bluuebunny/crossref_metadata_2025_split huggingface dataset:
RobustH∞glucose control in diabetes using a physiological model
Authors: Parker Robert S. , Doyle Francis J. , Ward Jennifer H. , Peppas Nicholas A. 
Published: April 2004

AbstractA robust H∞controller was developed to deliver insulin via a mechanical pump in Type I diabetic patients. A fundamental nonlinear diabetic patient model was linearized and then reduced to a third‐order linear form for controller synthesis. Uncertainty in the nonlinear model was characterized by up to ±40% variation in eight physiological parameters. A sensitivity analysis identified the three‐parameter set having the most significant effect on glucose and insulin dynamics over the frequency range of interest ω = [0.002, 0.2] (rad/min). This uncertainty was represented in the frequency domain and incorporated in the controller design. Controller performance was assessed in terms of its ability to track a normoglycemic set point (81.1 mg/dL) in response to a 50 g meal disturbance. In the nominal continuous‐time case, the controller maintained glucose concentrations within ±3.3 mg/dL of set point. A controller tuned to accommodate uncertainty yielded a maximum deviation of 17.6 mg/dL for the worst‐case parameter variation.
Scale‐up in plug‐flow reactors: Laminar feed
Authors: Forney L. J. , Penney W. R. , Vo Hanh X. 
Published: April 2004

AbstractSimilarity parameters are derived to correlate the selectivity of mixing controlled paraliel reactions within plug‐flow reactors with two types of static mixing elements for both aqueous and viscous solutions. For the case of laminar reactor feed, the Kolmogoroff time is shown to correlate selectivity in turbulent reactors provided the reactor Reynolds number Re < ReC. The upper limit ReC for the reactor Reynolds number is constrained by the ratio of reactant feed‐to‐total volumetric flow rate. Moreover, for larger reactor Reynolds number Re > ReC, the inertial time scale defined in terms of a reactor feed length correlates selectivity. Scaling laws are derived for both reactor diameter and length, and suggestions are made for predicting selectivity with larger turbulent feed rates.
Generalized correlation for bubble motion
Authors: Rodrigue D. 
Published: April 2004

AbstractThe motion of a single gas bubble rising steadily in an uncontaminated Newtonian viscous fluid of infinite extent is reviewed. Using experimental data gathered from the literature over the past century, a data bunk is set up for bubble velocities as a function of their diameters. These data provided a very broad range of liquid properties and bubble hydrodynamic regimes as density (722–1,380 kg/m3), viscosity (2.2×10−4−18 Pa·s), surface tension (15.9–91.0 mN/m), Reynolds number (1.9×10−7−1.1 × 104), and Morton number (1.0×10−11−1.0×107). From a dimensional analysis, a single equation is proposed to predict bubble velocities. The simplicity and good precision over the whole range of parameters facilitate its use in design calculations of chemical engineering.
Evaluation of instability criterion for bidisperse sedimentation
Authors: Biesheuvel P. Maarten , Verweij Henk , Breedveld Victor 
Published: April 2004

AbstractThe instability criterion for bidisperse sedimentation derived by Batchelor and Janse van Rensburg was combined with two empirical models for the particle velocities that are consistent with conservation of momentum and used to construct theoretical stability diagrams. The stability boundaries were fully determined by the particle volume fractions, the particle‐size ratio, and the ratio of the density differences with the liquid. The results showed that on increasing the particle‐size ratio sufficiently, stability, always is attained. For particles of similar size, instabilities occur mainly if the liquid density is intermediate between the particle densities. The stability diagrams agree well with the limited experimental data, if so‐called “vertical columns” are excluded. This seems reasonable since similar structures observed in monodisperse suspensions are not captured by the bidisperse instability criterion either.
Structure simulation of concentrated suspensions of hard spherical particles
Authors: He D. , Ekere N. N. 
Published: April 2004

AbstractA monte Carlo technique is applied to simulate the structure of concentrated suspensions of hard spherical particles that obey lognormal distribution. With this technique, the random loose packing, with packing density Φm is obtained first, and then the particles in the packing are randomly separated to achieve a specified solid‐volume fraction Φ. The simulated structure is evaluated both in the microscale, the neighboring number distribution, and the distribution of gaps between neighboring particles; and in the macroscale, the distribution of the solid‐area fractions on a series of parallel cross sections. Results show that, at the same solid‐volume fraction, the increase in the standard deviation of particle diameters leads to the decrease in the mean neighboring number and leads to the increase in the mean gap. The mean relative gap obtained from the simulation is larger than that from theoretical prediction, δ=[(Φm/Φ)1/3−1]. With particles of lognormal distribution, both the gap sizes and the neighboring numbers distributed over broader ranges than that with equal particles. Results also show that, with equal particles and particles of lognormal distribution, there is no significant differenence between the distributions of the solid‐area fractions on the cross sections. The structures obtained in this study are shown to be completely random, homogeneous, and isotropic by statistical tests.
Particle sizing in dense, rapidly flowing KCI suspensions by photon migration techniques
Authors: Bartlett Matthew , Jiang Huabei 
Published: April 2004

AbstractThe first experimental measurement of particle‐size distribution (PSD) from undiluted, rapidly flowing potassium chloride (KCl) suspensions using continuous‐wave photon migration techniques is presented. PSDs were obtained from a laboratory simulation of production‐line slurries used in the chemical fertilizer industry. Spectral measurements of concentrated, rapidly flowing slurry containing 25–40% KCl particles were used to calculate the suspensions' reduced scattering coefficient and PSD using inverse algorithms. Our PSD results agree excellently with sieving measurements. Refractive index is important in the calculations of the PSD and the suspensions' reduced scattering coefficient.
Synthesis and characterization of catalytic nanoporous carbon membranes
Authors: Strano Michael S. , Foley Henry C. 
Published: April 2004

AbstractA method is reported for the synthesis of nobel catalyic nanoporous carbon membranes. Defect‐free, nanoporous carbon films of 12.5−μm average thickness containing a dispersion of Ptx were synthesized on macroporous stainless‐steel supports. Ideal gas selectivities for the catalytic membranes were simliar to those of inert nanoporous carbon membranes with He–N2=58.6 and O2N2=4.9. The selective hydrogenation of monoolefins (propylen, l‐buiene, isobutylene) was used to probe the shape‐selective catalytic proerties nad the transport selectivities of the membranes. The results were modeled using the linear regime of coupled sdsorption, transport and rection in the membrane. Model regression yielded 14.9, 19.7. and 18.4 kJ/mol for the activation energies of permeation for propylene, isobutylene, and l‐butene, respectively. The system demonstrated selective reaction and transport favoring propane production with selectiveity ratios of 28.9:3.2.I for propane:n‐butane:isobutane at 125°C.
Crystal temperature control in the Czochralski crystal growth process
Authors: Armaou Antonios , Christofides Panagiotis D. 
Published: April 2004

AbstractThis work proposes a control configuration and a nonlinear multivariable model‐based feedback controller for the reduction of thermal gradients inside the crystal in the Czochralski crystal growth process after the crystal radius has reached its final value. Initially, a mathematical model which describes the evolution of the temperature inside the crystal in the radial and axial directions and accounts for radiative heat exchange between the crystal and its surroundings and motion of the crystal boundary is derived from first principles. This model is numericully solved using Galerkin's method and the behaviour of the crystal temperature is studied to obtain valuable insights which lead to the precise formulation of the control problem, the design of a new control configuration for the reduction of thermal gradients inside the crystal and the derivation of a simplified 1‐D in a space dynamic model. Then, a model reduction procedure for partial differential equation systems with time‐dependent spatial domains (Armaou and Christofides, 1999) based on a combination of Galerkin's method with approximate inertial manifolds is used to construct a fourth‐order model that describes the dominant thermal dynamics of the Czochralski process. This low‐order model is employed for the synthesis of a fourth‐order nonlinear multivariable controller that can be readily implemented in practice. The proposed control scheme is successfully implemented on a Czochralski process used to produce a 0.7 m long silicon crystal with a radius of 0.05 m and is shown to significantly reduce the axial and radial thermal gradients inside the crystal. The robustness of the proposed controller with respect to model uncertainty is demonstrated through simulations.
Artificial neural‐network‐assisted stochastic process optimization strategies
Authors: Nandi Somnath , Ghosh Soumitra , Tambe Sanjeev S. , Kulkarni Bhaskar D. 
Published: April 2004

AbstractThis article presents two hybrid robust process optimization approaches integrating artificial neural networks (ANN) and stochastic optimization formalism—genetic algorithms (Gas) and simultaneous perturbation stochastic approximation (SPSA). An ANN‐based process model was developed solely from process input–output data and then its input space comprising design and operating variables was optimized by employing either the GA or the SPSA methodology. These methods possess certain advantages over widely used deterministic gradient‐based techniques. The efficacy of ANN‐GA and ANN‐SPSA formalisms in the presence of noise‐free as well as noisy process data was demonstrated for a representative system involving a nonisothermal CSTR. The case study considered a nontrivial optimization objective, which, in addition to the conventional parameter design, also addresses the issue of optimal tolerance design. Comparison of the results with those from a robust deterministic modeling/optimization strategy suggests that the hybrid methodologies can be gainfully employed for process optimization.
Experimental design and inferential modeling in pharmaceutical crystallization
Authors: Togkalidou Timokleia , Braatz Richard D. , Johnson Brian K. , Davidson Omar , Andrews Arthur 
Published: April 2004

AbstractA fractional factorial experimental design was used to investigate relative effects of operating conditions on the filtration resistance of a slurry produced in a pharmaceutical semicontinuous batch crystallizer. The six operating variables were seed type, seed amount, temperature, solvent ratio, addition time, and filtration resistance was used to define the factory operating procedure, which reduced filtration time 3.7‐fold. Several chemometric techniques were used to construct inferential models between the in‐process measurement of partcle chord‐length distribution and filtration resistance to help detect operational problems before completing the batch and decide when batch crystal lization runs should end. Depending on the model quality criterion, the most popular chemometric models of partial least squares and top‐down principal‐component regression can produce lower quality models. Another chemometric approach, confidence‐interval principal‐component regression, predicted 70% more accurately than the best OLS model. The main effects and inferential models serve different but complementary roles in developing and implementing high performance crystallization process opertions. A main‐effects model constructed from statistical experimental design data determined optimal operating conditions rapidly, while the inferential model can determine opertional problems and batch end times during batch end time during batch‐process operations.
Decolorization of dyes using ozone in gas‐induced a reactor
Authors: Hsu Yung‐Chien , Chen Jia‐Tsween , Yang Hsiang‐Cheng , Chen Jyh‐Herng 
Published: April 2004

AbstractTreatahility of aqueous dye solutions usirig a new gas‐induced ozonator was investigated, as well as feasihiliry of decolorizing dyes using ozone, the ozone utilization efficiency, and the chemical oxygen demand (COD) under various pH values and initialdye concentrations. Expeiimental results indicate that all of the dyes used can he decolorized within 15 min. For most of the dyes used, ozone decolorizing was more rapid in acidic media. The ozone utilization efficiency can be raised to 90% or higher with proper agitation speeds. The ozone utilization efficiency and COD removal rate increased with an increase in pH value; however, the COD removal remained nearly constant for various categories of dye regardless of the initial dye concentration. The kinetics of decolorization were also examined.
Polymerization kinetics of rodlike molecules under quiescent conditions
Authors: Gupta J. Srinivasalu , Agge Ameya , Khakhar D. V. 
Published: April 2004

AbstractThe kinetics of solution polymerization to synthesize poly(p‐phenylene terephthalamide), a rodlike polymer, was studied theoretically and experimentally. The reaction was conducted under quiescent conditions to eliminate effects of flow‐induced orientation that are known to affect the kinetics of the process. Experiments included determining the degree of polymerization and polydispersity index for different times of reaction. Theoretical study comprised calculating the effective rate constant for the diffusion‐controlled reaction using Smoluchowski's approach and computing the evolution of the molecular‐weight distribution using the length‐dependent effective rate constant obtained in the first part. Experiments showed significant slowing of the reaction and narrow molecular‐weight distributions due to diffusion control. The degree of polymerization and the polydispersity index variation with time is nearly the same for the two initial monomer concentrations. The Smoluchowski theory predicts the effective rate constant to be keƒƒ α ρ−0.8L−3.5 for large L, with ρ the local number concentration of rods and L the length of the reacting rodlike molecule. The model has two parameters obtained by a least‐squares fit to one set of data of degree of polymerization vs. time. Results of the population balance calculations using the computed effective rate constant matched with experimental data for degree of polymerization and polydispersity vs. time for both initial monomer concentrations. The model, augmented to account for low, end‐capping side reactions, predicted an optimal initial monomer concentration for obtaining the highest degree of polymerization for a fixed reaction time, as reported in previous experimental studies.
Control strategies for front stabilization in a tubular reactor model
Authors: Panfilov Vadim , Sheintuch Moshe 
Published: April 2004

AbstractThe stabilization of a front pattern in a homogeneous tubular reactor model was studied. Linear stability analysis combined with the Galerkin method is used for state feedback control of the distributed parameter system. The capabilities of the global control and point‐sensor control to stabilize the front solution were studied by manipulating various reactor parameters, including fluid flow and feed conditions. Point‐sensor control in coolant flow (heat‐loss coefficient) or coolant temperature are the most effective when the temperature sensor is located close to the front position. Global control based on a space‐averaged sensor and other strategies failed. A qualitative analysis is suggested for selection of proper control of front stabilization.
Modified syntheses of Ca‐resinates by fusion method
Authors: Sundqvist S. , Turunen S. , Paatero E. , Twigt F. 
Published: April 2004

AbstractTall oil rosin was modified with fumaric acid or maleic acid anhydride to get fortified rosin. which was used as u raw material in fusion Ca‐resinate syntheses. Two reaction step were observed in the syntheses. A fast resination reaction takes place at 235°C, and a slow decarboxylation of rosin acids forms neutral rosin oil at 265°C. A mechanistic model for the decarboxylation reaction step was derived to explain the effect of fortifying substances on the reaction kinetics. A multivariate calibration method using partial least‐spare (PLS) regression was applied to monitor the acid concentration decrease on the basis of infrared spectroscopic data during the fortified syntheses. A mixture of unmodified rosin and rosin oil (decarboxylated rosin) was used as a raw material in a novel modification of fusion syntheses to increase the mass yield of the resinate. In the modified rosin oil syntheses, decarboxylation of rosin acids is avoided, and recycling the added rosin oil considerably improves the mass yield of the resinate syntheses.
Estimate of red‐cell deformability and plasma viscosity based on flow curve
Authors: Ookawara S. , Yano A. , Ogawa K. , Taniguchi K. 
Published: April 2004

AbstractA new estimation method of clinical blood indices based on the flow characteristics of unadjusted whole blood is proposed, such as red‐cell deformability and plasma viscosity. Parameter values of Bingham and power law models were calculated based on the measured flow characteristics. Red‐cell deformability was measured by the method of laser diffractometry. The clinical indices were related with the non‐Newtonian model parameters by a feedforward neural network (NN). Inputs of the NN are the parameter values and hematocrit. Outputs are red‐cell deformability and plasma viscosity. It was verified that estimated values agreed well with those measured values after sufficient learning. By applying this method to 20 healthy persons, it was confirmed that the estimated values by NN were within normal range. According to these experimental results, this estimation method can be applied to clinical use.
Calculation of Brownian particle transmission in long, wide channels
Authors: Myers Matthew R. 
Published: April 2004

AbstractThe transport of Brownian particles in channels which are long and wide compared to their height is addressed. The cross‐sectional shape of the channel is assumed to be slowly varying, but otherwise arbitrary. A solution to the convective‐diffusive equation with reaction‐rate boundary condition was obtained by locally incorporating the modified Graetz solution in a flat channel. The solution was evaluated asymptotically for the cases of a channel with a maximum height occurring at an endpoint and at an interior maximum. The asymptotic method was applied in two example geometries: the calibration apparatus used to determine reaction‐rate constants for virus adsorption to latex barriers, and overlapping pores in a nucleation‐track membrane. The asymptotic expressions compared well with finite‐element calculations in the examples. The utility of the asymptotic approach lies in rapid estimation of particle transmission through a channel as a function of geometric and physical parameters.
Drag reduction of non‐newtonian fluids in a circular pipe with a highly water‐repellent wall
Authors: Watanabe Keizo , Udagawa Hiroshi 
Published: April 2004

AbstractWith a highly water‐repellent wall pipe in the drag reduction of polymer solutions, a flow system in which drag reduction is obtained in both laminar and turbulent flow ranges was realized. Experiments were carried out to measure the pressure drop in pipes with a highly water‐repellent wall and an acrylic resin wall by a pressure transducer. The basic material of the highly water‐repellent coating is fluorine‐alkane‐modified acrylic resin with added hydrophobic silica, which was left overnight in air after it was coated to the pipe wall. The diameter of the pipe was 6 mm. The polymer solutions tested were PEO15 aqueous solutions in the concentration range of 30∼1,000 ppm. The drag‐reduction ratio for laminar flow was about 11∼15%. To understand this effect, the pressure drop was measured by using surfactant solutions and degassed water, and by pressurizing tap water in the pipeline. The laminar drag was not reduced in sufuctant solutions, although degassed water and pressurizing tap water in the pipeline had no effect on the reduction. In the laminar flow range, the friction factor of a power‐law fluid with fluid slip was analyzed by applying the modified boundary condition on fluid slip at the pipe wall, and the analytical results agreed with the experimental results in the low Reynolds number range.
Reactive barrier films
Authors: Yang Chuanfang , Nuxoll Eric E. , Cussler E. L. 
Published: April 2004

AbstractImmobile reactive groups within films used as packaging materials can retard transport of solutes like oqgen and water uapor. A theoy developed for these films shows that these groups do not affect the steady‐state transport across the film, but that they do increase the time before permeability begins. The theory is verified by experiments with acid barriers made of polyvinylalcohol containing colloidal zinc oxide. These results imply that the time that barrier polymers are effectiue can be increased about two orders of magnitude. When reactive groups are combined with impermeable flakes, this time can be increased about three orders of magnitude. For example, a polymer barrier currently effective for one hour can be made effectiue for over one year.
Factorized approach to nonlinear MPC using a radial basis function model
Authors: Bhartiya Sharad , Whiteley James R. 
Published: April 2004

AbstractA new computationally efficient approach for nonlinear model predictive control (NMPC) presented here uses the factorability of radial basis function (RBF) process models in a traditional model predictive control (MPC) framework. The key to the approach is to formulate the RBF process model that can make nonlinear predictions across a p‐step horizon without using future unknown process measurements. The RBF model avoids error propagation from use of model predictions us input in a recursive or iterative manner. The resulting NMPC formulation using the RBF model provides analytic expressions for the gradient and Hessian of the controller's objective function in terms of RBF network parameters. Solution of the NMPC optimization problem is simplifed significantly by factorization of the RBF model output into terms containing only known and unknown parts of the process.
Synthesis of chiral crystallization processes
Authors: Schroer Joseph W. , Wibowo Christianto , Ng Ka M. 
Published: April 2004

AbstractA process synthesis procedure is presented for the resolution of racemic mixtures by crystallizaiion. The phase behaviors of racemic mixtures and of those in the presence of solvents and resolving agents are discussed. The Corresponding separation schemes are synthesized by considering the separation steps in a flowsheet as movements on a phase diagram. Separations with and without involving racemization and deracemization are considered. The procedure is illustrated with several examples, including the manufacture of ibuprofen and naproxen.