VictorJuiz/thesis huggingface dataset:
Sensing using ubiquitous wireless communication infrastructure [electronic resource]
Keywords: Electrical Engineering.

An estimated 12 billion connected devices exist today and this number is expected to grow to 30 billion by 2020. These connected devices will be used to control everyday objects like thermostat, light bulb, or even our coffee machines. Sensors and network connectivity are two very important enablers for these devices. Most of these devices will be connected via ubiquitous wireless networks like WiFi, Bluetooth, and ZigBee. Despite their widespread deployment, these wireless networks so far have been used solely for the purpose of transferring digital data between radios. In this thesis, we will describe how we can overload functionalities to these ubiquitous wireless networks by adding novel sensing modalities into them. We first describe the design and implementation of a localization system that can pinpoint radios to sub-meter accuracy in an indoor environment. This system provides localization by simply analyzing the wireless signal that is used for communication. Such a localization system can help network managers to identify and locate unauthorized interferers. At the same time, such a localization technique can also enable navigation of large indoor spaces like airports and malls using smartphones. Next, we describe a technique that allows a wireless Access Point (AP) to detect and analyze reflections of wireless signal from its own transmission. In particular, we demonstrate how it enables a WiFi AP to trace human motion by simply listening to and analyzing reflections from its own transmission. But this technique also has many more applications beyond motion tracing. As an example, we describe design and implementation of a system which allows us to passively read data from Internet of Things (IoT) sensors using ambient WiFi signals. Such a system can prolong life of battery operated sensors or even pave path for RF powered sensors in the future.
Shock tube studies of kinetics of conventional and alternative engine fuels [electronic resource]
Keywords: Mechanical Engineering.

Experiments were performed using shock tube and laser absorption methods to investigate the oxidation and pyrolysis systems of conventional and alternative fuels, and fuel components, under engine-relevant conditions. Ignition delays were measured during fuel oxidation and several stable intermediates were measured during fuel pyrolysis. Ignition delay times were measured in the gas-phase for several engine fuels in various oxidizers behind reflected shock waves in a heated high-pressure shock tube. Initial reflected shock conditions were as follows: temperatures of 1000 - 1500 K, pressures of 2 - 60 atm, equivalence ratios of 0.2 - 2, and oxygen concentrations of 4% and 21% with argon and 21% in synthetic air. Ignition delay times were measured using sidewall pressure, OH* emission at 306 nm as well as 3.39 µm mid-infrared He-Ne laser absorbance. The new experimental results were modeled using several kinetic mechanisms with the most current jet fuel surrogate mixtures as well as with a new hybrid model currently in development at Stanford. Measurements of stable decomposition products of engine fuel pyrolysis were performed behind reflected shock waves at temperatures from 1100 to 1600 K and pressure of 12 atm for all engine fuels tested. Species time-history measurements of ethylene and methane were made in pyrolysis experiments using laser absorption. Similar product yields were found for conventional fuels but not for alternative fuels at current conditions. These data provide needed input for the development and validation of a new compact hybrid kinetic model under development at Stanford. A traditional jet fuel chemical kinetics model using surrogate fuel compounds and combined detailed mechanisms of these surrogates was also discussed and compared with the hybrid model. The performance of the hybrid model appears better than that of the surrogate model, but still needs improvement. Finally, we applied a new driven-gas loading method that constrains the volume of reactive gases, thereby producing near-constant-pressure test conditions for reflected shock measurements. The near-constant-pressure ignition delay times provide a new database for low-temperature 1-butanol mechanism development independent of non-idealities caused by either shock attenuation or pre-ignition perturbations. Comparisons of these near-constant-pressure measurements with predictions using several reaction mechanisms available in the literature were performed. All current studies of kinetics of conventional engine fuels, engine fuel component (decalin), alternative engine fuels, and alternative fuel component (butanol) provide useful kinetic targets for the development, validation, and refinement of combustion kinetics models, and provide valuable insights on the pre-ignition phenomenon typically observed in shock tube ignition delay experiments.
Signal preconditioning using feedforward equalizers in ADC-based data links [electronic resource]
Keywords: Electrical Engineering.

As the data rates for high-speed wireline transceivers continue to increase, intersymbol interference (ISI) due to channel loss is becoming more pronounced and multiple techniques have been suggested to address this issue. One technique that has recently been gaining popularity is the ADC-based receiver. In ADC-based receivers, a digital feedforward equalizer (FFE) is used in conjunction with a decision feedback equalizer (DFE) to equalize the channel and recover the data. However, in order to recover the data with a high fidelity, a power-hungry ADC is needed to digitize the signal. Recent work has shown that an analog receive-side FFE (RX-FFE) prior to the ADC can reduce the required ADC resolution while achieving the same BER. In order to obtain a net improvement for the system, the RX-FFE must be implemented with low power consumption, low noise, and small chip area. In this thesis, an RX-FFE is demonstrated that meets these requirements and outperforms state-of-the-art designs. The RX-FFE is constructed entirely with low-noise and power-efficient analog-inverter transconductors and capacitors, avoiding the use of area-intensive inductors. The delay element is implemented as a single-path Pade-inspired delay shown to be equivalent to the first-order Pade delay in terms of RX-FFE performance. The proof-of-concept RX-FFE is demonstrated to reduce the signal dynamic range by 2x resulting in a 1 bit ADC resolution relaxation. The total power consumed is less than 26 mW with less than 0.62 mVrms output noise for all coefficient values and an area of only 0.003 mm^2 in 40 nm CMOS.
Signals or substitutes? Why economic sanctions undermine threats of force [electronic resource]
Keywords: Political Science.

This dissertation investigates how the choice to use economic sanctions undermines threats of force. When faced with a crisis, leaders must choose among a menu of coercive strategies, and the choice of strategy conveys information about the leader's resolve. While some scholars and policymakers look to sanctions as tools for escalation, I argue that sanctions are poor signals of resolve for three reasons. First, sanctions have become attractive instruments for addressing low-level disputes where the use of force would be excessive. Second, sanctions exact pain on opposing states and can be used to ameliorate audience demands to ``do something" in crises where leaders are unwilling to fight. Third, since leaders have the option of directly threatening force, targets should expect the most resolved leaders to do so, and doubt the resolve of leaders who initially apply sanctions as an alternative strategy. This dissertation consists of three papers to support this argument, utilizing formal theory, quantitative analysis, qualitative historical study, and survey experiments to demonstrate why the choice to use sanctions signals a lack of resolve to fight.
Simulation and computation of human and camera image systems [electronic resource]
Keywords: Electrical Engineering.

Image systems capture, encode, analyze and reconstruct the information in the visual environment. Most image systems focus on light that is visible to humans with wavelengths ranging from 400 to 800 nm. Though the precise design and capabilities of different types of image systems vary widely, the ultimate goal for the image systems are similar: capture and estimate information in the environment. As Hermann von Helmholtz mentioned in 1857, the sensations of our nerves of sense are mere symbols indicating certain external objects. Bearing this in mind, we can revisit a series of image system problems from the perspective of how the system use the symbols to infer the external objects. In this dissertation, I use simulation and computation methods to address different backward estimation problems for imaging systems. I apply these methods to study two image systems: the human vision system and the consumer digital camera. Although the combination of computation and simulation methods may generate different algorithms and models for each image system, I believe the methodology can be generalized across many types of image systems.
Simulation of dusty plasmas and characterization of their effects on irregularities in the upper atmosphere [electronic resource]
Keywords: Aeronautics and Astronautics.

Earth's atmosphere is a complex system composed of different layers of gas surrounding the Earth. Approximately between 50 and 1000 km above Earth's surface, solar radiation ionizes the gas to from a region of plasma in our atmosphere known as the ionosphere. Dynamics in the ionosphere are driven by a number of mechanisms. The predictable portion of the ionosphere is made up of three layers that shift in height and width depending on the time of day and the solar activity. In addition, the ionosphere hosts a number of transient non-dusty and dusty plasma irregularities that can affect the dynamics of the ionosphere. Understanding and predicting the dynamics of these irregularities is important in properly communicating between ground systems and space satellites because the ionosphere lies directly between these two. While non-dusty ionospheric irregularities have been studied for many years, the dust component in ionospheric phenomenon is only beginning to be considered, even though dusty plasma dynamics are far more complex to understand and predict. In order to better mitigate communication error in the ionosphere, a deeper understanding of the physics and dynamics of dusty plasmas is required. This thesis describes the simulation of dusty plasmas in ionospheric phenomena, namely polar mesospheric summer echoes (PMSEs) and meteors. The simulation methods utilized are a 1-D (PMSE) and 2-D (meteor) particle-in-cell (PIC) simulation. The simulations incorporate additional models for simulating the composition and growth of dust particles, the charge attachment of plasma particles to dust particles, and the collisions with neutral particles in the ionosphere. The PMSE simulation results demonstrate that presence of dust particles can lead to the development of the ice-plasma growth instability, which can lead to the development and detection of sharp small-scale structures as seen in PMSE rocket and radar measurements. In addition, the meteor simulation shows that the presence of dust during meteor expansion can reduce the overall diffusion rate of the meteoric particles and extend the detection lifetime of the meteor. These meteor simulation results will aid in explaining the detection of long duration meteor trails. The two simulations presented in this thesis are only a first step in exploring the effects that dusty plasmas can have on irregularities in the ionosphere. Understanding how dust can alter the dynamics of ionospheric irregularities will assist in reducing the noise and error when communicating through Earth's ionosphere in the future.
Single antenna null-steering for GPS & GNSS aerial applications [electronic resource]
Keywords: Electrical Engineering.

As the utility of the Global Positioning System (GPS) and other Global Navigation Satellite Systems (GNSS) continue to pervade -and upgrade- our daily activities, our increased reliance makes us more vulnerable to the inherent weaknesses of GPS. The incredible faintness and unencrypted nature of the GNSS signal exposes it to both unintentional and intentional overwhelming, via mechanisms such as interference, jamming and spoofing (the broadcast of counterfeit GNSS signals intended to deceive a GNSS receiver). However some may argue that despite the great risk, the probability of a jamming or spoofing event is thankfully low. The argument may continue, that correspondingly few resources should be dedicated to protect against a low probability event. I attempt to resolve the tension between these high risk yet low probability scenarios by establishing antenna designs that provide protection while exploiting existing infrastructure and equipment, thus requiring minimal additional resource dedication. This thesis will start with an introduction of a low complexity mechanism for generating radiation pattern nulls and beams with a single antenna, without requiring any additional hardware or signal processing blocks beyond those already inherent to GNSS receiver systems. I will describe the basic mathematical model that underlies this mechanism and share simulation results. I will then introduce two applications of this mechanism: single antenna interference/jam suppression and single antenna spoof detection. Results from simulations and two field trials will be presented: one with a software implementation using a software defined radio, and the other with a hardware prototype implemented in off-the-shelf components using a standard GPS receiver. Results show about 15 dB of interference/jam suppression and robust spoof detection, when the threatening signals originate from below the horizon of the GNSS antenna, making aerial platforms an ideal application.
The social, economic and cultural dimensions of bushmeat in Yaounde, Cameroon [electronic resource]
Keywords: Anthropology.

Urban bushmeat demand may now account for the majority of wild meat consumed in Central Africa, posing environmental, health, and economic dilemmas. The bushmeat trade represents a complex and dynamic interaction of cultural, political, socio-economic, and status-seeking behaviors that I investigate in this dissertation through interdisciplinary inquiries framed in political ecology, social capital theory, and grounded theory. The study took place in a major Central African city: Yaoundé, Cameroon. A census of profiles and sourcing relationships between Yaoundé's 211 bushmeat-selling restaurants, street stalls and hotels, 13 open bushmeat markets, and rural bushmeat source points revealed a decentralized trade, with the exception of a centralized primary market. Yaoundé's thriving open bushmeat markets circulated ca. 660 - 1320 tons of bushmeat per year, generating ca. US$ 4.4 - 8.8M annual gross revenues. Restaurant, street stall and hotel bushmeat sales accounted for US$ 1.8M annual gross revenues. Primary market sales data for 4112 purchases over 12 months documented over 24 taxa sold in the primary market, including rodents (31% of carcass sales), ungulates (17%), primates (13%), scaly anteaters (12%), and reptiles (11%). While women were the primary sellers at low-priced, high volume street stalls and bar-restaurants, men were associated with the sale of high-priced, endangered species at restaurants and hotels, reflecting distinct gendered approaches to the trade. Ethnography in the primary market revealed that more-educated traders and sellers are relegated to the trade but would prefer other work, while less educated marketers with ethnic ties to forest zones found bushmeat trading an appealing option. Participant observation and interviews with 211 consumers revealed that eating bushmeat in Yaoundé appears to reaffirm cultural and kin connections for people originating in forest zones; buffer food security needs for lower economic classes; and meet luxury and social status seeking desires for high economic-status consumers of endangered species. Combined, these results reveal possibilities for reshaping a regulated trade that would incorporate the suite of livelihood and socio-cultural needs currently met through consuming and selling bushmeat in urban Central Africa.
Social meaning in linguistic perception [electronic resource]
Keywords: Linguistics.

As individuals position themselves and others in the social landscape, they use language to convey and to understand the social meanings indexed by linguistic forms. Research taking social meaning as central to the study of linguistic variation has shown that linguistic features are deployed as components of styles, or clusters of features, and speakers use these styles to enact particular personae, or social types. Though a majority of studies in this realm have focused on speakers' production of styles, semiotic links between styles and personae are formed, reproduced, and reinterpreted in the interactional space between the speaker, who produces these styles, and the listener, who construes them. This dissertation focuses on the listener perspective, exploring the cognitive underpinnings of links between social meaning and linguistic variation at various levels of awareness. This dissertation provides evidence that social meanings and linguistic features are inextricably intertwined in listener perceptions. The same links between a single linguistic feature (the backing of the TRAP vowel) and its social meanings are examined in four paradigms that range from more controlled to more automatic perceptual behavior, asking (1) how persona-based information can affect linguistic categorization, (2) when in processing links between social and linguistic information become evident, (3) how these links can affect memory (and thus, cognitive representations), and (4) the relation of all of these processes to explicit social evaluations. At all of these levels, I show that social meanings crucially shape the way that linguistic perceptions unfold. Specifically, I argue that the constructs of social personae are integral to the way that language is interpreted online, in interactions, advocating for movement beyond the heavy focus on macro-social information in studies of sociolinguistic perception. Further, I demonstrate gradience in listener awareness of feature-meaning links below the level of consciousness, showing that explicit social evaluations of language do not straightforwardly predict effects in more implicit perceptions.
Soil microbial community responses to long-term multifactorial global change in a California annual grassland ecosystem
Keywords:  Department of Biology
biology
microbial ecology
global change
soil microbial communities
arbuscular mycorrhizae
nitrogen limitation
elevated CO2
warming
precipitation
grassland
Jasper Ridge Global Change Experiment
Thesis

Soil microbial communities (SMCs) are important regulators of biogeochemical cycles and plant nutrition in terrestrial ecosystems, but the diversity, composition, and function of SMCs are expected change in response to anthropogenic global change. While field-based, manipulative global change experiments have helped to build a nuanced understanding of plant community responses to multiple interacting environmental changes in a variety of ecosystems, relatively little research has investigated the response of SMCs to similar conditions. To this end, we used next-generation DNA sequencing to assess the soil fungal and bacterial communities in the bulk soil (0–7cm depth) of the Jasper Ridge Global Change Experiment: a full-factorial global change experiment that has tested two levels of nitrogen deposition, atmospheric CO2 concentration, temperature, and precipitation in a California annual grassland since 1998. Of the four global change treatments, nitrogen deposition had the strongest effect on the composition of SMCs, and also explained the most variation in fungal richness. Although all individual treatments had significant effects on SMC composition and diversity, treatment interactions in this experiment were infrequent and could only be identified at finer taxonomic scales in the bacterial community. Furthermore, the best covariates for most SMC composition and diversity were usually not the global change factors themselves; SMC properties could be better explained by soil chemical properties that were, in turn, affected by a global change treatment. In particular, fungal and bacterial community composition were the best covariates for each other, suggesting that despite differential effects of global change on fungal and bacterial communities, as a whole their relationship is resilient to global change. Finally, we found a significant decrease in the relative abundance of arbuscular mycorrhizal fungi under elevated CO2, which has never been described in the literature. Our results support the hypotheses that increased nutrient inputs can cause strong shifts in SMCs in grasslands, and that the ultimate effect of global change factors on SMCs is mediated by changes to the local soil environment.
Some finiteness results for groups of automorphisms of manifolds [electronic resource]
Keywords: Mathematics.

We prove that in dimensions not equal to 4,5,7 the homology and homotopy groups of the topological group of diffeomorphisms of a disk fixing the boundary are finitely generated in each degree. The proof uses homological stability, embedding calculus and the arithmeticity of mapping class groups. From this we deduce similar results for the homeomorphisms of R^n and various types of automorphisms of 2-connected manifolds.
Sound and vision [electronic resource] : sonic experience in Wordsworth, Blake, and Clare
Keywords: English.

This dissertation re-orients the study of Romantic poetry by advocating a shift in Romanticist critical discourse away from the visual sensorium and towards a focus on sound. I examine three major poets—William Wordsworth, William Blake, and John Clare—whose work has been critiqued, celebrated, or otherwise understood through a critical focus both centered on and shaped by tropes of visuality. An investigation of poetic sound, I argue, helps us understand the work of these poets on a more fundamental level. Sound was used by these writers to promote the aesthetic mode of experience over and against social and intellectual forces that threatened the essential freedom of the human imagination. In doing so, they were also writing against a millenia-old tradition in Western thought that privileged visual over audible experience.
Sounding the nation [electronic resource] : dialect and the making of modern China
Keywords: History.

This dissertation argues that the concept of "dialect" was fundamental to the formation of modern Chinese nationalism and identity. I contend that elite and non-elite groups, inspired by diverse conceptualizations of nation, local place, and self, relegated China's myriad local languages to the status of 'dialect' -- a category that simultaneously webbed local communities to the broader concept of the Chinese nation, but also excluded them by placing them outside of the idealized form of "standard" Chinese. By tracing how the meaning of dialect was transformed by nineteenth-century Western missionaries, early twentieth-century artists and academics, and finally, the Nationalist and Communist governments, I show how Chinese—both as a language and as a national and ethnic moniker— was not just heterogeneous, but something that state-defined standards could not adequately capture.