bluuebunny/crossref_metadata_2025 huggingface dataset:
Physiological consequences of the P2328S mutation in the ryanodine receptor (RyR2) gene in genetically modified murine hearts
Authors: Goddard C. A. , Ghais N. S. , Zhang Y. , Williams A. J. , Colledge W. H. , Grace A. A. , Huang C. L.‐H.
Published: April 2008

Aim:  To explore the physiological consequences of the ryanodine receptor (RyR2)‐P2328S mutation associated with catecholaminergic polymorphic ventricular tachycardia (CPVT).

Methods:  We generated heterozygotic (RyR2p/s) and homozygotic (RyR2s/s) transgenic mice and studied Ca2+ signals from regularly stimulated, Fluo‐3‐loaded, cardiac myocytes. Results were compared with monophasic action potentials (MAPs) in Langendorff‐perfused hearts under both regular and programmed electrical stimulation (PES).

Results:  Evoked Ca2+ transients from wild‐type (WT), heterozygote (RyR2p/s) and homozygote (RyR2s/s) myocytes had indistinguishable peak amplitudes with RyR2s/s showing subsidiary events. Adding 100 nm isoproterenol produced both ectopic peaks and subsidiary events in WT but not RyR2p/s and ectopic peaks and reduced amplitudes of evoked peaks in RyR2s/s. Regularly stimulated WT, RyR2p/s and RyR2s/s hearts showed indistinguishable MAP durations and refractory periods. RyR2p/s hearts showed non‐sustained ventricular tachycardias (nsVTs) only with PES. Both nsVTs and sustained VTs (sVTs) occurred with regular stimuli and PES with isoproterenol treatment. RyR2s/s hearts showed higher incidences of nsVTs before but mainly sVTs after introduction of isoproterenol with both regular stimuli and PES, particularly at higher pacing frequencies. Additionally, intrinsically beating RyR2s/s showed extrasystolic events often followed by spontaneous sVT.

Conclusion:  The RyR2‐P2328S mutation results in marked alterations in cellular Ca2+ homeostasis and arrhythmogenic properties resembling CPVT with greater effects in the homozygote than the heterozygote demonstrating an important gene dosage effect.
Advances in gene chip technique in Barrett's metaplasia and adenocarcinoma
Authors: WANG Xing Wei , GAO Heng Jun , FANG Dian Chun
Published: April 2008

Gene chip methods are applied to the study of gene expression. The differentially expressed genes in different specimens may be detected with parallel analysis by gene chip, which has greatly improved the traditional experiments in that only a single or several gene expressions need to be observed for each test, thereby speeding up the identification of differentially expressed genes and the construction of differential expression profiles. Many studies have applied this technology for Barrett's metaplasia and adenocarcinoma, and identified a number of candidate genes useful as biomarkers in cancer staging, prediction of recurrence, prognosis and treatment selection. This review described the gene expression profile and molecular changes related to Barrett's metaplasia and adenocarcinoma of the esophagus, with emphasis on its prognostic value and possibilities for targeted therapy in a clinical setting.
Endoscopic clipping
Authors: GRUPKA Michael J , BENSON Jay
Published: April 2008

Endoscopic clips are relatively new devices that have been shown to be effective for the control of acute gastrointestinal hemorrhage. Various different models are available and offer simplicity of use with relatively few complications. Recently, endoscopic clips have been used for a variety of non‐hemorrhagic conditions. In this article we review the literature and present current thinking about the indications, efficacy and safety of these devices.
CYP2C9 polymorphism in non‐steroidal anti‐inflammatory drugs‐induced gastropathy
Authors: MA Juan , YANG Xiu Yan , QIAO Liang , LIANG Liu Qin , CHEN Min Hu
Published: April 2008

OBJECTIVE:  Non‐steroidal anti‐inflammatory drugs (NSAID) induce gastroduodenal mucosal injury and are metabolized by cytochrome P450 2C9 (CYP2C9). It is postulated that CYP2C9 genotype is associated with NSAID‐induced gastropathy. This study aims to determine whether individuals with a CYP2C9 allele mutation are susceptible to NSAID‐induced gastropathy.

METHODS:  A total of 109 patients diagnosed as having rheumatic diseases and taking NSAID were appraised as having gastropathy by endoscopy, stool occult blood test and questionnaire two weeks after entering the study. Their peripheral blood was analyzed by polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP).

RESULTS:  A total of 47.7% gastropathy (33% erosions, 14.7% ulcers, 2.75% ulcer bleeding) and 56% dyspeptic symptoms were presented. Only one CYP2C9*2 heterozygote (*1/*2) was found in the group with gastropathy and two variant alleles (CYP2C9*2 and CYP2C9* 3) could not be found in the group without gastropathy. There was no significant difference in both CYP2C9 genotype (0.96%vs 0%) and CYP2C9 variant allele frequency (1.92%vs 0%) between patients with and without gastropathy.

CONCLUSION:  These results confirm the high prevalence of NSAID‐induced gastropathy but do not support the postulation that CYP2C9*2 and CYP2C9*3 contribute to the development of NSAID‐induced gastropathy. This may be due to the low frequency of the two alleles in the population studied.
The case for public‐private partnerships in infrastructure
Authors: Murphy Timothy J.
Published: April 2008

Abstract: Much of the public debate about public‐private partnerships (P3s) has occurred through the lens of those who either oppose or support this increasingly popular method of delivering public infrastructure assets. Despite some scepticism in the academic literature, an analysis of the key arguments for and against P3s concludes that the P3 model can successfully deliver public infrastructure goods and services, provided that certain key thresholds are met. Lessons learned from early experiments in P3s and from the experience of the newer government P3 procurement agencies suggest that P3s can provide value for money if risk is allocated to the party best able to manage it. An appropriate risk allocation requires that governments have the expertise to identify all of the relevant risks before entering into the partnership contract. Governments must also have the contract management skills to ensure that those risks are in fact borne by the private sector. To maintain public confidence in the P3 model, governments must live up to their own obligations of transparency and accountability and not succumb to private‐sector demands for confidentiality. The article recognizes that not all government goods and services can meet the threshold but that, if they do, it argues strongly for the efficiency and effectiveness of the P3 model.

Sommaire: Une grande partie du débat public au sujet des partenariats entre le secteur public et le secteur privé (les P3) a eu lieu par l'entremise de ceux qui opposent ou soutiennent cette méthode de plus en plus populaire de livrer de l'infrastructure publique. En dépit d'un certain scepticisme émanant des documents d'universitaires, une analyse des principaux arguments en faveur des P3 et contre ceux‐ci conclut que les P3 peuvent livrer avec succès des produits et services d'infrastructure publique, à condition que certains seuils clés soient atteints. Les enseignements tirés des premières expériences de P3 et de l'expérience des plus récents organismes d'approvisionnement gouvernementaux P3 laissent entendre que les P3 peuvent apporter une optimisation des ressources si le risque est attribuéà la partie la plus apte à le gérer. Une bonne répartition du risque exige que les gouvernements aient l'expertise pour identifier tous les risques pertinents avant de signer le contrat de partenariat. Les gouvernements doivent aussi avoir les compétences en gestion de contrats nécessaires pour veiller à ce que les risques soient en fait assumés par le secteur privé. Pour maintenir la confiance du public dans le modèle de P3, les gouvernements doivent respecter leurs engagements de transparence et de reddition de comptes et ne pas céder aux exigences du secteur privé concernant la protection des renseignements personnels. L'article reconnaît que tous les produits et services gouvernementaux ne peuvent pas tous atteindre le seuil de conformités mais que, lorsqu'ils y parviennent, le modèle de P3 est alors hautement efficace et efficient.
Implementation of a restrictive transfusion protocol reduces the need for allogeneic blood transfusion in proximal humerus fracture repair without affecting patient outcome: preliminary observations
Authors: CUENCA JORGE , GARCÍA‐ERCE JOSÉ A. , MUÑOZ MANUEL , MARTÍNEZ ÁNGEL A. , PEGUERO ANTONIO , HERRERA ANTONIO
Published: April 2008

Shoulder arthroplasty may be associated with considerable blood loss, and some patients require allogeneic blood transfusion (ABT). However, there is almost no information available for proximal humerus fracture (PHF) repair surgery. We therefore evaluated the influence of two transfusion protocols on ABT requirements in patients undergoing hemiarthroplasty surgery for PFH. We assessed the requirements for ABT in 78 patients receiving hemiarthroplasty for PHF, who were managed with a conservative transfusion protocol [hemoglobin(Hb) < 9.0 g/dL; group 1; n = 31] or a restrictive transfusion protocol (Hb < 8.0 g/dL and/or clinical signs/symptoms of anemia/hypoxemia; group 2; n = 47). Overall, the ABT rate (12% vs. 48%; P = 0.001) and the transfusion index (0.2 ± 0.7 vs. 0.9 ± 1.0 unit/patient; P = 0.001) were lower in group 2 than in group 1. The differences in transfusion rate and transfusion index between groups were significant for patients with Hb < 13.0 g/dL (75% vs. 18%, for groups 1 and 2, respectively; P = 0.001), but not for those with Hb ≥ 13.0 g/dL (20% vs. 7%; P = 0.180). The implementation of a restrictive transfusion protocol seems to be effective in reducing ABT, especially in PHF patients with preoperative Hb < 13.0 g/dL.
A Model of Piston Sliding Process for a Double Piston-Actuated Shock Tube
Authors: da S. Rêgo I. , Ando T. , Misumi K. , Miyazaki T. , Nishiyori S. , Sato K. N. , Sakamoto M. , Kawasaki S.
Published: April 2008

A double piston-actuated structure designed for replacing the use of diaphragms in conventional shock tubes has been recently developed. In order to clarify the piston sliding process for this structure, a simplified model based on the motion equation of its main sliding piston has been developed. Calculated piston sliding time against pressure ratio has been numerically obtained and indirectly evaluated by examining the experimental curves of the performance of the diaphragmless structure.
Turbulence and Secondary Flows in an Axial Flow Fan With Variable Pitch Blades
Authors: Fernández Oro Jesús Manuel , Ballesteros-Tajadura Rafael , Blanco Marigorta Eduardo , Argüelles Díaz Katia María , Santolaria Morros Carlos
Published: April 2008

This paper analyzes the structure of turbulence and secondary flows at the exit of an axial flow fan with variable pitch blades. The influence of changing the blades’ pitch angle over the turbulent structures is assessed by means of turbulence intensity values and integral length scales, obtained by using hot-wire anemometry for several test conditions. Since total unsteadiness is composed of both periodic and random unsteadiness, it is necessary to filter deterministic unsteadiness from the raw velocity traces in order to obtain turbulence data. Consequently, coherent flow structures were decoupled and thus, levels of turbulence—rms values of random fluctuations—were determined using a filtering procedure that removes all the contributions stemming from the rotational frequency, the blade passing frequency, and its harmonics. The results, shown in terms of phase-averaged distributions in the relative frame of reference, revealed valuable information about the transport of the turbulent structures in the unsteady, deterministic flow patterns. The anisotropic turbulence generated at the shear layers of the blade wakes was identified as a major mechanism of turbulence generation, and significant links between the blade pitch angle and the wake turbulent intensity were established. In addition, the autocorrelation analysis of random fluctuations was also used to estimate integral length scales—larger eddy sizes—of turbulence, providing useful data for computational fluid dynamics applications based on large eddy simulation algorithms. Finally, contours of radial vorticity and helicity gave a detailed picture of the vortical characteristics of the flow patterns, and the definition of secondary flow as the deviation of the streamwise component from the inviscid kinematics was introduced to determine the efficiency of the blade design in the energy exchange of the rotor.
Vorticity Dynamics in Axial Compressor Flow Diagnosis and Design
Authors: Yang Yantao , Wu Hong , Li Qiushi , Zhou Sheng , Wu Jiezhi
Published: April 2008

It is well recognized that vorticity and vortical structures appear inevitably in viscous compressor flows and have strong influence on the compressor performance. However, conventional analysis and design procedure cannot pinpoint the quantitative contribution of each individual vortical structure to the integrated performance of a compressor, such as the stagnation-pressure ratio and efficiency. We fill this gap by using the so-called derivative-moment transformation, which has been successfully applied to external aerodynamics. We show that the compressor performance is mainly controlled by the radial distribution of azimuthal vorticity, of which an optimization in the through-flow design stage leads to a simple Abel equation of the second kind. The satisfaction of the equation yields desired circulation distribution that optimizes the blade geometry. The advantage of this new procedure is demonstrated by numerical examples, including the posterior performance check by 3D Navier–Stokes simulation.
Plasma-Based Flow-Control Strategies for Transitional Highly Loaded Low-Pressure Turbines
Authors: Rizzetta Donald P. , Visbal Miguel R.
Published: April 2008

Recent numerical simulations have indicated the potential of plasma-based active flow control for improving the efficiency of highly loaded low-pressure turbines. The configuration considered in the current and earlier simulations correspond to previous experiments and computations for the flow at a Reynolds number of 25,000 based on axial chord and inlet conditions. In this situation, massive separation occurs on the suction surface of each blade due to uncovered turning, causing blockage in the flow passage. It was numerically demonstrated that asymmetric dielectric-barrier-discharge actuators were able to mitigate separation, thereby decreasing turbine wake losses. The present investigation extends this work by investigating a number of plasma-based flow control strategies. These include the chordwise location of actuation, spanwise periodic arrays of actuators, multiple actuation in the streamwise direction, and spanwise-direct actuation. The effect of alternate plasma-force models is also considered. Solutions were obtained to the Navier–Stokes equations, which were augmented by source terms used to represent plasma-induced body forces imparted by an actuator on the fluid. The numerical method utilized a high-fidelity time-implicit scheme, employing domain decomposition to carry out calculations on a parallel computing platform. A high-order overset grid approach preserved spatial accuracy in locally refined embedded regions. Features of the flowfields are described, and resultant solutions are compared to each other, with a previously obtained control case, and with the base line situation where no control was enforced.
The Flow of Slugs in Horizontal, Two-Phase Pipelines
Authors: Kouba G. E. , Jepson W. P.
Published: April 2008

The flow characteristics in horizontal slug flow are studied experimentally in the Harwell Laboratory 150-mm-dia pipeline. If a frame of reference is taken as moving with the translational velocity of the slug, measurements of the Froude number in the liquid film ahead of the slug were always greater than unity while the Froude number within the slug was in general less than unity. This illustrates a change in flow from super to subcritical flow and the presence of a hydraulic jump. Different types of flow are noticed using high-speed video equipment and these types closely resemble those reported by open-channel hydraulics tests. The distribution of gas in the slug body is only homogeneous at high-mixture velocities and the effect of buoyancy on the gas is more noticeable at low gas velocities. The liquid fraction in the slug is shown to be directly dependent on the Froude number in the liquid film. The ratio of the translational velocity of the slug to the mixture velocity decreases continuously from 2.0 at low-mixture velocities to 1.25 and a mixture velocity of approximately 3m/s. After this point, it remains constant at 1.25.
Studying Transient Multi-Phase Flow Using the Pipeline Analysis Code (PLAC)
Authors: Black P. S. , Daniels L. C. , Hoyle N. C. , Jepson W. P.
Published: April 2008

The Pipeline Analysis Code, PLAC, is utilized to study the flow generated from a shallow dip in a long pipeline. It shows that much longer and infrequent slugs are formed when liquid is swept out of the dip than would be expected from horizontal pipeline data. These slugs eventually propagate along the entire length of the pipeline. These dip-induced slugs are similar to the one-in-a-thousand slugs reported from existing long pipelines.
Friction Gages for In-Situ Rock-Mass Deformability and Stress Measurements
Authors: Karfakis M. G.
Published: April 2008

The in-situ deformability of rocks and the state-of-stress must be known for the analysis and design of surface and underground structures. This paper presents a method for determining the in-situ deformability of rock-masses using friction gages. Friction gages utilize the friction between the gage and the rock surface for detecting the strain changes. The method involves impressing friction gages on two opposite quadrants of the borehole wall, then radially loading the other two quadrants over 45-deg contact with a self-equilibrating pair of forces of sufficient magnitude to initiate and propagate tensile fractures. While loading, the friction gages detect the tangential strains on the borehole wall before, during and after fracturing of the rock. From the linear portion of the tangential stress-strain data, the elastic properties of the rock can be determined using the appropriate relationships. Furthermore, from the failure and post-failure portions of the tangential stress-strain data the tensile strength of the rock-mass and the in-situ state-of-stress can also be estimated. The theoretical basis of the method, and the fabrication, calibration and testing of the friction gage system, are described. Furthermore, practical field applications of the method are given.
Strain Hardening in Salt—Results of the SALMON Experiment
Authors: Glenn L. A.
Published: April 2008

SALMON was a nuclear explosion in the Tatum salt dome, near Hattiesburg, Mississippi, that took place on October 22, 1964. Computational attempts to simulate the experimental results had been largely unsuccessful. Recent calculations suggest that the reason is that the salt yield strength is extremely sensitive to strain hardening. The hardening effect had not been observed in laboratory-scale measurements, which were not made at small enough strain levels and may not have been representative of in-situ pore-fluid pressure.
Effect of Drillstring Vibrations on MWD Pressure Pulse Signals
Authors: Lear W. E. , Dareing D. W.
Published: April 2008

Axial vibrations of drillstrings produce pressure variations within the drilling fluid column. These pressure variations are imposed on controlled pressure pulse signals from Measurement-While-Drilling (MWD) tools producing background noise in pressure pulse data measured at the rig. The paper shows the effect on signal-to-noise ratio for various operating conditions, such as vibration frequency, valve opening/closing time, pulsing interval, and flow rate.
Concerning the Techniques for Plugging Coning Fluids in Oil Wells
Authors: Lekia D. L. , Knapp R. M. , Evans R. D.
Published: April 2008

A technique is presented for the determination of the size of a horizontal permeability barrier (plug) that can be displaced from the wellbore to suppress cone-fluid production in individual oil wells with coning problems. Details are given concerning the computation of the plug size for any well with known wellbore and completion constants. Also discussed are materials which can be used to create the plugs. Based on literature data and rock stress considerations, plugging by fluid injection is found to be much more practical and general in application than methods based upon hydraulic fracturing technology. Two types of plugging fluids are recommended for injection into the formation as a function of pressure and flow rate conditions. The injected plug-fluid penetrates the reservoir rock surrounding the wellbore to the radial distance given by a predetermined radius of the plug. Predictive calculations show that production of cone-fluid-free oil can be enhanced by as much as 100 percent after a successful plugging job is done using the method presented.
Non-Newtonian Flow in Eccentric Annuli
Authors: Haciislamoglu M. , Langlinais J.
Published: April 2008

A common assumption for annular flow used in the petroleum industry is that the inner pipe is concentrically located inside the flow geometry; however, this is rarely the case, even in slightly deviated wells. Considering the increasing number of directional and horizontal wells, the flow behavior of drilling fluids and cement slurries in eccentric annuli is becoming particularly important. In this paper, the governing equation of laminar flow is numerically solved using a finite differences technique to obtain velocity and viscosity profiles of yield-power law fluids (including Bingham plastic and power law fluids). Later, the velocity profile is integrated to obtain flow rate. Results show that the velocity profile is substantially altered in the annulus when the inner pipe is no longer concentric. Stagnant regions of flow were calculated in the low side of the hole. Viscosity profiles predicted for an eccentric annulus show how misleading the widely used single-value apparent viscosity term can be for non-Newtonian fluids. Profiles of velocity and viscosity in concentric and varying eccentric annuli are presented in 3-D and 2-D contour plots for a better visualization of annular flow. Frictional pressure loss gradient versus flow rate relationship data for power law fluids is generated using the computer program. Later, this data is fitted to obtain a simple equation utilizing regressional analysis, allowing for a quick calculation of friction pressure losses in eccentric annuli. For a given flow rate, frictional pressure loss is reduced as the inner pipe becomes eccentric. In most cases, about a 50-percent reduction in frictional pressure loss is predicted when the inner pipe lies on the low side.
Peak Wind Power Statistics
Authors: Alibe B.
Published: April 2008

Probability distribution functions, mean upcrossing rates and other descriptors are developed for the power that can be potentially extracted from the wind. Wind power is proportional to the cube of the wind velocity. The wind velocity is modeled as a stationary Gaussian process. The distribution of the extreme power is developed from mean upcrossing rates and the assumption that crossings of high thresholds follow a Poisson probability law. The results obtained are valid for any amount of the mean wind speed.
A Poroelastic PKN Hydraulic Fracture Model Based on an Explicit Moving Mesh Algorithm
Authors: Detournay E. , Cheng A. H.-D. , McLennan J. D.
Published: April 2008

This paper describes the mathematical formulation of a Perkins-Kern-Nordgren (PKN) fracture model, that accounts for the existence of poroelastic effects in the reservoir. The poroelastic effects, induced by leak-off of the fracturing fluid, are treated in a manner consistent with the basic assumptions of the PKN model, by means of a transient influence function. The fracture model is formulated in a moving coordinates system and solved using an explicit finite difference technique. The numerical algorithm has the following features: fixed mesh, adaptive control of the time step, and unconstrained fracture length during shut-in. Numerical simulation with this model indicates that poroelastic processes could be responsible for a significant increase of the treatment pressure, but that they have virtually no influence on the fracture length and fracture width.
A Reservoir Simulation Study of Naturally Fractured Lenticular Tight Gas Sand Reservoirs
Authors: Evans R. D. , Lekia S. D. L.
Published: April 2008

The results of parametric studies of two naturally fractured lenticular tight gas reservoirs, Fluvial E-1 and Puludal Zones 3 and 4, of the U.S. Department of Energy Multi-Well Experiment (MWX) site of Northwestern Colorado are presented and discussed. The three-dimensional, two-phase, black oil reservoir simulator that was developed in a previous phase of this research program is also discussed and the capabilities further explored by applying it to several example problems. The simulation studies lead to the conclusion that 1) at early times the reservoir performance does not depend on lenticularity; 2) the initial reservoir performance does not depend on natural fracture concentration, although at later times the performance predictions of systems with lower natural fracture concentrations begin to fall below the ones with higher concentrations; 3) porosity change with time and pressure leads to double performance prediction reversals when comparing gas flow rates and cumulative gas production from naturally fractured and non-naturally fractured tight gas reservoirs; 4) the assumption of zero capillary pressure in the fractures can lead to erroneous predictions in the simulation of naturally fractured tight gas reservoir performance; and 5) the simulator developed in a prior phase of this project is capable of handling a reservoir block that is blanket sand, lenticular, completely fractured, partially fractured or completely unfractured and is amenable to an anisotropic heterogeneous reservoir whether the reservoir is fractured or not.
A Water-Gas Relative Permeability Relationship for Tight Gas Sand Reservoirs
Authors: Lekia S. D. L. , Evans R. D.
Published: April 2008

This paper presents a new approach for the analyses of laboratory-derived capillary pressure data for tight gas sands. The method uses the fact that a log-log plot of capillary pressure against water saturation is a straight line to derive new expressions for both wetting and nonwetting phase relative permeabilities. The new relative permeability equations are explicit functions of water saturation and the slope of the log-log straight line of capillary pressure plotted against water saturation. Relative permeabilities determined with the new expressions have been successfully used in simulation studies of naturally fractured tight gas sands where those determined with Corey-type expressions which are functions of reduced water saturation have failed. A dependence trend is observed between capillary pressure and gas permeability data from some of the tight gas sands of the North American Continent. The trend suggests that the lower the gas permeability, the higher the capillary pressure values at the same wetting phase saturation—especially for saturations less than 60 percent.
A Predictive Approach for the Flammability Limits of Methane-Nitrogen Mixtures
Authors: Wierzba I. , Karim G. A.
Published: April 2008

The present contribution describes a relatively simple procedure for predicting the lean and rich flammability limits of methane-nitrogen mixtures in air from a knowledge of the composition of the fuel mixture and the corresponding limit for methane. It is shown that this approach can be extended similarly to consider the limits of natural gas-nitrogen mixtures yielding relatively good agreement with experimental values over a relatively wide range of composition and pressure.
Modeling of the Combustion Process in a Dual Fuel Direct Injection Engine
Authors: Karim G. A. , Zhaoda Y.
Published: April 2008

Analytical methods to provide a guideline for predicting the limit for acceptable power output of dual fuel engines due to the onset of autoignition and knock are described. This is achieved primarily through improved modeling of the chemical reaction rates of the charge during compression and subsequently following pilot ignition. Some performance results with methane as a fuel are presented.
Unsteady Mass Transfer From Oil Sand Spheres in Convective Streams at Low Reynolds Number
Authors: Abdrabboh M. A. , Karim G. A.
Published: April 2008

The process of transient mass transfer in and around oil sand spheres was investigated experimentally. Preshaped molded spherical particles of Athabasca oil sands were subjected to hot air streams at atmospheric pressure and constant temperature ranging from 150°C up to 475°C with a uniform stream velocity covering the range 0.15 m/s up to 1.7 m/s and Reynolds number over the range 33–1650. The rate of mass loss due to fluid volatilization for each set of experimental conditions was established and correlated with the residence time in terms of dimensionless groupings.
Investigation of a Composite Tubing Connection Performance
Authors: Dilintas G.
Published: April 2008

The purpose of this study is the understanding of the mechanical behavior of a threaded tubing connection made out of composite materials. The threaded tubing connection has been calculated under several loading cases which simulate the real functioning of the structure. A failure mechanism and design criteria have been established. Some suggestions for the improvement of the connection are also given.
Oxygen Enrichment in Combustion Processes: Comparative Experimental Results From Several Application Fields
Authors: De Lucia M.
Published: April 2008

The effects of using oxygen to partially or wholly replace fuel air in small-size melting furnaces were studied over a range of application fields. Following definition of the useful parameters, testing was conducted on furnaces for melting glass, ferrous metals (pigiron), nonferrous metals (copper alloys), and ceramic materials. In all cases, oxygen-enrichment was found to provide significant energy savings, as well as notable advantages in terms of both plant output and energy consumption.
Direct-Contact Heat Transfer for Air Bubbling Through Water
Authors: Ghazi H. S.
Published: April 2008

Experiments on direct-contact heat transfer of air injected through an orifice and bubbling through a constant temperature, stagnant, pool of water showed an increase in air temperature ranging from about 100 to 200 percent. The process follows a relationship which describes heat transfer in conventional, closed-type, heat exchangers where one fluid is maintained at a constant temperature. The data is correlated by a relationship for the Nusselt number which is based on an average overall heat transfer coefficient.
Smearing of a Kick While Being Displaced From a Well
Authors: Haciislamoglu M. , Langlinais J.
Published: April 2008

Well control operations while drilling with an oil-base mud can suffer several unexpected phenomena. One of these is the dispersion (smearing) of the gas in solution whenever a gas kick is being circulated from the well. If the gas influx has gone into solution, it is very important to predict the movement of this gas-contaminated mud as it is circulated from the well. A computer model of non-Newtonian fluids flowing in an annulus of any eccentricity has been developed with which to accurately model this dispersion. The movement of the gas-contaminated mud is predicted as a consequence of the velocity profiles established as the displacement of the annulus progresses.
Mechanical and Electrical Properties of Glass and Carbon Fiber-Reinforced Composites
Authors: Headifen G. R. , Fahrenthold E. P.
Published: April 2008

The design of composite rotors for high-energy density pulsed power supplies demands accurate characterization of both the mechanical and electrical properties of fiber-reinforced epoxy. The mechanical properties of S-2 glass-epoxy, IM6 graphite-epoxy, and hybrid graphite-glass epoxy composites were measured in tension and torsion tests, providing strength and stiffness parameters for rotor dynamics modeling. Variable frequency electrical resistivity tests were conducted to allow estimation of eddy current losses arising in carbon-reinforced materials. Volume fraction measurements using electron microscopy and analysis by digestion allow for normalization of the test results with respect to composite fiber content. The experimental results were used to evaluate the micromechanical rule of mixtures and Halpin-Tsai correlations.
A Model of the Enhancement of Combustion of Coal-Water Slurry Fuels Using High-Intensity Acoustic Fields
Authors: Yavuzkurt S. , Ha M. Y.
Published: April 2008

Combustion of coal-water slurry fuels is simulated in the presence of high-intensity acoustic fields which increases heat and mass transfer from the droplets and particles, and thereby enhances the combustion. The steady-slip velocity and acoustically induced slip velocity are calculated along particle trajectories, giving the augmented Nusselt and Sherwood numbers in the presence of high-intensity acoustic fields compared with no-sound conditions. The paper also presents the water evaporation and char burn-out history for particles with diameters between 90–110 μm exposed to sound pressure levels of 160–170 dB and compares the results to similar cases under no acoustic field. A decrease in the char burn-out length of about 12.1 percent at 160 dB, 18 percent at 165 dB, and 24 percent at 170 dB sound pressure level is obtained compared to the case with no sound for 100-μm particles introduced at centerline.
Flammability Characteristics of Treated Coals
Authors: Collins P. K. , Schroeder A. R. , Buckius R. O. , Krier H. , Peters J. E.
Published: April 2008

The effects of two processes used to treat coal on the flammability characteristics of the coal are presented. Experiments were conducted on an Entrained Dust Flow Facility which supports a stationary premixed coal dust and air flame. The facility is designed to provide access for thermocouples so that detailed axial and radial temperature profiles of the coal flames can be used to investigate the flame structure. Flame speeds of the coal and air mixtures were determined based on the inlet velocity of the flow and the temperature maps. Flame speed increases of over 35 percent were observed as a direct result of an aggregate flotation process which reduced the ash content and the average size of the coal and increased the volatile content and heating value. Partially devolatilized chars were burned to simulate the use of a low-volatile solid by-product of a gasification process. Under most conditions either methane addition or inlet air heating was required to establish a flame. Both methane addition and inlet air heating with the low-volatile chars resulted in improved flame stability and higher flame speeds. Relatively modest amounts (2.2 percent by volume) of methane addition with the parent coal increased the flame speed by a factor of 2 to 3.
The Component Equations of Energy and Exergy
Authors: Dunbar W. R. , Lior N. , Gaggioli R. A.
Published: April 2008

Energy conversion processes inherently have associated irreversibility. A better understanding of energy conversion will motivate intuition to create new energy-conversion and energy-utilization technology. In the present article, such understanding is further enhanced by decomposing the equations of energy and exergy (availability, available energy, useful energy) to reveal the reversible and irreversible parts of energy transformations. New definitions of thermal, strain, chemical, mechanical and thermochemical forms of energy/exergy are justified and expressions for these properties and their changes are rigorously developed. In the resulting equations, terms appear which explicitly reveal the interconversions between the different forms of energy/exergy, including the breakdown into reversible and irreversible conversions. The equations are valid for chemically reacting or non-reacting inelastic fluids, with or without diffusion.
A Mori-Tanaka Theory for Textured Short-Fiber Composites: Application
Authors: Ferrari M. , Marzari N.
Published: April 2008

The homogenizing scheme of Ferrari and Johnson yields the effective elasticities of short-fiber composites with arbitrary orientation distributions. As a foundation for the relative numerical analysis, their homogenizing scheme is here recast in the space of invertible 6×6 matrices with an appropriate operation. Averaging procedures for isotropic-isotropic composite with nonunidirectional transversely isotropic fiber orientation distributions are presented.
The Thermal Performance of the Cross-Flow Three-Dimensional Flat Plate Indirect Evaporative Cooler
Authors: Kettleborough C. F. , Waugaman D. G. , Johnson M.
Published: April 2008

Evaporative coolers consist of two main types: (a) the direct evaporative cooler in which water mixes with the air to be cooled; and (b) the indirect evaporative cooler in which water is sprayed into alternate passages cooling the secondary airflow, which in turns cools the primary flow which then passes to the building to be cooled. A three-dimensional numerical evaluation of the indirect cooler is given. Energy and mass balance equations are derived for the primary and secondary flows and the effectiveness is calculated for different variable inlet velocities and compared with experimental values.
Thermal-Hydraulics of OC-OTEC Spout Flash Evaporators
Authors: Ghiaasiaan S. M.
Published: April 2008

A mechanistic model was developed for the thermal-hydraulic processes in the spout flash evaporator of an OC-OTEC plant. Nonequilibrium, two-fluid, conservation equations were solved for the two-phase flow in the spout, accounting for evaporation at the gas-liquid interface, and using a two-phase flow regime map consisting of bubbly, churn-turbulent and dispersed droplet flow patterns. Solution of the two-phase conservation equations provided the flow conditions at the spout exit, which were used in modeling the fluid mechanics and heat transfer in the evaporator, where the liquid was assumed to shatter into a spray with a log-normal size distribution. Droplet size distribution was approximated by using 30 discrete droplet size groups. Droplet momentum conservation equations were numerically solved to obtain the residence time of various droplet size groups in the evaporator. Evaporative cooling of droplets was modeled by solving the 1-D heat conduction equation in spheres, and accounting for droplet internal circulation by an empirical thermal diffusivity multiplier. The model was shown to favorably predict the available single-spout experimental data.
Flame Propagation and Lean-Limit Extinction Within Stratified Mixtures Involving a Diluent Gas
Authors: Karim G. A. , Panlilio V.
Published: April 2008

Flame propagation within confined, stratified gaseous environments were investigated experimentally. The diluents nitrogen and helium were used in turn to overlay initially combustible methane-air or hydrogen-air mixtures. Gas stratification was achieved by allowing the two initially homogeneous gases to interdiffuse for a certain period of time at constant temperature and pressure within a long, vertical, smooth, closed, circular tube. Upward flame propagation was examined following spark ignition while the tube was closed at the top but open at the bottom. Near-extinction flame speeds, lower than those predicted according to Davies and Taylor (1950), were obtained with helium dilution. Moreover, estimated reactant concentrations at the observed location of flame extinction indicated, in specific instances, that mixture stratification appears to slightly enhance locally the lean flammability limit. Nonuniform, stratified combustible gaseous mixtures and flame propagation within such mixtures are found in many situations, including in numerous technical applications, as well as in various potentially hazardous circumstances. The leakage of a fuel from storage tanks or pipelines, the formation of layered combustible mixtures within rooms, corridors, or elevator shafts of buildings, the formation of gas pockets in coal mine galleries, and the inerting of flammable mixtures through diluent gas addition are some examples. Some relevant information about the stratification process and the flame propagation characteristics in these specific circumstances has already been reported in the literature by Bakke and Leach (1962), James and Purdy (1962), Girard et al. (1979), Karim and Lam (1986) and Karim et al. (1987). This investigation considers some aspects of flame propagation and mass transfer within confined, stratified gaseous environment. The diluents nitrogen and helium were used in turn to overlay initially combustible methane-air or hydrogen-air mixtures. Mixture stratification was produced by permitting the two initially homogeneous gaseous systems to interdiffuse at constant temperature within a long, vertical, smooth, closed, circular tube. Only upward flame propagation was examined, as this mode is expected to involve the widest flammability limits and the fastest propagation for both homogeneous and stratified methane-air mixtures when confined in tubes (Liebman et al., 1971).
The Optimal Intercooling of Compressors by a Finite Number of Intercoolers
Authors: Vadasz P. , Weiner D.
Published: April 2008

Intercooling of compressors is necessary for an efficient process. Among the optimal criteria required, minimizing the compression-specific work is one of the more commonly used. Upon ideal conditions, such a criterion leads to an isothermal compression whose importance is purely theoretical, since it requires an infinite number of intercoolers. In this paper the evaluation of correction factors to the well-known relations of the optimal location of intercoolers in a compression process and its corresponding work of compression was performed for a general compression process which accounts for pressure losses and other irreversibilities as well. As a result of including the pressure losses in the equations, a finite number of intercoolers is evaluated as optimum. The results, although qualitatively expected, show a quantitative nonempirical figure of the optimal number of intercoolers as a function of the terminal pressure ratio and as a function of the relative pressure losses. The ideal conditions are evaluated and verified as a particular case by assuming no pressure losses. In practice, these results can be used as an upper limit for technoeconomical optimization processes.
Wind Evaporator Heat Pumps—Part I: Test Methods
Authors: Monaghan P. F. , Finn D. P. , O’Reilly J. M.
Published: April 2008

Wind evaporators are alternative evaporators for air source heat pumps which rely on wind-driven or natural convection to move air across the heat transfer surfaces. It is believed that, in certain climates, wind evaporators can operate satisfactorily with frost on their surfaces for extended periods of time and defrost passively during switch-off periods. If so, an active defrost cycle would be unnecessary in these climates. Wind evaporators present an opportunity for heat pumps to be less expensive, more reliable, and more energy-efficient. However, the heat transfer performance of wind evaporators varies as a result of changes in a wide range of climatic variables. To determine the technical feasibility of wind evaporators, it is necessary to test complete wind evaporator heat pumps and to compare their monitored field performance over extended periods to that of conventional heat pumps with fan-assisted, finned-tube evaporators. In this paper, a test facility which allows side-by-side testing of wind evaporator and conventional heat pumps and monitoring of weather conditions is described. The choice of measurement technique for each variable is discussed and estimates of the measurement uncertainty for each sensor are made.
Simulation Study of the Matsukawa Geothermal Reservoir: Natural State and Its Response to Exploitation
Authors: Hanano M.
Published: April 2008

A numerical simulation study on the natural state of the Matsukawa, Japan geothermal reservoir was carried out with a simplified two-dimensional cross-sectional model. The results agreed reasonably well with the observed data and showed that there was a thin vapor-dominated zone at the shallow part of the reservoir. The results clearly indicate that the ideas on the natural state of the Matsukawa geothermal reservoir presented by Hanano and Matsuo (1990) are feasible.
Analytical Approach to Selecting and Designing a Miniature Downhole Refrigerator
Authors: Bennett G. A.
Published: April 2008

The design approach and results from a series of analyses used to select a miniature high-temperature multi-watt refrigerator for thermally protecting downhole instruments are described. Thirty-one systems from nine physical or chemical processes were investigated and compared against the design criteria and constraints. Preliminary thermodynamic analyses and the results of a search for high-temperature components and refrigerants eliminated all but three processes and seven systems. These seven systems were re-evaluated based on a set of proposed design changes that reflect natural evolution from a prototype to commercial system application. Final selection considered refrigerator interactions with the geothermal logging system to define failure modes, ensure compatibility, and allow adaptability to changing conditions. The selected refrigerator design permits reliable, long-term active cooling of downhole instruments in hot wells. The consistent design, systematic analysis and unbiased selection process represent a new body of research results that provide potential for substantial advances in downhole thermal protection technology.
Computer Modeling of the Continuous Annealing Furnace
Authors: Jeong S. H. , Ha M. Y.
Published: April 2008

A computer program to calculate the strip temperature heated in the continuous annealing furnace was developed, using the zone method for radiative heat transfer analysis with the measured gas temperature in the furnace. Using the FE operator, the present study considered the effects of soot and transient species in addition to the H2O-CO2 gas mixture on the gas radiative heat transfer. The predicted strip temperature distribution for FE = 1.05 represented well the measured data. The maximum difference in the heat flux transfered to the strip from the combustion gas for FE = 1.0 (without soot and transient species gas radiation) and 1.05 (with soot and transient species gas radiation) was about 15 percent. The present study also investigated the effects of line speed and thickness variations on the strip temperature, establishing the bases for the on-line computer model.
System Optimization of the Cogeneration Facility at Texas A&M University—Present Operation and Load
Authors: Athar A. , Somasundaram S. , Turner W. D.
Published: April 2008

The combined-cycle cogeneration facility on the central campus of Texas A&M University was analyzed for its present performance and an optimized mode of operation. The analysis was carried out using a plant Energy Optimization Program (EOP) that has been developed by Sega, Inc. The program uses Dither algorithms to match the energy demand and supply at each energy level (node), by choosing the lowest cost supplier among all the energy suppliers at the energy node. When this is done for all the energy nodes as the campus load varies throughout the year, one can determine the hourly and then the annual cost of operating the plant under both the existing and the optimized modes. The results were also compared with those obtained by using the Navy’s Civil Engineering Laboratory Cogeneration Analysis Program (CELCAP), and the agreement was within 5 percent. Comparison with actual costs produced an agreement to within 1 percent. Finally, certain recommendations are made as to a more cost-efficient mode of operating the present facility.