IYTE GCRIS Database (Izmir Institute of Technology)
Not a member yet
11968 research outputs found
Sort by
Determination of the Equivalent Stress-Strain Curves of Ductile Metals Through Image Analysis
No full textThis thesis presents a methodology for determining the equivalent stress-strain and the failure strain-stress triaxiality curves of ductile metallic materials using the advanced computing and image analysis methods. The determined curves were then used to calculate the parameters of the Johnson and Cook (JC) flow stress and damage models. A code was developed in Python to perform the numerical calculations and image analysis using the Python's libraries and image analysis tools. The main entries to the code were the experimental force-displacement curves at different strain rates, the experimental failure strain-stress triaxiality curve at a reference quasi-static strain rate, the experimental failure strain-strain rate curve at a constant stress triaxiality and the video images of the deforming test specimens. The correctness and reliability of the developed code in predicting the equivalent stress-strain curves and the parameters of the JC flow stress and damage models were clearly demonstrated for the selected 316L and AISI 4340 alloys. The code could also be easily adopted to other well-now constitutive equations commonly used in the finite element software. Finally, the results of present study contribute to the field of mechanical engineering by providing a robust tool for the materials characterization essential for designing and optimizing engineering components subjected to complex states of stresses.Bu tez ileri hesaplama ve görüntü analiz teknikleri kullanarak sünek metallerin eşdeğer gerilim-gerinim ve kırılma gerinimi-üç eksenli gerilme eğrilerini belirlemek için yeni bir metodoloji sunmaktadır. Belirlenen eğriler daha sonra Johnson-Cook (JC) gerilme ve hasar denklemleri parametrelerini belirlemek için kullanılmıştır. Tüm numerik hesaplamalar ve görüntü analizi Python Kütüphanesi ve görüntü analiz araçları kullanılarak yapılmıştır. Kodun ana gidileri deneysel farklı gerinin hızlardaki kuvvet-deplasman verileri, statik kırılma gerinimi-üç eksenli gerilme verileri, farklı gerinim hızlarındaki kırılma gerinimi verileri ve kırılma test numunesinin deformasyon görüntü videolardır. Kullanılan metodoloji eşdeğer gerilim-gerinim eğrilerini ve JC gerilme ve hasar denklemleri parametrelerini tahmin etmekteki doğruluğu ve etkinliği 316L ve AISI 4340 alaşımları için açıkça gösterilmiştir. Geliştirilen kod yapısal analizde kullanılan sonlu elaman yazılımlarında kullanılan birçok yapısal denkleme de kolayca uygulanabilmektir. Son olarak, bu çalışma hassas malzeme özelliklerinin performans ve güvenlik açısından kritik olduğu çeşitli mühendislik alanlarındaki potansiyel uygulamalarla birlikte, sünek metallerin mekanik davranışını anlamak ve tahmin etmek için kapsamlı bir yaklaşım sunmaktadır
Improving the Stability of Ink-Jet Printed Red Qleds by Optimizing the Device Fabrication Process
No full textRed-light emitting Cadmium Sulfide0.8 Selenide0.2 / Zinc Sulfide (CdS0.8 Se0.2 /ZnS) based quantum dots (QDs) were synthesized by hot injection method and utilized as the emissive layer in the quantum dot light emitting diode (QLED) with the device structure of Indium Tin Oxide/Poly(3,4-ethylenedioxythiophene): Polystyrene Sulfonate /Polyvinylcarbazole(or Poly (N,N'-bis-4-butylphenyl-N,N'-bisphenyl)benzidin)/QD/ZincOxide/ LithiumFluoride/ Aluminum [ITO/ PEDOT: PSS/PVK(or p-TPD)/ QD/ZnO/LiF/Al]. QD inks were formulated and prepared in octane: decane; (1/1, v/v) solvent system and mixed with the nonionic surfactant, TritonX-100, to make the QD inks inkjet printable. In addition to the inkjet printing technique, spin coating was also employed to form the QD emissive layer for comparing device performance. Compared to the p-TPD-based QLED device, the PVK-based device fabricated via spin coating exhibited ~6-fold higher performance in terms of luminance and efficiency values. In the case of using the ink-jet printer, ~2-fold higher maximum luminance value and slightly lower external quantum efficiency at the lower current density region were obtained in the p-TPD-based device. Furthermore, compared to the PVK layer, the p-TPD layer provided higher device stability regardless of the coating method at the higher current density regions. We suggest that the coating method applied and the choice of hole transport layer (HTL) materials may control the device parameters. © The Author(s), 2024
Energy Management in Organized Industrial Zones: Promoting the Green Energy Transition in Turkish Manufacturing Industry
No full textOrganized Industrial Zones (OIZ), which gained legal status by Law 4562 of 2000, played a significant role in Turkish industrialization policies, particularly in improving Small and Medium-sized Enterprises (SMEs). The energy management (EM) within OIZs is essential for Turkiye's green transition and 2053 net-zero pathway. Following the publication of a directive on OIZ's electricity market activities in 2006, enterprises can purchase electricity directly from OIZ management. Moreover, the Energy Efficiency Law No. 5627 of 2007 required OIZs to establish an energy management unit (EMU) to serve the participants with less than 1000 tons of oil equivalent (toe) energy consumption. EMUs provide OIZ management with a unique opportunity to enhance sustainable energy transition by increasing renewable energy production and improving the energy efficiency of participating enterprises. The primary goal of this research is to evaluate the effectiveness of energy management units in OIZs in encouraging energy efficiency and green energy transition in the Turkish manufacturing industry. As a case study, we examine EM in the Adana Haci Sabanci Organized Industrial Zone (Adana OIZ), which ranks third among OIZs regarding electricity consumption. We analyze data on electricity infrastructures, roof-top PVs, invoice settlements/offsets, energy efficiency investments, and GHG emissions between 2017 and 2023. Our preliminary findings suggest that EMU in the Adana OIZ makes a very important contribution to the green transition of industrial establishments and that regulatory changes over the last decades have had positive effects. The share of renewable energy in the total energy mix increased from 1.6% to 21.4% over six years, and there has been a noteworthy enhancement in energy efficiency, reaching 27% in 22 companies evaluated. The main policy implication of our findings is that the role of regulatory bodies and efficient energy management in OIZs will be critical in achieving Turkiye's net zero target of 2053
Türkiye Makes Strides in Open Science Thanks To Openaire
No full textİYTE Kütüphanesi Daire Başkanı Gültekin Gürdal, 10-12 Nisan 2024 tarihleri arasında Krakow’da gerçekleştirilen Polonya Açık Bilim Konferansı’na konuşmacı olarak davet edilmiş ve gerçekleştirdiği sunumla Türkiye’de Açık Bilim ile ilgili yapılan çalışmaları ve bu çalışmalara OpenAIRE’in etkisini anlatmıştır. Gültekin Gürdal sunumunda genel olarak, Türkiye'nin Açık Bilim alanında kaydettiği ilerlemeyi vurgulamıştır. Yapılan sunumda OpenAIRE'in kurucu üyesi ve birçok Açık Bilim projesinin ortağı olan İYTE’nin, Türkiye ile Açık Bilim dünyası arasında bir köprü görevi görmeye ve EOSC ile entegrasyonun yanı sıra Türkiye'de OpenAIRE çalışmalarının gerçekleştirilmesini teşvik etmeye devam ettiğine değinilmiştir. Konuya ilişkin OpenAIRE Blog sayfasında bir blog yazısı yayınlanmıştır
Development of a Unique Integrated Bioreactor for Simultaneous Desalination and Bioenergy and Biohydrogen Production
No full textIn the wastewater treatment challenge, it is really essential to develop integrated systems in reducing greenhouse gases, producing green energy and achieving sustainable development. In this regard, an integrated electro-biomembrane reactor was developed and performed in this study for simultaneous biohydrogen (bioH2) production from energetic poplar leaves using dark fermentation (DF) process, conventional H2 production, bioenergy production in the DF process, and saline water desalination in a single system. The results of this study showed that pH was the main controlling parameter in bioH2 production, and the superior production of 40.2 mL/g-biomass was obtained at a pH of 5.5. The maximum current and power density values were 2861.7 mW/m2 and 2819.4 mA/m2 at pH 5.5 under improved conditions. Furthermore, the maximum conventional H2 production was found to be 1341.6 mL using 2 M of KOH solution. Overall, the results further proved that the proposed integrated system can be a sustainable and promising process for industrial applications, considering its high desalination, energy production, and conventional and biological H2 production efficiencies. © 2024 The Author
Multi-Objective Optimization of Residential Buildings for Improving Indoor Thermal Comfort While Reducing Energy Consumption
No full textSon yıllarda yön gözetmeksizin yüksek cam-cephe oranı ile tasarlanan konut yapıları yaygınlaşmaktadır. Bu tasarım çözümleri başta aşırı ısınma olmak üzere, ısıl rahatsızlık ile yüksek enerji tüketimi ve soğutma yükü gibi sorunlara yol açmaktadır. Bu çalışmanın ana amacı, mevcut bir konut binasının enerji tüketimi ve ısıl konforu üzerinde en yüksek ve en düşük hassasiyete sahip tasarım değişkenlerini belirlemek ve enerji tüketimini azaltırken ısıl konforu iyileştiren optimum yenileme çözümlerini bulmaktır. Akdeniz iklim bölgesinde yer alan, 2019 yılında inşa edilmiş, güneye cepheli bir konut bloğu örnek olarak seçilmiştir. DesignBuilder'da oluşturulan model, saatlik iç mekan sıcaklık izleme verilerine göre sekiz aylık bir dönem için kalibre edilmiştir. Çalışma kapsamında belirsizlik ve duyarlılık analizi yapılmış, analiz sonuçlarına göre duyarlılığı düşük bulunan değişkenler dikkate alınmamıştır. NSGA-II algoritması kullanılmıştır. Altı adet iyileştirme senaryosu tanımlanmıştır: bina zarfı özelliklerini değerlendiren pasif olanlar, HVAC sistemi özelliklerini değerlendiren aktif olanlar ve ilk iki senaryoda alınan tüm tasarım değişkenlerini değerlendiren senaryolar. İlk üç senaryoda enerji tüketimini ve konforsuz saatleri en aza indirmek hedeflenirken, diğer üç senaryoda soğutma yükünü ve konforsuz saatleri en aza indirmek amaçlanmaktadır. Duyarlılık analizi sonuçlarına göre soğutma-ısıtma ayar noktası, gölgeleme tipi, sızma oranı, pencere duvar oranları her iki amaç fonksiyonu için de yüksek hassasiyete sahip değişkenlerdir. Isıtma sistemi çalışma takvimi, soğutma sistemi performans katsayısı, ısıtma sistemi verimliliği, iç duvar tipi ve pencere çerçeve tipi değişkenlerinin duyarlılığının düşük olduğu sonucuna ulaşılmıştır. Üçüncü ve altıncı senaryolarda her iki amaç fonksiyonunun da temel duruma göre azaldığı optimum çözümler bulunmuştur. Bu senaryolarda, aşırı ısınma problemi hem aktif hem de pasif çözümler değerlendirilerek çözülmüştür.In recent years, residential buildings designed with high window-to-wall ratios regardless of direction have become widespread. These design solutions cause thermal discomfort, especially overheating, and increased energy consumption and cooling load. The main aim of this study is to determine the most and least sensitive design variables affecting energy consumption and thermal comfort of an existing residential building and to find optimum retrofit solutions reducing energy consumption while improving thermal comfort. The south-facing residential block built in 2019, located in the Mediterranean climate region, was selected as the case. The simulation model created in DesignBuilder was calibrated according to hourly monitored indoor temperature data for eight-months period. Uncertainty and sensitivity analysis was performed due to eliminate the design variables with low sensitivity. NSGA-II algorithm was performed. Six retrofit scenarios were defined: building envelope features as passive ones, HVAC system features as active ones, and all design variables as combination. While the first three scenarios aim to minimize energy consumption and discomfort hours, the other three scenarios aim to minimize cooling load and discomfort hours. In conclusion, cooling-heating set point, shading type, infiltration rate, and window-to-wall ratios were defined high sensitivity variables. The heating system operating schedule, cooling system performance coefficient, heating system efficiency, partition wall type, and window frame type variables have low sensitivity for thermal comfort and energy consumption. Optimum solutions in which both objective functions decreased compared to the base case were found in the third and sixth scenarios. In these scenarios, the overheating problem has been solved by evaluating both active and passive solutions
Novel Neural Style Transfer Based Data Synthesis Method for Phase-Contrast Wound Healing Assay Images
No full textRecent advancements in the field of image synthesis have led to the development of Neural Style Transfer (NST) and Generative Adversarial Networks (GANs) which have proven to be powerful tools for data augmentation and realistic data generation. While GANs have been widely used for both data augmentation and generation, NST has not been employed for data generation tasks. Nonetheless, the simpler structure of NST compared to GANs makes it a promising alternative. In this research, we introduce an NST-based method for data generation, which to the best of our knowledge, is the first of its kind. By taking advantage of simplified architecture of NST models attributed to the utilization of a real image as the style input, our method enhances performance in data generation tasks under limited resource conditions. Additionally by utilizing patch-based training and high-resolution inference process high quality images are synthesized with limited resources. Furthermore multi-model and noised input is utilized for increased diversity with the novel NST-based data generation approach. Our proposed method utilizes binary segmentation maps as the condition input, representing the cell and wound regions. We evaluate the performance of our proposed NST-based method and compare it with a modified and fine-tuned conditional GAN (C-GAN) methods for the purpose of conditional generation of phase-contrast wound healing assay images. Through a series of quantitative and qualitative analyses, we demonstrate that our NST-based method outperforms the modified C-GAN while utilizing fewer resources. Additionally, we show that our NST-based method enhances segmentation performance when used as a data augmentation method. Our findings provide compelling evidence regarding the potential of NST for data generation tasks and its superiority over traditional GAN-based methods. The NST for data generation method was implemented in Python language and will be accessible at https://github.com/IDU-CVLab/NST_for_Gen under the MIT licence. © 2024 Elsevier Lt
Optimization of Isolators Between Floors of a High-Rise Building
No full textEarthquake vibrations are natural phenomena that can cause tremors on the ground surface and lead to serious loss of life and property. Especially large-scale earthquakes have the potential to significantly damage infrastructure systems and the durability of structures. Several strategies are available to reduce these damages and increase the resistance of structures to earthquakes. One of these strategies is the implementation of seismic isolators. Seismic isolation minimizes earthquake damage to structures. The main purpose of the study is to examine the effectiveness of the seismic isolator being installed at various story levels of 3D 20-story steel building model. The building had two sets of 20 evaluation models, each with a different isolator story. The first set had identical evaluation models, except for the isolation story which is incremented in each model. The second set is similar to the first set except that the lower stories are strengthened by shear walls. The goal was to determine the best dimensions for the isolator to minimize the inter-story drift values. For this purpose, a set of 12 earthquake records are selected. These records are scaled according to the determined design spectrum. The optimization is performed for one of these earthquake records. Nonlinear dynamic analyses are carried out to evaluate the building model responses for all 12 earthquake records. Response values such as story shear forces and story drift ratios were analyzed and interpreted. This analysis will contribute to a better understanding of the impact of isolators with optimization methods on structural performance.Deprem titreşimleri, zemin yüzeyinde titremelere neden olabilen ve ciddi can ve mal kaybına yol açabilen doğal olaylardır. Özellikle büyük ölçekli depremler altyapı sistemlerine ve yapıların dayanıklılığına önemli ölçüde zarar verme potansiyeline sahiptir. Bu hasarları azaltmak ve yapıların depreme karşı direncini artırmak için çeşitli strateji ve yöntemler mevcuttur. Bu stratejilerden biri sismik izolatörlerin uygulanmasıdır. Sismik izolasyon, deprem sırasında yapılarda oluşabilecek hasarı en aza indirmek için etkili bir strateji olarak öne çıkmaktadır. Bu çalışmanın temel amacı, 3 boyutlu 20 katlı çelik çerçeve bina modelinin çeşitli kat seviyelerinde kurulan sismik izolatörün etkinliğini incelemektir. Bina modeli, her biri izolatör katının farklı olduğu 20 değerlendirme modeline sahip iki farklı sete bölünmüştür. İlk sette, her modelde artan izolasyon katı dışında değerlendirme modelleri aynıdır. İkinci set ise, izolatör altında kalan katlara perde duvar ile güçlendirilmesi dışında birinci sete benzerdir. Amaç, en az göreli kat ötelemesi oranı değerleriyle sonuçlanan en uygun izolatör boyutlarını bulmaktır. Bu amaçla bir dizi 12 deprem kaydı seçilmiştir. Bu kayıtlar belirlenen tasarım spektrumuna göre ölçeklendirilir. Bu deprem kayıtlarından biri için optimizasyon yapılır. 12 deprem kaydının tamamında bina modeli tepkilerini değerlendirmek için doğrusal olmayan dinamik analizler yapılmaktadır. Kat kesme kuvvetleri ve göreli kat ötelemesi oranları gibi tepki değerleri analiz edildi ve yorumlandı. Bu kapsamlı analiz, optimizasyon yöntemleriyle 20 katlı bir bina için tasarlanan izolatörlerin yapısal performans üzerindeki etkisinin daha iyi anlaşılmasına katkıda bulunacaktır
Effect of Random Structural Variations on the Optical Properties of Honeycomb Photonic Crystals
No full textPeriodic dielectric structures called photonic crystals are being used in various sensors and devices. Since photonic crystals are designed to operate within certain frequency ranges, accuracy in structure becomes important. In this work, we investigate the effects of two types of randomness, surface roughness and positional randomness, on the optical properties of the honeycomb photonic crystal. We employed the plane wave expansion method to investigate the effects of random perturbations of the shape and the position of the structure on the density of states. We also employ the finite-difference time-domain method to calculate the transmission spectrum as a consistency check. We find that both surface roughness and positional imperfections cause significant changes in the DOS. As the degree of randomness is increased, transverse electric and transverse magnetic gaps are narrowed and complete gaps totally disappear at 45% of surface roughness
Improving Mechanical Behavior of Adhesively Bonded Composite Joints by Incorporating Reduced Graphene Oxide Added Polyamide 6,6 Electrospun Nanofibers
No full textAdhesive joining of fiber-reinforced polymer (FRP) composites requires adequate interface tailoring and careful surface preparation to obtain a strong bond between components. This study aimed to improve the mechanical performance of adhesively bonded unidirectional carbon fiber-based (CFRP) composite parts by modifying joint surfaces with graphene-added electrospun Polyamide 6,6 (PA66) nanofibers. Reduced graphene oxide (rGO) was dispersed at 10 % wt/v PA66 solution at three different concentrations below rGO saturation limits. Bead-free nanofibers with homogenous graphene distribution were obtained on a prepreg by electrospinning. Addition of up to 2 % rGO yielded complete dispersion through the nanofiber network while the higher values created local agglomerations. Surface wetting experiments showed conversion of slightly hydrophobic surfaces to complete hydrophilic with electrospun nanofiber coating and the lowest contact angle was obtained at 2 % wt/v rGO addition (26.18 degrees +/- 2.03 degrees). Composite plates were produced in a hot press keeping the modified prepregs on top. Plates with different surface treatments joined by secondary bonding using 3 plies of FM 300 K film adhesive. Mechanical properties of adhesively bonded composites were tested by Single lap joint and Charpy impact tests. We achieved an 18 % increase in shear strength and 31 % increase in impact strength by adding 2 % wt/v ratio rGO into PA66 electrospun nanofiber