bluuebunny/crossref_metadata_2025_split huggingface dataset:
Process identification using discrete wavelet transforms: Design of prefilters
Authors: Palavajjhala Srinivas , Motard Rodolphe L. , Joseph Babu 
Published: June 2004

AbstractMost advanced control applications rely on good dynamic process models. The performance of the control system depends on the accuracy of the model used. Typically, such models are developed by conducting off‐line identification experiments on the process. These identification experiments often result in input–output data with small output signal‐to‐noise ratio, and using these data results in inaccurate model parameter estimates. Prefilters are used to separate useful information from the noise in the input–output data and to improve parameter estimates. A systematic design procedure for selecting a prefilter using discrete wavelet transforms is presented. The design procedure provides explicit information on the compromises in prefilter design, interpreted in terms of parameter variance and bias. The prefilter design procedure is then applied to identify a second‐order output error model.
Robust Smith‐predictor controller for uncertain delay systems
Authors: Lee T. H. , Wang Q. G. , Tan K. K. 
Published: June 2004

AbstractNecessary and sufficient conditions for the robust stability and performance of the Smith‐predictor controller, modeled under a norm‐bounded uncertainty, are given in a general formulation. In addition, a practical stability condition is obtained as a special corollary of the main results. These conditions provide useful and practical guidelines for the development of a systematic robust design method. In particular, an application is developed for the robust control of first‐order deadtime systems with simultaneous uncertainties in all three parameters of the model. A simulation example and the results of a case study on the robust level control of a coupled‐tanks apparatus are provided for illustration.
Reaction of methanol with chlorate ions in acid solution containing Hg+2 by NMR
Authors: Ernst William R. , Indu Bhart , Crump Brian , Gelbaum Leslie T. 
Published: June 2004

AbstractThe reaction rate of methanol was measured in solutions of sodium chlorate and sulfuric acid at several levels of temperature and concentration, in the presence of mercuric nitrate. The progress of the reaction was monitored by proton NMR signals corresponding to methanol and formic acid. Chlorine dioxide formation was suppressed by adding mercuric nitrate, which was shown earlier to catalyze the disproportionation of the intermediate species, chlorous acid, and sequester chloride ions. The reaction is first order in methanol and chlorate concentration and in the Hammett acidity function. The reaction of formic acid, sodium chlorate and sulfuric acid was also studied using the same technique. Formic acid was stable and did not react with chlorate at a measurable rate, even at concentrations and temperatures of a commercial process. This study relates to commerical processes that produce chlorine dioxide by reducing chlorate ions with methanol.
Closed‐form solution for the reconstruction problem in porous media
Authors: Giona Massimiliano , Adrover Alessandra 
Published: June 2004

AbstractThe statistical reconstruction of lattice models of real porous media is one of the basic engineering problems in the theory of porous structure and has a variety of applications in the study of transport, in mineral processing, and in material characterization. A systematic analysis of the reconstruction problem of porous media is presented, as well as a closed‐form solution. The solution is presented in the form of a linear filter acting on Gaussian processes by means of a superposition of elementary correlated processes with prescribed correlation properties, and in the form of a memoryless process recalling the theory of Khinchin on the properties of correlation functions. The connection of this approach with models of correlated percolation is also discussed.
Asymptotic analysis of die flow for shear‐thinning fluids
Authors: Weinstein Steven J. , Ruschak Kenneth J. 
Published: June 2004

AbstractThe flow in a single‐cavity extrusion die is considered by using 1‐D equations. Since the fluid flow in a well‐performing die does not deviate much from the case of perfect widthwise distribution, linearization of 1‐D governing equations is often justified. It is demonstrated how linearization can lead to significant simplifications in the analysis of die flow. A self‐consistent asymptotic expansion is identified to accomplish this linearization; the expansion can be generalized to obtain higher‐order corrections if necessary. In contrast to previous analyses, which have generally been numerical, analytic solutions are obtained to predict widthwise flow nonuniformities in a die having a specific cavity area variation and in which cavity inertial effects are important; these solutions are valid for power‐law and Newtonian fluids. A novel truncated power‐law approach to modeling the flow of shear‐thinning fluids in a die is proposed that combines, by using analytical criteria, the solutions for purely Newtonian or power‐law flow in the cavity and slot. The validity of this approach is demonstrated through comparison with numerical results of a 1‐D die model for a Carreau constitutive equation.
Maximum stable drop diameter in stirred dispersions
Authors: Lam Andrew , Sathyagal A. N. , Kumar Sanjeev , Ramkrishna D. 
Published: June 2004

AbstractTransient drop‐size distributions of stirred dispersions undergoing breakage were experimentally measured at long stirring times. The results show that drops continue to break the entire duration of the experiment (at least up to 10 h) and force a reevaluation of the widely held concept of a maximum stable drop diameter, dmax. Transient distributions show the existence of self‐similarity, which is the same as that observed in transient distributions obtained at short times (up to ∼ 1 h, Sathyagal et al., 1995b) indicating that the nature of breakage does not change with time. The existence of similarity at long stirring times can be used to obtain good estimates of breakage rates of small drops by an inverse problem procedure.
Particles flow pattern and local heat transfer around tube in moving bed
Authors: Takeuchi Hiromi 
Published: June 2004

AbstractFlow visualization of flowing particles around a tube of various types of tube arrangements in a moving bed was studied using X‐ray video films to obtain a relation between particles behavior and local heat‐transfer coefficients. A stagnant part of solid particles was observed on the tube in the case of a staggered arrangement. This part did not appear in the case of the single tube and the single row of tubes. The measured local heat‐transfer coefficients around a tube was decreased in this stagnant part. Furthermore, influences of different tube arrangements both on flow patterns of particles and on local heat‐transfer coefficients between tubes and bed were examined.
Codeposition on hot CVD surfaces: Particle dynamics and deposit roughness interactions
Authors: Tandon Pushkar , Rosner Daniel E. 
Published: June 2004

AbstractTo capture in a tractable manner essential coupling effects in CVD systems when particles generated in thermal boundary layers also deposit, a film theory was developed that predicts simultaneous vapor and particle deposition rates at a hot deposition surface. The codeposition rate prediction method also calculates for the first time the corresponding solid deposit roughness using recently published results of particle‐level simulations. For the numerical illustrations, the growth of TiO2(s) films by the codeposition of titanium tetra‐isopropoxide vapor and film‐nucleated/grown TiO2 particles (generated in the thermal boundary layer) was considered. Experimental rate data for this system are available. The continuum and particle‐level simulation methods provide: the interplay of vapor precursor kinetics, particle nucleation, growth, coagulation and diffusion in determining the complex “structure” of such multiphase chemically reacting boundary layers; wall deposition rates of both surviving vapors and film‐nucleated particles; and the “self‐consistent” microstructure (surface roughness) of the resulting solid deposit. Timely and tractable generalizations are discussed in the light of recent results for the transport properties and stability of “fractal‐like” aggregated particles.
Measuring vapor‐liquid equilibrium for aqueous‐organic systems: Review and a new technique
Authors: Turner Louis H. , Chiew Yee C. , Ahlert Robert C. , Kosson David S. 
Published: June 2004

AbstractThe vapor–liquid equilibrium (VLE) of aqueous–organic mixtures is important in understanding the physical chemistry behind the contamination and remediation of contaminated surface water, ground water and unsaturated soils. The state of the science is assessed, and available VLE and solubility data are reviewed comprehensively for several organic compounds. Benzene, toluene, o‐, m‐, p‐xylene, ethylbenzene, chloroform, 1,1,1‐trichloroethane (TCA), and trichloroethylene (TCE) were included in this study. Correlations are provided for estimation of VLE as a function of temperature. A new VLE apparatus was developed to extend experimental techniques found in the literature. Partitioning data for several aqueous–organic systems were measured. The collected data compared very favorably to data available in the literature. The new procedure is capable of providing high‐quality data over a wide range of liquid concentrations and temperatures.
Heat and mass transfer along a wetted porous plate in an air stream
Authors: Belhamri A. , Fohr J.‐P. 
Published: June 2004

AbstractThis experimental study examines 2‐D effects on long plate drying due to heat and moisture transfer through boundary layers and porous medium interaction. Many innovative techniques are used to measure accurately boundary layers (velocity, temperature, moisture), the wall surface (infrared sensors for temperature and moisture), and the medium (water content). Gradual decrease in surface saturation measured for several kinds of materials shows that their behavior is more complex than described by the Suzuki–Maeda model, which does not predict the mass exchange sufficiently. Based on the analysis of the transfer between the surrounding air and the porous medium at the scale of the pore on a rough surface, a flow classification is defined and other characteristics are proposed. The drying rate depends on the mass‐transfer coefficient, which varies along the plate with the air flow. The study of boundary layers gives the corresponding profiles with an acceptable accuracy. The laminar‐to‐turbulent transition increases mass‐transfer rates resulting in two drying fronts. The diffusive model proposed here predicts a gradual change in the drying rate along the plate similar to the experimental one.
Two‐dimensional model for circulating fluidized‐bed reactors
Authors: Schoenfelder H. , Kruse M. , Werther J. 
Published: June 2004

AbstractA two‐dimensional reactor model for circulating fluidized beds (CFB) was studied based on the assumption that at every location within the riser, a descending dense phase and a rising lean phase coexist. Fluid mechanical variables may be calculated from one measured radial solids flux profile (upward and downward). The internal mass‐transfer behavior is described on the basis of tracer gas experiments. The CFB reactor model was tested against data from ozone decomposition experiments in a CFB cold flow model (15.6‐m height, 0.4‐m ID) operated in the ranges 2.5–4.5 m/s and 9–45 kg/(m2·s) of superficial gas velocity and solids mass flux, respectively. Based on effective reaction rate constants determined from the ozone exit concentration, the model was used to predict the spatial reactant distribution within the reactor. Model predictions agreed well with measurements.
Hierarchical data analysis of a replicate experiment in emulsion terpolymerization
Authors: Dubé Marc A. , Penlidis Alexander 
Published: June 2004

AbstractA systematic study of the terpolymerization of butyl acrylate/methyl methacrylate/vinyl acetate (BA/MMA/VAc) was conducted. Complete replication of an emulsion terpolymerization experimental run was performed in a 5‐L stainless‐steel batch pilot‐plant reactor. The polymers produced were characterized for conversion, terpolymer composition, molecular weight averages, and average particle size. A hierarchical (nested) data analysis was performed on the experimental data to ascertain various sources of error and to allow for comments to be made regarding the data quality.
Catalytic supercritical water oxidation: Stability of Cr2O3 catalyst
Authors: Aki Sudhir N. V. K. , Ding Zhong‐Yi , Abraham Martin A. 
Published: June 2004

AbstractSupercritical water oxidation has become a well‐known treatment technology for conversion of aqueous wastes. By introducing a catalyst, higher conversion and selectivity to carbon dioxide can be achieved at a lower temperature and at shorter residence times. The stability of chromium oxide in supercritical water was studied to determine the feasibility of using catalysts during supercritical water oxidation. Various process variables, including oxygen and water concentrations, fluid flow rate, and temperature were found to affect the reactivity of the chromium oxide catalyst. Under these conditions, chromium was present in the reactor effluent as chromic acid, H2CrO4. The visual observation of the catalyst after the completion of the experiments suggested that a reaction front moved along the length of the reactor. A rate expression, based on Langmuir–Hinshelwood kinetics, with dissociative chemisorption of oxygen on a hydrated chromium oxide surface, was proposed. The model, developed based on this rate expression and the continuity equation for the fluid phase, was consistent with the experimental results.
Solvatochromic characterization of the liquid phase in liquid—supercritical CO2 mixtures
Authors: Kelley Sean P. , Lemert Richard M. 
Published: June 2004

AbstractThe solvatochromic dye phenol blue (N, N‐dimethylindoaniline) is used to characterize the solvent strength (polarity) of the saturated liquid phase in a series of solvent–carbon dioxide binary mixtures. Data were obtained at 35 and 55°C and at pressures up to ∼70 bar. Five solvents were investigated—acetone, cyclohexane, methanol, THF, and toluene. The polarity of the liquid phase decreases significantly with increasing pressure due to the increasing carbon dioxide content of this phase at equilibrium. For example, the polarity of acetone saturated with carbon dioxide at 35°C and ∼60 bar is equivalent to the polarity of pure cyclohexane at ambient pressure. The local environment about the dye is significantly richer in the polar liquid component than the bulk composition would indicate. The degree of enrichment reflects concentration effects at low pressure, and both concentration and pressure effects at high pressure where the mixtures are highly compressible. The NRTL model of Renon and Prausnitz is able to predict these local compositions with reasonable accuracy except at CO2‐rich conditions where compressibility effects are important.
Modeling of solid/liquid expression for cellular materials
Authors: Lanoisellé Jean‐Louis , Vorobyov Eugène I. , Bouvier Jean‐Marie , Pair Georges 
Published: June 2004

AbstractA general theory is developed for the mechanical expression of agrofood, cellular materials. The so‐called, Liquid‐containing biporous particles expression model considers liquid transfer within a network of three different volumes: extraparticle, extracellular and intracellular volumes. The system of partial differential equations is solved for the expression under constant pressure, allowing calculation of the total layer settlement, as well as the deformation of extraparticle, extracellular and intracellular volumes. The model is able to predict the behavior of four different steps in the consolidation stage: the primary deformation and the creep deformation of extraparticle volume, and the deformation and deliquoring of both extracellular and intracellular volumes. The model is applied to the hydraulic pressing of rapeseeds. The theoretical model agrees well with experimental data for the overall range of pressing time.
Effect of unstable density gradients on back‐mixing in a reciprocating plate column
Authors: Aravamudan Kannan , Baird Malcolm H. I. 
Published: June 2004

AbstractAxial dispersion coefficients were measured in the continuous phase in a 5‐cm‐dia. Karr column, operated cocurrently with the system kerosene(d)‐water(c). The effect of unstable density gradient in the continuous phase was studied by injecting a steady stream of sodium chloride solution as a tracer near the top of the column. The effects of energy dissipation due to unstable density gradient, mechanical agitation, and the flow of the dispersed phase were investigated as the three principal variables, and two plate spacings (2.55 and 5.10 cm) were also employed. The axial dispersion results were correlated in terms of a weighted power‐law model based on Kolmogoroff's mixing length concept and incorporating contributions due to each of the three modes of energy dissipation. Axial mixing was significantly increased in the presence of unstable density gradients even though these contributed very little (typically less than 1 mW/kg) to the total specific energy dissipation rate.
Batch tracking via nonlinear principal component analysis
Authors: Dong Dong , McAvoy Thomas J. 
Published: June 2004

AbstractBatch processes are very important to the chemical and manufacturing industries. Techniques for monitoring these batch processes to ensure their safe operation and to produce consistently high‐quality products are needed. Nomikos and MacGregor (1994) presented a multiway principal component analysis (MPCA) approach for monitoring batch processes, and test results show that the method is simple, powerful, and effective. MPCA, however, is a linear method, and most batch processes are nonlinear. Although data treatment techniques can remove some nonlinearity from the data, nonlinearity is still a problem when using MPCA for monitoring. In this article a nonlinear principal component analysis (NLPCA) method (Dong and McAvoy, 1993) is used for batch process monitoring. Results show that this method is excellent for this problem. Another interesting extension of this approach involves multistage batch process monitoring, which is illustrated through a detailed simulation study.
Mediating operation of heterogeneous CSTR
Authors: Gol'dstein Vladimir , Panfilov Vadim , Shreiber Isaac 
Published: June 2004

AbstractA new type of periodic operation is investigated for a simple model of a heterogeneous catalytic continuous stirred tank reactor. For the heterogeneous case, two scales of response times were derived, slow for heat processes and fast for concentration processes. Periodic operation in intermediate mode between slow and fast processes is studied by manipulation of the feed flow rate. The new approach is designated as mediating operation, which demonstrates ability to control interaction between fast and slow reactor subsystems due to desired separation of dynamic responses for temperature and concentration processes by a single input variable. The conversion improvement at lower temperature can be achieved for lower and upper stable steady states. For the system analysis, analytical investigation of the slow manifolds is used as well as numerical study.
Compressive yield stress of flocculated suspensions: Determination via experiment
Authors: Green Matthew D. , Eberl Maria , Landman Kerry A. 
Published: June 2004

AbstractThe compressive yield stressPy(ϕ) is an extremely useful parameter for the characterization of concentrated flocculated suspensions. It is a measure of the strength of inter‐particle bonds in a networked suspension structure and is used in process design and control of mineral colloidal suspension dewatering. Previous work developed a method for determining this compressive yield stress via the equilibrium sediment height technique using a centrifuge. Here justification for a simple approximate technique to obtainPy(ϕ) is discussed. A new more accurate iterative algorithm is also described. By generating synthetic data, where the exactPy(ϕ) is known, the accuracy of the two techniques can be evaluated properly for the first time. The relative merits and failings of the techniques are discussed. An example is given to show how these techniques work on real experimental data.
Phase equilibria for aqueous protein/polyelectrolyte gel systems
Authors: Sassi Alexander P. , Blanch Harvey W. , Prausnitz John M. 
Published: June 2004

AbstractA molecular‐thermodynamic analysis is directed toward predicting the partitioning of aqueous proteins into charged hydrogels. This analysis takes into account size exclusion by the network, electrostatic interactions, and the osmotic‐pressure difference between a hydrogel and its surrounding solution. Electrostatic interactions in the polyelectrolyte gel can be described by Debye – Hückel theory, or the Mean Spherical Approximation, or Katchalsky's cell model for polyelectrolyte solutions. The cell model gives best agreement with experimental partition coefficients for cytochrome c. The quasi‐electrostatic potential difference between a gel and its surrounding solution demonstrates how the electrostatic contribution to the protein partition coefficient depends on protein charge, gel‐charge density, and solution ionic strength. Finally, a qualitative guide is presented for design of a polyelectrolyte gel such that it exhibits specified swelling and partitioning properties.
Collisional viscosity of FCC particles in a CFB
Authors: Gidaspow Dimitri , Huilin Lu 
Published: June 2004

AbstractParticle velocity distributions were measured for a flow of 75‐μm FCC particles in a CFB using a new video‐digital camera technique. From the spread of particle histograms, a random oscillating particle velocity was determined. This random velocity was used to compute the powder viscosity with the help of dense‐phase kinetic theory of granular flow. There was excellent agreement between this kinetic‐theory measurement and previous macroscopic viscosity measurements. The dimensionless group kinematic viscosity divided by the oscillating velocity and particle diameter correlated all available data as a function of particle volume fraction.
Modeling gradient elution of proteins in ion‐exchange chromatography
Authors: Gallant Stuart R. , Vunnum Suresh , Cramer Steven M. 
Published: June 2004

AbstractThe steric mass action (SMA) model of ion exchange is employed in concert with appropriate mass balance equations to describe the behavior of a concentrated band of protein under gradient‐elution conditions. A method of characteristics approach is employed to solve the model equations rapidly. The model is shown to accurately predict the gradient elution of the protein cytochrome C in a strong cation‐exchange column. This work constitutes an advance over previously available models as it allows engineers to rapidly consider the effects of nonlinear adsorption in gradient‐elution chromatography using a spreadsheet. Further, it provides significant physical insight into the process of gradient elution for preparative and large‐scale separations.