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1

Shortest path and Schramm-Loewner Evolution

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

Posé, N.; Schrenk, K. J.; Araújo, N. A. M.; Herrmann, H. J.

2014-01-01

2

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

3

Physarum can compute shortest paths.

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

4

Shortest viable path algorithm in multimodal networks

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

5

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

6

Floats, Integers, and Single Source Shortest Paths

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

7

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

8

Floats, Integers, and Single Source Shortest Paths

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

9

Balancing minimum spanning and shortest path trees

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

10

Shortest path in complete bipartite digraph problem and it applications

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

11

Shortest paths synthesis for a car-like robot

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

12

Balancing Minimum Spanning Trees and Shortest-Path Trees

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

13

Exact Geodesics and Shortest Paths on Polyhedral Surfaces

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

14

Using shortest path to discover criminal community

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

15

Balancing Minimum Spanning Trees and Shortest-Path Trees

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

16

Distributional properties of stochastic shortest paths for smuggled nuclear material

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

17

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

18

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

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

19

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

20

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

21

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

22

Balancing Minimum Spanning Trees and ShortestPath Trees

Balancing Minimum Spanning Trees and ShortestÂPath Trees Samir Khuller \\Lambda University and a minimum spanning tree. The algorithm provides a continuous tradeÂoff: 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

23

Modeling wildfire propagation with Delaunay triangulation and shortest path algorithms

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

24

Finding Shortest Path for Developed Cognitive Map Using Medial Axis

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

25

An improved Physarum polycephalum algorithm for the shortest path problem.

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

26

An Improved Physarum polycephalum Algorithm for the Shortest Path Problem

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

27

Multiple Object Tracking Using the Shortest Path Faster Association Algorithm

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

28

Shortest Path Queries in Digraphs of Small Treewidth

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

29

Parallel Shortest Path Algorithms for Solving Large-Scale Instances

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

30

ON THE ACCELERATION OF SHORTEST PATH CALCULATIONS IN TRANSPORTATION NETWORKS

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

31

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

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

32

A Graph Search Heuristic for Shortest Distance Paths

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

33

A Shortest Path Based Path Planning Algorithm for Nonholonomic Mobile Robots

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

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

35

A Bio-Inspired Method for the Constrained Shortest Path Problem

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

36

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

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

37

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

38

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

39

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

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

40

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

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

41

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

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

42

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

43

Shortest paths in the Tower of Hanoi graph and finite automata

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

44

Time depending shortest-path problems with applications to railway networks

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

45

Color texture classification using shortest paths in graphs.

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

46

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

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.

47

Trans-dichotomous Algorithms for Minimum Spanning Trees and Shortest Paths

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

48

Discrete Approximation to Continuous Anisotropic Shortest-Path Problem

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 JoÃ£o Hespanha INFORMS Meeting November 6, 2007 #12;start point ? Cost may depend on Â· duration of path Â· fuel consumed along path Â· probability of detection

Hespanha, JoÃ£o Pedro

49

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

50

Traffic Grooming Based on Shortest Path in Optical WDM Mesh Networks

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

51

Snell's law and light traveling along the shortest path

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

52

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

53

Shortest Paths in Digraphs of Small Part I: Sequential Algorithms

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

54

Geodesics and Shortest Paths Approach in Pedestrian Motions

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

55

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

56

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

57

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

58

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

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; László Lipták; Ke Qiu; Zhizhang Shen

2010-01-01

59

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

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, UniversitÃ© de

60

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

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

61

.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

62

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

63

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

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

64

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

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

65

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

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.

66

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

67

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

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

68

, 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

69

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

70

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

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

71

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

72

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

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

73

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?wiÈ©cimka, Pawe?

2015-03-01

74

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

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

75

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

76

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

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

77

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

78

Parsimonious path openings and closings.

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

79

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

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

80

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

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

81

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

82

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

83

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

84

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

85

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

86

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 a—model independent—efficient 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

Kröger, Martin

2005-06-01

87

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

88

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

]. 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

89

Efficient Processing of Which-Edge Questions on Shortest Path Queries

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.

90

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

91

On Shortest Random Walks under Adversarial Uncertainty

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

92

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

93

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

94

Paths and stochastic order in open systems

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

95

NASA Astrophysics Data System (ADS)

The eddy covariance method has become one of the most common methods for measuring evaporation and carbon dioxide fluxes as it makes direct measurements and can be used at different spatial scales. Eddy covariance measurement devices are divided into two different designs, designated open path and closed path depending on where the gas of interest is measured. There is currently no preferred eddy covariance design, with the decision on which design to use usually based on the local precipitation conditions and power availability. A recent long term field comparison by Haslwanter et al. (2009) found differences in the measured and corrected evaporation between the different designs, with the largest differences in the latent heat flux occurring during periods of above average meteorological conditions. All previous comparison studies have been performed using the LI-7500 OP analyser which must be placed a distance away from the closed path intake and the path of the sonic anemometer. This must be accounted for by including corrections for high frequency filtering and sensor heating. The objective of this study is to use the IRGASON open-path design from Campbell Scientific where the gas analyser and sonic anemometer will be directly aligned with the intake to a closed path sensor to compare the different sensor designs. The measurements will be performed at the HOAL catchment at Petzenkirchen, Austria, which is equipped with a weather and energy balance station as well as an extensive soil moisture network to measure evaporation. This project will perform a comparison between open path and closed path eddy covariance systems using a new integrated open path design. The measurements will then be used to study the differences between the corrections required for the different designs and the effects of meteorological variables on the measured latent heat fluxes to address the issue of open and closed path gas analyser comparisons.

Hogan, Patrick; Parajka, Juraj; Blöschl, Günter

2014-05-01

96

Completely automated open-path FT-IR spectrometry

Technology Transfer Automated Retrieval System (TEKTRAN)

Atmospheric analysis by open-path Fourier transform infrared (OP/FT-IR) spectrometry has been possible for over two decades but has not been widely used because of the limitations of the software of commercial instruments. In this paper, we describe the current state-of-the-art of the hardware and s...

97

An Open-path Laser Transmissometer for Atmospheric Extinction Measurements

A transmissometer is an optical instrument which measures transmitted intensity of monochromatic light over a fixed pathlength. Prototype of a simple laser transmissometer has been developed for transmission (or extinction) measurements through suspended absorbers and scatterers in the atmosphere over tens of meters. Instrument consists of a continuous green diode pumped solid state laser, transmission optics, photodiode detectors and A/D data acquisition components. A modulated laser beam is transmitted and subsequently reflected and returned to the unit by a retroreflecting mirror assembly placed several tens of meters away. Results from an open-path field measurement of the instrument are described.

Chandran, P. M. Satheesh; Krishnakumar, C. P.; Varma, Ravi [Department of Physics, National Institute of Technology Calicut, Calicut, Kerala 673 601 (India); Yuen, Wangki; Rood, Mark J. [Department of Civil and Environmental Engineering, University of Illinois Urbana-Champaign, Urbana (United States)

2011-10-20

98

Applicability of open-path monitors at Superfund sites

NASA Astrophysics Data System (ADS)

Air emissions from Superfund sites can potentially have a significant impact on air quality affecting the health and safety of surrounding populations. Although the air pathway is well understood, these air emissions may be difficult to characterize. Remote sensors or open path monitors (OPMs) can have useful applications in measuring site emissions of air toxic compounds during the Superfund process. The air monitoring needs for each step of the Superfund process are identified in this paper and OPMs are compared and contrasted with traditional point monitoring techniques. Example applications of OPMs to Superfund activities are presented. Desirable improvements in OPM technology are also discussed.

Padgett, Joseph; Pritchett, Thomas H.

1991-05-01

99

APPLYING OPEN-PATH OPTICAL SPECTROSCOPY TO HEAVY-DUTY DIESEL EMISSIONS

Non-dispersive infrared absorption has been used to measure gaseous emissions for both stationary and mobile sources. Fourier transform infrared spectroscopy has been used for stationary sources as both extractive and open-path methods. We have applied the open-path method for bo...

100

Scalable shortest paths browsing on land surface

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

101

Shortest-Path Kernels on Graphs

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

102

Optimal Distributed All Pairs Shortest Paths

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

103

Querying Approximate Shortest Paths in Anisotropic Regions

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

104

Querying Approximate Shortest Paths in Anisotropic Regions

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

105

Assessment of Hydrogen Sulfide Minimum Detection Limits of an Open Path Tunable Diode Laser

During June 2007, U.S. EPA conducted a feasibility study to determine whether the EPA OTM 10 measurement approach, also known as radial plume mapping (RPM), was feasible. A Boreal open-path tunable diode laser (OP-TDL) to collect path-integrated hydrogen sulfide measurements alon...

106

Chirped Laser Dispersion Spectroscopy for Remote Open-Path Trace-Gas Sensing

In this paper we present a prototype instrument for remote open-path detection of nitrous oxide. The sensor is based on a 4.53 ?m quantum cascade laser and uses the chirped laser dispersion spectroscopy (CLaDS) technique for molecular concentration measurements. To the best of our knowledge this is the first demonstration of open-path laser-based trace-gas detection using a molecular dispersion measurement. The prototype sensor achieves a detection limit down to the single-ppbv level and exhibits excellent stability and robustness. The instrument characterization, field deployment performance, and the advantages of applying dispersion sensing to sensitive trace-gas detection in a remote open-path configuration are presented. PMID:23443389

Nikodem, Michal; Wysocki, Gerard

2012-01-01

107

Technology Transfer Automated Retrieval System (TEKTRAN)

The automated quantification of three greenhouse gases, ammonia, methane and nitrous oxide, in the vicinity of a large dairy farm by open-path Fourier transform infrared (OP/FT-IR) spectrometry at intervals of 5 minutes is demonstrated. Spectral pretreatment, including the detection and correction ...

108

Technology Transfer Automated Retrieval System (TEKTRAN)

The U.S. EPA recently demonstrated the open-path optical remote sensing technology to identify hot spots and estimate mass flux of fugitive gases from closed landfill. The objective of this research is to validate this technology for estimating ammonia and methane emission from concentrated animal f...

109

We have performed a series of experiments to determine the tradeoff in detection sensitivity for implementing design features for an Open-Path Fourier Transform Infrared (OP-FTIR) chemical analyzer that would be quick to deploy under emergency response conditions. The fast-deplo...

110

OPEN PATH TUNABLE DIODE LASER ABSORPTION SPECTROSCOPY FOR ACQUISITION OF FUGITIVE EMISSION FLUX DATA

Air pollutant emission from unconfined sources is an increasingly important environmental issue. The U.S. EPA has developed a gorund-based optical remote sensing method that enables direct measurement of fugitive emission flux from large area sources. Open-path Fourier transfor...

111

Technology Transfer Automated Retrieval System (TEKTRAN)

Over 32,000 interferograms measured during open-path Fourier transform infrared (OP/FT-IR) measurements at dairy and hog farms were evaluated for anomalies. Five types of anomalies could be distinguished: a reduction in the interferogram intensity because of weather-related optical misalignment; an ...

112

Open-path atmospheric transmission for a diode-pumped cesium laser.

A tunable diode laser absorption spectroscopy device was developed to study atmospheric propagation for emerging high-energy laser weapons. The cesium diode-pumped alkali laser operates near 895 nm in the vicinity of several water-vapor absorption lines. Temperature, pressure, and water vapor concentration were determined for 150 m and 1 km open paths with statistical errors of ?0.2%. Comparison with meteorological instruments yields agreement for the 1 km path to within 0.6% for temperature, 3.7% for pressure, and 2.4% for concentration. PMID:23207380

Rice, Christopher A; Lott, Gordon E; Perram, Glen P

2012-12-01

113

A two-stage dilution system and an associated procedure to simultaneously calibrate both open-path (long-path) and conventional point air monitors have been used successfully during a comparison test study of open-path monitoring systems in Houston during August, 1 993. wo open-p...

114

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

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

115

Assessment of data intercomparability and data quality for multiple open-path FTIR systems

There exists little information concerning the quality of data generated from open-path Fourier transform infrared spectrometer (OP-FTIR) systems as applied to measuring toxic air pollutants. The U.S. Environmental Protection Agency, Region VII conducted a study designed to assess the intercomparability and data quality for several OP-FTIR systems. This paper describes the design of the study, presents the resulting data, and

Jody L. Hudson; M. J. Thomas; John R. Helvig; Billy J. Fairless; Ray E. Carter; Glen A. Marotz

1993-01-01

116

Linear approximation of shortest superstrings

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

117

Open-path millimeter-wave spectroscopy in the 225--315 GHz range

This paper discusses the development of an open-path millimeter-wave (mm-wave) spectroscopy system in the 225--315 GHz atmospheric window. The new system is primarily a monostatic swept-frequency radar consisting of a mm-wave sweeper, hot-electron-bolometer or Schottky detector, and trihedral reflector. The heart of the system is a Russian backward-wave oscillator (BWO) tube that is tunable over 225--350 GHz. A mm-wave sweeper has been built with the BWO tube to sweep the entire frequency range within 1 s. The chemical plume to be detected is situated between the transmitter/receiver and the reflector. Millimeter-wave absorption spectra of chemicals in the plume are determined by measuring swept-frequency radar signals with and without the plume in the beam path. Because of power supply noise and thermal instabilities within the BWO structure over time, the BWO frequencies fluctuate between sweeps and thus cause errors in baseline subtraction. To reduce this frequency-jitter problem, a quasi-optical Fabry-Perot cavity is used in conjunction with the radar for on-line calibration of sweep traces, allowing excellent baseline subtraction and signal averaging. Initial results of the new system are given for open-path detection of chemicals.

Gopalsami, N.; Bakhtiari, S.; Raptis, A.C. [Argonne National Lab., IL (United States). Energy Technology Div.

1996-10-01

118

Object location using path separators

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

119

Closed- and open-path methane gas analyzers are used in eddy covariance systems to compare three potential methane emitting ecosystems in the Sacramento-San Joaquin Delta (CA, USA): a rice field, a peatland pasture and a restored wetland. The study points out similarities and differences of the systems in field experiments and data processing. The closed-path system, despite a less intrusive placement with the sonic anemometer, required more care and power. In contrast, the open-path system appears more versatile for a remote and unattended experimental site. Overall, the two systems have comparable minimum detectable limits, but synchronization between wind speed and methane data, air density corrections and spectral losses have different impacts on the computed flux covariances. For the closed-path analyzer, air density effects are less important, but the synchronization and spectral losses may represent a problem when fluxes are small or when an undersized pump is used. For the open-path analyzer air density corrections are greater, due to spectroscopy effects and the classic Webb-Pearman-Leuning correction. Comparison between the 30-min fluxes reveals good agreement in terms of magnitudes between open-path and closed-path flux systems. However, the scatter is large, as consequence of the intensive data processing which both systems require. ?? 2011.

Detto, M.; Verfaillie, J.; Anderson, F.; Xu, L.; Baldocchi, D.

2011-01-01

120

NASA Astrophysics Data System (ADS)

Higher order factorization schemes are developed for path integral molecular dynamics in order to improve the convergence of estimators for physical observables as a function of the Trotter number. The methods are based on the Takahashi-Imada and Susuki decompositions of the Boltzmann operator. The methods introduced improve the averages of the estimators by using the classical forces needed to carry out the dynamics to construct a posteriori weighting factors for standard path integral molecular dynamics. The new approaches are straightforward to implement in existing path integral codes and carry no significant overhead. The Suzuki higher order factorization was also used to improve the end-to-end distance estimator in open path integral molecular dynamics. The new schemes are tested in various model systems, including an ab initio path integral molecular dynamics calculation on the hydrogen molecule and a quantum water model. The proposed algorithms have potential utility for reducing the cost of path integral molecular dynamics calculations of bulk systems.

Pérez, Alejandro; Tuckerman, Mark E.

2011-08-01

121

An open path, fast response infrared absorption gas analyzer for H2O and CO2

NASA Astrophysics Data System (ADS)

An open path infrared absorption based instrument for fast response measurements of H2O and CO2 fluctuations is described. This instrument performed reliably in several field experiments in both terrestrial and marine environments, on both fixed (tower) and mobile (boat, plane) flux platforms. Noise levels for H2O and CO2 concentrations were less than 10 mg/m3 and 300 ?g/m3, respectively for frequencies between 0.005 and 10 Hz. Drifts in instrument output, associated with changes in instrument temperature, are compensated for electronically.

Auble, David L.; Meyers, Tilden P.

1992-05-01

122

Open-path and extractive FT-IR environmental monitoring above and below the ground

To demonstrate the versatility of Fourier transform infrared (FT-IR) spectrometry, two site investigations are discussed. The first is the monitoring of emissions from active volcanoes. The second is the analysis of soil gases from a site that is currently under remediation for ground water and soil contamination. The monitoring performed at the volcanoes used open-path FT-IR methods and the monitoring at the remediation site used extractive FT-IR methods. Descriptions of the sampling systems employed and the missions monitored at these sites will be used to demonstrate the advantages and limitations of environmental monitoring using FT-IR spectrometry.

Fateley, W.G.; Hammaker, R.M. [Kansas State Univ., Manhattan, KS (United States). Dept. of Chemistry; Chaffin, C.T.; Marshall, T.L. [AeroSurvey, Inc., Manhattan, KS (United States)

1995-12-31

123

NASA Astrophysics Data System (ADS)

Open-path Fourier transform infrared (OP/FT-IR) spectrometry is susceptible to interferences, especially those due to atmospheric water and carbon dioxide. To overcome these interferences, multivariate techniques such as classical least squares (CLS) and partial least squares (PLS) regression are used. The CLS method is very sensitive to variations in the background and the presence of lines due to water and carbon dioxide in the spectrum, and usually requires calculations to be made over small spectral windows to minimize these effects. The windows are usually chosen by the user and can reflect the user's bias. We have used a heuristic program called a genetic algorithm to select spectral windows that are independent of user bias and often yield results 2-4 times better than the generally accepted method of spectral window selection. We have also investigated the use of spectral window selection by a genetic algorithm for PLS using much larger spectral windows and found it to be advantageous.

Berry, R. James; Griffiths, Peter R.

1998-06-01

124

NASA Astrophysics Data System (ADS)

Biogenic emissions from and dry deposition to terrestrial surfaces are important processes determining the trace gas composition of the atmosphere. We have developed an instrument for flux measurements of gases such as CH4, N2O, and O3 based on the eddy correlation technique which combines trace gas fluctuation measurements with simultaneous windfield measurements. The instrument combines a tunable diode laser infrared light source with an open-path multipass absorption cell in order to provide the fast time response (approximately equals 0.1 s) and short base pathlength (0.6 m) required for the eddy correlation method. Initial field tests using the instrument to measure methane emissions from a local wetland demonstrate the capability for high precision eddy correlation flux measurements.

Anderson, Stuart M.; Zahniser, Mark S.

1991-05-01

125

Open-path FT-IR spectrometry: is completely unattended operation feasible?

Most protocols used for open-path Fourier transform infrared spectrometry (OP/FT-IR) require that spectra be measured at a resolution of 1 cm(-1) and that the concentrations of the analytes be calculated by classical least squares regression (CLS). These specifications were largely developed for monitoring light molecules with easily resolvable rotational fine structure. For most volatile organic compounds in air, the rotational fine structure is not resolvable and better accuracy can be obtained when the spectrum is measured at lower resolution (typically 8 cm(-1)), provided that the algorithm used for quantification is partial least squares regression (PLS). By measuring the spectrum at low resolution, the need for a liquid-nitrogen-cooled mercury cadmium telluride detector is reduced and a pyroelectric detector operating at ambient temperature can be used instead. By using PLS rather than CLS, spectral features due to water vapor do not have to be compensated and a short-path background spectrum can be used, greatly simplifying field measurements. PMID:18968107

Griffiths, P R; Hart, B K; Yang, H; Berry, R J

2000-10-01

126

Technology Transfer Automated Retrieval System (TEKTRAN)

In this study, we evaluated the accuracies of two relatively new micrometeorological methods using open-path tunable diode laser absorption spectrometers: vertical radial plume mapping method (US EPA OTM-10) and the backward Lagragian stochastic method (Wintrax®). We have evaluated the accuracy of t...

127

Emissions of ammonia and methane from an anaerobic lagoon at a swine animal feeding operation were evaluated five times over a period of two years. The plane-integrated (PI) open-path Fourier transform infrared spectrometry (OP-FTIR) methodology was used to transect the plume at ...

128

NASA Astrophysics Data System (ADS)

A low-power mobile sensing platform has been developed with multiple open-path gas sensors to measure the ambient concentrations of greenhouse gases and air pollutants with high temporal and spatial resolutions over extensive spatial domains. The sensing system consists of four trace gas sensors including two custom quantum cascade laser-based open-path sensors and two LICOR open-path sensors to measure CO2, CO, CH4, N2O, NH3, and H2O mixing ratios simultaneously at 10 Hz. In addition, sensors for meteorological and geolocation data are incorporated into the system. The system is powered by car batteries with a low total power consumption (~200 W) and is easily transportable due to its low total mass (35 kg). Multiple measures have been taken to ensure robust performance of the custom, open-path sensors located on top of the vehicle where the optics are exposed to the harsh on-road environment. The mobile sensing system has been integrated and installed on top of common passenger vehicles and participated in extensive field campaigns (>400 h on-road time with >18,000 km total distance) in both the USA and China. The simultaneous detection of multiple trace gas species makes the mobile sensing platform a unique and powerful tool to identify and quantify different emission sources through mobile mapping.

Tao, Lei; Sun, Kang; Miller, David J.; Pan, Dan; Golston, Levi M.; Zondlo, Mark A.

2015-03-01

129

Classical molecular dynamics simulations are reported for the deazetisation and ring opening of meso-2,3-difluoro-2,3-dimethyldiazocyclopropane in three solvents: CHCl3, CHFClBr and CH3CH(OH)CF3 (TFIPA). The achiral reactant leads to enantiomeric allene products, and the question addressed in the study is whether either of the chiral, enantiomerically pure solvents can induce significant enantiomeric excess in the products. The direct dynamics calculations use an empirical valence bond potential for the solute, with empirical parameters optimised against M06-2X/cc-pVTZ density functional results. The results reveal that the exothermic N2 loss and ring opening promote transient strong solvent-solute interactions within the first ?100 fs of the reaction. Because of the bifurcating reaction path, these interactions occur at time when the "decision" about which enantiomer of the product to form has yet to be made (at least for many of the trajectories). Hence, it is possible in principle that the solvent could exert a larger-than-normal influence on the course of the reaction. In fact, the results reveal no such effect for CHFClBr but do predict that TFIPA should induce 15.2 ± 2.1% enantiomeric excess. This is roughly an order of magnitude larger than solvent-induced enantiomeric excesses found experimentally in reactions where the conversion of reactant(s) to enantiomeric products occur over separate transition states. PMID:25521804

Carpenter, Barry K; Harvey, Jeremy N; Glowacki, David R

2015-04-01

130

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

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

131

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

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.

132

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

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

133

Mapping Atmospheric Ammonia Emissions Using a Mobile Quantum Cascade Laser-based Open-path Sensor

NASA Astrophysics Data System (ADS)

Ammonia (NH3) is a key precursor to atmospheric fine particulate matter, with strong implications for regional air quality and global climate change. Despite the importance of atmospheric ammonia, its spatial/temporal variation is poorly characterized, and the knowledge of its sources, sinks, and transport is severely limited. Existing measurements suggest that traffic exhaust may provide significant amounts of ammonia in urban areas, which cause greater impacts on particulate matter formation and urban air quality. To capture the spatial and temporal variation of ammonia emissions, a portable, low power sensor with high time resolution is necessary. We have developed a portable open-path ammonia sensor with a detection limit of 0.5 ppbv ammonia for 1 s measurements. The sensor has a power consumption of about 60 W and is capable of running on a car battery continuously for 24 hours. An additional laser has been coupled to the sensor to yield concurrent N2O and CO measurements as tracers for determining various sources. The overall sensor prototype fits on a 60 cm × 20 cm aluminum breadboard. Roadside measurements indicated NH3/CO emission ratios of 4.1±5.4 ppbv/ppmv from a fleet of 320 vehicles, which agree with existing on-ramp measurements. Urban measurements in the Baltimore and Washington, DC metropolitan areas have shown significant ammonia mixing ratios concurrent with carbon monoxide levels from the morning and evening rush hours. On-road measurements of our open-path sensor have also been performed continuously from the Midwest to Princeton, NJ including urban areas such as Pittsburgh, tunnels, and relatively clean conditions. The emission ratios of ammonia against CO and/or CO2 help identify the sources and amounts of both urban and agricultural ammonia emissions. Preliminary data from both spatial mapping, monitoring, and vehicle exhaust measurements suggest that urban ammonia emissions from fossil fuel combustion are significant and may provide an unrecognized source in the atmospheric ammonia budget. Ongoing efforts include spatial mapping of ammonia and other tracers in the New York City and Philadelphia metropolitan areas. Further comparison with TES satellite ammonia retrieval will help to put the measurements into a larger geographical and temporal context.

Sun, K.; Tao, L.; Miller, D. J.; Khan, M. A.; Zondlo, M. A.

2012-12-01

134

The value of information in shortest path optimization/

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

135

Carpooling : the 2 Synchronization Points Shortest Paths Problem

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, UniversitÃ© de

136

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

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

137

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

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

138

Geometric Containers for Efficient Shortest-Path Computation

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.

139

Scaling inequalities for shortest paths in regular and invasion percolation.

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

140

Shortest Path Computation with No Information Leakage Kyriakos Mouratidis

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

141

Methodology for Augmenting Existing Paths with Additional Parallel Transects

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

Wilson, John E.

2013-09-30

142

NASA Astrophysics Data System (ADS)

The stable isotopes in atmospheric water vapor contain rich information on the hydrologic cycles and gaseous exchange processes between biosphere and atmosphere. About one-week field experiment was conducted to continuously measure the isotope composition of water vapor in ambient air using an open-path FTIR system. Mixing ratios of H2 16O and HD16O were measured simultaneously. Analysis of water vapor isotopes revealed that the variations of H2 16O and HD16O were highly related. Mixing ratios of both isotopes varied considerably on a daily timescale or between days, with no obvious diurnal cycle, whereas the deuterium isotopic [delta]D showed clear diel cycle. The results illustrated that the correlation between [delta]D and H2O mixing ratio was relatively weak, which was also demonstrated by the Keeling plot analysis with the whole data. Yet the further Keeling analysis on a daily timescale displayed more obvious linear relationship between [delta]D and the total H2O concentration. All daily isotopic values of evapotranspiration source were obtained, with the range between -113.93±10.25‰ and -245.63±17.61‰ over the observation period.

Wang, Wei; Liu, Wenqing; Zhang, Tianshu

2012-12-01

143

[Open-path online monitoring of ambient atmospheric CO2 based on laser absorption spectrum].

With the conjunction of tunable diode laser absorption spectroscopy technology (TDLAS) and the open long optical path technology, the system designing scheme of CO2 on-line monitoring based on near infrared tunable diode laser absorption spectroscopy technology was discussed in detail, and the instrument for large-range measurement was set up. By choosing the infrared absorption line of CO2 at 1.57 microm whose line strength is strong and suitable for measurement, the ambient atmospheric CO2 was measured continuously with a 30 s temporal resolution at an suburb site in the autumn of 2007. The diurnal atmospheric variations of CO2 and continuous monitoring results were presented. The results show that the variation in CO2 concentration has an obvious diurnal periodicity in suburb where the air is free of interference and contamination. The general characteristic of diurnal variation is that the concentration is low in the daytime and high at night, so it matches the photosynthesis trend. The instrument can detect gas concentration online with high resolution, high sensitivity, high precision, short response time and many other advantages, the monitoring requires no gas sampling, the calibration is easy, and the detection limit is about 4.2 x 10(-7). It has been proved that the system and measurement project are feasible, so it is an effective method for gas flux continuous online monitoring of large range in ecosystem based on TDLAS technology. PMID:19385195

He, Ying; Zhang, Yu-Jun; Kan, Rui-Feng; Xia, Hui; Geng, Hui; Ruan, Jun; Wang, Min; Cui, Xiao-Juan; Liu, Wen-Qing

2009-01-01

144

Use of an open-path FTIR sensor at Camacari Petrochemical Complex--Bahia, Brazil

NASA Astrophysics Data System (ADS)

CETREL--Empresa de Protecao Ambiental, is an environmental engineering company, which is owned by the member companies in the Camacari Petrochemical Complex, the largest petrochemical complex in Brazil. CETREL operates a centralized waste treatment plant, treatment and disposal facilities, an incineration unit, groundwater monitoring and air quality monitoring networks. The air monitoring network was designed based on mathematical modeling, and the results showed that the monoitoring of hydrocarbons is important not just within the complex but also at the area surrounding the complex. There are presently no regulations for hydrocarbons in Brazil, however they are monitored due to concerns about health problems arising from human exposure. The network has eight multiparameter monitoring stations, located at the villages nearby, where hydrocarbons are sampled with Summa canisters and subsequently analyzed with a GC/MS, using a Cryogenic trap at the interface. The open-path FTIR is used to monitor at the individual plants and in the areas in between because it is more efficient and costs less than it would to attempt to achieve the same level of coverage using the canisters. Ten locations were selected based on mathematical modeling and knowledge of the likely emission sources. Since August 1993, there have been five different measurement campaigns.

Neves, Neuza; Couto, Elizabeth d. R.; Kagann, Robert H.

1995-05-01

145

Open-path Fourier Transform Infrared Spectroscopy (OP-FTIR) was used to conduct an air monitoring survey at a Fourier manufactured gas plant (FMGP) superfund site. This survey was performed in support and at the request of the Waste Management Division, U.S. EPA, Region VII. A three day study was conducted in which the OP- FTIR instrument was operated at several fenceline locations

Michael F. Davis; Joseph Arello; John R. Helvig; Jody L. Hudson; Melissa D. Tucker; John M. Poholarz; Robert M. Hammaker; William G. Fateley

1995-01-01

146

Public confidence in safety is a prerequisite to the success of carbon dioxide (CO2) capture and storage for any program that intends to mitigate greenhouse gas emissions. In that regard, this project addresses the security of CO2 containment by undertaking development of what is called Ã?Â¢Ã?Â?Ã?Â?an open path deviceÃ?Â¢Ã?Â?Ã?Â to measure CO2 concentrations near the ground above a CO2 storage area.

Sheng Wu

2012-10-02

147

Comparison of eddy-covariance measurements of CO2 fluxes by open- and closed-path CO2 analysers

NASA Astrophysics Data System (ADS)

Eddy fluxes of CO2 estimated using a sonic anemometer and a closed-path analyser were, on average, 16% lower than those obtained with the same anemometer and an adjacent open-path CO2 analyser. Covariances between vertical windspeed and CO2 density from the closed-path analyser were calculated using data points for CO2 that were delayed relative to anemometer data by the time required for a parcel of air to travel from the tube inlet to the CO2 sensor. Air flow in the intake tube was laminar. Densities of CO2 that had been corrected for spurious fluctuations arising from fluctuations in temperature and humidity were used in the flux calculations. Corrections for the cross-sensitivity of CO2 analysers to water vapour were also incorporated. Spectral analysis of the corrected CO2 signal from the closed-path analyser showed that damping of fluctuations in the sampling tube at frequencies f > 0.1 Hz caused the apparent loss in flux. The measured losses can be predicted accurately using theory that describes the damping of oscillations in a sampling tube. High-frequency response of the closed-path system can be improved substantially by ensuring turbulent flow in the tube, using a combination of high volumetric flow rate and small tube diameter. The analysis of attenuation of turbulent fluctuations in flow through tubes is applicable to the measurement of fluxes of other minor atmospheric constituents using the eddy covariance method.

Leuning, R.; King, K. M.

1992-05-01

148

Finding Smallest Paths in Rectilinear Polygons on a Hypercube Multiprocessor

Finding Smallest Paths in Rectilinear Polygons on a Hypercube Multiprocessor Afonso Ferreira techniques for designing geometric algorithms for the (sharedÂmemory) 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"

149

On-road ammonia emissions characterized by mobile, open-path measurements.

Ammonia (NH3) is a key precursor species to atmospheric fine particulate matter with strong implications for regional air quality and global climate change. NH3 from vehicles accounts for a significant fraction of total emissions of NH3 in urban areas. A mobile platform is developed to measure NH3, CO, and CO2 from the top of a passenger car. The mobile platform conducted 87 h of on-road measurements, covering 4500 km in New Jersey and California. The average on-road emission factor (EF) in CA is 0.49 ± 0.06 g NH3 per kg fuel and agrees with previous studies in CA (0.3-0.8 g/kg). The mean on-road NH3:CO emission ratio is 0.029 ± 0.005, and there is no systematic difference between NJ and CA. On-road NH3 EFs increase with road gradient by an enhancement of 53 mg/kg fuel per percentage of gradient. On-road NH3 EFs show higher values in both stop-and-go driving conditions and freeway speeds with a minimum near 70 km/h. Consistent with prior studies, the on-road emission ratios suggest a highly skewed distribution of NH3 emitters. Comparisons with existing NJ and CA on-road emission inventories indicate that there may be an underestimation of on-road NH3 emissions in both NJ and CA. We demonstrate that mobile, open-path measurements provide a unique tool to help quantitatively understand the on-road NH3 emissions in urban and suburban settings. PMID:24517544

Sun, Kang; Tao, Lei; Miller, David J; Khan, M Amir; Zondlo, Mark A

2014-04-01

150

Open-path FTIR spectroscopy of magma degassing processes during eight lava fountains on Mount Etna

NASA Astrophysics Data System (ADS)

In June-July 2001 a series of 16 discrete lava fountain paroxysms occurred at the Southeast summit crater (SEC) of Mount Etna, preceding a 28-day long violent flank eruption. Each paroxysm was preceded by lava effusion, growing seismic tremor and a crescendo of Strombolian explosive activity culminating into powerful lava fountaining up to 500 m in height. During 8 of these 16 events we could measure the chemical composition of the magmatic gas phase (H2O, CO2, SO2, HCl, HF and CO), using open-path Fourier transform infrared (OP-FTIR) spectrometry at ?1-2 km distance from SEC and absorption spectra of the radiation emitted by hot lava fragments. We show that each fountaining episode was characterized by increasingly CO2-rich gas release, with CO2/SO2 and CO2/HCl ratios peaking in coincidence with maxima in seismic tremor and fountain height, whilst the SO2/HCl ratio showed a weak inverse relationship with respect to eruption intensity. Moreover, peak values in both CO2/SO2 ratio and seismic tremor amplitude for each paroxysm were found to increase linearly in proportion with the repose interval (2-6 days) between lava fountains. These observations, together with a model of volatile degassing at Etna, support the following driving process. Prior to and during the June-July 2001 lava fountain sequence, the shallow (?2 km) magma reservoir feeding SEC received an increasing influx of deeply derived carbon dioxide, likely promoted by the deep ascent of volatile-rich primitive basalt that produced the subsequent flank eruption. This CO2-rich gas supply led to gas accumulation and overpressure in SEC reservoir, generating a bubble foam layer whose periodical collapse powered the successive fountaining events. The anti-correlation between SO2/HCl and eruption intensity is best explained by enhanced syn-eruptive degassing of chlorine from finer particles produced during more intense magma fragmentation.

La Spina, Alessandro; Burton, Mike; Allard, Patrick; Alparone, Salvatore; Muré, Filippo

2015-03-01

151

Open-path Fourier transform infrared (OP/FT-IR) spectrometry was used to measure the concentrations of ammonia, methane, and other atmospheric eases at a concentrated swine production facility. A total of 2200 OP/FT-IR spectra were acquired along nine different monitoring paths d...

152

We propose a scheme to generate hybrid Greenberger-Horne-Zeilinger (GHZ) entanglement where multiple photons are entangled in different degrees of freedom of spin, orbital angular momentum (OAM), and path (linear momentum). The generation involves mapping the preliminary OAM entanglement of photon pairs onto their spin-orbit and spin-path degrees of freedom, respectively. Based on the hybrid GHZ entanglement, we demonstrate an open-destination teleportation with multiples degrees of freedom, via which a spin state of a single photon is teleported onto a superposition of multiple photons with the postselection technique and the original information could be read out at any photon in individual spin, OAM, or the linear-momentum state. Our scheme holds promise for asymmetric optical quantum network.

Chen Lixiang [Department of Physics, Xiamen University, Xiamen 361005 (China); State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275 (China); She Weilong [State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275 (China)

2011-03-15

153

NASA Astrophysics Data System (ADS)

Optical soundings of i.c. engines' exhaust and urban atmosphere have been carried out, using an Open-Path UV Spectrophotometer, based on a Laser-Produced Plasma as the light source. The measured optical depths are numerically inverted in terms of known species, by means of the Non-negative Least-Squares (NLS) algorithm. Concentrations of major UV-absorbing species are evaluated at the tailpipe of in-use vehicles (NO, NO2, EC) and in urban atmosphere over a 200m-long optical path (O2, O3. NO2, EC, nitrates). Also, we report on the detection in both environments of an additional compound, the nanometric organic carbon (NOC), known to form in fuel-rich flames, which is not considered yet in ordinary emissions inventories. Also, the problem of dilution/dispersion of primary species is addressed, by tracking the combustion-formed CO2 at the tailpipe and in urban atmosphere.

Borghese, Antonio; Speranza, Luciano

2009-08-01

154

Shortest Expected Delay Routing for Erlang Servers

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

155

The ability of an open-path, fourier-transform infrared spectrometer to detect vehicle exhaust emissions approximately 3 meters above the roadway surface at a busy Albuquerque suburban intersection was evaluated in this study. Multiple measurements of carbon monoxide and carbon dioxide were carried out over pathlengths up to 100 meters during the morning commute period on multiple days in the summer of 1993. The carbon monoxide to fuel carbon ratio was computed from all spectral data in order to derive a vehicle fleet average ratio. The data were determined to be normally distributed with an overall carbon monoxide-fuel carbon ratio of 0.15. The 95% confidence interval about the mean was {+-} 0.009. Day-to-day variation of the mean ratio was determined to be on the order of 3%. The results indicate that anticipated reductions in carbon monoxide emissions following the implementation of a winter-season oxygenated fuel program could be reliably detected with an open-path fourier transform spectrometer. The periodic use of such an instrument may offer a cost-effective means of generating a city-wide carbon monoxide emission budget for vehicles sources.

Einfield, W. [Sandia National Labs., Albuquerque, NM (United States). Environmental Characterization and Monitoring Dept.

1997-05-01

156

The development of spectroscopic techniques has offered continuous measurement of stable isotopes in the ambient air. The method of measuring environmental stable isotopes based on Fourier transform infrared spectrometry (FTIR) is described. In order to verify the feasibility of the method for continuous measurement of the stable isotopes, an open-path FTIR system was used to measure stable isotopes of CO2 and H2O in ambient air directly in a seven-day field experiment, including 12CO2, 3CO2, H2 16O and HD16 O. Also, the time course of carbon isotopic ratio delta13 C and deuterium isotope composition deltaD was calculated. The measurement precision is about 1.08 per thousand for delta13 C and 1.32 per thousand for deltaD. The measured stable isotopes of CO2 and H2O were analyzed on different time scales by Keeling plot methods, and the deuterium isotopic ratios of evapotranspiration were determined. The results of the field experiment demonstrate the potential of the open-path FTIR system for continuous measurement of stable isotopes in the air. PMID:24159837

Wang, Wei; Liu, Wen-Qing; Zhang, Tian-Shu

2013-08-01

157

Water vapor absorption, which exists in mid-infrared region, is an interferential element for infrared spectra analysis. A new method, which can be used to eliminate the water vapor interference in FTIR measurement, is presented. To calculate the high resolution absorbance of water vapor, a fast line by line method which computed with the HITRAN database (eg. line strength, self broadening, air broadening, etc) and meteorological parameters (eg. temperature, pressure, and relative humidity) was used. After convolving with Instrumental line shape (eg. divergence angle, resolution, etc), the absorbance of water vapor was then transferred from high resolution to low resolution, which matched the instrumental parameters. After the acquirement of water vapor absorbance spectrum, it will be subtracted from the measured spectrum to calculate the spectrum with the water vapor was eliminated. In the present work, analysis of measured data from open path FTIR is described. Only the absorbing character and noise was left in the spectrum after eliminating the water vapor interference. Consequently, this method has an ideal effect on water vapor elimination when there is no dryer can be used, especially in the case of open path FTIR measurement. PMID:18720800

Xu, Liang; Liu, Jian-Guo; Gao, Min-Guang; Lu, Yi-Huai; Liu, Wen-Qing; Wei, Xiu-Li; Zhang, Tian-Shu; Chen, Hua; Liu, Zhi-Ming

2008-05-01

158

NASA Astrophysics Data System (ADS)

An open-path cavity ring down spectroscopy (CRDS) instrument for measurement of atmospheric iodine monoxide (IO) radicals has been tested in the laboratory and subsequently deployed in Roscoff as part of the Reactive Halogens in the Marine Boundary Layer (RHaMBLe) project in September 2006. In situ measurements are reported of local IO mixing ratios in the marine boundary layer. The absorption cross section at the bandhead of the IO A^2?_{3/2} - X^2?_{3/2} (3,0) vibronic band was used to obtain the mixing ratios of atmospheric IO. The mixing ratios of IO were obtained on two days, peaked close to low tide, and were 5 - 10 times higher than values calculated from column densities previously reported by long-path, differential optical absorption spectroscopy (DOAS) in coastal regions. The typical detection limit of the instrument was estimated to be 10 pptv of IO with the total accumulation time of 30 s. The observations of relatively high concentration, compared to the values previously reported by DOAS, are consistent with the concurrent observations using a LIF (Laser induced Fluorescence) instrument. The observed IO mixing ratios fluctuated, in part, because the open-path configurations had disadvantages that included perturbation of ring-down measurements by air currents and light scattering caused by aerosols. However these problems were more than amply compensated for by elimination of unknown sampling losses. The contribution of aerosol particles to the obtained IO mixing ratios will be discussed at the meeting. R. Wada, J. M. Beames and A. J. Orr-Ewing J. Atoms. Chem. 58, 69, 2007. L. K. Whalley, K. L. Furneaux, T. Gravestock, H. M. Atkinson, C. S. E. Bale, T. Ingham, W. J. Bloss and D. E. Heard J. Atoms. Chem. 58, 19, 2007.

Wada, Ryuichi; Beames, Joseph M.; Orr-Ewing, Andrew J.

2009-06-01

159

for weighted timed automata to a parametric shortestÂpath problem in directed graphs. We give a fixÂpoinOptimal 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) shortestÂpath problem in a finite directed graph

Alur, Rajeev

160

Walking the Walk: A Path to Support Open Access Publishing [Poster

Scholarly communication is the lifeblood of universities. Threats to the free flow of research and ideas continue to jeopardize the entire academy; however administrators, scholars, and librarians are now pursuing options to reclaim research produced in the academy's domain. One way to do this is with Open Access. Open Access has been a topic of interest and intense depabe for

Linda L. Phillips; Donna Braquet

2009-01-01

161

Many-body Propagator Theory with Three-Body Interactions: a Path to Exotic Open Shell Isotopes

Ab-initio predictions of nuclei with masses up to A~100 or more is becoming possible thanks to novel advances in computations and in the formalism of many-body physics. Some of the most fundamental issues include how to deal with many-nucleon interactions, how to calculate degenerate--open shell--systems, and pursuing ab-initio approaches to reaction theory. Self-consistent Green's function (SCGF) theory is a natural approach to address these challenges. Its formalism has recently been extended to three- and many-body interactions and reformulated within the Gorkov framework to reach semi-magic open shell isotopes. These exciting developments, together with the predictive power of chiral nuclear Hamiltonians, are opening the path to understanding large portions of the nuclear chart, especially within the $sd$ and $pf$ shells. The present talk reviews the most recent advances in ab-initio nuclear structure and many-body theory that have been possible through the SCGF approach.

C. Barbieri

2014-06-11

162

Water vapor, cloud liquid water paths, and rain rates over northern high latitude open seas

NASA Astrophysics Data System (ADS)

Data from the Special Sensor Microwave Imager (SSMI; years 1987-2006), Advanced Microwave Scanning Radiometer, and a surface-based radiometer at Barrow, Alaska are examined for insights into the behavior of water vapor, cloud liquid water and rainrates over the northern high latitude seas. We evaluated two separate sets of retrievals, and achieved the best results through combining one that contained explicit monthly mean sea ice fractions with the Wentz V6 water vapor path (WVP), cloud liquid water path (LWP), and rainrate (RR) retrievals. The water vapor path retrieval shows no sensitivity to a proxy for sub-pixel sea ice presence, while the liquid water path retrievals are sensitive to sea ice presence during summertime but otherwise the Wentz internal sea-ice screening appears effective. The rainrate retrieval is highly sensitive to any sea ice during all seasons. The seasonal cycle and 1987-2006 time trends are examined. The WVP annual cycle has an amplitude of ˜1 cm at all locations, approximately double a broad winter minimum, with a July maximum phasing that is consistent with a continental influence. Little change occurs between January and April in WVP and LWP. The springtime LWP increase usually occurs in tandem with the WVP increase and slightly lags the falltime WVP decrease. The maximum lag occurs over the northern Pacific, where the maximum LWP occurs in August, one month later than over the northern Atlantic, and is correlated to an August precipitation maximum. The strongest SSMI-derived trend is an increase in wintertime moisture south of Greenland, with wintertime LWP increases in the Labrador Sea. North of the Bering Strait, where much of the recent summer and autumn sea ice loss has occurred, the autumn WVP and LWP increased from 1989 to 2001 with a subsequent LWP decrease in recent years. The recent decline appears linked to a decrease in cyclone activity. Winter and spring LWP increases from 2002 to the present are noted in the surface-based data set from Barrow, Alaska. Over the Barents Sea, where much of the recent winter sea ice loss has occurred, winter WVP and LWP have increased over the past decade. A comparison to National Center for Atmospheric Research Community Atmospheric Model Version 3.5 values finds modeled WVPs are slightly underestimated but the amplitude of the annual cycle is similar to that observed. Modeled winter LWPs slightly exceed those measured while the modeled summer LWPs exceed by a factor of two those observed (which are more likely to be positively biased also). The modeled rainrates are similar to retrieved values in the north Pacific, and exceed retrieved values by approximately a factor of 2 in the northeast Atlantic.

Zuidema, Paquita; Joyce, Robert

2008-03-01

163

NASA Astrophysics Data System (ADS)

The ambient concentration of nitrous oxide (N2O), the fourth most abundant greenhouse gas, is rapidly increasing with emissions from both natural and anthropogenic sources [1]. Soil and aquatic areas are important sources and sinks for N2O due to complicated biogenic processes. However, N2O emissions are poorly constrained in space and time, despite its importance to global climate change and ozone depletion. We report our recent N2O emission measurements with an open-path quantum cascade laser (QCL)-based sensor for ecological systems. The newly emergent QCLs have been used to build compact, sensitive trace gas sensors in the mid-IR spectral region. A compact open-path QCL based sensor was developed to detect atmospheric N2O and CO at ~ 4.5 ?m using wavelength modulation spectroscopy (WMS) to achieve a sensitivity of 0.26 ppbv of N2O and 0.24 ppbv of CO in 1 s with a power consumption of ~50 W [2]. This portable sensor system has been used to perform N2O emission flux measurement both with a static flux chamber and on an eddy covariance (EC) flux tower. In the flux chamber measurements, custom chambers were used to host the laser sensor, while gas samples for gas chromatograph (GC) were collected at the same time in the same chamber for validation and comparison. Different soil treatments have been applied in different chambers to study the relationship between N2O emission and the amount of fertilizer (and water) addition. Measurements from two methods agreed with each other (95% or higher confidence interval) for emission flux results, while laser sensor gave measurements with a much high temporal resolution. We have also performed the first open-path eddy covariance N2O flux measurement at Kellogg research station, Michigan State University for a month in June, 2012. Our sensor was placed on a 4-meter tower in a corn field and powered by batteries (connected with solar panels). We have observed the diurnal cycle of N2O flux. During this deployment, an inter-comparison between our sensor and a commercial gas sensor was done to check the sensor's performance. Overall, our sensor showed a good performance with both static chamber measurement and EC flux measurement of N2O. Its open-path, compact and portable design with low power consumption provides lots of advantages for N2O emission flux measurement in the ecological systems. [1] S. A. Montzka, E. J. Dlugokencky, and J. H. Butler, "Non-CO2 greenhouse gases and climate change," Nature 476, 43-50 (2011). [2] L. Tao, K, Sun, D. J. Miller, M. A. Khan and M.A. Zondlo, "Optimizations for simultaneous detection of atmospheric N2O and CO with a quantum cascade laser," CLEO, 2012

Tao, L.; Sun, K.; Cavigelli, M. A.; Gelfand, I.; Zenone, T.; Cui, M.; Miller, D. J.; Khan, M. A.; Zondlo, M. A.

2012-12-01

164

Portable long open-path FTIR applied to in-situ measurement of trace gases of ambient air pollution

NASA Astrophysics Data System (ADS)

A long open path Fourier-transform infrared (FTIR) system operable at pathlengths up to 1 kilometer has been constructed for the simultaneous detection and measurement of trace pollutant gases in the Taiwan urban air. Good mid-IR spectra at 0.5 cm1 resolution covering most pollutant gases of greater than a few ppbv are recored hourly on full 24 hours bases. The spectral absorptions in the region due to HCOOH, C2H4, H2CO and O3 are investigated. A good correlation among HCOOH, C2H4. and 03 is found. On the basis of the kinetics rate information, most formic acid is not formed directly through the oxidation of C2H4. by O3 in the environment of high humidify. This organic acid in the urban air is the dominant form.

Tso, Tai-Ly; Liao, Wen-Chung; Chang, Shih-Yi

1992-05-01

165

Atmospheric methane concentration levels were detected using a custom built laser dispersion spectrometer in a long open-path beam configuration. The instrument is driven by a chirped distributed feedback mid-infrared quantum cascade laser centered at ~1283.46 cm^{-1} and covers intense rotational-vibrational transitions from the fundamental ?_{4} band of methane. A full forward model simulating molecular absorption and dispersion profiles, as well as instrumental noise, is demonstrated. The instrument's analytical model is validated and used for quantitative instrumental optimization. The temporal evolution of atmospheric methane mixing ratios is retrieved using a fitting algorithm based on the model. Full error propagation analysis on precision gives a normalized sensitivity of ~3 ppm.m.Hz^{-0.5} for atmospheric methane. PMID:25607487

Daghestani, Nart S; Brownsword, Richard; Weidmann, Damien

2014-12-15

166

Studies were performed to evaluate the accuracy of open-path Fourier Transform Infrared (OP-FTIR) spectrometers using a 35 foot outdoor exposure chamber in Pittsboro, North Carolina. Results obtained with the OP-FTIR spectrometer were compared to results obtained with a reference method (a gas chromatograph equipped with a flame ionization detector, GC-FID). Concentration results were evaluated in terms of the mathematical methods and spectral libraries used for quantification. In addition, the research investigated the effect on quantification of using different backgrounds obtained at various times during the day. The chemicals used in this study were toluene, cyclohexane, and methanol; and these were evaluated over the concentration range of 5-30 ppm.

Tomasko, M.S.

1995-12-31

167

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

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

168

ERIC Educational Resources Information Center

Open educational resources (OER) are making their way into a variety of educational contexts from formal lesson planning to just in time learning. Educators and training professionals have been recognized as an important audience for these materials. The concepts of "self-efficacy" and "outcome judgment" from social cognitive…

Kelly, Hope

2014-01-01

169

Open access to tree genomes: the path to a better forest

An open-access culture and a well-developed comparative-genomics infrastructure must be developed in forest trees to derive the full potential of genome sequencing in this diverse group of plants that are the dominant species in much of the earth's terrestrial ecosystems. PMID:23796049

2013-01-01

170

The paper describes a rapid and cost effective methodology developed to estimate emissions factors of organic compounds from a variety of area sources. he methodology involves using an open-path Fourier transform infrared (FTIR) spectrometer to measure concentrations of hydrocarb...

171

Preferred signal path delay and high-pass cut-off in open fittings.

The combination of delayed sound from a digital hearing aid with direct sound through an open or vented fitting can potentially degrade the sound quality due to audible changes in timbre and/or perception of echo. The present study was designed to test a number of delay and high-pass combinations under worst-case (i.e. most sensitive) conditions. Eighteen normal-hearing and 18 mildly hearing-impaired subjects performed the test in a paired comparison (A/B) task. The subjects were asked to select a preferred setting with respect to sound quality. The test was set in an anechoic chamber using recorded speech, environmental sounds, and own voice. Experimental hearing aids were fitted binaurally with open domes thus providing maximum ventilation. The preference data were processed using a statistical choice model that derives a ratio-scale. The analysis indicated that in these test conditions there was no change in sound quality when varying the delay in the range 5-10 ms and that there was a preference for 2000 Hz high-pass filtering in most conditions, regardless of the hearing losses tested. PMID:20602601

Bramsløw, Lars

2010-09-01

172

NASA Astrophysics Data System (ADS)

Because of the high travel speed, the complex flow dynamics around an aircraft, and the complex dependency of the fluid dynamics on numerous airborne parameters, it is quite difficult to obtain accurate pressure values at a specific instrument location of an aircraft's fuselage. Complex simulations using computational fluid dynamics (CFD) models can in theory computationally "transfer" pressure values from one location to another. However, for long flight patterns, this process is inconvenient and cumbersome. Furthermore, these CFD transfer models require a local experimental validation, which is rarely available. In this paper, we describe an integrated approach for a spectroscopic, calibration-free, in-flight pressure determination in an open-path White cell on an aircraft fuselage using ambient, atmospheric water vapour as the "sensor species". The presented measurements are realised with the HAI (Hygrometer for Atmospheric Investigations) instrument, built for multiphase water detection via calibration-free TDLAS (tunable diode laser absorption spectroscopy). The pressure determination is based on raw data used for H2O concentration measurement, but with a different post-flight evaluation method, and can therefore be conducted at deferred time intervals on any desired flight track. The spectroscopic pressure is compared in-flight with the static ambient pressure of the aircraft avionic system and a micro-mechanical pressure sensor, located next to the open-path cell, over a pressure range from 150 to 800 hPa, and a water vapour concentration range of more than 3 orders of magnitude. The correlation between the micro-mechanical pressure sensor measurements and the spectroscopic pressure measurements shows an average deviation from linearity of only 0.14% and a small offset of 9.5 hPa. For the spectroscopic pressure evaluation we derive measurement uncertainties under laboratory conditions of 3.2 and 5.1% during in-flight operation on the HALO airplane. Under certain flight conditions we quantified, for the first time, stalling-induced, dynamic pressure deviations of up to 30% (at 200 hPa) between the avionic sensor and the optical and mechanical pressure sensors integrated in HAI. Such severe local pressure deviations from the typically used avionic pressure are important to take into account for other airborne sensors employed on such fast flying platforms as the HALO aircraft.

Buchholz, B.; Afchine, A.; Ebert, V.

2014-11-01

173

NASA Astrophysics Data System (ADS)

Because of the high travel speed, the complex flow dynamics around an aircraft and the complex dependency of the fluid dynamics on numerous airborne parameters, it is quite difficult to obtain accurate pressure values at a specific instrument location of an aircraft's fuselage. Complex simulations using computational fluid dynamics (CFD) models can in theory computationally "transfer" pressure values from one location to another. However, for long flight patterns, this process is inconvenient and cumbersome. Furthermore these CFD transfer models require a local experimental validation, which is rarely available. In this paper, we describe an integrated approach for a spectroscopic, calibration-free, in-flight pressure determination in an open-path White cell on an aircraft fuselage using ambient, atmospheric water vapour as the "sensor species". The presented measurements are realized with the HAI (Hygrometer for Atmospheric Investigations) instrument, built for multiphase water detection via calibration-free TDLAS (tunable diode laser absorption spectroscopy). The pressure determination is based on raw data used for H2O concentration measurement, but with a different post-flight evaluation method, and can therefore be conducted at deferred time intervals on any desired flight track. The spectroscopic pressure is compared in-flight with the static ambient pressure of the aircraft avionic system and a micro-mechanical pressure sensor, located next to the open-path cell, over a pressure range from 150 hPa to 800 hPa, and a water vapour concentration range of more than three orders of magnitude. The correlation between the micro-mechanical pressure sensor measurements and the spectroscopic pressure measurements show an average deviation from linearity of only 0.14% and a small offset of 9.5 hPa. For the spectroscopic pressure evaluation we derive measurement uncertainties under laboratory conditions of 3.2% and 5.1% during in flight operation on the HALO airplane. Under certain flight conditions we quantified for the first time stalling-induced, dynamic pressure deviations of up to 30% (at 200 hPa) between the avionic sensor and the optical and mechanical pressure sensors integrated in HAI. Such severe local pressure deviations from the usually used avionic pressure are important to take into account for other airborne sensors employed on such fast flying platforms as the HALO aircraft.

Buchholz, B.; Afchine, A.; Ebert, V.

2014-05-01

174

Open Innovation Drug Discovery (OIDD): a potential path to novel therapeutic chemical space.

The continued development of computational and synthetic methods has enabled the enumeration or preparation of a nearly endless universe of chemical structures. Nevertheless, the ability of this chemical universe to deliver small molecules that can both modulate biological targets and have drug-like physicochemical properties continues to be a topic of interest to the pharmaceutical industry and academic researchers alike. The chemical space described by public, commercial, in-house and virtual compound collections has been interrogated by multiple approaches including biochemical, cellular and virtual screening, diversity analysis, and in-silico profiling. However, current drugs and known chemical probes derived from these efforts are contained within a remarkably small volume of the predicted chemical space. Access to more diverse classes of chemical scaffolds that maintain the properties relevant for drug discovery is certainly needed to meet the increasing demands for pharmaceutical innovation. The Lilly Open Innovation Drug Discovery platform (OIDD) was designed to tackle barriers to innovation through the identification of novel molecules active in relevant disease biology models. In this article we will discuss several computational approaches towards describing novel, biologically active, drug-like chemical space and illustrate how the OIDD program may facilitate access to previously untapped molecules that may aid in the search for innovative pharmaceuticals. PMID:24283973

Alvim-Gaston, Maria; Grese, Timothy; Mahoui, Abdelaziz; Palkowitz, Alan D; Pineiro-Nunez, Marta; Watson, Ian

2014-01-01

175

NASA Astrophysics Data System (ADS)

An open-path tunable diode laser absorption spectroscopy (OP-TDLAS) detector was applied to detect the methane emission from a biogas plant in a dairy farm. Two OP-TDLAS scanning systems were built according to maximum likelihood with expectation minimization (MLEM) and smooth basis function minimization (SBFM) algorithms to reconstruct the two-dimensional (2-D) distribution maps. Six reconstruction maps with the resolution of 30×80 were obtained by the MLEM algorithm with "grid translation method" and three reconstruction maps were obtained by the SBFM algorithm with 2-D Gaussian model. The maximum mixing ratio in the first result was between 0.85 and 1.30 ppm, while it was between 1.14 and 1.30 ppm in the second result. The average mixing ratio in the first result was between 0.54 and 0.49 ppm, and between 0.56 and 0.65 ppm in the second result. The reconstruction results validated that the two algorithms could effectively reflect the methane mixing ratio distribution within the target area. However, with the more simple optical rays and less equipment requirements, the OP-TDLAS scanning system based on SBFM algorithm provides a useful monitoring tool of methane emissions in agricultural production.

Zhang, Shirui; Wang, Jihua; Dong, Daming; Zheng, Wengang; Zhao, Xiande

2013-02-01

176

A continuous-wave, rapidly swept cavity-ringdown spectroscopic technique has been developed for localized atmospheric sensing of trace gases at remote sites. It uses one or more passive open-path optical sensor units, coupled by optical fiber over distances of >1 km to a single transmitter/receiver console incorporating a photodetector and a swept-frequency diode laser tuned to molecule-specific near-infrared wavelengths. Ways to avoid interference from stimulated Brillouin scattering in long optical fibers have been devised. This rugged open-path system, deployable in agricultural, industrial, and natural atmospheric environments, is used to monitor ammonia in air. A noise-limited minimum detectable mixing ratio of ~11 ppbv is attained for ammonia in nitrogen at atmospheric pressure. PMID:24921513

He, Yabai; Jin, Chunjiang; Kan, Ruifeng; Liu, Jianguo; Liu, Wenqing; Hill, Julian; Jamie, Ian M; Orr, Brian J

2014-06-01

177

Exact Algorithms for the Canadian Traveller Problem on Paths and Trees

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

178

Open-path FT-IR spectra were measured while fireworks were emitting smoke and incandescent particles into the infrared beam.\\u000a These conditions were designed to simulate the appearance of smoke and explosions in a battlefield. Diethyl ether was used\\u000a to simulate the vapor-phase spectra of G agents such as sarin. The measured interferograms were corrected by a high-pass filter\\u000a and were rejected when

Limin Shao; Christopher W. Roske; Peter R. Griffiths

2010-01-01

179

Formal language constrained path problems

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

180

Optimal paths for a car that goes both forwards and backwards

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

181

Parallel transport of long mean-free-path plasma along open magnetic field lines: Parallel heat flux

NASA Astrophysics Data System (ADS)

In a long mean-free-path plasma where temperature anisotropy can be sustained, the parallel heat flux has two components with one associated with the parallel thermal energy and the other the perpendicular thermal energy. Due to the large deviation of the distribution function from local Maxwellian in an open field line plasma with low collisionality, the conventional perturbative calculation of the parallel heat flux closure in its local or non-local form is no longer applicable. Here, a non-perturbative calculation is presented for a collisionless plasma in a two-dimensional flux expander bounded by absorbing walls. Specifically, closures of previously unfamiliar form are obtained for ions and electrons, which relate two distinct components of the species parallel heat flux to the lower order fluid moments such as density, parallel flow, parallel and perpendicular temperatures, and the field quantities such as the magnetic field strength and the electrostatic potential. The plasma source and boundary condition at the absorbing wall enter explicitly in the closure calculation. Although the closure calculation does not take into account wave-particle interactions, the results based on passing orbits from steady-state collisionless drift-kinetic equation show remarkable agreement with fully kinetic-Maxwell simulations. As an example of the physical implications of the theory, the parallel heat flux closures are found to predict a surprising observation in the kinetic-Maxwell simulation of the 2D magnetic flux expander problem, where the parallel heat flux of the parallel thermal energy flows from low to high parallel temperature region.

Guo, Zehua; Tang, Xian-Zhu

2012-06-01

182

Parallel transport of long mean-free-path plasma along open magnetic field lines: Parallel heat flux

In a long mean-free-path plasma where temperature anisotropy can be sustained, the parallel heat flux has two components with one associated with the parallel thermal energy and the other the perpendicular thermal energy. Due to the large deviation of the distribution function from local Maxwellian in an open field line plasma with low collisionality, the conventional perturbative calculation of the parallel heat flux closure in its local or non-local form is no longer applicable. Here, a non-perturbative calculation is presented for a collisionless plasma in a two-dimensional flux expander bounded by absorbing walls. Specifically, closures of previously unfamiliar form are obtained for ions and electrons, which relate two distinct components of the species parallel heat flux to the lower order fluid moments such as density, parallel flow, parallel and perpendicular temperatures, and the field quantities such as the magnetic field strength and the electrostatic potential. The plasma source and boundary condition at the absorbing wall enter explicitly in the closure calculation. Although the closure calculation does not take into account wave-particle interactions, the results based on passing orbits from steady-state collisionless drift-kinetic equation show remarkable agreement with fully kinetic-Maxwell simulations. As an example of the physical implications of the theory, the parallel heat flux closures are found to predict a surprising observation in the kinetic-Maxwell simulation of the 2D magnetic flux expander problem, where the parallel heat flux of the parallel thermal energy flows from low to high parallel temperature region.

Guo Zehua; Tang Xianzhu [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2012-06-15

183

NASA Astrophysics Data System (ADS)

This study introduced a quantitative method that can be used to measure the concentration of analytes directly from a single-beam spectrum of open-path Fourier Transform Infrared Spectroscopy (OP-FTIR). The peak shapes of the analytes in a single-beam spectrum were gradually canceled (i.e., "titrated") by dividing an aliquot of a standard transmittance spectrum with a known concentration, and the sum of the squared differential synthetic spectrum was calculated as an indicator for the end point of this titration. The quantity of a standard transmittance spectrum that is needed to reach the end point can be used to calculate the concentrations of the analytes. A NIST traceable gas standard containing six known compounds was used to compare the quantitative accuracy of both this titration method and that of a classic least square (CLS) using a closed-cell FTIR spectrum. The continuous FTIR analysis of industrial exhausting stack showed that concentration trends were consistent between the CLS and titration methods. The titration method allowed the quantification to be performed without the need of a clean single-beam background spectrum, which was beneficial for the field measurement of OP-FTIR. Persistent constituents of the atmosphere, such as NH3, CH4 and CO, were successfully quantified using the single-beam titration method with OP-FTIR data that is normally inaccurate when using the CLS method due to the lack of a suitable background spectrum. Also, the synthetic spectrum at the titration end point contained virtually no peaks of analytes, but it did contain the remaining information needed to provide an alternative means of obtaining an ideal single-beam background for OP-FTIR.

Sung, Lung-Yu; Lu, Chia-Jung

2014-09-01

184

Technology Transfer Automated Retrieval System (TEKTRAN)

A technique of using multiple calibration sets in partial least squares regression (PLS) was proposed to improve the quantitative determination of ammonia from open-path Fourier transform infrared spectra. The spectra were measured near animal farms, and the path-integrated concentration of ammonia...

185

The paper describes preliminary results from a field experiment designed to evaluate a new approach to quantifying gaseous fugitive emissions from area air pollution sources. The new approach combines path-integrated concentration data acquired with any path-integrated optical re...

186

FIELD EVALUATION OF A METHOD FOR ESTIMATING GASEOUS FLUXES FROM AREA SOURCES USING OPEN-PATH FTIR

The paper gives preliminary results from a field evaluation of a new approach for quantifying gaseous fugitive emissions of area air pollution sources. The approach combines path-integrated concentration data acquired with any path-integrated optical remote sensing (PI-ORS) ...

187

The paper describes a new approach to quantify emissions from area air pollution sources. The approach combines path-integrated concentration data acquired with any path-integrated optical remote sensing (PI-ORS) technique and computed tomography (CT) technique. In this study, an...

188

The Dwarf Novae of Shortest Period

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

189

The choice of the type of background spectrum affects the credibility of open-path Fourier transform infrared spectroscopy (OP/FT-IR) data, and consequently, the quality of data analysis. We systematically investigated several properties of the background spectrum. The results show that a short-path background measured with the lowest amplifier gain could significantly reduce noise in the calculated absorbance spectrum, by at least 30% in our case. We demonstrated that by using a short-path background, data analysis is more resistant to interferences such as wavenumber shift or resolution alteration that occurs as a consequence of aging hardware or misalignment. We discussed a systematic error introduced into quantitative analyses by the short-path background and developed a procedure to correct that error. With this correction approach, a short-path background established five years ago was still found to be valid. By incorporating these findings into the protocol for quantitative analysis, we processed the measurements with two OP/FT-IR instruments set up side by side in the vicinity of a large dairy farm, to monitor NH3, CH4, and N2O. The two sets of calculated concentrations showed high agreement with each other. The findings of our investigations are helpful to atmospheric monitoring practitioners of OP/FT-IR spectroscopy and could also be a reference for future amendments to the protocols outlined in the guidelines of the U.S. Environmental Protection Agency, the American Society for Testing and Materials, and the European Committee for Standardization. PMID:23452499

Shao, Limin; Wang, Wanping; Griffiths, Peter R; Leytem, April B

2013-03-01

190

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

191

A compact and portable open-path sensor for simultaneous detection of atmospheric N(2)O and CO has been developed with a 4.5 ?m quantum cascade laser (QCL). An in-line acetylene (C(2)H(2)) gas reference cell allows for continuous monitoring of the sensor drift and calibration in rapidly changing field environments and thereby allows for open-path detection at high precision and stability. Wavelength modulation spectroscopy (WMS) is used to detect simultaneously both the second and fourth harmonic absorption spectra with an optimized dual modulation amplitude scheme. Multi-harmonic spectra containing atmospheric N(2)O, CO, and the reference C(2)H(2) signals are fit in real-time (10 Hz) by combining a software-based lock-in amplifier with a computationally fast numerical model for WMS. The sensor consumes ~50 W of power and has a mass of ~15 kg. Precision of 0.15 ppbv N(2)O and 0.36 ppbv CO at 10 Hz under laboratory conditions was demonstrated. The sensor has been deployed for extended periods in the field. Simultaneous N(2)O and CO measurements distinguished between natural and fossil fuel combustion sources of N(2)O, an important greenhouse gas with poorly quantified emissions in space and time. PMID:23263046

Tao, Lei; Sun, Kang; Khan, M Amir; Miller, David J; Zondlo, Mark A

2012-12-17

192

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

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

193

Spatial cognition: robot target localization in open arenas based on rat studies

NASA Astrophysics Data System (ADS)

We describe our latest work in understanding spatial localization in open arenas based on rat studies and corresponding modeling with simulated and physical robots. The studies and experiments focus on goal-oriented navigation where both rats and robots exploit distal cues to localize and find a goal in an open environment. The task involves training of both rats and robots to find the shortest path to the goal from multiple starting points in the environment. The spatial cognition model is based on the rat's brain neurophysiology of the hippocampus extending previous work by analyzing granularity of localization in relation to a varying number and position of landmarks. The robot integrates internal and external information to create a topological map of the environment and to generate shortest routes to the goal through path integration. One of the critical challenges for the robot is to analyze the similarity of positions and distinguish among different locations using visual cues and previous paths followed to reach the current position. We describe the robotics architecture used to develop, simulate and experiment with physical robots.

Tejera, Gonzalo; Barrera, Alejandra; Fellous, Jean-Marc; Llofriu, Martin; Weitzenfeld, Alfredo

2013-05-01

194

Spectroscopic measurements of a CO2 absorption line in an open vertical path using an airborne lidar

We use an airborne pulsed integrated path differential absorption lidar to make spectroscopic measurements of the pressure-induced line broadening and line center shift of atmospheric CO2 at the 1572.335 nm absorption line. We measure the absorption lineshape in the vertical column between the aircraft and ground. A comparison of our measured absorption lineshape to calculations based on HITRAN shows excellent agreement with the peak optical depth accurate to within 0.3%. Additionally, we measure changes in the line center position to within 5.2 MHz of calculations, and the absorption linewidth to within 0.6% of calculations.

Ramanathan, Anand; Allan, Graham R; Riris, Haris; Weaver, Clark J; Hasselbrack, William E; Browell, Edward V; Abshire, James B

2013-01-01

195

Open-path FT-IR spectra were measured while fireworks were emitting smoke and incandescent particles into the infrared beam. These conditions were designed to simulate the appearance of smoke and explosions in a battlefield. Diethyl ether was used to simulate the vapor-phase spectra of G agents such as sarin. The measured interferograms were corrected by a high-pass filter and were rejected when interfering features were of such high frequency that they could not be removed by application of this filter. The concentration of diethyl ether was calculated correctly by partial least squares regression in the absence of fireworks but significant errors were encountered when the spectra of the oxide particles were not included in the calibration set. Target factor analysis allowed the presence of the analyte to be detected even when the incandescent particles were present in the beam. PMID:20401469

Shao, Limin; Roske, Christopher W; Griffiths, Peter R

2010-06-01

196

NASA Astrophysics Data System (ADS)

We report trace-gas emission factors from three pine-understory prescribed fires in South Carolina, US measured during the fall of 2011. The fires were more intense than many prescribed burns because the fuels included mature pine stands not subjected to prescribed fire in decades that were lit following an extended drought. Emission factors were measured with a fixed open-path Fourier transform infrared (OP-FTIR) system that was deployed on the fire control lines. We compare these emission factors to those measured with a roving, point sampling, land-based FTIR and an airborne FTIR deployed on the same fires. We also compare to emission factors measured by a similar OP-FTIR system deployed on savanna fires in Africa. The data suggest that the method used to sample smoke can strongly influence the relative abundance of the emissions that are observed. The majority of fire emissions were lofted in the convection column and were sampled by the airborne FTIR. The roving, ground-based, point sampling FTIR measured the contribution of individual residual smoldering combustion fuel elements scattered throughout the burn site. The OP-FTIR provided a ~ 30 m path-integrated sample of emissions transported to the fixed path via complex ground-level circulation. The OP-FTIR typically probed two distinct combustion regimes, "flaming-like" (immediately after adjacent ignition and before the adjacent plume achieved significant vertical development) and "smoldering-like." These two regimes are denoted "early" and "late", respectively. The path-integrated sample of the ground-level smoke layer adjacent to the fire from the OP-FTIR provided our best estimate of fire-line exposure to smoke for wildland fire personnel. We provide a table of estimated fire-line exposures for numerous known air toxics based on synthesizing results from several studies. Our data suggest that peak exposures are more likely to challenge permissible exposure limits for wildland fire personnel than shift-average (8 h) exposures.

Akagi, S. K.; Burling, I. R.; Mendoza, A.; Johnson, T. J.; Cameron, M.; Griffith, D. W. T.; Paton-Walsh, C.; Weise, D. R.; Reardon, J.; Yokelson, R. J.

2014-01-01

197

Internet Traffic Engineering by Optimizing OSPF Weights

Open Shortest Path First (OSPF) is the most commonly used intra-domain internet routing protocol. Traffic flow is routed along shortest paths, splitting flow at nodes where several outgoing links are on shortest paths to the destination. The weights of the links, and thereby the shortest path routes, can be changed by the network opera- tor. The weights could be set

Bernard Fortz; Mikkel Thorup

2000-01-01

198

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

199

Solving Stochastic Shortest-Path Problems with RTDP Cognitive Systems Laboratory

Departamento de ComputaciÂ´on Universidad SimÂ´on BolÂ´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

200

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

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

201

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

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

202

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

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

203

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

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

204

Monotonicity Testing and Shortest-Path Routing on the Jop Briet1

],[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

205

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

206

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

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

207

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

208

NASA Astrophysics Data System (ADS)

An open-path Fourier transform infrared (OP-FTIR) spectroscopic technique in combination with a backward Lagrangian stochastic (bLS) dispersion model (WindTrax) can be used to simultaneously measure gaseous emissions of N2O, NH3, CH4 and CO2. We assessed the capability of this technique for measuring NH3 and N2O emissions following the application of calcium nitrate (Ca(NO3)2), Nitrophoska (NPK) and chicken manure on a celery farm at Boneo, Victoria, during April and May 2013. We found that the OP-FTIR/WindTrax method was able to measure the diurnal variation in NH3 flux from the field site following application of chicken manure with measured emissions ranging from approximately 0.1-9.8 kg NH3-N ha-1 day-1. The OP-FTIR/WindTrax method also detected a diurnal variation in N2O flux of 1.5-6.2 kg N2O-N ha-1 day-1 and N2O flux increased in response to application of the Ca(NO3)2. We concluded that the OP-FTIR/WindTrax technique can quantify gaseous N loss from vegetable production systems.

Bai, Mei; Suter, Helen; Lam, Shu Kee; Sun, Jianlei; Chen, Deli

2014-09-01

209

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

210

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

211

NASA Astrophysics Data System (ADS)

Savanna fires contribute approximately 40-50% of total global annual biomass burning carbon emissions. Recent comparisons of emission factors from different savanna regions have highlighted the need for a regional approach to emission factor development, and better assessment of the drivers of the temporal and spatial variation in emission factors. This paper describes the results of open-path Fourier Transform Infrared (OP-FTIR) spectroscopic field measurements at twenty-one fires occurring in the tropical savannas of the Northern Territory, Australia, within different vegetation assemblages and at different stages of the dry season. Spectra of infrared light passing through a long (22-70 m) open-path through ground-level smoke released from these fires were collected using an infrared lamp and a field-portable FTIR system. The IR spectra were used to retrieve the mole fractions of fourteen different gases present within the smoke, and these measurements used to calculate the emission ratios and emission factors of the various gases emitted by the burning. Only a handful of previous emission factor measures are available specifically for the tropical savannas of Australia and here we present the first reported emission factors for methanol, acetic acid, and formic acid for this biome. Given the relatively large sample size, it was possible to study the potential causes of the within-biome variation of the derived emission factors. We find that the emission factors vary substantially between different savanna vegetation assemblages; with a majority of this variation being mirrored by variations in the modified combustion efficiency (MCE) of different vegetation classes. We conclude that a significant majority of the variation in the emission factor for trace gases can be explained by MCE, irrespective of vegetation class, as illustrated by variations in the calculated methane emission factor for different vegetation classes using data subsetted by different combustion efficiencies. Therefore, the selection of emission factors for emissions modelling purposes need not necessarily require detailed fuel type information, if data on MCE (e.g. from future spaceborne total column measurements) or a correlated variable were available. From measurements at twenty-one fires, we recommend the following emission factors for Australian tropical savanna fires (in grams of gas emitted per kilogram of dry fuel burned) which are our mean measured values: 1674 g kg-1 of carbon dioxide; 87 g kg-1 of carbon monoxide; 2.1 g kg-1 of methane; 0.11 g kg-1 of acetylene; 0.49 g kg-1 of ethylene; 0.08 g kg-1 of ethane; 1.57 g kg-1 of formaldehyde; 1.06 g kg-1 of methanol; 1.54 g kg-1 of acetic acid; 0.16 g kg-1 of formic acid; 0.53 g kg-1 of hydrogen cyanide; and 0.70 g kg-1 of ammonia.

Smith, T. E. L.; Paton-Walsh, C.; Meyer, C. P.; Cook, G. D.; Maier, S. W.; Russell-Smith, J.; Wooster, M. J.; Yates, C. P.

2014-03-01

212

NASA Astrophysics Data System (ADS)

Savanna fires contribute approximately 40-50% of total global annual biomass burning carbon emissions. Recent comparisons of emission factors from different savanna regions have highlighted the need for a regional approach to emission factor development, and better assessment of the drivers of the temporal and spatial variation in emission factors. This paper describes the results of open-path Fourier transform infrared (OP-FTIR) spectroscopic field measurements at 21 fires occurring in the tropical savannas of the Northern~Territory, Australia, within different vegetation assemblages and at different stages of the dry season. Spectra of infrared light passing through a long (22-70 m) open-path through ground-level smoke released from these fires were collected using an infrared lamp and a field-portable FTIR system. The IR spectra were used to retrieve the mole fractions of 14 different gases present within the smoke, and these measurements used to calculate the emission ratios and emission factors of the various gases emitted by the burning. Only a handful of previous emission factor measures are available specifically for the tropical savannas of Australia and here we present the first reported emission factors for methanol, acetic acid, and formic acid for this biome. Given the relatively large sample size, it was possible to study the potential causes of the within-biome variation of the derived emission factors. We find that the emission factors vary substantially between different savanna vegetation assemblages; with a majority of this variation being mirrored by variations in the modified combustion efficiency (MCE) of different vegetation classes. We conclude that a significant majority of the variation in the emission factor for trace gases can be explained by MCE, irrespective of vegetation class, as illustrated by variations in the calculated methane emission factor for different vegetation classes using data sub-set by different combustion efficiencies. Therefore, the selection of emission factors for emissions modelling purposes need not necessarily require detailed fuel type information, if data on MCE (e.g. from future spaceborne total column measurements) or a correlated variable were available. From measurements at 21 fires, we recommend the following emission factors for Australian tropical savanna fires (in grams of gas emitted per kilogram of dry fuel burned), which are our mean measured values: 1674 ± 56 g kg-1 of carbon dioxide; 87 ± 33 g kg-1 of carbon monoxide; 2.1 ± 1.2 g kg-1 of methane; 0.11 ± 0.04 g kg-1 of acetylene; 0.49 ± 0.22 g kg-1 of ethylene; 0.08 ± 0.05 g kg-1 of ethane; 1.57 ± 0.44 g kg-1 of formaldehyde; 1.06 ± 0.87 g kg-1 of methanol; 1.54 ± 0.64 g kg-1 of acetic acid; 0.16 ± 0.07 g kg-1 of formic acid; 0.53 ± 0.31 g kg-1 of hydrogen cyanide; and 0.70 ± 0.36 g kg-1 of ammonia. In a companion paper, similar techniques are used to characterise the emissions from Australian temperate forest fires.

Smith, T. E. L.; Paton-Walsh, C.; Meyer, C. P.; Cook, G. D.; Maier, S. W.; Russell-Smith, J.; Wooster, M. J.; Yates, C. P.

2014-10-01

213

NASA Astrophysics Data System (ADS)

Biomass burning releases trace gases and aerosol particles that significantly affect the composition and chemistry of the atmosphere. Australia contributes approximately 8% of gross global carbon emissions from biomass burning, yet there are few previous measurements of emissions from Australian forest fires available in the literature. This paper describes the results of field measurements of trace gases emitted during hazard reduction burns in Australian temperate forests using open-path Fourier transform infrared spectroscopy. In a companion paper, similar techniques are used to characterise the emissions from hazard reduction burns in the savanna regions of the Northern Territory. Details of the experimental methods are explained, including both the measurement set-up and the analysis techniques employed. The advantages and disadvantages of different ways to estimate whole-fire emission factors are discussed and a measurement uncertainty budget is developed. Emission factors for Australian temperate forest fires are measured locally for the first time for many trace gases. Where ecosystem-relevant data are required, we recommend the following emission factors for Australian temperate forest fires (in grams of gas emitted per kilogram of dry fuel burned) which are our mean measured values: 1620 ± 160 g kg-1 of carbon dioxide; 120 ± 20 g kg-1 of carbon monoxide; 3.6 ± 1.1 g kg-1 of methane; 1.3 ± 0.3 g kg-1 of ethylene; 1.7 ± 0.4 g kg-1 of formaldehyde; 2.4 ± 1.2 g kg-1 of methanol; 3.8 ± 1.3 g kg-1 of acetic acid; 0.4 ± 0.2 g kg-1 of formic acid; 1.6 ± 0.6 g kg-1 of ammonia; 0.15 ± 0.09 g kg-1 of nitrous oxide and 0.5 ± 0.2 g kg-1 of ethane.

Paton-Walsh, C.; Smith, T. E. L.; Young, E. L.; Griffith, D. W. T.; Guérette, É.-A.

2014-10-01

214

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

215

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

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

216

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

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.

217

ORIGINAL ARTICLE Multi-objective optimal path selection in electric vehicles

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.

218

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

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

219

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

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

Stamp, Mark

220

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

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

Khot, Subhash

221

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

222

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

223

NASA Astrophysics Data System (ADS)

Domestic biomass fuels (biofuels) were recently estimated to be the second largest source of carbon emissions from global biomass burning. Wood and charcoal provide approximately 90% and 10% of domestic energy in tropical Africa. In September 2000, we used open-path Fourier transform infrared (OP-FTIR) spectroscopy to quantify 18 of the most abundant trace gases emitted by wood and charcoal cooking fires and an earthen charcoal-making kiln in Zambia. These are the first in situ measurements of an extensive suite of trace gases emitted by tropical biofuel burning. We report emission ratios (ER) and emission factors (EF) for (in order of abundance) carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), acetic acid (CH3COOH), methanol (CH3OH), formaldehyde (HCHO), ethene (C2H4), ammonia (NH3), acetylene (C2H2), nitric oxide (NO), ethane (C2H6), phenol (C6H5OH), propene (C3H6), formic acid (HCOOH), nitrogen dioxide (NO2), hydroxyacetaldehyde (HOCH2CHO), and furan (C4H4O). Compared to previous work, our emissions of organic acids and NH3 are 3-6.5 times larger. Another significant finding is that reactive oxygenated organic compounds account for 70-80% of the total nonmethane organic compounds (NMOC). For most compounds, the combined emissions from charcoal production and charcoal burning are larger than the emissions from wood fires by factors of 3-10 per unit mass of fuel burned and ˜2 per unit energy released. We estimate that Zambian savanna fires produce more annual CO2, HCOOH, and NOx than Zambian biofuel use by factors of 2.5, 1.7, and 5, respectively. However, biofuels contribute larger annual emissions of CH4, CH3OH, C2H2, CH3COOH, HCHO, and NH3 by factors of 5.1, 3.9, 2.7, 2.4, 2.2, and 2.0, respectively. Annual CO and C2H4 emissions are approximately equal from both sources. Coupling our data with recent estimates of global biofuel consumption implies that global biomass burning emissions for several compounds are significantly larger than previously reported. Biofuel emissions are produced year-round, disperse differently than savanna fire emissions, and could strongly impact the tropical troposphere.

Bertschi, Isaac T.; Yokelson, Robert J.; Ward, Darold E.; Christian, Ted J.; Hao, Wei Min

2003-07-01

224

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

225

NASA Astrophysics Data System (ADS)

Biomass burning emissions factors are vital to quantifying trace gases releases from vegetation fires. Here we evaluate emissions factors for a series of savannah fires in Kruger National Park (KNP), South Africa using ground-based open path Fourier transform infrared (FTIR) spectroscopy and an infrared lamp separated by 150-250 m distance. Molecular abundances along the extended open path are retrieved using a spectral forward model coupled to a non-linear least squares fitting approach. We demonstrate derivation of trace gas column amounts for horizontal paths transecting the width of the advected plume, and find, for example, that CO mixing ratio changes of ~0.001 ?mol mol-1 (~10 ppbv) can be detected across the relatively long optical paths used here. We focus analysis on five key compounds whose production is preferential during the pyrolysis (CH2O), flaming (CO2) and smoldering (CO, CH4, NH3) fire phases. We demonstrate that well constrained emissions ratios for these gases to both CO2 and CO can be derived for the backfire, headfire and residual smouldering combustion stages of these savannah fires, from which stage-specific emission factors can then be calculated. Headfires and backfires in general show similar emission ratios and emission factors, but those of the residual smouldering combustion stage can differ substantially (e.g., ERCH4/CO2 up to ~7 times higher than for the flaming stages). The timing of each fire stage was identified via airborne optical and thermal IR imagery and ground-observer reports, with the airborne IR imagery also used to derive estimates of fire radiative energy, thus allowing the relative amount of fuel burned in each stage to be calculated and the "fire averaged" emission ratios and emission factors to be determined. The derived "fire averaged" emission ratios are dominated by the headfire contribution, since the vast majority of the fuel is burned in this stage. Our fire averaged emission ratios and factors for CO2 and CH4 agree with those from published studies conducted in the same area using airborne plume sampling, and we concur with past suggestions that emission factors for formaldehyde in this environment appear substantially underestimated in widely used databases. We also find the emission ratios and factors for CO and NH3 to be somewhat higher than most other estimates, however, we see no evidence to support suggestions of a major overestimation in the emission factor of ammonia. Our data also suggest that the contribution of burning animal (elephant) dung can be a significant factor in the emissions characteristics of certain KNP fires, and indicate some similarities between the time series of fire brightness temperature and modified combustion efficiency (MCE) that supports suggestions that EO-derived fire temperature estimates maybe useful when attempting to remotely classify fire activity into its different phases. We conclude that ground-based, extended open path FTIR spectroscopy is a practical and very effective means for determining emission ratios, emission factors and modified combustion efficiencies at open vegetation fire plumes, allowing these to be probed at temporal and spatial scales difficult to explore using other ground-based approaches. Though we limited our study to five key emissions products, open path FTIR spectroscopy can detect dozens of other species, as has been demonstrated during previous closed-path FTIR airborne deployments in the same study area.

Wooster, M. J.; Freeborn, P. H.; Archibald, S.; Oppenheimer, C.; Roberts, G. J.; Smith, T. E. L.; Govender, N.; Burton, M.; Palumbo, I.

2011-02-01

226

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; Aragonès, Àngels

2011-05-01

227

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

228

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

229

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

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, José J; de La Lama, Marta S; López, Eduardo; Boettcher, Stefan

2010-09-01

230

The shortest modulation period Blazhko RR Lyrae star: SS Cnc

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; Á. Sódor; I. Dékány; Zs. Hurta; K. Posztobányi; K. Vida; M. Váradi; A. Szing

2006-03-20

231

Identification of biochemical network modules based on shortest retroactive distances.

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

232

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

233

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

234

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

235

A new class of machine codes for the specification of Pythagorean-hodograph (PH) curve tool paths, and associated feedrate functions, is proposed. The PH curves are a special family of free-form curves, compatible with the Bézier\\/B-spline representations of CAD systems, that are amenable to real-time interpolation at constant or variable feedrate directly from their exact analytic descriptions. The proposed codes are

Rida T. Farouki; Jairam Manjunathaiah; Guo-Feng Yuan

1999-01-01

236

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

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

237

Nonclassical paths in quantum interference experiments.

In a double slit interference experiment, the wave function at the screen with both slits open is not exactly equal to the sum of the wave functions with the slits individually open one at a time. The three scenarios represent three different boundary conditions and as such, the superposition principle should not be applicable. However, most well-known text books in quantum mechanics implicitly and/or explicitly use this assumption that is only approximately true. In our present study, we have used the Feynman path integral formalism to quantify contributions from nonclassical paths in quantum interference experiments that provide a measurable deviation from a naive application of the superposition principle. A direct experimental demonstration for the existence of these nonclassical paths is difficult to present. We find that contributions from such paths can be significant and we propose simple three-slit interference experiments to directly confirm their existence. PMID:25279612

Sawant, Rahul; Samuel, Joseph; Sinha, Aninda; Sinha, Supurna; Sinha, Urbasi

2014-09-19

238

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

239

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

240

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

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

241

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

242

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

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

243

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

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

244

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

245

Traveling salesman path problems

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

246

Information Spread of Emergency Events: Path Searching on Social Networks

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

247

The ELM Survey: Finding the Shortest Period Binary White Dwarfs

NASA Astrophysics Data System (ADS)

A new discovery space for short period binary white dwarfs has opened up with the availability of 14,600 deg^2 of SDSS Data Release 9 photometry. The Extremely Low-Mass (ELM) Survey takes advantage of this photometry and SDSS spectroscopy to identify compact systems with 1 hour or shorter orbital periods. To significantly increase the number of merging white dwarf systems known, we have proposed to obtain follow- up spectroscopic observations of all candidates with g ? 19 mag and photometric colors consistent with extremely low-mass (? 0.3 M_?) white dwarfs. Most of our 2012A Hale and 2012B KP 4m observing runs were lost to weather, yet we managed to identify at least one new short period binary. Our 2013A run on the KP 4m was successful in identifying many new ELM white dwarfs, and in our 2013B follow-up run we observed two new 3 hour binaries while also obtaining further data on a number of other merging systems. Here we propose to continue our program by observing our fall targets on the KP 4m telescope to constrain their binary orbital periods. Our two major science goals are to discover detached gravitational wave sources for fundamental tests of general relativity, and to constrain the formation rate and space density of merging white dwarfs. The latter is important for constraining the contribution of double degenerates to Type Ia and underluminous supernovae.

Canton, Paul; Gianninas, Alexandros; Kilic, Mukremin; Brown, Warren; Kenyon, Scott

2014-08-01

248

NASA Astrophysics Data System (ADS)

Biomass burning emissions factors are vital to quantifying trace gas release from vegetation fires. Here we evaluate emissions factors for a series of savannah fires in Kruger National Park (KNP), South Africa using ground-based open path Fourier transform infrared (FTIR) spectroscopy and an IR source separated by 150-250 m distance. Molecular abundances along the extended open path are retrieved using a spectral forward model coupled to a non-linear least squares fitting approach. We demonstrate derivation of trace gas column amounts for horizontal paths transecting the width of the advected plume, and find for example that CO mixing ratio changes of ~0.01 ?mol mol-1 [10 ppbv] can be detected across the relatively long optical paths used here. Though FTIR spectroscopy can detect dozens of different chemical species present in vegetation fire smoke, we focus our analysis on five key combustion products released preferentially during the pyrolysis (CH2O), flaming (CO2) and smoldering (CO, CH4, NH3) processes. We demonstrate that well constrained emissions ratios for these gases to both CO2 and CO can be derived for the backfire, headfire and residual smouldering combustion (RSC) stages of these savannah fires, from which stage-specific emission factors can then be calculated. Headfires and backfires often show similar emission ratios and emission factors, but those of the RSC stage can differ substantially. The timing of each fire stage was identified via airborne optical and thermal IR imagery and ground-observer reports, with the airborne IR imagery also used to derive estimates of fire radiative energy (FRE), allowing the relative amount of fuel burned in each stage to be calculated and "fire averaged" emission ratios and emission factors to be determined. These "fire averaged" metrics are dominated by the headfire contribution, since the FRE data indicate that the vast majority of the fuel is burned in this stage. Our fire averaged emission ratios and factors for CO2 and CH4 agree well with those from prior studies conducted in the same area using e.g. airborne plume sampling. We also concur with past suggestions that emission factors for formaldehyde in this environment appear substantially underestimated in widely used databases, but see no evidence to support suggestions by Sinha et al. (2003) of a major overestimation in the emission factor of ammonia in works such as Andreae and Merlet (2001) and Akagi et al. (2011). We also measure somewhat higher CO and NH3 emission ratios and factors than are usually reported for this environment, which is interpreted to result from the OP-FTIR ground-based technique sampling a greater proportion of smoke from smouldering processes than is generally the case with methods such as airborne sampling. Finally, our results suggest that the contribution of burning animal (elephant) dung can be a significant factor in the emissions characteristics of certain KNP fires, and that the ability of remotely sensed fire temperatures to provide information useful in tailoring modified combustion efficiency (MCE) and emissions factor estimates maybe rather limited, at least until the generally available precision of such temperature estimates can be substantially improved. One limitation of the OP-FTIR method is its ability to sample only near-ground level smoke, which may limit application at more intense fires where the majority of smoke is released into a vertically rising convection column. Nevertheless, even in such cases the method potentially enables a much better assessment of the emissions contribution of the RSC stage than is typically conducted currently.

Wooster, M. J.; Freeborn, P. H.; Archibald, S.; Oppenheimer, C.; Roberts, G. J.; Smith, T. E. L.; Govender, N.; Burton, M.; Palumbo, I.

2011-11-01

249

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

250

How Do Paths Look From Different Perspectives?

NSDL National Science Digital Library

Using both literature (a book featuring a path, such as Little Red Riding Hood) and satellite images, students will identify paths, observe and analyze them from different altitudes, and distinguish natural paths from those made by humans. Students will learn how images can inform the building, use and maintenance of paths. The URL opens to the investigation directory, with links to teacher and student materials, lesson extensions, resources, teaching tips, and assessment strategies. This is Investigation 2 of four found in the Grades K-4 Module 4 of Mission Geography. The Mission Geography curriculum integrates data and images from NASA missions with the National Geography Standards. Each of the four investigations in Module 4, while related, can be done independently. Please see Investigation 1 of this module for a two-page module overview and list of all standards addressed.

251

Super-Brownian motion with reflecting historical paths

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

252

Two thermoelectrically cooled mid-infrared distributed feedback quantum cascade lasers operated in pulsed mode have been used for the quasi-simultaneous determination of NO and NO2 in the sub-parts per million meter (sub-ppm-m) range. Using a beam splitter, the beams of the two lasers were combined and sent to a retro-reflector. The returned light was recorded with a thermoelectrically cooled mercury cadmium telluride detector with a rise time of 4 ns. Alternate operation of the lasers with pulse lengths of 300 ns and a repetition rate of 66 kHz allowed quasi-simultaneous measurements. During each pulse the laser temperature increased, causing a thermal chirp of the laser line of up to 1.3 cm(-1). These laser chirps were sufficient to scan rotational bands of NO centered at 1902 cm(-1) and NO2 located at 1632 cm(-1). In that way an absorption spectrum could be recorded from a single laser pulse. Currently achieved limits of detection are 600 parts per billion meter (ppb-m) for NO and 260 ppb-m for NO2 using signal averaging over 1 min. This work presents the first steps toward a portable stand-off, open-path instrument that uses thermoelectrically cooled detector and lasers. PMID:24359649

Reidl-Leuthner, Christoph; Lendl, Bernhard

2013-12-01

253

Purpose. Primary open-angle glaucoma (POAG) is a complex disease with a genetic architecture that can be simplified through the investigation of individual traits underlying disease risk. It has been well studied in twin models, and this study was undertaken to investigate the heritability of some of these key endophenotypes in extended pedigrees. Methods. These data are derived from a large, multicenter study of extended, Caucasian POAG families from Australia and the United States. The study included 1181 people from 22 extended pedigrees. Variance components modeling was used to determine the heritabilities of maximum intraocular pressure (IOP), maximum vertical cup-to-disc ratio (VCDR), and mean central corneal thickness (CCT). Bivariate quantitative genetic analysis between these eye-related phenotypes and POAG itself was performed to determine whether any of these traits represent true endophenotypes. Results. Heritability estimates for IOP, VCDR, and CCT (0.42, 0.66, and 0.72, respectively) were significant and show strong concordance with data in previous studies. Bivariate analysis revealed that both IOP (RhoG = 0.80; P = 9.6 × 10?6) and VCDR (RhoG = 0.76; P = 4.8 × 10?10) showed strong evidence of genetic correlation with POAG susceptibility. These two traits also correlated genetically with each other (RhoG = 0.45; P = 0.0012). Alternatively, CCT did not correlate genetically with risk of POAG. Conclusions. All the proposed POAG-related traits have genetic components. However, the significant genetic correlations observed between IOP, VCDR, and POAG itself suggest that they most likely represent true endophenotypes that could aid in the identification of genes underlying POAG susceptibility. CCT did not correlate genetically with disease and is unlikely to be a useful surrogate endophenotype for POAG. PMID:20237253

Charlesworth, Jac; Kramer, Patricia L.; Dyer, Tom; Diego, Victor; Samples, John R.; Craig, Jamie E.; Mackey, David A.; Hewitt, Alex W.; Blangero, John

2010-01-01

254

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

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

255

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

256

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

257

NASA Astrophysics Data System (ADS)

Nitrous oxide (N2O) is an important greenhouse gas with an atmospheric lifetime of ~ 120 years and a global warming potential ~300 times that of CO2. Atmospheric N2O concentrations have increased from ~270 ppbv during pre-industrial times to ~330 ppbv today. Anthropic emissions are a major source of atmospheric N2O and about half of global anthropic emissions are from the agricultural sector. N2Oemissions from soils exhibit high spatial and temporal variability. Estimation of N2O emissions from agricultural soils is particularly challenging because N2O fluxes are affected by fertilizer type and application rates, land-use history and management, as well as soil biological activity. We studied ecosystem level N2O emissions from agricultural lands using a combination of static chamber methods and continuous N2O exchange measured by a quantum cascade laser-based, open-path analyzer coupled with an eddy-covariance system. We also compared N2O emissions between different static chamber methods, using both laboratory-based gas chromatography (GC) and an in situ quantum cascade (QC) laser for N2O analyses. Finally, we compared emissions estimated by the two static chamber methods to those estimated by eddy-covariance. We examined pre- and post- fertilization N2O fluxes from soils in two no-till continuous corn fields with distinct land-use histories: one field converted from permanent grassland (CRP-C) and the other from conventional corn-soybean rotation (AGR-C). Both fields were fertilized with ~160 kg urea-N ha-1. We compared N2O emissions from these fields to those from an unmanaged grassland (REF). In addition, we examined the potential effect of post-fertilization precipitation on N2O emissions by applying 50 mm of artificial rainfall to the static chambers at all three locations. Measurements of N2O emissions using both GC and QC laser methods with static chambers were in good agreement (R2 = 0.96). Even though average soil N2O fluxes before fertilization were low, they still exhibited high temporal and spatial variability. Fluxes from the CRP-C site were higher than fluxes from the AGR-C site, and fluxes from the REF site were lowest, ranging from 2 - 22, 1 - 3, and ~1 g N2O-N ha-1 day-1, respectively. Post-fertilization fluxes were minor as well due to very dry soil conditions in 2012. However, after applying artificial rain, soil N2O fluxes were distinctly higher in all systems, increasing to 106 - 208 g N2O-N ha-1 day-1 at the CRP-C site, to 36 g N2O-N ha-1 day-1 at Ag-C, and to 5 g N2O-N ha-1 day-1 at the REF site. Fluxes decreased to pre-rain levels 1-2 days after wetting. This single rain event resulted in total emissions of 5, 43, and 251 g N2O-N ha-1 from REF, Ag-C, and CRP-C systems, respectively. A comparison between static chambers and the open-path method at CRP-C system revealed similar diurnal trends in N2O fluxes and similar cumulative N2O-N emissions. Overall, we found a strong relationship between land-use history and soil N2O emissions: soils with higher organic carbon content (CRP-C) exhibited greater fluxes. In addition, we found that N2O emissions increased significantly after a post-fertilization rain event, accounting for a significant proportion of typical total annual emission from these no-till corn fields. We also present the first measurements of ecosystem level N2O fluxes using an open-path N2O analyzer and show the potential of this novel system to study ecosystem level N2O fluxes.

Gelfand, I.; Cui, M.; Tao, L.; Sun, K.; Tang, J.; Zondlo, M. A.; Robertson, G. P.

2012-12-01

258

Michael Grunwald Transition path sampling

Michael Gr¨unwald 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

259

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

260

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

261

OPEN PATH OPTICAL SENSING OF PARTICULATE MATTER

The paper discusses the concepts behind recent developments in optical remote sensing (ORS) and the results from experiments. Airborne fugitive and fine particulate matter (PM) from various sources contribute to exceedances of state and federal PM and visibility standards. Recent...

262

Tortuous path chemical preconcentrator

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

263

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

264

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.

265

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.

266

The lawnmower problem and other geometric path covering problems

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

267

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

268

Detection of deregulated modules using deregulatory linked path.

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

269

Advisory Algorithm for Scheduling Open Sectors, Operating Positions, and Workstations

NASA Technical Reports Server (NTRS)

Air traffic controller supervisors configure available sector, operating position, and work-station resources to safely and efficiently control air traffic in a region of airspace. In this paper, an algorithm for assisting supervisors with this task is described and demonstrated on two sample problem instances. The algorithm produces configuration schedule advisories that minimize a cost. The cost is a weighted sum of two competing costs: one penalizing mismatches between configurations and predicted air traffic demand and another penalizing the effort associated with changing configurations. The problem considered by the algorithm is a shortest path problem that is solved with a dynamic programming value iteration algorithm. The cost function contains numerous parameters. Default values for most of these are suggested based on descriptions of air traffic control procedures and subject-matter expert feedback. The parameter determining the relative importance of the two competing costs is tuned by comparing historical configurations with corresponding algorithm advisories. Two sample problem instances for which appropriate configuration advisories are obvious were designed to illustrate characteristics of the algorithm. Results demonstrate how the algorithm suggests advisories that appropriately utilize changes in airspace configurations and changes in the number of operating positions allocated to each open sector. The results also demonstrate how the advisories suggest appropriate times for configuration changes.

Bloem, Michael; Drew, Michael; Lai, Chok Fung; Bilimoria, Karl D.

2012-01-01

270

Sampling diffusive transition paths

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

271

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

272

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

273

Super-Brownian motion with reflecting historical paths

. 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-François Le Gall

2001-01-01

274

Covariant path integrals on hyperbolic surfaces

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

275

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

276

DNA Computing Hamiltonian path

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

277

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

278

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

279

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.

280

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

281

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

282

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

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

2012-12-01

283

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

284

Modeling DNA Dynamics by Path Integrals

NASA Astrophysics Data System (ADS)

Complementary strands in DNA double helix show temporary fluctuational openings which are essential to biological functions such as transcription and replication of the genetic information. Such large amplitude fluctuations, known as the breathing of DNA, are generally localized and, microscopically, are due to the breaking of the hydrogen bonds linking the base pairs (bps). I apply imaginary time path integral techniques to a mesoscopic Hamiltonian which accounts for the helicoidal geometry of a short circular DNA molecule. The bps displacements with respect to the ground state are interpreted as time dependent paths whose amplitudes are consistent with the model potential for the hydrogen bonds. The portion of the paths configuration space contributing to the partition function is determined by selecting the ensemble of paths which fulfill the second law of thermodynamics. Computations of the thermodynamics in the denaturation range show the energetic advantage for the equilibrium helicoidal geometry peculiar of B-DNA. I discuss the interplay between twisting of the double helix and anharmonic stacking along the molecule backbone suggesting an interesting relation between intrinsic nonlinear character of the microscopic interactions and molecular topology.

Zoli, Marco

2013-02-01

285

Path allocation for wavelength path sharing University College London

: 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

286

PATHS groundwater hydrologic model

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

287

CO2 phase and amplitude spectra measured over 2 km outdoor path with a dual-comb spectrometer

NASA Astrophysics Data System (ADS)

We present dispersive dual-comb spectroscopy of atmospheric CO2 across a 2-km open-air path. By sending a single comb through the open-air path, both molecular phase spectrum and conventional absorbance spectrum are obtained. The measured phase spectra match expected molecular lineshape models.

Coddington, I.; Giorgetta, F. R.; Rieker, G. B.; Swann, W. C.; Zolot, A. M.; Sinclair, L. C.; Baumann, E.; Cromer, C.; Newbury, N. R.

2014-09-01

288

To study the differences in functional brain networks between eyes-closed (EC) and eyes-open (EO) at resting state, electroencephalographic (EEG) activity was recorded in 21 normal adults during EC and EO states. The synchronization likelihood (SL) was applied to measure correlations between all pairwise EEG channels, and then the SL matrices were converted to graphs by thresholding. Graphs were measured by topological parameters in theta (4-7?Hz), alpha (8-13?Hz), and beta (14-30?Hz) bands. By changing from EC to EO states, mean cluster coefficients decreased in both theta and alpha bands, but mean shortest path lengths became shorter only in the alpha band. In addition, local efficiencies decreased in both theta and alpha bands, while global efficiencies in the alpha band increased inversely. Opening the eyes decreased both nodes and connections in frontal area in the theta band, and also decreased those in bilateral posterior areas in the alpha band. These results suggested that a combination of the SL and graph theory methods may be a useful tool for distinguishing states of EC and EO. The differences in functional connectivity between EC and EO states may reflect the difference of information communication in human brain. PMID:23690886

Tan, Bo; Kong, Xianxian; Yang, Ping; Jin, Zhenlan; Li, Ling

2013-01-01

289

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

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 clones–pl7-2.3EE (D8S43), L24 (D8S45), and L40 (D8S49)–which flank the SRO recognize evolutionarily conserved sequences. ImagesFigure 1Figure 3Figure 4 PMID:1836105

Lüdecke, 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

290

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

291

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.

292

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

293

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

294

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

295

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

296

Time-Optimal Control of Robotic Manipulators Along Specified Paths

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

297

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

298

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

299

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

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

300

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.

301

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

302

[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

303

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.; Gänsicke, B. T.; Groot, P. J.; Hakala, P.; Koester, D.; Nelemans, G.; Roelofs, G.; Southworth, J.; Steeghs, D.; Tulloch, S.

2011-01-01

304

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

305

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

306

Thermoalgebras and path integral

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

307

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

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

308

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

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

309

Robust optimization of OSPF\\/ISIS weights

In this paper, we adapt the heuristic of Fortz and Thorup for optimizing the weights of Shortest Path First protocols such as Open Shortest Path First (OSPF) or Intermediate System-Intermediate System (IS-IS), in order to take into account failure scenarios. More precisely, we want to find a set of weights that is robust to all single link failures. A direct

Bernard Fortz; Mikkel Thorup

2003-01-01

310

Obstacle avoidance and path planning

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

311

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

312

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

313

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.; Díaz Trigo, M.; Homan, J.; Ibarra, A.; Kennea, J. A.; Muñoz-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

314

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

315

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

316

Heuristically optimal path scanning for high-speed multiphoton circuit imaging

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

317

In recent years, a new class of enclosed, closed-path gas analyzers suitable for eddy covariance applications has come to market, designed to combine the advantages of traditional closed-path systems (small density corrections, good performance in poor weather) and open-path syst...

318

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

319

XCB, the last of the shortest single axioms for the classical equivalential calculus.

It has long been an open question whether the formula XCB = EpEEEpqErqr is, with the rules of substitution and detachment, a single axiom for the classical equivalential calculus. This paper answers that question affirmatively, thus completing a search for all such eleven-symbol single axioms that began seventy years ago.

Wos, L.; Ulrich, D.; Fitelson, B.; Mathematics and Computer Science; Purdue Univ.; San Jose State Univ.

2003-01-01

320

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

321

An introduction to critical paths.

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

322

COMPUTER SCIENCE: MISCONCEPTIONS, CAREER PATHS

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

323

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

324

Collaborative Authoring of Walden's Paths

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

325

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

326

Scattering theory with path integrals

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

327

Survivable paths in multilayer networks

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

328

3. Aerial view of turnpike path showing realignment of 1917. ...

3. Aerial view of turnpike path showing realignment of 1917. Modernized Orange Turnpike visible running diagonally up from lower left to open area where it veers to the west around the Migel Estate. The beginning of the realignment is located by the cluster of white trailers. Original alignment visible as a row of trees cutting through the base landscape. View looking northwest. - Orange Turnpike, Parallel to new Orange Turnpike, Monroe, Orange County, NY

329

A Path Integral Approach¶to the Kontsevich Quantization Formula

: We give a quantum field theory interpretation of Kontsevich's deformation quantization formula for Poisson manifolds. We\\u000a show that it is given by the perturbative expansion of the path integral of a simple topological bosonic open string theory.\\u000a Its Batalin–Vilkovisky quantization yields a superconformal field theory. The associativity of the star product, and more\\u000a generally the formality conjecture can then

Alberto S. Cattaneo; Giovanni Felder

2000-01-01

330

On hallucinated garden paths UC San Diego

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

331

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

332

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

333

PATH DECOMPOSITION METHOD FOR POTENTIALS

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

334

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

335

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

336

Career Paths in Environmental Sciences

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...

337

Equivariant Localization of Path Integrals

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

338

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

339

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

340

Low bias integrated path estimators

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

341

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 10100·µm along the shortest axis (e from mitochondria to sites of ATP demand (Mainwood and Rakusan, 1982). However, some muscle fibers from

Kinsey, Stephen

342

Critical Path-Based Thread Placement for NUMA Systems

Multicore multiprocessors use a Non Uniform Memory Architecture (NUMA) to improve their scalability. However, NUMA introduces performance penalties due to remote memory accesses. Without efficiently managing data layout and thread mapping to cores, scientific applications, even if they are optimized for NUMA, may suffer performance loss. In this paper, we present algorithms and a runtime system that optimize the execution of OpenMP applications on NUMA architectures. By collecting information from hardware counters, the runtime system directs thread placement and reduces performance penalties by minimizing the critical path of OpenMP parallel regions. The runtime system uses a scalable algorithm that derives placement decisions with negligible overhead. We evaluate our algorithms and runtime system with four NPB applications implemented in OpenMP. On average the algorithms achieve between 8.13% and 25.68% performance improvement compared to the default Linux thread placement scheme. The algorithms miss the optimal thread placement in only 8.9% of the cases.

Su, C Y; Li, D; Nikolopoulos, D S; Grove, M; Cameron, K; de Supinski, B R

2011-11-01

343

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

344

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

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; Amlôt, Richard; Page, Lisa; Pearce, Julia; Wessely, Simon

2013-08-01

345

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

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) Â· Participants no path (2 = 5.19, p = 0.02, = 0.22). Water Scarcity Â· Respondents from water-scarce sites were found

Hall, Sharon J.

346

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

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

347

Beam path average data from an open path Fourier transform infrared (OP-FTIR) spectrometer can be used to reconstruct 2D concentration maps of the gas and vapor contaminants in workplaces using computed tomographic (CT) techniques. However, a practical limitation arises because many source and detector units are required to produce a sufficient number of intersecting beam paths in order to reconstruct

Doo Y. Park; Michael G. Yost; Anushka C. Drescher; Ashok J. Gadgil; Yi Zhou; Steven P. Levine

1995-01-01

348

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.

349

Model for Delay Faults Based upon Paths

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

350

Time optimal paths for high speed maneuvering

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

351

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

352

Understanding Delay Variations on Internet Paths

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

353

Interior point path following algorithms

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

354

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 electron–electron and electron–phonon 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

355

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

356

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

357

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

358

Path Integrals and Coherent States

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.

359

CALIFORNIA PATH PROGRAM INSTITUTE OF TRANSPORTATION STUDIES

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.

360

Quantifying the Causes of Path Inflation

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

361

Chip layout optimization using critical path weighting

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

362

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

363

Accelerating cleanup: Paths to closure

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

364

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

365

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

366

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

367

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

368

Random paths and current fluctuations in nonequilibrium statistical mechanics

An overview is given of recent advances in nonequilibrium statistical mechanics about the statistics of random paths and current fluctuations. Although statistics is carried out in space for equilibrium statistical mechanics, statistics is considered in time or spacetime for nonequilibrium systems. In this approach, relationships have been established between nonequilibrium properties such as the transport coefficients, the thermodynamic entropy production, or the affinities, and quantities characterizing the microscopic Hamiltonian dynamics and the chaos or fluctuations it may generate. This overview presents results for classical systems in the escape-rate formalism, stochastic processes, and open quantum systems.

Gaspard, Pierre [Center for Nonlinear Phenomena and Complex Systems and Department of Physics, Université Libre de Bruxelles, Code Postal 231, Campus Plaine, B-1050 Brussels (Belgium)

2014-07-15

369

Characterizing the evolutionary path(s) to early Homo.

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

370

An advanced open path atmospheric pollution monitor for large areas

Over 100 million gallons of radioactive and toxic waste materials generated in weapon materials production are stored in 322 tanks buried within large areas at DOE sites. Toxic vapors occur in the tank headspace due to the solvents used and chemical reactions within the tanks. To prevent flammable or explosive concentration of volatile vapors, the headspace are vented, either manually or automatically, to the atmosphere when the headspace pressure exceeds preset values. Furthermore, 67 of the 177 tanks at the DOE Hanford Site are suspected or are known to be leaking into the ground. These underground storage tanks are grouped into tank farms which contain closely spaced tanks in areas as large as 1 km{sup 2}. The objective of this program is to protect DOE personnel and the public by monitoring the air above these tank farms for toxic air pollutants without the monitor entering the tanks farms, which can be radioactive. A secondary objective is to protect personnel by monitoring the air above buried 50 gallon drums containing moderately low radioactive materials but which could also emit toxic air pollutants.

Taylor, L.; Suhre, D.; Mani, S. [and others

1996-12-31

371

GPS moving performance on open sky and forested paths

In this paper we present a systematic study of the performance of seven different configurations of GPS on a moving vehicle using three different GPS receivers. The seven different configurations are 1)single frequency code differential DGPS, 2)double frequency code differential DGPS, 3)RTK-GPS receiving RTCM correction from a mobile phone, 4)RTK-GPS receiving RTCM correction information via wireless module from base antenna,

Luis Yoichi Morales Saiki; Takashi Tsubouchi

2007-01-01

372

Improved FTIR open-path remote sensing data reduction technique

NASA Astrophysics Data System (ADS)

Progress on the developement of a nonlinear curve fitting computer algorithm for data reduction of optical remote sensing Fourier transform spectrometer (FTS) data is presented. This new algorithm is an adaptation of an existing algorithm employed at the Arnold Engineering Development Center for the analysis of infrared plume signature and optical gas diagnostic data on rocket and turbine engine exhaust. Because it is a nonlinear model, the algorithm can be used to determine parameters not readily determined by linear methods such as classical least squares. Unlike linear methods this procedure can simultaneously determine atmospheric gas concetrations, spectral resolution, spectral shift, and the background or (Io(omega) spectrum. Additionally, species which possess spectra that are strongly masked by atmospheric absorption features such as BTX can also be incorporated into the procedure. The basic theory behind the algorithm is presented as well as test results on FTS data and synthetic data containing benzene and toluene spectral features.

Phillips, Bill; Moyers, Rick; Lay, Lori T.

1995-05-01

373

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

374

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.

375

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

376

Staff detection with stable paths.

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

377

Technology Transfer Automated Retrieval System (TEKTRAN)

The U.S. EPA recently demonstrated the open-path optical remote sensing technology to identify hot spots and estimate mass flux of fugitive gases from closed landfill. The objective of this research is to validate this technology for estimating ammonia and methane emission from concentrated animal f...

378

LONG-PATH FTIR MEASUREMENTS OF VOLATILE ORGANIC COMPOUNDS IN AN INDUSTRIAL SETTING

As part of a Superfund Innovative Technology Evaluation (SITE) field program, a Fourier transform infrared (FTIR) spectrometer vas used to make open path measurements of volatile organic compounds in the New Castle, Delaware, area. he SITE program requires that new technologies b...

379

Effective Path Selection for Delay Fault Testing of Sequential Circuits

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

380

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

381

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

382

Endhost path selection—the ability for endhosts to spec- ify the paths which their packets should traverse—has 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

383

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

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

384

Paths - What Are They and Who Makes Them?

NSDL National Science Digital Library

Students will complete several activities in which they will describe, draw, examine and explore paths. Activities range from describing, drawing and exploring local paths (roads/sidewalks to school, hiking trails, trails in the local school environment, etc.) to comparing and contrasting larger-scale paths (streets, bridges, runways, rivers) on maps and in satellite images of three major world cities. NASA satellite images of Boston, Paris and Houston are included in the lesson. This investigation also introduces students to the need for "ground truthing." The URL opens to the investigation directory, with links to teacher and student materials, lesson extensions, resources, teaching tips, and assessment strategies. The teacher's guide will begin with a two-page module overview and list of all standards addressed. This is Investigation 1 of four found in the Grades K-4 Module 4 of Mission Geography. The Mission Geography curriculum integrates data and images from NASA missions with the National Geography Standards. Each of the four investigations in Module 4, while related, can be done independently.

385

Extracting Critical Path Graphs from MPI Applications

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

386

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

387

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

388

The calculation of ionospheric ray paths

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

389

The Logic behind Feynman's Paths

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

390

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

391

Investigation of leakage current paths in n-GaN by conductive atomic force microscopy

NASA Astrophysics Data System (ADS)

We have investigated electrical characteristics of leakage current paths in n-GaN layer grown by metal-organic chemical vapor deposition with conductive-atomic force microscopy (C-AFM). The C-AFM mapping shows two kinds of leakage current paths existing in the n-GaN layer: open-core dislocation and pure screw dislocation. From the localized I-V curves measured by C-AFM, we confirmed that the open-core screw dislocation shows more significant leakage current. We explained these results in terms of a modified Schottky band model based on donor states formed by oxygen segregation at the {10-10} sidewall of the open-core screw dislocation.

Kim, Bumho; Moon, Daeyoung; Joo, Kisu; Oh, Sewoung; Lee, Young Kuk; Park, Yongjo; Nanishi, Yasushi; Yoon, Euijoon

2014-03-01

392

Investigation of leakage current paths in n-GaN by conductive atomic force microscopy

We have investigated electrical characteristics of leakage current paths in n-GaN layer grown by metal-organic chemical vapor deposition with conductive-atomic force microscopy (C-AFM). The C-AFM mapping shows two kinds of leakage current paths existing in the n-GaN layer: open-core dislocation and pure screw dislocation. From the localized I-V curves measured by C-AFM, we confirmed that the open-core screw dislocation shows more significant leakage current. We explained these results in terms of a modified Schottky band model based on donor states formed by oxygen segregation at the (10?10) sidewall of the open-core screw dislocation.

Kim, Bumho; Park, Yongjo, E-mail: yp0520@snu.ac.kr, E-mail: eyoon@snu.ac.kr [Energy Semiconductor Research Center, Advanced Institutes of Convergence Technology, Seoul National University, Suwon 443-270 (Korea, Republic of)] [Energy Semiconductor Research Center, Advanced Institutes of Convergence Technology, Seoul National University, Suwon 443-270 (Korea, Republic of); Moon, Daeyoung; Nanishi, Yasushi [WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of)] [WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Joo, Kisu [Energy Semiconductor Research Center, Advanced Institutes of Convergence Technology, Seoul National University, Suwon 443-270 (Korea, Republic of) [Energy Semiconductor Research Center, Advanced Institutes of Convergence Technology, Seoul National University, Suwon 443-270 (Korea, Republic of); Department of Nano Science and Technology, Graduate School of Convergence Science and Technology, Seoul National University, Suwon 443-270 (Korea, Republic of); Oh, Sewoung [Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of)] [Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Lee, Young Kuk [Korea Research Institute of Chemical Technology, Daejon 305-600 (Korea, Republic of)] [Korea Research Institute of Chemical Technology, Daejon 305-600 (Korea, Republic of); Yoon, Euijoon, E-mail: yp0520@snu.ac.kr, E-mail: eyoon@snu.ac.kr [Energy Semiconductor Research Center, Advanced Institutes of Convergence Technology, Seoul National University, Suwon 443-270 (Korea, Republic of) [Energy Semiconductor Research Center, Advanced Institutes of Convergence Technology, Seoul National University, Suwon 443-270 (Korea, Republic of); WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Department of Nano Science and Technology, Graduate School of Convergence Science and Technology, Seoul National University, Suwon 443-270 (Korea, Republic of); Department of Materials Science and Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of)

2014-03-10

393

Quantum Path Interference through Incoherent Motions in Multilevel Quantum Systems

Quantum path interferences or resonances in multilevel dissipative quantum systems play an important and intriguing role in the transport processes of nanoscale systems. Many previous minimalistic models used to describe the quantum path interference driven by incoherent fields are based on the approximations including the second order perturbation for the weak coupling limit, the ad-hoc choices of two-time correlation functions and $\\it{etc}$. On the other hand, the similar model to study the non-adiabatic molecular electronic excitation have been extensively developed and many efficient quantum molecular dynamics simulation schemes, such as the Ehrenfest scheme, have been proposed. In this paper, I aim to propose an unified model, extend the Ehrenfest scheme to study the interactions of system-light and system-phonon simultaneously and gain insight into and principles of the roles of quantum path interferences in the realistic molecular systems. I discuss how to derive the time-dependent stochastic Schr$\\ddot{o}$dinger equation from the Ehrenfest scheme as a foundation to discuss the detailed balance for the weak coupling limit and therefore the quantum correction in the Ehrenfest scheme. Different from the master equation technique, the Ehrenfest scheme doesn't need any specific assumptions about spectral densities and two time correlation functions. With simple open two-level and three-level quantum systems, I show the effect of the quantum path interference on the steady state populations. Currently I only focus on the role of the phonon thermal reservoir. The electromagnetic field (solar light) will be modeled as a thermal reservoir and discussed in detail in the future paper.

Xin Chen

2013-10-21

394

Finding Regular Simple Paths in Graph Databases

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

395

Collaborative path planning for a robotic wheelchair.

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

396

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

397

A Methodology for Intelligent Path Planning

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

398

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

399

Plasma Facing Components (The Path to DEMO)

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

400

CALIFORNIA PATH PROGRAM INSTITUTE OF TRANSPORTATION STUDIES

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.

401

Asymmetric fluctuation relaxation paths in FPU models

NASA Astrophysics Data System (ADS)

A recent theory by Bertini, De Sole, Gabrielli, Jona-Lasinio and Landim predicts a temporal asymmetry in the fluctuation-relaxation paths of certain observables of nonequilibrium systems in local thermodynamic equilibrium. We find temporal asymmetries in the fluctuation-relaxation paths of a form of local heat flow, in the nonequilibrium FPU- ? model of Lepri, Livi and Politi.

Giberti, C.; Rondoni, L.; Vernia, C.

2006-06-01

402

Outdoor Path Labeling Using Polynomial Mahalanobis Distance

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

403

Katrina'sPath Lake Pontchartrain

'sPath Katrina's Storm Surge #12;Now Scenario Hurricane Toufectis Â· Approaches from the ESE, traveling WNW Â· SSC to Katrina #12;Gotwals'Path Now Scenario Hurricane Gotwals Â· Katrina is as Katrina was Â· Storm track moved 4 Hurricane Horton Â· Katrina is as Katrina was Â· Adding roughly 10" sea level rise (25cm) Impacts Â· Similar

404

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

405

ON LANDSCAPE FUNCTIONS ASSOCIATED WITH TRANSPORT PATHS

ON LANDSCAPE FUNCTIONS ASSOCIATED WITH TRANSPORT PATHS QINGLAN XIA Abstract. In this paper, we by Santambrogio in [10]. More precisely, we study landscape functions associated with a transport path be- tween for nonpositive p. We show an equivalence relation be- tween landscape functions associated with an -transport

Xia, Qinglan

406

Evaluation of Calcine Disposition Path Forward

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

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

2003-02-26

407

Evaluation of Calcine Disposition - Path Forward

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

Steve Birrer

2003-02-01

408

Adaptively Ubiquitous Learning in Campus Math Path

ERIC Educational Resources Information Center

The purposes of this study are to develop and evaluate the instructional model and learning system which integrate ubiquitous learning, computerized adaptive diagnostic testing system and campus math path learning. The researcher first creates a ubiquitous learning environment which is called "adaptive U-learning math path system". This system…

Shih, Shu-Chuan; Kuo, Bor-Chen; Liu, Yu-Lung

2012-01-01

409

A Pilot Plant: The Fastest Path to

and then building Demo to produce net electricity may not be the fastest path. Consider construction of a device1/14 A Pilot Plant: The Fastest Path to Net Electricity from Fusion Fusion Power Associates Thirty seconds in 2028. The MFE Program Needs to Move Faster Implications Building a Component Test Facility

410

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

411

Converging towards the optimal path to extinction

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

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

2011-01-01

412

On Path Decomposition Conjecture of Tibor Gallai

We settle the Path Decomposition Conjecture (P.D.C.) due to Tibor Gallai for minimally connected graphs, i.e. trees. We use this validity for trees and settle the P. D. C. using induction on the number of edges for all connected graphs. We then obtain a new bound for the number of paths in a path cover in terms of the number of edges using idea of associating a tree with a connected graph. We then make use of a spanning tree in the given connected graph and its associated basic path cover to settle the conjecture of Tibor Gallai in an alternative way. Finally, we show the existence of Hamiltonian path cover satisfying Gallai bound for complete graphs of even order and discuss some of its possible ramifications.

Dhananjay P. Mehendale

2011-06-02

413

The Polyakov path integral over bordered surfaces: II. The closed string off-shell amplitudes

NASA Astrophysics Data System (ADS)

Following the general scheme of the convariant path integral quantization of gauge systems, two alternative formulations of the first quantized closed bosonic string in a position representation are presented. In both approaches the covariant path integral representations of the propagator and of the higher order off-shell amplitudes are constructed. For a wide class of gauges the explicit formulae for off-shell amplitudes are obtained. This paper is the continuation of our previous work where the corresponding problems in the open string case were considered [20].

Jaskólski, Zbigniew

1991-08-01

414

Success of Path Dependence Through Perpetuation of Failure During Reform

The primary purpose of this paper is to extend current debates about path dependence and to contribute to scholarship by addressing inadequately researched aspects of path dependence: the role of individuals in sustaining long-standing 'inefficient' institutions; the balance of 'path following' and 'path violation'; and path dependent resource utilisation, not resource allocation. These matters are illustrated through and discussed in

E Kasabov

2010-01-01

415

Precision Cleaning - Path to Premier

NASA Technical Reports Server (NTRS)

ITT Space Systems Division s new Precision Cleaning facility provides critical cleaning and packaging of aerospace flight hardware and optical payloads to meet customer performance requirements. The Precision Cleaning Path to Premier Project was a 2007 capital project and is a key element in the approved Premier Resource Management - Integrated Supply Chain Footprint Optimization Project. Formerly precision cleaning was located offsite in a leased building. A new facility equipped with modern precision cleaning equipment including advanced process analytical technology and improved capabilities was designed and built after outsourcing solutions were investigated and found lacking in ability to meet quality specifications and schedule needs. SSD cleans parts that can range in size from a single threaded fastener all the way up to large composite structures. Materials that can be processed include optics, composites, metals and various high performance coatings. We are required to provide verification to our customers that we have met their particulate and molecular cleanliness requirements and we have that analytical capability in this new facility. The new facility footprint is approximately half the size of the former leased operation and provides double the amount of throughput. Process improvements and new cleaning equipment are projected to increase 1st pass yield from 78% to 98% avoiding $300K+/yr in rework costs. Cost avoidance of $350K/yr will result from elimination of rent, IT services, transportation, and decreased utility costs. Savings due to reduced staff expected to net $4-500K/yr.

Mackler, Scott E.

2008-01-01

416

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

417

Path integral for inflationary perturbations

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

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

2010-07-15

418

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

419

Oriented paths in n-chromatic digraphs

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

420

Openness in Higher Education: Open Source, Open Standards, Open Access

For national advisory services in the UK (UKOLN, CETIS, and OSS Watch), varieties of openness (open source software, open standards, and open access to research publications and data) present an interesting challenge. Higher education is often keen to embrace openness, including new tools such as blogs and wikis for students and staff. For advisory services, the goal is to achieve

Brian Kelly; Scott Wilson; Randy Metcalfe

2007-01-01

421

Polynomial Sequences of Binomial Type Path Integrals

Polynomial sequences $ p_n (x) $ of binomial type are a principal tool in the umbral calculus of enumerative combinatorics. We express $ \\\\mathbb{N} \\\\times [-\\\\pi, \\\\pi] $ as a path integral in the \\

Vladimir V. Kisil

2002-01-01

422

Identifying decohering paths in closed quantum systems

NASA Technical Reports Server (NTRS)

A specific proposal is discussed for how to identify decohering paths in a wavefunction of the universe. The emphasis is on determining the correlations among subsystems and then considering how these correlations evolve. The proposal is similar to earlier ideas of Schroedinger and of Zeh, but in other ways it is closer to the decoherence functional of Griffiths, Omnes, and Gell-Mann and Hartle. There are interesting differences with each of these which are discussed. Once a given coarse-graining is chosen, the candidate paths are fixed in this scheme, and a single well defined number measures the degree of decoherence for each path. The normal probability sum rules are exactly obeyed (instantaneously) by these paths regardless of the level of decoherence. Also briefly discussed is how one might quantify some other aspects of classicality. The important role that concrete calculations play in testing this and other proposals is stressed.

Albrecht, Andreas

1990-01-01

423

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

424

Path integration in relativistic quantum mechanics

The simple physics of a free particle reveals important features of the path-integral formulation of relativistic quantum theories. The exact quantum-mechanical propagator is calculated here for a particle described by the simple relativistic action proportional to its proper time. This propagator is nonvanishing outside the light cone, implying that spacelike trajectories must be included in the path integral. The propagator matches the WKB approximation to the corresponding configuration-space path integral far from the light cone; outside the light cone that approximation consists of the contribution from a single spacelike geodesic. This propagator also has the unusual property that its short-time limit does not coincide with the WKB approximation, making the construction of a concrete skeletonized version of the path integral more complicated than in nonrelativistic theory.

Ian H. Redmount; Wai-Mo Suen

1992-10-28

425

Riemann Curvature Tensor and Closed Geodesic Paths

ERIC Educational Resources Information Center

Demonstrates erroneous results obtained if change in a vector under parallel transport about a closed path in Riemannian spacetime is made in a complete circuit rather than just half a circuit. (Author/SL)

Morganstern, Ralph E.

1977-01-01

426

PATH-RELINKING INTENSIFICATION METHODS FOR ...

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

427

A chemist building paths to cell biology.

Galileo is reported to have stated, "Measure what is measurable and make measurable what is not so." My group's trajectory in cell biology has closely followed this philosophy, although it took some searching to find this path. PMID:24174456

Weibel, Douglas B

2013-11-01

428

Predicting missing links via effective paths

NASA Astrophysics Data System (ADS)

Recently, in complex network, link prediction has brought a surge of researches, among which similarity based link prediction outstandingly gains considerable success, especially similarity in terms of paths. In investigation of paths based similarity, we find that the effective influence of endpoints and strong connectivity make paths contribute more similarity between two unconnected endpoints, leading to a more accurate link prediction. Accordingly, we propose a so-called effective path index (EP) in this paper to leverage effective influence of endpoints and strong connectivity in similarity calculation. For demonstrating excellence of our index, the comparisons with six mainstream indices are performed on experiments in 15 real datasets and results show a great improvement of performance via our index.

Zhu, Xuzhen; Tian, Hui; Cai, Shimin

2014-11-01

429

A chemist building paths to cell biology

Galileo is reported to have stated, “Measure what is measurable and make measurable what is not so.” My group's trajectory in cell biology has closely followed this philosophy, although it took some searching to find this path. PMID:24174456

Weibel, Douglas B.

2013-01-01

430

Paths and stability number in digraphs

The Gallai-Milgram theorem says that the vertex set of any digraph with stability number k can be partitioned into k directed paths. In 1990, Hahn and Jackson conjectured that this theorem is best possible in the following strong sense. For each positive integer k, there is a digraph D with stability number k such that deleting the vertices of any k-1 directed paths in D leaves a digraph with stability number k. In this note, we prove this conjecture.

Fox, Jacob

2009-01-01

431

The prediction of radio-path characteristics

NASA Astrophysics Data System (ADS)

The paper examines algorithms for the long-term prediction of radio-path characteristics in the ionosphere, the main characteristic being the MUF at a given distance. The proposed approach is based on long-term memories called DATA BANKS. Attention is given to the characteritics of the various banks, including the BANK OF CITIES, the BANK OF RADIO PATHS, the REFERENCE DATA BANK, and the OUTPUT DATA BANK.

Gitina, G. M.; Kalinin, Iu. K.

432

A Path Algorithm for Constrained Estimation

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

433

Path integral approach on Schrodinger's cat

From the following thought experiments, it is demonstrated that the collapse of wave function of an isolated system is possible without external observer. It will be shown that the analysis by Feynman path integral method supports this conclusion. The argument is based on two assumptions: 1. The condition of Schrodinger's cat experiment 2. Feynman path integral; This could explain Schrodinger's cat paradox and its implication on the black hole information paradox will be discussed.

Zinkoo Yun

2014-01-24

434

HomePath: Your On-Line Path to a Home of Your Own

NSDL National Science Digital Library

Whether you're thinking about if you're ready to buy a home, are in the process of buying a home, or are considering refinancing your current home, there's information for you on Fannie Mae's newest website. Fannie Mae is America's largest source of home mortgage funds, and has designed HomePath to be "your on-line path to a home of your own." There are three different paths through the information on the website: HomeStarterPath has resources for people deciding whether home ownership is right for them, including a comparison of renting vs. buying and a calculator for estimating how much house one can afford to buy; HomePurchasePath offers services for people who are ready to buy, including mortgage application information and how to shop for a lender; HomeRefinancePath helps homeowners determine when refinancing is beneficial, and outlines the costs involved.

435

Computing Diffeomorphic Paths for Large Motion Interpolation.

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

436

Long-length contaminated equipment disposal process path document

The first objective of the LLCE Process Path Document is to guide future users of this system on how to accomplish the cradle-to-grave process for the disposal of long-length equipment. Information will be provided describing the function and approach to each step in the process. Pertinent documentation, prerequisites, drawings, procedures, hardware, software, and key interfacing organizations will be identified. The second objective is related to the decision to lay up the program until funding is made available to complete it or until a need arises due to failure of an important component in a waste tank. To this end, the document will identify work remaining to be completed for each step of the process and open items or issues that remain to be resolved.

McCormick, W.A.

1998-09-30

437

Superconducting optical conductivity for arbitrary temperature and mean free path

NASA Astrophysics Data System (ADS)

Calculations of the optical conductivity of a superconductor valid for any temperature T and any mean free path l are presented. They are based on the method of Marsiglio, Schossmann, and Carbotte of computing the real-frequency-axis gap and renormalization function. The work is applied to a study of the signature of the opening of the gap edge ?(T) as the superconducting state develops. At finite temperature, the presence of a normal-fluid component leads to absorption down to zero frequency (?). For sufficiently impure systems there remains, nevertheless, a sharp threshold for additional absorption from the condensate which starts at ?=2?(T), so that it is possible to deduce from it an accurate value of ?(T). For the pure limit, the situation is more ambiguous.

Akis, R.; Carbotte, J. P.; Timusk, T.

1991-06-01

438

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

439

Studying motion along cycloidal paths by means of digital video analysis

NASA Astrophysics Data System (ADS)

The motion of a pendulum whose mass is constrained to move on a cycloid path and of a small sphere running on a frictionless cycloid track are investigated theoretically and experimentally. Measurements are carried out through analysing videos acquired using a digital camera by means of open-access video analysis software. The results obtained are in agreement with theoretical expectations. The topic, the accessibility of the experiments and the level of analysis are appropriate for an undergraduate classical mechanics course.

Onorato, P.; Mascheretti, P.; DeAmbrosis, A.

2013-07-01

440

INVERSES OF MOTZKIN AND SCHRDER PATHS Heinrich Niederhausen

the paths inside a horizontal band, and for the inverse Schröder 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

441

Off-axis paths in spherical mirror interferometers

vO = 24r, and g being integers, the rays retrace their paths. These ray paths give rise to additional resonances which were observed. Pictures of the points of reflection are reproduced. The theory is in good agreement with the experi- mental observations. In laser amplifiers these ray paths enable one to obtain long effective path lengths in the active medium

D. Herriott; H. Kogelnik; R. Kompfner

1964-01-01

442

Diagnosis for Covariance Structure Models by Analyzing the Path

ERIC Educational Resources Information Center

When a covariance structure model is misspecified, parameter estimates will be affected. It is important to know which estimates are systematically affected and which are not. The approach of analyzing the path is both intuitive and informative for such a purpose. Different from path analysis, analyzing the path uses path tracing and elementary…

Yuan, Ke-Hai; Kouros, Chrystyna D.; Kelley, Ken

2008-01-01

443

Exploring Career Paths. A Guide for Students and Their Families.

ERIC Educational Resources Information Center

This five-section guide is designed to help students and their parents explore career paths. The first part of the guide is an introduction to the concept of career paths and an explanation of the steps students follow in exploring career paths. The second section, which makes up most of the booklet, covers five steps for exploring career paths:…

Missouri Univ., Columbia. Instructional Materials Lab.

444

The formal path integral and quantum mechanics

Given an arbitrary Lagrangian function on R{sup d} and a choice of classical path, one can try to define Feynman's path integral supported near the classical path as a formal power series parameterized by 'Feynman diagrams', although these diagrams may diverge. We compute this expansion and show that it is (formally, if there are ultraviolet divergences) invariant under volume-preserving changes of coordinates. We prove that if the ultraviolet divergences cancel at each order, then our formal path integral satisfies a 'Fubini theorem' expressing the standard composition law for the time evolution operator in quantum mechanics. Moreover, we show that when the Lagrangian is inhomogeneous quadratic in velocity such that its homogeneous-quadratic part is given by a matrix with constant determinant, then the divergences cancel at each order. Thus, by 'cutting and pasting' and choosing volume-compatible local coordinates, our construction defines a Feynman-diagrammatic 'formal path integral' for the nonrelativistic quantum mechanics of a charged particle moving in a Riemannian manifold with an external electromagnetic field.

Johnson-Freyd, Theo [Department of Mathematics, University of California - Berkeley, 970 Evans Hall, Berkeley, California 94720 (United States)

2010-11-15

445

Fermionic path integrals and local anomalies

NASA Astrophysics Data System (ADS)

No doubt, the subject of path integrals proved to be an immensely fruitful human, i.e. Feynman's idea. No wonder it is more timely than ever. Some even claim that it is the most daring, innovative and revolutionary idea since the days of Heisenberg and Bohr. It is thus likely to generate enthusiasm, if not addiction among physicists who seek simplicity together with perfection. Professor Devreese's long-lasting interest in, if not passion on the subject stems from his firm conviction that, beyond being the tool of choice, path integration provides the key to all quantum phenomena, be it in solid state, atomic, molecular or particle physics as evidenced by the impressive list of publications at the address http://lib.ua.ac.be/AB/a867.html. In this note, I review a pitfall of fermionic path integrals and a way to get around it in situations relevant to the Standard Model of particle physics.

Roepstorff, G.

2003-05-01

446

Molecular path control in zeolite membranes

We report molecular simulations of diffusion in confinement showing a phenomenon that we denote as molecular path control (MPC); depending on loading, molecules follow a preferred pathway. MPC raises the important question to which extent the loading may affect the molecular trajectories in nanoporous materials. Through MPC one is able to manually adjust the ratio of the diffusivities through different types of pores, and as an application one can direct the flow of diffusing particles in membranes forward or sideward by simply adjusting the pressure, without the need for mechanical parts like valves. We show that the key ingredient of MPC is the anisotropic nature of the nanoporous material that results in a complex interplay between different diffusion paths as a function of loading. These paths may be controlled by changing the loading, either through a change in pressure or temperature. PMID:16109769

Dubbeldam, D.; Beerdsen, E.; Calero, S.; Smit, B.

2005-01-01

447

A taxonomy of integral reaction path analysis

W. C. Gardiner observed that achieving understanding through combustion modeling is limited by the ability to recognize the implications of what has been computed and to draw conclusions about the elementary steps underlying the reaction mechanism. This difficulty can be overcome in part by making better use of reaction path analysis in the context of multidimensional flame simulations. Following a survey of current practice, an integral reaction flux is formulated in terms of conserved scalars that can be calculated in a fully automated way. Conditional analyses are then introduced, and a taxonomy for bidirectional path analysis is explored. Many examples illustrate the resulting path analysis and uncover some new results about nonpremixed methane-air laminar jets.

Grcar, Joseph F.; Day, Marcus S.; Bell, John B.

2004-12-23

448

Piecewise Linear Paths Among Convex Obstacles

Let ? be a set ofn arbitrary (possibly intersecting) convex obstacles in ?\\u000a d\\u000a . It is shown that any two points which can be connected by a path avoiding the obstacles can also be connected by a path\\u000a consisting ofO(n\\u000a (d?1)[d\\/2+1]) segments. The bound cannot be improved below ?(n\\u000a \\u000a d\\u000a ); thus, in ?3, the answer is betweenn\\u000a 3

Mark De Berg; Jirí Matousek; Otfried Schwarzkopf

1995-01-01

449

Path Factorization Approach to Stochastic Simulations

NASA Astrophysics Data System (ADS)

The computational efficiency of stochastic simulation algorithms is notoriously limited by the kinetic trapping of the simulated trajectories within low energy basins. Here we present a new method that overcomes kinetic trapping while still preserving exact statistics of escape paths from the trapping basins. The method is based on path factorization of the evolution operator and requires no prior knowledge of the underlying energy landscape. The efficiency of the new method is demonstrated in simulations of anomalous diffusion and phase separation in a binary alloy, two stochastic models presenting severe kinetic trapping.

Athènes, Manuel; Bulatov, Vasily V.

2014-12-01

450

Path planning for everday robotics with SANDROS

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

451

Connections on decorated path space bundles

For a principal bundle $P\\to M$ equipped with a connection ${\\bar A}$, we study an infinite dimensional bundle ${\\mathcal P}^{\\rm dec}_{\\bar A}P$ over the space of paths on $M$, with the points of ${\\mathcal P}^{\\rm dec}_{\\bar A}P$ being horizontal paths on $P$ decorated with elements of a second structure group. We construct parallel transport processes on such bundles and study holonomy bundles in this setting. We explain the relationship with categorical geometry and explore the notion of categorical connections on categorical principal bundles in a concrete differential geometric way.

Saikat Chatterjee; Amitabha Lahiri; Ambar N. Sengupta

2015-02-11

452

Towards an Error Model for OpenMP

OpenMP lacks essential features for developing mission-critical software. In particular, it has no support for detecting and handling errors or even a concept of them. In this paper, the OpenMP Error Model Subcommittee reports on solutions under consideration for this major omission. We identify issues with the current OpenMP specification and propose a path to extend OpenMP with error-handling capabilities. We add a construct that cleanly shuts down parallel regions as a first step. We then discuss two orthogonal proposals that extend OpenMP with features to handle system-level and user-defined errors.

Wong, M; Klemm, M; Duran, A; Mattson, T; Haab, G; de Supinski, B R; Churbanov, A

2010-03-22

453

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

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

454

Energy transfer: On the right path

NASA Astrophysics Data System (ADS)

Controlled energy-transfer on a molecular scale is a goal in many areas of science, from artificial photosynthesis to molecular electronics. Now, DNA origami has been used to direct the transfer of energy from an excited input dye down one of two paths by precisely arranging a mediator dye.

Albinsson, Bo

2011-04-01

455

The Path to Disaster The Deepwater Horizon

21/08/2013 1 The Path to Disaster The Deepwater Horizon BP's disaster in the Gulf of Mexico Professor Patrick Hudson & Tim Hudson Hudson Global Consulting 4th Annual Plexus Industrial Safety Lecture Industrial Psychology Research Centre 14th August, 2013 Transocean Deepwater Horizon #12;21/08/2013 2

Pym, David J.

456

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

457

Path Integration in the Field of Dispiration

NASA Astrophysics Data System (ADS)

Path integration is carried out for the bound states of a particle in the combined field of a wedge disclination and a screw dislocation. The energy spectrum extracted from the Feynman kernel differs from that obtained by solving the Schrödinger equation.

Inomata, A.

2008-11-01

458

Learning to improve path planning performance

In robotics, path planning refers to finding a short. collision-free path from an initial robot configuration to a desired configuratioin. It has to be fast to support real-time task-level 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 remedy this situation, we present and analyze a learning algorithm that uses past experience to increase 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 robot configurations is learned to support faster planning. More generally, the algorithm provides a speedup-learning framework in which a slow but capable planner may be improved both cost-wise and capability-wise by a faster but less capable planner coupled with experience. The basic algorithm is suitable for stationary environments, and can be extended to accommodate changing environments with on-demand experience repair and object-attached experience abstraction. To analyze the algorithm, we characterize the situations in which the adaptive planner is useful, provide quantitative bounds to predict its behavior, and confirm our theoretical results with experiments in path planning of manipulators. Our algorithm and analysis are sufficiently, general that they may also be applied to other planning domains in which experience is useful.

Chen, Pang C.

1995-04-01

459

Predictors of Retirement Satisfaction: A Path Model.

ERIC Educational Resources Information Center

Examined adjustment to retirement among 310 former industrial and service workers. Respondents had come to terms with retirement and enjoyed their more relaxed lifestyle. Dominant variables in the path model were retirees' satisfaction with specific aspects of retirement: giving up work, activities with family and friends, rest, and free time. (BH)

Kremer, Yael

1985-01-01

460

Planning Flight Paths of Autonomous Aerobots

NASA Technical Reports Server (NTRS)

Algorithms for planning flight paths of autonomous aerobots (robotic blimps) to be deployed in scientific exploration of remote planets are undergoing development. These algorithms are also adaptable to terrestrial applications involving robotic submarines as well as aerobots and other autonomous aircraft used to acquire scientific data or to perform surveying or monitoring functions.

Kulczycki, Eric; Elfes, Alberto; Sharma, Shivanjli

2009-01-01

461

Efficient Data Mining for Path Traversal Patterns

In this paper, we explore a new data mining capability that involves mining path traversal patterns in a distributed information-providing environment where documents or objects are linked together to facilitate interactive access. Our solution procedure consists of two steps. First, we derive an algorithm to convert the original sequence of log data into a set of maximal forward references. By

Ming-syan Chen; Jong Soo Park; Philip S. Yu

1998-01-01

462

The Erratic Path of Hungarian Higher Education

ERIC Educational Resources Information Center

This article reviews the path of funding higher education in Hungary, where funding cuts have resulted in understaffing, escalating tuition, growing student debt, and declining enrollment. Graduation rates are low, government policies favor vocational disciplines, and the system of preparation and access gives preference to students from wealthier…

Marcus, Jon

2014-01-01

463

Asymmetrical Path Interference Test of Light

The asymmetrical path interference test of light is put forward in the paper. In the test, two different results would arise under the same experimental conditions if light is regarded as wave or particle. Therefore, the test can help us to comprehend which concept, wave or particle, is more essential for micro-particles.

Mei Xiaochun

2006-03-05

464

Code of Federal Regulations, 2014 CFR

...up to the point at which the airplane is out of ground effect and...to the continous path. The airplane is considered to be out of the...reaches a height equal to its wing span. (e) For airplanes equipped with standby...

2014-01-01

465

Code of Federal Regulations, 2013 CFR

...up to the point at which the airplane is out of ground effect and...to the continous path. The airplane is considered to be out of the...reaches a height equal to its wing span. (e) For airplanes equipped with standby...

2013-01-01

466

Code of Federal Regulations, 2012 CFR

...up to the point at which the airplane is out of ground effect and...to the continous path. The airplane is considered to be out of the...reaches a height equal to its wing span. (e) For airplanes equipped with standby...

2012-01-01

467

Geometry of particle paths in turbulent flows

We use the intrinsic geometrical characteristics of space curves, i.e. curvature and torsion, to describe the paths of particles passively advected in a turbulent flow. We find that curvature increases with the Reynolds number and that the maxima in vorticity and curvature times local velocity are linearly correlated. Fluctuations around the maximal values in runs at a fixed Reynolds number

W. Braun; F. de Lillo; B. Eckhardt

2006-01-01

468

Career Paths for Managers in the Arts

ERIC Educational Resources Information Center

In this article we examine the career paths of top-level managers in the arts. By analysing the training and work history of 23 managers in a variety of arts organisations we evaluate the utility of several existing theories for understanding careers that are characterised by low levels of initial knowledge, the absence of a clear method of entry…

Inglis, Loretta; Cray, David

2012-01-01

469

2012 Winter Issue Page The Critical Path

Analysis at Mars (SAM) instrument suite on Curiosity continues to perform well, also. Several Mars2012 Winter Issue Page The Critical Path MAVEN--Definitive Answers about Mars Climate History When the Mars Atmosphere and Volatile Evolution (MAVEN) mission launches in November 2013 it will make history

Christian, Eric

470

Path detection and the uncertainty principle

QUANTUM mechanics predicts that any detector capable of determining the path taken by a particle through a double slit will destroy the interference. This follows from the principle of complementarity formulated by Niels Bohr: simultaneous observation of wave and particle behaviour is prohibited. But such a description makes no reference to the physical mechanism by which the interference is lost.

Pippa Storey; Sze Tan; Matthew Collett; Daniel Walls

1994-01-01

471

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

472

Air Path Estimation on Diesel HCCI Engine

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

473

Code of Federal Regulations, 2011 CFR

...the takeoff path to be determined for flight in icing conditions, the airborne part of the takeoff must be based on the airplane drag: (i) With the takeoff ice accretion defined in appendix C, from a height of 35 feet above the takeoff surface up to...

2011-01-01

474

Code of Federal Regulations, 2010 CFR

...the takeoff path to be determined for flight in icing conditions, the airborne part of the takeoff must be based on the airplane drag: (i) With the takeoff ice accretion defined in appendix C, from a height of 35 feet above the takeoff surface up to...

2010-01-01

475

The Many Paths of Hypervalent Iodine Reactions

The Many Paths of Hypervalent Iodine Reactions Ryan McFadden Stoltz Literature Group Meeting June! In Outline I. What is Hypervalency? A. The Martin-Arduengo Notation B. Bonding in Hypervalent Iodine Compounds C. A Brief History of IBX and DMP II. Oxidation Chemistry of Hypervalent Iodine A. Oxidations

Stoltz, Brian M.

476

LONG PATH LASER OZONE MONITOR EVALUATION

The purpose of the study reported here was to evaluate a long path laser air pollution monitor developed for the U.S. Environmental Protection Agency (EPA) by the General Electric (GE) Company. The monitor was known as ILAMS (Infrared Laser Atmospheric Monitoring System) and desi...

477

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

478

Folded-path optical analysis gas cell

A folded-path gas cell employs an elliptical concave mirror in confronting relationship to two substantially spherical concave mirrors. At least one of the spherical mirrors, and usually both, are formed with an added cylindrical component to increase orthogonal focii coincidence and thereby to increase the radiation energy throughput characteristic of the cell.

Carangelo, Robert M. (Glastonbury, CT); Wright, David D. (Vershire, VT)

1995-01-01

479

The RFP Development Path S. C. Prager

of non-tokamak research concept A concept B concept Z reactor A reactor B reactor Z configurationThe RFP Development Path S. C. Prager University of Wisconsin January, 2003 #12;Reminder: Two views A configuration B configuration Z reactor Each concept as a fusion reactor each configuration building fusion

480

Dynamic path-based software watermarking

Software watermarking is a tool used to combat software piracy by embedding identifying information into a program. Most existing proposals for software watermarking have the shortcoming that the mark can be destroyed via fairly straightforward semantics-preserving code transformations. This paper introduces path-based watermarking, a new approach to software watermarking based on the dynamic branching behavior of programs. The advantage of

Christian S. Collberg; Edward Carter; Saumya K. Debray; Andrew Huntwork; John D. Kececioglu; Cullen Linn; Michael Stepp

2004-01-01

481

The diagnosis and cure of garden paths

We propose that, for the human parser, recovery from garden paths consists in repairing the structure built so far, rather than reparsing the input. The difficulty of a repair is attributable not to the cost of effecting the structural alterations but to the cost of deducing which alterations are needed. The parser must diagnose its error in order to correct

Janet Dean Fodor; Atsu Inoue

1994-01-01

482

Finding optimal paths in MREP routing

Maximum Residual Energy Path (MREP) routing has been shown an effective routing scheme for energy conservation in battery powered wireless networks. Past studies on MREP routing are based on the assumption that the transmitting node consumes power, but the receiving node does not. This assumption is false if acknowledgment is required as occurs, for example, in some Bluetooth applications. If

Rudolf Fleischer; Mordecai J. Golin; Chin-tau A. Lea; Steven Wong

2004-01-01

483

Particle RRT for Path Planning with Uncertainty

This paper describes a new extension to the Rapidly-exploring Random Tree (RRT) path planning algo- rithm. The Particle RRT algorithm explicitly considers uncer- tainty in its domain, similar to the operation of a particle filter. Each extension to the search tree is treated as a stochastic process and is simulated multiple times. The behavior of the robot can be characterized

Nik A. Melchior; Reid G. Simmons

2007-01-01

484

Current SPE Hydrodynamic Modeling and Path Forward

Extensive work has been conducted on SPE analysis efforts: Fault effects Non-uniform weathered layer analysis MUNROU: material library incorporation, parallelization, and development of non-locking tets Development of a unique continuum-based-visco-plastic strain-rate-dependent material model With corrected SPE data path is now set for a multipronged approach to fully understand experimental series shot effects.

Knight, Earl E. [Los Alamos National Laboratory; Rougier, Esteban [Los Alamos National Laboratory

2012-08-14

485

Volcanic eruption induced WWVB transmission path interruption

It is reported that the 60 kHz transmission of WWVB from Fort Collins, Colorado, was not received in Calgary, Alberta, Canada, for about 11 h from 1109 UT to 2153 UT on July 23, 1980. It is suggested that this transmission path interruption is correlated with the 15 km height ash cloud due to the July 22, 1980 volcanic eruption

H. A. Buckmaster; C. H. Hansen

1985-01-01

486

Issues affecting specialty career paths in dermatology.

As the field of medicine changes, physicians deal with ever-increasing challenges and pressures. An overview of broad career paths within the specialty of dermatology is presented and important issues affecting these subspecialty tracks are discussed. These issues include increasing regulatory controls, the medical liability crisis, competitive forces, corporate and global outsourcing threats, managed care, and reimbursement. PMID:18189057

Leonard, Aimee L; Hanke, C William; Bechtel, Mark A; Brownell, Isaac; Buckel, Larry J; Hurwitz, Robert M; Hsiung, Sherry H; Paller, Amy S; Turchan, Kirsten

2007-12-01

487

Encoding folding paths of RNA switches

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

488

Motion on Cycloid Paths: A Project

ERIC Educational Resources Information Center

This article reports a high school laboratory project whose theme is the motion of a small ball on cycloidal tracks. Models were built both of a brachistochrone and of a Huygens pendulum clock whose bob is constrained to move on a cycloidal path. Photogates and a data acquisition system were employed in order to investigate experimentally the…

Gluck, P.

2010-01-01

489

Photon path length retrieval from GOSAT observations

NASA Astrophysics Data System (ADS)

The influence of clouds on the atmospheric radiation budget is investigated, focussing on the photon path length distributions of the scattered sunlight. Apart from the reflection of incoming solar radiation at the cloud top, clouds can also introduce a large number of additional scattering events causing an enhancement of the photon paths. In certain cloud formations, these scattering events also result in a ``ping-pong`` behaviour between different cloud patches and cloud layers. It has been shown from ground based measurements that it is possible to retrieve photon path lengths by analysis of high resolution oxygen A-band spectra (O. Funk et al.). This study uses similar space based measurements of the oxygen A-band for the path length retrieval. The oxygen A-band spectra are retrieved from the Japanese Greenhouse Gases Observing Satellite (GOSAT) which was successfully launched in 2009. The high spectral resolution of the GOSAT TANSO-FTS instrument allows to almost completely resolve the individual absorption lines. The considered spectral range is particularly suitable for this study because it shows clear absorption structures of different strength. From the analysis of the spectral signatures, cloud properties and the underlying path length distributions can be derived. The retrieval is done by analysis and comparison of the extracted TANSO-FTS spectra with simulations from the Monte Carlo radiative transfer Model McArtim. The model permits modelling of altitude dependent oxygen absorption cross sections and three-dimensional cloud patterns. Case studies of clear and cloudy sky scenarios will be presented. Future studies will focus on more complicated cloud structures, especially considering three-dimensional geometries and heterogeneities.

Kremmling, Beke; Penning de Vries, Marloes; Deutschmann, Tim; Wagner, Thomas

2013-04-01

490

Path-consistency: When space misses time

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

491

Two paths of cluster evolution: global expansion versus core collapse

NASA Astrophysics Data System (ADS)

All gravitationally bound clusters expand, due to both gas loss from their most massive members and binary heating. All are eventually disrupted tidally, either by passing molecular clouds or the gravitational potential of their host galaxies. However, their interior evolution can follow two very different paths. Only clusters of sufficiently large initial population and size undergo the combined interior contraction and exterior expansion that leads eventually to core collapse. In all other systems, core collapse is frustrated by binary heating. These clusters globally expand for their entire lives, up to the point of tidal disruption. Using a suite of direct N-body calculations, we trace the `collapse line' in rv-N space that separates these two paths. Here, rv and N are the cluster's initial virial radius and population, respectively. For realistic starting radii, the dividing N-value is from 104 to over 105. We also show that there exists a minimum population, Nmin, for core collapse. Clusters with N < Nmin tidally disrupt before core collapse occurs. At the Sun's Galactocentric radius, RG = 8.5 kpc, we find Nmin ? 300. The minimum population scales with Galactocentric radius as R_G^{-9/8}. The position of an observed cluster relative to the collapse line can be used to predict its future evolution. Using a small sample of open clusters, we find that most lie below the collapse line, and thus will never undergo core collapse. Most globular clusters, on the other hand, lie well above the line. In such a case, the cluster may or may not go through core collapse, depending on its initial size. We show how an accurate age determination can help settle this issue.

O'Leary, Ryan M.; Stahler, Steven W.; Ma, Chung-Pei

2014-10-01

492

Path planning and Ground Control Station simulator for UAV

NASA Astrophysics Data System (ADS)

In this paper we present a Universal and Interoperable Ground Control Station (UIGCS) simulator for fixed and rotary wing Unmanned Aerial Vehicles (UAVs), and all types of payloads. One of the major constraints is to operate and manage multiple legacy and future UAVs, taking into account the compliance with NATO Combined/Joint Services Operational Environment (STANAG 4586). Another purpose of the station is to assign the UAV a certain degree of autonomy, via autonomous planification/replanification strategies. The paper is organized as follows. In Section 2, we describe the non-linear models of the fixed and rotary wing UAVs that we use in the simulator. In Section 3, we describe the simulator architecture, which is based upon interacting modules programmed independently. This simulator is linked with an open source flight simulator, to simulate the video flow and the moving target in 3D. To conclude this part, we tackle briefly the problem of the Matlab/Simulink software connection (used to model the UAV's dynamic) with the simulation of the virtual environment. Section 5 dea