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2020, International Journal of Advanced Trends in Computer Science and Engineering
https://doi.org/10.30534/ijatcse/2020/210932020…
6 pages
1 file
When it comes to finding the shortest path in a graph, most people think of Dijkstra's algorithm. While Dijkstra's algorithm is indeed very useful, there are some other parameters that can be used to find the shortest path while communicating in a weighted network. In a graph network, there are different types of centrality measures used to find the importance of a node. In that Degree Centrality, Closeness Centrality and Betweenness Centrality are useful for identifying the amount of importanceof a node in a graph. Centrality measures are used to find nodes that act as a bridge from one part of a network to another part of a network. In this paper, results shows that there is better possibility to find shortest path using Degree Centrality or Closeness Centrality or Betweenness centrality compared with Dijkstra's algorithm.
— Calculating betweenness centrality is one way to find influential vertices of a graph and identify vertices more traversed than others. The common method takes advantage of the shortest paths between two vertices in order to find the centrality. The problem with this approach is that in many real-world applications, traversing edges and vertices does not necessarily take place in the shortest paths (news, rumors and messages do not always pass from the shortest path to reach the target). For this purpose, random Betweenness centrality approach (or Random-Walk Betweenness) has been developed, in which the paths between source and destination are randomly selected. Random Betweenness centrality of the vertex v shows the number of traverses from vertex v in all random paths between all vertices. This algorithm has a high time complexity of O (n 3) and high computational requirement; therefore, it hat a limited use for very large graphs. Motivated by this limitation, different estimation methods are presented in this research to estimate the random Betweenness centrality. Estimation methods such as random, linear and bisection have been already tested on different algorithms. In shortest path based betweenness centralities, linear estimation gives better result comparing to random and bisection estimations. Here, a novel linear and bisection estimation methods are proposed particularly for random walk betweenness and then it is shown linear method gives better results comparing to other available methods. It also requires less computational complexity comparing to bisection method. The main contribution of this work is to develop an estimation method to achieve a fair estimation of random-walk betweenness centrality using linear estimation.
Social Networks, 2010
Weighted networks a b s t r a c t Ties often have a strength naturally associated with them that differentiate them from each other. Tie strength has been operationalized as weights. A few network measures have been proposed for weighted networks, including three common measures of node centrality: degree, closeness, and betweenness. However, these generalizations have solely focused on tie weights, and not on the number of ties, which was the central component of the original measures. This paper proposes generalizations that combine both these aspects. We illustrate the benefits of this approach by applying one of them to Freeman's EIES dataset.
Journal of Mathematical Chemistry, 2010
Centrality of an edge of a graph is proposed to be viewed as a degree of global sensitivity of a graph distance function (i.e., a graph metric) on the weight of the considered edge. For different choices of distance function, contact is made with several previous ideas of centrality, whence their different characteristics are clarified, and strengths or shortcomings are indicated, via selected examples. The centrality based on "resistance distance" exhibits several nice features, and might be termed "amongness" centrality.
Information Sciences, 2012
The centrality of vertices has been a key issue in network analysis. For unweighted networks where edges are just present or absent and have no weight attached, many centrality measures have been presented, such as degree, betweenness, closeness, eigenvector and subgraph centrality. There has been a growing need to design centrality measures for weighted networks, because weighted networks where edges are attached weights would contain rich information. Some network measures have been proposed for weighted networks, including three common measures of vertex centrality: degree, closeness, and betweenness. In this paper, we propose a new centrality measure called the Laplacian centrality measure for weighted networks. The Laplacian energy is defined as E L ðGÞ ¼ P i k 2 i , where k i 's are eigenvalues of the Laplacian matrix of weighted network G. The importance (centrality) of a vertex v is reflected by the drop of the Laplacian energy of the network to respond to the deactivation (deletion) of the vertex from the network. We also prove an algebraic graph theory result that provides a structural description of the Laplacian centrality measure which is in terms of the number of all kinds of 2-walks. Laplacian centrality unveils more structural information about connectivity and density around v (further than its immediate neighborhood). That is, comparing with other standard centrality measures proposed for weighted networks (e.g. degree, closeness or betweenness centrality), Laplacian centrality is an intermediate measuring between global and local characterization of the importance (centrality) of a vertex. We further investigate the validness and robustness of this new centrality measure by illustrating this method to some classical weighted social network data sets and obtain reliable results, which provide strong evidences of the new measure's utility.
The centrality of an edge in a graph is proposed to be the degree of sensitivity of a graph distance function to the weight of the edge under consideration. Many centrality metrics are available in network analysis and are effectively used in the investigation of social network properties. Node position is one of them. In this paper, we propose a novel importance of nodes showing how to locate the most essential nodes in a network and to construct a centrality measure for each node in the network, sort the nodes by centralities, and focus on the top ranked nodes, which are the most relevant in terms of this centrality measure. Our research aims to explain how to identify the most important nodes in networks. A centrality metric should be established for each node in the network, and then the nodes based on their centralities, focusing on the top-ranked nodes, which in light of this importance, might be regarded as the most pertinent measure.
Algorithms and Models for the Web-Graph
Betweenness is a centrality measure based on shortest paths, widely used in complex network analysis. It is computationally-expensive to exactly determine betweenness; currently the fastest-known algorithm by Brandes requires O(nm) time for unweighted graphs and O(nm + n 2 log n) time for weighted graphs, where n is the number of vertices and m is the number of edges in the network. These are also the worstcase time bounds for computing the betweenness score of a single vertex. In this paper, we present a novel approximation algorithm for computing betweenness centrality of a given vertex, for both weighted and unweighted graphs. Our approximation algorithm is based on an adaptive sampling technique that significantly reduces the number of single-source shortest path computations for vertices with high centrality. We conduct an extensive experimental study on real-world graph instances, and observe that our random sampling algorithm gives very good betweenness approximations for biological networks, road networks and web crawls.
Journal of the ACM, 2010
Betweenness-Centrality measure is often used in social and computer communication networks to estimate the potential monitoring and control capabilities a vertex may have on data flowing in the network. In this article, we define the Routing Betweenness Centrality (RBC) measure that generalizes previously well known Betweenness measures such as the Shortest Path Betweenness, Flow Betweenness, and Traffic Load Centrality by considering network flows created by arbitrary loop-free routing strategies. We present algorithms for computing RBC of all the individual vertices in the network and algorithms for computing the RBC of a given group of vertices, where the RBC of a group of vertices represents their potential to collaboratively monitor and control data flows in the network. Two types of collaborations are considered: (i) conjunctive—the group is a sequences of vertices controlling traffic where all members of the sequence process the traffic in the order defined by the sequence an...
Genetic mechanisms of the influence of light and phototransduction on Drosophila melanogaster lifespan, 2018
The light of the visible spectrum (with wavelengths of 380–780 nm) is one of the fundamental abiotic factors to which organisms have been adapting since the start of biological evolution on the Earth. Numerous literature sources establish a connection between the duration of exposure to daylight, carcinogenesis and longevity, con-vincingly showing a significant reduction in the incidence of cancer in blind people, as well as in animal models. On the other hand, the stimulating nature of the effect of continuous illumination on reproductive function was noted, in particular, the effects of increasing the fecundity of females of various species are known. Increase in motor activity and, as a result, in metabolic rate and thermogenesis during permanent exposure to light also reduces the body’s energy reserves and lifespan. In principle, in the context of aging, not only the exposure time, but also the age at the onset of exposure to constant illumination matter, the reverse effects are valid for the maintenance of experimental animals in the constant darkness. Over the long period of the evolution of light signal transduc- tion systems, many mechanisms have emerged that allow to form an adequate response of the organism to illumination, modulating the highly conservative signaling cas- cades, including those associated with aging and lifespan (FOXO, SIRT1, NF-κB, mTOR/S6k, PPARα, etc). In this review, we consider the relationship between life expectancy, pho-toregimens, and also the expression of the genes encoding the phototransduction cascade and the circadian oscillator elements of animal cells. In the present paper, basic trans-ducers of light and other signals, such as the family of TRP receptors, G proteins, phospholipase C, and others, are considered in the context of aging and longevity. A relationship between the mechanisms of thermoreception, the temperature synchronization of the circadian oscillator and the life span is established in the review. Analysis of experimental data obtained from the Drosophila melanogaster model allowed us to formulate the hypothesis of age-dependent photoresistance – a gradual decrease in the expression of genes associated with phototransduc-tion and circadian oscillators, leading to deterioration in the ability to adapt to the photoregimen and to the increase in the rate of aging.
Environmental Pollution is one of the global issues that has been the agenda ever since. In a global scale, almost 80% of our marine pollution comes from the land based activities such as oil spills, fertilizers, seas of garbage, sewage disposal, and toxic chemicals from industries. This case study is done in Madang town along the Madang Star International Hotel towards the main town Market. It is approximately 1km drive from Divine Word University. Rationale of this study is to identify the environmental damage done to the rivers/ oceans and in public places where people do marketing and at the same time the resting places. The area was quiet alarming where it is full of rubbish from plastic bags, tin cans, bags, and old materials from the neighboring residence all are dumped into the sea. However, this paper will give analyses and give mitigation approached for conserving the environment to deter from water pollution.
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