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<p>As intrusion attacks on systems become more and more complex, the tools trying to stop these attacks must follow. This thesis has developed a testbed to test and evaluated three freely available protection tools for the GNU/Linux platform to see how they fare against attacks.</p>

The main topic of this research is the impact to the tsunami-inundated area of the southeast coast of Taiwan caused by earthquakes. According to regression relationship (G-R relation) between the earthquake magnitude and frequency proposed by Gutenberg and Richter (1944), the expected number of tsunamigenic earthquake is estimated. Using the linear shallow water equations of COMCOT (COrnell Multigrid COupled Tsunami model), the propagation of tsunami in the ocean is simulated, and the reciprocal Green's function was applied to save the computing time of COMCOT model. Then, the seismic solution parameters are substituted to acquire a water level distribution of tsunami. Solitary waves of different wave height are used to compute the range and the probability of tsunami inundation at the southeast coast of Taiwan.

As intrusion attacks on systems become more and more complex, the tools trying to stop these attacks must follow. This thesis has developed a testbed to test and evaluated three freely available protection tools for the GNU/Linux platform to see how they fare against attacks.

Programmers who want to improve their skills and background in software development rely heavily on developer social platforms such as GitHub and Stack Overflow to enhance their learning. Stack Overflow provides answers to questions they have about languages or library skills they wish to acquire, while contributing to open-source projects hosted on sites like GitHub gives them valuable experience. Students also use these platforms during their education: most will rely heavily on Stack Overflow at some point in their schooling, while many can benefit from contributing to GitHub projects to build their expertise and professional portfolios. We already know from previous research that developers face barriers participating on these platforms, and therefore we may expect that at least some students will experience similar or possibly even bigger barriers. This research describes a semi-structured interview study followed by a survey with university students to explore how they use the GitHub and Stack Overflow platforms. I identified the benefits the students report from using these tools and the barriers they face. I have concluded with some preliminary recommendations on how to reduce the hurdles students may face with these and other developer social platforms, and I have also suggested future work to mitigate these roadblocks. / Graduate

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In the era of Linux being omnipresent, the demand for dynamically extending kernel capabil- ities without requiring changes to kernel source code or loading kernel modules at runtime is increasing. This is driven by numerous use cases such as observability, security, and network- ing, which can be efficiently addressed at the system level, underscoring the importance of such extensions. Any extension requires programmers to possess high levels of skill and thor- ough testing to ensure complete safety. The eBPF subsystem in the Linux kernel addresses this challenge by allowing applications to enhance the kernel's capabilities at runtime, while ensuring stability and security. This guaranteed safety is facilitated by the verifier engine, which statically verifies BPF code. In this thesis, we identify that the verifier implicitly relies on safety assumptions about its runtime execution environment, which are not being upheld in certain scenarios. One such critical aspect of the execution environment is the availability of stack space for use while executing the BPF program. Specifically, we high- light this fundamental issue in certain configuration of the BPF runtime environment within the Linux kernel and how this unsafe composition allowed for kernel stack overflow, thus violating safety guarantees. To tackle this problem, we propose a stack switching approach to ensure stack safety and evaluate its effectiveness. / Master of Science / Many platforms worldwide, including Meta, Netflix, Google, Cloudflare, and others, rely on the Linux kernel to manage their servers. To ensure system security, improve monitoring, and enhance networking efficiency, various kernel capabilities are dynamically added or re- moved at runtime without the need for reboots, thus minimizing downtime for users. The Linux Extended Berkeley Packet Filter (eBPF) subsystem facilitates dynamic and safe ex- tension by securely verifying the code injected into the kernel. This eases server maintenance tasks, eliminating concerns about system crashes when making runtime changes as eBPF is guaranteeing safety at all times. In our research, we demonstrate that if we attach verified eBPF in a certain manner, we can potentially stack overflow the kernel stack and crash the whole kernel due to unsafe composition with the Kernel. We also propose two solutions to this problem, which can ensure that eBPF remains safe while adhering to the guarantees it provides.

The phenomenal experience of our visual perception, what it is like to be in that state, is something that we might take for granted. However, looking closer at the neural correlates of visual processing in relation to phenomenal experience we recognize that it is a complex issue. Whether our subjective experience of our visual representation of the world is attached to cognitive functions, like working memory and attention, or whether some sort of richness overflows such functions, is an ongoing debate within cognitive neuroscience. Advocates for overflow argue that phenomenal experience is the result of activity in posterior occipito-temporo-parietal areas and is independent of attention, while those within the non-overflow position mean that for phenomenal awareness to arise activity in higher-level areas like the prefrontal lobe is needed. Finding evidence for unattended visual phenomenal consciousness without access consciousness would support the overflow position since it could indicate phenomenal experience as independent of attention. In addition to this debate, researchers need to keep in mind what methods are being used to measure phenomenal experience, since several biases potentially follow studies using introspective measures. Through this systematic review, a search string provided empirical studies based on fMRI that investigated unconscious and conscious visual processing. The results of this review show little or weak evidence for unattended visual phenomenal consciousness and do not seem to overflow cognitive functions.

Master of Science / Department of Computing and Information Sciences / William Hsu / The Lambda Architecture is the new paradigm for big data, that helps in data processing with a balance on throughput, latency and fault-tolerance. There exists no single tool that provides a complete solution in terms of better accuracy, low latency and high throughput. This initiated the idea to use a set of tools and techniques to build a complete big data system. The Lambda Architecture defines a set of layers to fit in a set of tools and techniques rightly for building a complete big data system: Speed Layer, Serving Layer, Batch Layer. Each layer satisfies a set of properties and builds upon the functionality provided by the layers beneath it. The Batch layer is the place where the master dataset is stored, which is an immutable and append-only set of raw data. Also, batch layer pre-computes results using a distributed processing system like Hadoop, Apache Spark that can handle large quantities of data. The Speed Layer captures new data coming in real time and processes it. The Serving Layer contains a parallel processing query engine, which takes results from both Batch and Speed layers and responds to queries in real time with low latency. Stack Overflow is a Question & Answer forum with a huge user community, millions of posts with a rapid growth over the years. This project demonstrates The Lambda Architecture by constructing a data pipeline, to add a new “Recommended Questions” section in Stack Overflow user profile and update the questions suggested in real time. Also, various statistics such as trending tags, user performance numbers such as UpVotes, DownVotes are shown in user dashboard by querying through batch processing layer.

Os vertedores são estruturas hidráulicas construídas para controlar o nível d’água do reservatório, permitindo a passagem das vazões escoadas com a máxima eficiência possível sem provocar problemas à estrutura. Para atingir este objetivo, as condições de aproximação do escoamento à estrutura e a forma geométrica do perfil vertente são muito importantes. O controle da soleira por comportas provoca uma mudança significativa nas condições de escoamento sobre o perfil vertente. O posicionamento e a forma da comporta tem forte influência no comportamento do coeficiente de vazão e nas pressões sobre a soleira. A formação de vórtice é um fenômeno indesejável que pode ocorrer quando a operação da comporta é parcial, prejudicando a capacidade de vazão e provocando vibrações na estrutura. Este trabalho apresenta uma abordagem teórica sobre o assunto vertedor de superfície e escoamento sob comportas, apresentando resultados de diferentes estudos para melhor compreensão do funcionamento do vertedor. / Spillways are hydraulic structures constructed to control the water level of the reservoir, allowing the overflows with the maximum possible efficiency without provoking problems to the structure. The approach flow pattern to the structure and the geometric form of the spillway profile are basic importance. The control of the spillway by the floodgates modifies the draining conditions. The positioning and the form of the gate have strong influence in the behavior of the discharge coefficient and the pressures on the surface profile. A vortex formation is an undesirable phenomenon that it can occur when the operation of the floodgate is partial, reducing the discharge coefficient and produce vibrations in structure. This work presents a theoretical approach about flow over spillway and under of the partial opening of the floodgate, presenting results of different studies for better understanding the function of the spillway.