Local measurements of velocity fluctuations and diffusion coefficients for a granular material flow

Measurements were made of two components of the average and fluctuating velocities, and of the local self-diffusion coefficients in a flow of granular material. The experiments were performed in a 1 m-high vertical channel with roughened sidewalls and with polished glass plates at the front and the back to create a two-dimensional flow. The particles used were glass spheres with a nominal diameter of 3 mm. The flows were high density and were characterized by the presence of long-duration frictional contacts between particles. The velocity measurements indicated that the flows consisted of a central uniform regime and a shear regime close to the walls. The fluctuating velocities in the transverse direction increased in magnitude from the centre towards the walls. A similar variation was not observed for the streamwise fluctuations. The self-diffusion coefficients showed a significant dependence on the fluctuating velocities and the shear rate. The velocity fluctuations were highly anistropic with the streamwise components being 2 to 2.5 times the transverse components. The self-diffusion coefficients for the streamwise direction were an order-of-magnitude higher than those for the transverse direction. The surface roughness of the particles led to a decrease in the self-diffusion coefficients

Vinyl polymerization. VIII. Photopolymerization of vinyl monomers by azidopentamminecobalt (III) chloride

A systematic study of the kinetics of photopolymerization of vinyl monomers initiated by the complex azidopentamminecobalt (III) chloride in aqueous solution has been made. The determinations of monomer disappearance, complex disappearance, chainlengths of polymers, obtained against the different variables like light intensity, concentrations of monomer, light absorption fraction, etc., have been made. A kinetic mechanism proposed for the overall reaction is discussed in the light of the experimental results and certain rate constants have also been evaluated

Experimental Metrics for Identifying Origins of Combustion Variability during Spark-Assisted Compression Ignition

Spark-assisted compression ignition, SACI, can be used to control the combustion phasing of compression-ignition gasoline engines. However, implementation of this technique can be confounded by cyclic variability. The purpose of this paper is to define experimental metrics that describe the SACI process and to demonstrate the use of these metrics for identifying the source(s) of cyclic variability during the SACI process. This study focused on a light load condition (7 mg/cycle, 200 kPa i.m.e.p.), where spray-guided direct fuel injection with spark ignition and an exhaust-rebreathing strategy was employed to achieve flame propagation, which led to compression ignition. This study employed a combination of measurements including pressure-based heat-release analysis, spark-discharge voltage/current measurements, and cycle-resolved combustion imaging. Based on these measurements, four distinct combustion periods were identified; namely, the spark discharge, the early kernel growth (EKG), flame propagation, and the compression ignition periods. Metrics were defined to characterize each period and used to identify the contribution of each period to the cyclic variability of the main heat release. For the light load condition studied here, the EKG period had the largest effect on the crank angle (CA) position of 50 per cent mass burned, CA50. The spark-discharge event may affect CA50 indirectly through its influence on EKG. However, this could not be definitively assessed here since the camera was incapable of recording both the spark-discharge event and the flame images during cycles of the same tests.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86770/1/Sick18.pd

4-Azido-2-chloro-6-methyl­quinoline

In the title compound, C10H7ClN4, the quinoline ring system is planar [maximum deviation 0.0035 (10) Å]. The crystal structure is stabilized by van der Waals and π–π stacking inter­actions [centroid–centroid distance 3.6456 (17) Å]

1,1′-[4-(2,4-Dichloro­phen­yl)-2,6-di­methyl-1,4-di­hydro­pyridine-3,5-di­yl]diethanone

In the title compound, C17H17Cl2NO2, the central 1,4-dihydro­pyridine ring adopts a flattened-boat conformation. The ethanone substituents of the dihydro­pyridine ring at positions 3 and 5 have synperiplanar (cis) or anti­periplanar (trans) conformations with respect to the adjacent C=C bonds in the dihydro­pyridine ring. The 2,4-dichloro­phenyl ring is almost planar [r.m.s. deviation = 0.0045 (1) Å] and almost perpendicular [89.27 (3)°] to the mean plane of the dihydro­pyridine ring. In the crystal, an N—H⋯O hydrogen bond links mol­ecules into a zigzag chain along the ac diagonal. C—H⋯Cl contacts form centrosymmetric dimers and additional weak C—H⋯O contacts further consolidate the packing

Precise measurements of UV atomic lines: Hyperfine structure and isotope shifts in the 398.8 nm line of Yb

We demonstrate a technique for frequency measurements of UV transitions with sub-MHz precision. The frequency is measured using a ring-cavity resonator whose length is calibrated against a reference laser locked to the $D_2$ line of $^{87}$Rb. We have used this to measure the 398.8 nm ${^1S}_0 \leftrightarrow {^1P}_1$ line of atomic Yb. We report isotope shifts of all the seven stable isotopes, including the rarest isotope $^{168}$Yb. We have been able to resolve the overlapping $^{173}$Yb($F = 3/2$) and $^{172}$Yb transitions for the first time. We also obtain high-precision measurements of excited-state hyperfine structure in the odd isotopes, $^{171}$Yb and $^{173}$Yb. The measurements resolve several discrepancies among earlier measurements.Comment: 7 pages, 6 figure

4,8,9,10-Tetra­kis(4-fluoro­phen­yl)-1,3-diaza­tricyclo­[3.3.1.1]decan-6-one

In the title compound, C32H24F4N2O, all four six-membered rings that constitute the diaza­adamantanone cage adopt chair conformations. Two of the four fluoro­phenyl substituents occupy axial positions and the other two occupy equatorial positions relative to their respective C5N rings of the adamantane framework. The crystal structure is stabilized by C—H⋯O inter­actions, generating a C(5) chain along the a axis