Elektronik ve Haberleşme Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/260
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Article Citation - WoS: 5Citation - Scopus: 9Strategy Creation, Decomposition and Distribution in Particle Navigation(Elsevier Science inc, 2007) Leblebicioglu, Kemal; Beldek, UlasStrategy planning is crucial to control a group to achieve a number of tasks in a closed area full of obstacles. In this study, genetic programming has been used to evolve rule-based hierarchical structures to move the particles in a grid region to accomplish navigation tasks. Communications operations such as receiving and sending commands between particles are also provided to develop improved strategies. In order to produce more capable strategies, a task decomposition procedure is proposed. In addition, a conflict module is constructed to handle the challenging situations and conflicts such as blockage of a particle's pathway to destination by other particles. (C) 2006 Elsevier Inc. All rights reserved.Article Diffraction in Time of Matter Waves Located in a Confined Region(Springer Heidelberg, 2022) Umul, Yusuf Z.The process of diffraction in time of a standing matter wave is studied. This case occurs generally when a quantum particle is confined in a trap or infinite potential well. First of all, the wave-function of a classical time diffracted matter wave is studied by considering a separation of the Fresnel function in terms of geometrical optics and diffracted waves. The behavior of the matter wave which is the counterpart of a geometrical optics field is investigated. Then a confined particle in a one-dimensional infinite potential well is taken into account. One of the walls of the trap is remained at an initial time and the process of diffraction in time is formulated by using the information, obtained from the geometrical optics fields. Some numerical results are given. This paper proposes two original approaches. The first one is the application of the optical diffraction theory to quantum physics. This is the separation of the scattered field into geometric optics and diffracted wave components. The second novelty is the addition of the effects of both of the traveling waves, which compose the standing wave, to the scattering integral.Article Citation - WoS: 1Citation - Scopus: 2Wave Diffraction by a Thin Lossy Dielectric Half-Plane(Elsevier Gmbh, 2021) Umul, Yusuf ZiyaThe scattering of electromagnetic waves by a thin lossy dielectric half-plane is investigated. With this aim, the interaction process of waves with a dielectric layer is studied. The reflection and transmission coefficients are obtained in the limiting case, which is defined when the thickness of the layer is sufficiently smaller than the wavelength. The diffracted waves by the half-plane are evaluated using the method of transition boundary. Some numerical results are given. We will study the interaction problem of electromagnetic waves by a thin lossy dielectric half-plane in this paper. It will be supposed that the width of the dielectric layer is sufficiently smaller than the wavelength of the incident field. In the literature, such a structure is modeled by the resistive boundary conditions [1]. The scattering of waves by a resistive half-plane has been investigated in the literature by some authors [2-9]. Rawlins [10] solved the diffraction problem of plane waves by a thin dielectric half-screen by using approximate boundary conditions. Anderson [11] studied the same scenario and obtained a solution with the method of dual integral equation. A Wiener-Hopf approach was applied by Chakrabarti [12] to the dielectric half-plane, illuminated by a plane electromagnetic wave. Senior and Volakis [13] derived approximate boundary conditions for a thin dielectric layer and applied them to the diffraction problem, under consideration, for magnetic polarization [14]. We will take into consideration a lossy dielectric layer with finite width d and derive the reflected and transmitted electromagneticArticle Citation - WoS: 1Citation - Scopus: 1Wave Diffraction by a Perfect Magnetic Conductor Half-Plane Between Free Space and Anisotropic Plasma(Elsevier Gmbh, 2020) Umul, Yusuf ZiyaThe diffraction of magnetic polarized electromagnetic plane waves by a perfect magnetic conductor half-screen, located between free space and anisotropic plasma, is studied. The method of transition boundary is used for the solution of the problem. The scattered GO wave is obtained. The diffracted fields are derived with the aid of the scattered GO wave. The uniform expressions of the edge diffracted waves are derived. The behaviors of the evaluated fields are investigated numerically.Article Citation - WoS: 17Citation - Scopus: 23Voronoi Boundary Visibility for Efficient Path Planning(Ieee-inst Electrical Electronics Engineers inc, 2020) Al-Dahhan, Mohammed Rabeea Hashim; Schmidt, Klaus WernerThe subject of this paper is the computation of paths for mobile robots that navigate from a start position to a goal position in environments with static obstacles. Specifically, we focus on paths that are represented by straight lines. Such paths can for example directly be followed by omni-directional robots or can be used as an initial solution for path smoothing. In this context, the most common performance metrics are the path length, the obstacle clearance and the computation time. In this paper, we develop a new path planning algorithm that addresses all the stated performance metrics. Our method first determines all possible connections between the start position and goal position along the edges of the generalized Voronoi diagram (GVD) of a given obstacle map. The shortest connections are then refined using a balanced method for creating shortcuts along existing waypoints and introducing new waypoints in order to cut corners. As an important feature, our method reduces the number of required waypoints by iteratively adding new waypoints and then removing unnecessary waypoints along solution paths. Moreover, our method takes into account multiple start-goal connections, since the shortest start-goal connection along the edges of the GVD might not lead to the shortest solution path. A comprehensive computational evaluation for a large number of maps with different properties shows that the proposed method outperforms sampling-based algorithms such as Probabilistic Roadmaps (PRM) and exact methods such as Visibility Graphs (VG) by computing close-to-optimal solution paths with a specified minimum obstacle clearance in less time.Article The Standing Matter Waves and Bohm's Quantum Potential(Elsevier Gmbh, 2021) Umul, Yusuf ZiyaThe standing wave type wave functions are investigated in terms of Bohm's decomposition of the Schro spacing diaeresis dinger equation. It is shown that the quantum potential, obtained for the standing matter waves, is always different from zero. However, it is also put forth that the wave function do not satisfy the Bohm's equations except one case, which is defined in the Cartesian coordinates. The Airy type matter wave is also analyzed in terms of the Bohmian approach.Article Citation - WoS: 2Citation - Scopus: 8Scattering of Electromagnetic Waves by an Impedance Sheet Junction in Anisotropic Plasma(Elsevier Gmbh, 2020) Umul, Yusuf ZiyaThe diffraction of electromagnetic plane waves by the edge discontinuity of an impedance sheet junction, which is located in an anisotropic plasma, is investigated. The problem is solved by the integral theory of diffraction. The scattering integral is obtained from the scattered geometric optics wave. The diffracted fields are derived by the edge point evaluation of the scattering integral. The evaluated field expressions are analyzed numerically.Article Propagation and Diffraction of Surface Plasmons on a Resistive Half-Plane(Elsevier Gmbh, 2020) Umul, Yusuf ZiyaThe propagation, radiation and diffraction characteristics of surface plasmons, on a discontinuous dielectric layer, are investigated. The layer is modeled by a resistive surface. The physical optics based formulation of the surface waves is taken into account. The physical optics integral includes the propagating and diffracting fields. These wave components are evaluated asymptotically and their behaviors are studied numerically.Article Citation - WoS: 3Citation - Scopus: 5On the Reality of the Bohmian Potential(Elsevier Gmbh, 2020) Umul, Yusuf ZiyaThe existence of the Bohmian quantum potential is investigated in terms of the energy relation of a quantum particle. The derivation process of the quantum potential is applied to the Helmholtz equation and it is shown that a similar term also occurs in this case. The possibility of the existence of a potential term is questioned according to the frequency and wave-number quantities of a wave which is the solution of the Helmholtz equation. By using the same approach, it is shown that the quantum potential should be equal to zero. Some examples are studied in terms of the wave function.Article Citation - WoS: 3Citation - Scopus: 3Diffraction of Electromagnetic Waves by an Anomalously Transmitting Metasurface Half-Plane in Anisotropic Plasma(Elsevier Gmbh, 2020) Umul, Yusuf Z.The paper deals with the scattering of magnetic polarized electromagnetic plane waves by a anomalously transmitting metasurface half-plane, located in anisotropic plasma. Such a medium occurs for cold magnetized plasma, in which a static magnetic field exists. In this case the permittivity of the medium is expressed as a tensor, the elements of which are functions of the magnetostatic field, electron's mass and charge and angular frequency of the plasma. The metasurface half-plane transmits part of the incoming electromagnetic wave with a different angle from the angle of incidence, absorbing the remaining part. First of all, we will obtain the scattered geometric optics wave by subtracting the incident field from the total geometric optics wave. Then the kernel of a physical optics type scattering integral will be constructed with the aid of the integral theory of diffraction. The uniform diffracted magnetic field will be obtained from the physical optics integral. The total magnetic field will be evaluated as a sum of the total geometric optics and diffracted waves. The behaviours of the derived fields will be analyzed numerically.