Unstable sinking of spheres at higher air velocity in a gas-solid fluidized bed

Float-sink of large objects (on order of cm) in a gas-solid fluidized bed of powder (on order of 100 s of microns) based on density difference has been utilized for dry density separation in industry. The air velocity u₀/u_mf is one of the important factors operating the fluidized bed, where u₀ and u_mf are the superficial air velocity and the minimum fluidization air velocity, respectively. It is empirically known that the sinking of heavy objects is “occasionally” unstable in the fluidized bed combustor, for which the higher air velocity u₀/u_mf > 4 is used. Unstable sinking means heavy objects that are expected to sink but sometimes do not. However, the precise conditions at which the unstable sinking occurs are not clear. In this study, we investigated the float-sink characteristics at a given air velocity u₀/u_mf = 2–7 using glass beads of size D_gb = 425–600 μm and 600–850 μm as the fluidized powder bed media. The float-sink experiments were carried out at the bed height h_gb = 150 mm and 75 mm using density adjusted spheres (diameter = 30 mm). We found that the spheres stably float or sink based on density difference at D_gb = 425–600 μm & h_gb = 150 mm and at D_gb = 600–850 μm & h_gb = 75 mm. However, the unstable sinking does occur at u₀/u_mf > 4 at D_gb = 600–850 μm & h_gb = 150 mm. These results indicate that the powder size and the bed height are key factors to induce the unstable sinking at the higher air velocity.     

An aspect of bitumen emulsification by steam condensation: Effect of formation temperature and bitumen content

The experiments to form emulsions of bitumen including fine droplets of condensate water were carried out for an average formation temperature range; T_f = 38–69°C and bitumen content; C_B = 29–82%. It was observed that the water retention capacity or stability of the emulsions after mild agitation was significantly affected by formation temperature and content of the bitumen. The particle size of water droplets in emulsion decreased with increasing formation temperature. However, bitumen emulsions showed similar shear thinning non-Newtonian behavior in spite of the formation temperature, since water droplets in the emulsions changed under shear flow to smaller size similar to ones formed at the higher formation temperature.     

Raman Studies of Anisotropic Magnetic Excitations in Fluctuating Nematic Striped La2−x Sr x CuO4 and the Comparison to Uniform Nd2−x Ce x CuO4

The mechanism of the high temperature hole-doped superconductivity was investigated by Raman scattering. The Raman selection rule is unique, so that anisotropic magnetic excitations in a fluctuating spin-charge stripe can be detected as if it is static. We use different Raman selection rules for two kinds of magnetic Raman scattering processes, two-magnon scattering and high-energy electronic scattering. In order to confirm the stripe effect, the Raman spectra of striped La_2?x Sr _x CuO₄ (LSCO) and nonstriped Nd_2?x Ce _x CuO₄ (NCCO) were compared. The main results in LSCO are (1) magnetic excitations are presented by individual energy dispersions for the k∥ stripe and the k⊥ stripe, (2) the charge transfer is allowed only in the direction perpendicular to the stripe. The direction is the same as the Burgers vector of an edge dislocation. Hence, we assume that a charge moves together with the edge dislocation of the charge stripe. The superconducting coherence length is close to the intercharge stripe distance at x<0.2. Therefore, we propose a model that superconducting pairs are formed in the edge dislocations. The binding energy is related to the stripe formation energy.     

Effect of the growth rate of Pseudomonas aeruginosa biofilms on the susceptibility to antimicrobial agents: beta-lactams and fluoroquinolones

The combined effects of meal cost and food flavor on meal size were studied with a method that avoided the covariation of nutrient composition and caloric density with palatability. As rats (Rattus norvegicus) drank flavored fluids (unpalatable 0.05% sucrose octaacetate [SOA], neutral 0.05% saccharin, and palatable 2% Polycose + 0.2% saccharin [P + S]), liquid diet was infused intragastrically. Relative to saccharin, rats with free access ate 10% more calories in larger meals while consuming P + S and initially ate fewer calories in smaller but more frequent meals while drinking SOA. Other rats lever-pressed to begin meals, which halved meal number and doubled meal size relative to the free-access group. Although foraging rats also ate larger P + S meals and smaller SOA meals, the changes did not affect total intake. Without the usual differential postingestive effects of foods that differ in palatability, making food more costly blunts rats' response to its flavor.     

Area selective epitaxy of indium phosphide on silicon (100) substrates without buffer layers by liquid phase epitaxy

Area selective epitaxy (ASE) of InP was performed by liquid phase epitaxy on Si (100) substrates without the use of buffer layers. At the start of epitaxy, the growth temperature was rapidly lowered to obtain high supersaturation. Epitaxial growth was then carried out at constant temperature. While small InP nuclei were observed in the broader open areas, ASE layers and layers showing slight epitaxial lateral overgrowth were formed in the narrow openings. Etch pit density of the InP ASE layers on Si is dependent on the length of open seed region and X-ray diffraction results indicate that the lattice strain in the InP nuclei on the Si substrate was fully relaxed.     

Stability and robust stability of positive linear Volterra difference equations

We first introduce a class of positive linear Volterra difference equations. Then, we offer explicit criteria for uniform asymptotic stability of positive equations. Furthermore, we get a new Perron–Frobenius theorem for positive linear Volterra difference equations. Finally, we study robust stability of positive equations under structured perturbations and affine perturbations. Two explicit stability bounds with respect to these perturbations are given. Copyright © 2008 John Wiley & Sons, Ltd.     

Hotspot analysis of COVID-19 infection using mobile-phone location data

Artificial Life and Robotics - Restrictions on outdoor activities are required to suppress the COVID-19 pandemic. To monitor social risks and control the pandemic through sustainable restrictions,...     

Design systems for gear elements made of cotton fiber-reinforced plastics

We look on the cotton fiber reinforced plastics as industrial gear materials, and have been developing design systems for industrial gears made of cotton fiber-reinforced plastics. In this report, we deal with a method estimating for tooth root stresses caused by bending movements under running conditions. The gear material used was cotton fiber plain woven cloth reinforced phenolic resin laminates. Paper-reinforced phenolic resin laminates, a commonly used material, was used as a control for comparison. The main dimensions of the gears were module 3–5 mm and tooth width 25 mm. First, accelerations of gears were measured under running conditions to estimate dynamic performance. Second, fracture tests of gear teeth were carried out under bending loads. Different fracture modes at tooth roots for cotton fiber-reinforced plastics and phenolic resin gears were observed. The fractures occurred at a high position from the tooth root in the case of the cotton fiber-reinforced plastics gear because the cotton fiber-reinforced plastics had excellent cleavage and shear strength. This gear also had higher strength for tooth bending loads. Third, the mechanical properties of the gears were researched by tensile, bending, and shearing tests. It was clear that the cotton fiber-reinforced plastics had excellent properties in cleavage fracture between laminates and shear strength. Finally, we proposed a design method for this gear, which considers the cleavage and shear strength.