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.     

Effect of Rigid Blocks on the Mechanical Characteristics and Abrasive Resistance of Polyurethanes

We study the interrelation of the chemical structure of thermoplastic polyurethanes (TPU) with their deformation-mechanical and tribotechnical characteristics. We have established that the concentration of rigid blocks is the determining parameter of structure that controls the properties of TPU. We discovered three characteristic regions, within the limits of which the shapes of concentration dependences are substantially different: < 24%, 24% < < 42%, and > 42%. These regularities can be useful in obtaining TPU with a given complex of physicomechanical and tribotechnical characteristics.     

Structural optimization of composite material for aircraft panels with strength,stability, and deflection restrictions

A theoretical approach is put forward for the structural design (in terms of the number of layers, layer thickness, and reinforcement orientation angle) for laminated composite material of minimalweight aircraft panels with restrictions on their strength, stability, and deflection. We deduce dependences for calculation of potential number of uniform-strength layers in a stack, for which the strength criterion in the form of equality is satisfied. A problem of structural optimization for a composite made up of uniform-strength layers is formulated and solved. The structures with reinforcement orientation angles [0], [90], [0, 90], [±], [±₁, ±₂], [0, ±], [90, ±], and [0, 90, ±] are demonstrated to be the optimal ones, depending on the load type and magnitude. We derived the necessary and sufficient sets of equations for the determination of design parameters. Several examples and particular loading cases are discussed.Translated from Problemy Prochnosti, No. 6, pp. 33–47, November–December, 2004     

Viscoelastic and rheological behavior of concentrated colloidal suspensions

Molecular approaches are discussed to the density (), viscoeleastic (), and rheological () behavior of the viscosity(,,) of concentrated colloidal suspensions with 0.3 < < 0.6, where, is the volume fraction, the applied frequency, and ; the shear rate. These theories are based on the calculation of the pair distribution functionP ₂(r,,), wherer is the relative position of a pair of colloidal particles. The linear viscoelastic behavior(,,=0) follows from an equation forP ₂(r,,) derived from the Smoluchowski equation for small, generalized to large by introducing the spatial ordering and (cage) diffusion typical for concentrated suspensions. The rheological behavior(,,=0) follows from an equation forP ₂(r,) of a dense hard-sphere fluid derived from the Liouville equation. This leads to a hard-sphere viscosity^hs(,) which yields the colloidal one(,) by the scaling relation(,) ₀=^hs(,) _B, where ₀ is the solvent viscosity. _B is the dilute hard-sphere (Boltzmann ) viscosity and the's are appropriately scaled,(,) and(,) agree well with experiment. A unified theore for(,,) is clearly needed and pursued.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994. Boulder, Colorado, U.S.A.     

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.     

Low-cycle biaxial fatigue of a polycrystalline magnesium-lithium alloy

We analyze the life duration of a magnesium-lithium alloy subjected to biaxial low-cycle fatigue under out-of-phase combined tension-compression and torsion. It was discovered that the life duration depends on the angle of the phase shift between the two perpendicular cyclic loads. The maximum life duration is attained in the case where the phase shift is absent, i.e., =0. It was also shown that deformation always remains plastic if exceeds a critical angle _c, i.e., no unloading of the specimen may occur. Fatigue properties are studied using the von Mises equivalent stresses and strains. We also present data on the evolution of the density of deformation twinning. It is assumed that the decrease in life duration is explained by permanent changes in the direction of loading in the presence of a phase shift, which inhibits the process of stabilization of plastic deformation in the constituent grains of polycrystals.Published in Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 31, No. 1, pp. 19–30, January – February, 1995.     

Temperature field in a plate containing a system of heat sources

The temperature field is determined in a circular plate with a system of thin extrinsic heat sources.Notation T temperature in the plate with the inclusions - r polar radius - polar angle - time - (r,) coefficient of thermal conductivity - (r,) heat transfer coefficient - C(r,) volume heat capacity - W(r,, ) specific intensity of the heat sources - half thickness of the plate - (x) Dirac's delta function - ¯T finite Fourier cosine transform of the temperature - p parameter for this transformation - T Laplace transform of the temperature - s its parameter - Iv(x) Bessel function with imaginary argument of order - K _v (x) the MacDonald function of order - and dimensionless temperature - Po Pomerantz number - Bi Biot number - Fo Fourier's number - dimensionless polar radius - b₁ ^* dimensionless radius of the circle on which the inclusions are placed - R^* dimensionless radius of the plate Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 40, No. 3, pp. 495–502, March, 1981.     

A note on the solution of a differential equation arising in boundary-layer theory

Summary The differential equation f + ff + f² = 0 (where dashes denote differentiation with respect to the independent variable ) subject to the boundary conditions f(0)=0, f()=0 and either f(0)=1 or f(0)=–1 is considered. It is shown that by using pf as dependent variable and =C–f (where C=f()) as independent variable and then expanding in powers of , a very good approximation to the solution can be obtained using only a few terms in the expansion.     

Volt-ampere characteristics of an ac arc in a transverse gas flow

An analytical dependence of the volt-ampere characteristic of an arc on the velocity of the incoming transverse gas flow is obtained. The stability threshold of arc combustion is determined.Notation h enthalpy - density - t time - v velocity - , thermal conductivity and electrical conductivity - E electric field strength - U potential at the arc - Q radiant flux - T period of oscillation of the current - r radius - l length of electric arc - d, L diameter and length of electrode - temperature - kinematic viscosity - Pr Prandtl number - current function Indices 0 gas parameters far from arc - 1 parameters at arc boundary - x projection on the axis 0x - y projection on the axis 0y - E effective value - e characteristic value Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 1, pp. 133–138, July, 1984.     

Dephasing Rate and Superconducting Proximity

We show that the maximum penetration depth of the anomalous quasiclassical Green's function from a superconductor into an adjacent normal metal is directly related to the phase relaxation time . The latter describes normal-metal phase correlations between two electrons with opposite spins. In the presence of spin-dependent interactions this phase relaxation time differs from the one found in weak localization corrections to the conductivity. The Josephson current measurements in a SINIS-structure could be used to determine experimentally.     

Underpinning of a simple blunt flaw fracture initiation relation

With the cohesive process zone representation of the micro-mechanistic processes that are associated with fracture as a basis, the author is involved in a wide-ranging research programme, the objective being to extend the fracture mechanics methodology for sharp cracks to blunt flaws, so as to take credit for the blunt flaw geometry. In earlier work, a Mode I fracture initiation relation has been derived, subject to the restriction that the process zone size s is small compared with the flaw depth (length) and any characteristic dimension other than the flaw root radius . The relation gives the critical elastic flaw-tip peak stress _pcr, and has been derived using a two-extremes procedure, whereby the separate, and indeed exact, solutions for small and large s/ values are blended together to give an all-embracing relation that is valid for all s/ values. _pcr is expressed in terms of the process zone material parameters and geometrical parameters but, for a wide range of flaw geometry parameters, _pcr essentially depends on only one geometrical parameter . This paper provides underpinning for the general thrust of the two-extremes procedure by appealing to exact results for the complete spectrum of s/ values from analyses of appropriate Mode III models. Results obtained by applying the two-extremes procedure are shown to be in very good agreement with the exact results.     

Evaporation rate of concentrated electrolyte solutions from fine capillaries

Solution concentration at the meniscus is elevated above the initial value, but does not vary during evaporation from capillaries. The reduction in evaporation rate as compared to water determined experimentally is in agreement with previously developed theory.Notation mass of a mole of water, g/mole - D diffusion coefficient of vapor through air, cm²/sec - relative vapor pressure in chamber (relative air humidity) - M relative vapor pressure above meniscus - density of water, g/cm³ - R gas constant, erg/mole·deg - T temperature, °K - D_* diffusion coefficient for molecules in solution, cm²/sec Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 37, No. 5, pp. 849–853, November, 1979.     

A flat jet in a granular bed of finite height

The distribution of gas flows in the vicinity of the jet is discussed and the conditions of disruption of the static equilibrium of the bed, the formation and growth of a cavity, and the jet breakthrough of the bed are investigated qualitatively.Notation a, b functions calculated in [11] - C, C constants in (7) - F derivative of the complex potential - f function in (6) - G function defined in (19) - H dimensionless height of bed - h height of cavity - k coefficient introduced in (15) - p, po pressure inside bed and in cavity - p dimensionless pressure drop - Q, q dimensional and dimensionless jet flow rates - q₁, q₂ critical values - T dimensionless height of cavity - T₀, T₁ T₁, T₂ characteristic values of T - u,v filtration velocities - u, u_* initial filtration velocity in the bed and minimum fluidization velocity - u_o velocity scale introduced in (14) - u * velocity scale introduced in (14) - u* velocity of fictitious flow defined in (15) - U complex velocity - Z=X+iY, z=x+iy dimensionless coordinates - z=x+iy dimensional coordinates - coefficient of hydraulic resistance - parameter from (5) - specific weight of particles' material - porosity - =+i coordinates in the plane obtained from z=x+iy as a result a of conformai transformation - _m value of giving a minimum of the function G - f complex and real flow potentials - angle of internal friction - stream function - angle of inclination of boundaries of the region of plastic flow to the vertical Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 37, No. 5, pp. 804–812, November, 1979.     

Calculation of radiative fluxes in flame power units

An engineering procedure is suggested for calculation of radiation properties of gas-dust media. It is based on using factors (attenuation, scattering factors, etc.) tabulated for discrete spectral ranges and averaged on particle size fractions. Application of the procedure is demonstrated using the example of a coal dust flame and the furnace working volume with account of ash and triatomic gases.Notation C_i mass fraction of the i-th component - _j mass fraction of the j-th particle fraction - n(r) calculated function of the particle size distribution - r particle radius - radiation wave length - diffraction parameter - m complex refraction index of the particle material - k_s attenuation, scattering, and scattering anisotropy factors for individual particles - K_s attenuation, scattering, and scattering anisotropy factors for the whole dust - averaged scattering anisotropy cosine - a_a, b_n Mie coefficients - , , volumetric attenuation, scattering, absorption factors for a dust flow - single-scattering albedo - emissivity All-Union Research and Design Institute of Metallurgical Heat Power Engineering, Nonferrous Metallurgy, and Refractory Materials, Ekaterinburg, Russia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 64, No. 3, pp. 287–291, March, 1993.     

Off-axis creep of a ceramic-matrix/continuous-ceramic-fiber composite: Experimental evaluation

The compression creep of a unidirectionally reinforced, SiC continuous fiber/calcium aluminosilicate (anorthite) glass-ceramic matrix composite was evaluated experimentally. Experiments covered the stress (–₁) and temperature (T) ranges of 20–40 MPa and 1300–1320°C, respectively. The experiments also emphasized characterization of the rheology as a function of the angle of misorientation () between the applied compressive load and the direction of reinforcement. For any given , T condition, the highest steady-state strain rate occurred for 50° (up to an order of magnitude faster than in the transverse, = 90°, case); overall composite strain in this case included a substantial contribution from displacement across the fiber-matrix interface. The data reveal that the interfacial rheology responsible for the displacement is distinctly temperature sensitive. Evaluation of the composite flow through its comparison to numerical/rheological models that scrutinize the interfacial effect implies that the interface is characterized by a non-Newtonian viscous rheology; this suggests that the interface response involves specifically the flow of the thin amorphous silica interphase that comprises a portion of the fiber-matrix interface in this material. The overall plastic response of the unidirectionally reinforced material is nevertheless rate-limited by plastic flow of the matrix and can be described by the superposition of three modes of strain, the magnitude of each being dependent specifically on .     

Assessment of the role of cytokines in bone resorption in patients with total joint replacement

Periprosthetic osteolysis is known to be a consequence of a local chronic inflammatory reaction in the synovial tissue and the bone-implant interface membrane, and is mediated by macrophages (M) and foreign body multinucleated giant cells (MNGC) in these tissues. Activated M produce major classes of cytokines which have been documented in the regulation of bone cell formation, function and activity. In rheumatoid arthritis, inflammatory mediators released by M participate significantly in articular tissue destruction. In this study we have analysed the production and tissue distribution of 4 cytokines in the interface membranes obtained from patients with osteolysis associated aseptic loosening and in rheumatoid synovium to determine their role in the functional transformation of effector cells in these two conditions. The production of IL-1, GM-CSF, IL-6 and TNF- was assessed using immunohistochemistry on cryostat sections of the interface and the synovial tissues. IL-1 and GM-CSF were detected in significantly high numbers of the inflammatory M in both RA and aseptic loosening. A specific pattern of expression was noted in the interface. IL-1 production was sporadic throughout the sections, while GM-CSF was immunolocalized in a distinct subset of phagocytic macrophages on the implant side. IL-6 showed moderate expression in both conditions and was more widely produced at sites near the bone side in the interface. TNF- expression was absent or reduced in the interface but was more abundant in RA synovial M. The differential expression of cytokines indicates that bone lysis in these two pathological conditions is mediated by different mechanisms and regulated by different cytokines.     

Direct observation of non-collinear vortex structures induced by twin boundaries in YBa2Cu3Oy single crystals

Using vector magnetic moment measurements, in twinned YBa₂Cu₃O_y single crystals we observe a nearly reversible M_ab component of the magnetisation with sharp peaks in the dependence of M_ab on the magnetic field H and angle between c-axis and magnetic field. The association of these features with twin boundaries is supported by geometrical arguments and by comparison with detwinned samples. For a crystal with a single dominant direction of twin boundaries, the initial slope of the M_ab(H) and M_ab() dependences corresponds closely to ideal shielding of the transverse H component, as expected for the fully-locked vortex state. The peak position, which is related to the locking angle, shows a close to linear H_p ^–1 vs dependence, which corresponds to a fixed value of H_L, the locking field. The influence of twins vanishes above a trapping angle T which shows rather weak temperature and magnetic field dependences; at 60K and 1T these parameters are _oH_L=27mT and _T 10 °.     

Analysis and interpolation of a primitive error function by the results of difference measurements

Conclusions The measurement schematics of many instruments based on the difference principle of measurement can be reduced to two fundamental equivalent schematics using one or two reference bases.Amplitudes A_nu and phase angles _nu (the latter only in the case of testing with a single reference base) appear with a distorted scale in practical harmonic analyses of difference measurements. The actual values of _n and A_n are obtained by correcting A_nu and _nu with the relationships given in this article taken into consideration.The values of ordinates in the harmonic analysis should be counted from the abscissa axis determined by the least squares method.     

Dielectric properties of thin solid films formed on silicon

We report on the measurement of the frequency-dependent complex permittivity, ()=()-i(), over the frequency range, 30 MHz to 6 GHz, of silicon wafers and of thin dielectric films formed on silicon. Measurements, as a function of temperature and time treatments, were obtained by means of an HP Network Analyzer and dielectric probe and the resulting ()and()plots for the silicon wafers are shown to have a Debye-type [1] profile, thereby indicating that the associated polarization mechanism is of the orientational variety.     

TEM study of metastable β-phase decomposition in rapidly solidified Ti-6Al-4V alloy

A new rationale is presented for various decomposition products obtained from the metastable -phase found in Ti-6A1-4V alloy produced by hot isostatic pressing comminuted melt-spun fibres and cooled to room temperature by furnace cooling. This alloy has an -matrix with about 8 vol% retained -phase, which is supersaturated with -stabilizers to such an extent that the martensitic transformation has been suppressed. The metastable -phase decomposes by different modes during continuous cooling, depending on the actual composition of individual -grains. Less enrichment of vanadium and iron favours the direct formation of the equilibrium -phase from the -matrix, while greater enrichment of vanadium and iron leads to a spinodal decomposition of the metastable -phase, resulting in a + two-phase structure. During further continuous cooling, the -phase which is lean in -stabilizers will transform into isothermal -phase. In addition, an unknown phase has also been observed in the -phase, which is typified by the appearance of 1/2{112} reflections in the SAD patterns.