Showing papers on "Crossover published in 1975"
TL;DR: In this article, the model is taken in the thermal-Condon approximation with the overlap integrals evaluated through the Manneback recursion formulas, and a numerical matrix method is described which can handle all cases and which explicitly exhibits the multiple activation energies mħωυ in every case.
249 citations
54 citations
20 citations
TL;DR: In this paper, a universal n-and m-dependent amplitude locating the singularity of the crossover scaling function is derived to second order in epsilon = 4-d and found to give fair agreement with the results of recently derived series expansions.
Abstract: Feynman graph methods are used to analyse crossover behaviour in an n-component Heisenberg system, with a spin anisotropy that results asymptotically in m-component critical behaviour. An expression for the universal n- and m-dependent amplitude locating the singularity of the crossover scaling function is derived to second order in epsilon =4-d and found to give fair agreement with the results of recently derived series expansions. The same techniques are used to obtain, to 0( epsilon 2), a universal amplitude ratio characterizing the shape of the phase boundary in the vicinity of spin-flop bicritical point.
13 citations
01 Aug 1975
TL;DR: In this article, the solution of the wave equation for a plane stratified medium is obtained by using a fourth-order accurate numerical integration technique and the general solution is described in terms of four characteristic waves, two upgoing and two downgoing.
Abstract: The solution of the wave equation for a plane stratified medium is obtained by using a fourth-order accurate numerical integration technique. The general solution thus obtained is described in terms of four characteristic waves, two upgoing and two downgoing. A compact expression for the coupling coefficients Γij(i ≠j), which is suitable for numerical calculation, is also derived. These techniques are then used in a quantitative study of transmission coefficients, coupling factors, and wave structures through the crossover region where the proton whistlers are generated. The negligible influence of collisions upon the transmitted energies in the two upgoing modes is discussed. The results are then compared with previous works in which the thin-slab full-wave method was used.
7 citations
3 citations
TL;DR: Simple crossover studies with drugs may introduce artifactual results, but volunteers are frequently less apprehensive when tested on the second occasion and experimental medication may result in different performance measures.
Abstract: Simple crossover studies with drugs may introduce artifactual results. Volunteers are frequently less apprehensive when tested on the second occasion and experimental medication may result in different performance measures. Empirical evidence is given to demonstrate this point and a suggestion is made as to how it can be overcome.
2 citations
01 May 1975
TL;DR: In this article, the performance of a human in a closed loop tracking task can be determined by using a simple low pass filter model with a least squares identification algorithm, which can be easily determined by mean square tracking error.
Abstract: The performance of a human in a closed loop tracking task can be determined by using a simple low pass filter model with a least squares identification algorithm. The crossover model and the extended crossover model can be shown to be special cases of the low pass filter model presented here. Performance in tracking can be easily determined by mean square tracking error which can be written in terms of the parameters of the low pass filter model. A closed form expression for the effective time delay is also obtained. Experimental data from a roll axis tracking simulation is presented and simple prediction rules are determined. A comparison is made between this model and the crossover model with respect to their differences and similarities.
1 citations