2,726 research outputs found
Effectiveness evaluation of STOL transport operations (phase 2)
A computer simulation program which models a commercial short-haul aircraft operating in the civil air system was developed. The purpose of the program is to evaluate the effect of a given aircraft avionics capability on the ability of the aircraft to perform on-time carrier operations. The program outputs consist primarily of those quantities which can be used to determine direct operating costs. These include: (1) schedule reliability or delays, (2) repairs/replacements, (3) fuel consumption, and (4) cancellations. More comprehensive models of the terminal area environment were added and a simulation of an existing airline operation was conducted to obtain a form of model verification. The capability of the program to provide comparative results (sensitivity analysis) was then demonstrated by modifying the aircraft avionics capability for additional computer simulations
Private Multiplicative Weights Beyond Linear Queries
A wide variety of fundamental data analyses in machine learning, such as
linear and logistic regression, require minimizing a convex function defined by
the data. Since the data may contain sensitive information about individuals,
and these analyses can leak that sensitive information, it is important to be
able to solve convex minimization in a privacy-preserving way.
A series of recent results show how to accurately solve a single convex
minimization problem in a differentially private manner. However, the same data
is often analyzed repeatedly, and little is known about solving multiple convex
minimization problems with differential privacy. For simpler data analyses,
such as linear queries, there are remarkable differentially private algorithms
such as the private multiplicative weights mechanism (Hardt and Rothblum, FOCS
2010) that accurately answer exponentially many distinct queries. In this work,
we extend these results to the case of convex minimization and show how to give
accurate and differentially private solutions to *exponentially many* convex
minimization problems on a sensitive dataset
An Anomalous Near-Bottom Cross-Shelf Intrusion of Slope Water on the Southern New England Continental Shelf
Hydrographic surveys and moored observations in Rhode Island Sound (RIS) in water depths of 30â50 m, off the southern New England coast, revealed a near-bottom intrusion of anomalously warm and saline water in late fall 2009. The properties of this water mass, with peak salinity of nearly 35, are typical of slope water that is normally found offshore of the shelfbreak front, located approximately 100 km to the south. The slope water intrusion, with a horizontal spatial scale of about 45 km, appears to have been brought onto the outer shelf during the interaction of a Gulf Stream warm core ring with the shelfbreak east (upshelf) of RIS. The along-shelf transport rate of the intrusion can be explained as due to advection by the mean outer-shelf along-isobath current, although the transit time of the intrusion is also consistent with the self-advection of a dense bolus on a sloping shelf. The mechanism responsible for the large onshore movement of the intrusion from the outer shelf is not entirely clear, although a wind-driven upwelling circulation appeared to be responsible for its final movement into the RIS region. Depth-averaged salinity at all RIS mooring sites increased by 0.5â1 over the 3â4 week intrusion period suggesting that the intrusion mixed irreversibly, at least partially, with the ambient shelf water. The mixing of the salty intrusion over the shelf indicates that net cross-isobath fluxes of salt and other water properties have occurred
The impact of sound field systems on learning and attention in elementary school classrooms
Purpose: An evaluation of the installation and use of sound field systems (SFS) was carried out to investigate their impact on teaching and learning in elementary school classrooms. Methods: The evaluation included acoustic surveys of classrooms, questionnaire surveys of students and teachers and experimental testing of students with and without the use of SFS. Students â perceptions of classroom environments and objective data evaluating change in performance on cognitive and academic assessments with amplification over a six month period are reported. Results: Teachers were positive about the use of SFS in improving childrenâs listening and attention to verbal instructions. Over time students in amplified classrooms did not differ from those in nonamplified classrooms in their reports of listening conditions, nor did their performance differ in measures of numeracy, reading or spelling. Use of SFS in the classrooms resulted in significantly larger gains in performance in the number of correct items on the nonverbal measure of speed of processing and the measure of listening comprehension. Analysis controlling for classroom acoustics indicated that students â listening comprehension score
Assessing the impact of Laurentide Ice Sheet topography on glacial climate
Simulations of past climates require altered boundary conditions to account
for known shifts in the Earth system. For the Last Glacial Maximum (LGM) and
subsequent deglaciation, the existence of large Northern Hemisphere ice
sheets caused profound changes in surface topography and albedo. While
ice-sheet extent is fairly well known, numerous conflicting reconstructions
of ice-sheet topography suggest that precision in this boundary condition is
lacking. Here we use a high-resolution and oxygen-isotope-enabled
fully coupled global circulation model (GCM) (GISS ModelE2-R), along with
two different reconstructions of the Laurentide Ice Sheet (LIS) that provide
maximum and minimum estimates of LIS elevation, to assess the range of
climate variability in response to uncertainty in this boundary condition.
We present this comparison at two equilibrium time slices: the LGM, when
differences in ice-sheet topography are maximized, and 14 ka, when
differences in maximum ice-sheet height are smaller but still exist.
Overall, we find significant differences in the climate response to LIS
topography, with the larger LIS resulting in enhanced Atlantic Meridional
Overturning Circulation and warmer surface air temperatures, particularly
over northeastern Asia and the North Pacific. These up- and downstream effects
are associated with differences in the development of planetary waves in the
upper atmosphere, with the larger LIS resulting in a weaker trough over
northeastern Asia that leads to the warmer temperatures and decreased albedo
from snow and sea-ice cover. Differences between the 14 ka simulations are
similar in spatial extent but smaller in magnitude, suggesting that climate
is responding primarily to the larger difference in maximum LIS elevation in
the LGM simulations. These results suggest that such uncertainty in
ice-sheet boundary conditions alone may significantly impact the results of
paleoclimate simulations and their ability to successfully simulate past
climates, with implications for estimating climate sensitivity to greenhouse
gas forcing utilizing past climate states
Acceptability with general orderings
We present a new approach to termination analysis of logic programs. The
essence of the approach is that we make use of general orderings (instead of
level mappings), like it is done in transformational approaches to logic
program termination analysis, but we apply these orderings directly to the
logic program and not to the term-rewrite system obtained through some
transformation. We define some variants of acceptability, based on general
orderings, and show how they are equivalent to LD-termination. We develop a
demand driven, constraint-based approach to verify these
acceptability-variants.
The advantage of the approach over standard acceptability is that in some
cases, where complex level mappings are needed, fairly simple orderings may be
easily generated. The advantage over transformational approaches is that it
avoids the transformation step all together.
{\bf Keywords:} termination analysis, acceptability, orderings.Comment: To appear in "Computational Logic: From Logic Programming into the
Future
Medium-separation binaries do not affect the first steps of planet formation
The first steps of planet formation are marked by the growth and
crystallization of sub-micrometer-sized dust grains accompanied by dust
settling toward the disk midplane. In this paper we explore whether the first
steps of planet formation are affected by the presence of medium-separation
stellar companions. We selected two large samples of disks around single and
binary T Tauri stars in Taurus that are thought to have only a modest age
spread of a few Myr. The companions of our binary sample are at projected
separations between 10 and 450 AU with masses down to about 0.1 solar masses.
We used the strength and shape of the 10 micron silicate emission feature as a
proxy for grain growth and for crystallization respectively. The degree of dust
settling was evaluated from the ratio of fluxes at two different mid-infrared
wavelengths. We find no statistically significant difference between the
distribution of 10 micron silicate emission features from single and binary
systems. In addition, the distribution of disk flaring is indistinguishable
between the single and binary system samples. These results show that the first
steps of planet formation are not affected by the presence of a companion at
tens of AU.Comment: To appear in the Astrophysical Journa
Exploring the meaning in meaningful coincidences: an interpretative phenomenological analysis of synchronicity in therapy
Synchronicity experiences (SEs) are defined as psychologically meaningful connections between inner events (e.g. thought, dream or vision) and one or more external events occurring simultaneously or at a future point in time. There has been limited systematic research that has investigated the phenomenology of SEs in therapy. This study aimed to redress this by exploring the process and nature of such experiences from the perspective of the practitioner. Semi-structured face-to-face interviews were conducted with a purposive sample of nine practitioners who reported SEs in their therapeutic sessions (three counsellors, three psychologists and three psychotherapists), and focused on how participants make sense of their experiences of synchronicity in therapy. Interpretative phenomenological analysis was used to identify three superordinate themes: sense of connectedness, therapeutic process, and professional issues. Findings suggest that SEs can serve to strengthen the therapeutic relationship and are perceived as useful harbingers of information about the therapeutic process, as well as being a means of overcoming communication difficulties, as they are seen to provide insights into the clientâs experiencing of themselves and others, regardless of whether or not the SE is acknowledged by the client or disclosed by the therapist
- âŠ