YorkSpace

YorkSpace is York University's Institutional Repository. It supports York University's Senate Policy on Open Access by providing York community members with a place to preserve their research online in an institutional context.

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Recent Submissions

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    Robust changepoint detection in the variability of multivariate functional data
    (Taylor and Francis, 2025-05-12) Ramsay, Kelly; Chenouri, Shoja'eddin
    We consider the problem of robustly detecting changepoints in the variability of a sequence of independent multivariate functions. We develop a novel changepoint procedure, called the functional Kruskal–Wallis for covariance changepoint procedure, based on rank statistics and multivariate functional data depth. The functional Kruskal–Wallis for covariance changepoint procedure allows the user to test for at most one changepoint or an epidemic period, or to estimate the number and locations of an unknown number of changepoints in the data. We show that when the ‘signal-to-noise’ ratio is bounded below, the changepoint estimates produced by the functional Kruskal–Wallis for covariance changepoint procedure attain the minimax localisation rate for detecting general changes in distribution in the univariate setting. We also provide the behaviour of the proposed test statistics for the at-most-one-change and epidemic settings under the null hypothesis and, as a simple consequence of our main result, these tests are consistent. In simulation, we show that our method is particularly robust when compared to similar changepoint methods. We present an application of the functional Kruskal–Wallis for covariance changepoint procedure to intraday asset returns and functional magnetic resonance imaging scans. As a by-product of our main result, we provide a concentration result for integrated functional depth functions, which may be of general interest.
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    Optimized Volt/VAR Control for Inverter-Interfaced Distributed Energy Resources in Compliance with IEEE 1547 Standards
    (Institute of Central Computation and Knowledge, 2025-06-05) Shaterabadi, Mohammad
    The increasing integration of distributed energy resources (DERs), such as photovoltaic(PV) systems and battery storage, into distribution networks necessitates advanced inverter controls to maintain stable grid operations. IEEE Standard 1547 permits smart inverter functionalities, including Volt/VAR control, enabling DERs to autonomously manage voltage fluctuations caused by varying load and generation conditions. However, configuring these Volt/VAR settings optimally is challenging, as default parameters provided by standards may not ensure optimal performance or dynamic stability. This paper proposes a customized, per-node Volt/VAR control optimization framework for single-phase distribution feeders, adapting inverter control parameters based on expected short-term load and solar generation patterns. Leveraging a projected gradient descent optimization approach, proposed methodology guarantees dynamic stability by approximating feasible operational parameters within a convex polytope and ensuring full compliance with IEEE 1547 voltage and reactive power specifications. Comprehensive numerical evaluations conducted on the IEEE 141-bus distribution system using realistic operational data demonstrate the effectiveness and practicality of the proposed method, highlighting improved voltage stability and regulation compared to conventional approaches.
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    Stochastic Optimal Energy Planning of the Multi-connected Grids by the Presence of Bi-facial PV Panels: Interaction of Micro-nano and Main Grid
    (Institute of Central Computation and Knowledge, 2025-12-10) Shaterabadi, Mohammad
    The increasing greenhouse gas (GHG) emissions from fossil fuel-based energy systems have accelerated the global push toward cleaner technologies. Bi-facial photovoltaic (BPV) panels, capable of capturing solar irradiance from both sides, have emerged as a promising solution due to their higher energy yield and comparable costs to traditional PV systems. This paper explores the integration of BPV panels into a multi-connected grid comprising nano-, micro-, and main grid layers. A stochastic optimization framework is developed to address the uncertainties of solar irradiance. The problem is formulated as a Mixed-Integer Linear Programming (MILP) model and solved using the Augmented Epsilon Constraint (AEC) method in the General Algebraic Modeling System (GAMS) environment. Results demonstrate that incorporating BPV panels reduces microgrid operational costs by approximately 20%, boosts nano-grid profits by about 81%, and cuts emissions by about 10%, highlighting their potential to enhance system efficiency, flexibility, and sustainability.
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    Social Media as a Tool for Future-Making: The Cases of Two Entrepreneurs in Kakuma Refugee Camp
    (Berghahn Journals, 2026-03-01) Böhme, Claudia
    In this article I will look at the relationship between offline suffering and online happiness through the example of two young entrepreneurs living in Kakuma refugee camp in Kenya who strongly leverage social media for their business. From a basic communication device, the smartphone has become the door to a world of seemingly glamorous self-representation and a tool for future-making. I trace the young professionals’ motivations and inspirations for their work, and how they make a ‘brand’ in efforts to find a way of being self-reliant. In showcasing what they want and aim to be, these entrepreneurs actively engage in creating a self-image that is ‘beyond suffering’, one that can widen the gap and exemplify the ambiguous relationship between their real-world uncertainties and online images of success.