Simulation of Severe Slugging Formation and Control in Offshore Riser

In this paper, available elimination techniques are assessed. OLGA2000 software is used to simulate severe slugging formation mechanism in certain offshore riser. The simulation results show that pressure fluctuations of riser base and riser top is very large and severe slugging easily forms. Sensibility analysis shows that the measures and methods which include properly reducing pipe riser diameter, reducing water cut increasing terminal pressure, decreasing the height and inclination of riser and increasing GOR can eliminate or control severe slugging in riser pipe.

Formation and Structure of Composite Coating of HAD and Micro-Plasma Oxidation on A3 Steel

Composite coatings were obtained on A3 steel by hot dipping aluminum(HAD) at 720 degreesC for 6 min and micro-plasma oxidation (MPO) in alkali electrolyte. The surface morphology, element distribution and interface structure of composite coatings were studied by means of XRD, SEM and EDS. The results show that the composite coatings obtained through HAD/MPO on A3 steel consist of four layers. From the surface to the substrate, the layer is loose Al2O3 ceramic, compact Al2O3 ceramic, At and FeAl intermetallic compound layer in turn. The adhesions among all the layers are strengthened because the ceramic layer formed at the At surface originally, FeAl intermetallic compound layer and substrate are combined in metallurgical form through mutual diffusion during HAD process. Initial experiment results disclose that the anti-corrosion performance and wear resistance of composite coating are obviously improved through HAD/MPO treatment.

Chemical equilibrium analysis and CFD simulation of coal combustion and NOx formation

A full two-fluid model of reacting gas-particle flows with an algebraic unified second-order moment (AUSM) turbulence-chemistry model is used to simulate Beijing coal combustion and NOx formation. The sub-models are the k-epsilon-kp two-phase turbulence model, the EBU-Arrhenius volatile and CO combustion model, the six-flux radiation model, coal devolatilization model and char combustion model. The blocking effect on NOx formation is discussed. In addition, the chemical equilibrium analysis is used to predict NOx concentration at different temperature. Results of CID simulation and chemical equilibrium analysis show that, optimizing air dynamic parameters can delay the NOx formation and decrease NOx emission, but it is effective only in a restricted range. In order to decrease NOx emission near to zero, the re-burning or other chemical methods must be used.

Numerical Solution for Polymer Transient Flows in a Circle Bounded Composite Formation

A new numerical model for transient flows of polymer solution in a circular bounded composite formation is presented in this paper. Typical curves of the wellbore transient pressure are yielded by FEM. The effects of non-Newtonian power-law index, mobility and boundary distance have been considered. It is found that for the mobility ratio larger than 1, which is favorable for the polymer flooding, the pressure derivative curve in log-log form rises up without any hollow. On the other hand, if the pressure derivative curve has a hollow and then is raised up, we say that the polymer flooding fails. Finally, the new model has been extended to more complicated boundary case.

Nanocrystalline Formation during Mechanical Attrition of Cobalt

The nanocrystalline (nc) formation was studied in cobalt (a mixture of c (hexagonal close packed) and gamma (face-centered cubic) phases) subjected to surface mechanical attrition treatment. Electron microscopy revealed the operation of {10(1) over bar 0}< 11(2) over bar 0 > prismatic and {0001}< 11(2) over bar 0 > basal slip in the E phase, leading to the successive subdivision of grains to nanoscale. In particular, the dislocation splitting into the stacking faults was observed to occur in ultrafine and nc grains. By contrast, the planar dislocation arrays, twins and martensites were evidenced in the gamma phase. The strain-induced gamma ->epsilon martensitic transformation was found to progress continuously in ultrafine and nc grains as the strain increased. The nc formation in the gamma phase was interpreted in terms of the martensitic transformation and twinning.

Formation of dendritic nanostructures in Pyrex glass anodically bonded to silicon coated with an aluminum thin film

Anodic bonding with thin films of metal or alloy as an intermediate layer, finds increasing applications in micro/nanoelectromechanical systems. At the bonding temperature of 350 degrees C, voltage of 400 V, and 30 min duration, the anodic bonding is completed between Pyrex glass and crystalline silicon coated with an aluminum thin film with a thickness comprised between 50 and 230 nm. Sodium-depleted layers and dendritic nanostructures were observed in Pyrex 7740 glass adjacent to the bonding interface. The sodium depletion width does not increase remarkably with the thickness of aluminum film. The dendritic nanostructures result from aluminum diffusion into the Pyrex glass. This experimental research is expected to enhance the understanding of how the depletion layer and dendritic nanostructures affect the quality of anodic bonding. (C) 2007 Elsevier B.V. All rights reserved.

Expected Fair Allocation in Farsighted Network Formation

I consider cooperation situations where players have network relations. Networks evolve according to a stationary transition probability matrix and at each moment in time players receive payoffs from a stationary allocation rule. Players discount the future by a common factor. The pair formed by an allocation rule and a transition probability matrix is called expected fair if for every link in the network both participants gain, marginally, and in discounted, expected terms, the same from it; and it is called a pairwise network formation procedure if the probability that a link is created (or eliminated) is positive if the discounted, expected gains to its two participants are positive too. The main result is the existence, for the discount factor small enough, of an expected fair and pairwise network formation procedure where the allocation rule is component balanced, meaning it distributes the total value of any maximal connected subnetwork among its participants. This existence result holds for all discount factors when the pairwise network formation procedure is restricted. I finally provide some comparison with previous models of farsighted network formation.

Seasonal, horizontal, and vertical distribution of phytoplankton chlorophyll a in the Northeast U.S. Continental Shelf Ecosystem

The broad scale features in the horizontal, vertical, and seasonal distribution of phytoplankton chlorophyll a on the northeast U.S. continental shelf are described based on 57,088 measurements made during 78 oceanographic surveys from 1977 through 1988. Highest mean water column chlorophyll concentration (Chlw,) is usually observed in nearshore areas adjacent to the mouths of the estuaries in the Middle Atlantic Bight (MAB), over the shallow water on Georges Bank, and a small area sampled along the southeast edge of Nantucket Shoals. Lowest Chlw «0.125 ug l-1) is usually restricted to the most seaward stations sampled along the shelf-break and the central deep waters in the Gulf of Maine. There is at least a twofold seasonal variation in phytoplankton biomass in all areas, with highest phytoplankton concentrations (m3) and highest integrated standing stocks (m2) occurring during the winter-spring (WS) bloom, and the lowest during summer, when vertical density stratification is maximal. In most regions, a secondary phytoplankton biomass pulse is evident during convective destratification in fall, usually in October. Fall bloom in some areas of Georges Bank approaches the magnitude of the WS-bloom, but Georges Bank and Middle Atlantic Bight fall blooms are clearly subordinate to WS-blooms. Measurements of chlorophyll in two size-fractions of the phytoplankton, netplankton (>20 um) and nanoplankton «20 um), revealed that the smaller nanoplankton are responsible for most of the phytoplankton biomass on the northeast U.S. shelf. Netplankton tend to be more abundant in nearshore areas of the MAB and shallow water on Georges Bank, where chlorophyll a is usually high; nanoplankton dominate deeper water at the shelf-break and deep water in the Gulf of Maine, where Chlw is usually low. As a general rule, the percent of phytoplankton in the netplankton size-fraction increases with increasing depth below surface and decreases proceeding offshore. There are distinct seasonal and regional patterns in the vertical distribution of chlorophyll a and percent netplankton, as revealed in composite vertical profiles of chlorophyll a constructed for 11 layers of the water column. Subsurface chlorophyll a maxima are ubiquitous during summer in stratified water. Chlorophyll a in the subsurface maximum layer is generally 2-8 times the concentration in the overlying and underlying water and approaches 50 to 75% of the levels observed in surface water during WS-bloom. The distribution of the ratio of the subsurface maximum chlorophyll a to surface chlorophyll a (SSR) during summer parallels the shelfwide pattern for stability, indexed as the difference in density (sigma-t) between 40 m and surface (stability 40. The weakest stability and lowest SSR's are found in shallow tidally-mixed water on Georges Bank; the greatest stability and highest SSR's (8-12:1) are along the mid and outer MAB shelf, over the winter residual water known as the "cold band." On Georges Bank, the distribution of SSR and the stability40 are roughly congruent with the pattern for maximum surface tidal current velocity, with values above 50 cms-1 defining SSR's less than 2:1 and the well-mixed area. Physical factors (bathymetry, vertical mixing by strong tidal currents, and seasonal and regional differences in the intensity and duration of vertical stratification) appear to explain much of the variability in phytoplankton chlorophyll a throughout this ecosystem. (PDF file contains 126 pages.)

Primary production, chlorophyll, and zooplankton volumes in the tropical Eastern Pacific Ocean

ENGLISH: Between 1 October and 17 December 1955 investigations of the physical, chemical and biological oceanography of the Eastern Pacific Ocean in a region bounded approximately by 30° N. latitude, 9° S. latitude, 120° W. longitude and the mainland coast were conducted from the vessels Horizon and Spencer F. Baird of the Scripps Institution of Oceanography of the University of California. These were part of a cooperative operation, designated for convenience by the code name "Eastropic," in which a vessel of the U. S. Fish and Wildlife Service worked, during this same period, further west and a vessel of the Peruvian Navy worked further south, offshore from Peru. A vessel of the California State Fisheries Laboratory also conducted certain sub-surface tuna fishing operations and other studies in the same general region as the Scripps vessels. In addition to carrying out a number of special studies related to particular oceanographic features, the Scripps vessels occupied a considerable number of hydrographic stations. The locations of these stations, at each of which were made net-hauls for zooplankton, are shown in Figure 4 and Tables 2 and 3. At some of the hydrographic stations, and in Some places between stations, there were made from the Spencer F. Baird measurements of chlorophyll "a" and of primary production (by the C14 technique), both in situ and in a shipboard incubator. The purpose of this paper is to report on the results of these biological observations. SPANISH: Entre el 1° de octubre y el 17 de diciembre de 1955, a bordo de los barcos Horizon y Spencer F. Baird) de la Institución Scripps de Oceanografía de la Universidad de California, se hicieron investigaciones sobre la oceanografía física, química y biológica del Océano Pacífico Oriental, en una región limitada aproximadamente por los 30° N. de latitud, 9° S. de latitud, 120° O. de longitud y la costa continental. Estas investigaciones fueron parte de una operación que se realizó cooperativamente y a la que se convino darle el nombre codificado de "Eastropic". En ella, durante el mismo período, una embarcación del Servicio de Pesca y Vida Silvestre de los Estados Unidos (U. S. Fish and Wildlife Service) trabajó más hacia el oeste, y un barco de la armada peruana más hacia el sur, frente a la costa del Perú. También colaboró una nave del Laboratorio de Pesquerías del Estado de California (California State Fisheries Laboratory), realizando algunas operaciones de pesca de atún en aguas subsuperficiales, y otros estudios en la misma región general que recorrieron las embarcaciones de Scripps. Además de efectuar estudios especiales relacionados con las caracteristicas oceanográficas particulares de la región, las naves de Scripps establecieron un buen número de estaciones hidrográficas. La localización de estas estaciones se indica en la Figura 4 y en las Tablas 2 y 3; en cada una de ellas se hicieron rastreos con redes planctónicas para recoger muestras de zooplancton. En algunas de las estaciones hidrográficas, así como en algunos lugares entre estaciones, en el Spencer F. Baird se hicieron mediciones de la clorofila "a" y de la producción primaria (mediante la técnica del C14), tanto in situ como en una incubadora instalada a bordo. El propósito del presente trabajo es dar a conocer los resultados de estas observaciones biológicas. (PDF contains 44 pages.)

Water quality assessment and characterisation of chlorophyll-a variability related to river discharges, within the southeastern Bay of Biscay : evaluation and development of chlorophyll-a algorithms for MODIS and MERIS imagery

222 p. : il.

Design and synthesis of quasi-diastereomeric molecules with unchanging central, regenerating axial and switchable helical chirality via cleavage and formation of Ni(II)–O and Ni(II)–N coordination bonds

9 p.

Controls on river terrace formation in New Zealand

[EUS] Artikulu honek, argitaratutako bibliografiaren bidez, Zeelanda Berriko ibai-terrazen garapenari eragiten dieten agente morfogenetikoak aztertzen ditu. Erreferentzia gisa Ipar Irlako 4 kasu eta Hego Irlako 3 kasu erabili dira. Oro har, ibai-terrazak sortzeko orduan, klima, sedimentuen erabilgarritasunan eta prezipitazioan duen eraginaren bitartez, eragile nagusiena da. Altxaketa tektonikoak forma hauen kontserbazioa eragiten du. Hainbat kasutan, gertaera asaldatzaileen ondorioz sortutako sedimentu kopuru handiek, fase morfogenetiko desberdinak eragin dituzte lokal/erregional mailan, nazional/kontinental mailan beharrean. Gertaera asaldatzaileen artean, besteak beste, ekarpen bolkaniko naturalak eta gizakiok bultzatutako lur erabilera aldaketen ondorioz sortutako sedimentu ekarpenak barneratzen dira.

Increase in the density of resting microglia precedes neuritic plaque formation and microglial activation in a transgenic model of Alzheimer's disease

The formation of cerebral senile plaques composed of amyloid beta peptide (A beta) is a fundamental feature of Alzheimer's disease (AD). Glial cells and more specifically microglia become reactive in the presence of A beta. In a triple transgenic model of AD (3 x Tg-AD), we found a significant increase in activated microglia at 12 (by 111%) and 18 (by 88%) months of age when compared with non-transgenic (non-Tg) controls. This microglial activation correlated with A beta plaque formation, and the activation in microglia was closely associated with A beta plaques and smaller A beta deposits. We also found a significant increase in the area density of resting microglia in 3 x Tg-AD animals both at plaque-free stage (at 9 months by 105%) and after the development of A plaques (at 12 months by 54% and at 18 months by 131%). Our results show for the first time that the increase in the density of resting microglia precedes both plaque formation and activation of microglia by extracellular A beta accumulation. We suggest that AD pathology triggers a complex microglial reaction: at the initial stages of the disease the number of resting microglia increases, as if in preparation for the ensuing activation in an attempt to fight the extracellular A beta load that is characteristic of the terminal stages of the disease. Cell Death and Disease (2010) 1, e1; doi:10.1038/cddis.2009.2; published online 14 January 2010

Formation Mechanism Of Lamellar Chips During Machining Of Bulk Metallic Glass

The uniqThe unique lamellar chips formed in turning–machining of a Vit 1 bulk metallic glass (BMG) are found to be due to repeated shearband formation in the primary shear zone (PSZ). A coupled thermomechanical orthogonal cutting model, taking into account force, free volume and energy balance in the PSZ, is developed to quantitatively characterize lamellar chip formation. Its onset criterion is revealed through a linear perturbation analysis. Lamellar chip formation is understood as a self-sustained limit-cycle phenomenon: there is autonomous feedback in stress, free volume and temperature in the PSZ. The underlying mechanism is the symmetry breaking of free volume flow and source, rather than thermal instability. These results are fundamentally useful for machining BMGs and even for understanding the physical nature of inhomogeneous flow in BMGs.ue lamellar chips formed in turning–machining of a Vit 1 bulk metallic glass (BMG) are found to be due to repeated shearband.

Formation of Single and Multiple Deformation Twins in Nanocrystalline fcc Metals

Deformation twins are often observed to meet each other to form multi-fold twins in nanostructured face-centered cubic (fcc) metals.Here we propose two types of mechanism for the nucleation and growth of four different single and multiple twins. These mechanisms provide continuous generation of twinning partials for the growth of the twins after ucleation. A relatively high stress or high strain rate is needed to activate these mechanisms, making them more prevalent in nanocrystalline materials than in their coarse-grained counterparts.Experimental observations that support the proposed mechanisms are presented.