Numerical modeling of baffle location effects on the flow pattern of primary sedimentation tanks

Computational fluid dynamics (CFD) is used extensively by engineers to model and analyze complex issues related to hydraulic design, planning studies for future generating stations, civil maintenance and supply efficiency. In order to find the optimal position of a baffle in a rectangular primary sedimentation tank, computational investigations are performed. Also laboratory experiments are conducted to verify the numerical results and the measured velocity fields which were by Acoustic Doppler Velocimeter (ADV) are used. The GMRES algorithm as a pressure solver was used in the computational modeling. The results of computational investigations performed in the present study indicate that the favorable flow field (uniform in the settling zone) would be enhanced for the case that the baffle position provide small circulation regions volume and dissipate the kinetic energy in the tank. Also results show that the GMRES algorithm can obtain the good agreement between the results of numerical models and experimental tests.     

Speckle noise reduction by division and digital processing of a hologram

One of the common problems in classical and digital holography is presence of speckle in reconstructed images. Some methods have been predicted for speckle reduction. Speckle has a statistical distribution in size and intensity. Thus complete elimination of them is impossible. But, one can use this statistical characters to reduce its effects.In this paper a method is proposed for reduction of speckle effect by recording a hologram and then dividing it to several sub-holograms. Each sub-hologram is used to produce an image. Final image is constructed by superposition of these images. The final image has a smaller amount of speckle noise. Experimental results verify effectiveness of this technique.     

Fe3O4@SiO2—CPTMS—Guanidine—SO3H-catalyzed One-Pot Multicomponent Synthesis of Polysubstituted Pyrrole Derivatives under Solvent-Free Conditions

Russian Journal of Organic Chemistry - A highly efficient procedure for the one-pot synthesis of polysubstituted pyrrole derivatives by the reaction between of aniline derivatives, β-diketones...     

Sensitive,Fast, Solution‐Processed Ultraviolet Detectors Based on Passivated Zinc Oxide Nanorods

Solution‐processed ultraviolet photodetectors based on passivated and unpassivated zinc oxide (ZnO) nanorods, in which the ZnO nanoparticles are synthesized by a hydrothermal method, are demonstrated and characterized. Photoconductive photodetectors fabricated using simple solution processing have recently been shown to exhibit high gains and outstanding sensitivities. One ostensible disadvantage of exploiting photoconductive gain is that the temporal response is limited by the release of carriers from trap states. Herein, specific chemical species are introduced onto the surfaces of ZnO nanoparticles to produce desired trap states with a carefully selected lifetime. Compared with conventional photodetectors based on ZnO nanoparticles, the proposed UV photodetectors have much higher photoresponses and faster response times in the UV region. The photoconductive gain of the fabricated photodetectors varies from 26.83 to 2.32×10² for passivated samples, which indicates high gain. The best temporal response for the fabricated detectors is 34 ms rise time and 132 ms decay time for ZnO nanoparticles passivated by hexamethylenetetramine.     

Study of Limit Cycles and Stability Analysis of Fractional Arneodo Oscillator

This paper deals with the existence and the characteristics of the limit cycles in the fractional-order Arneodo system. The analysis is done using the describing function method. Our focus is on a special case where two limit cycles exist. The parametric range for the case of interest is derived, and the frequency and the amplitude of the oscillation are predicted. Numerical simulation results are presented to further demonstrate the reliability of the analysis.     

Solvent‐free one‐pot synthesis of pyrane derivatives

A straightforward and an efficient method for the synthesis of 2H‐pyrans via the one‐pot, reaction of alkyl bromides, carbon disulfide, secondary amines, activated acetylenes and isocyanides under solvent‐free conditions without using any catalyst at room temperature is reported. The method offers several advantages including high yields of products and an easy work‐up procedure. J. Heterocyclic Chem., (2011).     

Analysis method of physical processes occurring at the interface between vortex and Meissner regions in high-temperature superconductors

A technique for probing the sample interior using the leading edge of an alternating evanescent magnetic field is suggested. It makes it possible to highlight and study physical processes taking place at the vortex front in superconductors. Successively increasing the field amplitude by equal amounts, one can study the formation and transformation of the magnetic microstructure in response to variation of the sample’s crystal microstructure. For samples with different microstructures, qualitatively new results are obtained. The technique suggested may be used for testing high-temperature superconductor epitaxial films and magnetic materials.     

A Mild Method for the Protection of Aldehydes as Dithioacetals and Dithiolanes Catalyzed by I2 Generated in Situ Using Fe(NO3)3.9H2O/NaI Under Heterogeneous Conditions

Structurally diverse aromatic aldehydes were thioacetalated in a clean and efficient reaction with ethane‐1, 2‐dithiol and thiophenol based on the use of I₂ generated in situ from Fe(NO₃)₃.9H₂O/NaI. The reaction occurs in good to high yield in dichloromethane at room temperature and the use of toxic and corrosive molecular iodine is avoided.     

Highly stereoselective construction of functionalized cyclopropanes from the reaction between acetylenic esters and C-H acids in the presence of triphenylarsine

A one-pot triphenylarsine-catalyzed synthesis of trans-cyclopropane derivatives is achieved by means of the reaction between acetylenic esters and C-H acids in the presence of triphenylarsine. This procedure is simple and proceeds under mild reaction conditions. Its success depends on the choice of solvent, temperature and C-H acid used.     

Thermosetting polymers from epoxy resin and a Nickel catalyst of diethylenetriamine

The kinetics and mechanism of cure reaction of DGEBA using a chelate of Ni(II) with diethylenetriamine (dien), Ni(dien)₂I_2, as a curing agent was studied by DSC. TG curve of the complex curing agent showed mass loss in two region of temperature: 200–320 and 450–550 °C. Dynamic DSC measurements showed only one exothermic peak with a maximum about 250 °C depending on the heating rate. According to the methods of KAS and Ozawa–Flynn–Wall the values of E _a were 92.5 and 96.2 kJ/mol, respectively. The isoconversional kinetic analysis in whole range of conversion, α = 0.02–0.95, showed small changes in the E _a values in the region of α = 0.04–0.6 and most likely represent some average values (E _a = 110 kJ/mol) between the values of E _a of non-autocatalyzed and autocatalyzed reactions. Using the sole dependence of E _a on α, the time required to reach fully cured materials under isothermal conditions were also predicted and compared with the experimental results.