Meniscus distortion

It is well known in polymer rheology that a torsional parallel-plate flow cell develops certain secondary flow and meniscus distortion beyond some stress level [ 14]. For viscoelastic melts, this can happen at an embarrassingly low stress. The critical condition for these instabilities has not been clearly identified in terms of the shear stress, normal stress, and surface tension. It is very plausible that the boundary discontinuity and stress intensification discussed in Sect. 4 is the primary source for the meniscus instability. On the other hand, it is well documented that the first indication of an unstable flow in parallel plates is not a visually observable meniscus distortion or edge fracture, but a measurable decay of stress at a given shear rate [40]. The decay of the average stress can occur in both steady shear and frequency-dependent dynamic shear. 

Fig. 25.3 Time sequence of droplet formation in response to one pulse (Vp = 29 V). The ink is ejected rightward, and the vertical line shows the location of orifice. Meniscus distortion appears at t 30 is. Mirror images due to reflection from the printhead are visible on the right side of the orifice. Images from a solid ink printhead (Phaser 860 provided by Xerox Corporation, Rochester, NY) with orifice diameter of 20 pm (Reproduced from [28]. With permission. Copyright 2008)...

The use of the surface ultrasonic waves seems to be convenient for these purposes. However, this method has not found wide practical application. Peculiarities of excitation, propagation and registration of surface waves created before these time great difficulties for their application in automatic systems of duality testing. It is connected with the fact that the surface waves are weakened by soil on the surface itself In addition, the methods of testing by the surface waves do not yield to automation due to the difficulties of creation of the acoustic contact. In particular, a flow of contact liquid out of the zone of an acoustic line, presence of immersion liquid, availability of chink interval leads to the adsorption and reflection of waves on tlie front meniscus of a contact layer. The liquid for the acoustic contact must be located only in the places of contact, otherwise the influence on the amplitude will be uncontrolled. This phenomenon distorts the results of testing procedure. 

The distortion of the liquid is caused by the surface tension of that liquid and the walls of the container. This distorted line is called the meniscus. When liquid wets the walls of a container, you read the bottom of the meniscus. When liquid does not wet a containers walls (such as mercury or any liquid in a plastic container),... 

This equation can be used to explain that stable adsorption on the inner wall of a capillary tube is possible up to a certain critical thickness. Capillary condensation starts from this critical thickness. It appears that capillary condensation in the cylindrical pores with radii between 2 and 7 run is well described by the corrected Kelvin equation. The deviation from the ideal behavior can amount to up to +20%. Nevertheless, it is difficult to estimate the limits of the applicability of the Kelvin equation. It seems likely that distortions of the meniscus in small pores may occur and that the local pore geometry may have a marked influence [1,15]... 

The numericcd value we read for the volume of liquid contained in this cylinder will depend on what part of the meniscus we choose to look at. Graduated cylinders and other containers are Ccdibrated such that we should get the most accurate reading by looking at the center of the meniscus from eye level. If we don t look at the meniscus from eye level, something called parallax error will occur that will distort our perception of level of the meniscus. 

The field when turned on, will penetrate the solution near the spray capillary tip. This will cause a polarization of the solvent near the meniscus of the liquid. In the presence of even traces of an electrolyte, the solution will be sufficiently conducting and the positive and negative electrolyte ions in the solution will move under the influence of the field. This will lead to an enrichment of positive ions on or near the surface of the meniscus and enrichment of negative ions away from the meniscus. The forces due to the polarization cause a distortion of the meniscus into a cone pointing downfield (see Figure 1.1). The increase of surface due to the cone formation is resisted by the surface tension of the liquid. The cone formed is called a Taylor cone (see Taylor [11] and Fernandez de la Mora [12]). If the applied field is sufficiently high. 

The combined effects of capillary forces (resulting from the local distortion of the meniscus when the contact line is dragged over the structures) and geometrical confinement (induced by the structures) causes one or more particle being trapped close to the obstacle, whereas no particles are deposited in the surrounding areas (Fig. 15.Id). This capillary assembly mechanism is well suited for accurate placement of individual particles to create discontinuous ID structures (Fig. 15.3) and can be extended to 3D patterns. 

The carbon dioxide in the stripped gases is absorbed fairly rapidly but moving the liquid up and down the chamber assists in complete solution. Magnesium salts, etc, precipitate at this stage and may distort the meniscus and give difficulty when reading is most noticeable... 

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