VictorJuiz/thesis huggingface dataset:
On-board hydrogen production from natural gas via a metallic Pd-based membrane reactor [electronic resource]

This work describes the application of palladium-based composite membrane reactors (MRs) for performing steam methane reforming (SMR) and natural gas steam reforming reactions to produce a high-purity hydrogen stream for CO2 capture from the transportation sector. In particular, the effect of different operating conditions on the performance of several MRs has been investigated. Moreover, thin pure palladium and palladium-gold alloy membranes have been synthesized via electroless plating and housed in the membrane module for reaction and permeation testing. In particular, the SMR reaction across porous stainless steel-supported Pd membranes has been investigated with a focus on low temperature and pressure conditions to showcase the ability of the MR to obtain high conversions even at mild conditions. The feed composition ratio, i.e., H2O/CH4, was kept above the stoichiometric limit to enhance conversion, while a permeate sweep gas was used to promote the permeation of hydrogen through the membrane. This application of the Pd-based MR resulted in high methane conversion (84%) and hydrogen recovery (82%) with a pure hydrogen stream obtained from the permeate side at temperatures as low as 400 °C. Stable methane conversions and hydrogen permeation rates were obtained for > 700 reaction hours. Using a Pd-Au composite MR, further reaction testing took place with a real natural gas feed at 450 °C and 300 kPa. This MR operated under a SMR reaction continuously for > 250 hours without a decrease in performance, highlighting the long-term stability of the MR to produce pure hydrogen for long periods of time. More specifically, the conversion of higher hydrocarbons, e.g., propane, ethane, and butane, within the reactor were > 85% throughout the experimental tests. Using a membrane module comprised of a dense Pd77Ag23 membrane, hydrogen permeation decreased when exposed to H2S. This decrease in hydrogen flux was temporary and complete recovery was realized with 200 ppm and 40 ppm H2S exposure tests showing no long-term effects on the membrane. These results allow for an alternative use of pure Pd membranes, which are irreversibly poisoned by H2S.

Keywords: Energy Resources Engineering.
Advisor: Wilcox Jennifer
Brandt Adam (Adam R.) advisor. Thesis advisor
Edwards C. F. (Christopher Francis) advisor. Thesis advisor
Liguori Simona advisor. Thesis advisor
Opportunities, costs and benefits [electronic resource] : rethinking the education production function

My dissertation incorporates both traditional and non-traditional approaches to the specification and estimation of the education production function. I pursue three related questions: I use normative philosophical methods to consider whether implications of equal opportunity and adequacy distributive principles are compatible with the basic and intuitive right that all students have claim to at least some educational resources to develop their abilities. If an incompatibility is found, this suggests that these paradigmatic distributive principle are in need of revision. I propose a method for estimating an achievement scale that is equal-interval with respect to benefit. I develop and implement survey experiments to estimate individual preferences for math and reading academic skills. This quantitative description allows for both between and within attribute comparisons, making it possible to determine, for example, whether a 10-point gain at the low end of the math scale is preferable to a 20-point gain at the high end of the reading scale. Such a scale can be used for cost-effectiveness evaluations. I (with Christopher Candelaria) provide new evidence about the effect of court-ordered finance reform on per-pupil revenues and graduation rates. We account for cross-sectional dependence and heterogeneity in the treated and counterfactual groups to estimate the effect of overturning a state's finance system. Seven years after reform, the highest poverty quartile in a treated state experienced a 4 to 12 percent increase in per-pupil spending and a 5 to 8 percentage point increase in graduation rates.

Keywords: Education.
Advisor: Reardon Sean F. primary advisor. Thesis advisor
Callan Eamonn advisor. Thesis advisor
Loeb Susanna advisor. Thesis advisor
Satz Debra advisor. Thesis advisor
Optical network scaling using spatial multiplexing [electronic resource]

Spurred by information technologies, worldwide data traffic is growing exponentially. Optical fiber networks form the backbone of the global data connectivity, and scaling to higher throughput and lower cost per bit is essential to ensure continued growth of information technologies. As the throughput of single-mode fibers approaches information-theoretic limits, throughput may be increased by employing multi-input multi-output transmission to multiplex information in the plurality of modes of multi-mode fibers. Chapters 2-5 address spatial multiplexing in long-haul systems. After providing an overview of networking architectures, the benefits of spatial multiplexing for communication and switching are demonstrated. Receiver-based multi-input multi-output signal processing methods enabling spatial multiplexing in multi-mode fibers are described. Two efficient algorithms for multi-input multi-output signal processing -- least-mean squares and recursive least-squares -- are studied. Their performance and complexity are analyzed. Two fundamental mode-dependent propagation effects in long-haul systems are (i) distortion caused by the disparity between modal group velocities, and (ii) fading caused by the disparity between modal gains. Modeling approaches for (i) are developed, and the corresponding statistics are derived. Methods and devices for controlling the end-to-end group delays of a system are studied. The statistics of (ii) are presented, and the implications on information-theoretic capacity limits are studied. Chapter 6 addresses spatial multiplexing in short-reach systems. Canonical architectures to enable spatial multiplexing, based on transmitter- and received-based multi-input multi-output signal processing, are presented. Short-reach systems use noncoherent direct detection because of its low complexity and low cost. However, direct detection yields information on received intensity but not received phase. To enable multi-input multi-output signal processing, we propose to use adaptive learning algorithms based on phase-retrieval for channel estimation. Three fundamental approaches for phase retrieval -- sparse training sequences, alternating minimization and convex optimization -- are proposed, and compared in terms of their performance.

Keywords: Electrical Engineering.
Advisor: Kahn Joseph M. (Joseph Mardell) primary advisor. Thesis advisor
Ho Keang-Po
Solgaard Olav
Optimal outsourcing strategies under uncertainty [electronic resource]

This thesis includes two essays on outsourcing in the presence of uncertainty. The first concerns physical goods and multi-tier supply chains whereas the second discusses the outsourcing of innovation in the context of dynamic contests. In Chapter 2 we study multi-tier supply chain networks in the presence of disruption risk. Firms decide on how to source their inputs from upstream suppliers so as to maximize their expected profits, and prices of intermediate goods are set so that markets clear. We establish that a supply equilibrium exists and provide an explicit characterization of the equilibrium prices, profits, and sourcing decisions. Our characterization allows us to derive insights on how the network structure, i.e., the number of firms in each tier, production costs, and disruption risk affect firms' profits and the prices of intermediate goods. Furthermore, we establish that networks that maximize consumer surplus and aggregate profits for the supply chain are structurally different. In particular, the former have relatively less diversified downstream tiers and generate more variable output than the latter. Finally, we study the question of endogenous chain formation by considering a game of entry, i.e., firms decide whether to engage in production by forming beliefs about their profits in the post-entry supply chain. We argue that endogenous entry leads to chains that are inefficient in terms of the number of firms that engage in production. Chapter 3 studies the design of innovation contests as a tool to outsource innovation when there is uncertainty about the feasibility of the project. In such a contest, participants race towards completing an innovation project and learn about its feasibility from their own efforts and their competitors' gradual progress. Information about the status of competition can alleviate some of the uncertainty inherent in the contest, but it can also adversely affect effort provision from the laggards. We explores the problem of designing the award structure of a contest and its information disclosure policy in a dynamic framework and provides a number of guidelines for maximizing the designer's expected payoff.

Keywords: Management Science and Engineering.
Advisor: Bimpikis Kostas primary advisor. Thesis advisor
Ashlagi Itai advisor. Thesis advisor
Johari Ramesh
Optimal planning with rare catastrophic events [electronic resource]

Although rare catastrophic events, such as mid-air collisions between aircraft, occur infrequently, their impact is significant. Understanding and mitigating the risk of such events require estimating the likelihood of the events and planning proper actions for avoiding them. Estimation and planning problems are often approached using sampling-based methods. These methods use models for simulation and take into account events of interest. If the problems involve rare catastrophic events, these methods converge slowly and produce high variance estimates. Moreover, in planning, the rare occurrence of the events obstructs the sampling-based method from exploring and exploiting the best action. This thesis presents methods for addressing these challenges, by efficiently estimating the likelihood of the rare catastrophic events and making decisions under uncertainty to minimize the risk of the events while achieving mission objectives. The methods are presented with three real-world applications. First, the thesis explores the use of rare event simulation techniques in aircraft collision risk estimation. The cross-entropy method with weight limits and variable selection is applied for variance reduction. Second, the multilevel splitting method, which is a variance reduction technique, is incorporated into decision-theoretic single-shot decision problems. The resulting method is applied to wildfire surveillance using an unmanned aircraft. Lastly, the thesis proposes new approaches for exploration in sequential decision problems and applies a variance reduction technique. It presents a rerouting problem involving unmanned aircraft in GPS-denied environments. Empirical studies demonstrate significant improvements in performance when using the proposed methods.

Keywords: Aeronautics and Astronautics.
Advisor: Kochenderfer Mykel J.
Alonso Juan José
Pavone Marco
Optimal project termination with an informed agent [electronic resource]

This dissertation analyzes optimal incentive contracting for environments in which the state of a temporary project is monitored imperfectly by a firm. The firm must decide when to halt the project, assisted by an agent with private information about the project's state, limited liability, and incentives for delayed project termination. I develop techniques for solving the resulting novel mechanism design problem, which exhibits the feature that the agent extracts information rents despite the absence of time-zero asymmetric information. The firm's problem is to craft dynamic incentives to limit these rents while trading off against reduced efficiency. The optimal contract involves occasional inefficient early project termination, but no late termination; a golden parachute which declines with proximity to termination; and hard and soft deadlines exhibiting asymmetric sensitivity to news close to and far from termination.

Keywords: Business.
Advisor: Skrzypacz Andrzej
Di Tella Sebastian T. advisor. Thesis advisor
Wilson Robert
Optimization in spectral X-ray/CT imaging measurements [electronic resource]

Spectral imaging techniques can enhance clinical x-ray/CT applications by creating material discriminated images and facilitating quantitative analysis based on intrinsic tissue properties. This dissertation focused on improving the performance of spectral x-ray/CT imaging by optimizing system designs and scan protocols. I designed and demonstrated that a fixed K-edge x-ray filter can improve material decomposition precision of fast kVp-switching systems at modest flux penalty. Secondly, I optimized the protocols of dual source liver CT, where I showed that the dual energy blended images would not have as good contrast to noise ratio (CNR) as optimized single energy scans. Besides commercially available x-ray/CT systems, photon counting x-ray detectors (PCXD) are promising for spectral imaging applications, but for medical use they suffer from non-ideal energy response and slow counting speed. Edge-on PCXD with multi-layer segmentation was proposed to address the counting speed issue by splitting the counting burden into multiple layers. We hypothesized that segmenting detectors in the depth direction (a.k.a. "in-depth") and retaining the depth dependent signals can also significantly improve the spectral performance (e.g., noise of material discriminated images). Our research showed that the depth information is redundant when the pulse height information is perfect. With real-world, non-ideal energy response functions (ERF), however, the in-depth PCXD is more dose efficient than the edge-on PCXD. Firstly, when analytical ERF models were assumed, we found the benefit of the depth information varied across different detector materials but was relatively constant across various detector architectures, protocol settings, and the scanned object size. The dose efficiency improvement comes along with the fact that the depth information helps when photons that are recorded at wrong energies overlap with correctly measured ones. Next, we compared the in-depth and edge-on detectors using more realistic ERFs estimated from Monte Carlo simulation, which showed that the depth segmentation degrades the energy response by introducing inter-layer cross-talk. The results showed that severe data correlation between layers diminish the benefit from the depth segments, but with correction schemes applied, the dose improvement reappears. The improvements are ERF dependent, with high potential when ERF degradation is from K-escape photons and little impact for events in the Compton plateau.

Keywords: Bioengineering.
Advisor: Pelc Norbert J. primary advisor. Thesis advisor
Glover Gary H.
Nishimura Dwight George advisor. Thesis advisor
Optimizing CRISPR/Cas9 with rAAV6 Genome Editing in the HBB locus and Enrichment of Targeted Hematopoietic Stem Cells

β-hemoglobinpathies, such as sickle cell disease (SCD) and β-thalassemia, are blood disorders that directly affect millions of people around the world. The only curative treatment for these blood disorders is by allogeneic-hematopoietic stem cell transplant (allo-HSCT), which faces a shortage of immunologically matched donors and other severe limitations1, 2. With the lack of effective curative therapies, it is postulated that autologous HSCT of gene edited hematopoietic stem/progenitor cells (HSPCs) would be a potential cure for patients afflicted with either of the β-hemoglobinpathies. The goal of this project was to create an alternative curative approach for these diseases that uses genome correction to directly correct the HBB gene through insertion of a wild-type β-globin cDNA to an endogenous start codon in the patient’s own HSPCs. The Porteus lab has designed and optimized an HBB-specific CRISPR/Cas9 ribonucleic (RNP)3 –based platform, in which we achieved homologous recombination (HR)-mediated targeting rates of ~25%-30% in human CD34+ HSPCs shown with fluorescence-activated cell sorting (FACS) analysis. Our CRISPR/Cas9 complexed with chemically modified sgRNAs RNP platform using rAAV6 donor transduction can achieve therapeutically relevant frequencies of HR-mediated gene correction in an HSPC population. Further, we show that we can effectively enrich a targeted tNGFR+, a non-immunogenic, truncated nerve growth receptor (tNGFR)4, HSPC population to >85% HR-mediated cells through micro-magnetic bead enrichment by Day 3 post-electroporation. Notably, these genomically edited HSPCs are capable of multi-lineage differentiation and have progenitor potential further demonstrating how an optimized CRISPR/Cas9 nuclease platform in combination with rAAV6 can become an ideal candidate for therapeutic application.

Keywords: CRISPR/Cas9
Genome editing
molecular engineering
Thesis
Advisor: Porteus Matthew H.
Gozani Or
Optimizing power conversion in photon-enhanced thermionic emission solar energy converters [electronic resource]

Photon-Enhanced Thermionic Emission (PETE) is a recently demonstrated physical mechanism for direct conversion of solar energy to electricity. PETE has attracted significant attention for its high theoretical conversion efficiencies that are well in excess of thermodynamic limits for traditional single-junction photovoltaic devices. In a PETE device, photoexcited electrons in a semiconductor cathode are thermionically emitted into vacuum, and collected at an anode with lower temperature and work function. In effect, PETE combines the advantages of both photovoltaic cells and Thermionic Energy Converters (TECs). Realizing these high theoretical efficiencies requires significant engineering of materials and device geometries to maximize electron emission, transport, and collection while simultaneously maintaining or raising the output voltage. The critical component in a PETE device is a well-designed PETE cathode. In this dissertation I discuss a simple analytical model for PETE cathodes relating emission yield to a number of material parameters that can be tuned during device fabrication, and the implications of this new model for PETE cathode design. Our model predicts reasonable efficiency at high temperatures across a range of values for surface recombination, electron affinity, and cathode thickness. Operating in this high temperature regime requires thermal stability of electron emission, which has not been well established for commonly used photocathode materials. Here, I will present a series of measurements of photoemission yield from different cathode materials over a range of temperatures. I will then discuss potential material choices and constraints for highly efficient PETE cathodes based on these measurements. Efficient PETE device operation relies on more than just maximizing the electron emission current from the cathode. Emitted electrons can suffer significant losses associated with space-charge build-up in the vacuum gap between the cathode and anode. Traditionally, in-gap plasmas have been used to mitigate these losses and boost device current. These plasmas, however, result in a significant drop in output voltage. I will therefore discuss experimental results in TECs with microbead-defined micron-scale gaps showing vastly improved current and minimal voltage reduction, resulting in greater power conversion efficiencies. The TEC is used as a model system, and these results will be equally applicable to PETE devices. I conclude with a discussion of the outlook for PETE as an energy conversion technology.

Keywords: Applied Physics.
Advisor: Melosh Nicholas A. primary advisor. Thesis advisor
Shen Zhi-Xun primary advisor. Thesis advisor
Hwang Harold Yoonsung
Organocatalyzed ring opening polymerization and the design of materials for topological trapping [electronic resource]

Ring-opening polymerization (ROP) is a highly useful route to well-defined, high molecular weight polymers. In recent years, strongly nucleophilic neutral bases such as N-heterocyclic carbenes (NHCs) have been shown to catalyze ring opening polymerization with control over the topology of the polymer product. This mechanism has been termed Zwitterionic Ring Opening Polymerization (ZROP). Here, new catalysts and monomers have been explored for these processes. Two types of organocatalysts were developed. A recently reported superbase, cyclopropenimine, was tested for activity with a number of monomers. It was discovered that this catalyst polymerizes lactide not through ZROP, but through anionic ROP initiated by a previously unreported mechanism. It was demonstrated that cyclopropenimines deprotonate lactide to form the corresponding enolate, which serves as the initiator and endgroup for the polymerization. Additionally, an electrophilic co-catalyst for lactide polymerization based on a cationic bis(imidazolium) structure was discovered. Furthermore, a class of cyclic phosphotriesters was synthesized as a substrate for NHC-catalyzed polymerization. Mechanistic studies were consistent with the existing interpretation of ZROP. The topology of the polymer products was found to be highly impacted by slight changes in monomer structure. One of these monomers, 2-isoproxy-1,3,2-dioxophospholane 2-oxide (iPP), yielded high molecular weight cyclic products. To further interrogate the polymer architecture, a crosslinked polyacrylate network was formed in-situ with the poly(iPP). In this way cyclic macromolecules were topologically trapped, preventing their extraction by solvent washing. The gel platform used for this trapping protocol was optimized and this process was explored as a way to sort polymers based on their topology. Finally, the properties of these gels, a unique form of interpenetrating network, were studied.

Keywords: Chemistry.
Advisor: Waymouth Robert M. primary advisor. Thesis advisor
Kool Eric T. advisor. Thesis advisor
Wender Paul A. advisor. Thesis advisor
Parents' views of failure as good or bad predict children's growth and fixed mindsets [electronic resource]

Children's mindsets about intelligence (as fixed or malleable) robustly influence their motivation and learning. Yet, surprisingly, research has not linked parents' intelligence mindsets to their children's. We test the hypothesis that a different belief may be more visible to children (parents' failure mindsets) and therefore more prominent in shaping children's beliefs. Study 1 shows that parents can view failure as debilitating or enhancing, and these failure mindsets predict parenting practices and in turn children's intelligence mindsets. Study 2 probes more deeply into how parents display failure mindsets. Study 3 replicated these findings and additionally showed that parents who view failure as enhancing also reported more emotional responses to a similar scenario. Study 4 revealed that children can indeed accurately perceive their parents' failure but not intelligence mindsets. Study 5 showed that children's perceptions of their parents' failure mindsets also predicted their own intelligence mindsets. Finally, Study 6 showed a causal effect of parents' failure mindsets on responses to their child's hypothetical failure. Overall, parents who see failure as debilitating focus on children's performance and ability rather than learning, and this predicts whether their children believe that intelligence is fixed or malleable.

Keywords: Psychology.
Advisor: Dweck Carol S.
Gross James J.
Walton Gregory M. (Gregory Mariotti) advisor. Thesis advisor