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RSS FeedThu, 18 Feb 2016 13:37:39 GMT2016-02-18T13:37:39ZTime-predictable Stack Caching
http://orbit.dtu.dk/en/publications/timepredictable-stack-caching(e59c1c6a-46e8-4243-8740-5667577d1c22).html
<div style='font-size: 9px;'><div class="rendering rendering_publication rendering_publication_short rendering_bookanthology rendering_short rendering_bookanthology_short"><h2 class="title"><a rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/timepredictable-stack-caching(e59c1c6a-46e8-4243-8740-5667577d1c22).html" class="link"><span>Time-predictable Stack Caching</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/sahar-abbaspourseyedi(1413dab9-306e-469e-85bd-0b7e6ee9a738).html" class="link person"><span>Abbaspourseyedi, S.</span></a>, <a rel="Person" href="http://orbit.dtu.dk/en/persons/martin-schoeberl(63dcfd1c-cc7f-4e1b-8fdc-1d421f8fdb36).html" class="link person"><span>Schoeberl, M.</span></a> & <a rel="Person" href="http://orbit.dtu.dk/en/persons/jens-sparsoe(8ef14d93-7486-4521-adba-0ba0d0932be3).html" class="link person"><span>Sparsø, J.</span></a> <span class="date">2016</span> Kgs. Lyngby: <a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">133 p.</span> (DTU Compute PHD-2015; No. 385).<p class="type"><span class="type_family">Publication<span class="type_family_sep">: </span></span><span class="type_classification_parent">Research<span class="type_parent_sep"> › </span></span><span class="type_classification">Ph.D. thesis – Annual report year: 2016</span></p></div><div class="rendering rendering_publication rendering_publication_detailsportal rendering_bookanthology rendering_detailsportal rendering_bookanthology_detailsportal"><div class="abstract"><div class="textblock">Embedded systems are computing systems for controlling and interacting with physical environments. Embedded systems with special timing constraints where the system needs to meet deadlines are referred to as real-time systems. In hard real-time systems, missing a deadline causes the system to fail completely. Thus, in systems with hard deadlines the worst-case execution time (WCET) of the real-time software running on them needs to be bounded. <br /><br />Modern architectures use features such as pipelining and caches for improving the average performance. These features, however, make the WCET analysis more complicated and less imprecise. Time-predictable computer architectures provide solutions to this problem. As accesses to the data in caches are one source of timing unpredictability, devising methods for improving the timepredictability of caches are important. Stack data, with statically analyzable addresses, provides an opportunity to predict and tighten the WCET of accesses to data in caches.<br /><br />In this thesis, we introduce the time-predictable stack cache design and implementation within a time-predictable processor. We introduce several optimizations to our design for tightening the WCET while keeping the timepredictability of the design intact. Moreover, we provide a solution for reducing the cost of context switching in a system using the stack cache. In design of these caches, we use custom hardware and compiler support for delivering time-predictable stack data accesses. Furthermore, for systems where compiler support or hardware changes are not practical, we propose and explore two different alternatives based on only software and only hardware support.<br /></div></div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr></tbody></table><table class="properties"><tbody><tr><th>Place of Publication</th><td>Kgs. Lyngby</td></tr><tr><th>Publisher</th><td><a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>133</td></tr><tr class="status"><th>State</th><td><span class="prefix">Published - </span><span class="date">2016</span></td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Name</th><td>DTU Compute PHD-2015</td></tr><tr><th>Number</th><td>385</td></tr><tr><th>ISSN (print)</th><td>0909-3192</td></tr></tbody></table></div></div>Thu, 31 Dec 2015 23:00:00 GMThttp://orbit.dtu.dk/en/publications/timepredictable-stack-caching(e59c1c6a-46e8-4243-8740-5667577d1c22).html2015-12-31T23:00:00ZAspects of the Tutte polynomial
http://orbit.dtu.dk/en/publications/aspects-of-the-tutte-polynomial(b7bbd3d4-39f7-49cb-853a-139aae217468).html
<div style='font-size: 9px;'><div class="rendering rendering_publication rendering_publication_short rendering_bookanthology rendering_short rendering_bookanthology_short"><h2 class="title"><a rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/aspects-of-the-tutte-polynomial(b7bbd3d4-39f7-49cb-853a-139aae217468).html" class="link"><span>Aspects of the Tutte polynomial</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/seongmin-ok(43d463d6-b7a0-49f1-a3b7-ddf526b1934b).html" class="link person"><span>Ok, S.</span></a> & <a rel="Person" href="http://orbit.dtu.dk/en/persons/carsten-thomassen(88ab66ea-2b88-44e7-88f2-b8b883cf3ec0).html" class="link person"><span>Thomassen, C.</span></a> <span class="date">2016</span> Kgs. Lyngby: <a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">110 p.</span> (DTU Compute PHD-2015; No. 384).<p class="type"><span class="type_family">Publication<span class="type_family_sep">: </span></span><span class="type_classification_parent">Research<span class="type_parent_sep"> › </span></span><span class="type_classification">Ph.D. thesis – Annual report year: 2016</span></p></div><div class="rendering rendering_publication rendering_publication_detailsportal rendering_bookanthology rendering_detailsportal rendering_bookanthology_detailsportal"><div class="abstract"><div class="textblock">This thesis studies various aspects of the Tutte polynomial, especially focusing on the Merino-Welsh conjecture.<br /><br />We write T(G;x,y) for the Tutte polynomial of a graph G with variables x and y. In 1999, Merino and Welsh conjectured that if G is a loopless 2-connected graph, then<br /><br />T(G;1,1) ≤ max{T(G;2,0), T(G;0,2)}.<br /><br />The three numbers, T(G;1,1), T(G;2,0) and T(G;0,2) are respectively the numbers of spanning trees, acyclic orientations and totally cyclic orientations of G.<br /><br />First, I extend Negami's splitting formula to the multivariate Tutte polynomial. Using the splitting formula, Thomassen and I found a lower bound for the number of spanning trees in a k-edge-connected graph. Our bound is tight for k even, but for k odd we give a slightly better lower bound which we believe is not tight. We prove that the minimum number of spanning trees in a 3-edge-connected graph with n vertices is, not surprisingly, significantly smaller than the minimum number of spanning trees in a 4-edge-connected graph. However, we conjecture that the minimum number of spanning trees of a 5-edge-connected graph is actually obtained by a 6-edge-connected graph asymptotically.<br /><br />Thomassen proved the following partial result for the Merino-Welsh conjecture. Assume the graph G is loopless, bridgeless and has n vertices and m edges.<br /><br />If m ≤ 1.066 n then T(G;1,1) ≤ T(G;2,0).<br />If m ≥ 4(n-1) then T(G;1,1) ≤ T(G;0,2).<br /> <br />I improve in this thesis Thomassen's result as follows:<br /><br />If m ≤ 1.29(n-1) then T(G;1,1) ≤ T(G;2,0).<br />If m ≥ 3.58(n-1) and G is 3-edge-connected then T(G;1,1) ≤ T(G;0,2).<br /><br />Strengthening Thomassen's idea that acyclic orientations dominate spanning trees in sparse graphs, I conjecture that the ratio T(G;2,0)/T(G;1,1) increases as G gets sparser. To support this conjecture, I prove a variant of the conjecture for series-parallel graphs.<br /><br />The Merino-Welsh conjecture has a stronger version claiming that the Tutte polynomial is convex on the line segment between (2,0) and (0,2) for loopless 2-connected graphs. Chavez-Lomeli et al. proved that this holds for coloopless paving matroids, and I provide a shorter proof of their theorem. I also prove it for minimally 2-edge-connected graphs. As a general statement for the convexity of the Tutte polynomials, I show that the Tutte polynomial of a sparse paving matroid is almost surely convex in the first quadrant. In contrast, I conjecture that the Tutte polynomial of a sparse paving matroid with fixed rank is almost never convex in the first quadrant.<br /><br />The following multiplicative version of the Merino-Welsh conjecture was considered by Noble and Royle:<br /><br />T(G;1,1)2 ≤ T(G;2,0) T(G;0,2).<br /><br />Noble and Royle proved that this multiplicative version holds for series-parallel graphs, using a computer algorithm that they designed. Using a property of the splitting formula which I found, I improve their algorithm so that it is applicable to the class of graphs with bounded treewidth (or pathwidth). As an application, I verify that the multiplicative version holds for graphs with pathwidth at most 3.<br /></div></div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr></tbody></table><table class="properties"><tbody><tr><th>Place of Publication</th><td>Kgs. Lyngby</td></tr><tr><th>Publisher</th><td><a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>110</td></tr><tr class="status"><th>State</th><td><span class="prefix">Published - </span><span class="date">2016</span></td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Name</th><td>DTU Compute PHD-2015</td></tr><tr><th>Number</th><td>384</td></tr><tr><th>ISSN (print)</th><td>0909-3192</td></tr></tbody></table></div></div>Thu, 31 Dec 2015 23:00:00 GMThttp://orbit.dtu.dk/en/publications/aspects-of-the-tutte-polynomial(b7bbd3d4-39f7-49cb-853a-139aae217468).html2015-12-31T23:00:00ZDesign and Analysis of Symmetric Primitives
http://orbit.dtu.dk/en/publications/design-and-analysis-of-symmetric-primitives(7d94a26d-c657-4566-a265-461473931cd1).html
<div style='font-size: 9px;'><div class="rendering rendering_publication rendering_publication_short rendering_bookanthology rendering_short rendering_bookanthology_short"><h2 class="title"><a rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/design-and-analysis-of-symmetric-primitives(7d94a26d-c657-4566-a265-461473931cd1).html" class="link"><span>Design and Analysis of Symmetric Primitives</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/martin-mehl-lauridsen(6ff3a3ba-9819-4653-82ea-69d9bc128065).html" class="link person"><span>Lauridsen, M. M.</span></a>, <a rel="Person" href="http://orbit.dtu.dk/en/persons/christian-rechberger(2b326705-e9ce-4f75-8852-a312f3ed2260).html" class="link person"><span>Rechberger, C.</span></a> & <a rel="Person" href="http://orbit.dtu.dk/en/persons/lars-ramkilde-knudsen(a62b8acd-d07f-4943-a467-85af0eb5efe0).html" class="link person"><span>Knudsen, L. R.</span></a> <span class="date">2016</span> Kgs. Lyngby: <a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">213 p.</span> (DTU Compute PHD-2015; No. 382).<p class="type"><span class="type_family">Publication<span class="type_family_sep">: </span></span><span class="type_classification_parent">Research<span class="type_parent_sep"> › </span></span><span class="type_classification">Ph.D. thesis – Annual report year: 2016</span></p></div><div class="rendering rendering_publication rendering_publication_detailsportal rendering_bookanthology rendering_detailsportal rendering_bookanthology_detailsportal"><div class="abstract"><div class="textblock">The subject of this thesis is the study of symmetric cryptographic primitives. We investigate these objects from three different perspectives: cryptanalysis, design and implementation aspects. <br /><br />The first part deals with cryptanalysis of symmetric primitives, where one tries to leverage a property of the design to achieve some adversarial goal. Two of the most successful types of cryptanalysis are differential- and linear attacks. We apply variants of differential cryptanalysis to the lightweight block cipher SIMON which was proposed by researchers from the National Security Agency (NSA) in 2013. In particular, we present a search heuristic to find differentials of high probability, and we investigate the clustering of characteristics known as the differential effect. Finally, we apply impossible differential attacks using truncated differentials to a number of SIMON variants. Next, we define a theoretical model for key-less linear distinguishers, which captures the meaning of distinguishing a block cipher from an ideal permutation using linear cryptanalysis, when the key is either known or chosen by the adversary. Such models exist using differential properties but were never before defined using linear cryptanalysis. We apply this model to the standardized block cipher PRESENT. Finally, we present very generic attacks on two authenticated encryption schemes, AVALANCHE and RBS, by pointing out severe design flaws that can be leveraged to fully recover the secret key with very low complexity. <br /><br />In the second part, we delve into the matter of the various aspects of designing a symmetric cryptographic primitive. We start by considering generalizations of the widely acclaimed Advanced Encryption Standard (AES) block cipher. In particular, our focus is on a component operation in the cipher which permutes parts of the input to obtain dependency between the state bits. With this operation in focus, we give a range of theoretical results, reducing the possible choices for the operation in generalized ciphers to a particular set of classes. We then employ a computer-aided optimization technique to determine the best choices for the operation in terms of resistance towards differential- and linear cryptanalysis. Also in the vein of symmetric primitive design we present PRØST, a new and highly secure permutation. Employing existing third-party modes of operation, we present six proposals based on PRØST for the ongoing CAESAR competition for authenticated encryption with associated data. We describe the design criteria, the usage modes and give proofs of security.<br /><br />Finally, in the third part, we consider implementation aspects of symmetric cryptography, with focus on high-performance software. In more detail, we analyze and implement modes recommended by the National Institute of Standards and Technology (NIST), as well as authenticated encryption modes from the CAESAR competition, when instantiated with the AES. The data processed in our benchmarking has sizes representative to that of typical Internet traffic. Motivated by a significant improvement to special AES instructions in the most recent microarchitecture from Intel, codenamed Haswell, our implementations are tailored for this platform. Finally, we introduce the comb scheduler which is a low-overhead look-ahead strategy for processing multiple messages in parallel. We show that it significantly increases the throughput for sequential modes of operation especially, but also for parallel modes to a lesser extent.<br /></div></div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr></tbody></table><table class="properties"><tbody><tr><th>Place of Publication</th><td>Kgs. Lyngby</td></tr><tr><th>Publisher</th><td><a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>213</td></tr><tr class="status"><th>State</th><td><span class="prefix">Published - </span><span class="date">2016</span></td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Name</th><td>DTU Compute PHD-2015</td></tr><tr><th>Number</th><td>382</td></tr><tr><th>ISSN (print)</th><td>0909-3192</td></tr></tbody></table></div></div>Thu, 31 Dec 2015 23:00:00 GMThttp://orbit.dtu.dk/en/publications/design-and-analysis-of-symmetric-primitives(7d94a26d-c657-4566-a265-461473931cd1).html2015-12-31T23:00:00ZDevelopment and Application of Tools for MRI Analysis - A Study on the Effects of Exercise in Patients with Alzheimer's Disease and Generative Models for Bias Field Correction in MR Brain Imaging
http://orbit.dtu.dk/en/publications/development-and-application-of-tools-for-mri-analysis--a-study-on-the-effects-of-exercise-in-patients-with-alzheimers-disease-and-generative-models-for-bias-field-correction-in-mr-brain-imaging(5998e9ca-3c2b-4734-b528-3aed0f79380d).html
<div style='font-size: 9px;'><div class="rendering rendering_publication rendering_publication_short rendering_bookanthology rendering_short rendering_bookanthology_short"><h2 class="title"><a rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/development-and-application-of-tools-for-mri-analysis--a-study-on-the-effects-of-exercise-in-patients-with-alzheimers-disease-and-generative-models-for-bias-field-correction-in-mr-brain-imaging(5998e9ca-3c2b-4734-b528-3aed0f79380d).html" class="link"><span>Development and Application of Tools for MRI Analysis - A Study on the Effects of Exercise in Patients with Alzheimer's Disease and Generative Models for Bias Field Correction in MR Brain Imaging</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/christian-thode-larsen(05521ab1-11fa-4bf3-a4d1-a32d0382e79d).html" class="link person"><span>Larsen, C. T.</span></a> & <a rel="Person" href="http://orbit.dtu.dk/en/persons/koen-van-leemput(265767e4-0af5-4996-acf2-288bf3d27030).html" class="link person"><span>Van Leemput, K.</span></a> <span class="date">2016</span> Kgs. Lyngby: <a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">151 p.</span> (DTU Compute PHD-2015; No. 378).<p class="type"><span class="type_family">Publication<span class="type_family_sep">: </span></span><span class="type_classification_parent">Research<span class="type_parent_sep"> › </span></span><span class="type_classification">Ph.D. thesis – Annual report year: 2016</span></p></div><div class="rendering rendering_publication rendering_publication_detailsportal rendering_bookanthology rendering_detailsportal rendering_bookanthology_detailsportal"><div class="abstract"><div class="textblock">Magnetic resonance imaging (MRI) is the de facto modality in neuroimaging studies, due to its superior image contrast in soft tissue. These studies often employ automated software pipelines that segments the image into structures and tissue. This reduces the time needed for analysis as well as statistical bias that may arise due to disagreements in delineations made by human experts. One such pipeline is Freesurfer.<br /><br />This thesis presents results from the intervention study \Preserving cognition, quality of life, physical health and functional ability in Alzheimer’s disease: the effect of physical exercise” (ADEX), where longitudinal Freesurfer analysis was used to obtain segmentations of the hippocampal subfields and cortical regions in a subgroup of participants before and after a four-month exercise period. The participants performed moderate-to-high aerobic exercise for one hour, three times per week. The study hypothesized that the intervention would lead to reduced loss of tissue in the hippocampus and cortical regions, and that volumetric changes over time would correlate with cognitive performance measures. It was not possible to measure any effects in the hippocampus or cortical regions due to the intervention. However, it was found that exercise load (attendance and training intensity) correlated with changes in the hippocampus and in frontal and cingulate cortical thickness. Furthermore, changes in frontal and cingulate cortical thickness were found to correlate with changes in several cognitive performance measures, including mental speed, attention and verbal uency.<br /><br />MRI suffers from an image artifact often referred to as the "bias field”. This effect complicates automatized analysis of the images. For this reason, bias field correction is typical an early preprocessing step in many pipelines. Freesurfer currently employs the popular N3 bias field correction algorithm early in the pipeline, to solve this problem.<br /><br />In this thesis, the reader is introduced to generative models for bias field correction. It is further shown how N3, which has traditionally been described as a "histogram sharpening” method, actually employs an underlying generative model, and that the bias field is estimated using an algorithm that is identical to generalized expectation maximization, but relies on heuristic parameter updates.<br /><br />The thesis progresses to present a new generative model for longitudinal correction of the bias field, as well as a model that does not require brain masking or probabilistic, anatomical atlases in order to perform well. Finally, the thesis presents the realization of these models in the software package "Intensity Inhomogeneity Correction”, which will be made publicly available.<br /></div></div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr></tbody></table><table class="properties"><tbody><tr><th>Place of Publication</th><td>Kgs. Lyngby</td></tr><tr><th>Publisher</th><td><a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>151</td></tr><tr class="status"><th>State</th><td><span class="prefix">Published - </span><span class="date">2016</span></td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Name</th><td>DTU Compute PHD-2015</td></tr><tr><th>Number</th><td>378</td></tr><tr><th>ISSN (print)</th><td>0909-3192</td></tr></tbody></table></div></div>Thu, 31 Dec 2015 23:00:00 GMThttp://orbit.dtu.dk/en/publications/development-and-application-of-tools-for-mri-analysis--a-study-on-the-effects-of-exercise-in-patients-with-alzheimers-disease-and-generative-models-for-bias-field-correction-in-mr-brain-imaging(5998e9ca-3c2b-4734-b528-3aed0f79380d).html2015-12-31T23:00:00ZModelling of the Human Inner Ear Anatomy and Variability for Cochlear Implant Applications
http://orbit.dtu.dk/en/publications/modelling-of-the-human-inner-ear-anatomy-and-variability-for-cochlear-implant-applications(4590a0d0-f7b3-44fc-a4c7-06ba9c812a7a).html
<div style='font-size: 9px;'><div class="rendering rendering_publication rendering_publication_short rendering_bookanthology rendering_short rendering_bookanthology_short"><h2 class="title"><a rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/modelling-of-the-human-inner-ear-anatomy-and-variability-for-cochlear-implant-applications(4590a0d0-f7b3-44fc-a4c7-06ba9c812a7a).html" class="link"><span>Modelling of the Human Inner Ear Anatomy and Variability for Cochlear Implant Applications</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/hans-martin-kjer(a9705d27-ba4f-4760-8bb7-d2ddf31adf9f).html" class="link person"><span>Kjer, H. M.</span></a> & <a rel="Person" href="http://orbit.dtu.dk/en/persons/rasmus-reinhold-paulsen(d672590e-6b1e-4248-b5d7-0ecdb8553716).html" class="link person"><span>Paulsen, R. R.</span></a> <span class="date">2016</span> Kgs. Lyngby: <a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">219 p.</span> (DTU Compute PHD-2015; No. 381).<p class="type"><span class="type_family">Publication<span class="type_family_sep">: </span></span><span class="type_classification_parent">Research<span class="type_parent_sep"> › </span></span><span class="type_classification">Ph.D. thesis – Annual report year: 2016</span></p></div><div class="rendering rendering_publication rendering_publication_detailsportal rendering_bookanthology rendering_detailsportal rendering_bookanthology_detailsportal"><div class="abstract"><div class="textblock">This thesis takes the biomedical engineering approach to working with and understanding the anatomy and physiology of the inner ear. The purpose is to apply the acquired knowledge in the development of implantable hearing aids. <br /><br />The so-called Cochlear Implant (CI) is a fascinating technology that without underselling it provides hearing for the deaf. The technology faces a number of challenges, and a part of the solution to those is closely connected with an improved understanding of the inner ear anatomy, both with regards to the individual patient but also to the variation in the population. <br /><br />The inner ear is a relatively small structure and even with modern medical scanners only the coarsest details are revealed about the specific patient anatomy. To study the anatomy it is required to work on specimens from deceased subjects scanned with for instance μCT. The anatomy is complex and presents several challenges concerning data processing and analysis. <br /><br />Our approach is to describe the inner ear as a statistical shape model. The thesis covers our work with regards to data segmentation, shape characterization, development of image registration model suited for the inner ear and construction of statistical deformation models.<br /><br />The thesis results in a series of applications relating to CIs. The shape model can be used by CI-manufacturers for virtual product development and testing. At the same time, it can be applied to estimate the detailed inner ear shape from a clinical patient CT scan. This opens up for tools to optimize the programming of the CI, such that the hearing restoration is improved.<br /></div></div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr></tbody></table><table class="properties"><tbody><tr><th>Place of Publication</th><td>Kgs. Lyngby</td></tr><tr><th>Publisher</th><td><a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>219</td></tr><tr class="status"><th>State</th><td><span class="prefix">Published - </span><span class="date">2016</span></td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Name</th><td>DTU Compute PHD-2015</td></tr><tr><th>Number</th><td>381</td></tr><tr><th>ISSN (print)</th><td>0909-3192</td></tr></tbody></table></div></div>Thu, 31 Dec 2015 23:00:00 GMThttp://orbit.dtu.dk/en/publications/modelling-of-the-human-inner-ear-anatomy-and-variability-for-cochlear-implant-applications(4590a0d0-f7b3-44fc-a4c7-06ba9c812a7a).html2015-12-31T23:00:00ZTopological Fluid Dynamics For Free and Viscous Surfaces
http://orbit.dtu.dk/en/publications/topological-fluid-dynamics-for-free-and-viscous-surfaces(ab67ac82-d19d-401e-8999-69ced423d47a).html
<div style='font-size: 9px;'><div class="rendering rendering_publication rendering_publication_short rendering_bookanthology rendering_short rendering_bookanthology_short"><h2 class="title"><a rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/topological-fluid-dynamics-for-free-and-viscous-surfaces(ab67ac82-d19d-401e-8999-69ced423d47a).html" class="link"><span>Topological Fluid Dynamics For Free and Viscous Surfaces</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/adnan-balci(fbae18c4-41c1-4169-b597-e94fd4fa14f9).html" class="link person"><span>Balci, A.</span></a> & <a rel="Person" href="http://orbit.dtu.dk/en/persons/morten-broens(b364a278-ce14-4e88-be21-7d0cd7ea6a7a).html" class="link person"><span>Brøns, M.</span></a> <span class="date">2016</span> Kgs. Lyngby: <a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">194 p.</span> (DTU Compute PHD-2015; No. 379).<p class="type"><span class="type_family">Publication<span class="type_family_sep">: </span></span><span class="type_classification_parent">Research<span class="type_parent_sep"> › </span></span><span class="type_classification">Ph.D. thesis – Annual report year: 2016</span></p></div><div class="rendering rendering_publication rendering_publication_detailsportal rendering_bookanthology rendering_detailsportal rendering_bookanthology_detailsportal"><div class="abstract"><div class="textblock">In an incompressible fluid flow, streamline patterns and their bifurcations are investigated close to wall for two-dimensional system and close to free and viscous surfaces in three-dimensional system. Expanding the velocity field in a Taylor series, we conduct a local analysis at the given expansion point. Applying the boundary conditions, some relations are obtained among the coefficients of the expansions. Series of coordinate transformations, which preserves the boundary conditions, are used to reduce the number of coefficients. Finally, using the normal form and unfolding theory, the velocity field is analysed structurally and bifurcation diagrams are obtained.<br /><br />First, two-dimensional viscous flow close to wall for non-simple degenerate critical point is considered depending on three-parameter space. Second, threedimensional axisymmetric, viscous and steady flow is analysed close to free and viscous surfaces into three situations: Local analysis close to center axis; away from the axis and close to a stationary wall. Next, in the absence of axisymmetric condition, three-dimensional viscous flow is consider close to a free surface. <br /><br />As an application of the bifurcation diagrams for three-dimensional axisymmetric viscous flow, three different shaped container driven by a rotating top disk is considered. Using a spectral collocation method, a code is constructed to obtain the meridional and swirl velocities. In a result of this code, all structural changes on the streamline patterns are observed and the occurring bifurcations are determined. These bifurcations are compared with the bifurcations obtained from topologically.<br /></div></div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr></tbody></table><table class="properties"><tbody><tr><th>Place of Publication</th><td>Kgs. Lyngby</td></tr><tr><th>Publisher</th><td><a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>194</td></tr><tr class="status"><th>State</th><td><span class="prefix">Published - </span><span class="date">2016</span></td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Name</th><td>DTU Compute PHD-2015</td></tr><tr><th>Number</th><td>379</td></tr><tr><th>ISSN (print)</th><td>0909-3192</td></tr></tbody></table></div></div>Thu, 31 Dec 2015 23:00:00 GMThttp://orbit.dtu.dk/en/publications/topological-fluid-dynamics-for-free-and-viscous-surfaces(ab67ac82-d19d-401e-8999-69ced423d47a).html2015-12-31T23:00:00ZDesign of Cognitive Interfaces for Personal Informatics Feedback
http://orbit.dtu.dk/en/publications/design-of-cognitive-interfaces-for-personal-informatics-feedback(a98db9a4-027a-431e-a474-135ed2a9a985).html
<div style='font-size: 9px;'><div class="rendering rendering_publication rendering_publication_short rendering_bookanthology rendering_short rendering_bookanthology_short"><h2 class="title"><a rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/design-of-cognitive-interfaces-for-personal-informatics-feedback(a98db9a4-027a-431e-a474-135ed2a9a985).html" class="link"><span>Design of Cognitive Interfaces for Personal Informatics Feedback</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/camilla-birgitte-falk-jensen(e8ddddd9-a5ac-4c5e-9f90-def96a8ae695).html" class="link person"><span>Jensen, C. B. F.</span></a>, <a rel="Person" href="http://orbit.dtu.dk/en/persons/jakob-eg-larsen(691c8ae7-9a21-4b98-9b91-5e2d9806a4b9).html" class="link person"><span>Larsen, J. E.</span></a> & <a rel="Person" href="http://orbit.dtu.dk/en/persons/michael-kai-petersen(0184dad5-da00-4ca8-b00a-53165ce84766).html" class="link person"><span>Petersen, M. K.</span></a> <span class="date">2015</span> Kgs. Lyngby: <a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">144 p.</span> (DTU Compute PHD-2015; No. 383).<p class="type"><span class="type_family">Publication<span class="type_family_sep">: </span></span><span class="type_classification_parent">Research<span class="type_parent_sep"> › </span></span><span class="type_classification">Ph.D. thesis – Annual report year: 2015</span></p></div><div class="rendering rendering_publication rendering_publication_detailsportal rendering_bookanthology rendering_detailsportal rendering_bookanthology_detailsportal"><div class="abstract"><div class="textblock">The emergence of embedded low-cost sensors in mobile devices allows us to capture unprecedented data about human behavior. Hence personal informatics systems are becoming an integrated part of our everyday life: Capturing various aspects from our health, work-life, to economic balance, and utility consumption. All of which are aimed to provide knowledge of oneself, on which we can reflect. Many personal informatics systems are characterized by mainly focusing on collecting and analyzing data, rather than translating the data into meaningful feedback. This dissertation presents challenges related to personal informatics systems, and propose an approach to design cognitive interfaces, which considers both users’ motivations, needs, and goals.<br /><br />In this thesis I propose a new personal informatics framework, the feedback loop, which incorporates lean agile design principles. Including hierarchical modeling of goals, activities, and tasks to create minimal viable products. While considering how micro-interactions based on an understanding of data, couples with user needs and the context they appear in, can contribute to creating cognitive interfaces. Designing cognitive interfaces requires a focus on translating data into meaningful feedback, which the users can reflect on in order to gain insights. Thus I present tools such as personalized baselines and thresholds to enable reflection, while creating personalized goals, scenarios, trade-offs in order to provide actionable feedback, which can help users to adjust their behavior. Although feedback can be provided in many different ways, it basically consists of audio, visual, and haptic components, which combined may reinforce each other to support the underlying interaction.<br /><br />The papers included in this thesis cover selected parts of the feedback loop. For instance, examining emotional responses to pleasant and unpleasant media content from brain activity, reveals the large amount of data and extensive analysis required to apply this to future personal informatics systems. In addition we analyse challenges related to temporal aspects of the feedback loop, when users attempt to self-regulate their brain activity based on a real-time feedback. This leads to identification of underlying audio, visual and haptic feedback components, which combined may support the underlying interaction within personal informatics. And with the emerging availability of sensor packed wearable devices, haptic feedback may become an inherent part of personal informatics systems, which could enhance the interaction based visual feedback.</div></div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr></tbody></table><table class="properties"><tbody><tr><th>Place of Publication</th><td>Kgs. Lyngby</td></tr><tr><th>Publisher</th><td><a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>144</td></tr><tr class="status"><th>State</th><td><span class="prefix">Submitted - </span><span class="date">2015</span></td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Name</th><td>DTU Compute PHD-2015</td></tr><tr><th>Number</th><td>383</td></tr><tr><th>ISSN (print)</th><td>0909-3192</td></tr></tbody></table></div></div>Wed, 31 Dec 2014 23:00:00 GMThttp://orbit.dtu.dk/en/publications/design-of-cognitive-interfaces-for-personal-informatics-feedback(a98db9a4-027a-431e-a474-135ed2a9a985).html2014-12-31T23:00:00ZPredicting the emotions expressed in music
http://orbit.dtu.dk/en/publications/predicting-the-emotions-expressed-in-music(2406b142-1d8f-4d25-8e3a-2ab9a682420c).html
<div style='font-size: 9px;'><div class="rendering rendering_publication rendering_publication_short rendering_bookanthology rendering_short rendering_bookanthology_short"><h2 class="title"><a rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/predicting-the-emotions-expressed-in-music(2406b142-1d8f-4d25-8e3a-2ab9a682420c).html" class="link"><span>Predicting the emotions expressed in music</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/jens-madsen(37578fac-e747-4bc5-9d95-cceb30caeb16).html" class="link person"><span>Madsen, J.</span></a> & <a rel="Person" href="http://orbit.dtu.dk/en/persons/jan-larsen(172b79ba-ccb1-4bea-8cd3-30dfd62f4624).html" class="link person"><span>Larsen, J.</span></a> <span class="date">2015</span> Kgs. Lyngby: <a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">162 p.</span> (DTU Compute PHD-2015; No. 369).<p class="type"><span class="type_family">Publication<span class="type_family_sep">: </span></span><span class="type_classification_parent">Research<span class="type_parent_sep"> › </span></span><span class="type_classification">Ph.D. thesis – Annual report year: 2015</span></p></div><div class="rendering rendering_publication rendering_publication_detailsportal rendering_bookanthology rendering_detailsportal rendering_bookanthology_detailsportal"><div class="abstract"><div class="textblock">With the ever-growing popularity and availability of digital music through streaming services and digital download, making sense of the millions of songs, is ever more pertinent. However the traditional approach of creating music systems has treated songs like items in a store, like books and movies. However music is special, having origins in a number of evolutionary adaptations. The fundamental needs and goals of a users use of music, was investigated to create the next generation of music systems. People listen to music to regulate their mood and emotions was found to be the most important fundamental reason. (Mis)matching peoples mood with the emotions expressed in music was found to be an essential underlying mechanism, people use to regulate their emotions. This formed the basis and overall goal of the thesis, to investigate how to create a predictive model of emotions expressed in music. To use in the next generation of music systems.<br /><br />The thesis was divided into three main topics involved in creating a predictive model 1) Elicitation of emotion, 2) Audio representation and 3) Modelling framework, associating the emotion and audio representation, allowing to predict the emotions expressed in music.<br /><br />The traditional approach of quantifying musical stimuli on the valence and arousal representation of emotions using continuous or likert scales was questioned. An outline of a number of bias and the so-called confidence effect when using bipolar scales led to the use of relative scales in the form of pairwise comparisons. One issue with pairwise comparisons is the scaling, this was solved using an active learning approach through a Gaussian Process model. <br /><br />Traditional audio representation disregards all temporal information in audio features used for modelling the emotions expressed in music. Therefore a probabilistic feature representation framework was introduced enabling both temporal and non-temporal aspects to be coded in discrete and continuous features. Generative models are estimated for each feature time-series and used in a discriminative setting using the Probability Product Kernel (PPK) allowing the use of this approach in any kernel machine.<br /><br />To model the pairwise comparisons directly, a Generalized Linear Model, a kernel extension and a Gaussian Process model were used. These models can predict the ranking of songs on the valence and arousal dimensions directly. Furthermore use of the PPK allowed to find optimal combinations of both feature and feature representation using Multiple Kernel Learning.<br /></div></div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr></tbody></table><table class="properties"><tbody><tr><th>Place of Publication</th><td>Kgs. Lyngby</td></tr><tr><th>Publisher</th><td><a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>162</td></tr><tr class="status"><th>State</th><td><span class="prefix">Submitted - </span><span class="date">2015</span></td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Name</th><td>DTU Compute PHD-2015</td></tr><tr><th>Number</th><td>369</td></tr><tr><th>ISSN (print)</th><td>0909-3192</td></tr></tbody></table></div></div>Wed, 31 Dec 2014 23:00:00 GMThttp://orbit.dtu.dk/en/publications/predicting-the-emotions-expressed-in-music(2406b142-1d8f-4d25-8e3a-2ab9a682420c).html2014-12-31T23:00:00ZQuality assessment of turbid media: milk and pharmaceuticals
http://orbit.dtu.dk/en/publications/quality-assessment-of-turbid-media(4cd830bd-da9f-4a5a-b3c7-90e9b516218a).html
<div style='font-size: 9px;'><div class="rendering rendering_publication rendering_publication_short rendering_bookanthology rendering_short rendering_bookanthology_short"><h2 class="title"><a rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/quality-assessment-of-turbid-media(4cd830bd-da9f-4a5a-b3c7-90e9b516218a).html" class="link"><span>Quality assessment of turbid media: milk and pharmaceuticals</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/faisal-kamran(d8bf6e17-da91-4a8d-9b01-ddf26162275e).html" class="link person"><span>Kamran, F.</span></a> & <a rel="Person" href="http://orbit.dtu.dk/en/persons/peter-e-andersen(4628db49-ed5f-4535-aacd-94d18f776157).html" class="link person"><span>Andersen, P. E.</span></a> <span class="date">2014</span> Roskilde: <a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">136 p.</span><p class="type"><span class="type_family">Publication<span class="type_family_sep">: </span></span><span class="type_classification_parent">Research<span class="type_parent_sep"> › </span></span><span class="type_classification">Ph.D. thesis – Annual report year: 2014</span></p></div><div class="rendering rendering_publication rendering_publication_detailsportal rendering_bookanthology rendering_detailsportal rendering_bookanthology_detailsportal"><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr></tbody></table><table class="properties"><tbody><tr><th>Place of Publication</th><td>Roskilde</td></tr><tr><th>Publisher</th><td><a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>136</td></tr><tr class="status"><th>State</th><td><span class="prefix">Published - </span><span class="date">2014</span></td></tr></tbody></table></div></div></div>Tue, 31 Dec 2013 23:00:00 GMThttp://orbit.dtu.dk/en/publications/quality-assessment-of-turbid-media(4cd830bd-da9f-4a5a-b3c7-90e9b516218a).html2013-12-31T23:00:00ZInteractive Topology Optimization
http://orbit.dtu.dk/en/publications/interactive-topology-optimization(a34062e3-a5b2-44de-8df6-1c8f47ae87e1).html
<div style='font-size: 9px;'><div class="rendering rendering_publication rendering_publication_short rendering_bookanthology rendering_short rendering_bookanthology_short"><h2 class="title"><a rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/interactive-topology-optimization(a34062e3-a5b2-44de-8df6-1c8f47ae87e1).html" class="link"><span>Interactive Topology Optimization</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/morten-nobeljoergensen(066937e0-5103-47b3-beb3-817f2c04d465).html" class="link person"><span>Nobel-Jørgensen, M.</span></a> & <a rel="Person" href="http://orbit.dtu.dk/en/persons/jakob-andreas-baerentzen(f0d1a57d-f173-4c59-87ad-b554b3678a8c).html" class="link person"><span>Bærentzen, J. A.</span></a> <span class="date">2016</span> Kgs. Lyngby: <a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">124 p.</span> (DTU Compute PHD-2015; No. 375).<p class="type"><span class="type_family">Publication<span class="type_family_sep">: </span></span><span class="type_classification_parent">Research<span class="type_parent_sep"> › </span></span><span class="type_classification">Ph.D. thesis – Annual report year: 2016</span></p></div><div class="rendering rendering_publication rendering_publication_detailsportal rendering_bookanthology rendering_detailsportal rendering_bookanthology_detailsportal"><div class="abstract"><div class="textblock">Interactivity is the continuous interaction between the user and the application to solve a task. Topology optimization is the optimization of structures in order to improve stiffness or other objectives. The goal of the thesis is to explore how topology optimization can be used in applications in an interactive and intuitive way. By creating such applications with an intuitive and simple user interface we allow non-engineers like designers and architects to easily experiment with boundary conditions, design domains and other optimization settings. This is in contrast to commercial topology optimization software where the users are assumed to be well-educated both in the finite element method and topology optimization.<br /><br />This dissertation describes how various topology optimization methods have been used for creating cross-platform applications with high performance. The user interface design is based on theory of from human-computer interaction which is described in Chapter 2. Followed by a description of the foundations of topology optimization in Chapter 3. Our applications for topology optimization in 2D and 3D are described in Chapter 4 and a game which trains the human intuition of topology optimization is presented in Chapter 5. Topology optimization can also be used as an interactive modeling tool with local control which is presented in Chapter 6. Finally, Chapter 7 contains a summary of the findings and concludes the dissertation.<br /><br />Most of the presented applications of the thesis are available at: http://www. topopt.dtu.dk.</div></div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr></tbody></table><table class="properties"><tbody><tr><th>Place of Publication</th><td>Kgs. Lyngby</td></tr><tr><th>Publisher</th><td><a rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html" class="link"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>124</td></tr><tr class="status"><th>State</th><td><span class="prefix">Published - </span><span class="date">2016</span></td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Name</th><td>DTU Compute PHD-2015</td></tr><tr><th>Number</th><td>375</td></tr><tr><th>ISSN (print)</th><td>0909-3192</td></tr></tbody></table></div></div>Thu, 31 Dec 2015 23:00:00 GMThttp://orbit.dtu.dk/en/publications/interactive-topology-optimization(a34062e3-a5b2-44de-8df6-1c8f47ae87e1).html2015-12-31T23:00:00Z