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Koleksiyondaki öğeler
- MakaleYalnız künye2022Scopus SJRQ1Heat transfer performance by forced convection of microencapsulated phase change material-latent functional thermal fluid flowing in a mini-channels heat sink
Xu, Qian; Zhu, Lidong; Yan, Xinyu; Yang, Jingbin; Wang, Zhaoxiao; Liu, DingHai; Yang, Gang; Chen, Xingli; Akkurt, Nevzat; Liu, Lin
Conventional single-phase coolants have not been able to meet the high cooling requirements of electronic devices. Microencapsulated phase change material-latent functional thermal fluid (MPCM-LFTF), a solid–liquid two-phase cooling medium, has the dual advantages of active liquid cooling and passive phase change material cooling. However, it also increases the power consumption in the mini-channels, and the cooling efficiency of MPCM-LFTF in practical applications needs to be further studied. A new MPCM-LFTF was prepared by paraffin melamine resin MPCM and base fluid (absolute ethanol and deionized water) in this work. The heat transfer performance and hydrodynamic properties were investigated using the dimensionless wall temperature and friction factor, respectively. The efficiency factor was introduced to evaluate the cooling efficiency of MPCM-LFTF in mini-channels. The experimental results showed that the addition of MPCM increased the viscosity of MPCM-LFTF, which increased the friction factor. MPCM-LFTF with a mass fraction of 15 % had the best effect of temperature control and reduced the dimensionless wall temperature by 40.5 %. However, considering the characteristics of flow resistance and improved heat transfer, MPCM-LFTF with a mass fraction of 10 % had the highest cooling efficiency and the efficiency factor was 57.0 % higher than that of the base fluid.
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İncele - MakaleAçık Erişim2021Scopus SJRQ3On complex Sasakian manifolds
Turgut Vanlı, Aysel; Ünal, İnan; Avcu, Keziban
In this article, we study a class of normal complex contact metric manifold called a complex Sasakian manifolds. This kind of manifolds have a globally defined complex contact form and normal complex contact structure. We define a complex Sasakian manifold by considering the real case and we present general properties. Also, we obtain some useful curvature relations. Finally, we examine flatness conditions for general curvature tensor B.
AtıfScopus3OpenAlex2İncele - MakaleYalnız künye2021DISSEMINATION OF HEAVY METAL CONTAMINATION IN SURFACE SEDIMENTS OF BATLAMA STREAM, GIRESUN, TURKEY
Ustaoğlu, Fikret; Kutlu, Banu; Tepe, Yalçın; Aydin, Handan
The aim of this study is to detect the heavy metal contamination in the sediment of Batlama Stream and to evaluate the anthropogenic effect. Field studies were seasonally carried out in 3 stations between June 2014 and July 2015. In the sampling studies carried out in Batlama Stream, contamination factor (CF), enrichment factor (EF), potential ecological risk factor (Eri), lowest effect level (LEL), geoaccumulation index (Igeo) contamination indicators were used in order to evaluate sediment contamination. In Batlama Stream, average heavy metal level of three stations was detected in mg/dry kg in the sediment as Cr 7.08, Mn 63.62, Fe 858.04, Co 5.47, Ni 4.99, Cu 20.61, Zn 49.60, Cd 0.09, and Pb 20.68. Elements which the sediment has most are Fe, Mn, and Zn. According to EF, Pb was detected as an enriching element. Eri Pb is in the low risk group. In LEL value, the highest Pb average was found as 31. According to Igeo values, Pb is a moderate contaminant. This metal has anthropogenic sources and it is caused by domestic, agricultural, and waste waters. In the elements analysed in Batlama Stream sediment (apart from Pb), it is indicated that it is generally a clean stream and considered reference stream.
AtıfScopus3İncele - MakaleYalnız künye2023Scopus SJRQ2A weighted independence test based on smooth estimation of Kendall distribution
Susam, Selim Orhun; Hudaverdi, Burcu
In this study, we introduce a nonparametric test of independence which is based on a weighted Cramér-von Mises distance of the Bernstein estimate of the Kendall distribution function. We examine the power and the size of the new weighted test and, we compare it with the non-weighted nonparametric tests of independence through a Monte Carlo simulation study. The simulation results indicate that both of the choices of the weights and the polynomial degree has a significant effect on the test power. Finally, the procedure is applied to a dataset on chemical elements in water samples for the purpose of illustration.
AtıfScopus1WoS1OpenAlex1İncele - MakaleAçık Erişim2023Theoretical and Practical Investigation of Stability Performance for Power Regulation in Hydroelectric Power Plants
Kahraman, Gökhan; Işık, Erdem
Hydroelectric power plants are the insurance of the interconnected system in order to provide fast energy to the system compared to other fossil fueled power plants. Hydroelectric power plants control the balance between the energy it supplies to the interconnected system and the pressurized water it uses with a system based on the fully automatic control principle. The quality of the energy supplied to the interconnected system depends entirely on this automatic control mechanism. In this study, mathematical models of the mechanisms that affect the automatic control system during the generation of energy in hydroelectric power plants are formed. Transfer functions of the obtained mathematical models are calculated by laplace transform. With the calculated transfer functions, the responses of the units of a hydroelectric power plant to the change of the amount of energy produced under different operating conditions are determined. The obtained data are compared with the actual conditions in a 1330 MW hydroelectric power plant with 8 Francis turbines. It is seen that the mathematical model and the turbine responses in real conditions are similar. In the calculations made at 115, 125, 135, 145 m. net head, the best stability conditions were obtained at 135 m. In addition, as a result of the calculations obtained under different operating conditions, ideal operating conditions are determined to minimize the fluctuations in energy production.
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İncele - MakaleAçık Erişim2022Scopus SJRQ3Adsorptive removal of nickel ions from wastewater by synthesized a novel biocomposite material and process optimization by response surface methodology
Ince, Muharrem; Ince, Olcay Kaplan; Alp, Hevidar
In the present study, a fixed-bed column study was performed using a novel biocomposite mate-rial, Amanita vaginata immobilized on Amberlite XAD-4 resin, to find out the adsorption behavior of nickel (Ni2+) ions from industrial wastewater. The influence of some important operating conditions including pH (3–7), biocomposite material amount (150–250 mg (XAD-4:Amanita vaginata, 5:1)) influent flow rate (4–8 mL min–1) besides Ni2+ ions initial concentration (20–40 mg L–1) on the uptake of Ni2+ solution were also optimized using a synthetic water solution. A central composite design combined with response surface methodology was utilized to maximize Ni2+ ions removal using A. vaginata immobilized on Amberlite XAD-4 resin as a biocomposite material in a column biosorption process. A mathematical model was derived from the central composite design approach for predicting responses and analysis of variance. Also, for checking model adequacy a lack of fit test was carried out. It was determined that the checked and proposed quadratic model was derived from the experimental design data. The biocomposite material adsorption capacity was calculated as 6.28 mg g–1. A high coefficient of determination (R2 = 0.9887) was presented by analysis of variance. Results confirmed that the amount of adsorbed Ni2+ amount did not change with the increase of the flow rate ratio and dose when the initial concentration of Ni2+ ions increased. The maximum adsorp-tion capacity of biocomposite material was achieved at 6.9 pH, 150.1 mg of biocomposite material amount, 7.8 mL min–1 of solution flow rate, and 39.7 mg L–1 of Ni2+ ions initial concentration. Finally, the developed method was applied to industrial wastewater to determine Ni2+ ions concentrations.
AtıfScopus4WoS4OpenAlex5İncele - MakaleYayıncıda açık erişim2022Scopus SJRQ2Does social support affect menopausal symptoms in menopausal women?
Polat, Filiz; Orhan, Ilksen; Şimşek Küçükkelepçe, Didem
Purpose: To determine the effect of perceived social support of menopausal women on their menopausal complaints. Design and Methods: This descriptive and correlational study was conducted with 505 women. The data were obtained using personal information form, menopause rating scale, and multidimensional scale of perceived social support. Frequency, percentage, t test, analysis of variance Skewness and Kurtosis (±1) and correlation were used in the analysis of the data. Findings: In the study, it was found that there was a positive and significant relationship between menopausal symptoms and social support, and menopausal symptoms decreased as social support increased. Practice Implications: Nurses should provide consultancy for women to increase their social support systems to decrease their menopausal complaints.
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İncele - MakaleAçık Erişim2022Scopus SJRQ2Use of Differential Entropy for Automated Emotion Recognition in a Virtual Reality Environment with EEG Signals
Uyanık, Hakan; Ozcelik, Salih Taha A.; Duranay, Zeynep Bala; Sengur, Abdulkadir; Acharya, U. Rajendra
Emotion recognition is one of the most important issues in human–computer interaction (HCI), neuroscience, and psychology fields. It is generally accepted that emotion recognition with neural data such as electroencephalography (EEG) signals, functional magnetic resonance imaging (fMRI), and near-infrared spectroscopy (NIRS) is better than other emotion detection methods such as speech, mimics, body language, facial expressions, etc., in terms of reliability and accuracy. In particular, EEG signals are bioelectrical signals that are frequently used because of the many advantages they offer in the field of emotion recognition. This study proposes an improved approach for EEG-based emotion recognition on a publicly available newly published dataset, VREED. Differential entropy (DE) features were extracted from four wavebands (theta 4–8 Hz, alpha 8–13 Hz, beta 13–30 Hz, and gamma 30–49 Hz) to classify two emotional states (positive/negative). Five classifiers, namely Support Vector Machine (SVM), k-Nearest Neighbor (kNN), Naïve Bayesian (NB), Decision Tree (DT), and Logistic Regression (LR) were employed with DE features for the automated classification of two emotional states. In this work, we obtained the best average accuracy of 76.22% ± 2.06 with the SVM classifier in the classification of two states. Moreover, we observed from the results that the highest average accuracy score was produced with the gamma band, as previously reported in studies in EEG-based emotion recognition.
AtıfScopus29OpenAlex33İncele - MakaleAçık Erişim2021Scopus SJRQ1Evaluation of non-carcinogenic health risks of thallium in grapevine exposed to mine waters of an abandoned mining region in Turkey
Topal, Murat; Arslan Topal, E. Işıl; Öbek, Erdal
In this study, non-carcinogenic health risks of thallium in grapevine exposed to mine waters of an abandoned mining region in Turkey were evaluated. The values of thallium were investigated in leaves, stems, and roots. Translocation factors (TF) and bioaccumulation concentration factors (BCF) were determined. The maximum thallium value in grapevines (root) was 2.34 ± 0.12 mg/kg. Thallium values in grapevine were stem < leaf < root. The bioconcentration value calculated in our study is higher than 1 showing thallium bioaccumulation from the mine water to grapevines. Translocation factor value is calculated as 1.20. The high total estimated daily exposure dose (TED) in grapevines was determined as 1.10E-02 mg/kg day for children. TEDs values in grapevines were observed as male < female < children, respectively. The maximum HQ risk value for male was observed as 1060 for children. The non-carcinogenic risk values were children > female > male. Hazard index values of thallium in grapevines were ingestion < dietary. As a result, hazard and total hazard index values were > 1 for thallium in grapevines. Therefore, there are non-carcinogenic health risks of thallium in grapevine exposed to mine waters of an abandoned mining region.
AtıfScopus3WoS1OpenAlex2İncele - MakaleYalnız künye2021Scopus SJRQ2Two Medicinal Plants (Alkanna trichophila and Convolvulus galaticus) from Turkey: Chemical Characterization and Biological Perspectives
Mahomoodally, Mohamad Fawzi; Zengin, Gokhan; Sinan, Kouadio Ibrahime; Ak, Gunes; Sadeer, Nabeelah Bibi; Angeloni, Simone; Mustafa, Ahmed M.; Caprioli, Giovanni; Maggi, Filippo; Cakilcioglu, Ugur
The aim of the present study was to quantify selected phenolic compounds, determine antioxidant activity and enzyme inhibitory effects of the aerial parts of Alkanna trichophylla Hub.-Mor. (A. trichophylla) and Convolvulus galaticus Rost.ex Choisy (C. galaticus) extracts prepared by homogenizer-assisted extraction (HAE), maceration (MAC) and infusion techniques. This is the first time such study has been designed to validate the phytochemical composition and bioactivity of these plants. Multivariate analysis was conducted on collected data. Rutin and caffeoylquinic acid derivatives were the most significant compounds in A. trichophylla and C. galaticus, respectively. The highest antioxidant activity of A. trichophylla was mostly exhibited by HAE/methanolic extracts as determined by DPPH, ABTS, FRAP (51.39, 112.70 and 145.73 mg TE/g, respectively) and phosphomolybdenum (2.05 mmol TE/g) assays. However, significant antioxidant activities varied within the extracts of C. galaticus. HAE/methanolic extract of A. trichophylla significantly depressed AChE (2.70 mg GALAE/g), BChE (5.53 mg GALAE/g) and tyrosinase (26.34 mg KAE/g) activities and that of C. galaticus inhibited AChE (2.04 mg GALAE/g), tyrosinase (31.25 mg KAE/g) and α-amylase (0.53 mmol ACAE/g) activities significantly. We concluded that HAE was the most efficient extraction technique as high yield of compounds and promising bioactivities were recorded from extracts prepared. Multivariate analysis showed that types of solvents influenced recovery of compounds and biological activities. This research study can be used as one methodological starting point for further investigation on these plants as all results are clearly promising and open the door to further research challenges such as cytotoxicity evaluation, molecular docking analysis, and more screening of pharmacological actions.
AtıfScopus12OpenAlex10İncele - MakaleAçık Erişim2022Scopus SJRQ1Free convective trickling over a porous medium of fractional nanofluid with MHD and heat source/sink
Lin, Yuanjian; Rehman, Sadique; Akkurt, Nevzat; Shedd, Tim; Kamran, Muhammad; Qureshi, Muhammad Imran; Botmart, Thongchai; Alharbi, Abdulaziz N.; Farooq, Aamir; Khan, Ilyas
Nanofluids are considered as smart fluids that can improve heat and mass transfer and have numerous applications in industry and engineering fields such as electronics, manufacturing, and biomedicine. For this reason, blood-based nanofluids with carbon nanotubes (CNTs) as nanoparticles in the presence of a magnetic field are discussed. The nanofluid traverses the porous medium. The nanofluids move on a vertical plate that can be moved. The free convection heat transfer mode is considered when the heat source and heat fluxes are constant. Convective flows are often used in engineering processes, especially in heat removal, such as geothermal and petroleum extraction, building construction, and so on. Heat transfer is used in chemical processing, power generation, automobile manufacturing, air conditioning, refrigeration, and computer technology, among others. Heat transfer fluids such as water, methanol, air and glycerine are used as heat exchange media because these fluids have low thermal conductivity compared to other metals. We have studied the effects of MHD on the heat and velocity of nanofluids keeping efficiency in mind. Laplace transform is used to solve the mathematical model. The velocity and temperature profiles of MHD flow with free convection of nanofluids were described using Nusselt number and skin friction coefficient. An accurate solution is obtained for both the velocity and temperature profiles. The graph shows the effects of the different parameters on the velocity and temperature profiles. The temperature profile improved with increasing estimates of the fraction parameter and the volume friction parameter. The velocity of the nanofluid is also a de-escalating function with the increasing values of the magnetic parameter and the porosity parameter. The thickness of the thermal boundary layer decreases with increasing values of the fractional parameter.
AtıfScopus13OpenAlex12İncele - MakaleAçık Erişim2022Scopus SJRQ1How Covid-19 pandemic and partial lockdown decisions affect air quality of a city? The case of Istanbul, Turkey
Celik, Erkan; Gul, Muhammet
The world is currently struggling with a new type of coronavirus (2019-nCoV) pandemic that first appeared in Wuhan, China, and then spread to almost all countries. As in other countries of the world, public authorities in Turkey are implementing many preventive and mitigating partial lockdown (PL) actions against the virus's effects. Some decisions and policies implemented before and after March 11, 2020, when the first virus case has been identified, have reduced people and traffic circulation, which has also turned into some improvements in air quality. At this point, this study aims to investigate how this pandemic affects the air quality of a metropolis. A case study of the city of Istanbul, the most affected city with more than half of Turkey's cases, is performed. In our analysis, we observe, compare, and discuss the impact of the COVID-19 pandemic and PL decisions on Istanbul city's air quality. We consider the particulate matter (PM10), sulfur dioxide (SO2), carbon monoxide (CO), nitrogen dioxide (NO2), nitrogen oxide (NO), nitrogen oxides (NOx), and ozone (O3) concentrations. We used data from 19 air monitoring stations (AMSs) and obtained improvements in the air quality for the pandemic period. In summary, the concentration levels in PM10, NO2, NO, and NOx result in a clear decline in pandemic times compared to the normal times in Istanbul. On the other hand, a non-homogenous trend for SO2 and CO concentrations is observed for different AMSs. A partial increase in O2 concentration is obtained in the comparison of before and during the PL period.
AtıfScopus15WoS13OpenAlex22İncele - MakaleAçık Erişim2022Scopus SJRQ3USING OBSTACLE PERFORATION, RECONFIGURATION, AND INCLINATION TECHNIQUES TO ENHANCE THE DYNAMIC AND THERMAL STRUCTURE OF A TOP-ENTRY CHANNEL
Mahdi, Khaled; Bekrentchir, Khalida; Hussein, Ahmed Kadhim; Akgule, Ali; Shanak, Hussein; Asad, Jihad; Akkurt, Nevzat; Menni, Younes
This research is to incorporate three efficient ways that will increase the perfor-mance of baffled heat exchangers. The 1st technique is represented by baffle per-forating to create pores through which secondary streams pass in order to reduce main stream pressure on the flow areas. A 2nd technique represented in redesign-ing the baffle structure by replacing its square edge with the arched edge in or-der to increase the X-velocity to facilitate the flow towards the outlet and reduce the Y-velocity to reduce the values of fluid friction with the solid areas. Finally, a 3rd way was demonstrated by using the inclined baffle model. Reinforcement of the baffle structure allowed for enhanced vortices, increased thermal gradients, and thus a reinforced thermodynamic structure over the entire heat exchanger
AtıfScopus4OpenAlex4İncele - MakaleYalnız künye2023Scopus SJRQ2Effect of auto-exhaust pollution on leaf anatomy and micromorphology of Pistacia vera L.
Açar, Mikail
One of the important causes of air pollution is automobile emissions Automobile exhausts can be toxic and harmful to plants. In light of this, this study aimed to examine the anatomical and micromorphological effects of auto exhaust pollution on Pistacia vera L. (Pistachio), an important agricultural plant. Pistachio leaflet samples taken from heavy traffic areas and rural areas were compared anatomically and micromorphologically. Also, the data were statistically evaluated. As a result of the study, it was seen that there are anatomical and micromorphological differences between the plant in the rural area and the plant in the heavy traffic area in the city center where air pollution and the number of cars are high. In particular, significant differences were detected in the epidermis surface and cuticle structure, trichome cover, stomatal characteristics, as well as mesophyll width, and epidermis anticlinal outer wall width. As a result, the study revealed that the agriculturally important P. vera is affected by pollution anatomically and micromorphologically.
AtıfScopus6WoS6OpenAlex6İncele - MakaleYalnız künye2022Scopus SJRQ3Continuous Flow–Assisted Polyol Synthesis of Citric Acid Functionalized Iron Oxide Nanoparticles
Akkurt, Nevzat; Altan, Cem Levent; Sarac, Mehmet Fahri
The synthesis of nanoparticles by the continuous flow process is of great interest since it allows extensive control over reaction conditions with high precision and provides enhanced production capacity with excellent heat and mass transfer rates at high pressures and temperatures. In this study, iron oxide nanoparticles were synthesized via continuous flow process in combined micro- and milli-sized reactors in the presence of citric acid at variable functional ratios from 1:1 to 1:5. The results illustrated the possibility of continuous production of superparamagnetic magnetite and/or maghemite nanoparticles at the size range of 4.3 to 4.6 nm that exhibit remarkable colloidal stability in triethylene glycol (TEG) and saturation magnetizations up to 52 emu/g. Additionally, the nucleation and growth stages of nanoparticles were found to be unaffected by the presence of citric acid (CA) while an increase in the functional ratio was shown to affect the magnetic properties due to the presence of a non-magnetic layer around the particles. Furthermore, the viability of human lung adenocarcinoma (A549) cell lines was investigated with several concentrations of magnetic nanoparticles, and the biocompatibility of nanoparticles was illustrated at certain particle loadings after 48 h expressing the potential use in biomedical applications.
AtıfScopus9WoS9OpenAlex9İncele - MakaleAçık Erişim2021Scopus SJRQ3Ultrasonic assisted turning of AISI 52100 steel using nanoparticle-MQL method
Aǧar, Salih; Tosun, Nihat
High cutting force and high cutting tool-chip interface temperature occur during machining of high strength materials like AISI 52100 by using conventional turning method and this makes to the difficult machining operation. Besides, in conventional turning (CT) of these materials, which has high abrasion resistance and hardness properties, an additional process such as grinding is required to achieve the desired surface quality. Ultrasonic assisted turning (UAT) method has been widely used in the machining industry in recent years, as it exhibits better surface quality, lower cutting forces, and cutting temperature than the CT method. This paper focused on experimentally and statistically determining the effects of different cutting parameters and cooling conditions (dry and minimum quantity lubrication-MQL) on surface roughness, workpiece surface texture, tangential direction cutting force, and cutting tool-workpiece interface temperature in the machining of AISI 52100 material by using UAT and CT methods. The experimental results revealed that significant improvements determined in the cutting forces and the surface roughness occurred in UAT compared to CT in all the cooling conditions. However, the increasing cutting speeds caused to observe higher interface temperature values in dry turning by the UAT method. Variance Analysis (ANOVA) was carried out to determine the significance grade of independent variables on dependent variables. According to ANOVA results, while the cutting speed is the most important factor on the surface roughness and the cutting zone temperature, and the cooling method is the most important factor on the cutting force. The effects of turning methods on corresponding surface topography, including surface defects, were evaluated. It is determined that in the surface topography analysis, feed marks are the main texture of the workpiece in the CT method while micro-level indentations and protrusions occurred on the workpiece surface in the UAT method.
AtıfScopus14WoS12OpenAlex14İncele - MakaleYalnız künye2022Scopus SJRQ2Detailed Chemical Characterization and Biological Propensities of Malabaila lasiocarpa Extracts: An Endemic Plant to Turkey
Zengin, Gokhan; Zheleva-Dimitrova, Dimitrina; Babacan, Ebru Yüce; Polat, Rıdvan; Çakılcıoğlu, Uğur; Sadeer, Nabeelah Bibi; Costa, Emmanoel V.; Mahomoodally, Mohamad Fawzi; Naviglio, Daniele; Gallo, Monica
This study focused on the biological evaluation and chemical characterization of Malabaila lasiocarpa Boiss. (M. lasiocarpa) (Family: Apiaceae). The phytochemical profile, antioxidant, enzyme inhibitory of the methanolic, aqueous, dichloromethane, hexane extracts were investigated. Based on UHPLC-HRMS analyses, a total of 101 peaks were annotated or identified for the first time in M. lasiocarpa extracts. They include hydroxybenzoic, hydroxycinnamic, acylquinic acids and their glycosides, C- and O-glycosyl and O-diglycosyl flavonoids. In addition, 10 simple mono- and disubstituted coumarins together with 10 furanocoumarins were tentatively annotated. The methanolic extract possessing the highest phenolic (24.36±0.60 mg gallic acid equivalent/g extract) and flavonoid (69.15±0.37 mg rutin equivalent/g extract) content also exhibited the strongest radical scavenging potential against 2,2-diphenyl-1 picrylhydrazyl (21.73±0.42 mg Trolox equivalent/g extract, respectively), and highest reducing capacity (57.81±0.97 and 28.00±0.40 mg Trolox equivalent/g extract, for cupric reducing antioxidant capacity and ferric reducing antioxidant power, respectively). The dichloromethane extract substantially depressed the tyrosinase (73.92±5.37 mg kojic acid equivalent/g extract), α-amylase (0.63±0.01 mmol acarbose equivalent/g extract) and α-glucosidase (0.69±0.02 mmol acarbose equivalent/g extract) enzymes. This study has produced critical scientific data on M. lasiocarpa which are potential contenders for the development of novel phyto-pharmaceuticals.
AtıfScopus6OpenAlex5İncele - MakaleYalnız künye2021Scopus SJRQ1Production of Pectin from Lemon Peel Powder Using Ohmic Heating-Assisted Extraction Process
Çilingir, Seda; Goksu, Ali; Sabanci, Serdal
The ohmic heating process is known as homogeneous, efficient, and rapid heating. In the present study, it was aimed to analyze the extraction of pectin from lemon peel using ohmic heating, to evaluate the specific pectin production coefficient (SPPC, mg/kJ) and compared it with traditional pectin production (TPP). The extraction process was carried out at 3 different temperatures (70–90 °C), 3 different solid:liquid ratios (1:30, 1:40, 1:50 g/ml), 3 different extraction holding times (0–30 min), and a constant pH (pH 2 that adjusted with citric acid). From the results, extraction conditions affected the pectin yield. As the temperature and extraction holding time increased, the pectin yields increased. In general, the 30-min pectin yields of the ohmic heating-assisted extraction (OHAE) process were similar to the pectin yields obtained from the TPP under the same conditions. Performance evaluation of pectin production was made for 90 °C, and energy efficiency was found to be over 69% for 3 different solid to liquid ratios. It has been stated that as an alternative to the TPP method, the OHAE process can be applied.
AtıfScopus50WoS44OpenAlex53İncele - MakaleAçık Erişim2021Scopus SJRQ4Electrochemical Corrosion and Metal Ion Release Protective Efficiency of the Multilayer TaN Coatings on CoCrMo Biomedical Alloy
Aslan, Ali Kemal; Bahçe, Erkan; Güler, Mehmet Sami
CoCrMo alloy is widely used in artificial orthopedic joint applications due to its high mechanical properties. But, high levels of the metal ion release from alloy surfaces cause variable toxic and allergic effects on the patient in vivo use. This case restricts the lifetime of the implant and results in the failure of the artificial joint. In order to enhance the corrosion resistance and to decrease the metal ion release, alloy surface was multilayer-coated by closed field unbalanced magnetron system. The protective efficiency of the coatings was determined by potentiodynamic polarization tests and static immersion tests were performed for 45, 60 and 90 days in the simulated body fluid in order to understand the effect of the coatings on the metal ion release. The metal ion concentrations in the simulated body fluids were determined by using inductively coupled plasma mass spectrometry device. The electrochemical corrosion results showed that the multilayer coatings provided 93 % protective efficiency in terms of corrosion resistance. Multilayer coatings decreased the metal ions release levels significantly, especially Co leaking was decreased approximately 52 times compared to uncoated samples.
AtıfScopus2WoS3OpenAlex1İncele - MakaleYalnız künye2022Scopus SJRQ2Microstructure and corrosion investigation of FeCoCrNiMo0,5(MnAl)0,3 high entropy alloy produced by 316 L stainless steel scrap
Cihangir, Salih; Say, Yakup; Ozkul, İskender; Guler, Omer; Guler, Seval Hale
FeCrCoNiMo0,5(MnAl)0.3 high-entropy alloy (HEA) was manufactured via arc melting process by adding the related metal powders into scrap of 316 L stainless steel for corrosion resistance tests under salt and acid conditions. Cyclic potentiodynamic polarization experiments performed under acidic conditions revealed pre-passivation due to abundance of network modifying metals in HEA composition which was further analyzed by electrochemical impedance spectroscopy. Elemental resolved analysis of leftover solutions was used to compare metal ions released during corrosion. X-ray diffraction analysis indicated the phase change in heat treated HEA samples. Non-heat treated HEA samples can be compared with stainless steel under moderate corrosion conditions and had better hardness results.
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