The complexity of the path finding and navigation problem increases when multiple agents are involved and these agents have to maintain a predefined formation while moving on a 3-D terrain. In this thesis, a novel approach for multiresolution formation representation is proposed, that allows hierarchical formations of arbitrary depth to be defined using different referencing schemes. This formation representation approach is then utilized to find and realize a collision free optimal path from an initial location to a goal location on a 3-D terrain, while preserving the formation. The proposed metod first employs a terrain analysis technique that constructs a weighted search graph from height-map data. The graph is used by an off-line search algorithm to find the shortest path. The path is realized by an on-line planner, which guides the formation along the path while avoiding collisions and maintaining the formation. The methods proposed here are easily adaptable to several application areas, especially to real time strategy games and military simulations.

Expert finding is an Information Retrieval (IR) task that is used to find the needed experts. To find the needed experts is a noticeable problem in many commercial, educational or governmental organizations. It is highly crucial to find the appropriate experts, when seeking referees for a paper submitted to a conference or when looking for a consultant for a software project. It is also important to find the similar experts in case of the absence or the inability of the selected expert. Traditional expert finding methods are modeled based on three components which are a supporting document collection, a list of candidate experts and a set of pre-defined topics. In reality, most of the time pre-defined topics are not available. In this study, we propose an expert finding system which generates a semantic layer between domains and experts using Latent Dirichlet Allocation (LDA). A traditional expert finding method (voting approach) is used in order to match the domains and the experts as the baseline method. In case similar experts are needed, the system recommends experts matching the qualities of the selected experts. The proposed model is applied to a semi-synthetic data set to prove the concept and it performs better than the baseline method. The proposed model is also applied to the projects of the Technology and Innovation Funding Programs Directorate (TEYDEB) of The Scientific and Technological Research Council of Turkey (T&Uuml / B

A metagenome originated from a shotgun sequencing of a microbial community is a heterogeneous mixture of rather short sequences. A vast majority of microbial species in a given community (99%) are likely to be non-cultivable. Many protein-coding regions in a new metagenome are likely to code for barely detectable homologs of already known proteins. Therefore, an ab initio method that would accurately identify the new genes is a vitally important tool of metagenomic sequence analysis. However, a heuristic model method for finding genes in short prokaryotic sequences with anonymous origin was proposed in 1999 prior to the advent of metagenomics. With hundreds of new prokaryotic genomes available it is now possible to enhance the original approach and to utilize direct polynomial and logistic approximations of oligonucleotide frequencies. The idea was to bypass traditional ways of parameter estimation such as supervised training on a set of validated genes or unsupervised training on an anonymous sequence supposed to contain a large enough number of genes. The codon frequencies, critical for the model parameterization, could be derived from frequencies of nucleotides observed in the short sequence. This method could be further applied for initializing the algorithms for iterative parameters estimation for prokaryotic as well as eukaryotic gene finders.

As Internet communities such as question-answer (Q&A) forums and online social networks (OSNs) grow in prominence as knowledge sources, traditional editorial filters are unable to scale to their size and pace. This absence hinders the exchange of knowledge online, by creating an understandable lack of trust in information. This mistrust can be partially overcome by a forum by consistently providing reliable information, thus establishing itself as a reliable source. This work investigates how algorithmic approaches can contribute to building such a community of voluntary experts willing to contribute authoritative information. This work identifies two approaches: a) reducing the cost of participation for experts via matching user queries to experts (question recommendation), and b) identifying authoritative contributors for incentivization (authority estimation). The question recommendation problem is addressed by extending existing approaches via a new generative model that augments textual data with expert preference information among different questions. Another contribution to this domain is the introduction of a set of formalized metrics to include the expert's experience besides the questioner's. This is essential for expert retention in a voluntary community, and has not been addressed by previous work. The authority estimation problem is addressed by observing that the global graph structure of user interactions, results from two factors: a user's performance in local one-to-one interactions, and their activity levels. By positing an intrinsic authority 'strength' for each user node in the graph that governs the outcome of individual interactions via the Bradley-Terry model for pairwise comparison, this research establishes a relationship between intrinsic user authority, and global measures of influence. This approach overcomes many drawbacks of current measures of node importance in OSNs by naturally correcting for user activity levels, and providing an explanation for the frequent disconnect between real world reputation and online influence. Also, while existing research has been restricted to node ranking on a single OSN graph, this work demonstrates that co-ranking across multiple endorsement graphs drawn from the same OSN is a highly effective approach for aggregating complementary graph information. A new scalable co-ranking framework is introduced for this task. The resulting algorithms are evaluated on data from various online communities, and empirically shown to outperform existing approaches by a large margin. / text

The presence of structure in a computational problem can often be exploited and can lead to a more efficient numerical algorithm. In this dissertation, we look at structured numerical problems that arise from applications in wireless communications and machine learning that also impact other areas of scientific computing. In wireless communication system designs, certain structured matrices (frames) need to be generated. The design of such matrices is equivalent to a symmetric inverse eigenvalue problem where the values of the diagonal elements are prescribed. We present algorithms that are capable of generating a larger set of these constructions than previous algorithms. We also discuss the existence of equiangular tight frames---frames that satisfy additional structural properties. Kernel learning is an important class of problems in machine learning. It often relies on efficient numerical algorithms that solve underlying convex optimization problems. In our work, the objective functions to be minimized are the von Neumann and the LogDet Bregman matrix divergences. The algorithm that solves this optimization problem performs matrix updates based on repeated eigendecompositions of diagonal plus rank-one matrices in the case of von Neumann matrix divergence, and Cholesky updates in case of the LogDet Bregman matrix divergence. Our contribution exploits the low-rank representations and the structure of the constraint matrices, resulting in more efficient algorithms than previously known. We also present two specialized zero-finding algorithms where we exploit the structure through the shape and exact formulation of the objective function. The first zero-finding task arises during the matrix update step which is part of the above-mentioned kernel learning application. The second zero-finding problem is for the secular equation; it is equivalent to the computation of the eigenvalues of a diagonal plus rank-one matrix. The secular equation arises in various applications, the most well-known is the divide-and-conquer eigensolver. In our solutions, we build upon a somewhat forgotten zero-finding method by P. Jarratt, first described in 1966. The method employs first derivatives only and needs the same amount of evaluations as Newton's method, but converges faster. Our contributions are the more efficient specialized zero-finding algorithms. / text

ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California / A broadband passive direction finding system utilizing Luneburg lens has been investigated. With the simulated power level distribution at the detectors mounted on a Luneburg lens, both Cramér-Rao bound (CRB) and the root mean square error (RMS) based on the Correlation Algorithm (CA) for the direction of arrival (DoA) estimation have been derived and calculated. Guidelines on how to design the Luneburg lens detecting system have been studied. Finally, as a proof-of-concept demonstration, the DoA performance of a Luneburg lens fabricated using the polymer jetting technology with five detectors 10° equally spaced to receive the azimuth signal from -20° to 20° is demonstrated.

With advancements in computer technology and processing power, the ability to examine chemical systems using theory continues to be more practicable. Using ab initio methods, such as density functional theory, we are now able to routinely simulate hundreds of atoms. This system size allows us to directly simulate surfaces and nano-materials that are industrially relevant. With the expansion of accessible systems comes the opportunity to develop new computational methods to extract their chemical properties. Of particular interest is bridging the time scale gap between simulation and experiment. The evolution of a system chemical in time can be directly simulated using classical dynamics, however, molecules vibrate on the order of femtoseconds and interesting transitions tend to happen on much longer time scales: milliseconds to seconds. In condensed phase chemical systems these interesting transitions are hindered by energy barriers so state to state dynamics are dominated by rare evens. Luckily, rare event transitions tend to happen through mountain passes in the potential energy landscape. Within harmonic transition state theory, the transition states between minima can be characterized by saddle points. Finding saddle points is a challenging problem which has not been satisfactorily solved; nevertheless, there are algorithms currently being used despite their deficiency. In particular, my work strives to improve the efficiency and stability of the nudged elastic band method and compare its performance to similar algorithms on a variety of test systems. In addition, I present a method to predict how energy-based chemical properties change with respect to the chemical composition of the system. This is achieved by taking a derivative of the property with respect to the atomic numbers of the atoms present in the system. The accuracy and predictive quality of these derivatives are assessed for both model and industrially relevant systems. With this information, we can follow these derivatives to optimize a desired property in the space of chemical composition. This method is a step toward using theory to rationally design compounds with desirable properties. / text

This dissertation examines the application of various classical root finding methods to digital maximum power point tracking (DMPPT). An overview of root finding methods such as the Newton Raphson Method (NRM), Secant Method (SM), Bisection Method (BSM), Regula Falsi Method (RFM) and a proposed Modified Regula Falsi Method (MRFM) applied to photovoltaic (PV) applications is presented. These methods are compared among themselves. Some of their features are also compared with other commonly used maximum power point (MPP) tracking methods. Issues found when implementing these root finding methods based on continuous variables in a digital domain are explored. Some of these discussed issues include numerical stability, digital implementation of differential operators, and quantization error. Convergence speed is also explored. The analysis is used to provide practical insights into the design of a DMPPT based on classical root finding algorithms. A new DMPPT based on a MRFM is proposed and used as the basis for the discussion. It is shown that this proposed method is faster than the other discussed methods that ensure convergence to the MPP. The discussion is approached from a practical perspective and also includes theoretical analysis to support the observations. Extensive simulation and experimental results with hardware prototypes verify the analysis. / text

Šio darbo tema suformuluota probleminiu klausimu: Vaižganto „Laiškai Klimams“: laiškai, dienoraštis ar autobiografija? Darbo tyrimo objektu neatsitiktinai pasirinkti „Laiškai Klimams“, nes, autorės nuomone, laiškų tekstai geriau nei bet kuris grožinės literatūros kūrinys reprezentuoja Vaižganto asmenybę. Viena iš darbo rašymo priežasčių yra noras giliau ir visapusiškiau pažinti ir atskleisti Vaižganto, o tiksliau Juozo Tumo, asmenybę, akcentuojant jo žmogiškuosius bruožus. Antra, bene svarbiausia priežastis, tai noras parodyti, kad Vaižganto asmenybė verta dėmesio, kad ne veltui apie jį taip entuziastingai kalbėjo amžininkai, todėl negalima susitaikyti su tuo, kad Vaižgantas yra išbrauktas i�� mokyklinių programų, kad jo asmenybė ir kūryba pristatoma tik kaip pasirenkama tema. Atviras klausimas, kas yra Vaižganto „Laiškai Klimams“: laiškai, dienoraštis ar autobiografija, yra siejamoji darbo gija. Aišku viena, kad šių laiškų tekstai sunkiai įspraudžiami į žanrines ribas. Prasminis matmuo teikia jiems žanrinį neapibrėžtum��, dėl šios priežasties nustatyti laiško, dienoraščio ar autobiografijos ribas yra praktiškai neįmanoma. Dienoraštinis ir autobiografinis žiūros būdai leidžia atskleisti Vaižganto asmenybės modernumą. „Laiškų Klimams“ tekstai parankūs dar ir tuo, kad juose išryškėja plati rašytojo visuomeninė, kultūrinė, politinė veikla. Pagrindinis dėmesys laiškų tekstuose krypsta į komunikacinį momentą. Išryškėja bendravimo būtinybe persmelktas rašytojo gyvenimas. / Theme of the present paper work is formulated in problematic question: „Letters to the family of Klimas“ written by Vaižgantas – letters, diary or autobiography? As subject of research not incidentally is chosen the piece „Letters to the family of Klimas“, as, in opinion of the author, texts of these letters better than any work of imaginative literature represent personality of Vaižgantas. One of the reasons of writing this paper work is desire to cognize and reveal personality of Vaižgantas, and to be precise, Juozas Tumas – Vaižgantas, more profoundly and comprehensively by emphasizing his human features. Second and maybe the main reason is a desire to show that personality of Vaižgantas is worthy of regard, and not in vain hope contemporaries talked about him so enthusiastically, therefore, the facts that Vaižgantas is excluded from the school programs and his personality as well as his oeuvre is presented only as optional theme can not be accepted. Open question what is the piece „Letters to the family of Klimas“: letters, diary ar autobiography, is a binding thread of the work. One thing that the texts of these letters are being hardly squeezed in the genre margins is clear. Notional dimension gives to them genre uncertainty, and because of such reason to determine margins of the letter, diary or autobiography is practically not possible. Diary and autobiographical viewing manners enable to reveal modernity of Vaižgantas personality. Texts of the „Letters to the family... [to full text]

The human visual system has learned to assume that light originates from above, most likely because of the persistent natural overhead light source – the sun (Ramachandran, 1988). Asymmetries of perception in neurologically normal individuals, like assuming light is coming from above, in part result from efficiency measures of the visual system. Not only is light assumed to come from above, but light from above and to the left has been found to decrease reaction times in target finding as well as increase aesthetic preference (Sun & Perona, 1998; Smith & Elias, 2013). The underlying cause of the bias towards upper-left lighting is debated, and may have a relationship with another peculiar phenomenon in neurologically normal individuals where greater attention is paid to leftward space, called pseudoneglect (Bowers & Heilman, 1980). Alternatively, an explanation suggesting that directional reading influences lighting preferences has been proposed, as Smith and Elias (2013) found native right-to-left readers to be significantly different from leftward biased left-to-right readers. The current set of experiments used eye-tracking and a target finding paradigm to assess differences between left-to-right and right-to-left readers. Manipulating the position of the light illuminating a field of spheres generated targets, creating either 1 convex bubble among 15 concave depressions, or vice-versa. Results from these studies are mixed, and highlight differences between both upper and lower and lateral visual space. Light originating from above facilitated shorter average duration times for both groups, whereas left-to-right readers tended to prefer light from the upper-left, while right-to-left readers preferred light from the upper-right. No one target location in the array facilitated shorter average duration times for right-to-left readers, although left-to-right readers tended to exhibit shorter durations when identifying targets in the upper-left quadrant. Participants spent the greatest amount of time examining the upper quadrants of the array, tending to focus more on the side of the image that their native reading direction begins on. The influence of directional reading on light source perception, and the potential problems of using exclusively Western participant samples are discussed.