bluuebunny/crossref_metadata_2025_split huggingface dataset:
Operator-Based Multiscale Method for Compressible Flow
Authors: Zhou H. , Tchelepi H. A. 
Published: July 2008

Summary
Multiscale methods have been developed for accurate and efficient numerical solution of flow problems in large-scale heterogeneous reservoirs. A scalable and extendible Operator-Based Multiscale Method (OBMM) is described here. OBMM is cast as a general algebraic framework. It is natural and convenient to incorporate more physics in OBMM for multiscale computation. In OBMM, two operators are constructed: prolongation and restriction. The prolongation operator is constructed by assembling the multiscale basis functions. The specific form of the restriction operator depends on the coarse-scale discretization formulation (e.g., finite-volume or finite-element). The coarse-scale pressure equation is obtained algebraically by applying the prolongation and restriction operators to the fine-scale flow equations. Solving the coarse-scale equation results in a high-quality coarse-scale pressure. The fine-scale pressure can be reconstructed by applying the prolongation operator to the coarse-scale pressure. A conservative fine-scale velocity field is then reconstructed to solve the transport (saturation) equation. We describe the OBMM approach for multiscale modeling of compressible multiphase flow. We show that extension from incompressible to compressible flows is straightforward. No special treatment for compressibility is required. The efficiency of multi-scale formulations over standard fine-scale methods is retained by OBMM. The accuracy of OBMM is demonstrated using several numerical examples including a challenging depletion problem in a strongly heterogeneous permeability field (SPE 10).
MRI Visualization of Spontaneous Methane Production From Hydrates in Sandstone Core Plugs When Exposed to CO2
Authors: Graue A. , Kvamme B. , Baldwin B. A. , Stevens J. , Howard J. , Aspenes E. , Ersland G. , Husebø J. , Zornes D. 
Published: July 2008

Summary
Magnetic resonance imaging (MRI) of core samples in laboratory experiments showed that CO2 storage in gas hydrates formed in porous rock resulted in the spontaneous production of methane with no associated water production. The exposure of methane hydrate in the pores to liquid CO2 resulted in methane production from the hydrate that suggested the exchange of methane molecules with CO2 molecules within the hydrate without the addition or subtraction of significant amounts of heat. Thermodynamic simulations based on Phase Field Theory were in agreement with these results and predicted similar methane production rates that were observed in several experiments. MRI-based 3D visualizations of the formation of hydrates in the porous rock and the methane production improved the interpretation of the experiments. The sequestration of an important greenhouse gas while simultaneously producing the freed natural gas offers access to the significant amounts of energy bound in natural gas hydrates and also offers an attractive potential for CO2 storage. The potential danger associated with catastrophic dissociation of hydrate structures in nature and the corresponding collapse of geological formations is reduced because of the increased thermodynamic stability of the CO2 hydrate relative to the natural gas hydrate.
Atomic Force Microscopy Study of Wettability Alteration by Surfactants
Authors: Kumar K. , Dao E. K. , Mohanty K. K. 
Published: July 2008

Summary
Waterflooding recovers little oil from fractured carbonate reservoirs, if they are oil-wet or mixed-wet. Surfactant-aided gravity drainage has the potential to achieve significant oil recovery by wettability alteration and interfacial tension (IFT) reduction. The goal of this work is to investigate the mechanisms of wettability alteration by crude oil components and surfactants. Contact angles are measured on mineral plates treated with crude oils, crude oil components, and surfactants. Mineral surfaces are also studied by atomic force microscopy (AFM). Surfactant solution imbibition into parallel plates filled with a crude oil is investigated. Wettability of the plates is studied before and after imbibition. Results show that wettability is controlled by the adsorption of asphaltenes. Anionic surfactants can remove these adsorbed components from the mineral surface and induce preferential water wettability. Anionic surfactants studied can imbibe water into initially oil-wet parallel-plate assemblies faster than the cationic surfactant studied.
High-Resolution Prediction of Enhanced Condensate Recovery Processes
Authors: Jessen K. , Gerritsen M. G. , Mallison B. T. 
Published: July 2008

Summary
This paper investigates the accuracy of first- and high-order numerical methods in simulating enhanced condensate processes in 1D, 2D, and 3D. We compare the predictions of a standard single point upwind (SPU) scheme with a third-order accurate finite difference (FD) simulator based on a third-order essentially nonoscil-latory (ENO) flux reconstruction with matching temporal accuracy. We include physical dispersion in the mathematical model of these multiphase, multicomponent systems.
The comparisons demonstrate that SPU schemes may fail to predict the formation of the mobile liquid bank at the leading edge of the displacement unless an impractical number of gridblocks is used in the simulations. In contrast, the high-order FD simulator is demonstrated to accurately predict the liquid bank at much lower grid resolution, providing for a more efficient simulation approach. In 2D displacement calculations with gravity included, the CPU requirement of the SPU scheme was found to be more than 50 times larger than for the ENO scheme for a given level of accuracy. In 2D vertical cross-sections, the predicted component recovery is demonstrated to vary upward of 8% depending on the selected numerical scheme for a given grid resolution and disper-sivity. In these settings, the SPU solutions converge to the ENO results upon significant grid refinement.
In 3D displacement calculations, the magnitude ofthe predicted condensate bank is also found to be very different depending on the selected numerical scheme. Relative to the 2D displacement calculations, condensate banking and gravity segregation is observed to have less impact on the process performance prediction because of the permeability configuration in the 3D model used here, but it could have a high impact in different settings.
We include an explicit representation of longitudinal and transverse dispersion in the porous medium to demonstrate the grid resolution required to resolve physical dispersion at a given simulation length scale, and to show that condensate banks can also form in more realistic dispersive systems. Grid-refinement studies in 1D and 2D demonstrate, again, that the ENO scheme outperforms the SPU scheme for a given Peclet (Pe) number. Converged solutions are obtained with the ENO scheme using a relatively small number of grid cells. In addition, we show the behavior of the two schemes for varying Peclet numbers on a fixed simulation grid. For this grid, the ENO scheme is shown to be sensitive to the Peclet number, signifying that physical dispersion is not overwhelmed by numerical diffusion. For the SPU scheme, however, the solutions are almost independent of the Peclet number, which indicates that numerical diffusion dominates.
Laboratory Investigation of the Effect of Solvent Injection on In-Situ Combustion
Authors: Cristofari J. , Castanier L. M. , Kovscek A. R. 
Published: July 2008

Summary
Application of cyclic solvent injection into heavy and viscous crude oil followed by in-situ combustion of heavy residues is explored from a laboratory perspective. The solvent reduces oil viscosity in-situ and extracts the lighter crude-oil fractions. Combustion cleans the near-well region and stimulates thermally the oil production. Both solvent injection and in-situ combustion are technically effective. The combination of the two methods, however, has never been tried to our knowledge.
Hamaca (Venezuela) and West Sak (Alaska) crude oils were employed. First, ramped temperature oxidation studies were conducted to measure the kinetic properties of the oil prior to and following solvent injection. Pentane, decane, and kerosene were the solvents of interest. Second, solvent was injected in a cyclic fashion into a 1-m-long combustion tube. Then, the tube was combusted. Hamaca oil presented good burning properties, especially following pentane injection. The pentane extracted lighter components of the crude and deposited preferentially effective fuel for combustion. On the other hand, West Sak oil did not exhibit stable combustion properties without solvent injection, following solvent injection, and even when metallic additives were added to enhance the combustion. We were unable to propagate a burning front within the combustion tube. Nevertheless, the experimental results do show that this combined solvent combustion method is applicable to the broad range of oil reservoirs with properties similar to Hamaca.
One‐Step Synthesis of Conducting Polymer–Noble Metal Nanoparticle Composites using an Ionic Liquid
Authors: Pringle Jennifer M. , Winther‐Jensen (née Ngamna) Orawan , Lynam Carol , Wallace Gordon G. , Forsyth Maria , MacFarlane Douglas R. 
Published: July 2008

AbstractConducting polymers containing incorporated gold or silver nanoparticles have been synthesized using ionic liquid solutions of gold chloride or silver nitrate. Use of the metal salts as the oxidant for monomers such as pyrrole and terthiophene allows the composites to be formed in one simple step, without the need for templates or capping agents. The incorporated metal nanoparticles are clearly visible by TEM, and the composites have been further analyzed by TGA, CV, UV‐Vis, Raman, XPS and scanning TEM coupled with EDS analysis. Utilization of an ionic liquid allows the full oxidizing power of the gold chloride to be accessed, resulting in incorporation of metallic gold into the polymers.
A Unique Processable Green Polymer with a Transmissive Oxidized State for Realization of Potential RGB‐Based Electrochromic Device Applications
Authors: Gunbas Gorkem E. , Durmus Asuman , Toppare Levent 
Published: July 2008

AbstractRealization of commercial RGB‐based polymer electrochromic‐device applications can only be achieved by processable materials that possess three complementary colors in the reduced state and are transparent in the oxidized state. This report highlights the synthesis of the first processable green polymer with a transmissive oxidized state. The polymer revealed superior optical contrast in the visible region with fast switching times and robust stability. Hence, this material is the outstanding candidate for completion of RGB color space through commercial polymeric electrochromics.
The Relation Between Open‐Circuit Voltage and the Onset of Photocurrent Generation by Charge‐Transfer Absorption in Polymer : Fullerene Bulk Heterojunction Solar Cells
Authors: Vandewal Koen , Gadisa Abay , Oosterbaan Wibren D. , Bertho Sabine , Banishoeib Fateme , Van Severen Ineke , Lutsen Laurence , Cleij Thomas J. , Vanderzande Dirk , Manca Jean V. 
Published: July 2008

AbstractPhotocurrent generation by charge‐transfer (CT) absorption is detected in a range of conjugated polymer–[6,6]‐phenyl C61 butyric acid methyl ester (PCBM) based solar cells. The low intensity CT absorption bands are observed using a highly sensitive measurement of the external quantum efficiency (EQE) spectrum by means of Fourier‐transform photocurrent spectroscopy (FTPS). The presence of these CT bands implies the formation of weak ground‐state charge‐transfer complexes in the studied polymer–fullerene blends. The effective band gap (Eg) of the material blends used in these photovoltaic devices is determined from the energetic onset of the photocurrent generated by CT absorption. It is shown that for all devices, under various preparation conditions, the open‐circuit voltage (Voc) scales linearly with Eg. The redshift of the CT band upon thermal annealing of regioregular poly(3‐hexylthiophene):PCBM and thermal aging of poly(phenylenevinylene)(PPV):PCBM photovoltaic devices correlates with the observed drop in open‐circuit voltage of high‐temperature treated versus untreated devices. Increasing the weight fraction of PCBM also results in a redshift of Eg, proportional with the observed changes in Voc for different PPV:PCBM ratios. As Eg corresponds with the effective bandgap of the material blends, a measurement of the EQE spectrum by FTPS allows us to measure this energy directly on photovoltaic devices, and makes it a valuable technique in the study of organic bulk heterojunction solar cells.
Optical Properties and Growth Aspects of Silver Nanoprisms Produced by a Highly Reproducible and Rapid Synthesis at Room Temperature
Authors: Aherne Damian , Ledwith Deirdre M. , Gara Matthew , Kelly John M. 
Published: July 2008

AbstractA rapid and readily reproducible seed‐based method for the production of high quality silver nanoprisms in high yield is presented. The edge‐length and the position of the main plasmon resonance of the nanoprisms can be readily controlled through adjustment of reaction conditions. From UV‐vis spectra of solutions of the nanoprisms, the inhomogeneously broadened line width of the in‐plane dipole plasmon resonance is measured and trends in the extent of plasmon damping as a function of plasmon resonance energy and nanoprism size have been elucidated. In addition, an in‐depth analysis of the lamellar defect structure of silver nanoprisms is provided that confirms that the defects can lead to a transformation of the crystal structure in the vicinity of the defects. These defects can combine give rise to lamellar regions, thicker than 1 nm, that extend across the crystal, where the silver atoms are arranged in a continuous hexagonal‐close‐packed (hcp) structure. This hcp structure has a periodicity of 2.50 Å, thus explaining the 2.50 Å lattice fringes that are commonly observed in 〈111〉 oriented flat‐lying nanoprisms. A new understanding of the mechanisms behind anisotropic growth in silver nanoprisms is presented.
A Template‐Free Method Towards Conducting Polymer Nanostructures
Authors: Wan Meixiang 
Published: July 2008

AbstractConducting polymer nanostructures have recently received special attention in nanoscience and nanotechnology because of their highly π‐conjugated polymeric chains and metal‐like conductivity, such that they can be regarded not only as excellent molecular wires, but also as basic units for the formation of nanodevices. Although various approaches, such as hard‐template methods, soft‐template methods, electrospinning technology, and so on are widely employed to synthesize or fabricate conducting polymer nanostructures and their composite nanostructures, each of the currently used methods possess disadvantages. Therefore, finding a facile, efficient, and controlled method of forming conducting polymer nanostructures is desirable. Similar to other nanomaterials, the effect of size (in these cases 1–100 nm) on the properties of the conducting polymer nanostructures must be considered. Electrical measurements of single nanotubes or nanowires are desirable in order to be able to understand the pure electrical properties of conducting polymer nanostructures. Compared with bulk conducting polymers, conducting polymer nanostructures are expected to display improved performance in technological applications because of the unique properties arising from their nanometer‐scaled size: high conductivity, large surface area, and light weight. Thus, it is also desirable to develop promising applications for conducting polymer nanostructures. In accordance with the issues described above, our research focuses on a new synthesis method to form conducting polymer nanostructures and on the related formation mechanism of the resultant nanostructures. The electrical and transport properties of single nanotubes of conducting polymer, measured by a four‐probe method, and promising applications of such template‐free‐synthesized conducting polymer nanostructures as new microwave absorbing materials and sensors guided by a reversible wettability are also of interest. This article reports some of our main results and reviews some important contributions of others.magnified image
Promising Functional Materials Based on Ladder Polysiloxanes
Authors: Zhou Qilong , Yan Shouke , Han Charles C. , Xie Ping , Zhang Rongben 
Published: July 2008

AbstractPreparation of real ladder polysiloxanes (LPSs), including both oxygen‐bridged ladder polysilsesquioxanes (LPSQs) and organo‐bridged ladder polysiloxanes (OLPSs), had been a great challenge to polymer chemists from 1960 until the successful synthesis of LPSs via the supramolecular architecture‐directed stepwise coupling polymerization (SCP) in the early 1980s. This opened up a new field of LPS‐based advanced materials. As key building blocks, LPSs are used to construct a variety of polysiloxanes with special steric configurations and functions, such as mesomorphic LPSs, tubular polysiloxanes (TPs), and pseudo‐sieve‐plate polysiloxanes (pseudo‐SPSs). With excellent temperature and radiation resistance, good solubility, and fine optical and mechanical properties, all these polysiloxanes demonstrate very promising prospects in the advanced materials realm. Here, the synthesis of well‐ordered LPSs is presented and features of fishbone‐like and rowboat‐like liquid crystalline polysiloxanes are discussed. Special emphasis is given to typical applications of LPSs, TPSs, and pseudo‐SPSs in the areas of liquid crystal displays, microelectronics packaging, and nonlinear optical materials.
Self‐Similar Growth of Polyolefin Alloy Particles in a Single Granule Multi‐Catalyst Reactor
Authors: Du Jiang , Niu Hui , Dong Jin‐Yong , Dong Xia , Han Charles C. 
Published: July 2008

AbstractIn this news article, a new kind of in‐reactor alloying process (Chinese multi‐catalyst reactor granule technology, CMRGT) is introduced. It provides the possibility to produce series of new polyolefin materials that can be used in automotive and appliances parts by the substitution of some traditional engineering plastics. A characteristic ‘fractal (self‐similar) growth and pore‐filling mechanism’ for the CMRGT‐produced alloy particles is found. It reveals the fundamental scientific principles that govern the chemistry and physics in the formation mechanism of such novel olefinic alloys. This mechanism allows a detailed control of the dispersion and structure of these polyolefin alloys from a nanometer to micrometer size range, and possesses great potential to fulfil the requirements for a new generation of recyclable automotive materials.
Fabrication of Low‐Dimension Nanostructures Based on Organic Conjugated Molecules
Authors: Cui Shuang , Liu Huibiao , Gan Liangbing , Li Yuliang , Zhu Daoben 
Published: July 2008

AbstractThe aim of this review is to explore the fundamental and technological incentive for the molecular design, synthesis, and aggregation behavior of conjugated organic molecules with photo‐electronic activity, and the fabrication of low‐dimensional organic conjugated nanomaterials by self‐assembly techniques. The properties of large oriented nanostructure arrays of organic charge transfer complexes based on conjugated molecules are also discussed. The dimension‐dependent emission properties have been observed, and conductivity, field emission properties, and sensing properties have been studied for the low dimensional nanostructures of nanoparticles, nanowires, nanorods, and nanostructure arrays.magnified image
Fluorescent Conjugated Polyelectrolytes for Biomacromolecule Detection
Authors: Feng Fude , He Fang , An Lingling , Wang Shu , Li Yuliang , Zhu Daoben 
Published: July 2008

AbstractWater‐soluble conjugated polymers have attracted much attention in the biosensor community because of recent exciting experimental results. The transfer of excitation energy along the whole backbone of the conjugated polymer to the reporter results in an amplified fluorescence signal, which makes them useful as optical platforms in highly sensitive chemical and biological sensors. In this Research News Article, we provide a brief review of recent developments in this field, focusing especially on the application of water‐soluble optical conjugated polymers in biomacromolecule (DNA and protein) detection.
Template Synthesis of Hierarchically Structured Composites
Authors: Wei Wei , Yang Zhenzhong 
Published: July 2008

AbstractThe subtle performance of a virus is closely related to its specific hierarchical structure, which is composed of a rigid shell and transverse, responsive, nanometer‐sized channels. Virus‐like structured colloids are of great interest for their potential applications, for example in drug delivery. Adequate knowledge of the structure and composition control of both colloids and mesoporous materials is significant in the design and synthesis of hierarchically structured colloids to mimic viruses. Some recent developments in the synthesis of composite colloids and mesoporous materials are summarized. Template synthesis is a major tool to control both the macroscopic morphology and microstructures of these composites, in which gel colloids and supramolecular structures from amphiphilic species are used as templates.magnified image
Chemoenzymatic Approach to Enantiomerically Pure (R)‐3‐Hydroxy‐3‐methyl‐4‐pentenoic Acid Ester and Its Application to a Formal Total Synthesis of Taurospongin A
Authors: Fujino Aya , Sugai Takeshi 
Published: July 2008

Abstract(R)‐3‐Hydroxy‐3‐methyl‐5‐hexanoic acid p‐methoxybenzyl ester 1b was prepared by carbon‐chain elongation on both termini of the starting material, (R)‐3‐benzyloxy‐2‐methylpropane‐1,2‐diol 2a, which was prepared by an over‐expressed Bacillus subtilis epoxide hydrolase‐catalyzed enantioselective hydrolysis of the racemic 1‐benzyloxymethyl‐1‐methyloxirane 3. One of the key steps of the requisite transformation was the Rhodococcus rhodochrous NBRC 15564‐mediated hydrolysis of a cyano group to a carboxyl group under neutral conditions, to exclude any racemization of the intermediate and/or product. The enantiomerically pure form of (R)‐1b was applied to a new formal total synthesis of taurospongin A.
Integrating parameter selection with experimental design under uncertainty for nonlinear dynamic systems
Authors: Chu Yunfei , Hahn Juergen 
Published: July 2008

AbstractModels describing complex processes often contain a large number of parameters as part of the nonlinear system. It is usually not possible in practice to identify all parameters because of the number and quality of measurement data as well as interactions among the parameters. A common approach is to select a set of parameters for estimation whereas other parameters are fixed at their nominal values. Such a parameter selection procedure is often based on sensitivity analysis; however, the determined sensitivity values depend on assumed values of the parameters and initial states, as well as known trajectories of the input signals. In this work parameter selection and experiment design procedures are integrated into a unified framework, which optimizes a criterion of the Fisher information matrix and simultaneously takes the effect of uncertainty in the parameter values into account. A hybrid method combining a genetic algorithm and a simultaneous perturbation stochastic approximation is developed to solve the resulting mixed‐integer nonlinear programming problem. The technique is illustrated on a model of a continuously‐stirred tank reactor and of a signal transduction pathway. © 2008 American Institute of Chemical Engineers AIChE J, 2008