6,515 research outputs found
GEMPAK: An arbitrary aircraft geometry generator
A computer program, GEMPAK, has been developed to aid in the generation of detailed configuration geometry. The program was written to allow the user as much flexibility as possible in his choices of configurations and the detail of description desired and at the same time keep input requirements and program turnaround and cost to a minimum. The program consists of routines that generate fuselage and planar-surface (winglike) geometry and a routine that will determine the true intersection of all components with the fuselage. This paper describes the methods by which the various geometries are generated and provides input description with sample input and output. Also included are descriptions of the primary program variables and functions performed by the various routines. The FORTRAN program GEMPAK has been used extensively in conjunction with interfaces to several aerodynamic and plotting computer programs and has proven to be an effective aid in the preliminary design phase of aircraft configurations
Orbiter/launch system
The system includes reusable turbojet propelled booster vehicles releasably connected to a reusable rocket powered orbit vehicle. The coupled orbiter-booster combination takes off horizontally and ascends to staging altitude and speed under booster power with both orbiter and booster wings providing lift. After staging, the booster vehicles fly back to Earth for horizontal landing and the orbiter vehicle continues ascending to orbit
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A Dose Relationship Between Brain Functional Connectivity and Cumulative Head Impact Exposure in Collegiate Water Polo Players.
A growing body of evidence suggests that chronic, sport-related head impact exposure can impair brain functional integration and brain structure and function. Evidence of a robust inverse relationship between the frequency and magnitude of repeated head impacts and disturbed brain network function is needed to strengthen an argument for causality. In pursuing such a relationship, we used cap-worn inertial sensors to measure the frequency and magnitude of head impacts sustained by eighteen intercollegiate water polo athletes monitored over a single season of play. Participants were evaluated before and after the season using computerized cognitive tests of inhibitory control and resting electroencephalography. Greater head impact exposure was associated with increased phase synchrony [r (16) > 0.626, p < 0.03 corrected], global efficiency [r (16) > 0.601, p < 0.04 corrected], and mean clustering coefficient [r (16) > 0.625, p < 0.03 corrected] in the functional networks formed by slow-wave (delta, theta) oscillations. Head impact exposure was not associated with changes in performance on the inhibitory control tasks. However, those with the greatest impact exposure showed an association between changes in resting-state connectivity and a dissociation between performance on the tasks after the season [r (16) = 0.481, p = 0.043] that could also be attributed to increased slow-wave synchrony [F (4, 135) = 113.546, p < 0.001]. Collectively, our results suggest that athletes sustaining the greatest head impact exposure exhibited changes in whole-brain functional connectivity that were associated with altered information processing and inhibitory control
Models of Speech Processing
One of the fundamental questions about language is how listeners map the acoustic signal onto
syllables, words, and sentences, resulting in understanding of speech. For normal listeners, this
mapping is so effortless that one rarely stops to consider just how it takes place. However, studies
of speech have shown that this acoustic signal contains a great deal of underlying complexity.
A number of competing models seek to explain how these intricate processes work. Such models
have often narrowed the problem to mapping the speech signal onto isolated words, setting aside
the complexity of segmenting continuous speech. Continuous speech has presented a significant
challenge for many models because of the high variability of the signal and the difficulties involved
in resolving the signal into individual words.
The importance of understanding speech becomes particularly apparent when neurological
disease affects this seemingly basic ability. Lesion studies have explored impairments of speech
sound processing to determine whether deficits occur in perceptual analysis of acoustic-phonetic
information or in stored abstract phonological representations (e.g., Basso, Casati,& Vignolo, 1977;
Blumstein, Cooper, Zurif,& Caramazza, 1977). Furthermore, researchers have attempted to determine
in what ways underlying phonological/phonetic impairments may contribute to auditory
comprehension deficits (Blumstein, Baker, & Goodglass, 1977).
In this chapter, we discuss several psycholinguistic models of word recognition (the process of
mapping the speech signal onto the lexicon), and outline how components of such models might
correspond to the functional anatomy of the brain. We will also relate evidence from brain lesion
and brain activation studies to components of such models. We then present some approaches that
deal with speech perception more generally, and touch on a few current topics of debate.National Institutes of Health under grant NIH DC R01–3378 to the senior author (SLS
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