A computer approach for reliability evaluation of telecommunicationnetworks with heterogeneous link-capacities

The authors present a computer approach to obtaining a survivability index called capacity related reliability (CRR) in large telecommunication networks where links have different capacities. The method is a two-step approach. The first step deals with composite path enumeration (CPE). A k-composite path is defined as the union of the set of edges in any k simple paths and relates link capacity and network connectivity. The CPE approach is an improvement over the algorithms proposed by the authors earlier (1991). In step two, k-composite paths information is manipulated to generate the CRR. The authors use CAREL (computer aided reliability evaluator) to solve this step. The technique is automated using C on the Encore Multimax System. The results on CRR for three networks with various values of minimum message capacity are presented. An exhaustive technique is used to verify these results. An informal proof of the CPE approach is also included     

On a singular feature of critical G/M/1 queues

In this paper, we consider a critically loaded G/M/1 queue and contrast its transient behaviour with the transient behaviour of stable (or unstable) G/M/1 queues. We show that the departure process from a critical G/M/1 queue converges weakly to a Poisson process. However, as opposed to the stable (or unstable) case, we show that the departure process of a critical GI/M/1 queue does not couple in finite time with a Poisson process (even though it converges weakly to one). Thus, as the traffic intensity (ratio of arrival to service rates), , ranges over (0, ∞), the point = 1 represents a singularity with regard to the convergence mode of the departure process.     

Synthesis and biological activity of novel thiazolidinediones

Novel compounds having a dual pharmacophore were synthesised and evaluated for their insulin sensitiser and anti-inflammatory properties in different animal models.     

Studies in surface chemistry of carbon blacks-vi. adsorption isotherms of benzene on carbons associated with different surface oxygen complexes

Adsorption isotherms of benzene (35°C) on carbon blacks are of Type II and show complete reversibility. The presence of CO₂-complex, which imparts polar and hydrophilic character to the surface, suppresses the sorption of benzene but its elimination and the emergence of CO-complex as the only predominant complex enhances the sorption at all r.v.p's. The additional sorption amounts roughly to one molecule of benzene per quinonic oxygen as obtained by sodium borohydride treatment. This indicates probability of interaction of π electrons of benzene ring with partial positive charge on carbonyl carbon atom. The isosteric heat of adsorption is also higher in the presence of quinonic oxygen. The use of benzene isotherms for estimating surface area or pore volume of carbons may, therefore, be looked upon with caution. The isotherm on sugar charcoal also shifts bodily upward with the emergence of CO-complex but the adsorbed benzene cannot be recovered even on prolonged evacuation, showing that the benzene complexed at the quinonic sites within the microporous system requires activation energy to diffuse out of the pores. The interaction of benzene, due to the presence of π electrons, seems to be specific, since the isotherms of cyclohexane on a given carbon black are identical irrespective of the nature or amount of any of the surface oxygen complexes present in it.     

Differentiation of underivatized diastereomeric hexosamine monosaccharides and their quantification in a mixture using the kinetic method under electrospray ionization conditions

A simple method to differentiate underivatized diastereomeric hexosamine monosaccharides, glucosamine, galactosamine, and mannosamine is reported by applying the kinetic method using N-acetylhexosamines or naturally occurring amino acids as reference bases under electrospray ionization conditions. The observed differences to distinguish the diastereomeric hexosamines are found mainly due to the proton affinity (PA) differences between the analyte and the reference base. The PA values of the hexosamines are not available in the literature, and hence, we estimated them by the kinetic method using N-acetylhexosamines as reference bases. The determined PA values are 223.97 kcal/mol for glucosamine, 224.99 kcal/mol for mannosamine, and 224.71 kcal/mol for galactosamine. The similar PA values were also obtained by using amino acids as reference bases. We have applied the same methodology to quantify these hexosamines in a mixture following the three-point calibration method suggested in the literature.     

Dependability Under Priority Repair Disciplines

We have studied the operational behaviour of a complex system consisting of two classes of units (with standby redundancy in one class) under two repair disciplines, viz., preemptive-resume and preemptive-repeat. Units have constant failure rate, while repair follows general probability distributions. Supplementary variable and Laplace transform techniques have been used to obtain the transient state probabilities for such a system. From these, steady state behaviour of the complex system has been examined.     

Methods for calculating point-to-point congestion in switched communication networks

This paper presents two simple algorithms for computing the point-to-point congestion probability in a switched communication network. Methods are straightforward and can easily be computerized. Examples illustrate the methods.     

Fast similarity join for multi-dimensional data

The efficient processing of multidimensional similarity joins is important for a large class of applications. The dimensionality of the data for these applications ranges from low to high. Most existing methods have focused on the execution of high-dimensional joins over large amounts of disk-based data. The increasing sizes of main memory available on current computers, and the need for efficient processing of spatial joins suggest that spatial joins for a large class of problems can be processed in main memory. In this paper, we develop two new in-memory spatial join algorithms, the Grid-join and EGO*-join, and study their performance. Through evaluation, we explore the domain of applicability of each approach and provide recommendations for the choice of a join algorithm depending upon the dimensionality of the data as well as the expected selectivity of the join. We show that the two new proposed join techniques substantially outperform the state-of-the-art join algorithm, the EGO-join.     

On Lifetime-Based Node Failure and Stochastic Resilience of Decentralized Peer-to-Peer Networks

To model P2P networks that are commonly faced with high rates of churn and random departure decisions by end-users, this paper investigates the resilience of random graphs to lifetime-based node failure and derives the expected delay before a user is forcefully isolated from the graph and the probability that this occurs within his/her lifetime. Using these metrics, we show that systems with heavy-tailed lifetime distributions are more resilient than those with light-tailed (e.g., exponential) distributions and that for a given average degree, k-regular graphs exhibit the highest level of fault tolerance. As a practical illustration of our results, each user in a system with n = 100 billion peers, 30-minute average lifetime, and 1-minute node-replacement delay can stay connected to the graph with probability 1 - 1/n using only 9 neighbors. This is in contrast to 37 neighbors required under previous modeling efforts. We finish the paper by observing that many P2P networks are almost surely (i.e., with probability 1 - o(1)) connected if they have no isolated nodes and derive a simple model for the probability that a P2P system partitions under churn.     

Effect of various meandering slots in rectangular microstrip antenna ground plane for compact broadband operation

The study of the effect of various meandering slots in the rectangular microstrip antenna ground plane for compact broadband operation is presented. The rectangular microstrip antenna is meandered using three different types of ground plane meandering slots: (a) smaller meandering slots, (b) longer meandering slots, and (c) open-end meandering slots, and is studied experimentally and compared. In these meandering slots, the open-end meandering slot is proved to be effective in significantly enhancing the bandwidth of a compact meandered antenna. Using open-end meandering slots in the ground plane, an extreme compactness of 83% with a broad bandwidth of 38.3% is obtained.