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Design of Frequency-Selective Surfaces for Advanced Applications
Get PDFThe advancement of mobile technology is driven by the requirements for wider bandwidth, higher data rates, a large number of users, and reliable connectivity. The fifth generation (5G) mobile network is currently in its early stages of commercialization with two frequency bands allocated for its technology. Frequency-selective surfaces (FSS) form a promising technology to help meet these requirements. Extensive research has been conducted on the use of FSSs as spatial filters in the sub-6GHz and millimeter-wave (mm-wave) spectra, as they are able to impart screening properties in the spatial domain. Therefore, this dissertation presents works focused on FSS technology to demonstrate and verify its advantages.
First, a new polarization converter system using only a single-layer FSS is proposed. Design equations are introduced for the four-arms star geometry which is used as polarizing element. Polarization converters have become popular in different communication systems due to their characteristics of mitigating the effects of polarization mismatching, thus improving signal strength.
Second, an ultra-wide band-stop FSS operating at K- and Ka-bands for mm-wave applications is presented. This structure comprises of double-layer FSS with simple modeling, where a series of basic equations are implemented and described. When the proposed resonators are cascaded, they offer wide bandwidth, eliminating the need for extra layers.
Third, a new beam-tilting and gain enhancement system operating at 28 GHz is proposed. The system is composed of a bio-inspired bow-tie antenna as excitation source and a single-layer FSS positioned at the bottom of the antenna. The effect of FSS panel size is investigated to achieve the better antenna performance.
Fourth, a system of closely coupled complementary and passive FSSs that achieves dual- and triple-band operations is presented. Four configurations of the elements are investigated, which can present two and three transmission bands in one or both polarizations by inducing an electromagnetically induced transparency effect.
Fifth, a novel reconfigurable complementary-inspired FSS with reconfigurable frequency response is described. The proposed structure consists of two resonators with immersed biasing network, and only a single PIN diode per unit cell as active device. Single- and dual-passband performance is achieved by switching the diode’s state from off to on. When the threshold voltage is applied, no passband appears.
Sixth, two high-gain beam-switching antenna systems are presented. Both systems comprise of a dipole antenna as excitation source and single-layer PIN-diode-switched FSS panels as mechanism of reconfiguring the radiation pattern. The first system is configured as a reconfigurable corner antenna with large beam-switching range. The second system can steer the beam in the azimuth and elevation planes.
Therefore, the works developed in this dissertation prove the FSS’ reliability in the sub-6GHz and mm-wave frequency ranges for different and advanced applications.Graduat
Library usage analysis in the C++ codebase of Fedora Linux 37
Get PDFC++ source code analysis is conducted at scale. A framework is proposed for analyzing the C++ codebase of operating systems that employ the dnf package manager, such as Fedora Linux and Red Hat Enterprise Linux. The framework can run an arbitrary static analysis tool over software packages that contain C++ code from compatible operating systems. In order to evaluate the effectiveness of the framework and to better understand how the C++ language is used in practice, a C++ analysis tool is developed to study library usage with a fine level of granularity, considering instances of uses of types, type aliases, member/non-member functions, variables, and enumerators.
Our framework, combined with the C++ library usage analysis tool, is used to analyze 2 379 software packages from the codebase of Fedora Linux 37. The number of packages analyzed is two to three orders of magnitude larger than that of previous C++ research. We applied our library usage analysis tool to nearly 400 million lines of C++ code across these packages. Leveraging the Clang compiler front-end libraries, our tool extracts information from correctly parsed C++ code, which is an improved approach compared to many existing studies. As a result, the tool provides an accurate collection of library usage instances from C++ software.
Numerous observations are made regarding various aspects of library usage that can facilitate improved teaching of C++, aid in the refinement of C++ libraries, and help guide the future evolution of the C++ standard. For example, our analysis reveals that C++ programmers rarely use some C++ standard library algorithms designed for specialized purposes or combined operations. These algorithms often appear in less than 1% of all C++ software packages investigated. We suggest that the standard library exercise caution when adopting infrequently needed algorithms to maintain a streamlined interface. Such observations summarize current trends in C++ library usage and provide recommendations for improving the C++ language and its libraries.Graduat
Micro- and macro-scale topology optimization of multi-material functionally graded lattice structures
No full textLattice structures are becoming an increasingly attractive design approach for the most diverse engineering applications. This increase in popularity is mainly due to their high specific strength and stiffness, considerable heat dissipation, and relatively light weight, among many other advantages. Additive manufacturing techniques have made it possible to achieve greater flexibility and resolution, enabling more complex and better-performing lattice structures. Unrestricted material unit cell designs are often associated with high computational power and connectivity problems, and highly restricted lattice unit cell designs may not reach the optimal desired properties despite their lower computational cost. This work focuses on increasing the flexibility of a restricted unit cell design while achieving a lower computational cost. It is based on a two-scale concurrent optimization of the lattice structure, which involves simultaneously optimizing the topology at both the macro- and micro-scales to achieve an optimal topology. To ensure a continuous optimization approach, surrogate models are used to define material and geometrical properties. The elasticity tensors for a lattice unit cell are obtained using an energy-based homogenization method combined with voxelization. A multi-variable parameterization of the material unit cell is defined to allow for the synthesis of functionally graded lattice structures.The authors acknowledge Fundação para a Ciência e a Tecnologia (FCT) for its financial support via the project LAETA Base Funding (DOI: 10.54499/UIDB/50022/2020).FacultyReviewe
The salt cod saga: Examining drivers of decline in the Pacific cod fishery (1915-1940)
Get PDFMarine historical ecology and environmental history aim to reconstruct past fisheries to reveal ecological changes and human-ocean relationships. Most existing research emphasizes prominent fisheries with lasting economic and cultural impacts, often overlooking lesser-known fisheries, such as the early 20th-century Pacific salt cod fishery. This fishery operated in the shadow of the dominant Atlantic cod, failing to gain similar significance, and has remained largely understudied.
This research investigates the sociopolitical factors influencing the decline of the Pacific salt cod fishery in the 1930s, while also examining the changing relative abundance of Pacific cod during its operation. Utilizing the historical journal Pacific Fisherman, which documented contemporary fishery operations, this research identifies key constraints: limited markets, shifting consumer preferences, and high operational costs hindered mechanisation and product competitiveness in a changing societal landscape. Furthermore, localized depletions and a trend of decreasing fish body size occurred during the fishery's lifespan. The results suggest that the fishery's failure was profoundly shaped by its societal, political, and temporal contexts, particularly as it declined while other fisheries industrialised. This thesis addresses the gap in literature concerning the decline of the Pacific cod fishery and contributes to the understanding of lesser-studied, pre-industrial fisheries. It offers valuable insights into the importance of reconstructing historical fisheries data, especially when such data are scarce.Graduat
Nihonjin Kyoushi Dake?: The Perceptions and Beliefs of a Non-Native Speaking Teacher in a High-intermediate Japanese Language Class
Get PDFWithin non-native speaking teacher (NNST) research, literature concerning NNSTs within the Canadian Japanese-as-a-foreign language (JFL) context is limited. Previous research has shown that prevailing preferences for NSTs due to perceived linguistic and pedagogical capabilities creates negative implications for NNSTs, such as teaching anxiety, confidence issues, and workplace challenges (i.e., hiring and discrimination) (Holliday, 2006; Phillipson, 1992; Kickzokiak & Wu, 2018; Faez & Karas, 2017; Park, 2012; Tsuchiya, 2020). By using Scholarship of Teaching and Learning (SoTL) and qualitative and quantitative methods (i.e., reflexive journal entries, pre- and post-course surveys, language logs, follow-up interviews, and Likert-scale questions), this study addresses the gap of scarce literature on NNSTs in the Canadian JFL field by investigating the instructional practices used by a NNST and students’ and the instructor’s perceptions and beliefs of the NNSTs’ capabilities in a high-intermediate Japanese class. Key findings of this study are that tasks benefit students’ learning of professional Japanese communication, NNSTs have the capabilities to teach high-level and pragmatic-focused speaking courses, and, students’ preferences for their instructor are based on their instructors’ individual skills and teaching attitudes rather than their nativeness. These insights provide valuable implications for academic and practical fields, offering novel findings about NNST capabilities. Administrators can use this information for more informed hiring decisions and establish collaborative models based on the unique strengths of both NSTs and NNSTs. These recommendations foster hope for NNSTs by advocating for equity, diversity, and inclusion, thereby transforming student learning within higher education.Graduat
Water-soluble photoswitchable supramolecular hosts based on the hemiindigo chromophore
Get PDFThe constant search for new and unusual hosts is what pushing supramolecular chemistry forwards. The scope of their applications is immense: drug recognition and reversal, novel materials, catalysis, purification and separation of chemicals etc., not to mention a fundamental insight into chemical and biological systems that can be gained by studying them. Sulfonated calixarenes constitute an important family of such hosts. Their exceptional binding properties coupled with water-solubility, high stability and endless potential for synthetic modifications make them perfect candidates for study. There are numerous examples of those macrocycles, modified in a way that introduces a fluorescent chromophore, enabling them to be used as detectors for various guests. Yet, cases of them being able to change their properties upon irradiation with light – having a photoswitchable chromophore – remain particularly scarce. This work attempts to present such system – a pair of sulfonated calixarenes, calix[4] and calix[5]arene with a hemiindigo moieties installed on the upper rim. Here we demonstrate their synthesis, as well as a study into their photophysical and supramolecular properties. Various advanced NMR techniques such as DOSY and NOESY were used in conjunction to demonstrate differences in their aggregation.Graduate2025-08-1
Accelerating fluid dynamics problems in planet formation with machine learning
No full textI develop two machine learning tools for solving forward and inverse problems in protoplanetary disks. The first tool, Protoplanetary Disk Operator Network (PPDONet), predicts the solution of disk--planet interactions in real--time. PPDONet is based on Deep Operator Networks (DeepONets), a class of neural networks capable of learning non--linear operators to represent deterministic and stochastic differential equations. It maps three scalar parameters in a disk--planet system -- the Shakura \& Sunyaev viscosity , the disk aspect ratio , and the planet--star mass ratio -- to steady--state solutions of the disk surface density, radial velocity, and azimuthal velocity. Comprehensive testing demonstrates the accuracy of PPDONet, with predictions for one system made in less than a second on a laptop. A public implementation of PPDONet is available at \url{https://github.com/smao-astro/PPDONet}.
The second tool, Disk2Planet, infers key parameters in disk-planet systems from observed disk structures. It processes two-dimensional density and velocity maps to output the Shakura--Sunyaev viscosity, disk aspect ratio, planet--star mass ratio, and the planet's location. Disk2Planet integrates the Covariance Matrix Adaptation Evolution Strategy (CMA-ES), an evolutionary algorithm for complex optimization problems, with PPDONet. Fully automated, Disk2Planet retrieves parameters within three minutes on an Nvidia A100 GPU, achieving accuracies ranging from thousandths to percentages. It effectively handles data with missing parts and unknown levels of noise.
Together, these tools advance the field of planet formation by providing rapid, accurate solutions and parameter inferences for disk-planet systems, enhancing our understanding of the underlying physics of protoplanetary disks.Graduate2025-08-1
SERPINE1/PAI-1 role on blood flow, stalling and vessel width in stroke
No full textThe brain relies heavily on the proper function of microvascular hemodynamics such as blood flow for sufficient oxygenation and clearance of metabolic waste. Therefore, it is no surprise that damage to blood vessels can result in heterogenous blood flow and obstructions furthering the effects of injury. Ischemic stroke can lead to a long-lasting disruption of blood flow in microvessels surrounding the infarct site, exacerbating injury beyond the initial insult. Homeostatic blood clotting and proteolytic (clot-busting) pathways are likely fundamental to regulating post-ischemic capillary blood flow, and thus functional recovery. We have recently discovered that the SERPINE1 (Serp1) gene, encoding for Plasminogen Activator-Inhibitor-1 (PAI-1), is highly expressed along blood vessels following photothrombotic stroke in the rodent somatosensory cortex. Therefore, we explored the role of Serp1/PAI-1 on cortical blood flow and its potential downstream effects following experimentally induced ischemic stroke.
In the first aim, we examined the spatial and temporal expression of Serp1 post-stroke across multiple days using immunohistochemistry and confirmed with whole tissue RNA sequencing. We discovered that Serp1/PAI-1 expression is highly upregulated 3-days post-stroke (i.e., subacute), and interestingly, this expression was brain-wide. We also obtained RNA levels at 3-days confirming an upregulation in Serp1 post-stroke. We then successfully performed an endothelial-specific knockdown (KD) of Serp1 which we confirmed using RNA seq. In the second aim, using in vivo 2-photon imaging, we longitudinally imaged superficial cortical blood flow in adjacent and distant areas to the infarct in both Serp1+/+ and cerebral endothelial Serp1 KD mice (Serp1-/-). We discovered reduced blood flow in Serp1-/- mice in the penumbra and distant regions following stroke in the subacute (3d) and chronic phase (35d). The effects of the reduced blood were prominent in arteriole capillaries, and surprisingly, blood flow did not recover in Serp1-/-. In the third aim, we measured vessel width in the penumbra and distant regions across the imaging days and separated them by arteriole and venule capillaries. Surprisingly, we found that arteriole and venule capillaries in Serp1-/- were constricted in the subacute and chronic phase post-stroke, whereas in Serp1+/+, capillaries were dilated in the subacute phase only. These respective effects mimicked the observed heterogenous blood flow (increase in Serp1+/+ and decrease in Serp1-/-) between the genotypes. In the fourth aim, we used in vivo 2-photon imaging to longitudinally label leukocytes with anti-CD45.2 to distinguish between the type of stalling. Surprisingly, we found that, alongside Serp1+/+, the total number of stalls increased in Serp1-/- mice, despite the presumed coagulant role of PAI-1, which was mediated by a greater number of leukocyte stalls over red-blood cell (RBC) stalls. In the fifth aim, we analyzed neuroinflammatory gene expression in both Serp1+/+ and Serp1-/- mice in the subacute phase post-stroke. We found an asymmetrical distribution in favor of upregulating neuroinflammatory genes as an effect of stroke with Serp1 as one of the top genes in Serp1+/+. Interestingly, the effect of Serp1 KD overall reduced the fold change of the genes highly expressed in Serp1+/+ indicating for a potential beneficial and protective role of the KD. These findings reveal that Serp1 KD significantly affects microvascular hemodynamics and leukocyte recruitment, suggesting that merely increasing clot degradation (i.e., tissue plasminogen activator (tPA) treatment) following stroke may not necessarily improve local blood flow to penumbra. In combination with the genomic changes observed, Serp1 KD shifted the distribution of the neuroinflammatory genes, which may also suggest for a protective role in KD post-stroke. Altogether, Serp1 KD elucidated a complex set of microvascular-related and genomic changes that requires further investigation into its role in stroke recovery.Graduat
Lightweight and explainable deep learning model for EV battery voltage prediction
No full textElectric vehicles (EVs) play an important role in reducing the greenhouse gas emissions by providing an environment-friendly alternative to the fossil-fuel-based means of transportation. EVs are typically powered by Li-ion battery packs supported by a Battery Management System (BMS). The latter is tasked with monitoring and keeping the battery voltage, current, and temperature within safe operating limits, as well as estimating and improving the battery performance-related parameters, such as the battery state-of-charge and lifespan. In this thesis, we aim to extend the BMS capabilities by enabling battery voltage predictions under a given load profile (i.e., discharge/charge current varying over time). Such predictions are useful for proactive (as opposed to reactive) load management, as they allow a BMS to forecast the battery voltage behaviour under various anticipated load conditions.
Using a data-driven deep learning (DL) approach, we propose a novel model that generates battery voltage estimates given the battery current, temperature, and consumed charge over time. It has a V-shaped architecture that features two wings to enhance the model explainability. The first wing predicts the steady-state opencircuit voltage (OCV) component, based on the consumed battery charge information, while the second wing predicts the transient voltage component, based on the battery current and temperature information. The total number of the model parameters is under 2.6K.
A well-known experimental dataset was used in this study for training, validation, and testing purposes. This dataset contains measurements taken on a Li-ion battery subjected to various EV driving cycles interleaved with charging cycles. The mean absolute percentage error (between predicted and measured battery voltage values) was under 1%, demonstrating the accuracy of the proposed model. Given that a battery must operate within certain maximum and minimum voltage limits, early and accurate voltage estimation has the potential to extend the battery lifetime by enabling proactive optimizations of the battery discharge-charge cycles. An extended battery life implies that a battery-powered EV can remain operational for a longer duration of time, which in turn can facilitate a wider adoption of EVs as an environmentally-friendly transportation alternative.Graduate2025-12-1
Seals, script & sacred sites: A study of goshuin 御朱印 in modern Japan
Get PDFI argue in this thesis that while shinbutsu bunri was highly successful institutionally in many ways it failed in practice. Goshuin, provided at both Buddhist temples and Shinto shrines in the contemporary period exemplify the enduring complexity of Japanese cultural and religious practices. From an academic perspective however, they have been hiding in plain sight. Although goshuin have long endured as a cherished tradition in Japan they have not yet been studied in English language scholarship and remain underexplored even among Japanese academics and researchers. This lack of comprehensive investigation has left a significant gap in our understanding of the social and historical significance of goshuin as forms of material culture.Graduat