1,720,980 research outputs found
Speeding up Answer Set Programming by Quantum Computing
Full text linkQuantum Computing has become a more and more prominent research field in the last few decades. This growth in interest is mainly related to the so-called quantum speed up that some quantum procedure exhibits. The two main examples are Shor and Grover algorithms. The latter will be a key ingredient of this paper. In particular, we propose an attempt to speed up Answer Set Programming (ASP) exploiting Quantum Computing. We rely on two proposals in the literature that use quantum computation for: finding stable models of ASP programs; counting solutions of propositional formulae. For combining such proposals we embed in the quantum framework a third proposal from the literature, namely a purely classical approach for navigating the solution space of ASP models. We end up with a quantum method for counting stable models of ASP programs. After providing the details of our method, we briefly describe a Proof of Concept implementation of these techniques
Directed Graph Encoding in Quantum Computing Supporting Edge-Failures
No full textGraphs are one of the most common data structures in classical computer science and graph theory has been widely used in complexity and computability. Recently, the use of graphs in application domains such as routing, network analysis and resource allocation has become crucial. In these areas, graphs are often evolving in time: for example, connection links may fail due to temporary technical issues, meaning that edges of the graph cannot be traversed for some time interval and alternative paths have to be followed. In classical computation, where graphs are represented as adjacency matrices or lists, these problems are well studied and ad-hoc visit procedures have been developed. For specific problems quantum computation, through superpositions and entanglement has provided faster algorithms than their classical counterpart. However, in this model, only reversible operations are allowed and this poses the quest of augmenting a graph in order to be able to reverse edge traversals. In this paper we present a novel graph representation in quantum computation supporting dynamic connectivity typical of real-world network applications. Our proposal has the advantage of being closer than others in literature to the adjacency matrix of the graph. This makes easy dynamic edge-failure modeling. We introduce optimal algorithms for computing our graph encoding and we show the effectiveness of our proposal with some examples
A New Linear-Time Algorithm for Centroid Decomposition
Full text linkThe centroid of a tree is a node that, when removed, breaks the tree in connected components of size at most half of that of the original tree. By recursing this procedure on the components, one obtains the centroid decomposition of the tree, also known as centroid tree. The centroid tree has logarithmic height and its construction is a powerful pre-processing step in several tree-processing algorithms. The folklore recursive algorithm for computing the centroid tree runs in time. To the best of our knowledge, the only result claiming O(n) time is unpublished and relies on (dynamic) heavy path decomposition of the original tree. In this short paper, we describe a new simple and practical linear-time algorithm for the problem based on the idea of applying the folklore algorithm to a suitable decomposition of the original tree
Massive Generation of Customer Load Profiles for Large Scale State Estimation Deployment: An Approach to Exploit AMI Limited Data
No full textThe management of the distribution network is becoming increasingly important as the penetration of distributed energy resources is increasing. Reliable knowledge of the real-time status of the network is essential if algorithms are to be used to help distribution system operators define network configurations. State Estimation (SE) algorithms are capable of producing such an accurate snapshot of the network state but, in turn, require a wide range of information, e.g., network topology, real-time measurement and power profiles from customers/productions. Those profiles which may, in principle, be provided by smart meters are not always available due to technical limitations of existing Advanced Metering Infrastructure (AMI) in terms of communication, storage and computing power. That means that power profiles are only available for a subset of customers. The paper proposes an approach that can overcome these limitations: the remaining profiles, required by SE algorithms, are generated on the basis of customer-related information, identifying clusters of customers with similar features, such as the same contract and pattern of energy consumption. For each cluster, a power profile estimator is generated using long-term power profiles of a limited sub-set of customers, randomly selected from the cluster itself. The synthesized full power profile, representing each customer of the distribution network, is then obtained by scaling the power profile estimator of the cluster to which the customer belongs, by the monthly energy exchanged by that customer, data that are easily available. The feasibility of the proposed approach was validated considering the distribution grid of Unareti SpA, an Italian Distribution System Operator (DSO), operating in northern Italy and serving approximately one million customers. The application of the proposed approach to the actual infrastructure shows some limitations in terms of the accuracy of the estimation of the power profile of the customer. In particular, the proposed methodology is not fully able to properly represent clusters composed of customers with a large variability in terms of power exchange with the distribution network. In any case, the root mean square error of the synthesized full power profile with the respect to validation power profiles belonging to the same cluster is, in the worst case, on the order of 6.3%, while in the rest of cases is well below 5%. Thus, the proposed approach represents a good compromise between accuracy in representing the behavior of customers on the network and resources (in terms of computational power, data storage and communication resources) to achieve that results
Experimental characterization of time synchronization over a heterogeneous network for Smart Grids
No full textOpen UPQC power quality manager within distributed generation systems
No full textPower quality in distribution networks is already a concern in many European Countries where there is a strong presence of renewable energy generation. There is therefore a growing interest in new technologies able to improve the power quality level. Among them, the Open Uninterruptible Power Quality Conditioner (Open UPQC) is a possible solution. The system consists of a main three-phase AC/DC power converter in the MV/LV substation, and some single-phase or three-phase AC/DC power converter installed at customer's premises. The paper discusses design, simulation, implementation of an Open UPQC installed in real distribution grid in the city of Brescia (north of Italy) within Smart Domo Grid, a project co-funded by the Italian Ministry of Economic Development. Some experimental results are also reported
Statistical Analysis of Broadband Underground Medium Voltage Channels for PLC Applications
No full textThis work presents a statistical analysis performed on a set of channels that were measured in real-life underground medium voltage power line communication (PLC) networks. The aim is to improve the knowledge of the medium from experimental basis, providing usable and closed-form expressions of the main metrics in order to foster the design of PLC technologies tailored to such challenging scenario. The work targets the 2-40 MHz band, and focuses on the average channel gain (ACG), the root-mean-square delay spread (RMS-DS) and the coherence bandwidth. Furthermore, the work presents the relation between the ACG, the RMS-DS and the network topology, and it infers the capacity as a function of the transmission bandwidth under power spectral density or total power constraints. Some results about the line impedance are also show
Experimental characterization of service latency over Broadband Power Line in Medium Voltage grid
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