IYTE GCRIS Database (Izmir Institute of Technology)
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11968 research outputs found
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User Selection for Secure Massive Mimo Based Mobile Edge Computing With Delay-Sensitive Applications
No full textMobile edge computing (MEC) has been a promising technology that leverages cloud computing capabilities at the network edge to address compute-intensive and delay-sensitive applications of mobile users with limited resources. Employing massive multiple-input multiple-output (mMIMO) and nonorthogonal multiple access (NOMA) in the MEC system facilitates simultaneous task offloading for multiple users, resulting in increased spectral efficiency and decreased offloading delay. Despite the great potential of the mMIMO-NOMA-based MEC system, offloading computation tasks to MEC servers can introduce inherent security concerns and vulnerabilities. We address a notable gap in the existing literature by investigating the effect of user selection to minimize the delay in MEC while enhancing the security of this framework. Specifically, this paper presents a user selection strategy for an uplink mMIMO-NOMA-based secure MEC system in the presence of a malicious eavesdropper (Eve) to minimize offloading and computing delays, subject to the transmit power, computing resource, and secrecy rate constraints with remote computing. We propose a two-step secure user selection algorithm and solve the optimization problem with the active-set algorithm. The simulation results demonstrate the effectiveness of the proposed user selection strategy on secure MEC with a malicious Eve by minimizing the task execution delay compared to the benchmark schemes. © 2025 IEEE
Investigation of the Effects of Various Parameters on Wireless Power Transfer Efficiency
No full textElectric vehicles have dominated the automotive market, especially in recent years. However, the charging problem that stresses drivers continues. Although conductive charging is an established technology, it still needs to meet user expectations fully. On the other hand, wireless charging technology attracts users' attention with dynamic charging features. Although this technology improves daily, efficiency is not at the desired level. In this study, a wireless power transfer system was designed for electric vehicles, and the factors affecting the charging efficiency were investigated. This system consists of an inverter, a compensation system, and a load. The efficiency of the system according to cable type, air gap, cooling, and pulse-width modulation parameters was observed through 40 experiments, each lasting 20 min. In addition to efficiency, the frequency behavior was also investigated. Experimental results were compared with models designed in MATLAB and ANSYS software. The average errors between the experimental and simulation results are 1.75, 2.03, 1.85, 1.58, and 2.00% for air gaps of 19-20, 55-56, 91-92, 127-128, and 145-146 mm, respectively. Power was transferred wirelessly with a minimum efficiency of 59.25% at a 145 mm air gap and a maximum efficiency of 85.74% at a 56 mm air gap in 300 W tests
Practical and Cost-Effective Approach for Thermal Light Characterization Based on Confined Area Measurements
No full textPhoton statistics and optical coherence measurements are essential in understanding light sources' properties and behaviors. However, the measurement setups require sophisticated detectors with short integration times. Otherwise, the results are indeed time average, which poses a significant challenge, particularly for thermal light sources due to their very short coherence times. In this article, we present a novel, practical, and low-cost measurement procedure for characterizing photon statistics and the second-order coherence function of thermal light using an ordinary charge-coupled device (CCD) camera. We focus on single-pixel analysis through the experiments since measurements of randomly distributed light in a confined region follow Bose-Einstein statistics. This way, the likelihood of averaging during detection is reduced, allowing us to extract statistical information from the spatially distributed intensity values. The outcomes prove the effectiveness of confined area measurements method by overcoming the detector's long exposure time issue
Kütüphaneler için Dijital Pazarlama
No full textİzmir Yüksek Teknoloji Enstitüsü (İYTE) Kütüphanesi olarak, Daire Başkanı Gültekin Gürdal'ın Moderatörlüğünde ve Berry Dijital Reklam Ajansı Dijital Marka Uzmanı Ece Ekitöz Karagöz ile kütüphanelerin dijital dünyada etkili bir şekilde var olmalarına yönelik stratejilerin ele alınacağı "Kütüphaneler için Dijital Pazarlama" başlıklı bir web semineri düzenlenmiştir. Seminerde, dijital pazarlamanın temelleri, geleceği ve kütüphaneler için özel stratejiler konuşulmuştur
Temperature-Dependent Spectral Properties of Hexagonal Boron Nitride Color Centers
No full textColor centers in hexagonal boron nitride (hBN) are emerging as a mature platform for single-photon sources in quantum technology applications. In this study, we investigate the temperature-dependent spectral properties of a single defect in hBN to understand the dominant dephasing mechanisms due to phonons. We observe a sharp zero-phonon line (ZPL) emission accompanied by Stokes and anti-Stokes optical phonon sidebands assisted by the Raman-active low-energy (approximate to 6.5 meV) interlayer shear mode of hBN. The shape of the spectral lines around the ZPL is measured down to 78 K, at which the line width of the ZPL is measured as 211 mu eV. Using a quadratic electron-phonon interaction, the temperature-dependent broadening and the lineshift of the ZPL are found to follow a temperature dependence of T + T 5 and T + T 3, respectively. Furthermore, the temperature-dependent line shape around the ZPL at low-temperature conditions is modeled with a linear electron-phonon coupling theory, which results in a 0 K Debye-Waller factor of the ZPL emission as 0.59. Our results provide insights into the underlying mechanisms of electron-phonon coupling in hBN, which is critical to enhance their potential for applications in quantum technologies
Influence of Fluorine on Structural and Electrical Properties of VO2 Thin Films Deposited by Magnetron Sputtering
No full textThis study investigates whether fluorine-based thermal gel used during electrical measurements of vanadium oxide (VO2) films influences the structural, morphological, or compositional integrity of the films. High-quality VO2 films with a resistance ratio change of about 104 for metal–insulator transition were deposited by magnetron sputtering. During electrical characterization, VO2 film was heated from room temperature to ∼370 K with a fluorine-based thermal gel usage to achieve better heat contact between the film and substrate holder. Structural and chemical properties were assessed through XRD, Raman, XPS, SEM, and energy dispersive spectroscopy imaging. XRD revealed diffraction peaks consistent with monoclinic VO2 confirming that the crystal lattice remains the same although fluorine based thermal gel was used. Raman spectra exhibited vibrational modes indicating that the phonon structure of VO2 was preserved despite fluorine gel usage. XPS results showed only a minor F 1s signal (2.8%) limited only to the film surface. SEM and EDS analyses further confirmed that surface morphology and elemental composition remained belonging to VO2 film. These findings demonstrate that the usage of fluorine-based thermal gel results in only a minimal surface interaction, thereby preserving intrinsic material properties of VO2 and supporting a potential usage for future device fabrication applications. © 202
Transforming Crete's Sustainable Energy Landscape: a Modular Energy Island Approach
No full textThe present paper investigates the conceptual design of a floating offshore renewable energy system-an energy island-developed to provide a sustainable long-term solution to support and expedite the transition toward renewable energy sources (RESs) as a case study in Crete Island, Greece. The optimal site selection in Crete's coastal waters was detected by carefully evaluating the potential for wind, solar, and wave energy alongside environmental and social considerations. Later, the current electricity demand was analyzed, leading to the identification of suitable technologies for renewable energy harvesting and the conceptualization of a floating structure. The findings of this research emphasize the viability of integrating diverse energy sources as a pivotal step for Crete Island to advance toward energy independence and environmental sustainability. Crete's abundant wind and solar resources underscore its capacity to host innovative projects, warranting further exploration into energy surplus storage and export
Tracing the Values of Fading Rural Architectural Heritage: the Case of Cold-Water Baths in Western Anatolia
No full textThis research explores the underappreciated traditional cold-water baths of Western Anatolia, once integral to the region's agrarian culture. Due to waves of change, which had markedly begun by the pandemic in 2019 and the aftermath of the 2020 Samos earthquake, there has been a growing interest in living in peri-urban areas, resulting in the invasion of agricultural grounds by new construction, mainly including detached houses with gardens. Such a harsh growth not only threatens the fertile lands, but also the irreplaceable cultural heritage they embrace. In this regional frame, this study focuses on three surviving baths within the Karaburun Peninsula, casting light on their current precarious state as relics of a diminishing rural way of life and local heritage. The traditional cold-water baths, constructed amidst agricultural fields for seasonal use in select villages throughout ; Idot;zmir, stand as unique exemplars of rural architecture. Characterised by their singular domed chambers and their reliance on water from adjacent wells, these structures today face abandonment and disrepair. Through a multi-disciplinary lens blending ethnography, oral history, and spatial analysis, this paper portrays these unassuming yet culturally impactful baths, elucidating their intrinsic value within the heritage domain. The inquiry contributes significantly to the heritage conservation discussion, highlighting the broad spectrum of values beyond mere historical interest. By articulating the symbiotic relationship between heritage and its community, this research underscores the pressing need to weave these baths into the fabric of current social structures, safeguarding their place within the collective memory
Investigation of the Effect of the Cutting Parameters on Cutting Forces and Tool Wear in the Stack Drilling of a Carbon Fibre-Reinforced Thermoplastic Matrix Composite and Aa7075
No full textThis study investigate the stack drillability of unidirectional (UD) carbon fibre reinforced thermoplastic matrix PAEK/CF composite and AA7075 plate utilised in aerospace. The effects of the cutting parameters on cutting forces during the drilling process of thermoplastic matrix composites and aluminium materials were experimentally analysed. Drilling operations were carried out on a CNC Vertical Machining Centre under dry-cutting conditions. For three different drill types, three different cutting speeds, and feed rate combinations, a total of 810 holes were drilled in a full factorial experimental design with 30 replicates for each combination. The damage on the hole surfaces on the drilled composite was identified with an optical microscope. The numerical data were obtained in the composite testing laboratory and analysed using Minitab (R) 21.1 statistical software and transformed into graphs. The most suitable drill type and cutting parameters were determined for the drillability of composite with thermoplastic matrix and aluminium (AA7075) plates when stacked
Passive Matrix Schottky Barrier 2d Photodiode Array on Graphene/Soi Platform
No full textWe fabricated 4 × 4 pixel two-dimensional (2D) photodiode array (PDA) out of monolayer graphene and n-type silicon (n-Si) electrodes on a silicon-on-insulator (SOI) substrate. Our device design is based on passive matrix sensor array architecture consisting of individual graphene and silicon electrodes aligned perpendicular to each other. I-V measurements conducted at room temperature to reveal the electronic characteristics of graphene and Si junction in the device structure. The spectral responsivity, respond speed and the optical crosstalk of each G/Si pixels in the array have been determined by wavelength resolved and time dependent photocurrent spectroscopy measurements. Micro-Raman mapping measurements were conducted to examine the surface coverage of graphene electrode on each pixel. The results of Micro-Raman mapping measurements were correlated with the corresponding photocurrent data acquired under light illumination. We believe that this work constitutes a significant potential in integrating variety of 2D materials and SOI technology into next generation image sensing and multiple pixel light detection applications. © The Author(s) 2025