This paper reports time-dependent flow characteristics of a turbulent water jet impinging vertically upward upon a water-air interface. Mexican-hat wavelet transform was applied to the time-dependent velocity fluctuations obtained in the region near to the air-water interface in order to analyze spatiotemporal turbulent structure at different time scales. The further understanding of the physical meanings of the wavelet transforms was tried by the analysis using logarithmic expectation and information entropy of information theory. It has been found that the near-interface turbulent structure is constituted not only by the impingement of the large-scale structure of the approaching turbulent jet but also by the time-dependent deformation of the surface bump. Time-series images of the surface bump visualized by an argon laser sheet technique showed some periodical regulation of the surface bump coming from the large-scale structure of the impinging jet.
Characteristics of the laminar flow induced by reciprocating a disk impeller in a cylindrical vessel have been investigated by combining LDA velocity measurements with CFD calculations. From the variations of velocity fluctuation with Reynolds number, it is found that transition from laminar to turbulent flow takes place at Re = 2 × 102. The flow at 20 < Re < 2 × 102 is two-dimensional without producing tangential velocity component, and a vortex is generated behind the disk impeller. With increasing Reynolds number the center of the vortex departs from the disk edge and the vortex is elongated and strengthened in the rear region of the disk impeller. CFD calculations have been carried out for the case where the existence of the shaft is ignored. The velocity variations near the reciprocating disk are well represented by CFD calculations, which are symmetric between the upward and downward stroke except a small disk or small contraction of the flow through the gap. Influences of the narrow gap between the disk edge and the vessel wall and those of the shaft on the force acting on the disk are investigated by comparing the calculations with the measured data.
Velocity measurements have been conducted in order to examine characteristics of turbulent flow induced by reciprocating a disk impeller in a cylindrical vessel. Variations of the average velocity fluctuation show that the transition regime from laminar to turbulent flow is located at 2 × 102 < Re < 4 × 102. In turbulent flow regime, a circulating flow with radial and axial velocity components is generated in the rear region of the disk. At a moderate Reynolds number a secondary circulating flow is induced behind the original circulating flow, but at a sufficiently high Reynolds number the region of the original circulating flow elongates without generating such a secondary circulating flow. Trubulence level is much higher in the circulating flow region than in the front region of the reciprocating disk. The fluctuating velocity components in the radial, tangential and axial directions show similar periodic variations to each other irrespective of the magnitude of the Reynolds number, and the maximum fluctuating velocities attains about the same magnitude of the maximum disk velocity. The flow pattern and the magnitude of turbulence change violently during one cycle of reciprocation. In addition, at a sufficiently high Reynolds number, circumferential circulation of the fluid apperars in the front and rear regions near the disk, whose direction is opposite to each other. The excellent mixing performance of recipro-mixing in turbulent flow regime is reasonably explained by these findings.
An electrochemical reactor has been developed for the on-site electrochemical production of hydrogen peroxide. Comparison was made between a trickle-bed mode where gas and liquid phases flowed downward cocurrently in the graphite-felt cathode and a packed-bed mode where two phases flowed upward cocurrently. At the same flow condition of gas-liquid phase, the current efficiency Ce using the trickle-bed electrode was higher than that using the packed-bed electrode with gas-sparging. Mathematical analysis based on a three-phase bed model was made to fit the over-potential profiles in the cathode by using electrode kinetics and mass-transfer parameters, gas and liquid holdups in the bed, the effective conductivity of the solution phase and the effective surface area of electrode. The current efficiency Ce was affected by flow rates of gas and liquid, and the current density, because of the changes in the effective specific surface area aeff of electrode and liquid-solid mass transfer coefficient kmA of oxygen onto the electrode. In this experiment, Ce was increased mainly by increasing aeff rather than kmA. Using the trickle-bed electrode, aeff and kmA were higher than that using the packed-bed electrode, because oxygen gas and catholyte were dispersed uniformly in the cathode compartment, thus leading to higher Ce.
The packed structure of the lower part of a blast furnace is modeled with packing two different sizes of hydrophobic particles in a rectangular container. The interface between the small and large particle beds is inclined at a certain angle. Glycerin aqueous solutions with different concentrations are used to vary the liquid viscosity from 1 to 100 mPa·s. Isoamyl alcohol aqueous solution is used as the liquid with low surface tension. Two-dimensional distribution of liquid flow rate in the trickle bed with non-uniformly packed structure is measured. Both the packed angle and liquid physical properties have significant effcts on the distribution of liquid flow rate in the trickle bed with non-uniformly packed structure. The liquid flow rate in the small particle bed decreases with increasing packed angle. The liquid flow rate along the interface between different particle beds increases with increasing liquid viscosity. When the liquid surface tension is lower, the liquid flow rate at the interface between different particle beds becomes lower and the distribution of liquid flow rate becomes more uniform. The experimental equation proposed in previous paper is modified by using the data for small particle and low surface tension. A percolation model combined with the above experimental equation is developed to predict the liquid flow distribution in non-uniformly packed trickle bed. The calculated results show the same tendencies of the experimental data.
Kinetic behavior was investigated in an isothermal fixed-bed reactor for the catalytic esterification of acetic acid with amyl alcohol over Amberlyst 15, an acidic cation exchange resin. Both chemical equilibria and phase behavior of the reacting mixtures were also observed under different feed compositions. Four kinetic models, including the pseudo-homogeneous, the Langmuir-Hinshelwood, the Eley-Rideal, and a modified Langmuir-Hinshelwood, were applied to correlate the kinetic data at temperatures between 303.15 and 353.15 K and molar ratios of feed (amyl alcohol to acetic acid) from 1 to 15. The capabilities of these models were compared.
The filtration process of gel particle slurry was experimentally investigated with three kinds of gel particles. Gel particles have a high water content and are able to compress themselves, and so build up highly compressible filter cakes by filtration. The hydraulic pressure distributions in the gel particle cake were successfully measured by using a subminiature pressure sensor for evaluating the internal behavior of gel cake. This process was able to be divided into four different periods of separation. In this study, the separation modes were hypothesized and the methods for theoretical calculations were developed. The results of the study are useful in obtaining proper understanding of the filtration process of soft and hydrous materials.
Pyroaurite-like compounds with a series of crystal quality were synthesized in a strong alkali solution with pH above 13. The characterization of the synthesized compounds was carried out in terms of the crystal quality, specific surface area and intercalated anions of the compounds. The crystal quality of the compounds decreased with increase in the aging time. The lower crystal quality compound showed larger dissolution than the higher crystal quality one in a solution depending on buffering capacity of the solution. Removal of phosphate using the dissolution followed by coagulation and/or precipitation process of the compounds was demonstrated. Phosphate removal property of the compounds was examined as a function of the crystal quality of the compounds, buffering capacity of the solution and competitive anion in the solution. The phosphate removal was increased depending on decrease of the crystal quality of the compound and increase of the buffering capacity of the solution. The significance of crystal quality of the compounds on the phosphate removal was elucidated.
The elutriation of fine particles (group C or group A particles) from a fluidized bed of fine-coarse particle mixtures was investigated at a steady state. FCC, AL(OH)3, limestone, alumina, SiC, PVC and silica sand particles in the range of 22.44 to 650 μm were used as the fluidized particles. The elutriation rate constant of particles increased with increase of particle size in the range of group C particles at the constant superficial gas velocity and decreased with increase of the particle size in the rage of group A and B particles. The particle size corresponding to the maximum elutriation rate constant is defined as the critical particle size of the elutriation. The critical particle size decreases with increasing elutriated particle density and with increasing gas velocity. On the contrary, the critical particle size increases with increasing the mean diameter of bed particles. But, the coarse particle density has no effect on the critical particle size. An empirical equation is obtained to estimate the critical particle size.
NiO/YSZ composite particles with 20 to 35 mol% Y2O3 stabilized ZrO2 (YSZ) are prepared by Spray Pyrolysis (SP) method. The NiO/YSZ composite particles are NiO particles coated with fine YSZ grains. The morphology of Ni/YSZ cermet anode fabricated from the composite particles is noticeably influenced by the YSZ content of the composite particles. Ni/YSZ cermet anode with 25 mol% YSZ shows the highest electrochemical activity and the lowest IR. The electrochemical activity and internal resistance (IR) of the anode in Solid Oxide Fuel Cells (SOFCs) highly depend on the boundary structure between Ni and YSZ grains as well as the network structure of each Ni grains. Consequently, it is concluded that the performance of the Ni/YSZ cermet anode is improved by controlling the morphology of the NiO/YSZ composite particles.
A system for assessing dementia of the Alzheimer type (DAT) from electroencephalogram (EEG) data by means of fuzzy neural networks (FNNs) was investigated. The system consisted of two FNN models, one to discriminate DAT patients from normal subjects and the other to estimate the severity of the DAT patients' symptoms. EEG data were collected using 15 electrodes attached to the scalp. The power spectra were calculated by the fast Fourier transform. For each electrode, the power spectrum was divided into 9 frequency bands and relative power values were calculated. The θ1 (4.0-6.0 Hz), θ2 (6.0-8.0 Hz), and α (8.0-13.0 Hz) band data were used as the network input values. DAT severity was assessed by the Mini-Mental State (MMS) examination administered to each patient and the results were used as the output. The FNN model for DAT patient discrimination correctly distinguished 94% of the DAT patients from normal subjects. The FNN model for severity estimation gave an average error of 2.57 points out of 30 in the MMS scores. The FNNs were found to be useful tools for discrminating DAT patients from normal subjects as well as for estimating quantitatively the severity of DAT symptoms from EEG data.
Liposomes encapsulating coenzyme β-NAD+ were used for liposome immunosorbent assay (LISA) of antibodies and antigens in place of labeled antibodies in ELISA. Conjugated redox reactions involving β-NAD+ can accumulate a colored material and attained high signals in detection of the released marker. The sensitivities of sandwich LISA were compared with those of direct LISA, as well as with ELISA. The immunointeraction of antibody coupled on the surface of liposomes with antigen was studied. The liposomes encapsulating β-NAD+ could be used in LISA for measurement of antigens and antibodies, and sandwich LISA showed the higher sensitivity than direct LISA. Liposomes coupling many molecules showed higher affinities (avidity) to antigen than a single molecule of antibody.
Enhanced hydroxyl radical production in the Fenton reaction with ATP or ADP based on luminol chemiluminescence was clarified. Luminol chemiluminescence intensity increases with the concentration of ATP or ADP due to their influence on the Fenton reagents which produce hydroxyl radicals. Fenton reagents containing hydrogen peroxide and ferrous ion produce hydroxyl radicals which attack luminol and this emits light. The effect of ATP and ADP on the Fenton reaction is detected as luminol CL intensity with a photon counting system. This method allows measurement of ATP or ADP concentration ranging from 0 to 15 mM, which covers the physiological concentration range.
The dynamics of adsorption of Kr and Xe, which are constituents of the off-gas from the nuclear reprocessing process, on representative adsorbents (MS5A and activated charcoal) was studied using packed bed columns. The experimental breakthrough curves were analyzed by conducting direct numerical computations of the mass balance equations. The results of the analysis show that adsorption of Kr and Xe on the MS5A adsorbent is the pore diffusion control. With regard to the adsorption of Kr and Xe on the activated charcoal, it was found that the surface diffusion considerably contributes to the migration of adsorbate molecules. These results suggest that the kinetic adsorption performance of the activated charcoal adsorbent is enhanced even at lower temperatures with the help of the surface diffusion. Furthermore, the surface diffusivities were quantified from the experimental results using several models.
The UV-H2O2 technique, which is commonly known as a method of decomposing organic substances from wastewater, was applied into cleaning of a stainless steel surface fouled with protein. On a stainless steel surface fouled with bovine β-lactoglobulin (β-Lg), H2O2 solution was made to flow, and UV rays were irradiated over the flowing liquid. The amounts of β-Lg adsorbed before and during the UV-H2O2 cleaning were measured by a reflection absorption technique using Fourier transform infrared spectroscopy (RA-IR). The adsorbed amount approximately decreased linearly with time during the UV-H2O2 cleaning. There was an optimum H2O2 concentration for the removal rate. The H2O2 concentration dependency of the removal rate could be explained by considering the formation and disappearance rates of hydroxyl radicals (·OH), the decay of UV illuminance along the depth of the flow, and the rate of reaction between adsorbed β-Lg and ·OH.
The present paper is concerned with a novel heavy metal immobilization by mixing with additives of asphalt, sulfur and sodium hydroxide. To immobilize heavy metals, fly ash were mixed with each additive by using a bi-axial kneader heated at 403 K. Then the dissolution test was carried out based on the Japan Environment Agency notification No. 13. Seven samples of fly ash discharged from the melting process of MSW incineration fly ash were employed. The present immobilization of heavy metal were considered to consist of the conbination of the following two advantages; (1) common advantage of asphalt solidification, (2) additional advantage of low solubility by metal sulfuration. Results of the experiment show that the lead concentration in the eluted solution of the treated sample satisfied Japan's lead emission standard of 0.3 mg/l. It was considered that sodium sulfides, which were produced from the reaction of sulfur and sodium hydroxide, react with heavy metals to form insoluble metal sulfides. The minimum amounts of sulfur and sodium hydroxide needed to achieve the allowable limit had a linear relationship with the heavy metal content in fly ash.
Fundamental evolution characteristics of alkali metal compounds, especially sodium compounds in coal combustion/gasification were experimentally studied using a rapidly heated batch reactor under a wide range of temperature conditions. Six types of coal with different properties were reacted in the reactor. The evolution characteristics of sodium compounds obtained experimentally were compared with those predicted using both coal properties of cross-correlation coefficient between sodium and silicon in the raw coal and the fraction of condensed sodium aluminosilicates in the residue, calculated by the thermochemical equilibrium theory. The reason why the two indices were selected is that the sodium aluminosilicates was detected by X-ray diffraction analysis in the residue. The cross-correlation coefficient between sodium and silicon in the raw coal is calculated using two digital images of sodium and silicon distributions obtained by the Energy dispersed X-ray (EDX) analysis at the cross-section of raw coals. On the other hand, the chemical equilibrium calculation is performed by prescribing the experimental conditions and ultimate analysis data and ash compositions of the coal. The results predicted correlated well with the experimental data even when the evolution characteristics of sodium was dependent on the coal type and when the experimental conditions were varied widely. The coal with low cross-correlation coefficient between sodium and silicon and low fraction of condensed sodium aluminosilicates in the residue was found to release sodium compounds. Both of the two indices proposed can contribute to the prediction of fundamental evolution characteristics of alkali metal compounds in the coal combustion/gasification.