An improved two-dimensional agglomerate cathode model to study the influence of catalyst layer structural parameters

2005 ◽  
Vol 50 (16-17) ◽  
pp. 3359-3374 ◽  
Author(s):  
Wei Sun ◽  
Brant A. Peppley ◽  
Kunal Karan
Keyword(s):  
Structural Parameters ◽  
Catalyst Layer ◽  
Two Dimensional

Least-Squares Parameter Estimation for Catalyst Layer Agglomerate Models

2010 ◽  
Author(s):  
Peter Dobson ◽  
Marc Secanell
Keyword(s):  
Parameter Estimation ◽  
Fuel Cell ◽  
Least Squares ◽  
Least Squares Method ◽  
Structural Parameters ◽  
Catalyst Layer ◽  
Operating Conditions ◽  
Membrane Electrode ◽  
Two Dimensional

A framework is presented to estimate the micro-structural parameters of cathode fuel cell electrodes by means of a nonlinear least-squares method. This work represents the first attempt in the literature to characterize the structure of the catalyst layer by numerical parameter estimation using a two-dimensional membrane electrode assembly model with an ionomer-filled agglomerate catalyst layer approximation. The framework is developed by coupling a two-dimensional model to an optimization based least-squares algorithm in DAKOTA. The algorithm, NL2SOL, minimizes the sum-of-squares of the residuals for any number of data points and parameters. Employing the proposed methodology allows for accurate characterization of the electrode structure and quantification the quality of the curve fit. Extension of this methodology allows for parameter estimation as novel materials are incorporated into fuel cell construction. Results indicate that curves can be fit using micro-structural and electrochemical parameters consistent with values published in the literature. However, the quality of the fit deteriorates for large data sets over the entire range of operating conditions.

The response of a turbulent boundary layer to lateral divergence

1979 ◽  
Vol 94 (2) ◽  
pp. 243-268 ◽  
Author(s):  
A. J. Smits ◽  
J. A. Eaton ◽  
P. Bradshaw
Keyword(s):  
Boundary Layer ◽  
Circular Cylinder ◽  
Turbulent Boundary Layer ◽  
Structural Parameters ◽  
Axial Flow ◽  
Turbulence Structure ◽  
Two Dimensional ◽  
Transition Section ◽  
Two Dimensional Flow ◽  
Made In

Measurements have been made in the flow over an axisymmetric cylinder-flare body, in which the boundary layer developed in axial flow over a circular cylinder before diverging over a conical flare. The lateral divergence, and the concave curvature in the transition section between the cylinder and the flare, both tend to destabilize the turbulence. Well downstream of the transition section, the changes in turbulence structure are still significant and can be attributed to lateral divergence alone. The results confirm that lateral divergence alters the structural parameters in much the same way as longitudinal curvature, and can be allowed for by similar empirical formulae. The interaction between curvature and divergence effects in the transition section leads to qualitative differences between the behaviour of the present flow, in which the turbulence intensity is increased everywhere, and the results of Smits, Young & Bradshaw (1979) for a two-dimensional flow with the same curvature but no divergence, in which an unexpected collapse of the turbulence occurred downstream of the curved region.

Parametric Analysis of the Cathode Catalyst Layer of Proton Exchange Membrane Fuel Cells Using Artificial Neural Network

2011 ◽  
Author(s):  
N. Khajeh-Hosseini-Dalasm ◽  
S. Ahadian ◽  
K. Fushinobu ◽  
K. Okazaki
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Proton Exchange Membrane ◽  
Structural Parameters ◽  
Catalyst Layer ◽  
Proton Exchange ◽  
Cathode Catalyst ◽  
Cathode Catalyst Layer ◽  
Artificial Neural ◽  
Exchange Membrane

A mathematical model was developed to study the cathode catalyst layer (CL) performance of a proton exchange membrane fuel cell (PEMFC). A number of CL parameters affecting its performance are implemented into the CL agglomerate model. These parameters are: saturation and eight structural parameters, i.e., ionomer film thickness covering the agglomerate, agglomerate radius, platinum and carbon loading, membrane content, gas diffusion layer penetration content and CL thickness. An artificial neural network (ANN) approach along with statistical methods was used for modeling, prediction, and analysis of the CL performance, which is determined by activation over-potential. The ANN was constructed to develop a relationship between the named (input) parameters and activation overpotential. An statistical analysis, namely, analysis of means (ANOM) was performed on the data obtained by the trained ANN and resulted in the main effect of each input parameter, sensitivity factors of structural parameters and their mutual combination.

SAXS of self-assembled nanocomposite films with oriented two-dimensional cylinder arrays: an advanced method of evaluation

2005 ◽  
Vol 38 (1) ◽  
pp. 78-86 ◽  
Author(s):  
Wilhelm Ruland ◽  
Bernd Smarsly
Keyword(s):  
Structural Parameters ◽  
Hexagonal Lattice ◽  
Preferred Orientation ◽  
Nanocomposite Films ◽  
Two Dimensional ◽  
Advanced Method ◽  
Cylinder Arrays ◽  
X Ray Scattering ◽  
Comparable Method ◽  
Method Of Evaluation

In a recent paper [Ruland & Smarsly (2002).J. Appl. Cryst.35, 624–633], an advanced method for the evaluation of the small-angle X-ray scattering (SAXS) from oriented lamellar systems was presented. In the present work, a comparable method is developed for the study of oriented cylinder arrays. Basic differences between the two methods are found in the way in which the preferred orientation affects the intensity distribution. The method is applied to the SAXS of SiO2-surfactant nanocomposite films which contain highly oriented arrays of cylinders. It is shown that up to eight structural parameters can be obtained by this method which characterize size, imperfection and preferred orientation of the two-dimensional hexagonal lattice formed by the cylinders, the radius and the polydispersity of the cylinders, and the interface boundary.

A Parametric Study of Bipolar Plate Structural Parameters on the Performance of Proton Exchange Membrane Fuel Cell

2012 ◽  
Vol 9 (5) ◽  
Author(s):  
Salar Imanmehr ◽  
Nader Pourmahmod
Keyword(s):  
Fuel Cell ◽  
Proton Exchange Membrane ◽  
Structural Parameters ◽  
Catalyst Layer ◽  
Cell Polarization ◽  
Proton Exchange ◽  
Bipolar Plates ◽  
Fuel Cell Performance ◽  
Exchange Membrane ◽  
The Impact

In this research, the impact of structural parameters of bipolar plates on the proton exchange membrane (PEM) fuel cell performance has been investigated using numerical method, and this model incorporates all the essential fundamental physical and electrochemical processes occurring in the membrane electrolyte, cathode catalyst layer, electrode backing, and flow channel, with some assumptions in each part. In formulation of this model, the cell is assumed to work under steady state conditions. Also, since the thickness of the cell is negligible compared to other dimensions, one-dimensional and isothermal approximations are used. The structural parameters considered in this paper are: the width of channels (Wc), the width of support (Ws), the number of gas channels (ng), the height of channels (hc), and the height of supports (hp). The results show that structural parameters of bipolar plates have a great impact on outlet voltage in high current densities. Also, the number of gas channels, their surface area, the contacting area of bipolar plates, and electrodes have a great effect on the rate of reaction and consequently on outlet voltage. The model predictions have been compared with the existing experimental results available in the literature, and excellent agreement has been demonstrated between the model results and the experimental data for the cell polarization curve.

An Investigation Into the Characteristics of a Two Dimensional “2D” Flow Control Valve

2001 ◽  
Vol 124 (1) ◽  
pp. 214-220 ◽  
Author(s):  
J. Ruan ◽  
R. Burton ◽  
P. Ukrainetz
Keyword(s):  
Flow Control ◽  
Flow Rate ◽  
Structural Parameters ◽  
Control Valve ◽  
Favorable Effect ◽  
Flow Control Valve ◽  
Two Dimensional ◽  
System Pressure ◽  
Hydrostatic Force ◽  
2D Flow

In hydraulic servo systems, a pilot stage is often used to reduce the influence of Bernoulli’s forces and frictional forces when trying to accurately position a spool. A unique pilot controlled valve (defined as a two dimensional or “2D” flow control valve), which utilizes both rotary and linear motions of a single spool, is presented. The rotary motion uses a spiral groove in the sleeve combined with high and low pressure holes on the spool land to control the pressure in the spool chamber, while the linear motion of the spool is actuated by a hydrostatic force. Both linear theory and numerical simulation are adopted in the investigation of the characteristics of the valve. A criterion for stability is established from a linearized model of the valve. The analysis establishes the effects that certain structural parameters have on the valve’s static and dynamic characteristics. Special experimental procedures were designed to obtain properties such as mechanical stiffness, leakage flow rate, and dynamic response under different structural parameters and system pressure. It was shown that the leakage through the spool-sleeve clearance had a favorable effect on the valve stability. Theoretical and experimental results show that it is necessary to establish a balance between the static and dynamic performance in establishing appropriate structural parameters. It is also shown that the 2D flow control valve can demonstrate a high speed of response, while maintaining the pilot flow rate at a low level.

scholarly journals Automatic reconstruction of polycrystalline ice microstructure from image analysis: application to the EPICA ice core at Dome Concordia, Antarctica

1999 ◽  
Vol 45 (151) ◽  
pp. 547-554 ◽  
Author(s):  
Michel Gay ◽  
Jerome Weiss
Keyword(s):  
Preliminary Analysis ◽  
Structural Parameters ◽  
Ice Core ◽  
Grain Morphology ◽  
Two Dimensional ◽  
Cross Sectional ◽  
Thin Sections ◽  
Polycrystalline Ice ◽  
Analysis Application ◽  
The Mean

AbstractA digital image-processing approach is proposed which allows the extraction of two-dimensional polycrystalline ice microstructure (grain boundaries) from thin sections observed between cross-polarisers. It is based on image segmentation of colour images. The method is applied to the preliminary analysis of the shallow ( Holocene) ice of the European Project for Ice Coring in Antarctica (EPICA) ice core at Dome Concordia. Structural parameters, such as the mean cross-sectional area, shape anisotropy and grain morphology, are obtained. The interest and limitations of this automatic procedure are discussed.

scholarly journals Geometrical frustration as a potential design principle for peptide-based assemblies

2017 ◽  
Vol 7 (6) ◽  
pp. 20160141 ◽  
Author(s):  
Tao Jiang ◽  
Elizabeth L. Magnotti ◽  
Vincent P. Conticello
Keyword(s):  
Self Assembly ◽  
Rational Design ◽  
Structural Parameters ◽  
Two Dimensional ◽  
Protein Assemblies ◽  
Geometrical Frustration ◽  
Protein Motifs ◽  
Planar Shapes ◽  
And Function

Two-dimensional peptide and protein assemblies have been the focus of increased scientific research as they display significant potential for the creation of functional nanomaterials. Soluble subunits derived from a variety of protein motifs have been demonstrated to self-assemble into structurally defined nanosheets under environmentally benign conditions in which the components often retain their native structure and function. These types of two-dimensional assemblies may have an advantage for nanofabrication in that their extended planar shapes can be more straightforwardly incorporated into the current formats of nanoscale devices. However, significant challenges remain in the fabrication of these materials, particularly in devising methods to control the size, shape and internal structure of the resultant materials. Geometrical frustration may be envisioned as a possible mechanism to exert control over these structural parameters through rational design. While this objective has yet to be realized in practice, we discuss in this article the potential role of geometrical frustration as a principle to rationalize unusual self-assembly behaviour in several examples of two-dimensional peptide assemblies.

Octagonal symmetry in low-discrepancy β-manganese

2014 ◽  
Vol 70 (5) ◽  
pp. 441-447 ◽  
Author(s):  
Wolfgang Hornfeck ◽  
Philipp Kuhn
Keyword(s):  
Interatomic Distance ◽  
Structural Parameters ◽  
Structural Chemistry ◽  
Structural Parameter ◽  
Two Dimensional ◽  
Ideal Structure ◽  
Big 4 ◽  
Wide Range ◽  
Star Discrepancy ◽  
Made In

A low-discrepancy cubic variant of β-Mn is presented exhibiting local octagonal symmetry upon projection along any of the three mutually perpendicular 〈100〉 axes. Ideal structural parameters are derived to be x(8c) = (2-\sqrt{2})\big/16 and y(12d) = 1\big/(4 \sqrt{2}) for theP4132 enantiomorph. A comparison of the actual and ideal structure models of β-Mn is made in terms of the newly devised concept of geometrical discrepancy maps. Two-dimensional maps of both the geometrical star discrepancyD*and the minimal interatomic distancedminare calculated over the combined structural parameter range 0 \leq x(8c) \,\lt\, 1/8 and 1/8 \leq y(12d)\, \lt\, 1/4 of generalized β-Mn type structures, showing that the `octagonal' variant of β-Mn is almost optimal in terms of globally minimizingD*while at the same time globally maximizingdmin. Geometrical discrepancy maps combine predictive and discriminatory powers to appear useful within a wide range of structural chemistry studies.

Sign in / Sign up

Export Citation Format

Share Document