All Outputs (54)

Hand gesture recognition for user-defined textual inputs and gestures (2024)
Journal Article
Wang, J., Ivrissimtzis, I., Li, Z., & Shi, L. (online). Hand gesture recognition for user-defined textual inputs and gestures. Universal Access in the Information Society, https://doi.org/10.1007/s10209-024-01139-6

Despite recent progress, hand gesture recognition, a highly regarded method of human computer interaction, still faces considerable challenges. In this paper, we address the problem of individual user style variation, which can significantly affect s... Read More about Hand gesture recognition for user-defined textual inputs and gestures.

A multiscale optimisation algorithm for shape and material reconstruction from a single X-ray image (2024)
Presentation / Conference Contribution
Westmacott, H., Ivrissimtzis, I., & Weinzierl, T. (2024, January). A multiscale optimisation algorithm for shape and material reconstruction from a single X-ray image. Presented at ICIGP 2024: The 7th International Conference on Image and Graphics Processing, Beijing, China

We produce thickness and bone to soft tissue ratio estimations from a single, 2D medical X-ray image. For this, we simulate the scattering of the rays through a model of the object and embed this simulation into an optimiser which iteratively adjusts... Read More about A multiscale optimisation algorithm for shape and material reconstruction from a single X-ray image.

Anomaly Detection with Transformers in Face Anti-spoofing (2023)
Presentation / Conference Contribution
Abduh, L., Omar, L., & Ivrissimtzis, I. (2023). Anomaly Detection with Transformers in Face Anti-spoofing. . https://doi.org/10.24132/JWSCG.2023.10

Transformers are emerging as the new gold standard in various computer vision applications, and have already been used in face anti-spoofing demonstrating competitive performance. In this paper, we propose a network with the ViT transformer and ResNe... Read More about Anomaly Detection with Transformers in Face Anti-spoofing.

Race Bias Analysis of Bona Fide Errors in Face Anti-spoofing (2023)
Presentation / Conference Contribution
Abduh, L., & Ivrissimtzis, I. (2023, September). Race Bias Analysis of Bona Fide Errors in Face Anti-spoofing. Presented at CAIP 2023: The 20th International Conference on Computer Analysis of Images and Patterns, Limassol, Cyprus

The study of bias in Machine Learning is receiving a lot of attention in recent years, however, few only papers deal explicitly with the problem of race bias in face anti-spoofing. In this paper, we present a systematic study of race bias in face ant... Read More about Race Bias Analysis of Bona Fide Errors in Face Anti-spoofing.

Exploring the Potential of Immersive Virtual Environments for Learning American Sign Language (2023)
Presentation / Conference Contribution
Wang, J., Ivrissimtzis, I., Li, Z., Zhou, Y., & Shi, L. (2023, September). Exploring the Potential of Immersive Virtual Environments for Learning American Sign Language. Presented at ECTEL 2023: Eighteenth European Conference on Technology Enhanced Learning, Aveiro, Portugal

Sign languages enable effective communication between deaf and hearing people. Despite years of extensive pedagogical research, learning sign language online comes with a number of difficulties that might be frustrating for some students. Indeed, mos... Read More about Exploring the Potential of Immersive Virtual Environments for Learning American Sign Language.

Developing and Evaluating a Novel Gamified Virtual Learning Environment for ASL (2023)
Presentation / Conference Contribution
Wang, J., Ivrissimtzis, I., Li, Z., Zhou, Y., & Shi, L. (2023, August). Developing and Evaluating a Novel Gamified Virtual Learning Environment for ASL. Presented at INTERACT 2023: IFIP Conference on Human-Computer Interaction, York

The use of sign language is a highly effective way of communicating with individuals who experience hearing loss. Despite extensive research, many learners find traditional methods of learning sign language, such as web-based question-answer methods,... Read More about Developing and Evaluating a Novel Gamified Virtual Learning Environment for ASL.

Bivariate non-uniform subdivision schemes based on L-systems (2023)
Journal Article
Gérot, C., & Ivrissimtzis, I. (2023). Bivariate non-uniform subdivision schemes based on L-systems. Applied Mathematics and Computation, 457, Article 128156. https://doi.org/10.1016/j.amc.2023.128156

L–systems have been used to describe non-uniform, univariate, subdivision schemes, which offer more flexible refinement processes than the uniform schemes, while at the same time are easier to analyse than the geometry driven non-uniform schemes. In... Read More about Bivariate non-uniform subdivision schemes based on L-systems.

User-Defined Hand Gesture Interface to Improve User Experience of Learning American Sign Language (2023)
Book Chapter
Wang, J., Ivrissimtzis, I., Li, Z., Zhou, Y., & Shi, L. (2023). User-Defined Hand Gesture Interface to Improve User Experience of Learning American Sign Language. In C. Frasson, P. Mylonas, & C. Troussas (Eds.), Augmented Intelligence and Intelligent Tutoring Systems: 19th International Conference, ITS 2023, Corfu, Greece, June 2-5, 2023, Proceedings (479-490). Springer Verlag. https://doi.org/10.1007/978-3-031-32883-1_43

Sign language can make possible effective communication between hearing and deaf-mute people. Despite years of extensive pedagogical research, learning sign language remains a formidable task, with the majority of the current systems relying extensiv... Read More about User-Defined Hand Gesture Interface to Improve User Experience of Learning American Sign Language.

Big data for human security: The case of COVID-19 (2022)
Journal Article
Cárdenas, P., Ivrissimtzis, I., Obara, B., Kureshi, I., & Theodoropoulos, G. (2022). Big data for human security: The case of COVID-19. Journal of Computational Science, 60, Article 101574. https://doi.org/10.1016/j.jocs.2022.101574

The COVID-19 epidemic has changed the world dramatically since societies are changing their behaviour according to the new normal, which comes along with numerous challenges and uncertainties. These uncertainties have led to instabilities in several... Read More about Big data for human security: The case of COVID-19.

Quality perception and discrimination thresholds in quantised triangle meshes (2021)
Presentation / Conference Contribution
Almutairi, A., Saarela, T., & Ivrissimtzis, I. (2021). Quality perception and discrimination thresholds in quantised triangle meshes. . https://doi.org/10.1117/12.2604720

At certain stages of the graphics pipeline, and most notably during compression for transmission and storage, triangle meshes may undergo a fixed-point arithmetic quantisation of their vertex coordinates. This paper presents the results of a psychoph... Read More about Quality perception and discrimination thresholds in quantised triangle meshes.

From Farey fractions to the Klein quartic and beyond (2021)
Journal Article
Ivrissimtzis, I., Singerman, D., & Strudwick, J. (2021). From Farey fractions to the Klein quartic and beyond. Ars mathematica contemporanea (Spletna izd.), 20(1), 37-50. https://doi.org/10.26493/1855-3974.2046.cb6

In a paper published in 1878/79 Klein produced his famous 14-sided polygon representing the Klein quartic, his Riemann surface of genus 3 which has PSL(2,7) as its automorphism group. The construction and method of side pairings are fairly complicate... Read More about From Farey fractions to the Klein quartic and beyond.

Early Fault Diagnostic System for Rolling Bearing Faults in Wind Turbines (2021)
Journal Article
Xu, L., Wang, Q., Ivrissimtzis, I., & Li, S. (2022). Early Fault Diagnostic System for Rolling Bearing Faults in Wind Turbines. Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems, 5(1), Article 011004. https://doi.org/10.1115/1.4051222

The operation and maintenance costs of wind farms are always high due to high labor costs and the high replacement cost of parts. Thus, it is of great importance to have real-time monitoring and an early fault diagnostic system to prevent major event... Read More about Early Fault Diagnostic System for Rolling Bearing Faults in Wind Turbines.

Colour Processing in Adversarial Attacks on Face Liveness Systems (2019)
Presentation / Conference Contribution
Abduh, L., & Ivrissimtzis, I. (2019). Colour Processing in Adversarial Attacks on Face Liveness Systems. In F. P. Vidal, G. K. . L. Tam, & J. C. Roberts (Eds.), Proceedings of Computer Graphics and Visual Computing 2019 (CGVC) (149-152). https://doi.org/10.2312/cgvc.20191272

In the context of face recognition systems, liveness test is a binary classification task aiming at distinguishing between input images that come from real people’s faces and input images that come from photos or videos of those faces, and presented... Read More about Colour Processing in Adversarial Attacks on Face Liveness Systems.

Using theoretical ROC curves for analysing machine learning binary classifiers (2019)
Journal Article
Omar, L., & Ivrissimtzis, I. (2019). Using theoretical ROC curves for analysing machine learning binary classifiers. Pattern Recognition Letters, 128, 447-451. https://doi.org/10.1016/j.patrec.2019.10.004

Most binary classifiers work by processing the input to produce a scalar response and comparing it to a threshold value. The various measures of classifier performance assume, explicitly or implicitly, probability distributions Ps and Pn of the respo... Read More about Using theoretical ROC curves for analysing machine learning binary classifiers.

Trivalent expanders, $(Delta – Y)$-transformation, and hyperbolic surfaces (2019)
Journal Article
Ivrissimtzis, I., Peyerimhoff, N., & Vdovina, A. (2019). Trivalent expanders, $(Delta – Y)$-transformation, and hyperbolic surfaces. Groups, Geometry, and Dynamics, 13(3), 1103-1131. https://doi.org/10.4171/ggd/518

We construct a new family of trivalent expanders tessellating hyperbolic surfaces with large isometry groups. These graphs are obtained from a family of Cayley graphs of nilpotent groups via (Delta–Y)-transformations. We study combinatorial, topologi... Read More about Trivalent expanders, $(Delta – Y)$-transformation, and hyperbolic surfaces.

A Perceptual Difference Scaling Study on Quantized 3D Models (2018)
Presentation / Conference Contribution
Almutairi, A., Saarela, T., & Ivrissimtzis, I. (2018, December). A Perceptual Difference Scaling Study on Quantized 3D Models. Paper presented at ACM Symposium on Applied Perception, Vancouver, Canada

Single Image Watermark Retrieval from 3D Printed Surfaces via Convolutional Neural Networks (2018)
Presentation / Conference Contribution
Zhang, X., Wang, Q., & Ivrissimtzis, I. (2018). Single Image Watermark Retrieval from 3D Printed Surfaces via Convolutional Neural Networks. In G. Tam, & F. Vidal (Eds.), Computer Graphics & Visual Computing (CGVC) 2018 : Eurographics UK Chapter proceedings (117-120). https://doi.org/10.2312/cgvc.20182019

In this paper we propose and analyse a method for watermarking 3D printed objects, concentrating on the watermark retrieval problem. The method embeds the watermark in a planar region of the 3D printed object in the form of small semi-spherical or cu... Read More about Single Image Watermark Retrieval from 3D Printed Surfaces via Convolutional Neural Networks.

A user study on quantisation thresholds of triangle meshes (2017)
Presentation / Conference Contribution
Almutairi, A., Saarela, T., & Ivrissimtzis, I. (2017). A user study on quantisation thresholds of triangle meshes. In T. R. Wan, & F. Vidal (Eds.), Computer Graphics & Visual Computing (CGVC) 2017. Eurographics UK Chapter Proceedings, anchester Metropolitan University, United Kingdom, 14 – 15 September 2017. https://doi.org/10.2312/cgvc.20171283

We present the results of a user study on estimating a quantisation threshold above which the quantised triangle mesh is perceived as indistinguishable from its unquantised original. The design of the experiment and the analysis of the results focus... Read More about A user study on quantisation thresholds of triangle meshes.

Order-randomized Laplacian mesh smoothing (2017)
Presentation / Conference Contribution
Yang, Y., Rushmeier, H., & Ivrissimtzis, I. (2016, June). Order-randomized Laplacian mesh smoothing. Presented at 9th International Conference on Mathematical Methods for Curves and Surfaces, Tønsberg, Norway

In this paper we compare three variants of the graph Laplacian smoothing. The first is the standard synchronous implementation, corresponding to multiplication by the graph Laplacian matrix. The second is a voter process inspired asynchronous impleme... Read More about Order-randomized Laplacian mesh smoothing.

Designing a facial spoofing database for processed image attacks (2016)
Presentation / Conference Contribution
Omar, L., & Ivrissimtzis, I. (2016). Designing a facial spoofing database for processed image attacks. In 7th International Conference on Imaging for Crime Detection and Prevention (ICDP 2016) : Madrid, Spain, 23-25 November 2016 ; proceedings. https://doi.org/10.1049/ic.2016.0073

Face recognition systems are used for user authentication in everyday applications such as logging into a laptop or smartphone without need to memorize a password. However, they are still vulnerable to spoofing attacks, as for example when an imposte... Read More about Designing a facial spoofing database for processed image attacks.