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In this dissertation, I investigate how online social interactions and user-generated content affect sellers and consumers in online platforms. I conduct three empirical studies to understand the effect of user-generated content in three different types of online platforms: (1) an e-commerce marketplace, (2) an online reviews platform, and (3) an online health community. In study one, I examine how social features (e.g., following others, sharing others’ products) within an electronic commerce marketplace affect status and sales for sellers. This essay contributes to the literature on electronic commerce by deepening the understanding of online social processes among sellers. In study two, I explore how humorous appropriation of an online review platform affects purchase intention and consumer engagement. Utilizing both controlled experiments and analysis of real-world reviews, I demonstrate that humorous appropriation attenuates the effect of review valence on purchase intentions and increases consumer engagement. In study three, I investigate how community ratings are related to patient treatment evaluations and compliance in an online health community. I find that community ratings are positively associated with treatment evaluations and compliance. Moreover, I find that community size and ratings variance moderate the effect of community ratings on treatment evaluations and compliance. Taken together, these essays contribute to the literature on Information Systems by augmenting the understanding of the effects of different types of user-generated content on social (status, engagement, and evaluations) and economic outcomes (purchase intentions and sales). The studies also offer insights for strategic decisions regarding user-generated content in online platforms. / Business Administration/Management Information Systems

No / With the rapid growth of the scale, complexity, and heterogeneity of Peer-to-Peer (P2P) systems, it has become a great challenge to deal with the peer's network-oblivious traffic and self-organization problems. A potential solution is to deploy servers in appropriate locations. However, due to the unique features and requirements of P2P systems, the traditional placement models cannot yield the desirable service performance. To fill this gap, we propose an efficient server placement model for P2P live streaming systems. Compared to the existing solutions, this model takes the Internet Service Provider (ISP) friendly problem into account and can reduce the cross-network traffic among ISPs. Specifically, we introduce the peers' contribution into the proposed model, which makes it more suitable for P2P live streaming systems. Moreover, we deploy servers based on the theoretical solution subject to practical data and apply them to practical live streaming applications. The experimental results show that this new model can reduce the amount of cross-network traffic and improve the system efficiency, has a better adaptability to Internet environment, and is more suitable for P2P systems than the traditional placement models.

This thesis describes the application of microprocessor based relays with internet communication capabilities in distribution protection systems. The traditional distribution protection system (recloser, sectionalizers) was configured to automatically isolate faulted circuits as well as to reenergize unfaulted loads after a certain number of reclosing operations. Internet Peer-to-Peer communication enables distribution relays to communicate with others connected to the communication network without having a master device. According to the results, the addition of peer-to-peer communication to a traditional distribution protection system significantly enhances its general performance eliminating undesired losses of unfaulted load. Additionally, it reduces outage duration as well as thermal and mechanical stress due to successive re-energizations under faults condition. / Master of Science

The purpose of the current study was to investigate the relationships between physical and emotional peer victimization, parental and peer support and depressive symptoms. The moderating role of parental and peer support and gender differences in such moderation were the focus of the study in examining the association between peer victimization forms and depressive symptoms. Two hundred and sixty one youths (ages 10-14) completed self report measures of parental and peer support and depressive symptoms and were interviewed about their victimization experiences. Physical victimization rates were higher for boys whereas girls reported higher emotional victimization experiences and higher peer support than boys did. Correlations indicated that the experience of physical and emotional victimization by peer is linked to depressive symptoms. For boys, but not for girls, a significant moderation effect indicated that physical victimization was significantly related to depressive symptoms among youths with low peer support whereas physical victimization was not related to depressive symptoms among youths with high peer support. There were significant main effects of parental and peer support for both genders suggesting the importance of such support against depressive symptoms. The study's findings contribute to the literature regarding peer victimization's effects on mental health by illustrating the beneficial effect of parent and peer support during adolescence. / Master of Science

This dissertation comprises two manuscripts formatted for publication, preceded by a brief introduction to the dissertation project. The first manuscript addresses the recent history and development of peer observation in the United States and synthesizes the body available peer observation scholarship. Five fundamental elements of peer observation (design, community, control, training, reflection) are put forth as a nexus at which meaningful and formative peer observation can be undertaken. A selection of empirically based methods for conducting peer observation is also presented. The second manuscript is a mixed-methods descriptive study of the five fundamentals of peer observation. Three academic departments at a large land-grant university were identified, via questionnaire, as having programs of peer observation that aligned with attributes of the five fundamentals. These academic departments participated in individual case studies designed to bring-about a description of the five fundamentals as they were and were not manifest in authentic university/college contexts. / Ph. D.

The key goal in this work is to enable a flexible ground station that is not constrained to a particular mission or set of hardware. In addition, with the concepts and software produced in this thesis, it will play a significant role in educating engineers and students by providing critical infrastructure and a sandbox for ground station operations. Key pieces of software were developed in this work to create a flexible and robust software-defined ground station. Several digital transmission modes were developed in order to allow communication between the ground station and common amateur radio CubeSats and SmallSats. In order to handle distributed tasks and process at a ground station with multiple servers and controllers, a specialized actor framework was written in Python for ease of use. Actors have the ability to send messages to one another over a network, and they maintain their own memory in order to avoid synchronization problems that come with sharing memory. In addition to the software developed in this work, a novel Peer-to-Peer (P2P) protocol for a network of ground stations is proposed in order to increase coverage and access to spacecraft without requiring centralized server infrastructure. This protocol provides the method to scale the developed software architecture beyond a single ground station. Since the Virginia Tech Ground Station (VTGS) will have many concurrent processes running across multiple servers, it was necessary to apply the actor model in order to simplify the design of the system. The purpose of this thesis is to describe the developed software for the VTGS as well as the P2P protocol for a larger network of ground stations. There are three primary repositories: planck-dsp, gr-vtgs, and pystation. The planck-dsp library and gr-vtgs Out-of-tree (OOT) make up the primary digital signal processing and communications toolboxes, where GNU Radio serves as the scheduler for signal processing blocks used in flow graphs. The pystation module is the extensible software actor framework that connects various systems both locally and remotely. It is also responsible for scheduling and handling ground station requests. While the software was primarily created for the VTGS, it is general enough to apply to other ground station implementations. / Master of Science

No / The surprise advent of the peer-to-peer payment system Bitcoin in 2009 has raised various concerns regarding its relationship to established economic market ideologies. Unlike fiat currencies, Bitcoin is based on open-source software; it is a secure cryptocurrency, traded as an investment between two individuals over the internet, with no bank involvement. Computationally, this is a very innovative solution, but Bitcoin’s popularity has raised a number of security and trust concerns among mainstream economists. With cities and countries, including San Francisco and Germany, using Bitcoin as a unit of account in their financial systems, there is still a lack of understanding and a paucity of models for studying its use, and the role Bitcoin might play in real physical economies. This project tackles these issues by analysing the ramifications of Bitcoin within economic models, by building a computational model of the currency to test its performance in financial market models. The project uses established agent-based modelling techniques to build a decentralised Bitcoin model, which can be ‘plugged into’ existing agent-based models of key economic and financial markets. This allows various metrics to be subjected to critical analysis, gauging the progress of digital economies equipped with Bitcoin usage. This project contributes to the themes of privacy, consent, security and trust in the digital economy and digital technologies, enabling new business models of direct relevance to NEMODE. As computer scientists, we consider Bitcoin from a technical perspective; this contrasts with and complements other current Bitcoin research, and helps document the realizable risks Bitcoin and similar currencies bring to our current economic world. This report outlines a comprehensive collection of risks raised by Bitcoin. Risk management is a discipline that can be used to address the possibility of future threats which may cause harm to the existing systems. Although there has been considerable work on analysing Bitcoin in terms of the potential issues it brings to the economic landscape, this report performs a first ever attempt of identifying the threats and risks posed by the use of Bitcoin from the perspective of computational modeling and engineering. In this project we consider risk at all levels of interaction when Bitcoin is introduced and transferred across the systems. We look at the infrastructure and the computational working of the digital currency to identify the potential risks it brings. Additional information can be seen in our forthcoming companion report on the detailed modeling of Bitcoin.