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RSS FeedNumerical Modeling of Microelectrochemical Systems
http://orbit.dtu.dk/en/publications/numerical-modeling-of-microelectrochemical-systems(0416e54e-6781-49bb-a7d1-497a50065746).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 class="link" rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/numerical-modeling-of-microelectrochemical-systems(0416e54e-6781-49bb-a7d1-497a50065746).html"><span>Numerical Modeling of Microelectrochemical Systems</span></a></h2><a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/bolaji-james-adesokan(c3e1252a-6c2c-4d8e-b447-2925193e9b43).html"><span>Adesokan, B. J.</span></a>, <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/anton-evgrafov(5b5c3973-511e-41e0-b0f4-e6f7dce2c1d4).html"><span>Evgrafov, A.</span></a> & <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/mads-peter-soerensen(651b67f7-1e41-4719-8369-01b34075cd6b).html"><span>Sørensen, M. P.</span></a> <span class="date">2015</span> Kgs. Lyngby: <a class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">116 p.</span> (DTU Compute PHD-2015; No. 362).<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="textblock">The PhD dissertation is concerned with mathematical modeling and simulation of electrochemical systems. The first three chapters of the thesis consist of the introductory part, the model development chapter and the chapter on the summary of the main results. The remaining three chapters report three independent papers and manuscripts.<br /><br />As a preliminary to the study, we describe a general model for electrochemical systems and study their underlying mechanisms through electroanalytical techniques. We then extend the model to a more realistic model for microelectrochemical systems which incorporates the finite size of ionic species in the transport equation. The model presents a more appropriate boundary conditions which describe the modified Butler-Volmer reaction kinetics and account for the surface capacitance of the thin electric double layer. We also have found analytical solution for the reactants in the bulk electrolyte that are traveling waves.<br /><br />The first paper presents the mathematical model which describes an electrochemical system and simulates an electroanalytical technique called cyclic voltammetry. The model is governed by a system of advection–diffusion equations with a nonlinear reaction term at the boundary. We investigate the effect of flow rates, scan rates, and concentration on the cyclic voltammetry. We establish that high flow rates lead to the reduced hysteresis in the cyclic voltammetry curves and increasing scan rates lead to more pronounced current peaks. The final part of the paper shows that the response current in a cyclic voltammetry increases proportionally to the electrolyte concentration. <br /><br />In the second paper we present an experiment of an electrochemical system in a microfluidc system and compare the result to the numerical solutions. We investigate how the position of the electrodes in the system affects the recorded cyclic voltammetry. The result shows that convection influences the charge transfer dynamics on the electrode surface and hence the cyclic voltammetry recorded. In terms of relative high flow to scan rates, the current response is dominated by the convection due to the fresh supply of reactants towards the electrode surface and quick removal of the products. We also establish that at high scan rates and modest flow rates, peak currents are recorded. Finally, the results show that the position of the electrodes is critical when performing cyclic voltammetry under the flow condition. The numerical results show promising agreement with experimental findings which could be critical in designing highly sensitive electrochemical systems.<br /><br />The last paper explores the numerical solution which describes the non-linear transient responses to a large applied potential at the electrode in a microelectrochemical system. In our analysis, we account for the finite size properties of ions in the mass and the charge transport of ionic species in an electrochemical system. This term characterizes the saturation of the ionic species close to the electrode surface. We then analyse the responses of the system on the charging of the electric double layer. We consider an arbitrary electrolyte solution that is sandwiched between electrodes and allow for electrochemical reactions at the electrode/electrolyte interface. One of the electrodes is biased with a potential which triggers the reaction and the dynamics of the system. We establish that there is a quick build up of boundary layers in the double layer, but the finite size constraint on the ionic species prevents overcrowding of the ionic species. The result also shows that reactants which undergo charge transfer at the electrode/ electrolyte interface crowded the electric double layer and the dynamics of the electric double layer is controlled by the charge transfer.<br /></div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr><tr><th>Publication date</th><td><span class="date">2015</span></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 class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>116</td></tr><tr class="status"><th>State</th><td>Submitted</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>362</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/numerical-modeling-of-microelectrochemical-systems(0416e54e-6781-49bb-a7d1-497a50065746).html2014-12-31T23:00:00ZProbabilistic Approaches to Energy Systems
http://orbit.dtu.dk/en/publications/probabilistic-approaches-to-energy-systems(04b29769-d375-4fd3-892c-36fd62f150cc).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 class="link" rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/probabilistic-approaches-to-energy-systems(04b29769-d375-4fd3-892c-36fd62f150cc).html"><span>Probabilistic Approaches to Energy Systems</span></a></h2><a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/jan-emil-banning-iversen(72442f56-5041-4dad-87d6-48f8afc8d29a).html"><span>Iversen, J. E. B.</span></a>, <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/henrik-madsen(458e950b-adfd-4f2d-8d0d-ef39dee24bea).html"><span>Madsen, H.</span></a>, <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/juan-miguel-morales-gonzlez(f2f55c22-077c-4640-89b8-bba4bdc35412).html"><span>Morales González, J. M.</span></a> & <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/jan-kloppenborg-moeller(06a667bd-2e4d-493d-ada6-191296446a2e).html"><span>Møller, J. K.</span></a> <span class="date">2015</span> Kgs. Lyngby: <a class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">175 p.</span> (DTU Compute PHD-2015; No. 363).<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="textblock">Energy generation from wind and sun is increasing rapidly in many parts of the world. This presents new challenges on how to integrate this uncertain, intermittent and non-dispatchable energy source. This thesis deals with forecasting and decision making in energy systems with a large proportion of renewable energy generation. Particularly we focus on producing forecasting models that can predict renewable energy generation, single user demand, and provide advanced forecast products that are needed for an efficient integration of renewable energy into the power generation mix. Such forecasts can be useful on all levels of the energy systems, ranging from the highest level, where the transmission system operator is concerned with minimizing system failures and is aided by wind power forecasts, to the end user of energy where power price forecasts are useful for users with flexible power demand. <br /><br />The main contributions of this thesis lie in the realm of using gray box models to produce forecasts for energy systems. Gray box models can be defined as a crossover between physical models (or white box models), that base their model on a physical understanding of the system at hand, and data driven models (or black box models) that focus on accurately describing the data without considering physical limitations of the system. Integrating these physical structures into a data driven approach allows for producing better forecasts with more accurate predictions. In this thesis we have developed and applied methodologies for gray box modeling to produce forecasts for vehicle driving patterns, solar irradiance, wind speeds, wind power, and solar power. The model for driving patterns has subsequently been used as input into an optimization algorithm for charging a single electric vehicle. In a subsequent study the behavior of a fleet of electric vehicles has been studied. <br /><br />In the thesis we go through various examples of forecasts products and their applications. We emphasize that forecasting can not stand alone and should be complimented by optimization and decision making tools for an efficient integration of renewable energy.Thus forecast products should be developed in unison with the decision making tool as they are two sides of the same overall challenge.<br /></div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr><tr><th>Publication date</th><td><span class="date">2015</span></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 class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>175</td></tr><tr class="status"><th>State</th><td>Submitted</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>363</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/probabilistic-approaches-to-energy-systems(04b29769-d375-4fd3-892c-36fd62f150cc).html2014-12-31T23:00:00ZCryptanalysis of Selected Block Ciphers
http://orbit.dtu.dk/en/publications/cryptanalysis-of-selected-block-ciphers(0fb77cd6-fdab-4aa1-9e35-fc2c45de5f30).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 class="link" rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/cryptanalysis-of-selected-block-ciphers(0fb77cd6-fdab-4aa1-9e35-fc2c45de5f30).html"><span>Cryptanalysis of Selected Block Ciphers</span></a></h2><a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/hoda-a-alkhzaimi(98f54201-ca2c-46b3-a375-eb3958a6b81d).html"><span>Alkhzaimi, H. A.</span></a> & <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/lars-ramkilde-knudsen(a62b8acd-d07f-4943-a467-85af0eb5efe0).html"><span>Knudsen, L. R.</span></a> <span class="date">2015</span> Kgs. Lyngby: <a class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">140 p.</span> (DTU Compute PHD-2015; No. 360).<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="textblock">The focus of this dissertation is to present cryptanalytic results on selected block ciphers. Block ciphers are the mathematical structure that will take a plaintext message and convert it into a ciphertext one block at a time using a secret key. They play an essential role in many cryptographic architectures and frameworks. For a long time they were known as the main building block that will provide confidentiality in an information system. They would also be able to represent a full spectrum of cryptographic services as many block ciphers can be used to construct stream ciphers, hash functions, pseudorandom number generators, and authenticated encryption designs. <br /><br />For this reason a multitude of initiatives over the years has been established to provide a secure and sound designs for block ciphers as in the calls for Data Encryption Standard (DES) and Advanced Encryption Standard (AES), lightweight ciphers initiatives, and the Competition for Authenticated Encryption: Security, Applicability, and Robustness (CAESAR).<br /><br />In this thesis, we first present cryptanalytic results on different ciphers. We propose attack named the Invariant Subspace Attack. It is utilized to break the full block cipher PRINTcipher for a significant fraction of its keys. This new attack also gives us new insights into other, more well-established attacks. In addition, we also show that for weak keys, strongly biased linear approximations exists for any number of rounds. <br /><br />Furthermore, we provide variety of attacks on the family of lightweight block cipher SIMON that was published by the U.S National Security Agency (NSA). The ciphers are developed with optimization towards both hardware and software in mind. While the specification paper discusses design requirements and performance of the presented lightweight ciphers thoroughly, no security assessment is given. We present a series of observations on the presented construction that, in some cases, yield attacks, while in other cases may provide basis of further analysis by the cryptographic community. Specifically, The attacks obtained are using classical- as well as truncated differentials. In addition to that, we also investigate the security of SIMON against different linear cryptanalysis methods, i.e., classic linear,and linear hull attacks. we present a connection between linear characteristic and differential characteristic, multiple linear and differential and linear hull and differential, and employ it to adapt the current known results on differential cryptanalysis of SIMON to linear cryptanalysis results. <br /><br />Finally, we investigate links between different methods of cryptanalysis and how they can be utilized for block cipher cryptanalysis. We consider the known results on the links among integral, impossible differential and zero-correlation linear hulls in order to prove that constructing a zero-correlation linear hull always implies the existence of an integral distinguisher. Moreover, we show that constructing zero-correlation linear hull on a Feistel structure with SP-type round functions, where P is a binary matrix, is equivalent to constructing impossible differential on the same structure except that P is substituted by the transposed matrix PT . We present an integral distinguishers of 5-round Feistel structure with bijective round functions and 3-round Feistel structure with round functions not necessarily being bijective. In addition to an integral distinguishers of Camellia so far, i.e., 7-round integral distinguishers of Camellia with FL/FL−1 layer and 8-round integral distinguishers of Camellia without FL/FL−1 layer.<br /></div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr><tr><th>Publication date</th><td><span class="date">2015</span></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 class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>140</td></tr><tr class="status"><th>State</th><td>Submitted</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>360</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/cryptanalysis-of-selected-block-ciphers(0fb77cd6-fdab-4aa1-9e35-fc2c45de5f30).html2014-12-31T23:00:00ZMultispectral Imaging of Meat Quality - Color and Texture
http://orbit.dtu.dk/en/publications/multispectral-imaging-of-meat-quality--color-and-texture(d08fa738-d11c-421a-bd1e-5eb2b94c5b0b).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 class="link" rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/multispectral-imaging-of-meat-quality--color-and-texture(d08fa738-d11c-421a-bd1e-5eb2b94c5b0b).html"><span>Multispectral Imaging of Meat Quality - Color and Texture</span></a></h2><a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/camilla-himmelstrup-trinderup(722e6016-12eb-47f8-991e-84c87f900564).html"><span>Trinderup, C. H.</span></a>, <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/knut-conradsen(58fbfe83-3565-4584-8b50-3a01a72134e0).html"><span>Conradsen, K.</span></a> & <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/anders-bjorholm-dahl(c2bad3c8-b172-481b-bb99-d3c2bc4004ef).html"><span>Dahl, A. B.</span></a> <span class="date">2014</span> Kgs. Lyngby: <a class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">179 p.</span> (DTU Compute PHD-2014; No. 358).<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="textblock">The use of computer vision systems in food production and development is increasing. Computer vision systems offer fast, reliable, objective and noninvasive methods for assessment of wanted quality traits.<br /><br />This thesis investigates the applicability of computer vision systems in the assessment of meat quality parameters, especially with regards to meat color and texture. Several image modalities have been applied, all considering multi- or hyper spectral imaging.<br /><br />The work demonstrates the use of computer vision systems for meat color measurements. The color is assessed by suitable transformations to the CIELAB color space, the common color space within food science. The results show that meat color assessment with a multispectral imaging is a great alternative to the traditional colorimeter, i.e. the vision system meets some of the limitations that the colorimeter possesses. To mention one, it is possible to assess color of very complicated structures, such as salamis, with a vision system. More importantly though, the vision system embraces the complicated scattering properties of meat.<br /><br />The images can also lead to other analyses, e.g. image texture analysis relating to the structure of the meat. In the thesis it is presented how simple texture measures can be used for characterizing the texture changes in fermented salamis. Moreover, it was investigated if it was possible to relate structure in images to chemical compounds in lard from boars.</div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr><tr><th>Publication date</th><td><span class="date">2014</span></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 class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>179</td></tr><tr class="status"><th>State</th><td>Submitted</td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Name</th><td>DTU Compute PHD-2014</td></tr><tr><th>Number</th><td>358</td></tr><tr><th>ISSN (print)</th><td>0909-3192</td></tr></tbody></table></div></div>Tue, 31 Dec 2013 23:00:00 GMThttp://orbit.dtu.dk/en/publications/multispectral-imaging-of-meat-quality--color-and-texture(d08fa738-d11c-421a-bd1e-5eb2b94c5b0b).html2013-12-31T23:00:00ZAlgorithms and data structures for grammar-compressed strings
http://orbit.dtu.dk/en/publications/algorithms-and-data-structures-for-grammarcompressed-strings(78d89068-7c76-4105-8908-a2d474683732).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 class="link" rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/algorithms-and-data-structures-for-grammarcompressed-strings(78d89068-7c76-4105-8908-a2d474683732).html"><span>Algorithms and data structures for grammar-compressed strings</span></a></h2><a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/patrick-hagge-cording(5bccf823-af4b-47b6-b1c6-2d45a362a261).html"><span>Cording, P. H.</span></a>, <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/philip-bille(81ad6edf-aa11-47bc-adaf-227fe7e6963e).html"><span>Bille, P.</span></a> & <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/inge-li-goertz(08da98e0-b1f4-492e-94e7-15083cc40701).html"><span>Gørtz, I. L.</span></a> <span class="date">2014</span> Kgs. Lyngby: <a class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">66 p.</span> (DTU Compute PHD-2014; No. 357).<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="textblock">Textual databases for e.g. biological or web-data are growing rapidly, and it is often only feasible to store the data in compressed form. However, compressing the data comes at a price. Traditional algorithms for e.g. pattern matching requires all data to be decompressed - a computationally demanding task. In this thesis we design data structures for accessing and searching compressed data efficiently.<br /><br />Our results can be divided into two categories. In the first category we study problems related to pattern matching. In particular, we present new algorithms for counting and comparing substrings, and a new algorithm for finding all occurrences of a pattern in which we may insert gaps. In the other category we deal with accessing and decompressing parts of the compressed string. We show how to quickly access a single character of the compressed string, and present a data structure that supports fast decompression of substrings from prespecified positions.</div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr><tr><th>Publication date</th><td><span class="date">2014</span></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 class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>66</td></tr><tr class="status"><th>State</th><td>Submitted</td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Name</th><td>DTU Compute PHD-2014</td></tr><tr><th>Number</th><td>357</td></tr><tr><th>ISSN (print)</th><td>0909-3192</td></tr></tbody></table></div></div>Tue, 31 Dec 2013 23:00:00 GMThttp://orbit.dtu.dk/en/publications/algorithms-and-data-structures-for-grammarcompressed-strings(78d89068-7c76-4105-8908-a2d474683732).html2013-12-31T23:00:00ZAlgorithms for Electromagnetic Scattering Analysis of Electrically Large Structures
http://orbit.dtu.dk/en/publications/algorithms-for-electromagnetic-scattering-analysis-of-electrically-large-structures(68a87a2a-3b48-4d25-aac3-613f22505e72).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 class="link" rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/algorithms-for-electromagnetic-scattering-analysis-of-electrically-large-structures(68a87a2a-3b48-4d25-aac3-613f22505e72).html"><span>Algorithms for Electromagnetic Scattering Analysis of Electrically Large Structures</span></a></h2><a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/oscar-peter-borries(07ed5fe0-b447-49a9-9fb9-5555c76d072d).html"><span>Borries, O. P.</span></a> & <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/per-christian-hansen(6c6c6f32-e3b2-40d5-a407-aa8e2f051f7b).html"><span>Hansen, P. C.</span></a> <span class="date">2014</span> Kgs. Lyngby: <a class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">205 p.</span> (DTU Compute PHD-2014; No. 354).<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="textblock">Accurate analysis of electrically large antennas is often done using either Physical Optics (PO) or Method of Moments (MoM), where the former typically requires fewer computational resources but has a limited application regime. This study has focused on fast variants of these two methods, with the goal of reducing the computational complexity while maintaining accuracy. <br /><br />Regarding MoM, the complexity is reduced by applying the Multi-Level Fast Multipole Method (MLFMM) in combination with an iterative solver. Using MLFMM with a MoM implementation based on Higher-Order (HO) basis functions has, by several authors, been dismissed as being too memory intensive. In the present work, we demonstrate for the first time that by including a range of both novel and previously presented modifications to the standard MLFMM implementation, HO MLFMM can achieve both memory reduction and significant speed increase compared to Lower-Order (e.g., RWG) based MLFMM. Further, issues surrounding an iterative solution, such as the iterative solver and preconditioning, are discussed. Numerical results demonstrate the performance and stability of the algorithm for very large problems, including full satellites at Ku band.<br /><br />Accelerating PO is an entirely different matter. A few authors have discussed applying the Fast-PO technique to far fields, achieving relative errors of 0.1%−1% for moderately sized scatterers. For near-fields, the state-of-the-art implementation of Fast-PO has several difficulties, in particular low accuracy and limited application regime. For the problems considered in this thesis, the error limit for PO is ≈ 0.01%, and the application limitations of the published Fast-PO are too prohibitive for our use. Therefore, results based on an improved Fast-PO implementation for far-fields, as well as a novel algorithm for near-fields, are presented. These results demonstrate that it is possible to achieve very accurate results, with relative errors around 10<sup>−5</sup>, at a much reduced time consumption. The method behind this part of the code is deemed confidential by TICRA.<br /></div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr><tr><th>Publication date</th><td><span class="date">2014</span></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 class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>205</td></tr><tr class="status"><th>State</th><td>Submitted</td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Name</th><td>DTU Compute PHD-2014</td></tr><tr><th>Number</th><td>354</td></tr><tr><th>ISSN (print)</th><td>0909-3192</td></tr></tbody></table></div></div>Tue, 31 Dec 2013 23:00:00 GMThttp://orbit.dtu.dk/en/publications/algorithms-for-electromagnetic-scattering-analysis-of-electrically-large-structures(68a87a2a-3b48-4d25-aac3-613f22505e72).html2013-12-31T23:00:00ZFull Scale Measurements of the Hydro-Elastic Response of Large Container Ships for Decision Support
http://orbit.dtu.dk/en/publications/full-scale-measurements-of-the-hydroelastic-response-of-large-container-ships-for-decision-support(80015fe7-b181-4e59-97fd-61f330063fe3).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 class="link" rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/full-scale-measurements-of-the-hydroelastic-response-of-large-container-ships-for-decision-support(80015fe7-b181-4e59-97fd-61f330063fe3).html"><span>Full Scale Measurements of the Hydro-Elastic Response of Large Container Ships for Decision Support</span></a></h2><a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/ingrid-marie-vincent-andersen(817b53b7-4749-4650-93b8-48fe175ac288).html"><span>Andersen, I. M. V.</span></a>, <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/joergen-juncher-jensen(7ba41725-e940-4ecd-9bf5-d25e44c9aabe).html"><span>Jensen, J. J.</span></a> & <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/ulrik-dam-nielsen(106115f2-5a14-4e9b-ba17-0199c93439b5).html"><span>Nielsen, U. D.</span></a> <span class="date">2014</span> Kgs. Lyngby: <a class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">416 p.</span> (DCAMM Special Report; No. S166).<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="textblock">The overall topic of this thesis is decision support for operation of ships and several aspects are covered herein. However, the main focus is on the wave-induced hydro-elastic response of large container ships and its implications on the structural response. <br /><br />The analyses are based mainly on full scale measurements from four container ships of 4,400 TEU, 8,600 TEU, 9,400 TEU and 14,000 TEU Primarily, strains measured near the deck amidships are used. Furthermore, measurements of motions and the encountered sea state are available for one of the ships. The smallest ship is in operation on the North Atlantic, while the three largest ships are operated on the Europe - Asia route. <br /><br />In the design rules of the classification societies for container ships the minimum design sagging bending moment amidships is larger than the hogging bending moment. Due to their design (full midship section and slender bow and stern sections) and their normal cargo loading condition, container ships are typically operated in a still-water hogging condition (tension in deck and compression in the bottom structure). The wave-induced bending moment is added to the still-water bending moment, which, together with the smaller design hogging bending moment, generally makes the wave-induced hogging bending moment more critical than the sagging bending moment in the operation of container ships.<br /><br />As container ships of today become larger, their natural vibration frequencies become lower and approach the typical encounter frequency with the waves. Together with the relatively high design speed and often pronounced bow flare this makes large container ship more sensitive to slamming and, consequently, the effects of wave-induced hull girder vibrations. From full scale strain measurements of individual, measured hull girder responses in the four container ships, the wave-induced hull girder vibrations are found to increase the vertical bending moment amidships by 100% or more. From the full scale measurements the amplification, due to the hull girder flexibility, is found to be largest for the 8,600 TEU and the 9,400 TEU ships, but, in addition to ship size, speed and<br />bow flare angle are also believed to be important factors contributing to the hull girder vibrations.<br /><br />The hull girder vibrational response is found to be dominated by the 2-node vertical bending mode. No torsional vibrations are found but torsion may, however, still be a concern for ultra large container ships. The damping of the 2-node vertical bending mode is estimated from full scale measurements for the four ships to 1.3-2.5% of the critical damping. No effect of ship size on the damping is identified.<br /><br />In some cases the hogging bending moment is more amplified by the effect of the hull girder flexibility than the sagging bending moment. No general trend in the amplification of the response is found from the full scale measurements. In some cases, the rigid-body hogging bending moment, found from full scale measurements and model tests, is considerably larger than the corresponding sagging bending moment. Generally, the difference between the design sagging and hogging bending moments is not reflected in the full scale measurements considered here.<br /><br />The extreme value of the vertical hogging bending moment, as estimated from full scale measurements, is investigated using the peak-over-threshold method for different periods.<br />The tails of the peak distributions for the four different ships are found to be very different from case to case. The irregularity of the tail behaviour makes it difficult to determine<br />an appropriate extreme value distribution for the hogging bending moment. The Gumbel distribution is believed to be the appropriate extreme value distribution, but it may be necessary to fit other types of extreme value distributions to the largest peaks.<br /><br />From the full scale measurements it is difficult to assess the influence of operational parameters (ship speed, heading relative to the waves and wave height) on the extreme response because these data are not readily available in all cases. Model tests indicate that bow-quartering sea may induce larger structural loads on the ship than direct head sea and that the amplification of the response due to the hull girder flexibility is largest in bow-quartering waves. However, this fact is not necessarily reflected in the behaviour of ship masters who seemingly tend to prefer bow-quartering sea to head sea when encountering adverse weather.<br /><br />Numerical design tools are widely used in ship design, but may not be able to fully capture the effect of the hull girder flexibility and are here found to significantly underestimate the effect compared to model tests and full scale measurements. Hence, full scale measurements from ships are highly valuable in the evaluation of existing designs and may reveal effects that cannot be assessed numerically.<br /><br />For decision support, accurate knowledge of the encountered sea state parameters (wave height, period and relative wave direction) is crucial. One means to estimate the on-site sea state from an advancing ship is to use the wave buoy analogy, i.e. use the motions of the ship and the associated motion transfer functions to derive the sea state parameters.<br />The method is promising but needs further refinement before it can be implemented in decision support systems on board ships.<br /><br />Fatigue damage is estimated from full scale strain measurements from two of the container ships with focus on the assessment of the influence of the wave-induced high-frequency hull girder vibrations. In several cases, the high-frequency contribution to the fatigue damage is dominating the estimated fatigue damage. Spectral formulations for estimating fatigue damage from bi-modal processes are explored and found to yield results fairly similar to the outcome of classical fatigue damage estimation from rainflow counting. However, in a few cases higher fatigue damage rates were estimated from rainflow counting than from narrow-band approximations.<br /><br />In summary and only considering larger container ships, the new and original contributions of the thesis are believed to be:<br /><br />•From full scale measurements the hull girder vibrational response is generally found to be dominated by the 2-node vertical bending mode even when the ship is sailing in oblique seas.<br />•The vertical bending moment in hogging and sagging is amplified considerably by the effect of the hull girder flexibility and the wave-induced hull girder vibrations are found capable of increasing the vertical wave bending moment amidships by 100% or more.<br />•The vertical hogging bending moment can be as critical as the sagging bending moment in design.<br />•From comparison of models tests and numerical methods, it seems that the numerical methods are not capable of fully capturing the effect of hull girder flexibility seen in model tests.<br />•The peak-over-threshold method is found to be the most useful method for extreme value prediction of the vertical bending moment in combination with an appropriate asymptotic extreme value distribution.</div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr><tr><th>Publication date</th><td><span class="date">2014</span></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 class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>416</td></tr><tr><th>ISBN (print)</th><td> 978-87-7475-385-8</td></tr><tr class="status"><th>State</th><td>Published</td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Name</th><td>DCAMM Special Report</td></tr><tr><th>Number</th><td>S166</td></tr><tr><th>ISSN (print)</th><td>0903-1685</td></tr></tbody></table></div></div>Tue, 31 Dec 2013 23:00:00 GMThttp://orbit.dtu.dk/en/publications/full-scale-measurements-of-the-hydroelastic-response-of-large-container-ships-for-decision-support(80015fe7-b181-4e59-97fd-61f330063fe3).html2013-12-31T23:00:00ZEconomic Model Predictive Control for Large-Scale and Distributed Energy Systems
http://orbit.dtu.dk/en/publications/economic-model-predictive-control-for-largescale-and-distributed-energy-systems(8e96cd7e-66ed-4210-ba0c-36aa4ae36984).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 class="link" rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/economic-model-predictive-control-for-largescale-and-distributed-energy-systems(8e96cd7e-66ed-4210-ba0c-36aa4ae36984).html"><span>Economic Model Predictive Control for Large-Scale and Distributed Energy Systems</span></a></h2><a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/laura-standardi(f6f6929c-e6b2-4db7-aa06-0520df6b84c3).html"><span>Standardi, L.</span></a>, <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/john-bagterp-joergensen(d2bc6de4-a5c6-43f7-8712-606bd02a88e9).html"><span>Jørgensen, J. B.</span></a> & <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/niels-kjoelstad-poulsen(6c1bb106-d448-47cb-978c-3d9efee3ca97).html"><span>Poulsen, N. K.</span></a> <span class="date">2014</span> Kgs. Lyngby: <a class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">179 p.</span> (DTU Compute PHD-2014; No. 356).<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="textblock"><p class="MsoBodyText">In this thesis, we consider control strategies for large and distributed energy systems that are important for the implementation of smart grid technologies. An electrical grid has to ensure reliability and avoid long-term interruptions in the power supply. Moreover, the share of Renewable Energy Sources (RESs) in the smart grids is increasing. These energy sources bring uncertainty to the production due to their fluctuations. Hence,smart grids need suitable control systems that are able to continuously balance power production and consumption. We apply the Economic Model Predictive Control (EMPC) strategy to optimise the economic performances of the energy systems and to balance the power production and consumption. In the case of large-scale energy systems, the electrical grid connects a high number of power units. Because of this, the related control problem involves a high number of variables and constraints and its solution requires high computational times. Energy systems have a hierarchical control framework and the controllers have to work in the time-scale required by their hierarchy level. Dedicated optimisation techniques efficiently solve the control problem and reduce computational time. We implement the Dantzig-Wolfe decomposition technique to efficiently solve the EMPC problem.</p><p class="MsoBodyText">The contributions of this thesis are primarily on:</p><b>Large-scale energy system</b><p class="MsoBodyText">Smart-grids connect a high number of energy units. In such a large-scale scenario the energy units are independent and dynamically decoupled. The mathematical model of the large-scale energy system embodies the decoupled dynamics of each power units. Moreover,all units of the grid contribute to the overall power production.</p><p class="MsoBodyText"><b style="mso-bidi-font-weight:normal">Economic Model Predictive Control (EMPC)</b></p><p class="MsoBodyText">This control strategy is an extension of the Model Predictive Control (MPC)strategy. Energy systems often involve stochastic variables due to the share of fluctuating Renewable Energy Sources (RESs). Moreover, the related control problems are multi variables and they are hard, or impossible, to split into single-input-single-output control systems. MPC strategy can handle multi variables control problems and it can embody stochastic variables. The Economic MPC (EMPC) policy optimises the economic performances of the process. In this work, we apply the EMPC to energy systems and it computes the control trajectory for each energy unit. This control policy minimises production costs and ensures that the power production satisfies the customers’ demand. The EMPC designs a linear control problem that has a block-angular constraints matrix and it has two sets of constraints. The independent dynamics of the energy units define the decoupling constraints sited on the diagonal. The coupling constraints represent the common goal of all power units in the energy system and this is to satisfy the customers’ demand. The Dantzig-Wolfe optimisation technique applies to this structure of the constraints matrix in the view of fastening the control algorithm and increase its applicability.</p><b>Dantzig-Wolfe decomposition</b><p class="MsoBodyText">The Dantzig-Wolfe decomposition solves the EMPC problem through a distributed optimisation technique. The EMPC problem via Dantzig-Wolfe decomposition algorithm computes the optimal input trajectory for each energy unit and reduces the computation times. Moreover, such a control algorithm applies to large-scale energy systems and the number of energy units does not affect the performances of the controller. In this thesis, we also investigate suboptimal solutions of the EMPC problem via modified versions of the Dantzig-Wolfe decomposition algorithms. The feasibility of the suboptimal solutions suffices for stability. The goal of these modified Dantzig-Wolfe decomposition algorithms is to reduce computation time in the solution of the EMPC problem.</p></div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr><tr><th>Publication date</th><td><span class="date">2014</span></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 class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>179</td></tr><tr class="status"><th>State</th><td>Submitted</td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Name</th><td>DTU Compute PHD-2014</td></tr><tr><th>Number</th><td>356</td></tr><tr><th>ISSN (print)</th><td>0909-3192</td></tr></tbody></table></div></div>Tue, 31 Dec 2013 23:00:00 GMThttp://orbit.dtu.dk/en/publications/economic-model-predictive-control-for-largescale-and-distributed-energy-systems(8e96cd7e-66ed-4210-ba0c-36aa4ae36984).html2013-12-31T23:00:00ZStatistical learning for predictive targeting in online advertising
http://orbit.dtu.dk/en/publications/statistical-learning-for-predictive-targeting-in-online-advertising(01a99509-9ab8-4c2c-b370-2d7ee4a873ea).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 class="link" rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/statistical-learning-for-predictive-targeting-in-online-advertising(01a99509-9ab8-4c2c-b370-2d7ee4a873ea).html"><span>Statistical learning for predictive targeting in online advertising</span></a></h2><a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/bjarne-oerum-fruergaard(b7bb8d93-b296-422a-8953-2483a0345537).html"><span>Fruergaard, B. Ø.</span></a>, <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/lars-kai-hansen(3bdd1c4b-6c83-462b-a4cd-1ffbdcbff128).html"><span>Hansen, L. K.</span></a> & <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/jesper-urban(0047bd4a-77f5-49c0-aea4-79ef1d1ef3c5).html"><span>Urban, J.</span></a> <span class="date">2014</span> Kgs. Lyngby: <a class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">144 p.</span> (DTU Compute PHD-2014; No. 355).<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="textblock">The focus in this thesis is investigation of machine learning methods with applications in computational advertising. Computational advertising is the broad discipline of building systems which can reach audiences browsing the Internet with targeted advertisements. At the core of such systems, algorithms are needed for making decisions. It is in one such particular instance of computational advertising, namely in web banner advertising, that we investigate machine learning methods to assist and make decisions in order to optimize the placements of ads. <br />The industrial partner in this work is Adform, an international online advertising technology partner. This also means that the analyses and methods in this work are developed with particular use-cases within Adform in mind and thus need also to be applicable in Adform’s technology stack. This implies extra thought on scalability and performance.<br />The particular use-case which is used as a benchmark for our results, is clickthrough rate prediction. In this task one aims to predict the probability that a user will click on an advertisement, based on attributes about the user, the advertisement the context, and other signals, such as time. This has its main application in real-time bidding ad exchanges, where each advertiser is given a chance to place bids for showing their ad while the page loads, and the winning bid gets to display their banner. <br />The contributions of this thesis entail application of a hybrid model of explicit and latent features for learning probabilities of clicks, which is a methodological extension of the current model in production at Adform. Our findings confirm that latent features can increase predictive performance in the setup of click-through rate prediction. They also reveal a tedious process for tuning the model for optimal performance.<br />We also present variations of Bayesian generative models for stochastic blockmodeling for inference of structure based on browsing patterns. Applying this structural information to improve click-through rate prediction becomes a two-step procedure; 1) learn user and URL profiles from browsing patterns, 2) use the profiles as additional features in a click-through rate prediction model. The assumption we implicitly make is reasonable: Users and URLs that are grouped together based on browsing patterns will have similar responses to ads, e.g., can be used as predictors of clicks. We report successful examples of applying this approach in practice. <br />Finally, we introduce the multiple-networks stochastic blockmodel (MNSBM), a model for efficient overlapping community detection in complex networks which can be assumed to be an aggregation of multiple block-structured subnetworks.<br /></div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr><tr><th>Publication date</th><td><span class="date">2014</span></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 class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><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>Submitted</td></tr></tbody></table></div> <table class="properties"><tbody><tr><th>Name</th><td>DTU Compute PHD-2014</td></tr><tr><th>Number</th><td>355</td></tr><tr><th>ISSN (print)</th><td>0909-3192</td></tr></tbody></table></div></div>Tue, 31 Dec 2013 23:00:00 GMThttp://orbit.dtu.dk/en/publications/statistical-learning-for-predictive-targeting-in-online-advertising(01a99509-9ab8-4c2c-b370-2d7ee4a873ea).html2013-12-31T23:00:00ZNMR structural studies of oligosaccharides and other natural products
http://orbit.dtu.dk/en/publications/nmr-structural-studies-of-oligosaccharides-and-other-natural-products(7420df81-3623-497b-825c-09fa6e29c7db).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 class="link" rel="BookAnthology" href="http://orbit.dtu.dk/en/publications/nmr-structural-studies-of-oligosaccharides-and-other-natural-products(7420df81-3623-497b-825c-09fa6e29c7db).html"><span>NMR structural studies of oligosaccharides and other natural products</span></a></h2><a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/louise-kjaerulff(840d3acf-77d5-4323-84ed-14a6ff8aabfc).html"><span>Kjærulff, L.</span></a> & <a class="link person" rel="Person" href="http://orbit.dtu.dk/en/persons/charlotte-held-gotfredsen(1cf4df84-2d0e-4693-bf47-e9932e3bf0e3).html"><span>Gotfredsen, C. H.</span></a> <span class="date">2014</span> <a class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a>. <span class="numberofpages">311 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="textblock">NMR spectroscopy is an important tool in chemical analysis and for structural studies in various research areas. The subject of this thesis is liquid state NMR spectroscopy for structural analysis of small molecules, both regarding method development and structure elucidation by NMR spectroscopy.<br />HMBC+ is a new pseudo-3D NMR experiment for measurement of long-range homonuclear JHH coupling constants in small molecules. Based on two existing experiments, multiplicity edited HMBC and HAT HMBC by Benie, Nyberg, and Sørensen, the new HMBC+ experiment takes advantage of a π phase difference with respect to n+1JHH between these two experiments, observed in the nJCH HMBC cross peak. Through a double editing procedure this enables straightforward determination of both sign and magnitude of n+1JHH, including for very small coupling constants. Excellent results were obtained for the natural product strychnine, and 28 n+1JHH coupling constants were determined, of which 10 had not previously been measured due to their small sizes. By comparing to calculated coupling constants, an RMSD of 0.28 Hz was obtained, all coupling constant signs fit with the calculations, and all errors were below 1 Hz, also when comparing the absolute values to experimental coupling constants measured by Carter et al. using 1D 1H NMR on deuterated strychnine analogues. Providing an excellent tool for measurement of long-range JHH with the extra convenience of labeling the coupling constant information to the 13C chemical shift through the nJCH correlation, this experiment has exciting applications for configurational assignment of e.g. carbohydrates and for residual dipolar couplings.<br />Identification of known molecules and discovery of novel molecules are other important applications of NMR spectroscopy. Bacteria and fungi produce secondary metabolites for signaling and competing against other organisms, and these molecules are important in drug discovery due to their inherent biological activities. From a marine Photobacterium (P. halotolerans) we isolated the solonamides and the ngercheumicins, two families of cyclic depsipeptides capable of attenuating virulence in S. aureus by quorum sensing inhibition through the accessory gene regulator agr. This is likely due to their structural similarities with the auto-inducing peptides of S. aureus, controlling quorum sensing in bacterial populations. A filamentous fungus, A. fijiensis, was also investigated for production of novel secondary metabolites, and a new pyranonigrin (E) was isolated and structure elucidated by NMR spectroscopy along with JBIR-74 and decumbenone A, two known metabolites previously isolated from Aspergillus and Penicillium species.<br />Oligosaccharides found in human milk are important for infant nutrition, and a collaborative effort of university and industry partners was aimed at establishing methods for production of human milk oligosaccharides. Two different bioenzymatic methods for production of 3’-sialyllactose were investigated, and a screening of trans-fucosidases enabled the NMR spectroscopic identification of three pNP-fucosylfucopyranosides as major reaction products.</div><div class="phddissertation"><table class="properties"><tbody><tr class="language"><th>Original language</th><td>English</td></tr><tr><th>Publication date</th><td><span class="date">2014</span></td></tr></tbody></table><table class="properties"><tbody><tr><th>Publisher</th><td><a class="link" rel="Publisher" href="http://orbit.dtu.dk/en/publishers/technical-university-of-denmark-dtu(f7c040ab-194a-4da4-b458-670da24b2a08).html"><span>Technical University of Denmark (DTU)</span></a></td></tr><tr><th>Number of pages</th><td>311</td></tr><tr class="status"><th>State</th><td>Published</td></tr></tbody></table></div></div></div>Tue, 31 Dec 2013 23:00:00 GMThttp://orbit.dtu.dk/en/publications/nmr-structural-studies-of-oligosaccharides-and-other-natural-products(7420df81-3623-497b-825c-09fa6e29c7db).html2013-12-31T23:00:00Z