¿Invited Papers.- An Implementation of a Coarse-fine Mesh Stabilized Schwarz Method for a Three-space Dimensional PDE-problem.- Mixed Finite Element Methods for the Navier-Stokes-Biot Model.- Preconditioning and Multilevel Methods.- Numerical Comparison of Block Preconditioners for Poroelasticity.- Two-dimensional Semi-linear Riesz Space Fractional Diffusion Equations in Convex Domains: GLT Spectral Analysis and Multigrid Solvers.- Continuation Newton Methods with Applications to Plasticity.- Fractures and Mixed Dimensional Modeling: Discretizations, Solvers, and Methodology.- Mixed and Nitsche's Discretizations of Frictional Contact-mechanics in Fractured Porous Media.- Machine Learning and Model Order Reduction for Large Scale Predictive Simulations.- Towards Efficient SOT-assisted STT-MRAM Cell Switching Using Reinforcement Learning.- Machine Learning Algorithms for Parameter Identification for Reactive Flow in Porous Media.- Randomized Symplectic Model Order Reduction for Hamiltonian Systems.- Adaptive Localized Reduced Basis Methods for Large Scale PDE-constrained Optimization.- Application of Deep Kernel Models for Certified and Adaptive RB-ML-ROM Surrogate Modeling.- Fractional Differential Problems: Theoretical Aspects, Algorithms and Applications.- Parametric Analysis of Space-time Fractional Pennes Bioheat Model Using a Collocation Method Based on Radial Basis Functions and Chebyshev Polynomials.- Numerical Determination of Source from Point Observation in a Time-Fractional Boundary-Value Problem on Disjoint Intervals.- The Wright Function - Numerical Approximation and Hypergeometric Representation.- Study of Sparsification Schemes for the FEM Stiffness Matrix of Fractional Diffusion Problems.- Fractional Diffusion Problems with Reflecting Boundaries.- Variational Analysis and Optimal Control.- A Mean Field Model For Counter CBRN Threats.- A Sufficient Condition for a Discrete-Time Optimal Control Problem.- Stochastic Optimal Control and Numerical Methods in Economics and Finance.- Computation of the Unknown Time-Dependent Volatility of American Options from Integral Observations.- Tensor Methods for Big Data Analytics and Low-Rank Approximations of PDEs Solutions.- Efficient Solution of Stochastic Galerkin Matrix Equations via Reduced Basis and Tensor Train Approximation.- The Tensor-Train Mimetic Finite Difference Method For Three-dimensional Maxwell's Wave Propagation Equations.- A Functional Tensor Train Library in RUST for Numerical Integration and Resolution of Partial Differential Equations.- Applications of Metaheuristics to Large-Scale Problems.- Solving the Mountain Car Problem Using Genetic Algorithms.- Ant Algorithm with Local Search Procedure for Multiple Knapsack Problem.- Variable Neighborhood Search inHamming Space.- An Improved Algorithm for Fredholm Integral Equations.- Optimization of the Standard Lattice Sequence for Multidimensional Integrals Regarding Large-Scale Finance Problems.- Circular Intuitionistic Fuzzy Knapsack Problem.- Large-Scale Models: Numerical Methods, Parallel Computations and Applications.- Clouds Formed by Thermals Arising and Evolving under the Influence of the Coriolis Force.- A Nonstandard Finite Difference Method for a General Epidemic Model.- Minimization of Energy Functionals via FEM: Implementation of hp-FEM.- Influence of the Grid Resolutions on the Computer Simulated Transport and Transformation Atmospheric Composition Processes over the Territory of Bulgaria.- Development of New High Performance Computer Architectures and Improvements in Danish Eulerian Model for Long Range Transport of Air Pollutants.- Evaluation of the Effects of the National Emission Reduction Strategies for Years 2020-2029 and after 2030 on the AQI on the Territory of Bulgaria.- Mathematical and Computational Modeling of a Nonlinear Elliptic Problem in Divergence Form.- Two Approaches for Identifying Epidemiological Parameters Illustrated with COVID-19 Data for Bulgaria.- Improved Stochastic Lattice Methods for Large-scale Air Pollution Model.- HPC and HPDA: Algorithms and Applications.- Parallel Solution of the Schrödinger-Poisson Equation on GPUs.- Anastylosis of Frescos - a Web Service in an HPC Environment.- A Resolvent Quasi-Monte Carlo Method for Estimating the Minimum Eigenvalues Using the Error Balancing.- Influence of the Grid Resolutions on the Computer Simulated Air Quality Indices over the Territory of Bulgaria.- Application of Active Subspaces for Model Reduction and Identification of Design Space.- EOCSim: A CloudSim-Based Simulator for Earth Observation Data Processing in Clouds.- About Methods of Vector Addition over FiniteFields Using Extended Vector Registers.- Grid Search Optimization of Novel SNN-ESN Classifier on a Supercomputer Platform.- Parallelisms of PG(3,4) with a Great Number of Regular Spreads.- Contributed Papers.- On Some Quadratic Eigenvalue Problems.- Numerical Determination of Time-dependent Volatility for American Option When the Optimal Exercise Boundary Is Known.- Exploring the Global Solution Space of a Simple Schrödinger-Poisson Problem.