NANOSİLİKA KATKILI CAM/EPOKSİ KOMPOZİTLERİN ÇEKME DAYANIMLARININ VE KIRILMA YÜZEYLERİNİN İNCELENMESİ

NANOSİLİKA KATKILI CAM/EPOKSİ KOMPOZİTLERİN ÇEKME DAYANIMLARININ VE KIRILMA YÜZEYLERİNİN İNCELENMESİÖzetTeknolojinin gelişmesiyle birlikte kompozitlerin kullanımı artmaktadır.  Cam/Epoksi kompozitler üretim maliyetlerinin düşük olması ve yüksek dayanım sergilemeleri sayesinde birçok endüstriyel alanda kullanılmaktadır. Dolayısıyla bu durum Cam/Epoksi kompozitlerden beklentilerin artmasına neden olmakta ve araştırmacıları da çalışmalarını bu yöne odaklamaktadır. Bu çalışmada el yatırma yöntemiyle 10 tabakadan oluşan ağırlıkça %4 nanosilika katkılı ve katkısız Cam/Epoksi kompozit levhalar üretilmiştir. ASTM D 3039/D 3039M standartlarına uygun olarak üretilen levhalardan çekme numuneleri hazırlanmıştır. Hazırlanan numunelerin çekme deneyleri sonrasında hasar analizleri yapılmıştır. Elde edilen sonuçlara göre nanosilika katkılı Cam/Epoksi kompozitlerin çekme dayanımlarında ve birim uzama miktarlarında sırasıyla ortalama %30 ve % 14.5’lik artış tespit edilmiştir.  Anahtar Kelimeler: Cam Elyaflar, Kompozitler, Nanosilika, Mekanik ÖzelliklerINVESTIGATION OF FRACTURE SURFACES AND TENSILE STRENGTHS OF NANOSILICA FILLED GLASS/EPOXY COMPOSITES AbstractThe usage for composite materials is increasing with the development of technology. Glass/ Epoxy composites are used in many industrial fields due to their low production costs and high strength. Therefore, it increases the expectations of glass / epoxy composites and the researchers focus their studies on this aspect. In this study, 4%wt nanosilica filled and unfilled Glass / Epoxy composite layers consisting of 10 layers as were produced by hot press method. Tensile samples were prepared from plates produced in accordance with ASTM D 3039 / D 3039M standards. After the tensile tests of the prepared samples, damage analysis was performed. According to the obtained results, an average increase of 30% and 14.5% in tensile strength and elongation of nanosilica filled Glass / Epoxy composites were determined respectively.Keywords: Glass Fibers, Composites, Nanosilica, Mechanical Propertie

Optical properties of graphene-based materials in transparent polymer matrices

Different aspects of graphene-based materials (GBMs) and GBM-nanocomposites have been investigated due to their intriguing features; one of these features is their transparency. Transparency of GBMs has been of an interest to scientists and engineers mainly with regard to electronic devices. In this study, optical transmittance of structural, purpose-made nanocomposites reinforced with GBMs was analyzed to lay a foundation for optical microstructural characterization of nanocomposites in future studies. Two main types of GBM reinforcements were studied, graphene oxide (GO) and graphite nanoplates (GNPs). The nanocomposites investigated are GO/poly(vinyl alcohol), GO/sodium alginate, and GNP/epoxy with different volume fractions of GBMs. Together with UV-visible spectrophotometry, image-processing-assisted micro and macro photography were used to assess the transparency of GBMs embedded in the matrices. The micro and macro photography methods developed were proven to be an alternative way of measuring light transmittance of semi-transparent materials. It was found that there existed a linear relationship between light absorbance and a volume fraction of GBMs embedded in the same type of polymer matrices, provided that the nanocomposites of interest had the same thicknesses. This suggests that the GBM dispersion characteristics in the same type of polymer are similar and any possible change in crystal structure of polymer due to different volumetric contents of GBM does not have an effect on light transmittance of the matrices. The study also showed that the same types of GBMs could display different optical properties in different matrix materials. The results of this study will help to develop practical microstructural characterization techniques for GBM-based nanocomposites

Effect of morphological state of graphene on mechanical properties of nanocomposites

In the last decade, graphene has emerged as one of the best-performing reinforcement materials for nanocomposites. Incorporation of graphene into polymer results in a nanocomposite with a new microstructure responsible for its enhanced features. A morphological state of graphene flakes is one of the factors that govern formation of microstructure. Studies showed that graphene-oxide (GO) flakes can be found either as fully exfoliated or intercalated in polymer-based nanocomposites. While traditional parameters are commonly taken into consideration in theoretical assessment of properties of composites by means of micromechanical models, the morphological state is often ignored. This research aims to investigate the effect of morphological state of GO flakes on stiffness of nanocomposites with widely used micromechanical models, e.g., rule of mixtures, Hui-Shia and Halpin-Tsai. Pure sodium alginate and nanocomposites on its basis reinforced with 1.0 and 2.5 wt% GO were used in the study. Parameters required for modelling were quantified with microstructural characterisation. Micromechanical models were adapted to account for the morphological state of intercalation observed in the characterisation study. Tensile experiments were employed to assess the adopted models, and the effect matrix stiffness, GO thickness, spacing of intercalates as well as the Poisson’s ratio and stiffness of inter-flake polymer layers was studied

The effect of injection parameters on fuel consumption and emissions in a pfi small spark ignition engine

The fastening of emission standards and the desire to lower fuel consumption decide the direction of research on internal combustion engines. Mixture formation affects fuel consumption and harmful emissions. One of the common problems in spark-ignition engines with liquid fuels is the evaporation of fuel for mixing with air because of fuel stored in liquid form. The intake valve is hot in port fuel injection engines. The fuel is directed to the hot surface of the intake valve so it evaporates. The injection pressure, injection time, injection angle and the number of injections in one cycle affect mixture formation [1–7]

Optical properties of graphene-based materials in transparent polymer matrices

This paper was published in the journal, Applied Physics Letters [© American Institute of Physics]. It is also available at: http://dx.doi.org/10.1063/1.4961674Different aspects of graphene-based materials (GBMs) and GBM-nanocomposites have been investigated due to their intriguing features; one of these features is their transparency. Transparency of GBMs has been of an interest to scientists and engineers mainly with regard to electronic devices. In this study, optical transmittance of structural, purpose-made nanocomposites reinforced with GBMs was analyzed to lay a foundation for optical microstructural characterization of nanocomposites in future studies. Two main types of GBM reinforcements were studied, graphene oxide (GO) and graphite nanoplates (GNPs). The nanocomposites investigated are GO/poly(vinyl alcohol), GO/sodium alginate, and GNP/epoxy with different volume fractions of GBMs. Together with UV-visible spectrophotometry, image-processing-assisted micro and macro photography were used to assess the transparency of GBMs embedded in the matrices. The micro and macro photography methods developed were proven to be an alternative way of measuring light transmittance of semi-transparent materials. It was found that there existed a linear relationship between light absorbance and a volume fraction of GBMs embedded in the same type of polymer matrices, provided that the nanocomposites of interest had the same thicknesses. This suggests that the GBM dispersion characteristics in the same type of polymer are similar and any possible change in crystal structure of polymer due to different volumetric contents of GBM does not have an effect on light transmittance of the matrices. The study also showed that the same types of GBMs could display different optical properties in different matrix materials. The results of this study will help to develop practical microstructural characterization techniques for GBM-based nanocomposites

The Relationship between Intra-Abdominal Pressure and Abdominal Perfusion Pressure Measurements with Prognosis in Patients Monitored in Critical Emergency Care

Aim: Intra abdominal hypertension (IAH) and abdominal compartment syndrome have emerged as significant causes of morbidity and mortality in critically ill surgical and medical patients. The prognostic value of elevated intra-abdominal pressure (IAP) has led to its recognition as a near-routine vital parameter in high-risk patients. This study aimed to monitor IAP elevations, low abdominal perfusion pressure (APP), and their clinical implications in patients admitted to emergency critical care units. Materials and Methods: This study included 89 patients admitted to intensive care units (ICUs), whose IAP was measured using the bladder pressure method. A volume of 25 mL saline was instilled into the bladder, and measurements were taken with the symphysis pubis level as the zero-reference point. Patients were grouped based on IAP values (<12 mmHg and ≥12 mmHg) and APP values (<60 mmHg and ≥60 mmHg). Morbidity outcomes included inotropic support, ventilator dependency, sepsis incidence, SOFA scores, and mortality rates. Statistical analyses were performed. Results: Among 89 patients, 36 had IAH, and 34 exhibited low APP. Patients with IAH and low APP demonstrated a higher need for inotropic support, increased sepsis incidence, and higher rates of organ failure. A strong association was observed between mortality and low APP, particularly in cases of IAH. Conclusion: Bladder pressure measurement is a simple and effective method to evaluate IAP in critically ill ICU patients. Elevated IAP and low APP were associated with poorer morbidity and mortality outcomes. IAP measurement should be considered essential for the survival prediction of critically ill patients in future ICU protocols

Cancer incidence of larger thyroid nodules and the diagnostic value of palpation and ultrasound guided fine needle aspiration biopsy

In this prospective study, we aimed to determine the cancer incidence of thyroid nodules larger than 3cm and compare the efficacy of palpation and ultrasound guided fine needle aspiration biopsy (FNAB). The study was conducted at General Surgery Departments of Istanbul Okmeydanı and Antalya Training and Research Hospitals of Turkey from March 2008 to December 2011. In our clinics, between the years 2008 and 2011, both palpation and ultrasound guided FNAB were performed in all 55 patients having thyroid nodules larger than 3 cm. The results were determined as inadequate, benign, suspicious and malignant. Histopathological findings were compared with the results of both palpation and ultrasound guided FNAB and sensitivity, specificity and accuracy rates were calculated. The specificity (98%) and accuracy rate (92.72%) of ultrasound guided FNAB corresponded to those from the literature, except the rate of sensitivity (40%). This is explained by FNAB performed only on the dominant nodule. Ultrasound guided FNAB is an efficient and reliable diagnostic method when performed by experienced clinicians. Hematoma and pain are such rare complications. Ultrasound plays an important role in taking biopsy from the true solid thyroid nodules. We conclude that ultrasound guided FNAB is the gold standard method in the diagnosis of thyroid nodules

Problematic smartphone use: an empirically validated model

Given the prominent role that smartphones have in everyday life, research in the field has proliferated. From a theoretical perspective, problematic smartphone use (PSPU) is described as a multi-faceted phenomenon entailing a variety of dysfunctional manifestations (e.g., addictive, antisocial and dangerous use). To date, however, there is still a lack of empirical evidence supporting the identification of PSPU as a potential behavioural addiction. Driven by theory, the aim of the present study was to provide an empirically validated model by testing the contribution of specific factors leading to PSPU. Relationships among individual characteristics (internalised psychopathology, impulsivity and personality traits) and PSPU uses (addictive, antisocial and dangerous) were investigated according to the updated version of the theoretical framework provided by the Pathway Model of problematic smartphone use (Billieux et al., 2015). An online survey was administered to a convenience sample (N = 511) of smartphone users in order to examine their daily engagement, problematic usage patterns and related psychological correlates. Path analysis revealed important information about different PSPU components and results are discussed in light of the available literature. Recommendations for future research are proposed to further investigate the problematic behaviour, including the study of additional variables, such as the fear of missing out (FoMO), nomophobia and excessive social media use

Osmanlı medreselerinde kelam öğretimi: ( İznik, bursa, Edirne, İstanbul)

ÖZET İlk Osmanlı medresesi İznik'te kurulmuştur. Bu medresenin ilk öğretmen Davûd el-Kayserî’dir. Bu ilk dönemde medrese müfredatında hangi Kelam kitaplarının olduğunu bilmiyoruz. Osmanlı medrese müfredatında kelâm kitaplarının dâhil edilmesi, Fatih döneminde zorunlu hale getirilmiştir. Kelam ilmi medreselerde en parlak dönemi, Fatih dönemidir. En önemli kelam âlimleri bu dönemde yaşamış olsa da kelâm, kelam, akli bir ilim olarak değerlendirilmiş olduğundan yüksek medreselerin müfredatına girememiştir. Kanûnî Sultan Süleyman sonrası dönemde, birçok sebebe bağlı olarak medrese eğitimi bozulmaya başlamıştır. Medresedeki eğitimin bozulması, eğitim sürelerinin kısalması, yüksek kelam kitaplarının müfredattan çıkarılmasına yol açmıştır. Kadızâdeliler hareketi, medrese öğrencilerinin isyanları, Safevî-Şiîlerin yol açtığı problemler, medrese eğitimine zarar vermiştir. Klasik dönem Osmanlı medreselerinde, Şerhu'l-Makāsıd, Şerhu'l-Mevakıf gibi yüksek kelam kitapları müfredatta yer alırdı. 16. yüzyıl sonrasında, bu kitapların yerini daha düşük düzeyde kabul edilen Şerhu'l-Akāid ve Molla Celâl kitapları almıştır. Bununla birlikte, medrese müfredatında, kelam, her dönem yer almıştır.Medreselerin ıslahı döneminde ise müfredat programlarında en önemli yer, kelam eğitimine verilecektir.ABSTRACT The first Ottoman theological school was established in Iznik. Dawud al Kayseri is the first teacher of this madrasa. In the first period of Ottoman, we do not know which the madrasah curriculum that Kalam's books. In the Ottoman madrasas be included in the curriculum of theology books, has been made compulsory in period of Fatih. In the madrasas Knowledge of theology, the most brilliant period of time, lived period of Fatih. Although the most important scholars of theology who lived during this period. However, due from theology, as a science of mental sciences have been evaluated could not enter the curriculum of the high madrasas. The period after Suleiman the Magnificent, the madrasa education has deteriorated a lot of reasons. Degradation of madrasa education, training, shortening the duration led to the removal of the curriculum of the high theology books. The Kadızadeliler movement, riots of the madrasa students, caused by the Safavid-Shiites problems, madrasa education has been hurt. Classical period of Ottoman madrasas, Sharh Al-Makāsıd, Sharh Al- Mevakıf kalam books as high as would take place in the curriculum. 16. century later, the location of these books are considered lower-level books Sharh al-Akāid and the Mullah Celal. However, ın the madrasa curriculum, theology, took place in each period. The most important place in the curriculum in the period of reclamation madrasas training of theology will be given