Time redundancy

An alarm should sound if any time redundant inputs disagree. In many cases the operating personnel will have to decide what to do. In some cases the computer control system will have to decide by itself what to do if redundant inputs disagree. 

An alarm should sound any time redundant inputs disagree. In most cases, the operating personnel will have to decide what to do. In some cases the computer control system will have to decide by itself what to do if redundant inputs disagree. The more hazardous the process, the more it is necessary to use multiple sensors for flow, temperature, pressure, and other variables. Since it must be assumed that all measuring devices will fail, they should fail to an alarm state. If a device fails to a nonalarm condition, there can be serious problems. It is also serious if a device fails to an alarm condition, and there is really not an alarm condition. This is generally not as serious as the first case, but it can provide a false sense of security. Usually it is assumed that two... 

Differently from space redundancy, time redundancy uses the same computing hardware modules to compare its values, but shifted in time. Usually extra haidware is added to introduce a fixed time delay 5. Anghel (2000) proposed an architecture where the outputs of a combinational circuit were duphcated and stored with different time delays (0 and 5). A comparator was then introduced to compare the stored results after 5, flagging an error in case of mismatch. It is important to mention that 5 equals to the maximum expected transient pulse length. 

NICOLAIDIS, M. Time redundancy based soft-error tolerance to rescue nanometer technologies. In IEEE VLSI TEST SUMPOSIUM, 17., VTS 1999, Dana Point, USA. Proceedings... Washington, DC, USA IEEE Computer Society, 1999. pp. 86-94. 

Whitney J. Townsend, Jacob A. Abraham, and Earl E. Swartz-lander, Jr. Quadruple Time Redundancy Adders, 18th IEEE International Symposium on Defect and Fault Tolerance in VLSI Systems, pp. 250-256, Cambridge, MA, November 3-5, 2003... 

Lisnianski, A., Levitin, G. Ben-Haim, H. 2000. Stracture optimization of multi-state system with time redundancy, Reliability Rnpineerine and System Safety 67. 103-112. 

ABSTRACT Reliability analysis of complex systems is complicated by several factors. The possible unreliability of logistic support elements may lead to decrease of performance of the system being supported. As a result both systems must be considered in a single model. However, the simultaneous setting of all structural parameters (e.g. redundancy, repair shop capacity) and control variables (e.g. spare part inventory levels, maintenance policy parameters, repair job priorities, time redundancy) is mathematically a hard problem. That is why this paper describes FTTD modeling technique for handling these difficulties. Moreover, the application example of tram network performance is described. Fault tree with time dependencies model for the presented example and its analysis is discussed. 

There is also made an assumption, that the time redundancy (time resource) given for putting back to service of failed tram is defined as minimal time o f one tram course performance. Over crossing the defined time resource results in necessity of fine paying by the transportation company. 

Failed tram replacement after elapsed time redundancy provided there was redimdant tram available in a stem... 

Awaiting for redundant tram dismissing after elapsed time redundancy... 

Additionally, we known (from MCS A), that hazard (event 1) can occur only if minimal time redundancy (tymin) is equal or greater than replacement time of a tram by redundant one (t ). 

There is a passive system for providing make up water in the event of a LOCA, the Emergency Coolant Injection System (ECIS). This uses steam injectors to pump water from the containment tanks into the RPV. The steam is taken from the top of the pressuriser. There is two times redundancy. This system can be combined with a bleed system to provide a second route for decay heat removal. Fig. 7.5.2. gives a schematic diagram of the safety systems and the nonsafety grade heat removal systems. 

Failure modes Hardware failure modes have been discussed at length in this chapter. Software failure modes may be data and event failure modes and these may be repetitive in nature, because they may be caused by systematic failure. At times, redundancy may not really serve the purpose of avoiding such failures. 

Reddy, V., Rotenberg, E. Inherent time redundancy (itr) Using program repetition for low-overhead fault tolerance. In DSN 2007 Proceedings of the 37th Annual lEEE/IFIP International Conference on Dependable Systems and Networks, Washington, DC, USA. IEEE Computer Society, Los Alamitos (2007)... 

Time redundancy, including transient fault detection methods such as Alternate Logic... 

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