52,500 research outputs found
High-Resolution Crystal Truncation Rod Scattering: Application to Ultrathin Layers and Buried Interfaces
In crystalline materials, the presence of surfaces or interfaces gives rise to crystal truncation rods (CTRs) in their Xâray diffraction patterns. While structural properties related to the bulk of a crystal are contained in the intensity and position of Bragg peaks in Xâray diffraction, CTRs carry detailed information about the atomic structure at the interface. Developments in synchrotron Xâray sources, instrumentation, and analysis procedures have made CTR measurements into extremely powerful tools to study atomic reconstructions and relaxations occurring in a wide variety of interfacial systems, with relevance to chemical and electronic functionalities. In this review, an overview of the use of CTRs in the study of atomic structure at interfaces is provided. The basic theory, measurement, and analysis of CTRs are covered and applications from the literature are highlighted. Illustrative examples include studies of complex oxide thin films and multilayers
Evidence from RbâSr mineral ages for multiple orogenic events in the Caledonides of Shetland, Scotland
Shetland occupies a unique central location within the North Atlantic Caledonides. Thirty-three new high-precision RbâSr mineral ages indicate a polyorogenic history. Ages of 723â702 Ma obtained from the vicinity of the Wester Keolka Shear Zone indicate a Neoproterozoic (Knoydartian) age and preclude its correlation with the Silurian Moine Thrust. Ordovician ages of c. 480â443 Ma obtained from the Yell Sound Group and the East Mainland Succession constrain deformation fabrics and metamorphic assemblages to have formed during Grampian accretionary orogenic events, broadly contemporaneously with orogenesis of the Dalradian Supergroup in Ireland and mainland Scotland. The relative paucity of Silurian ages is attributed to a likely location at a high structural level in the Scandian nappe pile relative to mainland Scotland. Ages of c. 416 and c. 411 Ma for the Uyea Shear Zone suggest a late orogenic evolution that has more in common with East Greenland and Norway than with northern mainland Scotland
Individual and Domain Adaptation in Sentence Planning for Dialogue
One of the biggest challenges in the development and deployment of spoken
dialogue systems is the design of the spoken language generation module. This
challenge arises from the need for the generator to adapt to many features of
the dialogue domain, user population, and dialogue context. A promising
approach is trainable generation, which uses general-purpose linguistic
knowledge that is automatically adapted to the features of interest, such as
the application domain, individual user, or user group. In this paper we
present and evaluate a trainable sentence planner for providing restaurant
information in the MATCH dialogue system. We show that trainable sentence
planning can produce complex information presentations whose quality is
comparable to the output of a template-based generator tuned to this domain. We
also show that our method easily supports adapting the sentence planner to
individuals, and that the individualized sentence planners generally perform
better than models trained and tested on a population of individuals. Previous
work has documented and utilized individual preferences for content selection,
but to our knowledge, these results provide the first demonstration of
individual preferences for sentence planning operations, affecting the content
order, discourse structure and sentence structure of system responses. Finally,
we evaluate the contribution of different feature sets, and show that, in our
application, n-gram features often do as well as features based on higher-level
linguistic representations
Boussinesq-like multi-component lattice equations and multi-dimensional consistency
We consider quasilinear, multi-variable, constant coefficient, lattice
equations defined on the edges of the elementary square of the lattice, modeled
after the lattice modified Boussinesq (lmBSQ) equation, e.g., . These equations are classified into three canonical forms and
the consequences of their multidimensional consistency
(Consistency-Around-the-Cube, CAC) are derived. One of the consequences is a
restriction on form of the equation for the variable, which in turn implies
further consistency conditions, that are solved. As result we obtain a number
of integrable multi-component lattice equations, some generalizing lmBSQ.Comment: 24 page
The velocity field near the orifice of a Helmholtz resonator in grazing flow
Measurement of the time-dependent velocities induced inside and outside the opening of acoustically excited, two-dimensional Helmholtz resonator imbedded in a grazing flow are presented. The remarkably clear structure of the perturbation field which evokes a pulsating source and a coherently pulsating vortex-image pair is described. The simple phenomenological "lid-model" which correlates the variation in the components of the acoustic impedance with the velocity of the grazing flow is discussed and extended
The night-sky at the Calar Alto Observatory
We present a characterization of the main properties of the night-sky at the
Calar Alto observatory for the time period between 2004 and 2007. We use
optical spectrophotometric data, photometric calibrated images taken in
moonless observing periods, together with the observing conditions regularly
monitored at the observatory, such as atmospheric extinction and seeing. We
derive, for the first time, the typical moonless night-sky optical spectrum for
the observatory. The spectrum shows a strong contamination by different
pollution lines, in particular from Mercury lines, which contribution to the
sky-brightness in the different bands is of the order of ~0.09 mag, ~0.16 mag
and ~0.10 mag in B, V and R respectively. The zenith-corrected values of the
moonless night-sky surface brightness are 22.39, 22.86, 22.01, 21.36 and 19.25
mag arcsec^-2 in U, B, V, R and I, which indicates that Calar Alto is a
particularly dark site for optical observations up to the I-band. The fraction
of astronomical useful nights at the observatory is ~70%, with a ~30% of
photometric nights. The typical extinction at the observatory is k_V~0.15 mag
in the Winter season, with little dispersion. In summer the extinction has a
wider range of values, although it does not reach the extreme peaks observed at
other sites. The median seeing for the last two years (2005-6) was ~0.90",
being smaller in the Summer (~0.87") than in the Winter (~0.96"). We conclude
in general that after 26 years of operations Calar Alto is still a good
astronomical site, being a natural candidate for future large aperture optical
telescopes.Comment: 16 pages, 5 figures, accepted for publishing in the Publications of
Astronomical Society of the Pacific (PASP
National counter-terrorism (C-T) policies and challenges to human rights and civil liberties: Case study of United Kingdom
In the UK the rise post-2005 in âhome-grownâ terrorism, relying to a significant extent on strikes on soft targets by âself-starters,â means that the search for effective preventive measures remains a continuing concern. Below a number of the preventive counter-terror measures adopted post-9/11, and incrementally strengthened in response to the current threat, are found to fall into three categories and represent interventions at the stages in the path toward attacks. This chapter focuses on selected examples of these preventive measures. In terms of three key stages, firstly, there is the attempt to prevent radicalization, under the âPreventâ strategy. A second strategy relies on taking certain measures to control the activities of those considered likely â on the balance of probabilities â to engage in terrorist-related activity. A third preventive strategy relies on the special terrorism offences under the Terrorism Acts 2000 and 2006, as amended, intended to allow for intervention at a very early stage in terrorist plots and in preparing or instigating terrorist acts (âprecursorâ offences)
Task oriented nonlinear control laws for telerobotic assembly operations
The goal of this research is to achieve very intelligent telerobotic controllers which are capable of receiving high-level commands from the human operator and implementing them in an adaptive manner in the object/task/manipulator workspace. Initiatives by the authors at Integrated Systems, Inc. to identify and develop the key technologies necessary to create such a flexible, highly programmable, telerobotic controller are presented. The focus of the discussion is on the modeling of insertion tasks in three dimensions and nonlinear implicit force feedback control laws which incorporate tool/workspace constraints. Preliminary experiments with dual arm beam assembly in 2-D are presented
Extinction Map of Baade's Window
Recently Wo\'zniak \& Stanek (1996) proposed a new method to investigate
interstellar extinction, based on two band photometry, which uses red clump
stars as a means to construct the reddening curve. I apply this method to the
color-magnitude diagrams obtained by the Optical Gravitational Lensing
Experiment (OGLE) to construct an extinction map of region of
Baade's Window, with resolution of . Such a map should be
useful for studies of this frequently observed region of the Galactic bulge.
The map and software useful for its applications are available via {\tt
anonymous ftp}. The total extinction varies from to
within the field of view centered on (18:03:20.9,--30:02:06), i.e. . The
ratio is determined with this new method.Comment: revised version accepted for publication in ApJ Letters, 8 pages,
uuencoded PostScript with 4 figures included; complete paper available
through WWW at http://www.astro.princeton.edu/~library/prep.html; tables and
auxiliary software available at
ftp://www.astro.princeton.edu/stanek/Extinctio
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