2,134 research outputs found
Science for Global Ubiquitous Computing
This paper describes an initiative to provide theories that can underlie the development of the Global Ubiquitous Computer, the network of ubiquitous computing devices that will pervade the civilised world in the course of the next few decades. We define the goals of the initiative and the criteria for judging whether they are achieved; we then propose a strategy for the exercise. It must combine a bottom-up development of theories in directions that are currently pursued with success, together with a top-down approach in the form of collaborative projects relating these theories to engineered systems that exist or are imminent
COCOA Code for Creating Mock Observations of Star Cluster Models
We introduce and present results from the COCOA (Cluster simulatiOn
Comparison with ObservAtions) code that has been developed to create idealized
mock photometric observations using results from numerical simulations of star
cluster evolution. COCOA is able to present the output of realistic numerical
simulations of star clusters carried out using Monte Carlo or \textit{N}-body
codes in a way that is useful for direct comparison with photometric
observations. In this paper, we describe the COCOA code and demonstrate its
different applications by utilizing globular cluster (GC) models simulated with
the MOCCA (MOnte Carlo Cluster simulAtor) code. COCOA is used to synthetically
observe these different GC models with optical telescopes, perform PSF
photometry and subsequently produce observed colour magnitude diagrams. We also
use COCOA to compare the results from synthetic observations of a cluster model
that has the same age and metallicity as the Galactic GC NGC 2808 with
observations of the same cluster carried out with a 2.2 meter optical
telescope. We find that COCOA can effectively simulate realistic observations
and recover photometric data. COCOA has numerous scientific applications that
maybe be helpful for both theoreticians and observers that work on star
clusters. Plans for further improving and developing the code are also
discussed in this paper.Comment: 18 pages, 12 figures, accepted for publication in MNRAS. Revised
manuscript has a new title, better quality figures and many other
improvements. COCOA can be downloaded from: https://github.com/abs2k12/COCOA
(comments are welcome
Fitting and selecting scattering data
The main purpose of scattering experiments is to unveil the underlying
structure of the colliding particles and their interaction. Typically one
measures scattering observables (cross sections and polarizations) at discrete
angles and energies and mutually consistent data may validate or falsify
proposed theories or models. However, the accumulation of data from different
laboratories while potentially improves the statistical significance it may
sometimes generate mutually inconsistent data as a side-effect. Thus, some
decision has to be made on what are the maximal amount of data which are
mutually compatible. We show elastic and scattering as prominent
examples where this selection is called for. We discuss how it can be done in a
self-consistent manner invoking a principle of maximal consensus of the
database and with the help of a sufficiently flexible model involving a minimal
number of theoretical assumptions. In the NN case this has become possible with
a combination of long distance field theoretical constraints at the hadronic
level such as pion exchanges and electromagnetic effects and a coarse graining
of the unknown interaction over the shortest de Broglie wavelength being probed
in the scattering process.Comment: 7 pages, 5 figures, talk presented by ERA at XVII International
Conference on Hadron Spectroscopy and Structure - Hadron2017, Salamanca,
25-29 September 201
Banking Crises
The history of banking around the world has been punctuated by frequent systemic crises. As with Tolstoy's unhappy families, not all crises are the same; distinct roles have been played at different times by mismanagement, government interference and macroeconomic shocks. This review identifies common features of crises in recent decades and describes how costly they have been in terms of their fiscal burden and the impact on macroeconomic growth. It proceeds to outline the conceptual issues identified by theoreticians and considers appropriate policy responses. A lull in the new millennium led to optimism that banking crises might be a thing of the past, but the events of 2007-8 have shown such optimism, often characteristic of previous macro upswings, to be unwarranted.
The Stellar Abundances for Galactic Archeology (SAGA) Database - Compilation of the Characteristics of Known Extremely Metal-Poor Stars
We describe the construction of a database of extremely metal-poor (EMP)
stars in the Galactic halo whose elemental abundances have been determined. Our
database contains detailed elemental abundances, reported equivalent widths,
atmospheric parameters, photometry, and binarity status, compiled from papers
in the recent literature that report studies of EMP halo stars with [Fe/H] <
-2.5. The compilation procedures for this database have been designed to
assemble the data effectively from electronic tables available from online
journals. We have also developed a data retrieval system that enables data
searches by various criteria, and permits the user to explore relationships
between the stored variables graphically. Currently, our sample includes 1212
unique stars (many of which are studied by more than one group) with more than
15000 individual reported elemental abundances, covering all of the relevant
papers published by December 2007. We discuss the global characteristics of the
present database, as revealed by the EMP stars observed to date. For stars with
[Fe/H] < -2.5, the number of giants with reported abundances is larger than
that of dwarfs by a factor of two. The fraction of carbon-rich stars (among the
sample for which the carbon abundance is reported) amount to ~30 % for [Fe/H] <
-2.5. We find that known binaries exhibit different distributions of orbital
period, according to whether they are giants or dwarfs, and also as a function
of metallicity, although the total sample of such stars is still quite small.Comment: 24 pages, 10 figures, accepted by PASJ, final version. The SAGA
database is available at http://saga.sci.hokudai.ac.j
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