Variable-Influence Diagrams

Let us now see how the ideas of the previous section can be used to construct the variable-influence diagram, that defines the paths leading to top-level event. Consider a set of four modeling relationships, represented by the structural matrix shown below. 

Fig. 21. The variable-influence diagram resulting from Assumption-1 and Assumption-2. 

TLE is to change the heat of reaction and obviously implies a change in chemistry. Furthermore, the variable-influence diagram makes explicit that top-level event prevention necessitates the placement of control objectives on every variable that immediately precedes the top-level, i.e., variables Tq, Tp, (2ri Pi Pi should come under control. 

Influence diagrams can be used with the strategy tables to identify factors or variables that create uncertainty in assessing the value of various options. Issues can be quaUtatively prioritized in selecting the best path to generate value for the business. 

Feedback control is a fundamental concept that is employed in most control algorithms. Figure 9.2 shows a block diagram for a feedback control system. In feedback control the controlled variable is measured and compared to the set point, resulting in an error signal that is used by the controller to calculate the appropriate corrective action by the manipulated variable. The manipulated variable influences the controlled variable through the dynamic process. 

Count cells positive for FITC fluorescence in the cytoplasm under a fluorescence microscope in a defined area on the coverslip in relation to all cells in this area. Correct this rate for the number of cells that survived the electroporation using the control experiment. Optimal voltage is determined from a diagram of number of successfully electroporated cells versus voltage. This procedure can also be used to optimize other variables influencing the efficiency of electroporation experiments mentioned above. 

The diagram of the evaporator performance is shown in the Fig. 11-97. The character of the curvature of the hues (variable heat-transfer rate) indicates that the evaporator is coohng air. Influences of the flow rate of cooled fluid are also shown in this diagram i.e., higher flow rate will increase heat transfer. The same effect could be shown... 

The path diagram marks the correlations of all primary independent variables and their assumed causal influence on other independent variables and on dependent variables. In addition, all relationships between dependent variables are indicated. 

Equilibria involving reductive dissolution reactions add to the complexity of mineral solubility phenomena in just the way that pE-pH diagrams are more complicated than ordinary predominance diagrams, like that in Fig. 3.7. The electron activity or pE value becomes one of the master variables whose influence on dissolution reactions must be evaluated in tandem with other intensive master variables, like pH or p(H4Si04). Moreover, the status of microbial catalysis under the suboxic conditions that facilitate changes in the oxidation states of transition metals has to be considered in formulating a thermodynamic description of reductive dissolution. This consideration is connected closely to the existence of labile organic matter and, in some cases, to the availability of photons.26... 

In addition to the molecular weight of the free polymer, there axe other variables, such as the nature of the solvent, particle size, temperature, and thickness of adsorbed layer which have a major influence on the amount of polymer required to cause destabilization in mixtures of sterically stabilized dispersions and free polymer in solution. Using the second-order perturbation theory and a simple model for the pair potential, phase diagrams relat mg the compositions of the disordered (dilute) and ordered (concentrated) phases to the concentration of the free polymer in solution have been presented which can be used for dilute as well as concentrated dispersions. Qualitative arguments show that, if the adsorbed and free polymer are chemically different, it is advisable to have a solvent which is good for the adsorbed polymer but is poor for the free polymer, for increased stability of such dispersions. Larger particles, higher temperatures, thinner steric layers and better solvents for the free polymer are shown to lead to decreased stability, i.e. require smaller amounts of free polymer for the onset of phase separation. These trends are in accordance with the experimental observations. 

Local analysis of the Topo-Information diagram depends on the kinds of variables selected and on the sign and absolute values of the contributions assigned to them. The regular influence of certain structural modifications grouped in equivalence sites makes for a generalization of certain effects - chain-lengthening (3) (14) (21),... 

---