Deterministic multi-zone ice accretion modeling

The focus here is on a deterministic model of the surface roughness transition behavior of glaze ice. The initial smooth/rough transition location, bead formation, and the propagation of the transition location are analyzed. Based on the hypothesis that the smooth/rough transition location coincides with the laminar/turbulent boundary layer transition location, a multizone model is implemented in the LEWICE code. In order to verify the effectiveness of the model, ice accretion predictions for simple cylinders calculated by the multizone LEWICE are compared to experimental ice shapes. The glaze ice shapes are found to be sensitive to the laminar surface roughness and bead thickness parameters controlling the transition location, while the ice shapes are found to be insensitive to the turbulent surface roughness

Outer layer turbulence intensities in smooth- and rough-wall boundary layers

Clear differences in turbulence intensity profiles in smooth, transitional and fully rough zero-pressure-gradient boundary layers are demonstrated, using the diagnostic plot introduced by Alfredsson, Segalini & Örlü (Phys. Fluids, vol. 23, 2011, p. 041702) – u?/U versus U/Ue, where u? and U are the local (root mean square) fluctuating and mean velocities and Ue is the free stream velocity. A wide range of published data are considered and all zero-pressure-gradient boundary layers yield outer flow u?/U values that are roughly linearly related to U/Ue, just as for smooth walls, but with a significantly higher slope which is completely independent of the roughness morphology. The difference in slope is due largely to the influence of the roughness parameter (?U+ in the usual notation) and all the data can be fitted empirically by using a modified form of the scaling, dependent only on ?U/Ue. The turbulence intensity, at a location in the outer layer where U/Ue is fixed, rises monotonically with increasing ?U/Ue which, however, remains of O(1) for all possible zero-pressure-gradient rough-wall boundary layers even at the highest Reynolds numbers. A measurement of intensity at a point in the outer region of the boundary layer can provide an indication of whether the surface is aerodynamically fully rough, without having to determine the surface stress or effective roughness height. Discussion of the implication for smooth/rough flow universality of differences in outer-layer mean velocity wake strength is include

Protein retention in yeast rough endoplasmic reticulum: expression and assembly of human ribophorin I.

The RER retains a specific subset of ER proteins, many of which have been shown to participate in the translocation of nascent secretory and membrane proteins. The mechanism of retention of RER specific membrane proteins is unknown. To study this phenomenon in yeast, where no RER-specific membrane proteins have yet been identified, we expressed the human RER-specific protein, ribophorin I. In all mammalian cell types examined, ribophorin I has been shown to be restricted to the membrane of the RER. Here we ascertain that yeast cells correctly target, assemble, and retain ribophorin I in their RER. Floatation experiments demonstrated that human ribophorin I, expressed in yeast, was membrane associated. Carbonate (pH = 11) washing and Triton X-114 cloud-point precipitations of yeast microsomes indicated that ribophorin I was integrated into the membrane bilayer. Both chromatography on Con A and digestion with endoglycosidase H were used to prove that ribophorin I was glycosylated once, consistent with its expression in mammalian cells. Proteolysis of microsomal membranes and subsequent immunoblotting showed ribophorin I to have assumed the correct transmembrane topology. Sucrose gradient centrifugation studies found ribophorin I to be included only in fractions containing rough membranes and excluded from smooth ones that, on the basis of the distribution of BiP, included smooth ER. Ribosome removal from rough membranes and subsequent isopycnic centrifugation resulted in a shift in the buoyant density of the ribophorin I-containing membranes. Furthermore, the rough and density-shifted fractions were the exclusive location of protein translocation activity. Based on these studies we conclude that sequestration of membrane proteins to rough domains of ER probably occurs in a like manner in yeast and mammalian cells

Location optimization of biodiesel processing plant based on rough set and clustering algorithm - a case study in China

Biofuel has an important role in alleviating the environmental pollution problem. More attention has been paid to optimization of biofuel supply chain in recent years. In this paper, a scientific, rational and practical biodiesel processing plant location with waste oil as the raw material was proposed in order to provide a theoretical basis for guiding the planning and management of restaurants, waste oil collection points, and processing plants. Considering the merits and demerits of the subjective and objective weighting methods, this paper proposes a new weighting method which is namely the combination of rough set theory and clustering algorithm. It then verifies the location results with a plant carbon emission. At last, this paper analyzes the location of biodiesel processing plant in the Yangtze River Delta of China and finds that the precision has been greatly improved with the new method comparing the RMSE and the R2 of the Delphi method with the improved rough set theory. By using this method, the weights of the influencing factors of biodiesel processing plants are the following: Waste oil supply 0.143, Fixed construction cost factor 0.343, Biodiesel demand 0.143 and Location convenience 0.371. In the comparison between the robust optimization method and the improved rough set theory, it was found that the final location results are the same, all being Jiaxing City. However, the improved rough set theory is much simpler than the robust optimization algorithm in the calculation process

Reverse time migration for inverse acoustic scattering by locally rough surfaces

Consider the inverse scattering of time-harmonic point sources by an infinite rough surface which is supposed to be a local perturbation of a plane. A novel version of reverse time migration is proposed to reconstruct the shape and location of the rough surface. The method is based on a modified Helmholtz-Kirchhoff identity associated with a special rough surface, leading to a modified imaging functional which always reaches a peak on the boundary of the rough surface for sound-soft case and penetrable case, and hits a nadir on the boundary of the rough surface for sound-hard case. Numerical experiments are presented to show the powerful imaging quality, especially for multi-frequency data.Comment: 29 pages,26 figure

Investigation of surface water behavior during glaze ice accretion

A series of experimental investigations that focused on isolating the primary factors that control the behavior of unfrozen surface water during glaze ice accretion were conducted. Detailed microvideo observations were made of glaze ice accretions on 2.54 cm diam cylinders in a closed-loop refrigerated wind tunnel. Distinct zones of surface water behavior were observed; a smooth wet zone in the stagnation region with a uniform water film, a rough zone where surface tension effects caused coalescence of surface water into stationary beads, and a zone where surface water ran back as rivulets. The location of the transition from the smooth to the rough zone was found to migrate towards the stagnation point with time. Comparative tests were conducted to study the effect of the substrate thermal and roughness properties on ice accretion. The importance of surface water behavior was evaluated by the addition of a surface tension reducing agent to the icing tunnel water supply, which significantly altered the accreted glaze ice shape. Measurements were made to determine the contact angle behavior of water droplets on ice. A simple multizone modification to current glaze ice accretion models was proposed to include the observed surface roughness behavior

The Kinematics of Salamander Underwater Walking on Smooth and Rough Substrate

The transition from aquatic to terrestrial locomotion was a landmark event in the evolutionary history of vertebrates. In order to better understand how early tetrapods were able to transition to land, salamanders have proven to be a useful animal model. With current research focusing heavily on the anatomy, physiology, and kinematics defining salamander terrestrial walking capabilities, this experiment was designed to extract information about the kinematics of salamander walking underwater. Underwater walking of salamanders was analyzed on smooth and rough substrates to provide more insight into the early vertebrate water-to-land transition. Average salamander stride duration, time in stance phase, time in swing phase, duty factor, stride length, stride velocity, minimum foot velocity phase location, maximum foot velocity phase location, and foot slip distance were compared between salamander underwater walking on smooth and rough substrate conditions. It was found that stride duration, stance duration, and swing duration were significantly greater when salamanders walked underwater on rough substrate. Thus, the kinematics of underwater salamander walking differ to some degree when the salamander walks on smooth or rough substrate

Texas economy shakes off rough ride in 2009

While conditions remain weak, it appears that the Texas economy is on a steadier course after a rough ride last year. Recent economic data and anecdotal evidence suggest the worst of the state's economic woes may be over. Activity is growing in several sectors. The state maintains its traditional advantages--relatively low living costs, modest taxes, a central location and an attractive business climate. Barring further setbacks, the Texas economy should pick up steam in 2010 and beyond.Economic conditions - Texas ; Global financial crisis ; Recessions ; Economic indicators