Sharif Digital Repository

Since ultraviolet (UV) irradiation cannot be applied for a long time in practical applications, it is necessary to develop a narrow band gap photocatalyst to decompose environmental pollutants under visible irradiation. In this research, (WO3)x-(TiO2)1-x nano-porous layers were fabricated by micro arc oxidation (MAO) and influence of the electrical current type on their physical and chemical properties was investigated. Morphological studies, performed by SEM technique, revealed that pore size and roughness decreased with the frequency and increased with the duty cycle. The pulse-grown layers had a finer structure when compared to those fabricated under direct current. XRD and XPS results... 

Simple synthesis of silver doped TiO2 nanostructured layers by micro arc oxidation process is reported for the first time. The layers consisted of anatase and rutile phases whose characteristic XRD-peaks shifted toward lower diffraction angles when compared to the pure micro arc oxidized TiO 2 layers. Silver-doping was confirmed by XPS technique. The anatase phase crystalline size was determined as 27.6 and 21.8 nm for the layers grown under the voltages of 350 and 500 V. Employing a UV-Vis spectrophotometer, a red shift in the absorption edge of the layers was observed when silver was incorporated into the titania lattice  

Micro arc oxidation technique, as a facile and efficient process, was employed to grow sulfur doped titania porous layers. This research sheds light on the photocatalytic performance of the micro arc oxidized S-TiO2 nano-porous layers fabricated under pulse current. Morphological and topographical studies, performed by SEM and AFM techniques, revealed that increasing the frequency and/or decreasing the duty cycle resulted in formation of finer pores and smoother surfaces. XRD and XPS results showed that the layers consisted of anatase and rutile phases whose fraction was observed to change depending on the synthesis conditions. The highest anatase relative content was obtained at the... 

V2O5-TiO2 nanostructured porous layers were grown through micro arc oxidation of titanium in vanadate containing electrolytes. This study sheds light on the effect of the electric current type on the photocatalytic performance of the layers. Surface morphology of the layers was investigated by SEM. The results revealed a porous structure with a pores size of 30-180 nm depending on the frequency and the duty cycle. A uniform porous structure was obtained under the pulse-DC regime. Topographical investigations revealed a rough surface which is favorable for catalytic applications. Our XRD and XPS results showed that the layers consisted of anatase, rutile, and vanadium oxide phases whose... 

Very recently, we fabricated (WO3)x-(TiO 2)1-x layers via micro-arc oxidation process under different applied voltages. Morphological and topographical studies, accomplished by SEM and AFM techniques, revealed that the pores size as well as the surface roughness increased with the voltage. Phase structure and chemical composition of the layers were also investigated by XRD and XPS and the results showed the grown layers consisted of titanium and tungsten oxides. It was found that WO3 dispersed in the TiO2 matrix and also doped into the TiO2 lattice. In addition, optical properties of the synthesized layers were studied employing a UV-vis spectrophotometer. Band gap energy of the layers was... 

In the present study, we performed hydrothermal method as a simple and efficient route for the synthesis of rutile TiO 2 nanostructures in various concentrations of lithium hydroxide solutions. TiO 2 nanopowders with average sizes of 15 and 23 nm were prepared using 4 M and 7 M LiOH solutions. X-ray diffraction analysis (XRD), transmission electron microscope (FEG-STEM), scanning electron microscopy (SEM), and Brunauer-Emmet-Teller (BET) analyses were used in order to characterize the obtained products and comparison of the morphology of the powders obtained in different concentrations of LiOH solvent. It was shown that alkali solution concentration has affected the crystallinity,... 

Through a fast, simple, low cost, surfactant-free and convenient microwave-assisted route, narcis-like ZnO nanostructures (10-15 nm size) with flower diameters in the range of 1-2.5 μm were synthesized. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and room temperature photoluminescence (PL) measurements were used to characterize the produced ZnO nanostructures. The principle raw materials - ammonium hydroxide (NH4OH) and zinc acetate dihydrate [Zn(CH3COO)2·2H2O] - were both inexpensive. The method was fast, simple and surfactant-free capable of producing larger quantities of zinc oxide... 

Analysis of cancer mutational signatures have been instrumental in identification of responsible endogenous and exogenous molecular processes in cancer. The quantitative approach used to deconvolute mutational signatures is becoming an integral part of cancer research. Therefore, development of a stand-alone tool with a user-friendly interface for analysis of cancer mutational signatures is necessary. In this manuscript we introduce CANCERSIGN, which enables users to identify 3-mer and 5-mer mutational signatures within whole genome, whole exome or pooled samples. Additionally, this tool enables users to perform clustering on tumor samples based on the proportion of mutational signatures in... 

TiO2 layers were grown via pulse type microarc oxidation process under different applied voltages, frequencies, and duty cycles. Surface chemical composition and phase structure of the synthesized layers were studied utilizing X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Furthermore, scanning electron microscope (SEM) and atomic force microscope (AFM) were employed to investigate surface morphology and topography of the layers. It was revealed that the layers had a porous structure with both anatase and rutile phases. The anatase relative content in the layers increased with the applied frequency; meanwhile, it decreased with duty cycle at low applied voltages, but... 

The spatiotemporal dynamic of salinity concentration (SC) in saline lakes is strongly dependent on the rate of water flow into the lake, water circulation, wind speed, evaporation rate, and the phenomenon of salt precipitation and dissolution. Although in-situ observations most reliably quantify water quality metrics, the spatiotemporal distribution of such data are typically limited and cannot be readily extrapolated for either long-term projections or extensive areas. Alternatively, remotely sensed imagery has facilitated less expensive and a stronger ability to estimate water quality over a wide range of spatiotemporal resolutions. This study introduces an adaptive learning model that... 

We have studied systematically photocatalytic properties of the vertically aligned ZnO@CdS core-shell nanorods where the features were grown through a multistep procedure including sol-gel for the formation of ZnO seed layer, hydrothermal process to grow ZnO nanorods, and successive ion layer adsorption and reaction (SILAR) process to deposit CdS nanoshells onto the ZnO nanorods. Formation of the ZnO seed layer and vertically aligned ZnO nanorods (d ∼ 40 nm) with a hexagonal cross-section was confirmed by AFM and SEM imaging. Successful capping of ZnO nanorods with homogeneous CdS nanocrystallites (∼5 nm) was ascertained by HRTEM diffraction and imaging. Optical properties of the samples... 

Galvanostatic method was used to electrodeposit Fe nanostructures on platinum electrodes as catalysts. Scanning electron microscopy (SEM) revealed flower-like Fe deposits with high surface area. Carbon nanotubes were grown on flower-like Fe nanostructures by chemical vapor deposition. The structure of the synthesized carbon nanotubes was investigated by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and X-ray diffraction. According to X-ray diffraction patterns, Fe was the only detected constituent of the deposited coating. The carbon nanotubes had small wall-thickness and wide hollow core  

Dissolved air precipitation/solvent sublation (DAP/SS) was used for treatment of simulated and real oilfield produced water to generate very fine bubbles which are necessary for effective separation. In this method micro bubbles produced by saturation of air in a pressurized packed column were released in an atmospheric column leading the bubbles to raise resulting trapped contaminants in the Gibbs layer around them to be removed by a layer of immiscible solvent at the top of column. The method was conducted to solutions including Benzene, Toluene and Chlorobenzene (ClB) as part of BTEX contaminants in produced water, mixture of them as simulated produced water and real oilfield produced... 

In this paper, a heuristic method for determining the optimal number of clusters is proposed. Four clustering algorithms, namely K-means, Growing Neural Gas, Simulated Annealing based technique, and Fuzzy C-means in conjunction with three well known cluster validity indices, namely Davies-Bouldin index, Calinski-Harabasz index, Maulik-Bandyopadhyay index, in addition to the proposed index are used. Our simulations evaluate capability of mentioned indices in some artificial and medical datasets. © 2008 IEEE  

In this research, the effect of different amounts of Cr2O3 (2.5, 5, 7.5, and 10 wt.%) and sintering temperature (1850, 1900, and 1950 °C) on the sinterability and mechanical properties of liquid-phase sintered SiC-matrix composites was studied. First, raw materials were ground for 3 h using a planetary mill whose rotational speed was 180 rpm. The process of pressing the samples was completed using uniaxial pressing with the applied pressure of 90 MPa. Finally, the samples were sintered under an argon atmosphere at various temperatures for 1.5 h. In the end, the best sintered sample was annealed at 2000°C for 2 h. The phases, microstructure, and chemical composition of the samples were... 

S-doped TiO2 layers were grown on titanium substrates by MAO process. SEM results revealed a porous morphology with a pore size of 40-100 nm. Our XRD analysis showed that the anatase relative content reached its maximum value at the voltage of 500 V. The existence of sulfur in the states of S 4+ and S6+ which substituted Ti4+ in the titania crystalline lattice was confirmed by XPS results; meanwhile, no S 2- was detected. That is, a cationic doping was observed. EDS results showed that sulfur concentration in the layers increased with the voltage. The band gap energy was also calculated as 2.29 eV employing a UV-Vis spectrophotometer