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Article Citation - WoS: 1Citation - Scopus: 1An Inverse Problem for Two Spectra of Complex Finite Jacobi Matrices(Tech Science Press, 2012) Guseinov, Gusein Sh.; MathematicsThis paper deals with the inverse spectral problem for two spectra of finite order complex Jacobi matrices (tri-diagonal symmetric matrices with complex entries). The problem is to reconstruct the matrix using two sets of eigenvalues, one for the original Jacobi matrix and one for the matrix obtained by replacing the first diagonal element of the Jacobi matrix by some another number. The uniqueness and existence results for solution of the inverse problem are established and an explicit algorithm of reconstruction of the matrix from the two spectra is given.Article Citation - WoS: 3Citation - Scopus: 3Drbem Solution of Mhd Flow With Magnetic Induction and Heat Transfer(Tech Science Press, 2015) Pekmen, B.; Tezer-Sezgin, M.; MathematicsThis study proposes the dual reciprocity boundary element (DRBEM) solution for full magnetohydrodynamics (MHD) equations in a lid-driven square cavity. MHD equations are coupled with the heat transfer equation by means of the Boussinesq approximation. Induced magnetic field is also taken into consideration. The governing equations in terms of stream function, temperature, induced magnetic field components, and vorticity are solved employing DRBEM in space together with the implicit backward Euler formula for the time derivatives. The use of DRBEM with linear boundary elements which is a boundary discretization method enables one to obtain small sized linear systems. This makes the whole procedure computationally efficient and cheap. The results are depicted with respect to varying physical parameters such as Prandt1 (0.005 <= Pr <= 1), Reynolds (100 <= Re <= 2500), magnetic Reynolds (1 <= Rein <= 100), Hartmann (10 <= Ha <= 100) and Rayleigh (10 <= Ra <= 10(6)) numbers for discussing the effect of each parameter on the flow and temperature behaviors of the fluid. It is found that an increase in Ha slows down the fluid motion and heat transfer becomes conductive. Centered square blockage causes secondary flows on its left and light even for small Re. Strong temperature gradients occur around the blockage and near the moving lid for increasing values of Ra.Article Citation - WoS: 3Citation - Scopus: 4Robust Backstepping Control of a Quadrotor Unmanned Aerial Vehicle Under Colored Noises(Tech Science Press, 2025) Karahan, MehmetAdvances in software and hardware technologies have facilitated the production of quadrotor unmanned aerial vehicles (UAVs). Nowadays, people actively use quadrotor UAVs in essential missions such as search and rescue, counter-terrorism, firefighting, surveillance, and cargo transportation. While performing these tasks, quadrotors must operate in noisy environments. Therefore, a robust controller design that can control the altitude and attitude of the quadrotor in noisy environments is of great importance. Many researchers have focused only on white Gaussian noise in their studies, whereas researchers need to consider the effects of all colored noises during the operation of the quadrotor. This study aims to design a robust controller that is resistant to all colored noises. Firstly, a nonlinear quadrotor model was created with MATLAB. Then, a backstepping controller resistant to colored noises was designed. The designed backstepping controller was tested under Gaussian white, pink, brown, blue, and purple noises. PID and Lyapunov-based controller designs were also carried out, and their time responses (rise time, overshoot, settling time) were compared with those of the backstepping controller. In the simulations, time was in seconds, altitude was in meters, and roll, pitch, and yaw references were in radians. Rise and settling time values were in seconds, and overshoot value was in percent. When the obtained values are examined, simulations prove that the proposed backstepping controller has the least overshoot and the shortest settling time under all noise types.Article Citation - WoS: 15Citation - Scopus: 17A Parallel Boundary Element Formulation for Tracking Multiple Particle Trajectories in Stoke's Flow for Microfluidic Applications(Tech Science Press, 2015) Karakaya, Z.; Baranoglu, B.; Cetin, B.; Yazici, A.; Computer Engineering; Software EngineeringA new formulation for tracking multiple particles in slow viscous flow for microfluidic applications is presented. The method employs the manipulation of the boundary element matrices so that finally a system of equations is obtained relating the rigid body velocities of the particle to the forces applied on the particle. The formulation is specially designed for particle trajectory tracking and involves successive matrix multiplications for which SMP (Symmetric multiprocessing) parallelisation is applied. It is observed that present formulation offers an efficient numerical model to be used for particle tracking and can easily be extended for multiphysics simulations in which several physics involved.Article Citation - WoS: 1Citation - Scopus: 1Implementation of a Parallel Dual Reciprocity Boundary Element Method for the Solution of Coupled Thermoelasticity and Thermoviscoelasticity Problems(Tech Science Press, 2012) Koyuncu, M.; Ikikat, F. Y.; Icoz, G. C.; Baranoglu, B.; Yazici, A.; Information Systems Engineering; Manufacturing Engineering; Software EngineeringA parallel dual reciprocity boundary element method solution to thermoelasticity and thermoviscoelasticity problems is proposed. The DR-BEM formulation is given in Fourier Transform Space where the Time Space solutions are obtained through inverse Fourier Transform. The parallellization of the code is achieved through solving each frequency at a distinct computational node. The implemented parallel code is tested on 64-core IBM blade servers and it is seen that a linear speed-up is achieved.Article Citation - WoS: 1Citation - Scopus: 1Fair-News: Digital Journalism Model To Prevent Information Pollution and Manipulation(Tech Science Press, 2023) Takan, Savas; Ergun, Duygu; Katipoglu, GokmenAs digital data circulation increases, information pollution and manipulation in journalism have become more prevalent. In this study, a new digital journalism model is designed to contribute to the solution of the main current problems, such as information pollution, manipulation, and account-ability in digital journalism. The model uses blockchain technology due to its transparency, immutability, and traceability. However, it is tough to provide the mechanisms necessary for journalism, such as updating one piece of information, instantly updating all other information affected by the updated information, establishing logical relationships between news, making quick comparisons, sorting and indexing news, and keeping the changing informa-tion about the news in the system, with the blockchain data structure. For this reason, in our study, we have developed a new data structure that provides both the immutability, transparency and traceability properties of the blockchain and can support the communication mechanisms necessary for journalism. The functionality of our proposed data structure is demonstrated in terms of communication mechanisms such as mutability, context, consistency, and reliability through example scenarios. Additionally, our data structure is compared with the data structure of blockchain technology in terms of time, space, and maintenance costs. Accordingly, while the model size increases linearly in blockchain, the model's size remains approximately constant since the structure we developed is data-independent. In this way, maintenance costs are reduced. Since our model also has an indexing mechanism, it reduces the linear time search complexity to logarithmic time. As a result, the data structure we developed is found to have higher performance than blockchain in the journalism concept. In future studies, it is planned to test all aspects of the model with a pilot application, eliminate its shortcomings, and develop a holistic approach to the root causes of the problems in the journalism focus.Article Citation - WoS: 7Citation - Scopus: 12Genetic Algorithm and Tabu Search Memory With Course Sandwiching (gats_cs) for University Examination Timetabling(Tech Science Press, 2020) Abayomi-Alli, A.; Misra, S.; Fernandez-Sanz, L.; Abayomi-Alli, O.; Edun, A. R.University timetable scheduling is a complicated constraint problem because educational institutions use timetables to maximize and optimize scarce resources, such as tine and space. In this paper, an examination timetable system using Genetic Algorithm and Tabu Search memory with course sandwiching (GAT_CS), was developed fora lame public University. The concept of Genetic Algorithm with Selection and Evaluation was implemented while the memory properties of Tabu Search and course sandwiching replaced Crossover and Mutation. The result showed that GAT_CS had hall allocation accuracies of 96.07% and 99.02%, unallocated score of 3.93% and 0.98% for first and second semesters, respectively. It also automatically sandwiched (scheduled) multiple examinations into single halls with a simulation time in the range of 20-29.5 seconds. The GAT_CS outperformed previous related works on the same timetable dataset. It could, however, be improved to reduce clashes, duplications, multiple examinations and to accommodate more system-defined constraints.Article Citation - WoS: 4Citation - Scopus: 5Drbem Solution of Incompressible Mhd Flow With Magnetic Potential(Tech Science Press, 2013) Pekmen, B.; Tezer-Sezgin, M.; MathematicsThe dual reciprocity boundary element method (DRBEM) formulation is presented for solving incompressible magnetohydrodynamic (MHD) flow equations. The combination of Navier-Stokes equations of fluid dynamics and Maxwell's equations of electromagnetics through Ohm's law is considered in terms of stream function, vorticity and magnetic potential in 2D. The velocity field and the induced magnetic field can be determined through the relations with stream function and magnetic potential, respectively. The numerical results are visualized for several values of Reynolds (Re), Hartmann (Ha) and magnetic Reynolds number (Rem) in a lid-driven cavity, and in a channel with a square cylinder. The well-known characteristics of the fluid flow and MHD flow are exhibited. These are the shift of the core region of the flow and the development of the main vortex in the vorticity through the center of the cavity as Re increases. An increase in Ha causes Hartmann layers for the flow at the bottom and top walls. Higher values of Rem result in circulation of the magnetic potential at the center of the cavity. An increase in Re causes symmetric vortices behind the cylinder to elongate through the channel, and an increase in Hartmann number suppresses this elongation.Article Citation - WoS: 1Citation - Scopus: 1On Determination of a Finite Jacobi Matrix From Two Spectra(Tech Science Press, 2012) Guseinov, Gusein Sh; MathematicsIn this work we study the inverse spectral problem for two spectra of finite order real Jacobi matrices (tri-diagonal matrices). The problem is to reconstruct the matrix using two sets of eigenvalues, one for the original Jacobi matrix and one for the matrix obtained by replacing the first diagonal element of the Jacobi matrix by some another number. The uniqueness and existence results for solution of the inverse problem are established and an explicit procedure of reconstruction of the matrix from the two spectra is given.
