6,779 research outputs found
Attitude transfer assembly design for MAGSAT
A description is given of a design for an instrument system that will monitor the orientation of a boom-mounted vector magnetometer relative to the main spacecraft body. The attitude of the magnetometer is measured with respect to X and Z axes lateral to the boom length and also a twist axis around the boom center line. These measurements are made in a noncontact optical approach employing a three-axis autocollimator system mounted on the main body of the spacecraft with only passive elements (reflectors) located at the end of the 20-foot boom
Drip and Mate Operations Acting in Test Tube Systems and Tissue-like P systems
The operations drip and mate considered in (mem)brane computing resemble the
operations cut and recombination well known from DNA computing. We here
consider sets of vesicles with multisets of objects on their outside membrane
interacting by drip and mate in two different setups: in test tube systems, the
vesicles may pass from one tube to another one provided they fulfill specific
constraints; in tissue-like P systems, the vesicles are immediately passed to
specified cells after having undergone a drip or mate operation. In both
variants, computational completeness can be obtained, yet with different
constraints for the drip and mate operations
Revisiting the Core Ontology and Problem in Requirements Engineering
In their seminal paper in the ACM Transactions on Software Engineering and
Methodology, Zave and Jackson established a core ontology for Requirements
Engineering (RE) and used it to formulate the "requirements problem", thereby
defining what it means to successfully complete RE. Given that stakeholders of
the system-to-be communicate the information needed to perform RE, we show that
Zave and Jackson's ontology is incomplete. It does not cover all types of basic
concerns that the stakeholders communicate. These include beliefs, desires,
intentions, and attitudes. In response, we propose a core ontology that covers
these concerns and is grounded in sound conceptual foundations resting on a
foundational ontology. The new core ontology for RE leads to a new formulation
of the requirements problem that extends Zave and Jackson's formulation. We
thereby establish new standards for what minimum information should be
represented in RE languages and new criteria for determining whether RE has
been successfully completed.Comment: Appears in the proceedings of the 16th IEEE International
Requirements Engineering Conference, 2008 (RE'08). Best paper awar
New Results from NA49
We present recent results of the SPS experiment NA49 on production of strange
particles and event-by-event fluctuations of mean and of charged particle
ratios in central Pb+Pb collisions at various beam energies (40, 80, 158 AGeV)
as well as in different collisions at 158 AGeV, going from p+p over light-ion
collisions to peripheral and central Pb+Pb.Comment: 5 pages, 6 figures (in eps) talk given at XXXI International
Symposium on Multiparticle Dynamics, Sep. 1-7, 2001, Datong China URL
http://ismd31.ccnu.edu.cn
Finger somatotopy is preserved after tetraplegia but deteriorates over time
Previous studies showed reorganised and/or altered activity in the primary sensorimotor cortex after a spinal cord injury (SCI), suggested to reflect abnormal processing. However, little is known about whether somatotopically specific representations can be activated despite reduced or absent afferent hand inputs. In this observational study, we used functional MRI and a (attempted) finger movement task in tetraplegic patients to characterise the somatotopic hand layout in primary somatosensory cortex. We further used structural MRI to assess spared spinal tissue bridges. We found that somatotopic hand representations can be activated through attempted finger movements in the absence of sensory and motor hand functioning, and no spared spinal tissue bridges. Such preserved hand somatotopy could be exploited by rehabilitation approaches that aim to establish new hand-brain functional connections after SCI (e.g. neuroprosthetics). However, over years since SCI the hand representation somatotopy deteriorated, suggesting that somatotopic hand representations are more easily targeted within the first years after SCI
Parallel Perceptrons, Activation Margins and Imbalanced Training Set Pruning
The final publication is available at Springer via http://dx.doi.org/10.1007/11492542_6Proceedings of Second Iberian Conference, IbPRIA 2005, Estoril, Portugal, June 7-9, 2005, Part IIA natural way to deal with training samples in imbalanced class problems is to prune them removing redundant patterns, easy to classify and probably over represented, and label noisy patterns that belonging to one class are labelled as members of another. This allows classifier construction to focus on borderline patterns, likely to be the most informative ones. To appropriately define the above subsets, in this work we will use as base classifiers the so–called parallel perceptrons, a novel approach to committee machine training that allows, among other things, to naturally define margins for hidden unit activations. We shall use these margins to define the above pattern types and to iteratively perform subsample selections in an initial training set that enhance classification accuracy and allow for a balanced classifier performance even when class sizes are greatly different.With partial support of Spain’s CICyT, TIC 01–572, TIN2004–0767
Learning from Minimum Entropy Queries in a Large Committee Machine
In supervised learning, the redundancy contained in random examples can be
avoided by learning from queries. Using statistical mechanics, we study
learning from minimum entropy queries in a large tree-committee machine. The
generalization error decreases exponentially with the number of training
examples, providing a significant improvement over the algebraic decay for
random examples. The connection between entropy and generalization error in
multi-layer networks is discussed, and a computationally cheap algorithm for
constructing queries is suggested and analysed.Comment: 4 pages, REVTeX, multicol, epsf, two postscript figures. To appear in
Physical Review E (Rapid Communications
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