Let G=(V,E) be an arbitrary graph, and consider the following game. You are allowed to buy as many tokens from a bank as you like, at a cost of $1 each. For example, suppose you buy k tokens. You then place the tokens on some subset of k vertices of V. For each vertex of G which has no token on it, but is adjacent to a vertex with a token on it, you receive $1 from the bank. Your objective is to maximize your profit, that is, the total value received from the bank minus the cost of the tokens bought. Let bd(X) be the set of vertices in V-X that have a neighbor in a set X. From this game, we define the differential of a set X to be ∂(X) = |bd(X)|-|X|, and the differential of a graph to be equal to max{∂(X)} for any subset X of V. In this paper, we introduce several different variations of the differential of a graph and study bounds on and properties of these novel parameters.

Global supply chains have become increasingly complex and a critical source of competitive advantage, which makes the understanding of how supply chains create and distribute value an essential task. Prior literature on concentration risks has primarily focused on customer concentration and has overlooked the challenges posed by the major upstream supply chain partners. In addition, CEOs with an optimal mix of technical and behavioral abilities can shape the strategic decision-making process to obtain an advantage against the nonfinancial stakeholders. The existing literature has also overlooked the significant role of the CEO in reducing the impact of supplier-base/customer-base concentrations. Utilizing objective supply chain relation data collected from Bloomberg SPLC and Compustat, we map the supplier base and the customer base for each electronic and chemical manufacturing firm publicly listed under S&P1500 for the fiscal year 2017. We then construct objective measures of supplier and customer concentrations and examine their impacts on the focal firm's financial performance measured by Tobin's Q, gross profit margin, and net profit margin. The performance metrics also include the focal firm's payable period (against the supplier-base) and receivable period (against the customer-base). We also collect information related to the CEOs appointed by the focal manufacturing firm, such as gender, age, and tenure from Execucomp, and consequently investigate their impacts on the supplier concentration and the customer concentration. Our empirical analysis shows contradictory results in the context of supplier-base/customer-base concentrations: higher supplier-base concentration is observed to harm the focal firm’s financial performance, but higher customer-base concentration leads to an increase in the focal firm’s profitability. Although CEO characteristics such as tenure and age did not have any notable impact, female CEOs are found to reduce the adversarial impact of supplier-base concentration and are assumed to exercise a voluntary power restraint against the cooperative customer-base.

A new method and mechanism for generating non-uniform, or distorted, aircraft engine inlet flow is being developed in order to account for dynamic changes during the creation and propagation of the distortion. Total pressure distortions occur in gas turbine engines when the incoming flow is disturbed. Dynamic total pressure changes may happen slowly, or may occur very rapidly. The disturbance of the incoming flow can change engine operating characteristics, including lowering the surge limit and creating High Cycle Fatigue incidents. In order to create a distorted flow with dynamic characteristics, a mechanism must be developed that when actuated, can change the distortion pattern and intensity with respect to time. This work covers the initial design of both the distorting and actuating device. The design chosen is a low force design that is practically independent of flow forces. This allows the system to be easily sized for all flow conditions. The study also includes developing the working design into an overall prototype. Testing is also performed to validate the design as the most advantageous choice. / Master of Science

<p dir="ltr">The Cascadia margin in the Pacific Northwest of US is characterized by the subduction of the young and warm Juan De Fuca beneath the North American plate. This region shows strong correlations in spatial heterogeneities in geophysical observations such as thickness of low shear wave velocity zones in the lower crust, tremors distribution, intraslab seismicity, topography, uplift rates, and Bouguer gravity anomalies. In this thesis, both 3D and 2.5D forward gravity modeling have been conducted to understand the composition of the materials at ~20-40 km along the Cascadia subduction margin, that can explain the spatial heterogeneities by linking them together.</p>

Flank margin caves are karst features that develop in the freshwater/saline mixing zone within the carbonate islands of the Bahamas. The flank margin caves that are currently exposed developed during the last interglacial sea level highstand (+6 m; ~125 ka). Initially small ovid chambers, the caves increase in size to about 100 m2, then interconnect with adjacent chambers to form medium-sized caves. At about 1000 m2, these medium-size caves interlink forming large caves that are laterally extensive, vertically restricted, do not penetrate the fresh-water lens a significant amount, and run parallel to the axis of the ridge in which they formed. Small caves have a much smaller area to perimeter ratio than do large caves. As cave chambers grow and interconnect, perimeters become much more complex, and the number of bedrock columns in the cave increases. These results have implications for water resource management, and porosity modeling.

Caves on carbonate islands are useful indicators of past sea level because cave formation is dependent on sea-level controlled freshwater lens position (flank margin caves), or form in direct contact with coastal processes (sea caves). Sea-level curves present a useful proxy for glacioeustatic and paleoclimate studies, so caves offer useful data. Once a flank margin cave is breached, it may be modified and eroded by waves. This overprinting leads to morphology similar to that of sea caves. While both indicate past sea level, they reveal differing information about the amount of denudation that has occurred to expose them (a paleoclimate indicator), so differentiation of these cave types is important. This study presents some of the first sea cave data from carbonate islands, and makes morphological comparisons between flank margin caves and sea caves from the Bahamas, California, and Maine. Using morphometric techniques, these caves can be distinctly identified.

Tafoni have been confusingly defined in many ways: variations in size, rock type, and forming mechanisms. This study addresses tafoni in Quaternary eolian carbonates to help better define the term. Large tafoni were differentiated from other coastal caves in the Bahamas, specifically flank margin and sea caves, using morphometric analyses. The differentiation is important as all three cave types form in the same area, but flank margin and sea caves can be used as paleo-sea level indicators, while tafoni cannot. Small tafoni show a growth rate of 0.022 m3/yr; and may amalgmate to form larger tafoni, which grew at 0.65 m3/yr. Petrographic analysis helped identify tafoniorming mechanisms; results revealed no evaporites present, removing crystal wedging as a mechanism, while indicating wind erosion as the primary mechanism. This analysis found significantly greater cements within the Holocene rocks compared to previous studies, and SEM analysis revealed organic cements preserved by oil-based cutting.

Although Autonomous Vehicles (AVs) are quickly becoming a reality, there is much that needs to be understood before mainstream commercialization can occur. One critical issue is the interplay between multiple fields of engineering. Whereas the first part of this work is a granular treatment of a specific issue, the second part simultaneously examines numerous fields within the transportation industry. In the surge to understand and develop AVs, researchers tend to study specific subdivisions within the "vehicle engineering umbrella". In particular, mechanical and civil engineers study vehicle dynamics in two different levels of specificity. Mechanical engineers typically investigate small-scale dynamic behavior which applies to a single vehicle, such as vehicle-terrain interactions or the behavior of mechanical components. On the other hand, civil engineers tend to study kinematic behavior: the behavior of platoons as it pertains to large-scale traffic flow. Regardless of the scale of study, each subdivision has a set of performance metrics. Due to the differences among subdivisions, some performance metrics may (unintentionally) compete. Compromises must be made in the design stage to produce a vehicle which caters to an appropriate audience. The first part of this work features two major contributions to bridge the gap between the dynamic and kinematic perspectives. One is the application of Design Envelopes that establishes a framework to balance constraints and assess design tradeoffs arising from each viewpoints. Three Design Envelopes are introduced to reach compromises on a vehicle's velocity, acceleration, and jerk. Another contribution is a methodology to tune the parameters of a car-following model analytically. Current tuning practices require empirically collected traffic count data, which is cumbersome to obtain. Analytically parameterizing car-following models facilitates more robust planning and encompasses both the dynamic and kinematic perspectives. The second contribution utilizes these Design Envelopes to improve a currently-existing speed profile generator. Integrating the Design Envelopes reformulates the existing algorithm as a constrained LQR problem, which enhances ride comfort and maintains dynamic stability for not just one vehicle, but a platoon. Simulations demonstrate that the refined algorithm can reduce the travel time on a specific route by 3-4.4%. More importantly, the simulations demonstrate it is possible to synthesize multiple engineering fields to enhance AV design. The second part of this work features two contributions aimed at revisions to modern-day highway design policies based on the concept of combining microscopic and macroscopic principles. One common belief is that AVs should drive better than the best human drivers, which suggests operating at or close to the vehicle's theoretical handling limits. Operating in this manner requires a thorough understanding of the associated risks, particularly the risks stemming from uncertainty. This is especially pertinent as there are many inherently probabilistic quantities that are conveniently treated as deterministic in vehicle performance simulations, such as the coefficient of friction. This is a questionable practice when operating on the precipice of compromised safety. Thus, the second part of this work probabilistically examines the chance of handling loss given the amount of tire-road friction and driver acceleration. The result is a mathematically rigorous quantification of a safety margin for various road conditions and driver ability levels. Changes to the official US highway design handbook are recommended based on the findings. / Doctor of Philosophy / Autonomous vehicles (AVs) are quickly becoming a reality. In the surge to understand and develop AVs, researchers tend to study specific subdivisions within the vehicle engineering umbrella. In particular, mechanical and civil engineers study vehicle dynamics in two different levels of specificity. Mechanical engineers typically investigate the dynamics of a single vehicle, such as vehicle-terrain interactions or how various mechanical components operate. On the other hand, civil engineers tend to study traffic flow, which involves platoons (large groups of vehicles). Regardless of the scale of study, each subdivision has a set of performance metrics. Due to the differences among subdivisions, some performance metrics may (unintentionally) compete. Compromises must be made in the design stage to produce a vehicle which caters to an appropriate audience. This work features four main contributions. The first contribution is the application of Design Envelopes that establishes a framework to balance constraints arising from the different ways of studying vehicle dynamics. Three Design Envelopes are introduced to reach compromises on various facets of a vehicle's behavior, such as the vehicle's speed. The second contribution utilizes these Design Envelopes to improve a currently-existing speed profile generator. The current speed profile generator determines how to smoothly transition between two speeds (such as needing to decelerate to remain under a speed limit), but the ride may be uncomfortable to passengers. Integrating the Design Envelopes into the algorithm enhances the ride comfort for not just one vehicle, but a platoon. Simulations demonstrate that the refined algorithm can reduce the travel time on a specific route by 3-4.4%. The third contribution examines how horizontal curves on highways are designed, and a revision based on an acceleration-based safety margin is proposed. Finally, the fourth contribution considers important design variables probabilistically to establish a link between a motorist's acceleration and the chance of a tire skidding failure, which can impact the way straightaway road segments are designed to accommodate sudden braking maneuvers. As a whole, this work demonstrates it is possible to synthesize multiple engineering fields to enhance both current and future (full-scale AV implementation) roadway design.

The well-known clinoformal geometry of a basin-fill, with an alluvial to shelf segment, deep-water slope segment, and a basin floor segment, arises from the development of a wedge-shaped body of sediment at the basin-margin that has been termed a basin-margin wedge or a shelf-slope sedimentary prism. The basin-margin wedge characteristically has atopset-foreset clinoformal geometry, with its topset dominated by alluvial, coastal and shelfal processes, while its foreset is dominated by turbidite sedimentation. Tectonic configuration of the basin, sediment supply, and relative sea level variation are some of the major factors that control the development and growth of the basin-margin wedge. This dissertation documents two distinct stages of development of the basin-margin wedge at an Eocene active margin, and relates the observed variability in the nature of the shelf-margin, deep-water slope, and basin-floor deposits with these stages. The Tyee Basin in western Oregon was a forearc basin that was filled during late early Eocene and Middle Eocene under greenhouse climatic condition. The sedimentary succession of the Tyee Basin include continental, shallow-marine and deep-water sandstones that are well exposed in Coast Range area of Oregon. The variability observed within the thick and laterally extensive turbidite sandstones of the Tyee Basin led to contrasting depositional models for the Tyee basin in the past. Notably, the submarine ramp model, which provides an alternative model for deepwater coarse clastic deposition, was proposed based on the sedimentary succession of the Tyee Basin. Reconstruction of the clinoformal geometry of the Tyee Basin succession from detailed field data (more than 1000 outcrop locations) and subsurface data reveals two distinct stages of development of this active basin-margin. Each stage has a distinct style of clinoform development and a distinct character of associated sandy deepwater deposits. At the initial stage the basin-margin clinoforms appear to be small (< 250m clinoform height) and strongly progradational, with clinoform topset dominated by the feeder fluvial deposits. At this stage, sandy unconfined (not channelized) turbidite deposits accumulated on the Tyee deepwater slope and extended to the Tyee basin-floor. Large scale sediment conduits on the deepwater slope, in the form of slope channels or canyons, are notably absent in this stage. The second stage is characterized by larger clinoform height (> 500m), higher degree of topset aggradation with repeated fluvio-deltaic cycles on the shelf, and spectacular, sand-rich, well-organized turbidite channels and canyons on the slope. The slope channels active at this stage supplied coarse sediments to the basin-floor to form unusually thick basin-floor fans. The first infill stage represents the embryonic development of a basin-margin wedge on the Tyee continental margin, and could have some similarity with the previously mentioned submarine ramp model. But this was followed by a much longer period of basin-filling when repeated fluvial and shallow-marine cycles formed on the shelf and well-organized turbidite channels were active on the slope supplying sands to the Tyee Basin floor fans. It was concluded that the two stages of development of the basin-margin wedge in the Tyee Basin is controlled largely by the configuration of the basin, that is a result of the prominent topographic/bathymetric features in oceanic basement underlying the sedimentary succession of the Tyee Basin. Tectonically active hinterland and greenhouse climate may have contributed to a relatively high sediment supply to the basin. The relatively small-amplitude sea level variations expected under greenhouse climatic condition of the Early to Middle Eocene are likely to have relatively minor effect on the architecture of the basin-fill. The present work on Tyee Basin builds on earlier research on this basin, but now establishes a ground trothed clinoformal growth model, revises the existing interpretation of sediment transport direction during a major part of the basin-filling history, and demonstrates a two-stage evolution of margin accretion. The observations from the active Tyee Basin was compared and contrasted with a latest Pleistocene sediment wedge on the New Jersey outer shelf. This sediment wedge, developed under icehouse climatic condition, and on a passive margin, was studied using high resolution seismic data (CHIRP). In contrast to the sedimentary succession of the Tyee Basin, the depositional architecture of the sediment wedge on outer New Jersey shelf, which was interpreted as a set of falling stage deltaic clinothems, appears to be strongly controlled by eustatic sea level variation of latest Pleistocene. / text

Os métodos potenciais são conhecidos como uma ferramenta útil para estudos regionais. Na Ibéria Ocidental, a gravimetria e a magnetometria podem ser utilizadas para auxiliar no entendimento de algumas questões sobre a estruturação tectônica offshore. Nesta região, tanto as estruturas geradas pela quebra continental, quanto às herdadas do embasamento variscano, tem uma importante contribuição para a resposta geofísica regional observada com estes métodos. Este trabalho tem como objetivo correlacionar as feições geofísicas observadas com alguns modelos geológicos do arcabouço tectônico da Ibéria Ocidental já publicados na literatura. Mapas filtrados foram usados para auxiliar no reconhecimento de diferentes assinaturas geofísicas, os quais foram calculados a partir dos mapas de gravidade Bouguer e do campo magnético total tais como o gradiente horizontal total, derivada tilt, derivada vertical, e integral vertical. O domínio crustal continental foi definido a partir da interpretação dos dados gravimétricos, utilizando gradiente de gravidade horizontal total da Anomalia Bouguer. Os dados magnéticos, originais e filtrados, foram utilizados para identificar mais três domínios regionais offshore, que sugerem a existência de três tipos de crosta não-siálica. Dois deles são propostos como domínios de transição. A região da crosta de transição mais próxima do continente tem uma fraca resposta regional magnética, e a porção mais distal é um domínio de anomalia de alta amplitude, semelhante à resposta magnética oceânica. O limite crustal oceânico não pôde ser confirmado, mas um terceiro domínio offshore, a oeste da isócrona C34, poderia ser considerado como crosta oceânica, devido ao padrão magnético que apresenta. Alguns lineamentos do embasamento foram indicados na crosta continental offshore. As feições gravimétricas e magnéticas interpretadas coincidem, em termos de direção e posição, com zonas de sutura variscanas, mapeados em terra. Assim, esses contatos podem corresponder à continuação offshore destas feições paleozoicas, como o contato entre as zonas de Ossa Morena-Zona Centro-Ibérica. Nesta interpretação, sugere-se que a crosta continental offshore pode ser composta por unidades do Sudoeste da Península Ibérica. Isto permite considerar que a Falha de Porto-Tomar pertence a uma faixa de deformação strike-slip, onde parte das bacias mesozoicas da margem continental está localizada. / Potential field methods are known as a very useful tool to regional studies. On Western Iberia, gravimetric and magnetometric data could be helpful to understand some questions about the offshore tectonic framework. In this area, both continental break-up features and inherited continental basement structures have a strong contribution to compose the regional geophysical response on gravimetric and magnetometric maps. This work aims to correlate observed geophysical features of the Iberian margin with some geological models about the tectonic framework of Western Iberia, already published on literature. Filtered maps were used to recognize different geophysical signatures, which were computed from both calculated Bouguer gravity and total magnetic field, such as total horizontal gradient, tilt derivative, vertical derivative, and vertical integration. The continental crustal domain was defined from gravity data interpretation using an enhanced total horizontal gradient of Bouguer Anomaly maps. Magnetic data was used to identify three more regional offshore domains that could indicate three types of non-sialic crust. Two of them are proposed as transitional domains. The landward transitional crust has a very weak regional magnetic response, and the seaward one is a high amplitude anomaly domain, similar to oceanic magnetic response. The oceanic crustal boundary was not confirmed, but a third offshore domain, seaward from C34 isochron, could be considered as oceanic crust by its magnetic pattern. Some basement lineaments were indicated in the offshore continental crust. Gravimetric and magnetic features coincide in terms of their direction and position with Variscan suture zones mapped onshore. Therefore these contacts could correspond the offshore continuation of these Paleozoic features, such as the Ossa-Morena Zone and Centro-Ibérica Zone suture zone. In this interpretation, offshore continental crust could be formed by units from Southwest Iberia. It allows considering the Porto-Tomar fault as a part of a swath of strike-slip deformation, where mesozoic basins are located.