Relaxation in poly(alkyl methacrylate)s: Change of intermolecular coupling with molecular structure, tacticity, molecular weight, copolymerization, crosslinking, and nanoconfinement

The voluminous amount of data in the literature on the structural α- and the Johari-Goldstein β-relaxations of the poly(n-alkyl methacrylate)s allows a systematic study of the interrelation between the two important relaxation processes. The data bring out the systematic changes in the interrelation between the structural α- and the Johari-Goldstein β-relaxations with changes in molecular structure, molecular weight, tacticity and size (by nanoconfinement), and modifications by copolymerization, and crosslinking. The results can all be interpreted as primarily due to changes in intermolecular coupling, which have significant effects on the many-molecule dynamics constituting the structural α-relaxation, but not on the precursory Johari-Goldstein β-relaxation. Theoretically, the Coupling Model predicts a relation of intermolecular coupling (or degree of cooperativity of the α-relaxation) to the ratio of the α- and the β-relaxation times, and a correlation of intermolecular coupling to the steepness or “fragility” index. The predicted relation and correlation are compared with experimental data of the poly(alkyl methacrylate)s.     

Detection of stator short circuits in VSI-fed brushless DC motors using wavelet transform

The paper presents methodologies to detect and locate short-circuit faults on the stator winding of VSI-fed PM brushless dc motors. Normal performance characteristics of the motor are obtained through a discrete-time lumped-parameter network model. The model is modified to accommodate short-circuit faults in order to simulate faulty operation. Fault signatures are extracted from the waveforms of electromagnetic torque and phase-voltage summation using wavelet transform. Three independent detection techniques are introduced. Experimental measurements agree acceptably with simulation results, and validate the proposed methods. This work sets forth the fundamentals of an automatic fault detector and locator, which can be used in a fault-tolerant drive.     

VLSI parallel architecture for Kalman filterAn algorithm specific approach

An algorithm specific architecture for Kalman filter is presented. It is based on systolic arrays. Parallelism has been exploited on both algorithm and architecture levels. Faddeev's algorithm has been employed. The involved computation tasks, triangularization and nullification are performed in parallel which leads to a speedup of about 40%. Throughput has been increased by using bi-trapezoidal arrays. Techniques have been employed for data storage and skewing which enables fast data transfer rates. A VLSI implementation of a prototype of matrix of size 4×4 has been discussed.     

Control of the mutagenicity of arylamines by protein kinases and phosphatases: II. Lack of response of rat liver N-acetyl transferases to phosphorylation modulators

OBJECTIVES: Endoscopic sphincterotomy has become a generally accepted method for extracting common bile duct stones in high risk or cholecystectomized patients. However, stone extraction is impossible by the usual methods in 5 to 10% of cases. The purpose of this study was to evaluate the effect of a recently developed solvent system in patients with large bile duct stones. METHODS: Forty four patients (15 men and 29 women, median age of years) underwent contact dissolution after unsuccessful Dormia extraction. Solvents were administered via a nasobiliary catheter in 41 patients following papillotomy and through a T-tube in 3 patients. Solvent mixtures (26 mM ethylene diamine tetraacetic acid, 40 mM sodium deoxycholate and 30% dimethyl sulfoxide in an alkaline aqueous solution; and a 70/30 dimethyl sulfoxide/methyl tert-butyl ether mixture) were infused continuously and alternatively for 2 hours. RESULTS: Bile duct stones disappeared in 13-24 hours of infusion in 11 patients. In 29 patients, a clear reduction in stone volume occurred, allowing complete endoscopic extraction of the fragments. In 4 patients, the size of the stone did not change. Only mild and transient side-effects including abdominal pain (68%), nausea (72%), vomiting (52%), diarrhea and sleepiness (50%) were observed. CONCLUSION: Direct dissolution therapy could be an effective method for the non-surgical management of large bile duct stones in selected patients when intra- or extracorporeal lithotripsy is unsuccessful.     

An application of the contingent valuation method to estimate the loss of value of water resources due to pesticide contamination: the case of the Mekong Delta,Vietnam

This paper determines the degradation of the rural water system in the Mekong Delta, Vietnam, due to pesticide application for rice production. The theoretical framework of the contingent valuation method is identified and its empirical application to the valuation of the rural water resources is presented via a case study in the Mekong Delta. Study results show that the loss of value of the rural water resources due to pesticide contamination in the Mekong Delta is about US$251 million.     

Composition of clove (Syzygium aromaticum) bud oil extracted using carbon dioxide

Analysis of clove (Syzygium aromaticum L) bud oil extracted with liquid and supercritical carbon dioxide shows significant qualitative and quantitative compositional differences compared with oil obtained by the conventional hydrodistillation process. The parameters of pressure, temperature, contact time etc, and also the clove oil components, affect the extraction of the bud flavour from the spice.     

Grain orientation studies in YBCO superconductors by molten salt synthesis

The molten salt or the flux method is utilized in this study to fabricate a grainoriented YBa₂Cu₃O_7−x superconductor. The formation of YBa₂Cu₃O_7−x in the presence of molten salts of Na, K, Li belonging to chloride and iodide systems does not appear feasible due to the instability of the superconducting phase in these salt systems. Studies using the “green phase,” Y₂BaCuO₅, as seed crystals suggest a two-stage approach in the formation of YBa₂Cu₃O_7−x . The process uses Y₂BaCuO₅ formed by molten salt synthesis which has been observed to be stable in water and against most of the salts. The 211 crystals can be mixed with oxides and converted to 123. Analysis of X-ray data and SEM micrographs indicates a certain degree of grain orientation, which can be further enhanced by tape-casting or not-forging.     

Fracture Mechanics Model for Analysis of Plain and Reinforced High-Performance Concrete Beams

In developing a one-dimensional analysis and design procedure for reinforced concrete structures, research is generally based on yield phenomena and the plastic flow of steel in tension and concrete in compression. The ability of concrete to resist tension is considered in the form of tension stiffening or is completely disregarded. This procedure does not account for the influence of structural size in changing the failure mode and the stress distribution across the uncracked or cracked ligament. The key factor affecting this stress distribution is found to be the strain-softening modulus. This paper presents an improved model that is based on the fundamental equilibrium equation for the progressive failure of plain concrete beams. The concrete stress-strain relationship in tension is derived by calculating the peak tensile stress and softening modulus for different depths of beams on the basis of the fracture parameters obtained with the size effect law. Thus, the proposed model uses the peak tensile stress and the softening modulus, which vary depending on the size of the beam. To study the effect of the strength of high-performance concrete (HPC) on the concrete tensile stress-strain relationship, the experimental load-deflection plots of different-sized beams are compared with those obtained by using the proposed analytical model for eight different mixes made with locally available fly ash and slag. The model is also extended for lightly reinforced concrete beams, and the results are compared with those in the literature and are found to be in good agreement.     

Enhancement of corrosion protection of 3-glycidoxypropyltrimethoxysilane-based sol–gel coating through methylthiourea doping

Protection of aluminum metal and its alloys from corrosion is a key requirement for many engineering applications. Nowadays, sol–gel coating technology is recognized as the ideal replacement for chromate conversion coatings. The present work makes use of 3-glycidoxypropyltrimethoxysilane (GPTMS) as a precursor for sol–gel coating. GPTMS was subjected to hydrolysis and subsequent condensation reaction to get a three-dimensional network and methylthiourea (MTU) was incorporated into the sol–gel matrix. MTU-doped GPTMS-based sol–gel coatings were applied over aluminum metal by dip coating method. The resultant coating was studied by FTIR, XRD and SEM. MTU-doped GPTMS-based sol–gel coatings increased the hydrophobic nature of the coating and were stable up to a temperature of 450°C. The protective nature of the coatings was evaluated in a 1% NaCl environment using electrochemical impedance and polarization studies. The study has revealed that doping of MTU enhanced the protection ability of doped GPTMS-based sol–gel coating to a significant extent.