The structure of the crust and distribution of earthquakes in southern California

Nazareth, Julie Jeannine California Institute of Technology 2002 해외박사(DDOD)

The lithologically and tectonically complex crust of southern California and the current broad deformation zone accommodating the relative motion between the Pacific and North American plates, result in significant variations in style, depth distribution, and rate of earthquakes, and thus also in the seismic hazard across southern California. Although the thickness of the seismogenic crust is an important parameter in seismic hazard analysis, it has never been determined systematically for southern California. Seismogenic thickness can be predicted by the depth distribution of the moment release of regional seismicity. The seismogenic thickness of southern California is highly variable, ranging from less than 10 km in the Salton Trough to greater than 25 km at the southwestern edge of the San Joaquin Valley. On average, the seismogenic thickness of southern California is 15.0 km. Seismogenic thickness along the major strike slip systems of southern California can vary significantly along strike. Fault segmentation based upon surface features does not correspond to the variation in seismogenic thickness and thus the potential down-dip width of the fault. A model of the broad scale features of the crust and upper mantle structure of the borderland-continent transition zone adjacent to Los Angeles constrains the crustal thickness and the location and width of the transition zone. The data require the Moho to deepen significantly to the north, dramatically increasing the crustal thickness over a relatively short distance of 20–25 km. The Moho is coherent and laterally continuous beneath the Inner California Borderland and transition zone. The Inner Borderland seems to be modified and thickened oceanic crust, with the oceanic upper mantle intact beneath it. The static stress change triggering model has some validity and can be useful in explaining apparently triggered seismicity within one fault length of a large mainshock. However, because its applicability varies between different sequences, its general application to seismic hazard evaluation requires more refinement and the inclusion of parameters such as tectonic regime, regional stress state, and fault strength.

Portfolio selection with random transaction costs

Nazareth, Marcelo Oliveira Costa The University of Chicago 2000 해외박사(DDOD)

I develop a model of portfolio selection in continuous time where transaction costs are random. In the model, the consumer faces a trade off between getting good terms of trade and holding a well balanced portfolio. First, I formulate the relevant control problem and prove that the value function is the unique viscosity solution of the associated Hamilton-Jacoby-Bellman equation. Next, I present a numerical procedure to solve the equation and a proof that the numerical solution converges to the true solution of the problem. The actual implementation of the procedure fully characterizes the optimal consumer behavior.

Study On a Blockchain Framework Of Agriculture Information Sharing In Tanzania Using Solidity Technology

NIGANILE NAZARETH LEBBI 한동대학교 국제개발협력대학원 2024 국내석사

The United Republic of Tanzania, covering an area of 947,300 square kilometers, is ranked as the 23rd largest country globally and the 13th largest in Africa. Its population density is around 62 individuals per square kilometer, with a total population of over 64,363,425 people. It is worth noting that rural regions account for 64% of the population. Despite its vast potential in the agricultural sector, Tanzania remains classified as a Low-Income Food-Deficit Country. Moreover, partly attributed to the limited knowledge possessed by small-scale farmers in rural areas, including inadequate market information (such as prices and selling points), little understanding of reliable input sources (e.g., seeds and chemicals), insufficient knowledge of meteorological data (including rainfall patterns and climate change), and ignorance of crop insurance programs. This paper investigates the flow of information within Tanzania's agriculture sector. It proposes using blockchain technology to bridge the information gap and provide small-scale farmers with the required knowledge to boost agricultural production. This thesis aims to address the problem of inadequate flow of information between agriculture stakeholders in Tanzania by developing an agriculture information-sharing system using blockchain technology. The current methods for sharing agriculture information in Tanzania could be more effective and efficient, resulting in a need for more transparency and trust among stakeholders. This problem affects the entire agriculture value chain, leading to low productivity, poor market access, and limited growth opportunities. Therefore, blockchain technology offers a potential solution to this problem by improving the transparency and accountability of information sharing among stakeholders. This research will investigate the feasibility, challenges, and potential benefits of developing an agriculture information-sharing framework using Etherium-Solidity blockchain technology in Tanzania. The study uses a mixed-methodologies approach, incorporating qualitative and quantitative data gathering and analysis methods. The findings of this study will contribute to developing a sustainable and efficient agriculture information-sharing framework in Tanzania, which could improve the livelihoods of farmers, traders, and other actors in the agriculture value chain. This thesis aims to develop an agriculture information-sharing framework in Tanzania using blockchain technology. The framework aims to improve the dissemination of agriculture-related information to small-scale farmers in rural areas, such as market prices, weather forecasts, and farming techniques. The research questions addressed in this thesis include the feasibility of using blockchain technology in agriculture, the key factors contributing to poor communication between small-scale farmers and agriculture system stakeholders in rural Tanzania, and how they can be addressed to improve information flow. How can digital technologies be leveraged to improve information flow between small-scale farmers and agriculture system stakeholders in Tanzania? What key considerations are needed when designing such solutions? The research methods include a literature review, stakeholder interviews, and field experiments. The findings suggest the blockchain-based system can provide secure and transparent information sharing, increase the agricultural supply chain's efficiency, and improve small-scale farmers' livelihoods. The thesis concludes by discussing the implications of the research for agriculture and blockchain technology in Tanzania and elsewhere.

Embedded photonic crystals for high-efficiency gallium nitride-based optoelectronic devices

Matioli, Elison de Nazareth University of California, Santa Barbara 2010 해외박사(DDOD)

The application of photonic crystals (PhCs) as light extractors in LEDs has evoked increased interest over recent years due to their efficacy in controlling the direction of light emission and enhancing the extraction efficiency of LEDs. This dissertation presents the study of different schemes for higher light extraction based on PhCs. The higher theoretical light extraction provided by structures with embedded PhCs compared to all the other configurations motivated a more detailed investigation of this approach. The growth of embedded air-gap PhCs by MOCVD was successfully achieved with very short grating periods (230 nm) in a two-dimensional triangular lattice. Coalescence was obtained over the air-gap PhCs with thicknesses down to 50 nmand fairly smooth surface with no extra defects created by the embedded PhCs. Embedded PhC structures were optimized using full 3D electromagnetic models. The embedded PhC LEDs presented a very high extraction efficiency of 73% for unencapsulated and 94% for silicone encapsulated devices. In addition, we developed new techniques to measure intrinsic characteristics of PhC LEDs based on high resolution angle-resolved measurements. The measurement of the extraction and dissipation properties of guided modes in PhC-LEDs revealed the competition between these two mechanisms as well as the dynamical diffraction by the 2D PhCs. These experimental techniques were used to corroborate some of our theoretical results and to compare the performances of different PhC configurations. The diffraction of the guided modes with short extraction lengths, shorter than any absorption mechanism, explains the very high extraction efficiency of the embedded PhC LEDs presented in this PhD thesis, which makes this structure an excellent candidate for high efficiency and high brightness LEDs.