Scaling Law Analysis Research Articles

Thermomagnetic and crystallisation behaviour of amorphous Fe95-xW5Bxalloys

Thermomagnetic studies and X-ray analysis made on the amorphous Fe95-xW5Bx alloys with x=15, 20 and 25 show the presence of stable alpha -Fe, Fe2B and FeWB phases. Low-temperature (4.2-300 K) magnetisation measurements indicate the existence of spin waves and Stoner or single-particle excitations. Isochronal and isothermal annealing treatments reveal two stages of relaxation, one of which is attributed to compositional or chemical short-range ordering (CSRO). The value of the critical exponent beta for all the three compositions is determined to be 0.43 by means of scaling law analysis and it is found to be independent of annealing treatments.

Theoretical analysis of efficiency scaling laws for a self-sustained discharge pumped XeCl laser

By using a kinetic model developed for a self-sustained discharge pumped XeCl laser (B→X, 308 nm) with the Ne/Xe/HCl mixture, we determined operational conditions of the XeCl laser with commonly used pulse width of about 100 ns for attaining efficient lasing. According to the analysis of electron kinetics in the laser discharge, the XeCl* formation, the XeCl* relaxation, and the absorption of the B→X laser radiation, it is found that the discharge and kinetic characteristics are affected predominantly by the electron number density which is determined mainly by the ratio of Xe to HCl concentrations. Although the XeCl* formation, the XeCl* collisional quenching, and the absorption of the laser radiation increase with increasing total gas pressure, the optimum Xe and HCl concentrations which are almost independent of the total gas pressure can be determined. Furthermore, since the laser output energy does not increase linearly with the excitation rate, the optimum excitation rate can be determined for a given total gas pressure as it shifts to a higher value with increasing total gas pressure. As a result of the analysis by using the most reliable rate constants and cross sections for the reactions published so far involved in the XeCl laser kinetics, the maximum intrinsic efficiency of 12.5% is found to be obtainable with a 3-atm laser mixture of 0.2% HCl and 1% Xe in the Ne diluent pumped with an excitation rate of 3.5 MW/cm3.

PVT Measurements and Critical Parameters of Water

ABSTRACTThe PVT properties and vapor-pressures of water have been measured in the critical region by using a constantvolume apparatus immersed in the constant-temperature bath with the procedure of varying the sample mass along a prescribed isotherm. Ninety-one PVT and five vapor-pressure measurements along 11 isotherms cover the region of temperatures 643 to 673 K and of pressures 19.7 to 38.6 MPa, which corresponds to a density variation from 108 to 618 kg/m3. The experimental uncertainties of temperature, pressure and density are estimated 4 mK, 5 kPa and 0.04%, respectively. Based on these measurements, the critical parameters of water are proposed to be 647.061 K, 22.041 MPa and 322.4 kg/m3 by the scaling law analysis.

Spin Wave and Scaling Law Analysis of Amorphous (FexNi1-x)75P16B6Al3 by Magnetization Measurements

The magnetization of the amorphous (FexNi1-x)75P16B6Al3 system has been measured for iron concentrations larger than the percolation limit x = 0.17. Up to x ≈ 0.30 we find a low temperature regime of spin glass behaviour, followed at intermediate temperatures by a ferromagnetic state. For higher iron concentrations the strong exchange interactions result in ordinary ferromagnetism. For the low temperature magnetization a spin wave analysis is presented.The influence of structural relaxation upon the ferromagnetic transition is reported as well as possible attendant consequences of the scaling law analysis. In particular the effects of annealing temperature have been studied. Despite a definite shift in transition temperature with annealing above 380 K the critical exponents are shown to be unaffected. For the pure ion sample Fe75P16B6Al3 the critical exponents (β = 0.38, δ = 4.8, γ = 1.4) are close to a 3d Heisenberg behaviour, while the mixed (Fe, Ni) samples (x < 1) consistently give exponents (β ≈ 0.40, δ ≈ 5.1, γ ≈ 1.6) that deviate from the 3d Heisenberg values.

Influence of structural relaxation of scaling law analysis at the ferromagnetic transition of amorphous alloys

In this paper we report the influence of structural relaxation upon the ferromagnetic transition, T c, and the possible attendant consequences on the scaling law analyses for amorphous (Fe xNi 1−x) 75P 16B 6A1 3 alloys. Despite changes in T c with thermal annealing, consistent values for the critical exponents ( β ≅ 0.4, δ ≅ 5.1, γ ≅ 1.6) are observed.