Indirect measurements of streamwise solid fraction variations of granular flows accelerating down a smooth rectangular chute

In this study, we detail a method for estimating the flux-averaged solid fraction of a steady granular flows moving down an inclined rectangular chute using velocity measurements from along the perimeter cross section, combined with knowledge of the mass flow rate through the cross section. The chute is 5 cm wide and 150 cm long with an adjustable inclination angle. Four inclination angles, from 27° to 36° at 3° intervals, are tested. This angle range overlaps the internal friction angle of the glass beads, which are 4 mm nominal in diameter. Two slender mirrors are installed at the top and the bottom of the transparent chute to reflect images of the flow down the chute of the two surfaces. This allows photographic recording of the flow with a PIV imaging system and measurement of the flow depth. The mass flow rate can be calibrated simultaneously by collecting the accumulated mass at the chute exit. A linear interpolation scheme is proposed to interpolate the volume flow rate in each section of the chute. Sensitivity analysis suggests that the relative standard deviation of this scheme is about ±6%, i.e., the resultant solid volume fraction is only moderately dependent on the interpolation scheme for the tested cases. This is further confirmed by a direct intercepting method. Compared to the sophisticated magnetic resonance imaging (MRI) or the radioactive positron emission particle tracking (PEPT) methods, the present method is verified as a cost-effective and nonhazardous alternative for ordinary laboratories. Two distinct groups of streamwise dependence of the solid fractions are found. They are separated by the inclination angle of the chute and agreed with the internal friction angle. In the experiments using the two smaller inclination angles, the solid fraction ratios are found to be linear functions of the streamwise distance, while for the two larger inclination angles, the ratios have a nonlinear concave shape. All decrease with growing downstream distance.     

White light electroluminescence from graphene‐enhanced single polymer comprising two color emitters of equal molar ratios

White polymeric light‐emitting diode (WPLED) based on a single polymer, poly(3‐hexylthiophene‐alt‐9,9‐dioctylfluorene) (PTAF), has been successfully demonstrated. This conjugated alternating copolymer, PTAF, comprises 50 mol % of 3‐hexylthiophene which is an orange‐red color chromophore and 50 mol % 9,9‐dioctylfluorene which is a bluish‐green color chromophore. It was synthesized by Suzuki cross‐coupling reaction and has a molecular weight of 15,021 and polydispersity of 1.36. Nanocomposite consisting PTAF and graphene nanosheets enhances the optoelectronic properties and the device fabricated with a configuration of ITO/PEDOT:PSS/(PTAF + 1% graphene)/Ca/Al shows two‐color white electroluminescence with CIE 1931 coordinates of (0.28, 0.34). The white luminescence from a single polymer affords the WPLED device a simple structure and low fabrication cost. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Coupling Reaction of 4-Chloro-7-H-Pyrrolo[2,3-d]Pyrimidine with 2,3,5-Tri-O-Acetyl-β-D-Ribofuranosyl Chloride

Tubercidin (4-amino-7--D-riobofuranosyl-7-H-pyrrolo[2,3-d]pyrimidine) 1, an antibio-tic substance produced in the culture broth of Streptomyces tubericidus1, is an adenosine analog in which N-7 is replaced by a carbon atom. It has attracted much attention due to the biological activities for the growth inhibition of certain tumors, and many derivatives of tubercidin have been synthesized2-5.For the synthesis of tubercidin analogs, 4-chloro-7-H-pyrrolo[2,3-d]pyrimidine-2,3,5-tri-O-acetyl--D-r…     

A direct‐forcing pressure‐based lattice Boltzmann method for solving fluid–particle interaction problems

A direct‐forcing immersed boundary‐lattice Boltzmann method (IB–LBM) is developed to simulate fluid–particle interaction problems. This method uses the pressure‐based LBM to solve the incompressible flow field and the immersed boundary method to handle the fluid–particle interactions. The pressure‐based LBM uses the pressure distribution functions instead of the density distribution functions as the independent dynamic variables. The main idea is to explicitly eliminate the compressible effect due to the density fluctuation. In the IB method, a direct‐forcing method is introduced to capture the particle motion. It directly computes an IB force density at each lattice grid from the differences between the pressure distribution functions obtained by the LBM and the equilibrium pressure distribution functions computed from the particle velocity. By applying this direct‐forcing method, the IB–LBM becomes a purely LBM version. Also, by applying the Gauss theorem, the formulas for computing the force and the torque acting on the particle from the flows are derived from the volume integrals over the particle volume instead of from the surface integrals over the particle surface. The order of accuracy of the IB–LBM is demonstrated on the errors of velocity field, wall stress, and gradients of velocity and pressure. As a demonstration of the efficiency and capabilities of the new method, sedimentation of a large number of spherical particles in an enclosure is simulated. Copyright © 2010 John Wiley & Sons, Ltd.     

The Effect of the Buffering Capacity of the Supporting Electrolyte on the Electrochemical Oxidation of Dopamine and 4‐Methylcatechol in Aqueous and Nonaqueous Solvents

Dopamine was electrochemically oxidized in aqueous solutions and in the organic solvents N,N‐dimethyl‐formamide and dimethylsulfoxide containing varying amounts of supporting electrolyte and water, to form dopamine ortho‐quinone. It was found that the electrochemical oxidation mechanism in water and in organic solvents was strongly influenced by the buffering properties of the supporting electrolyte. In aqueous solutions close to pH 7, where buffers were not used, the protons released during the oxidation process were able to sufficiently change the localized pH at the electrode surface to reduce the deprotonation rate of dopamine ortho‐quinone, thereby slowing the conversion into leucoaminochrome. In N,N‐dimethylformamide and dimethylsulfoxide solutions, in the absence of buffers, dopamine was oxidized to dopamine ortho‐quinone that survived without further reaction for several minutes at 25 °C. The voltammetric data obtained in the organic solvents were made more complicated by the presence of HCl in commercial sources of dopamine, which also underwent an oxidation process.     

Facile and scalable fabrication engineering of fullerenol nanoparticles by improved alkaline-oxidation approach and its antioxidant potential in maize

A feasible in operation, labor-saving and low-cost one-step technology to fabricate fullerenol nanoparticles (FNPs) up to 10 g in laboratory was developed by improved alkaline-oxidation approach using moderately concentrated sodium hydroxide solution as the hydroxylation agent and o-dichlorobenzene as the solvent. This strategy paves the avenue for industrial-scale bulk production of FNPs. The resulted product, [C₆₀(OH)₂₂·8H₂O]_n, were characterized by various measurements including matrix-assisted laser desorption ionization time-of-flight mass spectrometry, high-resolution ¹H nuclear magnetic resonance spectrometry, Fourier transform infrared spectroscopy, UV-Visible spectrophotometer, thermogravimetric analysis, differential scanning calorimetry, dynamic light scattering analysis, scanning electron microscopy, and electron spin resonance spectrometer. Radical scavenging assay in vitro confirmed the high efficiency of water-soluble [C₆₀(OH)₂₂·8H₂O]_n as a novel radical scavenger. Furthermore, [C₆₀(OH)₂₂·8H₂O]_n as an excellent candidate has the potential to serve as the plant defense stimulation agent in maize.

Open image in new window

Graphical abstract ?