arXiv subjects

Konstantinos K. Delibasis

Publications and source records attributed to Konstantinos K. Delibasis.

At least 19 recordsLinked to original sources

arXiv2026

Optimizing Coverage in Convex Quadrilateral Regions with a Single UAV

The integration of unmanned aerial vehicles (UAVs) into next-generation wireless networks has emerged as a promising solution for providing flexible and efficient coverage. This paper investigates the optimal deployment of a single UAV over an arbitrary convex quadrilateral region, employing a directional antenna with adjustable tilt that results in an elliptical ground coverage footprint. Two coverage scenarios are considered: (i) the largest inscribed ellipse, which maximizes coverage within the quadrilateral while excluding boundary regions, and (ii) the smallest circumscribed ellipse, which guarantees full coverage of the entire area. An optimization framework is developed to determine the optimal UAV altitude by examining path loss, signal-to-noise ratio (SNR), and energy consumption. Based on a widely adopted path loss model, the altitude that minimizes the maximum path loss is derived, while the effect of antenna directivity on maximizing the minimum SNR at the coverage boundary is also analyzed. Furthermore, UAV energy consumption is evaluated by accounting for hovering, forward flight, and vertical take-off operations. Numerical results illustrate the trade-offs among coverage efficiency, communication performance, and energy consumption under different propagation environments and antenna configurations. The analysis is further extended to all feasible inscribed and circumscribed ellipse configurations, providing a complete parametric characterization of the optimal altitude. In addition, a large-scale evaluation over randomly generated convex quadrilaterals offers a statistical assessment of the proposed framework and demonstrates its robustness under geometric variability.

eess.SY↗

arXiv2026

Parametrization of microbial survival models under UVC exposure

This work presents a unified framework for the parametrization and comparison of microbial survival models under UVC exposure. Four dose-response models - the single-target, multi-target, linear-quadratic, and two-stage decay models - are analyzed with respect to their mathematical structure, parameter identifiability, and biological interpretability, while ensuring physically meaningful parameter estimates. To address the limited size and lack of replication in published datasets, parameter uncertainty is quantified using a parametric bootstrap approach under multiplicative dose uncertainty. Model comparison combines goodness-of-fit in logarithmic survival space, the Akaike Information Criterion corrected for small samples, and identifiability considerations. Application to data for 32 microorganisms shows that no single model is universally optimal, highlighting that reliable model selection requires combining statistical performance with physical and biological consistency, and providing a robust basis for UVC survival analysis and disinfection modeling.

physics.med-ph↗

arXiv2026

A new class of degenerate solutions to the massless Dirac equation and their potential applications in optical memories

In this article, we present a novel class of degenerate solutions to the massless Dirac equation, corresponding to a wide variety of electromagnetic 4-potentials and fields, including both zero field and circularly polarized electromagnetic waves. An interesting property of these solutions is that the spin of the particles rotates in synchronization with the electric and magnetic fields of the electromagnetic waves. These results could be utilized for the development of optical memories based on materials supporting massless Dirac fermions, such as graphene.

quant-ph↗

arXiv2026

Distance Distributions Between Nodes in Concentric Disk-Annulus or Sphere-Shell Regions

This letter derives closed-form expressions for the probability density function of the distance between two nodes located in heterogeneous concentric geometries, namely a disk or sphere and a surrounding annulus or spherical shell. Two scenarios are considered: (i) both nodes are independently distributed in different regions, disk or sphere and annulus or shell, and (ii) one node is static in the outer region while the other follows the stationary distribution of the random waypoint model in the inner region. The resulting expressions provide a tractable analytical tool for performance evaluation in concentric wireless regions.

cs.IT↗

arXiv2026

Internodal Distance Distributions for Static and Mobile Nodes in 2D/3D Wireless Networks

This letter presents a unified analytical framework for internodal distance distributions in 2D and 3D wireless networks, with nodes confined to concentric circular or spherical regions. Four deployment scenarios are considered, covering all combinations of static (uniform) and mobile (random waypoint-based) nodes. For each scenario, closed-form expressions for the internodal distance probability density functions are derived, incorporating both geometric constraints and spatial effects introduced by mobility. Equal-radius cases are also addressed. Beta-distribution approximations and Monte Carlo simulations demonstrate the accuracy and validity of the analytical results.

eess.SP↗

arXiv2026

Efficient UAV Coverage in Large Convex Quadrilateral Areas with Elliptical Footprints

Unmanned Aerial Vehicles (UAVs) have gained significant attention for improving wireless communication, especially in emergencies or as a complement to existing cellular infrastructure. This letter addresses the problem of efficiently covering a large convex quadrilateral using multiple UAVs, where each UAV generates elliptical coverage footprints based on its altitude and antenna tilt. The challenge is approached using circle-packing techniques within a unit square to arrange UAVs in an optimal configuration. Subsequently, a homography transformation is applied to map the unit square onto the quadrilateral area, ensuring that the UAVs' elliptical footprints cover the entire region. Numerical simulations demonstrate the effectiveness of the proposed method, providing insight into coverage density and optimal altitude configurations for different placement scenarios. The results highlight the scalability and potential for improving UAV-based communication systems, focusing on maximizing coverage efficiency in large areas with irregular shapes.

eess.SP↗

arXiv2025

Localized degenerate solutions to the massless Dirac and Weyl equations

In this article we present a general class of localized degenerate solutions to the massless Dirac and Weyl equations, which can also describe particles, or systems of particles, with varying energy and spin along their direction of motion. Another interesting characteristic of these solutions is that they remain unaltered in a wide range of electromagnetic 4-potentials and fields, which are analytically calculated. In addition, we propose a new method for spatially separating Weyl particles based on their helicity and direction of motion using appropriate magnetic fields, given in explicit form.

quant-ph↗

arXiv2025

On the Terminal Location Uncertainty in Elliptical Footprints: Application in Air-to-Ground Links

Wireless transmitters (Txs) that radiate downward in a direction often generate circular footprints on the ground. The configurational flexibility of these footprints is inherently limited as coverage adjustments are restricted to variations in radius, the only parameter available for tuning. This simplification is inadequate for scenarios that require asymmetric coverage, extended service areas, or dynamic footprint adaptation due to antenna tilt or changes in altitude of unmanned aerial vehicles (UAVs). In specific scenarios, the use of elliptical cells can offer increased flexibility for providing user coverage due to unique network characteristics. For example, an elliptical footprint can be produced when a practical directional antenna with unequal azimuth and elevation half-power beamwidths is used in high-speed railway networks. Another common scenario involves the production of an elliptical footprint when an airborne Tx radiates at an angle by tilting its directional antenna by a few degrees. This paper aims to investigate for the first time the association between the random location of the user within an elliptical coverage area and the performance of a wireless communication link considering these scenarios. We assume a UAV as a Tx, although a tall cellular base station tower could also be employed without losing generality. To gain a deeper understanding of the impact of random location, we derive the relevant distance and signal-to-noise ratio metrics and examine the outage probability for a single-user link, as well as the throughput in a multiuser scenario. This analysis accounts for both random terminal locations and fading impairments in both cases. The findings provide valuable insights into the performance of comparable wireless systems.

eess.SP↗

arXiv2025

Degenerate solutions to the Dirac and Weyl equations and their applications

In this review article we present a comprehensive review of degenerate solutions to the Dirac and Weyl equations, highlighting novel and significant findings. Specifically, we demonstrate that all Weyl particles, and under certain conditions Dirac particles, can occupy the same quantum state under an extensive range of electromagnetic 4-potentials and fields. These fields, which are infinite in number, have been explicitly derived and analysed. Additionally, we establish that Weyl particles can form localized states even in the absence of external electromagnetic fields. Moreover, we show that their localization can be precisely controlled through the application of simple electric fields, offering a tuneable mechanism for manipulating these particles. Building on these insights, we propose an innovative device that utilizes Weyl fermions to control the flow of information at an unprecedented rate of up to 100 petabits per second. This finding has significant implications regarding the development of next-generation electronic and quantum information technologies, as it presents a fundamentally new approach to high-speed data processing and transmission.

quant-ph↗

arXiv2024

A novel device for controlling the flow of information based on Weyl fermions and some interesting remarks regarding the electromagnetic interactions of high energy particles

In this work we propose a novel device for controlling the flow of information using Weyl fermions. Based on a previous work of our group, we show that it is possible to fully control the flow of Weyl fermions on several different channels, by applying an electric field perpendicular to the direction of motion of the particles on each channel. In this way, we can transmit information as logical bits, depending on the existence or not of a Weyl current on each channel. We also show that the response time of this device is exceptionally low, less than 1 ps, for typical values of its parameters, allowing the control of the flow of information at extremely high rates, of the order of 100 Petabits per second. Alternatively, this device could also operate as an electric field sensor. In addition, we demonstrate that Weyl fermions can be efficiently guided through the proposed device using appropriate magnetic fields. Finally, we discuss some particularly interesting remarks regarding the electromagnetic interactions of high energy particles.

quant-ph↗

arXiv2024

Hermite coordinate interpolation kernels: application to image zooming

A number of basic image processing tasks, such as any geometric transformation require interpolation at subpixel image values. In this work we utilize the multidimensional coordinate Hermite spline interpolation defined on non-equal spaced, rectilinear grids and apply it to a very common image processing task, image zooming. Since Hermite interpolation utilizes function values, as well as partial derivative values, it is natural to apply it to image processing tasks as a special case of equi-spaced grid, using numerical approximations of the image partial derivatives at each pixel. Furthermore, the task of image interpolation requires the calculation of image values at positions with nono-zero fractional part. Thus, any spline interpolation can be written as convolution with an appropriate kernel. In this context we generate the Hermite kernels according to the derived $n-$dimensional interpolant of Theorem 2 in [1]. We show that despite the increased complexity of the interpolant, once the kernels are constructed, the Hermite spline interpolation can be applied to images as efficiently as any other less complicated method. Finally, we perform illustrative numerical examples to showcase the applicability and high accuracy of the proposed Hermite kernels for image zooming, compared to other interpolation methods, both traditional convolution-based, as well as employing deep learning, in terms of PSNR, as well as SSIM error metrics. The proposed Hermite spline kernels outperform all other methods in the majority of the test images, in experiments using many cascaded repetitions of the zoom operation. Interesting conclusions can be drawn considering all methods under comparison.

cs.CV↗

arXiv2024

Classical multivariate Hermite coordinate interpolation on n-dimensional grids

In this work, we study the Hermite interpolation on $n$-dimensional non-equally spaced, rectilinear grids over a field $\Bbbk $ of characteristic zero, given the values of the function at each point of the grid and the partial derivatives up to a maximum degree. First, we prove the uniqueness of the interpolating polynomial, and we further obtain a compact closed form that uses a single summation, irrespective of the dimensionality, which is algebraically simpler than the only alternative closed form for the $n$-dimensional classical Hermite interpolation [1]. We provide the remainder of the interpolation in integral form; we derive the ideal of the interpolation and express the interpolation remainder using only polynomial divisions, in the case of interpolating a polynomial function. Moreover, we prove the continuity of Hermite polynomials defined on adjacent $n$-dimensional grids, thus establishing spline behavior. Finally, we perform illustrative numerical examples to showcase the applicability and high accuracy of the proposed interpolant, in the simple case of few points, as well as hundreds of points on 3D-grids using a spline-like interpolation, which compares favorably to state-of-the-art spline interpolation methods.

math.NA↗

arXiv2022

A general method for obtaining degenerate solutions to the Dirac and Weyl equations and a discussion on the experimental detection of degenerate states

In this work we describe a general method for obtaining degenerate solutions to the Dirac equation, corresponding to an infinite number of electromagnetic 4-potentials and fields, which are explicitly calculated. In more detail, using four arbitrary real functions, one can automatically construct a spinor which is solution to the Dirac equation for an infinite number of electromagnetic 4-potentials, defined by those functions. An interesting characteristic of these solutions is that, in the case of Dirac particles with non-zero mass, the degenerate spinors should be localized, both in space and time. Our method is also extended to the cases of massless Dirac and Weyl particles, where the localization of the spinors is no longer required. Finally, we propose two experimental methods for detecting the presence of degenerate states.

quant-ph↗

arXiv2022

Degenerate wave-like solutions to the Dirac equation for massive particles

In this work we provide a novel class of degenerate solutions to the Dirac equation for massive particles, where the rotation of the spin of the particles is synchronized with the rotation of the magnetic field of the wave-like electromagnetic fields corresponding to these solutions. We show that the state of the particles does not depend on the intensity of the electromagnetic fields but only on their frequency, which is proportional to the mass of the particles and lies in the region of Gamma/X-rays for typical elementary charged particles, such as electrons and protons. These novel theoretical results could play an important role in plasma physics, astrophysics, and other fields of physics, involving the interaction of charged particles with high energy photons.

quant-ph↗

arXiv2022

On the remarkable properties of Weyl particles

In this work we show that Weyl particles can exist at different states in zero electromagnetic field, either as free particles, or at localized states described by a parameter with dimensions of mass. We also calculate the electromagnetic fields that should be applied in order to modify the localization of Weyl particles at a desired rate. It is shown that they are simple electric fields, which can be easily implemented experimentally. Consequently, the localization of Weyl particles in certain materials supporting these particles could also be studied experimentally, in the framework of solid-state physics or in the framework of laser physics, using ions trapped by laser beams. In addition, a particularly important remark is that the localization of the energy of the particles can lead to the generation of gravitational mass, according to Einstein's field equations of general relativity. Furthermore, in the case that the energy and localization of the particles exceeds a critical level, tiny black holes could also be created, potential candidates for the dark matter of the universe.

quant-ph↗

arXiv2022

Degenerate solutions to the massless Dirac and Weyl equations and a proposed method for controlling the quantum state of Weyl particles

In a recent work, we have shown that all solutions to the Weyl equation and a special class of solutions to the Dirac equation are degenerate in the sense that they remain unaltered under the influence of a wide variety of different electromagnetic fields. In this study, our previous work is significantly extended, providing a wide class of degenerate solutions to the Dirac equation for massless particles. The electromagnetic fields corresponding to these solutions are calculated and examples regarding both spatially constant electromagnetic fields and electromagnetic waves are also provided. Furthermore, some general solutions to the Weyl equation are presented, and the corresponding electromagnetic fields are calculated. Based on these results, a method for fully controlling the quantum state of Weyl particles using appropriate electromagnetic fields is proposed. Finally, the transition from degenerate to non-degenerate solutions as the particles acquire mass is discussed.

quant-ph↗

arXiv2022

Degenerate solutions to the Dirac equation for massive particles and their applications in quantum tunneling

In a recent work we have proven the existence of degenerate solutions to the Dirac equation, corresponding to an infinite number of different electromagnetic fields, providing also some examples regarding massless particles. In the present article our results are extended significantly, providing degenerate solutions to the Dirac equation for particles with arbitrary mass, which, under certain conditions, could be interpreted as pairs of particles (or antiparticles) moving in a potential barrier with energy equal to the height of the barrier and spin opposite to each other. We calculate the electromagnetic fields corresponding to these solutions, providing also some examples regarding both spatially constant electromagnetic fields and electromagnetic waves. Further, we discuss some potential applications of our work, mainly regarding the control of the particles outside the potential barrier, without affecting their state inside the barrier. Finally, we study the effect of small perturbations to the degenerate solutions, showing that our results are still valid, in an approximate sense, provided that the amplitude of the electromagnetic fields corresponding to the exact degenerate solutions is sufficiently small.

quant-ph↗

arXiv2022

On the connection between the solutions to the Dirac and Weyl equations and the corresponding electromagnetic 4-potentials

In this paper we study in detail the connection between the solutions to the Dirac and Weyl equation and the associated electromagnetic 4-potentials. First, it is proven that all solutions to the Weyl equations are degenerate, in the sense that they correspond to an infinite number of electromagnetic 4-potentials. As far as the solutions to the Dirac equation are concerned, it is shown that they can be classified into two classes. The elements of the first class correspond to one and only one 4-potential, and are called non-degenerate Dirac solutions. On the other hand, the elements of the second class correspond to an infinite number of 4-potentials, and are called degenerate Dirac solutions. Further, it is proven that at least two of these 4-potentials are gauge-inequivalent, corresponding to different electromagnetic fields. In order to illustrate this particularly important result we have studied the denerate solutions to the force-free Dirac equation and shown that they correspond to massless particles. We have also provided explicit examples regarding solutions to the force-free Weyl equation and the Weyl equation for a constant magnetic field. In all cases we have calculated the infinite number of different electromagnetic fields corresponding to these solutions.

math-ph↗