Cloud-based video streaming systems such as YouTube and Netflix are usually supported by the content delivery networks and data centers that can consume many megawatts of power. Most existing work independently studie...
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Cloud-based video streaming systems such as YouTube and Netflix are usually supported by the content delivery networks and data centers that can consume many megawatts of power. Most existing work independently studies the issues of improving quality of experience (QoE) for viewers and reducing the cost and emissions associated with the enormous energy usage of data centers. By contrast, this paper addresses them both, and jointly optimizes the QoE, the energy cost and emissions by intelligently allocating data center bandwidth among different client groups. Specially, we propose a distributed algorithm to achieve the optimal bandwidth allocation, given the prediction of future workload. The algorithm novelly decomposes the optimization process into separate ones, which are solved iteratively across data centers and clients. Further, the algorithm has robust performance guarantee in terms of the variance of the prediction error. We demonstrate its convergence and robustness by both proofs using theoretical analysis and validation based on trace-driven simulations. The results further show that the proposed algorithm converges very fast and achieves much better QoE-cost balance than existing approaches.
This paper formalizes an optimal water-power flow (OWPF) problem to optimize the use of controllable assets across power and water systems while accounting for the couplings between the two infrastructures. Tanks and ...
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This paper formalizes an optimal water-power flow (OWPF) problem to optimize the use of controllable assets across power and water systems while accounting for the couplings between the two infrastructures. Tanks and pumps are optimally managed to satisfy water demand while improving power grid operations;for the power network, an ac optimal power-flow formulation is augmented to accommodate the controllability of water pumps. Unfortunately, the physics governing the operation of the two infrastructures and coupling constraints leads to a nonconvex (and, in fact, NP-hard) problem;however, after reformulating OWPF as a nonconvex, quadratically constrained quadratic problem, a feasible point pursuit-successive convex approximation approach is used to identify feasible and optimal solutions. In addition, a distributed solver based on the alternating direction method of multipliers enables water and power operators to pursue individual objectives while respecting the couplings between the two networks. The merits of the proposed approach are demonstrated for the case of a distribution feeder coupled with a municipal water distribution network.
In this work, we propose a hierarchical distributed model predictive control strategy to operate interconnected microgrids (MGs) with the goal of increasing the overall infeed of renewable energy sources. In particula...
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In this work, we propose a hierarchical distributed model predictive control strategy to operate interconnected microgrids (MGs) with the goal of increasing the overall infeed of renewable energy sources. In particular, we investigate how renewable infeed of MGs can be increased by using a transmission network allowing the exchange of energy. To obtain an model predictive control scheme, which is scalable with respect to the number of MGs and preserves their independent structure, we make use of the alternating direction method of multipliers leading to local controllers communicating through a central entity. This entity is in charge of the power lines and ensures that the constraints on the transmission capacities are met. The results are illustrated in a numerical case study.
We consider networks the nodes of which are interconnected via directed edges, each able to admit a flow (or weight) within a certain interval, with nonnegative end points that correspond to lower and upper flow limit...
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We consider networks the nodes of which are interconnected via directed edges, each able to admit a flow (or weight) within a certain interval, with nonnegative end points that correspond to lower and upper flow limits. This paper proposes and analyzes a distributed algorithm for obtaining admissible and balanced flows, i. e., flows that are within the given intervals at each edge and are balanced (the total in-flow equals the total out-flow) at each node. The algorithm can also be viewed as a distributed method for obtaining a set of weights that balance a weighted digraph for the case when there are lower and upper limit constraints on the edge weights. The proposed iterative algorithm assumes that communication among pairs of nodes that are interconnected is bidirectional (i. e., the communication topology is captured by the undirected graph that corresponds to the network digraph), and allows the nodes to asymptotically (with geometric rate) reach a set of balanced feasible flows, as long as the (necessary and sufficient) circulation conditions on the given digraph, with the given flow/weight interval constraints on each edge, are satisfied. We also provide a methodology that can be used by the nodes to asymptotically determine, in a distributedmanner, when the circulation conditions are not satisfied (thus, making the problem infeasible). Finally, we provide several examples and simulation studies to highlight the role of various parameters involved in the proposed distributed algorithm.
The Dedekind numbers are an integer sequence that describes the number of n-variable monotone Boolean functions. It is reducible to counting other distinguished mathematical notions: antichains of subsets of n-set and...
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The Dedekind numbers are an integer sequence that describes the number of n-variable monotone Boolean functions. It is reducible to counting other distinguished mathematical notions: antichains of subsets of n-set and simplicial complexes on an n-vertex set. The terms for $0 \le n\le 8$ are known and $n=9$ has been an open problem for over three decades. In this paper, we discuss the computability of the ninth Dedekind number with recent results involving partially ordered sets by Berman and Kohler [1] and combinatorial approaches with other relevant sequences
This paper endeavors to learn time-varying graphs by using structured temporal priors that assume underlying relations between arbitrary two graphs in the graph sequence. Different from many existing methods that only...
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ISBN:
(数字)9789082797091
ISBN:
(纸本)9781665467995
This paper endeavors to learn time-varying graphs by using structured temporal priors that assume underlying relations between arbitrary two graphs in the graph sequence. Different from many existing methods that only describe vari-ations between two consecutive graphs, we propose a structure named temporal graph to characterize the underlying real temporal relations. Under this framework, classic priors like temporal homogeneity are actually special cases of our temporal graph. To address computational issue, we further develop a distributed algorithm based on Alternating Direction Method of Multipliers (ADMM) to solve the induced optimization problem. Numerical experiments on synthetic and real data demonstrate the superiorities of our method.
Demand response technology offers the exciting potential to reduce peak energy demand, electricity infrastructure expenditure, and household electricity bills. In this paper, a pricing mechanism that relies on non-coo...
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Demand response technology offers the exciting potential to reduce peak energy demand, electricity infrastructure expenditure, and household electricity bills. In this paper, a pricing mechanism that relies on non-cooperative heterogeneous loads knowledgeable of future energy consumption-such as electric vehicles-transferring minimal amounts of information to achieve peak demand response in a distributed fashion, whilst maintaining the privacy of the players. The existence of a Nash equilibrium is proven, as well as convergence conditions proving uniqueness of a Nash equilibrium and the stability of an "Iterated Synchronous Best Response Algorithm." The price of anarchy (PoA) is proven to approach 1 as the number of homogeneous players approaches infinity, indicating there is no advantage to cooperation for a large number of similar players. Finally, simulation results are presented which suggest that the PoA for a system with heterogeneous players is likely to be proportional to the spread of energy consumption constraints.
This paper presents a non- cooperative, zero-sum, symmetric game approach to projecting the flexible demand-side resources to improve the reliability and robustness of long-term strategic energy planning models. A spe...
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ISBN:
(纸本)9781728169194
This paper presents a non- cooperative, zero-sum, symmetric game approach to projecting the flexible demand-side resources to improve the reliability and robustness of long-term strategic energy planning models. A specifically devised distributed algorithm is put forward to determine the unique, pure-strategy Nash equilibrium of a non-cooperative game formulated for the delivery of aggregator-mediated demand response resources, at which no player can yield a higher payoff by deviating from its best-response strategy. The simulation for the operation of renewable energy systems is run over the course of a year. Furthermore, using a metaheuristic-based solution algorithm proposed for the optimal capacity planning of microgrids, the model was satisfactorily applied to the energy infrastructure planning of a test-case system conceptualized for the town of Ohakune, in New Zealand. The simulation results suggest that not only does the proposed market-directed, incentive-based, strategic demand- side management planning framework help elicit further contributions from the customers, which, in turn, reduces the reserve capacity requirements to meet the peak demand, it also guarantees the highest possible payoff for all players of the game. According to the simulation results, the test-case system's life-cycle cost can be reduced by up to similar to 29% compared to the case, where no demand response is considered.
Aggregation is common in data analytics and crucial to distilling information from large datasets, but current data analytics frameworks do not fully exploit the potential for optimization in such phases. The lack of ...
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Aggregation is common in data analytics and crucial to distilling information from large datasets, but current data analytics frameworks do not fully exploit the potential for optimization in such phases. The lack of optimization is particularly notable in current "online" approaches that store data in main memory across nodes, shifting the bottleneck away from disk I/O toward network and compute resources, thus increasing the relative performance impact of distributed aggregation phases. We present ROME, an aggregation system for use within data analytics frameworks or in isolation. ROME uses a set of novel heuristics based primarily on basic knowledge of aggregation functions combined with deployment constraints to efficiently aggregate results from computations performed on individual data subsets across nodes (e.g., merging sorted lists resulting from top-k). The user can either provide minimal information that allows our heuristics to be applied directly, or ROME can autodetect the relevant information at little cost. We integrated ROME as a subsystem into the Spark and Flink data analytics frameworks. We use real-world data to experimentally demonstrate speedups up to 3x over single-level aggregation overlays, up to 21% over other multi-level overlays, and 50% for iterative algorithms like gradient descent at 100 iterations.
Active noise control (ANC) is an effective way for reducing the noise level in electroacoustic or electromechanical systems. Since its first introduction in 1936, this approach has been greatly developed. This paper f...
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Active noise control (ANC) is an effective way for reducing the noise level in electroacoustic or electromechanical systems. Since its first introduction in 1936, this approach has been greatly developed. This paper focuses on discussing the development of ANC techniques over the past decade. Linear ANC algorithms, including the celebrated filtered-x least-mean-square (FxLMS)-based algorithms and distributed ANC algorithms, are investigated and evaluated. Nonlinear ANC (NLANC) techniques, such as functional link artificial neural network (FLANN)-based algorithms, are pursued in Part II. Furthermore, some novel methods and applications of ANC emerging in the past decade are summarized. Finally, future research challenges regarding the ANC technique are discussed. (C) 2021 Elsevier B.V. All rights reserved.
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