WoS İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394

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Measuring Temperature Change on Photothermal Au Nanorod and Nanocage Upon Laser Irradiation
(Amer Chemical Soc, 2015) Cavusoglu, Halit; Sakalak, Huseyin; Buyukbekar, Burak Zafer; Demirel, Gokhan; Citir, Murat; Yavuz, Mustafa Selman
Quasi-Static Operation of 2-Axis Microscanners With AlN Piezoelectric Quad-Actuators
(Institute of Electrical and Electronics Engineers Inc., 2021) Hah, D.
Aluminum nitride (AlN) started to draw attentions as a material for piezoelectric actuation owing to its CMOS process compatibility and safeness for biomedical applications. Due to its relatively low piezoelectric coefficients, AlN-based piezoelectric actuators have been mostly operated in resonance modes, especially in optical scanning. This paper presents a novel design of a 2-axis-tilt microscanner with AlN piezoelectric quad-actuators and meander-shaped hinges for reasonable quasi-static operation. Through finite-element-method simulation, it is shown that the proposed device can have about 9 degree of optical scan angle in two dimensions with the voltage amplitude of 50 V. Lissajous scanning operation of the device is demonstrated as well via simulation. © 2021 Elsevier B.V., All rights reserved.
Citation - WoS: 1
GIS-AHP Approach for a Comprehensive Framework to Determine the Suitable Regions for Geothermal Power Plants in Izmir, Turkiye
(Konya Teknik Univ, 2024) Koca, Kemal; Karipoglu, Fatih; Ozturk, Emel Zeray
Geothermal energy is gaining more reputation and importance around the world. Correspondingly, suitable location selection is a critical step and has become necessary for the successful installation and operation of geothermal power plants. This study investigated suitability of & Idot;zmir region, located in the Aegean part of T & uuml;rkiye, in terms of geothermal power plants applications by using the combination of Geographical Information System and Analytic Hierarchy Process. Based on the request of power plants, thirteen important criteria were evaluated under three main categories named as physical (C1), environmental (C2) and technical (C3). Moreover, expert's opinions were taken into consideration to calculate the importance of these criteria. Key results showed that & Idot;zmir was suitable for geothermal power plants. The final suitability map layer pointed out that %8.73 (1.037 km2) of total area were determined as highly suitable regions in terms of installation. In addition, the obtained suitability map layer was compared with actual geothermal power plants. Based on the comparison study, power plants in Seferihisar were moderately suitable for geothermal power plants while the location of Bal & ccedil;ova power plant was highly suitable. Regarding the suitability assessment in the present study, the location of Dikili power plants had the least suitability score.
Citation - Scopus: 5
Emotion Detection Using Multivariate Synchrosqueezing Transform via 2D Circumplex Model
(Institute of Electrical and Electronics Engineers Inc., 2018) Ozel, Pinar; Akan, Aydin; Yilmaz, Bulent; Özel, Pınar; Akan, Aydin I.; Yilmaz, Bulent
Emotion detection by utilizing signal processing methods is a challenging area. An open issue in emotional modeling is to obtain an optimum feature set to use for the classification process. This study proposes an approach for emotional state classification by the investigation of EEG signals via multivariate synchrosqueezing transform (MSST). MSST is a post-processing technique to compose a localized time-frequency representation yielding multivariate syncyrosqueezing coefficients. After obtaining these coefficients from EEG signals for 18 subjects from DEAP dataset, coefficients and self-assessment-mannequins (SAM) labels of those subjects are used for emotional state classification by using support vector machines (SVM) nearest neighbor, decision tree, and ensemble methods. The accuracy rate is 70.6% for high valence high arousal (HVHA), 75.4% for low valence high arousal (LVHA), 77.8% for high valence low arousal (HVLA), and 77.2% for low valence low arousal (LVLA) cases using SVM. © 2019 Elsevier B.V., All rights reserved.
Citation - Scopus: 1
Detection of Epileptic Seizures With Tangent Space Mapping Features of EEG Signals
(IEEE, 2021) Altindis, Fatih; Yilmaz, Bulent
Detection of epileptic seizures from EEG signals is well-studied topic for the last couple of decades. Lately, automated signal processing and machine learning methods were developed to detect epileptic seizures. However, most of the methods are tailored to subjects and require fine tuning of many parameters. In this study, we proposed to use Riemannian geometry-based signal processing method that already showed superior performance on brain-computer interface problems, to extract features. We showed that tangent space mapping features of EEG signals can be used to detect seizures with high accuracy and precision.
Barriers in Sustainable Lean Supply Chain Management: Implementation in SMEs
(Ege Univ, Fac Economics & Admin Sciences, 2025) Takci, Ebru; Ada, Erhan; Kazancoglu, Yigit
As the world undergoes significant transformations in various domains, including technology, energy supply and communication, the idea of sustainability has become a significant issue. This study investigates the barriers to Sustainable Lean Supply Chain (SLSC) management within Small and Medium-Sized Enterprises (SMEs) and explores the structural interrelationships among these barriers. A comprehensive literature review was carried out to recognize critical elements relevant to the research topic, resulting in the identification of fifteen specific elements that account for 85% of the barriers in SLSC management. The DEMATEL method was used to evaluate the significance and influence levels of these factors. Furthermore, structured in-depth interviews were conducted with ten experts representing sectors that constitute 85% of the SMEs operating in Kayseri Organized Industrial Zone (OIZ), Turkey, including metal products, furniture, plastic packaging, construction materials, textiles and food. The findings reveal that strategies represent the most significant barrier to SLSC management in SMEs. The barriers were analyzed in two dimensions: influencing and influenced factors. The primary influencing factor identified was laws, standards, regulations, and legislation while the most significant influenced factor was found supply and suppliers. The study concludes with findings and actionable recommendations for practitioners and decision-makers.
Citation - WoS: 1
Citation - Scopus: 2
Vision-Based Autonomous Aerial Refueling
(Amer Inst Aeronautics & Astronautics, 2022) Erkin, Tevfik; Abdo, Omer; Sanli, Yilmaz; Celik, Harun; Isci, Hasan
Aerial refueling tasks are very challenging due to the high risk of aircraft close proximity. Currently, within the drogue-probe method, the receiver aircraft pilot manages the refueling task in accordance with the tanker aircraft pilot. Therefore, autonomous aerial refueling is still an unaccomplished task for aircrafts. In this paper, a fully automated aerial refueling procedure based on digital visual inspection is proposed. A nonlinear dynamic model of receiver aircraft is derived to track the motion of drogue. In order to control the receiver aircraft affected by tanker aircraft vortex during approach, and ensure the receiver aircraft to automatically track and dock the tanker aircraft, an autopilot system that considers visual sensing of drogue motion is designed. The receiver aircraft is controlled by the autopilot system via translational motion of tanker aircraft projected by a cameramounted on the receiver aircraft. Thanks to this vision-based controllers, the need of tanker aircraft positioning is denied since camera projection has the capability of perception of three-dimensional direction of tanker aircraft. In order to test the autopilots include vision-based controllers and algorithms, the vision-based autonomous aerial refueling is operated under presence of turbulence and vortex. Finally, the simulation results demonstrate that the proposed guidance-navigation-control system achieve aerial refueling autonomously, and make it feasible and realizable for aircrafts.
Citation - Scopus: 5
Development of Knowledge Based Response Correction for a Reconfigurable N-Shaped Microstrip Antenna Design
(Institute of Electrical and Electronics Engineers Inc., 2015) Aoad, Ashrf; Simsek, Murat; Aydin, Zafer
This study presents the use of prior knowledge of inverse artificial neural network (ANN) to model and optimize a reconfigurable N-shaped microstrip antenna. Three accurate prior knowledge inverse ANNs with large amount training data are proposed where the frequency information is incorporated into the structure of ANN. The complexity of the input/output relationship is reduced by using prior knowledge. Three separate methods of incorporating knowledge in the second step of the training process with a multilayer perceptron (MLP) in the first step are demonstrated and their results are compared to EM simulation. © 2023 Elsevier B.V., All rights reserved.
Range-Based Wireless Sensor Network Localization by a Circumnavigating Mobile Anchor Without Position Information
(IEEE, 2024) Guler, Samet
Typical range-based wireless sensor network (WSN) localization approaches aim at estimating the sensor node positions by using a set of anchors with known positions. In some applications, assuming the knowledge of the anchors' positions may be impractical, and estimation of the sensors' positions in an arbitrary fixed frame may be sufficient. Considering such scenarios, we propose a WSN localization algorithm by single mobile anchor without self location information. The mobile anchor obtains distance measurements from the sensors while tracking a custom trajectory which is shown to improve the localization performance over time for high signal-to-noise ratio cases. By utilizing two stationary reference nodes within the WSN, the proposed framework generates sensor node position estimation up to translation and rotation with sufficient precision in the absence of global positioning aids. We foresee that the proposed framework can demonstrate benefits in several WSN applications ranging from internet-of-things to service robotics.
Citation - WoS: 1
Citation - Scopus: 3
Endüstriyel Kablosuz Algılayıcı Ağlarda Hata Kontrol Sistemlerinin Ağ Yaşam Süresine Etkileri
(IEEE, 2019) Tekin, Nazli; Gungor, V. Cagri
Due to the harsh channel conditions of the industrial environment, the data transmission over wireless channel suffers from erroneous packets. The energy consumption of error control schemes is of vital importance for battery-powered Wireless Sensor Networks (WSNs). In this paper, the performance evaluation of error control schemes namely, Automatic Repeat Request (ARQ), Forward Error Correction (FEC) and Hybrid ARQ (HARQ) in industrial environment in terms of energy efficiency is presented. The impact of the existing error control schemes on the industrial wireless sensor network lifetime is analyzed. A novel Mixed Integer Programming (MIP) framework is developed to maximize network lifetime. Performance results show that utilizing BCH (31,21,5) for Telos at the link layer maximizes the network lifetime while attaining the desired application reliability rate.
Citation - WoS: 3
Citation - Scopus: 3
Performance Improvements of Photonic Lantern Based Coherent Receivers
(Institute of Electrical and Electronics Engineers Inc., 2014) Ozdur, Ibrahim T.; Toliver, Paul; Woodward, Ted K.
In this work, the signal-to-noise ratio improvement of photonic lantern-based coherent receivers over single-mode coherent receivers is demonstrated. The signal-to-noise ratio is improved by a factor of 2.8 when other parameters kept constant. © 2021 Elsevier B.V., All rights reserved.
Sustainable Water Management and Rehabilitation in the Mining Lakes, Ilgin-Konya, Turkey
(Agro Arge Danismanlik San ve Tic As, 2016) Delibalta, M. S.; Uzal, N.; Lermi, A.
The processes during the search, production and enrichment of mining operations naturally affects the air, soil, water resources in turn the natural environment and living organisms. In general, the environmental impact of coal opencast mining operations is much more significant than that of underground mining and mineral processing. After stripping of the material filling the holes in coal opencast production, with the rise of surface water and ground water level is composed of large or small ponds. Low pH (acidic characteristic) and high metal concentrations (Al, Ca, Mn, Fe, Cu, Zn, Pb) of these ponds, containing sulfide minerals and the waste materials, for the sustainability of natural resources is one of the biggest environmental problems. This paper is to investigate geochemical characteristics of the pond waters in the Ilgm Coal deposit area. Geochemical analyses were made by ICP-MS in waters taken from ponds in each three-month periods. Highest heavy metal contents 1839 ppb Mn and 9777 ppb Fe, the average pH values 6.49-7.81, turbidity (NTU) 0.1263.6, sulphate content 0.05-2.67 mg SO4/L, chemical oxygen demand 4-136 mg O-2/L, and electrical conductivity 285 mu S/cm4.68 mS/cm have been measured during the monitoring study of five different lignite opencast mine post-production lakes of the TKI GLI Ilgm. Analyses were performed in three-month periods. The results were evaluated within the framework of relevant laws and regulations.
Citation - WoS: 5
Citation - Scopus: 4
Single-Country Versus Multiple-Country Studies
(Academic Press Ltd-Elsevier Science Ltd, 2019) Aslan, Alper; Dogan, Eyup; Altinoz, Buket
Email Clustering & Generating Email Templates Based on Their Topics
(Assoc Computing Machinery, 2021) Coskun, Fatih; Gezer, Cengiz; Gungor, V. Cagri
Email templates have a significant impact on users in terms of productivity. Using an email template that is produced successfully is going to transfer the main information with a considerable impression. While the previous studies were focused on the email generation by text-differences in the content of the emails, generated templates based on email topics can provide better productivity for the companies. This article proposes a system, in which user emails are clustered according to the topics of the emails, and introduces an email template generation system that utilizes the sample emails belonging to the formed email clusters. For this purpose, the Enron email dataset has been used and the performance of different text preprocessing and topic modeling algorithms, such as DMM, GPU-DMM, GPU-PDMM, LF-DMM, LDA, LF-LDA, BTM, WNTM, PTM, SATM, have been investigated and compared to determine the most efficient one. After obtaining the email topics, the system shows the examples of the emails representing the selected topics and enables the authorized users to create templates that generalize these topics.
New Modeling of Reconfigurable Microstrip Antenna Using Hybrid Structure of Simulation Driven and Knowledge Based Artificial Neural Networks
(Pamukkale Univ, 2020) Aoad, Ashrf; Aydin, Zafer
Knowledge-based modeling has a critical role to embed existing knowledge to improve modeling performance. Since reconfigurable antenna can provide more operational frequencies than the classical antennas, a knowledge-based hybrid structure is used in this work to obtain efficient model and producing optimum new models for a reconfigurable microstrip antenna. The hybrid structure consists of two phases. The first phase generates initial knowledge which is used in knowledge-based modeling structure to obtain design parameters. Artificial neural network based multilayer perceptron can generate necessary knowledge for a knowledge-based model after the training process. Knowledge-based modeling improves the accuracy of the initial model to determine design parameters corresponding to the design target. Source difference, prior knowledge Input and prior knowledge input with difference can be applied to realize an efficient knowledge-based strategy. 3D-EM simulation generates the new model in terms of the design parameters of the proposed application. It has three switching states for operating, which are organized by two resistor circuits representing ON/OFF states. Switch positions and geometrical parameters can be used for satisfying design targets between 1 GHz and 6 GHz for the efficient antenna design.
Citation - WoS: 1
Citation - Scopus: 2
Effects of Curved-Beam Heights to Harvested Energy in a Blanaced Comb-Drive Configuration
(IEEE, 2021) Hah, Dooyoung
Energy harvesting devices have been gaining increasing interests, especially in the areas of internet of things (IoTs) and sensor networks. Due to the broadband and random nature of typical vibration energy sources available in the environment, significant amount of research efforts have been put into the bandwidth broadening of the energy harvesters. Utilization of spring nonlinearity has been one of the most studied subject in that regard. In this work, response of an energy harvesting device with curved-beam springs to colorednoise vibration is studied numerically, based on stochastic differential equations. The harvester considered in this study is an electrostatic type with electrets and a balanced comb-drive configuration. The study mainly focuses on the effect of the beam height to the harvested power. The results show that curved-beam springs can increase the harvested electric power by 52% (2.69 mW versus 1.77 mW) in comparison to straight-beam springs of the same dimensions. Buckling-induced rapid snapping of the curved beams is attributed to such a power increase.
Data-Driven Local Control Design for Dead Band Control of Load Tap Changers
(IEEE, 2024) Savasci, Alper; Ceylan, Oguzhan; Paudyal, Sumit
This study presents an off-line optimization-guided machine learning approach for coordinating the local control rules of on-load tap changers (OLTCs) and step-voltage regulators (SVRs). Based on a bang-bang control rule, these legacy devices autonomously regulate the feeder voltage around the nominal level by varying the tap position in the lower or raise direction. The characterizing parameter of the local control rule is the dead band, which affects the number of tap switching in operation and is directly related to the economical use life of the equipment. The bandwidth is typically set within a standard voltage range and is generally kept constant in daily operation. However, adjusting the bandwidth dynamically can prevent excessive tap switching while maintaining satisfactory voltage regulation for varying loading and distributed generation conditions. Our approach aims to set the bandwidth parameter systematically and efficiently through a machine learning-based scheme, which is trained with a dataset formed by solving the distribution network optimal power flow (DOPF) problem. The performance of learning the bandwidth parameter is demonstrated on the modified 33-node feeder, which is promising for integrated voltage control schemes.
Citation - WoS: 5
Citation - Scopus: 5
Design and Control of a Single Phase DC/Rectified AC/AC Inverter for Low THD Applications
(Institute of Electrical and Electronics Engineers Inc., 2018) Tekgun, Burak; Tekgun, Didem; Alan, İrfan; Badawy, Mohamed O.
In this paper, a single phase DC/Rectified AC/AC (DC/RAC/AC) inverter is analyzed and compared to classical single phase PWM inverters. A traditional AC power supply (PS) system consists of a DC/DC converter, a cascaded H-bridge inverter, and a passive filter to generate the sinusoidal output voltage. The presented DC/RAC/AC inverter has a similar structure; however, the control of the cascaded units differ. The presented method generates rectified sine wave at the output of the DC/DC converter unit and the H-bridge inverter alternates the rectified sine wave to generate the full sine wave without having an additional output filter; hence, the switching losses at the H-bridge inverter is limited to the line frequency (50-60 Hz). Moreover, the bulk DC bus capacity at the output of the DC/DC converter is reduced significantly. Therefore, the power consumed by the passive elements are minimized. The circuit modes of operation are analyzed and the system is simulated in Matlab/Simulink environment for both traditional and proposed topologies. Results show that the proposed system is superior to the traditional one in terms of efficiency, generated THD with a simplified control structure, and it offers a reduced system size and cost. © 2019 Elsevier B.V., All rights reserved.
A Horizontal Magnetic Tweezer for Single Molecule Micromanipulations
(Institute of Electrical and Electronics Engineers Inc., 2018) Ablay, Günyaz; Böyük, Mustafa; Eroǧlu, Yakup; İçöz, Kutay
Magnetic tweezers are able to manipulate cells or biomolecules for various applications and measurements. In this work, a horizontal magnetic tweezer is designed, modeled and controlled for single molecule manipulations. A method is presented for dynamic modeling of horizontal magnetic tweezers. A linear control method is designed to ensure a wide range of operation conditions with zero steady-state error. The horizontal magnetic tweezer is able to generate a wide range of piconewton scale forces on a superparamagnetic microparticle for single molecule separation, and biosensor developments. © 2019 Elsevier B.V., All rights reserved.
Rings With Variations of Flat Covers
(Honam Mathematical Soc, 2019) Demirci, Yilmaz Mehmet; Turkmen, Ergul
We introduce flat e-covers of modules and define e-perfect rings as a generalization of perfect rings. We prove that a ring is right perfect if and only if it is semilocal and right e-perfect which generalizes a result due to N. Ding and J. Chen. Moreover, in the light of the fact that a ring R is right perfect if and only if flat covers of any R-module are projective covers, we study on the rings over which flat covers of modules are (generalized) locally projective covers, and obtain some characterizations of (semi) perfect, A-perfect and B-perfect rings.

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