Sharif Digital Repository

Today, with the widespread use of decentralized systems, many people interact with each other and this interaction can endanger their safety. Therefore, the strategy should be to keep people safe. Interaction with a trusted and highly recommended people is essential and this is considered the first step toward security. Privacy preserving is critical in Successful operation of reputation system, in other words, the trust value should not be available. This method can prevent from positive and negative feedback of people because one person (may be due to personal animosity or to lack of commitment or person discomfort) can manipulate the trust value. For this reason, the trust value should be... 

Hydrogen is known to be a renewable and clean source of energy, which produces water vapor and zero carbon dioxide as a result of its combustion. Photoelectrochemical water splitting (PEC) could be a promising approach in order to generate hydrogen by sunlight. Hematite (α-Fe2O3), as the most abundant naturally occurring form of iron oxide with suitable band gap, low cost, high stability and nontoxicity is considered to be an ideal photoanode. However, intrinsic drawbacks of hematite including low electrical conductivity, limited hole diffusion length, and high recombination rate of electron-hole pairs restrict its photoelectrochemical performance efficiency. In the present research,... 

In this thesis a smart anticorrosive pH-responsive coat was developed with layer by layer (LbL) technique in the assembly of SiO2/CTAB/PSS/HMTA/PSS/PEI/PSS. SiO2 nanoparticles were prepared from Matland Company (Iran) with average size of 24 nm. At first, the corrosion inhibition of HMTA for API 5L Grade B steel in 3.5 wt.% NaCl solution was investigated. Tafel polarization technique showed the optimum concentration of HMTA was 0.08 M with 92% corrosion inhibition efficiency as the morphology of coverage and adsorption on the steel surface was confirmed by SEM and EDS. AFM results showed the roughness of the surface decreased from 241 nm to 56 nm that is attributed to HMTA adsorption on the... 

In this study, SiO2-CaO-MgO galsses and glass-ceramic powder doped with Nd3+ were synthesized with sol-gel method. Tetraethylorthosilicate (TEOS), Ca(NO3)2.4H2O, Mg(NO3)2.6H2O, Nd(NO3)3.6H2O, ethanol, distilled water, and HNO3 were used as starting materials. The synthesized powder’s properties were examined with STA, XRD, DRS, PL, FTIR and SEM analysis. From XRD patterns of glass samples, the role of dopant was introduced as intermediate oxide in glass matrix. The XRD patterns of glass-ceramic samples indicated that the bredigite and akermanite crystals were formed in glass matrix. The band gap energy of samples were calculated from DRS analysis and were seen with increasing the dopant... 

Pragmatic assessment and consistency in rating are among the subject matters which are still in need of more in-depth investigations. The significance of the issue is highlighted when remembering that inconsistency in ratings would surely damage the test fairness issue in assessment and lead to much diversity in ratings. The purpose of this study was investigating the criteria that native (American) and non-native (Iranian) English speaking teachers considered while rating the pragmatic productions of Iranian EFL learners regarding the two speech acts of compliment and compliment response. Overall, a hundred and twenty teachers (sixty native and sixty non-native raters) participated in this... 

One of the issues that has always been paid attention to financial markets is that the use of mathematical relations and formulas for the better estimation of the forecasts made by the process of indicators that are of great importance in financial markets. In financial markets, algorithms have been developed to help reduce the cost of executing transactions from a variety of factors, in order to impose less costs on traders. In these algorithms, a market order and a limited order are used in such a way that the cost of executing transactions can eventually be minimized. Under a limited order, traders determine how much their stake will be at what price they are willing to trade, but in the... 

Metasurfaces offer unique capabilities for the unconventional scattering and control of electromagnetic waves. By using metasurfaces, one can arbitrarily manipulate the amplitude, phase, and polarization of incident waves, enabling devices such as flat lenses, holograms, and electromagnetic wave beam deflectors. In recent years, time-varying electromagnetic structures, including time-modulated metasurfaces, have provided enhanced possibilities for controlling electromagnetic waves. By modulating the properties of metasurfaces over time, phenomena such as nonreciprocity, frequency shifts, and parametric amplification can be achieved, which traditionally require magnetic materials or nonlinear...