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Exploring the Invisible: FINDING STRUCTURE IN SCIENTIFIC DATA
Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering. (Scientific Visualization)
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, I present contributions towards the aim of understanding flow-related scientific data sets by communicating relation, properties, and structure. The individual papers are contributions to three different areas. First, real-world visualization challenges with domain specific tasks. The individual applications are ranging from analyzing transport behavior in a centrifugal pump, to visualization of the impact of volcano eruptions and their atmospheric aftermath, and studying circulation dynamics and eddy movements in the ocean currents of the Red Sea. Although the three individual publications target different domains, they share common demands. Furthermore, the experience shows that combining and adapting different visualization techniques to support experts is essential for these scenarios. Second, technical visualization research with a strong focus on geometry-based, interactive, and explorative techniques. In this area a new type of particle system and a novel geometry-based flow visualization technique based on evolutionary algorithms are presented. With both approaches, areas of interest can be highlighted in a semi-automatic fashion by facilitating user-defined importance measures. Lastly, a method for decoupling definition and tracking of features. Here, the development of a fast but flexible method for defining and tracking cyclonic features in pressure fields using a solid and robust mathematical basis is presented. The initial theoretical work is discussed in context of its practical applications by pointing to relevant follow-up publications.

The experience from real-world visualization tasks shows that understanding and gaining insight of scientific data with the help of visualization is an interactive, explorative, and non-linear process. Here, different methods must be combined and adapted such that they complement each other. Through this practice, relation, properties, and structure can be revealed, and a mental model can be created.

From the real-world visualization challenges and the contributions in research, demands on techniques and their embedding in a visualization toolkit can be derived. Here, the ideal software is flexible, adaptable, and allows for interactive exploration. Furthermore, the process is benefiting from a semi-automatic approach guiding the domain expert during analysis. These aspects are used as guidelines for the implementation and development work associated with the contributions of this thesis and are presented in a dedicated Chapter.

Abstract [sv]

Med denna avhandling presenterar jag bidrag som syftar till att förstå flödesrelaterade vetenskapliga datamängder genom att kommunicera relationer, egenskaper och struktur. De enskilda artiklarna i avhandlingen bidrar med kunskap till tre olika områden. Det första bidraget berör verkliga visualiseringsutmaningar med domänspecifika uppgifter. De individuella tillämpningarna sträcker sig från att analysera transportbeteende i en centrifugalpump till visualisering av effekterna av vulkanutbrott och deras atmosfäriska efterverkningar, samt att studera cirkulationsdynamik och virvelrörelser i Röda havets havsströmmar. Även om de tre enskilda publikationerna riktar sig till olika domäner delar de gemensamma krav, och erfarenheten visar att kombination och anpassning av olika visualiseringstekniker för att stödja experter i deras arbete är avgörande för dessa scenarier. Det andra bidraget är undersökning av teknisk visualiseringsforskning med starkt fokus på geometribaserade, interaktiva och utforskande tekniker. Detta bidrag presenterar en ny typ av partikelsystem samt en grupp metoder baserade på evolutionära algoritmer. Med båda tillvägagångssätten kan områden av intresse lyftas fram på ett halvautomatiskt sätt genom att underlätta användardefinierade betydelseåtgärder. Det tredje bidraget är en metod för att frikoppla definition och spårning av funktioner. Detta bidrag presenterar utvecklingen av en snabb men flexibel metod för att definiera och spåra cyklonegenskaper i tryckfält med hjälp av en solid och robust matematisk grund. Det första teoretiska arbetet sätts också i praktisk tillämpning med en uppföljande publikation.

Erfarenheterna från en verklig visualiseringsuppgift visar att förståelse och insikt i vetenskapliga data med hjälp av visualisering är en interaktiv, utforskande och icke-linjär process. Här måste olika metoder kombineras och anpassas så att de kompletterar varandra. Genom att göra så kan relationer, egenskaper och struktur i data avslöjas och en mental modell kan skapas.

Utifrån detta kan sedan krav skapas, både krav på visualiseringsteknikerna och krav på hur visualiseringsverktyg ska användas. Programvaran som används bör då vara flexibel, anpassningsbar och möjliggöra interaktiv utforskning. Dessutom drar data-analysprocessen nytta av ett halvautomatiskt tillvägagångssätt som styr domänexporten under analysen. Dessa aspekter har använts som riktlinjer för genomförandet och utvecklingsarbetet i samband med bidragen i denna avhandling.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2022. , p. 123
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 2192
National Category
Computer Sciences
Identifiers
URN: urn:nbn:se:liu:diva-183844DOI: 10.3384/9789179291266ISBN: 9789179291259 (print)ISBN: 9789179291266 (electronic)OAI: oai:DiVA.org:liu-183844DiVA, id: diva2:1647322
Public defence
2022-04-29, Täppan - TPM55, Bredgatan 33 602 21 Norrköping, Norrköping, 13:00 (English)
Opponent
Supervisors
Available from: 2022-04-07 Created: 2022-03-25 Last updated: 2022-05-16Bibliographically approved
List of papers
1. Atmospheric Impact of Volcano Eruptions
Open this publication in new window or tab >>Atmospheric Impact of Volcano Eruptions
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2014 (English)In: Proceedings IEEE SciVis 2014, Publication Server of Zuse Institute Berlin (ZIB) , 2014Conference paper, Oral presentation only (Refereed)
Abstract [en]

The analysis of data that captures volcanic eruptions and their atmospheric aftermath plays an important role for domain experts to gain a deeper understanding of the volcanic eruption and their consequences for atmosphere, climate and air traffic. Thereby, one major challenge is to extract and combine the essential information, which is spread over various, mostly sparse data sources. This requires a careful integration of each data set with its strength and limitations. The sparse, but more reliable measurement data is mainly used to calibrate the more dense simulation data. This work combines a collection of visualization approaches into an exploitative framework. The goal is to support the domain experts to build a complete picture of the situation. But it is also important to understand the individual data sources, the wealth of their information and the quality of the simulation results. All presented methods are designed for direct interaction with the data from different perspectives rather than the sole generation of some final images.

Place, publisher, year, edition, pages
Publication Server of Zuse Institute Berlin (ZIB), 2014
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:liu:diva-152358 (URN)
Conference
IEEE VIS 2014,9-14 November, Paris, France
Available from: 2018-10-30 Created: 2018-10-30 Last updated: 2022-03-25Bibliographically approved
2. Autonomous Particles for Interactive Flow Visualization
Open this publication in new window or tab >>Autonomous Particles for Interactive Flow Visualization
2019 (English)In: Computer graphics forum (Print), ISSN 0167-7055, E-ISSN 1467-8659, no 1, p. 248-259Article in journal (Refereed) Published
Abstract [en]

We present an interactive approach to analyse flow fields using a new type of particle system, which is composed of autonomous particles exploring the flow. While particles provide a very intuitive way to visualize flows, it is a challenge to capture the important features with such systems. Particles tend to cluster in regions of low velocity and regions of interest are often sparsely populated. To overcome these disadvantages, we propose an automatic adaption of the particle density with respect to local importance measures. These measures are user defined and the systems sensitivity to them can be adjusted interactively. Together with the particle history, these measures define a probability for particles to multiply or die, respectively. There is no communication between the particles and no neighbourhood information has to be maintained. Thus, the particles can be handled in parallel and support a real‐time investigation of flow fields. To enhance the visualization, the particles' properties and selected field measures are also used to specify the systems rendering parameters, such as colour and size. We demonstrate the effectiveness of our approach on different simulated vector fields from technical and medical applications.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
flow visualization, scientific visualization, visualization, real-time rendering, Visualization Human-centered computing: Visualization application domains–Scientific Visualization
National Category
Computer Sciences
Identifiers
urn:nbn:se:liu:diva-151724 (URN)10.1111/cgf.13528 (DOI)000462660600016 ()
Conference
EuroVis 2018, Conference on Visualization 4-8 June, Czech Republic
Note

Funding agencies: Stiftelsen for Strategisk Forskning Sweden (SSF) [BD15-0082]; Excellence Center at Linkoping and Lund in Information Technology (ELLIIT); Swedish e-Science Research Centre (SeRC)

Available from: 2018-10-03 Created: 2018-10-03 Last updated: 2022-03-25Bibliographically approved
3. Evolutionary Lines for Flow Visualization
Open this publication in new window or tab >>Evolutionary Lines for Flow Visualization
2018 (English)In: EuroVis 2018, 20th EG/VGTC Conference on Visualization, 4-8 June, Brno, Czech Republic / [ed] Jimmy Johansson and Filip Sadlo and Tobias Schreck, The Eurographics Association , 2018, p. 7-11Conference paper, Published paper (Refereed)
Abstract [en]

In this work we explore evolutionary algorithms for selected a visualization application. We demonstrate its potential using an example from flow visualization showing promising first results. Evolutionary algorithms, as guided search approach, find close-to-optimal solutions with respect to some fitness function in an iterative process using biologically motivated mechanisms like selection, mutation and recombination. As such, they provide a powerful alternative to filtering methods commonly used in visualization where the space of possible candidates is densely sampled in a pre-processing step from which the best candidates are selected and visualized. This approach however tends to be increasingly inefficient with growing data size or expensive candidate computations resulting in large pre-processing times. We present an evolutionary algorithm for the problem of streamline selection to highlight features of interest in flow data. Our approach directly optimizes the solution candidates with respect to a user selected fitness function requiring significantly less computations. At the same time the problem of possible under-sampling is solved since we are not tied to a preset resolution. We demonstrate our approach on the well-known flow around an obstacle as case with a two-dimensional search space. The blood flow in an aneurysm serves as an example with a three-dimensional search space. For both, the achieved results are comparable to line filtering approaches with much less line computations.

Place, publisher, year, edition, pages
The Eurographics Association, 2018
National Category
Computer Sciences
Identifiers
urn:nbn:se:liu:diva-151725 (URN)10.2312/eurovisshort.20181070 (DOI)9783038680604 (ISBN)
Conference
EuroVis 2018, 20th EG/VGTC Conference on Visualization, 4-8 June, Brno, Czech Republic
Available from: 2018-10-03 Created: 2018-10-03 Last updated: 2022-03-25
4. Evolutionary Pathlines for Blood Flow Exploration in Cerebral Aneurysms
Open this publication in new window or tab >>Evolutionary Pathlines for Blood Flow Exploration in Cerebral Aneurysms
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2019 (English)In: Eurographics Workshop on Visual Computing for Biology and Medicine / [ed] Kozlíková, Barbora and Linsen, Lars and Vázquez, Pere-Pau and Lawonn, Kai and Raidou, Renata Georgia, The Eurographics Association , 2019Conference paper, Published paper (Refereed)
Abstract [en]

Blood flow simulations play an important role for the understanding of vascular diseases, such as aneurysms. However, analysis of the resulting flow patterns, especially comparisons across patient groups, are challenging. Typically, the hemodynamic analysis relies on trial and error inspection of the flow data based on pathline visualizations and surface renderings. Visualizing too many pathlines at once may obstruct interesting features, e.g., embedded vortices, whereas with too little pathlines, particularities such as flow characteristics in aneurysm blebs might be missed. While filtering and clustering techniques support this task, they require the pre-computation of pathlines densely sampled in the space-time domain. Not only does this become prohibitively expensive for large patient groups, but the results often suffer from undersampling artifacts. In this work, we propose the usage of evolutionary algorithms to reduce the overhead of computing pathlines that do not contribute to the analysis, while simultaneously reducing the undersampling artifacts. Integrated in an interactive framework, it efficiently supports the evaluation of hemodynamics for clinical research and treatment planning in case of cerebral aneurysms. The specification of general optimization criteria for entire patient groups allows the blood flow data to be batch-processed. We present clinical cases to demonstrate the benefits of our approach especially in presence of aneurysm blebs. Furthermore, we conducted an evaluation with four expert neuroradiologists. As a result, we report advantages of our method for treatment planning to underpin its clinical potential.  

Place, publisher, year, edition, pages
The Eurographics Association, 2019
Keywords
Human-centered computing, Scientific visualization
National Category
Cardiac and Cardiovascular Systems
Identifiers
urn:nbn:se:liu:diva-184202 (URN)10.2312/vcbm.20191250 (DOI)978-3-03868-081-9 (ISBN)
Conference
VCBM 19: Eurographics Workshop on Visual Computing for Biology and Medicine
Available from: 2022-04-07 Created: 2022-04-07 Last updated: 2022-04-07
5. Topology-Based Feature Design and Tracking for Multi-center Cyclones
Open this publication in new window or tab >>Topology-Based Feature Design and Tracking for Multi-center Cyclones
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2021 (English)In: Topological Methods in Data Analysis and Visualization VI: Theory, Applications, and Software / [ed] Ingrid Hotz, Talha Bin Masood, Filip Sadlo and Julien Tierny, Springer, 2021, p. 71-85Chapter in book (Refereed)
Abstract [en]

In this paper, we propose a concept to design, track, and compare application-specific feature definitions expressed as sets of critical points. Our work has been inspired by the observation that in many applications a large variety of different feature definitions for the same concept are used. Often, these definitions compete with each other and it is unclear which definition should be used in which context. A prominent example is the definition of cyclones in climate research. Despite the differences, frequently these feature definitions can be related to topological concepts.

Place, publisher, year, edition, pages
Springer, 2021
National Category
Computer Sciences Human Computer Interaction Meteorology and Atmospheric Sciences
Identifiers
urn:nbn:se:liu:diva-182268 (URN)10.1007/978-3-030-83500-2_5 (DOI)2-s2.0-85116754849 (Scopus ID)9783030834999 (ISBN)9783030835002 (ISBN)
Funder
Swedish Foundation for Strategic Research, BD15-0082Swedish e‐Science Research CenterELLIIT - The Linköping‐Lund Initiative on IT and Mobile Communications
Available from: 2022-01-11 Created: 2022-01-11 Last updated: 2022-09-01Bibliographically approved

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