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Brown, Jason I. (author), Kolokolnikov, Theodore (author), Kooij, Robert (author)We introduce two new methods for approximating the all-terminal reliability of undirected graphs. First, we introduce an edge removal process: remove edges at random, one at a time, until the graph becomes disconnected. We show that the expected number of edges thus removed is equal to (Formula presented.), where (Formula presented.) is the...journal article 2024
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Xia, Z. (author), Booij, O. (author), Kooij, J.F.P. (author)We propose a novel end-to-end method for cross-view pose estimation. Given a ground-level query image and an aerial image that covers the query's local neighborhood, the 3 Degrees-of-Freedom camera pose of the query is estimated by matching its image descriptor to descriptors of local regions within the aerial image. The...journal article 2024
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Wang, F. (author), Kooij, Robert (author)Network controllability and its robustness have been widely studied. However, analytical methods to calculate network controllability with respect to node in- and out-degree targeted removals are currently lacking. This paper develops methods, based on generating functions for the in- and out-degree distributions, to approximate the minimum...journal article 2023
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Zaffar, M. (author), Nan, L. (author), Kooij, J.F.P. (author)Visual place recognition (VPR) is an image-based localization method that estimates the camera location of a query image by retrieving the most similar reference image from a map of geo-tagged reference images. In this work, we look into two fundamental bottlenecks for its localization accuracy: 1) reference map sparseness and 2) viewpoint...journal article 2023
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Wang, F. (author), Cetinay, Hale (author), He, Zhidong (author), Liu, L. (author), Van Mieghem, P.F.A. (author), Kooij, Robert (author)For this study, we investigated efficient strategies for the recovery of individual links in power grids governed by the direct current (DC) power flow model, under random link failures. Our primary objective was to explore the efficacy of recovering failed links based solely on topological network metrics. In total, we considered 13 recovery...journal article 2023
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Ibrahimli, N. (author), Ledoux, H. (author), Kooij, J.F.P. (author), Nan, L. (author)We propose an enhancement module called depth discontinuity learning (DDL) for learning-based multi-view stereo (MVS) methods. Traditional methods are known for their accuracy but struggle with completeness. While recent learning-based methods have improved completeness at the cost of accuracy, our DDL approach aims to improve accuracy while...journal article 2023
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Nederlof, R. (author), Kooij, R.N.F. (author), Veldhuis, L.L.M. (author), Sinnige, T. (author)With the rise of distributed propeller concepts, there is an increased interest in quantifying the interaction between propeller slipstream and wing. It is known from literature that the local upwash induced by the propeller swirl can lead to a reduction of the wing-induced drag, a phenomenon often referred to as swirl recovery. However, at the...conference paper 2023
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Wang, F. (author), Kooij, Robert (author)Network controllability is a critical attribute of dynamic networked systems. Investigating methods to restore network controllability after network degradation is crucial for enhancing system resilience. In this study, we develop an analytical method based on degree distributions to estimate the minimum fraction of required driver nodes for...journal article 2023
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Kooij, Robert (author), Zegeling, André (author)We present a mechanical model for an oscillator with one degree of freedom under the influence of a flowing medium. Under fairly general conditions we show that the ensuing differential equation has at most two limit cycles and we give examples where exactly two limit cycles will occur. The implications of this result are that it is possible...journal article 2023
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Wang, F. (author), Kooij, Robert (author)Network controllability and its robustness has been widely studied. However, analytical methods to calculate network controllability with respect to node removals are currently lacking. This paper develops methods, based upon generating functions for the in- and out-degree distributions, to approximate the minimum number of driver nodes...conference paper 2023
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Wezeman, Robert S. (author), Neumann, N.M.P. (author), Phillipson, F. (author), Kooij, Robert (author)In this paper we study encounter-based density estimation using different random walks and analyse the effects of the step-size on the convergence of the density approximation. Furthermore, we analyse different types of random walks, namely, a uniform random walk, with every position equally likely to be visited next, a classical random walk...conference paper 2023
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Kooij, Robert (author), Achterberg, M.A. (author)The effective graph resistance, also known as the Kirchhoff index, is metric that is used to quantify the robustness of a network. We show that the optimisation problem of minimizing the effective graph resistance of a graph by adding a fixed number of links, is NP-hard.journal article 2023
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Lentsch, T. (author), Xia, Z. (author), Caesar, Holger (author), Kooij, J.F.P. (author)This work addresses cross-view camera pose estimation, i.e., determining the 3-Degrees-of-Freedom camera pose of a given ground-level image w.r.t. an aerial image of the local area. We propose SliceMatch, which consists of ground and aerial feature extractors, feature aggregators, and a pose predictor. The feature extractors extract dense...conference paper 2023
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Predari, Maria (author), Berner, Lukas (author), Kooij, Robert (author), Meyerhenke, Henning (author)The total effective resistance, also called the Kirchhoff index, provides a robustness measure for a graph G. We consider two optimization problems of adding k new edges to G such that the resulting graph has minimal total effective resistance (i.e., is most robust)—one where the new edges can be anywhere in the graph and one where the new...journal article 2023
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Palffy, A. (author), Kooij, J.F.P. (author), Gavrila, D. (author)Early and accurate detection of crossing pedestrians is crucial in automated driving in order to perform timely emergency manoeuvres. However, this is a difficult task in urban scenarios where pedestrians are often occluded (not visible) behind objects, e.g., other parked vehicles. We propose an occlusion aware fusion of stereo camera and...journal article 2023
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Xu, Ran (author), Wang, F. (author), Kooij, Robert (author)In this paper we investigate the controller placement problem on networks using controller reachability as the network performance metric. This metric is defined as the probability that each node can reach at least one controller, given that each link is operational with a fixed probability. By exploring placements for more than 100 real-world...conference paper 2023
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Palffy, A. (author), Pool, E.A.I. (author), Baratam, Srimannarayana (author), Kooij, J.F.P. (author), Gavrila, D. (author)Next-generation automotive radars provide elevation data in addition to range-, azimuth- and Doppler velocity. In this experimental study, we apply a state-of-the-art object detector (PointPillars), previously used for LiDAR 3D data, to such 3+1D radar data (where 1D refers to Doppler). In ablation studies, we first explore the benefits of...journal article 2022
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Hafner, Frank M. (author), Bhuyian, Amran (author), Kooij, J.F.P. (author), Granger, Eric (author)Person re-identification is a key challenge for surveillance across multiple sensors. Prompted by the advent of powerful deep learning models for visual recognition, and inexpensive RGB-D cameras and sensor-rich mobile robotic platforms, e.g. self-driving vehicles, we investigate the relatively unexplored problem of cross-modal re...journal article 2022
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Hehn, T.M. (author), Kooij, J.F.P. (author), Gavrila, D. (author)State-of-the-art stixel methods fuse dense stereo disparity and semantic class information, e.g. from a Convolutional Neural Network (CNN), into a compact representation of driveable space, obstacles and background. However, they do not explicitly differentiate instances within the same semantic class. We investigate several ways to augment...journal article 2022
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de Geus-Moussault, S.R.A. (author), Kooij, C. (author), Koelman, H.J. (author)The digital and energy transition will change our industry. To be prepared for this challenge, NHL Stenden University of Applied Sciences puts quite some effort in developing new innovative courses and new types of digitally enabled education. An example is a new minor concentrated on engineering tools and methods that have emerged in the ...conference paper 2022