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Optimal and Compact Control Policies for Energy Storage Units With Single and Multiple Batteries

IEEE TRANSACTIONS ON SMART GRID 2014年第3期5卷 1308-1317页

作者： Erseghe, Tomaso Zanella, Andrea Codemo, Claudio G. Univ Padua Dipartimento Ingn Informaz Padua Italy

In this paper we investigate the use of energy storage units (ESUs) to reduce the average cost of power supply. Using a dynamic programming (DP) argument, we first show that the optimal control policy for a single-battery ESU, under piecewise linear cost functions, has a threshold structure that can be expressed and stored in a very compact form. We then extend the analysis to an ESU with multiple (heterogeneous) batteries, where DP is generally impractical because of the explosion of the computational complexity with the number of batteries. We hence define a simple method to map the optimal solution of a suitable single-battery ESU into an admissible policy for the multiple-battery ESU, whose complexity grows only linearly with the number of batteries. Extensive simulation results show that the proposed approach can yield significant cost reduction in comparison with other policies, under realistic users' power requests, and with different costs functions. Furthermore, the admissible policy for the multiple-battery ESU is shown to achieve almost optimal performance under realistic assumptions on the battery parameters.

关键词： Dynamic programming energy storage multiple batteries optimization smart grid threshold algorithm

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Best position algorithms for efficient top-k query processing

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INFORMATION SYSTEMS 2011年第6期36卷 973-989页

作者： Akbarinia, Reza Pacitti, Esther Valduriez, Patrick Univ Montpellier LIRMM Montpellier France Univ Montpellier INRIA Montpellier France

The general problem of answering top-k queries can be modeled using lists of data items sorted by their local scores. The main algorithm proposed so far for answering top-k queries over sorted lists is the threshold algorithm (TA). However, TA may still incur a lot of useless accesses to the lists. In this paper, we propose two algorithms that are much more efficient than TA. First, we propose the best position algorithm (BPA). For any database instance (i.e. set of sorted lists), we prove that BPA stops as early as TA, and that its execution cost is never higher than TA. We show that there are databases over which BPA executes top-k queries O(m) times faster than that of TA, where m is the number of lists. We also show that the execution cost of our algorithm can be (m - 1) times lower than that of TA. Second, we propose the BPA2 algorithm, which is much more efficient than BPA. We show that the number of accesses to the lists done by BPA2 can be about (m - 1) times lower than that of BPA. We evaluated the performance of our algorithms through extensive experimental tests. The results show that over our test databases, BPA and BPA2 achieve significant performance gains in comparison with TA. (C) 2011 Elsevier B.V. All rights reserved.

关键词： Query processing Top-k queries threshold algorithm Instance optimality

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Top-k queries on RDF graphs

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INFORMATION SCIENCES 2015年 316卷 201-217页

作者： Wang, Dong Zou, Lei Zhao, Dongyan Peking Univ Beijing 100871 Peoples R China

Recent years have witnessed unprecedented volumes of structured data published in RDF format. Taking full advantage of such data has attracted a growing amount of research interest from both academia and industry. However, efficient processing of top-k queries in RDF data is still a new topic. Most existing approaches ignore top-k queries, or only provide a limited number of ranking functions. In this paper, we provide an effective and efficient processing algorithm for top-k queries that consists of a novel tree-style index MS-tree and MS-tree-based filtering and pattern-matching functions. Firstly, candidate entities in RDF data were efficiently ranked and filtered through an MS-tree-based topdown method. Then, query structure patterns are matched in RDF data through graphic exploration. In order to handle more complex scoring functions, a dynamic variable selecting optimization is employed to accelerate the threshold decrease. We evaluate our solutions with both synthetic and real-world datasets. The experimental results show that our model significantly outperforms state-of-the-art approaches. (C) 2015 Elsevier Inc. All rights reserved.

关键词： Top-k SPARQL query Graph exploration Entity encoding threshold algorithm

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Efficient location-based search of trajectories with location importance

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KNOWLEDGE AND INFORMATION SYSTEMS 2015年第1期45卷 215-245页

作者： Yan, Da Cheng, James Zhao, Zhou Ng, Wilfred Chinese Univ Hong Kong Dept Comp Sci & Engn Shatin Hong Kong Peoples R China Hong Kong Univ Sci & Technol Dept Comp Sci & Engn Hong Kong Hong Kong Peoples R China

Given a database of trajectories and a set of query locations, location-based trajectory search finds trajectories in the database that are close to all the query locations. Location-based trajectory search has many applications such as providing reference routes for travelers who are planning a trip to multiple places of interest. However, previous studies only consider the spatial aspect of trajectories, which is inadequate for real applications. For example, one may obtain the reference route of a tourist who just passed by a place of interest without paying a visit. We propose the Important Connected Trajectories (k-ICT) query by associating trajectories with location importance. For any query location, the result trajectories should contain an important point close to it. We describe an effective method to infer the importance of trajectory points from the temporal information. We also propose efficient R-tree-based and grid-based algorithms to answer -ICT queries, and verify the efficiency of our algorithms through extensive experiments on both real and synthetic datasets.

关键词： Trajectory Location importance threshold algorithm Voronoi diagram

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A feasibility study of using smartphone built-in accelerometers to detect fall portents

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AUTOMATION IN CONSTRUCTION 2014年 38卷 74-86页

作者： Dzeng, Ren-Jye Fang, Yi-Cho Chen, I-Chung Natl Chiao Tung Univ Dept Civil Engn Hsinchu Taiwan

Fall accidents contribute to nearly half of all fatalities in the construction industry in Taiwan. Detecting fall portents using a smartphone, which many people carry daily, may help reduce fall accidents if the accuracy is acceptable. We designed two experiments with three algorithms to evaluate how well a smartphone can detect both falls and fall portents in a tiling operation scenario. The experiments show that work-related motions barely affected the detection of falls, and the result had a sensitivity and specificity of 100% and 96.1%, respectively. However, for detecting portents, the work-related motions had quite a large impact on the gyroscope-based algorithm, which demonstrated an accuracy rate of only 4.3%, but had only limited impact on the accelerometer-based algorithm, which still show acceptable accuracy rates of 73.5% and 88.5%. We conclude that using a smartphone to detect falls and portents in a construction site is feasible. (C) 2013 Elsevier B.V. All rights reserved.

关键词： Smartphone Accelerometer Fall detection Portent threshold algorithm Construction safety

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Detection of generated and measured transient power quality events using Teager Energy Operator

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ENERGY CONVERSION AND MANAGEMENT 2011年第4期52卷 1959-1967页

作者： Subasi, Abdulhamit Yilmaz, A. Serdar Tufan, Kadir Kahramanmaras Sutcu Imam Univ Dept Elect & Elect Eng TR-46100 Kahramanmaras Turkey Int Burch Univ Dept Informat Technol Sarajevo 71000 Bosnia & Herceg Fatih Univ Dept Comp Engn TR-34500 Istanbul Turkey

In this paper, a novel algorithm, based on the Teager Energy Operator (TEO) of a sinusoidal waveform, proposed to detect and analyze the voltage disturbances. Most common power quality (PQ) disturbances at the distribution level such as voltage sags, notches, and capacitor switching are presented. These examples provide the basis for further characterization of other power quality events. Magnitudes of transient PQ events are located in the width of the signal. Furthermore, meaningful components of transients are analyzed. The whole method is implemented and tested over a sample representing recorded disturbances. Simulation and experimental results of different PQ disturbances show that the proposed method is fast and robust in detecting voltage disturbances and requires only a few samples to calculate the energy of a signal. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.

关键词： Power quality (PQ) Power system disturbances Power system transients Teager Energy Operator (TEO) threshold algorithm

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Imposing Minimax and Quantile Constraints on Optimal Matching in Observational Studies

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JOURNAL OF COMPUTATIONAL AND GRAPHICAL STATISTICS 2017年第1期26卷 66-78页

作者： Rosenbaum, Paul R. Univ Penn Wharton Sch Dept Stat Philadelphia PA 19104 USA

Modern methods construct amatched sample byminimizing the total cost of a flow in a network, finding a pairing of treated and control individuals that minimizes the sum of within-pair covariate distances subject to constraints that ensure distributions of covariates are balanced. In aggregate, these methods work well;however, they can exhibit a lack of interest in a small number of pairs with large covariate distances. Here, a newmethod is proposed for imposing a minimax constraint on aminimum total distancematching. Such a match minimizes the total within-pair distance subject to various constraints including the constraint that the maximum pair difference is as small as possible. In an example with 1391 matched pairs, this constraint eliminates dozens of pairs with moderately large differences in age, but otherwise exhibits the same excellent covariate balance found without this additional constraint. A minimax constraint eliminates edges in the network, and can improve the worst-case time bound for the performance of the minimum cost flow algorithm, that is, a better match from a practical perspective may take less time to construct. The techni-ue adapts ideas for a different problem, the bottleneck assignment problem, whose sole objective is to minimize the maximum within-pair difference;however, here, that objective becomes a constraint on the minimum cost flow problem. The method generalizes. Rather than constrain the maximum distance, it can constrain an order statistic. Alternatively, the method can minimize the maximum difference in propensity scores, and subject to doing that, minimize the maximum robust Mahalanobis distance. An example from labor economics is used to illustrate. Supplementary materials for this article are available online.

关键词： Bottleneck assignment Fine balance threshold algorithm

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Spline retracker: a geometrical retracking algorithm for coastal and open ocean altimetry

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MARINE GEODESY 2024年第2期47卷 83-118页

作者： Mafi, Saleh Farzaneh, Saeed Sharifi, Mohammad Ali Forootan, Ehsan Univ Tehran Coll Engn Sch Surveying & Geospatial Engn Tehran Iran Aalborg Univ Dept Sustainabil & Planning Geodesy Grp Aalborg Denmark

Satellite altimetry has enhanced the understanding of ocean dynamics through high-rate sampling and global coverage. However, land contamination and bad reflection effects limit its accuracy. We present a geometrical method for retracking altimetry waveforms in coastal areas. Our method follows a geometrical assumption related to the symmetrical reciprocal motion of the radar pulse. Based on this assumption, the altimetry waveform is modelled as a continuous and differentiable third-order spline function, and the symmetry point of this function is considered as the retracking gate. The spline retracking algorithm is validated against the tide gauges at Onsala, Halmstad, and Muscat stations in Sweden and Oman, and its performance is compared with existing retracking algorithms. Our results showed a remarkable reduction of 50-91% in the unbiased-Root-Mean-Squared-Error (ubRMSE) and an increase of at least 13% in correlation coefficients when compared with other algorithms in Swedish coast. This algorithm presented equivalent results with the threshold and improved threshold retrackings in Muscat station, based on Jason-2 measurements. However, along the Jason-3 pass, our spline method showed a considerable reduction of 80% in ubRMSE and the minimum increase of 42% in correlation coefficients than the empirical algorithms. This method also outperformed the ALES algorithm in most cases.

关键词： Coastal altimetry OCOG algorithm retracking spline function threshold algorithm

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Cirrus OCT versus Spectralis OCT: differences in segmentation in fibrovascular pigment epithelial detachment

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GRAEFES ARCHIVE FOR CLINICAL AND EXPERIMENTAL OPHTHALMOLOGY 2010年第12期248卷 1693-1698页

作者： Smretschnig, Eva Krebs, Ilse Moussa, Sarah Ansari-Shahrezarei, Siamak Binder, Susanne Ludwig Boltzmann Inst Retinol & Biomicroscop Lase A-1030 Vienna Austria Rudolf Fdn Clin Dept Ophthalmol Vienna Austria Med Univ Graz Dept Ophthalmol Graz Austria

Background Automatically measurements of retinal thickness by optical coherence tomography (OCT) facilitate the assessment of various retinal diseases. The aim of this retrospective study was to report macular thickness measurements in eyes with vascular pigment epithelial detachment (PED) due to age-related macular degeneration (AMD) by using two different commercially available spectral domain (SD) OCT instruments and to consequently point out differences in their algorithm ***. Methods OCT images of patients with vascular PED due to AMD, obtained with Cirrus and Spectralis OCT, were retrospectively analyzed. Main objectives were to observe differences in central retinal thickness (CRT) values and failures in automated threshold delineation, as well as central point thickness values obtained after manual correction of threshold lines. Scanning with the Cirrus HD OCT was performed with the 512 x 128 scan pattern;scans performed with the Spectralis OCT were 20 x 15 degree raster scans consisting of 19 high-speed line scans. Results OCT images of 34 eyes of 28 patients with a mean age of 71 years and a mean distance visual acuity (VA) of 0.70 ETDRS were analyzed. Mean central retinal thickness (CRT) was 262.38 mu m +/- 133.18 (176-507 mu m) in Cirrus and 337.82 mu m +/- 137.75 (277-790 mu m) in Spectralis scans, mainly caused by different software approaches in positioning the posterior threshold line, following the PED in Cirrus OCT whereas remaining unelevated in Spectralis OCT. There were failures in positioning the outer retinal boundary line in 50% of Cirrus scans and in 73.52% of Spectralis scans. We obtained the mean value of central point neurosensory retinal thickness of each central single scan after manual delineation, and found a significant correlation (r=0.819, p<0.001). Conclusions Our study indicates that there are significant differences in CRT values in patients with vascular PED, due to different segmentation algorithms and a high erro

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A novel wavelet method for electric signals analysis in underwater arc welding

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China Welding 2009年第2期18卷 12-16页

作者：张为民王国荣石永华钟碧良 School of Mechanical and Automotive Engineering South China University of Technology Guangzhou 510640 Department of Computer Technology Guangzhou Maritime College Guangzhou 510725

Electric signals are acquired and analyzed in order to monitor the underwater arc welding process. Voltage break point and magnitude are extracted by detecting arc voltage singularity through the modulus maximum wavelet （MMW） method. A novel threshold algorithm, which compromises the hard-threshold wavelet （HTW） and soft-threshold wavelet （STW） methods, is investigated to eliminate welding current noise. Finally, advantages over traditional wavelet methods are verified by both simulation and experimental results.

关键词： underwater arc welding electric signals wavelet method threshold algorithm

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