Activity Diagram

Let us now rewrite equation 8.242 in logarithmic notation, assigning unitary activity to the solvent  

The relationship between thermodynamic activity and chemical potential is 

For two generic oxides i and j, the partial derivatives of equation 8.246 can be combined (Helgeson, 1967) to give 

Let us now imagine a process of hydrothermal alteration of arkose sandstones composed of Mg-chlorite, K-feldspar, K-mica, and quartz. Because precipitating Si02 during alteration is amorphous, we will assume the presence of amorphous silica instead of quartz, and we will consider MgO as the generic oxide / and K2O as the generic oxide j. 

Assigning unitary activity to the condensed phases and to solvent H2O, equihb-rium constant 349 takes the form 

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Fig. 7.71 An activity diagram showing the competing formation of sulphides and oxides on chromium. The XPS data (lower) show how sulphide replaced oxide as the surface anion when oxide samples were heated in the gas composition marked on the O-S diagram, implying that the boundary should be moved. (Reprinted with permission from Pergamon Press after...

Helgeson (1967) constructed an activity diagram depicting chemical equilibrium points (albite-sericite-K-feldspar and albite-sericite-Na-montmorillonite) of NazO-K20-Si02-Al203-H20 system at elevated temperatures. At these points,... 

Unfortunately, no software techniques exist currently to automatically search for additional roots. Instead, modelers must rely on their understanding of geochemistry to demonstrate uniqueness to their satisfaction. Activity-activity diagrams such as those presented in Figures 12.1-12.3 are the most useful tools for identifying additional roots. 

Action Describes a complex protocol of interaction between objects as a single action, again characterized by the effect it has on the participants. What sequences of detailed actions will realize the effect of the abstract action Use state charts, sequence or activity diagrams. 

We have found that temporal logic handles more general cases in a very concise form. The UML activity diagram is another alternative. 

Table 8.25 Equilibrium constants used for construction of figure 8.31 (activity diagram). ...

Helgeson H. C., Brown T. H., and Leeper R. H. (1976). Handbook of Theoretical Activity Diagrams Depicting Chemical Equilibria in Geologic Systems Involving an Aqueous Phase at 1 atm and O to 300 °C. Freeman, Cooper, San Francisco. 

In order to construct the activity diagrams in a rigorous fashion, a certain amount of information must be available. Some experimental data for the mica-feldspar-kaolinite-gibbsite-montmorillonite relations are available. Data for the other minerals are often inferred from measurements of natural chemical parameters (K+, SiC, H+ concentrations in solutions) in situations where the different minerals are assumed to be stable. The relations between minerals can also be calculated as a function of K+, SiO and pH using thermochemical data for the participating phase (Hess, 1966) when they are known with precision. Frequently it is... 

The most effective representation for which activity-activity diagrams can be used is in geological situations where solutions are in contact with great reservoirs of fluid, such as sea-water for example. The activity of ions in solution will impose phase equilibria on the solids. In these instances, silicate mineralogy will be simple, most likely single-phase. Mono- or bi-mineral zones adjacent to hydrothermal veins can also be effectively represented on activity-activity diagrams. 

Fig. 2. Logarithmic activity diagram depicting equilibrium phase relations among aluminosilicates and sea water in an idealized nine-component model of tire ocean system at the noted temperatures, one atmosphere total pressure, and unit activity of H20. The shaded area represents (lie composition range of sea water at the specified temperature, and the dot-dash lines indicate the composition of sea water saturated with quartz, amotphous silica, and sepiolite, respectively. The scale to the left of the diagram refers to calcite saturation foi different fugacities of CO2. The dashed contours designate the composition (in % illite) of a mixed-layer illitcmontmorillonitc solid solution phase in equilibrium with sea water (from Helgesun, H, C. and Mackenzie, F T.. 1970. Silicate-sea water equilibria in the ocean system Deep Sea Res.).

Use case specifications can be visualized using UML Activity Diagrams and System Sequence Diagrams (Larman, 2005). I always find a graphic model easy to understand and communicate. However, these visualized models should be used as supplements, not as a replacement for use case specifications in text. 

Figure 9.3 The activity diagram of Register Compound(s) Use Case.

The Business Layer is in the center of CRS where the core business functions reside. Any business application has a workflow—the steps it takes to accomplish one or many tasks or transactions. Clearly analyzing and understanding the workflow is essential to designing the Business Layer correctly. Use case specifications capture workflow from a user s perspective. The System Activity Diagram is an excellent tool to capture system workflow from a system perspective. Figure 12.1 is the System Activity Diagram (CAD) of CRS. 

Develop use case specification documents to capture detailed functional requirements (Chapter 9). Use System Sequence Diagrams and Activity Diagrams as complements. Use case specifications should be developed, communicated, and reviewed at the beginning of each iteration. 

Bowers T.S., Jackson K.J., and Helgeson H.C. (1984) Equilibrium Activity Diagrams (for Coexisting Minerals and Aqueous Solutions at Pressures and Temperatures of 5 KB and 600°C). Springer-Verlag, Berlin, 397 pp. 

User Procedures for operating and maintaining the computer systems, control system, or laboratory system must be specified, approved, and where possible tested, before the systems are approved for use. User procedures can make good use of Role Activity Diagrams (RAD) to help readers understand the specific responsibilities associated with different roles. An example RAD is shown in Figure 4.3 in Chapter 4. 

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