We have scrutinized the hydration and the potentials of mean force (PMFs) for the constituent ion pairs of tetramethylammonium chloride (TMA+Cl–) in ambient water at infinite dilution, using the blue moon ensemble method with molecular dynamics simulations, where the force fields and the simulation protocols were carefully selected because of their impacts on the resultant PMFs. As a result, it was found that (i) the PMF for the Cl––Cl– pair has two minima that correspond to the different solvent-separated solute pairs (SSSPs), (ii) the PMF for the TMA+–TMA+ pair shows a minimum that corresponds to an SSSP, whereas the contact solute pair (CSP) is unfavorable unlike that for the CH4–CH4 pair, and (iii) the PMF for the TMA+–Cl– pair has two broad minima that correspond to a CSP and an SSSP. We have also investigated how the treatments of electrostatics impact on the resulting PMFs, by performing the simulations with a truncation method as well as the Ewald method. The results will be compared with those from other simulations, the theoretical analyses, and the experiments.
The critical temperature, critical compressibility factor and the inversion temperature of cesium, rubidium and potassium are correlated through the generalized van der Waals equation of state. This three-parameter equation differs from the known van der Waals equation of state by the modified attractive term. For cesium, rubidium and potassium, the reduced inversion temperature and its ratio to the critical compressibility factor were estimated. The results of estimation were in agreement with experimental data. It has been established that cesium, rubidium and potassium obeyed the single-parameter law of corresponding states with the reduced inversion temperature or its ratio to the critical compressibility factor as the thermodynamic similarity parameter.
The reaction of 2,4,6-tribromophenol and α-bromoxylenes (o-, p- and m-) catalyzed by tetrabutylammonium bromide was carried out in an alkaline solution of KOH of low concentration/organic solvent two-phase medium. The concentration of tetrabutylammonium 2,4,6-tribromophenoxide (ArOQ) is constant throughout the path of reaction while more than 98% of the catalyst exists as tetrabutylammonium 2,4,6-tribromophenoxide (ArOQ) in the organic phase. The mass transfer resistance of ArOQ between the two phases is negligible compared to the rate of organic-phase reaction. The reaction in the organic phase is a rate-determining step. A pseudo-first-order rate law is proposed to express the kinetic data. The effects of potassium hydroxide, organic solvents, agitation speed, amount of aqueous-phase reactant (2,4,6-tribromophenol), amount of catalyst, organic-phase reactant (α-bromoxylene), inorganic salts and temperature on the conversion are investigated in detail. It is found that the reaction rate is not well-correlated to the polarity of the organic solvent. The solvolysis effect, which concerns with the polarity and Lewis-base of the organic solvents, is used to explain the characteristics of the reaction satisfactorily at low alkaline concentration. The stability of carbonium ions of different α-bromoxylenes is used to explain their reaction rates satisfactorily.
The time dependent drag reducing ability of a surfactant solution was investigated experimentally from the viewpoint of developing the surfactant solution as a drag reducing fluid in district heating systems. Aqueous solutions of a cationic surfactant were subjected to turbulent pipe flows continuously to induce degradation. The results show that surfactant solutions lose their drag reducing ability abruptly after a stable period. In this study, this phenomenon is named ‘break-down’ of drag reducing ability. In the broken-down solution large aggregates of surfactant and fragments of surfactant molecules were found. The loss of birefringence was also observed under high shear-flow. The break-down phenomenon appears to be caused by the lowering of effective micelle concentration caused by the precipitation of surfactant molecules and chemical reactions of surfactant molecules with dissolved oxygen at high temperature.
Thermal radiation dominates the heat transfer in an entrained bed type of coal or wastes gasification furnace operated in high temperature. This study is to evaluate the radiation properties of coal char or ash particles, which are necessary to predict the behavior of heat transfer of a multiphase flow in the furnace. The monochromatic extinction of the sample particles dispersed in carbon tetrachloride or KBr powder was measured spectroscopically under an atmospheric condition by using FT-IR. The spectra of extinction for any particle number density in a dispersion layer can be summarized in the form of the apparent extinction efficiency. The spectral extinction efficiency of fly ash was almost independent of the type of ash, but was influenced significantly by the carbon content in the char. The extinction efficiency measured was equivalent to the apparent extinction efficiency estimated by applying the refractive index from references in the past works into Mie’s theory assuming a strong forward scattering of fly ash particles.
The production of glucose 6-phosphate (G6P) and simultaneous carboxy-terminated PAMAM-bound adenine nucleotides regeneration by the conjugated enzymes, Bacillus stearothermophilus glucokinase (GK) and acetate kinase (AK), in a small batch reactor were investigated both theoretically and experimentally. As the cofactor, a new family of polymer-bound adenine nucleotides (ATP and ADP) was used which was prepared in our previous work (Abdelmoez et al., 2002) by binding native ATP or ADP to a carboxy-terminated polyamidoamine (PAMAM) dendrimer (polymer-bound ATP or ADP). The experimental time courses of the glucose conversion were in a good agreement with the theoretical predictions calculated using the rate equations of G6P synthesis catalyzed by B. stearothermophilus GK (Abdelmoez et al., 2004) and the simplified rate equation of polymer-bound ATP regeneration catalyzed by B. stearothermophilus (AK) which is proposed in the present work.
Removal of nitrogen oxides (NOx) using an ozonization and catalysis hybrid process was investigated. The role of the ozonization in the hybrid process is to increase NO2 content by oxidizing a part of NO, thereby leading to improving the performance of the catalytic reduction. It was found that the rate of the oxidation of NO to NO2 in the ozonization chamber was very fast in a temperature range of 443 to 473 K, almost completed in a few tens of milliseconds. The decomposition of ozone into molecular oxygen was not significant, and one mole of ozone approximately reacted with one mole of NO. In addition, a kinetic study revealed that the ozonization method produces a negligible amount of byproducts such as NO3 and N2O5. The effect of the content of NO2 in NOx on the catalytic reduction efficiency was examined by adjusting the degree of NO oxidation in the ozonization chamber. The selective reduction of NOx to N2 by a monolithic catalyst (V2O5-WO3/TiO2) was largely enhanced when the content of NO2 was equal to that of NO, indicating that the mixture of NO and NO2 reacts faster than NO.
Simultaneous purification of contaminated gas and water by using a cylindrical wetted-wall corona discharge reactor was proposed in this work. Gaseous acetaldehyde and aqueous phenol were chosen as target compounds. The gaseous acetaldehyde was continuously removed from gas stream by absorption into the aqueous phenol solution used for making a wetted-wall. Aqueous phenol and the absorbed acetaldehyde in water were effectively degraded by aqueous radicals, OH, produced by direct contact of gaseous corona with the interfacial water. In addition, ozone partly contributed to decompositions of phenol and some byproducts. The experimental results show that gaseous acetaldehyde can be completely removed from gas mixture when its inlet concentration was in a range of 30 to 200 ppm since decomposition of aqueous acetaldehyde can sustain the absorption of acetaldehyde. This concentration range of acetaldehyde scarcely affected the decomposition of phenol. However, decomposition of total organic carbon (TOC) in water was strongly attenuated when the acetaldehyde concentration is higher than 100 ppm. The influence of the solution pH ranging from 2 to 13 was also investigated.
To understand the mechanism by which titania (TiO2) nanoparticles are generated by a CVD method, the primary nucleation mode size distributions of TiO2 nanoparticles prepared from two different chemical precursors (TTIP and TiCl4) were directly measured using a DMA/PSM/CNC system. This represents the first report of such direct measurement in the nucleation mode. These results are particularly important for experimental investigation of particle nucleation and growth, something which has never been achieved before. In the nucleation mode, titania nanoparticles with a diameter of about 2 nm were produced by nucleation. At low reactor temperatures, nucleation and surface reaction were major contributors to particle generation. At a high reaction temperature, coagulation and sintering became more important. The morphology and crystallinity of the particles were investigated by TEM and XRD as a function of temperature and precursor concentration. The properties of the titania nanoparticles, such as particle size distribution, the morphology and crystallinity, changed as a function of reaction temperature and chemical reaction rate.
Hybrid differential evolution is applied to estimate the kinetic parameters of batch polymerization described by differential-algebraic equations. The dynamic behavior of the system consisted of the concentrations of the first and second initiators, the monomer conversion, the zeroth, first and second moments of dead polymer distributions and the total concentration of live polymer. The moments of dead polymer distributions and the total concentration of live polymer were in general difficult to measure in a real process. In this study, we considered that the estimation criterion consisted of some measurable data such as the concentrations of the first and second initiators, the monomer conversion, and the degree of polymerization and polydispersity. We used the worst observed error for all experiments as an objective function so that the parameter estimation problem becomes a min-max estimation problem. Several techniques were also employed to handle the estimation of kinetic parameters for comparison. Hybrid differential evolution could use five individuals to obtain a more satisfactory solution.
In order to predict the normal states of a continuous process with load fluctuations, a nonlinear modeling technique using historical data during normal operations has been proposed. This technique is called DB (database) modeling because historical data during normal operations are accumulated in the database and are used directly for the predictions. The prediction procedure using the DB model is quite simple; it simply searches for similar records to the inputs to the DB model and averages the outputs from the DB model. In advance, it is only necessary to calculate the distances between the records accumulated in the database in order to determine the reference distance used for searching for similar records to the model inputs. The DB model was demonstrated using experiments involving a tank-pipeline system.
A novel decentralized temperature controller is designed for a tubular packed bed reactor. The method estimates the concentration distribution of each component in the reactor as well as the temperature distribution. The estimated distributions of concentrations are integrated in a feedback control of temperature distribution in the reactor. The method was evaluated by experiments and showed good performance in the control of temperature distribution. Excellent agreement between estimated and measured outlet concentrations are also observed.
A mathematical model using the Weibull distribution that characterizes the fate of virus-infected insect cells to conduct viral replication and subsequent recombinant protein synthesis and finally to die due to the progress of viral infection is presented. This model also takes into account the degradation of synthesized protein due to intrinsic denaturation and/or proteolytic hydrolysis. Model parameters were determined from the literature and based on experimental data. The model agrees well with the experimental data from cultures under different infectious conditions. Model simulations of virus-infected insect cultures reveal the importance of the interaction of the cell density at time of infection and multiplicity of infection and the presence of the best time for harvesting.
A cylindrical wetted-wall reactor in which high-voltage corona discharge was generated in gaseous space was applied to decompose phenol dissolved in water. It was found that the decomposition efficiency depends on current and current-density. When the current density was decreased by extending the axial corona region length at a constant current, electron efficiency decreased with the increase of corona region length in the range of relatively low discharge current, while this trend was reversed in the range of high discharge current. Experiments with varied applied voltages by the use of varied cathode diameters suggested that these reversed trends can be explained as follows. (1) The effect of increasing voltage at increasing current density, which increases the reactive radicals, becomes significant at the relatively low current condition. (2) At the high current condition, the voltage becomes excessively high so that ion-wind will disturb the uniformity of the discharge due to a waving water surface. Nevertheless, the condition with relatively low voltage by the use of long discharge region length and thin cathode diameter leads to high energetic efficiency in all discharge current ranges examined here.
Nitrification performance of a nitrifying biofilm attached on silicone hollow fiber membrane was evaluated. The nitrogen surface loading was increased from 2.32 to 9.28 g/m2d in steps with the membrane-attached biofilm that was operated at an inlet air pressure of 98 kPa and hydraulic retention time of wastewater of 12 h. The nitrification rate of about 8.0 g/m2d was simultaneously obtained with the nitrification efficiency of about 90%. The results clearly demonstrated that the oxygen supply from the bottom of biofilm through an oxygen permeable silicone membrane largely contributed the nitrification performance and that the nitrification performance of the membrane-attached nitrifying biofilm was far superior to the conventional fixed biofilm processes.
In earlier work we demonstrated that in the presence of an external periodic force, the rheological parameters of slender rods in simple shear flow vary chaotically for a certain range of parameters. Algorithms are available in the literature to control the chaotic dynamics of these rheological parameters onto periodic solutions. In earlier work, we also showed that upon including hydrodynamic interactions between the particles, we can extend the range of parameters of the suspension in which the rheological parameters vary chaotically. This result suggested that we try to determine the effect of hydrodynamic interactions in the semi-dilute limit on control of chaos in the rheological parameters. We present numerical evidence that inclusion of hydrodynamic interactions in the semi-dilute regime greatly increases the difficulty of control of chaos. This suggests that inclusion of hydrodynamic interactions could lead to considerably different results when compared to dilute suspensions and thus it may be necessary to include these effects in simulations of moderately concentrated suspensions.