Coercivity analysis in R17Fe83−χBχ magnets

We studied the coercivity in magnets of composition R₁₇Fe_83−χB_χ (R = Nd, Pr and χ = 8, 30), using measurements of the coercive field H_c, its angular dependence, and the magnetic viscosity coefficient S_v, for temperatures between 4.2 and 500 K. The results are discussed in relation to a model which does not specifically consider the detailed mechanisms involved in magnetization reversal, but which provides information about the magnetic properties in the activation volume v where magnetization reversal is initiated. It is concluded that the ordering temperature in v tends to be slightly smaller than in the bulk and that the room temperature anisotropy in v is not strongly reduced with respect to the bulk value. Finally, a direct evaluation of the dipolar interactions is in good agreement with results obtained from H_c(T).     

Deuteron and neutron structure functions and the effect of relativistic Fermi motion

The deep-inelastic deuteron structure function (SF) F₂^D in the covariant approach in the light-cone variables is considered. The neutron SF F₂ⁿ is extracted from the deuteron and proton experimental data taking into account the relativistic deuteron model and the parametrization of F₂ⁿ is obtained. The effect of the relativistic Fermi motion is estimated to be 6% at x0.7. The extracted neutron SF is used to verify the Gottfried sum rule. It is shown that the violation of the flavour symmetry of the sea can be large with increasing Q².     

Thermotropic liquid-crystalline behaviour from mixtures of non-mesogenic molecules

A class of non-mesogenic molecules, which as mixtures exhibit monotropic nematic phases, is described.     

Ferroelectric polarization switching in nylon-11

Cold-drawn Nylon-11 films, which were prepared by stretching the melt-quenched films to a draw ratio of 2.8: 1 at room temperature, were found to exhibit an electric displacement versus electric field hysteresis loop. The results confirmed that the Nylon-11 film exhibited ferroelectric behavior at or below room temperature. The coercive fields were 65, 98, 125, 160, and 215 MV/m at 20, 0, ?20, ?40, and ?60°C and the remanent polarization at ?20°C (where there was considerably less dc conduction) was 56 mC/m². Switching of the polarization was almost completed within 20 ms.     

Canonical fields in the quantum sh-Gordon model

In the quantum sh model fundamental canonical fields are constructed with the help of the Gel'fand-Levitan-Marchenko equations.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Maternaticheskogo Instituta im. V. A. Steklova, Akad. Nauk SSSR, Vol. 172, pp. 145–159, 1989.     

A quantum chaotic clock and damping of the coherent nuclear rotation in the 28 Si +64 Ni dissipative collision

We employ the statistical reactions with memory approach to study oscillating excitation functions in the ²⁸ Si(E _lab = 120–126.75 MeV)+⁶⁴ Ni strongly dissipative reaction and the time evolution of the collision process. The nonself-averaging of the oscillations in the excitation functions is interpreted as indication of quantum chaos and damping of the coherent nuclear rotation in dissipative heavy-ion collisions.     

AN ENCOMPASSING APPROACH TO MODELING FISHERY DYNAMICS: MODELING DYNAMIC NONLINEAR SYSTEMS

Uncertainty about the nature and significance of nonlinearities and the manner in which dynamics affect future realizations makes model specification the most difficult aspect of modeling dynamic systems. By interpreting several popular fishery models as subcases of a nesting dynamic Taylor series approximation, we isolate the specification differences between these models in a way that accounts for commonalities. On the argument that the differences due to alternative nonlinear forms are likely to be small compared to more mundane considerations such as delay difference and general dynamic lag specification, we propose an alternative model that uses the terms from the first order approximation common to all models combined with a data-based determination of the appropriate lags using the methods of state space time series analysis. Finally, the success of the alternative models is judged in an application to Pacific halibut data.