Compression after Impact and Charpy Impact Characterizations of Glass Fiber/Epoxy/MWCNT Composites

Özgür Demircan,Kemal Kadıoğlu,Pınar Çolak,Erdinç Günaydın,Mustafa Doğu,Neslihan Topalömer,Volkan Eskizeybek 한국섬유공학회 2020 Fibers and polymers Vol.21 No.8

In this study, glass fiber/epoxy resin/multi-walled carbon nanotubes (MWCNTs) were used to fabricate hybridcomposites with biaxial warp-knitted fabrics. The biaxial warp-knitted fabrics were grafted with various amounts ofMWCNTs and the hybrid composites were fabricated using the resin transfer molding (RTM) method, subsequently. Thefabricated samples were subjected to compression after impact and Charpy impact tests. The hybrid composites exhibitedhigher compression after impact modulus and strength with 26 % and 17 % compared to the samples without nanotubes,respectively. Moreover, the MWCNTs integrated specimens showed 17 % improvement of Charpy impact strength againstspecimens without carbon nanotubes in 0odegree direction. Fracture surface analysis revealed lower number of cracks andshorter crack propagation lengths in the MWCNTs reinforced specimens. The improvement in mechanical properties of thehybrid composites can most likely be attributed to an increase in interfacial adhesion due to the presence of the carbonnanotubes.

Mitochondrial alternative oxidase (AOX1a) is required for the mitigation of arsenic-induced oxidative stress in Arabidopsis thaliana

Nil Demircan,Gokhan Cucun,Baris Uzilday 한국식물생명공학회 2020 Plant biotechnology reports Vol.14 No.2

The element arsenic (As) is a non-essential metalloid that is found naturally in all soils and at high concentrations it is toxic to plant cells. As (V) can act as a chemical analogue of phosphate, it can disrupt phosphate-related energy metabolism and lipid structure. In this study, the contribution of mitochondrial alternative oxidase (AOX) and chloroplastic plastid terminal oxidase (PTOX) to As (V) stress tolerance was investigated. Our data indicate that As (V) stress (100, 200 and 300 μM) induces AOX gene expression by 3.3- to 10.5-fold depending on AOX gene, but not PTOX expression in wild-type A. thaliana plants. To further elucidate the role of AOX in As (V) stress tolerance, we utilized aox1a mutants and observed that aox1a mutants had decreased growth and higher oxidative stress damage under stress conditions, while there were no diff erences under control conditions. Moreover, acclimation of aox1a plants to new cellular redox environment was investigated by measuring the activities of reactive oxygen species (ROS)-scavenging enzymes. Induction of mitochondrial MnSOD activity at 300 μM As (V) was higher in aox1a plants (70%), when compared to wild type (43%). However, total ascorbate peroxidase and dehydroascorbate reductase activities were lower in aox1a plants when compared to wild type, which might explain higher oxidative damage observed in this genotype. On the other hand, NADPH oxidase activity, which is involved in ROS signaling, was lower in aox1a plants under normal conditions but a higher induction was observed with As (V) stress. Overall, our data indicate that AOX1a is involved in adaptation to As (V)-induced oxidative stress.

Nuclear energy consumption, nuclear fusion reactors and environmental quality: The case of G7 countries

Nigar Demircan Çakar,Seyfettin Erdogan,Ayfer Gedikli,Mehmet Akif Oncü 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.4

Global climate change brings environmental quality sensitivity, especially in developed countries. Developed countries use non-renewable energy sources intensively both in their own countries and inother countries, they make productions that cause an enormous rate of increase in CO2 emissions andunsustainable environmental costs. This has increased the interest in environmentally friendly alternative energy sources. The aim of this study is to investigate the impact of nuclear energy consumptionand technological innovation on environmental quality in G7 countries using annual data over the period1970e2015. The Panel Threshold Regression Model was used for the analysis. Empirical findings haveindicated that the relationship between nuclear energy consumption and carbon emissions differs according to innovation for nuclear power plants. It was also concluded that nuclear energy consumptionreduces carbon emissions more after a certain level of innovation. This result shows that the increase ininnovative technologies for nuclear power plants not only increases energy efficiency but also contributes positively to environmental quality

Producing NiCrAl Alloy by the SHS Method for Use in Thermal Spray Powder Manufacturing

Bora Derin,Umut Demircan,Onuralp Yücel 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.2

A series of Ni alloys containing 36.15 - 44.54 wt.% Cr and 2.0 - 13.50 wt.% Al was synthesized by Self- Propagating High-Temperature Synthesis (SHS) using a mixture of NiO, Cr2O3 and Al powders in order to obtain low-cost starting materials for thermal spray powder production. The experiments were carried out with the addition of an excess stoichiometric amount of Al between 0 % and 30 %. Additions of CaO and CaF2 were also done to remove sulfur from the alloy and to investigate the effect on metal recovery. Thermochemical simulations of the SHS processes were examined with the FactSage program. The products were characterized by chemical analysis, X-ray diffraction (XRD), electron probe microanalysis (EPMA) and microhardness techniques. A series of Ni alloys containing 36.15 - 44.54 wt.% Cr and 2.0 - 13.50 wt.% Al was synthesized by Self- Propagating High-Temperature Synthesis (SHS) using a mixture of NiO, Cr2O3 and Al powders in order to obtain low-cost starting materials for thermal spray powder production. The experiments were carried out with the addition of an excess stoichiometric amount of Al between 0 % and 30 %. Additions of CaO and CaF2 were also done to remove sulfur from the alloy and to investigate the effect on metal recovery. Thermochemical simulations of the SHS processes were examined with the FactSage program. The products were characterized by chemical analysis, X-ray diffraction (XRD), electron probe microanalysis (EPMA) and microhardness techniques.

Correction of a maxillary canine-first premolar transposition using mini-implant anchorage

Oztoprak, Mehmet Oguz,Demircan, Cigdem,Arun, Tulin The Korean Association Of Orthodontists 2011 대한치과교정학회지 Vol.41 No.5

Transposition is defined as a dental anomaly manifested by a positional interchange of 2 adjacent teeth within the same quadrant of the dental arch. Maxillary canine-first premolar [Mx4-3] transposition is the most frequent tooth transposition reported in the literature. In this case report, an orthodontic correction of a transposition of the maxillary left canine and first premolar with the help of palatally located mini-implant anchorage is described. Esthetic and occlusal evaluations suggested alignment of the transposed teeth to their correct anatomic positions in the dental arch. The clinical result at the end of the treatment was satisfactory. Alignment was obtained, and intercuspation was adequate. Nevertheless, the maxillary canine showed facial recession, probably because it was initially positioned buccally. Supporting tissue was examined after treatment and no alveolar bone damage was observed.

Correction of a maxillary canine-first premolar transposition using mini-implant anchorage

Mehmet Oguz Oztoprak,Cigdem Demircan,Tulin Arun 대한치과교정학회 2011 대한치과교정학회지 Vol.41 No.5

Transposition is defined as a dental anomaly manifested by a positional interchange of 2 adjacent teeth within the same quadrant of the dental arch. Maxillary canine-first premolar [Mx4-3] transposition is the most frequent tooth transposition reported in the literature. In this case report, an orthodontic correction of a transposition of the maxillary left canine and first premolar with the help of palatally located mini-implant anchorage is described. Esthetic and occlusal evaluations suggested alignment of the transposed teeth to their correct anatomic positions in the dental arch. The clinical result at the end of the treatment was satisfactory. Alignment was obtained, and intercuspation was adequate. Nevertheless, the maxillary canine showed facial recession, probably because it was initially positioned buccally. Supporting tissue was examined after treatment and no alveolar bone damage was observed.

Effects of alloy ratio and coating thickness on temperature distribution of thermal barrier coatings

Can Ozturk,Tolga Demircan 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.4

Pistons on internal combustion engines that are constantly subjected to high pressure and temperature should be light,resistant to heat, resistant to corrosion and have adequate hardness to work more efficiently and to have longer lifecycles. Forthis purpose, piston surfaces are coated with thermal barrier that increases resistance against heat and corrosion. In this study,temperature distribution on piston surfaces were numerically analysed for ceramic coating on a piston. For this purpose, itis assumed that 100 μm NiCrAl coating is applied as bond coat on piston upper surface. This coating was coated withMgZrO3+NiCrAl alloy with different alloy ratios for different coating thicknesses. MgZrO3+NiCrAl alloy thickness waschanged between 200 μm and 600 μm. For all analysed coating thicknesses, MgZrO3 ratio in the alloy was changed between100 to 10% and simulations were repeated for different alloy rates. As a result of these analysis, it was determined that asMgZrO3 ratio in the alloy decreased, piston upper surface temperature decreased as well. For all alloy ratios, maximumtemperature was observed on piston upper surface. Additionally, it was determined that as piston upper surface coatingthickness increased, piston upper surface temperature increased as well.

Lumbar Disc Herniation in a Patient With Congenital Vertebral Body Anomaly: A Case Report

Cem Atabey,Ahmet Eroğlu,Ali Kivanc Topuz,Murat Velioğlu,Mehmet Nusret Demircan 대한척추신경외과학회 2014 Neurospine Vol.11 No.4

Lumbar disc herniation is characterized with low back and leg pain resulting from the degenerated lumbar disc compressing the spinal nerve root. The etiology of degenerative spine is related to age, smoking, microtrauma, obesity, disorders of familial collagen structure, occupational and sports-related physical activity. However, disc herniations induced by congenital lumbar vertebral anomalies are rarely seen. Vertebral fusion defect is one of the causes of congenital anomalies. The pathogenesis of embryological corpus vertebral fusion anomaly is not fully known. In this paper, a 30- year-old patient who had the complaints of low back and right leg pain after falling from a height is presented. She had right L5-S1 disc herniation that had developed on the basis of S1 vertebra corpus fusion anomaly in Lumbar computed tomography. This case has been discussed in the light of literature based on evaluations of Lumbar Computed Tomography (CT) and Magnetic Resonance Imaging (MRI). This case is unique in that it is the first case with development of lumbar disc herniation associated with S1 vertebral corpus fusion anomaly. Congenital malformations with unusual clinical presentation after trauma shouldbe evaluated through advanced radiological imaging techniques.

Further Discussion on the Period Change of YY Eridani

Kim, C.H.,J. H. Jeong,E. Budding,O. Demircan,Z. Muyesseroglu 한국우주과학회 1996 한국우주과학회보 Vol.5 No.2