Sürdürülebilir Kalkınma Amaçları
Yazarlar
- Gul, Muhammet(82)
- Akkurt, Nevzat(67)
- Güler, Ömer(66)
- Baskonus, Haci Mehmet(62)
- Bulut, Hasan(60)
- Tekin, H.O.(52)
- ALMisned, Ghada(49)
- Yucesan, Melih(43)
- Yildirim, Numan(42)
- Yildirim, Nuran Cikcikoglu(38)
- Paksoy, Mehmet Yavuz(36)
- Serdar, Osman(36)
- Zengin, Gokhan(36)
- Ince, Muharrem(34)
- Celik, Erkan(33)
- Benzer, Fulya(32)
- Kocabaş, Mehmet(30)
- Sulaiman, Tukur Abdulkadir(30)
- Tanyol, Mehtap(29)
- Yildirim, Ozal(28)
- Aslan, Naim(26)
- Kök, Mediha(26)
- Özkul, İskender(26)
- Ates, Mehmet(25)
- Danabas, Durali(25)
- Kutluyer, Filiz(25)
- Can, Erkan(24)
- Kutlu, Banu(23)
- Onat, Onur(23)
- Demir, Veysel(22)
- Erten, Fusun(22)
- Guler, Omer(22)
- Say, Yakup(22)
- Güler, Seval Hale(21)
- Yaman, Mehmet(21)
- Baykal, Duygu Sen(20)
- Sançar, Taylan(20)
- Susam, Selim Orhun(20)
- Cakilcioglu, Ugur(19)
- Orhan, Cemal(19)
Yayınlar
- MakaleYalnız künye2023Scopus SJRQ2Ag seed layer effects on SnO2 thin films for triboelectric devices
Yüzüak, E.; Yüzüak, G. Durak
Materials with triboelectric properties are critical to boosting the efficiency of triboelectric nanogenerators (TENG) by gathering power from waste force and mechanical movement. In this study, we explored tin-oxide (SnO2) thin films with silver (Ag) seed layer properties for friction surfaces at TENGs. Investigation of the triboelectric behavior of semi-conductor/polymer coupling structured TENGs formed by thin films with and without Ag seed layer after heat treatment was explored by X-ray diffraction (XRD), electron microscopy (SEM), atomic force microscopy (AFM), and semi-logarithmic current-voltage measurements. Similar structural characterization studies were carried out in indium tin oxide coated polyethylene terephthalate film (PET/ITO) for the polymer friction layer. Semiconductor/polymer coupling structured TENG efficiency was evaluated in contact-separation mode and the output voltage-current was enhanced to 80 V, 4 μA, and 210 μW of output power calculated by depositing a SnO2 thin film on an Ag seed layer, respectively. Our findings offer a different perspective for synthesizing the semi-conductor/polymer coupling structured TENGs for promising applications in a range of application technologies.
AtıfScopus2WoS2OpenAlex3
İncele - MakaleAçık Erişim2023Scopus SJRQ1Investigation of surface morphology, optical properties and the gamma radiation effect on selenium coated glass substrate containing rare earth oxide
Taşgin, Yahya; Kanca, Muhammed Sait; Kök, Mediha
In this study, in order to add different properties and functions to inorganic amorphous glasses, the applicability and effects of the thin film coating produced by thermal evaporation method were examined by metallographically imaging the effects of 3%–5% CeO2 and Tm2O3 rare earth elements (REE) oxide added to selenium to change the morphology of the glass surface. As a result of the study, it has been proved that CeO 2 and Tm2O3 added to selenium can be coated by thermal evaporation method with AFM images taken from the glass surface and metallographic analyses (SEM, EDX, Mapping). The lowest roughness value was observed in 95Se–5CeO2 coating glass substrate. In all coatings, selenium, which is the main sample, was found to be active, and XRD measurements showed that the thin films were formed by agglomeration on the (101) plane. According to UV-VIS measurements, the lowest optical band energy range was observed in the 95Se–5CeO2 coating.
AtıfScopus11WoS10OpenAlex12İncele - MakaleYalnız künye2023Scopus SJRQ2Detection of hateful twitter users with graph convolutional network model
Utku, Anıl; Can, Umit; Aslan, Serpil
Today, hate speech is widespread and persistent in various forms on social networking platforms, targeting different minority groups. These attacks can be carried out using various factors such as racial, religious, gender, and physical disability, etc. Considering the number of people and their interactions, social networks are the most important channels through which these discourses spread. The social network structure is considered a set of nodes and edges and is very suitable for the graph structure. The multidimensional structure of social networks carries social network data from Euclidean space to non-Euclidean space. In non-Euclidean space, the graph structure is used to represent data effectively. In this respect, solving the hate speech problem with graph-based methods in a complex dimensional space can produce more impressive results. In this study, a powerful method based on the Graph Convolutional Network (GCN) model, which is rarely used in this field, was proposed for the detection of hateful Twitter users in social networks. Well-known machine learning methods were used to measure the performance of this method. According to the results obtained, the proposed GCN model gave the most successful result.
AtıfScopus15WoS10OpenAlex16İncele - MakaleAçık Erişim2023Scopus SJRQ2Fabrication of hydroxyapatite-based nano-gold and nano-silver-doped bioceramic bone grafts: Enhanced mechanostructure, cell viability, and nuclear abnormality properties
Demirel, M.; Aslan, N.; Aksakal, B.; Arslan, M.E.
In this study, nano-gold (nAu) and nano-silver (nAg) were doped at the molar ratios of Molar5–Molar30 to the Hydroxyapatite (HAp)-based bioceramic bone graft synthesized by the sol–gel method. The effects of nAu and nAg on structural, mechanical, cell viability, and nuclear abnormality of the synthesized bioceramic grafts were evaluated. The chemical and morphological properties of the bone grafts after production were examined through XRD and SEM–EDX analyses and mechanical tests. To determine the biocompatibility of the bone grafts, cell viability tests were performed using human fibroblast cells. In the cytotoxicity analyses, only HAp and HAp-nAu5 grafts did not show toxicological properties at any concentration, while HAp-nAg5 among the nAg-containing grafts gave the best results at the 200–100 μg/mL concentrations and showed significant cytotoxicity in human fibroblast cells. The other nAu-containing grafts showed toxicological properties in the concentration range of 200–50 μg/mL and nAg-containing grafts in the concentration range of 200–100 μg/mL against the negative control. The micronucleus (MN) analyses showed that the lowest total MN and L (lobbed) amounts, while the lowest total N (notched) amount, was obtained from the only HAp graft. It was found that the nAg-doped bone grafts gave higher total MN, L, and N amounts compared to the nAu-doped bone grafts. Furthermore, while the mean nuclear abnormality (NA) values of all grafts gave close results, the highest values were again obtained from the nAg-doped bone grafts.
AtıfScopus7WoS6OpenAlex9
İncele - MakaleAçık Erişim2023Scopus SJRQ3WEAR AND ADHESION PROPERTIES OF MULTILAYER Ti/TiN, (/TiC)/ TiCN/ TaN THIN FILMS DEPOSITED ON Ti13Nb13Zr ALLOY BY CLOSED FIELD UNBALANCED MAGNETRON SPUTTERING
Aslan, Ali Kemal; Bahçe, Erkan
Ti13Nb13Zr alloy stands out as an alternative to Ti6Al4V alloy for orthopaedic joint implant applications due to its low modulus of elasticity, high mechanical properties, high corrosion resistance, high biocompatibility and low modulus of elasticity, as well as con-taining no cytotoxic elements. In this study, Ti13Nb13Zr alloy was coated with TiN/TiC/TiCN/TaN multilayer thin films by pulsed-dc CFBUMS method to increase wear resistance and improve surface properties. Characterization of the deposited films were con-ducted by XRD, SEM, AFM, pin-on-disk, progressive scratch experiments. As a result, it is observed that all the coatings enhanced the tribological properties of the Ti13Nb13Zr alloy surface. The 20-layer TiN/TiC/TiCN/TaN multilayer coatings gave the best results for wear resistance and adhesion properties. Enhancing the interlayer number resulted in increased wear and adhesion resistance. In addition, it was determined that using TiC instead of TiN in the interlayers gave higher results regarding adhesion, wear, and mechanical properties.
AtıfScopus1WoS1OpenAlex1İncele - MakaleAçık Erişim2023Scopus SJRQ1Orbitrap Mass Spectrometry-Based Profiling of Secondary Metabolites in Two Unexplored Eminium Species and Bioactivity Potential
Babacan, Ebru Yuce; Zheleva-Dimitrova, Dimitrina; Gevrenova, Reneta; Bouyahya, Abdelhakim; Balos, Mehmet Maruf; Cakilcioglu, Ugur; Sinan, Kouadio Ibrahime; Zengin, Gokhan
The study aimed at the metabolite profiling and evaluation of antioxidant and enzyme inhibitory properties of methanol extracts from flowers, leaves, and tubers of unexplored Eminium intortum (Banks & Sol.) Kuntze and E. spiculatum (Blume) Schott (Araceae). A total of 83 metabolites, including 19 phenolic acids, 46 flavonoids, 11 amino, and 7 fatty acids were identified by UHPLC-HRMS in the studied extracts for the first time. E. intortum flower and leaf extracts had the highest total phenolic and flavonoid contents (50.82 ± 0.71 mg GAE/g and 65.08 ± 0.38 RE/g, respectively). Significant radical scavenging activity (32.20 ± 1.26 and 54.34 ± 0.53 mg TE/g for DPPH and ABTS) and reducing power (88.27 ± 1.49 and 33.13 ± 0.68 mg TE/g for CUPRAC and FRAP) were observed in leaf extracts. E. intortum flowers showed the maximum anticholinesterase activity (2.72 ± 0.03 mg GALAE/g). E. spiculatum leaves and tubers exhibited the highest inhibition towards α-glucosidase (0.99 ± 0.02 ACAE/g) and tirosinase (50.73 ± 2.29 mg KAE/g), respectively. A multivariate analysis revealed that O-hydroxycinnamoylglycosyl-C-flavonoid glycosides mostly accounted for the discrimination of both species. Thus, E. intortum and E. spiculatum can be considered as potential candidates for designing functional ingredients in the pharmaceutical and nutraceutical industries.
AtıfScopus15OpenAlex11İncele - MakaleYalnız künye2023Scopus SJRQ1Latent heat thermal energy storage in a shell-tube design: Impact of metal foam inserts in the heat transfer fluid side
Ghalambaz, Mehdi; Sheremet, Mikhail; Raizah, Zehba; Akkurt, Nevzat; Ghalambaz, Mohammad
The improvement of heat transfer in latent heat thermal energy storage (LHTES) system is a crucial task. In the current study, the impact of diverse metal foam (MF) layer arrangements on heat transfer fluid (HTF) within a shell-tube LHTES is explored. Six distinct cases (A-F) with varied MF coverage percentages and layer dimensions were assessed. The local thermal non-equilibrium model was utilized to take into account the PCM and MF temperatures. The finite element method was used for solving the partial differential equations. The impact of MF configurations and inlet pressures (250 Pa, 500 Pa, and 750 Pa) on the thermal energy storage/release was addressed. Cases A-C, featuring a 50 % MF concentration, exhibit shorter melting times than Cases D–F, with decreasing MF concentrations. A higher MF concentration improves the melting process due to increased thermal conductivity and lower thermal resistance on the HTF side. Cases D–F, with a centralized MF layer and decreasing concentrations from 25 % to 6.25 %, display progressively shorter melting times, suggesting that a lower MF concentration leads to more efficient melting. Solidification times also decrease with increasing inlet pressures across all cases. Reynolds numbers, influenced by average HTF tube outlet velocity, vary substantially across cases and inlet pressure differences. Cases A-C demonstrate similar Reynolds numbers for each inlet pressure difference, while Cases D–F show a more pronounced increase in Reynolds numbers as the MF layer is reduced and flow resistance drops. Cases A (50 % MF layer) and F (6.5 % MF layer) provide the quickest charging and discharging times due to their unique combination of MF layer properties and inlet pressures. The study highlights the need to consider MF layer composition and inlet pressure when designing optimal LHTES systems for efficient energy storage/release.
AtıfScopus11WoS10OpenAlex11İncele - MakaleYalnız künye2023Scopus SJRQ2Does surgery cause anxiety, stress and fear in geriatric patients?
Karabulut, Neziha; Gürçayır, Dilek; Abi, Özlem; Kızıloğlu Ağgül, Beyzanur; Söylemez, Nilgün
Background: Because of physiological changes in geriatric patients, their surgical process differs from that of young adults. In this regard, the perioperative period is an extremely risky time for geriatric patients. The present study examined preoperative fear, anxiety, and perceived stress levels as well as the factors affecting them in elderly patients prior to surgical intervention. Methods: This study adopted a cross-sectional descriptive design. The study sample consisted of geriatric patients (n = 407) scheduled for elective laparoscopic cholecystectomy in a research and training hospital in northeast Turkey. Data were collected by the researchers using the personal information form, Perceived Stress Scale (PSS-10), Surgical Fear Questionnaire (SFQ) and Anxiety Specific to Surgery Questionnaire (ASSQ). In the data analysis, descriptive statistics, the t-test in independent groups, one-way analysis of variance (ANOVA), correlation analysis and Bonferroni tests for post hoc analyses were used. Results: On the PSS–10, the mean score was higher for the 75-and-older age group, single patients, patients with a disease requiring medication, and those who had previously undergone surgery (P < 0.05). On the ASSQ, the mean score was lower for patients aged 65–69, university graduates, patients without children, and those without a disease requiring medication (P < 0.05). On the SFQ, the mean score was higher for the 75-and-older age group, primary school graduates, and single patients (P < 0.05). Conclusion: It was determined that being single, having a chronic disability, and advancing age had an effect on the patients' surgery-specific anxiety, perceived stress, and fear of surgery. Long-standing chronic diseases can negatively affect both stress and anxiety levels of individuals.
AtıfScopus14WoS13OpenAlex13İncele - MakaleYalnız künye2023Scopus SJRQ2Engineering Properties of Geopolymer Mortars Containing Industrial Steel Shavings
Gülmez, Nihan; Koçkal, Niyazi Uğur
The purpose of using waste materials is to prevent the unnecessary use of resources and to reduce the amount of waste. Geopolymer, developed as an alternative to cementitious materials, prevents the depletion of natural resources and saves a large amount of energy. This paper presents the effect of waste steel shavings on the improvement of physical and mechanical properties of geopolymer mortars. For this purpose, geopolymer mortars were produced by using two binder types [slag (BFSb) and silica fume] as well as steel shavings in five different replacement percentages (0%, 2.5%, 5%, 7.5% and 10%) by volume instead of aggregate. A series of experiments on geopolymer mortars were carried out to determine properties such as bulk density, water absorption, apparent porosity, sorptivity coefficient, splitting tensile strength, flexural strength and compressive strength. Results showed that steel shavings recovered from metal processing and forming sector were highly effective at improving engineering properties of geopolymer mortars. Furthermore, although replacement of 20% by volume of BFSb with silica fume improved properties of geopolymer mortar, it was observed that the use of silica fume at higher ratios reduced mechanical properties by increasing porosity and sorptivity of BFSb-based geopolymer mortars.
AtıfScopus1OpenAlex1İncele - MakaleAçık Erişim2023Scopus SJRQ3Rotor Field-Oriented Control of Doubly Fed Induction Generator in Wind Energy Conversion System
Omac, Zeki; Erdem, Irfan
In this study, robust and high-performance vector control of a rotor side converter (RSC) was performed for stability and efficient operation doubly fed induction generator (DFIG) based on the variable speed wind turbine (VSWT). The mathematical model of the DFIG is simulated in the computer. Amplitude and frequency of the voltage in the DFIG were controlled for different values of load and variable speeds. In the experimental study, a DFIG-based wind turbine system was set up in the laboratory. The field position of the stator was detected from stator voltages by a phase-locked loop (PLL) circuit. The rotor position was measured with an incremental encoder connected to the rotor shaft of the DFIG. The angular position of the slip was calculated by the difference between the rotor and the stator field positions. The frequency and amplitude of rotor currents were determined with the angular position of slip. To generate output voltages of converter feeding rotor windings, the space vector pulse width modulation (SVPWM) technique was used. In the experimental study, the RSC was controlled with the DS1103 board. The prepared experiment set was tested at different operating speeds.
AtıfScopus4WoS3OpenAlex4
İncele - 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.
AtıfScopus103OpenAlex101İncele - 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 - 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 - MakaleAçık Erişim2023Scopus SJRQ3Effect of Spectrogram Parameters and Noise Types on The Performance of Spectro-temporal Peaks Based Audio Search Method
Koseoglu, Murat; Uyanik, Hakan
Audio search algorithms are used to detect the queried file in large databases, especially in multimedia applications. These algorithms are expected to perform the detection in a reliable and robust way within the shortest time. In this study, based on spectral peaks method, an audio fingerprint algorithm with a few minor modifications was developed to detect the matching audio file in target database. This method has two stages as the audio fingerprint extraction and matching. In the first stage, fingerprint features are extracted from spectral peaks on the spectrograms of audio files by hash functions. This state-of-art technique reduces the processing load and time considerably compared to traditional methods. In the second stage, fingerprint data of the queried file are compared with the data created in the first stage in the database. The algorithm was demonstrated, and the effect of spectrogram parameters (window size, overlap, number of FFT) was investigated by considering reliability and robustness under different noise sources. Also, it was aimed to contribute to new audio retrieval studies based on spectral peaks method. It was observed that the variation in the spectrogram parameters significantly affected the number of matchings, reliability and robustness. Under high noise conditions, the optimal spectrogram parameters were determined as 512 (window size), 50% (overlap), 512 (number of FFT). It was seen in general that the algorithm successfully detected the queried file in the database even in high noise conditions for these parameters. No significant effect of music genre was observed.
AtıfScopus9WoS6OpenAlex11TR Dizin1İncele - MakaleYalnız künye2023Scopus SJRQ1An integrated hybrid MCDM approach to evaluate countries’ COVID-19 risks
Mete, Suleyman; Yucesan, Melih; Gul, Muhammet; Ozceylan, Eren
To enable planning and early reaction efforts, it is important to identify the nations most at risk from COVID-19's health and humanitarian effects, which could exceed present national response capabilities. INFORM COVID-19 Risk Index developed by European Commission is one of the initiatives to meet the aforementioned need. However, the Index has 40 conflicting and comprehensive indicators (e.g., health system capacity, hygiene, vulnerability) and different countries that lead to a need for multicriteria decision-making (MCDM) approaches. This paper offers an integrated MCDM approach with two phases to re-assess the countries' COVID-19 risks based on INFORM COVID-19 Risk Index. In the first phase, the 40 indicators are prioritized using the Entropy-based multi-choice best-worst method (MC-BWM) to provide multiple viewpoints for the preferences values. In the second phase, 29 countries from different geographical regions are ranked using the COPRAS (Complex Proportional Assessment) method. Applying these three methods together on the COVID-19 risk assessment of countries is the most significant novelty for the relevant literature. The proposed approach has undergone a thorough comparative evaluation with the released INFORM COVID-19 Risk Index, and recommendations are provided based on different scenario analyses.
AtıfScopus21WoS16OpenAlex18İncele - MakaleAçık Erişim2023Scopus SJRQ1Detailed investigation of zinc coating behaviours in various deep eutectic solvents
Cihangir, Salih; Ryder, Karl S.; Unal, Asuman
Determining the optimum conditions of a metal coating is significant for its possible applications in many fields. The present work described the electrodynamic process of zinc coating from six different deep eutectic solvents (DESs), especially type-III DES systems prepared with a quaternary ammonium salt and hydrogen bond type. Non-reversible processes without oxidation were found in DES systems prepared with choline chloride and zinc nitrate salts, and also, propylene glycol and zinc nitrate salts, termed as type-II and type-IV, respectively. The most attracted type-III DES prepared by a mixture of 1 molar choline chloride and 2 molar ethylene glycols, commercially known as Ethaline (E200), were examined for its electronucleation and possible reactions for zinc electrodeposition. For the first time, the Pt working electrode was investigated under high-resolution optical microscopy to visualize the in-situ morphology change during oxidation and reduction in E200. Furthermore, the morphological change during the anodic dissolution of zinc was also investigated in situ under a high-resolution microscope. It was found that insoluble species forming during anodic dissolution blocks the surface. Bulk electrolysis was performed in these solvents to investigate the formed zinc nucleates' morphological differences. XRD analysis was performed to differentiate the crystal planes of each deposition obtained from six DESs. It was found that the type-II and type-IV DESs consisting of zinc nitrates revealed zinc hydroxy nitrate dominated zinc deposition, which can be helpful in various applications.
AtıfScopus14WoS11OpenAlex15İncele - MakaleAçık Erişim2023Scopus SJRQ3The biosorption of Co(II) by Homalothecium sericeum from aqueous solutions under batch conditions: response surface methodology optimization and Daphnia magna bioassay
Tanyol, Mehtap; Korkmaz, Volkan; Yildirim, Numan; Erguven, Gokhan Onder; Ayhan, Nagihan Karaaslan; Alatas, Mevlut
In the present work, Homalothecium sericeum biomass was used for removal of Co(II) from aqueous solution. The effects of process parameters (contact time, biosorbent amount, and initial Co(II) con-centration) on the response (Co(II) % removal) were investigated using a batch adsorption system optimized with response surface methodology/central composite design method. Under optimized conditions the maximum Co(II) removal efficiency achieved is 94.07% at an initial Co(II) concentration of 2.05 mg/L, a H. sericeum amount of 0.34 g/50 mL, and a process time of 36.09 min. In this study, the toxicity of the medium after biosorption carried out under optimized conditions was also tested with Daphnia magna bioassay. When mortality results with D. magna were evaluated, although a removal efficiency of 94.07% was obtained after biosorption, this was not sufficient to reduce mortality of D. magna.
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