25,178 research outputs found
Biomimetic flow fields for proton exchange membrane fuel cells: A review of design trends
Bipolar Plate design is one of the most active research fields in Polymer Electrolyte Membrane Fuel Cells (PEMFCs) development. Bipolar Plates are key components for ensuring an appropriate water management within the cell, preventing flooding and enhancing the cell operation at high current densities. This work presents a literature review covering bipolar plate designs based on nature or biological structures such as fractals, leaves or lungs. Biological inspiration comes from the fact that fluid distribution systems found in plants and animals such as leaves, blood vessels, or lungs perform their functions (mostly the same functions that are required for bipolar plates) with a remarkable efficiency, after millions of years of natural evolution. Such biomimetic designs have been explored to date with success, but it is generally acknowledged that biomimetic designs have not yet achieved their full potential. Many biomimetic designs have been derived using computer simulation tools, in particular Computational Fluid Dynamics (CFD) so that the use of CFD is included in the review. A detailed review including performance benchmarking, time line evolution, challenges and proposals, as well as manufacturing issues is discussed.Ministerio de Ciencia, Innovación y Universidades ENE2017-91159-EXPMinisterio de Economía y Competitividad UNSE15-CE296
Analytical modeling and 3D finite element simulation of line edge roughness in scatterometry
The influence of edge roughness in angle resolved scatterometry at
periodically structured surfaces is investigated. A good description of the
radiation interaction with structured surfaces is crucial for the understanding
of optical imaging processes like, e.g. in photolithography. We compared an
analytical 2D model and a numerical 3D simulation with respect to the
characterization of 2D diffraction of a line grating involving structure
roughness. The results show a remarkably high agreement. The diffraction
intensities of a rough structure can therefore be estimated using the numerical
simulation result of an undisturbed structure and an analytically derived
correction function. This work allows to improve scatterometric results for the
case of practically relevant 2D structures
Open source environment to define constraints in route planning for GIS-T
Route planning for transportation systems is strongly related to shortest path algorithms, an optimization problem extensively studied in the literature. To find the shortest path in a network one usually assigns weights to each branch to represent the difficulty of taking such branch. The weights construct a linear preference function ordering the variety of alternatives from the most to the least attractive.Postprint (published version
VisIVOWeb: A WWW Environment for Large-Scale Astrophysical Visualization
This article presents a newly developed Web portal called VisIVOWeb that aims
to provide the astrophysical community with powerful visualization tools for
large-scale data sets in the context of Web 2.0. VisIVOWeb can effectively
handle modern numerical simulations and real-world observations. Our
open-source software is based on established visualization toolkits offering
high-quality rendering algorithms. The underlying data management is discussed
with the supported visualization interfaces and movie-making functionality. We
introduce VisIVOWeb Network, a robust network of customized Web portals for
visual discovery, and VisIVOWeb Connect, a lightweight and efficient solution
for seamlessly connecting to existing astrophysical archives. A significant
effort has been devoted for ensuring interoperability with existing tools by
adhering to IVOA standards. We conclude with a summary of our work and a
discussion on future developments
Visualization, Exploration and Data Analysis of Complex Astrophysical Data
In this paper we show how advanced visualization tools can help the
researcher in investigating and extracting information from data. The focus is
on VisIVO, a novel open source graphics application, which blends high
performance multidimensional visualization techniques and up-to-date
technologies to cooperate with other applications and to access remote,
distributed data archives. VisIVO supports the standards defined by the
International Virtual Observatory Alliance in order to make it interoperable
with VO data repositories. The paper describes the basic technical details and
features of the software and it dedicates a large section to show how VisIVO
can be used in several scientific cases.Comment: 32 pages, 15 figures, accepted by PAS
Helicity of convective flows from localized heat source in a rotating layer
Experimental and numerical study of the steady-state cyclonic vortex from
isolated heat source in a rotating fluid layer is described. The structure of
laboratory cyclonic vortex is similar to the typical structure of tropical
cyclones from observational data and numerical modelling including secondary
flows in the boundary layer. Differential characteristics of the flow were
studied by numerical simulation using CFD software FlowVision. Helicity
distribution in rotating fluid layer with localized heat source was analysed.
Two mechanisms which play role in helicity generation are found. The first one
is the strong correlation of cyclonic vortex and intensive upward motion in the
central part of the vessel. The second one is due to large gradients of
velocity on the periphery. The integral helicity in the considered case is
substantial and its relative level is high
- …