A diagnosis system using object-oriented fault tree models

Spaceborne computing systems must provide reliable, continuous operation for extended periods. Due to weight, power, and volume constraints, these systems must manage resources very effectively. A fault diagnosis algorithm is described which enables fast and flexible diagnoses in the dynamic distributed computing environments planned for future space missions. The algorithm uses a knowledge base that is easily changed and updated to reflect current system status. Augmented fault trees represented in an object-oriented form provide deep system knowledge that is easy to access and revise as a system changes. Given such a fault tree, a set of failure events that have occurred, and a set of failure events that have not occurred, this diagnosis system uses forward and backward chaining to propagate causal and temporal information about other failure events in the system being diagnosed. Once the system has established temporal and causal constraints, it reasons backward from heuristically selected failure events to find a set of basic failure events which are a likely cause of the occurrence of the top failure event in the fault tree. The diagnosis system has been implemented in common LISP using Flavors

An integrated approach to system design, reliability, and diagnosis

The requirement for ultradependability of computer systems in future avionics and space applications necessitates a top-down, integrated systems engineering approach for design, implementation, testing, and operation. The functional analyses of hardware and software systems must be combined by models that are flexible enough to represent their interactions and behavior. The information contained in these models must be accessible throughout all phases of the system life cycle in order to maintain consistency and accuracy in design and operational decisions. One approach being taken by researchers at Ames Research Center is the creation of an object-oriented environment that integrates information about system components required in the reliability evaluation with behavioral information useful for diagnostic algorithms. Procedures have been developed at Ames that perform reliability evaluations during design and failure diagnoses during system operation. These procedures utilize information from a central source, structured as object-oriented fault trees. Fault trees were selected because they are a flexible model widely used in aerospace applications and because they give a concise, structured representation of system behavior. The utility of this integrated environment for aerospace applications in light of our experiences during its development and use is described. The techniques for reliability evaluation and failure diagnosis are discussed, and current extensions of the environment and areas requiring further development are summarized

Kinosternon integrum

Number of Pages: 6Integrative BiologyGeological Science

Half and Half Words

In the May 2005 Kickshaws, Dave Morice showed how VIOLET is a very unusual word: its letters are half vowels and half consonants, half from the first half of the alphabet and half from the last half, etc. In an attempt to find out how unusual this word is, compared with other English words, we propose the following ten rules for dividing the alphabet into two parts

Letter Lengths

Define the length of a letter as the sum of the lengths of its component straight lines and arcs (ignoring details such as serifs). Thus, the length of V is a little more than twice the length of I in most fonts, as O is greater than C, and B and R both greater than P. To fix ideas, we define the uppercase letters as a combination of straight lines and arcs of circles. Nearly all the letters can be embedded in rectangles 2 units by 1 unit in size, except for C, O, W and Q, all of which require a square 2 units on a side

Communicative and linguistic development in preterm children: a longitudinal study from 12 to 24 months.

BACKGROUND: Research conducted on preterm children's linguistic skills has provided varying pictures, and the question of whether and to what extent preterm children are delayed in early language acquisition remains largely unresolved. AIMS: To examine communicative and linguistic development during the second year in a group of Italian children born prematurely using the 'Primo Vocabolario del Bambino' (PVB), the Italian version of the MacArthur-Bates Communicative Development Inventory. The primary goal was to compare action/gesture production, word comprehension, and word production, and the relationship between these three domains in preterm children and to normative data obtained from a large sample of Italian children born at term. A second aim was to address the longstanding debate regarding the use of chronological versus corrected gestational age in the assessment of preterm children's abilities. METHODS & PROCEDURES: Parents of twelve preterm children completed the PVB questionnaire at five age points during the children's second year, and scores were compared with those from a normative sample of full-term children and those of 59 full-term children selected as a control group from the normative sample for the PVB. OUTCOMES & RESULTS: Preterm children exhibited a delay in all three aspects of communication and language. In particular, communicative-linguistic age tended to lag approximately 3 months behind chronological age when children were between the ages of 12 and 24 months. When chronological age was used, preterm children's percentile scores for all three components of communication and language fell within the lower limits of the normal range, while scores calculated using corrected age either fell at or above the 50th percentile. CONCLUSIONS & IMPLICATIONS: Findings suggest that despite the significant biological risk engendered by premature birth, early communicative and linguistic development appears to proceed in a relatively robust fashion among preterm children, with tight relations across communicative domains as in full-term children. Employing both chronological and corrected gestational age criteria in the evaluation of preterm children's abilities may provide important information about their progress in language acquisition. This may be especially important during the initial stages of communicative and linguistic development, inasmuch as comparisons of the two sets of scores may provide clinicians with a way to distinguish children who may be at risk for language problems from those who may be expected to progress normally

Comment on “The global tree restoration potential”

Bastin et al. (Reports, 5 July 2019, p. 76) neglect considerable research into forest-based climate change mitigation during the 1980s and 1990s. This research supports some of their findings on the area of land technically suitable for expanding tree cover, and can be used to extend their analysis to include the area of actually available land and operational feasibility

Effects of language experience on pre-categorical perception: Distinguishing general from specialized processes in speech perception

Cross-language differences in speech perception have traditionally been linked to phonological categories, but it has become increasingly clear that language experience has effects beginning at early stages of perception, which blurs the accepted distinctions between general and speech-specific processing. The present experiments explored this distinction by playing stimuli to English and Japanese speakers that manipulated the acoustic form of English /r/ and /l/, in order to determine how acoustically natural and phonologically identifiable a stimulus must be for cross-language discrimination differences to emerge. Discrimination differences were found for stimuli that did not sound subjectively like speech or /r/ and /l/, but overall they were strongly linked to phonological categorization. The results thus support the view that phonological categories are an important source of cross-language differences, but also show that these differences can extend to stimuli that do not clearly sound like speech

Ebola Hemorrhagic Fever

In 1976, epidemics of severe hemorrhagic fever occurred simultaneously in both Zaire and Sudan. Of 550 cases reported, fatalities reached 88% in Zaire and 53% in Sudan, resulting in a total of 430 deaths. Ebola virus, named after a small river in northwest Zaire, was isolated from both epidemics. It was discovered during this outbreak that the spread of the epidemic was dependent on close contact with clinical cases and that it was stifled when basic quarantine procedures were instituted