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RSS FeedWed, 02 Nov 2016 14:19:51 GMT2016-11-02T14:19:51ZModel Stickiness in Spray Drying
http://orbit.dtu.dk/en/publications/model-stickiness-in-spray-drying(fd944869-f19b-400c-ba5a-6e0c45d78c79).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/model-stickiness-in-spray-drying(fd944869-f19b-400c-ba5a-6e0c45d78c79).html" class="link"><span>Model Stickiness in Spray Drying</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/thomas-petersen(a0603943-26c7-42ee-9ccd-bba181353f85).html" class="link person"><span>Petersen, T.</span></a>, <a rel="Person" href="http://orbit.dtu.dk/en/persons/ole-hassager(b3b2f7bb-1e38-4937-ba11-7f4d63f0012d).html" class="link person"><span>Hassager, O.</span></a>, <a rel="Person" href="http://orbit.dtu.dk/en/persons/jakob-sloth(d5a03b4c-2dc1-4fad-b633-58128246f419).html" class="link person"><span>Sloth, J.</span></a> & <a rel="Person" href="http://orbit.dtu.dk/en/persons/thorvald-uhrskov-ullum(c0ddc42e-d7e3-49a8-b7af-f6731018443b).html" class="link person"><span>Ullum, T. U.</span></a> <span class="date">2015</span> Kgs. Kyngby: <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">103 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: 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 work presented in this thesis concerns wall deposits encountered in spray drying caused by products that exhibit so-called 'stickiness'. The thesis delves into the understanding of the phenomenon of sticky wall deposits in spray drying and proposes a simple criterion for use in industrial design of spray dryers.<br />The experimental work centers around a new technique for measuring when, during drying, a particle becomes non-sticky based on a single droplet drying technique used to study drying kinetics. An acoustic levitator is used to dry a levitated droplet in conditions similar to those a droplet would encounter in a spray dryer. The droplet is recorded using a CCD-camera during drying and the subsequent stickiness test. After a user-specifed drying time a piston strikes the partially dried particle at a user-specifed velocity. After the impact the piston surface is inspected and if the particle was sticky it is seen adhering to the surface, while a clean piston signifes a non-sticky particle. The setup was designed specically to test the stickiness of a particle produced by drying a droplet of the desired feed - something unlike methods of literature where dry particles have been humidied before tests. The setup allowed for parameter variations in the temperature and humidity of the drying air, impact velocity, piston surface and more.<br />Results of measuring the stickiness of skim milk is reported for varying impact velocity, drying temperature and relative humidity. It is found that normalizing the critical drying time to get non-sticky particles with the initial diameter squared leads to a single value for a given set of parameters, if the initial diameter is in a limited range. The normalized critical drying time was found to increase linearly when increasing the relative humidity ofthe drying air. Furthermore, the dependency was the same independently of temperature.The drying time appeared to decrease linearly with increasing temperature, although with a smaller dependence. Measurements with increasing impact velocity showed that the requireddrying time increased linearly. This nding is opposite of what is typically reportedin literature and it is an important part of the hypothesis for stickiness developed here .Finally, measurements with maltodextrin (with dextrose equivalent of 18) are reported for varying relative humidity and impact velocity and the same trends were shown as those found for skim milk. <br />Replacing the CCD-camera with a high-speed camera allows a user to produce videos of the impact of a sticky particle with a wall in very high temporal resolution. This was done for skim milk powder for varying impact velocity, humidity and piston surface material.The results were mostly qualitative, with a little quantitative analysis where possible.The first observation was that there was very little dierence between a particle that just adhered (sticky) and one that just bounced (non-sticky). Both were forced to make some contact with the piston upon impact, deformed only slightly and then typically moved slightly away before either stopping with contact (sticky) or bouncing with no contact (non-sticky). Sticky particles had a large apparent contact angle, similar to what would be expected for a liquid with poor wetting properties. The velocity did not seem to change this much, although slight deformation was seen when the impact velocity was at the highest used values. The phenomenon did not appear to change noticeable when the droplet was dried in a high relative humidity environment. The qualitative difference observable between Teon and stainless steel was very limited. On Stainless steel the droplet seemed to wet slightly more after the initial impact while the contact area was constant for Teon. Modelling work was carried out to help understand the phenomenon, but also to investigate how the impact scaled for particle size. This was done using the Level Set Method implemented in the Finite Element based COMSOL Microuidics software. Using two level functions allowed for the denition of density and viscosity functions which were different throughout the particle and different from the surrounding air. This was used to model an in homogeneous droplet which consisted of a skin with high viscosity and a core with lower viscosity. The surrounding air had an even lower viscosity and a lower density.The droplet was modelled without elastic properties. The simulations were initiated withthe condition that the droplet was moving towards the wall with a predened velocity.The simulation was run while individually varying initial droplet velocity, viscosity of skin, core and air, density of droplet and air, surface tension, droplet radius and the radius ofthe core relative to the droplet. A parameter analogous to the radius of the contact areawas dened and the dependency of this parameter upon the ones listed above was mapped.The radius of spreading, normalized with the droplet radius, correlated with the squareroot of the Reynolds' number (based on material properties of the skin) multiplied withthe volume of the droplet divided by the volume of the skin. A simple analytical model was used to show that this dependence on the Reynolds' number could be a result ofviscous dissipation of kinetic energy in a zone near the movement of the triple line.<br />The observations made in the experimental and modelling sections were combined to propose a simple criterion for use in conjunction with other tools for design or possible control of spray dryers. A single droplet drying technique is to be used to obtain a characteristic drying curve for the product of interest. The linear dependencies found is then used to reduce the necessary number of stickiness measurements to as little as three (although more measurements increase accuracy). These data are then used to produce a simple criterion which gives a critical residual moisture content under which a particle must be for it to be non-sticky as depending on the relative humidity in which it is dried, the initial radius of the droplet and the velocity with which it impacts the wall.<br />Finally, the hypothesis for stickiness that this work leads to is summarized as follows. Asa droplet is dried it forms a region near the surface in which the solvent concentrationdecreases and the viscosity increases. As it impacts a wall in the spray dryer it does sowith some kinetic energy. The kinetic energy forces the wet particle to deform and wetthe surface, while energy is dissipated in the viscous ow. If the viscosity in the surface region is high enough and the region is large enough the energy is dissipated with verylittle movement which means the contact area is small. A small contact area means a low energy of adhesion and the particle is easily removed by other eects. If the energy is not dissipated rapidly enough however a larger contact area is established and the particle will adhere strongly. This hypothesis suggests that the surface properties of the sticky particleare not the only effects that matter and therefore that measuring rehumidied particles is not the same as dried droplets. Furthermore it has the important dierence from the established hypothesis that the contact is forced and not spontaneous.</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. Kyngby</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>103</td></tr><tr class="status"><th>State</th><td><span class="prefix">Published - </span><span class="date">2015</span></td></tr></tbody></table></div></div></div>Thu, 01 Jan 2015 00:00:00 GMThttp://orbit.dtu.dk/en/publications/model-stickiness-in-spray-drying(fd944869-f19b-400c-ba5a-6e0c45d78c79).html2015-01-01T00:00:00ZThe Dynamics of a Railway Vehicle on a Disturbed Track: Modelling of lateral irregularities
http://orbit.dtu.dk/en/publications/the-dynamics-of-a-railway-vehicle-on-a-disturbed-track(6d24daac-617f-41f6-aaba-16dd18bfb16e).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/the-dynamics-of-a-railway-vehicle-on-a-disturbed-track(6d24daac-617f-41f6-aaba-16dd18bfb16e).html" class="link"><span>The Dynamics of a Railway Vehicle on a Disturbed Track: Modelling of lateral irregularities</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/lasse-engbo-christiansen(9d379f06-f620-404a-8397-3dfdaf9a3804).html" class="link person"><span>Christiansen, L. E.</span></a> <span class="date">2001</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">122 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">Report – Annual report year: 2001</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 work studies a mathematical model of a bogie, the aim being to investigate the correlation between the lateral motion of the bogie and lateral irregularities of the track that the bogie is running along. When modelling the wheel-rail forces real wheel and rail profiles are used. One of the main differences between this work and previous ones is that the vertical degrees of freedom are included making the model very realistic as this allows a dynamic calculation of the penetration depth in the contact area.<br /><br />In chapter two the model of the bogie is described, this is followed by a chapter describing how the wheel-rail interaction is modelled. The fourth chapter gives a presentation of the numerical algorithms used in this work.<br /><br />The fifth chapter presents the results obtained during this work, it begins with an brief investigation of the dynamics when running on a straight track. The second section introduces some statistical measures and treats centerline irregularities when running with a fixed speed of 30 m/s. The following section investigates the behaviour of the model when the track possesses gauge irregularities. The fourth and fifth sections describe the changes observed when changing the velocity of the railway vehicle and the phase between the sinusoidal irregularities of the rails. In the final section the eigenfrequencies of the bogie are found and the most important modes are described. Chapter six is a discussion of the obtained results, and these are related to the possibility of measuring track irregularities using accelerometers mounted on the bogie. Finally, some appendixes are included bringing some details of the derivations related to the wheel-rail interaction and details about the used pro files.</div></div><div class="scientificreport"><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>122</td></tr><tr class="status"><th>State</th><td><span class="prefix">Published - </span><span class="date">2001</span></td></tr></tbody></table></div><h3 class="subheader">Bibliographical note</h3><p>This is a Master of Science Thesis</p></div></div>Mon, 01 Jan 2001 00:00:00 GMThttp://orbit.dtu.dk/en/publications/the-dynamics-of-a-railway-vehicle-on-a-disturbed-track(6d24daac-617f-41f6-aaba-16dd18bfb16e).html2001-01-01T00:00:00ZCauchy Noise Removal by Nonconvex ADMM with Convergence Gaurantees
http://orbit.dtu.dk/en/publications/cauchy-noise-removal-by-nonconvex-admm-with-convergence-gaurantees(9353ee8b-835f-4063-9e72-c31893f7c4d0).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/cauchy-noise-removal-by-nonconvex-admm-with-convergence-gaurantees(9353ee8b-835f-4063-9e72-c31893f7c4d0).html" class="link"><span>Cauchy Noise Removal by Nonconvex ADMM with Convergence Gaurantees</span></a></h2>Mei, J-J., <a rel="Person" href="http://orbit.dtu.dk/en/persons/yiqiu-dong(fbd1dafa-2d1c-4149-85b8-8998ea308e5f).html" class="link person"><span>Dong, Y.</span></a>, Huang, T-Z. & Yin, W. <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">24 p.</span> (DTU Compute-Technical Report-2016; No. 10).<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">Report – 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">Image restoration is one of the most important and essential issues in image processing. Cauchy noise in engineering application has the non-Gaussian and impulsive property. In order to preserve edges and details of images, the total variation (TV) based variational model has been studied for restoring images degraded by blur and Cauchy noise. Due to the nonconvexity and nonsmoothness, there exist computational and theoretical challenges. In this paper, adapting recent results, we develop an alternating direction method of multiplier (ADMM) in spite of the challenges. The convergence to a stationary point is guaranteed theoretically under certain conditions. Experimental results demonstrate that the proposed method is competitive with other methods in terms of visual and quantitative measures. Especially, by comparing to the PSNR values, our method can improve about 0.5dB on average.</div></div><div class="scientificreport"><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>24</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>Series</th><td>DTU Compute-Technical Report-2016</td></tr><tr><th>Number</th><td>10</td></tr><tr><th>ISSN</th><td>1601-2321</td></tr></tbody></table></div></div>Fri, 01 Jan 2016 00:00:00 GMThttp://orbit.dtu.dk/en/publications/cauchy-noise-removal-by-nonconvex-admm-with-convergence-gaurantees(9353ee8b-835f-4063-9e72-c31893f7c4d0).html2016-01-01T00:00:00ZContrast Invariant SNR
http://orbit.dtu.dk/en/publications/contrast-invariant-snr(597f7317-fb88-4f7b-b736-9e29c8c71dae).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/contrast-invariant-snr(597f7317-fb88-4f7b-b736-9e29c8c71dae).html" class="link"><span>Contrast Invariant SNR</span></a></h2>Weiss, P., Escande, P. & <a rel="Person" href="http://orbit.dtu.dk/en/persons/yiqiu-dong(fbd1dafa-2d1c-4149-85b8-8998ea308e5f).html" class="link person"><span>Dong, Y.</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">8 p.</span> (DTU Compute-Technical Report-2016; No. 9).<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">Report – 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">We design an image quality measure independent of local contrast changes, which constitute simple models of illumination changes. Given two images, the algorithm provides the image closest to the first one with the component tree of the second. This problem can be cast as a specific convex program called isotonic regression. We provide a few analytic properties of the solutions to this problem. We also design a tailored first order optimization procedure together with a full complexity analysis. The proposed method turns out to be practically more efficient and reliable than the best existing algorithms based on interior point methods. The algorithm has potential applications in change detection, color image processing or image fusion. A Matlab implementation is available at http://www.math.univ-toulouse.fr/_weiss/PageCodes.html.</div></div><div class="scientificreport"><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>8</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>Series</th><td>DTU Compute-Technical Report-2016</td></tr><tr><th>Number</th><td>9</td></tr><tr><th>ISSN</th><td>1601-2321</td></tr></tbody></table></div></div>Fri, 01 Jan 2016 00:00:00 GMThttp://orbit.dtu.dk/en/publications/contrast-invariant-snr(597f7317-fb88-4f7b-b736-9e29c8c71dae).html2016-01-01T00:00:00ZBregman Cost for Non-Gaussian Noise
http://orbit.dtu.dk/en/publications/bregman-cost-for-nongaussian-noise(bedbd757-7604-4ea1-8bd6-d54ec7610919).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/bregman-cost-for-nongaussian-noise(bedbd757-7604-4ea1-8bd6-d54ec7610919).html" class="link"><span>Bregman Cost for Non-Gaussian Noise</span></a></h2>Burger, M., <a rel="Person" href="http://orbit.dtu.dk/en/persons/yiqiu-dong(fbd1dafa-2d1c-4149-85b8-8998ea308e5f).html" class="link person"><span>Dong, Y.</span></a> & <a rel="Person" href="http://orbit.dtu.dk/en/persons/federica-sciacchitano(595c3287-b609-4c3e-a8db-a390a74df2b1).html" class="link person"><span>Sciacchitano, F.</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">12 p.</span> (DTU Compute-Technical Report-2016; No. 8).<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">Report – 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">One of the tasks of the Bayesian inverse problem is to find a good estimate based on the posterior probability density. The most common point estimators are the con-ditional mean (CM) and maximum a posteriori (MAP) estimates, which correspond to the mean and the mode of the posterior, respectively. From a theoretical point of view it has been argued that the MAP estimate is only in an asymptotic sense a Bayes estimator for the uniform cost function, while the CM estimate is a Bayes estimator for the means squared cost function. Recently, it has been proven that the MAP estimate is a proper Bayes estimator for the Bregman cost if the image is corrupted by Gaussian noise. In this work we extend this result to other noise models with log-concave likelihood density, by introducing two related Bregman cost functions for which the CM and the MAP estimates are proper Bayes estima-tors. Moreover, we also prove that the CM estimate outperforms the MAP estimate, when the error is measured in a certain Bregman distance, a result previously unknown also in the case of additive Gaussian noise.</div></div><div class="scientificreport"><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>12</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>Series</th><td>DTU Compute-Technical Report-2016</td></tr><tr><th>Number</th><td>8</td></tr><tr><th>ISSN</th><td>1601-2321</td></tr></tbody></table></div></div>Fri, 01 Jan 2016 00:00:00 GMThttp://orbit.dtu.dk/en/publications/bregman-cost-for-nongaussian-noise(bedbd757-7604-4ea1-8bd6-d54ec7610919).html2016-01-01T00:00:00ZPre-Swirl Stator and Propeller Design for Varying Operating Conditions
http://orbit.dtu.dk/en/publications/preswirl-stator-and-propeller-design-for-varying-operating-conditions(37e6728b-cea5-42ef-974c-63e305fbafdf).html
<div style='font-size: 9px;'><div class="rendering rendering_publication rendering_publication_short rendering_contributiontobookanthology rendering_short rendering_contributiontobookanthology_short"><h2 class="title"><a rel="ContributionToBookAnthology" href="http://orbit.dtu.dk/en/publications/preswirl-stator-and-propeller-design-for-varying-operating-conditions(37e6728b-cea5-42ef-974c-63e305fbafdf).html" class="link"><span>Pre-Swirl Stator and Propeller Design for Varying Operating Conditions</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/simone-saettone(ac376213-0b03-4ba4-8414-da65287c7c19).html" class="link person"><span>Saettone, S.</span></a>, <a rel="Person" href="http://orbit.dtu.dk/en/persons/pelle-bo-regener(3ae5619d-22bf-4c88-a09b-51f1618c6bb0).html" class="link person"><span>Regener, P. B.</span></a> & <a rel="Person" href="http://orbit.dtu.dk/en/persons/poul-andersen(fe9622c5-8fc6-4cb1-b1e2-14ca2d897cb5).html" class="link person"><span>Andersen, P.</span></a> <span class="date">2016</span> <em>Proceedings of the 13th International Symposium on PRActical Design of Ships and Other Floating Structures (PRADS' 2016).</em> Dam Nielsen, U. & Juncher Jensen, J. (eds.). <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">8 p.</span><p class="type"><span class="type_family">Publication<span class="type_family_sep">: </span></span><span class="type_classification_parent">Research - peer-review<span class="type_parent_sep"> › </span></span><span class="type_classification">Article in proceedings – Annual report year: 2016</span></p></div><div class="rendering rendering_publication rendering_publication_detailsportal rendering_contributiontobookanthology rendering_detailsportal rendering_contributiontobookanthology_detailsportal"><div class="abstract"><div class="textblock">Over the last two decades, an increasing number of studies have been conducted to develop and improve energy saving devices (ESDs) in order to increase the propulsive effciency. One well-known example is the pre-swirlstator (PSS), which consists of an often asymmetric arrangement of fixed stator blades ahead of the propeller.This paper describes the hydrodynamic design of apre-swirl stator with radially variable pitch, paired with aconventional propeller. The aim is to achieve the highest possible effciency in various operating conditions, and to avoid effciency penalties in off-design operation.To investigate the propeller and stator designs and configurations in different operating conditions, the computationally inexpensive vortex-lattice method is used a sa first step to optimize the geometry in an initial parameter study. Then the flow over hull, stator and propelleris simulated in a CFD-based approach to confirm the results obtained in the first stage.</div></div><div class="conferencearticle"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr><tr><th>Title of host publication</th><td>Proceedings of the 13th International Symposium on PRActical Design of Ships and Other Floating Structures (PRADS' 2016)</td></tr><tr><th>Editors</th><td>Ulrik Dam Nielsen, Jørgen Juncher Jensen</td></tr><tr><th>Number of pages</th><td>8</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>Publication date</th><td><span class="date">2016</span></td></tr><tr class="isbn-electronic"><th>ISBN (electronic)</th><td>978-87-7475-473-2</td></tr><tr class="status"><th>State</th><td><span class="prefix">Published - </span><span class="date">2016</span></td></tr><tr class="event"><th>Event</th><td><span class="prefix">13th International Symposium on Practical Design of Ships and Other Floating Structures (PRADS'2016) - Copenhagen, Denmark</span></td></tr></tbody></table></div><h3 class="subheader">Conference</h3><table class="properties"><tbody><tr><th>Conference</th><td>13th International Symposium on Practical Design of Ships and Other Floating Structures (PRADS'2016)</td></tr><tr><th>Number</th><td>13</td></tr><tr><th>Location</th><td>Hotel Crowne Plaza</td></tr><tr><th>Country</th><td>Denmark</td></tr><tr><th>City</th><td>Copenhagen</td></tr><tr class="period"><th>Period</th><td><span class="date">04/09/2016</span> → <span class="date">08/09/2016</span></td></tr></tbody></table></div></div>Fri, 01 Jan 2016 00:00:00 GMThttp://orbit.dtu.dk/en/publications/preswirl-stator-and-propeller-design-for-varying-operating-conditions(37e6728b-cea5-42ef-974c-63e305fbafdf).html2016-01-01T00:00:00ZImplementation of Hardware Accelerators on Zynq
http://orbit.dtu.dk/en/publications/implementation-of-hardware-accelerators-on-zynq(cb6ecf31-d421-41f6-b39b-b76a553a0019).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/implementation-of-hardware-accelerators-on-zynq(cb6ecf31-d421-41f6-b39b-b76a553a0019).html" class="link"><span>Implementation of Hardware Accelerators on Zynq</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/jakob-kenn-toft(7e40da3b-84b9-4586-b064-b99861a2e20e).html" class="link person"><span>Toft, J. K.</span></a> & <a rel="Person" href="http://orbit.dtu.dk/en/persons/alberto-nannarelli(e1a0a7a2-7f9d-4a0b-bae5-b24f2fc93d2b).html" class="link person"><span>Nannarelli, 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">26 p.</span> (DTU Compute-Technical Report-2016; No. 7).<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">Report – 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 the recent years it has become obvious that the performance of general purpose processors are having trouble meeting the requirements of high performance computing applications of today. This is partly due to the relatively high power consumption, compared to the performance, of general purpose processors, which has made hardware accelerators an essential part of several datacentres and the worlds fastest super-computers. <br /><br />In this work, two different hardware accelerators were implemented on a Xilinx Zynq SoC platform mounted on the ZedBoard platform. The two accelerators are based on two different benchmarks, a Monte Carlo simulation of European stock options and a Telco telephone billing application. Each of the accelerators test different aspects of the Zynq platform in terms of floating-point and binary coded decimal processing speed. The two accelerators are compared with the performance of the ARM Cortex-9 processor featured on the Zynq SoC, with regard to execution time, power dissipation and energy consumption. <br /><br />The implementation of the hardware accelerators were successful. Use of the Monte Carlo processor resulted in a significant increase in performance. The Telco hardware accelerator showed a very high increase in performance over the ARM-processor.</div></div><div class="scientificreport"><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>26</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>Series</th><td>DTU Compute-Technical Report-2016</td></tr><tr><th>Number</th><td>7</td></tr><tr><th>ISSN</th><td>1601-2321</td></tr></tbody></table></div></div>Fri, 01 Jan 2016 00:00:00 GMThttp://orbit.dtu.dk/en/publications/implementation-of-hardware-accelerators-on-zynq(cb6ecf31-d421-41f6-b39b-b76a553a0019).html2016-01-01T00:00:00ZDesign and analysis of cryptographic algorithms
http://orbit.dtu.dk/en/publications/design-and-analysis-of-cryptographic-algorithms(c3ac3f18-2898-476c-957b-59b83ee77d0d).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-cryptographic-algorithms(c3ac3f18-2898-476c-957b-59b83ee77d0d).html" class="link"><span>Design and analysis of cryptographic algorithms</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/stefan-koelbl(45ab0201-3844-404a-bbff-1ba4b392a953).html" class="link person"><span>Kölbl, S.</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">257 p.</span> (DTU Compute PHD-2016; No. 434).<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 today’s world computers are ubiquitous. They can be found in virtually any industry and most households own at least one personal computer or have a mobile phone. Apart from these fairly large and complex devices, we also see computers on a much smaller scale appear in everyday objects in the form of micro-controllers and RFID chips.<br /><br />What truly transformed our society are large scale networks, like the Internet or mobile telephone networks, which can link billions of devices. Our ways of communicating and conducting business have severely changed over the last decades due to this development. However, most of this communication happens over inherently insecure channels requiring methods to protect our communication. A further issue is the vast amount of data generated, which raises serious privacy concerns.<br /><br />Cryptography provides the key components for protecting our communication. From securing our passwords and personal data to protecting mobile communication from eavesdroppers and our electronic bank transactions from manipulation. These applications would be impossible without cryptography. <br /><br />The main topic of this thesis is the design and security analysis of the most fundamental algorithms used in cryptography, namely block ciphers and cryptographic hash functions. These algorithms are the building blocks for a vast amount of applications and play a vital role in providing both confidentiality and integrity for our communication. <br /><br />This work is organized in two parts. First, an introduction to block ciphers and cryptographic hash functions is given to provide an overview over the state-of-the-art, the terminology, and how we can evaluate the security of an algorithm. The second part is a collection of scientific publications that have been written during the PhD studies and published. <br /><br />In the first publication we analyze the security of cryptographic hash functions based on the AES and demonstrate practical attacks on reduced-round versions of these algorithms. The second publication provides cryptanalysis of the lightweight block cipher SIMON in particular how resistant this type of block ciphers are against differential and linear cryptanalyis. In the fourth publication we present a short-input hash function utilizing AES-specific instructions on modern CPUs in order to improve the performance of hashbased signature schemes. The last publication deals with the design of the tweakable lightweight block cipher Skinny which provides strong security bounds against differential and linear attacks while also competing with the performance of SIMON.</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>257</td></tr><tr class="status"><th>State</th><td><span class="prefix">Submitted - </span><span class="date">2016</span></td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Series</th><td>DTU Compute PHD-2016</td></tr><tr><th>Number</th><td>434</td></tr><tr><th>ISSN</th><td>0909-3192</td></tr></tbody></table></div></div>Fri, 01 Jan 2016 00:00:00 GMThttp://orbit.dtu.dk/en/publications/design-and-analysis-of-cryptographic-algorithms(c3ac3f18-2898-476c-957b-59b83ee77d0d).html2016-01-01T00:00:00ZAn Investigation of Methods for CT Synthesis in MR-only Radiotherapy
http://orbit.dtu.dk/en/publications/an-investigation-of-methods-for-ct-synthesis-in-mronly-radiotherapy(9a1a2093-e7f9-4415-8233-dad1ba5460ff).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/an-investigation-of-methods-for-ct-synthesis-in-mronly-radiotherapy(9a1a2093-e7f9-4415-8233-dad1ba5460ff).html" class="link"><span>An Investigation of Methods for CT Synthesis in MR-only Radiotherapy</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/daniel-andreasen(d45d8ed5-c7b3-44eb-ac2e-1c3ecd43f8f2).html" class="link person"><span>Andreasen, D.</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">2017</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">72 p.</span> (DTU Compute PHD-2016; No. 428).<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: 2017</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 recent years, the interest in using magnetic resonance (MR) imaging in radiotherapy (RT) has increased. This is because MR has a superior soft tissue contrast compared to computed tomography (CT), which makes it a better modality for delineating the target volume (tumor) and possible organs at risk (OARs). In an MR/CT work-flow, independent MR and CT scans are acquired. The target and possible OARs are delineated on the MR and then transferred to CT by aligning the data using a registration. This introduces the risk of systematic registration errors especially in non-rigid body structures, the consequence being a systematic miss of target or increased dose to healthy tissue. <br /><br />Radiotherapy based on MR as the only modality removes this uncertainty and simplifies the clinical work-flow. However, the information on electron density which is usually contained in the CT must now be derived from the MR. A way to achieve this is to computationally estimate a so-called synthetic CT (sCT) from the MR data, which can then act as a substitute for the CT. This is a challenging task, since no unique relationship between MR and electron density exists.<br /><br />The goal of this thesis is to develop and investigate the right combination of MR acquisition protocols and computational models for accurate MR-based CT synthesis for use in RT. We investigate different categories of methods for CT synthesis and validate them using clinically relevant quality measures. Specifically, we implement a patch-based multi-atlas method in the brain, which compares favorably to state-of-the-art methods. In our next effort, we substantially improve the speed of the method and apply it in the pelvis, again with promising results. Our final contribution is a voxel-based method, which is developed to be registration-free and broadly applicable. In initial results, the performance of this method is close to the patch-based.</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>72</td></tr><tr class="status"><th>State</th><td><span class="prefix">Published - </span><span class="date">2017</span></td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Series</th><td>DTU Compute PHD-2016</td></tr><tr><th>Number</th><td>428</td></tr><tr><th>ISSN</th><td>0909-3192</td></tr></tbody></table></div></div>Sun, 01 Jan 2017 00:00:00 GMThttp://orbit.dtu.dk/en/publications/an-investigation-of-methods-for-ct-synthesis-in-mronly-radiotherapy(9a1a2093-e7f9-4415-8233-dad1ba5460ff).html2017-01-01T00:00:00ZOptimization on Spaces of Curves
http://orbit.dtu.dk/en/publications/optimization-on-spaces-of-curves(6ffa726c-50ce-416f-a64b-0b3f40bb70be).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/optimization-on-spaces-of-curves(6ffa726c-50ce-416f-a64b-0b3f40bb70be).html" class="link"><span>Optimization on Spaces of Curves</span></a></h2><a rel="Person" href="http://orbit.dtu.dk/en/persons/jakob-moellerandersen(4d0b40f9-31c1-497c-acef-e6f5660a42ff).html" class="link person"><span>Møller-Andersen, J.</span></a> & <a rel="Person" href="http://orbit.dtu.dk/en/persons/jens-gravesen(c4148734-4026-46f6-ac0d-8ddd781fb0b0).html" class="link person"><span>Gravesen, 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">113 p.</span> (DTU Compute PHD-2016; No. 432).<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 is concerned with computational and theoretical aspects of Riemannian metrics on spaces of regular curves, and their applications. It was recently proved that second order constant coefficient Sobolev metrics on curves are geodesically complete. We extend this result to the case of Sobolev metrics with coefficient functions depending on the length of the curve. We show how to apply this result to analyse a wide range of metrics on the submanifold of unit and constant speed curves.<br /><br />We present a numerical discretization of second order Sobolev metrics on the space of regular curves in R<sup>d</sup>, and methods to solve the initial and boundary value problem for geodesics allowing us to compute the Karcher mean and principal components analysis of data of curves. We apply the methods to study shape variation in synthetic data in the Kimia shape database, in HeLa cell nuclei and cycles of cardiac deformations.<br /><br />Finally we investigate a new application of Riemannian shape analysis in shape optimization. We setup a simple elliptic model problem, and describe how to apply shape calculus to obtain directional derivatives in the manifold of planar curves. We present an implementation based on parametrization of immersions by B-splines, which ties in naturally with Isogeometric Analysis to solve the PDE. We give numerical examples of solutions, and compare the Riemannian optimization algorithms with different choices of metrics to a naive unregularized discretize-first approach.</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>113</td></tr><tr class="status"><th>State</th><td><span class="prefix">Submitted - </span><span class="date">2016</span></td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Series</th><td>DTU Compute PHD-2016</td></tr><tr><th>Number</th><td>432</td></tr><tr><th>ISSN</th><td>0909-3192</td></tr></tbody></table></div></div>Fri, 01 Jan 2016 00:00:00 GMThttp://orbit.dtu.dk/en/publications/optimization-on-spaces-of-curves(6ffa726c-50ce-416f-a64b-0b3f40bb70be).html2016-01-01T00:00:00Z