arXiv subjects

Nikolaos Papadopoulos

Publications and source records attributed to Nikolaos Papadopoulos.

4 recordsLinked to original sources

arXiv2025

TeleViT1.0: Teleconnection-aware Vision Transformers for Subseasonal to Seasonal Wildfire Pattern Forecasts

Forecasting wildfires weeks to months in advance is difficult, yet crucial for planning fuel treatments and allocating resources. While short-term predictions typically rely on local weather conditions, long-term forecasting requires accounting for the Earth's interconnectedness, including global patterns and teleconnections. We introduce TeleViT, a Teleconnection-aware Vision Transformer that integrates (i) fine-scale local fire drivers, (ii) coarsened global fields, and (iii) teleconnection indices. This multi-scale fusion is achieved through an asymmetric tokenization strategy that produces heterogeneous tokens processed jointly by a transformer encoder, followed by a decoder that preserves spatial structure by mapping local tokens to their corresponding prediction patches. Using the global SeasFire dataset (2001-2021, 8-day resolution), TeleViT improves AUPRC performance over U-Net++, ViT, and climatology across all lead times, including horizons up to four months. At zero lead, TeleViT with indices and global inputs reaches AUPRC 0.630 (ViT 0.617, U-Net 0.620), at 16x8day lead (around 4 months), TeleViT variants using global input maintain 0.601-0.603 (ViT 0.582, U-Net 0.578), while surpassing the climatology (0.572) at all lead times. Regional results show the highest skill in seasonally consistent fire regimes, such as African savannas, and lower skill in boreal and arid regions. Attention and attribution analyses indicate that predictions rely mainly on local tokens, with global fields and indices contributing coarse contextual information. These findings suggest that architectures explicitly encoding large-scale Earth-system context can extend wildfire predictability on subseasonal-to-seasonal timescales.

cs.CV↗

arXiv2025

Physical blowups via buffered time change in a mean-field neural network

Idealized networks of integrate-and-fire neurons with impulse-like interactions obey McKean-Vlasov diffusion equations in the mean-field limit. These equations are prone to blowups: for a strong enough interaction coupling, the mean-field rate of interaction diverges in finite time with a finite fraction of neurons spiking simultaneously, thereby marking a macroscopic synchronous event. Characterizing these blowup singularities analytically is the key to understanding the emergence and persistence of spiking synchrony in mean-field neural models. Such a treatment is possible via time change techniques for a Poissonian variation of the classically considered integrate-and-fire dynamics. However, just as for shock solutions for nonlinear conservation laws, there are several admissible blowup solutions to the corresponding McKean-Vlasov equations. Because of this ambiguity, it is unclear which notion of blowup solutions shall be adopted. Here, we unambiguously define physical blowup dynamics as solutions to a fixed-point problem bearing on the time change associated to the McKean-Vlasov equation. To justify the physicality of this formulation, we introduce a buffering mechanism that regularizes blowup dynamics, while satisfying the same conservation principles as the finite-dimensional particle-system dynamics. We then show that physical blowup dynamics are recovered from these regularized solutions in the limit of vanishing buffering. Our approach also shows that these physical solutions are unique, globally defined, and avoid the so-called eternal blowup phenomenon, as long as the neurons exhibit nonzero, distributed refractory periods, a reasonable modeling assumption.

math.AP↗

arXiv2015

Are Game Platforms suitable for Parkinson Disease patients?

Parkinson's Disease (PD) is a progressive neurodegenerative movement disorder that affects more that 6 million people worldwide. Motor dysfunction gradually increases as the disease progress. It is usually mild in the early stages of the disease but it relentlessly progresses to a severe or very severe disability that is characterized by increasing degrees of bradykinesia, hypokinesia, muscle rigidity, loss of postural reflexes and balance control as well as freezing of gait. In addition to a line of treatment based on dopaminergic PD-specific drugs, attending neurologists strongly recommend regular exercise combined with physiotherapy. However, the routine of traditional rehabilitation often create boredom and loss of interest. Opportunities to liven up a daily exercise schedule may well take the form of character-based virtual reality games which engage the player to physically train in a non-linear and looser fashion, providing an experience that varies from one game loop the next. Such "exergames", a word that results from the amalgamation of the words "exercise" and "game" challenge patients into performing movements of varying complexity in a playful and immersive virtual environment. In fact, today's game consoles using controllers like Nintendo's Wii, Sony PlayStation Eye and the Microsoft Kinect sensor present new opportunities to infuse motivation and variety to an otherwise mundane physiotherapy routine. But are these controllers and the games built for them appropriate for PD patients? In this paper we present some of these approaches and discuss their suitability for these patients mainly on the basis of demands made on balance, agility and gesture precision.

cs.CY↗

arXiv2015

Parkinson's disease patient rehabilitation using gaming platforms: lessons learnt

Parkinson's disease (PD) is a progressive neurodegenerative movement disorder where motor dysfunction gradually increases as the disease progress. In addition to administering dopaminergic PD-specific drugs, attending neurologists strongly recommend regular exercise combined with physiotherapy. However, because of the long-term nature of the disease, patients following traditional rehabilitation programs may get bored, lose interest and eventually drop out as a direct result of the repeatability and predictability of the prescribed exercises. Technology supported opportunities to liven up a daily exercise schedule have appeared in the form of character-based, virtual reality games which promote physical training in a non-linear and looser fashion and provide an experience that varies from one game loop the next. Such "exergames", a word that results from the amalgamation of the words "exercise" and "game" challenge patients into performing movements of varying complexity in a playful and immersive virtual environment. Today's game consoles such as Nintendo's Wii, Sony PlayStation Eye and Microsoft's Kinect sensor present new opportunities to infuse motivation and variety to an otherwise mundane physiotherapy routine. In this paper we present some of these approaches, discuss their suitability for these PD patients, mainly on the basis of demands made on balance, agility and gesture precision, and present design principles that exergame platforms must comply with in order to be suitable for PD patients.

cs.CY↗