EXPANSION AND STRESS RELAXATION OF EXPRESSED CAKE

Expansion and stress relaxation of expressed cake are discussed.

The expansion process of expressed cake after release of load is very similar to consolidation of solidndashliquid mixtures, although a liquid flow in the expansion process is opposite in direction to that in consolidalion. This process can be analyzed well by use of the Terzaghi Voigt combined model. It is shown that the rate of primary deformation in expansion is much smaller than that in consolidation under the same change in compressive pressure. It is also found that the ratio of secondary deformation to total deformation in expansion is much larger than that in consolidation.

Stress relaxation of expressed cake, which is observed when expression is stopped before attaining an equilibrium compression state of a material, can be explained by use of a consolidation and expansion theory. In the relaxation process, local expansion appears near the drainage surface while local consolndash idation appears near the center of the cake. The equilibrium cake stress is uniquely determined by the average consolidation ratio when the expression is interrupted.     

Numerical simulation of oscillatory flow in melt during InSb single crystal growth by RF heating Czochralski method

Oscillatory flow present in the melt during InSb single crystal growth using an RF-heating Czochralski method has been numerically investigated by means of the finite difference method using the HSMAC algorithm. The thermal boundary conditions required for the numerical simulation model were obtained experimentally by measuring the temperature profile along the crucible of a Czochralski system by means of thermocouples mounted in the crucible. Results of numerical simulations showed that the use of a third-order upwind discretization scheme was necessary to catch the oscillatory behaviour of the fluid flow in the melt. It was shown that this oscillatory behaviour strongly depends on the crystal rotation rate. Indeed, the oscillation period increases when the crystal rotation rate is above a critical rotation rate. In order to avoid such oscillations, crystal rotation rates lower than this critical value of crystal rotation rate must be selected for the growth of high quality crystals free of striations. © 1998 John Wiley & Sons, Ltd.     

Preparation of Ba2YCu3O7-δ Thin Films with Preferred Orientation through an Organometallic Route

Superconducting Ba₂YCu₃O_7-δ thin films were prepared through an organometallic route. Single-phase Ba₂YCu₃O_7-δ thin films with preferred orientation were successfully prepared on SrTiO₃ (100) single-crystal substrates at 800°C by a dip coating method using partially hydrolyzed Ba-Y-Cu organometallic solutions. Preferentially oriented Ba₂YCu₃-O_7-δ thin films were also prepared on MgO (100) substrates. By controlling the partial hydrolysis conditions, a coating solution for precursor thin films was kept accurately at the stoichiometric composition. The use of ozone gas during the pyrolysis of the precursor thin films was found to suppress the formation of BaCO₃. Ba₂YCu₃O_7-δ thin films with c -axis orientation perpendicular to a SrTiO₃ (100) substrate, which were heat-treated at 900°C for 15 min, exhibited a superconductivity transition with an onset of 90 K and an end of 75 K.     

Electrical and Thermal Conductivity and Conduction Mechanism of Ge<Subscript>2</Subscript>Sb<Subscript>2</Subscript>Te<Subscript>5</Subscript> Alloy

Ge₂Sb₂Te₅ alloy has drawn much attention due to its application in phase-change random-access memory and potential as a thermoelectric material. Electrical and thermal conductivity are important material properties in both applications. The aim of this work is to investigate the temperature dependence of the electrical and thermal conductivity of Ge₂Sb₂Te₅ alloy and discuss the thermal conduction mechanism. The electrical resistivity and thermal conductivity of Ge₂Sb₂Te₅ alloy were measured from room temperature to 823 K by four-terminal and hot-strip method, respectively. With increasing temperature, the electrical resistivity increased while the thermal conductivity first decreased up to about 600 K then increased. The electronic component of the thermal conductivity was calculated from the Wiedemann–Franz law using the resistivity results. At room temperature, Ge₂Sb₂Te₅ alloy has large electronic thermal conductivity and low lattice thermal conductivity. Bipolar diffusion contributes more to the thermal conductivity with increasing temperature. The special crystallographic structure of Ge₂Sb₂Te₅ alloy accounts for the thermal conduction mechanism.     

Effects of Heavy Element Substitution on Electronic Structure and Lattice Thermal Conductivity of Fe2VAl Thermoelectric Material

By using first-principles cluster calculations, we identified that Ta or W substitution for V is useful for decreasing the lattice thermal conductivity of the Fe₂VAl Heusler alloy without greatly affecting the electron transport properties. It was clearly confirmed that the Fe₂(V_1?x Ta _x )Al_0.95Si_0.05 (x?=?0, 0.025, 0.05), Fe₂(V_0.9?x Ta _x Ti_0.1)Al (x?=?0, 0.10, 0.20), and Fe₂(V_0.9?2x W _x Ti_0.1+x )Al (x?=?0, 0.05, 0.10) alloys indeed possessed large Seebeck coefficient regardless of the amounts of substituted elements, while their lattice thermal conductivity was effectively reduced. As a result of partial substitution of Ta for V, we succeeded in increasing the magnitude of the dimensionless figure of merit of the Heusler phase up to 0.2, which is five times as large as the Ta-free compound.     

Enhancement of thermostability of kojibiose phosphorylase from Thermoanaerobacter brockii ATCC35047 by random mutagenesis

Random mutation by error-prone PCR was introduced into kojibiose phosphorylase from Thermoanaerobacter brockii ATCC35047. One thermostable mutant enzyme, D513N, was isolated. The D513N mutant enzyme showed an optimum temperature of 67.5-70 degrees C (the wild type, 65 degrees C), and thermostability up to 67.5 degrees C (the wild type, up to 60 degrees C). The half-lives of D513N were estimated to be 135 h at 60 degrees C, 110 min at 70 degrees C and 6 min at 75 degrees C, respectively. They were about 1.6-fold, 7-fold and 6-fold longer than those of the wild-type enzyme, respectively.     

Phytoextraction by a high-Cd-accumulating rice: reduction of Cd content of soybean seeds

Soybeans (Glycine max (L) Merr.) are the major summer crop grown in Japanese upland fields (characterized by aerobic soil) that have been converted from paddies. To evaluate the effect of phytoextraction by rice on the seed cadmium (Cd) content of soybeans grown subsequently, we grew Milyang 23, a high-Cd-accumulating rice cultivar, and then grew soybeans in three paddy soils contaminated with moderate Cd concentrations (2.50-4.27 mg Cd kg(-1)). The rice accumulated 7-14% of the total soil Cd in its shoots. The soybean seed Cd contents were 24-46% less than those grown on control soils. Phytoextraction by Milyang 23 rice is thus a promising remediation method for reducing seed Cd contents of soybeans grown on paddy soils under aerobic soil conditions.     

Effect of static pressure on intracellular pH of adhesive Chinese hamster ovary cells

The effect of static pressure on the intracellular pH of the Chinese hamster ovary (CHO) cell line DR1000L4N was investigated. In cultivation of CHO cells at 0.9 MPa, two distinct populations were observed in the histogram of a flow cytometer, while single population was observed in cultivation at 0.1 MPa. The intracellular pH of the major population at 0.9 MPa was markedly lower than that of the single population at 0.1 MPa.