21793 research outputs found
Sort by
Dependency Management Practices for the npm Software Ecosystem
Get PDFSoftware ecosystems provide developers with the opportunity to accelerate development by relying on third-party dependencies. Developers use third-party packages to increase productivity and improve quality. However, the increased reliance on third-party dependencies has emphasized dependency-related challenges. Developers need to be aware of such challenges and be equipped with techniques to mitigate their impact. Poor management of third-party dependencies can subject the project to breaking changes, bugs and vulnerabilities, which negatively impact the quality of software. In this thesis, we use a mixture of quantitative and qualitative methods to understand dependency management challenges in the npm ecosystem and provide actionable mitigation techniques to help developers better manage their dependencies.
We first study, catalog and quantify recurring patterns of dependency mis-management in the npm ecosystem and provide evidence of their prevalence and accumulation. In the second part of the thesis, we analyze the relationship between the characteristics of npm packages and how they are used by the community. We propose to developers a technique to determine the update strategy of their direct dependencies based on the individual characteristics of each package. In the last part of the thesis, we focus on the impact of transitive dependencies and quantify the impact of dependency decisions on continued exposure to security vulnerabilities. We propose a technique to select dependencies that mitigates the propagation of vulnerabilities to our project. Throughout our research, we identify implications that can serve both researchers and practitioners
Tailoring the Microstructure of Photoactive Ceramic Membranes Deposited by Suspension Plasma Spraying
Get PDFThe rise in the global water demand, coupled with the limited water resources readily usable on the planet, underscores the importance of developing cost-effective and modern approaches for safeguarding and reusing available water supplies. Consequently, membrane separation technologies have garnered increasing interest due to their ability to provide a sustainable, energy-efficient, and affordable solution for water treatment. Recently, ceramic membranes have been increasingly recognized in the commercial sphere due to their remarkable mechanical, thermal, and chemical stability, along with their hydrophilic properties, reduced fouling tendency, ease of cleaning, and sustained long-term flux. Nevertheless, the complex and costly manufacturing processes of these membranes limit their application to areas where polymer membranes are comparatively less efficient. Therefore, it is essential to investigate innovative membrane materials and manufacturing methods that can create cost-effective and high-performance membranes. One promising approach is the utilization of suspension plasma spray (SPS), a relatively new coating deposition technology that involves sub-micron to nano-sized feedstock materials. This single-step process holds the potential to offer a cost-effective solution for producing ceramic membranes. Additionally, the SPS process allows for the incorporation of photocatalysts like titanium dioxide (TiO2) into the feedstock, which can facilitate the degradation of organic contaminants on the membrane surface and enhance the anti-fouling properties of the membranes.
In this project, initially, the SPS process was used to produce porous TiO2 coatings with an average pore size of around 30 nm, which is in the range of ultrafiltration (UF) membranes, with pore sizes ranging from 2 to 100 nm. The coatings were then applied on the surface of the porous substrates to produce ultrafiltration membranes. The SPS membranes possess a distinct porous microstructure, where the porosity is mostly defined by the presence of unmelted feedstock particles retained within the matrix. The unmelted particles in the ultrafiltration membranes were deposited in the form of agglomerates of nanosized TiO2 particles found in the feedstock suspension. Therefore, the average pore size could be linked to the particle size of the original feedstock powder. The UF membranes exhibited a relatively high pure water flux, where the water flux decreased with increasing the thickness of the membranes. Furthermore, the SPS TiO2 membranes demonstrate photocatalytic properties under UV and visible light conditions due to the generation of oxygen vacancies in the lattice under SPS process conditions. Additionally, the feasibility of tailoring the level of porosity in the structure of SPS coatings as a potential approach to control the porosity and permeability of the membranes was investigated by employing a dual suspension injection method. Two water-based suspensions of TiO2 with different particle sizes were introduced into the plasma jet using injectors placed at two different radial distances from the plasma torch exit. The variation in the SPS parameters led to changes in the proportion of unmelted particles in the coatings originating from the injector located farther from the torch. As a result, the total porosity in the dual-injected coatings ranged from approximately 16% to about 36%. The proportion of the unmelted particles served as a reference for the fine porosity since the gaps among those particles were identified as the origin of nanosized pores. Among the spray parameters examined, it was found that the suspension feed rate and the distance between the injectors had the most notable impact on increasing the porosity levels in the coatings. Furthermore, based on previous work, microfiltration TiO2 membranes with an average pore size of around 200 nm were deposited using the SPS process. The ultrafiltration and microfiltration TiO2 membranes were characterized to assess their particle rejection ratio, where the membranes with high thickness and narrow pore size distribution showed a superior rejection efficiency. The influence of narrowing the pore size distribution of the membrane on the separation efficiency was confirmed after compacting the large pores in the membrane structure with the nanosized particles of the pristine SPS feedstock. Also, the membranes demonstrated self-cleaning properties under visible light
Immigrant Onboarding in Non-Gateway Quebec Small to Medium Enterprises
Get PDFResearch Problem: Manufacturing small to medium enterprises (SMEs) outside of Montreal, Toronto and Vancouver are turning to immigrants and temporary foreign workers to fill a labour shortage. This study investigated SMEs onboarding programs to attract, integrate and retain, immigrants and their perceived efficacy from the perspectives of executives, supervisors and immigrant and non-immigrant workers to identify stakeholders' support and training needs
Research Questions:
1. What onboarding strategies do non-gateway manufacturing SMEs use to recruit train and retain immigrant employees with technical or trade skills?
2. What are the perceived challenges that non-gateway manufacturing SMEs encounter when trying to recruit, train and retain immigrant employees with technical or trade skills?
3. How do non-gateway manufacturing SMEs see immigrants as meeting their labour needs and what drives this vision?
4. What are non-gateway manufacturing SMEs perceptions of government policies, and the immigrant integration services available to them and what additional support do they need to successfully onboard immigrant employees with technical or trade skills?
5. What are the onboarding experiences and challenges of immigrants with technical or trade skills in non-gateway SME manufacturing companies?
Methodology: Four manufacturing SMEs from different regions in the province of Quebec participated. Data was collected in three forms i) qualitative phenomenological interviews with six to eight employees per company, for a total of 28 participants, ii) company onboarding and community integration service artefacts and iii) field notes from company visits.
Results and Conclusions: Onboarding programs are an iterative learning process, that should be framed by a culture of organizational learning, communication, teamwork, and where training is provided for both incoming and existing workers. Stakeholders can improve the attraction and retention of immigrants through the two Bienvenue Onboard models emerging from this study. The models are adapted to the needs of immigrants and temporary foreign workers and consist of seven iterative steps: i) Prepare an action plan, ii) advertise and recruit strategically, iii) prepare existing and incoming staff, iv) offer workplace and job orientation programs, v) offer social integration support, vi) follow-up with further investments in people and vii) evaluate the onboarding experience
Numerical study of the wake characteristics of a notchback Ahmed body
Get PDFThis thesis investigates the effects of Reynolds number on the wake characteristics of a notchback Ahmed body with effective backlight angle, βe=17.8°. The Reynolds number based on the body height was varied from 5×10^3 to 5×10^4. Prior to the Reynolds number investigation, a Reynolds-Averaged Navier-Stokes (RANS) model assessment was performed using nine turbulence models consisting of one- and two-equation eddy-viscosity models and second moment closure models. The standard Spalart-Allmaras model was the only model that accurately predicted the asymmetric time-averaged wake topology, as reported in previous experimental and numerical studies, for the βe=17.8° notchback Ahmed body at Re= 5×10^4. The drag coefficient decreased with increasing Reynolds number, while the lift coefficient remained constant for Re≥ 1×10^4. The wake structure exhibited three regimes: symmetric (Re≤ 1×10^4), transitionally asymmetric (1 × 10^4 3.5 × 10^4) states. The wake asymmetry was attributed to an imbalance in entrainment from the sides and asymmetric separation from the roof and the C-pillars of the body. The tilting and stretching terms in the vorticity transport equation were used to provide insight into the source of asymmetry in the vorticity field around the body
‘Give me the same hold again’: The Three Political Justices in Plato’s Republic
Get PDFIn a dialogue about ostensibly about justice, Plato’s Republic has remarkably little to say about political justice: the justice between persons and within cities. The apparent discussions of politics in the main section of the dialogue (Books II to VII), I claim, serves as an analogue to show the proper ordering of the soul. Yet in this thesis, I argue that two other, disparate sections of The Republic, when read together, reveal a series of observations about political justice. In the introductory section of the text, Book I, we encounter three apparent definitions of political justice from Cephalus, Polemarchus, and Thrasymachus. Later, in the regression of the regimes, we encounter descriptions of cities, though these descriptions contain only passing references to justice.
I propose that the definitions of justice in Book I apply onto the three middle regimes of the Regression: the definition made for Cephalus is democratic, the definition presented Polemarchus is oligarchic, and Thrasymachus’ is timocratic. We know these sections are meant to be read together because Cephalus and Thrasymachus are representatives of the democratic and timocratic souls respectively. The synthesis of the two sections reveals a more complete description of three political justices, and offers a compelling account of the relationship between justice, politics, and desire. That being said, my approach does not conclude with a single cohesive understanding or satisfying account of political justice
Remapping Academic Embodiment: A Phenomenological Perspective to Center Queer Students' Experiences
Get PDFIn a contemporary academic landscape increasingly influenced by neoliberalism, this study highlights the enduring significance of university spaces for student queer communities as sites for both the reproduction of heterocisnormativity and queer community building. Within this context, the present research centers the embodied experiences of queer students to explore the presence and impact of power dynamics inscribed in academic spaces. Queer (Bell & Valentine, 1995; Johnston & Longhurst, 2010) and trans geographies (Nash, 2010) are at the forefront of this research due to their exploration of the tension between the body as a site of multi-scalar power dynamics and the intimacy of embodied queer emotions (Knopp, 2007). Ahmed's queer phenomenology (2006) is indispensable for its interpretation of orientation, disorientation, desire and embodiment as vectors of movement, action and experience in/of space. Focusing on two Montreal universities, the research seeks to answer a fundamental question: what does the embodied experience of queer students tell us about university spaces? This study uses sensitive and cognitive mapping (Gieseking, 2020; Olmedo, 2015) to center the embodied experiences of queer university students. Interpreted through the lens of queer phenomenology, the maps and qualitative interviews serve as creative research methods that contribute to the reconsideration of geography's theoretical and practical horizons. Key findings include unique campus trajectories shaped by the students’ identities, spatially perceivable tensions between the student body and the Administration, shared experiences of comfort and discomfort within specific contexts, and the utmost importance of student-led community spaces within universities
numerical study of vertical axis wind turbine performance in turbulent flows and behind turbine wakes
Get PDFWind energy is a clean, renewable, and cost-effective alternative to conventional power sources. It does not require fuel, does not emit pollution, and can be installed near the places where electricity is needed, reducing transmission losses. Vertical Axis Wind Turbines (VAWTs) are a type of wind energy technology that have some advantages over Horizontal Axis Wind Turbines (HAWTs), such as being able to able to harvest wind from all directions, generate less noise, and offering a simpler structure. However, VAWTs also have lower efficiency than HAWTs, and their performance is affected by the wake, which is a lower-velocity turbulent flow behind the rotating blades.
The wake can interfere with the operation of other wind turbines downstream, but it can also enhance the performance of smaller VAWTs. The aim of this research is to use Computational Fluid Dynamics (CFD) to study the effect of wake on different sizes of VAWTs, and to understand how the turbulence generated by the wake influences the power output of these turbines. This thesis presents a CFD methodology and identifies the strengths and weaknesses of CFD for the simulation of the interaction of the wake with downstream VAWTs. The contributions are threefold. First, the understanding of how turbulence intensity affects the VAWT’s performance. Second, calculating the performance of a wind turbine that is in the wake of another turbine and the study of some particular VAWTs placement configurations. Third, quantifying the limitations of CFD and identifying when it is appropriate to use two-dimensional models for flow simulations of multiple VAWTs. This research has documented an increased performance of about 20% for small turbines in high turbulence intensity flows. Furthermore, a 20% increase in power output from an optimization array of VAWTs was identified. Finally, this work suggests that two-dimensional CFD simulations are adequate for simulation pairs of upstream and downstream turbines if the turbines are low-solidity and low aspect ratio turbine types
Essays on Student Debt
Get PDFThe thesis studies student debt in the United States. The first chapter examines the quantitative effects of rising college costs, wage inequality, and delinquencies on growing student debt balances in the U.S. We build an incomplete markets overlapping-generation (OLG) model with choices for a college education, student loans, and delinquency. We solve transitional dynamics with the estimated time-varying changes in college costs and wage inequality, in addition to a stronger preference for college education, that affect the repayment decision of borrowers. We find that these sources increase aggregate student debt balances by $480 billion between 1979 and 2015. Rising college costs increases borrowing by recent college students. The declining average ability of college students and increasing volatility of wage shocks lead to a higher delinquency rate among borrowers over time. Importantly, we find that when borrowers are not delinquent on their payments, the aggregate student debt only increases by 50% of the increase in the benchmark economy, despite all the time-varying sources. This suggests that although the rising college costs largely affect the borrowing behavior of college students, the increasing delinquency rate over time significantly contributes to the rapid growth of U.S. student debt. The second chapter empirically studies how holding student debt affects initial labor market outcomes for college graduates in the United States. In particular, I examine the implications of student debt on college graduates’ initial unemployment duration, underemployment rate, and initial labor income. By conducting hazards models analyses using the NLSY97 and O*NET dataset, I first find that college students graduating with student debt, on average, have a shorter unemployment duration before their first job compared to those graduating without student debt. Furthermore, using the average, excluding a self-amount, institution-level grant amount as an instrument, I find that graduating with a higher level of student debt increases the probability of underemployment for college graduates and decreases the initial labor income at their first jobs. The results highlight the impact of student debt on the trade-off between search time and the job quality
Community art therapy clinical intervention program for BIPOC after a traumatic community death: A theoretical intervention-based research paper
Get PDFThis theoretical intervention paper proposes a community art therapy program which could be utilized following a traumatic event in a BIPOC community. Mental health services are often inaccessible within BIPOC communities and when accessible, are not always trauma informed and culturally sensitive. Group art therapy holds the potential of offering shared experience and support to BIPOC following a community trauma. Additionally, it is hoped that this will in turn, lower the risk of developing PTSD. Using steps one and two of Fraser & Galinsky’s (2010) fives step model, I compile and synthesize pertinent existing research between art therapy, psychotherapy with BIPOC, trauma informed care, existing community art therapy interventions, etc., to propose a 5-week, 10 session community based art therapy program for BIPOC following a traumatic event in the community. This is followed by a discission on findings, conclusion, and future recommendations.
Keywords: art therapy, psychotherapy, trauma, intervention and BIPO
Live Testing of Cloud Services
Get PDFService providers use the cloud due to the dynamic infrastructure it offers at a low cost. However, sharing the infrastructure with other service providers as well as relying on remote services that may be inaccessible from the development environment create major limitations for development time testing. Modern service providers have an increasing need to test their services in the production environment. Such testing helps increase the reliability of the test results and detect problems that could not be detected in the development environment such as the noisy neighbor problem. Furthermore, testing in production enables other software engineering activities such as fault prediction and fault localization and makes them more efficient.
Test interferences are a major problem for testing in production as they can have damaging effects ranging from unreliable and degraded performance to a malfunctioning or inaccessible system. The countermeasures that are taken to alleviate the risk of test interferences are called test isolation. Existing approaches for test isolation have limited applicability in the cloud context because the assumptions under which they operate are seldom satisfied in the cloud context. Moreover, when running tests in production, failures can happen and whether they are due to the testing activity or not the damage they cause cannot be ignored. To deal with such issues and manage to quickly get the system back to a healthy state in the case of a failure, human intervention should be reduced in the orchestration and execution of testing activities in production. Thus, the need for a solution that automates the orchestration of tests in production while taking into consideration the particularity of a cloud system such as the existence of multiple fault tolerance mechanisms.
In this thesis, we define live testing as testing a system in its production environment, while it is serving, without causing any intolerable disruption to its usage. We propose an architecture that can help cope with the major challenges of live testing, namely reducing human intervention and providing test isolation. Our proposed architecture is composed of two building blocks, the Test Planner and the Test Execution Framework. To make the solution we are proposing independent from the technologies used in a cloud system, we propose the use of UML Testing Profile (UTP) to model the artifacts involved in this architecture. To reduce human intervention in testing activities, we start by automating test execution and orchestration in production. To achieve this goal, we propose an execution semantics that we associate with UTP concepts that are relevant for test execution. Such an execution semantics represent the behavior that the Test Execution Framework exhibits while executing tests. We propose a test case selection method and test plan generation method to automate the activities that are performed by the Test Planner. To alleviate the risk of test interferences, we also propose a set of test methods that can be used for test isolation. As opposed to existing test isolation techniques, our test methods do not make any assumptions about the parts of the system for which test isolation can be provided, nor about the feature to be tested. These test methods are used in the design of test plans. In fact, the applicability of each test method varies according to several factors including the risk of test interferences that parts of the system present, the availability of resources, and the impact of the test method on the provisioning of the service. To be able to select the right test method for each situation, information about the risk of test interference and the cost of test isolation need to be provided. We propose a method, configured instance evaluation method, that automates the process of obtaining such information. Our method evaluates the software involved in the realization of the system in terms of the risk of test interference it presents, and the cost to provide test isolation for that software.
In this thesis, we also discuss the feasibility of our proposed methods and evaluate the provided solutions. We implemented a prototype for the test plan generation and showcased it in a case study. We also implemented a part of the configured instance evaluation method, and we show that it can help confirm the presence of a risk of test interference. We showcase one of our test methods on a case study using an application deployed in a Kubernetes managed cluster. We also provide proof of the soundness of our execution semantics. Furthermore, we evaluate, in terms of the resulting test plan’s execution time, the algorithms involved in the test plan generation method. We show that for two of the activities in our solution our proposed algorithms provide optimal solutions; and, for one activity we identify in which situations our algorithm does not manage to give the optimal solution. Finally, we prove that our test case selection method reduces the test suite without compromising the configuration fault detection power