Degrade mode

Degraded failure A failure that is gradual or partial it does not cease all function but compromises that function. It may lower output below a designated point, raise output above a designated point or result in erratic output. A degraded mode might allow only one mode of operation. If left unattended, the degraded mode may result in a catastrophic failure. 

One further degradation mode related to catalysis is a consequence of operating at low current densities typical of portable power application. Under these conditions, overoxidation of the Pt cathode catalyst occurs, reducing cathode and overall MEA performance. Zelenay has shown that starving the cathode of air flow lowers the cathode potential to low values, causing reduction of Pt oxides and restoring cathode activity. ... 

Separate Accelerated Stress Test (AST) protocols have been proposed by the US Department of Energy to assess the durability of fuel cell under conditions that promote distinct degradation modes... 

The most common failures are associated with oxidation, carburization and metal dusting, sulfidation, chlorination, and nitridation. The most common high-temperature degradation mode is oxidation, and the protection against oxidation, in general, is given by the formation of a chromium oxide scale. The presence of a small amount of aluminum or silicon in the alloy may improve the resistance against oxidation of a... 

The cyclic degradation mode A is particularly usefiil to simulate the degradation induced by daylight exposure and is characterized by a sequence of successive periods of brightness (TB) and darkness (TD). The brightness duration and the darkness duration (hours, minutes, seconds) and the total number of cycles (brightness + darkness) are entered via a user-friendly graphic software interface. 

In the continuous degradation mode B, the input time sequences and parameters are the same as in the cyclic mode except for the darkness duration, which is reduced to one minute, i.e., the time required to stabilize the PMT. The fatigue resistance tR is calculated as for mode A. 

The flash degradation mode C requires a preset number n of flashes followed by one measuring flash, with the input being the number of degradation flashes and sequences. The fatigue resistance is now defined as the number of flashes needed to reach A0/2. 

Aerobic bacteria complete most of the petroleum bioremediation applications, particularly those above the groundwater table. Aerobes are those bacteria that require an oxygen source as their TEA. Conversely, anaerobic species require the absence of oxygen (anoxic conditions) for their respiration. In situ anaerobic bioremediation is typically only conducted in the saturated zone because of the difficulty in maintaining a strict anaerobic environment. In some instances, facultative anaerobes are utilized because they can alter the respiration to be metabolically active under both anaerobic and aerobic conditions. As such, the type of TEA available will dictate the metabolism and subsequent degradation mode. The most common TEAs used for bioremediation are listed in Table 2. Careful selection of microbe-TEA combinations can enable a specific degradation pathway to facilitate cometabolism and prevent undesired degradation by-products. 

Electrochemical corrosion is important to the stability and longevity of implants. Evidence suggests that uniform attack and crevice and pitting corrosion are the most important degradation modes with multipart orthopedic devices (17). Corrosion of devices with blood contact is more complex, due to the oxygenated flowing electrolyte. The cost of this corrosion has not been estimated, but it could be substantially greater than the battery market because the latter is a small fraction of the total cost of the device and associated medical operations. 

Otherwise, the heterochain polymers that contain heteroatom as part of the chemical constitution of the polymer along the main chain, besides degradation described for homopolymers, and also other mechanisms may be considered in their degradation mode, that is, depolymerization or elimination reactions. 

Given all of the possible degradation modes of MCFCs cited above, reliability issues have yet to be fully resolved and thus the ultimate service life remains to be demonstrated. 

The degradation modes of coatings are essentially the same as those described for cyclic oxidation of alloys in Chapter 5, mixed-oxidant corrosion of alloys in Chapter 7, and hot corrosion of alloys in Chapter 8. However, additional factors arise with coatings since they are relatively thin, they contain a finite reservoir of the scale-forming elements (Al, Cr, Si), and interdiffusion with the substrate can both deplete the scale-forming element and introduce other elements into the coating. Additional mechanical affects also arise, which can lead to deformation of the coating. Mechanical effects are also critical to the durability of TBCs. 

Interdiffusion of elements at the interface with the substrate that results in a creation of undesirable phases is, sometimes, also mentioned as an independent degradation mode [18]. 

Figure F-20. Single Fault Degradation Modes of 2oo3 Architecture...

Failure is the abbreviation of service failure and is defined as a system malfunction, or in other words, when the delivered service deviates from the correct one. The delivered service is considered correct when it is according to the system specification. When the service specification includes a set of several functions, the failure of one or more of the services implementing the functions may lead the system to a degraded mode that still offers a subset of needed services. We define this case as a partial failure. 

Based on this assessment, all filters would be fully functional in an accident scenario most of the time (75%). An additional 22% of the time, a single charcoal or a single HEPA filter would be assumed to be operating with reduced efficiency, 2% of the time at least one charcoal filter is fully functional with the other filters operating in a degraded mode. Thus, scenarios where two charcoal filters are degraded or where filters would be assumed to be totally failed will occur less than 1% of the time, and scenarios where more than one filter Is failed are very to extremely unlikely. 

Degraded Mode Service characterized by the provision of services at a level below the nominal operating performance, limiting the quantities of controlled aircraft or lengthening the response time of control. 

Figure 8. WSN availability mapping at t=1000 h with components 10 15 in a degraded mode. X4 = 10- /i4 = 10-. ...

Long-term durability of adhesively bonded joints may require resistance to a number of individual or combined degradation modes, including environmental attack, fatigue and time-dependent failures. Time-dependent failure mechanisms are often characterized nsing either a strength approach, involving creep and creep-rupture tests, or a fracture approach, in which debond rate is determined. In creep-rupture tests, adhesive joints are subjected to... 

Long-term durability of adhesively bonded joints may require resistance to a number of individual or combined degradation modes, including environmental attack, fatigue... 

Figure 12.1 Degradation modes for biopolymers under (a) surface erosion, (b) bulk degradation and (c) core-accelerated bulk erosion.

Trade-off between efficiency and degradation performance Bus city driving cycles effect on voltage degradation Review of literature on effects and potential mitigation of various degradation modes... 

Safety is a property of the operational system and therefore safety arguments should address all the operational domain including the normal and degraded modes of the system, its maintenance, data updates and data passed across the boundary of the operational system. System hazard identification and subsequent hazard analysis should consider all system hazards including those that arise from data errors. If data is not considered within the hazard analysis stage, no data-related hazards will be identified, suggesting that the data has no specific safety... 

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