Logical model

Fault Tree Analysis Faiilt tree analysis permits the hazardous incident (called the top event) frequency to be estimated from a logic model of the failure mechanisms of a system. The top event is traced downward to more basic failures using logic gates to determine its causes and hkelihood. The model is based on the combinations of fail-... 

Adequate support from the facility staff is absolutely essential. The facility staff must help the analysis team gather pertinent documents (e.g., PSilDs, procedures, software descriptions, material inventories, meteorological data, population data) and must describe current operating and maintenance practices. The facility staff must then critique the logic model(s) and calculation(s) to ensure that the assumptions are correct and that the results seem reasonable. The facility staff should also be involved in developing any recommendations to reduce risk so they will fully understand the rationale behind all proposed improvements and can help ensure that the proposed improvements are feasible. Table 12 summarizes the types of facility resources and personnel needed for a typical QRA. 

A logic model that graphically portrays the range of outcomes from the combinations of events and circumstances in an accident sequence. For example, a flammable vapor release may result in a fire, an explosion, or in no consequence depending on meteorological conditions, the degree of confinement, the presence of ignition sources, etc. These trees are often shown with the probability of each outcome at each branch of the pathway... 

A logic model that graphically portrays the combinations of failures that can lead to a particular main failure (TOP event) or accident of interest. Given appropriate data, fault tree models can be quantitatively solved for an array of system performance characteristics (mean time between failures, probability of failure on demand, etc.)... 

The use of component logic models to build system fault logic has been discussed by several authors for chemical and electrical systems (Powers and Thompkins, 1974 Fussell, 197.S and Powers and Lapp, 1976). In addition, generic sabotage fault trees have been used for some time in the analysis of security concerns for nuclear power plants (NUREG /CR-0809, NUREG/CR. 121,... 

NUREG/CR-3098, and NUREG/ CR-2635). MF7 draws on this experience for logical modeling of process plants. 

A library of generic fault logic for common system configurations and components. The.se MIT logic models are those needed by the analyst for constructing system models. 

The analysis of human actions is complicated because a human is a responsive system like a servo. Such analysis does not lend itself to simple models as do inanimate components. Classifying human actions into the success or failure states used in logic models for plant equipment dix. s not account for the wide range of possible human actions. A generally applicable model of the parameters that affect human performance is not yet available. 

Fault tree analysis of mitigating systems to develop logic models of how system failure may occur ... 

Accident Sequence Modeling using a logic model for the facility was developed. The model included all initiators of potential accidents and the response of the installation to these initiators. Specific accident sequences are defined in event trees consisting of an initiating... 

Source Hauser, V.L. and Gimon, D.M., Evaluating Evapotranspiration (ET) Landfill Cover Performance Using Hydro-logic Models, Air Force Center for Environmental Excellence (AFCEE), Brooks City-Base, TX, January 2004. 

Event tree A graphical logic model that identifies and potentially quantifies possible outcomes following an initiating event. 

Fault tree A graphical logic model for representing the combinations of various system states which lead to a particular outcome, known as the top event. 

Logic Model Methods The following tools are most commonly used in quantitative risk analysis, but can also be useful qualitatively to understand the combinations of events which can cause an accident. The logic models can also be useful in understanding how protective systems impact various potential accident scenarios. These methods will be thoroughly discussed in the Risk Analysis subsection. Also, hazard identification and evaluation tools discussed in this section are valuable precursors to a quantitative risk analysis (QRA). Generally a QRA quantifies the risk of hazard scenarios which have been identified by using tools such as those discussed above. 

Event Trees (ET) - A mathematical logic model that mathematically and graphically portrays the combination of events and circumstances in an accident sequence, expressed in an annual estimation. 

The theory had never been tested on a logical model system. Let us consider in detail one representative case, the superimposable stacking of the two benzene rings, one from each triplet diphenylcarbene molecule. These are considered to represent idealized modes of dimeric interaction of the aromatic ring parts of open-shell molecules in ordered molecular assemblies like crystals, liquid crystals and membranes. 

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. 

Fault Tree Analysis (ETA)—Estimation of the hazardous incident (top event) frequency from a logic model of the failure mechanisms of a system. 

Fig. 2. Input lithological units and structures in the Fuzzy Logic model.

Figure 9. (a) Batrachotoxin (BTX) docked into the KcSA X-ray structure. Residue positions superimposed in green correspond to those implicated in the sodium channel Navi.4 and (b) its display as projected on the generic logical model of ion channels and predicted interaction with an ion channel Theme. 

The logical model of geotechnical surveys to be performed at different development stages of a main pipeline project is given in Figure 1. The main distinctive feature of the model is that the geotechnical survey is considered... 

Control based on neural network. Similar to fuzzy logic modeling, neural network analysis uses a series of previous data to execute simulations of the process, with a high degree of success, without however using formal mathematical models (Chen and Rollins, 2000). To this goal, it is necessary to define inputs, outputs, and how many layers of neurons will be used, which depends on the number of variables and the available data. 

Fuzzy logic modeling. A linguistically interpretable rule-based model, based on the available expert knowledge and measured data. 

In the absence of reliable fossils it is difficult or even impossible to address the historical question of how, and via which specific routes, homochirality emerged on Earth. Therefore, in this regard, we can only provide logical models that can outline scenarios of how the transition from racemic chemistry to homo chiral biology might have happened. 

Kecman, V., Learning and Soft Computing Support Vector Machines, Neural Networks, and Fuzzy Logic Models (Complex Adaptive Systems), MIT Press, Cambridge, MA, 2001. 

Here is an example of a combinational logic model of a 2-to-l multiplexer with an enable. 

---