Large scale outages have occurred worldwide in recent decades with some impacting 15-25% of a nation’s population. The complexity of blackouts has been extensively studied but many questions remain. As there are no perfect solutions to prevent blackouts, usually caused by a complex sequence of cascading events, a number of different measures need to be undertaken to minimize impact of future disturbances. Increase in deployment of phasor measurement units (PMUs) across the grid has given power industry an unprecedented technology to study dynamic behavior of the system in real time. Integration of large scale synchronized measurements with SCADA system requires a careful roadmap and methodology. When properly engineered, tested, and implemented, information extracted from synchrophasor data streams provides realtime observability for transmission system. Synchrophasor data can provide operators with quick insight into precursors of blackout (e.g., angular divergence) which are unavailable in traditional SCADA systems. Current visualization tools and SE functions, supported by SCADA, provide some basic monitoring. Inaccuracies in measurements and system models, absence of redundancy in the measured parameters or breaker statuses in most cases, and lack of synchronization and time resolution in SCADA data result in limited functionality and precision for a typical EMS required in today’s operating environment of tighter margins that require more frequent and more precise data. Addition of synchrophasor data, typically having several orders of magnitude higher temporal resolution, (i.e., 60 to 120 measurements per second as opposed to one measurement every 4 to 8 seconds), can help detect higher speed phenomena and system oscillations. Also, time synchronization to one micro-second allows for accurate comparison of phase angles across the grid and identification of major disturbances and islanding. This dissertation proposes a more comprehensive, holistic set of criteria for optimizing PMU placement with consideration for diverse factors that can influence PMU siting decision-making process and incorporates several practical implementation aspects. An innovative approach to interoperability testing is presented and solutions are offered to address the challenges. The proposed methodology is tested to prove the concept and address real-life implementation challenges, such as interoperability among the PMUs located across a large area.

An optimal wing shape is necessary for the survival of winged insects since it enables different survival strategies and is expected to vary between environments due to different selection pressures. However, few studies have explored wing shape variation across the whole range of a species.  In this study, geographic variation in wing shape in male Lestes sponsa was examined from 14 localities along a latitudinal gradient in Europe. The wings were analyzed using a comparative geometric morphometric approach, where the different shapes were digitized, statistically analyzed, and visualized on thin spline deformation grids. The results showed significant differences in wing shape in both the fore- and hindwings between locations. Wings at some localities showed a slender appearance with a narrow tip, and wings from other localities showed a broader appearance with a convex tip. A significant trend in wing shape was found from the central populations to the northern one. However, no continuous trend in wing shape was found across the latitudinal range suggesting that local abiotic or biotic factors might drive the difference observed.

No description available.

This dissertation investigates the effects of changes in technologies and trade-related policies on income inequality. The first chapter shows that an advancement in labor saving technologies, known as automation, raises the agglomeration of economic activity in large cities and increases wage inequality across regions. I show novel stylized facts about the relationship between city size and the routineness of tasks performed by workers. I develop a general equilibrium model of a spatial economy where automation affects the type of tasks performed by workers and is related to a firm's choice of production location. The model generates several predictions that are consistent with stylized facts and existing empirical evidence: larger cities have greater agglomerations of firms and grow larger when firms can automate more tasks in the production process. The model predicts that an increase in automation raises wage dispersion between larger and smaller cities. A 20% rise in automation increases wages in the top decile of largest cities by about 8% and lowers wages in smaller cities by about 2-8% and hence widens the wage gap by about 10 to 16 %. The second chapter investigates the effect of exchange rate volatility on the intensive and extensive margin of trade, and on income inequality within a country. It finds that the greater volatility in exchange rates lowers trade margins and income inequality. I derive testable predictions regarding the impact of exchange rate volatility on trade margins at the firm level and on income distribution at the industry level. I empirically test these predictions using firm-level microdata. Empirical results provide clear support in favor of the model's predictions about the effects of volatility on trade margins. Finally, in the third chapter, my coauthors and I investigate the effect of Bangladesh’s graduation from Least Developed Country (LDC) status on the price of insulin, an essential medicine for diabetes, and on households’ welfare and poverty. We find that upon Bangladesh’s graduation from LDC status, the price of insulin could rise as much as 11 times the current price for patented insulin if an unregulated monopoly is allowed. This would significantly reduce welfare and increase the incidence of poverty for households with members suffering from diabetes.

No description available.

Seafloor sedimentary depositional and erosional processes create a record of near and far-field climatic and tectonic signals adjacent to continental margins and within oceanic basins worldwide. In this dissertation I study both modern and paleo-seafloor surface processes at three separate and distinct study sites; Cascadia offshore Oregon, U.S.A., the Eastern North American Margin from south Georgia in the south to Massachusetts in the north, and the Deep Galicia Margin offshore Spain. I have the advantage of using modern geophysical methods and high power computing resources, however the study of seafloor processes at Columbia University's Lamont-Doherty Earth Observatory (LDEO) stretches back over ~80 yrs. Specifically I use data collected during a variety of geophysical research cruises spanning the past ~50 yrs.-the majority of which can be directly attributed to seagoing programs managed by LDEO. The modern seafloor is the integrated result of all previous near and far field processes. As such, I look below the seafloor using multi-channel seismic reflection data, which is the result of innumerable soundings stacked together to create an image of the sub-seafloor (paleo) horizons. I map, analyze and interpret the sub-seafloor sedimentary horizons using a variety of both novel and established methods. In turn, I use multi-beam sonar data, which is also the result of innumerable soundings to map, analyze, and interpret the modern seafloor topography (bathymetry). Additionally, I look to the results from academic ocean drilling programs, which can provide information on both the composition and physical properties of sediments. The sediment composition alone can provide important information about both near and far-field processes, however when supplemented with physical properties (e.g., density/porosity) the results become invaluable. In my second chapter, I use a compilation of multi-beam sonar bathymetry data to identify and evaluate 86 seafloor morphological features interpreted to represent large-scale erosional scours not previously recognized on the Astoria Fan offshore Oregon, U.S.A. The Astoria Fan is primarily composed of sediments transported from the margin to the deep ocean during Late Pleistocene interglacial periods. A significant portion of the sediments have been found to be associated with Late Pleistocene outburst flood events attributed to glacial lakes Bonneville and Missoula. The erosional scours provide a record of the flow path of the scouring event(s), which if well understood can provide important information for the study of past earthquakes as the sedimentary record remains intact outside of the erosional force created by the massive flood events. I design and implement a Monte Carlo inversion to calculate the event(s) flow path at each individual scour location, which results in a comprehensive map of Late Pleistocene erosion on the Astoria Fan. The results indicate that at least 4 outburst flood events are recorded by the scour marks. In my third chapter, I build a stratigraphic framework of the Eastern North American margin using a compilation of multi-channel seismic data. Horizon Au is a primary horizon within the stratigraphic framework and is thought to represent a significant margin wide bottom-water erosional event associated with subsidence of the Greenland-Scotland Ridge and opening of Fram Strait in the late Eocene/early Oligocene. A recent study found that the bottom-water was enriched in fossil carbon, leading us to hypothesize that the bottom-water erosion recorded by horizon Au may have been facilitated by chemical weathering of the carbonate sediments. I use sediment isopach(s) to build a margin-wide model of the late Eocene/early Oligocene continental margin in order to estimate the volume of sediments eroded/dissolved during the event marked by horizon Au. The results indicate that ~170,000 km3 of sediments were removed with a carbonate fraction of 42,500 km³, resulting in 1.15e18 mol CaCO₃ going into solution. An influx of this magnitude likely played a role in significant climatic changes identified at the Eocene-Oligocene transition (EOT). In my fourth chapter, I use a combination of 3D multi-channel seismic and multi-beam sonar bathymetry data collected during the Galicia 3D Seismic Experiment in 2013. The Galicia Bank is the largest of many crustal blocks and is located 120 km west of the coast on the Iberian Margin. The crustal blocks have been attributed to the opening of the North Atlantic Ocean in the Late Triassic/Middle Jurassic. The Galicia Bank is the source for the majority of sediments delivered to the Deep Galicia Margin, the focus of this study. I map the seafloor and 5 paleo-seafloor surfaces in order to study controls on sediment delivery provided by the crustal blocks. The results show that the crustal blocks begin as a barrier to and remain a primary control on sediment delivery pathways to the Deep Galicia basin. Additionally, the paleo-seafloor surfaces record morphological structures that can inform us on both near and far field past climatic and tectonic events e.g., the Alpine Orogeny and Pleistocene inter-glacial periods.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1979. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 163-184. / by James Albert Austin, Jr. / Ph.D.

Many passive margins experience pulsed exhumation events late in their history as a result of plate boundary distal geodynamic mechanisms or climatic events. The onset of late Cenozoic glaciation, often associated with enhanced rates of erosion, is one such possible cause of passive margin rejuvenation. However, along passive margins the effectiveness of Plio-Pleistocene glaciers at eroding the landscape may be limited by low tectonic rock uplift rates or as a result of erosionally inefficient cold based continental ice-sheets. In this dissertation the evolution of post-orogenic topography and the effect of glaciations on denuding landscapes along the North Atlantic Passive Margin, in the White Mountains of New Hampshire and the western Scottish Highlands, was investigated. Background exhumation rates averaged over 106-7 yr timescale were determined using apatite (U-Th)/He thermochronology. To resolve whether or not a change in exhumation rate occurred coincident with glaciation these background exhumation rates were compared to magnitudes of erosion averaged over the glacially relevant 103-4 yr timescale using the in situ terrestrial cosmogenic nuclide 10Be. In chapter two, 106-7 yr timescale exhumation and burial histories across the western Scottish Highlands were determined. The results show that post-orogenic burial and exhumation is mostly a result of plate margin distal tectonic and magmatic factors that are variable across short distances (i.e., <100 km). In chapter three, patterns and magnitudes of erosion during glaciation and following deglaciation in the Scottish Highlands were investigated. The results indicate that polythermal glacial erosion denuded low elevation portions of the Scottish Highlands and preserved summits. This produced relief but did not significantly lower the maximum elevation of the landscape. Following deglaciation Scotland's sediment budget remains dominated by glaciogenic sediment. In the fourth chapter, magnitudes of background exhumation in the Presidential and Carter Ranges of the White Mountains, New Hampshire were compared to magnitudes of glacial erosion. The results indicate that most relief was produced prior to glaciation and that background exhumation rates in the Cenozoic are low (<0.01 mm yr-1). In the late-Cenozoic, cold- based glaciation prevented an acceleration of erosion in the White Mountains. The post- glacial sediment budget is made up of dominantly glaciogenic sediment. Overall, the main findings of this dissertation are; (1) post-orogenic burial, exhumation, and relief production are mainly the result of spatially heterogeneous plate margin distal vertical crustal motions; across passive margins covered by large continental ice sheets; (2) cold-based ice limits the magnitudes of late Cenozoic glacial erosion sediment budgets continue to be dominated by glaciogenic sediment, >10 ka after and (3) post-glacial deglaciation. / Ph. D. / Far away from the edges of modern tectonic plates, old mountain ranges (~300 million years old) may experience changes in rates of erosion long after the forces that built those mountains have gone away. Tectonic forces that occur far away from the edges of tectonic plates could cause these changes in erosion rate or they could be a result of changes in climate that create conditions in which erosion rates could increase. One change in climate that could have caused faster rates of erosion in old mountain ranges is climatic cooling causing the repeated advance and retreat of glaciers in mid to high latitudes over the past ~2.6 million years. Glaciers are usually seen as having the ability to erode faster than non-glacial processes (e.g., rivers). However, not all glaciers have the ability to erode really fast. In old mountain ranges glacial erosion might be limited because the mountains are not being uplifted very fast supplying new land to be subjected to erosion. Also, big ice sheets that covered many old mountain ranges can be very cold, freezing ice to the ground and therefore acting to protect the underlying landscape rather than eroding it. In this dissertation the question of whether glaciation caused an acceleration in erosion rates in old mountain ranges far away from the edges of tectonic plates is investigated, specifically in White Mountains of New Hampshire and the western Scottish Highlands. To this end, erosion rates in these mountain ranges were determined prior to glaciation and then compared to erosion rates during glaciation and following deglaciation. The results of the research presented in this dissertation indicate that; (1) pre-glacial erosion resulting from tectonic forces far from the edges of tectonic plates was more important at producing relief and eroding the landscape than glaciers; (2) ice covering old mountain ranges was at least partially cold-based, inhibiting erosion; and (3) following deglaciation sediments in streams are mostly sourced from remobilized glacially produced sediments rather than direct bedrock erosion.

International trade encourages innovation, boosts development, reduces poverty, creates new markets, enhances competitiveness, improves product quality, and expands the consumer choice set. This dissertation is composed of three papers examining barriers to agricultural trade. The first two papers examine the impact of tariff and non-tariff barriers to agricultural trade while the third paper investigates China's domestic agricultural and international trade policies in order to promote U.S. market access in China. The first paper investigates how trade liberalization expands the range of products available for import and consumption. A multinomial logit framework of unordered export categories is developed: no trade margin, disappearing margin, intensive margin, and extensive margin. The findings of this paper suggest exporters gain from tariff reductions because they can establish new product relationships with the U.S. and enhance their U.S., and potentially global, supply chains. In addition, if consumers value variety in consumption, the extensive product margin results can be viewed as a positive welfare gain for U.S. agri-food consumers. The second paper focuses on non-tariff measures (NTM), which have significant implications for agricultural trade and food marketing. This paper focuses on maximum residue limits (MRLs) for pesticides and their trade restricting nature on U.S. fresh fruit and vegetable trade under the Trans-Atlantic Trade and Investment Partnership (T-TIP) and the Trans-Pacific Partnership (TPP). Specifically, this research develops a bilateral index to measure the stringency of destination market tolerances for pesticide residues relative to those faced in the United States. Using a Heckman two-step model, the results shed considerable light on existing regulatory heterogeneity, which has important implications for policy to focus on increasing compatibility of NTMs across trading nations. The third paper examines China's evolving agricultural and trade policies and discusses the potential impact on U.S. exports to China. China's agricultural imports, and policies affecting those agricultural products, have important implications for the U.S. as the leading export supplier to the Chinese market. China's price support programs, aimed at improving food security and Chinese farmers' incomes, increased domestic prices. This created a gap between domestic and international prices that led to excessive Chinese stockpiles. In response, China implemented respective target prices for cotton and soybeans, eliminated the price support for corn, and continues to introduce new policies. / Ph. D. / International trade encourages innovation, boosts development, reduces poverty, creates new markets, enhances competitiveness, improves product quality, and expands the consumer choice set. This dissertation is composed of three papers examining barriers to agricultural trade. The first two papers examine the impact of tariff and non-tariff barriers to agricultural trade while the third paper investigates China’s domestic agricultural and international trade policies in order to promote U.S. market access in China. The first paper investigates how trade liberalization expands the range of products available for import and consumption. The findings of this paper suggest exporters gain from tariff reductions because they can establish new product relationships with the U.S. and enhance their U.S., and potentially global, supply chains. In addition, if consumers value variety in consumption, the extensive product margin results can be viewed as a positive welfare gain for U.S. agri-food consumers. The second paper focuses on non-tariff measures (NTM), which have significant implications for agricultural trade and food marketing. This paper focuses on maximum residue limits (MRLs) for pesticides and their trade restricting nature on U.S. fresh fruit and vegetable trade under the Trans-Atlantic Trade and Investment Partnership (T-TIP) and the Trans-Pacific Partnership (TPP). Specifically, this research develops a bilateral index to measure the stringency of destination market tolerances for pesticide residues relative to those faced in the United States. The results show that there are considerable differences in existing MRL regulations across trading nations. The third paper examines China’s evolving agricultural and trade policies and discusses the potential impact on U.S. exports to China. China's agricultural imports, and policies affecting those agricultural products, have important implications for the U.S. as the leading export supplier to the Chinese market. China’s price support programs, aimed at improving food security and Chinese farmers’ incomes, increased domestic prices. This created a gap between domestic and international prices that led to excessive Chinese stockpiles. In response, China implemented respective target prices for cotton and soybeans, eliminated the price support for corn, and continues to introduce new policies.

The Generalized System of Preferences (GSP) is a unilateral trade liberalization program in which developed countries offer non-reciprocal tariff reductions (tariff preferences) on certain products imported from designated developing and least developed countries. GSP is considered an important tool in the World Trade Organization's approach to development. This dissertation--composed of three essays--explores whether low-income countries have achieved an increased access to high-income markets as a result of these non-reciprocal tariff preferences offered to their exports. The first essay provides an overview of the GSP program. The second essay presents an evaluation of the GSP program by considering the products and markets where low-income countries' exports are concentrated. Using a theoretically consistent gravity equation for primary and processed agri-food trade over the period 1962-2010, the results illustrate that the GSP program and modifications of it have delivered significant positive effects in developing countries' exports to developed country markets in agricultural trade but not necessarily so in non-agricultural goods. The third essay develops two theoretically founded novel indices to measure preference margins offered by high-income countries to low-income countries through tariff reduction. One index captures the restrictions bilateral tariff rates impose on market access conditions of a country as compared to the most favored nation rate, called the Exponential Trade Restrictiveness Index (ETRI). The other index captures the relative ease with which a country can access foreign markets compared to its competing suppliers, called the Exponential Relative Preferential Margin (ERPM). Then, these two bilateral indices are used to develop a model of sector-based bilateral trade to re-evaluate the Generalized System of Preferences (GSP) in terms of relative market access preferences. The results show that the GSP has increased relative market accessibility for low-income countries and in turn boosted exports from these countries by 26 to 28 percent. / Ph. D.