Slab

Titanium is produced commercially by converting titanium oxide ore to titanium tetrachloride, then reducing it to produce a crude titanium product, //-tanium sponge. Titanium sponge can react with carbon dioxide to generate oxygen. 

Many metals oxidize in contact with the air or moisture. For reactive metals, this reaction may be particularly violent and evolve high heat. When in contact with water, hydrogen gas is liberated which will ignite if temperatures are sufficiently high. Alternatively other combustibles may be similarly ig- 

Microns, see Units of Measure, p.258 Powder, see Terminology, Powder, p.246 Pyrophoric, see Spontaneously Combustible Materials and Division 4.2, p.226 Self-heating, see Spontaneously Combustible Materials and Division 4.2, p.226 Sponge, see Terminology, Sponge, p.248 Wetted, see Terminology, Wetted, p.253 

Alkali Metal Dispersion Alkaline Earth Metal Dispersion Finely divided alkali or alkaline earth metal, e.g. metallic sodium suspended in a flammable liquid such as toluene, xylene, naphtha, kerosene, etc. Reacts violently with moisture, water or acids, evolving hydrogen, which may be ignited by the heat of reaction. IMO 4324 

Aluminium Powder. The uncoated powder may evolve hydrogen in contact with water, and finely divided dust may be ignited by naked lights or sparks. Coated aluminium powders which have been treated with oils or wax for printing or paint purposes are generally not dangerous. ICAOA2 

---

Keywords d rec methods, indirect methods, rock properties, coring, core barrel, standard core analysis, special core analysis, slabbed core, sidewall samples, direct indications, microfossils, sonde, logging unit, invasion, mudcake, formation pressure measurement, fluid sampling, measurement while drilling, formation evaluation while drilling. 

In addition to a geological evaluation on a macroscopio and microscopic scale, plugs (small cylinders 2 cm diameter and 5 cm long) are cut from the slabbed core, usually at about 30 cm intervals. Core analysis is carried out on these samples. 

T.M. Habashy, W.C. Chew, and E.Y. Chow, Simultaneous reconstruction of permittivity and conductivity profiles in a radially inhomogeneous slab, Radio Sci., 1986,21,... 

It has been found that the contrast in film density caused by very small local variations in mass density of the concrete is considerable, e g. S D = 0.12 for a 6 mm diameter hole in a 250 mm thick concrete beam. The image quality provided by fine-grained films (Agfa Gaevert D7) was sufficient to distinguish the thin walls of a pre-stressing duct in a 750 mm thick concrete bridge slab. 

A problem obviously exists in trying to characterise anomalies in concrete due to the limitations of the individual techniques. Even a simple problem such as measurement of concrete thickness can result in misleading data if complementary measurements are not made In Fig. 7 and 8 the results of Impact Echo and SASW on concrete slabs are shown. The lE-result indicates a reflecting boundary at a depth corresponding to a frequency of transient stress wave reflection of 5.2 KHz. This is equivalent to a depth of 530 mm for a compression wave speed (Cp) of 3000 m/s, or 706 mm if Cp = 4000 m/s. Does the reflection come from a crack, void or back-side of a wall, and what is the true Cp ... 

The total interaction between two slabs of infinite extent and depth can be obtained by a summation over all atom-atom interactions if pairwise additivity of forces can be assumed. While definitely not exact for a condensed phase, this conventional approach is quite useful for many purposes [1,3]. This summation, expressed as an integral, has been done by de Boer [8] using the simple dispersion formula, Eq. VI-15, and following the nomenclature in Eq. VI-19 ... 

Thus for equal-size spheres the force between them is just xn f/siab-siab(J ) d is directly related to the potential energy between two slabs [13]. This point is examined further in the problems at the end of the chapter. 

The long-range van der Waals interaction provides a cohesive pressure for a thin film that is equal to the mutual attractive force per square centimeter of two slabs of the same material as the film and separated by a thickness equal to that of the film. Consider a long column of the material of unit cross section. Let it be cut in the middle and the two halves separated by d, the film thickness. Then, from one outside end of one of each half, slice off a layer of thickness d insert one of these into the gap. The system now differs from the starting point by the presence of an isolated thin layer. Show by suitable analysis of this sequence that the opening statement is correct. Note About the only assumptions needed are that interactions are superimposable and that they are finite in range. 

W L Bragg [7] observed that if a crystal was composed of copies of identical unit cells, it could then be divided in many ways into slabs with parallel, plane faces whose distributions of scattering matter were identical and that if the pathlengths travelled by waves reflected from successive, parallel planes differed by integral multiples of the... 

First-principles models of solid surfaces and adsorption and reaction of atoms and molecules on those surfaces range from ab initio quantum chemistry (HF configuration interaction (Cl), perturbation theory (PT), etc for details see chapter B3.1 ) on small, finite clusters of atoms to HF or DFT on two-dimensionally infinite slabs. In between these... 

Figure B3.2.12. Schematic illustration of geometries used in the simulation of the chemisorption of a diatomic molecule on a surface (the third dimension is suppressed). The molecule is shown on a surface simulated by (A) a semi-infinite crystal, (B) a slab and an embedding region, (C) a slab with two-dimensional periodicity, (D) a slab in a siipercell geometry and (E) a cluster.

The siipercell plane wave DFT approach is periodic in tliree dimensions, which has some disadvantages (i) thick vacuum layers are required so the slab does not interact with its images, (ii) for a tractably sized unit cell, only high adsorbate coverages are modelled readily and (iii) one is limited in accuracy by the fonn of the... 

Pisani [169] has used the density of states from periodic FIP (see B3.2.2.4) slab calculations to describe the host in which the cluster is embedded, where the applications have been primarily to ionic crystals such as LiE. The original calculation to derive the external Coulomb and exchange fields is usually done on a finite cluster and at a low level of ab initio theory (typically minimum basis set FIP, one electron only per atom treated explicitly). 

Kruger and Rosch implemented within DFT the Green s matrix approach of Pisani withm an approximate periodic slab enviromnent [180]. They were able to successfiilly extend Pisani s embeddmg approach to metal surfaces by smoothing out the step fiinction that detenuines the occupation numbers near the Fenui level. 

Flead and Silva used occupation numbers obtained from a periodic FIF density matrix for the substrate to define localized orbitals in the chemisorption region, which then defines a cluster subspace on which to carry out FIF calculations [181]. Contributions from the surroundings also only come from the bare slab, as in the Green s matrix approach. Increases in computational power and improvements in minimization teclmiques have made it easier to obtain the electronic properties of adsorbates by supercell slab teclmiques, leading to the Green s fiinction methods becommg less popular [182]. 

Philipsen P H T, te Velde G and Baerends E J 1994 The effect of density-gradient corrections for a molecule-surface potential energy surface. Slab calculations on Cu(100)c(2x2)-C0 Chem. Phys. Lett. 226 583... 

Equilibration of the interface, and the establislnnent of equilibrium between the two phases, may be very slow. Holcomb et al [183] found that the density profile p(z) equilibrated much more quickly than tire profiles of nonnal and transverse pressure, f yy(z) and f jfz), respectively. The surface tension is proportional to the z-integral of Pj z)-Pj z). The bulk liquid in the slab may continue to contribute to this integral, indicatmg lack of equilibrium, for very long times if the initial liquid density is chosen a little too high or too low. A recent example of this kind of study, is the MD simulation of the liquid-vapour surface of water at temperatures between 316 and 573 K by Alejandre et al [184]. 

Lotspeioh J F 1975 Explioit general eigenvalue solutions for dieleotrio slab waveguides Appl. Opt. 14 327... 

In the case of slab geometry, this is to be interpreted as the component of N along the coordinate axis normal to the faces, of course. 

More computational results are provided by Hite [75], including a second order reaction with different stoichiometry, and slab, as well as sphere geometry for the pellet. Overall it can be concluded that the approximate procedure of Hite and Jackson gives results of quite adequate... 

---