1,617 research outputs found
The initial gas-phase sulfur abundance in the Orion Molecular Cloud from sulfur radio recombination lines
The abundances of chemical elements and their depletion factors are essential
parameters for understanding the composition of the gas and dust that are
ultimately incorporated into stars and planets. Sulfur is an abundant but
peculiar element in the sense that, despite being less volatile than other
elements (e.g., carbon), it is not a major constituent of dust grains in
diffuse interstellar clouds. Here, we determine the gas-phase carbon-to-sulfur
abundance ratio, [C]/[S], and the sulfur abundance [S] in a dense star-forming
cloud from new radio recombination lines (RRLs) detected with the Yebes 40m
telescope - at relatively high frequencies (~40 GHz ~7 mm) and angular
resolutions (down to 36'') - in the Orion Bar, a rim of the Orion Molecular
Cloud (OMC). We detect nine Cn\alpha RRLs (with n=51 to 59) as well as nine
narrow line features separated from the Cn\alpha lines by delta v=-8.4+/-0.3 km
s^-1. Based on this velocity separation, we assign these features to sulfur
RRLs, with little contribution of RRLs from the more condensable elements Mg,
Si, or Fe. Sulfur RRLs lines trace the photodissociation region (PDR) of the
OMC. In these predominantly neutral gas layers, up to A_V~4, the ions C+ and S+
lock in most of the C and S gas-phase reservoir. We determine a relative
abundance of [C]_Ori/[S]_Ori=10.4+/-0.6 and, adopting the same [C]_Ori measured
in the translucent gas toward star theta^1 Ori B, an absolute abundance of
[S]_Ori=(1.4+/-0.4)x10^-5. This value is consistent with emission models of the
observed sulfur RRLs if N(S+)~7x10^17 cm^-2 (beam-averaged). The [S]_Ori is the
''initial'' sulfur abundance in the OMC, before an undetermined fraction of the
[S]_Ori goes into molecules and ice mantles in the cloud interior. The inferred
abundance [S]_Ori matches the solar abundance, thus implying that there is
little depletion of sulfur onto rocky dust grains, with D(S)=0.0+/-0.2 dex.Comment: Accepted for publication in Astronomy & Astrophysics Letters. 9 pages
including Appendi
Editorial of Special Issue Combining Sensors and Multibody Models for Applications in Vehicles, Machines, Robots and Humans
[Abstract] The combination of physical sensors and computational models to provide additional information about system states, inputs and/or parameters, in what is known as virtual sensing, is becoming more and more popular in many sectors, such as the automotive, aeronautics, aerospatial, railway, machinery, robotics and human biomechanics sector
ValidaciĂłn experimental de un modelo de mĂşsculo activado de forma artificial
Postprint (published version
Computational Analysis of a Spiral Thermoelectric Nanoantenna for Solar Energy Harvesting Applications
Thermo-electrical nanoantennas have been proposed as an alternative option
for conversion solar energy harvesting applications. In this work, the response
of a spiral broadband antenna has been obtained from numerical and theoretical
simulations perspectives. The results show that this device exhibits a
responsivity of 20mV/W under 117W/cm2, for a single-frequency radiation. We
discuss strategies for enhanced efficiency
Design of a patient-tailored active knee-ankle-foot orthosis to assist the gait of spinal cord injured subjects
—This paper presents the main design steps in the
development of an active knee-ankle-foot orthosis (KAFO)
conceived to assist the gait of incomplete spinal cord injured
(SCI) subjects. The design approach is based on the idea of
modifying the available passive orthoses by adding
adaptable mechatronic modules at the joints. This approach
has resulted in a prototype that has been tested on SCI
patients. The design and control problems found and their
adopted solutions are thoroughly described.Postprint (published version
Seebeck Nanoantennas for Infrared Detection and Energy Harvesting Applications
In this letter we introduce a new type of infrared sensor, based on
thermocouple nanoantennas, which enables the energy detection and gathering in
the mid-infrared region. The proposed detector combines the Seebeck effect, as
a transduction mechanism, with the functionalities of the optical antennas for
optical sensing. By using finite-element numerical simulations we evaluate the
performance and optical-to-electrical conversion efficiency of the proposed
device, unveiling its potential for optical sensing and energy harvesting
applications.Comment: 4 pages, 3 figures, Invited paper at EUCAP 201
Index-3 divide-and-conquer algorithm for efficient multibody system dynamics simulations: theory and parallel implementation
[Abstract] There has been a growing attention to efficient simulations of multibody systems, which is apparently seen in many areas of computer-aided engineering and design both in academia and in industry. The need for efficient or real-time simulations requires high fidelity techniques and formulations that should significantly minimize computational time. Parallel computing is one of the approaches to achieve this objective. This paper presents a novel index-3 divide-and-conquer algorithm for efficient multibody dynamics simulations that elegantly handles multibody systems in generalized topologies through the application of the augmented Lagrangian method. The proposed algorithm exploits a redundant set of absolute coordinates. The trapezoidal integration rule is embedded into the formulation and a set of nonlinear equations need to be solved every time instant. Consequently, the Newton–Raphson iterative scheme is applied to find the system coordinates and joint constraint loads in an efficient and highly parallelizable manner. Two divide-and-conquer based mass-orthogonal projections are performed then to circumvent the effect of constraint violation errors at the velocity and acceleration level. Sample open- and closed-loop multibody system test cases are investigated in the paper to confirm the validity of the approach. Challenging simulations of multibody systems featuring long kinematic chains are also performed in the work to demonstrate the robustness of the algorithm. The details of OpenMP-based parallel implementation on an eight-core shared memory computer are presented in the text and the parallel performance results are extensively discussed. Significant speedups are obtained for the simulations of small- to large-scale multibody open-loop systems. The mentioned features make the proposed algorithm a good general purpose approach for high-fidelity, efficient or real-time multibody dynamics simulations.Ministerio de EconomĂa y Competitividad; JCI-2012-12376Poland. National Science Center; DEC-2012/07/B/ST8/0399
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