Showing papers in "Journal of the Indian Institute of Science in 1981"

Catechol 1 ,2-dioxygenase from aspergillus niger : purification and properties.

Abstract: Catcchol 1,2-dioxygenase was partially purified to 60-fold from cell-free extracts of Aspergillus niger grown on anthranilic acid. The purified enzyme was found to be highly unstable. The effects of pH. temperature, metal ions and metal chelating agents on enzyme activity have been studied. The enzyme catalyzes the oxidation of catechol and 4-methyl catechol at the same rate, but does not catalyze the oxidation of 3-methyl ca.techol, 3-isopropyl eatechol and other substrate analogues. The enzyme is completely inhibited by thiol compounds and not affected by thiol inhibitors. The km value for catechol was found to be 5.2 x 103 M.

Acquisition time improvement of pll' using some aiding functions.

Abstract: Phase-Lock loops (PLL) are now receiving with attention from communication system designers. Though the primary function of a PLL is to track a received signal, it has to acquire the signal first. A low value of acquisition tine (t..) is of immense practical importance for PLL applications, particularly in at communication, electronic warfare, etc. Therefore. analytical studies have been carried out for the minimization of t R using some aiding functions. To experimentally verify the analytical evaluation, a second order aided PLL has been realized along with the chosen aiding functions using the state-of-the-art components and this has yielded satisfactory results. The analytical. and experimental studies are presented in this paper.

Erosion Studies Due to Liquid Jet Impingement with Plain and Cavitating Jets

Abstract: Experimental investigations were made on the characteristics of erosion resulting from the impingement of liquid jets ; six plain jets and four jets with cavitation inducers in a velocity range of 5 to 45 Infs. A detailed dimensional analysis of the several parameters governing liquid impingement erosion is presented. The growth of the jet size with stand-off distance for plain jets and the erosion characteristics due to variation in stand-off distance are also discussed. The normalized erosion rate increased with jet velocity and approached a constant value at higher jet velocities. The erosion rate decreased rapidly and then remained approximately constant with an increase in cavitation number. The erosion rate increased faster with frequency of impingement than with increase in jet velocity. A maximum value in peak erosion rate occurred around angles of impingement of 25 to 40 deg. The erosion rate-time curves for impingement of jets with cavitation inducers did not show the incubation an.' accumulation zones significantly. The cavity patterns obtained in the case of jets with cavitation inducers are similar to those reported in cavitation studies. The length and width of cavity increase with decrease in cavitation number.

EXTRACTION OF HECOGENIN FROM SISAL (Agave Vera—cruz) LEAVES.

Abstract: Preliminiry investigations on the utilization of sisal waste give a hecogenin yield of about 0.1% of the leaf weight, with the miximum amount being present in the sediment of the juice.

Fault-Detection By Adaptive Non-Linear Filtering

Abstract: In a lintar iyitern perturbed by Gaussian noise, the state can be estimated from the observations by using Kalman filter. However, if a fault develops in the system at any random time, the Kalman filter will not be able to track the fault and large errors will develop in the state estimate. Consequently, the innovations process will no longer be white. If the random time of occurrence is coaiidered as a state then the system of state equations become nonlinear. In this paper, the Fujisaki, Killianpur arid Kunita nonlinear filtering results have been applied to obtain a representation for the stage estimite given the observations. The non-white nature of the innovations process has been modelled as an autoregressive process and an adaptive scheme has been proposed to improve the filter performance.

Prediction of void ratio-osmotic pressure relationship of clays

Abstract: The osmotic pressuie or the repulsne pressure due to difference in concentration of ions between clay platelets and the bulk solution is popularly predicted by the use of Gouy—Chapman theory. The existing procedures arc time consuming, difficult and laborious. In this paper a simple, quick and yet an accurate procedure has been presented to obtain the repulsive pressure at any value of d (half distance betwecn clay platelets) or the void ratio or the vice versa. The results are obtained directly by using the figures and tables presented.

An experimental investigation of turbulent wake behind 's'-shaped profiles.

Abstract: The wake characteristics behind a cascade of 'S' profiles have been studied under turbine and pump conditions at wider and closer spacings. The mean velocity distributions indicate asymmetry predominantly during pump cascade condition and for high cambered 'S' profiles. The higher total pressure loss under decelerating flow conditions was indicated by larger values of wake momentum thickness. Sample turbulence measurements made also show asymmetry. The region of maximum turbulence intensity is skewed towards one side of the wake.