Generalisation of the Routh-Hurwitz criterion and its applications

A generalisation of the Routh-Hurwitz stability criterion for testing the presence of unstable roots of a polynomial with complex coefficients is presented. Numerical examples are given to illustrate the application of the generalisation.     

Carry-over round robin: a simple cell scheduling mechanism for ATMnetworks

We propose a simple mechanism named carry-over round robin (CORR) for scheduling cells in asynchronous transfer mode networks. We quantify the operational complexity of CORR scheduling and show that it is comparable to that of a simple round-robin scheduler. We then show that, albeit its simplicity, CORR is very competitive with much more sophisticated and significantly more complex scheduling disciplines in terms of performance. We evaluate the performance of CORR using both analysis and simulation, We derive analytical bounds on the worst case end-to-end delay achieved by a CORR scheduler for different traffic arrival patterns. Using traffic traces from MPEG video streams, we compare the delay performance of CORR with that of packet-by-packet generalized processor sharing (PGPS) and stop-and-go (SG). Our results show that, in terms of delay performance, CORR compares favorably with both PGPS and SG. We also analyze the fairness properties of CORR and show that it achieves near perfect fairness     

Rantest: a fortran iv program for testing randomness of uniform pseudorandom numbers

Computer-generated random numbers form the basis of most Monte-Carlo simulations and similar work. A FORTRAN program—RANTEST—was written that performs various statistical and empirical tests of randomness on uniform (0, 1) pseudorandom numbers.     

Cedrus oil—A promising storage fungitoxicant

Seeds of two spices Coriandrum sativum and Foeniculum vulgare, were dressed separately with essential oil of Cedrus deodara as well as with five synthetic fungicides viz., phenylmercury acetate, 2-methoxyethyl mercury chloride, copper oxychloride, mancozeb and wettable sulphur. Treated seeds were stored in polythene bags for 12 months. On mycofloral analysis, the oil had checked the appearance of ten fungi, Absidia sp., Alternaria alternata, Aspergillus flavus, A. fumigatus, A. niger, A. ruber, A. versicolor, Cladosporium cladosporioides, Curvularia lunata, and Paecilomyces variotii on the seeds of C. sativum, and seven fungi, Absidia sp., A. flavus, A. fumigatus, A. niger, A. ruber, A. versicolor, and Rhizopus spp., on the seeds of F. vulgare. The oil proved to be more effective than the synthetic fungicides. Further, the oil did not show any adverse effect on seed germination and seedling growth of both spices.     

Intrinsic viscosity of polymers and biopolymers measured by microchip

Intrinsic viscosity provides insight to molecular structure and interactions in solution. A new microchip method is described for fast and accurate measurements of viscosity and intrinsic viscosity of polymer and biopolymer solutions. Polymer samples are diluted with solvent in the microfluidic chip by imposing pressure gradients across the channel network. The concentration and flow dilutions of the polymer sample are calculated from the fluorescent signals recorded over a range of dilutions. The viscosities at various polymer dilutions are evaluated using mass and momentum balances in the pressure-driven microchannel flow. The technique is particularly important to many chemical, biological, and medical applications where sample is available in very small quantities. The intrinsic viscosity experiments were performed for three classes of polymer solutions: (a) poly(ethylene glycol), polymers with linear hydrocarbon chains; (b) bovine serum albumin, biopolymer chains with hydrophobic and hydrophilic amino acids, and (c) DNA fragments, biological macromolecules with double-stranded polymeric chains. The measured values of intrinsic viscosity agree remarkably well with the available data obtained using different methods. The data exhibit power law behavior for molecular weight as described by the Mark-Houwink-Sakurada equation. Experiments were performed to understand the effect of solvent quality and salt concentration on molecular conformations and the intrinsic viscosity of the polymers. This method offers a new way to study the conformational changes in proteins and DNA solutions in various buffer conditions such as pH, ionic strength, and surfactants. The effects of shear rate in the microchannel and mixing time on the accuracy and limitation of the measurement method are discussed.     

A study of charge transfer complexes of chloranil with some donors by conductometric measurements

The charge-transfer complexes of chloranil as acceptor component, with p-phenylene diamine and p-ethoxyaniline as donors have been studied in methyl alcohol by conductometric measurements. The stoichiometry of charge transfer complexes has been determined from the position of the conductivity maximum obtained during the titration of donor solution with acceptor solution. The stoichiometry of the p-phenylene diamine—chloranil is 3:2 and that of the p-ethoxyaniline—chloranil is 1:2. The molar conductivity coefficients for all these systems at temperatures 20°, 25°, 30°, 35° and 40°C have been calculated, and are found to increase with increase in temperature in all the systems studied here.     

Kinetic studies on dehydrogenation of butanol to butyraldehyde using zinc oxide as catalyst

Butyraldehyde is an important chemical for many industrial applications, especially in the production of polyvinylbutyral. A systematic study of its synthesis by catalytic dehydrogenation of butanol, using zinc oxide as catalyst has been carried out. The effect of the method of preparation of zinc oxide on its catalytic activity for the title reaction has also been studied. The optimum conditions for maximum yield have been worked out and on the basis of secondary electron micrograms the reasons for higher activity/selectivity in the case of zinc oxide calcined from zinc hydroxide is attributed to the presence of hexagonal morphology. A kinetic study for the best zinc oxide catalyst has been carried out and the rate equation has been determined.     

On an exponential server with general cyclic arrivals

Summary A E ⁿ¦ M ¦ 1 queue is defined as a single server queue with exponential service time and general cyclic arrival distributions of cycle length n. The waiting time distribution for such a queue is proved to be a sum of n exponential terms; this is a generalization of G ¦ M ¦ 1 queue results. Based on this a method for obtaining the steady-state waiting time distributions for E ⁿ¦ M ¦ 1 queues is introduced. An example is presented to show an application of E ⁿ¦ M ¦ 1 queues in deterministic routing.The work was supported in part by the U.S. Air Force Office of Scientific Research under grant AFOSR 78-3654 A to the Department of Computer Science