Conditional events

To distinguish between a review and an audit, some definitions will be provided. A review is a critical examination or evaluation of any operation, procedure, condition, event, or equipment item. Reviews can take many forms and be identified as project reviews, design reviews, safety reviews, pre-start-up reviews, and so on. The following discussion of the review process will deal with project reviews associated with capital projects and focus on the area of process safety. 

Priority And Output occurs if ail of the Input faults occur in a specific sequence (the sequence Is represented by a conditioning event drawn to the right Of the gate. 

Inhibit - Output ftuK ocura H one input fault occurs in the presence of an enabling condition (the enabling condition is prepresentad by a conditioning event to the right of the gate. 

It is often important to be able to extend our present notion of conditional probability to the case where the conditioning event has probability zero. An example of such a situation arises when we observe a time function X and ask the question, given that the value of X at some instant is x, what is the probability that the value of X r seconds in the future will be in the interval [a,6] As long as the first order probability density of X does not have a Dirac delta function at point x, P X(t) = x = 0 and our present definition of conditional probability is inapplicable. (The reader should verify that the definition, Eq. (3-159), reduces to the indeterminate form in this case.)... 

Event trees are used to perform postrelease frequency analysis. Event trees are pictorial representations of logic models or truth tables. Their foundation is based on logic theory. The frequency of n outcomes is defined as the product of the initiating event frequency and all succeeding conditional event probabilities leading to that outcome. The process is similar to fault tree analysis, but in reverse. 

John Barrow and Frank Tipler, in the Anthropic Cosmological Principle, are fascinated by the number of seemingly coincidental conditions, events, and physical constants that guide our Universe. For example, they find the number of coincidences involving 1039 remarkable. 

It is also possible to state the probability of an event. A, as a function of two or more conditional events. If the events B and C are mutually exclusive and exhaustive - for example, they represent male and female - the probability of event A can be expressed as ... 

This expression can be extended to more than two conditional events. 

Recall also from Chapter 6 that the marginal probability of an event can be expressed as a series of conditional probabilities as long as the conditional events are mutually exclusive and exhaustive. This allows us to express the probability. 

Regnier, M. and Denise, A. (2004) Rare events and conditional events on random strings. Discrete Math. Theor. Comput. Sci. 6, 191-214. 

CONSTRUCTING THE FAULT TREE. Fault tree construction begins at the top event and proceeds, level by level, until all fault events have been traced to their basic contributing events or basic events. The analysis starts with a review of system requirements, function, design, environment, and other factors to determine the conditions, events, and failures that could contribute to an occurrence of the undesired top event. The top event is then defined in terms of sub-top events, i.e., events that describe the specific "whens and wheres" of the hazard in the top event. Next, the analysts examine the sub-top events and determine the immediate, necessary, and sufficient causes that result in each of these events. Normally, these are not basic causes, but are intermediate faults that require further development. For each intermediate fault, the causes are determined and shown on the fault tree with the appropriate logic gate. The analysts follow this process until all intermediate faults have... 

The internal V V reports of Eaton will be prepared by Eaton nuclear quality assurance team based on Eaton s software V V plan to perform the internal V V activities. These reports and abnormal condition event reports will be summarized to V V summary reports and delivered to GE IWT for review. 

Descriptions of the events in the timeline (Figure 11.8) are shown in the rectangles. An event usually represents an action, such as operator opens valve, or a sudden change in operating circumstances, such as gasket failed. Conditional events are shown in the ovals below the event. They represent environmental or background conditions that allow the sequence to move forward. For example, if the event is operator opens valve, then conditions may be that (i) an operating procedure existed and (ii) the operator was not trained in this task. ... 

Conditional Events EEE installed EEE about 5 years old Truck used for chemical Truck about 10 years old EEE installed EEE about 5 years old... 

Conditional Events Truck exists Truck is of modern design Truck driver has not entered this facility before ... 

Conditional events or environmental factors associated with that event... 

The new conditional events can be expanded further. For example, Vapors Present depends on the backflow into the tank and the fact that a direct vent pipe exists. The expanded tree is shown in Figure 11.16. 

Analysis (refer Step 3) that shows that aU potential human errors have been identified and mitigated (including conditions/events that increase the probabihty/impact of error), refer Step 3. 

Conditions/events to which system products should respond ... 

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... 

The Oval This configuration denotes a conditional event or a conditional input into the logic tree that further defines the state of the system that... 

The very usage of the term moral panic, so this argument starts, implies that societal reaction is disproportionate to the actual seriousness (risk, damage, threat) of the event. The reaction is always more severe (hence exaggerated, irrational, unjustified) than the condition (event, threat, behaviour, risk) warrants. Why is this just assumed And on what grounds is the sociologist s view always correct, rational and justified ... 

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