Sürdürülebilir Kalkınma Amaçları
Yazarlar
- Kaya, Yunus(20)
- Ertugrul, Mehmet(9)
- Hasar, Ugur C.(9)
- Hasar, Ugur Cem(9)
- Ozturk, Gokhan(7)
- Abdioglu, Murat(5)
- Korkmaz, Huseyin(5)
- Barroso, Joaquim J.(4)
- Guler, Evrim(4)
- Iliev, Teodor(4)
- Karakus, Murat(4)
- Ozturk, Hamdullah(3)
- Ozturk, Kemal(3)
- Uludag, Suleyman(3)
- Ali, Husain(2)
- Aslan, Nevzat(2)
- Barroso, Joaquim José(2)
- Buldu, Gul(2)
- Celik, Sukru(2)
- Cem Hasar, Ugur(2)
- Gedikli, Hasan(2)
- Hasar, Hafize(2)
- Izginli, Mucahit(2)
- Mollahasanoglu, Hakki(2)
- Oztas, Taskin(2)
- Ramahi, Omar M.(2)
- Savaskan, Burcu(2)
- Stoyanov, Ivaylo(2)
- Akcay, Latif(1)
- Alptekin Engin, Mustafa(1)
- Ates, Kayhan(1)
- Ayberkin, Doruk(1)
- Badia-Majos, Antonio(1)
- Basci, Abdullah(1)
- Bute, Musa(1)
- Cakil, Turan(1)
- Cakir, Mehmet(1)
- Canbolat, Mustafa Y.(1)
- Cansiz, Ahmet(1)
- Dilek, Durukan Burak(1)
Yayınlar
- MakaleAçık Erişim2021Scopus SJRQ1Parameter Retrieval of Samples on a Substrate from Reflection-Only Waveguide Measurements
Hasar, Ugur Cem; Ozturk, Hamdullah; Kaya, Yunus; Izginli, Mucahit; Ertugrul, Mehmet
A microwave method has been proposed for constitutive parameters' extraction of samples on a known substrate. The advantage of this method is that it relies on noniterative reflection-only (air-and metal-backed) scattering (S-) parameters so that it is a good candidate for the characterization of samples when only one-port measurements are available. It is validated by the X-band (8.2-12.4 GHz) waveguide S-parameter measurements. A sensitivity analysis is followed to evaluate and improve the performance of our method.
AtıfScopus5WoS5OpenAlex3
İncele - MakaleAçık Erişim2021Scopus SJRQ2Design and Experimental Studies on Superconducting Maglev Systems with Multisurface HTS-PMG Arrangements
Abdioglu, Murat; Ozturk, Kemal; Ekici, Mehmet; Savaskan, Burcu; Celik, Sukru; Cansiz, Ahmet
In this article, we have designed and constructed a new multisurface (MS) high temperature superconductor (HTS) Maglev measurement system to investigate the enhancement of magnetic force properties of Maglev systems via MS HTS configurations above conventional permanent magnetic guideway (PMG). We have investigated both the static force and stiffness behavior and dynamic response characteristics of these MS HTS-PMG arrangements in different field cooling heights (FCHs). Optimum cooling height is determined as FCH 20-30 for both six- and four-HTS configurations. The maximum levitation force values of HTS-PMG arrangement with six-HTS were obtained bigger than that of four-HTS in the unit cryostat volume of MS arrangement, indicating that the HTSs at the bottom side of the cryostat make contribution to the loading capacity of Maglev systems. In the present article, it is observed that the magnetic flux density of bottom surface in addition to upper surface of the PMG can make a contribution to loading performance, vertical and lateral stability of Maglev systems. It is thought that the designed measurement facility and results of this study will be beneficial to increase the magnetic flux density in the unit volume via MS HTS-PMG arrangements for future design and construction of the HTS Maglev systems.
AtıfScopus16WoS6OpenAlex15İncele - MakaleYalnız künye2021Scopus SJRQ1Graphical Method for Examining Complex Natural Frequencies of Dispersive Materials
Hasar, Ugur C.; Ozturk, Gokhan; Barroso, Joaquim J.; Gurbuz, Tolga U.; Kaya, Yunus; Ertugrul, Mehmet
A graphical method is extended to and applied for visual inspection of solution patterns (region of complex natural frequencies sₙ) in the complexs-plane for dispersive materials characterized by the Debye and Lorentz models. These patterns are in the form of exponential decay and C-shaped profiles for the Debye and Lorentz models, respectively. Their forms are observed to be affected (e.g., moving left/right) in different manners with a variation of dispersion parameters. This method, thanks to its visual inspection capability, can help in analyzing/synthesizing filters and frequency-selective surfaces.
AtıfScopus6WoS6OpenAlex7İncele - MakaleYalnız künye2021Scopus SJRQ1QoSChain: Provisioning Inter-AS QoS in Software-Defined Networks with Blockchain
Karakus, Murat; Guler, Evrim; Uludag, Suleyman
Data flows of various applications, such as video conferencing, telesurgery, online-gaming, etc., require particular treatment regarding Quality of Service (QoS) because of their sensitivity to such parameters as high bandwidth, low delay, and so on. However, provisioning of QoS-based routing services across Autonomous Systems (ASes) poses gruelling challenges due to the distributed nature and business confidentially hesitations. This study presents a novel blockchain-aided QoS-enabled inter-AS routing framework, QoSChain (QC), by blending merits of Software-Defined Networking (SDN) and Blockchain technologies. QC framework introduces a coordination framework with mutually distrusting participants that eliminates centralized mediators in provisioning QoS among SDN-enabled ASes. Also, QC reduces the time to set up an end-to-end (E2E) path and the number of messages exchanged and processed by SDN controllers for a QoS flow. Furthermore, it alleviates the concerns of network operators regarding potentially sensitive information disclosure resulting from the required information sharing for QoS-based cross-AS paths by masking details of any confidential information. Experimental results verify the feasibility of the proposed framework on E2E QoS-based routing among SDN networks. This work aims at being a useful primer for researchers in providing insights on how blockchain can be deployed in QoS-enabled routing.
AtıfScopus32WoS21OpenAlex30İncele - BildiriAçık Erişim2021Custom TTA Operations for Accelerating Kyber Algorithm
Akcay, Latif; Örs, Berna
In recent years, quantum computer development projects have progressed considerably in terms of quality and quantity. These studies also pose a serious risk for widely used security systems based on classical public-key cryptography algorithms. Therefore, development of hardware and software applications that use post-quantum methods are considered a necessity both for today and for the future. Kyber is one of the most promising key encapsulation mechanism in the final round of NIST post-quantum cryptography standardization process. In this study, we present a 64-bit application specific transport triggered architecture processor which has custom operations for accelerating the Kyber algorithm. Moreover, we compare the processor and its various versions with a 64-bit RISC-V core in terms of performance, total energy consumption and resource utilization. According to the test results, our custom processor provides at least 2x better performance and 1.5x lower energy consumption while increasing the required chip area approximately 1.4x.
AtıfScopus2OpenAlex8İncele - MakaleAçık Erişim2021Scopus SJRQ2Experimental and Numerical Investigation of Levitation Force Parameters of Novel Multisurface Halbach HTS-PMG Arrangement for Superconducting Maglev System
Ozturk, Kemal; Badia-Majos, Antonio; Abdioglu, Murat; Dilek, Durukan Burak; Gedikli, Hasan
We have designed multisurface Halbach high temperature superconductor-permanent magnetic guideway (HTS-PMG) arrangements for magnetically levitated transportation (Maglev) and investigated the static force parameters in addition to the dynamic response characteristics. Three different Halbach HTS-PMG arrangements were used with multisurface (6 HTS, 4 HTS) and single surface (2 HTS) configurations and static and dynamic measurements were carried out in three different field cooling heights (FCHs). The bigger vertical loading capacity and wider loading gap were obtained with multisurface Halbach HTS-PMG arrangements. In addition, nearly four times bigger guidance force values of multisurface arrangements than that of single surface one indicates that the side HTSs in multisurface arrangements make a significant contribution to the guidance force and thus lateral movement stability of Maglev systems. Both the vertical and lateral dynamic stiffness values increased with decreasing FCH and it can be also said that the dynamic stiffness properties of Maglev systems can be enhanced especially in lateral direction by using the multisurface Halbach HTS-PMG arrangements. Understanding of these experimental observations is supported by dedicated theoretical modelling through a 2-D approximation of the system. We show that by using a single material parameter (the critical current density J_bf c) for the whole superconducting set, one may satisfactorily predict the complete series of experiments. The static and dynamic parameters obtained from this study and the results of dedicated theoretical modeling for single-surface and multisurface HTS-PMG arrangements are thought to be helpful for the researchers working on static and dynamic performances of HTS Maglev systems.
AtıfScopus28WoS22OpenAlex26İncele - BildiriYalnız künye2020RoutingChain: A Proof-of-Concept Model for a Blockchain-Enabled QoS-Based Inter-AS Routing in SDN
Karakus, Murat; Guler, Evrim
A Software-Defined Networking (SDN) architecture and OpenFlow can help network administrators to provide end-to-end (E2E) Quality of Service (QoS)-guaranteed paths for flows among networks while providing finer-granular flow management along with global network view. In this context, we introduce a proof-of-concept for a blockchain-enabled QoS-based inter-Autonomous System (AS) routing framework, RoutingChain, that blends a QoS-concerned routing model and blockchain technology. This study's contributions can mainly be stated in five-fold: (i) Competitors-tailored routing coordination framework, (ii) eliminating centralized mediators while coordinating QoS-based inter-AS routing, (iii) an emerging use-case for blockchain technology in networking, (iv) reducing the number of QoS signaling-based message overhead, and (v) mitigating privacy/security concerns in inter-AS routing. Experimental results indicate that the blockchain technology can be applied on E2E QoS-based routing among networks. To the best of our knowledge, this is the first study exploiting the merits of blockchain technology to establish a novel coordination framework for QoS-enabled inter-AS routing in SDN.
AtıfScopus10WoS6OpenAlex12İncele - MakaleAçık Erişim2019Scopus SJRQ1Transient plane-wave transmission through an N-Layer structure by the method of subregions
Hasar, Ugur Cem; Kaya, Yunus; Barroso, Joaquim J.
The temporal transmission properties of an N-layer structure under planar wave incidence are investigated by the method of subregions via the wave matrix approach. The transmission coefficient expression is first expressed in the frequency-domain by reduced transmission coefficients and then transformed into the time domain, which includes unit step functions with different effective time periods and weightings. The analysis is validated by numerical computations and three-dimensional electromagnetic simulations at gigahertz frequencies.
AtıfScopus12WoS12OpenAlex13İncele - MakaleAçık Erişim2018Scopus SJRQ1Self-Calibrating Noniterative Complex Permittivity Extraction of Thin Dielectric Samples
Hasar, Ugur Cem; Kaya, Yunus
A microwave method relying on uncalibrated scattering (S-) parameters is proposed to measure the complex permittivity (ϵr) of thin dielectric samples. It has the following two main advantages. First, it takes into account effect of the sample holder, used for holding the sample, especially important for thin sample electromagnetic property characterization. Second, it does not require any specific information about the location of the sample (and its holder) inside its measurement cell for ϵr extraction. For validation of our method, we applied a commercial three-dimensional electromagnetic simulation program-CST Microwave Studio-and the Lorentz dispersion model. Uncalibrated (as well as calibrated) S-parameter measurements were conducted to measure ϵr of a 0.7 mm thick polyethylene sample (the sample holder was a 5.18 mm thick PVC sample) by our method and other similar methods in the literature. From the comparison, we observed that while the accuracy of tested methods significantly changed with inaccurate knowledge of the sample position inside its cell, the accuracy of our method did not much alter.
AtıfScopus18WoS16OpenAlex18İncele - MakaleAçık Erişim2018Scopus SJRQ1Determination of effective constitutive parameters of inhomogeneous metamaterials with bianisotropy
Hasar, Ugur Cem; Buldu, Gul; Kaya, Yunus; Ozturk, Gokhan
A recursive algorithm is proposed to accurately extract the electromagnetic parameters of isotropic/bianisotropic metamaterial (MM) slabs of inhomogeneous structures. The algorithm is based on the recursive calculations of measured/ simulated forward and backward scattering (S-) parameters from previously extracted wave impedances and refractive indices of each homogeneous layer (except the analyzed intermediate layer) by a suitable retrieval method. There are two main advantages of our proposed method over existing extraction algorithms. First, it could retrieve the electromagnetic parameters of both isotropic and bianisotropic MM slabs. Second, it is applicable for electromagnetic parameter extraction of inhomogeneous structures. For validation of our method and assessing its accuracy over existing extraction methods, we used the simulation results of various inhomogeneous structures constructed by different isotropic/bianisotropic MM slabs (split-ring-resonator (SRR), SRR-wire, omega, and omega-wire). For completeness, the effects of noise present in S-parameters and iterative error (by increasing the value of iteration numbers) are examined to test the robustness of the proposed algorithm.
AtıfScopus43WoS42OpenAlex47İncele - BildiriAçık Erişim2017Relations of attention and meditation level with learning in engineering education
Ülker, Büsra; Tabakcioǧlu, Mehmet Bariş; Çizmeci, Hüseyin; Ayberkin, Doruk
Neurons use electricity in order to communicate to each other. Due to numerous signals sent by neurons, there are oodles of electrical activity in the brain. Sensitive equipment like electroencephalogram (EEG) biosensor perceives the brainwaves emanated from neurons. Beta waves are responsible for problem solving or decision making and associated with attention. Alpha waves are associated with now and meditation. Neurosky EEG biosensor perceives the brainwaves and transforms these brainwaves into attention and meditation values. In this study, Neurosky EEG biosensor is used for measuring the attention and meditation levels of students. A program is developed in C# medium. The developed program records raw brainwave data, attention and meditation average while the students are studying. As the attention and meditation levels are high, the students learn the subjects in the course. If predetermined meditation and attention level are not caught, the developed program does not give permission to pass to another subject. Because of that the students have less meditation and attention average than the predetermined value; they get fewer grades in the exam.
AtıfScopus16OpenAlex16İncele - MakaleAçık Erişim2016Scopus SJRQ1A New Energy Prediction Algorithm for Energy-Harvesting Wireless Sensor Networks With Q-Learning
Kosunalp, Selahattin
Traditional wireless sensor networks (WSNs) face the problem of a limited-energy source, typically batteries, resulting in the need for careful and effective utilization of the energy source. However, inevitable energy depletion will eventually disturb the operation of a WSN. Energy harvesting (EH) technology is acquiring particular interest, because it has the potential to provide a continuous energy supply in battery-powered WSNs. Solar energy is the most effective environmental energy for EH-WSNs because of its high energy intensity, which comes from a non-controllable source. Therefore, the prediction of future energy availability is a critical issue, as the amount of the harvestable energy may vary over time. In this paper, a novel solar energy prediction algorithm with Q-learning, called Q-learning-based solar energy prediction (QL-SEP), is proposed. Q-learning is an effective way of predicting future actions based on past observations. The distinctive feature of QL-SEP is that not only past days' observations but also the current weather conditions are considered for prediction. The performance of QL-SEP is simulated in this paper using real-world measurements obtained from a solar panel in comparison with the state-of-art approaches.
AtıfScopus128WoS96OpenAlex135İncele - MakaleAçık Erişim2015Scopus SJRQ1Determination of Reference-Plane Invariant, Thickness-Independent, and Broadband Constitutive Parameters of Thin Materials
Hasar, Ugur C.; Kaya, Yunus; Barroso, Joaquim José; Ertugrul, Mehmet
We propose an effective microwave method for reference-plane-invariant and thickness-independent constitutive parameters measurement of thin materials. A function depending only on the interface reflection coefficient to facilitate fast computations of constitutive parameters is derived. In addition to the extraction of sample thickness, the method can also be applied to unique retrieval of constitutive parameters whose electromagnetic properties are yet unknown. We have performed an uncertainty analysis to examine how the accuracy of the method can be improved. Finally, we have compared the proposed method with other similar methods in the literature using measurements of distilled water and a thinner Plexiglas sample (1 mm). From the comparison, we note that the accuracy of our proposed method is not affected by any inaccurate knowledge of reference-plane positions and the sample length (or both) while those of compared methods are seriously decreased.
AtıfScopus53WoS52OpenAlex52İncele - MakaleAçık Erişim2015Scopus SJRQ2The effect of magnetic field distribution and pole array on the vertical levitation force properties of HTS Maglev systems
Ozturk, Kemal; Abdioglu, Murat; Sahin, Ercin; Celik, Sukru; Gedikli, Hasan; Savaskan, Burcu
In this paper, the levitation force measurements have been carried out by the magnetic force measurement system under both field-cooling and zero-field-cooling regimes, whereas the magnetic field distribution over the permanent-magnet guideway (PMG) was calculated by numerical analysis based on the finite-element method. It was shown in this study that the vertical levitation capability and stability of Maglev systems can be improved depending on the cooling regime, pole number, and suitable arrangement of the PMG. In this paper, it was shown that when the pole number increases, the levitation force density increases. It also appeared that the reasonable position of the supplementary permanent magnet and appropriate cooling heights are key parameters for both levitation performance and stabilization of the high-temperature superconductor (HTS) Maglev. It is believed that the numerical and experimental data in this paper are useful for relative design and practical application of HTS Maglev systems.
AtıfScopus38WoS33OpenAlex36İncele - MakaleYalnız künye2015Scopus SJRQ1Reference-Plane-Invariant Effective Thickness and Electromagnetic Property Determination of Isotropic Metamaterials Involving Boundary Effects
Hasar, Ugur Cem; Barroso, Joaquim José; Buldu, Gul; Bute, Musa; Kaya, Yunus; Karacali, Tevhit; Ertugrul, Mehmet
It is well recognized that near-field effects become dominant when the metamaterial (MM) is in resonance. In addition, any inaccurate information of the location of reference planes, and the effective length can seriously affect the accuracy of retrieved electromagnetic properties of MMs. By considering all these issues, in this research paper, we propose a retrieval method for reference-plane invariant and thickness-independent determination of electromagnetic parameters of MM slabs involving boundary effects. Our method first accomplishes determination of effective length of MMs and calibration-plane factors using scattering parameter measurements, aside the resonance region, of two identical MMs with different lengths. Our method then incorporates near-field effects in accurate retrieval of electromagnetic properties of MMs. The method is verified by scattering parameters simulated for a homogeneous conventional material and a weakly or negligibly coupled inhomogeneous MM slab made by two metallic concentric split-ring-resonators. Consequences of an inaccurate information of reference-plane transformation factors and the value of effective lengths and of noninclusion of near field effects on the retrieved electromagnetic properties are thoroughly discussed by way of few examples to substantiate the accuracy of the proposed method.
AtıfScopus15WoS15OpenAlex15İncele - Dergi2020 IEEE International Black Sea Conference on Communications and Networking, BlackSeaCom 2020
- DergiIEEE Transactions on Electromagnetic Compatibility
- DergiIEEE Antennas and Wireless Propagation Letters
- DergiIEEE Geoscience and Remote Sensing Letters
- DergiIEEE International Conference on Communications