This volume contains four different chapters. The first chapter contains the contributed papers focusing on various aspects of the theory of functions and functional spaces. The second chapter is devoted to the research on difference and differential equations and boundary value problems. The third chapter contains the results of studies on differential and integral operators and on the spectral theory. The fourth chapter is focused on the simulation of problems arising in real-world applications of applied sciences.

Part I Theory of Functions and Functional Spaces: G. B. Bakanov, Investigation of Finite-Difference Analogue of the Integral Geometry Problem with a Weight Function.- A. Auwalu and A. Denker, Cone Rectangular Metric Spaces over Banach Algebras and Fixed Point Results of T-contraction Mappings.- F. Kh. Muradov, On the Ternary Semigroups of Continuous Mappings.- F. Hezenci and Y. Sozen, A Note on Representation Variety of Abelian Groups and Reidemeister Torsion.- A. Ashyralyev and A. Taskin, The Structure of Fractional Spaces Generated by a Two-Dimensional Difference Neutron Transport Operator and Its Applications.- M. A. Sadybekov and B. O. Derbissaly, Boundary Conditions of Volume Hyperbolic Potential in a Domain with Curvilinear Boundary.- Part II Differential Equations and Boundary Value Problems: S. C. Buranay and L. A. Farinola, Six Point Implicit Methods for the Approximation of the Derivatives of the Solution of First Type Boundary Value Problem for HeatEquation.- C. Ashyralyyev, Identification Elliptic Problem with Dirichlet and Integral Conditions.- V. V. Karachik and B. Kh.Turmetov, On Solvability of Some Boundary Value Problems with Involution for the Biharmonic Equation.- A. Ashyralyev, T. A. Hidayat and A. Sarsanbi, On the stability of Schrodinger type involutory differential equations.- M. Ashyraliyev, A. Ashyralyev and V. Zvyagin, A Space-Dependent Source Identification Problem for Hyperbolic-Parabolic Equations.- A. Ashyralyev, K. Turk and D. Agirseven, On the Stability of the Time Delay Telegraph Equation with Neumann Condition.- M. Ashyraliyev and M. A. Ashyralyyeva, A Note on a Hyperbolic-Parabolic Problem with Involution.- A. Ashyralyev and A. S. Erdogan, Numerical Solution of a Parabolic Source Identification Problem with Involution and Neumann Condition.- Part III Differential and Integral Operators and Spectral Theory: D. Shilibekova, Uncertainty Type Principles for Radial Derivatives.- A. Kashkynbayev and M. Mustafa,Basic Theory of Impulsive Quaternion-Valued Linear Systems.- A. Kassymov and D. Suragan, Lyapunov-Type Inequality for Fractional Sub-Laplacians.- Part IV Mathematical Methods in Physical Sciences: A. Boldyrev and V. Zvyagin, Attractors for Weak Solutions of a Regularized Model of Viscoelastic Mediums Motion With Memory in Non-Autonomous Case.- E. Hincal, M. Sayan, B. Kaymakamzade, T. Sanlidag, F. Tijjani Sa'ad and Isa A. Baba, Trends and Risk of HIV/AIDS in Turkey and Its Cities.- O. Yildirim and M. Uzun, A Unified Numerical Method for Solving System of Nonlinear Wave Equations.- E. Hincal, G. Soykut, F. Tijjani Sa'ad, S. Vatansever, Isa A. Baba, I. Çalis, B. Kaymakamzade and Eda Becer, Comparison of The Rate of Induced Intrinsic Pathway of Apoptosis on COLO-320 and COLO-741.