Inertia of measurements with “auxiliary-wall” type heat meters

The article examines the problem of thermal inertia on the basis of an auxiliary-wall type heat meter, it demonstrates the boundaries of applicability of the approximate relationship for calculating non-steady-state heat fluxes.Notation q() non-steady-state heat flux through the heat meter - _i,a _i thermal conductivity, thermal diffusivity, and thickness of the heat meter, respectively - ₂,a ₂ thermal conductivity and thermal diffusivity, respectively, of the base of the heat meter - t() temperature gradient over the thickness of the heat meter - index of thermal inertia - time - s parameter of Laplace transform - t₁ (x, ) temperature of the heat meter at point x - t₂(x, ) temperature of the base - t_c ambient temperature - Y_q(s) transfer function from the heat flux q() to the temperature gradient t() Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 2, pp. 298–305, August, 1980.     

Automation of the primary processing of data of a thermal experiment

The problems involved in automating the processing of experimental data are considered. Primary-processing algorithms based on methods of analyzing nonstationary random processes are described.Notation {x()} a nonstationary random process - {y()} an unknown random process (in a special case, a stationary random process) - A() a deterministic process - time - M[y()] mean value of the random process {y()} - d[y()] =² variance of the random process {y()} - R_i difference between the recorded and predicted values - c relative accuracy - estimate of the mean value of the random process - C_s a weighting coefficient - and T observation period Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 2, pp. 220–224, August, 1980.     

Transient heat conduction in hollow spheres with a moving inner boundary

The finite integral transform method is used to obtain the solution of unsteady heat conduction problems for a hollow sphere with a moving internal boundary and various boundary conditions at the outer surface. For the solution of the problems of interest integral transform formulas are presented with kernels (16), (20), and (24) and the corresponding inversion formulas (18), (22), (26), (29) and characteristic equations (17), (21), (25), (28), (31), (33).Nomenclature a, thermal diffusivity and conductivity - t temperature of phase transformation - density - heat transfer coefficient - Q total quantity of heat passing through inner boundary - F latent heat of phase transformation - Fo(1,)=a/R ₁ ² , Fo(i,)=/r _i ² , Fo(i, _i)=a _i/r _i ² Fourier numbers - Bi₂=R₂/ Biot number     

High-frequency dielectric properties of Mg-Al-Si,Ca-Al-Si and Y-Al-Si oxynitride glasses

Recently developed coaxial line techniques [1] have been used to determine, at room temperature, the values of the real () and imaginary (') parts of the dielectric constants for some Mg-Al-Si, Ca-Al-Si and Y-Al-Si oxynitride glasses over the frequency range 500 MHz to 5 GHz. The frequency dependencies of and ' are consistent with the universal law of dielectric response in that (-_t8)^(n–1) and '^(n–1) for all glass compositions; the high experimental value of the exponent (n=1.0±0.1) suggests the limiting form of lattice loss [2] situation. In this frequency range, as previously reported [3] at longer wavelengths, the addition of nitrogen increases the dielectric constant, (); in both the oxide and oxynitride glasses is also influenced by the cation, being increased with cation type in the order magnesium, yttrium, calcium as at lower frequencies.     

Smoothing splines applied in thermal experiments

Cubic smoothing splines are applied to heat transfer in a region of detached flow on a plate with a cylindrical obstacle.Notation M Mach number of incoming flow - t temperature - q specific heat flux - thermal conductivity - c specific heat - p density - x longitudinal coordinate - x relative longitudinal coordinate - z transverse coordinate - r, cylindrical coordinates - r₀ radius of curvature of isothermal lines - current time - transient-state duration - d cylinder diameter - wall thickness Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 2, pp. 246–249, August, 1980.     

Asymptotic behavior of the vector potential and the order parameter for an isolated vortex

Eilenberger's formulation of the theory of inhomogeneous superconductors is used to study an isolated vortex in a type-II superconductor. Exact integral expressions for the vector potential and the order parameter are obtained and used to determine the asymptotic behavior of these quantities. Far from the axis of the vortex, the vector potential approaches its BCS value in an approximately exponential fashion, the decay constant being equal to the quantity obtained by Eilenberger and Büttner in the local case, and equal to {2[(k _BT)²+ _BCS ² ]^1/2/v_F+(1/v _F)}^–1 in the case where nonlocal effects dominate. The order parameter also approaches its BCS value approximately exponentially, the decay constant being equal to the quantity of Eilenberger and Büttner when <2, and equal to 1/2 when >2.Supported in part by the National Research Council of Canada.Sole affiliation is now the University of Toronto.     

Dynamic scaling and ultrasonic attenuation in 4He near the superfluid transition point

Attenuation of first sound has been measured in ⁴He under saturated vapor pressure near the lambda temperature T at frequencies /2 ranging from 10.2 to 271 MHz. The frequency dependence of the critical part of the attenuation is determined and the dynamic scaling hypothesis is examined. Above the lambda point, it is found that the critical attenuation is described by a scaling function (, ) = ^1+y F(), where = ₀^–x and = T/T – 1, with the results x = 1.02±0.05 and y = 0.33±0.03. The characteristic frequency of the order-parameter fluctuation with the wave number k equal to the inverse correlation length is then proportional to ^x , which is in an excellent agreement with the prediction of dynamic scaling. Below the lambda point, a characteristic relaxation time or times shorter than previously expected at lower frequencies appears to exist in the present frequency range.Based on a Ph.D dissertation submitted by K. Tozaki to the University of Tokyo (1977).     

Determination of the thermophysical characteristics of alternatively freezing and thawing dispersed media by the method of solving inverse problems of heat conduction

The article explains an algorithm for determining the thermophysical characteristics of dispersed media with phase transitions based on the method of solving inverse problems of heat conduction.Notation r space coordinate - time - T temperature of the specimen - T₀ initial temperature - c_i, c_w, c_sk specific heat of ice, water, and of the organic-mineral skeleton, respectively - c_f, c_m, _f, _m specific heat and thermal conductivity in the frozen and melted zones, respectively - c effective heat capacity - thermal conductivity - p density - ₀, _sb bound and strongly bound moisture, respectively - (T) amount of nonfrozen water - R radius of the cylinder - q() heat flux - I functional - u₁(), U₂() measured temperatures of the specimen at the points r = 0 and r = R, respectively, at the instant - ₁, ₂ degree of confidence of the supplementary information - final instant of time - a, b, k, _s positive constants - L specific heat of melting - N number of grid nodes over space - n number of grid nodes over time - h grid step over space - grid step over time - solution of the conjugate system - s number of iteration Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 2, pp. 292–297, August, 1980.     

Effect of elastic interaction energy on coarsening of γ′ precipitates in a mechanically alloyed ODS Ni-base superalloy

The coarsening behavior of precipitates with a uniform size distribution and with a bimodal size distribution in a mechanically alloyed ODS Ni-base superalloy were investigated to clarify the effect of elastic interaction energy on the coarsening behavior of precipitates. The coarsening rate decreased with increasing size of precipitates with a uniform size distribution, contrary to the classical LSW theory, and the coarsening behavior of precipitates with a bimodal size distribution exhibited Ostwald ripening in which the larger precipitates grow at the expense of smaller precipitates. The driving force for coarsening of precipitates was analyzed based on the two-particle model, considering the effect of elastic interaction energy in addition to the effect of interfacial energy. The contribution of elastic interaction energy on the total energy was found to increase with increasing size of precipitates, and the decelerated coarsening of precipitates was attributed to the decrease in the driving force for coarsening with increasing size of precipitates.     

Localized spin fluctuations

Scaling arguments and renormalization group techniques are used in the Anderson model Hamiltonian for the nonmagnetic limit of a magnetic impurity. The range of validity of the theory is limited toU/ 1, where the electron-electron collisions can already compete strongly with the electron-hole collisions. A parquet approximation is developed; it gives for the static susceptibility in the symmetric case = ()^–1 exp (+U/). There are some hints that the exchange force might play a crucial role in the formation of localized magnetic moment. These considerations are consistent with the electron-hole symmetry in the symmetric Anderson model.     

Recovery of a creep-deformed Type 316 stainless steel

The recovery of the dislocation structures produced in a Type 316 steel during creep has been examined by annealing over a range of temperatures and times, both in the presence and in the absence of stress. The influence of dislocation recovery on subsequent reloading behaviour has also been examined.Initial dislocation recovery occurs rapidly but the rate of recovery subsequently decreases as precipitate effects become more important. Dislocation recovery in the early, rapid stage appears to be controlled by vacancy diffusion between the dislocation links. The application of stress during recovery leads to an enhancement of the recovery rate in agreement with the network coarsening model whilst the incremental strains observed on reloading after recovery correlate well with the changes in dislocation structure produced during the recovery periods.List of symbols and appropriate values l dislocation link length - D _s self diffusion coefficient - b Burgers vector (2.5×10^–1 m) - C _j equilibrium jog concentration - dislocation link tension - k Boltzman's constant (1.38×10^–23 J atom^–1 K^–1) - T absolute temperature - t recovery time - M mobility term - Z frictional term associated with particles - _d dislocation density determined from micrographs - N _d number of dislocation intersections on test line - p length of test line - S foil thickness - ¯l mean dislocation link length - _c mean intragranular particle (carbide) spacing - r ₀ mean intragranular particle radius at timet=0 - r _t mean intragranular particle radius at timet - D solute diffusion coefficient - B solubility of M₂₃C₆ in austenite - particle-matrix interface energy - atomic volume (10^–29m³) - change in dislocation density during recovery period - incremental strain associated with reloading after recovery period - K constant - dislocation density - ₀ dislocation density at timet=0 - _t dislocation density at timet - ₀ friction stress associated with particles - constant (1) - shear modulus - angle between dislocation segments as dislocation breaks through a particle - A 1 cos (/2) - E constant - creep rate - F Taylor factor - L mean slip distance of dislocations - rate of dislocation recovery - stress - _y yield stress - J strength coefficient - _p plastic strain     

Thermal conductivity of hydrocarbons in the naphthene group under high pressures

The thermal conductivity of hydrocarbons in the naphthene group has been experimentally determined. An equation is now proposed for calculating the thermal conductivity over the given temperature and pressure ranges.Notation thermal conductivity - ₂₀ and ₃₀ values of the thermal conductivity at 20 and 30°C, respectively - t₀,P₀ thermal conductivity at t₀, p₀ - _t p thermal conductivity at temperature t and under pressure P - change in thermal conductivity - P pressure - P_melt melting pressure - P₀ atmospheric pressure - t₀ 20°C temperature - T, t temperature - T_cr critical temperature - temperature coefficient of thermal conductivity - ₂₀ temperature coefficient of density - density - ₂₀ density at 20°C - _cr critical density - M molar mass - =T/T_cr referred temperature - v specific volume - v₀ specific volume at 20°C - v change in specific volume - _{3 0} a coefficient - B (t) a function of the temperature - S a quadratic functional - W_i, weight of the i-th experimental point - _i error of the i-th experimental value of thermal conductivity - B _{y, =0.6} value of B (t) at T = 0.6T_cr - B = B (t)/B_{, =0.6} referred value of coefficient B (t) Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 3, pp. 491–499, September, 1981.     

Inhomogeneous shear flows of linear polymers

Solutions of a system of equations of nonlinear viscoelastic fluid motion describing inhomogeneous shear flows of linear polymers are indicated.Notation _ij stress tensor - p pressure - F_i mass force vector - _ij Kronecker delta - coefficient of shear viscosity - relaxation time - _ij inner parameter - _ij=vi/x_j velocity gradient tensor - ₀ initial value of the shear viscosity coefficient - ₀ initial value of the relaxation time - D dimensionless first invariant of the additional stress tensor - A, B, C constants of integration - f(D) universal function characterizing the material - r, , z cylindrical coordinates - u=v_z axial component of the velocity vector - v=v circumferential component of the velocity vector - ₁, ₂ first and second differences of the normal stress - Q volume mass flow rate - R radius of a circular tube - R₁, R₂ radii of the inner and outer cylinders, respectively - M moment per unit length Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 3, pp. 449–456, September, 1981.     

Some observations on the deformation characteristics of bulk polycrystalline zirconium hydrides

The deformation behaviour of bulk polycrystalline zirconium hydrides in the composition range ZrH_1.27 to ZrH_1.66 has been investigated by compressive loading at temperatures between room temperature and 500° C. Single-phase -zirconium hydride is brittle below 100° C. Analyses of slip traces on specimens deformed at temperatures between 100 and 250° C have shown that the glide planes are {111} types. The deformation characteristics of and ( + ) alloys at temperatures between 100 and 500° C are consistent with the hydrogen vacancies in the -phase providing significant lattice friction to the movement of dislocations in the zirconium lattice of the hydride structure. The room temperature fracture stress of ( + ) alloys increases with the volume fraction of the -phase and this can be related to the resistance offered by platelets to the propagation of cleavage cracks in the matrix. In a ( + + ) alloy the resistance to crack propagation at room temperature is further increased by the soft -zirconium phase.     

Thermodynamics of the quasiequilibrial growth of crazes

By comparing the morphology and physical properties (averaged over the scale of 1 to 10m) of a crazed and uncrazed polymer, it can be concluded that crazing is a new phase development in the initially homogeneous material. The present study is based on recent work on the general thermodynamic explanation of the development of a damaged layer of material. The treatment generalizes the model of a crack-cut in mechanics. The complete system of equations for the quasiequilibrial craze growth follows from the conditions of local and global phase equilibrium, mechanical equilibrium and a kinematic condition. Constitutive equations of craze growth-equations are proposed that are between the geometric characteristics of a craze and generalized forces. It is shown that these forces, conjugated with the geometric characteristics of a craze, can be expressed through the known path independent integrals (J, L, M,). The criterion of craze growth is developed from the condition of global phase equilibrium. F Helmholtz's free energy - G Gibb's free energy (thermodynamic potential) - f density ofF - g density ofG - T absolute temperature - S density of entropy - strain tensor - components of - stress tensor - components of - _y stress along the boundary of an active zone (yield stress) - _b stress along the boundary of an inert zone - applied stress - value of at the moment of craze initiation - K stress intensity factor - C tensor of elastic moduli - C ^–1 tensor of compliance - internal tensorial product - V volume occupied by sample - V ₁ volume occupied by original material - V ₂ volume occupied by crazed material - V boundary ofV - (V) vector-function localized on V - (x) characteristic function of an area - (x) variation of(x) - (x) a finite function - tensor of alternation - components of the boundary displacement vector - l components of the vector of translation - n components of the normal to a boundary - _k components of the vector of rotation - e symmetric tensor of deviatoric deformation of an active zone - expansion of an active zone - J ⁽ⁱ⁾ ,L _k ⁽ⁱ⁾ ,M ⁽ⁱ⁾,N ⁽ⁱ⁾ partial derivatives ofG ⁽ⁱ⁾ with respect tol , _k, ande , respectively - [ ] jump of the parameter inside the brackets - thickness of a craze - 2l length of a craze - 2b length of an active zone - l _c distance between the geometrical centres of the active zone and the craze - ^* craze thickness on the boundary of an active and the inert zone - l ^* craze parameter (length dimension) - A craze parameter (dimensionless) - ^* extension of craze material     

Nonlinear Response of a Continuous Wave NMR Spectrometer for Samples with a Large Magnetization

We present a new insight in the response of a CW NMR spectrometer for highly magnetized samples above 100 MHz. The spectrometer is a bridge made of a magic T. The output of the bridge is proportional to the reflection coefficient, , of a resonant circuit, which is built with a coil containing the sample. The sensitivity of the reflection coefficient to the complex susceptibility of the sample, () = () – j(), depends on the quality factor, Q, of the circuit and filling factor, . When the condition Q 1 is not fulfilled, we show indeed that the use of a simple crystal detector, which is only sensitive to || gives rise to a strong nonlinear response of the spectrometer. Measurements of the complex value of by means of phase sensitive detection allow to recover a linear behavior. We discuss and illustrate those issues with a few circuits we designed for our measurements on liquid ³ He with spin polarizations up to 15 %. A method is described to build in a reproducible and predictable way resonant circuits matched to 50 in the frequency range 100 – 400 MHz with a quality factor as high as 1000 at 4 K.     

Simulation of the Process of Water Freezing in a Round Pipe

The problem of freezing of pure water in a round pipe is treated with due regard for convection under asymmetric thermal boundary conditions in the absence of motion along the pipe. The problem is solved numerically using the control volume approach, SIMPLER algorithm, and the enthalpy method. Results are obtained for three Grashof (Gr) and six Biot (Bi) numbers: Gr = 1.55 × 10⁶, Bi = 0.305 (0 < ), Bi = 0.044 ( < 2); Gr = 1.24 × 10⁷, Bi = 0.610 (0 < ), Bi = 0.087 ( < 2); Gr = 9.89 × 10⁷, Bi = 1.220 (0 < ), Bi = 0.174 ( < 2). The correctness of calculation of the problem disregarding free-convection flows is analyzed.     

Universal simulation of degenerating homogeneous turbulence

The problem of universal simulation of the dynamics of a turbulent velocity field (universal in the sense of arbitrary values of the Reynolds turbulence number) is treated on the basis of the moment model in the second approximation.Notation ¯q² _i ² double the kinetic turbulence energy - _u ² =5v¯q²/_u Taylor turbulence scale squared - _u=v1/x_k)²> kinetic-energy dissipation function - N_Re,=¯q²_u / Reynolds turbulence number Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 1, pp. 46–52, January, 1982.     

Switching and Hysteresis on the I-V Curves of Submicron BSCCO (2212) Bridges

No Heading In thin BSCCO (2212) whisker-based superconducting bridges with width and length 1 m we observe random telegraph noise at discrete values of current. We show that the noise is associated with spontaneous processes of addition and removal of discrete vortex trains and reflects the regular structure of steps on the I–V curves. The average lifetime of the trains falls down with increasing temperature T in a complex way: intervals of steep drop ( an order of magnitude per Kelvin) are separated with a plateau of (T) with 10^–2 s. The 70 GHz irradiation with 100 W power results in the growth of the average switching frequency by 5 orders of magnitude; thus the HTSC bridges could be efficient detectors of microwave radiation. We discuss the peculiar features of (T).PACS Numbers: 74.25.Fy, 74.40.+k, 74.60.Ge, 74.72.Hs     

Optimal choice of descent steps in gradient methods of solution of inverse heat-conduction problems

Modifications are proposed for the methods of steepest descent and conjugate gradients for the solution of multiparameter inverse problems in heat conduction.Notation A, B, L linear operators - u element of the solution space U - f exact initial data - f error in the initial data - value of the error in the initial data - A^–1 inverse operator - u^(k)() k-th derivative of the function u - _i() polynomials of degree i–1 - A^*, B^*, L^* operators conjugate to the operators A, B, L - J(g) discrepancy functional - J'g gradient of the discrepancy functional - _n ⁱ depth of descent with respect to the i-th component of the antigradient of the discrepancy in the n-th iteration - _m length of the observation interval Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 2, pp. 264–269, August, 1980.