bluuebunny/crossref_metadata_2025 huggingface dataset:
Power consumption and mass transfer in agitated gas‐liquid columns: A comparative study
Authors: Gagnon Hélène , Lounès Mustapha , Thibault Jules
Published: March 2009

Power consumption, gas holdup and oxygen mass transfer in agitated gas‐liquid columns have been studied for an air‐water system. Measurements have been carried out in a reciprocating plate reactor using five different types of perforated plates and in a stirred tank reactor with one, two and three Rushton turbines, a helical ribbon impeller with and without surface baffles. Each mixing vessel had an identical geometry with a working volume of 17 L. For reciprocating plate stacks, the gas holdup is a complex function of the perforation diameter, the frequency of agitation and the gas superficial velocity. For radial‐type mixing devices, the gas holdup increases more rapidly with the speed of rotation for the helical ribbon. The power imparted to the fluid by the mixing device is independent of the gas superficial velocity for the plate stacks and the helical ribbon impeller for a given frequency or speed of agitation whereas it decreases for Rushton turbines. The correlation of the power consumption obtained for all mixing devices plotted against the reciprocating frequency or speed of rotation to the third power shows a linear fit. KLa values were correlated very well with the power input per unit volume and superficial gas velocity for all mixing devices. At lower power input per unit volume, KLa is a function of only the gas superficial velocity. At higher input power per unit volume, KLa increases rapidly with an increase in the intensity of agitation. Reciprocating plates with larger diameter perforations led to higher KLa values whereas the lowest KLa were obtained with the helical ribbon impeller. Correlations for one and three Rushton impeller assemblies were almost identical whereas measured KLa were much higher for the two‐impeller assembly due to the presence of a highly mixed zone in the vicinity of the dissolved oxygen probe.
Unsuspended mass of solid particles in stirred tanks
Authors: Brucato Alberto , Brucato Valerio
Published: March 2009

An original technique for the determination of the fraction of unsuspended solid particles at agitation speeds smaller than Njs, is proposed. The technique is based on the “twin‐systems” concept and is completed by a suitable tracing and detection technique for the solid phase. Results obtained with a fully baffled tank stirred by a Rushton turbine impeller show that the fraction of solids never leaving the tank bottom can be simply correlated to the ratio between agitation speed and Zwietering's complete suspension speed. It is shown that at agitator speeds of about 80% of Zwietering's complete suspension speed, practically all particles but a few, are already suspended. This finding implies that large energy and installation cost savings can be achieved, with respect to current design practices, without significantly affecting the solid‐liquid mixing performance.
Agitation power for solid‐liquid suspensions containing large particles
Authors: Bubbico Roberto , Cave Sergio Di , Mazzarotta Barbara
Published: March 2009

The agitation power required by liquid‐solid suspensions of large PVC discs (4.3 mm) and sand granules (1.29 mm) in water was measured for various solids concentration, up to 16% by volume, using 5 different impellers. In all cases the dispersed power increased with increasing solids content, more than expected based on the suspension density. The solid phase actually dissipates energy due to particle‐liquid friction and in the collisions of the particles. The amount of energy dispersed according to these mechanisms is generally low, but becomes evident with the large particles as the solid concentration increases above 4%.
Calculation of the particle size distribution in suspension polymerization using a compartment‐mixing model
Authors: Vivaldo‐Lima Eduardo , Wood Philip E. , Hamielec Archie E. , Penlidis Alexander
Published: March 2009

A modelling strategy for effective estimation of the particle size distribution (PSD) in suspension polymerization is presented. The strategy consists of coupling a population balance equation (PBE) and a compartment‐mixing (CM) model to account for the non‐homogeneous mixing in the tank reactor. The values for the rate of energy dissipation of each compartment are estimated from Computational Fluid Dynamics (CFD) calculations and experimental reports on systems with the same agitator and geometric characteristics. Model predictions using the CM model are compared with predictions that assume homogeneous mixing and experimental data on PSD from styrene and divinylbenzene pilot‐plant suspension polymerization reactors of 1 and 5 L with Rushton and PBT impellers.
Effect of blade pitch on the structure of the trailing vortex around rushton turbine impellers
Authors: Lu Wei‐Ming , Yang Bing‐Shiou
Published: March 2009

Effect of blade number on the structure of the trailing vortex around the Rushton turbine impeller is examined by analyzing the data of mean velocities, deformation rates, turbulent kinetic energy and energy dissipation rates for 2‐, 4‐, 6‐ and 8‐straight blades disk turbine impellers in a baffled standard geometry stirred tank. The data of Sauter mean bubble diameter near the blade tip are combined with the turbulent characteristics around the vortex to discuss how the blade number and the strength of the vortex affect the performance of the gas dispersion around the Rushton turbines under a low gassing rate. The results of this analysis show that if power input per each blade is the same, the impeller having four blades not only has the strongest average mean deformation rates and the largest turbulent kinetic energy, but also disperses the smallest average bubbles under the same gassing rate.
A study of an up‐ and a down‐pumping wide blade hydrofoil impeller: Part I. LDA measurements
Authors: Mishra Ved P. , Dyster Kate N. , Nienow Alvin W. , Mckemmie Jack , Jaworski Zdzislaw
Published: March 2009

A wide blade, high solidity ratio, axial flow hydrofoil impeller has been developed particularly for gas dispersion when used in the upward‐pumping mode. It has a low power number so that a relatively low torque is required when using it with a large impeller to tank diameter ratio, a commonly desired aim of retrofitting. As part of the work characterising these impellers, laser Doppler anemometry has been used to study the single phase flow both down‐ and up‐pumping, the latter for the first time. Mean and root‐mean‐square velocities were measured throughout a fully baffled, flat bottomed cylindrical tank. When down‐pumping, the discharge flow was almost axial but when up‐pumping, it had a strong radial component. Turbulence energy dissipation rates in the impeller region and the discharge stream when up‐pumping were found to be higher than those when down‐pumping. In both modes, the impeller was found to have a high circulation efficiency. In Part II, the data presented here are used for obtaining computational fluid dynamic solutions of the flow field.
Numerical prediction of wall mass transfer rates in turbulent flow through a 90° two‐dimensional bend
Authors: Bergstrom Donald J. , Bender Trevor , Adamopoulos George , Postlethwaite John
Published: March 2009

The present paper reports a numerical study of mass transfer in a curved channel flow using a low Reynolds number k–ε model modified to include the influence of curvature on the turbulent transport. Predictions were obtained of flow through a 90° 2‐D bend for Reynolds numbers of Re = 2 × 104, 105 and 106, curvature ratio's of Rc/d = 1, 1.5 and 3, and Schmidt numbers of Sc = 500, 1 500 and 5 000. Based on the numerial simulations, the value of the mass transfer coefficient, k, was observed to generally decrease and increase along the inner and outer walls, respectively, compared to the value in a straight duct. The behaviour appears to be sensitive to both the curvature ratio and Reynolds number, being most pronounced for the case of tight bends and low Reynolds numbers.
The solubility of methane in aqueous solutions of monoethanolamine, diethanolamine and triethanolamine
Authors: Carroll John J. , Jou Fang‐Yuan , Mather Alan E. , Otto Frederick D.
Published: March 2009

The solubility of methane in 3 kmol/m3 solutions of monoethanolamine, diethanolamine, and triethanolamine was measured from 25° to 125°C and pressures up to about 13 MPa. Measurements were also made for the solubility of methane in water at 25° to 125°C and pressures up to 18 MPa in order to confirm the accuracy of the experimental technique. It is demonstrated that methane is more soluble (in terms of mole fraction) in the amine solution than in pure water. Furthermore, the solubility is an increasing function of the size of the alkanolamine. The solubility data were modeled using a Henry's‐law approach and the results summarized in terms of salting‐in coefficients.
Application of iterative dynamic programming to optimal control of a distiltation column
Authors: Fikar Miroslav , Latif Abderrazak M. , Fournier Frantz , Creff Yann
Published: March 2009

Iterative Dynamic Programming (IDP) is proven to be a useful technique for solving constrained dynamic optimisation problems. A high purity binary distillation column model has been chosen to investigate some of the IDP properties as well as its applicability. The investigated problems cover transitions from one steady state to another with the minimization of a quadratic cost function with associated terminal constraints.
Two‐liquid flotation of fine oxide particles with 8‐hydroxyquinoline
Authors: Kusaka E. , Maegawa K. , Nakahiro Y. , Fukunaka Y. , Ninae M.
Published: March 2009

The two‐liquid flotation of fine oxide particles has been investigated using a chelating‐type collector of oxine and the isooctane‐water two‐liquids system. The recovery was enhanced in a certain pH range. The oil‐floatability during two‐liquid flotation was concerned with the oxine adsorption on the solids. In addition, solution‐chemical calculations indicated that the reactivity of the metal cation with oxine based upon a surface precipitation model was closely related to the adsorbability of oxine and, hence, to the oil‐floatability of the solids. Also, the possible conditions for collection by two‐liquid flotation were experimentally determined and were related to the solution‐chemical criterion.
Heat transfer between FCC catalyst and an electrically heated horizontal cylinder in a circulating fluidized bed
Authors: Courbariaux Yann , Pugsley Todd , Couturier Michel
Published: March 2009

The heat transfer coefficient between a suspension of FCC particles and a horizontal cylindrical heat transfer probe inserted into the riser or the standpipe of a CFB has been quantified. With the heat transfer probe located in the riser 4.75 meters above the L‐valve, and solids mass flux varied between 0 to 100 kg/(m2·s), the heat transfer coefficient ranged from 70 W/(m2·K) to 475 W/(m2·K). On a plot of heat transfer coefficient versus solids mass flux, three zones have been identified, which correspond to the difference in the flow structure of the solids around the heat transfer probe as the solids mass flux increases. Also, measurements were taken of the radial solids flux in two orthogonal directions using an isokinetic sampling system. The data shows the asymmetry due to the perturbations introduced by the heat transfer probe. Finally, the heat transfer in the downcomer was investigated. It has been found that the magnitude of the heat transfer coefficient in the downcomer is dominated by the solids flux; variation in gas bypassing in the standpipe has little effect. Results obtained by traversing the heat transfer probe across the diameter of the standpipe suggest that the heat transfer coefficient is nearly independent of radial position within the standpipe.
Characterization of gas fluidized beds of group C, A and B particles based on pressure fluctuations
Authors: Bai Dingrong , Grace John R. , Zhu Jing‐Xu
Published: March 2009

Pressure fluctuation data were obtained with a quick response transducer at a sampling frequency of 100 Hz for periods of 100 s (i.e. 10,000 points) in order to characterize the gas‐solid flow behaviour of fluidized beds of six powders. For beds of Geldart group B and group A particles, the occurrence and movement of bubbles caused vigourous pressure fluctuations of relatively large scale and weak dominant frequency. For beds of group C particles, on the other hand, pressure fluctuations were significantly smaller in scale and exhibited large dominant frequencies, with no clear formation of bubbles. The standard deviation of pressure fluctuations was markedly higher for the group A particles than for the group C powders. Group C particles could be characterized by gas voids and channels which exhibit periodic behavior, while beds of group A and B particles behaved in a less periodic manner and were dominated by more random and intensive bubble motion. Chaotic time series analysis was carried out for the six different species of particles. The Hurst exponent demonstrated differences between the three different powder groups. The two‐phase character of gas‐solids flow was more distinguishable for the group B and A powders than for the group C powders.
Kinetics of acetalization of perfumery aldehydes with alkanols over solid acid catalysts
Authors: Yadav G. D. , Pujari A. A.
Published: March 2009

Abstract temporarily removed. Please refer to PDF file.
Pressure losses in orifices for the flow of gas‐non‐newtonian liquids
Authors: Samanta Arun Kumar , Banerjee Tapan Kumar , Das Sudip Kumar
Published: March 2009

An investigation has been carried out to evaluate the two‐phase pressure drop for gas‐non‐Newtonian liquid flow across orifices. The method of dimensional analysis was used to correlate the experimental data. The correlation developed predicts the two‐phase frictional pressure drop across the orifices with acceptable statistical accuracy.
The effects of temperature and viscosity on glucose diffusivity through saccharomyces cerevisiae biofilms
Authors: Converti Attilio , Zilli Mario , Arni Saleh , Di Felice Renzo , Del Borghi Marco
Published: March 2009

The present study helps us to understand the effects of temperature and viscosity on bioprocesses in immobilized cell bioreactors. Glucose diffusivities through Saccharomyces cerevisiae biofilms are experimentally investigated at variable biofilm thickness, temperature, and concentration of carboxymethylcellulose (CMC) used as viscosity‐raising additive. Comparing these experimental values with those for free diffusion of glucose in water shows us that biofilm strongly reduces diffusivity (about 74%), mainly due to a decrease in the effective diffusion area. Only a slight increase in diffusivity is observed when biofilm thickness is increased. In addition, the results obtained in this work demonstrate that the well‐known empirical equations of Wilke and Chang, and of Guzman and Andrade can be combined to a relationship which takes into account the simultaneous effects of temperature and viscosity on the effective glucose diffusivity. This equation appears to be valid in glucose aqueous solutions whether or not biofilm is used, whereas it is not applicable when viscosity‐raising additives, such as CMC, are used.
An experimental study of double‐to‐single‐loop transition in stirred vessels
Authors: Montante G. , Brucato A. , Lee K. C. , Yianneskis M.
Published: March 2009

The velocity characteristics of the flows in a fully baffled vessel of diameter T = 290 mm stirred by a Rushton impeller of diameter D = T/3 were investigated by means of laser‐Doppler anemometry measurements. The effects of clearance and rotational speed on the flow patterns in the vessel were studied. It was found that at impeller clearances from the bottom of the vessel (C) around 0.2 T the characteristic double‐loop flow pattern undergoes a transition to a single‐loop one with the impeller stream direction becoming partly axial and being inclined at around 25 to 30° to the horizontal. The impeller stream inclination varied with radial distance from the impeller, as well as with angular position between blades (blade angle). Impeller speed was found to have no effect on the flow pattern or the mean velocities and turbulence levels normalized by Vtip for C/T > 0.20 or C/T ≤ 0.15. The flow structure measured with C = 0.15T is described in detail and the implications of the data for fluid mixing in stirred vessels are discussed.
Theoretical and experimental analysis of methane steam reforming in a membrane reactor
Authors: Madia Giuseppe S. , Barbieri Giuseppe , Drioli Enrico
Published: March 2009

Thermal effects on methane steam reforming process were analyzed, in a Pd‐Ag (23wt%) membrane reactor as a function of several parameters, such as temperature, reactant and sweep‐gas flow rate, and reactant molar ratio. Heat transfer from the oven was very important for the outlet methane conversion, which also depends on the temperature profile along the reactor. In particular, when the reactant flow rate was high the conversion degree decreased because the energy supplied was not sufficient to maintain the temperature in the reactor. A non‐isothermal mathematical model was presented which reproduced the experimental data.
Optimization of air distribution in direct reduction process in rotary kilns
Authors: Ramakrishnan V. , Sai P. S. T.
Published: March 2009

An algorithm for optimization of the air distribution in direct reduction process in rotary kilns akin to the SL/RN process is proposed, based on Pontryagin's continuous maximum principle. The optimum air distribution has been obtained for given operating conditions. The optimum air distribution has been found to have a definite pattern with small changes due to variation in process conditions. Air distribution has been found to be the most important parameter, which could be suitably chosen to obtain desired operating conditions. The influence of operating parameters, such as iron and carbon concentration in the charge, oxide and coal reactivity, have been studied and the process behaviour has been analyzed. Performance of the process has been observed to improve for an increase in oxide and coal reactivity and iron and carbon concentrations in the charge.
Mixing in multiple‐impeller stirred tank reactors with boiling liquids
Authors: Dohi Naoki , Matsuda Yukimasa , Itano Norihiro , Shimizu Kazuhiro , Wa Kimio Mineka , Wase Yoshinorika
Published: March 2009

Mixing in a boil‐off mechanically stirred tank reactor with multiple impellers was examined. Power consumption and gas hold‐up were measured in boiling water in a 0.2 m i.d. stirred tank reactor with three four‐pitched blade downflow disk turbines. Vapour was generated from both the immersed ring heater and the impellers. At low vapour generation rates, vapour was mainly generated from the impellers rather than from the heater, whereas nucleation occurred at the heater instead of the impeller at higher vapour generation rates. The mechanical power consumption decreased due to vapour generation. The change in boiling‐to‐non‐boiling mechanical power ratio with varying impeller rotational speed and boiling rate was complicated and not monotonous except at higher impeller speeds and boiling rates. The gas hold‐ups increased with increasing vapour generation rate but were rather small as compared to those in cold gas dispersing systems. Empirical correlations for power consumption and gas hold‐up in boiling liquids were developed using the present experimental data.
kL a correlation established on the basis of a neural network model
Authors: Yang He , Fang Bais. , Reuss Matthias
Published: March 2009

A kL a correlation has been developed with the aid of a neural network model. The neural network model has served as a non‐linear relationship performer correlating the volumetric mass transfer coefficient kL a in stirred tank reactors with the operating conditions, reactor geometry and material properties. In order to achieve an optimum correlation, experimental data taken from different sources have been used to train the network. The correlation obtained in this way is able to predict kL a in stirrer tanks reasonably well, if the operating conditions, reactor geometry and material properties fall into the trained ranges. Although the experimental data were widely spread and could only be fitted to individual correlations, the neural network is in a position to give a general correlation for all the data.
Polyethyleneimine‐containing sol‐gels as novel sorbents for the removal of cadmium from aqueous solutions
Authors: Bahrami Shirin , Bassi Amarjeet S. , Yanful Ernest
Published: March 2009

The removal of cadmium ions from aqueous solutions is described using polyethyleneimine (PEI) entrapped in sol‐gel matrices. The process is optimized with respect to operating conditions and both sorption and desorption are considered. The sorption process followed the Langmuir isotherm, and the corresponding Langmuir constants qmax and Kdwere found to be 80.64 mg Cd2+/g PEI and 236.36 mg/L, respectively, using the immobilized PEI polymer. More than 90% of the cadmium could be recovered in 2 h using 2 M NaCl solutions. This technique has potential applications in the recovery of cadmium in aqueous waste streams.
Performance assessment of processes with abrupt changes of disturbances
Authors: Huang Biao
Published: March 2009

This paper is concerned with feedback controller performance assessment of time‐variant processes due to abrupt changes of disturbances. It is shown that in addition to minimum variance control, alternative performance benchmarks that are more suitable for time‐variant processes can be found from routine operating data. Three types of performance assessment problems and their solutions are discussed. The proposed methods are illustrated through a simulated example as well as a case study on Shell distillation column data.
The fouling of alloy‐800 heat exchange surfaces by magnetite particles
Authors: Basset Mark , Mcinerney Jeff , Arbeau Norm , Lister Derek H.
Published: March 2009

The deposition of magnetite particles from suspension in water at nominally 90°C onto Alloy‐800 surfaces has been studied by chemical and radiotracing techniques under various conditions of flow, chemistry and boiling heat transfer. The experiments indicated that, under non‐boiling conditions, mechanisms based on diffusion and thermophoresis control deposition while removal is negligible. For sub‐cooled boiling at a low rate, the trapping of particles by bubbles is important; at a high rate, deposition during micro‐layer evaporation dominates. Removal occurs during sub‐cooled boiling and is nicely described by a mathematical model in which it proceeds concomitantly with deposition.
Voidage and particle velocity profiles in a spout‐fluid bed
Authors: Pianarosa Denis L. , Freitas Luis A. P. , Lim C. Jim , Grace John R. , Dogan O. Murat
Published: March 2009

Detailed hydodynamic measurements have been obtained for fully cylindrical spout‐fluid beds of 1.3 mm, 1.8 mm and 2.5 mm glass beads in a fully cylindrical column of diameter 152 mm using three different types of optical fibre probes. The reallocation of up to 43% of the air to auxiliary air introduced through the conical base caused some decrease in spout voidages, but remarkably little change in spout diameter compared with spouted beds where there was no auxiliary air addition. Auxiliary air led also to some decrease in particle velocities in the spout and to a modest decrease in the net solids circulation rate.
Measurement and correlation of the individual ionic activity coefficients of aqueous electrolyte solutions of KF, NaF and KBr
Authors: Taghikhani Vahid , Vera Juan H. , Modarress Hamid
Published: March 2009

Ion selective electrodes were used to measure the activity coefficients of individual ions at 298.2 K in aqueous solutions of KF, KBr and NaF up to 3, 2 and 1 molal, respectively. The mean ionic activity coefficients of the electrolytes obtained from the values of individual ions show good agreement with values reported in the literature. The experimental results confirm that the activity coefficients are different for the anion and the cation in an aqueous solution of a single electrolyte. It is also confirmed that the deviation from ideality for each ion depends on its counterion. The Khoshkbarchi—Vera equation was used to correlate the experimental data.
Physical solubility of hydrogen sulfide in several aqueous solvents
Authors: Rinker Edward B. , Sandall Orville C.
Published: March 2009

The solubility of hydrogen sulfide in several aqueous solutions was measured over the temperature range 25°C to 60°C. The solvents investigated in this work include 0 to 50% aqueous solutions of polyethylene glycol, ethylene glycol, methyldiethanolamine and diethanolamine. The amine solutions used in this work were neutralized by the addition of hydrochloric acid in order to suppress the hydrogen sulfide reaction (H2S → H+ + HS−) so that only the physical solubility of hydrogen sulfide would be measured. The solubility data determined in this work are expressed in terms of Henry's law. The Henry's law constants found in this work were correlated well by a particularly simple empirical formula based on the molecular weight of the solvent.
Nonlinear control of competitive mixed‐culture bioreactors via specific cell adhesion
Authors: Kurtz Michael J. , Henson Michael A. , Hjortsø Martin A.
Published: March 2009

A nonlinear control strategy is developed for competitive mixed‐culture bioreactors in which two cell populations compete for a common growth limiting substrate. A stream is periodically removed from the reactor, and the two cell populations are separated using specific cell adhesion. The steady state corresponding to the desired population fraction is stabilized by discarding faster growing cells and recycling slower growing cells to the reactor. The recycle loop must be operated periodically to allow regeneration of the adhesion column after each separation. As a result, the manipulated input is chosen as the sampling interval during which material is removed from the reactor. The nonlinear controller is designed using a simplified dynamic model that assumes continuous separation of the cell populations. The controller is implemented by calculating the sampling interval that leads to the same amount of material being removed from the reactor as that computed from the continuous control law. A nonlinear, closed‐loop observer is used to generate one‐time‐delay‐ahead predictions of the measured cell concentrations and the unmeasured substrate concentration. The efficacy of the proposed control strategy is evaluated via simulation.
Étude de l'influence de l'évaporation d'un bac d'eau sur les transferts dans un canal corrugué
Authors: Maamir Seghir , Zeghmati Belkacem , Hadjadj Ahmed , Rondot Daniel
Published: March 2009

Les auteurs présentent une étude numérique et expérimentale des transferts qui s'effectuent par convection forcée dans un canal comportant une protubérance sinusoîdale et par convection naturelle dans un bac d'eau. L'étude numérique a été effectuée pour des nombres de Reynolds compris entre 35 et 350, plusieurs densité de flux de chaleur et pour des amplitudes de la protubérance comprises entre 0.005 et 0.02 m. Les résultats montrent que la diffusion de la vapeur d'eau dans l'air modifie le profil des lignes de courant qui devient convexe au‐dessus de la surface libre de l'eau. En outre, l'evaporation atténue la perturbation engendrée par la protubérance et augmente les transferts de chaleur dans le canal. La visualisation de l'ecoulement, réalisée à l'aide d'un générateur de fumée d'encens, d'un laser à argon et d'une caméra vidéo à mis en évidence la complexité de l'interaction entre le flux de vapeur engendré par l'évaporation de l'eau du bac, l'écoulement de l'air dans le canal et les déperditions de chaleur à travers les parois latérales. Les résultats théoriques et expéri‐mentaux sont en bon accord qualitatif.
A generalized correlation of solute inclusion in ice formed from aqueous solutions and food liquids on sub‐cooled surface
Authors: Chen Ping , Chen Xiao Dong
Published: March 2009

Solute inclusion in an ice layer formed on a smooth stainless steel surface under sub‐cooled flow conditions has been studied experimentally. The effects of ice growth rate, solution velocity and bulk concentration of solute on the solute inclusion in the ice layer have been investigated using a controlled flow surface crystallizer (CFSC). For several aqueous solutions (sucrose, NaCI, glycol, fructose), food liquids (skim milk, whole milk, orange juice) and particulate suspension (potato starch particles), the effective molecular weights were calculated and their effects on solid inclusion determined. This effect was then conveniently related to the freezing point depression (FPD) of each liquid tested. A generalized empirical correlation has been established for all the liquids tested.
Neural network‐based optimal iterative controller for nonlinear processes
Authors: Gao Furong , Wang Fuli , Li Mingzhong
Published: March 2009

A new optimal iterative neural network‐based control (OINNC) strategy with simple computation and fast convergence is proposed for the control of processes with nonlinear dynamics. The process dynamics is captured by a forward neural network, and the control is determined by a simple iterative optimization during each sampling interval based on a linearized neural network model. In addition, a feedback control is incorporated into the system to compensate for any model mismatches and to reject disturbances. With the proposed system, the tracking error is shown to be confined to the origin. An application of the proposed OINNC scheme to a nonlinear process results in superior performance when compared with a well‐tuned conventional PID controller.
RTD studies in a falling film graphite evaporator with internal spiral fins: Influence of the geometry
Authors: Bessenet Sébastien , Renaudin Viviane , Leclerc Jean‐Pierre , Hornut Jean‐Marie
Published: March 2009

A hydrodynamic study of a new graphite evaporator has been performed. In this exchanger the fluid flows as a thin film on a spirally wound fin which forms a spiral staircase inside a tube. The slope θm of the spirally wound fin is modifiable. The residence time distribution (RTD) of the film was measured for different fin slopes θm and several film flowrates mf. The flow pattern was then modelled thanks to the DTS software as a cascade of perfect mixed cells and the mean residence time τm was calculated. The evolution of τm as a function of θm and mf is accurately represented by a power law relation.
One‐ and two‐phase isochoric heat capacity measurements of aqueous solution of nacl near the critical point of pure water
Authors: Abdulagatov Ilmutdin M. , Dvoryanchikov Vasilii I. , Kamalov Abdurakhman N. , Abramova Elena G. , Abdurashidova Madina A.
Published: March 2009

Isochoric heat capacities of H2O+NaCl solutions (0.0031 and 0.0063 mole fraction of NaCl) were measured with a high temperature and high pressure adiabatic calorimeter near the sub‐critical and near the supercritical point of pure water. Temperatures ranged from 361 to 677 K. Measurements were made at six densities, namely: 367.07 and 485.59 kg·m−3 for x = 0.0031 mol fraction of NaCl and 388.65, 560.03, 607.05, and 973.70 kg·m−3 for x = 0.0063 mol fraction of NaCl. Measurements were conducted in the two‐and one‐phase regions including near phase transition temperatures TS(ρ). The phase transition temperatures TS(ρ) and saturated isochoric heat capacity values CVX have been determined for each isochore. The uncertainty in heat capacity measurements is estimated to be 3.5% to 4.5% near the phase transition and critical points. Present and previous results of heat capacity measurements were compared with predictions from the crossover (CREOS) and Pitzer—Tanger–Hovey equations of state (PTH EOS). Our previous heat capacity measurements were found to deviate systematically from crossover‐model predictions. The present results show good agreement with the crossover model for the composition x = 0.0031 mol fraction.
Improving the simplified‐perturbed‐hard‐chain theory equation of state using a new non‐attracting hard‐sphere equation
Authors: Nasrifar Kh. , Ayatollahi Sh. , Moshfeghian M.
Published: March 2009

In this research a new simple non‐attracting hard‐sphere equation is introduced. The equation meets the ideal gas and close‐packed limits and is in accordance with computer simulation data with reasonable accuracy. When this equation is used with the simpli‐fied‐perturbed‐hard‐chain theory equation of state, improvements on the calculation of vapour pressure and saturated liquid density of pure compounds are observed. For 35 pure compounds of different classes, the averages of absolute error are 3.31% and 4.20% for the calculation of vapour pressure and saturated liquid density, respectively. The respected errors for the original equation of state are 3.53% and 4.96%, respectively. Moreover, the use of the new hard‐sphere equation in place of the Carnahan‐Starling equation in the simplified‐perturbed‐hard‐chain theory equation of state, does not have any appreciable effect on the prediction of K factors in VLE calculations.
Esterification of ethanol with sulfuric acid: A kinetic study
Authors: Theodore Shammi , Sai P. S. T.
Published: March 2009

Experiments were conducted in a stirred batch reactor under isothermal conditions for obtaining kinetics of the esterification reaction between ethanol and sulfuric acid. Reactive adsorption technique was employed to enhance the conversion. Anhydrous sodium sulfate was used as an adsorbing agent to remove the water formed during the reaction. The variables include the mole ratio of ethanol to sulfuric acid, reaction temperature, purity of the reactants, and the amount of adsorbing agent. The reaction was found to be reversible and second order at low mole ratios, and irreversible and first order at high mole ratios. The kinetic parameters of the rate law were estimated. A possible reaction mechanism was proposed and validated with the experimental data. The effect of the mole ratio of reactants, anhydrous sodium sulfate loading, and purity of the reactants on the yield of ethyl hydrogen sulfate was studied, using full‐factorial search and optimized conditions were obtained by the method of steepest ascent. More precise optimum conditions were obtained using the Box‐Wilson composite method.
An accurate model for prediction of gas hydrate formation conditions in mixtures of aqueous electrolyte solutions and alcohol
Authors: Javanmardi Jafar , Moshfeghian Mahmood , Maddox Robert N.
Published: March 2009

A new thermodynamic model for calculating the hydrate formation temperature of different hydrate formers in aqueous solutions of both electrolytes and a single alcohol has been presented. This method uses a generalization of the Aasberg‐Petersen model for water activity. For calculation of water activity in the presence of electrolytes, the effect of alcohols was taken into account without using any new fitting parameters. The results are in good agreement with published experimental data. Calculated values of the hydrate formation temperature in the presence of alcohols and electrolytes are compared with those obtained by other existing models. The average absolute error of hydrate formation temperature for 524 available experimental data points is about 0.87 K.
On the costs of parameter uncertainties. Part 2: Impact of EVOP procedures on the optimization and design of experiments
Authors: Pinto José Carlos
Published: March 2009

Pinto (1998) showed that an economical value might be assigned to model parameter uncertainties, which could be used for process optimization and for taking decisions during sequential experimental designs. The procedure is extended to take into account the fact that plant operation conditions change with time, leading to improvements of the plant operation and allowing the partial recovering of losses introduced by uncertain parameters during plant design. It is shown that the use of EVOP (Evolutionary Operation Procedures) during plant operation may reduce the cost of parameter uncertainties, exerting a major impact on process optimization and optimal design of experiments.
On the use of heat belts for energy integration across many plants in the total site
Authors: Bagajewicz Miguel , Rodera Hernàn
Published: March 2009

Indirect heat integration across plants using intermediate fluids is, in many cases, a preferable alternative to direct integration. Previous work has discussed the use of independent circuits capable of transferring the maximum possible heat. Piping cost and the location of the plants were proven an important factor when intermediate fluids are used. This paper analyzes the concept of a ‘heat belt’ that consists of a single‐pipe circuit used to extract heat from and release it to the plants. Since a general model is MINLP, the analysis focuses on the particular case of three plants for which an MILP model can be formulated.
Morphological changes of human skin cells exposed to a DC electric field in vitro using a new exposure system
Authors: Méthot Stéphane , Moulin Véronique , Rancourt Denis , Bourdages Michel , Goulet Daniel , Plante Michel , Auger Francois A. , Germain Lucie
Published: March 2009

The human skin contains a physiological battery that could be implicated in the healing process, by creating an endogenous electric field. Skin cells undergo morphological changes in response to an external DC electric field (EF). We found that fibroblasts reorient their cell bodies in a manner perpendicular to the EF direction, for normal and above physiological intensities. Actin and tubulin filaments (cytoskeleton proteins) follow the same pattern of reorientation. Keratinocytes tend to elongate in the same direction, although to a lesser extent. The study of the response of human skin cells to an external EF is a first step toward a better understanding of the mechanisms involved in wound healing and eventually toward the improvement of wound repair.
Solid‐liquid mass transfer in a rotary drum
Authors: Parsons Trevor G. , Masliyah Jacob H. , Gray Murray R.
Published: March 2009

The solid‐liquid mass transfer coefficient for slurries agitated in rotating drums with baffles was measured using the dissolution of β‐naphthol as a tracer in silica sand slurries. The effects of drum rotation rate (0.33 to 15 min−1), slurry holdup (4.4% to 17%) and solids volume fraction (0 to 0.62) on the solid‐liquid mass transfer were investigated with a slurry particle diameter of 4.6 × 10−4 m. Mass transfer coefficients were corrected for the effect of particle shrinkage due to dissolution of the tracer. The mass transfer coefficient increased with increasing rotational speed of the drum from 0.005 to 0.045 mm.5‐1. Two types of slurry motion were observed; well mixed slurry flowing over the baffles and segregation of solids on the baffles. The mass transfer coefficients from the present study, along with literature data, correlated with the Froude number to the 0.36 power, for Froude numbers from 10−6 to 10−1.
Kinetic analysis of phenol adsorption from aqueous systems
Authors: Mijangos Federico , Navarro Ana , Jodra Yolanda
Published: March 2009

The kinetic adsorption of mixtures of phenolic compounds onto a polymeric adsorbent from aqueous solutions was studied. Experimental data for single‐component solutions were obtained and fitted to a parallel diffusion model. Effective diffusion coefficients were related to liquid‐phase diffusion and surface diffusion. The effect of solute concentration and salinity on these parameters was also analysed. Van Laar's equation is proposed to evaluate the influence of concentration on diffusion. The adsorption kinetics for phenol and pcresol mixtures at different initial concentration ratios were determined and correctly adjusted to the mentioned kinetic model. Results confirm that adsorption from multicomponent aqueous solutions is a surface diffusion‐controlled process.
Quantitative multiplexed analysis of ErbB family coexpression for primary breast cancer prognosis in a large retrospective cohort
Authors: Giltnane Jennifer M. , Moeder Christopher B. , Camp Robert L. , Rimm David L.
Published: March 2009

BACKGROUND:

Assessment of outcome using a single prognostic or predictive marker is the current basis of targeted therapy, but is inherently limited by its simplicity. Multiplexing has provided better classification, but has only been done quantitatively using RNA or DNA. Automated quantitative analysis is a new technology that allows quantitative in situ assessment of protein expression. The authors hypothesized that multiplexed quantitative measurement of ErbB receptor family proteins may allow better prediction of outcome.

METHODS:

The authors quantitatively assessed the expression of 6 proteins in 4 subcellular compartments in 676 patients using breast carcinoma tissue microarrays. Then using Cox proportional hazards modeling and unsupervised hierarchical clustering, they assessed the prognostic value of the expression singly and multiplexed.

RESULTS:

Epidermal growth factor receptor (EGFR), HER‐2, and HER‐3 expression were associated with decreased survival. Multivariate analysis showed high HER‐2 and HER‐3 expression maintained independence as prognostic markers. Hierarchical clustering of expression data defined a small class enriched for HER‐2 expression with 40% 10‐year survival, compared with 55% using conventional methods. Clustering also revealed a similarly poor‐prognostic subgroup coexpressing EGFR and HER‐3 (but low for estrogen receptor, progesterone receptor, and HER‐2) with a 42% 10‐year survival.

CONCLUSIONS:

This work shows that the combined analysis of protein expression improved prognostic classification, and that multiplexed models were superior to any single‐marker–based method for prediction of 10‐year survival. These methods illustrate a protein‐based, multiplexed approach that could more accurately identify patients for targeted therapies. Cancer 2009. © 2009 American Cancer Society.
Serum high‐molecular weight adiponectin is related to early postprandial glycemic increases and gastric emptying in patients with type 2 diabetes mellitus
Authors: Iwase M. , Iino K. , Oku M. , Nohara S. , Asano T. , Doi Y. , Iida M.
Published: March 2009

Background

Postprandial hyperglycemia and hyperlipidemia are frequently associated with type 2 diabetes mellitus. The aim of the present study is to investigate the clinical determinants of postprandial glycemia and lipemia, especially serum high‐molecular weight adiponectin.

Methods

Twenty‐seven diabetic patients treated with diet alone and 13 healthy volunteers took liquid test meal containing 53 g carbohydrate and 47 g lipid, dosed with nonradioactive isotope 13C‐acetate. Venous blood and breath samples were obtained for 180 min after the meal. Gastric emptying was evaluated by peak excretion time of 13CO2 in the breath samples. Delayed gastric emptying was defined as peak excretion time > 2.5 h (mean + 2 SD in the healthy volunteers).

Results

Diabetic patients showed delayed insulin secretion, postprandial hyperglycemia and hyperlipidemia compared with control. Postprandial glycemic increases significantly correlated with enhanced gastric emptying. Serum high‐molecular weight adiponectin correlated with postprandial glycemic increases at 30 and 60 min after meal (r = 0.42, p < 0.05; r = 0.37, p < 0.05, respectively). Serum high‐molecular weight adiponectin also correlated with gastric emptying (versus peak excretion time r = − 0.58, p < 0.05). In addition, diabetic patients with delayed gastric emptying showed the suppressed postprandial glycemia with lower serum high‐molecular weight adiponectin than those with normal gastric emptying. On the other hand, postprandial increases in serum triglyceride were not related to serum high‐molecular weight adiponectin or gastric emptying, but significantly related to liver function test (serum transaminases) and body mass index.

Conclusions

Early postprandial glycemic increases were related to elevated serum high‐molecular weight adiponectin, which might be associated with enhanced gastric emptying. Copyright © 2009 John Wiley & Sons, Ltd.
Synthesis, Characterization, Electrochemical, and Optic Limiting Properties of Novel CoII, CuII, and Double‐Decker LuIII Phthalocyanines
Authors: Saydam Sinan , Yılmaz Engin , Bağcı Fulya , Yağlıoğlu H. Gül , Elmalı Ayhan , Salih Bekir , Bekaroğlu Özer
Published: March 2009

The synthesis, spectroscopic, electrochemical, and optical properties of tetrasubstituted CoII, CuII, and double‐decker LuIII phthalocyanines are reported. The new compounds were characterized by elemental analysis, IR and UV/Vis spectroscopy, and MALDI TOF mass spectrometry. Their electrochemistry was studied by cyclic voltammetry and Osteryoung square‐wave voltammetry in nonaqueous medium. Nonlinear absorption and optical limiting performance of peripheral‐substituted (C30H28N30)4Co (5), (C30H28N30)4Cu (6), and [(C30H28N30)4]2Lu (7) were investigated by the Z‐scan technique. Whereas 6 and 7 showed good nonlinear absorption, 5 did not. Optical limiting parameters of the ratio of the excited state to the ground state absorption cross sections κ, the effective nonlinear absorption coefficient βeff, the linear absorption coefficient α0, limiting threshold Fth, and the saturation density or energy density Fsat values were determined for 6 and 7. The results indicated that both compounds exhibited good optical limiting performances. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Mit Müsli die Welt verändern
Authors: Fritzen Florentine
Published: March 2009

Die Lebensreformer warben für naturnahes Leben. Passende Produkte gab es im Reformhaus. Heute ist die Bewegung Geschichte, doch hat sie das Gesundheitsbewusstsein geprägt
Positive modulation of AMPA receptors prevents downregulation of GluR2 expression and activates the Lyn‐ERK1/2‐CREB signaling in rat brain ischemia
Authors: Zhang Quan‐Guang , Han Dong , Hu Shu‐Qun , Li Chong , Yu Chang‐Zhou , Wang Ran , Zhang Guang‐Yi
Published: March 2009

α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid receptors (AMPARs) are responsible for excitotoxicity induced by ischemic injury in hippocampal CA1 neurons, whereas the molecular mechanisms responsible for their neurotrophic activities are much less studied. Here, we examined the neuroprotective effect of positive modeulation of AMPARs by coapplication of AMPA with PEPA, an allosteric potentiator of AMPARs. We showed that coapplication of AMPA with PEPA protected hippocampal CA1 neurons from brain ischemia‐induced death. Coapplication of AMPA with PEPA could prevent downregulated expression of GluR2 subunit caused by ischemia and increase BDNF expression via Lyn‐ERK1/2‐CREB signaling. Furthermore, TrkB receptor‐mediated PI3K/Akt signal pathway was activated after coapplication of AMPA with PEPA, which was related to MAPK pathway and protected CA1 neurons against ischemic insults through depression of JNK3 activity, release of cytochrome c to cytosol and depression of capase‐3 activity. Our results revealed that positive modulation of AMPARs could exert neuroprotective effects and the possible signaling pathways underlied. © 2009 Wiley‐Liss, Inc.