Sharif Digital Repository

Nickel/silicon carbide composite electrodeposits were prepared on a rotating disk electrode (RDE), under pulse current condition. The effect of pulse parameters, current density, SiC content in the electrolyte on the codeposition of SiC were studied. Afterwards, the effect of codeposited SiC amount was investigated on electrochemical behavior and nanomechanical properties of coatings. The coatings were analyzed with Scanning Electron Microscopy (SEM), linear polarization, nanoindentation and Atomic Force Microscopy (AFM). The Ni-SiC electrocomposites, prepared at optimum conditions, exhibited improved nanomechanical properties in comparison to pure nickel electrodeposits. With increasing... 

In this research, a new transient mathematical model based upon tanks-in-series configuration was developed to simulate the direct synthesis of dimethyl ether (DME) from syngas in a commercial-scale slurry bubble column reactor. A comparison between the simulation results and experimental data showed that the applied model might acceptably describe the behavior of the slurry reactor. Furthermore, simulation results in the heterogeneous bubble flow regime indicated that the proposed model with 10 tanks-in-series provided the optimum condition. Utilizing this transient model and considering catalyst deactivation, the effect of operating conditions on DME productivity and CO conversion were... 

Anatase and amorphous TiO2 nanoparticles were used to improve recovery of heavy oil from sandstone cores. Before performing core floods, the stability of nanoparticles at different salinities was tested using ζ potential and ultraviolet-visible (UV-vis) methods. While water recovered only 49% of the oil in the core flood experiments, 0.01% anatase structure solution recovered 80% of the oil after injecting two pore volumes at optimum conditions. To understand the mechanism responsible for improved recovery, contact angle measurements were performed on the rock surface before and after treatment with the nanoparticle solution. Contact angle measurements showed that the rock wettability... 

To the best of our knowledge, this work presents the first successful effort to fabricate and study nanostructured Ni-based composite coatings using the electrophoretic deposition method with nanostructured SiO2 particles. In this work, Ni/SiO2 nanoparticle composite coatings were prepared by electrophoretic deposition (EPD) [1] and their hardness, wear and corrosion resistances [2] were examined. After studying the morphology of the coatings and finding the optimum conditions for uniform coating, in order to improve the mechanical properties as well as resistance to corrosion, sintering was performed. The Ni/SiO2 nanocomposite coatings show excellent hardness (∼376 HV), reduced Young's... 

4-hydroxycoumarin 2a and 4-hydroxy-6-methyl-pyran-2-one 2b were applied in a one-pot reaction with Baylis-Hillman adduct acetates 1 to form novel 3-benzylpyrano [3, 2-c] pyran-2, 5-diones 3 in high yields (70-85%). The synthesized framework is available in many biologically active moieties. The reaction was carried out under different conditions to achieve optimum conditions. The results indicated that Et3N, as a base under solvent-free conditions, was optimum. The reaction procedure and purification method are mild and straightforward  

The vanillin assay is a spectrophotometric method for anthocyanin determination that is simple, quick and inexpensive. The method is preferred because of its high sensitivity, specificity and simplicity; however, the results of this test are influenced by several factors. Hence, a D-optimal experimental design approach was investigated to simultaneously, without loss of information, optimize five factors that influence the vanillin assay: acid normality, vanillin concentration, temperature, time and acid type. Further optimization with a D-optimal design and response surface analysis (RSM) showed that a second-order polynomial model fit the experimental data appropriately. The optimum... 

In this study, Glucoamylase production by Aspergillus niger was investigated under solid state fermentation using low cost by-products of agricultural processes as substrate. Highest enzyme production was observed when a combination of wheat bran (WB) and corn flour (CF) was used as compared to WB+ rice bran, WB+ rice flour and WB alone. Several compositions of corn flours were experimented. The best combination of WB in addition of 10% corn flour resulted maximum enzyme activities. Study of the fermentations in flasks revealed 373.3 IU/gds and 41.4 g/l for the enzyme activity and protein concentration respectively under conditions of 30± 1°C, pH 4.7 and time 96 h. Optimum conditions... 

Penicillin G is an active pharmaceutical ingredient of great importance in health sectors. Meanwhile, because of its huge quantity production and resistance to biodegradability, this antibiotic is ubiquitously presented in aquatic environment. In this study, the degradation of effluent wastewater from Penicillin G production plant by Photo- Fenton process and Ultrasound process (Sonolysis) was investigated, the effects of different process variables in both methods were evaluated and at last the degradation of Pen-G by these two processes in the optimum conditions was compared. Pen-G concentration and Chemical Oxygen Demand (COD) were selected as the environmental parameters to follow the... 

Experimental design of directly suspended droplet liquid-liquid-liquid microextraction has been used to determine residue of 2,4-D, in environmental water samples. A free suspended droplet of 5.5 μL of receiving phase is delivered to the top-center position of 1-Octanol, which is an immiscible organic solvent, floating on the top of a 2.5 mL aqueous sample while being agitated by a stirring bar to create a mild vortex at the center of the vial. Central composite rotatable design has been used for studying the effect of the parameters, the factors interacting with each other and finding the optimum condition. The chromatographic separation was accomplished on a shim-Pak C18 column using a... 

Al-1100/St-12 aluminum clad steel sheets were produced using roll bonding process at different reductions in thickness and with various supplemental annealing treatments. Experiments were conducted by applying the Taguchi method to obtain optimum condition for maximizing the joint strength. The joint strengths of the bi-layer sheets were evaluated by peel test. The Al/Fe intermetallic phases at the joint interface and the peeled surfaces were examined using scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) and Vickers microhardness test were performed to characterize the intermetallic compounds. The results indicate that at the optimum condition of 0.50 reduction in... 

In this research a mathematical model for direct oxidization of hydrogen sulfide into elemental sulfur in a fluidized bed reactor with external circulation was developed. As the catalyst is deactivated in the fluidized bed, it might be placed in a reduction tank in order to remove sulfur through heating above its dew point. The reactor model demonstrated via MATLAB software. It was shown that variations of H 2S conversion as well as; products formed were reasonable in comparison with corresponding results of a fixed bed reactor. Through analyzing results of this model, it became possible to propose the main optimized operating conditions for the process considered. These conditions included;... 

Palm oil (PO) and sunflower oil (SFO) blends with varying proportions were subjected to enzymatic interesterification (EIE) using a 1,3-specific immobilised lipase. The interesterified blends were evaluated for their slip melting point (SMP), solid fat content (SFC) at 10-40°C, p-anisidine value, peroxide value, free fatty acids (FFA), induction period of oxidation at 110°C (IP110) and composition of fatty acids by gas chromatography. Under EIE treatment, the blends of PO and SFO in different proportions (20:80, 40:60, 50:50, 60:40 and 80:20) had saturated and unsaturated fatty acid content in the range of 37.6-52.0% and 48.0-62.4%, respectively. The blends showed a considerable reduction in... 

TiO2 nanorods have been successfully grown into a track-etched polycarbonate (PC) membrane by a particulate sol-electrophoretic deposition from an aqueous medium. The prepared sols had a narrow particle size distribution around 17 nm and excellent stability against aging, with zeta potentials in the range of 47-50 mV at pH 2. It was found that TiO2 nanorods were grown from dilute aqueous sol with a low, 0.1-M concentration. Fourier transform infrared spectroscopy (FT-IR) analysis confirmed that a full conversion of titanium isopropoxide was obtained by hydrolysis, resulting in the formation of TiO2 particles. X-ray diffraction (XRD) results revealed that TiO2 nanorods dried at 100 °C were a... 

In this paper, an industrial ethylbenzene production unit has been simulated and the results are compared against five-day experimental data. According to prevailing unit condition, i.e. recycled ratio of benzene, benzene selectivity, and energy consumption, the unit is not working under its optimum conditions for minimum cost of ethylbenzene production. In the current design, high amount of benzene recycle (6:1) causes to have an additional cost due to fractionation of ethylbenzene from benzene. A new approach is proposed to modify the benzene alkylation process and reduce the unit's energy consumption. In the newly designed scheme, two double-bed alkylation reactors converted into four... 

In this study simulation results for three double-fiber optical designs for the reflection measurements are reported. Modeling is perused for three cases namely Equal Fibers (EF), transmitter fiber shorter (TS) and receiver fiber shorter (RS) designs. By proper modeling and written programs the operations of such symmetric double-fiber probes are simulated and the role of different crucial parameters such as fiber-to-fiber distance (t), fiber core radius (r) and fiber Numerical Aperture (NA) are investigated. In the second study simulation results for the transmitter fiber shorter and receiver fiber shorter designs are investigated for different fiber length differences (w). Finally... 

In this study, the effect of electromagnetic vibration on joining of aluminum alloy 2024 was investigated. Simultaneously applying a static magnetic field and alternating electrical current passing through a conductor produced electromagnetic vibration. Joining was accomplished using constant electric current (60 A) and the magnetic flux of 75, 110, and 145 mT in the presence of argon gas. After joining, samples were cooled first by argon gas as a shielding gas and then by water. The microstructure and mechanical properties of the welded samples were studied for different electromagnetic vibrations. The optimum microstructure and mechanical properties were obtained when applied... 

A heterogeneous magnetic copper catalyst was prepared via anchoring of copper sulfate onto multi-layered poly(2-dimethylaminoethyl acrylamide)-coated magnetic nanoparticles and was characterized using various techniques. The catalyst was found to be active, effective and selective for one-pot three-component reaction of alkyl halide, sodium azide and alkyne, known as copper-catalyzed click synthesis of 1,2,3-triazoles. As little as 0.3 mol% of catalyst was found to be effective under the optimum conditions. The catalyst could also be recycled and reused up to seven times without significant loss of activity. Thermal stability, high loading level of copper on catalyst, broad diversity of... 

The bioinertness makes surface treatments essential to improve the bioactivity of porous titanium scaffold, and surface treatment might affect their mechanical properties. So finding an optimum condition lying between bioactivity and mechanical properties seems to be curial. In this research, the effect of the time of the thermal oxidation at 600 °C on apatite formation and mechanical properties of the porous titanium scaffold was studied. The results of thin film X-ray diffraction and Raman spectroscopy indicated that the surface of heat treated samples up to 480 min was mainly covered by rutile. Also, wettability measurement and in vitro apatite formation ability assessment indicated that...