bluuebunny/crossref_metadata_2025 huggingface dataset:
Service Life Assessment of a Low-Slope 55 % Al–Zn Alloy-Coated Steel Standing Seam Roof System
Authors: Haddock Rob , Dutton Ron
Published: July 2011

Published surveys concerning roof service life incorporate estimates from roofing professionals based on their observations and opinions. In cases where roofing products have been in service long enough for the end of life to be observed, these data have some merit, but when end-of-life empirical data are not available, accurate projections are difficult to verify. Other attempts at defining the service life relate to product warranties or lab testing. In the case of standing seam metal roofing, the variability of the materials and installation methods strongly colors the survey opinions. In steel roofing, this variability includes that of the steel thickness, the metallic coating type and thickness, the presence or absence of paint films, the types of sealants, the seam-folding details, and other construction or installation details. Related accessories and flashings of different materials and designs further confuse survey criteria and results. In the case of 55 % Al–Zn alloy-coated steel roofing systems, the prediction of service life is complicated by the fact that the product has been commercially available for under 40 years, and end of life has rarely been observed. In this paper, we combine field inspection procedures with a novel technique for securing roof samples for subsequent laboratory analysis in order to enable the prediction of roof service life for a 55 % Al–Zn alloy-coated steel roof in Denver, CO. The performance of other roof components is also quantified. A methodology is then presented that utilizes the current best practices, together with the results of this roof analysis, to predict the total roof service life of similar constructions when built using today’s practices. This work confirms previously published work that used experimental corrosion specimens to establish the long-term durability of 55 % Al–Zn alloy-coated steel. It is suggested that this work can be replicated in order to develop meaningful corrosion and material performance data for any climate in which this type of roof is constructed.
Creep and Environmental Effects on the High Temperature Creep-Fatigue Behavior of Alloy 617
Authors: Carroll L. J. , Cabet C. , Madland R. , Wright R. N.
Published: July 2011

Alloy 617 is the leading candidate material for an intermediate heat exchanger (IHX) of the very high temperature reactor (VHTR), expected to have an outlet temperature as high as 950°C. Acceptance of Alloy 617 in Section III of the ASME Code for nuclear construction requires a detailed understanding of the creep-fatigue behavior. Strain-controlled low cycle fatigue (LCF) tests including hold times up to 1800 s at maximum tensile strain were conducted at 950°C and a total strain range of 0.3 % in air and in a simulated VHTR impure helium. For similar test conditions, the creep-fatigue behavior was globally similar in both environments. The fatigue resistance decreased when a hold time was added at peak tensile strain, consistent with the observed change in fracture mode from transgranular to intergranular. Further increases in the tensile hold time, beyond 180 s, were not detrimental to the creep-fatigue resistance. The influence of oxidation on the fatigue crack initiation and propagation is discussed. Bulk damage in the form of grain boundary cracking was present in the interior of the creep-fatigue specimens. This bulk cracking was quantified and found to be similar for hold times of up to 1800 s consistent with the saturation in failure lives.
Advanced Ductility Exhaustion Methods for the Calculation of Creep Damage During Creep-Fatigue Cycling
Authors: Spindler Mike W , Payten Warwick M
Published: July 2011

The thermal mechanical cycling of high temperature components can result in creep-fatigue cycles in which the creep dwell has a wide variety of positions within the cycle. During in-phase cycling the creep dwell is placed at the maximum strain in the cycle. Out of phase cycling gives compressive dwells and phase cycling between 0° and 180° gives a cycle in which the dwell is placed before the maximum strain is reached, i.e., at an intermediate position within the cycle. Furthermore, components often experience cycles with a variety of different strain amplitudes, which can result in cycle sequencing effects. The effects of these different types of creep dwells have been investigated as part of the development programme for the R5 High Temperature Life Assessment Procedure. The materials included in the R5 programme were two low alloy ferritic steels; a cast 1CrMoV and a cast 1/2 CrMoV and three austenitic stainless steels; a type 316H steel, a cast type 304L, and a type 347 weld metal. The analysis of these tests has resulted in the proposal of a new method to calculate creep damage. This has been shown to give better predictions for the creep damage at failure in laboratory tests compared with both the current R5 ductility exhaustion approach and the time fraction approach, which is used in typical design codes such as ASME III and RCC-MR. In particular, the new method gives significantly improved predictions of creep damage at failure for creep-fatigue cycles with intermediate dwells and for cycles with low strain ranges, which are of particular relevance to the service cycles in real plant. This paper reviews the findings of the work on the new method, the effects of multiaxial states of stress and the effects of compressive dwells.
Fetal and infant growth and the risk of obesity during early childhood: the Generation R Study
Authors: Mook-Kanamori Dennis O , Durmuş Büşra , Sovio Ulla , Hofman Albert , Raat Hein , Steegers Eric A P , Jarvelin Marjo-Riitta , Jaddoe Vincent W V
Published: July 2011

Objective

To examine whether infant growth rates are influenced by fetal growth characteristics and are associated with the risks of overweight and obesity in early childhood.

Design

This study was embedded in the Generation R Study, a population-based prospective cohort study from fetal life onward.

Methods

Fetal growth characteristics (femur length (FL) and estimated fetal weight (EFW)) were assessed in the second and third trimesters and at birth (length and weight). Infant peak weight velocity (PWV), peak height velocity (PHV), and body mass index at adiposity peak (BMIAP) were derived for 6267 infants with multiple height and weight measurements.

Results

EFW measured during the second trimester was positively associated with PWV and BMIAP during infancy. Subjects with a smaller weight gain between the third trimester and birth had a higher PWV. FL measured during the second trimester was positively associated with PHV. Gradual length gain between the second and third trimesters and between the third trimester and birth were associated with higher PHV. Compared with infants in the lowest quintile, the infants in the highest quintile of PWV had strongly increased risks of overweight/obesity at the age of 4 years (odds ratio (95% confidence interval): 15.01 (9.63, 23.38)).

Conclusion

Fetal growth characteristics strongly influence infant growth rates. A higher PWV, which generally occurs in the first month after birth, was associated with an increased risk of overweight and obesity at 4 years of age. Longer follow-up studies are necessary to determine how fetal and infant growth patterns affect the risk of disease in later life.
Decreased expression of genes involved in oxidative phosphorylation in human pancreatic islets from patients with type 2 diabetes
Authors: Olsson Anders H , Yang Beatrice T , Hall Elin , Taneera Jalal , Salehi Albert , Dekker Nitert Marloes , Ling Charlotte
Published: July 2011

Objective

Gene expression alterations, especially in target tissues of insulin, have been associated with type 2 diabetes (T2D). In this study, we examined if genes involved in oxidative phosphorylation (OXPHOS) show differential gene expression and DNA methylation in pancreatic islets from patients with T2D compared with non-diabetic donors.

Design and methods

Gene expression was analyzed in human pancreatic islets from 55 non-diabetic donors and nine T2D donors using microarray.

Results

While the expected number of OXPHOS genes with reduced gene expression is 7.21, we identified 21 downregulated OXPHOS genes in pancreatic islets from patients with T2D using microarray analysis. This gives a ratio of observed over expected OXPHOS genes of 26.37 by aχ2-test withP=2.81×10−7. The microarray data was validated by qRT-PCR for four selected OXPHOS genes:NDUFA5, NDUFA10, COX11, andATP6V1H. All four OXPHOS genes were significantly downregulated in islets from patients with T2D compared with non-diabetic donors using qRT-PCR (P≤0.01). Furthermore, HbAlc levels correlated negatively with gene expression ofNDUFA5, COX11, andATP6V1H(P<0.05). Gene expression ofNDUFA5, NDUFA10, COX11, andATP6V1Hcorrelated positively with glucose-stimulated insulin secretion (P<0.03). Finally, DNA methylation was analyzed upstream of the transcription start forNDUFA5, COX11, andATP6V1H. However, none of the analyzed CpG sites in the three genes showed differences in DNA methylation in islets from donors with T2D compared with non-diabetic donors.

Conclusion

Pancreatic islets from patients with T2D show decreased expression of a set of OXPHOS genes, which may lead to impaired insulin secretion.
Coalescence-Time Distributions in a Serial Founder Model of Human Evolutionary History
Authors: DeGiorgio Michael , Degnan James H , Rosenberg Noah A
Published: July 2011

Simulation studies have demonstrated that a variety of patterns in worldwide genetic variation are compatible with the trends predicted by a serial founder model, in which populations expand outward from an initial source via a process in which new populations contain only subsets of the genetic diversity present in their parental populations. Here, we provide analytical results for key quantities under the serial founder model, deriving distributions of coalescence times for pairs of lineages sampled either from the same population or from different populations. We use these distributions to obtain expectations for coalescence times and for homozygosity and heterozygosity values. A predicted approximate linear decline in expected heterozygosity with increasing distance from the source population reproduces a pattern that has been observed both in human genetic data and in simulations. Our formulas predict that populations close to the source location have lower between-population gene identity than populations far from the source, also mirroring results obtained from data and simulations. We show that different models that produce similar declining patterns in heterozygosity generate quite distinct patterns in coalescence-time distributions and gene identity measures, thereby providing a basis for distinguishing these models. We interpret the theoretical results in relation to their implications for human population genetics.
A Drosophila Model for Genetic Analysis of Influenza Viral/Host Interactions
Authors: Adamson Amy L , Chohan Kultaran , Swenson Jennifer , LaJeunesse Dennis
Published: July 2011

Influenza viruses impose a constant threat to vertebrates susceptible to this family of viruses. We have developed a new tool to study virus–host interactions that play key roles in viral replication and to help identify novel anti-influenza drug targets. Via the UAS/Gal4 system we ectopically expressed the influenza virus M2 gene in Drosophila melanogaster and generated dose-sensitive phenotypes in the eye and wing. We have confirmed that the M2 proton channel is properly targeted to cell membranes in Drosophila tissues and functions as a proton channel by altering intracellular pH. As part of the efficacy for potential anti-influenza drug screens, we have also demonstrated that the anti-influenza drug amantadine, which targets the M2 proton channel, suppressed the UAS-M2 mutant phenotype when fed to larvae. In a candidate gene screen we identified mutations in components of the vacuolar V1V0 ATPase that modify the UAS-M2 phenotype. Importantly, in this study we demonstrate that Drosophila genetic interactions translate directly to physiological requirements of the influenza A virus for these components in mammalian cells. Overexpressing specific V1 subunits altered the replication capacity of influenza virus in cell culture and suggests that drugs targeting the enzyme complex via these subunits may be useful in anti-influenza drug therapies. Moreover, this study adds credence to the idea of using the M2 “flu fly” to identify new and previously unconsidered cellular genes as potential drug targets and to provide insight into basic mechanisms of influenza virus biology.
Gas-Compositional Effects on Mineralogical Reactions in Carbon Dioxide Sequestration
Authors: Mandalaparty Prashanth , Deo Milind , Moore Joseph
Published: July 2011

It may be possible to lower costs of carbon capture and sequestration by keeping constituents such as sulfur dioxide (SO2) in the flue-gas stream. The reactive behavior of pure carbon dioxide (CO2) and CO2+SO2 mixtures within a geologically realistic environment was examined in this paper. The experimental apparatus consisted of a series of high-pressure reactors operated at different conditions and with different feed-gas compositions to observe changes in both the rock and water compositions. The rock consisted of equal proportions of quartz, calcite, andesine, dolomite, chlorite, and magnesite (constituents in arkose or dirty sandstone). The brine was prepared from laboratory-grade sodium chloride. Several long-term batch experiments with pure CO2 were carried out at different temperatures. Each mineral in the mixture showed evidence of participating in the geochemical reactions. Layers of calcite were seen growing on the surface of the arkose. Analcime deposits were omnipresent, occurring either as large connected aggregates or as deposits on the surfaces of other minerals (quartz). Calcite depositions were observed as amorphous masses intergrown with the feed. The CO2+SO2 mixture experiments showed growth of euhedral anhydrite crystals and pronounced dissolution patterns over the examined surfaces. The growth of these new phases would lead to significant changes in the petrophysical properties of the rock. The trends in ionic-concentration changes in the aqueous phase complemented the changes in the rock chemistry.
Probabilistic Modeling for Decision Support in Integrated Operations
Authors: Giese Martin , Bratvold Reidar B.
Published: July 2011

We report work carried out within the project on collaborative decision support for integrated operations (CODIO). As one part of this project, we have designed a system to provide assistance in operational decisions based on real-time sensor readings in a typical scenario: While drilling close to the transition to a high-pressure formation, a gas influx is observed. The drilling team needs to decide whether to circulate, increase the mud weight, plug back, or set a casing.

After a brief description of the technology we used to model decision problems [Bayesian networks, influence diagrams (IDs)], we describe our case study and discuss the particular challenge of applying decision analysis to the kind of operational decision that is central to the case study. We then proceed to apply the method of decision analysis to our case study. We discuss how the resulting ID was tested using a simulation and discuss challenges in applying the technology, as well as lessons learned in the process. We also give a list of desiderata to establish better decision-making practices in the petroleum industry.
Propagation and Retention of Viscoelastic Surfactants Following Matrix-Acidizing Treatments in Carbonate Cores
Authors: Yu M.. , Mahmoud M.A.. A. , Nasr-El-Din H.A.. A.
Published: July 2011

Viscoelastic surfactants have been used extensively in the field. They have the ability to form long rod-like micelles with an increase in pH and calcium concentration, which results in increasing the viscosity and elasticity of partially spent acids. There is ongoing debate in the industry about whether the gel generated by these surfactants causes formation damage, especially in dry-gas wells. The objectives of the present study are to quantitatively determine surfactant retention in calcite cores and assess the benefits of using mutual solvents to break the surfactant gel formed inside the cores.

Coreflood tests were performed using Pink Desert limestone cores (1.5 in. in diameter and 20 in. in length). The cores were injected with a surfactant-based acid that contained 15 wt% HCl, 7 vol% viscoelastic surfactant, and 0.3 vol% corrosion inhibitor. Coreflood tests were conducted at a constant injection flow rate ranging from 1.5 to 40 cm3/min. Surfactant and calcium concentrations were measured in the injected acid and core effluent. Mutual solvent (ethylene glycol monobutyl ether) was used in several tests to break surfactant gel.

Propagation of viscoelastic surfactants in linear calcite cores was found to be a function of flow rate. Surfactant lagged calcium in the core effluent samples, especially at low flow rates. The volume of acid needed to break through the core and the amount of surfactant retained varied with acid injection rate, and exhibited a minimum at 10 cm3/min. A significant amount of surfactant was retained in the cores. Injection of 2 pore volumes (PV) of 10 vol% mutual solvent removed only 20% of the surfactant injected. Based on these results, there is a need to use internal breakers when surfactant-based acids are used in dry-gas wells or water injectors.
Mechanisms for High Displacement Efficiency of Low-Temperature CO2 Floods
Authors: Okuno R.. , Johns R.T.. T. , Sepehrnoori K..
Published: July 2011

CO2 floods at temperatures typically below 120°F can involve complex phase behavior, where a third CO2-rich liquid (L2) phase coexists with the oleic (L1) and gaseous (V) phases. Results of slimtube measurements in the literature show that an oil displacement by CO2 can achieve high displacement efficiency of more than 90% when three hydrocarbon phases coexist during the displacement. However, the mechanism for the high-displacement efficiency is uncertain because the complex interaction of phase behavior with flow during the displacement is not fully understood.

In this paper, we present the first detailed study of three-phase behavior predictions and displacement efficiency for low-temperature CO2 floods. Four-component EOS models are initially used to investigate systematically the effects of pressure, temperature, and oil properties on development of three-phase regions and displacement efficiency. Multicomponent oil displacements by CO2 are then considered. We use a compositional reservoir simulator capable of robust three-phase equilibrium calculations.

Results show that high displacement efficiency of low-temperature CO2 floods is a consequence of both condensing and vaporizing behavior. The L2 phase serves as a buffer between the immiscible V and L1 phases within the three-phase region. Components in the L1 phase first transfer efficiently to the L2 phase near a lower critical endpoint (LCEP). These oil components then transfer to the V phase near an upper critical endpoint (UCEP) at the trailing edge of the three-phase region. The CEPs are defined where two of the three coexisting phases merge in the presence of the other immiscible phase. Unlike two-phase displacements, condensation and vaporization of intermediate components occur simultaneously within the three-phase region. The simultaneous condensing/vaporizing behavior involving the CEPs is also confirmed for simulations of several west Texas oil displacements. Quaternary fluid models can predict qualitatively the complex displacements because four is the minimum number of components to develop CEP behavior in composition space at a fixed temperature and pressure.
Survey of Stranded Gas and Delivered Costs to Europe of Selected Gas Resources
Authors: Attanasi E.D.. D. , Freeman P.A.. A.
Published: July 2011

Two important trends affecting the expected growth of global gas markets are (1) the shift by many industrialized countries from coal-fired electricity generation to the use of natural gas to generate electricity and (2) the industrialization of the heavily populated Asian countries of India and China. This paper surveys discovered gas in stranded conventional gas accumulations and presents estimates of the cost of developing and producing stranded gas in selected countries. Stranded gas is natural gas in discovered or identified fields that is not currently commercially producible for either physical or economic reasons. Published reserves of gas at the global level do not distinguish between volumes of gas in producing fields and volumes in nonproducing fields. Data on stranded gas reported here—that is the volumes, geographical distribution, and size distributions of stranded gas fields at the country and regional level—are based on the examination of individual-field data and represent a significant improvement in information available to industry and government decision makers. Globally, stranded gas is pervasive, but large volumes in large accumulations are concentrated in only a few areas.

The cost component of the paper focuses on stranded conventional gas accumulations in Africa and South America that have the potential to augment supplies to Europe. The methods described for the computation of extraction and transport costs are innovative in that they use information on the sizes and geographical distribution of the identified stranded gas fields. The costs are based on industry data specific to the country and geologic basin where the stranded gas is located. Gas supplies to Europe can be increased significantly at competitive costs by the development of stranded gas. Net extraction costs of producing the identified gas depend critically on the natural-gas-liquids (NGLs) content, the prevailing prices of liquids, the size of the gas accumulation, and the deposit's location. The diversity of the distribution of stranded gas is one obstacle to the exercise of market power by the Gas Exporting Countries Forum (GECF).
Modeling Gas-Phase Mass Transfer Between Fracture and Matrix in Naturally Fractured Reservoirs
Authors: Jamili A.. , Willhite G.P.. P. , Green D.W.. W.
Published: July 2011

Gas injection in naturally fractured reservoirs maintains the reservoir pressure and increases oil recovery primarily by gravity drainage and to a lesser extent by mass transfer between the flowing gas in the fracture and the porous matrix. Although gravity drainage has been studied extensively, there has been limited research on mass-transfer mechanisms between the gas flowing in the fracture and fluids in the porous matrix.

This paper presents a mathematical model that describes the mass transfer between a gas flowing in a fracture and a matrix block. The model accounts for diffusion and convection mechanisms in both gas and liquid phases in the porous matrix. The injected gas diffuses into the porous matrix through gas and liquid phases, causing the vaporization of oil in the porous matrix, which is transported by convection and diffusion to the gas flowing in the fracture. Compositions of equilibrium phases are computed using the Peng-Robinson EOS.

The mathematical model was validated by comparing calculations to two sets of experimental data reported in the literature (Morel et. al. 1990; Le Romancer et. al. 1994), one involving nitrogen (N2) flow in the fracture and the second with carbon dioxide (CO2) flow. The matrix was a chalk. The resident fluid in the porous matrix was a mixture of methane and pentane. In the N2-diffusion experiment, liquid and vapor phases were initially present, while in the CO2 experiment, the matrix was saturated with liquid-hydrocarbon and water phases.

Calculated results were compared with the experimental data, including recovery of each component, saturation profiles, and pressure gradient between matrix and fracture. Agreement was generally good. The simulation revealed the presence of countercurrent flow inside the block. Diffusion was the main mass-transfer mechanism between matrix and fracture during N2 injection. In the CO2 experiment, diffusion and convection were both important.
Permanent Abandonment of a North Sea Well Using Unconsolidated Well-Plugging Material
Authors: Saasen Arild , Wold Sturla , Ribesen Bjørn Thore , Tran Tu Nhat , Huse Arve , Rygg Vidar , Grannes Ingvar , Svindland Alf
Published: July 2011

The traditional plug-and-abandonment (P&A) method of exploration wells in the North Sea is to set a series of cement plugs to isolate the pressurized zones from each other and from surface. This paper describes a North Sea P&A field case. In this case, an alternative method was used with a Bingham-plastic unconsolidated plugging material with high solids concentrations. This alternative method addresses well-integrity issues such as those caused by shrinking of cement or gas migration during setting, fracturing after setting, or long-term degradation by exposure to heat and chemical substances in the well.

The gas-tight well-barrier element described here does not set up after placement and does not shrink. Furthermore, it cannot fracture even when shear forces exceed its strength. When this happens, the material floats and shear forces are reduced below yield strength, causing the plug to reshape. Because this is a purely mechanical process, the transition between solid and fluid phase is repeatedly reversible (in principle, an infinite number of times).

The plug is thermodynamically stable because its sealing property is decided by the solids particle-size distribution (PSD) and bound water only. The closely packed particles and absence of free water mean that the entire column is kept homogeneous and no internal redistribution of particles may occur. Hence, the permanent gas-tight barrier will prevent influx through the wellbore.

In the field case, a successful implementation of the technology was obtained. The field case shows how the fast and efficient placement of the plug contributes to overall cost reduction. The paper explains how the well-barrier element complies with Norwegian requirements for permanent P&A; these requirements also apply to the UK sector (NORSOK D-010 2004; Oil and Gas UK 2009). Operational procedures are also presented in some detail.
Qualifying Seismic as a "Reliable Technology"—An Example of Downdip Water-Contact Location
Authors: Sidle R.E.. E. , Lee W.J.. J.
Published: July 2011

The term "reliable technology" was added to the lexicon of oil and gas reserves estimation with the updated regulations published by the US Securities and Exchange Commission in late 2008 (US Securities and Exchange Commission 2008). A previous paper (Sidle and Lee 2010) described an approach to the demonstration that a technology satisfied the criteria of a reliable technology. This paper builds on the use of the scientific method, as described in the previous paper, by examining a real-life example of seismic interpretation to define water contacts downdip of hydrocarbon-column penetrations.

Complex technologies, such as seismic, require careful and detailed calibration and testing to demonstrate the consistency and repeatability needed to qualify as a reliable technology. However, this complexity need not preclude that technology from use as reliable. Proper analysis of the science behind the technology and testing to demonstrate those circumstances that allow reliable conclusions from the technology will permit even a complex technology to be qualified as acceptable.

The example used is from the Gulf of Mexico (GoM) deep water. It gives the results from several turbidite sand reservoirs in multiple fields to demonstrate the conditions under which certain seismic can be shown as reliable. The learnings from these applications allow the development of a "reliability qualification checklist" that defines the conditions under which the seismic data are definitive. Then, it describes the final testing of the "reliable data" to determine when a seismically interpreted water contact is sufficiently conclusive to be reasonably certain.

This paper will provide a useful description of how the qualification of a technology can be planned, tested, and conclusions drawn. It will provide examples of constraints that develop from the theoretical analysis and testing results and show how these constraints can be incorporated into a set of limitations on the application of the technology. While certain elements of the technology are discussed in this paper, it is not the authors’ intent to provide an exhaustive description of the seismic theory and methods used for this example. Rather, the paper will focus on the reliability demonstration process.
Hydrogen Sulfide Absorption Phenomena in Brine/Oil Mixtures
Authors: Zea Luis , Cooper David , Kumar Ranganathan
Published: July 2011

Brine and oil absorb hydrogen sulfide (H2S) under pressure in the underground oil reservoir and then undergo a decompression during the extraction process, during which a certain amount of H2S is released from the liquid phase. This paper reports experimental data on how much of the corrosive gas is absorbed into different brine/oil mixtures [0, 33, 66, and 100% water cuts (WCs)]. Different reservoir-simulation scenarios were created at 20 and 70 atm at room temperature. H2S gas concentration was varied as tests were conducted with 50, 100, and 300 ppm in nitrogen. These experiments took place in an autoclave system that simulates the hydrostatic process that occurs inside a reservoir. This paper also reports Henry's law constants for H2S in different WCs. It is found that for all WCs, total pressure plays only a minor role in the absorption phenomena when the initial H2S concentration is increased. In addition, the highest mass-absorption ratios are found at lower H2S concentrations.
Discretization, Simulation, and Swanson's (Inaccurate) Mean
Authors: Bickel J. Eric , Lake Larry W. , Lehman John
Published: July 2011

Swanson's mean (SM) is heavily used within the oil and gas industry to approximate continuous probability distributions such as the log-normal. In this paper, we document the errors induced by this practice, which, as we show, has no theoretical justification for any distribution other than the normal. In parallel, we review methods to discretize continuous distributions and compare these methods to Monte Carlo (MC) simulation. We demonstrate that the best discretization methods have an accuracy equivalent to that of tens of thousands of MC trials.
CO2 Breakthrough vs. Gas-Processing Facilities: Qualitative Appraisal
Authors: Belhaj Hadi , Abdulwahab Haytham
Published: July 2011

This study describes how gas-processing facilities are impacted by injected CO2 returning to surface through production streams, with the goal to improve profitability of the enhanced-oil-recovery (EOR) project by postponing the expenses of handling returning CO2. In the short term, mixing the incremental oil that has a higher CO2 content with the remaining production streams of lower CO2 content will allow the existing gas-processing facilities to accommodate the returning CO2. In the long term, the compression capacity should be increased and acid gas should be enriched with H2S before being fed to sulphur-recovery units. Another alternative is to isolate the impact of CO2 on the existing facilities by using an exclusive separation train, reinjecting the associated gas (or the acid part of it) and sending the sweet part to existing facilities for natural-gas-liquid (NGL) recovery--provided that the capacity is available. Enrichment units can be used to extract H2S from acid gas for sulphur recovery in existing units, provided that the capacity is available, while pure CO2 can be injected. Cryogenic fractionation will be required to separate mixtures of ethane and CO2.
A New Model for Modern Production-Decline Analysis of Gas/Condensate Reservoirs
Authors: Sureshjani M. Heidari , Gerami Shahab
Published: July 2011

Modern production-decline analysis is a robust technique for analysis of production data from a well under variable operating conditions. It uses production rates and flowing pressures to provide reliable estimates of recoverable reserves and fluid in place. The mathematics behind this technique is similar to that of pressure-transient theory; however, the focus is different. It deals with long-term variable production data instead of short-term constant-rate transient data.

Using modern decline analysis for two-phase-flow conditions (e.g., gas/condensate reservoirs) is under question because of the single-phase-flow assumption in the development of a "material-balance time" function. This is a time function that converts any decline (e.g., exponential decline) to harmonic decline to account for variable operating conditions. The purpose of this work is to develop a model to use the concepts of modern techniques for analyzing production data of single-porosity gas/condensate reservoirs. For this purpose, the governing flow equation is linearized, using appropriately defined pseudopressure and pseudotime functions. Then, the solution is obtained for constant-well-rate condition. This is followed by employing the superposition theorem to account for variable well pressure/rate conditions, resulting in definition of two-phase material-balance pseudotime. The solution developed here is coupled with an appropriate material-balance equation and used to estimate the average reservoir pressure and original gas in place from analyzing production data. The dependency of relative permeability on capillary number and non-Darcy flow is included in the formulation.

Verification of the proposed method is obtained with the analysis of synthetic production data using a series of fine-grid compositional numerical simulations over a typical range of gas/condensate-reservoir parameters.
Optimization of Styrene Reactor Using Tabu Search and Genetic Algorithm Methods
Authors: Shahhosseini Shahrokh , Vakili Samaneh
Published: July 2011

This paper deals with multi-objective optimization of styrene reactor using Tabu search (TS) and genetic algorithm (GA) methods. Styrene is produced commercially by catalytic dehydrogenation of ethyl benzene. As styrene is an important monomer, the capacity of the plant is usually very high, as a result the investment cost is also very high, and even a small enhancement in the plant operation can generate major income. The adiabatic reactor using the pseudo homogeneous model was considered in this study for maximizing the styrene conversion and selectivity. A computer program was written to simulate an adiabatic reactor in order to evaluate the possibility of optimizing the process in simulation environment. The simulation results were compared with the experimental data. This comparison indicated that the value of overall mean squarer of errors for conversion of the compounds was 7.09E-05 and overall means relative error of them was 2.18 percent. In order to optimize the performance of the reactors, conversion of styrene was adopted as the objective function. Six decision variables, namely, ethyl benzene feed temperature at the entrance of each bed, pressure, the ratio of steam to ethyl benzene and initial ethyl benzene flow rate were used for the optimization. The results of GA optimization showed final conversion of styrene increased from an initial value of 0.710 to 0.75 after 100 generation of population. Applying Tabu algorithm optimization, the value rose from 0.725 to 0.813 after generation of 100 neighborhoods. The results revealed that the CPU time needed to optimize the reactor for TS was shorter than that of GA method. In addition, using the same iteration numbers for both methods, the optimum value of styrene conversion was greater when TS method was applied.
Making the Move to Blended Learning: Reflections on a Faculty Development Program
Authors: Myers Carole R , Mixer Sandra J , Wyatt Tami H , Paulus Trena M. , Lee Debra S
Published: July 2011

Lessons learned from a faculty development program that preceded the move of a traditional PhD program in nursing to a blended learning model using online and face-to-face strategies are discussed. The majority of lessons and strategies presented are universal to any faculty development program. The lessons are organized into seven topics: Situational Leadership, Adult Learners, Just in Time Teaching, Thinking About Learning and Teaching, Lifelong Learning, Transparency and Collaboration, and Community. Our far-reaching lessons are related to the contextual nature of leadership, how to effectively design and time learning experiences for adults, the importance of open and supportive communities working for a common purpose, and how each person’s perspective shapes his or her learning experience and how the lessons learned are applied.
The influence of THI values at different periods of lactation on milk quality and characteristics of lactation curve
Authors: Cincovic Marko , Belic Branislava , Toholj Bojan , Radovic Ivan , Vidovic Bojana
Published: July 2011

The experiment included 90 cows. Cows were chosen according to the time of
calving, so that the first third of lactation occurred during the summer in
30 cows (G1), the second third of lactation occurred during the summer in 30
cows (G2), and in the last 30 cows the last third of lactation was in summer
period (G3). The value of THI was between 72 and 82, which indicates the
existence of the moderate intensity of heat stress. Heat stress does not
damage the milk yield, milk fat and protein percentage on the level of the
whole lactation, regardless of the lactation period in which the cows were
exposed to stress. There was no correlation between THI and milk yield and
quality at the level of the whole lactation. Heat stress did not show a
significant effect on the parameters of lactation curve, except the peak of
yield, which occurred later in cows exposed to heat stress. Increased value
of THI showed nonsignificant effect on yield and quality of milk in the first
third of lactation. In the middle and at the end of lactation THI was in a
significant negative correlation with the yield and quality of milk. Our
study showed a significantly lower heat-induced milk yield, milk fat and
protein percent in the middle and at the end of lactation.
Austenite grain growth calculation of 0.028% Nb steel
Authors: Priadi D. , Napitupulu R.A.M. , Siradj E.S.
Published: July 2011

Modeling of microstructural evolution has become a powerful tool for
materials and process design by providing quantitative relationships for
microstructure, composition and processing. Insufficient attention has been
paid to predicting the austenite grain growth of microalloyed steel and the
effect of undissolved microalloys. In this research, we attempted to
calculate a mathematical model for austenite grain growth of 0.028% Nb
steel, which can account for abnormal grain growth. The quantitative
calculation of austenite grain growth generated from this model fit well
with the experimental grain growth data obtained during reheating of niobium
steels. The results of this study showed that increasing the temperature
increases the austenite grain size, with a sharp gradient observed at higher
temperatures.
Experimental investigation on the formation mechanism of the TiFe alloy by the molten-salt electrolytic titanium concentrate
Authors: Shi R. , Bai C. , Hu M. , Liu X. , Du J.
Published: July 2011

The ferrotitanium alloy was prepared in the molten CaCl2 system, in which
resolidified ilmenite and the graphite crucible were used as cathode and
anode. In this study, the electrolytic voltage was fixed at 3.1V, and three
different temperatures were applied: 850oC, 875oC and 900?C. Finally, the
product was examined by SEM and XRD to determine the phase transformation
after the electrolysis. The results show that the ilmenite was firstly
reduced to Fe, and finally the TiFe alloy was formed. The intermediate
products include CaTiO3, TiO2, Ti2O3, TiO, Fe, TiFe2, and Ti. Different
product and structure can be obtained by changing temperature. According to
thermodynamic calculation, the principal electroreduction products are Ti and
TiFe2 and then Ti and TiFe2 are formed by interdiffusion which is governed by
temperature.
Deoxidization mechanism of preparation FeTi alloy using ilmenite concentrate
Authors: Hu M. , Bai C. , Liu X. , Lv X.I. , Du J.
Published: July 2011

An investigation into the deoxidization mechanism of the electrochemical
reduction of ilmenite concentrate to FeTi alloy in molten calcium chloride
has been performed. The results show that deoxidization proceeds through a
number of individual stages some of which involve reduction of iron,
formation and desposition of calcium titanates(CaTiO3), reduction of the
various low value titanium oxides and formation of Fe2Ti and FeTi. CaTiO3 is
formed because Ca2+ contained in electrolyte take part in the deoxidization
process.
Fuller’s theory of war and the changes in the concepts of warfare in the second half of XX century: The rise of "creative" war
Authors: Sekulic Nada
Published: July 2011

Current scientific and scholarly discourse on war, which represents the
legitimate knowledge and theory on war today, has been narrowed to the topics
and issues related to war doctrine and technology of war. It has become
reserved for the privileged ?green collars?, highly skilled professionals and
officers inside the military structure, which act in cooperation with the
political and economic elites, forming the triumvirate of power in
contemporary world. The opportunities for civil critique of military politics
and strategies of wars have been decreased enormously, in spite of the fact
that contemporary wars have spread deeply into the civil sector of society.
By looking into the social context and political background of the knowledge
reserved for the military experts, we can develop insights into the process
of the ideological framing of wars today, marked by naturalization and
purposeful interpretations of wars, as if they are fought in the name of
democratization of global world. At the same time, the image of the
importance of human factor in war has been decreased, as much as
responsibility for causalities. Citizens have been pacified for the silent
acceptance of military politics promoted in their countries.
Changes in BMI, Duration of Overweight and Obesity, and Glucose Metabolism: 45 Years of Follow-up of a Birth Cohort
Authors: Power Chris , Thomas Claudia
Published: July 2011

OBJECTIVE

Long-term implications of childhood obesity and BMI change over the life course for risk of type 2 diabetes remain uncertain. The objective was to establish whether there are effects on adult glucose metabolism of 1) sensitive periods of BMI gain or 2) long duration of overweight and obesity.

RESEARCH DESIGN AND METHODS

Participants in the 1958 British birth cohort with child to adult BMI and glycosylated hemoglobin (HbA1c) at 45 years (n = 7,855).

RESULTS

Prevalence of type 2 diabetes or HbA1c ≥7 was 2%. BMI gains in child- and adulthood were associated with higher HbA1c: for every SD of 5-year BMI increase from 0 to 7 years, there was a 75% (95% CI 1.42–2.16) increased risk of HbA1c ≥7, increasing to a 4.7-fold (3.12–7.00) risk for the interval 23–33 years. Associations for BMI gain in adulthood were related to attained BMI but were independent for the longer period birth (or 7 years) to 45 years. Duration of obesity was also associated with HbA1c; compared with the never obese, those with childhood onset had a 23.9-fold risk (13.5–42.1) of HbA1c ≥7%; odds ratios were 16.0 (10.6–24.2) and 2.99 (1.77–5.03), respectively, for young and midadulthood onset. Similar trends by onset age were found in mean HbA1c levels and for onset of overweight. Those with the earliest age of onset had higher BMI and waist circumference at 45 years, which markedly explained the associations for onset age and HbA1c.

CONCLUSIONS

Excessive BMI gain across the life span and earlier onset of overweight/obesity are associated with impaired glucose metabolism, in part through attained adult BMI.
Type 1 Diabetes and Interferon Therapy
Authors: Nakamura Kan , Kawasaki Eiji , Imagawa Akihisa , Awata Takuya , Ikegami Hiroshi , Uchigata Yasuko , Kobayashi Tetsuro , Shimada Akira , Nakanishi Koji , Makino Hideichi , Maruyama Taro , Hanafusa Toshiaki ,   the Research Committee on Type 1 Diabetes of the Japan Diabetes Society
Published: July 2011

OBJECTIVE

Interferon therapy can trigger induction of several autoimmune diseases, including type 1 diabetes. To assess the clinical, immunologic, and genetic characteristics of type 1 diabetes induced by interferon therapy, we conducted a nationwide cross-sectional survey.

RESEARCH DESIGN AND METHODS

Clinical characteristics, anti-islet autoantibodies, and HLA-DR typing were examined in 91 patients for whom type 1 diabetes developed during or shortly after interferon therapy.

RESULTS

Median age at the onset of type 1 diabetes was 56 (interquartile range 48–63) years and mean ± SD BMI was 20.8 ± 2.7 kg/m2. The time period from the initiation of interferon therapy to type 1 diabetes onset in patients receiving pegylated interferon and ribavirin was significantly shorter than that in patients with nonpegylated interferon single therapy (P < 0.05). Anti-islet autoantibodies were detected in 94.5% of patients at diabetes onset. Type 1 diabetes susceptibility HLA-DRs in the Japanese population, DR4 and DR9, were also associated with interferon treatment–related type 1 diabetes. Furthermore, the prevalence of HLA-DR13 was significantly higher in interferon treatment–related type 1 diabetes than in healthy control subjects (odds ratio 3.80 [95% CI 2.20–7.55]; P < 0.0001) and classical type 1 diabetes (2.15 [1.17–3.93]; P < 0.05).

CONCLUSIONS

Anti-islet autoantibodies should be investigated before and during interferon therapy to identify subjects at high risk of type 1 diabetes. Stronger antiviral treatment may induce earlier development of type 1 diabetes. Furthermore, patients who develop interferon-induced type 1 diabetes are genetically susceptible.
Clinical Usefulness of Different Lipid Measures for Prediction of Coronary Heart Disease in Type 2 Diabetes
Authors: Eliasson Björn , Cederholm Jan , Eeg-Olofsson Katarina , Svensson Anne-Marie , Zethelius Björn , Gudbjörnsdottir Soffia ,   on behalf of the National Diabetes Register
Published: July 2011

OBJECTIVE

We assessed the association between different blood lipid measures and risk of fatal/nonfatal coronary heart disease (CHD).

RESEARCH DESIGN AND METHODS

We conducted an observational study of patients with type 2 diabetes from the Swedish National Diabetes Register. Baseline LDL cholesterol, non-HDL cholesterol, ratio of non-HDL to HDL cholesterol (non-HDL:HDL), and ratio of triacylglycerol to HDL cholesterol (TG:HDL) was measured in 18,673 patients aged 30–70 years, followed for a mean of 4.8 years from 2003 to 2007.

RESULTS

Hazard ratios (HRs) for CHD per 1-SD increment in lipid measures were 1.23 with non-HDL:HDL, 1.20 with non-HDL cholesterol, 1.17 with LDL cholesterol, and 1.15 with TG:HDL (all P < 0.001 when adjusted for clinical characteristics and nonlipid risk factors). The best global model fit was found with non-HDL:HDL. When patients within the lowest tertile of a lipid measure were compared with those with all lipid measures within the highest tertile, the adjusted HR for CHD was 0.62 with non-HDL:HDL <3.5 mmol/L, 0.65 with non-HDL cholesterol <3.3 mmol/L, and 0.70 with LDL cholesterol <2.5 mmol/L (all P < 0.001). The lowest tertile of LDL and non-HDL cholesterol corresponded with treatment targets according to U.S. and European guidelines. HRs for CHD were 0.52, 0.62, and 0.66 with the lowest deciles of non-HDL:HDL, non-HDL cholesterol, and LDL cholesterol ≤1.8 mmol/L (all P < 0.001). Mean TG:HDL was considerably lower in patients within the lowest tertile of non-HDL:HDL, 0.82 ± 0.47, than in those within the lowest tertile of LDL cholesterol (<2.5 mmol/L), 1.49 ± 1.03.

CONCLUSIONS

Non-HDL:HDL had a stronger effect on CHD risk than LDL cholesterol, and low TG:HDL values were more often seen within the lowest non-HDL:HDL tertile than within the lowest LDL cholesterol tertile. LDL cholesterol was not the best predictor of CHD risk in type 2 diabetes.