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Sample records for high critical field

  1. High Upper Critical Field and Irreversibility Field in MgB2 Coated-Conductor Fibers

    Science.gov (United States)

    2016-06-13

    High upper critical field and irreversibility field in MgB2 coated-conductor fibers V. Ferrando,a P. Orgiani,b A. V. Pogrebnyakov, J. Chen, Qi Li...show a high upper critical field of 55 T at 1.5 K and a high irreversibility field of 40 T at 1.5 K. The result demonstrates great potential of MgB2...using cryocoolers. Unlike high temperature superconductors where critical current den- sity Jc drops sharply across the grain boundary when the grains

  2. High critical field NbC superconductor on carbon spheres.

    Science.gov (United States)

    Bhattacharjee, Kaustav; Pati, Satya Prakash; Maity, Arjun

    2016-06-01

    Niobium carbide (NbC) nanoparticles embedded on the surface of carbon spheres (CS) were synthesized at 1350 °C by the carbothermal reduction of niobium oxide precursor in flowing argon (Nbc@CS). The morphology, crystal structure, and magnetic properties of the hybrid nanocomposite were investigated by means of electron microscopy, X-ray diffraction and a superconducting quantum interference device. It was found that the NbC@CS nanocomposites exhibit type-II superconductivity with a critical temperature (Tc) of 8-12 K, typical for stoichiometric NbC. The superconducting hysteresis loop reveals several interesting traits, including strong vortex pinning, the presence of asymmetry and a high penetration field. Moreover, the sample shows much improved irreversible (Hirr), lower (Hc1) and upper (Hc2) critical fields. The coherence length (ξ), penetration depth (λ), and Ginzburg-Landau (κ) parameters for the sample were estimated to be 9.78 nm, 33 nm and 3.39, respectively.

  3. AC losses in sintered high-temperature superconductors. Dependence on frequency and intergranular lower critical field

    Energy Technology Data Exchange (ETDEWEB)

    Lofland, S.; Huang, M.X.; Bhagat, S.M. (Dept. of Physics and Center for Superconductivity Research, Univ. of Maryland, College Park (United States))

    1992-12-10

    The intergranular AC susceptibility loss peak in high-Tc superconductors is measured as a function of frequency and field amplitude. The variation of peak temperature with frequency is strongly influenced by the grain size. For large grains, the maximum loss increases with field amplitude. This is ascribed to a non-zero intergranular lower critical field H[sub cl]. (orig.).

  4. Field-induced quantum critical route to a Fermi liquid in high-temperature superconductors.

    Science.gov (United States)

    Shibauchi, Takasada; Krusin-Elbaum, Lia; Hasegawa, Masashi; Kasahara, Yuichi; Okazaki, Ryuji; Matsuda, Yuji

    2008-05-20

    In high-transition-temperature (T(c)) superconductivity, charge doping is a natural tuning parameter that takes copper oxides from the antiferromagnet to the superconducting region. In the metallic state above T(c), the standard Landau's Fermi-liquid theory of metals as typified by the temperature squared (T(2)) dependence of resistivity appears to break down. Whether the origin of the non-Fermi-liquid behavior is related to physics specific to the cuprates is a fundamental question still under debate. We uncover a transformation from the non-Fermi-liquid state to a standard Fermi-liquid state driven not by doping but by magnetic field in the overdoped high-T(c) superconductor Tl(2)Ba(2)CuO(6+x). From the c-axis resistivity measured up to 45 T, we show that the Fermi-liquid features appear above a sufficiently high field that decreases linearly with temperature and lands at a quantum critical point near the superconductivity's upper critical field-with the Fermi-liquid coefficient of the T(2) dependence showing a power-law diverging behavior on the approach to the critical point. This field-induced quantum criticality bears a striking resemblance to that in quasi-two-dimensional heavy-Fermion superconductors, suggesting a common underlying spin-related physics in these superconductors with strong electron correlations.

  5. High magnetic-field scales and critical currents in SmFeAs(O, F) crystals

    Science.gov (United States)

    Moll, Philip J. W.; Puzniak, Roman; Balakirev, Fedor; Rogacki, Krzysztof; Karpinski, Janusz; Zhigadlo, Nikolai D.; Batlogg, Bertram

    2010-08-01

    With the discovery of new superconducting materials, such as the iron pnictides, exploring their potential for applications is one of the foremost tasks. Even if the critical temperature Tc is high, intrinsic electronic properties might render applications difficult, particularly if extreme electronic anisotropy prevents effective pinning of vortices and thus severely limits the critical current density, a problem well known for cuprates. Although many questions concerning microscopic electronic properties of the iron pnictides have been successfully addressed and estimates point to a very high upper critical field, their application potential is less clear. Thus, we focus here on the critical currents, their anisotropy and the onset of electrical dissipation in high magnetic fields up to 65T. Our detailed study of the transport properties of SmFeAsO0.7F0.25 single crystals reveals a promising combination of high (>2×106Acm-2) and nearly isotropic critical current densities along all crystal directions. This favourable intragrain current transport in SmFeAs(O, F), which shows the highest Tc of 54K at ambient pressure, is a crucial requirement for possible applications. Essential in these experiments are four-probe measurements on focused-ion-beam-cut single crystals with a sub-square-micrometre cross-section, with current along and perpendicular to the crystallographic c axis.

  6. High critical current density and enhanced irreversibility field in superconducting MgB2 thin films.

    Science.gov (United States)

    Eom, C B; Lee, M K; Choi, J H; Belenky, L J; Song, X; Cooley, L D; Naus, M T; Patnaik, S; Jiang, J; Rikel, M; Polyanskii, A; Gurevich, A; Cai, X Y; Bu, S D; Babcock, S E; Hellstrom, E E; Larbalestier, D C; Rogado, N; Regan, K A; Hayward, M A; He, T; Slusky, J S; Inumaru, K; Haas, M K; Cava, R J

    2001-05-31

    The discovery of superconductivity at 39 K in magnesium diboride offers the possibility of a new class of low-cost, high-performance superconducting materials for magnets and electronic applications. This compound has twice the transition temperature of Nb3Sn and four times that of Nb-Ti alloy, and the vital prerequisite of strongly linked current flow has already been demonstrated. One possible drawback, however, is that the magnetic field at which superconductivity is destroyed is modest. Furthermore, the field which limits the range of practical applications-the irreversibility field H*(T)-is approximately 7 T at liquid helium temperature (4.2 K), significantly lower than about 10 T for Nb-Ti (ref. 6) and approximately 20 T for Nb3Sn (ref. 7). Here we show that MgB2 thin films that are alloyed with oxygen can exhibit a much steeper temperature dependence of H*(T) than is observed in bulk materials, yielding an H* value at 4.2 K greater than 14 T. In addition, very high critical current densities at 4.2 K are achieved: 1 MA cm-2 at 1 T and 105 A cm-2 at 10 T. These results demonstrate that MgB2 has potential for high-field superconducting applications.

  7. Field-dependent critical state of high-Tc superconducting strip simultaneously exposed to transport current and perpendicular magnetic field

    Science.gov (United States)

    Xue, Cun; He, An; Yong, Huadong; Zhou, Youhe

    2013-12-01

    We present an exact analytical approach for arbitrary field-dependent critical state of high-Tc superconducting strip with transport current. The sheet current and flux-density profiles are derived by solving the integral equations, which agree with experiments quite well. For small transport current, the approximate explicit expressions of sheet current, flux-density and penetration depth for the Kim model are derived based on the mean value theorem for integration. We also extend the results to the field-dependent critical state of superconducting strip in the simultaneous presence of applied field and transport current. The sheet current distributions calculated by the Kim model agree with experiments better than that by the Bean model. Moreover, the lines in the Ia-Ba plane for the Kim model are not monotonic, which is quite different from that the Bean model. The results reveal that the maximum transport current in thin superconducting strip will decrease with increasing applied field which vanishes for the Bean model. The results of this paper are useful to calculate ac susceptibility and ac loss.

  8. Field-dependent critical state of high-Tc superconducting strip simultaneously exposed to transport current and perpendicular magnetic field

    Directory of Open Access Journals (Sweden)

    Cun Xue

    2013-12-01

    Full Text Available We present an exact analytical approach for arbitrary field-dependent critical state of high-Tc superconducting strip with transport current. The sheet current and flux-density profiles are derived by solving the integral equations, which agree with experiments quite well. For small transport current, the approximate explicit expressions of sheet current, flux-density and penetration depth for the Kim model are derived based on the mean value theorem for integration. We also extend the results to the field-dependent critical state of superconducting strip in the simultaneous presence of applied field and transport current. The sheet current distributions calculated by the Kim model agree with experiments better than that by the Bean model. Moreover, the lines in the Ia-Ba plane for the Kim model are not monotonic, which is quite different from that the Bean model. The results reveal that the maximum transport current in thin superconducting strip will decrease with increasing applied field which vanishes for the Bean model. The results of this paper are useful to calculate ac susceptibility and ac loss.

  9. Field-dependent critical state of high-Tc superconducting strip simultaneously exposed to transport current and perpendicular magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Cun; He, An; Yong, Huadong; Zhou, Youhe, E-mail: zhouyh@lzu.edu.cn [Key Laboratory of Mechanics on Disaster and Environment in Western China attached to the Ministry of Education of China, and Department of Mechanics and Engineering Sciences, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China)

    2013-12-15

    We present an exact analytical approach for arbitrary field-dependent critical state of high-T{sub c} superconducting strip with transport current. The sheet current and flux-density profiles are derived by solving the integral equations, which agree with experiments quite well. For small transport current, the approximate explicit expressions of sheet current, flux-density and penetration depth for the Kim model are derived based on the mean value theorem for integration. We also extend the results to the field-dependent critical state of superconducting strip in the simultaneous presence of applied field and transport current. The sheet current distributions calculated by the Kim model agree with experiments better than that by the Bean model. Moreover, the lines in the I{sub a}-B{sub a} plane for the Kim model are not monotonic, which is quite different from that the Bean model. The results reveal that the maximum transport current in thin superconducting strip will decrease with increasing applied field which vanishes for the Bean model. The results of this paper are useful to calculate ac susceptibility and ac loss.

  10. Microstructural understanding and critical current optimization of advanced high field superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bonney, L.A.; Willis, T.C.; Larbalestier, D.C.

    1993-01-01

    It is of great importance to improve critical current density, J[sub c] in A15 superconductors for high field magnet applications. Most current work to improve J[sub c] in A15 wires concentrates on increasing the overall J[sub c] by increasing the fraction of superconducting phase in the wire, by improving the uniformity of the superconductor cross section along the length of the wire and by adjusting the strainstate of the A15 layer. The goal of the A15 work in this group was to investigate the intrinsic J[sub c] of the A15 layer itself. To do this, a better understanding of factors controlling the intrinsic J[sub c]of the Nb[sub 3]Sn was pursued.

  11. Enhancement of the high-magnetic-field critical current density of superconducting MgB2 by proton irradiation.

    Science.gov (United States)

    Bugoslavsky, Y; Cohen, L F; Perkins, G K; Polichetti, M; Tate, T J; Gwilliam, R; Caplin, A D

    2001-05-31

    Magnesium diboride, MgB2, has a relatively high superconducting transition temperature, placing it between the families of low- and high-temperature (copper oxide based) superconductors. Supercurrent flow in MgB2 is unhindered by grain boundaries, making it potentially attractive for technological applications in the temperature range 20-30 K. But in the bulk material, the critical current density (Jc) drops rapidly with increasing magnetic field strength. The magnitude and field dependence of the critical current are related to the presence of structural defects that can 'pin' the quantized magnetic vortices that permeate the material, and a lack of natural defects in MgB2 may be responsible for the rapid decline of Jc with increasing field strength. Here we show that modest levels of atomic disorder induced by proton irradiation enhance the pinning of vortices, thereby significantly increasing Jc at high field strengths. We anticipate that either chemical doping or mechanical processing should generate similar levels of disorder, and so achieve performance that is technologically attractive in an economically viable way.

  12. Fabrication of Chemically Doped, High Upper Critical Field Magnesium Diboride Superconducting Wires

    Energy Technology Data Exchange (ETDEWEB)

    Marzik, James, V.

    2005-10-13

    Controlled chemical doping of magnesium diboride (MgB2) has been shown to substantially improve its superconducting properties to the levels required for high field magnets, but the doping is difficult to accomplish through the usual route of solid state reaction and diffusion. Further, superconducting cables of MgB2 are difficult to fabricate because of the friable nature of the material. In this Phase I STTR project, doped and undoped boron fibers were made by chemical vapor deposition (CVD). Several >100m long batches of doped and undoped fiber were made by CVD codeposition of boron plus dopants. Bundles of these fibers infiltrated with liquid magnesium and subsequently converted to MgB2 to form Mg-MgB2 metal matrix composites. In a parallel path, doped boron nano-sized powder was produced by a plasma synthesis technique, reacted with magnesium to produce doped MgB2 superconducting ceramic bodies. The doped powder was also fabricated into superconducting wires several meters long. The doped boron fibers and powders made in this program were fabricated into fiber-metal composites and powder-metal composites by a liquid metal infiltration technique. The kinetics of the reaction between boron fiber and magnesium metal was investigated in fiber-metal composites. It was found that the presence of dopants had significantly slowed the reaction between magnesium and boron. The superconducting properties were measured for MgB2 fibers and MgB2 powders made by liquid metal infiltration. Properties of MgB2 products (Jc, Hc2) from Phase I are among the highest reported to date for MgB2 bulk superconductors. Chemically doped MgB2 superconducting magnets can perform at least as well as NbTi and NbSn3 in high magnetic fields and still offer an improvement over the latter two in terms of operating temperature. These characteristics make doped MgB2 an effective material for high magnetic field applications, such as magnetic confined fusion, and medical MRI devices. Developing

  13. Thermodynamic Critical Field and Superconducting Fluctuation of Vortices for High Temperature Cuprate Superconductor: La-214

    Energy Technology Data Exchange (ETDEWEB)

    Finnemore, Douglas K. [Iowa State Univ., Ames, IA (United States)

    2001-01-01

    Thermodynamics has been studied systematically for the high temperature cuprate superconductor La2-xSrxCuO4-δ, La-214, in the entire superconductive region from strongly underdoped to strongly overdoped regimes. Magnetization studies with H $\\parallel$ c have been made in order to investigate the changes in free energy of the system as the number of carriers is reduced. Above the superconducting transition temperature, the normal-state magnetization exhibits a two-dimensional Heisenberg antiferromagnetic behavior. Below Tc, magnetization data are thermodynamically reversible over large portions of the H-T plane, so the free energy is well defined in these regions. As the Sr concentration is varied over the wide range from 0.060 (strongly underdoped) to 0.234 (strongly overdoped), the free energy change goes through a maximum at the optimum doped in a manner similar to the Tc0 vs. x curve. The density of states, N(0), remains nearly constant in the overdoped and optimum doped regimes, taking a broad maximum around x = 0.188, and then drops abruptly towards zero in the underdoped regime. The La2-xSrxCuO4 (La-214) system displays the fluctuating vortex behavior with the characteristic of either 2D or 3D fluctuations as indicated by clearly identifiable crossing points T* close to Tc. The dimensional character of the fluctuations depends on both applied magnetic fields and the density of charge carriers. The dimensional crossover from 2D to 3D occurs in the strongly underdoped regime when the c-axis coherence distance ξc becomes comparable to the spacing between adjacent CuO2 layers s at sufficiently high magnetic field near Hc2.

  14. Thermodynamic Critical Field and Superconducting Fluctuation of Vortices for High Temperature Cuprate Superconductor: La-214

    Energy Technology Data Exchange (ETDEWEB)

    Douglas K. Finnemore

    2001-06-25

    Thermodynamics has been studied systematically for the high temperature cuprate superconductor La{sub 2-x}Sr{sub x}CuO{sub 4-{delta}}, La-214, in the entire superconductive region from strongly underdoped to strongly overdoped regimes. Magnetization studies with H {parallel} c have been made in order to investigate the changes in free energy of the system as the number of carriers is reduced. Above the superconducting transition temperature, the normal-state magnetization exhibits a two-dimensional Heisenberg antiferromagnetic behavior. Below T{sub c}, magnetization data are thermodynamically reversible over large portions of the H-T plane, so the free energy is well defined in these regions. As the Sr concentration is varied over the wide range from 0.060 (strongly underdoped) to 0.234 (strongly overdoped), the free energy change goes through a maximum at the optimum doped in a manner similar to the T{sub c0} vs. x curve. The density of states, N(0), remains nearly constant in the overdoped and optimum doped regimes, taking a broad maximum around x = 0.188, and then drops abruptly towards zero in the underdoped regime. The La{sub 2-x}Sr{sub x}CuO{sub 4} (La-214) system displays the fluctuating vortex behavior with the characteristic of either 2D or 3D fluctuations as indicated by clearly identifiable crossing points T* close to T{sub c}. The dimensional character of the fluctuations depends on both applied magnetic fields and the density of charge carriers. The dimensional crossover from 2D to 3D occurs in the strongly underdoped regime when the c-axis coherence distance {xi}{sub c} becomes comparable to the spacing between adjacent CuO{sub 2} layers s at sufficiently high magnetic field near H{sub c2}.

  15. Thermodynamic Critical Field and Superconducting Fluctuation of Vortices for High Temperature Cuprate Superconductor: La-214

    Energy Technology Data Exchange (ETDEWEB)

    Yung Moo Huh

    2001-05-01

    Thermodynamics has been studied systematically for the high temperature cuprate superconductor La{sub 2-x}Sr{sub x}CuO{sub 4-{delta}}, La-214, in the entire superconductive region from strongly underdoped to strongly overdoped regimes. Magnetization studies with H{parallel}c have been made in order to investigate the changes in free energy of the system as the number of carriers is reduced. Above the superconducting transition temperature, the normal-state magnetization exhibits a two-dimensional Heisenberg antiferromagnetic behavior. Below T{sub c}, magnetization data are thermodynamically reversible over large portions of the H-T plane, so the free energy is well defined in these regions. As the Sr concentration is varied over the wide range from 0.060 (strongly underdoped) to 0.234 (strongly overdoped), the free energy change goes through a maximum at the optimum doped in a manner similar to the T{sub c0} vs. x curve. The density of states, N(0), remains nearly constant in the overdoped and optimum doped regimes, taking a broad maximum around x = 0.188, and then drops abruptly towards zero in the underdoped regime. The La{sub 2-x}Sr{sub x}CuO{sub 4} (La-214) system displays the fluctuating vortex behavior with the characteristic of either 2D or 3D fluctuations as indicated by clearly identifiable crossing points T* close to T{sub c}. The dimensional character of the fluctuations depends on both applied magnetic fields and the density of charge carriers. The dimensional crossover from 2D to 3D occurs in the strongly underdoped regime when the c-axis coherence distance {zeta}{sub c} becomes comparable to the spacing between adjacent CuO{sub 2} layers s at sufficiently high magnetic fields near H{sub c2}.

  16. Thermodynamic Critical Field and Superconducting Fluctuation of Vortices for High Temperature Cuprate Superconductor La-214

    CERN Document Server

    Yung Moo Hu

    2001-01-01

    charge carriers. The dimensional crossover from 2D to 3D occurs in the strongly underdoped regime when the c-axis coherence distance zeta sub c becomes comparable to the spacing between adjacent CuO sub 2 layers s at sufficiently high magnetic fields near H sub c sub 2. Thermodynamics has been studied systematically for the high temperature cuprate superconductor La sub 2 sub - sub x Sr sub x CuO sub 4 sub - subdelta, La-214, in the entire superconductive region from strongly underdoped to strongly overdoped regimes. Magnetization studies with H(parallel)c have been made in order to investigate the changes in free energy of the system as the number of carriers is reduced. Above the superconducting transition temperature, the normal-state magnetization exhibits a two-dimensional Heisenberg antiferromagnetic behavior. Below T sub c , magnetization data are thermodynamically reversible over large portions of the H-T plane, so the free energy is well defined in these regions. As the Sr concentration is varied ove...

  17. Choice of sample size for high transport critical current density in a granular superconductor: percolation versus self-field effects

    Energy Technology Data Exchange (ETDEWEB)

    Mulet, R.; Diaz, O.; Altshuler, E. [Superconductivity Laboratory, IMRE-Physics Faculty, University of Havana, La Habana (Cuba)

    1997-10-01

    The percolative character of the current paths and the self-field effects were considered to estimate optimal sample dimensions for the transport current of a granular superconductor by means of a Monte Carlo algorithm and critical-state model calculations. We showed that, under certain conditions, self-field effects are negligible and the J{sub c} dependence on sample dimensions is determined by the percolative character of the current. Optimal dimensions are demonstrated to be a function of the fraction of superconducting phase in the sample. (author)

  18. Superconductivity in Strong Magnetic Field (Greater Than Upper Critical Field)

    Energy Technology Data Exchange (ETDEWEB)

    Tessema, G.X.; Gamble, B.K.; Skove, M.J.; Lacerda, A.H.; Mielke, C.H.

    1998-08-22

    The National High Magnetic Field Laboratory, funded by the National Science Foundation and other US federal Agencies, has in recent years built a wide range of magnetic fields, DC 25 to 35 Tesla, short pulse 50 - 60 Tesla, and quasi-continuous 60 Tesla. Future plans are to push the frontiers to 45 Tesla DC and 70 to 100 Tesla pulse. This user facility, is open for national and international users, and creates an excellent tool for materials research (metals, semiconductors, superconductors, biological systems ..., etc). Here we present results of a systematic study of the upper critical field of a novel superconducting material which is considered a promising candidate for the search for superconductivity beyond H{sub c2} as proposed by several new theories. These theories predict that superconductors with low carrier density can reenter the superconducting phase beyond the conventional upper critical field H{sub c2}. This negates the conventional thinking that superconductivity and magnetic fields are antagonistic.

  19. Upper critical fields in as-grown MgB{sub 2} films prepared by ultra-high-vacuum MBE

    Energy Technology Data Exchange (ETDEWEB)

    Noguchi, S. [Department of Physics and Electronics, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); Institute for Nanofabrication Research, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); CREST, Japan Science and Technology Agency, 4-1-8, Honcho, Kawaguchi, Saitama 332-0012 (Japan)], E-mail: noguchi@pe.osakafu-u.ac.jp; Kuribayashi, A. [Department of Physics and Electronics, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); CREST, Japan Science and Technology Agency, 4-1-8, Honcho, Kawaguchi, Saitama 332-0012 (Japan); Oba, T.; Iriuda, H. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan); Harada, Y. [JST Satellite Iwate, 3-35-2 Iioka-shinden, Morioka, Iwate 020-0852 (Japan); Yoshizawa, M. [Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551 (Japan); JST Satellite Iwate, 3-35-2 Iioka-shinden, Morioka, Iwate 020-0852 (Japan); Ishida, T. [Department of Physics and Electronics, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); Institute for Nanofabrication Research, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); CREST, Japan Science and Technology Agency, 4-1-8, Honcho, Kawaguchi, Saitama 332-0012 (Japan)

    2007-10-01

    We report on the upper critical fields (H{sub c2}'s) of as-grown MgB{sub 2} thin films deposited on the epitaxial Ti buffer layer on c-plane ZnO substrates by using a molecular beam epitaxy (MBE) apparatus. The H{sub c2} was estimated from the magnetoresistance measurements under the pulsed magnetic field up to 37 T. H{sub c2}(T) for both H -parallel ab-plane and H -parallel c-axis were measured to obtain the anisotropic superconducting properties. The results are successfully analyzed with the Gurevich theory of dirty two-gap superconductivity with a cleaner {pi} band case.

  20. High, magnetic-field-insensitive transport critical currents in unoriented polycrystalline thin films of Tl 2CaBa 2Cu 2O y

    Science.gov (United States)

    Kwak, J. F.; Venturini, E. L.; Baughman, R. J.; Morosin, B.; Ginley, D. S.

    1988-08-01

    We report critical current measurements for unoriented polycrystalline films of Tl 2CaBa 2Cu 2O y. At 77 K these films show critical current densities ranging from 10 000 to 110 000 A/cm 2, with a median value of 50 000 A/cm 2. Moreover, the best films' critical currents at 77 K drop less than 50% in an applied magnetic field of 1 T, and less than a factor of 20 at 6 T. At 4 K, critical current densities over 10 6A/cm 2 with less than 15% drop at 6 T have been obtained. The zero-field temperature dependence of the critical current from 4 to 95 K is well described as quadratic. High-field magnetization loops on the films at 76 K show a striking collapse in hysteresis below 0.6 T. Our results indicate that, although the grains in these films are Josephson-coupled, the strength of the coupling is greatly improved over other high- Tc granular systems.

  1. Coercivity and the critical switching field

    Energy Technology Data Exchange (ETDEWEB)

    Kahler, G.R. [George Washington University, Washington, DC 20052 (United States)]. E-mail: grkahler@aol.com; Bennett, L.H. [George Washington University, Washington, DC 20052 (United States); Della Torre, E. [George Washington University, Washington, DC 20052 (United States)

    2006-02-01

    The critical switching field and the coercivity of a material are not necessarily the same; these field values depend upon the magnetization process. Several field-related parameters are used to identify the major hysteresis loop of a material: the saturation field, remanent coercivity, critical field, average critical field, coercivity, median coercivity, and intrinsic coercivity. The parameters vary with changes in the magnetization process, which usually is assumed to be quasi-static. If the process is not quasi-static; i.e., it is faster or slower, the results of the process will change, and the field parameters will be differen000.

  2. Temperature dependence of the upper critical field of type-II superconductors from isothermal magnetization data: Application to high-temperature superconductors

    Science.gov (United States)

    Landau, I. L.; Ott, H. R.

    2002-10-01

    Using the Ginzburg-Landau theory in very general terms, we develop a simple scaling procedure which allows to establish the temperature dependence of the upper critical field Hc2 and the value of the superconducting critical temperature Tc of type-II superconductors from measurements of the reversible isothermal magnetization. An analysis of existing experimental data shows that the normalized dependencies of Hc2 on T/Tc are practically identical for all families of high-Tc superconductors at all temperatures for which the magnetization data are available.

  3. High-pressure study of the basal-plane anisotropy of the upper critical field of the topological superconductor SrxBi2Se3

    Science.gov (United States)

    Nikitin, A. M.; Pan, Y.; Huang, Y. K.; Naka, T.; de Visser, A.

    2016-10-01

    We report a high-pressure transport study of the upper-critical field Bc 2(T ) of the topological superconductor Sr0.15Bi2Se3 (Tc=3.0 K). Bc 2(T ) was measured for magnetic fields directed along two orthogonal directions, a and a*, in the trigonal basal plane. While superconductivity is rapidly suppressed at the critical pressure pc˜3.5 GPa, the pronounced two-fold basal-plane anisotropy Bc2 a/Bc2 a*=3.2 at T =0.3 K, recently reported at ambient pressure [Pan et al., Sci. Rep. 6, 28632 (2016), 10.1038/srep28632], is reinforced and attains a value of ˜5 at the highest pressure (2.2 GPa). The data reveal that the unconventional superconducting state with broken rotational symmetry is robust under pressure.

  4. Analysis of Magnetic Critical Fields in Iron-Based SmFeAsO0.85 HIGH-Tc Superconductor

    Science.gov (United States)

    Ahmad, Dawood; Song, Tae Kwon; Park, In Suk; Kim, G. C.; Ren, Zhi-An; Kim, Y. C.

    The magnetic properties of the newly discovered iron-oxypnictide SmFeAsO0.85 high-Tc superconductor with a Tc of around 55 K were investigated. Bulk SmFeAsO0.85 was prepared by a method for high-pressure synthesis. The lower critical field Hc1 was estimated from the magnetization at low fields; Hc1(0) was measured to be 212 Oe. A linear temperature dependence instead of saturation at low temperatures in Hc1(T) revealed unconventional superconductivity with a nodal gap structure in our SmFeAsO0.85 superconductor. The results showed that the well-known secondary peak in the temperature dependence of the critical current density Jc is absent in the SmFeAsO0.85 high-Tc superconductor. The irreversibility line Birr was fitted well by the power law dependence (1 - T/Tc)n with n ~ 1.5. This is indicative of the flux creep phenomena in the SmFeAsO0.85 high-Tc superconductor. In addition, within the range of measurement temperatures in this study, no crossover was observed in the temperature dependence of the irreversibility line Birr which may be due to low anisotropy in our SmFeAsO0.85 superconductor.

  5. Critical Magnetic Field Determination of Superconducting Materials

    Energy Technology Data Exchange (ETDEWEB)

    Canabal, A.; Tajima, T.; /Los Alamos; Dolgashev, V.A.; Tantawi, S.G.; /SLAC; Yamamoto, T.; /Tsukuba, Natl. Res. Lab. Metrol.

    2011-11-04

    Superconducting RF technology is becoming more and more important. With some recent cavity test results showing close to or even higher than the critical magnetic field of 170-180 mT that had been considered a limit, it is very important to develop a way to correctly measure the critical magnetic field (H{sup RF}{sub c}) of superconductors in the RF regime. Using a 11.4 GHz, 50-MW, <1 {mu}s, pulsed power source and a TE013-like mode copper cavity, we have been measuring critical magnetic fields of superconductors for accelerator cavity applications. This device can eliminate both thermal and field emission effects due to a short pulse and no electric field at the sample surface. A model of the system is presented in this paper along with a discussion of preliminary experimental data.

  6. Reactive spark plasma sintering of MgB2 in nitrogen atmosphere for the enhancement of the high-field critical current density

    Science.gov (United States)

    Badica, P.; Burdusel, M.; Popa, S.; Pasuk, I.; Ivan, I.; Borodianska, H.; Vasylkiv, O.; Kuncser, A.; Ionescu, A. M.; Miu, L.; Aldica, G.

    2016-10-01

    High density bulks (97%-99%) of MgB2 were prepared by spark plasma sintering (SPS) in nitrogen (N2) atmosphere for different heating rates (10, 20 and 100 °C min-1) and compared with reference samples processed in vacuum and Ar. N2 reacts with MgB2 and forms MgB9N along the MgB2 grain boundaries. The high-field critical current density is enhanced for the sample processed in N2 with a heating rate of 100 °C min-1. At 2-35 K, this sample shows the strongest contribution of the grain boundary pinning (GBP). All samples are in the point pinning (PP) limit and by increasing temperature the GBP contribution decreases.

  7. Critical Metadata for Spectroscopy Field Campaigns

    Directory of Open Access Journals (Sweden)

    Barbara A. Rasaiah

    2014-04-01

    Full Text Available A field spectroscopy metadata standard is defined as those data elements that explicitly document the spectroscopy dataset and field protocols, sampling strategies, instrument properties and environmental and logistical variables. Standards for field spectroscopy metadata affect the quality, completeness, reliability, and usability of datasets created in situ. Currently there is no standardized methodology for documentation of in situ spectroscopy data or metadata. This paper presents results of an international experiment comprising a web-based survey and expert panel evaluation that investigated critical metadata in field spectroscopy. The survey participants were a diverse group of scientists experienced in gathering spectroscopy data across a wide range of disciplines. Overall, respondents were in agreement about a core metadataset for generic campaign metadata, allowing for a prioritization of critical metadata elements to be proposed including those relating to viewing geometry, location, general target and sampling properties, illumination, instrument properties, reference standards, calibration, hyperspectral signal properties, atmospheric conditions, and general project details. Consensus was greatest among individual expert groups in specific application domains. The results allow the identification of a core set of metadata fields that enforce long term data storage and serve as a foundation for a metadata standard. This paper is part one in a series about the core elements of a robust and flexible field spectroscopy metadata standard.

  8. Critical Number of Fields in Stochastic Inflation

    Science.gov (United States)

    Vennin, Vincent; Assadullahi, Hooshyar; Firouzjahi, Hassan; Noorbala, Mahdiyar; Wands, David

    2017-01-01

    Stochastic effects in generic scenarios of inflation with multiple fields are investigated. First passage time techniques are employed to calculate the statistical moments of the number of inflationary e -folds, which give rise to all correlation functions of primordial curvature perturbations through the stochastic δ N formalism. The number of fields is a critical parameter. The probability of exploring arbitrarily large-field regions of the potential becomes nonvanishing when more than two fields are driving inflation. The mean number of e -folds can be infinite, depending on the number of fields; for plateau potentials, this occurs even with one field. In such cases, correlation functions of curvature perturbations are infinite. They can, however, be regularized if a reflecting (or absorbing) wall is added at large energy or field value. The results are found to be independent of the exact location of the wall and this procedure is, therefore, well defined for a wide range of cutoffs, above or below the Planck scale. Finally, we show that, contrary to single-field setups, multifield models can yield large stochastic corrections even at sub-Planckian energy, opening interesting prospects for probing quantum effects on cosmological fluctuations.

  9. Temperature dependence of the upper critical field of high- Tc superconductors from isothermal magnetization data: influence of a temperature dependent Ginzburg-Landau parameter

    Science.gov (United States)

    Landau, I. L.; Ott, H. R.

    2003-11-01

    We show that the scaling procedure, recently proposed for the evaluation of the temperature variation of the normalized upper critical field of type-II superconductors, may easily be modified in order to take into account a possible temperature dependence of the Ginzburg-Landau parameter κ. As an example we consider κ( T) as it follows from the microscopic theory of superconductivity.

  10. Quantum field theory and critical phenomena

    CERN Document Server

    Zinn-Justin, Jean

    1996-01-01

    Over the last twenty years quantum field theory has become not only the framework for the discussion of all fundamental interactions except gravity, but also for the understanding of second-order phase transitions in statistical mechanics. This advanced text is based on graduate courses and summer schools given by the author over a number of years. It approaches the subject in terms of path and functional intergrals, adopting a Euclidean metric and using the language of partition and correlation functions. Renormalization and the renormalization group are examined, as are critical phenomena and the role of instantons. Changes for this edition 1. Extensive revision to eliminate a few bugs that had survived the second edition and (mainly) to improve the pedagogical presentation, as a result of experience gathered by lecturing. 2. Additional new topics; holomorphic or coherent state path integral; functional integral and representation of the field theory S-matrix in the holomorphic formalis; non-relativistic li...

  11. Enhancement of the critical current density in FeO-coated MgB2 thin films at high magnetic fields

    Directory of Open Access Journals (Sweden)

    Andrei E. Surdu

    2011-12-01

    Full Text Available The effect of depositing FeO nanoparticles with a diameter of 10 nm onto the surface of MgB2 thin films on the critical current density was studied in comparison with the case of uncoated MgB2 thin films. We calculated the superconducting critical current densities (Jc from the magnetization hysteresis (M–H curves for both sets of samples and found that the Jc value of FeO-coated films is higher at all fields and temperatures than the Jc value for uncoated films, and that it decreases to ~105 A/cm2 at B = 1 T and T = 20 K and remains approximately constant at higher fields up to 7 T.

  12. Effective and fundamental quantum fields at criticality

    Energy Technology Data Exchange (ETDEWEB)

    Scherer, Michael

    2010-10-28

    We employ Wetterich's approach to functional renormalization as a suitable method to investigate universal phenomena in non-perturbative quantum field theories both qualitatively and quantitatively. Therefore we derive and investigate flow equations for a class of chiral Yukawa models with and without gauge bosons and reveal fixed-point mechanisms. In four dimensions chiral Yukawa systems serve as toy models for the standard model Higgs sector and show signatures of asymptotically safe fixed points by a balancing of bosonic and fermionic contributions. In the approximations investigated this renders the theory fundamental and solves the triviality problem. Further, we obtain predictions for the Higgs mass and even for the top mass of our toy model. In three dimensions we compute the critical exponents which define new universality classes and provide benchmark values for systems of strongly correlated chiral fermions. In a Yukawa system of non-relativistic two-component fermions a fixed point dominates the renormalization flow giving rise to universality in the BCS-BEC crossover. We push the functional renormalization method to a quantitative level and we compute the critical temperature and the single-particle gap with a considerable precision for the whole crossover. Finally, we provide further evidence for the asymptotic safety scenario in quantum gravity by confirming the existence of an ultraviolet fixed point under inclusion of a curvature-ghost coupling. (orig.)

  13. Critical suppression of spin Seebeck effect by magnetic fields

    Science.gov (United States)

    Kikkawa, Takashi; Uchida, Ken-ichi; Daimon, Shunsuke; Qiu, Zhiyong; Shiomi, Yuki; Saitoh, Eiji

    2015-08-01

    The longitudinal spin Seebeck effect (LSSE) in Pt /Y3Fe5O12(YIG ) junction systems has been investigated at various magnetic fields and temperatures. We found that the LSSE voltage in a Pt/YIG-slab system is suppressed by applying high magnetic fields and this suppression is critically enhanced at low temperatures. The field-induced suppression of the LSSE in the Pt/YIG-slab system is too large at around room temperature to be explained simply by considering the effect of the Zeeman gap in magnon excitation. This result requires us to introduce a magnon-frequency-dependent mechanism into the scenario of LSSE; low-frequency magnons dominantly contribute to the LSSE. The magnetic field dependence of the LSSE voltage was observed to change by changing the thickness of YIG, suggesting that the thermospin conversion by the low-frequency magnons is suppressed in thin YIG films due to the long characteristic lengths of such magnons.

  14. High-temperature superconductors in high-field magnets

    NARCIS (Netherlands)

    Weijers, Hubertus Wilhelmus

    2009-01-01

    The properties of both BSCCO conductors and YBCO coated conductors and coils are studied to assess their applicability in high-field magnets. First, the magnetic field dependence of the critical current density in these HTS conductors is measured at 4.2 K in magnetic field conditions ranging from s

  15. High critical current density under magnetic fields in as-grown MgB{sub 2} thin films deposited by molecular-beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Haruta, M [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Fujiyoshi, T [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Kihara, S [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Sueyoshi, T [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Miyahara, K [Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Harada, Y [Iwate Industry Promotion Centre, Iioka-shinden 3-35-2, Morioka, Iwate 020-0852 (Japan); Yoshizawa, M [Graduate School of Engineering, Iwate University, Ueda 4-3-5, Morioka, Iwate 020-8551 (Japan); Takahashi, T [Graduate School of Engineering, Iwate University, Ueda 4-3-5, Morioka, Iwate 020-8551 (Japan); Iriuda, H [Graduate School of Engineering, Iwate University, Ueda 4-3-5, Morioka, Iwate 020-8551 (Japan); Oba, T [Graduate School of Engineering, Iwate University, Ueda 4-3-5, Morioka, Iwate 020-8551 (Japan); Awaji, S [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Watanabe, K [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Miyagawa, R [Kumamoto Industrial Research Institute, 3-11-38 Higashi-machi, Kumamoto 862-0901 (Japan)

    2007-01-15

    As-grown MgB{sub 2} thin films were prepared by a MBE method under the conditions of low temperature, low deposition rate and high vacuum for applications in electric devices. The MgB{sub 2} thin films deposited on MgO and Ti buffered ZnO substrates have considerably higher J{sub c} under magnetic fields among MgB{sub 2} thin films reported before. The value of J{sub c} for the MgB{sub 2} thin film deposited on Ti buffered ZnO has been 5.8 x 10{sup 5} A cm{sup -2} at 10 K, 5 T in the magnetic field applied parallel to the c axis. In the angular dependence of J{sub c}, the peak of J{sub c} attributable to c-axis-correlated pinning centres has been observed when the magnetic field was applied parallel to the c axis. (rapid communication)

  16. Enhanced high-field transport critical current densities observed for ex situ PIT processed Ag/(Ba, K)Fe2As2 thin tapes

    Science.gov (United States)

    Togano, Kazumasa; Gao, Zhaoshun; Taira, Hideaki; Ishida, Shigeyuki; Kihou, Kunihiro; Iyo, Akira; Eisaki, Hiroshi; Matsumoto, Akiyoshi; Kumakura, Hiroaki

    2013-06-01

    We found that the transport Jc of ex situ PIT (powder-in-tube) processed (Ba,K)Fe2As2 (Ba-122) wires with a single Ag sheath can be significantly enhanced by repeating a combined process of rolling and heat treatment. A transport Jc (4.2 K and 10 T) of 4.4 × 103 A cm-2 (Ic = 15.7 A) was obtained for a thin tape (0.3 mm thick) produced by this method, which is the highest reported so far for Ag-sheathed Ba-122 and Sr-122 wires processed by the conventional PIT route. The measurement by a hybrid magnet showed that the Jc-H curve maintains a very small field dependence up to the strong magnetic field of 28 T, as expected from the previously reported high Hc2 value. The core of the thin tape shows dense grain structure with fewer cracks and voids, which is considered to be responsible for the large enhancement of Jc. We believe that this new approach is useful for further development of 122 wires with higher transport Jc.

  17. Effective critical electric field for runaway electron generation

    CERN Document Server

    Stahl, Adam; Decker, Joan; Embréus, Ola; Fülöp, Tünde

    2014-01-01

    In this letter we investigate factors that influence the effective critical electric field for runaway electron generation in plasmas. We present numerical solutions of the kinetic equation, and discuss the implications for the threshold electric field. We show that the effective electric field necessary for significant runaway formation often is higher than previously calculated due to both (1) extremely strong dependence of primary generation on temperature, and (2) synchrotron radiation losses. We also address the effective critical field in the context of a transition from runaway growth to decay. We find agreement with recent experiments, but show that the observation of an elevated effective critical field can mainly be attributed to changes in the momentum-space distribution of runaways, and only to a lesser extent to a de facto change in the critical field.

  18. Magnetic field and temperature dependence of the critical vortex velocity in type-II superconducting films.

    Science.gov (United States)

    Grimaldi, G; Leo, A; Cirillo, C; Attanasio, C; Nigro, A; Pace, S

    2009-06-24

    We study the vortex dynamics in the instability regime induced by high dissipative states well above the critical current in Nb superconducting strips. The magnetic field and temperature behavior of the critical vortex velocity corresponding to the observed dynamic instability is ascribed to intrinsic non-equilibrium phenomena. The Larkin-Ovchinnikov (LO) theory of electronic instability in high velocity vortex motion has been applied to interpret the temperature dependence of the critical vortex velocity. The magnetic field dependence of the vortex critical velocity shows new features in the low-field regime not predicted by LO.

  19. Magnetic field and temperature dependence of the critical vortex velocity in type-II superconducting films

    Energy Technology Data Exchange (ETDEWEB)

    Grimaldi, G; Leo, A; Cirillo, C; Attanasio, C; Nigro, A; Pace, S [CNR-INFM Laboratorio Regionale SuperMat, Via Salvador Allende, I-84081 Baronissi (Italy)], E-mail: grimaldi@sa.infn.it

    2009-06-24

    We study the vortex dynamics in the instability regime induced by high dissipative states well above the critical current in Nb superconducting strips. The magnetic field and temperature behavior of the critical vortex velocity corresponding to the observed dynamic instability is ascribed to intrinsic non-equilibrium phenomena. The Larkin-Ovchinnikov (LO) theory of electronic instability in high velocity vortex motion has been applied to interpret the temperature dependence of the critical vortex velocity. The magnetic field dependence of the vortex critical velocity shows new features in the low-field regime not predicted by LO.

  20. Critical field enhancement near a superconductor-insulator transition.

    Science.gov (United States)

    Lee, I J; Chaikin, P M; Naughton, M J

    2002-05-20

    We have discovered a phenomenon where the orbital pair breaking effect is reduced, if not eliminated. It appears as a striking enhancement in the upper critical field H(c2) for (TMTSF)2PF6 and a strong upward curvature in the critical field versus temperature in the region of pressure-temperature phase space near the superconductor-spin density wave insulator boundary. A simple model based on self-consistently dividing the superconductor into layers explains the observations remarkably well and provides a unique way around orbital frustration and toward higher critical fields.

  1. Participative Critical Enquiry in Graduate Field-Based Learning

    Science.gov (United States)

    Reilly, Kathy; Clavin, Alma; Morrissey, John

    2016-01-01

    This paper outlines a critical pedagogic approach to field-based learning (FBL) at graduate level. Drawing on student experience stemming from a FBL module and as part of an MA programme in Environment, Society and Development, the paper addresses the complexities associated with student-led, participative critical enquiry during fieldwork in…

  2. Superconducting transition width (ΔT c) characteristics of 25 mol% Zr-added (Gd, Y)Ba2Cu3O7-δ superconductor tapes with high in-field critical current density at 30 K

    Science.gov (United States)

    Heydari Gharahcheshmeh, M.; Galstyan, E.; Xu, A.; Kukunuru, J.; Katta, R.; Zhang, Y.; Majkic, G.; Li, X.-F.; Selvamanickam, V.

    2017-01-01

    The superconducting transition width (∆T c) characteristics of REBa2Cu3O7-δ (REBCO and RE = Gd, Y) superconductor tapes with Zr content of 25 mol% with high lift factor (ratio of critical current density (J c) at 30 K, 3 T (B||c) to the J c at 77 K, 0 T) has been determined. In this work, heavily doped (Gd, Y)Ba2Cu3O7-δ superconductor tapes with 25 mol% Zr addition were fabricated by metal organic chemical vapor deposition using a reel-to reel process. The optimal chemical composition range of (Gd, Y)Ba2Cu3O7-δ superconductor tapes with Zr content of 25 mol% to achieve critical current densities above 3.5 MA cm-2 at 77 K in zero applied magnetic field has been determined. A superconducting transition width (∆T c) as narrow as 0.4 K and an onset critical transition temperature (T c-onset) as high as 92 K were obtained in the 25 mol% Zr-added (Gd, Y)BaCuO superconductor tapes. Based on the mapped compositional phase diagram of the ∆Tc and lift factor, ∆T c in the range of 0.7-0.9 K is observed in 25 mol% Zr-added (Gd, Y)BaCuO superconductor tapes with a high lift factor.

  3. The external field dependence of the BCS critical temperature

    DEFF Research Database (Denmark)

    Frank, Rupert L.; Hainzl, Christian; Seiringer, Robert

    2016-01-01

    We consider the Bardeen-Cooper-Schrieffer free energy functional for particles interacting via a two-body potential on a microscopic scale and in the presence of weak external fields varying on a macroscopic scale. We study the influence of the external fields on the critical temperature. We show...

  4. On the Ginzburg-Landau critical field in three dimensions

    DEFF Research Database (Denmark)

    Fournais, Søren; Helffer, Bernard

    2009-01-01

    We study the three-dimensional Ginzburg-Landau model of superconductivity. Several natural definitions of the (third) critical field, HC3, governing the transition from the superconducting state to the normal state, are considered. We analyze the relation between these fields and give conditions...

  5. Transport signatures of quantum critically in Cr at high pressure.

    Energy Technology Data Exchange (ETDEWEB)

    Jaramillo, R.; Feng, Y.; Wang, J.; Rosenbaum, T. F. (X-Ray Science Division); ( PSC-USR); (Harvard Univ.); (Univ. of Chicago)

    2010-08-03

    The elemental antiferromagnet Cr at high pressure presents a new type of naked quantum critical point that is free of disorder and symmetry-breaking fields. Here we measure magnetotransport in fine detail around the critical pressure, P{sub c} {approx} 10 GPa, in a diamond anvil cell and reveal the role of quantum critical fluctuations at the phase transition. As the magnetism disappears and T {yields} 0, the magntotransport scaling converges to a non-mean-field form that illustrates the reconstruction of the magnetic Fermi surface, and is distinct from the critical scaling measured in chemically disordered Cr:V under pressure. The breakdown of itinerant antiferromagnetism only comes clearly into view in the clean limit, establishing disorder as a relevant variable at a quantum phase transition.

  6. On the third critical field in Ginzburg-Landau theory

    OpenAIRE

    Fournais, S.; Helffer, B.

    2005-01-01

    Using recent results by the authors on the spectral asymptotics of the Neumann Laplacian with magnetic field, we give precise estimates on the critical field, $H_{C_3}$, describing the appearance of superconductivity in superconductors of type II. Furthermore, we prove that the local and global definitions of this field coincide. Near $H_{C_3}$ only a small part, near the boundary points where the curvature is maximal, of the sample carries superconductivity. We give precise estimates on the ...

  7. Scaling critical behavior of superconductors at zero magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Calan, C. de; Nogueira, F.S. [Ecole Polytechnique (France). Centre de Physique Theorique

    2000-07-01

    Full text follows: We consider the scaling behavior in the critical domain of superconductors at zero external magnetic field. The Josephson's relation for a charged superfluid is proved without assuming the hyperscaling relation. On the other hand we discuss the dual Ginzburg-Landau model. In this dual model, due to the presence of two mass scales, a continuous family of non equivalent scalings can be defined. The relevant critical regimes are identified, and the corresponding critical exponents are predicted. (author)

  8. High field superconducting magnets

    Science.gov (United States)

    Hait, Thomas P. (Inventor); Shirron, Peter J. (Inventor)

    2011-01-01

    A superconducting magnet includes an insulating layer disposed about the surface of a mandrel; a superconducting wire wound in adjacent turns about the mandrel to form the superconducting magnet, wherein the superconducting wire is in thermal communication with the mandrel, and the superconducting magnet has a field-to-current ratio equal to or greater than 1.1 Tesla per Ampere; a thermally conductive potting material configured to fill interstices between the adjacent turns, wherein the thermally conductive potting material and the superconducting wire provide a path for dissipation of heat; and a voltage limiting device disposed across each end of the superconducting wire, wherein the voltage limiting device is configured to prevent a voltage excursion across the superconducting wire during quench of the superconducting magnet.

  9. Magnetic Field Effect on Critical Behavior of Perovskite Ferromagnet

    Institute of Scientific and Technical Information of China (English)

    Tian Hongwei; Zheng Weitao; Chen Yanping; Ding Tao; Wang Xin; Kan Dongwu

    2005-01-01

    The polycrystalline samples of La2/3Ca1/3MnO3 were prepared by a conventional solid state reaction method. The magnetizations (ZFC, FC and initial magnetization) of the polycrystalline La2/3Ca1/3MnO3 were measured with superconducting quantum interference device magnetometer. The scaling theory was employed to study the changes of critical behavior arising from the applied external field. The critical parameter β decreases with increasing the external magnetic field results in an increase in the magnitude of ferromagnetic ordering.

  10. Influence of critical current density on levitation force of high - Tc superconducting system under field cooling condition%临界电流密度对场冷超导磁悬浮力的影响研究

    Institute of Scientific and Technical Information of China (English)

    赵宪锋; 周又和

    2011-01-01

    After the penetration depth of superconducting currents and the internal magnetic field interior of the HTS were calculated, the influence of critical current density (Jc) on the interaction forces between a high - Tc superconductor (HTS) and a permanent magnet (PM) was investigated under field cooling process based on Kim critical state model. It was found that the maximum levitation forces including the attractive force and the repulsive force increased as an exponential function with the increasing of the Jc. They became to saturate at high Jc. The hysteresis energy loss of vertical force - displacement curve under field cooling condition was larger than the one under zero -field cooling condition. There was a force ratio k, which was important on estimating the mechanics capability of superconducting levitation system with large Jc. All these relations could be explained with the penetration history of superconducting currents under field cooling condition.%基于Kim临界态模型,通过考虑超导块材内部屏蔽电流的穿透历史过程,讨论了场冷条件下临界电流密度对高温超导悬浮系统磁悬浮排斥力和吸引力的影响.结果显示:最大超导磁悬浮排斥力和吸引力均随临界电流密度的增加呈指数关系增加,并趋于饱和;场冷条件下的磁悬浮力回滞能量损耗远高于零场冷情况;存在一个磁悬浮力比率κ,κ值对于评价大电流超导磁悬浮系统的机械性能具有重要作用.磁悬浮力随临界电流密度的这些变化特征可以用超导块材内部屏蔽电流的穿透情况进行合理地解释,为高温超导悬浮系统的工业应用提供了重要的理论依据.

  11. Critical properties of the classical Heisenberg and XY models : A mean field renormalization group study

    Directory of Open Access Journals (Sweden)

    A. Sadeghi

    2007-03-01

    Full Text Available  Using both mean field renormalization group (MFRG and Surface-Bulk MFRG (SBMFRG, we study the critical behavior of the classical Heisenberg and XY models on a simple cubic lattice. Critical temperatures as well as critical exponents, characteristic the universality classes of these two models were calculated, analytically for1, 2, 3 and 4 spin clusters. The results are in good agreement with higher accurate methods such as Monte Carlo and High- temperature series.

  12. Critical fluctuations for quantum mean-field models

    Energy Technology Data Exchange (ETDEWEB)

    Fannes, M.; Kossakowski, A.; Verbeure, A. (Univ. Louvain (Belgium))

    1991-11-01

    A Ginzburg-Landau-type approximation is proposed for the local Gibbs states for quantum mean-field models that leads to the exact thermodynamics. Using this approach, the spin fluctuations are computed for some spin-1/2 models. At the critical temperature, the distribution function showing abnormal fluctuations is found explicitly.

  13. Acute enhancement of the upper critical field for superconductivity approaching a quantum critical point in URhGe

    Science.gov (United States)

    Lévy, F.; Sheikin, I.; Huxley, A.

    2007-07-01

    When a pure material is tuned to the point where a continuous phase-transition line is crossed at zero temperature, known as a quantum critical point (QCP), completely new correlated quantum ordered states can form. These phases include exotic forms of superconductivity. However, as superconductivity is generally suppressed by a magnetic field, the formation of superconductivity ought not to be possible at extremely high field. Here, we report that as we tune the ferromagnet, URhGe, towards a QCP by applying a component of magnetic field in the material's easy magnetic plane, superconductivity survives in progressively higher fields applied simultaneously along the material's magnetic hard axis. Thus, although superconductivity never occurs above a temperature of 0.5K, we find that it can survive in extremely high magnetic fields, exceeding 28T.

  14. Acute enhancement of the upper critical field for superconductivity approaching a quantum critical point in URhGe

    Energy Technology Data Exchange (ETDEWEB)

    Levy, F.; Huxley, A. [CEA, SPSMS, DRFMC, F-38054 Grenoble, (France); Levy, F.; Sheikin, I. [CNRS, GHMFL, F-38042 Grenoble, (France); Huxley, A. [Univ Edinburgh, Scottish Univ Phys Alliance, Sch Phys, Edinburgh EH9 3JZ, Midlothian, (United Kingdom)

    2007-07-01

    When a pure material is tuned to the point where a continuous phase-transition line is crossed at zero temperature, known as a quantum critical point (QCP), completely new correlated quantum ordered states can form. These phases include exotic forms of superconductivity. However, as superconductivity is generally suppressed by a magnetic field, the formation of superconductivity ought not to be possible at extremely high field. Here, we report that as we tune the ferromagnet, URhGe, towards a QCP by applying a component of magnetic field in the material's easy magnetic plane, superconductivity survives in progressively higher fields applied simultaneously along the material's magnetic hard axis. Thus, although superconductivity never occurs above a temperature of 0.5 K, we find that it can survive in extremely high magnetic fields, exceeding 28 T. (authors)

  15. Critical exact solutions for self-gravitating Dirac fields

    CERN Document Server

    Cianci, Roberto; Vignolo, Stefano

    2016-01-01

    We consider the Einstein-Dirac field equations describing a self-gravitating massive neutrino, looking for axially-symmetric exact solutions; in the search of general solutions, we find some that are specific and which have critical features, such as the fact that the space-time curvature turns out to be flat and the spinor field gives rise to a vanishing bi-linear scalar $\\overline{\\psi}\\psi=0$ with non-vanishing bi-linear pseudo-scalar $i\\overline{\\psi}\\gamma^5\\psi\

  16. IN SEARCH OF A CRITICAL PSYCHOLOGY IN THE WORK FIELDS

    OpenAIRE

    HERNÁN CAMILO PULIDO-MARTÍNEZ

    2004-01-01

    Critical psychology (Walkerdine, 2001) has not deeply considered the possibilities of construction ofalternative approaches to industrial and organizational psychology. This paper presents research andintervention fields that do not have left aside questions about efficiency but are formulating questionabout why and what for we are organized in certain ways for work. The studies conducted within thediscursive psychology (Parker, 1997), social psychology of organizations Schvarstein (1992), so...

  17. Field-induced quantum criticality in CeCu{sub 6-x}Au{sub x}

    Energy Technology Data Exchange (ETDEWEB)

    Grube, Kai; Eilers, Felix; Zocco, Diego; Schaefer, Roland [Karlsruher Institut fuer Technologie, Institut fuer Festkoerperphysik, 76021 Karlsruhe (Germany); Zaum, Sebastian; Loehneysen, Hilbert von [Karlsruher Institut fuer Technologie, Institut fuer Festkoerperphysik, 76021 Karlsruhe (Germany); Karlsruher Institut fuer Technologie, Physikalisches Institut, Karlsruhe (Germany); Fritsch, Veronika [Karlsruher Institut fuer Technologie, Physikalisches Institut, Karlsruhe (Germany); Stockert, Oliver [Max-Planck-Institut fuer Chemische Physik Fester Stoffe, 01187 Dresden (Germany)

    2013-07-01

    The heavy-fermion system CeCu{sub 6-x}Au{sub x} is an archetype for pressure-induced quantum criticality at the onset of antiferromagnetic order. Up to now, investigations focused mainly on the behavior close to the critical concentration x{sub c}∼0.1. The antiferromagnetic order of samples with higher Au content can, however, be also suppressed by magnetic fields. We studied the field-induced quantum critical behavior of samples with Au contents x=0.3, 0.5 and 1.0 in fields applied along the magnetic easy axis by using thermal expansion and magnetostriction measurements. Due to their high sensitivities these measurements are especially suited to expose deviations from Fermi-liquid behavior. The measurements have been performed for temperatures ranging between 20 mK and 10 K, and in magnetic fields up to 14 T. With increasing Au content and critical field B{sub c} they show strongly varying critical behavior. We discuss our results taking into account the field-dependent Zeeman splitting of the CEF ground-state doublet, which manifests itself as a Schottky-like anomaly at low temperatures and fields larger than B{sub c}.

  18. Critical exact solutions for self-gravitating Dirac fields

    Energy Technology Data Exchange (ETDEWEB)

    Cianci, Roberto; Fabbri, Luca; Vignolo, Stefano [Universita di Genova, DIME Sez. Metodi e Modelli Matematici, Genova (Italy)

    2016-11-15

    We consider the Einstein-Dirac field equations describing a self-gravitating massive neutrino, looking for axially symmetric exact solutions; in the search of general solutions, we find some that are specific and which have critical features, such as the fact that the space-time curvature turns out to be flat and the spinor field gives rise to a vanishing bi-linear scalar ψψ =0 with non-vanishing bi-linear pseudo-scalar iψγ{sup 5}ψ ≠ 0: because in quantum-field theory general computational methods are built on plane-wave solutions, for which the bi-linear pseudo-scalar vanishes while the bi-linear scalar does not vanish, then the solutions we found cannot be treated with the usual machinery of quantum-field theory. This means that for the Einstein-Dirac system there exist admissible solutions which nevertheless cannot be quantized with the common prescriptions; we regard this situation as yet another issue of tension between Einstein gravity and quantum principles. Possible ways to quench this tension can be seen either in enlarging the validity of quantum-field theory or by restricting the space of the solutions of the Einstein-Dirac system of field equations. (orig.)

  19. Parallel Critical Field in Thin Niobium Films: Comparison to Theory

    Science.gov (United States)

    Broussard, P. R.

    2017-10-01

    For the first time, a comparison to the predicted behavior for parallel critical field is carried out for the model of Kogan and the model of Hara and Nagai. In this study, thin niobium films in the moderately dirty regime were considered. Experimental values of the -C2 term are seen to be lower than those from the model of Hara and Nagai. A possible reason for this could be not including the non-spherical Fermi surface of niobium into the model. There is clearly disagreement with the model of Kogan as the films get cleaner and thinner, and two films which should be below his critical thickness still show positive values of -C2, in disagreement with his theory.

  20. IN SEARCH OF A CRITICAL PSYCHOLOGY IN THE WORK FIELDS

    Directory of Open Access Journals (Sweden)

    HERNÁN CAMILO PULIDO-MARTÍNEZ

    2004-07-01

    Full Text Available Critical psychology (Walkerdine, 2001 has not deeply considered the possibilities of construction ofalternative approaches to industrial and organizational psychology. This paper presents research andintervention fields that do not have left aside questions about efficiency but are formulating questionabout why and what for we are organized in certain ways for work. The studies conducted within thediscursive psychology (Parker, 1997, social psychology of organizations Schvarstein (1992, social psychologyof unemployment (Jahoda, 1982, and ideological (Prilleltensky, 1994 and post structuralistcritiques to psychology (Hollway, 1991 are visited. It is point out possible pathways for the constructionof a critical psychology in regards to work. The pertinence of psychological critique and new ways ofresearch and intervention in face of the contemporary work conditions are discussed.

  1. The upper critical field in two-band layered superconductors

    Institute of Scientific and Technical Information of China (English)

    Liu Min-Xia; Gan Zi-Zhao

    2007-01-01

    The upper critical field of clean MgB2 is investigated using the two-band layered Ginzburg-Landau (GL) theory.The calculated results are fitted to the experimental data of clean MgB2 crystal very well in a broad temperature range.Based on the GL theory for clean superconductors,a phenomenOlogical theory for dirty superconductor is proposed.Selecting appropriate parameters,two-band layered GL theory is successfully applied to the crystal of Mg(B1-xCx)2 and the neutron irradiation samples of MgB2.

  2. Field and Classroom Strategies for Improving Critical Thinking on Introductory Geoscience Field Trips

    Science.gov (United States)

    Boryta, M. D.; Walker, B.; Long, T.

    2011-12-01

    Although field experiences for introductory geoscience students have tremendous potential with respect to recruiting and retaining majors and enriching their understanding of geologic concepts, implementing field trips that promote critical thinking for introductory students is challenging. After observing that many of our students struggled at applying concepts they learned in the classroom to unfamiliar field areas, we developed teaching strategies and instructional materials for the classroom and the field to promote critical thinking and self-directed learning on field trips. We assessed the effectiveness of these modifications using video, interviews, student field trip reports and field notebooks. Student co-inquirers played a vital role during the project in field instruction and data analysis. We will discuss think-alouds, the importance of repetition in the classroom, allowing adequate processing time, field trip preparation exercises for the classroom, and other significant pedagogical changes that we made. Video of students in the field at the beginning, middle, and end of the project will be shown to illustrate the progressive changes in students' approaches to outcrop analysis over the course of the project.

  3. BEHAVIOUR OF A THREE-DIMENSIONAL UNIAXIAL MAGNET NEAR THE CRITICAL POINT IN AN EXTERNAL FIELD

    Directory of Open Access Journals (Sweden)

    M.P.Kozlovskii

    2004-01-01

    Full Text Available The behaviour of a three-dimensional magnet with a one-component order parameter near the critical point in a homogeneous external field is investigated. The calculations are performed in the case when the field and temperature are dependent and related by some expression (the system tends to the critical point along some trajectory. The high- and low-temperature regions in the vicinity of Tc (Tc is the phase transition temperature in the absence of an external field are considered. It is shown that in the weak fields the system behaviour is described in general by the temperature variable, but in the case of the strong fields the role of the temperature variable is not dominant. The corresponding expressions for the free energy, susceptibility and other characteristics of the system are obtained for each of these regions.

  4. Critical electric field strengths of onion tissues treated by pulsed electric fields.

    Science.gov (United States)

    Asavasanti, Suvaluk; Ersus, Seda; Ristenpart, William; Stroeve, Pieter; Barrett, Diane M

    2010-09-01

    The impact of pulsed electric fields (PEF) on cellular integrity and texture of Ranchero and Sabroso onions (Allium cepa L.) was investigated. Electrical properties, ion leakage rate, texture, and amount of enzymatically formed pyruvate were measured before and after PEF treatment for a range of applied field strengths and number of pulses. Critical electric field strengths or thresholds (E(c)) necessary to initiate membrane rupture were different because dissimilar properties were measured. Measurement of electrical characteristics was the most sensitive method and was used to detect the early stage of plasma membrane breakdown, while pyruvate formation by the enzyme alliinase was used to identify tonoplast membrane breakdown. Our results for 100-μs pulses indicate that breakdown of the plasma membrane occurs above E(c)= 67 V/cm for 10 pulses, but breakdown of the tonoplast membrane is above either E(c)= 200 V/cm for 10 pulses or 133 V/cm for 100 pulses. This disparity in field strength suggests there may be 2 critical electrical field strengths: a lower field strength for plasma membrane breakdown and a higher field strength for tonoplast membrane breakdown. Both critical electric field strengths depended on the number of pulses applied. Application of a single pulse at an electric field up to 333 V/cm had no observable effect on any measured properties, while significant differences were observed for n≥10. The minimum electric field strength required to cause a measurable property change decreased with the number of pulses. The results also suggest that PEF treatment may be more efficient if a higher electric field strength is applied for a fewer pulses.

  5. High field superconductor development and understanding

    Energy Technology Data Exchange (ETDEWEB)

    Larbalestier, David C. [Florida State Univ., Tallahassee, FL (United States); Lee, Peter J. [Florida State Univ., Tallahassee, FL (United States); Tarantini, Chiara [Florida State Univ., Tallahassee, FL (United States)

    2014-09-28

    All present circular accelerators use superconducting magnets to bend and to focus the particle beams. The most powerful of these machines is the large hadron collider (LHC) at CERN. The main ring dipole magnets of the LHC are made from Nb-Ti but, as the machine is upgraded to higher luminosity, more powerful magnets made of Nb3Sn will be required. Our work addresses how to make the Nb3Sn conductors more effective and more suitable for use in the LHC. The most important property of the superconducting conductor used for an accelerator magnet is that it must have very high critical current density, the property that allows the generation of high magnetic fields in small spaces. Nb3Sn is the original high field superconductor, the material which was discovered in 1960 to allow a high current density in the field of about 9 T. For the high luminosity upgrade of the LHC, much higher current densities in fields of about 12 Tesla will be required. The critical value of the current density is of order 2600 A/mm2 in a field of 12 Tesla. But there are very important secondary factors that complicate the attainment of this critical current density. The first is that the effective filament diameter must be no larger than about 40 µm. The second factor is that 50% of the cross-section of the Nb3Sn conductor that is pure copper must be protected from any poisoning by any Sn leakage through the diffusion barrier that protects the package of niobium and tin from which the Nb3Sn is formed by a high temperature reaction. These three, somewhat conflicting requirements, mean that optimization of the conductor is complex. The work described in this contract report addresses these conflicting requirements. They show that very sophisticated characterizations can uncover the way to satisfy all 3 requirements and they also suggest that the ultimate optimization of Nb3Sn is still not yet in sight

  6. Dimension dependence of the critical phenomena in gravitational collapse of massless scalar field

    Science.gov (United States)

    Bland, Jason Bryan

    2007-12-01

    A study of the critical behaviour which is observed in numerical calculations of spherically symmetric scalar field collapse has been performed. The gravitational collapse calculations are carried out using the field equations of Einstein's general theory of relativity in the context of a two dimensional dilaton gravity theory. The problem is formulated by considering a spherically symmetric matter distribution in an arbitrary number of space-time dimensions greater than three. A spherical distribution will only depend on two space-time coordinates, therefore, the action of the model can be reduced to a specific case of a 1 + 1 dilaton gravity theory. The evolution equations of the problem are simplified by carrying out a conformal transformation of the metric field. The number of space-time dimensions then appears as an input parameter of the field equations. Initial data is defined on a discrete space-time grid and numerical simulations of gravitational collapse are carried out. The computer code is optimized to increase numerical stability near the critical solutions. Discrete self-similarity and mass scaling in the near critical solutions are observed for each of the dimensions studied. The critical phenomena are described with a high level of confidence by smooth functions of space-time dimension. It is hypothesized that the critical solution of the theory at the limit of large dimension is discretely self-similar with a period of 5/2 and contains critical scaling with a constant of 1/2. Evidence will also be presented which suggests the critical solution in three dimensions with zero cosmological constant is not discretely self-similar but contains a critical scaling constant of approximately 0.11.

  7. Dependence of the critical current density on the first matching field density

    Energy Technology Data Exchange (ETDEWEB)

    Obaidat, I.M. [Department of Physics, United Arab Emirates University, Al-Ain 17551 (United Arab Emirates)], E-mail: iobaidat@uaeu.ac.ae; Benkraouda, M.; Khawaja, U. Al [Department of Physics, United Arab Emirates University, Al-Ain 17551 (United Arab Emirates)

    2008-10-01

    Molecular dynamic simulations were carried out to investigate the properties of the critical depinning force in high temperature superconductors at several vortex densities at the first matching field. The study was conducted on samples with periodic square arrays of vortices and pinning sites. The variables in the simulations were the vortex density, the pinning sites density, the temperature, the pinning strength, the size of pinning sites. The critical depinning force is found to decrease with temperature for all first matching field densities. The rate of this decrease was found to be slower as the pinning strength and size of pinning site gets larger. At low temperatures and for large pinning strengths, the critical depinning force was found to decrease with increasing the first matching field density. But very interesting results were obtained at moderate temperatures where the critical depinning force was found to increase as the first matching field density increases. The same behavior of the critical depinning force was found at low temperatures, for small pinning strengths. These unexpected results were attributed to a vortex structural phase transition from a disordered state to an ordered state.

  8. Development of high temperature superconductors having high critical current density

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Gye Wong; Kim, C. J.; Lee, H.G.; Kwon, S. C.; Lee, H. J.; Kim, K. B.; Park, J. Y.; Jung, C. H

    2000-08-01

    Fabrication of high T{sub c} superconductors and its applications for electric power device were carried out for developing superconductor application technologies. High quality YBCO superconductors was fabricated by melt texture growth, top-seeded melt growth process and multi-seeded melt growth process and the properties was compared. The critical current density of the melt processed YBCO superconductors was about few 10,000 A/cm{sup 2} and the levitation force was 50 N. The processing time needed for the growth of the 123 single grain was greatly reduced by applying multi-seeding without no significant degradation of the levitation force. The multi-seeded melt growth process was confirmed as a time-saving and cost-effective method for the fabrication of bulk superconductors with controlled crystallographic orientation.

  9. Static Magnetic Field Therapy: A Critical Review of Treatment Parameters

    Directory of Open Access Journals (Sweden)

    Agatha P. Colbert

    2009-01-01

    Full Text Available Static magnetic field (SMF therapy, applied via a permanent magnet attached to the skin, is used by people worldwide for self-care. Despite a lack of established SMF dosage and treatment regimens, multiple studies are conducted to evaluate SMF therapy effectiveness. Our objectives in conducting this review are to: (i summarize SMF research conducted in humans; (ii critically evaluate reporting quality of SMF dosages and treatment parameters and (iii propose a set of criteria for reporting SMF treatment parameters in future clinical trials. We searched 27 electronic databases and reference lists. Only English language human studies were included. Excluded were studies of electromagnetic fields, transcranial magnetic stimulation, magnets placed on acupuncture points, animal studies, abstracts, posters and editorials. Data were extracted on clinical indication, study design and 10 essential SMF parameters. Three reviewers assessed quality of reporting and calculated a quality assessment score for each of the 10 treatment parameters. Fifty-six studies were reviewed, 42 conducted in patient populations and 14 in healthy volunteers. The SMF treatment parameters most often and most completely described were site of application, magnet support device and frequency and duration of application. Least often and least completely described were characteristics of the SMF: magnet dimensions, measured field strength and estimated distance of the magnet from the target tissue. Thirty-four (61% of studies failed to provide enough detail about SMF dosage to permit protocol replication by other investigators. Our findings highlight the need to optimize SMF dosing parameters for individual clinical conditions before proceeding to a full-scale clinical trial.

  10. Electromagnetic waves destabilized by runaway electrons in near-critical electric fields

    CERN Document Server

    Kómár, A; Fülöp, T

    2013-01-01

    Runaway electron distributions are strongly anisotropic in velocity space. This anisotropy is a source of free energy that may destabilize electromagnetic waves through a resonant interaction between the waves and the energetic electrons. In this work we investigate the high-frequency electromagnetic waves that are destabilized by runaway electron beams when the electric field is close to the critical field for runaway acceleration. Using a runaway electron distribution appropriate for the near-critical case we calculate the linear instability growth rate of these waves and conclude that the obliquely propagating whistler waves are most unstable. We show that the frequencies, wave numbers and propagation angles of the most unstable waves depend strongly on the magnetic field. Taking into account collisional and convective damping of the waves, we determine the number density of runaways that is required to destabilize the waves and show its parametric dependences.

  11. Gauge-field-assisted Kekul\\'e quantum criticality

    CERN Document Server

    Scherer, Michael M

    2016-01-01

    We study the quantum phase transition of $U(1)$ - charged Dirac fermions Yukawa-coupled to the Kekul\\'e valence bond solid order parameter with $Z_3$ symmetry of the honeycomb lattice. The symmetry allows for the presence of the term in the action which is cubic in the Kekul\\'e order parameter, and which is expected to prevent the quantum phase transition in question from being continuous. The Gross-Neveu-Yukawa theory for the transition is investigated using a perturbative renormalization group and within the $\\epsilon$ expansion close to four space-time dimensions. For a vanishing $U(1)$ charge we show that quantum fluctuations may render the phase transition continuous only sufficiently far away from 3+1 dimensions, where the validity of the conclusions based on the leading order $\\epsilon$ expansion appear questionable. In the presence of a fluctuating gauge field, on the other hand, we find quantum critical behavior even at weak coupling to appear close to 3+1 dimensions, that is, within the domain of va...

  12. Anisotropies of the lower and upper critical fields in MgB2 single crystals.

    Science.gov (United States)

    Lyard, L; Szabó, P; Klein, T; Marcus, J; Marcenat, C; Kim, K H; Kang, B W; Lee, H S; Lee, S I

    2004-02-01

    The temperature dependence of the upper (H(c2)) and lower (H(c1)) critical fields has been deduced from Hall probe magnetization measurements of high quality MgB2 single crystals along the two main crystallographic directions. We show that Gamma(H(c2))=H(c2 axially ab)/H(c2 axially c) and Gamma(H(c1))=H(c1 axially c)/H(c1 axially ab) differ significantly at low temperature (being approximately 5 and approximately 1, respectively) and have opposite temperature dependencies. We suggest that MgB2 can be described by a single field dependent anisotropy parameter gamma(H) (=lambda(c)/lambda(ab)=xi(ab)/xi(c)) that increases from Gamma(H(c1)) at low field to Gamma(H(c2)) at high field.

  13. Criticality issues with highly enriched fuels in a repository environment

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, L.L. [Lockheed Martin Idaho Technologies Co., Idaho Falls, ID (United States); Sanchez, L.C.; Rath, J.S. [Sandia National Labs., Albuquerque, NM (United States)

    1998-03-01

    This paper presents preliminary analysis of a volcanic tuff repository containing a combination of low enrichment commercial spent nuclear fuels (SNF) and DOE-owned SNF packages. These SNFs were analyzed with respect to their criticality risks. Disposal of SNF packages containing significant fissile mass within a geologic repository must comply with current regulations relative to criticality safety during transportation and handling within operational facilities. However, once the repository is closed, the double contingency credits for criticality safety are subject to unremediable degradation, (e.g., water intrusion, continued presence of neutron absorbers in proximity to fissile material, and fissile material reconfiguration). The work presented in this paper focused on two attributes of criticality in a volcanic tuff repository for near-field and far-field scenarios: (1) scenario conditions necessary to have a criticality, and (2) consequences of a nuclear excursion that are components of risk. All criticality consequences are dependent upon eventual water intrusion into the repository and subsequent breach of the disposal package. Key criticality parameters necessary for a critical assembly are: (1) adequate thermal fissile mass, (2) adequate concentration of fissile material, (3) separation of neutron poison from fissile materials, and (4) sufficient neutron moderation (expressed in units of moderator to fissile atom ratios). Key results from this study indicated that the total energies released during a single excursion are minimal (comparable to those released in previous solution accidents), and the maximum frequency of occurrence is bounded by the saturation and temperature recycle times, thus resulting in small criticality risks.

  14. High Critical Current in Metal Organic Derived YBCO Films

    Science.gov (United States)

    2010-10-31

    Contract No. FA9550-07-C-0034 “High Critical Current in Metal Organic Derived YBCO Films” Final Report Prepared for: Dr. Harold...Critical Current in Metal Organic Derived YBCO Films 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT...Project focused on optimization of the Metal Organic Deposition (MOD) process for deposition thick, high critical current YBCO films for use in the

  15. Critical Assessment 14: High Entropy Alloys and Their Development as Structural Materials (Postprint)

    Science.gov (United States)

    2015-01-01

    AFRL-RX-WP-JA-2015-0219 CRITICAL ASSESSMENT 14: HIGH ENTROPY ALLOYS AND THEIR DEVELOPMENT AS STRUCTURAL MATERIALS (POSTPRINT) Daniel...December 2014 4. TITLE AND SUBTITLE CRITICAL ASSESSMENT 14: HIGH ENTROPY ALLOYS AND THEIR DEVELOPMENT AS STRUCTURAL MATERIALS (POSTPRINT) 5a...available at DOI 10.1179/1743284714Y.1142 0000000749. 14. ABSTRACT The field of high entropy alloys has exploded in its first 10 years. Vast

  16. Penetration dynamics of a magnetic field pulse into high-? superconductors

    Science.gov (United States)

    Meerovich, V.; Sinder, M.; Sokolovsky, V.; Goren, S.; Jung, G.; Shter, G. E.; Grader, G. S.

    1996-12-01

    The penetration of a magnetic field pulse into a high-0953-2048/9/12/004/img9 superconducting plate is investigated experimentally and theoretically. It follows from our experiments that the threshold of penetration increases with increasing amplitude and/or decreasing duration of the applied pulse. The penetrating field continues to grow as the applied magnetic field decreases. The peculiarities observed are explained in the framework of the extended critical state model. It appears that the deviations from Bean's classical critical state model are characterized by a parameter equal to the square of the ratio of plate thickness to skin depth. The applicability of the classical critical state model is restricted by the condition that this parameter is much less than 1. This condition is also the criterion for the applicability of pulse methods of critical current measurements.

  17. Affective and neural reactivity to criticism in individuals high and low on perceived criticism.

    Science.gov (United States)

    Hooley, Jill M; Siegle, Greg; Gruber, Staci A

    2012-01-01

    People who have remitted from depression are at increased risk for relapse if they rate their relatives as being critical of them on a simple self-report measure of Perceived Criticism (PC). To explore neural mechanisms associated with this we used functional magnetic resonance imaging (fMRI) to examine how people with different levels of PC responded to hearing criticism from their own mothers. To maximize variability in affective reactivity, depressed, recovered depressed, and healthy control participants (n = 33) were classified as high or low in PC based on a median split. They were then exposed to personally-relevant critical and praising comments from their mothers. Perceived Criticism levels were unrelated to depression status and to negative mood change after hearing criticism. However, compared to low PC participants, those who scored high on PC showed differential activation in a network of regions associated with emotion reactivity and regulation, including increased amygdala activity and decreased reactions in prefrontal regulatory regions when they heard criticism. This was not the case for praise. Criticism may be a risk factor for relapse because it helps to "train" pathways characteristic of depressive information processing. The Perceived Criticism measure may help identify people who are more susceptible to this vulnerability.

  18. Critical Development? Using a Critical Theory Lens to Examine the Current Role of Evaluation in the Youth-Development Field

    Science.gov (United States)

    Zeller-Berkman, Sarah

    2010-01-01

    A critical theory lens is used to explore the role of evaluation in youth development, a field aimed at recognizing youth as assets. A theory of change in the field is questioned for its emphasis on individual youth outcomes as programmatic outcome measures. A review of 209 evaluations of 131 programs in the Harvard Family Research Project's…

  19. Anisotropy of the critical current in MgB2 tapes made of high energy milled precursor powder

    DEFF Research Database (Denmark)

    Hässler, W.; Kovac, P.; Eisterer, M.;

    2010-01-01

    For applications of MgB2 wires or tapes, high critical currents in high magnetic fields are essential. By using tapes in superconducting coils the anisotropic behaviour of the critical current, i.e. the dependence on the direction of the external field in relation to the tape surface, has...

  20. Criticality safety in high explosives dissolution

    Energy Technology Data Exchange (ETDEWEB)

    Troyer, S.D.

    1997-06-01

    In 1992, an incident occurred at the Pantex Plant in which the cladding around a fissile material component (pit) cracked during dismantlement of the high explosives portion of a nuclear weapon. Although the event did not result in any significant contamination or personnel exposures, concerns about the incident led to the conclusion that the current dismantlement process was unacceptable. Options considered for redesign, dissolution tooling design considerations, dissolution tooling design features, and the analysis of the new dissolution tooling are summarized. The final tooling design developed incorporated a number of safety features and provides a simple, self-contained, low-maintenance method of high explosives removal for nuclear explosive dismantlement. Analyses demonstrate that the tooling design will remain subcritical under normal, abnormal, and credible accident scenarios. 1 fig.

  1. Torsional oscillations of neutron stars with highly tangled magnetic fields

    CERN Document Server

    Sotani, Hajime

    2015-01-01

    To determine the frequencies of magnetic oscillations in the neutron stars with highly tangled magnetic fields, we derive the perturbation equations. We assume that the field strength of the global magnetic structure is so small that such fields are negligible compared with the tangled fields, which may still be far from a realistic configuration. Then, we systematically examine the spectra of the magnetic oscillations, as varying the magnetic field strength and stellar mass. The frequencies without crust elasticity are completely proportional to the strength of magnetic field, whose proportionality constant depends strongly on the stellar mass. On the other hand, the oscillation spectra with crust elasticity become more complicated, where the frequencies even for weak magnetic fields are different from the crustal torsional oscillations without magnetic fields. For discussing the spectra, the critical field strength can play an important role, which is determined in such a way that the shear velocity is equi...

  2. Critical state in a low-dimensional metal induced by strong magnetic fields

    Science.gov (United States)

    Harrison, N.; Balicas, L.; Brooks, J. S.; Tokumoto, M.

    2000-12-01

    We present the results of magnetotransport and magnetic torque measurements on the α-(BEDT-TTF)2KHg(SCN)4 charge-transfer salt within its high-magnetic-field phase, in magnetic fields extending to 33 T and temperatures as low as 27 mK. While the experimentally determined phase diagram closely resembles that predicted by theoretical models for charge-density waves in strong magnetic fields, the phase that occurs at fields above ~23 T, which is expected to be either a modulated charge-density wave phase or a charge/spin-density wave hybrid, exhibits unusual physical properties that are most atypical of a density wave ground state. Notably, the resistivity undergoes a dramatic drop below ~3 K within this phase, falling in an approximately exponential fashion at low temperatures, while the magnetic torque undergoes extensive hysteresis. This hysteresis, which occurs over a broad range of fields and gives rise to a large negative differential susceptibility ∂M/∂B on reversing the direction of sweep of the magnetic field, is strongly temperature dependent and also has several of the physical characteristics predicted by critical-state models normally used to describe the pinning of vortices in type II superconductors. Such a behavior appears therefore only to be explained consistently in terms of persistent currents within the high-magnetic-field phase of α-(BEDT-TTF)2KHg(SCN)4, although the origin of these currents remains an open question.

  3. Upper critical field of as-grown MgB{sub 2} thin films by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Y. [Department of Material Science and Engineering, Iwate University, Iwate Industrial Promotion Center, Iioka shinden 3-35-2, Morioka 020-0852 (Japan)]. E-mail: yharada@luck.ocn.ne.jp; Udsuka, M. [Graduate School of Engineering, Iwate University, Ueda 4-3-5, Morioka 020-8551 (Japan); Takahashi, T. [Graduate School of Engineering, Iwate University, Ueda 4-3-5, Morioka 020-8551 (Japan); Nakanishi, Y. [Graduate School of Engineering, Iwate University, Ueda 4-3-5, Morioka 020-8551 (Japan); Yoshizawa, M. [Graduate School of Engineering, Iwate University, Ueda 4-3-5, Morioka 020-8551 (Japan)

    2005-04-30

    Superconducting thin films of magnesium diboride (MgB{sub 2}) were prepared on MgO(001) substrate by molecular beam epitaxy in the co-evaporation conditions of low deposition rate and ultra-high vacuum. A superconducting transition with the onset temperature of 31.2K was confirmed by both transport and magnetization measurements. The upper critical fields are obtained from measurement of the field dependence of the resistivity. It was estimated that the upper critical field at 0K was more than 15T. The upper critical field anisotropy ratio, H{sub C2,ab}(0)/H{sub C2,c}(0), was estimated to be 1.78 from the magnetic field-temperature phase diagram for as-grown MgB{sub 2} thin films.

  4. Critical $O(N)$ models in the complex field plane

    CERN Document Server

    Litim, Daniel F

    2016-01-01

    Local and global scaling solutions for $O(N)$ symmetric scalar field theories are studied in the complexified field plane with the help of the renormalisation group. Using expansions of the effective action about small, large, and purely imaginary fields, we obtain and solve exact recursion relations for all couplings and determine the $3d$ Wilson-Fisher fixed point analytically. For all $O(N)$ universality classes, we further establish that Wilson-Fisher fixed point solutions display singularities in the complex field plane, which dictate the radius of convergence for real-field expansions of the effective action. At infinite $N$, we find closed expressions for the convergence-limiting singularities and prove that local expansions of the effective action are powerful enough to uniquely determine the global Wilson-Fisher fixed point for any value of the fields. Implications of our findings for interacting fixed points in more complicated theories are indicated.

  5. The critical role of force-fields in property prediction

    DEFF Research Database (Denmark)

    Jonsdottir, Svava Osk; Welsh, William J.; Rasmussen, Kjeld

    1999-01-01

    of conformational energydifferences and interaction energies vary significantly from one force-field to another. As a test for the reliability of the non-bonded interactions, vapor-liquid equilibrium (VLE) data have been calculated for a small number of systems using three different force-fields. The force...

  6. Curator and Critic: Role of the Assessor in Aesthetic Fields

    Science.gov (United States)

    Jacobs, Rachael

    2012-01-01

    Assessment in aesthetic fields presents a myriad of challenges in the higher education environment. This paper uses a metaphorical representation to explore the role of assessors within aesthetic assessment settings in higher education. It begins with a discussion of aesthetic fields and an exploration of the role of assessment in this area.…

  7. Investigation of the Critical Current Density of YBaCuO high-temperature Superconductor Ceramic

    OpenAIRE

    METSKHVARISHVILI, I. R.; KEKELIDZE, N. P.; METSKHVARISHVILI, M. R.

    2002-01-01

    The method of high harmonics is used to investigate penetration of low magnetic fields within the Y1Ba2Cu3O7 high-temperature superconductor ceramic. Given experimental results are explained by the modal dependencies between the value of critical current density and the magnetic induction B: jc(B) = jc(0){\\frac{{B02}} {{B02 + B2}}}.

  8. High-field spin dynamics of antiferromagnetic quantum spin chains

    DEFF Research Database (Denmark)

    Enderle, M.; Regnault, L.P.; Broholm, C.;

    2000-01-01

    The characteristic internal order of macroscopic quantum ground states in one-dimensional spin systems is usually not directly accessible, but reflected in the spin dynamics and the field dependence of the magnetic excitations. In high magnetic fields quantum phase transitions are expected. We...... present recent work on the high-field spin dynamics of the S = I antiferromagnetic Heisenberg chains NENP (Haldane ground state) and CsNiCl3 (quasi-1D HAF close to the quantum critical point), the uniform S = 1/2 chain CTS, and the spin-Peierls system CuGeO3. (C) 2000 Elsevier Science B,V. All rights...

  9. Vortex-lattice pinning and critical current density in anisotropic high-temperature superconductors

    Science.gov (United States)

    Li, Yingxu; Li, Xiangyu; Kang, Guozheng; Gao, Yuanwen

    2016-10-01

    The anisotropy of critical current density is an impressive manifestation in the physics of high-temperature superconductors. We develop an analytical characterization of anisotropic flux-lattice pinning and critical current density in a system of random point defects. The effect of superconducting anisotropy on the pinning force and critical current density is formulated. The in-plane/out-of-plane anisotropy and microscopic characteristic lengths are incorporated in the field and angular dependence of the critical current density. This is helpful in understanding the physical essence of the scaling behavior in the experiments for critical current anisotropy. We discuss the role of strong and weak point defects in the anisotropic flux-lattice pinning. Relevance of the theory to the critical-state model is dictated as well.

  10. Dynamics of Gauge Fields at High Temperature

    NARCIS (Netherlands)

    Nauta, B.J.

    2000-01-01

    An effective description of dynamical Bose fields is provided by the classical (high-temperature) limit of thermal field theory. The main subject of this thesis is to improve the ensuing classical field theory, that is, to include the dominant quantum corrections and to add counter terms for the Ray

  11. Dynamics of Gauge Fields at High Temperature

    NARCIS (Netherlands)

    Nauta, B.J.

    2000-01-01

    An effective description of dynamical Bose fields is provided by the classical (high-temperature) limit of thermal field theory. The main subject of this thesis is to improve the ensuing classical field theory, that is, to include the dominant quantum corrections and to add counter terms for the Ray

  12. Automated Critical Peak Pricing Field Tests: Program Descriptionand Results

    Energy Technology Data Exchange (ETDEWEB)

    Piette, Mary Ann; Watson, David; Motegi, Naoya; Kiliccote, Sila; Xu, Peng

    2006-04-06

    California utilities have been exploring the use of critical peak prices (CPP) to help reduce needle peaks in customer end-use loads. CPP is a form of price-responsive demand response (DR). Recent experience has shown that customers have limited knowledge of how to operate their facilities in order to reduce their electricity costs under CPP (Quantum 2004). While the lack of knowledge about how to develop and implement DR control strategies is a barrier to participation in DR programs like CPP, another barrier is the lack of automation of DR systems. During 2003 and 2004, the PIER Demand Response Research Center (DRRC) conducted a series of tests of fully automated electric demand response (Auto-DR) at 18 facilities. Overall, the average of the site-specific average coincident demand reductions was 8% from a variety of building types and facilities. Many electricity customers have suggested that automation will help them institutionalize their electric demand savings and improve their overall response and DR repeatability. This report focuses on and discusses the specific results of the Automated Critical Peak Pricing (Auto-CPP, a specific type of Auto-DR) tests that took place during 2005, which build on the automated demand response (Auto-DR) research conducted through PIER and the DRRC in 2003 and 2004. The long-term goal of this project is to understand the technical opportunities of automating demand response and to remove technical and market impediments to large-scale implementation of automated demand response (Auto-DR) in buildings and industry. A second goal of this research is to understand and identify best practices for DR strategies and opportunities. The specific objectives of the Automated Critical Peak Pricing test were as follows: (1) Demonstrate how an automated notification system for critical peak pricing can be used in large commercial facilities for demand response (DR). (2) Evaluate effectiveness of such a system. (3) Determine how customers

  13. Automated Critical Peak Pricing Field Tests: Program Descriptionand Results

    Energy Technology Data Exchange (ETDEWEB)

    Piette, Mary Ann; Watson, David; Motegi, Naoya; Kiliccote, Sila; Xu, Peng

    2006-04-06

    California utilities have been exploring the use of critical peak prices (CPP) to help reduce needle peaks in customer end-use loads. CPP is a form of price-responsive demand response (DR). Recent experience has shown that customers have limited knowledge of how to operate their facilities in order to reduce their electricity costs under CPP (Quantum 2004). While the lack of knowledge about how to develop and implement DR control strategies is a barrier to participation in DR programs like CPP, another barrier is the lack of automation of DR systems. During 2003 and 2004, the PIER Demand Response Research Center (DRRC) conducted a series of tests of fully automated electric demand response (Auto-DR) at 18 facilities. Overall, the average of the site-specific average coincident demand reductions was 8% from a variety of building types and facilities. Many electricity customers have suggested that automation will help them institutionalize their electric demand savings and improve their overall response and DR repeatability. This report focuses on and discusses the specific results of the Automated Critical Peak Pricing (Auto-CPP, a specific type of Auto-DR) tests that took place during 2005, which build on the automated demand response (Auto-DR) research conducted through PIER and the DRRC in 2003 and 2004. The long-term goal of this project is to understand the technical opportunities of automating demand response and to remove technical and market impediments to large-scale implementation of automated demand response (Auto-DR) in buildings and industry. A second goal of this research is to understand and identify best practices for DR strategies and opportunities. The specific objectives of the Automated Critical Peak Pricing test were as follows: (1) Demonstrate how an automated notification system for critical peak pricing can be used in large commercial facilities for demand response (DR). (2) Evaluate effectiveness of such a system. (3) Determine how customers

  14. Computational and experimental analysis of TMS-induced electric field vectors critical to neuronal activation

    Science.gov (United States)

    Krieg, Todd D.; Salinas, Felipe S.; Narayana, Shalini; Fox, Peter T.; Mogul, David J.

    2015-08-01

    Objective. Transcranial magnetic stimulation (TMS) represents a powerful technique to noninvasively modulate cortical neurophysiology in the brain. However, the relationship between the magnetic fields created by TMS coils and neuronal activation in the cortex is still not well-understood, making predictable cortical activation by TMS difficult to achieve. Our goal in this study was to investigate the relationship between induced electric fields and cortical activation measured by blood flow response. Particularly, we sought to discover the E-field characteristics that lead to cortical activation. Approach. Subject-specific finite element models (FEMs) of the head and brain were constructed for each of six subjects using magnetic resonance image scans. Positron emission tomography (PET) measured each subject’s cortical response to image-guided robotically-positioned TMS to the primary motor cortex. FEM models that employed the given coil position, orientation, and stimulus intensity in experimental applications of TMS were used to calculate the electric field (E-field) vectors within a region of interest for each subject. TMS-induced E-fields were analyzed to better understand what vector components led to regional cerebral blood flow (CBF) responses recorded by PET. Main results. This study found that decomposing the E-field into orthogonal vector components based on the cortical surface geometry (and hence, cortical neuron directions) led to significant differences between the regions of cortex that were active and nonactive. Specifically, active regions had significantly higher E-field components in the normal inward direction (i.e., parallel to pyramidal neurons in the dendrite-to-axon orientation) and in the tangential direction (i.e., parallel to interneurons) at high gradient. In contrast, nonactive regions had higher E-field vectors in the outward normal direction suggesting inhibitory responses. Significance. These results provide critical new

  15. Nucleation of bulk superconductivity close to critical magnetic fields

    DEFF Research Database (Denmark)

    Fournais, Søren; Kachmar, Ayman

    2011-01-01

    threshold value of the applied magnetic field for which bulk superconductivity contributes to the leading order of the energy. Furthermore, the energy of the bulk is related to that of the Abrikosov problem in a periodic lattice. A key ingredient of the proof is a novel L∞ -bound which is of independent...

  16. Cyclotron Line Features from Near-Critical Fields II on the Effect of Anisotropic Radiation Fields

    CERN Document Server

    Araya-Gochez, R A; Araya-Gochez, Rafael A.; Harding, Alice K.

    2000-01-01

    We assess the impact of radiation anisotropy on the line shapes that result from relativistic magnetic Compton scattering in the low-density/high-field regime. A Monte Carlo implementation of radiation transport allows for spatial diffusion of photons in arbitrary geometries and accounts for relativistic angular redistribution. The cross section includes natural line widths and photon "spawning" from up to fourth harmonic photons. In our first paper we noted that even if the photon injection is isotropic a strongly anisotropic radiation field rapidly ensues. We now investigate the angular distribution of cyclotron spectra emerging from an internally irradiated magnetized plasma with a prescribed global geometry (either cylindrical or plane parallel) and the effects of anisotropic photon injection on the line shapes. Varying the input angular distribution permits a better understanding of the line formation process in more realistic scenarios where the radiative mechanisms are influenced by the intrinsic aniso...

  17. Synchrotron Applications of High Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-07-01

    This workshop aims at discussing the scientific potential of X-ray diffraction and spectroscopy in magnetic fields above 30 T. Pulsed magnetic fields in the range of 30 to 40 T have recently become available at Spring-8 and the ESRF (European synchrotron radiation facility). This document gathers the transparencies of the 6 following presentations: 1) pulsed magnetic fields at ESRF: first results; 2) X-ray spectroscopy and diffraction experiments by using mini-coils: applications to valence state transition and frustrated magnet; 3) R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}: an ideal system to be studied in X-ray under high magnetic field?; 4) high field studies at the Advanced Photon Source: present status and future plans; 5) synchrotron X-ray diffraction studies under extreme conditions; and 6) projects for pulsed and steady high magnetic fields at the ESRF.

  18. Magnet Lab Highlight: Upper critical field reaches 90 tesla near the Mott transition in fulleride superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Mcdonald, Ross David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-06-05

    The alkali-doped fullerides provide the first example of a transition from a three-dimensional Mott insulator to a superconductor, enabling the effects of both dimensionality and electron correlation on superconductivity to be explored. Chemically the alkali species tunes the superconductivity in the vicinity of the the Mott transition via sample volume. Measuring the relationship between the superconducting transition temperature and upper critical field reveals a crossover from weak- to strong-coupling associated with the dynamical Jahn–Teller effect as the Mott transition is approached. The use of pulsed magnets is required because the upper critical field is enhanced in the vicinity of the Mott insulating phase, reaching 90 T for RbxCs3-xC60 — the highest among cubic crystals. This required close collaboration between Prof Kasahara’s group and the Mag Lab to design rf-measurements compatible with sample encapsulation in an inert atmosphere. The concomitant increase of pairing strength with lattice volume near the Mott transition suggest that the cooperative interplay between molecular electronic structure and strong electron correlations plays a key role in realizing robust superconductivity (with high-TC and high-HC2).

  19. Effect of External Magnetic Field on Critical Current for the Onset of Virtual Cathode Oscillations in Relativistic Electron Beams

    CERN Document Server

    Hramov, Alexander E; Morozov, Mikhail; Mushtakov, Alexander

    2008-01-01

    In this Letter we research the space charge limiting current value at which the oscillating virtual cathode is formed in the relativistic electron beam as a function of the external magnetic field guiding the beam electrons. It is shown that the space charge limiting (critical) current decreases with growth of the external magnetic field, and that there is an optimal induction value of the magnetic field at which the critical current for the onset of virtual cathode oscillations in the electron beam is minimum. For the strong external magnetic field the space charge limiting current corresponds to the analytical relation derived under the assumption that the motion of the electron beam is one-dimensional [High Power Microwave Sources. Artech House Microwave Library, 1987. Chapter~13]. Such behavior is explained by the characteristic features of the dynamics of electron space charge in the longitudinal and radial directions in the drift space at the different external magnetic fields.

  20. Rotating sample magnetometer for cryogenic temperatures and high magnetic fields.

    Science.gov (United States)

    Eisterer, M; Hengstberger, F; Voutsinas, C S; Hörhager, N; Sorta, S; Hecher, J; Weber, H W

    2011-06-01

    We report on the design and implementation of a rotating sample magnetometer (RSM) operating in the variable temperature insert (VTI) of a cryostat equipped with a high-field magnet. The limited space and the cryogenic temperatures impose the most critical design parameters: the small bore size of the magnet requires a very compact pick-up coil system and the low temperatures demand a very careful design of the bearings. Despite these difficulties the RSM achieves excellent resolution at high magnetic field sweep rates, exceeding that of a typical vibrating sample magnetometer by about a factor of ten. In addition the gas-flow cryostat and the high-field superconducting magnet provide a temperature and magnetic field range unprecedented for this type of magnetometer.

  1. Critical Science Education in a Suburban High School Chemistry Class

    Science.gov (United States)

    Ashby, Patrick

    To improve students' scientific literacy and their general perceptions of chemistry, I enacted critical chemistry education (CCE) in two "regular level" chemistry classes with a group of 25 students in a suburban, private high school as part of this study. CCE combined the efforts of critical science educators (Fusco & Calabrese Barton, 2001; Gilbert 2013) with the performance expectations of the Next Generation Science Standards (NGSS) (NGSS Lead States, 2013a) to critically transform the traditional chemistry curriculum at this setting. Essentially, CCE engages students in the critical exploration of socially situated chemistry content knowledge and requires them to demonstrate this knowledge through the practices of science. The purpose of this study was to gauge these students development of chemistry content knowledge, chemistry interest, and critical scientific literacy (CSL) as they engaged in CCE. CSL was a construct developed for this study that necessarily combined the National Research Center's (2012) definition of scientific literacy with a critical component. As such, CSL entailed demonstrating content knowledge through the practices of science as well as the ability to critically analyze the intersections between science content and socially relevant issues. A mixed methods, critical ethnographic approach framed the collection of data from open-ended questionnaires, focus group interviews, Likert surveys, pre- and post unit tests, and student artifacts. These data revealed three main findings: (1) students began to develop CSL in specific, significant ways working through the activities of CCE, (2) student participants of CCE developed a comparable level of chemistry content understanding to students who participated in a traditional chemistry curriculum, and (3) CCE developed a group of students' perceptions of interest in chemistry. In addition to being able to teach students discipline specific content knowledge, the implications of this study are

  2. Study of HTS Wires at High Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    Turrioni, D.; Barzi, E.; Lamm, M.J.; Yamada, R.; Zlobin, A.V.; Kikuchi, A.; /Fermilab

    2009-01-01

    Fermilab is working on the development of high field magnet systems for ionization cooling of muon beams. The use of high temperature superconducting (HTS) materials is being considered for these magnets using Helium refrigeration. Critical current (I{sub c}) measurements of HTS conductors were performed at FNAL and at NIMS up to 28 T under magnetic fields at zero to 90 degree with respect to the sample face. A description of the test setups and results on a BSCCO-2223 tape and second generation (2G) coated conductors are presented.

  3. Upper critical field in dirty two-band superconductors: breakdown of the anisotropic Ginzburg-Landau theory

    NARCIS (Netherlands)

    Golubov, Alexandre Avraamovitch; Koshelev, A.E.

    2003-01-01

    We investigate the upper critical field in a dirty two-band superconductor within quasiclassical Usadel equations. The regime of very high anisotropy in the quasi-2D band, relevant for MgB2, is considered. We show that strong disparities in pairing interactions and diffusion constant anisotropies fo

  4. High critical temperature superconductor Josephson junctions for quantum circuit applications

    Energy Technology Data Exchange (ETDEWEB)

    Bauch, T; Gustafsson, D; Cedergren, K; Nawaz, S; Mumtaz Virk, M; Lombardi, F [Department of Microtechnology and Nanoscience, MC2, Chalmers University of Technology, Goeteborg (Sweden); Pettersson, H; Olsson, E [Department of Applied Physics, Chalmers University of Technology, Goeteborg (Sweden)], E-mail: bauch@chalmers.se

    2009-12-15

    Recent findings of macroscopic quantum properties in high critical temperature superconductor (HTS) Josephson junctions (JJs) point toward the need to revise the role of zero energy quasi-particles in this novel superconductor. We will discuss the possibility of designing superconducting artificial atoms in a transmon configuration to study the low energy excitation spectra of HTS. We have engineered high quality grain boundary JJs on low dielectric constant substrates. By fabricating submicron junctions, we extract values of capacitance and Josephson critical current densities that satisfy the main transmon design requirements. Moreover, the measured critical current noise power extrapolated at 1 Hz gives a dephasing time of 25 ns, which indicates that the observation of macroscopic quantum coherent effects in HTS JJ is a feasible task.

  5. Pressure Evolution of a Field-Induced Fermi Surface Reconstruction and of the Neel Critical Field in CeIn3

    Energy Technology Data Exchange (ETDEWEB)

    Petrovic, C.; Purcell, K.M.; Graf, D.; Kano, M.; Bourg, J.; Palm, E.C.; Murphy, T.; McDonald, R.; Mielke, C.H.; Altarawneh, M.M.; Hu, R.; Ebihara, T.; Cooley, J.; Schlottmann, P.; Tozer, S.W.

    2009-06-01

    We report high-pressure skin-depth measurements on the heavy fermion material CeIn{sub 3} in magnetic fields up to 64 T using a self-resonant tank circuit based on a tunnel diode oscillator. At ambient pressure, an anomaly in the skin depth is seen at 45 T. The field where this anomaly occurs decreases with applied pressure until approximately 1.0 GPa, where it begins to increase before merging with the antiferromagnetic phase boundary. Possible origins for this transport anomaly are explored in terms of a Fermi surface reconstruction. The critical magnetic field at which the Neel-ordered phase is suppressed, is also mapped as a function of pressure and extrapolates to the previous ambient-pressure measurements at high magnetic fields and high-pressure measurements at zero magnetic field.

  6. Rydberg EIT in High Magnetic Field

    Science.gov (United States)

    Ma, Lu; Anderson, David; Miller, Stephanie; Raithel, Georg

    2016-05-01

    We present progress towards an all-optical approach for measurements of strong magnetic fields using electromagnetically induced transparency (EIT) with Rydberg atoms in an atomic vapor. Rydberg EIT spectroscopy is a promising technique for the development of atom-based, calibration- and drift-free technology for high magnetic field sensing. In this effort, Rydberg EIT is employed to spectroscopically investigate the response of Rydberg atoms exposed to strong magnetic fields, in which Rydberg atoms are in the strong-field regime. In our setup, two neodymium block magnets are used to generate fields of about 0.8 Tesla, which strongly perturb the atoms. Information on the field strength and direction is obtained by a comparison of experimental spectra with calculated spectral maps. Investigations of magnetic-field inhomogeneities and other decoherence sources will be discussed.

  7. Teaching Critical Reflexivity in Short-Term International Field Courses: Practices and Problems

    Science.gov (United States)

    Glass, Michael R.

    2015-01-01

    This study critiques the use of critical reflexivity in short-term international field courses. Critical reflexivity's benefits include preparing students for professional research, deepening their learning, and giving the chance to see how student perspectives on fieldwork sites are influenced by their own identity and positionality. I use an…

  8. High-field bipolar loss measurement apparatus

    Science.gov (United States)

    Weldon, D.; Thullen, P.; Wollan, J.

    1980-09-01

    An apparatus was constructed to measure dissipation in superconducting wire in high alternating fields. The circuit incorporates a pair of locomotive traction motors as the capacitive circuit element for the bipolar swing. The design, construction and operating characteristics of the field coil and the associated circuitry are described.

  9. Critical endpoint in the QCD phase diagram for extremely strong background magnetic fields

    CERN Document Server

    Endrodi, Gergely

    2015-01-01

    Lattice simulations have demonstrated that a background (electro)magnetic field reduces the chiral/deconfinement transition temperature of quantum chromodynamics for eB < 1 GeV^2. On the level of observables, this reduction manifests itself in an enhancement of the Polyakov loop and in a suppression of the light quark condensates (inverse magnetic catalysis) in the transition region. In this paper, we report on lattice simulations of 1+1+1-flavor QCD at an unprecedentedly high value of the magnetic field eB = 3.25 GeV^2. Based on the behavior of various observables, it is shown that even at this extremely strong field, inverse magnetic catalysis prevails and the transition, albeit becoming sharper, remains an analytic crossover. In addition, we develop an algorithm to directly simulate the asymptotically strong magnetic field limit of QCD. We find strong evidence for a first-order deconfinement phase transition in this limiting theory, implying the presence of a critical endpoint in the QCD phase diagram. ...

  10. Overlay control methodology comparison: field-by-field and high-order methods

    Science.gov (United States)

    Huang, Chun-Yen; Chiu, Chui-Fu; Wu, Wen-Bin; Shih, Chiang-Lin; Huang, Chin-Chou Kevin; Huang, Healthy; Choi, DongSub; Pierson, Bill; Robinson, John C.

    2012-03-01

    Overlay control in advanced integrated circuit (IC) manufacturing is becoming one of the leading lithographic challenges in the 3x and 2x nm process nodes. Production overlay control can no longer meet the stringent emerging requirements based on linear composite wafer and field models with sampling of 10 to 20 fields and 4 to 5 sites per field, which was the industry standard for many years. Methods that have emerged include overlay metrology in many or all fields, including the high order field model method called high order control (HOC), and field by field control (FxFc) methods also called correction per exposure. The HOC and FxFc methods were initially introduced as relatively infrequent scanner qualification activities meant to supplement linear production schemes. More recently, however, it is clear that production control is also requiring intense sampling, similar high order and FxFc methods. The added control benefits of high order and FxFc overlay methods need to be balanced with the increased metrology requirements, however, without putting material at risk. Of critical importance is the proper control of edge fields, which requires intensive sampling in order to minimize signatures. In this study we compare various methods of overlay control including the performance levels that can be achieved.

  11. Microstructures and critical currents in high-{Tc} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Suenaga, Masaki

    1998-11-01

    Microstructural defects are the primary determining factors for the values of critical-current densities in a high {Tc} superconductor after the electronic anisotropy along the a-b plane and the c-direction. A review is made to assess firstly what would be the maximum achievable critical-current density in YBa{sub 2}Cu{sub 3}O{sub 7} if nearly ideal pinning sites were introduced and secondly what types of pinning defects are currently introduced or exist in YBa{sub 2}Cu{sub 3}O{sub 7} and how effective are these in pinning vortices.

  12. Critical behavior in the presence of an order-parameter pinning field

    Science.gov (United States)

    Parisen Toldin, Francesco; Assaad, Fakher F.; Wessel, Stefan

    2017-01-01

    We apply a recently advocated simulation scheme that employs a local order-parameter pinning field to study quantum critical phenomena in the two-dimensional square-lattice bilayer quantum Heisenberg model. Using a world-line quantum Monte Carlo approach, we show that for this model, the pinning-field approach allows to locate the quantum critical point over a wide range of pinning-field strengths. However, the identification of the quantum critical scaling behavior is found to be hard since the pinning field introduces strong corrections to scaling. In order to further elucidate the scaling behavior in this situation, we also study an improved classical lattice model in the three-dimensional Ising universality class by means of Monte Carlo simulations on large lattice sizes, which allow us to employ refined finite-size scaling considerations. A renormalization group analysis exhibits the presence of an important crossover effect from the zero pinning-field to a critical adsorption fixed point. In line with field-theoretical results, we find that at the critical adsorption fixed point the short-distance expansion of the order-parameter profile exhibits a new universal critical exponent. This result also implies the presence of slowly decaying scaling corrections, which we analyze in detail.

  13. Temperature and magnetic field dependence of the critical current in polycrystalline Ba2YCu3O(y)

    Science.gov (United States)

    Obara, H.; Yamasaki, H.; Kimura, Y.; Higashida, Y.; Ishihara, T.

    Temperature and magnetic field dependence on the critical current density Jc of polycrystalline high-Tc oxide superconductor, Ba2YCu3O(y), have been measured. In the low magnetic field range, 0.6 to about 7 kOe, the Jc behavior changed at around 70 K. Below 70 K, Jc showed different temperature dependence between field cooling and zero-field cooling, that is, the Jc value measured when the sample was cooled in a fixed magnetic field, was different from that measured when the sample was cooled in zero magnetic field and then a magnetic field was applied. Above 70 K, however, such different temperature dependence on Jc was not observed. These experimental results can be attributed to the effects of anisotropy. A crossover between the two- and three-dimensional superconductivity is considered to occur.

  14. Application Fields of High-Temperature Superconductors

    OpenAIRE

    Hott, Roland

    2003-01-01

    Potential application fields for cuprate high-temperature superconductors (HTS) and the status of respective projects are reviewed. The availability of a reliable and inexpensive cooling technique will be essential for a future broad acceptance of HTS applications.

  15. Construction of high magnetic field facilities approved

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ On 25 January, the National Development and Reform Commission gave the green light to a proposal to construct high magnetic field facilities for experimental use. The suggestion was jointly submitted by the Ministry of Education and CAS.

  16. Biological systems in high magnetic field

    Science.gov (United States)

    Yamagishi, A.

    1990-12-01

    Diamagnetic orientation of biological systems have been investigated theoretically and experimentally. Fibrinogen, one of blood proteins, were polymerized in static high magnetic fields up to 8 T. Clotted gels composed of oriented fibrin fibers were obtained even in a field as low as 1 T. Red blood cells (RBC) show full orientation with their plane parallel to the applied field of 4 T. It is confirmed experimentally that the magnetic orientation of RBC is caused by diamagnetic anisotropy. Full orientation is also obtained with blood platelet in a field of 3 T.

  17. Magnetic Field Dependence of the Critical Current in S-N Bilayer Thin Films

    Science.gov (United States)

    Sadleir, John E.; Lee, Sang-Jun; Smith, Stephen James; Bandler, Simon; Chervenak, James; Kilbourne, Caroline A.; Finkbeiner, Fred M.; Porter, Frederick S.; Kelley, Richard L.; Adams, Joseph S.; Eckart, Megan E.; Busch, Sarah; Porst, Jan-Patrick

    2013-01-01

    Here we investigate the effects a non-uniform applied magnetic field has on superconducting transition-edge sensors (TESs) critical current. This has implications on TES optimization. It has been shown that TESs resistive transition can be altered by magnetic fields. We have observed critical current rectification effects and explained these effects in terms of a magnetic self-field arising from asymmetric current injection into the sensor. Our TES physical model shows that this magnetic self-field can result in significantly degraded or improved TES performance. In order for this magnetically tuned TES strategy to reach its full potential we are investigating the effect a non-uniform applied magnetic field has on the critical current.

  18. Critical Behavior of Gaussian Model on X Fractal Lattices in External Magnetic Fields

    Institute of Scientific and Technical Information of China (English)

    LI Ying; KONG Xiang-Mu; HUANG Jia-Yin

    2003-01-01

    Using the renormalization group method, the critical behavior of Gaussian model is studied in external magnetic fields on X fractal lattices embedded in two-dimensional and d-dimensional (d > 2) Euclidean spaces, respectively. Critical points and exponents are calculated. It is found that there is long-range order at finite temperature for this model, and that the critical points do not change with the space dimensionality d (or the fractal dimensionality dr). It is also found that the critical exponents are very different from results of Ising model on the same lattices, and that the exponents on X lattices are different from the exact results on translationally symmetric lattices.

  19. Analysis and prediction of the critical regions of antimicrobial peptides based on conditional random fields.

    Directory of Open Access Journals (Sweden)

    Kuan Y Chang

    Full Text Available Antimicrobial peptides (AMPs are potent drug candidates against microbes such as bacteria, fungi, parasites, and viruses. The size of AMPs ranges from less than ten to hundreds of amino acids. Often only a few amino acids or the critical regions of antimicrobial proteins matter the functionality. Accurately predicting the AMP critical regions could benefit the experimental designs. However, no extensive analyses have been done specifically on the AMP critical regions and computational modeling on them is either non-existent or settled to other problems. With a focus on the AMP critical regions, we thus develop a computational model AMPcore by introducing a state-of-the-art machine learning method, conditional random fields. We generate a comprehensive dataset of 798 AMPs cores and a low similarity dataset of 510 representative AMP cores. AMPcore could reach a maximal accuracy of 90% and 0.79 Matthew's correlation coefficient on the comprehensive dataset and a maximal accuracy of 83% and 0.66 MCC on the low similarity dataset. Our analyses of AMP cores follow what we know about AMPs: High in glycine and lysine, but low in aspartic acid, glutamic acid, and methionine; the abundance of α-helical structures; the dominance of positive net charges; the peculiarity of amphipathicity. Two amphipathic sequence motifs within the AMP cores, an amphipathic α-helix and an amphipathic π-helix, are revealed. In addition, a short sequence motif at the N-terminal boundary of AMP cores is reported for the first time: arginine at the P(-1 coupling with glycine at the P1 of AMP cores occurs the most, which might link to microbial cell adhesion.

  20. Electronic in-plane symmetry breaking at field-tuned quantum criticality in CeRhIn5

    Energy Technology Data Exchange (ETDEWEB)

    Helm, T. [MPI-CPFS (Germany); Bachmann, M. [MPI-CPFS (Germany); Moll, P.J.W. [MPI-CPFS (Germany); Balicas, L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). National High Magnetic Field Lab. (MagLab); Chan, Mun Keat [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ramshaw, Brad [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mcdonald, Ross David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Balakirev, Fedor Fedorovich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bauer, Eric Dietzgen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ronning, Filip [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-23

    Electronic nematicity appears in proximity to unconventional high-temperature superconductivity in the cuprates and iron-arsenides, yet whether they cooperate or compete is widely discussed. While many parallels are drawn between high-Tc and heavy fermion superconductors, electronic nematicity was not believed to be an important aspect in their superconductivity. We have found evidence for a field-induced strong electronic in-plane symmetry breaking in the tetragonal heavy fermion superconductor CeRhIn5. At ambient pressure and zero field, it hosts an anti-ferromagnetic order (AFM) of nominally localized 4f electrons at TN=3.8K(1). Moderate pressure of 17kBar suppresses the AFM order and a dome of superconductivity appears around the quantum critical point. Similarly, a density-wave-like correlated phase appears centered around the field-induced AFM quantum critical point. In this phase, we have now observed electronic nematic behavior.

  1. Transport coefficients of O(N) scalar field theories close to the critical point

    CERN Document Server

    Nakano, Eiji; Friman, Bengt

    2011-01-01

    We investigate the critical dynamics of O(N)-symmetric scalar field theories to determine the critical exponents of transport coefficients as a second-order phase transition is approached from the symmetric phase. A set of stochastic equations of motion for the slow modes is formulated, and the long wavelength dynamics is examined for an arbitrary number of field components, $N$, in the framework of the dynamical renormalization group within the $\\epsilon$ expansion. We find that for a single component scalar field theory, N=1, the system reduces to the model C of critical dynamics, whereas for $N>1$ the model G is effectively restored owing to dominance of O(N)-symmetric charge fluctuations. In both cases, the shear viscosity remains finite in the critical region. On the other hand, we find that the bulk viscosity diverges as the correlation length squared, for N=1, whereas it remains finite for $N>1$.

  2. High RF Magnetic Field Near-Field Microwave Microscope

    Science.gov (United States)

    Tai, Tamin; Mircea, Dragos I.; Anlage, Steven M.

    2010-03-01

    Near-field microwave microscopes have been developed to quantitatively image RF and microwave properties of a variety of materials on deep sub-wavelength scales [1]. Microscopes that develop high-RF magnetic fields on short length scales are useful for examining the fundamental electrodynamic properties of superconductors [2]. We are creating a new class of near-field microwave microscopes that develop RF fields on the scale of 1 Tesla on sub-micron length scales. These microscopes will be employed to investigate defects that limit the RF properties of bulk Nb materials used in accelerator cavities, and the nonlinear Meissner effect in novel superconductors. Work funded by the US Department of Energy. [1] S. M. Anlage, V. V. Talanov, A. R. Schwartz, ``Principles of Near-Field Microwave Microscopy,'' in Scanning Probe Microscopy: Electrical and Electromechanical Phenomena at the Nanoscale, Volume 1, edited by S. V. Kalinin and A. Gruverman (Springer-Verlag, New York, 2007), pp. 215-253. [2] D. I. Mircea, H. Xu, S. M. Anlage, ``Phase-sensitive Harmonic Measurements of Microwave Nonlinearities in Cuprate Thin Films,'' Phys. Rev. B 80, 144505 (2009).

  3. Background field coils for the High Field Test Facility

    Energy Technology Data Exchange (ETDEWEB)

    Zbasnik, J.P.; Cornish, D.N.; Scanlan, R.M.; Jewell, A.M.; Leber, R.L.; Rosdahl, A.R.; Chaplin, M.R.

    1980-09-22

    The High Field Test Facility (HFTF), presently under construction at LLNL, is a set of superconducting coils that will be used to test 1-m-o.d. coils of prototype conductors for fusion magnets in fields up to 12 T. The facility consists of two concentric sets of coils; the outer set is a stack of Nb-Ti solenoids, and the inner set is a pair of solenoids made of cryogenically-stabilized, multifilamentary Nb/sub 3/Sn superconductor, developed for use in mirror-fusion magnets. The HFTF system is designed to be parted along the midplane to allow high-field conductors, under development for Tokamak fusion machines, to be inserted and tested. The background field coils were wound pancake-fashion, with cold-welded joints at both the inner and outer diameters. Turn-to-turn insulation was fabricated at LLNL from epoxy-fiberglass strip. The coils were assembled and tested in our 2-m-diam cryostat to verify their operation.

  4. Antenna development for high field plasma imaging.

    Science.gov (United States)

    Kong, X; Domier, C W; Luhmann, N C

    2010-10-01

    Electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR) are two microwave nonperturbing plasma visualization techniques that employ millimeter-wave imaging arrays with lens-coupled planar antennas, yielding time-resolved images of temperature (via ECEI) and electron density (via MIR) fluctuations within high temperature magnetic fusion plasmas. A series of new planar antennas have been developed that extend this technology to frequencies as high as 220 GHz for use on high field plasma devices with toroidal fields in excess of 3 T. Antenna designs are presented together with theoretical calculations, simulations, and experimental measurements.

  5. The Role of Field Electron Emission in Polypropylene/Aluminum Nanodielectrics Under High Electric Fields.

    Science.gov (United States)

    Zhang, Guoqiang; Li, Yue; Tang, Saide; Thompson, Rhett D; Zhu, Lei

    2017-03-09

    Polymer/metallic particle nanocomposites or nanodielectrics can exhibit colossal dielectric constants with a relatively low dissipation factor under low electric fields and thus seem to be promising for high-energy density dielectric capacitors. To study this possibility, this work focused on the dielectric performance and loss mechanisms in polypropylene (PP)/aluminum nanoparticle (nAl NP) composites under high electric fields. Phosphonic acid-terminated poly(ethylene-co-1-butene) was grafted to the Al2O3 surface layer on the nAl NPs in order to achieve reasonable dispersion in the PP matrix. The dielectric breakdown study showed that the breakdown strength decreased to nearly 1/20 that of the neat PP film as the nAl content increased to 25.0 vol %. The leakage current study revealed three electronic conduction mechanisms in the PP/100 nm nAl nanocomposites, namely, ohmic conduction at low fields, hopping conduction at intermediate fields, and Fowler-Nordheim (FN) field electron emission above a critical field, depending on the filler content. Compared to the 100 nm nAl NPs, smaller (e.g., 18 nm) nAl NPs needed a much higher electric field to exhibit FN field electron emission. It was the FN electron tunneling that induced a substantial reduction in breakdown strength for the PP/nAl nanocomposites. Meanwhile, electron-tunneling injected space charges (electrons) from nAl NPs into the PP matrix, and internal electronic conduction led to significant dielectric nonlinearity at high poling fields. Although polymer/metallic NP composites are not suitable for high-field electric applications, they can be good candidates for electrical switches and quantum tunneling composites operated at relatively low electric fields.

  6. Anisotropy and pressure dependence of the upper critical field of the ferromagnetic superconductor UGe2

    Science.gov (United States)

    Sheikin, I.; Huxley, A.; Braithwaite, D.; Brison, J. P.; Watanabe, S.; Miyake, K.; Flouquet, J.

    2001-12-01

    The temperature and pressure dependence of the upper critical field, Hc2, of the ferromagnetic superconductor UGe2 is reported for fields applied along all three crystallographic axes. For fields parallel to the easy magnetic a axis, the relationship between an unusual reentrant behavior of Hc2 and a field-induced transition associated with a change in the electronic density of states is reviewed. For transverse field directions a significant evolution in the behavior of Hc2 with pressure is found. As the pressure is decreased the dependence of Hc2 on temperature for fields along the crystal's c axis acquires a positive curvature that extends from the critical temperature, Tc, down to almost the lowest temperature measured (Tc/10) where Hc2 exceeds the usual weak coupling paramagnetic and orbital limits.

  7. Field-Reversed Configuration Power Plant Critical-Issue Scoping Study

    Energy Technology Data Exchange (ETDEWEB)

    Santarius, J. F.; Mogahed, E. A.; Emmert, G. A.; Khater, H. Y.; Nguyen, C. N.; Ryzhkov, S. V.; Stubna, M. D.

    2000-03-31

    A team from the Universities of Wisconsin, Washington, and Illinois performed an engineering scoping study of critical issues for field-reversed configuration (FRC) power plants. The key tasks for this research were (1) systems analysis for deuterium-tritium (D-T) FRC fusion power plants, and (2) conceptual design of the blanket and shield module for an FRC fusion core. For the engineering conceptual design of the fusion core, the project team focused on intermediate-term technology. For example, one decision was to use steele structure. The FRC systems analysis led to a fusion power plant with attractive features including modest size, cylindrical symmetry, good thermal efficiency (52%), relatively easy maintenance, and a high ratio of electric power to fusion core mass, indicating that it would have favorable economics.

  8. Approach to Achieve High Availability in Critical Infrastructure

    Science.gov (United States)

    2015-09-01

    Regardless, current technology includes RFID tags for systems, and tablets can be implemented to assist in real-time updates. Current Wi-Fi technology can...APPROACH TO ACHIEVE HIGH AVAILABILITY IN CRITICAL INFRASTRUCTURE Yew Kee Hoo Senior Engineer, Defence Science and Technology Agency, Singapore B.E...Between Failure MTTF Mean Time to Repair NAVFAC Naval Facilities Engineering Command xvi O&M Operations and Maintenance RFID Radio Frequency

  9. Weak magnetic field effects on chiral critical temperature in a nonlocal Nambu--Jona-Lasinio model

    CERN Document Server

    Loewe, M; Villavicencio, C; Zamora, R

    2014-01-01

    In this article we study the nonlocal Nambu--Jona-Lasinio model with a Gaussian regulator in the chiral limit. Finite temperature effects and the presence of a homogeneous magnetic field are considered. The magnetic evolution of the critical temperature for chiral symmetry restoration is then obtained. Here we restrict ourselves to the case of low magnetic field values, being this a complementary discussion to the exisiting analysis in nonlocal models in the strong magnetic field regime.

  10. Magnetic fields during high redshift structure formation

    CERN Document Server

    Schleicher, Dominik R G; Schober, Jennifer; Schmidt, Wolfram; Bovino, Stefano; Federrath, Christoph; Niemeyer, Jens; Banerjee, Robi; Klessen, Ralf S

    2012-01-01

    We explore the amplification of magnetic fields in the high-redshift Universe. For this purpose, we perform high-resolution cosmological simulations following the formation of primordial halos with \\sim10^7 M_solar, revealing the presence of turbulent structures and complex morphologies at resolutions of at least 32 cells per Jeans length. Employing a turbulence subgrid-scale model, we quantify the amount of unresolved turbulence and show that the resulting turbulent viscosity has a significant impact on the gas morphology, suppressing the formation of low-mass clumps. We further demonstrate that such turbulence implies the efficient amplification of magnetic fields via the small-scale dynamo. We discuss the properties of the dynamo in the kinematic and non-linear regime, and explore the resulting magnetic field amplification during primordial star formation. We show that field strengths of \\sim10^{-5} G can be expected at number densities of \\sim5 cm^{-3}.

  11. CRITICAL ISSUES IN HIGH END COMPUTING - FINAL REPORT

    Energy Technology Data Exchange (ETDEWEB)

    Corones, James [Krell Institute

    2013-09-23

    High-End computing (HEC) has been a driver for advances in science and engineering for the past four decades. Increasingly HEC has become a significant element in the national security, economic vitality, and competitiveness of the United States. Advances in HEC provide results that cut across traditional disciplinary and organizational boundaries. This program provides opportunities to share information about HEC systems and computational techniques across multiple disciplines and organizations through conferences and exhibitions of HEC advances held in Washington DC so that mission agency staff, scientists, and industry can come together with White House, Congressional and Legislative staff in an environment conducive to the sharing of technical information, accomplishments, goals, and plans. A common thread across this series of conferences is the understanding of computational science and applied mathematics techniques across a diverse set of application areas of interest to the Nation. The specific objectives of this program are: Program Objective 1. To provide opportunities to share information about advances in high-end computing systems and computational techniques between mission critical agencies, agency laboratories, academics, and industry. Program Objective 2. To gather pertinent data, address specific topics of wide interest to mission critical agencies. Program Objective 3. To promote a continuing discussion of critical issues in high-end computing. Program Objective 4.To provide a venue where a multidisciplinary scientific audience can discuss the difficulties applying computational science techniques to specific problems and can specify future research that, if successful, will eliminate these problems.

  12. Bulk singularities at critical end points: a field-theory analysis

    Science.gov (United States)

    Diehl, H. W.; Smock, M.

    2001-06-01

    A class of continuum models with a critical end point is considered whose Hamiltonian [φ,ψ] involves two densities: a primary order-parameter field, φ, and a secondary (noncritical) one, ψ. Field-theoretic methods (renormalization group results in conjunction with functional methods) are used to give a systematic derivation of singularities occurring at critical end points. Specifically, the thermal singularity | t|2 - α of the first-order line on which the disordered or ordered phase coexists with the noncritical spectator phase, and the coexistence singularity | t|1 - α or | t|β of the secondary density are derived. It is clarified how the renormalization group (RG) scenario found in position-space RG calculations, in which the critical end point and the critical line are mapped onto two separate fixed points CEP* and λ*, translates into field theory. The critical RG eigenexponents of CEP* and λ* are shown to match. CEP* is demonstrated to have a discontinuity eigenperturbation (with eigenvalue y = d), tangent to the unstable trajectory that emanates from CEP* and leads to λ*. The nature and origin of this eigenperturbation as well as the role redundant operators play are elucidated. The results validate that the critical behavior at the end point is the same as on the critical line.

  13. Molecular dynamics in high electric fields

    Science.gov (United States)

    Apostol, M.; Cune, L. C.

    2016-06-01

    Molecular rotation spectra, generated by the coupling of the molecular electric-dipole moments to an external time-dependent electric field, are discussed in a few particular conditions which can be of some experimental interest. First, the spherical-pendulum molecular model is reviewed, with the aim of introducing an approximate method which consists in the separation of the azimuthal and zenithal motions. Second, rotation spectra are considered in the presence of a static electric field. Two particular cases are analyzed, corresponding to strong and weak fields. In both cases the classical motion of the dipoles consists of rotations and vibrations about equilibrium positions; this motion may exhibit parametric resonances. For strong fields a large macroscopic electric polarization may appear. This situation may be relevant for polar matter (like pyroelectrics, ferroelectrics), or for heavy impurities embedded in a polar solid. The dipolar interaction is analyzed in polar condensed matter, where it is shown that new polarization modes appear for a spontaneous macroscopic electric polarization (these modes are tentatively called "dipolons"); one of the polarization modes is related to parametric resonances. The extension of these considerations to magnetic dipoles is briefly discussed. The treatment is extended to strong electric fields which oscillate with a high frequency, as those provided by high-power lasers. It is shown that the effect of such fields on molecular dynamics is governed by a much weaker, effective, renormalized, static electric field.

  14. High magnetic fields science and technology

    CERN Document Server

    Miura, Noboru

    2003-01-01

    This three-volume book provides a comprehensive review of experiments in very strong magnetic fields that can only be generated with very special magnets. The first volume is entirely devoted to the technology of laboratory magnets: permanent, superconducting, high-power water-cooled and hybrid; pulsed magnets, both nondestructive and destructive (megagauss fields). Volumes 2 and 3 contain reviews of the different areas of research where strong magnetic fields are an essential research tool. These volumes deal primarily with solid-state physics; other research areas covered are biological syst

  15. Specific features of the states of cobalt fluoride in the vicinity of the critical field

    Science.gov (United States)

    Medvedovskaya, O. G.; Fedorenko, T. A.; Chepurnykh, G. K.

    2016-12-01

    The state of cobalt fluoride in the vicinity of the critical value H c of a longitudinal magnetic field H, in which the magnetic subsystem of a CoF2 crystal with a strong Dzyaloshinskii interaction is transformed from the antiferromagnetic phase into the canted phase, has been investigated taking into account the increasing number of experimental studies related to the use of cobalt fluoride. It has been found that, despite the unusually high magnetic anisotropy of the crystal, the state of the magnetic subsystem at H = H c is extremely sensitive to a small deviation of the vector H from the C 4 axis. Another feature is that the high sensitivity disappears with an increase or decrease in the magnetic field by only a few thousandths of H c . The results of the investigations performed in this work are applicable to magnetically ordered crystals FeF3 and Cu2OSeO3, which, as well as the CoF2 crystals, are characterized by a strong Dzyaloshinskii interaction and a significant magnetic anisotropy. The revealed anomaly in the reduction of the effective magnetic anisotropy is of interest in connection with numerous attempts to decrease the magnetic anisotropy in crystals with giant magnetostriction, which are necessary for the use as sensors and vibrators.

  16. Critical Point Cancellation in 3D Vector Fields: Robustness and Discussion.

    Science.gov (United States)

    Skraba, Primoz; Rosen, Paul; Wang, Bei; Chen, Guoning; Bhatia, Harsh; Pascucci, Valerio

    2016-02-29

    Vector field topology has been successfully applied to represent the structure of steady vector fields. Critical points, one of the essential components of vector field topology, play an important role in describing the complexity of the extracted structure. Simplifying vector fields via critical point cancellation has practical merit for interpreting the behaviors of complex vector fields such as turbulence. However, there is no effective technique that allows direct cancellation of critical points in 3D. This work fills this gap and introduces the first framework to directly cancel pairs or groups of 3D critical points in a hierarchical manner with a guaranteed minimum amount of perturbation based on their robustness, a quantitative measure of their stability. In addition, our framework does not require the extraction of the entire 3D topology, which contains non-trivial separation structures, and thus is computationally effective. Furthermore, our algorithm can remove critical points in any subregion of the domain whose degree is zero and handle complex boundary configurations, making it capable of addressing challenging scenarios that may not be resolved otherwise. We apply our method to synthetic and simulation datasets to demonstrate its effectiveness.

  17. High-power FEL design issues - a critical review

    Energy Technology Data Exchange (ETDEWEB)

    Litvinenko, V.N.; Madey, J.M.J.; O`Shea, P.G. [Duke Univ., Durham, NC (United States)

    1995-12-31

    The high-average power capability of FELs has been much advertised but little realized. In this paper we provide a critical analysis of the technological and economic issues associated with high-average power FEL operation from the UV to near IR. The project of IR FEL for the Siberian Center of photochemical researches is described. The distinguished features of this project are the use of the race-track microtron-recuperator and the {open_quotes}electron output of radiation{close_quotes}. The building for the machine is under reconstruction now. About half of hardware has been manufactured. The assembly of installation began.

  18. High-field dipoles for future accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Wipf, S.L.

    1984-09-01

    This report presents the concept for building superconducting accelerator dipoles with record high fields. Economic considerations favor the highest possible current density in the windings. Further discussion indicates that there is an optimal range of pinning strength for a superconducting material and that it is not likely for multifilamentary conductors to ever equal the potential performance of tape conductors. A dipole design with a tape-wound, inner high-field winding is suggested. Methods are detailed to avoid degradation caused by flux jumps and to overcome problems with the dipole ends. Concerns for force support structure and field precision are also addressed. An R and D program leading to a prototype 11-T dipole is outlined. Past and future importance of superconductivity to high-energy physics is evident from a short historical survey. Successful dipoles in the 10- to 20-T range will allow interesting options for upgrading present largest accelerators.

  19. Magnetic hysteresis of the zero-resistance critical temperature of high-T{sub c} granular superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Flores, L.; Altshuler, E.; Garcia, S. [Univ. of Havana (Cuba)] [and others

    1995-10-01

    The authors have found a notorious hysteretic behavior in the dependence of the zero-resistance critical temperature obtained through resistivity ({rho}) versus temperature (T) measurements with applied field (H{sub c}) in High-T{sub c} granular superconductors. This behavior is explained semi-quantitatively based on the analogy between the present observation and a similar hysteresis found in the field dependence of the transport critical current in these materials.

  20. High-quality Critical Heat Flux in Horizontally Coiled Tubes

    Institute of Scientific and Technical Information of China (English)

    1995-01-01

    An investigation on the high-quality dryout in two electrically heated coiled tubes with horizontally helix axes is reported.The temperature profiles both along the tube and around the circumference are measured.and it is found that the temperature profiles around the circumference are not identical for the corss-sections at different parts of the coil.The “local condition hypothesis” seems applicable under present conditions,and the critical heat flux qcr decreases with increasing critical quality xcr.The CHF increases as mass velocity and ratio of tube diameter to coil diameter(d/D) increases,and it seems not to be affected hby the system pressure.The CHF is larger with coils than that with straight tubes,and the difference increases with increasing mass velocity and d/D.

  1. Upper critical field reaches 90 tesla near the Mott transition in fulleride superconductors.

    Science.gov (United States)

    Kasahara, Y; Takeuchi, Y; Zadik, R H; Takabayashi, Y; Colman, R H; McDonald, R D; Rosseinsky, M J; Prassides, K; Iwasa, Y

    2017-02-17

    Controlled access to the border of the Mott insulating state by variation of control parameters offers exotic electronic states such as anomalous and possibly high-transition-temperature (Tc) superconductivity. The alkali-doped fullerides show a transition from a Mott insulator to a superconductor for the first time in three-dimensional materials, but the impact of dimensionality and electron correlation on superconducting properties has remained unclear. Here we show that, near the Mott insulating phase, the upper critical field Hc2 of the fulleride superconductors reaches values as high as ∼90 T-the highest among cubic crystals. This is accompanied by a crossover from weak- to strong-coupling superconductivity and appears upon entering the metallic state with the dynamical Jahn-Teller effect as the Mott transition is approached. These results suggest that the cooperative interplay between molecular electronic structure and strong electron correlations plays a key role in realizing robust superconductivity with high-Tc and high-Hc2.

  2. Upper critical field reaches 90 tesla near the Mott transition in fulleride superconductors

    Science.gov (United States)

    Kasahara, Y.; Takeuchi, Y.; Zadik, R. H.; Takabayashi, Y.; Colman, R. H.; McDonald, R. D.; Rosseinsky, M. J.; Prassides, K.; Iwasa, Y.

    2017-02-01

    Controlled access to the border of the Mott insulating state by variation of control parameters offers exotic electronic states such as anomalous and possibly high-transition-temperature (Tc) superconductivity. The alkali-doped fullerides show a transition from a Mott insulator to a superconductor for the first time in three-dimensional materials, but the impact of dimensionality and electron correlation on superconducting properties has remained unclear. Here we show that, near the Mott insulating phase, the upper critical field Hc2 of the fulleride superconductors reaches values as high as ~90 T--the highest among cubic crystals. This is accompanied by a crossover from weak- to strong-coupling superconductivity and appears upon entering the metallic state with the dynamical Jahn-Teller effect as the Mott transition is approached. These results suggest that the cooperative interplay between molecular electronic structure and strong electron correlations plays a key role in realizing robust superconductivity with high-Tc and high-Hc2.

  3. Upper critical field reaches 90 tesla near the Mott transition in fulleride superconductors

    Science.gov (United States)

    Kasahara, Y.; Takeuchi, Y.; Zadik, R. H.; Takabayashi, Y.; Colman, R. H.; McDonald, R. D.; Rosseinsky, M. J.; Prassides, K.; Iwasa, Y.

    2017-01-01

    Controlled access to the border of the Mott insulating state by variation of control parameters offers exotic electronic states such as anomalous and possibly high-transition-temperature (Tc) superconductivity. The alkali-doped fullerides show a transition from a Mott insulator to a superconductor for the first time in three-dimensional materials, but the impact of dimensionality and electron correlation on superconducting properties has remained unclear. Here we show that, near the Mott insulating phase, the upper critical field Hc2 of the fulleride superconductors reaches values as high as ∼90 T—the highest among cubic crystals. This is accompanied by a crossover from weak- to strong-coupling superconductivity and appears upon entering the metallic state with the dynamical Jahn–Teller effect as the Mott transition is approached. These results suggest that the cooperative interplay between molecular electronic structure and strong electron correlations plays a key role in realizing robust superconductivity with high-Tc and high-Hc2. PMID:28211544

  4. Matrix product states and variational methods applied to critical quantum field theory

    CERN Document Server

    Milsted, Ashley; Osborne, Tobias J

    2013-01-01

    We study the second-order quantum phase-transition of massive real scalar field theory with a quartic interaction in (1+1) dimensions on an infinite spatial lattice using matrix product states (MPS). We introduce and apply a naive variational conjugate gradient method, based on the time-dependent variational principle (TDVP) for imaginary time, to obtain approximate ground states, using a related ansatz for excitations to calculate the particle and soliton masses and to obtain the spectral density. We also estimate the central charge using finite-entanglement scaling. Our value for the critical parameter agrees well with recent Monte Carlo results, improving on an earlier study which used the related DMRG method, verifying that these techniques are well-suited to studying critical field systems. We also obtain critical exponents that agree, as expected, with those of the transverse Ising model. Additionally, we treat the special case of uniform product states (mean field theory) separately, showing that they ...

  5. Upper critical fields of periodic and quasiperiodic Nb-Ta superlattices

    Science.gov (United States)

    Cohn, J. L.; Lin, J. J.; Lamelas, F. J.; He, H.; Clarke, R.; Uher, C.

    1988-08-01

    Upper critical fields have been studied for two series of Nb-Ta superlattices grown by molecular-beam epitaxy with both periodic and quasiperiodic (Fibonacci sequence) layering. X-ray results are presented to characterize the nature and quality of the layering. Positive curvature in the perpendicular upper critical field (Hc2⊥), pronounced negative curvature near Tc in the parallel upper critical field (Hc2), and dimensional crossover are observed in both types of samples. For quasiperiodic samples two upturns are observed in Hc2 with decreasing temperature. These are shown to be associated with dimensional crossover occurring twice as the superconducting coherence length in the growth direction, ξ⊥, samples the two length scales, 2dNb and dNb, that are present in these structures.

  6. High-field bipolar loss measurement apparatus

    Energy Technology Data Exchange (ETDEWEB)

    Thullen, P.; Weldon, D.; Wollan, J.

    1980-01-01

    An apparatus was constructed to measure dissipation in superconducting wire in high alternating fields. The apparatus will be used to make measurements on conductors which must operate in fields up to 7.0 T and rates of field change up to 15 T/s. The magnet for this facility is wound of uninsulated, 15 strand Rutherford cable in which the strand is a 0.812 mm diameter, fully mixed matrix, Cu plus CuNi, multifilament NbTi conductor. The coil is wound in a bath cooled configuration with an overall current density of 7.8 kA/cm/sup 2/. The circuit incorporates a pair of locomotive traction motors as the capacitive circuit element for the bipolar swing. The design, construction and operating characteristics of the field coil and the associated circuitry are described.

  7. High magnetic fields in the USA

    Science.gov (United States)

    Campbell, Laurence J.; Parkin, Don E.; Crow, Jack E.; Schneider-Muntau, Hans J.; Sullivan, Neil S.

    During the past thirty years research using high magnetic fields has technically evolved in the manner, but not the magnitude, of the so-called big science areas of particle physics, plasma physics, neutron scattering, synchrotron light scattering, and astronomy. Starting from the laboratories of individual researchers it moved to a few larger universities, then to centralized national facilities with research and maintenance staffs, and, finally, to joint international ventures to build unique facilities, as illustrated by the subject of this conference. To better understand the nature of this type of research and its societal justification it is helpful to compare it, in general terms, with the aforementioned big-science fields. High magnetic field research differs from particle physics, plasma physics, and astronomy in three respects: (1) it is generic research that cuts across a wide range of scientific disciplines in physics, chemistry, biology, medicine, and engineering; (2) it studies materials and processes that are relevant for a variety of technological applications and it gives insight into biological processes; (3) it has produced, at least, comparably significant results with incomparably smaller resources. Unlike neutron and synchrotron light scattering, which probe matter, high magnetic fields change the thermodynamic state of matter. This change of state is fundamental and independent of other state variables, such as pressure and temperature. After the magnetic field is applied, various techniques are then used to study the new state.

  8. Visualizing Robustness of Critical Points for 2D Time-Varying Vector Fields

    KAUST Repository

    Wang, B.

    2013-06-01

    Analyzing critical points and their temporal evolutions plays a crucial role in understanding the behavior of vector fields. A key challenge is to quantify the stability of critical points: more stable points may represent more important phenomena or vice versa. The topological notion of robustness is a tool which allows us to quantify rigorously the stability of each critical point. Intuitively, the robustness of a critical point is the minimum amount of perturbation necessary to cancel it within a local neighborhood, measured under an appropriate metric. In this paper, we introduce a new analysis and visualization framework which enables interactive exploration of robustness of critical points for both stationary and time-varying 2D vector fields. This framework allows the end-users, for the first time, to investigate how the stability of a critical point evolves over time. We show that this depends heavily on the global properties of the vector field and that structural changes can correspond to interesting behavior. We demonstrate the practicality of our theories and techniques on several datasets involving combustion and oceanic eddy simulations and obtain some key insights regarding their stable and unstable features. © 2013 The Author(s) Computer Graphics Forum © 2013 The Eurographics Association and Blackwell Publishing Ltd.

  9. High-field phase-diagram of Fe arsenide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Y.J.; Jaroszynski, J.; Yamamoto, A.; Gurevich, A.; Riggs, S.C.; Boebinger, G.S.; Larbalestier, D. [National High Magnetic Field Laboratory, Florida State University, Tallahassee-FL 32310 (United States); Wen, H.H. [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Zhigadlo, N.D.; Katrych, S.; Bukowski, Z.; Karpinski, J. [Laboratory for Solid State Physics, ETH Zuerich, CH-8093 Zuerich (Switzerland); Liu, R.H.; Chen, H.; Chen, X.H. [Hefei National Laboratory for Physical Science a Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Balicas, L., E-mail: balicas@magnet.fsu.ed [National High Magnetic Field Laboratory, Florida State University, Tallahassee-FL 32310 (United States)

    2009-05-01

    Here, we report an overview of the phase-diagram of single-layered and double-layered Fe arsenide superconductors at high magnetic fields. Our systematic magneto-transport measurements of polycrystalline SmFeAsO{sub 1-x}F{sub x} at different doping levels confirm the upward curvature of the upper critical magnetic field H{sub c2}(T) as a function of temperature T defining the phase boundary between the superconducting and metallic states for crystallites with the ab planes oriented nearly perpendicular to the magnetic field. We further show from measurements on single-crystals that this feature, which was interpreted in terms of the existence of two superconducting gaps, is ubiquitous among both series of single- and double-layered compounds. In all compounds explored by us the zero temperature upper critical field H{sub c2}(0), estimated either through the Ginzburg-Landau or the Werthamer-Helfand-Hohenberg single gap theories, strongly surpasses the weak-coupling Pauli paramagnetic limiting field. This clearly indicates the strong-coupling nature of the superconducting state and the importance of magnetic correlations for these materials. Our measurements indicate that the superconducting anisotropy, as estimated through the ratio of the effective masses gamma = (m{sub c}/m{sub ab}){sup 1/2} for carriers moving along the c-axis and the ab-planes, respectively, is relatively modest as compared to the high-T{sub c} cuprates, but it is temperature, field and even doping dependent. Finally, our preliminary estimations of the irreversibility field H{sub m}(T), separating the vortex-solid from the vortex-liquid phase in the single-layered compounds, indicates that it is well described by the melting of a vortex lattice in a moderately anisotropic uniaxial superconductor.

  10. High-intensity, focused ultrasonic fields

    DEFF Research Database (Denmark)

    Jensen, Leif Bjørnø

    1988-01-01

    distribution, etc. involving nonlinearity, diffraction, and absorption in the high-intensity focused ultrasonic fields produced by an ellipsoid as well as a spherical cap focusing geometry. Data from the development of an ESWL of the piezoelectric disk type are reported including demands to transducers...

  11. Physics of semiconductors in high magnetic fields

    CERN Document Server

    Miura, Noboru

    2008-01-01

    This book summarizes most of the fundamental physical phenomena which semiconductors and their modulated structures exhibit in high magnetic fields. Readers can learn not only the basic theoretical background but also the present state of the art from the most advanced data in this rapidly growing research area.

  12. Nonlinear Temperature Dependence of Magnetization of Two-Band Superconductors Near Upper Critical Field

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Temperature dependence of the magnetization M(T) of two-band superconductors is studied in the vicinity of upper critical field Hc2 by using a two-band Ginzburg-Landau (GL) theory. It is shown that magnetization M(T) has a nonlinear character due to positive curvature of upper critical field Hc2(T) and temperature dependence of effective Ginzburg-Landau parameter (n)eff(T). The results are shown to be in qualitative agreement with experimental data for the superconducting magnesium diboride, MgB2.

  13. Magnetic behavior of dirty multiband superconductors near the upper critical field

    Science.gov (United States)

    Silaev, Mikhail

    2016-06-01

    Magnetic properties of dirty multiband superconductors near the upper critical field are studied. The parameter κ2 characterizing magnetization slope is shown to have a significant temperature variation which is quite sensitive to the pairing interactions and relative strengths of intraband impurity scattering. In contrast to single-band superconductors the increase of κ2 at low temperatures can be arbitrarily large determined by the ratio of maximal and minimal diffusion coefficients in different bands. Temperature dependencies of κ2(T ) in two-band MgB2 and iron-based superconductors are shown to be much more sensitive to the multiband effects than the upper critical field Hc 2(T ) .

  14. Enhancement of critical current in mesoscopic superconducting strips by external magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Ilin, Konstantin; Henrich, Dagmar; Luck, Yannick; Fuchs, Lea; Meckbach, Johannes Maximilian; Siegel, Michael [Institut fuer Mikro- und Nanoelektronische Systeme, Karlsruher Institut fuer Technologie, Hertzstrasse 16, 76187 Karlsruhe (Germany)

    2013-07-01

    Current crowding in superconducting mesoscopic strips with bends results in decrease of critical current in these structures with respect to the strips without geometrical non-uniformities. Recently it has been shown that Meissner currents induced by externally applied magnetic field of appropriate direction allow to suppress this effect so that I{sub c}(B) can exceed I{sub c}(0). Experimental dependencies of critical current in mesoscopic bended strips made from ultra-thin superconducting films on externally applied magnetic field and their comparison to the theoretical predictions are presented and discussed.

  15. Characterization of non equilibrium effects on high quality critical flows

    Energy Technology Data Exchange (ETDEWEB)

    Camelo, E.; Lemonnier, H.; Ochterbeck, J. [Commissariat a l Energie Atomique, Grenoble (France)] [and others

    1995-09-01

    The appropriate design of various pieces of safety equipment such as relief systems, relies on the accurate description of critical flow phenomena. Most of the systems of industrial interest are willing to be described by one-dimensional area-averaged models and a large fraction of them involves multi-component high gas quality flows. Within these circumstances, the flow is very likely to be of an annular dispersed nature and its description by two-fluid models requires various closure relations. Among the most sensitive closures, there is the interfacial area and the liquid entrained fraction. The critical flowrate depends tremendously on the accurate description of the non equilibrium which results from the correctness of the closure equations. In this study, two-component flows are emphasized and non equilibrium results mainly form the differences in the phase velocities. It is therefore of the utmost importance to have reliable data to characterize non equilibrium phenomena and to assess the validity of the closure models. A comprehensive description of air-water nozzle flows, with emphasis on the effect of the nozzle geometry, has been undertaken and some of the results are presented here which helps understanding the overall flow dynamics. Besides the critical flowrate, the presented material includes pressure profiles, droplet size and velocity, liquid film flowrate and liquid film thickness.

  16. High-performance phase-field modeling

    KAUST Repository

    Vignal, Philippe

    2015-04-27

    Many processes in engineering and sciences involve the evolution of interfaces. Among the mathematical frameworks developed to model these types of problems, the phase-field method has emerged as a possible solution. Phase-fields nonetheless lead to complex nonlinear, high-order partial differential equations, whose solution poses mathematical and computational challenges. Guaranteeing some of the physical properties of the equations has lead to the development of efficient algorithms and discretizations capable of recovering said properties by construction [2, 5]. This work builds-up on these ideas, and proposes novel discretization strategies that guarantee numerical energy dissipation for both conserved and non-conserved phase-field models. The temporal discretization is based on a novel method which relies on Taylor series and ensures strong energy stability. It is second-order accurate, and can also be rendered linear to speed-up the solution process [4]. The spatial discretization relies on Isogeometric Analysis, a finite element method that possesses the k-refinement technology and enables the generation of high-order, high-continuity basis functions. These basis functions are well suited to handle the high-order operators present in phase-field models. Two-dimensional and three dimensional results of the Allen-Cahn, Cahn-Hilliard, Swift-Hohenberg and phase-field crystal equation will be presented, which corroborate the theoretical findings, and illustrate the robustness of the method. Results related to more challenging examples, namely the Navier-Stokes Cahn-Hilliard and a diusion-reaction Cahn-Hilliard system, will also be presented. The implementation was done in PetIGA and PetIGA-MF, high-performance Isogeometric Analysis frameworks [1, 3], designed to handle non-linear, time-dependent problems.

  17. William Morris and the critical utopia of high fantasy

    Directory of Open Access Journals (Sweden)

    Matic Večko

    2009-12-01

    Full Text Available The novels The Wood Beyond the World (1894 and The Weil at the World's End (1896 by William Morris are considered the formative works of the type of literature which has been labelled high fantasy. The latter is one of the commercially most successful genres of fantasy literature. The two novels are analysed from the perspective of critical utopianism as articulated through a distinc­tive type of aesthetic structure which was established in these works and has become characteristic of the high fantasy literature. The author of the article suggests that it is this complex of aesthetic structiire-aiid ifs iiiherent iitopian lmpulse which may be one of the important faciors-in the perennia popularity of high fantasy.

  18. Derivation of the high field semiconductor equations

    Energy Technology Data Exchange (ETDEWEB)

    Hagan, P.S. (Los Alamos National Lab., NM (United States)); Cox, R.W. (Department of Computer Information Science, Indiana University, Purdue University, Indianapolis (USA)); Wagner, B.A. (Arizona Univ., Tucson, AZ (United States). Dept. of Mathematics)

    1991-01-01

    Electron and hole densities evolve in x-z phase space according to Boltzmann equations. When the mean free path of the particles is short and electric force on the particles is weak, a well-known expansion can be used to solve the Boltzmann equation. This asymptotic solution shows that the spatial density of electrons and holes evolves according to diffusion-drift equations. As devices become smaller, electric fields become stronger, which renders the Basic Semiconductor Equations increasingly inaccurate. To remedy this problem, we use singular perturbation techniques to obtain a new asymptotic expansion for the Boltzmann equation. Like the Hilbert expansion, the new expansion requires the mean free path to be short compared to all macroscopic length scales. However, it does not require the electric forces to be weak. The new expansion shows that spatial densities obey diffusion-drift equations as before, but the diffusivity D and mobility {mu} turn out to be nonlinear functions of the electric field. In particular, our analysis determines the field-dependent mobilities {mu}(E) and diffusivities D(E) directly from the scattering operator. By carrying out this asymptotic expansion to higher order, we obtain the high frequency corrections to the drift velocity and diffusivity, and also the corrections due to gradients in the electric field. Remarkably, we find that Einsteins's relation is still satisfied, even with these corrections. The new diffusion-drift equations, together with Poissons' equation for the electric field, form the high-field semiconductor equations, which can be expected to be accurate regardless of the strength of the electric fields within the semiconductor. In addition, our analysis determines the entire momentum distribution of the particles, so we derive a very accurate first moment model for semi-conductors by substituting the asymptotically-correct distribution back into the Boltzmann equation and taking moments.

  19. Continuum theory of critical phenomena in polymer solutions: Formalism and mean field approximation

    Science.gov (United States)

    Goldstein, Raymond E.; Cherayil, Binny J.

    1989-06-01

    A theoretical description of the critical point of a polymer solution is formulated directly from the Edwards continuum model of polymers with two- and three-body excluded-volume interactions. A Hubbard-Stratonovich transformation analogous to that used in recent work on the liquid-vapor critical point of simple fluids is used to recast the grand partition function of the polymer solution as a functional integral over continuous fields. The resulting Landau-Ginzburg-Wilson (LGW) Hamiltonian is of the form of a generalized nonsymmetric n=1 component vector model, with operators directly related to certain connected correlation functions of a reference system. The latter is taken to be an ensemble of Gaussian chains with three-body excluded-volume repulsions, and the operators are computed in three dimensions by means of a perturbation theory that is rapidly convergent for long chains. A mean field theory of the functional integral yields a description of the critical point in which the power-law variations of the critical polymer volume fraction φc, critical temperature Tc, and critical amplitudes on polymerization index N are essentially identical to those found in the Flory-Huggins theory. In particular, we find φc ˜N-1/2, Tθ-Tc˜N-1/2 with (Tθ the theta temperature), and that the composition difference between coexisting phases varies with reduced temperature t as N-1/4t1/2. The mean field theory of the interfacial tension σ between coexisting phases near the critical point, developed by considering the LGW Hamiltonian for a weakly inhomogeneous solution, yields σ˜N-1/4t3/2, with the correlation length diverging as ξ˜N1/4t-1/2 within the same approximation, consistent with the mean field limit of de Gennes' scaling form. Generalizations to polydisperse systems are discussed.

  20. Development of high temperature superconductors for magnetic field applications

    Energy Technology Data Exchange (ETDEWEB)

    Larbalestier, D.C.

    1991-12-31

    The key requirement for magnetic field applications of high temperature superconductor (HTS) materials is to have conductors with high transport critical current density available for magnet builders. After 3 or 4 years of being without any such object, conductor makers have had recent success in producing simple conductor prototypes. These have permitted the construction of simple HTS magnets having self fields exceeding 1 tesla at 4K. Thus the scientific feasibility of making powerful HTS magnets has been demonstrated. Attention to the technological aspects of making HTS conductors for magnets with strong flux pinning and reduced superconducting granularity is now sensible and attractive. However, extrinsic defects such as filament sausaging, cracking, misaligned grains and other perturbation to long range current flow must be controlled at a low level if the benefit of intrinsic improvements to the critical current density is to be maintained in the conductor form. Due to the great complexity of the HTS materials, there is sometimes confusion as to whether a given sample has an intrinsically or extrinsically limited critical current density. Systematic microstructure variation experiments and resistive transition analysis are shown to be particularly helpful in this phase of conductor development.

  1. Development of high temperature superconductors for magnetic field applications

    Energy Technology Data Exchange (ETDEWEB)

    Larbalestier, D.C.

    1991-01-01

    The key requirement for magnetic field applications of high temperature superconductor (HTS) materials is to have conductors with high transport critical current density available for magnet builders. After 3 or 4 years of being without any such object, conductor makers have had recent success in producing simple conductor prototypes. These have permitted the construction of simple HTS magnets having self fields exceeding 1 tesla at 4K. Thus the scientific feasibility of making powerful HTS magnets has been demonstrated. Attention to the technological aspects of making HTS conductors for magnets with strong flux pinning and reduced superconducting granularity is now sensible and attractive. However, extrinsic defects such as filament sausaging, cracking, misaligned grains and other perturbation to long range current flow must be controlled at a low level if the benefit of intrinsic improvements to the critical current density is to be maintained in the conductor form. Due to the great complexity of the HTS materials, there is sometimes confusion as to whether a given sample has an intrinsically or extrinsically limited critical current density. Systematic microstructure variation experiments and resistive transition analysis are shown to be particularly helpful in this phase of conductor development.

  2. Wuhan pulsed high magnetic field center

    OpenAIRE

    Li, Liang; Peng, Tao; Ding, Honfa; Han, Xiaotao; Ding, Tonghai; Chen, Jin; Wang, Junfeng; Xie, Jianfeng; Wang, Shaoliang; Duan, Xianzhong; Wang, Cheng; Herlach, Fritz; Vanacken, Johan; Pan, Yuan

    2008-01-01

    Wuhan pulsed high magnetic field facility is under development. Magnets of bore sizes from 12 to 34 mm with the peak field in the range of 50 to 80 T have been designed. The pulsed power supplies consists of a 12 MJ, 25 kV capacitor bank and a 100 MVA/100 MJ flywheel pulse generator. A prototype 1 MJ, 25 kV capacitor bank is under construction. Five magnets wound with CuNb wire and copper wire reinforced internally with Zylon fiber composites and externally with stainless steel shells have be...

  3. Wuhan pulsed high magnetic field center

    OpenAIRE

    Li, Liang; Peng, Tao; Ding, Honfa; Han, Xiaotao; Ding, Tonghai; Chen, Jin; Wang, Junfeng; Xie, Jianfeng; Wang, Shaoliang; DUAN, Xianzhong; Wang, Cheng; Herlach, Fritz; Vanacken, Johan; Pan, Yuan

    2008-01-01

    Wuhan pulsed high magnetic field facility is under development. Magnets of bore sizes from 12 to 34 mm with the peak field in the range of 50 to 80 T have been designed. The pulsed power supplies consists of a 12 MJ, 25 kV capacitor bank and a 100 MVA/100 MJ flywheel pulse generator. A prototype 1 MJ, 25 kV capacitor bank is under construction. Five magnets wound with CuNb wire and copper wire reinforced internally with Zylon fiber composites and externally with stainless steel shells have be...

  4. Demystifying the Text: Literary Criticism in the High School Classroom.

    Science.gov (United States)

    Schade, Lisa

    1996-01-01

    Shows how one teacher answered student questions about how a particular piece of literature came to be regarded as worthy of in-depth examination. Proposes that students be taught about various critical approaches, including Jungian/archetypal criticism, formalism, reader-response criticism, socio-historical and biographical criticism, and…

  5. Demystifying the Text: Literary Criticism in the High School Classroom.

    Science.gov (United States)

    Schade, Lisa

    1996-01-01

    Shows how one teacher answered student questions about how a particular piece of literature came to be regarded as worthy of in-depth examination. Proposes that students be taught about various critical approaches, including Jungian/archetypal criticism, formalism, reader-response criticism, socio-historical and biographical criticism, and…

  6. Teaching Critical Thinking through Art History in High School.

    Science.gov (United States)

    Garoian, Charles R.

    1988-01-01

    Explains how the study of art history encourages the development of critical thinking in adolescents by comparing Bloom's Taxonomy of Educational Objectives with Feldman's stages of art criticism. Offers curriculum-based recommendations for using art history and criticism to encourage critical thinking. (LS)

  7. RAPID COMMUNICATION: High performance superconducting wire in high applied magnetic fields via nanoscale defect engineering

    Science.gov (United States)

    Wee, Sung Hun; Goyal, Amit; Zuev, Yuri L.; Cantoni, Claudia

    2008-09-01

    High temperature superconducting (HTS) wires capable of carrying large critical currents with low dissipation levels in high applied magnetic fields are needed for a wide range of applications. In particular, for electric power applications involving rotating machinery, such as large-scale motors and generators, a high critical current, Ic, and a high engineering critical current density, JE, in applied magnetic fields in the range of 3-5 Tesla (T) at 65 K are required. In addition, exceeding the minimum performance requirements needed for these applications results in a lower fabrication cost, which is regarded as crucial to realize or enable many large-scale bulk applications of HTS materials. Here we report the fabrication of short segments of a potential superconducting wire comprised of a 4 µm thick YBa2Cu3O7-δ (YBCO) layer on a biaxially textured substrate with a 50% higher Ic and JE than the highest values reported previously. The YBCO film contained columns of self-assembled nanodots of BaZrO3 (BZO) roughly oriented along the c-axis of YBCO. Although the YBCO film was grown at a high deposition rate, three-dimensional self-assembly of the insulating BZO nanodots still occurred. For all magnetic field orientations, minimum Ic and JE at 65 K, 3 T for the wire were 353 A cm-1 and 65.4 kA cm-2, respectively.

  8. High-field electron transport in GaN under crossed electric and magnetic fields

    Science.gov (United States)

    Kochelap, V. A.; Korotyeyev, V. V.; Syngayivska, G. I.; Varani, L.

    2015-10-01

    High-field electron transport studied in crossed electric and magnetic fields in bulk GaN with doping of 1016 cm-3, compensation around 90% at the low lattice temperature (30 K). It was found the range of the magnetic and electric fields where the non-equilibrium electron distribution function has a complicated topological structure in the momentum space with a tendency to the formation of the inversion population. Field dependences of dissipative and Hall components of the drift velocity were calculated for the samples with short- and open- circuited Hall contacts in wide ranges of applied electric (0 — 20 kV/cm) and magnetic (1 — 10 T) fields. For former sample, field dependences of dissipative and Hall components of the drift velocity have a non-monotonic behavior. The dissipative component has the inflection point which corresponds to the maximum point of the Hall component. For latter sample, the drift velocity demonstrate a usual sub-linear growth without any critical points. We found that GaN samples with controlled resistance of the Hall circuit can be utilized as a electronic high-power switch.

  9. Stochastic geometry of critical curves, Schramm-Loewner evolutions and conformal field theory

    Energy Technology Data Exchange (ETDEWEB)

    Gruzberg, Ilya A [James Franck Institute, University of Chicago, 5640 S. Ellis Avenue, Chicago, IL 60637 (United States)

    2006-10-13

    Conformally invariant curves that appear at critical points in two-dimensional statistical mechanics systems and their fractal geometry have received a lot of attention in recent years. On the one hand, Schramm (2000 Israel J. Math. 118 221 (Preprint math.PR/9904022)) has invented a new rigorous as well as practical calculational approach to critical curves, based on a beautiful unification of conformal maps and stochastic processes, and by now known as Schramm-Loewner evolution (SLE). On the other hand, Duplantier (2000 Phys. Rev. Lett. 84 1363; Fractal Geometry and Applications: A Jubilee of Benot Mandelbrot: Part 2 (Proc. Symp. Pure Math. vol 72) (Providence, RI: American Mathematical Society) p 365 (Preprint math-ph/0303034)) has applied boundary quantum gravity methods to calculate exact multifractal exponents associated with critical curves. In the first part of this paper, I provide a pedagogical introduction to SLE. I present mathematical facts from the theory of conformal maps and stochastic processes related to SLE. Then I review basic properties of SLE and provide practical derivation of various interesting quantities related to critical curves, including fractal dimensions and crossing probabilities. The second part of the paper is devoted to a way of describing critical curves using boundary conformal field theory (CFT) in the so-called Coulomb gas formalism. This description provides an alternative (to quantum gravity) way of obtaining the multifractal spectrum of critical curves using only traditional methods of CFT based on free bosonic fields.

  10. Critical Points of the Electric Field from a Collection of Point Charges

    Energy Technology Data Exchange (ETDEWEB)

    Max, N; Weinkauf, T

    2007-02-16

    The electric field around a molecule is generated by the charge distribution of its constituents: positively charged atomic nuclei, which are well approximated by point charges, and negatively charged electrons, whose probability density distribution can be computed from quantum mechanics. For the purposes of molecular mechanics or dynamics, the charge distribution is often approximated by a collection of point charges, with either a single partial charge at each atomic nucleus position, representing both the nucleus and the electrons near it, or as several different point charges per atom. The critical points in the electric field are useful in visualizing its geometrical and topological structure, and can help in understanding the forces and motion it induces on a charged ion or neutral dipole. Most visualization tools for vector fields use only samples of the field on the vertices of a regular grid, and some sort of interpolation, for example, trilinear, on the grid cells. There is less risk of missing or misinterpreting topological features if they can be derived directly from the analytic formula for the field, rather than from its samples. This work presents a method which is guaranteed to find all the critical points of the electric field from a finite set of point charges. To visualize the field topology, we have modified the saddle connector method to use the analytic formula for the field.

  11. A Critical Analysis and Assessment of High Power Switches

    Science.gov (United States)

    1978-09-01

    Spark Gap Switch Assembly ........ .225 vii List of Figures (cont.) FIGURE PAGE IV-10. Turbulent Flow Switch .... ............ . 227 IV-II. Spark Gap...provide such a low inductance that the current risetime is limited by the load rather than the switch itself. Many spark gaps with liquid or solid...Sympoisum, June, 1978. [4] M. A. Lutz and G. A. Hofmann, "The Gamitron - A High Power Crossed-Field Switch Tube for HVDC Interruption," IEEE Trans. on Plasma

  12. New Spinor Field Realizations of the Non-Critical W3 String

    Institute of Scientific and Technical Information of China (English)

    ZHANG Li-Jie; LIU Yu-Xiao; REN Ji-Rong

    2006-01-01

    @@ We investigate the new spinor field realizations of the W3 algebra, making use of the fact that the W3 algebra can be linearized by the addition of a spin-1 current. We then use these new realizations to build the nilpotent Becchi-Rouet-Stora-Tyutin charges of the spinor non-critical W3 string.

  13. Critical values of the external magnetic field leading biological effects in the human organism

    CERN Document Server

    Kanokov, Zakirjon

    2013-01-01

    In the framework of the simplified stochastic model the critical values of an induction of the external magnetic field leading to sharp increase of fluctuations of a casual current of biologically important ions in different blood vessels of a human body are calculated.

  14. Bourdieu's Habitus and Field: Implications on the Practice and Theory of Critical Action Learning

    Science.gov (United States)

    Warwick, Rob; McCray, Janet; Board, Douglas

    2017-01-01

    This paper considers the logic of practice of the French sociologist Pierre Bourdieu in relation to critical action learning: in particular "habitus" which is co-created with field and the interplay amongst the two in the form of misrecognition and risk. We draw on interviews with participants who have experienced action learning as part…

  15. Examining Graduate Dissertations in the Field of Critical Thinking: A Case from Turkey

    Science.gov (United States)

    Demirel, Melek; Derman, Ipek; Can Aran, Ozge

    2017-01-01

    Purpose: The aim of this study is to conduct content analyses of graduate dissertations about critical thinking skills in the field of educational sciences in Turkey and to document general trends in dissertations. Research Methods: This study is constructed using qualitative research methods and techniques. A document review was used to gather…

  16. Impact of high-critical-temperature superconductors on electromagnetic pump applications

    Science.gov (United States)

    Krazinski, J. L.; Holtz, R. E.; Jaross, R. A.

    1990-05-01

    The impact is studied of the development of practical, high critical temperature superconducting materials on applications involving electromagnetic (EM) pumping. Potential improvements in the operating characteristics of EM pumps were examined for current pump technology. In addition, the study addressed whether the development of high (Tc) superconductors could enable the implementation of EM pumps in applications where it has not been previously feasible. This assessment focused on two specific types of EM pumps: helical rotor pumps with rotating field coils and EM thruster pumps for ship propulsion. The design and performance of helical rotor pumps were analyzed for both liquid metals and nonmetallic fluids. For liquid metals, the impact of superconductors on the pump size, mass, and efficiency was examined for EM pumps operating at relatively lower magnetic field strengths. For nonmetallic fluids, the study investigated whether the use of high magnetic field strengths, in conjunction with high (Tc) superconductors, could enable the pumping of these fluids with EM pumps of reasonable size and efficiency. The impact of high (Tc) superconducting materials on the reliability and economics of EM pumps was also examined. In addition, the study assessed the impact of high field strength, superconducting magnets on the feasibility of using EM thrusters for ship propulsion. Parametric studies were conducted on the effects of magnetic field strength, thruster size, vessel speed, and vessel size on the predicted thruster efficiencies. The results were compared with these of earlier studies on electromagnetic propulsion that incorporated both superconducting and nonsuperconducting magnet designs.

  17. Investigation of radiation fields outside the Sub-critical Assembly in Dubna.

    Science.gov (United States)

    Seltbor, P; Lopatkin, A; Gudowski, W; Shvetsov, V; Polanski, A

    2005-01-01

    The radiation fields outside the planned experimental Sub-critical Assembly in Dubna (SAD) have been studied in order to provide a basis for the design of the concrete shielding that cover the reactor core. The effective doses around the reactor, induced by leakage of neutrons and photons through the shielding, have been determined for a shielding thickness varying from 100 to 200 cm. It was shown that the neutron flux and the effective dose is higher above the shielding than at the side of it, owing to the higher fraction of high-energy spallation neutrons emitted in the direction of the incident beam protons. At the top, the effective dose was found to be -150 microSv s(-1) for a concrete thickness of 100 cm, while -2.5 microSv s(-1) for a concrete thickness of 200 cm. It was also shown that the high-energy neutrons (> 10 MeV), which are created in the proton-induced spallation interactions in the target, contribute for the major part of the effective doses outside the reactor.

  18. Critical temperature and upper critical field of Li2Pd3-xCuxB (x=0.0, 0.1, 0.2) superconductors

    Science.gov (United States)

    Castro, A. A.; Olicón, O.; Escamilla, R.; Morales, F.

    2017-04-01

    We studied the effects of substitution of Pd by Cu on the upper critical field of the noncentrosymmetric superconductor Li2Pd3-xCuxB, with x=0.0, 0.1 and 0.2. The upper critical field as a function of temperature was determined by resistance measurements at different magnetic fields. We found that the superconducting transition temperature decreases as the Cu content increases. Moreover, the temperature dependence of the upper critical field is linear in the range of the temperature studied and, at low temperature, is enhanced compared with the prediction of the Werthamer-Helfan-Hohenberg theory. This indicates that the breaking of Cooper pairs by spin orbit scattering and Pauli paramagnetism is negligible, and that the upper critical field enhancement is mainly because the electron-phonon coupling and disorder.

  19. Applications of high dielectric materials in high field magnetic resonance

    Science.gov (United States)

    Haines, Kristina Noel

    At high magnetic fields, radiation losses, wavelength effects, self-resonance, and the high resistance of components all contribute to losses in conventional RF MRI coil designs. The hypothesis tested here is that these problems can be combated by the use of high permittivity ceramic materials at high fields. High permittivity ceramic dielectric resonators create strong uniform magnetic fields in compact structures at high frequencies and can potentially solve some of the challenges of high field coil design. In this study NMR probes were constructed for operation at 600 MHz (14.1 Tesla) and 900 MHz (21.1 Tesla) using inductively fed CaTiO3 (relative permittivity of 156-166) cylindrical hollow bore dielectric resonators. The designs showed the electric field is largely confined to the dielectric itself, with near zero values in the hollow bore, which accommodates the sample. The 600 MHz probe has an unmatched Q value greater than 2000. Experimental and simulation mapping of the RF field show good agreement, with the ceramic resonator giving a pulse width approximately 25% less than a loop gap resonator of similar inner dimensions. High resolution images, with voxel dimensions less than 50 microm3, have been acquired from fixed zebrafish samples, showing excellent delineation of several fine structures. The 900 MHz probe has an unmatched Q value of 940 and shows Q performance five times better than Alderman-Grant and loop-gap resonators of similar dimensions. High resolution images were acquired of an excised mouse spinal cord (25 microm 3) and an excised rat soleus muscle (20 microm3). The spatial distribution of electromagnetic fields within the human body can be tailored using external dielectric materials. Here, a new material is introduced with high dielectric constant and low background MRI signal. The material is based upon metal titanates, which can be made into geometrically formable suspensions in de-ionized water. The suspension's material properties are

  20. Avoided criticality in near-optimally doped high-temperature superconductors

    Science.gov (United States)

    Haule, Kristjan; Kotliar, Gabriel

    2007-09-01

    We study the crossover from the underdoped to the overdoped regime of the t-J model within a plaquette dynamical mean field approach. We find that the shortest electron lifetime occurs near optimal doping where the superconducting critical temperature is maximal. The mean field theory provides a simple physical picture of this effect. In the underdoped regime, the charge carriers propagate coherently among spin singlets, formed by the superexchange interaction. In the overdoped, large carrier concentration regime, the Kondo effect dominates resulting in spin-charge composite quasiparticles which are also coherent. Separating these two Fermi liquid regimes, there is a critical doping where the superexchange and the Kondo interaction balance each other. At this point, the normal phase is highly incoherent and the optical conductivity exhibits power law behavior at intermediate frequencies. The onset of superconductivity restores coherence, causing the appearance of a resonance in the spin channel.

  1. High Field Pulse Magnets with New Materials

    Science.gov (United States)

    Li, L.; Lesch, B.; Cochran, V. G.; Eyssa, Y.; Tozer, S.; Mielke, C. H.; Rickel, D.; van Sciver, S. W.; Schneider-Muntau, H. J.

    2004-11-01

    High performance pulse magnets using the combination of CuNb conductor and Zylon fiber composite reinforcement with bore sizes of 24, 15 and 10 mm have been designed, manufactured and tested to destruction. The magnets successfully reached the peak fields of 64, 70 and 77.8 T respectively with no destruction. Failures occurred near the end flanges at the layer. The magnet design, manufacturing and testing, and the mode of the failure are described and analyzed.

  2. Shift of the critical mixing temperature in strong electric fields. Theory and experiment.

    Science.gov (United States)

    Orzechowski, Kazimierz; Adamczyk, Mariusz; Wolny, Alicja; Tsori, Yoav

    2014-06-26

    We study the shift in the critical temperature T(c) in binary mixtures in strong electric fields. In experiments we measure the nonlinear dielectric effect (NDE) in a mixture of nitrobenze and n-octane and calculate Piekara's factor. We find that the critical anomaly of Piekara's factor is a function of an electric field strength. We propose to explain this observation as a result of a downward shift of T(c), and this allows us to calculate (∂T(c)/∂E(2)) = (-22 ± 10) × 10(-16) (K m(2))/V(2). In the theoretical part we amend Landau and Lifshitz's formula and show that the downward shift of Tc can be estimated from a simple mean-field theory taking into account the linear and quadratic terms in an expansion of the constitutive relation ε(x) between the electric constant ε and mixture composition x.

  3. Effect of longitudinal applied magnetic field on the self-pinched critical current in intense electron beam diode

    Institute of Scientific and Technical Information of China (English)

    Liu Guo-Zhi; Huang Wen-Hua; Shao Hao; Xiao Ren-Zhen

    2006-01-01

    The effect of applied longitudinal magnetic field on the self-pinched critical current in the intense electron beam diode is discussed. The self-pinched critical current is derived and its validity is tested by numerical simulations. The results shows that an applied longitudinal magnetic field tends to increase the self-pinched critical current. Without the effect of anode plasma, the maximal diode current approximately equals the self-pinched critical current with the longitudinal magnetic field applied; when self-pinched occurs, the diode current approaches the self-pinched critical current.

  4. Experimental consequences of quantum critical points at high temperatures

    Science.gov (United States)

    Freitas, D. C.; Rodière, P.; Núñez, M.; Garbarino, G.; Sulpice, A.; Marcus, J.; Gay, F.; Continentino, M. A.; Núñez-Regueiro, M.

    2015-11-01

    We study the C r1 -xR ex phase diagram finding that its phase transition temperature towards an antiferromagnetic order TN follows a quantum [(xc-x ) /xc ] ψ law, with ψ =1 /2 , from the quantum critical point (QCP) at xc=0.25 up to TN≈600 K . We compare this system to others in order to understand why this elemental material is affected by the QCP up to such unusually high temperatures. We determine a general criterion for the crossover, as a function of an external parameter such as concentration, from the region controlled solely by thermal fluctuations to that where quantum effects become observable. The properties of materials with low coherence lengths will thus be altered far away from the QCP.

  5. Critical behavior of the Gaussian model on fractal lattices in external magnetic field

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    For inhomogeneous lattices we generalize the classical Gaussian model, i.e. it is proposed that the Gaussian type distribution constant and the external magnetic field of site i in this model depend on the coordination number qi of site i, and that the relation bqi/bqj=qi/qj holds among bqi's, where bqi is the Gaussian type distribution constant of site i. Using the decimation real-space renormalization group following the spin-rescaling method, the critical points and critical exponents of the Gaussian model are calculated on some Koch type curves and a family of the diamond-type hierarchical (or DH) lattices. At the critical points, it is found that the nearest-neighbor interaction and the magnetic field of site i can be expressed in the form K*=bqi/qi and h*qi=0, respectively. It is also found that most critical exponents depend on the fractal dimensionality of a fractal system. For the family of the DH lattices, the results are identical with the exact results on translation symmetric lattices, and if the fractal dimensionality df=4, the Gaussian model and the mean field theories give the same results.

  6. High-field magnetization in transuranium compound

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, K. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan) and KYOKUGEN, Osaka University, Osaka 560-8531 (Japan)]. E-mail: sugiyama@phys.sci.osaka-u.ac.jp; Nakashima, H. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Aoki, D. [Institute of Material Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Ikeda, S. [Institute of Material Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Haga, Y. [Advanced Science and Research Centerer, JAEA, Tokai, Ibaraki 319-1195 (Japan); Yamamoto, E. [Advanced Science and Research Centerer, JAEA, Tokai, Ibaraki 319-1195 (Japan); Nakamura, A. [Advanced Science and Research Centerer, JAEA, Tokai, Ibaraki 319-1195 (Japan); Homma, Y. [Institute of Material Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Shiokawa, Y. [Institute of Material Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Kindo, K. [Institite of Solid State Physics, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8581 (Japan); Hagiwara, M. [KYOKUGEN, Osaka University, Osaka 560-8531 (Japan); Onuki, Y. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Advanced Science and Research Centerer, JAEA, Tokai, Ibaraki 319-1195 (Japan)

    2007-03-15

    We measured the high-field magnetization up to 55T and constructed a magnetic phase diagram for a transuranium antiferromagnet NpRhGa{sub 5} with the tetragonal structure. The magnetization at 4.2K for H(parallel) [100] indicates a sharp metamagnetic transition with a step at H{sub c}=26T and saturates above H{sub s}=38T, reaching 0.43{mu}{sub B}/Np. An ordered moment of 0.96{mu}{sub B}/Np at zero field, which was determined from the neutron scattering experiment, is found to be reduced to 0.43{mu}{sub B}/Np at H{sub s}, together with an orientation of the magnetic moment from the (001) plane to the (100) plane.

  7. The upper critical magnetic field of holographic superconductor with conformally invariant power-Maxwell electrodynamics

    CERN Document Server

    Sheykhi, A; Davatolhagh, S

    2016-01-01

    The properties of $(d-1)$-dimensional $s$-wave holographic superconductor in the presence of power-Maxwell field is explored. We study the probe limit in which the scalar and gauge fields do not backreact on the background geometry. Our study is based on the matching of solutions on the boundary and on the horizon at some intermediate point. At first, the case without external magnetic field is considered, and the critical temperature is obtained in terms of the charge density, the dimensionality, and the power-Maxwell exponent. Then, a magnetic field is turned on in the $d$-dimensional bulk which can influence the $(d-1)$-dimensional holographic superconductor at the boundary. The phase behavior of the corresponding holographic superconductor is obtained by computing the upper critical magnetic field in the presence of power-Maxwell electrodynamics, characterized by the power exponent $q$. Interestingly, it is observed that in the presence of magnetic field, the physically acceptable phase behavior of the ho...

  8. Second-order magnetic critical points at finite magnetic fields: Revisiting Arrott plots

    Science.gov (United States)

    Bustingorry, S.; Pomiro, F.; Aurelio, G.; Curiale, J.

    2016-06-01

    The so-called Arrott plot, which consists in plotting H /M against M2, with H the applied magnetic field and M the magnetization, is used to extract valuable information in second-order magnetic phase transitions. Besides, it is widely accepted that a negative slope in the Arrott plot is indicative of a first-order magnetic transition. This is known as the Banerjee criterion. In consequence, the zero-field transition temperature T* is reported as the characteristic first-order transition temperature. By carefully analyzing the mean-field Landau model used for studying first-order magnetic transitions, we show in this work that T* corresponds in fact to a triple point where three first-order lines meet. More importantly, this analysis reveals the existence of two symmetrical second-order critical points at finite magnetic field (Tc,±Hc) . We then show that a modified Arrott plot can be used to obtain information about these second-order critical points. To support this idea we analyze experimental data on La2 /3Ca1 /3MnO3 and discuss an estimate for the location of the triple point and the second-order critical points.

  9. Electronic in-plane symmetry breaking at field-tuned quantum criticality in CeRhIn5

    Science.gov (United States)

    Ronning, F.; Helm, T.; Shirer, K. R.; Bachmann, M. D.; Balicas, L.; Chan, M. K.; Ramshaw, B. J.; McDonald, R. D.; Balakirev, F. F.; Jaime, M.; Bauer, E. D.; Moll, P. J. W.

    2017-08-01

    Electronic nematic materials are characterized by a lowered symmetry of the electronic system compared to the underlying lattice, in analogy to the directional alignment without translational order in nematic liquid crystals. Such nematic phases appear in the copper- and iron-based high-temperature superconductors, and their role in establishing superconductivity remains an open question. Nematicity may take an active part, cooperating or competing with superconductivity, or may appear accidentally in such systems. Here we present experimental evidence for a phase of fluctuating nematic character in a heavy-fermion superconductor, CeRhIn5 (ref. 5). We observe a magnetic-field-induced state in the vicinity of a field-tuned antiferromagnetic quantum critical point at Hc ≈ 50 tesla. This phase appears above an out-of-plane critical field H* ≈ 28 tesla and is characterized by a substantial in-plane resistivity anisotropy in the presence of a small in-plane field component. The in-plane symmetry breaking has little apparent connection to the underlying lattice, as evidenced by the small magnitude of the magnetostriction anomaly at H*. Furthermore, no anomalies appear in the magnetic torque, suggesting the absence of metamagnetism in this field range. The appearance of nematic behaviour in a prototypical heavy-fermion superconductor highlights the interrelation of nematicity and unconventional superconductivity, suggesting nematicity to be common among correlated materials.

  10. Critical Current Test of Liquid Hydrogen Cooled HTC Superconductors under External Magnetic Field

    Science.gov (United States)

    Shirai, Yasuyuki; Shiotsu, Masahiro; Tatsumoto, Hideki; Kobayashi, Hiroaki; Naruo, Yoshihiro; Nonaka, Satoshi; Inatani, Yoshifumi

    High-Tc (HTC) superconductors including MgB2 will show excellent properties under temperature of Liquid Hydrogen (LH2:20K), which has large latent heat and low viscosity coefficient. In order to design and fabricate the LH2 cooled superconducting energy devices, we must clear the cooling property of LH2 for superconductors, the cooling system and safety design of LH2 cooled superconducting devices and electro-magnetic property evaluation of superconductors (BSCCO, REBCO and MgB2) and their magnets cooled by LH2. As the first step of the study, an experimental setup which can be used for investigating heat transfer characteristics of LH2 in a pool and also in forced flow (circulation loop with a pump), and also for evaluation of electro-magnetic properties of LH2 cooled superconductors under external magnetic field (up to 7 T). In this paper, we will show a short sketch of the experimental set-up, practical experiences in safety operation of liquid hydrogen cooling system and example test results of critical current evaluation of HTC superconductors cooled by LH2.

  11. Effect of equatorial line nodes on the upper critical field and London penetration depth

    Energy Technology Data Exchange (ETDEWEB)

    Kogan, V G [Ames Laboratory; Prozorov, R [Ames Laboratory

    2014-09-01

    The upper critical field Hc2 and its anisotropy are calculated for order parameters with line nodes at the equators, kz=0, of the Fermi surface of uniaxial superconductors. It is shown that characteristic features found in Fe-based materials (a nearly linear Hc2(T) in a broad T domain, a low and increasing on warming anisotropy γH=Hc2,ab/Hc2,c) can be caused by competing effects of the equatorial nodes and of the Fermi surface anisotropy. For certain material parameters, γH(T)-1 may change sign upon warming, in agreement with the recorded behavior of FeTeS systems. It is also shown that the anisotropy of the penetration depth γλ=λc/λab decreases upon warming to reach γH at Tc, in agreement with data available. For some materials γλ(T) may change upon warming, from γλ>1 at low Ts to γλ<1 at high Ts.

  12. Homogenous BSCCO-2212 Round Wires for Very High Field Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Scott Campbell

    2012-06-30

    the very significant advantage of an extremely high H{sub c2}. For this reason, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y} (Bi-2212, or 2212) in the form of a multifilamentary Ag alloy matrix composite is beginning to attract the interest of the magnet community for future extremely high-field magnets or magnet-insert coils for 4.2K operation. Fig. 1 shows an example of excellent JE (engineering current density) in Bi-2212 round wire at fields up to 45 T, demonstrating the potential for high field applications of this material. For comparison, the Nb{sub 3}Sn wires used in magnets in the 16-18 T range typically perform with J{sub E} in the range 200-500 A/mm{sup 2}; the Bi-2212 wire retains this level of performance to fields at least as high as 45 T, and probably significantly higher. Bi-2212 conductors have in fact been used to generate a 25 T field in a superconducting insert magnet. These two factors- the very high field critical current performance of Bi-2212, and the already demonstrated capability of this material for high field magnets up to 25 T, strongly suggest this material as a leading contender for the next generation high field superconducting (HFS) wire. This potential was recognized by the US Academy of Science's Committee on Opportunities in High Magnetic Field Science. Their report of the same name specifically calls out the high field potential for this material, and suggests that 30 T magnets appear feasible based on the performance of 2212. There are several requirements for HFS conductors. The most obvious is J{sub E} (B, T), the engineering current density at the field and temperature of operation. As shown in Fig. 1, Bi-2212 excels in this regard. Stability requirements for magnets dictate that the effective filament diameter should be less than 30 micrometers, something that Bi-2212 multifilamentary wire can uniquely satisfy among the HFS superconducting wire technologies. Additional requirements include mechanical properties that prevent

  13. Magnetic studies in organic superconductors bis(tetramethyltetraselenafulvalene) perchlorate: Upper critical fields and vortex matters

    Science.gov (United States)

    Oh, Jeong Il

    A thermodynamic determination of the upper critical field Hc2 in the quasi-one dimensional molecular organic superconductor (TMTSF) 2ClO4 has been obtained for magnetic field accurately aligned along the in-plane, inter-chain direction by utilizing silicon cantilever magnetometer technology. This magnetically-measured upper critical field, simultaneously confirmed by electrical transport measurements, was found to well-exceed all paramagnetic limits known to date for spin singlet superconductors, strongly indicating that (TMTSF)2ClO4 is a spin triplet superconductor. Also, we were able to investigate novel structure in the upper critical field, where we observed that Hc2(T) has three different temperature regimes, characterized by an usual upturn at a temperature T* ˜ 0.2 K and a very unusual kink at a temperature T0 ˜ 1.04 K. In addition, the magnetic field-temperature superconducting vortex phase diagram of (TMTSF)2ClO4 has been obtained. The phase diagram showed a variety of vortex phases, including solid (Bragg lattice and disordered glass) and liquid (liquid-1 and liquid-2) subphases. A distinct irreversibility line was found, likely separating the solid from the liquid phase. Within the solid phase, we observed an unusual inverse transition driven by the pinning force, splitting the solid phase into a disordered glass and a Bragg lattice. Also, within the Bragg lattice, we observed a temperature-independent magnetic crossover line at low field (˜0.05 T), interpreted as possibly indicating the existence of multiple Tc's in (TMTSF)2X, further evidence for claiming this system to be a triplet superconductor.

  14. The distribution of 3D superconductivity near the second critical field

    Science.gov (United States)

    Kachmar, Ayman; Nasrallah, Marwa

    2016-09-01

    We study the minimizers of the Ginzburg-Landau energy functional with a uniform magnetic field in a three dimensional bounded domain. The functional depends on two positive parameters, the Ginzburg-Landau parameter and the intensity of the applied magnetic field, and acts on complex-valued functions and vector fields. We establish a formula for the distribution of the L 2-norm of the minimizing complex-valued function (order parameter). The formula is valid in the regime where the Ginzburg-Landau parameter is large and the applied magnetic field is close to and strictly below the second critical field—the threshold value corresponding to the transition from the superconducting to the normal phase in the bulk of the sample. Earlier results are valid in 2D domains and for the L 4-norm in 3D domains.

  15. Tilting of the magnetic field in Majorana nanowires: Critical angle and zero-energy differential conductance

    Science.gov (United States)

    Rex, Stefan; Sudbø, Asle

    2014-09-01

    Semiconductor nanowires with strong spin-orbit coupling and proximity-induced s-wave superconductivity in an external magnetic field have been the most promising settings for approaches towards experimental evidence of topological Majorana zero modes. We investigate the effect of tilting the magnetic field relative to the spin-orbit coupling direction in a simple continuum model and provide an analytical derivation of the critical angle, at which the topological states disappear. We also obtain the differential conductance characteristic of a junction with a normal wire for different tilting angles and propose a qualitative change of the dependence of the zero-energy differential conductance on the tunnel barrier strength at the critical angle as a criterion for establishing the topological nature of the observed signal.

  16. Quasiperiodic superconducting V/Zr multilayers: critical magnetic fields and crossover

    Science.gov (United States)

    Fogel, N. Ya.; Cherkasova, V. G.; Mikhailov, M. Yu.; Bomze, Yu. V.; Yuzephovich, O. I.; Dmitrenko, I. M.; Stetsenko, A. N.

    1998-08-01

    Critical magnetic fields parallel and perpendicular to the planes of quasiperiodic superconducting Fibonacci multilayers (ML) consisting of vanadium and zirconium are measured. The temperature dependence of the parallel critical field Hc∥ displays two crossovers. The Hc∥(T) dependence is of square-root type in the vicinity of the transition temperature Tc and linear at low temperatures. Between these temperature intervals, the dependence follows a power law: Hc∥˜(1-T/Tc)α, α=0,78±0,02. The complex nature of this dependence can be explained in the framework of the Ginzburg-Landau theory for a quasiperiodic ML, as well as by the scaling theory for fractal multilayers which takes into account the different structure length scales in the case of ML with a complex sequence of layers.

  17. Seven-Step Framework for Critical Analysis and Its Application in the Field of Physical Therapy.

    Science.gov (United States)

    Nixon, Stephanie A; Yeung, Euson; Shaw, James A; Kuper, Ayelet; Gibson, Barbara E

    2016-09-29

    Critical analysis (or the ability to recognize taken-for-granted assumptions and their effects) is a skill that requires teaching and practice. The purpose of this article is to introduce a framework for critically analyzing assumptions within physical therapy and illustrate its utility through application to 2 examples: a physical therapy clinic logo and an outcome measure for health-related quality of life (HRQOL). This 7-step framework for critical analysis was created for a pilot project to develop reflexivity among senior physical therapist students and further developed through an iterative process of reflecting on its utility for advancing the field of physical therapy. The 7-step framework is an iterative process involving a cascade of 7 steps: (1) name the specific aspect of practice being analyzed, (2) identify the intended purposes of this aspect of practice, (3) uncover the assumptions that support these intended purposes, (4) identify who benefits, (5) identify who is disadvantaged, (6) link these specific ideas to society-level patterns, and (7) conceive of alternatives that mitigate actual or potential harms. It is emphasized that being theoretically critical does not equate to being negative. Rather, the word "critical" is used in the sense of thinking deeply and carefully about the intended and unintended consequences of actions (including common professional practices, ways of speaking, and visual representations) in order to reflect on and mature the field of physical therapy. The purpose of critical analysis is to invite and promote dialogue that assists physical therapist clinicians, researchers, and students to arrive at new insights about the impacts of their day-to-day actions.

  18. Anisotropic upper critical magnetic fields in Rb2Cr3As3 superconductor

    Science.gov (United States)

    Tang, Zhang-Tu; Liu, Yi; Bao, Jin-Ke; Xi, Chuan-Ying; Pi, Li; Cao, Guang-Han

    2017-10-01

    Rb2Cr3As3 is a structurally one-dimensional superconductor containing Cr3As3 chains with a superconducting transition temperature of T_c= 4.8 K. Here we report the electrical resistance measurements for Rb2Cr3As3 single crystals, under magnetic fields up to 29.5 T and at temperatures down to 0.36 K, from which the upper critical fields, Hc2(T) , can be obtained in a broad temperature range. For field parallel to the Cr3As3 chains, Hc2\\Vert (T) is paramagnetically limited with an initial slope of μ0 dHc2\\Vert /dT\\vert Tc=-16 T K-1 and a zero-temperature upper critical field of μ0Hc2\\Vert (0)= 17.5 T. For field perpendicular to the Cr3As3 chains, however, Hc2\\bot(T) is only limited by orbital pair-breaking effect with μ0 dHc2\\perp /dT\\vert Tc=-3 T K-1 . As a consequence, the anisotropy γH=Hc2\\Vert /Hc2\\bot decreases sharply near T c and reverses below 2 K. Remarkably, the low-temperature Hc2\\bot(T) down to 0.075 Tc remains to increase linearly up to over three times the Pauli paramagnetic limit, which strongly suggests dominant spin-triplet superconductivity in Rb2Cr3As3.

  19. Flow boiling critical heat flux enhancement by using magnetic nanofluids and external magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Lee, T.; Jeong, Y.H. [Korea Advanced Inst. of Science and Tech., Daejeon (Korea, Republic of)

    2011-07-01

    By using the nanofluid as a working fluid, we can expect the enhancement in the flow boiling critical heat flux mainly due to the deposition of nanoparticles on the heat transfer surface. In this study, we suggest the magnetic nanofluid, or magnetite-water nanofluid, as a working fluid which is regarded as a controllable nanofluid, that is, nanoparticles or magnetite nanoparticles in a nanofluid can be controlled by an external magnetic field. Therefore, we can expect the advantages of magnetic nanofluid such as, i) control of nanofluid concentration to maintain nanoparticle suspension and to localize nanofluid concentration, and ii) removal of nanoparticle from nanofluid when we want. In this study, we focused on the investigation of flow boiling critical heat flux characteristics for the magnetic nanofluid. Series of experiments were performed under the low pressure and low flow conditions, and based on the experimental results; we can conclude that the use of magnetic nanofluid improves the flow boiling critical heat flux characteristics. This is mainly due to the deposition of magnetite nanoparticles on the heat transfer surface, which results in the improvement of wettability and re-wetting characteristics of heat transfer surface. Preliminary results of the magnetic field effects on the flow boiling critical heat flux would be presented also. (author)

  20. Critical behavior of the Gaussian model on fractal lattices in external magnetic field

    Institute of Scientific and Technical Information of China (English)

    孔祥木; 林振权; 朱建阳

    2000-01-01

    For inhomogeneous lattices we generalize the classical Gaussian model, i. e. it is pro-posed that the Gaussian type distribution constant and the external magnetic field of site / in this model depend on the coordination number q, of site i, and that the relation bq1/bq1 = q1/q1 holds among bq1s, where bq1 is the Gaussian type distribution constant of site /. Using the decimation real-spacerenormalization group following the spin-rescaling method, the critical points and critical exponents of the Gaussian model are calculated on some Koch type curves and a family of the diamond-type hierar-chical (or DH) lattices. At the critical points, it is found that the nearest-neighbor interaction and the magnetic field of site i can be expressed in the form K’ = bq1/q1 and hq =0, respectively. it is also found that most critical exponents depend on the fractal dimensionality of a fractal system. For the family of the DH lattices, the results are identical with the exact results on translation symmetric lattices,

  1. Final report for the field-reversed configuration power plant critical-issue scoping study

    Energy Technology Data Exchange (ETDEWEB)

    Santarius, John F.; Mogahed, Elsayed A.; Emmert, Gilbert A.; Khater, Hesham Y.; Nguyen, Canh N.; Ryzhkov, Sergei V.; Stubna, Michael D.; Steinhauer, Loren C.; Miley, George H.

    2001-03-01

    This report describes research in which a team from the Universities of Wisconsin, Washington, and Illinois performed a scoping study of critical issues for field-reversed configuration (FRC) power plants. The key tasks for this research were (1) systems analysis of deuterium-tritium (D-T) FRC fusion power plants, and (2) conceptual design of the blanket and shield module for an FRC fusion core.

  2. A high performance field-reversed configuration

    Energy Technology Data Exchange (ETDEWEB)

    Binderbauer, M. W.; Tajima, T.; Steinhauer, L. C.; Garate, E.; Tuszewski, M.; Smirnov, A.; Gota, H.; Barnes, D.; Deng, B. H.; Thompson, M. C.; Trask, E.; Yang, X.; Putvinski, S.; Rostoker, N.; Andow, R.; Aefsky, S.; Bolte, N.; Bui, D. Q.; Ceccherini, F.; Clary, R. [Tri Alpha Energy, Inc., P.O. Box 7010, Rancho Santa Margarita, California 92688 (United States); and others

    2015-05-15

    Conventional field-reversed configurations (FRCs), high-beta, prolate compact toroids embedded in poloidal magnetic fields, face notable stability and confinement concerns. These can be ameliorated by various control techniques, such as introducing a significant fast ion population. Indeed, adding neutral beam injection into the FRC over the past half-decade has contributed to striking improvements in confinement and stability. Further, the addition of electrically biased plasma guns at the ends, magnetic end plugs, and advanced surface conditioning led to dramatic reductions in turbulence-driven losses and greatly improved stability. Together, these enabled the build-up of a well-confined and dominant fast-ion population. Under such conditions, highly reproducible, macroscopically stable hot FRCs (with total plasma temperature of ∼1 keV) with record lifetimes were achieved. These accomplishments point to the prospect of advanced, beam-driven FRCs as an intriguing path toward fusion reactors. This paper reviews key results and presents context for further interpretation.

  3. High-field Magnet Development toward the High Luminosity LHC

    Energy Technology Data Exchange (ETDEWEB)

    Apollinari, Giorgio [Fermilab

    2014-07-01

    The upcoming Luminosity upgrade of the LHC (HL-LHC) will rely on the use of Accelerator Quality Nb3Sn Magnets which have been the focus of an intense R&D effort in the last decade. This contribution will describe the R&D and results of Nb3Sn Accelerator Quality High Field Magnets development efforts, with emphasis on the activities considered for the HL-LHC upgrades.

  4. Critical point scaling of Ising spin glasses in a magnetic field

    Science.gov (United States)

    Yeo, Joonhyun; Moore, M. A.

    2015-03-01

    Critical point scaling in a field H applies for the limits t →0 (where t =T /Tc-1 ) and H →0 but with the ratio R =t /H2 /Δ finite. Δ is a critical exponent of the zero-field transition. We study the replicon correlation length ξ and from it the crossover scaling function f (R ) defined via 1 /(ξ H4 /(d +2 -η )) ˜f (R ) . We have calculated analytically f (R ) for the mean-field limit of the Sherrington-Kirkpatrick model. In dimension d =3 , we have determined the exponents and the critical scaling function f (R ) within two versions of the Migdal-Kadanoff (MK) renormalization group procedure. One of the MK versions gives results for f (R ) in d =3 in reasonable agreement with those of the Monte Carlo simulations at the values of R for which they can be compared. If there were a de Almeida-Thouless (AT) line for d ≤6 , it would appear as a zero of the function f (R ) at some negative value of R , but there is no evidence for such behavior. This is consistent with the arguments that there should be no AT line for d ≤6 , which we review.

  5. Field theory of bicritical and tetracritical points. IV. Critical dynamics including reversible terms.

    Science.gov (United States)

    Folk, R; Holovatch, Yu; Moser, G

    2012-02-01

    This article concludes a series of papers [Folk, Holovatch, and Moser, Phys. Rev. E 78, 041124 (2008); 78, 041125 (2008); 79, 031109 (2009)] where the tools of the field theoretical renormalization group were employed to explain and quantitatively describe different types of static and dynamic behavior in the vicinity of multicritical points. Here we give the complete two-loop calculation and analysis of the dynamic renormalization-group flow equations at the multicritical point in anisotropic antiferromagnets in an external magnetic field. We find that the time scales of the order parameters characterizing the parallel and perpendicular ordering with respect to the external field scale in the same way. This holds independent whether the Heisenberg fixed point or the biconical fixed point in statics is the stable one. The nonasymptotic analysis of the dynamic flow equations shows that due to cancellation effects the critical behavior is described, in distances from the critical point accessible to experiments, by the critical behavior qualitatively found in one-loop order. Although one may conclude from the effective dynamic exponents (taking almost their one-loop values) that weak scaling for the order parameter components is valid, the flow of the time-scale ratios is quite different, and they do not reach their asymptotic values.

  6. Critical behavior of an anisotropic Ising antiferromagnet in both external longitudinal and transverse fields

    Energy Technology Data Exchange (ETDEWEB)

    Nascimento, Denise A. do, E-mail: denise.a.n@bol.com.br [Departamento de Fisica, Universidade Federal do Amazonas, 3000, Japiim, 69077-000 Manaus-AM (Brazil); Departamento de Fisica, Universidade Federal de Roraima, BR 174, Km 12. Bairro Monte Cristo, CEP: 69300-000 Boa Vista/RR (Brazil); Neto, Minos A., E-mail: minosneto@hotmail.com [Departamento de Fisica, Universidade Federal do Amazonas, 3000, Japiim, 69077-000 Manaus-AM (Brazil); Ricardo de Sousa, J., E-mail: jsousa@edu.ufam.br [Departamento de Fisica, Universidade Federal do Amazonas, 3000, Japiim, 69077-000 Manaus-AM (Brazil); National Institute of Science and Technology for Complex Systems, 3000, Japiim, 69077-000 Manaus-AM (Brazil); Pacobahyba, Josefa T., E-mail: jtmpacobahyba@dfis.ufrr.br [Departamento de Fisica, Universidade Federal de Roraima, BR 174, Km 12. Bairro Monte Cristo, CEP: 69300-000 Boa Vista/RR (Brazil)

    2012-08-15

    In this paper we study the critical behavior of a two-sublattice Ising model on an anisotropic square lattice in both uniform longitudinal (H) and transverse ({Omega}) fields by using the effective-field theory. The model consists of ferromagnetic interaction J{sub x} in the x direction and antiferromagnetic interaction J{sub y} in the y direction in the presence of the H and {Omega} fields. We obtain the phase diagrams in the H-T and {Omega}-T planes changing values of the {Omega} and H parameters, respectively for fixed value at {lambda}=J{sub x}/J{sub y}=1. At null temperature, the ground state phase diagram in the {Omega}-H plane for several values of {lambda} parameter is analyzed. In the particular case of {lambda}=1 we compare our results with mean-field theory (MFT) and was not observed reentrant behavior around of the critical field H{sub c}/J{sub y}=2.0 for {Omega}=0 by using EFT. - Highlights: Black-Right-Pointing-Pointer In the last decade there has been a great interest in physics of the quantum phase transition in system at low dimensional. Black-Right-Pointing-Pointer In particular, the transverse Ising model has been studied by a variety of approximate methods. Black-Right-Pointing-Pointer In the context of quantum phase transition and critical phenomena. Black-Right-Pointing-Pointer First time, is presented a study of the superantiferromagnetic transverse Ising model on an anisotropic square lattice. Black-Right-Pointing-Pointer We have obtained finite temperature and ground state phase diagrams.

  7. High temperature superconductivity the road to higher critical temperature

    CERN Document Server

    Uchida, Shin-ichi

    2015-01-01

    This book presents an overview of material-specific factors that influence Tc and give rise to diverse Tc values for copper oxides and iron-based high- Tc superconductors on the basis of more than 25 years of experimental data, to most of which the author has made important contributions. The book then explains why both compounds are distinct from others with similar crystal structure and whether or not one can enhance Tc, which in turn gives a hint on the unresolved pairing mechanism. This is an unprecedented new approach to the problem of high-temperature superconductivity and thus will be inspiring to both specialists and non-specialists interested in this field.   Readers will receive in-depth information on the past, present, and future of high-temperature superconductors, along with special, updated information on what the real highest Tc values are and particularly on the possibility of enhancing Tc for each member material, which is important for application. At this time, the highest Tc has not been...

  8. High field rf superconductivity: to pulse or not to pulse

    Energy Technology Data Exchange (ETDEWEB)

    Campisi, I.E.

    1984-10-01

    Experimental data on the behavior of superconductors under the application of rf fields of amplitude comparable to their critical fields are sporadic and not always consistent. In many cases the field level at which breakdown in superconducting rf cavities should be expected has not been clearly established. Tests conducted with very short (approx. 1 ..mu..s) rf pulses indicate that in this mode of operation fields close to the critical values can be consistently reached in superconducting cavities without breakdown. The advantages and disadvantages of the pulsed method are discussed compared to those of the more standard continuous wave (cw) systems. 60 references.

  9. Role of high-field MR systems in neuroscience

    Energy Technology Data Exchange (ETDEWEB)

    Nakada, Tsutomu [Niigata Univ. (Japan). Brain Research Inst

    1999-07-01

    Nuclear magnetic resonance (NMR) is a remarkably versatile technology applicable to various aspects of medical science. Currently, there are three categories of MR techniques available for probing human brain function in detail. The first category comprises the most widely utilized techniques which make use of the metabolic effects of brain activation, represented by BOLD functional magnetic resonance imaging (fMRI) and EPISTAR cerebral blood flow imaging. The second category of techniques deals with apparent diffusion tensor in probing the cellular aspects of brain function and is represented by magnetic resonance axonography (MRX). The third category of techniques is the oldest and as yet the most underutilized. These techniques which include MR spectroscopy (MRS) and spectroscopic imaging (SI), are based on classical NMR spectroscopy and are capable of providing biochemical information in vivo. In these critically important but highly demanding techniques, high-field systems possess significant advantages over conventional systems. (author)

  10. Effects of rf current on critical field for magnetization reversal in spin torque devices

    Science.gov (United States)

    Chen, Wenyu; Florez, Sylvia; Katine, Jordan; Carey, Matthew; Folks, Liesl; Terris, Bruce

    2009-03-01

    Current induced switching assisted by rf current has recently been observed in spin torque devices at low temperature [1, 2]. This effect allows control of spin transfer induced magnetization reversal through the frequency of an injected rf current. In this study, the effects of the rf current injection on critical field for magnetization reversal in spin valve junctions have been investigated. Measurements were conducted at room temperature, and the magnetic field was applied along the easy axis of the junction. An rf current was injected into the nanojunction at various frequencies ranging between 1 and 20 GHz. The dynamic resistance, dV/dI, was measured as a function of the rf frequency, power and the dc bias current while ramping the magnetic field. The rf current injection was observed to change the critical field for free layer magnetization reversal when the intrinsic spin-transfer-induced dynamics is frequency-locked with the injected rf. The results will be discussed in the context of macrospin models of spin transfer in metallic spin valve structures. [1] S. H. Florez et al. Phys. Rev. B 78, 184403 (2008) [2] Y.-T. Cui et al. Phys. Rev. B 77, 214440 (2008)

  11. High sensitivity field asymmetric ion mobility spectrometer

    Science.gov (United States)

    Chavarria, Mario A.; Matheoud, Alessandro V.; Marmillod, Philippe; Liu, Youjiang; Kong, Deyi; Brugger, Jürgen; Boero, Giovanni

    2017-03-01

    A high sensitivity field asymmetric ion mobility spectrometer (FAIMS) was designed, fabricated, and tested. The main components of the system are a 10.6 eV UV photoionization source, an ion filter driven by a high voltage/high frequency n-MOS inverter circuit, and a low noise ion detector. The ion filter electronics are capable to generate square waveforms with peak-to-peak voltages up to 1000 V at frequencies up to 1 MHz with adjustable duty cycles. The ion detector current amplifier has a gain up to 1012 V/A with an effective equivalent input noise level down to about 1 fA/Hz1/2 during operation with the ion filter at the maximum voltage and frequency. The FAIMS system was characterized by detecting different standard chemical compounds. Additionally, we investigated the use of a synchronous modulation/demodulation technique to improve the signal-to-noise ratio in FAIMS measurements. In particular, we implemented the modulation of the compensation voltage with the synchronous demodulation of the ion current. The analysis of the measurements at low concentration levels led to an extrapolated limit of detection for acetone of 10 ppt with an averaging time of 1 s.

  12. Magnus effects at high angles of attack and critical Reynolds numbers

    Science.gov (United States)

    Seginer, A.; Ringel, M.

    1983-01-01

    The Magnus force and moment experienced by a yawed, spinning cylinder were studied experimentally in low speed and subsonic flows at high angles of attack and critical Reynolds numbers. Flow-field visualization aided in describing a flow model that divides the Magnus phenomenon into a subcritical region, where reverse Magnus loads are experienced, and a supercritical region where these loads are not encountered. The roles of the spin rate, angle of attack, and crossflow Reynolds number in determining the boundaries of the subcritical region and the variations of the Magnus loads were studied.

  13. Nonlinear relaxation field in charged systems under high electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Morawetz, K

    2000-07-01

    The influence of an external electric field on the current in charged systems is investigated. The results from the classical hierarchy of density matrices are compared with the results from the quantum kinetic theory. The kinetic theory yields a systematic treatment of the nonlinear current beyond linear response. To this end the dynamically screened and field-dependent Lenard-Balescu equation is integrated analytically and the nonlinear relaxation field is calculated. The classical linear response result known as Debye - On-Sager relaxation effect is only obtained if asymmetric screening is assumed. Considering the kinetic equation of one specie the other species have to be screened dynamically while the screening with the same specie itself has to be performed statically. Different other approximations are discussed and compared. (author)

  14. Fracture behaviors of thin superconducting films with field-dependent critical current density

    Science.gov (United States)

    He, An; Xue, Cun; Yong, Huadong; Zhou, Youhe

    2013-09-01

    The fracture behaviors under electromagnetic force with field-dependent critical current density in thin superconducting film are investigated. Applying finite element method, the energy release rates and stress intensity factors of one central crack versus applied field and crack length are obtained for the Bean model and Kim model. It is interesting that the profile of the stress intensity factor is generally the same as the magnetostrictive behavior during one full cycle applied field. Furthermore, the crack problem of two collinear cracks with respect to crack length and distance is also researched for the Kim model. The results show that the energy release rates and stress intensity factors of the two collinear cracks at left tip and right tip are remarkably different for relatively small crack distance and long crack length. This work can offer good estimations and provide a basis for interpretation of cracking and mechanical failure of HTS thin films in numerous real situations.

  15. Self-resonant Coil for Contactless Electrical Conductivity Measurement under Pulsed Ultra-high Magnetic Fields

    CERN Document Server

    Nakamura, Daisuke; Takeyama, Shojiro

    2014-01-01

    In this study, we develop experimental apparatus for contactless electrical conductivity measurements under pulsed high magnetic fields over 100 T using a self-resonant-type high-frequency circuit. The resonant power spectra were numerically analyzed, and the conducted simulations showed that the apparatus is optimal for electrical conductivity measurements of materials with high electrical conductivity. The newly developed instruments were applied to a high-temperature cuprate superconductor La$_{2-x}$Sr$_x$CuO$_4$ to show conductivity changes in magnetic fields up to 102 T with a good signal-to-noise ratio. The upper critical field was determined with high accuracy.

  16. Proceedings of the sixth Japan--US workshop on high-field superconducting materials and standard procedures for high-field superconducting materials testing

    Energy Technology Data Exchange (ETDEWEB)

    Tachikawa, K. (ed.) (Tokai Univ., Kanagawa (Japan). Faculty of Engineering); Yamafuji, K. (ed.) (Kyushu Univ., Fukuoka (Japan). Dept. of Electronics); Wada, H. (ed.) (National Research Inst. for Metals, Tsukuba, Ibaraki (Japan)); Ekin, J.W. (ed.) (National Inst. of Standards and Technology, Boulder, CO (United States)); Suenaga, M. (ed.) (Brookhaven National Lab., Upton, NY (United States))

    1989-01-01

    High critical current densities and high magnetic fields are needed for most important energy application of both conventional and high-Tc superconductors. This workshop brought together those engaged research on high-field superconductors in Japan and the US to present recent research results on performance of new high-field superconducting materials and to discuss the most promising directions for research, specifically as it relates to the fusion energy needs of both countries. Topics covered included critical currents, irradiation effects, ac losses, magnetization properties, and new fabrication processes for conventional superconductors. An entire session was devoted to presentations on the properties of Nb[sub 3]Al superconductors. Large magnet research programs for energy applications were reviewed, including the tokamak fusion machine at JAERI, the joint US-Japan Nb[sub 3]Sn poloidal-field-coll development program, and the proposed International Thermonuclear Experimental Reactor (ITER) project. Results were also presented on the VAMAS round robin in three areas; J[sub c], stress effects, and ac losses. Finally, some current research results on experimental high-[Tc] superconductors were reviewed, with particular emphasis on new fabrication processes and the factors limiting the critical current in high-current conductors. Separate abstracts have been prepared.

  17. Proceedings of the sixth Japan--US workshop on high-field superconducting materials and standard procedures for high-field superconducting materials testing

    Energy Technology Data Exchange (ETDEWEB)

    Tachikawa, K. [ed.] [Tokai Univ., Kanagawa (Japan). Faculty of Engineering; Yamafuji, K. [ed.] [Kyushu Univ., Fukuoka (Japan). Dept. of Electronics; Wada, H. [ed.] [National Research Inst. for Metals, Tsukuba, Ibaraki (Japan); Ekin, J.W. [ed.] [National Inst. of Standards and Technology, Boulder, CO (United States); Suenaga, M. [ed.] [Brookhaven National Lab., Upton, NY (United States)

    1989-12-31

    High critical current densities and high magnetic fields are needed for most important energy application of both conventional and high-Tc superconductors. This workshop brought together those engaged research on high-field superconductors in Japan and the US to present recent research results on performance of new high-field superconducting materials and to discuss the most promising directions for research, specifically as it relates to the fusion energy needs of both countries. Topics covered included critical currents, irradiation effects, ac losses, magnetization properties, and new fabrication processes for conventional superconductors. An entire session was devoted to presentations on the properties of Nb{sub 3}Al superconductors. Large magnet research programs for energy applications were reviewed, including the tokamak fusion machine at JAERI, the joint US-Japan Nb{sub 3}Sn poloidal-field-coll development program, and the proposed International Thermonuclear Experimental Reactor (ITER) project. Results were also presented on the VAMAS round robin in three areas; J{sub c}, stress effects, and ac losses. Finally, some current research results on experimental high-{Tc} superconductors were reviewed, with particular emphasis on new fabrication processes and the factors limiting the critical current in high-current conductors. Separate abstracts have been prepared.

  18. Field-induced quadrupolar quantum criticality in PrV2Al20

    Science.gov (United States)

    Shimura, Yasuyuki; Tsujimoto, Masaki; Zeng, Bin; Balicas, Luis; Sakai, Akito; Nakatsuji, Satoru

    2015-06-01

    PrV2Al20 is a heavy-fermion superconductor based on the cubic Γ3 doublet that exhibits nonmagnetic quadrupolar ordering below ˜0.6 K. Our magnetotransport study on PrV2Al20 reveals field-induced quadrupolar quantum criticality at μ0Hc˜11 T applied along the [111] direction. Near the critical field μ0Hc required to suppress the quadrupolar state, we find a marked enhancement of the resistivity ρ (H ,T ) , a divergent quasiparticle effective mass and concomitant non-Fermi-liquid (NFL) behavior [i.e., ρ (T ) ∝Tn with n ≤0.5 ]. We also observe the Shubnikov-de Haas effect above μ0Hc , indicating effective mass enhancement or m*/m0˜10 . This reveals the competition between the nonmagnetic Kondo effect and the intersite quadrupolar coupling which leads to pronounced NFL behavior in an extensive region of T and μ0H emerging from the quantum-critical point.

  19. Reliability of the Single-Visit Field Test of Critical Speed in Trained and Untrained Adolescents

    Directory of Open Access Journals (Sweden)

    Alfred Nimmerichter

    2015-12-01

    Full Text Available Recent studies in adults have shown that the critical intensity during running and cycling estimated from three prediction trials interspersed by 30 min is valid and reliable. To establish the reliability of the single-visit field test to determine critical speed (CS and the distance above critical speed (D′ in adolescents, 29 trained and 14 untrained participants (mean ± SD age: 17.5 ± 0.5 years performed three tests on a 400-m outdoor track separated by 48 h. Each test consisted of three distances selected to result in finishing times between 2 and 15 min that must be completed as fast as possible. CS and D′ were modeled using the linear 1/time model (Speed = D′(1/t + CS. While the coefficient of variation (CV of CS was between 2.4% and 4.3%, the CV of D′ was 9.3% to 13.6%. Also the intraclass correlation coefficient ranged from 0.919 to 0.983 for CS and from 0.325 to 0.828 for D′. The results show that the single-visit field test provides reliable estimates of CS but not D′ in trained and untrained adolescents.

  20. Josephson critical current of long SNS junctions in the presence of a magnetic field

    Science.gov (United States)

    Meier, Hendrik; Fal'Ko, Vladimir I.; Glazman, Leonid I.

    We evaluate the Josephson critical current of a long and wide two-dimensional superconductor-normal metal-superconductor (SNS) junction, taking into account the effect of electron reflection off the side edges of the junction. Considering clean junctions, we find that the effect of edges alters the usual Fraunhofer-like dependence of the Josephson critical current Ic on the magnetic flux Φ. At relatively weak fields, B edge effect lifts zeros of the Ic (Φ) dependence and gradually shifts the maxima of that function by Φ0 / 2 . (Here W is the width of the junction and Φ0 the magnetic flux quantum.) At higher fields, B >~Φ0 /W2 , the edge effect leads to an accelerated decay of the critical current Ic (Φ) with increasing Φ. Our results are robust with respect to the roughness of realistic boundaries. Finally, we discuss the role of mesoscopic fluctuations of Ic (Φ) originating from the scattering off the edges, and compare our findings to recent experiments.

  1. Homogenous BSCCO-2212 Round Wires for Very High Field Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Scott Campbell

    2012-06-30

    the very significant advantage of an extremely high H{sub c2}. For this reason, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y} (Bi-2212, or 2212) in the form of a multifilamentary Ag alloy matrix composite is beginning to attract the interest of the magnet community for future extremely high-field magnets or magnet-insert coils for 4.2K operation. Fig. 1 shows an example of excellent JE (engineering current density) in Bi-2212 round wire at fields up to 45 T, demonstrating the potential for high field applications of this material. For comparison, the Nb{sub 3}Sn wires used in magnets in the 16-18 T range typically perform with J{sub E} in the range 200-500 A/mm{sup 2}; the Bi-2212 wire retains this level of performance to fields at least as high as 45 T, and probably significantly higher. Bi-2212 conductors have in fact been used to generate a 25 T field in a superconducting insert magnet. These two factors- the very high field critical current performance of Bi-2212, and the already demonstrated capability of this material for high field magnets up to 25 T, strongly suggest this material as a leading contender for the next generation high field superconducting (HFS) wire. This potential was recognized by the US Academy of Science's Committee on Opportunities in High Magnetic Field Science. Their report of the same name specifically calls out the high field potential for this material, and suggests that 30 T magnets appear feasible based on the performance of 2212. There are several requirements for HFS conductors. The most obvious is J{sub E} (B, T), the engineering current density at the field and temperature of operation. As shown in Fig. 1, Bi-2212 excels in this regard. Stability requirements for magnets dictate that the effective filament diameter should be less than 30 micrometers, something that Bi-2212 multifilamentary wire can uniquely satisfy among the HFS superconducting wire technologies. Additional requirements include mechanical properties that prevent

  2. High-Gain High-Field Fusion Plasma

    Science.gov (United States)

    Li, Ge

    2015-01-01

    A Faraday wheel (FW)—an electric generator of constant electrical polarity that produces huge currents—could be implemented in an existing tokamak to study high-gain high-field (HGHF) fusion plasma, such as the Experimental Advanced Superconducting Tokamak (EAST). HGHF plasma can be realized in EAST by updating its pulsed-power system to compress plasma in two steps by induction fields; high gains of the Lawson trinity parameter and fusion power are both predicted by formulating the HGHF plasma. Both gain rates are faster than the decrease rate of the plasma volume. The formulation is checked by earlier ATC tests. Good agreement between theory and tests indicates that scaling to over 10 T at EAST may be possible by two-step compressions with a compression ratio of the minor radius of up to 3. These results point to a quick new path of fusion plasma study, i.e., simulating the Sun by EAST. PMID:26507314

  3. On the Critical Behaviour of Observed and Simulated Spatial Soil Moisture Fields during SGP97

    Directory of Open Access Journals (Sweden)

    Mekonnen Gebremichael

    2010-09-01

    Full Text Available The aircraft-based ESTAR soil moisture fields from the Southern Great Plains 1997 (SGP97 Hydrology Experiment are compared to the simulated ones obtained by Bertoldi et al. [1] with the GEOtop model [2], with a particular focus on their capability in capturing the critical point behaviour in their space-time dynamics (see [3]. The critical point behaviour should denote the transition of soil moisture spatial patterns from an unorganized to organized appearance, as conditions become wetter. The study region is the Little Washita watershed, located in the southwest Oklahoma, in the Southern Great Plains region of the USA. The case study takes place from June 27 to July 16 and encompasses wetting and drying cycles allowing for exploring the behaviour under transient conditions. Results show that the critical probability value is 0.85 for GEOtop, and 0.80 for ESTAR. The GEOtop patterns appear more fragmented, being more reluctant to organization, as confirmed by the higher value of critical probability. Such behaviour is probably inherited by the model’s parameterization: land use and soil classes impose additional spatial structures to those related to the meteorological forcings and the hillslope morphology, driving to higher degrees of heterogeneity.

  4. Plant Responses to High Frequency Electromagnetic Fields

    Directory of Open Access Journals (Sweden)

    Alain Vian

    2016-01-01

    Full Text Available High frequency nonionizing electromagnetic fields (HF-EMF that are increasingly present in the environment constitute a genuine environmental stimulus able to evoke specific responses in plants that share many similarities with those observed after a stressful treatment. Plants constitute an outstanding model to study such interactions since their architecture (high surface area to volume ratio optimizes their interaction with the environment. In the present review, after identifying the main exposure devices (transverse and gigahertz electromagnetic cells, wave guide, and mode stirred reverberating chamber and general physics laws that govern EMF interactions with plants, we illustrate some of the observed responses after exposure to HF-EMF at the cellular, molecular, and whole plant scale. Indeed, numerous metabolic activities (reactive oxygen species metabolism, α- and β-amylase, Krebs cycle, pentose phosphate pathway, chlorophyll content, terpene emission, etc. are modified, gene expression altered (calmodulin, calcium-dependent protein kinase, and proteinase inhibitor, and growth reduced (stem elongation and dry weight after low power (i.e., nonthermal HF-EMF exposure. These changes occur not only in the tissues directly exposed but also systemically in distant tissues. While the long-term impact of these metabolic changes remains largely unknown, we propose to consider nonionizing HF-EMF radiation as a noninjurious, genuine environmental factor that readily evokes changes in plant metabolism.

  5. Universal logarithmic temperature dependence of magnetic susceptibility of one-dimensional electrons at critical values of magnetic field

    OpenAIRE

    Vekua, Temo

    2014-01-01

    We study the leading low temperature dependence of magnetic susceptibility of one-dimensional electrons with fixed total number of particles at the magnetic fields equal to zero temperature critical values where magnetic field induces commensurate-incommensurate quantum phase transitions. For free and repulsively interacting electrons there is only one such critical field corresponding to the transition to the fully polarized state. For attractively interacting electrons besides saturation fi...

  6. Critical behavior of mean-field spin glasses on a dilute random graph

    Energy Technology Data Exchange (ETDEWEB)

    De Sanctis, Luca [Dipartimento di Matematica e di Psicologia, Universita di Bologna, P.zza di Porta San Donato 5, 40126 Bologna (Italy); Barra, Adriano; Folli, Viola [Dipartimento di Fisica, Universita La Sapienza, P.le Aldo Moro 5, 00185 Roma (Italy)], E-mail: desanctis@dm.unibo.it, E-mail: adriano.barra@roma1.infn.it, E-mail: viola.folli@roma1.infn.it

    2008-05-30

    We provide a rigorous strategy to find the critical exponents of the overlaps for dilute spin glasses, in the absence of an external field. Such a strategy is based on the expansion of a suitably perturbed average of the overlaps, which is used in the formulation of the free energy as the difference between a cavity part and the derivative of the free energy itself, considered as a function of the connectivity of the model. We assume the validity of certain reasonable approximations, equivalent to assuming a second-order transition, e.g. that higher powers of overlap monomials are of smaller magnitude near the critical point, of which we do not provide a rigorous proof.

  7. The role of disorder in the dynamics of critical fluctuations of mean field models

    CERN Document Server

    Collet, Francesca

    2011-01-01

    The purpose of this paper is to analyze how the disorder affects the dynamics of critical fluctuations for two different types of interacting particle system: the Curie-Weiss and Kuramoto model. The models under consideration are a collection of spins and rotators respectively. They both are subject to a mean field interaction and embedded in a site-dependent, i.i.d. random environment. As the number of particles goes to infinity their limiting dynamics become deterministic and exhibit phase transition. The main result concern the fluctuations around this deterministic limit at the critical point in the thermodynamic limit. From a qualitative point of view, it indicates that when disorder is added spin and rotator systems belong to two different classes of universality, which is not the case for the homogeneous models (i.e., without disorder).

  8. Critical dynamics a field theory approach to equilibrium and non-equilibrium scaling behavior

    CERN Document Server

    Täuber, Uwe C

    2014-01-01

    Introducing a unified framework for describing and understanding complex interacting systems common in physics, chemistry, biology, ecology, and the social sciences, this comprehensive overview of dynamic critical phenomena covers the description of systems at thermal equilibrium, quantum systems, and non-equilibrium systems. Powerful mathematical techniques for dealing with complex dynamic systems are carefully introduced, including field-theoretic tools and the perturbative dynamical renormalization group approach, rapidly building up a mathematical toolbox of relevant skills. Heuristic and qualitative arguments outlining the essential theory behind each type of system are introduced at the start of each chapter, alongside real-world numerical and experimental data, firmly linking new mathematical techniques to their practical applications. Each chapter is supported by carefully tailored problems for solution, and comprehensive suggestions for further reading, making this an excellent introduction to critic...

  9. Statistical field theory with constraints: Application to critical Casimir forces in the canonical ensemble.

    Science.gov (United States)

    Gross, Markus; Gambassi, Andrea; Dietrich, S

    2017-08-01

    The effect of imposing a constraint on a fluctuating scalar order parameter field in a system of finite volume is studied within statistical field theory. The canonical ensemble, corresponding to a fixed total integrated order parameter (e.g., the total number of particles), is obtained as a special case of the theory. A perturbative expansion is developed which allows one to systematically determine the constraint-induced finite-volume corrections to the free energy and to correlation functions. In particular, we focus on the Landau-Ginzburg model in a film geometry (i.e., in a rectangular parallelepiped with a small aspect ratio) with periodic, Dirichlet, or Neumann boundary conditions in the transverse direction and periodic boundary conditions in the remaining, lateral directions. Within the expansion in terms of ε=4-d, where d is the spatial dimension of the bulk, the finite-size contribution to the free energy of the confined system and the associated critical Casimir force are calculated to leading order in ε and are compared to the corresponding expressions for an unconstrained (grand canonical) system. The constraint restricts the fluctuations within the system and it accordingly modifies the residual finite-size free energy. The resulting critical Casimir force is shown to depend on whether it is defined by assuming a fixed transverse area or a fixed total volume. In the former case, the constraint is typically found to significantly enhance the attractive character of the force as compared to the grand canonical case. In contrast to the grand canonical Casimir force, which, for supercritical temperatures, vanishes in the limit of thick films, in the canonical case with fixed transverse area the critical Casimir force attains for thick films a negative value for all boundary conditions studied here. Typically, the dependence of the critical Casimir force both on the temperaturelike and on the fieldlike scaling variables is different in the two ensembles.

  10. Field measurement of critical shear stress for erosion and deposition of fine muddy sediments

    Science.gov (United States)

    Salehi, M.; Strom, K. B.; Field Study

    2010-12-01

    The movement of muddy sediment from one region to another is linked to the fate and transport of pollutants that can be attached to this sediment. Important in understanding this movement is the need to know the critical conditions for erosion and deposition of the fine muddy sediment. For non-cohesion sediment, such as sands and gravels, reasonable estimates for the critical conditions can often be made theoretically without in situ measurements of the critical fluid condition or sediment transport rate. However, the shear stress needed for the incipient motion of the mud (cohesive sediments) is inherently difficult to calculate theoretically or in research flumes due to the influence of (1) flow history; (2) local sediment composition; (3) biological activity within the bed; (4) water content of the bed; and (5) salinity of the water column. The complexity of the combination of these factors makes the field measurement necessary. A field experiment was conducted under tidal flow in the region surrounding the Houston Ship Channel (near Houston, TX) to determine these conditions. Observations were made using single point, simultaneous, in situ measurement of turbulent flow and suspended sediment concentration within bottom boundary layer. Measurements were primarily made with a 6 MHz Nortek Vector velocimeter (ADV). The ADV was programmed to record 3-minute turbulent velocity with 32 Hz frequency every 10 minute. The suspended sediment concentration (SSC) was measured using the calibration of acoustic backscatter recorded by ADV against sample derived SSC. Different methods such as turbulent kinetic energy (TKE), TKEw and direct covariance method (COV) are compared together. TKE showed much more reasonable estimation on bed shear stress. Combination of time varying SSC, distance from the bed to the sampling volume recorded by ADV and calculation of shear stress made the determination of critical conditions for erosion and deposition possible.

  11. High magnetic field ohmically decoupled non-contact technology

    Science.gov (United States)

    Wilgen, John [Oak Ridge, TN; Kisner, Roger [Knoxville, TN; Ludtka, Gerard [Oak Ridge, TN; Ludtka, Gail [Oak Ridge, TN; Jaramillo, Roger [Knoxville, TN

    2009-05-19

    Methods and apparatus are described for high magnetic field ohmically decoupled non-contact treatment of conductive materials in a high magnetic field. A method includes applying a high magnetic field to at least a portion of a conductive material; and applying an inductive magnetic field to at least a fraction of the conductive material to induce a surface current within the fraction of the conductive material, the surface current generating a substantially bi-directional force that defines a vibration. The high magnetic field and the inductive magnetic field are substantially confocal, the fraction of the conductive material is located within the portion of the conductive material and ohmic heating from the surface current is ohmically decoupled from the vibration. An apparatus includes a high magnetic field coil defining an applied high magnetic field; an inductive magnetic field coil coupled to the high magnetic field coil, the inductive magnetic field coil defining an applied inductive magnetic field; and a processing zone located within both the applied high magnetic field and the applied inductive magnetic field. The high magnetic field and the inductive magnetic field are substantially confocal, and ohmic heating of a conductive material located in the processing zone is ohmically decoupled from a vibration of the conductive material.

  12. Key techniques of the high precision gravity field system

    Science.gov (United States)

    Xu, Weimin; Chen, Shi; Lu, Hongyan; Shi, Lei

    2017-04-01

    Ground-based gravity time series provide a direct method to monitor all sources of mass changes from local to global scale. But the effectively infinite spatial sensitivity of gravity measurements make it difficult to isolate the signal of interest. The high precision gravity field system is an alternative approach of modeling mass changes under-ground. The field system, consists of absolute gravity, gravity and gravity gradient, GNSS, leveling and climate hydrology measurements, can improve the signal-to-noise ratio for many applications by removing contributions of unwanted signal from elevation changes, air pressure changes, local hydrology, and others. The networks of field system combination, such as field-profile in more than 100 kilometers, can be used in critical zone with high seismic risk for monitoring earth dynamics, volcanic and seismic phenomena. The system is constituted by 9 typical observation stations in 3*3 array (or 4 in 2*2 array) in 60 square meters field, each station is designed for integrated measurements, including absolute gravity, gravity gradient, elevation changes, air pressure and hydrology. Time-lapse gravity changes resulting from absolute gravimeter (FG5 or A10) with standard deviation less than 2 μGal, without the contributions of Earth tides, loading and polar motion. Additional measurements such as air pressure change, local hydrology and soil moisture are indispensable. The elevation changes resulting from GNSS (on the base station) and leveling (between stations) with precision less than 10 mm. The gravity gradient is the significant measurement for delimiting the location of the related mass changes underground the station, which is measured by Scintrex CG-5 gravimeters in different height (80cm in the test field), with precision less than 10 E. It is necessary to improve the precision of gravity gradient measurements by certain method in field experiment for the high precision measurement system. Acknowledgment: This

  13. Critical Trajectories for the Human Settlement of the High Frontier

    Science.gov (United States)

    Valentine, Lee S.

    2007-02-01

    If preservation and prosperity of humanity on the Earth and human settlement of space are our goals, we should concentrate on a commercial path to get there. Commercial enterprise has a long history of fortuitously aiding scientific progress. We expect radical changes in the cost of earth to orbit transportation, and in the methods and efficacy of deep space transportation, within the next two decades. A successful space tourism industry, beginning with suborbital tourism, will greatly drive down the cost of access to orbit over the next 15 years. Inexpensive transportation to low Earth orbit is the first requirement for a great future on the High Frontier. Inexpensive means the cost associated with a mature transportation system. A mature system has a cost of three to five times the cost of the propellant. The first cheap, reliable and highly reusable rocket engines are just now appearing in vehicles. With an assured market and high flight rate, the heretofore glacial progress in reducing the cost of space transportation is likely to become rapid. This is the first critical enabling example of synergy between free market economics and scientific and technical progress in space. It will not be the last. New high power switches and ultracapacitors developed for the automotive market make possible cheap, robust and reliable mass driver engines. In space construction, using masses of nonterrestrial materials make the gravity tractor technique much more capable than previous schemes to maneuver asteroids. Ion propulsion will continue to improve and the first solar sails will be flown. Advanced robotics will allow remarkable improvements in productivity. The computing power available to robots began to follow the exponential Moore's law less than decade ago. The first commercial autonomous mobile robots appeared in late summer 2006. Humans, however, will be required for the foreseeable future in repair and supervisory roles, particularly in unstructured settings such as

  14. Ethnopharmacological field studies: a critical assessment of their conceptual basis and methods.

    Science.gov (United States)

    Heinrich, Michael; Edwards, Sarah; Moerman, Daniel E; Leonti, Marco

    2009-07-06

    Ethnopharmacology as a well-defined field has a relatively short history, but for centuries researchers have been interested in the observation, description, and experimental investigation of indigenous drugs and their biological activities. Today, such articles are published in a variety of journals among which the Journal of Ethnopharmacology has a prominent position as well as in book monographs. As any other area of scientific endeavour, this field requires a critical and engaged discussion about the conceptual basis, the relevant methods and the overall standards necessary for excellence. Here we review recent ethnopharmacological field studies in order to highlight achievements and future needs for improving the quality of such studies. The basis for this review is 40 field studies published in the years 2007 and 2008 in the Journal of Ethnopharmacology. Researchers need to have a clear vision for what and how they want to achieve a conceptually and methodologically sound approach and as in all disciplines adherence to internationally recognized methodological standards is essential. Here we review not only the basic conceptual requirements but also the minimal methodological (i.e. botanical, anthropological/historical,ethnomedical) standards and ways how to quantify ethnopharmacological information. Future uses of such information both in the context of experimental research and in applied projects highlight the multiple roles of such data generated in ethnopharmacological field studies. This review cannot be a book of recipes on how to conduct such research but highlights minimal conceptual and methodological requirements for use in future projects.

  15. ADX: a high field, high power density, Advanced Divertor test eXperiment

    Science.gov (United States)

    Vieira, R.; Labombard, B.; Marmar, E.; Irby, J.; Shiraiwa, S.; Terry, J.; Wallace, G.; Whyte, D. G.; Wolfe, S.; Wukitch, S.; ADX Team

    2014-10-01

    The MIT PSFC and collaborators are proposing an advanced divertor experiment (ADX) - a tokamak specifically designed to address critical gaps in the world fusion research program on the pathway to FNSF/DEMO. This high field (6.5 tesla, 1.5 MA), high power density (P/S ~ 1.5 MW/m2) facility would utilize Alcator magnet technology to test innovative divertor concepts for next-step DT fusion devices (FNSF, DEMO) at reactor-level boundary plasma pressures and parallel heat flux densities while producing high performance core plasma conditions. The experimental platform would also test advanced lower hybrid current drive (LHCD) and ion-cyclotron range of frequency (ICRF) actuators and wave physics at the plasma densities and magnetic field strengths of a DEMO, with the unique ability to deploy launcher structures both on the low-magnetic-field side and the high-field side - a location where energetic plasma-material interactions can be controlled and wave physics is most favorable for efficient current drive, heating and flow drive. This innovative experiment would perform plasma science and technology R&D necessary to inform the conceptual development and accelerate the readiness-for-deployment of FNSF/DEMO - in a timely manner, on a cost-effective research platform. Supported by DE-FC02-99ER54512.

  16. Critical Role of Monoclinic Polarization Rotation in High-Performance Perovskite Piezoelectric Materials

    Science.gov (United States)

    Liu, Hui; Chen, Jun; Fan, Longlong; Ren, Yang; Pan, Zhao; Lalitha, K. V.; Rödel, Jürgen; Xing, Xianran

    2017-07-01

    High-performance piezoelectric materials constantly attract interest for both technological applications and fundamental research. The understanding of the origin of the high-performance piezoelectric property remains a challenge mainly due to the lack of direct experimental evidence. We perform in situ high-energy x-ray diffraction combined with 2D geometry scattering technology to reveal the underlying mechanism for the perovskite-type lead-based high-performance piezoelectric materials. The direct structural evidence reveals that the electric-field-driven continuous polarization rotation within the monoclinic plane plays a critical role to achieve the giant piezoelectric response. An intrinsic relationship between the crystal structure and piezoelectric performance in perovskite ferroelectrics has been established: A strong tendency of electric-field-driven polarization rotation generates peak piezoelectric performance and vice versa. Furthermore, the monoclinic MA structure is the key feature to superior piezoelectric properties as compared to other structures such as monoclinic MB , rhombohedral, and tetragonal. A high piezoelectric response originates from intrinsic lattice strain, but little from extrinsic domain switching. The present results will facilitate designing high-performance perovskite piezoelectric materials by enhancing the intrinsic lattice contribution with easy and continuous polarization rotation.

  17. In-field critical current property of IBAD/PLD coated conductors

    Science.gov (United States)

    Fujita, S.; Daibo, M.; Igarashi, M.; Kikutake, R.; Kakimoto, K.; Iijima, Y.; Itoh, M.; Saitoh, T.

    2014-05-01

    REBa2Cu3Oy, (RE : rare earth elements, RE123) coated conductors are expected to show high performance in superconducting applications, due to their high mechanical strength and high current density in magnetic fields. Fujikura has developed ion-beam-assisted-deposition (IBAD) and pulsed-laser-deposition (PLD) technique, and today we routinely manufacture coated conductors with length over 500 m and Ic over 500 A/cm-width at 77 K, self field. We have also been able to fabricate long conductors with higher Ic by thickening RE123 layer. Although Ic performances at 77 K, self field are important, but performances in magnetic fields at lower temperatures below 77 K are more important for coil applications. In this work, we evaluated coated conductors with thick RE123 layer in magnetic fields at low temperatures. All samples are fabricated with long length. We measured samples by four-probe transport method at wide temperature range from 77 K to 10 K by using cryo-cooled cryostat. A conductor with 5.5 μm thick RE123 exhibits high Ic values of 937 A/cm-width at 77 K, self field, 637 A/cm-width at 50 K, 5T and 976 A/cm-width at 40 K, 5T.

  18. Critical wetting transitions in two-dimensional systems subject to long-ranged boundary fields

    Science.gov (United States)

    Drzewiński, A.; Maciołek, A.; Barasiński, A.; Dietrich, S.

    2009-04-01

    Using the quasiexact density-matrix renormalization-group method and ground-state analysis we study interface delocalization transitions in wide two-dimensional Ising strips subject to long-ranged boundary fields with opposite signs at the two surfaces. Based on this approach, our explicit calculations demonstrate that critical wetting transitions do exist for semi-infinite two-dimensional systems even if the corresponding effective interface potentials decay asymptotically for large ℓ as slow as ℓ-δ with δinterface position from the one-dimensional surface. This supersedes opposite claims by Kroll and Lipowsky [Phys. Rev. B 28, 5273 (1983)] and by Privman and Švrakić [Phys. Rev. B 37, 5974 (1988)] obtained within effective interface models. The corresponding wetting phase diagram is determined, including the cases δ=2 and δ=49 with the latter mimicking short-ranged surface fields. Our analysis highlights the limits of reliability of effective interface models.

  19. Critical wetting transitions in two-dimensional systems subject to long-ranged boundary fields.

    Science.gov (United States)

    Drzewiński, A; Maciołek, A; Barasiński, A; Dietrich, S

    2009-04-01

    Using the quasiexact density-matrix renormalization-group method and ground-state analysis we study interface delocalization transitions in wide two-dimensional Ising strips subject to long-ranged boundary fields with opposite signs at the two surfaces. Based on this approach, our explicit calculations demonstrate that critical wetting transitions do exist for semi-infinite two-dimensional systems even if the corresponding effective interface potentials decay asymptotically for large l as slow as l(-delta) with deltainterface position from the one-dimensional surface. This supersedes opposite claims by Kroll and Lipowsky [Phys. Rev. B 28, 5273 (1983)] and by Privman and Svrakić [Phys. Rev. B 37, 5974 (1988)] obtained within effective interface models. The corresponding wetting phase diagram is determined, including the cases delta=2 and delta=49 with the latter mimicking short-ranged surface fields. Our analysis highlights the limits of reliability of effective interface models.

  20. Direct three-dimensional ordering of quasi-one-dimensional quantum dimer system near critical fields

    Science.gov (United States)

    Matsushita, Taku; Hori, Nobuyoshi; Takata, Seiya; Wada, Nobuo; Amaya, Naoki; Hosokoshi, Yuko

    2017-01-01

    Dimensionalities of X X Z spin orderings or degenerate hard-core bosons in a quasi-one-dimensional (1D) dimer system are examined by the ac susceptibility and specific heat of antiferromagnetic bond-alternating chains in pentafluorophenyl nitronyl nitroxide (F5PNN ). At intermediate fields in the gapless region, the 1D short-range order (SRO) corresponding to the Tomonaga-Luttinger liquid and three-dimensional (3D) long-range order (LRO BEC) at lower temperatures are separately observed, as expected from the small interchain interaction. In contrast, a definite region around the critical field was established where 3D LRO occurs without the development of 1D SRO at higher temperatures.

  1. Upper critical and irreversibility fields in Ni- and Co- doped pnictide bulk superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Nikolo, Martin [Saint Louis U., Physics; Singleton, John [Los Alamos National Laboratory; Solenov, Dmitry [Saint Louis U., Physics; Jiang, Jianyi [Applied Superconductivity Center, FSU and NHMFL; Weiss, Jeremy [Applied Superconductivity Center, FSU and NHMFL; Hellstorm, Eric [Applied Superconductivity Center, FSU and NHMFL

    2017-02-13

    Comprehensive study of upper critical and irreversibility magnetic fields in Ba(Fe0.95Ni0.05)2As2 (large grain and small grain samples or Ni5(SG), Ni5(LG)), Ba(Fe0.94Ni0.06)2As2 (Ni6), Ba(Fe0.92Co0.08)2As2 (Co8), and Ba(Fe0.92Co0.09)2As2 (Co9) polycrystalline bulk pnictide superconductors was made in pulsed fields of up to 65 T.

  2. Critical Language Pedagogy in an Urban High School English Class

    Science.gov (United States)

    Godley, Amanda J.; Minnici, Angela

    2008-01-01

    The purpose of this study was to examine how classroom conversations about diverse dialects of English can provide a useful foundation for critical language and literacy instruction for students who speak African American Vernacular English (AAVE) and other stigmatized dialects. This article describes a weeklong unit on language variety that…

  3. A critical comparison of two high-throughput ascorbate analyses methods for plant samples.

    Science.gov (United States)

    Ueda, Yoshiaki; Wu, Linbo; Frei, Michael

    2013-09-01

    Ascorbate (AsA) is an important metabolite involved in stress response and development of plants. Therefore it is necessary to quantify the AsA content in many fields of plant science, including high throughput and critical applications. In this study we compared two different microplate-based AsA assays, which are suitable for high throughput applications: an ascorbate oxidase (AO)-based assay and a dipyridyl (DPD)-based assay. These methods were compared in critical applications, i.e. (i) when AsA concentrations were very low such as in apoplastic extracts, (ii) when plants contained pigments interfering with the spectrometric measurements, and (iii) when plants contained high iron concentration interfering with the color reactions. The precision of measurements was higher with the DPD method, as illustrated by higher recovery rates of internal AsA standards. On the other hand, the AO method was more sensitive to low levels of AsA. This was an advantage in determining apoplastic AsA concentration in rice, which was substantially lower than that of whole tissues. The AO method also had the advantage that plant pigments and high iron concentrations in plants tissues did not interfere with the analysis, as opposed to the DPD assay. In conclusion, both assays had advantages and the choice of a suitable method depends on the specific application.

  4. Conformal field theory of critical Casimir forces between surfaces with alternating boundary conditions in two dimensions

    Science.gov (United States)

    Dubail, J.; Santachiara, R.; Emig, T.

    2017-03-01

    Systems as diverse as binary mixtures and inclusions in biological membranes, and many more, can be described effectively by interacting spins. When the critical fluctuations in these systems are constrained by boundary conditions, critical Casimir forces (CCF) emerge. Here we analyze CCF between boundaries with alternating boundary conditions in two dimensions, employing conformal field theory (CFT). After presenting the concept of boundary changing operators, we specifically consider two different boundary configurations for a strip of critical Ising spins: (I) alternating equi-sized domains of up and down spins on both sides of the strip, with a possible lateral shift, and (II) alternating domains of up and down spins of different size on one side and homogeneously fixed spins on the other side of the strip. Asymptotic results for the CCF at small and large distances are derived. We introduce a novel modified Szegö formula for determinants of real antisymmetric block Toeplitz matrices to obtain the exact CCF and the corresponding scaling functions at all distances. We demonstrate the existence of a surface renormalization group flow between universal force amplitudes of different magnitude and sign. The Casimir force can vanish at a stable equilibrium position that can be controlled by parameters of the boundary conditions. Lateral Casimir forces assume a universal simple cosine form at large separations.

  5. High-field superconductivity at an electronic topological transition in URhGe

    Science.gov (United States)

    Yelland, E. A.; Barraclough, J. M.; Wang, W.; Kamenev, K. V.; Huxley, A. D.

    2011-11-01

    The emergence of superconductivity at high magnetic fields in URhGe is regarded as a paradigm for new state formation approaching a quantum critical point. Until now, a divergence of the quasiparticle mass at the metamagnetic transition was considered essential for superconductivity to survive at magnetic fields above 30T. Here we report the observation of quantum oscillations in URhGe revealing a tiny pocket of heavy quasiparticles that shrinks continuously with increasing magnetic field, and finally disappears at a topological Fermi surface transition close to or at the metamagnetic field. The quasiparticle mass decreases and remains finite, implying that the Fermi velocity vanishes due to the collapse of the Fermi wavevector. This offers a novel explanation for the re-emergence of superconductivity at extreme magnetic fields and makes URhGe the first proven example of a material where magnetic field-tuning of the Fermi surface, rather than quantum criticality alone, governs quantum phase formation.

  6. Quantum entanglement and criticality of the antiferromagnetic Heisenberg model in an external field.

    Science.gov (United States)

    Liu, Guang-Hua; Li, Ruo-Yan; Tian, Guang-Shan

    2012-06-27

    By Lanczos exact diagonalization and the infinite time-evolving block decimation (iTEBD) technique, the two-site entanglement as well as the bipartite entanglement, the ground state energy, the nearest-neighbor correlations, and the magnetization in the antiferromagnetic Heisenberg (AFH) model under an external field are investigated. With increasing external field, the small size system shows some distinct upward magnetization stairsteps, accompanied synchronously with some downward two-site entanglement stairsteps. In the thermodynamic limit, the two-site entanglement, as well as the bipartite entanglement, the ground state energy, the nearest-neighbor correlations, and the magnetization are calculated, and the critical magnetic field h(c) = 2.0 is determined exactly. Our numerical results show that the quantum entanglement is sensitive to the subtle changing of the ground state, and can be used to describe the magnetization and quantum phase transition. Based on the discontinuous behavior of the first-order derivative of the entanglement entropy and fidelity per site, we think that the quantum phase transition in this model should belong to the second-order category. Furthermore, in the magnon existence region (h entanglement which can be described by a free bosonic field theory is observed, and the central charge c is determined to be 1.

  7. Investigating High Field Gravity using Astrophysical Techniques

    Energy Technology Data Exchange (ETDEWEB)

    Bloom, Elliott D.; /SLAC

    2008-02-01

    The purpose of these lectures is to introduce particle physicists to astrophysical techniques. These techniques can help us understand certain phenomena important to particle physics that are currently impossible to address using standard particle physics experimental techniques. As the subject matter is vast, compromises are necessary in order to convey the central ideas to the reader. Many general references are included for those who want to learn more. The paragraphs below elaborate on the structure of these lectures. I hope this discussion will clarify my motivation and make the lectures easier to follow. The lectures begin with a brief review of more theoretical ideas. First, elements of general relativity are reviewed, concentrating on those aspects that are needed to understand compact stellar objects (white dwarf stars, neutron stars, and black holes). I then review the equations of state of these objects, concentrating on the simplest standard models from astrophysics. After these mathematical preliminaries, Sec. 2(c) discusses 'The End State of Stars'. Most of this section also uses the simplest standard models. However, as these lectures are for particle physicists, I also discuss some of the more recent approaches to the equation of state of very dense compact objects. These particle-physics-motivated equations of state can dramatically change how we view the formation of black holes. Section 3 focuses on the properties of the objects that we want to characterize and measure. X-ray binary systems and Active Galactic Nuclei (AGN) are stressed because the lectures center on understanding very dense stellar objects, black hole candidates (BHCs), and their accompanying high gravitational fields. The use of x-ray timing and gamma-ray experiments is also introduced in this section. Sections 4 and 5 review information from x-ray and gamma-ray experiments. These sections also discuss the current state of the art in x-ray and gamma-ray satellite

  8. Threats to ultra-high-field MRI

    Science.gov (United States)

    Le Bihan, Denis

    2009-08-01

    In 2004 the European Commission (EC) adopted a directive restricting occupational exposure to electromagnetic fields. This directive (2004/40/CE), which examines the possible health risks of the electromagnetic fields from mobile phones, Wi-Fi, Bluetooth and other devices, concluded that upper limits on radiation and applied electromagnetic fields are necessary to prevent workers from suffering any undue acute health effects. But although not initially intended, the biggest impact of the directive could be on magnetic resonance imaging (MRI), which is used in hospitals worldwide to produce images of unrivalled quality of the brain and other soft tissues.

  9. Magnetocaloric properties and critical behavior of high relative cooling power FeNiB nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Chaudhary, V. [Interdisciplinary Graduate School, Nanyang Technological University, Singapore 639798 (Singapore); Energy Research Institute @NTU, Nanyang Technological University, Singapore 637553 (Singapore); School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Maheswar Repaka, D. V.; Chaturvedi, A.; Ramanujan, R. V., E-mail: ramanujan@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Sridhar, I. [School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

    2014-10-28

    Low cost magnetocaloric nanomaterials have attracted considerable attention for energy efficient applications. We report a very high relative cooling power (RCP) in a study of the magnetocaloric effect in quenched FeNiB nanoparticles. RCP increases from 89.8 to 640 J kg{sup −1} for a field change of 1 and 5 T, respectively, these values are the largest for rare earth free iron based magnetocaloric nanomaterials. To investigate the magnetocaloric behavior around the Curie temperature (T{sub C}), the critical behavior of these quenched nanoparticles was studied. Detailed analysis of the magnetic phase transition using the modified Arrott plot, Kouvel-Fisher method, and critical isotherm plots yields critical exponents of β = 0.364, γ = 1.319, δ = 4.623, and α = −0.055, which are close to the theoretical exponents obtained from the 3D-Heisenberg model. Our results indicate that these FeNiB nanoparticles are potential candidates for magnetocaloric fluid based heat pumps and low grade waste heat recovery.

  10. Magnetocaloric properties and critical behavior of high relative cooling power FeNiB nanoparticles

    Science.gov (United States)

    Chaudhary, V.; Maheswar Repaka, D. V.; Chaturvedi, A.; Sridhar, I.; Ramanujan, R. V.

    2014-10-01

    Low cost magnetocaloric nanomaterials have attracted considerable attention for energy efficient applications. We report a very high relative cooling power (RCP) in a study of the magnetocaloric effect in quenched FeNiB nanoparticles. RCP increases from 89.8 to 640 J kg-1 for a field change of 1 and 5 T, respectively, these values are the largest for rare earth free iron based magnetocaloric nanomaterials. To investigate the magnetocaloric behavior around the Curie temperature (TC), the critical behavior of these quenched nanoparticles was studied. Detailed analysis of the magnetic phase transition using the modified Arrott plot, Kouvel-Fisher method, and critical isotherm plots yields critical exponents of β = 0.364, γ = 1.319, δ = 4.623, and α = -0.055, which are close to the theoretical exponents obtained from the 3D-Heisenberg model. Our results indicate that these FeNiB nanoparticles are potential candidates for magnetocaloric fluid based heat pumps and low grade waste heat recovery.

  11. Determination of the third critical field of superconductors using constrained effective wave function containing two variational parameters

    Energy Technology Data Exchange (ETDEWEB)

    Xu Longdao; Gao Yuliang

    1985-09-01

    Two variational parameters are included in the most probable constrained effective wave function with the accurate Hamiltonian remained. The third critical field which coincides with the result in paper (1) has been easily obtained through the variational principle.

  12. National High Magnetic Field Laboratory (NHMFL)

    Data.gov (United States)

    Federal Laboratory Consortium — The Pulsed Field Program is located in Northern New Mexico at Los Alamos National Laboratory. The user program is designed to provide researchers with a balance of...

  13. National High Magnetic Field Laboratory (NHMFL)

    Data.gov (United States)

    Federal Laboratory Consortium — The Pulsed Field Program is located in Northern New Mexico at Los Alamos National Laboratory. The user program is designed to provide researchers with a balance of...

  14. High magnetic field properties of Fe-pnictide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kurth, Fritz

    2015-11-20

    The recent discovery of high-temperature superconductivity in Fe-based materials triggered worldwide efforts to investigate their fundamental properties. Despite a lot of similarities to cuprates and MgB{sub 2}, important differences like near isotropic behaviour in contrast to cuprates and the peculiar pairing symmetry of the order parameter (OP) have been reported. The OP symmetry of Fe-based superconductors (FBS) was theoretically predicted to be of so-called s± state prior to various experimental works. Still, most of the experimental results favour the s± scenario; however, definitive evidence has not yet been reported. Although no clear understanding of the superconducting mechanisms yet exists, potential applications such as high-field magnets and Josephson devices have been explored. Indeed, a lot of reports about FBS tapes, wires, and even SQUIDs have been published to this date. In this thesis, the feasibility of high-field magnet applications of FBS is addressed by studying their transport properties, involving doped BaFe{sub 2}As{sub 2} (Ba-122) and LnFeAs(O,F) [Ln=Sm and Nd]. Particularly, it is important to study physical properties in a sample form (i.e. thin films) that is close to the conditions found in applications. However, the realisation of epitaxial FBS thin films is not an easy undertaking. Recent success in growing epitaxial FBS thin films opens a new avenue to delve into transport critical current measurements. The information obtained through this research will be useful for exploring high-field magnet applications. This thesis consists of 7 chapters: Chapter 1 describes the motivation of this study, the basic background of superconductivity, and a brief summary of the thin film growth of FBS. Chapter 2 describes experimental methods employed in this study. Chapter 3 reports on the fabrication of Co-doped Ba-122 thin films on various substrates. Particular emphasis lies on the discovery of fluoride substrates to be beneficial for

  15. High fidelity simulation of nucleate boiling and transition to critical heat flux on enhanced structures

    Science.gov (United States)

    Yazdani, Miad; Alahyari, Abbas; Radcliff, Thomas; Soteriou, Marios

    2015-11-01

    Surface enhancement is often is the primary approach for improved heat transfer performance of two-phase thermal systems particularly when they operate in nucleate boiling regime. This paper exploits the modeling capability developed by Yazdani et al. for simulation of nucleate boiling and transition to critical heat flux to study the nucleation phenomenon on various enhanced structures. The multi-scale of two-phase flow associated with boiling phenomena is addressed through combination of deterministic CFD for the macro-scale transport, asymptotic based representation of micro-layer, and stochastic representation of surface roughness so as to allow a high-fidelity simulation of boiling on an arbitrary surface. In addition, given the excessive complexity of surface structures often used for enhancement of boiling heat transfer, a phase-field-based method is developed to generate the structures where the numerical parameters in the phase-field model determine the topology of a given structure. The ``generated'' structure is then embedded into the two-phase flow model through virtual boundary method for the boiling simulation. The model is validated against experimental data for the boiling curve and the critical heat flux as well as nucleation and bubble dynamics characteristics.

  16. Temperature and Magnetic Field Dependence of Critical Current Density of YBCO with Varying Flux Pinning Additions (POSTPRINT)

    Science.gov (United States)

    2010-03-01

    AFRL-RZ-WP-TP-2010-2083 TEMPERATURE AND MAGNETIC FIELD DEPENDENCE OF CRITICAL CURRENT DENSITY OF YBCO WITH VARYING FLUX PINNING ADDITIONS...MAGNETIC FIELD DEPENDENCE OF CRITICAL CURRENT DENSITY OF YBCO WITH VARYING FLUX PINNING ADDITIONS (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b...20 ‒ 77 K. Films were prepared with pulsed laser deposition by (M/ YBCO )N multilayer or ( YBCO )1-x Mx single-target methods, for different M phases

  17. Using Bourdieu in Critical Mediatization Research: Communicational Doxa and Osmotic Pressures in the Field of UN Organizations

    Directory of Open Access Journals (Sweden)

    André Jansson

    2015-05-01

    Full Text Available This article develops a Bourdieusian approach to mediatization. It is argued that the Bourdieusian theories of doxa and fields can make valuable contributions to a critical perspective on mediatization, one that moves beyond the divides between institutionalist, social-constructivist and materialist understandings (e.g., Bourdieu, 1972/1977. Mediatization is here seen as the historically growing dependence on media technologies and institutions within diverse social fields and settings. In order to establish the link between mediatization and Bourdieu’s theories (ibid., the article introduces the concept of communicational doxa, which refers to the taken for granted communicational conventions and demands that regulate the inclusion of membership within a particular field. The article also shows how communicational doxa can be applied as an analytical concept. Findings from qualitative fieldwork carried out among highly mobile and skilled professionals within the field of UN organizations in Geneva, show how the autonomy of social agents is negotiated in relation to an increasingly mediatized communicational doxa.

  18. A feasibility study of high-strength Bi-2223 conductor for high-field solenoids

    Science.gov (United States)

    Godeke, A.; Abraimov, D. V.; Arroyo, E.; Barret, N.; Bird, M. D.; Francis, A.; Jaroszynski, J.; Kurteva, D. V.; Markiewicz, W. D.; Marks, E. L.; Marshall, W. S.; McRae, D. M.; Noyes, P. D.; Pereira, R. C. P.; Viouchkov, Y. L.; Walsh, R. P.; White, J. M.

    2017-03-01

    We performed a feasibility study on a high-strength Bi{}2-xPb x Sr2Ca2Cu3O{}10-x(Bi-2223) tape conductor for high-field solenoid applications. The investigated conductor, DI-BSCCO Type HT-XX, is a pre-production version of Type HT-NX, which has recently become available from Sumitomo Electric Industries. It is based on their DI-BSCCO Type H tape, but laminated with a high-strength Ni-alloy. We used stress–strain characterizations, single- and double-bend tests, easy- and hard-way bent coil-turns at various radii, straight and helical samples in up to 31.2 T background field, and small 20-turn coils in up to 17 T background field to systematically determine the electro-mechanical limits in magnet-relevant conditions. In longitudinal tensile tests at 77 K, we found critical stress- and strain-levels of 516 MPa and 0.57%, respectively. In three decidedly different experiments we detected an amplification of the allowable strain with a combination of pure bending and Lorentz loading to ≥slant 0.92 % (calculated elastically at the outer tape edge). This significant strain level, and the fact that it is multi-filamentary conductor and available in the reacted and insulated state, makes DI-BSCCO HT-NX highly suitable for very high-field solenoids, for which high current densities and therefore high loads are required to retain manageable magnet dimensions.

  19. High-Field Superconducting Magnets Supporting PTOLEMY

    Science.gov (United States)

    Hopkins, Ann; Luo, Audrey; Osherson, Benjamin; Gentile, Charles; Tully, Chris; Cohen, Adam

    2013-10-01

    The Princeton Tritium Observatory for Light, Early Universe, Massive Neutrino Yield (PTOLEMY) is an experiment planned to collect data on Big Bang relic neutrinos, which are predicted to be amongst the oldest and smallest particles in the universe. Currently, a proof-of-principle prototype is being developed at Princeton Plasma Physics Laboratory to test key technologies associated with the experiment. A prominent technology in the experiment is the Magnetic Adiabatic Collimation with an Electrostatic Filter (MAC-E filter), which guides tritium betas along magnetic field lines generated by superconducting magnets while deflecting those of lower energies. B field mapping is performed to ensure the magnets produce a minimum field at the midpoint of the configuration of the magnets and to verify accuracy of existing models. Preliminary tests indicate the required rapid decrease in B field strength from the bore of the more powerful 3.35 T magnet, with the field dropping to 0.18 T approximately 0.5 feet from the outermost surface of the magnet.

  20. Field-induced magnetization jumps and quantum criticality in the 2D J-Q model

    Science.gov (United States)

    Iaizzi, Adam; Sandvik, Anders

    The J-Q model is a `designer hamiltonian' formed by adding a four spin `Q' term to the standard antiferromagnetic S = 1 / 2 Heisenberg model. The Q term drives a quantum phase transition to a valence-bond solid (VBS) state: a non-magnetic state with a pattern of local singlets which breaks lattice symmetries. The elementary excitations of the VBS are triplons, i.e. gapped S=1 quasiparticles. There is considerable interest in the quantum phase transition between the Néel and VBS states as an example of deconfined quantum criticality. Near the phase boundary, triplons deconfine into pairs of bosonic spin-1/2 excitations known as spinons. Using exact diagonalization and the stochastic series expansion quantum monte carlo method, we study the 2D J-Q model in the presence of an external magnetic field. We use the field to force a nonzero density of magnetic excitations at T=0 and look for signatures of Bose-Einstein condensation of spinons. At higher magnetic fields, there is a jump in the induced magnetization caused by the onset of an effective attractive interaction between magnons on a ferromagnetic background. We characterize the first order quantum phase transition and determine the minimum value of the coupling ratio q ≡ Q / J required to produce this jump. Funded by NSF DMR-1410126.

  1. Fracture behaviors of thin superconducting films with field-dependent critical current density

    Energy Technology Data Exchange (ETDEWEB)

    He, An; Xue, Cun; Yong, Huadong; Zhou, Youhe, E-mail: zhouyh@lzu.edu.cn

    2013-09-15

    Highlights: • The fracture behaviors of superconducting films for the Kim model are studied. • The profile of stress intensity factor is generally the same as magnetostriction. • The crack problem of two collinear cracks is also researched for the Kim model. -- Abstract: The fracture behaviors under electromagnetic force with field-dependent critical current density in thin superconducting film are investigated. Applying finite element method, the energy release rates and stress intensity factors of one central crack versus applied field and crack length are obtained for the Bean model and Kim model. It is interesting that the profile of the stress intensity factor is generally the same as the magnetostrictive behavior during one full cycle applied field. Furthermore, the crack problem of two collinear cracks with respect to crack length and distance is also researched for the Kim model. The results show that the energy release rates and stress intensity factors of the two collinear cracks at left tip and right tip are remarkably different for relatively small crack distance and long crack length. This work can offer good estimations and provide a basis for interpretation of cracking and mechanical failure of HTS thin films in numerous real situations.

  2. 7 CFR 12.22 - Highly erodible field determination criteria.

    Science.gov (United States)

    2010-01-01

    ... Section 12.22 Agriculture Office of the Secretary of Agriculture HIGHLY ERODIBLE LAND AND WETLAND CONSERVATION Highly Erodible Land Conservation § 12.22 Highly erodible field determination criteria. (a... included in an approved conservation plan for the entire highly erodible field....

  3. Mean field analysis of the high temperature magnetic properties of terbium iron garnet in strong DC fields

    Energy Technology Data Exchange (ETDEWEB)

    Lahoubi, Mahieddine, E-mail: mlahoubi@hotmail.fr [Department of Physics, Laboratory L.P.S., Faculty of Sciences, Badji Mokhtar-Annaba University, PO Box-12, 23000 Annaba (Algeria); Wang, Wei, E-mail: wangwei@mail.buct.edu.cn [Department of Physics and Electronics, Beijing University of Chemical Technology, Beijing 100029 (China); Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States)

    2015-11-01

    This paper is devoted to the description of the magnetic phase diagrams (MPD) together with a special interest to the determination of more precise values of some reliable parameters at the compensation point, T{sub comp}=243.5±0.5 K of the terbium iron garnet, Tb{sub 3}Fe{sub 5}O{sub 12} or TbIG. Using isothermal magnetizations performed on single crystal in strong DC magnetic fields up to 200 kOe applied along the 〈111〉, 〈110〉 and 〈100〉 directions within the temperature range 128–295 K, field-induced phase transitions between collinear and canted phases are observed in the vicinity of T{sub comp} at critical fields, H{sub c2}. In comparison with the measurement at zero external magnetic field, the specific heat, C{sub p}(T) at 80 kOe along 〈111〉 shows an excess around T{sub comp} characterized by an anomaly which has a width in the boundaries of the canted phase and a maximum at 252 K, the more accurate value of the critical temperature, T{sub C}{sup ⁎} of the MPD in the (H{sub c2}–T) plane. Better determinations of the molecular field coefficients which represent the magnetic interactions on the Tb sublattice are obtained by an improved molecular field model based on the saturation effects of the Tb sublattice and the differential susceptibility contribution due to the Fe sublattices to the total magnetic susceptibility of TbIG. The results are discussed in terms of the previous theoretical studies of the MPD predicted for weakly anisotropic ferrimagnets. - Highlights: • High-T magnetizations are made on single crystal of TbIG in strong DC magnetic fields. • FIPTs are observed in the vicinity of T{sub comp}=243.5 K at critical fields, H{sub c2}. • MPD are determined in the (H{sub c2}–T ) plane for H along the main crystallographic directions. • The critical temperature T{sub C}{sup ⁎} is well estimated by the C{sub p}(T ) data at H{sub ex}=80 kOe along 〈111〉. • The results are analyzed using a high-field method and a mean

  4. Idea Generation in Highly Institutionalized Fields

    DEFF Research Database (Denmark)

    Agoguè, Marine; Boxenbaum, Eva

    , bricolage and innovative design reasoning. We identify metaphors and bricolage as central to the subconscious system, which play an important role in maintaining the field frame, whereas conceptual blending and innovative design reasoning can be instrumental in generating ideas in the conscious system...

  5. Highly educated but in the wrong field?

    DEFF Research Database (Denmark)

    Reimer, David; Steinmetz, Stephanie

    2009-01-01

    and non-linear decomposition analyses generally confirm our expectation that the field of study explains a sizable portion of the gender gap in unemployment and low-status jobs in both countries. However, the level of tertiary degree earned explains only part of the female disadvantage behind holding...

  6. High Field Magnetization of Tb Single Crystals

    DEFF Research Database (Denmark)

    Roeland, L. W.; Cock, G. J.; Lindgård, Per-Anker

    1975-01-01

    The magnetization of Tb single crystals was measured in magnetic fields to 34T along the hard direction at temperature of 1.8, 4.2, 65.5 and 77K, and along with easy direction at 4.2 and 77K. The data are compared with the results of a self-consistent spin wave calculation using a phenomenological...

  7. Angular dependence of critical current density and magnetoresistance of sputtered high-T{sub c}-films

    Energy Technology Data Exchange (ETDEWEB)

    Geerkens, A.; Frenck, H.J.; Ewert, S. [Technical Univ. of Cottbus (Germany)] [and others

    1994-12-31

    The angular dependence of the critical current density and the magnetoresistance of high-T{sub c}-films in high and low magnetic fields and for different temperatures were measured to investigate the flux pinning and the superconducting properties. A comparison of the results for the different superconductors shows their increasing dependence on the angle {Theta} between the magnetic field and the c-axis of the film due to the anisotropy of the chosen superconductor. Furthermore the influence of the current direction to the {Theta}-rotation plane is discussed.

  8. Critical collapse of a rotating scalar field in 2 +1 dimensions

    Science.gov (United States)

    JałmuŻna, Joanna; Gundlach, Carsten

    2017-04-01

    We carry out numerical simulations of the collapse of a complex rotating scalar field of the form Ψ (t ,r ,θ )=ei m θΦ (t ,r ), giving rise to an axisymmetric metric, in 2 +1 spacetime dimensions with cosmological constant Λ 0 is very different from the case m =0 we have considered before: the thresholds for mass scaling and Ricci scaling are significantly different (for the same family); scaling stops well above the scale set by Λ , and the exponents depend strongly on the family. Hence, in contrast to the m =0 case, and to many other self-gravitating systems, there is only weak evidence for the collapse threshold being controlled by a self-similar critical solution and no evidence for it being universal.

  9. Mean-field dynamic criticality and geometric transition in the Gaussian core model

    Science.gov (United States)

    Coslovich, Daniele; Ikeda, Atsushi; Miyazaki, Kunimasa

    2016-04-01

    We use molecular dynamics simulations to investigate dynamic heterogeneities and the potential energy landscape of the Gaussian core model (GCM). Despite the nearly Gaussian statistics of particles' displacements, the GCM exhibits giant dynamic heterogeneities close to the dynamic transition temperature. The divergence of the four-point susceptibility is quantitatively well described by the inhomogeneous version of the mode-coupling theory. Furthermore, the potential energy landscape of the GCM is characterized by large energy barriers, as expected from the lack of activated, hopping dynamics, and display features compatible with a geometric transition. These observations demonstrate that all major features of mean-field dynamic criticality can be observed in a physically sound, three-dimensional model.

  10. Triplet generation and upper critical field in superconducting spin valves based on CrO2

    Science.gov (United States)

    Voltan, S.; Singh, A.; Aarts, J.

    2016-08-01

    It has been recently reported that a superconducting triplet spin valve (TSV) based on the half-metallic CrO2 can show "colossal" variations of the critical temperature, up to more than 1 K. This can be achieved when the magnetic noncollinearity between the mixer (F1) and the drainage ferromagnetic layer (F) is maximized. In this work we investigate further such TSV devices looking at two aspects: first, we present the dependence of the TSV effect on the thickness of the mixer layer; second, we look at the perpendicular upper critical field Hc 2 ⊥ as a function of the temperature. The thickness dependence, which is nonmonotonic as expected, represents a further proof that the effect is due to the generation of equal-spin triplet Cooper pairs, while what we observe for the Hc 2 ⊥ versus T curves is an interesting and peculiar behavior: there is a clear deviation from the universal linear dependence and the average slope is suppressed much more than what can be described with the formalism used for conventional proximized structures.

  11. Critical Behavior of the Gaussian Model with Periodic Interactions on Diamond-Type Hierarchical Lattices in External Magnetic Fields

    Institute of Scientific and Technical Information of China (English)

    LIN ZhenQuan; KONG XiangMu; JIN JinShuang; YANG ZhanRu

    2001-01-01

    The Gaussian spin model with periodic interactions on the diamond-type hierarchical lattices is constructed by generalizing that with uniform interactions on translationally invariant lattices according to a class of substitution sequences. The Gaussian distribution constants and imposed external magnetic fields are also periodic depending on the periodic characteristic of the interaction bonds. The critical behaviors of this generalized Gaussian model in external magnetic fields are studied by the exact renormalization-group approach and spin rescaling method. The critical points and all the critical exponents are obtained. The critical behaviors are found to be determined by the Gaussian distribution constants and the fractal dimensions of the lattices. When all the Gaussian distribution constants are the same, the dependence of the critical exponents on the dimensions of the lattices is the same as that of the Gaussian model with uniform interactions on translationally invariant lattices.

  12. Critical state and vortex dynamics in high temperature superconductors: Experimental and numerical investigations

    Energy Technology Data Exchange (ETDEWEB)

    Gjoelmesli, S.

    1995-05-01

    In this thesis, statics and dynamics of magnetic vortices in high temperature superconductors has been investigated by ac susceptibility, magnetic relaxation and transport measurements, using several different compounds. Measurements of the complex susceptibility of granular superconducting YBa{sub 2}Cu{sub 3}O{sub 7{sub -}x} (YBCO) reveal two distinct regimes of screening due to granular and intergranular currents respectively. In the critical state, the presence of a dc field breaks the symmetry of the experimental conditions if the critical current is field dependent. In such experiments two peaks in the loss component {chi}{sup ``}(B) of the complex susceptibility are found, both caused by intergranular currents. The symmetry breaking due to a dc field is seen directly in sampled waveforms of the pickup coil voltage, which represent the time derivative of the dynamic magnetization. In contrast to granular materials, a single crystal YBCO displays significant frequency dependence of the peak of the loss component {chi}{sup ``}(T). The power-law voltage current characteristic is equivalent to nonlinear vortex diffusion, with a characteristic length scale which reduces to the Bean depth and the classical skin-depth as the exponent tends to infinity and one, respectively. Magnetic relaxation measurements on the mercury based superconductor Hg-1212 has been done by means of a SQUID magnetometer. A new set-up for measurements of voltage-current characteristics of superconducting tapes and other samples has been constructed. Silver sheathed Bi-2223 tapes have been measured. 123 refs., 61 figs., 1 tab.

  13. High-field magnetization of dilute rare earths in yttrium

    DEFF Research Database (Denmark)

    Touborg, P.; Høg, J.; Cock, G. J.;

    1974-01-01

    Magnetization measurements have been performed on single crystals of Y containing small amounts of Tb, Dy, or Er at 4.2 K in fields up to 295 × 105 A/m (370 kOe). Crystal-field and molecular-field parameters obtained from measurements of the initial susceptibility versus temperature give...... a satisfactory quantitative account of the high-field magnetization. This includes characteristic features due to the crossing and mixing of crystal-field levels....

  14. A Critical, Bio-social Paradigm in Applied Linguistics:A new Flower Bloom-ing in the Field

    Institute of Scientific and Technical Information of China (English)

    LIU Ai-juan

    2014-01-01

    In this article, some new developments in the field of applied linguistics are summarized. In addition, it is illustrated that researchers’epistemology determines their methodology. And their research conclusions are also led by their epistemology. It is proposed that a critical, bio-social paradigm be taken in the field of applied linguistics.

  15. Comparative High Field Magneto-transport Of Rare Earth Oxypnictides With Maximum Transition Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Balakirev, Fedor F [Los Alamos National Laboratory; Migliori, A [MPA-NHMFL; Riggs, S [NHMFL-FSU; Hunte, F [NHMFL-FSU; Gurevich, A [NHMFL-FSU; Larbalestier, D [NHMFL-FSU; Boebinger, G [NHMFL-FSU; Jaroszynski, J [NHMFL-FSU; Ren, Z [CHINA; Lu, W [CHINA; Yang, J [CHINA; Shen, X [CHINA; Dong, X [CHINA; Zhao, Z [CHINA; Jin, R [ORNL; Sefat, A [ORNL; Mcguire, M [ORNL; Sales, B [ORNL; Christen, D [ORNL; Mandrus, D [ORNL

    2008-01-01

    We compare magnetotransport of the three iron-arsenide-based compounds ReFeAsO (Re=La, Sm, Nd) in very high DC and pulsed magnetic fields up to 45 and 54 T, respectively. Each sample studied exhibits a superconducting transition temperature near the maximum reported to date for that particular compound. While high magnetic fields do not suppress the superconducting state appreciably, the resistivity, Hall coefficient, and critical magnetic fields, taken together, suggest that the phenomenology and superconducting parameters of the oxypnictide superconductors bridges the gap between MgB{sub 2} and YBCO.

  16. Impact of high electromagnetic field levels on childhood leukemia incidence

    NARCIS (Netherlands)

    Teepen, J.C.; Dijck, J.A. van

    2012-01-01

    The increasing exposure to electromagnetic fields (EMFs) has raised concern, as increased exposure may result in an increased risk of childhood leukemia (CL). Besides a short introduction of CL and EMF, our article gives an evaluation of the evidence of a causal relation between EMF and CL by critic

  17. High precision simulation techniques for lattice field theory

    CERN Document Server

    Wolff, U

    1993-01-01

    An overview is given over the recently developed and now widely used Monte Carlo algorithms with reduced or eliminated critical slowing down. The basic techniques are overrelaxation, cluster algorithms and multigrid methods. With these tools one is able to probe much closer than before the universal continuum behavior of field theories on the lattice.

  18. Strain induced irreversible critical current degradation in highly dense Bi-2212 round wire

    CERN Document Server

    Bjoerstad, R; Rikel, M.O.; Ballarino, A; Bottura, L; Jiang, J; Matras, M; Sugano, M; Hudspeth, J; Di Michiel, M

    2015-01-01

    The strain induced critical current degradation of overpressure processed straight Bi 2212/Ag wires has been studied at 77 K in self-field. For the first time superconducting properties, lattice distortions, composite wire stress and strain have been measured simultaneously in a high energy synchrotron beamline. A permanent Ic degradation of 5% occurs when the wire strain exceeds 0.60%. At a wire strain of about 0.65% a drastic n value and Ic reduction occur, and the composite stress and the Bi-2212 lattice parameter reach a plateau, indicating Bi-2212 filament fracturing. The XRD measurements show that Bi-2212 exhibits linear elastic behaviour up to the irreversible strain limit.

  19. Anisotropy of the upper critical field in c-axis oriented MgB2 thin films

    Institute of Scientific and Technical Information of China (English)

    Wang Shu-Fang; Liu Zhen; Zhu Ya-Bin; Zhou Yue-Liang; Chen Zheng-Hao; Lü Hui-Bin; Yang Guo-Zhen

    2004-01-01

    C-axis oriented MgB2 thin films were synthesized on single-crystal MgO (111) substrates using a chemical vapour deposition technique. The as-formed films revealed a sharp superconducting transition temperature of 38K with the transition width 0.2K. The temperature dependence of the upper critical magnetic field Hc2 (T) in the films was determined via resistivity for magnetic field H parallel and perpendicular to the c axis of the films. Using the Werthamer-HelfandHohenberg formula, we obtained the anisotropy ratio of the upper critical field γ=1.2.

  20. The crossover from mean-field to 3D-Ising critical behaviour in a 3-component microemulsion

    DEFF Research Database (Denmark)

    Seto, H.; Schwahn, D.; Yokoi, E.

    1995-01-01

    Density fluctuations and associated critical phenomena of water droplets in a water-in-oil microemulsion system have been studied, We have recently found a mean-field behavior in the ''near-critical region'', and this evidence suggested that a crossover from mean-field to non-mean-field behavior...... should be observed. Therefore, a measurement of small-angle neutron scattering was carried out at JAERI with more precise temperature steps. Indeed, the crossover from mean-held to 3D-Ising behavior was observed, and the result could be interpreted by the asymptotic crossover theory proposed by Belyakov...

  1. A method for critical software event execution reliability in high assurance systems

    Energy Technology Data Exchange (ETDEWEB)

    Kidd, M.E.C.

    1997-03-01

    This paper presents a method for Critical Software Event Execution Reliability (Critical SEER). The Critical SEER method is intended for high assurance software that operates in an environment where transient upsets could occur, causing a disturbance of the critical software event execution order, which could cause safety or security hazards. The method has a finite automata based module that watches (hence SEER) and tracks the critical events and ensures they occur in the proper order or else a fail safe state is forced. This method is applied during the analysis, design and implementation phases of software engineering.

  2. Critical behaviours and magnetic properties of three-dimensional bond and anisotropy dilution Blume-Capel model in the presence of an applied field

    Institute of Scientific and Technical Information of China (English)

    Yan Shi-Lei; Zhu Hai-Xia

    2006-01-01

    This paper studies the critical behaviours and magnetic properties of three-dimensional bond and anisotropy dilution Blume-Capel model (BCM) in the presence of an applied field within the effective field theory. The trajectory of tricritical point, reentrant transitions and degenerate patterns of anisotropy are obtained both for the bond and the anisotropy dilutions. The global phase diagrams demonstrate unusually reentrant phenomena. The temperature dependences of magnetization curves undergo remarkable spin glass behaviour at low temperatures, and transform from ferromagnetism to paramagnetism at high temperature in applied fields. Temperature dependence of magnetic susceptibility curve is in qualitative agreement with experimental result.

  3. Upper critical field and quantum oscillations in tetragonal superconducting FeS

    Science.gov (United States)

    Terashima, Taichi; Kikugawa, Naoki; Lin, Hai; Zhu, Xiyu; Wen, Hai-Hu; Nomoto, Takuya; Suzuki, Katsuhiro; Ikeda, Hiroaki; Uji, Shinya

    2016-09-01

    The magnetoresistance and magnetic torque of FeS are measured in magnetic fields B of up to 18 T down to a temperature of 0.03 K. The superconducting transition temperature is found to be Tc=4.1 K , and the anisotropy ratio of the upper critical field Bc 2 at Tc is estimated from the initial slopes to be Γ (Tc)=6.9 . Bc 2(0 ) is estimated to be 2.2 and 0.36 T for B ∥a b and c , respectively. Quantum oscillations are observed in both the resistance and torque. Two frequencies F =0.15 and 0.20 kT are resolved and assigned to a quasi-two-dimensional Fermi surface cylinder. The carrier density and Sommerfeld coefficient associated with this cylinder are estimated to be 5.8 ×10-3 carriers/Fe and 0.48 mJ /(K2mol ) , respectively. Other Fermi surface pockets still remain to be found. Band-structure calculations are performed and compared to the experimental results.

  4. Magnetic Field Dependence of the Critical Current of Planar Geometry Josephson Junctions

    Science.gov (United States)

    Ma, Meng; Cho, Ethan; Huynh, Chuong; Cybart, Shane; Dynes, Robert

    2015-03-01

    We report a study on the magnetic field dependence of the critical current of planar geometry Josephson junctions. We have fabricated Josephson junctions by using a focused helium ion beam to irradiate a narrow barrier in the plane of a 25 nm thick Y-Ba-Cu-O film. The London penetration depth λL is large (~1 μm) because of the ultra-thin thickness of the film. As a result, calculations of the Josephson penetration depth λJ are not realistic nor physical. Therefore in this work, we measure λJ experimentally. We tested devices with bridge widths ranging from 4 to 50 μm, and present measurements of the Fraunhofer quantum diffraction pattern (IC (B)). We observe a crossover from short to long junction behavior, which gives an experimentally measured λJ that ranges between 3 μm to 5 μm. The shape of the IC (B) pattern is strongly affected by the width of the bridge because of self-field effects. As the bridge width increases, Josephson vortices enter the junction and skew the patterns. This work shows that the electronic properties of the planar junctions are very different than those classical ``sandwich'' junctions due to the differences in geometry.

  5. Field and temperature scaling of the critical current density in commercial REBCO coated conductors

    CERN Document Server

    Senatore, Carmine; Bonura, Marco; Kulich, Miloslav; Mondonico, Giorgio

    2016-01-01

    Scaling relations describing the electromagnetic behaviour of coated conductors (CCs) greatly simplify the design of REBCO-based devices. The performance of REBCO CCs is strongly influenced by fabrication route, conductor architecture and materials, and these parameters vary from one manufacturer to the others. In the present work we have examined the critical surface for the current density, Jc(T,B,θ ), of coated conductors from six different manufacturers: American Superconductor Co. (US), Bruker HTS GmbH (Germany), Fujikura Ltd. (Japan), SuNAM Co. Ltd. (Korea), SuperOx ZAO (Russia) and SuperPower Inc. (US). Electrical transport and magnetic measurements were performed at temperatures between 4.2 K and 77 K and in magnetic field up to 19 T. Experiments were conducted at three different orientations of the field with respect to the crystallographic c-axis of the REBCO layer, θ = 0deg , 45deg and 90deg , in order to probe the angular anisotropy of Jc. In spite of the large variability of CCs performance, ...

  6. Oscillations of a highly discrete breather with a critical regime

    Science.gov (United States)

    Coquet; Remoissenet; Dinda

    2000-10-01

    We analyze carefully the essential features of the dynamics of a stationary discrete breather in the ultimate degree of energy localization in a nonlinear Klein-Gordon lattice with an on-site double-well potential. We demonstrate the existence of three different regimes of oscillatory motion in the breather dynamics, which are closely related to the motion of the central particle in an effective potential having two nondegenerate wells. In given parameter regions, we observe an untrapped regime, in which the central particle executes large-amplitude oscillations from one to the other side of the potential barrier. In other parameter regions, we find the trapped regime, in which the central particle oscillates in one of the two wells of the effective potential. Between these two regimes we find a critical regime in which the central particle undergoes several temporary trappings within an untrapped regime. Importantly, our study reveals that in the presence of purely anharmonic coupling forces, the breather compactifies, i.e., the energy becomes abruptly localized within the breather.

  7. Field-induced quantum criticality and universal temperature dependence of the magnetization of a spin-1/2 heisenberg chain.

    Science.gov (United States)

    Kono, Y; Sakakibara, T; Aoyama, C P; Hotta, C; Turnbull, M M; Landee, C P; Takano, Y

    2015-01-23

    High-precision dc magnetization measurements have been made on Cu(C4H4N2) (NO3)2 in magnetic fields up to 14.7 T, slightly above the saturation field Hs=13.97  T, in the temperature range from 0.08 to 15 K. The magnetization curve and differential susceptibility at the lowest temperature show excellent agreement with exact theoretical results for the spin-1/2 Heisenberg antiferromagnet in one dimension. A broad peak is observed in magnetization measured as a function of temperature, signaling a crossover to a low-temperature Tomonaga-Luttinger-liquid regime. With an increasing field, the peak moves gradually to lower temperatures, compressing the regime, and, at Hs, the magnetization exhibits a strong upturn. This quantum critical behavior of the magnetization and that of the specific heat withstand quantitative tests against theory, demonstrating that the material is a practically perfect one-dimensional spin-1/2 Heisenberg antiferromagnet.

  8. Upper critical field and AC-Susceptibility studies on FeTe0.5Se0.5 superconductor

    Science.gov (United States)

    Zargar, Rayees A.; Pal, Anand; Hafiz, A. K.; Awana, V. P. S.

    2015-06-01

    In this study we present synthesis and characterization of FeTe0.5Se0.5 sample that has been prepared by solid state reaction route by encapsulation of stoichiometric high purity (5N) ingredients in an evacuated quartz tube at 750 °C. The resultant compound is crystallized in single phase tetragonal structure with space group P4/nmm, having lattice parameters a = 3.792(1) Å and c = 6.0081(3) Å. The studied compound is superconducting at below 13K in both magnetic and transport measurements. Further superconductivity is barely affected by external applied magnetic field, giving rise to upper critical field of above 180 Tesla at 0 K. The sample is studied extensively for AC susceptibility measurements in superconducting state. The AC drive field and frequency are varied from 1-13 Oe and 33-9999 Hz respectively. It is concluded that though the grain boundaries of this superconductor are mainly metallic the minor (undetectable in XRD) foreign phases and the role of porosity cannot be ruled out completely. This is because both frequency and amplitude affects slightly the superconductivity coupling temperature of the grains.

  9. Plasma instabilities in high electric fields

    DEFF Research Database (Denmark)

    Morawetz, K.; Jauho, Antti-Pekka

    1994-01-01

    We analyze nonequilibrium screening with nonequilibrium Green function techniques. By employing the generalized Kadanoff-Baym ansatz to relate the correlation function to the nonequilibrium distribution function, the latter of which is assumed to be a shifted Maxwellian, an analytically tractable...... expression is derived for the nonequilibrium dielectric function epsilon(K, omega). For certain values of momenta K and frequency omega, Imepsilon(K, omega) becomes negative, implying a plasma instability. This new instability exists only for strong electric fields, underlining its nonequilibrium origin....

  10. Critical magnetic field of V/sub 3/Ga thin films with third element additions

    Energy Technology Data Exchange (ETDEWEB)

    Tedrow, P.M.; Bending, S.J.; Hammond, R.; Meservey, R.; Tkaczyk, J.E.

    1985-03-01

    We have made thin films of V-Ga superconductors by electron beam codeposition with approximately one percent additions of Nb, Ta, Sn, Pt or Pb. We have measured the high-magnetic field properties of these films to observe the effect of these impurities on spin-orbit scattering. Although the residual resistivity of the films was affected by the additional elements, the rate of spin-orbit scattering did not appear to increase.

  11. New types of high field pinning centers and pinning centers for the peak effect

    Science.gov (United States)

    Gajda, Daniel; Zaleski, Andrzej; Morawski, Andrzej; Hossain, Md Shahriar A.

    2017-08-01

    In this article, we report the results of a study that shows the existence of pinning centers inside grains and between grains in NbTi wires. We accurately show the ranges of magnetic fields in which the individual pinning centers operate. The pinning centers inside grains are activated in high magnetic fields above 6 T. We show the range of magnetic fields in which individual defects, dislocations, precipitates inside grains and substitutions in the crystal lattice can operate. We show the existence of a new kind of high field pinning center, which operates in high magnetic fields from 8 to ˜9.5 T. We indicate that dislocations create pinning centers in the range of magnetic fields from 6 to 8 T. In addition, our measurements suggest that the peak effect (increased critical current density (J c) near the upper critical field (B c2)) could be attributed to martensitic (needle-shaped) α‧-Ti inclusions inside grains. These centers are very important because they work very effectively in magnetic fields above 9.5-10 T. We also show that the α-Ti precipitates (between grains) with a thickness similar to the coherence length create pinning centers which work very effectively in magnetic fields from 3 to 6 T. In magnetic fields below 3 T, they act very efficiently in grain boundaries. The measurements indicate that the pinning centers created by dislocations only can be tested by transport measurements. This indicates that dislocations do not increase the magnetic critical current density (J cm). Cold drawing improves pinning centers at grain boundaries and increases the dislocation density, and cold-drawing pinning centers are responsible for the peak effect.

  12. Inclusive STEM High School Design: 10 Critical Components

    Science.gov (United States)

    Peters-Burton, Erin E.; Lynch, Sharon J.; Behrend, Tara S.; Means, Barbara B.

    2014-01-01

    Historically, the mission of science, technology, engineering, and mathematics (STEM) schools emphasized providing gifted and talented students with advanced STEM coursework. However, a newer type of STEM school is emerging in the United States: inclusive STEM high schools (ISHSs). ISHSs have open enrollment and are focused on preparing…

  13. ADX: a high field, high power density, advanced divertor and RF tokamak

    Science.gov (United States)

    LaBombard, B.; Marmar, E.; Irby, J.; Terry, J. L.; Vieira, R.; Wallace, G.; Whyte, D. G.; Wolfe, S.; Wukitch, S.; Baek, S.; Beck, W.; Bonoli, P.; Brunner, D.; Doody, J.; Ellis, R.; Ernst, D.; Fiore, C.; Freidberg, J. P.; Golfinopoulos, T.; Granetz, R.; Greenwald, M.; Hartwig, Z. S.; Hubbard, A.; Hughes, J. W.; Hutchinson, I. H.; Kessel, C.; Kotschenreuther, M.; Leccacorvi, R.; Lin, Y.; Lipschultz, B.; Mahajan, S.; Minervini, J.; Mumgaard, R.; Nygren, R.; Parker, R.; Poli, F.; Porkolab, M.; Reinke, M. L.; Rice, J.; Rognlien, T.; Rowan, W.; Shiraiwa, S.; Terry, D.; Theiler, C.; Titus, P.; Umansky, M.; Valanju, P.; Walk, J.; White, A.; Wilson, J. R.; Wright, G.; Zweben, S. J.

    2015-05-01

    The MIT Plasma Science and Fusion Center and collaborators are proposing a high-performance Advanced Divertor and RF tokamak eXperiment (ADX)—a tokamak specifically designed to address critical gaps in the world fusion research programme on the pathway to next-step devices: fusion nuclear science facility (FNSF), fusion pilot plant (FPP) and/or demonstration power plant (DEMO). This high-field (⩾6.5 T, 1.5 MA), high power density facility (P/S ˜ 1.5 MW m-2) will test innovative divertor ideas, including an ‘X-point target divertor’ concept, at the required performance parameters—reactor-level boundary plasma pressures, magnetic field strengths and parallel heat flux densities entering into the divertor region—while simultaneously producing high-performance core plasma conditions that are prototypical of a reactor: equilibrated and strongly coupled electrons and ions, regimes with low or no torque, and no fuelling from external heating and current drive systems. Equally important, the experimental platform will test innovative concepts for lower hybrid current drive and ion cyclotron range of frequency actuators with the unprecedented ability to deploy launch structures both on the low-magnetic-field side and the high-magnetic-field side—the latter being a location where energetic plasma-material interactions can be controlled and favourable RF wave physics leads to efficient current drive, current profile control, heating and flow drive. This triple combination—advanced divertors, advanced RF actuators, reactor-prototypical core plasma conditions—will enable ADX to explore enhanced core confinement physics, such as made possible by reversed central shear, using only the types of external drive systems that are considered viable for a fusion power plant. Such an integrated demonstration of high-performance core-divertor operation with steady-state sustainment would pave the way towards an attractive pilot plant, as envisioned in the ARC concept

  14. A critical study of high efficiency deep grinding

    CERN Document Server

    Johnstone, I

    2002-01-01

    The recent years, the aerospace industry in particular has embraced and actively pursued the development of stronger high performance materials, namely nickel based superalloys and hardwearing steels. This has resulted in a need for a more efficient method of machining, and this need was answered with the advent of High Efficiency Deep Grinding (HEDG). This relatively new process using Cubic Boron Nitride (CBN) electroplated grinding wheels has been investigated through experimental and theoretical means applied to two widely used materials, M50 bearing steel and IN718 nickel based superalloy. It has been shown that this grinding method using a stiff grinding centre such as the Edgetek 5-axis machine is a viable process. Using a number of experimental designs, produced results which were analysed using a variety of methods including visual assessment, sub-surface microscopy and surface analysis using a Scanning Electron Microscope (SEM), residual stress measurement using X-Ray Diffraction (XRD) techniques, Ba...

  15. Critical Properties of Mixed Ising Spin System with Different Trimodal Transverse Fields in the Presence of Single-Ion Anisotropy

    Institute of Scientific and Technical Information of China (English)

    CHEN Qiang; YAN Shi-Lei

    2006-01-01

    Within the framework of an effective field approximation, the effects of single-ion anisotropy and different trimodal transverse fields of two sublattices on the critical properties of the mixed spin-1/2 and spin-1 Ising system are investigated on the simple cubic lattice. A smaller single-ion anisotropy can magnify magnetic ordering phases and a larger one can depress magnetic ordering phase for T-Ω1/2 space at low temperatures, while a smaller single-ion anisotropy can hardly change the value of critical transverse field for T-Ω1 space. On the other hand, influences of two different trimodal transverse fields concentrations on tricritical points and magnetic ordering phases take on some interesting results in T-D space. The main reason comes from the common action of single-ion anisotropy, different transverse fields and two trimodal distributions.

  16. Criticality Safety Evaluation of Hanford Site High Level Waste Storage Tanks

    Energy Technology Data Exchange (ETDEWEB)

    ROGERS, C.A.

    2000-02-17

    This criticality safety evaluation covers operations for waste in underground storage tanks at the high-level waste tank farms on the Hanford site. This evaluation provides the bases for criticality safety limits and controls to govern receipt, transfer, and long-term storage of tank waste. Justification is provided that a nuclear criticality accident cannot occur for tank farms operations, based on current fissile material and operating conditions.

  17. Possible field-tuned superconductor-insulator transition in high-Tc superconductors: implications for pairing at high magnetic fields.

    Science.gov (United States)

    Steiner, M A; Boebinger, G; Kapitulnik, A

    2005-03-18

    The behavior of some high temperature superconductors (HTSC), such as La(2-x)Sr(x)CuO(4) and Bi(2)Sr(2-x)La(x)CuO(6 + delta), at very high magnetic fields, is similar to that of thin films of amorphous InOx near the magnetic-field-tuned superconductor-insulator transition. Analyzing the InOx data at high fields in terms of persisting local pairing amplitude, we argue by analogy that the local pairing amplitude also persists well into the dissipative state of the HTSCs, the regime commonly denoted as the "normal state" in very high magnetic field experiments.

  18. High magnetic field pulsars and magnetars a unified picture

    CERN Document Server

    Zhang, B; Zhang, Bing; Harding, Alice K.

    2000-01-01

    We propose a unified picture of high magnetic field radio pulsars and magnetars by arguing that they are all rotating high-field neutron stars, but have different orientations of their magnetic axes with respective to their rotation axes. In strong magnetic fields where photon splitting suppresses pair creation near the surface, the high-field pulsars can have active inner accelerators while the anomalous X-ray pulsars cannot. This can account for the very different observed emission characteristics of the anomalous X-ray pulsar 1E 2259+586 and the high field radio pulsar PSR J1814-1744. A predicted consequence of this picture is that radio pulsars having surface magnetic field greater than about $2\\times 10^{14}$ G should not exist.

  19. Ideal charge-density-wave order in the high-field state of superconducting YBCO

    Science.gov (United States)

    Jang, H.; Lee, W.-S.; Nojiri, H.; Matsuzawa, S.; Yasumura, H.; Nie, L.; Maharaj, A. V.; Gerber, S.; Liu, Y.-J.; Mehta, A.; Bonn, D. A.; Liang, R.; Hardy, W. N.; Burns, C. A.; Islam, Z.; Song, S.; Hastings, J.; Devereaux, T. P.; Shen, Z.-X.; Kivelson, S. A.; Kao, C.-C.; Zhu, D.; Lee, J.-S.

    2016-12-01

    The existence of charge-density-wave (CDW) correlations in cuprate superconductors has now been established. However, the nature of the CDW ground state has remained uncertain because disorder and the presence of superconductivity typically limit the CDW correlation lengths to only a dozen unit cells or less. Here we explore the field-induced 3D CDW correlations in extremely pure detwinned crystals of YBa2Cu3O2 (YBCO) ortho-II and ortho-VIII at magnetic fields in excess of the resistive upper critical field (Hc2Hc2) where superconductivity is heavily suppressed. We observe that the 3D CDW is unidirectional and possesses a long in-plane correlation length as well as significant correlations between neighboring CuO2 planes. It is significant that we observe only a single sharply defined transition at a critical field proportional to Hc2Hc2, given that the field range used in this investigation overlaps with other high-field experiments including quantum oscillation measurements. The correlation volume is at least two to three orders of magnitude larger than that of the zero-field CDW. This is by far the largest CDW correlation volume observed in any cuprate crystal and so is presumably representative of the high-field ground state of an “ideal” disorder-free cuprate.

  20. Linear processes in high dimensions: Phase space and critical properties

    Science.gov (United States)

    Mastromatteo, Iacopo; Bacry, Emmanuel; Muzy, Jean-François

    2015-04-01

    In this work we investigate the generic properties of a stochastic linear model in the regime of high dimensionality. We consider in particular the vector autoregressive (VAR) model and the multivariate Hawkes process. We analyze both deterministic and random versions of these models, showing the existence of a stable phase and an unstable phase. We find that along the transition region separating the two regimes the correlations of the process decay slowly, and we characterize the conditions under which these slow correlations are expected to become power laws. We check our findings with numerical simulations showing remarkable agreement with our predictions. We finally argue that real systems with a strong degree of self-interaction are naturally characterized by this type of slow relaxation of the correlations.

  1. The Project for the New High Field Facility

    OpenAIRE

    Motokawa, M.

    1996-01-01

    Since High Field Laboratory for Superconducting Materials attached to Institute for Materials Research of Tohoku University started, 15 years has passed. We have had plenty of fruitful scientific and technological results not only in a field of superconductivity but also in areas of magnetism, semiconductors, organic conductors, chemical and biological materials and crystallography. The equipments in the Laboratory, however, are now getting aged and the available high field of 31 T obtained b...

  2. Radiofrequency solutions in clinical high field magnetic resonance

    NARCIS (Netherlands)

    Andreychenko, A.|info:eu-repo/dai/nl/341697672

    2013-01-01

    Magnetic resonance imaging (MRI) and spectroscopy (MRS) benefit from the sensitivity gain at high field (≥7T). However, high field brings also certain challenges associated with growing frequency and spectral dispersion. Frequency growth results in degraded performance of large volume radiofrequency

  3. High-order-harmonic generation from field-distorted orbitals

    DEFF Research Database (Denmark)

    Spiewanowski, Maciek; Etches, Adam; Madsen, Lars Bojer

    2013-01-01

    We investigate the effect on high-order-harmonic generation of the distortion of molecular orbitals by the driving laser field. Calculations for high-order-harmonic generation including orbital distortion are performed for N2. Our results allow us to suggest that field distortion is the reason why...

  4. High School Students' Representations and Understandings of Electric Fields

    Science.gov (United States)

    Cao, Ying; Brizuela, Bárbara M.

    2016-01-01

    This study investigates the representations and understandings of electric fields expressed by Chinese high school students 15 to 16 years old who have not received high school level physics instruction. The physics education research literature has reported students' conceptions of electric fields post-instruction as indicated by students'…

  5. Directional point-contact spectroscopy of MgB$_{2}$ single crystals in magnetic fields two-band superconductivity and critical fields

    CERN Document Server

    Gonnelli, R S; Ummarino, G A; Della Rocca, V; Calzolari, A; Stepanov, V A; Jun, J; Kazakov, S M; Karpinski, J; Dellarocca, Valeria

    2004-01-01

    The results of the first directional point-contact measurements in MgB2 single crystals, in the presence of magnetic fields up to 9 T either parallel or perpendicular to the ab planes, are presented. By applying suitable magnetic fields, we separated the partial contributions of the sigma and pi bands to the total Andreev-reflection conductance. Their fit with the BTK model allowed a very accurate determination of the temperature dependency of the gaps (Delta_sigma and Delta_pi), that resulted in close agreement with the predictions of the two-band models for MgB2. We also obtained, for the first time with point-contact spectroscopy, the temperature dependence of the (anisotropic) upper critical field of the sigma band and of the (isotropic) upper critical field of the pi band.

  6. High critical current densities in industrial scale composites made from high homogeneity NB 46. 5 TI

    Energy Technology Data Exchange (ETDEWEB)

    Larbalestier, D.C.; Hemachalam, K.; Lee, P.; McDonald, W.K.; O' Larey, P.; Scanlan, R.; Starch, W.; Taylor, C.; Warnes, W.; West, A.W.; Zeitlin, B.

    1985-03-01

    Recent work in our group on the fabricationmicrostructure-superconducting properties of composites of Nb-Ti has produced much new information about the precipitate morphology and origins of high critical current density (J /SUB c/ ) in these materials./sup 1 -4/ Precipitation of Ti-rich phase is seen to commence as a grain boundary film 2 - 4 nm thick, the film then developing into approximately equiaxed particles of ..cap alpha..-Ti at the boundary triple points. The typical size of such precipitates is 50 - 100 nm. Controlled drawing of such a structure produces an array of locally ordered ribbon precipitates. These precipitates are typically 3 - 5 nm thick by 100 - 300 nm long (when observed in transverse section). Their length in longitudinal section appears to be several hundred nm, indicating great ductility in these small ..cap alpha..-Ti precipitates. The typical separation of the precipitates is 20 - 30 nm. Thus the dimensions of the precipitate array are quite comparable to that of the flux lattice since the fluxoid separation is 22 nm at 5 T and the fluxoid diameter of Nb 46.5 wt% Ti is approximately 10 nm. The flux pinning behavior of these precipitate structures is expected to be complex: /SUP 2.4/ the defect density is very high, the precipitate morphology has a very high aspect ratio and the extreme thinness of the precipitates must permit some superconductivity to be induced in them by the proximity effect./sup 5/

  7. Quantum critical scaling for field-induced quantum phase transition in a periodic Anderson-like model polymer chain

    Science.gov (United States)

    Ding, L. J.; Zhong, Y.

    2017-07-01

    The quantum phase transition and thermodynamics of a periodic Anderson-like polymer chain in a magnetic field are investigated by Green's function theory. The T-h phase diagram is explored, wherein a crossover temperature T∗ denoting the gapless phase crossover into quantum critical regimes, smoothly connects near the critical fields to the universal linear line T∗ ∼ (h - hc,s), and ends at hc,s, providing a new route to capture quantum critical point (QCP). The quantum critical scaling around QCPs is demonstrated by analyzing magnetization, specific heat and Grüneisen parameter Γh, which provide direct access to distill the power-law critical exponents (β, δ and α) obeying the critical scaling relation α + β(1 + δ) = 2, analogous to the quantum spin system. Furthermore, scaling hypothesis equations are proposed to check the scaling analysis, for which all the data collapse onto a single curve or two independent branches for the plot against an appropriate scaling variable, indicating the self-consistency and reliability of the obtained critical exponents.

  8. The Relationship between Critical Thinking Abilities and Classroom Management Skills of High School Teachers

    Science.gov (United States)

    Demirdag, Seyithan

    2015-01-01

    High school teachers experience difficulties while providing effective teaching approaches in their classrooms. Some of the difficulties are associated with the lack of classroom management skills and critical thinking abilities. This quantitative study includes non-random selection of the participants and aims to examine critical thinking…

  9. The Relationship between Critical Thinking Abilities and Classroom Management Skills of High School Teachers

    Science.gov (United States)

    Demirdag, Seyithan

    2015-01-01

    High school teachers experience difficulties while providing effective teaching approaches in their classrooms. Some of the difficulties are associated with the lack of classroom management skills and critical thinking abilities. This quantitative study includes non-random selection of the participants and aims to examine critical thinking…

  10. Magneto-elastic behaviour of thin type-II superconducting strip with field-dependent critical current

    Science.gov (United States)

    Xue, Cun; He, An; Yong, Huadong; Zhou, Youhe

    2013-01-01

    The magneto-elastic behavior of thin superconducting strip in perpendicular magnetic field with field-dependent critical current is studied. We calculate numerically the body force, strain, displacement, and thickness changes in the strip for the Bean model and Kim model during the field ascent and descent. The differences in magnetostriction between the Bean model and the Kim model are analyzed. The magnetostriction during one full cycle of the applied field for both models is presented. The results show that magnetostriction loops are different in these models, and at low temperatures Kim model is in better agreement with experiment than Bean model.

  11. Depinning transition of a driven interface in the random-field Ising model around the upper critical dimension.

    Science.gov (United States)

    Roters, L; Lübeck, S; Usadel, K D

    2002-12-01

    We investigate the depinning transition for driven interfaces in the random-field Ising model for various dimensions. We consider the order parameter as a function of the control parameter (driving field) and examine the effect of thermal fluctuations. Although thermal fluctuations drive the system away from criticality, the order parameter obeys a certain scaling law for sufficiently low temperatures and the corresponding exponents are determined. Our results suggest that the so-called upper critical dimension of the depinning transition is five and that the systems belongs to the universality class of the quenched Edward-Wilkinson equation.

  12. Influence of Critical Current Density on Guidance Force Decay of HTS Bulk Exposed to AC Magnetic Field Perturbation in a Maglev Vehicle System

    Science.gov (United States)

    Longcai, Zhang; Jianguo, Kong

    2012-07-01

    Superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the HTS bulks are always exposed to AC external magnetic field, which is generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, we studied the guidance force decay of the YBCO bulk over the NdFdB guideway used in the High-temperature superconducting maglev vehicle system with the application of the AC external magnetic field, and calculated the guidance force decay as a function of time based on an analytic model. In this paper, we investigated the influence of the critical current density on the guidance force decay of HTS bulk exposed to AC field perturbation in the maglev vehicle system and try to adopt a method to suppress the decay. From the results, it was found that the guidance force decay rate was higher for the bulk with lower critical current density. Therefore, we could suppress the guidance force decay of HTS bulk exposed to AC external magnetic field perturbation in the maglev vehicle system by improving critical current density of the bulk.

  13. Bipolaron theory of the low magnetic field properties of high-temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Alexandrov, A.S.; Traven, S.V. (Moscow Engineering Physics Inst. (USSR))

    1991-02-01

    The low magnetic field properties of the layered high-temperature superconductors are studied in the frame of the two-dimensional heavy charged Bose-gas model. The temperature dependencies of the magnetic field penetration depth {lambda}{sub H}(T) and of the lower critical field H{sub c1}(T) are calculated in the London limit. The discrepancy between the temperature dependence of the penetration depth from the {mu}SR measurements and that from the ac susceptibility and magnetization measurements is discussed. (orig.).

  14. High magnetic field studies of the hidden order transition in URu2Si2.

    Science.gov (United States)

    Jaime, M; Kim, K H; Jorge, G; McCall, S; Mydosh, J A

    2002-12-31

    We studied in detail the low temperature/high magnetic field phases of URu2Si2 single crystals with specific heat, magnetocaloric effect, and magnetoresistance in magnetic fields up to 45 T. Data obtained down to 0.5 K, and extrapolated to T=0, show a suppression of the hidden-order phase at H0(0)=35.9+/-0.35 T and the appearance of a new phase for magnetic fields in excess of H1(0)=36.1+/-0.35 T observed only at temperatures lower than 6 K. In turn, complete suppression of this high field state is attained at a critical magnetic field H2(0)=39.7+/-0.35 T. No phase transitions are observed above 40 T. We discuss our results in the context of itinerant versus localized f electrons.

  15. Field emission behavior of carbon nanotube field emitters after high temperature thermal annealing

    Directory of Open Access Journals (Sweden)

    Yuning Sun

    2014-07-01

    Full Text Available The carbon nanotube (CNT field emitters have been fabricated by attaching a CNT film on a graphite rod using graphite adhesive material. The CNT field emitters showed much improved field emission properties due to increasing crystallinity and decreasing defects in CNTs after the high temperature thermal annealing at 900 °C in vacuum ambient. The CNT field emitters showed the low turn-on electric field of 1.15 V/μm, the low threshold electric field of 1.62 V/μm, and the high emission current of 5.9 mA which corresponds to a current density of 8.5 A/cm2. In addition, the CNT field emitters indicated the enhanced field emission properties due to the multi-stage effect when the length of the graphite rod increases. The CNT field emitter showed good field emission stability after the high temperature thermal annealing. The CNT field emitter revealed a focused electron beam spot without any focusing electrodes and also showed good field emission repeatability.

  16. Large field-of-view transmission line resonator for high field MRI

    DEFF Research Database (Denmark)

    Zhurbenko, Vitaliy; Johannesson, Kristjan Sundgaard; Boer, Vincent

    2016-01-01

    Transmission line resonators is often a preferable choice for coils in high field magnetic resonance imaging (MRI), because they provide a number of advantages over traditional loop coils. The size of such resonators, however, is limited to shorter than half a wavelength due to high standing wave....... Achieved magnetic field distribution is compared to the conventional transmission line resonator. Imaging experiments are performed using 7 Tesla MRI system. The developed resonator is useful for building coils with large field-of-view....

  17. Large field-of-view transmission line resonator for high field MRI

    DEFF Research Database (Denmark)

    Zhurbenko, Vitaliy; Johannesson, Kristjan Sundgaard; Boer, Vincent;

    2016-01-01

    Transmission line resonators is often a preferable choice for coils in high field magnetic resonance imaging (MRI), because they provide a number of advantages over traditional loop coils. The size of such resonators, however, is limited to shorter than half a wavelength due to high standing wave....... Achieved magnetic field distribution is compared to the conventional transmission line resonator. Imaging experiments are performed using 7 Tesla MRI system. The developed resonator is useful for building coils with large field-of-view....

  18. Radiolysis of Serine in High Radiation Field

    Directory of Open Access Journals (Sweden)

    Ellen Y. Aguilar-Ovando

    2016-08-01

    Full Text Available The formation of amino acids under simulated condition suggests that this type of compounds were readily formed on the primitive Earth. Nevertheless, there is no conclusive explanation to the origin of their specific chirality in biological systems. Differences in their stability in the primitive conditions may give some clues about this unsolved problem. Protection mechanisms have been considered, such as the adsorption of the organic compounds onto mineral surfaces. By using HPLC/ELSD to analyze aqueous suspensions of serine adsorbed on clay (sodium montmorillonite and a meteorite (Allende irradiated in different doses with a cobalt-60 gamma source, the aim of this work was to study the possible protector role of these mineral surfaces when an amino acid, serine, is adsorbed onto them and the system is exposed to a high radiation source. The results showed that adsorption is better at acidic pH and desorption from the mineral at basic pH. The irradiation of the free amino acid destroyed it almost completely at a dose of 91 kGy, but the presence of the mineral abruptly decreases the decomposition, acting as a protective agent. At the same time, the results in aqueous solution show no statistically significant differences in adsorption or radiolysis of D and L serine.

  19. Atom probe field ion microscopy of high resistivity materials

    Energy Technology Data Exchange (ETDEWEB)

    Sibrandij, S.J.; Larson, D.J.; Miller, M.K.

    1998-02-01

    Over the last 30 years the atom probe has proved to be a powerful tool for studying nanometer-sized compositional fluctuations in a wide range of metallic alloys but has had only limited applications to semiconductors and ceramics. One of the primary reasons for this difference is the higher resistivity of semiconducting and ceramic specimens. Because of this high resistivity, the high voltage field evaporation pulse is attenuated before it reaches the apex of the specimen thereby making the pulse ineffective for field evaporation. Experiments have demonstrated that both variants of the voltage-pulsed atom probe (i.e., those instruments in which the field evaporation pulse is applied directly to the specimen and those in which the negative pulse is applied to a counter electrode in front of the specimen) are equally affected. In this overview, the limits of applicability of the voltage-pulsed atom probe to high resistivity materials are examined. In this study, a wide range of materials have been examined to determine whether field ion microscopy and voltage-pulsed field evaporation can be achieved and the results are summarized in the report. Field ion microscopy including dc field evaporation was possible for all materials except bulk ceramic insulators and glasses. Field ion microscopy requires some conductivity both to achieve a high electric field at the apex of the specimen, and also to support the field ion current. In contrast, voltage-pulsed field evaporation requires transmission of the pulse to the apex of the specimen. All metallic alloys including high resistance alloys and metallic glasses were successfully field evaporated with a voltage pulse. Specimens that were produced from bulk material of several conducting ceramics including MoSi, TiB and TiC were also successfully field evaporated with a voltage pulse.

  20. Magnetic probe array with high sensitivity for fluctuating field.

    Science.gov (United States)

    Kanamaru, Yuki; Gota, Hiroshi; Fujimoto, Kayoko; Ikeyama, Taeko; Asai, Tomohiko; Takahashi, Tsutomu; Nogi, Yasuyuki

    2007-03-01

    A magnetic probe array is constructed to measure precisely the spatial structure of a small fluctuating field included in a strong confinement field that varies with time. To exclude the effect of the confinement field, the magnetic probes consisting of figure-eight-wound coils are prepared. The spatial structure of the fluctuating field is obtained from a Fourier analysis of the probe signal. It is found that the probe array is more sensitive to the fluctuating field with a high mode number than that with a low mode number. An experimental demonstration of the present method is attempted using a field-reversed configuration plasma, where the fluctuating field with 0.1% of the confinement field is successfully detected.

  1. Field calibration studies for ionisation chambers in mixed high-energy radiation fields.

    Science.gov (United States)

    Theis, C; Forkel-Wirth, D; Fuerstner, M; Mayer, S; Otto, Th; Roesler, S; Vincke, H

    2007-01-01

    The monitoring of ambient doses at work places around high-energy accelerators is a challenging task due the complexity of the mixed stray radiation fields encountered. At CERN, mainly Centronics IG5 high-pressure ionisation chambers are used to monitor radiation exposure in mixed fields. The monitors are calibrated in the operational quantity ambient dose equivalent H*(10) using standard, source-generated photon- and neutron fields. However, the relationship between ionisation chamber reading and ambient dose equivalent in a mixed high-energy radiation field can only be assessed if the spectral response to every component and the field composition is known. Therefore, comprehensive studies were performed at the CERN-EU high-energy reference field facility where the spectral fluence for each particle type has been assessed with Monte Carlo simulations. Moreover, studies have been performed in an accessible controlled radiation area in the vicinity of a beam loss point of CERN's proton synchrotron. The comparison of measurements and calculations has shown reasonable agreement for most exposure conditions. The results indicate that conventionally calibrated ionisation chambers can give satisfactory response in terms of ambient dose equivalent in stray radiation fields at high-energy accelerators in many cases. These studies are one step towards establishing a method of 'field calibration' of radiation protection instruments in which Monte Carlo simulations will be used to establish a correct correlation between the response of specific detectors to a given high-energy radiation field.

  2. Phase Diagrams, Criticality, and Local Properties of Spin Glasses and Random-Field Ising Models from Renormalization - Calculations.

    Science.gov (United States)

    Hartford, Edward John

    This position-space renormalization-group study focuses on two systems with quenched disorder: the Ising spin glass and the asymmetric random-field Ising model. We have employed the Migdal-Kadanoff approach to determine local recursion relations and have retained the full correlated probability distribution of interactions and fields at each iteration in a series of histograms. We find an equilibrium spin-glass phase in three dimensions, but not in two. The spin glass is characterized by a distribution of effective interactions that broadens under iteration, signaling both the long-range order of the phase and the importance of competing interactions on all length scales. We have introduced a method to calculate the distribution of local properties by differentiating the free energy with respect to a particular magnetic field or interaction. Within the spin-glass phase, the nearest neighbor correlation ranges from negative one to one, showing the strong correlations and the local variation within the phase. The spin-glass-to-paramagnet phase transition is second order, with a smooth specific heat indicated by a negative critical exponent alpha. The multicritical point separating the spin-glass, paramagnetic, and ferromagnetic phases lies along the Nishimori line and also has a nondivergent specific heat. When the system undergoes quenched dilution, the resulting critical and multicritical behaviors are identical to those of the undiluted system. Even the addition of an infinitesimal magnetic field destroys the long-range spin-glass order; however, the characteristic broadening of the distribution continues for several iterations for small fields and low temperatures, suggesting the persistence of sizable spin-glass domains. Our study of the asymmetric random-field Ising model is motivated by recent experiments on phase transitions in porous media and mean-field treatments, which suggest that new critical behavior could occur when the distribution of fields is

  3. High-frequency electric field amplification in a magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Timofeev, Aleksandr V [Russian Research Centre ' Kurchatov Institute' , Moscow (Russian Federation)

    2006-11-30

    In the investigation of cyclotron ion heating in systems designed for plasma isotope separation, the high-frequency (HF) electric field amplification effect was found to occur in equilibrium plasma. In the present article this effect is treated as a result of the interaction of the plasma placed in a constant external magnetic field with the HF modes of the vacuum chamber. Consistent elaboration of this approach allowed obtaining a clear interpretation of the HF electric field amplification effect and constructing a simple model of HF field excitation in a plasma column embedded in the external magnetic field. (methodological notes)

  4. High throughput phenotyping to accelerate crop breeding and monitoring of diseases in the field.

    Science.gov (United States)

    Shakoor, Nadia; Lee, Scott; Mockler, Todd C

    2017-08-01

    Effective implementation of technology that facilitates accurate and high-throughput screening of thousands of field-grown lines is critical for accelerating crop improvement and breeding strategies for higher yield and disease tolerance. Progress in the development of field-based high throughput phenotyping methods has advanced considerably in the last 10 years through technological progress in sensor development and high-performance computing. Here, we review recent advances in high throughput field phenotyping technologies designed to inform the genetics of quantitative traits, including crop yield and disease tolerance. Successful application of phenotyping platforms to advance crop breeding and identify and monitor disease requires: (1) high resolution of imaging and environmental sensors; (2) quality data products that facilitate computer vision, machine learning and GIS; (3) capacity infrastructure for data management and analysis; and (4) automated environmental data collection. Accelerated breeding for agriculturally relevant crop traits is key to the development of improved varieties and is critically dependent on high-resolution, high-throughput field-scale phenotyping technologies that can efficiently discriminate better performing lines within a larger population and across multiple environments. Copyright © 2017. Published by Elsevier Ltd.

  5. Critical current densities and irreversibility fields of MgB 2 bulks

    Science.gov (United States)

    Kumakura, H.; Takano, Y.; Fujii, H.; Togano, K.; Kito, H.; Ihara, H.

    2001-11-01

    We prepared two MgB 2 bulks by applying conventional sintering and high-pressure sintering methods, and compared the current carrying properties. Jc obtained by the resistive method was larger than that obtained by the magnetic method. Jc- B curves obtained by the resistive method showed no history effect. These results indicate that most of the superconducting currents flowing in the MgB 2 bulks were intergrain (transport) currents and intragrain currents were negligibly small. The high-pressure sintered sample with smaller grain size showed smaller field dependence of Jc and higher Birr than the conventionally sintered sample with larger grain size. This behavior can be explained by the grain boundary flux pinning.

  6. Liquid Droplet Dynamics in Gravity Compensating High Magnetic Field

    Science.gov (United States)

    Bojarevics, V.; Easter, S.; Pericleous, K.

    2012-01-01

    Numerical models are used to investigate behavior of liquid droplets suspended in high DC magnetic fields of various configurations providing microgravity-like conditions. Using a DC field it is possible to create conditions with laminar viscosity and heat transfer to measure viscosity, surface tension, electrical and thermal conductivities, and heat capacity of a liquid sample. The oscillations in a high DC magnetic field are quite different for an electrically conducting droplet, like liquid silicon or metal. The droplet behavior in a high magnetic field is the subject of investigation in this paper. At the high values of magnetic field some oscillation modes are damped quickly, while others are modified with a considerable shift of the oscillating droplet frequencies and the damping constants from the non-magnetic case.

  7. HIGH FIELD Q-SLOPE AND THE BAKING EFFECT

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, Gianluigi [JLAB

    2009-11-01

    The performance of SRF cavities made of bulk Nb at high fields (peak surface magnetic field greater than about 90 mT) is characterized by exponentially increasing RF losses (high-field Q-slope), in the absence of field emission, which are often mitigated by a low temperature (100-140 °C, 12-48h) baking. In this contribution, recent experimental results and phenomenological models to explain this effect will be briefly reviewed. New experimental results on the high-field Q-slope will be presented for cavities that had been heat treated at high temperature in the presence of a small partial pressure of nitrogen. Improvement of the cavity performances have been obtained, while surface analysis measurements on Nb samples treated with the cavities revealed significantly lower hydrogen concentration than for samples that followed standard cavity treatments.

  8. Method for critical software event execution reliability in high integrity software

    Energy Technology Data Exchange (ETDEWEB)

    Kidd, M.E. [Sandia National Labs., Albuquerque, NM (United States)

    1997-11-01

    This report contains viewgraphs on a method called SEER, which provides a high level of confidence that critical software driven event execution sequences faithfully exceute in the face of transient computer architecture failures in both normal and abnormal operating environments.

  9. Development of Ti-sheathed MgB{sub 2} wires with high critical current density

    Energy Technology Data Exchange (ETDEWEB)

    Liang, G [Department of Physics, Sam Houston State University, Huntsville, TX 77341 (United States); Fang, H [Department of Physics, Sam Houston State University, Huntsville, TX 77341 (United States); Hanna, M [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, Houston, TX 77204-4006 (United States); Yen, F [Texas Center for Superconductivity, University of Houston, Houston, TX 77204-4006 (United States); Lv, B [Department of Chemistry, University of Houston, Houston, TX 77204-5003 (United States); Alessandrini, M [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, Houston, TX 77204-4006 (United States); Keith, S [Department of Physics, Sam Houston State University, Huntsville, TX 77341 (United States); Hoyt, C [Department of Physics, Sam Houston State University, Huntsville, TX 77341 (United States); Tang, Z [Department of Chemistry, University of Houston, Houston, TX 77204-5003 (United States); Salama, K [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, Houston, TX 77204-4006 (United States)

    2006-11-15

    Working towards developing lightweight superconducting magnets for future space and other applications, we have successfully fabricated mono-core Ti-sheathed MgB{sub 2} wires by the powder-in-tube method. The wires were characterized by magnetization, electrical resistivity, x-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry measurements. The results indicate that the Ti sheath does not react with the magnesium and boron, and the present wire rolling process can produce MgB{sub 2} wires with a superconducting volume fraction of at least 64% in the core. Using the Bean model, it was found that at 5 K, the magnetic critical current densities, J{sub c}, measured in magnetic fields of 0, 5, and 8 T are about 4.2 x 10{sup 5}, 3.6 x 10{sup 4}, and 1.4 x 10{sup 4} A cm{sup -2}, respectively. At 20 K and 0 T, the magnetic J{sub c} is about 2.4 x 10{sup 5} A cm{sup -2}. These results show that at zero and low fields, the values of the magnetic J{sub c} for Ti-sheathed MgB{sub 2} wires are comparable with the best results available for the Fe-sheathed MgB{sub 2} wires. At high fields, however, the J{sub c} for Ti-sheathed MgB{sub 2} wires appears higher than that for the Fe-sheathed MgB{sub 2} wires.

  10. The upper critical field and its anisotropy in (Li1-x Fe x )OHFe1-y Se

    Science.gov (United States)

    Wang, Zhaosheng; Yuan, Jie; Wosnitza, J.; Zhou, Huaxue; Huang, Yulong; Jin, Kui; Zhou, Fang; Dong, Xiaoli; Zhao, Zhongxian

    2017-01-01

    The temperature dependence of the upper critical field (H c2) in a (Li1-x Fe x )OHFe1-y Se single crystal ({{T}\\text{c}}≈ 40 K) has been determined by means of magnetotransport measurements down to 1.4 K both for inter-plane (H\\parallel c , H\\text{c2}//c ) and in-plane (H\\parallel ab , H\\text{c2}//ab ) field directions in static magnetic fields up to 14 T and pulsed magnetic fields up to 70 T. H\\text{c2}//c exhibits a quasilinear increase with decreasing temperature below the superconducting transition and can be described well by an effective two-band model with unbalanced diffusivity, while H\\text{c2}//ab shows a flattening below 35 K and follows the Werthamer-Helfand-Hohenberg (WHH) model incorporating orbital pair-breaking and spin-paramagnetic effects, yielding zero-temperature critical fields of H\\text{c2}//c(0)≈ 67 T and H\\text{c2}//ab(0)≈ 98 T. The anisotropy of the upper critical fields, γ (T)=H\\text{c2}//ab/H\\text{c2}//c monotonically decreases with decreasing temperature from about 7 near T c to 1.5 at 0 K. This reduced anisotropy, observed in most Fe-based superconductors, is caused by the Pauli limitation of H\\text{c2}//ab .

  11. High field magnetic behavior in Boron doped Fe2VAl Heusler alloys

    Science.gov (United States)

    Venkatesh, Ch.; Vasundhara, M.; Srinivas, V.; Rao, V. V.

    2016-11-01

    We have investigated the magnetic behavior of Fe2VAl1-xBx (x=0, 0.03, 0.06 and 0.1) alloys under high temperature and high magnetic field conditions separately. Although, the low temperature DC magnetization data for the alloys above x>0 show clear magnetic transitions, the zero field cooled (ZFC) and field cooled (FC) curves indicate the presence of spin cluster like features. Further, critical exponent (γ) deduced from the initial susceptibility above the Tc, does not agree with standard models derived for 3 dimensional long range magnetic systems. The deviation in γ values are consistent with the short range magnetic nature of these alloys. We further extend the analysis of magnetic behavior by carrying the magnetization measurements at high temperatures and high magnetic fields distinctly. We mainly emphasize the following observations; (i) The magnetic hysteresis loops show sharp upturns at lower fields even at 900 K for all the alloys. (ii) High temperature inverse susceptibility do not overlap until T=900 K, indicating the persistent short range magnetic correlations even at high temperatures. (iii) The Arrott's plot of magnetization data shows spontaneous moment (MS) for the x=0 alloy at higher magnetic fields which is absent at lower fields (magnetic heterogeneous phases which are not detected from the X-ray diffraction method.

  12. The 2011 Estonian High School Language Reform in the Context of Critical Language Policy and Planning

    Science.gov (United States)

    Skerrett, Delaney Michael

    2014-01-01

    This paper seeks to situate Estonian language use and policy within the emerging field of critical language policy and planning (CLPP) by investigating the discourses that frame linguistic behaviour. This done by way of an analysis of a series of interviews carried out with key actors in language policy in Estonia. The discourses framing language…

  13. Orbital upper critical field and its anisotropy of clean one- and two-band superconductors.

    Science.gov (United States)

    Kogan, V G; Prozorov, R

    2012-11-01

    The Helfand-Werthamer (HW) scheme (Helfand and Werthamer 1966 Phys. Rev. 147 288; another part of this work published as a separate paper by Werthamer et al 1966 Phys. Rev. 147 295) of evaluating the orbital upper critical field is generalized to anisotropic superconductors in general, and to two-band clean materials, in particular. Our formal procedure differs from those in the literature; it reproduces not only the isotropic HW limit but also the results of calculations for the two-band superconducting MgB(2) (Miranović et al 2003 J. Phys. Soc. Japan 72 221, Dahm and Schopohl 2003 Phys. Rev. Lett. 91 017001) along with the existing data on H(c2)(T) and its anisotropy γ(T) = H(c2,ab)(T)/H(c2,c)(T) (a, c are the principal directions of a uniaxial crystal). Using rotational ellipsoids as model Fermi surfaces we apply the formalism developed to study γ(T) for a few different anisotropies of the Fermi surface and of the order parameters. We find that even for a single band d-wave order parameter γ(T) decreases on warming; however, relatively weakly. For order parameters of the form Δ(k(z)) = Δ(0)(1 + η cos k(z)a) (Xu et al 2011 Nature Phys. 7 198), according to our simulations γ(T) may either increase or decrease on warming even for a single band depending on the sign of η. Hence, the common belief that the multi-band Fermi surface is responsible for the temperature variation of γ is proven incorrect. For two s-wave gaps, γ decreases on warming for all Fermi shapes examined. For two order parameters of the form Δ(k(z)) = Δ(0)(1 + η cos k(z)a), presumably relevant for pnictides, we obtain γ(T) increasing on warming provided both η(1) and η(2) are negative, whereas for η > 0, γ(T) decreases. We study the ratio of the two order parameters at H(c2)(T) and find that the ratio of the small gap to the large one does not vanish at any temperature, even at H(c2)(T), an indication that this does not happen at lower fields.

  14. Renyi entanglement entropies of descendant states in critical systems with boundaries: conformal field theory and spin chains

    Science.gov (United States)

    Taddia, Luca; Ortolani, Fabio; Pálmai, Tamás

    2016-09-01

    We discuss the Renyi entanglement entropies of descendant states in critical one-dimensional systems with boundaries, that map to boundary conformal field theories in the scaling limit. We unify the previous conformal-field-theory approaches to describe primary and descendant states in systems with both open and closed boundaries. We provide universal expressions for the first two descendants in the identity family. We apply our technique to critical systems belonging to different universality classes with non-trivial boundary conditions that preserve conformal invariance, and find excellent agreement with numerical results obtained for finite spin chains. We also demonstrate that entanglement entropies are a powerful tool to resolve degeneracy of higher excited states in critical lattice models.

  15. High magnetic field {mu}SR instrument scientific case

    Energy Technology Data Exchange (ETDEWEB)

    Amato, A

    2005-10-15

    In order to gain more insight into the specific behavior of materials, it is often necessary to perform measurements as a function of different external parameters. Despite its high sensitivity to internal fields, this simple observation also applies for the {mu}SR technique. The most common parameter which can be tuned during an experiment is the sample temperature. By using a range of cryostats, temperatures between 0.02 and 900 K can be covered at the PSI {mu}SR Facility. On the other hand, and by using high-energy muons, pressures as high as 10'000 bars can nowadays be reached during {mu}SR experiments. As will be demonstrated in the following Sections, the magnetic field is an additional external parameter playing a fundamental role when studying the ground state properties of materials in condensed matter physics and chemistry. However, the availability of high magnetic fields for {mu}SR experiments is still rather limited. Hence, if on one hand the high value of the gyromagnetic ratio of the muon provides the high magnetic sensitivity of the method, on the other hand it can lead to very high muon-spin precession frequencies when performing measurements in applied fields (the muon-spin precession frequency in a field of 1 Tesla s 135.5 MHz). Consequently, the use of ultra-fast detectors and electronics is mandatory when measuring in magnetic fields exceeding 1 Tesla. If such fields are very intense when compared to the Earth magnetic field < 10{sup -4} Tesla), the energy associated with them is still modest in view of the thermal energy. Hence, the Zeeman energy splitting of a free electron in a magnetic field of 1 Tesla corresponds to a thermal energy as low as 0.67 Kelvin. It is worth mentioning that nowadays magnetic fields of the order of 10 to 15 Tesla are quite common in condensed matter laboratories and have opened up vast new exciting experimental possibilities. (author)

  16. Spontaneous Radiation Emission from Short, High Field Strength Insertion Devices

    Energy Technology Data Exchange (ETDEWEB)

    Geoffrey Krafft

    2005-09-15

    Since the earliest papers on undulaters were published, it has been known how to calculate the spontaneous emission spectrum from ''short'' undulaters when the magnetic field strength parameter is small compared to unity, or in ''single'' frequency sinusoidal undulaters where the magnetic field strength parameter is comparable to or larger than unity, but where the magnetic field amplitude is constant throughout the undulater. Fewer general results have been obtained in the case where the insertion device is both short, i.e., the magnetic field strength parameter changes appreciably throughout the insertion device, and the magnetic field strength is high enough that ponderomotive effects, radiation retardation, and harmonic generation are important physical phenomena. In this paper a general method is presented for calculating the radiation spectrum for short, high-field insertion devices. It is used to calculate the emission from some insertion device designs of recent interest.

  17. Spontaneous radiation emission from short, high field strength magnetic devices

    Directory of Open Access Journals (Sweden)

    G. A. Krafft

    2006-01-01

    Full Text Available Since the earliest papers on undulators were published, it has been known how to calculate the spontaneous emission spectrum from short undulators when the magnetic field strength parameter is small compared to unity, or in “single” frequency sinusoidal undulators where the magnetic field strength parameter is comparable to or larger than unity, but where the magnetic field amplitude is constant throughout the undulator. Fewer general results have been obtained in the case where the magnetic device is both short, i.e., the magnetic field strength parameter changes appreciably throughout the device, and the magnetic field strength is high enough that ponderomotive effects, radiation retardation, and harmonic generation are important physical phenomena. In this paper a general method is presented for calculating the radiation spectrum for short, high-field magnetic devices. It is used to calculate the emission from some designs of recent interest.

  18. Improving Magnet Designs With High and Low Field Regions

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Bahl, Christian Robert Haffenden; Smith, Anders

    2011-01-01

    to low field regions. Also, a general way to replace magnet material with a high permeability soft magnetic material where appropriate is discussed. As an example, these schemes are applied to a two dimensional concentric Halbach cylinder design resulting in a reduction of the amount of magnet material......A general scheme for increasing the difference in magnetic flux density between a high and a low magnetic field region by removing unnecessary magnet material is presented. This is important in, e.g., magnetic refrigeration where magnet arrays have to deliver high field regions in close proximity...

  19. Highly Effective Action from Large N Gauge Fields

    CERN Document Server

    Yang, Hyun Seok

    2014-01-01

    Recently John H. Schwarz put forward a conjecture that the world-volume action of a probe $D3$-brane in an AdS5 x S5 background of type IIB superstring theory can be reinterpreted as the highly effective action (HEA) of four-dimensional N=4 superconformal field theory on the Coulomb branch. We argue that the HEA can be derived from the noncommutative (NC) field theory representation of the AdS/CFT correspondence and the Seiberg-Witten (SW) map defining a spacetime field redefinition between ordinary and NC gauge fields. It is based only on the well-known facts that the master fields of large N matrices are higher-dimensional NC U(1) gauge fields and the SW map is a local coordinate transformation eliminating U(1) gauge fields known as the Darboux theorem in symplectic geometry.

  20. Field high-throughput phenotyping: the new crop breeding frontier.

    Science.gov (United States)

    Araus, José Luis; Cairns, Jill E

    2014-01-01

    Constraints in field phenotyping capability limit our ability to dissect the genetics of quantitative traits, particularly those related to yield and stress tolerance (e.g., yield potential as well as increased drought, heat tolerance, and nutrient efficiency, etc.). The development of effective field-based high-throughput phenotyping platforms (HTPPs) remains a bottleneck for future breeding advances. However, progress in sensors, aeronautics, and high-performance computing are paving the way. Here, we review recent advances in field HTPPs, which should combine at an affordable cost, high capacity for data recording, scoring and processing, and non-invasive remote sensing methods, together with automated environmental data collection. Laboratory analyses of key plant parts may complement direct phenotyping under field conditions. Improvements in user-friendly data management together with a more powerful interpretation of results should increase the use of field HTPPs, therefore increasing the efficiency of crop genetic improvement to meet the needs of future generations.

  1. Dealing Collectively with Critical Incident Stress Reactions in High Risk Work Environments

    DEFF Research Database (Denmark)

    Müller-Leonhardt, Alice; Strøbæk, Pernille Solveig; Vogt, joachim

    2015-01-01

    aim of this paper is to shift the representation of coping patterns within high risk occupations to an existential part of cultural pattern and social structure, which characterises high reliability organisations. Drawing upon the specific peer model of critical incident stress management (CISM......), in which qualified operational peers support colleagues who experienced critical incident stress, the paper discusses critical incident stress management in air traffic control. Our study revealed coping patterns that co-vary with the culture that the CISM programme fostered within this specific high...... organisations. Indeed, we found that the CISM programme once integrated within the socio-cultural patterns of this specific working environment enhanced not only individual feelings of being supported but also organisational safety culture. Keywords: coping; safety culture; critical incident stress management...

  2. Probing High Temperature Superconductors with Magnetometry in Ultrahigh Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    Li, Lu [Univ. of Michigan, Ann Arbor, MI (United States)

    2017-07-26

    The objective of this research is to investigate the high-field magnetic properties of high temperature superconductors, materials that conduct electricity without loss. A technique known as high-resolution torque magnetometry that was developed to directly measure the magnetization of high temperature superconductors. This technique was implemented using the 65 Tesla pulsed magnetic field facility that is part of the National High Magnetic Field Laboratory at Los Alamos National Laboratory. This research addressed unanswered questions about the interplay between magnetism and superconductivity, determine the electronic structure of high temperature superconductors, and shed light on the mechanism of high temperature superconductivity and on potential applications of these materials in areas such as energy generation and power transmission. Further applications of the technology resolve the novel physical phenomena such as correlated topological insulators, and spin liquid state in quantum magnets.

  3. High critical current of Ti-sheathed MgB{sub 2} wires for AC and weight-critical applications

    Energy Technology Data Exchange (ETDEWEB)

    Alessandrini, M; Fang, H; Hanna, M; Putman, P; Zhou, Y X; Salama, K [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, Houston, TX 77204-4006 (United States)

    2006-01-15

    The peculiar features of magnesium diboride make it suitable for many potential applications. In the last four years of investigation of MgB{sub 2}, the scientific community's research was mainly motivated by features such as low cost, compatibility with straightforward processing methods, relatively high critical temperature, and absence of weak links between grains. Other applications suggest the accentuation of other MgB{sub 2} properties. In particular its very low mass density makes it attractive for space activities, where the cost per kilogram for orbiting is still a huge obstacle, e.g. the cost of transport to low Earth orbit can reach 15 k$ kg{sup -1}. In order to promote the use of this compound for space activities, we tested titanium as a sheath material. Titanium is non-magnetic and its alloys are almost half the weight of steel but with yield stresses up to three times higher. We fabricated Ti-sheathed MgB{sub 2} through the powder-in-tube process. These wires show similar results to those sheathed with Fe. At 4 K the critical current density J{sub c} is well above 7 x 10{sup 5} A cm{sup -2}. The interface between the superconducting intermetallic compound and the lightweight sheath does not show any evidence of reaction and diffusion up to 900 deg. C. An analysis was carried out using x-ray diffraction, scanning electron microscopy with an energy dispersive spectrometer, and electron microprobe analysis.

  4. The influence of chiral chemical potential, parallel electric and magnetic fields on the critical temperature of QCD

    CERN Document Server

    Ruggieri, M; Peng, G X

    2016-01-01

    We study the influence of external electric, $E$, and magnetic, $B$, fields parallel to each other, and of a chiral chemical potential, $\\mu_5$, on the chiral phase transition of Quantum Chromodynamics. Our theoretical framework is a Nambu-Jona-Lasinio model with a contact interaction. Within this model we compute the critical temperature of chiral symmetry restoration, $T_c$, as a function of the chiral chemical potential and field strengths. We find that the fields inhibit and $\\mu_5$ enhances chiral symmetry breaking, in agreement with previous studies.

  5. A METHOD FOR PRODUCING A HIGH QUALITY SOLENOIDAL FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Feinberg, B.; Brown, I.G.; Halbach, K.; Kunkel, W.B.

    1981-01-01

    A relatively simple and inexpensive device is described which can be used to provide a highly homogeneous solenoidal magnetic field when the solenoid windings are inadequate. Design considerations and experimental measurements are presented. A field straightness of approximately 10{sup -4} radians has been achieved.

  6. High-field EPR spectroscopy of thermal donors in silicon

    DEFF Research Database (Denmark)

    Dirksen, R.; Rasmussen, F.B.; Gregorkiewicz, T.

    1997-01-01

    Thermal donors generated in p-type boron-doped Czochralski-grown silicon by a 450 degrees C heat treatment have been studied by high-field magnetic resonance spectroscopy. In the experiments conducted at a microwave frequency of 140 GHz and in a magnetic field of approximately 5 T four individual...

  7. Effects of high external electric fields on protein conformation

    Science.gov (United States)

    Pompa, Pier Paolo; Bramanti, Alessandro; Maruccio, Giuseppe; del Mercato, Loretta Laureana; Chiuri, Rocco; Cingolani, Roberto; Rinaldi, Ross

    2005-06-01

    Resistance of biomolecules to high electric fields is a main concern for nanobioelectronics/nanobiosensing applications, and it is also a relevant issue from a fundamental perspective, to understand the dielectric properties and structural dynamics of proteins. In nanoscale devices, biomolecules may experience electric fields as high as 107 V/m in order to elicit charge transport/transfer. Understanding the effects of such fields on their structural integrity is thus crucial to assess the reliability of biomolecular devices. In this study, we show experimental evidence for the retention of native-like fold pattern by proteins embedded in high electric fields. We have tested the metalloprotein azurin, deposited onto SiO2 substrates in air with proper electrode configuration, by applying high static electric fields (up to 106-107 V/m). The effects on the conformational properties of protein molecules have been determined by means of intrinsic fluorescence measurements. Experimental results indicate that no significant field-induced conformational alteration occurs. This behavior is also discussed and supported by theoretical predictions of the intrinsic intra-protein electric fields. As the general features of such inner fields are not peculiar of azurin, the conclusions presented here should have general validity.

  8. Anisotropy and temperature dependence of the first critical field in 2H-NbS{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Leroux, M., E-mail: maxime.leroux@grenoble.cnrs.fr [Institut Neel, CNRS/UJF, 25 Avenue des Martyrs, B.P. 166, 38042 Grenoble Cedex 9 (France); Rodiere, P. [Institut Neel, CNRS/UJF, 25 Avenue des Martyrs, B.P. 166, 38042 Grenoble Cedex 9 (France); Cario, L. [Institut des Materiaux Jean Rouxel (IMN), Universite de Nantes-CNRS, 2 rue de la Houssiniere, B.P. 32229, 44322 Nantes Cedex 03 (France); Klein, T. [Institut Neel, CNRS/UJF, 25 Avenue des Martyrs, B.P. 166, 38042 Grenoble Cedex 9 (France)

    2012-06-01

    We report on {mu} Hall probe measurements on single crystals of 2H-NbS{sub 2}. This compound is the only superconducting 2H-dichalcogenide which does not develop a charge density wave. At low temperature and low magnetic field, a Bean profile is observed, allowing to evaluate the critical current. Moreover, the anisotropy and temperature dependence of the first critical field in 2H-NbS{sub 2} was measured down to 1.2 K. A linear temperature dependence of the first penetration field is clearly observed. The absolute magnetic penetration depth is found to be 83 nm which is slightly reduced compared to the iso-structural compound 2H-NbSe{sub 2}.

  9. Frontier Fields: High-Redshift Predictions and Early Results

    CERN Document Server

    Coe, Dan; Zitrin, Adi

    2014-01-01

    The Frontier Fields program is obtaining deep Hubble and Spitzer Space Telescope images of new "blank" fields and nearby fields gravitationally lensed by massive galaxy clusters. The Hubble images of the lensed fields are revealing nJy sources (AB mag > 31), the faintest galaxies yet observed. In this paper, we present high-redshift (z > 6) number count predictions for the full program and candidates in three of the first Hubble Frontier Fields images. The full program will transform our understanding of galaxy evolution in the first 600 million years (z > 9). Where previous programs yielded perhaps a dozen z > 9 candidates, the Frontier Fields may yield ~70 (~6 per field). We base this estimate on an extrapolation of luminosity functions observed between 4 9. This might suggest a deficit of faint z > 9 galaxies as also reported in the Ultra Deep Field (even while excesses of brighter z > 9 galaxies were reported in shallower fields). At these redshifts, cosmic variance (field-to-field variation) is expected...

  10. Improving magnet designs with high and low field regions

    CERN Document Server

    Bjørk, R; Smith, A; Pryds, N

    2014-01-01

    A general scheme for increasing the difference in magnetic flux density between a high and a low magnetic field region by removing unnecessary magnet material is presented. This is important in, e.g., magnetic refrigeration where magnet arrays has to deliver high field regions in close proximity to low field regions. Also, a general way to replace magnet material with a high permeability soft magnetic material where appropriate is discussed. As an example these schemes are applied to a two dimensional concentric Halbach cylinder design resulting in a reduction of the amount of magnet material used by 42% while increasing the difference in flux density between a high and a low field region by 45%.

  11. Design of a Linear Variable Differential Transformer With High Rejection to External Interfering Magnetic Field

    CERN Document Server

    Martino, M; Losito, R; Masi, A; Danisi, A

    2010-01-01

    The sensitivity of linear variable differential transformer (LVDT) position sensors to external slowly varying magnetic fields represents a critical issue when these sensors are installed close to high-current cables or electrical motors with significant fringe fields. The resulting position error can reach several hundreds of micrometers against a specified uncertainty normally below a few micrometers. In this paper, the design of a LVDT position sensor with high rejection to external constant or slowly varying magnetic fields is addressed by exploiting the finite element method (FEM) simulator FLUX. A shield, isolated from the sensor's magnetic circuit, has been considered to reduce the effect of magnetic fields on the secondary voltages of the LVDT. In addition, a dc current is used in order to polarize the magnetic circuit to reduce the sensitivity of the sensor to external interferences.

  12. High-field electron transport in nanoscale group-III nitride devices

    Energy Technology Data Exchange (ETDEWEB)

    Komirenko, S.M.; Kim, K.W. [North Carolina State Univ., Raleigh, NC (United States). Dept. of Electrical and Computer Engineering; Kochelap, V.A. [Inst. of Semiconductor Physics, National Academy of Sciences of Ukraine, Kiev-28 (Ukraine); Stroscio, M.A. [Army Research Office, Research Triangle Park, NC (United States). Mathematical Sciences Div.

    2001-11-08

    Focusing on the short-size group-III nitride heterostructures, we have developed a model which takes into account main features of transport of electrons injected into a polar semiconductor under high electric fields. The model is based on an exact analytical solution of Boltzmann transport equation. The electron velocity distribution over the device is analyzed at different fields and the basic characteristics of the high-field electron transport are obtained. The critical field for the runaway regime, when electron energies and velocities increase with distance which results in the average velocities higher than the peak velocity in bulk-like samples, is determined. We have found that the runaway electrons are characterized by a distribution function with population inversion. Different nitride-based small-size devices where this effect can have an impact on the device performance are considered. (orig.)

  13. Field transcriptome revealed critical developmental and physiological transitions involved in the expression of growth potential in japonica rice

    Directory of Open Access Journals (Sweden)

    Kamatsuki Kaori

    2011-01-01

    Full Text Available Abstract Background Plant growth depends on synergistic interactions between internal and external signals, and yield potential of crops is a manifestation of how these complex factors interact, particularly at critical stages of development. As an initial step towards developing a systems-level understanding of the biological processes underlying the expression of overall agronomic potential in cereal crops, a high-resolution transcriptome analysis of rice was conducted throughout life cycle of rice grown under natural field conditions. Results A wide range of gene expression profiles based on 48 organs and tissues at various developmental stages identified 731 organ/tissue specific genes as well as 215 growth stage-specific expressed genes universally in leaf blade, leaf sheath, and root. Continuous transcriptome profiling of leaf from transplanting until harvesting further elucidated the growth-stage specificity of gene expression and uncovered two major drastic changes in the leaf transcriptional program. The first major change occurred before the panicle differentiation, accompanied by the expression of RFT1, a putative florigen gene in long day conditions, and the downregulation of the precursors of two microRNAs. This transcriptome change was also associated with physiological alterations including phosphate-homeostasis state as evident from the behavior of several key regulators such as miR399. The second major transcriptome change occurred just after flowering, and based on analysis of sterile mutant lines, we further revealed that the formation of strong sink, i.e., a developing grain, is not the major cause but is rather a promoter of this change. Conclusions Our study provides not only the genetic basis for functional genomics in rice but also new insight into understanding the critical physiological processes involved in flowering and seed development, that could lead to novel strategies for optimizing crop productivity.

  14. Effective ionisation coefficients and critical breakdown electric field of CO2 at elevated temperature: effect of excited states and ion kinetics

    Science.gov (United States)

    Wang, Weizong; Bogaerts, Annemie

    2016-10-01

    Electrical breakdown by the application of an electric field occurs more easily in hot gases than in cold gases because of the extra electron-species interactions that occur as a result of dissociation, ionization and excitation at higher temperature. This paper discusses some overlooked physics and clarifies inaccuracies in the evaluation of the effective ionization coefficients and the critical reduced breakdown electric field of CO2 at elevated temperature, considering the influence of excited states and ion kinetics. The critical reduced breakdown electric field is obtained by balancing electron generation and loss mechanisms using the electron energy distribution function (EEDF) derived from the Boltzmann transport equation under the two-term approximation. The equilibrium compositions of the hot gas mixtures are determined based on Gibbs free energy minimization considering the ground states as well as vibrationally and electronically excited states as independent species, which follow a Boltzmann distribution with a fixed excitation temperature. The interaction cross sections between electrons and the excited species, not reported previously, are properly taken into account. Furthermore, the ion kinetics, including electron-ion recombination, associative electron detachment, charge transfer and ion conversion into stable negative ion clusters, are also considered. Our results indicate that the excited species lead to a greater population of high-energy electrons at higher gas temperature and this affects the Townsend rate coefficients (i.e. of electron impact ionization and attachment), but the critical reduced breakdown electric field strength of CO2 is only affected when also properly accounting for the ion kinetics. Indeed, the latter greatly influences the effective ionization coefficients and hence the critical reduced breakdown electric field at temperatures above 1500 K. The rapid increase of the dissociative electron attachment cross-section of

  15. Automated Critical PeakPricing Field Tests: 2006 Pilot ProgramDescription and Results

    Energy Technology Data Exchange (ETDEWEB)

    Piette, Mary Ann; Watson, David; Motegi, Naoya; Kiliccote, Sila

    2007-06-19

    During 2006 Lawrence Berkeley National Laboratory (LBNL) and the Demand Response Research Center (DRRC) performed a technology evaluation for the Pacific Gas and Electric Company (PG&E) Emerging Technologies Programs. This report summarizes the design, deployment, and results from the 2006 Automated Critical Peak Pricing Program (Auto-CPP). The program was designed to evaluate the feasibility of deploying automation systems that allow customers to participate in critical peak pricing (CPP) with a fully-automated response. The 2006 program was in operation during the entire six-month CPP period from May through October. The methodology for this field study included site recruitment, control strategy development, automation system deployment, and evaluation of sites' participation in actual CPP events through the summer of 2006. LBNL recruited sites in PG&E's territory in northern California through contacts from PG&E account managers, conferences, and industry meetings. Each site contact signed a memorandum of understanding with LBNL that outlined the activities needed to participate in the Auto-CPP program. Each facility worked with LBNL to select and implement control strategies for demand response and developed automation system designs based on existing Internet connectivity and building control systems. Once the automation systems were installed, LBNL conducted communications tests to ensure that the Demand Response Automation Server (DRAS) correctly provided and logged the continuous communications of the CPP signals with the energy management and control system (EMCS) for each site. LBNL also observed and evaluated Demand Response (DR) shed strategies to ensure proper commissioning of controls. The communication system allowed sites to receive day-ahead as well as day-of signals for pre-cooling, a DR strategy used at a few sites. Measurement of demand response was conducted using two different baseline models for estimating peak load savings. One

  16. Electric field induced phase transitions in polymers: a novel mechanism for high speed energy storage.

    Science.gov (United States)

    Ranjan, V; Nardelli, Marco Buongiorno; Bernholc, J

    2012-02-24

    Using first-principles simulations, we identify the microscopic origin of the nonlinear dielectric response and high energy density of polyvinylidene-fluoride-based polymers as a cooperative transition path that connects nonpolar and polar phases of the system. This path explores a complex torsional and rotational manifold and is thermodynamically and kinetically accessible at relatively low temperatures. Furthermore, the introduction of suitable copolymers significantly alters the energy barriers between phases providing tunability of both the energy density and the critical fields.

  17. Design of High Field Solenoids made of High Temperature Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bartalesi, Antonio; /Pisa U.

    2010-12-01

    This thesis starts from the analytical mechanical analysis of a superconducting solenoid, loaded by self generated Lorentz forces. Also, a finite element model is proposed and verified with the analytical results. To study the anisotropic behavior of a coil made by layers of superconductor and insulation, a finite element meso-mechanic model is proposed and designed. The resulting material properties are then used in the main solenoid analysis. In parallel, design work is performed as well: an existing Insert Test Facility (ITF) is adapted and structurally verified to support a coil made of YBa{sub 2}Cu{sub 3}O{sub 7}, a High Temperature Superconductor (HTS). Finally, a technological winding process was proposed and the required tooling is designed.

  18. Strong magnetic fields in normal galaxies at high redshifts

    CERN Document Server

    Bernet, Martin L; Lilly, Simon J; Kronberg, Philipp P; Dessauges-Zavadsky, Miroslava

    2008-01-01

    The origin and growth of magnetic fields in galaxies is still something of an enigma. It is generally assumed that seed fields are amplified over time through the dynamo effect, but there are few constraints on the timescale. It has recently been demonstrated that field strengths as traced by rotation measures of distant quasars are comparable to those seen today, but it was unclear whether the high fields were in the exotic environments of the quasars themselves or distributed along the line of sight. Here we demonstrate that the quasars with strong MgII absorption lines are unambiguously associated with larger rotation measures. Since MgII absorption occurs in the haloes of normal galaxies along the sightline to the quasars, this association requires that organized fields of surprisingly high strength are associated with normal galaxies when the Universe was only about one-third of its present age.

  19. Application of high magnetic fields in advanced materials processing

    Institute of Scientific and Technical Information of China (English)

    MA Yanwei; XIAO Liye; YAN Luguang

    2006-01-01

    Recently, steady magnetic fields available from cryogen-free superconducting magnets open up new ways to process materials. In this paper,the main results obtained by using a high magnetic field to process several advanced materials are reviewed. These processed objects primarily include superconducting, magnetic, metallic and nanometer-scaled materials. It has been found that a high magnetic field can effectively align grains when fabricating the magnetic and non-magnetic materials and make inclusions migrate in a molten metal. The mechanism is discussed from the theoretical viewpoint of magnetization energy.

  20. Experimental determination of the critical welding speed in high speed MAG welding

    Institute of Scientific and Technical Information of China (English)

    Hu Zhikun; Wu Chuansong

    2008-01-01

    In high speed MAG welding process, some weld formation defects may be encountered. To get good weld quality, the critical welding speed beyond which humping or undercutting weld bead can occur must be known for different conditions. In this research, high speed MAG welding tests were carried out to check out the effects of different factors on the critical welding speed. Through observing the weld bead profiles and the macrographs of the transverse sections of MAG welds, the occurrence tendency of humping weld was analyzed, and the values of critical welding speed were determined under different levels of welding current or voltage, and the effect of shielding gas compositions on the critical welding speed was also investigated.

  1. Micromagnetic simulation for high field sensors with perpendicular magnetizations

    Institute of Scientific and Technical Information of China (English)

    Jin Wei; Liu Yao-Wen

    2007-01-01

    In this paper, we present a micromagnetic design for high field sensors. The hard layer of the sensors is L10-FePt which is magnetized perpendicularly to film plane and the sense layer is NiFe which is magnetized in the film plane. The magnetization configurations of the hard and sense layers at different external magnetic fields have been simulated. In micromagnetic simulation, the sense field up to one tesla can be reached by using this sensor. We find that whether the sensor has a symmetric or an asymmetric field-sensing window is determined by the coercive field of the hard layer and the demagnetizing field of the sense layer.

  2. Landau-like theory for universality of critical exponents in quasistationary states of isolated mean-field systems

    Science.gov (United States)

    Ogawa, Shun; Yamaguchi, Yoshiyuki Y.

    2015-06-01

    An external force dynamically drives an isolated mean-field Hamiltonian system to a long-lasting quasistationary state, whose lifetime increases with population of the system. For second order phase transitions in quasistationary states, two nonclassical critical exponents have been reported individually by using a linear and a nonlinear response theories in a toy model. We provide a simple way to compute the critical exponents all at once, which is an analog of the Landau theory. The present theory extends the universality class of the nonclassical exponents to spatially periodic one-dimensional systems and shows that the exponents satisfy a classical scaling relation inevitably by using a key scaling of momentum.

  3. Landau-like theory for universality of critical exponents in quasistationary states of isolated mean-field systems.

    Science.gov (United States)

    Ogawa, Shun; Yamaguchi, Yoshiyuki Y

    2015-06-01

    An external force dynamically drives an isolated mean-field Hamiltonian system to a long-lasting quasistationary state, whose lifetime increases with population of the system. For second order phase transitions in quasistationary states, two nonclassical critical exponents have been reported individually by using a linear and a nonlinear response theories in a toy model. We provide a simple way to compute the critical exponents all at once, which is an analog of the Landau theory. The present theory extends the universality class of the nonclassical exponents to spatially periodic one-dimensional systems and shows that the exponents satisfy a classical scaling relation inevitably by using a key scaling of momentum.

  4. All-loop order critical exponents for massless scalar field theory with Lorentz violation in the BPHZ method

    Science.gov (United States)

    Carvalho, Paulo R. S.

    2016-12-01

    We compute analytically the all-loop level critical exponents for a massless thermal Lorentz-violating (LV) O(N) self-interacting λϕ4 scalar field theory. For that, we evaluate, firstly explicitly up to next-to-leading loop order and later in a proof by induction up to any loop level, the respective β-function and anomalous dimensions in a theory renormalized in the massless BPHZ method, where a reduced set of Feynman diagrams to be calculated is needed. We investigate the effect of the Lorentz violation in the outcome for the critical exponents and present the corresponding mathematical explanation and physical interpretation.

  5. R\\'enyi entanglement entropies of descendant states in critical systems with boundaries: conformal field theory and spin chains

    CERN Document Server

    Taddia, Luca; Pálmai, Tamás

    2016-01-01

    We discuss the R\\'enyi entanglement entropies of descendant states in critical one-dimensional systems with boundaries, that map to boundary conformal field theories (CFT) in the scaling limit. We unify the previous CFT approaches to describe primary and descendant states in systems with both open and closed boundaries. We apply the technique to critical systems belonging to different universality classes with non-trivial boundary conditions that preserve conformal invariance, and compare the results to numerical data obtained on finite spin chains.

  6. High critical current densities in bulk MgB{sub 2} fabricated using amorphous boron

    Energy Technology Data Exchange (ETDEWEB)

    Muralidhar, Miryala; Kenta, Nozaki; Murakami, Masato [Superconducting Materials Laboratory, Department of Materials Science and Engineering, Shibaura Institute of Technology, Tokyo 135-8548 (Japan); Koblischka, Michael R. [Institute of Experimental Physics, Saarland University, P.O. Box 151150, 66041 Saarbruecken (Germany)

    2015-10-15

    We prepared bulk MgB{sub 2} from high-purity commercial powders of Mg metal (99.9% purity) and amorphous B (99% purity) powders using a single-step solid state reaction at 775 C for varying sintering duration from 1 to 10 h in pure argon atmosphere. X-ray diffraction analysis showed that all the samples were single phase MgB{sub 2}. The magnetization measurements confirmed a sharp superconducting transition with T{sub c,onset} at around 38.2-38.8 K. The critical current density (J{sub c}) values for the MgB{sub 2} samples produced at 1 h sintering time is the highest one in all processed materials here. Scanning electron microscopy analyses indicated that the sintering time has a crucial influence on the grain size. As a result, the highest J{sub c} value of 270 kA cm{sup -2} at 20 K and self-field was achieved in the sample produced at 775 C for 1 h. Our results clearly demonstrate that the optimization of the sintering conditions is essential to improve the bulk MgB{sub 2} performance. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Field emission studies of novel ZnO nanostructures in high and low field regions

    Energy Technology Data Exchange (ETDEWEB)

    Ramgir, Niranjan S [Physical and Materials Chemistry Division, National Chemical Laboratory, Pune 411 008 (India); Late, Dattatray J [Center for Advanced Studies in Material Science and Solid State Physics, Department of Physics, University of Pune, Pune-411007 (India); Bhise, Ashok B [Center for Advanced Studies in Material Science and Solid State Physics, Department of Physics, University of Pune, Pune-411007 (India); Mulla, Imtiaz S [Physical and Materials Chemistry Division, National Chemical Laboratory, Pune 411 008 (India); More, Mahendra A [Center for Advanced Studies in Material Science and Solid State Physics, Department of Physics, University of Pune, Pune-411007 (India); Joag, Dilip S [Center for Advanced Studies in Material Science and Solid State Physics, Department of Physics, University of Pune, Pune-411007 (India); Pillai, Vijayamohanan K [Physical and Materials Chemistry Division, National Chemical Laboratory, Pune 411 008 (India)

    2006-06-14

    A study of the field emission characteristics of novel structures of ZnO, namely marigolds, multipods and microbelts, has been carried out in both the close proximity configuration and the conventional field emission microscope. The use of a conventional field emission microscope overcomes the drawback of arc formation at high field values. The nonlinearity in the Fowler-Nordheim (F-N) plot, a characteristic feature of semiconductors has been observed and explained on the basis of electron emission from both the conduction and the valence bands. The current stability exhibited by these structures is also promising for future device applications.

  8. Field emission studies of novel ZnO nanostructures in high and low field regions

    Science.gov (United States)

    Ramgir, Niranjan S.; Late, Dattatray J.; Bhise, Ashok B.; Mulla, Imtiaz S.; More, Mahendra A.; Joag, Dilip S.; Pillai, Vijayamohanan K.

    2006-06-01

    A study of the field emission characteristics of novel structures of ZnO, namely marigolds, multipods and microbelts, has been carried out in both the close proximity configuration and the conventional field emission microscope. The use of a conventional field emission microscope overcomes the drawback of arc formation at high field values. The nonlinearity in the Fowler-Nordheim (F-N) plot, a characteristic feature of semiconductors has been observed and explained on the basis of electron emission from both the conduction and the valence bands. The current stability exhibited by these structures is also promising for future device applications.

  9. $\\epsilon$-Expansion in Critical $\\phi^3$-Theory on Real Projective Space from Conformal Field Theory

    CERN Document Server

    Hasegawa, Chika

    2016-01-01

    We use a compatibility between the conformal symmetry and the equations of motion to solve the one-point function in the critical $\\phi^3$-theory (a.k.a the critical Lee-Yang model) on the $d = 6 - \\epsilon$ dimensional real projective space to the first non-trivial order in the $\\epsilon$-expansion. It reproduces the conventional perturbation theory and agrees with the numerical conformal bootstrap result.

  10. 𝜖-expansion in critical ϕ3-theory on real projective space from conformal field theory

    Science.gov (United States)

    Hasegawa, Chika; Nakayama, Yu

    2017-03-01

    We use a compatibility between the conformal symmetry and the equations of motion to solve the one-point function in the critical ϕ3-theory (a.k.a. the critical Lee-Yang model) on the d = 6 ‑ 𝜖 dimensional real projective space to the first nontrivial order in the 𝜖-expansion. It reproduces the conventional perturbation theory and agrees with the numerical conformal bootstrap result.

  11. Dipolar field effects on the critical current for spin transfer switch of iron and permalloy nanoelements

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, L. L.; Dantas, J. T. S.; Souza, R. M.; Carriço, A. S., E-mail: ascarrico@gmail.com [Departamento de Física, Universidade Federal do Rio Grande do Norte, 59072-970 Natal, RN (Brazil); Dantas, Ana L. [Departamento de Física, Universidade do Estado do Rio Grande do Norte, 59610-210 Mossoró, RN (Brazil)

    2014-05-07

    We report a theoretical study of dipolar effects on the switching current density of soft ferromagnetic elliptical nanoelements. Relevant changes on the critical current value are found according to the orientation of the magnetization and the spin polarization with the major axis. We show that the critical current density may be reduced by as much as 92% for thin nanoelements magnetized along the minor axis direction, using in-plane spin polarization parallel to the magnetization.

  12. Conceptualising Higher Education Research and/or Academic Development as "Fields": A Critical Analysis

    Science.gov (United States)

    Clegg, Sue

    2012-01-01

    This paper calls into question the idea that we can simply think about higher education as a research field and explores different meanings of the term field. It asks whether there are related fields: research into higher education, academic development and disciplinary teaching research, rather than one. The approach of the paper is conceptual,…

  13. Critical Temperature Characteristics of Layered High-Temperature Superconductor Under Pressure

    Institute of Scientific and Technical Information of China (English)

    LIANG Fang-Ying

    2009-01-01

    We consider a Ginzburg-Landau modified model of layered high-temperature superconductor under pres-sure. We have theoretically studied the relation between the pressure and the temperature of layered high-temperature superconductor. If the pressure is not a constant, we have a relation of quadratic equation between the pressure and the temperature of layered high-temperature superconductor. In a special case, we find the critical temperature decreases with further increasing pressure. In another special case, the critical temperature increases with further increasing pressure.

  14. Rotational symmetry breaking in the topological superconductor SrxBi2Se3 probed by upper-critical field experiments.

    Science.gov (United States)

    Pan, Y; Nikitin, A M; Araizi, G K; Huang, Y K; Matsushita, Y; Naka, T; de Visser, A

    2016-01-01

    Recently it was demonstrated that Sr intercalation provides a new route to induce superconductivity in the topological insulator Bi2Se3. Topological superconductors are predicted to be unconventional with an odd-parity pairing symmetry. An adequate probe to test for unconventional superconductivity is the upper critical field, Bc2. For a standard BCS layered superconductor Bc2 shows an anisotropy when the magnetic field is applied parallel and perpendicular to the layers, but is isotropic when the field is rotated in the plane of the layers. Here we report measurements of the upper critical field of superconducting SrxBi2Se3 crystals (Tc = 3.0 K). Surprisingly, field-angle dependent magnetotransport measurements reveal a large anisotropy of Bc2 when the magnet field is rotated in the basal plane. The large two-fold anisotropy, while six-fold is anticipated, cannot be explained with the Ginzburg-Landau anisotropic effective mass model or flux flow induced by the Lorentz force. The rotational symmetry breaking of Bc2 indicates unconventional superconductivity with odd-parity spin-triplet Cooper pairs (Δ4-pairing) recently proposed for rhombohedral topological superconductors, or might have a structural nature, such as self-organized stripe ordering of Sr atoms.

  15. Development of Assessment Instrument of Critical Thinking in Physics at Senior High School

    Science.gov (United States)

    Sugiarti, T.; Kaniawati, I.; Aviyanti, L.

    2017-02-01

    The result of preliminary study shows that the assessment of physics in school did not train students’ critical thinking skill. The assessment instrument just measured low cognitive aspects. Supposedly, critical thinking skill is trained in the assessment activity. The study aims to determine the characteristics and the quality of critical thinking skill instrument. It employs descriptive-qualitative method with research and development as the research design. The research participants are 35 students involved in the limited trial and 188 students in the wider trial from three public senior high school in Ciamis which in high level school. The data was collected through expert validation, tests and interviews. The results indicate that the characteristics of the assessment instrument of critical thinking skill is open-ended. The instrument fulfills some indicators namely analyzing argument, deduction, induction, and display information in the form of scenario, text, graphic and table. In addition, the data processing through V4 Anates program shows that the instrument reliability achieves 0.67 with high interpretation of 0.67 and the validity is 0.47 with enough interpretation. Thus, the assessment instrument of critical thinking skill in the form of open-ended essay meets the criteria of quality test, so it can use as instrument of assessment critical thinking skill.

  16. Anisotropy of the upper critical fields and the paramagnetic Meissner effect in La1.85Sr0.15CuO4 single crystals

    Science.gov (United States)

    Felner, I.; Tsindlekht, M. I.; Drachuck, G.; Keren, A.

    2013-02-01

    Optimally doped La1.85Sr0.15CuO4 single crystals have been investigated by dc and ac magnetic measurements. These crystals have rectangular needle-like shapes with the long needle axis parallel to the crystallographic c axis (c-crystal) or parallel to the basal planes (a-crystal). In both crystals, the temperature dependence of the upper critical fields (HC2) and the surface critical field (HC3) were measured. The H-T phase diagram is presented. Close to TC = 35 K, for the c-crystal, {\\boldsymbol{\\gamma}}^{c}={H}_{{C3}}^{c}/{H}_{{C2}}^{c}=1.8 0(2), whereas for the a-crystal the {\\boldsymbol{\\gamma}}^{a}={H}_{{C3}}^{a}/{H}_{{C2}}^{a}=4.0(2) obtained is much higher than 1.69, predicted by the ideal mathematical model. At low applied dc fields, positive field-cooled branches known as the ‘paramagnetic Meissner effect’ (PME) are observed; their magnitude is inversely proportional to H. The anisotropic PME is observed in both a- and c-crystals, only when the applied field is along the basal planes. It is speculated that the high γa and the PME are connected to each other.

  17. High harmonic generation in a two-color field composed of a pump field and a weak subsidiary high frequency field

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    “Coherent control of high-harmonic generation in a two-color field” has been widely concerned. Using split-operator algorithm, we have calculated the high-harmonic generation for helium ion He+ in a two-color field which is composed of a driving field and a weak subsidiary high frequency field (Is=I0/100, (ω,13ω), …(ω, 120ω)) and found that such a field can produce much higher harmonic intensity, typically increasing the harmonics corresponding to the incident frequency of the subsidiary field. The different effects coming from the different subsidiary fields are calculated and analyzed. It is indicated that one of the important underlying mechanisms is high frequency photon induced radiation.

  18. Shrink Tube Insulation Apparatus for Rebco Superconducting Tapes for Use in High Field Magnets

    CERN Document Server

    Whittington, Andrew

    An increasing number of applications require the use of high temperature superconductors (HTS) such as (RE=Rare Earth) Ba2Cu3O7-x (REBCO) coated conductors [1]. HTS conductors show particularly great potential for high field magnets applications [1] due to their high upper critical fields [2], But several groups have shown that REBCO coated conductors are prone to delamination failure [3] [4] [5]. Under relatively low transverse stress the HTS film separates from the substrate and the conductor degrades [6]. This is problematic due to high transverse stresses that occur in fully epoxy impregnated solenoids wound with this conductor. Application of thin walled heat shrink tubing introduces a weak plane around the conductor, preventing delamination degradation [7]. However, manual application of the shrink tubing is impractical, requiring three operators limited to insulating 100 m lengths or less of REBCO conductor. The high risk of damage to the conductor, also associated with this process, shows the need for...

  19. High resolution, large dynamic range field map estimation

    Science.gov (United States)

    Dagher, Joseph; Reese, Timothy; Bilgin, Ali

    2013-01-01

    Purpose We present a theory and a corresponding method to compute high resolution field maps over a large dynamic range. Theory and Methods We derive a closed-form expression for the error in the field map value when computed from two echoes. We formulate an optimization problem to choose three echo times which result in a pair of maximally distinct error distributions. We use standard field mapping sequences at the prescribed echo times. We then design a corresponding estimation algorithm which takes advantage of the optimized echo times to disambiguate the field offset value. Results We validate our method using high resolution images of a phantom at 7T. The resulting field maps demonstrate robust mapping over both a large dynamic range, and in low SNR regions. We also present high resolution offset maps in vivo using both, GRE and MEGE sequences. Even though the proposed echo time spacings are larger than the well known phase aliasing cutoff, the resulting field maps exhibit a large dynamic range without the use of phase unwrapping or spatial regularization techniques. Conclusion We demonstrate a novel 3-echo field map estimation method which overcomes the traditional noise-dynamic range trade-off. PMID:23401245

  20. MAGNETIC FIELDS IN HIGH-MASS INFRARED DARK CLOUDS

    Energy Technology Data Exchange (ETDEWEB)

    Pillai, T.; Kauffmann, J. [California Institute of Technology, Cahill Center for Astronomy and Astrophysics, Pasadena, CA 91125 (United States); Tan, J. C. [University of Florida, Gainesville, FL 32611 (United States); Goldsmith, P. F. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Carey, S. J. [Spitzer Science Center, California Institute of Technology, 1200 East California Boulevard, MC 314-6, Pasadena, CA 91125 (United States); Menten, K. M., E-mail: tpillai.astro@gmail.com [Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany)

    2015-01-20

    High-mass stars are cosmic engines known to dominate the energetics in the Milky Way and other galaxies. However, their formation is still not well understood. Massive, cold, dense clouds, often appearing as infrared dark clouds (IRDCs), are the nurseries of massive stars. No measurements of magnetic fields in IRDCs in a state prior to the onset of high-mass star formation (HMSF) have previously been available, and prevailing HMSF theories do not consider strong magnetic fields. Here, we report observations of magnetic fields in two of the most massive IRDCs in the Milky Way. We show that IRDCs G11.11–0.12 and G0.253+0.016 are strongly magnetized and that the strong magnetic field is as important as turbulence and gravity for HMSF. The main dense filament in G11.11–0.12 is perpendicular to the magnetic field, while the lower density filament merging onto the main filament is parallel to the magnetic field. The implied magnetic field is strong enough to suppress fragmentation sufficiently to allow HMSF. Other mechanisms reducing fragmentation, such as the entrapment of heating from young stars via high-mass surface densities, are not required to facilitate HMSF.

  1. Upper critical field, pressure-dependent superconductivity and electronic anisotropy of Sm4Fe2As2Te(1-x)O(4-y)F(y).

    Science.gov (United States)

    Pisoni, A; Katrych, S; Szirmai, P; Náfrádi, B; Gaál, R; Karpinski, J; Forró, L

    2016-03-23

    We present a detailed study of the electrical transport properties of a recently discovered iron-based superconductor: Sm4Fe2As2Te0.72O2.8F1.2. We followed the temperature dependence of the upper critical field by resistivity measurement of single crystals in magnetic fields up to 16 T, oriented along the two main crystallographic directions. This material exhibits a zero-temperature upper critical field of 90 T and 65 T parallel and perpendicular to the Fe2As2 planes, respectively. An unprecedented superconducting magnetic anisotropy γH=H(c2)(ab)/H(c2)(c) ~ 14 is observed near Tc, and it decreases at lower temperatures as expected in multiband superconductors. Direct measurement of the electronic anisotropy was performed on microfabricated samples, showing a value of ρ(c)/ρ(ab)(300K) ~ 5 that rises up to 19 near Tc . Finally, we have studied the pressure and temperature dependence of the in-plane resistivity. The critical temperature decreases linearly upon application of hydrostatic pressure (up to 2 GPa) similarly to overdoped cuprate superconductors. The resistivity shows saturation at high temperatures, suggesting that the material approaches the Mott-Ioffe-Regel limit for metallic conduction. Indeed, we have successfully modelled the resistivity in the normal state with a parallel resistor model that is widely accepted for this state. All the measured quantities suggest strong pressure dependence of the density of states.

  2. High Speed Multiple Valued Logic Full Adder Using Carbon Nano Tube Field Effect Transistor

    CERN Document Server

    Khatir, Ashkan; Mahmoudi, Iman

    2011-01-01

    High speed Full-Adder (FA) module is a critical element in designing high performance arithmetic circuits. In this paper, we propose a new high speed multiple-valued logic FA module. The proposed FA is constructed by 14 transistors and 3 capacitors, using carbon nano-tube field effect transistor (CNFET) technology. Furthermore, our proposed technique has been examined in different voltages (i.e., 0.65v and 0.9v). The observed results reveal power consumption and power delay product (PDP) improvements compared to existing FA counterparts

  3. High Speed Multiple Valued Logic Full Adder Using Carbon Nano Field Effect Transistor

    Directory of Open Access Journals (Sweden)

    Ashkan Khatir

    2011-03-01

    Full Text Available High speed Full-Adder (FA module is a critical element in designing high performance arithmeticcircuits. In this paper, we propose a new high speed multiple-valued logic FA module. The proposed FAis constructed by 14 transistors and 3 capacitors, using carbon nano-tube field effect transistor (CNFETtechnology. Furthermore, our proposed technique has been examined in different voltages (i.e., 0.65v and0.9v. The observed results reveal power consumption and power delay product (PDP improvementscompared to existing FA counterparts.

  4. High-field proton MRS of human brain

    Energy Technology Data Exchange (ETDEWEB)

    Di Costanzo, Alfonso E-mail: alfonso.dicostanzo@unina2.it; Trojsi, F.; Tosetti, M.; Giannatempo, G.M.; Nemore, F.; Piccirillo, M.; Bonavita, S.; Tedeschi, G.; Scarabino, T

    2003-11-01

    Proton magnetic resonance spectroscopy ({sup 1}H-MRS) of the brain reveals specific biochemical information about cerebral metabolites, which may support clinical diagnoses and enhance the understanding of neurological disorders. The advantages of performing {sup 1}H-MRS at higher field strengths include better signal to noise ratio (SNR) and increased spectral, spatial and temporal resolution, allowing the acquisition of high quality, easily quantifiable spectra in acceptable imaging times. In addition to improved measurement precision of N-acetylaspartate, choline, creatine and myo-inositol, high-field systems allow the high-resolution measurement of other metabolites, such as glutamate, glutamine, {gamma}-aminobutyric acid, scyllo-inositol, aspartate, taurine, N-acetylaspartylglutamate, glucose and branched amino acids, thus extending the range of metabolic information. However, these advantages may be hampered by intrinsic field-dependent technical difficulties, such as decreased T2 signal, chemical shift dispersion errors, J-modulation anomalies, increased magnetic susceptibility, eddy current artifacts, limitations in the design of homogeneous and sensitive radiofrequency (RF) coils, magnetic field instability and safety issues. Several studies demonstrated that these limitations could be overcome, suggesting that the appropriate optimization of high-field {sup 1}H-MRS would expand the application in the fields of clinical research and diagnostic routine.

  5. High Field Seeking State Atom Laser and Properties of Flux

    Institute of Scientific and Technical Information of China (English)

    XIA Lin; XIONG Wei; YANG Fan; YI Lin; ZHOU Xiao-Ji; CHEN Xu-Zong

    2008-01-01

    We present an experimental study on the continuous atom laser. The experiments show that a high field seeking state atom laser with stable flux can be formed by increasing the strength of outcoupling before large density fluctuations appear. It is easy to obtain a long length or high speed output with this kind of atom laser.

  6. Magnetic Field Structure in a High-mass System

    NARCIS (Netherlands)

    Beuther, H.; Vlemmings, W. H. T.; Rao, R.; van der Tak, F. F. S.

    2010-01-01

    To characterize the magnetic field structure of the outflow and core region within a prototypical high-mass star-forming region, we analyzed polarized CO(3-2)-for the first time observed with the Submillimeter Array-as well as 880 mu m submillimeter continuum emission from the high-mass outflow/disk

  7. Flux jump-assisted pulsed field magnetisation of high-J c bulk high-temperature superconductors

    Science.gov (United States)

    Ainslie, M. D.; Zhou, D.; Fujishiro, H.; Takahashi, K.; Shi, Y.-H.; Durrell, J. H.

    2016-12-01

    Investigating, predicting and optimising practical magnetisation techniques for charging bulk superconductors is a crucial prerequisite to their use as high performance ‘psuedo’ permanent magnets. The leading technique for such magnetisation is the pulsed field magnetisation (PFM) technique, in which a large magnetic field is applied via an external magnetic field pulse of duration of the order of milliseconds. Recently ‘giant field leaps’ have been observed during charging by PFM: this effect greatly aids magnetisation as flux jumps occur in the superconductor leading to magnetic flux suddenly intruding into the centre of the superconductor. This results in a large increase in the measured trapped field at the centre of the top surface of the bulk sample and full magnetisation. Due to the complex nature of the magnetic flux dynamics during the PFM process, simple analytical methods, such as those based on the Bean critical state model, are not applicable. Consequently, in order to successfully model this process, a multi-physical numerical model is required, including both electromagnetic and thermal considerations over short time scales. In this paper, we show that a standard numerical modelling technique, based on a 2D axisymmetric finite-element model implementing the H -formulation, can model this behaviour. In order to reproduce the observed behaviour in our model all that is required is the insertion of a bulk sample of high critical current density, J c. We further explore the consequences of this observation by examining the applicability of the model to a range of previously reported experimental results. Our key conclusion is that the ‘giant field leaps’ reported by Weinstein et al and others need no new physical explanation in terms of the behaviour of bulk superconductors: it is clear the ‘giant field leap’ or flux jump-assisted magnetisation of bulk superconductors will be a key enabling technology for practical applications.

  8. T1 and susceptibility contrast at high fields

    Science.gov (United States)

    Neelavalli, Jaladhar

    Clinical imaging at high magnetic field strengths (≥ 3Tesla) is sought after primarily due to the increased signal strength available at these fields. This increased SNR can be used to perform: (a) high resolution imaging in the same time as at lower field strengths; (b) the same resolution imaging with much faster acquisition; and (c) functional MR imaging (fMRI), dynamic perfusion and diffusion imaging with increased sensitivity. However they are also associated with increased power deposition (SAR) due to increase in imaging frequency and longer T1 relaxation times. Longer T1s mean longer imaging times for generating good T1 contrast images. On the other hand for faster imaging, at high fields fast spin echo or magnetization prepared sequences are conventionally proposed which are, however, associated with high SAR values. Imaging with low SAR is more and more important as we move towards high fields and particularly for patients with metallic implants like pacemakers or deep brain stimulator. The SAR limit acceptable for these patients is much less than the limit acceptable for normal subjects. A new method is proposed for imaging at high fields with good contrast with simultaneous reduction in power deposition. Further, T1 based contrast optimization problem in FLASH imaging is considered for tissues with different T1s but same spin densities. The solution providing optimal imaging parameters is simplified for quick and easy computation in a clinical setting. The efficacy of the simplification is evaluated and practical limits under which the simplification can be applied are worked out. The phase difference due to variation in magnetic susceptibility property among biological tissues is another unique source of contrast which is different from the conventional T1, T2 and T2* contrast. This susceptibility based phase contrast has become more and more important at high fields, partly due to contrast generation issues due to longer T 1s and shorter T2s and

  9. Modeling Critical Forest Habitat in the Southern Coal Fields of West Virginia

    Directory of Open Access Journals (Sweden)

    Aaron E. Maxwell

    2012-01-01

    Full Text Available Throughout the Central Appalachians of the United States resource extraction primarily from coal mining has contributed to the majority of the forest conversion to barren and reclaimed pasture and grass. The loss of forests in this ecoregion is significantly impacting biodiversity at a regional scale. Since not all forest stands provide equal levels of ecological functions, it is critical to identify and map existing forested resources by the benefits that accrue from their unique spatial patterns, watershed drainage, and landscape positions. We utilized spatial analysis and remote sensing techniques to define critical forest characteristics. The characteristics were defined by applying a forest fragmentation model utilizing morphological image analysis, defining headwater catchments at a 1 : 24,000 scale, and deriving ecological land units (ELUs from elevation data. Once critical forest values were calculated, it was possible to identify clusters of critical stands using spatial statistics. This spatially explicit method for modeling forest habitat could be implemented as a tool for assessing the impact of resource extraction and aid in the conservation of critical forest habitat throughout a landscape.

  10. Effect of a pinning field on the critical current density for current-induced domain wall motion in perpendicular magnetic anisotropy nanowires.

    Science.gov (United States)

    Ooba, Ayaka; Fujimura, Yuma; Takahashi, Kota; Komine, Takashi; Sugita, Ryuji

    2012-09-01

    In this study, the effect of a pinning field on the critical current density for current-induced domain wall motion in nanowires with perpendicular magnetic anisotropy was investigated using micromagnetic simulations. In order to estimate the pinning field in notched nanowires, we conducted wall energy calculations for nanowires with various saturation magnetizations. The pinning field increased as the notch size increased. The pinning field decreased as the saturation magnetization decreased. As a result, the decreased in the pinning field causes the reduction of the critical current density. Therefore, a significant reduction of the critical current density can be obtained by decreasing the saturation magnetization, even if wall pinning occurs.

  11. Polarization of radiation of electrons in highly turbulent magnetic fields

    Science.gov (United States)

    Prosekin, A. Yu.; Kelner, S. R.; Aharonian, F. A.

    2016-09-01

    We study the polarization properties of the jitter and synchrotron radiation produced by electrons in highly turbulent anisotropic magnetic fields. The net polarization is provided by the geometry of the magnetic field the directions of which are parallel to a certain plane. Such conditions may appear in the relativistic shocks during the amplification of the magnetic field through the so-called Weibel instability. While the polarization properties of the jitter radiation allows extraction of direct information on the turbulence spectrum as well as the geometry of magnetic field, the polarization of the synchrotron radiation reflects the distribution of the magnetic field over its strength. For the isotropic distribution of monoenergetic electrons, we found that the degree of polarization of the synchrotron radiation is larger than the polarization of the jitter radiation. For the power-law energy distribution of electrons the relation between the degree of polarization of synchrotron and jitter radiation depends on the spectral index of the distribution.

  12. Polarization of radiation of electrons in highly turbulent magnetic fields

    CERN Document Server

    Prosekin, A Yu; Aharonian, F A

    2016-01-01

    We study the polarization properties of the jitter and synchrotron radiation produced by electrons in highly turbulent anisotropic magnetic fields. The net polarization is provided by the geometry of the magnetic field the directions of which are parallel to a certain plane. Such conditions may appear in the relativistic shocks during the amplification of the magnetic field through the so-called Weibel instability. While the polarization properties of the jitter radiation allows extraction of direct information on the turbulence spectrum as well as the geometry of magnetic field, the polarization of the synchrotron radiation reflects the distribution of the magnetic field over its strength. For the isotropic distribution of monoenergetic electrons, we found that the degree of polarization of the synchrotron radiation is larger than the polarization of the jitter radiation. For the power-law energy distribution of electrons the relation between the degree of polarization of synchrotron and jitter radiation dep...

  13. Applications of Canonical transformations and nontrivial vacuum solutions to flavor mixing and critical phenomena in quantum field theory

    Energy Technology Data Exchange (ETDEWEB)

    Mishchenko, Yuriy [North Carolina State Univ., Raleigh, NC (United States)

    2004-12-01

    MISHCHENKO, YURIY. Applications of Canonical Transformations and Nontrivial Vacuum Solutions to flavor mixing and critical phenomena in Quantum Field Theory. (Under the direction of Chueng-Ryong Ji.) In this dissertation we consider two recent applications of Bogoliubov Transformation to the phenomenology of quantum mixing and the theory of critical phenomena. In recent years quantum mixing got in the focus of the searches for New Physics due to its unparalleled sensitivity to SM parameters and indications of neutrino mixing. It was recently suggested that Bogoliubov Transformation may be important in proper definition of the flavor states that otherwise results in problems in perturbative treatment. As first part of this dissertation we investigate this conjecture and develop a complete formulation of such a mixing field theory involving introduction of general formalism, analysis of space-time conversion and phenomenological implications. As second part of this dissertati

  14. Fermi surface topology and the upper critical field in two-band superconductors: application to MgB2.

    Science.gov (United States)

    Dahm, T; Schopohl, N

    2003-07-04

    Recent measurements of the anisotropy of the upper critical field B(c2) on MgB2 single crystals have shown a puzzling strong temperature dependence. Here, we present a calculation of the upper critical field based on a detailed modeling of band structure calculations that takes into account both the unusual Fermi surface topology and the two gap nature of the superconducting order parameter. Our results show that the strong temperature dependence of the B(c2) anisotropy can be understood as an interplay of the dominating gap on the sigma band, which possesses a small c-axis component of the Fermi velocity, with the induced superconductivity on the pi-band possessing a large c-axis component of the Fermi velocity. We provide analytic formulas for the anisotropy ratio at T=0 and T=T(c) and quantitatively predict the distortion of the vortex lattice based on our calculations.

  15. Perceived Criticism in the Treatment of a High-Risk Adolescent.

    Science.gov (United States)

    Hooley, Jill M; Miklowitz, David J

    2017-01-23

    Perceived criticism (PC) is a construct that plays a key role in family relationships of persons with psychiatric disorders. It can be assessed in a brief and simple way using the Perceived Criticism Measure. PC ratings made by patients about their caregivers predict adverse clinical outcomes including increases in symptoms and relapse across a broad range of psychiatric diagnoses. Although research supports the concurrent and predictive validity of PC, the measure is not widely used in clinical practice. Here, we describe the construct of PC and review evidence supporting its clinical utility. We then illustrate how criticism and perceptions of criticism can be addressed in a clinical context, describing a family focused treatment approach used with a depressed adolescent at high risk for bipolar disorder.

  16. On the origin of high-field magnetic white dwarfs

    CERN Document Server

    García-Berro, E; Lorén-Aguilar, P; Aznar-Siguán, G; Camacho, J; Külebi, B; Isern, J; Althaus, L G; Córsico, A H

    2012-01-01

    High-field magnetic white dwarfs have been long suspected to be the result of stellar mergers. However, the nature of the coalescing stars and the precise mechanism that produces the magnetic field are still unknown. Here we show that the hot, convective, differentially rotating corona present in the outer layers of the remnant of the merger of two degenerate cores is able to produce magnetic fields of the required strength that do not decay for long timescales. We also show, using an state-of-the-art Monte Carlo simulator, that the expected number of high-field magnetic white dwarfs produced in this way is consistent with that found in the solar neighborhood.

  17. Microchip electrophoresis at elevated temperatures and high separation field strengths.

    Science.gov (United States)

    Mitra, Indranil; Marczak, Steven P; Jacobson, Stephen C

    2014-02-01

    We report free-solution microchip electrophoresis performed at elevated temperatures and high separation field strengths. We used microfluidic devices with 11 cm long separation channels to conduct separations at temperatures between 22 (ambient) and 45°C and field strengths from 100 to 1000 V/cm. To evaluate separation performance, N-glycans were used as a model system and labeled with 8-aminopyrene-1,3,6-trisulfonic acid to impart charge for electrophoresis and render them fluorescent. Typically, increased diffusivity at higher temperatures leads to increased axial dispersion and poor separation performance; however, we demonstrate that sufficiently high separation field strengths offset the impact of increased diffusivity in order to maintain separation efficiency. Efficiencies for these free-solution separations are the same at temperatures of 25, 35, and 45°C with separation field strengths ≥ 500 V/cm.

  18. Suppression of the Shastry-Sutherland phase in Ce$_{2}$Pd$_{2}$Sn at a field induced critical point

    OpenAIRE

    Sereni, J. G.; Berisso, M. Gomez; Schmerber, G.; Braghta, A.; Kappler, J. P.

    2010-01-01

    The magnetic phase diagram of Ce$_2$Pd$_2$Sn is investigated through the field dependence of thermal, transport and magnetic measurements performed at low temperature. The upper transition, $T_M=4.8$ K is practically not affected by magnetic field up to B=1 T, whereas the lower one $T_C(B)$ rapidly increases from 2.1 K joining $T_M$ in a critical point at $T_{cr}=(4.2\\pm 0.3$)K for $B_{cr}=(0.12\\pm 0.03)$ T. At that point the intermediate phase, previously described as an unstable Shastry-Sut...

  19. Field Investigation of High Performance Pavements in Virginia

    OpenAIRE

    2005-01-01

    This study evaluated 18 pavement sections located in high-traffic highways in Virginia to find a premium pavement design with a life span of 40 years or more using current and past field experience. The selected pavement sections were thought to perform well. Eight flexible pavements, six composite pavements, two continuously reinforced concrete pavements, and two jointed plain concrete pavements were investigated. Field testing consisted of (1) falling weight deflectometer (FWD) testing to a...

  20. Experimental evidence for Froehlich superconductivity in high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Harrison, N. [National High Magnetic Field Laboratory, LANL, MS-E536, Los Alamos, NM (United States)]. E-mail: nharrison@lanl.gov; Mielke, C.H.; Singleton, J. [National High Magnetic Field Laboratory, LANL, MS-E536, Los Alamos, NM (United States); Brooks, J.S. [National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL (United States); Tokumoto, M. [Electrotechnical Laboratory, Tsukuba, Ibaraki (Japan)

    2001-05-14

    Resistivity and irreversible magnetization data taken within the high magnetic field CDW{sub x} phase of the quasi-two-dimensional organic metal {alpha}-(BEDT-TTF){sub 2}KHg(SCN){sub 4} are shown to be consistent with a field-induced inhomogeneous superconducting phase. In-plane skin depth measurements show that the resistive transition on entering the CDW{sub x} phase is both isotropic and representative of the bulk. (author). Letter-to-the-editor.

  1. High field optical nonlinearity and the Kramers-Kronig relations.

    Science.gov (United States)

    Wahlstrand, J K; Cheng, Y-H; Milchberg, H M

    2012-09-14

    The nonlinear optical response to high fields is absolutely measured for the noble gas atoms He, Ne, Ar, Kr, and Xe. We find that the response is quadratic in the laser field magnitude up to the ionization threshold of each gas. Its size and quadratic dependence are well predicted by a Kramers-Kronig analysis employing known ionization probabilities, and the results are consistent with calculations using the time-dependent Schrödinger equation.

  2. Magnetic Fields in High-Mass Infrared Dark Clouds

    CERN Document Server

    Pillai, Thushara; Tan, Jonathan; Goldsmith, Paul; Carey, Sean; Menten, Karl

    2014-01-01

    High-mass Stars are cosmic engines known to dominate the energetics in the Milky Way and other galaxies. However, their formation is still not well understood. Massive, cold, dense clouds, often appearing as Infrared Dark Clouds (IRDCs), are the nurseries of massive stars. No measurements of magnetic fields in IRDCs in a state prior to the onset of high-mass star formation (HMSF) have previously been available, and prevailing HMSF theories do not consider strong magnetic fields. Here, we report observations of magnetic fields in two of the most massive IRDCs in the Milky Way. We show that IRDCs G11.11-0.12 and G0.253+0.016 are strongly magnetized and that the strong magnetic field is as important as turbulence and gravity for HMSF. The main dense filament in G11.11-0.12 is perpendicular to the magnetic field, while the lower density filament merging onto the main filament is parallel to the magnetic field. The implied magnetic field is strong enough to suppress fragmentation sufficiently to allow HMSF. Other ...

  3. Magnetic Properties of Erbium Gallium Gallate under High Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    Zhang Xijuan; Cheng Haiying; Yang Cuihong; Wang Wei

    2004-01-01

    A theoretical investigation on the magnetic properties of rare-earth Er3+ in Er3 Ga5 O12 was reported. The average magnetic moments(M) for applied magnetic field H parallel to the [001 ], [ 100], [ 110], [ 111 ] direction was studied based on the quantum theory. Temperature dependence of the magnetic properties is analyzed for H applied parallel to the [ 100] and [ 111 ] crystallographic directions. The magnetization decreases with increasing temperature,showing good agreement with thermal effect. A strong anisotropy of the magnetization is found under high magnetic field, but when the magnetic field is small, M and H are proportional.

  4. High Dynamic Range Electric Field Sensor for Electromagnetic Pulse Detection

    CERN Document Server

    Lin, Che-Yun; Lee, Beom Suk; Zhang, Xingyu; Chen, Ray T

    2014-01-01

    We design a high dynamic range electric field sensor based on domain inverted electro-optic (E-O) polymer Y-fed directional coupler for electromagnetic wave detection. This electrode-less, all optical, wideband electrical field sensor is fabricated using standard processing for E-O polymer photonic devices. Experimental results demonstrate effective detection of electric field from 16.7V/m to 750KV/m at a frequency of 1GHz, and spurious free measurement range of 70dB.

  5. High field transport properties of MBE processed Fe-based superconducting thin films

    Energy Technology Data Exchange (ETDEWEB)

    Iida, Kazumasa [Nagoya University (Japan); IFW Dresden (Germany)

    2015-07-01

    It has been reported that Fe-based superconductors show high upper critical fields with low anisotropies at low temperatures. Hence these materials may offer a unique possibility for high field magnet applications. However, only a few reports on high-field transport properties of Co-doped Ba-122 and Fe(Se,Te) have been published and the only one for SmFeAs(O,F) thin films to date. In order to use this material class for applications, the knowledge of in-field and its orientation dependence of transport properties in a wide range of external fields need to be clarified. In this talk, I will report on high-field (up to dc 45 T) transport properties of P-doped Ba-122, SmFeAs(O,F) and NdFeAs(O,F) thin films prepared by MBE. Although P-doped Ba-122 has the lowest T{sub c}, self-field J{sub c} of over 6 MA/cm{sup 2} at 4.2 K is recorded, which is the highest value ever reported in Fe-based superconductors. Additionally, in-field performance of P-doped Ba-122 shows comparable to those of NdFeAs(O,F) and SmFeAs(O,F) for Hc. On the other hand, both NdFeAs(O,F) and SmFeAs(O,F) exhibited higher J{sub c} for H parallel ab due to the intrinsic pinning. These results indicate that P-doped Ba-122 is the most promising candidates for high-field magnet applications.

  6. Analysis of mechanical characteristics of superconducting field coil for 17 MW class high temperature superconducting synchronous motor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J. H.; Park, S. I.; Im, S. H.; Kim, H. M. [Jeju National University, Jeju (Korea, Republic of)

    2013-09-15

    Superconducting field coils using a high-temperature superconducting (HTS) wires with high current density generate high magnetic field of 2 to 5 [T] and electromagnetic force (Lorentz force) acting on the superconducting field coils also become a very strong from the point of view of a mechanical characteristics. Because mechanical stress caused by these powerful electromagnetic force is one of the factors which worsens the critical current performance and structural characteristics of HTS wire, the mechanical stress analysis should be performed when designing the superconducting field coils. In this paper, as part of structural design of superconducting field coils for 17 MW class superconducting ship propulsion motor, mechanical stress acting on the superconducting field coils was analyzed and structural safety was also determined by the coupling analysis system that is consists of commercial electromagnetic field analysis program and structural analysis program.

  7. Field-reversed configuration maintained by rotating magnetic field with high spatial harmonics.

    Science.gov (United States)

    Inomoto, Michiaki; Kitano, Katsuhisa; Okada, Shigefumi

    2007-10-26

    Field-reversed configurations (FRCs) driven by rotating magnetic fields (RMFs) with spatial high harmonics have been studied in the metal flux conserver of the FRC injection experiment. The experimental results show that the fundamental RMF component is observed to penetrate the plasma column, while the high harmonics are screened at the plasma edge due to their slower or reversed rotation. This selective penetration of the RMF provides good compatibility of radial and azimuthal force balances; significant radial inward force mostly from the high-harmonic components, and sufficient azimuthal torque solely provided by the fundamental component.

  8. Comparison of the scaling analysis of mixed-state magnetization data with direct measurements of the upper critical field for YBa2Cu3O7-x

    Science.gov (United States)

    Landau, I. L.

    2008-07-01

    By comparison of recent direct measurements of the temperature dependence of the upper critical field Hc2 of an YBa2Cu3O7-x high-Tc superconductor with the scaling analysis of magnetization data, collected in fields H \\ll H_{\\mathrm {c2}} , we demonstrate that the temperature dependence of the Ginzburg-Landau parameter κ is negligible. Another conclusion is that the normalized temperature dependence of Hc2 is independent of the orientation of the magnetic field with respect to the crystallographic axes of the sample. We also discuss the fact that isotropy of the temperature dependence of Hc2 straightforwardly follows from the Ginzburg-Landau theory if κ does not depend on the temperature.

  9. Anisotropy of superconducting critical fields of {alpha}-(BEDT-TTF){sub 2}KHg(SCN){sub 4} under pressure

    Energy Technology Data Exchange (ETDEWEB)

    Jakob, S.; Neumaier, K.; Biberacher, W.; Kartsovnik, M. [Walther-Meissner-Inst., Garching (Germany)

    2007-07-01

    Our previous studies of the ''magnetic field - pressure - temperature'' phase diagram of the layered organic conductor {alpha}-(BEDT-TTF){sub 2}KHg(SCN){sub 4} have revealed an interesting interplay between a charge density wave (CDW) and a superconducting (SC) state. At a critical pressure of 2.5 kbar the CDW state is completely suppressed and a sharp transition into a SC state is observed below 100 mK. For pressures below 2.5 kbar there is a coexistence of the superconducting and CDW state, but this is likely a spatially inhomogenous state. The neighbouring of a CDW and SC state is an interesting situation and rises questions about the nature of the superconductivity. We have therefore investigated the anisotropy of the critical fields at a pressure slightly above the critical one. The experiments were performed in a dilution refrigerator down to 25 mK. Two-axes rotation of the magnetic field allowed the exact determination of the anisotropy parallel and perpendicular to the layers, but also the inplane anisotropy. (orig.)

  10. Recycling high-performance carbon fiber reinforced polymer composites using sub-critical and supercritical water

    Science.gov (United States)

    Knight, Chase C.

    of the polymer matrix. To date, very few studies have been reported in this area and the studies thus far have only focused on small scale feasibility and have only shown the recovery of random fibers. The goal of this research is to advance the knowledge in the field of sub-critical and supercritical fluid recycling by providing fundamental information that will be necessary to move this process forward to an industrial scale. This dissertation work consists of several phases of studies. In the first phase of this research, the feasibility of recycling woven CFRP was established on a scale approximately 30 times larger than previously reported. The industrial relevance was also conveyed, as the process was shown to remove up 99% of a highly cross-linked resin from an aerospace grade composite system with 100% retention of the single filament tensile strength and modulus whilst also retaining the highly valuable woven fiber structure. The second phase of research demonstrated the power of this technology to recycle multi-layer composites and provide the ability to reuse the highly valuable materials. Up to 99% resin elimination was achieved for a woven 12-layer aerospace grade composite. The recycled woven fabric layers, with excellent retention of the fiber architecture, were directly reused to fabricate reclaimed fiber composites (RFC). Manufacturing issues associated with the use of the recycled fiber were investigated. Several fabrication technologies were used to fabricate the composite, and the composites show moderate short beam shear strength and may be suitable for certain industrial applications. Moreover, fresh composites were also recycled, recovered, and reused to investigate the retention of flexural properties of the fibers after recycling. Up to 95% of the flexural strength and 98% of the flexural modulus was retained in the reclaimed fiber composites. The recycled resin residual can be incorporated into fresh resin and cured, demonstrating a near

  11. Improving NASICON Sinterability through Crystallization under High Frequency Electrical Fields

    Directory of Open Access Journals (Sweden)

    Ilya eLisenker

    2016-03-01

    Full Text Available The effect of high frequency (HF electric fields on the crystallization and sintering rates of a lithium aluminum germanium phosphate (LAGP ion conducting ceramic was investigated. LAGP with the nominal composition Li1.5Al0.5Ge1.5(PO43 was crystallized and sintered, both conventionally and under effect of electrical field. Electrical field application, of 300V/cm at 1MHz, produced up to a 40% improvement in sintering rate of LAGP that was crystallized and sintered under the HF field. Heat sink effect of the electrodes appears to arrest thermal runaway and subsequent flash behavior. Sintered pellets were characterized using XRD, SEM, TEM and EIS to compare conventionally and field sintered processes. The as-sintered structure appears largely unaffected by the field as the sintering curves tend to converge beyond initial stages of sintering. Differences in densities and microstructure after 1 hour of sintering were minor with measured sintering strains of 31% vs. 26% with and without field, respectively . Ionic conductivity of the sintered pellets was evaluated and no deterioration due to the use of HF field was noted, though capacitance of grain boundaries due to secondary phases was significantly increased.

  12. CRITICAL BEHAVIOR OF S-3/2 ISING MODEL IN RANDOM LONGITUDINAL AND TRANSVERSE FIELDS

    Institute of Scientific and Technical Information of China (English)

    宋为基

    1995-01-01

    The phase diagrams and the other crtical properties of S-3/2 Ising model in random longitudinal and transverse fields(RLIM) are dicussed with the approximate scheme combined by mean-field renormalization group theory(MFRG) and the discretized path-integral representation(DPIR).

  13. A scenario for critical scalar field collapse in $AdS_3$

    CERN Document Server

    Clément, Gérard

    2014-01-01

    We present a family of exact solutions, depending on two parameters $\\alpha$ and $b$ (related to the scalar field strength), to the three-dimensional Einstein-scalar field equations with negative cosmological constant $\\Lambda$. For $b=0$ these solutions reduce to the static BTZ family of vacuum solutions, with mass $M = -\\alpha$. For $b\

  14. Language as a Field of Energy: A Critical Question for Language Pedagogy

    Science.gov (United States)

    Soter, Anna O.; Connors, Sean P.

    2017-01-01

    This essay offers a reorientation of our views on the interrelationships of language and thought as a field of constantly reprogrammable energy, and provides an argument as to why we believe this new metaphor (i.e., language as a field of energy) matters in language pedagogy, in classrooms at all levels, as well as within teacher education and…

  15. Sitting in the Waiting Room: Paulo Freire and the Critical Turn in the Field of Education

    Science.gov (United States)

    Gottesman, Isaac

    2010-01-01

    Although it is commonly assumed that Paulo Freire was widely influential in the field of education in the United States immediately upon publication of his classic work, "Pedagogy of the Oppressed", in 1970, the historical evidence indicates otherwise. In fact, Freire's work only began to gain wide reception in the field in the mid- and late…

  16. NMR in High Fields and Field Gradients up to 42 T

    Science.gov (United States)

    Sigmund, Eric E.

    2002-03-01

    We describe nuclear magnetic resonance (NMR) experiments performed in fields as high as 42 T. This work was done at Northwestern University and the National High Magnetic Field Laboratory (NHMFL) with superconducting magnets, resistive Bitter-style electromagnets, and a superconducting-resistive hybrid magnet. After reviewing crucial probe and spectrometer design features, we describe the scientific and technical advantages that high field provides for two experiments. First, we studied the mixed state of the high-temperature superconductor YBa_2Cu_3O_7-x through ^17O NMR.[1] The NMR spectrum gives the field distribution associated with vortices which we use to selectively inspect regions inside and outside the vortex core. We use the spin-lattice relaxation rate (T_1-1) to probe the electronic density-of-states in this spatially resolved fashion. Second, we have studied ultraslow diffusion in glass-forming liquids such as glycerol. These studies use the high magnetic field gradient at the edge of the solenoid, which can exceed 200 T/m for the resistive magnets at the NHMFL. We employed a 4 K inductive shield to stabilize the fluctuations in the resistive magnets' applied field over the necessarily long timescales of a slow diffusion NMR experiment. We have also made use of fast frequency jumping to enhance signal-to-noise by circumventing the finite spatial excitation bandwidth imposed by the large gradient. We show NMR experiments of slow diffusion in glass-formers up to high field (H0 = 21 T, G = 220 T/m) that have resolved diffusivities as low as 10-10 cm^2/s. [1] V. F. Mitrovic et.al., Nature 413, 501-504 (2001).

  17. Measurement of critical current of superconducting materials at the changing magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Qingrong; Hu Yongchang

    1986-06-01

    In this paper we present a new method for measuring the critical current of superconductor materials. The experimental results indicate the I/sub c/(H) character of the samples rather directly and, comparing with other methods, we can get more data at the same interval.

  18. AFM nano-plough planar YBCO micro-bridges: critical currents and magnetic field effects.

    Science.gov (United States)

    Elkaseh, A A O; Perold, W J; Srinivasu, V V

    2010-10-01

    The critical current (Ic) of YBa2Cu3O7-x (YBCO) AFM plough micro-constrictions is measured as a function of temperature, width and the magnetic flux density (B), which was applied perpendicular to the YBCO ab-plane and surface of the bridges. C-axis oriented thin films of YBa2Cu3O7-x were deposited on MgO substrates using an inverted cylindrical magnetron (ICM) sputtering technique. The films were then patterned into 8-10 micron size strips, using standard photolithography and dry etching processes. Micro-bridges with widths between 1.9 microm to 4.1 microm were fabricated by using atomic force microscope (AFM) nanolithography techniques. Critical current versus temperature data shows a straight-line behavior, which is typical of constriction type Josephson junctions. The Ic versus B characteristics exhibited a modulation, and a suppression of the critical current of up to 84%. It was also found that the critical current increases with increasing constriction width.

  19. Teacher and Student Perceptions of Critical and Creative Thinking within a Science Programme for High Ability Females in Singapore: Implications for Classroom Practice and Staff Development

    Science.gov (United States)

    Slatter, Christopher John

    2009-01-01

    It can be rationalised that the education of high ability students is of immense importance to society, based on the principle that many of tomorrow's pioneers within the field of science will originate from this group of individuals. Consequently, these students must be equipped with critical and creative thinking skills to fulfil their…

  20. Zero-field nuclear magnetic resonance in high field by modulated rf sequences.

    Science.gov (United States)

    Nishiyama, Yusuke; Yamazaki, Toshio

    2007-04-07

    The authors propose a novel approach to design and evaluate sequences for zero-field NMR spectra in high field (ZFHF) by using amplitude and phase modulated rf sequences. ZFHF provide sharp peaks for the dipolar interaction between two nuclear spins even if the orientation of the molecules is distributed. The internuclear distance r can be directly obtained from the peak position which is proportional to r-3. Numerous ZFHF sequences are obtained. A sequence is selected from them by the systematic evaluation of the sequences. The new ZFHF sequence is less affected by chemical shift anisotropy (CSA) than the previous sequences; the sequence can be used for systems with large CSA such as a dipolar coupled 13C-pair system under realistically high field. 13C ZFHF spectra of 13C2 diammonium succinate and 13C2 diammonium oxalate were observed under the 9.4 T field.

  1. Critical currents and superconductivity ferromagnetism coexistence in high-Tc oxides

    CERN Document Server

    Khene, Samir

    2016-01-01

    The book comprises six chapters which deal with the critical currents and the ferromagnetism-superconductivity coexistence in high-Tc oxides. It begins by gathering key data for superconducting state and the fundamental properties of the conventional superconductors, followed by a recap of the basic theories of superconductivity. It then discusses the differences introduced by the structural anisotropy on the Ginzburg-Landau approach and the Lawrence-Doniach model before addressing the dynamics of vortices and the ferromagnetism-superconductivity coexistence in high-Tc oxides, and provides an outline of the pinning phenomena of vortices in these materials, in particular the pinning of vortices by the spins. It elucidates the methods to improve the properties of superconducting materials for industrial applications. This optimization aims at obtaining critical temperatures and densities of critical currents at the maximum level possible. Whereas the primary objective is the basic mechanisms pushing the superco...

  2. Large Scale Structures at High Redshift in the GOODS Field

    CERN Document Server

    Castellano, M; Trevese, D; Pentericci, L; Grazian, A; Fontana, A; Giallongo, E; Santini, P; Cristiani, S; Nonino, M; Vanzella, E

    2008-01-01

    We present a catalogue of overdensities in the GOODS-South field. We find various high density peaks that are embedded in structures diffused on the entire field, up to z ~ 2.5. The slope of their colour-magnitude relation does not show significative evolution with z. We find evidence that galaxies forming these structures are more massive than galaxies located in low density regions. We also analyse the variation of galaxy properties with the associated environmental density and we find that the segregation of red galaxies with density is stronger at low redshift and at high luminosities while it gets much weaker for increasing z.

  3. Numerical evaluation of E-fields induced by body motion near high-field MRI scanner.

    Science.gov (United States)

    Crozier, S; Liu, F

    2004-01-01

    In modern magnetic resonance imaging (MRI), both patients and radiologists are exposed to strong, nonuniform static magnetic fields inside or outside of the scanner, in which the body movement may be able to induce electric currents in tissues which could be possibly harmful. This paper presents theoretical investigations into the spatial distribution of induced E-fields in the human model when moving at various positions around the magnet. The numerical calculations are based on an efficient, quasistatic, finite-difference scheme and an anatomically realistic, full-body, male model. 3D field profiles from an actively-shielded 4 T magnet system are used and the body model projected through the field profile with normalized velocity. The simulation shows that it is possible to induce E-fields/currents near the level of physiological significance under some circumstances and provides insight into the spatial characteristics of the induced fields. The results are easy to extrapolate to very high field strengths for the safety evaluation at a variety of field strengths and motion velocities.

  4. Flux jumps in high-J c MgB2 bulks during pulsed field magnetization

    Science.gov (United States)

    Fujishiro, H.; Mochizuki, H.; Naito, T.; Ainslie, M. D.; Giunchi, G.

    2016-03-01

    Pulsed field magnetization (PFM) of a high-J c MgB2 bulk disk has been investigated at 20 K, in which flux jumps frequently occur for high pulsed fields. Using a numerical simulation of the PFM procedure, we estimated the time dependence of the local magnetic field and temperature during PFM. We analyzed the electromagnetic and thermal instability of the high-J c MgB2 bulk to avoid flux jumps using the time dependence of the critical thickness, d c(t), which shows the upper safety thickness to stabilize the superconductor magnetically, and the minimum propagation zone length, l m(t), to obtain dynamical stability. The values of d c(t) and l m(t) change along the thermally-stabilized direction with increasing temperature below the critical temperature, T c. However, the flux jump can be qualitatively understood by the local temperature, T(t), which exceeds T c in the bulk. Finally, possible solutions to avoid flux jumps in high-J c MgB2 bulks are discussed.

  5. Coincidence spectroscopy of high-lying Rydberg states produced in strong laser fields

    Science.gov (United States)

    Larimian, Seyedreza; Erattupuzha, Sonia; Lemell, Christoph; Yoshida, Shuhei; Nagele, Stefan; Maurer, Raffael; Baltuška, Andrius; Burgdörfer, Joachim; Kitzler, Markus; Xie, Xinhua

    2016-09-01

    We demonstrate the detection of high-lying Rydberg states produced in strong laser fields with coincidence spectroscopy. Electron emission after the interaction of strong laser pulses with atoms and molecules is measured together with the parent ions in coincidence measurements. These electrons originate from high-lying Rydberg states with quantum numbers from n ˜20 up to n ≲120 formed by frustrated field ionization. Ionization rates are retrieved from the measured ionization signal of these Rydberg states. Simulations show that both tunneling ionization by a weak dc field and photoionization by blackbody radiation contribute to delayed electron emission on the nano- to microsecond scale. Furthermore, the dependence of the Rydberg-state production on the ellipticity of the driving laser field indicates that such high-lying Rydberg states are populated through electron recapture. The present experiment provides detailed quantitative information on Rydberg production in strong-field interaction.

  6. Quantification of local geometric distortion in structural magnetic resonance images: Application to ultra-high fields.

    Science.gov (United States)

    Lau, Jonathan C; Khan, Ali R; Zeng, Tony Y; MacDougall, Keith W; Parrent, Andrew G; Peters, Terry M

    2017-01-06

    Ultra-high field magnetic resonance imaging (MRI) provides superior visualization of brain structures compared to lower fields, but images may be prone to severe geometric inhomogeneity. We propose to quantify local geometric distortion at ultra-high fields in in vivo datasets of human subjects scanned at both ultra-high field and lower fields. By using the displacement field derived from nonlinear image registration between images of the same subject, focal areas of spatial uncertainty are quantified. Through group and subject-specific analysis, we were able to identify regions systematically affected by geometric distortion at air-tissue interfaces prone to magnetic susceptibility, where the gradient coil non-linearity occurs in the occipital and suboccipital regions, as well as with distance from image isocenter. The derived displacement maps, quantified in millimeters, can be used to prospectively evaluate subject-specific local spatial uncertainty that should be taken into account in neuroimaging studies, and also for clinical applications like stereotactic neurosurgery where accuracy is critical. Validation with manual fiducial displacement demonstrated excellent correlation and agreement. Our results point to the need for site-specific calibration of geometric inhomogeneity. Our methodology provides a framework to permit prospective evaluation of the effect of MRI sequences, distortion correction techniques, and scanner hardware/software upgrades on geometric distortion. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Sintering process and critical current density of low activation Mg11B2 superconductors from low temperature to high temperature

    Science.gov (United States)

    Cheng, Fang; Liu, Yongchang; Ma, Zongqing; Shahriar Al Hossain, Md; Somer, M.

    2016-08-01

    As the "low activation" superconductor, Mg11B2 has a potential application in superconducting coils for fusion reactor. In present work, the sintering process and critical current density of low activation Mg11B2 superconductors were systemically studied from low temperature to high temperature. It was found that the Jc and Hirr values of Mg11B2 bulks in present work are both obviously higher than that of those samples prepared in previous studies. Furthermore, the low-temperature sintered samples exhibit better Jc performance at high fields than the high-temperature sintered samples, due to strong grain boundaries pinning. On the other hand, the high-temperature sintered samples have higher Jc at low fields compared to low-temperature sintered samples, mainly owing to their better crystallinity and grain connectivity. The highest Jc value (2.20 ×105 A cm-2 at 20 K, self-field) is obtained in the Mg11B2 sample sintered at 850 °C for 45 min.

  8. Optimizing brain tumor resection. High-field interventional MR imaging.

    Science.gov (United States)

    Tummala, R P; Chu, R M; Liu, H; Truwit, C L; Hall, W A

    2001-11-01

    High-field strength iMRI guidance is an effective tool for brain tumor resection. Although its use lengthens the average time for a craniotomy, the reward is a more extensive tumor excision compared with conventional neurosurgery without an increased risk to the patient (Table 4). Although intraoperative patient transfer into and out of the magnet is cumbersome, the possibility for complete resection, especially for a low-grade glioma, makes the effort worthwhile. The cost and technical support required for this system presently limits its use to only a few sites worldwide. As with any technology, further refinements will make this system less expensive and more attainable. Practical consideration aside, high-field strength iMRI is presently [table: see text] the most effective tool available for brain tumor resection. Because of its novelty, future studies are necessary to determine if this technology lowers the incidence of and extends the duration to tumor recurrence as the preliminary data in children suggests. These are the ultimate measures of efficacy for any brain tumor treatment. Based on the rapid advancement of technology, will today's high-field strength interventional magnet become tomorrow's low-field system? Very high-field strength designs may improve diagnostic capabilities through higher resolution, but their interventional applications may be hindered by increased sensitivity for clinically insignificant abnormalities and decreased specificity for clinically relevant lesions. As new technology is developed, clinicians must continue to explore and refine the existing high-field strength iMRI to make it cost-effective and widely applicable.

  9. The Study of Electroluminescence and Reliability of Polyimide Films in High DC Fields

    Directory of Open Access Journals (Sweden)

    Jiaqi LIN

    2015-11-01

    Full Text Available Electroluminescence (EL intensity of the polyimide (PI films was tested under dc high electric field by home-made experimental device. The results showed that the EL intensity of PI films increased along with the electric field. EL intensity is approximately to background intensity when the electric-field intensity was less than 2.00 MV/cm. EL intensity increases along with increasing the electric field when electric-field intensity greater than 2.00 MV/cm. When electric-field at 2.80 MV/cm, EL intensity increasing strongly suggests that the excitation process related to hot electrons accelerated by the field approaching a critical threshold. Meanwhile, this work elaborates a method to deal with identical samples get different experimental data by using Weibull distribution method, and the concept of the reliability was presented. The nine groups of EL experimental data were analyzed, and the result showed that the lifetime of mid-value (t = 164.9 min. Mid-value of the breakdown field is E = 2.76 MV/cm.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9694

  10. Nb3Sn High Field Magnets for the High Luminosity LHC Upgrade Project

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosio, Giorgio

    2015-06-01

    The High Luminosity upgrade of the Large Hadron Collider at CERN requires a new generation of high field superconducting magnets. High field large aperture quadrupoles (MQXF) are needed for the low-beta triplets close to the ATLAS and CMS detectors, and high field two-in-one dipoles (11 T dipoles) are needed to make room for additional collimation. The MQXF quadrupoles, with a field gradient of 140 T/m in 150 mm aperture, have a peak coil field of 12.1 T at nominal current. The 11 T dipoles, with an aperture of 60 mm, have a peak coil field of 11.6 T at nominal current. Both magnets require Nb3Sn conductor and are the first applications of this superconductor to actual accelerator magnets.

  11. The AKARI Deep Field South: Pushing to High Redshift

    CERN Document Server

    Clements, David L

    2016-01-01

    The AKARI Deep Field South (ADF-S) is a large extragalactic survey field that is covered by multiple instruments, from optical to far-IR and radio. I summarise recent results in this and related fields prompted by the release of the Herschel far-IR/submm images, including studies of cold dust in nearby galaxies, the identification of strongly lensed distant galaxies, and the use of colour selection to find candidate very high redshift sources. I conclude that the potential for significant new results from the ADF-S is very great. The addition of new wavelength bands in the future, eg. from Euclid, SKA, ALMA and elsewhere, will boost the importance of this field still further.

  12. Low-field MRI can be more sensitive than high-field MRI

    Science.gov (United States)

    Coffey, Aaron M.; Truong, Milton L.; Chekmenev, Eduard Y.

    2013-12-01

    MRI signal-to-noise ratio (SNR) is the key factor for image quality. Conventionally, SNR is proportional to nuclear spin polarization, which scales linearly with magnetic field strength. Yet ever-stronger magnets present numerous technical and financial limitations. Low-field MRI can mitigate these constraints with equivalent SNR from non-equilibrium ‘hyperpolarization' schemes, which increase polarization by orders of magnitude independently of the magnetic field. Here, theory and experimental validation demonstrate that combination of field independent polarization (e.g. hyperpolarization) with frequency optimized MRI detection coils (i.e. multi-turn coils using the maximum allowed conductor length) results in low-field MRI sensitivity approaching and even rivaling that of high-field MRI. Four read-out frequencies were tested using samples with identical numbers of 1H and 13C spins. Experimental SNRs at 0.0475 T were ∼40% of those obtained at 4.7 T. Conservatively, theoretical SNRs at 0.0475 T 1.13-fold higher than those at 4.7 T were possible despite an ∼100-fold lower detection frequency, indicating feasibility of high-sensitivity MRI without technically challenging, expensive high-field magnets. The data at 4.7 T and 0.0475 T was obtained from different spectrometers with different RF probes. The SNR comparison between the two field strengths accounted for many differences in parameters such as system noise figures and variations in the probe detection coils including Q factors and coil diameters.

  13. Critical Race Theory, Hip Hop, and "Huck Finn": Narrative Inquiry in a High School English Classroom

    Science.gov (United States)

    Martin, Jennifer L.

    2014-01-01

    This study explores the impact of reading "Huckleberry Finn" through the lens of critical race theory for both teacher and students in a racially diverse urban high school environment. The teacher/researcher used narrative inquiry and creative non-fiction to examine student language usage, white privilege (including her own), and student…

  14. An Examination of Critical Thinking Skills in High School Choral Rehearsals

    Science.gov (United States)

    Garrett, Matthew L.

    2013-01-01

    The purpose of this study was to examine the relationship between time spent in nonperformance and critical thinking activities in high school choral rehearsals. Eighteen rehearsal observations were collected from public school music programs. Observed rehearsal behaviors were coded into three categories of nonperformance activity: lower-order…

  15. Critical phenomena in ethylbenzene oxidation in acetic acid solution at high cobalt(II) concentrations

    NARCIS (Netherlands)

    Gavrichkov, AA; Zakharov, [No Value

    2005-01-01

    Critical phenomena in ethylbenzene oxidation in an acetic acid solution at high cobalt(ill) concentrations (from 0.01 to 0.2 mol L-1) were studied at 60-90 degrees C by the gasometric (O-2 absorption), spectrophotometric (Co-III accumulation), and chemiluminescence (relative concentration of radical

  16. The Development and Validation of a Mechanical Critical Thinking Scale for High School Students

    Science.gov (United States)

    Yu, Kuang-Chao; Lin, Kuen-Yi; Chang, Shu-Fen

    2017-01-01

    The purpose of this study was to develop a mechanical critical thinking scale for high school students. A stratified random sampling method was used to establish the norms. After pre-tests and item analysis, the scale was determined to have five subtest sections (i.e., recognition of assumptions, induction, deduction, interpretation, and…

  17. Picturing Obama: Race, High School Students and a Critical Methodology of the Visual

    Science.gov (United States)

    Smith, William L.

    2017-01-01

    I draw on methodological findings from a case study on how high school students of color make sense of dominant narratives of race and politics in the Obama American Era. Incorporating literature from critical race theory, visual research methods, and the writings of cultural scholar Stuart Hall, I draw conclusions from this inquiry project as a…

  18. The Development and Validation of a Mechanical Critical Thinking Scale for High School Students

    Science.gov (United States)

    Yu, Kuang-Chao; Lin, Kuen-Yi; Chang, Shu-Fen

    2017-01-01

    The purpose of this study was to develop a mechanical critical thinking scale for high school students. A stratified random sampling method was used to establish the norms. After pre-tests and item analysis, the scale was determined to have five subtest sections (i.e., recognition of assumptions, induction, deduction, interpretation, and…

  19. Assessing Critical Thinking in Middle and High Schools: Meeting the Common Core

    Science.gov (United States)

    Stobaugh, Rebecca

    2013-01-01

    This practical, very effective resource helps middle and high school teachers and curriculum leaders develop the skills to design instructional tasks and assessments that engage students in higher-level critical thinking, as recommended by the Common Core State Standards. Real examples of formative and summative assessments from a variety of…

  20. An Examination of Critical Thinking Skills in High School Choral Rehearsals

    Science.gov (United States)

    Garrett, Matthew L.

    2013-01-01

    The purpose of this study was to examine the relationship between time spent in nonperformance and critical thinking activities in high school choral rehearsals. Eighteen rehearsal observations were collected from public school music programs. Observed rehearsal behaviors were coded into three categories of nonperformance activity: lower-order…

  1. Characterisation of practical high temperature superconductors in pulsed magnetic fields and development of associated technology

    CERN Document Server

    Saleh, P M

    2000-01-01

    including a innovative design of a 100ms pulsed magnet solenoid. Critical current measurements on state of the art practical high temperature superconductors are presented. Bi sub 2 Sr sub 2 CaCu sub 2 O silver-alloy matrix powder-in-tube and silver-alloy substrate dip-coated tapes, formed into various geometries, have been tested in pulsed magnetic fields of various pulse lengths. These measurements have been compared to tests performed in continuous magnetic fields. A distinct discrepancy between pulsed and continuous measurements has been observed in these silver-alloy, high temperature superconductor composites. The critical current measured in pulsed fields is depressed compared to those measured in continuous fields. Evidence is provided to strongly suggest that eddy current heating in the silver-alloy substrate/sheath of the conductor is responsible for this discrepancy. A model is presented to predict the temperature rise due to eddy current heating. This model shows good agreement with observations. ...

  2. Upper Critical Field and Irreversibility Line Determined by Transport Measurement of the New Superconductor MgB2

    Institute of Scientific and Technical Information of China (English)

    金灏; 闻海虎; 李世亮; 赵志文; 倪泳明; 任治安; 车广灿; 杨海鹏; 刘智勇; 郑东宁; 赵忠贤

    2001-01-01

    Resistive transitions of the new superconductor MgB2 are carried out under magnetic fields from 0 to 8 T.It is found that the irreversibility field Hirr(T) and the upper critical field Hc2(T) obtained are very close tothose determined in the magnetic measurements. By using the Arrhenius activation law p=poexp(- U/kB T), theactivation barrier U has been determined by the low dissipation part of R(T) curves. It is found that U 》 kBTmanifesting a very weak thermal activation and thermal fluctuation effect. This may further indicate that theflux dynamics near Hirr(T) is induced by strong quantum fluctuation and tunnelling of vortices.

  3. Influence of the vector interaction and an external magnetic field on the isentropes near the chiral critical end point

    CERN Document Server

    Costa, Pedro

    2016-01-01

    The location of the critical end point (CEP) and the isentropic trajectories in the QCD phase diagram are investigated. We use the (2+1) Nambu$-$Jona-Lasinio model with the Polyakov loop coupling for different scenarios, namely by imposing zero strange quark density, which is the case in the ultra relativistic heavy-ion collisions, and $\\beta$-equilibrium. The influence of strong magnetic fields and of the vector interaction on the isentropic trajectories around the CEP is discussed. It is shown that the vector interaction and the magnetic field, having opposite effects on the first-order transition, affect the isentropic trajectories differently: as the vector interaction increases, the first-order transition becomes weaker and the isentropes become smoother; when a strong magnetic field is considered, the first-order transition is strengthened and the isentropes are pushed to higher temperatures. No focusing of isentropes in region towards the CEP is seen.

  4. Upper critical fields and superconducting transition temperatures of some zirconium-base amorphous transition-metal alloys

    Science.gov (United States)

    Karkut, M. G.; Hake, R. R.

    1983-08-01

    Superconducting upper critical fields Hc2(T), transition temperatures Tc and normal-state electrical resistivities ρn have been measured in the amorphous transition-metal alloy series Zr1-xCox, Zr1-xNix, (Zr1-xTix)0.78Ni0.22, and (Zr1-xNbx)0.78Ni0.22. Structural integrity of these melt-spun alloys is indicated by x-ray, density, bend-ductility, normal-state electrical resistivity, superconducting transition width, and mixed-state flux-pinning measurements. The specimens display Tc=2.1-3.8 K, ρn=159-190 μΩ cm, and |(dHc2dT)Tc|=28-36 kG/K. These imply electron mean free paths l~2-6 Å, zero-temperature Ginzburg-Landau coherence distances ξG0~50-70 Å, penetration depths λG0~(7-10)×103 Å, and extremely high dirtiness parameters ξ0l~300-1300. All alloys display Hc2(T) curves with negative curvature and (with two exceptions) fair agreement with the standard dirty-limit theory of Werthamer, Helfand, Hohenberg, and Maki (WHHM) for physically reasonable values of spin-orbit-coupling induced, electron-spin-flip scattering time τso. This is in contrast to the anomalously elevated Hc2(T) behavior which is nearly linear in T that is observed by some, and the unphysically low-τso fits to WHHM theory obtained by others, for various amorphous alloys. Current ideas that such anomalies may be due to alloy inhomogeneity are supported by present results on two specimens for which relatively low-τso fits of Hc2(T) to WHHM theory are coupled with superconductive evidence for inhomogeneity: relatively broad transitions at Tc and Hc2 current-density-dependent transitions at Hc2 and (in one specimen) a J-dependent, high-H (>Hc2), resistive "beak effect." In the Zr1-xCox and Zr1-xNix series, Tc decreases linearly with x (and with unfilled-shell average electron-to-atom ratio in the range 5.05previous results for these systems and contrary to the Tc vs behavior of both amorphous and crystalline transition-metal alloys formed between near neighbors in the Periodic Table. Upper-critical-field

  5. High School Students' Understandings and Representations of the Electric Field

    CERN Document Server

    Cao, Ying

    2014-01-01

    This study investigates the understandings and representations of the electric field expressed by Chinese high school students ages 15 to 16 who have not yet received high school-level physics instruction. The literature has reported students' ideas of the electric field post-instruction as indicated by their performance on textbook-style questionnaires. However, by relying on measures such as questionnaires, previous research has inadequately captured the thinking process that led students to answer questions in the ways that they did. The present study portrays the beginning of this process by closely examining students' understandings pre-instruction. The participants in this study were asked to engage in a lesson that included informal group tasks that involved playing a Web-based hockey game that replicated an electric field and drawing comic strips that used charges as characters. The lesson was videotaped, students' work was collected, and three students were interviewed afterward to ascertain more det...

  6. Reflection type metasurface designed for high efficiency vectorial field generation

    Science.gov (United States)

    Wang, Shiyi; Zhan, Qiwen

    2016-07-01

    We propose a reflection type metal-insulator-metal (MIM) metasurface composed of hybrid nano-antennas for comprehensive spatial engineering of the properties of optical fields. The capability of such structure is illustrated in the design of a device that can be used to produce a radially polarized vectorial beam for optical needle field generation. This device consists of uniformly segmented sectors of high efficiency MIM metasurface. With each of the segment sector functioning as a local quarter-wave-plate (QWP), the device is designed to convert circularly polarized incidence into local linear polarization to create an overall radial polarization with corresponding binary phases and extremely high dynamic range amplitude modulation. The capability of such devices enables the generation of nearly arbitrarily complex optical fields that may find broad applications that transcend disciplinary boundaries.

  7. Analysis of Highly Wind Power Integrated Power System model performance during Critical Weather conditions

    DEFF Research Database (Denmark)

    Basit, Abdul; Hansen, Anca Daniela; Sørensen, Poul Ejnar

    2014-01-01

    . For this purpose, the power system model has been developed that represents the relevant dynamic features of power plants and compensates for power imbalances caused by the forecasting error during critical weather conditions. The regulating power plan, as an input time series for the developed power system model......Secure power system operation of a highly wind power integrated power system is always at risk during critical weather conditions, e.g. in extreme high winds. The risk is even higher when 50% of the total electricity consumption has to be supplied by wind power, as the case for the future Danish...... power system in 2020. This paper analyses and compares the performance of the future Danish power system during extreme wind speeds, where wind power plants are either controlled through a traditional High Wind Shut Down storm controller or a new High Wind Extended Production storm controller...

  8. On the 110 keV feature from A0535+26 direct evidence for a near-critical magnetic field

    CERN Document Server

    Araya-Gochez, R A; Araya, Rafael A; Harding, Alice K

    1996-01-01

    A recent high resolution measurement of an absorption line at 110 keV in the phase-averaged spectrum of A0535+26 (Grove et al. 1994) and the conspicuous absence of a previously reported harmonic feature at around 50 keV (Kendziorra et al. 1992, 1994) are indicative of cyclotron scattering in a magnetic field of about 10^{13}G. However, controversy has risen over whether a lower field scenario may account for the alleged absence or weakness of a lower energy fundamental harmonic feature. This work explores these two alternatives through the generation of theoretical cyclotron spectra. For lower field models, a cylindrical geometry of the line forming region and the strong angle dependence of the cross section for resonant scattering conspire to fill in a first harmonic at around 57 keV. Higher field models (B \\simeq 10.75 TG), however, yield significantly better fits ({\\cal X}^2_{low}/{\\cal X}^2_{high} \\sim 71), thus strengthening the case for a near-critical field (B_{crit} \\simeq 44 TG). Phase-resolved OSSE ...

  9. The Competitiveness of Highly Accomplished Individuals in Four Talent Fields.

    Science.gov (United States)

    Monsaas, Judith A.

    The study examined competitiveness among eight very high achievers in four talent fields: research mathematics, concert piano, swimming, and tennis. Retrospective interviews had previously been conducted with the subjects as part of B. Bloom's "Development of Talent Project." A 14-statement instrument was developed and applied to interview…

  10. High Redshift Galaxies in the Hubble Ultra Deep Field

    CERN Document Server

    Hathi, Nimish P

    2008-01-01

    My dissertation presents results from three recent investigations in the Hubble Ultra Deep Field (HUDF) focusing on understanding structural and physical properties of high redshift galaxies. Here I summarize results from these studies. This thesis work was conducted at Arizona State University under the guidance of Prof. Rogier Windhorst and Prof. Sangeeta Malhotra.

  11. Survey of high field superconducting material for accelerator magnets

    Energy Technology Data Exchange (ETDEWEB)

    Scahlan, R.; Greene, A.F.; Suenaga, M.

    1986-05-01

    The high field superconductors which could be used in accelerator dipole magnets are surveyed, ranking these candidates with respect to ease of fabrication and cost as well as superconducting properties. Emphasis is on Nb/sub 3/Sn and NbTi. 27 refs., 2 figs. (LEW)

  12. High intensity electromagnetic field gerenation using a transportable reverberation chamber

    NARCIS (Netherlands)

    Leferink, Frank

    2008-01-01

    A reverberation chamber can create very high field strength with moderate input power. Existing chambers are making use of a paddle wheel to change the resonant modes in the chamber. A transportable reverberation chamber with vibrating walls will be presented. Inside this Vibrating Intrinsic Reverbe

  13. Free-field calibration of measurement microphones at high frequencies

    DEFF Research Database (Denmark)

    Barrera Figueroa, Salvador; Rasmussen, Knud; Torras Rosell, Antoni;

    2011-01-01

    Measurement microphones are typically calibrated in a free field at frequencies up to 50 kHz. This is a sufficiently high frequency for the most of sound measurement applications related with noise assessment. However, other applications such as assessment of the noise emitted by ultrasound clean...

  14. Field testing of high-efficiency supermarket refrigeration

    Energy Technology Data Exchange (ETDEWEB)

    Walker, D. (Foster-Miller, Inc., Waltham, MA (United States))

    1992-12-01

    The Electric Power Research Institute (EPRI) has undertaken a field test to quantify the performance of high-efficiency supermarket refrigeration. The initial work on this project was presented in EPRI report CU-6268 Supermarket Refrigeration Modeling and Field Demonstration.'' The information given here was generated through continued testing at the field test site. The field test was conducted at a supermarket owned by Safeway Stores, Inc., that was located in Menlo Park, CA. Testing was performed with the existing conventional refrigeration system and a high-efficiency multiplex refrigeration system that was installed for these tests. The results of the testing showed that the high-efficiency multiplex system reduced refrigeration energy consumption by 23.9% and peak electric demand for refrigeration by 30.0%. Analyses of these savings showed that the largest portion was due to the use of high-efficiency compressors (29.5% of total saving). Floating head pressure control, ambient and mechanical subcooling, compressor multiplexing and hot gas defrost accounted for 50% of total savings. The remainder of the savings (20.5%) were attributed to the use of an evaporative condenser. Tests were also conducted with several retrofit technologies. The most promising results were obtained with external liquid-suction heat exchangers installed at the outlets of the display cases. Favorable paybacks were calculated for these exchangers when they were used with very low and low temperature refrigeration.

  15. FIELD EVALUATION OF A HIGH-VOLUME DICHOTOMOUS SAMPLER

    Science.gov (United States)

    This study presents the field evaluation of a high-volume dichotomous sampler that collects coarse (PM10-2.5) and fine (PM2.5) particulate matter. The key feature of this device is the utilization of a round-nozzle virtual impactor with a 50% cutpoint at 2.5 5m to split PM10 into...

  16. High-Energy Scattering in Non-Commutative Field Theory

    CERN Document Server

    Kumar, J; Kumar, Jason; Rajaraman, Arvind

    2005-01-01

    We analyze high energy scattering for non-commutative field theories using the dual gravity description. We find that the Froissart-Martin bound still holds, but that cross-sections stretch in the non-commutative directions in a way dependent on the infrared cutoff. This puzzling behavior suggests new aspects of UV/IR mixing.

  17. Shielding for Critical Organs and Radiation Exposure Dose Distribution in Patients with High Energy Radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Sung Sil; Suh, Chang Ok; Kim, Gwi Eon [Yonsei Univ., Seoul (Korea, Republic of)

    2002-03-15

    transected into transverse 36 slices of 2.5cm thickness. Photon dose was measured using a Capintec PR-06C ionization chamber with Capintec 192 electrometer (Capintec Inc., Ramsey, NJ), TLD(VICTOREEN 5000. LiF) and film dosimetry V-Omat, Kodak). In case of fetus, the dosimeter was placed at a depth of 10cm in this phantom at 100cm source to axis distance and located centrally 15cm from the inferior edge of the 30cm x 30cm{sup 2} x-ray beam irradiating the Rando phantom chest wall. A acryl bridge of size 40 cm x 40 cm{sup 2} and a clear space of about 20 cm was fabricated and placed on top of the rectangular polystyrene phantom representing the abdomen of the patient. The lead pot for testicle shielding was made as various shape, sizes, thickness and supporting stand. The scattered photon with and without shielding were measured at the representative position of the fetus and testicle. Measurement of radiation scattered dose outside fields and critical organs, like fetus position and testicle region, from chest or pelvic irradiation by large field of high energy radiation beam was performed using an ionization chamber and film dosimetry. The scattered doses outside field were measured 5 - 10% of maximum doses in fields and exponentially decrease from field margins. The scattered photon dose received the fetus and testicle from thorax field irradiation was measured about 1 mGy/Gy of photon treatment dose. Shielding construction to reduce this scattered dose was investigated using lead sheet and blocks. Lead pot shield for testicle reduced the scatter dose under 10 mGy when photon beam of 60 Gy was irradiated in abdomen region. The scattered photon dose is reduced when the lead shield was used while the no significant reduction of scattered photon dose was observed and 2-3 mm lead sheets reduced the skin dose under 80% and almost electron contamination. The results indicate that it was possible to improve shielding to reduce scattered photon for fetus and testicle when a young

  18. Diffraction line-shapes, Fermi surface nesting, and quantum criticality in antiferromagnetic chromium at high pressure.

    Energy Technology Data Exchange (ETDEWEB)

    Jaramillo, R.; Feng, Y.; Rosenbaum, T. F.; Harvard Univ.; Univ. of Chicago

    2010-05-01

    We explore the behavior of the nested bandstructure of chromium as a function of temperature and pressure to the point where magnetism disappears. X-ray diffraction measurements of the charge order parameter suggest that the nesting condition is maintained at high pressure, where the spin density wave ground state is destabilized by a continuous quantum phase transition. By comparing diffraction line-shapes measured throughout the temperature-pressure phase diagram we are able to identify and describe three regimes: thermal near-critical, weak coupling ground state, and quantum critical.

  19. High magnetic field studies of BEDT-TTF organic conductors

    Energy Technology Data Exchange (ETDEWEB)

    Honold, M.M

    1999-07-01

    This Thesis gives a detailed account of the high magnetic field properties of {alpha}-phase BEDT-TTF charge-transfer salts, with particular focus on the salts {alpha}-(BEDT-TTF){sub 2}KHg(SCN){sub 4} and {alpha}-(BEDT-TTF){sub 2}TlHg(SCN){sub 4}. The existence of the bulk quantum Hall effect and its eventual destruction in the high-field limit is shown by a variety of experimental means, including magnetoresistance, magnetisation and Hall potential oscillation studies; the latter are based on a new technique specifically developed for this purpose. Chapter 1 introduces the concept of organic conductors and emphasises their potential as prototype systems of reduced dimensionality; in Chapter 2, the necessary physics and experimental techniques for their investigation are outlined. Following model calculations which suggested the possibility of the quantum Hall effect in {alpha}-phase BEDT-TTF salts, measurements of the Hall resistivity were carried out on {alpha}-(BEDT-TTF){sub 2}TlHg(SCN){sub 4} (described in Chapter 3). These exhibit a series of plateaux and represent the direct observation of the quantum Hall effect in a bulk material. Chapter 4 reports the discovery of an anomalous magnetotransport mode in the interplane resistance of {alpha}-(BEDT-TTF){sub 2}KHg(SCN){sub 4} which involves the suppression and phase inversion of the Shubnikov-de Haas oscillations at low temperatures. This is interpreted as the action of a two-dimensional chiral Fermi liquid formed from the current-carrying edge states of each quantum Hall layer. Chapter 5 reports the first observation of magnetic breakdown in the high-field phase of {alpha}-(BEDT-TTF){sub 2}KHg(SCN){sub 4}, allowing an improved description of the high-field Fermi surface topology. These results are used to develop a new model for the nested low-field Fermi surface which can explain experimental evidence previously unaccounted for. Studies of the limiting behaviour of Hall potential oscillations in Chapter 6 show

  20. Oscillations of critical superconducting current in thin doubly-connected Sn films in an external perpendicular magnetic field

    Science.gov (United States)

    Sivakov, A. G.; Pokhila, A. S.; Glukhov, A. M.; Kuplevakhsky, S. V.; Omelyanchouk, A. N.

    2014-05-01

    We report the results of experimental and theoretical studies of critical current oscillations in thin doubly-connected Sn films in an external perpendicular magnetic field. The experiments were performed on samples that consisted of two wide electrodes joined together by two narrow channels. The length of the channels l satisfied the condition l ≫ ξ (ξ is the Ginzburg-Landau coherence length). At temperatures close to the critical temperature Tc, the dependence of the critical current Ic on average external magnetic flux Φ¯e has the form of a piecewise linear function, periodic with respect to the flux quantum Φ0. The amplitude of the Ic oscillation at a given temperature is proportional to the factor ξ/l. Moreover, the dependence Ic=Ic(Φ ¯e) is found to be multivalued, hence indicating the presence of metastable states. Based on the Ginzburg-Landau approximation, a theory was constructed that explains the above features of the oscillation phenomenon taking a perfectly symmetric system as an example. Further, the experiments displayed the effects related to the critical currents imbalance between the superconducting channels, i.e., shift of the maxima of the dependence Ic=Ic(Φ ¯e) accompanied by an asymmetry with respect to the transport current direction.

  1. High school students' representations and understandings of electric fields

    Science.gov (United States)

    Cao, Ying; Brizuela, Bárbara M.

    2016-12-01

    This study investigates the representations and understandings of electric fields expressed by Chinese high school students 15 to 16 years old who have not received high school level physics instruction. The physics education research literature has reported students' conceptions of electric fields postinstruction as indicated by students' performance on textbook-style questions. It has, however, inadequately captured student ideas expressed in other situations yet informative to educational research. In this study, we explore students' ideas of electric fields preinstruction as shown by students' representations produced in open-ended activities. 92 participant students completed a worksheet that involved drawing comic strips about electric charges as characters of a cartoon series. Three students who had spontaneously produced arrow diagrams were interviewed individually after class. We identified nine ideas related to electric fields that these three students spontaneously leveraged in the comic strip activity. In this paper, we describe in detail each idea and its situated context. As most research in the literature has understood students as having relatively fixed conceptions and mostly identified divergences in those conceptions from canonical targets, this study shows students' reasoning to be more variable in particular moments, and that variability includes common sense resources that can be productive for learning about electric fields.

  2. Field and pressure response of Yb compounds close to a quantum critical point

    Indian Academy of Sciences (India)

    C Seuring; E W Scheidt; E Bauer

    2002-05-01

    YbCu5-Al provides the possibility to tune ground state properties by a change of the valence due to the Cu/Al substitution, by pressure as well as by the application of a magnetic field. Near to the critical concentration cr ≈ 1.5 non-Fermi-liquid properties (NFL) are obvious, obeying hyperscaling. If magnetic order sets in for >1.5, the application of moderate magnetic fields quenches order and again NFL features become evident. Hyperscaling in this case indicates strongly interacting spin fluctuations.

  3. Iridate compound produces extraordinarily high coercive magnetic field

    Science.gov (United States)

    Zapf, Vivien; Topping, Craig; Kim, Jae-Wook; Mun, Eun-Deok; Goddard, Paul; Ghannadzadeh, Saman; Luo, Xuan; Cheong, Sang-Wook; Singleton, John

    2014-03-01

    We present a data on an iridate compound that shows an extraordinarily large magnetic hysteresis loop. The coercive magnetic field exceeds 40 Tesla in single-crystal samples. The hysteresis coexists with a linear background, and the total remanent magnetization is about half a Bohr magneton. We will discuss the emergence of these properties from the interplay of spin-orbit coupling, magnetic exchange and possible frustration. The single crystalline material exhibits a magnetic hysteresis loop for one orientation of the magnetic field and a smooth linear increase in the magnetization with field for the other. Measurements were conducted in 65 T short-pulse magnets and the 60 Tesla shaped-pulse magnet at the National High Magnetic Field Lab in Los Alamos. We do not observe any dependence of the magnetic hysteresis on magnetic field sweep rate. Compounds containing Ir4 + have attracted attention recently due to strong spin-orbit coupling that competes with crystal-electric field and exchange interactions. This competition can result in non-Hund's-rule ground states with unusual properties.

  4. Review - X-ray diffraction measurements in high magnetic fields and at high temperatures

    Directory of Open Access Journals (Sweden)

    Yoshifuru Mitsui, Keiichi Koyama and Kazuo Watanabe

    2009-01-01

    Full Text Available A system was developed measuring x-ray powder diffraction in high magnetic fields up to 5 T and at temperatures from 283 to 473 K. The stability of the temperature is within 1 K over 6 h. In order to examine the ability of the system, the high-field x-ray diffraction measurements were carried out for Si and a Ni-based ferromagnetic shape-memory alloy. The results show that the x-ray powder diffraction measurements in high magnetic fields and at high temperatures are useful for materials research.

  5. Magnetic resonance imaging and spectroscopy at ultra high fields

    Energy Technology Data Exchange (ETDEWEB)

    Neuberger, Thomas

    2009-06-23

    The goal of the work presented in this thesis was to explore the possibilities and limitations of MRI / MRS using an ultra high field of 17.6 tesla. A broad range of specific applications and MR methods, from MRI to MRSI and MRS were investigated. The main foci were on sodium magnetic resonance spectroscopic imaging of rodents, magnetic resonance spectroscopy of the mouse brain, and the detection of small amounts of iron labeled stem cells in the rat brain using MRI Sodium spectroscopic imaging was explored since it benefits tremendously from the high magnetic field. Due to the intrinsically low signal in vivo, originating from the low concentrations and short transverse relaxation times, only limited results have been achieved by other researchers until now. Results in the literature include studies conducted on large animals such as dogs to animals as small as rats. No studies performed on mice have been reported, despite the fact that the mouse is the most important laboratory animal due to the ready availability of transgenic strains. Hence, this study concentrated on sodium MRSI of small rodents, mostly mice (brain, heart, and kidney), and in the case of the brain on young rats. The second part of this work concentrated on proton magnetic resonance spectroscopy of the rodent brain. Due to the high magnetic field strength not only the increasing signal but also the extended spectral resolution was advantageous for such kind of studies. The difficulties/limitations of ultra high field MRS were also investigated. In the last part of the presented work detection limits of iron labeled stem cells in vivo using magnetic resonance imaging were explored. The studies provided very useful benchmarks for future researchers in terms of the number of labeled stem cells that are required for high-field MRI studies. Overall this work has shown many of the benefits and the areas that need special attention of ultra high fields in MR. Three topics in MRI, MRS and MRSI were

  6. Inverse field-based approach for simultaneous B₁ mapping at high fields - a phantom based study.

    Science.gov (United States)

    Jin, Jin; Liu, Feng; Zuo, Zhentao; Xue, Rong; Li, Mingyan; Li, Yu; Weber, Ewald; Crozier, Stuart

    2012-04-01

    Based on computational electromagnetics and multi-level optimization, an inverse approach of attaining accurate mapping of both transmit and receive sensitivity of radiofrequency coils is presented. This paper extends our previous study of inverse methods of receptivity mapping at low fields, to allow accurate mapping of RF magnetic fields (B(1)) for high-field applications. Accurate receive sensitivity mapping is essential to image domain parallel imaging methods, such as sensitivity encoding (SENSE), to reconstruct high quality images. Accurate transmit sensitivity mapping will facilitate RF-shimming and parallel transmission techniques that directly address the RF inhomogeneity issue, arguably the most challenging issue of high-field magnetic resonance imaging (MRI). The inverse field-based approach proposed herein is based on computational electromagnetics and iterative optimization. It fits an experimental image to the numerically calculated signal intensity by iteratively optimizing the coil-subject geometry to better resemble the experiments. Accurate transmit and receive sensitivities are derived as intermediate results of the optimization process. The method is validated by imaging studies using homogeneous saline phantom at 7T. A simulation study at 300MHz demonstrates that the proposed method is able to obtain receptivity mapping with errors an order of magnitude less than that of the conventional method. The more accurate receptivity mapping and simultaneously obtained transmit sensitivity mapping could enable artefact-reduced and intensity-corrected image reconstructions. It is hoped that by providing an approach to the accurate mapping of both transmit and receive sensitivity, the proposed method will facilitate a range of applications in high-field MRI and parallel imaging. Copyright © 2012 Elsevier Inc. All rights reserved.

  7. Consideration of critically when directly disposing highly enriched spent nuclear fuel in unsaturated tuff: Bounding estimates

    Energy Technology Data Exchange (ETDEWEB)

    Rechard, R.P.; Tierney, M.S.; Sanchez, L.C.; Martell, M.-A.

    1996-05-01

    This report presents one of 2 approaches (bounding calculations) which were used in a 1994 study to examine the possibility of a criticality in a repository. Bounding probabilities, although rough, point to the difficulty of creating conditions under which a critical mass could be assembled (container corrosion, separation of neutron absorbers from fissile material, collapse or precipitation of fissile material) and how significant the geochemical and hydrologic phenomena are. The study could not conceive of a mechanism consistent with conditions under which an atomic explosion could occur. Should a criticality occur in or near a container in the future, boundary consequence calculations showed that fissions from one critical event (<10{sup 20} fissions, if similar to aqueous and metal accidents and experiments) are quite small compared to the amount of fissions represented by the spent fuel itself. If it is assumed that the containers necessary to hold the highly enriched spent fuel went critical once per day for 1 million years, creating an energy release of about 10{sup 20} fissions, the number of fissions equals about 10{sup 28}, which corresponds to only 1% of the fission inventory in a repository containing 70,000 metric tons of heavy metal, the expected size for the proposed repository at Yucca Mountain, Nevada.

  8. Reactor Testing and Qualification: Prioritized High-level Criticality Testing Needs

    Energy Technology Data Exchange (ETDEWEB)

    S. Bragg-Sitton; J. Bess; J. Werner; G. Harms; S. Bailey

    2011-09-01

    Researchers at the Idaho National Laboratory (INL) were tasked with reviewing possible criticality testing needs to support development of the fission surface power system reactor design. Reactor physics testing can provide significant information to aid in development of technologies associated with small, fast spectrum reactors that could be applied for non-terrestrial power systems, leading to eventual system qualification. Several studies have been conducted in recent years to assess the data and analyses required to design and build a space fission power system with high confidence that the system will perform as designed [Marcille, 2004a, 2004b; Weaver, 2007; Parry et al., 2008]. This report will provide a summary of previous critical tests and physics measurements that are potentially applicable to the current reactor design (both those that have been benchmarked and those not yet benchmarked), summarize recent studies of potential nuclear testing needs for space reactor development and their applicability to the current baseline fission surface power (FSP) system design, and provide an overview of a suite of tests (separate effects, sub-critical or critical) that could fill in the information database to improve the accuracy of physics modeling efforts as the FSP design is refined. Some recommendations for tasks that could be completed in the near term are also included. Specific recommendations on critical test configurations will be reserved until after the sensitivity analyses being conducted by Los Alamos National Laboratory (LANL) are completed (due August 2011).

  9. Consideration of critically when directly disposing highly enriched spent nuclear fuel in unsaturated tuff: Bounding estimates

    Energy Technology Data Exchange (ETDEWEB)

    Rechard, R.P.; Tierney, M.S.; Sanchez, L.C.; Martell, M.-A.

    1996-05-01

    This report presents one of 2 approaches (bounding calculations) which were used in a 1994 study to examine the possibility of a criticality in a repository. Bounding probabilities, although rough, point to the difficulty of creating conditions under which a critical mass could be assembled (container corrosion, separation of neutron absorbers from fissile material, collapse or precipitation of fissile material) and how significant the geochemical and hydrologic phenomena are. The study could not conceive of a mechanism consistent with conditions under which an atomic explosion could occur. Should a criticality occur in or near a container in the future, boundary consequence calculations showed that fissions from one critical event (<10{sup 20} fissions, if similar to aqueous and metal accidents and experiments) are quite small compared to the amount of fissions represented by the spent fuel itself. If it is assumed that the containers necessary to hold the highly enriched spent fuel went critical once per day for 1 million years, creating an energy release of about 10{sup 20} fissions, the number of fissions equals about 10{sup 28}, which corresponds to only 1% of the fission inventory in a repository containing 70,000 metric tons of heavy metal, the expected size for the proposed repository at Yucca Mountain, Nevada.

  10. A FORMATIVE ASSESSMENT MODEL OF CRITICAL THINKING IN MATHEMATICS LEARNING IN JUNIOR HIGH SCHOOL

    Directory of Open Access Journals (Sweden)

    R. Rosnawati

    2015-12-01

    Full Text Available This study aims to obtain a valid and reliable formative evaluation model of critical thinking. The method used in this research was the research and development by integrating Borg & Gall's model and  Plomp's development model. The ten steps Borg & Gall’s model were modified into five stages as the stages in the Plomp's model. The subjects in this study were 1,446 students of junior high schools in DIY, 14 mathematics teacher, and six experts. The content validity employed was expert judgment, the empirical validity and reliability used were loading factor, item analysis used PCM 1PL, and the relationship between disposition and critical thinking skill used was structural equation modeling (SEM. The developed formative evaluation model is the procedural model. There are five aspects of critical thinking skill: mathematic reasoning, interpretation, analysis, evaluation, and inference, which entirely composed of 42 items. The validity of the critical thinking skill instruments achieves a significance degree as indicated by the lowest and the highest loading factors of 0.38 and 0.74 subsequently, the reliability of every aspect in a good category. The average level of difficulty is 0.00 with the standard deviation of 0.45 which is in a good category. The peer assessment questionnaire of critical thinking disposition consists of seven aspects: truth-seeking, open-minded, analysis, systematic, self-confidence, inquisitiveness, and maturity with 23 items. The critical thinking disposition validity achieves the significance degree as indicated by the lowest and the high factor loading of 0.66 and 0.76 subsequently, and the reliability of every aspect in a good category. Based on the analysis of the structural equation model, the model fits the data.

  11. Numerical simulation of aerodynamic derivatives and critical wind speed for long-span bridges based on simplified steady wind field

    Science.gov (United States)

    Xin, Dabo; Ou, Jinping

    2007-06-01

    Combining the computational fluid dynamics-based numerical simulation with the forced vibration technique for extraction of aerodynamic derivatives, an approach for calculating the aerodynamic derivatives and the critical flutter wind speed for long-span bridges is presented in this paper. The RNG k-ɛ turbulent model is introduced to establish the governing equations, including the continuity equation and the Navier-Stokes equations, for solving the wind flow field around a two-dimensional bridge section. To illustrate the effectiveness and accuracy of the proposed approach, a simple application to the Hume Bridge in China is provided, and the numerical results show that the aerodynamic derivatives and the critical flutter wind speed obtained agree well with the wind tunnel test results.

  12. Numerical simulation of aerodynamic derivatives and critical wind speed for long-span bridges based on simplified steady wind field

    Institute of Scientific and Technical Information of China (English)

    Xin Dabo; Ou Jinping

    2007-01-01

    Combining the computational fluid dynamics-based numerical simulation with the forced vibration technique for extraction of aerodynamic derivatives, an approach for calculating the aerodynamic derivatives and the critical flutter wind speed for long-span bridges is presented in this paper. The RNG κ-ε turbulent model is introduced to establish the governing equations, including the continuity equation and the Navier-Stokes equations, for solving the wind flow field around a two-dimensional bridge section. To illustrate the effectiveness and accuracy of the proposed approach, a simple application to the Hume Bridge in China is provided, and the numerical results show that the aerodynamic derivatives and the critical flutter wind speed obtained agree well with the wind tunnel test results.

  13. Classical-to-quantum crossover in the critical behavior of the transverse-field Sherrington-Kirkpatrick spin glass model

    Science.gov (United States)

    Mukherjee, Sudip; Rajak, Atanu; Chakrabarti, Bikas K.

    2015-10-01

    We study the critical behavior of the Sherrington-Kirkpatrick model in transverse field (at finite temperature) using Monte Carlo simulation and exact diagonalization (at zero temperature). We determine the phase diagram of the model by estimating the Binder cumulant. We also determine the correlation length exponent from the collapse of the scaled data. Our numerical studies here indicate that critical Binder cumulant (indicating the universality class of the transition behavior) and the correlation length exponent cross over from their "classical" to "quantum" values at a finite temperature (unlike the cases of pure systems, where such crossovers occur at zero temperature). We propose a qualitative argument supporting such an observation, employing a simple tunneling picture.

  14. Phase behaviour of colloids suspended in a near-critical solvent : A mean-field approach

    NARCIS (Netherlands)

    Edison, John R.; Belli, Simone; Evans, Robert; Van Roij, René; Dijkstra, Marjolein

    2015-01-01

    Colloids suspended in a binary solvent may, under suitable thermodynamic conditions, experience a wide variety of solvent-mediated interactions that can lead to colloidal phase transitions and aggregation phenomena. We present a simple mean-field theory, based on free-volume arguments, that describe

  15. Critical analysis of soil invertebrate biomarkers: a field case study in Avonmouth, UK.

    Science.gov (United States)

    Weeks, Jason M; Spurgeon, David J; Svendsen, Claus; Hankard, Peter K; Kammenga, Jan E; Dallinger, Reinhard; Köhler, Heinz-R; Simonsen, Vibeke; Scott-Fordsmand, Janeck

    2004-11-01

    During the period 1996-1999 a joint field research programme (BIOPRINT-II) funded by the European Union was undertaken. The main objective of this project was the deployment of biochemical fingerprint techniques of soil invertebrate biomarkers for assessing the exposure and effect of toxicants on soil invertebrates in the field. The aim was to apply these techniques in the field focusing on a a chronically polluted field near a lead and zinc smelter in Avonmouth (UK). Therefore six sites were selected from which organisms were either sampled or transplanted to or from the laboratory. The project has provided a unique opportunity to apply a series of biological test methodologies in order to determine the hazard posed to soil sustainability and by inference soil biodiversity and function. This work has attempted to understand the linkage between effects measured at the molecular or cellular level and relate these to changes at higher levels of biological organisation. Here we evaluated the links between biomarkers and soil function parameters. The paper aims to summarize and explore the necessary caveats that must be understood before soil biomarker test systems may be used to strengthen the risk assessment process.

  16. Critical Analysis of Soil Invertebrate Biomarkers: A Field Case Study in Avonmouth, UK

    NARCIS (Netherlands)

    Weeks, J.M.; Spurgeon, D.J.; Svendsen, C.; Hankard, P.K.; Kammenga, J.E.; Dallinger, R.; Köhler, H.R.; Simonsen, V.; Scott-Fordsmand, J.

    2004-01-01

    During the period 1996–1999 a joint field research programme (BIOPRINT-II) funded by the European Union was undertaken. The main objective of this project was the deployment of biochemical fingerprint techniques of soil invertebrate biomarkers for assessing the exposure and effect of toxicants on

  17. Critical Analysis of Soil Invertebrate Biomarkers: A Field Case Study in Avonmouth, UK

    NARCIS (Netherlands)

    Weeks, J.M.; Spurgeon, D.J.; Svendsen, C.; Hankard, P.K.; Kammenga, J.E.; Dallinger, R.; Köhler, H.R.; Simonsen, V.; Scott-Fordsmand, J.

    2004-01-01

    During the period 1996–1999 a joint field research programme (BIOPRINT-II) funded by the European Union was undertaken. The main objective of this project was the deployment of biochemical fingerprint techniques of soil invertebrate biomarkers for assessing the exposure and effect of toxicants on so

  18. Wide-field, high-resolution Fourier ptychographic microscopy

    CERN Document Server

    Zheng, Guoan; Yang, Changhuei

    2014-01-01

    In this article, we report an imaging method, termed Fourier ptychographic microscopy (FPM), which iteratively stitches together a number of variably illuminated, low-resolution intensity images in Fourier space to produce a wide-field, high-resolution complex sample image. By adopting a wavefront correction strategy, the FPM method can also correct for aberrations and digitally extend a microscope's depth-of-focus beyond the physical limitations of its optics. As a demonstration, we built a microscope prototype with a resolution of 0.78 um, a field-of-view of ~120 mm2, and a resolution-invariant depth-of-focus of 0.3 mm (characterized at 632 nm). Gigapixel colour images of histology slides verify FPM's successful operation. The reported imaging procedure transforms the general challenge of high-throughput, high-resolution microscopy from one that is coupled to the physical limitations of the system's optics to one that is solvable through computation.

  19. High field superconductor development and understanding project, Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Larbalestier, David C.; Lee, Peter J.

    2009-07-15

    Over 25 years the Applied Superconductivity Center at the University of Wisconsin-Madison provided a vital technical resource to the High Energy Physics community covering development in superconducting strand for HEP accelerator magnet development. In particular the work of the group has been to develop the next generation of high field superconductors for high field application. Grad students Mike Naus, Chad Fischer, Arno Godeke and Matt Jewell improved our understanding of the microstructure and microchemistry of Nb3Sn and their impact on the physical and mechanical properties. The success of this work has led to the continued funding of this work at the ASC after it moved to the NHMFL and also to direct funding from BNL for some aspects of Nb3Sn cable evaluation.

  20. Evidence of a quantum critical point in Ce1-xYbxCoIn5 alloys at high Yb doping

    Science.gov (United States)

    Singh, Y. P.; Haney, D. J.; Huang, X. Y.; White, B. D.; Maple, M. B.; Dzero, M.; Almasan, C. C.

    2015-03-01

    We performed this study on single crystals of Ce1-xYbxCoIn5 alloys with the motivation to further explore some of the previously reported unusual behaviors such as robust coherence and superconductivity, non-Fermi liquid (NFL) behavior, and the possibility of quantum criticality in higher Yb doping. Our specific heat and electronic magneto-transport measurements on the alloy with x = 0.75 nominal doping down to temperatures (T) as low as 0.5 K and magnetic fields (H) as high as 14 T. Our analysis of both specific heat and resistivity data unveils the presence of a crossover from NFL behavior at high temperatures to Fermi-liquid (FL) behavior at lower temperatures. Our analysis also indicates that the origin of the NFL behavior is a result of quantum fluctuations of unknown origin. The H-T phase diagram extracted from resistivity and specific heat shows that the crossover from NFL to FL behavior at zero temperature occurs at H = 0. This implies that the alloy with x = 0.75 Yb concentration is quantum critical, i.e., xc = 0.75. This result of zero field quantum critical point at x = 0.75 is also confirmed from our analysis of magneto-resistance data. This work was supported by the National Science Foundation (Grant NSF DMR-1006606) and Ohio Board of Regents (Grant OBR-RIP-220573) at KSU, and by the U.S. Department of Energy (Grant DE-FG02- 04ER46105) at UCSD.

  1. High field – low energy muon ionization cooling channel

    Directory of Open Access Journals (Sweden)

    Hisham Kamal Sayed

    2015-09-01

    Full Text Available Muon beams are generated with large transverse and longitudinal emittances. In order to achieve the low emittances required by a muon collider, within the short lifetime of the muons, ionization cooling is required. Cooling schemes have been developed to reduce the muon beam 6D emittances to ≈300  μm-rad in transverse and ≈1–1.5  mm in longitudinal dimensions. The transverse emittance has to be further reduced to ≈50–25  μm-rad with an upper limit on the longitudinal emittance of ≈76  mm in order to meet the high-energy muon collider luminosity requirements. Earlier studies of the transverse cooling of low energy muon beams in high field magnets showed a promising performance, but did not include transverse or longitudinal matching between the stages. In this study we present the first complete design of the high field-low energy ionization cooling channel with transverse and longitudinal matching. The channel design was based on strong focusing solenoids with fields of 25–30 T and low momentum muon beam starting at 135  MeV/c and gradually decreasing. The cooling channel design presented here is the first to reach ≈50 micron scale emittance beam. We present the channel’s optimized design parameters including the focusing solenoid fields, absorber parameters and the transverse and longitudinal matching.

  2. Critical behavior of the spin-1 and spin-3/2 Baxter-Wu model in a crystal field

    Science.gov (United States)

    Dias, D. A.; Xavier, J. C.; Plascak, J. A.

    2017-01-01

    The phase diagram and the critical behavior of the spin-1 and the spin-3/2 two-dimensional Baxter-Wu model in a crystal field are studied by conventional finite-size scaling and conformal invariance theory. The phase diagram of this model, for the spin-1 case, is qualitatively the same as those of the diluted 4-states Potts model and the spin-1 Blume-Capel model. However, for the present case, instead of a tricritical point one has a pentacritical point for a finite value of the crystal field, in disagreement with previous work based on finite-size calculations. On the other hand, for the spin-3/2 case, the phase diagram is much richer and can present, besides a pentacritical point, an additional multicritical end point. Our results also support that the universality class of the critical behavior of the spin-1 and spin-3/2 Baxter-Wu model in a crystal field is the same as the pure Baxter-Wu model, even at the multicritical points.

  3. High Power Laser-Plasma Interaction under a Strong Magnetic Field

    Science.gov (United States)

    Sano, Takayoshi; Tanaka, Yuki; Yamaguchi, Tomohito; Murakami, Masakatsu; Iwata, Natsumi; Hata, Masayasu; Mima, Kunioki

    2016-10-01

    We investigate laser-plasma interactions under a strong magnetic field by one-dimensional Particle-in-Cell (PIC) simulations. A simple setup is considered in our analysis, in which a thin foil is irradiated by a right-handed circularly polarized laser. A uniform magnetic field is assumed in the direction of the laser propagation. Then the whistler wave can penetrate the overdense plasma when the external field is larger than the critical field strength Bc =meω0 / e . In this situation, key parameters of the system are the plasma density and the size of the external field. We performed various models in the density-field strength diagram, which is actually the so-called CMA diagram, to evaluate the efficiency of the energy conversion from the laser to plasma and the reflectivity and transmittance of the laser. It is found that there are two important processes in the interaction between the whistler wave and overdense plasma, which are the cyclotron resonance of relativistic electrons and the parametric (Brillouin) instability. Because of the high temperature of electrons, ions can be accelerated dramatically by a large sheath field at the target surface.

  4. Criticality features in ultra-low frequency magnetic fields prior to the 2013 M6.3 Kobe earthquake

    Directory of Open Access Journals (Sweden)

    Stelios M. Potirakis

    2016-07-01

    Full Text Available The nonlinear criticality of ultra-low frequency (ULF magnetic variations is investigated before a particular earthquake (EQ occurred in Kobe on April 12, 2013, by applying the “natural time” analysis on a few ULF parameters: Fh, Fz and Dh. The first two refer to radiation from the lithosphere, and the last parameter corresponds to depression of horizontal component as a signature of ionospheric perturbation. A recent paper of our team has indicated, using the same data as in this paper but by means of conventional statistical analysis, a clear effect of depression in the horizontal component as an ionospheric signature. But there seems to be no convincing signature of lithospheric ULF radiation according to the specific analysis, so this paper aims at extending our study on the electromagnetic data recorded prior to the specific EQ by trying to find any significant phenomenon in ULF effects (both lithospheric radiation and the depression of horizontal component using the critical, natural time analysis. The natural time analysis has yielded that criticality at Shigaraki (SGA, as the station closest to the EQ epicenter, is reached on March 27-29 for Fh and March 27 to April 1 for Fz (about two weeks before the EQ. But, the criticality for Dh was not observed at SGA probably due to high noise, on the other hand such criticality was observed at Kanoya (KNY because of its known property of a wider range of detection of ULF depression.

  5. Improving the critical speeds of high-speed trains using magnetorheological technology

    Science.gov (United States)

    Sun, Shuaishuai; Deng, Huaxia; Li, Weihua; Du, Haiping; Qing Ni, Yi; Zhang, Jin; Yang, Jian

    2013-11-01

    With the rapid development of high-speed railways, vibration control for maintaining stability, passenger comfort, and safety has become an important area of research. In order to investigate the mechanism of train vibration, the critical speeds of various DOFs with respect to suspension stiffness and damping are first calculated and analyzed based on its dynamic equations. Then, the sensitivity of the critical speed is studied by analyzing the influence of different suspension parameters. On the basis of these analyses, a conclusion is drawn that secondary lateral damping is the most sensitive suspension damper. Subsequently, the secondary lateral dampers are replaced with magnetorheological fluid (MRF) dampers. Finally, a high-speed train model with MRF dampers is simulated by a combined ADAMS and MATLAB simulation and tested in a roller rig test platform to investigate the mechanism of how the MRF damper affects the train’s stability and critical speed. The results show that the semi-active suspension installed with MRF dampers substantially improves the stability and critical speed of the train.

  6. Rf Gun with High-Current Density Field Emission Cathode

    Energy Technology Data Exchange (ETDEWEB)

    Jay L. Hirshfield

    2005-12-19

    High current-density field emission from an array of carbon nanotubes, with field-emission-transistor control, and with secondary electron channel multiplication in a ceramic facing structure, have been combined in a cold cathode for rf guns and diode guns. Electrodynamic and space-charge flow simulations were conducted to specify the cathode configuration and range of emission current density from the field emission cold cathode. Design of this cathode has been made for installation and testing in an existing S-band 2-1/2 cell rf gun. With emission control and modulation, and with current density in the range of 0.1-1 kA/cm2, this cathode could provide performance and long-life not enjoyed by other currently-available cathodes

  7. High-order harmonic generation from inhomogeneous fields

    CERN Document Server

    Ciappina, M F; Quidant, R; Lewenstein, M

    2011-01-01

    We present theoretical studies of high-order harmonic generation (HHG) produced by non-homogeneous fields as resulting from the illumination of plasmonic nanostructures with a short laser pulse. We show that the inhomogeneity of the local fields plays an important role in the HHG process and lead to the generation of even harmonics and a significantly increased cutoff, more pronounced for the longer wavelengths cases studied. In order to understand and characterize the new HHG features we employ two different approaches: the numerical solution of the time dependent Schr\\"odinger equation (TDSE) and the semiclassical approach known as Strong Field Approximation (SFA). Both approaches predict comparable results and show the new features, but using the semiclassical arguments behind the SFA, we are able to fully understand the reasons of the cutoff extension.

  8. Control and data acquisition systems for high field superconducting wigglers

    CERN Document Server

    Batrakov, A; Karpov, G; Kozak, V; Kuzin, M; Kuper, E; Mamkin, V; Mezentsev, N A; Repkov, V V; Selivanov, A; Shkaruba, V A

    2001-01-01

    This paper describes the control and DAQ system of superconducting wigglers with magnetic field range up to 10.3 T. The first version of the system controls a 7 T superconducting wiggler prepared for installation at Bessy-II (Germany). The second one controls a 10 T wiggler which is under testing now at the SPring-8 site (Japan). Both systems are based on VME apparatus. The set of specialized VME modules is elaborated to arrange wiggler power supply control, full time wiggler monitoring, and magnetic field high accuracy measurement and field stabilization. The software for the control of the wigglers is written in C language for VxWorks operation system for a Motorola-162 VME controller. The task initialization, stops and acquisition of the data can be done from the nearest personal computer (FTP host for VME), or from the remote system as well.

  9. Criticality and novel quantum liquid phases in Ginzburg-Landau theories with compact and non-compact gauge fields

    Energy Technology Data Exchange (ETDEWEB)

    Smiseth, Jo

    2005-07-01

    The critical properties of three-dimensional U(1)-symmetric lattice gauge theories have been studied. The models apply to various physical systems such as insulating phases of strongly correlated electron systems as well as superconducting and superfluid states of liquid metallic hydrogen under extreme pressures. The thesis contains an introductory part and a collection of research papers of which seven are published works and one is submitted for publication. The outline of this thesis is as follows. In Chapter 2 the theory of phase transitions is discussed with emphasis on continuous phase transitions, critical phenomena and phase transitions in gauge theories. In the next chapter the phases of the abelian Higgs model are presented, and the critical phenomena are discussed. Furthermore, the multicomponent Ginzburg-Landau theory and the applications to liquid metallic hydrogen are presented. Chapter 4 contains an overview of the Monte Carlo integration scheme, including the Metropolis algorithm, error estimates, and re weighting techniques. This chapter is followed by the papers I-VIII. Paper I: Criticality in the (2+1)-Dimensional Compact Higgs Model and Fractionalized Insulators. Paper II: Phase structure of (2+1)-dimensional compact lattice gauge theories and the transition from Mott insulator to fractionalized insulator. Paper III: Compact U(1) gauge theories in 2+1 dimensions and the physics of low dimensional insulating materials. Paper IV: Phase structure of Abelian Chern-Simons gauge theories. Paper V: Critical Properties of the N-Color London Model. Paper VI: Field- and temperature induced topological phase transitions in the three-dimensional N-component London superconductor. Paper VII: Vortex Sublattice Melting in a Two-Component Superconductor. Paper VIII: Observation of a metallic superfluid in a numerical experiment (ml)

  10. High critical temperature superconducting quantum interference device magnetometer with feedforward active noise control system for magnetocardiographic measurement in unshielded circumstances

    Energy Technology Data Exchange (ETDEWEB)

    Mizukami, A.; Nishiura, H.; Sakuta, K.; Kobayashi, T

    2003-10-15

    Magnetocardiographic (MCG) measurement in unshielded environment for practical use requires to suppress the environmental magnetic noise. We have designed the high critical temperature superconducting quantum interference device (High-T{sub c} SQUID) magnetometer with feedforward active noise control (ANC) system to suppress the environmental magnetic noise. The compensatory system consisted of two SQUID magnetometers, a digital signal processor (DSP) and the coil wound around the input magnetometer. The DSP calculated the output data to minimize the environmental noise from the input and reference date and then the coil generated the magnetic field to cancel the environmental noise. This method achieved the effective noise attenuation below 100 Hz about 40 dB. MCG measurement in unshielded environment was also performed.

  11. Critical analysis of data concerning Saccharomyces cerevisiae free-cell proliferations and fermentations assisted by magnetic and electromagnetic fields

    CERN Document Server

    Hristov, Jordan

    2011-01-01

    The review analyses studies on magnetically assisted proliferations and batch fermentations with Saccharomyces cerevisiae yeasts. The results available in the literature are contradictory and show two tendencies: magnetic field suppression of the cell growth and positive effects in batch fermentation with increasing both biomass and metabolite production. The amount of data analyzed allows several concepts existing in the literature to be outlined and critically commented. Further, a new concept of magnetically induced micro-dynamos, recently conceived, is developed towards a unified explanation of the results provided by proliferation and batch fermentation experiments

  12. Finite Size Corrected Relativistic Mean-Field Model and QCD Critical End Point

    CERN Document Server

    Uddin, Saeed; Ahmad, Jan Shabir

    2012-01-01

    The effect of finite size of hadrons on the QCD phase diagram is analyzed using relativistic mean field model for the hadronic phase and the Bag model for the QGP phase. The corrections to the EOS for hadronic phase are incorporated in a thermodynamic consistent manner for Van der Waals like interaction. It is found that the effect of finite size of baryons is to shift CEP to higher chemical potential values.

  13. On the critical behaviour of the 2-point function in scalar field theories

    Energy Technology Data Exchange (ETDEWEB)

    Malbouisson, A.P.C. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)

    1999-09-01

    By the use of a Mellin representation of Feynman integrals, a convergent asymptotic expansion for generic Feynman amplitudes for any set of invariants going to zero or to {infinity}, may be obtained. In the case of scalar field theories in Euclidean metric, we use this expansion to analyse the behaviour of the two-point function for small values of the mass parameter, for fixed external momentum. (author)

  14. Design of wide field and high resolution video lens

    Science.gov (United States)

    Xiao, Ze-xin; Zhan, Binzhou; Han, Haimei

    2009-11-01

    Online detecting is increasingly used in industrial process for the requirement of product quality improving. It is a trend that the "machine detecting" with "machine version + computer intelligence" as new method replaces traditional manual "eye observation". The essential of "machine detecting" is that image of object being collected with high resolution video lens on sensor panel of photoelectric (CCD ,CMOS) and detecting result being automatically gained by computer after the image saved and processed. "Machine detecting" is developing rapidly with the universal reception by enterprises because of its fine accurateness, high efficiency and the real time. Video lens is one of the important components of machine version system. Requirements of wide field and high resolution enlarged the complexity of video lens design. In this paper a design case used in visible light with field diameter Φ32mm, β=-0.25× and NA'=0.15. We give design parameters of the video lens which obtained with theoretically calculating and Oslo software optimization: MTF>0.3 in full field and 215lp/mm, distortion <0.05%.This lens has an excellent optic performance to match with 1.3 million pixels 1/2"CCD, and a high performance price ratio for being consist of only 7 single lens in the way of 5 units.

  15. Dielectrophoretic spectra of translational velocity and critical frequency for a spheroid in traveling electric field.

    Science.gov (United States)

    Bunthawin, Sakshin; Wanichapichart, Pikul; Tuantranont, Adisorn; Coster, Hans G L

    2010-01-13

    An analysis has been made of the dielectrophoretic (DEP) forces acting on a spheroidal particle in a traveling alternating electric field. The traveling field can be generated by application of alternating current signals to an octapair electrode array arranged in phase quadrature sequence. The frequency dependent force can be resolved into two orthogonal forces that are determined by the real and the imaginary parts of the Clausius-Mossotti factor. The former is determined by the gradient in the electric field and directs the particle either toward or away from the tip of the electrodes in the electrode array. The force determined by the imaginary component is in a direction along the track of the octapair interdigitated electrode array. The DEP forces are related to the dielectric properties of the particle. Experiments were conducted to determine the DEP forces in such an electrode arrangement using yeast cells (Saccharomyces cervisiate TISTR 5088) with media of various conductivities. Experimental data are presented for both viable and nonviable cells. The dielectric properties so obtained were similar to those previously reported in literature using other DEP techniques.

  16. Nonlinear Force-Free Magnetic Field Modeling of the Solar Corona: A Critical Assessment

    Science.gov (United States)

    De Rosa, M. L.; Schrijver, C. J.; Barnes, G.; Leka, K. D.; Lites, B. W.; Aschwanden, M. J.; McTiernan, J. M.; Régnier, S.; Thalmann, J.; Valori, G.; Wheatland, M. S.; Wiegelmann, T.; Cheung, M.; Conlon, P. A.; Fuhrmann, M.; Inhester, B.; Tadesse, T.

    2008-12-01

    Nonlinear force-free field (NLFFF) modeling promises to provide accurate representations of the structure of the magnetic field above solar active regions, from which estimates of physical quantities of interest (e.g., free energy and helicity) can be made. However, the suite of NLFFF algorithms have so far failed to arrive at consistent solutions when applied to cases using the highest-available-resolution vector magnetogram data from Hinode/SOT-SP (in the region of the modeling area of interest) and line-of-sight magnetograms from SOHO/MDI (where vector data were not been available). It is our view that the lack of robust results indicates an endemic problem with the NLFFF modeling process, and that this process will likely continue to fail until (1) more of the far-reaching, current-carrying connections are within the observational field of view, (2) the solution algorithms incorporate the measurement uncertainties in the vector magnetogram data, and/or (3) a better way is found to account for the Lorentz forces within the layer between the photosphere and coronal base. In light of these issues, we conclude that it remains difficult to derive useful and significant estimates of physical quantities from NLFFF models.

  17. Nonlinear Force-Free Magnetic Field Modeling of AR 10953: A Critical Assessment

    Science.gov (United States)

    De Rosa, Marc L.; Schrijver, C. J.; Barnes, G.; Leka, K. D.; Lites, B. W.; Aschwanden, M. J.; Amari, T.; Canou, A.; McTiernan, J. M.; Régnier, S.; Thalmann, J. K.; Valori, G.; Wheatland, M. S.; Wiegelmann, T.; Cheung, M. C. M.; Conlon, P. A.; Fuhrmann, M.; Inhester, B.; Tadesse, T.

    2009-05-01

    Nonlinear force-free field (NLFFF) modeling seeks to provide accurate representations of the structure of the magnetic field above solar active regions, from which estimates of physical quantities of interest (e.g., free energy and helicity) can be made. However, the suite of NLFFF algorithms have failed to arrive at consistent solutions when applied to (thus far, two) cases using the highest-available-resolution vector magnetogram data from Hinode/SOT-SP (in the region of the modeling area of interest) and line-of-sight magnetograms from SOHO/MDI (where vector data were not available). One issue is that NLFFF models require consistent, force-free vector magnetic boundary data, and vector magnetogram data sampling the photosphere do not satisfy this requirement. Consequently, several problems have arisen that are believed to affect such modeling efforts. We use AR 10953 to illustrate these problems, namely: (1) some of the far-reaching, current-carrying connections are exterior to the observational field of view, (2) the solution algorithms do not (yet) incorporate the measurement uncertainties in the vector magnetogram data, and/or (3) a better way is needed to account for the Lorentz forces within the layer between the photosphere and coronal base. In light of these issues, we conclude that it remains difficult to derive useful and significant estimates of physical quantities from NLFFF models.

  18. Electron-electron interactions in graphene field-induced quantum dots in a high magnetic field

    DEFF Research Database (Denmark)

    Orlof, A.; Shylau, Artsem; Zozoulenko, I. V.

    2015-01-01

    We study the effect of electron-electron interaction in graphene quantum dots defined by an external electrostatic potential and a high magnetic field. To account for the electron-electron interaction, we use the Thomas-Fermi approximation and find that electron screening causes the formation...... of compressible strips in the potential profile and the electron density. We numerically solve the Dirac equations describing the electron dynamics in quantum dots, and we demonstrate that compressible strips lead to the appearance of plateaus in the electron energies as a function of the magnetic field. Finally...

  19. Dosimetry in radiation fields around high-energy proton accelerators

    CERN Document Server

    Agosteo, S; Silari, M; Theis, C

    2008-01-01

    Radiation dosimetry at high-energy proton accelerators is a difficult task because of the complexity of the stray radiation field. A good knowledge of this mixed radiation field is very important to be able to select the type of detectors (active and/or passive) to be employed for routine area monitoring and to choose the personal dosimeter legally required for estimating the effective dose received by individuals. At the same time, the response function of the detectors to the mixed field must be thoroughly understood. A proper calibration of a device, which may involve a complex series of measurements in various reference fields, is needed. Monte Carlo simulations provide a complementary – and sometimes the principal – mean of determining the response function. The ambient dose equivalent rates during operation range from a few hundreds of μSv per year to a few mSv per year. To measure such rates one needs detectors of high sensitivity and/or capable of integrating over long periods. The main challenge...

  20. Dynamics of conductive and nonconductive particles under high-voltage electrostatic coupling fields

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    With the high-voltage electrostatic theory and numerical analysis, the dynamics of conductive and nonconductive particles under high-voltage electrostatic coupling fields was studied. The oscillation behavior of the conductive particle between the corona electrode and ground electrode was analyzed and its oscillation amplitude was Sm=(ta+ts)·νm/2. It was found that there was the "lift-off voltage (Ulo)" for the conductive particle between the electrostatic electrode and ground electrode. The concepts of "critical charged rotational speed (n?)", "detaching critical rotational speed of nonconductive particle (n′)" and "ratio of voltage and distance between surface of electrodes (U/D)" were presented and their criteria were established. The trajectories of the conductive particles under the coupling fields of the corona electrode, electrostatic electrode and ground electrode were simulated by the computer. The simulative results were in good agreement with the experimental ones. This research enriches the high-voltage electrostatic theory and provides a theoretic basis for optimization of operating parameters and structure design of high-voltage electrostatic separator.