Failures specifications

Habibi B, Basty R, Chodez S, Prunat A. Thiopental-related immune hemolytic anemia and renal failure. Specific involvement of red-cell antigen I. N Engl J Med 1985 312(6) 353-5. 

Dunitz and Bernstein [5] have recently documented several cases of vanishing polymorphs. These are usually metastable forms which, despite their thermodynamic instability, may have crystallized preferentially due to more rapid nucleation. Such metastable forms may persist and be used for many years before being displaced , when a thermodynamically more stable form is prepared. Attempts to regenerate the original polymorph are frequently met with failure. Specific compounds with such a history include e.g. 1,2,3,5-tetra-0-acetyl- -D-ribofiiranose, benzocaine picrate and xylitoL This disturbing phenomenon extends to pseudopolymorphs. A previously known monohydrate of the antibiotic ampicillin has not been obtained since the appearance of the trihydrate [24]. A possible explanation for this behaviour is that after minute particles of the stable polymorph enter the environment, they eventually become widely disseminated ( planetary seeding [5]) and serve as nuclei promoting crystallization of their own kind exclusively. 

The potential of telehealth technology in CVD management has been investigated in several small- and large-scale studies on heart failure. Specifically, meta-analysis of a number of small-scale studies on patients with chronic heart failure (CHF) reported considerable clinical benefit from telemonitoring when compared with the usual care provided at... 

The overall quality refers to the precautions taken to guard against systematic failures. Specification errors, equipment errors, and software errors can easily occur during normal maintenance activities. Improving the overall quality involves careful thought and planning at every step of the lifecycle process. The use of an approved quality management system is recommended. 

Some specific corrosion environments, in the presence of applied tensile stress on the metal siuface (above some threshold vtilue), can cause stress-corrosion cracking (SCC). The somce of stresses can be extemtil, but residual stresses can tilso cause SCC failures. Specific corrosive pollutants, which may contribute to the SCC of carbon steels, are for example, the carbonates in water. Sulfide stress cracking (SSC) commonly occms on the outside of a pipe where sulfate-reducing bacteria me present at a soil pH of 3-7. Because of the produced iron sulfide (FeS), which adsorbs readily on the steel surface, hydrogen atoms generated... 

Safety nets allow households to take up investment opportunities that they would otherwise miss—both with regard to the human capital of their children and the livelihoods of household earners—despite credit market failures. Specifically, safety net programs can contribute to capital accumulation among the poor by preventing the negative outcomes... 

The team can also assess the impact of repeated weaning failures specifically when to consider noninvasive ventilation, nocturnal ventilation, or HMV as well as how to best address issues that impact health-related quality of life, such as speech, swallowing, and mobility. 

Functional specification and functional realization are the functional views of a component. These views are models that describe the desired data flow through a component on different levels of abstraction. Other functional and non-functional properties of a component, such as resource consumption, quality of services, or dependability, are modeled and separated by additional views (models). For example, the propagation of failures through a component is modeled by a failure specification and a failure realization view. The view concept helps to focus on a single property of a component and thus helps to handle complexity. In this paper, we focus only on the functional views and on the failure views already explained above, which are the results of fault tree analysis of the component. This analysis, the resulting failure specification and failure realization, as well as the relationship between both views will be discussed in the remainder of this paper. 

Abstraction is a view of an object that focuses on the information relevant to a particular purpose and ignores the remainder of the information [12], So, to define hierarchical abstraction from the failure realization to the specification, the difference between their purposes has to be determined, which is only the hierarchy level. This means that the specification has to abstract from the same information as the realization, plus from the inner details of the component that are shown in the realization. For the hierarchical abstraction of the functional specification from the functional realization this means that the subcomponents and their collaboration are hidden, as well as that the functionality of the component is specified only in terms of the component itself The failure realization must have the same level of hierarchical abstraction as the fiinctional realization and the failure specification the same level as the functional specification. This requirement is true for SpeedControl. The hierarchy level of the failure realization in Figure 4a is consistent with its functional reaUzation in Figure la, because it only shows failure modes of the functional in- and outputs as well as failure modes of the subcomponents that are shown in the functional reaUzation. The hierarchy level of the corresponding failure specification in Figure 4b is consistent with the functional specification in Figure lb, because it hides all details of the subcomponents and only shows the failure modes of SpeedControl (S). 

In the following, the SpeedControl example is used to determine, first, the information that is contained in the failure realization, and, afterwards, the information that should remain in the failure specification and the information that must be abstfacted. The failure realization, as shown for example in Figure 4a, contains the following information ... 

The failure propagation paths must be changed in such a way that no information about the inner structure and subcomponents is disclosed, i.e., the structure of the failure specification CFT must be independent of the structure of the failure realization CFT apart from the Boolean conditions of requirement 1. 

In some cases, it may be not applicable or necessary for both failure views to be equivalent to each other. For example, if we consider only coherent fault trees, it may be acceptable that the failure realization only implies the specification, i.e., every time an output failure mode in the realization is true, it is also true in the specification. In such a case, the specification is a pessimistic or conservative approximation of the realization. In a quantitative FTA, the probabilities of the output failure modes, which depend on the probabilities of the input failure modes, can be used to define other relations. For example, it can be requested that the output probabilities of the realization are either equal or below the probabilities of the specification, or between two thresholds. However, if any relation other than equality is used, the type of relation between the specification and the realization must be specified as part of the failure specification in order to use the component correctly. Additionally, the changes and mappings between the failure specification and the failure realization have to be known and stored as part of the component realization, in order to be able to eheck... 

Through this kind of hierarchical fault tree abstraction, the failure specification of a component can be derived from the failure realization and will be consistent with the failure realization and the hierarchy level of the component specification. In this way, unnecessary details and complexity of the levels below are hidden and only the information that is required to evaluate and assess the failure behavior of the current component is provided. Additionally, it can be checked and guaranteed that fault trees of different hierarchy levels are consistent with each other. 

Like the evaluation of fault trees, hierarchical fault tree abstraction cannot be done manually for larger systems, because of the complexity, error-proneness, and effort needed. Thus, for the application of hierarchical fault tree abstraction, it is mandatory to have an appropriate degree of automation and tool support. For this purpose, algorithms are needed that take a failure realization as input, automatically generate an abstract failure specification from it, and check that both are consistent to each other. 

If it is sufficient that the failure realization only implies the failure specification, but does not need to be equivalent, internal failure modes can also be merged if they do not constitute an internal module. For example, if the user of a component only needs to know that it has a detection mechanism for some input failure modes, all internal failure modes of the realization that represent the relevant detection mechanisms can be merged into an abstract internal detection failure mode of the failure specification [6]. In this way, all internal failure modes or any combination, such as all internal failure modes of the same failure type, can be merged into a new abstract internal failure mode, e.g., through the disjunction of the old ones. If probabilities are used, probabilities for the new internal failure modes of the specification can be calculated based on the probabilities of the failure realization. 

Independent of how the internal failure modes are merged and what other abstraction algorithms are applied, the mapping between the realization and the specification must be specified as part of the realization. Additionally, the kind of relation must be specified as part of the specification. Only in this way is it possible to guarantee traceability and to check if the assumed relation between failure realization and specification is true. For example, if modularization is used, the internal modules of the failure realization and the corresponding internal failure modes of the specification must be known in order to check equivalence. This is also true if the internal failure modes are only renamed from the realization to the specification. To efficiently check the equivalence or other qualitative relations between failure specification and realization. Binary Decision Diagrams (BDDs) are used. 

The active failures (specific errors), the type of each error and finm the classifications used to describe the error, the most appropriate route to improvement. 

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