IYTE GCRIS Database (Izmir Institute of Technology)
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Homodyne Detection Based Confocal Phase Diffraction Method for Thickness Characterization of Ultra-Thin Dielectric Films Coated on Optical Fibers
No full textCharacterizing the thickness of thin dielectric films is crucial in fiber optic sensor technologies due to their significant impact on sensor performance. However, non-destructive thickness characterization of films in the range of tens of nanometers, particularly on non-planar surfaces, is often a challenging, complex, and tedious process. In addition, the measurements often need highly calibrated devices under the control of specialists. In this paper, we propose a novel, non-destructive, and practical method for characterizing the thickness of ultra-thin (100 nm) curved transparent dielectric films using homodyne detection of the confocal phase diffraction. The numerical simulations and experimental results show that suppressing stray light improves the influence of thickness information in the diffracted field. This significantly enhances the system's sensitivity to nanometer-scale variations in dielectric film thickness, especially when integrated with a coherent detection scheme. According to the results, the film thickness can be precisely measured within a few nanometers, making it highly significant and promising for cost-effective optical metrology applications
Energy and exergy analysis of renewable energy utilization in cement production
No full textGeleneksel çimento üretim yöntemlerine kıyasla daha yeşil enerji sistemleri alternatiflerini keşfetmek için çimento üretiminin enerji ve ekserji analizi çalışılmıştır. İki farklı yeşil enerji senaryosu dikkate alınmıştır. Temel senaryo geleneksel çimento üretimidir. İlk senaryoda atık rüzgar türbini kanatlarının pirolizi ve gaz türbini çimento fabrikasına entegre edilmiştir ve elektrik ihtiyacı gaz türbini tarafından karşılanmıştır. Aynı zamanda hammadde piroliz ünitesinin katı ürününden sağlanmıştır. Bu senaryo için sıcak akımları kullanmak üzere bir ön ısıtma sistemi düşünülmüştür. İkinci senaryoda, PEM elektrolizörü de çimento fabrikasına dahil edilmiştir. Burada kömürle değiştirilmek üzere PEM elektrolizöründen hidrojen üretilmiştir. Tüm senaryoların termodinamik modellemesi Engineering Equation Solver (EES) yazılımı aracılığıyla gerçekleştirilmiştir. Temel senaryonun enerji ve ekserji verimliliği sırasıyla % 61,60 ve % 20,21 olarak bulunmuştur. Termodinamik analiz dışında, özgül enerji tüketimi (SEC) ve CO2 emisyonları hesaplanmıştır. En düşük SEC, 1704 kJ/kg olan senaryo 1 ile elde edilmiştir. CO2 emisyonları, 0,219 kg CO2/kg çimento ile senaryo 2 için minimum olarak sonuçlanmıştır. Tüm bunlar göz önüne alınarak, daha yeşil ve daha az enerji tüketen bir sistem oluşturulmaya çalışılmıştır.The energy and exergy analysis of cement production was investigated to explore greener energy system alternatives in contrast to traditional cement production methods. Two different greener energy systems scenarios were considered. The base scenario was conventional cement production. In the first scenario, the pyrolysis of waste wind turbine blades and the gas turbine were integrated with the cement factory, where electricity demand was met by the gas turbine. At the same time, the raw material was provided from the solid residue of the pyrolysis unit. For this scenario a preheating system was considered to harness hot streams. In the second scenario, PEM electrolyzer was also included in the cement factory. In here hydrogen was produced from PEM electrolyzer to be replaced with coal. The thermodynamic modeling of all scenarios was conducted via Engineering Equation Solver (EES) software. The energy and exergy efficiency of the base scenario were found to be 61.60% and 20.21%, respectively. Other than thermodynamic analysis, specific energy consumption (SEC) and CO2 emissions were calculated. The lowest SEC was obtained with scenario 1 which was 1704 kJ/kg. CO2 emissions resulted minimum for scenario 2 with 0.219 kg CO2/kg cement. Considering all of this, an attempt has been made to find a greener and less energy-consuming system
Bayesian Uncertainty Quantification in Temperature Simulation of Borehole Heat Exchanger Fields for Geothermal Energy Supply
No full textAccurate temperature prediction is crucial for optimizing the performance of borehole heat exchanger (BHE) fields. This study introduces an efficient Bayesian approach for improving the forecast of temperature changes in the ground caused by the operation of BHEs. The framework addresses the complexities of multi-layer subsurface structures and groundwater flow. By utilizing an affine invariant ensemble sampler, the framework estimates the distribution of key parameters, including heat extraction rate, thermal conductivity, and Darcy velocity. Validation of the proposed methodology is conducted through a synthetic case involving four active and one inactive BHE over five years, using monthly temperature changes around BHEs from a detailed numerical model as a reference. The moving finite line source model with anisotropy is employed as the forward model for efficient temperature approximations. Applying the proposed methodology at a monthly resolution for less than three years reduces uncertainty in long-term predictions by over 90%. Additionally, it enhances the applicability of the employed analytical forward model in real field conditions. Thus, this advancement offers a robust tool for stochastic prediction of thermal behavior and decision-making in BHE systems, particularly in scenarios with complex subsurface conditions and limited prior knowledge. © 2024 The Author(s
Temporal Electroencephalography Features Unveiled Via Olfactory Stimulus as Biomarkers for Mild Alzheimer's Disease
No full textAim: Our primary aim is to capture and use the timings of the characteristic brain responses to olfactory stimulation for mild Alzheimer's disease diagnosis purposes. Proposed method: Our method identifies the timings of short-lived signal segments where characteristic distances between pre- and post-stimulus relative spectral energies are attained for each EEG channel and frequency band. These timings and timing-derived features were subsequently used in a leave-one-subject-out cross-validation scenario to assess the diagnostic performance of our framework. We evaluated seven distinct statistical distance measures to determine the most effective one for characterizing the neurological conditions of the subjects. Results: The average cross-validation performance shows that our framework achieved 87.50% diagnosis performance. The frequently used features were mainly derived from the delta and alpha activity of the prefrontal region (Fp1) and the beta activity of the parietal region (Pz), which agree with the current findings of olfaction biophysics. Comparison with existing methods: We compared the performance of our method with that of four existing methods in the literature. Our method outperformed these four methods. Moreover, our method elicited the highest accuracy when the clinical olfactory score (UPSIT) was included as a feature. Conclusions: Our analysis framework reveals a significant alteration of the timing organization of the brain that emerged upon olfactory stimulation in Alzheimer's patients. The timings of characteristic response and the features calculated via these timings contribute to Alzheimer's disease diagnosis performance remarkably. The perspective proposed here may facilitate early diagnosis, thereby facilitating the exploration of novel therapeutic and treatment strategies
Experimental Study for Recovery of Heavy Metals From Contaminated Soil Using Arbuscular Mycorrhizal Fungi
No full textSoil micro-organisms like arbuscular mycorrhizal fungi can provide beneficial symbiosis to their host plant and have been adopted to recover metal-polluted soils. This study investigates the removal of heavy metals from soil using phytoremediation in the presence of fungi. The results indicate that the sunflower plant illustrates the highest copper accumulation, with 18.55 mg/kg. In contrast, sunflower and sorghum controls (non-microorganisms) showed weak capability to transfer copper through plant biomass with 0.91 and 0.97 mg/kg, respectively. Both plants showed that phytoremediation can be a promising approach to providing sustainable solutions for soil heavy metal contamination in the presence of fungi. Copyright © 2025 Inderscience Enterprises Ltd
A Comprehensive Study on the Effectiveness of the Stress and Damage Model Parameters in Predicting the Compression Fracture Behavior of Selective Laser Melted Alsi10mg Bcc Lattices
No full textThe Johnson and Cook (JC) stress and damage model parameters determined from the machined bulk cylindrical specimens and as-built struts through tension and compression tests were used to model quasi-static compression behavior of selective laser melt-fabricated AlSi10Mg alloy lattices. The lattices had the same cell size (10 mm) and strut diameter (1 mm), but different number of cells (2 × 2 × 2, 10 × 10 × 2 and 5 × 5 × 5) and geometries (sandwich and cubic). Four different sets of JC damage model parameters (brittle and ductile notch-insensitive and compression and tension notch-sensitive) were further implemented in the lattice compression numerical models. The brittle damage model parameters and smaller mesh sizes resulted in cracking the face-sheet corner strut nodes before the occurrence of a bending-dominated initial peak stress. The notch-sensitive damage model parameters exhibited no bent-strut fracture in the middle layers of the lattices and increased the crack initiation strains as compared with the notch-insensitive damage model parameters. Despite significant variations in the initial peak stresses of the tested 2 × 2 × 2 and 10 × 10 × 2 lattices, the implication of the strut micro-tension stress model together with the compression notch-sensitive damage model parameters using 0.25 mm mesh size conservatively approximated the experimental deformation stresses while the machined bulk specimen tension-stress model over predicted the experimental stresses. On the other side, the strut stress model with 0.15 mm mesh size accurately predicted the experimental diagonal shear/fracture mode of struts with a slightly higher numerical initial peak stress. The compression tests on the strut specimens extracted from the as-built lattices yielded similar stress model parameters with the micro-tension tests. The differences between the initial peak stresses of the investigated sandwich and cubic lattices were further explained by the differences in the lattice boundary conditions. © 2025 Elsevier Lt
Doku Mühendisliği ve Tanı Uygulamalarında Hücrelerin Manyetik Manipülasyonu
No full textIn the context of this thesis, the magnetic levitation technique, based on the negative magnetophoresis principle, was used in two different approaches. Firstly, the magnetic levitation system was employed as a bioprinting method to create scaffold-free three-dimensional tissue models. The first approach focused on developing and improving scaffold-free heterogeneous three-dimensional spheroid models that can better resemble the in vivo tissue. Heterogenous breast cancer spheroids were obtained in the single-ring magnet-based levitation system with various conformations. The effect of different cell loading parameters on the localization of two cell types within the spheroid structure was examined. Additionally, the macromolecular crowding method was integrated to enhance the accumulation of extracellular matrix, improving the in vivo-like nature of the scaffold-free spheroid models created by magnetic levitation. Secondly, the thesis explored the use of magnetic levitation for diagnostic purposes in neurodevelopmental disorders. Investigation of the relationship between the volumetric mass density and neural pathological conditions was carried out using the fibroblasts, and the neural progenitor cells, and induced pluripotent stem cells acquired from fibroblasts isolated from patients with rare neurodevelopmental disorders and healthy subjects. Furthermore, the study investigated how the single cell density is affected in lysosomal storage diseases using primary neuroglial cells isolated from mouse models with different types of lysosomal storage disorders. In this thesis, potential of magnetic levitation as a rapid, cost-effective, and safe technique for both tissue engineering applications and cell-based diagnostic studies was demonstrated.Bu tez kapsamında, negatif magnetoferez prensibine dayalı manyetik levitasyon tekniği, iki farklı yaklaşım için kullanılmıştır. İlk olarak, manyetik levitasyon sistemi, doku iskelesiz üç boyutlu doku modelleri oluşturmak için bir biyofabrikasyon yöntemi olarak kullanılmıştır. İlk yaklaşımda, in vivo dokuyu daha iyi taklit edebilen, üç boyutlu heterojen küresel modeller geliştirmek ve iyileştirmek amaçlanmıştır. Tek halka mıknatıs tabanlı levitasyon sisteminde çeşitli konfigürasyonlarda heterojen meme kanseri küreleri elde edilmiştir. İki farklı hücre tipinin lokalizasyonunda sferoid yapı içerisindeki farklı hücre yükleme parametrelerinin etkisi incelenmiştir. Ek olarak, hücre dışı matriks birikimini artırarak, manyetik levitasyon ile oluşturulan doku iskelesiz sferoid modellerin in vivo yapıyı taklit edebilme kapasitesini artırmak için makromoleküler kalabalıklaştırma yöntemi entegre edilmiştir. İkinci olarak, nörogelişimsel bozukluklarda teşhis amaçlı olarak manyetik levitasyonun kullanımı araştırılmıştır. Araştırmada, sağlıklı bireylerden ve nörogelişimsel bozukluğu olan bireylerden elde edilen fibroblastlar, sinir progenitör hücreleri ve indüklenmiş pluripotent kök hücreler arasındaki farkı belirlemek amacıyla hücrelerin özkütle profilleri analiz edilmiştir. Ayrıca, farklı tipte lizozomal depo hastalıklarının hücre özkütlesi üzerindeki etkisi fare modellerinden izole edilen primer nöroglial hücreler kullanılarak incelenmiştir. Bu tezde, hem doku mühendisliği uygulamaları hem de hücre bazlı tanı çalışmalarında hızlı, maliyet etkin ve güvenli bir yöntem olarak manyetik levitasyon tekniğinin potansiyeli gösterilmiştir
Investigating Early-Stage Mineralization Behavior and Bioactivity of Acid-Free Bioactive Glass 45s5 With Enhanced Dissolution Kinetics
No full textNanostructured bioactive glass (BG) was synthesized through an acid-free sol-gel route (bioglass-AF) and the conventional acid-catalyst sol-gel process (bioglass-AC). The aim here is to eliminate the risk of residual acidic components in the BG while enhancing its functionality through nano-scale propduction. Scanning electron microscopy revealed the presence of highly porous structures and dense agglomerates composed of particles with a mean diameter of 45 nm in both samples. Bioglass-AC and bioglass-AF had specific surface areas of 1.48 m(2)/g and 2.73 m(2)/g, respectively, with an average pore size of similar to 5 nm. Faster mineralization kinetics were evident in bioglass-AF, compared to bioglass-AC, in Hepes-buffered salt solution. Following 14 days of immersion in artificial saliva, bioglass-AC and bioglass-AF lost 16% and 20% of their initial weight, respectively, confirming their bioactivity. None of the synthesized BGs stimulated cell growth up to 24 h but longer exposure to moderate concentrations (1.25 and 2.5 mg/mL) of bioglass-AF significantly enhanced cell viability, reaching 170% at 48 h. Overall, the comparative in vitro investigations proved that nano-structured 45S5 bioglass powders with improved mineralization and dissolution kinetics can be produced with an acid-free route, eliminating the risk of residual acidic components in the final product
Zn/Na Co-Doped Hydroxyapatites: Synthesis, Antibacterial, and Bioactivity Studies
No full textThe most crucial challenge of post-orthopedic surgery is related to bacterial film formation, which leads to implant failure. In this work, zinc/sodium (Zn/Na) co-doped hydroxyapatite nanoparticles (HA NPs) with different Zn/Na concentrations, including 1, 3, and 5 mol.% were synthesized using a hydrothermal method. Several analyses such as X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Energy Dispersive X-ray Spectroscopy (EDX), Scanning Electron Microscopy (SEM), and N2 ad/desorption were used to pinpoint the properties of as-prepared materials. Field Emission Scanning Electron Microscopy (FE-SEM) and EDX analysis demonstrated that the HA NPs possess an average size of about 30-40 nm and hexagonal morphology with no impurity. XRD patterns confirm that by the increasing amounts of Zn/Na, the crystal size of samples was decreased. FT-IR affirms the correct doping of metal ions. Brunauer-Emmett-Teller (BET) results of co-doped samples demonstrated a microporous structure, which can improve fluid flow in the inner structure of implants. The colony-forming unit (CFU) method conducted the antibacterial test, which confirmed that 5 mol.% Zn/Na co-doped HA NPs showed the highest antibacterial properties against Escherichia coli (PTCC 1276) (E. coli). Cytotoxicity results affirmed that 1 and 3mol.% Zn/Na co-doped HA NPs demonstrated low toxicity. Bioactivity tests revealed that the Zn/Na co-doped samples showed a higher ability to facilitate bone marrow stem cells; thus, improving the proliferation after the immersion in simulated body fluid (SBF). Therefore, Zn/Na co-doped HA NPs could be a promising candidate for bone tissue engineering applications
Charting the Landscape of Design Cognition: Bridging the Gap Between Design Cognition and Cognitive Science
No full textThis study examines the trajectory of cognitive studies on design processes (DesCog), charting its scientific landscape and interactions with cognitive science (CogSci). First, the study delineates the boundaries of DesCog within all published scholarly works. The analysis indicates that DesCog is a focused field with lesser impact on other fields, showing divergent bibliographic positions and connections for 'design cognition' and 'design thinking'. Second, the longitudinal evolution of DesCog is identified as gradually becoming more diverse and more connected. Third, DesCog's foundational connections to CogSci demonstrate that the relationship is spontaneous rather than following 'generalising interdisciplinarity' aims. The analysis indicates a unidirectional flow from CogSci to DesCog, with occasional reciprocal interactions. The volume and diversity of CogSci literature cited by DesCog appear narrow, and most cited publications are based on the information-processing theory of cognition. Fourth, the study identifies common themes at the intersection of two fields, demonstrating that creativity has been a focal theme for both since earlier studies. Finally, the individual impact of CogSci researchers on DesCog highlights the significance of Simon and Newell's influence. The study contributes to reflections on DesCog's knowledge production, underlining unidirectional knowledge flows from CogSci to DesCog and partial theoretical connections within the field