Improvements in modeling and evaluation of electrical power systemreliability

This paper describes updates in an electrical reliability modeling process, first described in a 1993 paper for the Petroleum and Chemical Industry Committee of the IEEE Industry Applications Society. The paper also describes an additional new method for evaluating power system design options. The electrical reliability model has been expanded with more extensive component failure and repair values. Additional modeling techniques have been developed for evaluating typical electrical systems found in petroleum and chemical facilities. The reliability calculation results, based on the actual modeling of many refineries in the US, are described. The paper also describes a new method which was developed to evaluate and compare power system designs, based on the resulting composite reliability values and other factors, including recovery from faults, availability for maintenance, safety and cost. This new method provides an analytical approach to optimize the power system design to the plant operation and maintenance requirements     

Mass transfer from spherical particles and reservoirs into quiescent liquids

A continuous weighing technique was developed for measuring urea transfer (carbamide, a fertilizer) from a single opening on a coated sphere in a stagnant liquid. Urea release was determined from the changes of the particle weight with time. Mass transfer coefficients for Rayleigh numbers from 1.8 × 10⁷ to 6.8 × 10¹⁰ were measured and compared with those for uncoated urea spheres and literature data. For the opening oriented vertically upward in water, natural convection enhanced the transfer rate by 1.8 times compared to that for urea diffusion only. In other opening orientations (45°, 90°, 135° and 180° to the vertical), natural convection provided the major mechanism for the release. A model for urea diffusion was also developed. It agrees well with experimental data.     

Digestibility of common native starches with reference to starch granule size,shape and surface features towards guidelines for starch-containing food products

Influence of diverse botanical sources (wheat, maize, waxy maize, cassava, potato, rice or waxy rice) on in vitro native starch digestibility has been investigated. Physicochemical properties (chemical composition, particles size and shape, surface features) of starch granules were determined with a view to explaining digestibility differences between samples. Rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) contents were measured according to Englyst method. Potato starch was shown to be composed of large rounded granules having smooth surfaces, which explains its slow enzymatic breakdown. Potato starch displayed the highest RS (86%) content and the lowest RDS content (9.9%). Since RS positively influences health and SDS may result in cell, tissue and/or organ damages, potato starch is an ideal starch nutrient. Conversely, waxy rice starch was rich in amylopectin and displayed small diameters and angular shapes, which are both known to facilitate enzymatic starch hydrolysis. It exhibited a near-zero RS content (0.9%) and a high RDS fraction (60%). According to this study, potato starch exhibited the best nutrient profile, followed up in this order by cassava, waxy maize, wheat, maize and waxy rice starches.     

Effect of Addition Mode of Re in Bimetallic Pd–Re/TiO2 Catalysts Upon the Selective Aqueous-Phase Hydrogenation of Succinic Acid to 1,4-Butanediol

Hydrogenation of succinic acid aqueous solutions was performed using TiO₂-supported 2?wt% Pd and 2?wt%Pd?Cx?wt%Re catalysts, using either impregnation method or surface redox reduction of the monometallic catalyst. The former catalysts were superior in terms of activity and selectivity to 1,4-butanediol than the latter ones. However, higher Re loadings (3.4?C3.6?wt% compared to 0.6?C0.8?wt%) were necessary to initiate this synergy.     

Fluidic lens by using thermal lens effect

This research presents a novel fluidic lens based on thermal lens effect. Effects of the pump power and the pump beam intensity distribution to the probe beam profile in the dual thermal lens system are investigated experimentally and theoretically. A model, which accounts for heat conduction, natural heat convection and ray tracing in inhomogeneous medium is developed to predict the characteristics of the thermal lens system. Numerical results show the advantage of the uniform pump beam in reducing the spherical aberration compared with the Gaussian pump beam. An experiment with the uniform pump beam is carried out to confirm the numerical prediction. Experimental results show a good agreement with the calculated results. Finally, the pump power is varied to adjust the focal length of the system.     

Effect of shear history on flow instability at capillary extrusion for long‐chain branched polyethylene

Effect of applied processing history on flow instability at capillary extrusion is studied using a commercially available low‐density polyethylene (LDPE) having long‐chain branches. It is found that processing history in an internal mixer in a molten state depresses long‐time relaxation mechanism associated with long‐chain branches, which is known as “shear modification.” Consequently, the onset of output rate for melt fracture increases greatly. Furthermore, it should be noted that the sample having intense shear history shows shark‐skin failure without volumetric distortion, although it has been believed that LDPE exhibits gross melt fracture at capillary extrusion. The reduction of elongational viscosity by the alignment of long‐chain branches along to the main chain is responsible for the anomalous rheological response. As a result, the sample shows shark‐skin failure like a linear polyethylene at a lower output rate than the critical one for gross melt fracture. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Pseudo-Hydrodynamic Flow of Quasiparticles in Semimetal WTe2 at Room Temperature

Recently, much interest has emerged in fluid-like electric charge transport in various solid-state systems. The hydrodynamic behavior of the electronic fluid reveals itself as a decrease of the electrical resistance with increasing temperature (the Gurzhi effect) in narrow channels, polynomial scaling of the resistance as a function of the channel width, violation of the Wiedemann–Franz law supported by the emergence of the Poiseuille flow. Similar to whirlpools in flowing water, the viscous electronic flow generates vortices, resulting in abnormal sign-changing electrical response driven by backflow. However, the question of whether the long-ranged sign-changing electrical response can be produced by a mechanism other than hydrodynamics has not been addressed so far. Here polarization-sensitive laser microscopy is used to demonstrate the emergence of visually similar abnormal sign-alternating patterns in semi-metallic tungsten ditelluride at room temperature where this material does not exhibit true hydrodynamics. It is found that the neutral quasiparticle current consisting of electrons and holes obeys an equation remarkably similar to the Navier–Stokes equation. In particular, the momentum relaxation is replaced by the much slower process of quasiparticle recombination. This pseudo-hydrodynamic flow of quasiparticles leads to a sign-changing charge accumulation pattern via different diffusivities of electrons and holes.