Jet methods

It was determined, for example, that the surface tension of water relaxes to its equilibrium value with a relaxation time of 0.6 msec [104]. The oscillating jet method has been useful in studying the surface tension of surfactant solutions. Figure 11-21 illustrates the usual observation that at small times the jet appears to have the surface tension of pure water. The slowness in attaining the equilibrium value may partly be due to the times required for surfactant to diffuse to the surface and partly due to chemical rate processes at the interface. See Ref. 105 for similar studies with heptanoic acid and Ref. 106 for some anomalous effects. 

The oscillating jet method is not suitable for the study of liquid-air interfaces whose ages are in the range of tenths of a second, and an alternative method is based on the dependence of the shape of a falling column of liquid on its surface tension. Since the hydrostatic head, and hence the linear velocity, increases with h, the distance away from the nozzle, the cross-sectional area of the column must correspondingly decrease as a material balance requirement. The effect of surface tension is to oppose this shrinkage in cross section. The method is discussed in Refs. 110 and 111. A related method makes use of a falling sheet of liquid [112]. 

All tests are designed to provide high erosion rates on small specimens so that the test can be conducted in a reasonable time, and although vibratory and high-velocity jet methods may not simulate flow conditions they give rise to high-intensity erosion and can be used, therefore, for screening materials. 

Crystallization of CaCOj with the Anionic PAMAM Dendrimers by the Double Jet Method... 

The main difficulty in measuring the compensation voltage of voltaic cells is the very large resistance of the system caused by the presence of a dielectric gas phase. Therefore there are two possibilities for solving the problem reduce this resistance or measure the work of the charge transfer across the dielectric. The first possibihty is accomplished by the ionizing method and the second by condenser and jet methods. 

The principle of the jet method, which also utilizes a condenser, was originated by Kenrick and improved by Randles and later by McTigue et al. It may be summarized as follows A jet of one liquid is directed down the axis of a tube, the inner surface of which is covered by a stream of the second liquid. If the reference electrodes are the same and the outer... 

Usually before adding a surfactant it is necessary to clean the surface of the water solution by siphoning off the top layers of water with a glass capillary until the constant compensation voltage is obtained. This is not done in the jet method. 

Wilson, A. D., Groffman, D. M., Powis, D. R. Scott, R. P. (1986a). An evaluation of the significance of the impinging jet method for measuring the acid erosion of dental cements. Biomaterials, 7, 55-60. 

Osborne et al., 1978) and the laboratory impinging jet method (Beech Bandyopadhyay, 1983 Wilson et a/., 1986a). 

In vitro studies by Wilson et al. (1986) using the impinging jet method show the EBA cement to be the least resistant of all the cement types to erosion in neutral solution. Clinical studies confirm this result and show that there is greater dissolution in the mouth than for other dental cements (Mitchem Gronas, 1978 Osborne et al., 1978 Andrews and Hembree, 1976 Shilling, 1977). Despite this, a clinical survey by Silvey and Myers... 

Two dynamic methods have been developed for measurement of the surface tensions, the method of ripples first employed by Rayleigh and the vibrating jet method developed by Bohr. 

More closely approaching the conditions desirable for determining the true dynamic surface tension is the vibrating jet method. 

That adsorption occurs with great ease on mercury surfaces is demonstrated by the wide variations observed in the literature for the surface tension of this substance in contact with various gases. Thus Meyer obtained by the vibrating jet method the following values ... 

PC 2765-70, 1972, Gruppa 29 (CMEA, Group 29). Instrumenty abrazivnye (Abrasive Tools). Izmerenie tverdosti peskostruinym metodom (Hardness Measurements by Sand Jet Method). 

Monodisperse emulsions, prepared by the double-jet method, have a narrow range of grain sizes of uniform shape. The grains can be either cubic or octahedral, depending on the conditions of preparation. 

Surface image is formed predominantly in monodisperse, fine-grain emulsions prepared by the double-jet method. 

The inks can contain drying oil alkyds along with hydrocarbon resins and high boiling (200—370 °C) hydrocarbon solvents. Business form inks closely resemble the lithographic heatset or quickset inks. Business forms have also been printed by the ink jet method. These inks are usually based on water, glycols, and dyes. 

At the time of writing this article, there are only two instruments in the market in the U.S.A. - the Rheometrics Extensional Rheometer, the RFX, and the Rheometrics Elongation Melt Rheometer, based on Meissner s rotary clamp method. The RFX is based on the opposing jet method. 

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