Olga Liivapuu

Olga Liivapuu

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Research Focus & Metrics

Academic Career Length

17Years (2010-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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27 November 2016
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JOJüri Olt
Jüri Olt
OLOlga Liivapuu
Olga Liivapuu
VMViacheslav Maksarov
Viacheslav Maksarov
ALAlexander Liyvapuu
Alexander Liyvapuu
TTTanel Tärgla
Tanel Tärgla

29 November 2024 in Agriengineering
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Nesma MahmoudNesma Mahmoud
Nesma Mahmoud
IVIndrek Virro
Indrek Virro
AZA. G. M. Zaman
A. G. M. Zaman
TLTormi Lillerand
Tormi Lillerand
WCWai Tik Chan
Wai Tik Chan
JOJüri Olt
Jüri Olt
Machine learning algorithms are increasingly used to enhance agricultural productivity cost-effectively. A critical task in precision agriculture is locating a plant’s root collar. This is required for the site-specific fertilization of the plants. Though state-of-the-art machine learning models achieve stellar performance in object detection, they are often sensitive to noisy inputs and variation in environment settings. In this paper, we propose an innovative technique of smooth perturbations to improve the robustness of root collar detection tasks using the YOLOv5 neural network model. We train a YOLOv5 model on blueberry image data for root collar detection. A small amount noise is added as a smooth perturbation to the bounding box of dimensions 50× 50, and this perturbed image is fed for training. Furthermore, we introduce an additional test set that represents the out-of-distribution (O.O.D.) case by applying Gaussian blur on test images to simulate particle situation. We use three different image datasets to train our model, the (i) Estonian blueberry, (ii) Serbian blueberry image, and (iii) public dataset sourced from Roboflow datasets, of sample size 118, 2779, and 2993, respectively. We achieve an overall precision of 0.886 on perturbed blueberry images compared to 0.871 on original (unperturbed) images for the O.O.D. test set. Similarly, our smooth perturbation training has achieved an mAP of 0.828, which significantly increases against the result of normal training, which only reaches 0.794. The result proves that our proposed smooth perturbation is an effective method to increase the robustness and generalizability of the object detection task.

28 October 2010 in Proceedings of the Estonian Academy of Sciences
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Journal Article
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Viktor AbramovViktor Abramov
Viktor Abramov
OLOlga Liivapuu
Olga Liivapuu
We propose a generalization of the concept of connection form by means of a graded q-differential algebra Ωq, where q is a primitive Nth root of unity, and develop the concept of curvature N-form for this generalization of the connection form. The Bianchi identity for a curvature N-form is proved. We study an Ωq-connection on module and prove that every projective module admits an Ωq-connection. If the module is equipped with a Hermitian structure, we introduce a notion of an Ωq-connection consistent with the Hermitian structure.

21 December 2023 in Universe
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Viktor AbramovViktor Abramov
Viktor Abramov
OLOlga Liivapuu
Olga Liivapuu
Motivated by a ternary generalization of the Pauli exclusion principle proposed by R. Kerner, we propose a notion of a Z3-skew-symmetric covariant SO(3)-tensor of the third order, consider it as a 3-dimensional matrix, and study the geometry of the 10-dimensional complex space of these tensors. We split this 10-dimensional space into a direct sum of two 5-dimensional subspaces by means of a primitive third-order root of unity q, and in each subspace, there is an irreducible representation of the rotation group SO(3)↪SU(5). We find two SO(3)-invariants of Z3-skew-symmetric tensors: one is the canonical Hermitian metric in five-dimensional complex vector space and the other is a quadratic form denoted by K(z,z). We study the invariant properties of K(z,z) and find its stabilizer. Making use of these invariant properties, we define an SO(3)-irreducible geometric structure on a five-dimensional complex Hermitian manifold. We study a connection on a five-dimensional complex Hermitian manifold with an SO(3)-irreducible geometric structure and find its curvature and torsion.

1 December 2018 in Universe
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Viktor AbramovViktor Abramov
Viktor Abramov
OLOlga Liivapuu
Olga Liivapuu
Abdenacer MakhloufAbdenacer Makhlouf
Abdenacer Makhlouf
We propose the notion of ( q , σ , τ ) -differential graded algebra, which generalizes the notions of ( σ , τ ) -differential graded algebra and q-differential graded algebra. We construct two examples of ( q , σ , τ ) -differential graded algebra, where the first one is constructed by means of the generalized Clifford algebra with two generators (reduced quantum plane), where we use a ( σ , τ ) -twisted graded q-commutator. In order to construct the second example, we introduce the notion of ( σ , τ ) -pre-cosimplicial algebra.

5 December 2025 in Mathematics
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AAAnti Maria Aader
Anti Maria Aader
Viktor AbramovViktor Abramov
Viktor Abramov
OLOlga Liivapuu
Olga Liivapuu
We propose an approach to extend the concept of a Lie algebra to ternary structures based on ω-symmetry, where ω is a primitive cube root of unity. We give a definition of a corresponding structure, called a ternary Lie algebra at cube roots of unity, or a ternary ω-Lie algebra. A method for constructing ternary associative algebras has been developed. For ternary algebras, the notions of the ternary ω-associator and the ternary ω-commutator are introduced. It is shown that if a ternary algebra possesses the property of associativity of the first or second kind, then the ternary ω-commutator on this algebra determines the structure of a ternary ω-Lie algebra. Ternary algebras of cubic matrices with associative ternary multiplication of the second kind are considered. The structure of the 8-dimensional ternary ω-Lie algebra of cubic matrices of the second order is studied, and all its subalgebras of dimensions 2 and 3 are determined.