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Koleksiyondaki öğeler
- MakaleYalnız künye2023Scopus SJRQ2Graphene nanoplatelet-reinforced high entropy alloys (HEAs) through B4C incorporation: structural, physical, mechanical, and nuclear shielding properties
Gul, Ali Oktay; Kavaz, Esra; Basgoz, Oykum; Guler, Omer; ALMisned, Ghada; Bahceci, Ersin; Guler, Seval Hale; Tekin, H.O.
This study aims to explicate the diverse roles of high entropy alloys within nuclear environments. The study extensively investigates the impact of B4C on the structural, physical, mechanical, and nuclear shielding properties of synthesized high-entropy alloys (HEAs) comprising FeNiCoCrW, GNP, and B4C. The aim is to explore the monotonic effects of B4C on the behavioural changes of the HEAs. The present study initially investigates the internal morphology and structural characteristics of the produced composites through the utilization of X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The determination of coefficient of friction values is obtained via wear testing, wherein the values are measured as a function of the sliding distance. The shielding properties of nuclear radiation are determined through the experimental setups for gamma-ray and neutron radiation. The sample encoded as G2, which incorporates both B4C and GNPs as reinforcing agents, exhibits the most noteworthy mechanical properties among the samples that were examined. The findings of our study indicate that augmenting the concentration of B4C has a significant impact on the efficacy of nuclear radiation shielding. The present study infers that the B4C produced within the framework of GNPs plays a significant role in enhancing the overall characteristics of HEAs. This is particularly noteworthy in the context of nuclear applications, where HEAs are being examined as a prospective constituent of forthcoming nuclear reactors. Moreover, B4C serves as a versatile instrument in scenarios, where there is a need to enhance mechanical and nuclear shielding properties across a spectrum of radiation energies.
AtıfScopus15OpenAlex16
İncele - MakaleYalnız künye2024Scopus SJRQ2Alexithymia and Forgiveness Levels of Forensic Psychiatric Patients
Polat, Hatice; Karakaş, Sibel Asi; Erçel, Şeyda; Taşci, Gülay
The current cross-sectional study was performed to examine levels of alexithymia and forgiveness in forensic psychiatric patients. Data were collected between March 2022 and August 2022 at a high-security forensic psychiatric hospital affiliated with a city hospital in Turkey. A personal information form prepared by the researchers, the Toronto Alexithymia Scale, and the Heartland Forgiveness Scale were used to obtain data. Participants comprised 132 forensic psychiatric patients who agreed to participate in the study. A significant negative correlation was found between alexithymia and forgiveness levels of participants (p < 0.01, r = –0.259). In other words, as alexithymia levels increased, participants were found to be less forgiving. In addition, results suggest that forensic psychiatric patients are susceptible to alexithymia and higher levels of forgiveness. Determining forgiveness and alexithymia levels of forensic psychiatric patients will contribute to the structuring of care to be offered to these patients.
AtıfScopus1
İncele - MakaleYalnız künye2023Scopus SJRQ1Evaluation of container port sustainability using WASPAS technique using on type-2 neutrosophic fuzzy numbers
Kaya, Sema Kayapinar; Kundu, Pradip; Görçün, Ömer Faruk
According to the common opinion in the literature, the sustainability of container ports is a tremendously complex topic owing to the maritime sector's excessively dynamic form and many highly complex, predictable and unpredictable uncertainties in this industry. The current paper proposes two powerful, practical, inspiring approaches to fill these gaps. It proposes a novel type-2 neutrosophic fuzzy numbers (T2NFNs) based Delphi method to determine the criteria logically and optimal and extends the WASPAS technique based on the T2NFNs for evaluating the alternatives. The current paper presents practical managerial implications that many stakeholders can consider, such as port authorities, ship owners, logistics service providers, governments, and local authorities, when making strategic and managerial decisions. In addition, the results of a comprehensive sensitivity analysis performed to test the robustness and applicability of the model approve the validity of the proposed T2NFN-based integrated approach.
AtıfScopus20WoS16OpenAlex24İncele - MakaleYalnız künye2024Scopus SJRQ2Evaluation of effect of boric acid on thermoplastic starch: Morphological, mechanical, barrier, and optical properties
Yoğurtçu, Hakan; Gürler, Nedim
In this study, starch was modified with different amounts of boric acid, and the degree of substitution of the synthesized compounds at different temperatures and times was determined by Fourier transform infrared (FTIR) and titration methods. The degrees of substitution in both methods showed similar tendency. Optimum conditions were determined, and thermoplastic starch (TPS) and boric acid (B) films were prepared by casting method using glycerol as plasticizer. The morphological properties of the films were studied by scanning electron microscope-energy dispersive spectrometry (SEM-EDS). According to the FTIR results, it was observed that the B-O and B-O-C stretching vibrations increased when the amount of boric acid increased. The tensile strength, water barrier (swelling capacity, solubility, and water vapor permeability), and optical properties of samples were investigated. The swelling capacity, solubility, and water vapor permeability of the films decreased with the addition of 0.5% boric acid to the starch, but the highest tensile strength was achieved. The tensile strength for TPSB0.5% increased compared to control group TPS. In addition, the film showed the highest transparency. Thermoplastic film containing 0.5% boric acid can be used as a packaging material due to its improved mechanical and water barrier. Highlights: The thermoplastic starch and boric acid composite were successfully produced. The presence of boric acid was confirmed by energy dispersive spectrometry (EDS). The degree of substitution was determined by two different methods. Transparency increased with the addition of boric acid. Tensile strength improved with boric acid content.
AtıfScopus26WoS25OpenAlex27İncele - Kitap BölümüYalnız künye2023Organizational change models in practice: The case of michelin group
Uyan, Umut
In a competitive business environment, it is vital that firms consider implementing techniques to cope with constant change to remain competitive and survive. Most change initiatives, however, suffer from several difficulties and are often hampered by resistance, primarily caused by fear of adopting new practices or concern about competence. As a result, such initiatives could result in unintended consequences. In fact, they might result in irreversible situations, impairing the dynamics of an organization. Michelin Shanghai underwent an organizational change initiative to enhance its competitiveness. The initiative resulted in significant improvements in the company's productivity and profitability as well as increased employee satisfaction. The main objective of the study is to understand the organizationalchange dynamics of Michelin Shanghai Co. The chapter also attempts to evaluate challenges encountered during the process and critically analyze the leadership approaches that were applied by Mr. Ballarin (plant manager of Michelin Co.) based on related theories.
AtıfScopus1OpenAlex1İncele - BildiriAçık Erişim2024A New Hybrid CNN Model for Abnormal Behaviour Detection in Smart Campus
Yilmazer, Merve; Karakose, Mehmet; Ay, Berhan Turku
Security and monitoring systems are provided through video cameras in public places such as universities, hospitals, cinemas and theater halls. In smart campuses created by the integration of various sensors and digital technologies, there are many video cameras indoors and outdoors in the campus areas to ensure the safety of students, academics, administrators and visitors. Examining the images recorded with these video cameras in terms of security and detecting abnormal behaviours requires a long time and effort. In this study, a new hybrid convolutional neural network (CNN) model is proposed to detect abnormal behaviors occurring in smart campus areas. In the proposed method, firstly, the features of the UTI public dataset, which includes various student behaviors, are extracted with the hybrid use of InceptionV3 and MobileNetV2 deep transfer learning models. The extracted features of the images were combined and classified by converting them into a single feature vector. 6 different behavior classes, 3 of which are normal and 3 of which are abnormal, have been classified and detected with 92.7 % accuracy. Experimental results show that the proposed method for abnormal behavior detection produces more efficient results than other methods in terms of feature extraction, accuracy and computational costs.
AtıfScopus2OpenAlex1İncele - BildiriAçık Erişim2025Toplam Elektron Içeriǧi ve Uzay Iklim Verileri Kullanilarak Transfer Öǧrenme ile Deprem Öncüllerinin Analizi
Uyanik, Hakan; Şentürk, Erman; Köküm, Mehmet; Özçelik, Salih Taha Alperen; Akpinar, Muhammed Halil; Şengür, Abdulkadir
The stress changes occurring in the Earth's crust before earthquakes may cause some anomalies in the ionosphere and cause significant changes in the Total Electron Content (TEC) and Space Climate (SCC) parameters. The analysis of these changes offers a significant potential in the detection of earthquake precursors. In this study, the analysis of earthquake precursors was performed using TEC and UC data and the effectiveness of transfer learning and machine learning techniques was investigated. Features were extracted from five-day TEC and UC data using a pre-trained Multi-Input One-Dimensional Convolutional Mixer Network (ÇG-TB-EMA) and these features were classified with different machine learning algorithms. Within the scope of the study, earthquakes with a magnitude of Mw≥6.0 that occurred during the low and high solar activity periods of the 24th solar cycle were analyzed. The earthquakes were selected from the Far East region between 10°S-45°N latitudes and 120°E-160°E longitudes, where intense seismic activity is observed. Experimental studies have shown that during the low solar activity period, support vector machines (SVM) and artificial neural networks (ANN) models exhibited the highest performance with 96.04% accuracy and 96.08% F1 score, respectively. During the high solar activity period, the classification success decreased slightly, and SVM and ANN models achieved the best results with 90.28% accuracy and 89.86% F1 score. These findings reveal that the effect of solar activity on ionospheric variables should be taken into account in earthquake precursor detection. For future studies, long-term analyses are recommended to better understand the effects of solar activity.
- MakaleAçık Erişim2024Scopus SJRQ2Hysteresis gap-shrinking and structural effects of minor Al and Ti modifications on binary CuAl-based high-temperature shape memory alloys
Karaduman, Oktay; Özkul, İskender; Aksu Canbay, Canan
Cu-based shape memory alloys (SMAs), except for exhibiting shape recovery, superelasticity, and high damping, are desirable because these smart materials have higher electrical and thermal conductivity and much lower prices than NiTi SMAs. However, they also have some downsides in mechanical strength and brittleness (mostly stemming from their coarse grain structure) and thermal instability. Therefore, adding some grain refining elements to these SMAs to improve their shape memory effect (SME), and thermal, structural, and mechanical properties is a widespread and simple way that significantly affects their martensitic phase transitions, structure, and mechanical properties. One of these grain-refining elements is titanium. Its thermal conductivity is lower than those of Cu and Al elements and has a low solubility in Cu-matrix. Besides the effects of small Al variations, the use of minor amounts of titanium in binary CuAl-base alloys can show impressive effects on all characteristics of these shape memory alloys, such as shape memory effect properties, martensitic transformation kinetics parameters, and microstructural features. In this research work, CuAlTi ternary high-temperature shape memory alloys (HTSMAs) with new compositions were produced by the arc melting method without a complicating use of Mn or Ni components in usual ternary CuAlMn and CuAlNi shape memory alloys. Thermal analyses of the prepared samples of the alloys were investigated by using differential scanning calorimetry (DSC) and differential thermal analysis (DTA) measurements. In contrast, x-ray diffraction (XRD) test results and optical micrographs were used for analyzing the structure of the alloy samples. The effect of different amounts of low soluble and grain refining Ti element on the binary CuAl alloy system was investigated.
AtıfScopus2WoS2OpenAlex2İncele - MakaleYalnız künye2024Scopus SJRQ2A fuzzy Bayesian network risk assessment model for analyzing the causes of slow-down processes in two-stroke ship main engines
Başhan, Veysi; Yucesan, Melih; Gul, Muhammet; Demirel, Hakan
This paper presents a risk assessment approach for analyzing the causes of malfunction-related main engine slowdowns. A fuzzy Bayesian Network-based methodology is used to assess the factors contributing to the engine’s slow-down processes. The model addresses the complexity and uncertainty inherent in maritime operations with fuzzy sets where numerous interrelated factors can affect engine performance, and the Bayesian network to capture probabilistic dependencies. It considers various potential causes of the slow-down of ship engines that the manufacturer provides. Results demonstrate the model's ability to identify the influential factors leading to engine slow-down events and quantify the overall risk. Integrating fuzzy logic and Bayesian Networks comprehensively assesses relevant risk factors. It enables maritime stakeholders to manage engine performance and improves operational safety proactively. Findings can inform decision-makers, enabling the implementation of targeted maintenance strategies, fuel quality control measures, and crew training programs in the maritime industry.
AtıfScopus19WoS17OpenAlex18İncele - MakaleYalnız künye2024Scopus SJRQ3Simultaneous features of ternary hybrid nanoparticles on thermal radiative flow configured by Darcy–Forchheimer porous surface
Nasir, Saleem; Sirisubtawee, Sekson; Akkurt, Nevzat; Ali, Ishtiaq; Gul, Taza; Juntharee, Pongpol
Due to its remarkable thermodynamic development in various engineering sciences, the dispersion of nanostructures in classical base liquids is receiving greater attention from researchers and scientists. In light of the aforementioned inspirations, the suggested research is associated with using a water-based ternary-hybrid nanofluid that contains three unique nanostructures, silicon dioxide, titanium dioxide and aluminum oxide to optimize the heating process in science and engineering. In this situation, the influence of a chemically reactive magneto-hydrodynamics (MHD) Darcy–Forchheimer ternary hybrid composites transport involving nonlinear radiation across an exponentially permeable stretched surface is highlighted with the model's physical initial and boundary constraints. The simulation of the heat expression also includes the impacts of nonlinear thermal radiations, energy supply, energy dissipation and magnetic force. Furthermore, the interpretation of Buongiorno's theory involves spontaneous and thermophoresis diffusions. Entropy analysis is explained using the second law of thermodynamics. We converted the model framework for fluid movement, energy and mass transfer (together with ternary hybrid nanofluid characteristics) into self-similar nondimensional differential equations, that were then further analytically evaluated by using the homotopy asymptotic method (HAM) technique via Mathematica software. The acquired results are illustrated numerically and graphically to study the behavior of fluid flow, heat, concentration distribution, drag force, rate of heat and mass transfer for various emergent components to gain scientific comprehension. With the growing values of magnetic, porosity and Forchheimer number, the nature of the velocity profile goes down.
AtıfScopus10OpenAlex11İncele - MakaleYalnız künye2024Scopus SJRQ1Synthesis, characterization and application of cross-linked functional terpolymer through epoxy group as sorbent for extraction of cadmium from waters and foods: Multivariate optimization
Yılmaz, Ersen; Boztuğ, Ali; Ul Haq, Hameed; Boczkaj, Grzegorz; Altunay, Nail
The purpose of this study was to develop a selective sorbent for cadmium ions (Cd(II)) enrichment in orbital shaker assisted solid phase microextraction (OS-SPME) from different aqueous and food samples. A maleic anhydride-styrene-glycidyl methacrylate (MA-St-GMA) terpolymer was synthesized and characterized in detail. Experimental variables of sample preparation step were optimized using a central composite design (CCD). The final determination step was performed using flame atomic absorption spectroscopy (FAAS). The MA-St-GMA sorbent exhibited a high adsorption capacity (195.9 mg g−1) for the Cd(II) ion. The developed method under optimal conditions provides satisfactory performance and a significant improvement compared to other protocols available in the literature. The linear range and detection limit of the method is 0.1–130 ng mL−1 and 0.03 ng mL−1, respectively. The robustness, intraday/interday precision, selectivity, and accuracy of the method were investigated. To further validate the method, a dedicated series of analysis was performed using certified reference materials (CRMs). This part of the study confirmed the applicability of the method for routine analysis. The OS-SPME-FAAS method was validated using water and food samples. Relative standard deviations and recovery for real-world samples were in ranges 1.7–2.2 % and 95.5–98.5 %, respectively. As a result, the MA-St-GMA sorbent showed that it could quantitatively extract Cd(II) ions from aqueous solution.
AtıfScopus9WoS8OpenAlex9İncele - MakaleYalnız künye2025Scopus SJRQ2Assessment of seismic fragility of reinforced concrete buildings retrofitted with steel bracing elements: A numerical study
Tam, Gürkan; Yön, Burak
In this study, the effectiveness of reinforcement with steel diagonal elements in a reinforced concrete building was investigated. A typical reinforced concrete building with ground floor+4 floors was designed for the numerical study. All column dimensions were 400×400 mm, all beam dimensions were 250×500 mm, transverse reinforcement spacing in column and beam elements was 100 mm and floor heights were 3 meters. The existing building was strengthened with X steel diagonal elements and two models were obtained. Nonlinear static pushover and incremental dynamic analyses of the buildings were performed. 11 earthquake records were used for incremental dynamic analyses. The acceleration amplitudes of these records were increased from 0.1 g to 1.0 g by 0.1 g and the analyses were performed. In order to model the nonlinear behaviour, lumped plastic hinges were assumed at the ends of the structural elements. As a result of nonlinear static pushover and incremental dynamic analyses of the buildings, capacity curves, maximum responses, inter-storey drifts, hysteretic curves at the ends of selected columns and damage patterns were obtained. Fragility curves were created by considering the damage levels in the buildings. According to the results, the average inter-storey drifts of the building strengthened using X steel diagonal elements decreased by approximately 90% compared to its current condition for 1.0 g PGA, while the damage probability and vibration period were also significantly reduced. In addition, the base shear force encountered by the strengthened building increased more than 4 times compared to its current condition.
AtıfScopus11WoS8İncele - MakaleAçık Erişim2025Scopus SJRQ3Effect of polymer modification on bitumen rheology: A comparative study of bitumens obtained from different sources
Özdemir, Ahmet Münir; Yalçln, Beyza Furtana; Yllmaz, Mehmet
The rheological and mechanical properties of bituminous binders vary significantly depending on the crude oil source. Consequently, the response of binders from different sources to polymer modification also differs. This study compares the rheological performance of B160/220 penetration-grade binders sourced from the Turkey-Batman and Iraq-Lanaz refineries, modified with styrene-butadiene-styrene (SBS), the most widely used polymer additive. To evaluate high-temperature performance, performance grade and frequency sweep tests were conducted using a dynamic shear rheometer. In addition to experimental assessments, the rheological behavior of the binders was analyzed using the Christensen-Anderson, Cross, and Carreau-Yasuda models. Time-temperature superposition principle master curves were generated to characterize their viscoelastic behavior. Zero shear viscosity (ZSV) values were determined using the Cross and Carreau-Yasuda models to examine the impact of polymer modification on binder viscosity. The findings indicate that the initial rheological properties of bitumen significantly influence its response to SBS modification. For instance, the G∗/sin δvalue increased by up to 199% at 64°C with 4% SBS addition, while the softening point rose by 9.5°C compared to unmodified binders. Modelled ZSV values showed more than a sevenfold increase in some cases, especially in Iraqi binders. On the other hand, at -18°C, the m-value dropped to 0.282 in the B-SBS4 binder, indicating a potential risk of low-temperature cracking. While polymer modification improved the rheological properties of both bitumen types, its effectiveness varied depending on the source.
AtıfScopus8WoS8OpenAlex7İncele - MakaleYalnız künye2024Scopus SJRQ3Assessing the Chemical Composition, Antioxidant and enzyme Inhibitory Effects of Pentapleura subulifera and Cyclotrichium glabrescens Extracts
Nilofar, Nilofar; Zengin, Gokhan; Acar, Mikail; Bouyayha, Abdelhakim; Youssra, Aalilou; Eldahshan, Omayma; Fayez, Shaimaa; Fahmy, Nouran
The Lamiaceae family, encompassing diverse plant species, holds significant value in food, medicine, and cosmetics. Within this family, Pentapleura subulifera and Cyclotrichium glabrescens, relatively unexplored species, were investigated for their chemical composition, antioxidant capacity, and enzyme-inhibiting effects. The chemical composition of hexane, methanolic, and aqueous extracts from P. subulifera and C. glabrescens were analyzed using LC-ESI-MS/MS and the non-polar hexane fraction was investigated via GC-MS. The antioxidant potential of the extracts was determined through radical scavenging, reducing power and metal chelating assays. Additionally, inhibitory activity against six enzymes – acetylcholinesterase (AChE), butyrylcholinesterase (BChE), tyrosinase, amylase, and glucosidase – was examined. The aqueous extract of P. subulifera and the methanolic extract of C. glabrescens exhibited elevated phenolic content at 129.47 mg gallic acid equivalent (GAE)/g and 55.97 mg GAE/g, respectively. Chemical profiling of the constituents of the two plant species resulted in the identification of a total of twenty compounds. The majority of which belonged to flavonoids and quinic acid derivatives, primarily concentrated in the methanol and aqueous extracts. Among all antioxidant assays, the aqueous extracts of P. subulifera demonstrated superior antioxidant activity, with the highest recorded activity of 404.93 mg trolox equivalent (TE)/g in the cupric reducing antioxidant capacity (CUPRAC) test. Meanwhile, the hexane extract of C. glabrescens exhibited the highest AChE inhibitory activity at 2.71 mg galanthamine equivalent (GALAE)/g, followed by the methanol extract of P. subulifera at 2.41 mg GALAE/g. These findings unequivocally establish the notable antioxidant and enzyme inhibitory activity of P. subulifera and C. glabrescens extracts, underscoring their potential as a source of valuable natural antioxidants.
AtıfScopus15OpenAlex14İncele - MakaleYalnız künye2023Scopus SJRQ2Investigation of Leaching Kinetics of Molybdenum from MoO3 Concentrate in Ammonia–Ammonium Nitrate Solutions
Karacahan, Mehmet Kayra
MoO3 is a widely accessible foundation material and the primary compound used to produce numerous molybdenum products. The ore was first roasted, and the leaching behavior of concentrated molybdenite mineral was assessed. The optimal conditions for the leaching process were identified in the second step, and in a subsequent stage, the process' kinetics were assessed. Ammonia and ammonium nitrate concentration were used as independent variables in the trials, and the central composite design approach was used to analyze the results. At the conclusion of the tests, the optimum concentrations of ammonia and ammonium nitrate were found to be 2.42 mol/L and 1.86 mol/L, respectively. On the rate at which molybdenum leached from MoO3, the influences of temperature, stirring speed, solid-to-liquid ratio, and particle size were investigated. It was found that the leaching rate increased when temperature and stirring speed increased, along with decreasing the solid-to-liquid ratio and particle size. Leaching efficiency of molybdenum (93%) such as temperature 20 °C, 1.859 mol/L ammonium nitrate concentration, 2.419 mol/L ammonia concentration, solid/liquid ratio 6/100 g/mL, stirring speed 400 rpm, and average particle size 0.115 mm optimum conditions have been achieved. The kinetic study proposed a mathematical model for the leaching process, which revealed that the leaching kinetics matched the Avrami model. This process' activation energy was determined to be 22.66 kJ/mol. Calcium molybdate is used in various fields, such as construction, transportation, anti-corrosion pigments, and flame retardants. Graphical Abstract: [Figure not available: see fulltext.]
AtıfScopus8WoS7OpenAlex9İncele - MakaleYalnız künye2023Scopus SJRQ1Acrylamide formation in apple juice concentrates during storage
Aktağ, Işıl Gürsul; Gökmen, Vural
This study investigated the acrylamide formation in model systems, laboratory-scale produced apple juice concentrates obtained from different stages of process, and commercial apple juice concentrates at different Brix levels during the storage. Changes in the concentrations of reducing sugars, asparagine, 5-hydroxymethylfurfural, 3-deoxyglucosone, and acrylamide were monitored. In addition, Schiff bases of 3-deoxyglucosone and 5-hydroxymethylfurfural with asparagine were confirmed using high-resolution mass spectrometry in order to understand the contribution of intermediates to acrylamide formation. The results revealed that acrylamide formed in both acidic-aqueous model systems and laboratory-scale apple juice concentrates during production. The concentrations of 3-deoxyglucosone, 5-hydroxymethylfurfural, and acrylamide increased significantly (p < 0.05) with the increase in Brix levels whereas asparagine levels decreased in commercial apple juice concentrates during storage. The concentration of acrylamide reached at the maximum level of 0.30 ± 0.02 µmol/kg dry matter in 70°Bx of the concentrates. The findings showed that long-term storage of apple juice concentrates at high Brix levels contributes the acrylamide formation even in unsuitable systems such as acidic and high moisture medium. The confirmation of Schiff base of 3-deoxyglucosone and 5-hydroxymethylfurfural with asparagine demonstrated that the acrylamide formation was attributed to the accumulation of intermediates leading to the conversion of asparagine to acrylamide.
AtıfScopus9WoS8OpenAlex9İncele - MakaleYalnız künye2023Scopus SJRQ1Analysis of the mechanical characteristics and plasticity-hazardous zones development of natural gas pipeline under overload
Zheng, Qiang; Shu, Zekai; Yang, Gang; Zhang, Hui; AKKURT, Nevzat; Guan, Ben; Chen, Weiwang; Xu, Qian; Zang, Yong; Ding, Yulong
The problem of natural gas pipeline overload failure is of great significance, and the development law of critical mechanical properties of pipelines is of great importance to the safety design of natural gas pipelines. This study establishes a three-dimensional finite element computational model of the pipeline that integrates the changes in axial and circumferential mechanical characteristics, and uses the yield strength, safety factor and ellipticity indexes as criteria to dimensionless the axial depth and circumferential angle of the plastic zone to explore the characteristics of the plastic damage stage of the pipeline. By solving the plastic hazardous zones based on the safety factor, the applicability of the dimensionless parameters is extended to investigate the development laws of the hazardous zones and the correlation mechanism between failure criteria and hazardous zones. The results show that as the ground load increases, the pipeline deformation gradually develops into the plastic stage (P = 16 MPa) and then goes through three deformation stages. With the increase of safety factor, the change trend of the proportion of stage I in the whole loading process decreases to 4 %, the change trend of the proportion of stage III increases significantly to 52 %, while the proportion of stage II shows a change trend of decreasing and then increasing, the proportion of this stage ranges from 30 % to 38 %. Based on the law of variation of axial ellipticity of pipeline section, a high-risk section of pipeline was identified in the range of 0–2 m from the point of maximum local compression strain. The results of the study can serve as a basis for accurate evaluation of the safety status of natural gas pipelines under overload.
AtıfScopus3WoS3OpenAlex3İncele - EditoryalYalnız künye2025Scopus SJRQ4Preface
Castillo, Oscar; Çuvalcıoğlu, Gökhan; Tuğrul, Feride
- MakaleAçık Erişim2023Scopus SJRQ3Morpho-structural and compressive mechanical properties of graphene oxide reinforced hydroxyapatite scaffolds for bone tissue applications
Fidan, Ferzan; Aslan, Naim; Koç, Mümin Mehmet
Hydroxyapatite (HA) is a unique material that has the potential to be used to replace bones and teeth in the field of orthopedics and dentistry since HA exhibits quite similar biological and chemical characteristics to human bone. Hydroxyapatite ceramics are bioactive materials used to repair damaged human tissue. The pores in the porous hydroxyapatite ceramics provide a mechanical interlock, enabling a solid bond and fixation between the implant and bone. In this study, 0.5wt%, 1wt%, and 1.5wt% graphene oxide (GO) reinforced porous HA structures were obtained using the space-holder method to increase the strength of hydroxyapatite with low mechanical strength. NaCl was used as a spacer, and PEG 400 as a binder. Scaffold structures with 40% porosity rates were sintered at 1000 °C under vacuum. Finally, a compression test was applied to the samples which were previously analyzed by SEM, EDS and XRD. The compressive strengths of 0.5%, 1%, and 1.5% graphene oxide reinforced porous HA samples were determined between 8.04 and 31.14 MPa. The highest compressive strength was recorded as 31.14 MPa in the 1% GO added sample, and the lowest compressive strength was recorded as 8.04 MPa in the 1.5% GO added sample. In addition, it was understood that the mechanical properties did not increase regularly with the increase of graphene oxide reinforcing.
AtıfScopus4OpenAlex3
İncele - MakaleAçık Erişim2024Scopus SJRQ4Oxidative and physiological effects of carvedilol, a beta–blocker, in Daphnia magna; [Efectos oxidativos fisiológicos del carvedilol, un betabloqueante, en Daphnia magna]
Seker, Engin
Carvedilol is a beta–blocker. Beta–blockers affect the heart and circulation. carvedilol is used to treat heart failure and hypertension. Although this substance has effects in humans and some animals, its effect on the physiological and antioxidant status of daphnids is unknown. The aim of this study was to determine the effect of carvedilol doses (0, 0.125, 0.45 and 0.90 mg·L-1) on physiological activities (heart rate, postabdominal paw activity and thoracic limb movements) and oxidative stress. In Daphnia magna; malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), total glutathione (GSH) and glutathione S transferase (GST) markers were examined. The activity of physiological parameters in D. magna exposed to all carvedilol concentrations was found to be lower than in the control group, and the differences were statistically significant (P<0.01). Application of carvedilol to D. magna resulted in lower GSH content in all groups throughout the experimental period. MDA, SOD, CAT and GST activity were improved. These findings indicate that carvedilol causes physiological and biochemical changes in D. magna. Daphnia species have great potential to provide valuable insights into the mechanisms of human medicine. More comprehensive research is needed on this subject.
