Error tolerance

The flight control system has been subjected to a very strict process of design and manufacture and we can reasonably estimate that its safety level is consistent with its objectives. Protection has nonetheless been provided, which involves the use of two different types of computers for example, the ELAC A320 is based on microprocessors 68010 and the SEC on 80186 the PRIM A340 on 80386, and the SEC on 80286 the PRIM A380/A400M are based on Power PC and the SEC on Share processors. The automatic encoding tools are also difierent. 

The functional specification and, therefore, the software ate also different the ELAC and PRIM execute complex functions, while the SEC is simpler (fewer functions, such as flight envelope protection, autopilot on A380/A400M, passenger comfort requirements are less stringent) and, therefore, more robust. 

Within a single computer, COM and MON hardware have the same basic design but with different software. 

As part of the struggle against the common causes of failure, the system is loosely synehronized. The computers synchronize their data both internally (cormnand/monitoring) and between themselves (PRIMl, PRIM2, etc.), but not their 

A challenge for error tolerance is represented by reducing the number of suppliers of electronic components. It is increasingly likely that if two design teams (one for PRIM, one for the SEC) independently choose their components, they ultimately have some in common. In fact, we went from this type of random dissimilarity to a managed dissimilarity, so that the two design teams decide together to take different components. 

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Simplify Design facilities which eliminate unnecessary complexity and make operating errors less likely, and which are forgiving of errors which are made (also called Error Tolerance). 

Evaluation level create a system, in accordance with ergonomic criteria, that is error tolerant and supports error recovery redesign charging manifold (see Figure 7.7) using functional grouping corresponding to the actual layout of system. 

Root cause 6. The system was not error tolerant. The error made was not detectable. 

The final element in management s communication of a desire to reduce human error is the identification and elimination of error-likely situations. Every task is an opportunity for a human error, but some situahons represent greater risks than others. Identifying these high-risk situations is not easy and an expertise in applying human factors principles to the workplace is an essential prerequisite for this identification. Eliminating these hazardous situations is often relatively simple once they have been identified. In some cases it may be appropriate to provide error-tolerant systems, which are those that facilitate identification of and recovery from the errors. 

Equation 10.25 is of the form AAx=b which can be solved for Ax 1 and thus x0+l)(t .,) is obtained. Normally, we converge to x(tI+]) in very few iterations. If however, convergence is not achieved or the integration error tolerances are not satisfied, the time-step is reduced and the computations are repeated. 

Mann, M. Wilm, M. Error-tolerant identification of peptides in sequence databases by peptide sequence tags. Anal. Chem. 1994, 66,4390-4399. 

Dyson s model has been the subject of careful criticism as well as well-meaning agreement. Shneior Lifson (1997) found fault in particular with Dyson s assumption that metabolism (and other properties) could have developed without natural selection. In his third assumption, Dyson postulates that There is no Darwinian selection. Evolution of a molecule population occurs via genetic drift (Dyson, 1999). Lifson (1997) points out that, while Dyson stresses the role of primitive metabolism, its adaptability, error tolerance etc., he himself considers that such properties can only evolve via natural selection. 

Simplify (simplification and error tolerance) Keep piping systems neat and visually easy to follow Design control panels that are easy to comprehend Design plants for easy and safe maintenance Pick equipment that requires less maintenance Pick equipment with low failure rates Add fire- and explosion-resistant barricades Separate systems and controls into blocks that are easy to comprehend and understand Label pipes for easy walking the line Label vessels and controls to enhance understanding... 

One of the categories of inherent safety is simplification/error tolerance. What instrumentation could you add to the tank described in Problem 1-21 to eliminate problems ... 

The independence approach allows for a good encapsulation of the APS issue but requires major changes in business processes. It requires the creation and maintenance of an independent data model with its own data structure and the definition of new business processes. Introduction of the APS system must be done in a big bang. Integration is not fully guaranteed, its quality depends on the throughput and the error tolerance of the integration interface. 

M. Mann and M. Wilm. Error-Tolerant Identification of Peptides in Sequence Databases by Peptide Sequence Tags. Anal. Chem., 66(1994) 4390-4399. 

Develop new less-energetic chemical reaction systems for product manufacture, including alternate catalytic and biological routes where appropriate Emphasize need to develop economically viable inherently safer systems at the research and development stages of new process development Develop new process equipment and strategies for product manufacture using lower inventories of reactive chemicals, error tolerant approaches, and process conditions further from limits of control where appropriate... 

The reactor was optimized using (27) with the direct enforcement error criterion and the reduced SQP algorithm. Here the approximation error tolerance, e, was set to 10, and the dummy elements were added only at elements with active error constraints. In addition, four different choices of initial number of elements (NE = 2,3,4, and 5) were considered in initializing the element partition. The initial and final element partitions are shown in Table IV. The number of SQP iterations and the error norms, for each of these four cases, are also presented there. Initial and final optimal values for the state variables, measured at exit conditions, and the objective function are given in Table V. In addition, the calculated values of exit ammonia... 

Exceeding these known limits will result in unpredictable actions usually resulting in significantly reduced performance, and a resulting increase in human error. Investigators and designers should be constantly on the alert for opportunities to make a system more reliable by considering the worker-machine interface and search for every opportunity to make the system less error-prone and more error-tolerant. 

A better alternative is to use the difference structure factor AF in the summations. The electrostatic properties of the procrystal are rapidly convergent and can therefore be easily evaluated in direct space. Stewart (1991) describes a series of model calculations on the diatomic molecules N2, CO, and SiO, placed in cubic crystal lattices and assigned realistic mean-square amplitudes of vibration. He reports that for an error tolerance level of 1%, (sin 0/2)max = 1-1.1 A-1 is adequate for the deformation electrostatic potential, 1.5 A-1 for the electric field, and 2.0 A 1 for the deformation density and the deformation electric field gradient (which both have Fourier coefficients proportional to H°). 

Finally, we must recognize that die complexity of quantum chemistry concepts, theories, and approximations is such that it will be difficult to expect that instruction could leave no lingering misconceptions (zero error tolerance). However, instructors should be aware of the problems, and have themselves a deep knowledge and understanding of all variables , methods, and issues. 

In order to get this circuit to start, the UIC statement must be included in the. TRAN simulation. Flip-flops inside the model need the UIC directive in order to initialize properly. The SPICE engine has a difficult time determining the steady-state operating point of bistable circuit like the flip-flop without the UIC. Also, the ABSTOL OPTIONS parameter for current absolute current error tolerance has been changed from lp to 1/x to aid convergence. 

The error tolerance EP is set to the value EP = Xy lE-6, which is certainly smaller than the attainable accuracy based on the approximate equation (2.5). Due to the PRINT statement in the user supplied subroutine the program output is long, and only a few iterations are shown in Table 2.1. 

The golden section search guarantees that each new function evaluation will reduce the uncertainty interval to a length of >. times the previous interval. This is comparable to, but not as good as interval halving in the bisection method of solving a nonlinear equation. You can easily calculate that to attain an error tolerance EP we need... 

REM —. LONER AND UPPER LIMIT OF DOSE, ERROR TOLERANCE... 

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