Composite power law holdup correlations in horizontal pipes

A wide range of experimental holdup data, from different sources, are analyzed based on a theoretical model proposed in this work to evaluate the holdup in horizontal pipes. 2276 gas–liquid flow experiments in horizontal pipelines with a wide range of operational conditions and fluid properties are included in the database. The experiments are classified by mixture Reynolds number ranges and composite analytical expressions for the relationship between the liquid holdup and no-slip liquid holdup vs. the gas–liquid volumetric flow rate are obtained by fitting the data with logistic dose curves. The Reynolds number appropriate to classify the experimental data for gas–liquid flows in horizontal pipes is based on the mixture velocity and the liquid kinematic viscosity. Composite power law holdup correlations for flows sorted by flow pattern are also obtained. Error estimates for the predicted vs. measured holdup correlations together with standard deviation for each correlation are presented. The accuracy of the correlations developed in this study is compared with the accuracy of 26 previous correlations and models in the literature. Our correlations predict the liquid holdup in horizontal pipes with much greater accuracy than those presented by previous authors.     

Saint-Venant's principle in nonlinear plane elasticity with sufficiently small strains

A homogeneous, isotropic cylinder in an equilibrium state of plane strain, whose cross-section is a rectangle R : [0 < y ₁ < 2L; 0 < y ₂ < h] with h/L 1, is considered. There are no body forces and the long sides are stress free. At y ₁ = 0 and y ₁ = 2L, there are arbitrary loadings, each statically equivalent to a uniformly distributed tensile or compressive stress c. Within the theory of nonlinear elasticity and with the strains and strain gradients assumed to be sufficiently small (but with no such assumptions on the displacement gradients), it is proved that if (,=1,2) represents the Cauchy stress tensor and the Kronecker delta, then |–c₁₁| decays exponentially to zero in R with distance from the nearer end, and the decay constant depends only upon the material but is independent of L.     

Anomalous rolling of spheres down an inclined plane

A sphere in air will roll down a plane that is tilted away from the vertical. The only couple acting about the point of contact between the sphere and the plane is due to the component of the weight of the sphere along the plane, provided that air friction is negligible. If on the other hand the sphere is immersed in a liquid, hydrodynamic forces will enter into the couples that turn the sphere, and the rotation of the sphere can be anomalous, i.e., as if rolling up the plane while it falls. In this paper we shall show that anomalous rolling is a characteristic phenomenon that can be observed in every viscoelastic liquid tested so far. Anomalous rolling is normal for hydrodynamically levitated spheres, both in Newtonian and viscoelastic liquids. Normal and anomalous rolling are different names for dry and hydrodynamic rolling. Spheres dropped at a vertical wall in Newtonian liquids are forced into anomalous rotation and are pushed away from the wall while in viscoelastic liquids, they are forced into anomalous rotation, but are pushed toward the wall. If the wall is inclined and the fluid is Newtonian, the spheres will rotate normally for dry rolling, but the same spheres rotate anomalously in viscoelastic liquids when the angle of inclination from the vertical is less than some critical value. The hydrodynamic mechanisms underway in the settling of circular particles in a Newtonian fluid at a vertical wall are revealed by an exact numerical simulation based on a finite-element solution of the Navier-Stokes equations and Newton's equations of motion for a rigid body.     

A synthesis of bredinin (Mizoribine®) from an acyclic precursor

Bredinin (4-carbamoyl-1-β-d-ribofuranosylimidazolium-5-olate, 1) was synthesised by the formation of a malonamate from 2,3-isopropylidene-d-ribofuranosylamine and ethyl malonyl chloride, followed by a sequence involving amination, via reduction of an oxime, heterocycle formation and then deprotection.     

Exploring the heteroatom effect on polyelectrolyte multilayer assembly: the neglected polyoniums

Different positive polyelectrolytes having the same charge density, molecular weight, and molecular weight distribution were employed for polyelectrolyte multilayer (PEMU) assembly. The polycations differed only in the heteroatom on which the positive charge resided: poly(vinyl benzyl trimethyl ammonium) chloride, poly(vinyl benzyl trimethyl phosphonium) chloride, and poly(vinyl benzyl dimethyl sulfonium) chloride. While the ammonium repeat unit has been employed on numerous occasions for PEMU assembly, the phosphonium and sulfonium units are relatively neglected. The polyanions, poly(styrene sulfonate), PSS, or poly(acrylic acid), PAA, were typical pH-independent or pH-dependent polymers, respectively. All three polyoniums were quite similar in showing linear layer-by-layer buildup with PSS and exponential growth with PAA, under the conditions employed. Hydration and wettability were also similar between polyoniums.     

Photodegradation of azobenzene-based self-assembled monolayers characterized by in-plane birefringence

Azobenzene-based self-assembled monolayers (azo-SAMs) are photoactive and become orientationally ordered when illuminated with linearly polarized light (LPL), making them attractive as dynamic alignment layers in liquid crystal cells. Azo-SAMs, however, are chemically unstable when exposed to both air and light. We have characterized the photodegradation of a methyl red-based SAM by measuring with a high-sensitivity polarimeter the optical anisotropy induced by illumination with linearly polarized actinic light after the sample is irradiated with circularly polarized light (CPL) in air. The number of unbleached, photoactive molecules in the SAM decays exponentially with CPL exposure time, lowering the reorientation rate during photowriting with LPL. Azo-SAMs in an argon atmosphere, in contrast, are chemically stable and remain photoactive even after exposure to CPL.     

Effect of concentration on the photo-orientation and relaxation dynamics of self-assembled monolayers of mixtures of an azobenzene-based triethoxysilane with octyltriethoxysilane

Self-assembled monolayers (SAMs) were prepared from solutions with different proportions of a photoactive, azobenzene-based, silanized derivative of disperse red one (dDR1), and octyltriethoxysilane (OTE), a shorter, nonphotoactive molecule. The in-plane photoinduced orientational ordering of the resulting two component monolayers was monitored via precision measurement of in-plane birefringence using a dedicated high-extinction polarimeter. Measurements of contact angle, absorption, and birefringence show that introduction of OTE into the dDR1 deposition solution produces a continuous reduction of the surface density of dDR1 in the SAM, enabling the study of photowriting and relaxation dynamics in monolayers ranging from 100% dDR1 to samples where the dDR1 coverage is about 35%. The orientational dynamics depend strongly on the areal density of dDR1. As the fractional area of dDR1 is reduced, the rates of photowriting, photoerasing, and thermal relaxation increase, and the local orientational confinement of the molecules becomes more heterogeneous.     

Effect of reduction treatment on copper modified activated carbons on NO(x) adsorption at room temperature

Activated carbon was impregnated with copper salt and then exposed to reductive environment using hydrazine hydrate or heat treatment under nitrogen at 925 °C. On the obtained samples, adsorption of NO(2) was carried out at dynamic conditions at ambient temperature. The adsorbents before and after exposure to nitrogen dioxide were characterized by X-ray diffraction (XRD), thermal analysis, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectroscopy (XPS), N(2)-sorption at -196 °C, and potentiometric titration. Copper loading improved the adsorption capacity of NO(2) as well as the retention of NO formed in the process of NO(2) reduction on the carbon surface. That improvement is linked to the presence of copper metal and its high dispersion on the surface. Even though both reduction methods lead to the reduction of copper, different reactions with the carbon surface take place. Heat treatment results in a significant percentage of metallic copper and a reduction of oxygen functional groups of the carbon matrix, whereas hydrazine, besides reduction of copper, leads to an incorporation of nitrogen. The results suggest that NO(2) mainly is converted to copper nitrates although the possibility to its reduction to N(2) is not ruled out. A high capacity on hydrazine treated samples is linked to the high dispersion of metallic copper on the surface of this carbon.