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A DECOMPOSITION algorithm FOR OPTIMAL STATIC LOAD BALANCING IN TREE HIERARCHY NETWORK CONFIGURATIONS

IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS 1994年第5期5卷 540-548页

作者： LI, J KAMEDA, H Institute of Information Sciences and Electronics University of Tsukuba Tsukuba Ibaraki Japan

We study the static load balancing problem in a distributed computer system with the tree hierarchy configuration. It is formulated as a nonlinear optimization problem. After studying the conditions that the solution to the optimization problem of the tree hierarchy network satisfies, we demonstrate that the special structure of the optimization problem leads to an interesting decomposition technique. A new effective decomposition algorithm to solve the optimization problem is presented. The proposed algorithm is compared with two other well known algorithms: the Flow Deviation (FD) algorithm and the Dafermos-Sparrow (D-S) algorithm. It is shown that the amounts of the storage required for the proposed algorithm and the FD algorithm are O(n) for load balancing of an n-node system. However, the amount of the storage required for the D-S algorithm is O(n log(n)). By using numerical experiments, we show that both the proposed algorithm and the D-S algorithm have much faster convergence in terms of central processing unit (CPU) time than the FD algorithm.

关键词： algorithm performance COMPUTER NETWORKS DECOMPOSITION algorithm OPTIMAL LOAD BALANCING STAR NETWORK CONFIGURATIONS TREE HIERARCHY NETWORK CONFIGURATIONS

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THE DIAMETER OF THE RUBIK'S CUBE GROUP IS TWENTY

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SIAM JOURNAL ON DISCRETE MATHEMATICS 2013年第2期27卷 1082-1105页

作者： Rokicki, Tomas Kociemba, Herbert Davidson, Morley Dethridge, John Kent State Univ Dept Math Sci Kent OH 44242 USA Google Inc Mountain View CA 94043 USA

We give an expository account of our computational proof that every position of Rubik's Cube can be solved in 20 moves or less, where a move is defined as any twist of any face. The roughly 4.3 x 10(19) positions are partitioned into about two billion cosets of a specially chosen subgroup, and the count of cosets required to be treated is reduced by considering symmetry. The reduced space is searched with a program capable of solving one billion positions per second, using about one billion seconds of CPU time donated by Google. As a byproduct of determining that the diameter is 20, we also find the exact count of cube positions at distance 15.

关键词： group theory algorithm performance Rubik's Cube

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Qualitative Relational Mapping for Mobile Robots with Minimal Sensing

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JOURNAL OF AEROSPACE INFORMATION SYSTEMS 2014年第8期11卷 497-511页

作者： McClelland, Mark Campbell, Mark Estlin, Tara Cornell Univ Dept Mech & Aerosp Engn Ithaca NY 14853 USA Cornell Univ Sibley Sch Mech & Aerosp Engn Dept Mech & Aerosp Engn Ithaca NY 14853 USA CALTECH Jet Prop Lab Pasadena CA 91109 USA

This paper presents a novel method for autonomous robotic navigation and mapping of large-scale spaces with minimal sensing. The proposed algorithm constructs a graph-based map that encodes the relative location of landmarks in the environment. Uncertainty in these locations is captured by imposing qualitative constraints on the relationships between landmarks observed by the robot. These relationships are represented in terms of the relative geometrical layout of landmark triplets. A novel measurement method based on camera imagery is presented that extends previous work from the field of qualitative spatial reasoning. Measurements are fused into the map using a deterministic approach based on iterative graph updates. The generation of these maps does not depend on estimates of robot egomotion, and it is consequently suitable for high-slip environments. algorithm performance is evaluated using MonteCarlo simulations, and results are presented for an experiment using data gathered in the Jet Propulsion Laboratory, California Institute of Technology MarsYard.

关键词： Mobile Robots Monte Carlo Simulation algorithm performance Jet Propulsion Laboratory Scale Space Simultaneous Localization and Mapping Mars Exploration Rover Position Sensors Computer Vision Extended Kalman Filter

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Improvements to Time of Closest Approach Calculation

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JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2016年第9期39卷 1967-1979页

作者： Denenberg, Elad Gurfil, Pini Technion Israel Inst Technol Technion Autonomous Syst & Robot Program IL-3200003 Haifa Israel Technion Israel Inst Technol Fac Aerosp Engn IL-3200003 Haifa Israel

Space debris constitutes a major and growing threat to space missions. To assess the probability of collision, the time of closest approach between the spacecraft and the debris must first be calculated. This paper presents three new methods for the calculation of the time of closest approach. The first is a surrogate-based optimization algorithm, using the Alfano-Negron Close Approach Software as the model, allowing a compromise between calculation speed and accuracy. The second is a generalization of this software, treating a cloud of debris as a continuous object and searching for the time of closest approach over initial conditions as well as time. The third uses Alfano-Negron Close Approach Software generalization as a model for surrogate-based optimization. Using the third method, a strategy for safe operation of a spacecraft cluster in a debris-rich environment is proposed. All methods are demonstrated and compared. It is shown that Alfano-Negron Close Approach Software and the generalization thereof are very fast in estimating the time of closest approach, and that the surrogate-based optimization algorithms are somewhat slower, but are highly accurate.

关键词： Optimization algorithm Space Missions Space Debris Satellite Formation Flying FreeFlyer Fengyun Periapsis Singular Value Decomposition algorithm performance Orbital Elements

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A combined approach for analysing heuristic algorithms

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JOURNAL OF HEURISTICS 2019年第4-5期25卷 591-628页

作者： Corstjens, Jeroen Dang, Nguyen Depaire, Benoit Caris, An De Causmaecker, Patrick UHasselt Res Grp Logist Agoralaan B-3590 Diepenbeek Belgium Katholieke Univ Leuven CODeS Imec ITEC Etienne Sabbelaan 53 7659 B-8500 Kortrijk Belgium

When developing optimisation algorithms, the focus often lies on obtaining an algorithm that is able to outperform other existing algorithms for some performance measure. It is not common practice to question the reasons for possible performance differences observed. These types of questions relate to evaluating the impact of the various heuristic parameters and often remain unanswered. In this paper, the focus is on gaining insight in the behaviour of a heuristic algorithm by investigating how the various elements operating within the algorithm correlate with performance, obtaining indications of which combinations work well and which do not, and how all these effects are influenced by the specific problem instance the algorithm is solving. We consider two approaches for analysing algorithm parameters and components-functional analysis of variance and multilevel regression analysis-and study the benefits of using both approaches jointly. We present the results of a combined methodology that is able to provide more insights than when the two approaches are used separately. The illustrative case studies in this paper analyse a large neighbourhood search algorithm applied to the vehicle routing problem with time windows and an iterated local search algorithm for the unrelated parallel machine scheduling problem with sequence-dependent setup times.

关键词： Functional analysis of variance fANOVA Multilevel regression algorithm performance Vehicle routing problem with time windows Large neighbourhood search Iterated local search Unrelated parallel machine scheduling problem

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An automated algorithm for detection of hydrometeor returns in micropulse lidar data

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JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY 1998年第4期15卷 1035-1042页

作者： Clothiaux, EE Mace, GG Ackerman, TP Kane, TJ Spinhirne, JD Scott, VS Penn State Univ Dept Meteorol University Pk PA 16802 USA Penn State Univ Dept Elect Engn University Pk PA 16802 USA NASA Goddard Space Flight Ctr Greenbelt MD 20771 USA

A cloud detection algorithm for a low power micropulse lidar is presented that attempts to identify all of the significant power returns from the vertical column above the lidar at all times, The main feature of the algorithm is construction of lidar power return profiles during periods of clear sky against which cloudy-sky power returns are compared. This algorithm supplements algorithms designed to detect cloud-base height in that the tops of optically thin clouds are identified and it provides an alternative approach to algorithms that identify significant power returns by analysis of changes in the slope of the backscattered powers with height. The cloud-base heights produced by the current algorithm during nonprecipitating periods are comparable with the results of a cloud-base height algorithm applied to the same data. Although an objective validation of algorithm performance on high, thin cirrus is lacking because of no truth data, the current algorithm produces few false positive and false negative classifications as determined through manual comparison of the original photoelectron count data to the final cloud mask image.

关键词： .cloud detection Micropulse lidar positive original Backscattered false algorithm performance low power power returns cloud-base heights current algorithm distribution of clouds

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Image distance metric learning based on neighborhood sets for automatic image annotation

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JOURNAL OF VISUAL COMMUNICATION AND IMAGE REPRESENTATION 2016年 34卷 167-175页

作者： Jin, Cong Jin, Shu-Wei Cent China Normal Univ Sch Comp Wuhan 430079 Peoples R China Ecole Normale Super Dept Phys 24 Rue Lhomond F-75231 Paris 5 France

Since there is semantic gap between low-level visual features and high-level image semantic, the performance of many existing content-based image annotation algorithms is not satisfactory. In order to bridge the gap and improve the image annotation performance, a novel automatic image annotation (AIA) approach using neighborhood set (NS) based on image distance metric learning (IDML) algorithm is proposed in this paper. According to IDML, we can easily obtain the neighborhood set of each image since obtained image distance can effectively measure the distance between images for AIA task. By introducing NS, the proposed AIA approach can predict all possible labels of the image without caption. The experimental results confirm that the introduction of NS based on IDML can improve the efficiency of AIA approaches and achieve better annotation performance than the existing AIA approaches. (C) 2015 Elsevier Inc. All rights reserved.

关键词： Automatic image annotation Improve performance Image distance metric learning Neighborhood sets algorithm performance Visual similarity Semantic similarity Probability density ratio

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Workspace Modeling and Path Planning for Truss Structure Inspection by Unmanned Aircraft

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JOURNAL OF AEROSPACE INFORMATION SYSTEMS 2019年第1期16卷 37-51页

作者： Das, Arun Woolsey, Craig A. Tech Univ Munich Elect Engn D-80333 Munich Germany Virginia Polytech Inst & State Univ Crofton Dept Aerosp & Ocean Engn Blacksburg VA 24061 USA

Small unmanned aircraft systems can increase efficiency and reduce risk to humans during the inspection of truss-supported structures such as steel bridges. This paper describes a method to mathematically represent a truss and subsequently to plan an efficient collision-free inspection path. The algorithm checks user-defined perspectives for feasibility and redefines any infeasible perspectives. A deterministic roadmap is then generated as the complete graph over these perspectives, and some additional nodes are generated near the joints of the structure. A traveling salesman problem (TSP) is solved to find an efficient inspection path that tours all perspective points, and a local A* path planner then refines the inspection path to circumvent obstructions. The TSP is re-solved, with an updated cost based on local detours;and the process iterates until a feasible TSP solution is found. The "lazy" approach to global and local planning, for which paths are checked for feasibility after the fact and amended if necessary, ensures quick convergence to an efficient inspection path. Simulation results show the functionality of the algorithm. Comparison with a probabilistic roadmap method indicates the proposed algorithm's efficiency.

关键词： Trusses Path Planning Unmanned Aircraft Small Unmanned Aircraft System Cantilever Beam algorithm performance Particle Swarm Optimization Flight Control System Multirotor Robots

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Engineering design optimization using interior-point algorithms

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AIAA JOURNAL 2000年第11期38卷 2127-2132页

作者： Rao, SS Mulkay, EL Univ Miami Dept Mech Engn Coral Gables FL 33124 USA Exxon Prod Res Co Houston TX 77252 USA

The interior-point methods have emerged as highly efficient procedures for solving linear programming problems in recent years. The interior point methods have superior theoretical properties as well as observed computational advantages over simplex methods at solving large linear programming problems and are found to be immune to degeneracy. It is a common observation in literature that most nonlinear programming methods that work well for small and medium sized problems are not able to solve large-scale problems efficiently. It is to be expected that interior-point methods, when used in an adaptive sequential linear programming strategy, might prove to be a powerful engineering optimization tool. The development of an adaptive sequential linear programming algorithm, based on an infeasible primal-dual path-following interior-point algorithm and fuzzy heuristics, is considered in this work for the solution of large-scale engineering design optimization problems. Several numerical examples are considered to demonstrate the effectiveness and efficiency of the present method. The examples include a part stamping problem, a turbine rotor design problem, and an optimal control problem related to tidal power generation. The number of design variables and constraints range from 12 to 402 and 20 to 20,300, respectively, for the part stamping problem. The turbine rotor problem involves 905 variables and 1081 constraints, and the optimal control problem has 2002 variables and 1001 constraints. The numerical results clearly demonstrate the superiority of the interior-point methods compared with the well-known simplex-based linear solver in solving large-scale optimum design problems. The superior performance of the present method is shown in terms of both computational time and the ability to handle degenerate problems.

关键词： Sequential Linear Programming Optimal Control Nonlinear Programming Linear Programming Power Generation Circumferential Stress Cholesky Factorization Poisson's Ratio algorithm performance Thermal Expansion

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Analysis of Simulated Imagery for Real-Time Vision-Based Automated Aerial Refueling

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JOURNAL OF AEROSPACE INFORMATION SYSTEMS 2019年第3期16卷 77-93页

作者： Parsons, Christopher Paulson, Zachary Nykl, Scott Dallman, William Woolley, Brian G. Pecarina, John US Air Force Inst Technol AFIT ENG 2950 Hobson Way Wright Patterson AFB OH 45433 USA US Air Force Inst Technol AFIT ENG Comp Sci 2950 Hobson Way Wright Patterson AFB OH 45433 USA Def Informat Syst Agcy Operat Directorate Ft George G Meade MD 20755 USA US Air Force Space Command AFSPC A5 Colorado Springs CO 80916 USA

This Paper presents a three-dimensional graphical simulation (virtual world) that replicates a complete aerial refueling scenario including the tanker, the tanker's stereo vision system, and an approaching receiver aircraft. This virtual world generates real-time imagery of a geometrically accurate receiver flying a physically realistic aerial refueling approach. The approach is recorded from the perspective of the tanker's virtual stereo cameras. The stereo imagery is processed via a novel stereo vision pipeline that dynamically computes the position and orientation (pose) of the receiver relative to the tanker in near real time. Additionally, to increase the visual fidelity, emphasis is given to quantifying the negative aliasing effects caused by the rasterization of the virtual world. An antialiasing solution that mitigates these artifacts and allows simulated imagery to better approximate physically captured imagery is proposed. Results show antialiased imagery reduces epipolar error by a factor of 4. This reduction more than doubles the accuracy of our stereo vision algorithm at the refueling contact point. As simulated imagery is increasingly used to test and develop aeronautical vision pipelines, this aliasing must be mitigated to minimize artifacts intrinsic to rasterized synthetic imagery that negatively affect vision processing algorithms.

关键词： Automated Aerial Refueling Corner Detection algorithm performance Extended Kalman Filter Image Resolution Flight Testing IMU Yaw Fuselages LIDAR Sensor

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