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Lessons from collecting a million biometric samples

IMAGE AND VISION COMPUTING 2017年第Feb.期58卷 96-107页

作者： Phillips, P. Jonathon Flynn, Patrick J. Bowyer, Kevin W. NIST 100 Bur Dr MS 8490 Gaithersburg MD 20899 USA Univ Notre Dame Comp Sci & Engn Notre Dame IN 46556 USA

Over the past decade, independent evaluations have become commonplace in many areas of experimental computer science, including face and gesture recognition. A key attribute of many successful independent evaluations is a curated data set. Desired aspects associated with these data sets include appropriateness to the experimental design, a corpus size large enough to allow statistically rigorous characterization of results, and the availability of comprehensive metadata that allow inferences to be made on various data set attributes. In this paper, we review a ten-year biometric sampling effort that enabled the creation of several key biometrics challenge problems. We summarize the design and execution of data collections, identify key challenges, and convey some lessons learned. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Face recognition algorithm performance Human performance Challenge problem

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Optimizing graph algorithms for improved cache performance

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IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS 2004年第9期15卷 769-782页

作者： Park, JS Penner, M Prasanna, VK Univ Calif Los Angeles Dept Comp Sci Los Angeles CA 90095 USA Univ So Calif Dept Elect Engn Los Angeles CA 90089 USA

In this paper, we develop algorithmic optimizations to improve the cache performance of four fundamental graph algorithms. We present a cache-oblivious implementation of the Floyd-Warshall algorithm for the fundamental graph problem of all-pairs shortest paths by relaxing some dependencies in the iterative version. We show that this implementation achieves the lower bound on processor-memory traffic of Omega(N-3/rootC), where N and C are the problem size and cache size, respectively. Experimental results show that this cache-oblivious implementation shows more than six times the improvement in real execution time over that of the iterative implementation with the usual row major data layout, on three state-of-the-art architectures. Second, we address Dijkstra's algorithm for the single-source shortest paths problem and Prim's algorithm for minimum spanning tree problem. For these algorithms, we demonstrate up to two times the improvement in real execution time by using a simple cache-friendly graph representation, namely adjacency arrays. Finally, we address the matching algorithm for bipartite graphs. We show performance improvements of two to three times in real execution time by using the technique of making the algorithm initially work on subproblems to generate a suboptimal solution and, then, solving the whole problem using the suboptimal solution as a starting point. Experimental results are shown for the Pentium III, UltraSPARC III, Alpha 21264, and MIPS R12000 machines.

关键词： cache-friendly algorithms cache-oblivious algorithms graph algorithms shortest path minimum spanning trees graph matching data layout optimizations algorithm performance

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Rolling-Horizon Electric Vertical Takeoff and Landing Arrival Scheduling for On-Demand Urban Air Mobility

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JOURNAL OF AEROSPACE INFORMATION SYSTEMS 2020年第3期17卷 150-159页

作者： Kleinbekman, Imke C. Mitici, Mihaela Wei, Peng Delft Univ Technol Dept Control & Operat Fac Aerosp Engn Kluyverweg 1 NL-2926 HS Delft Netherlands Iowa State Univ Dept Aerosp Engn 2333 Howe Hall Ames IA 50011 USA

Urban air mobility with electric vertical takeoff and landing (eVTOL) vehicles is envisioned to become a fast and flexible urban transportation mode. Apart from technical challenges for eVTOLs regarding vehicle design and manufacturing, airspace design and traffic control mechanisms are most desired on the operation side. In particular, from an operational point of view, the arrival phase is expected to be the main bottleneck, with restricted vertiport resources, high air traffic density, frequent flight maneuvers, and limited eVTOL remaining battery energy, all leading to complex operational constraints. This work provides a framework to enable optimal and efficient on-demand eVTOLs arrivals in the context of on-demand urban air mobility. This paper investigates the throughput of a double-landing-pad vertiport by proposing a new vertiport terminal area airspace design and a novel rolling-horizon scheduling algorithm with route selection capability to compute the optimal required time of arrival for eVTOLs in a tactical manner. Finally, a case study on arrivals in a hexagonal vertiport network is performed to show the algorithm performance with different configurations. Our simulation results show that up to 50 s delay per eVTOL is expected during the commuter peak hours and less than 10 s delay is expected during off-peak hours.

关键词： Vertical Landing Urban Air Mobility Airspace Flight Maneuvers algorithm performance Estimated Time of Arrival Flight Path Angle Continuous Descent Approach Flight Phases Flight performance

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Two Heuristic algorithms for the Minimum Weighted Connected Vertex Cover Problem Under Greedy Strategy

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IEEE ACCESS 2022年 10卷 116467-116472页

作者： Xie, Qipeng Li, Yuchao Hu, Sengui Zhu, Yue Wang, Hongqiang Changan Univ Sch Sci Xian 710064 Shaanxi Peoples R China

The Minimum Weighted Connected Vertex Cover problem(MWCVC) is to find a subset F subset of V(G) with minimum weight in a node-weighted graph G, such that when removing the set F, the inducing graph of remaining vertices holds no edges, and the graph induced from set F in G is required to be connected. This problem comes from the classical combinatorial problem in graph theory, i.e., the Vertex Cover Problem. A large number of results on algorithms for the MWCVC problem have been reported. In this paper, we proposed two heuristic algorithms, denoted as VCC and LCVCC, to find a connected vertex cover set in a general weighted graph. The time complexity of both two algorithms are less than O(n(4)). We compare these two algorithms with two known heuristic algorithms GR and GD (proposed by Dagdeviren in 2021) on connected graphs, and draw a conclusion that both of VCC and LCVCC perform better than GR or GD. Relatively speaking, LCVCC is expected to have better performance in dense graphs than VCC.

关键词： Minimum weighted connected vertex cover problem heuristic algorithm greedy strategy algorithm performance

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Selecting an appropriate supervised machine learning algorithm for predictive maintenance

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INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY 2022年第7-8期119卷 4277-4301页

作者： Ouadah, Abdelfettah Zemmouchi-Ghomari, Leila Salhi, Nedjma ENST Ecole Natl Super Technol Ind Engn & Maintenance Dept Algiers Algeria

Predictive maintenance refers to predicting malfunctions using data from monitoring equipment and process performance measurements. Machine learning algorithms and techniques are often used to analyze equipment monitoring data. Machine learning is the process in which a computer can work more precisely by collecting and analyzing data. It is often the case that machine learning algorithms use supervised learning, in which labelled data is used to feed the algorithm. However, there are many supervised machine learning algorithms available. Therefore, choosing the best-supervised machine learning algorithm to resolve predictive maintenance issues is not trivial. This paper aims to increase the performance of predictive maintenance and achieve its goals by selecting the most suitable supervised machine learning algorithm. Based on the most commonly used criteria in research articles, we selected three supervised machine learning algorithms from a comparative study: Random forest, Decision tree and KNN. We then tested selected algorithms on data from real-world and simulation scenarios. Finally, we conducted the experiment based on vibration analysis and reliability evaluation. We noticed that Random forests and Decision trees obtained slightly the same performance. KNN is a better classification algorithm for extensive volumes of data;on the contrary, Random forest performs better in the case of small datasets.

关键词： Predictive maintenance Supervised machine learning Regression Classification Vibratory analysis Reliability algorithm selection algorithm performance Prediction Real-world data Simulation data

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Drag-Modulation Flight-Control System Options for Planetary Aerocapture

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JOURNAL OF SPACECRAFT AND ROCKETS 2014年第1期51卷 139-150页

作者： Putnam, Zachary R. Braun, Robert D. Georgia Inst Technol Sch Aerosp Engn Atlanta GA 30332 USA

Drag-modulation flight control may provide a simple method for controlling energy during aerocapture. Several drag-modulation flight-control system options are discussed and evaluated, including single-stage jettison, two-stage jettison, and continuously variable drag-modulation systems. performance is assessed using numeric simulation with real-time guidance and targeting algorithms. Monte Carlo simulation is used to evaluate system robustness to expected day-of-flight uncertainties. Results indicate that drag-modulation flight control is an attractive option for aerocapture systems at Mars, where low peak heat rates enable the use of lightweight inflatable drag areas. Aerocapture using drag modulation at Titan is found to require large drag areas to limit peak heat rates to nonablative thermal-protection system limits or advanced lightweight ablators. The large gravity well and high peak heat rates experienced during aerocapture at Venus make drag-modulation flight control unattractive when combined with a nonablative thermal-protection system. Significantly larger drag areas or advances in fabric-based material thermal properties are required to improve feasibility at Venus.

关键词： Flight Control System Aerobraking Thermal Protection System Monte Carlo Simulation algorithm performance Thermal Properties Periapsis Flight Path Angle Transfer Orbit Ballistic Coefficient

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IMPROVED COORDINATION IN NONHIERARCHIC SYSTEM OPTIMIZATION

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AIAA JOURNAL 1993年第12期31卷 2367-2373页

作者： RENAUD, JE GABRIELE, GA RENSSELAER POLYTECH INST DEPT MECH ENGN AERONATU ENGN & MECHTROYNY 12180

An improved coordination procedure for the optimization of nonhierarchic systems by decomposition into reduced subspaces is presented. A subspace coordination procedure based on sequential global approximation is extended to include second-order information. This second-order global approximation is formed using information obtained during subspace optimizations. The use of second-order information in the coordination procedure results in improved convergence for nonhierarchic system optimization as compared with the authors' earlier studies using a first-order coordination procedure. The same objective function and cumulative constraints are imposed at each subspace. Nonlocal functions are approximated at the subspaces using global sensitivities. The method optimizes subspace problems concurrently, allowing for parallel processing. Following each sequence of concurrent subspace optimizations, a second-order approximation of the global problem is formed using design data accumulated during the subspace optimizations. The solution of the global approximation problem is used as the starting point for subsequent subspace optimizations in an iterative solution procedure.

关键词： Iterative Solution Taylor Series Multidisciplinary Design Optimization algorithm performance Aeronautical Engineering Optimization algorithm Control Optimization Structural Dynamics Manufacturing Cost

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Spacecraft attitude estimation using the global positioning system: Methodology and results for RADCAL

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1996年第6期19卷 1201-1209页

作者： Axelrad, P Ward, LM Colorado Univ. Boulder

Methodology and results for the Global Positioning System based attitude determination of a gravity gradient stabilized satellite are presented. algorithms for on-orbit antenna baseline estimation, attitude initialization, point solution, and Kalman filtering are described. These algorithms are demonstrated using flight data collected on board the U.S. Air Force RADCAL Satellite. The precision of the final: attitude estimates is assessed to be at the level of 0.4 deg for pitch and roll and 0.7 deg for yaw.

关键词： GPS Spacecraft Attitude Earth Satellites Extended Kalman Filter Antenna Arrays Yaw Air Forces Flight Data Quaternions algorithm performance

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EXPERIMENTS IN PROJECTION AND CLUSTERING BY SIMULATED ANNEALING

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PATTERN RECOGNITION 1989年第2期22卷 213-220页

作者： KLEIN, RW DUBES, RC Department of Computer Science Michigan State University East Lansing Michigan 48824 U.S.A

Simulated annealing is a stochastic relaxation algorithm which has been used successfully to optimize functions of many variables. This paper analyzes the simulated annealing algorithm when applied to the minimization of functions from two common problems encountered in exploratory pattern analysis, projection and clustering. The projection is a nonlinear mapping of patterns in high dimension to two dimensions. The simulated annealing mapping is compared to gradient descent minimization of the same objective function as well as eigenvector projection. The simulated annealing clustering is compared to a k-means algorithm. Empirical results show that simulated annealing can produce results as good as those obtained by conventional methods, but are impractical for small data sets because of the high computational cost. Simulated annealing does, in the case of the mapping problem, yield a better optimization and better retained structure for large data sets containing tight gaussian clusters.

关键词： Projection Mapping Clustering Simulated annealing Optimization algorithm performance

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COMPARISON OF NONEQUILIBRIUM SOLUTION algorithmS APPLIED TO CHEMICALLY STIFF HYPERSONIC FLOWS

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AIAA JOURNAL 1995年第7期33卷 1211-1219页

作者： PALMER, G VENKATAPATHY, E ELORET INST PALO ALTOCA 94303

Three solution algorithms, explicit under relaxation, point implicit, and lower-upper symmetric Gauss-Seidel, are used to compute nonequilibrium flow around the Apollo 4 return capsule at the 62-km altitude point in its descent trajectory. By varying the Mach number, the efficiency and robustness of the solution algorithms were tested for different levels of chemical stiffness. The performance of the solution algorithms degraded as the Mach number and stiffness of the flow increased. At Mach 15 and 30, the lower-upper symmetric Gauss-Seidel method produces an eight order of magnitude drop in the energy residual in one-third to one-half the Cray C-90 computer time as compared to the point implicit and explicit under-relaxation methods. The explicit under-relaxation algorithm experienced convergence difficulties at Mach 30 and above. At Mach 40 the performance of the lower-upper symmetric Gauss-Seidel algorithm deteriorates to the point that it is out performed by the point implicit method. The effects of the viscous terms are investigated. Grid dependency questions are explored.

关键词： algorithm performance Nonequilibrium Flows Freestream Mach Number Explicit Methods Courant Friedrichs Lewy Chemical Equilibrium Numerical algorithms Angle of Attack Conservation of Mass Shock Layers

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