Extremal properties of three-dimensional sensor networks with applications

We analyze various critical transmitting/sensing ranges for connectivity and coverage in three-dimensional sensor networks. As in other large-scale complex systems, many global parameters of sensor networks undergo phase transitions. For a given property of the network, there is a critical threshold, corresponding to the minimum amount of the communication effort or power expenditure by individual nodes, above (respectively, below) which the property exists with high (respectively, a low) probability. For sensor networks, properties of interest include simple and multiple degrees of connectivity/coverage. First, we investigate the network topology according to the region of deployment, the number of deployed sensors, and their transmitting/sensing ranges. More specifically, we consider the following problems: assume that n nodes, each capable of sensing events within a radius of r, are randomly and uniformly distributed in a 3-dimensional region R of volume V, how large must the sensing range R/sub SENSE/ be to ensure a given degree of coverage of the region to monitor? For a given transmission range R/sub TRANS/, what is the minimum (respectively, maximum) degree of the network? What is then the typical hop diameter of the underlying network? Next, we show how these results affect algorithmic aspects of the network by designing specific distributed protocols for sensor networks.

Although most of the studies on coverage and connectivity in wireless sensor networks (WSNs) considered two-dimensional (2D) settings, such networks can in reality be accurately modeled in a three-dimensional (3D) space. The concepts of continuum percolation theory best fit the problem of connectivity in WSNs to find out whether the network provides long-distance multihop communication. In this paper, we focus on percolation in coverage and connectivity in 3D WSNs. We say that the network exhibits a coverage percolation (respectively, connectivity percolation) when a giant covered region (respectively, giant connected component) almost surely spans the entire network for the first time. Because of the dependency between coverage and connectivity, the problem is not only a continuum percolation problem but also an integrated continuum percolation problem. Thus, we propose an integrated-concentric-sphere model to address coverage and connectivity in 3D WSNs in an integrated way. First, we compute the critical density lambdaC con above which coverage percolation in 3D WSNs will almost surely occur. Second, we compute the critical density lambdac con above which connectivity percolation in 3D WSNs will almost surely occur. Third, we compute the critical density lambdac cov-con above which both coverage and connectivity percolation in 3D WSNs will almost surely occur. For each of these three problems, we also compute their corresponding critical network degree. Our results can be helpful in the design of energy-efficient topology control protocols for 3D WSNs in terms of coverage and connectivity.

Resting-state functional magnetic resonance imaging (rs-fMRI) is a non-invasive neuroimaging technique that utilizes spontaneous low-frequency fluctuations of blood-oxygenation-level dependent (BOLD) signals to examine resting-state functional connectivity in the brain. In the past two decades, this technique has been increasingly utilized to investigate properties of large-scale functional neural networks as well as their alterations in various cognitive and disease states. However, much less is known about large-scale functional neural networks of the rodent brain, particularly in the awake state. Therefore, we attempted to unveil local and global functional connectivity in awake rat through a combination of seed-based analysis, independent component analysis and graph-theory analysis. In the current studies, we revealed elementary local networks and their global organization in the awake rat brain. We further systematically compared the functional neural networks in awake and anesthetized states, revealing that the rat brain was locally reorganized while maintaining global topological properties from awake to anesthetized states. Furthermore, specific neural circuitries of the rat brain were examined using resting-state fMRI. First anticorrelated functional connectivity between infralimbic cortex and amygdala were found to be evident with different preprocessing methods (global signal regression, regression of ventricular and white matter signal and no signal regression). Secondly the thalamocortical connectivity was mapped for individual thalamic groups, revealing group-specific functional cortical connections that were generally consistent with known anatomical connections in rat. In conclusion, large-scale neural networks can be robustly and reliably studied using rs-fMRI in awake rat, and with this technique we established a baseline of local and global neural networks in the awake rat brain as well as their alterations in the anesthetized condition.

The main study of traditional probability coverage problem in wireless sensor networks (WSNs) is aiming at two-dimensional space, however, most practical applications of wireless sensor network is placed in a three-dimensional sensor networks. Therefore, probability model is introduced for three-dimensional WSNs. This paper presents a method that using Voronoi divide to control the Scheduling of the probability model nodes in the target area. Also, a coverage control algorithm based on probability model (PMCCA) is proposed. We verify the effectiveness and the practice of PMCCA algorithm by comparing PMCCA algorithm to another algorithm in simulation experiment.

Notice of Violation of IEEE Publication Principles Critical Density for Coverage and Connectivity in Two-Dimensional Aligned-Orientation Directional Sensor Networks Using Continuum Percolation, by Mohammad Khanjary, Masoud Sabaei, and Mohammad Reza Meybodi in IEEE Sensors Journal, vol. 14, no. 8, pp. 2856-2863, Aug. 2014 After careful and considered review of the content and authorship of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE's Publication Principles. This paper contains significant portions of original text from the paper cited below. The original text was copied without attribution (including appropriate references to the original author(s) and/or paper title) and without permission. Integrated Coverage and Connectivity in Wireless Sensor Networks: A Two-Dimensional Percolation Problem, by H. M. Ammari and S. K. Das, in IEEE Transactions on Computers, vol. 57, no. 10, pp. 1423-1434, Oct. 2008 Sensing coverage is one of the fundamental design issues in wireless sensor networks, which reflects the surveillance quality provided by them. Moreover, network connectivity enables the gathered data by sensors to reach to the sink node. Given an initially uncovered field, and as more and more directional sensors are continuously added to the sensor network, the size of partial covered areas increases. At some point, the situation abruptly changes from small fragmented covered areas to a single large covered area. We call this abrupt change the sensing-coverage phase transition (SCPT). Likewise, given an originally disconnected sensor network, as more and more sensors are added, the number of connected components changes such that the sensor network suddenly becomes connected at some point. We call this sudden change the network connectivity phase transition (NCPT). The nature of such phase transitions is a central topic in the percolation theory. In this paper, we introduce aligned-orientation directional sensor networks in which nodes are deployed based on Poisson point process and the orientation of all sensor nodes is the same. Then, we propose an approach to compute density of nodes at critical percolation for both of the SCPT and NCPT problems in such networks, for all angles of field-of-view between 0 and π by using continuum percolation. Due to percolation theory, the critical density is infimum density that for densities above it SCPT and NCPT almost surely occur. In addition, we propose a model for percolation in directional sensor networks, which provides a basis for solving the SCPT and NCPT problems together.

Functional brain connectivity from fMRI studies has become an important tool in studying functional interactions in the human brain as a complex network. Most recently, research has started focusing on whole brain functional networks at the voxel-level, where fMRI time-signals at each voxel are correlated with every other voxel in the brain to determine their functional connectivity. For a typical 4mm isotropic voxel resolution, this results in connectivity networks with more than twenty thousand nodes and over 400 million links. These cannot be effectively visualized or interactively explored using node-link representations, and due to their size are challenging to show as correlation matrix bitmaps. In this paper, we present a number of methods for the visualization and interactive visual analysis of this new high resolution brain network data, both in its matrix representation as well as in its anatomical context. We have implemented these methods in a GPU raycasting framework that enables real-time interaction, such as network probing and volume deformation, as well as real-time filtering. The techniques are integrated in a visual analysis application in which the different views are coupled, supporting linked interaction. Furthermore, we allow visual comparison of different brain networks with side-by-side and difference visualization. We have evaluated our approach via case studies with domain scientists at two different university medical centers.

The house of risk model represents an approach to mitigate risk through systematically analysing data risk agents based on empirical findings through prioritizing them. Food production is associated with uncertainty both within the production system as well as in environment. Given the state of current technology, including its rapid development impacting on connectivity in supply chains, the house of risk model is considered through this conceptual study applying an ecosystems approach on how to mitigate risk in food chains in their many-faceted environmental setting. Ecosystems thinking is rooted in a normative quest to secure sustainability. It also is at the operations level a complex system. It is pointed out that an ecosystems approach encompasses mixed methods, including both deterministic and complex systems. The nature of this complementarity is discussed. The study provides a list of four issues regarding using the house of risk model within an ecosystem: (1) ethical, (2) development, (3) operations and (4) discourse.

Uncertainty is an inescapable ingredient of life. Even in familiar situations – such as crossing a street – some level of uncertainty inevitably exists. Past experience is relevant for all decisions involving the future, but contexts change and new elements affecting risk may unexpectedly appear. Usually, this residual uncertainty remains within reasonable bounds and human beings make their way in an uncertain and changing world where existing knowledge and experience suffice as guides to future expectations (Pollack, 2003). But where highly complex systems with extensive connectivity and interaction exist, or where novel problems or technology limit experience as a resource, decisions often must be made under conditions of high uncertainty. It is not surprising, as the various chapters in the volume make clear, that in a world of complex systems involving rapid technological change, highly coupled human and natural systems, and a kaleidoscope of social, economic and political institutions, high levels of uncertainty challenge existing assessment methods and established decision and management procedures.

Countryside connections in later life: Setting the scene ~ Catherine Hagan Hennessy, Robin Means and Vanessa Burholt Conceptualising rural connectivities in later life ~ Nigel Curry, Vanessa Burholt, Catherine Hagan Hennessy Rural connectivity and older people's leisure participation ~ Catherine Hagan Hennessy, Yvette Staelens, Gloria Lankshear, Andy Phippen, Avril Silk, Daniel Zahra Connecting with community: The nature of belonging among rural elders ~ Vanessa Burholt, Nigel Curry, Norah Keating, Jacquie Eales Beyond transport: Understanding the role of mobilities in rural elders' connectivity in civic society ~ Graham Parkhurst, Kathleen Galvin, Charles Musselwhite, Judith Phillips, Ian Shergold, Les Todres Deep mapping and rural connectivities ~ Jane Bailey, Iain Biggs and Dan Buzzo Older people, low income and place: Making connections in rural Britain ~ Paul Milbourne, Shane Doheny Connecting with older people as project stakeholders: Lessons for public participation and engagement in rural research ~ Simon Evans, Ray Jones, Janet Smithson Towards connectivity in a Grey and Pleasant Land? ~ Robin Means, Vanessa Burholt, Catherine Hagan Hennessy.

The Hypertext 2015 Doctorial Consortium session is held the first day of the 26th ACM Conference on Hypertext and Social Media. It offers Ph.D. students an opportunity to present their ongoing research towards obtaining a Ph.D. degree in the disciplines related to the conference, mostly in Computer and Information Sciences but not limited to them. The themes of the submissions are strongly connected to the research tracks of this year's conference: Digital Connectivity, Data Connectivity and Digital Humanities. The Digital Connectivity track targets developing insights into the mechanisms of information generation and dissemination, characterization of evolutionary processes on online social networks, and studies of models and systems that support these processes. The second track, Data Connectivity, deals with the methods, techniques and technologies that can be used to make data available on the Web, with a special focus on how heterogeneous data sources can be connected to each other. Finally, the track of Digital Humanities seeks to attract work from an interdisciplinary perspective, on the intersection between computer science on one hand, and the humanities and social sciences on the other. During the DC session, students receive constructive feedback from their peers and from a panel of mentors to support them in envisioning added-value contributions to the state-of-the-art research in Hypertext and Social Media. The consortium session is open to all doctorial students by application. Each submission was reviewed by three senior researchers in the topics the students made their submissions. The DC session is aimed in particular at students who have defined a dissertation topic but are still more than one year from graduating at the time of application in order to obtain benefits from feedback. This year, the committee has accepted three contributions to be presented during the Doctorial Consortium session: Automated Methods for Identity Resolution in Heterogeneous Social Platforms by Paridhi Jahin. In this work, connected to the digital and data connectivity tracks of the conference, the author proposes novel methods to search and link user identities scattered across heterogeneous social networks. The methods consider carefully users' privacy, so they are designed to access only public and historic data. The evaluation is proposed on large datasets over multiple platforms to prove their significance in identity resolution of an online user. Language Innovation and Change in On-line Social Networks by Daniel Kershaw. As a fundamental aspect for human communication, this research focuses on forecasting online language change through the use of predictive and descriptive methodologies. This work is framed within structuration theory which helps the researcher in structuring the analysis of the dynamics of language (re)production - i.e. by the agent (user), the social structure and their interplay. A Framework to Provide Customized Reuse of Open Corpus Content for Adaptive Systems by Mostafa Bayomi. This work deals with issues of reusability of contents on adaptive systems. Adaptive systems tailor content specific to user's needs, but they face two big problems: (a) they use a closed corpus content that has been prepared for them a priori, and (b) the content is tightly coupled with other parts of the system, which hinders its reusability. This work presents a proposal that leverages the semantic web by extending an existing content provision system, Slice-pedia.

Background: Emergency departments (EDs) are notoriously busy and challenging working environments. Internationally and locally, demands on healthcare services, including the number of presentations to EDs, have increased substantially. Recognising the challenges faced by healthcare workers and, in particular, clinicians working in EDs has prompted growth in interest around healthcare-related occupational stress. Despite the interest in occupational stress there is a paucity of clinician-informed interventions to improve perceptions of working environment and/or coping among clinicians. Aim: The aim of this programme of research was to elicit the core components of a work-based strategy to improve the perceptions of working environment and/or the coping of clinicians. Methods: Underpinned by the transactional stress and coping theoretical framework, a three-phase mixed methods study utilising a sequential explanatory design was conducted at a single health service with two EDs (Site A and Site B) in south-east Queensland. In Phase One, a cross-sectional retrospective descriptive study was conducted to describe the perceived stressors and coping strategies of nursing and medical staff at Sites A and B. In Phase Two, twelve qualitative semi-structured interviews were undertaken to explore clinician perceptions of their working environment, perceived stressors, coping strategies, and clinician-informed solutions to occupational stressors. Phase Three consisted of two components: (i) a scoping review of the literature and (ii) a modified-nominal group technique study. The aim of this phase was to elicit core components of a work-based strategy designed to improve the working environment and/or coping of ED clinicians. The findings of early phases in the programme of research were used to inform and scaffold subsequent phases, with Phase One also being situated within a larger international study. Results: Workload was consistently identified as a leading stressor across all three phases of this PhD. In Phases Two and Three, staff also described perceptions of demoralisation, feelings of not being valued, and lack of leadership within the workplace. Wellness, staffing, and teamwork were the foci of the nominal group discussions, with three core inter-related themes emerging from these discussions: (i) increased individual and team support, (ii) development of professional resilience, and (iii) maximising opportunities for social connection. Increased psychological safety and team connection and synergy were central to the face-to-face discussions, along with increased sense of value, shared visions, and deeper connectivity. Many of the stressors experienced and described by the clinicians stemmed from system and organisational level issues. Both adaptive and maladaptive coping strategies were described in response to exposure to occupational stress. Conclusion: The findings of this programme of research have highlighted that occupational stress continues to be an issue for clinicians working in EDs. Continued exposure to occupational stressors in the absence of strategies or solutions to reduce exposure to occupational stressor(s) and/or improve coping among clinicians is likely to lead to staffing concerns, increased attrition rates, and poor staff retention. The unique working environment of the ED calls for ED-specific, tailored and focussed interventions designed to meet the unique demands and needs of clinicians working in the ED. The results of this study identified three key areas that, if embedded into a work-based strategy, will help to develop a psychologically safe working environment and improve team synergy. These elements are: (i) increasing individual and team support, (ii) developing professional resilience, and (iii) maximising opportunities for social connection. These findings can be used to inform both the processes and actualities of intervention development within EDs, locally and internationally. However, further research is recommended to ensure the stressors, coping strategies, and solutions identified in this study mirror that of other working environments to avoid a 'one-size-fits-all' approach.

The decreasing costs of computing devices, increases in connectivity, and improved performance are altering the computing environments of users in fundamental ways. Users are no longer restricted to operating single devices in isolation but rather distribute and accessinformation across many devices and develop complex sharing patterns among groups of users. Unfortunately, while these trends are significantly enriching the user's computing experience, they are also increasing the data management overhead as users must explicitlyreason about data placement and replication across multiple devices and logical sharing groups.In this thesis, we present the Wayfinder file system, which was designed to simplify the management of information in federate systems. Wayfinder focuses on three critical management deficiencies present in most current federated environments: 1) the lack of a consistent view for stored information across devices, 2) the required manual management of replicated information, and 3) the limited search/ranking capability for finding relevant information.The Wayfinder file system addresses these deficiencies by providing three synergistic abstractions: 1) a global namespace that is uniformly accessible across connected and disconnected operation, 2) a user-centric automatic availability management to ensure continuous access to information based on data-centric availability policies, and 3) a multi-dimensional fuzzy search framework that significantlyimproves relevance ranking. We will show that these abstractions simplify the management burden by requiring users to reason only about the data and its properties while ignoring the underlying physicalcomplexities of the system.Underlying all three abstractions is a common implementation layer that adheres to three principles. First, any subset of nodes in a Wayfinder community can interact normally when they are interconnected, regardless of the membership of the subset. Second,all protocols and interactions are tolerant of a weakly consistent model allowing them to suffer unexpected devices departures. Finally, devices are assumed to be owned by specific users and so should prioritize the needs of their owners in the presence of resourceconstraints, while using excess resources to benefit the community as a whole.

Cyber resilience is characterised by an ability to understand and adapt to changing network conditions, including cyber attacks. Cyber resilience may be characterised by an effects-based approach to missions or processes. One of the fundamental preconditions underpinning cyber resilience is an accurate representation of current network and machine states and what missions they are supporting. This research outlines the need for an ontological network representation, drawing on existing literature and implementations in the domain. This work then introduces an open-source ontological representation for modelling cyber assets for the purposes of Computer Network Defence. This representation encompasses computers, network connectivity, users, software, vulnerabilities and exploits and aims for interoperability with related representations in common use. The utility of this work is highlighted against a functional use-case depicting a realistic operational network and mission. Finally, a future research direction is defined.

Target Coverage and Network Connectivity in Wireless Sensor Networks (WSNs) plays a momentous role in the field of monitoring environment, habitant observing, disaster recovery, surveillance, etc. Coverage and Network Connectivity collectively can be considered as a proportion of Quality of Service (QoS) in a sensor network. It implies the coverage of each point in the detecting field while in the meantime fulfilling the measure that each node is surrounded by the equivalent neighbourhood of at least one other node. Many primary issues influence the outline and performance of WSN. A Comprehensive survey is made based on the scheduling algorithm and set cover approach, in which we analyze various approaches and their algorithm complexity. Firstly, the scheduling algorithm intermittently provides the required data service with guaranteed efficiency. This methodology can efficiently reduce the entire number of active nodes in the network, resulting in maximizing the network lifetime. Secondly, the set cover approach plays a major role in solving target coverage problem which group sensors into each cover set thereby, target coverage was achieved. Typical issues and open research challenges are addressed by classifying the approaches available in literature into three broad categories namely, adaptable coverage radius, coverage deployment strategy, and sleep scheduling. This survey aims to provide a better perceptive of the existing open challenges and possible futuristic approaches for target coverage and network connectivity in wireless sensor networks.

Design of biomaterials and cellular scaffolds for tissue-engineering applications and regenerative medicine requires a precise understanding of the principles underlying multicellular patterning. Adhesion, migration, division, differentiation, and apoptosis are characteristic cellular behaviors, the engineering of which has the potential to allow creation of custom, multicellular structures. These cellular events occur naturally during embryonic and postembryonic development of multicellular organisms. Development thus offers the opportunity to learn about the design principles and molecular mechanisms that guide cellular patterning. A key finding in developmental biology is that a limited set of conserved molecular signaling pathways act at multiple times and locations throughout the embryo to introduce cell-fate asymmetries in homogenous populations of cells. In turn, these asymmetries serve as starting points for the patterning of new organs. These signaling pathways interact quantitatively at multiple levels, including signaling cues, post-translational regulation, and gene-regulatory networks, to guide multicellular patterning. How does the quantitative performance of these signaling networks ensure the intended phenotype pattern? How do changes in the quantitative performance of these networks, possibly over the course of evolution, give rise to new phenotypes? These are the central questions pursued in this thesis. In order to answer such questions, we used vulva formation in the nematode Caenorhabditis elegans as a model system of cellular patterning. We formulated a mathematical model of the molecular network underlying cellular-fate specification in this system. Computational analysis of this molecular network reveals that cell–cell coupling through lateral LIN-12/Notch signaling amplifies the perception of the gradient in the epidermal-growth-factor-like soluble cue, LIN-3. Thus, the gradient in LIN-3 concentration produces an even steeper difference in LIN-3-mediated intracellular signals between adjoining cells. Such gradient amplification may be particularly important in converting a shallow, graded-specification signal into a spatial pattern of distinct fate choices. Through quantitative perturbations of interaction strengths between components of the vulval patterning network, we further show that our modeling approach can correctly predict phenotype patterns observed in C. elegans mutation studies. This study generated a framework for quantitative analysis of molecular networks that links quantitative molecular perturbations to patterning outcomes. This framework will prove useful in the analysis of other systems involving cellular fate decisions and in tissue engineering applications where the generation of precise cell patterns is needed. We demonstrate the generality of our approach through an application to evolutionary developmental biology. Since molecular connectivity of the vulva patterning network of several closely related Caenorhabditis species is preserved, we correctly predict the quantitative diversification that must have occurred in this network during species evolution.