4,946 research outputs found

    The role of technology as air transportation faces the fuel situation

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    Perspectives on the air transportation fuel stituation are discussed including intercity air traffic, airline fuel consumption, fuel price effects on ticket price, and projected traffic and fuel useage between now and the year 2000. Actions taken by the airlines to reduce consumption are reviewed, as well as efforts currently underway to improve fuel consumption. Longer range technology payoffs resulting from NASA research programs are reviewed and results from studies on the use of alternate fuels are discussed

    Progress in supersonic cruise aircraft technology

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    The supersonic cruise aircraft research program identified significant improvements in the technology areas of propulsion, aerodynamics, structures, takeoff and landing procedures, and advanced configuration concepts. Application of these technology areas to a commercial aircraft is discussed. An advanced SST family of aircraft which may be environmentally acceptable, have flexible range-payload capability, and be economically viable is projected

    Yang-Mills theory and the Segal-Bargmann transform

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    We use a variant of the classical Segal-Bargmann transform to understand the canonical quantization of Yang-Mills theory on a space-time cylinder. This transform gives a rigorous way to make sense of the Hamiltonian on the gauge-invariant subspace. Our results are a rigorous version of the widely accepted notion that on the gauge-invariant subspace the Hamiltonian should reduce to the Laplacian on the compact structure group. We show that the infinite-dimensional classical Segal-Bargmann transform for the space of connections, when restricted to the gauge-invariant subspace, becomes the generalized Segal-Bargmann transform for the the structure group

    Computational efficiency in continuous (and discrete!) time models: Comment on Hecht and Zitzmann

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    Late Pleistocene Collared Lemming (Dicrostonyx torquatus) from Northeastern British Columbia

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    Charlie Lake Cave is a terminal Pleistocene/Holocene archaeological and paleontological site in northeastern British Columbia (Driver, 1988; Fladmark et al., 1988; Driver et al., 1996). Located in the Peace River District to the east of the Rocky Mountains (56°16\u2735"N, 120°56\u27 15"W), the major feature of the site is a deep gully in front of a cave formed in a low sandstone escarpment. The gully runs parallel to the hillside, and has been filled with sediments moving down the hill since 10,500 B.P., resulting in up to 4.5 m thick deposits. The site is well stratified, and there is a strong correlation of radiocarbon age and depth, suggesting stratigraphic integrity. The site contains vertebrate assemblages deposited by natural agencies and human hunters, and there is also a long sequence of archaeological components at the site . The importance of the site was demonstrated by Fladmark\u27s excavations in 1983 (Fladmark et al., 1988). Further excavations at the site were undertaken in 1990-1991, and remains of collared lemming (Dicrostonyx torquatus) were recovered during the second series of excavations. The specimens are described and their significance evaluated.   Article Summary by Jonathan C. Driver, May 2015               This short paper provides information on an unexpected and unusual find from the lower layers at the site. After the 1991 excavations were finished we began to work on identifying the animal bones that were recovered. Somewhat to our surprise we found a few specimens of the collared lemming, an animal that today only inhabits the high tundra of the arctic. This wasn’t out of line with other species that indicated a cold and/or open unforested landscape during the earliest period of occupation – bison, ground squirrels and hares – but as collared lemming had not been found before in British Columbia it warranted a paper to itself.             The paper describes the specimens, noting that they were somewhat larger than modern lemmings, and then looks at the known distribution of lemmings at the end of the ice age. There are a number of specimens from fossil sites (mainly caves) well outside their modern distribution. This presumably suggests  lemming populations were able to colonize cold, open landscapes around the expanding ice sheets, and had enough time to move south as the ice sheets expanded and in turn created new habitat that was suitable for lemmings.             As the climate changed and as forests moved in, lemmings were unable to survive and their populations dwindled and soon became extinct in the Peace River region

    The Makeenko-Migdal equation for Yang-Mills theory on compact surfaces

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    We prove the Makeenko-Migdal equation for two-dimensional Euclidean Yang-Mills theory on an arbitrary compact surface, possibly with boundary. In particular, we show that two of the proofs given by the first, third, and fourth authors for the plane case extend essentially without change to compact surfaces.Comment: Final version, minor typographical corrections. To appear in Comm. Math. Phy

    Group study of an 'undercover' test for visuospatial neglect: Invisible cancellation can reveal more neglect than standard cancellation

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    Visual neglect is a relatively common deficit after brain damage, particularly strokes. Cancellation tests provide standard clinical measures of neglect severity and deficits in daily life. A recent single-case study introduced a new variation on standard cancellation. Instead of making a visible mark on each target found, the patient made invisible marks (recorded with carbon paper underneath, for later scoring). Such invisible cancellation was found to reveal more neglect than cancellation with visible marks. Here we test the generality of this. Twenty three successive cases with suspected neglect each performed cancellation with visible or invisible marks. Neglect of contralesional targets was more pronounced with invisible marks. Indeed, about half of the patients only showed neglect in this version. For cases showing more neglect with invisible marks, stronger neglect of contralesional targets correlated with more revisits to ipsilesional targets for making additional invisible marks upon them. These results indicate that cancellation with invisible marks can reveal more neglect than standard cancellation with visible marks, while still providing a practical bedside test. Our observations may be consistent with recent proposals that demands on spatial working memory (required to keep track of previously found items only when marked invisibly) can exacerbate spatial neglect

    The Significance of the Fauna from the Charlie Lake Cave Site

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    Article Summary by Jonathan C. Driver, May 2015               This paper and The Prehistory of Charlie Lake Cave by Knut R. Fladmark, are excerpts from Early Human Occupation in British Columbia, an archaeological book published in 1996. In 1988 the annual meeting of the Canadian Archaeological Association was held in Whistler, B.C. As part of the meeting, Roy Carlson, a professor at SFU, organized a symposium on the early human presence in British Columbia. Knut Fladmark and I each gave a paper on our work at Tse’K’wa, based on the 1983 excavation season.             Although it was intended to publish the book quickly, there were various delays, and Fladmark and I went back to Tse’K’wa in 1990 and 1991 before the proceedings of the Whistler symposium were finally published in 1996. We updated our papers slightly based on the later excavations, but both of these papers really reflect our thinking prior to the full analysis of the material from 1990 and 1991.             Fladmark’s paper is a good introduction to the location and geology of the site, and it provides an account of the cultural materials recovered in 1983.             Driver’s paper summarizes the animal bones from the 1983 excavations, and devotes more time to considering how the wide variety of animals were brought to the site. I noted that the bison bone was found in locations with lower amounts of small mammals and birds and suggested that most of the smaller animals were brought to the site by non-human predators, such as owls
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