Ultrasonic Sol/Gel Processing of Aluminoborosilicate Glass and Its Composite with Carbon Fiber Reinforcement

An ultrasonic sol/gel technique has been used to process aluminoborosilicate glass and its composite with carbon fiber reinforcement. In this new technique, ultrasonic energy is used in place of alcohol solvent. Gel time is easily controlled by varying the amount of ultrasonic energy and the resulting gel also exhibits less shrinkage during the densification process. The sonogel-based composite has lower flexural strengths than the alcogel and has close values between the measured moduli, while still retaining the same fracture toughness. Micromechanical analysis produces higher values; however, ill is suspected that the in situ modulus of matrix is lower than the value used in the analysis.     

An AlGaAs-GaAs dual-wavelength photodetector with 500 Å resolution

An Au-(N)Al_0.07Ga_0.93As-(n)GaAs Schottky barrier dual-wavelength photodetector with 500 Å resolution has been developed. By varying the reverse bias, the photothreshold of the detector can be changed from 0.82 to 0.87 μm. The diode can thus be applied to demultiplex two optical signals with respective wavelengths of 0.8 and 0.85 μm. This provides a useful detector for use in a dual-channel optical communication system. The principle is based on the band readjustment effect which is due to the interaction of the closely-spaced Au-AlGaAs Schottky barrier and the AlGaAs-GaAs heterojunction.     

A rapid and sensitive method for determination of theophylline in plasma and saliva by high pressure liquid chromatography

A fast and sensitive high pressure liquid chromatographic method for the monitoring of theophylline concentrations in plasma or saliva was developed. Each sample requires only about 15 minutes for the completion of the assay after receiving the plasma or saliva sample. Only 0.1 ml of sample is required, and concentrations as low as 1 mcg/ml can be accurately measured.     

Decomposition of 2-naphthalenesulfonate in electroplating solution by ozonation with UV radiation

This study investigates the ozonation of 2-naphthalenesulfonate (2-NS) combined with UV radiation in the electroplating solution. 2-NS is commonly used as a brightening and stabilization agent in the electroplating solution. Semibatch ozonation experiments were conducted under various reaction conditions to study the effects of ozone dosage and UV radiation on the oxidation of 2-NS. The concentrations of 2-NS were analyzed at specified time intervals to elucidate the decomposition of 2-NS. Total organic carbon (TOC) is chosen as a mineralization index of the ozonation of 2-NS. In addition, values of pH and oxidation reduction potential were continuously measured in the course of experiments. As a result, the nearly complete mineralization of 2-NS via the ozonation treatment can be achieved. The mineralization of 2-NS is found accelerated by the introduction of UV radiation and has a distinct relationship with the consumption of applied ozone. These results can provide useful information for the proper removal of 2-NS in the electroplating solution by the ozonation with UV radiation.     

Evaluating phenanthrene sorption on various wood chars

A certain amount of wood char or soot in a soil or sediment sample may cause the sorption of organic compounds to deviate significantly from the linear partitioning commonly observed with soil organic matter (SOM). Laboratory produced and field wood chars have been obtained and analyzed for their sorption isotherms of a model solute (phenanthrene) from water solution. The uptake capacities and nonlinear sorption effects with the laboratory wood chars are similar to those with the field wood chars. For phenanthrene aqueous concentrations of 1 microg l(-1), the organic carbon-normalized sorption coefficients (log K(oc)) ranging from 5.0 to 6.4 for field chars and 5.4-7.3 for laboratory wood chars, which is consistent with literature values (5.6-7.1). Data with artificial chars suggest that the variation in sorption potential can be attributed to heating temperature and starting material, and both the quantity and heterogeneity of surface-area impacts the sorption capacity. These results thus help to corroborate and explain the range of logK(oc) values reported in previous research for aquifer materials containing wood chars.     

Vortex flow of dilute polymer solutions

It has been observed that very d longchain polymers which are effective in turbulent drag reduction inhibit the formation of a vortex or air core as water drains from a tank. This paper considers the fluid mechanical velocity profile measurements have been performed. There appear to be at least two distinct mechanisms for the vortex inhibition—one involving the viscosity enhancement caused by polymer addition, and the other related to the viscoelastic properties of the polymer solutions. This second mechanism is shown to arise due to the generation of high normal stresses as the air core begins to form. The very close correlation between vortex inhibition and turbulent drag reduction suggests that normal stresses may also play an important role in this latter phenomenon.     

On-line measurement-based model parameter estimation forsynchronous generators: solution algorithm and numerical studies

In this paper, a sixth-order synchronous generator model identification technique from online measurements is considered. An algorithm is devised to identify the generator model. A constrained conjugate gradient method is incorporated into the algorithm to guarantee rapid convergence to the final solution. Using the algorithm, a complete generator model is derived from online measurements recorded by a plant transient recording system during a system disturbance. In addition, the algorithm does not greatly rely upon the accuracy of the initial estimates, allowing the initial estimates to deviate reasonably far from the true parameters. Detailed numerical studies of the Taipower system using raw and filtered data are included     

Characterization of Transdermal Delivery of Nefopam Hydrochloride under Iontophoresis

In vitro iontophoretic delivery of nefopam hydrochloride was conducted to study the effects initial drug concentration, pH, ionic strength and viscosity of the donor solutions on the transdermal flux through a hairless mouse skin. Stability of nefopam hydrochloride under the experimental conditions was investigated. Type of electrode, current intensity, electric voltage and electrode distance were evaluated. Appropriate conditions were selected to minimize the potential degradation problems of nefopam hydrochloride during iontophoresis. Results show that the silver/silver chloride electrode provides better drug stability than the platinum electrode. Higher current intensity resulted in faster transdermal flux and therefore better drug permeability. The increase in the drug permeability appears to be proportionally increased as the current intensity increases in the range of 0.253 to 1.265 mA/cm². The iontophoretic transdermal delivery of nefopam hydrochloride was observed to increase as the drug concentration in the donor site was increased until it's close to the equilibrium concentration. The optimum pH to achieve the best iontophoresis under constant current was determined to be at pH 3.0. This may be due to the highest available charge density of nefopam was achieved at this pH to provide the best conductance. A decrease in the iontophoretic transdermal flux was encountered as an increase in the solution ionic strength due to the increased competition of similar charged ions with the available current. The increase in the donor solution viscosity decreased the conductivity of the ions and hindered the trandermal flux of the drug under iontophoresis.     

Biodegradable composites based on starch/EVOH/glycerol blends and coconut fibers

Unripe coconut fibers were used as fillers in a biodegradable polymer matrix of starch/ethylene vinyl alcohol (EVOH)/glycerol. The effects of fiber content on the mechanical, thermal, and structural properties were evaluated. The addition of coconut fiber into starch/EVOH/glycerol blends reduced the ductile behavior of the matrix by making the composites more brittle. At low fiber content, blends were more flexible, with higher tensile strength than at higher fiber levels. The temperature at the maximum degradation rate slightly shifted to lower values as fiber content increased. Comparing blends with and without fibers, there was no drastic change in melt temperature of the matrix with increase of fiber content, indicating that fibers did not lead to significant changes in crystalline structure. The micrographs of the tensile fractured specimens showed a large number of holes resulting from fiber pull‐out from the matrix, indicating poor adhesion between fiber and matrix. Although starch alone degraded readily, starch/EVOH/glycerol blends exhibited much slower degradation in compost. Composites produced 24.4–28.8% less CO₂ compared with starch in a closed‐circuit respirometer. Addition of increasing amount of fiber in starch/EVOH/glycerol composite had no impact on its biodegradation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Degradation of di-n-butyl phthalate using photoreactor packed with TiO2 immobilized on glass beads

This study evaluated the performance of a photoreactor packed with TiO2/glass, TiO2 immobilized on glass beads, initiated by UV irradiation, denoted as UV/TiO2/glass, to decompose di-n-butyl phthalate (DBP) in an aqueous solution. The photodegradation rate of DBP by this UV/TiO2/glass process was found to obey pseudo first-order kinetics represented by the Langmuir-Hinshelwood model. The experimental results of this study show that the influence of pH value of an aqueous solution to reaction rate was negligible at the pH values 4.5-9. The effect of cations on the photodegradation rate of DBP reveals that the larger the charge and size of cations contained, the more the inhibition of reaction rate increased. The UV/TiO2/glass process yielded a 75% degradation efficiency of DBP with initial concentration of 5 mg L(-1) at 80 min reaction time.