Elektrik Elektronik Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/411
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Article Citation - WoS: 1Citation - Scopus: 1Sustainable Management of a Renewable Fishery Resource With Depensation Dynamics From a Control Systems Perspective(Gazi Univ, 2022) Cıfdaloz, OguzhanHuman societies are exploiting natural renewable sources such as fisheries, forests, groundwater basins, rivers, and soil at an increasing intensity. Around the world, these resources are being managed by various institutions or governments. One of the challenges faced by institutions is to develop strategies and policies to effectively manage these renewable resources under social and ecological uncertainties, disturbances, policy implementation difficulties, and measurement errors. In this paper, a fishery is considered as an example and the problem of managing a fishery is approached from a control systems perspective. The justification behind this approach is due to the observation that the problem of managing a renewable resource can be posed as a control systems problem and that the discipline of control systems possesses tools and methods to deal with model uncertainties, external disturbances, measurement errors and implementation issues. For the fishery, a depensation type population dynamics model is considered. Depensatory models are used in social/ecological systems in order to model dynamics of certain species of fish populations. An optimal control strategy based on Pontryagin’s Maximum Principle is derived and its sustainability and robustness properties with respect to parametric uncertainties, measurement errors and disturbances are examined. Finally, a sub-optimal but more robust control strategy is proposed and its robustness properties are provided. The main objective of the paper is to show that a control systems engineering approach can be applied to a social-ecological problem and it can provide easy to implement management strategies, insight, and guidance into the management of renewable resources.Article Citation - WoS: 1Citation - Scopus: 1Design Studies of Vsc Hvdc Converter According To Ac Voltage Tests(Mdpi, 2022) Iskender, Ires; Haliloglu, Ali BurhanSince high-voltage direct current (HVDC) systems are very expensive and operationally critical, these systems must be tested before they are put into service. Insulation and performance tests are the two main subjects of these tests. AC voltage tests, as part of the insulation tests, should be performed after system installation is complete and before commissioning. However, in this study, the objective was to perform these tests during the prototype phase of VSC HVDC. Unlike other studies, this study attempted to use COMSOL Multiphysics to determine in advance the problems that may occur in the real system. In this regard, the busbars connecting the submodules of the VSC HVDC system were first modeled in 3D, and the tests to be performed were simulated using COMSOL Multiphysics software. During the simulation, the finite element method (FEM) was used to identify critical points that could cause partial discharge. To validate the simulation results, partial discharge tests on a real system were conducted, and the design changes made in response to each test result were explained. After the improvement actions, the targeted partial discharge values were achieved.Article A Novel Solution for Network Flexibility Problem in Mobile Multi-Hop Tunneling Networks(Springer, 2023) Preveze, BarbarosSince the network throughput performance is limited by the available technology limits, there are too many attempts in the literature to improve the throughput performance of the network by modifying the routing algorithms currently in use. Although application of the tunneling on IP networks provides reserved paths for the higher priority packet streams and succeeds in providing faster communication performances, it is also determined in the literature that, the greatest up to date problem of tunneling networks is the flexibility problem, which is defined as the problem of difficulty to have minimal delay and highest throughput when congestions or node failures occur and the throughput decreases due to high traffic loads on the network. sIn this work, a high performance solution, called LB-ACN (Location Based- Avoid Congested Node) is proposed to solve this flexibility problem and to compensate the increased delay which came up due to the high traffic load and also due to inflexible tunneling network structure, considering the locations of the nodes in addition to their traffic loads. And it is shown that, it is succeeded to carry the throughput of the highly traffic loaded network back to 48.6 Mbps from 36.9 Mbps by about 31.7% performance improvement for which we could improve it from 36.9 Mbps up to 45.9 Mbps by 24.3% using the proposed ACN (Avoid Congested Node) algorithm in our previous work. As a result, we have succeeded in having about 7.4% more improvement on throughput performance in comparison with the previously proposed ACN algorithm.Article Line-Of Rate Construction for a Roll-Pitch Gimbal Via a Virtual Pitch-Yaw Gimbal(Tubitak Scientific & Technological Research Council Turkey, 2021) Cifdaloz, OguzhanIn this paper, a method to construct the line of sight rate of a target with a roll-pitch gimbal and tracker is described. Construction of line-of-sight rate is performed via utilizing a virtual pitch-yaw gimbal. Kinematics of both the roll-pitch and pitch-yaw gimbals are described. A dynamical model for the roll-pitch gimbal is developed, and a nested control structure is designed to control the angular rates and line of sight angles. A kinematic model of the tracker is developed and a tracker controller is designed to keep the target in the field of view. Conversion equations between roll-pitch and pitch-yaw gimbal configurations are provided. Finally, constructed line of sight rates are compared to true line of sight rates via simulations. Obtained results indicate that the constructed line of sight rates pertaining to a target satisfactorily converge to the actual line of sight rates.Article Citation - WoS: 3Citation - Scopus: 3Filter Design for Small Target Detection on Infrared Imagery Using Normalized-Cross Layer(Tubitak Scientific & Technological Research Council Turkey, 2020) Demir, H. Seckin; Akagunduz, ErdemIn this paper, we introduce a machine learning approach to the problem of infrared small target detection filter design. For this purpose, similar to a convolutional layer of a neural network, the normalized-cross-correlational (NCC) layer, which we utilize for designing a target detection/recognition filter bank, is proposed. By employing the NCC layer in a neural network structure, we introduce a framework, in which supervised training is used to calculate the optimal filter shape and the optimum number of filters required for a specific target detection/recognition task on infrared images. We also propose the mean-absolute-deviation NCC (MAD-NCC) layer, an efficient implementation of the proposed NCC layer, designed especially for FPGA systems, in which square root operations are avoided for real-time computation. As a case study we work on dim-target detection on midwave infrared imagery and obtain the filters that can discriminate a dim target from various types of background clutter, specific to our operational concept.Article Citation - WoS: 5Citation - Scopus: 5Raman Mode Non-Classicality Through Entangled Photon Coupling To Plasmonic Modes(Optical Soc Amer, 2018) Salmanogli, AhmadIn this article, non-classical properties of Raman modes are investigated. The original goal, actually, is to identify how and by which method we can induce non-classicality in Raman modes. We introduce a plasmonic system in which Raman dye molecules are buried between two shells of the plasmonic materials, similar to an onionlike core/shell nanoparticle. This system is excited by the entangled two-photon wave, followed by analysis of its dynamics of motion using the Heisenberg-Langevin equations by which the time evolution of the signalidler mode and Raman modes are derived. Interestingly, the entangled two-photon wave is coupled to the plasmonic modes, which are used to improve the non-classicality. It is shown that the exciting system with the entangled photons leads to inducing the non-classicality in Raman modes and entanglement between them. Moreover, it is seen that the plasmon-plasmon interaction in the gap region has a strong effect on the non-classicality of the input modes and also affects entangling of the Raman modes, which means that plasmonic modes generated by the core/shell nanoparticles manipulate the Raman modes' quantum properties. It is shown that the quantum properties in the designed system are dramatically influenced by the environmental temperature and the location of the Raman molecules in the gap region. The modeling results demonstrate that by changing the location of the Raman molecules, the non-classicality of the Raman modes and their entanglement are altered. Finally, as an important result, it is revealed that the Raman modes, such as the Stokes and anti-Stokes modes, show a revival behavior, which is a quantum phenomenon. (c) 2018 Optical Society of America.Article Non-Linear Eddy Current Loss and Thermal Analysis on Transformer Cover(Gazi Univ, 2019) İskender, İres; Zahedı, Mohammad ZiaHigh current conductors of transformers cause to produce losses and thermal problems in theirtank cover. Finite Difference (FD) Method (FDM) magnetic analysis is used to find out an exactestimation of the magnetic field and the losses near the bushings in the transient solution,considering the non-linear magnetic permeability of the cover plate, because FDM is moreflexible to deal with the nonlinear constitutive law and easy-to-be implemented especially in thecase of simple geometry. Finite Element Method (FEM) thermal analysis is used to determinethe plate temperature based on magnetic FD analysis, taking account non-linear heat fluxboundary condition. A calibration procedure is used between the analyses to ensure the precisionof assumptions. The reliability of the technique, confirmed by experimental and FEM results.