Model five-layer structure

The possibility of absorbed dose reduction for the heat source model of a Sr radioisotope battery was studied by adding graded structure to the model using MCNP 4A code. The results showed 17, 19 and 22 % reduction to the dose of the base structure for three, four and five layers, respectively. 

In the simulations reported above the interactions between the various components were mostly based on semiempir-ical potentials. In contrast, Price, Halley, and their collaborators attempt to model the whole interface in the spirit of the Car-Parinello method [16]. One of the first systems investigated was the interface between a copper electrode and water [67]. For this purpose these authors set up a simulation cell with approximate dimensions of 42 A X 15 A X 15 A. Each cell contained a slab of copper atoms that were five-layers thick, the two surfaces having (100) structure. The remaining space was filled with water molecules. CycKc boundary conditions were applied in all directions. Obviously, an ab initio, all electrons calculation is quite impossible for such a system, and may not even be desirable. Instead, Halley and collaborators used a mixture of pseudopotentials... 

The permeability skin barrier, a highly specialized structure responsible for retaining skin moisture, is localized mainly at the stratum corneum (Rudikoff 1998) however, its formation begins deeper in the epidermis and its constituents are progressively modified during the process of keratinization until they reach their highest efficiency in the five layers of the stratum compactum (Rawlings et al. 1994). The modified keratinocytes - the corneocytes - and the intercellular complex lipid matrix in which they are embedded form this specialized structure, which Elias compared to a bricks and mortar model, in which the corneocytes are the bricks and the lipid matrix the mortar (Elias 1983). 

If the polymer application is for viscosity control, then the simple model may be a 2-D areal or simple layered five-spot pattern the well locations will be known, and any faults that are known should be included using transmissibility modifiers. In this areal system, the key features in the calculation are that the oil viscosity is correct and reasonable estimates of the reservoir relative permeabilities are available. For a heterogeneity control flood, a multilayer cross-section similar to the eight-layer system described in Chapter 8 may be selected. Here, the most important factor is to get the layering structure and layer permeabilities correct, especially the permeability contrast between the high-permeability layer(s) and the position of this layer. The value of the kjk ratio may also be very important in this type of polymer flood, but it may be sufficient to know that it is > 0.05 for example (see Chapter 8). In such an application, the mobility ratio may be close to... 

Subsequently, Mitchell s group in Vancouver, by means of a tensor-LEED study17 of the Cu (110)-(2 x 3)N surface structure, supported a reconstruction model in which the topmost layer is described as a pseudo-(100)-c(2 x 2)N overlayer with metal corrugation of about 0.52 A in the reconstructed layer. Each nitrogen adatom is almost coplanar with the local plane formed by the four neighbouring copper atoms. Of the four N atoms present in the unit mesh, three are also bonded to Cu atoms in the layer below and therefore are five coordinate. 

Of crucial significance in deciding between various models have been estimates of the number of copper atoms required to transform the surface into a (2 x 3)N phase. This was the approach adopted by Takehiro et al 2 in their study of NO dissociation at Cu(110). They concluded that by determining the stoichiometry of the (2 x 3)N phase that there is good evidence for a pseudo-(100) model, where a Cu(ll0) row penetrates into the surface layer per three [ll0]Cu surface rows. It is the formation of the five-coordinated N atoms that drives the reconstruction. The authors are of the view that their observations are inconsistent with the added-row model. The structure of the (2 x 3)N phase produced by implantation of nitrogen atoms appears to be identical with that formed by the dissociative chemisorption of nitric oxide. 

Within the last five years, many fuel-cell models have come out of the Research Center in Julich, Germany. These models have different degrees of complexity and seek to identify the limiting factors in fuel-cell operation. The model of Kulikovsky et al. examined a 2-D structure of rib and channel on the cathode side of the fuel cell, and is similar to that of Springer et al. Other models by Kulikovsky included examination of depletion along long feed channels and effects in the catalyst layers.The most recent model by Kulikovsky relaxed the assumption of constant water content in the membrane and examined quasi 3-D profiles of it. Also at the research center, Eikerling et developed many... 

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