ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Articles  (102)
  • Other Sources
  • 74.72.Bk  (51)
  • anisotropy  (51)
  • Springer  (102)
  • American Geophysical Union
  • American Institute of Physics (AIP)
  • American Physical Society
  • Blackwell Publishing Ltd
  • Oxford University Press
  • 2000-2004  (12)
  • 1995-1999  (90)
  • 1945-1949
  • Physics  (101)
  • Electrical Engineering, Measurement and Control Technology  (11)
  • Natural Sciences in General
Collection
  • Articles  (102)
  • Other Sources
Publisher
  • Springer  (102)
  • American Geophysical Union
  • American Institute of Physics (AIP)
  • American Physical Society
  • Blackwell Publishing Ltd
  • +
Years
Year
  • 1
    ISSN: 1435-1528
    Keywords: Key words Polymeric liquid crystals ; anisotropy ; fillers ; string phases ; negative normal stresses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The effect of fillers on the flow curves of polymeric liquid crystals is investigated. Suspensions of polystyrene particles in liquid crystalline solutions of hydroxypropylcellulose (HPC) in water are used. By reducing the HPC concentration an isotropic solution can be prepared. It serves as a reference to isolate the effect of the isotropic/anisotropic structure of the suspending medium on the rheological behaviour. Suspensions in the isotropic solution behave as expected for filled viscoelastic matrices in general. In the anisotropic medium the shear rate rather than the shear stress seems to govern the changes in the relative viscosity. This behaviour is clearly different from isotropic viscoelastic media. The most dramatic effect however is that even small amounts of particles eliminate or drastically shift the region of negative normal stress differences. As far as the structure is concerned, microscopic observations show that particles align in anisotropic as well as in isotropic media. At rest or at relatively low shear stresses the liquid crystalline structure is, in the present case, hardly affected by the presence of the particles. If anything, it becomes more homogeneous.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Optical and quantum electronics 31 (1999), S. 733-749 
    ISSN: 1572-817X
    Keywords: anisotropy ; Leaky modes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract An exact numerical method for analyzing the propagation properties of leaky modes of inhomogeneous channel optical waveguides with a complex uniaxial diagonal permittivity tensor is developed. The method is based on solving the system of integro-differential equations formulated with respect to transversal components of the magnetic field and the longitudinal component of the electric field. Some results of investigation of leaky modes of diffused channel waveguides in LiNbO3 and LiTaO3 crystals are given.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1572-8854
    Keywords: Dipole parallel-alignment ; anisotropy ; arene–arene contacts ; intermolecular interactions ; nonlinear optics ; azines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound crystallizes in the space group Pna2(1) with cell parameters a = 6.4606(3), b = 7.2155(3) and c = 33.5878(16) Å. The azine shows a gauche conformation about the N—N bond and there is an angle of 58.1° between the benzene rings of each azine. This conformation allows for two intermolecular arene–arene T-contacts between pairs of benzene rings. The characteristic structural motif features T-contact formation between like–substituted arene rings and this architecture results in a highly dipole-parallel aligned lattice. All azines are perfectly colinear within each layer and the orientations of the azines in different layers are nearly the same. The surfaces of the layers exhibit a quadrilateral kite-shaped arrangement of I-atoms and of OCH3-substituents. The layers pack such that the OCH3—carbon atoms are placed above the interstices between the I-atoms in the adjacent layer.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für angewandte Mathematik und Physik 47 (1996), S. 617-630 
    ISSN: 1420-9039
    Keywords: Elasticity ; composite material ; Green's function ; plane problem ; anisotropy ; point force ; dislocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract Green's functions are derived for the in-plane deformation due to an in-plane point force and edge dislocation acting at a point in a plane of two joined semi-infinite anisotropic plates. The Lekhnitskii's complex potential approach is used, and a general expression of the solutions is obtained in closed-form. Including the case of an isotropic-anisotropic two-phase medium and the case of an isotropic-isotropic two-phase medium, the solutions are given for all possible combinations of materials with either s1 ≠ s2 or S1=s2, where si and s2 are the roots of the characteristic equation of the material.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 148 (1996), S. 637-683 
    ISSN: 1420-9136
    Keywords: Ray tracing ; kinematic inversion ; high-order perturbations ; sensitivity functions ; anisotropy ; cracks ; VSP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A comprehensive approach, based on the general nonlinear ray perturbation theory (Druzhinin, 1991), is proposed for both a fast and accurate uniform asymptotic solution of forward and inverse kinematic problems in anisotropic media. It has been developed to modify the standard ray linearization procedures when they become inconsistent, by providing a predictable truncation error of ray perturbation series. The theoretical background consists in a set of recurrent expressions for the perturbations of all orders for calculating approximately the body wave phase and group velocities, polarization, travel times, ray trajectories, paraxial rays and also the slowness vectors or reflected/transmitted waves in terms of elastic tensor perturbations. We assume that any elastic medium can be used as an unperturbed medium. A total 2-D numerical testing of these expressions has been established within the transverse isotropy to verify the accuracy and convergence of perturbation series when the elastic constants are perturbed. Seismological applications to determine crack-induced anisotropy parameters on VSP travel times for the different wave types in homogeneous and horizontally layered, transversally isotropic and orthorhombic structures are also presented. A number of numerical tests shows that this method is in general stable with respect to the choice of the reference model and the errors in the input data. A proof of uniqueness is provided by an interactive analysis of the sensitivity functions, which are also used for choosing optimum source/receiver locations. Finally, software has been developed for a desktop computer and applied to interpreting specific real VSP observations as well as explaining the results of physical modelling for a 3-D crack model with the estimation of crack parameters.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Marine geophysical researches 21 (2000), S. 289-306 
    ISSN: 1573-0581
    Keywords: Magnetic susceptibility ; anisotropy ; petrofabric ; Oman Ophiolite ; gabbros
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The anisotropy of magnetic susceptibility was measured on 42 gabbros sampled across a complete plutonic sequence from the Oman ophiolite. The rock fabrics, investigated in the field and through plagioclase crystallographic fabric measurements, were compared to the magnetic fabrics. This comparative study reveals that from the paleo-Moho to the top of the foliated gabbros level, 73% of the rocks display a good correspondence in orientation, between the magnetic and rock fabric orientation. In these rocks, the AMS is controlled by secondary magnetites located in the fracture network of the olivines, and probably, but to a lesser extent, by secondary magnetites located in the exsolution lamellae of the clinopyroxenes. The high correlation between the AMS ellipsoid orientation and the rock fabric orientation is explained by the fact that the magnetic foliation is essentially constrained by the orientation of the olivine fracture planes, which is in turn constrained by the orientation of the overall magmatic rock fabric. In contrast to the primary mineral phases, the orientation of magnetite crystals in these gabbros is not due to their alignment in a flowing magma, so their preferred orientation, although usually mimicking that of the rock fabric, does have not the same origin. Furthermore, given that the preferred orientation of the anisometric secondary magnetites is much less perfect than the preferred orientation of the plagioclases, no correlation between the shape and magnitude of the AMS and plagioclase fabrics can be established. In the uppermost levels of the sequence there is no correspondence between the magnetic and rock fabric orientation. The magnetism of these rocks is mainly carried by primary magnetite and ilmenite grains. These minerals occur as small and scattered interstitial grains that exhibit neither alignment nor parallelism with the pre-existing rock fabric. Hence, the anisotropy, shape and orientation of the AMS ellipsoid are independent of the rock fabric ellipsoid. Although in the Wadi Al Abyad gabbros, just like in other magnetite bearing rocks (Rochette et al., 1992; Archanjo et al., 1995), the AMS cannot be used to evaluate the shape and strength of the finite strain ellipsoid, it can be reliably used to get the orientation of the rock fabric ellipsoid when the AMS is controlled by secondary magnetites.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Surveys in geophysics 16 (1995), S. 37-46 
    ISSN: 1573-0956
    Keywords: resistivity ; anisotropy ; deep borehole ; KTB ; ARI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Information about electrical anisotropy in and around the deep borehole of the German Continental Deep Drilling Program (KTB) has been acquired using three different methods: (1) Under surface temperature and pressure conditions, the azimuthal dependence of resistivity has been measured in horizontal planes perpendicular to the axes of drill cores. (2) Simulated in-situ conditions (high temperature and pressure) have been applied to mini cores drilled at different orientations to structural features such as foliation. The resistivity was then measured in the direction of the mini cores' long axes. (3) Under quasi-in-situ (downhole) conditions, the azimuthal dependence of resistivity has been measured in horizontal planes using the Azimuthal Resistivity Imager (ARI), a down hole logging tool. These investigations have shown that electrical anisotropy is strongly related to structural features. The anisotropy of gneisses is the highest due to the strong foliation (averaged anisotropy factor 2.8). Lamprophyres are most isotropic (factor 1.2). Most rocks from KTB are amphibolites with intermediate anisotropies (factor 1.3). The anisotropies measured under surface temperature and pressure conditions and quasi-in-situ conditions on amphibolites are approximately the same, whereas anisotropies under simulated in-situ conditions are partially higher. Furthermore, the anisotropies measured on the cm to m scale using the various methods outlined above shall be compared with large scale anisotropies of the km scale measured around KTB using Magneto Tellurics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of superconductivity 12 (1999), S. 531-534 
    ISSN: 1572-9605
    Keywords: Organic superconductor ; superconductivity ; anisotropy ; Fermi surface
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The electronic states have been studied in the quasi-one-dimensional DMET-TSeF system, which includes several superconductors and nonsuperconductors. The origin of the different ground states has been examined by using the tight-binding band calculation. The type of the superconductivity has been discussed, considering the electronic wave functions that constitute the Fermi surface.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of superconductivity 11 (1998), S. 203-207 
    ISSN: 1572-9605
    Keywords: Thermoelectricity ; high-T c texture superconductor ; anisotropy ; oxygen content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Both the off-diagonal Seebeck effect and the off-diagonal Peltier effect were investigated on the same textured sample YBa2Cu3O7−δ and with the use of the same experimental setup. The effectiveness of several kinds of heat-conductive media was studied for the measurement. The flatness of both the sample and the heat-conducting block, and the matching between them were found very important for the reduction of the heat resistance of the interfaces. A reasonable agreement was found between the off-diagonal Seebeck coefficient measured by the off-diagonal Seebeck effect and that by the off-diagonal Peltier effect. The steplike feature in the relation between the off-diagonal Seebeck coefficient and the annealing temperature may imply a nonmonotonous change of the Seebeck coefficient along the c axis (S c) with oxygen content.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 93 (1998), S. 477-500 
    ISSN: 1572-9613
    Keywords: Erosion ; anisotropy ; stochastic equation ; renormalization group
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We formulate a stochastic equation to model the erosion of a surface with fixed inclination. Because the inclination imposes a preferred direction for material transport, the problem is intrinsically anisotropic. At zeroth order, the anisotropy manifests itself in a linear equation that predicts that the prefactor of the surface height–height correlations depends on direction. The first higher order nonlinear contribution from the anisotropy is studied by applying the dynamic renormalization group. Assuming an inhomogeneous distribution of soil substrate that is modeled by a source of static noise, we estimate the scaling exponents at first order in an ε-expansion. These exponents also depend on direction. We compare these predictions with empirical measurements made from real landscapes and find good agreement. We propose that our anisotropic theory applies principally to small scales and that a previously proposed isotropic theory applies principally to larger scales. Lastly, by considering our model as a transport equation for a driven diffusive system, we construct scaling arguments for the size distribution of erosion “events” or “avalanches.” We derive a relationship between the exponents characterizing the surface anisotropy and the avalanche size distribution, and indicate how this result may be used to interpret previous findings of power-law size distributions in real submarine avalanches.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 95 (1999), S. 981-996 
    ISSN: 1572-9613
    Keywords: nonequilibrium ; driven diffusive systems ; lattice gas ; kinetic Ising model ; anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Ising lattice gas, with its well known equilibrium properties, displays a number of surprising phenomena when driven into nonequilibrium steady states. We study such a model with anisotropic interparticle interactions (J ||≠J ⊥), using both Monte Carlo simulations and high temperature series techniques. Under saturation drive, the shift in the transition temperature can be both positive and negative, depending on the ratio J ||/J ⊥! For finite drives, both first- and second-order transitions are observed. Some aspects of the phase diagram can be predicted by investigating the two-point correlation function at the first nontrivial order of a high-temperature series expansion.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 95 (1999), S. 1337-1360 
    ISSN: 1572-9613
    Keywords: diffuse interfaces ; hexagonal close packing ; anisotropy ; mean-field theory ; Allen–Cahn equation ; interphase boundaries ; antiphase boundaries ; surface energy ; discrete free energy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A multiple-order-parameter mean-field theory of ordering on a binary hexagonal- close-packed (HCP) crystal structure is developed, and adapted to provide a continuum formulation that incorporates the underlying symmetries of the HCP crystal in both the bulk and gradient energy terms of the free energy. The work is an extension of the previous treatment by Braun et al. [Phil. Trans. Roy. Soc. Lond. A 355:1787 (1997)] of order–disorder transitions on a face-centered-cubic crystal (FCC) lattice. The theory is used to compute the orientation dependence of the structure and energy of interphase and antiphase boundaries in ordering to the Cd3Mg and CdMg structures, which are the HCP analogs of Cu3Au and CuAu structures in FCC. As in the corresponding FCC case, the multiple order parameters do not form a vector. Anisotropy is a natural consequence of the underlying crystal symmetries and the multiple-order-parameter continuum formation presented here. The isotropy transverse to the sixfold axis expected for a scalar order parameter is not found.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 13
    ISSN: 1090-6487
    Keywords: 74.72.Bk ; 74.72.Jt ; 64.75.+g ; 77.22.Gm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Low-temperature (120–180 K) relaxational effects are observed in oxygen-deficient RBa2Cu3O6+x (R=Y, Tm, Lu) single crystals. Isothermal holding of the crystals after rapid cooling increases their resistance. The characteristic times and the activation energy of the relaxation process, E a ≈0.46 eV, are determined. The possible relation between the observed effects and the appearance of “electronic phase separation” is discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 14
    ISSN: 1090-6487
    Keywords: 76.60.Gv ; 74.72.Bk ; 74.72.Yg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present a study of shape of the Cu(2) NQR spectra in YBa2Cu3O7, TmBa2Cum3O7, and TmBa2Cu4O8 compounds at temperatures of 4.2–300 K. The results of the quantitative analysis lead us to conclude that the shape of the Cu(2) NQR spectra in all the samples studied can be described in the framework of the “motional narrowing” model, which implies that the Cu(2) nucleus possesses two different NQR frequencies between which it can rapidly jump. The difference in frequencies seems to be related to the charge-stripe correlations in CuO2 planes resulting in a dynamical modulation of the electric field gradients at the Cu(2) nuclei.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 15
    ISSN: 1090-6487
    Keywords: 84.37.+q ; 74.72.Yg ; 74.72.Bk ; 74.72.Hs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The temperature dependences of the real part R s and the imaginary part X s of the surface impedance Z s =R s +iX s of the superconductor Ba0.6K0.4BiO3 (T c ≃30 K) are measured at a frequency of 9.4 GHz. Its temperature dependence Z s (T) and that of the complex conductivity σ s (T) can be described on the basis of a two-fluid model under two assumptions: The density of superconducting carriers increases linearly, and the relaxation time increases as a power law (∝1/T 5), with decreasing temperature T〈T c . This model also describes well the curves Z s (T) and σs (T) recently measured for YBa2Cu3O6.95 and Bi2Sr2CaCu2O8 single crystals.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 16
    ISSN: 1090-6487
    Keywords: 74.72.Bk ; 74.25.Fy ; 74.62.Bf
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In an investigation of the resistivity anisotropy of YBa2Cu3O7−x single crystals with suboptimal oxygen content it is observed that the superconducting transition for the component ρc of the resistivity tensor is shifted to lower temperatures with respect to the transition for the component ρab. A similar shift is also observed for the transition in the temperature dependence of the dynamic magnetic susceptibility.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 17
    ISSN: 1090-6487
    Keywords: 74.50.+r ; 74.25.Fy ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An experimental investigation is made of the subharmonic Shapiro steps observed on the I-V curves of high-T c superconductor Josephson junctions and on the bias-voltage dependences of the rf noise and detector response when the junctions are subjected to external submillimeter radiation. Structures of this type are ordinarily described by a nonsinusoidal current-phase relation, which is why subharmonic steps appear. Numerical modeling of the processes occurring in a Josephson junction by means of a simple current-phase relation, as in the case of an SNS junction, gives good agreement with experiment. The width of the characteristic Josephson generation line of the junction was estimated on the basis of the noise dependences and the selective detector response. The width can be explained by taking into account the shot noise of the tunneling component of the conductivity. A model of the conductivity of a high-T c superconductor Josephson junction, consisting of a tunnel junction with microshorts possessing metallic conductivity, is discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 18
    ISSN: 1090-6487
    Keywords: 78.47.+p ; 63.20.Kr ; 74.25.Jb ; 74.25.Kc ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The spectral dependence of the electron-phonon relaxation rate γe−ph(ℏω) in metals is studied in pump-supercontinuum-probe (PSCP) experiments with femtosecond time resolution. Investigation of this spectral dependence, which exhibits a substantial slowing of the relaxation rate γe−ph(ℏω) near the Fermi level E F , using the parametrization γe−ph(ℏω)∝λ〈Ω2〉 (ℏω−E F )2 makes it possible to determine directly the electron-phonon interaction parameter λ〈Ω2〉. The parameter λ〈Ω2〉 for YBa2Cu3O7−δ is analyzed using this method.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 19
    ISSN: 1090-6487
    Keywords: 61.72.Hh ; 74.72.Bk ; 74.80.−g ; 76.60.Gv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The NQR spectra of copper in the compounds YBa2Cu3O7, TmBa2Cu3O7, and Y0.9Pr0.1Ba2Cu3O7 at temperatures of 4.2–200 K are investigated by a pulsed NQR technique at frequencies of 28–33 MHz. Quantitative analysis of the spectra shows that the shape of the “plane” Cu(2) spectra is well described by using a model of 1D correlations of the charge and spin distribution in the CuO2 planes (stripe correlations). In the undoped superconductors the charge-spin stripe structure moves fast in the CuO2 planes, but doping the YBa2Cu3O7 lattice with praseodymium slows this motion down.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 20
    ISSN: 1090-6487
    Keywords: 74.60.+r ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The response of YBaCuO Josephson junctions on a bicrystalline substrate to the action of microwave radiation is found to contain, besides the Josephson response, a contribution associated with the tunneling of quasiparticles through channels formed by localized states in the region of the Josephson junction. It is shown that this contribution is associated with an increase in the conduction through these channels under the action of the radiation on the junction.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 21
    ISSN: 1090-6487
    Keywords: 74.72.Bk ; 76.60.Es
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A sharp kink in the temperature dependence of the electronic spin-lattice relaxation rate near 200 K was found in the high-temperature superconductors YBa2Cu4O8 and YBa2Cu3O6+x . The effect is correlated with opening of a spin gap and microscopic phase separation.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 22
    ISSN: 1090-6487
    Keywords: 74.25.Nf ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The real and imaginary parts of the surface impedance Z s =R s +iX s of YBa2Cu3O6.95 single crystals are measured at a frequency ω/π=9.4 GHz. The quantities R s (T) and X s (T) are linear functions of temperature for T〈0.3T c (T c =93.5 K). A maximum of R s (T) and a plateau of X s (T) are observed in the interval 35〈T〈65 K. Our experimental data, just as all recent measurements of R s (T) in YBa2Cu3O6.95 single crystals in the temperature range 0〈T〈1.3T c , are described well in a two-fluid model which assumes electron-phonon scattering of quasiparticles.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 23
    Electronic Resource
    Electronic Resource
    Springer
    JETP letters 72 (2000), S. 73-76 
    ISSN: 1090-6487
    Keywords: 74.25.Fy ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Temperature dependences of the resistivity tensor components ρab and ρc were measured for YBa2Cu3O7−x single crystals with different oxygen contents. The resistivity anisotropy ρc/ρab was found to grow exponentially with decreasing temperature. The results are compared with the predictions of different models describing transverse transport in the normal state of cuprate high-T c superconductors.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 24
    ISSN: 1090-6487
    Keywords: 61.80.Hg ; 76.60.Es ; 74.72.Bk ; 74.25.Nf
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The spin-spin relaxation rate 63 T 2 −1 of 63Cu nuclei in CuO2 layers is measured in the normal and superconducting states of the compound YBa2Cu3O6.9 (T c onset =94 K) subjected to radiation-induced disordering by a fast-neutron flux Φ to T c onset =68 K (Φ=7×1018 cm−2) and T c onset 〈4 K (Φ=12×1018 cm−2). It is found that as the structural disorder increases, the contribution of the indirect spin-spin interaction 63 T 2G −1 , which is related to the value of the spin susceptibility at the boundary of the Brillouin zone of the copper planes χs(q={π/a; π/a}), decreases slightly at the transition to the superconducting state for the initial sample and remains unchanged for the weakly disordered sample. This behavior of the short-wavelength contribution to the spin susceptibility attests to the stability of the x 2−y 2 symmetry of the energy gap against structural disorder, in accordance with proposed theoretical models of Cooper pairing for high-T c cuprates.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 25
    ISSN: 1090-6487
    Keywords: 74.72.Bk ; 74.25.Ha ; 75.50.Gg ; 76.60.Gv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Copper nuclear quadrupole resonance and zero-field nuclear magnetic resonance (ZFNMR) studies of YBa2Cu3O6.5 show that a magnetic phase appears in underdoped 123 superconductors treated in ambient moist air. The studies give convincing evidence that the “empty” CuO chains play the role of easy water insertion channels. The reaction occurs first in ordered regions of the crystallites. The final product of the reaction is a nonsuperconducting antiferromagnetic compound characterized by at least two types of magnetically ordered copper ions, with ZFNMR spectra in the frequency ranges 46–96 and 96–135 MHz, respectively. Even for powder samples fixed in an epoxy resin, this reaction is found to have partially occurred after a few years.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 26
    Electronic Resource
    Electronic Resource
    Springer
    JETP letters 69 (1999), S. 392-397 
    ISSN: 1090-6487
    Keywords: 74.72.Bk ; 61.12.Ex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Reasons for critical magnetic scattering of neutrons near T c in copper oxides with CuO2 layers whose nearest environment has no “up-down” symmetry are discussed. The intracrystalline electric field, which threads the CuO2 planes on account of the asymmetry, induces coupling between the spin and momentum of the current carriers. This coupling is shown to result in a manifestation of virtual Cooper pairs in the imaginary part of the spin susceptibility. Thus spin density fluctuations as well as current fluctuations should participate in the scattering. A way of experimentally distinguishing between the two mechanisms is pointed out.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 27
    ISSN: 1090-6487
    Keywords: 61.50.Ks ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract High-precision x-ray crystallographic studies of YBa2Cu4O8 single crystals (T c =70 K) are performed at eight temperatures in the interval 20–295 K. It is found that a number of structural parameters exhibit anomalous behavior near the superconducting transition of the crystal. A characteristic effect near the phase transition is the displacement of the O1 bridge atom that joins the Cu1 atom of the cuprate chain to the Cu2 atom of the cuprate plane. The shift of this oxygen toward the Cu2 atom is indicative of a change in the Cu2-O1 chemical bond and of charge transfer to the cuprate plane in the process of the transition of the crystal to the superconducting state.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 28
    ISSN: 1090-6487
    Keywords: 74.25.Jb ; 74.25.Gz ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Solutions of the integral equations for the pseudogap in the elementary excitation spectrum of current carriers in bilayer cuprates are found. In the general case, the pseudogap possesses s + id symmetry, where the s component is determined by the interaction of holes via the phonon field and the d component is due to the superexchange interaction of the copper spins and the Coulomb-repulsion screened holes. The s and d components exhibit different temperature dependences. This fact enabled us to explain the characteristic features of the temperature behavior of the normal-phase spin susceptibility of lightly doped cuprates, specifically, for the compound YBa2Cu4O8 in the entire temperature interval T〉T c . The wave-number dependence of the pseudogap agrees with the photoemission data for Bi2Sr2CaCu2O8+y .
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 29
    ISSN: 1090-6487
    Keywords: 61.72.Hh ; 74.72.Bk ; 74.80.Bj ; 76.60.Lz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The nuclear magnetic relaxation of 169Tm in TmBa2Cu3O6+x (x=0.1–1.0, Δ x=0.1) and TmBa2Cu4O8 is studied at temperatures below 5 K. In all the samples, the Tm spin-lattice relaxation proceeds via intrinsic paramagnetic centers (PCs) like Cu2+ or copper-oxygen spin-polarized clusters. The experimental data for TmBa2Cu3O6+x support the idea of the structural (chemical) micro-phase separation in oxygen-deficient 123 compounds. Apparently, the samples with x⩾0.4 contain hole-poor nonsuperconducting regions, enriched with PCs, and hole-rich (PC-poor) superconducting regions. The volume fraction f n of the PC-rich phase reaches a maximum value of 0.85 at x=0.4 and decreases monotonically with increasing x (f n=0.5, 0.3, and 0.25 at x=0.5, 0.6, and 0.7, respectively). The Tm spin-lattice relaxation in the underdoped TmBa2Cu4O8 compound indicates that this sample, in contrast to oxygen-deficient TmBa2Cu3O6+x , has a homogeneous composition. However, the Tm spin-spin relaxation measurements reveal two sorts of the Tm nuclear spins in Tm124, having different NMR spectra and different relaxation times T 2. The latter result is evidence of electronic phase separation in CuO2 phases.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 30
    ISSN: 1090-6487
    Keywords: 74.72.Bk ; 75.60.Ej ; 74.25.Ha
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Magnetization oscillations due to the commensurability of the vortex and crystal lattice periods in YBa2Cu3Oy (y=6.97±0.02) single crystals are investigated using a high angular resolution magnetometer. A sharp peak in the temperature dependence of the oscillation amplitude as well as other features in the behavior of the oscillation amplitude and of the irreversible magnetization are observed at T f ∼60 K. It is inferred that T f is the temperature of a transition of the solid vortex state to a smectic phase.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 31
    Electronic Resource
    Electronic Resource
    Springer
    Journal of nondestructive evaluation 19 (2000), S. 43-54 
    ISSN: 1573-4862
    Keywords: Ultrasonic testing ; modeling ; anisotropy ; shear horizontal wave ; field profile ; electromagnetic acoustic transducer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Based on the description of shear horizontal (SH) wave propagation in arbitrarily oriented transversely isotropic media, radiation characteristics of ultrasonic transducers for this wave type are determined. The radiated wavefields are obtained by point source superposition, making use of an analytical relationship for the wave propagation direction as a function of the spatial coordinates. Approximate formulae are given for the radiation characteristics of circular and rectangular transducers in the far-field, which are in a form similar to the isotropic material case. Focusing on transversely isotropic weld metal specimens and unidirectional composites, numerical evaluation is performed for normal-incidence probes as well as for electromagnetic acoustic transducers.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 32
    ISSN: 1573-4994
    Keywords: Fluorescence ; anisotropy ; one-photon excitation ; two-photon excitation ; anisotropy spectra ; horse liver alcohol dehydrogenase ; time-resolved fluorescence ; proteins ; tryptophan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We examined the steady-state and time-resolved emission of liver alcohol dehydrogenase resulting from one-photon and two-photon excitation. Previous studies with one-photon excitation revealed that the two nonidentical tryptophan residues display different emission spectra and decay times. The use of two-photon excitation resulted in similar emission spectra, multiexponential intensity decays, time-resolved emission spectra, and anisotropy decays as was observed for one-photon excitation. These results suggest that both nonidentical tryptophan residues are excited to a similar extent for one- and two-photon excitation. However, the limiting anisotropy (r 0) with two-photon excitation from 585 to 610 nm is below 0.1 and appears distinct from that observed previously forN-acetyl-l-tryptophanamide.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 33
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica Sinica 15 (1999), S. 355-365 
    ISSN: 1614-3116
    Keywords: dentin ; dentin tubules ; anisotropy ; inhomogeneity ; stress-strain relations ; strength criterion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract As known, there is a large number of dentin tubules in dentin. These tubules have varying radii and are shaped into radially parallel pattern. The anisotropy of microstructure of dentin shows that dentin should be treated as a material of varying transverse isotropy. In this Part, the elastic stress-strain relations and the quadratic strength criterion are established in the form of having varying transverse isotropy, in the framework of micromechanics to take into account of the effect of the microstructures-dentin tubules. Simplified forms for isotropic and homogeneous cases, as well as the corresponding plane stress form of the stress-strain relations are also given. These theoretical models are very well supported by the experiments shown later in the continued paper (Part II).
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 34
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica Sinica 16 (2000), S. 75-82 
    ISSN: 1614-3116
    Keywords: dentin ; dentin tubule ; anisotropy ; stress-strain relations ; experiments ; digital speckle correlation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract To verify the theoretical models of varying transversely isotropic stress-strain relations of dentin established in the preceding work (Part I), we perform a set of experiments. Because of the very fine tooth size, it usually seems to be difficult to directly measure the inhomogeneous and anisotropic parameters of dentin. In this paper, by the digital speckle correlation method, tensile experiments are made on the small dentin samples either parallel or perpendicular to the dentin tubules. With the theoretically predicted elastic stress-strain relations, an optimization method is proposed to fit the strain curve adapted to the experimental data. The results show that the theoretical elastic stress-strain relations coincides very well with the experimental observations. The determined Young's modulus and Poisson's ratio of dentin matrix are 29.5 GPa and 0.44, respectively, in the optimization sense.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 35
    ISSN: 1573-2754
    Keywords: composite laminate ; anisotropy ; damage ; constitutive relation ; stiffness partition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract The study on property degradation of damaged composite laminates is extended to anisotropic laminates with matrix cracking. In (I) of the paper, an idea of “stiffness patition” is proposed to deal with the puzzle that the in-plane normal response is coupled with the shear response of the laminates. For (θ m /90 n ), laminates containing transversely cracked layers under general in-plane loading, the constitutive relations are derived and the effective stiffnesses are expressed as the function of crack density.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 36
    ISSN: 1573-7357
    Keywords: 74.72.Bk ; 72.15.−v ; 76.60.−k
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The charge and spin dynamics in PrBa2Cu4O8 are investigated by means of transport and Cu NMR measurements. The magnetoresistance was found to be very small at high temperatures and increase rapidly with decreasing temperature below ∼100 K, which may be ascribed to the dimensional crossover from one to two dimensions in the charge transport in the CuO double chains. While the NMR signal from the chain Cu sites persists down to 4.2 K without any appreciable line broadening, the signal from the planar Ce sites disappears below ∼250 K indicating the long-range antiferromagnetic order of plane Cu moments. This is consistent with the view of metallic conduction along the quasi one-dimensional CuO chains.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 37
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 359-364 
    ISSN: 1573-7357
    Keywords: 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The distribution of charge states of all atoms in the unit cell of RBa2Cu3Ox; x=6,7 (R = Yb, Er, Ho, Y, Gd, Eu, Sm, Nd, Pr) is determined on the basis of comparison of the theoretical calculated electric field gradient tensor and existing experimental data. The variation of the charge states of the atoms as a function of the ionic radius is analyzed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 38
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 837-842 
    ISSN: 1573-7357
    Keywords: 74.72−h ; 74.72.Bk ; 87.64.Bx ; 74.25.Kc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have performed inelastic neutron scattering and total neutron scattering experiments on the under-doped superconductor YBa2Cu3O6.6. We have found that the dynamical structure and the local structure concerned about the CuO2 plane has an anomalous temperature dependence at Tc (=57K) and well above Tc (TSG∼150K), which may be explained by a spin-gap opening.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 39
    ISSN: 1573-7357
    Keywords: 74.60Jg ; 74.72.Bk ; 74.76.Bz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Epitaxial YBa2Cu3O7−δ films nucleate in c-axis oriented single-crystalline islands. The surface of the single-crystalline SrTiO3 substrates exhibit steps of one third of the YBa2Cu3O7−δ c-axis. These steps generate a mismatch in the island boundaries between the CuO2 superconducting blocks. We show that these defect regions are strong candidates for being the pinning centers responsible for the large critical currents observed in Laser Ablated and Sputtered thin films.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 40
    ISSN: 1573-7357
    Keywords: 74.25.Bt ; 74.25.Fy ; 74.62.Dk ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements of the anisotropic electrical resistivity, the Hall Effect, and the specific heat anomaly at Tc of Ca-doped YBa2Cu3Ox single crystals of various Ca and O contents are presented. The transport properties are discussed in terms of charge and spin separated quasiparticles and confirm that by doping Ca onto Y sites the hole concentration, nh, can be extended beyond the value achieved with O-doping alone at x=7.0. The jump in the specific heat at Tc which increases monotonously with x up to x=7.0 in Ca-free crystals displays a maximum in highly oxygenated Ca-doped crystals. This maximum, however, is displaced from the Tc(nh) maximum to higher values of nh, consistent with the model of induced superconductivity in the CuO chains.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 41
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 807-812 
    ISSN: 1573-7357
    Keywords: 74.72.Bk ; 74.25.Ke ; 63.20.Kr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Inelastic neutron experiments confirm the previously reported anomalous nature of the planar oxygen bond-stretching vibrations and furnish further details. It is shown that the frequency of the linear breathing mode is renormalized by 5 THz compared to insulating YBa2Cu3O6. Studies of the Cu1-apical O bond-stretching vibrations demonstrate that frequencies, line-widths and phonon intensities can well be understood within the framework of a harmonic lattice dynamical model. This rules out predictions of a double well potential and strong anharmonitity for this type of vibration.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 42
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 831-836 
    ISSN: 1573-7357
    Keywords: 61.85.+p ; 74.20.Mn ; 74.25.Kc ; 74.62. Bf ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Backscattering yields in the 〈001〉 axial channeling mode using D+ ions have been measured for YBa2Cu3O7−y single crystals with Tc=59K. 68K and 91K at temperatures between 40K and 295K. In 60 K-class YBa2Cu3O7−y with significant anomalies associated with the spin gap, it is found that the channeling anomalies are observed at 130–140 K(Tpa) in addition to anomalies at Tc. The channeling anomalies at Tc follow to the shift of Tc, suggesting the phonon anomalies induced by the superconducting-gap opening. On the other hand, Tpa is found to be almost unchanged for varying Tc, although Tpa appears near the temperature where the spin gap is opened. This leads a question whether the channeling anomalies at Tpa is directly related to the phonon anomalies induced by the spin-gap opening. The existence of lattice instability is suggested as one of possible explanations for the anomalies at Tpa.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 43
    ISSN: 1573-7357
    Keywords: 74.60.Ge ; 72.15.Lh ; 74.72.−h ; 72.15.Gd ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The “washboard frequency” ω of the moving vortex lattice in untwinned YBa2 Cu3 O6.93 may be observed through mode-locking to an externally applied ac current of frequency ωext. The interference between ω and ωext results in jumps in the dc current-voltage characteristics when ω and ωext are harmonically related1. The interference effect disappears in the vortex liquid state. The Hall conductivity σxy below Tc in YBCO contains contributions2 from a positive quasiparticle (qp) term (∼H) and a negative vortex term (∼1/H). The qp term is surprisingly large well below Tc and implies a large gap anisotropy and a long qp mean free path (mfp). The thermal Hall effect3 κxy is closely related to the qp σxy; κxy is produced by asymmetric scattering of qp by pinned vortices. The qp mfp at H = 0, extracted from σxy and extended to low T by κxy, increases remarkably from 90 Å at Tc to more than 0.5μm at 22 K.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 44
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 99 (1995), S. 205-221 
    ISSN: 1573-7357
    Keywords: 74.25.Gz ; 74.72.Bk ; 78.30.Er ; 71.25.−s
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Raman scattering by electronic excitations in normal and superconducting metals with complex Fermi surfaces is discussed. The theoretical results are applied to the case of high Tc superconductors. The possible implications of measurements of this scattering concerning the symmetry of the gap function is dealt with.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 45
    ISSN: 1573-7357
    Keywords: 73.50.Pz ; 74.50.+r ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Experiments of persistent photoinduced enhancement of the Josephson effect in YBaCuO junctions are reviewed in this paper. These experiments show that the critical current and the conductivity of these Josephson junctions can be increased after illumination. This effect is due to photodoping of the oxygen depleted region in the weak link.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 46
    ISSN: 1573-7357
    Keywords: 74.72.Bk ; 74.50.+r ; 74.80.Fp ; 73.40.Cg ; 73.40.Gk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have investigated a change of electrical properties of YBa2Cu3O7−δ/metal point contact immediately after its preparation depending on time, temperature as well as external bias voltage. The increase of the point contact differential resistance in time was experimentally observed at temperature above 200 K even if no external bias voltage was applied. The low external bias voltage considerably influences the time increase of the differential resistance indicating an important role of oxygen diffusion. It is shown on differential characteristics that for Au, In the parameters of tunneling barrier such as the average height and width are constant in time whereas for Al, Pb an evolution of the tunneling barrier was observed because of oxidation of Al and Pb. Applying of higher bias voltage (up to 1 V) enables the transport of oxygen even below 200 K (down to 4.2 K) and changes the electrical properties of YBCO/metal point contact interface. The differential characteristics change their behaviour from that typical for NIS contact with strong tunneling barrier to NS contact with a high transparency of the interface. All the above changes are reversible upon changing the bias voltage polarity.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 47
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 106 (1997), S. 447-452 
    ISSN: 1573-7357
    Keywords: 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract AC and DC virgin magnetizations of sintered YBa2Cu3O7−x samples have been measured in dependence of the sintering temperature. The samples were prepared by solid state reaction of stoichiometric decarbonated mixture of Y2O3, BaCO3 and CuO components. Magnetization curves were measured at 77K in the range of magnetic field (10−1−2×104 Am −1). The temperature of sintering was being changed in the range 910°C up to 950°C. In the range of weak magnetization fields the magnetization curves are affected by properties of the intergranular medium — the intergranular weak links. The parameters H 1 w1 , H 2 w1 and H 1 g characterising the flux penetration into intergrain and intragrain medium were estimated from the magnetization measurements.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 48
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 106 (1997), S. 469-474 
    ISSN: 1573-7357
    Keywords: 74.80.Bj ; 74.72.Bk ; 74.50.+r ; 78.70.Gq
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The results of measurements of the H-modulated microwave absorption of of YBa2Cu3O7 ceramic in the transition temperature region and with fields in the range 0–10 kOe are presented. They give clear evidence of the weak-link inter-grain nature of the gross part of the dissipation and support the idea of stronger links, or microbridges of a more intrinsic species, involved in the high-field intra-grain absorption component. A semiquantitative analysis of the absorption process is suggested and applied to the derivative spectra in the T-swept form (at fixed external field). It allows to deduce information about Tc, the superconductive coupling, and the H- and T-dependences of the critical currents involved in the inter- and intra-grain regions. When applied to YBa2Cu3O7 powders, obtained by finely grinding a ceramic pellet, it gives also evidence of a generalized suppression of coupling induced by the grinding process
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 49
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 106 (1997), S. 487-492 
    ISSN: 1573-7357
    Keywords: 74.25.Nf ; 74.60.Ge ; 74.72.Bk ; 78.70.Gq
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The recent experimental data by I. S. Ghosh et al. (1994) on microwave losses induced by flux motion in YBCO thin films are discussed, which seem to contradict a generalized use of the surface resistance model proposed by Coffey and Clem (1992) in the field range 0–8 Tesla. It is found that the necessary condition, in order to reproduce the upward curvature vs. field observed for B‖BMW‖ film surface, is to assume that the Campbell penetration depth is governed by a critical field dependence reminishent of the well known Bc∝(1−t)3/2 expression. Nevertheless, the experimental data for the perpendicular case B⊥BMW and the behaviours in very low fields for both orientations cannot be satisfactorily explained in this view. It is shown that the discrepancies may be rationalized in a quite natural way as due to losses in a network of Josephson junctions of an intrinsic species, located in the intragrain region of the film.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 50
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 377-382 
    ISSN: 1573-7357
    Keywords: 74.20.Mn ; 25.40.Fq ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Key features of Inelastic neutron scattering experiments in YBCO-based cuprates are discussed. We underline the importance of precise oxygen content determination in samples having similar TC as well as the resolution configuration used. This may explain the apparent contradictory results recently obtained by different groups.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 51
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 773-778 
    ISSN: 1573-7357
    Keywords: 78.30.Hv ; 74.72.Bk ; 74.25.Gz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Dense polycrystalline samples of YBa2Cu3O7−δ with a high degree of c-axis texture in the plane of the sample were prepared by magnetic alignment. The c-axis infrared reflectivity was measured between 300 and 6K on polished surfaces. Spectra compare well with measurements on single crystals indicating that magnetically aligned samples are a reliable alternative to single crystals for c-axis measurements.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 52
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 483-488 
    ISSN: 1573-7357
    Keywords: 74.20.De ; 74-50.+r ; 74.72.Bk ; 74.62.Bf
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A macroscopic symmetry group describing the superconducting state of an orthorhombically twinned crystal of YBCO is introduced. This macroscopic symmetry group is different for different symmetries of twin boundaries. Josephson tunneling experiments performed on twinned crystals of YBCO determine this macroscopic symmetry group and hence determine the twin boundary symmetry (but do not experimentally determine whether the microscopic order parameter is primarily d- or s-wave). A consequence of the odd-symmetry twin boundaries in YBCO is the stability of 1/2 Φo vortices at the intersection of a twin boundary and certain grain boundaries.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 53
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 681-686 
    ISSN: 1573-7357
    Keywords: 74.25.Fy ; 74.25.Ha ; 74.40.+k ; 74.50.+r ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this paper we summarize some of our theoretical results for the paraconductivity and for the fluctuation-induced in-plane magnetoconductivity in the weak magnetic field limit of layered superconductors with several interlayer separations. Also, we briefly discuss the existing experimental data obtained in untwinned Y Ba2Cu3O7-δ crystals.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 54
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 743-748 
    ISSN: 1573-7357
    Keywords: 74.72.Bk ; 74.25.Gz ; 74.62.Dh
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Zn-substitution effects on the c-axis optical spectra have been investigated for highly oxygenated YBa2 Cu3Oy crystals with y = 6.88 – 6.92. In the normal state, the Zn-substitution does not affect the high frequency conductivity but changes the ω-dependence of the scattering rate at low frequencies, leading to the increase in the dc resistivity in the c-direction. In the superconducting state, we observed a pronounced effect of Zn-substitution that a large number of unpaired carriers form a Drude-like absorption band within the gap, keeping the maximum gap amplitude unchanged. The missing area which gives the superfluid density is found to correlate with Tc.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 55
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 779-784 
    ISSN: 1573-7357
    Keywords: 74.25.Gz ; 74.72.Bk ; 78.30.Er ; 63.20.Kr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Performing optical reflectivity measurements with the electric field vector parallel to the c-axis of Zn-substituted, oxygen deficient YBa2Cu3Oy single crystals, we find a strong Zn-substitution effect on the anomaly of the inplane oxygen bending mode at 320 cm−1 and the new absorption band at 450 cm−1, which are observed in underdoped, non-substituted crystals. Contrary to that, the low-frequency suppression of the conductivity is almost not affected. We conclude that the phonon anomaly and the absorption band are related to each other, but that the suppression of the conductivity is an independent phenomenon. Moreover, the present work could be strong evidence for a model where some phonons couple to antiferromagnetic fluctuations at the (π, π)-point leading to anomalous behaviour of these phonons when a spin gap opens.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 56
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 1099-1104 
    ISSN: 1573-7357
    Keywords: 74.25.Bt ; 74.60.Ge ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract High resolution adiabatic specific heat experiments on YBa2Cu3O7−δ (0≤δ≤0.05) are performed in magnetic fields from 0 to 14 T (B∥c and B⊥c). In a 0.3 gram, twinned crystal with strong pinning, a step is consistently observed at the melting temperature Tm of the vortex solid up to a critical point that depends on δ. The field Bm and step temperature Tm obey the relation Bm=Bmo(δ)(1−Tm/Tc)≈4/3. The anisotropy of Bm and that of the upper critical field Bc2 are found to be equal. Alternatively, in a 18 mg, twinned crystal of high purity with low pinning, first-order-like specific heat peaks are observed on the melting line from 8 to 14 T. The entropy under these peaks is ≈0.5 kB /vortex/bilayer. These characteristic features are attributed to the melting of a vortex glass in the former case and that of a vortex lattice in the latter case.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 57
    ISSN: 1573-7357
    Keywords: 76.60.Ge ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The interplane (cb) and intraplane (ab) anisotropy of untwinned YBa2 Cu307 single crystals has been investigated by means of the torque magnetometry. To extract the reversible and irreversible components, the torque was measured as a function of increasing angle as well as decreasing angle. The interplane irreversible torque Γirr shows two-fold peaks at θc =90 ° and270 ° (of half width11 ° at77 K) due to the well-known intrinsic interplane pinning. A novel intrinsic pinning has been discovered in the intraplane irreversible torque, i.e., Γirr shows four-fold peaks of half width20° at77 K when θa =0 °, 90 °, 180 ° and270 °. We argue that the intrinsic intraplane pinning comes from the four-fold nature of the gap parameter.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 58
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 107 (1997), S. 467-472 
    ISSN: 1573-7357
    Keywords: 74.25.Fy ; 74.72.Bk ; 74.25.Jb
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The characteristic enhancement in the heat conduction below Tc is analyzed on sintered YBa2Cu3O7 from viewpoints of both d-wave and s-wave coupling. Assuming the existence of a large energy gap Δ0(≥1.5Δ BCS ), only d-wave coupling is consistent with experimental observation. It is found that the most reasonable explanation for the enhancement is provided by the weak-coupling phonon conduction model under d-wave energy gap.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 59
    ISSN: 1573-7357
    Keywords: 74.60.Ge ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Real part of the ac susceptibility X′1 of an untwinned YBa2 Cu3O7 single crystal jumps at the onset temperature in the narrow width (0.1 K in 0.7 T), suggesting the first-order melting transition. A sharp X′1 dip and a sharp X″ peak can be interpreted as synchronous trapping of vortices due to lattice softening prior to melting. At lower temperatures, the X′1-X″1 chart shows a single-parameter behavior while the melting occurs as a strong deviation from this.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 60
    ISSN: 1573-7357
    Keywords: 74.25.Fy ; 74.40.+k ; 74.60.Ge ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Pinning by point-like defects and twin boundaries in single-crystalline YBa2Cu3O7−δ has been investigated by measuring resistance and current-voltage characteristics in fields up to 5 T. A number of untwinned and twinned samples with different densities of point-like defects were studied. The experimental results are compared within the framework of vortex-entanglement.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 61
    ISSN: 1573-7357
    Keywords: 73.50.Jt ; 73.5O.Pz ; 74.72.Bk ; 74.76.Bz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report on in-situ resistivity and Hall-effect studies of partially oxygen-depleted YBa2Cu3Ox thin films during white light illumination. The measurements were performed at various temperatures between the superconducting transition and room temperature. At all temperatures the resistivity and the Hall coefficient decreased as a function of the illumination time. The Hall number pH and the Hall mobility μH, calculated within a simple one-band model, showed an increase of pH during the illumination without a saturation. At low temperatures, μH behaved similarly to pH. At 200 K, however, μH became constant after several hours of illumination, while at 260 K and 290 K, we observed a short increase of μH followed by a long-term decrease. From the different time dependences of μH and pH, we conclude that two mechanisms contribute to the photodoping effect. Additionally, we observed that after termination of the illumination at 290 K the photodoped values of pH and μH relaxed with substantially different time constants.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 62
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 1129-1134 
    ISSN: 1573-7357
    Keywords: 74.60.Ge ; 71.20.−b ; 74.50.+r ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Scanning Tunneling Spectroscopy (STS) measurements have been carried out on the high Tc superconductor (HTS) YBa2Cu3O7−δ (YBCO). Using very high quality single crystals as well as hard tips, we obtained differential conductance spectra which showed various conductance features in agreement with other spectroscopic techniques. The reproducibility of our spectra allowed us to map for the first time the vortex lattice on a HTS using a STS technique1. The vortices are arranged in a short range order oblique lattice, while the cores of the flux lines show an anisotropic shape. These observations can be related to the in-plane anisotropy of YBCO.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 63
    ISSN: 1573-7357
    Keywords: 74.25.Fy ; 74.40.+k ; 74.60.Ge ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Magnetotransport measurements on a clean, untwinned YBa2Cu3O7−δ single crystal show that the vortex dynamics at temperatures just below the vortex lattice melting transition are highly dependent on the type of modulation of the probing current. While in the case of DC current the flux flow is disordered, the “shaking” of the vortex lattice by a square-wave current leads to a more uniform vortex motion. A small asymmetry (∼10%) in the durations of the positive and negative parts of the square-wave period induces periodical oscillations of the voltage response amplitude. The period of oscillations (∼100 s) is the same order of magnitude as the time needed for vortices to cross the sample (transit time). We relate the observed voltage oscillations to a periodically ordered vortex motion.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 64
    ISSN: 1573-7357
    Keywords: 74.50.+r ; 74.72.Bk ; 74.76.Bz ; 85.25.Cp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements of the field-modulated critical currents of cuprate thin film microbridges on tricrystal substrates are reported. Two central peaks of equal height are observed in the field-dependent critical currents of YBCO tricrystal microbridges. However, the critical current is nonvanishing at zero field for YBCO, consistent with an orthorhombically distorted d-wave order parameter. An ion-irradiated YBCO tricrystal microbridge has also been measured, and has been found to exhibit more ideal dx2−y2-like behavior with increasing irradiation dosage.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 65
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 1421-1426 
    ISSN: 1573-7357
    Keywords: 74.72.Bk ; 74.60.Jg ; 74.80.Bj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The preparation of a long superconducting Y123 filaments is developed by using solution spinning for the precursor of the oxide. Long precursor filaments are prepared by dry spinning with a starting homogeneous aqueous PVA solution containing Y, Ba and Cu acetates. The as-drawn filament with 250 μm in diameter and 300 mm in length is pyrolyzed and partial-melted by using a tube furnace with a constant heating zone of 500 mm. A superconducting filament of 60 μm in diameter and 200 mm in length with high Jc of more than 104A/cm2 at 77 K and 0 T is obtained by controlling the partial melting.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 66
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 107 (1997), S. 445-454 
    ISSN: 1573-7357
    Keywords: 74.72.Bk ; 74.60. Ge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An unambiguous determination of the pairing symmetry in cuprate superconductors is important in order to understand the origin of high-temperature superconductivity. By making use of the effects of pair tunneling and flux quantization, we have designed and implemented several tricrystal experiments for phase-sensitive determination of the order parameter symmetry in high-Tc superconductors such as YBa2Cu3O7 Tl2Ba2CuO6, GdBa2Cu3O7, and Bi2Sr2CaCu2O8. By using a high-resolution scanning SQUID microscope, we have made the first direct observation of spontaneously generated half-flux quanta at the tricrystal point. The half-integer flux quantum effect in various specially designed tricrystal cuprate systems provides strong evidence for d-wave pairing in high-Tc cuprates. Our various tricrystal experiments have demonstrated that this effect can be used as a general probe of the microscopic phase of the pair wavefunction in unconventional superconductors.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 67
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 96 (1995), S. 319-324 
    ISSN: 1434-6036
    Keywords: 74.72.Bk ; 74.62.Bf ; 74.72.Dh ; 74.25.Fy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The aim of this paper is to study the influence of non-isovalent “doping” in YBa2Cu3O7−y in particular on its synthesis conditions and on the resistive properties both with and without a magnetic field. We concentrate on the study of possible alkali ions (Na, K, Cs) “substitution” at the barium sites. A low temperature sintering process is used in order to induce a reactive liquid phase. The final chemical composition is discussed as a function of the amount of the liquid phase. No alkali ion is substituted. Carbonate layers are present. However, this (lack of) “substitution” leads to induced vacancies and improved electrical transport properties which are as good as in highly pure materials. For conciseness the case of Na “substitution” only is illustrated. The use of such data in order to probe the microstructure is emphasized.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 68
    ISSN: 1434-6036
    Keywords: 74.25.Fy ; 74.40.+k ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have investigated both the transverse and the longitudinal magnetoresistance of oxygen-deficient YBa2Cu3O7−δ thin films above their critical temperatureT c =55 K. The magnetoresistance is solely caused by the magnetic-field suppression of superconducting orderparameter fluctuations, existing in the films up to 143 K, i.e. 2.6T c . The fluctuation effect provides a reliable determination of the Ginzburg-Landau coherence lengths, ξ ab = 2.5 nm and ξ c = 0.09 nm, with the anisotropy enhanced by oxygen depletion. No signature of the Maki-Thompson fluctuation process or a magnetoresistance resulting from the cyclotron motion of the normalstate quasiparticles was found.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 69
    Electronic Resource
    Electronic Resource
    Springer
    Journal of superconductivity 13 (2000), S. 995-998 
    ISSN: 1572-9605
    Keywords: disordered ; pseudogap ; superconductors ; cuprates ; anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We consider underdoped cuprates as disordered conductors. The diffusion coefficient D can be as low as 10−5 m2 s−1. In these conditions, Coulomb interaction between electrons must be taken into account. The main effect is to open a dip and even a gap in the density of state (DOS) near the Fermi level (FL). We show that this model explains most of the observed features of the so-called pseudogap in the normal state and in particular its value, anisotropy, and variation with doping.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 70
    Electronic Resource
    Electronic Resource
    Springer
    Journal of superconductivity 12 (1999), S. 511-514 
    ISSN: 1572-9605
    Keywords: Organic superconductors ; BETS ; superconductivity ; critical field ; anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The upper critical field B c2 of the organic superconductor λ-(BETS)2GaCl4 has been determined from resistance measurements for orientation of the magnetic field along three perpendicular crystallographic directions. The Ginzburg–Landau coherence length was estimated from the slope of B c2(T) curve near T c as 12.5 nm, 1.6 nm, and 12.5 nm for the a*-, b*-, and c-directions. Angular dependence of the critical field within highly conducting ac plane at 1.5 K was shown to possess two-fold symmetry, which can be related to the band structure anisotropy.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 71
    ISSN: 1572-9605
    Keywords: Bi2Sr2CaCu2O10/Ag ribbons ; I–V characteristics ; flux creep ; anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Current-voltage characteristics of high-critical-current Bi2Sr2CaCu2O10/Ag ribbons were measured using both transport and magnetization techniques. The slope of these curves changes with magnetic field and temperature in a way very similar to the observedj c (H, T) behavior. This correspondence between the critical current and the slope of theI–V characteristics can be explained within the thermally activated flux creep framework. The dependence ofj c on the angle between field and ribbon is compared to the existing intrinsic anisotropy models.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 72
    ISSN: 1572-9605
    Keywords: High-T c superconductivity ; Pb2Sr2Ho0.5Ca0.5Cu3O8 ; single crystal ; upper critical magnetic field ; anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Anisotropie properties of the single crystal Pb2Sr2Ho0.5Ca0.5Cu3O8 have been investigated by measuring the electrical resistivity in theab-planeρ ab (H, θ,T), which depends on the angleθ between theab-plane and the magnetic-field direction, in various constant fieldsH perpendicular to the current direction. All the angle-dependent values ofρ ab (H, θ,T) at a constant temperature are scaled to be on one curve as a function of reduced field. The anisotropic parameter γ≡(m c * /m ab * )1/2 is estimated as 12–13, which is larger than that of YBa2Cu3O7 and much smaller than that of Bi2Sr2CaCu2O8. It has been concluded that the anisotropy does not always depend on the thickness of the blocking layer but seems to depend on the overlap of the electronic wave functions along thec-axis. Anisotropy in the pinning potential has also been discussed from the resistive tail in the temperature dependence ofρ ab (H,θ,T).
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 73
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 78 (1995), S. 963-970 
    ISSN: 1572-9613
    Keywords: Stochastic spin systems ; majority vote models ; anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A majority vote model subject to anisotropic voting rules is studied in two dimensions using a first-order mean-field approximation and Monte Carlo simulations. The critical behavior is consistent with the 2D Ising universality class.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 74
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 87 (1997), S. 63-89 
    ISSN: 1572-9613
    Keywords: Ising model with general spin flip dynamics ; interfaces ; anisotropy ; motion by curvature ; Kubo-Green formulas for mobility and surface tension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We study Ising models with general spin-flip dynamics obeying the detailed balance law. After passing to suitable macroscopic limits, we obtain interfaces moving with normal velocity depending anisotropically on their principal curvatures and direction. In addition we deduce (direction-dependent) Kubo-Green-type formulas for the mobility and the Hessian of the surface tension, thus obtaining an explicit description of anisotropy in terms of microscopic quantities. The choice of dynamics affects only the mobility, a scalar function of the direction.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 75
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 86 (1997), S. 1153-1162 
    ISSN: 1572-9613
    Keywords: Potts model ; corner exponents ; anisotropy ; length rescaling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The critical behavior at a corner in two-dimensional Ising and three-state Potts models is studied numerically on the square lattice using transfer operator techniques. The local critical exponents for the magnetization and the energy density for various opening angles are deduced from finite-size scaling results at the critical point for isotropic or anisotropic couplings. The scaling dimensions compare quite well with the values expected from conformal invariance, provided the opening angle is replaced by an effective one in anisotropic systems.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 76
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 95 (1999), S. 1245-1280 
    ISSN: 1572-9613
    Keywords: anisotropy ; surface energy ; diffuse interface model ; phase-field model ; stress tensor ; equilibrium shapes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this paper we review two important theoretical areas to which J. W. Cahn has made major contributions: (i) The theory of the ξ-vector developed by Hoffman and Cahn, which provides an elegant setting for the description of the equilibrium shapes of sharp interfaces in the presence of anisotropic surface energy. (ii) Diffuse interface theories of phase transitions. We describe recent work which connects these two complementary facets of models of interfaces by the development of a generalized ξ-vector for diffuse interface models with anisotropic surface energy. We show that the generalized ξ-vector plays a central role in both the mathematical and physical aspects of a wide range of diffuse interface theories of interfaces with either anisotropic surface energy or attachment kinetics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 77
    ISSN: 1572-9605
    Keywords: High-temperature superconductors ; single crystal ; anisotropy ; resistivity ; thermoelectric power ; narrow-band model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The anisotropy of the resistivity and thermoelectric power (TEP)S of Nd1.85Ce0.15CuO4−δ single crystal (T c =17 K) has been investigated. In the temperature rangeT c 〈T〈300 K the ratioρ c/ρab≈104 and the dependencesρ ab (T) andρ c (T) change from quadratic to linear atT∼200 K. The dependencesS ab (T) andS c (T) reach a maximum atT〉T c and then decrease almost linearly with increasing temperature, changing sign from positive to negative nearT∼ 150 K. The features of the resistivity and TEP temperature dependences (the lawρ∝T 2 changing toρ∝T, the change in the sign of S with temperature, and the low TEP anisotropy at largeρ anisotropy) have been interpreted in the framework of the narrow-band model.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 78
    ISSN: 1572-9605
    Keywords: Kondo model ; anisotropy ; Fermi-liquid to non-Fermi-liquid behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We discuss the behavior of the two-channel Kondo model with channel anisotropic exchange couplings by using our recent solution of the model. This solution provides an analytic description of the interesting cross-over from a high-temperature regime, dominated by the non-Fermi-liquid behavior of the isotropic two-channel Kondo model, to a low-temperature regime characterized by the standard Fermi-liquid behavior of the single-channel Kondo model.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 79
    Electronic Resource
    Electronic Resource
    Springer
    Journal of superconductivity 9 (1996), S. 481-484 
    ISSN: 1572-9605
    Keywords: YBa2Cu3O7 −δ ; single crystal ; resistivity ; anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We have measured the in-plane longitudinal resistivitiesρ a andρ b as functions of temperature and magnetic field. The measurements were all made on the same detwinned single crystal of YBa2Cu3O7 −δ (YBCO). DefiningT c to be at the onset of resistance, it is the same forρ a andρ b in a magnetic field ranging from 0 to 3.5 T. In zero field,T c = 93.4 K, so the oxygen doping of the crystal was approximately optimal. In the mixed state, the anisotropy ratio of the resistivities (ρ a/ρb) decreases with decreasingT orH, and the chain conductivity (σ b-σa) is smaller than the plane conductivity (σ a). Bothσ a andσ b increase with decreasing temperature, and so does (σ b-σa).
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 80
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 19 (1998), S. 625-636 
    ISSN: 1572-9567
    Keywords: anisotropy ; modulated photothermal techniques ; polymer–carbon composites ; thermal diffusivity tensor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermal diffusivity tensor of a polymer–carbon fiber composite with unidirectionally distributed fibers has been measured using a modulated photothermal mirage device. The thermal diffusivity along the fibers is k ∥=6.0±0.5 mm2·s−1, that perpendicular to the fibers is k ⊥=0.35±0.05 mm2·s−1, and that perpendicular to the sample surface is k z=0.40±0.15 mm2·s−1. These results have been confirmed by independent measurements on the sample by other laboratories using three other different photothermal techniques. A previous claim on anomalous results found on this sample (k ∥〈k ⊥ and high thermal diffusivities) can be explained by the inappropriate use of the frequency range. We have also found that there is not perfect thermal contact between the fibers and the matrix, which can be characterized by the thermal contact resistance of R th=(9±2)×10−6m2·K·W−1.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 81
    Electronic Resource
    Electronic Resource
    Springer
    International journal of infrared and millimeter waves 21 (2000), S. 2023-2033 
    ISSN: 1572-9559
    Keywords: anisotropy ; Back-to-Back ; CMB ; corrugated ; gaussian ; profile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Novel corrugated horn have been modelled, manufactured and measured which give low-sidelobe patterns required by CMB Anisotropy experiments. These horns have a Back-to-Back structure with mode filtering at their centres. They are corrugated to give axial symmetric low-sidelobe patterns, profiled to reduce their length, and have a Gaussian flare at their entrance apertures to further suppress sidelobes to -40dB. Modelling and experimental results show excellent agreement to well below 50 dB.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 82
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 17 (1996), S. 1113-1124 
    ISSN: 1572-9567
    Keywords: anisotropy ; forced Rayleigh scattering method ; polymer melt ; thermal diffusivity ; transient behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Molecular orientation of polymer molecules created by shear force due to the flow of the polymer melt in a duct rapidly relaxes after the change in the shear rate. This relaxation causes the changes in anisotropic behavior of mechanical. thermal, and optical properties which have strong effect in precision forming of casted polymer products. Among these properties, thermal diffusivity is one of the most difficult properties to measure by the conventional techniques. The present paper describes and discusses the subsecond measurement of relaxation characteristics in thermal dilfusivity anisotropy of flowing polymer melt in conjunction with measurements of some typical flow characteristics. The method used was the forced Rayleigh scattering method, an optical method which was developed and modified by the authors' group for applying to oriented polymer materials. The measuring lime of I ms can trace the relaxation occurred in the order of several seconds. Measured results of thermal diffusivity anisotropy were compared with transient characteristics of the now and quantitatively showed a good agreement with estimated behavior of oriented polymer molecules.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 83
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 21 (2000), S. 1473-1483 
    ISSN: 1572-9567
    Keywords: anisotropy ; Bethe lattice ; semiflexible polymer ; statistical mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A combinatorial method to calculate the mean square end-to-end distance 〈R 2〉 of a polymer on a Bethe lattice is used. The case of an anisotropic lattice and semiflexible polymers is considered. The distance on the Cayley tree is defined by embedding the tree on an N-dimensional Euclidean space considering that every bend of the polymer defines a direction orthogonal to all the previous ones. The semiflexible polymer is effectively equivalent to a flexible one if one considers an effective (noninteger) coordination number. Although an analytical calculation is performed, a closed expression for 〈R 2〉 is possible only for the isotropic case. Numerical results are shown for the anisotropic case. Plots of 〈R 2〉 against N for different values of the anisotropy parameter y are shown. The power dependence for N does not depend on the anisotropy as expected, but the linear coefficient increases on increasing the anisotropy. The anisotropy tends to stretch the polymer.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 84
    Electronic Resource
    Electronic Resource
    Springer
    General relativity and gravitation 32 (2000), S. 1255-1269 
    ISSN: 1572-9532
    Keywords: Gravitation ; cosmology ; anisotropy ; above-barrier reflection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The classical and quantum evolution of an anisotropic cosmological Bianchi type I model is considered. In the classical case, the influence of the minimally coupled scalar field is taken into account. Thus the system of two equations is obtained, which are explored at the inflationary and scalaron stages. The quantum problem in view of the positive cosmological constant is considered. The principal moment of the account of an anisotropy is the occurrence of the potential barrier unbounded in zero and at infinity. Though the greatest value of the potential is less than zero and the total energy of the Universe E=0, there is an important opportunity for above-barrier reflection of the wave function of the Universe. After reflection the wave function describes the expanding Universe promptly losing anisotropy and transferring into the Friedmann Universe.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 85
    Electronic Resource
    Electronic Resource
    Springer
    Applied mathematics and mechanics 17 (1996), S. 1067-1074 
    ISSN: 1573-2754
    Keywords: quasi-flow corner theory ; modulus reduced function ; shear band ; anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract A quasi-flow corner theory on large plastic deformation of ductile metals is proposed in this paper. From orthogonal rule of plastic flow, the theory introduces a “modulus reduced function” and a corner effect of yield surface into the constitutive model of elastic-plastic large deformation. Thereby, the smooth and continuous transitions from orthogonal constitutive model to non-orthogonal one, and from plastic loading to elastic unloading are realized. In addition, the theory makes it possible to connect general anisotropic yield functions with corner hardening effect. The comparison between numerical simulation and experimental observation for the uniaxial tensile instability and shear band deformation of anisotropic sheet metals shows the validity of the present quasi-flow corner theory.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 86
    Electronic Resource
    Electronic Resource
    Springer
    Hyperfine interactions 120-121 (1999), S. 23-30 
    ISSN: 1572-9540
    Keywords: NMR ; Co/Cu ; multilayers ; anisotropy ; 59Co
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract 59Co NMR studies of multilayers are able to give three direct pieces of information: (i) the crystal phase of Co, fcc (217.4 MHz), hcp (220–228 MHz) and in exotic cases bcc (198 MHz) for films measured at T= 4.2 K, (ii) the nature of the interfaces from low frequency satellite lines, and (iii) the strain state deduced from small changes in the line positions. Extensive studies of Co/Cu multilayer interfacial structures as a function of deposition technique, layer thickness, substrate/buffer layer structure and annealing temperature have been undertaken. This work has shed new light on the relationship between interfacial structure and magnetoresistance and in particular has demonstrated that flat, atomic scale, interfaces lead to greater magnetoresistance. The difference between the Co and Cu lattice constant results in an extensive, tensile in-plane strain developing in Co layers provided that some epitaxial registry is present. Information on strain effects can be obtained from the position and width of the NMR lines. The magnetic anisotropy field can be determined by measuring the field dependence of the enhancement effect due to electronic magnetisation. This provides unique insight into the distribution of magnetic anisotropy within the Co layers, as the enhancement can be investigated independently for each NMR line and, hence, provides environment specific information on magnetic anisotropy at the interfaces and in the interior of the layers.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 87
    Electronic Resource
    Electronic Resource
    Springer
    Applied mathematics and mechanics 21 (2000), S. 43-48 
    ISSN: 1573-2754
    Keywords: algebraic stress model ; buoyant turbulence model ; anisotropy ; X522 ; X524
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract By analyzing the components of Reynolds stresses of implicit algebraic stress model (IASM) in this paper, that Reynolds stresses in buoyant turbulent flows were produced by both strain and buoyancy is considered. Consequently, a nonlinear anisotropy buoyant turbulence model was developed by applying linearity of equilibrium hypothesis to Reynolds stress transports. The model avoids numerical singularity and its reliability is verified by the comparisons between predictions and experimental data.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 88
    Electronic Resource
    Electronic Resource
    Springer
    Journal of elasticity 47 (1997), S. 179-203 
    ISSN: 1573-2681
    Keywords: anisotropy ; linear elasticity ; fibre-reinforced ; solidification ; wrinkling ; thermo-elasticity.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This paper presents a model of solidification for a fibre-reinforced circular cylindrical channel section under plane strain. Cooling from the inside surface of a cylindrical section of the liquid phase causes a solidification front to move radially through the thickness until solidification is complete. The principal area of interest is the mechanism by which the nature of the temperature field during solidification affects the shape and residual stresses in the final solid part. A special case of the solution is presented and compared with an equivalent result in which solidification of the whole section occurs instantaneously. The mechanism is also relevant to microstructural wrinkling.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 89
    Electronic Resource
    Electronic Resource
    Springer
    Journal of elasticity 49 (1997), S. 269-284 
    ISSN: 1573-2681
    Keywords: anisotropy ; wedges ; stress singularities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A material is cylindrically anisotropic when its elastic moduli referred to a cylindrical coordinate system are constants. Examples of cylindrically anisotropic materials are tree trunks, carbon fibers [1], certain steel bars, and manufactured composites [2]. Lekhnitskii [3] was the first one to observe that the stress at the axis of a circular rod of cylindrically monoclinic material can be infinite when the rod is subject to a uniform radial pressure (see also [4]). Ting [5] has shown that the stress at the axis of the circular rod can also be infinite under a torsion or a uniform extension. In this paper we first modify the Lekhnitskii formalism for a cylindrical coordinate system. We then consider a wedge of cylindrically monoclinic elastic material under anti-plane deformations. The stress singularity at the wedge apex depends on one material parameter γ. For a given wedge angle α, one can choose a γ so that the stress at the wedge apex is infinite. The wedge angle 2α can be any angle. It need not be larger than π, as is the case when the material is homogeneously isotropic or anisotropic. In the special case of a crack (2α=2π) there can be more than one stress singularity, some of them are stronger than the square root singularity. On the other hand, if γ 〈 $$ - \frac{1}{2}$$ there is no stress singularity at the wedge apex for any wedge angle, including the special case of a crack. The classical paradox of Levy [6] and Carothers [7] for an isotropic elastic wedge also appears for a cylindrically anisotropic elastic wedge. There can be more than one critical wedge angle and, again, the critical wedge angle can be any angle.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 90
    ISSN: 1573-2681
    Keywords: anisotropy ; cubic symmetry ; discrete orientation distribution ; invariant subspace ; isotropy ; linear elasticity ; polycrystals ; Reuss average ; special orthogonal group ; Voigt average
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We consider a model for the elastic behavior of a polycrystalline material based on volume averages. In this case the effective elastic properties depend only on the distribution of the grain orientations. The aggregate is assumed to consist of a finite number of grains each of which behaves elastically like a cubic single crystal. The material parameters are fixed over the grains. An important problem is to find discrete orientation distributions (DODs) which are isotropic, i.e., whose Voigt and Reuss averages of the grain stiffness tensors are isotropic. We succeed in finding isotropic DODs for any even number of grains N≥4 and uniform volume fractions of the grains. Also, N=4 is shown to be the minimum number of grains for an isotropic DOD.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 91
    Electronic Resource
    Electronic Resource
    Springer
    Journal of elasticity 57 (1999), S. 133-155 
    ISSN: 1573-2681
    Keywords: uncoupling of displacements ; elasticity ; anisotropy ; Green's function ; dislocation ; elliptic inclusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract It was shown in an earlier paper that, under a two-dimensional deformation, there are anisotropic elastic materials for which the antiplane displacement u 3 and the inplane displacements u 1, u 2 are uncoupled but the antiplane stresses σ31, σ32 and the inplane stresses σ11, σ12, σ22 remain coupled. The conditions for this to be possible were derived, but they have a complicated expression. In this paper new and simpler conditions are obtained, and a general anisotropic elastic material that satisfies the conditions is presented. For this material, and for certain monoclinic materials with the symmetry plane at x 3 = 0, we show that the unnormalized Stroh eigenvectors a k for k = 1, 2, 3 are all real. The matrix A =[a 1, a 2, a 3] is a unit matrix when the material has a symmetry plane at x 2 = 0. Thus any one of the u 1, u 2, u 3 can be the only nonzero displacement, and the solution is a one-displacement field. Application to the Green's function due to a line of concentrated force f and a line dislocation with Burgers vector v in the infinite space, the half-space with a rigid boundary, and the infinite space with an elliptic rigid inclusion shows that one can indeed have a one-displacement field u 1, u 2 or u 3. One can also have a two-displacement field polarized on a plane other than the (x 1, x 2)-plane. The material that uncouples u 1, u 2, u 3 is not as restrictive as one might have thought. It can be triclinic, monoclinic, orthotropic, tetragonal, transversely isotropic, or cubic. However, it cannot be isotropic.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 92
    Electronic Resource
    Electronic Resource
    Springer
    Interface science 3 (1996), S. 241-267 
    ISSN: 1573-2746
    Keywords: grain boundary segregation ; grain boundary cohesion ; fracture ; kinetics ; equilibrium ; anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This feature article summarizes the present art and science of grain boundary segregation from the viewpoint of the authors activities in this field. In the part on equilibrium segregation, fundamental effects on grain boundary segregation are discussed such as the nature of the solute/matrix binary system, presence of additional elements, temperature, grain boundary orientation and type of interface. In addition, the predictive capabilities of grain boundary segregation diagrams are outlined. The present models of segregation kinetics are reviewed and discussed in connection with recent experiments. The last part of the paper is focussed on the most important consequences of grain boundary segregation, i.e., grain boundary cohesion and fracture.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 93
    Electronic Resource
    Electronic Resource
    Springer
    Journal of elasticity 46 (1997), S. 151-180 
    ISSN: 1573-2681
    Keywords: elasticity ; anisotropy ; averaging ; elasticity tensor ; compliance tensor.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A method of averaging the data on the anisotropic elastic constants of a material is presented. The anisotropic elastic constants are represented by the elasticity tensor which is expressed as a second rank tensor in a space of six dimensions. The method consists of averaging eigenbases of different measurements of the elasticity tensor, then averaging the eigenvalues referred to the average eigenbasis. The eigenvalues and eigenvectors are obtained by using a representation of the stress-strain relations due, in principle, to Kelvin [17, 18]. The formulas for the representation of the averaged elasticity tensor are simple and concise. The applications of these formulas are illustrated using previously reported data, and are contrasted with the traditional analysis of the same data by Hearmon [9]. An interesting result that emerges from this analysis is a method dealing with variable composition anisotropic elastic materials whose elastic constants depend upon the particular composition. In the case of porous isotropic materials, for example, it is customary to regress the Young's modulus against porosity. The results of this paper suggest a structure or paradigm for extending to anisotropic materials this empirical method of regressing elastic constant data against composition or porosity.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 94
    ISSN: 1573-2681
    Keywords: linear elasticities ; classical ; micropolar ; elasticity tensors ; symmetry ; anisotropy ; complex vector basis ; complex tensor.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A complete and unified study of symmetries and anisotropies of classical and micropolar elasticity tensors is presented by virtue of a novel method based on a well-chosen complex vector basis and algebra of complex tensors. It is proved that every elasticity tensor has nothing but 1-fold, 2-fold, 3-fold, 4-fold and ∞-fold symmetry axes. From this fact it follows that the crystallographic symmetries plus the isotropic symmetry are complete in describing the symmetries of any kind of classical elasticity tensors and micropolar elasticity tensors. Further, it is proved that for each given integer m〉〉2 every classical Green elasticity tensor with an m-fold symmetry axis must have at least m elastic symmetry planes intersecting each other at this symmetry axis. From this fact and the aforementioned fact it follows that for all possible material symmetry groups, there exist only eight distinct symmetry classes for classical Green elasticity tensors, which correspond to the isotropy group and the seven crystal classes S 2, C 2h , D 2h , D 3d , D 4h , D 6h and O h , while it is shown that there exist twelve distinct symmetry classes for any other kind of elasticity tensors, including the classical Cauchy elasticity tensor and the micropolar elasticity tensors, which correspond to the eight subgroup classes just mentioned and the four crystal classes S 6, C 4h , C6h and T h . From these results, it turns out that all possible elasticity symmetry groups are nothing but the full orthogonal group, the transverse isotropy groups C ∞ h and D ∞ h , and the nine centrosymmetric crystallographic point groups except C 6h and D 6h .
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 95
    ISSN: 1573-2746
    Keywords: alpha alumina ; grain growth ; anisotropy ; template ; seeding ; modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Single crystals of α-alumina with {0001}, {11 $$\overline 2 $$ and {01 $$\overline 1 $$ 2} orientations were embedded in a matrix of liquid phase sintered alumina to study α-alumina single crystal growth in the presence of a calcium aluminosilicate liquid. Growth on the {11 $$\overline 2 $$ 0} and {01 $$\overline 1 $$ 2} surfaces was observed to occur by a diffusion-controlled mechanism while growth on the basal surface was controlled by two-dimensional nucleation. Growth models, which incorporate the change in matrix grain size, were derived and shown to fit the growth kinetics.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 96
    Electronic Resource
    Electronic Resource
    Springer
    Journal of elasticity 43 (1996), S. 203-225 
    ISSN: 1573-2681
    Keywords: elasticity ; hyperelasticity ; symmetry ; groups ; Kronecker ; isotropy ; anisotropy ; classification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A thorough investigation is made of the independent point-group symmetries and canonical matrix forms that the 2D elastic and hyperelastic tensors can have. Particular attention is paid to the concepts relevant to the proper definition of the independence of a symmetry from another one. It is shown that the numbers of all independent symmetries for the 2D elastic and hyperelastic tensors are six and four, respectively. In passing, a symmetry result useful for the homogenization theory of 2D linear elastic heterogeneous media is derived.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 97
    Electronic Resource
    Electronic Resource
    Springer
    Interface science 6 (1998), S. 23-39 
    ISSN: 1573-2746
    Keywords: grain boundary mobility ; ceramics ; solute drag ; pore drag ; pore boundary interactions ; liquid phases ; anisotropy ; microdesigned interfaces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract During ceramic fabrication, densification processes compete with coarsening processes to determine the path of microstructural evolution. Grain growth is a key coarsening process. This paper examines grain boundary migration in ceramics, and discusses the effects of solutes, pores, and liquid phases on grain boundary migration rates. An effort is made to highlight work in the past decade that has contributed to and advanced our understanding of solute drag effects, pore-boundary interactions, and the role of liquid phases in grain growth and microstructural evolution. Anisotropy of the grain boundary mobility, and its role in the development of anisotropic (anisometric) microstructures is discussed as it is a central issue in recent efforts to produce ceramic materials with new combinations of properties and functionality.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 98
    Electronic Resource
    Electronic Resource
    Springer
    Journal of elasticity 45 (1996), S. 13-32 
    ISSN: 1573-2681
    Keywords: 15A90 ; 70G05 ; 73B02 ; 73B10 ; elastic constitutive equations ; anisotropy ; minimal representation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The problem of determining minimal representations for anisotropic elastic constitutive equations is proposed and investigated. For elastic constitutive equations in any given case of anisotropy, it is shown that there exist generating sets consisting of six generators and such generating sets are minimal in all possible generating sets. This fact implies that most of the established results for representations of elastic constitutive equations are not minimal and remain to be sharpened. For elastic constitutive equations in some cases of anisotropy, including orthotropy, transverse isotropy, the trigonal crystal class S 6, and the classes C 2mh , m=1, 2, 3,..., etc., representations in terms of minimal generating sets are presented for the first time.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 99
    Electronic Resource
    Electronic Resource
    Springer
    Journal of elasticity 53 (1998), S. 47-64 
    ISSN: 1573-2681
    Keywords: elasticity ; anisotropy ; triclinic materials ; stress singularity.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Antman and Negron-Marrero [1] have shown the remarkable nature of a sphere of nonlinear elastic material subjected to a uniform pressure at the surface of the sphere. When the applied pressure exceeds a critical value the stress at the center r=0 of the sphere is infinite. Instead of nonlinear elastic material, we consider in this paper a spherically uniform linear anisotropic elastic material. It means that the stress-strain law referred to a spherical coordinate system is the same for any material point. We show that the same remarkable nature appears here. What distinguishes the present case from that considered in [1] is that the existence of the infinite stress at r=0 is independent of the magnitude of the applied traction σ0 at the surface of the sphere. It depends only on one nondimensional material parameter κ. For a certain range of κ a cavitation (if σ0〉0) or a blackhole (if σ0〈0) occurs at the center of the sphere. What is more remarkable is that, even though the deformation is radially symmetric, the material at any point need not be transversely isotropic with the radial direction being the axis of symmetry as assumed in [1]. We show that the material can be triclinic, i.e., it need not possess a plane of material symmetry. Triclinic materials that have as few as two independent elastic constants are presented. Also presented are conditions for the materials that are capable of a radially symmetric deformation to possess one or more symmetry planes.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 100
    ISSN: 1573-2681
    Keywords: elasticity ; anisotropy ; inclusion ; crack ; Peach-Koehler force
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Orlov and Indenbom [1] have shown that the net (integrated) interaction force F between two skew dislocations with Burgers vectors $$\hat b,b$$ separated by a distance h in an infinite anisotropic elastic medium is independent of h. Nix [2] computed numerically the net interaction force F between two skew dislocations that are parallel to the traction-free surface X2=0 of an isotropic elastic half-space. His numerical results showed that F was independent of h; a partial result of what Barnett [3] called Nix"s theorem. The separation-independence portion of Nix"s theorem has been proved to hold for a general anisotropic elastic half-space with a traction-free, rigid, or slippery surface, and for bimaterials [3-5]. In this paper, we show that the net interaction force $$F\left( {on \hat b} \right)$$ is independent of the presence of inclusions. We will consider the case in which the line dislocation b is a more general line singularity which can include a coincident line force with strength f per unit length of the line singularity. An inclusion is an infinitely long dissimilar anisotropic elastic cylinder of an arbitrary cross-section whose axis is parallel to the line singularity (f, b). The (skew) line dislocation $$\hat b$$ does not intersect the inclusion. The special cases of an inclusion are a void, crack, or rigid inclusion. There can be more than one inclusion of different cross sections and different materials. The line singularity (f, b) can be outside the inclusions or inside one of the inclusions. The inclusions and the matrix need not have a perfect bonding. One can have a debonding with or without friction.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...