14 research outputs found
Expect the unexpected: the co-construction of assistive artifacts
This paper aims to explain emerging design activities within community-based rehabilitation contexts through the science of self-organization and adaptivity. It applies an evolutionary systematic worldview (Heylighen, 2011) to frame spontaneous collaboration between different local agents which produce self-made assistive artifacts. Through a process of distinction creation and distinction destruction occupational therapist, professional non-designers, caregivers and disabled people co-evolve simultaneously towards novel possibilities which embody a contemporary state of fitness. The conversation language is build on the principles of emotional seeding through stigmergic prototyping and have been practically applied as a form of design hacking which blends design time and use time. Within this process of co-construction the thought experiment of Maxwellâs Demon is used to map perceived behavior and steer the selecting process of following user-product adaptation strategies. This practice-based approach is illustrated through a case study and tries to integrate both rationality and intuition within emerging participatory design activities
APEX CO(3-2) observations of NGC6822
We observed the CO(3-2) emission of the emission-line regions HubbleI,
HubbleV, HubbleX, Holmberg 18, and the stellar emission-line object S28 in
NGC6822 with the ESO Atacama Pathfinder Experiment (APEX) 12m telescope as part
of its science verification. The very low system temperature of 130-180K
enabled us to achieve detections in 4 single pointings and in a high spatial
resolution 70''x70'' map of HubbleV. We compare the spectra with HI
observations, obtained with the Australia Telescope Compact Array, of the same
regions. In combination with previous multi-line CO observations, we perform a
preliminary investigation of the physical conditions in HubbleV using a simple
LTE model. We estimate the mass of the HubbleV region and the H_2/I_CO(3-2)
conversion factor. Also, we show that HubbleV is located very near the
line-width versus size relation traced by the Milky Way and LMC molecular
clouds.Comment: 4 pages, 3 figures, accepted for publication in the Astronomy &
Astrophysics Letters special issue on the APEX science verificatio
Simulations of the formation and evolution of isolated dwarf galaxies - II. Angular momentum as a second parameter
We show results based on a large suite of N-Body/SPH simulations of isolated,
flat dwarf galaxies, both rotating and non-rotating. The main goal is to
investigate possible mechanisms to explain the observed dichotomy in radial
stellar metallicity profiles of dwarf galaxies: dwarf irregulars (dIrr) and
flat, rotating dwarf ellipticals (dE) generally possess flat metallicity
profiles, while rounder and non-rotating dEs show strong negative metallicity
gradients. These simulations show that flattening by rotation is key to
reproducing the observed characteristics of flat dwarf galaxies, proving
particularly efficient in erasing metallicity gradients. We propose a
"centrifugal barrier mechanism" as an alternative to the previously suggested
"fountain mechanism" for explaining the flat metallicity profiles of dIrrs and
flat, rotating dEs. While only flattening the dark-matter halo has little
influence, the addition of angular momentum slows down the infall of gas, so
that star formation (SF) and the ensuing feedback are less centrally
concentrated, occurring galaxy-wide. Additionally, this leads to more
continuous SFHs by preventing large-scale oscillations in the SFR
("breathing"), and creates low density holes in the ISM, in agreement with
observations of dIrrs. Our general conclusion is that rotation has a
significant influence on the evolution and appearance of dwarf galaxies, and we
suggest angular momentum as a second parameter (after galaxy mass as the
dominant parameter) in dwarf galaxy evolution. Angular momentum differentiates
between SF modes, making our fast rotating models qualitatively resemble dIrrs,
which does not seem possible without rotation.Comment: Accepted for publication in MNRAS | 19 pages, 20 figures | extra
online content available (animations) : on the publisher's website / on the
YouTube channel for the astronomy department of the University of Ghent :
http://www.youtube.com/user/AstroUGent / YouTube playlist specifically for
this article :
http://www.youtube.com/user/AstroUGent#grid/user/EFAA5AAE5C5E474
Axisymmetric Three-Integral Models for Galaxies
We describe an improved, practical method for constructing galaxy models that
match an arbitrary set of observational constraints, without prior assumptions
about the phase-space distribution function (DF). Our method is an extension of
Schwarzschild's orbit superposition technique. As in Schwarzschild's original
implementation, we compute a representative library of orbits in a given
potential. We then project each orbit onto the space of observables, consisting
of position on the sky and line-of-sight velocity, while properly taking into
account seeing convolution and pixel binning. We find the combination of orbits
that produces a dynamical model that best fits the observed photometry and
kinematics of the galaxy. A key new element of this work is the ability to
predict and match to the data the full line-of-sight velocity profile shapes. A
dark component (such as a black hole and/or a dark halo) can easily be included
in the models.
We have tested our method, by using it to reconstruct the properties of a
two-integral model built with independent software. The test model is
reproduced satisfactorily, either with the regular orbits, or with the
two-integral components. This paper mainly deals with the technical aspects of
the method, while applications to the galaxies M32 and NGC 4342 are described
elsewhere (van der Marel et al., Cretton & van den Bosch). (abridged)Comment: minor changes, accepted for publication in the Astrophysical Journal
Supplement
Dynamical Modeling of Velocity Profiles: The Dark Halo Around the Elliptical Galaxy NGC2434
We describe a powerful technique to model and interpret the stellar
line-of-sight velocity profiles of galaxies. Following Schwarzschild's modeling
approach, a representative library of orbits is calculated in a given
potential; then the non-negative superposition of these orbits is determined to
fit best a given set of observational constraints. Our implementation
incorporates several new features: (i) we calculate velocity profiles and
represent them by a Gauss-Hermite series. This allows us to constrain the
orbital anisotropy in the fit. (ii) we take into account the error on each
observational constraint to obtain an objective chi2 measure for the
quality-of-fit. Only projected, observable quantities are included in the fit,
and aperture binning and seeing convolution of the data are properly taken into
account. This scheme is valid for any geometry, but here we focus on spherical
geometry and the issue of dark halos around elliptical galaxies. We model
radially extended velocity profiles of the E0 galaxy NGC 2434, and find that
constant M/L models are clearly ruled out, regardless of the orbital
anisotropy. To study how much dark matter is needed, we considered a sequence
of cosmologically motivated `star+halo' potentials, which are specified by the
stellar mass-to-light ratio Gamma and the characteristic halo velocity, V_200
(from Navarro et al. 1996). The star+halo models provide an excellent fit to
the data, with Gamma=3.35+-0.25 (in B-band solar units) and V_200=450+-100km/s.
The best-fitting potential has a circular velocity Vc that is constant (at
~300km/s) to within 10% between 0.2--3 effective radii. In NGC 2434 roughly
half of the mass within an effective radius appears to be dark.Comment: 41 pages, Latex file with 11 PostScripts figures. Submitted to the
Astrophysical Journa
The role of subjective well-being in co-designing open-design assistive devices
In this paper we explore the role of subjective well-being within the process of making together a personalized assistive device. Through a process of social product adaptation, assistive artifacts become part of occupational therapy and co-evolve with clients. Personal digital fabrication tools enable small user groups to make and share their one-of-a-kind products with the world. This approach opens up new possibilities for disabled people and their caregivers to actively engage with their own skills and challenges. The paper describes a case study of an inclusive participatory design approach, which leads to qualitative occupational experiences within the feld of community-based practice. The aim is to show how the process of collaborative designing, making and using artifacts fosters several elements of subject well-being in itself. The starting point of this open design process is a threefold interaction involving industrial designers, patients and occupational therapists within their local product ecology. Co-experience driven design is an inter subjective process that enables all individual stakeholders to work on a common phenomenon in respect of each subjective experience. Participatory prototyping is applied as a mobilization medium that (a) coordinates and (b) motivates design actions towards collaborative well-being equilibriums. This form of artifact-mediated participatory design embodies simultaneously (1) a communication language between all stakeholders that identifies meaningful goals, (2) an explorative process to attain and challenge these goals, (3) a selection of meaningful and engaging prototyping activities and (4) an appropriateness process with local skills and technology. By implementing this creative process, disabled people and their carers become conscious actors in providing collaborative maintenance of their own physical, mental and social well-being.Industrial Desig