Sürdürülebilir Kalkınma Amaçları
Yazarlar
- Dertli, Enes(114)
- Kaya, Yunus(48)
- Şahin, Engin(48)
- İspirli, Hümeyra(47)
- Özen, Soner(38)
- Şenay, Volkan(37)
- Pat, Suat(36)
- Kutlu, Naciye(32)
- Artar, Musa(31)
- Can, Zehra(31)
- Korkmaz, Şadan(31)
- Yilmaz, Mustafa Tahsin(31)
- Öner, Erdal(31)
- Bayram, Sinan(30)
- Cuce, Erdem(30)
- Ertugrul, Mehmet(29)
- Hasar, Ugur Cem(29)
- Ecem Bayram, Nesrin(28)
- Mercan, Emin(28)
- Ayata, Ümit(27)
- Bayraktar, Bülent(27)
- Çolak, Murat(23)
- Özdemir, Akın(23)
- Ayazoglu, Rabil(22)
- Cuce, Pinar Mert(22)
- Sert, Durmuş(22)
- Bayram, Ozkan(21)
- Kamiloğlu, Aybike(21)
- Dirican, Ebubekir(20)
- Kadakal, Mahir(20)
- Abdioglu, Murat(19)
- Birinci, Ahmet(19)
- Tozlu, Alperen(19)
- Gerçek, Yusuf Can(18)
- Taylan, Osman(18)
- Cinar, Mehmet(17)
- Gul, Volkan(16)
- Hasar, Ugur C.(16)
- Kadakal, Huriye(16)
- Kara, Yakup(16)
Yayınlar
- MakaleYalnız künye2022Scopus SJRQ2A study on the effects of nanostructure reinforcement on the failure load in adhesively bonded joints after the subjected to fully reversed fatigue load
Akpinar, Salih; Demir, Kübra; Gavgali, Esma; Yetim, Ali Fatih
Today, adhesively bonded joints are frequently used in the space and aviation industries. Joints used in these sectors are generally subject to dynamic loads due to environmental factors. This study experimentally and numerically investigated the static tensile loads of adhesively bonded joints after fully reversed (combination of tensile and compressive) fatigue loading where nanoadhesives–obtained by adding carbon nanostructures into aerospace grade structural adhesive–were used to bond the joints. Single lap joint specimens were produced using a nanocomposite adhesive obtained by adding 1 wt. % graphene, 1 wt. % carbon nanotubes-COOH and 1 wt. % fullerene C60 nanostructures to a DP460 structural adhesive. AA2024-T3 aluminum alloy and carbon fiber-reinforced composites (CFRCs) with a plain weave fabric (0/90°) were used as adherend materials. First, static tensile tests were applied to these joints to obtain their failure loads and then fully reversed sinusoidal fatigue tests were applied under a constant load amplitude, a frequency of 20 Hz and a load ratio of R = −1. Considering the failure loads obtained from the static tensile tests, 106 fully reversed fatigue loading cycles were applied–which was accepted as an infinite life–at 400 N, 800 N and 1200 N load levels. The static tensile failure loads and energy values absorbed of these joints were obtained and the change in the failure loads and energy values absorbed of the joints subjected to fatigue was investigated. The static failure loads of aluminum joints bonded with nanoadhesive and subjected to fully reversed fatigue loading increased by approximately 5% to 17%, depending on the nanostructure type added to the adhesive. Moreover, it was observed that there was an increase in loading of approximately 3% to 20% for the nanostructure reinforced joints obtained by using CFRCs with [0/90]6 stacking sequence.
AtıfScopus24WoS26OpenAlex28
İncele - MakaleAçık Erişim2022Scopus SJRQ2A novel internal curing method for 3D-printed geopolymer structures reinforced with a steel cable: Electro-heating
Gökçe, H.S.; Güngör, O.; Öksüzer, N.
Buildability and structural integrity are the inherent challenges of 3D printed geopolymer structures needed to be overcome. Reinforcing with steel cable ensuring a higher structural integrity of the printed structure can simultaneously improve the buildability due to the heating capability of this component. The controllable instant heating capability of steel cable was achieved by the use of a specific circuit system in the study. As a novel internal curing technique, electro-heating is recommended in the additive manufacturing of steel cable-reinforced geopolymer structures by the authors.
AtıfScopus4WoS3OpenAlex5İncele - MakaleAçık Erişim2022Scopus SJRQ2Assessment of waste-to-energy potential of ELT management: An actual case study for Erzincan
Güngör, Osman; Tozlu, Alperen; Arslantürk, Cihat
End-of-life tires (ELTs) and their decomposition are becoming a major environmental issue in the local region as a result of economic and technological challenges. Despite this, ELT management is gaining popularity as an advanced function for treating tires to obtain char, oil, and gas products using pyrolysis. The main goal of this article is to integrate data from an actual recycling plant with the activities of pyrolysis products and their physical properties in the literature. This article presents energy potentials and basic applications of pyrolysis products as well as advances in the current situation in ELT management in the world. Accordingly, an existing ELT management in Erzincan, Turkey is explained in detail by considering the available energy recovery and material treatment activities. In this plant, which has an installed power capacity of 12 MW, approximately 25 tons of pyrolytic oil, 10.7 tons of pyrolytic gas, 24 tons of carbon black and, 10.4 tons of steel are produced daily. The calorific values of carbon black and pyrolytic oil for the products leaving the pyrolysis plant are close to the values in the literature, which is promising. In the plant, the overall thermal efficiency of the system and the engine is found to be 26.34% and 51.24%, respectively. On the other hand, to supply additional power to the plant utilizing exhaust gas discharged to the atmosphere, some thermodynamic models can be developed; additionally, more rational values can be obtained through thermoeconomic and optimization.
AtıfScopus1WoS2OpenAlex3İncele - MakaleAçık Erişim2022Scopus SJRQ1Grey Zone: A Gap between Heavy and Severe Exercise Domain
Ozkaya, Ozgur; Balci, Gorkem Aybars; As, Hakan; Cabuk, Refik; Norouzi, Mahdi
The aim of this study was to determine a critical threshold (CT) interpreted as “the highest exercise intensity where V̇O2 can be stabilized before reaching 95% of V̇O2max (V̇O2peak)” and compare it with commonly used anaerobic threshold indices. Ten well-trained male cyclists volunteered for this study. Ventilatory threshold (VT) was determined from incremental tests. Multisession constant-load trials were performed to reveal V̇O2max. Mathematically modeled critical power (CP) was estimated through the best individual fit parameter method. Maximal lactate steady state (MLSS) was detected by 30-minute constant-load exercises. The individual CT load of each cyclist was tested by constant-load exercises to exhaustion with +15 W intervals until minimal power output to elicit V̇O2peak. The results showed that work rate corresponding to CT (329.5 6 41.5 W) was significantly greater than that of the MLSS (269.5 ± 38.5 W; p = 0.000), VT (279.6 ± 33 W; p = 0.000), and CP (306.3 ± 39.4 W; p = 0.000), and CP overestimated both VT and MLSS (p = 0.000). There was no significant V̇O2 difference between the 10th and 30th minute of MLSS and MLSS + 15 W exercise (0.36–0.13 ml·min-1·kg-1; p = 0.621). Exercising V̇O2 response of MLSS + 15 W could not exceed the level of 95% V̇O2max (57.02 ± 3.87 ml·min-1·kg-1 and 87.2 ± 3.1% of V̇O2max; p = 0.000), whereas V̇O2 responses greater than 95% of V̇O2max were always attained during exercises performed at CT + 15 W (64.52 ± 4.37 ml·min-1·kg-1 and 98.6 6 1% of V̇O2max; p > 0.05). In conclusion, this study indicates that there is a “grey zone” between heavy and severe exercise domain. This information may play a key role in enhancing athletic performance by improving the quality of training programs.
AtıfScopus21WoS19OpenAlex27
İncele - MakaleAçık Erişim2022Scopus SJRQ1Thermoeconomic analysis of a low-temperature waste-energy assisted power and hydrogen plant at off-NG grid region
Tozlu, Alperen; Kayabasi, Erhan; Ozcan, Hasan
In this study, thermoeconomic analysis of a CO2 power cycle and PEM hydrogen system using ultra-low temperature waste heat from a milk production facility is conducted. In the transcritical CO2 cycle, low-temperature LNG evaporation is used for cooling the condenser to increase the temperature difference enabling low temperature waste heat use. In addition, a PEM electrolyzer produces hydrogen to reduce the LNG requirement at the plant. A CO2-water exchanger has been designed to recover the pasteurized water's excess heat and evaporate the CO2 using Simcenter-Flomaster software. The inlet mass flow rates and outlet temperatures of the heat exchanger were optimized by performing thermoecomic analysis, and the thermal and economic performance of the facility was examined. The power cycle has 14% higher efficiency when LNG is used as the heat sink compared to ambient temperature condensation with an electricity production cost range at 0.05–0.11 $/kWh, and the hydrogen generation cost is between $2.6–5.20 kg−1. It is found that the plant could only be economically feasible when less than 50% of the power produced is used for hydrogen generation. Consequently, the proposed system can co-generate power and on-demand hydrogen in off-NG grid regions with reasonable investment and product costs.
AtıfScopus6WoS6OpenAlex8İncele - MakaleAçık Erişim2022Scopus SJRQ3Research Tendencies of Postgraduate Theses Related to Pre-Service Turkish Teachers/Candidates
Maden, Aslı; Ustabulut, Mete Yusuf
In the study, it is aimed to determine the postgraduate theses related to pre-service Turkish teachers and their candidates and to reveal the research tendencies by analyzing them according to certain characteristics. For this purpose, the distribution of postgraduate theses on Turkish teacher candidates according to year, program type, university, subject, method and design characteristics was examined and thus their tendencies were revealed. This research was designed according to the qualitative research model. In the research, postgraduate theses on Turkish teacher candidates were scanned and the obtained documents were analyzed. As a result of the research, it has been determined that 84 postgraduate theses, 59 of which are postgraduate and 25 are doctoral dissertations, have been written from 2002 to 2022, related to Turkish teacher training and candidates before service. It has been observed that the most theses on the subject were completed in 2019, and these theses were mostly prepared in Gazi, Canakkale Onsekiz Mart and Atatürk Universities in Türkiye. In theses about Turkish teacher training and candidates, writing skills, professional competence, anxiety and attitudes, and self-efficacy perception were the most preferred subjects. In addition, quantitative research models are used more in theses on Turkish teacher training and candidates.
- MakaleAçık Erişim2022Scopus SJRQ3Investigation of biological activities of plant extract and green synthesis silver nanoparticles obtained from Gilaburu (Viburnum opulus L.) fruits
Şahin, Birgütay; Bülbül, Ali Savaş; Çelik, I. Seyfettin; Korkmaz, Nesrin; Karadağ, Ahmet
In this study, biological activities of silver nanoparticles (AgNP) synthesized by green synthesis method using the fruit extract of Gilaburu (Viburnum opulus L.) plant were investigated. The characterization of the synthesized AgNPs was performed by ultraviolet visible region spectroscopy (UV-Vis), Fourier transform - infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. The crystal size was found to be 52.32 nm when the XRD data were calculated with the Debye-Scherrer's equation. The antimicrobial activities of extract and AgNPs were investigated by microdilution and disk diffusion methods. Antibiofilm activities were examined by the crystal violet technique. The cytotoxic effects of the extract and AgNPs against MCF-7 (human breast cancer) and HUVEC (human umbilical vein endothelial cells) cell lines were evaluated by MTT assay. The IC50 values for the HUVEC line were found to be 0.97 mg/mL (AgNP) and 85.24 mg/mL (extract), while the IC50 values for the MCF-7 line were determined as 0.022 µg/mL (AgNP) and 0.021 µg/mL (extract). To our knowledge, this is the first report to comprehensively examine the biological activities of V. opulus L. extract and biosynthetic AgNPs.
AtıfScopus11WoS11OpenAlex10TR Dizin1
İncele - MakaleAçık Erişim2022Scopus SJRQ1Eumelanin protects the liver against diethylnitrosamine-induced liver injury
Altındağ, Fikret; Boğokşayan, Seda; Bayram, Sinan
This study aims to evaluate in vivo protective effects of eumelanin (EU) on diethylnitrosamine (DEN)-induced liver injury. Wistar albino male rats were divided into 6 groups (n = 6), Control, DMSO, DEN, DEN + EU10, DEN + EU15, and DEN + EU20. Animals in the DEN group were injected i.p a single dose of 200 mg/kg DEN, DEN + EU10 group was given 10 mg/kg EU, DEN + EU15 group was given 15 mg/kg, DEN + EU20 group was given 20 mg/kg EU for a week. The results showed that there was no significant difference in vessel volume density between the groups. Inflammatory cell infiltration, hydropic degeneration, and necrotic cells were observed in the DEN group, and these histopathological changes were significantly reduced in all treatment groups. Although there was a low intensity of PAS-positive staining in the DEN groups, moderate staining was observed in the treatment groups. While Caspase-3, PCNA, TNF-α, and IL-6 expressions increased in the DEN group, their expressions decreased in the EU-treated groups. DEN increased AST, ALT, and MDA levels and decreased CAT levels. In particular, the EU10 dose significantly improved these parameters. The present study revealed that eumelanin has protective effects against DEN-induced liver injury.
AtıfScopus9WoS8OpenAlex10İncele - MakaleYalnız künye2022Scopus SJRQ2Improvement of corrosion and stress corrosion properties of magnesium alloys by coating aluminum with the electric arc spray method
Catar, Recep; Altun, Hikmet
In this study, corrosion and stress corrosion behaviors of AZ31, AZ61, and AZ91 magnesium alloys coated with aluminum by the electric arc spray method were investigated in 3.5 wt.% NaCl solution. Structural properties of coated materials were investigated by scanning electron microscopy (SEM), energy dispersive X-ray analysis, and X-ray diffraction. Electrochemical properties were determined using the potentiodynamic polarization method in 3.5 wt.% NaCl solution. Potentiodynamic polarization curves showed that corrosion current density values did not change with coating in aluminum-coated samples by the electric arc spray method. In contrast, corrosion potential value increased toward positive values. Slow strain rate test (SSRT) was used to determine the stress corrosion behavior and stress corrosion indexes (ISCC), ultimate tensile strength (UTS), and elongation of AZ31, AZ61, and AZ91 magnesium (Mg) alloys were determined. As a result of the SSRT, the aluminum coating process decreased significantly the stress corrosion indexes of AZ31, AZ61, and AZ91 Mg alloys. The fracture of surface images was also examined in the SEM, and both intergranular and transgranular stress corrosion cracking were observed in all three alloys.
AtıfScopus6WoS5OpenAlex5İncele - MakaleYalnız künye2022Scopus SJRQ1Bioactive compounds of deep eutectic solvents extracts of Hypericum perforatum L.: Polyphenolic- organic acid profile by LC-MS/MS and pharmaceutical activity
Bayram, Sinan; Kutlu, Naciye; Gerçek, Yusuf Can; Çelik, Saffet; Ecem Bayram, Nesrin
Deep eutectic solvents (DESs) are known as environmentally-friendly solvents that have emerged as an alternative to conventional organic solvents in recent years. In this study, the effects of ten different DESs on the extraction of bioactive components from the Hypericum perforatum were investigated. Total phenolic content, total flavonoid content, phenolic profile (32 phenolics), organic acid profile (52 organic acids), as well as antioxidant and antimicrobial activities of H. perforatum extracts prepared using DESs and ultrasonic-assisted extraction method were determined. Total phenolic, total flavonoid content, and antioxidant activities of extracts were determined between 3.10 ± 0.86–16.64 ± 2.09 mg GA/g, 0.02 ± 0.00–12.29 ± 0.30 mg QE/g, and 8.40 ± 0.50–44.78 ± 2.66 mg TE/g, respectively. DES2 (choline chloride:ethylene glycol) and DES7 (choline chloride:lactic acid) demonstrated higher extraction success than other DESs for extracting phenolics and organic acids, respectively. DESs prepared using organic acid as hydrogen bond donor were found to have an antibacterial effect against all bacterial samples. However, the inhibitory effect against yeast-like fungi was observed in a narrower spectrum. Moreover, the results from principal component analysis also confirmed that the type of solvent used for extraction has a significant influence on the phenolics, organic acid, and other parameters. As a result, it was seen that DES components directly affect the extraction efficiency of target compounds from H. perforatum. This is a first and original report about use of DESs in extracting different bioactive components from H. perforatum.
AtıfScopus33WoS31OpenAlex32İncele - MakaleYalnız künye2022Scopus SJRQ1High-speed treatment of low strength domestic wastewater for irrigation water production in pilot-scale classical, moving bed and fixed bed hybrid MBRs
Tuluk, Banu; Yildiz, Ergun; Nuhoglu, Alper; Tataroglu, Numan Suadi; Gulluce, Ekrem; Cengiz, Ibrahim; Degermenci, Nejdet; Angin, Ilker
To evaluate the treatability of domestic wastewater under conditions of low hydraulic retention time and high organic loadings, 3 pilot-scale automatically controlled membrane bioreactors (MBRs) as classical (C-MBR), moving bed (MB-MBR), and fixed bed (FB-MBR) were established and operated for a total of 268 days. Established pilot plants were compared in terms of treatment performance, membrane fouling, irrigation water criteria, and power consumption values. Results obtained have shown that all three systems were able to achieve more than 93% removal of chemical oxygen demand (COD) in an average hydraulic retention time (HRT) of 1 hour, and MB-MBR and FB-MBR were superior in terms of total nitrogen (TN) and total phosphorus (TP) removals. It has been determined that MB-MBR and FB-MBR are also advantageous in terms of power consumption. Especially it has been found that FB-MBR can produce better quality irrigation water with 40% lower power consumption than C-MBR under the same conditions. It was concluded that biofilm-supported hybrid systems could be a practical application in the fight against increasing water scarcity and global warming, both in obtaining clean water with less power consumption and in protecting human and environmental health.
AtıfScopus16WoS11OpenAlex17İncele - MakaleAçık Erişim2022Scopus SJRQ1Recovery of Polyphenols Using Pressurized Hot Water Extraction (PHWE) from Black Rosehip Followed by Encapsulation for Increased Bioaccessibility and Antioxidant Activity
Kasapoğlu, Kadriye Nur; Demircan, Evren; Gültekin-Özgüven, Mine; Kruger, Johanita; Frank, Jan; Arslaner, Ayla; Özçelik, Beraat
In this work, pressurized hot water extraction (PHWE) of hydrophilic polyphenols from black rosehip fruit was maximized using response surface methodology for simultaneous optimization in terms of extraction yield, total antioxidant capacity, total (poly)phenols, catechin, total monomeric anthocyanins, and cyanidin-3-O-glucoside. Extraction parameters, including temperature (X1: 40–80 °C) and the solvent-to-solid ratio (X2: 10–40 mL/g), were investigated as independent variables. Experimentally obtained values were fitted to a second-order polynomial model, and optimal conditions were determined using multiple regression analysis and analysis of variance. The black rosehip extract (BRE) obtained at optimized PHWE conditions was further encapsulated in biopolymer-coated liposomes and spray dried to enhance its processing and digestive stability. After reconstitution, the fabricated particles had an average size of 247–380 nm and a zeta-potential of 15–45 mV. Moreover, encapsulation provided remarkable protection of the phenolics under in vitro gastrointestinal digestion conditions, resulting in up to a 5.6-fold more phenolics in the bioaccessible fraction, which also had 2.9–8.6-fold higher antioxidant activity compared to the nonencapsulated BRE. In conclusion, PHWE in combination with a biopolymer coating is a potent method for the production of stable and safe edible natural extracts for the delivery of (poly)phenolic compounds in food and dietary supplements.
AtıfScopus20WoS19OpenAlex20İncele - MakaleYalnız künye2022Scopus SJRQ3The Importance of Nutrition and a Balanced Diet in the Elderly during the COVID-19 Pandemic
Esgin, Özge; Erten, Tayyibe
Background: Age is an important risk factor for the mortality rate in the COVID-19 disease, and mostly, hospitalised patients over 60 years with chronic diseases are at high risk of death due to this disease. Along with preventive measures, proper nutrient intake might be helpful in maintaining a healthy state or reduce the severity of the COVID-19 disease in the elderly. Methods: The search was carried out in the PubMed, Scopus, Medline, Google Scholar and Web of Science using the following terms: COVID-19, coronavirus, elderly, elderly nutrition. Results: The requirement for some macro and micronutrients, especially the nutrients that support the immune activity, increases in this disease. During the pandemic, the daily energy requirement for the elderly is 27-30 kcal/kg, while the protein intake is at least 1g/kg, and the ratio of fat and carbohydrate is 30:70 or less than 50:50. The daily intake of vitamin A, B6, B12, C, D, zinc and selenium can also be increased due to their supporting function in the immune system. Probiotics include Bifidobacterium longum MM-2, Lactobacillus plantarum 06CC2, Lactobacillus bulgaricus OLL1073R-1 and Lactobacillus rhamnosus M21, and the consumption of prebiotics in diet enhances the immune function. Additionally, flavonoids, such as baicalin, epigallocatechin gallate, gallocatechin gallate, kaempferol, luteolin, resveratrol and quercetin, improve immunity by reducing oxidative stress in the elderly. Conclusion: Adequate and balanced nutrition diet should be applied during the pandemic; in addition to this, micronutrient deficiencies should also be overcome in the elderly at every stage of life. Nuron&The novel coronavirus, called SARS-CoV2 (Severe Acute Respiratory Syndrome CoronaVirus-2), emerged at the end of 2019 in China and was announced as a global pandemic by the World Health Organisation (WHO) on March 11th, 2020 [1]. It has spread more rapidly than previous coronavirus outbreaks, such as SARS-CoV and MERS-CoV (Middle East respiratory syndrome coronavirus); thus, it has affected most countries [2, 3]. By August 2021, WHO reported globally 206.958.371 confirmed cases of COVID-19, including 4.357.179 deaths [4]. Since SARS-CoV-2 enters the cells through angiotensin-converting enzyme 2 (ACE2), it binds to the ACE2 membrane of alveolar epithelial cells and attacks firstly the respiratory system [5].
AtıfScopus1WoS1OpenAlex1İncele - MakaleYayıncıda açık erişim2022Scopus SJRQ1Time-dependent fresh properties characterization of 3D printing engineered cementitious composites (3DP-ECC): On the evaluation of buildability
Zhou, Wen; McGee, Wes; Zhu, He; Gökçe, H. Süleyman; Li, Victor C.
Failure of the structure due to poor buildability is a major concern in 3D printing of cementitious materials. Evaluation of buildability based on fresh material properties and print parameters is of significance. In this paper, the buildability of printable engineered cementitious composites was investigated and quantified at the material and the structural scale. Fresh ECC material showed excellent load capacity and deformation resistance at the material scale, therefore preventing material failure of the bottom layers, as confirmed by constant shear rate tests and incremental loading tests. To predict vertical deformation of a 3DP structure, a time-dependent strain-stress model of printable ECC was proposed and validated based on the green strength evolution of the material and the buildup rate of the designed structure. At the structural scale, the approach of predicting critical height at self-buckling failure based on stiffness evolution was validated by printing a straight wall and a cylinder structure.
AtıfScopus56WoS46OpenAlex52İncele - MakaleYalnız künye2022Scopus SJRQ3Comparison of Statistical Methods to Graphical Method in Precipitation Trend Analysis, A Case Study: Coruh Basin, Turkey
Hırca, Tuğçe; Eryılmaz Türkkan, Gökçen
It is a known fact that the precipitation characteristics will become irregular as a result of climate change resulting from global warming. Trend analysis is one of the most effective methods of observing the effects of climate change on precipitation. This study compares the changes in precipitation with traditional trend analysis methods and graphical method (divided into subcategories using the Z-Score Index). Some preliminary analyzes (missing data estimation, homogeneity check, autocorrelation, and removal of the autocorrelation), which are lacking in many studies in the literature, have been performed. In this context, the monthly total precipitation data of the precipitation stations belonging to the Coruh Basin, one of the most important basins of Turkey, for the period 1972–2011 were used. As a result of the study, it was determined that all the stations’ data were homogeneous, and 92% of them were at the Class A level. While 100% trend is determined in Innovative Trend Analysis in total annual precipitation, this rate was just 40% at Mann–Kendall and Spearman's rho at 95% confidence. An increasing trend was determined in the “high” group of total spring precipitation at all stations.
AtıfScopus5WoS4OpenAlex5İncele - MakaleAçık Erişim2022Scopus SJRQ1Broadband, Stable, and Noniterative Dielectric Constant Measurement of Low-Loss Dielectric Slabs Using a Frequency-Domain Free-Space Method
Hasar, Ugur C.; Kaya, Yunus; Ozturk, Gokhan; Ertugrul, Mehmet; Korasli, Celal
A broadband, stable, and noniterative free-space method is proposed for dielectric constant ϵr′ determination of low-loss dielectric slabs from reflection-only measurements through simple calibration standards (reflect and air). It is applicable for dispersive samples and does not require thickness information. Simulations of nondisperive and dispersive samples are performed to validate our method. Dielectric constant measurements of polyethylene and polyoxymethylene samples (9-11 GHz) are carried out to examine the accuracy of our method.
AtıfScopus41WoS37OpenAlex35İncele - MakaleAçık Erişim2022Scopus SJRQ1Identification of Lactic Acid Bacteria (LAB) from pre-fermented liquids of selected cereals and legumes and characterization of their exopolysaccharides (EPS)
Yalmanci, Dilara; İspirli, Hümeyra; Dertli, Enes
Recently, isolation of Lactic Acid Bacteria (LAB) strains with important technological functions from plant-based products has gained special interests related with the increment of consumer preferences to the plant-based fermented products. In this context, various cereals and legumes that were underwent to germination or not were selected for the isolation of exopolysaccharide (EPS) producer LAB strains in this study. Following genotypic discrimination, 17 distinct strains belonging to Weissella confusa, Weissella cibaria, Lactococcus lactis subsp. hordniae, Leuconostoc lactis, Lactiplantibacillus plantarum and Leuconostoc mesenteroides were identified from pre-ferment liquids. Two strains Weissella confusa W-16 and Leuconostoc lactis GW-6 were the highest EPS producers, and their EPSs were further characterized. The 1H and 13C NMR results revealed that both strains were dextran producers containing (1 → 3)-linked α-D-glucose units as branches with 9.2% and 6.9% levels for Weissella confusa W-16 and Leuconostoc lactis GW-6, respectively. FTIR analysis also supported the dextran structure and demonstrated the functional groups within the dextrans. A high level of thermal stability was observed in both dextrans detected by TGA and DSC analysis. Both dextrans were in amorphous characteristics determined by XRD analysis. These findings demonstrate that pre-fermented liquids of different cereals and legumes can be source of technologically important LAB strains with EPS production characteristics.
AtıfScopus41WoS41OpenAlex42İncele - MakaleAçık Erişim2022Scopus SJRQ3IoT-TDMA: A performance evaluation of TDMA scheme for wireless sensor networks with Internet of Things
Kosunalp, Selahattin; Kaya, Yunus
This article focuses on the design and implementation of an improved version of TDMA scheme for wireless sensor networks (WSNs) exploiting the Internet of Things (IoT) phenomena. The main motivation behind this work is to create an environment for WSNs to benefit from IoT opportunities. An extensive review of the state-of-the-art medium access control (MAC) approaches proposed for IoT is carried out underlying their basic principles and features. An adaptation of TDMA strategy, called IoT-TDMA, is proposed to enhance the channel performances particularly throughput and latency. To test the performance of IoT-TDMA practically, a low-cost node hardware with the capability of Internet connection is essentially designed. IoT-TDMA has been implemented on real-world highly scalable single-hop and multi-hop topologies. Performance results indicate significant improvements in terms of channel throughput and end-to-end delay in comparison to a recently proposed efficient MAC scheme.
AtıfScopus17OpenAlex18İncele - MakaleYalnız künye2022Scopus SJRQ1Effect of using hybrid nanofluids as a coolant on the thermal performance of portable thermoelectric refrigerators
Mert Cuce, Pinar; Cuce, Erdem; Guclu, Tamer; Shaik, Saboor; Alshahrani, Saad; Ahamed Saleel, C.
This study investigated the effect of using hybrid nanofluids as a refrigerant in portable thermoelectric refrigerator applications on thermal performance. For this purpose, a cooling cabinet with an internal volume of 36 L was designed and produced. Then, the Peltier assembly, with a water-cooled block attached to its hot surface, was placed in this cooling cabinet from the middle of its front cover. With the help of a refrigerant, the heat was removed from the Peltier's hot surface and transferred to the atmosphere via a water-to-air heat exchanger. Hybrid nanofluids prepared with Al2O3-TiO2-SiO2 and nanoparticles and water were used as the refrigerant in the system. To evaluate the thermal performances of these hybrid nanofluids, the tests were repeated using water without added nanoparticles as the reference case. According to the results obtained from the experimental study, it was observed that in all cases, tests using nanofluids gave better results than the reference cases. In addition, it was determined that the efficiency obtained from the system increased as the nanoparticle ratio in the mixture increased in all cases. Despite significant improvements in cooling cabinet and cooled product temperatures in hybrid nanofluids, the COP values of the systems are slightly lower than in the reference case due to the Peltier effect. Considering the difference between the first and last temperatures of the cooled cabinet, the greatest improvement compared to the reference situation was determined as 30.3 % in the case of loaded state conditions and in the case of using 2 % Al2O3-TiO2-SiO2-Water nanofluid. For the unloaded conditions, this value was obtained as 25.1 % in the case of using 2 % Al2O3-TiO2-SiO2-Water nanofluid. On the other hand, for the unloaded condition, the lowest COP value was calculated as 0.47 and 0.45 when Al2O3-TiO2-SiO2-Water nanofluid was used in 1 % and 2 % mass fraction, respectively. For the loaded condition, this value was found as 0.48 in the case where 1 % Al2O3-TiO2-SiO2-Water and 0.47 in the case where 2 % Al2O3-TiO2-SiO2-Water nanofluid was used.
AtıfScopus27WoS21İncele - MakaleYalnız künye2022Scopus SJRQ1Global boundedness of solutions to a quasilinear parabolic-parabolic Keller-Segel system with variable logistic source
Ayazoglu, Rabil
This paper deals with the higher dimension quasilinear parabolic-parabolic Keller-Segel system involving a source term of variable logistic type ut=∇⋅(ϕ(u)∇u)−∇⋅(ψ(u)∇υ)+g(x,u), −Δυ=−υ+u, in (x,t)∈Ω×(0,T), subject to nonnegative initial data and homogeneous Neumann boundary condition, where Ω is a smooth and bounded domain in RN (N≥1) and g∈C1(Ω‾×[0,∞)) function satisfies g(x,s)≤ηsk(x)−μsm(x),s>0 with g(x,0)≥0, x∈Ω and η≥0,μ>0 are constants, k,m are measurable functions with 1<k−:=ess infx∈Ωk(x)≤k(x)≤k+:=esssup k(x)x∈Ω<+∞, 2≤m−:=ess infx∈Ωm(x)≤m(x)≤m+:=esssup m(x)x∈Ω<+∞. Positive functions ψ,ϕ∈C2([0,∞)) satisfy νsq≤ψ≤χsq and ϕ≥σsp with p,q∈R, ν,χ,σ>0 when s≥0. It is proved that if q=m−−1 (critical case) and [Formula presented] then there exists a classical solution which is global in time and bounded. Moreover, if q∈(k+−1,m−−1), we obtain that there is a classical solution of the above system uniformly in time bounded without any restrictions on m− and μ.
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