Design grid, construction

The positive electrode normally contains a grid (Pb), which serves as both the mechanical support for the active mass paste and the current collector, and a layer of active mass (Pb02). The designs and materials used for the grid were described in detail. In particular, various Pb alloys used for grid construction were discussed in terms of their compositions, functions, and their beneficial effect on electrode performance. Regarding the active mass pastes, the paste composition, curing, and formation processes, as well as associated physical/chemical processes, were described and discussed. Furthermore, fabrication procedures for positive electrodes were briefly introduced. We hope readers have found this chapter useful in their study and experimental approaches. 

The current needed for cathodic protection by impressed current is supplied from rectifier units. In Germany, the public electricity supply grid is so extensive that the CP transformer-rectifier (T-R) can be connected to it in most cases. Solar cells, thermogenerators or, for low protection currents, batteries, are only used as a source of current in exceptional cases (e.g., in sparsely populated areas) where there is no public electricity supply. Figure 8-1 shows the construction of a cathodic impressed current protection station for a pipeline. Housing, design and circuitry of the rectifier are described in this chapter. Chapter 7 gives information on impressed current anodes. 

The first step in applying FEA is the construction of a model that breaks a component into simple standardized shapes or (usual term) elements located in space by a common coordinate grid system. The coordinate points of the element corners, or nodes, are the locations in the model where output data are provided. In some cases, special elements can also be used that provide additional nodes along their length or sides. Nodal stiffness properties are identified, arranged into matrices, and loaded into a computer where they are processed with certain applied loads and boundary conditions to calculate displacements and strains imposed by the loads (Appendix A PLASTICS DESIGN TOOLBOX). 

The above example shows that in designing difference schemes it is very desirable to reproduce the appropriate conservative law on a grid, The schemes with this property are said to be conservative. In subsequent sections the general method for constructing conservative schemes, which are convergent in the class of discontinuity coefficients, will be appreciated. Before we undertake the complete description of this method, it is worth noting two things. 

By means of the integro-interpolation method it is possible to construct a homogeneous difference scheme, whose design reproduces the availability of the heat source Q of this sort at the point x = /. This can be done using an equidistant grid u)j and accepting / = x -f Oh, 0 <0 < 0.5. Under such an approach the difference equation takes the standard form at all the nodes x [i n). In this line we write down the balance equation on the segment x,j. 

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