With the emerging hybrid multi-core and many-core compute platforms delivering unprecedented high performance within a single chip, and making rapid strides toward the commodity processor market, they are widely expected to replace the multi-core processors in the existing High-Performance Computing (HPC) infrastructures, such as large scale clusters, grids and supercomputers. On the other hand in the realm of bioinformatics, the size of genomic databases is doubling every 12 months, and hence the need for novel approaches to parallelize sequence search algorithms has become increasingly important. This thesis puts a significant step forward in bridging the gap between software and hardware by presenting an efficient and scalable model to accelerate one of the popular sequence alignment algorithms by exploiting multigrain parallelism that is exposed by the emerging multiprocessor architectures. Specifically, we parallelize a dynamic programming algorithm called Smith-Waterman both within and across multiple Cell Broadband Engines and within an nVIDIA GeForce General Purpose Graphics Processing Unit (GPGPU). Cell Broadband Engine: We parallelize the Smith-Waterman algorithm within a Cell node by performing a blocked data decomposition of the dynamic programming matrix followed by pipelined execution of the blocks across the synergistic processing elements (SPEs) of the Cell. We also introduce novel optimization methods that completely utilize the vector processing power of the SPE. As a result, we achieve near-linear scalability or near-constant efficiency for up to 16 SPEs on the dual-Cell QS20 blades, and our design is highly scalable to more cores, if available. We further extend this design to accelerate the Smith-Waterman algorithm across nodes on both the IBM QS20 and the PlayStation3 Cell cluster platforms and achieve a maximum speedup of 44, when compared to the execution times on a single Cell node. We then introduce an analytical model to accurately estimate the execution times of parallel sequence alignments and wavefront algorithms in general on the Cell cluster platforms. Lastly, we contribute and evaluate TOSS -- a Throughput-Oriented Sequence Scheduler, which leverages the performance prediction model and dynamically partitions the available processing elements to simultaneously align multiple sequences. This scheme succeeds in aligning more sequences per unit time with an improvement of 33.5% over the naive first-come, first-serve (FCFS) scheduler. nVIDIA GPGPU: We parallelize the Smith-Waterman algorithm on the GPGPU by optimizing the code in stages, which include optimal data layout strategies, coalesced memory accesses and blocked data decomposition techniques. Results show that our methods provide a maximum speedup of 3.6 on the nVIDIA GPGPU when compared to the performance of the naive implementation of Smith-Waterman. / Master of Science

A bulk of the research on piezoelectric systems in recent years can be classified into two categories, 1) studies of linear piezoelectric oscillator arrays, 2) studies of nonlinear piezoelectric oscillators. This dissertation derives novel linear and nonlinear modeling and estimation methods for such piezoelectric systems. In the first part, this work develops modeling and design methods for Piezoelectric Subordinate Oscillator Arrays (PSOAs) for the wideband vibration attenuation problem. PSOAs offer a straightforward and low mass ratio solution to cancel out the resonant peaks in a host structure's frequency domain. Further, they provide adaptability through shunt tuning, which gives them the ability to recover performance losses because of structural parameter errors. This dissertation studies the derivation of governing equations that result in a closed-form expression for the frequency response function. It also analyzes systematic approaches to assign distributions to the nondimensional parameters in the frequency response function to achieve the desired flat-band frequency response. Finally, the effectiveness of PSOAs under ideal and nonideal conditions are demonstrated in this dissertation through extensive numerical and experimental studies. The concept of performance recovery, introduced in empirical studies, gives a measure of the PSOA's effectiveness in the presence of disorder before and after capacitive tuning. The second part of this dissertation introduces novel modeling and estimation methods for nonlinear piezoelectric oscillators. Traditional modeling techniques require knowledge of the structure as well as the source of nonlinearity. Data-driven modeling techniques used extensively in recent times build approximations. An adaptive estimation method, that uses reproducing kernel Hilbert space (RKHS) embedding methods, can estimate the underlying nonlinear function that governs the system's dynamics. A model built by such a method can overcome some of the limitations of the modeling approaches mentioned above. This dissertation discusses (i) how to construct the RKHS based estimator for the piezoelectric oscillator problem, (ii) how to choose kernel centers for approximating the RKHS, and (iii) derives sufficient conditions for convergence of the function estimate to the actual function. In each of these discussions, numerical studies are used to show the RKHS based adaptive estimator's effectiveness for identifying linearities in piezoelectric oscillators. / Doctor of Philosophy / Piezoelectric materials are materials that generate an electric charge when mechanical stress is applied, and vice versa, in a lossless transformation. Engineers have used piezoelectric materials for a variety of applications, including vibration control and energy harvesting. This dissertation introduces (1) novel methods for vibration attenuation using an array of piezoelectric oscillators, and (2) methods to model and estimate the nonlinear behavior exhibited by piezoelectric materials at very high mechanical forces or electric charges. Arrays of piezoelectric oscillators attached to a host structure are termed piezoelectric subordinate oscillator arrays (PSOAs). With the careful design of PSOAs, we show that we can reduce the vibration of the host structure. This dissertation analyzes methodologies for designing PSOAs and illustrates their vibration attenuation capabilities numerically and experimentally. The numerical and experimental studies also illustrate the robustness of PSOAs. In the second part of this dissertation, we analyze reproducing kernel Hilbert space embedding methods for adaptive estimation of nonlinearities in piezoelectric systems. Kernel methods are extensively used in machine learning, and control theorists have studied adaptive estimation of functions in finite-dimensional spaces. In this work, we adapt kernel methods for adaptive estimation of functions in infinite-dimensional spaces that appear while modeling piezoelectric systems. We derive theorems that ensure convergence of function estimates to the actual function and develop algorithms for careful selection of the kernel basis functions.

Thesis advisor: Michael Grubb / Thesis advisor: Charles Murry / This dissertation consists of two self-contained papers that explore the Industrial Organization of the UK television broadcasting market and broadband procurement by US K-12 schools Chapter 1: Welfare Effects of Competition in the UK Television Broadcasting Market In this chapter, I study the consumer welfare effects of a regulation that ended the exclusivity of telecast rights of live English Premier League games and induced entry into the UK television broadcasting market. Historically rights were owned by a single broadcaster. The regulation divided the games into mutually exclusive bundles and stipulated that a single broadcaster cannot own rights to all of them. This resulted in a new channel entering the market and showing some games. I estimate a model of household viewing preferences, channel subscription demand, and pricing using proprietary viewing and subscription choice data. Simulations show a 6.4\% (\pounds 10m per season) decline in consumer surplus driven by the higher prices consumers had to pay to view all the live games. This offset increased surplus from new content on the entrant channel. I propose an alternate regulation that breaks the exclusivity of games telecast on a channel and show that the estimated surplus could have been 29\% higher. Chapter 2: Bundling Demand in K-12 Broadband Procurement In this chapter coauthored with Gaurab Aryal, Charles Murry and Pallavi Pal, we evaluate the effects of bundling demand for broadband internet by K-12 schools. In 2014, New Jersey switched from decentralized procurements to a new procurement system that bundled schools into four regional groups. Using an event study approach, we find that, on average, prices for participants decreased by one-third, and broadband speed purchased increased sixfold. We bound the change in school expenditures due to the program and find that participants saved at least as much as their total ``E-rate" subsidy from the federal government. Under weak assumptions on demand, we show that participating schools experienced large welfare gains. Using an informal model and simulations, we analyze the main mechanisms that could lead to lower prices in the regional auctions. / Thesis (PhD) — Boston College, 2024. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Economics.

The ever-growing demand for higher bandwidth broadband communication has driven transistor operation to higher and higher frequencies. However, achieving cut-o frequencies in the terahertz regime have been unsuccessful with the current state-of-the-art transistors exhibiting no better than 800 GHz. While the high-frequency transistor eld is dominated by III-V semiconductors, it has been proposed that graphene may be a competitive material. Graphene exhibits electron and hole mobilities orders of magnitude larger than conventional semiconductors and has an atomically thin form factor. Despite these benets, high-frequency graphene transis tors have yet to realize high-frequency characteristics better than III-V's. This thesis expands on the current limitations of graphene transistors in terms of improved fabrication techniques (to achieve higher carrier mobilities and lower contact resistances) and fundamental, band structure limitations (like quantum capacitance and the zero energy band gap). First, graphene, fully encapsulated in hexagonal boron-nitride crystals, transistors are fabricated with self-aligned source and drain contacts with sub-100 nm gate lengths. The encapsulation technique shields the graphene from the external environment so that graphene retains its intrinsic high mobility characteristic. In this short-channel regime, transport is determined to be ballistic with an injection velocity close to the Fermi velocity of graphene. However, the transconductance and output conductance are only 0.6 mS/mm and 0.3 mS/mm, respectively. This lack-luster performance is due to a relatively thick (3.5 nm) eective oxide thickness but also due to the eects of quantum capacitance which diminishes the total gate capacitance by up to 60%. Furthermore, the output conductance is increased due to the onset of hole conduction which leads to a second linear regime in the I-V characteristic. This is a direct consequence of graphene's zero energy band gap electronic structure. Finally, the source and drain contact resistances are large, which leads to poorer output current, transconductance and output conductance. Second, improvement to the contact resistance is explored by means of using graphite as the contact metal to graphene. Since graphite is atomically smooth, a pristine graphite-graphene interface can be formed without grain asperities found in conventional metals. Graphite is also lattice matched to graphene and exhibits the same 60 symmetry. Consequently, it is discovered that the graphite-graphene contact resistance exhibits a 60 periodicity, with respect to crystal orientation. When the two lattices align, a contact resistivity under 10 Wmm² is observed. Furthermore, contact resistivity minima are observed at two of the commensurate angles of twisted bilayer graphene. Though graphene transistor performance is band structure limited, it may still be possible to achieve competitive high-frequency operation by use of h-BN encapsulation and graphite contacts.

In many engineering applications, including radar, sonar, communications and seismology, the direction of impinging signal wavefronts can be used to discriminate between competing sources. Often these source signals cover a wide bandwidth and conventional narrowband beamforming techniques are ineffective, since spatial resolution varies significantly across the band. In this thesis we consider the problem of beamforming for broadband signals, primarily when the spatial response remains constant as a function of frequency. This is called a frequency invariant beamformer (FIB).¶ Rather than applying the numerical technique of multi-parameter optimisation to solve for the beamformer parameters, we attempt to address the fundamental nature of the FIB problem. The general philosophy is to use a theoretical continuous sensor to derive relationships between a desired FI beampattern and the required signal processing structure. Beamforming using an array of discrete sensors can then be formulated as an approximation problem. This approach reveals a natural structure to the FIB which is otherwise buried in a numerical optimisation procedure.¶ Measured results from a microphone array are presented to verify that the simple FIB structure can be successfully implemented. We then consider imposing broadband pattern nulls in the FI beampattern, and show that (i) it is possible to impose an exact null which is present over all frequencies, and (ii) it is possible to calculate a priori how many constraints are required to achieve a null of a given depth in a FIB. We also show that the FIB can be applied to the problem of broadband direction of arrival (DOA) estimation and provides computational advantages over other broadband DOA estimators.¶ Through the theoretical continuous sensor approach, we show that the FIB theory can be generalised to the problem of designing a general broadband beamformer (GBB) which realizes a broadband angle-versus-frequency beampattern specification. Coupled with a technique for radial beampattern transformation, the GBB can be applied to a wide class of problems covering both nearfield beamforming (in which the shape of the impinging wavefront must be considered and farfield beamforming (which is simplified by the assumption of planar wavefronts) for a broadband beampattern specified over both angle and frequency.

This thesis describes the outcome of study to investigate methods of broadband matching to photonic devices such as lasers and high speed detectors. The thesis is divided into two areas of interest relating to the design of broadband fiber optic links. The first area is the application of numerical methods and commensurate line methods to the design of compact equalisers which allow an improved transducer power gain over a wide band. It is shown that physically small equalisers can yield an improvement of 4 dB over a 2 GHz bandwidth. The second area considered is the distortion inherent in a laser diode. Detailed measurements of the second order and intermodulation products are given. A small signal perturbation analysis is presented which helps to explain the observed distortion products. The results of numerical simulation of the distortion using a state variable implementation of the full rate equations and related first, second and intermodulation equations is presented and possible methods of reducing the distortion are explored. It is shown that in principle the distortion could be reduced by pre-generating the distortion and adding an inverted form of the distortion to the transmitted signal. The distortion can then be corrected in the fiber and simulation studies suggest that an improvement of 13 dB optical or 26 dB electrical may be possible.

Thesis (Ph. D.)--University of California, San Diego, 2010. / Title from first page of PDF file (viewed Feb. 22, 2010). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 421-450).

Community Wireless Networks (CWNs) are a fairly new phenomenon. One of the first projects, NYC Wireless, started in 2001. These wireless initiatives are often a response to the lack of high-speed ubiquitous computing. Many of the first users, frustrated neighborhood “techies,” jerry rigged low cost WiFi antennas to rooftops and the side of buildings in order to access a high-speed broadband service. By doing this the wireless pioneers shared high speed wireless signals with neighbors and anyone within reach of their signal. As wireless computing became more popular, and it’s social and economic benefits more obvious, CWNs became an attractive alternative for many rural and low-income urban communities. Populations that had been overlooked by large cable and telephone service companies. The success of CWNs has paved the way for municipalities to build publicly supported wireless projects. Cable and telephone companies, major providers of broadband service, view municipal networks as unfair competition, and thus began the legislative battle over municipal wireless networks. The battle continues to wage. Cable and telephone companies have had some success at the state level and the federal debate is underway at this moment. Therefore, the purpose of this report is to understand the role Austin’s nonprofits play to ensure that high speed broadband access is made available for everyone and how lessons learned in Austin can be applied to other cities and locations around the country. The study found that Austin, compared to other cities of the same size, has a very small nonprofit community to addresses the issue of universal broadband access. Although the group is small, networking and mingling between community service organizations, the city government and wireless projects has created a community that effectively addresses the issue of high-speed access to the Internet. / text

Η σπουδαιότητα των ευρυζωνικών υποδομών διεθνώς επιβεβαιώνεται από τη δραστηριοποίηση διαφόρων προηγμένων χωρών, µε τρόπο τέτοιο ώστε να αναπτυχθούν οι κατάλληλες υποδομές. Στόχος είναι οι υποδομές αυτές να υιοθετηθούν µε τρόπο επικουρικό στην ανάπτυξη της οικονομίας και στην αντιμετώπιση τυχόν «τεχνολογικών αποκλεισμών» των πολιτών. Η ανάπτυξη των ευρυζωνικών δικτύων έχει υιοθετηθεί από την κοινή Ευρωπαϊκή πολιτική για την υλοποίηση της Κοινωνίας της Πληροφορίας και βάσει των σχεδίων δράσης e-Europe 2002, e-Europe 2005 και i2010 η ευρυζωνική πρόσβαση έχει τεθεί ως σημαντική προτεραιότητα της Ευρωπαϊκής Ένωσης. Από τον Ιούλιο του 2003 ένα νέο νομικό πλαίσιο, το οποίο ρυθμίζει τις ηλεκτρονικές υπηρεσίες τηλεπικοινωνιών και δικτύων, τέθηκε σε εφαρμογή στην Ευρωπαϊκή Ένωση. Η χώρα µας µε το Νόμο περί τηλεπικοινωνιών του 2000 και το προς διαβούλευση σχέδιο νόμου της τωρινής κυβέρνησης, φιλοδοξεί να καλύψει τα υπάρχοντα νομικά κενά και να εγκαταστήσει ένα νομικό καθεστώς που θα παρέχει ασφάλεια για τους δυνητικούς επενδυτές. Εξάλλου, σε εξέλιξη βρίσκεται το Επιχειρησιακό Πρόγραμμα «Κοινωνία της Πληροφορίας», μέσω του οποίου, η χώρα µας φιλοδοξεί να αναπτύξει τις τοπικές δικτυακές υποδομές και την παροχή προηγμένων υπηρεσιών προς τον πολίτη. Στα πλαίσια που ορίζονται από όλα τα παραπάνω, σκοπός της παρούσας μεταπτυχιακής εργασίας ήταν η εκπόνηση ενός επιχειρηματικού μοντέλου εκμετάλλευσης και αξιοποίησης των υποδομών που θα εγκατασταθούν στην Περιφέρεια Δυτικής Ελλάδας. Ως οδηγός χρησιμοποιήθηκε η υπάρχουσα εμπειρία από διάφορες επιχειρηματικές προσπάθειες, όπως το Stokab Business Concept και οι περιπτώσεις των πόλεων Sollentuna και Hudiksvall στη Σουηδία, το UTOPIA - Utah Telecommunication Open Infrastructure Agency στην πολιτεία Utah των Ηνωμένων Πολιτειών, οι Ιρλανδικές πρωτοβουλίες ανάπτυξης MANs και το σχέδιο της πόλης της Philadelphia για τη δημιουργία του μεγαλύτερου Wireless Internet Hotspot. Συνοπτικά, το σχήμα που προκρίθηκε είναι η δημιουργία μιας μητρικής εταιρείας, η οποία θα έχει τη συνολική ευθύνη για την ανάπτυξη και δημιουργία ευρυζωνικών υποδομών στα όρια ευθύνης της και ουσιαστικά θα είναι ο διαχειριστής μιας ουδέτερης ευρυζωνικής υποδομής. Σε κάθε νομό θα πρέπει να υπάρχει από μια θυγατρική ή παρακλάδι αυτής της εταιρείας και η οποία ουσιαστικά θα παίζει τον ρόλο του ενδιάμεσου ανάμεσα στην εταιρεία και τις τοπικές κοινωνίες σε θέματα διαβούλευσης, προώθησης των σχεδίων, καταγραφών των αναγκών και των προτάσεων σε επίπεδο Νομού. Στόχος της εταιρείας θα είναι η κατασκευή αυτόνομων δικτύων παθητικού εξοπλισμού σε επίπεδο Νομών, τα οποία όμως θα υπάγονται σε ένα γενικότερο δικτυακό σχεδιασμό σε επίπεδο περιφέρειας. Το δίκτυο αυτό αναμένεται να προσελκύσει τηλεπικοινωνιακούς παρόχους, οι οποίοι θα μπορούν έναντι μίσθωσης να παρέχουν τις υπηρεσίες τους στις τοπικές κοινωνίες και να καλύπτει τις ανάγκες που οι προαναφερθείσες έρευνες κατέδειξαν. / The importance of broadband infrastructures is internationally confirmed by the activation of various advanced countries, to the direction of developing the suitable infrastructures. Their main objective is that these infrastructures can be implemented in a way complementary to the growth of the local economies and to the confrontation of by any chance “technological exclusions” of citizens. The development of broadband networks has become a common European policy in order to actually implement a European Information Society. Furthermore, the Action Plans e-Europe 2002, e-Europe 2005 and i2010 have placed broadband access as an important priority of the European Union. Since July 2003, a new regulatory framework, which regulates the electronic services of telecommunications and networks, was placed in application in the European Union. In Greece, all legal matters in this section where resolved under the law about telecommunications, but the new government brought to consultation a new law which aspires to cover all existing legal voids and to install a legal regime that will provide safety for the potential investors. Moreover, there is in progress the Operational Plan "Information Society", via which, Greece is expected to develop local network infrastructures and advanced services in benefit of the citizens. This thesis’ target was the development of a business model for the exploitation of the infrastructures that will be installed in the Region of Western Greece. Our guide was the existing experience from various business efforts, as the Stokab Business Concept and the cases of cities Sollentuna and Hudiksvall in Sweden, the UTOPIA – Utah Telecommunication Open Infrastructure Agency in the state Utah of United States, the Irish initiatives to develop MANs and the plan of the city of Philadelphia for the implementation of Wireless Internet Hotspots. Concisely, the plan that qualified is the creation of a company, which will have the total responsibility for the development and implementation of broadband infrastructures within her jurisdiction (The region of Western Greece) and will be the administrator of an operator-neutral broadband infrastructure. In each prefecture a subsidiary company must be created which will substantially play the role of the intermediate between the company and the local societies on issues of consultation, promotion of plans, recordings of needs and making proposals. The objective of the company will be the manufacture of autonomous networks of dark fiber in level of Prefectures, which however will depend in a more general network planning in the level of region. This network is expected to attract telecommunication provides, that are expected to rent part of the infrastructure in order to provide their services to the local societies and to cover the needs in electronic services.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.