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  • Öge
    A bibliometric analysis of metaverse technologies in healthcare services
    (Springer, 2024) Damar, Seçkin ; Hançerlioğulları Köksalmış, Gülşah ; 0000-0002-2713-2738 ; 0000-0002-2551-541X ; Endüstri Mühendisliği
    A bibliometric analysis was conducted to examine healthcare metaverse research using 3721 Web of Science publications covering the period 1994–2022. Using bibliometric and bibliographic link network analyses, this study aimed to uncover emerging trends, country and university contributions, author collaborations, and common metaverse themes. Contrary to expectations, inconsistent correlations between publication volume and citation impact emerged. This pioneering research evaluated empirical bibliometric laws, identified influential entities, and provided a structured thematic categorization for metaverse studies. Serving as the first comprehensive investigation of the healthcare metaverse, this study lays a solid foundation for subsequent research efforts and guides further scholarly research.
  • Öge
    A C0 continuous mixed FE formulation for bending of laminated composite plates based on unified HSDT
    (Wiley, 2024) Bab, Yonca ; Kutlu, Akif ; orcid.org/0000-0002-1807-9306 ; orcid.org/0000-0001-6865-3022 ; İnşaat Mühendisliği
    This study proposes a unified C0 continuous mixed finite element (MFE) formulation for the accurate and efficient prediction of stress components in laminated composite plates relying on Higher Order Shear Deformation Theory (HSDT). This unified form of the MFE accepts any convenient function for the representation of transverse shear deformation. The Hellinger–Reissner variational principle is employed for the derivation of MFE equations within a two-field formulation involving stress resultants along with kinematical variables. Thus, the displacement and stress resultant fields are obtained directly from the global solution of the system of equations. In this manner, the in-plane stress components are calculated over constitutive relations at the nodes without any need for error-prone spatial derivatives. Furthermore, the independent interpolation of kinematic and stress resultant type variables allows the numerical solution to overcome the shear-locking problem and ensure C0 continuity requirement. Numerical examples include convergence and comparison tests of predicted displacements and stress components under various boundary conditions and material configurations. Various test cases are considered for both the thin and thick plates subjected to sinusoidal and uniformly distributed loads. It is demonstrated that the proposed MFE formulation can capture stress components with high accuracy while being computationally efficient.
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    A comprehensive study on methane adsorption capacities and pore characteristics of coal seams: implications for efficient coalbed methane development in the Soma Basin, Türkiye
    (Springer, 2024) Esen, Olgun ; Fişne, Abdullah ; 0000-0001-8015-0962 ; 0000-0001-7449-0573 ; Maden Mühendisliği
    This study represents a comprehensive assessment of methane adsorption capacity and pore characteristics for the coal seams of the Soma Basin in Western Türkiye, with a focus on their implications for coalbed methane potential. Twenty-one exploration wells were utilized to obtain coal samples from the kP1 and kM2 coal seams in the Kınık coalfield of the Soma Basin. High-pressure methane adsorption experiments using the indirect gravimetric method were conducted to quantify the storage capacities of these coal seams. Results revealed a wide range of methane adsorption capacities, ranging from 10.5 to 28.3 m3/t (air-dry basis), indicating significant methane storage potential for the kP1 and kM2 coal seams. The gas contents, ranging from 1.1 to 4.3 m3/t (as-received basis), suggested that the coal seams were undersaturated. Low-pressure N2/CO2 adsorption tests, along with standard proximate and gross calorific value analyses, were performed to investigate the influence of coal quality and pore characteristics on methane adsorption capacities. The findings demonstrated correlations between coal quality parameters and adsorption capacity, with ash yield showing a moderately negative correlation and fixed carbon content and gross calorific values exhibiting moderately positive correlations. Microporosity was identified as the critical factor governing methane adsorption, with a strong positive correlation observed between micropore surface areas and volumes and adsorption capacity. These results highlight the significant methane storage capacities of the coal seams in the Soma Basin and underscore the importance of micropores in determining methane adsorption capacity. The findings provide valuable insights for optimizing methane extraction and utilization in the region and offer important considerations for reservoir characterization and development strategies in similar low-rank coal deposits.
  • Öge
    A distance-based approach to fuzzy cognitive maps using pythagorean fuzzy sets
    (Springer, 2024) Bozdağ, Erhan ; Kadaifçi, Çiğdem ; 0000-0001-6900-5238 ; 0000-0003-4522-9071
    Fuzzy Cognitive Maps (FCMs) have been attracting researchers from a wide application area due to being easy to apply and interpret. Since its proposal, the method has been improved to satisfy the diverse needs of practitioners such as solving different types of problems and representing particular types of uncertainty. The classical FCMs depend highly on the decision-maker judgments and the uncertainty inherent in the judgments deserves significant attention. Although there are several fuzzy extensions integrated into FCMs, the uncertainty caused by the lack of knowledge, the hesitancy of decision makers, and also the limited capacity of humans to deal with pre-defined rules should be considered. To address this issue, a new distance-based approach integrating Pythagorean Fuzzy Sets and FCMs is proposed. To the best of our knowledge, this is the first time this extension is integrated into FCMs. Besides allowing to represent the uncertainty until the end of the calculations, the new approach offers decision makers an easier and more flexible way to assess the strength of existing causal relationships. To provide a comparison between the proposed approach and the classical FCMs, two real-life applications are selected as case studies.
  • Öge
    A drug prescription recommendation system based on novel DIAKID ontology and extensive semantic rules
    (Springer, 2024) Göğebakan, Kadime ; Ulu, Ramazan ; Abiyev, Rahib ; Şah, Melike ; 0000-0002-2584-9647 ; 0000-0003-1461-2764 ; 0000-0002-3085-6219 ; 0000-0003-3869-7205 ; Bilişim Sistemleri Mühendisliği
    According to the World Health Organization (WHO) data from 2000 to 2019, the number of people living with Diabetes Mellitus and Chronic Kidney Disease (CKD) is increasing rapidly. It is observed that Diabetes Mellitus increased by 70% and ranked in the top 10 among all causes of death, while the rate of those who died from CKD increased by 63% and rose from the 13th place to the 10th place. In this work, we combined the drug dose prediction model, drug-drug interaction warnings and drugs that potassium raising (K-raising) warnings to create a novel and effective ontology-based assistive prescription recommendation system for patients having both Type-2 Diabetes Mellitus (T2DM) and CKD. Although there are several computational solutions that use ontology-based systems for treatment plans for these type of diseases, none of them combine information analysis and treatment plans prediction for T2DM and CKD. The proposed method is novel: (1) We develop a new drug-drug interaction model and drug dose ontology called DIAKID (for drugs of T2DM and CKD). (2) Using comprehensive Semantic Web Rule Language (SWRL) rules, we automatically extract the correct drug dose, K-raising drugs, and drug-drug interaction warnings based on the Glomerular Filtration Rate (GFR) value of T2DM and CKD patients. The proposed work achieves very competitive results, and this is the first time such a study conducted on both diseases. The proposed system will guide clinicians in preparing prescriptions by giving necessary warnings about drug-drug interactions and doses.
  • Öge
    A GNN model with adaptive weights for session-based recommendation systems
    (ACM, 2024) Özbay, Begüm ; Tugay, Resul ; Gündüz Öğüdücü, Şule ; Bilgisayar Mühendisliği
    Session-based recommendation systems aim to model users’ interests based on their sequential interactions to predict the next item in an ongoing session. In this work, we present a novel approach that can be used in session-based recommendations (SBRs). Our goal is to enhance the prediction accuracy of an existing session-based recommendation model, the SR-GNN model, by introducing an adaptive weighting mechanism applied to the graph neural network (GNN) vectors. This mechanism is designed to incorporate various types of side information obtained through different methods during the study. Items are assigned varying degrees of importance within each session as a result of the weighting mechanism. We hypothesize that this adaptive weighting strategy will contribute to more accurate predictions and thus improve the overall performance of SBRs in different scenarios. The adaptive weighting strategy can be utilized to address the cold start problem in SBRs by dynamically adjusting the importance of items in each session, thus providing better recommendations in cold start situations, such as for new users or newly added items. Our experimental evaluations on the Dressipi dataset demonstrate the effectiveness of the proposed approach compared to traditional models in enhancing the user experience and highlighting its potential to optimize the recommendation results in real-world applications.
  • Öge
    A histogram-based sampling method for point cloud registration
    (Wiley, 2023) Ervan, Osman ; Temeltas, Hakan ; orcid.org/0000-0001-9728-6970 ; Kontrol ve Otomasyon Mühendisliği
    Accurate and efficient point cloud registration is essential in various fields, such as robotics, autonomous driving and medical imaging. The size of point clouds presents a significant challenge for existing registration methods. In this paper, a novel point cloud sampling method to improve the performance of the point cloud registration process is proposed. Instead of geometric feature preservation, which is preferred in most existing sampling methods, our approach scales every point and groups the scaled points into clusters to generate a histogram for the point cloud. The histogram is then used to identify the most significant regions of the point cloud to create the downsampled output data. Experimental results demonstrate that the proposed method improves accuracy and is robust against noise. Registration errors are reduced by up to 7% in rotation and 116% in translation. Additionally, the proposed method filtered out up to 98% of noise from the point cloud that was uniformly distributed at a rate of 25%.
  • Öge
    A multi-stage localization framework for accurate and precise docking of autonomous mobile robots (AMRs)
    (Cambridge University Press, 2024) Yılmaz, Abdurrahman ; Temeltaş, Hakan ; https://orcid.org/0000-0001-8946-6664 ; Kontrol ve Otomasyon Mühendisliği
    Autonomous navigation has been a long-standing research topic, and researchers have worked on many challenging problems in indoor and outdoor environments. One application area of navigation solutions is material handling in industrial environments. With Industry 4.0, the simple problem in traditional factories has evolved into the use of autonomous mobile robots within flexible production islands in a self-decision-making structure. Two main stages of such a navigation system are safe transportation of the vehicle from one point to another and reaching destinations at industrial standards. The main concern in the former is roughly determining the vehicle’s pose to follow the route, while the latter aims to reach the target with high accuracy and precision. Often, it may not be possible or require extra effort to satisfy requirements with a single localization method. Therefore, a multi-stage localization approach is proposed in this study. Particle filter-based large-scale localization approaches are utilized during the vehicle’s movement from one point to another, while scan-matching-based methods are used in the docking stage. The localization system enables the appropriate approach based on the vehicle’s status and task through a decision-making mechanism. The decision-making mechanism uses a similarity metric obtained through the correntropy criterion to decide when and how to switch from large-scale localization to precise localization. The feasibility and performance of the developed method are corroborated through field tests. These evaluations demonstrate that the proposed method accomplishes tasks with sub-centimeter and sub-degree accuracy and precision without affecting the operation of the navigation algorithms in real time.
  • Öge
    A novel image denoising technique with Caputo type space–time fractional operators
    (Springer, 2024) Tanrıöver, Evren ; Kiriş, Ahmet ; Tunga, Burcu ; Tunga, M. Alper ; 0000-0003-4098-3155 ; 0000-0002-3687-6640 ; 0000-0001-7318-964X ; 0000-0003-3551-4549 ; Matematik Mühendisliği
    A novel image denoising model, namely Full Fractional Total Variation (TVFF), based on the Rudin-Osher-Fatemi (ROF) and the fractional total variation models is presented. The leading advantage of TVFF model is that it uses fractional derivatives with length scale parameters instead of ordinary derivatives with respect to both time and spatial variables in the diffusion equation. The Riesz–Caputo fractional derivative operator is used to disperse nonlocal influence throughout all directions, whereas the Caputo fractional derivative concept is employed for time fractional derivatives. Therefore, the influence of neighboring pixels is given greater weight compared to those situated farther away and this reflects the consideration behind denoising process better. Moreover, the numerical approach is constructed, and its stability and convergence properties are thoroughly examined. To show the superiority of our model, the denoised images are subjected to visual and numerical comparisons using metrics such as the Signal-to-Noise Ratio (SNR), the Structural Similarity Index Measure (SSIM) and the Edge-Retention Ratio (ERR). The performance of the TVFF method is evaluated under various types of noise, including Poisson, Speckle, and Salt & Pepper, and the results are compared with those obtained using Gauss and Median Filters. Furthermore, the proposed method is applied to both blind and synthetic images, thereby showcasing its versatility and applicability across diverse datasets. The outcomes showcase the substantial potential of our enhanced model as a versatile and efficient tool for image denoising.
  • Öge
    A quantum mechanical approach to the mechanism of asymmetric synthesis of chiral amine by imine reductase from stackebrandtia nassauensis
    (Wiley, 2024) Kopar, Merve ; Senyurt Tuzun, Nurcan ; orcid.org/0000-0003-2100-3844 ; orcid.org/0000-0001-5225-3876 ; Kimya Bölümü
    The asymmetric synthesis of tetrahydroisoquinolines (THIQs) has gained importance in recent years due to their significant potential in drug development studies. In this study, the conversion of 1-methyl-3,4-dihydroisoquinoline substrate to a chiral amine, 1-methyl-1,2,3,4-tetrahydroisoquinoline, under the catalysis of the stereoselective imine reductase enzyme from Stackebrandtia nassauensis (SnIR) was investigated in detail to elucidate the mechanism and explain the experimental enantioselectivity. The results were found to be in agreement with the experimental data. To elucidate the reaction mechanism, quantum mechanical calculations were performed by considering a large cluster of the active site of the enzyme. In this regard, possible reaction pathways leading to both R- and S-products with the corresponding intermediates and the transition states for the hydride transfer from the cofactor to the substrate were considered by density functional theory (DFT) calculations, and the factors contributing to the observed stereoselectivity were sought. The calculations supported a stepwise mechanism rather than the concerted protonation and the hydride transfer steps. The stereoselectivity in the hydride transfer was found to be due not only to the stability of the enzyme-subtrate complex but also to the corresponding reaction barriers. The calculations were performed at the wB97XD/6-311+G(2df,2p)//B3LYP/6-31G(d,p) level of theory using the PCM approach.
  • Öge
    A rare piedmont glaciation in the Mediterranean: insights from cosmogenic 36Cl dating of Davraz hummocky moraine field (SW Türkiye)
    (Wiley, 2024) Altınay, Onur ; Sarıkaya, Mehmet Akif ; Wilcken, Klaus M. ; orcid.org/0000-0003-1821-6814 ; Katı Yer Bilimleri
    Piedmont glaciers (lobes), typically found in high latitudes and large mountainous regions, extend from ice sheets and ice caps to lower altitudes. However, they can also occur, although less commonly, on mid-latitude mountains. When these fan-like glaciers retreat, they leave behind hummocky moraines scattered in a chaotic pattern. In this study, we have mapped one of these mid-latitude sites and established a Terrestrial cosmogenic nuclide (TCN) glacial chronology on Mount Davraz, namely Davraz hummocky moraine field (37°46′00″N, 30°43′15″E). Our findings indicate that the glaciers in this area started receding from the early local Last Glacial Maximum (LGM) period (21.8 ± 2.4 ka) to the early Late-glacial period (17.7 ± 2.2 ka), and eventually disappearing. The deglaciation of the Mt. Davraz palaeoglacier matches nearby mountains, supported by southerly winds as significant for regional glaciation. Our discoveries reveal a robust connection between southerly winds and nearby glaciation, contributing to our understanding of how climate influences glaciers. Likewise, the glacial timelines of the neighbouring mountains align with the glacial history of Mt. Davraz.
  • Öge
    A study on tailoring silver release from micro-arc oxidation coating fabricated on titanium
    (Wiley, 2024) Kayan, Gizem Özge ; Muhaffel, Faiz ; Kayan, Asgar ; Nofar, Mohammadreza ; Cimenoglu, Huseyin ; orcid.org/0000-0002-4364-2930 ; orcid.org/0000-0002-9921-7108 ; Metalurji ve Malzeme Mühendisliği
    This study is initiated with the aim of regulating the release of silver (Ag) as an antibacterial agent from the micro-arc oxidation (MAO) coating. Herein, an external 5 wt% Tin(II) chloride (SnCl2) containing biodegradable polycaprolactone (PCL) layer is formed on the 0.8 wt% Ag-incorporated MAO coating by the dip coating method. 5 wt% SnCl2 addition into PCL provides a steady release of Ag into concentrated simulated body fluid (1.5X SBF) from the underlying MAO coating at 37 °C. When the Ag release rate is taken into consideration, it is quantified as 0.0089 and 0.0586 ppm day−1 for PCL-covered MAO and PCL-free MAO coatings, respectively. It is finally concluded that the preliminary result of this study can be promising for minimizing the in vivo adverse effects of Ag+ ions arising from rapid release as well as maintaining antibacterial efficacy for prolonged periods, which is ideal for preventing the risk of postimplantation infections.
  • Öge
    A systematic literature review: setting a basis for smart and sustainable city performance measurement
    (Wiley, 2024) Karal, Fatma Sena ; Soyer, Ayberk ; orcid.org/0000-0002-1141-8934 ; orcid.org/0000-0002-4429-3525 ; Endüstri Mühendisliği
    The growing amount of data and the inventive solutions that arise from it create opportunities to construct and manage smart sustainable cities. Before attempting to establish appropriate solutions in this regard, it is crucial to clearly grasp what smart and sustainable cities are and the aspects around which they are built. The purpose of this study is to critically analyze and evaluate the studies that have been conducted on smart and/or sustainable cities and to provide a basis for the measurement of smartness and sustainability of cities. In this context, using Systematic Literature Review (SLR) methodology, the smart city, sustainable city, and smart sustainable city concepts are firstly defined. After that, the indicators for the assessment of the smartness and sustainability of cities and the selection processes of these indicators are analyzed. According to the analysis, the studies were grouped based on the use of (i) selection criteria, (ii) selection methods/tools, and (iii) models used and 14 criteria were deduced from the literature for the evaluation of performance assessment indicators: measurability, availability, completeness, relevance, independence, reliability, currency, responsiveness, simplicity, representativeness, cost-effectiveness, consistency, comparability, and consensus. This study aims to support other studies and applications of authorities on creating and assessing a smart and sustainable city (i.e., the indicators) that want to join the 2030 Agenda but face problems regarding their cities' specific conditions. The first step towards creating a smart sustainable city can be taken by determining the most suitable indicators for the city.
  • Öge
    A thienothiophene and anthracene based functional hyperbranched polymer: synthesis, photophysical properties and photocatalytic studies
    (Royal Society of Chemistry, 2024) İşçi, Recep ; Bildirir, Hakan ; Gunturkun, Dilara ; Gomez-Mendoza, Miguel ; Liras, Marta ; O’Shea, Victor A. de la Peña ; Öztürk, Turan ; https://orcid.org/0000-0001-9909-4585 ; https://orcid.org/0000-0003-3777-5320 ; Kimya Bölümü
    Conjugated polymer photocatalysts have been receiving extensive attention in the field of photocatalytic hydrogen evolution, owing to their tunable molecular structures and electronic properties. Herein, we report a hyperbranched conjugated polymer, containing thienothiophene and anthracene units (TT-Ant), synthesized via Pd(0) catalyzed Suzuki coupling. Its structural, photophysical and electrochemical features were investigated by using UV-vis and fluorescence spectroscopy, cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS). Photocatalytic hydrogen evolution tests, combining the material with two different additives, resulted in high hydrogen production rates from water. A steady state production rate of around 286 μmol g−1 h−1 for its hybridization with TiO2 was recorded, which is more than 3 times that for pristine TiO2 under the same conditions. Moreover, the combination of the polymeric material with platinum (1% wt) resulted in a maximum rate value of 700 μmol g−1 h−1. The surface properties of the latter combination before and after the reaction were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which demonstrated successful Pt deposition on the surface of the polymer. This work may provide a new strategy to construct stable photocatalysts with thienothiophene and anthracene cores as active sites for efficient catalytic reactions in energy conversion applications.
  • Öge
    Accelerating molecular docking using machine learning methods
    (Wiley, 2024) Bande, Abdulsalam Y. ; Baday, Sefer ; Yapay Zeka ve Veri Mühendisliği
    Virtual screening (VS) is one of the well-established approaches in drug discovery which speeds up the search for a bioactive molecule and, reduces costs and efforts associated with experiments. VS helps to narrow down the search space of chemical space and allows selecting fewer and more probable candidate compounds for experimental testing. Docking calculations are one of the commonly used and highly appreciated structure-based drug discovery methods. Databases for chemical structures of small molecules have been growing rapidly. However, at the moment virtual screening of large libraries via docking is not very common. In this work, we aim to accelerate docking studies by predicting docking scores without explicitly performing docking calculations. We experimented with an attention based long short-term memory (LSTM) neural network for an efficient prediction of docking scores as well as other machine learning models such as XGBoost. By using docking scores of a small number of ligands we trained our models and predicted docking scores of a few million molecules. Specifically, we tested our approaches on 11 datasets that were produced from in-house drug discovery studies. On average, by training models using only 7000 molecules we predicted docking scores of approximately 3.8 million molecules with R2 (coefficient of determination) of 0.77 and Spearman rank correlation coefficient of 0.85. We designed the system with ease of use in mind. All the user needs to provide is a csv file containing SMILES and their respective docking scores, the system then outputs a model that the user can use for the prediction of docking score for a new molecule.
  • Öge
    Active deformation pattern in the western flank of the central Taurides, southern margin of the central Anatolian plateau: inferences from geomorphic markers and kinematic indicators
    (Wiley, 2023) Aykut, Tunahan ; Yıldırım, Cengiz ; Uysal, I. Tonguç ; orcid.org/0000-0003-0503-3859 ; orcid.org/0000-0001-5253-028X ; orcid.org/0000-0002-8263-8774 ; Katı Yer Bilimleri
    The southwestern margin of the Central Anatolian Plateau corresponds to the upper crust of the subduction between African and Anatolian plates, with a high relief of up to 2 km. This mountainous region has distinctive geomorphological features and presents a unique setting to investigate the mechanism of orogenic plateau margin development related to subduction and topographic evolution around the Eastern Mediterranean. We present new kinematic data from exposed fault planes and tectonic landforms from high-resolution digital elevation models to elucidate the deformation pattern and its relation with the crustal deformation. We evaluate the deformation pattern based on the spatial distribution of kinematic analyses and geomorphic markers like low relief upland surfaces, disrupted karst basins, knickpoints, and deep bedrock incisions from watershed to shoreline. Our geomorphic analysis reveals a post-orogenic transient actively deforming topography. The geomorphic markers constrain long-term surface uplift pattern with a mean cumulative surface uplift of 1,710 ± 50 m and shows an increasing trend from west to east, from 1,600 ± 50 to 1,800 ± 50 m. Our results suggest a dome-like uplift pattern in the west-east direction across the southern margin that reaches up to maximum cumulative uplift values in the quadrangle of Alanya-Başyayla-Ermenek-Gazipaşa. Our kinematic measurements along the youngest generation of faults revealed an active NE-SW extensional deformation across a broad 200 km zone in the north of the subduction. Our findings have significant implications for understanding the morphotectonic evolution and post-orogenic deformation in the plateau margins and geodynamic evolution of the Eastern Mediterranean. Key Points River longitudinal profiles and low-relief upland surfaces indicated an increasing vertical deformation toward the eastern Central Taurides Geomorphic markers constrained mean cumulative 1,710 ± 50 m surface uplift that peaks in the quadrangle of Alanya-Başyayla-Ermenek-Gazipaşa Kinematic indicators from the youngest brittle structures revealed an active NE-SW extension above the Cyprus Subduction Zone
  • Öge
    Adaptive fault-tolerant multiplicative attitude filtering for small satellites
    (Wiley, 2024) Kınataş, Hasan ; Hajiyev, Chingiz ; orcid.org/0000-0003-2089-223X ; orcid.org/0000-0003-4115-341X ; Uzay Mühendisliği
    This study tackles the problem of fault-tolerant attitude estimation for small satellites. A probabilistic adaptive technique is presented for the multiplicative extended Kalman filter (MEKF) algorithm that is used in attitude estimation. The presented method is based on tracking the normalized measurement innovations in the filter and calculating the probability of the normal operation of the estimation system. Using this probability, the filter gain is corrected to maintain the tracking performance of the filter despite faulty measurements. In order to evaluate the performance of this method, several simulations are performed where different types of faults are introduced to the synthetic attitude sensor measurements (magnetometer and sun sensor) at different times. Simulation results are compared not only with a conventional EKF but also with another popular adaptive Kalman filter, an adaptive Kalman filter with multiple scaling factors (MSFs).
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    Aerodynamic performance evaluation of a coaxial octocopter based on taguchi method
    (ASME, 2024) Geydirici, Evren ; Derman, Kuzey C. ; Çadırcı, Sertaç ; Makina Mühendisliği
    The design and optimization of propellers for unmanned aerial vehicles (UAVs) are essential for optimal performance and high efficiency. This study presents a numerical investigation of the aerodynamic performance of coaxial octocopters using openfoam as flow solver. While the aerodynamic performance is affected by many parameters, the current study focuses on four main parameters: the propeller type, the horizontal and vertical separation distances between the propellers, and the ratio between the rotational speeds of the upper propeller and the lower one. To find the minimum number of simulations to be performed within defined limits, and reduce the number of computational fluid dynamics (CFD) simulations that cause high computational cost, Taguchi method was employed. In this study, average thrusts were calculated for the preliminary design of the octocopter by examining an isolated single propeller and dual- and quad propellers taking their rotation directions into account. The Taguchi design matrix revealed that for all cases investigated, the propeller type is the most dominant design parameter followed by the velocity ratio of the upper propeller to the lower one (⁠ ⁠) and vertical (z/D) and horizontal (⁠ ⁠) orientation of coaxial propellers. However, it was shown that and z/D may play a significant role in vortex formation and pressure fluctuations which should be considered as design criteria for coaxial octocopters associated with flow attributes. The results showed that the aerodynamic performance parameters are not dependent on all the selected parameters, and demonstrated that the selected propeller designs improved aerodynamic performance.
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    Alternative plant-based gluten-free sourdough pastry snack production by using beetroot and legumes: characterization of physical and sensorial attributes
    (American Chemical Society, 2024) Yolcu, Zeynep ; Demircan, Evren ; Mertdinç, Zehra ; Aydar, Elif Feyza ; Özçelik, Beraat ; 0000-0002-1810-8154 ; Gıda Mühendisliği
    Objective of this study was to design a formula of a sourdough pastry snack by adding starter inoculum into the formulation which was obtained by the fermentation process through beetroot (Beta vulgaris) puree with black-eyed pea (Vigna unguiculata) and fava bean (Vicia faba). With this development process, it was aimed to review the functional impact of legumes as gluten replacement and emphasize the importance regarding physical and sensory attributes in a pastry snack product. First, a starter inoculum was developed based on modification of the shalgam fermentation process with legumes. An experimental design suggested by the response surface methodology was used to optimize its microbial properties and level of antioxidants with the factors of amounts of beetroot puree, fava bean/black-eyed pea ratio, and fermentation time. In the second part, this starter inoculum was mixed with fava bean flour to obtain a sourdough pastry snack (FBS) with improved physical and sensory attributes and compared to the wheat control sourdough (WCS) pastry snack after the baking process. According to the optimization results to produce starter inoculum with the optimum results of lactic acid bacteria 9.55 log cfu/mL, the level of antioxidant activity 91.86 μM TE/mL, and total yeast level 6.96 log cfu/mL; 75 mL of beetroot puree, 100% for fava bean, and fermentation for 24 h were obtained. Compared to WCS, FBS has approximately 16% higher hardness values. Also, a significant difference was observed for stiffness and springiness among samples. The retention of moisture was higher in the first 4 days following the storage for 8 days; the moisture content continuously decreased with the final moisture content of 12.6%. When compared with the results of textural profile analysis in terms of hardness, stiffness, and springiness, sensory results were correlated. Comparing the overall acceptability of the FBS to WCS, FBS was from moderate to higher scores, which indicated that it could be a promising alternative to chemically developed snack products and a preferred product for people suffering from celiac disease and other gluten intolerances.
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    An adaptive neurofuzzy inference system controller design of an SPMSM drive for multicopter applications
    (SAGE Publications, 2024) Kuvvetli, İpek ; Tap, Alper ; Ergenç, Ali Fuat ; Ergene, Lale T. ; https://orcid.org/0000-0003-4142-032X ; Elektrik Mühendisliği
    This study proposes an adaptive neurofuzzy inference system (ANFIS) for field oriented control (FOC) of a permanent magnet synchronous motor (PMSM) for multicopter applications. FOC is the most widely used speed control method for PMSMs. The utilization of linear control algorithms may not be sufficient for this type of systems due to the nonlinear characteristic of the PMSM and the presence of uncertainties such as parameter variations and external disturbances. In particular, in high power and agility applications, conventional PI controllers alone may cause undesired speed overshoot which degrade the performance of the multicopter. This paper proposes more comprehensive speed control of a PMSM drive employing an ANFIS, which offers improved tracking performance in terms of settling time and overshoot under various operating conditions. The proposed ANFIS controller implements the adaptive approach using offline training data over a PI controller that is tuned to the nominal operation of the PMSM, specifically targeting the speed error and the rate of change of error in speed. The training data is obtained from a dynamic model of the PMSM operating with a conventional PI controller. The performance analysis of both controllers under different operating conditions is simulated, and experimentally verified. By using the ANFIS controller, the overshoot is reduced from 6.17% to 1.57% at no load condition, from 36.3% to 6.23% at load, and the settling time is almost halved in both cases compared to a conventional PI controller.