Layers, superimposed

The structure of millscale consists of three superimposed layers of iron oxides in progressively higher states of oxidation from the metal side outwards, viz. ferrous oxide (FeO) on the inside, magnetite (Fe304) in the middle and ferric oxide (Fe203) on the outside. The relative portions of the three oxides vary with the rolling temperatures. A typical millscale on 9.5 mm mild steel plate would be about 50/tm thick, and contain approximately 70% FeO, 20% Fej04 and 10% FejOj. 

Figure 3.19. Close-packed bi-dimensional arrangement of equal spheres. Their centres, marked by A, are in the nodes of a triangular net. The points B and C may correspond to the nodes of similar triangular nets in different relative positions. On the right a few spheres of three superimposed layers in the hexagonal close-packing are shown. In this structure the spheres of the layer III are just above those of the layer I. A lateral view of the same arrangement is shown in Fig. 3.20.

Figure 3.20. A lateral view of different stacking sequences of triangular nets. They correspond to some typical close-packed structures. The first layer sequence shown corresponds to a superimposition according to the scheme ABABAB... (equivalent to BCBCBC... or CACACA... descriptions) characteristic of the hexagonal close-packed, Mg-type, structure. With reference to the usual description of its unit cell, the full stacking symbol indicating the element, the relative position of the superimposed layers and their distance is Mg Mg. The other sequences correspond to the schemes ABC.ABC. (Cu, cubic), ABAC.ABAC. (La, hexagonal), ACACBCBAB. (Sm, hexagonal). For Cu the constant ch of the (equivalent, non-conventional) hexagonal cell is shown which may be obtained by a convenient re-description of the standard cubic cell (see 3.6.1.3). ch = cV 3, body diagonal of the cubic cell.

Figure 3.34. Holes in the closest packing of equal spheres. Two superimposed layers of spheres are shown (continuous and dotted lines). Tetrahedral (T) and octahedral (O) holes are indicated.

Figure 7.17. The As-hR6 structure (a) a puckered layer of As atoms is viewed along the c axis of the hexagonal cell and (b) lateral view of two superimposed layers. Notice the coordination 3 of the atoms, characteristic for the element of the 15th group (five valence electrons).

The three types of adsorption are (1) physical, (2) chemical, and (3) exchange adsorption. Especially important to the success of in situ treatment by Fe° are the soil characteristics, which affect soil sorptive behavior such as mineralogy, permeability, porosity texture, surface qualities, and pH. Physical adsorption is due to van der Waal s forces between molecules where the adsorbed molecule is not fixed on the solid surface but is free to move over the surface and may condense and form several superimposed layers. An important characteristic of physical adsorption is its reversibility. On the other hand, chemical adsorption is a result of much stronger forces with a layer forming, usually of one molecule thickness, where the molecules do not move. It is normally not reversible and must be removed by heat. The exchange adsorption and ion exchange process involves adsorption by electrical attraction between the adsorbate and the surface (Rulkens, 1998). 

During the tests, fuel and bed material samples were collected. These samples were mainly investigated with SEM-EDS, Bulk elemental analyses were also carried out. The unproblematic behaviour of the bed material was confirmed and no agglomerate formation was observed except in the close proximity of occasional quartz centres that were unintentionally present in bed. It was observed that the majority of the bed particles were coated with several thin superimposed layers. The composition of each layer was different. The outermost coating layer contains a significant amount of magnesium. It may be this outermost layer that hinders the agglomeration of the particles in this new bed. 

Conventional care often includes the application of an antibiotic cream or ointment. This local antibiotic carmot be applied in superimposed layers, and patients should wash their skin before applying a new layer of antibiotic. Cleaning the skin is a problem in itself, as it may injure the extremely sensitive skin and is often painful. As a result, patients do not always clean their skin before each new application, and put one layer of ointment on top of another. After a few days of maceration, it is almost inevitable that a secondary infection will develop. 

The multistep synthesis is classically used to repair defects or to increase the zeolite membrane thickness. This technique also allows to superimpose layers with different zeolite structures. We have also to notice that for certain zeolite structures such as FAU or LTA, when the synthesis duration is too long, other phases can appear by transformation of the initial zeolite structure. 

An electrochromic device embodies a number of superimposed layers on a transparent substrate or between two transparent substrates, and optical transmittance is altered when an electrical potential is applied so that charge is shuttled between layers serving in the same way as anodes and cathodes in an electrical battery. One specific design with a five-layer construction shown in Figure 30 uses cathodically coloring WO3 and anodically coloring nickel oxide joined by an ion-conducting electrolytic laminate. A potential of a few volts, preferably supplied by solar cells, is applied between... 

Films deposited from nonpolar solvents are relatively thick (>1000 A) and resistant to desorption films from polar solvents are generally thinner (<100 A) and easily disrupted by polar solvents. An adsorbed silane film can consist of different strata a silane interface with covalent bonding [10], a relatively cross-linked intermediate layer, and a superimposed layer of relatively un-cross-linked material. In practice, adsorbed films on both glass and metals are discontinuous and consist of discrete islands or agglomerates, called the button-down theory [37]. 

Carboxymethyl Cellulose (CMC) -In vivo cellulose ribbon formation prevented normal fasciation of fibril bundles into a typical ribbon -Thinner ribbon width and smaller crystallite fibril size -Aggregates and pellicle show birefringence, and contain crossed, superimposed layers of cellulose fibrils oriented in parallel -Less resistant to stress... 

Figure 5. Superimposed layers the helcies have been replaced by cylinders...

A pavement is a set of superimposed layers of imported materials (selected, processed unbound and bound materials) that are placed on the natural soil for the creation of a road. A pavement is a complex structure that has to accomplish various functions different from each other. 

The precise determination of the representative moisture content of the subgrade during the pavement s service life is a difficult, if not impossible, task. This is because the subgrade moisture content during the pavement s service life is affected by various factors, the most important of which are the seasonal variation of the depth of the water table level, the type of soil material (soil classification), the construction conditions in terms of provision of drainage system and the thickness of superimposed layers (thickness of pavement). 

Figure 5.89 illustrates how the presence of chain ends within the crystal must lead to dislocations. Three superimposed layers of chain molecules of a crystal are sketched schematically. Without chain-ends, one only would expect parallel lines, as... 

Laminate la-m3- nat (1665) (1, n). A product made by bonding together two or more layers of material or materials. The term most usually applies to preformed layers joined by adhesives or by heat and pressure. However, some authors apply the term to composites of plastic films, with other films, foils, and papers, even though they have been made by spread coating or by extrusion coating. In the reinforced-plastics industry, the term refers mainly to superimposed layers of resin-impregnated or resin-coated fabrics or fibrous reinforcements that have been... 

The issue with this type of superimposed layer strategy is that it creates a bulky and heavy protective clothing system, with a negative impact of comfort, ergonomics, and function. The same problem stands with other types of PPE, for example, helmets, boots, etc. On the other hand, if the PPE material or layer can combine several functions and protect against the whole list of hazards associated with a type of activity, for example, through the use of smart materials, gains in comfort and efficiency can be made (Peltonen et al., 2012). 

The physical principles of flow of complex mixtures are based on the interaction between the different phases, which may mix well or move in superimposed layers. In this chapter, the basic concepts of motion of particles in a carrying fluid will be presented, as well as the effect of their concentrations and boundaries. In the previous two chapters, we reviewed the physical properties of solids, single-phase flows, and some aspects of mixtures of both. 

In the past, engineers have tried to simplify the complexity of slurry flows by defining certain transition velocities. With the use of modern research tools, there is an emerging approach of rejecting the concept of an abrupt change from one state of flow to another, and a tendency to consider such a change over a band of the speed. Different approaches have been developed to examine the mixture of coarse and fine particles from superimposed layers to two-layer models. 

As the flow speed increases, turbulence is sufficient to lift more solids. All particles move in an asymmetric pattern with the coarsest at the bottom of a horizontal pipe covered with superimposed layers of medium- and fine-sized particles. Many particles may strike the bottom of the pipe and rebound. Wear on the bottom of the pipe must be taken into account in maintenance schedules and the pipes must be rotated at intervals suggested by the slurry engineer in order to maintain an even wear pattern of the internal wall of the pipe. Although the flow is not symmetric, from the point of view of power consumption, this regime may be the most economical for transporting a certain mass of solids. 

When it was developed in the early 1970s, the Wasp method was considered state of the art. It does, however, ignore or minimize one important parameter, namely the shear stress between the different superimposed layers. This is a topic that the two-layer method attempts to tackle, as we shall see in Section 4-10. It does, therefore, tend to predict pressure losses higher than those from stratified flows in certain circumstances of bimodal (fine and coarse) distribution. Nevertheless, the Wasp method remains a very useful method to this day for the design of pipelines, particularly when it is supported by lab tests, as we showed in Example 4-11. 

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