Inhibit gates

The INHIBIT gate iadicates that the output eveat occurs whea the iaput eveat occurs and the inhibit condition is satisfied. 

Condttlonlng evont - CondKlons or restrictions that apply to any logic gate (for priority and Inhibit gates). 

INHIBIT Gate The output event occurs when the input event... 

The problem of Example 11-5 is somewhat unrealistic in that it is highly likely that the operator will notice the high pressure even if the alarm and shutdown systems are not functioning. Draw a fault tree using an inhibit gate to include this situation. Determine the minimal cut sets. If the operator fails to notice the high pressure in 1 out of 4 occasions, what is the new probability of the top event ... 

Fig. 13 An INHIBIT gate with its corresponding truth table.

The enabled OR - another type of gate that requires a minimum of three inputs -has just become available. Figure 15 shows the equivalent electronic representation, with the appropriate connection of AND and OR gates. In this context we note that the INHIBIT gate discussed in Section 11.10 also involves an enabling/disabling input. One strand of Pina, Maestri, and Balzani s novel exploitation of flavylium derivative photochemistry was briefly mentioned in Section 11.4. This AND logic system used protons and ultraviolet photons as the two inputs, to create a visible... 

A two-input INHIBIT gate can be as simple as a receptor-phosphor system. With their inherent sensitivity to molecular oxygen, these systems can be... 

Arguably the most complex molecular system, showing characteristics of logic functions, is the three-input INHIBIT molecule 54- (Fig. 7) developed by de Silva [13]. The truth table for a three-input INHIBIT gate (Table 3) can be split into two portions - that where the INHIBIT input is turned off, and that where the INHIBIT input is turned on. With the INHIBIT input in an off state, the system acts as an AND gate with respect to inputs A and B. However, as before, if the INHIBIT input is turned on, all outputs are zero. The output from... 

Fig. 7. A three-input INHIBIT gate exemplified by the tetraanion 54 and /1-cyclodextrin (j8-CD). a With neither protons nor /1-CD present in the solution, phosphorescent output is low, because of both PET from the tertiary amine, and through intermolecular triplet-triplet collisions of the bromonaphthalene phosphor, b Addition of calcium ions leads to a reduction in the PET-based quenching of the phosphorescence - however, intermolecular collisions still lead to a low emission, c Shielding of the phosphor with /l-CD reduces intermolecular triplet annihilations, but quenching still occurs via PET. d Only with both Ca2+ and /1-CD present does the solution phosphoresce, e In any combination of Ca2+ and /1-CD, the solution will yield a low output in the presence of molecular oxygen (the INHIBIT stimulus), as a consequence of triplet-triplet collisions...

Then, in equation (8), Xj, or 1 — Xj, is a condition event with the associated left-hand side inhibit gate representing the control system i is performing either abnormal or normal respectively, e.g. see equation (3), while the structure fimctions for false alarm and inactive alarm are given by equations (6) and (7) respectively, which enter the corresponding inhibit gates . Thus, FAj occurs when occurs and... 

For some events, certain conditions must be present to include the input events in the tree. The input events may inhibit or enable the output event. A hexagon symbol represents an inhibit gate. 

Rotaxane from 54 and 55 [124] and a related polymeric rotaxane have also been converted into INHIBIT gates driven by H" " and polar solvents as inputs. 

This secondary failure is composed of component failures, so again, an OR gate is drawn. The same logic as used earlier is applied here to draw the secondary failure and the diamond. The INHIBIT gate documents that the input to the fault is a continuous, t > 60 s pump operatiou. Remember, this is conditional fault. The pump must operate longer than 60 s for the failure to occur. 

Conditional event (ellipse) Specific condition or restriction applied to a logic gate (mostly used with inhibit gate). 

Inhibit gate (hexagon) One input is a lower fault event and the other input is a conditional qualifier or accelerator (direct effect as a decreasing (< 1) or increasing factor (> 1)). 

The justification for including the people element as an inhibit gate or conditional event in the corrosion tree should be obvious (i.e., corrosion... 

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