975 research outputs found
A Novel Approach for Simplification of Industrial Robot Dynamic Model Using Interval Method
This paper proposes a new approach to simplify the dynamic model of industrial robot by means of interval method. Due to strong nonlinearities, some components of robot dynamic model such as the inertia matrix and the vector of centrifugal, Coriolis and gravitational torques, are very complicated for real-time control of industrial robots. Thus, a simplification algorithm is presented in this study in order to reduce the computation time and memory occupation. More importantly, this simplification is suitable for arbitrary trajectories in whole robot workspace. Furthermore, the method devotes to finding negligible inertia parameters, which is useful for robot model identification. A simulation has been carried out on a test trajectory using a 6-DOF industrial robot model, and the results have shown good performance and effectiveness of this method.ANR COROUSS
A GaN-HEMT compact model including dynamic r<sub>DSon</sub> effect for power electronics converters
In order to model GaN-HEMT switching transients and determine power losses, a compact model including dynamic RDSon effect is proposed herein. The model includes mathematical equations to represent device static and capacitance-voltage characteristics, and a behavioural voltage source, which includes multiple RC units to represent different time constants for trapping and detrapping effect from 100 ns to 100 s range. All the required parameters in the model can be obtained by fitting method using a datasheet or experimental characterisation results. The model is then implemented into our developed virtual prototyping software, where the device compact model is co-simulated with a parasitic inductance physical model to obtain the switching waveform. As model order reduction is applied in our software to resolve physical model, the device switching current and voltage waveform can be obtained in the range of minutes. By comparison with experimental measurements, the model is validated to accurately represent device switching transients as well as their spectrum in frequency domain until 100 MHz. In terms of dynamic RDSon value, the mismatch between the model and experimental results is within 10% under different power converter operation conditions in terms of switching frequencies and duty cycles, so designers can use this model to accurately obtain GaN-HEMT power losses due to trapping and detrapping effects for power electronics converters
Power asymmetry in CMB polarization maps from PLANCK : a local variance analysis
A persistent signal of power asymmetry on opposite hemispheres of CMB sky was
seen in full-sky temperature measurements made so far. This asymmetry was seen
in microwave sky from WMAP as well as PLANCK satellites, and calls for
attention the larger question of \emph{statistical isotropy}, one of the
foundational principles of modern cosmology. In this work we present an
analysis of polarized CMB maps from PLANCK 2015 full mission data. We apply the
local variance estimator on low resolution mode maps from PLANCK 2015
polarization \texttt{Commander} solution. We find a significant hemispherical
power asymmetry in polarization data on large angular scales, at the level of
depending on the galactic mask, and the circular disc radius
used for computing local variance maps. However the direction is found to be
pointing broadly towards CMB kinetic dipole direction. Precise measurements of
CMB polarization in future will shed light on this apparent discrepancy in the
anisotropy axis seen in temperature and polarized CMB sky, and likely influence
of systematics on our findings.Comment: 21 pages, 10 figures, 3 table
Carrier Trapping by Oxygen Impurities in Molybdenum Diselenide
Understanding defect effect on carrier dynamics is essential for both
fundamental physics and potential applications of transition metal
dichalcogenides. Here, the phenomenon of oxygen impurities trapping
photo-excited carriers has been studied with ultrafast pump-probe spectroscopy.
Oxygen impurities are intentionally created in exfoliated multilayer MoSe2 with
Ar+ plasma irradiation and air exposure. After plasma treatment, the signal of
transient absorption first increases and then decreases, which is a signature
of defect capturing carriers. With larger density of oxygen defects, the
trapping effect becomes more prominent. The trapping defect densities are
estimated from the transient absorption signal, and its increasing trend in the
longer-irradiated sample agrees with the results from X-ray photoelectron
spectroscopy. First principle calculations with density functional theory
reveal that oxygen atoms occupying Mo vacancies create mid-gap defect states,
which are responsible for the carrier trapping. Our findings shed light on the
important role of oxygen defects as carrier trappers in transition metal
dichalcogenides, and facilitates defect engineering in relevant material and
device applications
Connectionist perspectives on language learning, representation and processing.
The field of formal linguistics was founded on the premise that language is mentally represented as a deterministic symbolic grammar. While this approach has captured many important characteristics of the world\u27s languages, it has also led to a tendency to focus theoretical questions on the correct formalization of grammatical rules while also de-emphasizing the role of learning and statistics in language development and processing. In this review we present a different approach to language research that has emerged from the parallel distributed processing or \u27connectionist\u27 enterprise. In the connectionist framework, mental operations are studied by simulating learning and processing within networks of artificial neurons. With that in mind, we discuss recent progress in connectionist models of auditory word recognition, reading, morphology, and syntactic processing. We argue that connectionist models can capture many important characteristics of how language is learned, represented, and processed, as well as providing new insights about the source of these behavioral patterns. Just as importantly, the networks naturally capture irregular (non-rule-like) patterns that are common within languages, something that has been difficult to reconcile with rule-based accounts of language without positing separate mechanisms for rules and exceptions
Derivation of therapeutic lung spheroid cells from minimally invasive transbronchial pulmonary biopsies
BACKGROUND: Resident stem and progenitor cells have been identified in the lung over the last decade, but isolation and culture of these cells remains a challenge. Thus, although these lung stem and progenitor cells provide an ideal source for stem-cell based therapy, mesenchymal stem cells (MSCs) remain the most popular cell therapy product for the treatment of lung diseases. Surgical lung biopsies can be the tissue source but such procedures carry a high risk of mortality.
METHODS: In this study we demonstrate that therapeutic lung cells, termed "lung spheroid cells" (LSCs) can be generated from minimally invasive transbronchial lung biopsies using a three-dimensional culture technique. The cells were then characterized by flow cytometry and immunohistochemistry. Angiogenic potential was tested by in-vitro HUVEC tube formation assay. In-vivo bio- distribution of LSCs was examined in athymic nude mice after intravenous delivery.
RESULTS: From one lung biopsy, we are able to derive >50 million LSC cells at Passage 2. These cells were characterized by flow cytometry and immunohistochemistry and were shown to represent a mixture of lung stem cells and supporting cells. When introduced systemically into nude mice, LSCs were retained primarily in the lungs for up to 21Â days.
CONCLUSION: Here, for the first time, we demonstrated that direct culture and expansion of human lung progenitor cells from pulmonary tissues, acquired through a minimally invasive biopsy, is possible and straightforward with a three-dimensional culture technique. These cells could be utilized in long-term expansion of lung progenitor cells and as part of the development of cell-based therapies for the treatment of lung diseases such as chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF)
Anisotropic in-plane heat transport of Kitaev magnet NaCoTeO
We report a study on low-temperature heat transport of Kitaev magnet
NaCoTeO, with the heat current and magnetic fields along the
honeycomb spin layer (the plane). The zero-field thermal conductivity of
and display similar temperature dependence
and small difference in their magnitudes; whereas, their magnetic field
(parallel to the heat current) dependence are quite different and are related
to the field-induced magnetic transitions. The data for at very low temperatures have an anomaly at 10.25--10.5 T, which
reveals an unexplored magnetic transition. The planar thermal Hall conductivity
and show very weak signals at low fields and
rather large values with sign change at high fields. This may point to a
possible magnetic structure transition or the change of the magnon band
topology that induces a radical change of magnon Berry curvature distribution
before entering the spin polarized state. These results put clear constraints
on the high-field phase and the theoretical models for NaCoTeO.Comment: 7 pages, 4 figure
Early stressful experiences are associated with reduced neural responses to naturalistic emotional and social content in children
How do childrenâs experiences relate to their naturalistic emotional and social processing? Because children can struggle with tasks in the scanner, we collected fMRI data while 4-to-11-year-olds watched a short film with positive and negative emotional events, and rich parent-child interactions (n = 70). We captured broad, normative stressful experiences by examining socioeconomic status (SES) and stressful life events, as well as childrenâs more proximal experiences with their parents. For a sub-sample (n = 30), parenting behaviors were measured during a parent-child interaction, consisting of a picture book, a challenging puzzle, and free play with novel toys. We characterized positive parenting behaviors (e.g., warmth, praise) and negative parenting behaviors (e.g., harsh tone, physical control). We found that higher SES was related to greater activity in medial orbitofrontal cortex during parent-child interaction movie events. Negative parenting behaviors were associated with less activation of the ventral tegmental area and cerebellum during positive emotional events. In a region-of-interest analysis, we found that stressful life events and negative parenting behaviors were associated with less activation of the amygdala during positive emotional events. These exploratory results demonstrate the promise of using movie fMRI to study how early experiences may shape emotional, social, and motivational processes
The Oslo definitions for coeliac disease and related terms.
ObjectiveThe literature suggests a lack of consensus on the use of terms related to coeliac disease (CD) and gluten.DesignA multidisciplinary task force of 16 physicians from seven countries used the electronic database PubMed to review the literature for CD-related terms up to January 2011. Teams of physicians then suggested a definition for each term, followed by feedback of these definitions through a web survey on definitions, discussions during a meeting in Oslo and phone conferences. In addition to 'CD', the following descriptors of CD were evaluated (in alphabetical order): asymptomatic, atypical, classical, latent, non-classical, overt, paediatric classical, potential, refractory, silent, subclinical, symptomatic, typical, CD serology, CD autoimmunity, genetically at risk of CD, dermatitis herpetiformis, gluten, gluten ataxia, gluten intolerance, gluten sensitivity and gliadin-specific antibodies.ResultsCD was defined as 'a chronic small intestinal immune-mediated enteropathy precipitated by exposure to dietary gluten in genetically predisposed individuals'. Classical CD was defined as 'CD presenting with signs and symptoms of malabsorption. Diarrhoea, steatorrhoea, weight loss or growth failure is required.' 'Gluten-related disorders' is the suggested umbrella term for all diseases triggered by gluten and the term gluten intolerance should not to be used. Other definitions are presented in the paper.ConclusionThis paper presents the Oslo definitions for CD-related terms
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