28,852 research outputs found
Performance evaluation of secondary control policies with respect to digital communications properties in inverter-based islanded microgrids
A key challenge for inverted-based microgrids working in islanded mode is to maintain their own frequency and voltage to a certain reference values while regulating the active and reactive power among distributed generators and loads. The implementation of frequency and voltage restoration control policies often requires the use of a digital communication network for real-time data exchange (tertiary control covers the coordi- nated operation of the microgrid and the host grid). Whenever a digital network is placed within the loop, the operation of the secondary control may be affected by the inherent properties of the communication technology. This paper analyses the effect that properties like transmission intervals and message dropouts have for four existing representative approaches to secondary control in a scalable islanded microgrid. The simulated results reveals pros and cons for each approach, and identifies threats that properly avoided or handled in advance can prevent failures that otherwise would occur. Selected experimental results on a low- scale laboratory microgrid corroborate the conclusions extracted from the simulation study.Peer ReviewedPostprint (author's final draft
Community Detection in Networks with Node Attributes
Community detection algorithms are fundamental tools that allow us to uncover
organizational principles in networks. When detecting communities, there are
two possible sources of information one can use: the network structure, and the
features and attributes of nodes. Even though communities form around nodes
that have common edges and common attributes, typically, algorithms have only
focused on one of these two data modalities: community detection algorithms
traditionally focus only on the network structure, while clustering algorithms
mostly consider only node attributes. In this paper, we develop Communities
from Edge Structure and Node Attributes (CESNA), an accurate and scalable
algorithm for detecting overlapping communities in networks with node
attributes. CESNA statistically models the interaction between the network
structure and the node attributes, which leads to more accurate community
detection as well as improved robustness in the presence of noise in the
network structure. CESNA has a linear runtime in the network size and is able
to process networks an order of magnitude larger than comparable approaches.
Last, CESNA also helps with the interpretation of detected communities by
finding relevant node attributes for each community.Comment: Published in the proceedings of IEEE ICDM '1
Cross-Layer Peer-to-Peer Track Identification and Optimization Based on Active Networking
P2P applications appear to emerge as ultimate killer applications due to their ability to construct highly dynamic overlay topologies with rapidly-varying and unpredictable traffic dynamics, which can constitute a serious challenge even for significantly over-provisioned IP networks. As a result, ISPs are facing new, severe network management problems that are not guaranteed to be addressed by statically deployed network engineering mechanisms. As a first step to a more complete solution to these problems, this paper proposes a P2P measurement, identification and optimisation architecture, designed to cope with the dynamicity and unpredictability of existing, well-known and future, unknown P2P systems. The purpose of this architecture is to provide to the ISPs an effective and scalable approach to control and optimise the traffic produced by P2P applications in their networks. This can be achieved through a combination of different application and network-level programmable techniques, leading to a crosslayer identification and optimisation process. These techniques can be applied using Active Networking platforms, which are able to quickly and easily deploy architectural components on demand. This flexibility of the optimisation architecture is essential to address the rapid development of new P2P protocols and the variation of known protocols
A New Scheme for Minimizing Malicious Behavior of Mobile Nodes in Mobile Ad Hoc Networks
The performance of Mobile Ad hoc networks (MANET) depends on the cooperation
of all active nodes. However, supporting a MANET is a cost-intensive activity
for a mobile node. From a single mobile node perspective, the detection of
routes as well as forwarding packets consume local CPU time, memory,
network-bandwidth, and last but not least energy. We believe that this is one
of the main factors that strongly motivate a mobile node to deny packet
forwarding for others, while at the same time use their services to deliver its
own data. This behavior of an independent mobile node is commonly known as
misbehaving or selfishness. A vast amount of research has already been done for
minimizing malicious behavior of mobile nodes. However, most of them focused on
the methods/techniques/algorithms to remove such nodes from the MANET. We
believe that the frequent elimination of such miss-behaving nodes never allowed
a free and faster growth of MANET. This paper provides a critical analysis of
the recent research wok and its impact on the overall performance of a MANET.
In this paper, we clarify some of the misconceptions in the understating of
selfishness and miss-behavior of nodes. Moreover, we propose a mathematical
model that based on the time division technique to minimize the malicious
behavior of mobile nodes by avoiding unnecessary elimination of bad nodes. Our
proposed approach not only improves the resource sharing but also creates a
consistent trust and cooperation (CTC) environment among the mobile nodes. The
simulation results demonstrate the success of the proposed approach that
significantly minimizes the malicious nodes and consequently maximizes the
overall throughput of MANET than other well known schemes.Comment: 10 pages IEEE format, International Journal of Computer Science and
Information Security, IJCSIS July 2009, ISSN 1947 5500, Impact Factor 0.42
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