Sharif Digital Repository

Natural Boron consists of two stable isotopes, 10B (19.3%) and 11B (80.7%). 10B isotope has a large thermal neutron absorption and therefore, use widely in such aspects as modern industry, atomic energy industry (as control rods, chemical shim and etc.), Medical science and applications in disclosing neutrons to measure neutron reactors fluxes. Boron trifluoride is most importantly used as a reagent in organic synthesis, typically as a Lewis acid. In this study, we designed and built the related setup for preparation of high purity BF3 gas. And then we tried to optimize the efficiency with process design tools such as response surface methodology (RSM). At the end of this study, we were able... 

Hydrogen gas is considered as a clean fuel and energy carrier that its storage for future uses is a challenging issue. One of the methods to store it, is adsorption on a group of adsorbents called metal-organic frameworks. In this research, one of these frameworks called ZIF-8, has been selected to study hydrogen storage capability. To evaluate the effect of having two metals, a mixture of two metals was used in the synthesis process. To characterize the structure of the synthesized adsorbents, X-ray powder diffraction (XRD),adsorption and desorption of nitrogen at temperature of 77 K, Field Emission Scanning Electron Microscopy (FESEM), energy-dispersive X-ray Spectroscopy (EDS) and... 

In recent years membrane bioreactors (MBR) were widely used as an advanced process for industrial wastewater treatment. But fouling issue causes some restrictions in these systems. So for fouling reduction many researches were done.In this study for fouling improvement, blending of hydrophilic polymer (PAN) with main polymer PVDF was used. Blending membrane in phase inversion process with DMAC as solvent and water as non-solvent was made. For pore-forming in membranes, PVP as hydrophilic additive with three different composition was added and then for more enhancement of antifouling property of membrane, TiO2 nanoparticles with four different composition were added to polymeric... 

The aim of this dissertation is to investigate the extraction of calcium ions using an emulsion liquid membrane (ELM) with an isotopic perspective. Considering the importance of ion extraction as a preliminary step to isotope separation, the factors affecting the extraction of Ca(II) ions in the ELM process were investigated and optimization of the process was performed in this study. Dicyclohexano-18-crown-6 (DC18C6) was used as the carrier due to isotopic considerations. However, its extractability for calcium ions is limited. In order to address this issue, it is possible to introduce an organic acid, specifically di-(2-ethylhexyl) phosphoric acid (D2EHPA), into the membrane phase. This... 

Hydrothermal supercritical method is one of the most suitable methods for metal oxide nano powder, ceramics and mineral catalyst synthesis. Metal oxides nanopowder in its pure or mixed form has wide potential application as chemical industrial catalyst, hot Superconductors, magnetic material, gas sensors and car catalyst convertors. One of the most important metal oxides aspects of application is uranium oxide as nuclear reactor fuel is used. In addition, UO2 is selective catalyst for converting methane to methanol process and Decomposition of organic Chlorine material. In Supercritical hydrothermal method done in high pressure reactor with critical to fluid, is new method for the... 

Thin film graphene oxide(GO) membranes have been promising potential for gas purification due to thin lamellar microstructure, stable a few atom thick layers and very short intersheet distances. In this research, the nanoporous graphene oxide membranes have been prepared by vacuum and pressurized ultrafiltration on the modified polyacrylonitryle(mPAN) sublayer for helium separation from Nitrogen and carbon dioxide gas mixture. The separation performance of synthesized GO membrane was controlled by varying parameters such as concentration of stabilized aqueous GO solution, pores size range of support and its surface properties, centrifuge time, applied pressure after synthesis, humidity,... 

This projct includes the following sections: In the first section, Michael addition reaction of anthrone to nitroolefins is described in water without using any catalyst to prepare 9-(2-nitro-1-arylethyl)anthracene-10(9H)-ones. This method is green, efficient and gives high yields of products. The solvent effect is also investigated. In the second section, Considerable efforts have been directed in recent years towards the transition metal complex catalyzed oxidation of organic compounds such as olefins, sulfides, benzylics alcohols and phenolics. And due to the various advantages of supported heterogeneous catalysts and in our aim to develop a simple, more efficient and eco-friendly... 

In this research, we have tried to predict the morphology of the membranes that were prepared by phase inversion method. In this research Polyvinylinedifluoride (PVDF) and dimethylacetamide (DMAc) was used as the polymer and solvent. The affect of titanium oxide (TiO2 ) and polyvinylpyrolidene (PVP) which are respectively an inorganic and an organic additive, on the morphology of the membranes was investigated. Ternary and Quadratic phase diagrams were drawn based on the Flory Huggins theory. The interaction between components was determined and the effect of interactions and molar volumes of polymer, solvent, non-solvent and additives on the binodal line was investigated. To predict... 

The leaching process is the first stage in the process of extracting uranium out of the ore. The leaching, based on the used material is divided into two main methods of acidic and alkali leaching. Each of these two techniques have their own pros and cones. It is notable that due to lower costs, and faster kinetics, the acid leaching is the first option of the mines unless the percentage of carbonates (and the other acid-soluble materials) in the ore are too high that makes this process uneconomical because of higher acid consumption. The kinetics of the acid leaching of the uranium depends on various parameters such as acid concentration, the particle size, exposure time and the temperature... 

The use of medicinal plants to improve living standards has coincided with the history of human life. Throughout history, man has had no choice but to resort to plants. Among all the plants, Iranians have had a deep connection with Mohammadi flowers and throughout history have tried to extract the plant in various ways. Therefore, in this article, we have examined the method of supercritical extraction. In order to create a criterion for comparing the maximum extraction rate with the Soxhlet method and with the help of normal hexane solvent, the extraction operation was performed and its efficiency was estimated to be equal to 1.02%. Then, with supercritical experiments, it was found that... 

We present a deep neural network to classify dermatological disease from patient images. Using self-supervised learning method we have utilized large amount of unlabeled data. We have pre-trained our model on 27000 dermoscopic images gathered from razi hospital, the best dermatological hospital in Iran, along with 33000 images from ISIC 2020 dataset. We have evaluated our model performance in semi-supervised and transfer learning approaches. Our experiments show that using this approach can improve model accuracy and PRC up to 20 percent on semi-supervised setting. The results also show that pretraining can improve classification PRC up to 20 percent on transfer learning task on HAM10000...