Robustness Of Topology Research Articles

The influence of the existing network layout on water distribution system redesign analysis

The methodologies usually adopted in water distribution system redesign problems consider the topology of the network as an input fixed datum; optimisation solely allowing for the duplication/substitution of existing components. In order to contribute to the identification of optimal solutions that may lead to a lower risk of failure to supply the required water, together with a lower redesign cost, this paper proposes a novel methodology which reports the influence of the existing network configuration and its performance. In particular, the redundancy of loops and the robustness of the network topology are investigated by applying an optimisation technique based on a genetic algorithm and by taking into account the random water demand at each node. The methodology presented has been applied to two case studies, in which it considers the influence of the topology on the overall system reliability/risk. The results demonstrate that it is possible to obtain further configurations that are more reliable for a lower redesign cost. The analysis performed highlights the impact of the topology on the search for an optimal solution, which, as a principal conclusion of the work, should be considered among the decision variables taken into account by the optimisation in a redesign problem.

Quantifying all-to-one network topology robustness under budget constraints

To design robust network topologies that resist strategic attacks, one must first be able to quantify robustness. In a recent line of research, the theory of network blocking games has been used to derive robustness metrics for topologies. However, these previous works did not consider the budget constraints of the network operator. In this paper, we introduce a budget limit on the operator and study two budget constraint formulations: the maximum and the expected cost constraints. For practical applications, the greatest challenge posed by blocking games is their computational complexity. Therefore, we show that the expected cost constraint formulation leads to games that can be solved efficiently, while the maximum cost constraint leads to NP-hard problems. As an illustrative example, this paper discusses the particular case of All-to-One (e.g., sensor or access) networks.

Robustness Analyses of Internet Topology with Power-law Features

For a better predicting and a trying to improve the performance of Internet, we try to study the characteristics of the Internet topology in the autonomous system. Firstly, we put focus on power-law characteristics of Internet topology and give power-law distribution comparison experiments between Internet topology and that of the small-world network. Experiments show clearly that the topology of the Internet has power-law distribution. Secondly, we focus on study the robustness of Internet topology, and experiments show that Internet is robust to random failures and fragile to target attacks. However, a reasonable allocation of network redundancy and network load can make a network strong and low-cost with abilities to be robust under target attacks.

Dynamical and topological robustness of the mammalian cell cycle network: A reverse engineering approach

A common gene regulatory network model is the threshold Boolean network, used for example to model the Arabidopsis thaliana floral morphogenesis network or the fission yeast cell cycle network. In this paper, we analyze a logical model of the mammalian cell cycle network and its threshold Boolean network equivalent. Firstly, the robustness of the network was explored with respect to update perturbations, in particular, what happened to the attractors for all the deterministic updating schemes. Results on the number of different limit cycles, limit cycle lengths, basin of attraction size, for all the deterministic updating schemes were obtained through mathematical and computational tools. Secondly, we analyzed the topology robustness of the network, by reconstructing synthetic networks that contained exactly the same attractors as the original model by means of a swarm intelligence approach. Our results indicate that networks may not be very robust given the great variety of limit cycles that a network can obtain depending on the updating scheme. In addition, we identified an omnipresent network with interactions that match with the original model as well as the discovery of new interactions. The techniques presented in this paper are general, and can be used to analyze other logical or threshold Boolean network models of gene regulatory networks.

Energy-aware self-organisation algorithms with heterogeneous connectivity in wireless sensor networks

Heterogeneity of node energy is a common phenomenon in wireless sensor networks. In such node energy heterogeneous sensor network, how to balance the energy consumption is the key problem on extending the lifetime of the sensor network system. An energy-efficient self-organisation algorithm with heterogeneous connectivity based on energy-awareness is proposed. Each sensor node in the network adjusts its own transmission radius based on the local energy information during the constructing and operating phase. Thus heterogeneous network topology, in which the nodes can choose different transmission radius, is formed. In contrast to the homogeneous network model, in which the node carries the same radius, simulation and analysis are conducted to explore the topology characteristics and robustness with different node energy distribution. The degree distribution shows the scale-free property in the heterogeneous model. The proposed network model enjoys higher efficiency of transmitting data, less clustering, higher robustness under node random failures and longer network lifetime than those in the homogeneous ones.

A scoring mechanism for the rank aggregation of network robustness

To date, a number of metrics have been proposed to quantify inherent robustness of network topology against failures. However, each single metric usually only offers a limited view of network vulnerability to different types of random failures and targeted attacks. When applied to certain network configurations, different metrics rank network topology robustness in different orders which is rather inconsistent, and no single metric fully characterizes network robustness against different modes of failure. To overcome such inconsistency, this work proposes a multi-metric approach as the basis of evaluating aggregate ranking of network topology robustness. This is based on simultaneous utilization of a minimal set of distinct robustness metrics that are standardized so to give way to a direct comparison of vulnerability across networks with different sizes and configurations, hence leading to an initial scoring of inherent topology robustness. Subsequently, based on the inputs of initial scoring a rank aggregation method is employed to allocate an overall ranking of robustness to each network topology. A discussion is presented in support of the presented multi-metric approach and its applications to more realistically assess and rank network topology robustness.

Robustness Measure of China’s Railway Network Topology Using Relative Entropy

This study focused on China’s railway network topology issue from a robustness measure perspective. Relative entropy is used in the study as a measurement of robustness of railway network topology. It is found that the entropy-based measure provides more informative analyses compared to a traditional graph measure. The results indicate that the railway network in the 12th five-year plan has improved robustness when compare to 2008 with respect to deliberate and random attacks.

J121013 SOMを用いたロバストトポロジー最適解の探索([J121-01]解析・設計の高度化・最適化(1))

Among many structures in Super Sonic Transportation (SST) thin wing, the lug structure which is between the body and the main wing plays important role. In the lug structure, robust topology optimization is necessary to determine the optimal structural lay out solutions insensitive to loading uncertainties for design of the lug structure, because it is subjected many loads that have uncertainties of loading caused by aeroelastic forces. The present paper proposes a method to explore robust topologies in Pareto-solutions of topology optimization problem with multi-loadcase. Pareto-solutions are obtained by using Multi-Objective Evolutionary Algorithms (MOEA). After that to estimate the robustness of topology from Pareto optima solutions Monte Carlo simulations were used. And obtained robust topology solutions are explored by Self-Organizing Map that is an appropriate tool to explore properties of the high dimension data. Finally, proposed method approach is applied for the lug structure robust topology optimization.

A Permanent Magnet Brushless DC Motor With Bifilar Winding for Automotive Engine Cooling Application

This paper presents a sensorless bifilar wound permanent magnet brushless DC (BW-PMBLDC) motor fan for automotive engine cooling applications. The key is to incorporate the bifilar winding design into the conventional half-wave PMBLDC motor. Due to the perfect flux-coupling effect between bifilar winding, a regenerative capability is developed so that the trapped energy in the conducting winding during the turn-off period can be re-dumped to DC source through the other winding in the bifilar pair, hence effectively promoting the energy efficiency and repressing the voltage spikes. Moreover, the complementary scheme developed between the bifilar wound phases enables bipolar excitation on the unipolar converter topology. Therefore, the BWPMBLDC motor cannot only offer the advantages of full-wave motor in efficiency, voltage spike reduction, and low torque ripple, but also retain the advantages of simplicity and robustness of unipolar converter topology. Both simulation and experimental results are presented to validate the feasibility.

From where did the Western honeybee (Apis mellifera) originate?

The native range of the honeybee Apis mellifera encompasses Europe, Africa, and the Middle East, whereas the nine other species of Apis are found exclusively in Asia. It is therefore commonly assumed that A. mellifera arose in Asia and expanded into Europe and Africa. However, other hypotheses for the origin of A. mellifera have also been proposed based on phylogenetic trees constructed from genetic markers. In particular, an analysis based on >1000 single-nucleotide polymorphism markers placed the root of the tree of A. mellifera subspecies among samples from Africa, suggestive of an out-of-Africa expansion. Here, we re-evaluate the evidence for this and other hypotheses by testing the robustness of the tree topology to different tree-building methods and by removing specimens with a potentially hybrid background. These analyses do not unequivocally place the root of the tree of A. mellifera subspecies within Africa, and are potentially consistent with a variety of hypotheses for honeybee evolution, including an expansion out of Asia. Our analyses also support high divergence between western and eastern European populations of A. mellifera, suggesting they are likely derived from two distinct colonization routes, although the sources of these expansions are still unclear.

Distance based Phylogenetic Trees with Bootstrapping

PHYLOGENY is the concept of phylogenetic trees which is typically a graphical representation of the evolutionary relationships among three or more genes or organisms. The tree construction can be done through different tree-building methods which include methods based on distances and characters. After a phylogenetic tree is being constructed, it is important to access its accuracy which refers to the degree to which a tree approximates the true tree. The best approach to test the phylogeneies is bootstrap analysis or simply bootstrapping. Bootstrapping is not a technique to check the accuracy of a tree. Instead, it describes the robustness of the tree topology. This paper discusses the searching and analyses of different possible inputs selected on the basis of family of genes or organisms so as to obtain the most optimal result. An algorithm was developed to determine the reliability of an inferred phylogenetic tree.

因特网AS 级拓扑的健壮性测度与健壮性演化

The inter-domain routing system consisting of autonomous systems (AS) is the key infrastructure of the Internet. It is critical to study the robustness of the Internet AS topology for the design of the robustness of the whole Internet. The Northeast Blackout (2003) and the Taiwan earthquakes (December of 2006 and March of 2010) reveal that the robustness of todays Internet still needs to be improved. Taking into account both basic theory of network topology and practical compliance to routing policies, this paper investigates the robustness measurement and evolution of the Internet AS topology at two scales: 1)we propose a method for measuring the robustness of individual ASes against AS link and node failures; 2)we propose a k-fault tolerant model for measuring the robustness of the global AS topology; 3)based on the two measuring methods, we present mechanisms and methods for the robustness evolution at both of the scales. Studying on todays real AS topology, we find that: 1)25.8% of all ASes bear even single AS link failures, and 26.4% of all ASes cannot are still vulnerable to single AS node failures; 2)augmenting existing AS topology to <italic>k</italic>-fault tolerance cannot only guarantee the reachability of any node pairs under arbitrary <italic>k</italic> failures, but also providing significantly better robustness under cases of more than <italic>k</italic> failures.

Research on Robustness of Tree-based P2P Streaming

Research on P2P streaming media is a hot topic in the area of Internet technology. It has emerged as a promising technique. This new paradigm brings a number of unique advantages such as scalability, resilience and also effectiveness in coping with dynamics and heterogeneity. However, There are also many problems in P2P streaming media systems using traditional tree-based topology such as the bandwidth limits between parents and child nodes; node's joining or leaving has a great effect on robustness of tree-based topology. This paper will introduce a method of measuring the robustness of tree-based topology: using network measurement, we observe and record the bandwidth between all the nodes, analyses the correlation between all the sibling flows, measure the robustness of tree-based topology. And the result shows that in the Tree-based topology, the different links which have similar routing paths would share the bandwidth bottleneck, reduce the robustness of the Tree-based topology.

A Novel Kernel Matrix Isomap Algorithm Based on Partial Least Squares

In this paper, to alleviate the influence of the noise the inaccurate measurement in the complicated environment, based on the robust ability in multivariate linear regression of PLS, and in combination with nonlinear data dimension reduction of manifold learning, a novel kernel matrix Isomap algorithm is proposed. The contribution rate is used to find and delete the “short circuit” edge. The matrix constructed by double centered transformation and kernel transformation trick is mapped to a high dimensional feature space, finally the relative position is obtained by PLS. Compared with traditional Isomap and MDS, simulation results indicate that the algorithm has good topology stability, generalization property, robustness and lower computational complexity

Band structure engineering in (Bi1−xSbx)2Te3 ternary topological insulators

Topological insulators (TIs) are quantum materials with insulating bulk and topologically protected metallic surfaces with Dirac-like band structure. The most challenging problem faced by current investigations of these materials is to establish the existence of significant bulk conduction. Here we show how the band structure of topological insulators can be engineered by molecular beam epitaxy growth of (Bi(1-x)Sb(x))(2)Te(3) ternary compounds. The topological surface states are shown to exist over the entire composition range of (Bi(1-x)Sb(x))(2)Te(3), indicating the robustness of bulk Z(2) topology. Most remarkably, the band engineering leads to ideal TIs with truly insulating bulk and tunable surface states across the Dirac point that behaves like one-quarter of graphene. This work demonstrates a new route to achieving intrinsic quantum transport of the topological surface states and designing conceptually new topologically insulating devices based on well-established semiconductor technology.

Network design methods for mitigation of intentional attacks in scale-free networks

Network robustness and network reliability are important issues in the design of Internet Service Providers' topologies. In this paper, we examine the structural characteristics of network topologies that affect robustness and reliability. We examine the interplay between the structural characteristics of network topologies and the resource capacity over-provisioning strategies when the network breakdowns subject to practical constraints (router technology) and economic considerations (link costs). We study the robustness of the Internet connectivity under node intentional harmful attack using two attacks strategies: static degree-based and static load-based. We find that the robustness of network topologies is affected by the variation of their structural characteristics. In our proposed approach, we show that highly-heterogeneous topologies have less robustness compared with lightly-heterogeneous topologies. The observations from the robustness study provide us useful insights for proposing multiple efficient preventive resource capacity over-provisioning strategies for mitigation of intentional attacks. The proposed strategies utilize the structural properties by calculating the excess traffic in case of single global cascading failure for each node and measure its influence on the other nodes as well as locally. The results show that our proposed strategies can significantly enhance the robustness and increase the resilience of network topology. We also show that highly-heterogeneous topologies have high resilience compared with lightly-heterogeneous topologies. By using real data from the Sprint network at the router level, we provide further empirical evidence in support of the proposed approach.

A robust P2P streaming architecture and its application to a high quality live-video service

Abstract This paper explores the design of a P2P architecture that sends real-time video over the Internet. The aim is to provide good quality levels in a highly dynamic P2P topology, where the frequent connections/disconnections of the nodes makes it difficult to offer the Quality-of-Experience (QoE) needed by the client. We study a multi-source streaming approach where the stream is decomposed into several flows sent by different peers to each client including some level of redundancy, in order to cope with the fluctuations in network connectivity. We employ the recently proposed PSQA technology for evaluating automatically the perceived quality at the client side. We introduce a mathematical programming model to maximize the global expected QoE of the network (evaluated using PSQA), selecting a P2P connection scheme which enhances topology robustness. In addition, we provide an approximated algorithm to solve the proposed model, and we apply it to solve a case study based on real life data.

Evidence for 26 distinct acyl-coenzyme A synthetase genes in the human genome

Acyl-coenzyme A synthetases (ACSs) catalyze the fundamental, initial reaction in fatty acid metabolism. "Activation" of fatty acids by thioesterification to CoA allows their participation in both anabolic and catabolic pathways. The availability of the sequenced human genome has facilitated the investigation of the number of ACS genes present. Using two conserved amino acid sequence motifs to probe human DNA databases, 26 ACS family genes/proteins were identified. ACS activity in either humans or rodents was demonstrated previously for 20 proteins, but 6 remain candidate ACSs. For two candidates, cDNA was cloned, protein was expressed in COS-1 cells, and ACS activity was detected. Amino acid sequence similarities were used to assign enzymes into subfamilies, and subfamily assignments were consistent with acyl chain length preference. Four of the 26 proteins did not fit into a subfamily, and bootstrap analysis of phylograms was consistent with evolutionary divergence. Three additional conserved amino acid sequence motifs were identified that likely have functional or structural roles. The existence of many ACSs suggests that each plays a unique role, directing the acyl-CoA product to a specific metabolic fate. Knowing the full complement of ACS genes in the human genome will facilitate future studies to characterize their specific biological functions.

Phylogenetics of the brachyuran crabs (Crustacea: Decapoda): The status of Podotremata based on small subunit nuclear ribosomal RNA

The true crabs, the Brachyura, are generally divided into two major groups: Eubrachyura or 'advanced’ crabs, and Podotremata or 'primitive’ crabs. The status of Podotremata is one of the most controversial issues in brachyuran systematics. The podotreme crabs, best recognised by the possession of gonopores on the coxae of the pereopods, have variously been regarded as mono-, para- or polyphyletic, or even as non-brachyuran. For the first time, the phylogenetic positions of the podotreme crabs were studied by cladistic analysis of small subunit nuclear ribosomal RNA sequences. Eight of 10 podotreme families were represented along with representatives of 17 eubrachyuran families. Under both maximum parsimony and Bayesian Inference, Podotremata was found to be significantly paraphyletic, comprising three major clades: Dromiacea, Raninoida, and Cyclodorippoida. The most 'basal’ is Dromiacea, followed by Raninoida and Cylodorippoida. Notably, Cyclodorippoida was identified as the sister group of the Eubrachyura. Previous hypotheses that the dromiid crab, Hypoconcha, is an anomuran were unsupported, though Dromiidae as presently composed could be paraphyletic. Topologies constrained for podotreme monophyly were found to be significantly worse (P<0.04) than unconstrained topologies under Templeton and S–H tests. The clear pattern of podotreme paraphyly and robustness of topologies recovered indicates that Podotremata as a formal concept is untenable. Relationships among the eubrachyurans were generally equivocal, though results indicate the majoids or dorippoids were the least derived of the Eubrachyura. A new high level classification of the Brachyura is proposed.

Systematic Methodology for Designing Reconfigurable $\Delta\Sigma$ Modulator Topologies for Multimode Communication Systems

This paper proposes a systematic methodology for designing reconfigurable continuous-time DeltaSigma modulator topologies. Topologies are optimized by minimizing the complexity of the topologies, maximizing the sharing of circuits between the different modes, maximizing the topology robustness with respect to circuit nonidealities, and minimizing the total power consumption. This paper presents a case study for designing topologies for a three-mode reconfigurable DeltaSigma modulator and compares the obtained topologies with a state-of-the-art design and topologies obtained using the DeltaSigma Toolbox