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The security of workflow scheduling is a significant concern and even is one of the most important metrics of QoS (Quality of Service). This paper presents two approaches to provide a secure connection between users and servers and handle large and medium task size problems. Firstly, a multi-objective scheduling (MO-Ring-IC-NCCLA) algorithm for scientific workflow in the cloud environment is proposed. It tries to minimize workflow makespan and cost as well as increase the cost of attack from an invader. The proposed multi-objective is based on the New Caledonian Crow Learning Algorithm (NCCLA). However, this algorithm has a few drawbacks, including poor exploration activity and inability to balance exploration and exploitation. The social and asocial learning part of standard NCCLA has been modified to tackle these limitations, then a concept of ring topology is used to better Pareto optimal can be found. Secondly, the structure of virtual machines is modified so that the cost of attack from invaders increases. Experimental results based on various real-world workflows indicate the performance improvement of MO-Ring-IC-NCCLA over SBDE, NSGA-II, and MOHFHB algorithms in terms of FS-metric. According to the delta metric (i.e., diversity measures), the proposed algorithm is superior to 85% of the compared metaheuristics. In terms of Inverted Generational Distance (IGD) metric, it outperforms NSGAII and Multi-Objective Artificial Hummingbird Algorithm (MOAHA) for 95% and 80% of the cases, respectively. Based on experiments, makespan and cost improved by 23.12% and 18.43% over existing workflow algorithms. Compared to Multi-Objective Hybrid Fuzzy Hitchcock Bird (MOHFHB), Simulated-annealing Based Differential Evolution (SBDE), and non-dominated sorting genetic algorithm (NSGAII), it improves the FS-metric by 23.35% on average. [ABSTRACT FROM AUTHOR]

We consider power distribution networks containing source nodes producing electricity and nodes representing electricity consumers. These sources and these consumers are interconnected by a switched network. Configuring this network consists in deciding which switches are activated and the orientation of the links between these switches, so as to obtain a directed acyclic graph (DAG) from the producer nodes to the consumer nodes. This DAG is valid if the electric flow it induces satisfies the demand of each consumer without exceeding the production capacity of each source and the flow capacity of each switch. We show that the problem of deciding if such a valid DAG exists is NP-complete. In the case where such a valid DAG exists, we study the problem of determining a valid DAG that balances the ratio between the amount of electricity produced and the maximum production capacity for each source. We show that this minimization problem is also NP-complete in the general case but that it becomes polynomial in the case of ring network topologies. • We balance the ratio between effective and maximum production of electrical sources. • All the input flows of a node should be equal. The flow satisfies capacity constraints. • The flow is indirectly imposed by activating switches and directing electrical links. • The problem is NP-Hard but polynomial for ring networks. [ABSTRACT FROM AUTHOR]

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This paper presents a new particle swarm optimizer for solving multimodal multiobjective optimization problems which may have more than one Pareto-optimal solution corresponding to the same objective function value. The proposed method features an index-based ring topology to induce stable niches that allow the identification of a larger number of Pareto-optimal solutions, and adopts a special crowding distance concept as a density metric in the decision and objective spaces. The algorithm is shown to not only locate and maintain a larger number of Pareto-optimal solutions, but also to obtain good distributions in both the decision and objective spaces. In addition, new multimodal multiobjective optimization test functions and a novel performance indicator are designed for the purpose of assessing the performance of the proposed algorithms. An effectiveness validation study is carried out comparing the proposed method with five other algorithms using the benchmark functions to prove its effectiveness. [ABSTRACT FROM AUTHOR]

In essence, Network-on-Chip (NoC) also known as on-chip interconnection network has been proposed as a design solution to System-on-Chip (SoC). The routing algorithm, topology and switching technique are significant because of the most influential effect on the overall performance of Network-on- Chip (NoC). Designing of large scale topology alongside the support of deadlock free, low latency, high throughput and low power consumption is notably challenging in particular with expanding network size. This paper proposed an 8x8 XX-Torus and 64 nodes XX-Ring topology schemes for Network-on-Chip to minimize the latency by decrease the node diameter from the source node to destination node. Correspondingly, we compare in differences on the performance of mesh, full-mesh, torus and ring topologies with XX-Torus and XX-Ring topologies in term of latency. Results show that XX-Ring outperforms the conventional topologies in term of latency. XX-Ring decreases the average latency by 106.28%, 14.80%, 6.7 1%, 1.73%, 442.24% over the mesh, fully-mesh, torus, XX-torus, and Ring topologies. [ABSTRACT FROM AUTHOR]

Particle swarm optimization (PSO) algorithm has shown promising performances on various benchmark functions and engineering optimization problems. However, it is still difficult to achieve a satisfying trade-off between exploration and exploitation for all the optimization problems and different evolving stages. Furthermore, control parameters of some related mechanisms need pre-experience by the requirement of trial-and-error scheme. This paper presents a novel PSO algorithm, which adaptively adopts various search strategies, called Self-adapting Hybrid Strategy PSO (SaHSPS). Unlike some other peer PSO variants, this method dynamically changes the probabilities of different strategies according to their previous successful searching memories, without any additional control parameters. The probabilities of different strategies would be re-initialized according to a proposed dynamic probabilistic model to diverse the population. Besides, particles are updated by probabilistically selected strategies after niching PSO with Ring topology. Moreover, a dynamic updating mechanism by niching PSO is proposed to guarantee the parallel searching capability during the whole evolution process. Thus, this proposed algorithm might be problem-independent and search-stage-independent, yielding more satisfying solutions on various optimization problems. A comprehensive experimental study is conducted on 28 benchmark functions of CEC 2013 special session on real-parameter optimization, including shifted, rotated, multi-modal, high conditioned, expanded and composition problems, compared with several state-of-the-art variants of PSO and differential evolution (DE) algorithms. Comparison results show that SaHSPS obtains outstanding performances on the majority of the test problems. Moreover, a practical engineering problem, real power loss minimization of IEEE 30-bus power system, is used to further evaluate SaHSPS. The numerical results, compared with other stochastic search algorithms, show that SaHSPS could find high-quality solutions with higher probability. [ABSTRACT FROM AUTHOR]

We propose a wavelength-reuse wavelength-division multiplexing semipassive optical access network architecture with ring topology. Two access rings are controlled by one central office. The system capacity, as well as the network cover area, can be doubled with this proposal. When fiber failure occurs, the corresponding switches in remote nodes change to protection state to restore the network communication. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT Today, tree or hybrid tree-star topologies are mostly used for passive optical networks in practice. However, these topologies are significantly vulnerable against the failures of a central optical line termination (OLT) unit. Recently, an innovative idea about forming a simple ring topology by using asymmetric passive splitters together with secondary OLT unit has been presented and an elementary mathematical model for calculations of optimum splitting ratios of all splitters in a ring infrastructure has been described. The major advantage of presented ring topology is that both primary and secondary OLT units can be placed on the opposite sides of the ring, which could greatly increase the overall resistance of the whole network against critical failures, malfunctions, or sophisticated attacks. Next, this ring topology was successfully realized in practice by using real OLT and optical network units and the whole idea verified. The results of real measurements as well as theoretical calculations are presented in this article. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2201-2205, 2013 [ABSTRACT FROM AUTHOR]

A novel wavelength division multiplexing metro-access network based on dual-fiber ring of remote nodes and star topology of optical network units is designed to realize the reliable network in case of either single or dual fiber failure. In the design, the survivability of the network is largely enhanced by three work modes. Simultaneously, this network structure can also avoid the crosstalk between uplink and downlink. The simulation results demonstrated with 2.5-Gb/s up/downstream signals show this approach could work very well. [ABSTRACT FROM AUTHOR]

Today, passive optical networks (PONs) are mostly used as modern high-speed access networks for various applications. However, there are also several specific applications, such as in business, office, army or science sector, which require a complex protection and backup system against failures and malfunctions. Typically, tree or star topologies are used for passive optical networks PONs. These topologies are vulnerable mainly against the failures of central optical line termination (OUT) unit. This paper presents an innovative method for protecting PONs by using ring topologies, especially the OUT unit. The method is described in the article, and an elementary mathematical model for calculations of asymmetric passive optical splitters together with an example is included as well. [ABSTRACT FROM AUTHOR]

The analysis of previously evolved rhythmic asynchronous random Boolean networks [Biosystems 59 (2001) 185] reveals common topological characteristics indicating that rhythm originates from a circular functional structure. The rhythm generating core of the network has the form of a closed ring which operates as a synchronisation substrate by supporting a travelling wave of state change; the size of the ring corresponds well with the period of oscillation. The remaining nodes in the network are either stationary or follow the activity of the ring without feeding back into it so as to form a coherent whole. Rings are typically formed early on in the evolutionary search process. Alternatively, long chains of nodes are favoured before they close upon themselves to stabilize. Analysis of asynchronous networks with de-correlated (non-rhythmic, non-stationary) attractors reveals no such common topological characteristics. These results have been obtained using statistical analysis and a specifically developed bottom–up pruning algorithm. This algorithm works from local interactions to global configuration by eliminating redundant links. The suitability of the algorithm has been confirmed by both numerical and single lesion analysis. The ring topology solution for the generation of rhythm implies that it will be harder to evolve rhythmic networks for big sizes and small periods and for bigger number of connections per node. These trends are confirmed empirically. Finally, the identified mechanisms are utilised to handcraft rhythmic networks of different periods showing that a low number of connections suffices for a large variety of rhythms. Random asynchronous update forces the evolved solutions to be highly robust maintaining their performance in the presence of intrinsic noise. The biological implications of such robust designs for molecular clocks are discussed. [Copyright &y& Elsevier]