Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Improving Doppler Radar Performance through Optically-Reconfigurable Unequal Power Division with Semi-Analytical Approach(Taylor & Francis Ltd, 2025) Karatay, Anil; Atac, Enes; Dinleyici, Mehmet Salih; Yaman, FatihThe improvement of the signal-to-noise ratio (SNR) of Doppler radar systems, enabling the detection of targets at greater ranges even with limited power, has been a longstanding focus of research. However, while key limitations such as low target reflectivity and environmental interference are often addressed, the impact of efficient use of the input power remains an overlooked, yet crucial factor in overall sensitivity. Additionally, the power allocation needs to be examined from an analytical perspective for further enhancement. In this study, we present a novel measurement approach, utilizing both semi-analytical analysis and experimental methods, to improve the performance of a dual-antenna CW Doppler radar through the use of an optically reconfigurable unequal microwave power divider which provides well-directed power utilization. Comprehensive grid searches, supported by an analytical approach and considering various loss and noise scenarios, demonstrate the capability of the proposed reconfiguration method. In the Doppler radar experiments where the pendulum and servo motor were used as targets, an SNR increase of 3.04 and 2.11 dB in the radar signal was observed with the proposed method, respectively. This noticeable improvement in the SNR of the time-frequency plots indicates an enhancement in the measurement performance. The unequal power allocation enabled continuous detection of target motion with minimal signal loss, lowering the minimum detectable power level by more than 2 dB compared to the equal power division case. The experimental results show that integrating an optically reconfigurable microwave power divider into the Doppler radar system increases precision in velocity measurements.Article Enhancement of Corchorus Olitorius L. on Osteogenic Differentiation of MC3T3-E1 Pre-Osteoblast Cells by Increasing Alkaline Phosphatase and Hydroxyproline(Taylor & Francis Ltd, 2025) Ertugruloglu, Pinar; Baris, Elif; Okkali, Gaye Sumer; Boke Sarikahya, NazliCorchorus olitorius L. (jute mallow or molehiya) belongs to the Malvaceae family valued for its nutritional and medicinal properties. In this study, the potential to enhance osteogenesis in MC3T3-E1(Murine Calvaria-derived 3T3 Subclone E1) pre-osteoblastic cells was investigated to support bone formation and mineralisation. Leaf ethanolic extract was prepared and applied to MC3T3-E1 cells. Osteogenic effects were evaluated through three methods: MTT assays for cell viability, Alizarin Red S staining for calcium deposition, enzymatic analyses for alkaline phosphatase (ALP) and hydroxyproline (HYP). A non-cytotoxic concentration of C. olitorius extract (0.5 mg/mL) significantly increased ALP and HYP levels, promoting osteogenic differentiation in both undifferentiated and differentiated cells. HYP levels were notably elevated in differentiated cells. The findings suggested that C. olitorius extract may be a promising natural agent for enhancing bone health, warranting further in vivo and clinical studies to confirm its therapeutic potential.Article Enhanced Catalytic Performance of Rhizomucor Miehei Lipase on Di-N and Diethylhexyl Phthalates: Insights Into Substrate Specificity and Immobilization Strategy(Taylor & Francis Ltd, 2025) Balci, Esin; Rosales, Emilio; Curras, Marta Pazos; Sofuoglu, Aysun; Sanroman, M. A.Di-n-butyl (DnBP) and Diethylhexyl Phthalates (DEHP), known as potential endocrine disruptors, are priority pollutants categorized by many regulatory agencies. Enzymatic degradation is a green and efficient approach to remove PEs in the environment. In this study, the DnBP and DEHP degradation performance of Rhizomucor miehei lipase (palatase) in free and immobilized forms on Halloysite nanoclays (HNCs) in an aqueous system was investigated. Upon enzyme immobilization, the alterations in the palatase's secondary structure were examined using the circular dichroism (CD) analysis. The binding affinity of DnBP and DEHP to palatase was evaluated with molecular docking approaches. The enzyme's immobilization efficiency and relative activity were found to be 80.3% and 87.8%, respectively. CD results revealed that palatase retained its secondary structure to a significant extent. HNCs-palatase (HNCs-P) exhibited a high stability, as the structural integrity of palatase was mostly preserved. Both free palatase (FP) and HNCs-P fully degraded DnBP and DEHP (100 mg/L) to phthalic acid and a degradation pathway of DnBP and DEHP was suggested. Immobilization prevented the enzyme inhibition caused by the accumulation of metabolites. After seven consecutive uses, HNCs-P was still able to degrade DnBP (63.3%) and DEHP (72.8%). Molecular docking results showed that DEHP had a higher affinity for palatase than DnBP. This study suggests that enzyme immobilization onto HNCs can increase their stability and catalytic performance. FP and HNCs-P effectively hydrolyse ester bonds responsible for phthalate toxicity. Considering their high efficiency, FP and HNCs-P can be used as potential phthalate degraders in various environmental remediation processes.Article Analytical Techniques for Non-Relativistic Particles in the Presence of Topological Defects and External Potentials: Applications to Diatomic Molecules(Taylor & Francis Ltd, 2025) Joseph, Gabriel Wirdzelii; Targema, Terkaa Victor; Oyewumi, Kayode John; Omugbe, Ekwevugbe; Ajulo, Kayode Richard; Gabriel, Ochoche; Zoe, HeeseungIn this paper, we examine the effects of point-like and cosmic string topological defects on non-relativistic particles confined within external potentials using analytical methods. The external potentials under consideration include the Hellmann-Kratzer potential, the standard Kratzer potential, the energy-dependent Kratzer potential, and the modified Kratzer potential. The modified Kratzer potential is employed to illustrate the impact of topological defects on diatomic molecules, demonstrating that these defects impose significant constraints on the molecules. In all defect types, the depth of the effective potential increases with increasing curvature. In these regions, molecules become trapped and experience a substantial reduction in energy in the case of point-like defects. Conversely, when particles propagate in a cosmic string background, their energy increases. When the constraints imposed by the topological defects on these molecules are removed, the results obtained in this study align well with existing literature. Thus, we establish beyond reasonable doubt the effects of topological defects on non-relativistic particles and, consequently, on diatomic molecules, which arise from the geometry of these defects. Additionally, we have employed analytical methods to obtain the solutions without introducing any modification to the centrifugal term. The approach is straightforward, highly efficient, and effective.Article Dam Body Sediment Movement on Rough Bed Downstream Due to Earthfill Dam Break(Taylor & Francis Ltd, 2025) Aksoy, Aysegul Ozgenc; Dogan, Mustafa; Tayfur, GokmenThis study investigated movement of flow and sediment due to earthfill dam failure induced by piping and overtopping, using 12.8 m laboratory flume. Dam (60 cm high, 202 cm base width) was built in three zones with two sediment sizes, and downstream channel included a rough bed of cubic blocks. Water levels were monitored with sensors, and final sediment profiles were mapped via laser scanning. Results showed that dam body eventually collapses (in 265 s after the piping, and in 100 s after the overtopping start) while flood flow carries a great portion of its sediment away. Sediment spreading occurred all over downstream area with significant variation in non-uniform thickness (15 cm to 1 cm). In the residential area, the sediment depth variation ranged from 12 cm to 6 cm. The blocks were submerged under muddy flow in both modes of failures. Higher flow levels (22 cm) were observed over smooth bed than rough bed (15 cm), in overtopping break. This was almost the opposite in the piping failure mode (13 cm in smooth, and 15 cm in rough bed case). These findings highlights the dominant role of failure mechanism and bed roughness in sediment transport and flood dynamics.Article Review of the Relationship Between Growth Hormone and SARS-CoV-2 Infection(Taylor & Francis Ltd, 2025) Rasmi, Yousef; Kirboga, Kevser Kubra; Roshanravan, Neda; Tekin, Burcu; Jalali, Ladan; Ghazizadeh, FaridRecent evidence suggests that SARS-CoV-2 is associated with the endocrine system, particularly growth hormone (GH). GH modifies immune responses and its deficiency could be responsible for the uncontrolled immunity that occurs in severe cases of COVID-19. Recent research shows that patients suffering from lung complications have significantly lower levels of GH and insulin-like growth factor-1 (IGF-1), which are proportionate to the severity of the disease. This relationship supports the hypothesis that GH regulates the immunity and inflammatory processes of the SARS-CoV-2 virus. However, variables such as age, gender, and comorbidities, such as diabetes and obesity, which are associated with lower GH levels, are strong predictors of COVID-19 outcomes. Older individuals and men, who tend to have lower GH levels, are disproportionately represented among severely ill patients. The available evidence suggests that GH supplementation therapy should be evaluated as a supportive measure to reduce the severity of the disease in high-risk individuals. The main goal of the research is to understand how COVID-19 is related to GH so that researchers can identify new mechanisms of pathology and develop better solutions for patients.Article Citation - WoS: 1Citation - Scopus: 1Reliability Assessment of Structures With Bayesian Model Updating Accelerated Via Polynomial-Chaos Metamodeling(Taylor & Francis Ltd, 2025) Uzun, Ertugrul Turker; Hizal, Caglayan; Aktas, EnginFinite element models are often preferred in numerical modeling of structures, but model assumptions lead to inaccuracies and uncertainties. Measuring these is necessary to determine the reliability and accuracy of the numerical model. This has led to the development of FE model update methods that aim to calibrate the numerical model based on data obtained by structural health monitoring (SHM). However, a general framework that provides a realistic life cycle performance assessment of structures by efficiently incorporating monitored data into structural identification has not yet been impeccably presented. Bayesian modeling can characterize uncertain structural parameters as random variables and provide a systematic methodology for integrating a probabilistic SHM framework into model updating. Unfortunately, these lead to complex and time-consuming, causing limitations in their application. Metamodeling techniques which are effective stochastic predictors can be used to decrease the computational burden in the model updating. This study aims at adapting Polynomial-Chaos-Kriging metamodeling technique integrate to Bayesian model updating process to overcome the computational difficulties and reduce different source of uncertainty with using SHM, then, make more accurate reliability assessment. Therefore, an experimental study is used to assess reliability of structure that is exposed to different types of corrosion effects.Article Effect of Random Structural Variations on the Optical Properties of Honeycomb Photonic Crystals(Taylor & Francis Ltd, 2024) Tuncturk, Yigit; Sozuer, H. SamiPeriodic 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\% $ 45% of surface roughness.Article Citation - WoS: 4Citation - Scopus: 3Sediment Transport Modelling in Densly Populated Urban Areas Due To Earthfill Dam Break(Taylor & Francis Ltd, 2024) Zhang, Yaoxin; Tayfur, GokmenThis study simulates two dimensional sediment transport, as a result of overtopping earthfill dam break, in urban areas. The model can consider breaching, removal of sediment from dam body, and transport of sediment. The model is first validated by simulating laboratory experimental data that involved measurements of levels, and longitudinal sediment profiles, and sediment distribution. Downstream side of the experimental canal is designed as; (1) smooth bed, and (2) rough bed with concrete blocks. For both cases, the model simulations are found to be satisfactory. The model is then applied to simulate artificial overtopping break scenarios of two real earthfill dams. The AW3D30 is used as the source data for representing the topographic surfaces and the LULC dataset is generated from the ESA's Sentinel-2 imagery. The results reveal that downstream of the dams can be subject to both scour, at onset of the dam break, and substantial deposition after having reservoir completely emptied. The cut can go all the way to dam bed. The scoured areas can be refilled after peak discharge recedes. Sediment depths can reach up to 1.5 m in the case of Urkmez Dam break in some areas in the vicinity of Urkmez Town and up to 3 m at the downstream area of Alibey Dam in Istanbul, implying disastrous consequences for the settlement areas.