VictorJuiz/thesis huggingface dataset:
A ground structure method to optimize topology and sizing of steel frame structures to minimize material, fabrication and erection cost [electronic resource]

Engineers are often challenged to design steel structures that are safe, economical, constructible. This design process involves specifying each of the following three aspects of the structure: (i) topology, which concerns the number and connectivity of members; (ii) shape, which pertains to the location of structural joints; and (iii) sizing, which involves defining member cross-sections. This thesis presents a method to optimize topology and sizing of steel frame structures to minimize total installed cost while meeting defined safety and constructability requirements. Based on the Ground Structure Method (GSM), the proposed approach begins with an array of nodes that are interconnected with a dense mesh of linear members which have undergone a geometric check to ensure feasibility of fabrication and erection. Each member in the structure is then sized in an iterative process considering the applied forces and discrete set of section types provided. The sizing process ensures that the members are capable of bearing the applied loads and therefore result in a safe structure. Next, each connection in the structure is detailed based on the joint forces and incoming member sizes. The material quantities from the detailed structure are then used to estimate the cost of each member, including connections, based on unit rates that are intended to be provided by the steel fabricator, erector and material supplier. Finally, members in the structure are ranked according to their stress to cost ratio. The topology optimization process functions by systematically removing members in the structure which have a relatively low stress per unit cost until the converged solutions is found. The proposed Cost-Driven Deterministic Ground Structure Method (CDD-GSM) is applied to a typical two-dimensional building braced frame structure in order to demonstrate the method and compare its performance to a typical weight-based GSM approach. While being 18% heavier, CDD-GSM solution is approximately 8% cheaper than the weight-optimal design. These results highlight the limitations of existing weight-based approaches and demonstrates the importance of an accurate cost-based objective function in order to improve the practicality and effectiveness of topology and sizing optimization methods.

Keywords: Civil and Environmental Engineering.
Advisor: Fischer Martin
Flager Forest
Haptic jamming [electronic resource] : controllable mechanical properties in a shape-changing user interface

Haptic interfaces increase the richness and quality of user interaction with a virtual or remote environment by conveying physical information through the sense of touch. Beyond vibration of a mobile device or force feedback through the end effector of a robot, shape-changing interfaces provide more complete haptic feedback by allowing the user to explore the interface directly with his or her hands. This thesis presents the design, modeling, and control of a novel form of haptic interface inspired by advances in soft robotics and tangible interaction. Haptic Jamming is a technique that combines particle jamming and pneumatic actuation of a surface to achieve simultaneous control of its shape and mechanical properties. A hollow silicone membrane is molded into an array of thin cells, each filled with coffee grounds such that adjusting the vacuum level in any individual cell rapidly switches it between flexible and rigid states. The array clamps over a pressure-regulated air chamber with internal mechanisms designed to pin the nodes between cells at any given height, which provide an extra degree of control over the output shape. Various sequences of cell vacuuming, node pinning, and chamber pressurization allow the surface to balloon into a variety of shapes. Experiments were performed to define the rheological characteristics of jammed systems from a macroscopic perspective that is relevant to force-displacement interactions that would be experienced by human users, expanding upon existing physical models of jamming at the inter-particle level. This provides the framework to tune and control the mechanical properties of a jamming interface. A custom spring-mass deformable body simulation was built combining models of the three actuation inputs of a Haptic Jamming surface: node pinning, chamber pressurization, and cell jamming. The simulation guided the development of an algorithm to generate a sequence of actuation inputs for the surface in order to match desired output shapes ranging from topographical maps to three-dimensional solid object models. The construction of multi-cell arrays integrated with the depth map from an {RGB-D} sensor provides the capability to close the feedback loop on surface shape, resulting in a more compelling display of complex shapes. Ongoing research shows promise to develop Haptic Jamming into a fully three-dimensional device with embedded stretchable sensors, permitting its use as both a computer input and output interface. This technology can enable dynamic tangible environments for applications ranging from medical simulation to product design.

Keywords: Mechanical Engineering.
Advisor: Okamura Allison primary advisor. Thesis advisor
Cutkosky Mark R. advisor. Thesis advisor
Follmer Sean advisor. Thesis advisor
Hardware acceleration of graph analysis applications [electronic resource]

Graphs are powerful data representations favored in many computational domains. Analytics and knowledge extraction on these data structures has become an area of great interest, particularly with the increasing prevalence of large data sets now becoming commonplace in data centers. Due to the scale of these operations, energy efficiency on frequent tasks such as graph analysis will be very important as the domain and the data sizes continue to grow. Dedicated hardware accelerators are one high-performing yet energy-efficient approach to this problem. Unfortunately, they are notoriously labor-intensive to design and verify while meeting stringent time-to-market goals. This thesis presents GraphOps, a modular hardware library for quickly and easily constructing energy-efficient accelerators for graph analytics algorithms. GraphOps provide a hardware designer with a set of composable graph-specific building blocks broad enough to target a wide array of graph analytics algorithms. The system is built upon a streaming execution platform and targets FPGAs, allowing a vendor to use the same hardware to accelerate different types of analytics computation. Stubborn hardware implementation details such as flow control, input buffering, rate throttling, and host/interrupt interaction are automatically handled and built into the design of the GraphOps, greatly reducing design time. As an enabling contribution, this thesis presents a novel locality-optimized graph data structure that improves the efficiency of memory access to the graph.

Keywords: Electrical Engineering.
Advisor: Olukotun Oyekunle Ayinde primary advisor. Thesis advisor
Kozyrakis Christoforos
Mitra Subhasish advisor. Thesis advisor
Harnessing the complexity of complex oxides [electronic resource]

Human prosperity is driven by technology. And over the past 50 years, much of the tremendous progress in human prosperity has been driven by information technology, especially the semiconductor transistor and Moore's law. However, today Moore's law is ending. Going forward, humanity faces two broad possibilities: either stick with the transistor and settle for a reduced rate of technological progress or, as has been done many times in the past, develop a new computing paradigm with more initial difficulty but higher ultimate potential. One candidate materials platform for a future computing paradigm is complex oxides, whose complexity is both boon and bane. On the one hand, the complexity of complex oxides enables a wide range of tunable properties, such as ferromagnetism, ferroelectricity, and superconductivity. But on the other hand, their complexity makes them difficult to synthesize reliably and difficult to understand. In my PhD, I studied how the behavior of 3d electrons can be tuned in thin films of complex oxide materials. In my first major project, I studied how electrical conductivity could be turned on and off at the interface of LaAlO3/SrTiO3. And in my second major project, I studied how ferromagnetism could be turned on and off in RCo3, where R is a rare earth element. In my LaAlO3/SrTiO3 project, despite the interface's wide variation in reported electrical properties, I highlighted a scaling relationship between sheet carrier concentration and mobility common to nearly all research groups. I also discovered that the electrical transport is robust to the presence of magnetic and spin-orbit scatterers (Tm and Lu) at a 2% concentration in LaAlO3. In cobalt perovskites, I extended the phase diagram of thin film magnetism, exploring the roles of both chemical pressure (through A-site doping) and epitaxial strain. I discovered that although tensile epitaxial strain from SrTiO3 is enough to induce ferromagnetism in LaCoO3 and PrCoO3, it is not enough to induce ferromagnetism in P0.7Y0.3CoO3, which has a smaller and less cubic unit cell. X-ray magnetic circular dichroism revealed that although the Co ions Pr0.7Y0.3CoO3 in were not ferromagnetic, they still possessed magnetic moments, suggesting that the lack of ferromagnetism came from a lack of exchange rather than a lack of magnetic moment. These results highlight the importance of chemical bonding in stabilizing a ferromagnetic ground state and demonstrate new ways to tune magnetic order. Together, these projects provide new insights toward understanding and controlling the behavior of correlated 3d electrons. And they bring us a few steps closer to finally harnessing the complexity of the complex oxides.

Keywords: Applied Physics.
Advisor: Suzuki Yuri (Applied physicist) primary advisor. Thesis advisor
Hwang Harold Yoonsung
Qi Xiaoliang advisor. Thesis advisor
Health and Safety Conditions Within the Global Supply Chain of the Electronics Industry: An Investigation of Over 500 Manufacturing Facilities for a Prominent Consumer Electronics Multinational

With the advent of the globalized economy, this has posed a unique threat for the health and safety of workers globally. Now that multinationals can outsource their labor to developing countries for low wages and high scalability of labor forces, there is a growing concern that the working conditions found in these overseas factories—particularly for the electronics manufacturing industry— are dangerous in occupational safety practices, resulting in high rates of injury and documented occupational diseases. Working with a prominent electronics multinational, Firm X, we collected audit data from 538 factories spanning 23 separate countries and 259 cities, the largest of its kind for the multinational. We found that out of the 525 factories that documented accidents or incidents in the past two years, 485 factories (92.38%), reported 0 of either injuries or accidents. A similar trend of little to no reporting was observed for documented abnormal occupational health (OH) exams; out of the 526 factories that documented occupational health exam evaluations, 449 of them (85.36%) reported 0 abnormalities. Overall, 80% of the audited factories reported 0 occupational injuries or abnormal occupational health exams within the past two years, which is vastly below the hypothesized results, insomuch that the credibility of these data was called into question. When compared with national averages and nongovernmental organization (NGO) audits, these data are vastly lower, strongly indicating that underreporting has taken place within Firm X’s supply chain. Thus, we believe that these data do not provide an accurate depiction of injuries rates and occupational-related illnesses for workers within Firm X’s supply chain, calling for improved modes of collecting health and safety reports through the supply chain in order to protect worker health and safety. We believe this finding is not unique to Firm X, and that understanding the working conditions in the electronics manufacturing industry, especially within developing countries, is a continual challenge that must be further investigated.

Keywords:  Department of Biology
Biology
occupational health
Thesis
Advisor: Cullen Mark
Fernald Russ
Heat shock protein 90 and the evolution of antifungal drug resistance

Theory holds that the capacity of a population to evolve in response to a selective pressure is due to pre-existing variants. That is, successful alleles are not produced by selection itself but are rather enriched by selection. This line of thinking has recently been challenged by the observation that some types of environmental stress can induce mutations that confer an adaptive advantage in them. Although the generality of such findings is controversial, a number of induced mutagenesis systems have now been characterized at the genetic level in bacteria. Much less is known about whether and how such processes might operate in eukaryotic cells. The highly conserved molecular chaperone Hsp90, which assists in the folding of many proteins that are critical for growth and development, has been proposed to broadly influence the capacity of mutations to produce new phenotypes. Because the activity of Hsp90 is stress-regulated, I investigated whether it might provide a means through which the environment could influence the acquisition of adaptive phenotypes. Using the classic statistical assay known as the fluctuation test, I observed that changes in Hsp90 activity altered the mechanisms by which yeast cells acquire resistance to the commonly prescribed antifungal drug fluconazole. The distribution of resistant variants I obtained suggested that fluconazole exposure itself likely induced the acquisition of resistant phenotypes. In contrast, a distribution of resistant variants consistent with spontaneous appearance was evidence in cells with reduced Hsp90 activity. I observed similar results with the evolutionarily distant human pathogen Candida albicans. These findings establish a means through which environmental stress might influence the fundamental mechanisms of adaptation in eukaryotes and further point to an unappreciated benefit of modulating Hsp90 activity as a strategy to overcome drug resistance in fungi.

Keywords: Biology
Thesis
Advisor: Jarosz Daniel
Petrov Dmitri
Heterogeneity and depletion of the mantle assessed from abyssal peridotite geochemistry [electronic resource]

Mid-ocean ridges are the surface expressions of plate tectonics and mantle convection, where decompression melting of the upper mantle produces the basaltic crust. Despite the information provided by basalts on mantle composition, they are mixtures of melts sourced from large regions. In contrast, abyssal peridotites are the residues of melting and they can be used to directly study the Earth's mantle in locations where they are emplaced on the seafloor. In this dissertation, I use abyssal peridotites to constrain mantle composition, including evidence for long-term heterogeneity and an exploration of the behavior of the element lead (Pb) -- a key geochemical tracer -- during melting. In Chapter 1, I use peridotites from the ultraslow spreading Gakkel Ridge in the Arctic Ocean to assesses the spatial variation in chemical compositions of peridotite and to explore the long-term effects of ocean ridge melting and refertilization on mantle composition. In chapter 1, the spatial length-scale of compositional variability observed among Gakkel peridotites indicates the existence of a heterogeneous mantle, including refractory mantle produced by ancient melt depletion unrelated to the current ridge setting. Chapters 2 and 3 explore the distribution and partitioning of Pb in the mantle, using peridotites from the Gakkel and Southwest Indian Ridges. Despite the importance of Pb for isotopic models of Earth's geochemical evolution, the mineralogical host of Pb in the mantle is poorly constrained. Sulfide has been suggested to contain the majority of mantle Pb, even though it occurs at modal abundances < 0.1% in peridotite. In Chapter 2, I develop a method for the in situ measurement of Pb and other trace element abundances in sulfides. Sulfides have an average Pb concentration of 2 ppm, which I incorporate into a model of sulfide petrogenesis to suggest that current estimates for source mantle composition contain too little Pb. Finally, Chapter 3 presents a comprehensive mass balance for Pb, by using Pb concentrations in the silicate phases, in addition to the sulfides, to reconstruct whole rock compositions and compare these to the measured whole rock. The results of this calculation show that Pb is hosted in a combination of silicate and sulfide phases, which is key for understanding the transport and long-term storage and abundance of mantle Pb.

Keywords: Geological and Environmental Sciences.
Advisor: Grove Marty
Warren Jessica
Ernst W. G. (Wallace Gary)
High harmonic generation in rare gas solids [electronic resource]

Strong-field laser excitation in semiconductors and insulators has been shown to produce high harmonic generation (HHG) and other strong field effects familiar in atomic physics. However, in solids, the microscopic processes underlying these effects are not well understood. One way of getting a better understanding is to compare HHG of a single chemical element both in solid and gas phase. In this dissertation I will discuss results of a comparative study of HHG is solid Ar and Kr and their respective gas states. We found that HHG spectra in solid Ar and Kr , which extends to about 40 eV, have secondary plateaus. In addition the cutoff law is well above the one in gas states. Both effects have origin from purely solid state effects. We use a quantum model of laser excitation to interpret our results and make a connection to past results on HHG in solid state, where the apparent differences between interband and intraband currents might just be stemming from vantage view. In addition, there are signs that manybody effects might play an important role in HHG in rare gas solids. Finally, the ellipticity dependence of HHG is as strong as in the case of gases which points to the importance of electron recombination. This means that HHG in solids can be a powerful tool for studying the microscopic and band structure of solids and their excitations.

Keywords: Applied Physics.
Advisor: Reis David A.
Bucksbaum Philip H. advisor. Thesis advisor
Gaffney Kelly advisor. Thesis advisor
High speed links for flexible optical networks [electronic resource]

Web-based applications, content streaming, and cloud computing have been driving the need for large-scale high-bandwidth datacenter networks. Optical links from ultra-long-distance links between datacenters to short-reach Ethernet links inside a warehouse are critical for scaling datacenter networks. In this dissertation, we study spectrally efficient and high-speed optical links for various types of optical networks such as intra-datacenter networks as well as wide-area networks interconnecting datacenters. In the first part of this dissertation, we study short-reach intra-datacenter networks. More specifically, we investigate various schemes to scale these links to 100 Gbit/s per-wavelength using multi-level intensity modulation and direct detection, relying on digital signal processing to compensate for component bandwidth limitation. Moreover, we discuss the complexity and requirements for different components of the system. We further show that 100 Gbit/s per-wavelength links are constrained in their optical power budget and study the benefits and challenges of using semiconductor optical amplifiers to improve the power margin. Extra margin can enable future datacenter architectures based on high number of wavelength-division multiplexed channels and optical circuit switching. In the second part of this dissertation, we propose a modular architecture for long-haul optical networks interconnecting datacenters that can support spectrally efficient superchannels with variable bandwidth. In the proposed architecture, multiple synchronized transceivers can cooperate to modulate/detect a superchannel comprising of multiple subcarriers, enabling transmission at bit rates beyond 1 Tbit/s. We analyze and simulate the performance of the proposed system in the presence of linear fiber impairments and synchronization errors and establish design requirements for practical deployment of such an architecture.

Keywords: Electrical Engineering.
Advisor: Kahn Joseph M. (Joseph Mardell) primary advisor. Thesis advisor
Miller D. A. B. advisor. Thesis advisor
Solgaard Olav advisor. Thesis advisor
High-k gate dielectric interfaces with germanium and silicon-germanium substrates [electronic resource]

As transistors scale to their physical limits, germanium and silicon-germanium (SiGe) alloys are both promising candidate metal-oxide-semiconductor field effect transistor (MOSFET) channel materials to extend the roadmap. In this work, I used carefully-controlled atomic layer deposition (ALD) processes and a simple forming gas anneal (FGA), to form TiO2/Al2O3/Ge gate stacks with 0.65 nm EOT and low interface trap densities. For the first time, I applied bilayer gate dielectric stacks to Ge pMOSFETs with sub 1-nm EOT and a subthreshold swing (SS) as low as 71 mV/dec. For the first time, soft x-ray and hard x-ray photoelectron spectroscopy were used to rigorously study the formation of a GeO2 interface layer between an atomic layer deposited gate dielectric and a Ge(100) substrate during forming gas anneal (FGA). A new and simple method was demonstrated to selectively passivate interface traps with energies in the top half of the Ge band gap under annealing conditions that produce a GeO2 interface layer. I also describe how the sensitivity of the interface trap density in metal/Al2O3/Ge MOSCAPs is related to the nature of the H2/N2 anneal and the presence of a gate metal such as Pt that is effective in dissociating H2 to atomic hydrogen. The third part of this work focuses on SiGe substrates. Experiments show that, even though the native oxides of the SiGe channel are removed by 2% HF(aq)/ H2O cyclic cleans, a SiOx/GeOx interfacial layer is formed during Al2O3 ALD. Using Al as the gate metal instead of Pt, Al2O3/SiGe MOSCAPs show C-V curves with minimal frequency dispersion and much smaller Dit response. Experiments reveal that the Al-gate scavenges oxygen from the underlying GeOx, producting a SiOx/SiGe interface with much-reduced Dit.

Keywords: Electrical Engineering.
Advisor: McIntyre P. (Paul)
Nishi Yoshio
Pianetta Piero advisor. Thesis advisor
Saraswat Krishna advisor. Thesis advisor