Barim, Esra; Demir, Pınar; Değirmenci, Mustafa; Kirilmiş, Cumhur

The aim of this study was to determine the monomer reactivity ratios, thermal properties and thermal degradation behavior of new P(N-[2-(4-brombenzoyl)-benzofuran-3-yl]-2-methac-rylamide-co-styrene) polymers synthesized at different compositions. For this purpose, novel copolymers of N-[2-(4-brombenzoyl)-benzofuran-3-yl]-2-methacrylamide (NBBM) monomer with styrene (St) monomer were prepared using free radical polymerization method. The 1 H-NMR spectra was used to calculate the compositions of the copolymers. The reactivity ratios of monomers were calculated in line with the universal copolymerization equation using Kelen-Tüdös and Finemann-Ross linearization methods, and found to be r1:0,62 r2:1,09 and r1:0,61, r2:1,07 respectively (where r1 is reactivity ratio of NBBM). DSC, TGA and DTG were used to study the thermal behaviors of the copolymers. The Tg value of P(NBMM) was found to be 211oC and the Tg values of the studied copolymers were determined to increase from 144oC to 184oC with increasing concentration of NBMM units. Thermal data showed that the maximum degradation temperatures increased from 349oC to 391oC as the St units increased in the copolymer system. The activation energy (Ea) values of P(NBBM) and the studied copolymer were determined from the TGA curves obtained at different heating rates and the Flynn-Wall-Qzawa, Kissinger, Tang isoconversional methods were used. Solid state reaction mechanisms were also calculated by being used the Van Krevelen method, a non-isoconversion model. The Ea values obtained with isoconversion models for P(NBBM) and copolymer were found very close to the values obtained from non-isoconversion models. Moreover, the R3 mechanism was proposed for the homopolymer and copolymer.

İncele

Ustaoğlu, Fikret; Kutlu, Banu; Tepe, Yalçın; Aydin, Handan

The aim of this study is to detect the heavy metal contamination in the sediment of Batlama Stream and to evaluate the anthropogenic effect. Field studies were seasonally carried out in 3 stations between June 2014 and July 2015. In the sampling studies carried out in Batlama Stream, contamination factor (CF), enrichment factor (EF), potential ecological risk factor (Eri), lowest effect level (LEL), geoaccumulation index (Igeo) contamination indicators were used in order to evaluate sediment contamination. In Batlama Stream, average heavy metal level of three stations was detected in mg/dry kg in the sediment as Cr 7.08, Mn 63.62, Fe 858.04, Co 5.47, Ni 4.99, Cu 20.61, Zn 49.60, Cd 0.09, and Pb 20.68. Elements which the sediment has most are Fe, Mn, and Zn. According to EF, Pb was detected as an enriching element. Eri Pb is in the low risk group. In LEL value, the highest Pb average was found as 31. According to Igeo values, Pb is a moderate contaminant. This metal has anthropogenic sources and it is caused by domestic, agricultural, and waste waters. In the elements analysed in Batlama Stream sediment (apart from Pb), it is indicated that it is generally a clean stream and considered reference stream.

AtıfScopus3

İncele

Yilmazer Polat, Berivan; Uysal, Mucteba; Korkmaz, Volkan

Cement production is a polluting process for nature. For this reason, new types of concrete which can be produced with recycled materials and without cement continue to be investigated. On the other hand; cracks in structural elements reduce the strength and durability of a building. Extending service life of buildings has eliminated the cost of rebuilding and thus, contributed to both the economy and the ecosystem. Due to this, research on crack healing in Portland cement concretes with various bacteria is continuing for some time. However, there are not enough studies in literature regarding the improvement of metakaolin-based geopolymer mortars produced without using cement by urolytic bacteria. The parameters of temperature, pH and void ratio of bacterial geopolymer mortar affect the viability of bacteria. For example, pH value of the medium required for the survival of bacteria is, generally around nine. During the production of geopolymer concrete, a sudden increase in high alkali environment occurs due to use of activators. This reduces the survival rate of bacteria added to the mixture during the production of geopolymer mortar. In this study, the most suitable environment for geopolymer mortar, and the conditions for the bacteria to survive until the end of the curing process for the mortar to be strengthened were investigated. Analyses on the effects of urolytic bacteria and geopolymer mortar healing process on mechanical strength of the mortar were conducted. Sporosarcina Pasteurii were used for the self healing process. Various mixtures of geopolymer mortars were cured under different environmental conditions to observe changes in their mechanical strength and water absorption capacity. As the result of the study, the most suitable mixture ratio and curing medium were identified. It was observed that the nutrient, ensuring the life cycle of the urolytic bacteria, had no negative effect on the mechanical strength of mortar and reduced capillary water absorption of the mortar. This study is a specific text in the literature that analyzes bacterial curing conditions and the effect of improving geopolymer mortar.

AtıfScopus14

İncele

Kaya, Yusuf; Polat, Alper; Özsahin, Talat Sukru

The continuous and discontinuous contact problem of a homogeneous layer loaded with three rigid flat blocks and resting on the elastic semi-infinite plane was investigated in this study by using the finite element method (FEM). All surfaces are assumed to be frictionless. The homogenous layer was loaded by means of three rigid flat blocks whose external loads are Q and P (per unit thickness in z direction). Two dimensional finite element analysis of the problem was performed using ANSYS package program. Analyzes were performed for loading conditions which are Q=P, Q=2P, Q=4P, Q=8P and Q=10P, and different values of block widths, distances between blocks and shear modulus. The initial separation loads and initial separation distances (lambda(cr), chi(cr)) between the homogeneous layer and the elastic semi-infinite plane were determined for continuous contact condition. The length of the separation zone was obtained for discontinuous contact condition. In addition to these, normal stress distributions between the layer and the semi-infinite plane were determined for continuous and discontinuous contact conditions. As a result of the study, the analytical results, and the results of the finite element method were shown by comparing as graphs and tables.

AtıfWoS5

İncele

Nur, Ahmet; Omaç, Zeki; Öksüztepe, Eyyup

Squirrel cage induction motors are widely used in industry. These induction motors need smart control applications for high performance. In this paper an indirect vector control of squirrel cage induction motor is modelled mathematically. The mathematical model is moved to simulation using Matlab/Simulink software. For improvement, the indirect vector control simulation is based on fuzzy logic. Eventually, the simulation results for fuzzy logic speed control of induction motor are obtained for different reference speeds. The results showed effectiveness of fuzzy control system for indirect vector control of squirrel cage induction motor simulation model.

İncele

Gül, Muhammet; Güneri, Ali Fuat; Günes, Gizem

An ideal healthcare system is considered as a system that provides the most quality service level, lower costs and unlimited access. Any delay in patient flow may result in undesired consequences and losses in healthcare facilities such as hospitals and their sub units. Project management is defined as application of techniques to project activities to meet the project requirements. It has techniques that can help healthcare facilities and units standardize care and quality, reduce costs, improve effectiveness and decrease prolonged waits. The current study is carried out in an emergency department of a university hospital to understand the patient flow of the department with respect to the Fuzzy Critical Path Method (FCPM) and Fuzzy Program Evaluation Review Technique (FPERT). The reason for incorporating fuzzy sets is stemmed from that fuzzy numbers are more effective for high uncertainty processes as in emergency departments. Activities affecting patient flow through the ED are identified and project network is drawn. 1500 patients' data about the times of each activities are obtained from the observed ED. Findings through application of FCPM and FPERT, the expected time for completion of the project, the critical path and slack times are determined.

AtıfWoS2

İncele

Akbulut, Ekrem; Erdemir, Aysegul; Ozgen, Metin; Baskin, Yasemin; Yalcin, Femin; Balik, Dilek Turgut

İncele