Network Diameter Research Articles

A Social Network Analysis of Knowledge Infrastructure in the Second Language Acquisition Domain

This study utilizes the social network analysis (SNA) technique to analyze and better understand the semantic and knowledge networks that are associated with the linguistic domain of second language acquisition (SLA). Our analytic research helps to further define our understanding of SLA by constructing a detailed description of the domain’s network knowledge infrastructure. By analyzing 5,297 publications, authored by 9,220 authors, and published in 1471 outlets. Our study utilized the SNA tool to examine the author, institution, bibliographic coupling and keyword networks of the SLA domain. The results of our study show that SLA network is relatively fragmented containing several isolated clusters of authors. The study also found that the diameter of the co-authorship network is relatively small and has clustering co-efficient that is high and displays the small world phenomenon. (Konkuk University, Chungnam National University, University of Waikato Management School)

Node-independent spanning trees in Gaussian networks

Message broadcasting in networks can be efficiently carried over spanning trees. A set of spanning trees in the same network is node independent if two conditions are satisfied. First, all trees are rooted at the same node r. Second, for every node u in the network, all trees’ paths from r to u are node-disjoint, excluding the end nodes r and u. Independent spanning trees have applications in fault-tolerant communications and secure message distributions.Gaussian networks and two-dimensional toroidal networks share similar topological characteristics. They are regular of degree four, symmetric, and node-transitive. Gaussian networks, however, have relatively lesser network diameter that could result in a better performance. This promotes Gaussian networks to be a potential alternative for two-dimensional toroidal networks.In this paper, we present constructions for node independent spanning trees in dense Gaussian networks. Based on these constructions, we design routing algorithms that can be used in fault-tolerant routing and secure message distribution. We also design fault-tolerant algorithms to construct these trees in parallel.

The Modeling and Analysis for the Large-Scale Modular Energy Storage Systems Based on Complex Network

The large-scale modular energy storage systems (MESS) technology is one of the key technologies in relieving power contradictions and achieving the sustainable energy development. An accurate simulation model, which can capture the complicated and dynamic configuration characteristic of MESS, is very crucial for analyzing the performance of MESS with the architecture properties. In this paper, we have explored bipartite network method in complex networks to construct a network-architecture model of MESS. The coupling relationship between the electrical characteristics (voltage, current and power) and network characteristics (the network diameter, the degree of output terminals) was established. The structure coupling coefficient are presented to analysis the evolution and extension of MESS. Accordingly, the network-architecture model of MESS provides effective simulation analysis method for the plan and optimization of MESS.

An Experimental Evaluation of the Reliability of LoRa Long-Range Low-Power Wireless Communication

Recent technological innovations allow compact radios to transmit over long distances with minimal energy consumption and could drastically affect the way Internet of Things (IoT) technologies communicate in the near future. By extending the communication range of links, it is indeed possible to reduce the network diameter to a point that each node can communicate with almost every other node in the network directly. This drastically simplifies communication, removing the need of routing, and significantly reduces the overhead of data collection. Long-range low-power wireless technology, however, is still at its infancy, and it is yet unclear (i) whether it is sufficiently reliable to complement existing short-range and cellular technologies and (ii) which radio settings can sustain a high delivery rate while maximizing energy-efficiency. To shed light on this matter, this paper presents an extensive experimental study of the reliability of LoRa , one of the most promising long-range low-power wireless technologies to date. We focus our evaluation on the impact of physical layer settings on the effective data rate and energy efficiency of communications. Our results show that it is often not worth tuning parameters, thereby reducing the data rate in order to maximize the probability of successful reception, especially on links at the edge of their communication range. Furthermore, we study the impact of environmental factors on the performance of LoRa, and show that higher temperatures significantly decrease the received signal strength and may drastically affect packet reception.

Distributed Finite-Time Average-Consensus With Limited Computational and Storage Capability

Consensus is a fundamental feature of distributed systems, and it is the prerequisite for several complex tasks, such as flocking of mobile robots, localization in wireless-sensor networks, or decentralized control of smart grids. Average consensus, in particular, is quite challenging, because it is typically obtained asymptotically, while few finite-time algorithms are available. In this paper, we provide a methodology to achieve distributed average consensus in finite time, while maintaining low computational and memory requirements, and small completion times. The provided solution, namely, finite-time average-consensus by iterated max-consensus (FAIM) is based on several runs of the max-consensus algorithm, and has low memory requirements for each node. Compared to existing Flooding approaches, the proposed algorithm requires less memory, at the cost of a slight increase in the number of steps required for termination. The FAIM algorithm assumes that the nodes are aware of an upper bound on the network diameter. To relax this assumption, we complement this paper with a novel distributed algorithm that, in the case of undirected graphs, provides an upper bound on the network diameter which, in the worst case, is twice the actual diameter. A comparison of the proposed finite-time algorithm against the state of the art concludes this paper.

A Stabilizing Algorithm for Finding Two Node-Disjoint Paths in Arbitrary Networks

The problem of two node-disjoint paths is to identify two paths [Formula: see text] and [Formula: see text] from source [Formula: see text] to target [Formula: see text] without any common intermediate node in a communication network [Formula: see text], where each node (vertex) in [Formula: see text] denotes a process and each edge [Formula: see text] denotes a communication channel between nodes [Formula: see text] and [Formula: see text]. In this paper, we present the first adaptive stabilizing algorithm for finding a pair of node-disjoint paths in a semi-anonymous arbitrary network in [Formula: see text] rounds and the state-space complexity is [Formula: see text] bits per process, where [Formula: see text] is the diameter of the communication network. The algorithm assumes weakly fair distributed daemon and the knowledge of an upper bound on the number of processes by each process. If two disjoint paths exist between [Formula: see text] and [Formula: see text], two disjoint paths are guaranteed to be constructed. In addition, the algorithm detects if two node-disjoint paths exist or not. Since the proposed algorithm is stabilizing, it does not require initialization and is capable of withstanding transient faults. We view a fault that perturbs the state of the system but not its program as a transient fault. The proposed algorithm has a wide range of applications in ensuring reliability and security of sensor, mobile and fixed communication networks.

Efficient and scalable cross‐by‐pass‐mesh topology for networks‐on‐chip

This study presents an efficient and scalable networks-on-chip (NoC) topology termed as cross-by-pass-mesh (CBP-Mesh). The proposed architecture is derived from the traditional mesh topology by addition of cross-by-pass links in the network. The design and impact of adding cross-by-pass links on the topology is analysed in detail with the help of synthetic, hotspot as well as embedded traffic traces. The advantages of proposed CBP-Mesh as compared with its competitor topologies include reduction in the network diameter, increase in bisection bandwidth, reduction in average numbers of hops, improvement in symmetry and regularity of the network. The synthetic traffic traces and some real embedded system workloads are applied on the proposed CBP-Mesh and its competitor two-dimensional-based NoC topologies. The comparison of analytical results in terms of performance and costs for different network dimensions indicate that the proposed CBP-Mesh offers short latency, high throughput and good scalability at small increase in power and energy.

Fast protocols for leader election and spanning tree construction in a distributed network

We consider leader election and spanning tree construction problems in a synchronous network. Protocols are designed under the assumption that nodes in the network have identifiers but the size of an identifier is unlimited. We present fast protocols with runtime O(D log L+L), where L is the size of the minimal identifier and D is the network diameter.

Attraction Region Seeking for Power Grids

Motivated by growing interest in the smart grid technology and architecture, this brief explores an attraction region for the asymptotical locked phase agreement and frequency synchronization in power networks with a symmetrically connected interaction topology. By placing attention on the complicated system dynamics and network structure, two cases consisting of uniform and nonuniform ratios of the damping coefficient and the inertia strength, respectively, are discussed. The quantitative estimate on the attraction region is characterized explicitly that relates the initial configurations and the system parameters. For the uniform case, by resorting to the second-order Gronwall's differential inequality and the phase and frequency diameters, the uniform boundedness of fluctuations of phase and frequency is established, which requires that the network diameter is smaller than or equal to two. For the nonuniform case, an energy estimate method is applied to ensure the uniform boundedness of fluctuations of phase and frequency, which, however, does not require the network spectral information. The convergence of phase and frequency to a certain equilibrium point is achieved by employing a second-order gradient-like system with an analytic nonlinearity. The obtained results are helpful to the insight into the stability study of large power grids since the model that we considered can be highly heterogeneous.

Optical switching based small-world data center network

Redesigning data center networks, particularly taking advantages of optical switching technologies to reduce cost-per-bandwidth and energy consumption, has spawned interests of researchers worldwide in recent years. In this paper, we introduce and analysis our recently proposed optical switching technology powered data center network architecture, which is inspired from the small world data center network topology yet has additional flexibility brought by optical lightpath's reconfigurability. Specifically, logically full-meshed optical burst switching rings are employed to compose a lattice substrate, which provide dense connectivity for small groups of ToR switches to accommodate highly clustered and dynamic regional data traffic, while a reconfigurable wavelength circuit switching plane offers direct connections among the racks to effectively reduce overall network diameter. A centralized control plane is employed to realize traffic-adaptive optical lightpath scheduling mechanisms. We thoroughly study the throughput and latency performance of the proposed architecture through numerical simulations, and particularly reveal the impact of traffic patterns. It turns out that, the proposed network architecture can achieve high throughput with significantly reduced cost, and exploiting its traffic-adaptive reconfiguration capability can effectively improve throughput and reduce latency under varying traffic distributions.

An Approach for Understanding and Promoting Coal Mine Safety by Exploring Coal Mine Risk Network

Capturing the interrelations among risks is essential to thoroughly understand and promote coal mining safety. From this standpoint, 105 risks and 135 interrelations among risks had been identified from 126 typical accidents, which were also the foundation of constructing coal mine risk network (CMRN). Based on the complex network theory and Pajek, six parameters (i.e., network diameter, network density, average path length, degree, betweenness, and clustering coefficient) were employed to reveal the topological properties of CMRN. As indicated by the results, CMRN possesses scale-free network property because its cumulative degree distribution obeys power-law distribution. This means that CMRN is robust to random hazard and vulnerable to deliberate attack. CMRN is also a small-world network due to its relatively small average path length as well as high clustering coefficient, implying that accident propagation in CMRN is faster than regular network. Furthermore, the effect of risk control is explored. According to the result, it shows that roof collapse, fire, and gas concentration exceeding limit refer to three most valuable targets for risk control among all the risks. This study will help offer recommendations and proposals for making beforehand strategies that can restrain original risks and reduce accidents.

Optimization of the Critical Diameter and Average Path Length of Social Networks

Optimizing average path length (APL) by adding shortcut edges has been widely discussed in connection with social networks, but the relationship between network diameter and APL is generally ignored in the dynamic optimization of APL. In this paper, we analyze this relationship and transform the problem of optimizing APL into the problem of decreasing diameter to 2. We propose a mathematic model based on a memetic algorithm. Experimental results show that our algorithm can efficiently solve this problem as well as optimize APL.

Complexity and Vulnerability Analysis of Critical Infrastructures: A Methodological Approach

Vulnerability analysis of network models has been widely adopted to explore the potential impacts of random disturbances, deliberate attacks, and natural disasters. However, almost all these models are based on a fixed topological structure, in which the physical properties of infrastructure components and their interrelationships are not well captured. In this paper, a new research framework is put forward to quantitatively explore and assess the complexity and vulnerability of critical infrastructure systems. Then, a case study is presented to prove the feasibility and validity of the proposed framework. After constructing metro physical network (MPN), Pajek is employed to analyze its corresponding topological properties, including degree, betweenness, average path length, network diameter, and clustering coefficient. With a comprehensive understanding of the complexity of MPN, it would be beneficial for metro system to restrain original near-miss or accidents and support decision-making in emergency situations. Moreover, through the analysis of two simulation protocols for system component failure, it is found that the MPN turned to be vulnerable under the condition that the high-degree nodes or high-betweenness edges are attacked. These findings will be conductive to offer recommendations and proposals for robust design, risk-based decision-making, and prioritization of risk reduction investment.

Evolution of the Mesoscopic Parameters and Mechanical Properties of Granular Materials upon Loading

Biaxial tests of granular materials under different lateral pressures were numerically simulated to study both the macromechanical behavior and evolution of mesoscopic parameters, including the coordination number, degree, clustering coefficient, and average shortest path length, which can provide information bridging mesoscale to macroscale of the mechanical properties of granular materials in a different and new way. The analysis results demonstrate that, with the increasing lateral pressure, there is a higher coordination number for denser granular material, and the coordination number of the samples eventually tends to the similar value at critical state with the same lateral pressure for different initial porosities; the distribution of the degree is very similar for samples with different initial porosities at critical state; the evolution of the clustering coefficients with axial strain is almost the same as that of the coordination number. At critical state, the clustering coefficients of all samples are almost identical, which means that the internal structures of samples with various initial porosities are similar; the average shortest path decreases with increasing lateral pressure and tends to be stable in the critical state. Additionally, the diameter of the contact network of granular material hardly changes at different lateral pressures at critical state.

Nanofiber-Structured TiO2 Nanocrystals as a Scattering Layer in Dye-Sensitized Solar Cells

We developed a scattering layer composed of TiO2 nanocrystals assembled into a densely packed three-dimensional network of nanofibers to localize light within a photoanode used in dye sensitized solar cells (DSSCs). The electro-netting approach was applied to obtain polyamide 6 nanofibers with bi-modal diameter distribution, followed by solvothermal synthesis for the coating of TiO2 nanocrystals on the polymer template. The resulting nanofiber-structured scattering layer (NFSL) is composed of TiO2 nanofibers (200–300 nm in diameter) supporting an ultrathin nanofiber network (diameters within 10–50 nm) and exhibits strong light scattering in the visible range (400 to 700 nm). This NFSL was applied on top of a transparent active TiO2 layer (TL) forming the photoanode in DSSCs. The performance of the bi-layered photoanode was compared to its analogue, fabricated with commercial scattering layers containing different sizes of nanoparticles. The DSSCs assembled with the NFSL showed an 18% enhancement in power conversion efficiency (PCE) compared to that of DSSCs whose photoanode contained only a TL. This enhancement factor was improved up to 31% when the bi-layered structure was post-treated with TiCl4. The PCE improvement was mainly associated with the light harvesting efficiency within the photoanode because of scattering from the NFSL and increased dye adsorption due to the addition of this top layer. These conclusions were inferred from diffuse reflectance behavior, dye loading measurements, external quantum efficiency and electrochemical properties. Our work demonstrates a promising approach without the requirement of time consuming and complicated procedures for the fabrication of a densely packed 3D nanofiber network scattering layer for diverse energy conversion devices and photocatalytic applications.

A New Cross-By-Pass-Torus Architecture Based on CBP-Mesh and Torus Interconnection for On-Chip Communication.

A Mesh topology is one of the most promising architecture due to its regular and simple structure for on-chip communication. Performance of mesh topology degraded greatly by increasing the network size due to small bisection width and large network diameter. In order to overcome this limitation, many researchers presented modified Mesh design by adding some extra links to improve its performance in terms of network latency and power consumption. The Cross-By-Pass-Mesh was presented by us as an improved version of Mesh topology by intelligent addition of extra links. This paper presents an efficient topology named Cross-By-Pass-Torus for further increase in the performance of the Cross-By-Pass-Mesh topology. The proposed design merges the best features of the Cross-By-Pass-Mesh and Torus, to reduce the network diameter, minimize the average number of hops between nodes, increase the bisection width and to enhance the overall performance of the network. In this paper, the architectural design of the topology is presented and analyzed against similar kind of 2D topologies in terms of average latency, throughput and power consumption. In order to certify the actual behavior of proposed topology, the synthetic traffic trace and five different real embedded application workloads are applied to the proposed as well as other competitor network topologies. The simulation results indicate that Cross-By-Pass-Torus is an efficient candidate among its predecessor’s and competitor topologies due to its less average latency and increased throughput at a slight cost in network power and energy for on-chip communication.

BCCC: An Expandable Network for Data Centers

Designing a cost-effective network topology for data centers that can deliver sufficient bandwidth and consistent latency performance to a large number of servers has been an important and challenging problem. Many server-centric data center network topologies have been proposed recently due to their significant advantage in cost efficiency and data center agility, such as BCube, FiConn, and Bidimensional Compound Network (BCN). However, existing server-centric topologies are either not expandable or demanding prohibitive expansion cost. As the scale of data centers increases rapidly, the lack of expandability in existing server-centric data center networks imposes a severe obstacle for data center upgrade. In this paper, we present a novel server-centric data center network topology called BCube connected crossbars (BCCCs), which can provide good network performance using inexpensive commodity off-the-shelf switches and commodity servers with only two network interface card (NIC) ports. A significant advantage of BCCC is its good expandability. When there is a need for expansion, we can easily add new servers and switches into the existing BCCC with little alteration of the existing structure. Meanwhile, BCCC can accommodate a large number of servers while keeping a very small network diameter. A desirable property of BCCC is that its diameter increases only linearly to the network order (i.e., the number of dimensions), which is superior to most of the existing server-centric networks, such as FiConn and BCN, whose diameters increase exponentially with network order. In addition, there are a rich set of parallel paths with similar length between any pair of servers in BCCC, which enables BCCC to not only deliver sufficient bandwidth capacity and predictable latency to end hosts, but also provide graceful performance degradation in case of component failure. We conduct comprehensive comparisons between BCCC with other popular server-centric network topologies, such as FiConn and BCN. We also propose an effective addressing scheme and routing algorithms for BCCC. We show that BCCC has significant advantages over the existing server-centric topologies in many important metrics, such as expandability, server port utilization, and network diameter.

A Highly Scalable Optical Network-on-Chip With Small Network Diameter and Deadlock Freedom

To increase the performance of chip multiprocessors, optical network-on-chip (ONoC) becomes promising because of its high bandwidth and low energy consumption. In this paper, we propose an architecture called RPNoC (Ring-based Packet-switched NoC), which uses few optical devices. Specifically, Single-waveguide RPNoC employs only one waveguide. Multiwaveguide RPNoC introduces space division multiplexing to make the architecture highly scalable. A novel wavelength assignment method and a deadlock-free deterministic routing algorithm are jointly designed, which make the network diameter quite small. This design also guarantees deadlock freedom, a little resource use, and low complexity at the same time. Evaluation is carried out for the 64-node RPNoC under different synthetic and realistic traffic patterns. The simulation result shows that it yields high throughput and low latency. Comparison with other packet-switched ONoCs shows that RPNoC has the lowest energy consumption.

Check-in based routing strategy in scale-free networks

Abstract In many real complex artificial networks, a navigation route between a pair of source and destination is often desired to pass through at least a specified node called check-in node for doing check-in like services, such as gas fuel supplement for vehicles, GPS recording for express packages and so on. However, currently, there is a lack of routing study for complex networks equipped with check-in nodes. In this work, we first propose a general routing mechanism called check-in based routing (CBR) which can guarantee that every efficient path must include at least one check-in node. With a finite fraction of check-in nodes in the network, it can be observed that the higher the degrees of check-in nodes, the higher the network traffic capacity will be by employing the shortest path routing into CBR (namely CBR-SP). It is a great challenge on routing optimization for a network with a fraction of check-in nodes of the lowest degrees. We then employ the degree-based efficient routing (ER) into the CBR to efficiently redistribute heavy traffic from hub nodes to non-hub nodes. Under the CBR-ER, the traffic capacity can be significantly enhanced at the cost of a little network diameter and average path lengthening. The extensive simulations in scale-free networks can well confirm the effectiveness of CBR-ER.

3D network-on-chip design for embedded ubiquitous computing systems

A novel 3D NoC topology for embedded ubiquitous computing is proposed.A minimal routing algorithm with path diversity in the 3D NoC Topology is used.A power efficient architecture design for NoC-based embedded ubiquitous computing is introduced. Ubiquitous High-Performance Computing applications, such as cyber-physical systems, sensor networks and virtual reality require the support of terascale embedded systems that can deliver higher performance than current systems. Multi-cores, many-cores and heterogeneous processors are becoming the typical design choices to satisfy these requirements. Inter core communication has been one of the major challenges as it affects the bandwidth and power consumption of the multi-cores processors. Network-on-Chips (NoCs) present a fast and scalable interconnection solution to fulfill the requirements of Ubiquitous High-Performance Computing applications. This paper proposes a novel 3D Network-on-Chip called Octagon for Ubiquitous Computing (OUC) that is designed for Embedded Ubiquitous Computing Systems. OUC provides low network diameter and path diversity. Simulation results show that the proposed topology achieves a significant decrease in latency and an average 21.54% and 12.89% improvement in average throughput under hotspot and uniform traffic pattern respectively.