Browsing by Subject "Antennas"
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Item Structural behaviour of steel lattice towers under wind loads(CI-Premier Pte Ltd, 2011) Seker S.; Erdem R.T.; Gücüyen E.; Bagci M.Latticed steel towers are used widely in a variety of civil engineering applications. In this paper, structural behavior of 50 and 75 meters lattice towers which are made of L sectioned frame members under 160km/h wind velocity that causes wind force into structure and have 10m2 square antenna area are investigated. The structures (160-10-50, 160-10-75) are handled in two types as space truss composed of pin-jointed (Model A) and rigid main legs surround space truss composed of pin-jointed (Model B). Wind force is based on Gust Factor and calculated according to EIA-TIA 222-F (Structural Standards Abstract for Steel Antenna Towers & Antenna Supporting Structures) code. The aim of this study is obtaining the effective periods, mass sources, inter story drift ratios, maximum displacements of peak points and maximum frame forces of four structures which have different joint connections and height to determine the safety of them.Item Structural behaviour of four legged tubular steel lattice towers under wind loads(CI-Premier Pte Ltd, 2011) Gücüyen E.; Erdem R.T.; Seker S.; Gökkus U.Latticed steel towers are widely used in a variety of civil engineering applications. In this paper, structural behavior of 50 and 75 meters lattice towers which are made of tubular sectioned frame members under 160km/h wind velocity that causes wind force into structure and have 10m2 square antenna area are investigated. The structures (160-10-50, 160-10-75) are handled in two types as space truss composed of pin-jointed (Model A) and rigit main legs surround space truss composed of pin-jointed (Model B). Wind force is based on Gust Factor and calculated according to EIA-TIA 222-F (Structural Standards Abstract for Steel Antenna Towers & Antenna Supporting Structures) code. The aim of this study is obtaining the effective periods, mass sources, interstory drift ratios, maximum displacements of peak points and maximum frame forces of four structures which have different joint connections and height to determine the safety of them.Item Analysis of thin dielectric cylindrical reflector having an arbitrary conic section profile illuminated by complex line source: H-polarization case(IEEE Computer Society, 2014) Oguzer T.; Kuyucuoglu F.; Avgin I.; Altintas A.Arbitrary conic section profile and thin dielectric reflector is analyzed by using the Method of Analytical Regularization (MAR) technique based on Riemann-Hilbert problem and Fourier inversion procedures. The reflector surface is assumed to be illuminated by an H-polarized complex line source type feed antenna. The convergence of the solution is verified and some changes in the radiation patterns are obtained especially for rather thicker cases. © 2014 IEEE.Item Design of antenna-applicator for electromagnetic field applications and excitation model for rat and heat transfer analysis; [Elektromanyetik Alan Uygulamalari için Anten-Aplikatör Tasarimi, Sicąn için Uyartim Modeli ve Isi Daglimi Analizi](Institute of Electrical and Electronics Engineers Inc., 2017) Gumusay M.; Gulbagca F.; Aydemir I.; Saygili S.; Kaya A.; Tuglu M.I.There has been only a few technical progress which contribute to wound healing in the last century. Despite these advances wound healing is very hard issue to study because of its subjectivity, diversity and complexity of the wound healing process and diversity of patients. Molecules are insufficient in the chronic wound and unlike other cells multiplying endothelial cells interrupt the healing process. To restart this process, cells can be excitated by pulsed electromagnetic fields stimulation method. When a suitable frequency and waveform electromagnetic field (EMF) signal is applied to the target tissue with the help of a coil or applicator physiological effects occurs at the cellular size. Low-frequency electromagnetic fields are non-ionizing part of the EM spectrum and they are used as adjunct therapy in soft tissue injuries. In this study, an antenna-applicator design was performed and the effect of non-thermal pulsed radio frequency energy (PRFE) system to the wound created rat skin was examined. © 2016 The Chamber of Turkish Electrical Engineers.Item Phenolic profile, antioxidant and enzyme inhibitory potential of Onosma tauricum var. tauricum(Elsevier B.V., 2018) Kirkan B.; Sarikurkcu C.; Ozer M.S.; Cengiz M.; Atılgan N.; Ceylan O.; Tepe B.This study focused on phytochemical characterization and biological evaluation, both antioxidant and enzymatic inhibition, of ethyl acetate (OTT-EtOAc), methanol (OTT-MeOH), and water (OTT-W) extracts from Onosma tauricum var. tauricum aerial parts. The OTT-W extract was found to be the richest one in terms of its phenolic and flavonoid contents. Amounts of the phenolic and flavonoid compounds were determined as 40.88 μmol GAEs/g and 7.40 μmol REs/g dry plant (dp), respectively. The OTT-MeOH and OTT-W extracts were also found to contain significant amounts of chlorogenic acid, rosmarinic acid, p-hydroxybenzoic acid, caffeic acid, rutin, p-coumaric acid, trans-cinnamic acid, luteolin, and apigenin. The OTT-W extract showed remarkable antioxidant activity in phosphomolybdenum, ferrous ion chelating, reducing power, and radical scavenging assays. The OTT-MeOH extract exhibited inhibitory activity on acetylcholinesterase (AChE) (54.62 μmol GALAEs/g dp), while the extracts remained almost inactive on butyrylcholinesterase (BChE). The OTT-W extract also exhibited inhibitory activity on tyrosinase (90.66 μmol KAEs/g dp) and α-glucosidase (2258.87 μmol ACEs/g dp). The results suggest that especially the OTT-MeOH and OTT-W extracts can be used as a source of alternative natural products in the treatment of diseases caused by the enzymes evaluated here. © 2018 Elsevier B.V.Item Essential oil composition and antioxidant activity of endemic Marrubium parviflorum subsp. oligodon(Elsevier B.V., 2018) Sarikurkcu C.; Ozer M.S.; Calli N.; Popović-Djordjević J.In this study, chemical composition and antioxidant activity of the essential oil and solvent extracts (hexane, dichloromethane, ethyl acetate, methanol and water) obtained from aerial parts of the endemic plant Marrubium parviflorum subsp. oligodon collected from Afyonkarahisar province in Turkey were examined. The antioxidant ability of solvent extracts and essential oil was evaluated using various methods (β-carotene-linoleic acid, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, and reducing power assays) and the content of total phenolics and flavonoids were determined. In the essential oil, thirty-one compounds were identified by GC/MS analysis. The major components were (Z,Z)-farnesyl acetone (19.28%), caryophyllene oxide (15.85%) and pulegone (7.15%). In all assays, water extract showed the strongest antioxidant properties due to the highest content of total phenolics. The significantly high correlations were observed between the content of total phenolics and DPPH radical (0.894) and reducing power (0.983) assays. Methanol extract was the richest in total flavonoids. The present results support the traditional and possible use of the essential oil and extracts from M. parviflorum subsp. oligodon in food, pharmaceutical, and cosmetic industries. © 2018 Elsevier B.V.Item Calamintha incana: Essential oil composition and biological activity(Elsevier B.V., 2019) Popović-Djordjević J.; Cengiz M.; Ozer M.S.; Sarikurkcu C.The chemical composition of the essential oils (EO) isolated aerial parts of Calamintha incana (Sm.) Boiss. from Turkey was characterized by GC-FID and GC–MS analysis. The oxygenated monoterpenes trans-piperitone oxide (41.37%), piperitenone oxide (34.47%), piperitenone (6.67%), and monoterpene phenol thymol (3.37%) were found to be the major constituents of the essential oils of C. incana. The results of the antioxidant activity in phosphomolybdenum, radical scavenging (DPPH and ABTS) and reducing power activity (CUPRAC and FRAP) as well as metal chelating effects (ferrous ion chelating) showed that EO was the most potent in ABTS (129.58 ± 2.21 mg TEs/g oil) and CUPRAC and FRAP (51.14 ± 0.05 and 53.63 ± 0.10 mg TEs/g, respectively) assays. In enzymes inhibitory activity assays of EO, the best result was achieved for tyrosinase (2.10 ± 0.30 mg KAEs/g oil). The results suggest that EO might be considered as a potential source of bioactive agents to be used in food and pharmacological industries. © 2018 Elsevier B.V.Item Performance Analysis of EEG Signal Processing Based Device Control Applications(Institute of Electrical and Electronics Engineers Inc., 2019) Altundogan T.G.; Karakose M.Nowadays, many types of devices are controlled by electroselenography (EEG) signals. In the literature and in daily life, related studies with EEG controlled devices are increasing day by day. EEG based control applications are applied on many devices such as robot arm, robot, vehicle and unmanned aerial vehicle (UAV). EEG based control procedures usually involve taking, pre-processing, classifying EEG signals, and applying the resulting command to the controlled device. In this study, a performance analysis was carried out by examining the control application studies using EEG signals in the literature. In this analysis study, firstly all studies related to the subject in the literature are examined and the devices, methods, signal processing techniques and classification algorithms used in these studies are handled separately. Appropriate electrode selection for the type of device used in device control applications using EEG signals and type of interaction for command extraction from EEG signal appears to be an important step. In this respect, performance correlations between the types of EEG devices used in the literature studies and the electrode choices used in these studies were compared. Since there are a variety of preprocessing steps for EEG signals, this study provides comparisons based on EEG signal preprocessing techniques. Artificial neural networks (ANN), support vector machines (SVM) and K nearest neighbours (Knn) are used to classify the works in the literature. In this study, comparative studies based on classification methods used in literature studies are also included. As a result, in this study, the studies in the literature for the device control using the EEG signal are examined, compared, interpreted and evaluated, and the points to be considered in the designs to be performed in this area are given. © 2018 IEEE.Item Valeriana dioscoridis aerial parts' extracts - A new source of phytochemicals with antioxidant and enzyme inhibitory activities(Elsevier B.V., 2020) Sarikurkcu C.; Jeszka-Skowron M.; Ozer M.S.Valeriana root extracts are used in herbal medicine for treating sleep disorders. There is a lack of information of phytochemical composition of Valeriana dioscoridis aerial parts’ extracts. The aim of the study was to measure antioxidant activity, determine the phenolic compounds from different groups such as phenolic acids and polyphenolic compounds: verbascoside or eriodictyol, and enzyme inhibitory activities in ethyl acetate, methanol and water extracts. The methanol extract showed the highest antioxidant activity almost in all assays (excluding ferrous ion chelating activity). Moreover, the concentrations of the determined phytochemicals mainly chlorogenic acid content (21.4 ± 0.7 mg/g), hesperidin (2.10 ± 0.05 mg/g) and protocatechuic acid (0.94 ± 0.02 mg/g) were the greatest for this extract. It was also the richest in all determined compounds – 21 phytochemicals were identified and water extract was the second most abundant in analytes (20 phytochemicals). The predominant compounds in water extract were the following: chlorogenic acid (20.3 ± 0.12 mg/g), protocatechuic acid (0.83 ± 0.02 mg/g) and caffeic acid (0.72 ± 0.01 mg/g). Protocatechuic acid was prevailing in ethyl acetate extract (0.59 ± 0.01 mg/g). In addition, in this extract the highest inhibitory activity of α-amylase was found and the highest amount of verbascoside was determined in comparison to other extracts (0.53 ± 0.01 mg/g). The tyrosinase inhibitory effect especially of methanol extract was also shown. Pearson correlation confirmed that the strong biological activity of methanol extract from V. dioscoridis resulted mainly from its high content of chlorogenic acid. © 2020 Elsevier B.V.Item LC-MS/MS profiles and interrelationships between the enzyme inhibition activity, total phenolic content and antioxidant potential of Micromeria nervosa extracts(Elsevier Ltd, 2020) Sarikurkcu C.; Andrade J.C.; Ozer M.S.; de Lima Silva J.M.F.; Ceylan O.; de Sousa E.O.; Coutinho H.D.M.The objective of this study was to quantify the phenolic compounds and to evaluate and compare the biological activities of the ethyl acetate (EtOAc), methanolic (MeOH) and aqueous extracts from the Micromeria nervosa aerial parts, based on their antioxidant activity and enzymatic inhibition. Total phenolic and flavonoid contents were calculated and individual compo3unds were detected using LC-ESI-MS/MS. The antioxidant activity was determined using six different assays while enzymatic activity was determined by α-amylase and tyrosinase enzyme inhibition. The main phenolic constituents detected in the extracts were rosmarinic acid. In the antioxidant assays the aqueous extract was shown to be more efficient than the others. The EtOAc and MeOH extracts presented higher inhibitory activity with respect to α-amylase and tyrosinase. Regardless of the solvent, the results suggest M. nervosa aerial extracts present a biological potential due to their antioxidant activity and enzymatic inhibition. © 2020 Elsevier LtdItem GA-based Energy Aware Path Planning Framework for Aerial Network Assistance(European Alliance for Innovation, 2021) Özçevik' Y.; Bozkaya E.; Akkoç M.; Erol M.R.; Canberk B.Aerial networks have enormous potential to assist terrestrial communications under heavy traffic requests for a predictable duration. However, such potential for improving both the performance and the coverage through the use of drones can face a major challenge in terms of power limitation. Hence, we consider the energy consumption characteristic of the components in such networks to provide energy aware flight path planning. For this purpose, a flight path planning scheme is proposed on an underlying topology graph that models the energy consumption of path traversals in the aerial network. In the proposed model, we offer to seek for the minimum energy consumption on a global problem domain during the entire operational time. Thus, we provide a concrete problem formulation and implement a flight path planning with Genetic Algorithms (GA) approach. Moreover, a novel end-system initiated handover procedure is illustrated to preserve connectivity of terrestrial users in the network architecture. In the end, the evaluation of the proposed model is conducted under three different scales of social event scenarios. A comparison with a dummy path planning scheme without energy awareness concerns is presented according to a set of parameters. The evaluation outcomes show that the proposed model is able to save 20% energy consumption, provides 15% less number of terrestrial replenishment, and 18% more average endurance for the topology. Besides, another energy aware path planning scheme in the literature offering a deployment with Bellman Ford algorithm is also included in the evaluation to evaluate the feasibility of the proposed framework for the enhanced problem domain. © 2021 OZCEVIK et al., licensed to EAI. All Rights Reserved.Item Energy-efficiency maximization for multi-antenna OFDMA networks; [Çok antenli DFBÇE aǧlari için enerji verimliliǧi maksimizasyonu](Institute of Electrical and Electronics Engineers Inc., 2021) Basturk I.Energy efficient or green communication has been one of the most important targets of the next generation communication systems in the last years because of the massive energy usage. In the light of these targets, energy efficient communication is studied for the multi-antenna Orthogonal Frequency Division Multiple Access (OFDMA) cellular networks in this study. Energy efficiency maximization problem is defined by considering the quality of service requirements of the users. A solution which allocates sub-bands and power disjointly is proposed for this complex Mixed-integer non-linear programming (MINLP) type problem, which is in the fractional form and contains not only discrete but also continuous parameters. The performance of the proposed solution is evaluated by using simulation results. © 2021 IEEE.Item UAV-Coin: Blockchain assisted UAV as a Service(Institute of Electrical and Electronics Engineers Inc., 2022) Erel-Ozcevik M.The vast majority of 5G users are in eMBB content which requires high bandwidth and moderate latency under a few milliseconds. Today's applications are irregular and not predictable and current fixed wireless access cannot meet these requirements of eMBB traffic. This leads to the use of unmanned aerial vehicles (UAVs) as mobile base stations to increase the capacity of physical infrastructure. However; due to serving eMBB users, the replacement of UAVs for recharging becomes frequent. There are many studies proposing to increase the serving time without any replacement in the literature. Due to the economic limitations of service providers, they prefer partial recovery on the topology. All of these leads use UAV as a service between multi-providers by hiring it from infrastructure on-demand. On the other hand, security is an urgent requirement of 5G while integrating multi-providers. Therefore, this paper proposes blockchain-assisted UAV as a service to handle the smart contracts between providers and UAVs in exchange for UAV-Coin. Thanks to that, multi-providers can hire a UAV on-demand to enhance network capacity without any full recovery on the physical topology. This is implemented by using edge servers that execute UAV, Content, and Database manager modules, respectively. The proof algorithm for blockchain-assisted UAVaaS is proposed. Here, the Proof of Stake (PoS) is preferred for the validation of transactions and adding them into a blockchain in order to meet the latency requirement of eMBB content. According to performance evaluation, the blockchain can be used by up to 10 service providers while considering the processing delay. Moreover, the service providers can earn much more UAV-Coin by being selected as a winner more than once for validation in proof of algorithm. © 2022 IEEE.Item Energy-aware mobility for aerial networks: A reinforcement learning approach(John Wiley and Sons Ltd, 2022) Bozkaya E.; Özçevik Y.; Akkoç M.; Erol M.R.; Canberk B.With recent advancements in aerial networks, aerial base stations (ABSs) have become a promising mobile network technology to enhance the coverage and capacity of the cellular networks. ABS deployment can assist cellular networks to support network infrastructure or minimize the disruptions caused by unexpected and temporary situations. However, with 3D ABS placement, the continuity of the service has increased the challenge of providing satisfactory Quality of Service (QoS). The limited battery capacity of ABSs and continuous movement of users result in frequent interruptions. Although aerial networks provide quick and effective coverage, ABS deployment is challenging due to the user mobility, increased interference, handover delay, and handover failure. In addition, once an ABS is deployed, an intelligent management must be applied. In this paper, we model user mobility pattern and formulate energy-aware ABS deployment problem with a goal of minimizing energy consumption and handover delay. To this end, the contributions of this paper are threefold: (i) analysis of reinforcement learning (RL)-based state action reward state action (SARSA) algorithm to deploy ABSs with an energy consumption model, (ii) predicting the user next-place with a hidden Markov model (HMM), and (iii) managing the dynamic movement of ABSs with a handover procedure. Our model is validated by comprehensive simulation, and the results indicate superiority of the proposed model on deploying multiple ABSs to provide the communication coverage. © 2021 John Wiley & Sons, Ltd.Item Energy-efficient communication for UAV-enabled mobile relay networks(Elsevier B.V., 2022) Baştürk İ.Relaying that can be classified as fixed or mobile is an effective technique to improve the throughput and reliability and also to extend the coverage in wireless networks. Compared with the conventional fixed relaying, mobile relaying has attracted great interest recently, because of the the rapid development of unmanned aerial vehicles (UAVs) having high mobility, low cost and deployment flexibility properties. Thus, in this study, mobile relaying technique in which the relay nodes are mounted on the fixed wing UAVs is considered. Due to the increasing energy consumption costs, environmental reasons, low lifetime of the mobile devices and limited on-board energy of the UAVs, energy-efficient communication is an important topic for the future wireless network design. Therefore, energy-efficient communication is examined for the UAV-enabled Decode-and-Forward (DF) mobile relay networks in this paper. Energy-efficiency (EE) maximization problem is formulated as the ratio of the total data rate to the total energy consumption by considering the quality of service (QoS) requirements of the users. As the formulated problem is mixed integer non-convex, it is hard to solve in this form. Thus, we decompose it into two subproblems as user-scheduling and power allocation and propose to solve each subproblem separately to overcome the complexity of the problem. The efficiency of the proposed algorithm is shown by performing extensive simulations for various system parameters. © 2022Item HeatWatch: Identification of Parameters Influencing the Urban Heat Island Effect through Deep Learning Techniques(International Society for Photogrammetry and Remote Sensing, 2024) Kılınç M.; Aydın C.; Aydın G.E.; Balcı D.Global climate change (GCC) is accelerated by factors such as greenhouse gas emissions from human activities and the urban heat island (UHI) effect, particularly in densely urbanized areas. According to the WMO's 2023 data, GCC warming effects increased by 49% from 1990s to 2021, 80% of this increase was due to CO2. Furthermore, average global temperatures have increased by 1.1°C since the early 1900s. In this respect, the urban heat island (UHI) effect has gained importance with global temperatures. Environmental problems that cause cities to be warmer than rural areas, especially due to hard ground surfaces, building density and decreasing green areas, have the potential to create negative impacts on human health. Therefore, it is important to identify and manage the impact of UHI. This is because traditional methods are limited to fixed station data, but technologies such as remote sensing and geographic information systems (GIS) provide more comprehensive results for this management. In an innovative approach, deep learning and artificial intelligence techniques can provide more accurate analysis by processing large datasets. In this context, this research proposes a conceptual framework for using deep learning techniques to detect the UHI effect with data obtained from street images and unmanned aerial vehicles. With the proposal, the UHI value will be calculated by detecting objects such as trees, air conditioners, vehicles and building cladding with the YOLO-Real-Time Object Detection algorithm. With this approach, it is aimed to obtaining more precise and accurate results in determining the UHI effect. In addition, a web-based management panel will be designed for managers to review the results and use them in decision-making mechanisms. It is aimed at disseminating this model and making it an important tool in the planning of urban areas. © Author(s) 2024. CC BY 4.0 License.