been made a reality through the London School of Economics. We commissioned the report, t...

  14. Optimal Life Cycle Portfolio Choice with Housing Market Cycles

    Fischer, Marcel; Stamos, Michael Z.

    2013-01-01

    In recent decades U.S. households have experienced residential house prices moving persistently, that is, returns being positively serially correlated. We set up a realistically calibrated life cycle model with slow-moving time variation in expected housing returns, showing that not only age, labor...... income, and pre-existing housing wealth but also the state of the housing market significantly affect household decisions. Consistently with the data, the model predicts that in good states of housing market cycles (1) homeownership rates increase, (2) households buying homes invest a larger share of...

  15. Candu fuel and fuel cycles

    A primary rationale for Indonesia to proceed with a nuclear power program is to diversity its energy sources and achieve freedom from future resource constraints. While other considerations, such as economy of power supply, hedging against potential future increases in the price of fossil fuels, fostering the technological development of the Indonesia economy and minimizing greenhouse and other gaseous emissions are important, the strategic resource issue is key. In considering candidate nuclear power technologies upon which to base such a program, a major consideration will be the potential for those technologies to be economically sustained in the face of large future increases in demand for nuclear fuels. The technology or technologies selected should be amenable to evaluation in a rapidly changing technical, economic, resource and environmental policy. The world's proven uranium resources which can be economically recovered represent a fairly modest energy resource if utilization is based on the currently commercialized fuel cycles, even with the use of recovered plutonium in mixed oxide fuels. In the long term, fuel cycles relying solely on the use of light water reactors will encounter increasing fuel supply constraints. Because of its outstanding neutron economy and the flexibility of on-power refueling, CANDU reactors are the most fuel resource efficient commercial reactors and offer the potential for accommodating an almost unlimited variety of advanced and even more fuel efficient cycles. Most of these cycles utilize nuclear fuels which are too low grade to be used in light water reactors, including many products now considered to be waste, such as spent light water reactor fuel and reprocessing products such as recovered uranium. The fuel-cycle flexibility of the CANDU reactor provides a ready path to sustainable energy development in both the short and the long terms. Most of the potential CANDU fuel cycle developments can be accommodated in existing

  16. Antifreeze life cycle assessment (LCA

    Kesić Jelena

    2005-01-01

    Full Text Available Antifreeze based on ethylene glycol is a commonly used commercial product The classification of ethylene glycol as a toxic material increased the disposal costs for used antifreeze and life cycle assessment became a necessity. Life Cycle Assessment (LCA considers the identification and quantification of raw materials and energy inputs and waste outputs during the whole life cycle of the analyzed product. The objectives of LCA are the evaluation of impacts on the environment and improvements of processes in order to reduce and/or eliminate waste. LCA is conducted through a mathematical model derived from mass and energy balances of all the processes included in the life cycle. In all energy processes the part of energy that can be transformed into some other kind of energy is called exergy. The concept of exergy considers the quality of different types of energy and the quality of different materials. It is also a connection between energy and mass transformations. The whole life cycle can be described by the value of the total loss of exergy. The physical meaning of this value is the loss of material and energy that can be used. The results of LCA are very useful for the analyzed products and processes and for the determined conditions under which the analysis was conducted. The results of this study indicate that recycling is the most satisfactory solution for the treatment of used antifreeze regarding material and energy consumption but the re-use of antifreeze should not be neglected as a solution.

  17. Answering Key Fuel Cycle Questions

    Given the range of fuel cycle goals and criteria, and the wide range of fuel cycle options, how can the set of options eventually be narrowed in a transparent and justifiable fashion? It is impractical to develop all options. We suggest an approach that starts by considering a range of goals for the Advanced Fuel Cycle Initiative (AFCI) and then posits seven questions, such as whether Cs and Sr isotopes should be separated from spent fuel and, if so, what should be done with them. For each question, we consider which of the goals may be relevant to eventually providing answers. The AFCI program has both ''outcome'' and ''process'' goals because it must address both waste already accumulating as well as completing the fuel cycle in connection with advanced nuclear power plant concepts. The outcome objectives are waste geologic repository capacity and cost, energy security and sustainability, proliferation resistance, fuel cycle economics, and safety. The process objectives are rea diness to proceed and adaptability and robustness in the face of uncertainties

  18. Air bottoming cycle, an alternative to combined cycles. Final report

    Kaikko, J. [Royal Inst. of Techn., Stockholm (Sweden). Dept. of Energy Technology

    2001-10-01

    In this work, the idea of Air Bottoming Cycle (ABC) has been studied. The objectives for the work have been to establish an understanding of the concept for power and heat generation as well as to find - if possible - feasible concepts for future use in the Swedish energy system. Combined cycle in power generation is an established technology. In the conventional combined cycle, a gas turbine works as a topping cycle together with the steam (Rankine) bottoming cycle. In the ABC the steam bottoming cycle is replaced with a gas turbine (Brayton) bottoming cycle having air as a working fluid. The two gas turbines are thermally connected over a gas-to-gas heat exchanger. This concept promises savings in weight and cost, as well as operating benefits, compared to the Rankine bottoming technology. The ABC has been modelled using a heat balance program, and a parametric study for the concept optimisation as well as for off-design analysis has been performed. Performance of the ABC has been compared to other, established technologies. A preliminary economic evaluation has been made. As a result of the study, it is clarified that the Rankine bottoming cycle with steam remains superior to the ABC as regards electrical efficiency in the medium and large power scale. For small-scale applications (<10 MW{sub e}) where the thermodynamic advantage of the Rankine cycle is not dominating any longer and its economy is burdened by the heavy investment structure, the ABC becomes the better alternative for energy utilisation. A preliminary economic evaluation shows that (at energy prices autumn 2000) the ABC is at the same level as the comparable small-scale cogeneration installations. Due to high power-to-heat ratio however, higher electricity prices will favour the ABC. One interesting feature of the ABC is that about 50% of the dissipated low-value heat from the cycle is carried by clean (sterile) air at the temperature around 200 deg C. This air can be utilised for space heating or

  19. Air bottoming cycle, an alternative to combined cycles. Final report

    Kaikko, J. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Energy Technology

    2002-02-01

    In this work, the idea of Air Bottoming Cycle (ABC) has been studied. The objectives for the work have been to establish an understanding of the concept for power and heat generation as well as to find - if possible - feasible concepts for future use in the Swedish energy system. Combined cycle in power generation is an established technology. In the conventional combined cycle, a gas turbine works as a topping cycle together with the steam (Rankine) bottoming cycle. In the ABC the steam bottoming cycle is replaced with a gas turbine (Brayton) bottoming cycle having air as a working fluid. The two gas turbines are thermally connected over a gas-to-gas heat exchanger. This concept promises savings in weight and cost, as well as operating benefits, compared to the Rankine bottoming technology. The ABC has been modelled using a heat balance program, and a parametric study for the concept optimisation as well as for off-design analysis has been performed. Performance of the ABC has been compared to other, established technologies. A preliminary economic evaluation has been made. As a result of the study, it is clarified that the Rankine bottoming cycle with steam remains superior to the ABC as regards electrical efficiency in the medium and large power scale. For small-scale applications (<10 MW{sub e}) where the thermodynamic advantage of the Rankine cycle is not dominating any longer and its economy is burdened by the heavy investment structure, the ABC becomes the better alternative for energy utilisation. A preliminary economic evaluation shows that (at energy prices autumn 2000) the ABC is at the same level as the comparable small-scale cogeneration installations. Due to high power-to-heat ratio however, higher electricity prices will favour the ABC. One interesting feature of the ABC is that about 50% of the dissipated low-value heat from the cycle is carried by clean (sterile) air at the temperature around 200 deg C. This air can be utilised for space heating or

  20. ALMA Cycle 0 Publication Statistics

    Stoehr, Felix; Meakins, Silvia; Bishop, Marsha; Uchida, Ayako; Testi, Leonardo; Iono, Daisuke; Tatematsu, Kenichi; Wootten, Al

    2016-01-01

    The scientific impact of a facility is the most important measure of its success. Monitoring and analysing the scientific return can help to modify and optimise operations and adapt to the changing needs of scientific research. The methodology that we have developed to monitor the scientific productivity of the ALMA Observatory, as well as the first results, are described. We focus on the outcome of the first cycle (Cycle 0) of ALMA Early Science operations. Despite the fact that only two years have passed since the completion of Cycle 0 and operations have already changed substantially, this analysisconfirms the effectiveness of the underlying concepts. We find that ALMA is fulfilling its promise as a transformational facility for the observation of the Universe in the submillimetre.

  1. Endogenous, Imperfectly Competitive Business Cycles

    Whitta-Jacobsen, Hans Jørgen

    below -½ (at stationary equilibrium). Market power on the labor markets may have the effect that imperfectly competitive cycles are in accordance with certain empirical regularities (some well known, some reported in the paper) concerning fluctuations in output and involuntary unemployment. Since......We investigate how imperfect competition affects the occurrence and the properties of endogenous, rational expectations business cycles in an overlapping generations model with constant returns to scale in production. The model has explicit product and labor markets all characterized by...... monopolistic competition. An implicit assumption of barriers to entry justifies that the number of firms is fixed even when positive profits occur. It turns out that both market power of firms on the product markets and market power of unions on the labor markets make the occurrence of cycles more likely. In...

  2. Corporate governance cycles during transition

    Mygind, Niels; Demina, Natalia; Gregoric, Aleksandra;

    2004-01-01

    -ing or exit stage. During transition the cycle reflects: privatization often with a high proportion of employee ownership like in Russia and in Slovenia; strong pressures for restructuring and owner-ship changes; limited possibility for external finance because of embryonic development of the fi......-nancial system. To provide simple hypothesis tests, we use Russian enterprise data for 1995-2003 and Slovenian data covering 1998-2003. In spite of differences in institutional development, con-cerning privatization and development of corporate governance institutions, we find that govern-ance cycles are broadly...... ownership on managers, external domestic and foreign owners. JEL-codes: G3, J5, P2, P3 - Keywords: corporate governance, life-cycle, privatization, ownership change, transition economies, Russia and Slovenia....

  3. Proliferation resistance fuel cycle technology

    The issues of dual use in nuclear technology are analysed for nuclear fuel cycle with special focus on uranium enrichment and spent fuel reprocessing which are considered as the most sensitive components in terms of vulnerability to diversion. Technical alternatives to mitigrate the vulnerability, as has been analysed in depth during the NASAP and INFCE era in the late seventies, are reviewed to characterize the DUPIC fuel cycle alternative. On the other hand, the new realities in nuclear energy including the disposition of weapon materials as a legacy of cold war are recast in an angle of nuclear proliferation resistance and safeguards with a discussion on the concept of spent fuel standard concept and its compliance with the DUPIC fuel cycle technology. (author)

  4. Optimization of data life cycles

    Jung, C.; Gasthuber, M.; Giesler, A.; Hardt, M.; Meyer, J.; Rigoll, F.; Schwarz, K.; Stotzka, R.; Streit, A.

    2014-06-01

    Data play a central role in most fields of science. In recent years, the amount of data from experiment, observation, and simulation has increased rapidly and data complexity has grown. Also, communities and shared storage have become geographically more distributed. Therefore, methods and techniques applied to scientific data need to be revised and partially be replaced, while keeping the community-specific needs in focus. The German Helmholtz Association project "Large Scale Data Management and Analysis" (LSDMA) aims to maximize the efficiency of data life cycles in different research areas, ranging from high energy physics to systems biology. In its five Data Life Cycle Labs (DLCLs), data experts closely collaborate with the communities in joint research and development to optimize the respective data life cycle. In addition, the Data Services Integration Team (DSIT) provides data analysis tools and services which are common to several DLCLs. This paper describes the various activities within LSDMA and focuses on the work performed in the DLCLs.

  5. CANDU fuel-cycle vision

    The fuel-cycle path chosen by a particular country will depend on a range of local and global factors. The CANDU reactor provides the fuel-cycle flexibility to enable any country to optimize its fuel-cycle strategy to suit its own needs. AECL has developed the CANFLEX fuel bundle as the near-term carrier of advanced fuel cycles. A demonstration irradiation of 24 CANFLEX bundles in the Point Lepreau power station, and a full-scale critical heat flux (CHF) test in water are planned in 1998, before commercial implementation of CANFLEX fuelling. CANFLEX fuel provides a reduction in peak linear element ratings, and a significant enhancement in thermalhydraulic performance. Whereas natural uranium fuel provides many advantages, the use of slightly enriched uranium (SEU) in CANDU reactors offers even lower fuel-cycle costs and other benefits, such as uprating capability through flattening the channel power distribution across the core. Recycled uranium (RU) from reprocessing spent PWR fuel is a subset of SEU that has significant economic promise. AECL views the use of SEU/RU in the CANFLEX bundle as the first logical step from natural uranium. High neutron economy enables the use of low-fissile fuel in CANDU reactors, which opens up a spectrum of unique fuel-cycle opportunities that exploit the synergism between CANDU reactors and LWRs. At one end of this spectrum is the use of materials from conventional reprocessing: CANDU reactors can utilize the RU directly without re-enrichment, the plutonium as conventional Mixed-oxide (MOX) fuel, and the actinide waste mixed with plutonium in an inert-matrix carrier. At the other end of the spectrum is the DUPIC cycle, employing only thermal-mechanical processes to convert spent LWR fuel into CANDU fuel, with no purposeful separation of isotopes from the fuel, and possessing a high degree of proliferation resistance. Between these two extremes are other advanced recycling options that offer particular advantages in exploiting the

  6. CANDU fuel-cycle vision

    The fuel-cycle path chosen by a particular country will depend on a range of local and global factors. The CANDU reactor provides the fuel-cycle flexibility to enable any country to optimize its fuel-cycle strategy to suit its own needs. AECL has developed the CANFLEX fuel bundle as the near-term carrier of advanced fuel cycles. A demonstration irradiation of 24 CANFLEX bundles in the Point Lepreau power station, and a full-scale critical heat flux (CHF) test in water are planned in 1998, before commercial implementation of CANFLEX fuelling. CANFLEX fuel provides a reduction in peak linear element ratings, and a significant enhancement in thermalhydraulic performance. Whereas natural uranium fuel provides many advantages, the use of slightly enriched uranium (SEU) in CANDU reactors offers even lower fuel-cycle costs and other benefits, such as uprating capability through flattening the channel power distribution across the core. Recycled uranium (RU) from reprocessing spent PWR fuel is a subset of SEU that has significant economic promise. AECL views the use of SEU/RU in the CANFLEX bundle as the first logical step from natural uranium. High neutron economy enables the use of low-fissile fuel in CANDU reactors, which opens up a spectrum of unique fuel-cycle opportunities that exploit the synergism between CANDU reactors and LWRs. At one end of this spectrum is the use of materials from conventional reprocessing: CANDU reactors can utilize the RU directly without reenrichment, the plutonium as conventional mixed-oxide (MOX) fuel, and the actinide waste mixed with plutonium in an inert-matrix carrier. At the other end of the spectrum is the DUPIC cycle, employing only thermal-mechanical processes to convert spent LWR fuel into CANDU fuel, with no purposeful separation of isotopes from the fuel, and possessing a high degree of proliferation resistance. Between these two extremes are other advanced recycling options that offer particular advantages in exploiting the

  7. Cycling in multimodal transport behaviours

    Olafsson, Anton Stahl; Nielsen, Thomas Sick; Carstensen, Trine Agervig

    2016-01-01

    explores how cycling forms part of multimodal transport behaviour based on survey data on transport modes and travel purposes and the weekly frequency of out-of-home activities and travel mode use in a representative sample of adult Danes (n = 1957). The following five distinct multimodal travel segments...... or 'modality styles' are identified: 'education transport'; 'public-based transport'; 'limited transport'; 'bicycle-based transport'; and 'car-based transport'. Travel behaviour is predominantly multimodal with few unimodal car-drivers being identified. Substantial cycling takes place in all modality...... urban settings and small towns. Thus, the way in which travel modes relate to the urban environment and variations in modality styles must serve as the starting point for policies aiming to fulfil the potential of multimodal transport behaviour and promote cycling....

  8. Proliferation resistance fuel cycle technology

    Lee, J. S.; Ko, W. I

    1999-02-01

    The issues of dual use in nuclear technology are analysed for nuclear fuel cycle with special focus on uranium enrichment and spent fuel reprocessing which are considered as the most sensitive components in terms of vulnerability to diversion. Technical alternatives to mitigrate the vulnerability, as has been analysed in depth during the NASAP and INFCE era in the late seventies, are reviewed to characterize the DUPIC fuel cycle alternative. On the other hand, the new realities in nuclear energy including the disposition of weapon materials as a legacy of cold war are recast in an angle of nuclear proliferation resistance and safeguards with a discussion on the concept of spent fuel standard concept and its compliance with the DUPIC fuel cycle technology. (author)

  9. SIRTF Cycle-1 Research Opportunities

    Soifer, B. T.; Bicay, M. D.

    2003-12-01

    The Space InfraRed Telescope Facility (SIRTF), the fourth and final element in NASA's family of Great Observatories, was successfully launched into an Earth-trailing heliocentric orbit on August 25, 2003. The SIRTF Science Center (SSC) at Caltech is now soliciting Cycle-1 research proposals from the worldwide scientific community. Proposals must be submitted electronically to the SSC by February 14, 2004. A preliminary version of the Cycle-1 Call for Proposals (CP) was issued by the SSC in November 2002. A CP Update and supporting technical documentation, which incorporates the on-orbit performance of the observatory, were released in December 2003. Investigations may be proposed for new SIRTF observations, through the General Observer (GO) program, or for archival research. About 3700 hours of observing time is being offered for the Cycle-1 GO Program, in small (less than 50 hours) and medium (50 to 200 hours) categories. More than \\15 million in NASA data analysis support is available to qualified GO investigators. For GO proposals, a detailed list of proposed observations, generated by the SIRTF Planning Observations Tool, must accompany the research proposal. The Archival Research (AR) Program in Cycle-1 is limited to the analysis of data from the First-Look Survey, a 100-hour program to be executed by the SSC at the start of the science mission. Up to \\750,000 in NASA data analysis support is available to qualified AR investigators. All documents supporting the Cycle-1 solicitation are available online in the Proposal Kit section of the SSC public Web site (http://sirtf.caltech.edu/SSC/). Questions pertaining to the Cycle-1 CP should be sent electronically to the SSC HelpDesk at sirtf@ipac.caltech.edu. SIRTF is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.

  10. Simple ocean carbon cycle models

    Caldeira, K. [Lawrence Livermore National Lab., CA (United States); Hoffert, M.I. [New York Univ., NY (United States). Dept. of Earth System Sciences; Siegenthaler, U. [Bern Univ. (Switzerland). Inst. fuer Physik

    1994-02-01

    Simple ocean carbon cycle models can be used to calculate the rate at which the oceans are likely to absorb CO{sub 2} from the atmosphere. For problems involving steady-state ocean circulation, well calibrated ocean models produce results that are very similar to results obtained using general circulation models. Hence, simple ocean carbon cycle models may be appropriate for use in studies in which the time or expense of running large scale general circulation models would be prohibitive. Simple ocean models have the advantage of being based on a small number of explicit assumptions. The simplicity of these ocean models facilitates the understanding of model results.

  11. Fuel cycle math - part two

    This article is Part 2 of a two part series on simple mathematics associated with the nuclear fuel cycle. While not addressing any of the financial aspects of the fuel cycle, this article does discuss the following: conversion between English and metric systems; uranium content expressed in equivalent forms, such as U3O8, and the method of determining these equivalencies; the uranium conversion process, considering different input and output compounds; and the enrichment process, including feed, tails, and product assays, as well as SWU and feed requirements

  12. Business Cycles in Developing Countries

    Rand, John; Tarp, Finn

    2002-01-01

    This paper demonstrates that developing countries differ considerably from their developed counterparts when focus is on the nature and characteristics of short run macroeconomic fluctuations. Cycles are generally shorter, and the stylized facts of business cycles across countries are more diverse...... than those of the rather uniform industrialized countries. Supply-side models are generally superior in explaining changes in output, but a “one-size fits all” approach in formulating policy is inappropriate. Our results also illustrate the critical importance of understanding business regularities as...

  13. Life cycle of remanufactured engines

    YANG Ming; CHEN Ming

    2005-01-01

    The life cycle index of remanufactured engines was assessed by using the method of life cycle assessment (LCA). A remanufactured engine of a certain domestic brand was taken as researching object. Engine reproducing engineering was investigated from three aspects which were energy, material and environment. The application of LCA on remanufacturing engines was discussed in detail with a practical case. The results indicate that remanufackg CO2 , 6.09 kg CO, 1.01 kg NOx, 3. 985 kg SOx and 288. 725 kg solid waste. The remanufacturing of engines possesses great economic value and practicability.

  14. SNMR pulse sequence phase cycling

    Walsh, David O; Grunewald, Elliot D

    2013-11-12

    Technologies applicable to SNMR pulse sequence phase cycling are disclosed, including SNMR acquisition apparatus and methods, SNMR processing apparatus and methods, and combinations thereof. SNMR acquisition may include transmitting two or more SNMR pulse sequences and applying a phase shift to a pulse in at least one of the pulse sequences, according to any of a variety cycling techniques. SNMR processing may include combining SNMR from a plurality of pulse sequences comprising pulses of different phases, so that desired signals are preserved and indesired signals are canceled.

  15. WWER-1000 fuel cycle improvement

    The problems of organization of fuel cycles with different operation time of stationary load for the reactor WWER-1000 are considered. The outcomes of matching of the characteristics for stationary load constructed on fuel cells of existing and improved designs are presented. Improved designs of a fuel cell are include increase of an altitude of a fuel stake, change of outside and axial diameters of a fuel pellet, change thickness of a cladding of a fuel cell. Effect of the layout solutions on improving of a fuel cycle WWER-1000 also considered (Authors)

  16. Long operating cycle simplified BWR

    Considering next generation requirement for nuclear plants, a long cycle operating simplified BWR (LSBWR) concept is proposed. The major features of LSBWR are; 1) Long cycle operation core using uranium fuels; 2) Simplified system and component as well as passive systems; 3) Combined building concept with ship hull structure. This concept have potential to reduce construction cost and to Increase availability. Safety feature of LSBWR makes possible to attain no evacuation capability in case of a severe accident. Further research and development is underway. (author)

  17. Digital calculations of engine cycles

    Starkman, E S; Taylor, C Fayette

    1964-01-01

    Digital Calculations of Engine Cycles is a collection of seven papers which were presented before technical meetings of the Society of Automotive Engineers during 1962 and 1963. The papers cover the spectrum of the subject of engine cycle events, ranging from an examination of composition and properties of the working fluid to simulation of the pressure-time events in the combustion chamber. The volume has been organized to present the material in a logical sequence. The first two chapters are concerned with the equilibrium states of the working fluid. These include the concentrations of var

  18. Properties of stellar activity cycles

    Korhonen, Heidi

    2015-01-01

    The current photometric datasets, that span decades, allow for studying long-term cycles on active stars. Complementary Ca H&K observations give information also on the cycles of normal solar-like stars, which have significantly smaller, and less easily detectable, spots. In the recent years, high precision space-based observations, for example from the Kepler satellite, have allowed also to study the sunspot-like spot sizes in other stars. Here I review what is known about the properties of the cyclic stellar activity in other stars than our Sun.

  19. Properties of stellar activity cycles

    Korhonen, Heidi

    2015-01-01

    The current photometric datasets, that span decades, allow for studying long-term cycles on active stars. Complementary Ca H&K observations give information also on the cycles of normal solar-like stars, which have significantly smaller, and less easily detectable, spots. In the recent years, high precision space-based observations, for example from the Kepler satellite, have allowed also to study the sunspot-like spot sizes in other stars. Here I review what is known about the properties of ...

  20. IAEA activities on nuclear fuel cycle 1997

    The presentation discussing the IAEA activities on nuclear fuel cycle reviews the following issues: organizational charts of IAEA, division of nuclear power and the fuel cycle, nuclear fuel cycle and materials section; 1997 budget estimates; budget trends; the nuclear fuel cycle programme

  1. A short note on Reitlinger thermodynamic cycles

    Sparavigna, Amelia Carolina

    2015-01-01

    It is well known that Carnot cycle is the thermodynamic cycle which has the best thermal efficiency. However, an entire class of cycles exists that can have the same maximum efficiency: this class is that of the regenerative Reitlinger cycles. Here we discuss them.

  2. On polytropic cycles in finite time

    Efficiencies at maximum power regime for Stirling and Ericsson cycles are calculated. The Curzon and Ahlborn formula, for efficiency of a Carnot cycle at finite time, for such cycles is obtained also. A theorem for ideal gas polytropic cycles is proposed (Author)

  3. Fundamental Cycles of Cognitive Growth.

    Pegg, John

    Over recent years, various theories have arisen to explain and predict cognitive development in mathematics education. We focus on an underlying theme that recurs throughout such theories: a fundamental cycle of growth in the learning of specific concepts, which we frame within broader global theories of individual cognitive growth. Our purpose is…

  4. Time Cycles in Indian Cosmology

    Narayan, R. H.

    2007-01-01

    In this article we review some key time cycles in ancient Indian astronomy, especially those that have emerged from researches in the past couple of decades expressing knowledge of the changing frame of earth's axis. The article also briefly reviews the philosophy related to the interconnection between the inner and the outer cosmos that was used in the analytical narrative related to this astronomy.

  5. Dynamics of the carbon cycle

    The short article describes the development of the increase in atmospheric CO2 in the past 35 years. The interdependence between CO2 levels and changes in fuel consumption is discussed, but other contributing cycles are discussed as well, e.g. enhanced timber production, ocean warming, reverse ocean currents in the South Pacific. (VHE)

  6. Sourcing Life Cycle Inventory Data

    The collection and validation of quality lifecycle inventory (LCI) data can be the most difficult and time-consuming aspect of developing a life cycle assessment (LCA). Large amounts of process and production data are needed to complete the LCI. For many studies, the LCA analyst ...

  7. H gas turbine combined cycle

    Corman, J. [General Electric Co., Schenectady, NY (United States)

    1995-10-01

    A major step has been taken in the development of the Next Power Generation System - {open_quotes}H{close_quotes} Technology Combined Cycle. This new gas turbine combined-cycle system increases thermal performance to the 60% level by increasing gas turbine operating temperature to 1430 C (2600 F) at a pressure ratio of 23 to 1. Although this represents a significant increase in operating temperature for the gas turbine, the potential for single digit NOx levels (based upon 15% O{sub 2}, in the exhaust) has been retained. The combined effect of performance increase and environmental control is achieved by an innovative closed loop steam cooling system which tightly integrates the gas turbine and steam turbine cycles. The {open_quotes}H{close_quotes} Gas Turbine Combined Cycle System meets the goals and objectives of the DOE Advanced Turbine System Program. The development and demonstration of this new system is being carried out as part of the Industrial/Government cooperative agreement under the ATS Program. This program will achieve first commercial operation of this new system before the end of the century.

  8. The product life cycle revisited

    Ulhøi, John Parm

    1995-01-01

    Efter et introduktionsafsnit følger afsnit II, hvor der gives en historisk analyse af Life Cycle Assessment (LCA) og Environmental Impact Assessment (EIA). I afsnit III munder analysen ud i en vurdering af ligheder og forskelle mellem LCA analyser og EIA analyser, og en diskussion følger af...

  9. Nuclear fuel cycle. V. 2

    Nuclear fuel cycle information in some countries that develop, supply or use nuclear energy is presented. Data about Argentina, Australia, Belgium, Netherlands, Italy, Denmarmark, Norway, Sweden, Switzerland, Finland, Spain and India are included. The information is presented in a tree-like graphic way. (C.S.A.)

  10. Business Cycle Dependent Unemployment Insurance

    Andersen, Torben M.; Svarer, Michael

    The consequences of business cycle contingencies in unemployment insurance systems are considered in a search-matching model allowing for shifts between "good" and "bad" states of nature. We show that not only is there an insurance argument for such contingencies, but there may also be an incentive...

  11. Combined cycle power plant Skopje

    Regarding the new directions in constructing combined cycle power plants, in this work an idea of such plant in Skopje with power of 190 MW has been elaborated. This plant will be constructed on the site of the existing TPP 'Energetika', AD ESM. The rates of efficiency for different condition of operation has been estimated. (Author)

  12. The Passive Aggressive Conflict Cycle

    Whitson, Signe

    2013-01-01

    Understanding the Passive Aggressive Conflict Cycle (PACC) helps observers to be able to look beyond behavior and better understand what is occurring beneath the surface. This article presents a real-life example of a seemingly minor conflict between a teacher and child that elicited an apparent major overreaction by the adult. Also provided is a…

  13. Cycles and events in stratigraphy

    Einsele, G.; Ricken, W.; Seilacher, A. (eds.)

    1991-01-01

    This book reviews and discusses the most up-to-date knowledge in the fields of cyclostratigraphy and event stratigraphy. The book contains 48 papers contributed by the most knowledgeable geologists and paleontologists in the fields of cycle and event stratigraphy. It is divided into two parts. Part one is concerned with the structure of individual beds and larger cycles and sequences and discusses; rhythmic stratification, event stratification, diagenetic overprint, cherts and phosphorites, and preservation and biologic destruction of laminated sediments. Part two, on larger cycles and sequences, looks at sequences, hierarchies, causes and environmental expression, and timing and correlation, i.e. the cycles of frequencies from millions of years to thousands of years (Milankovich band). Summaries on spectral analysis are also presented. There are 80 pages of references and a comprehensive index. It is extensively illustrated with line drawings and graphs. Practicing sedimentary geologists without access to a good library or find it hard to keep up with the plethora of journal articles and want a refresher in this area of stratigraphy will find the book particularly useful.

  14. Nuclear fuel cycle. V. 1

    Nuclear fuel cycle information in the main countries that develop, supply or use nuclear energy is presented. Data about Japan, FRG, United Kingdom, France and Canada are included. The information is presented in a tree-like graphic way. (C.S.A.)

  15. Activity cycles of M dwarfs

    Savanov, I. S.

    2012-09-01

    We have determined activity cycles for coolest M dwarfs using photometry from the ASAS survey. The time scales of brightness variations were determined for the program stars using calculated amplitude power spectra and wavelet spectra. Most of ther program stars display periodicities in their light-curve variations, with periods from hundreds of days to years. Analysis of diagrams plotting P cyc/ P rot versus 1/ P rot in logarithmic coordinates shows that the data for all our program objects fit the general relation quite well. No differences in the activity cycles are found for our sample stars, which have different masses and thus internal structures, some having convective envelopes and others being totally convective. Our analysis indicates that the slope i of this relation is close to unity, regardless of whether it is determined from all data, from data for the shortest cycles, or from data for the longest cycles. This value of i differs from values in the literature for stars of other spectral types. Our analysis of the P cyc- P rot relation indicates that the activity cycles for the studied sample of M dwarfs do not depend on the rotation periods of these objects. The data for the studied objects do not agree with any of the relations for relatively young (active) stars or older (less active) stars. The studied M dwarfs probably form another branch of low-mass stars that display more random, irregular magnetic activity on their surfaces, which is generated and supported by the distributed dynamo mechanism or a small-scale dynamo mechanism.

  16. The Timing of the Cognitive Cycle

    Madl, Tamas; Baars, Bernard J.; Franklin, Stan

    2011-01-01

    We propose that human cognition consists of cascading cycles of recurring brain events. Each cognitive cycle senses the current situation, interprets it with reference to ongoing goals, and then selects an internal or external action in response. While most aspects of the cognitive cycle are unconscious, each cycle also yields a momentary “ignition” of conscious broadcasting. Neuroscientists have independently proposed ideas similar to the cognitive cycle, the fundamental hypothesis of the LI...

  17. Evaluation, Generation, and Transformation of Driving Cycles

    Nyberg, Peter

    2015-01-01

    Driving cycles are important components for evaluation and design of vehicles. They determine the focus of vehicle manufacturers, and indirectly they affect the environmental impact of vehicles since the vehicle control system is usually tuned to one or several driving cycles. Thus, the driving cycle affects the design of the vehicle since cost, fuel consumption, and emissions all depend on the driving cycle used for design. Since the existing standard driving cycles cannot keep up with the c...

  18. The economics of thorium fuel cycles

    The individual cost components and the total fuel cycle costs for natural uranium and thorium fuel cycles are discussed. The thorium cycles are initiated by using either enriched uranium or plutonium. Subsequent thorium cycles utilize recycled uranium-233 and, where necessary, either uranium-235 or plutonium as topping. A calculation is performed to establish the economic conditions under which thorium cycles are economically attractive. (auth)

  19. When Product Life Cycle Meets Customer Activity Cycle

    Tan, Adrian Ronald

    2007-01-01

    Manufacturing companies have traditionally focused their efforts on designing, developing and producing products to offer on the market. Today global competition and demands for greater company responsibility of products throughout their entire life cycle are driving manufacturing companies to...... products throughout their life cycle by designing integrated solutions of products and services. This approach has been dubbed ‘product/service-systems (PSS)’ (Mont, 2004). Although relationship marketing and product/service-system design have their roots in each their own research fields - marketing and...... engineering design - it seems that the two approaches are complimentary. The principle behind PSS is a shift from a perception that value is mainly embedded in a physical artefact to a perception where the activities associated with the product are considered to be a better definition of value. In this new...

  20. When Product Life Cycle Meets Customer Activity Cycle

    Tan, Adrian Ronald

    2007-01-01

    Manufacturing companies have traditionally focused their efforts on designing, developing and producing products to offer on the market. Today global competition and demands for greater company responsibility of products throughout their entire life cycle are driving manufacturing companies to shift market strategies from a transactional approach to an approach based on the establishment and management of customer relationships (Grönroos, 1999). A growing number of studies and research progra...

  1. Multi-cycle boiling water reactor fuel cycle optimization

    Ottinger, K.; Maldonado, G.I. [University of Tennessee, 311 Pasqua Engineering Building, Knoxville, TN 37996-2300 (United States)

    2013-07-01

    In this work a new computer code, BWROPT (Boiling Water Reactor Optimization), is presented. BWROPT uses the Parallel Simulated Annealing (PSA) algorithm to solve the out-of-core optimization problem coupled with an in-core optimization that determines the optimum fuel loading pattern. However it uses a Haling power profile for the depletion instead of optimizing the operating strategy. The result of this optimization is the optimum new fuel inventory and the core loading pattern for the first cycle considered in the optimization. Several changes were made to the optimization algorithm with respect to other nuclear fuel cycle optimization codes that use PSA. Instead of using constant sampling probabilities for the solution perturbation types throughout the optimization as is usually done in PSA optimizations the sampling probabilities are varied to get a better solution and/or decrease runtime. The new fuel types available for use can be sorted into an array based on any number of parameters so that each parameter can be incremented or decremented, which allows for more precise fuel type selection compared to random sampling. Also, the results are sorted by the new fuel inventory of the first cycle for ease of comparing alternative solutions. (authors)

  2. VISION - Verifiable Fuel Cycle Simulation of Nuclear Fuel Cycle Dynamics

    The U.S. DOE Advanced Fuel Cycle Initiative's (AFCI) fundamental objective is to provide technology options that--if implemented--would enable long-term growth of nuclear power while improving sustainability and energy security. The AFCI organization structure consists of four areas; Systems Analysis, Fuels, Separations and Transmutations. The Systems Analysis Working Group is tasked with bridging the program technical areas and providing the models, tools, and analyses required to assess the feasibility of design and deployment options and inform key decision makers. An integral part of the Systems Analysis tool set is the development of a system level model that can be used to examine the implications of the different mixes of reactors, implications of fuel reprocessing, impact of deployment technologies, as well as potential ''exit'' or ''off ramp'' approaches to phase out technologies, waste management issues and long-term repository needs. The Verifiable Fuel Cycle Simulation Model (VISION) is a computer-based simulation model that allows performing dynamic simulations of fuel cycles to quantify infrastructure requirements and identify key trade-offs between alternatives. It is based on the current AFCI system analysis tool ''DYMOND-US'' functionalities in addition to economics, isotopic decay, and other new functionalities. VISION is intended to serve as a broad systems analysis and study tool applicable to work conducted as part of the AFCI and Generation IV reactor development studies

  3. ITER-FEAT fuel cycle

    The Fuel Cycle, which includes plasma fuelling and exhaust, as well as exhaust processing and isotope separation, is one of the key elements on which the successful operation of ITER will depend. This paper provides an overview of this system, reviewing requirements, operational scenarios, and the integration of the various subsystems using the ITER fuel cycle dynamic simulation program CFTSIM. The requirements to provide a plasma fuelling rate of 200 Pam3s-1, with a flat-top burn of ∼400s and a repetition rate of two pulses per hour have the greatest influence on the design. However, while a flat-top burn of ∼400s is the initial design basis, the capability to extend the pulse to 3,000s in the longer term is essential from an operational perspective. (author)

  4. Single-cycle nonlinear optics

    Max-Planck-Institut fur Quantenoptik; Goulielmakis, E.; Schultze, M.; Hofstetter, M.; Yakovlev, V. S.; Gagnon, J.; Uiberacker, M.; Aquila, A. L.; gullikson, E. M.; attwood, D. T.; Kienberger, R.; Krausz, F.; Kleineberg, U.

    2008-11-05

    Nonlinear optics plays a central role in the advancement of optical science and laser-based technologies. We report on the confinement of the nonlinear interaction of light with matter to a single wave cycle and demonstrate its utility for time-resolved and strong-field science. The electric field of 3.3-femtosecond, 0.72-micron laser pulses with a controlled and measured waveform ionizes atoms near the crests of the central wave cycle, with ionization being virtually switched off outside this interval. Isolated sub-100-attosecond pulses of extreme ultraviolet light (photon energy {approx} 80 electron volts), containing {approx} 0.5 nanojoule of energy, emerge from the interaction with a conversion efficiency of {approx} 10{sup -6}. These tools enable the study of the precision control of electron motion with light fields and electron-electron interactions with a resolution approaching the atomic unit of time ({approx} 24 attoseconds).

  5. Swimming as a limit cycle

    Jacobs, Henry O

    2012-01-01

    Steady swimming can be characterized as both periodic and stable. These characteristics are the very definition of limit cycles, and so we ask "Can we view swimming as a limit cycle?" In this paper we will find that the answer is "yes". We will define a class of dissipative systems which correspond to the passive dynamics of a body immersed in a Navier-Stokes fluid (i.e. the dynamics of a dead fish). Upon performing reduction by symmetry we will find a hyperbolically stable fixed point which corresponds to the stability of a dead fish in stagnant water. Given a periodic force on the shape of the body we will invoke the persistence theorem to assert the existence of a loop which approximately satisfies the exact equations of motion. If we lift this loop with a phase reconstruction formula we will find that the lifted loops are not loops, but stable trajectories which represent regular periodic motion reminiscent of swimming.

  6. Carnot cycle for an oscillator

    Arnaud, J; Philippe, F

    2002-01-01

    Carnot established in 1824 that the efficiency of cyclic engines operating between a hot bath at absolute temperature Th and a cold bath at temperature Tc cannot exceed 1-Tc/Th. This result implies the existence of an entropy function S(U) with the property that d^2S/dU^2 less equal 0, where U denotes the average energy. Linear single-mode systems alternately in contact with hot and cold baths obey these principles. A specific expression of the work done per cycle by an oscillator is derived from a prescription established by Einstein in 1906: heat baths may exchange energy with oscillators at angular frequency omega only by amounts hbar *omega, where 2*pi*hbar denotes the Planck constant. Non-reversible cycles are illustrated. The paper is essentially self-contained.

  7. THE CANADIAN POLITICAL BUSINESS CYCLE

    Barbara Libby

    2000-01-01

    Full Text Available This paper will discuss the existence of a Canadian Political Business Cycle (PBC during the period 1946-1989. Logit analysis was used to determine if changes in the unemployment rate, growth of real GNE and the rate of inflation are significantly different in the period before an election than during the rest of the electoral term. It was found that the rate of growth in the unemployment rate declines and the rate of growth of real GNP increases in the four quarters before an election. The behavior of these variables reverses in the period after an election. These findings are consistent with a political business cycle. Policy variables, under a majority government, also behave in a manner associated with a PBC, with the government stimulating the economy approximately two years into its term so that good economic news will occur before it has to call an election. Minority governments tend to simulate the economy immediately after taking office.

  8. Life cycle assessment of turbines

    NONE

    2004-10-15

    This report forms part of the final reporting of the project 'LCA and turbines, which has been carried out as a cooperation between Vestas Wind Systems A/S and Tech-wise A/S on behalf of Elsam A/S. The goal of the project was to create a life cycle model for a big Vestas offshore turbine. Based on the offshore model an analysis has been prepared and this analysis will show the most significant environmental impacts a turbine will be subject to during its life cycle. Furthermore we have prepared a recommendation on how an improvement strategy on a selected area can be drafted. Finally, a preliminary environmental declaration of contents will be prepared for the turbine in question and 1 kWh generated from here. (BA)

  9. Breaking the cycle of abuse.

    Egeland, B; Jacobvitz, D; Sroufe, L A

    1988-08-01

    The aim of this study was to identify variables that distinguish mothers who broke the cycle of abuse from mothers who were abused as children and who also abused their own children. Based on maternal interviews and questionnaires completed over a 64-month period, measures of mothers' past and current relationship experiences, stressful life events, and personality characteristics were obtained. Abused mothers who were able to break the abusive cycle were significantly more likely to have received emotional support from a nonabusive adult during childhood, participated in therapy during any period of their lives, and to have had a nonabusive and more stable, emotionally supportive, and satisfying relationship with a mate. Abused mothers who reenacted their maltreatment with their own children experienced significantly more life stress and were more anxious, dependent, immature, and depressed. PMID:3168615

  10. National Policy on Nuclear Fuel Cycle

    National policy on nuclear fuel cycle is aimed at attaining the expected condition, i.e. being able to support optimality the national energy policy and other related Government policies taking into account current domestic nuclear fuel cycle condition and the trend of international nuclear fuel cycle development, the national strength, weakness, thread and opportunity in the field of energy. This policy has to be followed by the strategy to accomplish covering the optimization of domestic efforts, cooperation with other countries, and or purchasing licences. These policy and strategy have to be broken down into various nuclear fuel cycle programmes covering basically assesment of the whole cycle, performing research and development of the whole cycle without enrichment and reprocessing being able for weapon, as well as programmes for industrialization of the fuel cycle stepwisery commencing with the middle part of the cycle and ending with the edge of the back-end of the cycle

  11. Fuel cycle math - part one

    This article is Part One of a two-part article that reviews some of the numbers associated with the nuclear fuel cycle. The contents of Part One include: composition of the element uranium, considering atomic mass and weight-percent of the isotopes; uranium in the ground, including ore grades; mining, with dilution factors and recovery rates; ore sorting, including concentration factors; and uranium recovery. No financial information is presented in either Part One or Part Two

  12. Immigration, remittances, and business cycles

    Federico S. Mandelman; Zlate, Andrei

    2010-01-01

    We use data on border enforcement and macroeconomic indicators from the United States and Mexico to estimate a two-country business cycle model of labor migration and remittances. The model matches the cyclical dynamics of labor migration to the United States and documents how remittances to Mexico serve an insurance role to smooth consumption across the border. During expansions in the destination economy, immigration increases with the expected stream of future wage gains, but it is dampene...

  13. Cycling Behavior and Memory Formation

    Gerstner, Jason R.; Lyons, Lisa C.; Wright, Kenneth P.; Loh, Dawn H; Rawashdeh, Oliver; Eckel-Mahan, Kristin L.; Roman, Gregg W.

    2009-01-01

    Circadian research has spent considerable effort in the determining clock output pathways, including identifying both physiological and behavioral processes that demonstrate significant time-of-day variation. Memory formation and consolidation represent notable processes shaped by endogenous circadian oscillators. To date, very few studies on memory mechanisms have considered potential confounding effects of time-of-day and the organism’s innate activity cycles (e.g., nocturnal, diurnal, or c...

  14. Branes wrapped on coassociative cycles

    We obtain a supergravity solution arising when D6-branes are wrapped on coassociative four-cycles of constant curvature in seven manifolds of G2 holonomy. The solutions preserve two supercharges and thus represent supergravity duals of three dimensional Yang-Mills with N=1 supersymmetry. When uplifted to eleven dimensions our solution describes M-theory on the background of an eight manifold with Spin(7) holonomy. (author)

  15. Sickness Absence and Business Cycles

    Jan Erik Askildsen; Espen Bratberg; Oivind Anti Nilsen

    2000-01-01

    Absenteeism is affected by the sickness benefit system. Countries with generous compensation during sick leaves also experience high numbers of sick leave. Sick leaves may vary over the business cycle due to unemployment disciplining effects or changes in labour force composition. The latter hypothesis maintains that sickness may be pro-cyclical due to employment of `marginal' workers with poorer health when demand increases. Using individual records of labour force participants in Norway, we...

  16. Accounting for Spanish business cycles.

    Jesús Rodríguez-López; Mario Solís-García

    2014-01-01

    We apply the business cycle methodology proposed by Chari, Kehoe, and McGrattan (2007) to identify the sources of Spanish business fluctuations during two outstanding cyclical episodes: the recession alongside the transition to democracy in 1977 and the great recession of 2008. We find that the labor wedge plays a key role during both recessions and that taxes and labor market institutions are likely behind the wedge movements. We conclude that any model that tries to understand the causes of...

  17. Entrepreneurship and the Business Cycle

    KOELLINGER, Philipp; Thurik, Roy

    2009-01-01

    This discussion paper resulted in a publication in 'The Review of Economics and Statistics' (2012). Volume 94, issue 4, pages 1143-1156. We study the cyclical pattern of entrepreneurial activity. Results across 22 OECD countries for the period 1972-2007 show that entrepreneurial activity is a leading indicator of the business cycle in a Granger-causality sense. This contradicts existing theoretical hypotheses which predict that entrepreneurship is pro-cyclical or not cyclical. We discuss poss...

  18. Technology cycles and technology revolutions

    Paganetto, Luigi; Scandizzo, Pasquale Lucio

    2010-09-15

    Technological cycles have been characterized as the basis of long and continuous periods economic growth through sustained changes in total factor productivity. While this hypothesis is in part consistent with several theories of growth, the sheer magnitude and length of the economic revolutions experienced by humankind seems to indicate surmise that more attention should be given to the origin of major technological and economic changes, with reference to one crucial question: role of production and use of energy in economic development.

  19. Business Cycle Synchronization in Croatia

    Šergo Zdravko; Poropat Amorino; Gržinić Jasmina

    2012-01-01

    The purpose of this paper is to analyze business cycle synchronization in the Croatian economy using various annualized growth rate variables over a period of eighteen years (1992-2010), de-trended by a Hodrick-Prescott filter, and following the Harding and Pagan methodological procedure in the determination of its turning points. Our conceptual analysis of synchronization is based on the technique of concordance indexes and correlation coefficients obtained by the HAC estimators. The main re...

  20. Business cycle dependent unemployment insurance

    Andersen, Torben M.; Svarer, Michael

    2010-01-01

    The consequences of business cycle contingencies in unemployment insurance systems are considered in a search-matching model allowing for shifts between "good" and "bad" states of nature. We show that not only is there an insurance argument for such contingencies, but there may also be an incentive argument. Since benefits may be less distortionary in a recession than a boom, it follows that counter-cyclical benefits reduce average distortions compared to state independent benefits. We show t...

  1. Cardiac Biomarkers and Cycling Race

    Caroline Le Goff, Jean-François Kaux, Sébastien Goffaux, Etienne Cavalier

    2015-01-01

    In cycling as in other types of strenuous exercise, there exists a risk of sudden death. It is important both to understand its causes and to see if the behavior of certain biomarkers might highlight athletes at risk. Many reports describe changes in biomarkers after strenuous exercise (Nie et al., 2011), but interpreting these changes, and notably distinguishing normal physiological responses from pathological changes, is not easy. Here we have focused on the kinetics of different cardiac bi...

  2. Miller cycle analysis using EGM

    Ribeiro, Bernardo Sousa; Martins, Jorge

    2005-01-01

    The Entropy Generation Minimization (EGM) method is based on the analysis by three sciences (thermodynamics, fluid flow and heat transfer) of the different processes that may occur in a system or in an equipment. Herein the EGM method is applied to internal combustion engines to determine the entropy generation caused by different processes. A model incorporating entropy generation calculations is used to assess various engines configurations. Otto cycle was tested and...

  3. Creative Cycling of News Professionals

    Astrid Gynnild, PhD.

    2007-01-01

    The theory of creative cycling emerged from my PhD study of news professionals in Norway. The study was carried out according to classic grounded theory principles (Glaser and Strauss 1967, Glaser 1978, 1998, 2001, 2005), and the area of interest was the performance of news journalism in the multimedia age. The theory runs counter to widespread tendencies of industrial age thinking in news media. It emphasizes news professionals’ search for meaning in their daily work, and suggests that their...

  4. The parenting cycle of deployment.

    DeVoe, Ellen R; Ross, Abigail

    2012-02-01

    Parents of dependent children comprise approximately 42% of Active Duty and National Guard/Reserve military members serving in Operation Iraqi Freedom/Operation Enduring Freedom. Recent estimates indicate that more than two million children have experienced parental deployment since the terrorist attacks on September 11, 2001. This article seeks to characterize the impact of the deployment life cycle on parenting roles among service members and at-home partners/caregivers of dependent children. Specifically, a new conceptual framework is presented for considering the ways in which parenting and co-parenting processes are affected by the demands and transitions inherent in contemporary deployment to a war zone. Although the phase-based emotional cycle of deployment continues to offer an instructive description of the broad challenges faced by military couples, a parenting cycle of deployment model shifts the perspective to the critical and largely ignored processes of parenting in the context of deployment and war, and to the realities faced by parents serving in the U.S. military. Implications for prevention, intervention, and future research related to military families are addressed. PMID:22360065

  5. The Life Cycle Analysis Toolbox

    The life cycle analysis toolbox is a valuable integration of decision-making tools and supporting materials developed by Oak Ridge National Laboratory (ORNL) to help Department of Energy managers improve environmental quality, reduce costs, and minimize risk. The toolbox provides decision-makers access to a wide variety of proven tools for pollution prevention (P2) and waste minimization (WMin), as well as ORNL expertise to select from this toolbox exactly the right tool to solve any given P2/WMin problem. The central element of the toolbox is a multiple criteria approach to life cycle analysis developed specifically to aid P2/WMin decision-making. ORNL has developed numerous tools that support this life cycle analysis approach. Tools are available to help model P2/WMin processes, estimate human health risks, estimate costs, and represent and manipulate uncertainties. Tools are available to help document P2/WMin decision-making and implement programs. Tools are also available to help track potential future environmental regulations that could impact P2/WMin programs and current regulations that must be followed. An Internet-site will provide broad access to the tools

  6. Digital Daily Cycles of Individuals

    Aledavood, Talayeh; Lehmann, Sune; Saramäki, Jari

    2015-10-01

    Humans, like almost all animals, are phase-locked to the diurnal cycle. Most of us sleep at night and are active through the day. Because we have evolved to function with this cycle, the circadian rhythm is deeply ingrained and even detectable at the biochemical level. However, within the broader day-night pattern, there are individual differences: e.g., some of us are intrinsically morning-active, while others prefer evenings. In this article, we look at digital daily cycles: circadian patterns of activity viewed through the lens of auto-recorded data of communication and online activity. We begin at the aggregate level, discuss earlier results, and illustrate differences between population-level daily rhythms in different media. Then we move on to the individual level, and show that there is a strong individual-level variation beyond averages: individuals typically have their distinctive daily pattern that persists in time. We conclude by discussing the driving forces behind these signature daily patterns, from personal traits (morningness/eveningness) to variation in activity level and external constraints, and outline possibilities for future research.

  7. Solar storms, cycles and topology

    Lundstedt H.

    2010-12-01

    Full Text Available Solar storms are produced due to plasma processes inside and between coronal loops. These loops are topologically examined using knot and braid theory. Solar cycles are topologically explored with a complex generalization of the three ordinary differential equations studied by Lorenz. By studying the Poincaré map we give numerical evidence that the flow has an attractor with fractal structure. The period is defined as the time needed for a point on a hyperplane to return to the hyperplane again. The periods are distributed in an interval. For large values of the Dynamo number there is a long tail toward long periods and other interesting comet-like features. We also found a relationship between the intensity of a cycle and the length for the previous cycle. Maunder like minima are also appearing. These general relations found for periods can further be physically interpreted with improved helioseismic estimates of the parameters used by the dynamical systems. Solar Dynamic Observatory is expected to offer such improved measurements.

  8. Advanced Fuel Cycle Cost Basis

    D. E. Shropshire; K. A. Williams; W. B. Boore; J. D. Smith; B. W. Dixon; M. Dunzik-Gougar; R. D. Adams; D. Gombert

    2007-04-01

    This report, commissioned by the U.S. Department of Energy (DOE), provides a comprehensive set of cost data supporting a cost analysis for the relative economic comparison of options for use in the Advanced Fuel Cycle Initiative (AFCI) Program. The report describes the AFCI cost basis development process, reference information on AFCI cost modules, a procedure for estimating fuel cycle costs, economic evaluation guidelines, and a discussion on the integration of cost data into economic computer models. This report contains reference cost data for 26 cost modules—24 fuel cycle cost modules and 2 reactor modules. The cost modules were developed in the areas of natural uranium mining and milling, conversion, enrichment, depleted uranium disposition, fuel fabrication, interim spent fuel storage, reprocessing, waste conditioning, spent nuclear fuel (SNF) packaging, long-term monitored retrievable storage, near surface disposal of low-level waste (LLW), geologic repository and other disposal concepts, and transportation processes for nuclear fuel, LLW, SNF, and high-level waste.

  9. Nutrient cycling in mango trees

    Cinara Xavier de Almeida

    2014-02-01

    Full Text Available Estimates of nutrient amounts both shedding and demanding replacement in the maintenance of productivity of fruit trees require studies on element dynamics within the many ecosystem components generally made up of nutrient cycling. Thus, it was the objective of this study to evaluate the nutrient biochemical cycling in a mango tree (Mangifera indica L. orchard, Palmer variety. Macronutrients [nitrogen (N, phosphorus (P, potassium (K, calcium (Ca, magnesium (Mg, and sulfur (S] had their contents evaluated in leaves at different stages: new, mature, senescent, and litter. First exploratory analysis was performed for main components which preserve the multivariate structure shown by the data. It was possible to observe the association of new leaves with N, P, K, Mg, and S; senescent leaves and the leaves from the litter were associated to Ca, while mature leaves, to K. As a complement, taking the independent variables into consideration, Tukey test (p?0.01 showed that the averages of N, P, and Ca differ between the new and the mature leaves; average of Mg in new leaves differs from the others, and S does not differ along the stages. Also observed was the re-translocation of 41%, 63% and 57% of N, P, and K, respectively, when comparison was made among the contents of the elements in mature leaves as well as in litter, which indicates that the biochemical cycling is important for the mango tree cultivation.

  10. Digital Daily Cycles of Individuals

    Talayeh eAledavood

    2015-10-01

    Full Text Available Humans, like almost all animals, are phase-locked to the diurnal cycle. Most of us sleep at night and are active through the day. Because we have evolved to function with this cycle, the circadian rhythm is deeply ingrained and even detectable at the biochemical level. However, within the broader day-night pattern, there are individual differences: e.g., some of us are intrinsically morning-active, while others prefer evenings. In this article, we look at digital daily cycles: circadian patterns of activity viewed through the lens of auto-recorded data of communication and online activity. We begin at the aggregate level, discuss earlier results, and illustrate differences between population-level daily rhythms in different media. Then we move on to the individual level, and show that there is a strong individual-level variation beyond averages: individuals typically have their distinctive daily pattern that persists in time. We conclude by discussing the driving forces behind these signature daily patterns, from personal traits (morningness/eveningness to variation in activity level and external constraints, and outline possibilities for future research.

  11. Advanced Fuel Cycle Cost Basis

    D. E. Shropshire; K. A. Williams; W. B. Boore; J. D. Smith; B. W. Dixon; M. Dunzik-Gougar; R. D. Adams; D. Gombert; E. Schneider

    2009-12-01

    This report, commissioned by the U.S. Department of Energy (DOE), provides a comprehensive set of cost data supporting a cost analysis for the relative economic comparison of options for use in the Advanced Fuel Cycle Initiative (AFCI) Program. The report describes the AFCI cost basis development process, reference information on AFCI cost modules, a procedure for estimating fuel cycle costs, economic evaluation guidelines, and a discussion on the integration of cost data into economic computer models. This report contains reference cost data for 25 cost modules—23 fuel cycle cost modules and 2 reactor modules. The cost modules were developed in the areas of natural uranium mining and milling, conversion, enrichment, depleted uranium disposition, fuel fabrication, interim spent fuel storage, reprocessing, waste conditioning, spent nuclear fuel (SNF) packaging, long-term monitored retrievable storage, near surface disposal of low-level waste (LLW), geologic repository and other disposal concepts, and transportation processes for nuclear fuel, LLW, SNF, transuranic, and high-level waste.

  12. Advanced Fuel Cycle Cost Basis

    D. E. Shropshire; K. A. Williams; W. B. Boore; J. D. Smith; B. W. Dixon; M. Dunzik-Gougar; R. D. Adams; D. Gombert; E. Schneider

    2008-03-01

    This report, commissioned by the U.S. Department of Energy (DOE), provides a comprehensive set of cost data supporting a cost analysis for the relative economic comparison of options for use in the Advanced Fuel Cycle Initiative (AFCI) Program. The report describes the AFCI cost basis development process, reference information on AFCI cost modules, a procedure for estimating fuel cycle costs, economic evaluation guidelines, and a discussion on the integration of cost data into economic computer models. This report contains reference cost data for 25 cost modules—23 fuel cycle cost modules and 2 reactor modules. The cost modules were developed in the areas of natural uranium mining and milling, conversion, enrichment, depleted uranium disposition, fuel fabrication, interim spent fuel storage, reprocessing, waste conditioning, spent nuclear fuel (SNF) packaging, long-term monitored retrievable storage, near surface disposal of low-level waste (LLW), geologic repository and other disposal concepts, and transportation processes for nuclear fuel, LLW, SNF, transuranic, and high-level waste.

  13. Optimization of data life cycles

    Data play a central role in most fields of science. In recent years, the amount of data from experiment, observation, and simulation has increased rapidly and data complexity has grown. Also, communities and shared storage have become geographically more distributed. Therefore, methods and techniques applied to scientific data need to be revised and partially be replaced, while keeping the community-specific needs in focus. The German Helmholtz Association project 'Large Scale Data Management and Analysis' (LSDMA) aims to maximize the efficiency of data life cycles in different research areas, ranging from high energy physics to systems biology. In its five Data Life Cycle Labs (DLCLs), data experts closely collaborate with the communities in joint research and development to optimize the respective data life cycle. In addition, the Data Services Integration Team (DSIT) provides data analysis tools and services which are common to several DLCLs. This paper describes the various activities within LSDMA and focuses on the work performed in the DLCLs.

  14. Forging the anthropogenic iron cycle.

    Wang, Tao; Müller, Daniel B; Graedel, T E

    2007-07-15

    Metallurgical iron cycles are characterized for four anthropogenic life stages: production, fabrication and manufacturing, use, and waste management and recycling. This analysis is conducted for year 2000 and at three spatial levels: 68 countries and territories, nine world regions, and the planet. Findings include the following: (1) contemporary iron cycles are basically open and substantially dependent on environmental sources and sinks; (2) Asia leads the world regions in iron production and use; Oceania, Latin America and the Caribbean, Africa, and the Commonwealth of Independent States present a highly production-biased iron cycle; (3) purchased scrap contributes a quarter of the global iron and steel production; (4) iron exiting use is three times less than that entering use; (5) about 45% of global iron entering use is devoted to construction, 24% is devoted to transport equipment, and 20% goes to industrial machinery; (6) with respect to international trade of iron ore, iron and steel products, and scrap, 54 out of the 68 countries are net iron importers, while only 14 are net exporters; (7) global iron discharges in tailings, slag, and landfill approximate one-third of the iron mined. Overall, these results provide a foundation for studies of iron-related resource policy, industrial development, and waste and environmental management. PMID:17711233

  15. Endoreversible Meletis-Georgiou cycle

    Chang Liu, Lingen Chen, Fengrui Sun

    2012-01-01

    Full Text Available An endoreversible Meletis-Georgiou (MG cycle model with constant specific heat of working fluid is established and the analytical formulae of performance parameters including working fluid temperatures, work output and efficiency are derived using the finite time thermodynamic theory. The performance of the endoreversible MG cycle is analyzed and optimized. The characteristics of the work output versus compression ratio, efficiency versus compression ratio, and work output versus efficiency are obtained, respectively, by detailed numerical examples, and the effects of changeover ratio, over-expansion ratio, heating value of fuel, heat transfer loss coefficient, initial temperature of working fluid, and the transferred volume ratio on the relationship mentioned above are also discussed. The maximum work output and the corresponding optimal compression ratio, changeover ratio, over-expansion ratio as well as the maximum efficiency and the corresponding optimal changeover ratio and over-expansion ratio are obtained by taking the cycle work output and efficiency as the optimization objectives, respectively. Moreover, the effects of the parameters such as the heating value of fuel, heat transfer loss coefficient, initial temperature of working fluid, and the transferred volume ratio on the maximum work output, the maximum efficiency and the corresponding optimal ratios are analyzed. The results may provide guidelines for the optimal design of practical MG engine.

  16. Solar Cycle 24: Where are you?

    Chapman, Gary A.; Cookson, A.; Preminger, D.

    2009-05-01

    Photometric images have been obtained on a daily basis since 1986 at the San Fernando Observatory. We will compare sunspot and facular areas from cycle 22 with those of cycle 23. Both spot areas and facular areas were lower during the maximum of cycle 23 compared to cycle 22. The distribution in spot areas will be compared. The extended minimum in spot area following cycle 23 is delaying the beginning of cycle 24. This work has been partially supported by NSF grant ATM-0533511.

  17. On The Cycle Double Cover Problem

    Ghassab, Ali

    2012-01-01

    In this paper, for each graph G, a free edge set F is defined. To study the existence of cycle double cover, the naive cycle double cover of G and F have been defined and studied. In the main theorem, the paper, based on the Kuratowski minor properties, presents a condition to guarantee the existence of a naive cycle double cover for couple (G,F). As a result, the cycle double cover conjecture has been concluded. Moreover, Goddyn's conjecture - asserting if C is a cycle in bridgeless graph G, there is a cycle double cover of G containing C - will have been proved.

  18. The nuclear fuel cycle; Le cycle du combustible nucleaire

    NONE

    1998-05-01

    After a short introduction about nuclear power in the world, fission physics and the French nuclear power plants, this brochure describes in a digest way the different steps of the nuclear fuel cycle: uranium prospecting, mining activity, processing of uranium ores and production of uranium concentrates (yellow cake), uranium chemistry (conversion of the yellow cake into uranium hexafluoride), fabrication of nuclear fuels, use of fuels, reprocessing of spent fuels (uranium, plutonium and fission products), recycling of energetic materials, and storage of radioactive wastes. (J.S.)

  19. VVER fuel cycle development at Slovakia

    Four VVER-440 units are now under exploitation at Bohunice-site in Slovakia. Fuel cycle development of Unit No.3 and No.4 (type 213) is discussed and compared with equilibrium cycles in this paper. (author)

  20. Not all counterclockwise thermodynamic cycles are refrigerators

    Dickerson, R. H.; Mottmann, J.

    2016-06-01

    Clockwise cycles on PV diagrams always represent heat engines. It is therefore tempting to assume that counterclockwise cycles always represent refrigerators. This common assumption is incorrect: most counterclockwise cycles cannot be refrigerators. This surprising result is explored here for quasi-static ideal gas cycles, and the necessary conditions for refrigeration cycles are clarified. Three logically self-consistent criteria can be used to determine if a counterclockwise cycle is a refrigerator. The most fundamental test compares the counterclockwise cycle with a correctly determined corresponding Carnot cycle. Other criteria we employ include a widely accepted description of the functional behavior of refrigerators, and a corollary to the second law that limits a refrigerator's coefficient of performance.

  1. Development Plan for the Fuel Cycle Simulator

    The Fuel Cycle Simulator (FCS) project was initiated late in FY-10 as the activity to develop a next generation fuel cycle dynamic analysis tool for achieving the Systems Analysis Campaign 'Grand Challenge.' This challenge, as documented in the Campaign Implementation Plan, is to: 'Develop a fuel cycle simulator as part of a suite of tools to support decision-making, communication, and education, that synthesizes and visually explains the multiple attributes of potential fuel cycles.'

  2. An introduction to global carbon cycle management

    Sundquist, Eric T.; Ackerman, Katherine V.; Parker, Lauren; Huntzinger, Deborah N.

    2009-01-01

    Past and current human activities have fundamentally altered the global carbon cycle. Potential future efforts to control atmospheric CO2 will also involve significant changes in the global carbon cycle. Carbon cycle scientists and engineers now face not only the difficulties of recording and understanding past and present changes but also the challenge of providing information and tools for new management strategies that are responsive to societal needs. The challenge is nothing less than managing the global carbon cycle.

  3. Oconee 1, cycle 5 design report

    The Oconee 1, cycle 5 fuel cycle was designed to irradiate five fuel assemblies to a burnup of approximately 40,000 MWd/mtU. The fuel cycle design was performed using standard Babcock and Wilcox calculational techniques for nuclear fuel cycles. All applicable design criteria were satisfied. Valuable experimental data on the performance characteristics of high-burnup fuel assemblies will be obtained from these assemblies in subsequent post-irradiation examinations

  4. Seasonality and equilibrium business cycle theories

    R. Anton Braun; Evans, Charles L.

    1991-01-01

    Barksy-Miron [1989] find that the postwar U.S. economy exhibits a regular seasonal cycle, as well as the business cycle phenomenon. Are these findings consistent with current equilibrium business cycle theories as surveyed by Prescott [1986]? We consider a dynamic, stochastic equilibrium business cycle model which includes deterministic seasonals and nontime-separable preferences. We show how to compute a perfect foresight seasonal equilibrium path for this economy. An approximation to the st...

  5. Population crises and population cycles.

    Russell, C; Russell, W M

    2000-01-01

    To prevent a population irretrievably depleting its resources, mammals have evolved a behavioural and physiological response to population crisis. When a mammalian population becomes dangerously dense, there is a reversal of behaviour. Co-operation and parental behaviour are replaced by competition, dominance and aggressive violence, leading to high mortality, especially of females and young, and a reduced population. The stress of overpopulation and the resulting violence impairs both the immune and the reproductive systems. Hence epidemics complete the crash of the population, and reproduction is slowed for three or four generations, giving the resources ample time to recover. In some mammal species, crisis and crisis response recur regularly, leading to cycles of population growth and relapse, oscillating about a fixed mean. Population crisis response and population cycles have been equally prominent in the history of human societies. But in man successive advances in food production have made possible growing populations, though with every such advance population soon outgrew resources again. Hence human cycles have been superimposed on a rising curve, producing a saw-tooth graph. Because advances in food production amounted to sudden disturbances in the relations between human populations and their environments, the crisis response in man has failed to avert famine and resource damage. In the large human societies evolved since the coming of settled agriculture and cities, the basic effects of violence, epidemics, famine and resource damage have been mediated by such specifically human disasters as inflation, unemployment, and political tyranny. An account of past crises, periods of relative relief from population pressure, and resulting cycles, is given for a number of regions: China, North Africa and Western Asia, the northern Mediterranean, and north-western Europe. The paper ends with an account of the present world-wide population crisis, and the solution

  6. Business cycle synchronization in Europe

    Bergman, Ulf Michael; Jonung, Lars

    2011-01-01

    In this paper we study business cycle synchronization in the three Scandinavian countries Denmark, Norway and Sweden prior to, during and after the Scandinavian Currency Union 1873–1913. We find that the degree of synchronization tended to increase during the currency union, thus supporting earlier...... empirical evidence. Estimates of factor models suggest that common Scandinavian shocks are important for these three countries. At the same time we find evidence suggesting that the importance of these shocks does not depend on the monetary regime....

  7. Radioecology of nuclear fuel cycles

    This study provides information to help assess the environmental impacts and certain potential human hazards associated with nuclear fuel cycles. A data base is being developed to define and quantify biological transport routes, which will permit credible predictions and assessment of routine and potential large-scale releases of radionuclides and other toxic materials. These data, used in assessment models, will increase the accuracy of estimating radiation doses to man and other life forms. Results will provide information to determine if waste management procedures on the Hanford site have caused ecological perturbations, and, if so, to determine the source, nature and magnitude of such disturbances

  8. Carnot cycle for an oscillator

    Arnaud, J.; Chusseau, L.; Philippe, F.

    2001-01-01

    Carnot established in 1824 that the efficiency of cyclic engines operating between a hot bath at absolute temperature $T_{hot}$ and a bath at a lower temperature $T_{cold}$ cannot exceed $1-T_{cold}/T_{hot}$. We show that linear oscillators alternately in contact with hot and cold baths obey this principle in the quantum as well as in the classical regime. The expression of the work performed is derived from a simple prescription. Reversible and non-reversible cycles are illustrated. The pape...

  9. A Coupled Quantum Otto Cycle

    Thomas, George; Johal, Ramandeep S.

    2010-01-01

    We study the 1-d isotropic Heisenberg model of two spin-1/2 systems as a quantum heat engine. The engine undergoes a four-step Otto cycle where the two adiabatic branches involve changing the external magnetic field at a fixed value of the coupling constant. We find conditions for the engine efficiency to be higher than the uncoupled model; in particular, we find an upper bound which is tighter than the Carnot bound. A new domain of parameter values is pointed out which was not feasible in th...

  10. New technology and fuel cycles

    The means of improving uranium utilization in nuclear power reactors are reviewed with respect to economic considerations, assurance of adequate fuel supplies and risk of weapons proliferation. Reference is made to what can be done to improve fuel economy in existing reactor systems operating on a once-through fuel cycle and the potential for improvement offered by fuel recycle in those systems. The state of development of new reactor systems that offer significant savings in uranium utilization is also reviewed and conclusions are made respecting the policy implications of the search for fuel economy. (author)

  11. The biogeochemistry of metal cycling

    Nealson, Kenneth H. (Editor); Nealson, Molly (Editor); Dutcher, F. Ronald (Editor)

    1990-01-01

    The results of the Planetary Biology and Microbial Ecology's summer 1987 program are summarized. The purpose of the interdisciplinary PBME program is to integrate, via lectures and laboratory work, the contributions of university and NASA scientists and student interns. The 1987 program examined various aspects of the biogeochemistry of metal cycling, and included such areas as limnology, metal chemistry, metal geochemistry, microbial ecology, and interactions with metals. A particular area of focus was the use of remote sensing in the study of biogeochemistry. Abstracts and bibliographies of the lectures and reports of the laboratory projects are presented.

  12. Heteroclinic Cycles in Hopfield Networks

    Chossat, Pascal; Krupa, Maciej

    2016-04-01

    It is widely believed that information is stored in the brain by means of the varying strength of synaptic connections between neurons. Stored patterns can be replayed upon the arrival of an appropriate stimulus. Hence, it is interesting to understand how an information pattern can be represented by the dynamics of the system. In this work, we consider a class of network neuron models, known as Hopfield networks, with a learning rule which consists of transforming an information string to a coupling pattern. Within this class of models, we study dynamic patterns, known as robust heteroclinic cycles, and establish a tight connection between their existence and the structure of the coupling.

  13. Search for relationship between duration of the extended solar cycles and amplitude of sunspot cycle

    Tlatov, A G

    2007-01-01

    Duration of the extended solar cycles is taken into the consideration. The beginning of cycles is counted from the moment of polarity reversal of large-scale magnetic field in high latitudes, occurring in the sunspot cycle n till the minimum of the cycle n+2. The connection between cycle duration and its amplitude is established. Duration of the "latent" period of evolution of extended cycle between reversals and a minimum of the current sunspot cycle is entered. It is shown, that the latent period of cycles evolution is connected with the next sunspot cycle amplitude and can be used for the prognosis of a level and time of a sunspot maximum. The 24-th activity cycle prognosis is done. Long-term behavior of extended cycle's lengths is considered.

  14. Multiple Limit Cycles in an Immune System

    Xun-cheng Huang; Le-min Zhu; Minaya Villasana

    2008-01-01

    The nonlinear oscillatory phenomenon has been observed in the system of immune response, which corresponds to the limit cycles in the mathematical models. We prove that the system simulating an immune response studied by Huang has at least three limit cycles in the system. The conditions for the multiple limit cycles are useful in analyzing the nonlinear oscillation in immune response.

  15. Hopf limit cycles estimation in power systems

    Barquin, J.; Gomez, T.; Pagola, L.F. [Univ. Pontificia Comillas, Madrid (Spain). Inst. de Investigacion Tecnologica

    1995-11-01

    This paper addresses the computation of the Hopf limit cycle. This limit cycle is associated to the appearance of an oscillatory instability in dynamical power systems. An algorithm is proposed to estimate the dimensions and shape of this limit cycle. The algorithm is computationally efficient and is able to deal with large power systems. 7 refs, 4 figs, 1 tab

  16. Does It Have a Life Cycle?

    Keeley, Page

    2010-01-01

    If life continues from generation to generation, then all plants and animals must go through a life cycle, even though it may be different from organism to organism. Is this what students have "learned," or do they have their own private conceptions about life cycles? The formative assessment probe "Does It Have a Life Cycle?" reveals some…

  17. Aspects of the fast reactors fuel cycle

    The fuel cycle for fast reactors, is analysed, regarding the technical aspects of the developing of the reprocessing stages and the fuel fabrication. The environmental impact of LMFBRs and the waste management of this cycle are studied. The economic aspects of the fuel cycle, are studied too. Some coments about the Brazilian fast reactors programs are done. (E.G.)

  18. The benefits of getting England cycling

    Crawford, F; Lovelace, R

    2015-01-01

    This report compares the economic benefits of achieving the ambitions for cycling proposed in the Cycling Development Plan and the 'Get Britain Cycling' report against a zero-growth baseline. Monetary estimates of the benefits to health, the environment, safety and congestion are presented for the period 2015 to 2050.

  19. Dormancy cycling in seeds: mechanisms and regulation

    Claessens, S.M.C.

    2012-01-01

    The life cycle of most plants starts, and ends, at the seed stage. In most species mature seeds are shed and dispersed on the ground. At this stage of its life cycle the seed may be dormant and will, by definition, not germinate under favourable conditions (Bewley, 1997). Seasonal dormancy cycling

  20. VVER-1000 at KNPP - nuclear fuel cycle

    Information about the realized fuel cycles in the Kozloduy NPP units 5 and 6 is presented - fuel assemblies, fuel maps, transition from 2 years fuel cycle to 3 years fuel cycle, main characteristics of the fueling, combustion depth. Some possibilities for improvements of the campaigns and usage of fuels are discussed

  1. Proposal of a nuclear cycle research and development plan in Tokai works. The roadmap from LWR cycle to FBR cycle

    The Generation-II Project Task Force Team has investigated a research and development plan of a future nuclear fuel cycle in Tokai works for about three months from December 19, 2002. First we have discussed about the present condition of Japanese nuclear fuel cycle and have recognized it as the following. The relation of the technology between the LWR-cycle and the FBR-cycle is not clear. MOX Fuel Use in Light Water Reactors is important to establish technology of the FBR fuel cycle. Radioactive waste disposal issue is urgent. Next we have proposed the three basic policies on R and D plan of nuclear fuel cycle in consideration of the F.S. on FBR-cycle. Establishment and advancement of 'the tough nuclear fuel cycle'. Early establishment of the FBR cycle technology to be able to supply energy stably for long-term. Establishment of the radioactive waste treatment and disposal technology, and optimization of nuclear fuel cycle technology from the viewpoint of radioactive waste. And we have proposed the Japanese technical holder system to integrate all LWR and FBR cycle technology. (author)

  2. Rock weathering and Carbon cycle

    Strozza, Patrick

    2010-05-01

    In the history of the Earth system, we can find indicators of hot or glacial periods, as well as brutal climatic change… How can we explain those climate variations on a geological timescale ? One of the causative agents is probably the fluctuation of atmospheric CO2 amounts, (gas responsible for the greenhouse effect). A concrete study of some CO2 fluxes between Earth system reservoirs (atmo, hydro and lithosphere) is proposed in this poster. Hydrogencarbonate is the major ion in river surface waters and its amount is so high that it can not be explained by a simple atmospheric Carbon diffusion. From a simple measurement of river HCO3- concentration, we can estimate the consumption of atmospheric CO2 that arises from carbonate and silicate weathering processes. Practical experiments are proposed. These are carried out in the local environment, and are conform to the curriculums of Chemistry and Earth sciences. These tests enable us to outline long-term Carbon cycles and global climatic changes. Key words : Erosion, rock weathering, CO2 cycle, Hydrogencarbonate in waters, climatic changes

  3. Social Life Cycle Assessment Revisited

    Ruqun Wu

    2014-07-01

    Full Text Available To promote the development of Social Life Cycle Assessment (SLCA, we conducted a comprehensive review of recently developed frameworks, methods, and characterization models for impact assessment for future method developers and SLCA practitioners. Two previous reviews served as our foundations for this review. We updated the review by including a comprehensive list of recently-developed SLCA frameworks, methods and characterization models. While a brief discussion from goal, data, and indicator perspectives is provided in Sections 2 to 4 for different frameworks/methods, the focus of this review is Section 5 where discussion on characterization models for impact assessment of different methods is provided. The characterization models are categorized into two types following the UNEP/SETAC guidelines: type I models without impact pathways and type II models with impact pathways. Different from methods incorporating type I/II characterization models, another LCA modeling approach, Life Cycle Attribute Assessment (LCAA, is also discussed in this review. We concluded that methods incorporating either type I or type II models have limitations. For type I models, the challenge lies in the systematic identification of relevant stakeholders and materiality issues; while for type II models, identification of impact pathways that most closely and accurately represent the real-world causal relationships is the key. LCAA may avoid these problems, but the ultimate questions differ from those asked by the methods using type I and II models.

  4. Life Cycle Assessment of Concrete

    Sjunnesson, Jeannette

    2005-09-15

    This is an environmental study on concrete that follows the standard protocol of life cycle assessment (LCA). The study is done for two types of concrete, ordinary and frost-resistant concrete, and has an extra focus on the superplasticizers used as admixtures. The utilization phase is not included in this study since the type of construction for which the concrete is used is not defined and the concrete is assumed to be inert during this phase. The results show that it is the production of the raw material and the transports involved in the life cycle of concrete that are the main contributors to the total environmental load. The one single step in the raw material production that has the highest impact is the production of cement. Within the transportation operations the transportation of concrete is the largest contributor, followed by the transportation of the cement. The environmental impact of frost-resistant concrete is between 24-41 % higher than that of ordinary concrete due to its higher content of cement. Superplasticizers contribute with approximately 0.4-10.4 % of the total environmental impact of concrete, the least to the global warming potential (GWP) and the most to the photochemical ozone creation potential (POCP). Also the toxicity of the superplasticizers is investigated and the conclusion is that the low amount of leakage of superplasticizers from concrete leads to a low risk for the environment and for humans.

  5. Opportunities for fuel cycle development

    Today the Nuclear Industry is faced with several key challenges, not least that in all it does it has to achieve the highest levels of safety, pursue waste management options acceptable to the industry and general public, operate within varying political climates, and tackle these within a cost regime competitive with fossil fuel generated electricity. These are undoubtedly testing challenges, but on looking to the future there are certain trends which may prove beneficial to the industry and assist in mitigating them - namely that global energy demands are forecast to steadily increase over the next twenty years and beyond, and that in meeting this demand, the desire is to do so with minimal environmental impact. This paper will describe the part nuclear generation can play in servicing future energy demands, how the nuclear resource can best be utilised, how the 'holistic fuel cycle' philosophy can provide a framework for tackling the challenges faced by the industry, and the extent by which international co-operation can support certain advances in the fuel cycle. (author)

  6. MHD Integrated Topping Cycle Project

    1992-03-01

    The Magnetohydrodynamics (MHD) Integrated Topping Cycle (ITC) Project represents the culmination of the proof-of-concept (POC) development stage in the US Department of Energy (DOE) program to advance MHD technology to early commercial development stage utility power applications. The project is a joint effort, combining the skills of three topping cycle component developers: TRW, Avco/TDS, and Westinghouse. TRW, the prime contractor and system integrator, is responsible for the 50 thermal megawatt (50 MW{sub t}) slagging coal combustion subsystem. Avco/TDS is responsible for the MHD channel subsystem (nozzle, channel, diffuser, and power conditioning circuits), and Westinghouse is responsible for the current consolidation subsystem. The ITC Project will advance the state-of-the-art in MHD power systems with the design, construction, and integrated testing of 50 MW{sub t} power train components which are prototypical of the equipment that will be used in an early commercial scale MHD utility retrofit. Long duration testing of the integrated power train at the Component Development and Integration Facility (CDIF) in Butte, Montana will be performed, so that by the early 1990's, an engineering data base on the reliability, availability, maintainability and performance of the system will be available to allow scaleup of the prototypical designs to the next development level. This Sixteenth Quarterly Technical Progress Report covers the period May 1, 1991 to July 31, 1991.

  7. MHD Integrated Topping Cycle Project

    1992-01-01

    The overall objective of the project is to design and construct prototypical hardware for an integrated MHD topping cycle, and conduct long duration proof-of-concept tests of integrated system at the US DOE Component Development and Integration Facility in Butte, Montana. The results of the long duration tests will augment the existing engineering design data base on MHD power train reliability, availability, maintainability, and performance, and will serve as a basis for scaling up the topping cycle design to the next level of development, an early commercial scale power plant retrofit. The components of the MHD power train to be designed, fabricated, and tested include: A slagging coal combustor with a rated capacity of 50 MW thermal input, capable of operation with an Eastern (Illinois {number sign}6) or Western (Montana Rosebud) coal, a segmented supersonic nozzle, a supersonic MHD channel capable of generating at least 1.5 MW of electrical power, a segmented supersonic diffuser section to interface the channel with existing facility quench and exhaust systems, a complete set of current control circuits for local diagonal current control along the channel, and a set of current consolidation circuits to interface the channel with the existing facility inverter.

  8. Technology development life cycle processes.

    Beck, David Franklin

    2013-05-01

    This report and set of appendices are a collection of memoranda originally drafted in 2009 for the purpose of providing motivation and the necessary background material to support the definition and integration of engineering and management processes related to technology development. At the time there was interest and support to move from Capability Maturity Model Integration (CMMI) Level One (ad hoc processes) to Level Three. As presented herein, the material begins with a survey of open literature perspectives on technology development life cycles, including published data on %E2%80%9Cwhat went wrong.%E2%80%9D The main thrust of the material presents a rational expose%CC%81 of a structured technology development life cycle that uses the scientific method as a framework, with further rigor added from adapting relevant portions of the systems engineering process. The material concludes with a discussion on the use of multiple measures to assess technology maturity, including consideration of the viewpoint of potential users.

  9. Water Cycling &the GPM Mission

    Smith, E. A.

    2003-04-01

    The GPM mission is currently planned for start in the late'07 - early'08 time frame. Its main scientific goal is to help answer pressing scientific problems arising within the context of global and regional water cycles. These problems cut across a hierarchy of scales and include climate-water cycle interactions, techniques for improving weather and climate predictions, and better methods for combining observed precipitation with hydrometeorological prediction models for applications to hazardous flood-producing storms, seasonal flood/draught conditions, and fresh water resource assessments. The GPM mission will expand the scope of precipitation measurement through the use of a constellation of some 9 satellites, one of which will be an advanced TRMM-like "core" satellite carrying a dual-frequency Ku-Ka band precipitation radar and an advanced, multifrequency passive microwave radiometer with vertical-horizontal polarization discrimination. The other constellation members will include new dedicated satellites and co-existing operational/research satellites carrying similar (but not identical) passive microwave radiometers. The goal of the constellation is to achieve 3-hour sampling at any spot on the globe - continuously. The constellation's orbit architecture will consist of a mix of sun-synchronous and non-sun-synchronous satellites with the "core" satellite providing measurements of cloud-precipitation microphysical processes plus calibration-quality rainrates to be used with the other retrieval information to ensure bias-free constellation coverage. GPM is organized internationally, involving existing, pending, projected, and under-study partnerships which will link NASA and NOAA in the US, NASDA in Japan, ESA in Europe, ISRO in India, CNES in France, and possibly ASI in Italy, KARI in South Korea, CSA in Canada, and AEB in Brazil. Additionally, the program is actively pursuing agreements with other international collaborators and domestic scientific agencies

  10. Open-cycle OTEC system performance analysis. [Claude cycle

    Lewandowski, A.A.; Olson, D.A.; Johnson, D.H.

    1980-10-01

    An algorithm developed to calculate the performance of Claude-Cycle ocean thermal energy conversion (OTEC) systems is described. The algorithm treats each component of the system separately and then interfaces them to form a complete system, allowing a component to be changed without changing the rest of the algorithm. Two components that are subject to change are the evaporator and condenser. For this study we developed mathematical models of a channel-flow evaporator and both a horizontal jet and spray director contact condenser. The algorithm was then programmed to run on SERI's CDC 7600 computer and used to calculate the effect on performance of deaerating the warm and cold water streams before entering the evaporator and condenser, respectively. This study indicates that there is no advantage to removing air from these streams compared with removing the air from the condenser.

  11. Thermal cycling in multifilamentary superconducting composites

    NbTi-Cu multifilamentary superconducting composites were embedded, polished, characterized by microscopic techniques, and analyzed in a qualitative and semiquantitative way by energy dispersion technique. The superconductors were submitted to thermal cycling between the ambient temperature and the boiling point of helium (4.2K), for different number of cycles. The aims were to study the correlation between the possible microstructural damages due to thermal stresses arising in the composite during cycling and the variation of properties of the material with the number of cycles as well as to verify the validity of an elastic model for thermal stresses for low temperature cycles. (author)

  12. Advanced Fuel Cycle Economic Sensitivity Analysis

    David Shropshire; Kent Williams; J.D. Smith; Brent Boore

    2006-12-01

    A fuel cycle economic analysis was performed on four fuel cycles to provide a baseline for initial cost comparison using the Gen IV Economic Modeling Work Group G4 ECON spreadsheet model, Decision Programming Language software, the 2006 Advanced Fuel Cycle Cost Basis report, industry cost data, international papers, the nuclear power related cost study from MIT, Harvard, and the University of Chicago. The analysis developed and compared the fuel cycle cost component of the total cost of energy for a wide range of fuel cycles including: once through, thermal with fast recycle, continuous fast recycle, and thermal recycle.

  13. Understanding the petrochemical cycle: Part 1

    Fitness in the hydrocarbon processing industry (HPI) arena involves understanding and coping with business cycles: supply and demand. This becomes increasingly more important as the industry globalizes and matures. Competitive-edge thinking needs to look hard at the forces that influence business cycles. Recognition of potential pitfalls is very important when considering: future capacity expansion, mergers and acquisitions, market departure, plant closure, potential product substitution, etc. Understanding pricing mechanisms and the workings of hockey-stick profitability profiles help HPI operators endure cycle downturns and prepare plants to maximize profits for the next upswing. The paper discusses characteristic trends, cycles in the hydrocarbon processing industry, current conditions, and mitigating cycle effects

  14. Advanced Fuel Cycle Economic Sensitivity Analysis

    A fuel cycle economic analysis was performed on four fuel cycles to provide a baseline for initial cost comparison using the Gen IV Economic Modeling Work Group G4 ECON spreadsheet model, Decision Programming Language software, the 2006 Advanced Fuel Cycle Cost Basis report, industry cost data, international papers, the nuclear power related cost study from MIT, Harvard, and the University of Chicago. The analysis developed and compared the fuel cycle cost component of the total cost of energy for a wide range of fuel cycles including: once through, thermal with fast recycle, continuous fast recycle, and thermal recycle

  15. Country nuclear fuel cycle profiles. Second ed

    This publication presents an overall review of worldwide nuclear fuel cycle activities, followed by country specific nuclear fuel cycle information. This information is presented in a concise form and focuses on the essential activities related to the nuclear fuel cycle in each country operating commercial nuclear power reactors or providing nuclear fuel cycle services. It also includes country specific diagrams which illustrate the main material flow in the nuclear fuel cycle. These illustrations are intended to help clarify understanding of both the essential nuclear fuel cycle activities in each country and international relationships. Section 1 provides an introduction and Section 2 a review of worldwide nuclear fuel cycle activities, dealing with mining and milling, conversion, enrichment, fuel fabrication, heavy water production, spent fuel management, and the dismantling of facilities. Individual country profiles are then given in Section 3

  16. A class of internally irreversible refrigeration cycles

    Ait-Ali, Mohand A.

    1996-03-01

    A Carnot-like irreversible refrigeration cycle is modelled with two isothermal and two non-adiabatic, irreversible processes. The generic source of internal irreversibility, measured by the Clausius inequality, is a general irreversibility term which could include any heat leaks into the Joule - Thompson expansion valve, the evaporator and compressor cold boxes. This cycle is optimized first for maximum refrigeration power and maximum refrigeration load, then for maximum coefficient of performance. Its performances are compared with those of the endoreversible refrigeration cycle, based on a propane stage of a classical cascade liquefaction cycle example. Both cycle models achieve optimum power and maximum refrigeration load at nearly the same refrigeration temperature, but only the coefficient of performance of the irreversible refrigeration cycle reaches a maximum. Moreover, its prediction of heat conductance allocation between evaporator and condenser appears to be not only more conservative, but also more realistic for actual design considerations of refrigeration cycles.

  17. VISION: Verifiable Fuel Cycle Simulation Model

    Jacob J. Jacobson; Abdellatif M. Yacout; Gretchen E. Matthern; Steven J. Piet; David E. Shropshire

    2009-04-01

    The nuclear fuel cycle is a very complex system that includes considerable dynamic complexity as well as detail complexity. In the nuclear power realm, there are experts and considerable research and development in nuclear fuel development, separations technology, reactor physics and waste management. What is lacking is an overall understanding of the entire nuclear fuel cycle and how the deployment of new fuel cycle technologies affects the overall performance of the fuel cycle. The Advanced Fuel Cycle Initiative’s systems analysis group is developing a dynamic simulation model, VISION, to capture the relationships, timing and delays in and among the fuel cycle components to help develop an understanding of how the overall fuel cycle works and can transition as technologies are changed. This paper is an overview of the philosophy and development strategy behind VISION. The paper includes some descriptions of the model and some examples of how to use VISION.

  18. Search for relationship between duration of the extended solar cycles and amplitude of sunspot cycle

    Tlatov, A. G.

    2007-01-01

    Duration of the extended solar cycles is taken into the consideration. The beginning of cycles is counted from the moment of polarity reversal of large-scale magnetic field in high latitudes, occurring in the sunspot cycle n till the minimum of the cycle n+2. The connection between cycle duration and its amplitude is established. Duration of the "latent" period of evolution of extended cycle between reversals and a minimum of the current sunspot cycle is entered. It is shown, that the latent ...

  19. Conceptual design of an advanced absorption cycle: the double-effect regenerative absorption refrigeration cycle

    Dao, K.

    1978-09-01

    An advanced absorption refrigeration cycle was proposed as a heat-activated refrigeration system. Referred to as the double-effect regenerative absorption cycle of cycle 2R, it improves the performance of the conventional single-effect absorption cycle at high heat source temperatures. The performance of cycle 2R continually improves as input temperatures rise, in contrast to the conventional double-effect absorption cycle that has a sharp cut-off temperature below which it ceases to operate. Cycle 2R operates with two subcycles, the first-effect and the second-effect subcycles.

  20. The heat engine cycle, the heat removal cycle, and ergonomics of the control room displays

    This paper discusses and illustrates the ergonomics of an integrated display, which will allow operators to monitor the heat engine cycle during normal operation of the plant, and the heat removal cycle during emergency operation of the plant. A computer-based iconic display is discussed as an overview to monitor these cycles. Specific emphasis is placed upon the process variables and process functions within each cycle, and the action of control systems and engineered safeguard systems within each cycle. This paper contains examples of display formats for the heat engine cycle and the heat removal cycle in a pressurized water reactor

  1. Fuel Cycle System Analysis Handbook

    This Handbook aims to improve understanding and communication regarding nuclear fuel cycle options. It is intended to assist DOE, Campaign Managers, and other presenters prepare presentations and reports. When looking for information, check here. The Handbook generally includes few details of how calculations were performed, which can be found by consulting references provided to the reader. The Handbook emphasizes results in the form of graphics and diagrams, with only enough text to explain the graphic, to ensure that the messages associated with the graphic is clear, and to explain key assumptions and methods that cause the graphed results. Some of the material is new and is not found in previous reports, for example: (1) Section 3 has system-level mass flow diagrams for 0-tier (once-through), 1-tier (UOX to CR=0.50 fast reactor), and 2-tier (UOX to MOX-Pu to CR=0.50 fast reactor) scenarios - at both static and dynamic equilibrium. (2) To help inform fast reactor transuranic (TRU) conversion ratio and uranium supply behavior, section 5 provides the sustainable fast reactor growth rate as a function of TRU conversion ratio. (3) To help clarify the difference in recycling Pu, NpPu, NpPuAm, and all-TRU, section 5 provides mass fraction, gamma, and neutron emission for those four cases for MOX, heterogeneous LWR IMF (assemblies mixing IMF and UOX pins), and a CR=0.50 fast reactor. There are data for the first 10 LWR recycle passes and equilibrium. (4) Section 6 provides information on the cycle length, planned and unplanned outages, and TRU enrichment as a function of fast reactor TRU conversion ratio, as well as the dilution of TRU feedstock by uranium in making fast reactor fuel. (The recovered uranium is considered to be more pure than recovered TRU.) The latter parameter impacts the required TRU impurity limits specified by the Fuels Campaign. (5) Section 7 provides flows for an 800-tonne UOX separation plant. (6) To complement 'tornado' economic uncertainty

  2. Fuel Cycle System Analysis Handbook

    Steven J. Piet; Brent W. Dixon; Dirk Gombert; Edward A. Hoffman; Gretchen E. Matthern; Kent A. Williams

    2009-06-01

    This Handbook aims to improve understanding and communication regarding nuclear fuel cycle options. It is intended to assist DOE, Campaign Managers, and other presenters prepare presentations and reports. When looking for information, check here. The Handbook generally includes few details of how calculations were performed, which can be found by consulting references provided to the reader. The Handbook emphasizes results in the form of graphics and diagrams, with only enough text to explain the graphic, to ensure that the messages associated with the graphic is clear, and to explain key assumptions and methods that cause the graphed results. Some of the material is new and is not found in previous reports, for example: (1) Section 3 has system-level mass flow diagrams for 0-tier (once-through), 1-tier (UOX to CR=0.50 fast reactor), and 2-tier (UOX to MOX-Pu to CR=0.50 fast reactor) scenarios - at both static and dynamic equilibrium. (2) To help inform fast reactor transuranic (TRU) conversion ratio and uranium supply behavior, section 5 provides the sustainable fast reactor growth rate as a function of TRU conversion ratio. (3) To help clarify the difference in recycling Pu, NpPu, NpPuAm, and all-TRU, section 5 provides mass fraction, gamma, and neutron emission for those four cases for MOX, heterogeneous LWR IMF (assemblies mixing IMF and UOX pins), and a CR=0.50 fast reactor. There are data for the first 10 LWR recycle passes and equilibrium. (4) Section 6 provides information on the cycle length, planned and unplanned outages, and TRU enrichment as a function of fast reactor TRU conversion ratio, as well as the dilution of TRU feedstock by uranium in making fast reactor fuel. (The recovered uranium is considered to be more pure than recovered TRU.) The latter parameter impacts the required TRU impurity limits specified by the Fuels Campaign. (5) Section 7 provides flows for an 800-tonne UOX separation plant. (6) To complement 'tornado' economic

  3. MAPK uncouples cell cycle progression from cell spreading and cytoskeletal organization in cycling cells

    Margadant, Coert; Cremers, Lobke; Sonnenberg, Arnoud; Boonstra, Johannes

    2012-01-01

    Integrin-mediated cytoskeletal tension supports growth-factor-induced proliferation, and disruption of the actin cytoskeleton in growth factor-stimulated cells prevents the re-expression of cyclin D and cell cycle re-entry from quiescence. In contrast to cells that enter the cell cycle from G0, cycling cells continuously express cyclin D, and are subject to major cell shape changes during the cell cycle. Here, we investigated the cell cycle requirements for cytoskeletal tension and cell sprea...

  4. Thorium nuclear fuel cycle technology

    Eom, Tae Yoon; Do, Jae Bum; Choi, Yoon Dong; Park, Kyoung Kyum; Choi, In Kyu; Lee, Jae Won; Song, Woong Sup; Kim, Heong Woo

    1998-03-01

    Since thorium produces relatively small amount of TRU elements after irradiation in the reactor, it is considered one of possible media to mix with the elements to be transmuted. Both solid and molten-salt thorium fuel cycles were investigated. Transmutation concepts being studied involved fast breeder reactor, accelerator-driven subcritical reactor, and energy amplifier with thorium. Long-lived radionuclides, especially TRU elements, could be separated from spent fuel by a pyrochemical process which is evaluated to be proliferation resistance. Pyrochemical processes of IFR, MSRE and ATW were reviewed and evaluated in detail, regarding technological feasibility, compatibility of thorium with TRU, proliferation resistance, their economy and safety. (author). 26 refs., 22 figs

  5. Canard cycles in global dynamics

    Vidal, Alexandre

    2009-01-01

    Fast-slow systems are studied usually by "geometrical dissection". The fast dynamics exhibit attractors which may bifurcate under the influence of the slow dynamics which is seen as a parameter of the fast dynamics. A generic solution comes close to a connected component of the stable invariant sets of the fast dynamics. As the slow dynamics evolves, this attractor may lose its stability and the solution eventually reaches quickly another connected component of attractors of the fast dynamics and the process may repeat. This scenario explains quite well relaxation and bursting oscillations. More recently, in relation both with theory of dynamical systems and with applications to physiology, a new interest has emerged in canard cycles. These orbits share the property that they remain for a while close to an unstable invariant set (either singular set or periodic orbits of the fast dynamics). Although canards were first discovered when the transition points are folds, in this article, we focus on the case where...

  6. Violence as a Vicious Cycle

    Huseyin Gulec

    2012-03-01

    Full Text Available Since the conclusion that the violence as a behavior is not (cannot be determined within an absolute genetic determinism has been reached for long years, environmental factors are increasingly examined. We witness that human behavior in society can easily convert into coping with stressful events with violence. Individual or social violence as a behavior has a similar pattern with violence committed in primitive society and by children. After a brief review of violence, its description, etiological theories and types, this article majorly focuses on children and their early and late response to violence. The purpose here is to draw attention to the individuals who were previously exposed to violence (either directly or indirectly resort to violence, perpetuating a vicious cycle.

  7. The evolution of nitrogen cycling

    Mancinelli, Rocco L.; Mckay, Christopher P.

    1988-01-01

    The energetics of nitrogen transformation reactions and the evolution of nitrogen cycling are examined. It is suggested that meteor impact-produced fixed nitrogen could have caused the entire reservoir of the earth's N2 to convert into fixed nitrogen at the end of accretion. The abiotic fixation rate on the early earth by lightning is estimated at about 1-3 X 10 to the 16th molecules of NO/J. It is found that biological nitrogen fixation may have evolved after the development of an aerobic atmosphere. It is shown that HNO could eventually become NO2(-) and NO3(-) after reaching the earth's surface. It is concluded that the evolutionary sequence for the biological transformation of nitrogen compounds is ammonification - denitrification - nitrification - nitrogen fixation.

  8. A Coupled Quantum Otto Cycle

    Thomas, George

    2010-01-01

    We study the 1-d isotropic Heisenberg model of two spin-1/2 systems as a quantum heat engine. The engine undergoes a four-step Otto cycle where the two adiabatic branches involve changing the external magnetic field at a fixed value of the coupling constant. We find conditions for the engine efficiency to be higher than the uncoupled model; in particular, we find an upper bound which is tighter than the Carnot bound. A new domain of parameter values is pointed out which was not feasible in the interaction-free model. Locally, each spin seems to effect the flow of heat in a direction opposite to the global temperature gradient. This seeming contradiction to the second law can be resolved in terms of local effective temperature of the spins.

  9. Business cycles in oil economies

    This study examines the impact of oil price shocks on output fluctuations of several oil-exporting economies. In most studies of business cycles, the role of oil price is ignored; the few studies that use oil price as one of the variables in the system focus on modeling oil-importing economies. The vector autoregression (VAR) technique is used to consider the cases of Norway, Nigeria, and Mexico. Both atheoretical and 'structural' VARs are estimated to determine the importance of oil price impulses on output variations. The study reports two types of results: variance decomposition and impulse response functions, with particular emphasis on the issues of stationarity and co-integration among the series. The empirical results suggest that shocks to oil price are important in explaining output variations. In most cases, shocks to oil price are shown to explain more than 20% of the forecast variance of output over a 40-quarter horizon

  10. Fuel cycle of the AVR

    All the stages of development were secured by irradiation tests and by the use of the elements concerned in the AVR. Summarising, these were: The first charge with fuel elements from Union Carbide, with U-Th mixed carbide particles, wallpaper variants, U-Th mixed carbide particles, the pressed fuel element with U-Th mixed carbide particles, the pressed fuel element with U-Th mixed oxide particles, with an intermediate boundary layer; the present THTR element, the pressed fuel element with U-Th mixed oxide particles and low temperature PyC coating, the pressed fuel element with U-Th mixed oxide particles, with PyC and SiC layers, i.e.: TRISO particles, the pressed fuel element with pure uranium oxide particles for the low enrichment cycle, one coated only by 2 PyC layers, the other coated with PyC and SiC, i.e.: TRISO coating. (orig.)

  11. Carbon cycling in Lake Superior

    Urban, N. R.; Auer, M. T.; Green, S. A.; Lu, X.; Apul, D. S.; Powell, K. D.; Bub, L.

    2005-06-01

    Carbon (C) cycling in Lake Superior was studied within the Keweenaw Interdisciplinary Transport Experiment in Superior (KITES) project to assess (1) whether the lake is net heterotrophic, (2) sources, sinks and residence time for dissolved organic carbon (DOC), (3) importance of terrigenous organic C subsidies, and (4) factors limiting C flow through bacteria. During 3 years of fieldwork, measurements were made of spatial and temporal distributions of C pools and rates of photosynthesis, community respiration, and bacterial production. Measurements were made of the composition of dissolved organic matter (DOM), rates of DOM photolysis, lability of DOM toward microbial consumption, and river inputs of DOM. All measurements suggest the lake is net heterotrophic. The C:N ratios of DOM suggest that it is primarily of terrigenous origin, but other characteristics (size distribution, UV absorption) point to the presence of autochthonous DOM and to alteration of terrigenous material. The lake mass balance indicates that the residence time (˜8 years) of the DOC pool (17 Tg) is short relative to the hydrologic residence time (170 years). The known flux of terrigenous DOC (˜1 Tg/yr) is too low to support annual bacterial carbon demand (6-38 Tg/yr), but microbial respiration is the major sink for terrigenous DOC. A rapidly cycling, autochthonous DOC pool must exist. Microbial activity was correlated with temperature, phosphorus availability, and DOC concentration but not with photosynthesis rates. Measurements of respiration (˜40 Tg/yr), photosynthesis (2-7 Tg/yr), and bacterial production (0.5-2 Tg/yr) are not all mutually compatible and result in a discrepancy in the organic carbon budget.

  12. Solar Cycle Predictions Near Sunspot Minimum

    Hathaway, David H.

    1997-01-01

    Observations of solar magnetic activity and the dynamics of the solar convection zone have produced severe constraints on models of the Sun's magnetic dynamo. These constraints are so severe that, at present, we do not have numerical models that can accept the current conditions and then march forward in time to predict future activity. Given this state of solar dynamo theory we are forced to examine previous behavior to discover patterns and trends that afford us some measure of predictability. Here we examine the behavior of several indicators of solar activity near solar minimum that are well correlated with the amplitude of the following solar maximum to predict the level of solar activity over cycle 23. Sunspot numbers, areas, and positions are useful for characterizing solar cycle behavior due to the extent of the data (12 cycles or more). These data exhibit several patterns that relate future activity to past behavior. With the Odd-Even effect the odd numbered cycles have been larger than their even numbered predecessors for each of the last six cycle pairs. With the Amplitude-Period effect short period cycles have been followed by large amplitude cycles and long period cycles have been followed by small amplitude cycles for 10 of the last 13 cycles. With the Maximum-Minimum effect the sunspot number at minimum is directly correlated with the sunspot number at maximum for a given cycle. The geomagnetic indices aa and Ap are also related to solar activity by the connections between disturbances in the solar wind and variations in the Earth's magnetic field. Like the Maximum-Minimum effect for sunspots, the size of the aa and Ap indices at minimum are directly related to the amplitude of the following maximum. The number of geomagnetically disturbed days (days with Ap >= 25) over the course of a cycle is another indicator for the size of the next cycle. The aa and Ap indices can each be separated into a component in phase with the current sunspot cycle and an

  13. Battery charging in float vs. cycling environments

    COREY,GARTH P.

    2000-04-20

    In lead-acid battery systems, cycling systems are often managed using float management strategies. There are many differences in battery management strategies for a float environment and battery management strategies for a cycling environment. To complicate matters further, in many cycling environments, such as off-grid domestic power systems, there is usually not an available charging source capable of efficiently equalizing a lead-acid battery let alone bring it to a full state of charge. Typically, rules for battery management which have worked quite well in a floating environment have been routinely applied to cycling batteries without full appreciation of what the cycling battery really needs to reach a full state of charge and to maintain a high state of health. For example, charge target voltages for batteries that are regularly deep cycled in off-grid power sources are the same as voltages applied to stand-by systems following a discharge event. In other charging operations equalization charge requirements are frequently ignored or incorrectly applied in cycled systems which frequently leads to premature capacity loss. The cause of this serious problem: the application of float battery management strategies to cycling battery systems. This paper describes the outcomes to be expected when managing cycling batteries with float strategies and discusses the techniques and benefits for the use of cycling battery management strategies.

  14. Thermodynamic Analysis of Combined Cycle Power Plant

    A.K.Tiwari,

    2010-04-01

    Full Text Available Air Bottoming Cycle (ABC can replace the heat recovery steam generator and the steam turbine of the conventionalcombined cycle plant. The exhaust energy of the topping gas turbine of existing combine cycle is sent to gas-air heat exchange, which heats the air in the secondary gas turbine cycle. In 1980’s the ABC was proposed as an alternative for the conventional steam bottoming cycle. In spite of the cost of reducing hardware installations it could achieve a thermal efficiency of 80%. The complete thermodynamic analysis of the system has been performed by using specially designed programme, enabling the variation of main independent variables. The result shows the gain in net work output as well as efficiency of combined cycle is 35% to 68%.

  15. Automatic control of clock duty cycle

    Feng, Xiaoxin (Inventor); Roper, Weston (Inventor); Seefeldt, James D. (Inventor)

    2010-01-01

    In general, this disclosure is directed to a duty cycle correction (DCC) circuit that adjusts a falling edge of a clock signal to achieve a desired duty cycle. In some examples, the DCC circuit may generate a pulse in response to a falling edge of an input clock signal, delay the pulse based on a control voltage, adjust the falling edge of the input clock signal based on the delayed pulse to produce an output clock signal, and adjust the control voltage based on the difference between a duty cycle of the output clock signal and a desired duty cycle. Since the DCC circuit adjusts the falling edge of the clock cycle to achieve a desired duty cycle, the DCC may be incorporated into existing PLL control loops that adjust the rising edge of a clock signal without interfering with the operation of such PLL control loops.

  16. Short Time Cycles of Purely Quantum Refrigerators

    Feldmann, Tova

    2012-01-01

    Four stroke Otto refrigerator cycles with no classical analogue are studied. Extremely short cycle times with respect to the internal time scale of the working medium characterize these refrigerators. Therefore these cycles are termed sudden. The sudden cycles are characterized by the stable limit cycle which is the invariant of the global cycle propagator. During their operation the state of the working medium possesses significant coherence which is not erased in the equilibration segments due to the very short time allocated. This characteristic is reflected in a difference between the energy entropy and the Von Neumann entropy of the working medium. A classification scheme for sudden refrigerators is developed allowing simple approximations for the cooling power and coefficient of performance.

  17. Life cycle of transformer oil

    Đurđević Ksenija R.

    2008-01-01

    Full Text Available The consumption of electric power is constantly increasing due to industrialization and population growth. This results in much more severe operating conditions of transformers, the most important electrical devices that make integral parts of power transmission and distribution systems. The designed operating life of the majority of worldwide transformers has already expired, which puts the increase of transformer reliability and operating life extension in the spotlight. Transformer oil plays a very important role in transformer operation, since it provides insulation and cooling, helps extinguishing sparks and dissolves gases formed during oil degradation. In addition to this, it also dissolves moisture and gases from cellulose insulation and atmosphere it is exposed to. Further and by no means less important functions of transformer are of diagnostic purpose. It has been determined that examination and inspection of insulation oil provide 70% of information on transformer condition, which can be divided in three main groups: dielectric condition, aged transformer condition and oil degradation condition. By inspecting and examining the application oil it is possible to determine the condition of insulation, oil and solid insulation (paper, as well as irregularities in transformer operation. All of the above-mentioned reasons and facts create ground for the subject of this research covering two stages of transformer oil life cycle: (1 proactive maintenance and monitoring of transformer oils in the course of utilization with reference to influence of transformer oil condition on paper insulation condition, as well as the condition of the transformer itself; (2 regeneration of transformer oils for the purpose of extension of utilization period and paper insulation revitalization potential by means of oil purification. The study highlights advantages of oil-paper insulation revitalization over oil replacement. Besides economic, there are

  18. Nuclear reactors and fuel cycle

    contribute in improving the quality of life of the Brazilian people. The nuclear fuel cycle is a series of steps involved in the production and use of fuel for nuclear reactors. The Laboratories of Chemistry and Environmental Diagnosis Center, CQMA, support the demand of Nuclear Fuel Cycle Program providing chemical characterization of uranium compounds and other related materials. In this period the Research Reactor Center (CRPq) concentrated efforts on improving equipment and systems to enable the IEA-R1 research reactor to operate at higher power, increasing the capacity of radioisotopes production, samples irradiation, tests and experiments. (author)

  19. Variants of closing the nuclear fuel cycle

    Andrianova, E. A., E-mail: Andrianova-EA@nrcki.ru; Davidenko, V. D.; Tsibulskiy, V. F.; Tsibulskiy, S. V. [National Research Center Kurchatov Institute (Russian Federation)

    2015-12-15

    Influence of the nuclear energy structure, the conditions of fuel burnup, and accumulation of new fissile isotopes from the raw isotopes on the main parameters of a closed fuel cycle is considered. The effects of the breeding ratio, the cooling time of the spent fuel in the external fuel cycle, and the separation of the breeding area and the fissile isotope burning area on the parameters of the fuel cycle are analyzed.

  20. LIFE CYCLE ANALYSIS CONSTRUCTION OF HIGHWAYS

    ЛІСНІЧЕНКО, Т. В.; Національний авіаційний університет

    2016-01-01

    It proposed and studied the life cycle of the construction of public roads. We considere allphases of construction: from design to repiar. The scheme of the life cycle of the constructionof public roads is proposed. Construction of highway is seen as a project. The life cycle of theproject, known as a set of logically interrelated works in the completion of which achieved oneof the main results of the project. The complex of road construction works related to construction,reconstruction and r...