VictorJuiz/thesis huggingface dataset:
Adhesion and time-dependent fracture in integrated circuit technologies [electronic resource]

In order to maintain scaling in accordance with Moore's Law, a number of novel materials are being integrated at both the device and interconnect levels in modern microprocessors. The successful integration of these new materials requires that they tolerate the inherent stresses present in the structure, as well as the environments, temperatures, and loads associated with fabrication and packaging. This dissertation presents results from several studies focused on the fracture properties of materials at both the device and interconnect levels in modern integrated circuits. Innovative methods for performing thin film adhesion measurements on high strength films are introduced and were used to measure interface fracture energies as high as 35 J/m^2. Additionally, a novel technique for quantifying the effects of environment and temperature on the kinetics of thin film interface debonding is described and was used to quantify growth rates on the order of 1 nm / sec. Using these techniques, combined with surface science measurements of the resulting fracture surfaces, correlations between thin film fracture properties and other device or film properties are explored. While this dissertation specifically addresses materials used in integrated circuits, the techniques and concepts outlined here are applicable to a number of emerging nanoscience and energy technologies. At the device level, a correlation between adhesion and work function tuning behavior of bilayer metal gate electrodes on high-k films is explored. Angle-resolved X-ray photoelectron spectroscopy of the high-k and metal gate fracture surfaces provides strong evidence of a diffusion mechanism responsible for this behavior. At the interconnect level, effects of Cu electroplating chemistry and diffusion barrier composition on barrier adhesion and stress-induced voiding in Cu films are examined, and the critical role of electroplating impurities and interfacial oxygen is addressed. Additionally, the first evidence of time-dependent environmentally assisted debonding of Cu / barrier interfaces in oxidizing and reducing environments is reported and modeled. The kinetics of debonding vary over six orders of magnitude depending on environment and temperature, demonstrating the important role that environment may play in determining defect growth in Cu interconnects.

Keywords: Materials Science and Engineering
Advisor: Dauskardt R. H. (Reinhold H.) primary advisor. Thesis advisor
Nix William D. advisor. Thesis advisor
Pease R. (R. Fabian W.) advisor. Thesis advisor
Advanced chemistry and understanding of acene-containing conjugated polymers for functional electronics [electronic resource]

Conjugated organic polymers and small molecules could potentially be employed as active material for high-throughput, low-cost and large-area device fabrication through solution processing. Electronic devices employing organic systems, such as organic light emitting diodes (OLEDs), organic photovoltaic cells (OPVCs) and organic thin-film transistors (OTFTs) for sensors and displays, have seen improved performances and commercialization in the recent decade. Continuous material innovation is the key towards the achievement of higher and better performances. Among various high-performing materials, large fused ring linear acenes, such as pentacene (Pn) and anthradithiophene (ADT) have maintained the benchmark for charge transport. Okamoto et al have since employed these structures into polymer backbones for solution-processable functional materials. This thesis explores in details the utility of Pn and ADT as building blocks in conjugated polymers. A variety of material and device characterization was carried out for the new materials developed. These include: (A) regio-regular Pn-containing copolymers. The direction of conjugation-extension (from 2,9- or 2,10-positions) was found to impact molecular order and charge-transport properties. (B) 2,8-conjugation-extended ADT-cyclopentadithiophene copolymers. Adjusting the bulkiness of the central substituents on the acene was found to impact molecular packing and charge-transport properties. Triisobutylethynyl-functionalized ADT achieved a photovoltaic power conversion efficiency of 2.7% in a polymer:fullerene bulk heterojunction device. (C) 5,11-conjugation-extended ADT copolymers. To explore impact on polymer electronic and packing behavior, ADT was incorporated with its long molecular axis orthogonal to the polymer backbone via in situ desilylation and Horner Emmons condensation. Using the first methodology, copolymerization with diketopyrrolopyrrole resulted in a low-bandgap polymer due to extended electron delocalization in the direction orthogonal to backbone. This polymer showed out-of-plane layered packing structure, and a high transistor hole mobility of 0.11 cm2 V-1 s-1. The second methodology enabled the development of an ADT monomer precursor exhibiting high ambient stability. Both 5,11-conjugation extended polymers yielded photovoltaic power conversion efficiencies of around 0.8 %. Through the development of these novel monomers and polymer, this thesis demonstrates the synthetic versatility that could be applied to pentacene and ADT in polymers, and the resulting ability to engineer the materials' energy levels and packing behavior. It shows that acene-containing polymers are promising materials for organic electronic devices.

Keywords: Chemical Engineering
Advisor: Bao Zhenan primary advisor. Thesis advisor
Jaramillo Thomas Francisco advisor. Thesis advisor
McGehee Michael
Aeroacoustics of turbulent mixing layers [electronic resource]

Jet noise is an important contributor to overall aircraft noise. The flow near the jet nozzle is a spatially developing mixing layer and influences flow dynamics further downstream. The present study focuses on the influence of inflow conditions on mixing layer development and noise generation mechanisms using large-eddy simulations. Large-eddy simulations of spatially developing, turbulent mixing layers with splitter plate included in the computational domain are presented. Different inflow condition cases with initially laminar boundary layers (abbreviated as LBL) and turbulent boundary layers (abbreviated as TBL) are considered. Effect of heating, keeping the velocity ratio fixed, is analyzed for both. For each case, the mean and turbulent intensity profiles collapse when plotted in similarity coordinates. The development distance to achieve self-similarity in the mean velocity profile is found to be shortest for cases with turbulent exit boundary layers. The growth rate of the shear layer and peak self-similar values of the turbulent intensities are found to be in agreement with available experiments. It is observed that with heating, the initial instability is accelerated but the saturation self-similar amplitude of Reynolds stress components do not vary. The saturation amplitudes of density fluctuations were found to increase proportionally to difference in free-stream densities whereas near-field pressure fluctuations were found to decrease with heating. A simple scaling is suggested for the near-field pressure fluctuation amplitude. The observed scaling laws were also confirmed by simulation data from two-dimensional direct numerical simulations. For LBL, sound radiation is observed in downstream direction peaked roughly at 30 degrees. The vortex pairing and breakdown to turbulence contribute significantly to the radiated sound. For TBL, the acoustic field near the shear layer is significantly weaker and noise due to passage of boundary layer eddies over the trailing edge is observed. For both the cases, a reduction in overall sound pressure levels in the far-field is observed with heating. Analysis of relative importance of Reynolds stress autocorrelation tensor components is presented to explain the effects of heating.

Keywords: Mechanical Engineering
Advisor: Lele Sanjiva K. (Sanjiva Keshava)
Cantwell Brian advisor. Thesis advisor
Moin Parviz advisor. Thesis advisor
Aggregate investment and its consequences [electronic resource]

I use financial statement information to examine intertemporal investment decisions by publicly traded firms at the aggregate level. I find that aggregate corporate investment negatively predicts stock market returns in the US and in a number of foreign countries. Corporations invest more when: (i) investor sentiment is higher; (ii) the yield curve is flatter; and (iii) analysts are more optimistic about future earnings. Moreover, higher aggregate investment forecasts: (i) lower aggregate ROA; (ii) lower short-window returns around earnings announcements; (iii) lower returns on growth stocks and a widening of the 'value premium'; and (iv) deteriorating macroeconomic growth and a higher risk of recession. Several dimensions of these findings are difficult to reconcile in an efficient framework and suggest that inefficient investment plays a role in driving prices and fundamentals at the aggregate level.

Keywords: Business.
Advisor: Lee Charles M. C. primary advisor. Thesis advisor
Piotroski Joseph D. (Joseph David) primary advisor. Thesis advisor
Barth Mary E. advisor. Thesis advisor
Aircraft design for reduced climate impact [electronic resource]

Aircraft affect global climate through emissions of greenhouse gases and their precursors and by altering cirrus cloudiness. Changes in operations and design of future aircraft may be necessary to meet goals for limiting climate change. One method for reducing climate impacts involves designing aircraft to fly at altitudes where the impacts of NOx emissions are less severe and persistent contrail formation is less likely. By considering these altitude effects and additionally applying climate mitigation technologies, impacts can be reduced by 45-70% with simultaneous savings in total operating costs. Uncertainty is assessed, demonstrating that relative climate impact savings can be expected despite large scientific uncertainties. Strategies for improving climate performance of existing aircraft are also explored, revealing potential climate impact savings of 20-40%, traded for a 2% increase in total operating costs and reduced maximum range.

Keywords: Aeronautics and Astronautics
Advisor: Kroo Ilan primary advisor. Thesis advisor
Alonso Juan José
Jacobson Mark Z. (Mark Zachary) advisor. Thesis advisor
Aircraft drag reduction through extended formation flight [electronic resource]

Formation flight has the potential to significantly reduce the fuel consumption of long range flights, even with existing aircraft. This research explores a safer approach to formation flying of transport aircraft, which we term extended formation flight. Extended formations take advantage of the persistence of cruise wakes and extend the streamwise separation between the aircraft by at least five wingspans. Classical aerodynamic theory suggests that the total induced drag of the formation should not change as the streamwise separation is increased, but the large separation distances of extended formation flight violate the simple assumptions of these theorems. At large distances, considerations such as wake rollup, atmospheric effects on circulation decay, and vortex motion become important to consider. We first examine the wake rollup process in the context of extended formations and develop an appropriate physics-based model. Using this model, this dissertation addresses three aspects of formation flight: longitudinally extended formations, compressibility effects, and formations of heterogeneous aircraft. Uncertainty analysis is used to investigate the induced drag savings of extended formations in the presence of variation in atmospheric properties, limitations of positioning accuracy, and uncertainty in model parameters. Next, the methodology is integrated with an Euler solver to assess the impact of compressibility while flying in formation. Finally, we examine the important considerations for optimally arranging formations of non-identical aircraft.

Keywords: Aeronautics and Astronautics
Advisor: Kroo Ilan primary advisor. Thesis advisor
Alonso Juan José
Lele Sanjiva K. (Sanjiva Keshava)
Airfoil aeroacoustics, LES and acoustic analogy predictions [electronic resource]

The development of physics-based noise prediction tools for analysis of aerodynamic noise sources is of paramount importance since noise regulations have become more stringent. Direct simulation of aerodynamic noise remains prohibitively expensive for engineering problems because of the resolution requirements. Therefore, hybrid approaches that consist of predicting nearfield flow quantities by a suitable CFD simulation and farfield sound radiation by aeroacoustic integral methods are more attractive. In this work, we apply the fast multipole method (FMM) to accelerate the solution of boundary integral equation methods such as the boundary element method (BEM) and the Ffowcs Williams & Hawkings (FWH) acoustic analogy formulation. The FMM-BEM is implemented for the solution of acoustic scattering problems and the effects of non-uniform potential flows on acoustic scattering are investigated. The FMM-FWH is implemented for the solution of two and three-dimensional problems of sound propagation. The effects of flow convection and non-linear quadrupole sources are assessed through the study of sound generated by unsteady laminar flows. Finally, a hybrid methodology is applied for the investigation of airfoil noise. This study is important for the design of aerodynamic shapes such as wings and high-lift devices, as well as wind turbine blades, fans and propellers. The present investigation of airfoil self-noise generation and propagation concerns the broadband noise that arises from the interaction of turbulent boundary layers with the airfoil trailing edge and tonal noise that arises from vortex shedding generated by laminar boundary layers. Nearfield acoustic sources are computed using compressible large eddy simulation (LES) and acoustic predictions are performed by the FMM-FWH. Numerical simulations are conducted for a NACA0012 airfoil with tripped boundary layers and blunt rounded trailing edge at different Mach numbers and angles of incidence. The effects of non-linear quadrupole sources and convection are assessed. In order to validate the numerical solutions, flow simulation and acoustic prediction results are compared to experimental data available in the literature and excellent agreement is observed.

Keywords: Aeronautics and Astronautics
Advisor: Lele Sanjiva K. (Sanjiva Keshava)
Alonso Juan José
Darve Eric advisor. Thesis advisor
An algebraic geometry based approach to decentralized control [electronic resource]

Decentralized control has been one of the important problems in systems and control engineering. Computing an optimal decentralized controller for general linear systems, however, is known to be a very challenging task. In particular, designing an optimal decentralized controller in the standard framework of a linear system with quadratic cost and Gaussian noise is well known to be extremely hard even in very simple and small sized problems. Because of this fact, previous work has focused on characterizing several different classes of problems for which an optimal decentralized controller may be efficiently computed. The set of quadratically invariant problems is one of the largest known class of such problems. This dissertation provides a novel, general, and powerful framework for addressing decentralized control by introducing the idea of using rational elimination theory of algebraic geometry. We show that, in certain cases, this approach reduces the set of closed-loop maps of decentralized control to the solution set of a collection of linear equations. We show how to use these linear equations to find an optimal decentralized controller. We also prove that if a system is quadratically invariant then under an appropriate technical condition the resulting elimination set is affine. We further illustrate that our approach can be well applied to a strictly larger class of decentralized control problem than the quadratically invariant one by presenting a simple example: the example shows that there are problems which are not quadratically invariant but for which the resulting elimination description is affine.

Keywords: Electrical Engineering
Advisor: Lall Sanjay primary advisor. Thesis advisor
Boyd Stephen P. advisor. Thesis advisor
Johari Ramesh
Algebraic space-time block codes with manageable complexity of maximum-likelihood detection [electronic resource]

Multiple-input multiple-output (MIMO) wireless systems provide tremendous throughput and reliability gains by utilizing multiple antennas at the transmitters and receivers. As a result, numerous papers have addressed communication and signal-processing topics like space-time code design and signal detection theory. However, today's industry still faces problems with integrating MIMO into products owing to the implementation complexity. Management of complexity is therefore essential to realize the promise of MIMO technology. Previous research on designing space-time block codes was mostly concerned with maximizing transmit diversity and coding gains, and with achieving the optimal diversity-multiplexing trade-off. In contrast, this thesis aims at designing new transmission strategies that can be efficiently decoded while retaining or approaching the optimal performance. The first part of this thesis proposes a new set of rate-1 space-time block codes in systems with 2^n-transmit antennas. These designs achieve the full spatial diversity in quadrature amplitude modulation (QAM). Furthermore, the column vectors of each code matrix can be partitioned into two classes such that any two vectors from different classes are orthogonal. As a result, the maximum-likelihood (ML) detection can be implemented in reduced time complexity. For a system with four transmit antennas, the proposed encoders attain the optimal bit error rate (BER) in QAM without the necessity of extra modulation. These results will be extended to new rate-1 codes employing four transmit antennas for which the ML detection can be determined in linear time. These codes similarly achieve the full diversity in QAM, and moreover in 4M-phase-shift keying (4M-PSK), while the corresponding ML detection can be accomplished by independently decoding each symbol. The reduction in detection complexity simply necessitates an increment of 0.21 dB in the signal-to-noise ratio (SNR) for sustaining the same BER.

Keywords: Electrical Engineering
Advisor: Cioffi John M. primary advisor. Thesis advisor
El Gamal Abbas A. primary advisor. Thesis advisor
Gill John T.
Algorithms and strategies for web advertising [electronic resource]

Web advertising is a multi-billion dollar business and the main revenue source of the most popular web sites such as Google, Yahoo and Facebook. Web advertisers reach their potential customers mainly through two different channels: sponsored search, the display of textual ads next to the search engine organic results and display advertising, the display of graphical ads as part of web pages. In the simplest form of web advertising three parties are involved: the advertisers, the medium, i.e., the search engine or the publisher, and the users. Their interactions can be grouped in three steps: (a) Bidding: The advertisers provide the medium with their ads, their bids, and some preferences regarding the users of interest; (b) Delivery: Given the ads and a user in a particular context, i.e., a query or a web page, the medium selects an ad that respects advertiser preferences and maximizes its own expected profit; (c) Response: The user sees the selected ad and he either ignores it or proceeds to an action related to it, e.g., he clicks a link or buys a product. Such actions fulfill the advertiser goals and, consequently, they drive the whole procedure. In this thesis we study each of these steps and we propose new algorithms and strategies that tackle inefficiencies of current solutions. In bidding, we introduce output URL bidding, a new bidding mechanism for sponsored search, where advertisers bid on search result URLs, as opposed to keywords in the input query. For example, an advertiser may want his ad to appear whenever the search result includes the sites www.imdb.com and en.wikipedia.org, instead of bidding on keywords that lead to these sites, e.g., particular movie titles or actor names. We have shown that output bidding can provide a more concise language among advertisers and the search engine and it can increase the recall of relevant queries. In ad selection, we introduce sponsored search auctions with conflicts. In such auctions, advertisers can condition their bids on the non-appearance of certain undesired ads on the results page. With such constraints the ad selection becomes computationally challenging. However, we introduce algorithms that can deal with the computational cost, while providing advertisers with higher utility and the search engine with increased revenue. Finally, our work includes also novel ways to quantify the user response. Using a field experiment we have measured the impact of display advertising on user search behavior. Our results show that display ads can increase the volume of queries that are related to an ad by 5% to 25% for a two-week period. Surprisingly, the impact of advertising is not limited to exposed users but also to their social friends.

Keywords: Electrical Engineering
Advisor: Garcia-Molina Hector primary advisor. Thesis advisor
Bambos Nicholas advisor. Thesis advisor
Goel Ashish advisor. Thesis advisor
Algorithms for congestion control and bandwidth-partitioning in data centers [electronic resource]

Data Center Networks represent the convergence of computing and networking, of data and storage networks, and of packet transport mechanisms in Layers 2 and 4. These networks provide a rich opportunity for developing new algorithms and architectures. In this thesis, we propose a Layer 2 congestion management algorithm called QCN (Quantized Congestion Notification), which we have developed for the IEEE 802.1Qau Congestion Notification standard for Data Center Ethernet. QCN has been designed to be stable, responsive, and simple to implement. This thesis also introduces ECN-hat, a slightly modified version of the TCP algorithm that mimics QCN's multi-bit rate cuts, leading to significantly higher utilization and lower latency. It does this by using the ECN marks in the acks of packets in a non-traditional way, one which extracts more information about the congestion in network. We also show how QCN and Data Center TCP (DCTCP) can be easily extended via light-weight switch modifications to provide programmable bandwidth partitioning in multi-tenanted Cloud Computing and Data Center environments. Our Approximately Fair extensions, AF-QCN and AF-DCTCP, achieve weighted fairness at the granularity of a few milliseconds while retaining the good properties of QCN and DCTCP (stability, responsiveness, and simplicity).

Keywords: Electrical Engineering
Advisor: Prabhakar Balaji
McKeown Nick advisor. Thesis advisor
Tobagi Fouad A.