VictorJuiz/thesis huggingface dataset:
Quantum simulation of the 2D-3D superfluid deconfinement transition with quantum degenerate 87Rb gases [electronic resource]
Keywords: Applied Physics

Since Bose Einstein condensate (BEC) of alkali atomic gases was realized in 1995, its novel material properties have inspired tremendous research ideas and experiments. BEC is characterized by macroscopic occupation of ground state and has long range order. The coherent wave property of BEC provides a new target to implement and test knowledge gained from quantum optics. Furthermore, the application of optical lattices into condensate boosts the diversity of research. The implementation of optical lattice not only makes realization of Heisenberg interferometer via number squeezed state possible, but also provides a periodic potential to investigate condensed matter physics in atomic system. For research conducted by former members in 87Rb group, they mainly studied squeezed state and dynamics of condensates in 1D optical lattice at zero temperature. The intention of my research is meant to explore coherence property of 87Rb quantum degenerated gases at finite temperature as a function of inter-layer tunnelling probability for potential application of atomic interferometry. On my way of investigating coherence of 2D Bose gases confined in 1D optical, I observe deconfinement transition from 2D Berezinskii-Kosterlitz-Thouless superfluids to 3D anisotropic superfluids. Moreover, I also realize this system can potentially serve as a quantum simulator of layered high-Tc superconductor in 2D regime. In this thesis, I will mention how I investigate coherence of ensemble of 2D Bose gases. Later, I'll also simulate deconfinement transition based on Renormalization Group(RG) theory with our experimental parameters.
Quantum transport in one-dimensional nanostructures [electronic resource]
Keywords: Physics

One-dimensional (1D) electronic nanostructures comprise a class of systems that boast tremendous promise for both technological innovation as well as fundamental scientific discovery. To fully harness their potential, it is crucial to understand transport through 1D systems at the most fundamental, quantum level. In this thesis, we describe our investigations down three avenues of quantum transport in 1D: (1) ballistic transport in quantum wires, (2) quantum capacitance measurements of nanostructures, and (3) tunneling measurements in carbon nanotubes. First, we discuss measurements and modeling of hole transport in ballistic quantum wires fabricated by GaAs/AlGaAs cleaved-edge overgrowth, where we find strong g-factor anisotropy, which we associate with spin-orbit coupling, and evidence for the importance of charge interactions, indicated by the observation of "0.7" structure. Additionally, we present the first experimental observation of a predicted spin-orbit gap in the 1D density of states, where counter-propagating spins constituting a spin current are accompanied by a clear signal in the conductance. Next, we present the development of a highly sensitive integrated capacitance bridge for quantum capacitance measurements to be used as a novel probe of 1D systems. We demonstrate the utility of our bridge by measuring the capacitance of top-gated graphene devices, where we cleanly resolve the density of states, and also present preliminary measurements of carbon nanotube devices, where we ultimately aim to extract their mobility. Finally, we discuss a set of transport measurements in carbon nanotubes designed to probe interactions between fermions in 1D in which top gates are used to introduce tunable tunnel barriers.
Race, class, age, and appearance [electronic resource] : matching, exchange, and other properties of dating and marriage markets
Keywords: Sociology.

This dissertation is composed of three related papers, all addressing processes of romantic relationship formation. In the first of these papers I use a combination of quantitative and qualitative data to address the attitudinal and social network causes of racial matching in intimate relationships among Stanford Undergraduates (this paper is published in Journal of Marriage and Family 72 (1): 45-72). In the second section of my dissertation I investigate patterns of exchange and matching on physical attractiveness and socioeconomic status, using data from the National Longitudinal Study of Adolescent Health Romantic Pair Data (2001-2002). In the third paper in my dissertation I use data from the National Longitudinal Survey of Youth 1979-2008 to test whether occupational sex segregation influences individuals' odds of marriage.
Raising Taxes to Balance the Budget: How Effects on Output and Labor Supply Complicate the Matter
Keywords:  Department of Economics
Stanford Department of Economics
Labor supply
tax rates
government spending
budget deficit
United States
Continental Europe
Scandinavia
Thesis

The United States and many major European countries currently are running large budget deficits, and most of these countries also confront significant national debt. Many are now seeking to restore fiscal discipline by cutting spending, raising taxes, or doing both. In this thesis, I explore what would occur if the United States or any of seven major European countries (France, Germany, Italy, the United Kingdom, Greece, Spain, and Sweden) attempted to balance its budget simply by raising taxes. I also determine what would occur if a country decided to balance its budget by using tax increases to accomplish half of its budget fix and cutting government spending to do the rest. To pursue this analysis, I first employ a simple static model to gain some understanding of how changes in tax rates affect how much people work. I then develop a more realistic and sophisticated dynamic general equilibrium model and gradually add refinements to it. With that model, I find that if government spending is not reduced, all countries except Sweden, which has only a small budget deficit, are either incapable of achieving a balanced budget in one year or could do so only by suffering dire economic consequences. Even if cuts in government spending account for 50% of the budget fix, all countries under analysis (except Greece which is unable to balance its budget under any of the four scenarios I posit) would experience at least some loss in output, and many would face considerable hardship.
Rapid melt growth of silicon germanium for heterogeneous integration on silicon [electronic resource]
Keywords: Electrical Engineering

Silicon has made modern integrated circuit technology possible. As MOSFET gate lengths are scaled to 22nm and beyond, it has become apparent that new materials must be introduced to the silicon-based CMOS process for improved performance and functionality. This dissertation begins with a review of the MOSFET leakage current problem and presents one potential solution: Band-to-Band Tunneling (BTBT) transistors, which have the potential for steeper subthreshold slopes because they do not have the fundamental 'kT/q' limit in the rate at which conventional MOSFETs can be turned on or off. It is clear that these devices must be fabricated in materials with smaller bandgaps for improved performance. Silicon Germanium (SiGe) is one possible material system that could be used to fabricate enhanced BTBT transistors. Rapid Melt Growth (RMG) is a technique that has been used to recrystallize materials on Si substrates. RMG, however, has not previously been applied to SiGe, a binary alloy with large separation in the liquidus-solidus curve in its phase diagram. The development of process and experimental results for obtaining SiGe-on-insulator (SGOI) from bulk Si substrates through RMG are presented. The theory of RMG is analyzed and compositional profiles obtained during RMG of SiGe are modeled to understand why we were able to obtain high quality lateral compositionally graded SGOI substrates. The success of RMG SiGe suggests that the RMG technique can also be applied to III-V ternary and quaternary compounds with similar pseudo-binary phase diagrams. This opens up a wide range of material possibilities with the potential for novel applications in heterogeneous integration and 3-D device technology.
Rate-adaptive modulation and coding for optical fiber transmission systems [electronic resource]
Keywords: Electrical Engineering

Modern wireline and wireless communication systems adapt link parameters, such as bandwidth utilization, power allocation, constellation size and forward error correction (FEC) code rate, depending on link quality (often time-varying), trading off bit rate (and thus spectral efficiency) for robustness. By contrast, to date, optical transmission systems have employed fixed bit rates. Rate-adaptive optical transmission techniques trade off information bit rate for transmission distance and other factors affecting signal quality. These techniques enable increased bit rates over shorter links, while enabling transmission over longer links when regeneration is not available. They are likely to become more important with increasing network traffic and a continuing evolution toward optically switched mesh networks, which make signal quality more variable. Rate-adaptive optical transmission could help improve network robustness, flexibility and throughput. This study proposes a rate-adaptive transmission scheme using variable-rate FEC codes and variable-size constellations with a fixed symbol rate. To vary the FEC code rate, we use two different schemes: (a) hard-decision decoding (HDD) using serially concatenated Reed-Solomon (RS) codes and inner repetition codes (b) soft-decision decoding (SDD) using outer RS codes and inner low-density parity-check codes. The FEC schemes are combined with single-carrier polarization-multiplexed quadrature amplitude modulation with variable constellation sizes and digital coherent detection. A rate adaptation algorithm uses the signal-to-noise ratio (SNR) or the bit-error ratio (BER) estimated by a receiver to determine the FEC code rate and constellation size that maximizes the information bit rate while satisfying a target decoded BER and an SNR margin. We simulate single-channel transmission through a long-haul fiber system incorporating numerous optical switches, evaluating the impact of fiber nonlinearity and bandwidth narrowing. In systems with or without inline chromatic dispersion (CD) compensation, we quantify how achievable bit rates vary with distance, and compare the performance of the proposed schemes to an ideal coding scheme. From HDD-based system to SDD-based system, we observed approximately 50% increases in transmission distance, and approximately 2.5-dB reductions in the performance gap from an ideal coding scheme.
Reading like a historian [electronic resource] : a document-based history curriculum intervention in urban high schools
Keywords: Education.

Enthusiasm about the instructional potential of primary sources dates to the late 19th century and has been echoed recently in the work of literacy experts, historians, and educational psychologists. Yet, no extended intervention study has been undertaken to test the effectiveness of primary source instruction in real history classrooms. This study, with 236 eleventh-grade students in five San Francisco high schools, represented the first large-scale extended curriculum intervention in disciplinary reading in an urban district. The Reading Like a Historian (RLH) curriculum constituted a radical departure from traditional textbook-driven instruction by using a new activity structure, the "Document-Based Lesson, " in which students used background knowledge and disciplinary reading strategies to interrogate, and then reconcile, historical accounts from multiple texts. A quasi-experiment control design measured the effects of a six-month intervention on four dimensions: 1) students' historical thinking; 2) their ability to transfer historical thinking strategies to contemporary issues; 3) their mastery of factual knowledge; and 4) their growth in general reading comprehension. MANCOVA analysis yielded significant main effects for the treatment condition on all four outcome-measures. Qualitative analyses of videotaped classroom lessons were conducted to determine the frequency and nature of whole-class text-based discussion. Only nine whole-class text-based discussions were identified in over 100 videotaped classroom lessons, despite the presence of instructional materials explicitly designed to support student discussion of debatable historical questions. Analysis of teacher and student participation suggests a relationship between active teacher facilitation that reviews background knowledge and poses direct questions about texts and higher levels of student argumentation. This dissertation is structured as three free-standing papers, each of which addresses one aspect of the larger study. In the first paper, I discuss the design of the quasi-experimental study and report quantitative findings. In the second paper, I locate teacher facilitation of whole-class historical discussion in the literature on classroom discourse, and I propose a developmental framework for analyzing student historical argumentation in classroom discussion. In the third and final paper, I discuss the theoretical underpinnings of the intervention curriculum and offer two examples to illustrate the structure of the "Document-Based Lesson.".
Realigning international trade negotiation asymmetry [electronic resource] : developing country coalition strategy in the WTO Doha round agriculture negotiations
Keywords: Law.

Recently, it has become apparent to developing countries in the WTO that their limited bargaining power has, in fact, been a stumbling block to obtaining desired negotiation outcomes in the multilateral trade system. Thus, to execute any fundamental changes to the status quo, there was a need to cluster together, pool resources and form alliances to leverage their collective strength in the negotiations. What remained unclear, however, was what role this increased coalition activity by developing countries played in the current WTO negotiations process. Therefore, the primary purpose of this dissertation is to describe how this shift toward coalitions as a negotiation strategy by developing countries occurred and to consider the possible implications of this coalition strategy for the future of the multilateral trading system. Due to the complexity of the Doha Round, I restricted my area of study to the Doha Round agriculture negotiations as a single case study, since agriculture is the undisputed "locomotive" of the Round, having set the tone for the majority of the negotiations. Using qualitative data, I captured a contextual description of four developing country agriculture coalitions -- Cotton-4, G-20, G-33 and G-90 -- as "nested cases" throughout the agriculture negotiation process from March 2003 to March 2010. I described the function of developing country coalitions in the negotiations by comparing and contrasting aspects of each coalition's negotiation strategy or tactics during the research study period. In sum, I investigate my preliminary assessment of the reason coalition strategy emerged as the dominant negotiation tool for developing countries in this particular WTO Round. I then describe how these coalitions maneuvered in the ongoing negotiations during the study period. At the end of my descriptive comparative analysis, I was able to explain the significance of coalitions as a strategic tool for developing countries in WTO trade rules negotiations as well as assess the specific role that each of the four case study coalitions have played in the negotiation process. In conclusion, the study highlights some of the lessons learned from developing country coalition strategy in this Round. The information derived could serve as a platform for further research in this area and eventually explain the raison d'être behind the negotiated outcomes.
Recognizing phonemes and their distinctive features in the brain [electronic resource]
Keywords: Electrical Engineering

How the human brain processes phonemes has been a subject of interest for linguists and neuroscientists for a long time. Electroencephalography (EEG) offers a promising approach to observe neural activities of phoneme processing in the brain, thanks to its high temporal resolution, low cost and noninvasiveness. The studies on Mismatch Negativity (MMN) effects in EEG activities in the 1990s suggested the existence of a language-specific central phoneme representation in the brain. Recent findings using magnetoencephalograph (MEG) also suggested that the brain encodes the complex acoustic-phonetic information of speech into the representations of phonological features before the lexical information is retrieved. However, very little success has yet been reported in classifying the brain activities associated with phoneme processing. In my work, I proposed a classification framework which incorporates Principal Components Analysis (PCA), cross-validation and support vector machine (SVM) methods. The initial classification rates were not very good. Progress was made by using bootstrap aggregation (Bagging) scheme and introducing phase calculations. To calculate phase, I computed the Discrete Fourier Transform (DFT) of the original time-domain signal and kept the angles of the finite sample of frequencies. The resulting EEG spectral representation contains only the phase and frequency information and ignores the amplitudes. Using this method, the accurate rate of classifying averaged test samples of eight consonants improved from 41% to 51%. Furthermore, the qualitative analysis of the similarities between the EEG representations, derived from the confusion matrices, illustrates the invariance of brain and perceptual representation of phonemes. For brain and perceptual representation of consonants, voicing is the most distinguishable feature among voicing, continuant and place of articulation. And the feature vowel-height is more robust than vowel-backness in both brain and perceptual representation of vowels. By extending and further refining these methods, it is likely significant classification of other phonemes and features can be made.
Recomposed corporealities, purity, body, and self in the mishnah [electronic resource]
Keywords: Religious Studies

The purpose of this dissertation is to trace and analyze the ways in which the rabbis who created the Mishnah, a Palestinian rabbinic legal codex whose final compilation is dated to the first half of the third century C.E., developed a unique notion of a bodily self in their remaking of the biblical laws of purity and impurity. As I show throughout the dissertation, while the rabbis adhere to the basic scheme of purity and impurity as it is portrayed in the Priestly Code, they suggest a whole new set of principles regarding the contraction, conveyance, and management of impurity. At times these principles are not only unprecedented in the Bible, but actually run contrary to the biblical understanding of impurity as a phenomenon. These remarkable innovations, I argue, are a strong indication that the rabbis reshaped the inherited system of purity and impurity not only in an attempt to preserve it but also in an attempt to make it relevant, and to adapt it to a changing conceptual and cultural framework. By examining some of the fundamental innovations that the rabbis introduced to the system of purity and impurity that they had inherited from their predecessors, I show that questions of subjectivity and consciousness profoundly shape the concepts of purity and impurity as those are developed in the Mishnah, ultimately presenting the self as a new focal point in the discourse of ritual impurity. In particular, I emphasize the ways in which the human body, which is the main and most critical site in which the drama of purity and impurity takes place, is negotiated in the Mishnah as both subject and object, both as identical to the self and as disparate from it. Through my analysis of various themes in the mishnaic discourse of purity and impurity, I demonstrate that the rabbis constructed the daily engagement with impurity and the ongoing pursuit of ritual purity as closely reflective of one's relations with one's self, with one's human and non-human environment, and with one's body.
Reconfigurable technology for future optical access networks [electronic resource]
Keywords: Electrical Engineering

Fiber-based access is recognized as the most promising technology for solving broadband bandwidth bottlenecks. Time division multiplexing passive optical networks (TDM-PONs) that are passive and non-reconfigurable are currently the most widely deployed type of fiber access networks. However, due to their passive nature, TDM-PONs faces several limitations such as inflexible service area coverage, lack of intelligence for control, and inability to counteract security attacks. In order to address the current limitations of optical access networks, we propose reconfigurable technologies for next generation PONs. Two novel reconfigurable technologies are proposed, analyzed, and experimentally evaluated. The first solution is a reconfigurable power-and wavelength- assignment technology based on a novel non-volatile, reconfiguration node. The proposed remote node can reconfigure the network to adapt it to varying degrees of deployment conditions and/or network attacks. Moreover, the proposed remote node incorporates a novel quasi-passive device that does not consume energy once it is reconfigured into a new latching state. Therefore, the proposed remote node has very low energy consumption and does not require local power supply to preserve the passive character of the distribution network. In particular, two novel quasi-passive optical power splitter technologies based on Micro-Electro-Mechanical Systems (MEMS) and transition metal oxide have been designed for the reconfigurable device. A simulation study shows the proposed reconfigurable device would outperform traditional passive splitter in terms of maximum number of supportable users under realistic deployment conditions. The second solution addresses the issue of reconfigurable network consolidation and infrastructure simplification. Current TDM-PONs suffers from limited reach and split-ratio. To enhance the performance in terms of service range and quality of service, reconfigurable network consolidation is a promising solution. It can also simplify the network and reduce cost. We propose the following novel reconfigurable technologies for consolidation and simplification of next generation access networks: (1) Passive reach-extension technology for the drop section of optical access networks; (2) Sleep mode ONUs for energy saving; (3) Centrally managed optical signature that can monitor and protect the upstream link; and (4) Multi-rate burst mode receivers. These reconfigurable technologies can bring the intelligence into optical access networks and improve the efficiency and flexibility for next generation optical access networks.