On routing in large WDM networks

An important problem in WDM network design is to construct a logical topology and determine an optimal routing over that topology. Mixed Integer Linear Program (MILP) formulations to generate optimal solutions for this problem have been presented. Such formulations are computationally intractable, even for moderate sized networks. A standard approach is to decouple the problem of logical topology design and the problem of routing the traffic on this logical topology. Heuristics for finding the logical topology exist and a straight-forward linear program (LP), based on the node-arc formulation can be used to solve the routing problem over a given logical topology. We have found that such LP formulations become computationally infeasible for large networks. In this paper, we present a new formulation, based on the arc-chain representation, for optimally routing the specified traffic over a given logical topology to minimize the congestion of the network. We have used the revised simplex method incorporating an implicit column generation technique, and exploited the special Generalized Upper Bounding structure as well as the possibility of eta-factorization for efficiently updating the dual variables and finding the solution. Experimental results on a number of networks demonstrate the suitability of this approach.     

Social Profile Aware AODV Protocol for Ad-Hoc Social Networks

Wireless Personal Communications - Ad-hoc social networks are required to strengthen local communication between people. Mobile ad-hoc social networks have emerged as self-configuring and...     

Bounds tightening based on optimality conditions for nonconvex box-constrained optimization

First-order optimality conditions have been extensively studied for the development of algorithms for identifying locally optimal solutions. In this work, we propose two novel methods that directly exploit these conditions to expedite the solution of box-constrained global optimization problems. These methods carry out domain reduction by application of bounds tightening methods on optimality conditions. This scheme is implicit and avoids explicit generation of optimality conditions through symbolic differentation, which can be memory and time intensive. The proposed bounds tightening methods are implemented in the global solver BARON. Computational results on a test library of 327 problems demonstrate the value of our proposed approach in reducing the computational time and number of nodes required to solve these problems to global optimality.     

On generalized balanced optimization problems

In the generalized balanced optimization problem (GBaOP) the objective value \({\max_{e \in S}{|c(e)-k\max(S)|}}\) is minimized over all feasible subsets S of E = {1, . . . , m}. We show that the algorithm proposed in Punnen and Aneja (Oper Res Lett 32:27–30, 2004) can be modified to ensure that the resulting solution is indeed optimal. This modification is attained at the expense of increased worst-case complexity, but still maintains polynomial solvability of various special cases that are of general interest. In particular, we show that GBaOP can be solved in polynomial time if an associated bottleneck problem can be solved in polynomial time. For the solution of this bottleneck problem, we propose two alternative approaches.     

Synthesis of benzo-furan derivatives-I Karanj ketone, karanjin and pongapin

A new method of preparing benzo-furan derivatives using substituted allyl phenols has been worked out. Ozonolysis of the allyl derivatives and subsequent ring closure of the resulting o-hydroxy-acetaldehydes by means of o-phosphoric acid give good yields of karanj ketone, karanjin, pongapin and the corresponding 2-methyl furanochromone. As an alternative route oxidation of the allyl phenol in two stages using performing acid followed by periodic acid has been successfully employed in the synthesis of karanjin.     

Polypropylene/Poly (Trimethylene Terephthalate)–Blend Fibers

Polypropylene (PP)/polyester (PES)–blend fibers were prepared by extruder melt spinning. The polymer blend consisted of PP and a “master batch” (MB) based on polytrimethylene terephthalate (PTT) or polyethylene terephthalate (PET), binary PTT/PET or PP/PTT blends, and also on a ternary PP/(PTT/PET) blend. The phase structure of PP/PES–blend fibers was examined. PES microfibers showed separation from the PP matrix in blend fibers. The impact of MB composition and rheological characteristics on phase structure parameters indicate a significant contribution of the PTT in the binary MB on the length of dispersed PES microfibers in the PP matrix. However, the blends of PP and ternary MB (PP/PTT/PET) have a lower diameter and length of the PES microfibers. The presence of PTT/PET (PES) enhances the structural and mechanical properties of the blend PP/PES fibers. In addition, PTT increases the tensile strength of the PP/PES–blend fibers if a binary MB is used, while the fiber nonuniformity is reduced in the presence of a ternary MB.     

Scalable synthesis of cladosporin

Cladosporin, a secondary metabolite isolated from fungal sources like Cladosporium cladosporioides and Aspergillus flavus was found to exhibit selective nano-molar activity against malarial parasite Plasmodium falciparum by inhibiting parasitic protein biosynthesis. In addition, this natural product has a broad range of bioactivities including, antiparasitic, antifungal, antibacterial as well as plant growth inhibition. However, it has limited availability from the natural sources for further development. Herein, we report a modified and improved synthetic route which led us to produce this potent natural product in a gram scale. Conversion of the undesired diastereomer to desired one via Mitsunobu inversion of secondary alcohol and carbon monoxide insertion reaction towards the construction of isocoumarin unit are the key features of the present synthesis.     

Software defined vehicular networks: A comprehensive review

The recent breakthroughs in the automobile industries and telecommunication technologies along with the exceptional multimodal mobility services brought focus on intelligent transportation system (ITS), of which vehicular ad hoc networks (VANETs) gain much more attention. The distinctive features of software‐defined networking (SDN) leverages the vehicular networks by its state of the centralized art having a comprehensive view of the network. Its potential to bring the flexibility, programmability and other extensive advancements to vehicular networks has set the stage for a novel networking paradigm termed as software‐defined vehicular networks (SDVNs). Many researchers have demonstrated the SDN‐based VANETs with the various configuration of the SDN components in VANET architecture. However, a compilation of the work on the SDN‐based VANET system as a whole, incorporating its architecture, use‐cases, and opportunities, is still inadequate. We start with the summary of the recent studies that exist on the SDVNs, followed by the comprehensive explanation of its components. Next, we present the taxonomy of SDVN based on the architecture modes, protocols, access technologies, and opportunities with trending technologies. Finally, we highlight the challenges, open research issues, and future research directions.