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Latency of Neighborhood Based Recommender Systems

FUNDAMENTA INFORMATICAE 2015年第3期139卷 229-248页

作者： Chojnacki, Szymon Klopotek, Mieczyslaw Polish Acad Sci Inst Comp Sci PL-01248 Warsaw Poland

Latency of user-based and item-based recommenders is evaluated. The two algorithms can deliver high quality predictions in dynamically changing environments. However, their response time depends not only on the size, but also on the structure of underlying datasets. This constitutes a major drawback when compared to two other competitive approaches i.e. content-based and model-based systems. Therefore, we believe that there exists a need for comprehensive evaluation of the latency of the two algorithms. During a typical worst case scenario analysis of collaborative filtering algorithms two assumption are made. The first assumption says that data are stored in dense collections. The second assumption states that large amount of computations can be performed in advance during the training phase. As a result it is advised to deploy user-based system when the number of users is relatively small. Item-based algorithms are believed to have better technical properties when the number of items is small. We consider a situation in which the two assumptions are not necessarily met. We show that even though the latency of the two methods depends heavily on the proportion of users to items, this factor does not differentiate the two methods. We evaluate the algorithms with several real-life datasets. We augment the analysis with both graph-theoretical and experimental techniques.

关键词： RECOMMENDER systems (Information filtering) computer users computer algorithms REACTION time DATA analysis

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Rational Design of Digital Assays

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ANALYTICAL CHEMISTRY 2015年第16期87卷 8203-8209页

作者： Debski, Pawel R. Gewartowski, Kamil Sulima, Magdalena Kaminski, Tomasz S. Garstecki, Piotr Polish Acad Sci Inst Phys Chem PL-01224 Warsaw Poland Curios Diagnost Sp Zoo PL-01224 Warsaw Poland

Optimum algorithm for digital assays treats chemical compartments as bits of probabilistic information and arranges these bits in a fractional positional system. Maximization of information gain reduces, by orders of magnitude, the number of partitions required to achieve the requested dynamic range and precision of the assay. The method simplifies the execution of digital analytical methods providing for more accessible use of absolute quantization in research and in diagnostics.

关键词： COMPUTATIONAL chemistry MATHEMATICAL optimization PRECISION (Information retrieval) computer algorithms ANALYTICAL chemistry

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Natural variability of aerosol inherent optical properties: consequences for atmospheric correction over water

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INTERNATIONAL JOURNAL OF REMOTE SENSING 2015年第9期36卷 2460-2485页

作者： Santer, Richard Zagolski, Francis Aznay, Ouahid Univ Littoral Cote dOpale MREN F-62930 Wimereux France PARBLEU Technol Inc St Jean PQ J3B 3W7 Canada ZAC Grande Plaine CS Syst Informat F-31506 Toulouse France

A good knowledge of the inherent optical properties (IOPs) of aerosols is a strong requirement for accurately performing atmospheric correction over the ocean. For several decades, IOPs have been computed using standard aerosol models (SAMs) that characterize the micro-physical properties of aerosols. These SAMs were used in the last generation of the Medium Resolution Imaging Spectrometer (MERIS) auxiliary data files (ADFs) to feed the atmospheric correction algorithm. Alternatively, Aerosol Robotic Network (AERONET) measurements can also provide IOPs. We built a database with the aerosol IOPs encountered over four AERONET stations in the North Sea plus one at the Acqua Alta Oceanographic Tower (AAOT, Venice, Italy). Several thousands of data sequences containing the aerosol IOPs were processed with filtering techniques and statistical methods to produce 16 classes of IOPs. An analysis of the dispersion of the IOPs within each class was conducted to evaluate the induced errors in the MERIS level-2 (L2) products in European coastal waters. We also investigated the reduction in the errors that can be achieved if there is access to auxiliary meteorological data (i.e. the relative humidity) or by using the bidirectionality in the satellite measurements, such as for advanced along-track scanning radiometer (AATSR) data.

关键词： ATMOSPHERIC aerosols -- Optical properties ATMOSPHERIC aerosols MATHEMATICAL models SATELLITE meteorology computer algorithms ATMOSPHERE -- Remote sensing

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Multiview Sample Classification Algorithm Based on L1-Graph Domain Adaptation Learning

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MATHEMATICAL PROBLEMS IN ENGINEERING 2015年第1期2015卷 1-8页

作者： Lu, Huibin Hu, Zhengping Gao, Hongxiao Yanshan Univ Sch Informat Sci & Engn Qinhuangdao 066004 Peoples R China

In the case of multiview sample classification with different distribution, training and testing samples are from different domains. In order to improve the classification performance, a multiview sample classification algorithm based on L1-Graph domain adaptation learning is presented. First of all, a framework of nonnegative matrix trifactorization based on domain adaptation learning is formed, in which the unchanged information is regarded as the bridge of knowledge transformation from the source domain to the target domain;the second step is to construct L1-Graph on the basis of sparse representation, so as to search for the nearest neighbor data with self-adaptation and preserve the samples and the geometric structure;lastly, we integrate two complementary objective functions into the unified optimization issue and use the iterative algorithm to cope with it, and then the estimation of the testing sample classification is completed. Comparative experiments are conducted in USPS-Binary digital database, Three-Domain Object Benchmark database, and ALOI database;the experimental results verify the effectiveness of the proposed algorithm, which improves the recognition accuracy and ensures the robustness of algorithm.

关键词： computer algorithms GRAPH theory FUNCTIONS (Mathematics) MATHEMATICAL optimization DATA analysis

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Methods for Fault Diagnosability Analysis of a Class of Affine Nonlinear Systems

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MATHEMATICAL PROBLEMS IN ENGINEERING 2015年第1期2015卷 p1-6页

作者： Peng, Xiafu Lin, Lixiong Zhong, Xunyu Liu, Chengrui Xiamen Univ Dept Automat Xiamen 361005 Peoples R China Sci & Technol Space Intelligent Control Lab Beijing 100190 Peoples R China Beijing Inst Control Engn Beijing 100190 Peoples R China

The fault diagnosability analysis for a given model, before developing a diagnosis algorithm, can be used to answer questions like "can the fault f(i) be detected by observed states?" and "can it separate fault f(i) from fault f(j) by observed states?" If not, we should redesign the sensor placement. This paper deals with the problem of the evaluation of detectability and separability for the diagnosability analysis of affine nonlinear system. First, we used differential geometry theory to analyze the nonlinear system and proposed new detectability criterion and separability criterion. Second, the related matrix between the faults and outputs of the system and the fault separable matrix are designed for quantitative fault diagnosability calculation and fault separability calculation, respectively. Finally, we illustrate our approach to exemplify how to analyze diagnosability by a certain nonlinear system example, and the experiment results indicate the effectiveness of the fault evaluation methods.

关键词： DEBUGGING in computer science SET theory NONLINEAR systems computer algorithms NUMERICAL calculations

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Distributed Formation Control of Quadrotors under Limited Sensor Field of View 16

Distributed Formation Control of Quadrotors under Limited Se...

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International Conference on Autonomous Agents and Multiagent Systems

作者： Duarte Dias Pedro U. Lima Alcherio Martinoli Distributed Intelligent Systems and Algorithms Laboratory EPFL Institute for Systems and Robotics IST Universidade de Lisboa

ISBN: (纸本)9781510855083

This work tackles the problem of quadrotor formation control, using exclusively on-board resources. Local inter-robot localization systems are typically characterized by limited sensing capabilities, either in range or in the field of view. Most of the existing literature on the subject uses inter-robot communication to obtain the unavailable information, but problems such as communication delays and packet loss can seriously compromise the system stability, especially when the system shows fast dynamics such as that of quadrotors. This work focuses on the sensor field of view limitation: it proposes a formation control algorithm that extends the existing methods to allow each quadrotor to control the occupied area of its sensor field of view, while moving to the right place in the formation. This decreases the situations when necessary inter-robot information is unavailable through local sensing, thus reducing the communication requirements. The system is proven to be stable when this algorithm is applied. Results, both using simulated and real quadrotors, show the correct behavior of the algorithm without the use of communications, even when each robot can only sense a subset of the robots in the group.

关键词： algorithms Experimentation Performance Quadrotors Formation Control Limited Field of View field of view algorithms experimentation computer algorithms Robot Communication Research Not Available System stability used area Sensors formation

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Person-following UAVs

Person-following UAVs

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IEEE Conference on Applications of computer Vision

作者： Francisca Vasconcelos Nuno Vasconcelos Torrey Pines High School University of California San Diego

ISBN: (纸本)9781509006427

We consider the design of vision-based control algorithms for unmanned aerial vehicles (UAVs), so as to enable a UAV to autonomously follow a person. A new vision-based control architecture is proposed with the goals of 1) robustly following the user and 2) implementing following behaviors programmed by manipulation of visual patterns. This is achieved within a detection/tracking paradigm, where the target is a programmable badge worn by the user. This badge contains a visual pattern with two components. The first is fixed and used to locate the user. The second is variable and implements a code used to program the UAV behavior. A biologically inspired tracking/recognition architecture, combining bottom-up and top-down saliency mechanisms, a novel image similarity measure, and an affine validation procedure, is proposed to detect the badge in the scene. The badge location is used by a control algorithm to adjust the UAV flight parameters so as to maintain the user in the center of the field of view. The detected badge is further analyzed to extract the visual code that commands the UAV behavior. This is used to control the height and distance of the UAV relative to the user.

关键词： Unmanned Aerial Vehicle drone honey bees computer algorithms Consumers similar measure Control Architecture Codes Visualization flight parameter

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An experimental evaluation of the forward propagating Riccati equation to nonlinear control of the Quanser 3 DOF Hover testbed

An experimental evaluation of the forward propagating Riccat...

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American Control Conference

作者： Anna Prach Erdal Kayacan Dennis S. Bernstein School of Mechanical and Aerospace Engineering Nanyang Technological University 639798 Singapore Department of Aerospace Engineering The University of Michigan Ann Arbor 48109-2140 USA

ISBN: (纸本)9781467386838

This study presents an experimental evaluation of the forward-propagating Riccati equation (FPRE) control. FPRE employs a state-dependent coefficient (SDC) parameterization of the nonlinear dynamics, and the feedback gains are updated in real time. The efficacy of the proposed control algorithm is verified by experimental studies on the Quanser 3 DOF Hover system. The ability of FPRE to follow the desired references is investigated, and its performance is compared with the conventional linear-quadratic regulator. Experimental results show the effectiveness of FPRE for following given references in the considered operating envelope.

关键词： Riccati equations Propellers Nonlinear dynamical systems Aerodynamics DC motors Voltage control Riccati equations PROPELLER DC motors Nonlinear dynamical systems Voltage regulation Aerodynamics nonlinear control feedback gain Hovering DEPTH OF FIELD computer algorithms

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Dynamic operation and control of a hybrid nanogrid system for future community houses

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IET GENERATION TRANSMISSION & DISTRIBUTION 2015年第11期9卷 1168-1178页

作者： Chandrasena, Ruwan P. S. Shahnia, Farhad Rajakaruna, Sumedha Ghosh, Arindam Univ Ruhuna Elect & Informat Engn Dept Galle Sri Lanka Curtin Univ Dept Elect & Comp Engn Perth WA 6845 Australia

A hybrid NanoGrid (NG) can be considered as the power supply system, for future community houses. In this study, the operation and control of an NG are presented. The NG consists of an AC bus and a DC bus, interconnected through a tie-converter (TC). All AC loads and distributed energy resources (DERs) of the community houses are connected to the AC bus while all their DC loads and DERs are connected to the DC bus. The NG has an adequate generation capacity to supply its loads in off-grid status as well as the capability to exchange power with the grid. The TC exchanges the power between two buses and regulates the voltage in both buses, in the case of off-grid operation. The NG dynamics, with the proposed structure and developed primary and secondary control algorithms are validated through extensive computer simulations in PSCAD/EMTDC.

关键词： Power supply systems Energy sources DC bus LOAD PLANT CAPACITY Surgery proposed structure computer algorithms

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Fault-tolerant optimal control of a building HVAC system

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SCIENCE AND TECHNOLOGY FOR THE BUILT ENVIRONMENT 2015年第6期21卷 734-751页

作者： Bengea, Sorin C. Li, Pengfei Sarkar, Soumik Vichik, Sergey Adetola, Veronica Kang, Keunmo Lovett, Teems Leonardi, Francesco Kelman, Anthony D. United Technol Corp Control & Diagnost Syst Pratt & Whitney E Hartford CT 06118 USA United Technol Res Ctr Thermofluid Dynam Grp E Hartford CT 06108 USA Iowa State Univ Dept Mech Engn Ames IA USA Univ Calif Berkeley Dept Mech Engn Berkeley CA 94720 USA United Technol Res Ctr Embedded Syst Grp E Hartford CT 06108 USA

This article presents the development and application of a fault-tolerant control technology, its online implementation, and results from several tests conducted for a large-sized HVAC system. By integrating model-based model predictive control and data-driven fault detection and diagnosis algorithms, the technology automatically adapts the HVAC control laws to a set of subsystem faults and can therefore reach and maintain the largest energy consumption reduction levels that are achievable at any point throughout a building lifecycle. The model predictive control algorithm generates optimal set-points that minimize energy consumption for the HVAC actuator loops while meeting equipment operational constraints and occupant thermal comfort constraints. The fault detection and diagnosis algorithm uses probabilistic graphical models to detect and classify in real time potential faults of the HVAC actuators based on data from multiple sensors. The fault-tolerant control system is realized by executing the two algorithms on the same platform, within the same framework, and by using the fault detection and diagnosis algorithm's output to continuously update the model predictive control algorithm constraints. The proposed integrated technology is executed at the supervisory level in a hierarchical control architecture as an extension of a baseline building management system. The performance and limitations of the fault detection and diagnosis, model predictive control, and fault-tolerant control algorithms are illustrated and discussed using measurement data recorded from multiple tests.

关键词： fault-tolerant control diagnostic model Model predictive control algorithms Defect detection High Voltage Alternating Current Systems heating ventilation and air conditioning Predictive control computer algorithms energy consumption

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