2,450 research outputs found
A simulation model for probabilistic analysis of Space Shuttle abort modes
A simulation model which was developed to provide a probabilistic analysis tool to study the various space transportation system abort mode situations is presented. The simulation model is based on Monte Carlo simulation of an event-tree diagram which accounts for events during the space transportation system's ascent and its abort modes. The simulation model considers just the propulsion elements of the shuttle system (i.e., external tank, main engines, and solid boosters). The model was developed to provide a better understanding of the probability of occurrence and successful completion of abort modes during the vehicle's ascent. The results of the simulation runs discussed are for demonstration purposes only, they are not official NASA probability estimates
Curate and storyspace: an ontology and web-based environment for describing curatorial narratives
Existing metadata schemes and content management systems used by museums focus on describing the heritage objects that the museum holds in its collection. These are used to manage and describe individual heritage objects according to properties such as artist, date and preservation requirements. Curatorial narratives, such as physical or online exhibitions tell a story that spans across heritage objects and have a meaning that does not necessarily reside in the individual heritage objects themselves. Here we present curate, an ontology for describing curatorial narratives. This draws on structuralist accounts that distinguish the narrative from the story and plot, and also a detailed analysis of two museum exhibitions and the curatorial processes that contributed to them. Storyspace, our web based interface and API to the ontology, is being used by curatorial staff in two museums to model curatorial narratives and the processes through which they are constructed
High Rayleigh number convection with double diffusive fingers
An electrodeposition cell is used to sustain a destabilizing concentration
difference of copper ions in aqueous solution between the top and bottom
boundaries of the cell. The resulting convecting motion is analogous to
Rayleigh-B\'enard convection at high Prandtl numbers. In addition, a
stabilizing temperature gradient is imposed across the cell. Even for thermal
buoyancy two orders of magnitude smaller than chemical buoyancy, the presence
of the weak stabilizing gradient has a profound effect on the convection
pattern. Double diffusive fingers appear in all cases. The size of these
fingers and the flow velocities are independent of the height of the cell, but
they depend on the ion concentration difference between top and bottom
boundaries as well as on the imposed temperature gradient. The scaling of the
mass transport is compatible with previous results on double diffusive
convection
Procedures for periodizing history: determining eras in the histories of Britain, France, Germany and Italy
Die Autoren entwickeln anhand konkreter Untersuchungen Vorschläge zum Problem der Periodisierung historischer Zeitabschnitte. Die theoretischen und methodischen Implikationen dieses Problems werden im Rahmen der Untersuchung des Wachstums der staatlichen Ausgaben für Erziehung, Gesundheit, Wohlfahrt und soziale Sicherung in den Ländern Großbritannien, Frankreich, Deutschland und Italien von 1870 bis 1965 dargestellt. Dieser Gegenstandsbereich wurde ausgewählt, weil sich an den Wandlungen in diesem Sektor auch die gesellschaftlichen Wandlungen ablesen lassen. Die Darstellung der Untersuchung umfaßt neben konkreten Ergebnissen die Analyse der methodischen und theoretischen Probleme, insbesondere die Behandlung der Daten und die alternativen Möglichkeiten der Periodisierung anhand einer Variable und mittels multipler Zeitläufe. Die Untersuchung ergibt, daß die traditionelle Chronologie nur in Einzelfällen zur Periodisierung ausreicht. (BG
Photon number discrimination without a photon counter and its application to reconstructing non-Gaussian states
The non-linearity of a conditional photon-counting measurement can be used to
`de-Gaussify' a Gaussian state of light. Here we present and experimentally
demonstrate a technique for photon number resolution using only homodyne
detection. We then apply this technique to inform a conditional measurement;
unambiguously reconstructing the statistics of the non-Gaussian one and two
photon subtracted squeezed vacuum states. Although our photon number
measurement relies on ensemble averages and cannot be used to prepare
non-Gaussian states of light, its high efficiency, photon number resolving
capabilities, and compatibility with the telecommunications band make it
suitable for quantum information tasks relying on the outcomes of mean values.Comment: 4 pages, 3 figures. Theory section expanded in response to referee
comment
Interactions In Space For Archaeological Models
In this article we examine a variety of quantitative models for describing
archaeological networks, with particular emphasis on the maritime networks of
the Aegean Middle Bronze Age. In particular, we discriminate between those
gravitational networks that are most likely (maximum entropy) and most
efficient (best cost/benefit outcomes).Comment: 21 pages, 6 figures, 2 tables. Contribution to special issue of
Advances in Complex Systems from the conference `Cultural Evolution in
Spatially Structured Populations', UCL, London, September 2010. To appear in
Advances in Complex System
Thyroid Disorders and Diabetes Mellitus
Studies have found that diabetes and thyroid disorders tend to coexist in patients. Both conditions involve a dysfunction of the endocrine system. Thyroid disorders can have a major impact on glucose control, and untreated thyroid disorders affect the management of diabetes in patients. Consequently, a systematic approach to thyroid testing in patients with diabetes is recommended
Direct Sampling of Negative Quasiprobabilities of a Squeezed State
Although squeezed states are nonclassical states, so far, their
nonclassicality could not be demonstrated by negative quasiprobabilities. In
this work we derive pattern functions for the direct experimental determination
of so-called nonclassicality quasiprobabilities. The negativities of these
quantities turn out to be necessary and sufficient for the nonclassicality of
an arbitrary quantum state and are therefore suitable for a direct and general
test of nonclassicality. We apply the method to a squeezed vacuum state of
light that was generated by parametric down-conversion in a second-order
nonlinear crystal.Comment: 4 pages, 4 figures, supplementary material adde
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