On the proximity effect in a superconductive slab bordered by metal

The first Ginzburg-Landau equation for the order parameter in the absence of magnetic fields is solved analytically for a superconducting slab of thickness 2d bordered by semi-infinite regions of normal metal at each face. The real-valued normalized wave function f=/ depends only on the transversal spatial coordinate x, normalized with respect to the coherence length of the superconductor, provided the de Gennes boundary condition df/dx=f/b is used. The closed-form solution expresses x as an elliptic integral of f, depending on the normalized parameters d and b. It is predicted theoretically that, for b< and dd_c=arctan(1/b), the proximity effect is so strong that the superconductivity is completely suppressed. In fact, in this case, the first Ginzburg-Landau equation possesses only the trivial solution f0.     

Certain mechanical properties of high-strength steels

Summary The concept of efficient conditions of treating steel is introduced. It is shown that, for various structural steels annealed or quenched under efficient conditions, there is an unequivocal relationship between strength and ductility defined by the lines of maximum efficiency A and B on the _v– and S_K–_v diagrams (Figs. 2 and 3). An analogous relation can be constructed for steels subjected to thermomechanical treatment, but the paucity of experimental data prevents us from establishing the final shape of the C-line of maximum efficiency over the whole range of . A great deal of published data indicates the effectiveness of thermomechanical treatment in improving the mechanical properties of steels. Empirical relations are given to show the influence of thermal and thermomechanical treatment of steels worked to various ductilities.     

Interaction of phase-shifted fields of two single-turn coils situated above a conducting medium

An analytical solution is obtained for the problem of the interaction of two phase-shifted electromagnetic fields generated by two coaxial single-turn coils carrying alternating currents of the same frequency, but of different amplitudes and nonzero phase difference, . Two cases are considered: coils situated above a conducting half-space and above a two-layer medium. Numerical results show that is the most important parameter. If the values of and of the other parameters are chosen properly, then the curve representing the change in impedance can lie in any quadrant of the complex plane. These results can be used for developing more sensitive and more selective eddy current testing methods.     

Studying the effect of the temperature factor on the transition from a laminar to a turbulent regime of flow in a boundary layer

Based on the generalization of experimental data, we propose a formula for the calculation of the effect of the temperature factor and the transition from a laminar flow regime to one that is turbulent in the boundary layer of a plate; this formula has been confirmed by experiments performed in the following range of parameter variation: 0.5 2.6; 0.2 M 3.6; 0.1 9%.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 16, No. 2, pp.218–224, February, 1969.     

The constitution of the Ni-Al-Ru system

The constitution of the Ni-Al-Ru system has been investigated in the range 0 to 50 at% Al. Isothermal sections at 1523 and 1273 K have been determined using microstructural observations, electron probe microanalysis and X-ray diffraction. The phases present were: nickel-based solid solution (); (based on Ni₃Al); solid solutions based on NiAl and RuAl, respectively (designated ₁ and ₂), and ruthenium-based solid solution (Ru). The maximum solubility of Ru in was 5 at%. ₁, and ₂ show extensive range of solubilities, namely up to 20at% Ru in ₁ and up to 25 to 35 at% Ni in ₂. Three-phase equilibrium between , ₂ and (Ru) existed at 1523 and 1273 K. Also at 1523 K, three-phase equilibria existed between , and ₁ and ,₁ and ₂, while at 1273 K, the equilibria were between , ₁,₂ and , , ₂ indicating the occurrence of a reaction +₁, +₂ at a temperature between 1523 and 1273 K. Liquidus features have been deduced from data on as-solidified structures. Lattice parameter data and hardnesses are also reported.     

Low-temperature critical phenomena in the spin-1/2 planar ferromagnet

The low-temperature critical behavior of the spin-1/2 planar ferromagnet is investigated. A functional integral expression for the partition function is obtained and analyzed using renormalization group techniques. The quantum-classical crossover phenomenon near the zero-temperature multicritical point is studied. A comparison with similar studies carried out for the XY model in a transverse field shows, as expected, that the critical properties are similar in both systems. However, for the critical line h _c(0)–h _c() ~ ^1/ we obtain = 1 for the shift exponent instead of the XY value = 2/d.Supported by a Graduate Studies Fellowship from CAPES (Brazil).     

Velocity of second sound and superfluid density near the superfluid transition in3He-4He mixtures

Using superleak condenser transducers, the velocity of second soundU ₂ has been measured near the superfluid transition temperature T in³He-⁴He mixtures with molar concentrationsX of³He of 0.0, 0.038, 0.122, 0.297, and 0.440. We have obtained the superfluid density _s/ fromU ₂ on the basis of linearized two-fluid hydrodynamics. The results for _s/ are consistent with those obtained from the oscillating disk method, as expected from two-fluid hydrodynamics. The value of _s/ at eachX could be expressed by a single power law, _s/=k, where =1-T/R, with the experimental uncertainty. It is found that the exponent is independent of concentration forX0.44 within the experimental uncertainty. This concentration independence of is in agreement with the universality concept. From the conclusion that the values of are universal forX0.44, the concentration dependence of the superfluid component _s is expressed by an empirical equation _s(X, )=²_s(0, ). It is found that corresponds to the volume fraction of⁴He in the superfluid³He-⁴He mixture. The value of is in agreement with that obtained from the measurement of the molar volume by others.This paper is based on a thesis submitted to Tokyo University of Education in partial fulfillment of the requirements for the Ph.D. degree.     

Spin-fluctuation theory of strong coupling corrections to the free energy in superfluid 3He

Previous spin-fluctuation theories yielding the strong coupling corrections \- _i to the five coefficients of the fourth-order invariants in the free energy functional are extended. First, the superfluid part of the susceptibility is calculated up to order ⁴ for all momenta and frequencies and the contribution arising from p-wave fluctuations of the order parameter is included. Then the frequency sums yielding the \- _i are calculated by taking into account the full momentum and frequency dependence of the superfluid susceptibility and the spin fluctuation propagator. The results for the \- _i are plotted vs. a cutoff q_c on the momentum integration for spin-fluctuation parameters N(0)I = 0.75 and = 0.95. The cutoff takes into account in a rough way the effect of additional terms in the free energy functional which were neglected in previous theories. These additional terms are due to the implicit dependence of the superfluid susceptibility on the spin-fluctuation parameter I via the gap parameter . The gap equation providing the relation between and I is derived in the weak coupling approximation. The cutoffs obtained by fitting the experimental values of the three combinations of \- _i (arising from the measured specific heat discontinuities on the melting curve) are comparable to the cutoff obtained from the spin-fluctuation contribution to the weak coupling freeenergy [q _c = 0.3(2k _F ) for = 0.75]. The corrections due to the momentum and frequency dependence of the superfluid susceptibility and the spinfluctuation propagator are large and point in the direction of better agreement with experiment: The ratio % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaiOuamaaBa% aaleaacaaIXaaabeaakiabg2da9iabfs5aejqbek7aIzaaraWaaSba% aSqaaiaaiwdaaeqaaOGaai4laiaacIcacqqHuoarcuaHYoGygaqeam% aaBaaaleaacaaIYaaabeaakiabgUcaRiabfs5aejqbek7aIzaaraWa% aSbaaSqaaiaaisdaaeqaaOGaaiykaaaa!47E0!\[R_1 = \Delta \bar \beta _5 /(\Delta \bar \beta _2 + \Delta \bar \beta _4 )\]decreases from 2 to about 1.2. However, in view of the large discrepancy with experiment (experimentally, R ₁= 0.14), we conclude that spin-fluctuation theory in its present form (without taking into account renormalization effects) cannot account quantitatively for the measured specific heat discontinuities on the melting curve.     

Mixing displacement of viscoplastic fluids feom a channel with a rectangular cavity

Different mixing displacement regimes for viscoplastic fluids are investigated theoretically and experimentally.Notation x and y Cartesian coordinates - h half-width of the gap - H, L dimensionless depth and length of the cavity - v_x, v_y velocity components - density - _ik components of the viscous stress tensor - e_ik components of the deformation rate tensor - dynamic viscosity - dynamic viscosity for infinitely high displacement velocity - ₀ analog of the limiting shear stress in Bingham's fluid - W parameter in Williamson's model - =/gh dimensionless viscosity - stream function - vorticity - ₀, ₀ distributions of and at the inlet - r,a, b, and c auxiliary constants - C concentration of the displacing fluid - D diffusion coefficient - Pe Peclet's number Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 40, No. 3, pp. 432–439, March, 1981.     

Hydrodynamics of a vortex ring

We considered the kinematics and dynamics of a vortex ring in an incompressible fluid in toroidal coordinates. We obtained the change in the pressure difference along the boundary between two flow regions in the case of a moving torus.Notation , , toroidal coordinates - (V ;V ;V ) velocity of a fluid particle and its projections in toroidal coordinates - g ,g ,g metric tensor components - the Jacobian of transition to curvilinear coordinates - V ₀ velocity at the center of a vortex ring on its symmetry axis - x, y, z Cartesian coordinates - z, y, cylindrical coordinates - a distance from the axis of a torus (V=0) to its axis of symmetry (Oz) - angle between the Oy axis and the line that connects a fluid particle on the streamline =const, which represents a circle [16], with the center of this circle - U _z,U _y velocities in the cylindrical system of coordinates - ₀ stream function of a stationary vortex ring - velocity circulation - U V ₁, velocity of a rectilinear flow at infinity - ₁ stream function of a rectilinear flow - = ₀ + ₁ superposition of two flows - n=k ⁴=V ₁/V ₀ velocity ratio coefficient - R radius of a vortical region - U velocity of fluid particles at the boundary in polar coordinates (r, ) with the center at the coordinate origin (point 0) - fluid density - p ₀,p pressure at infinity and at a certain point of flow - pressure difference Polotsk State University, Polotsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 4, pp. 531–536, July–August, 1995.     

A numerical method for flexible airfoils in incompressible inviscid flow

Summary The paper deals with the aerodynamic analysis of flexible airfoils, based on a quasi-lattice vortex method (QVLM). The analysis is formulated in matrix form and leads, as in other similar studies, to a linear algebraic system when the angle of attack is nonzero, and to an eigenvalue problem when the incidence angle is zero. The aerodynamic characteristic curvesC _L -,C _m - are presented. Finally, the airfoil shapes for several values of the tension coefficient and angles of attack are drawn. The results obtained with the present method are in good agreement with those reported in previous studies and evidentiate the flexibility of the QVLM as applied to flexible airfoils.Notation A aerodynamic matrix, defined in QVL method, (8) - B matrix, see Eq. (18) - c chord of airfoil - C matrix defined asAB - C _L lift coefficient, 2L/V ² c) - C _p moment coefficient, 2M/(V ² c ²) - C _p pressure coefficient,C _p =2p/(V ² ) - C _T tension coefficient, 2T/(V ² c) - D matrix, see Eq. (11) - I unit matrix - l curvilinear length of the flexible airfoil - N number of collocation points on the airfoil shape - q dynamic pressure, V ² /2 - T tension force in the sail - V freestream velocity - w downwash - x nondimensional coordinate,x/c - X _i control points, Eq. (9) - X _max dimensionless position of the maximum camber - Y _k source points, Eq. (9) - z coordinate normal tox axis - Z nondimensional coordinate,z/c - Z _s camber equation in dimensionless form,z _s /c - incidence with respect to the upstream flow velocity - column vector of the local curvatures {₁, ₂,..., _N } ^T - nondimensional membrane excess ratio - eigenvalue of the problem (23) - _k zeroes of the Chebyshev polynomia of the first kind, 1kN - column vector of the local slopes, {₀, ₁, ₂,..., _N } ^T - column vector, {₁, ₂,..., _N } ^T - ₀ slope at airfoil leading edge     

The influence of ageing on the stability of β-γ/γ′ derived microstructures in Ni-Al-Cr-(Co) alloys

Multiphase Ni-Al-(Fe)-(Cr)-(Co)-based intermetallics with (B2)- (A1)/(L1₂), - or - microstructures can exhibit significant room-temperature tensile ductility. In the case of Ni-Al-Cr-based alloys, microstructural development is complicated by the precipitation of -Cr, which can supplant the -phase during ageing of three-phase -/ microstructures. An investigation of the stability, during ageing, of cast Ni-Al-Cr-(Co) alloys with microstructures derived from -/ is reported. In the as-cast condition, the materials investigated consisted of a dendritic matrix containing L1₀ type martensite and interdendritic /. Extensive intra- and interdendritic -Cr precipitation was also observed. The stability during ageing of the interdendritic / microstructure is also considered and transformation of the L1₀ martensite is examined.     

Nonlinear viscoelasticity and relaxation phenomena of polymer solids

Summary The specific Helmholtz free energy of nonlinear viscoelastic isotropic polymer solids is assumed to be a separable, symmetric function along three orthogonal principal strain directions, i.e.=( ₁,q _n ⁽¹⁾)+( ₂,q _n ⁽²⁾)+( ₃,q _n ⁽³⁾), where the _r (r=1, 2, 3) are three principal stretch ratios and theq _n ( ^r ) are a set of internal state variables. It is shown that, by using this postulated form of the free energy function, one can readily characterize the mechanical response of viscoelastic polymer solids.

---

Nichtlineare Viskoelastizität und Relaxationserscheinungen in festen Polymeren

Zusammenfassung Die spezifische Helmholtzsche freie Energie nichtlinear-viskoelastischer, isotroper, fester Polymere wird als separable, symmetrische Funktion der Form=( ₁,q _n ⁽¹⁾)+( ₂,q _n ⁽²⁾)+( ₃,q _n ⁽³⁾) angenommen mit den drei Hauptdehnungsverhältnissen _r (r=1, 2, 3) und inneren Zustandsvariablenq _n ( ^r ). Es wird gezeigt, daß dann das mechanische Verhalten der viskoelastischen festen Polymere schnell charakterisiert werden kann.

---

---

This represents the results of one phase of research being carried out at the Jet Propulsion Laboratory, California Institute of Technology, under Contract NAS 7-100, sponsored by the National Aeronautics and Space Administration.     

On a complex potential suitable for construction of C-type grids

Summary The following complex function is derived, such that its real and imaginary parts (, , resp.), determine two families of orthogonal lines around a circle, which belongs itself to the family (, )=const. Lines of both families form a so calledC-type grid, tending to parabolas with increasing distance from the circle. This grid can be transformed into aC-type grid around any given Jordan curve provided that a holomorphic function is known, which maps conformally the infinite exterior of the circle onto such an exterior of this curve.A so calledO-type grid corresponding to the logarithmic functionW()=–i ln·(/a) is also considered for the sake of completeness, and examples of both types of grids are presented.Finally, it is shown, that the grids can be locally refined by algebraical means, the computational grid remaining, however, uniform and consisting of equal squares.     

Question of the convergence of iteration methods of solving the inverse heat-conduction problem

The convergence of iteration methods of solving the inverse heat-conduction problem depending on the type of desired boundary function is numerically investigated.Notation t time - t_p length of the time interval - x space coordinate - b thickness - T(x, t) temperature - C(T) bulk specific heat of the material - (T) heat conduction coefficient of the material - (x) initial temperature distribution - q thermal flux density - f(t) measured temperature - (x, t) adjoint variable - , , p parameters of the method of conjugate gradients - k number of the iteration Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 45, No. 5, pp. 770–773, November, 1983.     

The effects of residual α phase on the 1370°C creep performance of yttria-doped HIPed silicon nitride

The creep behaviour at 1370°C (2500°F) of yttria-doped, hot isostatically pressed silicon nitride was examined as a function of residual phase content. The pre-test silicon nitride materials had either 30% or 40% phase content. The creep resistance was found to increase as the residual phase content decreased. For equivalent times and stresses, the higher -containing silicon nitride accumulated more creep strain and exhibited faster creep rates. The residual phase decreased as a function of time at 1370°C and converted to phase; it was also found that the to phase transformation rate was enhanced by stress. In the absence of stress, the kinetics of the to phase transformation at 1370°C followed a first-order reaction. If a first-order reaction was assumed for the to phase transformation in the presence of stress at 1370°C, then the magnitude of the reaction rate constant for this transformation was twice as large for tensile stresses equal to or greater than 130 MPa than for the reaction rate constant describing the transformation with no applied stress. © 1998 Chapman & Hall     

Phase relationship between β′- and O′-sialon at 1623 K

-sialon whiskers and co-products of synthesis, such as -sialon powders and O-sialon powders, were annealed at 1623 K for 8 h in a closed graphite reaction tube under 1 atm nitrogen. Phase stabilities, Si/Al ratios, and crystallographic features were investigated. The O-sialon phase, which formed in the early stage of synthesis when oxygen partial pressure was relatively high, became less stable in the present annealing condition and decomposed. The majority of released aluminium and possibly oxygen from the decomposed O-powder was incorporated into -sialon whiskers with little change in its lattice parameters, when the -sialon whiskers were included in annealing. The aluminium contents were always lower in the -whiskers than in the powders even after increasing its aluminium content during 8 h annealing. The lattice parameters of both -whiskers and powders increased with increasing aluminium content and became closer after annealing. The lattice parameters of -whiskers remained the same before and after annealing despite the increased aluminium content, while the lattice parameters of -powders decreased despite its aluminium content remaining unchanged. The lattice parameters of O-sialon increased with increasing aluminium content, and the increase in thea direction is the largest when compared with other parameters.     

Formation of Friction Layers and Wear Resistance of Steels under Conditions of Boundary Friction

We studied the influence of the lubricant compositions Grafitol with 10% graphite (1), Aerol containing 17% MoS₂ (2), Limol containing 60% MoS₂ (3), Limol + 10% chlorine-paraffin (4), and Limol + 10% copper powder (5) on the wear rate and formation of the fine structure of surface friction layers of structural steels. We established a correlation between the tribological characteristics of steels and lubricants. The abrasive wear of 40KhFA steel was minimum if it was lubricated with Limol + 10% copper powder. In this case, its wear was smaller by a factor of 10, 2, 1.25, and 7.25 as compared with lubricant compositions 1–4, respectively. In the course of minimum wear of 40KhFA steel, in the surface friction layers, we observed the minimum values of second-kind distortions (a/a) and of the true size of domains of X-ray coherent scattering (D) as well as the minimum difference between the crystal lattice constants (a) of steel before and after friction.     

Residual strain and texture in strontium-doped lanthanum manganite thin films

Thin films of La_0.67Sr_0.33MnO₃ (LSMO) have been deposited using liquid-delivery metal-organic chemical vapor deposition (MOCVD). X-ray diffraction (XRD) 2/ scans showed that all the films has a cubic structure. Studies of the in-plane crystallographic orientations (pole figure) revealed an (0 0 1) preferred growth structure on LAO, a weak (1 1 0) texture on Y-ZrO₂ (YSZ), a random texture on sapphire (SAP) and silicon (Si). Our attention is focused on residual strain and its deviations from linearity for vs. sin² plots. The strain evolution from 02<0.8 showed a curvature and a snake-like pattern. These anomalies are attributed to texture and strain gradients. In-plane strain decreased as the lattice mismatch increased and varied from 0.05 to 3.03% depending on the substrate. An attempt is made to establish a relationship between lattice mismatch, growth process, and residual strain.     

Spin glass behavior of Mn2+ ions in zeolite-Y at very low temperature

Magnetic properties of manganese ion spin systems in zeolite-Y have been measured. These ions act as almost free ions in the zeolite. Low frequency ac-susceptibility can be described with the Curie-Weiss law down to 50 mK. The susceptibility has a maximum around 30 mK showing a magnetic anomaly. Characteristic relaxation times deduced from frequency dependence of the maxima are studied. They diverge towardsT _c = 0 K according to the following formula, = ₀exp{(b/T)⁺¹} where ₀ = 3 x 10_–10 sec, b = 0.28K, and = 0.4, respectively. It is expected from ESR measurements that the dominant interaction between the manganese ions is dipole-dipole like. This divergence is interpreted as that of a dipolar spin glass.