Porous object

Shapes of inside objects which are only partly permeable to airflow (sometimes referred to as porous objects), such as inlet grills, vents, etc. 

Additionally, there is interest in determining the density of porous objects, powders or very irregular crystals. It is often difficult to obtain... 

The densities of comets Halley and Tempel 2 were estimated to be 0.3 g cm 3, consistent with highly porous objects. However, comet 81 P/Wild2, imaged by the Stardust spacecraft in 2004, appears to be a more coherent object, implying that it has a higher density, -0.6 gcm 3. 

Fractal geometry was employed to study surface geometry effects on adsorption conformations of polymers.1771 Using poly(styrene) for the case study, it was shown, that for highly porous objects, solution conformation changed very little after solvent adsorption. 

Void space (volume) in porous objects. (See also porosity.) The amount of pores (voids) in an object expressed as percentage of the object s total volume. 

Void space (volume) in POROUS objects. (See also POROSITY)... 

Cyanoacrylates are also used by forensic scientists to collect fingerprints at crime scenes. The object to be tested is suspended inside a container with at least one transparent side. A few drops of Super Glue or similar cyanoacrylate product is added to the container and the container is sealed and heated to about ioo°C (2i2°F). That heat causes vaporization and polymerization of the cyanoacrylate, resulting in the formation of distinctive white print patterns, a process that make take two hours or more. This cyanoacrylate fuming test has now become the procedure of choice for the detection of latent prints deposited on non-porous objects, such as glass, plastic, rubber, and leather. 

The physical macroscopic notion of porosity or pores in a solid and the phenomenon of absorption of a fluid in a porous object are both quite familiar to all of us. Further, wide varieties of natural or synthetic solids, compounds, species, and materials are known to be of porous nature, for example, minerals, wood, cellulose fibers, seashells. 

On the basis of what previously reported in literature (i/) and after some preliminary studies carried out in our latoratories, it has been found that FP can work into porous objects such as textiles, woods, stones, 3Y) papers, etc. 

Chemical vapor infiltration (CVI) is a CVD variant capable of internally coating porous objects, e.g., an object made out of carbon fibers, with a ceramic material. Silicon carbide (SiC) or boron carbide (B4C) are examples of ceramic matrix materials that are used in combination with carbon fibers. Strong, light, durable, wear-resistant, and biocompatible joint prostheses made of ceramic-ceramic composites are manufactured by means of CVI. Figure 6.18 shows how the degree of penetration is affected by temperature and pressure. Clearly, to get deposit deep in the interior of the porous object low temperatures are necessary for reaction limitation and low pressures for helping the diffusion. Under these conditions growth rates are low. 

The iodine method When heated, iodine sublimes and its vapor reacts with the carbon-carbon double bonds in fats and oils, turning the ridge pattern to a yellow-brown color. This method is particularly well suited for fingerprints on porous objects like papers and cardboard. Write an equation showing the reaction of I2 with fats and oils. 

In the literature, there exists a relationship which relates the permeability K with the relative density p, and the mean pore size d of porous object [13]. This relation is called the Carman-Kozeni equation... 

For w 4, unhydrolyzed sites are incorporated into the growing cluster. The probability of condensation at these sites is less than at hydrolyzed sites. Under these conditions, growth is described by a poisoned Eden model. Depending on the number and distribution of the poisoned sites, mass fractals, surface fractals or uniformly porous objects can result. The addition of more water in a second hydrolysis step is expected to completely hydrolyze the clusters and further growth should be described by the Eden model. 

The heating step is a critical part of the cycle. If it is overlong, polymer degradation can take place. On the other hand, not allowing enough time for sufficient melting and sintering produces a porous object not suitable for use. 

Many treatments have no known method of reversal. There is no method of removing a cross-linked polymer from a porous object, e.g. silanes in stone. 

The consolidation process appears to take place because of the combination of various factors, discussed below for a standard consolidation of a porous object using a polymer dissolved in solvent ... 

Consolidant A consolidant is a solid material that changes the properties of a porous object by filling the pores or joining the particles. A consolidant is usually used for strengthening, but can also change the optical properties or the hydrophobicity. 

The disagreement between data and theory is attributed to the following rationale The screen is a porous object with millions of micron sized holes, each with its own L/V interface. Statistically speaking, it is unlikely that every pore will have the same mixture composition at equilibrium. During pressurization underneath the screen, a bubble will pass... 

Porous objects such as plaster and concrete can be strengthened by UP impregnation. However vinyl monomer impregnation is often substituted for UP impregnation since vinyl monomers have much lower viscosities and they penetrate into much smaller pores [12], Strengthening of the lo< archeological objects, or adhesion of broken parts can be successftilly accomplished by UP resins. 

Rarum est quod. . [ A porous object contains little material within a large... 

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