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Koleksiyondaki öğeler
- MakaleAçık Erişim2023Scopus SJRQ1PatchResNet: Multiple Patch Division–Based Deep Feature Fusion Framework for Brain Tumor Classification Using MRI Images
Muezzinoglu, Taha; Baygin, Nursena; Tuncer, Ilknur; Barua, Prabal Datta; Baygin, Mehmet; Dogan, Sengul; Tuncer, Turker; Palmer, Elizabeth Emma; Cheong, Kang Hao; Acharya, U. Rajendra
Modern computer vision algorithms are based on convolutional neural networks (CNNs), and both end-to-end learning and transfer learning modes have been used with CNN for image classification. Thus, automated brain tumor classification models have been proposed by deploying CNNs to help medical professionals. Our primary objective is to increase the classification performance using CNN. Therefore, a patch-based deep feature engineering model has been proposed in this work. Nowadays, patch division techniques have been used to attain high classification performance, and variable-sized patches have achieved good results. In this work, we have used three types of patches of different sizes (32 × 32, 56 × 56, 112 × 112). Six feature vectors have been obtained using these patches and two layers of the pretrained ResNet50 (global average pooling and fully connected layers). In the feature selection phase, three selectors—neighborhood component analysis (NCA), Chi2, and ReliefF—have been used, and 18 final feature vectors have been obtained. By deploying k nearest neighbors (kNN), 18 results have been calculated. Iterative hard majority voting (IHMV) has been applied to compute the general classification accuracy of this framework. This model uses different patches, feature extractors (two layers of the ResNet50 have been utilized as feature extractors), and selectors, making this a framework that we have named PatchResNet. A public brain image dataset containing four classes (glioblastoma multiforme (GBM), meningioma, pituitary tumor, healthy) has been used to develop the proposed PatchResNet model. Our proposed PatchResNet attained 98.10% classification accuracy using the public brain tumor image dataset. The developed PatchResNet model obtained high classification accuracy and has the advantage of being a self-organized framework. Therefore, the proposed method can choose the best result validation prediction vectors and achieve high image classification performance.
AtıfScopus103OpenAlex101
İncele - MakaleYayıncıda açık erişim2024Scopus SJRQ2A new post-processing approach for improvement of nonlinearity property in substitution boxes
Artuğer, Fırat; Özkaynak, Fatih
The main reason that makes chaos theory attractive for cryptology studies is the unpredictable nature of chaotic systems. However, the fact that the statistical and cryptographical properties of cryptographic primitives based on the values obtained as a result of the electronic circuit implementation of a chaotic system are not as good as the designs based on mathematical transformations has occupied the agenda of researchers. One of the most striking examples of this problem in practical applications is substitution-box (s-box) structures. While the nonlinearity value is 112 for s-box designs based on mathematical transformations, this value is in the range of 103–106.75 for s-box designs based on random (chaotic) transformations. Thanks to the post-processing algorithm proposed in this study, it has been shown that this problem can be resolved and the nonlinearity values of chaos-based s-box structures can be improved up to 111.5. It is thought that the proposed post-processing algorithm may have various potential contributions not only to improve the nonlinearity criterion of s-box structures but also to other information security applications such as cryptographic random number generators in future studies.
AtıfScopus19WoS13OpenAlex16İncele - BildiriYalnız künye2024Assessing Environmental Pollution and Noise Levels at End-of-Life Vehicle Recycling Centers: A Comparative Study
Harun, Zambri; Akkurt, Nevzat; Hashim, Hashimah; Molla, Altaf Hossain; Cahyadi, Mokhamad Nur; Zuhal, Lavi R.
This study investigates the environmental impact of end-of-life vehicle (EL V) recycling operations by assessing pollution parameters and noise levels at formal and informal recycling centers compared to a green zone reference area. U sing an integrated monitoring system. This research measured concentrations of particulate matter (PM2.5, PMlO), nitrogen dioxide (N02), carbon dioxide (C02), ozone (03), and noise levels at selected sites in Selangor, Malaysia. Results reveal elevated pollutant concentrations and noise levels at both formal and informal EL V recycling centers relative to the green zone reference area. Diurnal variations in pollutant levels highlight the influence of operational activities and atmospheric conditions. The findings underscore the need for stringent regulatory measures and pollution control strategies to mitigate environmental and health risks associated with EL V recycling activities and promote sustainable practices in the recycling industry.
AtıfScopus2OpenAlex2İncele - MakaleAçık Erişim2024Scopus SJRQ1Parameterizing Haverkamp Model From the Steady-State of Numerically Generated Infiltration: Influence of Algorithms for Steady-State Selection
Autovino, Dario; Bagarello, Vincenzo; Iovino, Massimo; Lassabatere, Laurent; Yilmaz, Deniz
BEST (Beerkan Estimation of Soil Transfer parameters) methods of soil hydraulic characterisation are widely applied for estimating sorptivity, S, and saturated hydraulic conductivity, Ks. Calculating these properties requires choosing the β and γ parameters of the Haverkamp infiltration model. These parameters can be obtained from numerically simulated three-dimensional (3D) infiltration runs reaching steady-state. This investigation tested dependence of the estimated β and γ parameters on the algorithm for steady-state selection using simulated 3D cumulative infiltrations for different soils and initial conditions. Two algorithms used the original simulation outputs and included using (i) a threshold defining steadiness (T-algorithm) and (ii) the last four data points, yielding a reference value of steady-state infiltration rate (R-algorithm). A third algorithm, similar to the R-algorithm, was applied to previously re-sampled infiltration data at fixed time intervals (RR-algorithm). The intercept, bs, of the straight line fitted to the data describing steady-state on the cumulative infiltration plot depended on the applied algorithm more than the slope of this line. Consequently, β varied with the applied algorithm more than γ. The RR-algorithm, yielding 0.62 ≤ β ≤ 1.99 and 0.74 ≤ γ ≤ 0.98, was preferred since it mediated between advantages and disadvantages of T- and R-algorithms. The influence of the choice of proper values for β and γ on the estimates of S and Ks was evaluated using BEST. Using the default values of β (0.6) and γ (0.75) yielded accurate estimates of S but not of Ks. Soil dependent β and γ values should be used in this case. A check of the reliability of the estimates of bs can be made by a sequential analysis of the cumulative infiltration data. Future developments include considering sources differing in size and establishing if the suggested β and γ values apply in general to the available BEST algorithms.
AtıfScopus2OpenAlex2İncele - MakaleYalnız künye2024Scopus SJRQ3Allium euphraticum (Amaryllidaceae), a New Species in Sect. Codonoprasum from Eastern Anatolia, Turkey
Sonay, Veysel; Balos, Mehmet Maruf; Çakllclolu, Uur
Allium euphraticum Balos, Sonay & U. Çakllclolu (Amaryllidaceae) is described as a new species in sect. Codonoprasum from Elazl Province, eastern Turkey. It is morphologically similar to A. sultaniae-ferhanii and A. turcicum, but differs from them by, for example, scabrid leaf sheath, backwards curved apex of perigon, creamy and brownish perigon, and presence of teeth at the filament base. Herein, we present a detailed description of the species, along with images, an overview of its habitat and ecological characteristics, and a conservation assessment.
AtıfScopus6OpenAlex5İncele - MakaleAçık Erişim2025Scopus SJRQ4The profile of fatty acids in the gametes of brook trout (Salvelinus fontinalis) during the spawning period under culture conditions; [Perfil de ácidos grasos en gametos de trucha de arro yo (Salvelinus fontinalis) cultivada en época de desove]
Kocabaş, Mehmet; Kutluyer-Kocabaş, Filiz; Başçinar, Nadir; Özçiçek, Esin; Kirmizikaya-Özmen, Görkem; Yilmaz, Ökkeş
The fertilization and subsequently embryo and larvae development are linked to gamete quality and FA (fatty acid) content is one of the specific factors affecting egg or sperm quality. Hence, FA profile of gametes (egg and sperm) was documented in brook trout (Sa lve linus fontinalis) under cultivation. FAs were detected and measured using gas chromatography. These results indicated that a total of 26 and 22 FAs were determined in egg and sperm, respectively. The levels of PUFAs were determined in nearly identical quantities in both egg (47.57%) and sperm (47.53%). DHA (Docosahexaenoic acid), LA (Linoleic acid), EPA (Eicosapentaenoic acid) and ARA (Arachidon ic acid) were predominant PUFAs for egg and sperm. Interestingly, vaccenic acid (C18:1 n-11) (24.07%) was major FAs in egg. In conclusion, the analysis of fatty acids in broodstock gametes contributes valuable insights into the dietary requirements necessary for effective aquaculture breeding programs.
- Kitap BölümüYalnız künye2024Adaptive AI and Interactive Narrative Possibilities in Media
Deniz, Kemal
This chapter examines the influence of advancements in adaptive artificial intelligence (AI) on interactive narrative solutions in both current media and emerging communication environments that are expected to gain significance in the future. This study explores the potential benefits of integrating narratives and adaptive AI into a communication process that involves human-machine interaction. The objective of this chapter is to focus on interactive and autonomous narration to understand the capabilities of new narrative structures that can incorporate AI technology across many media platforms, ranging from television to the metaverse.
- MakaleAçık Erişim2024Scopus SJRQ1Preparation of carbon dot/polyaniline composites as voltage based dielectric material for capacitor applications
Coğalmış, Fatma Tuba; Demirelli, Kadir; Barım, Esra; Ük, Nida; Ünlü, Caner; Şenkal, Bahire Filiz; Dere, Ayşegül; Tuncer, Hülya; Yakuphanoğlu, Fahrettin
Polyaniline-carbon dot (CD/PANI) composites were prepared via in-situ oxidative polymerization of aniline in the presence of carbon dots, with specific concentrations carefully controlled during synthesis. The composite was characterized using spectroscopic (FT-IR), morphological (TEM, SEM) and electrical methods. Impedance analysis was employed to investigate the transport behavior of charge carriers in the frequency range of 500 Hz to 10 MHz at 25 °C. This study provides a comprehensive analysis of the dielectric properties of the CD/PANI composite, including dielectric constant, dielectric loss, loss factor, AC conductivity, admittance, impedance, and Cole–Cole plots. The dielectric constant of the CD/PANI composite was 6.97 for 1 kHz at 0.5 V and 12.87 for 1 kHz at 5 V. The values indicate that the increase in the dielectric constant of nanocomposite with increasing voltage. This suggests that CD/PANI composite is a dielectric material whose dielectric constants are controlled by applied voltage. Notably, the dielectric constant increased with rising applied voltage and decreased with increasing frequency. Current-voltage (I-V) measurements revealed that the composite's dielectric parameters could be tuned by varying the applied DC voltage, suggesting its potential as a voltage-dependent dielectric (VDD) material for capacitor applications. Furthermore, the enhanced electrical conductivity indicates that the CD/PANI composite is a promising candidate for next-generation dielectric devices.
AtıfScopus7OpenAlex7İncele - MakaleYalnız künye2025Scopus SJRQ1Effect of light and noise pollution on oxidative stress and proximate composition in Dreissena polymorpha
Serdar, Osman; Demirtaş Erol, Nida; Aydin, Ayşe Nur
In this study, it was aimed to determine the effect of sound and light pollution on Zebra mussel (Dreissena polymorpha) by biomarker and nutritional composition. For this purpose, an experimental design was carried out in laboratory conditions where the model was exposed to live sound, light, and combined sound + light parameters for 30 min every hour over 96 h. Changes in the biomarkers superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities, as well as glutathione (GSH) and thiobarbituric acid (TBARS) levels, were assessed in the model organism exposed to sound, light, and sound + light pollution. The changes in protein and fat amounts were determined. When the changes in biomarkers were examined statistically compared to the control, there was no significant decrease in SOD activity (p < 0.05), a significant increase in CAT activity in sound and sound+light, but a significant decrease in light (p < 0.05), no significant difference in GPx activity (p > 0.05). It was determined that there was a significant increase in GSH and TBARS levels in all three parameters. Significant changes were also observed in the proximate composition. As a result, exposure to sound, light and sound+light pollution caused an increase in oxidative damage and decreases in protein and lipid composition were detected.
AtıfScopus7WoS6OpenAlex8İncele - MakaleAçık Erişim2024Scopus SJRQ2New sulfa drug derivatives and their zinc(II) complexes: synthesis, spectroscopic properties and in vitro cytotoxic activities
Şahal, Hakan; Öz, Samet; Keskin, Tuba; Tekin, Suat; Canpolat, Erdal; Kaya, Mehmet
Synthesis of four sulfa drug derivatives (L1–L4) and Zn(II) complexes derived from sulfonamide group antibiotic substances was carried out using the hydrothermal technique (HT) and their structures of the obtained compounds were explained using elemental analysis (EA), FT-IR and NMR (1H- and 13C-). Cytotoxic activities of four novel sulfa drug based-Schiff base compounds and their Zn(II) complexes were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay using MCF-7 (human breast cancer), Caco-2 (human colorectal adenocarcinoma), A2780 (human ovarian cancer) and LNCaP (human prostate adenocarcinoma) cell lines. LogIC50 values of all obtained compounds were computed with the Graphpad Prism 6 program after 24 h of treatment for MCF-7, Caco-2, A2780 and LNCaP cells. Comet assay experiments were performed using LogIC50 concentrations of all compounds to determine DNA damage. Based on the data obtained, all compounds significantly decreased MCF-7, Caco-2, A2780 and LNCaP cell viability compared to the control groups (p < 0.05).
AtıfScopus6OpenAlex5İncele - MakaleAçık Erişim2024Scopus SJRQ1Effect of curing conditions on cement based self-compacting mortar produced with mortar waste aggregate
Akgül, Melek
Concrete and mortar wastes, which have a large volume and economic value among construction demolition wastes, are the most targeted demolition waste group to be recycled. An important area where construction demolition waste can be utilized is self-compacting mortar (SCM) systems. SCMs are innovative and economical systems designed to minimize the labor requirements that are difficult to meet in the production process. In this study, mortar waste aggregate (MWA) obtained by mechanical crushing and grinding was used in SCM elements by substituting different ratios (5-10-20-30-40 %) by mass to aggregate. In this way, it was aimed to evaluate both the sustainability of MWAs and the usability of MWAs in SCMs, which are considered as a new production technology. The fresh and hardened mortar tests performed in the study are presented comparatively. The physical (dry unit volume weight, porosity), durability (capillary water absorption) and mechanical properties (flexural tensile, compressive strength) of the hardened SCM elements are based on the determinations made at 3, 7 and 28 test days and according to different curing conditions (water curing, air curing and heat curing). In addition, X-ray Diffractometer (XRD) analysis was performed on specimens obtained from 0 %, 10 %, 20 % and 40 % MWA substituted specimens after heat curing (after 7 days water curing) and 28 days water curing. In the light of the data obtained, it is reported that SCM production with 10 % MWA substitution is feasible in terms of sustainability and engineering properties evaluated in this study.
AtıfScopus2WoS1OpenAlex2İncele - MakaleAçık Erişim2023Scopus SJRQ2The Epiphytic Bryophyte Vegetation of Buxus sempervirens L. forests in the Fırtına Valley (Rize, Turkey); [Végétation de bryophytes épiphytes des forêts de Buxus sempervirens L. dans la vallée de Fırtına (Rize, Turquie).]
Alataş, Mevlüt; Ezer, Tülay; Erata, Hüseyin; Batan, Nevzat; Ursavaş, Serhat
The Fırtına Valley forests are of the 100 forests in the world whose conservation is a priority due to the natural old forests they have. In this study, the epiphytic bryophyte vegetation of the Buxus sempervirens L. forests located in the Fırtına Valley (Rize, Northern Turkey), which is one of the nine hotspots in Turkey and Turkey’s only boxwood forest, was investigated. The relevés taken from living tree trunks in 2020 were analyzed according to the Braun-Blanquet methodology, and ordinated and classified using the Detrended Correspondence Analysis (DECORANA) and the Two-Way Indicator Species Analysis (TWINSPAN). As a result of the analyses, Exsertotheco crispae-Allenielletum besseri ass. nov. subass. typicum and leucodontetosum sciuroidis subass. nov., and Alleniello besseri-Palamocladietum euchloronis ass. nov. were described and characterized. All syntaxa were presented by analyzing them in terms of their ecological and floristic classifications.
AtıfScopus2OpenAlex4İncele - MakaleAçık Erişim2023Scopus SJRQ4Single and combined effects of dimethoate and malathion on oxidative stress biomarkers in the non-target freshwater mussel Dreissena polymorpha
Serdar, Osman; Yildirim, Numan; Yildirim, Nuran Cikcikoglu
This study evaluates the single and combined effects of dimethoate (DI) and malathion (MA) on oxidative stress biomarkers in the freshwater mussel Dreissena polymorpha, estimating the potential harm of these pesticides on aquatic ecosystems. Superoxide dismutase (SOD) and catalase (CAT) activities, and glutathione (GSH) and lipid peroxidation (TBARS) levels were determined in D. polymorpha exposed to sublethal concentrations of DI, MA and a combination of the two during 24 and 96 h periods. The results showed that the GSH levels were decreased but the TBARS levels were increased in all the exposure groups after 24 and 96 h compared to the control. It was observed that SOD activity decreased but CAT activity increased in all the DI exposure groups after 24 h compared to the control. At the end of 96 hours, it was observed that CAT and SOD activities increased again in some exposure groups compared to the control. Exposure time also had an effect on biomarkers in different levels. According to the results, the cytotoxicity of DI and MA combination depended on their concentrations. DI or/ and MA, in sub-lethal concentrations, induced oxidative damages in D. polymorpha. Combined exposure of the pesticides can alter their toxicity and may be evidence of increased toxicity and oxidative stress.
AtıfScopus3WoS3OpenAlex2İncele - DüzeltmeAçık Erişim2023Correction to: A new approach based on convolutional neural network and feature selection for recognizing vehicle types(Iran Journal of Computer Science, 10.1007/s42044-022-00125-6)
Doğan, Gürkan; Ergen, Burhan
The sentence beginning 'Bu nedenle bu …' in this article should have read 'Therefore, in this study, a combination of OMobileNetv1, OMobileNetv2, ONASNetMobile CNN methods for feature extraction, LSVC method for feature selection and SVM method for classification is proposed.' The original article has been corrected.
- MakaleAçık Erişim2024Scopus SJRQ2Development of new generation cakes fortified with zinc oxide nanoparticles
Kaplan Ince, Olcay; Aydogdu, Burcu; Ince, Muharrem
This study aimed to develop new generation cakes that were fortified with calcined ZnO nanoparticles (CZnO), uncalcined ZnO nanoparticles (UCZnO), beads (B(CZnO)) synthesized by encapsulating the CZnO with sodium alginate (SA), and the beads (B(UCZnO)) synthesized by encapsulating the UCZnO with sodium alginate (SA) and investigated the zinc (Zn) release in fortified cakes in simulated body fluids (SBF). The present study represents a novel method for increasing intestinal absorption and bioavailability of dietary zinc with zinc nanoparticles for use in the preparation of Zn fortified cakes as a dietary supplement to compensate for zinc deficiency in humans. The results revealed that a rapid increase in the release time and rate in the SGF solution was noted in the UCZnO added cakes. It was attributed to increased intestinal absorption and bioavailability as a result of the ultra-small size of ZnO. Also, ZnO release kinetics in SBF was also studied and data were adjusted into different kinetic models involving zero-order, first-order, Higuchi, and Korsmeyer–Peppas models. The present investigation recommends adding UCZnO to the cakes to control and increase the release from the cakes.
AtıfScopus3WoS2OpenAlex3İncele - MakaleAçık Erişim2024Scopus SJRQ3Heracleum munzurense (Apiaceae), a new species from East Anatolia, Turkey and taxonomic position of Tetrataenium lasiopetalum
Duran, Ahmet; Lyskov, Dmitry; Samigullin, Tahir; Paksoy, Mehmet Yavuz
A new species, Heracleum munzurense (Apiaceae), is described from East Anatolia, Turkey. It grows in damp places formation of the Munzur Mountains in the district of Pülümür (Tunceli Province). The taxonomic affinities of the new species were determined by analyzing morphological data and through a molecular phylogenetic study of nrITS/ETS. The new species is morphologically and genetically related to H. apiifolium and H. pastinaca, but differs mainly in stems, leaves, pedicels, rays and petals pubescence, petals size, fruit hairs, and size features. The anatomical structure of the fruit is given. The diagnostic morphological characters of the new species are discussed. In this study, the geographical distribution of the new species and the related taxa H. apiifolium, H. lasiopetalum, and H. pastinaca is mapped. In addition, the habitat, ecology, phenology, and conservation status of the new species are also provided. Tetrataenium lasiopetalum is also closely related to this group of species. Common morphological features and results of molecular phylogenetic study suggest to transfer this species back to the genus Heracleum.
AtıfScopus1İncele - MakaleYayıncıda açık erişim2023Scopus SJRQ2The Symptom Experience and Functioning of Non-Hospitalized COVID-19 Patients Within the First 20 days
Tütün Yümin, Eylem; Sürmeli, Mahmut; Topcuoğlu, Ceyhun; Başol Göksülük, Merve; Yümin, Murat
The adverse physical, psychological, and mental health consequences associated with COVID-19 illness are well-documented. However, how specific symptoms change over time and how COVID-19 affects one’s day-to-day activities of daily living (ADL), Quality of Life (QoL), sleep quality, and fatigue severity are not well described. This longitudinal and descriptive study examined the changes in COVID-19 symptoms, ADL, QoL, sleep quality, and fatigue severity within the first 20 days. A convenience sample (n = 41) of non-hospitalized SARS-CoV-2 positive patients were recruited and followed for 20 days. Participants completed self-report measures: COVID-19 symptoms, ADL, QoL, sleep quality, and fatigue severity at days: 1, 10, and 20 following a diagnosis. Findings revealed that symptoms decreased over 20 days (p <.001). In parallel with the decrease in symptoms, QoL and ADL improved over 20 days (p <.05). However, sleep quality and fatigue severity did not improve within 20 days (p >.05). Our findings contribute to the growing evidence that COVID-19 symptoms can linger, especially fatigue and sleep quality, that affect overall day-to-day functioning for at least 20 days after diagnosis. To mitigate the effect of COVID-19 on QOL and ADL, findings underscore the need for clinicians to work collaboratively with patients to develop a symptom management plan for a variety of symptoms including fatigue and sleep quality. Beginning to repurpose existing self-management strategies for the longer term COVID-19 symptoms could be beneficial and help to optimize patient outcomes. Future work should examine these variables over a longer timeframe and among different samples of non-hospitalized patients.
AtıfScopus1WoS1İncele - MakaleYalnız künye2023Scopus SJRQ2Replacement of Cu with One-Step Production of CuAg (Ag0.04Cu3.96): Superior Conductivity, Corrosion Resistance, and Hardness
Cihangir, Salih
Copper is the forefront of the fundamental metals used in various industries. It is utilized as bulk or electrodeposited on PCBs or interconnects. However, poor corrosion resistance and hardness reduce copper performance and limit its applicability in the fields that require mechanical strength, such as probing applications. Facile electrochemical deposition of Cu(Ag) films was examined in a deep eutectic solvent known for its green nature. SEM–EDS technique was applied for morphostructural and crsytal plane analysis. XRD analysis revealed Cu3.96Ag0.04 phase, and 2% Ag was identified in the Cu(Ag) film in EDS. Four-prope point resistivity analysis was performed via galvano-impedance spectroscopy. Obtained resistivity value of 5 µm thick Cu(Ag) coating was lower than the compliance limit of International Technology Roadmap for Semiconductors. Corrosion analysis was carried out via electrochemical impedance spectroscopy technique, and Cu(Ag) films demonstrated better resistance. Hardness tests also revealed that Cu(Ag) was approximately two times harder than Cu. Graphical Abstract: [Figure not available: see fulltext.]
AtıfScopus6WoS6OpenAlex6İncele - MakaleAçık Erişim2023Scopus SJRQ1Modeling and numerical simulation of non-Newtonian arterial blood flow for mild to severe stenosis
Nadeem, Sohail; Ali, Shahbaz; Akkurt, Nevzat; Ben Hamida, Mohamed Bechir; Almutairi, Shahah; Ali Ghazwani, Hassan; Eldin, Sayed M; Khan, Zareen A.; Al-Shafay, A.S.
The fundamental cause of coronary heart disease is thought to be atherosclerosis. Blood flow in arteries under plaque formation is widely studied using both experimental and theoretical methods in literature. This paper presents a comprehensive study on the mathematical modelling and numerical simulation of non-Newtonian blood flow in an idealized stenosed artery. Non-Newtonian behavior of blood flow is assumed by Casson and Quemada fluid models. An analysis is performed for four forms of stenosis, 50%, 60%, 70%, and 80%, which are defined by a narrowing of the artery's diameter. The mathematical model for non-Newtonian fluid transport is presented in the form of highly nonlinear coupled partial differential equations. A finite-volume approach is used to solve the system of equations numerically. The solutions are obtained using a hybrid mesh with hexahedron and tetrahedron control volumes. Numerical solutions are validated first with experimental results from the literature for a Newtonian fluid, and then the results are extended to non-Newtonian fluid models. It can be observed that the non-Newtonian nature of the fluid model influences flow dynamics and is a significant aspect to consider for arteries with small diameter. The velocity and pressure drop rise as the degree of stenosis develops. Wall shear is substantially larger in stenotic passages and severity of stenosis is directly related with this increasing behavior.
AtıfScopus32OpenAlex33İncele - Kitap BölümüYalnız künye2025Magnetic energy conversion
Yüzüak, Ercüment; Yüzüak, Gizem Durak; Dinçer, İlker; Elerman, Yalcin
This paper provides a comprehensive and comprehensible analysis of the conversion of magnetic energy in magnetocaloric materials, as well as the application of magnetic refrigeration that relies on the magnetocaloric effect. The magnetocaloric effect (MCE) refers to the phenomenon of cooling or heating that takes place in a magnetic material when an external magnetic field is introduced or removed under adiabatic conditions. This effect also occurs in reverse, when the application or removal of an external magnetic field induces cooling or warming in the material. For a considerable period, the phenomena referred to as “adiabatic demagnetization” has been recognized, wherein the practical use of the magnetocaloric effect (MCE) in magnetic materials is observed. Magnetic materials exhibit the phenomenon known as the magnetocaloric effect close to their critical temperature. The magnetocaloric system exhibits superior environmental friendliness and efficiency compared to conventional refrigeration cycle systems that rely on vapor compression. Magnetic refrigeration is a cooling system that operates by utilizing the magnetocaloric effect. This methodology can be employed to achieve reduced temperatures, including those within the typical operational range of conventional refrigeration systems. In the realm of magnetic and electromagnetic energy conversion, the system's coefficient of performance (COP) attains a theoretical efficiency of 30%–60% of the Carnot cycle. The exploration of magnetic refrigeration is now underway, with a focus on utilizing low magnetic fields in the vicinity of room temperature. The objective is to facilitate the development of commercial devices that employ permanent magnets as the primary source of magnetic field. The utilization of a magnetocaloric heat pump in a magnetic refrigerator is employed as a cooling mechanism, relying on magnetocaloric materials. These materials present a promising substitute for conventional refrigeration technology that relies on compressors. Theoretical investigations have indicated that refrigeration systems utilizing the magnetocaloric effect have the potential to achieve energy efficiency levels that are around 35% higher compared to vapor compression systems. In addition, it should be noted that cooling systems utilizing magnetocaloric materials exhibit reduced noise levels as a result of the lack of a compressor. This particular technological approach involves the utilization of coolants that are water-based, as opposed to the conventional use of gaseous refrigerants.
