Bulletin of the Transilvania University of Brasov. Series III: Mathematics and Computer Science

Multispectral image visualization and NDVI-based anomaly detection

A. Baicoianu, M. Ivanovici, I.C. Plajer — Tue, 23 Jun 2026 00:00:00 +0000

Satellite imagery is essential for advancing precision agriculture, providing the foundation for accurate monitoring and decision-making. A key initial step in analyzing multispectral images is achieving a visualization that accurately reflects real-world conditions. Effective visualization mechanisms, such as those driven by Machine Learning (ML), depend on the availability of well-structured datasets. This study investigates how characteristics such as the quantity, variability, and quality of datasets influence the quality of visualization outcomes. Our findings highlight that data quantity and variability are more critical than quality in achieving optimal results. The research also explores the use of standard Macbeth color charts to improve dataset consistency in spectral analysis. Additionally, we propose a straightforward and computationally efficient methodology for interpreting and analyzing multispectral images in the context of anomaly detection. Using the Normalized Difference Vegetation Index (NDVI), this approach enables automatic identification of potential crop development issues, offering practical benefits for agricultural health monitoring and early intervention strategies. By addressing the challenges of data availability and proposing an anomaly detection methodology, this study provides valuable insights into the use of satellite imagery for monitoring and improving agricultural practices. These findings contribute to the broader understanding of optimizing satellite imagery analysis for agricultural applications.

A multidimensional approach to predicting action probability from text

V. Belciug, E. Pelican — Tue, 23 Jun 2026 00:00:00 +0000

Predicting the probability of action from textual data has been an area of growing interest in various domains, including social media analysis, customer support, psychology, criminology, and online marketing. Our paper proposes a novel approach that combines multiple text representation techniques, ensemble methods, and a multidimensional linguistic analysis framework to predict the probability of action from text data. The approach consists of five main phases: data preprocessing, text representation, feature fusion and selection, multidimensional analysis and action probability prediction.

In memoriam Professor Dr. Nicolae Tita

M. Talpau Dumitriu, A. Danila — Tue, 23 Jun 2026 00:00:00 +0000

No abstract

Existence and uniqueness of solutions for a nonlinear equation with convection term

Mustapha Ait Hammou — Tue, 23 Jun 2026 00:00:00 +0000

In this paper, we consider the existence and uniqueness of weak solutions of a nonlinear elliptic equation with a variable exponent, a monotonic type operator, and a convection term. With the topological degree theory, we prove the existence of at least one weak solution under some Leray-Lions and growth conditions. Moreover, we obtain the uniqueness of the solution of the problem under some additional assumptions. Our results generalize and improve existing results with another approach.

Remarks on the coefficients of ternary cyclotomic and inverse cyclotomic polynomials

D. Andrica, O. Bagdasar, M.Th. Rassias, G.C. Turcas — Tue, 23 Jun 2026 00:00:00 +0000

Using a formula attributed to Von Sterneck, we present a method for deriving recursive relations for the coefficients of ternary cyclotomic polynomials Φ_n(x) and ternary inverse cyclotomic polynomials Ψ_n(x). We consider n = pqr with p < q < r are primes. As an application, we determine exact values for the first (p + 1) coefficients. For an infinite subfamily, the first r coefficients are computed. In the case of ternary cyclotomic polynomials, we identify an explicit infinite family whose r-th coefficient is equal to −2. Additionally, we include a section on numerical simulations that demonstrates the computation of non-flat coefficients in specific cases for Φ₁₀₅ and Ψ₅₆₁.

Fractional ψ-Hilfer derivative spaces: study of Kirchhoff problem with p(•)-Laplacian operator

E. Arhrrabi, H. El-Houari — Tue, 23 Jun 2026 00:00:00 +0000

The paper focuses on the existence and multiplicity of weak solutions to the nonlinear Kirchhoff-type equations involving ψ-Hilfer derivatives with p(・)-Laplacian operators and Dirichlet boundary conditions. Through the application of a critical point approach, along with genus theory and variational techniques, we establish the existence of infinitely many positive solutions within appropriate ψ-Hilfer fractional derivative spaces. Our novel main results contribute to the advancement of the literature on differential equations involving the ψ-Hilfer fractional derivative.

A pursuit-evasion differential game on a compact subset of ℝ^2 with geometric constraints

A. Asgharzadeh-Bonab, H. Bigdeli, J. Mohammadkarimi — Tue, 23 Jun 2026 00:00:00 +0000

In this paper, we study a pursuit differential game with many pursuers and evaders on a compact and not necessarily convex subset M of ℝ². Their motion’s equation is a first-order differential equation. Players must play in this set M. For control functions of the players, we use geometric constraints. Completion of the pursuit means that the state of each of the evaders coincides with that of a pursuer in the plane. We derive sufficient conditions for completion of pursuit on this set M. We constructed a strategy of the pursuers that guarantees completion of the pursuit. Moreover, we construct winning strategies for pursuers.

Boas-type theorems for the modified Whittaker transform

M. El Bouazizi, M. El Hamma, R Daher — Tue, 23 Jun 2026 00:00:00 +0000

In this paper, we give necessary and sufficient conditions in terms of FW(f), the modified Whittaker transform of f, to ensure that f belongs either to one of the generalized Lipschitz classes H^p_δ and h^p_δ for δ > 0.

Univalence criteria for certain integral operator

M. Dicu, P. Dicu, E.S. Grigoriciuc — Tue, 23 Jun 2026 00:00:00 +0000

Dedicated to the memory of Professor Petric˘a Dicu
In this paper, we introduce a new general integral operator for analytic functions in the open unit disk U in ℂ as an extension of the integral operator defined by P. Dicu, M. Dicu, and A.F. Albi¸soru. We focus our attention on some sufficient conditions for the univalence of the integral operator. We end this paper with a remark on a modification of the studied integral operator.

Analysis of results for a quasistatic frictional contact problem with normal damped response in thermo-viscoelasticity

Ahmed Hamidat — Tue, 23 Jun 2026 00:00:00 +0000

In this manuscript, we explore a mathematical model that describes the quasistatic contact process with friction between a body governed by a nonlinear thermo-viscoelastic constitutive law and an obstacle. The contact is represented using a general condition for a normal damped response. We then develop a variational formulation for the mechanical problem and prove the existence of a weak solution. The proof is based on techniques involving variational inequalities, parabolic variational equality, and fixed-point methods. Finally, a perturbation of the data is introduced, and a convergence result is established as the perturbation parameter approaches zero.

Starlike functions associated with Q-multiplicative derivative

Kadhavoor R. Karthikeyan — Tue, 23 Jun 2026 00:00:00 +0000

The rate of change of a function in the sense of multiplicative complex derivative, expressed in terms of quantum derivative, has not been used to study the various subclasses of univalent functions. Here, we attempt to define a new family of analytic functions by replacing the ordinary derivative in the analytic characterization of the starlike function with a quantity influenced by the definition of Q-multiplicative derivative. We explore the properties of a class of functions involving such a restrictive calculus. We obtain the estimates for the initial coefficients and Fekete-Szeg˝o inequalities of the defined function classes. Also, we have obtained the coefficient estimates for the inverse function.

On Cauchy-Riemann structure and integrability conditions of F-structure satisfying F3-F2+F=0

F. Latti, A. Zagane — Tue, 23 Jun 2026 00:00:00 +0000

In this paper, we present the F-structures satisfying F3−F2+F = 0, and then we study the Cauchy-Riemann structure and the relationship between it and the F-structure. We also discuss some problems of integrability, partial integrability, and complete integrability for this structure. Finally, we also provide some examples of the F-structure.

An alternative proof of the Catalan conjecture

C. Liu, P. Mihailescu — Tue, 23 Jun 2026 00:00:00 +0000

The original proof [8] of Catalan’s conjecture uses real binomial power series expansions and annihilation of real class groups, based on a Theorem of Thaine. In this paper we provide a simplified approach to this proof, which uses Stickelberger annihilation of the minus part of the class group, and thus does not require the Theorem of Thaine.

Introduction to generalized Leonardo-Alwyn hybrid numbers

G. Morales — Tue, 23 Jun 2026 00:00:00 +0000

In [6], Gokbas defined a new type of number sequence called the Leonardo-Alwyn sequence. In this paper, we consider the generalized Leonardo-Alwyn hybrid numbers and investigate some of their properties. We also give some applications related to the generalized Leonardo-Alwyn hybrid numbers in matrices.

Study of vector fields under some special transformation

H.G. Nagaraja, Y. Ramanaik — Tue, 23 Jun 2026 00:00:00 +0000

In this paper, we examine holomorphic conformal vector fields on almost contact metric manifolds subjected to a special transformation. Furthermore, we establish the invariance of concircular, projective, and affine conformal vector fields on a Sasakian manifold under the special transformation.

Convergence of Steffensen’s method in Riemannian manifolds

P.K. Parida, C. Prasad — Tue, 23 Jun 2026 00:00:00 +0000

The main purpose of this article is to establish the semilocal convergence analysis of Steffensen’s method in Riemannian manifolds. We establish the semilocal convergence analysis of Steffensen’s method in Riemannian manifolds by using the majorant principle. Finally, some examples are presented to verify the convergence criteria.

Some important characterizations of pseudo W8-curvature tensor within the framework of (LCS)n-manifolds

P. Sharma, G.P. Singh — Tue, 23 Jun 2026 00:00:00 +0000

This study investigates the pseudo W₈-curvature tensor bW₈ on (LCS)_n-manifolds. The study examines pseudoW8-flat and ζ-pseudo W₈-flat (LCS)_n-manifolds, leading to notable findings. An (LCS)_n-manifold satisfying the φ- pseudo W₈- semisymmetric condition is found to be a generalized η-Einstein manifold. Curvature conditions bW₈ ・Q = 0, bW₈ ・R = 0, and R(ζ,H₁)・bW₈ = 0 lead to the manifold being Einstein or η-Einstein. The pseudo W8-Ricci pseudosymmetric condition and η-Ricci solitons under bW₈(ζ,H₁) ・S = 0 and S(ζ,H₁) ・ bW₈ = 0 yield notable results. Conservative, irrotational, cyclic parallel, and η-parallel Ricci tensors are also analyzed.

On k-modified harmonic polynomials and their dimensions

Eleutherius Symeonidis — Tue, 23 Jun 2026 00:00:00 +0000

In this article, we find out the dimensions of the various spaces of homogeneous k-modified harmonic polynomials for every degree of homogeneity and for all exceptional values of k, the general case in k having been studied before.