Showing papers by "Delhi Technological University published in 1983"

On the stability of plane Poiseuille flow to finite-amplitude disturbances, considering the higher-order Landau coefficients

Abstract: In this work a study has been made of the Stuart (1960)–Watson (1960) formalism as applied to plane Poiseuille flow. In particular, the higher-order Landau coefficients have been calculated for the Reynolds & Potter (1967) method and for the Watson (1960) method. The results have been used to study the convergence of the Stuart–Landau series. A convergence curve in the (α, R)-plane has been obtained by using suitable Domb–Sykes plots. In the region of poor convergence of the series, and also in a part of the divergent region of the series, it has been found that the Shanks (1955) method, using the em1 transformation, serves as a very effective way of finding the proper sum of the series, or of finding the proper antilimit of the series. The results for the velocity calculations at R = 5000 are in very good agreement with Herbert's (1977) Fourier-truncation method using N = 4. The Watson method and the Reynolds & Potter method have also been compared inthe subcritical and supercritical regions. It is found in the supercritical region that there is not much difference in the results by the ‘true problem’ of Watson and the ‘false problem’ of Reynolds & Potter when the respective series in both methods are summed by the Shanks method. This fact could possibly be capitalized upon in the subcritical region, where the Watson method is difficult to apply.

Reduction of stress concentration around a hole in a uniaxially loaded plate

Abstract: The stress concentration around a circular hole in a plate can be reduced by up to 21 per cent by introducing auxiliary holes on either side of the original hole. But this approach of auxiliary holes creates two more regions of stress concentration in the plate.In the present study, the hole geometry has been modified to effect stress reductions as high as 22 per cent. The problem has been analysed numerically by the finite element method and experimentally by two-dimensional photoelasticity. It has been observed that by making the hole oblong in the direction of loading, a high order of reduction in stress concentration around the hole can be obtained.

On a Novel Approach of Fault Detection in an Easily Testable Sequential Machine with Extra Inputs and Extra Outputs

Abstract: By augmenting a given sequential machine M with two extra input symbols Ie1 and Ie2 and with one extra output terminal Z', a method is developed in this paper for designing an efficient checking experiment for the machine M and for its fault diagnosis to cover the types of faults which may result in an increase in the number of states of the original machine M. The method is an extension of the works of Fujiwara et al.[6], and the scheme of modification never alters the modified machine M' from its easily testable nature as defined by Fujiwara et al [16]. The checking sequences exhibit remarkable savings of the number of input symbols for many sequential machines having a large number of states as compared to that of Fujiwara et al [16].

Effect of zinc diisopropyl dithiophosphate on the photooxidative degradation of poly(2,6‐dimethyl‐1,4‐phenylene oxide) films

Abstract: The effect of zinc diisopropyl dithiophosphate (ZnDTP) chelate over the range of 0.1 to 1.0 wt.% on the photostabilized degradation of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) films was examined. The degradation of the polymer was remarkably affected by the concentration of the ZnDTP which acted as photostabilizer at all concentrations. Der Einflus von Zink-diisopropyl-dithiophosphat (ZnDTP) auf den photostabilisierten Abbau von Filmen aus Poly(2,6-dimethyl-1,4-phenylen-oxid) wurde im Konzentrationsbereich 0,1 bis 1,0 Masse-% untersucht. Der Abbau des Polymers hangt deutlich von der Konzentration des ZnDTP ab, das bei allen Konzentrationen als Photostabilisator wirkte.

Photosensitization and photostabilization of isotactic poly(1-butene) film with triazine complexes

Abstract: This work describes the results of the 3-(o-carboxyphenyl)-1-phenyltriazine-N-oxide [CPT] -sensitized and copper(II) bis-3-(o-carboxyphenyl)-1-phenyltriazine-N-oxide [CCPT] — stabilized photodegradation of isotactic poly(1-butene) film in air at a temperature range of 267–313 °K with a light intensity flux 2.38 × 10−9 einsteins sec−1cm−2. The degradation was followed by viscometry, potassium ferri-oxalate actinometry and by measuring carbonyl index. The intrinsic viscosity, quantum yield and carbonyl index depend on several factors, i.e., temperature and triazene concentration.