Momentum and heat transfer from a continuous moving surface to a power-law fluid

Summary Momentum and heat transfer from a continuous moving surface with an arbitrary surface velocity distribution and uniform surface temperature in a power-law fluid have been considered. Using a coordinate transformation, the boundary layer equations are reduced to a simple form. Modified Merk's series method has been used for momentum equation and universal function approach for energy equation. The resulting equations have been integrated numerically by using fourth-order Runge-Kutta method and method of continuation. Two types of plate velocity distributions are considered: (i) surface velocity proportional to positive power of distance from the slot, (ii) linearly stretched velocity distribution with nonzero slot velocity. It is found that the displacement thickness is much thicker for pseudoplastic fluids than for Newtonian and dilatant fluids for both cases. The local Nusselt number, obtained by the universal function method, has been compared with non-similar results. The results are in good agreement.     

Microwave cavity technique to study the dielectric response in 4′-n-Heptyl-4-biphenyl nematic liquid crystal at 20.900 GHz and 29.867 GHz

The experimental studies of the dielectric response in liquid crystal at different temperatures have been done by using a microwave cavity spectrometer. The Microwave Cavity Spectrometer has been used to measure and compare the relative shift, width and amplitude of the resonance profile for the sample loaded in the cavity operated in TM₀₁₀ mode at two different frequencies 20.900 GHz and 29.867 GHz. The comparative study of dielectric loss, and relaxation time of above liquid crystal at different frequencies has also been done at different temperatures. The method is used for its inherent accuracy and requirement of minute quantity of sample. Importance of nematic liquid crystal for infiltrating photonic crystal fibers for modification of their properties is indicated.     

Modeling of creep crack growth and fracture toughness behaviour of directionally solidified GTD 111 superalloy

In the present study, fracture toughness and creep crack growth behavior of directionally solidified Ni-base superalloy was investigated at elevated temperatures. Creep crack growth rate was correlated to the parameter C _t . Change in fracture toughness as a function of temperature followed the same trend as the variation of yield strength of Ni₃ Al with temperature.     

Variation in Transistor Performance and Leakage in Nanometer-Scale Technologies

Variation in transistor characteristics is increasing as CMOS transistors are scaled to nanometer feature sizes. This increase in transistor variability poses a serious challenge to the cost-effective utilization of scaled technologies. Meeting this challenge requires comprehensive and efficient approaches for variability characterization, minimization, and mitigation. This paper describes an efficient infrastructure for characterizing the various types of variation in transistor characteristics. A sample of results obtained from applying this infrastructure to a number of technologies at the 90-, 65-, and 45-nm nodes is presented. This paper then illustrates the impact of the observed variability on SRAM, analog and digital circuit blocks used in system-on-chip designs. Different approaches for minimizing transistor variation and mitigating its impact on product performance and yield are also described.     

Exploitation of dietary tannins to improve rumen metabolism and ruminant nutrition

Tannins (hydrolysable and condensed tannin) are polyphenolic polymers of relatively high molecular weight with the capacity to form complexes mainly with proteins due to the presence of a large number of phenolic hydroxyl groups. They are widely distributed in nutritionally important forage trees, shrubs and legumes, cereals and grains, which are considered as anti‐nutritional compounds due to their adverse effects on intake and animal performance. However, tannins have been recognised to modulate rumen fermentation favourably such as reducing protein degradation in the rumen, prevention of bloat, inhibition of methanogenesis and increasing conjugated linoleic acid concentrations in ruminant‐derived foods. The inclusion of tannins in diets has been shown to improve body weight and wool growth, milk yields and reproductive performance. However, the beneficial effects on rumen modulation and animal performance have not been consistently observed. This review discusses the effects of tannins on nitrogen metabolism in the rumen and intestine, and microbial populations (bacteria, protozoa, fungi and archaea), metabolism of tannins, microbial tolerance mechanisms to tannins, inhibition of methanogenesis, ruminal biohydrogenation processes and performance of animals. The discrepancies of responses of tannins among different studies are attributed to the different chemical structures (degree of polymerisation, procyanidins to propdelphinidins, stereochemistry and C? C bonding) and concentrations of tannins, and type of diets. An establishment of structure–activity relationship would be required to explain differences among studies and obtain consistent beneficial tannin effects. Copyright © 2010 Society of Chemical Industry     

On Gabor's Alternate-Slab Model

Abstract

Gabor's alternate-slab model for calculating heat transfer between a wall and a moving packed or fluidized bed has been further developed using a physically more realistic numerical procedure. Two explicit techniques were examined. In one scheme, the new temperatures were calculated from the temperatures determined during the previous time interval. In the second scheme, the new temperatures were calculated using an average value of old and new temperatures calculated during the current time interval. The predictions of heat transfer rates for the refined alternate-slab model using old temperatures and those of the Mickley-Fairbanks model agree with each other at large values of t/dp² for the same gas gap thickness of 0.13d_p. The second scheme, which has more realistic attributes, leads to a gas gap of 0.16d_p, which is in better agreement with the experimental data for air-glass and air-copper systems.     

Use of thresholding algorithms in the processing of raindrop imagery

Several thresholding algorithms are applied to the analysis of drop images, and their performance is compared. Images were obtained by use of a digital camera setup in which drops were illuminated from behind, resulting in an image of the drop silhouette. Each algorithm was evaluated based on the accuracy of the drop diameter obtained from the thresholded image and on the size of the depth of field. Because of the difficulty associated with creating drops that have a known diameter, solid spheres composed of a glass with an index of refraction close to that of water were used in computing the depth of field and in determining the accuracy of measured diameter. The application of this study is to the automatic measurement of raindrops and images were obtained during several storms. With each thresholding algorithm this raindrop imagery was used to compute the probability density function of drop diameter, and the rain rate. The performance of each thresholding algorithm was quantified by comparison of these measurements with simultaneous measurements obtained by use of a Joss-Waldvogel disdrometer.     

Aflatoxin B1 contamination in wheat grain samples collected from different geographical regions of India: A multicenter study

In a multicenter study conducted by the Indian Council of Medical Research, 1,646 samples of wheat grain collected from rural and urban areas of 10 states representing different geographical regions of India were analyzed for aflatoxin B1 (AFB1). AFB1 concentrations of > or = 5 microg kg(-1) were recorded in 40.3% of the samples, and concentrations above the Indian permissible regulatory limit of 30 microg kg(-1) were found in 16% of the samples. The proportion of samples with AFB1 concentrations above the Indian regulatory limit ranged from 1.7 to 55.8% in different states, with the minimum in Haryana and the maximum in Orissa. The variation in wheat contamination among states seems to be mainly the result of unsatisfactory storage conditions. Median AFB1 concentrations of 11, 18, and 32 microg kg(-1) were observed in samples from Uttar Pradesh, Assam, and Orissa, respectively; concentrations in other states were <5 microg kg(-1). The maximum AFB1 concentration of 606 microg kg(-1) was observed in a sample from the state of Uttar Pradesh. The calculated probable daily intakes of AFB1 through consumption of contaminated wheat for the population in some states were much higher than the suggested provisional maximum tolerable daily intake. Human health hazards associated with such AFB1 exposure over time cannot be ruled out.