2,002 research outputs found
On track for solar grade silicon through a Siemens process-type laboratory reactor: operating conditions and energy savings
Polysilicon cost impacts significantly on the photovoltaics (PV) cost and on the energy payback time. Nowadays, the besetting production process is the so called Siemens process, polysilicon deposition by chemical vapor deposition (CVD) from Trichlorosilane. Polysilicon purification level for PV is to a certain extent less demanding that for microelectronics. At the Instituto de EnergÃa Solar (IES) research on this subject is performed through a Siemens process-type laboratory reactor. Through the laboratory CVD prototype at the IES laboratories, valuable information about the phenomena involved in the polysilicon deposition process and the operating conditions is obtained. Polysilicon deposition by CVD is a complex process due to the big number of parameters involved. A study on the influence of temperature and inlet gas mixture composition on the polysilicon deposition growth rate, based on experimental experience, is shown. Moreover, CVD process accounts for the largest contribution to the energy consumption of the polysilicon production. In addition, radiation phenomenon is the major responsible for low energetic efficiency of the whole process. This work presents a model of radiation heat loss, and the theoretical calculations are confirmed experimentally through a prototype reactor at our disposal, yielding a valuable know-how for energy consumption reduction at industrial Siemens reactorsPostprint (published version
Physics Of Eclipsing Binaries. II. Towards the Increased Model Fidelity
The precision of photometric and spectroscopic observations has been
systematically improved in the last decade, mostly thanks to space-borne
photometric missions and ground-based spectrographs dedicated to finding
exoplanets. The field of eclipsing binary stars strongly benefited from this
development. Eclipsing binaries serve as critical tools for determining
fundamental stellar properties (masses, radii, temperatures and luminosities),
yet the models are not capable of reproducing observed data well either because
of the missing physics or because of insufficient precision. This led to a
predicament where radiative and dynamical effects, insofar buried in noise,
started showing up routinely in the data, but were not accounted for in the
models. PHOEBE (PHysics Of Eclipsing BinariEs; http://phoebe-project.org) is an
open source modeling code for computing theoretical light and radial velocity
curves that addresses both problems by incorporating missing physics and by
increasing the computational fidelity. In particular, we discuss triangulation
as a superior surface discretization algorithm, meshing of rotating single
stars, light time travel effect, advanced phase computation, volume
conservation in eccentric orbits, and improved computation of local intensity
across the stellar surfaces that includes photon-weighted mode, enhanced limb
darkening treatment, better reflection treatment and Doppler boosting. Here we
present the concepts on which PHOEBE is built on and proofs of concept that
demonstrate the increased model fidelity.Comment: 60 pages, 15 figures, published in ApJS; accompanied by the release
of PHOEBE 2.0 on http://phoebe-project.or
Surface temperatures in New York City: Geospatial data enables the accurate prediction of radiative heat transfer
Three decades into the research seeking to derive the urban energy budget,
the dynamics of the thermal exchange between the densely built infrastructure
and the environment are still not well understood. We present a novel hybrid
experimental-numerical approach for the analysis of the radiative heat transfer
in New York City. The aim of this work is to contribute to the calculation of
the urban energy budget, in particular the stored energy. Improved
understanding of urban thermodynamics incorporating the interaction of the
various bodies will have implications on energy conservation at the building
scale, as well as human health and comfort at the urban scale. The platform
presented is based on longwave hyperspectral imaging of nearly 100 blocks of
Manhattan, and a geospatial radiosity model that describes the collective
radiative heat exchange between multiple buildings. The close comparison of
temperature values derived from measurements and the computed surface
temperatures (including streets and roads) implies that this geospatial,
thermodynamic numerical model applied to urban structures, is promising for
accurate and high resolution analysis of urban surface temperatures.Comment: 11 pages, 5 figure
AirCode: Unobtrusive Physical Tags for Digital Fabrication
We present AirCode, a technique that allows the user to tag physically
fabricated objects with given information. An AirCode tag consists of a group
of carefully designed air pockets placed beneath the object surface. These air
pockets are easily produced during the fabrication process of the object,
without any additional material or postprocessing. Meanwhile, the air pockets
affect only the scattering light transport under the surface, and thus are hard
to notice to our naked eyes. But, by using a computational imaging method, the
tags become detectable. We present a tool that automates the design of air
pockets for the user to encode information. AirCode system also allows the user
to retrieve the information from captured images via a robust decoding
algorithm. We demonstrate our tagging technique with applications for metadata
embedding, robotic grasping, as well as conveying object affordances.Comment: ACM UIST 2017 Technical Paper
Illumination and Temperature on Rough Terrain: Fast Methods for Solving the Radiosity Equation
No abstract availabl
Engineering study to determine feasible methods of simulating planetary albedo and radiation effects upon the thermal balance of spacecraft Final report
Planetary radiation and albedo effects on thermal balance of spacecraft orbiting Mars and Venu
- …