Folksonomier, system som låter användare klassificera innehåll, blir allt vanligare på webben. Typiskt sker denna klassificering genom att användare fritt beskriver innehållsobjekt med hjälp av nyckelord.Denna uppsats presenterar en underökning av hur nyckelord förhåller sig till varandra hierarkiskt, inom ett folksonomisystem. Undersökningen är baserad på ett webbgränssnitt, där besökare kunde förfina eller förkasta förslag på hierarkier av nyckelord. Dessa förslag genererades utifrån av ett verkligt folksonomisystem.Efter analys av 400 inkomna svar dras slutsatsen att flera aspekter av metodologin måste förfinas för att tydliga resultat ska kunna uppnås. Förslag på sådana förändringar presenteras slutligen. / Folksonomies, systems for user classified content, are becoming more common on the web. Typically, these classification systems let users describe content objects by assigning them keywords ("tags").This thesis presents a study on how keywords in a folksonomy system relate hierarchically. The study is based on a web interface, where visitors could refine or reject suggestions of hierarchies of keywords. Suggestions where generated from a real folksonomy system.After analysis of 400 responses, the conclusion is made that to reach clear results, several aspects of the methodology have to be modified. The thesis ends with presenting possible ways to achieve this.

User-generated content (UGC) is a ubiquitous phenomenon on the Internet. UGC inform, entertain, and facilitate conversations among online users. The three essays of this dissertation examine different antecedents of UGC characteristics with text analytics. The first essay explored the effects of psychological distance on UGC positivity and found that spatial and temporal distance boost UGC positivity. The second essay investigates the effects of social media integration on the linguistic characteristic of UGC and showed that social media integration leads to increased review quantity, while more emotional, less rational and less negative language in UGC content. The third essay examines the impact of book-to-film adaptation on the rating and linguistic characteristics of UGC. The results suggest that, after the release of book-to-film adaptations, book ratings decline, and the use of language reflecting viewing, comparison and affective processes increase in book reviews. To summarize, the three essays in this dissertation contributes to research on UGC by improving our understanding on the various antecedents of UGC characteristics. / Business Administration/Marketing

Self-generated questions are a central mechanism for learning, yet students' questions are often infrequent during classroom instruction. As a result, little is known about the nature of student questioning during typical instructional contexts such as listening to a lecture, including the extent and nature of student-generated questions, how students evaluate their questions, and the relations among questions, motivations, and achievement. This study examined the questions undergraduate students (N = 103) generated during 8 lectures in an introductory chemistry course. Students recorded and appraised their question in daily question logs and reported lecture-specific self-efficacy beliefs. Self-efficacy, personal interest, goal orientations, and other motivational self-beliefs were measured before and after the unit. Primary analyses included testing path models, multiple regressions, and latent class analyses. Overall, results indicated that several characteristics of student questioning during lectures were significantly related to various motivations and achievement. Higher end-of-class self-efficacy was associated with fewer procedural questions and more questions that reflected smaller knowledge deficits. Lower exam scores were associated with questions reflecting broader knowledge deficits and students' appraisals that their questions had less value for others than for themselves. Individual goal orientations collectively and positively predicted question appraisals. The questions students generated and their relations with motivational variables and achievement are discussed in light of the learning task and academic context. / Educational Psychology

Journalists rely on image and video verification to support their investigations and often utilize open source tools to verify user generated content, but current practice requires experts be involved in every step of the process. Additionally, lacking custom tools to support verification efforts, experts are often limited to the utility of existing, openly available tools, which may or may not support the interactions and information gathering they require. We aim to support the process of geolocating images and videos through crowdsourcing. By enabling crowd workers to participate in the geolocation process, we can provide investigative journalists with efficient and complete verification of image locations. Parallelizing searching speeds up the verification process as well as provides a more extensive search, all while allowing the expert to follow up on other leads or investigative work. We produced a software prototype called GroundTruth which enables crowd workers to support investigative journalists in the geolocation of visual media quickly and accurately. Additionally, this work contributes experimental results demonstrating how the crowd can be utilized to support complex sensemaking tasks. / Master of Science / Journalists rely on image and video verification to support their investigations and often utilize freely available tools to verify online and digital content. Currently, experts are involved in every step of this verification process, researching and confirming or refuting the claims of images or videos. Since experts often do not have access to custom tools, they rely on already existing tools, which do not always meet their needs. One type of image verification is geolocation, in which investigators work to identify the location where a photo or video was made. We aim to support this process through crowdsourcing. By enabling a large number of people, most with no experience or prior training, to help find the location, we can provide investigative journalists with efficient and complete verification of image locations. Multiple people searching at the same time speeds up the verification process as well as provides a more extensive search, all while allowing the expert to follow up on other leads or investigative work. We produced a software prototype called GroundTruth which enables novice individuals to support investigative journalists in determining the location of images and videos quickly and accurately. Additionally, this work contributes experimental results demonstrating how these individuals can collectively support complex sensemaking tasks.

Engaging the student's prior knowledge is considered by educational researchers to be an important part of constructing a strong foundation for new learning. Diagrams are one technique used in the classroom. Jill Larkin and Herbert Simon described the computational advantages of diagrams over text when used to communicate information in their 1987 article entitled 'Why a Diagram is (Sometimes) Worth Ten Thousand Words.' This case study describes a novel abstract diagramming technique facilitated in four separate university classroom settings. Using paper and crayons, the students created three diagrams that represented the externalization of their unconscious perceptions of their own prior knowledge. The study illustrates how differences in prior knowledge can be visualized using diagrams with greater speed in less time than the traditional use of text-based descriptions. The use of the abstract diagramming technique led to an unexpected finding. The student diagrams were shown to contain a hidden conceptual topology, one that is described by Egenhofer in his 1991 article entitled 'Reasoning About Binary Topological Relations.' This topology is recommended as a framework for structuring and facilitating student collaboration and sharing of prior knowledge and new learning. The present study recommends the diagramming technique as the basis for the establishment of a standard diagram research framework that can be used across multiple research disciplines and subject domains. This dissertation describes a domain-general abstract diagram technique that can be adapted for domain-specific subjects and made operational using basic materials (paper and crayons). The study also describes the instructors' responses to questions about the diagram technique used in their classes. The case study offers recommendations for future diagram research. / Ph. D.

This dissertation presents three essays that focus on various aspects pertaining to the management of online platforms, defined as "digital services that facilitate interactions between two or more distinct, but interdependent sets of users (whether firms or individuals) who interact through the service via the Internet" (OECD, 2019). The interactions benefit both the users and the platform. Managing online platforms involves developing strategies for one or more of three value adding functions: (a) lowering search costs for the parties connecting through the platform, (b) providing a technology infrastructure that facilitates transactions at scale by sharing both demand and supply side costs; and (c) locating other audiences or consumers for the output that results from the transaction. The platform manager must manage these value adding functions. Thus, one important management task is to recognize potential asymmetries in the economic and/or psychological motivations of the transacting parties connected through the platform. In this dissertation, I empirically examine these issues in greater detail. The first essay, "Incentivizing User-Generated Content—A Double-Edged Sword: Evidence from Field Data and a Controlled Experiment," addresses the conundrum faced by online platform managers interested in crowdsourcing user-generated content (UGC) in prosocial contexts. The dilemma stems from the fact that offering monetary incentives to stimulate UGC contributions also has a damping effect on peer approval, which is an important source of non-monetary recognition valued by UGC contributors in prosocial contexts. The second essay, "Matching and Making in Matchmaking Platforms: A Structural Analysis," examines matchmaking platforms, focusing specifically on the problem of misaligned incentives between the platform and the agents. Based on data from the Ultimate Fighting Championship (UFC) on fighter characteristics, and pay-per-view revenues associated with specific bouts, we identify the potential for conflicts of interest and examine strategies that may be used to mitigate such problems. The third essay, "Matching and Making in Matching Markets: A Managerial Decision Calculus," extends the empirical model and analytical work to a class of commonly encountered one-sided matching market problems. It provides the conceptual outline of a decision calculus that allows managers to explore the revenue and profitability implications of adaptive changes to the tier structures and matching algorithms. / Doctor of Philosophy / The 21st century has witnessed the rise of the platform economy. Consumers routinely interact with online platforms ways in their day to day activities. For instance, they interact with platforms such as Quora, StackOverflow, Uber, and Airbnb to name only a few. Such platforms address a variety of needs starting from providing users with answers to a variety of questions to matching them with a range of service providers (e.g., for travel and dining needs). However, the rapid growth of the platform economy has created a knowledge gap for both consumers and platforms. The three essays in this dissertation attempt to contribute to the literature in this area. The first essay, "Incentivizing User-Generated Content—A Double-Edged Sword: Evidence from Field Data and a Controlled Experiment," examines how crowdsourcing contests influence the quantity and quality of user-generated content (UGC). Analyzing data from the popular question and answer website Quora, we find that offering monetary incentives to stimulate UGC contributions increases contributions but also has a simultaneous damping effect on peer endorsement, which is an important source of non-monetary recognition for UGC contributors in prosocial contexts. The second essay, "Matching and Making in Matchmaking Platforms: A Structural Analysis," examines matchmaking platforms, focusing on the problem of misaligned incentives between the platform and the agents. Based on data from the Ultimate Fighting Championship (UFC) on fighter characteristics, and pay-per-view revenues associated with specific bouts, we identify the potential for conflicts of interest and examine strategies that may be used to mitigate such problems. The third essay, "Matching and Making in Matching Markets: A Managerial Decision Calculus," extends the empirical model and analytical work to a class of commonly encountered one-sided matching market problems. It provides the conceptual outline of a decision calculus that allows managers to explore the revenue and profitability implications of adaptive changes to the tier structures and matching algorithms.

Background: Social media platforms, particularly through user-generated content (UGC), have been recognized as impactful channels to build communities and spread messages through content sharing. TikTok differentiates itself from other platforms by their short video format and personalized algorithm, making it an effective channel for brand-related strategic marketing activities, aimed at understanding customers engagement and brand message. Purpose: That said, this study aims to help brands effectively communicate their brand image and leverage on TikTok using UGC, by understanding what attributes of TikTok-based UGC that influences brand image. Method: To serve the purpose of this study, the research employs a quantitative approach, utilizing a survey instrument distributed to a sample of TikTok users aged 18-35. The data collected was analyzed using descriptive statistics and Pearson correlation analysis to determine the relationship between various TikTok-based UGC attributes and their influence on brand image. Conclusion: Empirical analysis reveals that attributes such as personalized content on TikTok, consumers engagement with UGC on TikTok, and positive UGC reviews were found to have a direct correlation to consumer perceptions of brand image. This underscores the potential benefits for brands that strategically incorporate these attributes into their marketing strategies through UGC on TikTok to effectively control their brand image.

In this work, we focus on two attractive crowd-based business models, i.e., user-generated content creation and freight-matching long-haul trucking. First, as elaborated in CHAPTER 2, we consider a game theoretical modeling approach for understanding the operation of non-profit UGC platforms that rely on users to create content and maintain financial sustainability. In particular, we examine several interesting research questions with practical importance and unique contributions to the literature. These research questions mainly investigate how changes in critical business factors influence the platforms' strategic effort allocation, user participation, and overall performance. Second, in CHAPTER 3, we focus on the flourishing freight-matching businesses that rely on crowdsourced drivers for long-haul trucking. In particular, although the practice suggests that shippers' ordering behaviors of freight-matching services may remarkably impact crowdsourced drivers' bidding behaviors, the literature has yet to examine this issue formally. Therefore, we collect industrial data and construct a strict empirical schema for understanding the association between shippers' order timing and freight-matching performance. Besides, by deliberately building a theoretical modeling framework and using a data-driven estimation of model parameters, we are able to simulate the freight-matching performance of adopting our empirical findings and evaluate the practical value of our study. By investigating these two prominent business models, we aim to understand the advantages of crowdsourcing businesses and the role of crowds in nowadays' business innovations. Besides, we also provide valuable managerial insights for business runners who are interested in this "young" market of crowdsourcing businesses. / Business Administration/Strategic Management

Scramjets have been identified as a potential long-term replacement for rocket and ramjet propulsion systems due to their enhanced performance at high Mach numbers. The introduction of solid fuels in these scramjet systems allows for shaping of the solid fuel cavity by additive manufacturing and introduces the possibility of enhancing combustion rates and stability. The present investigation aims to develop a coupled, high-order computational model to study the combustion of solid fuel scramjets. The primary objectives are to identify the effects of changing geometry on combustion and to better characterize the combustion process and flow patterns within a solid fuel scramjet engine. The high-Mach number of the air inflow over a scramjet cavity introduces a strong coupling between fluid dynamics, combustion, and regression time scales. Existing models often use simplified treatments of melt-layer conditions and combustion models that over-predict experimental rates, along with highly dissipative numerical schemes that inhibit the study of thermo-acoustic interactions between coherent pressure waves and the burning walls of the cavity. These limitations in current models suggest the need for a Navier-Stokes solver based on a high-order, discontinuous Galerkin method, incorporating melt layer equations and enhanced combustion manifolds. These manifolds should account for the effects of pressure and high oxidizer temperatures on flamelet dynamics. The focus is on modeling the flow field with accurate chemical heat release and residence time, to better study the effects of heat flux on the solid surface and the resulting coupling. An investigation of solid fuel scramjets was performed, and the numerical methodology with which the problem was tackled is described. A novel combustion mechanism was developed using a counterflow burner to study the combustion and regression of solid model fuel polymethyl methacrylate (PMMA). The diffusion flame between the fuel and oxidizer was studied numerically using a solid fuel decomposition and melt layer model to simulate convection and pyrolysis of the material. This model was validated using new experimental data as well as previously published works. The foam layer parameters are critical to the success of the validation. Results showed that the increased residence time of the gas in the bubbles facilitates the fuel breakdown. Fully coupled fuel injection and solid fuel surface monitoring was implemented based on this counterflow model and was a function of heat flux. Fuel regression was handled using adaptive control points for a B-Spline basis that updates based on surface movement. This methodology was used due to its resilience against the creation of surface discontinuities likely to result from large temperature gradients during combustion. Fourth-order computational simulations of ramjet combustion without regressing fuel walls using an in-house Discontinuous Galerkin approach were performed with a fully conjugate solution for the thermal wave in the solid. Results in ramjet geometries showed the turbulent combustion strongly affects the heat feedback to the walls and thus increases both the regression and fuel injection rates. Scramjet geometries were also simulated using the flamelet-progress variable approach in two different oxidizer conditions. All of these simulations showed strong agreement with experimental data and helped to uncover flame holding characteristics of the scramjet cavities and the strong coupling between the recirculation region and pyrolysis of fuel. The analysis has led to a better understanding of the effects of solid fuel scramjet geometries on mixing, enhanced modeling of acoustic instabilities in solid fuel air-breathing propulsion, and improved fuel chemistry modeling. It has been shown that cavity design significantly influences heat transfer to the solid fuel in both ramjet and scramjet conditions. The presence and thickness of the melt layer will guide designs that aim to reduce or enhance mechanical removal of fuel. Additionally, ramjet results indicate that longer cavities can couple with acoustics to induce self-excited conditions, leading to increased heat transfer to the solid. The importance of self-sustained instability and its coupling with melt layer fuel injection will contribute to improved acoustic stability. Developing pressure/temperature-dependent manifolds and melt layer models will advance our understanding of solid fuel supersonic combustion and its effects on phenomena such as blowout, fuel residence time, and solid fuel dual-mode transition. / Doctor of Philosophy / Scramjets, a type of high-speed jet engine, could one day replace rockets due to their efficiency at very high speeds. By introducing solid fuels into these engines, researchers can use advanced manufacturing techniques to shape fuel cavities, potentially enhancing the engine's performance. This study focuses on developing a sophisticated computational model to understand how changes in engine geometry affect the combustion process in solid fuel scramjets. The research aims to better understand the complex interactions between airflow, combustion, and fuel consumption, with the ultimate goal of improving engine design. The findings from this research provide valuable insights into how different scramjet designs impact fuel combustion. For instance, the design of the fuel cavity can significantly affect heat transfer, influencing the efficiency and stability of the engine. The study also highlights the importance of understanding the interaction between airflow and fuel injection, which is critical for optimizing engine performance and ensuring reliable operation at high speeds. Overall, this research advances our understanding of solid fuel scramjets and contributes to the development of more efficient and stable high-speed propulsion systems. By improving our ability to model and predict the behavior of these engines, the findings will guide future designs, potentially leading to more effective and reliable scramjets for various applications, including space exploration and high-speed flight.

Yes / This study uncovers hotel brand positioning and competitive landscape mapping by text-mining user-generated content (UGC). Rather than relying on a single dimension of consumer evaluation, the current study detects brand attributes by using both customer preferences as well as perceptual performance to develop meaningful insights. For this, the study combines content analysis and repertory grid analysis (RGA) to answer three key research issues. 111,986 hotel reviews from two biggest Chinese cities are used to explore and visualize the competitive landscape of six selected hotel brands across three hotel categories. Findings from the study will not only advance the existing literature on brand positioning and competitive landscape mapping but also help practitioners in developing brand positioning strategies to fight competitors within and across hotel categories.