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Effect of saturation tone on spectral EDFA gain spectrum
No full text<p>Accurate characterization of spectral gain of C-band EDFAs in WDM system design is crucial; however, traditional methods often require expensive WDM equipment. This study presents a cost-effective alternative, validated through both experimental measurements and simulations, that utilizes a weak signal probe and a carefully selected saturation tone. By comparing results with a 32-channel WDM reference, we demonstrate that the proposed method achieves high accuracy. The optimal saturation tone wavelength depends on the pump wavelength (980 nm or 1480 nm) and configuration (forward or bidirectional). Nevertheless, a good fit with the reference can be obtained in all scenarios, especially at higher saturation levels. This work provides valuable insights for developing affordable and efficient EDFA gain measurement techniques.</p>
Sayısal Yükseklik Modeli Verisi ile Alt Havza Ayrımı: ArcSWAT Tabanlı Bir Yaklaşım
No full text<p>Hidrolojik ve hidrodinamik modelleme çalışmaları, su kaynaklarının sürdürülebilir yönetimi, taşkın riski analizi ve çevresel planlama açısından büyük önem taşımaktadır. Bu tür modellemelerin doğruluğu, havzanın fiziksel ve hidrolojik özelliklerinin gerçekçi biçimde temsil edilmesine bağlıdır. Bu bağlamda, havza sınırlarının belirlenmesi (watershed delineation) ve buna bağlı olarak alt havzaların tanımlanması, modelleme sürecinin temel yapı taşlarından birini oluşturmaktadır. Bu çalışmada, Yukarı Fırat Havzası içerisinde yer alan ve Doğu Anadolu Bölgesi'nin önemli su kaynaklarından biri olan Karasu Nehri’nin üst havzası, hidrolojik ve hidrodinamik modelleme çalışmaları için alt havzalara ayrılmıştır. Bu amaçla, 5 metrelik çözünürlüğe sahip yüksek hassasiyetli Sayısal Yükseklik Modeli (DEM) kullanılarak, mekânsal verilerin entegre bir modelleme ortamında işlenmesini mümkün kılan ArcSWAT arayüzü üzerinden havza sınırlarının belirlenmesi işlemi gerçekleştirilmiştir. Havzanın hidrolojik karakteristiğini temsil edebilecek dört adet akım gözlem istasyonu referans alınarak yapılan analiz sonucunda, toplamda dört alt havza tanımlanmıştır. Kullanılan istasyonlar; D21A052 numaralı Serçeme, D21A152 Köşk Suyu, D21A132 Pulur Çayı ve E21A054 Aşağı Kağdariç’tir. Ayrıca çalışmada, akış yönü (flow direction), eğim (slope), kabartma (hillshade), arazi kullanımı/örtüsü (land use/land cover) ve akarsu akışı ağı (stream network) gibi temel hidrolojik ve topografik haritalar da üretilmiş ve bu veriler alt havzaların sınırlandırılmasında destekleyici katmanlar olarak kullanılmıştır. Sonuç olarak elde edilen alt havza yapısı, bölgesel ölçekte gerçekleştirilecek ileri düzey hidrolojik ve hidrodinamik modelleme çalışmalarına katkı sağlayacak nitelikte bir temel veri seti oluşturmuştur.</p>
On saturated flow boiling heat transfer of deionized water/ferrofluid on structured surfaces with or without external magnetic field
No full text<p>Flow boiling is one of the most effective methods for achieving high heat dissipation rates. The manipulation of magnetic fluids (ferrofluid) is one of the popular approaches for heat transfer enhancement. This study aims to experimentally investigate the effect of magnetic nanoparticles on saturated flow boiling heat transfer (FBHT) on microstructured silicon surfaces. The FBHT performance was assessed in the absence and presence of an external magnetic field with bubble force analysis by considering a single bubble under flow boiling conditions. The experimental setup consisted of a rectangular minichannel with two heating blocks on the bottom and top sides. Two different structures, including square and circular cavities, were tested. SPIONs (superparamagnetic iron oxide nanoparticles) were employed as magnetic nanoparticles. Two different types of working fluid were utilized, including deionized water (DW) and ferrofluid (FF), which contained diluted SPIONs in water. Helmholtz coils were utilized to generate an external magnetic field. Visualization with a high-speed camera enabled the study of boiling heat transfer (BHT) and bubble dynamics characteristics along with parametric effects. Experimental tests were conducted under three conditions: tests with DW, tests with FF, and ferrofluid in the presence of a magnetic field (FF/MF). These tests were carried out at two mass fluxes (300 and 400 kg/m2s) and over a heat flux range of 26.28 - 142.8 W/cm2. Adding nanoparticles further enhanced heat transfer and resulted in an increase in heat transfer coefficient (HTC) by up to 21% (from 32 to 38.7 kW/m2K). Moreover, application of an external magnetic field to the ferrofluid resulted in a reduction in the bubble departure size and an increase in HTC on the top surface, especially at high heat fluxes. The maximum HTC enhancement in the presence of the magnetic field was 25% (from 31.7 to 39.7 kW/m2K). These findings demonstrate the potential benefits of the use of magnetic nanoparticles and external magnetic fields to enhance flow boiling heat transfer on microstructured surfaces.</p>
Developing a Multidimensional Measure for Understanding Refugee Integration in Protracted Displacement Contexts: Evidence from Turkey
No full text<p>The debates on durable solutions for refugees takes place in the absence of well-designed measures for monitoring and assessing integration processes in protracted displacement contexts. Addressing this gap, this study develops a multidimensional measure of refugee integration by introducing conceptual modifications to the key components of immigrant integration framework offered by Ager and Strang (J Refug Stud 21(2):166-191, 2008. https://doi.org/10.1093/jrs/fen016). Leveraging survey data from 1630 Syrian refugees in Turkey, a typical forced migration context in the Global South, this study employs a structural equation modeling approach to capture the multifaceted refugee integration process. The proposed multidimensional construct contributes to research into immigrant integration in two significant ways. Firstly, the proposed measurement model overcomes the limitations of aggregative/compensative models commonly used to assess integration outcomes by also enabling the examination of relationships between various domains of integration. Secondly, by acknowledging the precarity inherent in forced migration contexts in the Global South, the multidimentional measure facilitates the monitoring and assessment of refugee integration in protracted displacement contexts. The proposed measurement model facilitates a nuanced understanding of the relationships among conceptual dimensions of the multifaceted integration process and offers a methodologically sound tool for comparison of integration outcomes across refugee groups and over time in protracted displacement contexts of the Global South.</p>
Evaluation of epicardial adipose tissue in children with type 1 diabetes
No full text<p>Introduction Epicardial adipose tissue (EAT), the visceral fat surrounding the heart between the myocardium and visceral pericardium, intersects with Type 1 diabetes (T1D). This review aims to elucidate the intricate association between EAT and childhood T1D.Materials and methods In this retrospective study, two pediatric groups were involved children with type 1 diabetes, and healthy children. Epicardial fat thickness was measured appropriately, and the study documented HbA1c levels and time to diabetes diagnosis for comprehensive analysis.Results Encompassing 51 children with T1D and 69 healthy controls, revealed that children with type 1 diabetes had a mean HbA1c level of 9.4 +/- 0.2, and a mean insulin dose of 0.94 units/kg/day. Epicardial adipose tissue (EAT) values were significantly higher in the Type 1 DM group. It has been shown that epicardial fat thickness may have a specific and sensitive value in type 1 diabetics.Discussion The increased presence of epicardial fat tissue in children with type 1 diabetes is highlighted, prompting the consideration of various mechanisms. However, the complexity of this relationship underscores the need for further studies to provide a more comprehensive understanding of the underlying factors. Ongoing research in this area is crucial for advancing our knowledge and potential therapeutic interventions.Impacts Cardiac complications are one of the most important causes of morbidity and mortality in people with type 1 diabetes. Being able to detect cardiological complications of diabetes at an early stage contributes to morbidity. We found that epicardial fat tissue thickness was thicker in children with type 1 diabetes than in healthy children. Epicardial fat tissue thickness may be associated with poor control in children with type 1 diabetes and maybe a guide in terms of cardiac risks.</p>
CFD modelling and experimental analysis of aromatic amine extraction in a flat sheet supported liquid membrane contactor
No full text<p>Supported liquid membranes (SLMs) using ionic liquids are effective for the extraction of aromatic amines. This experimental study employed a flat sheet SLM contactor with the ionic liquid trihexyltetradecylphosphonium bis (trifluoromethylsulfonyl)imide ([P6,6,6,14][N(Tf)2]) as the solvent to investigate the separation of alpha-methylbenzylamine (MBA) and 1-methyl-3-phenylpropylamine (MPPA) from isopropyl amine (IPA). A detailed process study was conducted to examine the effects of flow rate (5-10 L/h), feed concentration (0.5-2.5 g/L), and feed pH (9-11) on extraction performance. Under standard experimental conditions (10 L/h, 1.0 g/L, pH 10), MBA and MPPA demonstrated high solute fluxes of 2.39 and 5.47 g/(m2h), respectively, compared with IPA, which had a solute flux of 0.84 g/(m2h). However, after 24 h, the recoveries were relatively low, at 17.9 % for MBA, 32.6 % for MPPA, and 5.2 % for IPA. No significant velocity dependency was observed, with slight variations attributed to minor pH changes, while a linear flux increase was noted for higher feed concentrations. The feed pH had a significant impact on the extraction performance, with higher pH levels resulting in increased solute fluxes and recoveries. To complement the experimental results, computational fluid dynamics (CFD) simulations were employed using COMSOL Multiphysics 5.1. The model demonstrated satisfactory agreement across various conditions, but underestimated fluxes and recoveries at higher pH values. Consequently, a new mass transfer mechanism was proposed to explain the variations observed in the experimental results.</p>
High-performance supercapacitors based on nonfunctionalized MXenes
No full text<p>MXenes are a group of two-dimensional materials that have attracted significant research interest worldwide due to their intriguing electrochemical characteristics for use in energy storage applications. However, the conductivity of MXenes and their performance as supercapacitor electrodes can be hindered by surface terminations. This study investigates the capability of non-functionalized MXenes, synthesized via chemical vapor deposition for use as supercapacitor electrodes, presenting a novel approach that explores the potential of these materials in energy storage applications. The synthesized MXenes are used to create supercapacitor electrodes, which are subjected to detailed analysis. The specific areal capacitance (SAC) of these electrodes (48.6 nm thick) is found to be 39.5 mFcm- 2 at a scan rate of 2 mVs- 1, equivalent to 928.4 Fg-1. Further investigation using galvanostatic charge-discharge (GCD) analysis reveals an initial specific gravimetric capacitance (SGC) of 442.6 Fg-1 at a current density of 0.5 Ag-1, which progressively decreases to 13.4 Fg-1 at 10 Ag-1. Remarkably, the MXene supercapacitors exhibit excellent stability over 10,000 charge-discharge cycles, retaining 85 % of their initial capacitance. These findings contribute to our understanding of MXene-based energy storage devices and pave the way for practical applications in high-performance supercapacitors.</p>
Towards carbon neutral cities: An insight for Istanbul, Turkey
No full text<p>Turkey pledged net-zero emissions by 2053 under the Paris Agreement. Istanbul, its largest city, aims to be carbon-neutral by 2050. To accomplish this goal, the first step involves identifying emissions and devising reduction plans, with a focus on utilizing natural carbon sinks. This study assessed emissions and potential reductions across Istanbul's 39 districts. Greenhouse gas emissions were calculated using Intergovernmental Panel on Climate Change guidelines. Despite limited data on sink efficacy, a practical approach was adopted. According to the results, Istanbul emitted 58.5 million tons of CO2 equivalent, varying by district in 2022. In Istanbul, 32% of emissions come from electricity consumption, 29% from heating, 29% from transportation, and 10% from waste disposal. High emissions were observed near waste sites or airports. Carbon sinks reduced emissions by 11.5%, with only two districts achieving neutrality. Natural processes alone are not enough; urgent reduction strategies are needed, prioritizing high-emission districts over citywide measures.</p>
Artificial Intelligence Applications in Composites: A Survey
No full text<p>It is known that raw material resources have reached the point of depletion. Therefore, the search for alternative sources is becoming more and more common. The only product that can be considered as an alternative to raw material sources is composites. With the increase in its use in the industrial fields, studies in relation to increasing the quality of composites and reducing the production cost have recently gained attention. Experimental studies based on personal experience have now left their place to Information Technologies. Because IT is a good approach that can provide a solution to the improvement of low quality, long timeframes, and high cost in the experimental studies process. In this context, Artificial Intelligence technologies have the potential to provide better solutions and results. In this survey, a literature review on composites using AI technology was conducted. We have mainly focused on the foundations of the AI technology and its advantages in the field of composites. Consequently, it has been seen that the production of composites via IT approaches increases the quality, reduces the production costs, and abridges the experimental production process.</p>
Excited-state electronic, optical and magneto-optical properties of ferromagnetic monolayer NiCl<sub>2</sub>
No full text<p>The discovery of atomically thin van der Waals magnetic materials has triggered numerous opportunities for exploring light-matter interactions and magneto-optical phenomena in the two-dimensional limit. In this paper, the excited state electronic, optical, and magneto-optical properties of monolayer nickel dichloride ( NiCl 2 ), as a member of the family of two-dimensional ferromagnetic semiconductors, are studied using highly accurate many-body Green's function perturbation theory. We compute the quasiparticle energies, dielectric function tensor, optical absorption spectrum, magnetic circular dichroism, and magneto-optical Kerr and Faraday spectra through the full-spinor GW and GW plus Bethe-Salpeter equation (GW+BSE) methods. Due to reduced screening in two-dimensional and the presence of highly localized d orbitals in Ni, monolayer NiCl2 exhibits enhanced self-energy corrections in the ground state band structure and strong excitonic effects dominating the optical and magneto-optical responses. Also to mimic the experimental setup, we provide a detailed theoretical formalism based on the transfer matrix method for simulating these signals in van der Waals heterostructures including monolayer NiCl2. We observe that the illumination wavelength and the thickness of layers composing the van der Waals heterostructure can be used to engineer the magnitude and sign of magneto-optical signals.</p>