Efficient and Robust Segmentations Based on Eikonal and Diffusion PDEs

In this paper, we present efficient and simple image segmentations based on the solution of two separate Eikonal equations, each originating from a different region. Distance functions from the interior and exterior regions are computed, and final segmentation labels are determined by a competition criterion between the distance functions. We also consider applying a diffusion partial differential equation (PDE) based method to propagate information in a manner inspired by the information propagation feature of the Eikonal equation. Experimental results are presented in a particular medical image segmentation application, and demonstrate the proposed methods

Efficient segmentation based on Eikonal and diffusion equations

Segmentation of regions of interest in an image has important applications in medical image analysis, particularly in computer aided diagnosis. Segmentation can enable further quantitative analysis of anatomical structures. We present efficient image segmentation schemes based on the solution of distinct partial differential equations (PDEs). For each known image region, a PDE is solved, the solution of which locally represents the weighted distance from a region known to have a certain segmentation label. To achieve this goal, we propose the use of two separate PDEs, the Eikonal equation and a diffusion equation. In each method, the segmentation labels are obtained by a competition criterion between the solutions to the PDEs corresponding to each region. We discuss how each method applies the concept of information propagation from the labelled image regions to the unknown image regions. Experimental results are presented on magnetic resonance, computed tomography, and ultrasound images and for both two-region and multi-region segmentation problems. These results demonstrate the high level of efficiency as well as the accuracy of the proposed methods

Image Analysis and Platform Development for Automated Phenotyping in Cytomics

This thesis is dedicated to the empirical study of image analysis in HT/HC screen study. Often a HT/HC screening produces extensive amounts that cannot be manually analyzed. Thus, an automated image analysis solution is prior to an objective understanding of the raw image data. Compared to general application domain, the efficiency of HT/HC image analysis is highly subjected to image quantity and quality. Accordingly, this thesis will address two major procedures, namely image segmentation and object tracking, in the image analysis step of HT/HC screen study. Moreover, this thesis focuses on expending generic computer science and machine learning theorems into the design of dedicated algorithms for HT/HC image analysis. Additionally, this thesis exemplifies a practical implementation of image analysis and data analysis workflow via empirical case studies with different image modalities and experiment settings. However, the data analysis theorem will be generally illustrated without further expansions. Finally, the thesis will briefly address supplementary infrastructures for end-user interaction and data visualization.Netherlands Bioinformatics CentreComputer Systems, Imagery and Medi

MS FT-2-2 7 Orthogonal polynomials and quadrature: Theory, computation, and applications

Quadrature rules find many applications in science and engineering. Their analysis is a classical area of applied mathematics and continues to attract considerable attention. This seminar brings together speakers with expertise in a large variety of quadrature rules. It is the aim of the seminar to provide an overview of recent developments in the analysis of quadrature rules. The computation of error estimates and novel applications also are described

Generalized averaged Gaussian quadrature and applications

A simple numerical method for constructing the optimal generalized averaged Gaussian quadrature formulas will be presented. These formulas exist in many cases in which real positive GaussKronrod formulas do not exist, and can be used as an adequate alternative in order to estimate the error of a Gaussian rule. We also investigate the conditions under which the optimal averaged Gaussian quadrature formulas and their truncated variants are internal

Simulations of one and two-phase flows in porous microstructures, from tomographic images of gas diffusion layers of proton exchange membrane fuel cells

Hydrogen as an energy carrier is a promising solution for reducing emissions of greenhouse gases. Indeed, hydrogen can be used to store large amounts of energy in a completely carbon-free way. To promote the widespread use of hydrogen energy, it is essential to reduce the cost of fuel cells and increase their durability and performance. The materials in the heart of fuel cells have a strong impact on their performance and durability. In this context, opti-mizing the materials is crucial. We develop in this thesis a modeling approach of porous materials in proton exchange membrane fuel cells. We focus on a specific material that takes part in the gas diffusion layers (GDL). The gas diffusion layers are crossed by gas, electron, heat and water fluxes. To allow such multiple transports, GDL are composed of a fluid phase and a solid phase, itself consisting of several materials. The microstructure of the GDL plays an essential role on the tradeoffs between transports. To model these tradeoffs, we use X-ray tomography to image the microstructure at micrometer scales, and develop digital tools to simulate the transport on tomographic images. We validate the simulations with experimental characterizations and tomographic images of GDL. Great care has been taken in the computer performance of the numerical tools, because tomographic images in three dimensions are a challenge because of the size of the data. The first chapter of this thesis is devoted to modeling of an ex-situ water injection experiment in a GDL. We develop a pore network model extracted from tomographic images, to simulate liquid water flows in GDL in the presence of ca-pillary forces. We validate pore networks simulations using tomographic images showing the liquid water in a GDL dur-ing a water injection experiment. We show that the capillary pressure curves can be determined reliably by pore net-work simulations or full morphology simulations on tomographic images. The second chapter is devoted to one-phase transport simulations in GDL. The first part of this chapter is devoted to the development of pore networks simulations for the diffusivity and the electrical conductivities of the GDL. We de-velop a two-scale simulation methodology, which consists of decomposing the image into elements having simple shapes, and to calibrate physical models on these elements. This method considers the effect of the microstructure on the physical transfers in an economical way, reducing the computing time. We compare the pore network simulations to direct simulation on microstructures and to analytical formulas. The second part is devoted to the comparison of transport simulations with experimental measurements. We show that the transports in the fluid phase can be deter-mined reliably by direct simulations on the tomographic images, while transports in the solid phase require additional information not provided by X-ray tomography. The third chapter is devoted to modeling of the condensation of water in the GDL. The steam produced by the reaction of the hydrogen with the oxygen passes through the GDL and condenses in the cold areas of the GDL. A pore network model coupling diffusion of steam, phase change and capillary forces is developed. We study this model on virtually generated pore networks. The last chapter is devoted to the study of virtually designed microstructures. Virtually exploring new materials designs has advantages over the experimental approach, in terms of speed, cost and control over the microstructures. We show that it is possible to virtually produce microstructures close to those of real materials, to seek optimal microstructures, and control the microstructure to better study some physical effects using simulation

Proceedings of the 10th International Chemical and Biological Engineering Conference - CHEMPOR 2008

This volume contains full papers presented at the 10th International Chemical and Biological Engineering Conference - CHEMPOR 2008, held in Braga, Portugal, between September 4th and 6th, 2008.FC