Novel cascadable current-mode first order all-pass sections

This paper presents some new current mode first order all-pass sections with grounded components employing a modified current conveyor. The new circuits are ideal for current-mode cascading by possessing high output impedance. As an application of the circuits, a new quadrature oscillator is also given. The theory is validated through PSPICE simulation using 0.5μ CMOS parameters.     

Role of Fiber Length and Pore Former on the Porous Network of Carbon Paper Electrode and its Performance in PEMFC

Porous conducting carbon paper has been recognized as one of the ideal materials to be used as an electrode backing in a fuel cell assembly. Carbon paper is prepared by the combined process of papermaking followed by composite formation. Two different studies, i.e. (i) using chopped carbon fiber of different lengths in the papermaking process, and (ii) introducing pore formers (blowing agents) in the sample during the resin impregnation/composite formation step, were adopted separately to control the porosity of the paper. The effect of the above processes on the various properties of the carbon paper electrode affecting its performance in a unit polymer electrolyte membrane fuel cell has been discussed. A maximum power density of 766 mW cm^–2 has been achieved for carbon paper with 0.6 cm fiber length, an increase of nearly 12% as compared to 684 mW cm^–2 for sample with 1.0 cm fiber length and tested under similar conditions. The introduction of pore former demonstrates increased performance of the fuel cell at high current densities.     

Modified Stanley's approach for statistical analysis of compression strength test data of rock specimens

A very wide scatter is usually observed in laboratory compressive strength test (uniaxial and triaxial) data of rock specimens due to randomness in the number, orientation and distribution of micro-cracks. This leads to an uncertainty in choosing the representative design strength which leads to the need for a probabilistic approach to the analysis of test data. An attempt has been made in this paper to propose such an approach which is a modified version of Stanley's approach and employs Weibull's statistical strength theory. Uniaxial compressive strength (UCS) test data from three sources have been analyzed and results compared with those from Weibull's theory. As the proposed approach employs Weibull's parameters, goodness-of-fit tests have been performed to check the fitness of tests data to Weibull's distribution. Further, the proposed approach for uniaxial conditions has been extended to triaxial stress conditions. Corresponding cumulative distribution functions of the applied stress level have been obtained which have been subsequently invoked to correlate the applied stress level at failure with the associated risk of failure. For the UCS test data, the proposed approach yields higher design strengths than does Weibull's theory when Weibull's m parameter is greater than unity. Strength under triaxial stress condition can be predicted by employing the proposed approach even though triaxial tests cannot be conducted, provided the UCS test data are available.     

Lipids of some thermophilic fungi

Total lipid content in the thermophilic fungi—Thermoascus aurantiacus, Humicola lanuginosa, Malbranchea pulchella var.sulfurea, andAbsidia ramosa—varied from 5.3 to 19.1% of mycelial dry weight. The neutral and polar lipid fractions accounted for 56.4 to 80.2% and 19.8 to 43.6%, respectively. All the fungi contained monoglycerides, diglycerides, triglycerides, free fatty acids, and sterols in variable amounts. Sterol ester was detected only inA. ramosa. Phosphatide composition was: phosphatidyl choline (15.9–47%), phosphatidyl ethanolamine (23.4–67%), phosphatidyl serine (9.3–17.6%), and phosphatidyl inositol (1.9–11.9%). Diphosphatidyl glycerol occurred in considerable quantity only inH. lanuginosa andM. pulchella var.sulfurea. Phosphatidic acid, detected as a minor component only inM. pulchella var.sulfurea andA. ramosa, does not appear to be a characteristic phosphatide of thermophilic fungi as suggested earlier. The 16∶0, 16∶1, 18∶0, 18∶1, and 18∶2 acids were the main fatty acid components. In addition,A. ramosa contained 18∶3 acid. Total lipids contained an average of 0.93 double bonds per mole of fatty acids, and neutral lipids tend to be more unsaturated than phospholipids.     

Effect of heat treatment on the structure and stability of multiwalled carbon nanotubes produced by catalytic chemical vapor deposition technique

The multiwalled carbon nanotubes (MWCNTs) produced by catalytic chemical vapor deposition (CCVD) route were heat treated to 2500 °C to improve the structure, morphology and purity level. The process has lead to substantial reduction in the catalytic impurity along with an improved thermal stability and degree of graphitization of these tubes that can possibly lead to its better utilization in various applications. The structural changes following heat treatment have been correlated using various characterization techniques such as Raman spectroscopy, X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, thermo gravimetric analysis and electron paramagnetic resonance spectroscopy. The electrical and mechanical properties of the polymer composites prepared with heat treated MWCNT show improved properties over the one prepared by as produced MWCNT.     

Off-flavor removal from soy-protein isolate by using liquid and supercritical carbon dioxide

The efficacy of liquid carbon dioxide (L-CO₂), supercritical carbon dioxide (SC-CO₂), and SC-CO₂ containing 5% ethanol in the removal of off-flavors from soybean protein isolate was studied. Medium-chain aldehydes:n-butanal,n-pentanal, andn-hexanal; ketones: 2-butanone, 2-pentanone, and 2-hexanone; and alcohols: 1-butanol and 2-butanol; were the major compounds extracted. The extractions were performed at a constant fluid density of 901 kg/m³ with 100, 500, and 1000 standard liter of carbon dioxide. None of the treatments had a detrimental effect on soy-protein functionality. Headspace gas chromatography (GC) and sensory analysis of the treated samples were compared with the untreated soy isolate (control). In general, L-CO₂ was the least effective, and SC-CO₂ was the most effective in removing the off-flavor volatiles. Addition of ethanol as an entrainer did not improve the efficiency of off-flavor removal by SC-CO₂. The results of sensory analysis correlated well with the GC analysis. Sensory analysis of a 33% (wt/vol) slurry of treated soy-protein isolate had more off-flavor notes than the dry soy isolate. Dry and slurried treated soy-protein isolates had significantly less off-flavors and significantly more acceptability than the untreated control.     

Application of probabilistic neural network for differential relaying of power transformer

Investigations towards the applicability of probabilistic neural networks (PNNs) as core classifiers to discriminate between magnetising inrush and internal fault of power transformer are made. An algorithm has been developed around the theme of conventional differential protection of transformer. It makes use of the ratio of the voltage-to-frequency and the amplitude of differential current for the detection of the operating condition of the transformer. The PNN has a significant advantage in terms of a much faster learning capability because it is constructed with a single pass of exemplar pattern set and without any iteration for weight adaptation. For the evaluation of the developed algorithm, transformer modelling and simulation of fault are carried out in power system computer-aided designing PSCAD/EMTDC. The operating condition detection algorithm is implemented in MATLAB     

OPTIMIZATION STUDIES OF PORTABLE METALLIC STOVES FOR ENERGY CONSERVATION

Priagni portable stoves have been recently introduced in rural areas to improve fuel efficiency. These stoves are available in two sizes (medium and large) for domestic application. The stoves are particularly suitable for those areas where wood is used as fuel. The stoves have been accepted for use in southern coastal areas and also in the hilly areas. Optimization studies on determining the pot raiser height of top plate were conducted on large size Priagni stove. The studies indicate that 50 mm is the optimum pot raiser height keeping in view the thermal efficiency and combustion quality.