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Property
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Description
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Force Monte Carlo simulation
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Indicates whether Monte Carlo simulation must be performed. When cleared (default), a simulation is performed only if the diagram cannot be calculated using standard analytical methods. When selected, a simulation is performed regardless of whether it is required. Because analytical calculations are more accurate than simulated results, this checkbox is not generally selected. For more information, see Analytical Methods Versus Simulation.
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Number of simulation iterations
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The number of simulations to perform on the diagram. The default is 1000. A Monte Carlo simulation performs random tests on the specified system to provide an analysis of the overall reliability and availability of the system. The result of these simulations determines system performance measures such as reliability and availability. The greater the number of simulation iterations requested, the greater number of random analyses performed, yielding more accurate results.
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Number of system failures to reach steady state
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The number of failure-repair cycles that the system must experience in each iteration. The default is 1. This value is used when calculating steady state availability, cost, and MTBF. Because the time between failures can change with time, you may want to simulate more failures to get a more accurate view of the steady state.
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Begin repairs (default)
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The choice to use when Use default is selected for Begin Repairs on the Corrective Maintenance page in the block’s Calculation Properties window. Choices are:
• Immediately. When selected, the maintenance can be performed immediately, even when the system is online.
• Upon inspection. When selected, the maintenance cannot be performed until the next inspection occurs.
• Upon system failure. When selected, the maintenance cannot be performed until the next system failure occurs.
• Upon system failure or inspection. When selected, the maintenance cannot be performed until the next system failure or inspection occurs.
The above choices are also available for Begin repairs on the Corrective Maintenance page in the block’s Calculation Properties. For more information, see Corrective Maintenance Page.
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Network type
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The type of network for RBD capacity calculations. For more information, see Capacity Calculations. Choices are:
• Flow Network. When selected, capacity is split evenly among all active outputs at a junction. For example, a junction with an input capacity of 100% and two outputs has a capacity of 50% on each output.
• Electrical Network. When selected (default), capacity propagates evenly for all active outputs at a junction. Unlike in a flow network, capacity does not get split. You get the same amount of power available at all output branches. For example, a junction with an input capacity of 100% and two outputs has a capacity of 100% on each output.
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Specify random number seed
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Indicates whether the random number seed for Monte Carlo simulation is specified. When this checkbox is selected (default), the field to the right becomes available so that you can enter the starting seed value. The default is 1. When this checkbox is cleared, a different starting seed value is used each time you run RBD calculations. Using the same starting seed value for each calculation run provides for duplicating results.
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Components continue to operate when system is failed
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Indicates whether components are considered to remain in an active state after a system failure occurs. When this checkbox is selected (default), components are considered to be in an active state. When it is cleared, components are considered to be in an inactive state. Indicating that components remain active after a system failure occurs can help lead to the identification of more potential part failures. If all parts are shut down during system repair, you clear this checkbox. An indication of this situation is if the MCT (mean corrective time) is a significant fraction of the MTTF (greater than 1.0%). Monte Carlo simulation is required when this checkbox is cleared.
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Treat switch delays as failures
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Indicates whether to treat every switch delay as a failure for the purpose of reliability calculations. For standby redundancy, switch delays occur when activating backup or standby components. The system or subsystem is not available during the switchover. When this checkbox is selected (default), switch delays are treated as failures. For switch delays, RBD calculations are always performed using simulation, regardless of how you specified that they be performed. When this checkbox is cleared, switch delays are not treated as failures for reliability calculations. However, they are still included in downtime for availability calculations.
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Record simulation log for first iteration of availability measures
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Indicates whether to create an RBD Simulation Log for the first iteration. When this checkbox is cleared (default), no log is created. When it is selected, a log is created. Maximum number of records to log becomes available so that you can specify the maximum number of events to record in the log. For more information, see Viewing the RBD Simulation Log.
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Maximum number of records to log
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Specifies the maximum number of records to include in the RBD Simulation Log. This property is available only when Record simulation log for first iteration of availability measures is selected. The default is 1000000.
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Confidence intervals
The properties under this heading provide for specifying confidence interval percentages for the lower and upper bound determinations when results are calculated by simulation. The properties available depend on the results selected for calculation on the > page. For more information, see General Page. The default for the confidence level percentage is 95. However, you can specify any percentage value for Confidence level. The lower and upper bounds are then computed and shown in the results.
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Reliability
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When selected, you specify the confidence interval for the lower and upper bound determination when reliability is calculated by simulation. For more information, see Confidence Intervals on Reliability and Availability.
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Availability
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When selected, you specify the confidence interval for the lower and upper bound determination when availability is calculated by simulation. For more information, see Confidence Intervals on Reliability and Availability.
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MTBF
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When selected, you specify the confidence interval for the lower and upper bound determination when MTBF (mean time between failures) is calculated by simulation. For more information, see Confidence Intervals on MTTF and MTBF.
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MTTF
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When selected, you specify the confidence interval for the lower and upper bound determination when MTTF (mean time to failure) is calculated by simulation. For more information, see Confidence Intervals on MTTF and MTBF.
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Linked diagrams
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Save linked diagram results
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Indicates whether to save results calculated for linked diagrams. When this checkbox is cleared (default), results are not saved. When it is selected, results are saved. Any existing results for this diagram are overwritten with new results. If a diagram has multiple links to it, only one set of results is saved for the diagram. When a linked diagram is active, you can view the results calculated for it in its View Calculation Results window. Cut sets and path sets are not calculated for a linked diagram. Results for linked diagram are available on reports.
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