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Cost optimization of high strength concretes by soft computing techniques
Erdogan Ozbay,Ahmet Oztas,Adil Baykasoglu 사단법인 한국계산역학회 2010 Computers and Concrete, An International Journal Vol.7 No.3
In this study 72 different high strength concrete (HSC) mixes were produced according to the Taguchi design of experiment method. The specimens were divided into four groups based on the range of their compressive strengths 40-60, 60-80, 80-100 and 100-125 MPa. Each group included 18 different concrete mixes. The slump and air-content values of each mix were measured at the production time. The compressive strength, splitting tensile strength and water absorption properties were obtained at 28 days. Using this data the Genetic Programming technique was used to construct models to predict mechanical properties of HSC based on its constituients. These models, together with the cost data, were then used with a Genetic Algorithm to obtain an HSC mix that has minimum cost and at the same time meets all the strength and workability requirements. The paper describes details of the experimental results, model development, and optimization results.
ITO/Au/ITO multilayer thin films on transparent polycarbonate with enhanced EMI shielding properties
Nursev Erdogan,Fuat Erden,A. Taner Astarlioglu,Mehtap Ozdemir,Salih Ozbay,Gulnur Aygun,Lutfi Ozyuzer 한국물리학회 2020 Current Applied Physics Vol.20 No.4
ITO/Au/ITO multilayer thin films were deposited onto polycarbonate substrate via magnetron sputtering technique without intentional heating. The deposition times of both ITO and Au layers were studied to optimize the overall transparency and conductivity. As-prepared thin films were characterized using X-ray diffraction analysis, secondary ion mass spectroscopy, scanning and transmission electron microscopy, atomic force microscopy and physical property measurement system. The optical measurement results revealed that the transmittance of the films were enhanced by increasing the gold deposition time up to 15 s. Beyond this point, further increasing the duration caused a decrease in optical transmittance. Upon optimization of the Au deposition time, the deposition duration of ITO layers was also studied to increase electromagnetic interference (EMI) shielding effectiveness (SE). Maximum EMI SE in this work was measured as 26.8 dB, yielding 99.8% power attenuation, which was verified by simulation results.
Effects of Milled Cut Steel Fibers on the Properties of Concrete
Okan Karahan,Erdogan Ozbay,Cengiz D. Atis,Mohamed Lachemi,Khandaker M. A. Hossain 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.7
This study presents the mechanical and transport properties of milled cut steel fiber reinforced concretes (MCSFRC). Properties studied include unit weight, workability, compressive strength, flexural strength, splitting tensile strength, bond strength, water absorption, water porosity, water sorptivity, rapid chloride ion permeability and drying shrinkage of concrete. Mixtures with a waterbinder ratio of 0.40, total binder content of 500 kg/m3 and milled cut steel fiber content of 0, 0.25, 0.50 and 1.00% by concrete volume were produced and tested. The laboratory results showed a slight reduction in compressive strength with the use of milled cut steel fiber. On the other hand milled cut steel fibers significantly improved the tensile strength and decreased the drying shrinkage. Although no significant increase was observed in the absorption, porosity and sorptivity, chloride ion permeability increased drastically with the increase of milled cut steel fiber content.