903 research outputs found
Passiv damping on spacecraft sandwich panels
For reusable and expendable launch vehicles as well as for other spacecraft structural
vibration loads are safety critical design drivers impacting mass and lifetime. Here, the
improvement of reliability and safety, the reduction of mass, the extension of service life, as well
as the reduction of cost for manufacturing are desired. Spacecraft structural design in general is a
compromise between lightweight design and robustness with regard to dynamic loads. The
structural stresses and strains due to displacements caused by dynamic loads can be reduced by
mechanical damping based on passive or active measures. Passive damping systems can be
relatively simple and yet are capable of suppressing a wide range of mechanical vibrations.
Concepts are low priced in development, manufacturing and application as well as maintenancefree.
Compared to active damping measures passive elements do not require electronics, control
algorithms, power, actuators, sensors as well as complex maintenance. Moreover, a reliable
application of active dampers for higher temperatures and short response times (e. g. re-entry
environment) is questionable. The physical effect of passive dampers is based on the dissipation of
load induced energy. Recent activities performed by OHB have shown the function of a passive
friction-damping device for a vertical tail model of the German X-vehicle PHÖNIX but also for
general sandwich structures. The present paper shows brand new results from a corresponding
ESA-funded activity where passive damping elements are placed between the face sheets of large
spacecraft relevant composite sandwich panels to demonstrate dynamic load reduction in vibration
experiments on a shaker. Several passive damping measures are investigated and compared
Global and local statistical regularities control visual attention to object sequences
Many previous studies have shown that both infants and adults are skilled statistical learners. Because statistical learning is affected by attention, learners' ability to manage their attention can play a large role in what they learn. However, it is still unclear how learners allocate their attention in order to gain information in a visual environment containing multiple objects, especially how prior visual experience (i.e., familiarly of objects) influences where people look. To answer these questions, we collected eye movement data from adults exploring multiple novel objects while manipulating object familiarity with global (frequencies) and local (repetitions) regularities. We found that participants are sensitive to both global and local statistics embedded in their visual environment and they dynamically shift their attention to prioritize some objects over others as they gain knowledge of the objects and their distributions within the task
Multiscale Discriminant Saliency for Visual Attention
The bottom-up saliency, an early stage of humans' visual attention, can be
considered as a binary classification problem between center and surround
classes. Discriminant power of features for the classification is measured as
mutual information between features and two classes distribution. The estimated
discrepancy of two feature classes very much depends on considered scale
levels; then, multi-scale structure and discriminant power are integrated by
employing discrete wavelet features and Hidden markov tree (HMT). With wavelet
coefficients and Hidden Markov Tree parameters, quad-tree like label structures
are constructed and utilized in maximum a posterior probability (MAP) of hidden
class variables at corresponding dyadic sub-squares. Then, saliency value for
each dyadic square at each scale level is computed with discriminant power
principle and the MAP. Finally, across multiple scales is integrated the final
saliency map by an information maximization rule. Both standard quantitative
tools such as NSS, LCC, AUC and qualitative assessments are used for evaluating
the proposed multiscale discriminant saliency method (MDIS) against the
well-know information-based saliency method AIM on its Bruce Database wity
eye-tracking data. Simulation results are presented and analyzed to verify the
validity of MDIS as well as point out its disadvantages for further research
direction.Comment: 16 pages, ICCSA 2013 - BIOCA sessio
Real-World Goal Setting and Use of Outcome Measures According to the International Classification of Functioning, Disability and Health: A European Survey of Physical Therapy Practice in Multiple Sclerosis
Goal setting is a core component of physical therapy in multiple sclerosis (MS). It is unknown whether and to what extent goals are set at different levels of the International Classification of Functioning, Disability and Health (ICF), and whether, and to which, standardized outcome measures are used in real life for evaluation at the different ICF levels. Our aim was to describe the real-world use of goal setting and outcome measures in Europe. An online cross-sectional survey, completed by 212 physical therapists (PTs) specialized in MS from 26 European countries, was conducted. Differences between European regions and relationships between goals and assessments were analyzed. PTs regularly set goals, but did not always apply the Specific, Measurable, Achievable, Realistic, Timed (SMART) criteria. Regions did not differ in the range of activities assessed, but in goals set (e.g., Western and Northern regions set significantly more goals regarding leisure and work) and outcome measures used (e.g., the Berg Balance Scale was more frequently used in Northern regions). Quality of life was not routinely assessed, despite being viewed as an important therapy goal. Discrepancies existed both in goal setting and assessment across European regions. ICF assists in understanding these discrepancies and in guiding improved health-care for the future.</jats:p
Frenkel and charge transfer excitons in C60
We have studied the low energy electronic excitations of C60 using momentum
dependent electron energy-loss spectroscopy in transmission. The momentum
dependent intensity of the gap excitation allows the first direct experimental
determination of the energy of the 1Hg excitation and thus also of the total
width of the multiplet resulting from the gap transition. In addition, we could
elucidate the nature of the following excitations - as either Frenkel or charge
transfer excitons.Comment: RevTEX, 3 Figures, to appear in Phys. Rev.
Parameters of the Effective Singlet-Triplet Model for Band Structure of High- Cuprates by Different Approaches
The present paper covers the problem of parameters determination for
High- superconductive copper oxides. Different approaches, {\it ab initio}
LDA and LDA+U calculations and Generalized Tight-Binding (GTB) method for
strongly correlated electron systems, are used to calculate hopping and
exchange parameters of the effective singlet-triplet model for -layer.
The resulting parameters are in remarkably good agreement with each other and
with parameters extracted from experiment. This set of parameters is proposed
for proper quantitative description of physics of hole doped High-
cuprates in the framework of effective models.Comment: PACS 74.72.h; 74.20.z; 74.25.Jb; 31.15.A
Strong correlation effects in the doped Hubbard model in infinite dimensions
The density of states and the optical conductivity of the doped Hubbard model
on a Bethe lattice with infinite connectivities have been studied using an
analytic variant of the Lanczos continued fraction method. The spectral weight
of the gap states and the position of the chemical potential upon hole or
electron doping have been studied. We argue that the strong correlation effects
such as gap states and midinfrared band shown in two dimensions also appear in
infinite dimensions.Comment: 9 pages, revtex, 3 figures upon reques
Trial-unique, delayed nonmatching-to-location (TUNL) touchscreen testing for mice: sensitivity to dorsal hippocampal dysfunction.
RATIONALE: The hippocampus is implicated in many of the cognitive impairments observed in conditions such as Alzheimer's disease (AD) and schizophrenia (SCZ). Often, mice are the species of choice for models of these diseases and the study of the relationship between brain and behaviour more generally. Thus, automated and efficient hippocampal-sensitive cognitive tests for the mouse are important for developing therapeutic targets for these diseases, and understanding brain-behaviour relationships. One promising option is to adapt the touchscreen-based trial-unique nonmatching-to-location (TUNL) task that has been shown to be sensitive to hippocampal dysfunction in the rat. OBJECTIVES: This study aims to adapt the TUNL task for use in mice and to test for hippocampus-dependency of the task. METHODS: TUNL training protocols were altered such that C57BL/6 mice were able to acquire the task. Following acquisition, dysfunction of the dorsal hippocampus (dHp) was induced using a fibre-sparing excitotoxin, and the effects of manipulation of several task parameters were examined. RESULTS: Mice could acquire the TUNL task using training optimised for the mouse (experiments 1). TUNL was found to be sensitive to dHp dysfunction in the mouse (experiments 2, 3 and 4). In addition, we observed that performance of dHp dysfunction group was somewhat consistently lower when sample locations were presented in the centre of the screen. CONCLUSIONS: This study opens up the possibility of testing both mouse and rat models on this flexible and hippocampus-sensitive touchscreen task.CHK received funding from the Korean Health Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (HI11C1183). CJH, LMS and TJB were funded by Medical Research Council/Wellcome Trust grant 089703/Z/09/Z. CR, LMS and TJB were funded by Alzheimer’s Research UK [ART/ESG2010/1]. ACM, MHE, CAO, LMS and TJB also received funding from the Innovative Medicine Initiative Joint Undertaking under grant agreement no 115008 of which resources are composed of EFPIA in-kind contribution and financial contribution from the European Union’s Seventh Framework Programme (FP7/2007-2013).This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s00213-015-4017-
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