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1

Sensitivity Analysis for Shortest Path Problems and Maximum Capacity Path Problems in Undirected Graphs  

E-print Network

This paper addresses sensitivity analysis questions concerning the shortest path problem and the maximum capacity path problem in an undirected network. For both problems, we determine the maximum and minimum weights that ...

Ramaswamy, Ramkumar

2004-04-30

2

Sensitivity Analysis for Shortest Path Problems and Maximum Capacity Path Problems in Undirected Graphs  

E-print Network

This paper addresses sensitivity analysis questions concerning the shortest path problem and the maximum capacity path problem in an undirected network. For both problems, we determine the maximum and ...

Ramaswamy, Ramkumar

2004-12-10

3

Shortest path in complete bipartite digraph problem and it applications  

SciTech Connect

We introduce the shortest path in complete bipartite digraph (SPCB) problem: Given a weighted complete bipartite digraph G = (X, Y, E) with X = (x{sub 0},{hor_ellipsis}, Xn) and Y = (y{sub 0},{hor_ellipsis},y{sub m}), find a shortest path from x{sub 0} to x{sub n} in G. For arbitrary weights, the problem needs at least {Omega}(nm) time to solve. We show if the weight matrices are concave, the problem can be solved in O(n + m log n) time. As applications, we discuss the traveling salesman problem for points on a convex polygon and the minimum latency tour problem for points on a straight line. The known algorithms for both problems require {Theta}(n{sup 2}) time. Using our SPCB algorithm, we show they can be solved in O(n log n) time. These results solve two open questions.

He, Xin [State Univ. of New York, Buffalo, NY (United States); Chen, Zhi-Zhong [Tokyo Denki Univ., Saitama (Japan)

1997-06-01

4

An improved Physarum polycephalum algorithm for the shortest path problem.  

PubMed

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

Zhang, Xiaoge; Wang, Qing; Adamatzky, Andrew; Chan, Felix T S; Mahadevan, Sankaran; Deng, Yong

2014-01-01

5

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

6

An Effective Evolutionary Approach for Bicriteria Shortest Path Routing Problems  

NASA Astrophysics Data System (ADS)

Routing problem is one of the important research issues in communication network fields. In this paper, we consider a bicriteria shortest path routing (bSPR) model dedicated to calculating nondominated paths for (1) the minimum total cost and (2) the minimum transmission delay. To solve this bSPR problem, we propose a new multiobjective genetic algorithm (moGA): (1) an efficient chromosome representation using the priority-based encoding method; (2) a new operator of GA parameters auto-tuning, which is adaptively regulation of exploration and exploitation based on the change of the average fitness of parents and offspring which is occurred at each generation; and (3) an interactive adaptive-weight fitness assignment mechanism is implemented that assigns weights to each objective and combines the weighted objectives into a single objective function. Numerical experiments with various scales of network design problems show the effectiveness and the efficiency of our approach by comparing with the recent researches.

Lin, Lin; Gen, Mitsuo

7

An improved bio-inspired algorithm for the directed shortest path problem.  

PubMed

Because most networks are intrinsically directed, the directed shortest path problem has been one of the fundamental issues in network optimization. In this paper, a novel algorithm for finding the shortest path in directed networks is proposed. It extends a bio-inspired path finding model of Physarum polycephalum, which is designed only for undirected networks, by adopting analog circuit analysis. Illustrative examples are given to show the effectiveness of the proposed algorithm in finding the directed shortest path. PMID:25405318

Zhang, Xiaoge; Zhang, Yajuan; Deng, Yong

2014-12-01

8

Self-organization and solution of shortest-path optimization problems with memristive networks  

NASA Astrophysics Data System (ADS)

We show that memristive networks, namely networks of resistors with memory, can efficiently solve shortest-path optimization problems. Indeed, the presence of memory (time nonlocality) promotes self organization of the network into the shortest possible path(s). We introduce a network entropy function to characterize the self-organized evolution, show the solution of the shortest-path problem and demonstrate the healing property of the solution path. Finally, we provide an algorithm to solve the traveling salesman problem. Similar considerations apply to networks of memcapacitors and meminductors, and networks with memory in various dimensions.

Pershin, Yuriy V.; Di Ventra, Massimiliano

2013-07-01

9

Time depending shortest-path problems with applications to railway networks  

Microsoft Academic Search

In this paper the shortest path problem in a time depending transit network is discussed. A usual approach in public transport is to compute the shortest path for every possible starting time separately by the use of a modified Dijkstra procedure. Here a label correcting method is used to calculate the desired transit function for all starting times with one

K. Nachtigall

1995-01-01

10

A Faster Algorithm for the Single Source Shortest Path Problem with Few Distinct Positive Lengths  

E-print Network

In this paper, we propose an efficient method for implementing Dijkstra's algorithm for the Single Source Shortest Path Problem (SSSPP) in a graph whose edges have positive length, and where there are few distinct edge ...

Orlin, James B.

11

Discrete Approximation to Continuous Anisotropic Shortest-Path Problem  

E-print Network

Probability that some UAV will be detected along path on time interval [0, T]: Probability of jth UAV being-Risk Path Planning for Groups of UAVs James Riehl João Hespanha INFORMS Meeting November 6, 2007 #12;start point ? Cost may depend on · duration of path · fuel consumed along path · probability of detection

Hespanha, João Pedro

12

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

13

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

14

Parallel shortest augmenting path algorithm for the assignment problem. Technical report  

SciTech Connect

We describe a parallel version of the shortest augmenting path algorithm for the assignment problem. While generating the initial dual solution and partial assignment in parallel does not require substantive changes in the sequential algorithm, using several augmenting paths in parallel does require a new dual variable recalculation method. The parallel algorithm was tested on a 14-processor Butterfly Plus computer, on problems with up to 900 million variables. The speedup obtained increases with problem size. The algorithm was also embedded into a parallel branch and bound procedure for the traveling salesman problem on a directed graph, which was tested on the Butterfly Plus on problems involving up to 7,500 cities. To our knowledge, these are the largest assignment problems and traveling salesman problems solved so far.

Balas, E.; Miller, D.; Pekny, J.; Toth, P.

1989-04-01

15

An Improved Ant Colony Algorithm for the Shortest Path Problem in Time-Dependent Networks  

NASA Astrophysics Data System (ADS)

Research of the shortest path problem in time-dependent networks has important practical value. An improved pheromone update strategy suitable for time-dependent networks was proposed. Under this strategy, the residual pheromone of each road can accurately reflect the change of weighted value of each road. An improved selection strategy between adjacent cities was used to compute the cities' transfer probabilities, as a result, the amount of calculation is greatly reduced. To avoid the algorithm converging to the local optimal solution, the ant colony algorithm was combined with genetic algorithm. In this way, the solutions after each traversal were used as the initial species to carry out single-point crossover. An improved ant colony algorithm for the shortest path problem in time-dependent networks based on these improved strategies was presented. The simulation results show that the improved algorithm has greater probability to get the global optimal solution, and the convergence rate of algorithm is better than traditional ant colony algorithm.

Chang, Qing; Liu, Yongqiang; Xiong, Huagang

16

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

17

Physarum can compute shortest paths.  

PubMed

Physarum polycephalum is a slime mold that is apparently able to solve shortest path problems. A mathematical model has been proposed by Tero et al. (Journal of Theoretical Biology, 244, 2007, pp. 553-564) to describe the feedback mechanism used by the slime mold to adapt its tubular channels while foraging two food sources s(0) and s(1). We prove that, under this model, the mass of the mold will eventually converge to the shortest s(0)-s(1) path of the network that the mold lies on, independently of the structure of the network or of the initial mass distribution. This matches the experimental observations by Tero et al. and can be seen as an example of a "natural algorithm", that is, an algorithm developed by evolution over millions of years. PMID:22732274

Bonifaci, Vincenzo; Mehlhorn, Kurt; Varma, Girish

2012-09-21

18

Floats, Integers, and Single Source Shortest Paths  

Microsoft Academic Search

Floats are ugly, but to everyone but theoretical computer scientists, they are the real thing. A linear time algorithm is presented for the undirected single-source shortest paths problem with nonnegative floating point weights.

Mikkel Thorup

2000-01-01

19

On the Shortest Path Game  

E-print Network

Sep 19, 2014 ... Institute of Public Economics, University of Graz, ... s, t ? V . The aim of Shortest Path Game is to find a directed path from s to t in the following .... Assigning arbitrary but fixed numbers to each vertex in the beginning,. e.g. 1,...

2014-09-19

20

Floats, Integers, and Single Source Shortest Paths  

Microsoft Academic Search

Floats are ugly, but to everyone but theoretical computer scientists, they are thereal thing. A linear time algorithm is presented for the undirected single source shortestpaths problem with positive floating point weights.1 IntroductionThe technical goal of this paper is to present a linear time solution to the undirected singlesource shortest paths problem (USSSP) where the weights are positive floating points,

Mikkel Thorup

1998-01-01

21

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

RCSP into an unconstrained shortest path problem (SPP) and then solves the resulting SPP after new values of dual variables are used to update objective function coefficients (i.e., reduced costs) at each iteration. Network reduction techniques...

Zhu, Xiaoyan

2007-04-25

22

Shortest viable path algorithm in multimodal networks  

Microsoft Academic Search

We consider an approach using label correcting techniques to find the shortest viable path from an origin to a destination, in a multimodal transportation network. A path is called viable if its sequence of modes is feasible with respect to a set of constraints. We present an ad hoc modification of the Chronological Algorithm to solve the multimodal shortest viable

Angelica Lozano; Giovanni Storchi

2001-01-01

23

Shortest path and Schramm-Loewner Evolution  

PubMed Central

We numerically show that the statistical properties of the shortest path on critical percolation clusters are consistent with the ones predicted for Schramm-Loewner evolution (SLE) curves for ? = 1.04 0.02. The shortest path results from a global optimization process. To identify it, one needs to explore an entire area. Establishing a relation with SLE permits to generate curves statistically equivalent to the shortest path from a Brownian motion. We numerically analyze the winding angle, the left passage probability, and the driving function of the shortest path and compare them to the distributions predicted for SLE curves with the same fractal dimension. The consistency with SLE opens the possibility of using a solid theoretical framework to describe the shortest path and it raises relevant questions regarding conformal invariance and domain Markov properties, which we also discuss. PMID:24975019

Pos, N.; Schrenk, K. J.; Arajo, N. A. M.; Herrmann, H. J.

2014-01-01

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

Approximate Shortest Path Queries Using Voronoi Duals  

NASA Astrophysics Data System (ADS)

We propose an approximation method to answer point-to-point shortest path queries in undirected edge-weighted graphs, based on random sampling and Voronoi duals. We compute a simplification of the graph by selecting nodes independently at random with probability p. Edges are generated as the Voronoi dual of the original graph, using the selected nodes as Voronoi sites. This overlay graph allows for fast computation of approximate shortest paths for general, undirected graphs. The time-quality tradeoff decision can be made at query time. We provide bounds on the approximation ratio of the path lengths as well as experimental results. The theoretical worst-case approximation ratio is bounded by a logarithmic factor. Experiments show that our approximation method based on Voronoi duals has extremely fast preprocessing time and efficiently computes reasonably short paths.

Honiden, Shinichi; Houle, Michael E.; Sommer, Christian; Wolff, Martin

26

Balancing minimum spanning and shortest path trees  

Microsoft Academic Search

This paper give a simple linear-time algorithm that, given a weighted\\u000adigraph, finds a spanning tree that simultaneously approximates a shortest-path\\u000atree and a minimum spanning tree. The algorithm provides a continuous\\u000atrade-off: given the two trees and epsilon > 0, the algorithm returns a\\u000aspanning tree in which the distance between any vertex and the root of the\\u000ashortest-path

Samir Khuller; Balaji Raghavacharit; Neal E. Young

1993-01-01

27

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

28

Undirected single-source shortest paths with positive integer weights in linear time  

Microsoft Academic Search

The single-source shortest paths problem (SSSP) is one of the classic problems in algorithmic graph theory: given a positively weighted graph G with a source vertex s, find the shortest path from s to all other vertices in the graph.Since 1959, all theoretical developments in SSSP for general directed and undirected graphs have been based on Dijkstra's algorithm, visiting the

Mikkel Thorup

1999-01-01

29

Multiple Object Tracking Using the Shortest Path Faster Association Algorithm  

PubMed Central

To solve the persistently multiple object tracking in cluttered environments, this paper presents a novel tracking association approach based on the shortest path faster algorithm. First, the multiple object tracking is formulated as an integer programming problem of the flow network. Then we relax the integer programming to a standard linear programming problem. Therefore, the global optimum can be quickly obtained using the shortest path faster algorithm. The proposed method avoids the difficulties of integer programming, and it has a lower worst-case complexity than competing methods but better robustness and tracking accuracy in complex environments. Simulation results show that the proposed algorithm takes less time than other state-of-the-art methods and can operate in real time. PMID:25215322

Liu, Heping; Liu, Huaping; Yang, Bin

2014-01-01

30

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

31

Shortest Path Queries in Digraphs of Small Treewidth  

Microsoft Academic Search

We consider the problem of preprocessing an n-vertex di- graph with real edge weights so that subsequent queries for the shortest path or distance between any two vertices can be e-ciently answered. We give algorithms that depend on the treewidth of the input graph. When the treewidth is a constant, our algorithms can answer distance queries in O(fi(n)) time after

Shiva Chaudhuri; Christos D. Zaroliagis

1995-01-01

32

Parallel Shortest Path Algorithms for Solving Large-Scale Instances  

Microsoft Academic Search

We present an experimental study of parallel algorithms for solving the single source shortest path problem with non-negative edge weights (NSSP) on large-scale graphs. We implement Meyer and Sander's ?-stepping algorithm and report performance re- sults on the Cray MTA-2, a multithreaded parallel architecture. The MTA-2 is a high-end shared memory system offering two unique features that aid the efficient

Kamesh Madduri; David A. Bader; Jonathan W. Berry; Bruce A. Hendrickson

33

A Shortest Path Based Path Planning Algorithm for Nonholonomic Mobile Robots  

Microsoft Academic Search

A path planning algorithm for a mobile robot subject to nonholonomic constraints is presented. The algorithmemploys a global- local strategy, and solves the problem in the 2D workspace of the robot, without generating the complexconfiguration space. Firstly, a visibility graph is constructed for finding a collision-free shortest path for a point. Secondly,the path for a point is evaluated to find

Kaichun Jiang; Lakmal D. Seneviratne; S. W. E. Earles

1999-01-01

34

Balancing Minimum Spanning Trees and Shortest-Path Trees  

Microsoft Academic Search

We give a simple algorithm to find a spanning tree that simultaneously approximates a shortest-path tree and a minimum spanning tree. The algorithm provides a continuous tradeoff: given the two trees and a 7 > 0, the algorithm returns a spanning tree in which the distance between any vertex and the root of the shortest-path tree is at most 1

Samir Khuller; Balaji Raghavachari; Neal E. Young

1995-01-01

35

Exact Geodesics and Shortest Paths on Polyhedral Surfaces  

Microsoft Academic Search

We present two algorithms for computing distances along convex and non-convex polyhedral surfaces. The first algorithm computes exact minimal-geodesic distances and the second algorithm combines these distances to compute exact shortest-path distances along the surface. Both algorithms have been extended to compute the exact minimal-geodesic paths and shortest paths. These algorithms have been implemented and validated on surfaces for which

Mukund Balasubramanian; Jonathan R. Polimeni; Eric L. Schwartz

2009-01-01

36

Using shortest path to discover criminal community  

E-print Network

Extracting communities using existing community detection algorithms yields dense sub-networks that are difficult to analyse. Extracting a smaller sample that embodies the relationships of a list of suspects is an important part of the beginning of an investigation. In this paper, we present the efficacy of our shortest paths network search algorithm (SPNSA) that begins with an "algorithm feed", a small subset of nodes of particular interest, and builds an investigative sub-network. The algorithm feed may consist of known criminals or suspects, or persons of influence. This sets our approach apart from existing community detection algorithms. We apply the SPNSA on the Enron Dataset of e-mail communications starting with those convicted of money laundering in relation to the collapse of Enron as the algorithm feed. The algorithm produces sparse and small sub-networks that could feasibly identify a list of persons and relationships to be further investigated. In contrast, we show that identifying sub-networks o...

Magalingam, Pritheega; Rao, Asha

2015-01-01

37

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

38

Balancing Minimum Spanning Trees and Shortest-Path Trees  

Microsoft Academic Search

We give a simple algorithm to find a spanning tree that simultaneously approxi- mates a shortest-path tree and a minimum spanning tree. The algorithm provides a continuous trade-off: given the two trees and a > 0, the algorithm returns a span- ning tree in which the distance between any vertex and the root of the shortest-path tree is at most

Samir Khuller; Penn State

1993-01-01

39

Trans-dichotomous Algorithms for Minimum Spanning Trees and Shortest Paths  

Microsoft Academic Search

The fusion tree method is extended to develop a linear-time algorithm for the minimum spanning tree problem and an O(m +n log n\\/log log n) implementation of Dijkstra's shortest-path algorithm for a graph with n vertices and m edges. The shortest-path algorithm surpasses information-theoretic limitations. The extension of the fusion tree method involves the development of a new data structure,

Michael L. Fredman; Dan E. Willard

1990-01-01

40

Primal-dual algorithms for computing weight-constrained shortest paths and weight-constrained minimum spanning trees  

Microsoft Academic Search

In the QoS shortest path problem, we want to find a path connecting two given vertices u and v to minimize path cost subject to the constraint that the path weight is no greater than a given bound. In the QoS minimum spanning tree problem, we want to find a spanning tree to minimize tree cost subject to the constraint

Guoliang Xue

2000-01-01

41

Influence of the link weight structure on the shortest path  

NASA Astrophysics Data System (ADS)

The shortest path tree rooted at a source to all other nodes is investigated in a graph with polynomial link weights tunable by the power exponent ? . By varying ? , different types of shortest path trees, in short ? trees, appear. Especially, the ??0 regime that corresponds to heavily fluctuating link weights possesses a peculiar type of tree. The most important properties of this ??0 tree are derived in the asymptotic limit for large N . The application of the theoretical insights to real networks (such as the Internet) are discussed: steering flow by adjusting link weights (traffic engineering), sensitivity of link weights and modeling of the network by ? trees.

van Mieghem, Piet; van Langen, Stijn

2005-05-01

42

Copyright 2000, Kevin Wayne 1 Dijkstra's Shortest Path Algorithm  

E-print Network

14 0 S = { s, 2, 3, 6, 7 } PQ = { 4, 5, t } X X X 44 X 35X 59 XX51 X 34 X 33X 32 14 Dijkstra, 7 } PQ = { 4, 5, t } X X X 44 X 35X 59 XX51 X 34 delmin X 33X 32 24 15 Dijkstra's Shortest Path = { 4, t } X X X 44 X 35X 59 XX51 X 34 24 X50 X45 X 33X 32 16 Dijkstra's Shortest Path Algorithm s 3

Kosecka, Jana

43

Competition for Shortest Paths on Sparse Graphs  

NASA Astrophysics Data System (ADS)

Optimal paths connecting randomly selected network nodes and fixed routers are studied analytically in the presence of a nonlinear overlap cost that penalizes congestion. Routing becomes more difficult as the number of selected nodes increases and exhibits ergodicity breaking in the case of multiple routers. The ground state of such systems reveals nonmonotonic complex behaviors in average path length and algorithmic convergence, depending on the network topology, and densities of communicating nodes and routers. A distributed linearly scalable routing algorithm is also devised.

Yeung, Chi Ho; Saad, David

2012-05-01

44

Dynamic shortest path association for multiple object tracking in video sequence  

NASA Astrophysics Data System (ADS)

Persistently tracking multiple objects in cluttered environments is very challenging. We present a tracking association approach based on the shortest path faster algorithm. We first formulate the multiple object tracking as an integer programming problem of the flow network. Under this framework, the integer assumption is relaxed to a standard linear programming problem. Therefore, the global optimal solution can quickly be obtained using the fast dynamic shortest path algorithm, which highlights the dynamic programming characteristic of the shortest path, thus faster, algorithm. The proposed method avoids the difficulties of integer programming; more importantly, it has a lower worst-case complexity than competing methods but a better tracking accuracy and robustness in complex environments. Simulation results show that our proposed algorithm takes less time than other methods and can operate in real time.

Xi, Zhenghao; Liu, Heping; Liu, Huaping; Zheng, Yang

2015-01-01

45

: A Directed On-The-Fly Algorithm for Finding the k Shortest Paths  

E-print Network

K : A Directed On-The-Fly Algorithm for Finding the k Shortest Paths Husain Aljazzar and Stefan prominent algorithm for solving this problem, K has two advan- tages. First, K performs on-the-fly, which. Application domain examples for KSP problems include computer chess, sequence alignment and probabilistic

Reiterer, Harald

46

Balancing Minimum Spanning Trees and ShortestPath Trees  

E-print Network

Balancing Minimum Spanning Trees and Shortest­Path Trees Samir Khuller \\Lambda University and a minimum spanning tree. The algorithm provides a continuous trade­off: given the two trees and a fl ? 0 is at most 1 + p 2=fl times the weight of a minimum spanning tree. Our algorithm runs in linear time

Khuller, Samir

47

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

48

Finding Shortest Path for Developed Cognitive Map Using Medial Axis  

E-print Network

this paper presents an enhancement of the medial axis algorithm to be used for finding the optimal shortest path for developed cognitive map. The cognitive map has been developed, based on the architectural blueprint maps. The idea for using the medial-axis is to find main path central pixels; each center pixel represents the center distance between two side boarder pixels. The need for these pixels in the algorithm comes from the need of building a network of nodes for the path, where each node represents a turning in the real world (left, right, critical left, critical right...). The algorithm also ignores from finding the center pixels paths that are too small for intelligent robot navigation. The Idea of this algorithm is to find the possible shortest path between start and end points. The goal of this research is to extract a simple, robust representation of the shape of the cognitive map together with the optimal shortest path between start and end points. The intelligent robot will use this algorithm i...

Farhan, Hazim A; Al-Ghazi, Suhaib I

2011-01-01

49

Shortest-Path Kernels on Graphs  

Microsoft Academic Search

Data mining algorithms are facing the challenge to deal with an increasing number of complex objects. For graph data, a whole toolbox of data mining algorithms becomes available by defining a kernel function on instances of graphs. Graph kernels based on walks, subtrees and cycles in graphs have been proposed so far. As a general problem, these kernels are either

Karsten M. Borgwardt; Hans-peter Kriegel

2005-01-01

50

Distance formula and shortest paths for the (n, k)-star graphs  

Microsoft Academic Search

The class of (n,k)-star graphs is a generalization of the class of star graphs. Thus a distance formula for the first class implies one for the second. In this paper, we show that the converse is also true. Another important concept is the number of shortest paths between two vertices. This problem has been solved for the star graphs. We

Eddie Cheng; Jerrold W. Grossman; Lszl Liptk; Ke Qiu; Zhizhang Shen

2010-01-01

51

Parallel implementation of geometric shortest path algorithms Mark Lanthier Doron Nussbaum Jorg-Rudiger Sack  

E-print Network

.g., water, rock, forest). Considering weighted metrics however increases the run-time of algorithms consid-of-the-art Beowulf cluster with gigabit interconnect and a shared-memory architecture, SunFire. 1 Introduction algorithms for realistic shortest path problems are either very complex and/or have very large time and space

Lanthier, Mark

52

: Heuristics-Guided, On-the-Fly k Shortest Paths Husain Aljazzar and Stefan Leue  

E-print Network

K : Heuristics-Guided, On-the-Fly k Shortest Paths Search Husain Aljazzar and Stefan Leue to current KSP algorithms. First, K performs on-the-fly, which means that it does not require the graph examples for KSP problems in- clude logistics, finance analysis, scheduling, sequence alignment, networking

Leue, Stefan

53

Modeling shortest path selection of the ant Linepithema humile using psychophysical theory and realistic parameter values.  

PubMed

The emergence of self-organizing behavior in ants has been modeled in various theoretical approaches in the past decades. One model explains experimental observations in which Argentine ants (Linepithema humile) selected the shorter of two alternative paths from their nest to a food source (shortest path experiments). This model serves as an important example for the emergence of collective behavior and self-organization in biological systems. In addition, it inspired the development of computer algorithms for optimization problems called ant colony optimization (ACO). In the model, a choice function describing how ants react to different pheromone concentrations is fundamental. However, the parameters of the choice function were not deduced experimentally but freely adapted so that the model fitted the observations of the shortest path experiments. Thus, important knowledge was lacking about crucial model assumptions. A recent study on the Argentine ant provided this information by measuring the response of the ants to varying pheromone concentrations. In said study, the above mentioned choice function was fitted to the experimental data and its parameters were deduced. In addition, a psychometric function was fitted to the data and its parameters deduced. Based on these findings, it is possible to test the shortest path model by applying realistic parameter values. Here we present the results of such tests using Monte Carlo simulations of shortest path experiments with Argentine ants. We compare the choice function and the psychometric function, both with parameter values deduced from the above-mentioned experiments. Our results show that by applying the psychometric function, the shortest path experiments can be explained satisfactorily by the model. The study represents the first example of how psychophysical theory can be used to understand and model collective foraging behavior of ants based on trail pheromones. These findings may be important for other models of pheromone guided ant behavior and might inspire improved ACO algorithms. PMID:25769943

von Thienen, Wolfhard; Metzler, Dirk; Witte, Volker

2015-05-01

54

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

55

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

56

Shortest Path and Distance Queries on Road Networks: An Experimental Evaluation  

E-print Network

Computing the shortest path between two given locations in a road network is an important problem that finds applications in various map services and commercial navigation products. The state-of-the-art solutions for the problem can be divided into two categories: spatial-coherence-based methods and vertex-importance-based approaches. The two categories of techniques, however, have not been compared systematically under the same experimental framework, as they were developed from two independent lines of research that do not refer to each other. This renders it difficult for a practitioner to decide which technique should be adopted for a specific application. Furthermore, the experimental evaluation of the existing techniques, as presented in previous work, falls short in several aspects. Some methods were tested only on small road networks with up to one hundred thousand vertices; some approaches were evaluated using distance queries (instead of shortest path queries), namely, queries that ask only for the ...

Wu, Lingkun; Deng, Dingxiong; Cong, Gao; Zhu, Andy Diwen; Zhou, Shuigeng

2012-01-01

57

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

58

The shortest time and/or the shortest path strategies in a CA FF pedestrian dynamics model  

E-print Network

This paper deals with a mathematical model of a pedestrian movement. A stochastic cellular automata (CA) approach is used here. The Floor Field (FF) model is a basis model. FF models imply that virtual people follow the shortest path strategy. But people are followed by a strategy of the shortest time as well. This paper is focused on how to mathematically formalize and implement to a model these features of the pedestrian movement. Some results of a simulation are presented.

Ekaterina Kirik; Tat'yana Yurgel'yan; Dmitriy Krouglov

2009-06-23

59

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

60

Shortest Paths in Digraphs of Small Part I: Sequential Algorithms  

E-print Network

weight path between them, while a distance query only asks for the weight of such a path. This approach preprocessing time). Recently, in 17], the distance query time is improved to O( (n)), where (n) is the inverse Abstract We consider the problem of preprocessing an n-vertex digraph with real edge weights so

61

Fully Dynamic Algorithms for Maintaining All-Pairs Shortest Paths and Transitive Closure in Digraphs  

Microsoft Academic Search

This paper presents the first fully dynamic algorithms for maintaining all-pairs shortest paths in digraphs with posi- tive integer weights less than . For approximate shortest paths with an error factor of 2 , for any positive con- stant , the amortized update time is 2 log2 log log ; for an error factor of 1 the amortized update time

Valerie King

1999-01-01

62

Semi-Dynamic Shortest Paths and Breadth-First Search in Digraphs  

Microsoft Academic Search

We show how to maintain a shortest path tree of a general directed graph G with unit edge weights and n vertices, during a sequence of edge deletions or a sequence of edge insertions, in O(n) amortized time per operation using linear space. Distance queries can be answered in constant time, while shortest path queries can be answered in time

Paolo Giulio Franciosa; Daniele Frigioni; Roberto Giaccio

1997-01-01

63

Dynamic shortest path in stochastic traffic networks based on fluid neural network and Particle Swarm Optimization  

Microsoft Academic Search

The shortest path algorithm is critical for dynamic traffic assignment and for the realization of route guidance in intelligent transportation systems (ITS). In this paper, a hybrid Particle Swarm Optimization (PSO) algorithm combined fluid neural network (FNN) to search for the shortest path in stochastic traffic networks is introduced. The algorithm overcomes the weight coefficient symmetry restrictions of the traditional

Yanfang Deng; Hengqing Tong; Xiedong Zhang

2010-01-01

64

Shortest paths in the Tower of Hanoi graph and finite automata  

Microsoft Academic Search

We present efficient algorithms for constructing a shortest path be- tween two states in the Tower of Hanoi graph, and for computing the length of the shortest path. The key element is a finite-state machine which decides, after examining on the average only 63 38 ? 1.66 of the largest discs, whether the largest disc will be moved once or

Dan Romik

2003-01-01

65

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

66

Color texture classification using shortest paths in graphs.  

PubMed

Color textures are among the most important visual attributes in image analysis. This paper presents a novel method to analyze color textures by modeling a color image as a graph in two different and complementary manners (each color channel separately and the three color channels altogether) and by obtaining statistical moments from the shortest paths between specific vertices of this graph. Such an approach allows to create a set of feature vectors, which were extracted from VisTex, USPTex, and TC00013 color texture databases. The best classification results were 99.07%, 96.85%, and 91.54% (LDA with leave-one-out), 87.62%, 66.71%, and 88.06% (1NN with holdout), and 98.62%, 96.16%, and 91.34% (LDA with holdout) of success rate (percentage of samples correctly classified) for these three databases, respectively. These results prove that the proposed approach is a powerful tool for color texture analysis to be explored. PMID:24988594

de Mesquita Sa Junior, Jarbas Joaci; Cortez, Paulo Cesar; Backes, Andre Ricardo

2014-09-01

67

Traveling salesman path problems  

E-print Network

In the Traveling Salesman Path Problem, we are given a set of cities, traveling costs between city pairs and fixed source and destination cities. The objective is to find a minimum cost path from the source to destination ...

Lam, Fumei

2005-01-01

68

a Shortest Path Algorithm for a Network with Various Fuzzy Arc Lengths  

NASA Astrophysics Data System (ADS)

We are concerned with the design of a model and an algorithm for computing a shortest path in a network having various types of fuzzy arc lengths. First, we develop a new technique for the addition of various fuzzy numbers in a path using ? -cuts. Then, we propose a regression model for obtaining membership function for the considered addition. Finally, we present a dynamic programming method for finding a shortest path in the network. An example is worked out to illustrate the applicability of the proposed approach.

Tajdin, Ali; Mahdavi, Iraj; Mahdavi-Amiri, Nezam; Sadeghpour-Gildeh, Bahram; hadighi, Rofideh

2010-06-01

69

Traffic Grooming Based on Shortest Path in Optical WDM Mesh Networks  

E-print Network

propose Shortest-path First Traffic grooming(SFT) algo- rithm. The comprehensive computer simulation shows-path First Traffic grooming (SFT) algorithm in objective to maximize the network throughput and to minimize together and carried. According to the computer simulation, the SFT algorithm achieves 14% improved

Lee, Tae-Jin

70

Geodesics and Shortest Paths Approach in Pedestrian Motions  

E-print Network

of optimal paths for visitors of French national parks [12] ... and for Rascle by previous works on mesh, no conservation of momentum etc ... The aim is simply to propose one optimization principle which might govern

Rascle, Michel

71

The approach for shortest paths in fire succor based on component GIS technology  

NASA Astrophysics Data System (ADS)

Fire safety is an important issue for the national economy and people's living. Efficiency and exactness of fire department succor directly relate to safety of peoples' lives and property. Many disadvantages of the traditional fire system have been emerged in practical applications. The preparation of pumpers is guided by wireless communication or wire communication, so its real-time and accurate performances are much poorer. The information about the reported fire, such as the position, disaster and map, et al., for alarm and command was processed by persons, which slows the reaction speed and delays the combat opportunity. In order to solve these disadvantages, it has an important role to construct a modern fire command center based on high technology. The construction of modern fire command center can realize the modernization and automation of fire command and management. It will play a great role in protecting safety of peoples' lives and property. The center can enhance battle ability and can reduce the direct and indirect loss of fire damage at most. With the development of science technology, Geographic Information System (GIS) has becoming a new information industry for hardware production, software development, data collection, space analysis and counseling. With the popularization of computers and the development of GIS, GIS has gained increasing broad applications for its strong functionality. Network analysis is one of the most important functions of GIS, and the most elementary and pivotal issue of network analysis is the calculation of shortest paths. The shortest paths are mostly applied to some emergent systems such as 119 fire alarms. These systems mainly require that the computation time of the optimal path should be 1-3 seconds. And during traveling, the next running path of the vehicles should be calculated in time. So the implement of the shortest paths must have a high efficiency. In this paper, the component GIS technology was applied to collect and record the data information (such as, the situation of this disaster, map and road status et al) of the reported fire firstly. The ant colony optimization was used to calculate the shortest path of fire succor secondly. The optimization results were sent to the pumpers, which can let pumpers choose the shortest paths intelligently and come to fire position with least time. The programming method for shortest paths is proposed in section 3. There are three parts in this section. The elementary framework of the proposed programming method is presented in part one. The systematic framework of GIS component is described in part two. The ant colony optimization employed is presented in part three. In section 4, a simple application instance was presented to demonstrate the proposed programming method. There are three parts in this section. The distributed Web application based on component GIS was described in part one. The optimization results without traffic constraint were presented in part two. The optimization results with traffic constraint were presented in part three. The contributions of this paper can be summarized as follows. (1) It proposed an effective approach for shortest paths in fire succor based on component GIS technology. This proposed approach can achieve the real-time decisions of shortest paths for fire succor. (2) It applied the ant colony optimization to implement the shortest path decision. The traffic information was considered in the shortest path decision using ant colony optimization. The final application instance suggests that the proposed approach is feasible, correct and valid.

Han, Jie; Zhao, Yong; Dai, K. W.

2007-06-01

72

Graph Calculus: Scalable Shortest Path Analytics for Large Social Graphs through Core Net Department of Computer Science  

E-print Network

between two people. There have been many algorithms addressing the shortest path analytics. For example such as the massive Facebook graph. Extensive applications of such shortest-path analytics are naturally expected two users are on social networks as well as how fast/far any interesting post from one user can reach

Deng, Jing

73

SUBMITTED TO IEEE PAMI, 2008 1 Watershed cuts: thinnings, shortest-path forests and  

E-print Network

and diffusion tensor images. Index Terms-- Watershed, thinning, minimum spanning forest, shortest-path forest. The digital image is seen as a topographic surface: the gray level becomes the elevation, the basins and valleys of the topographic surface correspond to dark areas, whereas the mountains and crest lines

Paris-Sud XI, Université de

74

Transitive Functional Annotation by Shortest-path Analysis of Gene Expression Data  

Microsoft Academic Search

attribute to link genes of the same biological pathway. Based on large-scale yeast microarray expression data, we use the shortest-path analysis to identify transitive genes between two given genes from the same biological process. We find that not only functionally related genes with correlated expression profiles are identified but also those without. In the latter case, we compare our method

Xianghong Zhou; Ming-Chih J. Kao; Wing Hung Wong

2002-01-01

75

Spatial interpolation of fine particulate matter concentrations using the shortest wind-field path distance.  

PubMed

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

76

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

E-print Network

1 of 28 Shortest Path Stochastic Control for Hybrid Electric Vehicles Ed Tate1 , J.W. Grizzle2 , Huei Peng3 Abstract: When a Hybrid Electric Vehicle (HEV) is certified for emissions and fuel economy this is the Hybrid Electric Vehicle (HEV) which consists of an electric powertrain coupled to a conventional

Grizzle, Jessy W.

77

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

78

Multicast Routing in Wireless Mesh Networks: Minimum Cost Trees or Shortest Path Trees?  

Microsoft Academic Search

There exist two fundamental approaches to multicast routing: shortest path trees (SPTs) and minimum cost trees (MCTs). The SPT algorithms minimize the distance (or cost) from the sender to each receiver, whereas the MCT algorithms minimize the overall cost of the multicast tree. Due to the very large scale and unknown topology of the Internet, computing MCTs for multicast routing

Uyen Trang Nguyen; Jin Xu

2007-01-01

79

Enhanced Shortest Path Computation for Multiagent-based Intermodal Transport Planning in Dynamic Environments  

E-print Network

, Germany 2Center for Infrastructure, Sustainable Transportation and Urban Planning, Indian InstituteEnhanced Shortest Path Computation for Multiagent-based Intermodal Transport Planning in Dynamic,humi,herzog}@tzi.de,sitharam@civil.iisc.ernet.in Keywords: Multiagent-based Simulation Abstract: This paper addresses improved urban mobility using

80

Shortest multiple disconnected path for the analysis of entanglements in two- and three-dimensional polymeric systems  

NASA Astrophysics Data System (ADS)

We present an algorithm which returns a shortest path and related number of entanglements for a given configuration of a polymeric system in 2 or 3 dimensions. Rubinstein and Helfand, and later Everaers et al. introduced a concept to extract primitive paths for dense polymeric melts made of linear chains (a multiple disconnected multibead 'path'), where each primitive path is defined as a path connecting the (space-fixed) ends of a polymer under the constraint of non-interpenetration (excluded volume) between primitive paths of different chains, such that the multiple disconnected path fulfills a minimization criterion. The present algorithm uses geometrical operations and provides amodel independentefficient approximate solution to this challenging problem. Primitive paths are treated as 'infinitely' thin (we further allow for finite thickness to model excluded volume), and tensionless lines rather than multibead chains, excluded volume is taken into account without a force law. The present implementation allows to construct a shortest multiple disconnected path (SP) for 2D systems (polymeric chain within spherical obstacles) and an optimal SP for 3D systems (collection of polymeric chains). The number of entanglements is then simply obtained from the SP as either the number of interior kinks, or from the average length of a line segment. Further, information about structure and potentially also the dynamics of entanglements is immediately available from the SP. We apply the method to study the 'concentration' dependence of the degree of entanglement in phantom chain systems. Program summaryTitle of program:Z Catalogue number:ADVG Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADVG Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer for which the program is designed and others on which it has been tested: Silicon Graphics (Irix), Sun (Solaris), PC (Linux) Operating systems or monitors under which the program has been tested: UNIX, Linux Program language used: USANSI Fortran 77 and Fortran 90 Memory required to execute with typical data: 1 MByte No. of lines in distributed program, including test data, etc.: 10 660 No. of bytes in distributed program, including test data, etc.: 119 551 Distribution formet:tar.gz Nature of physical problem: The problem is to obtain primitive paths substantiating a shortest multiple disconnected path (SP) for a given polymer configuration (chains of particles, with or without additional single particles as obstacles for the 2D case). Primitive paths are here defined as in [M. Rubinstein, E. Helfand, J. Chem. Phys. 82 (1985) 2477; R. Everaers, S.K. Sukumaran, G.S. Grest, C. Svaneborg, A. Sivasubramanian, K. Kremer, Science 303 (2004) 823] as the shortest line (path) respecting 'topological' constraints (from neighboring polymers or point obstacles) between ends of polymers. There is a unique solution for the 2D case. For the 3D case it is unique if we construct a primitive path of a single chain embedded within fixed line obstacles [J.S.B. Mitchell, Geometric shortest paths and network optimization, in: J.-R. Sack, J. Urrutia (Eds.), Handbook of Computational Geometry, Elsevier, Amsterdam, 2000, pp. 633-701]. For a large 3D configuration made of several chains, short is meant to be the Euclidean shortest multiple disconnected path (SP) where primitive paths are constructed for all chains simultaneously. While the latter problem, in general, does not possess a unique solution, the algorithm must return a locally optimal solution, robust against minor displacements of the disconnected path and chain re-labeling. The problem is solved if the number of kinks (or entanglements Z), explicitly deduced from the SP, is quite insensitive to the exact conformation of the SP which allows to estimate Z with a small error. Efficient method of solution: Primitive paths are constructed from the given polymer configuration (a non-shortest multiple disconnected path, including obstacles, if present) by first replacing each polymer contour by a line wi

Krger, Martin

2005-06-01

81

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

NASA Astrophysics Data System (ADS)

In this paper we present weighted Koch networks based on classic Koch networks. A new method is used to determine the average receiving time (ART), whose key step is to write the sum of mean first-passage times (MFPTs) for all nodes to absorption at the trap located at a hub node as a recursive relation. We show that the ART exhibits a sublinear or linear dependence on network order. Thus, the weighted Koch networks are more efficient than classic Koch networks in receiving information. Moreover, average weighted shortest path (AWSP) is calculated. In the infinite network order limit, the AWSP depends on the scaling factor. The weighted Koch network grows unbounded but with the logarithm of the network size, while the weighted shortest paths stay bounded.

Dai, Meifeng; Chen, Dandan; Dong, Yujuan; Liu, Jie

2012-12-01

82

Modeling the average shortest-path length in growth of word-adjacency networks  

NASA Astrophysics Data System (ADS)

We investigate properties of evolving linguistic networks defined by the word-adjacency relation. Such networks belong to the category of networks with accelerated growth but their shortest-path length appears to reveal the network size dependence of different functional form than the ones known so far. We thus compare the networks created from literary texts with their artificial substitutes based on different variants of the Dorogovtsev-Mendes model and observe that none of them is able to properly simulate the novel asymptotics of the shortest-path length. Then, we identify the local chainlike linear growth induced by grammar and style as a missing element in this model and extend it by incorporating such effects. It is in this way that a satisfactory agreement with the empirical result is obtained.

Kulig, Andrzej; Dro?d?, Stanis?aw; Kwapie?, Jaros?aw; O?wiȩcimka, Pawe?

2015-03-01

83

Soft-decision Decoding of Block Codes using the k Shortest Paths Algorithm  

Microsoft Academic Search

In this paper, we develop a soft-decision decoding algorithm for block codes using the k shortest paths algorithm. The performance of this algorithm is investigated and compared with other decoding schemes. The results show the proposed algorithm gives large gains over the generalised minimum distance (GMD) decoding algorithm and algebraic hard-decision decoding. Further, the proposed algorithm achieves near-MLD performance for

Ismail Shakeel; Alex Grant

2006-01-01

84

Exact Algorithms for the Canadian Traveller Problem on Paths and Trees  

E-print Network

The Canadian Traveller problem is a stochastic shortest paths problem in which one learns the cost of an edge only when arriving at one of its endpoints. The goal is to find an adaptive policy (adjusting as one learns more ...

Karger, David

2008-01-28

85

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 ( 3.5mm) were acquired. Several independent guidewire ( 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.; Nol, Peter B.; Xu, Jinhui

2007-03-01

86

k-Link Rectilinear Shortest Paths Among Rectilinear Obstacles in the Plane Valentin Polishchuk  

E-print Network

]. More efficient algorithms, running in nearly linear time, are known for optimal paths in a "combined]. In rectilinear polygonal domains, efficient algorithms are known for the bi-criteria path problem that com- bines], which has been applied successfully to solving many optimal path problems in geometry. Since our new

87

Hardness of Approximating the Shortest Vector Problem in High L p Norms  

E-print Network

Hardness of Approximating the Shortest Vector Problem in High L p Norms Subhash Khot email : khot integers p #21; p(#15;), it is NP­hard to approximate the Shortest Vector Problem in L p norm within factor hardness shown by Micciancio [27]. 1 #12; 1 Introduction An n­dimensional lattice L is a set of vectors f P

Khot, Subhash

88

The lawnmower problem and other geometric path covering problems  

SciTech Connect

We discuss the Lawnmower Problem: Given a polygonal region, find the shortest closed path along which we have to move a given object (typically a square or a circle), such that any point of the region will be covered by the object for some position of it movement. In another version of the problem, known as the Milling Problem, the object has to stay within the region at all times. Practical motivations for considering the Lawnmower Problem come from manufacturing (spray painting, quality control), geography (aerial surveys), optimization (tour planning for a large number of clients with limited mobility), and gardening. The Milling Problem has gained attention by its importance for NC pocket machining. We show that both problems are NP-hard and discuss approximation methods for various versions of the problem.

Fekete, S.; Arkin, E.; Mitchell, J.

1994-12-31

89

Identification of Novel Thyroid Cancer-Related Genes and Chemicals Using Shortest Path Algorithm  

PubMed Central

Thyroid cancer is a typical endocrine malignancy. In the past three decades, the continued growth of its incidence has made it urgent to design effective treatments to treat this disease. To this end, it is necessary to uncover the mechanism underlying this disease. Identification of thyroid cancer-related genes and chemicals is helpful to understand the mechanism of thyroid cancer. In this study, we generalized some previous methods to discover both disease genes and chemicals. The method was based on shortest path algorithm and applied to discover novel thyroid cancer-related genes and chemicals. The analysis of the final obtained genes and chemicals suggests that some of them are crucial to the formation and development of thyroid cancer. It is indicated that the proposed method is effective for the discovery of novel disease genes and chemicals.

Zhang, Peiwei; Li, Li-Peng; He, Yi-Chun; Gao, Ru-jian; Gao, Yu-Fei

2015-01-01

90

Efficient Processing of Which-Edge Questions on Shortest Path Queries  

E-print Network

path queries on a graph. This problem has important applications in logistics, urban planning, and net path queries have a wide range of applications in logistics, urban planning, and network planning domains, too. In urban planning where the road network is modeled as a graph, one may ask "(Q3): which

Zhu, Kenny Q.

91

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

92

Impact Analysis of the Shortest Path Movement Model on Routing Strategies for VDTNs in a Rural Region  

Microsoft Academic Search

Vehicular Delay-Tolerant Network (VDTN) appears as a particular application of the Delay-Tolerant Network (DTN) concept to transit networks. In this paper we analyze the use of a VDTN to provide asynchronous Internet access on a rural remote region scenario. Through simulation we evaluate the impact of a shortest path based movement model on the performance of four DTN routing protocols

Vasco N. G. J. Soares; Joel J. P. C. Rodrigues; Farid Farahmand

93

Technical note: Quantification of neurocranial shape variation using the shortest paths connecting pairs of anatomical landmarks.  

PubMed

Three-dimensional geometric morphometric techniques have been widely used in quantitative comparisons of craniofacial morphology in humans and nonhuman primates. However, few anatomical landmarks can actually be defined on the neurocranium. In this study, an alternative method is proposed for defining semi-landmarks on neurocranial surfaces for use in detailed analysis of cranial shape. Specifically, midsagittal, nuchal, and temporal lines were approximated using Bezier curves and equally spaced points along each of the curves were defined as semi-landmarks. The shortest paths connecting pairs of anatomical landmarks as well as semi-landmarks were then calculated in order to represent the surface morphology between landmarks using equally spaced points along the paths. To evaluate the efficacy of this method, the previously outlined technique was used in morphological analysis of sexual dimorphism in modern Japanese crania. The study sample comprised 22 specimens that were used to generate 110 anatomical semi-landmarks, which were used in geometric morphometric analysis. Although variations due to sexual dimorphism in human crania are very small, differences could be identified using the proposed landmark placement, which demonstrated the efficacy of the proposed method. PMID:23868177

Morita, Yusuke; Ogihara, Naomichi; Kanai, Takashi; Suzuki, Hiromasa

2013-08-01

94

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 mr-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

95

Carpooling : the 2 Synchronization Points Shortest Paths Problem  

E-print Network

Carpooling is an appropriate solution to address traffic congestion and to reduce the ecological footprint encouraged to park private cars near multimodal hubs (i.e. park and ride stations) and to use the public to the public transport system. An appropriate solution, requiring little investment and reducing the ecological

Paris-Sud XI, Université de

96

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

97

Ant Colony Algorithm for Multiple-Depot Vehicle Routing Problem with Shortest Finish Time  

NASA Astrophysics Data System (ADS)

The objective of the multiple-depot vehicle routing problem (MDVRP) is to shorten the finish time, in the emergency management and special delivery research. In this paper, an ant colony algorithm for multiple-depot vehicle routing problem with shortest finish time (FTMDVRP) is studied. We discuss the concept and framework of FTMDVRP. The methods of making use of improved split algorithm to divide cars for given customer sequence is presented. We use the max flow algorithm allocate cars to each depot. Our experimental results confirm that our approach is effective in multiple-depot vehicle routing.

Ma, Jianhua; Yuan, Jie

98

Monotonicity Testing and Shortest-Path Routing on the Jop Briet1  

E-print Network

],[Bha08],[HK08] is one of the oldest and most studied problems in Property Testing. The problem], [GGL+ 00], [Fis04], [Ras99], [Bha08], [BGJ+ 09]. Here the order relation x y is defined to hold for x

Ben-Sasson, Eli

99

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

100

On Shortest Random Walks under Adversarial Uncertainty  

Microsoft Academic Search

Finding shortest feasible paths in a weighted graph has numerous applications including admission and routing in communication networks. This paper discusses a game theoretic framework intended to incorporate a concept of path stability into the process of shortest path selection. Route stability is an important issue in a wire-line and especially in wireless network due to node mobility as well

Vladimir Marbukh

101

Optimal Paths in Weighted Timed Automata ? Rajeev Alur 1;2 , Salvatore La Torre 1;3 , and George J. Pappas 1  

E-print Network

for weighted timed automata to a parametric shortest­path problem in directed graphs. We give a fix­poinOptimal Paths in Weighted Timed Automata ? Rajeev Alur 1;2 , Salvatore La Torre 1;3 , and George J to this optimization problem consists of reducing it to a (parametric) shortest­path problem in a finite directed graph

Alur, Rajeev

102

Path Covering Problems and Testing of Printed Circuits  

Microsoft Academic Search

This work deals with a problem, arising in the context of printed circuit testing, that will be formulated as a path covering problem on trees. For this problem, which consists in minimizing the number of continuity testing, an exact algorithm of linear complexity is here proposed for the first time. A general classification of path covering problems is also presented

Giovanni Andreatta; Francesco Mason

1995-01-01

103

Object location using path separators  

Microsoft Academic Search

We study a novel separator property called k-path separa- ble. Roughly speaking, a k-path separable graph can be re- cursively separated into smaller components by sequentially removing k shortest paths. Our main result is that every minor free weighted graph is k-path separable. We then show that k-path separable graphs can be used to solve sev- eral object location problems:

Ittai Abraham; Cyril Gavoille

2006-01-01

104

Solving Stochastic Shortest-Path Problems with RTDP Cognitive Systems Laboratory  

E-print Network

Departamento de Computaci´on Universidad Sim´on Bol´ivar Aptdo. 89000, Caracas 1080-A Venezuela Abstract We Decision Processes (mdps) that is of central importance to AI: they are the natural gen- eralization

Bonet, Blai

105

Relative Improvement by Alternative Solutions for Classes of Simple Shortest Path Problems  

E-print Network

with Uncertain Data -- Part I: Strings of Pearls Gn with Unbiased Perturbations l l l l l l l l s s s s s s s 3 3 of this section we introduce the considered model in detail: the graph model (string of pearls Gn) and an unbiased.1 The Model We consider the following graph model: Definition 1.1 (string of pearls Gn) Consider a weighted

106

Relative Improvement by Alternative Solutions for Classes of Simple Shortest Path Problems  

E-print Network

with Uncertain Data -- Part II: Strings of Pearls Gn,r with Biased Perturbations l l l l l l l l the considered models in detail: the graph model (string of pearls Gn,r) and two different biased perturbation. We finish with conclusions in Section 5. 1.1 The Models Definition 1.1 (string of pearls Gn

107

Solving a Hamiltonian Path Problem with a bacterial computer  

Microsoft Academic Search

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

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

2009-01-01

108

Identification of Influenza A/H7N9 Virus Infection-Related Human Genes Based on Shortest Paths in a Virus-Human Protein Interaction Network  

PubMed Central

The recently emerging Influenza A/H7N9 virus is reported to be able to infect humans and cause mortality. However, viral and host factors associated with the infection are poorly understood. It is suggested by the guilt by association rule that interacting proteins share the same or similar functions and hence may be involved in the same pathway. In this study, we developed a computational method to identify Influenza A/H7N9 virus infection-related human genes based on this rule from the shortest paths in a virus-human protein interaction network. Finally, we screened out the most significant 20 human genes, which could be the potential infection related genes, providing guidelines for further experimental validation. Analysis of the 20 genes showed that they were enriched in protein binding, saccharide or polysaccharide metabolism related pathways and oxidative phosphorylation pathways. We also compared the results with those from human rhinovirus (HRV) and respiratory syncytial virus (RSV) by the same method. It was indicated that saccharide or polysaccharide metabolism related pathways might be especially associated with the H7N9 infection. These results could shed some light on the understanding of the virus infection mechanism, providing basis for future experimental biology studies and for the development of effective strategies for H7N9 clinical therapies. PMID:24955349

Huang, Tao; Cai, Yu-Dong

2014-01-01

109

Identification of Influenza A/H7N9 virus infection-related human genes based on shortest paths in a virus-human protein interaction network.  

PubMed

The recently emerging Influenza A/H7N9 virus is reported to be able to infect humans and cause mortality. However, viral and host factors associated with the infection are poorly understood. It is suggested by the "guilt by association" rule that interacting proteins share the same or similar functions and hence may be involved in the same pathway. In this study, we developed a computational method to identify Influenza A/H7N9 virus infection-related human genes based on this rule from the shortest paths in a virus-human protein interaction network. Finally, we screened out the most significant 20 human genes, which could be the potential infection related genes, providing guidelines for further experimental validation. Analysis of the 20 genes showed that they were enriched in protein binding, saccharide or polysaccharide metabolism related pathways and oxidative phosphorylation pathways. We also compared the results with those from human rhinovirus (HRV) and respiratory syncytial virus (RSV) by the same method. It was indicated that saccharide or polysaccharide metabolism related pathways might be especially associated with the H7N9 infection. These results could shed some light on the understanding of the virus infection mechanism, providing basis for future experimental biology studies and for the development of effective strategies for H7N9 clinical therapies. PMID:24955349

Zhang, Ning; Jiang, Min; Huang, Tao; Cai, Yu-Dong

2014-01-01

110

978-1-4244-7265-9/10/$26.00 c 2010 IEEE Conditional Shortest Path Routing in  

E-print Network

the conventional intermeeting time as the link metric. I. INTRODUCTION Routing in delay tolerant networks (DTN in DTN's. Therefore, the routing problem is still an active research area in DTN's [1]. Routing algorithms in DTN's utilize a paradigm called store-carry-and-forward. When a node receives a message from

Varela, Carlos

111

The Loss Path Multiplicity Problem in Multicast Congestion Control  

Microsoft Academic Search

An important concern for source-based multicast congestion control algorithms is the loss path multiplicity (LPM) problem that arises because a transmitted packet can be lost on one or more of the many end-to- end paths in a multicast tree. Consequently, if a multicast source's trans- mission rate is regulated according to loss indications from receivers, the rate may be completely

Supratik Bhattacharyya; Donald F. Towsley; James F. Kurose

1999-01-01

112

Complementarity Problems in GAMS and the PATH Solver \\Lambda  

E-print Network

Complementarity Problems in GAMS and the PATH Solver \\Lambda Michael C. Ferris y Todd S. Munson y of nonlinear equations. There are many methods to approach this problem, the most famous of which is Newton solver, a generalization of Newton's method, for finding a solution. While the modeling format

Ferris, Michael C.

113

Linear approximation of shortest superstrings  

Microsoft Academic Search

We consider the following problem: given a collection of strings s1,, sm, find the shortest string s such that each si appears as a substring (a consecutive block) of s. Although this problem is known to be NP-hard, a simple greedy procedure appears to do quite well and is routinely used in DNA sequencing and data compression practice, namely: repeatedly

Avrim Blum; Tao Jiang; Ming Li; John Tromp; Mihalis Yannakakis

1994-01-01

114

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

115

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

116

An overview of constraint-based path selection algorithms for QoS routing  

Microsoft Academic Search

Constraint-based path selection aims at identifying a path that satisfies a set of quality of service (QoS) constraints. In general, this problem is known to be NP-complete, leading to the proposal of many heuristic algorithms. We provide an overview of these algorithms, focusing on restricted shortest path and multi-constrained path algorithms.

Fernando Kuipers; Piet Van Mieghem; T. Korkmaz; M. Krunz

2002-01-01

117

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

118

A path following algorithm for the graph matching problem.  

PubMed

We propose a convex-concave programming approach for the labeled weighted graph matching problem. The convex-concave programming formulation is obtained by rewriting the weighted graph matching problem as a least-square problem on the set of permutation matrices and relaxing it to two different optimization problems: a quadratic convex and a quadratic concave optimization problem on the set of doubly stochastic matrices. The concave relaxation has the same global minimum as the initial graph matching problem, but the search for its global minimum is also a hard combinatorial problem. We, therefore, construct an approximation of the concave problem solution by following a solution path of a convex-concave problem obtained by linear interpolation of the convex and concave formulations, starting from the convex relaxation. This method allows to easily integrate the information on graph label similarities into the optimization problem, and therefore, perform labeled weighted graph matching. The algorithm is compared with some of the best performing graph matching methods on four data sets: simulated graphs, QAPLib, retina vessel images, and handwritten Chinese characters. In all cases, the results are competitive with the state of the art. PMID:19834143

Zaslavskiy, Mikhail; Bach, Francis; Vert, Jean-Philippe

2009-12-01

119

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

120

On Path Cover Problems in Digraphs and Applications to Program Testing  

Microsoft Academic Search

In this paper various path cover problems, arising in program testing, are discussed. Dilworth's theorem for acyclic digraphs is generalized. Two methods for fmding a minimum set of paths (minimum path cover) that covers the vertices (or the edges) of a digraph are given. To model interactions among code segments, the notions of required pairs and required paths are introduced.

Simeon C. Ntafos; S. Louis Hakimi

1979-01-01

121

Hammock-on-Ears Decomposition: A Technique for the Efficient Parallel Solution of Shortest Paths and Other Problems  

Microsoft Academic Search

We show how to decompose efficiently in parallel any graph into a number, ~ fl, ofouterplanar subgraphs (called hammocks) satisfying certain separator properties. Ourwork combines and extends the sequential hammock decomposition technique introducedby Frederickson and the parallel ear decomposition technique, thus we call itthe hammock-on-ears decomposition. We mention that hammock-on-ears decompositionalso draws from techniques in computational geometry and that an

Dimitris J. Kavvadias; Grammati E. Pantziou; Paul G. Spirakis; Christos D. Zaroliagis

1996-01-01

122

A 2-dimensional optical architecture for solving Hamiltonian path problem based on micro ring resonators  

NASA Astrophysics Data System (ADS)

The problem of finding the Hamiltonian path in a graph, or deciding whether a graph has a Hamiltonian path or not, is an NP-complete problem. No exact solution has been found yet, to solve this problem using polynomial amount of time and space. In this paper, we propose a two dimensional (2-D) optical architecture based on optical electronic devices such as micro ring resonators, optical circulators and MEMS based mirror (MEMS-M) to solve the Hamiltonian Path Problem, for undirected graphs in linear time. It uses a heuristic algorithm and employs n+1 different wavelengths of a light ray, to check whether a Hamiltonian path exists or not on a graph with n vertices. Then if a Hamiltonian path exists, it reports the path. The device complexity of the proposed architecture is O(n2).

Shakeri, Nadim; Jalili, Saeed; Ahmadi, Vahid; Rasoulzadeh Zali, Aref; Goliaei, Sama

2015-01-01

123

Shortest Expected Delay Routing for Erlang Servers  

Microsoft Academic Search

The queueing problem with Poisson arrivals and two identical parallel Erlang servers is analyzed for the case of shortest expected delay routing. This problem may be represented as a random walk on the integer grid in the first quadrant of the plane. An important aspect of the random walk is that it is possible to make large jumps in the

Ivo J. B. F. Adan; Jaap Wessels

1996-01-01

124

A motion planning algorithm for smooth paths of bounded curvature and curvature derivative  

Microsoft Academic Search

This paper proposes an algorithm for planning Cinfin paths with bound curvature and curvature derivative linking two fixed (initial and final) configurations and passing through a given number of intermediate via-points. The proposed solution is derived solving an optimization problem such that a smooth curve of bounded curvature and curvature derivative approximates Dubin's shortest paths. The effectiveness of such strategy

G. Parlangeli; L. Ostuni; L. Mancarella; G. Indiveri

2009-01-01

125

Complementarity Problems in GAMS and the PATH Solver  

Microsoft Academic Search

A fundamental mathematical problem is to find a solution to a square system of nonlinear equations. There are many methods to approach this problem, the most famous of which is Newton's method. In this paper, we describe a generalization of this problem, the comple- mentarity problem. We show how such problems are modeled within the GAMS modeling language and provide

Michael C. Ferris; Todd S. Munson

1998-01-01

126

Scalable shortest paths browsing on land surface  

Microsoft Academic Search

The growing popularity of online Earth visualization tools and geo-realistic games and the availability of high resolution terrain data have motivated a new class of queries to the interests of the GIS and spatial database community: spatial queries (e.g., kNN) over land surface. However, the fundamental challenges that restrict the applicability of these studies to real world applications are the

Songhua Xing; Cyrus Shahabi

2010-01-01

127

Optimal Distributed All Pairs Shortest Paths  

E-print Network

nodes Diameter of this network? #12;· Spanning Tree ­ Broadcasting, Aggregation, etc · Minimum Spanning #12;· Spanning Tree ­ Broadcasting, Aggregation, etc · Minimum Spanning Tree ­ Efficient broadcasting;· Spanning Tree ­ Broadcasting, Aggregation, etc · Minimum Spanning Tree ­ Efficient broadcasting, etc

128

Querying Approximate Shortest Paths in Anisotropic Regions  

E-print Network

face of this subdivision are measured by a possibly asymmetric convex distance function whose unit disk is contained in a concentric unit Euclidean disk, and contains a concentric Euclidean disk with radius 1 in the faces of the subdivision are measured using possibly asymmetric convex distance functions. This model

Vigneron, Antoine

129

Querying Approximate Shortest Paths in Anisotropic Regions  

E-print Network

of this subdivision are measured by a possibly asymmetric convex distance function whose unit disk is contained in a concentric unit Euclidean disk, and contains a concentric Euclidean disk with radius 1/. Different convex using possibly asymmetric convex distance functions. This model covers the Euclidean case and other non

Cheng, Siu-Wing

130

A Path Following Algorithm for the Graph Matching Problem  

Microsoft Academic Search

We propose a convex-concave programming approach for the labeled weighted graph matching problem. The convex-concave programming formulation is obtained by rewriting the weighted graph matching problem as a least-square problem on the set of permutation matrices and relaxing it to two different optimization problems: a quadratic convex and a quadratic concave optimization problem on the set of doubly stochastic matrices.

Mikhail Zaslavskiy; Francis R. Bach; Jean-philippe Vert

2009-01-01

131

Path following algorithm for the graph matching problem  

Microsoft Academic Search

Abstract We propose a convex-concave programming,approach for the labeled weighted graph matching problem. The convex-concave programming,formulation is obtained by rewriting the weighted graph matching problem as a least-square problem on the set of permutation matrices and relaxing it to two different optimization problems: a quadratic convex and a quadratic concave optimization problem on the set of doubly stochastic matrices. The

Mikhail Zaslavskiy; Francis Bach; Jean-Philippe Vert

2008-01-01

132

Near-optimal hardness results and approximation algorithms for edge-disjoint paths and related problems  

Microsoft Academic Search

We study the approximability of edge-disjoint paths and related problems. In theedge-disjoint paths problem (EDP), we are given a network G with source-sink pairs(s i ; t i ), 1 i k, and the goal is to nd a largest subset of source-sink pairs thatcan be simultaneously connected in an edge-disjoint manner. We show that in directednetworks, for any >

Venkatesan Guruswami; Sanjeev Khanna; Rajmohan Rajaraman; Bruce Shepherd; Mihalis Yannakakis

1999-01-01

133

Fusion proteins as alternate crystallization paths to difficult structure problems  

NASA Technical Reports Server (NTRS)

The three-dimensional structure of a peptide fusion product with glutathione transferase from Schistosoma japonicum (SjGST) has been solved by crystallographic methods to 2.5 A resolution. Peptides or proteins can be fused to SjGST and expressed in a plasmid for rapid synthesis in Escherichia coli. Fusion proteins created by this commercial method can be purified rapidly by chromatography on immobilized glutathione. The potential utility of using SjGST fusion proteins as alternate paths to the crystallization and structure determination of proteins is demonstrated.

Carter, Daniel C.; Rueker, Florian; Ho, Joseph X.; Lim, Kap; Keeling, Kim; Gilliland, Gary; Ji, Xinhua

1994-01-01

134

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

2014-07-22

135

Solving the broken link problem in Walden's Paths  

E-print Network

With the extent of the web expanding at an increasing rate, the problems caused by broken links are reaching epidemic proportions. Studies have indicated that a substantial number of links on the Internet are broken. User surveys indicate broken...

Dalal, Zubin Jamshed

2004-09-30

136

Constrained Graph Optimization: Interdiction and Preservation Problems  

SciTech Connect

The maximum flow, shortest path, and maximum matching problems are a set of basic graph problems that are critical in theoretical computer science and applications. Constrained graph optimization, a variation of these basic graph problems involving modification of the underlying graph, is equally important but sometimes significantly harder. In particular, one can explore these optimization problems with additional cost constraints. In the preservation case, the optimizer has a budget to preserve vertices or edges of a graph, preventing them from being deleted. The optimizer wants to find the best set of preserved edges/vertices in which the cost constraints are satisfied and the basic graph problems are optimized. For example, in shortest path preservation, the optimizer wants to find a set of edges/vertices within which the shortest path between two predetermined points is smallest. In interdiction problems, one deletes vertices or edges from the graph with a particular cost in order to impede the basic graph problems as much as possible (for example, delete edges/vertices to maximize the shortest path between two predetermined vertices). Applications of preservation problems include optimal road maintenance, power grid maintenance, and job scheduling, while interdiction problems are related to drug trafficking prevention, network stability assessment, and counterterrorism. Computational hardness results are presented, along with heuristic methods for approximating solutions to the matching interdiction problem. Also, efficient algorithms are presented for special cases of graphs, including on planar graphs. The graphs in many of the listed applications are planar, so these algorithms have important practical implications.

Schild, Aaron V [Los Alamos National Laboratory

2012-07-30

137

A new integer linear programming formulation for the scheduling problem in data path synthesis  

Microsoft Academic Search

A novel approach is presented to the operation scheduling problem in a data path synthesis. After obtaining the start time and the require time of each operation by the ASAP (as soon as possible) and ALAP (as late as possible) methods, respectively, an integer linear programming (ILP) formulation is formed to solve the scheduling problem. The objective is to fully

Jiahn-Hung Lee; Yu-Chin Hsu; Youn-long Steve Lin

1989-01-01

138

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

139

The Problems and Path Thinking of China's Rural Logistics Development  

Microsoft Academic Search

This paper introduces seasonal characteristic, scattered characteristic and diversified characteristic of rural logistics in China, developing rural logistics is significant to increasing farmers' income, promoting life quality, reducing cost of agricultural products, increasing job opportunities and quickening the process of urbanization. This paper also analyzes the Status quo and existing problems of China's rural logistics as follows. China's rural logistics,

Rui Jiao; Xiaoqiong Yu

2011-01-01

140

A Path Following Algorithm for the Graph Matching Problem  

E-print Network

, gradient methods, machine learning, classification, image processing. ? 1 INTRODUCTION THE graph matching problem is among the most important challenges of graph processing and plays a central role in various as well. A nonexhaus- tive list of graph matching applications includes document processing tasks like

Bach, Francis

141

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

142

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

143

A Path Analysis of Social Problem-Solving as a Predictor of White Racial Identity  

ERIC Educational Resources Information Center

This study examined (a) whether a developmental model or a model in which all subscales' measurement errors are correlated best explains the relationships among White racial identity (WRI) statuses, and (b) social problem-solving (SPS) skills as a predictor of WRI. Path analysis was conducted with a sample of 255 White undergraduate students from

Carr, Amanda G.; Caskie, Grace I. L.

2010-01-01

144

High-order path-integral Monte Carlo methods for solving quantum dot problems  

NASA Astrophysics Data System (ADS)

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 antisymmetric 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 five 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.

2015-03-01

145

Evolutionary path control strategy for solving many-objective optimization problem.  

PubMed

The number of objectives in many-objective optimization problems (MaOPs) is typically high and evolutionary algorithms face severe difficulties in solving such problems. In this paper, we propose a new scalable evolutionary algorithm, called evolutionary path control strategy (EPCS), for solving MaOPs. The central component of our algorithm is the use of a reference vector that helps simultaneously minimizing all the objectives of an MaOP. In doing so, EPCS employs a new fitness assignment strategy for survival selection. This strategy consists of two procedures and our algorithm applies them sequentially. It encourages a population of solutions to follow a certain path reaching toward the Pareto optimal front. The essence of our strategy is that it reduces the number of nondominated solutions to increase selection pressure in evolution. Furthermore, unlike previous work, EPCS is able to apply the classical Pareto-dominance relation with the new fitness assignment strategy. Our algorithm has been tested extensively on several scalable test problems, namely five DTLZ problems with 5 to 40 objectives and six WFG problems with 2 to 13 objectives. Furthermore, the algorithm has been tested on six CEC09 problems having 2 or 3 objectives. The experimental results show that EPCS is capable of finding better solutions compared to other existing algorithms for problems with an increasing number of objectives. PMID:25055389

Roy, Proteek Chandan; Islam, Md Monirul; Murase, Kazuyuki; Yao, Xin

2015-04-01

146

A Hierarchical Path View Model for Path Finding in Intelligent Transportation Systems  

Microsoft Academic Search

Effective path finding has been identified as an important requirement for dynamic route guidance in Intelligent Transportation Systems (ITS). Path finding is most efficient if the all-pair (shortest) paths are precomputed because path search requires only simple lookups of the precomputed path views. Such an approach however incurs path view maintenance (computation and update) and storage costs which can be

Yun-Wu Huang; Ning Jing; ELKE A. RUNDENSTEINER

1997-01-01

147

A novel approach for multiple mobile objects path planning: Parametrization method and conflict resolution strategy  

NASA Astrophysics Data System (ADS)

We present a new approach containing two steps to determine conflict-free paths for mobile objects in two and three dimensions with moving obstacles. Firstly, the shortest path of each object is set as goal function which is subject to collision-avoidance criterion, path smoothness, and velocity and acceleration constraints. This problem is formulated as calculus of variation problem (CVP). Using parametrization method, CVP is converted to time-varying nonlinear programming problems (TNLPP) and then resolved. Secondly, move sequence of object is assigned by priority scheme; conflicts are resolved by multilevel conflict resolution strategy. Approach efficiency is confirmed by numerical examples.

Ma, Yong; Wang, Hongwei; Zamirian, M.

2012-01-01

148

Robot path planning with distance-safety criterion  

NASA Technical Reports Server (NTRS)

A method for determining an optimal path with a weighted distance-safety criterion is developed. The goal is to strike a compromise between the shortest path and the centerline path, which is safer. The method is composed of three parts: (i) construction of a region map by dividing the workspace, (ii) interregion optimization to determine the entry and departure points of the path in each region, and (iii) intraregion optimization for determining the (optimal) path segment within each region. The region map is generated by using an approximate Voronoi diagram, and region optimization is achieved using variational dynamic programming. Although developed for 2-D problems, the method can be easily extended to a class of 3-D problems. Numerical examples are presented to demonstrate the method.

Suh, Suk-Hwan; Shin, Kang G.

1987-01-01

149

Solution to the variation problem for information path functional of a controlled random process  

NASA Astrophysics Data System (ADS)

The paper introduces a new approach to dynamic modeling, using the variation principle, applied to a functional on trajectories of a controlled random process, and its connection to the process' information functional. In [V.S. Lerner, Dynamic approximation of a random information functional, J. Math. Anal. Appl. 327 (1) (2007) 494-514, available online 5-24-06], we presented the information path functional with the Lagrangian, determined by the parameters of a controlled stochastic equation. In this paper, the solution to the path functional's variation problem provides both a dynamic model of a random process and the model's optimal control, which allows us to build a two-level information model with a random process at the microlevel and a dynamic process at the macrolevel. A wide class of random objects, modeled by the Markov diffusion process and a common structure of the process' information functional, leads to a universal information structure of the dynamic model, which is specified and identified on a particular object with the applied optimal control functions. The developed mathematical formalism, based on classical methods, is aimed toward the solution of problems identification, combined with an optimal control synthesis, which is practically implemented and also demonstrated in the paper's example.

Lerner, Vladimir S.

2007-10-01

150

Path planning strategies for autonomous ground vehicles  

NASA Astrophysics Data System (ADS)

Several key issues involved with the planning and executing of optimally generated paths for autonomous vehicles are addressed. Two new path planning algorithms are developed, and examined, which effectively minimize replanning as unmapped hazards are encountered. The individual algorithms are compared via extensive simulation. The search strategy results are implemented and tested using the University of Colorado's autonomous vehicle test-bed, RoboCar, and results show the advantages of solving the single-destination all-paths problem for autonomous vehicle path planning. Both path planners implement a graph search methodology incorporating dynamic programming that solves the single-destination shortest-paths problem. Algorithm 1, termed DP for dynamic programming, searches a state space where each state represents a potential vehicle location in a breadth-first fashion expanding from the goal to all potential start locations in the state space. Algorithm 2, termed DP*, couples the heuristic search power of the well-known A* search procedure (Nilsson-80) with the dynamic programming principle applied to graph searching to efficiently make use of overlapping subproblems. DP* is the primary research contribution of the work contained within this thesis. The advantage of solving the single-destination shortest-paths problem is that the entire terrain map is solved in terms of reaching a specified goal. Therefore, if the robot is diverted from the pre-planned path, an alternative path is already computed. The search algorithms are extended to include a probabilistic approach using empirical loss functions to incorporate terrain map uncertainties into the path considering terrain planning process. The results show the importance of considering terrain uncertainty. If the map representation ignores uncertainty by marking any area with less than perfect confidence as unpassable or assigns it the worst case rating, then the paths are longer than intuitively necessary. A hierarchical software control architecture is introduced that uses as the main guidance function an arbitration-based scheme which is able to efficiently and robustly integrate disparate sensor data. The flexibility provided by such an architecture allows for very easy integration of any type of environmental sensing device into the path planning algorithm.

Gifford, Kevin Kent

151

Finding the dominant energy transmission paths in statistical energy analysis  

NASA Astrophysics Data System (ADS)

A key issue for noise, vibration and harshness purposes, when modelling the vibroacoustic behaviour of a system, is that of determining how energy is transmitted from a given source, where external energy is being input, to a target where energy is to be reduced. In many situations of practical interest, a high percentage of the transmitted energy is driven by a limited set of dominant paths. For instance, this is at the core of the existence of transmission loss regulations between dwellings. In this work, it is shown that in the case of a system modelled with statistical energy analysis (SEA), the problem of ranking dominant paths can be posed as a variation of the so-called K shortest path problem in graph theory. An algorithm for the latter is then modified and adapted to obtain the sorted set of K dominant energy transmission paths in a SEA model. A numerical example to show its potential for practical applications is included.

Guasch, Oriol; Aragons, ngels

2011-05-01

152

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

153

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

154

Hammock-on-Ears Decomposition: A Technique for the E cient Parallel Solution of Shortest  

E-print Network

Hammock-on-Ears Decomposition: A Technique for the E cient Parallel Solution of Shortest Paths, ~, of outerplanar subgraphs (called hammocks) satisfying certain separator properties. Our work combines and extends the sequential hammock decomposition technique intro- duced by G. Frederickson and the parallel ear decomposition

155

Hammock-on-Ears Decomposition: A Technique for the Efficient Parallel Solution of Shortest  

E-print Network

Hammock-on-Ears Decomposition: A Technique for the Efficient Parallel Solution of Shortest Paths (called hammocks) satis- fying certain separator properties. We achieve this decomposition in O(log n log algo- rithm for decomposing any (di)graph into a set of outerplanar subgraphs (called hammocks

Zaroliagis, Christos D.

156

Shortest-Cycle Photonic Network Restoration K J Warbrick, X Lu, R Friskney and K Durrani  

E-print Network

Shortest-Cycle Photonic Network Restoration K J Warbrick, X Lu, R Friskney and K Durrani Nortel is currently based upon point-to-point optical connections organised into physical rings. This architecture has and protection paths and nodes configured in the ring. This is the basis of protection in SONET/SDH ring networks

Haddadi, Hamed

157

The value of information in shortest path optimization/  

E-print Network

Information about a random event (termed the source) is typically treated as a (possibly noisy) function of that event. Information has a destination, an agent, that uses the information to make a decision. In traditional ...

Rinehart, Michael David

2010-01-01

158

Scientific collaboration networks. II. Shortest paths, weighted networks, and centrality  

Microsoft Academic Search

Using computer databases of scientific papers in physics, biomedical research, and computer science, we have constructed networks of collaboration between scientists in each of these disciplines. In these networks two scientists are considered connected if they have coauthored one or more papers together. Here we study a variety of nonlocal statistics for these networks, such as typical distances between scientists

M. E. J. Newman

2001-01-01

159

Solution Methods for the Multi-trip Elementary Shortest Path ...  

E-print Network

Constraints (3) require that the vehicle should enter and leave a customer ..... Instead of searching a node in an ordered list of nodes from 1 to |I|+2, we choose the ..... Algorithm 2P-CS with U = 12 outperforms the other variants in terms of the.

2011-03-15

160

Geometric Containers for Efficient Shortest-Path Computation  

E-print Network

Theory]: Graph algorithms, Network prob- lems; G.2.3 [Applications]: Traffic information systems; F.2 efficiently best routes or optimal itineraries in traffic infor- mation systems is to reduce the search space structures, created during a preprocess- ing phase, of size linear (i.e., optimal) to the size of the graph

Zaroliagis, Christos D.

161

Scaling inequalities for shortest paths in regular and invasion percolation.  

E-print Network

not hold in d = 2, [Kesten, 1987].) Using a partly di#erent approach we prove a similar theorem in two systems, [Kesten & Zhang, 1993] and [Aizenman & Burchard, 1999]. In the second part of the paper we

162

Shortest Path Computation with No Information Leakage Kyriakos Mouratidis  

E-print Network

reveal personal information, such as social habits, health condition, shop- ping preferences, lifestyle systems and the diffusion of smart-phones has led to an expanding market of location-based services (LBSs, lifestyle choices, etc) which may be tracked and misused by the LBS. Pos- sible forms of misuse include

Yiu, Man Lung

163

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 paththe 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

164

Minimum Cost Path Problem for Plug-in Hybrid Electric Vehicles  

E-print Network

data and artificially generated road networks of various sizes and provide signifi- cant insights about the ... cost path, vehicle routing, energy management, integer programming, dynamic programming. 1 ...... Artificial Intelligence. Springer, pp.

2014-07-22

165

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

E-print Network

heterogeneous vehicles. As the addressed routing problem is NP-Hard, we develop an approximation algorithm and heuristics to solve the problem. Our approach involves dividing the routing problem into two sub-problems: Partitioning and Sequencing. Partitioning...

Doshi, Riddhi Rajeev

2011-10-21

166

An affine scaling interior trust region method via optimal path for solving monotone variational inequality problem with linear constraints  

Microsoft Academic Search

Based on a differentiable merit function proposed by Taji et al. in Math. Prog. Stud., 58, 1993, 369383, the authors propose an affine scaling interior trust region strategy via optimal path to modify Newton method\\u000a for the strictly monotone variational inequality problem subject to linear equality and inequality constraints. By using the\\u000a eigensystem decomposition and affine scaling mapping, the authors

Yunjuan Wang; Detong Zhu

2008-01-01

167

Finding Smallest Paths in Rectilinear Polygons on a Hypercube Multiprocessor  

E-print Network

Finding Smallest Paths in Rectilinear Polygons on a Hypercube Multiprocessor Afonso Ferreira techniques for designing geometric algorithms for the (shared­memory) PRAM model of parallel computation (e that is simultaneously a shortest path with respect to the L 1 metric, and a straightest path (i.e., minimum link path

Zhang, Richard "Hao"

168

Linear approximation of shortest superstrings  

Microsoft Academic Search

We consider the following problem: given a collection of strings s 1 ; . . . ; s m , find the shorteststring s such that each s i appears as a substring (a consecutive block) of s. Although thisproblem is known to be NP-hard, a simple greedy procedure appears to do quite well and isroutinely used in DNA sequencing

Avrim Blum; Tao Jiangt; Ming Li; John Tromp; Mihalis Yannakakis

1991-01-01

169

Designing a dynamic path guidance system based on electronic maps by using Q-learning  

NASA Astrophysics Data System (ADS)

Shortest path problem from one origin node to one destination node in non-FIFO (First In First Out) dynamic networks is an unsolved hard problem in dynamic path guidance system. A new approach based on Q-learning is adopted to solve the problem based on electronic maps in this paper. The approach uses geographical information on electronic maps to define Q-learning's value function. Q-learning algorithm's strategy train learning method and training process on path searching are presented. Finally based on Guangzhou City's electronic map, we randomly generate a dynamic network containing 20000 nodes, 40000 links and 144 time intervals, which do not satisfy FIFO to test the approach proposed in this paper. The approach is implemented with this dynamic network and its computational performance is analyzed experimentally. The experimental results prove the effectiveness of the approach.

Zou, Liang; Xu, Jianmin; Zhu, Lingxiang

2005-11-01

170

A Linear Algorithm for the Pos\\/Neg-Weighted 1Median Problem on a Cactus  

Microsoft Academic Search

The 1-median problem on a network asks for a vertex minimizing the sum of the weighted shortest path distances from itself\\u000a to all other vertices, each associated with a certain positive weight. We allow fornegative weights as well and devise an exact algorithm for the resulting pos\\/neg-weighted problem defined on a cactus. The algorithm\\u000a visits every vertex just once and

Rainer E. Burkard; Jakob Krarup

1998-01-01

171

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

172

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

173

Optimal parallel algorithms for problems modeled by a family of intervals  

NASA Technical Reports Server (NTRS)

A family of intervals on the real line provides a natural model for a vast number of scheduling and VLSI problems. Recently, a number of parallel algorithms to solve a variety of practical problems on such a family of intervals have been proposed in the literature. Computational tools are developed, and it is shown how they can be used for the purpose of devising cost-optimal parallel algorithms for a number of interval-related problems including finding a largest subset of pairwise nonoverlapping intervals, a minimum dominating subset of intervals, along with algorithms to compute the shortest path between a pair of intervals and, based on the shortest path, a parallel algorithm to find the center of the family of intervals. More precisely, with an arbitrary family of n intervals as input, all algorithms run in O(log n) time using O(n) processors in the EREW-PRAM model of computation.

Olariu, Stephan; Schwing, James L.; Zhang, Jingyuan

1992-01-01

174

Path Model of the Processes Influencing Drinking-Related Problems among College Students.  

ERIC Educational Resources Information Center

This study tested a causal model of the prediction of the rate of occurrence of social and academic problems that results from college students' drinking. The model posited two pathways, one examining self-worth perceptions and symptoms of depression as mediators and one examining binge-drinking frequency as a mediator. Predictors included:

Fenzel, L. Mickey; Patel, Shreya

175

Constraint-based local search for solving non-simple paths problems on graphs  

E-print Network

in the context of res- cue after a natural disaster in which we have to route a fleet of identical vehicles with limited capacity on a trans- portation network in order to collect the informations of the disaster. Given is to minimize the number of vehicles used. This paper discusses the challenge around this problem and applies

Deville, Yves

176

Status Problem and Expectations of Competence: A Challenging Path for Teachers  

ERIC Educational Resources Information Center

Complex Instruction (CI) is a cooperative learning approach, which aims at improving the equal status interaction among students working in groups who may be at different academic and social levels. Based on an ethnographic research, the article examines how a group of Italian primary school teachers understand the status problem and how the

Pescarmona, Isabella

2015-01-01

177

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

178

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

E-print Network

Simon Cox Show me the (shortest) way to go home Foams, soap films and minimization #12;The force two possible (non-trivial) soap film combinations that touch all edges: Wire Frames foams not be straight. Wire Frames foams@aber.ac.uk #12;Soap films solve the Steiner problem: Given n cities on a plain

Cox, Simon

179

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

180

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

181

Fast marching methods for the continuous traveling salesman problem  

SciTech Connect

We consider a problem in which we are given a domain, a cost function which depends on position at each point in the domain, and a subset of points ('cities') in the domain. The goal is to determine the cheapest closed path that visits each city in the domain once. This can be thought of as a version of the Traveling Salesman Problem, in which an underlying known metric determines the cost of moving through each point of the domain, but in which the actual shortest path between cities is unknown at the outset. We describe algorithms for both a heuristic and an optimal solution to this problem. The order of the heuristic algorithm is at worst case M * N logN, where M is the number of cities, and N the size of the computational mesh used to approximate the solutions to the shortest paths problems. The average runtime of the heuristic algorithm is linear in the number of cities and O(N log N) in the size N of the mesh.

Andrews, J.; Sethian, J.A.

2008-12-01

182

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

183

Parallel message-passing architecture for path planning  

NASA Astrophysics Data System (ADS)

A prototype solving the Shortest Path Problem (SPP) by a parallel message-passing algorithm is presented. The system, an OCCAM program running on a transputer board hosted by a PC, implements a known distributed algorithm for the SPP, based on the 'diffused computation' paradigm. A new parallel message-passing architecture is proposed, built upon a static packet-switching network with a fractal topology. The recursive, unlimited network, features an interesting property when applied to four-link processors (like transputers): it's decomposable, at any hierarchical level, in four-link modules or supernodes. Labelling and routing algorithms for the network, exploiting self-similarity, are described. Experimental results, obtained with a single transputer solving irregular random graphs (up to 256 nodes) are presented, showing a time complexity function growing linearly with the total number of arcs.

Tavora, Jose; Lourtie, Pedro M. G.

1991-03-01

184

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

185

Path integral approach to the problem of rotational excitation of molecules by an ultrashort laser pulses sequence  

E-print Network

The amplitude and probability of quantum transitions are represented as a path integrals in energy state space of the investigated multi-level quantum system. Using this approach we consider rotational dynamics of nitrogen molecules $^{14}N_{2}$ and $^{15}N_{2}$ which interact with a sequence of ultrashort laser pulses. Our computer simulations indicate the complex dependency of the high rotation states excitation probability upon ultrashort laser pulses sequence periods. We observe pronounced resonances, which correspond to the results of some experiments.

Alexander Biryukov; Mark Shleenkov

2014-07-15

186

Computing the Length of the Shortest Telomere in the Nucleus  

NASA Astrophysics Data System (ADS)

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.

Dao Duc, K.; Holcman, D.

2013-11-01

187

A path following algorithm for the graph matching problem Mikhail Zaslavskiy, Francis Bach, and Jean-Philippe Vert  

E-print Network

, gradient methods, machine learning, classification, image processing 1 Introduction The graph matching problem is among the most important challenges of graph processing, and plays a central role in various as well. A non-exhaustive list of graph matching applications includes document processing tasks like

Paris-Sud XI, Université de

188

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

189

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

190

A new approach to the maximum flow problem  

Microsoft Academic Search

All previously known efftcient maximum-flow algorithms work by finding augmenting paths, either one path at a time (as in the original Ford and Fulkerson algorithm) or all shortest-length augmenting paths at once (using the layered network approach of Dinic). An alternative method based on the preflow concept of Karzanov is introduced. A preflow is like a flow, except that the

Andrew V. Goldberg; Robert Endre Tarjan

1986-01-01

191

Adaptive Path Following Primal Dual Interior Point Methods for Shape Optimization of Linear and Nonlinear Stokes Flow Problems  

Microsoft Academic Search

Summary. We are concerned with structural optimization problems in CFD where the state variables are supposed to satisfy a linear or nonlinear Stokes system and the design variables are subject to bilateral pointwise constraints. Within a primal- dual setting, we suggest an all-at-once approach based on interior-point methods. The discretization is taken care of by Taylor-Hood elements with respect to

Ronald H. W. Hoppe; Christopher Linsenmann; Harbir Antil

2007-01-01

192

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

193

Frugality in path auctions  

Microsoft Academic Search

We consider the problem of picking (buying) an inexpensive s -- t path in a graph where edges are owned by independent (selfish) agents, and the cost of an edge is known to its owner only. We study the problem of finding frugal mechanisms for this task, i.e. we investigate the payments the buyer must make in order to buy

Edith Elkind; Amit Sahai; Kenneth Steiglitz

2004-01-01

194

Effective Path Selection for Delay Fault Testing of Sequential Circuits  

Microsoft Academic Search

This paper outlines several problems related to the delay fault testing of sequential circuits. For timing test of a circuit and for layout optimization, critical path data are needed. When critical paths are identified by a static timing analyzer many of the selected paths cannot be activated functionally. Such paths are sequential false paths. However, many of these paths can

Tapan J. Chakraborty; Vishwani D. Agrawal

1997-01-01

195

A Dynamic Programming Approach to Identifying the Shortest Path in Virtual Learning Environments  

ERIC Educational Resources Information Center

E-learning has been widely adopted as a promising solution by many organizations to offer learning-on-demand opportunities to individual employees (learners) in order to reduce training time and cost. While successful information systems models have received much attention among researchers, little research has been conducted to assess the success

Fazlollahtabar, Hamed

2008-01-01

196

Transitive functional annotation by shortest-path analysis of gene expression data  

E-print Network

be used as an important attribute to link genes of the same biological pathway. Based on large-scale yeast to completely capture the relationship between two expression profiles for such reasons as time-shift (5

Zhou, Xianghong Jasmine

197

Numer. Math. 44, 111-126 (1984) Applications of Shortest Path Algorithms  

E-print Network

several points of view. At one extreme some papers concentrate on theoretical characterizations, e.g. [12J of us in [10, 11J and is there applied in the consideration of asymmetric scalings: A' = XA Y. In [11J a corresponding result on asym- metric scalings, see [19, Sect. 3]. The asymmetric formulation of some of our

Schneider, Hans

198

Parsimonious path openings and closings.  

PubMed

Path openings and closings are morphological tools used to preserve long, thin, and tortuous structures in gray level images. They explore all paths from a defined class, and filter them with a length criterion. However, most paths are redundant, making the process generally slow. Parsimonious path openings and closings are introduced in this paper to solve this problem. These operators only consider a subset of the paths considered by classical path openings, thus achieving a substantial speed-up, while obtaining similar results. In addition, a recently introduced 1D opening algorithm is applied along each selected path. Its complexity is linear with respect to the number of pixels, independent of the size of the opening. Furthermore, it is fast for any input data accuracy (integer or floating point) and works in stream. Parsimonious path openings are also extended to incomplete paths, i.e., paths containing gaps. Noise-corrupted paths can thus be processed with the same approach and complexity. These parsimonious operators achieve a several orders of magnitude speed-up. Examples are shown for incomplete path openings, where computing times are brought from minutes to tens of milliseconds, while obtaining similar results. PMID:24569442

Morard, Vincent; Dokladal, Petr; Decenciere, Etienne

2014-04-01

199

Primal-dual approximation algorithms for the survivable network design problem  

SciTech Connect

We consider the survivable network design problem (SNDP), the problem of designing a minimum cost network satisfying connectivity requirements between pairs of vertices. We describe a heuristic algorithm with a provable worst-case performance guarantee for this problem, as well as for a host of related problems. The algorithm is primal-dual and generalizes exact algorithms for the shortest path and minimum spanning tree problems. The most recent version of the algorithm, due to M. Goemans, A. Goldberg, S. Plotkin, D. Shmoys, {acute E}. Tardos and D. Williamson, has the best known performance guarantee both in general and for most special cases. The talk will be a survey of a stream of results of the authors and a number of colleagues, including the above-mentioned researchers and H. Gabow, M. Mihail and V. Vazirani. The emphasis of the talk will be on the methodology behind this approximation algorithm.

Goemans, M.; Williamson, D.

1994-12-31

200

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

201

Complexity analysis of pipeline mapping problems in distributed heterogeneous networks  

SciTech Connect

Largescale scientific applications require using various system resources to execute complex computing pipelines in distributed networks to support collaborative research. System resources are typically shared in the Internet or over dedicated connections based on their location, availability, capability, and capacity. Optimizing the network performance of computing pipelines in such distributed environments is critical to the success of these applications. We consider two types of largescale distributed applications: (1) interactive applications where a single dataset is sequentially processed along a pipeline; and (2) streaming applications where a series of datasets continuously flow through a pipeline. The computing pipelines of these applications consist of a number of modules executed in a linear order in network environments with heterogeneous resources under different constraints. Our goal is to find an efficient mapping scheme that allocates the modules of a pipeline to network nodes for minimum endtoend delay or maximum frame rate. We formulate the pipeline mappings in distributed environments as optimization problems and categorize them into six classes with different optimization goals and mapping constraints: (1) Minimum Endtoend Delay with No Node Reuse (MEDNNR), (2) Minimum Endtoend Delay with Contiguous Node Reuse (MEDCNR), (3) Minimum Endtoend Delay with Arbitrary Node Reuse (MEDANR), (4) Maximum Frame Rate with No Node Reuse or Share (MFRNNRS), (5) Maximum Frame Rate with Contiguous Node Reuse and Share (MFRCNRS), and (6) Maximum Frame Rate with Arbitrary Node Reuse and Share (MFRANRS). Here, 'contiguous node reuse' means that multiple contiguous modules along the pipeline may run on the same node and 'arbitrary node reuse' imposes no restriction on node reuse. Note that in interactive applications, a node can be reused but its resource is not shared. We prove that MEDANR is polynomially solvable and the rest are NP-complete. MEDANR, where either contiguous or noncontiguous modules in the pipeline can be mapped onto the same node, is essentially the Maximum n-hop Shortest Path problem, and can be solved using a dynamic programming method. In MEDNNR and MFRNNRS, any network node can be used only once, which requires selecting the same number of nodes for onetoone onto mapping. We show its NP-completeness by reducing from the Hamiltonian Path problem. Node reuse is allowed in MEDCNR, MFRCNRS and MFRANRS, which are similar to the Maximum n-hop Shortest Path problem that considers resource sharing. We prove their NP-completeness by reducing from the Disjoint-Connecting-Path Problem and Widest path with the Linear Capacity Constraints problem, respectively.

Lin, Ying [University of Tennessee, Knoxville (UTK); Wu, Qishi [ORNL; Zhu, Mengxia [ORNL; Rao, Nageswara S [ORNL

2009-04-01

202

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

203

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

204

Survivable paths in multilayer networks  

E-print Network

We consider the problem of protection in multilayer networks. In single-layer net- works, a pair of disjoint paths can be used to provide protection for a source-destination pair. However, this approach cannot be directly ...

Parandehgheibi, Marzieh

2012-01-01

205

Counting paths in digraphs  

SciTech Connect

Say a digraph is k-free if it has no directed cycles of length at most k, for k {element_of} Z{sup +}. Thomasse conjectured that the number of induced 3-vertex directed paths in a simple 2-free digraph on n vertices is at most (n-1)n(n+1)/15. We present an unpublished result of Bondy proving there are at most 2n{sup 3}/25 such paths, and prove that for the class of circular interval digraphs, an upper bound of n{sup 3}/16 holds. We also study the problem of bounding the number of (non-induced) 4-vertex paths in 3-free digraphs. We show an upper bound of 4n{sup 4}/75 using Bondy's result for Thomasse's conjecture.

Sullivan, Blair D [ORNL; Seymour, Dr. Paul Douglas [Princeton University

2010-01-01

206

An Optimal Level of Adding Edges for a Simple Path to a Complete K-ary Tree  

NASA Astrophysics Data System (ADS)

This study proposes a model of adding edges of forming a simple path to a level of depth N in a complete K-ary (K?3) tree of height H under giving priority to edges between two nodes of which the deepest common ancestor is deeper. An optimal depth N* is obtained by maximizing the total shortening path length which is the sum of shortening lengths of shortest paths between every pair of all nodes in the complete K-ary tree.

Sawada, Kiyoshi

2010-10-01

207

The shortest period detached binary white dwarf system  

NASA Astrophysics Data System (ADS)

We identify SDSS J010657.39-100003.3 (hereafter J0106-1000) as the shortest period detached binary white dwarf (WD) system currently known. We targeted J0106-1000 as part of our radial velocity programme to search for companions around known extremely low-mass (ELM; 0.2 M?) WDs using the 6.5-m Multiple Mirror Telescope. We detect peak-to-peak radial velocity variations of 740 km s-1 with an orbital period of 39.1 min. The mass function and optical photometry rule out a main-sequence star companion. Follow-up high-speed photometric observations obtained at the McDonald 2.1-m telescope reveal ellipsoidal variations from the distorted primary but no eclipses. This is the first example of a tidally distorted WD. Modelling the light curve, we constrain the inclination angle of the system to be 67 13. J0106-1000 contains a pair of WDs (0.17 M? primary + 0.43 M? invisible secondary) at a separation of 0.32 R?. The two WDs will merge in 37 Myr and most likely form a core He-burning single subdwarf star. J0106-1000 is the shortest time-scale merger system currently known. The gravitational wave strain from J0106-1000 is at the detection limit of the Laser Interferometer Space Antenna (LISA). However, accurate ephemeris and orbital period measurements may enable LISA to detect J0106-1000 above the Galactic background noise. Based on observations obtained at the Multiple Mirror Telescope (MMT) Observatory, a joint facility of the Smithsonian Institution and the University of Arizona.

Kilic, Mukremin; Brown, Warren R.; Kenyon, S. J.; Allende Prieto, Carlos; Andrews, J.; Kleinman, S. J.; Winget, K. I.; Winget, D. E.; Hermes, J. J.

2011-05-01

208

TIME-OPTIMAL PATHS FOR LATERAL NAVIGATION OF AN AUTONOMOUS UNDERACTUATED AIRSHIP  

Microsoft Academic Search

This paper deals with a characterization of the shortest paths for lateral navigation of an autonomous underactuated airship taking into account its dynamics and actuator limitations. The initial and terminal positions are given. We would like to specify the control forces that steer the unmanned aerial vehicle to the given terminal position requiring the minimal time for lateral navigation. The

Salim Hima; Yasmina Bestaoui

209

UAV Intelligent Path Planning for Wilderness Search and Rescue Computer Science Department  

E-print Network

has a 100% target detection rate. This means that as the UAV camera footprint moves alongUAV Intelligent Path Planning for Wilderness Search and Rescue Lanny Lin Computer Science in order to find the missing person in the shortest expected time. When using a UAV to support search

Goodrich, Michael A.

210

ORIGINAL ARTICLE Multi-objective optimal path selection in electric vehicles  

E-print Network

include recharging time in their cri- teria for shortest paths in addition to traveling time and distance. The two main obstacles that hamper the popularity of EVs are their traveling limits and recharging time. The traveling limit of an EV is the maximum time that it can travel without recharging. Rechargeable batteries

Sait, Sadiq M.

211

Vanquishing the XCB Question: The Methodological Discovery of the Last Shortest Single Axiom for the  

E-print Network

Vanquishing the XCB Question: The Methodological Discovery of the Last Shortest Single Axiom(z y)) z)) a single axiom for the classical equivalential calculus when the rules of inference consist on the other two axioms.) Heretofore, thirteen shortest single axioms for classical equivalence of length

Fitelson, Branden

212

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

213

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.

Cynthia Ann Radle (McCullough High School REV)

1995-06-30

214

Flight Path Optimization subject to Instationary Heat Constraints  

E-print Network

Flight Path Optimization subject to Instationary Heat Constraints Matthias Witzgall Kurt Chudej consider a flight path optimization problem in the hypersonic flight regime. The aerothermic heating in hypersonic flight regimes. Mathematically this leads to a trajectory optimization problem s

Dettweiler, Michael

215

Minimum-Risk Path Finding by an Adaptive Amoebal Network  

NASA Astrophysics Data System (ADS)

When two food sources are presented to the slime mold Physarum in the dark, a thick tube for absorbing nutrients is formed that connects the food sources through the shortest route. When the light-avoiding organism is partially illuminated, however, the tube connecting the food sources follows a different route. Defining risk as the experimentally measurable rate of light-avoiding movement, the minimum-risk path is exhibited by the organism, determined by integrating along the path. A model for an adaptive-tube network is presented that is in good agreement with the experimental observations.

Nakagaki, Toshiyuki; Iima, Makoto; Ueda, Tetsuo; Nishiura, Yasumasa; Saigusa, Tetsu; Tero, Atsushi; Kobayashi, Ryo; Showalter, Kenneth

2007-08-01

216

Packing paths in digraphs  

E-print Network

f ~P1g, or f ~P1; ~P2g, the G-packing problem is NP-complete. When G = f ~P1g, the G-packing problem is simply the matching problem. We treat in detail the one remaining case, G = f ~P1; ~P2g. We give in this case a polynomial algorithm for the packing problem. We also give the following positive results: a Berge type augmenting configuration theorem, a min-max characterization, and a reduction to bipartite matching. These results apply also to packings by the family G consisting of all directed paths and cycles. We also explore weighted variants of the problem and include a polyhedral analysis.

Richard C. Brewster; Pavol Hell; Sarah H. Pantel; Romeo Rizzi; Anders Yeo

217

Solving a four-destination traveling salesman problem using Escherichia coli cells as biocomputers.  

PubMed

The Traveling Salesman Problem involves finding the shortest possible route visiting all destinations on a map only once before returning to the point of origin. The present study demonstrates a strategy for solving Traveling Salesman Problems using modified E. coli cells as processors for massively parallel computing. Sequential, combinatorial DNA assembly was used to generate routes, in the form of plasmids made up of marker genes, each representing a path between destinations, and short connecting linkers, each representing a given destination. Upon growth of the population of modified E. coli, phenotypic selection was used to eliminate invalid routes, and statistical analysis was performed to successfully identify the optimal solution. The strategy was successfully employed to solve a four-destination test problem. PMID:25524102

Esau, Michael; Rozema, Mark; Zhang, Tuo Huang; Zeng, Dawson; Chiu, Stephanie; Kwan, Rachel; Moorhouse, Cadence; Murray, Cameron; Tseng, Nien-Tsu; Ridgway, Doug; Sauvageau, Dominic; Ellison, Michael

2014-12-19

218

Path planning control  

NASA Technical Reports Server (NTRS)

Viewgraphs on path planning control are presented. Topics covered include: model based path planning; sensor based path planning; hybrid path planning; proximity sensor array; and applications for fuzzy logic.

Mcroberts, Malcolm

1990-01-01

219

Trajectory Generation and Path Planning for Autonomous Aerobots  

NASA Technical Reports Server (NTRS)

This paper presents global path planning algorithms for the Titan aerobot based on user defined waypoints in 2D and 3D space. The algorithms were implemented using information obtained through a planner user interface. The trajectory planning algorithms were designed to accurately represent the aerobot's characteristics, such as minimum turning radius. Additionally, trajectory planning techniques were implemented to allow for surveying of a planar area based solely on camera fields of view, airship altitude, and the location of the planar area's perimeter. The developed paths allow for planar navigation and three-dimensional path planning. These calculated trajectories are optimized to produce the shortest possible path while still remaining within realistic bounds of airship dynamics.

Sharma, Shivanjli; Kulczycki, Eric A.; Elfes, Alberto

2007-01-01

220

Calculating Least Risk Paths in 3d Indoor Space  

NASA Astrophysics Data System (ADS)

Over the last couple of years, research on indoor environments has gained a fresh impetus; more specifically applications that support navigation and wayfinding have become one of the booming industries. Indoor navigation research currently covers the technological aspect of indoor positioning and the modelling of indoor space. The algorithmic development to support navigation has so far been left mostly untouched, as most applications mainly rely on adapting Dijkstra's shortest path algorithm to an indoor network. However, alternative algorithms for outdoor navigation have been proposed adding a more cognitive notion to the calculated paths and as such adhering to the natural wayfinding behaviour (e.g. simplest paths, least risk paths). These algorithms are currently restricted to outdoor applications. The need for indoor cognitive algorithms is highlighted by a more challenged navigation and orientation due to the specific indoor structure (e.g. fragmentation, less visibility, confined areas). As such, the clarity and easiness of route instructions is of paramount importance when distributing indoor routes. A shortest or fastest path indoors not necessarily aligns with the cognitive mapping of the building. Therefore, the aim of this research is to extend those richer cognitive algorithms to three-dimensional indoor environments. More specifically for this paper, we will focus on the application of the least risk path algorithm of Grum (2005) to an indoor space. The algorithm as proposed by Grum (2005) is duplicated and tested in a complex multi-storey building. The results of several least risk path calculations are compared to the shortest paths in indoor environments in terms of total length, improvement in route description complexity and number of turns. Several scenarios are tested in this comparison: paths covering a single floor, paths crossing several building wings and/or floors. Adjustments to the algorithm are proposed to be more aligned to the specific structure of indoor environments (e.g. no turn restrictions, restricted usage of rooms, vertical movement) and common wayfinding strategies indoors. In a later stage, other cognitive algorithms will be implemented and tested in both an indoor and combined indoor-outdoor setting, in an effort to improve the overall user experience during navigation in indoor environments.

Vanclooster, A.; De Maeyer, Ph.; Fack, V.; Van de Weghe, N.

2013-08-01

221

Optimization of transport protocols with path-length constraints in complex networks.  

PubMed

We propose a protocol optimization technique that is applicable to both weighted and unweighted graphs. Our aim is to explore by how much a small variation around the shortest-path or optimal-path protocols can enhance protocol performance. Such an optimization strategy can be necessary because even though some protocols can achieve very high traffic tolerance levels, this is commonly done by enlarging the path lengths, which may jeopardize scalability. We use ideas borrowed from extremal optimization to guide our algorithm, which proves to be an effective technique. Our method exploits the degeneracy of the paths or their close-weight alternatives, which significantly improves the scalability of the protocols in comparison to shortest-path or optimal-path protocols, keeping at the same time almost intact the length or weight of the paths. This characteristic ensures that the optimized routing protocols are composed of paths that are quick to traverse, avoiding negative effects in data communication due to path-length increases that can become specially relevant when information losses are present. PMID:21230151

Ramasco, Jos J; de La Lama, Marta S; Lpez, Eduardo; Boettcher, Stefan

2010-09-01

222

Finding Regular Simple Paths in Graph Databases  

Microsoft Academic Search

We consider the following problem: given a labelled directed graph and a regular expression , find all pairs of nodes connected by a simple path such that theconcatenation of the labels along the path satisfies . The problem is motivated by the observation that many recursive queries in relational databases can be expressed in this form, and by the implementation

Alberto O. Mendelzon; Peter T. Wood

1989-01-01

223

The shortest modulation period Blazhko RR Lyrae star: SS Cnc  

E-print Network

Extended BV(RI)c CCD observations of SS Cnc, a short period RRab star are presented. Nearly 1400 data points in each band have been obtained spanning over 79 days during the spring of 2005. The star exhibits light curve modulation, the so called Blazhko effect with small amplitude (B maximum brightness varies 0.1 mag) and with the shortest modulation period (5.309 d) ever observed. In the Fourier spectrum of the V light curve the pulsation frequency components are detected up to the 24th harmonic order, and modulation side lobe frequencies with significantly asymmetric amplitudes are seen up to the 15th and 9th orders for the lower and higher frequency components, respectively. Detailed comparison of the modulation behavior of SS Cnc and RR Gem, the two recently discovered small amplitude, short modulation period Blazhko stars is presented. The modulation frequency (f_m) appears in the Fourier spectrum of both stars with similar amplitude. We also demonstrate that the modulation frequencies have basically different properties as the pulsation and modulation side lobe frequencies have, indicating that the physics behind these frequency components are not the same. The discovery of small amplitude modulations of RRab stars cautions that the large photometric surveys (MACHO, OGLE) may seriously underestimate the number of modulated RR Lyrae stars.

J. Jurcsik; B. Szeidl; . Sdor; I. Dkny; Zs. Hurta; K. Posztobnyi; K. Vida; M. Vradi; A. Szing

2006-03-20

224

Identification of biochemical network modules based on shortest retroactive distances.  

PubMed

Modularity analysis offers a route to better understand the organization of cellular biochemical networks as well as to derive practically useful, simplified models of these complex systems. While there is general agreement regarding the qualitative properties of a biochemical module, there is no clear consensus on the quantitative criteria that may be used to systematically derive these modules. In this work, we investigate cyclical interactions as the defining characteristic of a biochemical module. We utilize a round trip distance metric, termed Shortest Retroactive Distance (ShReD), to characterize the retroactive connectivity between any two reactions in a biochemical network and to group together network components that mutually influence each other. We evaluate the metric on two types of networks that feature feedback interactions: (i) epidermal growth factor receptor (EGFR) signaling and (ii) liver metabolism supporting drug transformation. For both networks, the ShReD partitions found hierarchically arranged modules that confirm biological intuition. In addition, the partitions also revealed modules that are less intuitive. In particular, ShReD-based partition of the metabolic network identified a 'redox' module that couples reactions of glucose, pyruvate, lipid and drug metabolism through shared production and consumption of NADPH. Our results suggest that retroactive interactions arising from feedback loops and metabolic cycles significantly contribute to the modularity of biochemical networks. For metabolic networks, cofactors play an important role as allosteric effectors that mediate the retroactive interactions. PMID:22102800

Sridharan, Gautham Vivek; Hassoun, Soha; Lee, Kyongbum

2011-11-01

225

Time optimal paths for high speed maneuvering  

SciTech Connect

Recent theoretical results have completely solved the problem of determining the minimum length path for a vehicle with a minimum turning radius moving from an initial configuration to a final configuration. Time optimal paths for a constant speed vehicle are a subset of the minimum length paths. This paper uses the Pontryagin maximum principle to find time optimal paths for a constant speed vehicle. The time optimal paths consist of sequences of axes of circles and straight lines. The maximum principle introduces concepts (dual variables, bang-bang solutions, singular solutions, and transversality conditions) that provide important insight into the nature of the time optimal paths. We explore the properties of the optimal paths and present some experimental results for a mobile robot following an optimal path.

Reister, D.B.; Lenhart, S.M.

1993-01-01

226

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

227

INVERSES OF MOTZKIN AND SCHRDER PATHS Heinrich Niederhausen  

E-print Network

the paths inside a horizontal band, and for the inverse Schrder matrix we look at the paths inside the same band, but ending on the top side of the band. 1. Introduction A Motzkin paths takes steps or Motzkin paths are at the heart of your problem, and will help to solve it. Here we show that the paradigm

Niederhausen, Heinrich

228

Analyzing the applicability of the least risk path algorithm in indoor space  

NASA Astrophysics Data System (ADS)

Over the last couple of years, applications that support navigation and wayfinding in indoor environments have become one of the booming industries. However, the algorithmic support for indoor navigation has so far been left mostly untouched, as most applications mainly rely on adapting Dijkstra's shortest path algorithm to an indoor network. In outdoor space, several alternative algorithms have been proposed adding a more cognitive notion to the calculated paths and as such adhering to the natural wayfinding behavior (e.g. simplest paths, least risk paths). The need for indoor cognitive algorithms is highlighted by a more challenged navigation and orientation due to the specific indoor structure (e.g. fragmentation, less visibility, confined areas). Therefore, the aim of this research is to extend those richer cognitive algorithms to three-dimensional indoor environments. More specifically for this paper, we will focus on the application of the least risk path algorithm of Grum (2005) to an indoor space. The algorithm as proposed by Grum (2005) is duplicated and tested in a complex multi-story building. Several analyses compare shortest and least risk paths in indoor and in outdoor space. The results of these analyses indicate that the current outdoor least risk path algorithm does not calculate less risky paths compared to its shortest paths. In some cases, worse routes have been suggested. Adjustments to the original algorithm are proposed to be more aligned to the specific structure of indoor environments. In a later stage, other cognitive algorithms will be implemented and tested in both an indoor and combined indoor-outdoor setting, in an effort to improve the overall user experience during navigation in indoor environments.

Vanclooster, A.; Viaene, P.; Van de Weghe, N.; Fack, V.; De Maeyer, Ph.

2013-11-01

229

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

230

Path parameters consensus based formation control for multiple mobile robots  

Microsoft Academic Search

This paper addresses the problem of designing distributed feedback laws to fore the outputs of mobile robots to follow geometric paths while holding a desired formation pattern. The solution to formation problem, unfolds in two basic parts. Firstly, a path following control law based on Lyapunov and backstepping is designed out to drive each robot to its desired path regardless

Yintao Wang; Weisheng Yan; Yue Huang; Zhaoyong Mao

2010-01-01

231

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

232

The Knigsberg 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

233

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

234

Low bias integrated path estimators  

Microsoft Academic Search

We consider the problem of estimating the time-average variance constant for a stationary process. A previous paper described an approach based on multiple integrations of the simulation output path, and described the efficiency improvement that can result compared with the method of batch means (which is a special case of the method). In this paper we describe versions of the

James M. Calvin

2007-01-01

235

A Methodology for Intelligent Path Planning  

Microsoft Academic Search

In this work we present a methodology for intelligent path planning in an uncertain environment. Examples would include a mobile robot exploring an unknown terrain or a UAV navigating enemy territory while avoiding radar detection. We show that the problem of path planning in an uncertain environment, under certain assumptions, can be posed as the adaptive optimal control of an

Suman Chakravorty; John L. Junkins

2005-01-01

236

Outdoor Path Labeling Using Polynomial Mahalanobis Distance  

Microsoft Academic Search

Autonomous robot navigation in outdoor environ- ments remains a challenging and unsolved problem. A key issue is our ability to identify safe or navigable paths far enough ahead of the robot to allow smooth trajectories at acceptable speeds. Colour or texture-based labeling of safe path regions in image sequences is one way to achieve this far field prediction. A challenge

Gregory Z. Grudic; Jane Mulligan

2006-01-01

237

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

238

Paths from Mother-Child and Father-Child Relationships to Externalizing Behavior Problems in Children Differing in Electrodermal Reactivity: a Longitudinal Study from Infancy to Age 10.  

PubMed

Electrodermal hyporeactivity (or low skin conductance level, SCL) has been long established as a correlate of and diathesis for antisocial behavior, aggression, disregard for rules of conduct and feelings of others, and generally, externalizing behavior problems in children and adults. Much less is known, however, about how individual differences in children's SCL and qualities of their early experiences in relationships with parents interact to produce antisocial outcomes. In a community sample of 102 families (51 girls), we examined children's SCL, assessed in standard laboratory tasks at age 8 (N?=?81), as a moderator of the links between parent-child socialization history and children's externalizing behavior problems at ages 8 and 10, reported by mothers and fathers in well-established instruments and by children in clinical interviews. Mother- and father-child socialization history was assessed in frequent, intensive observations. Parent-child mutually responsive orientation (MRO) was observed from infancy to age 10, parental power assertion was observed from 15months to age 6 , and children reported their attachment security in interviews at age 8 and 10. For children with lower SCL, variations in mothers' power assertion and father-child MRO were associated with parent-rated externalizing problems. The former interaction was consistent with diathesis-stress, and the latter with differential susceptibility. For children with higher SCL, there were no links between socialization history and externalizing problems. PMID:25218772

Kochanska, Grazyna; Brock, Rebecca L; Chen, Kuan-Hua; Aksan, Nazan; Anderson, Steven W

2014-09-14

239

The mixture problem in computer mapping of terrain: Improved techniques for establishing spectral signature, atmospheric path radiance, and transmittance. [in Colorado  

NASA Technical Reports Server (NTRS)

The results of LANDSAT and Skylab research programs on the effects of the atmosphere on computer mapping of terrain include: (1) the concept of a ground truth map needs to be drastically revised; (2) the concept of training areas and test areas is not as simple as generally thought because of the problem of pixels that represent a mixture of terrain classes; (3) this mixture problem needs to be more widely recognized and dealt with by techniques of calculating spectral signatures of mixed classes, or by other methods; (4) atmospheric effects should be considered in computer mapping of terrain and in monitoring changes; and (5) terrain features may be used as calibration panels on the ground, from which atmospheric conditions can be determined and monitored. Results are presented of a test area in mountainous terrain of south-central Colorado for which an initial classification was made using simulated mixture-class spectral signatures and actual LANDSAT-1-MSS data.

Smedes, H. W.; Hulstrom, R. L.; Ranson, K. J.

1975-01-01

240

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

241

Covering Points of a Digraph with Point-Disjoint Paths and Its Application to Code Optimization  

Microsoft Academic Search

A point-disjoint path cover of a directed graph is a collection of point-disjoint paths (some paths possibly having zero length) which covers all the points. A path cover which minimizes the number of paths corresponds to an optimal sequence of the steps of a computer program for efficient coding and documentation. The minimization problem for the general directed graph is

Francis T. Boesch; James F. Gimpel

1977-01-01

242

PATH-RELINKING INTENSIFICATION METHODS FOR ...  

E-print Network

Apr 1, 2010 ... In the case of the classical traveling salesman problem, the ground set E is that of all edges connecting ... words and phrases. Path-relinking, metaheuristics, hybrid metaheurisics. ...... Transmission network design by a greedy...

user

243

Project: Virtual motion planning system. Combines ideas from graphics, artificial intelligence, and algorithms. Integrates theoretical ideas on shortest-path  

E-print Network

programming. Project: Dialogue system to query a course registration database via voice commands. Combines recognition with software integration and database programming. Project: Web search engine. Combines ideas from database systems, artificial intelligence, and networking. Integrates theoretical ideas from graph

Musicant, Dave

244

The shortest path is not the one you know: application of biological network resources in precision oncology research.  

PubMed

Several decades of molecular biology research have delivered a wealth of detailed descriptions of molecular interactions in normal and tumour cells. This knowledge has been functionally organised and assembled into dedicated biological pathway resources that serve as an invaluable tool, not only for structuring the information about molecular interactions but also for making it available for biological, clinical and computational studies. With the advent of high-throughput molecular profiling of tumours, close to complete molecular catalogues of mutations, gene expression and epigenetic modifications are available and require adequate interpretation. Taking into account the information about biological signalling machinery in cells may help to better interpret molecular profiles of tumours. Making sense out of these descriptions requires biological pathway resources for functional interpretation of the data. In this review, we describe the available biological pathway resources, their characteristics in terms of construction mode, focus, aims and paradigms of biological knowledge representation. We present a new resource that is focused on cancer-related signalling, the Atlas of Cancer Signalling Networks. We briefly discuss current approaches for data integration, visualisation and analysis, using biological networks, such as pathway scoring, guilt-by-association and network propagation. Finally, we illustrate with several examples the added value of data interpretation in the context of biological networks and demonstrate that it may help in analysis of high-throughput data like mutation, gene expression or small interfering RNA screening and can guide in patients stratification. Finally, we discuss perspectives for improving precision medicine using biological network resources and tools. Taking into account the information about biological signalling machinery in cells may help to better interpret molecular patterns of tumours and enable to put precision oncology into general clinical practice. PMID:25688112

Kuperstein, Inna; Grieco, Luca; Cohen, David P A; Thieffry, Denis; Zinovyev, Andrei; Barillot, Emmanuel

2015-03-01

245

Solving the Shortest Lattice Vector Problem in Time 22.465n Xavier Pujol1  

E-print Network

independent vectors b1, . . . , bd. These vectors form a basis of L and we write L = L(b1, . . . , bd). Since]. SVP is of prime interest in cryptography for two reasons: first, the security of several lattice

246

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

247

Characterization of spatial channel model based on ray path analysis in high-rise urban environment  

Microsoft Academic Search

The strongest ray analysis based on the computer simulation of wave propagation between a base station(BS) and mobile stations(MSs) is carried out to obtain the spatial-time wideband channel characteristics. The strongest rays are responsible for about 70% of the total received power for BS-MS pairs on the average and their arrival angles rarely deviate from the shortest path lines between

Do-Young Kwak; Nogyoung Kang; Jaewon Lee; Seong-Cheol Kim; Joonsoo Choi

2003-01-01

248

Computing Shortest, Fastest, and Foremost Journeys in Dynamic Networks  

Microsoft Academic Search

ABSTRACT New technologies and the deployment of mobile and nomadic,services are driving the emergence of complex communications networks, that have a highly dynamic behavior. This naturally engenders new route-discovery problems under changing conditions over these networks. Unfortunately, the temporal variations in the network topology are hard to be eectively captured in a classical graph model. In this paper, we use

Binh-minh Bui-xuan; Afonso Ferreira; Aubin Jarry

2003-01-01

249

On the Generation of Nearly Optimal, Planar Paths of Bounded Curvature and Bounded Curvature Gradient  

E-print Network

is a generalization of the Dubins problem to account for more realistic vehicle dynamics. The problem is solved. First, the generated path should be compatible to the vehicle dynamics, and second, the path should is the total length of the path, whereas the vehicle's dynamics may be incorporated into the path generation

Tsiotras, Panagiotis

250

Thermoalgebras and path integral  

SciTech Connect

Using a representation for Lie groups closely associated with thermal problems, we derive the algebraic rules of the real-time formalism for thermal quantum field theories, the so-called thermo-field dynamics (TFD), including the tilde conjugation rules for interacting fields. These thermo-group representations provide a unified view of different approaches for finite-temperature quantum fields in terms of a symmetry group. On these grounds, a path integral formalism is constructed, using Bogoliubov transformations, for bosons, fermions and non-abelian gauge fields. The generalization of the results for quantum fields in (S{sup 1}){sup d}xR{sup D-d} topology is addressed.

Khanna, F.C. [Theoretical Physics Institute, University of Alberta, Edmonton, AB T6G 2J1 (Canada); TRIUMF, Vancouver, BC, V6T 2A3 (Canada)], E-mail: khanna@phys.ualberta.ca; Malbouisson, A.P.C. [Centro Brasileiro de Pesquisas Fisicas/MCT, 22290-180 Rio de Janeiro, RJ (Brazil)], E-mail: adolfo@cbpf.br; Malbouisson, J.M.C. [Instituto de Fisicas, Universidade Federal da Bahia, 40210-340 Salvador, BA (Brazil)], E-mail: jmalboui@ufba.br; Santana, A.E. [Instituto de Fisicas, Universidade de Brasilia, 70910-900 Brasilia, DF (Brazil)], E-mail: asantana@fis.unb.br

2009-09-15

251

A new approach to CNC tool path generation  

Microsoft Academic Search

The feedrate is one of the most important factors to machining efficiency and quality. Current methods for tool path generation adopt a constant velocity along the cutter location path and do not satisfy the desired feedrate along the sculptured surface. This paper presents a new approach to tool path generation so as to cope with this problem. Methods based on

Chih-ching Lo

1998-01-01

252

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

253

Walden's Paths - Ensemble Edition  

NSDL National Science Digital Library

Walden?s 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. Walden?s 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

254

At-Least Version of the Generalized Minimum Spanning Tree Problem: Optimization Through Ant Colony System and Genetic Algorithms  

NASA Technical Reports Server (NTRS)

The At-Least version of the Generalized Minimum Spanning Tree Problem (L-GMST) is a problem in which the optimal solution connects all defined clusters of nodes in a given network at a minimum cost. The L-GMST is NPHard; therefore, metaheuristic algorithms have been used to find reasonable solutions to the problem as opposed to computationally feasible exact algorithms, which many believe do not exist for such a problem. One such metaheuristic uses a swarm-intelligent Ant Colony System (ACS) algorithm, in which agents converge on a solution through the weighing of local heuristics, such as the shortest available path and the number of agents that recently used a given path. However, in a network using a solution derived from the ACS algorithm, some nodes may move around to different clusters and cause small changes in the network makeup. Rerunning the algorithm from the start would be somewhat inefficient due to the significance of the changes, so a genetic algorithm based on the top few solutions found in the ACS algorithm is proposed to quickly and efficiently adapt the network to these small changes.

Janich, Karl W.

2005-01-01

255

Oriented paths in n-chromatic digraphs  

E-print Network

In this thesis, we try to treat the problem of oriented paths in n-chromatic digraphs. We first treat the case of antidirected paths in 5-chromatic digraphs, where we explain El-Sahili's theorem and provide an elementary and shorter proof of it. We then treat the case of paths with two blocks in n-chromatic digraphs with n greater than 4, where we explain the two different approaches of Addario-Berry et al. and of El-Sahili. We indicate a mistake in Addario-Berry et al.'s proof and provide a correction for it.

Nasser, Rajai

2011-01-01

256

Chain Based Path Formation in Swarms of Robots  

Microsoft Academic Search

In this paper we analyse a previously introduced swarm intel- ligence control mechanism used for solving problems of robot path forma- tion. We determine the impact of two probabilistic control parameters. In particular, the problem we consider consists in forming a path between two objects which an individual robot cannot perceive simultaneously. Our experiments were conducted in simulation. We compare

Shervin Nouyan; Marco Dorigo

2006-01-01

257

Wealth-Path Dependent Utility Maximization in Incomplete Markets  

E-print Network

Wealth-Path Dependent Utility Maximization in Incomplete Markets #3; Bruno BOUCHARD Laboratoire de for an incomplete semimartin- gale model extending the classical terminal wealth utility maximization problem. This modelling leads to the formulation of a wealth path-dependent utility maximization problem. Our main result

Pham, Huyên

258

Adaptable Path Planning in Regionalized Environments  

NASA Astrophysics Data System (ADS)

Human path planning relies on several more aspects than only geometric distance between two locations. These additional aspects mostly relate to the complexity of the traveled path. Accordingly, in recent years several cognitively motivated path search algorithms have been developed that try to minimize wayfinding complexity. However, the calculated paths may result in large detours as geometric properties of the network wayfinding occurs in are ignored. Simply adding distance as an additional factor to the cost function is a possible, but insufficient way of dealing with this problem. Instead, taking a global view on an environment by accounting for the heterogeneity of its structure allows for adapting the path search strategy. This heterogeneity can be used to regionalize the environment; each emerging region may require a different strategy for path planning. This paper presents such an approach to regionalized path planning. It argues for the advantages of the chosen approach, develops a measure for calculating wayfinding complexity that accounts for structural and functional aspects of wayfinding, and states a generic algorithm for regionalization. Finally, regionalized path planning is demonstrated in a sample scenario.

Richter, Kai-Florian

259

Path Resummations and the Fermion Sign Problem  

E-print Network

, Chemistry Department, Lensfield Road, Cambridge CB2 1EW, U.K. asa10@cam.ac.uk 2 University of Cambridge, Chemistry Department, Lensfield Road, Cambridge CB2 1EW, U.K. ajwt3@cam.ac.uk Ali Alavi A. Alavi and A

Alavi, Ali

260

Design of Elevator Group Control System Simulation Platform Based on Shortest Distance Algorithm  

Microsoft Academic Search

From the perspective of the characteristics of the elevator group control system, this paper selects the shortest distance algorithm as a scheduling strategy, and constructs elevator running model. On this basis, this paper uses VC++6.0 as development platform, by adding SQL server database as the background, using multi-threaded, dynamic allocation of memory and other technology to build an elevator group

Wang Chuansheng; Chen Chunping

2010-01-01

261

Interior point path following algorithms  

SciTech Connect

In the last few years the research on interior point methods for linear programming has been dominated by the study of primal-dual algorithms. Most of these methods are easily extended to monotone linear complementarity problems, preserving the convergence properties. In this talk we concentrate mostly on the basic techniques used for following the primal-dual central path associated with a monotone horizontal LCP. The emphasis is on feasible interior point methods, but we also describe the main techniques for dealing with infeasible starting points. We define the central path and construct homotopy methods for following it, with iterations based on the application of Newton`s method. We show how these Newton steps are combinations of two special directions, the affine-scaling and the centering direction, and describe how this fact can be used to generate large step methods with low polynomial bounds and superlinear rates of convergence.

Gonzaga, C.C.

1994-12-31

262

Generic Equations for Constructing Smooth Paths Along Circles and Tangent Lines With Application to Airport Ground Paths  

NASA Technical Reports Server (NTRS)

The primary purpose of this publication is to develop a mathematical model to describe smooth paths along any combination of circles and tangent lines. Two consecutive circles in a path are either tangent (externally or internally) or they appear on the same (lateral) or opposite (transverse) sides of a connecting tangent line. A path may start or end on either a segment or circle. The approach is to use mathematics common to robotics to design the path as a multilink manipulator. This approach allows a hierarchical view of the problem and keeps the notation manageable. A user simply specifies a few parameters to configure a path. Necessary and sufficient conditions automatically ensure the consistency of the inputs for a smooth path. Two example runway exit paths are given, and an angle to go assists in knowing when to switch from one path element to the next.

Barker, L. Keith

1998-01-01

263

Generating Feasible Transition Paths for Testing from an Extended Finite State Machine (EFSM)  

Microsoft Academic Search

The problem of testing from an extended finite state machine (EFSM) can be expressed in terms of finding suitable paths through the EFSM and then deriving test data to follow the paths. A chosen path may be infeasible and so it is desirable to have methods that can direct the search for appropriate paths through the EFSM towards those that

Abdul Salam Kalaji; Stephen Swift

2009-01-01

264

Multi-Objective Path Selection Model and Algorithm for Emergency Evacuation  

Microsoft Academic Search

Evacuation planning is one of the most important aspects of emergency management. Path selection is one of the fundamental problems in evacuation planning. A multi-objective mathematical model is presented for path selection in emergency evacuation. The two objectives of the model are to minimize the total travel time along a path and to minimize the path complexity respectively. Taking into

Yuan Yuan; Dingwei Wang

2007-01-01

265

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

266

Advanced Physics: Path Integral  

NSDL National Science Digital Library

A cursor is shown in an x-y graph. The cursor can be dragged around the graph and its path is marked as it is moved. The data are sent to a DataTable which shows x, y, and the value of the path integral, F.dl.

Wolfgang Christian

267

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.

Australian National University

268

Suggested Problems A. Czygrinow  

E-print Network

Suggested Problems Set 10 A. Czygrinow Department of Mathematics Arizona State University Suggested Problems ­ p.1/9 #12;Problem 1 Show that in any tree any two nodes are connected by exactly one path Show that tree is a bipartite graph Show that any tree on ¡ nodes has ¡ ¢ £ arcs Suggested Problems

Czygrinow, Andrzej

269

Parallel dynamic programming for on-line flight path optimization  

NASA Technical Reports Server (NTRS)

Parallel systolic algorithms for dynamic programming(DP) and their respective hardware implementations are presented for a problem in on-line trajectory optimization. The method is applied to a model for helicopter flight path optimization through a complex constraint region. This problem has application to an air traffic control problem and also to a terrain following/threat avoidance problem.

Slater, G. L.; Hu, K.

1989-01-01

270

Michael Grunwald Transition path sampling  

E-print Network

Michael Grunwald Transition path sampling simulations of structural phase transformations compromises the comparability of simulation and experiment considerably. Here, we use transition path sam of parallel crystal planes. We subject the pathways obtained with transition path sam- pling

Gruenwald, Michael

271

The Complexity of the Covering Radius Problem on Lattices and Codes  

Microsoft Academic Search

We initiate the study of the computational complexity of the covering radius problem for point lat- tices, and approximation versions of the problem for both lattices and linear codes. We also investigate the computational complexity of the shortest linearly independent vectors problem, and its relation to the covering radius problem for lattices. For the covering radius on n-dimensional lattices, we

Venkatesan GuruswamiDaniele

272

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.

273

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

274

A Path to Discovery  

ERIC Educational Resources Information Center

The path taken and the turns made as a turtle traces a polygon are examined to discover an important theorem in geometry. A unique tool, the Angle Adder, is implemented in the investigation. (Contains 9 figures.)

Stegemoller, William; Stegemoller, Rebecca

2004-01-01

275

PathFinder Science  

NSDL National Science Digital Library

PathFinder Science contains research projects about water conservation, tardigrades, a winter bird survey, ozone, ultraviolet light and DNA, global warming, spot removal, lichens, stream monitoring, amphibian biomonitoring, and particulate monitoring. Free registration to the PathFinder Science Network offers the opportunity to be a part of the listserv, upload collaborative project data or publish research work. There are tools and tips to help students publish their research on the web.

276

Follow the Paths  

NSDL National Science Digital Library

In this lesson, younger students will be introduced to the various orbital paths that are used for satellites. Using a globe and a satellite model or a large picture of Earth, the teacher will introduce three types of orbital paths (polar, elliptical, and geosynchronous). The students should be able to define 'satellite', define the three types of orbits, describe how satellites orbit the Earth, and understand how they are slowed down by drag from the atmosphere.

277

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

278

A modified reconfigurable data path processor  

NASA Technical Reports Server (NTRS)

High throughput is an overriding factor dictating system performance. A configurable data processor is presented which can be modified to optimize performance for a wide class of problems. The new processor is specifically designed for arbitrary data path operations and can be dynamically reconfigured.

Ganesh, G.; Whitaker, S.; Maki, G.

1991-01-01

279

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

280

Computing Diffeomorphic Paths for Large Motion Interpolation.  

PubMed

In this paper, we introduce a novel framework for computing a path of diffeomorphisms between a pair of input diffeomorphisms. Direct computation of a geodesic path on the space of diffeomorphisms Diff(?) is difficult, and it can be attributed mainly to the infinite dimensionality of Diff(?). Our proposed framework, to some degree, bypasses this difficulty using the quotient map of Diff(?) to the quotient space Diff(M)/Diff(M) ? obtained by quotienting out the subgroup of volume-preserving diffeomorphisms Diff(M) ? . This quotient space was recently identified as the unit sphere in a Hilbert space in mathematics literature, a space with well-known geometric properties. Our framework leverages this recent result by computing the diffeomorphic path in two stages. First, we project the given diffeomorphism pair onto this sphere and then compute the geodesic path between these projected points. Second, we lift the geodesic on the sphere back to the space of diffeomerphisms, by solving a quadratic programming problem with bilinear constraints using the augmented Lagrangian technique with penalty terms. In this way, we can estimate the path of diffeomorphisms, first, staying in the space of diffeomorphisms, and second, preserving shapes/volumes in the deformed images along the path as much as possible. We have applied our framework to interpolate intermediate frames of frame-sub-sampled video sequences. In the reported experiments, our approach compares favorably with the popular Large Deformation Diffeomorphic Metric Mapping framework (LDDMM). PMID:25364222

Seo, Dohyung; Jeffrey, Ho; Vemuri, Baba C

2013-06-01

281

Super-Brownian motion with reflecting historical paths  

Microsoft Academic Search

We consider super-Brownian motion whose historical paths reflect from each other, unlike those of the usual historical super-Brownian motion. We prove tightness for the family of distributions corresponding to a sequence of discrete approximations but we leave the problem of uniqueness of the limit open. We prove a few results about path behavior for processes under any limit distribution. In

Krzysztof Burdzy; Jean-Francois Le Gall

2000-01-01

282

Car-like robot path following in large unstructured environments  

Microsoft Academic Search

This paper addresses the problem of on-line path following for a car working in unstructured outdoor environments. The partially known map of the environment is updated and expanded in real time by a Simultaneous Localization and Mapping (SLAM) algorithm. This information is used to implement global path planning. A cost graph is initially constructed followed by a search to find

Shahram Rezaei; Jose Guivant; Eduardo M. Nebot

2003-01-01

283

Mission Path Following for an Autonomous Unmanned Airship  

Microsoft Academic Search

The development of an unmanned airship capable of autonomous flight over user-defined locations for aerial data and imagery acquisition is the objective of the AURORA project. One important mission problem is the flight path following of the vehicle through a set of pre-defined points at a given altitude and velocity. In this article, a path tracking error generation methodology is

Jose Raul Azinheira; E. Carneiro de Paiva; Josu Jr. Guimares Ramos; Samuel Siqueira Bueno

2000-01-01

284

VISCOSITY SOLUTIONS OF FULLY NONLINEAR ELLIPTIC PATH DEPENDENT PDES  

E-print Network

VISCOSITY SOLUTIONS OF FULLY NONLINEAR ELLIPTIC PATH DEPENDENT PDES ZHENJIE REN Abstract, inspired by [3], we define the viscosity solution, by using the nonlinear expectation. The paper contains , that for any bounded viscosity subsolution u1 and Key words and phrases. Path dependent PDEs, Dirichlet problem

Paris-Sud XI, Université de

285

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

286

Detection of deregulated modules using deregulatory linked path.  

PubMed

The identification of deregulated modules (such as induced by oncogenes) is a crucial step for exploring the pathogenic process of complex diseases. Most of the existing methods focus on deregulation of genes rather than the links of the path among them. In this study, we emphasize on the detection of deregulated links, and develop a novel and effective regulatory path-based approach in finding deregulated modules. Observing that a regulatory pathway between two genes might involve in multiple rather than a single path, we identify condition-specific core regulatory path (CCRP) to detect the significant deregulation of regulatory links. Using time-series gene expression, we define the regulatory strength within each gene pair based on statistical dependence analysis. The CCRPs in regulatory networks can then be identified using the shortest path algorithm. Finally, we derive the deregulated modules by integrating the differential edges (as deregulated links) of the CCRPs between the case and the control group. To demonstrate the effectiveness of our approach, we apply the method to expression data associated with different states of Human Epidermal Growth Factor Receptor 2 (HER2). The experimental results show that the genes as well as the links in the deregulated modules are significantly enriched in multiple KEGG pathways and GO biological processes, most of which can be validated to suffer from impact of this oncogene based on previous studies. Additionally, we find the regulatory mechanism associated with the crucial gene SNAI1 significantly deregulated resulting from the activation of HER2. Hence, our method provides not only a strategy for detecting the deregulated links in regulatory networks, but also a way to identify concerning deregulated modules, thus contributing to the target selection of edgetic drugs. PMID:23894653

Hu, Yuxuan; Gao, Lin; Shi, Kai; Chiu, David K Y

2013-01-01

287

vPath: Precise Discovery of Request Processing Paths from BlackBox Observations of Thread and Network Activities  

Microsoft Academic Search

Discovering end-to-end request-processing paths is crucial in many modern IT environments for reasons varying from debugging and bottleneck analysis to billing and auditing. Existing solutions for this problem fall into two broad categories: statistical inference and intrusive instrumentation. The statistical approaches in - fer request-processing paths in a \\

Byung Chul Tak; Chunqiang Tang; Chun Zhang; Sriram Govindan; Bhuvan Urgaonkar; Rong N. Chang

288

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

289

Stochastic Evolutionary Algorithms for Planning Robot Paths  

NASA Technical Reports Server (NTRS)

A computer program implements stochastic evolutionary algorithms for planning and optimizing collision-free paths for robots and their jointed limbs. Stochastic evolutionary algorithms can be made to produce acceptably close approximations to exact, optimal solutions for path-planning problems while often demanding much less computation than do exhaustive-search and deterministic inverse-kinematics algorithms that have been used previously for this purpose. Hence, the present software is better suited for application aboard robots having limited computing capabilities (see figure). The stochastic aspect lies in the use of simulated annealing to (1) prevent trapping of an optimization algorithm in local minima of an energy-like error measure by which the fitness of a trial solution is evaluated while (2) ensuring that the entire multidimensional configuration and parameter space of the path-planning problem is sampled efficiently with respect to both robot joint angles and computation time. Simulated annealing is an established technique for avoiding local minima in multidimensional optimization problems, but has not, until now, been applied to planning collision-free robot paths by use of low-power computers.

Fink, Wolfgang; Aghazarian, Hrand; Huntsberger, Terrance; Terrile, Richard

2006-01-01

290

Asymptotically optimal path planning and surface reconstruction for inspection  

E-print Network

Motivated by inspection applications for marine structures, this thesis develops algorithms to enable their autonomous inspection. Two essential parts of the inspection problem are (1) path planning and (2) surface ...

Papadopoulos, Georgios

2014-01-01

291

Threat-aware Path Planning in Uncertain Urban Environments  

E-print Network

This paper considers the path planning problem for an autonomous vehicle in an urban environment populated with static obstacles and moving vehicles with uncertain intents. We propose a novel threat assessment module, ...

Aoude, Georges

292

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

293

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

294

Path-consistency: When space misses time  

SciTech Connect

Within the framework of constraint programming, particulary concerning the Constraint Satisfaction Problems (CSPs), the techniques of preprocessing based on filtering algorithms were shown to be very important for the search phase. In particular, two filtering methods have been studied, these methods exploit two properties of local consistency: arc- and path-consistency. Concerning the arc-consistency methods, there is a linear time algorithm (in the size of the problem) which is efficient in practice. But the limitations of the arc-consistency algorithms requires often filtering methods with higher order like path-consistency filterings. The best path-consistency algorithm proposed is PC-6, a natural generalization of AC-6 to path-consistency. Its time complexity is O(n{sup 3}d{sup 4}) and its space complexity is O(n{sup 3}d{sup 4}), where n is the number of variables and d is the size of domains. We have remarked that PC-6, though it is widely better than PC-4, was not very efficient in practice, specially for those classes of problems that require an important space to be run. Therefore, we propose here a new path-consistency algorithm called PC-7, its space complexity is O(n{sup 3}d{sup 4}) but its time complexity is O(n{sup 3}d{sup 4}) i.e. worse than that of PC-6. However, the simplicity of PC-7 as well as the data structures used for its implementation offer really a higher performance than PC-6. Furthermore, it turns out that when the size of domains is a constant of the problems, the time complexity of PC-7 becomes. like PC-6, optimal i.e. O(n{sup 3}).

Chmeiss, A.; Jegou, P. [Universite de Provence, Marseille (France)

1996-12-31

295

Path integral control and state-dependent feedback  

NASA Astrophysics Data System (ADS)

In this paper we address the problem of computing state-dependent feedback controls for path integral control problems. To this end we generalize the path integral control formula and utilize this to construct parametrized state-dependent feedback controllers. In addition, we show a relation between control and importance sampling: Better control, in terms of control cost, yields more efficient importance sampling, in terms of effective sample size. The optimal control provides a zero-variance estimate.

Thijssen, Sep; Kappen, H. J.

2015-03-01

296

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; Gnter Bauer; Gustav M. Obermair; Ingo Morgenstern; Johannes Schneider

2001-01-01

297

Use of a Colony of Cooperating Agents and MAPLE To Solve the Traveling Salesman Problem.  

ERIC Educational Resources Information Center

This paper reviews an approach for finding optimal solutions to the traveling salesman problem, a well-known problem in combinational optimization, and describes implementing the approach using the MAPLE computer algebra system. The method employed in this approach to the problem is similar to the way ant colonies manage to establish shortest

Guerrieri, Bruno

298

Configuration Path Integral Monte Carlo  

NASA Astrophysics Data System (ADS)

A novel path integral Monte Carlo (PIMC) approach for correlated many-particle systems with arbitrary pair interaction in continuous space at low temperatures is presented. It is based on a representation of the N-particle density operator in a basis of (anti-)symmetrized N-particle states (``configurations'' of occupation numbers) [1]. The path integral is transformed into a sum over trajectories with the same topology and, finally, the limit of M to infinity, (M is the number of high-temperature factors), is analytically performed. This yields exact expressions for the thermodynamic quantities and allows to perform efficient simulations for fermions at low temperature and weak to moderate coupling. Our method is applicable to dense quantum plasmas in the regime of strong degeneracy where conventional PIMC, e.g. [2], fails due to the fermion sign problem. [4pt] [1] T. Schoof, M. Bonitz, A. Filinov, D. Hochstuhl, and J.W. Dufty, Contrib. Plasma Phys. (2011), DOI 10.1002/ctpp.201100012;.[0pt] [2] ``Introduction to computational methods for many-body physics,'' M. Bonitz and D. Semkat (eds.). Rinton Press, Princeton 2006, chapter 4.

Bonitz, Michael; Schoof, Tim; Groth, Simon; Filinov, Alexei; Hochstuhl, David

2011-11-01

299

Gas path seal  

NASA Technical Reports Server (NTRS)

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 backing is a yieldingly deformable porous material covered with a thin ductile layer. A mounting fixture surrounds the backing.

Bill, R. C.; Johnson, R. D. (inventors)

1979-01-01

300

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

301

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

302

Paths to Teaching.  

ERIC Educational Resources Information Center

This report uses the national Baccalaureate and Beyond longitudinal database to look at the early career paths of 1993 college graduates. The results provide information on which college graduates became teachers, where they taught, and whether they left teaching within 3 years. Overall, it is not easy to predict who may be potential teachers when

Lee, John B.; Clery, Suzanne B.; Presley, Jennifer B.

303

Path to the Profession  

ERIC Educational Resources Information Center

A growing number of institutions are being more deliberate about bringing in fundraisers who fit the culture of the development department and about assessing skills and providing training that fill specific needs. Development shops are paying more attention to cultivating their staffs, staying attuned to employees' needs and creating career paths

Coleman, Toni

2012-01-01

304

Paths to Remarriage  

Microsoft Academic Search

High divorce rates and the traditionally discrepant ages at death for husbands and wives indicate a need for a more complete understanding of the paths to remarriage in contemporary America. This study uses data from the U.S. Bureau of the Census' Current Population Survey to examine the extent and timing of remarriage, social factors associated with remarriage, and the impact

Graham B. Spanier; Paul C. Glick

1980-01-01

305

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, Martn A; Ramrez, Miguel A; Daranas, Antonio H; Martn, Vctor S; Padrn, Juan I

2012-12-01

306

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

307

Path integral quantization of parametrized field theory  

NASA Astrophysics Data System (ADS)

Free scalar field theory on a flat spacetime can be cast into a generally covariant form known as parametrized 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 parametrized field theory in order to analyze 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 nontrivial and is the analog of the Fradkin-Vilkovisky measure for quantum gravity. We construct Euclidean functional integrals in the generally covariant setting of parametrized field theory using key ideas of Schleich and show that our constructions imply the existence of nonstandard Wick rotations of the standard free scalar field two-point function. We develop a framework to study the problem of time through computations of scalar field two-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 parametrized field theory.

Varadarajan, Madhavan

2004-10-01

308

Path allocation for wavelength path sharing University College London  

E-print Network

: Wavelength path sharing (WPS) was introduced previously as a means of bridging the gap between the bit answers can be found depending upon the method used for the comparison. 2. Wavelength path sharing (WPS A logical path segment between WPS nodes S & T being transparently routed through X. Key #12;2 shows

Haddadi, Hamed

309

Optimal Obstacle Avoidance Based on the Hamilton-Jacobi-Bellman Equation  

Microsoft Academic Search

This paper presents a method for generating shortest paths in cluttered environments, based on the Hamilton-Jacobi-Bellman (HJB) equation. Formulating the shortest obstacle avoidance problem as a time optimal control problem, the shortest paths are generated by following the negative gradient of the return function, which satisfies the HJB equation. A method to generate near-optimal paths is also presented, based on

Satish Sundar; Zvi Shiller

1994-01-01

310

Time-optimal path generation for continuous and quasi-continuous path control of industrial robots  

Microsoft Academic Search

For a given continuous path, the problem of designing a time-optimal time-parametrization is considered. First, algorithms are presented which, under rather mild assumptions, yield the exact solution within two computational steps consisting of a forward and a backward computation. Then, the problem of quasi-continuous robot motion is investigated in detail. An algorithm of the same type results, but the computational

I. Troch

1989-01-01

311

A new probabilistic approach to the path criticality in stochastic PERT  

Microsoft Academic Search

The notion of critical path is a key issue in the temporal analysis of project scheduling in deterministic setting. The very\\u000a essence of the CPM consists in identifying the critical path, i.e., the longest path in a project network, because this path\\u000a conveys information on how long it should take to complete the project to the project manager. The problem

Davaadorjin Monhor

312

Generating minimax-curvature and shorter ?3-spline path using multi-objective variable-length genetic algorithm  

Microsoft Academic Search

As a continuing work on G3-continuous path planning for nonholonomic wheeled unicycle-type nonholo-nomic mobile robot in the predefined static environment, this paper accounts for a multi-objective path optimization problem that directly incorporates the objectives of simultaneously minimizes the total path length and the maximum curvature along the path. Using easily customized variable-length Island-based Parallel Genetic Algorithm (IPGA) as a path

Jiun-Hau Wei; Jing-Sin Liu

2010-01-01

313

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.

David Joiner

314

Molecular definition of the shortest region of deletion overlap in the Langer-Giedion syndrome  

PubMed Central

The Langer-Giedion syndrome (LGS), which is characterized by craniofacial dysmorphism and skeletal abnormalities, is caused by a genetic defect in 8q24.1. We have used 13 anonymous DNA markers from an 8q24.1-specific microdissection library, as well as c-myc and thyroglobulin gene probes, to map the deletion breakpoints in 16 patients with LGS. Twelve patients had a cytogenetically visible deletion, two patients had an apparently balanced translocation, and two patients had an apparently normal karyotype. In all cases except one translocation patient, loss of genetic material was detected. The DNA markers fall into 10 deletion intervals. Clone L48 (D8S51) defines the shortest region of deletion overlap (SRO), which is estimated to be less than 2 Mbp. Three clonespl7-2.3EE (D8S43), L24 (D8S45), and L40 (D8S49)which flank the SRO recognize evolutionarily conserved sequences. ImagesFigure 1Figure 3Figure 4 PMID:1836105

Ldecke, Hermann-Josef; Johnson, Carey; Wagner, Michael J.; Wells, Dan E.; Turleau, Catherine; Tommerup, Niels; Latos-Bielenska, Anna; Sandig, Klaus-Rainer; Meinecke, Peter; Zabel, Bernhard; Horsthemke, Bernhard

1991-01-01

315

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

316

The California PATH Database  

NSDL National Science Digital Library

The well known Berkeley Digital Library SunSite, discussed in the February 9, 1996 Scout Report, has recently added a new resource to its collection. The PATH database, maintained by the Harmer E. Davis Transportation Library at the University of California, is "the world's largest bibliographical database pertaining to Intelligent Transportation Systems (ITS)." It is searchable and browsable (Browse by ITS Thesaurus Term), and contains over 9,000 records and abstracts "including monographs, journal articles, conference papers, technical reports, theses and selected media coverage," dating back to the 1940s.

317

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

318

Pick-a-Path  

NSDL National Science Digital Library

This mobile app (available for both iOS and Android devices) was developed by the National Council of Teachers of Mathematics with funding from Verizon Foundation. The app is based on the Decimal Maze from the popular lesson "Too Big or Too Small". The goal is to help Okta reach the target (maximum, minimum, or a specific value) by choosing a path from the top of the maze to the bottom adding, subtracting, multiplying and dividing as the player goes. Seven levels with seven puzzles in each level test the player's skills with operation with powers of ten, negative numbers, fractions, decimals, and exponents.

2012-01-01

319

Portage and Path Dependence*  

PubMed Central

We examine portage sites in the U.S. South, Mid-Atlantic, and Midwest, including those on the fall line, a geomorphological feature in the southeastern U.S. marking the final rapids on rivers before the ocean. Historically, waterborne transport of goods required portage around the falls at these points, while some falls provided water power during early industrialization. These factors attracted commerce and manufacturing. Although these original advantages have long since been made obsolete, we document the continuing importance of these portage sites over time. We interpret these results as path dependence and contrast explanations based on sunk costs interacting with decreasing versus increasing returns to scale. PMID:23935217

Bleakley, Hoyt; Lin, Jeffrey

2012-01-01

320

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.

Tom Biddlecome

1999-11-08

321

Program Search as a Path to Artificial General Intelligence  

E-print Network

and how problems can be specified. We use the general representation that dates back to the birth of AIProgram Search as a Path to Artificial General Intelligence Lukasz Kaiser Mathematische Grundlagen of intelligence. Therefore we consider the general problem of searching for programs with specified properties

Kaiser, ukasz

322

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

323

Encoding folding paths of RNA switches  

PubMed Central

RNA co-transcriptional folding has long been suspected to play an active role in helping proper native folding of ribozymes and structured regulatory motifs in mRNA untranslated regions (UTRs). Yet, the underlying mechanisms and coding requirements for efficient co-transcriptional folding remain unclear. Traditional approaches have intrinsic limitations to dissect RNA folding paths, as they rely on sequence mutations or circular permutations that typically perturb both RNA folding paths and equilibrium structures. Here, we show that exploiting sequence symmetries instead of mutations can circumvent this problem by essentially decoupling folding paths from equilibrium structures of designed RNA sequences. Using bistable RNA switches with symmetrical helices conserved under sequence reversal, we demonstrate experimentally that native and transiently formed helices can guide efficient co-transcriptional folding into either long-lived structure of these RNA switches. Their folding path is controlled by the order of helix nucleations and subsequent exchanges during transcription, and may also be redirected by transient antisense interactions. Hence, transient intra- and inter-molecular base pair interactions can effectively regulate the folding of nascent RNA molecules into different native structures, provided limited coding requirements, as discussed from an information theory perspective. This constitutive coupling between RNA synthesis and RNA folding regulation may have enabled the early emergence of autonomous RNA-based regulation networks. PMID:17178750

Xayaphoummine, A.; Viasnoff, V.; Harlepp, S.; Isambert, H.

2007-01-01

324

An analogue approach to the travelling salesman problem using an elastic net method  

Microsoft Academic Search

The travelling salesman problem1 is a classical problem in the field of combinatorial optimization, concerned with efficient methods for maximizing or minimizing a function of many independent variables. Given the positions of N cities, which in the simplest case lie in the plane, what is the shortest closed tour in which each city can be visited once? We describe how

Richard Durbin; David Willshaw

1987-01-01

325

An efficient evolutionary algorithm for the degree-constrained minimum spanning tree problem  

Microsoft Academic Search

The representation of candidate solutions and the variation operators are fundamental design choices in an evolutionary algorithm (EA). This paper proposes a novel representation technique and suitable variation operators for the degree-constrained minimum spanning tree problem. For a weighted, undirected graph G(V, E), this problem seeks to identify the shortest spanning tree whose node degrees do not exceed an upper

G. R. Raidl

2000-01-01

326

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

Gnther R. Raidl; Bryant A. Julstrom

2000-01-01

327

A new class of projection and contraction methods for solving variational inequality problems  

Microsoft Academic Search

This paper presents a new class of projection and contraction methods for solving monotone variational inequality problems. The methods can be viewed as combinations of some existing projection and contraction methods and the method of shortest residuals, a special case of conjugate gradient methods for solving unconstrained nonlinear programming problems. Under mild assumptions, we show the global convergence of the

D. Han

2006-01-01

328

The shortest known prion protein gene allele occurs in goats, has only three octapeptide repeats and is non-pathogenic  

Microsoft Academic Search

The prion protein (PrP) gene modulates the in- cidence and incubation periods of transmissible spongiform encephalopathies of sheep, goats, mice and man. Here, a new caprine PrP allele encoding the shortest naturally occurring PrP protein so far described is reported. This variant contains only three instead of the usual five copies of a short peptide repeat (Pro-Gln\\/His-Gly-Gly-Gly-(Gly)-Trp- Gly-Gln) characteristic of

Wilfred Goldmann; Angela Chong; James Foster; James Hope; Nora Hunter

1998-01-01

329

Real time path planning for UAV based on Focused D  

Microsoft Academic Search

With its long endurance, high safety and low signature, an Unmanned Aerial Vehicle (UAV) plays a great part in intelligence collection, surveillance, reconnaissance, patrol, and target acquisition. Path planning is of significant interest for the autonomous navigation of UAV. A three-dimensional path-planning algorithm based on Focused Dynamic A? algorithm is presented for UAV under three-dimensional dynamic environments. The problem is

Yingchun Chen; Ye Zhao; Huakui Wang

2011-01-01

330

Super-Brownian motion with reflecting historical paths  

Microsoft Academic Search

. We consider super-Brownian motion whose historical paths reflect from each other, unlike those of the usual historical super-Brownian\\u000a motion. We prove tightness for the family of distributions corresponding to a sequence of discrete approximations but we leave\\u000a the problem of uniqueness of the limit open. We prove a few results about path behavior for processes under any limit distribution.

Krzysztof Burdzy; Jean-Franois Le Gall

2001-01-01

331

Improving VoIP quality through path switching  

Microsoft Academic Search

The current best-effort Internet cannot readily pro- vide the service guarantees that VoIP applications often require. Path switching can potentially address this problem without requiring new network mechanisms, simply by leveraging the robustness to performance variations available from connectivity options such as multi-homing and overlays. In this paper, we evaluate the effectiveness and benefits of path switching in improving the

Shu Tao; Kuai Xu; Antonio Estepa; Teng Fei; Lixin Gao; Roch Gurin; James F. Kurose; Donald F. Towsley; Zhi-li Zhang

2005-01-01

332

Path Integral Bosonization  

E-print Network

We establish the direct $d=2$ on-shell bosonization $\\psi_{L}(x_{+}) = e^{i\\xi(x_{+})}$ and~$\\psi_{R}^{\\dagger}(x_{-}) = e^{i\\xi(x_{-})}$ in path integral formulation by deriving the off-shell relations $\\psi_{L}(x)\\psi_{R}^{\\dagger}(x) = \\exp[i\\xi(x)]$ and $\\psi_{R}(x)\\psi_{L}^{\\dagger}(x) = \\exp[-i\\xi(x)]$. Similarly, the on-shell bosonization of the bosonic commuting spinor, $\\phi_{L}(x_{+}) = ie^{-i\\xi(x_{+})}\\partial^{+}e^{-i\\chi(x_{+})}$, $\\phi^{\\dagger}_{R}(x_{-}) = e^{-i\\xi(x_{-})-i\\chi(x_{-})}$ and $\\phi_{R}(x_{-}) = ie^{i\\xi(x_{-})}\\partial^{-}e^{+i\\chi(x_{-})}$, $\\phi^{\\dagger}_{L}(x_{+}) = e^{i\\xi(x_{+})+i\\chi(x_{+})}$, is established in path integral formulation by deriving the off-shell relations $\\phi_{L}(x)\\phi^{\\dagger}_{R}(x) = ie^{-i\\xi(x)}\\partial^{+}e^{-i\\chi(x)}$ and $\\phi_{R}(x)\\phi^{\\dagger}_{L}(x) = ie^{i\\xi(x)}\\partial^{-}e^{i\\chi(x)}$.

Fujikawa, Kazuo

2015-01-01

333

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.

334

Interactive cutting path analysis programs  

NASA Technical Reports Server (NTRS)

The operation of numerically controlled machine tools is interactively simulated. Four programs were developed to graphically display the cutting paths for a Monarch lathe, Cintimatic mill, Strippit sheet metal punch, and the wiring path for a Standard wire wrap machine. These programs are run on a IMLAC PDS-ID graphic display system under the DOS-3 disk operating system. The cutting path analysis programs accept input via both paper tape and disk file.

Weiner, J. M.; Williams, D. S.; Colley, S. R.

1975-01-01

335

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

336

SDSS J0926+3624: the shortest period eclipsing binary star  

NASA Astrophysics Data System (ADS)

With orbital periods of the order of tens of minutes or less, the AM Canum Venaticorum stars are ultracompact, hydrogen-deficient binaries with the shortest periods of any binary subclass, and are expected to be among the strongest gravitational wave sources in the sky. To date, the only known eclipsing source of this type is the P= 28 min binary SDSS J0926+3624. We present multiband, high time resolution light curves of this system, collected with William Herschel Telescope (WHT)/ULTRACAM in 2006 and 2009. We supplement these data with additional observations made with Liverpool Telescope/Rapid Imager to Search for Exoplanets (LT/RISE), XMM-Newton and the Catalina Real-Time Transient Survey. From light curve models we determine the mass ratio to be q=M2/M1= 0.041 0.002 and the inclination to be ?. We calculate the mass of the primary white dwarf to be 0.85 0.04 M? and the donor to be 0.035 0.003 M?, implying a partially degenerate state for this component. We observe superhump variations that are characteristic of an elliptical, precessing accretion disc. Our determination of the superhump period excess is in agreement with the established relationship between this parameter and the mass ratio, and is the most precise calibration of this relationship at low q. We also observe a quasi-periodic oscillation in the 2006 data, and we examine the outbursting behaviour of the system over a 4.5 year period.

Copperwheat, C. M.; Marsh, T. R.; Littlefair, S. P.; Dhillon, V. S.; Ramsay, G.; Drake, A. J.; Gnsicke, B. T.; Groot, P. J.; Hakala, P.; Koester, D.; Nelemans, G.; Roelofs, G.; Southworth, J.; Steeghs, D.; Tulloch, S.

2011-01-01

337

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

338

The flow-refueling location problem for alternative-fuel vehicles  

Microsoft Academic Search

Beginning with Hodgson (Geogr.Anal.22(1990) 270), several researchers have been developing a new kind of location-allocation model for flow capturing. Instead of locating central facilities to serve demand at fixed points in space, their models aim to serve demand consisting of origin-destination flows along their shortest paths. This paper extends flow-capturing models to optimal location of refueling facilities for alternative-fuel (alt-fuel)

Michael Kuby; Seow Lim

2005-01-01

339

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

340

Integrated flight path planning system and flight control system for unmanned helicopters.  

PubMed

This paper focuses on the design of an integrated navigation and guidance system for unmanned helicopters. The integrated navigation system comprises two systems: the Flight Path Planning System (FPPS) and the Flight Control System (FCS). The FPPS finds the shortest flight path by the A-Star (A*) algorithm in an adaptive manner for different flight conditions, and the FPPS can add a forbidden zone to stop the unmanned helicopter from crossing over into dangerous areas. In this paper, the FPPS computation time is reduced by the multi-resolution scheme, and the flight path quality is improved by the path smoothing methods. Meanwhile, the FCS includes the fuzzy inference systems (FISs) based on the fuzzy logic. By using expert knowledge and experience to train the FIS, the controller can operate the unmanned helicopter without dynamic models. The integrated system of the FPPS and the FCS is aimed at providing navigation and guidance to the mission destination and it is implemented by coupling the flight simulation software, X-Plane, and the computing software, MATLAB. Simulations are performed and shown in real time three-dimensional animations. Finally, the integrated system is demonstrated to work successfully in controlling the unmanned helicopter to operate in various terrains of a digital elevation model (DEM). PMID:22164029

Jan, Shau Shiun; Lin, Yu Hsiang

2011-01-01

341

Integrated Flight Path Planning System and Flight Control System for Unmanned Helicopters  

PubMed Central

This paper focuses on the design of an integrated navigation and guidance system for unmanned helicopters. The integrated navigation system comprises two systems: the Flight Path Planning System (FPPS) and the Flight Control System (FCS). The FPPS finds the shortest flight path by the A-Star (A*) algorithm in an adaptive manner for different flight conditions, and the FPPS can add a forbidden zone to stop the unmanned helicopter from crossing over into dangerous areas. In this paper, the FPPS computation time is reduced by the multi-resolution scheme, and the flight path quality is improved by the path smoothing methods. Meanwhile, the FCS includes the fuzzy inference systems (FISs) based on the fuzzy logic. By using expert knowledge and experience to train the FIS, the controller can operate the unmanned helicopter without dynamic models. The integrated system of the FPPS and the FCS is aimed at providing navigation and guidance to the mission destination and it is implemented by coupling the flight simulation software, X-Plane, and the computing software, MATLAB. Simulations are performed and shown in real time three-dimensional animations. Finally, the integrated system is demonstrated to work successfully in controlling the unmanned helicopter to operate in various terrains of a digital elevation model (DEM). PMID:22164029

Jan, Shau Shiun; Lin, Yu Hsiang

2011-01-01

342

DistanceJoin: Pattern Match Query In a Large Graph Database  

Microsoft Academic Search

The growing popularity of graph databases has generated interesting data management problems, such as subgraph search, shortest-path query, reachability veriflcation, and pattern match. Among these, a pattern match query is more ?exible compared to a subgraph search and more informa- tive compared to a shortest-path or reachability query. In this paper, we address pattern match problems over a large data

Lei Zou; Lei Chen; M. Tamer zsu

2009-01-01

343

Obstacle avoidance and path planning  

Microsoft Academic Search

Outlines the state-of-the-art in obstacle avoidance and path planning for industrial robots that is practical on the current generation of computer hardware. Describes practical vehicle planners and planning for manipulators. Summarizes that obstacle avoidance and path planning are techniques with differing goals. Sonar is the standard method of obstacle avoidance systems which is largely limited by the reliability of the

Stephen Cameron

1994-01-01

344

Solving Semi-Infinite Optimization Problems with Interior Point Techniques  

Microsoft Academic Search

We introduce a new numerical solution method for semi-infinite optimization prob- lems with convex lower level problems. The method is based on a reformulation of the semi-infinite problem as a Stackelberg game and the use of regularized nonlinear complementarity problem func- tions. This approach leads to central path conditions for the lower level problems, where for a given path parameter

Oliver Stein; Georg Still

2003-01-01

345

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

346

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

347

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

348

MAXI J1659-152: the shortest orbital period black-hole transient in outburst  

NASA Astrophysics Data System (ADS)

MAXI J1659-152 is a bright X-ray transient black-hole candidate binary system discovered in September 2010. We report here on MAXI, RXTE, Swift, and XMM-Newton observations during its 2010/2011 outburst. We find that during the first one and a half week of the outburst the X-ray light curves display drops in intensity at regular intervals, which we interpret as absorption dips. About three weeks into the outbursts, again drops in intensity are seen. These dips have, however, a spectral behaviour opposite to that of the absorption dips, and are related to fast spectral state changes (hence referred to as transition dips). The absorption dips recur with a period of 2.414 0.005 h, which we interpret as the orbital period of the system. This implies that MAXI J1659-152 is the shortest period black-hole candidate binary known to date. The inclination of the accretion disk with respect to the line of sight is estimated to be 65-80. We propose the companion to the black-hole candidate to be close to an M5 dwarf star, with a mass and radius of about 0.15-0.25 M? and 0.2-0.25 R?, respectively. We derive that the companion had an initial mass of about 1.5 M?, which evolved to its current mass in about 5-6 billion years. The system is rather compact (orbital separation of ?1.33 R?), and is located at a distance of 8.6 3.7 kpc, with a height above the Galactic plane of 2.4 1.0 kpc. The characteristics of short orbital period and high Galactic scale height are shared with two other transient black-hole candidate X-ray binaries, i.e., XTE J1118+480 and Swift J1735.5-0127. We suggest that all three are kicked out of the Galactic plane into the halo, rather than being formed in a globular cluster. Table 1 is available in electronic form at http://www.aanda.org

Kuulkers, E.; Kouveliotou, C.; Belloni, T.; Cadolle Bel, M.; Chenevez, J.; Daz Trigo, M.; Homan, J.; Ibarra, A.; Kennea, J. A.; Muoz-Darias, T.; Ness, J.-U.; Parmar, A. N.; Pollock, A. M. T.; van den Heuvel, E. P. J.; van der Horst, A. J.

2013-04-01

349

Perturbative Methods in Path Integration  

NASA Astrophysics Data System (ADS)

This dissertation addresses a number of related questions concerning perturbative "path" integrals. Perturbative methods are one of the few successful ways physicists have worked with (or even defined) these infinite-dimensional integrals, and it is important as mathematicians to check that they are correct. Chapter 0 provides a detailed introduction. We take a classical approach to path integrals in Chapter 1. Following standard arguments, we posit a Feynman-diagrammatic description of the asymptotics of the time-evolution operator for the quantum mechanics of a charged particle moving nonrelativistically through a curved manifold under the influence of an external electromagnetic field. We check that our sum of Feynman diagrams has all desired properties: it is coordinate-independent and well-defined without ultraviolet divergences, it satisfies the correct composition law, and it satisfies Schrodinger's equation thought of as a boundary-value problem in PDE. Path integrals in quantum mechanics and elsewhere in quantum field theory are almost always of the shape ? f es for some functions f (the "observable") and s (the "action"). In Chapter 2 we step back to analyze integrals of this type more generally. Integration by parts provides algebraic relations between the values of ? (-) es for different inputs, which can be packaged into a Batalin--Vilkovisky-type chain complex. Using some simple homological perturbation theory, we study the version of this complex that arises when f and s are taken to be polynomial functions, and power series are banished. We find that in such cases, the entire scheme-theoretic critical locus (complex points included) of s plays an important role, and that one can uniformly (but noncanonically) integrate out in a purely algebraic way the contributions to the integral from all "higher modes," reducing ? f es to an integral over the critical locus. This may help explain the presence of analytic continuation in questions like the Volume Conjecture. We end with Chapter 3, in which the role of integration is somewhat obscured, but perturbation theory is prominent. The Batalin--Vilkovisky homological approach to integration illustrates that there are generalizations of the notion of "integral" analogous to the generalization from cotangent bundles to Poisson manifolds. The AKSZ construction of topological quantum field theories fits into this approach; in what is usually called "AKSZ theory," everything is still required to be symplectic. Using factorization algebras as a framework for (topological) quantum field theory, we construct a one-dimensional Poisson AKSZ field theory for any formal Poisson manifold M. Quantizations of our field theory correspond to formal star-products on M. By using a "universal'' formal Poisson manifold and abandoning configuration-space integrals in favor of other homological-perturbation techniques, we construct a universal formal star-product all of whose coefficients are manifestly rational numbers.

Johnson-Freyd, Theodore Paul

350

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

351

British Pathe Newsreels Online  

NSDL National Science Digital Library

British Pathe, one of the oldest media companies in the world, recently made available its entire 3500-hour film archive, covering "news, sport, social history and entertainment from 1896 to 1970." At the Web site, users can search by keyword or try out advanced search, if details such as reel numbers or exact titles are known. Casual users may prefer the "Lucky Dip" search, which provides a random selection of films to see. After a search returns a hit list of films, choices include "Preview Film: a page of stills, with a textual description of the clip;" "Download Now: a free, low resolution clip;" or "Add to basket, to purchase higher resolutions of the film." (A rate card giving prices for low and high resolution clips is provided.) One hint for first-time users, though: if files do not seem to download properly, check your email, because you will be sent the URL to retrieve your film. After just a bit of finagling on our first visit, we watched the Beatles at a water-skiing show, Charlie Chaplin, and Sir Ernest Shackleton and his sled dogs photographed in 1916 on returning from their Antarctic expedition.

2002-01-01

352

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

353

Topological quantization by controlled paths: application to Cooper pairs pumps  

E-print Network

When physical systems are tunable by three classical parameters, level degeneracies may occur at isolated points in parameter space. A topological singularity in the phase of the degenerate eigenvectors exists at these points. When a path encloses such point, the accumulated geometrical phase is sensitive to its presence. Furthermore, surfaces in parameter space enclosing such point can be used to characterize the eigenvector singularities through their Chern indices, which are integers. They can be used to quantize a physical quantity of interest. This quantity changes continuously during an adiabatic evolution along a path in parameter space. Quantization requires to turn this path into a surface with a well defined Chern index. We analyze the conditions necessary to a {\\em Topological Quantization by Controlled Paths}. It is applied to Cooper pair pumps. For more general problems, a set of four criteria are proposed to check if topological quantization is possible.

Raphal Leone; Laurent Lvy

2007-11-05

354

PCB Drill Path Optimization by Combinatorial Cuckoo Search Algorithm  

PubMed Central

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

355

Heuristically optimal path scanning for high-speed multiphoton circuit imaging  

PubMed Central

Population dynamics of patterned neuronal firing are fundamental to information processing in the brain. Multiphoton microscopy in combination with calcium indicator dyes allows circuit dynamics to be imaged with single-neuron resolution. However, the temporal resolution of fluorescent measures is constrained by the imaging frequency imposed by standard raster scanning techniques. As a result, traditional raster scans limit the ability to detect the relative timing of action potentials in the imaged neuronal population. To maximize the speed of fluorescence measures from large populations of neurons using a standard multiphoton laser scanning microscope (MPLSM) setup, we have developed heuristically optimal path scanning (HOPS). HOPS optimizes the laser travel path length, and thus the temporal resolution of neuronal fluorescent measures, using standard galvanometer scan mirrors. Minimizing the scan path alone is insufficient for prolonged high-speed imaging of neuronal populations. Path stability and the signal-to-noise ratio become increasingly important factors as scan rates increase. HOPS addresses this by characterizing the scan mirror galvanometers to achieve prolonged path stability. In addition, the neuronal dwell time is optimized to sharpen the detection of action potentials while maximizing scan rate. The combination of shortest path calculation and minimization of mirror positioning time allows us to optically monitor a population of neurons in a field of view at high rates with single-spike resolution, ?125 Hz for 50 neurons and ?8.5 Hz for 1,000 neurons. Our approach introduces an accessible method for rapid imaging of large neuronal populations using traditional MPLSMs, facilitating new insights into neuronal circuit dynamics. PMID:21715667

Sadovsky, Alexander J.; Kruskal, Peter B.; Kimmel, Joseph M.; Ostmeyer, Jared; Neubauer, Florian B.

2011-01-01

356

DICOM involving XML path-tag  

NASA Astrophysics Data System (ADS)

Digital Imaging and Communications in Medicine (DICOM) is a standard for handling, storing, printing, and transmitting information in medical imaging. XML (Extensible Markup Language) is a set of rules for encoding documents in machine-readable form which has become more and more popular. The combination of these two is very necessary and promising. Using XML tags instead of numeric labels in DICOM files will effectively increase the readability and enhance the clear hierarchical structure of DICOM files. However, due to the fact that the XML tags rely heavily on the orders of the tags, the strong data dependency has a lot of influence on the flexibility of inserting and exchanging data. In order to improve the extensibility and sharing of DICOM files, this paper introduces XML Path-Tag to DICOM. When a DICOM file is converted to XML format, adding simple Path-Tag into the DICOM file in place of complex tags will keep the flexibility of a DICOM file while inserting data elements and give full play to the advantages of the structure and readability of an XML file. Our method can solve the weak readability problem of DICOM files and the tedious work of inserting data into an XML file. In addition, we set up a conversion engine that can transform among traditional DICOM files, XML-DCM and XML-DCM files involving XML Path-Tag efficiently.

Zeng, Qiang; Yao, Zhihong; Liu, Lei

2011-03-01

357

The Traveling Salesman and Related Stochastic Problems  

NASA Astrophysics Data System (ADS)

In the traveling salesman problem, one must find the length of the shortest closed tour visiting given ``cities''. We study the stochastic version of the problem, taking the locations of cities and the distances separating them to be random variables drawn from an ensemble. We consider first the ensemble where cities are placed in Euclidean space. We investigate how the optimum tour length scales with number of cities and with number of spatial dimensions. We then examine the analytical theory behind the random link ensemble, where distances between cities are independent random variables. Finally, we look at the related geometric issue of nearest neighbor distances, and find some remarkable universalities.

Percus, A. G.

1998-03-01

358

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

359

Modelling of radiative transfer by the Monte Carlo method and solving the inverse problem based on a genetic algorithm according to experimental results of aerosol sensing on short paths using a femtosecond laser source  

NASA Astrophysics Data System (ADS)

We consider the algorithms that implement a broadband ('multiwave') radiative transfer with allowance for multiple (aerosol) scattering and absorption by main atmospheric gases. In the spectral range of 0.6 1 ?m, a closed numerical simulation of modifications of the supercontinuum component of a probing femtosecond pulse is performed. In the framework of the algorithms for solving the inverse atmospheric-optics problems with the help of a genetic algorithm, we give an interpretation of the experimental backscattered spectrum of the supercontinuum. An adequate reconstruction of the distribution mode for the particles of artificial aerosol with the narrow-modal distributions in a size range of 0.5 2 mm and a step of 0.5 mm is obtained.

Matvienko, G. G.; Oshlakov, V. K.; Stepanov, A. N.; Sukhanov, A. Ya

2015-02-01

360

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

361

Variable path cryogenic acoustic interferometer  

NASA Astrophysics Data System (ADS)

We describe a variable path acoustic interferometer for use at cryogenic temperatures. Movement is enabled without mechanical coupling via two piezoelectric bimorphs wired and mounted in a manner that preserves the parallelism of two ultrasonic transducers that define the acoustic path. A certain degree of in situ alignment can also be accomplished. Path length sweeps from 0 to 180 ?m have been made at cryogenic temperatures and preliminary sound velocity measurements in liquid 4He and gaseous 3He near 4 K are presented which agree well with past measurements.

Kucera, D. M.; Ketterson, J. B.

1998-12-01

362

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

363

Dual-Path VCO Design With Partitioned Coarse-Tuning Control in 65 nm CMOS  

Microsoft Academic Search

This letter describes a dual-path LC voltage controlled oscillator (VCO) design that reduces both coarse-tuning and fine-tuning sensitivities. By using a combination of discrete and continuous tuning methods for the coarse-tuning control, a very high gain ratio between the coarse-tuning path and the fine-tuning path can be avoided, significantly alleviating noise and coupling problems due to high coarse-tuning gain. A

Yuanfeng Sun; Xueyi Yu; Woogeun Rhee; Sangsoo Ko; Wooseung Choo; Byeong-Ha Park; Zhihua Wang

2010-01-01

364

Energy aware path planning in complex four dimensional environments  

NASA Astrophysics Data System (ADS)

This dissertation addresses the problem of energy-aware path planning for small autonomous vehicles. While small autonomous vehicles can perform missions that are too risky (or infeasible) for larger vehicles, the missions are limited by the amount of energy that can be carried on board the vehicle. Path planning techniques that either minimize energy consumption or exploit energy available in the environment can thus increase range and endurance. Path planning is complicated by significant spatial (and potentially temporal) variations in the environment. While the main focus is on autonomous aircraft, this research also addresses autonomous ground vehicles. Range and endurance of small unmanned aerial vehicles (UAVs) can be greatly improved by utilizing energy from the atmosphere. Wind can be exploited to minimize energy consumption of a small UAV. But wind, like any other atmospheric component , is a space and time varying phenomenon. To effectively use wind for long range missions, both exploration and exploitation of wind is critical. This research presents a kinematics based tree algorithm which efficiently handles the four dimensional (three spatial and time) path planning problem. The Kinematic Tree algorithm provides a sequence of waypoints, airspeeds, heading and bank angle commands for each segment of the path. The planner is shown to be resolution complete and computationally efficient. Global optimality of the cost function cannot be claimed, as energy is gained from the atmosphere, making the cost function inadmissible. However the Kinematic Tree is shown to be optimal up to resolution if the cost function is admissible. Simulation results show the efficacy of this planning method for a glider in complex real wind data. Simulation results verify that the planner is able to extract energy from the atmosphere enabling long range missions. The Kinematic Tree planning framework, developed to minimize energy consumption of UAVs, is applied for path planning in ground robots. In traditional path planning problem the focus is on obstacle avoidance and navigation. The optimal Kinematic Tree algorithm named Kinematic Tree* is shown to find optimal paths to reach the destination while avoiding obstacles. A more challenging path planning scenario arises for planning in complex terrain. This research shows how the Kinematic Tree* algorithm can be extended to find minimum energy paths for a ground vehicle in difficult mountainous terrain.

Chakrabarty, Anjan

365

Scattering theory with path integrals  

NASA Astrophysics Data System (ADS)

Starting from well-known expressions for the T-matrix and its derivative in standard nonrelativistic potential scattering, I rederive recent path-integral formulations due to Efimov and Barbashov et al. Some new relations follow immediately.

Rosenfelder, R.

2014-03-01

366

An introduction to critical paths.  

PubMed

A critical path defines the optimal sequencing and timing of interventions by physicians, nurses, and other staff for a particular diagnosis or procedure. Critical paths are developed through collaborative efforts of physicians, nurses, pharmacists, and others to improve the quality and value of patient care. They are designed to minimize delays and resource utilization and to maximize quality of care. Critical paths have been shown to reduce variation in the care provided, facilitate expected outcomes, reduce delays, reduce length of stay, and improve cost-effectiveness. The approach and goals of critical paths are consistent with those of total quality management (TQM) and can be an important part of an organization's TQM process. PMID:15739581

Coffey, Richard J; Richards, Janet S; Remmert, Carl S; LeRoy, Sarah S; Schoville, Rhonda R; Baldwin, Phyllis J

2005-01-01

367

COMPUTER SCIENCE: MISCONCEPTIONS, CAREER PATHS  

E-print Network

COMPUTER SCIENCE: MISCONCEPTIONS, CAREER PATHS AND RESEARCH CHALLENGES School of Computing Undergraduate Student) #12;Computer Science Misconceptions Intro to Computer Science - Florida International University 2 Some preconceived ideas & stereotypes about Computer Science (CS) are quite common

Hristidis, Vagelis

368

What is a MISR path?  

Atmospheric Science Data Center

... orbits that observe the same areas under the same nominal angular conditions. Areas that are close to each other in longitude will be ... 1 crosses the equator at 64.60 west longitude. Orbital Paths/Blocks ...

2014-12-08

369

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

370

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

371

Scattering theory with path integrals  

SciTech Connect

Starting from well-known expressions for the T-matrix and its derivative in standard nonrelativistic potential scattering, I rederive recent path-integral formulations due to Efimov and Barbashov et al. Some new relations follow immediately.

Rosenfelder, R. [Particle Theory Group, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland)] [Particle Theory Group, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland)

2014-03-15

372

Adaptive path planning: Algorithm and analysis  

SciTech Connect

Path planning has to be fast to support real-time robot programming. Unfortunately, current planning techniques are still too slow to be effective, as they often require several minutes, if not hours of computation. To alleviate this problem, we present a learning algorithm that uses past experience to enhance future performance. The algorithm relies on an existing path planner to provide solutions to difficult tasks. From these solutions, an evolving sparse network of useful subgoals is learned to support faster planning. The algorithm is suitable for both stationary and incrementally-changing environments. To analyze our algorithm, we use a previously developed stochastic model that quantifies experience utility. Using this model, we characterize the situations in which the adaptive planner is useful, and provide quantitative bounds to predict its behavior. The results are demonstrated with problems in manipulator planning. Our algorithm and analysis are sufficiently general that they may also be applied to task planning or other planning domains in which experience is useful.

Chen, Pang C.

1993-03-01

373

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

374

Chain Based Path Formation in Swarms of Robots  

E-print Network

Chain Based Path Formation in Swarms of Robots Shervin Nouyan and Marco Dorigo IRIDIA, Co analyse a previously introduced swarm intel- ligence control mechanism used for solving problems of robot related to dynamic environments and multiple robots. In swarm robotics, the goal is to emphasize

Libre de Bruxelles, Universit

375

TRANSITION PATH SAMPLING STUDIES OF SOLID-SOLID TRANSFORMATIONS  

E-print Network

PRESSURE MICHAEL GRNWALD AND CHRISTOPH DELLAGO University of Vienna, Faculty of Physics, Boltzmanngasse 5, 1090, Vienna, Austria e-mail: michael.gruenwald@univie.ac.at; christoph.dellago@univie.ac.at Abstract this timescale problem. As an application, we show how transition path sam- pling can be used to identify

Gruenwald, Michael

376

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

377

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

378

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

379

Vision-based path-planning in unstructured environments  

Microsoft Academic Search

Autonomous driving in unstructured environments has attracted an unprecedented level of attention when the DARPA announced the Grand Challenge Competitions in 2004 and 2005. Autonomous driving involves (at least) three major subtasks: perception of the environment, path planning and subsequent vehicle control. Whereas the latter has proven a solved problem, the first two constituted, apart from hardware failures, the most

Britta Hummel; S. Kammel; Thao Dang; C. Duchow; C. Stiller

2006-01-01

380

Dynamic path planning in sensor-based terrain acquisition  

Microsoft Academic Search

The terrain acquisition problem is formulated as that of continuous motion planning, and no constraints are imposed on obstacle geometry. Two algorithms are described for acquiring planar terrains with obstacles of arbitrary shape. Estimates of the algorithm performance are derived as upper bounds on the lengths of generated paths

V. J. Lumelsky; S. Mukhopadhyay; K. Sun

1990-01-01

381

Improved Path Exploration in shim6-based Multihoming Sbastien Barr  

E-print Network

is the REAchability Protocol (REAP) that allows multihomed hosts to switch to an alternate path when a failure occurs.lastname}@uclouvain.be ABSTRACT The shim6 host-based solution to IPv6 multihoming was designed within the IETF to provide a solution to the multihoming problem by using several IPv6 addresses per host. In this paper, we briefly

Bonaventure, Olivier

382

Leap-Frog Path Design for Multi-Robot Cooperative Localization  

E-print Network

Leap-Frog Path Design for Multi-Robot Cooperative Localization Stephen Tully, George Kantor a "leap-frog" path designed for a team of three robots per- forming cooperative localization. Two robots vegetation, and underwater. To solve the localization problem, a team of robots can employ cooperative

Choset, Howie

383

Adapting the Laban Effort System to Design Affect-Communicating Locomotion Path for a  

E-print Network

Adapting the Laban Effort System to Design Affect-Communicating Locomotion Path for a Flying Robot Affect-Communicating Locomotion Path for a Flying Robot Abstract People and animals use various kinds this locomotion-style communication channel for com- municating their states to people. One problem in leveraging

384

FPGA-based tool path computation: An application for shoe last machining on CNC lathes  

Microsoft Academic Search

Tool path generation is one of the most complex problems in computer aided manufacturing. Although some efficient strategies have been developed, most of them are only useful for standard machining. The algorithm called Virtual Digitizing computes the tool path by means of a virtually digitized model of the surface and a geometry specification of the tool and its motion, so

Antonio Jimeno; Jos Luis Snchez; Higinio Mora Mora; Jernimo Mora Pascual; Juan Manuel Garca Chamizo

2006-01-01

385

Topological charge quantization via path integration: An application of the Kustaanheimo-Stiefel transformation  

Microsoft Academic Search

The unified treatment of the Dirac monopole, the Schwinger monopole, and the Aharonov-Bohm problem by Barut and Wilson is revisited via a path integral approach. The Kustaanheimo-Stiefel transformation of space and time is utilized to calculate the path integral for a charged particle in the singular vector potential. In the process of dimensional reduction, a topological charge quantization rule is

Akira Inomata; Georg Junker; Raj Wilson

1993-01-01

386

Super-Brownian motion with reflecting historical paths. II. Convergence of approximations  

Microsoft Academic Search

We prove that the sequence of finite reflecting branching Brownian motion forests defined by Burdzy and Le Gall ([1]) converges in probability to the super-Brownian motion with reflecting historical paths. This solves an open problem posed in [1], where only tightness was proved for the sequence of approximations. Several results on path behavior were proved in [1] for all subsequential

Krzysztof Burdzy; Leonid Mytnik

2005-01-01

387

Traffic Grooming in Path, Star, and Tree Networks: Complexity, Bounds, and Algorithms  

E-print Network

Traffic Grooming in Path, Star, and Tree Networks: Complexity, Bounds, and Algorithms Rudra Dutta of Computer Science, North Carolina State University, Raleigh, NC 1. INTRODUCTION In wavelength division consider the problem of traffic grooming in path, star, and tree networks, which are useful topologies

Dutta, Rudra

388

Finding optimal weighted bridges with applications  

Microsoft Academic Search

The computation of shortest paths, distances and feature relationships is a key problem in many applications. In finding shortest distances or paths one often must respect features of the domain. For example, in medical applications such as radiation therapy, the features may include tissue density, risk to radiation exposure, etc. In computing an optimal treatment plan, one can think of

Ovidiu Daescu; James D. Palmer

2006-01-01

389

ETH Zurich Distributed Computing Group Stephan Holzer SODA 2012 Stephan Holzer  

E-print Network

· Minimum Spanning Tree ­ Efficient broadcasting, etc. · Shortest path ­ Routing, etc. · Steiner tree, Aggregation, etc · Minimum Spanning Tree ­ Efficient broadcasting, etc. · Shortest path ­ Routing, etc Holzer SODA 2012 Fundamental problems · Spanning Tree ­ Broadcasting, Aggregation, etc · Minimum Spanning

390

A Graph-Theoretical Approach to the Selection of the Minimum Tiling Path from a Physical Map  

E-print Network

A Graph-Theoretical Approach to the Selection of the Minimum Tiling Path from a Physical Map Serdar Bozdag, Timothy J. Close, and Stefano Lonardi Abstract--The problem of computing the minimum tiling path-by-clone) genome sequencing projects. We formulate this problem in a graph theoretical framework, and then solve

Lonardi, Stefano

391

On hallucinated garden paths UC San Diego  

E-print Network

On hallucinated garden paths Roger Levy UC San Diego Department of Linguistics 2010 LSA Annual., 1995) #12;Garden-pathing in incremental parsing · Garden-path sentence a consequence of incrementality recent examples don't match this definition · Tabor et al. (2004): garden-paths on continuous substrings

392

Path integral simulation of polarized solitons in optical fibers  

NASA Astrophysics Data System (ADS)

An efficient computational approach based on the path integral concept is described to solve nonlinear pulse propagation dynamics in realistic optical fibers. As model equations which can predict the propagation, we consider the perturbed (scalar) and the coupled (vectorial) nonlinear Schrdinger equations for monomode and birefringent fibers, respectively. With the equivalence between path integration and Fresnel transform, an efficient algorithm can be employed which has been developed for use in the field of wave signal processing of holographic data. After ensuring the validity of the method through the application to canonical soliton problems, results are shown for nonlinear pulse propagation under realistic conditions.

Hayata, K.; Saka, K.; Koshiba, M.

1990-11-01

393

Solving the Curriculum Sequencing Problem with DNA Computing Approach  

ERIC Educational Resources Information Center

In the e-learning systems, a learning path is known as a sequence of learning materials linked to each others to help learners achieving their learning goals. As it is impossible to have the same learning path that suits different learners, the Curriculum Sequencing problem (CS) consists of the generation of a personalized learning path for each

Debbah, Amina; Ben Ali, Yamina Mohamed

2014-01-01

394

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

395

Light transport on path-space manifolds  

NASA Astrophysics Data System (ADS)

The pervasive use of computer-generated graphics in our society has led to strict demands on their visual realism. Generally, users of rendering software want their images to look, in various ways, "real", which has been a key driving force towards methods that are based on the physics of light transport. Until recently, industrial practice has relied on a different set of methods that had comparatively little rigorous grounding in physics---but within the last decade, advances in rendering methods and computing power have come together to create a sudden and dramatic shift, in which physics-based methods that were formerly thought impractical have become the standard tool. As a consequence, considerable attention is now devoted towards making these methods as robust as possible. In this context, robustness refers to an algorithm's ability to process arbitrary input without large increases of the rendering time or degradation of the output image. One particularly challenging aspect of robustness entails simulating the precise interaction of light with all the materials that comprise the input scene. This dissertation focuses on one specific group of materials that has fundamentally been the most important source of difficulties in this process. Specular materials, such as glass windows, mirrors or smooth coatings (e.g. on finished wood), account for a significant percentage of the objects that surround us every day. It is perhaps surprising, then, that it is not well-understood how they can be accommodated within the theoretical framework that underlies some of the most sophisticated rendering methods available today. Many of these methods operate using a theoretical framework known as path space integration. But this framework makes no provisions for specular materials: to date, it is not clear how to write down a path space integral involving something as simple as a piece of glass. Although implementations can in practice still render these materials by side-stepping limitations of the theory, they often suffer from unusably slow convergence; improvements to this situation have been hampered by the lack of a thorough theoretical understanding. We address these problems by developing a new theory of path-space light transport which, for the first time, cleanly incorporates specular scattering into the standard framework. Most of the results obtained in the analysis of the ideally smooth case can also be generalized to rendering of glossy materials and volumetric scattering so that this dissertation also provides a powerful new set of tools for dealing with them. The basis of our approach is that each specular material interaction locally collapses the dimension of the space of light paths so that all relevant paths lie on a submanifold of path space. We analyze the high-dimensional differential geometry of this submanifold and use the resulting information to construct an algorithm that is able to "walk" around on it using a simple and efficient equation-solving iteration. This manifold walking algorithm then constitutes the key operation of a new type of Markov Chain Monte Carlo (MCMC) rendering method that computes lighting through very general families of paths that can involve arbitrary combinations of specular, near-specular, glossy, and diffuse surface interactions as well as isotropic or highly anisotropic volume scattering. We demonstrate our implementation on a range of challenging scenes and evaluate it against previous methods.

Jakob, Wenzel Alban

396

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

397

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

398

Improving accuracy and precision in estimating fractal dimension of animal movement paths.  

PubMed

It is difficult to watch wild animals while they move, so often biologists analyse characteristics of animal movement paths. One common path characteristic used is tortuousity, measured using the fractal dimension (D). The typical method for estimating fractal D, the divider method, is biased and imprecise. The bias occurs because the path length is truncated. I present a method for minimising the truncation error. The imprecision occurs because sometimes the divider steps land inside the bends of curves, and sometimes they miss the curves. I present three methods for minimising this variation and test the methods with simulated correlated random walks. The traditional divider method significantly overestimates fractal D when paths are short and the range of spatial scales is narrow. The best method to overcome these problems consists of walking the dividers forwards and backwards along the path, and then estimating the path length remaining at the end of the last divider step. PMID:16823606

Nams, Vilis O

2006-01-01

399

Path Planning for UAVs Under Communication Constraints Using SPLAT! and MILP  

Microsoft Academic Search

We will in this paper address the problem of offline path planning for Unmanned Aerial Vehicles (UAVs). Our goal is to find\\u000a paths that meet mission objectives, are safe with respect to collision and grounding, fuel efficient and satisfy criteria\\u000a for communication. Due to the many nonconvex constraints of the problem, Mixed Integer Linear Programming (MILP) will be used\\u000a in

Esten Ingar Grtli; Tor Arne Johansen

400

Towards a nonperturbative path integral in gauge theories  

NASA Astrophysics Data System (ADS)

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.

Shabanov, Sergei V.; Klauder, John R.

1999-06-01

401

Feedback path variability modeling for robust hearing aids.  

PubMed

Acoustic feedback is a common problem in hearing aids with vented earmolds. Hearing aids designed to work under normal conditions become unstable when the feedback path varies under changing conditions. A comprehensive study of the variability of the feedback path under various conditions and for different users is presented in this paper. A multiplicative uncertainty bound widely used in H-infinity robust control is suggested to model the variations, which is then used to formulate a robust stability condition for the hearing aid. The upper limit of the closed-loop acoustic gain of the hearing aid for maintaining robust stability is also derived. Examples of robust constant amplification hearing aids, which maintain stability in the face of the given variations in the feedback path, are presented. The robust stability condition is also suggested as a tool to design more robust digital, hearing aids. PMID:10830388

Rafaely, B; Roccasalva-Firenze, M; Payne, E

2000-05-01

402

Economic Path Scheduling for Mobile Agent System on Computer Network  

NASA Astrophysics Data System (ADS)

Mobile agent technology has a lot of gains to offer network-centric applications. The technology promises to be very suitable for narrow-bandwidth networks by reducing network latency and allowing transparent per-to-per computing. Multi-agent technology had been proposed for many network-centric applications with little or no path scheduling algorithms. This paper describes the need for path scheduling algorithms for agents in multi-agent systems. Traveling salesman problem (TSP) scheme is used to model ordered agents and the unordered agents schedule their path based on random distribution. The two types of agents were modeled and simulated based on bandwidth usage and response time as performance metrics. Our simulation results shows that ordered agents have superior performance against unordered agents. The ordered agents exhibit lower bandwidth usage and higher response time.

Olajubu, E. A.

403

The career path choices of veterinary radiologists.  

PubMed

Concerns of a shortage of board certified specialists willing to work in academia have shadowed the medical and veterinary communities for decades. As a result, a number of studies have been conducted to determine how to foster, attract, and retain specialists in academia. More recently, there has been a growing perception that it is difficult for academic institutions to hire board certified veterinary radiologists. The objective of this study was to describe the career paths (academia vs. private sector) of veterinary radiologists and to determine what factors influenced their career path decisions. A mixed mode cross-sectional survey was used to survey ACVR radiologists and residents-in-training, 48% (255/529) of which responded. There was a near unidirectional movement of radiologists from academia to the private sector: 45.7% (59/129) of the respondents who began their careers in academia had switched to the private sector while only 8% (7/88) had left the private sector for academia. If a shortage of academic radiologists exists, then perhaps the issue should be framed as a problem with retention vs. recruitment. The most influential factors in the decision to leave academia were remuneration (wages and benefits), lack of interest/enjoyment in research, geographical location, and family considerations. It is salient that average salaries increased by twofold after leaving academia for the private sector. PMID:24920350

Jelinski, Murray D; Silver, Tawni I

2015-01-01

404

Algorithms for an Unmanned Vehicle Path Planning Problem  

E-print Network

deployed in military operations in Afghanistan in 2002. These robots have been used to detect and disarm explosive devices. It has also been used to collect air samples to detect chemical and radiological agents[10]. Like Packbots, many other UVs...

Qin, Jianglei

2013-06-25

405

Reversals of fortune: path dependency, problem solving, and temporal cases  

E-print Network

solving tells us to track actors pursuing customary goalsU.S. entered the war, to government awards. The customaryUS tax protest since the 1970s traces popular grievances back to the rationalizing reforms of local assessors, who began to withdraw customary

Haydu, Jeffrey

2010-01-01

406

Modelling dynamic programming problems by generalized d-graphs  

E-print Network

In this paper we introduce the concept of generalized d-graph (admitting cycles) as special dependency-graphs for modelling dynamic programming (DP) problems. We describe the d-graph versions of three famous single-source shortest algorithms (The algorithm based on the topological order of the vertices, Dijkstra algorithm and Bellman-Ford algorithm), which can be viewed as general DP strategies in the case of three different class of optimization problems. The new modelling method also makes possible to classify DP problems and the corresponding DP strategies in term of graph theory.

Ktai, Zoltn

2010-01-01

407

PATH DECOMPOSITION METHOD FOR POTENTIALS  

Microsoft Academic Search

We know all that thanks the development of the various formulations, moreover all equiva- lent, the physical phenomena explained by quantum mechanics are understood better. Among these formulations, we can quote most known because of its success: the formulation of Feyn- man (1) which uses the tool of the path integral. Not a long time ago, obtaining solutions for certain

A. Laissaoui; L. Chetouani

408

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

409

SSME propellant path leak detection  

NASA Technical Reports Server (NTRS)

The complicated high-pressure cycle of the space shuttle main engine (SSME) propellant path provides many opportunities for external propellant path leaks while the engine is running. This mode of engine failure may be detected and analyzed with sufficient speed to save critical engine test hardware from destruction. The leaks indicate hardware failures which will damage or destroy an engine if undetected; therefore, detection of both cryogenic and hot gas leaks is the objective of this investigation. The primary objective of this phase of the investigation is the experimental validation of techniques for detecting and analyzing propellant path external leaks which have a high probability of occurring on the SSME. The selection of candidate detection methods requires a good analytic model for leak plumes which would develop from external leaks and an understanding of radiation transfer through the leak plume. One advanced propellant path leak detection technique is obtained by using state-of-the-art technology infrared (IR) thermal imaging systems combined with computer, digital image processing, and expert systems for the engine protection. The feasibility of IR leak plume detection is evaluated on subscale simulated laboratory plumes to determine sensitivity, signal to noise, and general suitability for the application.

Crawford, Roger; Shohadaee, Ahmad Ali

1989-01-01

410

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...

411

Equivariant Localization of Path Integrals  

E-print Network

We review equivariant localization techniques for the evaluation of Feynman path integrals. We develop systematic geometric methods for studying the semi-classical properties of phase space path integrals for dynamical systems, emphasizing the relations with integrable and topological quantum field theories. Beginning with a detailed review of the relevant mathematical background -- equivariant cohomology and the Duistermaat-Heckman theorem, we demonstrate how the localization ideas are related to classical integrability and how they can be formally extended to derive explicit localization formulas for path integrals in special instances using BRST quantization techniques. Various loop space localizations are presented and related to notions in quantum integrability and topological field theory. We emphasize the common symmetries that such localizable models always possess and use these symmetries to discuss the range of applicability of the localization formulas. A number of physical and mathematical applications are presented in connection with elementary quantum mechanics, Morse theory, index theorems, character formulas for semi-simple Lie groups, quantization of spin systems, unitary integrations in matrix models, modular invariants of Riemann surfaces, supersymmetric quantum field theories, two-dimensional Yang-Mills theory, conformal field theory, cohomological field theories and the loop expansion in quantum field theory. Some modern techniques of path integral quantization, such as coherent state methods, are also discussed. The relations between equivariant localization and other ideas in topological field theory, such as the Batalin-Fradkin-Vilkovisky and Mathai-Quillen formalisms, are presented.

Richard J. Szabo

1996-08-12

412

Employer Resource Manual. Project Path.  

ERIC Educational Resources Information Center

Project Path at Illinois' College of DuPage was established to provide pre-employment training and career counseling for disabled students. To encourage the integration of qualified individuals with disabilities into the workplace, the project compiled this resource manual for area businesses, providing tips for interacting with disabled people

Kane, Karen R.; Del George, Eve

413

Perceived Shrinkage of Motion Paths  

ERIC Educational Resources Information Center

We show that human observers strongly underestimate a linear or circular trajectory that a luminous spot follows in the dark. At slow speeds, observers are relatively accurate, but, as the speed increases, the size of the path is progressively underestimated, by up to 35%. The underestimation imposes little memory load and does not require

Sinico, Michele; Parovel, Giulia; Casco, Clara; Anstis, Stuart

2009-01-01

414

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

E-print Network

was monitored during recovery from anaerobic, burst exercise in white and dark muscle, and in hemolymph4045 Muscle fibers typically fall within a size range of 10100m along the shortest axis (e from mitochondria to sites of ATP demand (Mainwood and Rakusan, 1982). However, some muscle fibers from

Kinsey, Stephen

415

IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 24, NO. 4, APRIL 2006 1 Traffic Grooming in Path, Star, and Tree Networks  

E-print Network

in Path, Star, and Tree Networks: Complexity, Bounds, and Algorithms Shu Huang, Rudra Dutta, and George N. Rouskas Abstract-- We consider the problem of traffic grooming in WDM path, star, and tree networks of results which settle the complexity of traffic grooming in path and star networks, by proving

Dutta, Rudra

416

Finding Out Critical Points For Real-Time Path Planning  

NASA Astrophysics Data System (ADS)

Path planning for a mobile robot is a classic topic, but the path planning under real-time environment is a different issue. The system sources including sampling time, processing time, processes communicating time, and memory space are very limited for this type of application. This paper presents a method which abstracts the world representation from the sensory data and makes the decision as to which point will be a potentially critical point to span the world map by using incomplete knowledge about physical world and heuristic rule. Without any previous knowledge or map of the workspace, the robot will determine the world map by roving through the workspace. The computational complexity for building and searching such a map is not more than O( n2 ) The find-path problem is well-known in robotics. Given an object with an initial location and orientation, a goal location and orientation, and a set of obstacles located in space, the problem is to find a continuous path for the object from the initial position to the goal position which avoids collisions with obstacles along the way. There are a lot of methods to find a collision-free path in given environment. Techniques for solving this problem can be classified into three approaches: 1) the configuration space approach [1],[2],[3] which represents the polygonal obstacles by vertices in a graph. The idea is to determine those parts of the free space which a reference point of the moving object can occupy without colliding with any obstacles. A path is then found for the reference point through this truly free space. Dealing with rotations turns out to be a major difficulty with the approach, requiring complex geometric algorithms which are computationally expensive. 2) the direct representation of the free space using basic shape primitives such as convex polygons [4] and overlapping generalized cones [5]. 3) the combination of technique 1 and 2 [6] by which the space is divided into the primary convex region, overlap region and obstacle region, then obstacle boundaries with attribute values are represented by the vertices of the hypergraph. The primary convex region and overlap region are represented by hyperedges, the centroids of overlap form the critical points. The difficulty is generating segment graph and estimating of minimum path width. The all techniques mentioned above need previous knowledge about the world to make path planning and the computational cost is not low. They are not available in an unknow and uncertain environment. Due to limited system resources such as CPU time, memory size and knowledge about the special application in an intelligent system (such as mobile robot), it is necessary to use algorithms that provide the good decision which is feasible with the available resources in real time rather than the best answer that could be achieved in unlimited time with unlimited resources. A real-time path planner should meet following requirements: - Quickly abstract the representation of the world from the sensory data without any previous knowledge about the robot environment. - Easily update the world model to spell out the global-path map and to reflect changes in the robot environment. - Must make a decision of where the robot must go and which direction the range sensor should point to in real time with limited resources. The method presented here assumes that the data from range sensors has been processed by signal process unite. The path planner will guide the scan of range sensor, find critical points, make decision where the robot should go and which point is poten- tial critical point, generate the path map and monitor the robot moves to the given point. The program runs recursively until the goal is reached or the whole workspace is roved through.

Chen, Wei

1989-03-01

417

Enzymatic reaction paths as determined by transition path sampling  

NASA Astrophysics Data System (ADS)

Enzymes are biological catalysts capable of enhancing the rates of chemical reactions by many orders of magnitude as compared to solution chemistry. Since the catalytic power of enzymes routinely exceeds that of the best artificial catalysts available, there is much interest in understanding the complete nature of chemical barrier crossing in enzymatic reactions. Two specific questions pertaining to the source of enzymatic rate enhancements are investigated in this work. The first is the issue of how fast protein motions of an enzyme contribute to chemical barrier crossing. Our group has previously identified sub-picosecond protein motions, termed promoting vibrations (PVs), that dynamically modulate chemical transformation in several enzymes. In the case of human heart lactate dehydrogenase (hhLDH), prior studies have shown that a specific axis of residues undergoes a compressional fluctuation towards the active site, decreasing a hydride and a proton donor--acceptor distance on a sub-picosecond timescale to promote particle transfer. To more thoroughly understand the contribution of this dynamic motion to the enzymatic reaction coordinate of hhLDH, we conducted transition path sampling (TPS) using four versions of the enzymatic system: a wild type enzyme with natural isotopic abundance; a heavy enzyme where all the carbons, nitrogens, and non-exchangeable hydrogens were replaced with heavy isotopes; and two versions of the enzyme with mutations in the axis of PV residues. We generated four separate ensembles of reaction paths and analyzed each in terms of the reaction mechanism, time of barrier crossing, dynamics of the PV, and residues involved in the enzymatic reaction coordinate. We found that heavy isotopic substitution of hhLDH altered the sub-picosecond dynamics of the PV, changed the favored reaction mechanism, dramatically increased the time of barrier crossing, but did not have an effect on the specific residues involved in the PV. In the mutant systems, we observed changes in the reaction mechanism and altered contributions of the mutated residues to the enzymatic reaction coordinate, but we did not detect a substantial change in the time of barrier crossing. These results confirm the importance of maintaining the dynamics and structural scaffolding of the hhLDH PV in order to facilitate facile barrier passage. We also utilized TPS to investigate the possible role of fast protein dynamics in the enzymatic reaction coordinate of human dihydrofolate reductase (hsDHFR). We found that sub-picosecond dynamics of hsDHFR do contribute to the reaction coordinate, whereas this is not the case in the E. coli version of the enzyme. This result indicates a shift in the DHFR family to a more dynamic version of catalysis. The second inquiry we addressed in this thesis regarding enzymatic barrier passage concerns the variability of paths through reactive phase space for a given enzymatic reaction. We further investigated the hhLDH-catalyzed reaction using a high-perturbation TPS algorithm. Though we saw that alternate reaction paths were possible, the dominant reaction path we observed corresponded to that previously elucidated in prior hhLDH TPS studies. Since the additional reaction paths we observed were likely high-energy, these results indicate that only the dominant reaction path contributes significantly to the overall reaction rate. In conclusion, we show that the enzymes hhLDH and hsDHFR exhibit paths through reactive phase space where fast protein motions are involved in the enzymatic reaction coordinate and exhibit a non-negligible contribution to chemical barrier crossing.

Masterson, Jean Emily

418

Assessing perceptions about hazardous substances (PATHS): the PATHS questionnaire.  

PubMed

How people perceive the nature of a hazardous substance may determine how they respond when potentially exposed to it. We tested a new Perceptions AbouT Hazardous Substances (PATHS) questionnaire. In Study 1 (N = 21), we assessed the face validity of items concerning perceptions about eight properties of a hazardous substance. In Study 2 (N = 2030), we tested the factor structure, reliability and validity of the PATHS questionnaire across four qualitatively different substances. In Study 3 (N = 760), we tested the impact of information provision on Perceptions AbouT Hazardous Substances scores. Our results showed that our eight measures demonstrated good reliability and validity when used for non-contagious hazards. PMID:23104995

Rubin, G James; Amlt, Richard; Page, Lisa; Pearce, Julia; Wessely, Simon

2013-08-01

419

Path-average kernels for long wavelength traveltime tomography  

NASA Astrophysics Data System (ADS)

Although much effort goes into improving the resolution of tomographic models, investigating their quality has only just started. Probabilistic tomography provides a framework for the quantitative assessment of uncertainties of long-wavelength tomographic models. So far, this technique has been used to invert maps of surface wave phase velocities and normal-mode splitting functions. Including body waves would substantially increase the depth resolution in the lowermost mantle. In surface wave tomography, the construction of phase velocity maps and splitting functions is a well-defined inverse problem, and the depth inversion is less well constrained but characterized by a small number of dimensions suitable for a Monte Carlo search. Traveltime tomography is mostly based on ray theory that covers the 3-D Earth, thus the dimension of the inverse problem is too large for a Monte Carlo search. The ray-mode duality suggests to apply the path-average approximation to body wave traveltimes. In this way the measured traveltime residual as a function of ray parameter can be inverted using path-average kernels, which depend on depth only, similar to surface wave tomography. We investigate the validity of the path-average approximation for delay times in both the forward and the inverse problem using the velocity model S20RTS as well as random models. We numerically illustrate the precision of such kernels compared with ray-theoretic and finite-frequency ones. We further invert traveltime residuals, calculated from Fermat rays, using the path-average kernels. We find that the agreement between classical ray theory and path-average theory is good for long wavelength structures. We suggest that for mapping long wavelength structures, body waves can be inverted in two steps, similar to surface waves, where the ray parameter and the vertical traveltime play the role of frequency and phase velocity, respectively.

Mosca, I.; Trampert, J.

2009-05-01

420

Robust Path Planning and Feedback Design Under Stochastic Uncertainty  

NASA Technical Reports Server (NTRS)

Autonomous vehicles require optimal path planning algorithms to achieve mission goals while avoiding obstacles and being robust to uncertainties. The uncertainties arise from exogenous disturbances, modeling errors, and sensor noise, which can be characterized via stochastic models. Previous work defined a notion of robustness in a stochastic setting by using the concept of chance constraints. This requires that mission constraint violation can occur with a probability less than a prescribed value.In this paper we describe a novel method for optimal chance constrained path planning with feedback design. The approach optimizes both the reference trajectory to be followed and the feedback controller used to reject uncertainty. Our method extends recent results in constrained control synthesis based on convex optimization to solve control problems with nonconvex constraints. This extension is essential for path planning problems, which inherently have nonconvex obstacle avoidance constraints. Unlike previous approaches to chance constrained path planning, the new approach optimizes the feedback gain as wellas the reference trajectory.The key idea is to couple a fast, nonconvex solver that does not take into account uncertainty, with existing robust approaches that apply only to convex feasible regions. By alternating between robust and nonrobust solutions, the new algorithm guarantees convergence to a global optimum. We apply the new method to an unmanned aircraft and show simulation results that demonstrate the efficacy of the approach.

Blackmore, Lars

2008-01-01

421

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

E-print Network

status play in shaping how people conceptualize water solutions? 3) What role does water scarcity play selected based on their diversity in development status and water scarcity (Figure 1) · Participants no path (2 = 5.19, p = 0.02, = 0.22). Water Scarcity · Respondents from water-scarce sites were found

Hall, Sharon J.

422

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

423

An Efficient Evolutionary Algorithm for the Degree-Constrained Minimum Spanning Tree Problem  

Microsoft Academic Search

The representation of candidate solutions and the variation operators are fundamental design choices in an evolutionary algorithm (EA). This paper proposes a novel representation technique and suitable variation operators for the degree-constrained minimum spanning tree problem. For a weighted, undirected graph G(V;E), this problem seeks to identify the shortest spanning tree whose node degrees do not exceed an upper bound

R. Raidl

2000-01-01

424

Working on interesting problems  

NASA Astrophysics Data System (ADS)

BSc Chemistry, The University of Sheffield 2001... PhD Astrochemistry, The University of Nottingham 2006... Scientist at GitHub Inc. 2013.From the outside, the path an individual has taken from academia to industry is not an obvious one. In this session I'll (try and) explain how an interest in software, engineering and chasing interesting problems makes internet startup in San Francisco a great home.

Smith, Arfon M.

2015-01-01

425

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.

426

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

427

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

428

Understanding Delay Variations on Internet Paths  

Microsoft Academic Search

In this paper we investigate the network factors that may affect the user perceived end-to-end delay jitter. In parti cular, we iden- tify the following three major factors: per hop queueing delay varia- tions along an Internet path; intra-domain multi-path routing; and inter- domain route (i.e., AS path) alterations. By studying traceroutedata collected on Internet paths, we find that 1)

Zhenhai Duan; Kuai Xu; Zhi-Li Zhang

429

Path entanglement of surface plasmons  

NASA Astrophysics Data System (ADS)

Metals can sustain traveling electromagnetic waves at their surfaces supported by the collective oscillations of their free electrons in unison. Remarkably, classical electromagnetism captures the essential physics of these surface plasma waves using simple models with only macroscopic features, accounting for microscopic electronelectron and electronphonon interactions with a single, semi-empirical damping parameter. Nevertheless, in quantum theory these microscopic interactions could be important, as any substantial environmental interactions could decohere quantum superpositions of surface plasmons, the quanta of these waves. Here we report a measurement of path entanglement between surface plasmons with 95% contrast, confirming that a path-entangled state can indeed survive without measurable decoherence. Our measurement suggests that elastic scattering mechanisms of the type that might cause pure dephasing in plasmonic systems must be weak enough not to significantly perturb the state of the metal under the experimental conditions we investigated.

Fakonas, James S.; Mitskovets, Anna; Atwater, Harry A.

2015-02-01

430

Path perception during rotation: influence of instructions, depth range, and dot density  

NASA Technical Reports Server (NTRS)

How do observers perceive their direction of self-motion when traveling on a straight path while their eyes are rotating? Our previous findings suggest that information from retinal flow and extra-retinal information about eye movements are each sufficient to solve this problem for both perception and active control of self-motion [Vision Res. 40 (2000) 3873; Psych. Sci. 13 (2002) 485]. In this paper, using displays depicting translation with simulated eye rotation, we investigated how task variables such as instructions, depth range, and dot density influenced the visual system's reliance on retinal vs. extra-retinal information for path perception during rotation. We found that path errors were small when observers expected to travel on a straight path or with neutral instructions, but errors increased markedly when observers expected to travel on a curved path. Increasing depth range or dot density did not improve path judgments. We conclude that the expectation of the shape of an upcoming path can influence the interpretation of the ambiguous retinal flow. A large depth range and dense motion parallax are not essential for accurate path perception during rotation, but reference objects and a large field of view appear to improve path judgments.

Li, Li; Warren, William H Jr

2004-01-01

431

Diffusion weighted imaging-based maximum density path analysis and classification of Alzheimer's disease.  

PubMed

Characterizing brain changes in Alzheimer's disease (AD) is important for patient prognosis and for assessing brain deterioration in clinical trials. In this diffusion weighted imaging study, we used a new fiber-tract modeling method to investigate white matter integrity in 50 elderly controls (CTL), 113 people with mild cognitive impairment, and 37 AD patients. After clustering tractography using a region-of-interest atlas, we used a shortest path graph search through each bundle's fiber density map to derive maximum density paths (MDPs), which we registered across subjects. We calculated the fractional anisotropy (FA) and mean diffusivity (MD) along all MDPs and found significant MD and FA differences between AD patients and CTL subjects, as well as MD differences between CTL and late mild cognitive impairment subjects. MD and FA were also associated with widely used clinical scores. As an MDP is a compact low-dimensional representation of white matter organization, we tested the utility of diffusion tensor imaging measures along these MDPs as features for support vector machine based classification of AD. PMID:25444597

Nir, Talia M; Villalon-Reina, Julio E; Prasad, Gautam; Jahanshad, Neda; Joshi, Shantanu H; Toga, Arthur W; Bernstein, Matt A; Jack, Clifford R; Weiner, Michael W; Thompson, Paul M

2015-01-01

432

Extracting contours of oval-shaped objects by Hough transform and minimal path algorithms  

NASA Astrophysics Data System (ADS)

Circular and oval-like objects are very common in cell and micro biology. These objects need to be analyzed, and to that end, digitized images from the microscope are used so as to come to an automated analysis pipeline. It is essential to detect all the objects in an image as well as to extract the exact contour of each individual object. In this manner it becomes possible to perform measurements on these objects, i.e. shape and texture features. Our measurement objective is achieved by probing contour detection through dynamic programming. In this paper we describe a method that uses Hough transform and two minimal path algorithms to detect contours of (ovoid-like) objects. These algorithms are based on an existing grey-weighted distance transform and a new algorithm to extract the circular shortest path in an image. The methods are tested on an artificial dataset of a 1000 images, with an F1-score of 0.972. In a case study with yeast cells, contours from our methods were compared with another solution using Pratt's figure of merit. Results indicate that our methods were more precise based on a comparison with a ground-truth dataset. As far as yeast cells are concerned, the segmentation and measurement results enable, in future work, to retrieve information from different developmental stages of the cell using complex features.

Tleis, Mohamed; Verbeek, Fons J.

2014-04-01

433

Squeezed states and path integrals  

NASA Technical Reports Server (NTRS)

The continuous-time regularization scheme for defining phase-space path integrals is briefly reviewed as a method to define a quantization procedure that is completely covariant under all smooth canonical coordinate transformations. As an illustration of this method, a limited set of transformations is discussed that have an image in the set of the usual squeezed states. It is noteworthy that even this limited set of transformations offers new possibilities for stationary phase approximations to quantum mechanical propagators.

Daubechies, Ingrid; Klauder, John R.

1992-01-01

434

Path Integrals and Coherent States  

E-print Network

propagator, on the other hand, is ^ / ( ) iHT U T e- = ^( ) 1 /U iH = - Motivations for a path integral evolutions as a composition of infinitesimal evolutions. ^( ) 1 /U iH = - #12;DIRAC: is there a Lagrangian ''| | ' | | | | | | N iHT iH iH N N N N iH N N i q e q q e q q e q q e q dq dq dq

de Aguiar, Marcus A. M.

435

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

436

Path integral Monte Carlo and the electron gas  

NASA Astrophysics Data System (ADS)

Path integral Monte Carlo is a proven method for accurately simulating quantum mechanical systems at finite-temperature. By stochastically sampling Feynman's path integral representation of the quantum many-body density matrix, path integral Monte Carlo includes non-perturbative effects like thermal fluctuations and particle correlations in a natural way. Over the past 30 years, path integral Monte Carlo has been successfully employed to study the low density electron gas, high-pressure hydrogen, and superfluid helium. For systems where the role of Fermi statistics is important, however, traditional path integral Monte Carlo simulations have an exponentially decreasing efficiency with decreased temperature and increased system size. In this thesis, we work towards improving this efficiency, both through approximate and exact methods, as specifically applied to the homogeneous electron gas. We begin with a brief overview of the current state of atomic simulations at finite-temperature before we delve into a pedagogical review of the path integral Monte Carlo method. We then spend some time discussing the one major issue preventing exact simulation of Fermi systems, the sign problem. Afterwards, we introduce a way to circumvent the sign problem in PIMC simulations through a fixed-node constraint. We then apply this method to the homogeneous electron gas at a large swatch of densities and temperatures in order to map out the warm-dense matter regime. The electron gas can be a representative model for a host of real systems, from simple medals to stellar interiors. However, its most common use is as input into density functional theory. To this end, we aim to build an accurate representation of the electron gas from the ground state to the classical limit and examine its use in finite-temperature density functional formulations. The latter half of this thesis focuses on possible routes beyond the fixed-node approximation. As a first step, we utilize the variational principle inherent in the path integral Monte Carlo method to optimize the nodal surface. By using a ansatz resembling a free particle density matrix, we make a unique connection between a nodal effective mass and the traditional effective mass of many-body quantum theory. We then propose and test several alternate nodal ansatzes and apply them to single atomic systems. Finally, we propose a method to tackle the sign problem head on, by leveraging the relatively simple structure of permutation space. Using this method, we find we can perform exact simulations this of the electron gas and 3He that were previously impossible.

Brown, Ethan W.

437

CALIFORNIA PATH PROGRAM INSTITUTE OF TRANSPORTATION STUDIES  

E-print Network

CALIFORNIA PATH PROGRAM INSTITUTE OF TRANSPORTATION STUDIES UNIVERFITY OF CALIFORNIA, BERKELEY Agogino, Kai Goebel SatnamAlag University of California,Berkeley CaliforniaPATH Research Report UCB-ITS-PRR-97-31 This work was performed as part of the CaliforniaPATH Program of the University of California

Agogino, Alice M.

438

Quantifying the Causes of Path Inflation  

Microsoft Academic Search

Researchers have shown that the Internet exhibits path inflation - end-to-end paths can be significantly longer than necessary. We present a trace-driven study of 65 ISPs that characterizes the root causes of path inflation, namely topology and routing policy choices within an ISP, between pairs of ISPs, and across the global Inter- net. To do so, we develop and validate

Neil Spring; Ratul Mahajan; Thomas Anderson

2003-01-01

439

Chip layout optimization using critical path weighting  

Microsoft Academic Search

A chip layout procedure for optimizing the performance of critical timing paths in a synchronous digital circuit is presented. The procedure uses the path analysis data produced by a static timing analysis program to generate weights for critical nets on clock and data paths. These weights are then used to bias automatic placement and routing in the layout program. This

A. E. Dunlop; V. D. Agrawal; D. N. Deutsch; M. F. Jukl; P. Kozak; M. Wiesel

1984-01-01

440

Path optimization for oil probe  

NASA Astrophysics Data System (ADS)

We discuss a robust method for optimal oil probe path planning inspired by medical imaging. Horizontal wells require three-dimensional steering made possible by the rotary steerable capabilities of the system, which allows the hole to intersect multiple target shale gas zones. Horizontal "legs" can be over a mile long; the longer the exposure length, the more oil and natural gas is drained and the faster it can flow. More oil and natural gas can be produced with fewer wells and less surface disturbance. Horizontal drilling can help producers tap oil and natural gas deposits under surface areas where a vertical well cannot be drilled, such as under developed or environmentally sensitive areas. Drilling creates well paths which have multiple twists and turns to try to hit multiple accumulations from a single well location. Our algorithm can be used to augment current state of the art methods. Our goal is to obtain a 3D path with nodes describing the optimal route to the destination. This algorithm works with BIG data and saves cost in planning for probe insertion. Our solution may be able to help increase the energy extracted vs. input energy.

Smith, O'Neil; Rahmes, Mark; Blue, Mark; Peter, Adrian

2014-05-01

441

Accelerating cleanup: Paths to closure  

SciTech Connect

This document was previously referred to as the Draft 2006 Plan. As part of the DOE`s national strategy, the Richland Operations Office`s Paths to Closure summarizes an integrated path forward for environmental cleanup at the Hanford Site. The Hanford Site underwent a concerted effort between 1994 and 1996 to accelerate the cleanup of the Site. These efforts are reflected in the current Site Baseline. This document describes the current Site Baseline and suggests strategies for further improvements in scope, schedule and cost. The Environmental Management program decided to change the name of the draft strategy and the document describing it in response to a series of stakeholder concerns, including the practicality of achieving widespread cleanup by 2006. Also, EM was concerned that calling the document a plan could be misconstrued to be a proposal by DOE or a decision-making document. The change in name, however, does not diminish the 2006 vision. To that end, Paths to Closure retains a focus on 2006, which serves as a point in time around which objectives and goals are established.

Edwards, C.

1998-06-30

442

Preserving Topology Confidentiality in Inter-Domain Path Computation Using a Path-Key-Based Mechanism  

Microsoft Academic Search

Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering (TE) Label Switched Paths (LSPs) may be computed by Path Computation Elements (PCEs). Where the TE LSP crosses multiple domains, such as Autonomous Systems (ASes), the path may be computed by multiple PCEs that cooperate, with each responsible for computing a segment of the path. However, in some cases (e.g.,

A. Farrel

443

Limited path entanglement percolation in quantum complex networks  

E-print Network

We study entanglement distribution in quantum complex networks where nodes are connected by bipartite entangled states. These networks are characterized by a complex structure, which dramatically affects how information is transmitted through them. For pure quantum state links, quantum networks exhibit a remarkable feature absent in classical networks: it is possible to effectively rewire the network by performing local operations on the nodes. We propose a family of such quantum operations that decrease the entanglement percolation threshold of the network and increase the size of the giant connected component. We provide analytic results for complex networks with arbitrary (uncorrelated) degree distribution. These results are in good agreement with numerical simulations, which also show enhancement in correlated and real world networks. The proposed quantum preprocessing strategies are not robust in the presence of noise. However, even when the links consist of (noisy) mixed state links, one can send quantum information through a connecting path with a fidelity that decreases with the path length. In this noisy scenario, complex networks offer a clear advantage over regular lattices, namely the fact that two arbitrary nodes can be connected through a relatively small number of steps, known as the small world effect. We calculate the probability that two arbitrary nodes in the network can successfully communicate with a fidelity above a given threshold. This amounts to working out the classical problem of percolation with limited path length. We find that this probability can be significant even for paths limited to few connections, and that the results for standard (unlimited) percolation are soon recovered if the path length exceeds by a finite amount the average path length, which in complex networks generally scales logarithmically with the size of the network.

Mart Cuquet; John Calsamiglia

2010-11-25

444

Limited-path-length entanglement percolation in quantum complex networks  

SciTech Connect

We study entanglement distribution in quantum complex networks where nodes are connected by bipartite entangled states. These networks are characterized by a complex structure, which dramatically affects how information is transmitted through them. For pure quantum state links, quantum networks exhibit a remarkable feature absent in classical networks: it is possible to effectively rewire the network by performing local operations on the nodes. We propose a family of such quantum operations that decrease the entanglement percolation threshold of the network and increase the size of the giant connected component. We provide analytic results for complex networks with an arbitrary (uncorrelated) degree distribution. These results are in good agreement with numerical simulations, which also show enhancement in correlated and real-world networks. The proposed quantum preprocessing strategies are not robust in the presence of noise. However, even when the links consist of (noisy) mixed-state links, one can send quantum information through a connecting path with a fidelity that decreases with the path length. In this noisy scenario, complex networks offer a clear advantage over regular lattices, namely, the fact that two arbitrary nodes can be connected through a relatively small number of steps, known as the small-world effect. We calculate the probability that two arbitrary nodes in the network can successfully communicate with a fidelity above a given threshold. This amounts to working out the classical problem of percolation with a limited path length. We find that this probability can be significant even for paths limited to few connections and that the results for standard (unlimited) percolation are soon recovered if the path length exceeds by a finite amount the average path length, which in complex networks generally scales logarithmically with the size of the network.

Cuquet, Marti; Calsamiglia, John [Grup de Fisica Teorica: Informacio i Fenomens Quantics, Universitat Autonoma de Barcelona, E-08193 Bellaterra, Barcelona (Spain)

2011-03-15

445

V753 MON: A UNIQUE CLOSE BINARY JUST AFTER THE EVOLUTIONARY STAGE WITH THE SHORTEST PERIOD DURING MASS TRANSFER  

SciTech Connect

We discovered that the O-C curve of V753 Mon shows an upward parabolic change while undergoing a cyclic variation with a period of 13.5 yr. The upward parabolic change reveals a long-term period increase at a rate of P-dot = +7.8 x 10{sup -8} days yr{sup -1}. Photometric solutions determined using the Wilson-Devinney method confirm that V753 Mon is a semi-detached binary system where the slightly less massive, hotter component star is transferring mass to the more massive one. This is in agreement with the long-term increase of the orbital period. The increase of the orbital period, the mass ratio very close to unity, and the semi-detached configuration with a less massive lobe-filling component all suggest that V753 Mon is on a key evolutionary stage just after the evolutionary stage with the shortest period during mass transfer. The results in this paper will shed light on the formation of massive contact binaries and the evolution of binary stars. The cyclic oscillation in the O-C diagram indicates that V753 Mon may be a triple system containing an extremely cool stellar companion that may play an important role for the formation and evolution in the binary system.

Qian, S.-B.; Zhang, J.; Wang, J.-J.; Zhu, L.-Y.; Liu, L.; Zhao, E. G.; Li, L.-J.; He, J.-J., E-mail: qsb@ynao.ac.cn [Yunnan Observatories, Chinese Academy of Sciences (CAS), P.O. Box 110, 650011 Kunming (China)

2013-08-15

446

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

447

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

448

Path-Following Control of Wheeled Planetary Exploration Robots Moving on Deformable Rough Terrain  

PubMed Central

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

449

Counting Paths in VPA Is Complete for #NC1  

Microsoft Academic Search

\\u000a We give a #NC\\u000a 1 upper bound for the problem of counting accepting paths in any fixed visibly pushdown automaton. Our algorithm involves a\\u000a non-trivial adaptation of the arithmetic formula evaluation algorithm of Buss, Cook, Gupta, Ramachandran ([9]). We also show\\u000a that the problem is #NC\\u000a 1 hard. Our results show that the difference between #BWBP and #NC\\u000a 1 is

Andreas Krebs; Nutan Limaye; Meena Mahajan

2010-01-01

450

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

451

Characterizing the evolutionary path(s) to early Homo.  

PubMed

Numerous studies suggest that the transition from Australopithecus to Homo was characterized by evolutionary innovation, resulting in the emergence and coexistence of a diversity of forms. However, the evolutionary processes necessary to drive such a transition have not been examined. Here, we apply statistical tests developed from quantitative evolutionary theory to assess whether morphological differences among late australopith and early Homo species in Africa have been shaped by natural selection. Where selection is demonstrated, we identify aspects of morphology that were most likely under selective pressure, and determine the nature (type, rate) of that selection. Results demonstrate that selection must be invoked to explain an Au. africanus-Au. sediba-Homo transition, while transitions from late australopiths to various early Homo species that exclude Au. sediba can be achieved through drift alone. Rate tests indicate that selection is largely directional, acting to rapidly differentiate these taxa. Reconstructions of patterns of directional selection needed to drive the Au. africanus-Au. sediba-Homo transition suggest that selection would have affected all regions of the skull. These results may indicate that an evolutionary path to Homo without Au. sediba is the simpler path and/or provide evidence that this pathway involved more reliance on cultural adaptations to cope with environmental change. PMID:25470780

Schroeder, Lauren; Roseman, Charles C; Cheverud, James M; Ackermann, Rebecca R

2014-01-01

452

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

453

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.

454

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

455

Staff detection with stable paths.  

PubMed

The preservation of musical works produced in the past requires their digitalization and transformation into a machine-readable format. The processing of handwritten musical scores by computers remains far from ideal. One of the fundamental stages to carry out this task is the staff line detection. We investigate a general-purpose, knowledge-free method for the automatic detection of music staff lines based on a stable path approach. Lines affected by curvature, discontinuities, and inclination are robustly detected. Experimental results show that the proposed technique consistently outperforms well-established algorithms. PMID:19372615

Dos Santos Cardoso, Jaime; Capela, Artur; Rebelo, Ana; Guedes, Carlos; Pinto da Costa, Joaquim

2009-06-01

456

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

2012-07-02

457

Combining Collision Avoidance and Operator Workload Reduction with Cooperative Task Assignment and Path Planning  

Microsoft Academic Search

This paper develops a method of assignment and path allocation that incorporates a priori collision avoidance and operator workload reduction in assigning multiple tasks to cooperative unmanned aerial vehicles (UAV). The problem is posed as a combinatorial optimization problem. A branch and bound tree search algorithm is implemented for a satisficing solution using a cost function that integrates distance travelled,

Jeffery B. Saunders; Steven J. Rasmussen; Corey J. Schumacher

2007-01-01

458

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 Cuellar 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, Universit de

459

Trip matrix and path flow reconstruction and estimation based on plate scanning and link observations  

Microsoft Academic Search

This paper deals with the problem of trip matrix and path flow reconstruction and estimation based on plate scanning and link flow observations. To solve the problem, the following steps are used. First, the class F of feasible subsets of scanned links for single users is identified. Second, the conservation laws are stated in terms of flows associated with the

Enrique Castillo; Jos Mara Menndez; Pilar Jimnez

2008-01-01

460

The Path-of-Probability Algorithm for Steering and Feedback Control of Flexible Needles  

PubMed Central

In this paper we develop a new framework for path planning of flexible needles with bevel tips. Based on a stochastic model of needle steering, the probability density function for the needle tip pose is approximated as a Gaussian. The means and covariances are estimated using an error propagation algorithm which has second order accuracy. Then we adapt the path-of-probability (POP) algorithm to path planning of flexible needles with bevel tips. We demonstrate how our planning algorithm can be used for feedback control of flexible needles. We also derive a closed-form solution for the port placement problem for finding good insertion locations for flexible needles in the case when there are no obstacles. Furthermore, we propose a new method using reference splines with the POP algorithm to solve the path planning problem for flexible needles in more general cases that include obstacles. PMID:21151708

Park, Wooram; Wang, Yunfeng; Chirikjian, Gregory S.

2010-01-01

461

Substation automation problems and possibilities  

SciTech Connect

The evolutionary growth in the use and application of microprocessors in substations has brought the industry to the point of considering integrated substation protection, control, and monitoring systems. An integrated system holds the promise of greatly reducing the design, documentation, and implementation cost for the substation control, protection, and monitoring systems. This article examines the technical development path and the present implementation problems.

Smith, H.L.

1996-10-01

462

Transition paths of Met-enkephalin from Markov state modeling of a molecular dynamics trajectory.  

PubMed

Conformational states and their interconversion pathways of the zwitterionic form of the pentapeptide Met-enkephalin (MetEnk) are identified. An explicit solvent molecular dynamics (MD) trajectory is used to construct a Markov state model (MSM) based on dihedral space clustering of the trajectory, and transition path theory (TPT) is applied to identify pathways between open and closed conformers. In the MD trajectory, only four of the eight backbone dihedrals exhibit bistable behavior. Defining a conformer as the string XXXX with X = "+" or "-" denoting, respectively, positive or negative values of a given dihedral angle and obtaining the populations of these conformers shows that only four conformers are highly populated, implying a strong correlation among these dihedrals. Clustering in dihedral space to construct the MSM finds the same four bistable dihedral angles. These state populations are very similar to those found directly from the MD trajectory. TPT is used to obtain pathways, parametrized by committor values, in dihedral state space that are followed in transitioning from closed to open states. Pathway costs are estimated by introducing a kinetics-based procedure that orders pathways from least (shortest) to greater cost paths. The least costly pathways in dihedral space are found to only involve the same XXXX set of dihedral angles, and the conformers accessed in the closed to open transition pathways are identified. For these major pathways, a correlation between reaction path progress (committors) and the end-to-end distance is identified. A dihedral space principal component analysis of the MD trajectory shows that the first three modes capture most of the overall fluctuation, and pick out the same four dihedrals having essentially all the weight in those modes. A MSM based on root-mean-square backbone clustering was also carried out, with good agreement found with dihedral clustering for the static information, but with results that differ significantly for the pathway analysis. PMID:24571787

Banerjee, Rahul; Cukier, Robert I

2014-03-20

463

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

464

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

465

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

466

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

467

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

468

Preventive Intervention for School-Age Deaf Children: The PATHS Curriculum  

Microsoft Academic Search

This study examined the effectiveness of the PATHS (Pro- moting Alternative THinking Strategies) Curriculum on the social, cognitive, and behavioral status of elementary school- age deaf children. PATHS, a school-based preventive in- tervention model, was designed to improve children's self- control, emotional understanding, and problem-solving skills. The intervention field trial included a quasi-experime ntal, wait-list control design involving 57 children

Mark T. Greenberg

1998-01-01

469

PATH PLANNING FOR UNMANNED AERIAL VEHICLES IN UNCERTAIN AND ADVERSARIAL ENVIRONMENTS  

Microsoft Academic Search

Abstract One of the main objectives when,planning paths for unmanned,aerial vehicles in adversarial environments is to arrive at the given target, while maximizing,the safety of the vehicles. If one has perfect infor- mation of the threats that will be encountered, a safe path can always be constructed by solving an optimization problem. If there are un- certainties in the information,

Myungsoo Jun

470

Real-Time Generation of Collision-Free Paths for a Mobile Sphere  

Microsoft Academic Search

A novel and fast technique for solving the basic motion-planning problem is introduced. Obstacle avoidance is based on the computation of minimum translational distances that allows one to obtain collision-free intermediate configurations. When path planning is constrained to two degrees of freedom, Hough transform is applied to such configurations. After that, several collision-free paths are generating by joining different sets

Enrique J. Bernabeu; Josep Tornero

2000-01-01

471

Topological charge quantization via path integration: An application of the Kustaanheimo-Stiefel transformation  

SciTech Connect

The unified treatment of the Dirac monopole, the Schwinger monopole, and the Aharonov-Bahn problem by Barut and Wilson is revisited via a path integral approach. The Kustaanheimo-Stiefel transformation of space and time is utilized to calculate the path integral for a charged particle in the singular vector potential. In the process of dimensional reduction, a topological charge quantization rule is derived, which contains Dirac's quantization condition as a special case. 32 refs.

Inomata, A. (State Univ. of New York, Albany, NY (United States)); Junker, G. (Universitaet Erlangen-Nuernberg (Germany)); Wilson, R. (Univ. of Texas, San Antonio TX (United States))

1993-08-01

472

Overview of Constraint-Based Path Selection Algorithms for QoS Routing  

E-print Network

Overview of Constraint-Based Path Selection Algorithms for QoS Routing F.A. Kuipers, Delft at identifying a path that satises a set of quality-of- service (QoS) constraints. In general, this problem-service (QoS) based networking frameworks (e.g., IntServ, DiffServ, MPLS). One of the key issues in all

Kuipers, Fernando A.

473

Obstacle Avoidance and Path Planning Based on Flow Field for Biomimetic Robotic Fish  

Microsoft Academic Search

\\u000a This paper investigates the problem of obstacle avoidance and path planning for robotic fish. The swimming of the robot fish\\u000a to avoid some obstacles is viewed as potential flow around the obstacles. Then the streamlines from the robot position to\\u000a the target are chosen as the desired paths for the mobile robot to move to the destination. Since there are

Jinyan Shao; Guangming Xie; Weicun Zhang

2005-01-01

474

Open-Ended Math Problems  

NSDL National Science Digital Library

An eight-month slate of open-ended problems for middle school students to solve in preparation for standardized testing. The authors have composed and selected problems that lend themselves to multiple solution paths, and then organized them into three levels of difficulty and the five strands from the Philadelphia math standards: number theory; measurement; geometry; patterns, algebra, and functions; data, statistics, and probability. Possible answers and rubrics for assessment available.

Math Forum

2000-01-01

475

SSME propellant path leak detection  

NASA Technical Reports Server (NTRS)

The primary objective of this phase of the investigation is the experimental validation of techniques for detecting and analyzing propellant path external leaks which have a high probability of occurring on the SSME. The selection of candidate detection methods requires a good analytic model for leak plumes which would develop from external leaks and an understanding of radiation transfer through the leak plume. One advanced propellant path leak detection technique is obtained by using state-of-art technology of infrared (IR) thermal imaging systems combined with computer, digital image processing and expert systems for the engine protection. The feasibility of the IR leak plume detection will be evaluated on subscale simulated laboratory plumes to determine sensitivity, signal to noise, and general suitability for the application. The theoretical analysis was undertaken with the objective of developing and testing simple, easy-to-use models to predict the amount of radiation coming from a radiation source, background plate (BP), which can be absorbed, emitted and scattered by the gas leaks.

Crawford, Roger; Shohadaee, Ahmad Ali; Powers, W. T.

1995-01-01

476

Path brokering for end-host path selection: toward a path-centric billing method for a multipath internet  

Microsoft Academic Search

Endhost path selectionthe ability for endhosts to spec- ify the paths which their packets should traversehas been proposed as a promising means for meeting next-generation Internet goals such as high availability and application- tailored routing. However, current proposals have serious shortcomings. First, they typically allow only limited path selection; second, they generally do not provide a billing method by which

Akihiro Nakao

2008-01-01

477

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

478

Extracting Critical Path Graphs from MPI Applications  

SciTech Connect

The critical path is one of the fundamental runtime characteristics of a parallel program. It identifies the longest execution sequence without wait delays. In other words, the critical path is the global execution path that inflicts wait operations on other nodes without itself being stalled. Hence, it dictates the overall runtime and knowing it is important to understand an application's runtime and message behavior and to target optimizations. We have developed a toolset that identifies the critical path of MPI applications, extracts it, and then produces a graphical representation of the corresponding program execution graph to visualize it. To implement this, we intercept all MPI library calls, use the information to build the relevant subset of the execution graph, and then extract the critical path from there. We have applied our technique to several scientific benchmarks and successfully produced critical path diagrams for applications running on up to 128 processors.

Schulz, M

2005-07-27

479

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

480

Lemke paths and P-matrices  

SciTech Connect

One can define for an LCP (A, b) with artificial vector d, n internally vertex disjoint Lemke paths to solve the LCP, where A is an n {times} n matrix. The lengths of the set of Lemke paths are investigated in the case that A is a P-matrix. We introduce a class of matrices, the complete hidden Minkowski matrices, that guarantee a set of short Lemke paths.

Morris, W.

1994-12-31

481

On AS-level path inference  

Microsoft Academic Search

The ability to discover the AS-level path between two end-points is valuable for network diagnosis, performance optimization, and reliability enhancement. Virtually all existing techniques and tools for path discovery require direct access to the source. However, the uncooperative nature of the Internet makes it difficult to get direct access to any remote end-point. Path inference becomes challenging when we have

Zhuoqing Morley Mao; Lili Qiu; Jia Wang; Yin Zhang

2005-01-01

482

The calculation of ionospheric ray paths  

E-print Network

path calculation by calculating ray paths from a cosmic radio source to a satellite in orbit above the level of the ionosphere. Radiation of this type may be totally reflected by the ionosphere thus making reception on the earth impossible... ray paths with constant frequency and variable angle of propagation and range, parabolic ionosphere of electrons assumed, earth's magnetic field neglected 2- 1 The vertical and lateral deviations of a radio wave propagated in a plane ionosphere...

Koehler, Buford Ray

1967-01-01

483

Paths and stochastic order in open systems  

E-print Network

The principle of maximum irreversible is proved to be a consequence of a stochastic order of the paths inside the phase space; indeed, the system evolves on the greatest path in the stochastic order. The result obtained is that, at the stability, the entropy generation is maximum and, this maximum value is consequence of the stochastic order of the paths in the phase space, while, conversely, the stochastic order of the paths in the phase space is a consequence of the maximum of the entropy generation at the stability.

Umberto Lucia

2011-01-07

484

On Models of Nonlinear Evolution Paths in Adiabatic Quantum Algorithms  

NASA Astrophysics Data System (ADS)

In this paper, we study two different nonlinear interpolating paths in adiabatic evolution algorithms for solving a particular class of quantum search problems where both the initial and final Hamiltonian are one-dimensional projector Hamiltonians on the corresponding ground state. If the overlap between the initial state and final state of the quantum system is not equal to zero, both of these models can provide a constant time speedup over the usual adiabatic algorithms by increasing some another corresponding complexity". But when the initial state has a zero overlap with the solution state in the problem, the second model leads to an infinite time complexity of the algorithm for whatever interpolating functions being applied while the first one can still provide a constant running time. However, inspired by a related reference, a variant of the first model can be constructed which also fails for the problem when the overlap is exactly equal to zero if we want to make up the intrinsic" fault of the second model an increase in energy. Two concrete theorems are given to serve as explanations why neither of these two models can improve the usual adiabatic evolution algorithms for the phenomenon above. These just tell us what should be noted when using certain nonlinear evolution paths in adiabatic quantum algorithms for some special kind of problems.

Sun, Jie; Lu, Song-Feng; Samuel, L. Braunstein

2013-01-01

485

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

486

Vision-based path-planning in unstructured environments  

E-print Network

Abstract Autonomous driving in unstructed environments has attracted an unprecedented level of attention when the DARPA announced the Grand Challenge Competitions in 2004 and 2005. Autonomous driving involves (at least) three major subtasks: perception of the environment, path planning and subsequent vehicle control. Whereas the latter has proven a solved problem, the first two constituted, apart from hardware failures, the most prominent source of errors in both Grand Challenges. This paper presents a system for real-time feature detection and subsequent path planning based on multiple stereoscopic and monoscopic vision cues. The algorithm is, in principle, suitable for arbitrary environments as the features are not tailored to a particular application. A slightly modified version of the system described here has been succesfully used in the Qualifications and the Final Race of the Grand Challenge 2005 within the Desert Buckeyes autonomous vehicle. I.

Britta Hummel; Sren Kammel; Thao Dang; Christian Duchow; Christoph Stiller

487

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

488

Seismic ray Paths in Anisotropic Medium Based on Higher-Order Geometry  

NASA Astrophysics Data System (ADS)

In this study, a seismic ray path in an anisotropic medium is studied by differential geometric view point. In seismological studies, the seismic ray theory for high frequency wave is based on Fermat's principle that renders the traveltime minimum. Generally, a shortest ray path connected to two different points becomes a straight line. In other words, the ray propagates in Euclidean space. However, a real seismic ray path is not straight but curve in nature. This geometrically means that the ray path propagates through a crust as non- Euclidean space. Especially, when the seismic ray propagates through anisotropic medium, the ray velocity depends on both position and direction. Geometrically, this ray velocity in the non-Euclidean anisotropic medium is regarded as a Lagrangian in Finsler space. Hence, the seismic ray theory in the anisotropic medium can be studied based on Finsler space. The ray velocity in the anisotropic medium can be expressed by a special Finslerian metric function called mth root metric. Mathematically, this seismic Finsler space belongs to a higher-order space called Kawaguchi space. This implies that the Finslerian ray velocity can be expressed by a metric in Kawaguchi space. However, the relation between the Finslerian ray velocity and the metric in higher-order space has not been cleared yet. Therefore, it is shown that the Finslerian ray velocity can be derived from a metric in higher-order space. Next, specifically a wavefront of Finslerian ray velocity is investigated in two-dimensional horizontally uniform medium. The seismic ray paths are defined as the normal to the wavefronts, which are loci of points that undergo the same motion at a given instant. Geometrically, the seismic wavefront in anisotropic media can be viewed as the indicatrix of the Finsler geometry. For example, when the ray propagates the isotropic material, the indicatrices are spheres whose radii are velocities at any point. On the other hand, when the ray propagates the anisotropic material, the indicatrices are no longer spheres. Therefore, we can know anisotropy of material in crust from the shape of wavefront. Using a parameter m of Finsler metric, we classify the anisotropic envelopes of seismic wavefront. Finally, we estimate the m-value from the seismic observational data.

Yajima, T.; Nagahama, H.

2006-12-01

489

Balance Problems  

MedlinePLUS

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

490

Path planning for robotic truss assembly  

NASA Technical Reports Server (NTRS)

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.

1993-01-01

491

Vacuum stress and closed paths in rectangles, pistons and pistols  

NASA Astrophysics Data System (ADS)

Rectangular cavities are solvable models that nevertheless touch on many of the controversial or mysterious aspects of the vacuum energy of quantum fields. This paper is a thorough study of the two-dimensional scalar field in a rectangle by the method of images, or closed classical (or optical) paths, which is exact in this case. For each point r and each specularly reflecting path beginning and ending at r, we provide formulae for all components of the stress tensor T??(r), for all values of the curvature coupling constant ? and all values of an ultraviolet cutoff parameter. Arbitrary combinations of Dirichlet and Neumann conditions on the four sides can be treated. The total energy is also investigated, path by path. These results are used in an attempt to clarify the physical reality of the repulsive (outward) force on the sides of the box predicted by calculations that neglect both boundary divergences and the exterior of the box. Previous authors have studied 'piston' geometries that avoid these problems and have found the force to be attractive. We consider a 'pistol' geometry that comes closer to the original problem of a box with a movable lid. We find again an attractive force, although its origin and detailed behavior are somewhat different from the piston case. However, the pistol (and the piston) model can be criticized for extending idealized boundary conditions into short distances where they are physically implausible. Therefore, it is of interest to see whether leaving the ultraviolet cutoff finite yields results that are more plausible. We then find that the force depends strongly on a geometrical parameter; it can be made repulsive, but only by forcing that parameter into the regime where the model is least convincing physically.

Fulling, S. A.; Kaplan, L.; Kirsten, K.; Liu, Z. H.; Milton, K. A.

2009-04-01

492

Matching Based Augmentations for Approximating Connectivity Problems  

Microsoft Academic Search

We describe a very simple idea for designing approximation algorithms for connectivity problems: For a spanning tree problem, the idea is to start with the empty set of edges, and add matching paths between pairs of components in the current graph that have desirable properties in terms of the objective function of the spanning tree prob- lem being solved. Such

R. Ravi

2006-01-01

493

Microfluidics {sjauh, btzhang}@bi.snu.ac.kr  

E-print Network

Microfluidics {sjauh, btzhang}@bi.snu.ac.kr Solving Shortest Path Problems Using Microfluidics Sahng-Joon Auh and Byoung-Tak Zhang Biointelligence Lab, School of Computer Science and Engineering Seoul National University . microfluidics MEMS

494

Evolutionary dynamic optimization: A survey of the state of the art  

E-print Network

There are some open questions about performance measures in EDO. First ...... scheme for dynamic shortest path routing problems in mobile ad hoc net-. 1678 ... scheduling, in: M. E. Cohen, D. L. Hudson (Eds.), ISCA Eleventh Interna-. 1721.

2012-04-09

495

The Relationships between Problem Characteristics, Achievement-Related Behaviors, and Academic Achievement in Problem-Based Learning  

ERIC Educational Resources Information Center

This study investigated the influence of five problem characteristics on students' achievement-related classroom behaviors and academic achievement. Data from 5,949 polytechnic students in PBL curricula across 170 courses were analyzed by means of path analysis. The five problem characteristics were: (1) problem clarity, (2) problem familiarity,

Sockalingam, Nachamma; Rotgans, Jerome I.; Schmidt, Henk G.

2011-01-01

496

Collaborative path planning for a robotic wheelchair.  

PubMed

Generating a path to guide a wheelchair's motion faces two challenges. First, the path is located in the human environment and that is usually unstructured and dynamic. Thus, it is difficult to generate a reliable map and plan paths on it by artificial intelligence. Second, the wheelchair, whose task is to carry a human user, should move on a smooth and comfortable path adapted to the user's intentions. To meet these challenges, we propose that the human operator and the robot interact to create and gradually improve a guide path. This paper introduces design tools to enable an intuitive interaction, and reports experiments performed with healthy subjects in order to investigate this collaborative path learning strategy. We analyzed features of the optimal paths and user evaluation in representative conditions. This was complemented by a questionnaire filled out by the subjects after the experiments. The results demonstrate the effectiveness of this approach, and show the utility and complementarity of the tools to design ergonomic guide paths. PMID:19117192

Zeng, Qiang; Teo, Chee Leong; Rebsamen, Brice; Burdet, Etienne

2008-11-01

497

Career Path Guide for Adult Career Choices.  

ERIC Educational Resources Information Center

Intended for adults who are considering career choices or changes, this booklet provides opportunities for self-study and reflection in six career paths. The booklet begins with tips for long-term career survival and myths and realities of career planning. After a brief career survey, readers are introduced to six career paths: arts and

Case, Clydia

498

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.

The Concord Consortium

499

Plasma Facing Components (The Path to DEMO)  

E-print Network

Plasma Facing Components (The Path to DEMO) Michael Ulrickson Presented at FESAC Development Path metals ­ Helium gas is the prime candidate in the future · Heat sink designs ­ For water swirl tapes, hypervapotron, screw tube, ... are all well established ­ Porous metal heat sinks are in the initial stages

500

CALIFORNIA PATH PROGRAM INSTITUTE OF TRANSPORTATION STUDIES  

E-print Network

CALIFORNIA PATH PROGRAM INSTITUTE OF TRANSPORTATION STUDIES UNIVERSITY OF CALIFORNIA, BERKELEY This work was performed as part of the California PATH Program of the University of California, in cooperation with the State of California Business, Transportation, and Housing Agency, Department of Trans

Levinson, David M.