Mishaps with Oxygen in NASA Operations

Data from a substantial number of oxygen mishaps obtained from NASA and contractor records are presented. Information from several Air Force records, concerning oxygen accidents involving aircraft operations, are also included. Descriptions of the mishaps and their causes, for both liquid and gaseous oxygen in ground test facilities and space vehicle systems, are given. A number of safety regulations aimed at reducing the accident probability is discussed. The problems related to material compatibility and materials testing are considered, and the limited information on factors affecting the ignition of materials in oxygen is presented. In addition, details are given of several of the accident/incidents listed in order to define the combination of conditions causing the mishap. In addition to propellant system mishaps, accident/incidents which occurred in space and ground system structures were included, as well as those in electrical systems, ground support facilities, ordnance, and related operations

Mechanical impact tests of materials in oxygen effects of contamination

The effect of contaminants on the mechanical impact sensitivity of Teflon, stainless steel, and aluminum in a high-pressure oxygen environment was investigated. Uncontaminated Teflon did not ignite under the test conditions. The liquid contaminants - cutting oil, motor lubricating oil, and toolmaker dye - caused Teflon to ignite. Raising the temperature lowered the impact energy required for ignition. Stainless steel was insensitive to ignition under the test conditions with the contaminants used. Aluminum appeared to react without contaminants under certain test conditions; however, contamination with cutting oil, motor lubricating oil, and toolmakers dye increased the sensitivity of aluminum to mechanical impact. The grit contaminants silicon dioxide and copper powder did not conclusively affect the sensitivity of aluminum

Speech rhythm as naturally occurring and culturally transmitted behavioral patterns

First published: 09 September 2019Rhythm is fundamental to every motor activity. Neural and physiological mechanisms that underlie rhythmic cognition, in general, and rhythmic pattern generation, in particular, are evolutionarily ancient. As speech production is a kind of motor activity, investigating speech rhythm can provide insight into how general motor patterns have been adapted for more specific use in articulation and speech production. Studies on speech rhythm may further provide insight into the development of speech capacity in humans. As speech capacity is putatively a prerequisite for developing a language faculty, studies on speech rhythm may cast some light on the mystery of language evolution in the human genus. Hereby, we propose an approach to exploring speech rhythm as a window on speech emergence in ontogenesis and phylogenesis, as well as on diachronic linguistic changes.This research is supported by the Basque Government through the BERC2018–2021 programand by the Spanish State Research Agency through BCBL Severo Ochoa excellence accreditation SEV-2015- 0490 and through project RTI 2018-098317-B-I00 funded by AEI/FEDER

Allowed Spatial Transitions and Cancellation of the Richardson-Langmuir Ban

The ancient emission formulas of Langmuir and Richardson entered the calculations of subtle effects in semiconductor devices as basic ones. But, in the physics of semiconductor devices, these models have long played a purely decorative role, since they can describe in the most rough approximation only individual sections of the I – V characteristic. But it is precisely the fact that these formulas are basic when describing the barrier current-voltage characteristics (CVC) and prevented the consideration and use of thermoelectric effects in materials on a nano-scale. Thus, as these basic emission models actually imposed a ban on the MEASURABILITY of local thermoelectric effects, the existence of which has already been proven both phenomenologically and experimentally. The quantum transition technique is based on classical models. But it can also be used to correct these classic formulas. The calculation of the spatial transition of electrons over the potential barrier, taking into account the polarity of the kinetic energy, gives currents that are significantly higher than the currents of Langmuir and Richardson, including in the initial section of the I – V characteristic. Moreover, ballistic currents are concentrated at energy levels close to the threshold. This effect of condensation of electrons flowing down the barrier transforms the "anomalous" Seebeck coefficients into normal EASURABLE Local Thermal EMF, including in p-n junctions

Cross-Linguistic Differences in Bilinguals’ Fundamental Frequency Ranges

Accepted December 13, 2016Purpose We investigated cross-linguistic differences in fundamental frequency range (FFR) in Welsh-English bilingual speech. This is the first study that reports gender-specific behavior in switching FFRs across languages in bilingual speech. Method FFR was conceptualized as a behavioral pattern using measures of span (range of fundamental frequency—in semitones—covered by the speaker's voice) and level (overall height of fundamental frequency maxima, minima, and means of speaker's voice) in each language. Results FFR measures were taken from recordings of 30 Welsh-English bilinguals (14 women and 16 men), who read 70 semantically matched sentences, 35 in each language. Comparisons were made within speakers across languages, separately in male and female speech. Language background and language use information was elicited for qualitative analysis of extralinguistic factors that might affect the FFR. Conclusions Cross-linguistic differences in FFR were found to be consistent across female bilinguals but random across male bilinguals. Most female bilinguals showed distinct FFRs for each language. Most male bilinguals, however, were found not to change their FFR when switching languages. Those who did change used different strategies than women when differentiating FFRs between languages. Detected cross-linguistic differences in FFR can be explained by sociocultural factors. Therefore, sociolinguistic factors are to be taken into account in any further study of language-specific pitch setting and cross-linguistic differences in FFR

Bibliography on Liquefied Natural Gas (LNG) safety

Approximately 600 citations concerning safety of liquefied natural gas and liquid methane are presented. Each entry includes the title, author, abstract, source, description of figures, key references, and major descriptors for retrieving the document. An author index is provided as well as an index of descriptors

The effect of speech rhythm and speaking rate on assessment of pronunciation in a second language

Published online: 24 April 2019The study explores the effect of deviations from native speech rhythm and rate norms on the assessement of pronunciation mastery of a second language (L2) when the native language of the learner is either rhythmically similar to or different from the target language. Using the concatenative speech synthesis technique, different versions of the same sentence were created in order to produce segmentally and intonationally identical utterances that differed only in rhythmic patterns and/or speaking rate. Speech rhythm and tempo patterns modeled those from the speech of French or German native learners of English at different proficiency levels. Native British English speakers rated the original sentences and the synthesized utterances for accentedness. The analysis shows that (a) differences in speech rhythm and speaking tempo influence the perception of accentedness; (b) idiosyncratic differences in speech rhythm and speech rate are sufficient to differentiate between the proficiency levels of L2 learners; (c) the relative salience of rhythm and rate on perceived accentedness in L2 speech is modulated by the native language of the learners; and (d) intonation facilitates the perception of finer differences in speech rhythm between otherwise identical utterances. These results emphasize the importance of prosodic timing patterns for the perception of speech delivered by L2 learners.L.P. was supported by the Spanish Ministry of Economy and Competitiveness (MINECO) via Juan de la Cierva fellowship. M.O. was supported by the IKERBASQUE–Basque Foundation for Science. The research institution was supported through the “Severo Ochoa” Programme for Centres/Units of Excellence in R&D (SEV-2015-490)

Native Language Influence in the Segmentation of a Novel Language

Published online: 04 Apr 2016.A major problem in second language acquisition (SLA) is the segmentation of fluent speech in the target language, i.e., detecting the boundaries of phonological constituents like words and phrases in the speech stream. To this end, among a variety of cues, people extensively use prosody and statistical regularities. We examined the role of pitch, duration, and transitional probabilities (TPs) between adjacent syllables in the segmentation of a novel language by native speakers of German and compared their responses with the segmentation by the listeners with a phonologically different native language: Italian. We used an artificial language with different prosodic cues marking the boundaries of statistically defined words. In artificial-language learning experiments, we compared how Germans and Italians use prosodic and statistical cues for segmenting continuous speech. We show that native phonology modulates the processing of prosodic cues in novel languages. While native speakers of Italian interpret prosodic cues at both the word and the phrasal level, native speakers of German interpret them exclusively at the phrasal level. Phrasal prosody can facilitate the segmentation of a novel language when prosodic and statistical cues lead to the same segmentation solution. Word-level prosody does not necessarily facilitate segmentation, but it can disrupt it when statistical and prosodic cues lead to different segmentation solutions.The research leading to these results was supported by the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007–2013)/ERC Grant Agreement Number 269502 (PASCAL), by the Alexander von Humboldt Foundation, Germany, and by the Basque Foundation of Science, Spain