9,125 research outputs found
TypEx : a type based approach to XML stream querying
We consider the topic of query evaluation over semistructured information streams, and XML data streams in particular. Streaming evaluation methods are necessarily eventdriven, which is in tension with high-level query models; in general, the more expressive the query language, the harder it is to translate queries into an event-based implementation with finite resource bounds
System controls challenges of hypersonic combined-cycle engine powered vehicles
Hypersonic aircraft with air-breathing engines have been described as the most complex and challenging air/space vehicle designs ever attempted. This is particularly true for aircraft designed to accelerate to orbital velocities. The propulsion system for the National Aerospace Plane will be an active factor in maintaining the aircraft on course. Typically addressed are the difficulties with the aerodynamic vehicle design and development, materials limitations and propulsion performance. The propulsion control system requires equal materials limitations and propulsion performance. The propulsion control system requires equal concern. Far more important than merely a subset of propulsion performance, the propulsion control system resides at the crossroads of trajectory optimization, engine static performance, and vehicle-engine configuration optimization. To date, solutions at these crossroads are multidisciplinary and generally lag behind the broader performance issues. Just how daunting these demands will be is suggested. A somewhat simplified treatment of the behavioral characteristics of hypersonic aircraft and the issues associated with their air-breathing propulsion control system design are presented
Preference and Order in First and Second Language Referential Strategies
Kellerman, Ammerlaan, Bongaerts, and Poulisse (1986) examined referential strategies used by Dutch speakers of English as a second language in a shapedescription task. Kellerman, et al. classified these strategies as holistic, partitive, or linear, and proposed a hierarchy of preference of holistic over partitive over linear. The hierarchy was, they claimed, operational both for pairs of L1 and L2 descriptions (cross-language) and for single descriptions in either L1 or L2 (within-language). The present study replicated Kellerman, et al., but used Japanese speakers of English as a second language as subjects. In the present study, there were more within-language violations of the hierarchy than crosslanguage violations. Some of the within-language violations may reflect the nature of Japanese discourse, and, therefore, reveal an L1 influence on L2 strategy use. The present study proposes that the possibility of such an influence be investigated
Higgs Assisted Q-balls from Pseudo-Nambu-Goldstone Bosons
Motivated by recent constructions of TeV-scale strongly-coupled dynamics,
either associated with the Higgs sector itself as in pseudo-Nambu-Goldstone
boson (pNGB) Higgs models or in theories of asymmetric dark matter, we show
that stable solitonic Q- balls can be formed from light pion-like pNGB fields
carrying a conserved global quantum number in the presence of the Higgs field.
We focus on the case of thick-wall Q-balls, where solutions satisfying all
constraints are shown to exist over a range of parameter values. In the limit
that our approximations hold, the Q-balls are weakly bound and parametrically
large, and the form of the interactions of the light physical Higgs with the
Q-ball is determined by the breaking of scale symmetry.Comment: 24 pages, 6 figures, 1 tabl
Projector - a partially typed language for querying XML
We describe Projector, a language that can be used to perform a mixture of typed and untyped computation against data represented in XML. For some problems, notably when the data is unstructured or semistructured, the most desirable programming model is against the tree structure underlying the document. When this tree structure has been used to model regular data structures, then these regular structures themselves are a more desirable programming model. The language Projector, described here in outline, gives both models within a single partially typed algebra and is well suited for hybrid applications, for example when fragments of a known structure are embedded in a document whose overall structure is unknown. Projector is an extension of ECMA-262 (aka JavaScript), and therefore inherits an untyped DOM interface. To this has been added some static typing and a dynamic projection primitive, which can be used to assert the presence of a regular structure modelled within the XML. If this structure does exist, the data is extracted and presented as a typed value within the programming language
Reverence for Life: An Ethic for High School Biology Curricula
Ethical and pedagogical arguments are presented against the use of animals by high school students in experiments causing pain/suffering/death of the animal. No justification is seen for such experimentation when perfectly valid alternatives, using noninvasive techniques, exist or could be developed. An important concern is the emotional and psychological growth of young people. An overall objective of high school biology curricula must be to assist students in making viable connections with living biological processes and the natural world
Differences in cyst(e)ine content between vegetative cells and spores of clostridium botulinum
M.S.Nancy W. Wall
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