30,493 research outputs found
Robotized FSW â Evolution of forces and torque with nonlinear welds
The main purpose of the article is to study the evolution of the welding forces and torque with non-straight welding path. The main studies performed on forces and torque are usually done on plane straight welding path when the processing parameter are developed. As industrializing robotized FSW, the robot structure deformation under FSW load depends on the forces generated on the tool. Thus, in order to compensate the robot deformation automatically through the control, statistical model giving the welding forces and torque as function of the process parameters is established. This article deals with the study of the forces and torque generated as welding circular and semi-circular welds. The effect of the welding direction (i.e. position of advancing and retreating side) is also analyzed. The objective is to determine if the statistical model giving the welding forces and torque as function of the process parameters developed on straight line can be applied for welding different weld path geometries
Ono: an open platform for social robotics
In recent times, the focal point of research in robotics has shifted from industrial ro- bots toward robots that interact with humans in an intuitive and safe manner. This evolution has resulted in the subfield of social robotics, which pertains to robots that function in a human environment and that can communicate with humans in an int- uitive way, e.g. with facial expressions. Social robots have the potential to impact many different aspects of our lives, but one particularly promising application is the use of robots in therapy, such as the treatment of children with autism. Unfortunately, many of the existing social robots are neither suited for practical use in therapy nor for large scale studies, mainly because they are expensive, one-of-a-kind robots that are hard to modify to suit a specific need. We created Ono, a social robotics platform, to tackle these issues. Ono is composed entirely from off-the-shelf components and cheap materials, and can be built at a local FabLab at the fraction of the cost of other robots. Ono is also entirely open source and the modular design further encourages modification and reuse of parts of the platform
BDGS: A Scalable Big Data Generator Suite in Big Data Benchmarking
Data generation is a key issue in big data benchmarking that aims to generate
application-specific data sets to meet the 4V requirements of big data.
Specifically, big data generators need to generate scalable data (Volume) of
different types (Variety) under controllable generation rates (Velocity) while
keeping the important characteristics of raw data (Veracity). This gives rise
to various new challenges about how we design generators efficiently and
successfully. To date, most existing techniques can only generate limited types
of data and support specific big data systems such as Hadoop. Hence we develop
a tool, called Big Data Generator Suite (BDGS), to efficiently generate
scalable big data while employing data models derived from real data to
preserve data veracity. The effectiveness of BDGS is demonstrated by developing
six data generators covering three representative data types (structured,
semi-structured and unstructured) and three data sources (text, graph, and
table data)
Particle image velocimetry studies of bubble growth and detachment by high speed photography
An understanding of bubble flows is important in the design of process equipment, particularly in the chemical and power industries. In vapour-liquid processes the mass and heat transfer between the phases is dominated by the liquid-vapour interface and is determined by the number, size and shape of the bubbles. For bubble flows these characteristics are often controlled by the generation mechanisms and, since bubble flows are often generated at an orifice, it is important to determine the controlling parameters which dictate how bubbles grow and detach. For bubbles growing at orifices the liquid displacement is an important feature and affects the pressure distribution acting on the bubble and the heat and mass transfer that may occur at the bubble interface. Therefore, in this study, the characteristics of the liquid velocity field are studied experimentally using Particle Image Velocimetry (PIV) during growth, detachment and translation of a bubble being generated at an orifice supplied with a constant mass flow rate of air. The process is transient and occurs over a period of approximately 50 msecs. In order to map the transient flow field a combination of high speed cine and cross correlation PIV image processing has been used to determine the liquid velocity vector field during the bubble growth process. The paper contains details of the PIV technique and presents several of the velocity vector maps calculated
Leakage flow simulation in a specific pump model
This paper deals with the influence of leakage flow existing in SHF pump model on the analysis of internal flow behaviour inside the vane diffuser of the pump model performance using both experiments and calculations. PIV measurements have been performed at different hub to shroud planes inside one diffuser channel passage for a given speed of rotation and various flow rates. For each operating condition, the PIV measurements have been trigged with different angular impeller positions. The performances and the static pressure rise of the diffuser were also measured using a three-hole probe. The numerical simulations were carried out with Star CCM+ 8.06 code (RANS frozen and unsteady calculations). Comparisons between numerical and experimental results are presented and discussed for three flow rates. The performances of the diffuser obtained by numerical simulation results are compared to the performances obtained by three-hole probe indications. The comparisons show few influence of fluid leakage on global performances but a real improvement concerning the efficiency of the impeller, the pump and the velocity distributions. These results show that leakage is an important parameter that has to be taken into account in order to make improved comparisons between numerical approaches and experiments in such a specific model set up
How Dark Matter Came to Matter
The history of the dark matter problem can be traced back to at least the
1930s, but it was not until the early 1970s that the issue of 'missing matter'
was widely recognized as problematic. In the latter period, previously separate
issues involving missing mass were brought together in a single anomaly. We
argue that reference to a straightforward 'accumulation of evidence' alone is
inadequate to comprehend this episode. Rather, the rise of cosmological
research, the accompanying renewed interest in the theory of relativity and
changes in the manpower division of astronomy in the 1960s are key to
understanding how dark matter came to matter. At the same time, this story may
also enlighten us on the methodological dimensions of past practices of physics
and cosmology.Comment: Accepted for publication in Nature Astronomy. Corrected typ
POLLUX : a database of synthetic stellar spectra
Synthetic spectra are needed to determine fundamental stellar and wind
parameters of all types of stars. They are also used for the construction of
theoretical spectral libraries helpful for stellar population synthesis.
Therefore, a database of theoretical spectra is required to allow rapid and
quantitative comparisons to spectroscopic data. We provide such a database
offering an unprecedented coverage of the entire Hertzsprung-Russell diagram.
We present the POLLUX database of synthetic stellar spectra. For objects with
Teff < 6 000 K, MARCS atmosphere models are computed and the program
TURBOSPECTRUM provides the synthetic spectra. ATLAS12 models are computed for
stars with 7 000 K <Teff <15 000 K. SYNSPEC gives the corresponding spectra.
Finally, the code CMFGEN provides atmosphere models for the hottest stars (Teff
> 25 000 K). Their spectra are computed with CMF_FLUX. Both high resolution
(R>150 000) optical spectra in the range 3 000 to 12 000 A and spectral energy
distributions extending from the UV to near--IR ranges are presented. These
spectra cover the HR diagram at solar metallicity. We propose a wide variety of
synthetic spectra for various types of stars in a format that is compliant with
the Virtual Observatory standards. A user--friendly web interface allows an
easy selection of spectra and data retrieval. Upcoming developments will
include an extension to a large range of metallicities and to the near--IR high
resolution spectra, as well as a better coverage of the HR diagram, with the
inclusion of models for Wolf-Rayet stars and large datasets for cool stars. The
POLLUX database is accessible at http://pollux.graal.univ-montp2.fr/ and
through the Virtual Observatory.Comment: 9 pages, 5 figures, accepted for publication in Astronomy ans
Astrophysic
Spectral analysis of unsteady flow simulation in a small VAWT
The vertical axis wind turbine studied in this paper combine two rotations: one rotating movement of each blade around its own axis and one rotating movement around turbineâs axis. The aim of this paper is to analyse the effect of this two combine movements on fields of pressure and on global forces on each blade with time. Preliminary calculations showed, for some initial blade stagger angles (angle between blade 1 and x axis), that flow is highly unsteady and sometimes hardly periodic. The main goal here is to present spectral analysis of unsteady results like temporal pressure on specific points in the domain and temporal forces on blades and to show the influence of the two combine movements for two different blade stagger angles for elliptic blades
- âŠ