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1

The Shortest Path Problem Under Partial Monitoring  

Microsoft Academic Search

Abstract. The on-line shortest path problem is considered under partial monitoring scenarios. At each round, a decision maker has to choose a path between two distinguished vertices of a weighted directed acyclic graph whose edge weights can change in an arbitrary (adversarial) way such that the loss of the chosen path (dened as the sum of the weights of its

András György; Tamás Linder; György Ottucsák

2006-01-01

2

The on-line shortest path problem under partial monitoring  

Microsoft Academic Search

The on-line shortest path problem is considered under various models of partial monitoring. Given a weighted directed acyclic graph whose edge weights can change in an arbitrary (adversarial) way, a decision maker has to choose in each round of a game a path between two distinguished vertices such that the loss of the chosen path (defined as the sum of

Andras Gyorgy; Tamas Linder; Gabor Lugosi; Gyorgy Ottucsak

2007-01-01

3

An Improved Physarum polycephalum Algorithm for the Shortest Path Problem  

PubMed Central

Shortest path is among classical problems of computer science. The problems are solved by hundreds of algorithms, silicon computing architectures and novel substrate, unconventional, computing devices. Acellular slime mould P. polycephalum is originally famous as a computing biological substrate due to its alleged ability to approximate shortest path from its inoculation site to a source of nutrients. Several algorithms were designed based on properties of the slime mould. Many of the Physarum-inspired algorithms suffer from a low converge speed. To accelerate the search of a solution and reduce a number of iterations we combined an original model of Physarum-inspired path solver with a new a parameter, called energy. We undertook a series of computational experiments on approximating shortest paths in networks with different topologies, and number of nodes varying from 15 to 2000. We found that the improved Physarum algorithm matches well with existing Physarum-inspired approaches yet outperforms them in number of iterations executed and a total running time. We also compare our algorithm with other existing algorithms, including the ant colony optimization algorithm and Dijkstra algorithm. PMID:24982960

Wang, Qing; Adamatzky, Andrew; Chan, Felix T. S.; Mahadevan, Sankaran

2014-01-01

4

E cient Algorithms for the Minimum Shortest Path Steiner Arborescence Problem with Applications to VLSI Physical Design  

E-print Network

E cient Algorithms for the Minimum Shortest Path Steiner Arborescence Problem with Applications is a shortest path in G. Given a triple G;N;r, the MinimumShortest-Path Steiner Arborescence MSPSA problem seeks is a shortest path in G. Given a triple G;N;r, the MinimumShortest-Path Steiner Arborescence MSPSA problem seeks

Kahng, Andrew B.

5

A Heuristic Genetic Algorithm for the Single Source Shortest Path Problem  

Microsoft Academic Search

This paper addresses one of the potential graph-based problems that arises when an optimal shortest path solution, or near optimal solution is acceptable, namely the Single Source Shortest Path (SSP) problem. To this end, a novel Heuristic Genetic Algorithm (HGA) to solve the SSSP problem is developed and evaluated. The proposed algorithm employs knowledge from deterministic techniques and the genetic

Basela S. Hasan; Mohammad A. Khamees; Ashraf S. Hasan Mahmoud

2007-01-01

6

The role of convexity for solving some shortest path problems in plane without triangulation  

NASA Astrophysics Data System (ADS)

Solving shortest path problems inside simple polygons is a very classical problem in motion planning. To date, it has usually relied on triangulation of the polygons. The question: "Can one devise a simple O(n) time algorithm for computing the shortest path between two points in a simple polygon (with n vertices), without resorting to a (complicated) linear-time triangulation algorithm?" raised by J. S. B. Mitchell in Handbook of Computational Geometry (J. Sack and J. Urrutia, eds., Elsevier Science B.V., 2000), is still open. The aim of this paper is to show that convexity contributes to the design of efficient algorithms for solving some versions of shortest path problems (namely, computing the convex hull of a finite set of points and convex rope on rays in 2D, computing approximate shortest path between two points inside a simple polygon) without triangulation on the entire polygons. New algorithms are implemented in C and numerical examples are presented.

An, Phan Thanh; Hai, Nguyen Ngoc; Hoai, Tran Van

2013-09-01

7

Greedy partitioned algorithms for the shortest-path problem  

SciTech Connect

A partitioned, priority-queue algorithm for solving the single-source best-path problem is defined and evaluated. Finding single-source paths for sparse graphs is notable because of its definite lack of parallelism-no known algorithm are scalable. Qualitatively, they discuss the close relationship between the algorithm and previous work by Quinn, Chikayama, and others. Performance measurements of variations of the algorithm, implemented both in concurrent and imperative programming languages on a shared-memory multiprocessor, are presented. This quantitative analysis of the algorithms provides insights into the tradeoffs between complexity and overhead in graph-searching executed in high-level parallel languages with automatic task scheduling.

Adamson, P.; Tick, E. (Univ. of Oregon (United States))

1991-08-01

8

A bio-inspired method for the constrained shortest path problem.  

PubMed

The constrained shortest path (CSP) problem has been widely used in transportation optimization, crew scheduling, network routing and so on. It is an open issue since it is a NP-hard problem. In this paper, we propose an innovative method which is based on the internal mechanism of the adaptive amoeba algorithm. The proposed method is divided into two parts. In the first part, we employ the original amoeba algorithm to solve the shortest path problem in directed networks. In the second part, we combine the Physarum algorithm with a bio-inspired rule to deal with the CSP. Finally, by comparing the results with other method using an examples in DCLC problem, we demonstrate the accuracy of the proposed method. PMID:24959603

Wang, Hongping; Lu, Xi; Zhang, Xiaoge; Wang, Qing; Deng, Yong

2014-01-01

9

A Bio-Inspired Method for the Constrained Shortest Path Problem  

PubMed Central

The constrained shortest path (CSP) problem has been widely used in transportation optimization, crew scheduling, network routing and so on. It is an open issue since it is a NP-hard problem. In this paper, we propose an innovative method which is based on the internal mechanism of the adaptive amoeba algorithm. The proposed method is divided into two parts. In the first part, we employ the original amoeba algorithm to solve the shortest path problem in directed networks. In the second part, we combine the Physarum algorithm with a bio-inspired rule to deal with the CSP. Finally, by comparing the results with other method using an examples in DCLC problem, we demonstrate the accuracy of the proposed method. PMID:24959603

Wang, Hongping; Lu, Xi; Wang, Qing

2014-01-01

10

The d-edge shortest-path problem for a Monge graph  

SciTech Connect

A complete edge-weighted directed graph on vertices 1,2,...,n that assigns cost c(i,j) to the edge (i,j) is called Monge if its edge costs form a Monge array, i.e., for all i < k and j < l, c[i, j]+c[k,l]{le} < c[i,l]+c[k,j]. One reason Monge graphs are interesting is that shortest paths can be computed quite quickly in such graphs. In particular, Wilber showed that the shortest path from vertex 1 to vertex n of a Monge graph can be computed in O(n) time, and Aggarwal, Klawe, Moran, Shor, and Wilber showed that the shortest d-edge 1-to-n path (i.e., the shortest path among all 1-to-n paths with exactly d edges) can be computed in O(dn) time. This paper`s contribution is a new algorithm for the latter problem. Assuming 0 {le} c[i,j] {le} U and c[i,j + 1] + c[i + 1,j] {minus} c[i,j] {minus} c[i + 1, j + 1] {ge} L > 0 for all i and j, our algorithm runs in O(n(1 + 1g(U/L))) time. Thus, when d {much_gt} 1 + 1g(U/L), our algorithm represents a significant improvement over Aggarwal et al.`s O(dn)-time algorithm. We also present several applications of our algorithm; they include length-limited Huffman coding, finding the maximum-perimeter d-gon inscribed in a given convex n-gon, and a digital-signal-compression problem.

Bein, W.W. [New Mexico Univ., Albuquerque, NM (United States). Dept. of Computer Science; Larmore, L.L. [California Univ., Riverside, CA (United States). Dept. of Computer Science; Park, J.K. [Sandia National Labs.,Albuquerque, NM (United States)

1992-07-14

11

Shortest Paths for Disc Obstacles  

Microsoft Academic Search

\\u000a Given a number of obstacles in a plane, the problem of computing a geodesic (or the shortest path) between two points has\\u000a been studied extensively. However, the case where the obstacles are circular discs has not been explored as much as it deserves.\\u000a In this paper, we present an algorithm to compute a geodesic among a set of mutually disjoint

Deok-soo Kim; Kwangseok Yu; Youngsong Cho; Donguk Kim; Chee-keng Yap

2004-01-01

12

Shortest distance problems in graphs using history-dependent transition costs with application to kinodynamic path planning  

Microsoft Academic Search

A new algorithm is presented to compute the shortest path on a graph when the node transition costs depend on the prior history of the path to the current node. The algorithm is applied to solve path planning problems with curvature constraints.

Raghvendra V. Cowlagi; Panagiotis Tsiotras

2009-01-01

13

A minimum resource neural network framework for solving multiconstraint shortest path problems.  

PubMed

Characterized by using minimum hard (structural) and soft (computational) resources, a novel parameter-free minimal resource neural network (MRNN) framework is proposed for solving a wide range of single-source shortest path (SP) problems for various graph types. The problems are the k-shortest time path problems with any combination of three constraints: time, hop, and label constraints, and the graphs can be directed, undirected, or bidirected with symmetric and/or asymmetric traversal time, which can be real and time dependent. Isomorphic to the graph where the SP is to be sought, the network is activated by generating autowave at source neuron and the autowave travels automatically along the paths with the speed of a hop in an iteration. Properties of the network are studied, algorithms are presented, and computation complexity is analyzed. The framework guarantees globally optimal solutions of a series of problems during the iteration process of the network, which provides insight into why even the SP is still too long to be satisfied. The network facilitates very large scale integrated circuit implementation and adapt to very large scale problems due to its massively parallel processing and minimum resource utilization. When implemented in a sequentially processing computer, experiments on synthetic graphs, road maps of cities of the USA, and vehicle routing with time windows indicate that the MRNN is especially efficient for large scale sparse graphs and even dense graphs with some constraints, e.g., the CPU time taken and the iteration number used for the road maps of cities of the USA is even less than  ? 2% and 0.5% that of the Dijkstra's algorithm. PMID:25050952

Zhang, Junying; Zhao, Xiaoxue; He, Xiaotao

2014-08-01

14

On shortest paths and sorting  

Microsoft Academic Search

In finding shortest paths, the operation of finding, successively, a minimum from a list of numbers may require more work than the remainder of the algorithm. It is shown how algorithms from sorting literature can be used to accomplish this part of the shortest path algorithm. Bounds on the largest possible amount of work are established, and results of a

Ellis L. Johnson

1972-01-01

15

Efficient algorithms for the minimum shortest path Steiner arborescence problem with applications to VLSI physical design  

Microsoft Academic Search

Given an undirected graph G = (V; E) with positive edge weights (lengths) w : E ! <,, a set of termi-nals (sinks) N V, and a unique root node r 2 N, a shortest-path Steiner arborescence (simply called an arborescence in the following) is a Steiner tree rooted at r spanning all terminals in N such that every source-to-sink

Jason Cong; Andrew B. Kahng; Kwok-shing Leung

1998-01-01

16

Shortest paths algorithms: theory and experimental evaluation  

Microsoft Academic Search

We conduct an extensive computational study of shortest paths algorithms, including some very recent algorithms. We also suggest new algorithms motivated by the experimental results and prove interesting theoretical results suggested by the experimental data. Our computational study is based on several natural problem classes which identify strengths and weaknesses of various algorithms. These problem classes and algorithm implementations form

Boris V. Cherkassky; Andrew V. Goldberg; Tomasz Radzikt

1994-01-01

17

Gauss Meets Canadian Traveler: Shortest-Path Problems with Correlated Natural Dynamics  

E-print Network

experiments in the aircraft navigation sce- nario with real wind data demonstrate that our framework can Planning; Canadian Traveler Problem; Gaussian Process; Aircraft Routing ABSTRACT In a variety of real world problems from robot navigation to logistics, agents face the challenge of path optimization on a graph

Horvitz, Eric

18

Layered Shortest Path (LASH) Routing in Irregular System Area Networks  

Microsoft Academic Search

In recent years we have seen a growing interest in ir- regular network topologies for cluster interconnects. One problem related to such topologies is that the combination of shortest path and deadlock free routing is difficult. As a result of this the existing solutions for routing in irreg- ular networks either guarantee shortest paths relative to some constraint (like up*\\/down*),

Tor Skeie; Olav Lysne; Ingebjørg Theiss

2002-01-01

19

Shortest Paths in Microseconds Rachit Agarwal  

E-print Network

to compute and store a partial shortest path tree (PSPT) for each node. The PSPTs have the property to be an extremely small frac- tion of the entire network; hence, PSPTs can be stored efficiently and each shortest path can be computed ex- tremely quickly. For a real network with 5 million nodes and 69 mil- lion

20

The Shortest-Network Problem  

Microsoft Academic Search

The Steiner problem asks for the shortest network of line segments that will interconnect a set of given points. The Steiner problem cannot be solved by simply drawing lines between the given points, but it can be solved by adding new ones, called Steiner points, that serve as junctions in a shortest network. To determine the location and number of

Marshall W. Bern; Ronald L. Graham

1989-01-01

21

Shortest Paths Help Solve Geometric Optimization Problems in Planar Regions \\Lambda  

E-print Network

problem and maximum area contained triangle problem have applications to robotics and stock­cutting. The results of this paper will appear also in [33]. Key Words and Phrases: robotics, stock­cutting

Souvaine, Diane

22

Efficient Algorithms for the Minimum Shortest Path Steiner Arborescence Problem with Applications to VLSI Physical Design  

E-print Network

]. The rectilinear version of the MSPSA problem is called the Minimum Rectilinear Steiner Arborescence (MRSA) problem(N) ) be the induced Hanan grid graph [10] of N . It can be shown that an MSPSA of (G H(N) ; N; r) is an MRSA of N . Exact methods for the MRSA problem can be classified into (1) dynamic programming, (2) integer

Kahng, Andrew B.

23

Highway Hierarchies Hasten Exact Shortest Path Queries  

Microsoft Academic Search

\\u000a We present a new speedup technique for route planning that exploits the hierarchy inherent in real world road networks. Our\\u000a algorithm preprocesses the eight digit number of nodes needed for maps of the USA or Western Europe in a few hours using linear\\u000a space. Shortest (i.e. fastest) path queries then take around eight milliseconds to produce exact shortest paths. This

Peter Sanders; Dominik Schultes

2005-01-01

24

Distributional properties of stochastic shortest paths for smuggled nuclear material  

SciTech Connect

The shortest path problem on a network with fixed weights is a well studied problem with applications to many diverse areas such as transportation and telecommunications. We are particularly interested in the scenario where a nuclear material smuggler tries to succesfully reach herlhis target by identifying the most likely path to the target. The identification of the path relies on reliabilities (weights) associated with each link and node in a multi-modal transportation network. In order to account for the adversary's uncertainty and to perform sensitivity analysis we introduce random reliabilities. We perform some controlled experiments on the grid and present the distributional properties of the resulting stochastic shortest paths.

Cuellar, Leticia [Los Alamos National Laboratory; Pan, Feng [Los Alamos National Laboratory; Roach, Fred [Los Alamos National Laboratory; Saeger, Kevin J [Los Alamos National Laboratory

2011-01-05

25

On the Shortest Path Game  

E-print Network

Sep 19, 2014 ... tree, whose child nodes are all leaves, the associated player can reach a decision by simply ... moved to its parent node. In this way, we can ... towards t, since the cost of the path from s to v does not influence the decision in v.

2014-09-19

26

On the Representability of Arbitrary Path Sets as Shortest Paths: Theory, Algorithms, and Complexity  

Microsoft Academic Search

\\u000a The question, whether an optional set of routes can be represented as shortest paths, and if yes, then how, has been a rather\\u000a scarcely investigated problem up until now. In turn, an algorithm that, given an arbitrary set of traffic engineered paths,\\u000a can efficiently compute OSPF link weights as to map the given paths to shortest paths may be of

Gábor Rétvári; Róbert Szabó; József Bíró

2004-01-01

27

The shortest-network problem  

SciTech Connect

The Steiner problem asks for the shortest network of line segments that will interconnect a set of given points. The Steiner problem cannot be solved by simply drawing lines between the given points, but it can be solved by adding new ones, called Steiner points, that serve as junctions in a shortest network. To determine the location and number of Steiner points, mathematicians and computer scientists have developed algorithms, or precise procedures. Yet even the best of these algorithms running on the fastest computers cannot provide a solution for a large set of given points because the time it would take to solve such a problem is impractically long. Furthermore, the Steiner problem belongs to a class of problem for which many computer scientists now believe an efficient algorithm may never be found. Approximate solutions to the shortest-network problem are computed routinely for numerous applications, among them designing integrated circuits, determining the evolutionary tree of a group of organisms and minimizing materials used for networks of telephone lines, pipelines and roadways.

Bern, M.W.; Graham, R.L.

1989-01-01

28

VAN: Vehicle-assisted shortest-time path navigation  

Microsoft Academic Search

Traffic congestion is a very serious problem in large cities. With the number of vehicles increasing rapidly, especially in cities whose economy is booming, the situation is getting even worse. In this paper, by leveraging the techniques of Vehicular Ad hoc Networks (VANETs) we present a dynamic navigation protocol called VAN for individual vehicles to find the shortest-time paths toward

Wenping Chen; Sencun Zhu; Deying Li

2010-01-01

29

Efficient Algorithms for Shortest Paths in Sparse Networks  

Microsoft Academic Search

Algorithms for finding shortest paths are presented which are faster than algorithms previously known on networks which are relatively sparse in arcs. Known results which the results of this paper extend are surveyed briefly and analyzed. A new implementation for priority queues is employed, and a class of “arc set partition” algorithms is introduced. For the single source problem on

Donald B. Johnson

1977-01-01

30

Shortest Paths, Soap Films, and Minimal Surfaces  

NSDL National Science Digital Library

You know you're in for a real treat when a lecture starts off with "I just happen to have with me today this bucket filled with soap solution, water, and some glycerin." That happens to be the opening line from a talk given by Professor Michael Dorff at the Mathematical Association of America (MAA). Dorff's talk was quite hands-on and it included a number of skeletal Zometool creations and deconstructed Slinkies, among other items. The title of the talk was "Shortest Paths, Soap Films, and Minimal Surfaces" and it is available here in its entirety. In the lecture, Dorff talks (and demonstrates) the shortest distance between four points, neighborhood accessibility, and a number of fascinating topics.

Dorff, Michael

2012-10-10

31

Shortest paths synthesis for a car-like robot  

Microsoft Academic Search

This paper deals with the complete characterization of the shortest paths for a car-like robot. Previous works have shown that the search for a shortest path may be limited to a simple family of trajectories. Our work completes this study by providing a way to select inside this family an optimal path to link any two configurations. We combine the

P. Soueres; J.-P. Laumond

1996-01-01

32

Fractal Structure of Shortest Interaction Paths in Native Proteins and Determination of Residues on a Given Shortest Path  

E-print Network

Fractal structure of shortest paths depends strongly on interresidue interaction cutoff distance. Taking the cutoff distance as variable, the paths are self similar above 6.8 {\\AA} with a fractal dimension of 1.12, remarkably close to Euclidean dimension. Below 6.8 {\\AA}, paths are multifractal. The number of steps to traverse a shortest path is a discontinuous function of cutoff size at short wavelengths. An algorithm is introduced to determine the residues on a given shortest path. Shannon entropy of information transport between two residues along a shortest path is lower than the entropies along longer paths between the same two points leading to the conclusion that communication over shortest paths results in highest lossless encoding.

Erman, Burak

2014-01-01

33

The Routing Continuum from Shortest-path to All-path: A Unifying Theory  

E-print Network

The Routing Continuum from Shortest-path to All-path: A Unifying Theory Yanhua Li, Zhi-Li Zhang of data and sensor networks, routing strategies such as shortest-path, multi-path and potential-based ("all-path") routing have been developed. Based on the connection between routing and flow optimization

Boley, Daniel

34

Corridor location: the multi-gateway shortest path model  

NASA Astrophysics Data System (ADS)

The problem of corridor location can be found in a number of fields including power transmission, highways, and pipelines. It involves the placement of a corridor or rights-of-way that traverses a landscape starting at an origin and ending at a destination. Since most systems are subject to environmental review, it is important to generate competitive, but different alternatives. This paper addresses the problem of generating efficient, spatially different alternatives to the corridor location problem. We discuss the weaknesses in current models and propose a new approach which is designed to overcome many of these problems. We present an application of this model to a real landscape and compare the results to past work. Overall, the new model called the multi-gateway shortest path problem can generate a wide variety of efficient alignments, which eclipse what could be generated by past work.

Scaparra, Maria P.; Church, Richard L.; Medrano, F. Antonio

2014-07-01

35

ON THE ACCELERATION OF SHORTEST PATH CALCULATIONS IN TRANSPORTATION NETWORKS  

SciTech Connect

Shortest path algorithms are a key element of many graph problems. They are used in such applications as online direction finding and navigation, as well as modeling of traffic for large scale simulations of major metropolitan areas. As the shortest path algorithms are an execution bottleneck, it is beneficial to move their execution to parallel hardware such as Field-Programmable Gate Arrays (FPGAs). Hardware implementation is accomplished through the use of a small A core replicated on the order of 20 times on an FPGA device. The objective is to maximize the use of on-board random-access memory bandwidth through the use of multi-threaded latency tolerance. Each shortest path core is responsible for one shortest path calculation, and when it is finished it outputs its result and requests the next source from a queue. One of the innovations of this approach is the use of a small bubble sort core to produce the extract-min function. While bubble sort is not usually considered an appropriate algorithm for any non-trivial usage, it is appropriate in this case as it can produce a single minimum out of the list in O(n) cycles, whwere n is the number of elements in the vertext list. The cost of this min operation does not impact the running time of the architecture, because the queue depth for fetching the next set of edges from memory is roughly equivalent to the number of cores in the system. Additionally, this work provides a collection of simulation results that model the behavior of the node queue in hardware. The results show that a hardware queue, implementing a small bubble-type minimum function, need only be on the order of 16 elements to provide both correct and optimal paths. Because the graph database size is measured in the hundreds of megabytes, the Cray SRAM memory is insufficient. In addition to the A* cores, they have developed a memory management system allowing round-robin servicing of the nodes as well as virtual memory managed over the Hypertransport bus. With support for a DRAM graph store with SRAM-based caching on the FPGA, the system provides a speedup of roughly 8.9x over the CPU-based implementation.

BAKER, ZACHARY K. [Los Alamos National Laboratory; GOKHALE, MAYA B. [Los Alamos National Laboratory

2007-01-08

36

Incremental Network Design with Shortest Paths  

E-print Network

We introduce a class of incremental network design problems focused on inves- tigating the ...... The Annals of Regional Science, 42:621–642,. 2008. ... ceedings of the fifth annual ACM-SIAM symposium on Discrete algorithms, SODA '94,.

2013-01-11

37

Modeling wildfire propagation with Delaunay triangulation and shortest path algorithms  

E-print Network

Modeling wildfire propagation with Delaunay triangulation and shortest path algorithms Alexander In this paper, a methodology for modeling surface wildfire propagation through a complex landscape is presented, wildfire modeling 1 Introduction During the years 2000-2004, the National Interagency Fire Center (NIFC

Smith, J. MacGregor

38

Research of SoPC-based improved genetic algorithm on shortest path  

NASA Astrophysics Data System (ADS)

The shortest path problem is a classic problem and is unlikely to find an efficient algorithm for solving it directly. It is applied broadly in practice. Thus rapid and effective solving shortest path problem is very important application value in practice. Genetic Algorithm (GA) is a kind of heuristic global optimization search algorithm that simulates the biology evolutionary system. It is resolved efficiently by this improvement Genetic Algorithm. In this paper, a SoPC-based GA framework is proposed .The experiment results show that improved Genetic Algorithm enhances extremely in the same environment.

Ruan, Hang; Ren, Aifeng; Meng, Ming; Zhao, Wei; Luo, Ming

2011-10-01

39

Min-Link Shortest Path Maps and Frchet Distance Atlas F. Cook IV  

E-print Network

, so we use our shortest path map structure to represent a free space cell. 1. INTRODUCTIONMin-Link Shortest Path Maps and Fréchet Distance Atlas F. Cook IV Carola Wenk Abstract We present shortest path maps that support min-link queries from any source point on a line segment to destination

Texas at San Antonio, University of

40

A Graph Search Heuristic for Shortest Distance Paths  

SciTech Connect

This paper presents a heuristic for guiding A* search for finding the shortest distance path between two vertices in a connected, undirected, and explicitly stored graph. The heuristic requires a small amount of data to be stored at each vertex. The heuristic has application to quickly detecting relationships between two vertices in a large information or knowledge network. We compare the performance of this heuristic with breadth-first search on graphs with various topological properties. The results show that one or more orders of magnitude improvement in the number of vertices expanded is possible for large graphs, including Poisson random graphs.

Chow, E

2005-03-24

41

Snell's law and light traveling along the shortest path  

Microsoft Academic Search

the problem to be analyzed follows: Given a starting point s, an ending point t and a set of n Weighted Faces (or regions) in a 2-dimensional space, find the best path from s to t, where the length of the path is defined as the weighted sum of the Euclidean length of the sub paths inside each region. Let

Carlos Lara

2006-01-01

42

Damage detection via shortest-path network sampling  

NASA Astrophysics Data System (ADS)

Large networked systems are constantly exposed to local damages and failures that can alter their functionality. The knowledge of the structure of these systems is, however, often derived through sampling strategies whose effectiveness at damage detection has not been thoroughly investigated so far. Here, we study the performance of shortest-path sampling for damage detection in large-scale networks. We define appropriate metrics to characterize the sampling process before and after the damage, providing statistical estimates for the status of nodes (damaged, not damaged). The proposed methodology is flexible and allows tuning the trade-off between the accuracy of the damage detection and the number of probes used to sample the network. We test and measure the efficiency of our approach considering both synthetic and real networks data. Remarkably, in all of the systems studied, the number of correctly identified damaged nodes exceeds the number of false positives, allowing us to uncover the damage precisely.

Ciulla, Fabio; Perra, Nicola; Baronchelli, Andrea; Vespignani, Alessandro

2014-05-01

43

Arrival Time Dependent Shortest Path by On-Road Routing in Mobile Ad-Hoc Network  

Microsoft Academic Search

\\u000a Arrival time dependent shortest path finding is an important function in the field of traffic information systems or telematics.\\u000a However large number of mobile objects on the road network results in a scalability problem for frequently updating and handling\\u000a their real-time location. In this paper, we propose a query processing method in MANET(Mobile Ad-hoc Network) environment\\u000a to find an arrival

Kyoung-sook Kim; So-young Hwang; Ki-joune Li

2004-01-01

44

Energy-efficient broadcasting in ad-hoc networks: combining MSTs with shortest-path trees  

Microsoft Academic Search

We investigate the problem of constructing a multicast tree in ad-hoc networks. In particular, we address the issue of the power consumption, that is, the overall energy that the stations must spend to implement such a tree. We focus on two extreme cases of multicast: broadcast (one-to-all) and unicast (one-to-one). Minimum Spanning Trees (MSTs) and Shortest-Path Trees (SPTs) yield optimal

Paolo Penna; Carmine Ventre

2004-01-01

45

SHORTEST PATHS FOR THE REEDS-SHEPP CAR: A WORKED OUT EXAMPLE OF THE USE OF GEOMETRIC TECHNIQUES IN NONLINEAR OPTIMAL CONTROL. 1  

Microsoft Academic Search

We illustrate the use of the techniques of modern geometric optimal control theory by studying the shortest paths for a model of a car that can move forwards and backwards. This problem was discussed in recent work by Reeds and Shepp who showed, by special methods, (a) that shortest path motion could always be achieved by means of trajectories of

J. Sussmann; Guoqing Tang

1991-01-01

46

The Weight of the Shortest Path Tree Remco van der Hofstad  

E-print Network

The Weight of the Shortest Path Tree Remco van der Hofstad Gerard Hooghiemstra Piet Van Mieghem December 22, 2005 Abstract The minimal weight of the shortest path tree in a complete graph with independent and expo- nential (mean 1) random link weights, is shown to converge to a Gaussian distribution

Van Mieghem, Piet

47

Weight of a link in a shortest path tree and the Dedekind Eta Piet Van Mieghem  

E-print Network

Weight of a link in a shortest path tree and the Dedekind Eta function Piet Van Mieghem Delft University of Technology September 11, 2009 Abstract The weight of a randomly chosen link in the shortest path tree on the complete graph with exponential i.i.d. link weights is studied. The corresponding

Van Mieghem, Piet

48

The dynamic, resource-constrained shortest path problem on an acyclic graph with application in column generation and literature review on sequence-dependent scheduling  

E-print Network

of scheduling problems that involve SDS times (costs), an important consideration in many practical applications. It focuses on papers published within the last decade, addressing a variety of machine configurations - single machine, parallel machine, flow shop...

Zhu, Xiaoyan

2007-04-25

49

A Continuous-State Version of Discrete Randomized Shortest-Paths, with Application to Path Planning  

E-print Network

are of capital importance in a variety of problems, from robot path planning, to maze solving. Path planning [16] is a well-known problem in the robotics community, described by [26] as "checking the consequences. This distribution, though peaked around optimal paths, let the random walker take a random transition according

Del Moral , Pierre

50

: A Heuristic Search Algorithm for Finding the k Shortest Paths Husain Aljazzar  

E-print Network

K : A Heuristic Search Algorithm for Finding the k Shortest Paths Husain Aljazzar , Stefan Leue, Germany Email addresses: husain.aljazzar@email.de (Husain Aljazzar), Stefan.Leue@uni-konstanz.de (Stefan

Leue, Stefan

51

Efficient shortest-path-tree computation in network routing based on pulse-coupled neural networks.  

PubMed

Shortest path tree (SPT) computation is a critical issue for routers using link-state routing protocols, such as the most commonly used open shortest path first and intermediate system to intermediate system. Each router needs to recompute a new SPT rooted from itself whenever a change happens in the link state. Most commercial routers do this computation by deleting the current SPT and building a new one using static algorithms such as the Dijkstra algorithm at the beginning. Such recomputation of an entire SPT is inefficient, which may consume a considerable amount of CPU time and result in a time delay in the network. Some dynamic updating methods using the information in the updated SPT have been proposed in recent years. However, there are still many limitations in those dynamic algorithms. In this paper, a new modified model of pulse-coupled neural networks (M-PCNNs) is proposed for the SPT computation. It is rigorously proved that the proposed model is capable of solving some optimization problems, such as the SPT. A static algorithm is proposed based on the M-PCNNs to compute the SPT efficiently for large-scale problems. In addition, a dynamic algorithm that makes use of the structure of the previously computed SPT is proposed, which significantly improves the efficiency of the algorithm. Simulation results demonstrate the effective and efficient performance of the proposed approach. PMID:23144039

Qu, Hong; Yi, Zhang; Yang, Simon X

2013-06-01

52

Formal language constrained path problems  

SciTech Connect

In many path finding problems arising in practice, certain patterns of edge/vertex labels in the labeled graph being traversed are allowed/preferred, while others are disallowed. Motivated by such applications as intermodal transportation planning, the authors investigate the complexity of finding feasible paths in a labeled network, where the mode choice for each traveler is specified by a formal language. The main contributions of this paper include the following: (1) the authors show that the problem of finding a shortest path between a source and destination for a traveler whose mode choice is specified as a context free language is solvable efficiently in polynomial time, when the mode choice is specified as a regular language they provide algorithms with improved space and time bounds; (2) in contrast, they show that the problem of finding simple paths between a source and a given destination is NP-hard, even when restricted to very simple regular expressions and/or very simple graphs; (3) for the class of treewidth bounded graphs, they show that (i) the problem of finding a regular language constrained simple path between source and a destination is solvable in polynomial time and (ii) the extension to finding context free language constrained simple paths is NP-complete. Several extensions of these results are presented in the context of finding shortest paths with additional constraints. These results significantly extend the results in [MW95]. As a corollary of the results, they obtain a polynomial time algorithm for the BEST k-SIMILAR PATH problem studied in [SJB97]. The previous best algorithm was given by [SJB97] and takes exponential time in the worst case.

Barrett, C.; Jacob, R.; Marathe, M.

1997-07-08

53

Finding the K shortest hyperpaths  

Microsoft Academic Search

The K shortest paths problem has been extensively studied for many years. Ecien t methods have been devised, and many practical applications are known. Shortest hyperpath models have been proposed for several problems in dieren t areas, for example in relation with routing in dynamic networks. However, the K shortest hyperpaths problem has not yet been investigated. In this paper

Lars Relund Nielsen; Kim Allan Andersen; Daniele Pretolani

2005-01-01

54

Texture recognition by the shortest path on 3D discrete gray-level surface  

NASA Astrophysics Data System (ADS)

In this paper, we apply geodesic paths (the shortest path which is an important object in the task of 3D shape analysis) to the description of natural textures. We first introduce an approach called propagation algorithm to estimate the shortest paths on discrete surfaces and then derive a set of texture features (LR, PLR, SDR, DIF and 1c) from them. The results of the experiments indicate that these features can reflect texture surface patterns in various aspects and are suitable for texture description.

Liao, Mengyang; Li, Xinliang; Qin, Jiamei; Wang, Sixian

1995-05-01

55

Performance of multihop wireless networks: shortest path is not enough  

Microsoft Academic Search

Existing wireless ad hoc routing protocols typically find routes with the minimum hop-count. This paper presents experimental evidence from two wireless test-beds which shows that there are usually multiple minimum hop-count paths, many of which have poor throughput. As a result, minimum-hop-count routing often chooses routes that have significantly less capacity than the best paths that exist in the network.

Douglas S. J. De Couto; Daniel Aguayo; Benjamin A. Chambers; Robert Morris

2003-01-01

56

Path Sensitization in Critical Path Problem  

Microsoft Academic Search

Since the delay of a circuit is determined by the delay of its longest sensitizable paths (such paths are called critical paths), the problem of estimating the delay of a circuit is called critical path problem. One important aspect of the critical path problem is to decide whether a path is sensitizable. A framework which allows various previously proposed path

Hsi-chuan Chen; David Hung-chang Du

1991-01-01

57

Effective usage of shortest paths promotes transportation efficiency on scale-free networks  

NASA Astrophysics Data System (ADS)

With rapid economic and social development, the problem of traffic congestion is getting more and more serious. Accordingly, network traffic models have attracted extensive attention. In this paper, we introduce a shortest-remaining-path-first queuing strategy into a network traffic model on Barabási-Albert scale-free networks under efficient routing protocol, where one packet’s delivery priority is related to its current distance to the destination. Compared with the traditional first-in-first-out queuing strategy, although the network capacity has no evident changes, some other indexes reflecting transportation efficiency are significantly improved in the congestion state. Extensive simulation results and discussions are carried out to explain the phenomena. Our work may be helpful for the designing of optimal networked-traffic systems.

Du, Wen-Bo; Wu, Zhi-Xi; Cai, Kai-Quan

2013-09-01

58

Integer programming formulations for the elementary shortest path ...  

E-print Network

cost path between two nodes s and t such that each node of G is visited ..... In order to compare MCF and GCS, we need to project out also the q-variables .... generated by building a connected component including all the nodes, and then.

2014-09-26

59

Fast Shortest-path Distance Queries on Road Networks by Pruned Highway Labeling  

E-print Network

Fast Shortest-path Distance Queries on Road Networks by Pruned Highway Labeling Takuya Akiba Yoichi- ferred to as highway-based labelings and a preprocessing algorithm for it named pruned highway labeling to as the highway-based labeling framework and a preprocessing algorithm for the framework named pruned highway

Imai, Hiroshi

60

Spatial Interpolation of Fine Particulate Matter Concentrations Using the Shortest Wind-Field Path Distance  

PubMed Central

Effective assessments of air-pollution exposure depend on the ability to accurately predict pollutant concentrations at unmonitored locations, which can be achieved through spatial interpolation. However, most interpolation approaches currently in use are based on the Euclidean distance, which cannot account for the complex nonlinear features displayed by air-pollution distributions in the wind-field. In this study, an interpolation method based on the shortest path distance is developed to characterize the impact of complex urban wind-field on the distribution of the particulate matter concentration. In this method, the wind-field is incorporated by first interpolating the observed wind-field from a meteorological-station network, then using this continuous wind-field to construct a cost surface based on Gaussian dispersion model and calculating the shortest wind-field path distances between locations, and finally replacing the Euclidean distances typically used in Inverse Distance Weighting (IDW) with the shortest wind-field path distances. This proposed methodology is used to generate daily and hourly estimation surfaces for the particulate matter concentration in the urban area of Beijing in May 2013. This study demonstrates that wind-fields can be incorporated into an interpolation framework using the shortest wind-field path distance, which leads to a remarkable improvement in both the prediction accuracy and the visual reproduction of the wind-flow effect, both of which are of great importance for the assessment of the effects of pollutants on human health. PMID:24798197

Li, Longxiang; Gong, Jianhua; Zhou, Jieping

2014-01-01

61

Design and Analysis of Improved Shortest Path Tree Update for Network Routing  

Microsoft Academic Search

The quick construction of the Shortest Path Tree (SPT) is essential to achieve fast routing speed for an interior net- work using link state protocols, such as OSPF and IS-IS. Whenever the network topology changes, the old SPT must be updated. In a network with a large number of nodes, the technology with the whole SPT re-computation by tra- ditional

Bin Xiao; Qingfeng Zhuge; Zili Shao; Edwin Hsing-mean Sha

2003-01-01

62

k-Link Shortest Paths in Weighted Subdivisions Ovidiu Daescu1  

E-print Network

k-Link Shortest Paths in Weighted Subdivisions Ovidiu Daescu1 , Joseph S.B. Mitchell2 , Simeon nonnegative weight. The weighted length of a line segment, ab, joining two points a and b within the same by NSF grant CCF-0430366. J. Mitchell is partially supported by the U.S.-Israel Binational Science

Mitchell, Joseph S.B.

63

Shortest-Path Network Analysis Is a Useful Approach toward Identifying Genetic Determinants of Longevity  

PubMed Central

Background Identification of genes that modulate longevity is a major focus of aging-related research and an area of intense public interest. In addition to facilitating an improved understanding of the basic mechanisms of aging, such genes represent potential targets for therapeutic intervention in multiple age-associated diseases, including cancer, heart disease, diabetes, and neurodegenerative disorders. To date, however, targeted efforts at identifying longevity-associated genes have been limited by a lack of predictive power, and useful algorithms for candidate gene-identification have also been lacking. Methodology/Principal Findings We have utilized a shortest-path network analysis to identify novel genes that modulate longevity in Saccharomyces cerevisiae. Based on a set of previously reported genes associated with increased life span, we applied a shortest-path network algorithm to a pre-existing protein–protein interaction dataset in order to construct a shortest-path longevity network. To validate this network, the replicative aging potential of 88 single-gene deletion strains corresponding to predicted components of the shortest-path longevity network was determined. Here we report that the single-gene deletion strains identified by our shortest-path longevity analysis are significantly enriched for mutations conferring either increased or decreased replicative life span, relative to a randomly selected set of 564 single-gene deletion strains or to the current data set available for the entire haploid deletion collection. Further, we report the identification of previously unknown longevity genes, several of which function in a conserved longevity pathway believed to mediate life span extension in response to dietary restriction. Conclusions/Significance This work demonstrates that shortest-path network analysis is a useful approach toward identifying genetic determinants of longevity and represents the first application of network analysis of aging to be extensively validated in a biological system. The novel longevity genes identified in this study are likely to yield further insight into the molecular mechanisms of aging and age-associated disease. PMID:19030232

Managbanag, J. R.; Witten, Tarynn M.; Bonchev, Danail; Fox, Lindsay A.; Tsuchiya, Mitsuhiro; Kennedy, Brian K.; Kaeberlein, Matt

2008-01-01

64

Shortest-path queries for complex networks: exploiting low tree-width outside the core  

Microsoft Academic Search

We present new and improved methods for efficient shortest-path query processing. Our methods are tailored to work for two specific classes of graphs: graphs with small tree-width and complex networks. Seemingly unrelated at first glance, these two classes of graphs have some commonalities: complex networks are known to have a core--fringe structure with a dense core and a tree-like fringe.

Takuya Akiba; Christian Sommer; Ken-ichi Kawarabayashi

2012-01-01

65

Planning image-guided endovascular interventions: guidewire simulation using shortest path algorithms  

NASA Astrophysics Data System (ADS)

Endovascular interventional procedures are being used more frequently in cardiovascular surgery. Unfortunately, procedural failure, e.g., vessel dissection, may occur and is often related to improper guidewire and/or device selection. To support the surgeon's decision process and because of the importance of the guidewire in positioning devices, we propose a method to determine the guidewire path prior to insertion using a model of its elastic potential energy coupled with a representative graph construction. The 3D vessel centerline and sizes are determined for a specified vessel. Points in planes perpendicular to the vessel centerline are generated. For each pair of consecutive planes, a vector set is generated which joins all points in these planes. We construct a graph representing these vector sets as nodes. The nodes representing adjacent vector sets are joined by edges with weights calculated as a function of the angle between the corresponding vectors (nodes). The optimal path through this weighted directed graph is then determined using shortest path algorithms, such as topological sort based shortest path algorithm or Dijkstra's algorithm. Volumetric data of an internal carotid artery phantom (Ø 3.5mm) were acquired. Several independent guidewire (Ø 0.4mm) placements were performed, and the 3D paths were determined using rotational angiography. The average RMS distance between the actual and the average simulated guidewire path was 0.7mm; the computation time to determine the path was 3 seconds. The ability to predict the guidewire path inside vessels may facilitate calculation of vessel-branch access and force estimation on devices and the vessel wall.

Schafer, Sebastian; Singh, Vikas; Hoffmann, Kenneth R.; Noël, Peter B.; Xu, Jinhui

2007-03-01

66

On Bounded Distance Decoding, Unique Shortest Vectors, and the Minimum Distance Problem  

Microsoft Academic Search

We prove the equivalence, up to a small polynomial approximation factor Ö{n\\/logn}\\\\sqrt{n\\/\\\\log n}, of the lattice problems uSVP (unique Shortest Vector Problem), BDD (Bounded Distance Decoding) and GapSVP (the decision version of the Shortest Vector Problem). This resolves a long-standing open problem about the relationship\\u000a between uSVP and the more standard GapSVP, as well the BDD problem commonly used in

Vadim Lyubashevsky; Daniele Micciancio

2009-01-01

67

Identification of Colorectal Cancer Related Genes with mRMR and Shortest Path in Protein-Protein Interaction Network  

PubMed Central

One of the most important and challenging problems in biomedicine and genomics is how to identify the disease genes. In this study, we developed a computational method to identify colorectal cancer-related genes based on (i) the gene expression profiles, and (ii) the shortest path analysis of functional protein association networks. The former has been used to select differentially expressed genes as disease genes for quite a long time, while the latter has been widely used to study the mechanism of diseases. With the existing protein-protein interaction data from STRING (Search Tool for the Retrieval of Interacting Genes), a weighted functional protein association network was constructed. By means of the mRMR (Maximum Relevance Minimum Redundancy) approach, six genes were identified that can distinguish the colorectal tumors and normal adjacent colonic tissues from their gene expression profiles. Meanwhile, according to the shortest path approach, we further found an additional 35 genes, of which some have been reported to be relevant to colorectal cancer and some are very likely to be relevant to it. Interestingly, the genes we identified from both the gene expression profiles and the functional protein association network have more cancer genes than the genes identified from the gene expression profiles alone. Besides, these genes also had greater functional similarity with the reported colorectal cancer genes than the genes identified from the gene expression profiles alone. All these indicate that our method as presented in this paper is quite promising. The method may become a useful tool, or at least plays a complementary role to the existing method, for identifying colorectal cancer genes. It has not escaped our notice that the method can be applied to identify the genes of other diseases as well. PMID:22496748

Liu, Lei; Cai, Yu-Dong; Chou, Kuo-Chen

2012-01-01

68

Shortest-path constraints for 3D multiobject semiautomatic segmentation via clustering and Graph Cut.  

PubMed

We derive shortest-path constraints from graph models of structure adjacency relations and introduce them in a joint centroidal Voronoi image clustering and Graph Cut multiobject semiautomatic segmentation framework. The vicinity prior model thus defined is a piecewise-constant model incurring multiple levels of penalization capturing the spatial configuration of structures in multiobject segmentation. Qualitative and quantitative analyses and comparison with a Potts prior-based approach and our previous contribution on synthetic, simulated, and real medical images show that the vicinity prior allows for the correct segmentation of distinct structures having identical intensity profiles and improves the precision of segmentation boundary placement while being fairly robust to clustering resolution. The clustering approach we take to simplify images prior to segmentation strikes a good balance between boundary adaptivity and cluster compactness criteria furthermore allowing to control the trade-off. Compared with a direct application of segmentation on voxels, the clustering step improves the overall runtime and memory footprint of the segmentation process up to an order of magnitude without compromising the quality of the result. PMID:23807445

Kéchichian, Razmig; Valette, Sébastien; Desvignes, Michel; Prost, Rémy

2013-11-01

69

Scaling of average weighted shortest path and average receiving time on weighted expanded Koch networks  

NASA Astrophysics Data System (ADS)

Deterministic network models have been attractive media for discussing dynamical processes' dependence on network structural features. On the other hand, the heterogeneity of weights affect dynamical processes taking place on networks. In this paper, we present a family of weighted expanded Koch networks based on Koch networks. They originate from a r-polygon, and each node of current generation produces m r-polygons including the node and whose weighted edges are scaled by factor w in subsequent evolutionary step. We derive closed-form expressions for average weighted shortest path length (AWSP). In large network, AWSP stays bounded with network order growing (0 < w < 1). Then, we focus on a special random walks and trapping issue on the networks. In more detail, we calculate exactly the average receiving time (ART). ART exhibits a sub-linear dependence on network order (0 < w < 1), which implies that nontrivial weighted expanded Koch networks are more efficient than un-weighted expanded Koch networks in receiving information. Besides, efficiency of receiving information at hub nodes is also dependent on parameters m and r. These findings may pave the way for controlling information transportation on general weighted networks.

Wu, Zikai; Hou, Baoyu; Zhang, Hongjuan; Jin, Feng

2014-04-01

70

Fast and accurate global multiphase arrival tracking: the irregular shortest-path method in a 3-D spherical earth model  

NASA Astrophysics Data System (ADS)

The traditional grid/cell-based wavefront expansion algorithms, such as the shortest path algorithm, can only find the first arrivals or multiply reflected (or mode converted) waves transmitted from subsurface interfaces, but cannot calculate the other later reflections/conversions having a minimax time path. In order to overcome the above limitations, we introduce the concept of a stationary minimax time path of Fermat's Principle into the multistage irregular shortest path method. Here we extend it from Cartesian coordinates for a flat earth model to global ray tracing of multiple phases in a 3-D complex spherical earth model. The ray tracing results for 49 different kinds of crustal, mantle and core phases show that the maximum absolute traveltime error is less than 0.12 s and the average absolute traveltime error is within 0.09 s when compared with the AK135 theoretical traveltime tables for a 1-D reference model. Numerical tests in terms of computational accuracy and CPU time consumption indicate that the new scheme is an accurate, efficient and a practical way to perform 3-D multiphase arrival tracking in regional or global traveltime tomography.

Huang, Guo-Jiao; Bai, Chao-Ying; Greenhalgh, Stewart

2013-09-01

71

A Multilevel Probabilistic Beam Search Algorithm for the Shortest Common Supersequence Problem  

PubMed Central

The shortest common supersequence problem is a classical problem with many applications in different fields such as planning, Artificial Intelligence and especially in Bioinformatics. Due to its NP-hardness, we can not expect to efficiently solve this problem using conventional exact techniques. This paper presents a heuristic to tackle this problem based on the use at different levels of a probabilistic variant of a classical heuristic known as Beam Search. The proposed algorithm is empirically analysed and compared to current approaches in the literature. Experiments show that it provides better quality solutions in a reasonable time for medium and large instances of the problem. For very large instances, our heuristic also provides better solutions, but required execution times may increase considerably. PMID:23300667

Gallardo, Jose E.

2012-01-01

72

A Computational Study Identifies HIV Progression-Related Genes Using mRMR and Shortest Path Tracing  

PubMed Central

Since statistical relationships between HIV load and CD4+ T cell loss have been demonstrated to be weak, searching for host factors contributing to the pathogenesis of HIV infection becomes a key point for both understanding the disease pathology and developing treatments. We applied Maximum Relevance Minimum Redundancy (mRMR) algorithm to a set of microarray data generated from the CD4+ T cells of viremic non-progressors (VNPs) and rapid progressors (RPs) to identify host factors associated with the different responses to HIV infection. Using mRMR algorithm, 147 gene had been identified. Furthermore, we constructed a weighted molecular interaction network with the existing protein-protein interaction data from STRING database and identified 1331 genes on the shortest-paths among the genes identified with mRMR. Functional analysis shows that the functions relating to apoptosis play important roles during the pathogenesis of HIV infection. These results bring new insights of understanding HIV progression. PMID:24244287

Liu, Lei

2013-01-01

73

Multi-population Genetic Algorithms with Immigrants Scheme for Dynamic Shortest Path  

E-print Network

Memory-Based Immigrants for Genetic Algorithms in Dynamic Environments Shengxiang Yang Department optimization problems. Among these approches, random immigrants and memory schemes have shown to be bene- ficial in many dynamic problems. This paper proposes a hybrid memory and random immigrants scheme

Yang, Shengxiang

74

Shortest Path Stochastic Control for Hybrid Electric Vehicles , J.W. Grizzle2  

E-print Network

, its power management system must be charge sustaining over the drive cycle, meaning that the battery of the test. During the test cycle, the power management system is free to vary the battery SOC so problem associated with the design of the power management system because it allows deviations of battery

Grizzle, Jessy W.

75

Cooperative optimal path planning for herding problems  

E-print Network

destination following weighted time-optimal and effort-optimal control paths. Simulation of this herding problem is accomplished through dynamic programming by utilizing the SNOPT software in the MATLAB environment. The numerical solution gives us the optimal...

Lu, Zhenyu

2009-05-15

76

An Alternate Path To Stoichiometric Problem Solving.  

ERIC Educational Resources Information Center

Discusses an alternate path to teaching introductory stoichiometry based on research findings. The recommendation is to use problems that can be solved easily by rapid mental calculation as well as by pure logic. (AIM)

Schmidt, Hans-Jurgen

1997-01-01

77

Path-Distance Heuristics for the Steiner Problem in Undirected Networks  

Microsoft Academic Search

An integrative overview of the algorithmic characteristics of three well-known polynomialtime heuristics for the undirected\\u000a Steiner minimum tree problem:shortest path heuristic (SPH),distance network heuristic (DNH), andaverage distance heuristic (ADH) is given. The performance of thesesingle-pass heuristics (and some variants) is compared and contrasted with several heuristics based onrepetitive applications of the SPH. It is shown that two of these repetitive

Pawel Winter; J. Macgregor Smith

1992-01-01

78

To appear in the International Journal of Robotics Research, 2004 Expected Shortest Paths for Landmark-Based  

E-print Network

strategies in the presence of significant sensor uncertainty. The navigation environments are modeled is continually updated during subsequent navigation. All motion paths are planned from landmark to landmark can be detected. These estimates are based on the history of all observations made by the robot

Scharstein, Daniel

79

An integer programming approach to the OSPF weight setting problem  

Microsoft Academic Search

Under the Open Shortest Path First (OSPF) protocol, tra-c ?ow in an Internet Protocol (IP) network is routed on the shortest paths between each source and destination. The shortest path is calculated based on pre-assigned weights on the network links. The OSPF weight setting problem is to determine a set of weights such that, if the ?ow is routed based

Amandeep Parmar; Shabbir Ahmedy; Joel Sokol

80

Parallel implementations of dynamic traffic assignment models and algorithms for dynamic shortest path problems  

E-print Network

This thesis aims at the development of faster Dynamic Traffic Assignment (DTA) models to meet the computational efficiency required by real world applications. A DTA model can be decomposed into several sub-models, of which ...

Jiang, Hai, 1979-

2004-01-01

81

Performance Evaluation 48 (2002) 201223 On open shortest path first related network optimisation problems  

E-print Network

a Department of Communication Systems, Lund Institute of Technology, Lund, Sweden b Institute of Telecommunications, Warsaw University of Technology, Nowowiejska 15/19, 00-665 Warszawa, Poland c Ericsson Research of Technology, Nowowiejska 15/19, 00665 Warszawa, Poland. Tel.: +48-22-825-98-20; fax: +48-22-660-7564. E

Jüttner, Alpár

82

Neither Shortest Path Nor Dominating Set: Aggregation Scheduling by Greedy Growing Tree in Multihop Wireless Sensor Networks  

Microsoft Academic Search

Data aggregation is a fundamental task in multihop wireless sensor networks. Minimum-latency aggregation schedul- ing (MLAS) seeks to minimize the number of scheduled time slots to perform an aggregation. In this paper, we present the first work on a solvable mathematical formulation of the MLAS problem. The optimal solution of small example networks sug- gests that an optimal scheduling can

Chen Tian; Hongbo Jiang; Chonggang Wang; Zuodong Wu; Jinhua Chen; Wenyu Liu

2011-01-01

83

Spreading paths in partially observed social networks.  

PubMed

Understanding how and how far information, behaviors, or pathogens spread in social networks is an important problem, having implications for both predicting the size of epidemics, as well as for planning effective interventions. There are, however, two main challenges for inferring spreading paths in real-world networks. One is the practical difficulty of observing a dynamic process on a network, and the other is the typical constraint of only partially observing a network. Using static, structurally realistic social networks as platforms for simulations, we juxtapose three distinct paths: (1) the stochastic path taken by a simulated spreading process from source to target; (2) the topologically shortest path in the fully observed network, and hence the single most likely stochastic path, between the two nodes; and (3) the topologically shortest path in a partially observed network. In a sampled network, how closely does the partially observed shortest path (3) emulate the unobserved spreading path (1)? Although partial observation inflates the length of the shortest path, the stochastic nature of the spreading process also frequently derails the dynamic path from the shortest path. We find that the partially observed shortest path does not necessarily give an inflated estimate of the length of the process path; in fact, partial observation may, counterintuitively, make the path seem shorter than it actually is. PMID:22587148

Onnela, Jukka-Pekka; Christakis, Nicholas A

2012-03-01

84

Spreading paths in partially observed social networks  

PubMed Central

Understanding how and how far information, behaviors, or pathogens spread in social networks is an important problem, having implications for both predicting the size of epidemics, as well as for planning effective interventions. There are, however, two main challenges for inferring spreading paths in real-world networks. One is the practical difficulty of observing a dynamic process on a network, and the other is the typical constraint of only partially observing a network. Using a static, structurally realistic social network as a platform for simulations, we juxtapose three distinct paths: (1) the stochastic path taken by a simulated spreading process from source to target; (2) the topologically shortest path in the fully observed network, and hence the single most likely stochastic path, between the two nodes; and (3) the topologically shortest path in a partially observed network. In a sampled network, how closely does the partially observed shortest path (3) emulate the unobserved spreading path (1)? Although partial observation inflates the length of the shortest path, the stochastic nature of the spreading process also frequently derails the dynamic path from the shortest path. We find that the partially observed shortest path does not necessarily give an inflated estimate of the length of the process path; in fact, partial observation may, counterintuitively, make the path seem shorter than it actually is. PMID:22587148

Onnela, Jukka-Pekka; Christakis, Nicholas A.

2012-01-01

85

Spreading paths in partially observed social networks  

NASA Astrophysics Data System (ADS)

Understanding how and how far information, behaviors, or pathogens spread in social networks is an important problem, having implications for both predicting the size of epidemics, as well as for planning effective interventions. There are, however, two main challenges for inferring spreading paths in real-world networks. One is the practical difficulty of observing a dynamic process on a network, and the other is the typical constraint of only partially observing a network. Using static, structurally realistic social networks as platforms for simulations, we juxtapose three distinct paths: (1) the stochastic path taken by a simulated spreading process from source to target; (2) the topologically shortest path in the fully observed network, and hence the single most likely stochastic path, between the two nodes; and (3) the topologically shortest path in a partially observed network. In a sampled network, how closely does the partially observed shortest path (3) emulate the unobserved spreading path (1)? Although partial observation inflates the length of the shortest path, the stochastic nature of the spreading process also frequently derails the dynamic path from the shortest path. We find that the partially observed shortest path does not necessarily give an inflated estimate of the length of the process path; in fact, partial observation may, counterintuitively, make the path seem shorter than it actually is.

Onnela, Jukka-Pekka; Christakis, Nicholas A.

2012-03-01

86

On the All-Pairs Euclidean Short Path Problem  

Microsoft Academic Search

Given a set of polygonal obstacles of n vertices in the plane', the problem of processing the all-pairs Euclidean short path queries is that of reporting an obstacle-avoiding path P (or its length) between two arbitrary query points p and q in the plane, such that the length of P is within a small factor of the length of a

Danny Z. Chent

87

On the all-pairs Euclidean short path problem  

Microsoft Academic Search

Given a set of polygonal obstacles of n vertices in the plane’, the problem of processing the all-pairs Euclidean short path queries is that of reporting an obstacle-avoiding path P (or its length) between two arbitrary query points p and q in the plane, such that the length of P is within a small factor of the length of a

Danny Z. Chent

1995-01-01

88

The traffic equilibrium problem with nonadditive path costs  

SciTech Connect

In this paper the authors present a version of the (static) traffic equilibrium problem in which the cost incurred on a path is not simply the sum of the costs on the arcs that constitute that path. The authors motivate this nonadditive version of the problem by describing several situations in which the classical additivity assumption fails. They also present an algorithm for solving nonadditive problems that is based on the recent NE/SQP algorithm, a fast and robust method for the nonlinear complementarity problem. Finally, they present a small example that illustrates both the importance of using nonadditive costs and the effectiveness of the NE/SQP method.

Gabriel, S.A. [Argonne National Lab., IL (United States). Mathematics and Computer Science Div.; Bernstein, D. [Princeton Univ., NJ (United States). Dept. of Civil Engineering and Operations Research

1995-08-21

89

Ranking Sports Teams and the Inverse Equal Paths Problem  

E-print Network

of football and other sports, and also in general, [11]. There are numerous ranking schemes each with itsRanking Sports Teams and the Inverse Equal Paths Problem Dorit S. Hochbaum Department of Industrial hochbaum@ieor.berkeley.edu Abstract. The problem of rank aggregation has been studied in con- texts varying

Hochbaum, Dorit S.

90

HAMILTONIAN PATHS ALGORITHMS FOR DISK SCHEDULING  

Microsoft Academic Search

The problem of optimally scheduling the read\\/write requests in a disk storage system is considered. A new class of algorithms for the disk scheduling problem is presented, and the relations between this problem and the shortest hamiltonian path problem on asymmetric graphs are investigated. The problem of deriving realistic upper bounds for the disk utilization factor, one of the main

Giorgio Gallo; Federico Malucelli; Martina Marrè

91

An Application of Calculus: Optimum Parabolic Path Problem  

ERIC Educational Resources Information Center

A practical and technological application of calculus problem is posed to motivate freshman students or junior high school students. A variable coefficient of friction is used in modelling air friction. The case in which the coefficient of friction is a decreasing function of altitude is considered. The optimum parabolic path for a flying object…

Atasever, Merve; Pakdemirli, Mehmet; Yurtsever, Hasan Ali

2009-01-01

92

Adleman[1] 1994 DNA Hamiltonian Path Problem , DNA  

E-print Network

1. Adleman[1] 1994 DNA Hamiltonian Path Problem , DNA DNA [2]. DNA DNA , . , , 2 , DNA 4 . DNA 4 A(Adenine), C(Cytosine), G(Guanine), T(Thymine) 2 4 . , . 1 mole 6x10 23 DNA DNA . , . DNA NP-complete [1, 2], [2

93

Genetic Algorithms with Elitism-based Immigrants for Dynamic Shortest Path Problem in Mobile Ad Hoc Networks  

E-print Network

William Berthomière L'immigration d'ex-URSS et les colonies de Cisjordanie et de Gaza In: Revue : Berthomière William. L'immigration d'ex-URSS et les colonies de Cisjordanie et de Gaza. In: Revue européenne. 201-218 201 NOTE D'ACTUALIT� L'immigration d'ex-URSS et les colonies de Cisjordanie et de Gaza William

Yang, Shengxiang

94

Solving a Hamiltonian Path Problem with a bacterial computer  

PubMed Central

Background The Hamiltonian Path Problem asks whether there is a route in a directed graph from a beginning node to an ending node, visiting each node exactly once. The Hamiltonian Path Problem is NP complete, achieving surprising computational complexity with modest increases in size. This challenge has inspired researchers to broaden the definition of a computer. DNA computers have been developed that solve NP complete problems. Bacterial computers can be programmed by constructing genetic circuits to execute an algorithm that is responsive to the environment and whose result can be observed. Each bacterium can examine a solution to a mathematical problem and billions of them can explore billions of possible solutions. Bacterial computers can be automated, made responsive to selection, and reproduce themselves so that more processing capacity is applied to problems over time. Results We programmed bacteria with a genetic circuit that enables them to evaluate all possible paths in a directed graph in order to find a Hamiltonian path. We encoded a three node directed graph as DNA segments that were autonomously shuffled randomly inside bacteria by a Hin/hixC recombination system we previously adapted from Salmonella typhimurium for use in Escherichia coli. We represented nodes in the graph as linked halves of two different genes encoding red or green fluorescent proteins. Bacterial populations displayed phenotypes that reflected random ordering of edges in the graph. Individual bacterial clones that found a Hamiltonian path reported their success by fluorescing both red and green, resulting in yellow colonies. We used DNA sequencing to verify that the yellow phenotype resulted from genotypes that represented Hamiltonian path solutions, demonstrating that our bacterial computer functioned as expected. Conclusion We successfully designed, constructed, and tested a bacterial computer capable of finding a Hamiltonian path in a three node directed graph. This proof-of-concept experiment demonstrates that bacterial computing is a new way to address NP-complete problems using the inherent advantages of genetic systems. The results of our experiments also validate synthetic biology as a valuable approach to biological engineering. We designed and constructed basic parts, devices, and systems using synthetic biology principles of standardization and abstraction. PMID:19630940

Baumgardner, Jordan; Acker, Karen; Adefuye, Oyinade; Crowley, Samuel Thomas; DeLoache, Will; Dickson, James O; Heard, Lane; Martens, Andrew T; Morton, Nickolaus; Ritter, Michelle; Shoecraft, Amber; Treece, Jessica; Unzicker, Matthew; Valencia, Amanda; Waters, Mike; Campbell, A Malcolm; Heyer, Laurie J; Poet, Jeffrey L; Eckdahl, Todd T

2009-01-01

95

THE PATH-PARTITION PROBLEM IN BIPARTITE DISTANCE-HEREDITARY GRAPHS  

Microsoft Academic Search

A path partition of a graph is a collection of vertex-disjoint paths that cover all vertices of the graph. The path-partition problem is to nd a path partition of minimum size. This paper gives a linear-time algorithm for the path-partition problem in bipartite distance-hereditary graphs.

Hong-Gwa Yeh; Gerard J. Chang

1998-01-01

96

On-line exact shortest distance query processing  

Microsoft Academic Search

Shortest-path query processing not only serves as a long es- tablished routine for numerous applications in the past but also is of increasing popularity to support novel graph appli- cations in very large databases nowadays. For a large graph, there is the new scenario to query intensively against arbi- trary nodes, asking to quickly return node distance or even shortest

Jiefeng Cheng; Jeffrey Xu Yu

2009-01-01

97

Prizing on Paths: A PTAS for the Highway Problem  

E-print Network

In the highway problem, we are given an n-edge line graph (the highway), and a set of paths (the drivers), each one with its own budget. For a given assignment of edge weights (the tolls), the highway owner collects from each driver the weight of the associated path, when it does not exceed the budget of the driver, and zero otherwise. The goal is choosing weights so as to maximize the profit. A lot of research has been devoted to this apparently simple problem. The highway problem was shown to be strongly NP-hard only recently [Elbassioni,Raman,Ray-'09]. The best-known approximation is O(\\log n/\\log\\log n) [Gamzu,Segev-'10], which improves on the previous-best O(\\log n) approximation [Balcan,Blum-'06]. In this paper we present a PTAS for the highway problem, hence closing the complexity status of the problem. Our result is based on a novel randomized dissection approach, which has some points in common with Arora's quadtree dissection for Euclidean network design [Arora-'98]. The basic idea is enclosing the ...

Grandoni, Fabrizio

2010-01-01

98

Operator calculus in generalized zeon algebras: theory and application to multi-constrained path  

E-print Network

Operator calculus in generalized zeon algebras: theory and application to multi-constrained path single-source Pareto paths remaining. 2 Theory: Generalized zeon algebras Zeon algebras are commutative-constrained path problems is described. keywords: shortest paths, message routing, operator calculus, semigroup

Paris-Sud XI, Université de

99

Operator calculus in generalized zeon algebras: theory and application to multi-constrained path  

E-print Network

Operator calculus in generalized zeon algebras: theory and application to multi-constrained path-constrained path problems is described. keywords: shortest paths, message routing, operator calculus, semigroup about self-avoiding structures (paths, cycles, trails, etc.) in the graph are revealed by computing

Schott, René - Institut de Mathématiques �lie Cartan, Université Henri Poincaré

100

Using a modified invasive weed optimization algorithm for a personalized urban multi-criteria path optimization problem  

NASA Astrophysics Data System (ADS)

The personalized urban multi-criteria quasi-optimum path problem (PUMQPP) is a branch of multi-criteria shortest path problems (MSPPs) and it is classified as a NP-hard problem. To solve the PUMQPP, by considering dependent criteria in route selection, there is a need for approaches that achieve the best compromise of possible solutions/routes. Recently, invasive weed optimization (IWO) algorithm is introduced and used as a novel algorithm to solve many continuous optimization problems. In this study, the modified algorithm of IWO was designed, implemented, evaluated, and compared with the genetic algorithm (GA) to solve the PUMQPP in a directed urban transportation network. In comparison with the GA, the results have shown the significant superiority of the proposed modified IWO algorithm in exploring a discrete search-space of the urban transportation network. In this regard, the proposed modified IWO algorithm has reached better results in fitness function, quality metric and running-time values in comparison with those of the GA.

Pahlavani, Parham; Delavar, Mahmoud R.; Frank, Andrew U.

2012-08-01

101

Variants of the Min-Sum Link-Disjoint Paths Problem  

E-print Network

1 Variants of the Min-Sum Link-Disjoint Paths Problem Anteneh Beshir and Fernando Kuipers Faculty requires computing link-disjoint primary and backup paths. Finding a min-sum pair of link-disjoint paths render the problem NP-complete. In this paper, we study different variants of the min-sum link

Kuipers, Fernando A.

102

Integrating analogical mapping and general problem solving: the path-mapping theory  

E-print Network

Integrating analogical mapping and general problem solving: the path-mapping theory Dario D the path-mapping theory of how humans integrate analogical mapping and general problem solving. The theory in the ACT-R cognitive architecture, the path-mapping theory enables models of analogical mapping behavior

Salvucci, Dario D.

103

The Greedy Algorithm for Shortest Superstrings Haim Kaplan Nira Shafrir  

E-print Network

The Greedy Algorithm for Shortest Superstrings Haim Kaplan #3; Nira Shafrir #3; August 26, 2004 molecule. There is a natural greedy algorithm for the shortest superstring problem, which we refer to as GREEDY. The GREEDY algorithm maintains a set of strings, initialized to be equal to S. At each iteration

Kaplan, Haim

104

Approximating Disjoint-Path Problems Using Greedy Algorithms and Packing Integer Programs  

Microsoft Academic Search

The edge and vertex-disjoint path problems together with their unsplittable flow generalization are NP-hard problems with a multi- tude of applications in areas such as routing, scheduling and bin packing. Given the hardness of the problems, we study polynomial-time approxi- mation algorithms with bounded performance guarantees. We introduce techniques which yield new algorithms for a wide range of disjoint-path problems.

Stavros G. Kolliopoulos; Clifford Stein

1998-01-01

105

A general approximation technique for constrained forest problems  

Microsoft Academic Search

We present a general approximation technique for a large class of graph problems. Our technique mostly applies to problems of covering, at minimum cost, the vertices of a graph with trees, cycles or paths satisfying certain requirements. In particular, many basic combinatorial optimization problems fit in this framework, including the shortest path, minimum spanning tree, minimum-weight perfect matching, traveling salesman

Michel X. Goemans; David P. Williamson

1992-01-01

106

Integrating analogical mapping and general problem solving: the path-mapping theory  

Microsoft Academic Search

This article describes the path-mapping theory of how humans integrate analogical mapping and general problem solving. The theory posits that humans represent analogs with declarative roles, map analogs by lower-level retrieval of analogous role paths, and coordinate mappings with higher-level organizational knowledge. Implemented in the ACT-R cognitive architecture, the path-mapping theory enables models of analogical mapping behavior to incorporate and

Dario D. Salvucci; John R. Anderson

2001-01-01

107

A path-integral approach to Bayesian inference for inverse problems using the semiclassical approximation  

E-print Network

We demonstrate how path integrals often used in problems of theoretical physics can be adapted to provide a machinery for performing Bayesian inference in function spaces. Such inference comes about naturally in the study of inverse problems of recovering continuous (infinite dimensional) coefficient functions from ordinary or partial differential equations (ODE, PDE), a problem which is typically ill-posed. Regularization of these problems using $L^2$ function spaces (Tikhonov regularization) is equivalent to Bayesian probabilistic inference, using a Gaussian prior. The Bayesian interpretation of inverse problem regularization is useful since it allows one to quantify and characterize error and degree of precision in the solution of inverse problems, as well as examine assumptions made in solving the problem -- namely whether the subjective choice of regularization is compatible with prior knowledge. Using path-integral formalism, Bayesian inference can be explored through various perturbative techniques, such as the semiclassical approximation, which we use in this manuscript. Perturbative path-integral approaches, while offering alternatives to computational approaches like Markov-Chain-Monte-Carlo (MCMC), also provide natural starting points for MCMC methods that can be used to refine approximations. In this manuscript, we illustrate a path-integral formulation for inverse problems and demonstrate it on an inverse problem in membrane biophysics as well as inverse problems in potential theories involving the Poisson equation.

Joshua C Chang; Van Savage; Tom Chou

2013-12-10

108

A Path-Integral Approach to Bayesian Inference for Inverse Problems Using the Semiclassical Approximation  

NASA Astrophysics Data System (ADS)

We demonstrate how path integrals often used in problems of theoretical physics can be adapted to provide a machinery for performing Bayesian inference in function spaces. Such inference comes about naturally in the study of inverse problems of recovering continuous (infinite dimensional) coefficient functions from ordinary or partial differential equations (ODE, PDE), a problem which is typically ill-posed. Regularization of these problems using $L^2$ function spaces (Tikhonov regularization) is equivalent to Bayesian probabilistic inference, using a Gaussian prior. The Bayesian interpretation of inverse problem regularization is useful since it allows one to quantify and characterize error and degree of precision in the solution of inverse problems, as well as examine assumptions made in solving the problem -- namely whether the subjective choice of regularization is compatible with prior knowledge. Using path-integral formalism, Bayesian inference can be explored through various perturbative techniques, such as the semiclassical approximation, which we use in this manuscript. Perturbative path-integral approaches, while offering alternatives to computational approaches like Markov-Chain-Monte-Carlo (MCMC), also provide natural starting points for MCMC methods that can be used to refine approximations. In this manuscript, we illustrate a path-integral formulation for inverse problems and demonstrate it on an inverse problem in membrane biophysics as well as inverse problems in potential theories involving the Poisson equation.

Chang, Joshua C.; Savage, Van M.; Chou, Tom

2014-11-01

109

Ranking Sports Teams and the Inverse Equal Paths Problem  

Microsoft Academic Search

The problem of rank aggregation has been studied in con- texts varying from sports, to multi-criteria decision making, to machine learning, to academic citations, to ranking web pages, and to descriptive decision theory. Rank aggregation is the mapping of inputs that rank subsets of a set of objects into a consistent ranking that represents in some meaningful way the various

Dorit S. Hochbaum; Walter A. Haas

2006-01-01

110

Proof of a Lattice Paths Conjecture Connected to the Tennis Ball Problem  

E-print Network

Proof of a Lattice Paths Conjecture Connected to the Tennis Ball Problem Joshua Fallon a Shanzhen Abstract The authors give a history of the so-called tennis ball problem, and discuss its relation when the number of balls removed each turn is exactly half the number inserted. Key words: Tennis Ball

Niederhausen, Heinrich

111

An Analysis of the Elastic Net Approach to the Traveling Salesman Problem  

Microsoft Academic Search

This paper analyzes the elastic net approach (Durbin and Willshaw 1987) to the traveling salesman problem of finding the shortest path through a set of cities. The elastic net approach jointly minimizes the length of an arbitrary path in the plane and the distance between the path points and the cities. The tradeoff between these two requirements is controlled by

Richard Durbin; Richard Szeliski; Alan Yuille

1989-01-01

112

Shortest Recurrence Periods of Novae  

NASA Astrophysics Data System (ADS)

Stimulated by the recent discovery of the 1 yr recurrence period nova M31N 2008-12a, we examined the shortest recurrence periods of hydrogen shell flashes on mass-accreting white dwarfs (WDs). We discuss the mechanism that yields a finite minimum recurrence period for a given WD mass. Calculating the unstable flashes for various WD masses and mass accretion rates, we identified a shortest recurrence period of about two months for a non-rotating 1.38 M ? WD with a mass accretion rate of 3.6 × 10-7 M ? yr-1. A 1 yr recurrence period is realized for very massive (gsim 1.3 M ?) WDs with very high accretion rates (gsim 1.5 × 10-7 M ? yr-1). We revised our stability limit of hydrogen shell burning, which will be useful for binary evolution calculations toward Type Ia supernovae.

Kato, Mariko; Saio, Hideyuki; Hachisu, Izumi; Nomoto, Ken'ichi

2014-10-01

113

Shortest Recurrence Periods of Novae  

E-print Network

Stimulated by the recent discovery of the 1 yr recurrence period nova M31N 2008-12a, we examined shortest recurrence periods of hydrogen shell flashes on mass-accreting white dwarfs (WDs). We discuss the mechanism that yields a finite minimum recurrence period for a given WD mass. Calculating unstable flashes for various WD masses and mass-accretion rates, we identified the shortest recurrence period of about two months for a non-rotating 1.38 M_\\sun WD with a mass-accretion rate of 3.6 \\times 10^{-7} M_\\sun yr^{-1}. One year recurrence period is realized for very massive (> 1.3 M_\\sun) WDs with very high accretion rates (>1.5 \\times 10^{-7} M_\\sun yr^{-1}). We also present a revised stability limit of hydrogen shell burning, which will be useful for binary evolution calculations toward Type Ia supernovae.

Kato, Mariko; Hachisu, Izumi; Nomoto, Ken'ichi

2014-01-01

114

Application of the CIRSSE cooperating robot path planner to the NASA Langley truss assembly problem  

NASA Technical Reports Server (NTRS)

A method for autonomously planning collision free paths for two cooperating robots in a static environment was developed at the Center for Intelligent Robotic Systems for Space Exploration (CIRSSE). The method utilizes a divide-and-conquer type of heuristic and involves non-exhaustive mapping of configuration space. While there is no guarantee of finding a solution, the planner was successfully applied to a variety of problems including two cooperating 9 degrees of freedom (dof) robots. Although developed primarily for cooperating robots the method is also applicable to single robot path planning problems. A single 6 dof version of the planner was implemented for the truss assembly east, at NASA Langley's Automated Structural Assembly Lab (ASAL). The results indicate that the planner could be very useful in addressing the ASAL path planning problem and that further work along these lines is warranted.

Weaver, Jonathan M.; Derby, Stephen J.

1993-01-01

115

GRASP WITH PATH-RELINKING FOR THE COOPERATIVE COMMUNICATION PROBLEM ON AD-HOC NETWORKS  

E-print Network

GRASP WITH PATH-RELINKING FOR THE COOPERATIVE COMMUNICATION PROBLEM ON AD-HOC NETWORKS C of maximizing the connection time between a set of mobile agents in an ad-hoc network. Given a network and a set COMMUNICATION ON AD-HOC NETWORKS is known to be NP-hard. We look for heuristic algorithms that are able

Resende, Mauricio G. C.

116

Balancing safety and speed in the military path finding problem: analysis of different ACO algorithms  

Microsoft Academic Search

hCHAC, a MOACO implemented to solve the problem of finding the path that minimizes resources, while maximi- zing safety for a military unit in realistic battlefields, is compared with some other approaches: two extreme me- thods, which only considers one objective in the search, and a mono-objective algorithm, which combines the two objec- tives terms of the formulae in a

Antonio Miguel Mora; Juan Julián Merelo Guervós; Juan Luís Jiménez Laredo; Pedro A. Castillo Valdivieso; Cristian Millán; Juan Torrecillas

2007-01-01

117

Discrete-time classical and quantum Markovian evolutions: Maximum entropy problems on path space  

E-print Network

The theory of Schroedinger bridges for diffusion processes is extended to classical and quantum discrete-time Markovian evolutions. The solution of the path space maximum entropy problems is obtained from the a priori model in both cases via a suitable multiplicative functional transformation. In the quantum case, nonequilibrium time reversal of quantum channels is discussed and space-time harmonic processes are introduced.

Michele Pavon; Francesco Ticozzi

2008-11-06

118

Search Path Mapping: A Versatile Approach for Visualizing Problem-Solving Behavior.  

ERIC Educational Resources Information Center

Computer-based problem-solving examinations in immunology generate graphic representations of students' search paths, allowing evaluation of how organized and focused their knowledge is, how well their organization relates to critical concepts in immunology, where major misconceptions exist, and whether proper knowledge links exist between content…

Stevens, Ronald H.

1991-01-01

119

A Hamilton Path Heuristic with Applications to the Middle Two Levels Problem  

E-print Network

A Hamilton Path Heuristic with Applications to the Middle Two Levels Problem Ian Shields IBM P is to find a Hamilton cycle in the middle two levels, M 2k+1 , of the Hasse diagram of B 2k+1 (the partially by inclusion. The Hasse diagram, # Research supported in part by NSF grant DMS9622772 1 #12; 10101 11001 10011

Savage, Carla D.

120

A guided tabu search\\/path relinking algorithm for the job shop problem  

Microsoft Academic Search

The job shop scheduling problem with makespan criterion is valuable from both practical and theoretical points of view. This\\u000a problem has been attacked by most of the well-known meta-heuristic algorithms. Among them, tabu search has emerged as the\\u000a most effective approach. The proposed algorithm takes advantages of both N1 and N6 neighborhoods. N1 neighborhood is used\\u000a as a path relinking

Mohammad Mahdi Nasiri; Farhad Kianfar

121

High-order Path Integral Monte Carlo methods for solving quantum dot problems  

E-print Network

The conventional second-order Path Integral Monte Carlo method is plagued with the sign problem in solving many-fermion systems. This is due to the large number of anti-symmetric free fermion propagators that are needed to extract the ground state wave function at large imaginary time. In this work, we show that optimized fourth-order Path Integral Monte Carlo methods, which use no more than 5 free-fermion propagators, can yield accurate quantum dot energies for up to 20 polarized electrons with the use of the Hamiltonian energy estimator.

Chin, Siu A

2014-01-01

122

Altitude/path-angle transitions in fuel-optimal problems for transport aircraft  

NASA Technical Reports Server (NTRS)

Altitude/path angle transitions to fuel-optimal, energy climb and descent paths are examined for subsonic transport aircraft. These transitions are termed boundary layers in singular perturbation theory, the framework used herein to simplify solutions to the state-Euler system. The energy climb and descent paths provide equilibrium or stationary points for the boundary layer system, and thus for moderate transitions, presumed valid for the class of aircraft considered, the boundary layer system may be linearized. This simplification allows derivation of an explicit solution to the two-point boundary-value, boundary layer problem and, as a consequence, yields a nearly optimal control law, in feedback form, for the transitions. Numerical simulation results using the feedback control law are presented for a Boeing 737 airframe (NASA-ATOPS Vehicle) employing twin JT8D-7-7A engines.

Gracey, C.; Price, D. B.

1983-01-01

123

Algorithm for the Optimal Riding Scheme Problem in Public traffic  

Microsoft Academic Search

A two-stage algorithm is proposed for the optimal riding scheme problem in public traffic querying system. The first stage is to find out the least transfer schemes, in which bus line network model is presented to convert the least transfer scheme problem into the shortest path problem. The second stage is to search out the optimal riding scheme from the

Dong Jiyang; Chen Luzhuo

2005-01-01

124

A General Approximation Technique for Constrained Forest Problems  

Microsoft Academic Search

Abstract.,We present,a general approximation technique for a large class of graph problems.,Our technique mostly applies to problems of covering, at minimum cost, the vertices ofa graph with trees, cycles, or paths satisfying certain requirements. In particular, many basic combinatorial optimization problems fit in this framework, including the shortest path, minimum-cost spanning tree, minimum-weight perfect matching, traveling salesman, and Steiner tree,problems.

Michel X. Goemans; David P. Williamson

1995-01-01

125

Orbital Systolic Algorithms and Array Processors for Solution of the Algebraic Path Problem  

NASA Astrophysics Data System (ADS)

The algebraic path problem (APP) is a general framework which unifies several solution procedures for a number of well-known matrix and graph problems. In this paper, we present a new 3-dimensional (3-D) orbital algebraic path algorithm and corresponding 2-D toroidal array processors which solve the n × n APP in the theoretically minimal number of 3n time-steps. The coordinated time-space scheduling of the computing and data movement in this 3-D algorithm is based on the modular function which preserves the main technological advantages of systolic processing: simplicity, regularity, locality of communications, pipelining, etc. Our design of the 2-D systolic array processors is based on a classical 3-D?2-D space transformation. We have also shown how a data manipulation (copying and alignment) can be effectively implemented in these array processors in a massively-parallel fashion by using a matrix-matrix multiply-add operation.

Sedukhin, Stanislav G.; Miyazaki, Toshiaki; Kuroda, Kenichi

126

Short paths in expander graphs  

SciTech Connect

Graph expansion has proved to be a powerful general tool for analyzing the behavior of routing algorithms and the interconnection networks on which they run. We develop new routing algorithms and structural results for bounded-degree expander graphs. Our results are unified by the fact that they are all based upon, and extend, a body of work asserting that expanders are rich in short, disjoint paths. In particular, our work has consequences for the disjoint paths problem, multicommodify flow, and graph minor containment. We show: (i) A greedy algorithm for approximating the maximum disjoint paths problem achieves a polylogarithmic approximation ratio in bounded-degree expanders. Although our algorithm is both deterministic and on-line, its performance guarantee is an improvement over previous bounds in expanders. (ii) For a multicommodily flow problem with arbitrary demands on a bounded-degree expander, there is a (1 + {epsilon})-optimal solution using only flow paths of polylogarithmic length. It follows that the multicommodity flow algorithm of Awerbuch and Leighton runs in nearly linear time per commodity in expanders. Our analysis is based on establishing the following: given edge weights on an expander G, one can increase some of the weights very slightly so the resulting shortest-path metric is smooth - the min-weight path between any pair of nodes uses a polylogarithmic number of edges. (iii) Every bounded-degree expander on n nodes contains every graph with O(n/log{sup O(1)} n) nodes and edges as a minor.

Kleinberg, J. [MIT, Cambridge, MA (United States); Rubinfeld, R. [Cornell Univ., Ithaca, NY (United States)

1996-12-31

127

Generalized Greedy Algorithm for Shortest Superstring  

E-print Network

Generalized Greedy Algorithm for Shortest Superstring Zhengjun Cao1,2 , Lihua Liu3 , and Olivier University, China Abstract. In the primitive greedy algorithm for shortest superstring, if a pair of strings of optimal set and generalize the primitive greedy algorithm. The generalized algorithm can be reduced

Markowitch, Olivier

128

Path dependence of J in three numerical examples. [J integral in three crack propagation problems  

NASA Technical Reports Server (NTRS)

Three cracked geometries are studied with the aid of a new finite element model. The procedure employs a variable singularity at the crack tip that tracks changes in the material response during the loading process. Two of the problems are tension-loaded center-crack panels and the other is a three-point bend specimen. Results usually agree with other numerical and analytical analyses, except the finding that J is path dependent as a substantial plastic zone develops. Credible J values are obtained near the crack tip and J shows a significant increase as the radius of J path increases over two orders of magnitude. Incremental and deformation theories are identical provided the stresses exhibit proportionality found in the far field stresses but not near the tip.

Karabin, M. E., Jr.; Swedlow, J. L.

1979-01-01

129

Optimal network problem: a branch-and-bound algorithm  

Microsoft Academic Search

The problem of selecting a subset of links so as to minimize the sum of shortest path distances between all pairs of nodes, subject to a budget constraint on total length of links, may be solved by a modification of a branch-and-bound algorithm developed for optimal variable selection problems in statistics. The modified algorithm is described in detail, and encouraging

D E Boyce; A Farhi; R Weischedel

1973-01-01

130

The complexity of the network design problem  

Microsoft Academic Search

In the network design problem we are given a weighted un- We wish to find a subgraph which connects all directed graph. the original vertices and minimizes the sum of the shortest path weights between all vertex pairs, subject to a budget con- straint on the sum of its edge weights. In this note Me estab- lish NP-completeness for the

D. S. Johnson; J. K. Lenstra; A. H. G. Rinnooy Kan

1978-01-01

131

Approximation Algorithms for Shortest Path Motion Planning extended abstract  

E-print Network

in time O(n=#15; + n log n). The data structure is associated with a new variety of Voronoi diagram. Given]. As for approximation algorithms, Papadimitriou [Pap85] has shown that O(n 3 (L + log(n=#15;)) 2 =#15;) time su in this paper is faster than that of [Pap85] when n#15; 3 is large. Also, the number of arithmetic operations

Clarkson, Kenneth L.

132

Continuous-Time Dynamic Shortest Path BRIAN C. DEAN  

E-print Network

and Computer Science on May 21, 1999, in partial fulfillment of the requirements for the degrees of Bachelor of Electrical Engineering and Computer Science in partial fulfillment of the requirements for the degrees of Bachelor of Science in Electrical Engineering and Computer Science and Master of Engineering in Computer

Dean, Brian C.

133

DT-MRI Fiber Tracking: A Shortest Paths Approach  

Microsoft Academic Search

We derive a new fiber tracking algorithm for DT- MRI that parts with the locally 'greedy' paradigm intrinsic to conventional tracking algorithms. We demonstrate the ability to precisely reconstruct a diverse range of fiber trajectori es in authentic and computer-generated DT-MRI data, for which well- known conventional tracking algorithms are shown to fail. Our approach is to pose fiber tracking

Andrew Zalesky

2008-01-01

134

Assignment of Shortest Paths Spanning Trees in Meshes  

Microsoft Academic Search

Summary form only given. Broadcast operations are commonly used in a large variety of applications like: video-conference, television, etc. These applications need high level of QoS. Moreover, in such applications, each receiver has to pay to receive data. In the particular case of broadcast, the price paid by a given receiver is determined by multiple parameters like its location in

Christian Destré; Christian Laforest; Sandrine Vial

2004-01-01

135

Expected Shortest Paths for Landmark-Based Robot Navigation  

E-print Network

of planning reliable landmark- based robot navigation strategies in the presence of significant sensor and constructs their visibility graph. This graph is continually updated during subsequent navigation. All motion can be detected. These estimates are based on the history of all observations made by the robot

Scharstein, Daniel

136

All-Optical Monitoring Path Computation Using Lower Bounds of Required Number of Paths  

NASA Astrophysics Data System (ADS)

To reduce the cost of fault management in all-optical networks, it is a promising approach to detect the degradation of optical signal quality solely at the terminal points of all-optical monitoring paths. The all-optical monitoring paths must be routed so that all single-link failures can be localized using route information of monitoring paths where signal quality degradation is detected. However, route computation for the all-optical monitoring paths that satisfy the above condition is time consuming. This paper proposes a procedure for deriving the lower bounds of the required number of monitoring paths to localize all single-link failures, and proposes an efficient monitoring path computation method based on the derived lower bounds. The proposed method repeats the route computation for the monitoring paths until feasible routes can be found, while the assumed number of monitoring paths increases, starting from the lower bounds. With the proposed method, the minimum number of monitoring paths with the overall shortest routes can be obtained quickly by solving several small-scale integer linear programming problems when the possible terminal nodes of monitoring paths are arbitrarily given. Thus, the proposed method can minimize the required number of monitors for detecting the degradation of signal quality and the total overhead traffic volume transferred through the monitoring paths.

Ogino, Nagao; Nakamura, Hajime

137

Minimum Cost Path Problem for Plug-in Hybrid Electric Vehicles  

E-print Network

gasoline as sources of energy with different cost structures and limitations. We show that this ..... electricity balance equations for those arcs that are on the path. For the non- path arcs, the ...... A column generation approach to the urban transit

2014-07-22

138

Nonequilibrium problems in quantum field theory and Schwinger's Closed Time Path formalism  

E-print Network

We review the closed time path formalism of Schwinger using a path integral approach. We apply this formalism to the study of pair production from strong external fields as well as the time evolution of a nonequilibrium chiral phase transition.

Fred Cooper

1995-04-13

139

Solving the Find-Path Problem by Representing Free Space as Generalized Cones  

Microsoft Academic Search

Free space is represented as a union of (possibly overlapping) generalized cones. Analgorithm is presented which efficiently finds good collision free paths for convex polygonalbodies through space littered with obstacle polygons. The paths are good in the sense thatthe distance of closest approach to an obstacle over the path is usually far from minimalover the class of topologically equivalent collision

Rodney A. Brooks

1982-01-01

140

Maximal Covering Location Problems on networks with regional ...  

E-print Network

Received: date / Accepted: date. Abstract ... which leads to a Mixed Integer Nonlinear Program (MINLP): locations of p facilities are sought .... identification, the shortest-path distance between the nodes in V is readily extended to ...... challenging extension consists of incorporating in the covering problem competition issues, ...

2014-09-18

141

RECENT PROGRESS ON THE BOUNDARY RIGIDITY PROBLEM 1 ...  

E-print Network

the result of [25] that one can solve this problem for generic simple metrics. Moreover ... Therefore, the natural question is whether this is the ... account the shortest paths and it is easy to find counterexamples where ?g does not carry any .... our case we have a non-trivial kernel, and complications due to the presence of a.

142

Path Planning with obstacle avoidance  

NASA Technical Reports Server (NTRS)

The research report here summarizes a solution for two dimensional Path Planning with obstacle avoidance in a workspace with stationary obstacles. The solution finds the shortest path for the end effector of a manipulator arm. The program uses an overhead image of the robot work space and the starting and ending positions of the manipulator arm end effector to generate a search graph which is used to find the shortest path through the work area. The solution was originally implemented in VAX Pascal, but was later converted to VAX C.

Krause, Donald M.

1987-01-01

143

Metric location problems with nonshortest service routes  

Microsoft Academic Search

We study the generalizations of the classical metric location problems in which the route of a service team passes through\\u000a a remote depository containing some components needed for replacement. Generally speaking, in this case the path to the client\\u000a is not shortest and the problem ceases to be metric. We show that the available approximation algorithms for the classical\\u000a metric

A. A. Ageev

2008-01-01

144

Role of self-efficacy and self-concept beliefs in mathematical problem solving: A path analysis  

Microsoft Academic Search

Path analysis was used to test the predictive and mediational role of self-efficacy beliefs in mathematical problem solving. Results revealed that math self-efficacy was more predictive of problem solving than was math self-concept, perceived usefulness of mathematics, prior experi- ence with mathematics, or gender (N = 350). Self-efficacy also mediated the effect of gender and prior experience on self-concept, perceived

Frank Pajares; M. David Miller

1994-01-01

145

Solving the Find-Path Problem by Representing Free Space as Generalized Cones  

E-print Network

Free space is represented as a union of (possibly overlapping) generalized cones. An algorithm is presented which efficiently finds good collision free paths for convex polygonal bodies through space littered with ...

Brooks, Rodney A.

1982-05-01

146

Path Integral Methods in the Su–Schrieffer–Heeger Polaron Problem  

Microsoft Academic Search

I propose a path integral description of the Su–Schrieffer–Heeger Hamiltonian, both in one and two dimensions, after mapping\\u000a the real space model onto the time scale. While the lattice degrees of freedom are classical functions of time and are integrated\\u000a out exactly, the electron particle paths are treated quantum mechanically. The method accounts for the variable range of the\\u000a electronic

Marco Zoli

2007-01-01

147

Approximation of greedy algorithms for Max-ATSP, Maximal Compression, and Shortest Cyclic Cover of Strings  

E-print Network

Approximation of greedy algorithms for Max-ATSP, Maximal Compression, and Shortest Cyclic Cover the approximation of associated greedy algorithms for these four problems, and show they reach a ratio of 1. For these problems, greedy algorithms are easier to implement and often faster than existing approximation algorithms

Paris-Sud XI, Université de

148

On Traveling Salesperson Problems for Dubins’ vehicle: stochastic and dynamic environments  

Microsoft Academic Search

In this paper we propose some novel planning and routing strategies for Dubins’ vehicle, i.e., for a nonholonomic vehicle moving along paths with bounded curvature, without reversing direction. First, we study a stochastic version of the Traveling Salesperson Problem (TSP): given n targets randomly sampled from a uniform distribution in a rectangle, what is the shortest Dubins'tour through the targets

Ketan Savla; Francesco Bullo; Emilio Frazzoli

2005-01-01

149

Sinkhole intrusion in mobile ad hoc networks: The problem and some detection indicators  

Microsoft Academic Search

We analyze the “sinkhole” problem in the context of the Dynamic Source Routing (DSR) protocol for wireless mobile ad hoc networks (MANETs). The sinkhole effect is caused by attempts to draw all network traffic to malicious nodes that broadcast fake shortest path routing information. Two reliable indicators of sinkhole intrusion are proposed and analyzed. We will study how these sinkholes

H. Chris Tseng; Benjamin Jack Culpepper

2005-01-01

150

On Dirac-Coulomb problem in (2+1) dimensional space-time and path integral quantization  

SciTech Connect

The problem of Dirac particle interacting with Coulomb potential in (2+1) dimensions is formulated in the framework of super-symmetric path integrals where the spin degrees of freedom are described by odd Grassmannian variables. The relative propagator is expressed through Cartesian coordinates in a Hamiltonian form by the use of an adequate transformation. The passage to the polar coordinates permitted us to calculate the fixed energy Green's function and to extract bound states and associating wave functions.

Haouat, S. [L.P.Th, Departement de physique, Universite de Jijel, BP 98, Ouled Aissa, Jijel 18000 (Algeria); Chetouani, L. [Departement de Physique, Faculte de Sciences, Universite Mentouri, Route Ain El-Bey, Constantine 25000 (Algeria)

2012-06-15

151

Methodology for Augmenting Existing Paths with Additional Parallel Transects  

SciTech Connect

Visual Sample Plan (VSP) is sample planning software that is used, among other purposes, to plan transect sampling paths to detect areas that were potentially used for munition training. This module was developed for application on a large site where existing roads and trails were to be used as primary sampling paths. Gap areas between these primary paths needed to found and covered with parallel transect paths. These gap areas represent areas on the site that are more than a specified distance from a primary path. These added parallel paths needed to optionally be connected together into a single path—the shortest path possible. The paths also needed to optionally be attached to existing primary paths, again with the shortest possible path. Finally, the process must be repeatable and predictable so that the same inputs (primary paths, specified distance, and path options) will result in the same set of new paths every time. This methodology was developed to meet those specifications.

Wilson, John E.

2013-09-30

152

Path Integral Methods in the Su-Schrieffer-Heeger Polaron Problem  

NASA Astrophysics Data System (ADS)

I propose a path integral description of the Su-Schrieffer-Heeger Hamiltonian, both in one and two dimensions, after mapping the real space model onto the time scale. While the lattice degrees of freedom are classical functions of time and are integrated out exactly, the electron particle paths are treated quantum mechanically. The method accounts for the variable range of the electronic hopping processes. The free energy of the system and its temperature derivatives are computed by summing at any Tover the ensemble of relevant particle paths which mainly contribute to the total partition function. In the low Tregime, the heat capacity over Tratio shows an upturn peculiar to a glass-like behavior. This feature is more sizeable in the square lattice than in the linear chain as the overall hopping potential contribution to the total action is larger in higher dimensionality. The effects of the electron-phonon anharmonic interactions on the phonon subsystem are studied by the path integral cumulant expansion method.

Zoli, Marco

153

Adaptive path A priori path  

E-print Network

of being the shortest: Sigal et al. (1980) Least possible travel time: Miller-hooks & Mahmassani (1998) Maximize the probability of being the shortest: Sigal et al. (1980) Least possible travel time: Miller

Illinois at Chicago, University of

154

Approximation Algorithms and Heuristics for a 2-depot, Heterogeneous Hamiltonian Path Problem  

E-print Network

to optimize the use of resources available such as sensors, fuel etc. These vehicles may differ either in their structural (design and dynamics) or functional (sensing) capabilities. This thesis addresses an important routing problem involving two...

Doshi, Riddhi Rajeev

2011-10-21

155

A sample path approach for solving the ground-holding policy problem in air traffic control  

Microsoft Academic Search

We address the ground-holding problem in air traffic control and propose two techniques that can be used to dynamically solve this problem. The first is motivated by the kanban control policy extensively used in manufacturing systems to reduce the work-in-process inventory, while the second one uses finite perturbation analysis (FPA) for discrete-event systems. We show that the latter leads to

Christos G. Panayiotou; Christos G. Cassandras

1999-01-01

156

Extremal paths on a random Cayley tree  

Microsoft Academic Search

We investigate the statistics of extremal path(s) (both the shortest and the longest) from the root to the bottom of a Cayley tree. The lengths of the edges are assumed to be independent identically distributed random variables drawn from a distribution rho(l). Besides, the number of branches from any node is also random. Exact results are derived for arbitrary distribution

Satya N. Majumdar; P. L. Krapivsky

2000-01-01

157

Neighborhood-privacy protected shortest distance computing in cloud  

Microsoft Academic Search

With the advent of cloud computing, it becomes desirable to utilize cloud computing to efficiently process complex operations on large graphs without compromising their sensitive information. This paper studies shortest distance computing in the cloud, which aims at the following goals: i) preventing outsourced graphs from neighborhood attack, ii) preserving shortest distances in outsourced graphs, iii) minimizing overhead on the

Jun Gao; Jeffrey Xu Yu; Ruoming Jin; Jiashuai Zhou; Tengjiao Wang; Dongqing Yang

2011-01-01

158

Spatial Reasoning Based on Rough Mereology: A Notion of a Robot Formation and Path Planning Problem for Formations of Mobile Autonomous Robots  

Microsoft Academic Search

\\u000a We address in this work problems of path planning for autonomous robots; we extend this topic by introducing a new definition\\u000a of a robot formation and we give a parallel treatment of planning and navigation problems for robot formations. In our investigations\\u000a into problems of multi-robot planning and navigation, we apply rough mereological theory of spatial reasoning to problems\\u000a of

Pawei O'smiaiowski; Lech Polkowski

2010-01-01

159

The Dwarf Novae of Shortest Period  

E-print Network

We present observations of the dwarf novae GW Lib, V844 Her, and DI UMa. Radial velocities of H-alph yield orbital periods of 0.05332 +- 0.00002 d (= 76.78 m) for GW Lib and and 0.054643 +- 0.000007 d (= 78.69 m) for V844 Her. Recently, the orbital period of DI UMa was found to be only 0.054564 +- 0.000002 d (= 78.57 m) by Fried et al. (1999), so these are the three shortest orbital periods among dwarf novae with normal-abundance secondaries. GW Lib has attracted attention as a cataclysmic binary showing apparent ZZ Ceti-type pulsations of the white dwarf primary. Its spectrum shows sharp Balmer emission flanked by strong, broad Balmer absorption, indicating a dominant contribution by white-dwarf light. Analysis of the Balmer absorption profiles is complicated by the unknown residual accretion luminosity and lack of coverage of the high Balmer lines. Our best-fit model atmospheres are marginally hotter than the ZZ Ceti instability strip, in rough agreement with recent ultraviolet results from HST. The spectrum and outburst behavior of GW Lib make it a near twin of WZ Sge, and we estimate it to have a quiescent V absolute magnitude 12. Comparison with archival data reveals proper motion of 65 +- 12 mas/yr. The mean spectrum of V844 Her is typical of SU UMa dwarf novae. We detected superhumps in the 1997 May superoutburst with superhump period = 0.05597 +- 0.00005 d. The spectrum of DI UMa appears normal for a dwarf nova near minimum light. These three dwarf novae have nearly identical short periods but completely dissimilar outburst characteristics. We discuss possible implications.

J. R. Thorstensen; J. O. Patterson; J. Kemp; S. Vennes

2002-06-25

160

A Well-Balanced Path-Integral f-Wave Method for Hyperbolic Problems with Source Terms  

PubMed Central

Systems of hyperbolic partial differential equations with source terms (balance laws) arise in many applications where it is important to compute accurate time-dependent solutions modeling small perturbations of equilibrium solutions in which the source terms balance the hyperbolic part. The f-wave version of the wave-propagation algorithm is one approach, but requires the use of a particular averaged value of the source terms at each cell interface in order to be “well balanced” and exactly maintain steady states. A general approach to choosing this average is developed using the theory of path conservative methods. A scalar advection equation with a decay or growth term is introduced as a model problem for numerical experiments. PMID:24563581

2014-01-01

161

The Role of Youth Problem Behaviors in the Path From Child Abuse and Neglect to Prostitution: A Prospective Examination  

PubMed Central

Behaviors beginning in childhood or adolescence may mediate the relationship between childhood maltreatment and involvement in prostitution. This paper examines five potential mediators: early sexual initiation, running away, juvenile crime, school problems, and early drug use. Using a prospective cohort design, abused and neglected children (ages 0–11) with cases processed during 1967–1971 were matched with non-abused, non-neglected children and followed into young adulthood. Data are from in-person interviews at approximate age 29 and arrest records through 1994. Structural Equation Modeling tested path models. Results indicated that victims of child abuse and neglect were at increased risk for all problem behaviors, except drug use. In the full model, only early sexual initiation remained significant as a mediator in the pathway from child abuse and neglect to prostitution. Findings were generally consistent for physical and sexual abuse and neglect. These findings suggest that interventions to reduce problem behaviors among maltreated children may also reduce their risk for prostitution later in life. PMID:20186260

Wilson, Helen W.; Widom, Cathy Spatz

2009-01-01

162

Extracting optimal paths from roadmaps for motion planning  

Microsoft Academic Search

We present methods for extracting optimal paths from motion planning roadmaps. Our system enables any combination of opti- mization criteria, such as collision detection, kinematic\\/dynamic constraints, or minimum clearance, and relaxed definitions of the goal state, to be used when selecting paths from roadmaps. Our algorithm is an augmented version of Dijkstra's shortest path algorithm which allows edge weights to

Jinsuck Kim; Roger A. Pearce; Nancy M. Amato

2003-01-01

163

From Parent to Child to Parent…: Paths In and Out of Problem Behavior  

PubMed Central

This study used data from the NICHD Study of Early Child Care and Youth Development to examine relations between parenting, self-control and externalizing behavior from early childhood to mid-adolescence (N=956; 49.9% male). Results indicated that maternal sensitivity, parental harshness and productive activity are related to externalizing problems but that patterns of relations change from early childhood to middle childhood to adolescence, with evidence suggesting that externalizing behavior influences parenting more than the reverse from middle childhood onward. Self-control measured during early adolescence partially mediated relations between maternal sensitivity and adolescent-reported externalizing behavior. Parental monitoring during adolescence was also related to externalizing behavior at age 15. Monitoring partially mediated the relation between externalizing behavior in early adolescence and externalizing at age 15. PMID:23135289

Bradley, Robert H.; Corwyn, Robert

2014-01-01

164

On the Method of Shortest Residuals for Unconstrained Optimization  

Microsoft Academic Search

The paper discusses several versions of the method of shortest residuals, a specific variant of the conjugate gradient algorithm,\\u000a first introduced by Lemarchal and Wolfe and discussed by Hestenes in a quadratic case. In the paper we analyze the global\\u000a convergence of the versions considered. Numerical comparison of these versions of the method of shortest residuals and an\\u000a implementation of

R. Pytlak; T. Tarnawski

2007-01-01

165

Information Spread of Emergency Events: Path Searching on Social Networks  

PubMed Central

Emergency has attracted global attentions of government and the public, and it will easily trigger a series of serious social problems if it is not supervised effectively in the dissemination process. In the Internet world, people communicate with each other and form various virtual communities based on social networks, which lead to a complex and fast information spread pattern of emergency events. This paper collects Internet data based on data acquisition and topic detection technology, analyzes the process of information spread on social networks, describes the diffusions and impacts of that information from the perspective of random graph, and finally seeks the key paths through an improved IBF algorithm. Application cases have shown that this algorithm can search the shortest spread paths efficiently, which may help us to guide and control the information dissemination of emergency events on early warning. PMID:24600323

Hu, Hongzhi; Wu, Tunan

2014-01-01

166

Computing the length of the shortest telomere in the nucleus.  

PubMed

The telomere length can either be shortened or elongated by an enzyme called telomerase after each cell division. Interestingly, the shortest telomere is involved in controlling the ability of a cell to divide. Yet, its dynamics remains elusive. We present here a stochastic approach where we model this dynamics using a Markov jump process. We solve the forward Fokker-Planck equation to obtain the steady state distribution and the statistical moments of telomere lengths. We focus specifically on the shortest one and we estimate its length difference with the second shortest telomere. After extracting key parameters such as elongation and shortening dynamics from experimental data, we compute the length of telomeres in yeast and obtain as a possible prediction the minimum concentration of telomerase required to ensure a proper cell division. PMID:24329474

Duc, K Dao; Holcman, D

2013-11-27

167

Minimum distance collision-free path planning for industrial robots with a prismatic joint  

NASA Astrophysics Data System (ADS)

A collision-free path is a path which an industrial robot can physically take while traveling from one location to another in an environment containing obstacles. Usually the obstacles are expanded to compensate for the body width of the robot. For robots with a prismatic joint, which allows only a translational motion along its axis, additional problems created by the long boom are handled by means of pseudoobstacles which are generated by real obstacle's edges and faces. The environment is then modified by the inclusion of pseudoobstacles which contribute to the forbidden regions. This process allows the robot itself again to be represented by a point specifying the location of its end effector in space. An algorithm for determining the shortest distance collision-free path given a sequence of edges to be traversed has been developed for the case of stationary obstacles.

Luh, J. U. S.; Campbell, C. E., Jr.

1984-08-01

168

Extremal paths on a random Cayley tree  

Microsoft Academic Search

We investigate the statistics of extremal path(s) (both the shortest and the\\u000alongest) from the root to the bottom of a Cayley tree. The lengths of the edges\\u000aare assumed to be independent identically distributed random variables drawn\\u000afrom a distribution \\\\rho(l). Besides, the number of branches from any node is\\u000aalso random. Exact results are derived for arbitrary distribution

Satya N. Majumdar; P. L. Krapivsky

2000-01-01

169

Optimal paths for a car that goes both forwards and backwards  

Microsoft Academic Search

The path taken by a car with a given minimum turning radius has a lower bound on its radius of curvature at each point, but the path has cusps if the car shifts into or out of reverse gear. What is the shortest such path a car can travel between two points if its starting and ending directions are specified?

J. A. Reeds; L. A. Shepp

1990-01-01

170

Random Generation of Shortest Path Test Networks Dennis J. Adams-Smith Douglas R. Shier  

E-print Network

, 200 trials Method Mean Deg(r) STD Deg(r) Mean D2(G) STD D2(G) Mean diam Uniform 2.835 1.578 6.855 4 edges, 200 trials Method Mean Deg(r) STD Deg(r) Mean D2(G) STD D2(G) Mean diam Uniform 3.050 1.674 8 nodes, 350 edges, 200 trials Method Mean Deg(r) STD Deg(r) Mean D2(G) STD D2(G) Mean diam Uniform 3

Shier, Douglas R.

171

An Optimal Algorithm for L1 Shortest Paths Among Obstacles in the Plane  

E-print Network

) [Mi3] and O(n log1.5 n) [CKV, Wi]), but before this work the question of obtaining an optimal case of polygonal obstacles). In more recent work, [Mi2, Mi3] have used a continuous Dijkstra algorithm report [Mi3] erroneously claimed that [BG] had proved that g(n) is bounded by O( n log n log log n

Mitchell, Joseph S.B.

172

An E cient Algorithm for Euclidean Shortest Paths Among Polygonal Obstacles in the Plane  

E-print Network

Kapoor Sachindra N. Maheshwari y Joseph S. B. Mitchell z Abstract We give an algorithm to compute, 4, 6, 8, 10, 15, 13, 17, 22, 21, 23], as well as the recent survey chapter of Mitchell 14 of Mitchell 15], which develops the \\continuous Dijkstra" paradigm, and its improvement by Hershberger

Mitchell, Joseph S.B.

173

Drinking and desired self-images: path models of self-image goals, coping motives, heavy-episodic drinking, and alcohol problems.  

PubMed

Coping motives for drinking initiate alcohol-related problems. Interpersonal goals, which powerfully influence affect, could provide a starting point for this relation. Here we tested effects of self-image goals (which aim to construct and defend desired self-views) and compassionate goals (which aim to support others) on heavy-episodic drinking and alcohol-related problems. Undergraduate drinkers (N=258) completed measures of self-image and compassionate goals in academics and friendships, coping and enhancement drinking motives, heavy-episodic drinking, and alcohol-related problems in a cross-sectional design. As predicted, self-image goals, but not compassionate goals, positively related to alcohol-related problems. Path models showed that self-image goals relate to coping motives, but not enhancement motives; coping motives then relate to heavy-episodic drinking, which in turn relate to alcohol-related problems. Self-image goals remained a significant predictor in the final model, which accounted for 34% of the variance in alcohol-related problems. These findings indicate that self-image goals contribute to alcohol-related problems in college students both independently and through coping motives. Interventions can center on reducing self-image goals and their attendant negative affect. PMID:19586150

Moeller, Scott J; Crocker, Jennifer

2009-06-01

174

MINIMUM WEIGHT PATHS TIMEDEPENDENT NETWORKS  

E-print Network

MINIMUM WEIGHT PATHS in TIME­DEPENDENT NETWORKS Ariel Orda Raphael Rom Department of Electrical) ABSTRACT We investigate the minimum weight path problem in networks whose link weights and link delays weight problem always has a solution. We also characterize the structure of an infinite optimal path

Orda, Ariel

175

Penetration distances and their applications to path planning  

NASA Astrophysics Data System (ADS)

The proximal relationship of two objects is of interest for many reasons, e.g., the interference detection problem in robot motion planning. When the mathematical representations of two objects are separated the natural measure of the proximal relationship is the shortest Euclidean distance. However, much less is known when the representations intersect. In this dissertation, one of the main foci is the characterization and computation of measures of the proximal relationship between two intersecting objects. We call these measures penetration distances. A formal exposition of penetration distances and their mathematical properties is given. A penetration distance is defined by the least 'movement' needed to separate the two objects. In general, 'movement' involves both rotation and translation. Several ways of measuring the degree of rotation and translation are introduced and each yields a different definition of penetration distance. In the special case of convex objects, it is shown that the various penetration distances are the same and are determined from translational motion alone. The above-mentioned penetration distances are difficult to compute. An important contribution of this thesis is the development of a new penetration distance based on ideas of 'growing' the mathematical representations of objects. It is called the growth distance and can be computed easily for a pair of convex objects. The mathematical properties and computational aspects of the growth distance are developed at length. For instance, its relationship to the other penetration distances is determined. When two objects are separated, the growth distance is also a measure of separation. An important application of the growth distance is to path finding for robotic systems in the presence of obstacles. Our approach is to convert the path finding problem into an optimization problem. path. &This novel approach involves searching among collision paths. Problems unique to this formulation are discussed. Our approach has several advantages over existing approaches and has performed well in several examples.

Ong, Chong Jin

176

A new efficient optimal path planner for mobile robot based on Invasive Weed Optimization algorithm  

NASA Astrophysics Data System (ADS)

Planning of the shortest/optimal route is essential for efficient operation of autonomous mobile robot or vehicle. In this paper Invasive Weed Optimization (IWO), a new meta-heuristic algorithm, has been implemented for solving the path planning problem of mobile robot in partially or totally unknown environments. This meta-heuristic optimization is based on the colonizing property of weeds. First we have framed an objective function that satisfied the conditions of obstacle avoidance and target seeking behavior of robot in partially or completely unknown environments. Depending upon the value of objective function of each weed in colony, the robot avoids obstacles and proceeds towards destination. The optimal trajectory is generated with this navigational algorithm when robot reaches its destination. The effectiveness, feasibility, and robustness of the proposed algorithm has been demonstrated through series of simulation and experimental results. Finally, it has been found that the developed path planning algorithm can be effectively applied to any kinds of complex situation.

Mohanty, Prases K.; Parhi, Dayal R.

2014-08-01

177

Dispersion of nonlinear group velocity determines shortest envelope solitons  

SciTech Connect

We demonstrate that a generalized nonlinear Schroedinger equation (NSE), which includes dispersion of the intensity-dependent group velocity, allows for exact solitary solutions. In the limit of a long pulse duration, these solutions naturally converge to a fundamental soliton of the standard NSE. In particular, the peak pulse intensity times squared pulse duration is constant. For short durations, this scaling gets violated and a cusp of the envelope may be formed. The limiting singular solution determines then the shortest possible pulse duration and the largest possible peak power. We obtain these parameters explicitly in terms of the parameters of the generalized NSE.

Amiranashvili, Sh.; Bandelow, U.; Akhmediev, N. [Weierstrass Institute for Applied Analysis and Stochastics, Mohrenstrasse 39, D-10117 Berlin (Germany); Optical Sciences Group, Research School of Physics and Engineering, Institute of Advanced Studies, Australian National University, Canberra ACT 0200 (Australia)

2011-10-15

178

Steiner's Problem in Graphs and Its Implications.  

National Technical Information Service (NTIS)

A graph theoretic version of Steiner's problem in plane geometry is described. An approach for solving the problem, related to Melzak's solution to Steiner's problem, is presented. The problems of finding shortest route and minimal spanning tree in graphs...

S. L. Hakimi

1970-01-01

179

The Role of Youth Problem Behaviors in the Path from Child Abuse and Neglect to Prostitution: A Prospective Examination  

ERIC Educational Resources Information Center

Behaviors beginning in childhood or adolescence may mediate the relationship between childhood maltreatment and involvement in prostitution. This paper examines 5 potential mediators: early sexual initiation, running away, juvenile crime, school problems, and early drug use. Using a prospective cohort design, abused and neglected children (ages…

Wilson, Helen W.; Widom, Cathy Spatz

2010-01-01

180

Multiresolution path planning for mobile robots  

Microsoft Academic Search

The problem of automatic collision-free path planning is central to mobile robot applications. An approach to automatic path planning based on a quadtree representation is presented. Hierarchical path-searching methods are introduced, which make use of this multiresolution representation, to speed up the path planning process considerably. The applicability of this approach to mobile robot path planning is discussed.

S. Kambhampati; L. S. Davis

1986-01-01

181

Quartz fabric-based deformation thermometry: examples of its application, relationships to petrology-based PT paths, and potential problems  

NASA Astrophysics Data System (ADS)

The quartz c-axis fabric opening-angle thermometer proposed by Kruhl (1998) offers a potential analytical technique for estimating deformation temperatures in rocks deformed by crystal plastic flow. However, in addition to deformation temperature, opening-angle is also sensitive to other variables such as strain rate, degree of hydrolytic weakening, and 3D strain type. Unless the influence of these individual variables can be quantified, use of fabric opening-angle as a deformation thermometer remains problematic and controversial. Over the last decade close correlations between: a) deformation temperatures indicated by fabric opening-angles and, b) temperatures of metamorphism indicated by trace element and mineral phase equilibria analyses, have been reported from a range of different tectonic settings, thereby arguably giving support to the use of opening-angles as a deformation thermometer. However, it needs to be demonstrated that the similar temperatures estimated by the different methods are related to the same geologic event, and therefore occupy at least a similar position on the PTt path - something that is in practice difficult to achieve for an individual rock sample. In cases where temperatures indicated by opening angles and mineral assemblages are markedly different, these differences could, for example, be explained by penetrative deformation and mineral growth/diffusion occurring at different times. Alternatively, when apparent deformation temperatures based on quartz fabrics are significantly greater than temperatures indicated by synchronous metamorphic mineral assemblages, this might be due to extreme hydrolytic weakening of quartz. We illustrate this talk on the pros and cons of using fabric opening-angles as a deformation thermometer with examples from: a) Aureoles of forcibly emplaced plutons in the White-Inyo Range of eastern California where crystal-plastic deformation and recrystallization was short-lived and synchronous with contact metamorphism. b) Footwall to the South Tibetan Detachment in the Mount Everest area where deformation is demonstrably related to the exhumation stage of a petrologically well-constrained PT path. c) Hanging wall to the Main Central Thrust in the Sutlej Valley of NW India where deformation temperatures inferred from fabric opening angles are closely similar to temperatures of metamorphism indicated by garnet-biotite and oxygen isotope-based thermometry. d) Moine, Ben Hope and Naver thrust sheets of NW Scotland where structurally upwards-increasing deformation temperatures are compared with temperatures indicated by garnet-biotite thermometry. e) Mylonitic quartzites in footwall to Moine thrust at the Stack of Glencoul where hydrolytic weakening may have played an important role in deformation/recrystallization and associated fabric development. f) Thrust sheets in the Appalachians of Vermont that display a complex PTt history due to thrust sheet loading. Kruhl, J.H. 1998. Reply: Prism- and basal-plane parallel subgrain boundaries in quartz: a microstructural geothermobarometer. Journal of Metamorphic Geology, 16, 142-146.

Law, Richard; Waters, Dave; Morgan, Sven; Stahr, Don; Francsis, Matthew; Ashley, Kyle; Kronenberg, Andreas; Thomas, Jay; Mazza, Sarah; Heaverlo, Nicholas

2013-04-01

182

Measurement of the world's shortest X-ray pulses  

NASA Astrophysics Data System (ADS)

One of the essential characteristics of LCLS and other FELs that are currently in operation or still under development is their ultrashort pulse duration, further enhanced just recently by novel schemes of electron bunch compression, which opens up unprecedented opportunities for the detailed investigation of reaction dynamics. However, to date there is no measuring device or concept which is able to determine precisely the pulse duration of the generated X-ray pulses. By overlapping the FEL with a synchronized optical laser in a gas target and measuring the energy of the IR laser dressed photoelectrons ('streaking spectroscopy') we were able to determine the pulse duration of the shortest FEL pulses available at LCLS to be not more than 4 fs. In addition, an analysis of the pulse substructure yields an estimation for the length of the underlying single-spikes in the order of 600 as.

Helml, Wolfram; Maier, Andreas R.; Schweinberger, Wolfgang; Gagnon, Justin; Cavalieri, Adrian L.; Grguras, Ivanka; Radcliffe, Paul; Tschentscher, Thomas; Meyer, Michael; Doumy, Gilles; Roedig, Chris; Bozek, John D.; Coffee, Ryan; Costello, John; Duesterer, Stefan; Kienberger, Reinhard

2011-06-01

183

Mobile transporter path planning  

NASA Technical Reports Server (NTRS)

The use of a genetic algorithm (GA) for solving the mobile transporter path planning problem is investigated. The mobile transporter is a traveling robotic vehicle proposed for the space station which must be able to reach any point of the structure autonomously. Elements of the genetic algorithm are explored in both a theoretical and experimental sense. Specifically, double crossover, greedy crossover, and tournament selection techniques are examined. Additionally, the use of local optimization techniques working in concert with the GA are also explored. Recent developments in genetic algorithm theory are shown to be particularly effective in a path planning problem domain, though problem areas can be cited which require more research.

Baffes, Paul; Wang, Lui

1990-01-01

184

Tornado Paths  

NSDL National Science Digital Library

This website catalogs all the tornado paths in the United States since 1950. The tornado path data is overlaid onto a Google Maps base for easy browsing and manipulation of the map view. Clicking on individual tornados provides the user with information such as its Fujita rating, the amount of damage caused by the tornado, the size of the path that the tornado made, and the length of time the tornado was on the ground.

Samson, Perry; Michigan, University O.

185

Pokemon Cards and the Shortest Common Superstring Mark Stamp Austin E Stamp  

E-print Network

Pok´emon Cards and the Shortest Common Superstring Mark Stamp Austin E Stamp June 12, 2003 Abstract Evidence is presented that certain sequences of Pok´emon cards are determined by selecting consecutive (SCS), i.e., the shortest string that contains each of the Pok´emon card sequences as a consecutive

Stamp, Mark

186

Inter-Domain Redundancy Path Computation Methods Based on PCE  

NASA Astrophysics Data System (ADS)

This paper evaluates three inter-domain redundancy path computation methods based on PCE (Path Computation Element). Some inter-domain paths carry traffic that must be assured of high quality and high reliability transfer such as telephony over IP and premium virtual private networks (VPNs). It is, therefore, important to set inter-domain redundancy paths, i. e. primary and secondary paths. The first scheme utilizes an existing protocol and the basic PCE implementation. It does not need any extension or modification. In the second scheme, PCEs make a virtual shortest path tree (VSPT) considering the candidates of primary paths that have corresponding secondary paths. The goal is to reduce blocking probability; corresponding secondary paths may be found more often after a primary path is decided; no protocol extension is necessary. In the third scheme, PCEs make a VSPT considering all candidates of primary and secondary paths. Blocking probability is further decreased since all possible candidates are located, and the sum of primary and secondary path cost is reduced by choosing the pair with minimum cost among all path pairs. Numerical evaluations show that the second and third schemes offer only a few percent reduction in blocking probability and path pair total cost, while the overheads imposed by protocol revision and increase of the amount of calculation and information to be exchanged are large. This suggests that the first scheme, the most basic and simple one, is the best choice.

Hayashi, Rie; Oki, Eiji; Shiomoto, Kohei

187

[27] H. Rohnert, A dynamization of the all pairs least cost path problem, Proc. 2nd Annual Symp. on Theoretical Aspects of Computer Science Lecture Notes in Computer Science,  

E-print Network

[27] H. Rohnert, A dynamization of the all pairs least cost path problem, Proc. 2nd Annual Symp algorithms, CBMS­NSF Regional Confer­ ence Series in Applied Mathematics, vol. 44, SIAM, 1983. [32] R. E. on Programming Language Design and Implementation, 1988, 115--124. 24 #12; [13] G. N. Frederickson, Data

188

Path Pascal  

NASA Technical Reports Server (NTRS)

Path Pascal is high-level experimental programming language based on PASCAL, which incorporates extensions for systems and real-time programming. Pascal is extended to treat real-time concurrent systems.

Campbell, R. H.; Kolstad, R. B.; Holle, D. F.; Miller, T. J.; Krause, P.; Horton, K.; Macke, T.

1983-01-01

189

Path Layout in ATM Networks  

Microsoft Academic Search

This paper surveys recent results in the area of virtual path layout in ATM networks. We focus on the one-to-all (or broadcast) and the all-to-all problems. We present a model for theoretical studies of these layouts, which amounts to covering the network with simple paths, under various constraints. The constraints are the hop count (the number of paths traversed between

Shmuel Zaks

1997-01-01

190

Sampling diffusive transition paths  

SciTech Connect

We address the problem of sampling double-ended diffusive paths. The ensemble of paths is expressed using a symmetric version of the Onsager-Machlup formula, which only requires evaluation of the force field and which, upon direct time discretization, gives rise to a symmetric integrator that is accurate to second order. Efficiently sampling this ensemble requires avoiding the well-known stiffness problem associated with sampling infinitesimal Brownian increments of the path, as well as a different type of stiffness associated with sampling the coarse features of long paths. The fine-features sampling stiffness is eliminated with the use of the fast sampling algorithm (FSA), and the coarse-feature sampling stiffness is avoided by introducing the sliding and sampling (S&S) algorithm. A key feature of the S&S algorithm is that it enables massively parallel computers to sample diffusive trajectories that are long in time. We use the algorithm to sample the transition path ensemble for the structural interconversion of the 38-atom Lennard-Jones cluster at low temperature.

F. Miller III, Thomas; Predescu, Cristian

2006-10-12

191

Analysis of Crossing Path Crashes.  

National Technical Information Service (NTIS)

This report defines the problem of crossing path crashes in the United States. This crash type involves one moving vehicle that cuts across the path of another when their initial approach comes from either lateral or opposite directions and they typically...

W. G. Najm, J. D. Smith, D. L. Smith

2001-01-01

192

An approach for the Steiner problem in directed graphs  

Microsoft Academic Search

We present a scheme to solve the Steiner problem in directed graphs using a heuristic method to obtain upper bounds and thek shortest arborescences algorithm to compute lower bounds. We propose to combine these ideas in an enumerative algorithm. Computational results are presented for both thek shortest arborescences algorithm and the heuristic method, including reduction tests for the problem.

Nelson Maculan; Paulo Souza; Alfredo Candia Vejar

1991-01-01

193

Challenging of path planning algorithms for autonomous robot in known environment  

NASA Astrophysics Data System (ADS)

Most of the mobile robot path planning is estimated to reach its predetermined aim through the shortest path and avoiding the obstacles. This paper is a survey on path planning algorithms of various current research and existing system of Unmanned Ground Vehicles (UGV) where their challenging issues to be intelligent autonomous robot. The focuses are some short reviews on individual papers for UGV in the known environment. Methods and algorithms in path planning for the autonomous robot had been discussed. From the reviews, we obtained that the algorithms proposed are appropriate for some cases such as single or multiple obstacles, static or movement obstacle and optimal shortest path. This paper also describes some pros and cons for every reviewed paper toward algorithms improvement for further work.

Farah, R. N.; Irwan, N.; Zuraida, Raja Lailatul; Shaharum, Umairah; Hanafi@Omar, Hafiz Mohd

2014-06-01

194

Bicriteria network design problems  

SciTech Connect

We study several bicriteria network design problems phrased as follows: given an undirected graph and two minimization objectives with a budget specified on one objective, find a subgraph satisfying certain connectivity requirements that minimizes the second objective subject to the budget on the first. Define an ({alpha}, {beta})-approximation algorithm as a polynomial-time algorithm that produces a solution in which the first objective value is at most {alpha} times the budget, and the second objective value is at most {alpha} times the minimum cost of a network obeying the budget oil the first objective. We, present the first approximation algorithms for bicriteria problems obtained by combining classical minimization objectives such as the total edge cost of the network, the diameter of the network and a weighted generalization of the maximum degree of any node in the network. We first develop some formalism related to bicriteria problems that leads to a clean way to state bicriteria approximation results. Secondly, when the two objectives are similar but only differ based on the cost function under which they are computed we present a general parametric search technique that yields approximation algorithms by reducing the problem to one of minimizing a single objective of the same type. Thirdly, we present an O(log n, log n)-approximation algorithm for finding a diameter-constrained minimum cost spanning tree of an undirected graph on n nodes generalizing the notion of shallow, light trees and light approximate shortest-path trees that have been studied before. Finally, for the class of treewidth-bounded graphs, we provide pseudopolynomial-time algorithms for a number of bicriteria problems using dynamic programming. These pseudopolynomial-time algorithms can be converted to fully polynomial-time approximation schemes using a scaling technique.

Marathe, M.V.; Ravi, R.; Sundaram, R.; Ravi, S.S.; Rosenkrantz, D.J.; Hunt, H.B. III

1994-12-31

195

Path Abstraction for Combined Navigation and Animation  

NASA Astrophysics Data System (ADS)

Natural motion of virtual characters is crucial in games and simulations. The quality of such motion strongly depends on the path the character walks and the animation of the character locomotion. Therefore, much work has been done on path planning and character animation. However, the combination of both fields has received less attention. Combining path planning and motion synthesis introduces several problems. A path generated by a path planner is often a simplification of the character movement. This raises the question which (body) part of the character should follow the path generated by the path planner and to what extent it should closely follow the path. We will show that enforcing the pelvis to follow the path will lead to unnatural animations and that our proposed solution, using path abstractions, generates significantly better animations.

van Basten, Ben J. H.; Egges, Arjan

196

Term Paths  

NSDL National Science Digital Library

Students follow several pathways using anatomical directions on a simulated "body" produced from a copy of a school building's fire evacuation plan. The main hallways are designated as major blood vessels and the various areas of the school, the head, chest, abdomen, etc. Students complete several pathways using anatomical terms as directions. For example, one of my paths begins, "Ex- ot-, ad- superior, ecto- derm-, peri-frontal, circum- rhino-, " which loosely means, exit the ear, go to the superior region, outside the skin, around the frontal region, around the nose. At the end of each path I leave a clue that lets me know the students actually made it. The combined clues form a sentence.

BEGIN:VCARD VERSION:2.1 FN:Cynthia Ann Radle N:Ann Radle;Cynthia ORG:McCullough High School REV:2005-04-13 END:VCARD

1995-06-30

197

On r-locating-dominating sets in paths  

Microsoft Academic Search

Assume that G=(V,E) is a simple undirected graph, and C is a nonempty subset of V. For every v?V, we define Ir(v)={u?C?dG(u,v)?r}, where dG(u,v) denotes the number of edges on any shortest path between u and v. If the sets Ir(v) for v??C are pairwise different, and none of them is the empty set, we say that C is an

Iiro S. Honkala

2009-01-01

198

Route choices of transport bicyclists: a comparison of actually used and shortest routes  

PubMed Central

Background Despite evidence that environmental features are related to physical activity, the association between the built environment and bicycling for transportation remains a poorly investigated subject. The aim of the study was to improve our understanding of the environmental determinants of bicycling as a means of transportation in urban European settings by comparing the spatial differences between the routes actually used by bicyclists and the shortest possible routes. Methods In the present study we examined differences in the currently used and the shortest possible bicycling routes, with respect to distance, type of street, and environmental characteristics, in the city of Graz, Austria. The objective measurement methods of a Global Positioning System (GPS) and a Geographic Information System (GIS) were used. Results Bicycling routes actually used were significantly longer than the shortest possible routes. Furthermore, the following attributes were also significantly different between the used route compared to the shortest possible route: Bicyclists often used bicycle lanes and pathways, flat and green areas, and they rarely used main roads and crossings. Conclusion The results of the study support our hypothesis that bicyclists prefer bicycle pathways and lanes instead of the shortest possible routes. This underlines the importance of a well-developed bicycling infrastructure in urban communities. PMID:24597725

2014-01-01

199

Better approximation bounds for the network and Euclidean Steiner tree problems  

E-print Network

Better approximation bounds for the network and Euclidean Steiner tree problems Alexander Zelikovsky \\Lambda Abstract The network and Euclidean Steiner tree problems require a shortest tree spanning of T . Network Steiner Problem (NSP). Given G and S, find the shortest Steiner tree (also called the Steiner

Zelikovsky, Alexander

200

The parameterized Steiner problem and the singular Plateau problem via energy  

E-print Network

The parameterized Steiner problem and the singular Plateau problem via energy July 13, 2005 Chikako by grant NSF DMS-0450083 and the second by DMS-0071862. Abstract The Steiner problem is the problem of the Steiner problem of finding the shortest network connecting given points in space and the problem

Mese, Chikako

201

Ray Paths  

NSDL National Science Digital Library

For the next two exercises, we will break up into groups of four. Each member of the group will represent one of four waves leaving the source: direct wave, ground roll, reflected wave, and head wave. All four "waves" will leave the source at the same time and travel at a particular speed and path as directed by the instructor. ALL students will record the arrival time of each "wave" at each geophone until all 12 geophones have been used. Plot arrival time versus distance for each "wave". Do any of the time versus distance curves fit a straight line? Do any of them not fit a straight line? Explain why they do or don't fit a straight line. Uses online and/or real-time data Has minimal/no quantitative component

202

Simulation-efficient shortest probability intervals Ying Liu, Andrew Gelman, and Tian Zheng  

E-print Network

, these can be noisy (that is, have a high Monte Carlo error). We derive an optimal weighting strategy using Monte Carlo error than empirical shortest intervals. We implement the new method in an R package (SPIn such as the nor- mal and gamma but are more difficult to compute from simulations. We would like to go back

Gelman, Andrew

203

The Length of the Shortest Telomere as the Major Determinant of the Onset of Replicative Senescence  

PubMed Central

The absence of telomerase in many eukaryotes leads to the gradual shortening of telomeres, causing replicative senescence. In humans, this proliferation barrier constitutes a tumor suppressor mechanism and may be involved in cellular aging. Yet the heterogeneity of the senescence phenotype has hindered the understanding of its onset. Here we investigated the regulation of telomere length and its control of senescence heterogeneity. Because the length of the shortest telomeres can potentially regulate cell fate, we focus on their dynamics in Saccharomyces cerevisiae. We developed a stochastic model of telomere dynamics built on the protein-counting model, where an increasing number of protein-bound telomeric repeats shift telomeres into a nonextendable state by telomerase. Using numerical simulations, we found that the length of the shortest telomere is well separated from the length of the others, suggesting a prominent role in triggering senescence. We evaluated this possibility using classical genetic analyses of tetrads, combined with a quantitative and sensitive assay for senescence. In contrast to mitosis of telomerase-negative cells, which produces two cells with identical senescence onset, meiosis is able to segregate a determinant of senescence onset among the telomerase-negative spores. The frequency of such segregation is in accordance with this determinant being the length of the shortest telomere. Taken together, our results substantiate the length of the shortest telomere as being the key genetic marker determining senescence onset in S. cerevisiae. PMID:23733785

Xu, Zhou; Duc, Khanh Dao; Holcman, David; Teixeira, Maria Teresa

2013-01-01

204

Multi-Cluster Interleaving on Paths and Cycles Anxiao (Andrew) Jiang, Member, IEEE, Jehoshua Bruck, Fellow, IEEE  

E-print Network

-Cluster Interleaving (MCI), a generalization of traditional interleaving problems. MCI problems for paths and cycles the second interleaving problem for paths that are asymptotically as long as the longest path on which an MCI

Bruck, Jehoshua (Shuki)

205

Optical Path Cross-Connect System Scale Evaluation Using Path Accommodation Design for Restricted Wavelength Multiplexing  

Microsoft Academic Search

The optical path (OP) technology, which employs both wavelength-division multiplexing and wavelength routing, will be the key to enhanced network integrity and an ubiquitous broadband integrated services digital network (B-ISDN) in the future. To construct the OP network, path accommodation design that can solve simultaneously the problems of path routing and wavelength assignment must be established. Since optical wavelengths are

Naohide Nagatsu; Satoru Okamoto; Ken-ichi Sato

1996-01-01

206

Multicriteria adaptive paths in stochastic, time-varying networks  

Microsoft Academic Search

In this paper, exact algorithms are proposed for addressing multicriteria adaptive path problems, where arc attributes are stochastic and time-varying. Adaptive paths comprise a set of path strategies that enable the traveler to select a direction among all Pareto-optimal solutions at each node in response to knowledge of the arrival time at the intermediate nodes. Such paths can be viewed

Sathaporn Opasanon; Elise Miller-hooks

2006-01-01

207

PATHS groundwater hydrologic model  

SciTech Connect

A preliminary evaluation capability for two-dimensional groundwater pollution problems was developed as part of the Transport Modeling Task for the Waste Isolation Safety Assessment Program (WISAP). Our approach was to use the data limitations as a guide in setting the level of modeling detail. PATHS Groundwater Hydrologic Model is the first level (simplest) idealized hybrid analytical/numerical model for two-dimensional, saturated groundwater flow and single component transport; homogeneous geology. This document consists of the description of the PATHS groundwater hydrologic model. The preliminary evaluation capability prepared for WISAP, including the enhancements that were made because of the authors' experience using the earlier capability is described. Appendixes A through D supplement the report as follows: complete derivations of the background equations are provided in Appendix A. Appendix B is a comprehensive set of instructions for users of PATHS. It is written for users who have little or no experience with computers. Appendix C is for the programmer. It contains information on how input parameters are passed between programs in the system. It also contains program listings and test case listing. Appendix D is a definition of terms.

Nelson, R.W.; Schur, J.A.

1980-04-01

208

Real-Time Disk Scheduling Based on Urgent Group and Shortest Seek Time First  

Microsoft Academic Search

Real-time applications dealing with a large amount of data often require timely service of disk I\\/O requests. This paper presents a new real-time disk scheduling method called Urgent Group and Shortest Seek Time First(UG-SSTF) for soft real-time systems. According to this algorithm, the urgent group is formed by identifying urgent requests awaiting the disk service in a queue, among which

Kitae Hwang; Heonshik Shin

1993-01-01

209

Minimum-Risk Path Finding by an Adaptive Amoebal Network Toshiyuki Nakagaki,1,2,* Makoto Iima,1  

E-print Network

is formed that connects the food sources through the shortest route. When the light- avoiding organism risk as the experimentally measurable rate of light-avoiding movement, the minimum-risk path maintaining sufficient connectivity to permit intracellular communication. Such behavior in a primitive

Showalter, Kenneth

210

Mechanics of the crack path formation  

NASA Technical Reports Server (NTRS)

A detailed analysis of experimentally obtained curvilinear crack path trajectories formed in a heterogeneous stress field is presented. Experimental crack path trajectories were used as data for numerical simulations, recreating the actual stress field governing the development of the crack path. Thus, the current theories of crack curving and kinking could be examined by comparing them with the actual stress field parameters as they develop along the experimentally observed crack path. The experimental curvilinear crack path trajectories were formed in the tensile specimens with a hole positioned in the vicinity of a potential crack path. The numerical simulation, based on the solution of equivalent boundary value problems with the possible perturbations of the crack path, is presented here.

Rubinstein, Asher A.

1989-01-01

211

Mechanics of the crack path formation  

NASA Technical Reports Server (NTRS)

A detailed analysis of experimentally obtained curvilinear crack path trajectories formed in a heterogeneous stress field is presented. Experimental crack path trajectories were used as data for the numerical simulations, recreating the actual stress field governing the development of the crack path. Thus, the current theories of crack curving and kinking could be examined by comparing them with the actual stress field parameters as they develop along the experimentally observed crack path. The experimental curvilinear crack path trajectories were formed in the tensile specimens with a hole positioned in the vicinity of a potential crack path. The numerical simulation, based on the solution of equivalent boundary value problems with the possible perturbations of the crack path, is presented.

Rubinstein, Asher A.

1991-01-01

212

A hybrid genetic algorithm for the weight setting problem in OSPF\\/ISIS routing  

Microsoft Academic Search

Intradomain traffic engineering aims to make more effi- cient use of network resources within an autonomous system. Interior Gateway Protocols such as OSPF (Open Shortest Path First) and IS-IS (Intermediate System- Intermediate System) are commonly used to select the paths along which traffic is routed within an autonomous system. These routing protocols direct traffic based on link weights assigned by

Luciana S. Buriol; Mauricio G. C. Resende; Celso C. Ribeiro; Mikkel Thorup

2005-01-01

213

Average path length for Sierpinski pentagon  

E-print Network

In this paper,we investigate diameter and average path length(APL) of Sierpinski pentagon based on its recursive construction and self-similar structure.We find that the diameter of Sierpinski pentagon is just the shortest path lengths between two nodes of generation 0. Deriving and solving the linear homogenous recurrence relation the diameter satisfies, we obtain rigorous solution for the diameter. We also obtain approximate solution for APL of Sierpinski pentagon, both diameter and APL grow approximately as a power-law function of network order $N(t)$, with the exponent equals $\\frac{\\ln(1+\\sqrt{3})}{\\ln(5)}$. Although the solution for APL is approximate,it is trusted because we have calculated all items of APL accurately except for the compensation($\\Delta_{t}$) of total distances between non-adjacent branches($\\Lambda_t^{1,3}$), which is obtained approximately by least-squares curve fitting. The compensation($\\Delta_{t}$) is only a small part of total distances between non-adjacent branches($\\Lambda_t^{1,3}$) and has little effect on APL. Further more,using the data obtained by iteration to test the fitting results, we find the relative error for $\\Delta_{t}$ is less than $10^{-7}$, hence the approximate solution for average path length is almost accurate.

Junhao Peng; Guoai Xu

2011-12-21

214

Maximum Flux Transition Paths of Conformational Change  

PubMed Central

Given two metastable states A and B of a biomolecular system, the problem is to calculate the likely paths of the transition from A to B. Such a calculation is more informative and more manageable if done for a reduced set of collective variables chosen so that paths cluster in collective variable space. The computational task becomes that of computing the “center” of such a cluster. A good way to define the center employs the concept of a committor, whose value at a point in collective variable space is the probability that a trajectory at that point will reach B before A. The committor “foliates” the transition region into a set of isocommittors. The maximum flux transition path is defined as a path that crosses each isocommittor at a point which (locally) has the highest crossing rate of distinct reactive trajectories. This path is based on the same principle as the minimum resistance path of Berkowitz et al (1983), but it has two advantages: (i) the path is invariant with respect to a change of coordinates in collective variable space and (ii) the differential equations that define the path are simpler. It is argued that such a path is nearer to an ideal path than others that have been proposed with the possible exception of the finite-temperature string method path. To make the calculation tractable, three approximations are introduced, yielding a path that is the solution of a nonsingular two-point boundary-value problem. For such a problem, one can construct a simple and robust algorithm. One such algorithm and its performance is discussed. PMID:20890401

Zhao, Ruijun; Shen, Juanfang; Skeel, Robert D.

2010-01-01

215

Gas-path seal technology  

NASA Technical Reports Server (NTRS)

Improved gas-path seals are needed for better fuel economy, longer performance retention, and lower maintenance, particularly in advanced, high-performance gas turbine engines. Problems encountered in gas-path sealing are described, as well as new blade-tip sealing approaches for high-pressure compressors and turbines. These include a lubricant coating for conventional, porous-metal, rub-strip materials used in compressors. An improved hot-press metal alloy shows promise to increase the operating surface temperatures of high-pressure-turbine, blade-tip seals to 1450 K (2150 F). Three ceramic seal materials are also described that have the potential to allow much higher gas-path surface operating temperatures than are possible with metal systems.

Zuk, J.

1976-01-01

216

Robot Path Integration in Manufacturing Processes: Genetic Algorithm Versus Ant Colony Optimization  

Microsoft Academic Search

Tool path planning for automated manufacturing processes is a computationally complex task. This paper addresses the problem of tool path integration in the context of spray-forming processes. Tool paths for geometry-complicated parts are generated by partitioning them into individual freeform surfaces, generating the paths for each partition, and then, finally, interconnecting the paths from the different patches so as to

Tewolde S. Tewolde; Weihua Sheng

2008-01-01

217

Identifying codes and locating-dominating sets on paths and cycles  

Microsoft Academic Search

Let $G=(V,E)$ be a graph and let $r\\\\ge 1$ be an integer. For a set $D \\\\subseteq V$, define $N_r[x] = \\\\{y \\\\in V: d(x, y) \\\\leq r\\\\}$ and $D_r(x) = N_r[x] \\\\cap D$, where $d(x,y)$ denotes the number of edges in any shortest path between $x$ and $y$. $D$ is known as an $r$-identifying code ($r$-locating-dominating set, respectively), if

Chunxia Chen; Changhong Lu; Zhengke Miao

2009-01-01

218

DISCUSS: Critical Path Analysis  

NSDL National Science Digital Library

This module, by Barrie Baker and Neville Hunt of Coventry University, introduces critical path analysis and addresses the following topics: Networks, Critical paths, Floats, Activity-on-node (AON) networks. Excel spreadsheets are used to provide examples and exercises.

Baker, Barrie; Hunt, Neville

2009-04-23

219

Extremal paths on a random cayley tree  

PubMed

We investigate the statistics of extremal path(s) (both the shortest and the longest) from the root to the bottom of a Cayley tree. The lengths of the edges are assumed to be independent identically distributed random variables drawn from a distribution rho(l). Besides, the number of branches from any node is also random. Exact results are derived for arbitrary distribution rho(l). In particular, for the binary 0,1 distribution rho(l)=pdelta(l,1)+(1-p)delta(l, 0), we show that as p increases, the minimal length undergoes an unbinding transition from a "localized" phase to a "moving" phase at the critical value, p=p(c)=1-b(-1), where b is the average branch number of the tree. As the height n of the tree increases, the minimal length saturates to a finite constant in the localized phase (pp(c)) where the velocity v(min)(p) is determined via a front selection mechanism. At p=p(c), the minimal length grows with n in an extremely slow double-logarithmic fashion. The length of the maximal path, on the other hand, increases linearly as v(max)(p)n for all p. The maximal and minimal velocities satisfy a general duality relation, v(min)(p)+v(max)(1-p)=1, which is also valid for directed paths on finite-dimensional lattices. PMID:11138046

Majumdar; Krapivsky

2000-12-01

220

Path planning for UAVs  

Microsoft Academic Search

In this paper, a two step path-planning algorithm for UAVs is proposed. The algorithm generates a stealthy path through a set of enemy radar sites of known location, and provides an intuitive way to trade-off stealth versus path length. In the first step, a suboptimal rough-cut path is generated through the radar sites by constructing and searching a graph based

S. A. Bortoff; E. Hartford

2000-01-01

221

Average path length for Sierpinski pentagon  

E-print Network

In this paper,we investigate diameter and average path length(APL) of Sierpinski pentagon based on its recursive construction and self-similar structure.We find that the diameter of Sierpinski pentagon is just the shortest path lengths between two nodes of generation 0. Deriving and solving the linear homogenous recurrence relation the diameter satisfies, we obtain rigorous solution for the diameter. We also obtain approximate solution for APL of Sierpinski pentagon, both diameter and APL grow approximately as a power-law function of network order $N(t)$, with the exponent equals $\\frac{\\ln(1+\\sqrt{3})}{\\ln(5)}$. Although the solution for APL is approximate,it is trusted because we have calculated all items of APL accurately except for the compensation($\\Delta_{t}$) of total distances between non-adjacent branches($\\Lambda_t^{1,3}$), which is obtained approximately by least-squares curve fitting. The compensation($\\Delta_{t}$) is only a small part of total distances between non-adjacent branches($\\Lambda_t^{1...

Peng, Junhao

2011-01-01

222

Empirical Sampling of Path Sets for Local Area Motion Planning  

Microsoft Academic Search

Summary. We consider the problem of online planning for a mobile robot among obstacles, where it is impractical to test all possible future paths. One approach is for the runtime task to test some subset of the possible paths and select a path that does not collide with obstacles while advancing the robot toward its goal. Performance depends on the

Ross A. Knepper; Matthew T. Mason

2008-01-01

223

Hard paths, soft paths or no paths? Cross-cultural perceptions of water solutions  

E-print Network

Hard paths, soft paths or no paths? Cross-cultural perceptions of water solutions Drew Blasco1 to the availability of clean, safe water. In this study we examined cross cultural preferences for soft path vs. hard conceptualize water solutions (hard paths, soft paths, no paths) cross-culturally? 2) What role does development

Hall, Sharon J.

224

A global path planning approach for redundant manipulators  

NASA Technical Reports Server (NTRS)

A new approach for global path planning of redundant manipulators is proposed. It poses the path planning problem as a finite time nonlinear control problem. The solution is found by a Newton-Raphson type algorithm. This technique is capable of handling various goal task descriptions as well as incorporating both joint and task space constraints. The algorithm has shown promising preliminary results in planning joint path sequences for 3R and 4R planar robots to meet Cartesian tip tracking and goal endpoint planning. It is robust with respect to local path planning problems such as singularity considerations and local minimum problems. Repetitive joint path solutions for cyclic end-effector tasks are also generated. Eventual goals of this work include implementation on full spatial robots, as well as provision of an interface for supervisory input to aid in path planning for more complex problems.

Seereeram, Sanjeev; Wen, J.

1993-01-01

225

Walden's Paths - Ensemble Edition  

NSDL National Science Digital Library

WaldenÂs Paths enables users of digital document collections (e.g. the Web) to exploit these documents by reusing them for previously unintended audiences in an academic setting. Authors of paths (usually educators) overlay a linear, directed meta-structure over the Web documents and recontextualize these by adding explanatory text to achieve their curricular goals. Paths do not modifythe structure or content of the Web resources that they include. The creation of a path over pre-organized content (e.g. books, Web pages) to reorganize and associate related information serves to facilitate easy retrieval and communication. WaldenÂs Paths displays the information that the path points to in conjunction with the textual annotations added by the author of the path.

2011-01-04

226

Path Relaxation: Path Planning for a Mobile Robot  

Microsoft Academic Search

Path Relaxation is a method of planning safe paths around obstacles for mobile robots. It works in two steps: a global grid starch that finds a rough path, followed by a local relaxation step that adjusts each node on the path to lower the overall path cost. The representation used by Path Relaxation allows an explicit tradeoff among length of

Charles E. Thorpe; L. Matthies

1984-01-01

227

Breakdown of the Coherent State Path Integral: Two Simple Examples  

SciTech Connect

We show how the time-continuous coherent state path integral breaks down for both the single-site Bose-Hubbard model and the spin-path integral. Specifically, when the Hamiltonian is quadratic in a generator of the algebra used to construct coherent states, the path integral fails to produce correct results following from an operator approach. As suggested by previous authors, we note that the problems do not arise in the time-discretized version of the path integral.

Wilson, Justin H.; Galitski, Victor [Joint Quantum Institute and Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742-4111 (United States)

2011-03-18

228

A novel approach to the prediction of musculotendon paths.  

PubMed

One of the most important aspects of the modelling of musculoskeletal systems is the determination of muscle moment arms which are dependent upon the paths of the muscles. These paths are often required to wrap around passive structures that can be modelled as simple geometric shapes. A novel technique for the prediction of the paths of muscles modelled as strings when wrapping around smooth analytical surfaces is presented. The theory of geodesics is used to calculate the shortest path of the string on the surface and a smoothness constraint is used to determine the correct solutions for the string path between insertions. The application of the technique to tapered cylinders and ellipsoids is presented as an extension of previous work on right-circular cylinders and spheres. The technique is assessed with reference to a particular biomechanical scenario; string lengths and moment arms are calculated and compared with alternative approximate methods. This illustrates the potential of the technique to provide more accurate muscle moment arm predictions. PMID:18335718

Marsden, S P; Swailes, D C

2008-01-01

229

Combinatorially Simple Pickup and Delivery Paths  

Microsoft Academic Search

Pickup and delivery problems discussed in the literature of ten allow for only particularly sim- ple solutions in terms of the sequence of visited locations. We study the very simplest pickup and delivery paths which are concatenations of short patter ns visiting one or two requests. This restricted variant, still NP -hard, is close to the traveling salesman problem with

Marco E. Lubbecke

2002-01-01

230

Path Integrals and Hamiltonians  

NASA Astrophysics Data System (ADS)

1. Synopsis; Part I. Fundamental Principles: 2. The mathematical structure of quantum mechanics; 3. Operators; 4. The Feynman path integral; 5. Hamiltonian mechanics; 6. Path integral quantization; Part II. Stochastic Processes: 7. Stochastic systems; Part III. Discrete Degrees of Freedom: 8. Ising model; 9. Ising model: magnetic field; 10. Fermions; Part IV. Quadratic Path Integrals: 11. Simple harmonic oscillators; 12. Gaussian path integrals; Part V. Action with Acceleration: 13. Acceleration Lagrangian; 14. Pseudo-Hermitian Euclidean Hamiltonian; 15. Non-Hermitian Hamiltonian: Jordan blocks; 16. The quartic potential: instantons; 17. Compact degrees of freedom; Index.

Baaquie, Belal E.

2014-03-01

231

Path-integral formulation of ion heating  

SciTech Connect

A description of the generation and evolution of ionospheric oxygen-ion conic distributions by electromagnetic ion-cyclotron-resonance heating is formulated in terms of a path integral. All of the relevant physics is contained in this path integral, which may be used to calculate measurable properties of the conic distribution. Although the presentation is applied to this specific ionospheric context, the treatment may be generalized to treat other diffusion problems of interest.

Crew, G.B.; Chang, T.

1986-11-01

232

Iron(III) catalyzed direct synthesis of cis-2,7-disubstituted oxepanes. The shortest total synthesis of (+)-isolaurepan.  

PubMed

Prins cyclization of bis-homoallylic alcohols with aldehydes catalyzed by iron(III) salts shows excellent cis selectivity and yields to form 2,7-disubstituted oxepanes. The iron(III) is able to catalyze this process with unactivated olefins. This cyclization was used as the key step in the shortest total synthesis of (+)-isolaurepan. PMID:23167915

Purino, Martín A; Ramírez, Miguel A; Daranas, Antonio H; Martín, Víctor S; Padrón, Juan I

2012-12-01

233

A nonholonomic approach to isoparallel problems and some applications  

Microsoft Academic Search

Isoparallel problems are a class of optimal control problems on principal fibre bundles endowed with a connection and a Riemannian metric on the base space. These problems consist of finding the shortest curve on the base among those with a given parallel transport operator. It has been shown that when the structure group of the principal bundle admits a bi-invariant

HernáN Cendra; SebastiáN J. Ferraro

2006-01-01

234

New Approximation Algorithms for the Steiner Tree Problems  

E-print Network

New Approximation Algorithms for the Steiner Tree Problems Marek Karpinski \\Lambda Alexander Zelikovsky y Abstract The Steiner tree problem asks for the shortest tree connecting a given set of terminal points in a metric space. We design new approximation algorithms for the Steiner tree problems using

Karpinski, Marek

235

The Essential of Steiner's Problem in normed planes  

E-print Network

The Essential of Steiner's Problem in normed planes of "Shortest Connectivity" has a long and convoluted history. Usually, the problem is known as Steiner are given which use Steiner's Problem or one of its relatives as an application, as a subproblem

Schürmann, Michael

236

Bootlegging and path dependency  

Microsoft Academic Search

This paper confirms the importance of path dependency in the accumulation of firm-specific technological competencies. It shows that firms are guided by the selective logic of path dependency in their innovation processes, even if management has no part in decisions to invest in a new business idea. The research focuses on the output of bootlegging, defined as research in which

Peter Augsdorfer

2005-01-01

237

The SunPath  

NSDL National Science Digital Library

This site features an interactive applet that models the Sun's path from a geocentric view. It calculates and visualizes the position of the Sun based on latitude and time, and allows students to simulate the Sun's position and path for an hour, a day, a month or a year.

University, Australian N.

238

A Path Algorithm for Constrained Estimation  

PubMed Central

Many least-square problems involve affine equality and inequality constraints. Although there are a variety of methods for solving such problems, most statisticians find constrained estimation challenging. The current article proposes a new path-following algorithm for quadratic programming that replaces hard constraints by what are called exact penalties. Similar penalties arise in l1 regularization in model selection. In the regularization setting, penalties encapsulate prior knowledge, and penalized parameter estimates represent a trade-off between the observed data and the prior knowledge. Classical penalty methods of optimization, such as the quadratic penalty method, solve a sequence of unconstrained problems that put greater and greater stress on meeting the constraints. In the limit as the penalty constant tends to ?, one recovers the constrained solution. In the exact penalty method, squared penalties!are replaced by absolute value penalties, and the solution is recovered for a finite value of the penalty constant. The exact path-following method starts at the unconstrained solution and follows the solution path as the penalty constant increases. In the process, the solution path hits, slides along, and exits from the various constraints. Path following in Lasso penalized regression, in contrast, starts with a large value of the penalty constant and works its way downward. In both settings, inspection of the entire solution path is revealing. Just as with the Lasso and generalized Lasso, it is possible to plot the effective degrees of freedom along the solution path. For a strictly convex quadratic program, the exact penalty algorithm can be framed entirely in terms of the sweep operator of regression analysis. A few well-chosen examples illustrate the mechanics and potential of path following. This article has supplementary materials available online. PMID:24039382

Zhou, Hua; Lange, Kenneth

2013-01-01

239

Constrained Optimization Path Following of Wheeled Robots  

E-print Network

Abstract. A smooth-primitive constrained-optimization-based path-tracking algorithm for mobile robots that compensates for rough terrain, predictable vehicle dynamics, and vehicle mobility constraints has been developed, implemented, and tested on the DARPA LAGR platform. Traditional methods for the geometric path following control problem involve trying to meet position constraints at fixed or velocity dependent look-ahead distances using arcs. We have reformulated the problem as an optimal control problem, using a trajectory generator that can meet arbitrary boundary state constraints. The goal state along the target path is determined dynamically by minimizing a utility function based on corrective trajectory feasibility and cross-track error. A set of field tests compared the proposed method to an implementation of the pure pursuit algorithm and showed that the smooth corrective trajectory constrained optimization approach exhibited higher performance than pure pursuit by achieving rough four times lower average cross-track error and two times lower heading error. 1

Thomas M. Howard; Alonzo Kelly

2006-01-01

240

On condition numbers and the distance to the nearest ill-posed problem  

Microsoft Academic Search

Summary The condition number of a problem measures the sensitivity of the answer to small changes in the input. We call the problem ill-posed if its condition number is infinite. It turns out that for many problems of numerical analysis, there is a simple relationship between the condition number of a problem and the shortest distance from that problem to

James Weldon Demmel

1987-01-01

241

Beyond Steiner's Problem: A VLSI Oriented Generalization  

Microsoft Academic Search

We consider a generalized version of Steiner's problem in graphs, motivated by the wire routing phase in physical VLSI design: given a connected, undirected distance graph with groups of required vertices and Steiner vertices, find a shortest connected subgraph containing at least one required vertex of each group. We propose two efficient approximation algorithms computing different approximate solutions in time

Gabriele Reich I; Peter Widmayer

1989-01-01

242

The Rectilinear Steiner Arborescence Problem  

Microsoft Academic Search

The Rectilinear Steiner Arborescence (RSA) problem is “Given a setN ofn nodes lying in the first quadrant of E2, find the shortest directed tree rooted at the origin, containing all nodes inN, and composed solely of horizontal and vertical arcs oriented only from left to right or from bottom to top.” In this paper\\u000a we investigate many fundamental properties of

Sailesh K. Rao; P. Sadayappan; Frank K. Hwang; Peter W. Shor

1992-01-01

243

Tortuous path chemical preconcentrator  

DOEpatents

A non-planar, tortuous path chemical preconcentrator has a high internal surface area having a heatable sorptive coating that can be used to selectively collect and concentrate one or more chemical species of interest from a fluid stream that can be rapidly released as a concentrated plug into an analytical or microanalytical chain for separation and detection. The non-planar chemical preconcentrator comprises a sorptive support structure having a tortuous flow path. The tortuosity provides repeated twists, turns, and bends to the flow, thereby increasing the interfacial contact between sample fluid stream and the sorptive material. The tortuous path also provides more opportunities for desorption and readsorption of volatile species. Further, the thermal efficiency of the tortuous path chemical preconcentrator is comparable or superior to the prior non-planar chemical preconcentrator. Finally, the tortuosity can be varied in different directions to optimize flow rates during the adsorption and desorption phases of operation of the preconcentrator.

Manginell, Ronald P. (Albuquerque, NM); Lewis, Patrick R. (Albuquerque, NM); Adkins, Douglas R. (Albuquerque, NM); Wheeler, David R. (Albuquerque, NM); Simonson, Robert J. (Cedar Crest, NM)

2010-09-21

244

Accretion disc mapping of the shortest period eclipsing binary SDSS J0926+36  

NASA Astrophysics Data System (ADS)

AM CVn stars are ultracompact binaries (P_{orb}< 65 min) where a hydrogen-deficient low-mass, degenerate donor star overfills its Roche lobe and transfers matter to a companion white dwarf via an accretion disc. SDSS J0926+36 is currently the only eclipsing AM CVn star and also the shortest period eclipsing binary known. Its light curve displays deep (˜ 2 mag) eclipses every 28.3 min, which last for ˜ 2 min, as well as ˜ 2 mag amplitude outbursts every ˜ 100-200 d. Superhumps were seen in its quiescent light curve in some occasions, probably as a reminiscence of a (in some cases undetected) previous outburst. Its eclipsing nature allows a unique opportunity to disentangle the emission from several different light sources, and to map the surface brightness distribution of its hydrogen-deficient accretion disc with the aid of maximum entropy eclipse mapping techniques. Here we report the eclipse mapping analysis of optical light curves of SDSS J0926+36, collected with the 2.4 m Liverpool Robotic Telescope, covering 20 orbits of the binary over 5 nights of observations between 2012 February and March. The object was in quiescence at all runs. Our data show no evidence of superhumps nor of orbital modulation due to anisotropic emission from a bright spot at disc rim. Accordingly, the average out-of-eclipse flux level is consistent with that of the superhump-subtracted previous light curves. We combined all runs to obtain an orbital light curve of improved S/N. The corresponding eclipse map shows a compact source at disc centre (T_{b}simeq 17000 K), a faint, cool accretion disc (˜ 4000 K) plus enhanced emission along the gas stream (˜ 6000 K) beyond the impact point at the outer disc rim, suggesting the occurrence of gas stream overflow at that epoch.

Schlindwein, W.; Baptista, R.

2014-10-01

245

NLTT 5306: the shortest period detached white dwarf+brown dwarf binary  

NASA Astrophysics Data System (ADS)

We have spectroscopically confirmed a brown dwarf mass companion to the hydrogen atmosphere white dwarf NLTT 5306. The white dwarf's atmospheric parameters were measured using the Sloan Digital Sky Survey and X-shooter spectroscopy as Teff = 7756 ± 35 K and log(g) = 7.68 ± 0.08, giving a mass for the primary of MWD = 0.44 ± 0.04 M? at a distance of 71 ± 4 pc with a cooling age of 710 ± 50 Myr. The existence of the brown dwarf secondary was confirmed through the near-infrared arm of the X-shooter data and a spectral type of dL4-dL7 was estimated using standard spectral indices. Combined radial velocity measurements from the Sloan Digital Sky Survey, X-shooter and the Hobby-Eberly Telescope's High Resolution Spectrograph of the white dwarf give a minimum mass of 56 ± 3 MJup for the secondary, confirming the substellar nature. The period of the binary was measured as 101.88 ± 0.02 min using both the radial velocity data and i'-band variability detected with the Isaac Newton Telescope. This variability indicates `day' side heating of the brown dwarf companion. We also observe H? emission in our higher resolution data in phase with the white dwarf radial velocity, indicating that this system is in a low level of accretion, most likely via a stellar wind. This system represents the shortest period white dwarf+brown dwarf binary and the secondary has survived a stage of common envelope evolution, much like its longer period counterpart, WD 0137-349. Both systems likely represent bona fide progenitors of cataclysmic variables with a low-mass white dwarf and a brown dwarf donor.

Steele, P. R.; Saglia, R. P.; Burleigh, M. R.; Marsh, T. R.; Gänsicke, B. T.; Lawrie, K.; Cappetta, M.; Girven, J.; Napiwotzki, R.

2013-03-01

246

AH Cam: A metal-rich RR Lyrae star with the shortest known Blazhko period  

NASA Technical Reports Server (NTRS)

Analysis of 746 new V-band observations of the RR Lyrae star AH Cam obtained during 1989 - 1992 clearly show that its light curve cannot be described by a single period. In fact, at first glance, the Fourier spectrum of the photometry resembles that of a double-mode pulsator, with peaks at a fundamental period of 0.3686 d and an apparent secondary period of 0.2628 d. Nevertheless, the dual-mode solution is a poor fit to the data. Rather, we believe that AH Cam is a single-mode RR Lyrae star undergoing the Blazhko effect: periodic modulation of the amplitude and shape of its light curve. What was originally taken to be the period of the second mode is instead the 1-cycle/d alias of a modulation sidelobe in the Fourier spectrum. The data are well described by a modulation period of just under 11 d, which is the shortest Blazhko period reported to date in the literature and confirms the earlier suggestion by Goranskii. A low-resolution spectrum of AH Cam indicates that it is relatively metal rich, with delta-S less than or = 2. Its high metallicity and short modulation period may provide a critical test of at least one theory for the Blazhko effect. Moskalik's internal resonance model makes specific predictions of the growth rate of the fundamental model vs fundamental period. AH Cam falls outside the regime of other known Blazhko variables and resonance model predictions, but these are appropriate for metal-poor RR Lyrae stars. If the theory matches the behavior of AH Cam for a metal-rich stellar model, this would bolster the resonance hypothesis.

Smith, Horace A.; Matthews, Jaymie M.; Lee, Kevin M.; Williams, Jeffrey; Silbermann, N. A.; Bolte, Michael

1994-01-01

247

Ad-Hoc Analysis of Synop Observations to enhance shortest-term wind power predictions  

NASA Astrophysics Data System (ADS)

Shortest term wind power predictions with forecast horizons less than 12 hours benefit from observed data. So comparison between Synop observations and numerical weather predictions can serve as assessment of the available forecasts. This ad-hoc analysis depends very much on the observed data whose spatial distribution is very patchy in some areas. A powerful interpolation method helps to create a correct representation of the observed fields. The Kriging method finds a correlation function which describes the variation of the spatial field best. An unknown data point is estimated by weighted observation points, taking distance and clustering effects into account. We use mean sea level pressure data measured at Synop and ship stations in Europe and the Atlantic to assess the quality of the predicted mean sea level pressure from Numerical Weather Prediction models. Those models serve as base of wind power predictions and influence the prediction error considerably. If this error can be estimated, a rating of different Numerical Weather Prediction Models which are taken into consideration can follow. The choice of the area that represents the area of interest in terms of prediction errors depend on the moving direction of the low pressure systems. First calculations show that errors of the ad-hoc analysis are in good agreement with the ECMWF analysis. The evaluation of the ad-hoc analysis in an area over Great Britain/North Sea and the comparison with available ECMWF forecasts over Germany reveals phase shifts for some time intervals. This supports the assumption of moving prediction errors along low pressure systems.

Busch-Saleck, N.; von Bremen, L.

2010-09-01

248

Partial charge transfer in the shortest possible metallofullerene peapod, la@c82 ?[11]cycloparaphenylene.  

PubMed

[11]Cycloparaphenylene ([11]CPP) selectively encapsulates La@C82 to form the shortest possible metallofullerene-carbon nanotube (CNT) peapod, La@C82 ?[11]CPP, in solution and in the solid state. Complexation in solution was affected by the polarity of the solvent and was 16?times stronger in the polar solvent nitrobenzene than in the nonpolar solvent 1,2-dichlorobenzene. Electrochemical analysis revealed that the redox potentials of La@C82 were negatively shifted upon complexation from free La@C82 . Furthermore, the shifts in the redox potentials increased with polarity of the solvent. These results are consistent with formation of a polar complex, (La@C82 )(?-) ?[11]CPP(?+) , by partial electron transfer from [11]CPP to La@C82 . This is the first observation of such an electronic interaction between a fullerene pea and CPP pod. Theoretical calculations also supported partial charge transfer (0.07) from [11]CPP to La@C82 . The structure of the complex was unambiguously determined by X-ray crystallographic analysis, which showed the La atom inside the C82 near the periphery of the [11]CPP. The dipole moment of La@C82 was projected toward the CPP pea, nearly perpendicular to the CPP axis. The position of the La atom and the direction of the dipole moment in La@C82 ?[11]CPP were significantly different from those observed in La@C82 ?CNT, thus indicating a difference in orientation of the fullerene peas between fullerene-CPP and fullerene-CNT peapods. These results highlight the importance of pea-pea interactions in determining the orientation of the metallofullerene in metallofullerene-CNT peapods. PMID:25224281

Iwamoto, Takahiro; Slanina, Zdenek; Mizorogi, Naomi; Guo, Jingdong; Akasaka, Takeshi; Nagase, Shigeru; Takaya, Hikaru; Yasuda, Nobuhiro; Kato, Tatsuhisa; Yamago, Shigeru

2014-10-27

249

The reweighted path ensemble.  

PubMed

We introduce a reweighting scheme for the path ensembles in the transition interface sampling framework. The reweighting allows for the analysis of free energy landscapes and committor projections in any collective variable space. We illustrate the reweighting scheme on a two dimensional potential with a nonlinear reaction coordinate and on a more realistic simulation of the Trp-cage folding process. We suggest that the reweighted path ensemble can be used to optimize possible nonlinear reaction coordinates. PMID:21054008

Rogal, Jutta; Lechner, Wolfgang; Juraszek, Jarek; Ensing, Bernd; Bolhuis, Peter G

2010-11-01

250

Method of path coefficients: a trademark of Sewall Wright.  

PubMed

This address is a tribute to a pioneer of population genetics, including human population genetics. The unique methodology employed by Sewall Wright in many genetic problems is the method of path coefficients. This essay traces the historical landmarks in the development of the path method and then shows how some of the conventional statistical results can be converted into expressions involving path coefficients. The construction of a path diagram to represent such statistical results is explained in terms of examples. In the last section an example of applying the path method to the problem of genetic linkage in a random mating population is given. I hope that, despite the ending of the Sewall Wright era, the path method will continue to serve the scientific world. PMID:2004740

Li, C C

1991-02-01

251

Intricacies of quantum computational paths  

NASA Astrophysics Data System (ADS)

Graph search represents a cornerstone in computer science and is employed when the best algorithmic solution to a problem consists in performing an analysis of a search space representing computational possibilities. Typically, in such problems it is crucial to determine the sequence of transitions performed that led to certain states. In this work we discuss how to adapt generic quantum search procedures, namely quantum random walks and Grover's algorithm, in order to obtain computational paths. We then compare these approaches in the context of tree graphs. In addition we demonstrate that in a best-case scenario both approaches differ, performance-wise, by a constant factor speedup of two, whilst still providing a quadratic speedup relatively to their classical equivalents. We discuss the different scenarios that are better suited for each approach.

Tarrataca, Luís; Wichert, Andreas

2013-02-01

252

APPLICATIONS OF LASERS AND OTHER PROBLEMS IN QUANTUM ELECTRONICS: Amplitude-time structure of the complete profile of the signal formed by backscattering along a combined atmosphere-hydrosphere path of exciting laser radiation  

Microsoft Academic Search

A study was made of the structure of the complete profile of a backscattering signal representing the scattering in the atmosphere, in a transition layer, and directly in the hydrosphere. Spatial and temporal anomalies were found in the backscattering signal and these were attributed to the changes in properties along the laser radiation path. Bibtex entry for this abstract Preferred

S. A. Zenchenko; I. A. Malevich; V. I. Pranovich; A. A. Svetlykh; M. V. Svintilov; Georgii B. Sochilin; B. I. Utenkov

1987-01-01

253

Tool path integration for spray forming processes using a genetic algorithm  

Microsoft Academic Search

Spray forming is a new manufacturing process. The automated tool planning for this process is a nontrivial problem, especially for geometry-complicated parts consisting of multiple freeform surfaces. We have developed a tool path planning system which can automatically generate optimized tool plans. This paper focuses on the path integration problem, or how to connect the paths from different surface patches

Weihua Sheng; Girma Tewolde; Heping Chen

2005-01-01

254

New Approximation Algorithms for the Steiner Tree Problems  

Microsoft Academic Search

The Steiner tree problem asks for the shortest tree connecting a given set of terminal points ina metric space. We design new approximation algorithms for the Steiner tree problems usinga novel technique of choosing Steiner points in dependence on the possible deviation from theoptimal solutions. We achieve the best up to now approximation ratios of 1.644 in arbitrarymetric and 1.267

Marek Karpinski; Alexander Zelikovsky

1995-01-01

255

Air Path Estimation on Diesel HCCI Engine  

Microsoft Academic Search

In this paper, we address the problem of air path variables estimation for an HCCI engine. Two observers are pro- posed. Both rely on physical assumptions on the com- bustion, but use different sensors. After proving conver- gence in the two cases, we carry out comparisons based on simulation results. We stress the impact of two particu- lar additional sensors

J. Chauvin; N. Petit; P. Rouchon; C. Vigild; Ford Forschungszentrum Aachen

2006-01-01

256

Planning smooth paths for mobile robots  

Microsoft Academic Search

The authors consider the problem of planning paths for a robot which has a minimum turning radius. This is a first step towards accurately modeling a robot with the kinematics of a car. The technique used is to define a set of canonical trajectories which satisfy the nonholonomic constraints imposed. A configuration space can be constructed for these trajectories in

P. Jacobs; J. Canny

1989-01-01

257

Flux Control in Networks of Diffusion Paths  

SciTech Connect

A class of optimization problems in networks of intersecting diffusion domains of a special form of thin paths has been considered. The system of equations describing stationary solutions is equivalent to an electrical circuit built of intersecting conductors. The solution of an optimization problem has been obtained and extended to the analogous electrical circuit. The interest in this network arises from, among other applications, an application to wave-particle diffusion through resonant interactions in plasma.

A. I. Zhmoginov and N. J. Fisch

2009-07-08

258

Progress in Horizontal and Slant-Path Imaging Using Specking Imaging.  

National Technical Information Service (NTIS)

The difficulty in terrestrial imaging over long horizontal or slant paths is that atmospheric aberrations and distortions reduce the resolution and contrast in images recorded at high resolution. This paper will describe the problem of horizontal-path ima...

C. J. Carrano

2003-01-01

259

A Simulation Method for Calculating the Path Travel Time in Dynamic Transportation Network  

E-print Network

The calculation of path travel times is an essential component for the dynamic traffic assignment and equilibrium problems. This paper presents a simulation method for calculating actual path travel times for the traffic ...

Lin, G.C.

260

Birds tended to display greater predator anxiety in mesic parks (Fig. 3), but birds in Palomino Park, a xeric park with low shrub density, cats, and no coyotes exhibited the greatest predator anxiety, i.e. shortest open foraging durations and shortest dis  

E-print Network

Results Birds tended to display greater predator anxiety in mesic parks (Fig. 3), but birds anxiety, i.e. shortest open foraging durations and shortest distances from cover (not shown). As predicted) significantly correlated with foraging anxiety. Sample sizes were too small to distinguish between effects

Hall, Sharon J.

261

Optimal path planning for unmanned air vehicles with kinematic and tactical constraints  

Microsoft Academic Search

We consider a class of 2D optimal path-planning problems for unmanned air vehicles (UAVs) with kinematic and tactical constraints. The existence of an optimal path class satisfying the UAV kinematic constraints and vector calculus are exploited to reduce this class of optimal path-planning problems to a parameter optimization problem. Illustrative tactical constraints arising in target touring and obstacle avoidance problems

Guang Yang; Vikram Kapila

2002-01-01

262

Multi-Vehicle Path Planning in Dynamically Changing Environments  

E-print Network

Multi-Vehicle Path Planning in Dynamically Changing Environments Ali Ahmadzadeh1, Nader Motee2, Ali such as rendezvous and area coverage. I. INTRODUCTION The problem of path planning for a vehicle in a dynam- ically multi-vehicle system in presence of moving obstacles. The objective is to find multiple fixed length

Pappas, George J.

263

Toward Efficient Trajectory Planning: The Path-Velocity Decomposition  

Microsoft Academic Search

We present a novel approach to solving the trajectory plan ning problem (TPP) in time-varying environments. The es sence of our approach lies in a heuristic but natural decom position of TPP into two subproblems: (1) planning a path to avoid collision with static obstacles and (2) planning the velocity along the path to avoid collision with moving obsta cles.

Kamal Kant; Steven W. Zucker

1986-01-01

264

Minimal entropy probability paths between genome families.  

PubMed

We develop a metric for probability distributions with applications to biological sequence analysis. Our distance metric is obtained by minimizing a functional defined on the class of paths over probability measures on N categories. The underlying mathematical theory is connected to a constrained problem in the calculus of variations. The solution presented is a numerical solution, which approximates the true solution in a set of cases called rich paths where none of the components of the path is zero. The functional to be minimized is motivated by entropy considerations, reflecting the idea that nature might efficiently carry out mutations of genome sequences in such a way that the increase in entropy involved in transformation is as small as possible. We characterize sequences by frequency profiles or probability vectors, in the case of DNA where N is 4 and the components of the probability vector are the frequency of occurrence of each of the bases A, C, G and T. Given two probability vectors a and b, we define a distance function based as the infimum of path integrals of the entropy function H( p) over all admissible paths p(t), 0 < or = t< or =1, with p(t) a probability vector such that p(0)=a and p(1)=b. If the probability paths p(t) are parameterized as y(s) in terms of arc length s and the optimal path is smooth with arc length L, then smooth and "rich" optimal probability paths may be numerically estimated by a hybrid method of iterating Newton's method on solutions of a two point boundary value problem, with unknown distance L between the abscissas, for the Euler-Lagrange equations resulting from a multiplier rule for the constrained optimization problem together with linear regression to improve the arc length estimate L. Matlab code for these numerical methods is provided which works only for "rich" optimal probability vectors. These methods motivate a definition of an elementary distance function which is easier and faster to calculate, works on non-rich vectors, does not involve variational theory and does not involve differential equations, but is a better approximation of the minimal entropy path distance than the distance //b-a//(2). We compute minimal entropy distance matrices for examples of DNA myostatin genes and amino-acid sequences across several species. Output tree dendograms for our minimal entropy metric are compared with dendograms based on BLAST and BLAST identity scores. PMID:15133624

Ahlbrandt, Calvin; Benson, Gary; Casey, William

2004-05-01

265

Show me the (shortest) way to go home Foams, soap films and minimization  

E-print Network

not be straight. Wire Frames foams@aber.ac.uk #12;Soap films solve the Steiner problem: Given n cities on a plain a 120º foams@aber.ac.uk Steiner problem #12;Four cities at the corners of a square of side a: L = 22a 2.83a L = 3a 60° a foams@aber.ac.uk Steiner problem L = (1+3)a 2.73a. #12;A Transport Strategy

Cox, Simon

266

Path planning for everday robotics with SANDROS  

SciTech Connect

We discuss the integration of the SANDROS path planner into a general robot simulation and control package with the inclusion of a fast geometry engine for distance calculations. This creates a single system that allows the path to be computed, simulated, and then executed on the physical robot. The architecture and usage procedures are presented. Also, we present examples of its usage in typical environments found in our organization. The resulting system is as easy to use as the general simulation system (which is in common use here) and is fast enough (example problems are solved in seconds) to be used interactively on an everyday basis.

Watterberg, P.; Xavier, P. [Sandia National Labs., Albuquerque, NM (United States); Hwang, Y. [Korea Inst. of Science and Technology, Seoul (Korea, Republic of)

1997-02-01

267

Identifying codes and locating–dominating sets on paths and cycles  

Microsoft Academic Search

Let G=(V,E) be a graph and let r?1 be an integer. For a set D?V, define Nr[x]={y?V:d(x,y)?r} and Dr(x)=Nr[x]?D, where d(x,y) denotes the number of edges in any shortest path between x and y. D is known as an r-identifying code (r-locating-dominating set, respectively), if for all vertices x?V (x?V?D, respectively), Dr(x) are all nonempty and different. Roberts and Roberts

Chunxia Chen; Changhong Lu; Zhengke Miao

2011-01-01

268

Gas Path Seal.  

National Technical Information Service (NTIS)

A gas path seal suitable for use with a turbine engine or compressor is described. A shroud wearable or abradable by the abrasion of the rotor blades of the turbine or compressor shrouds the rotor bades. A compliant backing surrounds the shroud. The backi...

R. C. Bill, R. D. Johnson

1979-01-01

269

DNA Computing Hamiltonian path  

E-print Network

2014 DNA DNA #12;DNA Computing · Feynman · Adleman · DNASIMD · ... · · · · · DNADNA #12;DNA · DNA · · · · DNA · · #12;2000 2005 2010 1995 Hamiltonian path DNA tweezers DNA tile DNA origami DNA box Sierpinski DNA tile self assembly DNA logic gates Whiplash PCR DNA automaton DNA spider MAYA

Hagiya, Masami

270

World nuclear energy paths  

Microsoft Academic Search

In examing the world nuclear energy paths, the following assumptions were adopted: the world economy will grow somewhat more slowly than in the past, leading to reductions in electricity demand growth rates; national and international political impediments to the deployment of nuclear power will gradually disappear over the next few years; further development of nuclear power will proceed steadily, without

T. J. Connolly; U. Hansen; W. Jaek; K. H. Beckurts

1979-01-01

271

Off the Beaten Path.  

ERIC Educational Resources Information Center

Describes "Off the Beaten Path", a program that takes at-risk students out of the traditional classroom and puts them into a camping atmosphere in order to increase academic achievement, improve self-esteem, and promote better social skills. (WRM)

Grimm, Karen

1999-01-01

272

An Unplanned Path  

ERIC Educational Resources Information Center

The authors elucidate what they saw as three important challenges to overcome along the path to becoming elementary school mathematics teacher leaders: marginal interest in math, low self-confidence, and teaching in isolation. To illustrate how these challenges were mitigated, they focus on the stories of two elementary school teachers--Laura and…

McGarvey, Lynn M.; Sterenberg, Gladys Y.; Long, Julie S.

2013-01-01

273

Horizontal and Slant-Path Surveillance with Speckle Imaging.  

National Technical Information Service (NTIS)

A fundamental problem in providing high-quality surveillance images recorded over long horizontal or slant paths is the blurring caused by atmospheric turbulence, which reduces both the resolution and contrast. The objective of the work reported here is t...

C. J. Carrano, J. M. Brase

2002-01-01

274

Path planning of Autonomous Underwater Vehicles for adaptive sampling  

E-print Network

This thesis develops new methods for path planning of Autonomous Underwater Vehicles for adaptive sampling. The problem is approached in an optimization framework and two methods are developed to solve it based on Mixed ...

Yilmaz, Namik Kemal, 1975-

2006-01-01

275

Human-Automation Path Planning Optimization and Decision Support  

E-print Network

Path planning is a problem encountered in multiple domains, including unmanned vehicle control, air traffic control, and future exploration missions to the Moon and Mars. Due to the voluminous and complex nature of the ...

Cummings, M.L.

2011-01-01

276

Quickest Paths for Different Network Router Mechanisms  

SciTech Connect

The quickest path problem deals with the transmission of a message of size {sigma} from a source to a destination with the minimum end-to-end delay over a network with bandwidth and delay constraints on the links. The authors consider four basic modes and two variations for the message delivery at the nodes reflecting the mechanisms such as circuit switching, Internet protocol, and their combinations. For each of the first three modes, they present O(m{sup 2} + mn log n) time algorithm to compute the quickest path for a given message size {sigma}. For the last mode, the quickest path can be computed in O(m + n log n) time.

Rao, N.S.V.; Grimmell, W.C.; Radhakrishnan, S.; Bang, Y.C.

2000-06-01

277

The Königsberg Bridge Problem  

NSDL National Science Digital Library

This article, written for middle grades students, relates the history of the famous Konigsberg Bridge problem and introduces the idea of networks and paths that do not retrace themselves. The article concludes with a path the student must work out.

2011-01-01

278

Path analysis in genetic epidemiology: a critique.  

PubMed Central

Path analysis, a form of general linear structural equation models, is used in studies of human genetics data to discern genetic, environmental, and cultural factors contributing to familial resemblance. It postulates a set of linear and additive parametric relationships between phenotypes and genetic and cultural variables and then essentially uses the assumption of multivariate normality to estimate and perform tests of hypothesis on parameters. Such an approach has been advocated for the analysis of genetic epidemiological data by D. C. Rao, N. Morton, C. R. Cloninger, L. J. Eaves, and W. E. Nance, among others. This paper reviews and evaluates the formulations, assumptions, methodological procedures, interpretations, and applications of path analysis. To give perspective, we begin with a discussion of path analysis as it occurs in the form of general linear causal models in several disciplines of the social sciences. Several specific path analysis models applied to lipoprotein concentrations, IQ, and twin data are then reviewed to keep the presentation self-contained. The bulk of the critical discussion that follows is directed toward the following four facets of path analysis: (1) coherence of model specification and applicability to data; (2) plausibility of modeling assumptions; (3) interpretability and utility of the model; and (4) validity of statistical and computational procedures. In the concluding section, a brief discussion of the problem of appropriate model selection is presented, followed by a number of suggestions of essentially model-free alternative methods of use in the treatment of complex structured data such as occurs in genetic epidemiology. PMID:6349335

Karlin, S; Cameron, E C; Chakraborty, R

1983-01-01

279

Perfect discretization of reparametrization invariant path integrals  

SciTech Connect

To obtain a well-defined path integral one often employs discretizations. In the case of gravity and reparametrization-invariant systems, the latter of which we consider here as a toy example, discretizations generically break diffeomorphism and reparametrization symmetry, respectively. This has severe implications, as these symmetries determine the dynamics of the corresponding system. Indeed we will show that a discretized path integral with reparametrization-invariance is necessarily also discretization independent and therefore uniquely determined by the corresponding continuum quantum mechanical propagator. We use this insight to develop an iterative method for constructing such a discretized path integral, akin to a Wilsonian RG flow. This allows us to address the problem of discretization ambiguities and of an anomaly-free path integral measure for such systems. The latter is needed to obtain a path integral, that can act as a projector onto the physical states, satisfying the quantum constraints. We will comment on implications for discrete quantum gravity models, such as spin foams.

Bahr, Benjamin [DAMTP, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); MPI for Gravitational Physics, Am Muehlenberg 1, D-14476 Potsdam (Germany); Dittrich, Bianca; Steinhaus, Sebastian [MPI for Gravitational Physics, Am Muehlenberg 1, D-14476 Potsdam (Germany)

2011-05-15

280

Stabilizing Intelligent Route Control: Randomized Path Monitoring, Randomized Path  

E-print Network

Stabilizing Intelligent Route Control: Randomized Path Monitoring, Randomized Path Switching or History-aware Path Switching? Alexandre Fonte1,2 , Jos´e Martins1 , Marilia Curado1 , and Edmundo Monteiro, Castelo Branco, Portugal Abstract. Multihoming Intelligent Route Control (IRC) plays a signif- icant role

Monteiro, Edmundo

281

Lander flight path analysis  

NASA Technical Reports Server (NTRS)

The primary functions of the Lander Flight Path Analysis Team (LFPAT) were to (1) design the Viking Lander (VL) descent trajectory and compute the descent guidance parameters for command transmission to the Viking Lander and Viking Orbiter (VO), (2) reconstruct the VL trajectory from separation to touchdown using data transmitted from the VL to Earth via the VO during descent, and (3) predict the VL/VO relay link system performance during descent and post touchdown. The preflight VL capability, the history of proposed descent trajectory designs as the site selection process evolved, and the final trajectory design and guidance parameters for each vehicle are addressed along with the trajectory reconstruction process, including the overall reconstructed VL flight path summary and a detailed discussion of the entry trajectory and atmosphere reconstruction results. The postland relay link prediction function is discussed.

Euler, E. A.; Adams, G. L.; Hopper, F. W.

1979-01-01

282

New Approximation Algorithms for the Steiner Trees Problems Marek Karpinski Alexander Zelikovskyy  

E-print Network

New Approximation Algorithms for the Steiner Trees Problems Marek Karpinski Alexander Zelikovskyy Abstract The Steiner tree problem requires to nd a shortest tree connecting a given set of terminal points in a metric space. We design approximation algorithms for the Steiner problems in graphs

Eckmiller, Rolf

283

New Approximation Algorithms for the Steiner Trees Problems Marek Karpinski \\Lambda Alexander Zelikovsky y  

E-print Network

New Approximation Algorithms for the Steiner Trees Problems Marek Karpinski \\Lambda Alexander Zelikovsky y Abstract The Steiner tree problem requires to find a shortest tree connecting a given set of terminal points in a metric space. We design approximation algorithms for the Steiner problems in graphs

Eckmiller, Rolf

284

Bounds on the quality of approximate solutions to the Group Steiner Problem  

Microsoft Academic Search

The Group Steiner Problem (GSP) is a generalized version of the well known Steiner Problem. For an undirected, connected distance graph with groups of required vertices and Steiner vertices, GSP asks for a shortest connected subgraph, containing at least one vertex of each group. As the Steiner Problem is NP-hard, GSP is too, and we are interested in approximation algorithms.

Edmund Ihler

1990-01-01

285

New Approximation Algorithms for the Steiner Tree Problems Marek Karpinski \\Lambda Alexander Zelikovsky y  

E-print Network

New Approximation Algorithms for the Steiner Tree Problems Marek Karpinski \\Lambda Alexander Zelikovsky y Abstract The Steiner tree problem asks for the shortest tree connecting a given set of terminal points in a metric space. We design new approximation algorithms for the Steiner tree problems using

Zelikovsky, Alexander

286

Seeding the Population: Improved Performance in a Genetic Algorithm for the Rectilinear Steiner Problem  

E-print Network

Steiner problem, genetic algorithms, seeding the pop- ulation. Abstract|A hybrid genetic algorithm of such seeding on a genetic algorithm for the rectilinear Steiner problem, which seeks a shortest rectilinear are called Steiner points. The problem of #12;nding a rectilinear Steiner tree of minimum length on a set

Julstrom, Bryant A.

287

Optimization of the time-dependent traveling salesman problem with Monte Carlo methods  

Microsoft Academic Search

A problem often considered in operations research and computational physics is the traveling salesman problem, in which a traveling salesperson has to find the shortest closed tour between a certain set of cities. This problem has been extended to more realistic scenarios, e.g., the ``real'' traveling salesperson has to take rush hours into consideration. We will show how this extended

Johannes Bentner; Günter Bauer; Gustav M. Obermair; Ingo Morgenstern; Johannes Schneider

2001-01-01

288

Path integral quantization of parametrised field theory  

E-print Network

Free scalar field theory on a flat spacetime can be cast into a generally covariant form known as parametrised field theory in which the action is a functional of the scalar field as well as the embedding variables which describe arbitrary, in general curved, foliations of the flat spacetime. We construct the path integral quantization of parametrised field theory in order to analyse issues at the interface of quantum field theory and general covariance in a path integral context. We show that the measure in the Lorentzian path integral is non-trivial and is the analog of the Fradkin- Vilkovisky measure for quantum gravity. We construct Euclidean functional integrals in the generally covariant setting of parametrised field theory using key ideas of Schleich and show that our constructions imply the existence of non-standard `Wick rotations' of the standard free scalar field 2 point function. We develop a framework to study the problem of time through computations of scalar field 2 point functions. We illustrate our ideas through explicit computation for a time independent 1+1 dimensional foliation. Although the problem of time seems to be absent in this simple example, the general case is still open. We discuss our results in the contexts of the path integral formulation of quantum gravity and the canonical quantization of parametrised field theory.

Madhavan Varadarajan

2004-04-06

289

Performance Analysis of Embedded Software Using Implicit Path Enumeration  

E-print Network

Embedded computer systems are characterized by the presence of a processor running application specific software. A large number of these systems must satisfy real-time constraints. This paper examines the problem of determining the bound on the running time of a given program on a given processor. An important aspect of this problem is determining the extreme case program paths. The state of the art solution here relies on an explicit enumeration of program paths. This runs out of steam rather quickly since the number of feasible program paths is typically exponential in the size of the program. We present a solution for this problem, which considers all paths implicitly by using integer linear programming. This solution is implemented in the program cinderella which currently targets a popular embedded processor -- the Intel i960. The preliminary results of using this tool are presented here.

Yau-Tsun Steven Li; Sharad Malik

1995-01-01

290

Sparsed potential-PCNN for real time path planning and indoor navigation scheme for mobile robots  

Microsoft Academic Search

One of the main problems associated with mobile intelligent agents is path planning. Numerous approaches have been presented for path planning of mobile robots. One of the most efficient methods is Pulse Coupled Neural Network (PCNN). This paper presents a novel approach we call the Sparsed Potential PCNN method for real time path planning for mobile robots. In the proposed

S. U. Ahmed; U. A. Malik; K. F. Iqbal; Y. Ayaz; F. Kunwar

2011-01-01

291

PathFinder: a negotiation-based performance-driven router for FPGAs  

Microsoft Academic Search

Routing FPGAs is a challenging problem because of the relative scarcity of routing resources, both wires and connection points. This can lead either to slow implementations caused by long wiring paths that avoid congestion or a failure to route all signals. This paper presents PathFinder, a router that balances the goals of performance and routability. PathFinder uses an iterative algorithm

Larry McMurchie; Carl Ebeling

1995-01-01

292

Path Integrals, and Classical and Quantum Constraints  

E-print Network

Systems with constraints pose problems when they are quantized. Moreover, the Dirac procedure of quantization prior to reduction is preferred. The projection operator method of quantization, which can be most conveniently described by coherent state path integrals, enables one to directly impose a regularized form of the quantum constraints. This procedure also overcomes conventional difficulties with normalization and second class constraints that invalidate conventional Dirac quantization procedures.

John R. Klauder

2005-07-22

293

Coherent state path integrals in the continuum  

E-print Network

We discuss the time-continuous path integration in the coherent states basis in a way that is free from inconsistencies. Employing this notion we reproduce known and exact results working directly in the continuum. Such a formalism can set the basis to develop perturbative and non-perturbative approximations already known in the quantum field theory community. These techniques can be proven useful in a great variety of problems where bosonic Hamiltonians are used.

G. Kordas; S. I. Mistakidis; A. I. Karanikas

2014-08-14

294

Tracking hurricane paths  

NASA Technical Reports Server (NTRS)

The South East coastal region experiences hurricane threat for almost six months in every year. To improve the accuracy of hurricane forecasts, meteorologists would need the storm paths of both the present and the past. A hurricane path can be established if we could identify the correct position of the storm at different times right from its birth to the end. We propose a method based on both spatial and temporal image correlations to locate the position of a storm from satellite images. During the hurricane season, the satellite images of the Atlantic ocean near the equator are examined for the hurricane presence. This is accomplished in two steps. In the first step, only segments with more than a particular value of cloud cover are selected for analysis. Next, we apply image processing algorithms to test the presence of a hurricane eye in the segment. If the eye is found, the coordinate of the eye is recorded along with the time stamp of the segment. If the eye is not found, we examine adjacent segments for the existence of hurricane eye. It is probable that more than one hurricane eye could be found from different segments of the same period. Hence, the above process is repeated till the entire potential area for hurricane birth is exhausted. The subsequent/previous position of each hurricane eye will be searched in the appropriate adjacent segments of the next/previous period to mark the hurricane path. The temporal coherence and spatial coherence of the images are taken into account by our scheme in determining the segments and the associated periods required for analysis.

Prabhakaran, Nagarajan; Rishe, Naphtali; Athauda, Rukshan

1997-01-01

295

JAVA PathFinder  

NASA Technical Reports Server (NTRS)

JPF is an explicit state software model checker for Java bytecode. Today, JPF is a swiss army knife for all sort of runtime based verification purposes. This basically means JPF is a Java virtual machine that executes your program not just once (like a normal VM), but theoretically in all possible ways, checking for property violations like deadlocks or unhandled exceptions along all potential execution paths. If it finds an error, JPF reports the whole execution that leads to it. Unlike a normal debugger, JPF keeps track of every step how it got to the defect.

Mehhtz, Peter

2005-01-01

296

Byrds Flight Path  

NSDL National Science Digital Library

The Ohio State Universitys Library web site notes As a navigational aviator, Byrd pioneered in the technology that would be the foundation for modern polar exploration and investigation. As a decorated and much celebrated hero, Byrd drew popular attention to areas of the world that became focal points of scientific investigation in numerous disciplines. More information about Admiral Richard E. Byrd can be found at (http:--www.lib.ohio-state.edu-arvweb-polar-byrd-byrd.htm). The next animation, #1001, shows Byrds plane as it follows the flight path presented in this animation.

Biddlecome, Tom; Snodgrass, Stuart; Newcombe, Marte; Jezek, Ken

1999-11-08

297

Identifying codes and locating-dominating sets on paths and cycles  

E-print Network

Let $G=(V,E)$ be a graph and let $r\\ge 1$ be an integer. For a set $D \\subseteq V$, define $N_r[x] = \\{y \\in V: d(x, y) \\leq r\\}$ and $D_r(x) = N_r[x] \\cap D$, where $d(x,y)$ denotes the number of edges in any shortest path between $x$ and $y$. $D$ is known as an $r$-identifying code ($r$-locating-dominating set, respectively), if for all vertices $x\\in V$ ($x \\in V\\backslash D$, respectively), $D_r(x)$ are all nonempty and different. In this paper, we provide complete results for $r$-identifying codes in paths and odd cycles; we also give complete results for 2-locating-dominating sets in cycles.

Chen, Chunxia; Miao, Zhengke

2009-01-01

298

Nonoptimal Component Placement, but Short Processing Paths, due to Long-Distance Projections in Neural Systems  

PubMed Central

It has been suggested that neural systems across several scales of organization show optimal component placement, in which any spatial rearrangement of the components would lead to an increase of total wiring. Using extensive connectivity datasets for diverse neural networks combined with spatial coordinates for network nodes, we applied an optimization algorithm to the network layouts, in order to search for wire-saving component rearrangements. We found that optimized component rearrangements could substantially reduce total wiring length in all tested neural networks. Specifically, total wiring among 95 primate (Macaque) cortical areas could be decreased by 32%, and wiring of neuronal networks in the nematode Caenorhabditis elegans could be reduced by 48% on the global level, and by 49% for neurons within frontal ganglia. Wiring length reductions were possible due to the existence of long-distance projections in neural networks. We explored the role of these projections by comparing the original networks with minimally rewired networks of the same size, which possessed only the shortest possible connections. In the minimally rewired networks, the number of processing steps along the shortest paths between components was significantly increased compared to the original networks. Additional benchmark comparisons also indicated that neural networks are more similar to network layouts that minimize the length of processing paths, rather than wiring length. These findings suggest that neural systems are not exclusively optimized for minimal global wiring, but for a variety of factors including the minimization of processing steps. PMID:16848638

Kaiser, Marcus; Hilgetag, Claus C

2006-01-01

299

The Rectilinear Steiner Problem is NP-Complete  

Microsoft Academic Search

. The rectilinear Steiner tree problem asks for a shortest treeconnecting given points in the plane with rectilinear distance. The besttheoretically analyzed algorithm for this problem with a fairly practicalbehaviour bases on dynamic programming and has a running timeof O(n2\\\\Delta 2:62n) (Ganley\\/Cohoon). The best implementation can solverandom problems of size 35 (Salowe\\/Warme) within a day. In this paperwe improve the

M. r. Garey; D. s. Johnson

1977-01-01

300

Parallel Traveling Salesman Problem  

NSDL National Science Digital Library

The traveling salesman problem is a classic optimization problem in which one seeks to minimize the path taken by a salesman in traveling between N cities, where the salesman stops at each city one and only one time, never retracing his/her route. This implementation is designed to run on UNIX systems with X-Windows, and includes parallelization using MPI.

Joiner, David; Hassinger, Jonathan

301

Quad-rotor flight path energy optimization  

NASA Astrophysics Data System (ADS)

Quad-Rotor unmanned areal vehicles (UAVs) have been a popular area of research and development in the last decade, especially with the advent of affordable microcontrollers like the MSP 430 and the Raspberry Pi. Path-Energy Optimization is an area that is well developed for linear systems. In this thesis, this idea of path-energy optimization is extended to the nonlinear model of the Quad-rotor UAV. The classical optimization technique is adapted to the nonlinear model that is derived for the problem at hand, coming up with a set of partial differential equations and boundary value conditions to solve these equations. Then, different techniques to implement energy optimization algorithms are tested using simulations in Python. First, a purely nonlinear approach is used. This method is shown to be computationally intensive, with no practical solution available in a reasonable amount of time. Second, heuristic techniques to minimize the energy of the flight path are tested, using Ziegler-Nichols' proportional integral derivative (PID) controller tuning technique. Finally, a brute force look-up table based PID controller is used. Simulation results of the heuristic method show that both reliable control of the system and path-energy optimization are achieved in a reasonable amount of time.

Kemper, Edward

302

Covariant path integrals on hyperbolic surfaces  

NASA Astrophysics Data System (ADS)

DeWitt's covariant formulation of path integration [B. De Witt, "Dynamical theory in curved spaces. I. A review of the classical and quantum action principles," Rev. Mod. Phys. 29, 377-397 (1957)] has two practical advantages over the traditional methods of "lattice approximations;" there is no ordering problem, and classical symmetries are manifestly preserved at the quantum level. Applying the spectral theorem for unbounded self-adjoint operators, we provide a rigorous proof of the convergence of certain path integrals on Riemann surfaces of constant curvature -1. The Pauli-DeWitt curvature correction term arises, as in DeWitt's work. Introducing a Fuchsian group ? of the first kind, and a continuous, bounded, ?-automorphic potential V, we obtain a Feynman-Kac formula for the automorphic Schrödinger equation on the Riemann surface ?H. We analyze the Wick rotation and prove the strong convergence of the so-called Feynman maps [K. D. Elworthy, Path Integration on Manifolds, Mathematical Aspects of Superspace, edited by Seifert, Clarke, and Rosenblum (Reidel, Boston, 1983), pp. 47-90] on a dense set of states. Finally, we give a new proof of some results in C. Grosche and F. Steiner, "The path integral on the Poincare upper half plane and for Liouville quantum mechanics," Phys. Lett. A 123, 319-328 (1987).

Schaefer, Joe

1997-11-01

303

Computational path planner for product assembly in complex environments  

NASA Astrophysics Data System (ADS)

Assembly path planning is a crucial problem in assembly related design and manufacturing processes. Sampling based motion planning algorithms are used for computational assembly path planning. However, the performance of such algorithms may degrade much in environments with complex product structure, narrow passages or other challenging scenarios. A computational path planner for automatic assembly path planning in complex 3D environments is presented. The global planning process is divided into three phases based on the environment and specific algorithms are proposed and utilized in each phase to solve the challenging issues. A novel ray test based stochastic collision detection method is proposed to evaluate the intersection between two polyhedral objects. This method avoids fake collisions in conventional methods and degrades the geometric constraint when a part has to be removed with surface contact with other parts. A refined history based rapidly-exploring random tree (RRT) algorithm which bias the growth of the tree based on its planning history is proposed and employed in the planning phase where the path is simple but the space is highly constrained. A novel adaptive RRT algorithm is developed for the path planning problem with challenging scenarios and uncertain environment. With extending values assigned on each tree node and extending schemes applied, the tree can adapts its growth to explore complex environments more efficiently. Experiments on the key algorithms are carried out and comparisons are made between the conventional path planning algorithms and the presented ones. The comparing results show that based on the proposed algorithms, the path planner can compute assembly path in challenging complex environments more efficiently and with higher success. This research provides the references to the study of computational assembly path planning under complex environments.

Shang, Wei; Liu, Jianhua; Ning, Ruxin; Liu, Mi

2013-03-01

304

757 Path Loss Measurements  

NASA Technical Reports Server (NTRS)

Path Loss Measurements were obtained on three (3) GPS equipped 757 aircraft. Systems measured were Marker Beacon, LOC, VOR, VHF (3), Glide Slope, ATC (2), DME (2), TCAS, and GPS. This data will provide the basis for assessing the EMI (Electromagnetic Interference) safety margins of comm/nav (communication and navigation) systems to portable electronic device emissions. These Portable Electronic Devices (PEDs) include all devices operated in or around the aircraft by crews, passengers, servicing personnel, as well as the general public in the airport terminals. EMI assessment capability is an important step in determining if one system-wide PED EMI policy is appropriate. This data may also be used comparatively with theoretical analysis and computer modeling data sponsored by NASA Langley Research Center and others.

Horton, Kent; Huffman, Mitch; Eppic, Brian; White, Harrison

2005-01-01

305

Flight Paths of Orbiting Satellites  

NSDL National Science Digital Library

This is an activity to help students visualize the relationship of motion, time and space as it relates to objects orbiting the earth. They will be able to track the path of an orbiting object on a globe, plot the path of an orbiting object on a flat world map, and explain that an object orbiting earth on a plane will produce a flight path which appears as wavy lines on the earths surface.

306

Path Integral for Dirac Particle in Plane Wave Field  

Microsoft Academic Search

The problem of a relativistic spinning particle in interaction with an electromagnetic plane wave field is treated via path integrals. The dynamics of the spin of the particle is described using the supersymmetric action proposed by Fradkin and Gitman. The problem has been solved by using two identities, one bosonic and the other fermionic, which are related directly to the

S. Zeggari; T. Boudjedaa; L. Chetouani

2001-01-01

307

Reaction Path Optimization with Holonomic Constraints and Kinetic Energy Potentials  

SciTech Connect

Two methods are developed to enhance the stability, efficiency, and robustness of reaction path optimization using a chain of replicas. First, distances between replicas are kept equal during path optimization via holonomic constraints. Finding a reaction path is, thus, transformed into a constrained optimization problem. This approach avoids force projections for finding minimum energy paths (MEPs), and fast-converging schemes such as quasi-Newton methods can be readily applied. Second, we define a new objective function - the total Hamiltonian - for reaction path optimization, by combining the kinetic energy potential of each replica with its potential energy function. Minimizing the total Hamiltonian of a chain determines a minimum Hamiltonian path (MHP). If the distances between replicas are kept equal and a consistent force constant is used, then the kinetic energy potentials of all replicas have the same value. The MHP in this case is the most probable isokinetic path. Our results indicate that low-temperature kinetic energy potentials (<5 K) can be used to prevent the development of kinks during path optimization and can significantly reduce the required steps of minimization by 2-3 times without causing noticeable differences between a MHP and MEP. These methods are applied to three test cases, the C?eq-to-Cax isomerization of an alanine dipeptide, the ?C?- to-¹C? transition of an ?-D-glucopyranose, and the helix-to-sheet transition of a GNNQQNY heptapeptide. By applying the methods developed in this work, convergence of reaction path optimization can be achieved for these complex transitions, involving full atomic details and a large number of replicas (>100). For the case of helix-to-sheet transition, we identify pathways whose energy barriers are consistent with experimental measurements. Further, we develop a method based on the work energy theorem to quantify the accuracy of reaction paths and to determine whether the atoms used to define a path are enough to provide quantitative estimation of energy barriers.

Brokaw, Jason B.; Haas, Kevin R.; Chu, Jhih-wei

2009-08-11

308

Constructs of highly effective heat transport paths by bionic optimization  

Microsoft Academic Search

The optimization approach based on the biological evolution principle is used to construct the heat transport paths for volume-to-point\\u000a problem. The transport paths are constructed by inserting high conductivity materials in the heat conduction domain where\\u000a uniform or nonuniform heat sources exist. In the bionic optimization process, the optimal constructs of the high conductivity\\u000a material are obtained by numerically simulating

Xinguang Cheng; Zhixin Li; Zengyuan Guo

2003-01-01

309

Path and path deviation equations for p-branes  

NASA Astrophysics Data System (ADS)

Path and path deviation equations for neutral, charged, spinning and spinning charged test particles, using a modified Bazanski Lagrangian, are derived. We extend this approach to strings and branes. We show how the Bazanski Lagrangian for charged point particles and charged branes arises à la Kaluza-Klein from the Bazanski Lagrangian in 5-dimensions.

Pavši?, Matej; Kahil, Magd E.

2012-04-01

310

Finding Minimum Energy Disjoint Paths in Wireless Ad-Hoc Networks  

Microsoft Academic Search

We develop algorithms for finding minimum energy disjoint paths in an all-wireless network, for both the node and link-disjoint cases. Our major results include a novel polynomial time algorithm that optimally solves the minimum energy 2 link-disjoint paths problem, as well as a polynomial time algorithm for the minimum energy k node-disjoint paths problem. In addition, we present efficient heuristic

Anand Srinivas; Eytan Modiano

2005-01-01

311

Decision paths in complex tasks  

NASA Technical Reports Server (NTRS)

Complex real world action and its prediction and control has escaped analysis by the classical methods of psychological research. The reason is that psychologists have no procedures to parse complex tasks into their constituents. Where such a division can be made, based say on expert judgment, there is no natural scale to measure the positive or negative values of the components. Even if we could assign numbers to task parts, we lack rules i.e., a theory, to combine them into a total task representation. We compare here two plausible theories for the amalgamation of the value of task components. Both of these theories require a numerical representation of motivation, for motivation is the primary variable that guides choice and action in well-learned tasks. We address this problem of motivational quantification and performance prediction by developing psychophysical scales of the desireability or aversiveness of task components based on utility scaling methods (Galanter 1990). We modify methods used originally to scale sensory magnitudes (Stevens and Galanter 1957), and that have been applied recently to the measure of task 'workload' by Gopher and Braune (1984). Our modification uses utility comparison scaling techniques which avoid the unnecessary assumptions made by Gopher and Braune. Formula for the utility of complex tasks based on the theoretical models are used to predict decision and choice of alternate paths to the same goal.

Galanter, Eugene

1991-01-01

312

A weighted coding in a genetic algorithm for the degree-constrained minimum spanning tree problem  

Microsoft Academic Search

The coding by which chromosomes represent candidate solu- tions is a fundamental design choice in a genetic algorithm. This paper describes a novel coding of spanning trees in a genetic algorithm for the degree-constrained minimum span- ning tree problem. For a connected, weighted graph, this problem seeks to identify the shortest spanning tree whose degree does not exceed an upper

Günther R. Raidl; Bryant A. Julstrom

2000-01-01

313

Generalized Steiner's Problem and its Solution with the Concepts in Field Thoery  

E-print Network

We generalized the Steiner's shortest line problem and found its connection with the concepts in classical field theory. We solved the generalized Steiner's problem by introducing a conservative potential and a dissipative force in the field and gave a computing method by using a testing point and a corresponding iterative curve.

Hai Lin

2001-05-01

314

Stabilizing Intelligent Route Control: Randomized Path Monitoring, Randomized Path Switching or History-Aware Path Switching?  

Microsoft Academic Search

Multihoming Intelligent Route Control (IRC) plays a significant role in improving the performance of Internet accesses. However,\\u000a in a competitive environment, IRC systems may introduce persistent route oscillations, causing significant performance degradation.\\u000a In this study, three design alternatives to cope with this issue are investigated: Randomized Path Monitoring, Randomized\\u000a Path Switching and History-aware Path Switching. The simulation results show that

Alexandre Fonte; José Martins; Marilia Curado; Edmundo Monteiro

2008-01-01

315

Path integral learning of multidimensional movement trajectories  

NASA Astrophysics Data System (ADS)

This paper explores the use of Path Integral Methods, particularly several variants of the recent Path Integral Policy Improvement (PI2) algorithm in multidimensional movement parametrized policy learning. We rely on Dynamic Movement Primitives (DMPs) to codify discrete and rhythmic trajectories, and apply the PI2-CMA and PIBB methods in the learning of optimal policy parameters, according to different cost functions that inherently encode movement objectives. Additionally we merge both of these variants and propose the PIBB-CMA algorithm, comparing all of them with the vanilla version of PI2. From the obtained results we conclude that PIBB-CMA surpasses all other methods in terms of convergence speed and iterative final cost, which leads to an increased interest in its application to more complex robotic problems.

André, João; Santos, Cristina; Costa, Lino

2013-10-01

316

On the Inapproximability of Disjoint Paths and Minimum Steiner Forest with Bandwidth Constraints  

E-print Network

­ tion scheme unless P = NP , and the minimum Steiner forest with bandwidth constraints problem cannotOn the Inapproximability of Disjoint Paths and Minimum Steiner Forest with Bandwidth Constraints \\Gammaffl n unless NP ` DTIME[2 polylog n ], the max directed edge­disjoint paths problem cannot

Ma, Bin

317

Muscle fibers typically fall within a size range of 10100m along the shortest axis (e.g. Russell et al., 2000). Dimensions  

E-print Network

is that the distribution of mitochondria varies as a function of fiber size. In juveniles, mitochondria are uniformly distributed throughout the fibers and the population is equally divided between subsarcolemmal4045 Muscle fibers typically fall within a size range of 10­100·µm along the shortest axis (e

Kinsey, Stephen

318

Path Jacobians: Theory and Applications  

Microsoft Academic Search

In accordance with Fermat's Variation Principle, a ray path connecting two arbitrary points in a scene via multiple reflectors is given by a non-linear system. If we fix one of the two points and let the other change, the system can be considered as a function relating the reflection points along the path to the varying point. In this paper,

Min Chen; James Arvo

1998-01-01

319

Reconfigurable data path processor  

NASA Technical Reports Server (NTRS)

A reconfigurable data path processor comprises a plurality of independent processing elements. Each of the processing elements advantageously comprising an identical architecture. Each processing element comprises a plurality of data processing means for generating a potential output. Each processor is also capable of through-putting an input as a potential output with little or no processing. Each processing element comprises a conditional multiplexer having a first conditional multiplexer input, a second conditional multiplexer input and a conditional multiplexer output. A first potential output value is transmitted to the first conditional multiplexer input, and a second potential output value is transmitted to the second conditional multiplexer output. The conditional multiplexer couples either the first conditional multiplexer input or the second conditional multiplexer input to the conditional multiplexer output, according to an output control command. The output control command is generated by processing a set of arithmetic status-bits through a logical mask. The conditional multiplexer output is coupled to a first processing element output. A first set of arithmetic bits are generated according to the processing of the first processable value. A second set of arithmetic bits may be generated from a second processing operation. The selection of the arithmetic status-bits is performed by an arithmetic-status bit multiplexer selects the desired set of arithmetic status bits from among the first and second set of arithmetic status bits. The conditional multiplexer evaluates the select arithmetic status bits according to logical mask defining an algorithm for evaluating the arithmetic status bits.

Donohoe, Gregory (Inventor)

2005-01-01

320

Hard paths, soft paths or no paths? Cross-cultural perceptions of water solutions  

NASA Astrophysics Data System (ADS)

In this study, we examine how development status and water scarcity shape people's perceptions of "hard path" and "soft path" water solutions. Based on ethnographic research conducted in four semi-rural/peri-urban sites (in Bolivia, Fiji, New Zealand, and the US), we use content analysis to conduct statistical and thematic comparisons of interview data. Our results indicate clear differences associated with development status and, to a lesser extent, water scarcity. People in the two less developed sites were more likely to suggest hard path solutions, less likely to suggest soft path solutions, and more likely to see no path to solutions than people in the more developed sites. Thematically, people in the two less developed sites envisioned solutions that involve small-scale water infrastructure and decentralized, community-based solutions, while people in the more developed sites envisioned solutions that involve large-scale infrastructure and centralized, regulatory water solutions. People in the two water-scarce sites were less likely to suggest soft path solutions and more likely to see no path to solutions (but no more likely to suggest hard path solutions) than people in the water-rich sites. Thematically, people in the two water-rich sites seemed to perceive a wider array of unrealized potential soft path solutions than those in the water-scarce sites. On balance, our findings are encouraging in that they indicate that people are receptive to soft path solutions in a range of sites, even those with limited financial or water resources. Our research points to the need for more studies that investigate the social feasibility of soft path water solutions, particularly in sites with significant financial and natural resource constraints.

Wutich, A.; White, A. C.; White, D. D.; Larson, K. L.; Brewis, A.; Roberts, C.

2014-01-01

321

Hard paths, soft paths or no paths? Cross-cultural perceptions of water solutions  

NASA Astrophysics Data System (ADS)

In this study, we examine how development status and water scarcity shape people's perceptions of "hard path" and "soft path" water solutions. Based on ethnographic research conducted in four semi-rural/peri-urban sites (in Bolivia, Fiji, New Zealand, and the US), we use content analysis to conduct statistical and thematic comparisons of interview data. Our results indicate clear differences based on development status and, to a lesser extent, water scarcity. People in less developed sites were more likely to suggest hard path solutions, less likely to suggest soft path solutions, and more likely to see no path to solutions than people in more developed sites. Thematically, people in less developed sites envisioned solutions that involve small-scale water infrastructure and decentralized, community based solutions, while people in more developed sites envisioned solutions that involve large-scale infrastructure and centralized, regulatory water solutions. People in water-scarce sites were less likely to suggest soft path solutions and more likely to see no path to solutions (but no more likely to suggest hard path solutions) than people in water-rich sites. Thematically, people in water-rich sites seemed to perceive a wider array of unrealized potential soft path solutions than those in water-scarce sites. On balance, our findings are encouraging in that they indicate that people are receptive to soft path solutions in a range of sites, even those with limited financial or water resources. Our research points to the need for more studies that investigate the social feasibility of soft path water solutions, particularly in sites with significant financial and natural resource constraints.

Wutich, A.; White, A. C.; Roberts, C. M.; White, D. D.; Larson, K. L.; Brewis, A.

2013-06-01

322

221A Lecture Notes Path Integral  

E-print Network

221A Lecture Notes Path Integral 1 Feynman's Path Integral Formulation Feynman's formulation with a weight factor given by the classical action for each path. Hence the name path integral. This is it. Note of quantum mechanics using the so-called path inte- gral is arguably the most elegant. It can be stated

Murayama, Hitoshi

323

Chemotaxis can take plant-parasitic nematodes to the source of a chemo-attractant via the shortest possible routes  

PubMed Central

It has long been recognized that chemotaxis is the primary means by which nematodes locate host plants. Nonetheless, chemotaxis has received scant attention. We show that chemotaxis is predicted to take nematodes to a source of a chemo-attractant via the shortest possible routes through the labyrinth of air-filled or water-filled channels within a soil through which the attractant diffuses. There are just two provisos: (i) all of the channels through which the attractant diffuses are accessible to the nematodes and (ii) nematodes can resolve all chemical gradients no matter how small. Previously, this remarkable consequence of chemotaxis had gone unnoticed. The predictions are supported by experimental studies of the movement patterns of the root-knot nematodes Meloidogyne incognita and Meloidogyne graminicola in modified Y-chamber olfactometers filled with Pluronic gel. By providing two routes to a source of the attractant, one long and one short, our experiments, the first to demonstrate the routes taken by nematodes to plant roots, serve to test our predictions. Our data show that nematodes take the most direct route to their preferred hosts (as predicted) but often take the longest route towards poor hosts. We hypothesize that a complex of repellent and attractant chemicals influences the interaction between nematodes and their hosts. PMID:20880854

Reynolds, Andy M.; Dutta, Tushar K.; Curtis, Rosane H. C.; Powers, Stephen J.; Gaur, Hari S.; Kerry, Brian R.

2011-01-01

324

Path planning for complex terrain navigation via dynamic programming  

SciTech Connect

This work considers the problem of planning optimal paths for a mobile robot traversing complex terrain. In addition to the existing obstacles, locations in the terrain where the slope is too steep for the mobile robot to navigate safely without tipping over become mathematically equivalent to extra obstacles. To solve the optimal path problem, the authors use a dynamic programming approach. The dynamic programming approach utilized herein does not suffer the difficulties associated with spurious local minima that the artificial potential field approaches do. In fact, a globally optimal solution is guaranteed to be found if a feasible solution exists. The method is demonstrated on several complex examples including very complex terrains.

Kwok, K.S.; Driessen, B.J.

1998-12-31

325

A Flight Examination of Operating Problems of V/STOL Aircraft in STOL-Type Landing and Approach  

NASA Technical Reports Server (NTRS)

A flight investigation has been conducted using a large twin-engine cargo aircraft to isolate the problems associated with operating propeller-driven aircraft in the STOL speed range where appreciable engine power is used to augment aerodynamic lift. The problems considered would also be representative of those of a large overloaded VTOL aircraft operating in an STOL manner with comparable thrust-to-weight ratios. The study showed that operation at low approach speeds was compromised by the necessity of maintaining high thrust to generate high lift and yet achieving the low lift-drag ratios needed for steep descents. The useable range of airspeed and flight path angle was limited by the pilot's demand for a positive climb margin at the approach speed, a suitable stall margin, and a control and/or performance margin for one engine inoperative. The optimum approach angle over an obstacle was found to be a compromise between obtaining the shortest air distance and the lowest touchdown velocity. In order to realize the greatest low-speed potential from STOL designs, the stability and control characteristics must be satisfactory.

Innis, Robert C.; Quigley, Hervey C.

1961-01-01

326

Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Path Testing  

E-print Network

Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Path Testing Mohammad Mousavi Eindhoven University of Technology, The Netherlands Software Testing, 2012 Mousavi: Path Testing #12;Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Outline Structural

Mousavi, Mohammad

327

Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Path Testing  

E-print Network

Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Path Testing Mohammad Mousavi Eindhoven University of Technology, The Netherlands Software Testing, 2013 Mousavi: Path Testing #12;Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Outline Structural

Mousavi, Mohammad

328

One-dimensional Gromov minimal filling problem  

SciTech Connect

The paper is devoted to a new branch in the theory of one-dimensional variational problems with branching extremals, the investigation of one-dimensional minimal fillings introduced by the authors. On the one hand, this problem is a one-dimensional version of a generalization of Gromov's minimal fillings problem to the case of stratified manifolds. On the other hand, this problem is interesting in itself and also can be considered as a generalization of another classical problem, the Steiner problem on the construction of a shortest network connecting a given set of terminals. Besides the statement of the problem, we discuss several properties of the minimal fillings and state several conjectures. Bibliography: 38 titles.

Ivanov, Alexandr O; Tuzhilin, Alexey A

2012-05-31

329

One-dimensional Gromov minimal filling problem  

NASA Astrophysics Data System (ADS)

The paper is devoted to a new branch in the theory of one-dimensional variational problems with branching extremals, the investigation of one-dimensional minimal fillings introduced by the authors. On the one hand, this problem is a one-dimensional version of a generalization of Gromov's minimal fillings problem to the case of stratified manifolds. On the other hand, this problem is interesting in itself and also can be considered as a generalization of another classical problem, the Steiner problem on the construction of a shortest network connecting a given set of terminals. Besides the statement of the problem, we discuss several properties of the minimal fillings and state several conjectures. Bibliography: 38 titles.

Ivanov, Alexandr O.; Tuzhilin, Alexey A.

2012-05-01

330

PCB drill path optimization by combinatorial cuckoo search algorithm.  

PubMed

Optimization of drill path can lead to significant reduction in machining time which directly improves productivity of manufacturing systems. In a batch production of a large number of items to be drilled such as printed circuit boards (PCB), the travel time of the drilling device is a significant portion of the overall manufacturing process. To increase PCB manufacturing productivity and to reduce production costs, a good option is to minimize the drill path route using an optimization algorithm. This paper reports a combinatorial cuckoo search algorithm for solving drill path optimization problem. The performance of the proposed algorithm is tested and verified with three case studies from the literature. The computational experience conducted in this research indicates that the proposed algorithm is capable of efficiently finding the optimal path for PCB holes drilling process. PMID:24707198

Lim, Wei Chen Esmonde; Kanagaraj, G; Ponnambalam, S G

2014-01-01

331

Mobile transporter path planning using a genetic algorithm approach  

NASA Technical Reports Server (NTRS)

The use of an optimization technique known as a genetic algorithm for solving the mobile transporter path planning problem is investigated. The mobile transporter is a traveling robotic vehicle proposed for the Space Station which must be able to reach any point of the structure autonomously. Specific elements of the genetic algorithm are explored in both a theoretical and experimental sense. Recent developments in genetic algorithm theory are shown to be particularly effective in a path planning problem domain, though problem areas can be cited which require more research. However, trajectory planning problems are common in space systems and the genetic algorithm provides an attractive alternative to the classical techniques used to solve these problems.

Baffes, Paul; Wang, Lui

1988-01-01

332

Covariant path integrals on hyperbolic surfaces  

SciTech Connect

DeWitt{close_quote}s covariant formulation of path integration [B. De Witt, {open_quotes}Dynamical theory in curved spaces. I. A review of the classical and quantum action principles,{close_quotes} Rev. Mod. Phys. {bold 29}, 377{endash}397 (1957)] has two practical advantages over the traditional methods of {open_quotes}lattice approximations;{close_quotes} there is no ordering problem, and classical symmetries are manifestly preserved at the quantum level. Applying the spectral theorem for unbounded self-adjoint operators, we provide a rigorous proof of the convergence of certain path integrals on Riemann surfaces of constant curvature {minus}1. The Pauli{endash}DeWitt curvature correction term arises, as in DeWitt{close_quote}s work. Introducing a Fuchsian group {Gamma} of the first kind, and a continuous, bounded, {Gamma}-automorphic potential V, we obtain a Feynman{endash}Kac formula for the automorphic Schr{umlt o}dinger equation on the Riemann surface {Gamma}{backslash}H. We analyze the Wick rotation and prove the strong convergence of the so-called Feynman maps [K. D. Elworthy, {ital Path Integration on Manifolds, Mathematical Aspects of Superspace}, edited by Seifert, Clarke, and Rosenblum (Reidel, Boston, 1983), pp. 47{endash}90] on a dense set of states. Finally, we give a new proof of some results in C. Grosche and F. Steiner, {open_quotes}The path integral on the Poincare upper half plane and for Liouville quantum mechanics,{close_quotes} Phys. Lett. A {bold 123}, 319{endash}328 (1987). {copyright} {ital 1997 American Institute of Physics.}

Schaefer, J. [Department of Mathematics, State University of New York at Stony Brook, Stony Brook, New York 11794-3651 (United States)] [Department of Mathematics, State University of New York at Stony Brook, Stony Brook, New York 11794-3651 (United States)

1997-11-01

333

Learning for informative path planning  

E-print Network

Through the combined use of regression techniques, we will learn models of the uncertainty propagation efficiently and accurately to replace computationally intensive Monte- Carlo simulations in informative path planning. ...

Park, Sooho, S.M. Massachusetts Institute of Technology

2008-01-01

334

Collaborative Authoring of Walden's Paths  

E-print Network

The World Wide Web contains rich collections of digital materials that can be used in education and learning settings. The collaborative authoring prototype of Walden's Paths targets two groups of users: educators and learners. From the perspective...

Li, Yuanling

2012-10-19

335

Morse theory in path space  

E-print Network

We consider the path space of a curved manifold on which a point particle is introduced in a conservative physical system with constant total energy to formulate its action functional and geodesic equation together with breaks on the path. The second variation of the action functional is exploited to yield the geodesic deviation equation and to discuss the Jacobi fields on the curved manifold. We investigate the topology of the path space using the action functional on it and its physical meaning by defining the gradient of the action functional, the space of bounded flow energy solutions and the moduli space associated with the critical points of the action functional. We also consider the particle motion on the $n$-sphere $S^{n}$ in the conservative physical system to discuss explicitly the moduli space of the path space and the corresponding homology groups.

Yong Seung Cho; Soon-Tae Hong

2007-06-01

336

A bat algorithm with mutation for UCAV path planning.  

PubMed

Path planning for uninhabited combat air vehicle (UCAV) is a complicated high dimension optimization problem, which mainly centralizes on optimizing the flight route considering the different kinds of constrains under complicated battle field environments. Original bat algorithm (BA) is used to solve the UCAV path planning problem. Furthermore, a new bat algorithm with mutation (BAM) is proposed to solve the UCAV path planning problem, and a modification is applied to mutate between bats during the process of the new solutions updating. Then, the UCAV can find the safe path by connecting the chosen nodes of the coordinates while avoiding the threat areas and costing minimum fuel. This new approach can accelerate the global convergence speed while preserving the strong robustness of the basic BA. The realization procedure for original BA and this improved metaheuristic approach BAM is also presented. To prove the performance of this proposed metaheuristic method, BAM is compared with BA and other population-based optimization methods, such as ACO, BBO, DE, ES, GA, PBIL, PSO, and SGA. The experiment shows that the proposed approach is more effective and feasible in UCAV path planning than the other models. PMID:23365518

Wang, Gaige; Guo, Lihong; Duan, Hong; Liu, Luo; Wang, Heqi

2012-01-01

337

Partnership for Advancing Technologies in Housing (PATH)  

NSF Publications Database

... Technology Systems Interactions and Whole House Approaches PATH?s mission is to advance technology ... technology arena. Far reaching exploratory research that can lead to breakthrough technologies and ...

338

THE SHORTEST PERIOD sdB PLUS WHITE DWARF BINARY CD-30 11223 (GALEX J1411-3053)  

SciTech Connect

We report on the discovery of the shortest period binary comprising a hot subdwarf star (CD-30 11223, GALEX J1411-3053) and a massive unseen companion. Photometric data from the All Sky Automated Survey show ellipsoidal variations of the hot subdwarf primary and spectroscopic series revealed an orbital period of 70.5 minutes. The large velocity amplitude suggests the presence of a massive white dwarf in the system (M{sub 2}/M{sub Sun} {approx}> 0.77) assuming a canonical mass for the hot subdwarf (0.48 M{sub Sun }), although a white dwarf mass as low as 0.75 M{sub Sun} is allowable by postulating a subdwarf mass as low as 0.44 M{sub Sun }. The amplitude of ellipsoidal variations and a high rotation velocity imposed a high-inclination to the system (i {approx}> 68 Degree-Sign ) and, possibly, observable secondary transits (i {approx}> 74 Degree-Sign ). At the lowest permissible inclination and assuming a subdwarf mass of {approx}0.48 M{sub Sun }, the total mass of the system reaches the Chandrasekhar mass limit at 1.35 M{sub Sun} and would exceed it for a subdwarf mass above 0.48 M{sub Sun }. The system should be considered, like its sibling KPD 1930+2752, a candidate progenitor for a Type Ia supernova. The system should become semi-detached and initiate mass transfer within Almost-Equal-To 30 Myr.

Vennes, S.; Kawka, A.; Nemeth, P. [Astronomicky ustav, Akademie ved Ceske republiky, Fricova 298, CZ-251 65 Ondrejov (Czech Republic); O'Toole, S. J. [Australian Astronomical Observatory, P.O. Box 915, 1670 North Ryde NSW (Australia); Burton, D. [Faculty of Sciences, University of Southern Queensland, Toowoomba, QLD 4350 (Australia)

2012-11-01

339

The path of kyosei.  

PubMed

Many global companies believe they have a moral duty to respond to the world's problems but are unsure how to do that and still pursue a reasonable profit for their shareholders. Ryuzaburo Kaku, honorary chairman of Canon, the Japanese technology company, suggests that companies consider kyosei, a business credo that he defines as a "spirit of cooperation" in which individuals and organizations work together for the common good. Kyosei, Kaku claims, has helped Canon make a significant and positive impact on many world problems as the company has grown to become one of the world's preeminent innovators and manufacturers of technology. The implementation of kyosei can be divided into five stages, with each stage building on the preceding one. In the first stage, companies must work to secure a predictable stream of profits and to establish strong market positions. From this foundation, they move on to the second stage, in which managers and workers resolve to cooperate with each other, recognizing that both groups are vital to the company's success. In the third stage, this sense of cooperation is extended beyond the company to encompass customers, suppliers, community groups, and even competitors. At the fourth stage, a company takes the cooperative spirit beyond national boundaries and addresses some of the global imbalances that plague the world. In the fifth stage, which companies rarely achieve, a company urges its national government to work toward rectifying global imbalances. For each stage, Kaku provides detailed examples from Cannon's own experience in putting the ideas of kyosei into practice. PMID:10168336

Kaku, R

1997-01-01

340

Path Planning Algorithms for Autonomous Border Patrol Vehicles  

NASA Astrophysics Data System (ADS)

This thesis presents an online path planning algorithm developed for unmanned vehicles in charge of autonomous border patrol. In this Pursuit-Evasion game, the unmanned vehicle is required to capture multiple trespassers on its own before any of them reach a target safe house where they are safe from capture. The problem formulation is based on Isaacs' Target Guarding problem, but extended to the case of multiple evaders. The proposed path planning method is based on Rapidly-exploring random trees (RRT) and is capable of producing trajectories within several seconds to capture 2 or 3 evaders. Simulations are carried out to demonstrate that the resulting trajectories approach the optimal solution produced by a nonlinear programming-based numerical optimal control solver. Experiments are also conducted on unmanned ground vehicles to show the feasibility of implementing the proposed online path planning algorithm on physical applications.

Lau, George Tin Lam

341

Seismic refraction analysis: the path forward  

USGS Publications Warehouse

Seismic Refraction Methods: Unleashing the Potential and Understanding the Limitations; Tucson, Arizona, 29 March 2012 A workshop focused on seismic refraction methods took place on 29 May 2012, associated with the 2012 Symposium on the Application of Geophysics to Engineering and Environmental Problems. This workshop was convened to assess the current state of the science and discuss paths forward, with a primary focus on near-surface problems but with an eye on all applications. The agenda included talks on these topics from a number of experts interspersed with discussion and a dedicated discussion period to finish the day. Discussion proved lively at times, and workshop participants delved into many topics central to seismic refraction work.

Haines, Seth S.; Zelt, Colin; Doll, William

2012-01-01

342

Evolutionary development of path planning algorithms  

SciTech Connect

This paper describes the use of evolutionary software techniques for developing both genetic algorithms and genetic programs. Genetic algorithms are evolved to solve a specific problem within a fixed and known environment. While genetic algorithms can evolve to become very optimized for their task, they often are very specialized and perform poorly if the environment changes. Genetic programs are evolved through simultaneous training in a variety of environments to develop a more general controller behavior that operates in unknown environments. Performance of genetic programs is less optimal than a specially bred algorithm for an individual environment, but the controller performs acceptably under a wider variety of circumstances. The example problem addressed in this paper is evolutionary development of algorithms and programs for path planning in nuclear environments, such as Chernobyl.

Hage, M

1998-09-01

343

Traceroute Probe Method and Forward IP Path Inference Matthew Luckie  

E-print Network

, operationally useful for diagnosing problems on In- ternet paths, and vital to researchers trying to develop or hard copies of all or part of this work for personal or classroom use is granted without fee provided of operational in- frastructure management and troubleshooting needs. For example, NANOG traceroute [2] has

California at San Diego, University of

344

On-line Mobile Robot Path Tracking Using PI Controller  

Microsoft Academic Search

This paper presents a method for the path tracking problem of a mobile robot using a PI controller. The proposed method inserts an ideal relay in parallel to a conventional PI controller to identify an equivalent FOPDT model for the kinematics of the mobile robot. The parallel connection of the ideal relay to the PI controller helps in designing a

P. K. Padhy; S. Majhi

2006-01-01

345

Complete Path Planning for Closed Kinematic Chains with Spherical Joints  

Microsoft Academic Search

We study the path planning problem, without obstacles, for closed kinematic chains with n links connected by spherical joints in space or revolute joints in the plane. The configuration space of such systems is a real algebraic variety whose structure is fully deter- mined using techniques from algebraic geometry and differential topology. This structure is then exploited to design a

Jeffrey Coates Trinkle; Richard James Milgram

2002-01-01

346

PARALLEL GRASP WITH PATH-RELINKING FOR JOB SHOP ...  

E-print Network

a time and once a job initiates processing on a given machine it must ...... In the GRASP with path-relinking for the 3-index assignment problem [2], the cost of a ...... it is possible to approximately achieve linear speed-up in solution time to target.

347

Covariant path integral for the Dirac equation with pseudoscalar potentials  

Microsoft Academic Search

The problem of a relativistic spinning particle interacting with pseudoscalar potentials in (3 + 1) dimensions is formulated in the framework of covariant supersymmetric path integrals. The relative Green's function is expressed through a functional integral over bosonic trajectories that describe the external motion and fermionic variables that describe the spin degrees of freedom. As an application, we have considered

S. Haouat; L. Chetouani

2007-01-01

348

Path Planning and Motion Coordination in Multiple Mobile Robot Teams  

E-print Network

Path Planning and Motion Coordination in Multiple Mobile Robot Teams Lynne E. Parker Department coordination addresses the problem of how teams of autonomous mobile robots can share the same workspace while applications of multiple autonomous mobile robots must address this issue of motion coordination, either

Parker, Lynne E.

349

The excess mean free path transport condensed history algorithm  

Microsoft Academic Search

A new Condensed History algorithm is introduced to enhance the Monte Carlo simulation of electron transport problems. Unlike established multiple scattering algorithms, this method is a true transport process--it simulates a transport equation that approximates the exact Boltzmann equation. The new equation has a larger mean free path than, and preserves two angular moments of, the Boltzmann equation. Thus, the

E W Larsen; D R Tolar

1999-01-01

350

Tracks of a Non-Main Path Traveler  

PubMed Central

After an unconventional beginning in stroke research, I veered off the main path repeatedly to view problems from a different perspective. In this lecture summary, I would like to return to several points along the byways that led to research with some continuity. PMID:22246691

Hallenbeck, John M.

2012-01-01

351

Path Integral Monte-Carlo Calculations for Relativistic Oscillator  

E-print Network

The problem of Relativistic Oscillator has been studied in the framework of Path Integral Monte-Carlo(PIMC) approach. Ultra-relativistic and non-relativistic limits have been discussed. We show that PIMC method can be effectively used for investigation of relativistic systems.

Alexandr Ivanov; Oleg Pavlovsky

2014-11-11

352

Tool path planning for compound surfaces in spray forming processes  

Microsoft Academic Search

Spray forming is an emerging manufacturing process. The automated tool planning for this process is a nontrivial problem, especially for geometry-complicated parts consisting of multiple freeform surfaces. Existing tool planning approaches are not able to deal with this kind of compound surface. This paper proposes a tool-path planning approach which optimizes the tool motion performance and the thickness uniformity. There

Weihua Sheng; Heping Chen; Ning Xi; Yifan Chen

2005-01-01

353

Gibbs Measures on Brownian Paths: Theory and Applications  

Microsoft Academic Search

We review our investigations on Gibbs measures relative to Brownian motion, in particular the existence of such measures and their path properties, uniqueness, resp. non-uniqueness. For the case when the energy only depends on increments, we present a functional central limit theorem. We also explain connections with other work and state open problems of interest.

Volker Betz; József L?rinczi; Herbert Spohn

2004-01-01

354

Gibbs measures on Brownian paths: Theory and applications  

E-print Network

We review our investigations on Gibbs measures relative to Brownian motion, in particular the existence of such measures and their path properties, uniqueness, resp. non-uniqueness. For the case when the energy only depends on increments, we present a functional central limit theorem. We also explain connections with other work and state open problems of interest.

Volker Betz; Jozsef Lorinczi; Herbert Spohn

2004-04-26

355

Time-Optimal Control of Robotic Manipulators Along Specified Paths  

Microsoft Academic Search

The minimum-time manipulator control problem is solved for the case when the path is specified and the actuator torque limitations are known. The optimal open-loop torques are found, and a method is given for implementing these torques with a conventional linear feedback control system. The algorithm allows bounds on the torques that may be arbitrary functions of the joint angles

J. E. Bobrow; S. Dubowsky; J. S. Gibson

1985-01-01

356

Algorithms for hardware allocation in data path synthesis  

Microsoft Academic Search

Novel algorithms for the simultaneous cost\\/resource-constrained allocation of registers, arithmetic units, and interconnect in a data path have been developed. The entire allocation process can be formulated as a two-dimensional placement problem of microinstructions in space and time. This formulation readily lends itself to the use of a variety of heuristics for solving the allocation problem. The authors present simulated-annealing-based

Srinivas Devadas; A. Richard Newton

1989-01-01

357

Sampling-based algorithms for optimal path planning problems  

E-print Network

Sampling-based motion planning received increasing attention during the last decade. In particular, some of the leading paradigms, such the Probabilistic RoadMap (PRM) and the Rapidly-exploring Random Tree (RRT) algorithms, ...

Karaman, Sertac

2012-01-01

358

Algorithms for an Unmanned Vehicle Path Planning Problem  

E-print Network

e e?E ? + zN N?V \\{o} ? ? i i?N ? Let S denote a subset of vertices not containing the root vertex o. If subset S only contains vertices spanned by solution tree T, obviously S and T intersect each other. Thus there must be at least... this constraint: x e e?? (S ) ? + zN N ?S ? ? 1 S ? V \\{o} To ensure that there is at most one subset N that satisfies zN = 1, we add a second constraint: zN N?V \\{o} ? ? 1 Noting that because of the second term of the objective function...

Qin, Jianglei

2013-06-25

359

Solving the broken link problem in Walden's Paths  

E-print Network

-side agents approach [Turney 2000] is effective however it requires the agent to be trained before it can be used. The agent must be trained by providing it with a corpus of documents with the keywords manually selected from them... the context of the document, will be of the form noun, noun-noun, adjective-noun, noun-noun-noun, or adjective-noun-noun. Hence in the context of this thesis, keyphrases are considered to be one, two or three word phrases, not separated by punctuation...

Dalal, Zubin Jamshed

2004-09-30

360

Efficient Algorithms for Path Problems in Weighted Graphs  

E-print Network

: Guy Blelloch, Chair Manuel Blum Anupam Gupta Uri Zwick (Tel Aviv University) Submitted in partial as a collective effort of a large group of people. This group includes my advisor and coauthors, my family help and for believing in me. Firstly, I am deeply grateful to my family: to my mother Tanya and my

361

An Integer Programming Approach to the Path Selection Problems  

E-print Network

cation, and production. They are defined over ..... e ,for all k ? K}. Let Projy(Qe) be the projection of Qe onto y-space, and let conv(Se) be the convex hull of. Se. ..... Design of Capacitated Networks with Tree Configurations. Telecommunication ...

2007-05-28

362

Robust start for population-based algorithms solving job-shop scheduling problems  

Microsoft Academic Search

Most of the methods to solve job-shop scheduling problem (JSSP) are population-based and one of the strategies to reduce the time to reach the optimal solution is to produce an initial population that firstly has suitable distribution on space solution, secondly some of its points settle nearby to the optimal solution and lastly generate it in the shortest possible time.

Majid Abdolrazzagh Nezhad; Salwani Abdullah

2011-01-01

363

Crack Path Selection Fatigue crack path imaged via SEM  

E-print Network

phases fail in a brittle manner Fatigue Crack Growth ABSTRACT Advanced aerospace materials continue Crack path selects secondary phases and interface Conclusions ·Nb-Si Alloys tested exhibited toughness at high temperatures. An important property of any high temperature aerospace engineering material is its

Rollins, Andrew M.

364

Multiple paths in complex tasks  

NASA Technical Reports Server (NTRS)

The relationship between utility judgments of subtask paths and the utility of the task as a whole was examined. The convergent validation procedure is based on the assumption that measurements of the same quantity done with different methods should covary. The utility measures of the subtasks were obtained during the performance of an aircraft flight controller navigation task. Analyses helped decide among various models of subtask utility combination, whether the utility ratings of subtask paths predict the whole tasks utility rating, and indirectly, whether judgmental models need to include the equivalent of cognitive noise.

Galanter, Eugene; Wiegand, Thomas; Mark, Gloria

1987-01-01

365

Cooperative path planning for multiple UAVs in dynamic and uncertain environments  

Microsoft Academic Search

This paper addresses the problem of cooperative path planning for a fleet of unmanned aerial vehicles (UAVs). The paths are optimized to account for uncertainty\\/adversaries in the environment by modeling the probability of UAV loss. The approach extends prior work by coupling the failure probabilities for each UAV to the selected missions for all other UAVs. In order to maximize

John S. Bellingham; Michael Tillerson; Mehdi Alighanbari

2002-01-01

366

An Experimental Comparison of Path Planning Techniques for Teams of Mobile Robots  

E-print Network

An Experimental Comparison of Path Planning Techniques for Teams of Mobile Robots Maren Bennewitz of the mobile robots in their environment. The first approach con- sidered is the coordination technique tech- nique. 1 Introduction Path planning is one of the fundamental problems in mobile robotics

Teschner, Matthias

367

An Experimental Comparison of Path Planning Techniques for Teams of Mobile Robots  

E-print Network

An Experimental Comparison of Path Planning Techniques for Teams of Mobile Robots Maren Bennewitz,burgardg@informatik.uni­freiburg.de Abstract. This paper considers the problem of path planning for teams of mobile robots. It investigates two decoupled and prioritized approaches to coordinate the movements of the mobile robots in their environment

Burgard, Wolfram

368

Kingdon’s multiple streams model and automobile dependence reversal path: the case of Curitiba, Brazil  

Microsoft Academic Search

This paper draws on Kingdon’s multiple streams model of problems, policies and politics to explain the process of automobile dependence reversal path in urban transport planning in Curitiba, Brazil. What significantly contributed to the automobile dependence reversal path was a diverse coalition of actors who mobilized capabilities and structures to exploit policy windows at different periods of time and even

Meleckidzedeck Khayesi; Adjo A. Amekudzi

369

A moment estimate of the derivative process in rough path theory  

Microsoft Academic Search

In this paper we prove the derivative process of a rough differential equation driven by Brownian rough path has finite $L^r$-moment for any $r \\/ge 1$. Thanks to Burkholder-Davis-Gundy's inequality, this kind of problem is easy in the usual SDE theory. In the context of rough path theory, however, it does not seem so obvious.

Yuzuru Inahama

2010-01-01

370

Path Integral Analysis of Arrival Times with a Complex Potential  

E-print Network

A number of approaches to the arrival time problem employ a complex potential of a simple step function type and the arrival time distribution may then be calculated using the stationary scattering wave functions. Here, it is shown that in the Zeno limit (in which the potential becomes very large), the arrival time distribution may be obtained in a clear and simple way using a path integral representation of the propagator together with the path decomposition expansion (in which the propagator is factored across a surface of constant time). This method also shows that the same result is obtained for a wide class of complex potentials.

J. J. Halliwell

2008-01-28

371

The Complexity of Approximating the Class Steiner Tree Problem  

Microsoft Academic Search

Given a connected, undirected distance graph with required classesof nodes and optional Steiner nodes, find a shortest tree containingat least one node of each required class. This problem called ClassSteiner Tree is NP-hard and therefore we are dependent on approximation.In this paper, we investigate various restrictions of the problemcomparing their complexities with respect to approximability. A mainresult is that for

Edmund Ihler

1991-01-01

372

COMPUTER SCIENCE: MISCONCEPTIONS, CAREER PATHS  

E-print Network

Undergraduate Student) #12;Computer Science Misconceptions Intro to Computer Science - Florida International much can I make out of college? Data from the Bureau of Labor Statistics #12;Computer ScienceCOMPUTER SCIENCE: MISCONCEPTIONS, CAREER PATHS AND RESEARCH CHALLENGES School of Computing

Hristidis, Vagelis

373

The Path of Human Evolution  

Microsoft Academic Search

A complex series of evolutionary steps, contingent upon a dynamic environmental context and a long biological heritage, have led to the ascent of Homo sapiens as a dominant component of the modern biosphere. In a field where missing links still abound and new discoveries regularly overturn theoretical paradigms, our understanding of the path of human evolution has made tremendous advances

C. S. Feibel

2004-01-01

374

Advances in steam path technology  

Microsoft Academic Search

For many years, GE has been conducting research to understand better the loss mechanisms that degrade the aerodynamic performance of steam turbine stages, and to develop new computational fluid dynamics (CFD) computer programs to predict these losses accurately. This paper describes a number of new steam path design features that have been introduced in the GE steam turbine product line

John I. Cofer; J. I. IV

1996-01-01

375

Commercializing Biorefineries The Path Forward  

E-print Network

Commercializing Biorefineries The Path Forward Bioenergy ExCo 59 Workshop Golden, CO Lawrence J/R&DFocus Timeframe for R&D Successes & Commercialization 2006 200920082007 20112010 2012: R&D on bench and pilot for commercial demonstration projects 2006: Announced loan guarantee program for projects employing new energy

376

Career Paths in Environmental Sciences  

EPA Science Inventory

Career paths, current and future, in the environmental sciences will be discussed, based on experiences and observations during the author's 40 + years in the field. An emphasis will be placed on the need for integrated, transdisciplinary systems thinking approaches toward achie...

377

Immigration: Rubio's path to presidency?  

E-print Network

Immigration: Rubio's path to presidency? In media blitz retorting conservative critics, he aims Writer Of the four Democratic and four Republican senators who wrote the immigration reform proposal now, both in Congress and nationwide, need more convincing on immigration reform than Democrats. And Rubio

Fernandez, Eduardo

378

Career Paths of Academic Deans.  

ERIC Educational Resources Information Center

This paper examines various career paths leading to deanship and considers the implications of the findings for women and minorities who aspire to this position. The paper is part of a larger study of academic deanship conducted by the Center for Academic Leadership at Washington State University between October 1996 and January 1997. Data for the…

Wolverton, Mimi; Gonzales, Mary Jo

379

A triangular path inverting interferometer  

Microsoft Academic Search

A triangular path inverting interferometer is described with application to the study of thermal 'schlieren'. This is practically free of any vibration and coherence troubles, and possesses the unique feature that either differential or total shear may be obtained only with proper positioning of the object; once aligned, the optical components need not be disturbed further. This simple and stable

D. Chakrabarti; S. P. Basu; M. De

1977-01-01

380

NPRE at Illinois Three Paths  

E-print Network

production; Nuclear power operations and control � Plasma sciences; Applied plasma physics; Nuclear fusionNPRE at Illinois Three Paths Students choose from three concentrations: � Plasma and Fusion � Power and interactions of radiation with matter � Applications of nuclear processes � Nuclear fission for electric power

Gilbert, Matthew

381

Aircraft Engine Gas Path Diagnostic Methods: Public Benchmarking Results  

NASA Technical Reports Server (NTRS)

Recent technology reviews have identified the need for objective assessments of aircraft engine health management (EHM) technologies. To help address this issue, a gas path diagnostic benchmark problem has been created and made publicly available. This software tool, referred to as the Propulsion Diagnostic Method Evaluation Strategy (ProDiMES), has been constructed based on feedback provided by the aircraft EHM community. It provides a standard benchmark problem enabling users to develop, evaluate and compare diagnostic methods. This paper will present an overview of ProDiMES along with a description of four gas path diagnostic methods developed and applied to the problem. These methods, which include analytical and empirical diagnostic techniques, will be described and associated blind-test-case metric results will be presented and compared. Lessons learned along with recommendations for improving the public benchmarking processes will also be presented and discussed.

Simon, Donald L.; Borguet, Sebastien; Leonard, Olivier; Zhang, Xiaodong (Frank)

2013-01-01

382

Benchmarking Gas Path Diagnostic Methods: A Public Approach  

NASA Technical Reports Server (NTRS)

Recent technology reviews have identified the need for objective assessments of engine health management (EHM) technology. The need is two-fold: technology developers require relevant data and problems to design and validate new algorithms and techniques while engine system integrators and operators need practical tools to direct development and then evaluate the effectiveness of proposed solutions. This paper presents a publicly available gas path diagnostic benchmark problem that has been developed by the Propulsion and Power Systems Panel of The Technical Cooperation Program (TTCP) to help address these needs. The problem is coded in MATLAB (The MathWorks, Inc.) and coupled with a non-linear turbofan engine simulation to produce "snap-shot" measurements, with relevant noise levels, as if collected from a fleet of engines over their lifetime of use. Each engine within the fleet will experience unique operating and deterioration profiles, and may encounter randomly occurring relevant gas path faults including sensor, actuator and component faults. The challenge to the EHM community is to develop gas path diagnostic algorithms to reliably perform fault detection and isolation. An example solution to the benchmark problem is provided along with associated evaluation metrics. A plan is presented to disseminate this benchmark problem to the engine health management technical community and invite technology solutions.

Simon, Donald L.; Bird, Jeff; Davison, Craig; Volponi, Al; Iverson, R. Eugene

2008-01-01

383

Optimal and receding-horizon path planning algorithms for communications relay vehicles in complex environments  

E-print Network

This thesis presents new algorithms for path planning in a communications constrained environment for teams of unmanned vehicles. This problem involves a lead vehicle that must gather information from a set of locations ...

Kulling, Karl Christian

2009-01-01

384

UV laser long-path absorption spectroscopy  

NASA Technical Reports Server (NTRS)

Long path Differential Optical Absorption Spectroscopy (DOAS) using a picosecond UV laser as a light source was developed in our institute. Tropospheric OH radicals are measured by their rotational absorption lines around 308 nm. The spectra are obtained using a high resolution spectrograph. The detection system has been improved over the formerly used optomechanical scanning device by application of a photodiode array which increased the observed spectral range by a factor of 6 and which utilizes the light much more effectively leading to a considerable reduction of the measurement time. This technique provides direct measurements of OH because the signal is given by the product of the absorption coefficient and the OH concentration along the light path according to Lambert-Beers law. No calibration is needed. Since the integrated absorption coefficient is well known the accuracy of the measurement essentially depends on the extent to which the OH absorption pattern can be detected in the spectra. No interference by self generated OH radicals in the detection lightpath has been observed. The large bandwidth (greater than 0.15 nm) and the high spectral resolution (1.5 pm) allows absolute determination of interferences by other trace gas absorptions. The measurement error is directly accessible from the absorption-signal to baseline-noise ratio in the spectra. The applicability of the method strongly depends on visibility. Elevated concentrations of aerosols lead to considerable attenuation of the laser light which reduces the S/N-ratio. In the moderately polluted air of Julich, where we performed a number of OH measurement spectra. In addition absorption features of unidentified species were frequently detected. A quantitative deconvolution even of the known species is not easy to achieve and can leave residual structures in the spectra. Thus interferences usually increase the noise and deteriorate the OH detection sensitivity. Using diode arrays for sensitive absorption measurements some specific problems of those detectors have to be solved experimentally (i.e. fixed pattern noise, dark signal noise, nonuniform efficiency of individual elements, spatial sensitivity variations). In order to improve the low spatial resolution we performed laboratory studies using a multiple reflection cell to convert the long path technique to a real in situ point measurement. Under the conditions of field experiments in Julich residual absorbance signals at present are about 1.5x10(exp -4) corresponding to an OH detection sensitivity of 2x10(exp 6) OH/cm(exp 3) using a light path of 5.8 km. Total integration times for one measurement point vary between a few minutes and an hour.

Dorn, Hans-Peter; Brauers, Theo; Neuroth, Rudolf

1994-01-01

385

Towards a Nonperturbative Path Integral in Gauge Theories  

E-print Network

We propose a modification of the Faddeev-Popov procedure to construct a path integral representation for the transition amplitude and the partition function for gauge theories whose orbit space has a non-Euclidean geometry. Our approach is based on the Kato-Trotter product formula modified appropriately to incorporate the gauge invariance condition, and thereby equivalence to the Dirac operator formalism is guaranteed by construction. The modified path integral provides a solution to the Gribov obstruction as well as to the operator ordering problem when the orbit space has curvature. A few explicit examples are given to illustrate new features of the formalism developed. The method is applied to the Kogut-Susskind lattice gauge theory to develop a nonperturbative functional integral for a quantum Yang-Mills theory. Feynman's conjecture about a relation between the mass gap and the orbit space geometry in gluodynamics is discussed in the framework of the modified path integral.

Sergei V. Shabanov; John R. Klauder

1999-02-01

386

Ab Initio Path to Heavy Nuclei  

E-print Network

We present the first ab initio calculations of nuclear ground states up into the domain of heavy nuclei, spanning the range from 16-O to 132-Sn based on two- plus three-nucleon interactions derived within chiral effective field theory. We employ the similarity renormalization group for preparing the Hamiltonian and use coupled-cluster theory to solve the many-body problem for nuclei with closed sub-shells. Through an analysis of theoretical uncertainties resulting from various truncations in this framework, we identify and eliminate the technical hurdles that previously inhibited the step beyond medium-mass nuclei, allowing for reliable validations of nuclear Hamiltonians in the heavy regime. Following this path we show that chiral Hamiltonians qualitatively reproduce the systematics of nuclear ground-state energies up to the neutron-rich Sn isotopes.

Sven Binder; Joachim Langhammer; Angelo Calci; Robert Roth

2013-12-19

387

High-quality path planning for autonomous mobile robots with ?3-splines and parallel genetic algorithms  

Microsoft Academic Search

In this paper we apply the composite eta3 splines to collision-free curvature-derivative continuous shorter path planning of wheeled mobile robots, modelled as unicycle, within known static environments. The path planning problem is formulated as a bi-objective optimization problem of searching a sequence of N ordered intermediate configurations between start and goal configurations over the group of all possible configurations that

Han-Chih Chang; Jing-Sin Liu

2009-01-01

388

Planning Curvature-Constrained Paths to Multiple Goals Using Circle Sampling  

E-print Network

Steiner tree over the roadmap. Since optimally solving the multi-goal planning problem requires) Optimal plan found by solving a directed Steiner tree problem (32% better than independent paths). (c the approach to 3D workspaces. We then formulate the multi- goal planning problem as finding a minimum directed

Alterovitz, Ron

389

Facilities layout design optimization with single loop material flow path configuration  

Microsoft Academic Search

Here we formulate the facilities layout design optimization problem for a single loop material flow path configuration. Because of the NP-bard nature of the overall search space, we employ a genetic approach to sample the decomposed search spaces. In addition we analyse the following features of the problem: (1) we estimate lower bounds for the unidirectional flow problem along the

P. BANERJEE; Y. ZHOU

1995-01-01

390

Hierarchical oriented genetic algorithms for coverage path planning of multi-robot teams with load balancing  

Microsoft Academic Search

Multi-robot coverage path planning problems require every point in a given area to be covered by at least one member of the robot team using their sensors. For a time-efficient coverage, the environment needs to be partitioned among robots in a balanced manner. So the problem can be modeled as task assignment problem with load balancing. In this study, we

Metin Ozkan; Ahmet Yazici; Muzaffer Kapanoglu; Osman Parlaktuna

2009-01-01

391

The Geometrical Representation of Path Planning Leo Dorst, Indur Mandhyan, Karen Trovato  

E-print Network

, and Rubik's Cube are given. These very different problems (holonomic, non­holonomic and discrete­ neuvering [3] and problems now outside the community such as discrete path planning for Rubik's Cube [10, permutational problems such as Rubik's Cube. Consider a device with n degrees of freedom (for a robot

Dorst, Leo

392

Global bifurcation criterion for oscillatory crack path instability.  

PubMed

A bifurcation criterion for the transition from straight to oscillatory quasistatic crack propagation in an isotropic material is derived from the requirement of pure mode I stress fields at the crack tip (K_{II}=0) on the entire crack path, henceforth called global bifurcation criterion. For a small-amplitude sine-shaped crack path which is observed in experiments at the transition, it is shown to be sufficient to postulate K_{II}=0 only for two phases of the crack path instead, which simplifies calculations. By using the measured temperature fields to solve the thermoelastic problem of dipping a hot thin glass slab into cold water, critical wavelengths of the oscillating crack growth obtained with the derived global bifurcation criterion agree remarkably well with those observed in experiments by Ronsin and Perrin. It is also shown that local bifurcation criteria, which do not take into account K_{II}=0 on the entire crack path, lead to incorrect results for the oscillatory crack path instability. PMID:18643343

Pham, Van-Bac; Bahr, Hans-Achim; Bahr, Ute; Balke, Herbert; Weiss, Hans-Jürgen

2008-06-01

393

Path integral on star graph  

NASA Astrophysics Data System (ADS)

In this paper we study path integral for a single spinless particle on a star graph with N edges, whose vertex is known to be described by U(N) family of boundary conditions. After carefully studying the free particle case, both at the critical and off-critical levels, we propose a new path integral formulation that correctly captures all the scale-invariant subfamily of boundary conditions realized at fixed points of boundary renormalization group flow. Our proposal is based on the folding trick, which maps a scalar-valued wave function on star graph to an N-component vector-valued wave function on half-line. All the parameters of scale-invariant subfamily of boundary conditions are encoded into the momentum independent weight factors, which appear to be associated with the two distinct path classes on half-line that form the cyclic group Z2. We show that, when bulk interactions are edge-independent, these weight factors are generally given by an N-dimensional unitary representation of Z2. Generalization to momentum dependent weight factors and applications to worldline formalism are briefly discussed.

Ohya, Satoshi

2012-06-01

394

Model for Delay Faults Based upon Paths  

Microsoft Academic Search

Delay testing of combinational logic in a clocked environment is analyzed. A model based upon paths is introduced for delay faults. Any path with a total delay exceeding the clock interval is called a \\

Gordon L. Smith

1985-01-01

395

Electron Inelastic-Mean-Free-Path Database  

National Institute of Standards and Technology Data Gateway

SRD 71 NIST Electron Inelastic-Mean-Free-Path Database (PC database, no charge)   This database provides values of electron inelastic mean free paths (IMFPs) for use in quantitative surface analyses by AES and XPS.

396

Path-Based, Randomized, Oblivious, Minimal Routing  

E-print Network

Path-based, Randomized, Oblivious, Minimal routing (PROM) is a family of oblivious, minimal, path-diverse routing algorithms especially suitable for Network-on-Chip applications with n x n mesh geometry. Rather than choosing ...

Cho, Myong Hyon

2009-01-01

397

Data-path layout design inside SOC  

Microsoft Academic Search

As more data-path stacks are integrated into system-on-a-chip (SOC), data-path is becoming a critical part of the whole giga-scale integrated circuits (GSI) design. The traditional layout design methodology can not satisfy the data-path performance requirements because it has no knowledge of the data-path bit-sliced structure and the strict performance (such as timing, coupling, and crosstalk) constraints. In this paper, we

Tong Jing; Xian-Long Hong; Yi-Ci Cai; Jing-Yu Xu; Chang-Qi Yang; Yi-Qian Zhang; Qiang Zhou; Weimin Wu

2002-01-01

398

Multiple Paths to Encephalization and Technical Civilizations  

NASA Astrophysics Data System (ADS)

We propose consideration of at least two possible evolutionary paths for the emergence of intelligent life with the potential for technical civilization. The first is the path via encephalization of homeothermic animals; the second is the path to swarm intelligence of so-called superorganisms, in particular the social insects. The path to each appears to be facilitated by environmental change: homeothermic animals by decreased climatic temperature and for swarm intelligence by increased oxygen levels.

Schwartzman, David; Middendorf, George

2011-12-01

399

Functional Equivalence and Spatial Path Memory  

Microsoft Academic Search

Loomis, Klatzky, Avraamides, Lippa & Golledge (2007) suggest that, when it comes to spatial information, verbal description and perceptual experience are nearly functionally equivalent with respect to the cognitive representations they produce. We tested this idea for the case of spatial memory for complex paths. Paths consisted entirely of unit-length segments followed by 90-degree turns, thus assuring that a path

Don R. Lyon; Glenn M. Gunzelmann

2011-01-01

400

Free Space Path Loss of UWB Communications  

Microsoft Academic Search

Although the Friis' formula is widely used to calculate the free space path loss of narrowband communications, it is considered only single frequency. Therefore, it should be extended to calculate the free space path loss of ultra wideband (UWB) communications by considering the frequency bandwidth. In this paper, the free space path loss of UWB communications is studies. The Friis'

Pichaya Supanakoon; Sathit Aroonpraparat; Sathaporn Promwong; Jun-ichi Takada

401

Path and Trajectory Diversity Theory and Algorithms  

E-print Network

Path and Trajectory Diversity Theory and Algorithms Ross A. Knepper International Conference and Kuffner, SIGGRAPH, 2006] Introduction ConclusionResultsAlgorithmsApproach Theory #12;R.A. Knepper PathResultsAlgorithmsApproach Theory #12;R.A. Knepper Path and Trajectory Diversity 4 Diversity Spectrum Easy to increase diversity

Branicky, Michael S.

402

Evaluation of the Learning Path Specification  

ERIC Educational Resources Information Center

Flexible lifelong learning requires that learners can compare and select learning paths that best meet individual needs, not just in terms of learning goals, but also in terms of planning, costs etc. To this end a learning path specification was developed, which describes both the contents and the structure of any learning path, be it formal,…

Janssen, Jose; Berlanga, Adriana J.; Koper, Rob

2011-01-01

403

Transition Path Theory E. Vanden-Eijnden  

E-print Network

Transition Path Theory E. Vanden-Eijnden Courant Institute of Mathematical Sciences, New York University New York, NY 10012 eve2cims.nyu.edu Eric Vanden-Eijnden E. Vanden-Eijnden: Transition Path Theory State Theory (TST) and Transition Path Sampling (TPS). . . . . . . . . . . . . . . . . . . . . . 455 6

Van Den Eijnden, Eric

404

Biodosimetry estimation using the ratio of the longest:shortest length in the premature chromosome condensation (PCC) method applying autocapture and automatic image analysis  

PubMed Central

The combination of automatic image acquisition and automatic image analysis of premature chromosome condensation (PCC) spreads was tested as a rapid biodosimeter protocol. Human peripheral lymphocytes were irradiated with 60Co gamma rays in a single dose of between 1 and 20 Gy, stimulated with phytohaemaglutinin and incubated for 48 h, division blocked with Colcemid, and PCC-induced by Calyculin A. Images of chromosome spreads were captured and analysed automatically by combining the Metafer 4 and CellProfiler platforms. Automatic measurement of chromosome lengths allows the calculation of the length ratio (LR) of the longest and the shortest piece that can be used for dose estimation since this ratio is correlated with ionizing radiation dose. The LR of the longest and the shortest chromosome pieces showed the best goodness-of-fit to a linear model in the dose interval tested. The application of the automatic analysis increases the potential use of the PCC method for triage in the event of massive radiation causalities. PMID:24789085

Gonzalez, Jorge E.; Romero, Ivonne; Gregoire, Eric; Martin, Cecile; Lamadrid, Ana I.; Voisin, Philippe; Barquinero, Joan-Francesc; GarcIa, Omar

2014-01-01

405

Biodosimetry estimation using the ratio of the longest:shortest length in the premature chromosome condensation (PCC) method applying autocapture and automatic image analysis.  

PubMed

The combination of automatic image acquisition and automatic image analysis of premature chromosome condensation (PCC) spreads was tested as a rapid biodosimeter protocol. Human peripheral lymphocytes were irradiated with (60)Co gamma rays in a single dose of between 1 and 20 Gy, stimulated with phytohaemaglutinin and incubated for 48 h, division blocked with Colcemid, and PCC-induced by Calyculin A. Images of chromosome spreads were captured and analysed automatically by combining the Metafer 4 and CellProfiler platforms. Automatic measurement of chromosome lengths allows the calculation of the length ratio (LR) of the longest and the shortest piece that can be used for dose estimation since this ratio is correlated with ionizing radiation dose. The LR of the longest and the shortest chromosome pieces showed the best goodness-of-fit to a linear model in the dose interval tested. The application of the automatic analysis increases the potential use of the PCC method for triage in the event of massive radiation causalities. PMID:24789085

González, Jorge E; Romero, Ivonne; Gregoire, Eric; Martin, Cécile; Lamadrid, Ana I; Voisin, Philippe; Barquinero, Joan-Francesc; García, Omar

2014-09-01

406

Dynamical path integral calculations for condensed phase processes  

NASA Astrophysics Data System (ADS)

As is well known, the computational effort in quantum mechanics grows exponentially with system size. Thus a typical computation of an interesting many-body problem quickly becomes prohibitive. In this work, we try to circumvent this exponential scaling by treating a few degrees of freedom explicitly (i.e. the system) while integrating out the rest of the degrees of freedom (i.e. the bath). For a bath of harmonic oscillators, this integration procedure is well known and we apply this result to problems of charge transfer across molecules by summing over statistically significant system paths. If we have a generic bath composed of classical like particles interacting with the system of interest, the classical behavior of the bath influences the quantum mechanical behavior of the system. Thus we arrive at a rigorous quantum-classical path integral formulation which we believe has very promising applications in chemistry and biology.

Lambert-Garrido, Roberto

407

Residues crucial for maintaining short paths in network communication mediate signaling in proteins  

PubMed Central

Here, we represent protein structures as residue interacting networks, which are assumed to involve a permanent flow of information between amino acids. By removal of nodes from the protein network, we identify fold centrally conserved residues, which are crucial for sustaining the shortest pathways and thus play key roles in long-range interactions. Analysis of seven protein families (myoglobins, G-protein-coupled receptors, the trypsin class of serine proteases, hemoglobins, oligosaccharide phosphorylases, nuclear receptor ligand-binding domains and retroviral proteases) confirms that experimentally many of these residues are important for allosteric communication. The agreement between the centrally conserved residues, which are key in preserving short path lengths, and residues experimentally suggested to mediate signaling further illustrates that topology plays an important role in network communication. Protein folds have evolved under constraints imposed by function. To maintain function, protein structures need to be robust to mutational events. On the other hand, robustness is accompanied by an extreme sensitivity at some crucial sites. Thus, here we propose that centrally conserved residues, whose removal increases the characteristic path length in protein networks, may relate to the system fragility. PMID:16738564

del Sol, Antonio; Fujihashi, Hirotomo; Amoros, Dolors; Nussinov, Ruth

2006-01-01

408

Enhancement of the Texas A&M University Autonomous Underwater Vehicle Controller through development of a middle level classical path planner  

E-print Network

in complicated environments which require backtracking or directed search for a valid path. The specific safe travel requirements of the prototype AUV allow reduction of the path planning problem for the AUV to that of path planning for a point robot. An octree...

Green, Jeremy Donald

2012-06-07

409

Better approximation bounds for the network and Euclidean Steiner tree problems  

Microsoft Academic Search

The network and Euclidean Steiner tree problems require a shortest tree spanninga given vertex subset within a network G = (V; E; d) and Euclidean plane, respectively.For these problems, we present a series of heuristics finding approximate Steiner tree withperformance guarantee coming arbitrary close to 1+ln2 1:693 and 1+ln2p3 1:1438,respectively. The best previously known corresponding values are close to 1.746

Alexander Zelikovsky

1995-01-01

410

Tool-Path Generation for Fractal Curve Making  

Microsoft Academic Search

Many fractal generation methods have been developed and used to create an image of a natural scene. Nonlinear dynamic systems\\u000a employ fractal theory for population growth. Fractals have also been used to model chaotic problems. In numerical control\\u000a (NC) machining, fractal curves have been used in tool-path generation. Although the visualisation of fractal geometry has\\u000a been successfully demonstrated by computer

S. C. Soo; K. M. Yu

2002-01-01

411

A Discrete History of the Lorentzian Path Integral  

Microsoft Academic Search

In these lecture notes, I describe the motivation behind a recent formulation of a non-perturbative gravitational path integral for Lorentzian (instead of the usual Euclidean) space-times, and give a pedagogical introduction to its main features. At the regularized, discrete level this approach solves the problems of (i) having a well-defined Wick rotation, (ii) possessing a coordinate-invariant cutoff, and (iii) leading

Renate Loll

2003-01-01

412

Quality Up in Polynomial Homotopy Continuation by Multithreaded Path Tracking  

E-print Network

Speedup measures how much faster we can solve the same problem using many cores. If we can afford to keep the execution time fixed, then quality up measures how much better the solution will be computed using many cores. In this paper we describe our multithreaded implementation to track one solution path defined by a polynomial homotopy. Limiting quality to accuracy and confusing accuracy with precision, we strive to offset the cost of multiprecision arithmetic running multithreaded code on many cores.

Verschelde, Jan

2011-01-01

413

Terminal area guidance along curved paths: A stochastic control approach  

NASA Technical Reports Server (NTRS)

Stochastic control theory is applied to the problem of designing a digital flight compensator for terminal guidance along a helical flight path as a prelude to landing. The development of aircraft, wind, and measurement models is discussed along with a control scheme consisting of feedback gains multiplying estimate of the aircraft and wind states obtained from a Kalman one step predictor. Preliminary results are presented which indicate that the compensator performs satisfactorily in the presence of both steady winds and gusts.

Quaranta, J. E.; Foulkes, R. H., Jr.

1976-01-01

414

Coherent-state path integrals in the continuum  

NASA Astrophysics Data System (ADS)

We discuss the time continuous path integration in the coherent-state basis in a way that is free from inconsistencies. Employing this notion we reproduce known and exact results working directly in the continuum. Such a formalism can set the basis to develop perturbative and nonperturbative approximations already known in the quantum-field-theory community. These techniques can be proven useful in a great variety of problems where bosonic Hamiltonians are used.

Kordas, G.; Mistakidis, S. I.; Karanikas, A. I.

2014-09-01

415

Attention trees and semantic paths  

NASA Astrophysics Data System (ADS)

In the last few decades several techniques for image content extraction, often based on segmentation, have been proposed. It has been suggested that under the assumption of very general image content, segmentation becomes unstable and classification becomes unreliable. According to recent psychological theories, certain image regions attract the attention of human observers more than others and, generally, the image main meaning appears concentrated in those regions. Initially, regions attracting our attention are perceived as a whole and hypotheses on their content are formulated; successively the components of those regions are carefully analyzed and a more precise interpretation is reached. It is interesting to observe that an image decomposition process performed according to these psychological visual attention theories might present advantages with respect to a traditional segmentation approach. In this paper we propose an automatic procedure generating image decomposition based on the detection of visual attention regions. A new clustering algorithm taking advantage of the Delaunay- Voronoi diagrams for achieving the decomposition target is proposed. By applying that algorithm recursively, starting from the whole image, a transformation of the image into a tree of related meaningful regions is obtained (Attention Tree). Successively, a semantic interpretation of the leaf nodes is carried out by using a structure of Neural Networks (Neural Tree) assisted by a knowledge base (Ontology Net). Starting from leaf nodes, paths toward the root node across the Attention Tree are attempted. The task of the path consists in relating the semantics of each child-parent node pair and, consequently, in merging the corresponding image regions. The relationship detected in this way between two tree nodes generates, as a result, the extension of the interpreted image area through each step of the path. The construction of several Attention Trees has been performed and partial results will be shown.

Giusti, Christian; Pieroni, Goffredo G.; Pieroni, Laura

2007-02-01

416

Intellimotion: California PATH's Quarterly Newsletter  

NSDL National Science Digital Library

The California Partners for Advanced Transit and Highways (PATH) researches methods for increasing highway safety, reducing congestion, and minimizing pollution and energy consumption. Intellimotion is one of its publications that highlights some of the current projects. Although it is labeled as a quarterly newsletter, Intellimotion is released on a very irregular basis. The 2002 issue covers several stories, including a project that makes vehicle navigation with the Global Positioning System extremely accurate. Another article looks at intelligent transportation systems and the issues regarding Bus Rapid Transit. Many past issues of Intellimotion are available on this Web site. This site is also reviewed in the October 25, 2002 Scout Report.

1998-01-01

417

Multiple order common path spectrometer  

NASA Technical Reports Server (NTRS)

The present invention relates to a dispersive spectrometer. The spectrometer allows detection of multiple orders of light on a single focal plane array by splitting the orders spatially using a dichroic assembly. A conventional dispersion mechanism such as a defraction grating disperses the light spectrally. As a result, multiple wavelength orders can be imaged on a single focal plane array of limited spectral extent, doubling (or more) the number of spectral channels as compared to a conventional spectrometer. In addition, this is achieved in a common path device.

Newbury, Amy B. (Inventor)

2010-01-01

418

Communication path for extreme environments  

NASA Technical Reports Server (NTRS)

Methods and systems for using one or more radio frequency identification devices (RFIDs), or other suitable signal transmitters and/or receivers, to provide a sensor information communication path, to provide location and/or spatial orientation information for an emergency service worker (ESW), to provide an ESW escape route, to indicate a direction from an ESW to an ES appliance, to provide updated information on a region or structure that presents an extreme environment (fire, hazardous fluid leak, underwater, nuclear, etc.) in which an ESW works, and to provide accumulated thermal load or thermal breakdown information on one or more locations in the region.

Jorgensen, Charles C. (Inventor); Betts, Bradley J. (Inventor)

2010-01-01

419

Least expected time paths in stochastic, time-varying transportation networks  

SciTech Connect

The authors consider stochastic, time-varying transportation networks, where the arc weights (arc travel times) are random variables with probability distribution functions that vary with time. Efficient procedures are widely available for determining least time paths in deterministic networks. In stochastic but time-invariant networks, least expected time paths can be determined by setting each random arc weight to its expected value and solving an equivalent deterministic problem. This paper addresses the problem of determining least expected time paths in stochastic, time-varying networks. Two procedures are presented. The first procedure determines the a priori least expected time paths from all origins to a single destination for each departure time in the peak period. The second procedure determines lower bounds on the expected times of these a priori least expected time paths. This procedure determines an exact solution for the problem where the driver is permitted to react to revealed travel times on traveled links en route, i.e. in a time-adaptive route choice framework. Modifications to each of these procedures for determining least expected cost (where cost is not necessarily travel time) paths and lower bounds on the expected costs of these paths are given. Extensive numerical tests are conducted to illustrate the algorithms` computational performance as well as the properties of the solution.

Miller-Hooks, E.D. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Civil and Environmental Engineering; Mahmassani, H.S. [Univ. of Texas, Austin, TX (United States)

1999-06-01

420

Potential theory, path integrals and the Laplacian of the indicator  

E-print Network

This paper links the field of potential theory -- i.e. the Dirichlet and Neumann problems for the heat and Laplace equation -- to that of the Feynman path integral, by postulating that the potential is equal to plus/minus the Laplacian of the indicator of the domain D. The Laplacian of the indicator is a generalized function: it is the d-dimensional analogue of the Dirac delta'-function. This function has -- according to the author's best knowledge -- not formally been defined before. We show, first, that the path integral's perturbation series (or Born series) matches the classical single and double boundary layer series of potential theory, thereby connecting two hitherto unrelated fields. Second, we show that the perturbation series is valid for all domains D that allow Green's theorem (i.e. with a finite number of corners, edges and cusps), thereby expanding the classical applicability of boundary layers. Third, we show that the minus (plus) in the potential holds for the Dirichlet (Neumann) boundary condition; showing for the first time a particularly close connection between these two classical problems. Fourth, we demonstrate that the perturbation series of the path integral converges in a monotone/alternating fashion, depending on the convexity/concavity of the domain. We also discuss the third boundary problem (which poses Robin boundary conditions) and discuss an extension to moving domains.

Rutger-Jan Lange

2013-02-04

421

Cumulative slant path rain attenuation associated with COMSTAR beacon at 28.56 GHz for Wallops Island, Virginia  

NASA Technical Reports Server (NTRS)

Yearly, monthly, and time of day fade statistics are presented and characterized. A 19.04 GHz yearly fade distribution, corresponding to a second COMSTAR beacon frequency, is predicted using the concept of effective path length, disdrometer, and rain rate results. The yearly attenuation and rain rate distributions follow with good approximation log normal variations for most fade and rain rate levels. Attenuations were exceeded for the longest and shortest periods of times for all fades in August and February, respectively. The eight hour time period showing the maximum and minimum number of minutes over the year for which fades exceeded 12 db were approximately between 1600 to 2400, and 0400 to 1200 hours, respectively. In employing the predictive method for obtaining the 19.04 GHz fade distribution, it is demonstrated theoretically that the ratio of attenuations at two frequencies is minimally dependent of raindrop size distribution providing these frequencies are not widely separated.

Goldhirsh, J.

1978-01-01

422

Regularization Paths for Generalized Linear Models via Coordinate Descent.  

PubMed

We develop fast algorithms for estimation of generalized linear models with convex penalties. The models include linear regression, two-class logistic regression, and multinomial regression problems while the penalties include ?(1) (the lasso), ?(2) (ridge regression) and mixtures of the two (the elastic net). The algorithms use cyclical coordinate descent, computed along a regularization path. The methods can handle large problems and can also deal efficiently with sparse features. In comparative timings we find that the new algorithms are considerably faster than competing methods. PMID:20808728

Friedman, Jerome; Hastie, Trevor; Tibshirani, Rob

2010-01-01

423

Regularization Paths for Generalized Linear Models via Coordinate Descent  

PubMed Central

We develop fast algorithms for estimation of generalized linear models with convex penalties. The models include linear regression, two-class logistic regression, and multinomial regression problems while the penalties include ?1 (the lasso), ?2 (ridge regression) and mixtures of the two (the elastic net). The algorithms use cyclical coordinate descent, computed along a regularization path. The methods can handle large problems and can also deal efficiently with sparse features. In comparative timings we find that the new algorithms are considerably faster than competing methods. PMID:20808728

Friedman, Jerome; Hastie, Trevor; Tibshirani, Rob

2010-01-01

424

Obstacle Bypassing in Optimal Ship Routing Using Simulated Annealing  

SciTech Connect

In this paper we are going to discuss a variation on the problem of finding the shortest path between two points in optimal ship routing problems consisting of obstacles that are not allowed to be crossed by the path. Our main goal are going to be the construction of an appropriate algorithm, based in an earlier work by computing the shortest path between two points in the plane that avoids a set of polygonal obstacles.

Kosmas, O. T.; Vlachos, D. S.; Simos, T. E. [University of Pelloponnese, 22100 Tripoli (Greece)

2008-11-06

425

Path-following control of wheeled planetary exploration robots moving on deformable rough terrain.  

PubMed

The control of planetary rovers, which are high performance mobile robots that move on deformable rough terrain, is a challenging problem. Taking lateral skid into account, this paper presents a rough terrain model and nonholonomic kinematics model for planetary rovers. An approach is proposed in which the reference path is generated according to the planned path by combining look-ahead distance and path updating distance on the basis of the carrot following method. A path-following strategy for wheeled planetary exploration robots incorporating slip compensation is designed. Simulation results of a four-wheeled robot on deformable rough terrain verify that it can be controlled to follow a planned path with good precision, despite the fact that the wheels will obviously skid and slip. PMID:24790582

Ding, Liang; Gao, Hai-bo; Deng, Zong-quan; Li, Zhijun; Xia, Ke-rui; Duan, Guang-ren

2014-01-01

426

A Path to Relevant Teaching  

ERIC Educational Resources Information Center

Discusses problems of college biology teachers in terms of content choice and student-teacher relationships. Advocates a deemphasis on molecular biology focussing on ecology in general biology courses. Discusses the relative values of interest in students and interest in subject matter, problems of releasing potential for learning, and the nature…

Hardin, Garrett

1970-01-01

427

Sequential Path Entanglement for Quantum Metrology  

PubMed Central

Path entanglement is a key resource for quantum metrology. Using path-entangled states, the standard quantum limit can be beaten, and the Heisenberg limit can be achieved. However, the preparation and detection of such states scales unfavourably with the number of photons. Here we introduce sequential path entanglement, in which photons are distributed across distinct time bins with arbitrary separation, as a resource for quantum metrology. We demonstrate a scheme for converting polarization Greenberger-Horne-Zeilinger entanglement into sequential path entanglement. We observe the same enhanced phase resolution expected for conventional path entanglement, independent of the delay between consecutive photons. Sequential path entanglement can be prepared comparably easily from polarization entanglement, can be detected without using photon-number-resolving detectors, and enables novel applications.

Jin, Xian-Min; Peng, Cheng-Zhi; Deng, Youjin; Barbieri, Marco; Nunn, Joshua; Walmsley, Ian A.

2013-01-01

428

The Logic behind Feynman's Paths  

E-print Network

The classical notions of continuity and mechanical causality are left in order to refor- mulate the Quantum Theory starting from two principles: I) the intrinsic randomness of quantum process at microphysical level, II) the projective representations of sym- metries of the system. The second principle determines the geometry and then a new logic for describing the history of events (Feynman's paths) that modifies the rules of classical probabilistic calculus. The notion of classical trajectory is replaced by a history of spontaneous, random an discontinuous events. So the theory is reduced to determin- ing the probability distribution for such histories according with the symmetries of the system. The representation of the logic in terms of amplitudes leads to Feynman rules and, alternatively, its representation in terms of projectors results in the Schwinger trace formula.

Edgardo T. Garcia Alvarez

2010-11-22

429

Choosing Your Geosciences Career Path  

NASA Astrophysics Data System (ADS)

There are many possibilities for rewarding careers in the geosciences including positions in academia, government, industry, and other parts of the private sector. How do you choose the right path to meet your goals and needs and find the right career? What are the tradeoffs and strategic moves that you should make at different stages in your career? Some of the pros and cons between soft-money research, government research, and management and industry positions are discussed from a personal perspective. In addition this presentation will provide some perspective on different career choices as seen by program managers in funding agencies. The competing priorities between work life and private life are discussed with the some thoughts on compromising between "having it all" and finding what works for you.

Paluszkiewicz, T.

2002-12-01

430

Robust Flight Path Determination for Mars Precision Landing Using Genetic Algorithms  

NASA Technical Reports Server (NTRS)

This paper documents the application of genetic algorithms (GAs) to the problem of robust flight path determination for Mars precision landing. The robust flight path problem is defined here as the determination of the flight path which delivers a low-lift open-loop controlled vehicle to its desired final landing location while minimizing the effect of perturbations due to uncertainty in the atmospheric model and entry conditions. The genetic algorithm was capable of finding solutions which reduced the landing error from 111 km RMS radial (open-loop optimal) to 43 km RMS radial (optimized with respect to perturbations) using 200 hours of computation on an Ultra-SPARC workstation. Further reduction in the landing error is possible by going to closed-loop control which can utilize the GA optimized paths as nominal trajectories for linearization.

Bayard, David S.; Kohen, Hamid

1997-01-01

431

The Feynman Path Integral: An Historical Slice  

E-print Network

Efforts to give an improved mathematical meaning to Feynman's path integral formulation of quantum mechanics started soon after its introduction and continue to this day. In the present paper, one common thread of development is followed over many years, with contributions made by various authors. The present version of this line of development involves a continuous-time regularization for a general phase space path integral and provides, in the author's opinion at least, perhaps the optimal formulation of the path integral.

John R. Klauder

2003-03-07

432

The path integral for dendritic trees  

Microsoft Academic Search

We construct the path integral for determining the potential on any dendritic tree described by a linear cable equation. This is done by generalizing Brownian motion from a line to a tree. We also construct the path integral for dendritic structures with spatially-varying and\\/or time-dependent membrane conductivities due, for example, to synaptic inputs. The path integral allows novel computational techniques

L. F. Abbott; Edward Farhi; Sam Gutmann

1991-01-01

433

Accelerating tool path computing in CAD\\/CAM: A FPGA architecture for turning lathe machining  

Microsoft Academic Search

Tool path generation is one of the most complex problems in computer aided manufacturing. The algorithm called virtual digitizing avoids this problem by its own definition but its computing cost is high. Presented in the paper there is a virtual digitizing hardware\\/software architecture that takes advantage of field programmable gate arrays (FPGAs) to improve the algorithm efficiency and to meet

Antonio Jimeno-morenilla; Antonio Martínez; Sergio Cuenca; Jose Luis Sánchez-romero

2007-01-01

434

Control of Delayed Recycling Systems with an Unstable Pole at Forward Path  

E-print Network

Control of Delayed Recycling Systems with an Unstable Pole at Forward Path J. F. Marquez Rubio, B. del Muro Cu´ellar and Olivier Sename Abstract-- Unstable time delay system and recycling system pose a challenge problem in their own. When unstable time delay system have recycle the control problem becomes

Paris-Sud XI, Université de

435

Balance Problems  

MedlinePLUS

... often, it could be a sign of a balance problem. Balance problems can make you feel unsteady or as ... fall-related injuries, such as hip fracture. Some balance problems are due to problems in the inner ...

436

ChanderjitBajaj Departmentof Computer Science,  

E-print Network

of polyhedral obstacles is a special case of the more general problem of planning optimal collision-free paths- test path is polynomial time computable, Lozano-Perez, Wesley [4]. This problem for Euclidean 3-space, the problem of determining the points of contact of the shortest path with these edges can without loss of gen

Texas at Austin, University of

437

Combined Single-Path Routing and Flow Control in Many-User Region: A Case for Nash Efficiency  

E-print Network

Combined Single-Path Routing and Flow Control in Many-User Region: A Case for Nash Efficiency Huigang Chen and John S. Baras Abstract-- We consider the problem of combined single- path routing on the solutions brought out by the simplest local algorithm, the Nash algorithm. We first examine a special type

Baras, John S.

438

A Theory of Refractive and Specular 3D Shape by Light-Path Triangulation Kiriakos N. Kutulakos  

E-print Network

A Theory of Refractive and Specular 3D Shape by Light-Path Triangulation Kiriakos N. Kutulakos Eron-shaped specular scene (refractive or mirror-like) from one or more viewpoints. By reducing shape recovery to the problem of reconstructing individual 3D light paths that cross the image plane, we obtain three key

Jepson, Allan D.

439

Domains of bosonic Functional integrals and some applications to the mathematical physics of path integrals and String Theory  

E-print Network

By means of the Minlos Theorem on support of cylindrical measures on vectorial topological spaces, we present several results on the rigorous definitions of Euclidean path integrals and applications to some problems on non-linear diffusion, nonlinear wave propagations and covariant Polyakov"s path Integrals yielding news results on the subject as well.

Luiz. C. L. Botelho

2009-02-23

440

Generalized path dependent representations for gauge theories  

SciTech Connect

A set of differential operators acting by continuous deformations on path dependent functionals of open and closed curves is introduced. Geometrically, these path operators are interpreted as infinitesimal generators of curves in the base manifold of the gauge theory. They furnish a representation with the action of the group of loops having a fundamental role. We show that the path derivative, which is covariant by construction, satisfies the Ricci and Bianchi identities. Also, we provide a geometrical derivation of covariant Taylor expansions based on particular deformations of open curves. The formalism includes, as special cases, other path dependent operators such as end point derivatives and area derivatives.

Reyes, Marat C. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, 04510 Mexico D.F. (Mexico) and Universidad Tecnica Federico Santa Maria, Campus Santiago, C.P. 766-0251, Santiago (Chile)

2007-05-15

441

Generalized Path Dependent Representations for Gauge Theories  

E-print Network

A set of differential operators acting by continuous deformations on path dependent functionals of open and closed curves is introduced. Geometrically, these path operators are interpreted as infinitesimal generators of curves in the base manifold of the gauge theory. They furnish a representation with the action of the group of loops having a fundamental role. We show that the path derivative, which is covariant by construction, satisfies the Ricci and Bianchi identities. Also, we provide a geometrical derivation of covariant Taylor expansions based on particular deformations of open curves. The formalism includes, as special cases, other path dependent operators such as end point derivatives and area derivatives.

Marat C. Reyes

2006-11-15

442

Path Deviation Equations in AP-Geometry  

NASA Astrophysics Data System (ADS)

Recently, it has been shown that Absolute Parallelism (AP) geometry admits paths that are naturally quantized. These paths have been used to describe the motion of spinning particles in a background gravitational field. In case of a weak static gravitational field limits, the paths are applied successfully to interpret the discrepancy in the motion of thermal neutrons in the Earth's gravitational field (COW-experiment). The aim of the present work is to explore the properties of the deviation equations corresponding to these paths. In the present work the deviation equations are derived and compared to the geodesic deviation equation of the Riemannian geometry.

Wanas, M. I.; Kahil, M. E.

2006-02-01

443

A Hybrid Metaheuristic DE/CS Algorithm for UCAV Three-Dimension Path Planning  

PubMed Central

Three-dimension path planning for uninhabited combat air vehicle (UCAV) is a complicated high-dimension optimization problem, which primarily centralizes on optimizing the flight route considering the different kinds of constrains under complicated battle field environments. A new hybrid metaheuristic differential evolution (DE) and cuckoo search (CS) algorithm is proposed to solve the UCAV three-dimension path planning problem. DE is applied to optimize the process of selecting cuckoos of the improved CS model during the process of cuckoo updating in nest. The cuckoos can act as an agent in searching the optimal UCAV path. And then, the UCAV can find the safe path by connecting the chosen nodes of the coordinates while avoiding the threat areas and costing minimum fuel. This new approach can accelerate the global convergence speed while preserving the strong robustness of the basic CS. The realization procedure for this hybrid metaheuristic approach DE/CS is also presented. In order to make the optimized UCAV path more feasible, the B-Spline curve is adopted for smoothing the path. To prove the performance of this proposed hybrid metaheuristic method, it is compared with basic CS algorithm. The experiment shows that the proposed approach is more effective and feasible in UCAV three-dimension path planning than the basic CS model. PMID:23193383

Wang, Gaige; Guo, Lihong; Duan, Hong; Wang, Heqi; Liu, Luo; Shao, Mingzhen

2012-01-01

444

A hybrid metaheuristic DE/CS algorithm for UCAV three-dimension path planning.  

PubMed

Three-dimension path planning for uninhabited combat air vehicle (UCAV) is a complicated high-dimension optimization problem, which primarily centralizes on optimizing the flight route considering the different kinds of constrains under complicated battle field environments. A new hybrid metaheuristic differential evolution (DE) and cuckoo search (CS) algorithm is proposed to solve the UCAV three-dimension path planning problem. DE is applied to optimize the process of selecting cuckoos of the improved CS model during the process of cuckoo updating in nest. The cuckoos can act as an agent in searching the optimal UCAV path. And then, the UCAV can find the safe path by connecting the chosen nodes of the coordinates while avoiding the threat areas and costing minimum fuel. This new approach can accelerate the global convergence speed while preserving the strong robustness of the basic CS. The realization procedure for this hybrid metaheuristic approach DE/CS is also presented. In order to make the optimized UCAV path more feasible, the B-Spline curve is adopted for smoothing the path. To prove the performance of this proposed hybrid metaheuristic method, it is compared with basic CS algorithm. The experiment shows that the proposed approach is more effective and feasible in UCAV three-dimension path planning than the basic CS model. PMID:23193383

Wang, Gaige; Guo, Lihong; Duan, Hong; Wang, Heqi; Liu, Luo; Shao, Mingzhen

2012-01-01

445

Ensuring critical event sequences in high consequence computer based systems as inspired by path expressions  

SciTech Connect

The goal of our work is to provide a high level of confidence that critical software driven event sequences are maintained in the face of hardware failures, malevolent attacks and harsh or unstable operating environments. This will be accomplished by providing dynamic fault management measures directly to the software developer and to their varied development environments. The methodology employed here is inspired by previous work in path expressions. This paper discusses the perceived problems, a brief overview of path expressions, the proposed methods, and a discussion of the differences between the proposed methods and traditional path expression usage and implementation.

Kidd, M.E.C.

1997-02-01

446

Ensuring critical event sequences in high integrity software by applying path expressions  

SciTech Connect

The goal of this work is to extend the use of existing path expression theory and methodologies to ensure that critical software event sequences are maintained even in the face of malevolent attacks and harsh or unstable operating environments. This will be accomplished by providing dynamic fault management measures directly to the software developer and to their varied development environments. This paper discusses the perceived problems, a brief overview of path expressions, and the author`s proposed extension areas. The authors discuss how the traditional path expression usage and implementation differs from the intended usage and implementation.

Kidd, M.E.C.

1996-07-01

447

A path-independent integral for fracture of solids under combined electrochemical and mechanical loadings  

NASA Astrophysics Data System (ADS)

In this study, we first demonstrate that the J-integral in classical linear elasticity becomes path-dependent when the solid is subjected to combined electrical, chemical and mechanical loadings. We then construct an electro-chemo-mechanical J-integral that is path-independent under such combined multiple driving forces. Further, we show that this electro-chemo-mechanical J-integral represents the rate at which the grand potential releases per unit crack growth. As an example, the path-independent nature of the electro-chemo-mechanical J-integral is demonstrated by solving the problem of a thin elastic film delaminated from a thick elastic substrate.

Haftbaradaran, Hamed; Qu, Jianmin

2014-11-01

448

Path Diversity over Packet Switched Networks: Performance Analysis and Rate Allocation  

E-print Network

Path diversity works by setting up multiple parallel connections between the end points using the topological path redundancy of the network. In this paper, \\textit{Forward Error Correction} (FEC) is applied across multiple independent paths to enhance the end-to-end reliability. Network paths are modeled as erasure Gilbert-Elliot channels. It is known that over any erasure channel, \\textit{Maximum Distance Separable} (MDS) codes achieve the minimum probability of irrecoverable loss among all block codes of the same size. Based on the adopted model for the error behavior, we prove that the probability of irrecoverable loss for MDS codes decays exponentially for an asymptotically large number of paths. Then, optimal rate allocation problem is solved for the asymptotic case where the number of paths is large. Moreover, it is shown that in such asymptotically optimal rate allocation, each path is assigned a positive rate \\textit{iff} its quality is above a certain threshold. The quality of a path is defined as t...

Fashandi, Shervan; Khandani, Amir K

2008-01-01

449

Triple RRTs: An Effective Method for Path Planning in Narrow Passages  

Microsoft Academic Search

Although Rapidly-exploring Random Trees (RRTs) have been successfully applied in path planning of robots with many degrees of freedom under non-holonomic and differential constraints, rapidly identifying and passing through narrow passages in a robot's configuration space remains a challenge for RRTs-based planners. This paper presents a novel two-stage approach to address the problem of multi-d.o.f. robot path planning in high-dimensional

Wei Wang; Xin Xu; Yan Li; Jinze Song; Hangen He

2010-01-01

450

FASTEST PATHS IN TIME-DEPENDENT NETWORKS FOR INTELLIGENT VEHICLE-HIGHWAY SYSTEMS APPLICATION  

Microsoft Academic Search

We consider the problem of individual route guidance in an Intelligent Vehicle-Highway Systems (IVHS ) environment, based on time-dependent forecasts of link travel time. We propose a consistency condition which deterministic forecasts should be constrained to satisfy, and show that under consistency, the time-dependent fastest path can be calculated with exactly the same computational complexity as for static fastest paths,

David E. Kaufman; Robert L. Smith

1993-01-01

451

Higher order and infinite Trotter-number extrapolations in path integral Monte Carlo  

Microsoft Academic Search

Improvements beyond the primitive approximation in the path integral Monte Carlo method are explored both in a model problem and in real systems. Two different strategies are studied: The Richardson extrapolation on top of the path integral Monte Carlo data and the Takahashi-Imada action. The Richardson extrapolation, mainly combined with the primitive action, always reduces the number-of-beads dependence, helps in

L. Brualla; K. Sakkos; J. Boronat; J. Casulleras

2004-01-01

452

The (1+1) Dimensional Dirac Equation With Pseudoscalar Potentials: Path Integral Treatment  

Microsoft Academic Search

The supersymetric path integrals in solving the problem of relativistic spinning particle interacting with pseudoscalar potentials\\u000a is examined. The relative propagator is presented by means of path integral, where the spin degrees of freedom are described\\u000a by odd Grassmannian variables and the gauge invariant part of the effective action has a form similar to the standard pseudoclassical\\u000a action given by

S. Haouat; L. Chetouani

2007-01-01

453

Path planning for robotic truss assembly  

NASA Astrophysics Data System (ADS)

A new Potential Fields approach to the robotic path planning problem is proposed and implemented. Our approach, which is based on one originally proposed by Munger, computes an incremental joint vector based upon attraction to a goal and repulsion from obstacles. By repetitively adding and computing these 'steps', it is hoped (but not guaranteed) that the robot will reach its goal. An attractive force exerted by the goal is found by solving for the the minimum norm solution to the linear Jacobian equation. A repulsive force between obstacles and the robot's links is used to avoid collisions. Its magnitude is inversely proportional to the distance. Together, these forces make the goal the global minimum potential point, but local minima can stop the robot from ever reaching that point. Our approach improves on a basic, potential field paradigm developed by Munger by using an active, adaptive field - what we will call a 'flexible' potential field. Active fields are stronger when objects move towards one another and weaker when they move apart. An adaptive field's strength is individually tailored to be just strong enough to avoid any collision. In addition to the local planner, a global planning algorithm helps the planner to avoid local field minima by providing subgoals. These subgoals are based on the obstacles which caused the local planner to fail. A best-first search algorithm A* is used for graph search.

Sanderson, Arthur C.

1993-09-01

454

A path-oriented matrix-based knowledge representation system  

NASA Technical Reports Server (NTRS)

Experience has shown that designing a good representation is often the key to turning hard problems into simple ones. Most AI (Artificial Intelligence) search/representation techniques are oriented toward an infinite domain of objects and arbitrary relations among them. In reality much of what needs to be represented in AI can be expressed using a finite domain and unary or binary predicates. Well-known vector- and matrix-based representations can efficiently represent finite domains and unary/binary predicates, and allow effective extraction of path information by generalized transitive closure/path matrix computations. In order to avoid space limitations a set of abstract sparse matrix data types was developed along with a set of operations on them. This representation forms the basis of an intelligent information system for representing and manipulating relational data.

Feyock, Stefan; Karamouzis, Stamos T.

1993-01-01

455

Path degeneracy and EXAFS analysis of disordered materials.  

PubMed

Analysis of EXAFS data measured on a material with a disordered local configuration environment around the absorbing atom can be challenging owing to the proliferation of photoelectron scattering paths that must be considered in the analysis. In the case where the absorbing atom exists in multiple inequivalent sites, the problem is compounded by having to consider each site separately. A method is proposed for automating the calculation of theory for inequivalent sites, then averaging the contributions from sufficiently similar scattering paths. With this approach, the complexity of implementing a successful fitting model on a highly disordered sample is reduced. As an example, an analysis of Ti K-edge data on zirconolite, CaZrTi2O7, which has three inequivalent Ti sites, is presented. PMID:25343794

Ravel, Bruce

2014-11-01

456

Path-based rules in object-oriented programming  

SciTech Connect

Object-oriented programming has recently emerged as one of the most important programming paradigms. While object-oriented programming clearly owes an intellectual debt to AI, it appears to be displacing some AI techniques, such as rule-based programming, from the marketplace. This need not be so as path-based rules-forward-chaining production rules that are restricted to follow pointers between objects-fit into the object-oriented paradigm in a clean and elegant way. The combination of path-based rules and object-oriented programming should be useful in AI applications, and in the more general problem of transferring AI techniques to the larger computer science community.

Crawford, J.M. [Univ. of Oregon, Eugene, OR (United States); Dvorak, D.; Litman, D.; Mishra, A.; Patel-Schneider, P.F. [AT& T Laboratories, Murray Hill, NJ (United States)

1996-12-31

457

Maximum distributions of bridges of noncolliding Brownian paths  

E-print Network

The one-dimensional Brownian motion starting from the origin at time $t=0$, conditioned to return to the origin at time $t=1$ and to stay positive during time interval $0 bridge with duration 1. We consider the $N$-particle system of such Bessel bridges conditioned never to collide with each other in $0 bridges is realized as the positive-eigenvalue process of the $2N \\times 2N$ matrix-valued Brownian bridge in the symmetry class C. Using this fact computer simulations are performed and numerical results on the $N$-dependence of the maximum-value distributions of the inner paths are reported. The present work demonstrates that the extreme-value problems of noncolliding paths are related with the random matrix theory, representation theory of symmetry, and the number theory.

Naoki Kobayashi; Minami Izumi; Makoto Katori

2008-08-27

458

Design and performance of an optical path cross-connect system based on wavelength path concept  

Microsoft Academic Search

This paper describes the system design and performance of an optical path cross-connect (OPXC) system based on wavelength path concept. The (OPXC) is designed to offer 16 sets of input and output fiber ports with each fiber transporting eight multiwavelength signals for optical paths. Each optical path has a capacity of 2.5 Gb\\/s. Consequently, the total system throughput is 8×16×2.5=320

Masafumi Koga; Yoshiyuki Hamazumi; Atsushi Watanabe; Satoru Okamoto; Hitoshi Obara; Ken-Ichi Sato; Masayuki Okuno; Senichi Suzuki

1996-01-01

459

Path planning by optimal-path-map construction for homogeneous-cost two-dimensional regions  

Microsoft Academic Search

Algorithms to construct optimal-path maps for single isolated homogeneous-cost convex-polygonal regions are discussed. Assuming the ability to construct optimal paths for a certain set of key points, a complete analysis is given of one of the four possible single-region situations, showing how to partition the map into regions of similar path behavior. An algorithm is then proposed for constructing optimal-path

Robert S. Alexander; Neil C. Rowe

1990-01-01

460

Path and Path Deviation Equations in Kaluza-Klein Type Theories  

E-print Network

Path and path deviation equations for charged, spinning and spinning charged objects in different versions of Kaluza-Klein (KK) theory using a modified Bazanski Lagrangian have been derived. The significance of motion in five dimensions, especially for a charged spinning object, has been examined. We have also extended the modified Bazanski approach to derive the path and path deviation equations of a test particle in a version of non-symmetric KK theory.

M. E. Kahil

2005-11-07

461

The k-client problem  

SciTech Connect

To model on-line systems which deal with multi-threaded inputs, we define and analyze the {kappa}-client problem, a dual of the {kappa}-server problem. In the {kappa}-client problem, there is a single server and {kappa} clients, each of which generates a sequence of requests for service in a metric space. At any time, each client has at most one outstanding request; that is, the i + 1{sup st} request of a client will not arrive until the i{sup th} request has been serviced. The crux of the problem is deciding which client`s request the single server should service rather than which server should be used to service the current request. We evaluate the performance of algorithms using the makespan, total completion time, and maximum response time cost functions. When restricted to the line metric space, the {kappa}-client problem models the disk scheduling problem in a multi-threaded environment. We derive tight results for several commonly studied disk scheduling algorithms such as the shortest seek time first and the elevator algorithms which help explain why elevator type algorithms perform well in practice when the disk is heavily loaded. In general, we show that several algorithms axe (2k - 1)-competitive and that no on-line algorithm is better than 1gk/2-competitive for the makespan and total completion time cost functions. When k = 2, the lower bounds improve to 25/9 and 3 for the makespan and total completion time cost functions, respectively. For the maximum response time cost function, we show that no on-line algorithm is better than {Omega}({sup 3}{radical}{Delta})-competitive where {Delta} is the maximum distance between any two requests. Surprisingly, our results axe essentially identical for both the line and general metric spaces.

Alborzi, H.; Torng, E.; Uthaisombut, P.; Wagner, S. [Michigan State Univ., East Lansing, MI (United States)

1997-06-01

462

Polymer density functional approach to efficient evaluation of path integrals.  

PubMed

A polymer density functional theory (P-DFT) has been extended to the case of quantum statistics within the framework of Feynman path integrals. We start with the exact P-DFT formalism for an ideal open chain and adapt its efficient numerical solution to the case of a ring. We show that, similarly, the path integral problem can, in principle, be solved exactly by making use of the two-particle pair correlation function (2p-PCF) for the ends of an open polymer, half of the original. This way the exact data for one-dimensional quantum harmonic oscillator are reproduced in a wide range of temperatures. The exact solution is not, though, reachable in three dimensions (3D) because of a vast amount of storage required for 2p-PCF. In order to treat closed paths in 3D, we introduce a so-called "open ring" approximation which proves to be rather accurate in the limit of long chains. We also employ a simple self-consistent iteration so as to correctly account for the interparticle interactions. The algorithm is speeded up by taking convolutions with the aid of fast Fourier transforms. We apply this approximate path integral DFT (PI-DFT) method to systems within spherical symmetry: 3D harmonic oscillator, atoms of hydrogen and helium, and ions of He and Li. Our results compare rather well to the known data, while the computational effort (some seconds or minutes) is about 100 times less than that with Monte Carlo simulations. Moreover, the well-known "sign problem" is expected to be considerably reduced within the reported PI-DFT, since it allows for a direct estimate of the corresponding partition functions. PMID:16383563

Broukhno, Andrei; Vorontsov-Velyaminov, Pavel N; Bohr, Henrik

2005-10-01

463

Path planning and path tracking control of unmanned ground vehicles (UGVs)  

Microsoft Academic Search

Unmanned ground vehicles (UGVs) will be playing increasingly important role in the future battlefields. How to automatically guide and control UGVs under varying environment conditions represents a challenging issue. This paper presents a novel approach to achieving path planning and path tracking of UGVs under dynamic environments. We apply the topology theory to find the optimal path given any starting

Liguo Weng; D. Y. Song

2005-01-01

464

MODELING DENDRITIC SHAPES Using Path Planning  

E-print Network

the humble to the spectacular: lichens, coral, river systems, and lightning are all examples of naturally of objects exhibiting dendritic shape include lichens, coral, trees, lightning, rivers, crystals least-cost paths through the lattice. Multiple paths from a single starting location (or gen- erator

Mould, David

465

A Random Walk on a Circular Path  

ERIC Educational Resources Information Center

This short note introduces an interesting random walk on a circular path with cards of numbers. By using high school probability theory, it is proved that under some assumptions on the number of cards, the probability that a walker will return to a fixed position will tend to one as the length of the circular path tends to infinity.

Ching, W.-K.; Lee, M. S.

2005-01-01

466

Katrina'sPath Lake Pontchartrain  

E-print Network

miles to the west · Eye-wall pushes into Pearl River floodplain Impacts · Spillway overtopped into canal #12;Hudson'sPath Future Scenario Hurricane Hudson · Same Katrina path · Intensity increased 3 · 15mph forward speed Jourdan River Basin Pearl River Basin Rolls Royce Test Complex Building 1100

467

Evaluation of Calcine Disposition Path Forward  

SciTech Connect

This document describes an evaluation of the baseline and two alternative disposition paths for the final disposition of the calcine wastes stored at the Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory. The pathways are evaluated against a prescribed set of criteria and a recommendation is made for the path forward.

Birrer, S.A.; Heiser, M.B.

2003-02-26

468

Evaluation of Calcine Disposition - Path Forward  

SciTech Connect

This document describes an evaluation of the baseline and two alternative disposition paths for the final disposition of the calcine wastes stored at the Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory. The pathways are evaluated against a prescribed set of criteria and a recommendation is made for the path forward.

Steve Birrer

2003-02-01

469

Bounding the error of path loss models  

Microsoft Academic Search

In this paper we analyze the efficacy of basic path loss models at predicting median path loss in urban environments. We attempt to bound the practical error of these models and look at how they may hinder practical wireless applications, and in particular dynamic spectrum access networks. This analysis is made using a large set of measurements from production networks

Caleb Phillips; Douglas Sicker; Dirk Grunwald

2011-01-01

470

Functional test generation for path delay faults  

Microsoft Academic Search

We present a novel test generation technique for path delay faults, based on the growth (G) and disappearance (D) faults of programmable logic arrays (PLA). The circuit is modeled as a PLA that is prime and irredundant with respect to every output. Certain tests for G faults, generated by using known efficient methods are transformed into tests for path delay

Mandyam-komar Srinivas; Vishwani D. Agrawal; Michael L. Bushnell

1995-01-01

471

Path-based control of smoke simulations  

Microsoft Academic Search

In this paper, we propose a novel path-based control method for generating realistic smoke animations. Our method allows an animator to specify a 3D curve for the smoke to follow. Path control is then achieved using a linear (closed) feedback loop to match the velocity field obtained from a 3D flow simulation with a target velocity field. The target velocity

Yootai Kim; Raghu Machiraju; David Thompson

2006-01-01

472

Protecting Location Privacy Through Path Confusion  

Microsoft Academic Search

We present a path perturbation algorithm which can maximize users? location privacy given a quality of service constraint. This work concentrates on a class of applications that continuously collect location samples from a large group of users, where just removing user identifiers from all samples is insufficient because an adversary could use trajectory information to track paths and follow users?

Baik Hoh; Marco Gruteser

2005-01-01

473

Next Generation Science Standards (NGSS) Path Finder  

NSDL National Science Digital Library

This interactive visual 'path finder' from the Concord Consortium allows users to explore the component pieces of the Next Generation Science Standards. After selecting the appropriate practices, core ideas, and crosscutting concepts, the path finder will suggest relevant resources from the Concord Consortium's collection.

Consortium, The C.

474

Control-path Oriented Workflow Intelligence Analyses  

Microsoft Academic Search

This paper proposes two kinds of control-path oriented workflow knowledge analy- sis approaches which will be applied to a workflow intelligence and quality improve- ment framework aiming at the high degree of the workflow traceability and rediscover- ability. The framework needs two kinds of algorithms ? One is for generating the total sequences of the control-paths from a workflow model,

Minjae Park; Kwanghoon Kim

2008-01-01

475

Path integral for inflationary perturbations  

SciTech Connect

The quantum theory of cosmological perturbations in single-field inflation is formulated in terms of a path integral. Starting from a canonical formulation, we show how the free propagators can be obtained from the well-known gauge-invariant quadratic action for scalar and tensor perturbations, and determine the interactions to arbitrary order. This approach does not require the explicit solution of the energy and momentum constraints, a novel feature which simplifies the determination of the interaction vertices. The constraints and the necessary imposition of gauge conditions is reflected in the appearance of various commuting and anticommuting auxiliary fields in the action. These auxiliary fields are not propagating physical degrees of freedom but need to be included in internal lines and loops in a diagrammatic expansion. To illustrate the formalism we discuss the tree-level three-point and four-point functions of the inflaton perturbations, reproducing the results already obtained by the methods used in the current literature. Loop calculations are left for future work.

Prokopec, Tomislav [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht (Netherlands); Rigopoulos, Gerasimos [Helsinki Institute of Physics, P.O. Box 64, FIN-00014, University of Helsinki (Finland)

2010-07-15

476

Converging towards the optimal path to extinction  

PubMed Central

Extinction appears ubiquitously in many fields, including chemical reactions, population biology, evolution and epidemiology. Even though extinction as a random process is a rare event, its occurrence is observed in large finite populations. Extinction occurs when fluctuations owing to random transitions act as an effective force that drives one or more components or species to vanish. Although there are many random paths to an extinct state, there is an optimal path that maximizes the probability to extinction. In this paper, we show that the optimal path is associated with the dynamical systems idea of having maximum sensitive dependence to initial conditions. Using the equivalence between the sensitive dependence and the path to extinction, we show that the dynamical systems picture of extinction evolves naturally towards the optimal path in several stochastic models of epidemics. PMID:21571943

Schwartz, Ira B.; Forgoston, Eric; Bianco, Simone; Shaw, Leah B.

2011-01-01

477

The roles of the convex hull and the number of potential intersections in performance on visually presented traveling salesperson problems  

Microsoft Academic Search

The planar Euclidean version of the traveling salesperson problem requires finding the shortest tour through a two-dimensional\\u000a array of points. MacGregor and Ormerod (1996) have suggested that people solve such problems by using a global-to-local perceptual\\u000a organizing process based on the convex hull of the array. We review evidence for and against this idea, before considering\\u000a an alternative, local-to-global perceptual

Douglas Vickers; Michael D. Lee; Matthew Dry; Peter Hughes

2003-01-01

478

A Data Mining Approach for Predicting Reliable Path for Congestion Free Routing Using Self-motivated Neural Network  

Microsoft Academic Search

Congestion in computer networks is a significant problem due to the growth of networks and increased link speeds. Now it is\\u000a common to see internet gateway drops 10 the incoming packets because of local buffer overflows. An optimal solution for this\\u000a problem is Predicting congestion free path(s) by learning the dynamic characteristics of networks and its topology. The factors\\u000a that

B. Chandra Mohan; R. Sandeep; D. Sridharan

2008-01-01

479

The Path of Human Evolution  

NASA Astrophysics Data System (ADS)

A complex series of evolutionary steps, contingent upon a dynamic environmental context and a long biological heritage, have led to the ascent of Homo sapiens as a dominant component of the modern biosphere. In a field where missing links still abound and new discoveries regularly overturn theoretical paradigms, our understanding of the path of human evolution has made tremendous advances in recent years. Two major trends characterize the development of the hominin clade subsequent to its origins with the advent of upright bipedalism in the Late Miocene of Africa. One is a diversification into two prominent morphological branches, each with a series of 'twigs' representing evolutionary experimentation at the species or subspecies level. The second important trend, which in its earliest manifestations cannot clearly be ascribed to one or the other branch, is the behavioral complexity of an increasing reliance on technology to expand upon limited inherent morphological specializations and to buffer the organism from its environment. This technological dependence is directly associated with the expansion of hominin range outside Africa by the genus Homo, and is accelerated in the sole extant form Homo sapiens through the last 100 Ka. There are interesting correlates between the evolutionary and behavioral patterns seen in the hominin clade and environmental dynamics of the Neogene. In particular, the tempo of morphological and behavioral innovation may be tracking major events in Neogene climatic development as well as reflecting intervals of variability or stability. Major improvements in analytical techniques, coupled with important new collections and a growing body of contextual data are now making possible the integration of global, regional and local environmental archives with an improved biological understanding of the hominin clade to address questions of coincidence and causality.

Feibel, C. S.

2004-12-01

480

A global approach to kinematic path planning to robots with holonomic and nonholonomic constraints  

NASA Astrophysics Data System (ADS)

Robots in applications may be subject to holonomic or nonholonomic constraints. Examples of holonomic constraints include a manipulator constrained through the contact with the environment, e.g., inserting a part, turning a crank, etc., and multiple manipulators constrained through a common payload. Examples of nonholonomic constraints include no-slip constraints on mobile robot wheels, local normal rotation constraints for soft finger and rolling contacts in grasping, and conservation of angular momentum of in-orbit space robots. The above examples all involve equality constraints; in applications, there are usually additional inequality constraints such as robot joint limits, self collision and environment collision avoidance constraints, steering angle constraints in mobile robots, etc. The problem of finding a kinematically feasible path that satisfies a given set of holonomic and nonholonomic constraints, of both equality and inequality types is addressed. The path planning problem is first posed as a finite time nonlinear control problem. This problem is subsequently transformed to a static root finding problem in an augmented space which can then be iteratively solved. The algorithm has shown promising results in planning feasible paths for redundant arms satisfying Cartesian path following and goal endpoint specifications, and mobile vehicles with multiple trailers. In contrast to local approaches, this algorithm is less prone to problems such as singularities and local minima.

Divelbiss, Adam; Seereeram, Sanjeev; Wen, John T.

1993-12-01

481

A global approach to kinematic path planning to robots with holonomic and nonholonomic constraints  

NASA Technical Reports Server (NTRS)

Robots in applications may be subject to holonomic or nonholonomic constraints. Examples of holonomic constraints include a manipulator constrained through the contact with the environment, e.g., inserting a part, turning a crank, etc., and multiple manipulators constrained through a common payload. Examples of nonholonomic constraints include no-slip constraints on mobile robot wheels, local normal rotation constraints for soft finger and rolling contacts in grasping, and conservation of angular momentum of in-orbit space robots. The above examples all involve equality constraints; in applications, there are usually additional inequality constraints such as robot joint limits, self collision and environment collision avoidance constraints, steering angle constraints in mobile robots, etc. The problem of finding a kinematically feasible path that satisfies a given set of holonomic and nonholonomic constraints, of both equality and inequality types is addressed. The path planning problem is first posed as a finite time nonlinear control problem. This problem is subsequently transformed to a static root finding problem in an augmented space which can then be iteratively solved. The algorithm has shown promising results in planning feasible paths for redundant arms satisfying Cartesian path following and goal endpoint specifications, and mobile vehicles with multiple trailers. In contrast to local approaches, this algorithm is less prone to problems such as singularities and local minima.

Divelbiss, Adam; Seereeram, Sanjeev; Wen, John T.

1993-01-01

482

An Analysis of Path-Vector Routing Protocol Convergence Algorithms  

Microsoft Academic Search

Today's Internet uses a path vector routing protocol, BGP, for global routing. After a connectivity change, a path vector protocol tends to explore a potentially large number of alternative paths before converging on new stable paths. Several techniques for improving path vector convergence have been proposed, however there has been no comparative analysis to judge the relative merit of each

Dan Pei; UCLA CSD; Beichuan Zhang; Dan Massey; Lixia Zhang

483

Problem Solving  

NSDL National Science Digital Library

Problem solving is the thought processes involved in solving a problem. It is both a means of developing students' knowledge of mathematics and a critical outcome of a good mathematics education. A mathematical problem, as distinct from an exercise, requires the solver to search for a method for solving the problem rather than following a set procedure. Mathematical problem solving, therefore, requires an understanding of relevant concepts, procedures, and strategies. To become good problem solvers, students need many opportunities to formulate questions, model problem situations in a variety of ways, generalize mathematical relationships, and solve problems in both mathematical and everyday contexts.

K-12 Outreach,

484

Robot path planning using a genetic algorithm  

NASA Technical Reports Server (NTRS)

Robot path planning can refer either to a mobile vehicle such as a Mars Rover, or to an end effector on an arm moving through a cluttered workspace. In both instances there may exist many solutions, some of which are better than others, either in terms of distance traversed, energy expended, or joint angle or reach capabilities. A path planning program has been developed based upon a genetic algorithm. This program assumes global knowledge of the terrain or workspace, and provides a family of good paths between the initial and final points. Initially, a set of valid random paths are constructed. Successive generations of valid paths are obtained using one of several possible reproduction strategies similar to those found in biological communities. A fitness function is defined to describe the goodness of the path, in this case including length, slope, and obstacle avoidance considerations. It was found that with some reproduction strategies, the average value of the fitness function improved for successive generations, and that by saving the best paths of each generation, one could quite rapidly obtain a collection of good candidate solutions.

Cleghorn, Timothy F.; Baffes, Paul T.; Wang, Liu

1988-01-01

485

Path Planning Via CPLEX Optimization  

Microsoft Academic Search

This paper presents an optimized solution of finding time-optimal trajectories for autonomous systems. These systems are subject to avoidance requirements, which include avoidance of collisions with other systems and obstacles, either static or dynamic. The necessary constraints for avoidance are added to a time-optimizing linear program by including a binary variable in the optimization. The resulting problem is a mixed-integer

Taoridi A. Ademoye; A. Davaril; Charles C. Castello; Sharon Fan; Jeffrey Fan

2008-01-01

486

Hot gas path analysis and data evaluation of the performance parameters of a gas turbine  

E-print Network

-cans are causing the problem was conducted. By knowing the turbine wheel diameters, number of stages, blade dimensions, gas velocity, and the location of the exhaust temperature Fig. 5. 1 Combustor-Can 5S thermocouples, the shift of the gas path from a...-cans are causing the problem was conducted. By knowing the turbine wheel diameters, number of stages, blade dimensions, gas velocity, and the location of the exhaust temperature Fig. 5. 1 Combustor-Can 5S thermocouples, the shift of the gas path from a...

Hanawa, David Allen

2012-06-07

487

Path integral measure, constraints and ghosts for massive gravitons with a cosmological constant  

SciTech Connect

For massive gravity in a de Sitter background one encounters problems of stability when the curvature is larger than the graviton mass. I analyze this situation from the path integral point of view and show that it is related to the conformal factor problem of Euclidean quantum (massless) gravity. When a constraint for massive gravity is incorporated and the proper treatment of the path integral measure is taken into account one finds that, for particular choices of the DeWitt metric on the space of metrics (in fact, the same choices as in the massless case), one obtains the opposite bound on the graviton mass.

Metaxas, Dimitrios [Department of Physics, National Technical University of Athens, Zografou Campus, 15780 Athens (Greece)

2009-12-15

488

Graphs and matroids weighted in a bounded incline algebra.  

PubMed

Firstly, for a graph weighted in a bounded incline algebra (or called a dioid), a longest path problem (LPP, for short) is presented, which can be considered the uniform approach to the famous shortest path problem, the widest path problem, and the most reliable path problem. The solutions for LPP and related algorithms are given. Secondly, for a matroid weighted in a linear matroid, the maximum independent set problem is studied. PMID:25126607

Lu, Ling-Xia; Zhang, Bei

2014-01-01

489

Planning Paths Through Singularities in the Center of Mass Space  

NASA Technical Reports Server (NTRS)

The center of mass space is a convenient space for planning motions that minimize reaction forces at the robot's base or optimize the stability of a mechanism. A unique problem associated with path planning in the center of mass space is the potential existence of multiple center of mass images for a single Cartesian obstacle, since a single center of mass location can correspond to multiple robot joint configurations. The existence of multiple images results in a need to either maintain multiple center of mass obstacle maps or to update obstacle locations when the robot passes through a singularity, such as when it moves from an elbow-up to an elbow-down configuration. To illustrate the concepts presented in this paper, a path is planned for an example task requiring motion through multiple center of mass space maps. The object of the path planning algorithm is to locate the bang- bang acceleration profile that minimizes the robot's base reactions in the presence of a single Cartesian obstacle. To simplify the presentation, only non-redundant robots are considered and joint non-linearities are neglected.

Doggett, William R.; Messner, William C.; Juang, Jer-Nan

1998-01-01

490

Direct path planning in image plane and tracking for visual servoing  

NASA Astrophysics Data System (ADS)

The image-based visual servoing would lead to image singularities that might cause control instabilities, and there exit other constraints such as the object should remain in the camera field of view and avoid obstacles. This problem can be solved by coupling path planning and image-based control. The trajectory is planned directly in the image space in our strategy to avoid the 3D estimation of the object, which is required in the motion space based path planning method. In the presented method, the initial path is given using the artificial potential field method without considering the constraints and then genetic algorithm based method is used to check and modify the initial path. This method can achieve satisfactory task while decrease the computation. The proposed method is used to align the micro peg and hole, and the simulation results show that the object can reach its desired position accurately without violation these constrains.

Wang, Junping; Liu, An; Cho, Hyungsuck

2007-10-01

491

Optimal impulsive time-fixed orbital rendezvous and interception with path constraints  

NASA Technical Reports Server (NTRS)

Minimum-fuel, impulsive, time-fixed solutions are obtained for the problem of orbital rendezvous and interception with interior path constraints. Transfers between coplanar circular orbits in an inverse-square gravitational field are considered, subject to a circular path constraint representing a minimum or maximum permissible orbital radius. Primer vector theory is extended to incorporate path constraints. The optimal number of impulses, their times and positions, and the presence of initial or final coasting arcs are determined. The existence of constraint boundary arcs and boundary points is investigated as well as the optimality of a class of singular arc solutions. To illustrate the complexities introduced by path constraints, an analysis is made of optimal rendezvous in field-free space subject to a minimum radius constraint.

Taur, D.-R.; Prussing, J. E.; Coverstone-Carroll, V.

1990-01-01

492

In vivo quantification of chromophore concentration using fluorescence differential path length spectroscopy  

NASA Astrophysics Data System (ADS)

We present an optical method based on fluorescence spectroscopy for measuring chromophore concentrations in vivo. Fluorescence differential path length spectroscopy (FPDS) determines chromophore concentration based on the fluorescence intensity corrected for absorption. The concentration of the photosensitizer m-THPC (Foscan®) was studied in vivo in normal rat liver, which is highly vascularized and therefore highly absorbing. Concentration estimates of m-THPC measured by FDPS on the liver are compared with chemical extraction. Twenty-five rats were injected with 0.3 mg/kg m-THPC. In vivo optical concentration measurements were performed on tissue 3, 24, 48, and 96 h after m-THPC administration to yield a 10-fold variation in tissue concentration. After the optical measurements, the liver was harvested for chemical extraction. FDPS showed good correlation with chemical extraction. FDPS also showed a correlation between m-THPC fluorescence and blood volume fraction at the two shortest drug-light intervals. This suggests different compartmental localization of m-THPC for different drug-light intervals that can be resolved using fluorescence spectroscopy. Differences in measured m-THPC concentration between FDPS and chemical extraction are related to the interrogation volume of each technique; ~0.2 mm3 and ~102 mm3, respectively. This indicates intra-animal variation in m-THPC distribution in the liver on the scale of the FDPS sampling volume.

Kruijt, Bastiaan; Kascakova, Slavka; de Bruijn, Henriette S.; van der Ploeg-van den Heuvel, Angelique; Sterenborg, Henricus J. C. M.; Robinson, Dominic J.; Amelink, Arjen

2009-05-01

493

Path discrepancies between great circle and rhumb line  

NASA Technical Reports Server (NTRS)

A simulation of a mathematical model to compute path discrepancies between great circle and rhumb line flight paths is presented. The model illustrates that the path errors depend on the latitude, the bearing, and the trip length of the flight.

Kaul, Rajan

1987-01-01

494

Transports along paths in Fibre Bundles. I. General Theory  

E-print Network

Transports along path in fibre bundles are axiomatically introduced. Their general functional form and some their simple properties are investigated. The relationships of the transports along paths and lifting of paths are studied.

Bozhidar Z. Iliev

2005-03-01

495

Realistic Human Walking Paths David C. Brogan  

E-print Network

development for entertainment applications and many classes of simulations. We present a novel behav- ioral- served paths in black on the floor. A library exit (a) and a university hallway (b). A realistic walking

Brogan, David

496

Riemann Curvature Tensor and Closed Geodesic Paths  

ERIC Educational Resources Information Center

Demonstrates erroneous results obtained if change in a vector under parallel transport about a closed path in Riemannian spacetime is made in a complete circuit rather than just half a circuit. (Author/SL)

Morganstern, Ralph E.

1977-01-01

497

Path integration in relativistic quantum mechanics  

E-print Network

The simple physics of a free particle reveals important features of the path-integral formulation of relativistic quantum theories. The exact quantum-mechanical propagator is calculated here for a particle described by the simple relativistic action proportional to its proper time. This propagator is nonvanishing outside the light cone, implying that spacelike trajectories must be included in the path integral. The propagator matches the WKB approximation to the corresponding configuration-space path integral far from the light cone; outside the light cone that approximation consists of the contribution from a single spacelike geodesic. This propagator also has the unusual property that its short-time limit does not coincide with the WKB approximation, making the construction of a concrete skeletonized version of the path integral more complicated than in nonrelativistic theory.

Ian H. Redmount; Wai-Mo Suen

1992-10-28

498

How Do Paths Look From Different Perspectives?  

NSDL National Science Digital Library

Using both literature (a book featuring a path, such as Little Red Riding Hood) and satellite images, students will identify paths, observe and analyze them from different altitudes, and distinguish natural paths from those made by humans. Students will learn how images can inform the building, use and maintenance of paths. The URL opens to the investigation directory, with links to teacher and student materials, lesson extensions, resources, teaching tips, and assessment strategies. This is Investigation 2 of four found in the Grades K-4 Module 4 of Mission Geography. The Mission Geography curriculum integrates data and images from NASA missions with the National Geography Standards. Each of the four investigations in Module 4, while related, can be done independently. Please see Investigation 1 of this module for a two-page module overview and list of all standards addressed.

499

Predicting missing links via effective paths  

NASA Astrophysics Data System (ADS)

Recently, in complex network, link prediction has brought a surge of researches, among which similarity based link prediction outstandingly gains considerable success, especially similarity in terms of paths. In investigation of paths based similarity, we find that the effective influence of endpoints and strong connectivity make paths contribute more similarity between two unconnected endpoints, leading to a more accurate link prediction. Accordingly, we propose a so-called effective path index (EP) in this paper to leverage effective influence of endpoints and strong connectivity in similarity calculation. For demonstrating excellence of our index, the comparisons with six mainstream indices are performed on experiments in 15 real datasets and results show a great improvement of performance via our index.

Zhu, Xuzhen; Tian, Hui; Cai, Shimin

2014-11-01

500

IRIS Optical Instrument and Light Paths  

NASA Video Gallery

The optical portion of the instrument and the light paths from the primary and secondary mirror of the telescope assembly into the spectrograph. The spectrograph then breaks the light into 2 Near U...