Sharif Digital Repository

Surface crack patterns can easily show the behavior of concrete elements and structures. However, visual damage inspection performed by experts is a subjective approach and is prone to inaccuracies. The quantification makes this process objective and more reliable. In that regards, the maximum crack width is used as a practical measurement. It has been shown that the crack width is not a good indicator of damage due to its inherent uncertainties; In fact, it might bounce back after unloading. As such, a dimensionless parameter so-called Fractal Dimension has been introduced as a robust index that can quantify the complexity of crack distribution efficiently. The present study aims to... 

In this research, a triethylene glycol (TEG)/nano-zeolite Na-Y liquid membrane was developed in order to investigate the effect of zeolite nanoparticles on separation performance of a liquid membrane. To do this, a high yield nano-zeolite Na-Y was synthesized using mid-synthesis addition method. The synthesized samples were characterized by XRD, FT-IR, and SEM (EDX) instrumental techniques. A supported liquid membrane was prepared by impregnating a porous hydrophilic PVDF support with TEG and nano-zeolite Na-Y. The permeation tests of single gas components of O2, N2 and CO2 were carried out at pressure differences of 0.8 and 1.8 bar. The permeances of the single gases were found to be: CO2 >... 

MFI-type zeolite was successfully synthesized by hydrothermal crystallization of clear synthesis mixtures. A statistical experimental design method (the Taguchi method with an L8 orthogonal array) was implemented to optimize the experimental conditions for the preparation of MFI nanocrystals with respect to particle size and distribution as the desirable properties. In the Taguchi experimental design, crystallization temperature, water content, template/silica molar ratio, aluminum content, as well as the presence of alkaline cations were chosen as significant parameters affecting the properties. It was shown that water and aluminum content of the synthesis solution were the most important... 

In order to produce an inexpensive catalyst for the Fischer-Tropsch synthesis (FTS), zeolitized high silicon fly ash utilized as a catalytic support for cobalt nanoparticles. The ability of this new support in proper hosting of nanoparticles studied through various characterization methods such as X-ray diffraction, nitrogen sorption, transmission electron microscopy, energy-dispersive spectroscopic and temperature-programmed reduction. In addition, the catalytic properties for the FTS evaluated at 523 K and 20 MPa. The obtained results show remarkable influence of utilized support specifications upon the formation and catalytic behavior of cobalt nanoparticles in the FTS  

Modified perovskite-type oxides were synthesized through co-precipitation and conventional citrate methods. The synthesized perovskite materials had the nominal compositions of LaCoO3, LaCo0.8Cu0.2O3, La0.8Sr0.2Co0.8Cu0.2O 3, and La0.8M0.2FeO3 (where M = Ce and Sr). The catalytic activity of the perovskite samples (for low-temperature CO oxidation) was measured using a quartz reactor with an inlet gas mixture containing 97% N2, 1% O2, and 2% CO. The prepared perovskite samples were characterized by SEM, nitrogen adsorption (BET), XRF, and XRD analyses. The perovskite catalysts showed good structural and chemical stability up to 600 °C and high activity for the catalytic CO oxidation... 

In the study, the daily and monthly performance of a photovoltaic thermal system integrated with phase change material is investigated in Shanghai, China. A three-dimensional model of photovoltaic thermal system integrated with phase change material system is developed and numerically simulated. Water is considered as working fluid, and the fluid flow regime is laminar and incompressible. Both quasi-steady and transient models are compared together, and the transient model is selected because of its higher accuracy. Validation analysis is performed on the numerical model to show the reasonable agreement of current research compared to some other research. After obtaining the suitable... 

Gravitational microlensing, the lensing of stars in the Milky Way with other stars, has been used for exploring compact dark matter objects, exoplanets, and black holes. The duration of microlensing events, the so-called Einstein crossing time, is a function of distance, mass, and velocities of lens objects. Lenses with different ages and masses might have various characteristic velocities inside the Galaxy and this might lead to our misinterpretation of microlensing events. In this work, we use the Gaia archived data to find a relation between the velocity dispersion and mass, and the age of stars. This mass-velocity dispersion relation confirms the known age-velocity relation for... 

The effects of H2O/SiO2, TMAOH/SiO2, Na/(Na+K), and SiO2/Al2O3 ratios in the parent gels on the crystallization of nanoparticles of T-type zeolites were studied. A Taguchi orthogonal experimental design with the above-mentioned parameters (each at three levels) was used to optimize the experiment parameters by the analysis of variances (ANOVA). Applying the Taguchi method significantly reduced the time and cost required for optimization. The synthesized products were characterized by X-ray diffraction and scanning electron microscopy. As a result of the Taguchi analysis, H2O/SiO2 and TMAOH/SiO2 were the most influencing parameters for the synthesis of zeolite T. © 2009 WILEY-VCH Verlag GmbH...