Critical fields

The theory and appHcation of SF BDV and COV have been studied in both uniform and nonuniform electric fields (37). The ionization potentials of SFg and electron attachment coefficients are the basis for one set of correlation equations. A critical field exists at 89 kV/ (cmkPa) above which coronas can appear. Relative field uniformity is characterized in terms of electrode radii of curvature. Peak voltages up to 100 kV can be sustained. A second BDV analysis (38) also uses electrode radii of curvature in rod-plane data at 60 Hz, and can be used to correlate results up to 150 kV. With d-c voltages (39), a similarity rule can be used to treat BDV in fields up to 500 kV/cm at pressures of 101—709 kPa (1—7 atm). It relates field strength, SF pressure, and electrode radii to coaxial electrodes having 2.5-cm gaps. At elevated pressures and large electrode areas, a faH-off from this rule appears. The BDV properties ofHquid SF are described in thehterature (40—41). 

This critical field called coercivity or switching field is also equal to If a field is appHed in between 0 and 90° the coercivity varies from maximum to zero. In the case of this special example the appHed field = H/. Based on the classical theory, Stoner-Wohlfarth (33)... 

The alloy niobium titanium (NbTi) and the intermetaUic compound of niobium and tin (Nb.3 Sn) are the most technologically advanced LTS materials presently available. Even though NbTi has a lower critical field and critical current density, it is often selected because its metallurgical properties favor convenient wire fabrication. In contrast, Nb.3Sn is a veiy brittle material and requires wire fabrication under very well-defined temperature conditions. 

Chapter 9 shows the importance of PLC in the critical field of medical research, with representative examples of the applications to amino acids, carbohydrates, lipids, and pharmacokinetic studies. 

These are the critical fields from the WHODrug medicinal product data file ... 

A surprising prediction of the Hong-Noolandi (1978b) theory is the existence of a critical field Fc above which the long-time decay becomes purely... 

Table 10.2 lists the critical field Ec in various nonpolar liquids along with the approximate nature of field dependence of mobility when E > Eq. It is remarkable that the higher the zero-field mobility is, the smaller is the value of Ec, indicating the role of field-induced heating. Also note that in the sublinear case, Ec is larger in the case of molecular liquids than for liquefied rare gases,... 

TABLE 10.2 Critical Field E and Nature of Field Dependence of Mobility in Various Nonpolar Liquids... 

In Table 8.11, the approximate transition temperature of some elements in zero magnetic field and critical fields are reported [31]. 

In the last decades, aluminium and aluminium alloys have received an increasing interest in cryogenic applications [5-7], Pure aluminium is used in the building of superconducting heat switches (see Section 4.3) because of its high switching ratio [8,9] and convenient critical field. Satisfactory procedures for welding have also been found [10,11],... 

Table 1 Cation and anion S values basic structural motives Weiss constants transition temperatures, magnetic ordering critical fields of the salts based on metallocenium and on metal bisdichalcogenate complexes ... 

The magnetic behavior of [Fe(Cp )2][Ni(edt)2] is consistent with the coexistence of FM intrachain interactions, due to D+A intrachain short contacts, with AF interchain interactions, resulting from the D+A- and A A interchain contacts, as predicted by the McConnell I mechanism [44], In this case the interchain interactions must be particularly large as they seem to be the dominant interactions at high temperatures. The value of the critical field, 14 kG, much higher than any of the... 

Applying resonance overlap criterion to this Hamiltonian we get the following estimate for the critical field strength ... 

This estimate for the critical field assumes that n is large. If the external field strength has the value exceeding ecr, breaking of KAM surfaces in... 

Table I. The values of the critical field strength for various quarkonia.

Critical currents, 23 821-823 in superconducting, 23 819-825 Critical event (CE), 15 462 Critical failure, 26 982 Critical features, in separating nonideal liquid mixtures, 22 307 Critical fields, thermodynamic, 23 809-811 Critical flocculation concentration, 11 631 Critical item evaluation, for reliability, 26 991... 

Peskin and Raco (P3) have given a theoretical analysis of both ultrasonic and electrostatic atomization from the point of view of liquid instability. They conclude that atomization with low frequency ac will require about twice the field strength as dc but that, by going to high frequency, lower fields are possible with conducting liquids. The value for the critical field for atomization given by these authors for a dc field is, however, smaller than that which would be calculated from Eq. (39) by a factor of (1/32)1/2. This presumably reflects the simplified one-dimensional model used in their derivation. 

The critical ac field strength depends on d, but the minimum critical field strength, which corresponds to (5 = 0 is given by = 0.908. Thus, a particle can be stably levitated provided that p < P = 0.908 or, in terms of the ac voltage and frequency, stable trapping occurs provided that... 

As can be seen from Fig. 11c, the anisotropic frozen polar cluster component increases in intensity if the crystal is cooled at low enough temperatures in an electric field larger than the critical field and applied along the (111) direction. A transition to the ferroelectric phase is induced for E > Eq. The difference between the FC and ZFC Pb NMR spectra is striking and... 

The bistable character of the zero-field Hamiltonian will be destroyed by a sufficiently large field. The critical field for n h is called the anisotropy field, and is expressed by... 

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