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Pranas Baltr?nas,Andrea Crivellini,Terese Leonavi?ien?,Aleksandras Chlebnikovas 대한환경공학회 2022 Environmental Engineering Research Vol.27 No.1
Research into gas flow motion as a transported phase and pollutant - particulate matter (PM) is of crucial importance, their changes in particular areas of the object require knowledge of improving the apparatus. A cyclone is considered one of the most popular devices due to the new modified multi-channel design that involves combined separation and filtration phenomena. The findings of an accurate numerical model provide an opportunity to verify long-term experimental studies. In addition, it is possible to determine the impact of the designed principal elements of the structure comprising secondary gas inlets, inner slits and the convex bottom on gas and PM motion through verification conducting experimental research. The study focuses on simulating the upgraded cyclone using the SST k-omega model. The research has been conducted under the specified gas flow conditions such as high temperature and relative humidity (aggressive) gas and presents the results of the physical model to compare with. To achieve greater computational accuracy, a digital model of the cyclone made of specific volumetric elements has been developed thus expanding the grid and stepping to form the boundary zone. As a result, numerical simulation results differ by no more than 12.8% compared to the experimental studies results.
Na, S.,Ahn, Y.G.,Cui, M.,Khim, J. Academic Press 2012 Journal of environmental management Vol.101 No.-
Ultrasound (US) combined with ultraviolet (UV) irradiation and a titanium dioxide (TiO<SUB>2</SUB>) catalyst was used to effectively remove diethyl phthalate (DEP) from aqueous solutions. Single (sonolysis, photolysis, photocatalysis) and combined (sonophotolysis, sonophotocatalysis) processes were performed to confirm the synergistic effects and DEP degradation mechanism. Using only US, the optimum frequency for DEP degradation was 283 kHz. At this frequency a high rate of hydrogen peroxide (H<SUB>2</SUB>O<SUB>2</SUB>) formation was observed of approximately 0.32 mM min<SUP>-1</SUP>. The pseudo-first order degradation rate constants were 10<SUP>-2</SUP>-10<SUP>-4</SUP> min<SUP>-1</SUP> depending on the process. Significant degradation and mineralization (TOC) of DEP were observed with the sonophotolytic and sonophotocatalytic processes. Moreover, synergistic effects of 1.29 and 1.95 were exhibited at the sonophotocatalytic and sonophotolytic DEP degradation, respectively. Furthermore, additional advantageous reactions may occur in the heterogeneous sonophotocatalytic process due to interactions between US, UV, and the photocatalyst.
Na, S.,Yoon, D.,Kim, J.,Kim, H.,Kim, D. IPC Science and Technology Press ; Elsevier Scienc 2017 International journal of fatigue Vol.101 No.1
<P>This study investigates the fatigue-crack propagation behavior of a powder metallurgical nickel-based superalloy, used in aircraft turbine disks. Taking into consideration the various operating conditions, the fatigue-crack propagation tests were conducted at various temperatures and stress ratios. These tests were performed with using the direct current potential drop method suggested by ASTM E647. Using Paris' law, the fatigue life can be predicted and the fatigue strengths can be calculated for developing a damage-tolerant design to predict the defects at elevated temperatures. The fatigue crack propagation rates at elevated temperatures are higher than that at room temperature. In addition, scanning electron microscope (SEM) observations of the fracture surface at different temperatures were examined and compared. At elevated temperatures, intergranular fractures are appeared with the oxidation. (C) 2017 Elsevier Ltd. All rights reserved.</P>
Durability properties of concrete containing metakaolin
Nas, Memduh,Kurbetci, Sirin Techno-Press 2018 Advances in concrete construction Vol.6 No.2
The main aim of this study is to investigate the possible effects of metakaolin on strength and durability properties of concrete. For this purpose, concrete mixtures are produced by substituting cement with metakaolin 0, 5, 10 and 20% by weight. The amount of binder for the concrete mixtures are 300 and $400kg/m^3$ with a constant water to cement ratio of 0.6. Compressive and bending strengths, freeze-thaw and high-temperature resistances, capillary coefficients and rapid chloride permeability properties were determined and compared each other. Because of all the experiments conducted, it has been found that the use of metakaolin as a pozzolanic additive in concrete have positive effects especially on compressive and bending strengths, capillary, rapid chloride permeability, freeze-thaw resistance, and high temperatures, up to $800^{\circ}C$. The results indicated that the performance of concrete can be enhanced by metakaolin. Particularly, compressive strength and durability properties have found to be improved with increasing metakaolin content which is attributed to pozzolanic activity and filler effect. Furthermore, metakaolin has relatively positive impacts under elevated temperatures and freeze-thaw effects. However, almost all the strengths of entire concrete specimens are lost at $800^{\circ}C$. Consequently, the optimum metakaolin substitution ratio can be suggested to be 20% as per this study.
Mechanical, durability and microstructure properties of concrete containing natural zeolite
Memduh Nas,Şirin Kurbetci 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.22 No.5
Concrete is one of the most widely used construction materials in the world. Producing economical and durable concrete is possible by employing pozzolanic materials. The aim of this study is to underline the possibility of the utilization of natural zeolite in producing concrete and investigate its effects basically on the strength and durability of concrete. In the production of concrete mixes, Portland cement was replaced by the natural zeolite at ratios of 0%, 10%, 15%, and 20% by weight. Concretes were produced with total binder contents of 300 kg/m3 and 400 kg/m3, but with a constant water to cement ratio of 0.60. In addition to compressive and flexural strength measurements, freeze-thaw and high temperature resistance measurements, rapid chloride permeability, and capillary water absorption tests were performed on the concrete mixes. Compared to the rest mixes, concrete mixes containing 10% zeolite yielded in with the highest compressive and flexural strengths. The rapid chloride permeability and the capillary measurements were decreased as the natural zeolite replacement was increased. Freeze-thaw resistance also improved significantly as the replacement ratio of zeolite was increased. Under the effect of elevated temperature, natural zeolite incorporated concretes with lower binder content yielded higher compressive strength. However, the compressive strengths of concretes with higher binder content after elevated temperature effect were found to be lower than the reference concrete.
Durability properties of mortars with fly ash containing recycled aggregates
Kurbetci, Sirin,Nas, Memduh,Sahin, Mustafa Techno-Press 2022 Advances in concrete construction Vol.13 No.1
The rapid development of the construction industry in the world causes a rapid increase in the consumption of aggregate resources, which leads to the depletion of existing aggregate reserves. The use of recycled aggregate in the production of concrete and mortar may be a good solution to reduce the use of natural raw materials and to reduce demolition waste in the environment. In this study investigating the use of recycled aggregate in mortar production, mortar mixtures were produced by substituting 0%, 25%, 50% and 100% fine recycled aggregate (FRA) instead of natural aggregate. The effect of 20% and 40% fly ash (FA) substitutes on cement mortar performance was also investigated. Compressive and flexural strength, drying shrinkage, abrasion resistance, water absorption and capillary water absorption were investigated on the produced mortars. The increase in the use of FRA reduced the compressive and flexural strengths of mortars. While the capillarity coefficients, water absorption, rapid chloride permeability and drying shrinkage of the mortars increased with the increase in the use of FRA, the effect of the use of fly ash on the rate of increase remained lower. The increased use of FRA has improved abrasion resistance as well.