Energy
On-Line Reconfigurable Machines
Crawford, Lara S. (Palo Alto Research Center (PARC)) | Do, Minh Binh (Palo Alto Research Center (PARC)) | Ruml, Wheeler S. (University of New Hampshire) | Hindi, Haitham (Accuray, Inc.) | Eldershaw, Craig (Palo Alto Research Center (PARC)) | Zhou, Rong (Palo Alto Research Center (PARC)) | Kuhn, Lukas (Qualcomm R&D) | Fromherz, Markus P. J. (Xerox) | Biegelsen, David (Palo Alto Research Center (PARC)) | Kleer, Johan de (Palo Alto Research Center (PARC)) | Larner, Daniel (Google)
We believe that these goals can be attained through the use of a very high level of modularity, both in hardware and software, combined with intelligent software. To test this hypothesis, Palo Alto Research Center (PARC) designed and built a prototype highly modular system in the printing domain. This "hypermodular" printer explores the extremes of modularity, reconfigurability, and parallelism in both hardware and software. The hardware prototype connects four standard Xerox marking engines (the component of a printer that does the actual printing) in parallel using a highly modular paper path. This configuration can achieve a print rate of four times that of an individual print engine. Reconfigurable manufacturing systems supports flexibility in configuration, graceful degradation (RMSs) were introduced as a concept in the late under component failure, and rerouting of inprocess 1990s (Koren et al. 1999), but the prerequisites, in sheets under exception conditions. These both software and hardware, for implementing them capabilities were made possible by utilizing advanced successfully have proved daunting; very few examples AI techniques in model-based planning, scheduling, of RMSs exist today in practice. These prerequisites search, and temporal reasoning such as state-space include modular, reconfigurable hardware components regression planning, partial-order scheduling, temporal as well as the software and control planning graph-based heuristic estimates, multiobjective architectures and logic to support them. RMSs can search, and fast, simple temporal network include both hard reconfigurability (physical reconfiguration) reasoning. The AI planner / scheduler incorporates and soft reconfigurability (logical reconfiguration) mostly domain-independent techniques from the (ElMaraghy 2006). This latter concept planning and scheduling research community, includes the idea of flexible routing as well as replanning enabling its flexibility and configurability to be and rescheduling.
Gaussian Processes for Nonlinear Signal Processing
Pรฉrez-Cruz, Fernando, Van Vaerenbergh, Steven, Murillo-Fuentes, Juan Josรฉ, Lรกzaro-Gredilla, Miguel, Santamaria, Ignacio
Gaussian processes (GPs) are Bayesian state-of-the-art tools for discriminative machine learning, i.e., regression [1], classification [2] and dimensionality reduction [3]. GPs were first proposed in statistics by Tony O'Hagan [4] and they are well-known to the geostatistics community as kriging. However, due to their high computational complexity they did not become widely applied tools in machine learning until the early XXI century [5]. GPs can be interpreted as a family of kernel methods with the additional advantage of providing a full conditional statistical description for the predicted variable, which can be primarily used to establish confidence intervals and to set hyper-parameters. In a nutshell, Gaussian processes assume that a Gaussian process prior governs the set of possible latent functions (which are unobserved), and the likelihood (of the latent function) and observations shape this prior to produce posterior probabilistic estimates.
Recovering Non-negative and Combined Sparse Representations
Ramamurthy, Karthikeyan Natesan, Thiagarajan, Jayaraman J., Spanias, Andreas
The non-negative solution to an underdetermined linear system can be uniquely recovered sometimes, even without imposing any additional sparsity constraints. In this paper, we derive conditions under which a unique non-negative solution for such a system can exist, based on the theory of polytopes. Furthermore, we develop the paradigm of combined sparse representations, where only a part of the coefficient vector is constrained to be non-negative, and the rest is unconstrained (general). We analyze the recovery of the unique, sparsest solution, for combined representations, under three different cases of coefficient support knowledge: (a) the non-zero supports of non-negative and general coefficients are known, (b) the non-zero support of general coefficients alone is known, and (c) both the non-zero supports are unknown. For case (c), we propose the combined orthogonal matching pursuit algorithm for coefficient recovery and derive the deterministic sparsity threshold under which recovery of the unique, sparsest coefficient vector is possible. We quantify the order complexity of the algorithms, and examine their performance in exact and approximate recovery of coefficients under various conditions of noise. Furthermore, we also obtain their empirical phase transition characteristics. We show that the basis pursuit algorithm, with partial non-negative constraints, and the proposed greedy algorithm perform better in recovering the unique sparse representation when compared to their unconstrained counterparts. Finally, we demonstrate the utility of the proposed methods in recovering images corrupted by saturation noise.
A new framework for optimal classifier design
Di Martino, Matรญas, Hernรกndez, Guzman, Fiori, Marcelo, Fernรกndez, Alicia
Accuracy, Recall, Precision, F-measure, Kappa, ACU [Garcรญa et al. (2012)] and some other new proposed measures like Informedness and Markedness [Powers (2011)] are examples of different evaluation measures. Depending on the problem and the field of application one measure could be more suitable than another. While in the Behavioral Sciences, Specificity and Sensitivity are commonly used, in the Medical Sciences, ROC analysis is a standard for evaluation. On the other hand, in the Information Retrieval community and fraud detection, Recall, Precision and F-measure are considered appropriate measures for testing effectiveness. In a learning design strategy, the best rule for the specific application will be the one that get the optimal performance for the chosen measure. Looking for the best decision rule, in a Bayesian framework, implies to minimize the overall risk taking into account the different misclassification cost [Duda et al. (2001)]; in an equal misclassification cost problem we can find this optimal solution, with maximum accuracy, selecting the class that has the maximum a posteriori probability. However, finding a decision rule that looks for minimum error rate or maximum accuracy in an imbalanced domain gives solutions strongly biased to favor the majority class, getting poor performance. This problem is particularly important in those applications where the instances of a class (the majority one) heavily outnumber the instances of the other (the minority) class and it is costly to misclassify samples from the minority class.
Spectral redemption: clustering sparse networks
Krzakala, Florent, Moore, Cristopher, Mossel, Elchanan, Neeman, Joe, Sly, Allan, Zdeborovรก, Lenka, Zhang, Pan
Spectral algorithms are classic approaches to clustering and community detection in networks. However, for sparse networks the standard versions of these algorithms are suboptimal, in some cases completely failing to detect communities even when other algorithms such as belief propagation can do so. Here we introduce a new class of spectral algorithms based on a non-backtracking walk on the directed edges of the graph. The spectrum of this operator is much better-behaved than that of the adjacency matrix or other commonly used matrices, maintaining a strong separation between the bulk eigenvalues and the eigenvalues relevant to community structure even in the sparse case. We show that our algorithm is optimal for graphs generated by the stochastic block model, detecting communities all the way down to the theoretical limit. We also show the spectrum of the non-backtracking operator for some real-world networks, illustrating its advantages over traditional spectral clustering.
Matching Demand with Supply in the Smart Grid using Agent-Based Multiunit Auction
Wijaya, Tri Kurniawan, Larson, Kate, Aberer, Karl
Recent work has suggested reducing electricity generation cost by cutting the peak to average ratio (PAR) without reducing the total amount of the loads. However, most of these proposals rely on consumer's willingness to act. In this paper, we propose an approach to cut PAR explicitly from the supply side. The resulting cut loads are then distributed among consumers by the means of a multiunit auction which is done by an intelligent agent on behalf of the consumer. This approach is also in line with the future vision of the smart grid to have the demand side matched with the supply side. Experiments suggest that our approach reduces overall system cost and gives benefit to both consumers and the energy provider.
A Linear-Programming Approximation of AC Power Flows
Coffrin, Carleton, Van Hentenryck, Pascal
Linear active-power-only DC power flow approximations are pervasive in the planning and control of power systems. However, these approximations fail to capture reactive power and voltage magnitudes, both of which are necessary in many applications to ensure voltage stability and AC power flow feasibility. This paper proposes linear-programming models (the LPAC models) that incorporate reactive power and voltage magnitudes in a linear power flow approximation. The LPAC models are built on a convex approximation of the cosine terms in the AC equations, as well as Taylor approximations of the remaining nonlinear terms. Experimental comparisons with AC solutions on a variety of standard IEEE and MatPower benchmarks show that the LPAC models produce accurate values for active and reactive power, phase angles, and voltage magnitudes. The potential benefits of the LPAC models are illustrated on two "proof-of-concept" studies in power restoration and capacitor placement.
An Active Learning Approach to Home Heating in the Smart Grid
Shann, Mike (University of Zurich) | Seuken, Sven (University of Zurich)
A key issue for the realization of the smart grid vision is the implementation of effective demand-side management. One possible approach involves exposing dynamic energy prices to end-users. In this paper, we consider a resulting problem on the user's side: how to adaptively heat a home given dynamic prices. The user faces the challenge of having to react to dynamic prices in real time, trading off his comfort with the costs of heating his home to a certain temperature. We propose an active learning approach to adjust the home temperature in a semi-automatic way. Our algorithm learns the user's preferences over time and automatically adjusts the temperature in real-time as prices change. In addition, the algorithm asks the user for feedback once a day. To find the best query time, the algorithm solves an optimal stopping problem. Via simulations, we show that our algorithm learns users' preferences quickly, and that using the expected utility loss as the query criterion outperforms standard approaches from the active learning literature.
Short-Term Wind Power Forecasting Using Gaussian Processes
Chen, Niya (Beihang University) | Qian, Zheng (Beihang University) | Nabney, Ian T. (Aston University) | Meng, Xiaofeng (Beihang University)
Since wind has an intrinsically complex and stochastic nature, accurate wind power forecasts are necessary for the safety and economics of wind energy utilization. In this paper, we investigate a combination of numeric and probabilistic models: one-day-ahead wind power forecasts were made with Gaussian Processes (GPs) applied to the outputs of a Numerical Weather Prediction (NWP) model. Firstly the wind speed data from NWP was corrected by a GP. Then, as there is always a defined limit on power generated in a wind turbine due the turbine controlling strategy, a Censored GP was used to model the relationship between the corrected wind speed and power output. To validate the proposed approach, two real world datasets were used for model construction and testing. The simulation results were compared with the persistence method and Artificial Neural Networks (ANNs); the proposed model achieves about 11% improvement in forecasting accuracy (Mean Absolute Error) compared to the ANN model on one dataset, and nearly 5% improvement on another.
An Intelligent Broker Agent for Energy Trading: An MDP Approach
Kuate, Rodrigue Talla (Aston University) | He, Minghua (Aston University) | Chli, Maria (Aston University) | Wang, Hai H. (Aston University)
This paper details the development and evaluation of AstonTAC, an energy broker that successfully participated in the 2012 Power Trading Agent Competition (Power TAC). AstonTAC buys electrical energy from the wholesale market and sells it in the retail market. The main focus of the paper is on the broker's bidding strategy in the wholesale market. In particular, it employs Markov Decision Processes (MDP) to purchase energy at low prices in a day-ahead power wholesale market, and keeps energy supply and demand balanced. Moreover, we explain how the agent uses Non-Homogeneous Hidden Markov Model (NHHMM) to forecast energy demand and price. An evaluation and analysis of the 2012 Power TAC finals show that AstonTAC is the only agent that can buy energy at low price in the wholesale market and keep energy imbalance low.