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Integrating the Top-down and Bottom-up Controls of Community Assembly
Get PDFCommunity assembly theory investigates the mechanisms through which species from a broader pool of potential colonizers form local communities at finer spatiotemporal scales. The theory is heuristic because it reduces the large number of possible mechanisms shaping communities into a tractable number of fundamental high-level processes. However, despite its heuristic value, community assembly theory is inherently context-dependent, i.e., its predictions regarding community dynamics are only valid within specific ecological conditions. Thus, a synthetic understanding of community assembly relies on identifying a few influential ecological axes that regulate the context-dependent nature of community dynamics. In this thesis, I set out to investigate community assembly along two latent ecological axes that determine the context of community dynamics. The first represents the top-down control of species pools on the membership of local communities. The second represents the bottom-up control of landscape features on species movement and interactions. By employing process-based simulation models that replicated community assembly across varied landscape structures and species pool compositions, I generated theoretical predictions about the isolated and interactive effects of both forms of control on: (i) spatiotemporal patterns in community composition; (ii) the ecological selection of prevailing life-history strategies observed in (meta)communities; (iii) the relative importance of assembly processes across space and time and throughout large-scale ecological gradients; and (iv) the trajectories of communities (towards differentiation or homogenization) in response to natural or anthropogenic disturbances. I provide empirical validation for these theoretical predictions by investigating the assembly of insect communities in distinct (bio)geographic contexts or by contrasting model predictions with empirical patterns observed in the literature. In parallel, I introduced new analytical frameworks that allowed the testing of the predictions outlined in this thesis and can be used to address other pertinent questions in community ecology. Collectively, the chapters in this thesis derive a mechanistic understanding of causal links between landscape-mediated bottom-up control, species pool-mediated top-down control, and the context-dependent nature of community assembly. Beyond its theoretical significance, this knowledge is crucial for predicting how the impact of human activities on landscapes and species pools can alter the structure, dynamics, and regulation of ecological communities
Making Books with Generative AI
Get PDFThe advent of powerful generative artificial intelligence (AI) has the potential to transform the way we create and consume artistic works, including artists’ books. This research explores the impacts of generative AI on independent publishing and book arts.
Powerful new models like GPT-3 have the potential to transform creative workflows, raising questions around automation's role and preserving human craftsmanship. Through conceptual prototypes and speculative interfaces, this study reveals opportunities and critical challenges when adopting generative techniques. Integrating GPT-3, the prototypes demonstrate AI's capabilities for enhancing ideation and production, while highlighting issues like training bias. This research aims to contribute frameworks promoting thoughtful human-machine teamwork in this context. Drawing from computational creativity research, the prototypes are evaluated for different types of exhibited creativity. By exploring the partnerships between generative models and artisanal creation, findings uncover strategies for ethical co-invention. The speculative prototypes of creative bookworks encourage discussion on emerging impacts of automation on creative roles. By revealing the current limitations and potential of AI automation, this research provides a conceptual foundation and prompts further interdisciplinary work at the intersection of independent publishing, book arts, and artificial intelligence, further exploring the codex as a site for research and creation
Emulating Android Device Drivers via Replicated Execution Context
Get PDFThe Android operating system is characterized by the many variants of its kernel, each variant being specific to the manufacturer and the hardware it is running on. At scale, this makes emulating these kernels highly challenging, as existing emulators implement only a handful of hardware boards, and extending them is impractical due to the plethora of devices in existence today. Inability to emulate Android kernels means that dynamic analysis, which can be very effective in finding security vulnerabilities, is only possible on the device itself. This not only makes such analysis more expensive, as one needs to purchase physical copies of the device, but it also limits its usefulness, as some techniques require fine-grained monitoring of the internal state, which can only be achieved in an emulated environment.
In this thesis, we present LiLi, a framework that allows security analysts to emulate selected bug-prone parts of an Android kernel. This limits the number of hardware peripherals that we need to deal with, and also allows for a more targeted analysis. It takes advantage of the fact that the Android OS is based on Linux, whose default configuration is supported by existing emulators. LiLi executes a modified stock Linux kernel within an emulator, wraps and injects the Android kernel under test into the same memory space, connects the two kernels, and successfully redirects execution to any portion of the Android kernel, while providing it a valid execution context.
We evaluate our approach by further extending LiLi with coverage-based fuzzing and testing 57 Android device drivers from ten different Android kernels, from a total of four vendors. For 40\% of the drivers, LiLi is able to successfully restore a valid execution context and enable correct emulation. Using LiLi, we were able to discover 4 zero-day vulnerabilities (2 of which are high-severity) which were confirmed by the Google security team and were awarded bounties totaling 6,000 USD
Uncured Thermoset Towpreg Tensile Characterisation: Experimental and Finite Element Analyses
No full textThis thesis presents an experimental analysis of the tensile behavior of unidirectional carbon/epoxy towpreg, focusing on the nonlinearity observed at the beginning of the stress-strain curve. Due to the matrix's high viscosity, securely holding specimens during testing was challenging, prompting modifications in the gripping method to ensure reliable data. By using a longer gauge length, the slippage impact on elastic modulus measurement was minimized, resulting in good repeatability among the test samples. Experimental findings highlighted the significant interaction between fiber waviness and the viscous matrix, leading to nonlinear tensile behavior in the beginning. The linear stiffness of the samples closely matched that of the fibers and remained unaffected by temperature variations. However, at higher temperatures, the epoxy matrix's decreased viscosity caused an upward shift in the stiffness within the non-linear region. To support the experimental findings, a micromechanical model of prepreg tow with fiber waviness was proposed. An RVE model of periodically distributed unidirectional wavy cylindrical fibers embedded within the matrix was developed to predict effective material stiffness parameters. The simulation outcomes aligned well with the result of the uniaxial tensile test of the towpreg, demonstrating the proposed RVE model's capability to predict elastic properties, considering factors like fiber arrangement, waviness, and temperature
Assessing Canadian Municipal Climate Change Adaptation Plans: Investigating Equity Considerations in Adaptation Planning
Get PDFThis research examines whether Canadian municipalities are integrating equity considerations into their local adaptation plans. I also examine whether population size, region, and consulting group involvement influence adaptation plan quality and equity considerations. My research questions are as follows:
1. Do Canadian municipalities consider equity in relation to adaptation planning?
2. Are vulnerable and marginalized groups included in the adaptation planning process?
3. Are local adaptation plans likely to reduce vulnerability for marginalized groups?
I performed a content analysis on 67 official municipal adaptation planning documents, qualitatively coding them for plan quality indicators and equity considerations. The findings reveal that neither population size nor regional affiliation significantly influences the adoption of an equity lens in adaptation plans. Moreover, there is limited insight into vulnerability reduction for marginalized communities, and the participation of these communities in the planning process is weak across all municipalities. Equity is most commonly discussed in relation to the fact base of local plans. The lack of implementation details in many plans and a deficiency in monitoring and evaluation data hinders the ability to assess whether the plans are effective in reducing vulnerability for these groups. This study emphasizes the need to move beyond symbolic gestures, urging governments to actively prioritize equity considerations in adaptation planning for the resilience and wellbeing of all community members to address the complex challenges of climate change
Force Estimation and Shape Reconstruction of Soft Robots in Contact with Fluid Flow: theory and experiment
Get PDFThis thesis explores two significant aspects of robotic-assisted surgeries. The first part focuses on a procedure called Robotic Catheter Ablation, which utilizes robots to treat a heart condition known as Atrial fibrillation. The procedure aims to determine the contact force at the robot's tip without the direct use of a force sensor, ensuring proper contact with the patient's heart. Recent findings have highlighted the importance of considering blood flow within the heart, as it can significantly impact the procedure's success, often neglected in similar studies. This research examines the experimental effects of blood flow on the movement of soft robots and demonstrates how disregarding this effect can lead to less effective treatments. Simultaneously, this study focuses on enhancing soft robots, introducing a method for determining their shape when subjected to varying forces, similar to the way blood flow affects them. This is accomplished through mathematical modeling, employing Euler-Bernoulli beam theory and cubic Bézier curves. The model's accuracy is confirmed through finite element method testing. Additionally, the research goes beyond shape prediction by including an approach known as Bayesian neural network (BNN). This BNN significantly improves our ability to update information rapidly, valuable for various real-time applications. In the final part of this research, applying the reshaped dataset from the shape reconstruction phase, it is demonstrated that the results obtained from the mathematical model can estimate forces using a new neural network, validated through experimentation. The proposed model holds potential for use in different fields of soft robotics, crucial for surgical procedures
Measuring the Leakage and Exploitability of Authentication Secrets in Super-apps: The WeChat Case
Get PDFSuper-apps such as WeChat and Baidu host millions of mini-apps, which are very popular among users and developers because of the mini-apps' convenience, lightweight, ease of sharing, and not requiring explicit installation. Such ecosystems involve several entities, such as the super-app and mini-app clients, the super-app backend server, the mini-app developer server, and other hosting platforms and services used by the mini-app developer. To support various user-level functionalities, these components must authenticate each other, which is different from regular user authentication to the super-app platform. In this paper, we explore the mini-app to super-app authentication problem, where mini-app code gets authenticated to access super-app services on the developer's behalf.
We conduct a large-scale measurement of developers' insecure practices leading to mini-app to super-app authentication flaws, among which hard-coding developer secrets for such authentication is a major contributor. We also analyze the exploitability and security consequences of these authentication flaws by examining individual super-app server-side APIs. We develop an analysis framework for measuring such authentication flaws, and primarily analyze 110,993 WeChat mini-apps, and 10,000 Baidu mini-apps (two of the most prominent super-app platforms), along with a few more datasets to test the evolution of developer practices and platform security enforcements over time. We found a large number of WeChat mini-apps (36,425, 32.8%) and a few Baidu mini-apps (112) leak their developer secrets, which can cause severe security and privacy problems for the users and developers of mini-apps. A network attacker who does not even have an account on the super-app platform, can effectively take down a mini-app, send malicious and phishing links to users, and access sensitive information of the mini-app developer and its users. We responsibly disclosed our findings and also put forward potential directions that could be considered to alleviate/eliminate the root causes of these authentication flaws
Spatial and Temporal Perspectives on the Canadian Lake Microbiome
No full textLakes are critical freshwater resources and occupy an important place in Canadian culture and recreation. Underpinning lake ecosystems are a broad diversity of microorganisms, which play central roles in regulating water quality, elemental cycles, and food webs. Lakes are increasingly menaced by a range of human pressures which are changing the composition of microbial communities in ways that are challenging to predict, largely because of the immense environmental heterogeneity among lakes at multiple spatial and temporal scales. This dissertation unites spatial and temporal perspectives on the lake microbiome to elucidate its structure, function, and environmental drivers, including human impact. To begin, two studies investigated the contemporary distributions of bacteria and protists using genome-resolved metagenomics and amplicon analyses in over 300 lakes across Canada based on the standardized sampling conducted by the LakePulse Network. For bacteria and protists, lake trophic state and the terrestrial influences of soils and land use – namely, agriculture and human population density – were drivers of taxonomic diversity and various components of microbiome function. The next two studies leveraged sediment DNA archives and paleogenetic techniques to reconstruct the historical diversity and dynamics contextualizing the contemporary lake microbiome. First, metagenome fragment recruitment was used to probe the taxonomic breadth of microorganisms preserved in preindustrial-age sediment records. Small fractions of sediment metagenomes were associated with the preferential preservation of previously undiscovered viruses and bacterioplankton, including lineages with well-characterized ecotypic diversity of paleoindicator potential. Next, multidecadal monitoring and sediment DNA records were compared from the IISD Experimental Lakes Area to evaluate how each of these time series detects eutrophication and climate change signals in lakes with different trophic state histories. Strong congruence was found between algal community turnover in monitoring and sediment records, validating the paleogenetic approach to reconstructing past ecosystem dynamics. While both time series tracked nutrient drivers in fertilized lakes, the 120-year perspective opened by paleogenetics signaled the effects of warming a decade earlier in the continuously fertilized lake than the oligotrophic systems, pointing to synergisms between eutrophication and climate change. Overall, this dissertation shows that the lake microbiome is responding to rising human impact over the past century at a continental scale, notably to effects across the land-water interface and increasingly to a changing climate
SyDRA: An Exploratory Approach to Game Engine Architecture Recovery
Get PDFGame engines provide video game developers with a wide range of fundamental subsystems for creating games, such as 2D/3D graphics rendering, input device management, and audio playback. In order to understand, develop and maintain game engines, developers need access to architectural information to make informed decisions. However, architectural information is not always readily available and is often overlooked in this kind of system. In this work, we propose, implement and evaluate an approach for software architecture recovery we call the Subsystem-Dependency Recovery Approach (SyDRA, pronounced SEE-dra). We apply it to 10 popular open-source game engines, demonstrating how the resultant architectural models can be used to visualize and grasp subsystem coupling patterns unique to each game engine. Additionally, we describe and discuss emergent architectural characteristics shared by all these game engines. Through a qualitative evaluation and a user study, we show the architectural models and visualisations we produced with SyDRA help developers understand game engine architecture more swiftly and correctly
Examining History, Design, and Pedagogy through the Eat, Waste, Make Project: A Feminist New Materialism Exploration of Canadian Food-based Waste
Get PDFThis dissertation uses a critical design praxis to explore domestic waste practices and their link to food consumption in the Canadian context. Employing feminist new materialism discourse, which challenges nature-culture divisions and human-nonhuman distinctions, I examine waste through a broad lens covering living and non-living entities. This involves three main approaches: analyzing design and pedagogy history in Canadian archives; studying the experiences of three Canadian women raised in the 1950s; and reflecting on the “Eat, Waste, Make” project, an iterative series of public pedagogy workshops designed to engage diverse food publics with food waste. The historical investigation targets key points in design and pedagogy that contributed to household waste, especially in the post-World War II era (1950s-1970s). Cultural shifts during this time promoted immediate disposal over salvage practices. I highlight the life histories of three women to whom I am related, in relation to food and waste in order to challenge archival discourses and highlight the role of everyday pedagogies. For the “Eat, Waste, Make” project I describe and reflect on the evolution of the workshops, and explain the incorporation of critical design and public pedagogy practices in the workshop series. This research contributes to interdisciplinary understandings of food waste practices, revealing gender dynamics, materiality, and patterns of consumption. Through historical analysis, personal narratives, and creative interventions, this study sheds light on the complex human-waste-materiality relationship in food consumption