bluuebunny/crossref_metadata_2025_split huggingface dataset:
Drag coefficient and velocity of rise of a single collasping two‐phase bubble
Authors: Wanchoo R. K. , Sharma S. K. , Raina G. K. 
Published: June 2004

AbstractThe velocity of rise and the drag of a single vapor bubble collapsing in another immiscible liquid were measured experimentally. During the process of collapse, the dispersed‐phase vapor bubble was transformed to a two‐phase bubble with condensate accumulating at the rear of the two‐phase bubble and vapor at its top. Such a configuration of a two‐phse bubble is commonly known as a drobble. Experimental data for the six pairs of liquids covered a range of drobble (two‐phase bubble) Reynolds numbers from 0.003 to 3,000. Two regimes of drobble movement were encountered. In the first regime (Re < 100), the drobble maintained its sphericity, and the observed drag was less than the solid‐sphere drag predicted by the established solid sphere or Hadamard et al. fluid‐sphere drag models. In the second regime, the drobble was deformed and oscillated; the observed drag departed suddenly from predictions of spherical models and increased with increasing Reynolds numbers. The critical Reynolds number covered a range from 100 to 1,000. Empirical models for drobble velocity and drag coefficient are derived.
Mapping regions with different bifurcation diagrams of a reverse‐flow reactor
Authors: Khinast J. , Luss D. 
Published: June 2004

AbstractA systematic method is presented for constructing maps of parameter regions with qualitatively different bifurcation diagrams of the reverse‐flow reactor (RFR). These maps are most useful for the rational design and periodic operation of an RFR. The method is illustrated by two examples. The map for a single, exothermic first‐order reaction contains five regions with qualitatively different bifurcation diagrams when the Damköhler number is the bifurcation variable. The high‐temperature branch is isolated in two of these regions. The map for two independent, exothermic first‐order reactions contains seven regions with qualitatively different bifurcation diagrams when the adiabatic temperature rise is the bifurcation parameter. Three stable periodic states exist for some values of the bifurcation variable in five of the regions. In some of these regions the intermediate state cannot be obtained upon a slow change in the concentration of the reactants. In all the examples we studied, a stability exchanges of the pseudohomogeneous model occurred only at the limit points of the bifurcation diagrams. An efficient numerical scheme is presented for computing the loci of the singular points of the RFR model.
Effects of operating conditions on heat removal from polyethylene reactors
Authors: Jiang Yan , McAuley Kim B. , Hsu James C. C. 
Published: June 2004

AbstractA one‐dimensional nonequilibrium model for multicomponent condensation is used to simulate a vertical single‐pass shell‐and‐tube heat exchanger in an industrial gas‐phase polyethylene reactor system. Starting the calculation at the top of the exchanger, the model can predict temperatures at the bottom of the exchanger within an accuracy of ±5 K as compared to three sets of industrial data. Sensitivities of model predictions were analyzed, including uncertainties associated with physical and transport property estimates, step size, and convergence criterion. Model predictions are not particularly sensitive to the estimation errors of physical and transport properties if K values are calculated using an equation of state applicable to both liquid and vapor phases. Effects of operating conditions on heat removal from polyethylene reactors were investigated for an existing process. It was quantitatively demonstrated why and how severely noncondensable gases impede condensation heat transfer. The level of noncondensable gases and the cooling water temperature are the two most important factors influencing the heat‐removal rate. Replacing a portion of noncondensable gas, such as N2, with a condensable fluid that is inert to polymerization reactions can substantially increase the heat‐removal rate from the reactor, thereby allowing for an increase in polymer production rate.
Generalized approach to NMR analysis of flow and dispersion in porous media
Authors: Seymour Joseph D. , Callaghan Paul T. 
Published: June 2004

AbstractA generalized approach to the use of pulsed‐gradient spin echo (PGSE) NMR methods for the measurement of flow and diffusion in porous media is presented, in which the fluid dynamics is probed over well‐defined temporal and spatial domains. Various NMR techniques based on PGSE encoding are described in the context of standard theories of dispersion, with reference to Eulerian and Lagrangian coordinate frames. This array of methods provides access not only to the dispersion coefficient and the mean local velocity but also to propagators relevant to spatial and temporal correlations. Methods investigated include flow imaging, average propagator analysis, dispersion measurement, velocity exchange spectroscopy, and flow and disffraction based on scattering analysis. We apply these to a study of flow and dispersion of water in a packed bed of 90.7‐μm‐dia. polystyrene latex spheres. Our measurements of the dependence on Peclet number of dispersion (parallel and perpendicular to the mean flow direction) are in excellent agreement with results reported in the literature. The scattering approach used here has potential for studying complex flow properties involving the interplay between hydrodynamic and structural characteristics of porous media.
Fractal‐like behavior of a mass‐transport process
Authors: Kinoshita Masahiro , Harada Makoto , Sato Yasuo , Tsubata Kyoichi , Nakamura Yasutaka 
Published: June 2004

AbstractAfter an aqueous solution containing Sr2+ was flowed through a bed packed with particles of activated charcoal for a very long time, the flow was abruptly switched to deionized water. The variation in ionic concentration at the outlet with time was characterized by the power law, Cout ∼ t−α, for sufficiently large t. This fractal‐like behavior we reported previously has further been studied theoretically and experimentally. A major concern is to examine dependency of α on experimental conditions. Adsorption sites predominate over dead‐end pores or spaces as “trappers” in our case where Sr2+ or Ba2+ is adsorbed on activated charcoal. The experimental results can well be explained by our theoretical model. It has been found, however, that the response curve for Sr2+ deviates from the power law after a very long time. This deviation can be explained by introducing the assumption that there exists a maximum value of the activation energy for the desorption process. The curve for Ba2+, on the other hand, exhibits no such deviation until Cout decreases to the detection limit of the analytical device used.
Thermodynamic behavior of reactive azeotropes
Authors: Okasinski Matthew J. , Doherty Michael F. 
Published: June 2004

AbstractDuring process design of reactive distillation systems, there is often uncertainty in the value of the reaction equilibrium constant (Keq), whether it is determined experimentally or calculated from thermochemical data. The effect of the reaction equilibrium constant on the existence and location of reactive azeotropes (constant boiling reactive mixtures) is explored for chemical equilibrium systems with a single chemical reaction. With a known set of starting points, arc‐length continuation was used to track solutions of the equations for reactive azeotropy as a function of the reaction equilibrium constant. The results, portrayed in bifurcation diagrams, reveal that azeotropes may appear or disappear as the equilibrium constant is varied. Results for the esterification of acetic acid with ethanol indicate three distinct regions of phase behavior. The first regime (Keq < 0.449) contains a quaternary saddle reactive azeotrope. At intermediate values of the reaction equilibrium constant (0.449 < Keq <12.5), there are no reactive azeotropes in the system. In the third regime (Keq < 12.5), a minimum‐boiling quaternary reactive azeotrope appears. In addition, for three reported literature values of the reaction equilibrium constant, each one lies in a different regime. Other examples also illustrate the broad taxonomy of reactive azeotropic systems.
Bubble coalescence dynamics
Authors: Stover Richard L. , Tobias Charles W. , Denn Morton M. 
Published: June 2004

AbstractCoalescence of electrolytically‐generated, 50‐ to 600– μm‐diameter gas bubbles was observed using an optical technique that employs a linear photodiode array to detect interface movement with a resolution of 10−6s. When two bubbles coalesce, the surface energy that is released causes interface velocities of 2 to 4 m/s; these are followed by large‐amplitude damped oblate–prolate oscillations. Within the viscosity range studied, the oscillation period is insensitive to the viscosity and damping is insensitive to surface tension, in agreement with a scaling analysis based on a damped harmonic oscillator. Surface waves are superimposed on the motion. Finite‐element solutions of the free‐surface, nonlinear Navier‐Stokes equations are consistent with the experiments.
Turbulence structure and scalar transfer in stratified free–surface flows
Authors: Nagaosa Ryuichi , Saito Takayuki 
Published: June 2004

AbstractDirect numerical simulations were used to investigate turbulence structure and scalar transfer across a shear‐free, nonwavy gas‐liquid interface (free surface) in stably stratified turbulent flows. These simulations solve the Navier–Stokes and thermal‐energy conservation equations, using a finite difference approximation. The relation between the turbulence structure in the stably stratified turbulent boundary layer and organized motion near the free surface are discussed. In addition, scalar transfer across a free surface is investigated by solving a passive scalcr conservation equation after both velocity and temperature fields are fully developed. The effects of stable stratification on the scalar transfer process in a region very close to the free surface are also discussed.
Measurement of velocity profiles in reverse‐screw elements of a twin‐screw extruder
Authors: Chandrasekaran Murali , Karwe Mukund V. 
Published: June 2004

AbstractA laser Doppler anemometer was used to measure velocity components for the flow of a Newtonian fluid in a reversing section of a pilot‐scale corotating twin‐screw extruder. Measurements were made at a fixed axial position in the intermeshing (nip) region and the translational region (áway from the nip). Tangential and axial velocity profiles reached a maximum in the middle of the screw channel, indicating pressure flow. Leakage flow through the gaps between screw flights and backflow toward the hopper were observed only in the nip region. No reversal of flow was detected in the translational region. Measured velocity profiles showed substantially higher shear rates in the reversing section of the screw as compared to those in the forward‐conveying section.
Integral approach to plant linear dynamic reconciliation
Authors: Bagajewicz Miguel J. , Jiang Qiyou 
Published: June 2004

AbstractAn integral method is proposed that performs dynamic data reconciliation on linear systems, in contrast with recent methods that utilize differential algebraic equations. The differential equations representing this system are first rearranged to obtain a system of equations containing only redundant measurements. These equations are formally integrated using polynomial approximations, and the reconciliation is then performed using analytical solutions. A new statistic to detect gross errors is proposed, and a procedure to detect biased measurement is presented.
Bubble formation at orifice in viscoelastic liquids
Authors: Terasaka Koichi , Tsuge Hideki 
Published: June 2004

AbstractTo evaluate the effect of viscoelasticity on bubble formation, four rheological parameters of viscoelastic liquids were defined and measured by a rheometer. The effects of operating conditions and concentration of polyacrylamide aqueous solutions (PAA) as viscoelastic liquids on bubble volume and the growth curve were experimentally measured. A high‐speed video camera showed that the shapes of a bubble growing in vis‐coelastic liquids are not spherical. In this study, a nonspherical bubble formation model was proposed to theoretically estimate the volume, shape and growth curve of bubbles formed from an orifice submerged in viscoelastic liquids which are assumed to follow Maxwell's viscoelastic model. This experimental results in relatively low concentrations of PAA, as well as previous researchers' results, agreed relatively well with the calculated ones by this model.
Experimental study of the influence of the flow rates in SMB chromatography
Authors: Yun Tong , Zhong Guoming , Guiochon Georges 
Published: June 2004

AbstractA Sorbex‐type SMB separation instrument was operated for the separation of mixtures of 2‐phenyl ethanol and 3‐phenyl‐l‐propanol on a series of eight columns packed with Zorbax C18 bonded silica, using a 60:40 (u/v) solution of methanol and water as the mobile phase. The experiments were carried out with low‐concentration mixtures under linear conditions. The elution profiles of both compounds between any two successive columns of the set under steady‐state conditions were recorded while compositions of the raffinate and extract were measured. The four safety margin factors, βj, were divided into two groups: β1 and β4; β2 and β3 with different influence. Within the framework of the linear, ideal model of chromatography, a range of flow rates enables an SMB to operate successfully by completely separating the feed into its two components. The influence of different flow rates on the performance of the separator was studied by calculations and experiments with excellent agreement between both sets. With a simple optimization strategy, the four flow rates are selected to maximize the production rate or the concentration of extract and raffinate products, or to minimize the desorbent consumption. These optimum conditions are obtained by controlling the locations of concentration profiles inside the SMB. A reliable model for SMB operation allows a rapid and easy selection of the optimum experimental conditions.
Optimal thermodynamic feed conditions for distillation of ideal binary mixtures
Authors: Agrawal Rakesh , Herron D. Michael 
Published: June 2004

AbstractOptimal thermodynamic feed conditions for distillation of ideal binary mixtures are identified through thermodynamic efficiency analysis of distillation columns. Due to simplifying assumptions, temperatures do not appear explicitly in the final thermodynamic efficiency equations. These equations are found to be functions of only feed composition, the thermodynamic state of the feed, and the relative volatility of the more volatile component A with respect to component B! When a single one‐phase feed, AB, is used, the preferred state of the feed is all liquid when the amount of heavy component B is greater than 50% and is all uapor when the amount of volatile component A is greater than 50%. For a single two‐phase feed, a simple heuristic is presented to adjust the liquid fraction of a given feed to maximize the thermodynamic efficiency of the distillation column. For most binary mixtures, two feeds with the same composition, but one saturated vapor and the other saturated liquid, can improve a distillation column's efficiency substantially. The maximum benefit is obtained for a 50–50 mixture. This two‐feed case is less efficient than the single two‐phase feed case when the relative volatilities exceed certain calculable values.
Coatable splice process in film coating: A fluid mechanical stability problem
Authors: Hackler Mark A. , Brandon Noel C. , Hirshburg Robert I. , Christodoulou Kostas N. 
Published: June 2004

AbstractIn slide coating of photographic films, liquid layers flow down an inclined plane, across a small gap under a pressure differential (vacuum), and onto a fast‐moving substrate. Process interruptions to allow splices of adjoining rolls of substrate to pass through the coater result in significant waste. Coating over splices fails due to air entrainment and/or two free‐surface flow instabilities during the necessary gap widening: (1) standing waves (ribbing) or rupture of the liquid bridge when vacuum is kept high or (2) lateral contraction when vacuum is lowered. The problem of coating over splices is solved here by reducing it to a fluid‐mechanical stability problem. First, air entrainment was eliminated by serrating the splice trailing edge and lateral contraction by prewetting the substrate with liquid streams. Avoiding rupture of the liquid bridge then reduces the problem to finding the vacuum at which the bridge becomes unstable to small disturbances. This “critical” vacuum is found by finite‐element stability analysis of the quasi‐steady 2‐D free‐surface flow to small 2‐D and 3‐D disturbances, direct tracking of critical points, and verification by solving the transient 2‐D skip‐out process. Three modes of failure are predicted if the vacuum is not sufficiently reduced with gap widening. Implementation of a computed vacuum strategy in a production line gave sufficient latitude for coating over imprecise splices.
Electrical properties of conductive adhesives as affected by particle compositions, particle shapes, and oxidizing temperatures of copper powders in a polymer matrix
Authors: Lin Yung‐Sen , Chiu Sheng‐Shiang 
Published: June 2004

AbstractThe effects of particle compositions, particle shapes, and oxidation temperatures on the electrical properties of conductive adhesives have been investigated. Silver‐coated copper powders and uncoated copper powders with spherical and flake‐shaped particles are oxidized at temperatures such as 30, 175, 240, 300°C and 350°C for 2 h and dispersed in an epoxy matrix. The results of this study indicate that the electrical properties of the conductive adhesives are strongly affected by the particle compositions and oxidation temperatures and only slightly affected by the particle shapes. Silver‐coated copper powders show significantly greater oxidation resistance than uncoated copper powders. To understand how silver‐coated copper powders show such oxidation resistance, they are analyzed by the techniques of thermogravimetric analysis (TGA), X‐ray diffraction (XRD), and Auger spectroscopy to observe how metal oxides such as AgO, Cu2O, and CuO affect the electrical properties of the conductive adhesives. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2045–2053, 2004
The complete chirospectroscopic signature of the peptide 310‐helix in aqueous solution
Authors: Toniolo Claudio , Formaggio Fernando , Tognon Sabrina , Broxterman Quirinus B. , Kaptein Bernard , Huang Rong , Setnicka Vladimir , Keiderling Timothy A. , McColl Iain H. , Hecht Lutz , Barron Laurence D. 
Published: June 2004

AbstractWe synthesized by solution methods a water‐soluble, terminally blocked heptapeptide based on five markedly helicogenic, Cα‐tetrasubstituted α‐amino acids Cα‐methyl‐L‐norvalines and two strongly hydrophilic 2‐amino‐3‐[1‐(1,4,7‐triazacyclononane)]‐L‐propanoic acid residues at positions 2 and 5. A Fourier transform infrared absorption and NMR analysis in deuterated chloroform and aqueous solutions of the heptapeptide and two side‐chain protected synthetic precursors confirmed our working hypothesis that all oligomers are folded in the 310‐helical conformation. Based on these findings, we exploited this heptapeptide as a chiral reference compound for detailed electronic CD, vibrational CD, and Raman optical activity characterizations of the 310‐helix in aqueous solution. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
Retroinfusion‐supported stenting in high‐risk patients for percutaneous intervention and bypass surgery: Results of the prospective randomized myoprotect I study
Authors: Pohl Tilmann , Giehrl Wolfgang , Reichart Bruno , Kupatt Christian , Raake Philip , Paul Stefan , Reichenspurner Hermann , Steinbeck Gerhard , Boekstegers Peter 
Published: June 2004

AbstractThe objective of this study was to assess event‐free survival and total treatment costs of retroinfusion‐supported stenting in high‐risk patients compared to bypass surgery. An increasing number of patients with main‐stem and main‐stem‐equivalent stenosis are treated by stent implantation, which appears to be safe in the short‐term follow‐up. However, there is a lack of randomized studies comparing conventional bypass surgery with stent implantation, particularly in patients with high risk for both treatments. We here report on the 1‐year results of a prospective randomized single‐center study in patients with symptomatic main‐stem and main‐stem‐equivalent lesions with substantially increased risk for bypass surgery. Patients where randomized to undergo either percutaneous transluminal coronary angioplasty/stent procedure (n = 23) or bypass surgery (n = 21). Patients randomized to stent implantation were supported by selective pressure‐regulated retroinfusion of the anterior cardiac vein during ischemia. Patients of the stent group and the bypass group did not differ in baseline characteristics, including Parsonnet score and quality‐of‐life score. Twenty‐eight‐day mortality and 1‐year mortality rate as well as quality‐of‐life scores were similar in both groups. Event‐free survival after 1 year was higher in the bypass group (71.4% vs. 52.3%; P = 0.02) due to a lower target lesion revascularization rate. With regard to total treatment costs, however, the stent group compared favorably to the bypass group (9,346 ± 807 vs. 26,874 ± 3,985 euro), predominantly as a result of a shorter intensive care and hospital stay. In this first randomized study in high‐risk patients for stent implantation and bypass surgery, patients with retroinfusion‐supported stent implantation had a similar 1‐year outcome and quality of life compared to patients with bypass surgery. Though in the stent group event‐free survival was lower and target lesion revascularization rate was higher, retroinfusion‐supported stent implantation was associated with substantially lower costs and might be considered as an alternative treatment option in this selected group of high‐risk patients. Catheter Cardiovasc Interv 2004;62:323–330. © 2004 Wiley‐Liss, Inc.
Impact of radiation dose on late clinical outcome after intracoronary radiation therapy: Three‐year follow‐up of Long WRIST
Authors: Cheneau Edouard , Canos Daniel , Pinnow Ellen , Ajani Andrew E. , Satler Lowell F. , Pichard Augusto D. , Kent Kenneth M. , Lindsay Joseph , Waksman Ron 
Published: June 2004

AbstractTo determine the safety and efficacy, including the impact, on the late recurrence rate of an incremental γ‐radiation dose from 15 to 18 Gy, we report the 3‐year clinical outcome of Washington Radiation for In‐Stent Restenosis Trial for Long Lesions (Long WRIST). One hundred eighty patients with recurrent in‐stent restenosis (ISR) were enrolled in the Long WRIST series and treated with 192Ir with 1 month of antiplatelet therapy. Between 6 months and 3 years, the need for repeat revascularization was low and similar among the three groups. At 3 years, target lesion revascularization (TLR) and major adverse cardiac events (MACE) were less frequent in the 18 Gy group than in the 15 Gy group (P = 0.12 for TLR, P < 0.05 for MACE) and less frequent in the 15 Gy group as compared to the placebo group (P < 0.05 for TLR and MACE). At 3 years, a higher dose of 18 Gy with 192Ir continues to improve the outcome of patients treated for ISR when compared to patients treated with 15 Gy or placebo. Catheter Cardiovasc Interv 2004;62:318–322. © 2004 Wiley‐Liss, Inc.