Sharif Digital Repository

In this paper a probabilistic methodology based on core nodalization is proposed to estimate the core power in the presence of xenon oscillation. A time-dependent Monte Carlo neutron transport code named MCSP-NOD is developed for dynamic analysis in arbitrary 3D geometries to simulate xenon oscillations as well as sub-critical condition with feedbacks. The new code is based on the approach adopted in MCNP-NOD which was previously introduced as a tool for core transient analysis using the MCNPX platform. As before, the core is divided into nodes of arbitrary dimensions, and all terms of the transport equation e.g. interaction rates, leakage ratio are estimated using the MC techniques.... 

Development of new techniques for detection and analysis of xenon/krypton mixtures is significant for both industrial and environmental purposes. In this research, direct simulation Monte Carlo is applied to analysis Xenon/Krypton gas mixtures through different molecular forces inside a new micro gas sensor (MIKRA). In this device, a temperature difference inside a rectangular enclosure with heat and cold arms as the non-isothermal walls induces a molecular force known as Knudsen force at low pressure condition. This force is proportional to the main characteristics of the gas mixture. In order to simulate a rarefied gas inside the micro gas detector, Boltzmann equations are applied to... 

The potentials of carbon nanotubes (CNTs) as mechanical resonators for atomic-scale mass sensing are presented. To this aim, a nonlocal continuum-based model is proposed to study the dynamic behavior of bridged single-walled carbon nanotube-based mass nanosensors. The carbon nanotube (CNT) is considered as an elastic Euler–Bernoulli beam with von Kármán type geometric nonlinearity. Eringen’s nonlocal elastic field theory is utilized to model the interatomic long-range interactions within the structure of the CNT. This developed model accounts for the arbitrary position of the deposited atomic-mass. The natural frequencies and associated mode shapes are determined based on an eigenvalue... 

Henry's law constant and crystal diffusivity of xenon in the granulated nano-NaY zeolite were measured by the pulse gas chromatography method. For this purpose the moments of response peaks of xenon were analyzed. The effect of extra column parts of the utilized chromatographic system was also considered by analyzing the moments of the response peak which was obtained by pulse injection of inert gas of helium into the carrier gas of nitrogen. In addition, the measurement of average velocity of the carrier gas regarding the pressure drop in the extra column parts of the system attributed to precise results. By carrying out the experiments at various temperatures in the range of 30-110 °C the... 

In this study, the effects of TiO2 addition on the physical and photoelectrochemical properties of ZnO thin films have been investigated. The (TiO2)x-(ZnO)1-x nanocomposite thin films were dip-coated on both glass and indium tin oxide (ITO)-coated conducting glass substrates with various values of x, specifically 0, 0.05, 0.1, 0.25 and 0.5. Optical properties of the samples were studied by UV-vis spectrophotometry in the range of 300-1100 nm. The optical spectra of the nanocomposite thin films showed high transparency in the visible region. The optical bandgap energy of the (TiO2)x-(ZnO)1-x films increased slightly with increasing values of x. The crystalline structure of the nanocomposite... 

The synergistic effect of plasmonic Au-Ag nanoparticles (NPs) on the increase of absorption band of nano-sized TiO2 and magnetic property of Fe3O4 NPs on the separation-ability of this semiconductor was applied for preparation of eight magneto-plasmonic photocatalysts for degradation of rhodamine-6G (Rh6G) in textile wastewater. The size, structure, morphology, crystallinity and optical and magnetic properties of prepared photocatalysts have been evaluated by various characterization techniques. Their photocatalytic activities were assessed under irradiation of an intense linear 405-nm laser and a continuous solar-simulated xenon lamp. The results were demonstrated that in comparison to the... 

In this study, two new composite membranes with antifouling and anti-biofouling properties were prepared through the modification of commercial polyamide (PA) discs using combination of in-situ polymerization of polyacrylic acid (PAA) and grafting of two synthesized bi-plasmonic Au-Ag and Ag-Au photocatalysts. The synthesis and characterization of the photocatalysts in batch mode were discussed in details as primary studies. Two intense 405-nm and 532-nm lasers for Ag-Au and Au-Ag photocatalysts, respectively and a solar-simulated xenon lamp for both photocatalysts were applied for photodegradation studies and the results were compared. In addition, the effect of other parameters such as... 

This study focused on the synthesis of TiO2-Zeolite nanocomposite through a sol-gel approach. The decrease in the size of the nanocomposite is considered a primary parameter to improve photocatalytic activity. In this regard, fabricated samples were exposed to laser irradiation (532 nm) for four different time intervals in order to investigate the size variation of the nanocomposite. FTIR, UV-Vis, XRD, DLS, SEM and EDX analyses were applied to characterize and determine the size of the products. An optimized nanocomposite sample, in term of the particle size, was used for photodegradation of 2,4-D herbicide from aqueous solution. Photodegradation was carried out under UV irradiation (12 W)...