Given two replication schemes X old and X new , the replica transfer scheduling problem (RTSP) aims at reaching X new , starting from X old , with minimal implementation cost. In this paper we generalize the problem ...
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Given two replication schemes X old and X new , the replica transfer scheduling problem (RTSP) aims at reaching X new , starting from X old , with minimal implementation cost. In this paper we generalize the problem description to include special cases, where deadlocks can occur while in the process of implementing X new . We address this impediment by introducing artificial (dummy) transfers. We then prove that RTSP-decision is NP-complete and propose two kinds of heuristics. The first attempts to replace dummy transfers with valid ones, while the second minimizes the implementation cost. Experimental evaluation of the algorithms illustrates the merits of our approach.
The dynamics of a single qubit, encoded in the charge states of a singly ionized phosphorus atom embedded in silicon bulk material are studied. For the simulation of the system a suitably modified version of the MATLA...
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The dynamics of a single qubit, encoded in the charge states of a singly ionized phosphorus atom embedded in silicon bulk material are studied. For the simulation of the system a suitably modified version of the MATLAB package SCHRODINGER was used. Preliminary results were in agreement with previously published work regarding single qubit rotations. For the Hadamard Gate, the duration of the pulse T was computed as a function of input parameters the results produced outputs of the order of 9×10-10 sec. [ABSTRACT FROM AUTHOR]
Clustering is particularly useful in problems where there is little prior information about the data under analysis. This is usually the case when attempting to evaluate a software system's maintainability, as man...
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Clustering is particularly useful in problems where there is little prior information about the data under analysis. This is usually the case when attempting to evaluate a software system's maintainability, as many dimensions must be taken into account in order to reach a conclusion. On the other hand partitional clustering algorithms suffer from being sensitive to noise and to the initial partitioning. In this paper we propose a novel partitional clustering algorithm, k-Attractors. It employs the maximal frequent itemset discovery and partitioning in order to define the number of desired clusters and the initial cluster attractors. Then it utilizes a similarity measure which is adapted to the way initial attractors are determined. We apply the k-Attractors algorithm to two custom industrial systems and we compare it with WEKA 's implementation of K-Means. We present preliminary results that show our approach is better in terms of clustering accuracy and speed.
Today we are experiencing a major reconsideration of the computing paradigm, as witnessed by the abundance and increasing frequency of use of terms such as ambient intelligence, ubiquitous computing, disappearing comp...
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ISBN:
(纸本)9780769527758;0769527752
Today we are experiencing a major reconsideration of the computing paradigm, as witnessed by the abundance and increasing frequency of use of terms such as ambient intelligence, ubiquitous computing, disappearing computer, grid computer, global computing and mobile ad-hoc networks. Systems that can be described with such terms are of a dynamic, with no clear physical boundary, nature and it seems that it is impossible (or, at least, difficult) to define sharply a number of important properties holding with certainty as well as holding throughout the whole lifetime of the system. One such system property, which is important for the viability of a system, is trust. Our departure point is the assumption that it seems very difficult to define static system properties related to trust and expect that they hold eternally in the rapidly changing systems falling under the new computing paradigm. One should, rather, attempt to define trust in terms of properties that hold with some limiting probability as the system grows and try to establish conditions that ensure that "good" properties hold almost certainly. Based on this viewpoint, in this paper we provide a new framework for defining trust through formally definable properties that hold, almost certainly, in the limit in randomly growing combinatorial structures that model "shapeless" computing systems (e.g., ad-hoc networks), drawing on results that establish the threshold behavior of predicates written in the first and second order logic
Wireless sensor networks (WSNs) are used in many applications which often include the monitoring and recording of sensitive information. Hence, their critical importance raises many security concerns. In the context o...
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Wireless sensor networks (WSNs) are used in many applications which often include the monitoring and recording of sensitive information. Hence, their critical importance raises many security concerns. In the context of WSNs, jamming is the type of attack which interferes with the radio frequencies used by network nodes. In the event that an attacker uses a rather powerful jamming source, disruptions of WSNs proper function are likely to occur. As a result, the use of countermeasures against jamming in WSN environments is of immense importance. The main contribution of this article is the discussion of various defence methods against jamming that would allow a WSN to survive and work properly in a hostile jamming environment. Our focus is on frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS), two of the most effective countermeasures against jamming. We suggest the use of a specific FHSS technique in 5 GHz band with 55 frequency channels wherein the channel sequence is generated using a secret word, known only to the sink and the sensor nodes, as a seed. Each channel uses DSSS modulation with 16 bit Pseudo Noise (PN) code, which derives from the same secret word used for FHSS channel generation.
Large-scale sensor networks, monitoring an environment at close range with high spatial and temporal resolutions are expected to play an important role in various applications, e.g., assessing the "health" o...
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Large-scale sensor networks, monitoring an environment at close range with high spatial and temporal resolutions are expected to play an important role in various applications, e.g., assessing the "health" of machines;environmental, medical, food-safety, and habitat monitoring;inventory control, building automation, etc. Ensuring the security of these complex and yet resource-constrained systems has emerged as one of the most pressing challenges for researchers. In this paper (i) we present the major threats, and (ii) we present a new approach for decentralized energy efficient intrusion detection that can be used to improve security from both external and internal adversaries.
Wireless sensor networks are comprised of a vast number of ultra-small autonomous computing, communication and sensing devices, with restricted energy and computing capabilities, that co-operate to accomplish a large ...
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Wireless sensor networks are comprised of a vast number of ultra-small autonomous computing, communication and sensing devices, with restricted energy and computing capabilities, that co-operate to accomplish a large sensing task. Such networks can be very useful in practice, e.g. in the local monitoring of ambient conditions and reporting them to a control center. In this paper we propose a distributed group key establishment protocol that uses mobile agents (software) and is particularly suitable for energy constrained, dynamically evolving ad-hoc networks. Our approach totally avoids the construction and the maintenance of a distributed structure that reflects the topology of the network. Moreover, it trades-off complex message exchanges by performing some amount of additional local computations in order to be applicable at dense and dynamic sensor networks. The extra computations are simple for the devices to implement and are evenly distributed across the participants of the network leading to good energy balance. We evaluate the performance of our protocol in a simulated environment and compare our results with existing group key establishment protocols. The security of the protocol is based on the Diffie-Hellman problem and we used in our experiments its elliptic curve analog. Our findings basically indicate the feasibility of implementing our protocol in real sensor network devices and highlight the advantages and disadvantages of each approach given the available technology and the corresponding efficiency (energy, time) criteria.
Electroencephalograph (EEG) recordings during the right and the left hand motor imagery can be used to move a cursor to a target on a computer screen. Such an EEG-based brain-computer interface (BCI) can provide a new...
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ISBN:
(纸本)4907764278
Electroencephalograph (EEG) recordings during the right and the left hand motor imagery can be used to move a cursor to a target on a computer screen. Such an EEG-based brain-computer interface (BCI) can provide a new communication channel to replace an impaired motor function. It can be used by e.g., handicap users with amyotrophic lateral sclerosis (ALS). The conventional method purposes the recognition of the right hand and the left hand motor imagery. In this sturdy, feature extraction based on Directed Information analysis is introduced to discriminate the EEG signals recorded during the right hand, the left hand and the right foot motor imagery. The effectiveness of our method is confirmed through the experimental studies.
This paper proposes a business model for the successful operation of the currently developing broadband metropolitan area networks in Greece. Having recorded and examined relevant international practices, we describe ...
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This paper proposes a business model for the successful operation of the currently developing broadband metropolitan area networks in Greece. Having recorded and examined relevant international practices, we describe in detail the way that these networks should be managed, operated, maintained and expanded. Taking into consideration that these infrastructures will alter the broadband map of Greece widely, that Greece currently has one of the lowest broadband penetration percentages in Europe and that the proper exploitation of the networks to be deployed could boost the demand for broadband connections and applications, the proposition of the business model appears to be of vital importance. We present the proposed business model in detail including information regarding network management and network expansion of the broadband metropolitan networks and viability issues regarding the authority which will manage the broadband metropolitan networks.
This paper treats the output feedback H 2 control with H ∞ norm constraint (mixed H 2 /H ∞ control problem). In general, this problem is a BMI problem which is difficult to be solved theoretically. The purpose of...
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This paper treats the output feedback H 2 control with H ∞ norm constraint (mixed H 2 /H ∞ control problem). In general, this problem is a BMI problem which is difficult to be solved theoretically. The purpose of this paper is to propose an iterative method for obtaining a sub-optimal solution of the mixed H 2 /H ∞ control problem. The key idea of this paper is to employ a full-order observer-based controller. The proposed method produces a sequence of controllers which approaches to the unconstrained globally optimal H 2 controller while it satisfies the H ∞ norm constraint. A numerical example shows the effectiveness of our method.
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