DSpace@ATÜ (Adana Alparslan Türkeş Bilim ve Teknoloji Universiti)
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ABS/PVC karışık polimer çekirdekli sandviç panellerin mekanik ve eğılme karakteristikleri üzerine nano katkı maddeleri ve malzeme ekstrüzyon parametrelerinin deneysel ve sayısal incelemesi
No full textLisansüstü Eğitim Enstitüsü, Makine Mühendisliği Ana Bilim DalıBu tez, erimiş biriktirme modellemesi (EBM) kullanılarak üretilen kompozit çekirdek kabuk yapıların eğilme tepkisi üzerinde farklı çekirdek yapılarının etkilerini araştırmaktadır. Çalışma, çeşitli EBM parametrelerinin ve temel matris malzemesinin kompozit yapıların mekanik özellikleri üzerindeki etkisini keşfetmektedir. Yapay sinir ağları (YSA) ile regresyon modelleme kullanılarak 3D baskı örneklerinin düzlem içi ve düzlem dışı elastiklik modülü ve maksimum çekme mukavemeti gibi mekanik değişkenleri tahmin etmektedir. Karınca kolonisi optimizasyonu (KKO) kullanarak EBM parametrelerini ve malzeme bileşimini optimize etmek için optimizasyon teknikleri uygulanarak mekanik performansı artırılmaktadır. Elde edilen regresyon modelleri mekanik özelliklerdeki değişimleri analiz etmek için çubuk grafikleri ve yüzey tepkileri ile görselleştirilmekte ve optimizasyon algoritmaları, yanıt değişkenlerini bireysel ve toplu olarak maksimize eden malzeme ekstrüzyon parametrelerini belirlemektedir. Çalışmada, PVC ve karbon nanofiber (CNF) gibi katkı maddelerinin, 3D baskı örneklerinin ve kompozit çekirdek kabuk sandviç panel (KÇKSP) numunelerinin mekanik özellikleri üzerindeki etkisi hakkında bilgiler sunulmaktadır. Çalışma, malzeme ekstrüzyon parametrelerinin ve katkı maddelerinin uyumluluğunun, özellikle malzeme ekstrüzyon parametrelerinin dikkatli seçimi ve optimize edilmesiyle 3D baskı malzemelerinin mekanik özelliklerinin belirli uygulamalara uygun şekilde şekillendirilebileceğini vurgulamaktadır. Ayrıca, araştırma, EBM'nin özelleştirilmiş mekanik özelliklere sahip kompozit çekirdek kabuk yapıların üretimi için geçerli bir üretim tekniği olarak potansiyelini göstermektedir. Çekirdek yapılarının ve EBM parametrelerinin optimize edilmesiyle, üretilen yapıların eğilme tepkisi ve genel performansı artırılabilmektedir. Bu araştırmanın sonuçları, özellikle kompozit çekirdek kabuk yapılarının bağlamında, eklemeli imalatın ilerlemesine katkıda bulunmaktadır. Bulgular, EBM süreçlerini ve malzeme bileşimlerini optimize etme konusunda mühendisler ve araştırmacılar için değerli bir bilgi sunmaktadır. Bu çalışmanın temel bulguları şunları içermektedir: Ana eksenlerin farklı yönelimlerinde üretilen 3D baskı örneklerinin mekanik özelliklerinin analizi, PVC katkısının özellikle daha düşük ekstrüzyon hızlarında ve baskı yönelimlerinde düzlem içi sertliği iyileştirdiğini göstermektedir. CNF varlığının ise farklı baskı yönelimlerinde sertliğe sınırlı etkisi vardır. Nihai mukavemetin incelenmesi, PVC'nin tek başına etkili bir şekilde artırmadığını, ancak CNF katkısının artan ekstrüzyon hızlarına bağlı olarak azalmayı engellediğini özellikle [0/90°] raster yönelimli örneklerde göstermektedir. CNF'nin katılması, ABS ve PVC molekülleri arasındaki mekanik bağlantılarla birlikte bir yük taşıma ağı oluşturarak numunelerin nihai mukavemetini artırmaktadır. Hibrit dairesel/üçgen dalgalı çekirdekler ile KÇKSP'lerin yanıt yüzeyi analizi, malzeme ekstrüzyon parametrelerinin ve polimer bileşiminin eğilme tepkisine olan etkisini açıklamaktadır. PVC katkısı eğilme sertliği artırırken, CNF varlığı özellikle daha yüksek ekstrüzyon hızlarında sertliği azaltabilmektedir. Optimizasyon süreci, optimal parametre kombinasyonlarının genellikle matris içinde CNF olmadığı örnekleri içerdiğini, ancak PVC konsantrasyonu daha yüksek bileşimlerde CNF katkısının mekanik ve eğilme tepkisine olumlu etkisi olabileceğini göstermektedir. CNF konsantrasyonu, PVC oranı ve ekstrüzyon parametrelerinin istenen mekanik özelliklerin elde edilmesi ve 3D baskı yapılarının performansının şekillendirilmesi açısından önemlidir.This thesis investigates the effects of different core structures on the flexural response of composite core shell structures fabricated using fused deposition modeling (FDM). The study explores the influence of various FDM parameters and the composition of the base matrix material on the mechanical properties of the structures. Regression modeling with artificial neural networks (ANN) is employed to predict the mechanical variables of the 3D printed samples, such as in-plane and out-of-plane modulus of elasticity and ultimate strength. Optimization techniques using ant colony optimization (ACO) are applied to optimize the FDM parameters and material composition, resulting in improved mechanical performance. The obtained regression models are used to analyze variations in mechanical properties, visualized through bar-charts and surface responses, and optimization algorithms determine the material extrusion parameters that maximize the response variables individually and cumulatively. Insights are provided into the influence of material extrusion parameters and the compatibility of additives, such as PVC and carbon nanofibers (CNFs), on the mechanical characteristics of 3D printed samples and composite core shell sandwich panel (CCSSP) specimens. The study highlights the potential for tailoring the mechanical properties of 3D printed materials for specific applications through careful selection and optimization of material extrusion parameters. Furthermore, the research demonstrates the potential of FDM as a viable manufacturing technique for producing composite core shell structures with tailored mechanical properties. By optimizing the core structures and FDM parameters, the flexural response and overall performance of the fabricated structures can be enhanced. The outcomes of this research contribute to the advancement of additive manufacturing, particularly in the context of composite core shell structures. The findings offer valuable knowledge for engineers and researchers in optimizing FDM processes and material compositions to achieve desired mechanical properties for specific applications. Key findings of this study include the analysis of mechanical properties of 3D printed samples fabricated at different orientations of principal axes, with the addition of PVC improving in-plane stiffness, particularly at lower extrusion rates and printing orientations. The presence of CNFs has a limited effect on stiffness at different printing orientations. Investigation of ultimate strength reveals that PVC alone does not effectively enhance it, but the inclusion of CNFs counteracts the reduction caused by increased extrusion rates, particularly for samples with a raster orientation of [0/90°]. The addition of CNFs creates a load-carrying network through mechanical interlocking, improving the compatibility between ABS and PVC molecules and the ultimate strength of the samples. The response surface analysis of CCSSPs with hybrid circular/triangular corrugated cores (HCTC) elucidates the influence of material extrusion parameters and polymer composition on the flexural response. PVC addition improves flexural stiffness, while CNF presence can reduce stiffness, especially at higher extrusion rates. The optimization process indicates that optimal parameter combinations often involve samples without CNF in the matrix, although the addition of CNF can positively influence the mechanical and flexural response of 3D printed samples for compositions with higher PVC concentrations. Considering CNF concentration, PVC ratio, and extrusion parameters is crucial for achieving desired mechanical properties and tailoring the performance of 3D printed structures
Composite Cryogels for Drug Delivery Applications: A Preliminary Study with Dye as a Model Drug
No full textCryogels are suitable candidates to be used as drug release systems due to their interconnected pore structures, high surface areas, high liquid absorption capacities, and elasticity. With this purpose, we aimed to produce a cryogel structure to be used in drug release applications with the approach of tissue engineering. As biodegradable and biocompatible polymers chitosan and gelation were selected. The cryogels were fabricated using the combination of these polymers in the presence of glutaraldehyde under cryogenic conditions. The produced optimum gel scaffold was first characterized using FTIR, SEM, porosity, swelling ability, and degradation analyses. Successfully crosslinked gels exhibited an interconnected pore structure with an average pore diameter of 52.95 µm. As a result of the examination of the time-dependent weight change, it was also revealed that the cryogels have a liquid absorption capacity of about 500 times their dry weight and are biodegradable. The mainly characterized cryogel sample was evaluated for potential drug loading and release applications using methyl orange (MO) as a model drug. Gels, which swell in a short time, absorb the dye quickly and the cumulative release of the dye indicates that the gels are suitable for extended-release systems
Effect of Stocking Densities on Growth and Production Performance of Bheda (Nandus nandus) in Pond Aquaculture
No full textThe current study's goal was to look at how stocking densities affected Bheda (Nandus nandus) growth and production over the course of a 120-day period. Three treatments were T 1 (20,000 fish ha -1 ), T 2 (30,000 fish ha -1 ), and T 3 (40,000 fish ha -1 ), each with three replicates. Those fishes were fed daily with commercial sinking feed and a live food mixture at 9-3% fish body weight up to harvest- ing. Temperature, dissolved oxygen, pH, and other water quality indicators were measured every two weeks, along with the growth performance of Bheda fish. T2 had the highest yield of Bheda (3439.08±207.31 kg ha -1 ), followed by T 3 (3422.78±224.42 kg ha -1 ), and T1 (3136.62±150.00 kg ha-1 ). The harvesting weight (g), individual weight gain (g), individual percent (%) weight gain (g), SGR (% per day), and survival rate (%) of fish were significantly higher (p<0.05) in T1 , followed by T2 and T3 , respectively, where combined production of fishes was significantly higher at T2 followed by T3 and T 1 . Net profit and benefit-cost ratio were significantly higher in T1 than T2 and T3 . Based on the re- sults of this experiment, it can be concluded that stocking density of Bheda fingerlings at the rate of 20,000 fish ha -1 in T 1 showed the highest production performance for profitable pond aquacul- ture. However, further research on the standardisation of stocking density with economic profitabil- ity of this fish at the on-station or on-farm level in ponds may be required before widespread dis- semination of this culture technology to farmers, particularly in Bangladesh and elsewhere
Preparation of Transparent ZIF-8/TiO2 Nanocomposite Thin Films for Photocatalytic Applications
No full textTransparent ZIF-8/TiO2 nanocomposite thin films were prepared by a two-stage dip-coating method. TiO2 was first deposited on glass substrates by sol-gel dip-coating. Heat treatment temperature, number of layers and doping metal type/level were optimized in the first step. In the next step, ZIF-8 was grown by solvent based crystallization method on TiO2 layers. Cu, Ce, Fe or Zn doped TiO2 thin films were prepared in order to increase the photocatalytic performance of ZIF-8/TiO2 nanocomposite. The highest photocatalytic methylene blue degradation activities were obtained with the ZIF-8/TiO2 nanocomposite thin films prepared by using 1% Cu or 1% Ce doped TiO2 thin films as the substrates. Both films exhibited 19% dye removal in 1 hour under 254 nm LED light irradiation whereas the dye removal efficiencies were 36% and 29%, respectively, in 1 hour under 365 nm LED light irradiation
Concentration study of a specularite ore via shaking table, reverse flotation, and microwave-assisted magnetic separation
No full textDespite the difficulties in pelletizing specularite-type refractory iron ores, the utilization of these resources is indispensable for the steel industry due to the increasing need for iron. This study investigated Fe recovery from a refractory iron ore using gravity separation, reverse flotation, and two-stage magnetic separation. Tilt angle and particle size had a significant effect on the grade and recovery of concentrates in shaking table tests. Gravity concentration at optimum conditions resulted in an iron concentrate with 64.47% Fe grade and 90.73% Fe recovery. In the reverse flotation tests, the frother and depressant substantially affected the Fe grade of concentrates while the collector influenced the Fe recovery. A 90% Fe recovery with 64.69% Fe grade was obtained within optimum flotation conditions. The Fe grades were raised to >67.5% in products after the first magnetic separation. The tailings of the first magnetic separation were subjected to the second magnetic separation after microwave-assisted roasting to increase the magnetic susceptibility. In the second magnetic separation, a concentrate containing 66.06% Fe was separated from the microwave-roasted non-magnetic material with 82.23% Fe recovery. To the best of our knowledge, the microwave-roasting method has been applied to a specularite-type refractory iron ore for the first time.Scientific Research Projects Unit of Cukurova University [FLY-2019-11823]This study was supported by the Scientific Research Projects Unit of Cukurova University [Project No: FLY-2019-11823]
Sulphur and Boron Fertilization Increased Productivity of Boro Rice (BRRI dhan28) by Increasing Pollen Fertility and Agronomic Efficiency in Calcareous Soils
No full textTo study the effect of sulphur (S) and boron (B) on the performance of yield, agronomic efficiency, economic return of boro rice (cv. BRRI dhan28) was evaluated at the Reseahc Field of the Department of Crop Science and Technology, University of Rajshahi, Rajshahi- 6205, during the Rabi season from November 2015 to April 2016 in High Ganges River Floodplain under AgroEcological Zone-11 (AEZ-11). The experiment was consisted three level of sulphur, viz., S0: without sulphur (control), S20: 20 kg S ha-1, S30: 30 kg S ha-1, and three level of boron viz., B0: without boron (control), B2: 2 kg B ha- 1, B3: 3 kg B ha-1. The experiment was conducted in a Randomized Complete Block Design (RCBD) with three replications. The results revealed that S and B significantly influenced the yield straw yield, biomass yield, sterility percentage, agronomic efficiency and economic return of BRRI dhan28. The treatment combination of S20B2 (20 kg S ha-1 with 2 kg B ha-1) performed the best results of the aforesaid traits. So, it can be suggested to apply S at 20 kg ha-1 and B at 2 kg ha-1 with recommended dose of NPK and Zn for maximizing yield, agronomic efficiency and economic point of view of boro rice in calcareous soils of AEZ-11
Muhasebe Meslek Mensuplarının Etik İdeoloji ve Adalet Yaklaşımı: İstanbul Örneği
No full textMuhasebe meslek mensuplarının mesleki faaliyetlerini yerine getirirken kişisel tutumları, inançları, davranışları, kültürel özellikleri, sosyal statüleri, gelir düzeyleri, adalet ve etik anlayışları finansal ve finansal olmayan bilginin güvenilirliğinde önemli bir rol oynamaktadır. Çünkü finansal ve finansal olmayan bilginin güvenilir olması işletmelerin doğru karar almasını sağlamaktadır. Bu kapsamda bu çalışmanın amacı, İstanbul ilinde faaliyet gösteren muhasebe meslek mensuplarının etik ideoloji ve adalet yaklaşımlarını idealizm ve görecilik boyutları çerçevesinde ölçmektir. Bu amacı yerine getirirken Forsyth (1980)’nin geliştirdiği Etik Durum Ölçeği kullanılmıştır. Çalışmanın bulguları, araştırmaya katılan muhasebe meslek mensuplarının idealizm seviyelerinin yüksek ve görecilik seviyelerinin düşük olduğunu göstermiştir. Göreciliğin düşük ve idealizmin yüksek olması durumu, muhasebe meslek mensuplarının başkalarına zarar verecek davranışlarından kaçınan ve diğer bireylerin refahını önemseyen bireyler olduklarını göstermektedir. Bu durum ayrıca muhasebe meslek mensuplarının etik davranışlara duyarlılık gösterdiklerini ve etik dışı davranışlardan kaçınma eğiliminde oldukları yönünde kanıtlar sunmaktadır
Large Eddy Simulation of the Biased Wake Flow Downstream of Circular Cylinders with a Slit
No full textThe characteristics of flow around slit-inserted cylinders were investigated using the three-dimensional large eddy simulation (LES). In the investigations, three different slit width-to-cylinder diameter ratios, i.e., s/D = 0.1, 0.2 and 0.3, together with regular cylinder were used. Slits were placed inside the cylinders with a zero-inclination angle, ? = 0o. The Reynolds number of the flow was ReD = 3900 based on the cylinder diameter, D, and free stream velocity, U?. The results presented that the jet flow emerging from the slits deviated in crossflow direction forming a biased wake flow downstream of the slit cylinders. Compared with the regular cylinder, relative per cent reductions in drag coefficients of the slit cylinders with s/D = 0.1, 0.2 and 0.3 were 3.1%, 11.3% and 6.5%, respectively. The rates of turbulence quantities in downstream wakes of the slit cylinders were reduced. Formations of shear layers in the downstream wake changed drastically as the slit width-to-diameter ratio, s/D, increased
Production, Optimization and Partial Characterization of Alkaline Protease from Bacillus subtilis spp. subtilis NRRL B-3384 and B-3387
No full textBacillus subtilis has been a reliable platform for the expression of extracellular proteases for several decades. Although a majority of Bacillus subtilis subspecies express proteases, the amount of secreted enzyme varies depending on the strain and environmental conditions used. Here, two Bacillus subtilis spp. subtilis strains, NRRL B-3384 and NRRL B-3387, from the ARS Culture collection (NRRL), were compared for secreted protease activity. The highest activity was found in strain NRRL B-3384, and proteolysis occurred at temperatures as high as 80°C and across a broad range of pH, with maximum activity at pH 9.0 and 60°C indicating the presence of a thermostable alkaline protease. To our knowledge, this is the first study to evaluate protease production in Bacillus subtilis spp. subtilis strains NRRL B-3384 and B3387 and suggests that NRRL B-3384 may have utility in the production of enzymes for industrial use
Certain Curvature Conditions on Kenmotsu Manifolds and *-?-Ricci Solitons
No full textThe present paper deals with the investigations of a Kenmotsu manifold satisfying certain curvature conditions endowed with ??-?-Ricci solitons. First we find some necessary conditions for such a manifold to be f-Einstein. Then, we study the notion of ??-?-Ricci soliton on this manifold and prove some significant results related to this notion. Finally, we construct a nontrivial example of three-dimensional Kenmotsu manifolds to verify some of our results.Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia [PNURSP2023R27]Fatemah Mofarreh expresses her gratitude to Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2023R27), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia