Elektrik - Elektronik Mühendisliği Bölümü Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/202

Browse

Now showing 1 - 20 of 350

Electrochemical and Optical Multi-Detection of Escherichia coli Through Magneto-Optic Nanoparticles: A Pencil-on-Paper Biosensor
(MDPI, 2024) Soysaldi, Furkan; Ekici, Derya Dincyurek; Soylu, Mehmet cagri; Mutlugun, Evren; 0000-0003-1120-5557; 0000-0001-5807-9944; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Ekici, Derya Dincyurek; Mutlugun, Evren
Escherichia coli (E. coli) detection suffers from slow analysis time and high costs, along with the need for specificity. While state-of-the-art electrochemical biosensors are cost-efficient and easy to implement, their sensitivity and analysis time still require improvement. In this work, we present a paper-based electrochemical biosensor utilizing magnetic core-shell Fe2O3@CdSe/ZnS quantum dots (MQDs) to achieve fast detection, low cost, and high sensitivity. Using electrochemical impedance spectroscopy (EIS) as the detection technique, the biosensor achieved a limit of detection of 2.7 x 10(2) CFU/mL for E. coli bacteria across a concentration range of 10(2)-10(8) CFU/mL, with a relative standard deviation (RSD) of 3.5781%. From an optical perspective, as E. coli concentration increased steadily from 10(4) to 10(7) CFU/mL, quantum dot fluorescence showed over 60% lifetime quenching. This hybrid biosensor thus provides rapid, highly sensitive E. coli detection with a fast analysis time of 30 min. This study, which combines the detection advantages of electrochemical and optical biosensor systems in a graphite-based paper sensor for the first time, has the potential to meet the needs of point-of-care applications. It is thought that future studies that will aim to examine the performance of the production-optimized, portable, graphite-based sensor system on real food samples, environmental samples, and especially medical clinical samples will be promising.
Molecular Separation by Using Active and Passive Microfluidic chip Designs: A Comprehensive Review
(WILEY Advanced, 2024) Ebrahimi, Aliakbar; Icoz, Kutay; Didarian, Reza; Shih, Chih-Hsin; Tarim, E. Alperay; Nasseri, Behzad; Akpek, Ali; Cecen, Berivan; Bal-Ozturk, Ayca; Gulec, Kadri; Li, Yi-Chen Ethan; Shih, Steven; Tarim, Burcu Sirma; Tekin, H. Cumhur; Alarcin, Emine; Tayybi-Azar, Mehdi; Ghorbanpoor, Hamed; Ozel, Ceren; Sariboyaci, Ayla Eker; Guzel, Fatma Dogan; Bassous, Nicole; Shin, Su Ryon; Avci, Huseyin; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Icoz, Kutay
Separation and identification of molecules and biomolecules such as nucleic acids, proteins, and polysaccharides from complex fluids are known to be important due to unmet needs in various applications. Generally, many different separation techniques, including chromatography, electrophoresis, and magnetophoresis, have been developed to identify the target molecules precisely. However, these techniques are expensive and time consuming. “Lab-on-a-chip” systems with low cost per device, quick analysis capabilities, and minimal sample consumption seem to be ideal candidates for separating particles, cells, blood samples, and molecules. From this perspective, different microfluidic-based techniques have been extensively developed in the past two decades to separate samples with different origins. In this review, “lab-on-a-chip” methods by passive, active, and hybrid approaches for the separation of biomolecules developed in the past decade are comprehensively discussed. Due to the wide variety in the field, it will be impossible to cover every facet of the subject. Therefore, this review paper covers passive and active methods generally used for biomolecule separation. Then, an investigation of the combined sophisticated methods is highlighted. The spotlight also will be shined on the elegance of separation successes in recent years, and the remainder of the article explores how these permit the development of novel techniques.
Exploring CsPbX3 (X = Cl, Br, I) Perovskite Nanocrystals in Amorphous Oxide Glasses: Innovations in Fabrication and Applications
(WILEY Online Library, 2024) Samiei, Sadaf; Soheyli, Ehsan; Vighnesh, Kunnathodi; Nabiyouni, Gholamreza; Rogach, Andrey L.; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Soheyli, Ehsan
Metal halide perovskites with excellent optical and electronic properties have become a trending material in the current research. However, their limited stability under ambient conditions degrades quality and threatens their potential commercialization as optoelectronic devices. Various approaches are adopted to improve the stability of perovskite nanocrystals (PeNC) while maintaining their advantageous optical properties, particularly strong luminescence. Among different possible improvement strategies, encapsulation of PeNCs within the amorphous glass matrices of inorganic oxides has drawn widespread attention because it ensures high resistance against chemical corrosion and high temperature, thus enhancing their chemical, thermal, and mechanical stability with improved light-emission characteristics. In this article, two types of materials, namely all-inorganic metal halide PeNCs and amorphous oxide glasses are briefly introduced, and then the methods are reviewed to fabricate and improve the quality of PeNC@glass composites. These methods are classified into three universal categories: compositional modification, structural modification, and dual encapsulation. In the final part of this review paper, examples of applications of PeNCs@glass composites in light-emitting devices and displays, data storage and anti-counterfeiting, lasing, photodetectors and X-ray detectors, photocatalysis, optical filters, solar concentrators, and batteries are provided.
ATOM: AI-Powered Sustainable Resource Management for Serverless Edge Computing Environments
(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2024) Golec, Muhammed; Gill, Sukhpal Singh; Cuadrado, Felix; Parlikad, Ajith Kumar; Xu, Minxian; Wu, Huaming; Uhlig, Steve; AGÜ, Fen Bilimleri Enstitüsü, Elektrik ve Bilgisayar Mühendisliği Ana Bilim Dalı; Golec, Muhammed
Serverless edge computing decreases unnecessary resource usage on end devices with limited processing power and storage capacity. Despite its benefits, serverless edge computing's zero scalability is the major source of the cold start delay, which is yet unsolved. This latency is unacceptable for time-sensitive Internet of Things (IoT) applications like autonomous cars. Most existing approaches need containers to idle and use extra computing resources. Edge devices have fewer resources than cloud-based systems, requiring new sustainable solutions. Therefore, we propose an AI-powered, sustainable resource management framework called ATOM for serverless edge computing. ATOM utilizes a deep reinforcement learning model to predict exactly when cold start latency will happen. We create a cold start dataset using a heart disease risk scenario and deploy using Google Cloud Functions. To demonstrate the superiority of ATOM, its performance is compared with two different baselines, which use the warm-start containers and a two-layer adaptive approach. The experimental results showed that although the ATOM required more calculation time of 118.76 seconds, it performed better in predicting cold start than baseline models with an RMSE ratio of 148.76. Additionally, the energy consumption and CO2 emission amount of these models are evaluated and compared for the training and prediction phases.
Distinguishing Resting State From Motor Imagery Swallowing Using EEG and Deep Learning Models
(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2024) Aslan, Sevgi Gökçe; Yılmaz, Bülent; 0000-0001-9425-1916; AGÜ, Mühendislik Fakültesi, Bilgisayar Mühendisliği Bölümü; Aslan, Sevgi Gökçe
The primary aim of this study was to assess the classification performance of deep learning models in distinguishing between resting state and motor imagery swallowing, utilizing various preprocessing and data visualization techniques applied to electroencephalography (EEG) data. In this study, we performed experiments using four distinct paradigms such as natural swallowing, induced saliva swallowing, induced water swallowing, and induced tongue protrusion on 30 right-handed individuals (aged 18 to 56). We utilized a 16-channel wearable EEG headset. We thoroughly investigated the impact of different preprocessing methods (Independent Component Analysis, Empirical Mode Decomposition, bandpass filtering) and visualization techniques (spectrograms, scalograms) on the classification performance of multichannel EEG signals. Additionally, we explored the utilization and potential contributions of deep learning models, particularly Convolutional Neural Networks (CNNs), in EEG-based classification processes. The novelty of this study lies in its comprehensive examination of the potential of deep learning models, specifically in distinguishing between resting state and motor imagery swallowing processes, using a diverse combination of EEG signal preprocessing and visualization techniques. The results showed that it was possible to distinguish the resting state from the imagination of swallowing with 89.8% accuracy, especially using continuous wavelet transform (CWT) based scalograms. The findings of this study may provide significant contributions to the development of effective methods for the rehabilitation and treatment of swallowing difficulties based on motor imagery-based brain computer interfaces.
Dron ve Arabalar gibi Hareketli Platformların İletişimine Yönelik Farklı Rezonanslarda Konik Radyasyon ve Konik Tarama Yapılmasına Olanak Sağlayan Çift Taraflı E Şeklindeki Düzlemsel Dizi Yama Antenlerin Tasarımı ve Geliştirilmesi
(2023) Kılıç, Veli Tayfun; Tosun, Hüseyin; Şanlıer, Şaban Duran; 0000-0001-6806-9053; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Kılıç, Veli Tayfun
Bu projede dron ve arabalar gibi hareketli platformların iletişimine yönelik farklı rezonanslarda konik yayılım ve konik tarama yapılmasına olanak sağlayan çift taraflı E şeklindeki anten elemanlarından oluşan düzlemsel dizi yama antenlerin tasarımı, analizleri, üretimi ve testleri gerçekleştirilmiştir. Tasarlanan dizilerin elektromanyetik simülasyonlar ile rezonans davranışları ve yayılım örüntüleri hesaplanmıştır. Modellenen dizilerin üretimleri tarafımızca gerçekleştirilmiş ve ölçümleri yapılmıştır. Ölçüm ve simülasyon sonuçları birbirleriyle uyumlu bulunmuştur. Sonuçlar tasarlanan dizilerin öngörüldüğü üzere 2.4 GHz ve 4.8 GHz?de ilk ve ikinci rezonanslarının oluştuğunu ve bu rezonanslarda konik yayılım ve konik taramanın gerçekleştiğini göstermektedir. Daha sonra, dizideki elemanların beslenmesine yönelik 1?e 8?lik güç bölücü tasarımları yapılmıştır. Tasarlanan güç bölücü simülasyonlar ile modellenmiş ve iletim ve yansıma kaybı parametreleri hesaplanmıştır. Modellenen güç bölücülerin üretim ve testleri de yine tarafımızca gerçekleştirilmiştir. Ölçüm ve simülasyon sonuçları birbirini desteklemektedir. Sonuçlar tasarlanan güç bölücünün 2.4 GHz frekansında giriş portunda düşük yansıma kaybı ve çıkış portlarında eşit sinyal seviyelerini gerçekleştirdiğini göstermektedir. Son adım olarak dizi antenin dronun altına yerleştirildiği uzak alan yayılım örüntü ölçümünü gerçekleştirdiğimiz bir deneysel kurulum meydana getirilmiştir. Gerçekleştirdiğimiz ölçümlerde dizi antenin simülasyonlarda olduğu gibi belirli düşey eksen açılarında en yüksek yayılımı sağladığı gözlemlenmiştir.
Hemispherical-shell-shaped organic photovoltaic cells for absorption enhancement and improved angular coverage
(SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 2024) Hah, Dooyoung; 0000-0002-1290-0597; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Dooyoung, Hah
A hemispherical shell shape is proposed for an organic photovoltaic cell structure, aiming at enhancing both light absorption and angular coverage. Three-dimensional finite element analysis method is used to study the absorption spectra within the hemispherical-shell-shaped active layer. The study reveals that the proposed structure can result in 66% and 36% of absorption improvements compared to a flatstructured device when the incoming light is transverse electric (TE)- and transverse magnetic (TM)-polarized, respectively. It is also learned that the proposed hemispherical shell structure has absorption improvement as high as 13% (TE) and 21% (TM) when compared to the previously reported semicylindrical shell structure. The angular coverage of the proposed structure is improved as well, reaching 81 deg (TE) and 82 deg (TM), which becomes quite useful for the wearable electronics applications where the incidence angle can vary in a random manner. These improvements can be attributed to better light coupling and guiding through the active layer made possible by the hemispherical shell shape of the device.
Four Switch Buck-Boost Quasi Single-Stage Inverter with Smooth Mode Transition Using Three-Mod Modulation Technique
(IEEE, 2024) Keskinkılıç, Ebubekir; Tekgun, Burak; 0000-0002-4913-6684; 0000-0003-2720-8816; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Keskinkılıç, Ebubekir; Tekgun, Burak
Quasi-single-stage inverters (QSSI) attract attention due to their simple structure and bidirectional operation capability. However, in the buck-boost DC-DC conversion stage, smooth transition, and efficient conversion cannot be achieved when the output voltage is close to the input voltage with the traditional two-mode control method. This is due to the pulse width ratio limitations, and non-idealities of the active and passive components. In this paper, a comparative analysis of the mode transition techniques in QSSIs is presented using methods available for DC/DC converters. The system efficiency and output voltage signal quality are selected as the performance metrics as they are important performance parameters in many applications. A 2kW QSSI is controlled using single-mode, two-mode, and three-mode modulation techniques. Simulation and experimental studies are conducted for validation. Based on these studies, it is concluded that the single-mode modulation technique performed the best in eliminating dead zone effects and reducing total harmonic distortion (THD), whereas the two-mode modulation technique achieved the highest system efficiency. The three-mode modulation has superior performance on dead zone elimination compared to the two-mode modulation and better system efficiency than the single-mode modulation method. Experimental results indicate that the three-mode modulation achieved an efficiency of 91.12% with a THD of 3.73%.
Graph-based Biomedical Knowledge Discovery
(IEEE, 2024) Altuner, Osman; Bakir-Gungor, Burcu; Bakal, Gokhan; 0000-0003-2897-3894; 0000-0002-2272-6270; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Altuner, Osman; Bakir-Gungor, Burcu; Bakal, Gökhan
Dijitalleşme süreci tüm dünyada oldukça yüksek bir hızla ilerlemektedir. Bu durum günümüz yaşantısında bir çok kolaylık sağladığı gibi ortaya çıkan devasa dijital verilerin analizi ve işlenmesi gibi bir problemi de beraberinde getirmektedir. Bu durum yayınlanan akademik çalışmalar için de geçerlidir. Bu anlamda çalışmalar dahilinde bulunan yenilikçi bilgilere ulaşmak için her bir çalışmayı değerlendirme süreci oldukça zahmetli bir süreci gerektirmektedir. Bu sebeple yapılan bu çalışmada hedef hastalıklar özelinde elde edilmiş yayınlar metin analiz süreçleriyle analiz edilmiş ve anlamlı terimlerin biyomedikal ilişkiler üzerinden bağlanmasını sağlayan çizge yapısına dönüştürülmüştür. Elde edilen yoğun çizge yapısı üzerinde treats (tedavi edici), causes (sebep verici), associated_with (ilişkili) gibi önemli bağlantılara sahip ikili biyomedikal varlıklar sorgulanmıştır. Sorgu sonuçlarına göre elde edilen varlık ikilileri manuel arama yöntemiyle de teyit edilmiş ve gerçek bağlantılar olduğu ispatlanmıştır. Bu çalışmayla birlikte, bilinen biyomedikal varlıkların önerilen yaklaşımla elde edilmesi uzun zaman gerektiren manuel arama problemini çözmesi hedeflenmektedir. Ayrıca birden fazla ikili bağlantı örüntüleriyle bilinmeyen/keşfedilmemiş olası yeni ilişkiler (tedavi edici, sebep verici, ilişkili vb.) elde etme potansiyeli de bulunmaktadır.
CCPred: Global and population-specific colorectal cancer prediction and metagenomic biomarker identification at different molecular levels using machine learning techniques
(ELSEVIER, 2024) Bakir-Gungor, Burcu; Temiz, Mustafa; Inal, Yasin; Cicekyurt, Emre; Yousef, Malik; 0000-0002-2272-6270; 0000-0002-2839-1424; 0009-0002-4373-8526; AGÜ, Mühendislik Fakültesi, Bilgisayar Mühendisliği Bölümü; Bakir-Gungor, Burcu; Temiz, Mustafa; Inal, Yasin; Cicekyurt, Emre
Colorectal cancer (CRC) ranks as the third most common cancer globally and the second leading cause of cancer-related deaths. Recent research highlights the pivotal role of the gut microbiota in CRC development and progression. Understanding the complex interplay between disease development and metagenomic data is essential for CRC diagnosis and treatment. Current computational models employ machine learning to identify metagenomic biomarkers associated with CRC, yet there is a need to improve their accuracy through a holistic biological knowledge perspective. This study aims to evaluate CRC-associated metagenomic data at species, enzymes, and pathway levels via conducting global and population-specific analyses. These analyses utilize relative abundance values from human gut microbiome sequencing data and robust classification models are built for disease prediction and biomarker identification. For global CRC prediction and biomarker identification, the features that are identified by SelectKBest (SKB), Information Gain (IG), and Extreme Gradient Boosting (XGBoost) methods are combined. Population-based analysis includes within-population, leave-one-dataset-out (LODO) and cross-population approaches. Four classification algorithms are employed for CRC classification. Random Forest achieved an AUC of 0.83 for species data, 0.78 for enzyme data and 0.76 for pathway data globally. On the global scale, potential taxonomic biomarkers include ruthenibacterium lactatiformanas; enzyme biomarkers include RNA 2′ 3′ cyclic 3′ phosphodiesterase; and pathway biomarkers include pyruvate fermentation to acetone pathway. This study underscores the potential of machine learning models trained on metagenomic data for improved disease prediction and biomarker discovery. The proposed model and associated files are available at https://github.com/TemizMus/CCPRED.
Design and real-time implementation of a sliding mode observer utilizing voltage signal injection and PLL for sensorless control of IPMSMs
(ELSEVIER, 2024) Ates, Ertugrul; Tekgun, Burak; Ablay, Gunyaz; Barut, Murat; 0000-0001-6628-5350; 0000-0003-2720-8816; 0000-0003-2862-6761; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Ates, Ertugrul; Tekgun, Burak; Ablay, Gunyaz
In this study, a sliding mode observer (SMO) based on high-frequency (HF) voltage signal injection and a phase-locked loop (PLL) is proposed for estimating the extended electromotive force (EEMF), rotor position, and rotor velocity of an interior permanent magnet synchronous machine (IPMSM). This approach addresses real-time estimation challenges associated with standard SMO and PLL at very low speeds and standstill. A reliable and accurate sensorless speed control system for IPMSM is then developed and implemented in real time using the proposed SMO and PLL, covering a wide range of speeds, including low-speed and standstill conditions. The SMO effectively estimates the EEMF, while the PLL extracts the rotor velocity and position based on these estimates. Compared to conventional SMO and PLL methods, real-time results from an 8-pole, 0.4 kW IPMSM demonstrate the superior efficiency of the proposed system.
Nonequilibrium phase diagrams in a multilayer Ising ferrimagnet system: The Glauber type stochastic dynamics approach
(ELSEVIER, 2024) Paran, Nejdet; Ertaş, Mehmet; 0000-0003-0317-0438; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Paran, Nejdet
Multilayer Ising ferrimagnet system is studied with nonequilibrium phase diagrams employing the Glauber stochastic dynamics approach. Firstly, nonequilibrium phase transition temperatures and their phase transition nature are investigated in detail. The study shows that the system displays both the second and first-phase transition behaviors. Then, it is determined that the essential phases of nonequilibrium phase diagrams consist of five phases (i1, i2, nm1, nm2, p), four mixed phases (i1+ p, nm1 +nm2, nm2 + p, i1 + nm2), and four special points (A, B, E, TP). Lastly, the study demonstrates that the dynamic magnetic characteristics of the system exhibit a significant dependence on the parameters of the Hamiltonian.
Triple band diamond-shaped polarization insensitive plasmonic nano emitter for thermal camouflage and radiative cooling
(Springer Link, 2024) Şanlı, Atıf Kerem; Tabaru, Timuçin Emre; Kılıç, Veli Tayfun; 0000-0001-6806-9053; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Şanlı, Atıf Kerem; Kılıç, Veli Tayfun
This study proposes the design of a novel Metal-Insulator-Metal (MIM) nano-infrared emitter that uses a unique diamond-shaped grating to achieve selective infrared absorption. Diamond-shaped nano emitter (DNE) structure exhibits four narrow resonant peaks within key absorption windows such as short-wave infrared (SWIR) mid-wave infrared (MWIR), alongside with a wide absorption band in the Non-Transmissive Infrared Range (NTIR) for thermal camouflage applications compatible with radiative cooling. Moreover, the proposed DNE is polarization insensitive as it has an in-plane symmetric design. Using the 3D Finite-Difference Time-Domain (FDTD) simulations, we demonstrate the nanoantenna’s superior performance characterized by its high absorption rates and tuned effective impedance matching. As of our knowledge, the findings suggest that this is the first time that a MIM structure achieved multiple narrow resonance peaks, located in SWIR and MWIR simultaneously, with a wide absorption range in NTIR. Represented DNE stands as a significant innovation in the field of stealth technology, providing a tunable, high-efficiency solution for managing and controlling thermal emissions across diverse applications.
Sustainable next-generation color converters from P. harmala seed extracts for solid-state lighting
(Royal Society of Chemistry, 2024) Erdem, Talha; Orenc, Ali; Akcan, Dilber; Duman, Fatih; Soran-Erdem, Zeliha; 0000-0003-3905-376X; 0000-0001-7607-9286; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Erdem, Talha; Akcan, Dilber; Soran-Erdem, Zeliha
Traditional solid-state lighting heavily relies on color converters, which often have a significant environmental footprint. As an alternative, natural materials such as plant extracts could be employed if their low quantum yields (QYs) in liquid and solid states were higher. With this motivation, here, we investigate the optical properties of aqueous P. harmala extract, develop efficient color-converting solids through a cost-effective and environmentally friendly method, and integrate them with light-emitting diodes (LEDs). To achieve high-efficiency solid hosts for P. harmala-based fluorophores, we optically and structurally compare two crystalline and two cellulose-based platforms. Structural analyses reveal that sucrose crystals, cellulose-based cotton, and paper platforms enable a relatively homogeneous distribution of fluorophores compared to KCl crystals. Optical characterization demonstrates that the extracted solution and the extract-embedded paper possess QYs of 75.6% and 44.7%, respectively, whereas the QYs of the cotton, sucrose, and KCl crystals remain below 10%. We demonstrated that the paper host with the highest efficiency causes a blueshift in the P. harmala fluorescence, whereas the cotton host induces a redshift. We attribute this to the passivation of nonradiative transitions related to the structure of the hosts. Subsequently, as a proof-of-concept demonstration, we integrate the as-prepared efficient solids of P. harmala for the first time with a light-emitting diode (LED) chip to produce a color-converting LED. The resulting blue-emitting LED achieves a luminous efficiency of 21.9 lm Welect−1 with CIE color coordinates of (0.139, 0.070). These findings mark a significant step toward the utilization of plant-based fluorescent biomolecules in solid-state lighting, offering promising environmentally friendly organic color conversion solutions for future lighting applications.
Opportunities, Challenges, and Strategies for Scalable Deposition of Metal Halide Perovskite Solar Cells and Modules
(John Wiley and Sons Inc, 2024) Khorasani, Azam; Mohamadkhani, Fateme; Marandi, Maziar; Luo, Huiming; Abdi-Jalebi, Mojtaba; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Khorasani, Azam
Hybrid organic-inorganic perovskite solar cells (PSCs) have rapidly advanced in the new generation of photovoltaic devices. As the demand for energy continues to grow, the pursuit of more stable, highly efficient, and cost-effective solar cells has intensified in both academic research and the industry. Consequently, the development of scalable fabrication techniques that yield a uniform and dense perovskite absorber layer with optimal crystallization plays a crucial role to enhance stability and higher efficiency of perovskite solar modules. This review provides a comprehensive summary of recent advancements, comparison, and future prospects of scalable deposition techniques for perovskite photovoltaics. We discuss various techniques, including solution-based and physical methods such as blade coating, inkjet printing (IJP), screen printing, slot-die coating, physical vapor deposition, and spray coating that have been employed for fabrication of perovskite modules. The advantages and challenges associated with these techniques, such as contactless and maskless deposition, scalability, and compatibility with roll-to-roll processes, have been thoroughly examined. Finally, the integration of multiple subcells in perovskite solar modules is explored using different scalable deposition techniques.
Tailoring Quantum Dot Shell Thickness and Polyethylenimine Interlayers for Optimization of Inverted Quantum Dot Light-Emitting Diodes
(MDPI, 2024) Yazici, Ahmet F.; Ocal, Sema Karabel; Bicer, Aysenur; Serin, Ramis B.; Kacar, Rifat; Ucar, Esin; Ulku, Alper; Erdem, Talha; Mutlugun, Evren; 0000-0003-3905-376X; 0000-0003-3715-5594; 0000-0003-2747-7856; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Yazici, Ahmet F.; Ocal, Sema Karabel; Bicer, Aysenur; Erdem, Talha; Mutlugun, Evren
Quantum dot light-emitting diodes (QLEDs) hold great promise for next-generation display applications owing to their exceptional optical properties and versatile tunability. In this study, we investigate the effects of quantum dot (QD) shell thickness, polyethylenimine (PEI) concentration, and PEI layer position on the performance of inverted QLED devices. Two types of alloyed-core/shell QDs with varying shell thicknesses were synthesized using a one-pot method with mean particle sizes of 8.0 ± 0.9 nm and 10.3 ± 1.3 nm for thin- and thick-shelled QDs, respectively. Thick-shelled QDs exhibited a higher photoluminescence quantum yield (PLQY) and a narrower emission linewidth compared to their thin-shelled counterparts. Next, QLEDs employing these QDs were fabricated. The incorporation of PEI layers on either side of the QD emissive layer significantly enhanced device performance. Using PEI on the hole transport side resulted in greater improvement than on the electron injection side. Sandwiching the QD layer between two PEI layers led to the best performance, with a maximum external quantum efficiency (EQE) of 17% and a peak luminance of 91,174 cd/m2 achieved using an optimized PEI concentration of 0.025 wt% on both electron injection and hole injection sides. This study highlights the critical role of QD shell engineering and interfacial modification in achieving high-performance QLEDs for display applications.
Enhanced photoluminescence emission intensity and stability of deep blue-emissive (Et3NH)PbBr3 perovskite nanocrystals by using metal-organic frameworks
(ELSEVIER, 2024) Hemmati, Tayebeh; Naghipour, Ali; Sahraei, Reza; Soheyli, Ehsan; 0000-0002-1403-7934; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Soheyli, Ehsan
The primary obstacle faced by researchers in the field of luminescent metal-halide perovskites is their inherent instability, prompting a shift in focus towards enhancing the stability of perovskite nanocrystals (PNCs). One of the promising approaches to address this challenge involves the utilization of metal-organic frameworks (MOFs) to fabricate PNCs@MOF composites. The present study reports a facile and low-cost colloidal strategy to prepare (Et3NH)PbBr3 PNCs followed by their encapsulation within UiO-67 to enhance their photoluminescence (PL) emission stability. The PNCs and modified UiO-67 were prepared separately via simple and efficient ligand-assisted reprecipitation (LARP) and hydrothermal methods, respectively. After modification of the UiO-67, the pore sizes experienced a substantial increase from 1.90 to 28.84 nm which significantly facilitated the localization of PNCs within the porous matrix. Under a full survey of experimental conditions, the resulting (Et3NH)PbBr3@UiO-67 composite exhibited a bright deep-blue emission at around 410 nm with an emission quantum yield of 52 %. The emission durability of the fabricated PNCs@MOF composites was assessed against temperature and long-time of storage, confirming the superior advantages of MOF even at elevated temperatures of up to 100 °C. The stable and luminous deep-blue emission displayed by the PNCs@MOF composites in this investigation, offers a promising advancement in materials development for optoelectronic applications.
MoO3/WO3/rGO as electrode material for supercapacitor and catalyst for methanol and ethanol electrooxidation
(Nature Research, 2024) Askari, Mohammad Bagher; Salarizadeh, Parisa; Ramezan zadeh, Mohammad Hassan; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Ramezan zadeh, Mohammad Hassan
The potential of metal oxides in electrochemical energy storage encouraged our research team to synthesize molybdenum oxide/tungsten oxide nanocomposites (MoO3/WO3) and their hybrid with reduced graphene oxide (rGO), in the form of MoO3/WO3/rGO as a substrate with relatively good electrical conductivity and suitable electrochemical active surface. In this context, we presented the electrochemical behavior of these nanocomposites as an electrode for supercapacitors and as a catalyst in the oxidation process of methanol/ethanol. Our engineered samples were characterized by X-ray diffraction pattern and scanning electron microscopy. As a result, MoO3/WO3 and MoO3/WO3/rGO indicated specific capacitances of 452 and 583 F/g and stability of 88.9% and 92.6% after 2000 consecutive GCD cycles, respectively. Also, MoO3/WO3 and MoO3/WO3/rGO nanocatalysts showed oxidation current densities of 117 and 170 mA/cm2 at scan rate of 50 mV/s, and stability of 71 and 89%, respectively in chronoamperometry analysis, in the MOR process. Interestingly, in the ethanol oxidation process, corresponding oxidation current densities of 42 and 106 mA/cm2 and stability values of 70 and 82% were achieved. MoO3/WO3 and MoO3/WO3/rGO can be attractive options paving the way for prospective alcohol-based fuel cells.
Alçaltıcı/Yükseltici Dc/Dc/Ac Eviricilerle Yüksek Performanslı Anahtarlamalı Relüktans Motoru Sürücü Sistemi Tasarımı Ve Gerçeklemesi
(2021) Tekgün, Burak; Boynuegri, Ali Rifat; Yaşa , Yusuf; Alan, Irfan; 0000-0003-2720-8816; 0000-0001-7995-0540; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Tekgün, Burak; Alan, Irfan
Anahtarlamalı relüktans motorları (ARM) 1800?lü yılların ortalarında keşfedilmesine rağmen, 1960?lı yıllarda yarı iletken anahtarların icat edilmesine kadar potansiyeli anlaşılamamış makinalardır. Modern yarı iletken teknolojisinin icadı ve gelişmesi ile birlikte ARM?lerin kullanımı yaygınlaşmıştır. ARM?ler basit yapıları, düşük üretim maliyetleri ve sağlamlıklarından dolayı birçok uygulamada tercih edilmişlerdir. Geleneksel olarak ARM, her bir faz için iki yarı iletken anahtar ve iki diyot kullanılarak oluşturulan sürücülerle sabit giriş gerilimi işlenerek, sırasıyla fazlar enerjilendirilmektedir. Faz sargılarındaki akımın enerjilendirilme esnasında yükselme süresi ve enerji kesildiği durumdaki akımın azalma süresi DC bara voltajına bağlıdır. Bu durum uygulamalarda enerjilendirme süresinin akımın sıfıra gitme süresi de göz önüne alınıp kısa tutulmasına, dolayısıyla komütasyon esnasında düşük tork üretimine, yüksek tork salınımına ve ortalama tork üretiminde azalmaya sebep olmaktadır. Bu projede, geleneksel sürücü topolojisinden farklı olarak ARM, bir DC/DC dönüştürücü ve tek fazlı bir tam-köprü evirici yardımı ile ideale yakın bir enerjilendirme akımı oluşturularak ARM daha yüksek performans ile kontrol edilmesi sağlanmıştır. Projede önerilen ARM sürücüsü her bir fazı bir DC/DC dönüştürücü ve bir tam-köprü evirici içeren modüler yapılı sürücülerden oluşmaktadır. Önerilen sürücü yapısını geleneksel ARM topolojilerinden ayıran özelliği DC/DC dönüştürücü devresidir. Burada makinanın faz sargılarının ihtiyaç duyduğu akım dalga şekli DC/DC dönüştürücü ile sağlanmaktadır. Tork üretiminin pozitif olabilmesi için stator ve rotor kutuplarının tam hizalandığı andan kısa bir süre önce negatif gerilim uygulanarak, faz akımının hızlı bir şekilde kesilmesi gerekmektedir. Bu durumda ise gerilim önerilen devredeki tam-köprü devresi yardımıyla tersine çevrilerek ve DC/DC dönüştürücünün çıkış gerilimi en yüksek seviyesine getirilmek suretiyle akımın hızlı şekilde sıfıra inmesi sağlanmıştır ve böylelikle makinanın performansı artmıştır. sadece DC/DC çevirici katında yüksek frekanslı anahtarlama olduğundan anahtarlama kayıplarının azalarak ve geleneksel topolojiye göre daha yüksek verim sağlanmıştır. Önerilen sürücü sisteminin AC motorların sürücüleri olarak yenilenebilir enerji sistemlerinde ara yüz elemanı olarak uygulanabilir olması, arıza giderme zamanında önemli ölçüde azalmaya neden olarak üretimdeki sürdürülebilirliğin artırılmasına destek olacağı öngörülmektedir.
Mrd Biyoçip: Minimal Rezidüel Hastalığın Güvenilir ve Basit Bir Yolla İzlenmesi
(TÜBİTAK, 2019) İçöz, Kutay; Karakükçü, Musa; Özdemir, Mehmet Akif; Deniz, Günnur; Ünal, Ekrem; Çınar, Suzan; Küpesiz, Osman Alphan; Kaya, Zühre; Yılmaz, Bülent; Gerçek, Tayyibe; Akar, Ünal; 0000-0002-0947-6166; 0000-0003-2954-1217; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; İçöz, Kutay; Yılmaz, Bülent; Gerçek, Tayyibe
Türkiye Halk Sağlığı Kurumu verilerine göre Türkiye?de çocukluk çağında en sık görülen kanser türü lösemidir ve lösemi türleri arasında Akut Lenfoid Lösemi (ALL) 15 yaş altındaki çocuklarda gözlenen lösemilerin %80?inini oluşturur. Lösemiden korunmanın kesin bir yöntemi şu an için bilinmemektedir ve lösemi hastalarına uygulanan kemoterapi (ilaç tedavisi), radyoterapi, kemik iliği nakli ve immünoterapi gibi farklı tedaviler mevcuttur. Akut lenfoblastik lösemi hastalarının tedavi sürecinde uygulanan kemoterapi her hastaya aynı şekilde etki etmemekte; bazı hastalar tedaviye yanıt verirken bazı hastalarda lösemik hücreler (blastlar) kemoterapiye direnç göstermektedir. Sonuçta tedaviden kaçan bu lösemik blastlar hastalık tekrarlarına (relapslara) neden olabilmektedirler. Tedavinin 15. gününde incelenen minimal rezidüel (kalıntı) hastalık (minimal residuel disease, MRD) akut lösemi hastalarında sağ kalımın en önemli göstergesi olup uluslararası tedavi protokollerinde standart olarak kullanılmaktadır. Bu protokollere göre MRD pozitif tespit edilir ise kemoterapi tedavisi daha da yoğunlaştırılmaktadır. MRD ölçümü günümüzde akım sitometrisi (flow cytometry FC) ve polimeraz zincir reaksiyonu (PCR) ile yapılabilmektedir. Her iki yöntemde de sonuç almak uzun vakit almakta, her iki yöntemin de maliyeti yüksek olup, sadece uzman kullanıcılar tarafından akredite olmuş referans laboratuvar ortamlarında gerçekleştirilebilmektedir. Alt yapı yetersizliği ve yüksek maliyetlerden dolayı tedavi edilen ALL hastalarının çoğunluğunda MRD tespiti mümkün olamamaktadır. Oysa kemoterapi gören hastalarda, relapslara neden olan hücreler için MRD taraması ile, tedavinin seyri değişebilecek, her hastaya uygun ilaç dozajı ayarlanabilecek ve ileri dönemde relapslar azaltılabilecektir. Günümüzde MRD testi için kullanılan laboratuvar yöntemleri kadar hassas, fakat maliyeti daha düşük biyosensör cihazların geliştirilmesi lösemi tedavisinde çığır açacak potansiyele sahiptir. Mikro/nano teknoloji tabanlı biyoçipler üreterek alternatif bir metot geliştirerek, hastaların tedavi sürecini iyileştirmek, hekimlere büyük kolaylık sağlamak, ülkemize katma değeri yüksek bir ürün kazandırmak mümkündür. Geliştirilmek istenen biyoçip ile B öncül ALL hastalarındaki kanserli hücrelerin kemoterapi sürecindeki durumları ve tedaviye gösterdikleri yanıt izlenebilecek, bu da hastalara en uygun ilaç dozajının ayarlanarak kişiye özel tedavi uygulanmasını mümkün kılabilecektir.

Browse

Recent Submissions