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  • 1.
    Fernlund, Joanne M. Robison
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Tafesse, Solomon
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Magnusson, Mimmi K.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Total analysis of till using resistivity and 3D image analysisArticle in journal (Other academic)
  • 2.
    Fernlund, Joanne
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Tafesse, Solomon
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Magnusson, Mimmi
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Lithological analysis of multiple size fractions of tillArticle in journal (Other academic)
  • 3.
    Tafesse, Solomon
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Physical characterization of coarse clasts with 3D image-analysis method: development, evaluation and application2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents a novel three dimensional (3D) image-analysis method for characterizing the physical characteristics of coarse particles in the field, and introduces new methodology for the total analysis of glacial till samples.

    The novel image analysis method, called the GID method, is capable of determining the size, shape and surface texture of each individual clast analysed. Images of particles are taken in the field and analysis is done in the laboratory. Therefore the GID method makes it feasible to analyse statistically representative large sample in short period; for poorly sorted sediments, such as till, one-tonne is required if the analysis includes cobble size. The capability of the GID method was demonstrated by studying coarse clasts (20-200 mm) from till. There is excellent agreement in the results of the size distribution obtained from the GID method and sieve analysis. The GID method results for size and shape parameters show high and very high repeatability. The particle angularity in the GID method has not been measured to acceptable level; the repeatability test shows some variability.

    The new methodology for total analysis of till applied the GID method at four different locations in Sweden. The total analysis included 3D size and shape distribution of coarse particles coupled to electrical resistivity, lithological distribution and magnetic susceptibility of the clasts. The results show clear difference in the till samples from the different sites.

  • 4.
    Tafesse, Solomon
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Physical properties of coarse particles in till coupled to bedrock composition based on new 3D image analysis method2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The physical properties of the coarse fraction of the till (0.4 to 20 cm) and the surface boulders have been studied at two different sites in Sweden. The research work included: development of a new image analysis software for 3D size and shape measurements of particles; lithological analysis on multiple size fractions in till and magnetic susceptibility survey on coarse till clasts, surface boulders and local bedrock.

    The new 3D image analysis method provides an enormous amount of size and shape data for each particle in the coarse fraction (2 to 20 cm) in till. The method is suitable for field study, cost effective and the software is executable in Matlab. The field imaging method together with the image analysis software give non subjective results of size and shape of coarse particles and makes it feasible and easy to study representative sample size, which is one tonne for testing clasts of size up to 20 cm.

    The lithological analysis of the multiple size fraction of the till clasts has been investigated on six different size fractions of the till (0.4 to 20 cm); the result of the different samples from the two sites shows that this method can potentially be used as a stratigraphic tool in the areas where there is no unique indicator lithologies.

    The magnetic susceptibility has been made on the surface boulders, the 6-20 cm till fraction and on insitu bedrock outcrops near to the study sites. The method has good potential for determining stratigraphic relationships between different till units as well as for determining the provenance ofcoarse clasts and surface boulders.

  • 5.
    Tafesse, Solomon
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Fernlund, Joanne
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Bergholm, Fredrik
    KTH, School of Technology and Health (STH), Medical Engineering.
    Digital sieving-Matlab based 3-D image analysis2012In: Engineering Geology, ISSN 0013-7952, E-ISSN 1872-6917, Vol. 137-138, p. 74-84Article in journal (Refereed)
    Abstract [en]

    A new image analysis technique for determining the three-dimensional size and shape distribution of coarse particles has been developed. It entails acquiring a pair of images, one each of the maximum and minimum projected area of the particles. Glow-In-the-Dark beads were used to create luminous background, thus it is named the GID method. In this study the size and shape distribution of four coarse-grained samples, size varies from 2 to 20. cm, have been analyzed. The size distribution of the samples obtained from the GID analysis is comparable to sieve analysis results, and has an extra advantage of being applicable in the field. The algorithm was developed in Matlab; therefore users could make some optimization in the program to meet their own needs as the program code is open source.

  • 6.
    Tafesse, Solomon
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Fernlund, Joanne M. Robison
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Repeatability of GID Image-analysis method for assessment size, shape and angularity of coarse particlesIn: Engineering Geology, ISSN 0013-7952, E-ISSN 1872-6917Article in journal (Other academic)
  • 7.
    Tafesse, Solomon
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Fernlund, Joanne M. Robison
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Sun, Wenjuan
    Bergholm, Fredrik
    KTH, School of Technology and Health (STH), Medical Engineering.
    Evaluation of image analysis methods for the quantification of particle angularityIn: Sedimentology, ISSN 0037-0746, E-ISSN 1365-3091Article in journal (Other academic)
  • 8.
    Tafesse, Solomon
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Robison Fernlund, Joanne M.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Sun, Wenjuan
    Bergholm, Fredrik
    KTH, School of Technology and Health (STH), Medical Engineering.
    Evaluation of image analysis methods used for quantification of particle angularity2013In: Sedimentology, ISSN 0037-0746, E-ISSN 1365-3091, Vol. 60, no 4, p. 1100-1110Article in journal (Refereed)
    Abstract [en]

    Angularity is an important parameter in the characterization of particle morphology that is used to interpret the transport history of particles in sedimentary deposits. In the past, visual classification using silhouette charts was widely used to determine particle angularity, but this approach is subjective and time-consuming. With advances in modern image analysis techniques and low-cost software packages, it is possible to rapidly quantify particle angularity more objectively than using visual classification methods. This study re-examines the performance of three existing image analysis methods and one new image analysis procedure, applied to six rock and sediment samples that were visually different in angularity. To facilitate comparison between the angularity results, measurements were reduced to rankings for each aggregate sample. These results show that the four image analysis methods rank the angularity of the samples differently, and that none rank the mean angularity index in the same order as the angularity ranking using visual classification. Therefore, further research is needed to develop an image analysis method that can quantify the angularity of sedimentary particles more precisely.

  • 9.
    Tafesse, Solomon
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Sun, Wenjuan
    Virginia Tech, Department of Civil and Environmental Engineering.
    Fernlund, Joanne
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Engineering Geology and Geophysics.
    Linbing, Wang
    Virginia Tech, Department of Civil and Environmental Engineering.
    A New Image Analysis Technique to Quantify Particle AngularityArticle in journal (Refereed)
    Abstract [en]

    Angularity is a fundamental morphological descriptor of a particle; it determines the aggregate performance in asphalt and concrete works. This paper introduces an innovative matlab based image analysis technique to quantify the angularity of an aggregate. The algorithm is based on application of two successive b-spline smoothing techniques around the aggregate profile. The first b-spline smoothing curve is generated by joining the mid-points of the adjacent segments; and the second smoothing curve is generated by a smoothing function upon the first b-spline. Then the distribution of the perpendicular distance between these two-b-splines is evaluated, which provides an excellent estimate to the aggregate angularity. In this paper the angularity index of six aggregate samples is determined using our new technique. Then we compared the index obtained with an existing Aggregate Imaging Measurement System (AIMS) and the measurement from the two methods revealed good similarity. Therefore our new method can be considered as a useful alternative in the aggregate industry for distinguishing the angularity of the samples obtained from different sources.

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