PIXE projects for students

Water and heat transfers through a material are strongly influenced by the size and structure of the its porosity.
Based on the high-resolution analysis of the porosity by X-ray micro-CT, this  semester project aims at numerically modeling (Flow 3D) the water and heat transfers at the scale of selected samples of a few cm3.

This project is conceived as a pilot study with the major aims to: 1) obtain the pore structure of 2 to 3 samples of building materials from micro-CT analyses 2) import this structure into a modeling software (Flow 3D) and perform simulation tests with different boundary conditions and 3) report on the results and perspectives of this new approach.

This interdisciplinary semester project will be supervised by the R&D teams from the Hydraulic Constructions Platform (G. De Cesare, Azin Amini) and of the PIXE platform (P. Turberg, A. Taureg, G. Perrenoud). 

This project will be composed of lab work (micro-CT measurements), image analysis (3D microstructure analysis) and hydraulic numerical modelling (relationship between 3D microstructures and material hydraulic conductivity). The content of the project will be adapted to the selected material.

The project will be evaluated by a written report and an oral defense.

Contact: Pascal Turberg

The mechanical resistance of vascular plants (e.g. conifers) is strongly influenced by the hardening of the cellulose cell walls due to the lignification process. The lignification is classically characterized, under the microscope, on 2D stained cross sections of a wood stem (above figure, left).
One can hypothesize that lignification could also be identified (in 3D) by high resolution X-ray computed tomography or X-ray micro CT (above figure, middle) since lignified cell walls should appear denser than non-lignified ones (above figure, right).
This semester project aims at testing this hypothesis by comparing, at high resolution, stained cross sections of selected plant species with their micro-CT imaging. To do this, a calibration method for transforming the micro CT grey values into absolute densities has to be set up and results from both methods have to be critically compared.

This project is conceived as a pilot study with the major aims to: 1) obtain high-resolution and high-quality CT slices and stained cross sections on selected vegetal materials, 2) calibrate CT grey values to get density maps of the material and 3) evaluate statistically the correspondence between CT-based density and cross sections-based lignification maps of the material.

This semester project will be supervised by Prof. Charlotte Grossiord (PERL) and Dr. P. Turberg (PIXE). It will be evaluated by a written report and an oral defense.

No prerequisite. Interest for image processing and lab work.

Contact: Pascal Turberg

The analysis of tree rings leads to multiple information on trees and on their environment. In particular, one can determine the age of the tree, the climatic conditions during the growth of the tree, the mechanical stresses that were exerted on the tree as well as the impact of natural or human induced stresses.
This master project aims at testing the micro-CT method to identify and analyze the distributional patterns of rings for different tree species in relation to climatic changes.
This project is conceived as a pilot study with the major aims to: 1) design a methodology to analyze the tree rings from micro-CT images 2) test this methodology on the tree rings of selected tree specimens and 3) report on the pros and cons of this methodology in comparison with present practices.

This master project is interdisciplinary (tree physiology, ecosystem ecology, wood structure, dendrochronology, micro-CT, image analysis) and will be supervised by a team composed of scientists from the UNIGE and EPFL.

No prerequisite. Interest for image processing and lab work.

Contact: Pascal Turberg

Water and heat transfers through a material are strongly influenced by the size and structure of the its porosity.
Based on the high-resolution analysis of the porosity by X-ray micro-CT, this  semester project aims at numerically modeling (Flow 3D) the water and heat transfers at the scale of selected samples of a few cm3.

This project is conceived as a pilot study with the major aims to: 1) obtain the pore structure of 2 to 3 samples of building materials from micro-CT analyses 2) import this structure into a modeling software (Flow 3D) and perform simulation tests with different boundary conditions and 3) report on the results and perspectives of this new approach.

This interdisciplinary semester project will be supervised by the R&D teams from the Hydraulic Constructions Platform (G. De Cesare, Azin Amini) and of the PIXE platform (P. Turberg, A. Taureg, G. Perrenoud). 

This project will be composed of lab work (micro-CT measurements), image analysis (3D microstructure analysis) and hydraulic numerical modelling (relationship between 3D microstructures and material hydraulic conductivity). The content of the project will be adapted to the selected material.

The project will be evaluated by a written report and an oral defense.

Contact: Pascal Turberg

The exploration of rock masses by destructive boreholes is increasing in geotechnical and geothermal engineering as it represents a rapid and cost-efficient method to diagnose the geological conditions of the underground (rock type and rock quality). However, the major drawback of this method stays in the fact that it produces small rock fragments, so-called “cuttings”, which are uneasy to interpret as they provide only very “fragmented” and discontinuous possibilities for petrographic observations and poor information on the state of fracturation of the rock.

A possibility to better characterize these cuttings would be to analyse their shapes and density variations by X-ray computed tomography at high resolution (so-called micro CT) in order to determine indicators which could indirectly reflect either variations in rock content (rock composition) or in rock fracturation or weathering (rock quality). This analytic method produces huge image datasets.

In this lab semester project, one is essentially interested to test the performance of machine learning algorithms to classify rock cuttings from different rock types on the basis of available micro-CT image datasets. This approach could be also applied to other materials (concrete, wood, soils, etc.) according to students’ interests.

This project will be composed of lab work (micro-CT measurements), image analysis (3D microstructure analysis) and machine learning analysis.

This semester project will be supervised by Prof. Alexandre Alahi  (VITA) and Dr. P. Turberg (PIXE). It will be evaluated by a written report and an oral defense.

Contact: Pascal Turberg

Thanks to the new PIXE platform for radioscopy and tomography, the analysis of the internal structure of nearly all materials is possible at the micron scale.
In this project, the objective will be to learn how to determine or represent the microstructure of a given material which is analysed by micro-CT. The student will have to choose a material that interests him/her and whose fine structure is poorly known. He/She will have to better understand the relationships between the 3D microstructure of this material and one of its remarkable properties (e.g. the relation between its voids distribution and its resistance).

This project will be composed of lab work (micro-CT measurements), image analysis (3D microstructure analysis) and microstructure interpretation, representation and/or modelling (relationship between 3D microstructures and physical properties). The content of the project will be adapted to the selected material.

According to the studied material, another teacher of the ENAC faculty will co-supervise the project. This semester project will be supervised by Prof. Charlotte Grossiord (PERL) and Dr. P. Turberg (PIXE). It will be evaluated by a written report and an oral defense.

Contact: Pascal Turberg

The imaging of water transfer in the vessels of vascular plants by X-ray computed tomography (X-ray micro CT) is a challenging objective due to the lack of density contrast between the water and the plant organic material itself. A classical solution to enhance this contrast is the addition of a contrasting agent (e.g. iodine-based) to the water to make it denser than the organic material and thus improve its detection (i.e segmentation) in the plant vessels.
The proposed semester project aims at testing the imaging performances of different contrasting agents (e.g. Lugol’s solution, PTA, PMA, Cesium iodide) in vascular plants with different vessels geometry.

This project is conceived as a pilot study with the major aims to: 1) select the most appropriate contrasting agents and plants based on published results, 2) produce high quality dynamic CT imaging of water transfer with and without contrasting agent, 3) evaluate the effectiveness of the contrasting agent on the detectability of water transfer in the selected plants.

This semester project will be supervised by Prof. Charlotte Grossiord (PERL) and Dr. P. Turberg (PIXE). It will be evaluated by a written report and an oral defense.

No prerequisite. Interest for image processing and lab work.

Contact: Pascal Turberg

The mechanical resistance of vascular plants (e.g. conifers) is strongly influenced by the hardening of the cellulose cell walls due to the lignification process. The lignification is classically characterized, under the microscope, on 2D stained cross sections of a wood stem (above figure, left).
One can hypothesize that lignification could also be identified (in 3D) by high resolution X-ray computed tomography or X-ray micro CT (above figure, middle) since lignified cell walls should appear denser than non-lignified ones (above figure, right).
This semester project aims at testing this hypothesis by comparing, at high resolution, stained cross sections of selected plant species with their micro-CT imaging. To do this, a calibration method for transforming the micro CT grey values into absolute densities has to be set up and results from both methods have to be critically compared.

This project is conceived as a pilot study with the major aims to: 1) obtain high-resolution and high-quality CT slices and stained cross sections on selected vegetal materials, 2) calibrate CT grey values to get density maps of the material and 3) evaluate statistically the correspondence between CT-based density and cross sections-based lignification maps of the material.

This semester project will be supervised by Prof. Charlotte Grossiord (PERL) and Dr. P. Turberg (PIXE). It will be evaluated by a written report and an oral defense.

No prerequisite. Interest for image processing and lab work.

Contact: Pascal Turberg

The analysis of tree rings leads to multiple information on trees and on their environment. In particular, one can determine the age of the tree, the climatic conditions during the growth of the tree, the mechanical stresses that were exerted on the tree as well as the impact of natural or human induced stresses.
This master project aims at testing the micro-CT method to identify and analyze the distributional patterns of rings for different tree species in relation to climatic changes.
This project is conceived as a pilot study with the major aims to: 1) design a methodology to analyze the tree rings from micro-CT images 2) test this methodology on the tree rings of selected tree specimens and 3) report on the pros and cons of this methodology in comparison with present practices.

This master project is interdisciplinary (tree physiology, ecosystem ecology, wood structure, dendrochronology, micro-CT, image analysis) and will be supervised by a team composed of scientists from the UNIGE and EPFL.

No prerequisite. Interest for image processing and lab work.

Contact: Pascal Turberg

Recent micro-CT analyses performed on Opalinus Clay of the Mont Terri (see images above) show a systematic presence of biogenic tubular-like network structures. This bioturbation network developed during the deposition of the clay in a warm and shallow sea before consolidation. Therefore, this network pre-dates the rock deformation and could be used as 3D deformation proxies. This working hypothesis is supported by the fact that these network structures appear more discontinuous in fault zones than outside of them. In addition to the continuity criterion, the density of these structures, their orientation, tortuosity, and relative displacement on either side of the fracture plane could also be deformation markers that would be worth studying. In case the network structure is made of or enriched in soluble carbonates (e.g. calcite), these structures could represent preferential paths of dissolution and could lead to increased rock permeability. Thus, the more continuous these structures are, i.e. in undeformed clay, the higher the permeability due to this dissolution process.
The first part of this project consists of a characterization of the Opalinus Clay as a function of its biogenic structures and a comparison between the typology of these structures and the mechanical and mineralogical properties of the rocks. It aims at evaluating the potential of these biogenic structures to serve as deformation markers.
The second part of this project would consist in measuring by micro-CT, on selected rock samples, the changes in porosity (and permeability) due to the dissolution of the biogenic structures as a function of the degree of continuity of these structures. It aims at evaluating the increase of clay permeability due to the preferential dissolution of biogenic structures.

Main steps of the study:
– Bibliography on clay biogenic structures (mineralogy, mechanical characteristics, undeformed structures, biological context, types of host rocks, generalization to all clay formations, methods of observation, dissolution test, etc.).
– Characterization of undeformed clay biogenic structure and composition (microscopy, micro-CT, other).
– Calibration by in situ step-by-step micro-CT monitoring of the biogenic structures deformation under loading.
– Correlation between biogenic structures and rock deformation (based on Mont-Terri available mechanical, geological and micro-CT data).
– In situ step-by-step micro-CT monitoring of the biogenic structure evolution under dissolution solicitation.
– Correlation between biogenic structures dissolution and rock permeability.
– Results and discussion.
Materials:
– existing core materials and CT measures (e.g. BFS-B1, BPF-2 rock cores)
– new core or rock samples specific to the master thesis

Supervision and collaboration:
EPFL: Prof. Marie Violay EPFL IIC LEMR, Dr. Pascal Turberg, EPFL IIC PIXE
ETHZ/SWISSTOPO: Dr. Martin Ziegler

This Lab project is a great opportunity for students interested in geotechnics, rock deformation and image analysis.

Contact: Pascal Turberg