223 research outputs found
Change Impact Analysis based on Formalization of Trace Relations for Requirements
Evolving customer needs is one of the driving factors in software development. There is a need to analyze the impact of requirement changes in order to determine possible conflicts and design alternatives influenced by these changes. The analysis of the impact of requirement changes on related requirements can be based on requirements traceability. In this paper, we propose a requirements metamodel with well defined types of requirements relations. This metamodel represents the common concepts extracted from some prevalent requirements engineering approaches. The requirements relations in the metamodel are used to trace related requirements for change impact analysis. We formalize the relations. Based on this formalization, we define change impact rules for requirements. As a case study, we apply these rules to changes in the requirements specification for Course Management System
Traceability-based change management in operational mappings
This paper describes an approach for the analysis of changes in model transformations in the Model Driven Architecture (MDA). Models should be amenable to changes in user requirements and technological platforms. Impact analysis of changes can be based on traceability of model elements. We propose a model for generating trace links between model elements and study scenarios for changes in source models and how to identify the impacted elements in the target model
Identifying the ejected population from disintegrating multiple systems
Kinematic studies of the Hipparcos catalogue have revealed associations that
are best explained as disintegrating multiple systems, presumably resulting
from a dynamical encounter between single/multiple systems in the field (Li et
al. 2009). In this work we explore the possibility that known ultra-cool dwarfs
may be components of disintegrating multiple systems, and consider the
implications for the properties of these objects. We will present here the
methods/techniques that can be used to search for and identify disintegrating
benchmark systems in three database/catalogues: Dwarf Archive, the Hipparcos
Main Catalogue, and the Gliese-Jahrei{\ss} Catalogue. Placing distance
constraints on objects with parallax or colour-magnitude information from
spectrophotometry allowed us to identify common distance associations. Proper
motion measurements allowed us to separate common proper motion multiples from
our sample of disintegrating candidates. Moreover, proper motion and positional
information allowed us to select candidate systems based on relative component
positions that were tracked back and projected forward through time. Using this
method we identified one candidate disintegrating quadruple association, and
two candidate disintegrating binaries, all of them containing one ultra-cool
dwarf.Comment: 5 pages, 1 figure, proceeding of The 19th Cambridge Workshop on Cool
Stars, Stellar Systems, and the Su
A multi-wavelength view on the dusty Wolf-Rayet star WR 48a
We present results from the first attempts to derive various physical
characteristics of the dusty Wolf-Rayet star WR 48a based on a multi-wavelength
view of its observational properties. This is done on the basis of new optical
and near-infrared spectral observations and on data from various archives in
the optical, radio and X-rays. The optical spectrum of WR 48a is acceptably
well represented by a sum of two spectra: of a WR star of the WC8 type and of a
WR star of the WN8h type. The strength of the interstellar absorption features
in the optical spectra of WR 48a and the near-by stars D2-3 and D2-7 (both
members of the open cluster Danks 2) indicates that WR 48a is located at a
distance of ~4 kpc from us. WR 48a is very likely a thermal radio source and
for such a case and smooth (no clumps) wind its radio emission suggests a
relatively high mass-loss rate of this dusty WR star (dM/dt = a few x 10^(-4)
solar masses per year). Long timescale (years) variability of WR 48a is
established in the optical, radio and X-rays. Colliding stellar winds likely
play a very important role in the physics of this object. However, some
LBV-like (luminous blue variable) activity could not be excluded as well.Comment: Accepted for publication in MNRAS; 16 pages, 16 figures, 6 table
The embedded clusters DBS 77, 78, 102, and 160-161 and their link with the interstellar medium
Aims. We report a study of the global properties of some embedded clusters
placed in the fourth quadrant of the Milky Way to clarify some issues related
with their location into the Galaxy and their stellar formation processes.
Methods. We performed BVI photometric observations in the region of DBS 77, 78,
102, 160, and 161 clusters and infrared spectroscopy in DBS 77 region. They
were complemented with JHK data from VVV survey combined with 2MASS catalogue,
and used mid-infrared information from GLIMPSE catalogue. We also searched for
HI data from SGPS and PMN radio surveys, and previous spectroscopic stellar
classification. The spectroscopic and photometric information allowed us to
estimate the spectral classification of the brightest stars of each studied
region. On the other hand, we used the radio data to investigate the
interstellar material parameters and the continuum sources probably associated
with the respective stellar components. Results. We estimated the basic
physical parameters of the clusters (reddening, distance, age, and initial mass
function). We searched for HII regions located near to the studied clusters and
we analyzed the possible link between them. In the particular case of DBS
160-161 clusters, we identified the HI bubble B332.5-0.1-42 located around
them. We found that the mechanical energy injected to the interstellar medium
by the more massive stars of this couple of clusters was enough to generate the
bubble.Comment: 15 pages, 14 figures, 6 tables, accepted for publication in A&
Identifying Ultra-Cool Dwarfs at Low Galactic Latitudes: A Southern Candidate Catalogue
We present an Ultra-Cool Dwarf (UCD) catalogue compiled from low southern
Galactic latitudes and mid-plane, from a cross-correlation of the 2MASS and
SuperCOSMOS surveys. The catalogue contains 246 members identified from 5042
sq. deg. within 220 deg. <= l <= 360 deg. and 0 deg. < l <= 30 deg., for |b| <=
15 deg. Sixteen candidates are spectroscopically confirmed in the near-IR as
UCDs with spectral types from M7.5V to L9. Our catalogue selection method is
presented enabling UCDs from ~M8V to the L-T transition to be selected down to
a 2MASS limiting magnitude of Ks ~= 14.5 mag. This method does not require
candidates to have optical detections for catalogue inclusion. An optimal set
of optical/near-IR and reduced proper-motion selection criteria have been
defined that includes: an Rf and Ivn photometric surface gravity test, a dual
Rf-band variability check, and an additional photometric classification scheme
to selectively limit contaminants. We identify four candidates as possible
companions to nearby Hipparcos stars -- observations are needed to identify
these as potential benchmark UCD companions. We also identify twelve UCDs
within a possible distance 20 pc, three are previously unknown of which two are
estimated within 10 pc, complimenting the nearby volume-limited census of UCDs.
An analysis of the catalogue spatial completeness provides estimates for
distance completeness over three UCD MJ ranges, while Monte-Carlo simulations
provide an estimate of catalogue areal completeness at the 75 per cent level.
We estimate a UCD space density of Rho (total) = (6.41+-3.01)x10^3/pc^3 over
the range of 10.5 <= MJ ~< 14.9, similar to values measured at higher Galactic
latitudes (|b| ~> 10 deg.) in the field population and obtained from more
robust spectroscopically confirmed UCD samples.Comment: MNRAS accepted April 2012. Contains 30 figures and 11 tables. Tables
2 and 6 to be published in full and on-line only. The on-line tables can also
be obtained by contacting the author
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