Static redundancy

A 162-modular redundant system uses the same resources as the self-assembling self-repairing design. A simple analysis shows the self-assembling solution can tolerate a greater number of failures than its static-redundancy equivalent. 

Static redundancy In this system n versions of the programs are written and run for performing the same function. There will be a few checkpoints where each of the output from different versions will be voted to be selected as final output. 

N-version programming This is similar to static redundancy. Here, independently written programs (versions) for the same functions are executed parallel and their outputs are voted at special checkpoints. Naturally, the voted data may not be exactly the same. So, criteria must be used to identify and reject faulty versions and to determine all good versions for use. See Fig. XI/1.1.5-2A. 

GL 2010 gives no particular prescriptions on the structural model to be adopted. However, because at least three modes have to be included in the vibration response, the use of a multi-degree-of-freedom (MDOF) structural model is implicitly suggested. In general, a linear elastic behavior shall be assumed. A ductile response can be considered only when the support structure has a sufficient static redundancy, such as a lattice tower. However, if ductile behavior is assumed, the structure shall be mandatorily inspected after occurrence of an earthquake. 

The need for redundancy in the culture system needs to be assessed. Failure of a well pump that brings up water to supply a static pond system may not be a serious problem in countries where new pumps can be purchased in a nearby town. However, it can be disastrous in developing countries where new pumps and pump parts are often not available, but must be ordered from another country. Several weeks or months may pass before the situation can be remedied unless the culturist maintains a selection of spares. 

We saw in Section 3.5, Actions with Invariants, that invariants are implicitly conjoined with action specifications. Static invariants factor those constraints that apply to every state, and effect invariants capture rules about every state change. Both of them simplify action specs by making them fess redundant. 

The braced frame must develop the ultimate capacity of the members which it supports, namely the girts and end wall columns. The force applied to the top of the column is equal to the tributary area times the resistance as a static load. Each braced frame will be designed to resist the entire load even though there will be a frame at each end of the building. This will provide redundancy and will eliminate large axial forces in the top perimeter beams at the interior frames. 

It is also possible to create a redundancy between measurements with models linking several variables. Static and robust models like acid-base equilibrium and gas-liquid equilibrium can be used easily. However, models with strong assumptions and/or with unknown validity should be used with caution. In this last case, we also have to take into account that the model itself can be faulty and a dimension of the state-universe of the corresponding bba is the faulty state of the model. 

R. Pagh, Low redundancy in static dictionaries with 0(1) lookup time. Proceedings of ICALP 99, Lecture Notes in Computer Science 1644, Springer, 1999, pp. 595-604. 

A better method, also called standby redundant, is to incorporate a static switch in each of the inverter output circuits. Static switches can function rapidly, with an almost imperceptible disturbance at the load terminals. One static switch is kept open whilst the other is closed . 

A more reliable method is called a parallel redundant UPS system, but it requires a more sophisticated control system. Both UPS units are energised to share the common load equally. When one unit fails it is switched out of service and the second unit takes over the full load. Figure 17.3 shows the system which also has an off-load bypass supply switched in service by a static switch. This method can be expanded to incorporate three or more units in parallel, although this is seldom found in oil industry practice. It is a practice used in the computer-based industries such as banking and flnancial investment. It is a method that lends itself to piecemeal expansion. 

Figure 17.3 Dual redundant UPS with a bypass supply and static switches.

An example of the use of these ideas is in the consideration of the static determinacy of pin-jointed structural frameworks. If the number of members i a two-dimensional framework is equal to 2/ — 3, where / is the number c joints, then the framework is said to be just stiff and determinate. If n is greatc than 2/ - 3, then the frame is redundant, and if less it becomes a mechanisn This rule is a necessary but not a sufficient condition for static determinac [28] because the members must be arranged in a suitable manner. 

The fault tree analysis describes a hazardous top event and the basic event which maybe leads to such a top event in a top-down method. The methods are dev-ided in static fault tree analysis and dynamic fault tree analysis. The static fault tree analysis describes the system top event in static way. In further steps it is not possible to describe functional system redundancy with this static Fault Tree Analysis (FTA). Especially if cold and hot spares are integrated or if triggers are used, the static fault tree analysis is unsatisfying these requirements. Therefore it is more suitable to use the extended Dynamic Fault Tree Analysis. The DIFTree (Dynamic Innovative Fault Tree) software package could be a helpful tool for the system development... 

In principle, the concrete structures undamaged are statically stable with high redundancy. AE activity is very low in a stable structure, because the Kaiser effect is closely associated with structural stability. Such ratios as the load ratio and the calm ratio are defined to estimate the Kaiser effect. 

Passive Residual Heat Removal System X 2 100% trains of natural-circulation water loops permanently connected to the primary circuit and cooled by external air. Only one non-static component, passive type (special check valve), 400% redundant... 

Decay I leat Remo al Passive Deca Heat Removal Svstem Passive Mainly static (only one non-static aimponent, but passive, with 400% redundancy)... 

A diagnosis procedure based on evaluation of physical constraint laws derived from bond graph models is described here. Symbolically written constraints, called analytical redundancy relations (ARRs), are expressed in terms of known variables (measurements and inputs). ARRs are static or dynamic constraints which link the time evolution of the known variables when a system operates according to its normal operation model. The error or deviation from the constraint model is called a residual. The objective of quantitative diagnosis is to evaluate the residuals and associate the fault symptoms with deviations of residuals. 

An isolated redundant system, illustrated in Fig. 10.153, divides the load among several UPS units. If one of the active systems fails, a static bypass switch will connect the affected load to a standby UPS system dedicated to that purpose. The isolated redundant system does not permit the unused capacity of one UPS unit to be utilized on a DP system that is loading another UPS to full capacity. The benefit of the isolated configuration is its immunity to systemwide failures. 

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