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Polymer electrolyte fuel cells (PEFCs) provide a promising way to mitigate global warming since these power sources produce no emissions of greenhouse gases. PEFCs convert chemical energy of hydrogen and air to electricity via electrochemical pathway. For broad deployment of PEFCs in transportation sector cost and durability need to be addressed. At the heart of the fuel cell is the catalyst layer, where platinum (Pt) catalyst is used to catalyze oxygen reduction reaction (ORR). Pt is typically dispersed on carbon support and with ionomer (such as Nafion) to enable ORR. Understanding Pt-ionomer interface is critical to enable PEFCs with low Pt content. Therefore, in this work Pt- ionomer interfacial and transport properties within the catalyst layers were examined using variety of electrochemical diagnostic techniques. Optimizing electrode morphology with a more uniform ionomer distribution is key to reducing ohmic losses and increasing electrocatalyst utilization in PEFCs. For ionomer transport properties, we determined three different methods including direct current (DC) hydrogen pump (HP), HP electrochemical impedance spectroscopy (EIS) and H2/N2 EIS to investigate catalyst layer ionic conductivity, and it was the first and unique study to compare each method. Apart from that, we developed an 1D H2/N2 EIS impedance fitting model, which enable us to evaluate catalyst layer ionic conductivity with good accuracy. For Pt ionomer interfacial properties study, we first studied performance and electrochemical characterizations for MEAs containing novel high oxygen permeability ionomers (HOPIs) synthesized by Giner, and a comparison was made between novel ionomer and commercial Nafion ionomer. After that, we investigated some possible factors which influence cell performance and catalyst/ionomer interfacial properties using 3M materials including Pt loading, ionomer content and carbon support types, which would bring thoughts and inspirations to community regarding the design of optimal catalyst layer. Finally, we studied Pt ionomer transport and interfacial properties change during carbon corrosion accelerated stress tests (ASTs). We performed both in-situ and ex-situ measurements on MEAs containing different types of carbon support, which enable us to better understand the causes for drop of performance from ionomer interfacial properties perspective.

Abstract: Online trajectory prediction is central to the function of air traffic control of improving the flow of air traffic and preventing collisions, particularly considering the ever-increasing number of air travellers. In this thesis, we propose an approach to predict the mid-flight trajectory of an aircraft using models learned from historical trajectories. The main idea is based on Markov Models with transition probabilities for multiple timesteps, representing the location of aircraft as states and movement of aircraft over a certain number of minutes (i.e. timestep) as transition probabilities between states. Using our approach, one is able to make predictions of future positions of mid-flight aircraft for each minute up to twenty minutes into the future, and concatenate them to form the predicted trajectory of the aircraft for the next twenty minutes. We evaluated the effectiveness of the proposed approach using a dataset of historical trajectories over the USA. Using prediction accuracy metrics from the aviation domain, we demonstrated that our approach was able to make accurate predictions of future trajectories of mid-flight aircraft, achieving an improvement of 24.6% in horizontal error and 34.2% in vertical error over baseline models from conventional approaches, with each prediction requiring mere milliseconds to compute.

Under the tensions of nationalization and globalization, mainland Chinese cinema has undergone tremendous changes in terms of industrial transformations, diversification of film language, style and genre, revenues, etc. in the new century. This is epitomized in a new surge of commercial entertainment cinema. This dissertation examines Lu Chuan and his films among this surge and as a representative of the new development of Chinese popular cinema. The study reveals a new political regime and a new popular imagination in China with its greater integration into the international system of global capitalism in in the first decade of the twenty-first century. I apply Pierre Bourdieu’s theory of the field of cultural production to explore structural transformations in the field of Chinese cinema, and trace these changes to the shaping forces in the larger fields of Chinese power and economy. This structural examination is related to the agency of individuals as cultural entrepreneurs maneuvering their way within the state system through alliance of power, capital and talent, and forming their own voices and a public space. Theories of popular cultural studies help me analyze Lu Chuan’s films as a site where different international and domestic social, political, and cultural forces contend and negotiate with each other. I also draw upon theories of film studies to illustrate Lu Chuan’s application of international film language and styles including classical Hollywood cinema and the art film in rendering Chinese socialist stories in the age of globalization. Instead of treating Lu Chuan as an auteur or artistic creator, I look into his authorship as a site of different discourses and a technique of the self, which helps him distinguish his films from others and establish his position in the field. Trauma studies provide a useful tool in discussing Chinese cinematic representations of the national trauma, the Nanjing Massacre, during different historical periods, and Chinese nation’s continuing effort in grappling with this trauma. This textual analysis is to illustrate the newest development in Chinese cinema. The purpose of this study is to demonstrate the historical transformation of Chinese society and to identify the forces that shaped Chinese cinema, which took form in a new alliance amongst power, capital, and art, and contributed to a post-socialist popular imagination in China in the first decade of the new century.