7,267 research outputs found
Exergame design for elderly users: the case study of SilverBalance
In this paper, we discuss chances and challenges of game design for an elderly audience with a focus on the development of safe and usable exertion games for frail senior citizens. Based on an analysis of theoretical constraints, we conducted a case study which implements different balance tasks for elderly players featuring the Nintendo Wii Balance Board which encourages users to actively engage in game play. Furthermore, we tested the feasibility of the board as input device for our case study SilverBalance. Our results indicate that age-related impairments influence the use of video games among frail elderly in many respects, hence their needs have to be considered during the design process. In this context, our paper provides a foundation for future research regarding digital games for the elderly. © 2010 ACM
Properties of Poly (isoprene) - Model Building in the Melt and in Solution
Properties of 1,4-\textit{trans} poly (isoprene) at ambient conditions are
determined by simulations on two length scales based on two different models: a
full-atomistic and a mesoscopic one. The models are linked via a mapping scheme
such that one mesoscopic bead represents one chemical repeat unit. Melts as
well as solutions of several chain lengths were investigated and mapped
individually to the meso-scale. The resulting models are compared to each
other. The meso-scale models could be simulated over a large variety of chain
lengths and time-scales relevant for experimental comparison. Concerning static
properties, we determined the persistence length of our systems and the scaling
behavior of the radius of gyration. The latter was compared to experiments and
the agreement is satisfactory. Furthermore, we find deviations from Rouse
dynamics at all chain lengths at ambient conditions.Comment: 11 pictures 7 figure
Non-Blocking Signature of very large SOAP Messages
Data transfer and staging services are common components in Grid-based, or
more generally, in service-oriented applications. Security mechanisms play a
central role in such services, especially when they are deployed in sensitive
application fields like e-health. The adoption of WS-Security and related
standards to SOAP-based transfer services is, however, problematic as a
straightforward adoption of SOAP with MTOM introduces considerable
inefficiencies in the signature generation process when large data sets are
involved. This paper proposes a non-blocking, signature generation approach
enabling a stream-like processing with considerable performance enhancements.Comment: 13 pages, 5 figure
Learning to Understand by Evolving Theories
In this paper, we describe an approach that enables an autonomous system to
infer the semantics of a command (i.e. a symbol sequence representing an
action) in terms of the relations between changes in the observations and the
action instances. We present a method of how to induce a theory (i.e. a
semantic description) of the meaning of a command in terms of a minimal set of
background knowledge. The only thing we have is a sequence of observations from
which we extract what kinds of effects were caused by performing the command.
This way, we yield a description of the semantics of the action and, hence, a
definition.Comment: KRR Workshop at ICLP 201
Mapping atomistic to coarse-grained polymer models using automatic simplex optimization to fit structural properties
We develop coarse-grained force fields for poly (vinyl alcohol) and poly
(acrylic acid) oligomers. In both cases, one monomer is mapped onto a
coarse-grained bead. The new force fields are designed to match structural
properties such as radial distribution functions of various kinds derived by
atomistic simulations of these polymers. The mapping is therefore constructed
in a way to take into account as much atomistic information as possible. On the
technical side, our approach consists of a simplex algorithm which is used to
optimize automatically non-bonded parameters as well as bonded parameters.
Besides their similar conformation (only the functional side group differs),
poly (acrylic acid) was chosen to be in aqueous solution in contrast to a poly
(vinyl alcohol) melt. For poly (vinyl alcohol) a non-optimized bond angle
potential turns out to be sufficient in connection with a special, optimized
non-bonded potential. No torsional potential has to be applied here. For poly
(acrylic acid), we show that each peak of the radial distribution function is
usually dominated by some specific model parameter(s). Optimization of the bond
angle parameters is essential. The coarse-grained forcefield reproduces the
radius of gyration of the atomistic model. As a first application, we use the
force field to simulate longer chains and compare the hydrodynamic radius with
experimental data.Comment: 34 pages, 3 tables, 16 figure
Detection of OD towards the low-mass protostar IRAS16293-2422
Although water is an essential and widespread molecule in star-forming
regions, its chemical formation pathways are still not very well constrained.
Observing the level of deuterium fractionation of OH, a radical involved in the
water chemical network, is a promising way to infer its chemical origin. We aim
at understanding the formation mechanisms of water by investigating the origin
of its deuterium fractionation. This can be achieved by observing the abundance
of OD towards the low-mass protostar IRAS16293-2422, where the HDO distribution
is already known. Using the GREAT receiver on board SOFIA, we observed the
ground-state OD transition at 1391.5 GHz towards the low-mass protostar
IRAS16293-2422. We also present the detection of the HDO 111-000 line using the
APEX telescope. We compare the OD/HDO abundance ratio inferred from these
observations with the predictions of chemical models. The OD line is detected
in absorption towards the source continuum. This is the first detection of OD
outside the solar system. The SOFIA observation, coupled to the observation of
the HDO 111-000 line, provides an estimate of the abundance ratio OD/HDO ~
17-90 in the gas where the absorption takes place. This value is fairly high
compared with model predictions. This may be reconciled if reprocessing in the
gas by means of the dissociative recombination of H2DO+ further fractionates OH
with respect to water. The present observation demonstrates the capability of
the SOFIA/GREAT instrument to detect the ground transition of OD towards
star-forming regions in a frequency range that was not accessible before.
Dissociative recombination of H2DO+ may play an important role in setting a
high OD abundance. Measuring the branching ratios of this reaction in the
laboratory will be of great value for chemical models.Comment: 6 pages, 6 figures, 3 tables, accepted for publication in A&A
SOFIA/GREAT special issu
Submillimetre observations of RX J1856.5--3754
We report on submillimetre bolometer observations of the isolated neutron
star RX J1856.5--3754 using the LABOCA bolometer array on the Atacama
Pathfinder Experiment (APEX) Telescope. No cold dust continuum emission peak at
the position of RX J1856.5--3754 was detected. The 3 sigma flux density upper
limit of 5 mJy translates into a cold dust mass limit of a few earth masses. We
use the new submillimetre limit, together with a previously obtained H-band
limit, to constrain the presence of a gaseous, circumpulsar disc. Adopting a
simple irradiated-disc model, we obtain a mass accretion limit of dM/dt less
than 10^{14} g/s, and a maximum outer disc radius of around 10^{14} cm. By
examining the projected proper motion of RX J1856.5--3754, we speculate about a
possible encounter of the neutron star with a dense fragment of the CrA
molecular cloud a few thousand years ago.Comment: 6 pages, 3 figures, 1 table; accepted by MNRA
Optimal Binary Search Trees with Near Minimal Height
Suppose we have n keys, n access probabilities for the keys, and n+1 access
probabilities for the gaps between the keys. Let h_min(n) be the minimal height
of a binary search tree for n keys. We consider the problem to construct an
optimal binary search tree with near minimal height, i.e.\ with height h <=
h_min(n) + Delta for some fixed Delta. It is shown, that for any fixed Delta
optimal binary search trees with near minimal height can be constructed in time
O(n^2). This is as fast as in the unrestricted case.
So far, the best known algorithms for the construction of height-restricted
optimal binary search trees have running time O(L n^2), whereby L is the
maximal permitted height. Compared to these algorithms our algorithm is at
least faster by a factor of log n, because L is lower bounded by log n
Submission of content to a digital object repository using a configurable workflow system
The prototype of a workflow system for the submission of content to a digital
object repository is here presented. It is based entirely on open-source
standard components and features a service-oriented architecture. The front-end
consists of Java Business Process Management (jBPM), Java Server Faces (JSF),
and Java Server Pages (JSP). A Fedora Repository and a mySQL data base
management system serve as a back-end. The communication between front-end and
back-end uses a SOAP minimal binding stub. We describe the design principles
and the construction of the prototype and discuss the possibilities and
limitations of work ow creation by administrators. The code of the prototype is
open-source and can be retrieved in the project escipub at
http://sourceforge.ne
Corrections to Scaling in the Hydrodynamic Properties of Dilute Polymer Solutions
We discuss the hydrodynamic radius of polymer chains in good solvent,
and show that the leading order correction to the asymptotic law ( degree of polymerization, ) is an ``analytic''
term of order , which is directly related to the discretization
of the chain into a finite number of beads. This result is further corroborated
by exact calculations for Gaussian chains, and extensive numerical simulations
of different models of good--solvent chains, where we find a value of for the asymptotic universal ratio , being the
chain's gyration radius. For chains the data apparently extrapolate to
, which is different from the Gaussian value 1.5045,
but in accordance with previous simulations. We also show that the
experimentally observed deviations of the initial decay rate in dynamic light
scattering from the asymptotic Benmouna--Akcasu value can partly be understood
by similar arguments.Comment: 13 pages, 10 figures. submitted to J. Chem. Phy
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