18,770 research outputs found
SRAT-Distribution Voltage Sags and Reliability Assessment Tool
Interruptions to supply and sags of distribution system voltage are the main aspects causing customer complaints. There is a need for analysis of supply reliability and voltage sag to relate system performance with network structure and equipment design parameters. This analysis can also give prediction of voltage dips, as well as relating traditional reliability and momentary outage measures to the properties of protection systems and to network impedances. Existing reliability analysis software often requires substantial training, lacks automated facilities, and suffers from data availability. Thus it requires time-consuming manual intervention for the study of large networks. A user-friendly sag and reliability assessment tool (SRAT) has been developed based on existing impedance data, protection characteristics, and a model of failure probability. The new features included in SRAT are a) efficient reliability and sag assessments for a radial network with limited loops, b) reliability evaluation associated with realistic protection and restoration schemes, c) inclusion of momentary outages in the same model as permanent outage evaluation, d) evaluation of the sag transfer through meshed subtransmission network, and e) simplified probability distribution model determined from available faults records. Examples of the application of the tools to an Australian distribution network are used to illustrate the application of this model
Planning Rural Water Services in Nicaragua: A Systems-Based Analysis of Impact Factors Using Graphical Modeling
The success or failure of rural water services in the developing world is a result of numerous factors that interact in a complex set of connections that are difficult to separate and identify. This research effort presented a novel means to empirically reveal the systemic interactions of factors that influence rural water service sustainability in the municipalities of DarĂo and Terrabona, Nicaragua. To accomplish this, the study employed graphical modeling to build and analyze factor networks. Influential factors were first identified by qualitatively and quantitatively analyzing transcribed interviews from community water committee members. Factor influences were then inferred by graphical modeling to create factor network diagrams that revealed the direct and indirect interaction of factors. Finally, network analysis measures were used to identify âimpact factorsâ based on their relative influence within each factor network. Findings from this study elucidated the systematic nature of such factor interactions in both DarĂo and Terrabona, and highlighted key areas for programmatic impact on water service sustainability for both municipalities. Specifically, in DarĂo, the impact areas related to the current importance of water service management by community water committees, while in Terrabona, the impact areas related to the current importance of finances, viable water sources, and community capacity building by external support. Overall, this study presents a rigorous and useful means to identify impact factors as a way to facilitate the thoughtful planning and evaluation of sustainable rural water services in Nicaragua and beyond
Robustness of airline alliance route networks
The aim of this study is to analyze the robustness of the three major airline alliancesâ (i.e., Star Alliance, oneworld and SkyTeam) route networks. Firstly, the normalization of a multi-scale measure of vulnerability is proposed in order to perform the analysis in networks with different sizes, i.e., number of nodes. An alternative node selection criterion is also proposed in order to study robustness and vulnerability of such complex networks, based on network efficiency. And lastly, a new procedure â the inverted adaptive strategy â is presented to sort the nodes in order to anticipate network breakdown. Finally, the robustness of the three alliance networks are analyzed with (1) a normalized multi-scale measure of vulnerability, (2) an adaptive strategy based on four different criteria and (3) an inverted adaptive strategy based on the efficiency criterion. The results show that Star Alliance has the most resilient route network, followed by SkyTeam and then oneworld. It was also shown that the inverted adaptive strategy based on the efficiency criterion â inverted efficiency â shows a great success in quickly breaking networks similar to that found with betweenness criterion but with even better results.Peer ReviewedPostprint (authorâs final draft
Robotic Wireless Sensor Networks
In this chapter, we present a literature survey of an emerging, cutting-edge,
and multi-disciplinary field of research at the intersection of Robotics and
Wireless Sensor Networks (WSN) which we refer to as Robotic Wireless Sensor
Networks (RWSN). We define a RWSN as an autonomous networked multi-robot system
that aims to achieve certain sensing goals while meeting and maintaining
certain communication performance requirements, through cooperative control,
learning and adaptation. While both of the component areas, i.e., Robotics and
WSN, are very well-known and well-explored, there exist a whole set of new
opportunities and research directions at the intersection of these two fields
which are relatively or even completely unexplored. One such example would be
the use of a set of robotic routers to set up a temporary communication path
between a sender and a receiver that uses the controlled mobility to the
advantage of packet routing. We find that there exist only a limited number of
articles to be directly categorized as RWSN related works whereas there exist a
range of articles in the robotics and the WSN literature that are also relevant
to this new field of research. To connect the dots, we first identify the core
problems and research trends related to RWSN such as connectivity,
localization, routing, and robust flow of information. Next, we classify the
existing research on RWSN as well as the relevant state-of-the-arts from
robotics and WSN community according to the problems and trends identified in
the first step. Lastly, we analyze what is missing in the existing literature,
and identify topics that require more research attention in the future
Considering Structural Properties of Inter-organizational Network Fragments during Business-IT Alignment
Value exchange models can be used to reason about possible
networked business constellations. Such inter-organizational business settings are determined in most cases solely from a financial point of view, i.e. by assessing the economic sustainability of the constellation. In this paper we discuss also other criteria that are relevant and
should additionally be considered, namely the structural properties of the inter-organizational constellation itself. The multitude of possible interorganizational business constellations â and underlying systems constellations
respectively â makes it a necessary requirement to split such constellations into recurring structural patterns, which we call fragments. The structural properties are helping the designer to reason about quality
related issues of the inter-organizational network, and may have an influence on design choices to be made. The paper suggests to design new e-business constellations not only on the basis of financial criteria, but to consider also quality issues of the inter-organizational network
Investigation of the robustness of star graph networks
The star interconnection network has been known as an attractive alternative to n-cube for interconnecting a large number of processors. It possesses many nice properties, such as vertex/edge symmetry, recursiveness, sublogarithmic degree and diameter, and maximal fault tolerance, which are all desirable when building an interconnection topology for a parallel and distributed system. Investigation of the robustness of the star network architecture is essential since the star network has the potential of use in critical applications. In this study, three different reliability measures are proposed to investigate the robustness of the star network. First, a constrained two-terminal reliability measure referred to as Distance Reliability (DR) between the source node u and the destination node I with the shortest distance, in an n-dimensional star network, Sn, is introduced to assess the robustness of the star network. A combinatorial analysis on DR especially for u having a single cycle is performed under different failure models (node, link, combined node/link failure). Lower bounds on the special case of the DR: antipode reliability, are derived, compared with n-cube, and shown to be more fault-tolerant than n-cube. The degradation of a container in a Sn having at least one operational optimal path between u and I is also examined to measure the system effectiveness in the presence of failures under different failure models. The values of MTTF to each transition state are calculated and compared with similar size containers in n-cube. Meanwhile, an upper bound under the probability fault model and an approximation under the fixed partitioning approach on the ( n-1)-star reliability are derived, and proved to be similarly accurate and close to the simulations results. Conservative comparisons between similar size star networks and n-cubes show that the star network is more robust than n-cube in terms of ( n-1)-network reliability
What the eye does not see: visualizations strategies for the data collection of personal networks
The graphic representation of relational data is one of the central elements of social network analysis. In this paper, the author describe
the use of visualization in interview-based data collection procedures
designed to obtain personal networks information, exploring four
main contributions. First, the author shows a procedure by which the
visualization is integrated with traditional name generators to facilitate obtaining information and reducing the burden of the interview
process. Second, the author describes the reactions and qualitative
interpretation of the interviewees when they are presented with an
analytical visualization of their personal network. The most frequent
strategies consist in identifying the key individuals, dividing the personal network in groups and classifying alters in concentric circles
of relative importance. Next, the author explores how the visualization of groups in personal networks facilitates the enumeration of the
communities in which individuals participate. This allows the author
to reflect on the role of social circles in determining the structure of
personal networks. Finally, the author compares the graphic representation obtained through spontaneous, hand-drawn sociograms
with the analytical visualizations elicited through software tools. This
allows the author to demonstrate that analytical procedures reveal
aspects of the structure of personal networks that respondents are
not aware of, as well as the advantages and disadvantages of using
both modes of data collection. For this, the author presents findings
from a study of highly skilled migrants living in Spain (n = 95) through
which the author illustrates the challenges, in terms of data reliability,
validity and burden on both the researcher and the participants
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