Magnetic domain behaviour of MgFe2O4-CoFe2O4 system

Ferrites with the composition Mg_1−x CO _x Fe₂O₄(0<x≤0·33) were synthesized by solid state reaction between MgO,α-Fe₂O₃ and CoFe₂O₄ at 1300°C. The compounds were analyzed from the results of x-ray diffraction, magnetic hysteresis and initial susceptibility (χ) studies. All the compounds of the series were found to be monophasic with no appreciable change in their lattice parameter. The saturation magnetization and coercive field (H _c ) values increased with increasing cobalt ferrite content. Similarly, the shapes of theχ-T curves and temperature variations ofH _c values indicated that the magnetic behaviour changes from multi-domain to single domain with increasing cobalt content. The results are similar to those observed for the (MgFe₂O₄)_1−x (Co₃O₄) system.     

Linear programming with multiple fuzzy goals

This paper describes the use of fuzzy set theory in goal programming (GP) problems. In particular, it is demonstrated how fuzzy or imprecise aspirations of the decision maker (DM) can be quantified through the use of piecewise linear and continuous functions. Models are then presented for the use of fuzzy goal programming with preemptive priorities, with Archimedean weights, and with the maximization of the membership function corresponding to the minimum goal. Examples are also provided.     

Annealing of melt-crystallized nylon 6

Effect of annealing on thermal behaviour and crystalline structure of meltcrystallized nylon 6 has been investigated.The annealing process is found to be characterized by an incubation period followed by a more or less doubling of the SAXS long spacing and of the crystallinity.The extrapolated heat of melting of the crystalline phase of nylon 6 in the-modification is 188 Jg^–1 and its extrapolated equilibrium melting temperature is 260 °C.Presented in part at 28th IUPAC Symposium on Macromolecules, Strasbourg, July, 1981.     

Microcomputer Simulation of Elution Behaviour for Dicarboxylic Acids in Ion－Exclusion Chromatography

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Monte carlo simulations of microemulsions

Summary We describe the Larson-Stauffer model of a microemulsion and report results which strongly indicate that this is a successful model. Particular attention is paid to the structure of the surfactant which appears to be the decisive factor for modelling a microemulsion. We study the kinetics of micelle formation, the miscibility gap of oil and water, the coexistence of various phases, the segregation of three phases (oil rich, water rich and the bicontinuous surfactant rich) as a function of temperature, the relative interaction strengths of hydrophobic and hydrophilic monomers of the surfactant with oil and water, and concentration of surfactant. The model is capable of describing most of the observed properties of a microemulsion. In addition, we are now in the position to study the properties of ?designer? surfactant,e.g., ?bola-form?. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

Isobaric and isothermal glass transition of PMMA: pressure-volume-temperature experiments and modelling predictions

The scaling law for relaxation times, recently proposed by Casalini and Roland, is utilized in the framework of KAHR (Kovacs, Aklonis, Hutchinson, and Ramos) phenomenological theory. With this approach it is shown that the pressure, volume, and temperature (PVT) data obtained on Poly(methyl-methacrylate) (PMMA) can be reliably predicted, in the region of the alpha-relaxation, by using only two fitting parameters, namely: the relaxation time in the reference state, τ_g, and the fractional exponent, β, that describes the dispersion of the alpha-relaxation.     

The magnetization reversal behaviour for SmCo6.8Zr0.2 and SmCo6.8Zr0.2/α-（Fe,Co） nanocrystalline magnets at low temperature

This paper reports that the SmCo 6.8 Zr 0.2 nanocrystalline permanent magnets and SmCo 6.8 Zr 0.2 /α-(Fe,Co) nanocomposite permanent magnets are successfully produced by mechanical alloying and subsequently annealing at 700 C for 10 minutes.The x-ray diffraction results show that the phase structure of SmCo 6.8 Zr 0.2 nanocrystalline permanent magnets is composed of SmCo 7 phase and SmCo 6.8 Zr 0.2 /α-(Fe,Co) nanocomposite permanent magnets is composed of SmCo 7 and α-(Fe,Co) phases.The mechanism of magnetization reversal is mainly controlled by inhomogeneous domain wall pinning in SmCo 6.8 Zr 0.2 and SmCo 6.8 Zr 0.2 /α-(Fe,Co) magnets.The inter-grain exchange interaction at low temperature is investigated,which shows that the inter-grain exchange interaction of SmCo 6.8 Zr 0.2 /α-(Fe,Co) magnets increases greatly by the decrease of the measured temperature.According to Δm irr-H/H cj,Δm rev-H/H cj and χ irr-H/H cj curves at room temperature and 100 K,the changes of irreversible and reversible magnetization behaviours of SmCo 6.8 Zr 0.2 and SmCo 6.8 Zr 0.2 /α-(Fe,Co) magnets with the decreasing temperature are analysed in detail.The magnetic viscosity and the activation volume of SmCo 6.8 Zr 0.2 and SmCo 6.8 Zr 0.2 /α-(Fe,Co) magnets at different temperatures are also studied.     

Diauxic behaviour for biological processes at various timescales

In the present paper, we provide the conditions guaranteeing the generalization of so-called diauxic behaviour of solutions of ordinary differential equations (ODEs). This behaviour was described by Monod in 1949 in the context of bacterial growth. Then, a similar behaviour was observed and described referring to dynamic of CDK1 protein activity during cell cycle. The diauxic behaviour is described in terms of inflection points.     

ON ENERGY CONSERVATION BY TRIGONOMETRIC INTEGRATORS IN THE LINEAR CASE WITH APPLICATION TO WAVE EQUATIONS

Trigonometric integrators for oscillatory linear Hamiltonian differential equations are considered. Under a condition of Hairer & Lubich on the filter functions in the method, a modified energy is derived that is exactly preserved by trigonometric integrators. This implies and extends a known result on all-time near-conservation of energy. The extension can be applied to linear wave equations.