The research was carried out to develop geopolymers mortars and concrete from fly ash and bottom ash and compare the characteristics deriving from either of these products. The mortars were produced by mixing the ashes with sodium silicate and sodium hydroxide as activator solution. After curing and drying, the bulk density, apparent density and porosity, of geopolymer samples were evaluated. The microstructure, phase composition and thermal behavior of geopolymer samples were characterized by scanning electron microscopy, XRD and TGA-DTA analysis respectively. FTIR analysis revealed higher degree of reaction in bottom ash based geopolymer. Mechanical characterization shows, geopolymer processed from fly ash having a compressive strength 61.4 MPa and Young's modulus of 2.9 GPa, whereas bottom ash geopolymer shows a compressive strength up to 55.2 MPa and Young's modulus of 2.8 GPa. The mechanical characterization depicts that bottom ash geopolymers are almost equally viable as fly ash geopolymer. Thermal conductivity analysis reveals that fly ash geopolymer shows lower thermal conductivity of 0.58 W/mK compared to bottom ash geopolymer 0.85 W/mK. 相似文献
The thermomechanical behavior of micro/nano-alumina (Al2O3) ceramics reinforced with 1-5 wt.% of acid-treated oil fly ash (OFA) was investigated. Composites were sintered using spark plasma sintering (SPS) technique at a temperature of 1400°C by applying a constant uniaxial pressure of 50 MPa. It was evaluated that the fracture toughness of micro- and nanosized composites improved in contrast with the monolithic alumina. Highest fracture toughness value of 4.85 MPam1/2 was measured for the nanosized composite reinforced with 5 wt.% OFA. The thermal conductivity of the composites (nano-/microsized) decreased with the increase in temperature. However, the addition of OFA (1-5 wt.%) in nanosized alumina enhanced the thermal conductivity at an evaluated temperature. Furthermore, a minimum thermal expansion value of 6.17 ppm*K−1 was measured for nanosized Al2O3/5 wt.% OFA composite. Microstructural characterization of Al2O3-OFA composites was done by x-ray diffraction and Raman spectroscopy. Oil fly ash particles were seen to be well dispersed within the alumina matrix. Moreover, the comparative analysis of the nano-/microsized Al2O3/OFA composites shows that the mechanical and thermal properties were improved in nanosized alumina composites. 相似文献
The processing parameters in enzymatic reactions using CO2-expanded (CX) lipids have strong effects on the physical properties of liquid phase, degree of interesterification, and physicochemical properties of the final reaction products. CX-canola oil and fully hydrogenated canola oil (FHCO) were interesterified using Lipozyme TL IM in a high pressure stirred batch reactor. The effects of immobilised enzyme load, pressure, substrate ratio and reaction time on the formation of mixed triacylglycerols (TG) from trisaturated and triunsaturated TG were investigated. The optimal immobilised enzyme load, pressure, substrate ratio and time for the degree of interesterification to reach the highest equilibrium state were 6% (w/v) of initial substrates, 10 MPa, blend with 30% (w/w) of FHCO and 2 h, respectively. The physicochemical properties of the initial blend and interesterified products with different FHCO ratios obtained at optimal reaction conditions were determined in terms of TG composition, thermal behaviour and solid fat content (SFC). The amounts of saturated and triunsaturated TG decreased while the amounts of mixed TG increased as a result of interesterification. Thus, the interesterified product had a lower melting point, and broader melting and plasticity ranges compared to the initial blends. These findings are important for better understanding of CX-lipid reactions and for optimal formulation of base-stocks of margarine and confectionary fats to meet industry demands. 相似文献
ABSTRACTObjective: We systematically reviewed available randomized clinical trials (RCTs) to elucidate the overall effects of synbiotic supplementation in patients with nonalcoholic fatty liver disease (NAFLD).Methods: PubMed, Scopus, ISI Web of science and Google Scholar were searched up to December, 2017. All RCTs using synbiotic supplements to treat NAFLD included in this systematic review and meta-analysis. Mean Difference (MD) was pooled using a random-effects model.Results: Eleven eligible databases from seven RCTs were identified for the present meta-analysis. Our results showed that synbiotic supplementation can decrease body weight, fasting blood sugar, insulin, low density lipoprotein cholesterol, total cholesterol, triglyceride, high-sensitivity C-reactive protein, tumor necrosis factor alpha, alanine transaminase and aspartate transaminase levels among patients with NAFLD. In contrast, synbiotic did not have favorable effects on body mass index (BMI), waist circumference, homeostasis model assessment for insulin resistance (HOMA-IR), and high density lipoprotein cholesterol (HDL) levels compared with the placebo group.Conclusion: The current study revealed that synbiotic supplementation has favorable effect on inflammatory factors, liver enzymes and some anthropometric indices, lipid profiles and glucose homeostasis parameters in patients with NAFLD. 相似文献
We present processing (green and sintered), part shrinkage and warping, microstructural characterization, and mechanical properties of Si3N4 made by fused deposition of ceramics (FDC), using optical microscopy, scanning electron microscopy, and X-ray diffraction. The mechanical properties (fracture strength, fracture toughness, and Weibull modulus) are also reported. Proper FDC build parameters resulted in dense, homogeneous, near-net-shape Si3N4, with microstructures and mechanical properties similar to conventionally processed material. Mechanical properties are shown to be isotropic, while there is some degree of microstructural texturing (preferred β-Si3N4 grain orientation) in sintered components. 相似文献
This paper updates a method for generating small, accurate kinetic models for applications in computational fluid dynamics programs. This particular method first uses a time-integrated flux-based algorithm to generate the smallest possible skeletal model based on the detailed kinetic model. Then, it uses a multi-stage optimization process in which multiple runs of a genetic algorithm are used to optimize the rate constant parameters of the retained reactions. This optimization technique provides the user with the flexibility needed to balance the fidelity of the model with their time constraints. The updated method was applied to the reduction of a methane-air model under conditions meant to approximate the end of a compression stroke of an internal combustion engine. When compared to previous techniques, the results showed that this method could produce a more accurate model in considerably less time. The best model obtained in this study resulted in relative errors ranging from 0.22 to 1.14% on all six optimization targets. This reduced model was also able to adequately predict optimization targets for certain operating conditions, which were not included in the optimization process.
Due to their non-polluting nature and environment friendliness, Renewable Energies have gained great deal of attention and deserve a substantial body of both theoretical and empirical research. Amongst other factors, the low operational cost and simple maintenance procedures attributed the Oscillating Water Column (OWC) are perhaps the main reasons why this system is the most used concept for the ocean wave energy capture.In this paper, through extensive experimental research various geometrical designs of an OWC system is investigated and the optimized set up for the maximum energy harness is obtained.The initial chamber dimensions were 10 × 50 × 53 cm with the chamber being placed in an open channel with wave-simulating equipment with dimensions of 16 × 0.7 × .05 m. For various chamber geometries, with the aid of a air rotameter and a Pitot tube equipped with a digital manometer, the outlet air flow and velocity from the chamber was measured and registered.The measurements were then interpreted to provide design data for the optimal geometry of the chamber that may yield the maximum conversion of wave energy to useful energy. 相似文献