| 1. |
- Rafiq, Y., et al.
(författare)
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Learning to Share: Engineering Adaptive Decision-Support for Online Social Networks
- 2017
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Ingår i: PROCEEDINGS OF THE 2017 32ND IEEE/ACM INTERNATIONAL CONFERENCE ON AUTOMATED SOFTWARE ENGINEERING (ASE'17). - 1527-1366. - 9781538626849 ; , s. 280-285
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Some online social networks (OSNs) allow users to define friendship-groups as reusable shortcuts for sharing information with multiple contacts. Posting exclusively to a friendship-group gives some privacy control, while supporting communication with (and within) this group. However, recipients of such posts may want to reuse content for their own social advantage, and can bypass existing controls by copy-pasting into a new post; this cross-posting poses privacy risks. This paper presents a learning to share approach that enables the incorporation of more nuanced privacy controls into OSNs. Specifically, we propose a reusable, adaptive software architecture that uses rigorous runtime analysis to help OSN users to make informed decisions about suitable audiences for their posts. This is achieved by supporting dynamic formation of recipient-groups that benefit social interactions while reducing privacy risks. We exemplify the use of our approach in the context of Facebook.
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| 2. |
- Elowsson, Anders
(författare)
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Modeling Music : Studies of Music Transcription, Music Perception and Music Production
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation presents ten studies focusing on three important subfields of music information retrieval (MIR): music transcription (Part A), music perception (Part B), and music production (Part C).In Part A, systems capable of transcribing rhythm and polyphonic pitch are described. The first two publications present methods for tempo estimation and beat tracking. A method is developed for computing the most salient periodicity (the “cepstroid”), and the computed cepstroid is used to guide the machine learning processing. The polyphonic pitch tracking system uses novel pitch-invariant and tone-shift-invariant processing techniques. Furthermore, the neural flux is introduced – a latent feature for onset and offset detection. The transcription systems use a layered learning technique with separate intermediate networks of varying depth. Important music concepts are used as intermediate targets to create a processing chain with high generalization. State-of-the-art performance is reported for all tasks.Part B is devoted to perceptual features of music, which can be used as intermediate targets or as parameters for exploring fundamental music perception mechanisms. Systems are proposed that can predict the perceived speed and performed dynamics of an audio file with high accuracy, using the average ratings from around 20 listeners as ground truths. In Part C, aspects related to music production are explored. The first paper analyzes long-term average spectrum (LTAS) in popular music. A compact equation is derived to describe the mean LTAS of a large dataset, and the variation is visualized. Further analysis shows that the level of the percussion is an important factor for LTAS. The second paper examines songwriting and composition through the development of an algorithmic composer of popular music. Various factors relevant for writing good compositions are encoded, and a listening test employed that shows the validity of the proposed methods.The dissertation is concluded by Part D - Looking Back and Ahead, which acts as a discussion and provides a road-map for future work. The first paper discusses the deep layered learning (DLL) technique, outlining concepts and pointing out a direction for future MIR implementations. It is suggested that DLL can help generalization by enforcing the validity of intermediate representations, and by letting the inferred representations establish disentangled structures supporting high-level invariant processing. The second paper proposes an architecture for tempo-invariant processing of rhythm with convolutional neural networks. Log-frequency representations of rhythm-related activations are suggested at the main stage of processing. Methods relying on magnitude, relative phase, and raw phase information are described for a wide variety of rhythm processing tasks.
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| 3. |
- Jönsson, Daniel
(författare)
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Enhancing Salient Features in Volumetric Data Using Illumination and Transfer Functions
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The visualization of volume data is a fundamental component in the medical domain. Volume data is used in the clinical work-flow to diagnose patients and is therefore of uttermost importance. The amount of data is rapidly increasing as sensors, such as computed tomography scanners, become capable of measuring more details and gathering more data over time. Unfortunately, the increasing amount of data makes it computationally challenging to interactively apply high quality methods to increase shape and depth perception. Furthermore, methods for exploring volume data has mostly been designed for experts, which prohibits novice users from exploring volume data. This thesis aims to address these challenges by introducing efficient methods for enhancing salient features through high quality illumination as well as methods for intuitive volume data exploration.Humans are interpreting the world around them by observing how light interacts with objects. Shadows enable us to better determine distances while shifts in color enable us to better distinguish objects and identify their shape. These concepts are also applicable to computer generated content. The perception in volume data visualization can therefore be improved by simulating real-world light interaction. This thesis presents efficient methods that are capable of interactively simulating realistic light propagation in volume data. In particular, this work shows how a multi-resolution grid can be used to encode the attenuation of light from all directions using spherical harmonics and thereby enable advanced interactive dynamic light configurations. Two methods are also presented that allow photon mapping calculations to be focused on visually changing areas.The results demonstrate that photon mapping can be used in interactive volume visualization for both static and time-varying volume data.Efficient and intuitive exploration of volume data requires methods that are easy to use and reflect the objects that were measured. A value that has been collected by a sensor commonly represents the material existing within a small neighborhood around a location. Recreating the original materials is difficult since the value represents a mixture of them. This is referred to as the partial-volume problem. A method is presented that derives knowledge from the user in order to reconstruct the original materials in a way which is more in line with what the user would expect. Sharp boundaries are visualized where the certainty is high while uncertain areas are visualized with fuzzy boundaries. The volume exploration process of mapping data values to optical properties through the transfer function has traditionally been complex and performed by expert users. A study at a science center showed that visitors favor the presented dynamic gallery method compared to the most commonly used transfer function editor.
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| 4. |
- Koniaris, Christos, 1979-
(författare)
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Perceptually motivated speech recognition and mispronunciation detection
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This doctoral thesis is the result of a research effort performed in two fields of speech technology, i.e., speech recognition and mispronunciation detection. Although the two areas are clearly distinguishable, the proposed approaches share a common hypothesis based on psychoacoustic processing of speech signals. The conjecture implies that the human auditory periphery provides a relatively good separation of different sound classes. Hence, it is possible to use recent findings from psychoacoustic perception together with mathematical and computational tools to model the auditory sensitivities to small speech signal changes.The performance of an automatic speech recognition system strongly depends on the representation used for the front-end. If the extracted features do not include all relevant information, the performance of the classification stage is inherently suboptimal. The work described in Papers A, B and C is motivated by the fact that humans perform better at speech recognition than machines, particularly for noisy environments. The goal is to make use of knowledge of human perception in the selection and optimization of speech features for speech recognition. These papers show that maximizing the similarity of the Euclidean geometry of the features to the geometry of the perceptual domain is a powerful tool to select or optimize features. Experiments with a practical speech recognizer confirm the validity of the principle. It is also shown an approach to improve mel frequency cepstrum coefficients (MFCCs) through offline optimization. The method has three advantages: i) it is computationally inexpensive, ii) it does not use the auditory model directly, thus avoiding its computational cost, and iii) importantly, it provides better recognition performance than traditional MFCCs for both clean and noisy conditions.The second task concerns automatic pronunciation error detection. The research, described in Papers D, E and F, is motivated by the observation that almost all native speakers perceive, relatively easily, the acoustic characteristics of their own language when it is produced by speakers of the language. Small variations within a phoneme category, sometimes different for various phonemes, do not change significantly the perception of the language’s own sounds. Several methods are introduced based on similarity measures of the Euclidean space spanned by the acoustic representations of the speech signal and the Euclidean space spanned by an auditory model output, to identify the problematic phonemes for a given speaker. The methods are tested for groups of speakers from different languages and evaluated according to a theoretical linguistic study showing that they can capture many of the problematic phonemes that speakers from each language mispronounce. Finally, a listening test on the same dataset verifies the validity of these methods.
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| 5. |
- Lundin Palmerius, Karljohan, 1977-, et al.
(författare)
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Visualizing and Exploring Heat in a Science Center
- 2022
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Ingår i: Thermal Cameras in Science Education. - Cham, Schweiz : Springer. - 9783030852870 - 9783030852900 - 9783030852887 ; , s. 187-203
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Recent research shows that infrared cameras can help students visualize and interpret notoriously challenging thermal concepts. This chapter describes the application of thermal visualization in a public setting. Specifically, we present the design and implementation of an augmented reality system for the real-time projection of thermal imagery onto objects. Examples of hands-on activities for visualizing thermal processes with the system include conduction and insulation, rubber band thermodynamics, friction, impact heating, enthalpy of chemical reactions, radiation wavelength, mixing liquids, and heat of evaporation. We discuss how the interactive activities might provide pedagogical opportunities for accessing and engaging with thermal phenomena in a science center context. Practical considerations of the system for public exhibition spaces are also given attention.
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| 6. |
- Granlund, Gösta H.
(författare)
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A Nonlinear, Image-content Dependent Measure of Image Quality
- 1977
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, considerable research effort has been devoted to the development of useful descriptors for image quality. The attempts have been hampered by i n complete understanding of the operation of the human visual system. This has made it difficult to relate physical measures and perceptual traits.A new model for determination of image quality is proposed. Its main feature is that it tries to invoke image content into consideration. The model builds upon a theory of image linearization, which means that the information in an image can well enough be represented using linear segments or structures within local spatial regions and frequency ranges. This implies a l so a suggestion that information in an image has to do with one- dimensional correlations. This gives a possibility to separate image content from noise in images, and measure them both.Also a hypothesis is proposed that the visual system of humans does in fact perform such a linearization.
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| 7. |
- Enoksson, Fredrik, 1977-, et al.
(författare)
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Towards End-User Development for Metadata Creators
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Many organization, like libraries, museums, archives, etc. are dependent on metadata about their resources as a representation of their collection. This paper will present an approach aimed at reducing the need for a developer when constructing the metadata editing tool required for such systems, where the long term goal is to enable end-user development (EUD) for the metadata creators. The approach is still under development, but right now it includes a model and a code-library called RDForms that was designed for developers to quickly set up a form based metadata editor, where the metadata that can be edited is changed through a configuration mechanism. An evaluation on the use of RDForms in the wild is presented that seems to indicate that the developers are the ones also configuring the metadata editor. If the configuration instead could be made by the metadata creators the need for a developer would be even further reduced.
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| 8. |
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| 9. |
- Samini, Ali, 1979-
(författare)
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Perspective Correct Hand-held Augmented Reality for Improved Graphics and Interaction
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With Augmented Reality, also termed AR, a view of the real world is augmented by superimposing computer-generated graphics, thereby enriching or enhancing the perception of the reality. Today, lots of applications benefit from AR in different areas, such as education, medicine, navigation, construction, gaming, and multiple other areas, using primarily head-mounted AR displays and AR on hand-held smart devices. Tablets and phones are highly suitable for AR, as they are equipped with high resolution screens, good cameras and powerful processing units, while being readily available to both industry and home use. They are used with video see-through AR, were the live view of the world is captured by a camera in real time and subsequently presented together with the computer graphics on the display.In this thesis I put forth our recent work on improving video see-through Augmented Reality graphics and interaction for hand-held devices by applying and utilizing user perspective. On the rendering side, we introduce a geometry-based user perspective rending method aiming to align the on screen content with the real view of the world visible around the screen. Furthermore, we introduce a device calibration system to compensate for misalignment between system parts. On the interaction side we introduce two wand-like direct 3D pose manipulation techniques based on this user perspective. We also modified a selection technique and introduced a new one suitable to be used with our introduced manipulation techniques. Finally, I present several formal user studies, evaluating the introduced techniques and comparing them with concurrent state-of-the-art alternatives.
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| 10. |
- Stenlund, Jörgen, 1959-
(författare)
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Travelling through time : Students’ interpretation of evolutionary time in dynamic visualizations
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Evolutionary knowledge is important to understand and address contemporary challenges such as loss of biodiversity, climate change and antibiotic resistance. An important aspect that is considered to be a threshold concept in teaching and learning about evolution is the time it involves. The history of evolution comprises several scales of magnitude, some of which are far from direct human experience and therefore difficult to understand. One way of addressing this issue is to use dynamic visualizations that represent time, for example, to facilitate teaching and learning about evolution.This thesis investigates how students’ comprehension of evolution and evolutionary time can be facilitated by visualizations in educational settings. Two different dynamic visualizations were investigated. In paper I different temporal versions of a spatio-temporal animation depicting hominin evolution were explored. The temporal information was expressed as one or several timelines along which an animated cursor moved, indicating the rate of time. Two variables, the number of timelines with different scales, and the mode of the default animated time rate (either constant throughout the animation or decreasing as the animation progressed), were combined to give four different time representations. The temporal aspects investigated were undergraduate students' ability to find events at specific times, comprehend order, comprehend concurrent events, comprehend the length of time intervals, and their ability to compare the lengths of time intervals.In paper II, perceptions and comprehension of temporal aspects in an interactive, multi-touch tabletop application, DeepTree, were investigated. This application depicts the tree of life. The focus was on the interactive aspects, especially how the zooming feature was perceived, but also on any misinterpretations associated with the interaction. The same temporal aspects listed for paper I were also implicitly investigated.The findings indicate that handling the problem of large differences in scale by altering the rate of time in the visualization can facilitate perception of certain temporal aspects while, at the same time, can hinder a correct comprehension of other temporal aspects. Findings concerning DeepTree indicate that the level of interactions varies among users, and that the zooming feature is perceived in two ways, either as a movement in time or as a movement in the metaphorical tree. Several misinterpretations were observed, for example the assumption that the zooming time in the tree corresponds to real time, that there is an implicit coherent timeline along the y-axis of the tree, and that more nodes along a branch corresponds to a longer time.The research reported in this thesis supports the claim that careful choice, and informed use of visualizations matters, and that different visualizations are best suited for different educational purposes
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