Search

Clustering and routing algorithms are critical to collecting and processing data sensed by nodes of wireless sensor networks deployed in various missions including environmental monitoring, tracking, and rescue operations. In this paper, a clustering algorithm is presented for wireless sensor networks with balanced cluster size resulting in energy efficiency. The algorithm is based on forming clusters using topology of the network and routing aggregated data from each cluster head to the base station. The cluster formation phase involves using tree-based traversals on the underlying sensor network graph. Using simulations, it is demonstrated that clusters of similar sizes are obtained for networks of varying sensor radii. It is demonstrated that the time to death of the first node of this clustering algorithm is superior to well-known clustering algorithm for random networks. [ABSTRACT FROM AUTHOR]

Phylogenetic networks are mathematical representations of evolutionary history that are able to capture both tree-like evolutionary processes (speciations) and non-tree-like ‘reticulate’ processes such as hybridization or horizontal gene transfer. The additional complexity that comes with this capacity, however, makes networks harder to infer from data, and more complicated to work with as mathematical objects. In this paper, we define a new, large class of phylogenetic networks, that we call labellable, and show that they are in bijection with the set of ‘expanding covers’ of finite sets. This correspondence is a generalisation of the encoding of phylogenetic forests by partitions of finite sets. Labellable networks can be characterised by a simple combinatorial condition, and we describe the relationship between this large class and other commonly studied classes. Furthermore, we show that all phylogenetic networks have a quotient network that is labellable. [ABSTRACT FROM AUTHOR]

In phylogenetics, evolution is traditionally represented in a tree-like manner. However, phylogenetic networks can be more appropriate for representing evolutionary events such as hybridization, horizontal gene transfer, and others. In particular, the class of forest-based networks was recently introduced to represent introgression, in which genes are swapped between species. A network is forest-based if it can be obtained by adding arcs to a collection of trees, so that the endpoints of the new arcs are in different trees. This contrasts with so-called tree-based networks, which are formed by adding arcs within a single tree. We are interested in the computational complexity of recognizing forest-based networks, which was recently left as an open problem by Huber et al. It has been observed that forest-based networks coincide with directed acyclic graphs that can be partitioned into induced paths, each ending at a leaf of the original graph. Several types of path partitions have been studied in the graph theory literature, but to our best knowledge this type of 'leaf induced path partition' has not been directly considered before. The study of forest-based networks in terms of these partitions allows us to establish closer relationships between phylogenetics and algorithmic graph theory, and to provide answers to problems in both fields. More specifically, we show that deciding whether a network is forest-based is NP-complete, even on input networks that are tree-based, binary, and have only three leaves. This shows that partitioning a directed acyclic graph into a constant number of induced paths is NP-complete, answering a recent question of Fernau et al. We then show that the problem is polynomial-time solvable on binary networks with two leaves and on the recently introduced class of orchards, which we show to be always forest-based. Finally, for undirected graphs, we introduce unrooted forest-based networks and provide hardness results for this class as well. [ABSTRACT FROM AUTHOR]

Within the domain of the Internet of Things (IoT), wireless sensor networks (WSNs) play a pivotal role, facilitating advancements in sectors such as smart urban infrastructures, intelligent healthcare systems, and residential automation. Despite their versatility, WSNs grapple with challenges like limited energy reserves and constrained computational capacities, making energy conservation a paramount concern for IoT deployments underpinned by WSNs. This study introduces the Hybrid Routing Protocol for Efficient Energy (HRP-EE) designed to enhance the operational efficiency of WSNs. The HRP-EE protocol unfolds over three meticulous stages: the selection of cluster heads, the formation of clusters, and the establishment of routing pathways. Initially, the protocol evaluates nodes based on their residual energy and their Euclidean distance to the central sink (or gateway) device to designate apt cluster heads. Subsequently, these chosen cluster heads are integrated into the Voronoi diagram as central nodes to orchestrate cluster architectures. In the terminal stage, an innovative hybrid algorithm is instituted. This algorithm amalgamates the principles of the Minimum Spanning Tree for structuring intra-cluster communication trees and Dijkstra's algorithm to ascertain the most efficient paths for inter-cluster data transmission from cluster heads to the sink device. The primary objective of this protocol is the judicious utilization of the sensor nodes' energy, thereby optimizing the overall network longevity. To assess the proficiency of HRP-EE, we executed a series of simulations using NS2. Comparative analyses reveal that HRP-EE outperforms existing protocols such as LEACH-VA, PEGCP, and TBC, delivering superior energy efficiency, extended network lifespan, and enhanced throughput across both homogeneous and heterogeneous network architectures. [ABSTRACT FROM AUTHOR]

This paper proposes a Lightweight and Secure Tree-based Routing protocol (LSTR) for Wireless Sensor Networks. The security of data routing from sensor nodes to the Base Station (BS) is achieved based on an efficient ID-based authenticated key-agreement protocol. LSTR reduces the number of required keys to a single permanent private-key preloaded in sensor nodes. This key is used subsequently to generate authenticated pairwise keys with other nodes without further digital signatures or certificates. As a result, LSTR achieves both node's authenticity and confidentiality during data delivery at low cost and without involving the BS. In addition, a single message must be transmitted by the nodes for both the routing-tree construction and key-establishment at the same time, and which reduces the communication overheads. The performance analysis results show that LSTR reduces the storage requirements, the communication overheads and the energy dissipation compared to similar relevant works, particularly during the key-establishment. Additionally, the robustness of our scheme is highlighted through a security analysis. [ABSTRACT FROM AUTHOR]

All existing mining contrast subspace methods employ density-based likelihood contrast scoring function to measure the likelihood of a query object to a target class against other class in a subspace. However, the density tends to decrease when the dimensionality of subspaces increases causes its bounds to identify inaccurate contrast subspaces for the given query object. This paper proposes a novel contrast subspace mining method that employs tree-based likelihood contrast scoring function which is not affected by the dimensionality of subspaces. The tree-based scoring measure recursively binary partitions the subspace space in the way that objects belong to the target class are grouped together and separated from objects belonging to other class. In contrast subspace, the query object should be in a group having a higher number of objects of the target class than other class. It incorporates the feature selection approach to find a subset of onedimensional subspaces with high likelihood contrast score with respect to the query object. Therefore, the contrast subspaces are then searched through the selected subset of one-dimensional subspaces. An experiment is conducted to evaluate the effectiveness of the tree-based method in terms of classification accuracy. The experiment results show that the proposed method has higher classification accuracy and outperform the existing method on several real-world data sets. [ABSTRACT FROM AUTHOR]

Due to the limited computation and memory capabilities of the identification tags, RFID systems are susceptible to various attacks. In 2014, a lightweight mutual authentication RFID protocol that supports key update was proposed by Qian et al., and it was claimed to be secure against several known attacks. In this paper, however, we show that their protocol cannot resist key recovery attack, where an adversary, after interacting with the tag several times, can recover the authentication keys of the system in polynomial time with non-negligible probability. Additionally, we also prove that their protocol cannot provide strong backward security or strong forward security: an adversary who has compromised some continuous authentication keys, can successfully recover all the future authentication keys and some of the previous authentication keys, which completely breaks the security of the authentication protocol. We then propose a new protocol which provides key recovery resilience, both strong backward security and strong forward security, and also resistance against various known types of attacks. [ABSTRACT FROM AUTHOR]

Whenever web-application executes dynamic SQL statements it may come under SQL injection attack. To evaluate the existing practices of its detection, we consider two different security scenarios for the web-application authentication that generates dynamic SQL query with the user input data. Accordingly, we generate two different datasets by considering all possible vulnerabilities in the run-time queries. We present proposed approach based on edit-distance to classify a dynamic SQL query as normal or malicious using web-profile prepared with the dynamic SQL queries during training phase. We evaluate the dataset using proposed approach and some well-known supervised classification approaches. Our proposed method is found more effective in detecting SQL injection attack under both the scenarios of authentication security. [ABSTRACT FROM AUTHOR]

Mobile ad hoc networks (MANETs) can be used for applications which need to be quickly launched and set up. One of the most notable challenges in these networks is reliable and energy-efficient routing protocol. Since mobile nodes in MANET have limited resources, an efficient and reliable multicast routing protocol is needed to reduce the wastage of resources. In this paper, a reliable and energy-aware multicast ad hoc on demand distance vector (REA-MAODV) routing protocol is proposed which is based on MAODV (multicast ad hoc on demand distance vector) protocol. The proposed scheme achieves enhanced performance over ODMRP and finds energy-efficient multicast routes from source node to a group of destination nodes. The proposed REA-MAODV multicast routing protocol not only can update high-consumption and shorter tree branches but also can produce a multicast tree with supporting branches. For improving MAODV protocol, we used three phases: (1) selecting high-energy consumption path, (2) selecting process and adding supporting branches, and (3) maintaining mechanism of multicast tree. The simulation results in NS-2 indicated that REA-MAODV, on average, consumed 45% less energy than MAODV and it has more balance in energy consumption. Moreover, the proposed REA-MAODV protocol was able to enhance packet delivery rate (19%), and it also managed to reduce end-to-end delay in network (21%). [ABSTRACT FROM AUTHOR]

Rooted phylogenetic networks are used to describe evolutionary histories that contain non-treelike evolutionary events such as hybridization and horizontal gene transfer. In some cases, such histories can be described by a phylogenetic base-tree with additional linking arcs, which can, for example, represent gene transfer events. Such phylogenetic networks are called tree-based. Here, we consider two possible generalizations of this concept to nonbinary networks, which we call tree-based and strictly-tree-based nonbinary phylogenetic networks. We give simple graph-theoretic characterizations of tree-based and strictly-tree-based nonbinary phylogenetic networks. Moreover, we show for each of these two classes that it can be decided in polynomial time whether a given network is contained in the class. Our approach also provides a new view on tree-based binary phylogenetic networks. Finally, we discuss two examples of nonbinary phylogenetic networks in biology and show how our results can be applied to them. [ABSTRACT FROM PUBLISHER]

Kelly et al. (Coast Eng J 57(4):1-30, ) present a finite volume dynamic adaptive mesh model based on Osher's approximate Riemann solver for the prediction of storm surges over complex landscapes. Here, the model described in that paper is extended to use distributed memory parallel block tree-based mesh refinement via the PARAMESH library. The resulting model, called the fully adaptive storm tide (FAST) model, can thus be run on massively parallel supercomputers. In this paper, we validate the FAST model by conducting numerical simulations of the storm surges due to hurricanes Wilma (2005) on Lake Okeechobee and Ike (2008) in the Gulf of Mexico. The storm surge due to Wilma on Lake Okeechobee is interesting as it can be considered as an almost idealized case which comprises a closed system. The case of hurricane Ike is more complex as it involves a coastline and additional features such as barrier islands and tidally controlled boundaries. For both cases, results obtained using the FAST model compare favorably with the measured water elevation and high-water mark data. Moreover, we show that, with sufficient computational resource, low runtimes are possible for real-world surge simulations. The FAST model therefore has the potential to run the ensemble predictions necessary to account for the variability that is inherent in hurricane forecasting. [ABSTRACT FROM AUTHOR]

With the development of wireless sensor networks (WSNs), in most application scenarios traditional WSNs with static sink nodes will be gradually replaced by Mobile Sinks (MSs), and the corresponding application requires a secure communication environment. Current key management researches pay less attention to the security of sensor networks with MS. This paper proposes a hybrid key management schemes based on a Polynomial Pool-based key pre-distribution and Basic Random key pre-distribution (PPBR) to be used in WSNs with MS. The scheme takes full advantages of these two kinds of methods to improve the cracking difficulty of the key system. The storage effectiveness and the network resilience can be significantly enhanced as well. The tree-based path key establishment method is introduced to effectively solve the problem of communication link connectivity. Simulation clearly shows that the proposed scheme performs better in terms of network resilience, connectivity and storage effectiveness compared to other widely used schemes. [ABSTRACT FROM AUTHOR]

Tag collision severely affects the performance of radio-frequency identification (RFID) systems. Most anti-collision algorithms focus on preventing or reducing collisions but waste lots of idle slots. In this letter, we propose a time efficient anti-collision algorithm based on a query tree scheme. Specifically, the dual prefixes matching method is implemented based on the traditional query tree identification model when the reader detects the consecutive collision bits, which can significantly remove idle slots. Moreover, the proposed method can also make extensive use of collision slots to improve the identification efficiency. Both theoretical and simulation results indicate that the proposed algorithm can achieve better performance than existing tree-based algorithms. [ABSTRACT FROM PUBLISHER]

Hierarchical routing in wireless sensor networks (WSNs) is a very important topic that has been attracting the research community in the last decade. Typical hierarchical routing is called clustering routing, in which the network is divided into multiple clusters. Recently, some types of atypical hierarchical routing arise, including chain-based, tree-based, grid-based routing, and area-based routing. There are several survey papers that present and compare the hierarchical routing protocols from various perspectives, but a survey on atypical hierarchical routing is still missing. This paper makes a first attempt to provide a comprehensive review on atypical hierarchical routing. We offer a classification of atypical hierarchical routing of WSNs, and give detailed analysis of different logical topologies. The most representative atypical hierarchical routing protocols are described, discussed, and qualitatively compared. In particular, the advantages and disadvantages of different atypical hierarchical routing protocols are analyzed with respect to their significant performances and application scenarios. Finally, we put forward some open issues concerning the design of hierarchical WSNs. This survey aims to provide useful guidance for system designers on how to evaluate and select appropriate logical topologies and hierarchical routing protocols for specific applications. [ABSTRACT FROM PUBLISHER]

Delimitating species boundaries could be of critical importance when evaluating the species' evolving process and providing guidelines for conservation genetics. Here, species delimitation was carried out on three endemic and endangered Cycas species with resembling morphology and overlapped distribution range along the Red River (Yuanjiang) in China: Cycas diananensis Z. T. Guan et G. D. Tao, Cycas parvula S. L. Yang and Cycas multiovula D. Y. Wang. A total of 137 individuals from 15 populations were genotyped by using three chloroplastic (psbA-trnH, atpI-atpH, and trnL-rps4) and two single copy nuclear (RPB1 and SmHP) DNA sequences. Basing on the carefully morphological comparison and cladistic haplotype aggregation (CHA) analysis, we propose all the populations as one species, with the rest two incorporated into C. diannanensis. Genetic diversity and structure analysis of the conflated C. diannanensis revealed this species possessed a relative lower genetic diversity than estimates of other Cycas species. The higher genetic diversity among populations and relative lower genetic diversity within populations, as well as obvious genetic differentiation among populations inferred from chloroplastic DNA (cpDNA) suggested a recent genetic loss within this protected species. Additionally, a clear genetic structure of C. diannanensis corresponding with geography was detected based on cpDNA, dividing its population ranges into "Yuanjiang-Nanhun" basin and "Ejia-Jiepai" basin groups. Demographical history analyses based on combined cpDNA and one nuclear DNA (nDNA) SmHP both showed the population size of C. diannanensis began to decrease in Quaternary glaciation with no subsequent expansion, while another nDNA RPB1 revealed a more recent sudden expansion after long-term population size contraction, suggesting its probable bottleneck events in history. Our findings offer grounded views for clarifying species boundaries of C. diannanensis when determining the conservation objectives. For operational guidelines, the downstream populations which occupy high and peculiar haplotypes should be given prior in-situ conservation. In addition, ex-situ conservation and reintroduction measures for decades of generations are supplemented for improving the population size and genetic diversity of the endemic and endangered species. [ABSTRACT FROM AUTHOR]

In this paper, we propose an enhancement of the Tree-based authentication protocol, named as the Tree-LSHB+ protocol. The protocol is a lightweight authentication protocol that is suitable for use in radio frequency identification (RFID) systems. Compared with the Tree-based HB authentication protocol, our protocol provides mutual authentication in authentication stage. The authentication keys stored in the reader and the tag are also updated when the mutual authentication succeeds. It means that two drawbacks can be avoided in the Tree-based authentication protocol, one is that only the reader authenticates the tag and the other is that the secret keys stored in the tags remain unchanged all the time. We also improve the performance of Tree-based protocol with the property of Toeplitz matrix and find that the Tree-LSHB+ protocol is still a good choice for RFID authentication. [ABSTRACT FROM AUTHOR]

A leader in a network plays important roles for various services of the network and controls problems of the network. Therefore, when the nodes with high centrality are selected as the leader nodes in the network, the network can be more efficiently controlled, and the amount of wasted resources can be reduced. In this study, we propose a novel method for determining leader nodes by measuring centrality of nodes in the ad hoc networks. The proposed method can obtain the centrality of each node using the average depth of nodes based on the tree topology. Consequently, the amount of the information required for leader election becomes smaller and the calculation process is also simpler, compared with those of representative centrality methods in social network analysis (SNA). In the experiment, the proposed tree-based centrality technique is compared with the well-known centrality schemes such as degree, closeness, and betweenness. The proposed tree-based centrality method has similar centrality priority as degree, closeness, and betweenness and also has better performance in the comparison of the control messages generated. [ABSTRACT FROM AUTHOR]

Authenticated group key exchange protocols allow a group of users over a public network to establish a shared secret key for the subsequent cryptographic goals. In this paper, we extend BD-II scheme into a dynamic setting, and propose a tree-based authenticated key exchange protocol which is more suitable for dynamic groups in such as ad hoc networks. Our protocol is proven secure in random-oracle model. Additionally, we analyze the costs of our protocols in both communication and computation terms, and compare its performance with three well-known protocols. [ABSTRACT FROM AUTHOR]

Performance monitoring of HPC applications offers opportunities for adaptive optimization based on the dynamic performance behavior, unavailable in purely post-mortem performance views. However, a parallel performance monitoring system must have low overhead and high efficiency to make these opportunities tangible. We describe a scalable parallel performance monitor called TAUoverMRNet (ToM), created from the integration of the TAU performance system and the Multicast Reduction Network (MRNet). The integration is achieved through a plug-in architecture in TAU that allows the selection of different transport substrates to offload the online performance data. A method to establish the transport overlay structure of the monitor from within TAU, one that requires no added support from the job manager or application, is presented. We demonstrate the distribution of performance analysis from the sink to the overlay nodes and the reduction in the large-scale profile data that could, otherwise, overwhelm any single sink. The results show low perturbation and significant savings accrued from reduction at large processor-counts. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Phylogenetic networks are becoming of increasing interest to evolutionary biologists due to their ability to capture complex non-treelike evolutionary processes. From a combinatorial point of view, such networks are certain types of rooted directed acyclic graphs whose leaves are labelled by, for example, species. A number of mathematically interesting classes of phylogenetic networks are known. These include the biologically relevant class of stable phylogenetic networks whose members are defined via certain "fold-up" and "un-fold" operations that link them with concepts arising within the theory of, for example, graph fibrations. Despite this exciting link, the structural complexity of stable phylogenetic networks is still relatively poorly understood. Employing the popular tree-based, reticulation-visible, and tree-child properties which allow one to gauge this complexity in one way or another, we provide novel characterizations for when a stable phylogenetic network satisfies either one of these three properties. • (Phylogenetic) networks are of increasing interest for evolutionary biologists. • A stable network is a type of network defined via "un-fold" and "fold-up" operations. • The structural complexity of stable networks is poorly understood. • We characterize stable networks that are tree-based/tree-child/reticulation-visible. [ABSTRACT FROM AUTHOR]

In passive radio frequency identification systems, tag collision is a serious problem causing performance degradation. Most anti‐collision protocols waste numerous transmitted bits while eliminating or reducing the idle and collision slots. In this letter, an improved collision window tree (ICwT) algorithm is proposed by applying a parallel‐matching scheme to a fixed‐window scheme, in order to restrict the length of tag response as well as reduce the number of query cycles. As a result of the simulation, ICwT is proved to be more effective in terms of identification time and energy cost, compared to the existing tree‐based algorithms including collision tree, M‐ary query tree, dual prefix probe scheme, query window tree, and collision window tree. [ABSTRACT FROM AUTHOR]