About MacSphere

MacSphere is McMaster University's Institutional Repository (IR). The purpose of an IR is to bring together all of a University's research under one umbrella, with an aim to preserve and provide access to that research. The research and scholarly output included in MacSphere has been selected and deposited by the individual university departments and centres on campus.

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Recent Submissions

Efficient Transmission in the Presence and Absence of Data Privacy Using Digital Twins and Federated Optimization
(2025) Heydari, Mohammad
Mobile uplink transmission scheduling arises in many applications where devices periodically upload measurements, features, or model updates. Effective online schedulers typically rely on information that is considered private to its associated devices. For a mobile device, this may include its mobility profile, recent location(s), and experienced channel conditions. Schedulers use this type of information to perform tasks such as shared bandwidth and channel time slot assignments. In practice, however, this information may or may not be available to the scheduler due to data-privacy requirements. This thesis studies efficient transmission in both regimes while respecting practical limits on bandwidth and energy. In the first part, we study vehicles participating in FL over a shared wireless channel and seek to minimize the duration of each update period so that aggregation can proceed as quickly as possible. We formulate the joint transmission-time scheduling and bandwidth-assignment problem for each round as a mixed-integer nonlinear program and establish its NP-completeness. To obtain practical solutions, we develop approximation methods that perform a binary search on the round duration using fractional relaxations, followed by dependent rounding to produce feasible schedules. Simulation results show near-optimal update times when compared with an exact solver on the same instances, demonstrating both efficiency and scalability in the centralized, non-private setting. In the second part, we address scheduling when data privacy must be preserved. A Digital Twin (DT) may protect information that is considered private to its associated physical system, motivating the use of DTs to interact with the scheduler without exposing raw state information. We consider three energy-constrained transmission-scheduling problems: minimizing total transmission time under (i) fixed-power or (ii) fixed-rate time slotting with power control, and (iii) maximizing uploaded data within a fixed time horizon. We propose a real-time federated optimization framework in which the scheduler iteratively exchanges only aggregate signals with DTs to compute global fractional solutions without revealing private information; dependent rounding then yields implementable channel schedules for the physical systems. Experiments demonstrate consistent makespan reductions, near-zero bandwidth and energy violations, and millisecond-order end-to-end runtime on typical edge servers. To the best of our knowledge, this is the first framework that enables privacy-preserving channel sharing across DTs while maintaining strong performance. Together, these results provide a unified treatment of mobile uplink scheduling under bandwidth, energy, and data privacy considerations. The work shows how joint scheduling and fractional bandwidth assignment can accelerate learning and synchronization when full state is available and how DT assisted federated optimization can retain much of this performance when privacy requires that state remain local.
The genetic and phenotypic expression of condition dependence and sexual dimorphism within and across the Drosophila melanogaster species group and the Rhopaloa clade
(2025) Abass, Mariam
In species where the sexes face different selective pressures, the evolution of sexual dimorphism may reflect the evolution towards divergent sex-specific trait optima. Sexual dimorphism, often considered in the context of exaggerated male secondary sexual traits, is thought to be driven primarily by sexual selection. Sexually selected traits tend to exhibit heightened nutritionally sensitive expression, called condition dependence. The condition dependent expression of sexually selected traits is proposed to act as a mechanism for the maintenance of genetic variation in sexually dimorphic traits. This genic capture model has become a common explanation for the maintenance of variation in exaggerated male weapons and ornaments. In this thesis, I explore the relationship between the evolution and expression of sexual dimorphism and condition dependence using Drosophila as a model system. In chapter two, we explore the intra- and inter-specific patterns of sexual dimorphism and condition dependence and their relationship in 29 species in the Drosophila melanogaster species group. We find that sexual and fecundity selection may be acting together to drive the expression of condition dependent sexual dimorphism within species. However, sexual selection alone may not be sufficient to drive the evolution of condition dependent sexual dimorphism across species. We show that in a strongly male-biased species, D. prolongata, the relationship between sexual dimorphism and condition-dependent trait expression is not consistent with a genic capture model. In chapter three, we use RNA-sequencing to identify the degree of similarity between patterns of gene expression which coordinate sexually dimorphic trait expression and condition dependent growth in the developing forelegs of male D. prolongata. We used 1) within-species comparisons: comparing patterns of gene expression during development between the sexually dimorphic forelegs and the nearly monomorphic midlegs and 2) across-species comparisons: comparing patterns of gene expression between the developing legs of D. prolongata and D. carrolli, and D. rhopaloa (exhibiting extreme male biased dimorphism, near monomorphism, and female-biased dimorphism, respectively). In D. prolongata, we find evidence that sex and developmental condition may have a shared role in shaping the genomic architecture of the developing legs. We do not find evidence to suggest that the relationship between sex-biased and condition-dependent gene expression is consistent with the predictions of the genic capture model. Together, these findings attempt to identify how condition dependent and sexually dimorphic variation shape the genetic architecture of sexually selected traits.
Double Wahala: Help Seeking for Intimate Partner Violence among Women in Resource Constrained Settings
(2025) Alade, Omolola Titilayo
In resource constrained settings, the high prevalence of intimate partner violence (IPV) among women occurs in the context of limited access to social support systems and formal sources of help. This limits women’s access to help. Help seeking is a critical response to IPV that helps prevent and reduce re-occurrence or limit its negative consequences. Healthcare centres have been recognized as important sources of help in IPV. However, barriers to an effective healthcare response to IPV occur at various levels. Therefore, the studies in this thesis explored the latent classes of help seeking behaviour among women experiencing IPV in Nigeria, synthesized evidence on the perceptions and experiences of women seeking help for IPV from healthcare centres in sub-Saharan Africa and qualitatively described community considerations for women’s help seeking for IPV from healthcare centres in a community in Nigeria. Across the three studies, it was evident that more women sought help for IPV from informal sources compared to healthcare centres. This was corroborated by the qualitative evidence synthesis showing that of four themes described, three were barriers while only one theme reflected the hope that women have that they can get help for IPV in healthcare centres. The qualitative descriptive study built on these themes by describing community considerations for increasing and improving healthcare response to IPV. These considerations were better community engagement and awareness, better working conditions for healthcare professionals, and financial aid for women experiencing IPV. The studies in this thesis show that a lot more needs to be done to improve formal sources, specifically healthcare centres, as sources of help for women experiencing IPV. A community participatory approach is necessary to improve healthcare response to IPV without neglecting the strengthening of informal sources of help in IPV.
Stream-Based Intelligent Memory Architectures for High-Performance and Predictable Real-Time Systems
(2026) Abotaleb, Abdelrhman Mohamed Ibrahim Sayed
Emerging cyber-physical platforms such as autonomous vehicles and unmanned aerial systems increasingly integrate high-throughput workloads (e.g., perception and machine learning) with safety-critical real-time control on the same multicore, multi-channel Dynamic Random Access Memory (DRAM)-based system. While processor cores continue to scale, the memory system remains a major bottleneck: conventional hardware prefetchers and memory controllers are largely oblivious to program structure, leading to poor bandwidth utilization, high energy, and highly variable memory access latency that undermines real-time guarantees. This dissertation proposes a unified Hardware/Software (HW/SW) interface that leverages software-provided information, known prior to execution, to describe future memory access behavior to the hardware. A stream defines the underlying large, array-like data structure over which this access behavior, whether regular or irregular, occurs. Using compact stream descriptors, the software communicates future access sequences to a centralized hardware engine, which tags last-level cache misses and coordinates stream-aware optimizations across the memory hierarchy. Leveraging this interface, the thesis introduces three architectures: First, InterStellar and its multi-channel extension InterStellar 2.0 implement stream-aware DRAM controllers that perform intelligent page management and proactive DRAM-aware batching, substantially improving effective bandwidth and reducing row conflicts. Second, InterStellarRT adapts the same principles to real-time systems by forming analyzable real-time batches and applying a predictable scheduling policy, enabling tight worst-case memory-latency bounds for stream-based memory patterns. Third, COMPASS co-designs a stream-aware last-level cache prefetcher with a stream-aware memory controller, coordinating prefetch issuance with DRAM batching to reduce effective miss latency while sustaining high throughput. Evaluated across a broad set of scientific and high-performance computing workloads, these three architectures deliver substantial performance and energy improvements over state-of-the-art baselines. InterStellarRT, in addition, provides significantly tighter and formally analyzable worst-case latency bounds compared to contemporary real-time memory controllers. Collectively, the contributions demonstrate that stream-based memory intelligence is an effective approach to mitigating the memory-system vibottleneck in modern multicore platforms that integrate cache prefetching mechanisms and multi-channel DRAM subsystems The implementations of InterStellar 2.0, InterStellarRT, and COMPASS are available in the project repository: https://gitlab.com/fanosteam/fanosgem5. Each architecture is provided in a separate branch: 1) InterStellar 2.0 : https://gitlab.com/fanosteam/fanosgem5/-/tree/InterStellar-2.0 2) InterStellarRT https://gitlab.com/fanosteam/fanosgem5/-/tree/InterStellarRT 3) COMPASS https://gitlab.com/fanosteam/fanosgem5/-/tree/COMPASS
Electrochemical Carbon Dioxide Conversion into Multi-Carbon Products on Copper-Based Catalysts: from Materials to Real-World Application
(2026) Amirhossein Kora Rakhsha
In this project, we aim to transform carbon dioxide (CO₂), a key contributor to climate change, into valuable fuels and chemicals such as ethylene and ethanol, through electrocatalysis. By using renewable electricity, we seek to create a carbon-neutral pathway that reduces reliance on fossil fuels. We are particularly interested in fabrication of reliable catalysts (in this case copper-based ones), and understanding their behavior during the electrochemical reaction by using advanced characterization techniques that allow us to monitor them in real time. Ultimately, by connecting this CO₂ conversion process with existing carbon capture technologies, we hope to demonstrate a practical solution that can be scaled up for real-world application.

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