bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Microcirculation in Diabetes Mellitus
Authors: Tooke John E. 
Published: April 2004

AbstractExamination of human microvascular function in the two major forms of diabetes has revealed common abnormalities yet important differences in microvascular behavior. Early microvascular hypertension related to the degree of hyperglycemia appears to be fundamental to the expression of microangiopathy in type 1 diabetes millitus (T1DM), and although plausible biochemical explanations exist for this phenomenon, they remain to be verified in human diabetes. In type 2 diabetes millitus (T2DM) the interplay between preceding insulin resistance, hypertension, and vascular smooth muscle function modifies and confuses the pathophysiological findings, particularly in view of the fact that the emergence of hyperglycemia is difficult to date in this form of the disease. Unraveling of this puzzle may explain the subtle differences in the expression of microangiopathy in T1DM and T2DM, whereas primary manipulation of the hemodynamic and permeability changes may offer real therapeutic potential in the future.
The Diabetic Foot
Authors: Dinh Thanh L. , Veves Aristidis 
Published: April 2004

AbstractDiabetic foot complications are common manifestations with potentially devastating consequences. Foot pathology encountered in the clinical setting ranges from benign skin and nail changes to the more severe and debilitating ulcerations and infections. Despite adequate therapy, these more serious ulcerations and infections may progress to extensive hospitalizations, lower extremity amputations, and premature death. Over the last decade, considerable strides have been gained in identifying the risk factors and causal pathways leading to diabetic foot problems. Major risk factors for the development of diabetic foot ulcers include peripheral neuropathy, peripheral vascular disease, and high foot pressures. These, along with other predisposing elements in the formation of diabetic foot complications, will be discussed in greater detail later in the chapter. With a greater understanding of the pathogenesis of diabetic foot complications, preventative strategies aimed at limb salvage have been met with greater success.
Gas mixing and modeling of secondary gas distribution in a bench‐scale fluidized bed
Authors: Al‐Sherehy Fahad , Grace John , Adris Alaa‐Eldin 
Published: April 2004

AbstractThe effect of distributing gaseous feed along a bubbling fluidized bed of diameter 152 mm was studied with fluid catalytic cracking particles. Steady‐ and unsteady‐state experiments show that the secondary gas concentration profile at the injection level was almost uniform for high secondary and low primary gas velocities. Secondary gas readily mixed within a short distance above the injection level. Backmixing was primarily influenced by the primary feed superficial gas velocity. Regardless of its injection velocity, secondary gas was barely detectable below the injection level at low primary superficial velocities. Axial dispersion and mass transfer decreased significantly when some gas was introduced at higher levels, compared with a bed where all gas entered through the windbox. Two two‐phase models are proposed to simulate gas mixing, the first with a step‐change in gas flow rate at the injection level, the second accounting for additional mixing in the jet region. © 2004 American Institute of Chemical Engineers AIChE J, 50: 922–936, 2004
Turbulence properties of the impeller stream of a Rushton turbine
Authors: Lee K. C. , Yianneskis M. 
Published: April 2004

AbstractThe structure of the flow in a vessel stirred by a Rushton turbine was investigated using laser Doppler anemometry measurement techniques. The time and length scales of turbulence were determined and used to estimate the dissipation rate of turbulence energy. The levels of turbulence energy and dissipation are high near the turbine and decrease rapidly with increasing distance from the turbine blades. The turbulence in the impeller stream is mostly anisotropic close to the blades. The results are compared with the findings of earlier investigations, and their implications for computational fluid dynamics (CFD) predictions of the flows are discussed.
Block‐oriented NARMAX models with output multiplicities
Authors: Pottmann Martin , Pearson Ronald K. 
Published: April 2004

AbstractBlock‐oriented modeling approaches to the development of NARMAX models for processes exhibiting output multiplicities are introduced. “Feedback block‐oriented” model structures are proposed that can force the resulting NARMAX model to have a particular steady‐state behavior and reduce the model‐identification problem to a constrained, linear model identification. These models are particularly suitable for gray‐box modeling approaches where it is assumed that the steady‐state behavior of the process is known and a NARMAX model is sought to approximate its dynamic response. The proposed approaches are applied to a CSTR model with three steady states to illustrate their peformance.
Equation of state and radial distribution functions of FCC particles in a CFB
Authors: Gidaspow Dimitri , Huilin Lu 
Published: April 2004

AbstractKinetic theory of granular flow was verified experimentally for flow of fluid catalytic cracking particles in a vertical pipe. Measurements of particle pressure using a differential transducer and granular temperature with a digital camera as a function of bulk density, determined using an X‐ray densitometer, showed that a relation exists among pressure, temperature, and density, analogous to the ideal gas law. In the limit of zero solids volume fraction: (Solid Pressure)/[(Granular Temperature) × (Bulk Density)] = 1.0. Measurements of radial distribution functions using the digital camera showed that their peak values occur at particle contact and lie between the predictions from the Bagnold equation and Carnahan–Starling equation. The hard sphere model was corrected for a cohesive pressure using the minimum in the measured radial distribution function. The new model agrees with the pressure measurements in the dense regime.
Role of water in formic acid decomposition
Authors: Akiya Naoko , Savage Phillip E. 
Published: April 2004

AbstractFormic acid decomposes primarily to CO and H2O in the gas phase, but to CO2 and H2 in the aqueous phase. Ab‐initio quantum chemical calculations were performed, using Hartree‐Fock and density functional methods, to seek an explanation for this behavior. The effect of water on the two decomposition pathways and on the isomerization of formic acid was determined. The transition state structures were fully optimized and include up to two water molecules. In the absence of water, dehydration is more favorable than decarboxylation. The presence of water reduces the activation barriers for both decomposition pathways, but decarboxylation is consistently more favorable than dehydration. The water molecules actively participate in the bond‐breaking and bond‐forming processes in the transition state. The reduction in the activation barriers with the addition of water indicates that water acts as a homogeneous catalyst for both dehydration and decarboxylation, whereas isomerization of formic acid occurs independently of water. Water has a strong effect on the relative stability of the formic acid isomers, acid–water complexes, and transition states. The relative stability of the transition states plays an important role in determining the faster decomposition pathway.
Compositional variation in hydrocarbon reservoirs with natural convection and diffusion
Authors: Riley Mike F. , Firoozabadi Abbas 
Published: April 2004

AbstractThe knowledge of horizontal compositional variation is of prime importance in hydrocarbon reservoir delineation. However, the effect of natural convection on this variation is largely unknown. This work examines the effect of natural convection and diffusion (thermal, pressure and Fickian) on a two‐component, single‐phase fluid occupying a horizontal cross‐sectional reservoir in the presence of a prescribed linear temperature field. The behavior is investigated using a method of successive approximations, which iterates on solution of Poisson's equation. This behavior is then incorporated in a simplified perturbation solution (in the form of a cubic equation) which not only gives accurate values of horizontal compositional variation, but also clearly shows the interplay of reservoir/fluid properties. The perturbation and the full solutions indicate that a small amount of convection can cause the horizontal composition gradients to increase until a maximum is reached and then decay as 1/k. An alternative scenario is that the gradient asymptotes to a value where the horizontal density derivative approaches zero. Generalization of this perturbative solution to n‐components apparently requires the simultaneous solution of n − 1 cubic equations.
Novel photocatalytic reactor for water purification
Authors: Ray Ajay K. , Beenackers Antonie A. C. M. 
Published: April 2004

AbstractA novel photocatalytic reactor design for water treatment is characterized by the use of new extremely narrow diameter lamps, thus allowing for much higher surface area for catalyst coating per unit reactor volume and consequently for much higher specific reactor capacity. Experiments in a reactor containing 21 novel U‐shaped lamps coated with catalyst showed a 695% increase in efficiency of the reactor performance in comparison with a classical annular reactor and 259% in comparison with a slurry reactor. Both a classical annular reactor and a slurry reactor cannot be scaled up for large‐scale applications due to the low values of illuminated catalyst surface area per unit volume of liquid treated inside the reactor while this configuration is flexible enough for large‐scale applications.
Design of wire mesh mist eliminators
Authors: Brunazzi Elisabetta , Paglianti Alessandro 
Published: April 2004

AbstractKnitted wire mesh mist eliminators are used extensively in many industrial plants. Their widespread application is essentially due to the low cost and efficient removal of entrained liquid droplets from vapor and gas streams. Despite the broad range of entrainment removal applications, open literature on this topic is limited. All the available design relations are based on semiempirical equations with an uncertain range of application. In this work, a set of new experimental data was obtained by investigating the performances of commercial eliminators, and a mechanistic model is presented. Comparison between experimental data and the proposed model shows that it can be used to predict separation efficiency both for horizontal and vertical arrangements.
Estimating state probability distributions from noisy and corrupted data
Authors: Johnston Lloyd P. M. , Kramer Mark A. 
Published: April 2004

AbstractThe method of recursive state density estimation (RSDE) is developed for determining the probability distribution of the states of a system from measurements that contain both random noise and gross errors. The technique is based on the expectation maximization algorithm and is iterative in nature. Similar to EM, at each iteration the likelihood of the distribution estimated by the RSDE algorithm is guaranteed to increase, thus arriving at the most likely distribution of the true states, given the measurement data set and the algorithm initial conditions. Convergence of the algorithm to the correct solution, for a simple case where an analytical answer can be derived for comparison, is shown. Two chemical process examples that have more complex distributions are also shown. Once the probability distribution of the states has been determined, many monitoring and statistical process and quality control functions can be performed using the more accurate distributions of the process states, avoiding corruption of the distribution due to faulty measurements.
Role of range and precision of the independent variable in regression of data
Authors: Brauner Neima , Shacham Mordechai 
Published: April 2004

AbstractRegression of the experimental data of one independent variable, y vs. a linear combination of functions of an independent variable of the form y = Σβjfj(x) is considered. Inherent collinearity among the terms of such functions may prevent obtaining a model of a desired accuracy. Traditional collinearity indicators, condition number of the normal matrix, variance inflation factor, and a new indicator (truncation‐error‐to‐noise ratio) are used to investigate the effects of the range and precision of the independent‐variable data on collinearity among functions in a regression model. Statistical confidence intervals are used to demonstrate harmful effects of collinearity. The harmful effects increase by reducing the range of the independent variable data and/or its precision. Using only independent variable data, the new collinearity indicator allows the identification of the point where the number of terms in a particular regression model becomes larger than can be justified on statistical grounds. The use of the new criterion can improve experimental design in order to minimize the harmful effects of collinearity and enable a rapid screen of correlations published in the literature for identifying those that include more parameters than can be justified.
Phase transfer catalysis: Chemistry and engineering
Authors: Naik Sanjeev D. , Doraiswamy L. K. 
Published: April 2004

AbstractPhase transfer catalysis (PTC) uses catalytic amounts of phase transfer agents which facilitate interphase transfer of species, making reactions between reagents in two immiscible phases possible. PTC is used widely in the synthesis of various organic chemicals in both liquid‐liquid and solid‐liquid systems. Existing literature on PTC is chemistry‐intensive and a mere handful of recent articles constitute the entire information on engineering analysis. This article reviews the field comprehensively by combining the existing knowledge from chemistry with insights into mechanistic and kinetic analysis and mathematical modeling of soluble and insoluble PTC. By its very nature, PTC involves a series of equilibrium and mass‐transfer steps, beside the two main reactions. Neglect of mass‐transfer effects can grossly overpredict the conversion of a PTC mediated reaction. A practical way of using PTC, which enables easy separation, is to immobilize the catalyst on a solid support. Mass‐transfer limitations and higher costs, however, have precluded its commercial use so far, requiring further analysis of mass‐transfer limitations in these complex three‐phase systems. The use of PTC, combined with other rate enhancement techniques like sonochemistry, microwaves, electroorganic synthesis, and photochemistry, is being increasingly explored. Applications in this area in the manufacture of organic intermediates and fine chemicals seem almost unlimited.
Diffusivities of n‐alkanes in silicalite by steady‐state single‐crystal membrane technique
Authors: Talu Orhan , Sun Matthew S. , Shah D. B. 
Published: April 2004

AbstractA novel experimental technique that measures the diffusive flux through a single‐crystal membrane (SCM) was developed and tested. Unlike all other macroscopic techniques that depend on a transient response, SCM is used under steady‐state conditions, which results in a wide range of applicability from 10−2 to 10−11 cm2/s. Phenomenological equations for the steady‐state data analysis were developed. The variation of driving force over the diffusion path is included in the model. As required by thermodynamics, the micropore concentration is given as a function of surface‐excess amount adsorbed and gas density. The membrane configuration measures diffusivity in only one crystallographic direction. The micropore difusivities of C1 to C10 normal alkanes through silicalite crystal in the z‐direction were measured at 30, 50 and 70°C. The activation energies for micropore diffusion are also reported. The data agree excellently with the other two studies that measure directional diffusivities. Diffusion and adsorption of hexane and heptane in silicalite display structural heterogeneity induced by the comparable lengths of molecules and silicalite channels rather than diameter of molecule vis‐à‐vis pore diameter.
Mathematical model of combustion synthesis
Authors: Akiyama Tomohiro , Isogai Hiromichi , Yagi Jun‐ichiro 
Published: April 2004

AbstractMathematical modeling of the combustion synthesis was studied theoretically and experimentally by taking Mg2Ni synthesis as an example. An unsteady two‐dimensional mathematical model was constructed by reflecting drastic changes in thermo‐physical properties from starting material of magnesium nickel mixture to a product of inter‐metallic compound and measured solid‐phase reaction rate with/without melting. For validating the model experimentally, an end of the cylindrical sample of compressive powders was heated, and local temperatures of the sample were monitored. The comparison between calculated and measured temperatures showed plausible agreement when the model took partial melting effect of a eutectoid phase into the fundamental equations.
Drying kinetics of polymer films
Authors: Guerrier Béatrice , Bouchard Charles , Allain Catherine , Bénard Christine 
Published: April 2004

AbstractDrying kinetics of a polymer film cast from a polymer–soluent solution is studied. A modelization of the whole drying process is performed, including the difision of soluent through the varnish layer, the moving interface, and the coupled heat and mass transfer between the interface and the drying air. The assumptions and the ualdity domain of the proposed modelization are thoroughly analyzed. In particular, comparison of the varnish temperature with its glass transition temperature all along the process allows us to determine the validity domain of the Fickian difision assumption. Because of the hypodifisiue behavior of polymer solutions, uery large concentration gradients appear in the layer, and the drying kinetics is characterized by two successive regimes. This two‐ stage kinetics is investigated first for typical conditions encountered in the packaging industry, where a film of a few microns is dried in a few seconds, thanks to hot air blown through nozzles. Then, different drying conditions corresponding to evaporation experiments at room temperature of thicker films of the same varnish are studied.
Improved direct and indirect systems of columns for ternary distillation
Authors: Agrawal Rakesh , Fidkowski Zbigniew T. 
Published: April 2004

AbstractSeparation of a ternary mixture into almost pure components is discussed. Systems of distillation columns, with higher thermodynamic efficiency, are developed from a direct sequence (or indirect sequence) of distillation columns by allowing for two interconnecting streams of the same composition and different enthalpy. This increases the reversibility of distillation in the second column, which results in replacing a portion of the high‐temperature boiling duty with a lower‐temperature heat in the direct split case. For the indirect split case, the improvement allows a portion of the low‐temperature condensing duty to be replaced with a higher‐temperature condensation.
Effects of Marangoni surface tension forces on modern distillation packings
Authors: Proctor Sebastian J. , Biddulph Michael W. , Krishnamurthy Krish R. 
Published: April 2004

AbstractNew experimental data presented concern effects of Marangoni surface‐tension forces on the mass‐transfer eficiency of packed distillation columns. Various random packings of sizes 6 and 25 mm, as well as structured packings of sizes 30 mm diameter and 150 mm, were used with the system n‐propanol/water. This system can behave either as a Marangoni positive system at low concentrations of n‐propanol or as a negatiue system at high concentrations of n‐propanol. It was confirmed that small packings show lower eficiencies for Marangoni negative systems, due to the breakup of the film of liquid on the packing surface. In the larger column, howeuer, the situation is reversed with the negative mixtures often showing better eficiencies, especially at heauier loadings. This is attributed to the observation that spray and droplet formation are much more pronounced for the negative mixtures, providing extra surface for mass transfer and, hence, better mass‐transfer eficiency. There are also some indications that the pressure drop is unexpectedly high for these conditions and that premature flooding can occur. This may haue design implications for any mass‐transfer deuice in which vapor and liquid phases are contacted in narrow passageways.
Product and process development using artificial neural‐network model and information analysis
Authors: Chen Junghui , Wong David Shan Hill , Jang Shi‐Shang , Yang Seng‐Lu 
Published: April 2004

AbstractAn experimental design scheme proposed for process and product development integrates the artificial neural network, random‐search algorithm, fuzzy classification, and information theory. An initial batch of experimental data is first collected to construct a neural‐network model. Random search generates a number of candidates for the next batch of experiments. A fizzy classification algorithm is used to find the cluster centers of these candidates. An information free energy index is defined to balance the need for better classification and the relevance of each class in optimization. New experiments are performed at these cluster centers to validate the model. The procedure is repeated until an optimal solution is reached. Case studies using a mathematical model and a real industrial pigment‐blending project illustrate the abilities of this method to locate multiple optima and handle multivariable experimental design.
Design of single‐product campaign batch plants under demand uncertainty
Authors: Petkov Spas B. , Maranas Costas D. 
Published: April 2004

AbstractA new method is introduced for optimally designing multiproduct batch plants under the single‐product campaign (SPC) production mode. Uncertain future product demands are described with normal probability distributions, and more than one processing unit of equal size are allowed per stage. A t the expense of imposing the normality assumption for product demand uncertainty and the SPC production mode, the original two‐stage stochastic optimization problem is transformed into a deterministic mixed‐integer nonlinear programming problem without relying on implicit or explicit discretization of the uncertain variables. This is accomplished through the explicit solution of the inner problem and the analytical integration overall product demand realizations. This problem representation and solution strategy result in savings of orders of magnitude over existing methods in computational requirements.
Understanding and applying the extrapolation properties of serial gray‐box models
Authors: Van Can Henricus J. L. , Te Braake Hubert A. B. , Dubbelman Sander , Hellinga Chris , Luyben Karel Ch. A. M. , Heijnen Joseph J. 
Published: April 2004

AbstractThere is a need for efficient modeling strategies that quickly lead to reliable models. In the serial gray‐box modeling strategy the inaccurately known terms in the macroscopic balance are modeled with a black‐box model structure such as a neural network. This way one efficiently obtains an accurate model with good extrapolation properties without the need to develop a rigorous white‐box model in which much more knowledge would be involved and without the need to do many identification experiments. Different types of extrapolation are specified and analyzed and they are related to the different parts of the serial gray‐box model structure. The strategy is demonstrated for modeling pH effects on the enzymatic conversion of penicillin G using real‐life data. The resulting serial gray‐box model is compared with a model from a more knowledge‐driven white‐box strategy and with a model from a more data‐driven black‐box strategy. The serial gray‐box modeling strategy is especially advantageous at the medium level of process operation, which is mainly concerned with the calculation of optimal condition for (bio)chemical processes.