Fault masking

Logical masking is when the logic of the gate being hit by a fault masks its effect. The basic logic operators AND and OR both have a dominant value as property. 

The fault injection campaign was performed automatically. At the end of each execution, the results stored in memory were compared with the expected correct values. If the results matched, the fault was discarded. The amoimt of faults masked by the program is application related and it should not interfere with the analysis. In the end, only faults not masked by the application were considered in the analysis. When 100% signal coverage was achieved and at least 4 faults per signal were detected we normalized the faults, varying from 4 to 5 faults per signal. Those faults were then used to build the test case list. 

They are known as intrusion tolerant systems when protection mainly concerns with faults coming from intrusions. Fault-tolerant techniques can be subdivided [1] in several groups fault detection, fault recovery, fault handling and fault masking. In this work, we focus on proactive and reactive fault-tolerant recovery techniques. 

In instrumentation and control, triple modular redundancy is very important for fail safe operation. Fig. 1/6.1.2-1 shows the same. Here, each of the three elements are voted thrice in each stage to get the output. In network communications, especially for remote communication, there are a few other problems known as Two Army problem, Byzantine general problem, etc. The issues discussed so far basically belong to fault masking to get away with hardware fault. There is another term called dynamic recovery, in which case there shall be a special mechanism to detect hardware fault and isolate the faulty hardware and replace the same with a good one. This wiU be clear from an example. Say in a process control, there are two processors one working and the other standby. If there is another processor whose main function is to act a diagnostic processor to check health of other processors, when it finds fault with... 

Fault tolerance As defined earlier, fault tolerant designs are aimed at development of systems that could function correctly in the presence of faults. This is primarily achieved by some kind of redundancy to detect or mask a fault. Masking/detections are followed by fault location, containment, and recovery. 

TMR is a commonly used form in fault masking. Here, the circuit uses triplicate identical main and voting circuits, for example, Al, A2, A3, as shown in Fig. Xl/1.1.3-1. A TMR system fails whenever two modules in redundant... 

In the past, safety engineering has been applied to build dependable systems out of less reliable components. A multitude of practical techniques such as fault masking, error detection, fault diagnosis, and recovery have evolved to improve the reliability of safety-critical system. Since the operations of these systems also depends on software and communicated information, malicious attacks to information security must be considered and appropriately addressed. Commonly, the focus of security can be described by the Confidentiality, Integrity, and Availability (CIA) model. A safety analysis needs to include security risks, determined by vulnerability, threat, and impact with respect to the CIA model. 

Another option might have been the implementation of a triple modular redundant [4] (TMR, fault masking structural redundancy) system with robust majority voting schemes at the actuators. Such systems can be built either with synchronously running processor units and distributed local code/data memories, or asynchronously running processor units with local access to code and shared access to triple redundant data memories. The complexity and hardware demand of such a system architecture is so high, however, that this idea had to be rejected for technical reasons (mass, volume, harness, power consumption, etc.). 

Verdeck, n. cover (automobile) hood deck, verdecken, v.t. cover, conceal, mask, verdenken, v.t. find fault with. 

The problems of preventing faults in systems from leading to system failures, and of minimizing the severity of failures that do occur, vary greatly in difficulty depending on these assumptions. For example, one might choose to assume that (i) operational hardware faults can be cost-effectively masked... 

The first American effort in gas-ma k production was a lot of 25,000 masks of British typo intended for u.se of the 1st Division. These were made without sufficient knowledge of British specifications and fabrication im thuils. They were shipped to France in 1917 but proved fault) and wcHf never issued to troops. 

The structure of the deposit, with homoclinal northeast dip, is uncomplicated, although faulting occurs. This appears to be limited to a set of strike-normal faults, dipping to the northwest. The western margin of the basin is faulted the displacement is probably of considerable magnitude. The Tertiary beds are masked by up to 30m of alluvial gravels and sands. 

Masking of Multiple Faults When the region spanned by the model for one (outer) fault contains the model for another (inner) fault, their combination... 

Faults causing random variation about a mean value (such as excessive sensor noise) move a process less drastically off-target than step or ramp faults. Similarity measures should indicate that the random variation faults have more overlap with other models, particularly with each other. Ramp or step faults tend to be the outer models and mask secondary random variation faults. 

Faults can also be masked by three different ways in the circuit logical masking, electrical masking and latch window masking. Figures 2.3, 2.4 and 2.5 show each of them, respectively. 

The small hills east of the horst are deformed beds of the Santa Fe Group along the west side of a downfaulted block, or graben. Any faults that may be present at TA-V are masked by an alluvial fan. 

The sensitivity analysis of residuals to uncertainties and faults depends on sensitivity indices and fault detectability indices, to be defined. They allow control and improvement of diagnosis performance. In practice, the knowledge of fault detectable value allows the user to measure the damage that this fault can cause on the system, and the knowledge of uncertainties that could mask the appearance of faults may induce additional measurements to control their changes and achieve the desired performance. 

Software fault tolerance For software, fault tolerant design redundancies are required to mask residual design faults. Some of the issues related to this shall include but are not limited to ... 

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