Structure and Magnetism of the Composite Crystal Ca0.824CuO2

We have studied the magnetic state from a viewpoint of crystallographic features of the 1-D chain compound Ca_0.824CuO₂. A possible spin-hole arrangement in the magnetically coexisting state was determined by analyzing the local structural distortion in the CuO₂ chain by means of a modulated-crystal-structure analysis. The essential periodic sequence expected is (: up- and down-spin, : hole), which can be regarded as a kind of spin-1/2 ferromagnetic-antiferromagnetic alternating Heisenberg chain.     

Computation of particle settling speed and orientation distribution in suspensions of prolate spheroids

A numerical technique for the dynamical simulation of three-dimensional rigid particles in a Newtonian fluid is presented. The key idea is to satisfy the no-slip boundary condition on the particle surface by a localized force-density distribution in an otherwise force-free suspending fluid. The technique is used to model the sedimentation of prolate spheroids of aspect ratio b/a=5 at Reynolds number 03. For a periodic lattice of single spheroids, the ideas of Hasimoto are extended to obtain an estimate for the finite-size correction to the sedimentation velocity. For a system of several spheroids in periodic arrangement, a maximum of the settling speed is found at the effective volume fraction (b/a)²04, where is the solid-volume fraction. The occurence of a maximum of the settling speed is partially explained by the competition of two effects: (i) a change in the orientation distribution of the prolate spheroids whose major axes shift from a mostly horizontal orientation (corresponding to small sedimentation speeds) at small to a more uniform orientation at larger , and (ii) a monotonic decrease of the the settling speed with increasing solid-volume fraction similar to that predicted by the Richardson–Zaki law (1–)⁵⁵ for suspensions of spheres.     

Deviation from Wiedemann–Franz Law for the Thermal Conductivity of Liquid Tin and Lead at Elevated Temperature

The thermal conductivities of tin and lead in solid and liquid states have been determined using a nonstationary hot wire method. Measurements on tin and lead were carried out over temperature ranges of 293 to 1473 K and 293 to 1373 K, respectively. The thermal conductivity of solid tin is 63.9±1.3 Wm^–1K^–1 at 293 K and decreases with an increase in temperature, with a value of 56.6±0.9 Wm^–1K^–1 at 473 K. For solid lead, the thermal conductivity is 36.1±0.6 Wm^–1K^–1 at 293 K, decreases with an increase in temperature, and has a value of 29.1±1.1 Wm^–1K^–1 at 573 K. The temperature dependences for solid tin and lead are in good agreement with those estimated from the Wiedemann–Franz law using electrical conductivity values. The thermal conductivities of liquid tin displayed a value of 25.7±1.0 Wm^–1K^–1 at 573 K, and then increased, showing a maximum value of about 30.1 Wm^–1K^–1 at 673 K. Subsequently, the thermal conductivities gradually decreased with increasing temperature and the thermal conductivity was 10.1±1.0 Wm^–1K^–1 at 1473 K. In the case of liquid lead, the same tendency, as was the case of tin, was observed. The thermal conductivities of liquid lead displayed a value of 15.4±1.2 Wm^–1K^–1 at 673 K, with a maximum value of about 15.6 Wm^–1K^–1 at 773 K and a minimum value of about 11.4±0.6 Wm^–1K^–1 at 1373 K. The temperature dependence of thermal conductivity values in both liquids is discussed from the viewpoint of the Wiedemann–Franz law. The thermal conductivities for Group 14 elements at each temperature were compared.     

Synthesis and properties of Np(VI) and Pu(VI) monophthalates

Neptunium(VI) and plutonium(VI) monophthalates were prepared and characterized. The complexes AnO₂ (COO)₂C₆H₄ 2H₂O were isolated from cold solutions, and AnO₂ (COO)₂C₆H₄ 1.33H₂O, from hot solutions. NpO₂ (COO)₂C₆H₄ b. 2H₂O and PuO₂ (COO)₂C₆H₄ 2H₂O crystalize in the triclinic and monoclinic systems, respectively. The complexes AnO₂(COO)₂C₆H₄ 1.33H₂O are isostructural and crystallize in the rhombohedral system. The thermal behavior of these complexes was studied. Their IR and electronic absorption spectra were recorded. The properties of these complexes were compared to those of known U(VI) monophthalates.Translated from Radiokhimiya, Vol. 46, No. 5, 2004, pp. 389–395.Original Russian Text Copyright © 2004 by Krot, Bessonov, Grigorev, Charushnikova, Makarenkov.     

Torsional load transfer from a rigid shaft to an elastic plane with a slit

A plane elastostatic problem for an elastic wedge loaded by a concentrated moment at its apex provides an example of violation of the Saint-Venant principle for apex angles 2 larger than . Considering the problem for a truncated wedge, Neuber demonstrated the method of construction of an applicable solution for any apex angles in the range 22, despite the failure of the Saint-Venant principle. In the present paper the particularly important case of the truncated-wedge problem is examined. The truncated wedge degenerates into a slitted elastic plane, while a rigid circular shaft, acted upon by a torsional moment, is inserted into the plane. The analytical solution of the mixed boundary-value problem is obtained. Numerical results turn out to be in complete agreement with Neuber's results for the slitted elastic plane.     

Surface Tension and Density of Oxygen-Free Liquid Aluminum at High Temperature

New values of densities and surface tensions of liquid aluminum obtained in the range 1600 to 2360 K by contactless techniques in neutral gases are reported. Conditions for oxygen-free aluminum are fulfilled which allow determination of the surface tension of aluminum. Extrapolation to the melting point, T _m = 933 K, confirms the value of (T = 933K) = 1.05 N m^–1.     

The dielectric properties of glass-ceramic-on-metal substrates for microelectronics packaging

The dielectric properties of some glass-ceramic-on-metal substrates have been determined over the frequency range 500 Hz to 5 MHz using a.c. bridge techniques. The substrates consisted of cordierite-based glass-ceramics screen printed on molybdenum. For glass layers of thickness greater than 100 m both the permittivity, and the dielectric loss, , are frequency independent over this frequency range at room temperature giving the value of =6.5 and tan =8×10^–3; the room-temperature data are consistent with the universal law of dielectric response. The variation of permittivity with temperature has also been examined and, below 120 °C, the temperature coefficient [(–1) (+2)]^–1 (/T)_p, was found to be 1.3×10^–5 K^–1. The results are compared with those previously reported for Al₂O₃ and AIN substrates.     

On the Universal Curve in Superplasticity Mechanics

We have carried out a series of tests (tensile, compression, torsion, and tension+torsion) of a superplastic titanium alloy VT9 at 950°C, with strain-rate intensity _e = 5 10^-4 - 1 10^-2 s ^-1 . By plotting and analyzing the stress intensity vs strain-rate intensity curves for this material, we justified the validity of the universal curve hypothesis for finite strains with an accuracy acceptable in engineering practice.     

Phase transformation behavior of nanocrystalline χ-alumina powder obtained by thermal decomposition of AIP in inert organic solvent

Thermal decomposition of aluminum isopropoxide (AIP) in inert organic solvents (toluene and mineral oil) resulted in the formation of -alumina. Phase evolution by calcination at various temperatures for this alumina was studied via X-ray diffraction. The results suggest a direct transformation from -alumina to -alumina at approximately 1180°C, without the formation of -alumina phase, while still maintaining the small particle size (<100 nm). The transformation behavior was observed by TEM and the crytallite size was calculated by the Scherrer equation. The results indicate one -alumina crystal transforms into one -alumina crystal at its critical size in a nucleation step. This crystal exhibits a rapid grain growth following the transformation.     

Study of the relationship between J-integral and COD parameters under mixed mode I + II loading in aluminum alloy Ly 12

In this paper, the relationship between the J-integral and COD under mixed mode I+II loading was proposed and investigated. The J-integral was calculated by the Finite Element Method, and COD was defined by Rice`s model and measured by a duplicating method in an aluminum alloy Ly12. The critical values of the J-integral and COD for a stable mixed crack initiation were also determined by a resistance curve. It shows that: (1) the mixed J-integral, J _M, and the mixed COD satisfy the relations of J _M=dn₀CTOD+ds₀CTSD and J _M=d_yieldCOD, where dn, ds and d are coefficients; CTOD and CTSD are the mode I and mode II components of COD, respectively; ₀ and ₀ are the tensile and shear stresses at the crack tip strip, respectively, and (2) the initiation values of the J-integral and COD of mixed stable crack growth increase with an increasing mode II component, the J _IIC value is 2 times greater than that of J _IC, and the COD_i for a pure mode II crack is 6 times greater than that of COD_i for a pure mode I crack.     

The origin of heteroepitaxy in the system of uniaxially oriented isotactic polypropylene and polyethylene

The epitaxy of polyethylene (PE) on oriented and -form of isotactic polypropylene (PP) at different crystallization temperatures and rates have been investigated. The result shows that the epitaxy of PE on -form of PP does not differ from that on the -form of PP. The epitactic alignment of the PE lamellae on the PP films becomes more perfect with higher crystallization rates of PE. The epitaxy of PE on - or -form of PP does not occur at crystallization temperatures higher than 123 °C. A nucleation controlled process for the alignment of the PE is proposed.     

Numerical study of flow in a constricted curved annulus: An application to flow in a catheterised artery

The flow of an incompressible Newtonian fluid in a curved annulus with a local constriction at the outer wall is investigated numerically. The three-dimensional nonlinear elliptic partial differential equations governing the flow are simplified by use of small curvature and mild constriction approximations. The simplified equations of motion, which are locally two-dimensional elliptic in nature at each cross-section, are solved numerically by means of the finite-difference method described by Collins and Dennis [Quart. Jour. Mech. Appl. Math. 28 (1975) 133–156]. Although the results are restricted to small curvature and mild constriction, these are valid for all Dean numbers D in the entire laminar flow regime. The numerical results show that, for higher values of radii ratio k, the pressure gradient, pressure drop, and frictional resistance increase considerably and they vary markedly across the constricted length. These results are used to estimate the increase in frictional resistance in an artery when a catheter is inserted into it. In the absence of constriction (₁=0) and depending on the value of k ranging from 01 to 07, the frictional resistance increases by a factor ranging from 132 to 2391 for D=500 and 120 to 1656 for D=2000. But, in the presence of constriction (₁ = 01) with the same range for k, the increase in frictional resistance is by a factor ranging from 134 to 4232 for D=500 and 118 to 295 for D=2000. In a straight annulus, the increased factor ranges from 174 to 3261 for ₁=0 and 178 to 5827 for ₁ = 01 (for all Dean numbers D).     

Excitation spectrum and the density of states for a superconducting bilayer composite

The single-particle excitation spectrum and the density of states (DOS) for a superconducting bilayer composite are calculated by solving the Bogoliubov equations. The bilayer consists of two different superconducting films in contact. The superconducting order parameters of the films ₁ and ₂ are assumed constant. For various film thicknesses the dependence of the DOS on the ratio ₁/₂ is shown. This dependence is most prominent for states with excitation energy less than ₂.     

Nucleate boiling

The study deals with the effect of the surface conditions on the nucleate boiling curve. A relation is proposed which describes the complete nucleate boiling curve.Notation q thermal flux - q* thermal flux at which the liquid boils after one-phase convection - q_c thermal flux during one-phase convection - q_cr1, q_cr2 first and the second critical thermal flux - T saturation temperature - T superheat of the heating surface relative to the saturation temperature - T* superheat prior to boiling of the liquid after one-phase convection - T_cr1 superheat during the first boiling crisis - T_cr3min minimum superheat at which the third boiling crisis can occur - P pressure - P_cr critical pressure - heat transfer coefficient during nucleate boiling - R_cr radius of a critical vapor forming nucleus - coefficient of surface tension - r latent heat of evaporation - thermal conductivity of the liquid - kinematic viscosity of the liquid - , densities of the liquid and the vapor - g gravitational constant - k Boltzmann constant - N Avogadro number - h Planck's constant Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 40, No. 3, pp. 394–401, March, 1981.     

Theory of the hall effect in strongly correlated Fermi systems

The anomalous properties of the Hall constant in the normal state of high-T_c superconductors are investigated within the Hubbard model. In Mori theory, the frequency dependent Hall constant is given as the sum of its infinite frequency limit and a memory function contribution. The first term (R _H ) was already considered by Shastry et al.¹ In perturbation theory and in the limit of infinite spatial dimensions, the memory function contribution causes the Hall constant to change sign as a function of doping () and to decrease as a function of temperature, if we allow U to be 2W (U: Coulomb repulsion; W: bandwidth). In the limit U , the memory function is calculated via its moments. For frequencies W U, this leads to a decrease of R _H by a factor of (1 + )/2.     

The effect of explosive loading on the microstructure of some metals and alloys

The effects of explosive pulses on the microstructure of Al-4.5% Cu duralumin, tough pitch copper, pure magnetic iron and 18 chromium 8 nickel stainless steel have been studied using transmission electron microscopy. An explosive loading assembly was designed to investigate the effect of both the flanks and the length of shock pulses on the material microstructure. In copper and duralumin it was found that the microhardness increased with the duration of the rarefaction flank. The size of the shock transformed martensite particles in stainless steel also increased with rarefaction time. Three wave interactions could be related to the microstructure of baratol-loaded iron and were attributed to the double shock front caused by the a to phase transformation. Twinning was found to occur when the reflected elastic wave interacted with the first part of the double shock front. The abrupt hardness increase caused by the interaction of the first reflected wave and the second transformation shock front was observed. In addition, a second more gradual hardness increase is attributed to the interaction between the low pressure and the high pressure rarefaction waves which caused a relatively slowly increasing rarefaction shock. The microstructure of shocked stainless steel showed that hexagonal plates and twins could occur in the same grain and that martensite particles were formed at the intersection of two twins, or of plates and twins. Both Kurdjumov-Sachs and Nishyama-Wassermann orientations were observed and sometimes occurred on the same fault band. The short rise and fall times in the pulse flanks made it possible to discuss formation mechanisms for twins and martensite particles in terms of the available formation times.     

Swelling parameter of polypropylene used in household appliances

Samples of unfilled copolymer polypropylene were immersed in various solvents and the equilibrium swelling was recorded. Two-dimensional solubility maps of the Hildebrand parameter, , versus hydrogen bonding parameter, _c, and _h versus _v for polypropylene were plotted. Using the calculated percentage swell values and the solubility maps, the and _h values for detergent were postulated. No changes in the polypropylene backbone were revealed by mid- or far-infrared spectra, showing that the polypropylene polymer, when subjected to a number of different solvents, had not altered substantially.     

Thermophysical Property Measurements of Supercooled and Liquid Rhodium

The density, the isobaric heat capacity, the surface tension, and the viscosity of liquid rhodium were measured over wide temperature ranges, including the supercooled phase, using an electrostatic levitation furnace. Over the 1820 to 2250 K temperature span, the density can be expressed as (T)=10.82×10³–0.76(T–T _m ) (kgm^–3) with T _m =2236 K, yielding a volume expansion coefficient (T)=7.0×10^–5 (K^–1). The isobaric heat capacity can be estimated as C _P (T)=32.2+1.4×10^–3(T–T _m ) (Jmol^–1K^–1) if the hemispherical total emissivity of the liquid remains constant at 0.18 over the 1820 to 2250 K interval. The enthalpy and entropy of fusion have also been measured, respectively, as 23.0 kJmol^–1 and 10.3 Jmol^–1K^–1. In addition, the surface tension can be expressed as (T)=1.94×10³–0.30(T–T _m ) (mNm^–1) and the viscosity as (T)=0.09 exp[6.4×10⁴(RT)] (mPas) over the 1860 to 2380 K temperature range.     

Critical dynamics of a sheared micellar solution

We have investigated the dynamic behavior of a nonionic micellar solution of tetra-ethylene glycoln-decylether (C₁₀ E₄) in water near its critical point in the presence of shear. The non-Newtonian behavior of the viscosity can be represented by * = [ 1 +a(S₄)=]², where* is the viscosity in the absence of shear,S is the shear rate. ₄ is the lifetime of the critical Iluctuations,a is a system-dependent constant, and = 0.02 In addition, we have found that, before attaining a steady state, the sheared mixture undergoing phase separation shows significant shear-dependent rheological effects due to the presence of concentration domains.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24. 1994, Boulder, Colorado, U.S.A.     

Strength of the pyroceram So115M under lengthy static loading

The article presents the results of long-time strength tests of the casting pyroceram SO115M at room temperature by the method of three-point bending. We obtained the power dependence of the time to failure _f on the applied load : _f ^–11.7.Translated from Problemy Prochnosti, No. 1, pp. 102–104, January, 1996.