251 research outputs found
Museum display - fractions of a Truth
Paper presented at the Wits History Workshop: Myths, Monuments, Museums; New Premises? 16-18 July, 199
Large N and the Dine-Rajaraman problem
We compute the effective action for scattering of three well-separated
extremal brane solutions, in 11d supergravity, with zero p_ transfer and small
transverse velocities. Using an interpretation of the conjecture of Maldacena,
following Hyun, this can be viewed as the large N limit of the Matrix theory
description of three supergraviton scattering at leading order. The result is
consistent with the perturbative supergravity calculation.Comment: 10 pages, tex (harvmac
Recommended from our members
Review essay: Simon Frith, Sound effects: youth, leisure and the politics of rock‘n’roll
Teacher Retention Policy Coherence: An Analysis of Policies and Practices Across Federal, State, and Division Levels
As part of a larger MERC study, this report provides an overview of federal, state, and regional policies and practices relevant to teacher retention. Using key informant interviews and document analysis, the report addresses the following research questions: What teacher retention policies exist at the federal, state, and local levels? How are these policies structured at the state level and local levels? How do teacher retention policies vary across MERC divisions? Following the findings, the report presents recommendations for policy and practice
Thermal and stress analyses of a novel coated steam dual pipe system for use in advanced ultra-supercritical power plant
Implications of the Optical Observations of Neutron Stars
We show that observations of pulsars with pulsed optical emission indicate
that the peak flux scales according to the magnetic field strength at the light
cylinder. The derived relationships indicate that the emission mechanism is
common across all of the observed pulsars with periods ranging from 33ms to 385
ms and ages of 1000-300,000 years. It is noted that similar trends exist for
ray pulsars. Furthermore the model proposed by Pacini (1971) and
developed by Pacini and Salvati (1983,1987) still has validity and gives an
adequate explanation of the optical phenomena.Comment: 23 pages, 6 figures, accepted for publication in the Astrophysical
Journa
Is the meta-analysis of correlation coefficients accurate when population correlations vary?
One conceptualization of meta-analysis is that studies within the meta-analysis are sampled from populations with mean effect sizes that vary (random-effects models). The consequences of not applying such models and the comparison of different methods have been hotly debated. A Monte Carlo study compared the efficacy of Hedges and Vevea's random-effects methods of meta-analysis with Hunter and Schmidt's, over a wide range of conditions, as the variability in population correlations increases. (a) The Hunter-Schmidt method produced estimates of the average correlation with the least error, although estimates from both methods were very accurate; (b) confidence intervals from Hunter and Schmidt's method were always slightly too narrow but became more accurate than those from Hedges and Vevea's method as the number of studies included in the meta-analysis, the size of the true correlation, and the variability of correlations increased; and (c) the study weights did not explain the differences between the methods
Supernova Cosmology and the ESSENCE project
The proper usage of Type Ia supernovae (SNe Ia) as distance indicators has
revolutionized cosmology, and added a new dominant component to the energy
density of the Universe, dark energy. Following the discovery and confirmation
era, the currently ongoing SNe Ia surveys aim to determine the properties of
the dark energy. ESSENCE is a five year ground-based supernova survey aimed at
finding and characterizing 200 SNe Ia in the redshift domain z=[0.2-0.8]. The
goal of the project is to put constraints on the equation of state parameter,
w, of the dark energy with an accuracy of <10%. This paper presents these
ongoing efforts in the context of the current developments in observational
cosmology.Comment: Submitted to EPS1
REACT-ION: A model-based runtime environment for situation-aware adaptations
Trends such as the Internet of Things lead to a growing number of networked devices and to a variety of communication systems. Adding self-adaptive capabilities to these communication systems is one approach to reducing administrative effort and coping with changing execution contexts. Existing frameworks can help reducing development effort but are neither tailored toward the use in communication systems nor easily usable without knowledge in self-adaptive systems development. Accordingly, in previous work, we proposed REACT, a reusable, model-based runtime environment to complement communication systems with adaptive behavior. REACT addresses heterogeneity and distribution aspects of such systems and reduces development effort. In this article, we propose REACT-ION—an extension of REACT for situation awareness. REACT-ION offers a context management module that is able to acquire, store, disseminate, and reason on context data. The context management module is the basis for (i) proactive adaptation with REACT-ION and (ii) self-improvement of the underlying feedback loop. REACT-ION can be used to optimize adaptation decisions at runtime based on the current situation. Therefore, it can cope with uncertainty and situations that were not foreseeable at design time. We show and evaluate in two case studies how REACT-ION’s situation awareness enables proactive adaptation and self-improvement
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