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Comparative Performance Evaluation of Conventional and Folded Detector Structures for X-ray imaging
Get PDFX-ray photoconductor-based flat-panel X-ray imagers (FPXIs) produce superior X-ray image as compared to scintillator-based detectors and are the commercially available digital X-ray detectors for mammography. These detectors are, at present, under scrutiny for use in general radiography, fluoroscopy, tomosynthesis and portal imaging. Although amorphous selenium (a-Se) is the most successful photoconductor, recently, Hybrid Organic−Inorganic Perovskites (HOIPs) receive much attention for this application because of their good charge transport properties, higher attenuation coefficient and solution-based cheaper process techniques. These detectors need high detective quantum efficiency (DQE) for getting clear X-ray image.
The photoconductor layer thickness plays a very important role in conventional detector structure (i.e., a photoconductor layer is sandwiched between two electrodes where charges are collected in corresponding pixels) on imaging performances. A relatively thicker layer is required for better sensitivity. However, the thicker layer contributes to more noise and signal spreading as carriers must travel a longer distance to reach the electrodes, and thus adversely affects image resolution and DQE). In a folded structure, charge carriers travel perpendicular to the direction of incident X-rays and thus the X-ray quantum efficiency can be improved using a thicker layer without affecting the charge collection by keeping the charge collecting electrodes at a reasonable distance. It is essential to do a comparative analysis on DQE performance of both conventional and folded structure.
This dissertation focuses on developing mathematical model for studying the DQE of both folded and conventional detector structures by incorporating the quantum noise due to random charge carrier trapping in the cascaded linear system model. An analytical expression for the variance of charge collection in folded structure has been developed. The optimum values of photoconductor layer thickness and spacing between electrodes for maximizing the DQE under various material parameters and detector operating conditions are also investigated. The DQE critically depends on the detector thickness. As a result, the optimum DQE can be even below 0.3 for certain values of material and device parameters in conventional structure. On the contrary, the folded structure provides more design flexibility for achieving high DQE (even higher than 0.7) by adjusting the distance between electrodes without compromising the quantum efficiency. Since the folded structure is more complex than the conventional structure, one should prefer the folded structure if the photoconductor possesses relatively low linear attenuation coefficient for higher energy X-rays together with poor charge carrier transport properties. Moreover, it has also been found that the poly MAPbI3 detector shows significantly better DQE performance than the Amorphous Selenium Detector
PurityChecker: A Tool for Detecting Purity of Method-level Refactoring Operations
Get PDFSoftware refactoring is a vital practice in software engineering, aiming to improve code quality and maintainability. However, different refactoring instances serve different purposes. Some are purely intended to enhance code health by preserving program behavior, while others serve to eliminate defects and enable new functionality. Determining the purity of a refactoring instance, whether it is behavior-preserving (a.k.a. “pure”) or not, is an essential but often challenging task. This research introduces PurityChecker, a novel tool designed to automatically detect the purity of method-level refactoring instances in Java code through static source code analysis.
The contributions of this thesis are twofold. First, a tool has been created to assess the purity of refactoring instances, enabling the investigation of refactoring purity at a large scale. Extensive evaluations based on manually validated oracles demonstrated PurityChecker’s effectiveness, with precision and recall exceeding 90% in most cases. Second, a large-scale empirical study was con- ducted, resulting in two meticulously validated oracles, providing invaluable resources for research in software refactoring.
PurityChecker opens up new avenues for research and development. Its potential applications range from improving code reviewing processes and code quality maintenance to enabling empirical studies that leverage the concept of refactoring purity. This work is not only an important contribution to the field of software evolution analysis, but also a stepping stone for future research into refining and expanding refactoring assessment techniques
Integrity Verification for Virtualized Networks Using Side-Channel
Get PDFVirtualization of networks has recently attracted enormous interest as an enabler of high-performance, cost-effective, scalable, and reliable communication services (e.g., 5G). However, these advantages are accompanied by issues such as increased attack surface, software bugs, lack of visibility, and lack of control over in-the-cloud virtualized networks. These issues pose the risk of integrity breaches of virtualized networks preventing them from providing services as intended by their owners (i.e., network service providers). Therefore, to reap the benefits of virtualized networks, appropriate integrity verification mechanisms must be deployed to detect any integrity breaches that may arise due to these issues. On one hand, it is often challenging to find mechanisms to perform such verification under the constraints of limited access and high-scalability requirements of contemporary communication services, while, on the other hand, potential attacks are getting more and more sophisticated (e.g., attack on the underlying infrastructure, zero-day attacks, and runtime attacks). To that end, existing works can be mainly divided into two categories: pre-deployment and runtime. Firstly, existing pre-deployment approaches are applied before the deployment of virtualized networks and therefore, are unable to detect any breach of integrity at runtime. Secondly, existing runtime approaches require access to data that are typically unavailable to owners of virtualized network services. Moreover, even when such data are made available, collecting these data requires intrusive techniques that affect the performance and scalability of network services. In this thesis, we overcome all the above limitations of existing works by looking beyond what is possible with traditional direct observation-based approaches and focusing on the indirect effects of the attacks (a.k.a., side-channels). We propose a side-channel based integrity verification system that offers a practical and scalable approach without requiring access to data that are typically unavailable. For this purpose, we organize our work into three main phases. In the first phase, we propose an approach to verify the integrity of virtualized network function (VNF) chains; where the proposed system verifies a wide range of integrity breaches of VNF chains, such as, VNF bypassing, packet dropping, and packet injection without requiring access to the underlying cloud infrastructure on which the VNFs are deployed. In the second phase, we propose a mechanism to detect functional integrity breaches of the virtualized network functions (VNF) caused by code injection (through the exploitation of vulnerabilities at different levels of the virtualization ecosystem). Thus, the first two phases combined can provide overall integrity verification by guaranteeing that the components (i.e., VNFs) are working properly both collectively (i.e., packets are being forwarded properly through the service chains) and individually (i.e., each VNF is providing exactly the same functionality as intended). Finally, in the third phase, we improve the above solutions to become more efficient and resilient against adaptive attempts to deceive our mechanisms by proposing a continuous verification technique. In summary, this thesis contributes towards enhancing the comprehensiveness, practicality, and security of integrity verification for virtualized networks
Animating Gender: A Medium Drawn to Transness
Get PDFThis thesis puts animation studies and transgender studies in conversation with one another, resulting in a mutually beneficial dialogue for both disciplines. Though these fields may seem entirely unrelated, they bear many similarities. Animation studies’ central subject, animation, has (somewhat paradoxically) yet to be clearly defined. Karen Redrobe notes, the term animation is “rarely clear,” and this indeterminacy is largely attributed to the medium’s broad boundaries and numerous forms (255). Notably, trans studies’ relation to gender is similarly broad and ambiguous. During a recent seminar, Cáel Keegan responded to a question asking for a trans studies definition of gender by saying, “I usually tell my students, ‘We don’t know what gender is; we just know some things about it’” (“Getting Disciplined: A Conversation”). The similarities do not end there, as both disciplines also share contempt for deterministic logics, complex relations between performance and materiality, and debated links to reality/realism. My research uses these commonalities as a starting point for a dialogue between these fields of study so as to see how their respective insights and scholarship may benefit the other, with a focus primarily on the ways animation may contribute to trans studies’ understanding of gender. By employing a methodology similar to that of Thomas Lamarre’s The Anime Machine, I focus on the tendencies and inclinations of animation to demonstrate how the medium enables astute explorations of gender’s mechanisms, thereby yielding valuable insights into how traditional gender roles are maintained and how they may be reimagined... or perhaps, redrawn
“Bizindan aabajitoon Shkiizhiigoon gaye gitowagan” Listen using Eyes and Ears
Get PDFBoozhoo, Amanda Shawayahamish ni-di-shin-i-hkaaz, Animbiigoo Zaagi'igan Anishinaabek ni-n-doo-jii. Hi, my name is Amanda Shawayahamish. I come from Lake Nipigon Reserve. I am an Anishinaabe (Ojibwe) woman, wife, stepmother, Auntie, bead artist and graduate student at Concordia University exploring reconnection and reclamation to my Anishinaabe identity and traditions through beadwork, storytelling and strengthening relationships with my family and community. I blend autoethnographic and Indigenous Research Methodology to tell the story of my family and myself on this journey. Auto-ethnography in an Anishinaabe context will be a guide to tell my “story” in a narrative research-creation project. I share my experience and journal entries from my and my family’s visit to Ombabika and Auden, Ontario where my ancestors originated. My research collaborators are my family and cherished members of my community, so it is very personal. Sometimes, it feels as if the expectations of the university are counterchallenging what I know, and our ways of being as Anishinaabe. My process is not linear; it’s a circular path. I hope that my experiences will guide other Indigenous Peoples on their pathway. The objective of my MA research-creation project is to challenge academic conventions and demonstrate the importance of Indigenous Research Methodologies and approaches.
Keywords: Indigenous, Anishinaabe women, Anishinaabe, Indigenous autoethnography, Indigenous storytelling, Anishinaabe storytelling, Reclaiming Anishinaabe identity, reclamation, Anishinaabe and/or Indigenous beadwor
A Model and Performance Based Analysis of Cu/CeO2/ZrO2 for Methanol Synthesis from Syngas
Get PDFMeeting the ever-increasing energy demands while adhering to strict environmental regulations remains a significant global challenge. Methanol (CH3OH) is a significant sustainable chemical feedstock resulting from thermo-catalytic CO2 hydrogenation through heterogeneous catalysis. It serves as a vital fuel for internal combustion engines and fuel cells while also serving as a foundational molecule for the synthesis of various chemicals and sustainable fuels such as Dimethyl ether and biodiesel. The catalytic synthesis of methanol from CO2 typically requires high temperatures due to the high molecular stability of CO2. However, although higher temperatures facilitate the activation of CO2, a significant increase in the unwanted formation of CO through the reverse water-gas shift (RWGS) reaction is enhanced as well, thereby reducing the selectivity of methanol.
This research focuses on the synthesis of methanol from syngas, with specific emphasis on the catalyst type and the associated reaction kinetics and thermodynamics. It explores a novel catalyst, Cu/CeO2/ZrO2 that exhibits superior performance in terms of methanol yield and selectivity in addition to a delayed crossover temperature, the temperature beyond which the selectivity of CO is higher than that of methanol, when compared to the commercial catalyst Cu/ZnO/Al2O3. A distinctive aspect of this study is the modification of catalyst kinetics through a set of sensitivity analysis and design specs performed in the ASPEN PLUS V.12 software to align with documented lab and experimental results. This is followed by a scale-up of the chemical process to evaluate the catalyst's performance on an industrial level in comparison to the commercial catalyst currently in use, where the Cu/CeO2/ZrO2 catalyst prevailed as well in terms of methanol yield and selectivity.
The kinetic model studied is based on a dual-site LHHW adsorption mechanism where CO and CO2 adsorb competitively on one site (σ1) and H2 and H2O adsorb competitively on a second site (σ2), with the dissociation of H2 over metallic cupper. The adsorbed hydrogen preferentially hydrogenates the carbon atom giving rise to the formate route, where methanol can be formed either via the direct route (directly from CO2) or via the indirect one (CO obtained from the reverse water gas shift, RWGS, reaction). This work also encompasses the diverse formulations of driving force expressions, which are contingent upon the specific rate-determining step of the particular reaction. Additionally, the investigation considers optimal reactor dimensions and conditions for the catalyst's optimal performance and assesses the physical properties of both the new and commercial catalysts and their economic viability within the industry, taking into account factors such as reactor size, temperature, and pressure.
Overall, this research delves into the thermodynamics, kinetics, and reactor design associated with methanol synthesis from syngas, investigating the performance of a newly developed catalyst on an industrial scale, while considering its economic feasibility compared to the existing commercial catalyst
Pro Christo: Theological Motivations behind Irish Peregrinatio
Get PDFTo most modern-day thinkers a pilgrimage entails a journey to a sacred place. Thus, the primary purpose of the voyage is to reach a locale that holds special meaning for the pilgrim. Typically, the end destination is a place where a significant familial, historical, or religious event has occurred. In contrast to the contemporary understanding of pilgrimage, some Irish Christian monks of Late Antiquity undertook sacred journeys of an indefinite duration with no express terminus in mind and they vowed never to return to their homelands: a practice commonly known as peregrinatio. This thesis explores nine potential theological motivations behind the practice of permanent religious self-exile. To ascertain which religious impetuses prompted historical figures such as Saint Columba (521-597 CE) and Saint Columbanus (540-615 CE) to undertake peregrinatio I examine a variety of scriptural and traditional precedents, as well as early Christian treatises and contemporaneous writings associated with these two renowned
peregrini
Investigating the impact of feedback intervention and social facilitation on users’ satisfaction, productivity and mindfulness
Get PDFAmong many productions and lifestyle technological products, scheduling applications are emerging as a viable solution. Existing research has studied productivity with meagre attention to continuance intention to use the technology. The current study attempts to examine users’ continuance intention in the context of scheduling mobile application by integrating expectation confirmation theory with feedback intervention theory and social facilitation theory. Specifically, this study will extend the expectation confirmation model (ECM) by adding feedback interventions and social facilitation as antecedents to ECM to examine continuance intention based on variables of scheduling applications. A one week long longitudinal experiment with 55 participants was conducted assigning them different scheduling tasks of a mobile application followed by a post study questionnaire. Structural Equation Modeling (SEM) was employed to validate the proposed research model and test the hypotheses. We found a significant influence of perceived usefulness and satisfaction on users’ continuance intention leading to positive effect on productivity with use of application. However, no significant relationship was found between perceived usefulness and satisfaction. Furthermore, the study found a strong effect of confirmation on satisfaction and a positive influence of satisfaction on mindfulness. This study will contribute to expanding our understanding of the factors that influence users’ continuance intention of using scheduling mobile applications and their impact on productivity and mindfulness
« Everything in Moderation Except… »: histoires des pratiques médiatiques féministes au Studio XX/Ada X de 1995 à 2000
Get PDFAu début des années 90, parallèlement à la démocratisation de l’accès à Internet et à l’ouverture publique du World Wide Web, une vague d’artistes, de théoricien·nes et de technicien·nes féministes développe de nouvelles pratiques pour déconstruire les conceptions genrées de la technologie par l’entremise du cyberféminisme. À Montréal, au Canada, ce mouvement cyberféministe se traduit par l’émergence du Studio XX (aujourd’hui nommé Ada X), un organisme qui entend ouvrir le cyberespace aux femmes en leur fournissant les outils nécessaires pour le développement d’un engagement critique et créatif avec les technologies numériques. Le présent mémoire propose une analyse historique des pratiques médiatiques et du travail de connectivité féministes effectué par les membres du Studio XX, de sa fondation en 1995 jusqu’au tournant du nouveau millénaire. À partir d’une collecte documentaire et d’histoires orales, ce projet met en œuvre une méthodologie hybride qui s’intéresse tant aux réseaux de relations matérielles qu’aux discours et aux pratiques qui ont permis la formation du Studio XX
Upper Extremity Injury Prevention Programs for Adolescent Throwing Athletes and the Connection to Process-Oriented Assessment of Physical Competence: A Scoping Review
Get PDFChildren and adolescent athletes participating in throwing sports are particularly susceptible to upper extremity overuse injuries compared to adults, often attributed to factors such as poor technique and balance. This study aims to explore the potential correlation between process-oriented assessments of throwing skill and injury prevention in youth athletes. Through a systematic search of databases including PUBMED, MEDLINE, and SPORTDiscus, interventions focusing on upper extremity injury prevention programs and process-based physical competence assessment tools for throwing skill were identified. Criteria for study inclusion encompassed physically and mentally healthy participants aged 8-19 years, with exclusion criteria eliminating review papers, non-English language publications predating 2000, inaccessible full texts, and samples involving individuals with existing shoulder or elbow pain or injury. While formal risk of bias assessment was not conducted due to study heterogeneity, our findings indicate commonalities in process-based assessment criteria across throwing phases, highlighting specific pitching kinetic and kinematic flaws integral to evaluating technique quality and effectiveness. Despite this, existing injury prevention programs inadequately address the multifactorial nature of throwing injuries in youth athletes, necessitating further investigation into modifying throwing techniques through process-oriented physical competence assessment tools. Prospective assessments should prioritize integrating technique-oriented biomechanical analyses within injury prevention strategies to mitigate upper extremity injury risk effectively