Dynamic Shortest Paths Containers
Dorothea Wagner; Thomas Willhalm; Christos D. Zaroliagis
2004-01-01
Using a set of geometric containers to speed up shortest path queries in a weighted graph has been proven a useful tool for dealing with large sparse graphs. Given a layout of a graph G = (V; E), we store, for each edge (u; v) 2 E, the bounding box of all nodes t 2 V for which a shortest
Computing almost shortest paths
Michael Elkin
2005-01-01
We study the s-sources almost shortest paths(abbreviated s-ASP) problem. Given an unweightedgraph G = (V,E),and a subset S ? Vof s nodes, the goal is to compute almostshortest paths between all the pairs of nodes S× V. We devise an algorithm withrunning timeO(∣E∣n?+ s ·n1 + ?)for this problem that computes the pathsPu,wfor all pairs (u,w) ?S × V such
Geometric Shortest Path Containers
Dorothea Wagner; Thomas Willhalm; Christos Zaroliagis
2004-01-01
In this paper, we consider Dijkstra's algorithm for the single source single target shortest path problem in large sparse graphs. The goal is to reduce the response time for on-line queries by using precomputed information. Due to the size of the graph, preprocessing space requirements can be only linear in the number of nodes. We assume that a layout of
Shortest path and Schramm-Loewner Evolution
NASA Astrophysics Data System (ADS)
Posé, N.; Schrenk, K. J.; Araújo, N. A. M.; Herrmann, H. J.
2014-06-01
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.
Shortest path and Schramm-Loewner Evolution
Posé, N.; Schrenk, K. J.; Araújo, N. A. M.; Herrmann, H. J.
2014-01-01
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
Shortest path and Schramm-Loewner evolution.
Posé, N; Schrenk, K J; Araújo, N A M; Herrmann, H J
2014-01-01
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
Shortest Path Algorithm What is the Shortest Path Problem?
Razak, Saquib
at vertex B: The resulting vertex-weighted graph is: #12;Data structures required · The implementation. · The method returns a vertex-weighted Digraph from which the shortest path from s to any vertex can be found;What is the shortest path problem? · In an edge-weighted graph, the weight of an edge measures the cost
Shortest Paths in Euclidean Graphs
Robert Sedgewick; Jeffrey Scott Vitter
1986-01-01
We analyze a simple method for finding shortest paths inEuclidean graphs (where vertices are points in a Euclidean space and edge weights are Euclidean distances between points). For many graph\\u000a models, the average running time of the algorithm to find the shortest path between a specified pair of vertices in a graph\\u000a withV vertices andE edges is shown to beO(V)
Circular Shortest Path on Regular Grids
Changming Sun; Stefano Pallottino Csiro
2002-01-01
Shortest path algorithms have been used for a number of applications such as crack detection, road orlinear feature extraction on images. There are applications where the starting and ending positionsof the shortest path needs to be constrained. In this paper, we presents several new algorithms forthe extraction of a circular shortest path within an image such that the starting and
Dynamic Shortest Paths Containers Dorothea Wagnera,1
Zaroliagis, Christos D.
of nodes. In [17], angular sectors were introduced to speed up the processing of such shortest path queries of Patras, 26500 Patras, Greece Abstract Using a set of geometric containers to speed up shortest path is quite large (though sparse), and hence space requirements are only acceptable to be linear in the number
Shortest Path Problems on a Polyhedral Surface
Atlas F. Cook; Carola Wenk
2009-01-01
We develop algorithms to compute edge sequences, Voronoi diagrams, shortest path maps, the Fréchet distance, and the diameter for a polyhedral surface. Dis- tances on the surface are measured either by the length of a Euclidean shortest path or by link distance.
Highway Hierarchies Hasten Exact Shortest Path Queries
Peter Sanders; Dominik Schultes
2005-01-01
\\u000a We present a new speedup technique for route planning that exploits the hierarchy inherent in real world road networks. Our\\u000a algorithm preprocesses the eight digit number of nodes needed for maps of the USA or Western Europe in a few hours using linear\\u000a space. Shortest (i.e. fastest) path queries then take around eight milliseconds to produce exact shortest paths. This
Shortest Path Computation with No Information Leakage
Mouratidis, Kyriakos
2012-01-01
Shortest path computation is one of the most common queries in location-based services (LBSs). Although particularly useful, such queries raise serious privacy concerns. Exposing to a (potentially untrusted) LBS the client's position and her destination may reveal personal information, such as social habits, health condition, shopping preferences, lifestyle choices, etc. The only existing method for privacy-preserving shortest path computation follows the obfuscation paradigm; it prevents the LBS from inferring the source and destination of the query with a probability higher than a threshold. This implies, however, that the LBS still deduces some information (albeit not exact) about the client's location and her destination. In this paper we aim at strong privacy, where the adversary learns nothing about the shortest path query. We achieve this via established private information retrieval techniques, which we treat as black-box building blocks. Experiments on real, large-scale road networks assess the pract...
Inverse shortest path algorithms in protected UMTS access networks
István Gódor; János Harmatos; Alpár Jüttner
2005-01-01
In this paper, the application questions of OSPF (Open Shortest Path First) routing protocols in the all{IP based protected UMTS (Universal Mobile Telecommunications System) access networks is inves- tigated. The basic problem here is how the OSPF administrative weights should be adjusted in an ade- quate way, resulting near{optimal overall network per- formance both in nominal network operation and in
Shortest Paths in Microseconds Rachit Agarwal
, the goal is to minimize latency while maintaining feasible memory requirements. We present ASAP, a system that achieves this goal by exploiting the structure of social networks. ASAP preprocesses a given network edges, ASAP computes a shortest path for most node pairs in less than 49 microseconds per pair. ASAP
Optimal Distributed All Pairs Shortest Paths
Optimal Distributed All Pairs Shortest Paths ETH Zurich Distributed Computing Group Stephan Holzer ETH Zürich Roger Wattenhofer ETH Zürich #12;Distributed network Graph G of n nodes 2 4 5 1 3 #12;Distributed network Graph G of n nodes 2 4 5 1 3 Unique IDs #12;Distributed network Graph G of n nodes 2 4 5 1
Goal Directed Shortest Path Queries Using Precomputed Cluster Distances
Matijevic, Domagoj
of starting and end point as well as the length of the shortest connection between each pair of clusters[v] algorithm removes the closest node u, settles Dijkstra's algorithm for shortest path queries can be accelerated by using precomputed shortest path
Implicit Routing And Shortest Path Information
Evangelos Kranakis; Danny Krizanc; Jorge Urrutia
1995-01-01
)Evangelos Kranakisy(kranakis@scs.carleton.ca)Danny Krizancy(krizanc@scs.carleton.ca)Jorge Urrutiazy(jorge@csi.uottawa.ca)AbstractWe study the problem of constructing graphs from shortest path information(complete or partial). Consider graphs with labeled verticesand edges. Given a collection V of vertices and for each u 2 V a positiveinteger d(u), and a family F u = fF u;i : i ! d(u)g of subsets of Vconstruct a graph such that for each u
Shortest paths synthesis for a car-like robot
P. Soueres; J.-P. Laumond
1996-01-01
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
Traffic-engineering-aware shortest-path routing and its application in IP-over-WDM networks [Invited
Youngseok Lee; Biswanath Mukherjee
2004-01-01
Single shortest-path routing is known to perform poorly for Internet traffic engineering (TE) where the typical optimization objective is to minimize the maximum link load. Splitting traffic uniformly over equal-cost multiple shortest paths in open shortest path first and intermediate system-intermediate system protocols does not always minimize the maximum link load when multiple paths are not carefully selected for the
A shortest path algorithm for mobile satellite communication network
Zhang Tao; Zhang Jun; Liu Zhong Kan
2005-01-01
Mobile satellite network is a special time-varying network. Some classical network theories used in the current terrestrial networks, such as the shortest path algorithm, cannot be applied to it availably. In this paper, based on the proposed model of mobile satellite network, the classical shortest path algorithm of fixed topological network, such as the Dijkstra algorithm, is proved to be
Running Time Analysis of ACO Systems for Shortest Path Problems
NASA Astrophysics Data System (ADS)
Horoba, Christian; Sudholt, Dirk
Ant Colony Optimization (ACO) is inspired by the ability of ant colonies to find shortest paths between their nest and a food source. We analyze the running time of different ACO systems for shortest path problems. First, we improve running time bounds by Attiratanasunthron and Fakcharoenphol [Information Processing Letters, 105(3):88-92, 2008] for single-destination shortest paths and extend their results for acyclic graphs to arbitrary graphs. Our upper bound is asymptotically tight for large evaporation factors, holds with high probability, and transfers to the all-pairs shortest paths problem. There, a simple mechanism for exchanging information between ants with different destinations yields a significant improvement. Our results indicate that ACO is the best known metaheuristic for the all-pairs shortest paths problem.
Using shortest path to discover criminal community
Magalingam, Pritheega; Rao, Asha
2015-01-01
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...
Shortest Path Games: Computational Complexity of Solution Concepts
Amsterdam, University of
Shortest Path Games: Computational Complexity of Solution Concepts MSc Thesis (Afstudeerscriptie 9 2.1 Coalitional Games . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2 Concepts for Coalitional Games . . . . . . . . . . . . . . . . . . . . . . . 12 2.3.1 Power Indices
OBSTACLE-AVOIDING SIMILARITY METRICS AND SHORTEST PATH PROBLEMS
Texas at San Antonio, University of
-AVOIDING SIMILARITY METRICS AND SHORTEST PATH PROBLEMS Atlas F. Cook IV, Ph.D. The University of Texas at San Antonio COMMITTEE: ________________________________________ Carola Wenk, Ph.D., Chair ________________________________________ Tom Bylander, Ph.D. ________________________________________ José Iovino, Ph.D
Two Phase Shortest Path Algorithm for Nonnegative Weighted Undirected Graphs
Muhammad Aasim Qureshi; Mohd Fadzil Hassan; Sohail Safdar; Rehan Akbar
2010-01-01
Abstract-Breadth First Search (BFS) can calculate the shortest path for un-weighted graphs very efficiently but when it comes to non-negative weighted graphs it fails at a point when a successor updates a predecessor. Such nodes are being referred as Culprit nodes in this research. These Culprit nodes are the ones that cause error in shortest path in an algorithm that
Distributional properties of stochastic shortest paths for smuggled nuclear material
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
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.
Traffic-engineering-aware shortest-path routing and its application in IP-over-WDM networks [Invited
NASA Astrophysics Data System (ADS)
Lee, Youngseok; Mukherjee, Biswanath
2004-03-01
Single shortest-path routing is known to perform poorly for Internet traffic engineering (TE) where the typical optimization objective is to minimize the maximum link load. Splitting traffic uniformly over equal-cost multiple shortest paths in open shortest path first and intermediate system-intermediate system protocols does not always minimize the maximum link load when multiple paths are not carefully selected for the global traffic demand matrix. However, a TE-aware shortest path among all the equal-cost multiple shortest paths between each ingress-egress pair can be selected such that the maximum link load is significantly reduced. IP routers can use the globally optimal TE-aware shortest path without any change to existing routing protocols and without any serious configuration overhead. While calculating TE-aware shortest paths, the destination-based forwarding constraint at a node should be satisfied, because an IP router will forward a packet to the next hop toward the destination by looking up the destination prefix. We present a mathematical problem formulation for finding a set of TE-aware shortest paths for the given network as an integer linear program, and we propose a simple heuristic for solving large instances of the problem. Then we explore the usage of our proposed algorithm for the integrated TE method in IP-over-WDM networks. The proposed algorithm is evaluated through simulations in IP networks as well as in IP-over-WDM networks.
Ramaswamy, Ramkumar
2004-12-10
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 ...
Quantum algorithms for shortest paths problems in structured instances
Aran Nayebi; Virginia Vassilevska Williams
2014-10-23
We consider the quantum time complexity of the all pairs shortest paths (APSP) problem and some of its variants. The trivial classical algorithm for APSP and most all pairs path problems runs in $O(n^3)$ time, while the trivial algorithm in the quantum setting runs in $\\tilde{O}(n^{2.5})$ time, using Grover search. A major open problem in classical algorithms is to obtain a truly subcubic time algorithm for APSP, i.e. an algorithm running in $O(n^{3-\\varepsilon})$ time for constant $\\varepsilon>0$. To approach this problem, many truly subcubic time classical algorithms have been devised for APSP and its variants for structured inputs. Some examples of such problems are APSP in geometrically weighted graphs, graphs with small integer edge weights or a small number of weights incident to each vertex, and the all pairs earliest arrivals problem. In this paper we revisit these problems in the quantum setting and obtain the first nontrivial (i.e. $O(n^{2.5-\\varepsilon})$ time) quantum algorithms for the problems.
An edge-wise linear shortest path algorithm for non negative weighted undirected graphs
Muhammad Aasim Qureshi; Mohd Fadzil Hassan; Sohail Safdar; Rehan Akbar; Rabia Sammi
2009-01-01
In most of the shortest path problems like vehicle routing problems and network routing problems, we only need an efficient path between two points---source and destination, and it is not necessary to calculate the shortest path from source to all other nodes. This paper concentrates on this very idea and presents an algorithm for calculating shortest path for nonnegative weighted
Accumulative competition neural network for shortest path tree computation
Ji-Yang Dong; Wen-Jun Wang; Jun-Ying Zhang
2003-01-01
Shortest path tree (SPT) computation is an important combinatorial optimization problem with numerous applications. A novel neural network model called accumulative competition neural network (ACNN) is proposed in this paper to compute the SPT in a given weighted graph. Comparing with the other neural network based search algorithms, the algorithm presented here features in much less number of neurons needed,
Materialization Trade-Offs in Hierarchical Shortest Path Algorithms
Shashi Shekhar; Andrew Fetterer; Bjajesh Goyal
1997-01-01
Materialization and hierarchical routing algorithms are becoming important tools in querying databases for the shortest paths in time-critical applications like Intelligent Transportation Systems (ITS), due to the growing size of their spatial graph databases [16]. A hierarchical routing algorithm decomposes the original graph into a set of fragment graphs and a boundary graph which summarizes the fragment graphs. A fully
A near linear shortest path algorithm for weighted undirected graphs
Muhammad Aasim Qureshi; Mohd Fadzil Hassan; Sohail Safdar; Rehan Akbar
2011-01-01
This paper presents an algorithm for Shortest Path Tree (SPT) problem. The presented algorithm is an improvement over a previously published work of the authors. The effort is put in to improve the running\\/execution time of the SPT problem. Introduced improvement is simple and easy to incorporate in to the existing algorithm. This algorithm uses Depth First Search (DFS) like
Finding Shortest Path for Developed Cognitive Map Using Medial Axis
Farhan, Hazim A; Al-Ghazi, Suhaib I
2011-01-01
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...
122 IEEE COMMUNICATIONS LETTERS, VOL. 8, NO. 2, FEBRUARY 2004 Finding All Hops Shortest Paths
Ansari, Nirwan
122 IEEE COMMUNICATIONS LETTERS, VOL. 8, NO. 2, FEBRUARY 2004 Finding All Hops Shortest Paths Gang a new problem referred to as the All Hops Shortest Paths (AHSP) problem. The AHSP problem involves selecting, for all hop counts, the shortest paths from a given source to any other node in a network. We
An Improved Physarum polycephalum Algorithm for the Shortest Path Problem
Wang, Qing; Adamatzky, Andrew; Chan, Felix T. S.; Mahadevan, Sankaran
2014-01-01
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
Multiple Object Tracking Using the Shortest Path Faster Association Algorithm
Liu, Heping; Liu, Huaping; Yang, Bin
2014-01-01
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
Parallel Shortest Path Algorithms for Solving Large-Scale Instances
Kamesh Madduri; David A. Bader; Jonathan W. Berry; Bruce A. Hendrickson
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
Approximating shortest paths on a convex polytope in three dimensions
Pankaj K. Agarwal; Sariel Har-Peled; Micha Sharir; Kasturi R. Varadarajan
1997-01-01
Given a convex polytope P withn faces in R3, points s,t?6P, and a parameter 0e?1, we present an algorithm that constructs a path on6P from s tot whose length is at most1+edPs,t, where dPs,t is the length of the shortest path betweens andt on 6P. The algorithm runs in Onlog1\\/e+1\\/e3 time, and is relatively simple. The running time isOn+1\\/e3 if
The Bellman-Ford algorithm Most basic shortest-paths algorithm for the shortest-path problem
Bai, Zhaojun
the "lightest" or "closest" vertex in V - S to insert into S #12;The SSSP in DAG DAG: can have negative-weight negative-weight edges Compute d[v] and [v] for all v V d[v] = (s, v): the shortest-path weight from the source s to v. [v]: the parent (predecessor) of v. Return TRUE if no negative-weight cycles reachable
Finding Shortest Paths on Terrains by Killing Two Birds with One Stone
Wong, Raymond Chi-Wing
) of the terrain via shortest terrain paths. Other applications include robot path planning for unmanned vehicles. Such queries all rely on an important operation, that of finding shortest surface distances. However, shortest surface dis- tance computation is very time consuming. We propose techniques that enable efficient
ON THE ACCELERATION OF SHORTEST PATH CALCULATIONS IN TRANSPORTATION NETWORKS
BAKER, ZACHARY K. [Los Alamos National Laboratory; GOKHALE, MAYA B. [Los Alamos National Laboratory
2007-01-08
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.
Shortest Path Refinement for Motion Estimation from Tagged MR Images
Liu, Xiaofeng; Prince, Jerry L.
2013-01-01
Magnetic resonance tagging makes it possible to measure the motion of tissues such as muscles in the heart and tongue. The harmonic phase (HARP) method largely automates the process of tracking points within tagged MR images, permitting many motion properties to be computed. However, HARP tracking can yield erroneous motion estimates due to: (1) large deformations between image frames; (2) through-plane motion; and (3) tissue boundaries. Methods that incorporate the spatial continuity of motion—so-called refinement or floodfilling methods—have previously been reported to reduce tracking errors. This paper presents a new refinement method based on shortest path computations. The method uses a graph representation of the image and seeks an optimal tracking order from a specified seed to each point in the image by solving a single source shortest path problem. This minimizes the potential errors for those path dependent solutions that are found in other refinement methods. In addition to this, tracking in the presence of through-plane motion is improved by introducing synthetic tags at the reference time (when the tissue is not deformed). Experimental results on both tongue and cardiac images show that the proposed method can track the whole tissue more robustly and is also computationally efficient. PMID:20304720
A Bio-Inspired Method for the Constrained Shortest Path Problem
Wang, Hongping; Lu, Xi; Wang, Qing
2014-01-01
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
An Effective Evolutionary Approach for Bicriteria Shortest Path Routing Problems
NASA Astrophysics Data System (ADS)
Lin, Lin; Gen, Mitsuo
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.
Backbones and borders from shortest-path trees
NASA Astrophysics Data System (ADS)
Grady, Daniel; Thiemann, Christian; Brockmann, Dirk
2011-03-01
One of the most important tasks in complex network research is to distinguish between vertices and edges that are topologically essential and those that are not. To this end, a variety of vertex and edge centrality measures have been introduced, ranging from measuring local properties (degree, strength) to quantities that depend on the global structure of the graph (betweenness). Here we introduce a novel technique based on the family of shortest-path trees, which is applicable to strongly heterogeneous networks. This approach can identify significant edges in the network, distinct from conventional edge betweenness, and these edges make up a network backbone relevant to dynamical processes that evolve on such networks. We will show that important network structures can be extracted by investigating the similarity and differences of shortest-path trees and show that tree dissimilarity in combination with hierarchical clustering can identify communities in heterogeneous networks more successfully than ordinary reciprocal-weight distance measures. We demonstrate the success of this technique on complex multi-scale mobility networks.
Report SYCON91-10 SHORTEST PATHS FOR THE REEDS-SHEPP CAR
Sussmann, Hector
Report SYCON91-10 SHORTEST PATHS FOR THE REEDS-SHEPP CAR: A WORKED OUT EXAMPLE OF THE USE the shortest paths for a model of a car that can move forwards and backwards. This problem was discussed to derive some of the properties of the minimum paths of the Reeds-Shepp car, cf. [7]. 2 This author's work
Pomelo: accurate and decentralized shortest-path distance estimation in social graphs
Zhuo Chen; Yang Chen; Cong Ding; Beixing Deng; Xing Li
2011-01-01
Computing the shortest-path distances between nodes is a key problem in analyzing social graphs. Traditional methods like breadth-first search (BFS) do not scale well with graph size. Recently, a Graph Coordinate System, called Orion, has been proposed to estimate shortest-path distances in a scalable way. Orion uses a landmark-based approach, which does not take account of the shortest-path distances between
Membrane Boundary Extraction Using a Circular Shortest Path Technique
NASA Astrophysics Data System (ADS)
Sun, Changming; Vallotton, Pascal; Wang, Dadong; Lopez, Jamie; Ng, Yvonne; James, David
2007-11-01
Membrane proteins represent over 50% of known drug targets. Accordingly, several widely used assays in the High Content Analysis area rely on quantitative measures of the translocation of proteins between intracellular organelles and the cell surface. In order to increase the sensitivity of these assays, one needs to measure the signal specifically along the membrane, requiring a precise segmentation of this compartment. Doing this manually is a very time-consuming practice, limited to an academic setting. Manual tracing of the membrane compartment also confronts us with issues of objectivity and reproducibility. In this paper, we present an approach based on a circular shortest path technique that enables us to segment the membrane compartment accurately and rapidly. This feature is illustrated using cells expressing epitope-tagged membrane proteins.
Self-organization and solution of shortest-path optimization problems with memristive networks
Pershin, Yuriy V
2013-01-01
We show that memristive networks-namely networks of resistors with memory-can efficiently solve shortest-path optimization problems. Indeed, the presence of memory (time non-locality) 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.
Pomelo: Accurate and Decentralized Shortest-path Distance Estimation in Social Graphs
Hong, Jason I.
Pomelo: Accurate and Decentralized Shortest-path Distance Estimation in Social Graphs Zhuo Chen1 the graph structure well. In this paper, we propose Pomelo, which calculates the graph coordinates in a decentralized manner. Every node in Pomelo computes its shortest-path distances to both nearby neighbors
An Experimental Study of a Parallel Shortest Path Algorithm for Solving Large-Scale Graph Instances
Bader, David A.
shortest path problem with non-negative edge weights (NSSP) on large- scale graphs using the -stepping with competitive sequential algorithms, for low-diameter sparse graphs. For instance, -stepping on a directed scaleAn Experimental Study of a Parallel Shortest Path Algorithm for Solving Large-Scale Graph Instances
An Optimal Algorithm for L1 Shortest Paths Among Obstacles in the Plane
Mitchell, Joseph S.B.
orientation" metric, yielding an O(n log n ) approximation algorithm for finding Euclidean shortest pathsAn Optimal Algorithm for L1 Shortest Paths Among Obstacles in the Plane (Draft) Joseph S. B 11794-3600 jsbm@ams.sunysb.edu Abstract We present an optimal (n log n) algorithm for determining
Using Edge-Valued Decision Diagrams for Symbolic Generation of Shortest Paths
Gianfranco Ciardo; Radu Siminiceanu
2002-01-01
We present a new method for the symbolic construction of shortest paths in reachability graphs. Our algorithm relies on a variant of edge{valued decision diagrams that supports ecien t xed{p oint it- erations for the joint computation of both the reachable states and their distance from the initial states. Once the distance function is known, a shortest path from an
Color texture classification using shortest paths in graphs.
de Mesquita Sa Junior, Jarbas Joaci; Cortez, Paulo Cesar; Backes, Andre Ricardo
2014-09-01
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
All Pairs Shortest Paths for Graphs with Small Integer Length Edges
Zvi Galil; Oded Margalit
1997-01-01
The authors have solved the all pairs shortest distances (APSD) problem for graphs with integer edge lengths. Our algorithm is subcubic for edge lengths of small (?M) absolute value. In this paper we show how to transform these algorithms to solve the all pairs shortest paths (APSP), in the same time complexity, up to a polylogarithmic factor. Forn=|V| the number
A Faster Algorithm for the Single Source Shortest Path Problem with Few Distinct Positive Lengths
Orlin, James B.
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 ...
A New GPU-based Approach to the Shortest Path Problem
Llanos, Diego R.
. Llanos, and Arturo Gonzalez-Escribano Dept. Inform´atica, Universidad de Valladolid, Spain. {hector|yuri.torresA New GPU-based Approach to the Shortest Path Problem Hector Ortega-Arranz, Yuri Torres, Diego R
Reliability Theory Model and Expected Life Shortest Path in Stochastic and Time-Dependent Networks
Guo-zhen Tan; Xiang-fu Xia; Wen Gao
2003-01-01
We consider the priori expected shortest path problem from a single origin to a single destination for each departure time\\u000a in stochastic and time-dependent networks. Such problem requires more than standard shortest path techniques. First, we transform\\u000a this problem into the problem of systemic reliability, and identify a weaker consistent reliability condition that insures\\u000a the validity of generalized dynamic-programming method
Shortest-path and hot-potato routing on unbuffered 2-D tori
Miltos D. Grammatikakis; Miro Kraetzl; Eric Fleury
1997-01-01
We probabilistically model dynamic routing on unbuffered 2-dimensional tori. We consider shortest-path routing with packet loss and retransmissions versus a newly proposed all-link busy (ALB) hot-potato routing strategy with packet deflections. Computations of the sustained packet generating rate, node throughput, and average packet latency indicate that the proposed ALB strategy is a much better alternative to a shortest-path routing on
Fast Point-to-Point Shortest Path Computations with Arc-Flags
Moritz Hilger; Rolf H. Mohring; Heiko Schilling
2006-01-01
In this paper, we conduct a detailed study of the arc-flag approach introduced in (Lau97, Lau04). Arc-flags are a modification of Dijkstra's algorithm to accel erate point-to-point (p2p) shortest path computa- tions. The usage of arc-flags avoids exploring unnecessary p aths during shortest path query computations. We present two improvements of the original arc-flag method tha t reduce the pre-calculation
A O(E) Time Shortest Path Algorithm For Non Negative Weighted Undirected Graphs
Qureshi, Muhammad Aasim; Safdar, Sohail; Akbar, Rehan
2009-01-01
In most of the shortest path problems like vehicle routing problems and network routing problems, we only need an efficient path between two points source and destination, and it is not necessary to calculate the shortest path from source to all other nodes. This paper concentrates on this very idea and presents an algorithm for calculating shortest path for (i) nonnegative weighted undirected graphs (ii) unweighted undirected graphs. The algorithm completes its execution in O(E) for all graphs except few in which longer path (in terms of number of edges) from source to some node makes it best selection for that node. The main advantage of the algorithms is its simplicity and it does not need complex data structures for implementations.
An Experimental Study of a Parallel Shortest Path Algorithm for Solving Large-Scale Graph Instances
Hutter, Frank
of the single source short- est path problem with non-negative edge weights (NSSP) on large-scale graphs using with competitive sequential algorithms, for low-diameter sparse graphs. For instance, -stepping on a directed scaleAn Experimental Study of a Parallel Shortest Path Algorithm for Solving Large-Scale Graph Instances
Traffic Grooming Based on Shortest Path in Optical WDM Mesh Networks
Lee, Tae-Jin
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
An Evaluation of Potentials of Genetic Algorithm in Shortest Path Problem
NASA Astrophysics Data System (ADS)
Hassany Pazooky, S.; Rahmatollahi Namin, Sh; Soleymani, A.; Samadzadegan, F.
2009-04-01
One of the most typical issues considered in combinatorial systems in transportation networks, is the shortest path problem. In such networks, routing has a significant impact on the network's performance. Due to natural complexity in transportation networks and strong impact of routing in different fields of decision making, such as traffic management and vehicle routing problem (VRP), appropriate solutions to solve this problem are crucial to be determined. During last years, in order to solve the shortest path problem, different solutions are proposed. These techniques are divided into two categories of classic and evolutionary approaches. Two well-known classic algorithms are Dijkstra and A*. Dijkstra is known as a robust, but time consuming algorithm in finding the shortest path problem. A* is also another algorithm very similar to Dijkstra, less robust but with a higher performance. On the other hand, Genetic algorithms are introduced as most applicable evolutionary algorithms. Genetic Algorithm uses a parallel search method in several parts of the domain and is not trapped in local optimums. In this paper, the potentiality of Genetic algorithm for finding the shortest path is evaluated by making a comparison between this algorithm and classic algorithms (Dijkstra and A*). Evaluation of the potential of these techniques on a transportation network in an urban area shows that due to the problem of classic methods in their small search space, GA had a better performance in finding the shortest path.
NASA Astrophysics Data System (ADS)
Yu, Feng; Li, Yanjun; Wu, Tie-Jun
2010-02-01
A large number of networks in the real world have a scale-free structure, and the parameters of the networks change stochastically with time. Searching for the shortest paths in a scale-free dynamic and stochastic network is not only necessary for the estimation of the statistical characteristics such as the average shortest path length of the network, but also challenges the traditional concepts related to the “shortest path” of a network and the design of path searching strategies. In this paper, the concept of shortest path is defined on the basis of a scale-free dynamic and stochastic network model, and a temporal ant colony optimization (TACO) algorithm is proposed for searching for the shortest paths in the network. The convergence and the setup for some important parameters of the TACO algorithm are discussed through theoretical analysis and computer simulations, validating the effectiveness of the proposed algorithm.
The approach for shortest paths in fire succor based on component GIS technology
NASA Astrophysics Data System (ADS)
Han, Jie; Zhao, Yong; Dai, K. W.
2007-06-01
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.
von Thienen, Wolfhard; Metzler, Dirk; Witte, Volker
2015-05-01
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
Muhammad Aasim Qureshi; Mohd Fadzil Hassan; Sohail Safdar; Rehan Akbar; Rabia Sammi
2010-01-01
Shortest path and related problems have been a very hot topic for researchers since Dijekstra devised his first shortest path algorithm. In transportation and communication routing, during the execution of system, failure of any link needs robust and most effective recovery. In such problems we need some recovery mechanism and\\/or plan for the continuation of the process with minimum or
Fast Shortest-path Distance Queries on Road Networks by Pruned Highway Labeling
Imai, Hiroshi
Fast Shortest-path Distance Queries on Road Networks by Pruned Highway Labeling Takuya Akiba Yoichi- ferred to as highway-based labelings and a preprocessing algorithm for it named pruned highway labeling to as the highway-based labeling framework and a preprocessing algorithm for the framework named pruned highway
Li, Longxiang; Gong, Jianhua; Zhou, Jieping
2014-01-01
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
Edge Congestion of Shortest Path Systems for All-to-All Communication
Charles M. Fiduccia; Paul J. Hedrick
1997-01-01
The problem of choosing a static shortest-path system that minimizes maximum edge congestion in a network is studied. Bounds based on parameters, such as diameter, bisection width, and average distance, are derived and conditions for producing uniform congestion on all edges are explored. Trees are shown to have maximum congestion on edges that are incident to a centroid node. Cartesian
IE 170 Laboratory 8: Shortest Paths Drs. T.K. Ralphs and R.T. Berger
Ralphs, Ted
and generality of graph search in solving many important problems. 3. Understand the importance of object-oriented design and code re-use. 4. Understand the importance of and application of the shortest path problem. 1.4 Design and Analysis In this lab, you will recycle source code from two previous labs to implement
Li, Longxiang; Gong, Jianhua; Zhou, Jieping
2014-01-01
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
Disambiguating Road Names in Text Route Descriptions using Exact-All-Hop Shortest Path Algorithm
Klippel, Alexander
Disambiguating Road Names in Text Route Descriptions using Exact-All-Hop Shortest Path Algorithm issues involved, road name disambiguation is the most important, because one road name can refer to more than one road. Compared with traditional toponym (place name) disambiguation, the challenges
Stochastic Shortest Path MDPs with Dead Ends Andrey Kolobov Mausam Daniel S. Weld
Mausam
, weld}@cs.washington.edu Dept of Computer Science and Engineering University of Washington Seattle, USAStochastic Shortest Path MDPs with Dead Ends Andrey Kolobov Mausam Daniel S. Weld {akolobov, mausam with in many real-world planning problems, be it sending a rover on Mars or navigating a robot in a building
Do People Use the Shortest Path? Empirical Test of Wardrop's First
Levinson, David M.
(10). Zhu, Shanjiang, David Levinson and Henry Liu, Measuring Winners and Losers from New I 35W Mississippi (67%) #12;#12;Diversity in Commute Route (Source: Zhu and Levinson 2010b) #12;Conclusions · MajorityDo People Use the Shortest Path? Empirical Test of Wardrop's First Principle Shanjiang Zhu, Ph
Shortest Traversal Path of n Circles in Layered Manufacturing Applications
Chang-chien Chou; Yu-kumg Chen; Shuo-yan Chou
2007-01-01
Layered manufacturing in rapid prototyping is to fabricate prototype by using a laser beam to trace the cross-sectional contours of a product layer by layer. Such cross-sections of geometrical objects differ by layers and generally have more than one continuous contour in each layer. In an attempt to facilitate an efficient approach for path planning, the problem is simplified by
A new approach to shortest paths on networks based on the quantum bosonic mechanism
NASA Astrophysics Data System (ADS)
Jiang, Xin; Wang, Hailong; Tang, Shaoting; Ma, Lili; Zhang, Zhanli; Zheng, Zhiming
2011-01-01
This paper presents quantum bosonic shortest path searching (QBSPS), a natural, practical and highly heuristic physical algorithm for reasoning about the recognition of network structure via quantum dynamics. QBSPS is based on an Anderson-like itinerant bosonic system in which a boson's Green function is used as a navigation pointer for one to accurately approach the terminals. QBSPS is demonstrated by rigorous mathematical and physical proofs and plenty of simulations, showing how it can be used as a greedy routing to seek the shortest path between different locations. In methodology, it is an interesting and new algorithm rooted in the quantum mechanism other than combinatorics. In practice, for the all-pairs shortest-path problem in a random scale-free network with N vertices, QBSPS runs in O(?(N) ln ln N) time. In application, we suggest that the corresponding experimental realizations are feasible by considering path searching in quantum optical communication networks; in this situation, the method performs a pure local search on networks without requiring the global structure that is necessary for current graph algorithms.
The d-edge shortest-path problem for a Monge graph
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
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.
Finding splitting lines for touching cell nuclei with a shortest path algorithm.
Bai, Xiangzhi; Wang, Peng; Sun, Changming; Zhang, Yu; Zhou, Fugen; Meng, Cai
2014-10-22
A shortest path-based algorithm is proposed in this paper to find splitting lines for touching cell nuclei. First, an initial splitting line is obtained through the distance transform of a marker image and the watershed algorithm. The initial splitting line is then separated into different line segments as necessary, and the endpoint positions of these line segments are adjusted to the concave points on the contour. Finally, a shortest path algorithm is used to find the accurate splitting line between the starting-point and the end-point, and the final split can be achieved by the contour of the touching cell nuclei and the splitting lines. Comparisons of experimental results show that the proposed algorithm is effective for segmentation of different types of touching cell nuclei. PMID:25458811
An Efficient Shortest Triangle Paths Algorithm Applied to Multi-camera Self-calibration
Ferid Bajramovic; Marcel Brückner; Joachim Denzler
We propose a novel minimum uncertainty approach to relative pose selection for multi-camera self-calibration. We show how\\u000a this discrete global optimization problem can be expressed as a shortest triangle paths problem. For the latter, we present\\u000a an efficient algorithm and prove its correctness. It has several advantages compared to a similar approach of Vergés-Llahí,\\u000a Moldovan and Wada. In quantitative experiments
Parallel shortest augmenting path algorithm for the assignment problem. Technical report
Balas, E.; Miller, D.; Pekny, J.; Toth, P.
1989-04-01
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.
Transitive functional annotation by shortest-path analysis of gene expression data
Zhou, Xianghong; Kao, Ming-Chih J.; Wong, Wing Hung
2002-01-01
Current methods for the functional analysis of microarray gene expression data make the implicit assumption that genes with similar expression profiles have similar functions in cells. However, among genes involved in the same biological pathway, not all gene pairs show high expression similarity. Here, we propose that transitive expression similarity among genes can be used as an important 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 to hierarchical clustering, and show that our method can reveal functional relationships among genes in a more precise manner. Finally, we show that our method can be used to reliably predict the function of unknown genes from known genes lying on the same shortest path. We assigned functions for 146 yeast genes that are considered as unknown by the Saccharomyces Genome Database and by the Yeast Proteome Database. These genes constitute around 5% of the unknown yeast ORFome. PMID:12196633
NASA Astrophysics Data System (ADS)
Sun, Yu; Dai, Meifeng; Xi, Lifeng
Recent work on the networks has focused on the weighted hierarchical networks that are significantly different from the un-weighted hierarchical networks. In this paper we study a family of weighted hierarchical networks which are recursively defined from an initial uncompleted graph, in which the weights of edges have been assigned to different values with certain scale. Firstly, we study analytically the average weighted shortest path (AWSP) on the weighted hierarchical networks. Using a recursive method, we determine explicitly the AWSP. The obtained rigorous solution shows that the networks grow unbounded but with the logarithm of the network size, while the weighted shortest paths stay bounded. Then, depending on a biased random walk, we research the mean first-passage time (MFPT) between a hub node and any peripheral node. Finally, we deduce the analytical expression of the average of MFPTs for a random walker originating from any node to first visit to a hub node, which is named as the average receiving time (ART). The obtained result shows that ART is bounded or grows sublinearly with the network order relating to the number of initial nodes and the weighted factor or grows quadratically with the iteration.
PHA*: Finding the Shortest Path with A* in An Unknown Physical Environment
Ben-Yair, A; Kraus, S; Netanyahu, N; Stern, R; 10.1613/jair.1373
2011-01-01
We address the problem of finding the shortest path between two points in an unknown real physical environment, where a traveling agent must move around in the environment to explore unknown territory. We introduce the Physical-A* algorithm (PHA*) for solving this problem. PHA* expands all the mandatory nodes that A* would expand and returns the shortest path between the two points. However, due to the physical nature of the problem, the complexity of the algorithm is measured by the traveling effort of the moving agent and not by the number of generated nodes, as in standard A*. PHA* is presented as a two-level algorithm, such that its high level, A*, chooses the next node to be expanded and its low level directs the agent to that node in order to explore it. We present a number of variations for both the high-level and low-level procedures and evaluate their performance theoretically and experimentally. We show that the travel cost of our best variation is fairly close to the optimal travel cost, assuming t...
Zhang, Jian; Jiang, Min; Yuan, Fei; Feng, Kai-Yan; Cai, Yu-Dong; Xu, Xun; Chen, Lei
2013-01-01
This study attempted to find novel age-related macular degeneration (AMD) related genes based on 36 known AMD genes. The well-known shortest path algorithm, Dijkstra's algorithm, was applied to find the shortest path connecting each pair of known AMD related genes in protein-protein interaction (PPI) network. The genes occurring in any shortest path were considered as candidate AMD related genes. As a result, 125 novel AMD genes were predicted. The further analysis based on betweenness and permutation test indicates that there are 10 genes involved in the formation or development of AMD and may be the actual AMD related genes with high probability. We hope that this contribution would promote the study of age-related macular degeneration and discovery of novel effective treatments. PMID:24455700
The tomography of human mobility -- what do shortest-path trees reveal?
NASA Astrophysics Data System (ADS)
Grady, Daniel; Thiemann, Christian; Brockmann, Dirk
2010-03-01
Similar to illustrating the anatomy of organs using pictures of tissue slices taken at various depths, we construct shortest-path trees of different nodes to create a tomogram of large-scale mobility networks. This tomography allows us to measure global properties of the system conditioned on a reference location in the network to gain a fuller characterization of a node. Using this technqiue, we discovered a new symmetry that characterizes a large class of mobility networks. Furthermore, introducing the notion of tree similarity, we devised a new technique for clustering nodes with similar topological footprint, yielding a new, unique and efficient method for community identification in these networks and extracting their topological backbone. We applied these methods to a multi-scale human mobility network obtained from the dollar-bill-tracking site wheresgoerge.com and to the U.S. and world-wide air transportation network.
Nair, T R Gopalakrishnan; Yashoda, M B
2011-01-01
In Internet Routing, the static shortest path (SP) problem has been addressed using well known intelligent optimization techniques like artificial neural networks, genetic algorithms (GAs) and particle swarm optimization. Advancement in wireless communication lead more and more mobile wireless networks, such as mobile networks [mobile ad hoc networks (MANETs)] and wireless sensor networks. Dynamic nature of the network is the main characteristic of MANET. Therefore, the SP routing problem in MANET turns into dynamic optimization problem (DOP). Here the nodes ae made aware of the environmental condition, thereby making it intelligent, which goes as the input for GA. The implementation then uses GAs with immigrants and memory schemes to solve the dynamic SP routing problem (DSPRP) in MANETS. In our paper, once the network topology changes, the optimal solutions in the new environment can be searched using the new immigrants or the useful information stored in the memory. Results shows GA with new immigrants sho...
J. Sussmann; Guoqing Tang
1991-01-01
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
Chao-Ying Bai; Xiao-Ping Tang; Rui Zhao
2009-01-01
Grid-cell based schemes for tracing seismic arrivals, such as the finite difference eikonal equation solver or the shortest path method (SPM), are conventionally confined to locating first arrivals only. However, later arrivals are numerous and sometimes of greater amplitude than the first arrivals, making them valuable information, with the potential to be used for precise earthquake location, high-resolution seismic tomography,
Yang, Shengxiang
) problem has been well addressed using intelligent optimization techniques, e.g., artificial neural, they will be effective in fixed infrastructure wireless or wired networks. But, they exhibit unacceptably high Networks Hui Cheng, Shengxiang Yang Member, IEEE Abstract-- In recent years, the static shortest path (SP
Morita, Yusuke; Ogihara, Naomichi; Kanai, Takashi; Suzuki, Hiromasa
2013-08-01
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
Su, Ran; Sun, Changming; Zhang, Chao; Pham, Tuan D
2014-12-01
Dendritic spines are tiny membranous protrusions from neuron's dendrites. They play a very important role in the nervous system. A number of mental diseases such as Alzheimer's disease and mental retardation are revealed to have close relations with spine morphologies or spine number changes. Spines have various shapes, and spine images are often not of good quality; hence it is very challenging to detect spines in neuron images. This paper presents a novel pipeline to detect dendritic spines in 2D maximum intensity projection (MIP) images and a new dendrite backbone extraction method is developed in the pipeline. The strategy for the backbone extraction approach is that it iteratively refines the extraction result based on directional morphological filtering and improved Hessian filtering until a satisfactory extraction result is obtained. A shortest path method is applied along a backbone to extract the boundary of the dendrites. Spines are then segmented from the dendrites outside the extracted boundary. Touching spines will be split using a marker-controlled watershed algorithm. We present the results of our algorithm on real images and compare our algorithm with two other spine detection methods. The results show that the proposed approach can detect dendrites and spines more accurately. Measurements and classification of spines are also made in this paper. PMID:25155696
Analysis of Algorithms Problem Set no. 3 --Dynamic All-Pairs Shortest Paths
Zwick, Uri
of the graph. Show that there can be at most O(zn2) locally historical paths passing through a given vertex v. Guidance: Showing that there are at most O(zn2) such paths that start or end at v is relatively straightforward. The harder part of the proof is showing that there only O(zn2) locally historical paths having v
Curvature-Constrained Shortest Paths in a Convex Polygon (Extended Abstract)
Paris-Sud XI, Université de
naturally when the point robot models a real-world robot with a mini- mum turning radius; see for example Therese Biedl Sylvain Lazard Steve Robbins§ Subhash Suri¶ Sue Whitesides Abstract Let B be a point robot in robotics, involves planning a collision-free path for a robot moving amid obstacles, and has been widely
Paris-Sud XI, Université de
example of a non-holonomic robot is that of a car : assuming 1As we will see below, the optimal path-holonomic robot motion plan- ning 2, 3, 13, 15, 16, 17, 18, 19, 20, 24, 25]. A robot is said to be non wheels of the car is always tangent to the car axis. Though the problem considered in this paper is one
'Mini small worlds' of shortest link paths crossing domain boundaries in an academic Web space
Lennart Björneborn
2006-01-01
Summary Combining webometric and social network analytic approaches, this study developed a methodology to sample and identify Web\\u000a links, pages, and sites that function as small-world connectors affecting short link distances along link paths between different\\u000a topical domains in an academic Web space. The data set comprised 7669 subsites harvested from 109 UK universities. A novel\\u000a corona-shaped Web graph model revealed
Shortest paths for differential drive robots under visibility and sensor constraints
Jean-Bernard Hayet; Rafael Murrieta-Cid
Abstract—This article revisits the problem,of planning,short- est paths in terms of distance in the plane (i.e., not in time) for the differential drive robot (DDR) in the absence,of obstacles. We complete,the existing works,by explaining,and,deepening the remarks,made,recently in the literature [10] that exhibited more,cases that what,was,thought,until then. Motivated by that work, we show that there cannot be more than 4-word trajectories
NASA Astrophysics Data System (ADS)
Forkert, Nils Daniel; Schmidt-Richberg, Alexander; Säring, Dennis; Illies, Till; Fiehler, Jens; Handels, Heinz
2010-03-01
Exact segmentations of the cerebrovascular system are the basis for several medical applications, like preoperation planning, postoperative monitoring and medical research. Several automatic methods for the extraction of the vascular system have been proposed. These automatic approaches suffer from several problems. One of the major problems are interruptions in the vascular segmentation, especially in case of small vessels represented by low intensities. These breaks are problematic for the outcome of several applications e.g. FEM-simulations and quantitative vessel analysis. In this paper we propose an automatic post-processing method to connect broken vessel segmentations. The approach proposed consists of four steps. Based on an existing vessel segmentation the 3D-skeleton is computed first and used to detect the dead ends of the segmentation. In a following step possible connections between these dead ends are computed using a graph based approach based on the vesselness parameter image. After a consistency check is performed, the detected paths are used to obtain the final segmentation using a level set approach. The method proposed was validated using a synthetic dataset as well as two clinical datasets. The evaluation of the results yielded by the method proposed based on two Time-of-Flight MRA datasets showed that in mean 45 connections between dead ends per dataset were found. A quantitative comparison with semi-automatic segmentations by medical experts using the Dice coefficient revealed that a mean improvement of 0.0229 per dataset was achieved. In summary the approach presented can considerably improve the accuracy of vascular segmentations needed for following analysis steps.
Symbolic Shortest Path Planning
Morik, Katharina
efficiency, the paper analyzes the locality for weighted problem graphs and show that it matches the duplicate detection scope in best-first search graphs. Cost-optimal plans for compiled competition benchmark breadth- first to best-first search graphs. We show how to combine a set of disjoint weighted symbolic
Huang, Tao; Cai, Yu-Dong
2014-01-01
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
Zooplankton avoidance of a profiled open-path fluorometer
Benoit-Bird, Kelly J.
Zooplankton avoidance of a profiled open-path fluorometer KELLY J. BENOIT-BIRD1*, MARK A. MOLINE2 Harris Significant avoidance of acoustically detected zooplankton was observed in response to a profiling instrument package. Avoidance decreased acoustic scatter- ing from zooplankton averaged over the entire
OPEN PATH AMBIENT MEASUREMENTS OF POLLUTANTS WITH A DOAS SYSTEM
A differential optical absorption spectrometer (DOAS) has been in operation since August 1991 at the U.S. EPA in RTP, NC. he analyzer unit is located in an environmentally-controlled shelter in the EPA parking lot. our separate open optical paths have been established, ranging fr...
NASA Astrophysics Data System (ADS)
Iwata, Hiroki; Kosugi, Yoshiko; Ono, Keisuke; Mano, Masayoshi; Sakabe, Ayaka; Miyata, Akira; Takahashi, Kenshi
2014-04-01
Methane () fluxes observed with the eddy-covariance technique using an open-path analyzer and a closed-path analyzer in a rice paddy field were evaluated with an emphasis on the flux correction methodology. A comparison of the fluxes obtained by the analyzers revealed that both the open-path and closed-path techniques were reliable, provided that appropriate corrections were applied. For the open-path approach, the influence of fluctuations in air density and the line shape variation in laser absorption spectroscopy (hereafter, spectroscopic effect) was significant, and the relative importance of these corrections would increase when observing small fluxes. A new procedure proposed by Li-Cor Inc. enabled us to accurately adjust for these effects. The high-frequency loss of the open-path analyzer was relatively large (11 % of the uncorrected covariance) at an observation height of 2.5 m above the canopy owing to its longer physical path length, and this correction should be carefully applied before correcting for the influence of fluctuations in air density and the spectroscopic effect. Uncorrected fluxes observed with the closed-path analyzer were substantially underestimated (37 %) due to high-frequency loss because an undersized pump was used in the observation. Both the bandpass and transfer function approaches successfully corrected this flux loss. Careful determination of the bandpass frequency range or the transfer function and the cospectral model is required for the accurate calculation of fluxes with the closed-path technique.
New open-path remote optical sensing method to estimate methane emission from soil
Technology Transfer Automated Retrieval System (TEKTRAN)
The U.S. EPA recently developed an open-path remote sensing method to identify hot spots and estimate fugitive gas emissions from closed landfills. The method measures several path-integrated concentrations (PICs) of gases using open-path optical instruments. These PICs are then processed using a co...
An advanced open-path atmospheric monitor design
Taylor, L.; Suhre, D. [Westinghouse Electric Corp., Pittsburgh, PA (United States); Mech, S. [Westinghouse Hanford Co., Richland, WA (United States)
1996-05-01
The conceptual design of an open-path atmospheric monitor combines an acousto-optic tunable filter for emission spectroscopy (3-14 {mu}m) with a mid-IR (4.6-5.4 {mu}m) for absorption spectroscopy. It utilizes mostly commercially available components, covers a large area ({approximately}4 km radius), measures the distance to any reflecting object, can take measurements along any line-of-sight, and is eye safe. Of twenty test pollutants it is to detect, the concentrations of all twenty will be measurable via emission spectroscopy and ten by the more sensitive absorption spectroscopy.
A unique bistatic FTIR monitor for long path open-air measurements
Spellicy, R.L.; Brewer, R.J.
1999-07-01
A unique bistatic open-path FTIR monitor has been developed and deployed at an industrial site which eliminates the path radiance issues usually associated with bistatic systems. This system was developed to address long path open-air monitoring while preserving high signal-to-noise ratio for low level detection. Initial test results show excellent accuracy and precision when the systems are tested against an in-situ calibration cell in the instrument.
Robust constrained shortest path problems under budgeted ...
2014-09-12
The proposed solution approaches have been coded in JAVA and our numerical experiments have been carried out on an Intel(R) Core(TM) i7 CPU M 620, 2.67 GHz, 4 ..... Robust discrete optimization and its applications, volume 14. Springer
Distributed Shortest Paths Algorithms (Extended Abstract)
Rao, Satish
is an orientation of G(V, E), i.e. (i + j) E i? implies that (i - j) E E. Those problems appear to be fairly basic communication net- work. For the problem of Breadth First Search, the best previously known algorithms required is the diameter.) This constitutes a major step towards achieving the lower bounds, which are 0(E) communication
Su, S.D.; Baylor, K.J.; Engholm, B.A. (CEGA Corporation, San Diego, CA (United States))
1987-05-01
PATH is a highly flexible shielding code utilizing the common point-kernel integration technique primarily for treating gamma radiation from reactors, radioactive components and from complex piping systems. Major features of the code include complex geometry capability, various source options, extensive data library, simple but flexible input and well-organized output format.
NSDL National Science Digital Library
Started in the 1970s as an agency to assist men and women in gaining access to a variety of birth control methods, PATH has since expanded its focus to provide "sustainable, culturally relevant [health] solutions, enabling communities worldwide to break longstanding cycles of poor health." The PATH website has more than a dozen videos and slideshows available to visitors at the "Our Multimedia" link near the bottom right hand corner of the homepage. A three-minute video entitled "Better Nutrition For Life" educates visitors about an innovative rice product that could bring greater nutrition to millions of malnourished people where rice is a staple food. The product is Ultra Rice, and is actually fortified pasta that looks, cooks, and tastes like rice, but is fortified with nutrients. The "rice" can be fortified with the needed nutrients the particular population being served is lacking. A slideshow about TB in the Ukraine, explains to visitors why there has been a resurgence of TB in Eastern Europe, and how PATH and its partners set out to help control it throughout the region.
Chirped Laser Dispersion Spectroscopy for Remote Open-Path Trace-Gas Sensing
Nikodem, Michal; Wysocki, Gerard
2012-01-01
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
Long open path Fourier transform spectroscopy measurements of greenhouse gases in the near infrared
NASA Astrophysics Data System (ADS)
Griffith, David; Pöhler, Denis; Schmidt, Stefan; Hammer, Samuel; Vardag, Sanam; Levin, Ingeborg; Platt, Ulrich
2015-04-01
Atmospheric composition measurements are an important tool to quantify local and regional emissions and sinks of greenhouse gases. But how representative are in situ measurements at one point in an inhomogeneous environment? Open path Fourier Transform Spectroscopy (FTS) measurements potentially offer spatial averaging and continuous measurements of several trace gases (including CO2, CH4, CO and N2O) simultaneously in the same airmass. Spatial averaging over kilometre scales is a better fit to the finest scale atmospheric models becoming available, and helps bridge the gap between models and in situ measurements. With what precision, accuracy and reliability can such measurements be made? Building on our pooled experience in ground-level open path Fourier transform spectroscopy and TCCON solar FTS in the infrared (Wollongong) and long path DOAS techniques in the UV-visible (Heidelberg), we set up a new type of open path measurement system across a 1.5 km one-way path in urban Heidelberg, Germany, using FTS in the near infrared. Direct open-atmosphere measurements of trace gases CO2, CH4, CO and N2O as well as O2 were retrieved from several absorption bands between 4000 and 8000 cm-1 (2.5 - 1.25 micron). At one end of the path an in situ FTIR analyser simultaneously collected well calibrated measurements of the same species for comparison with the open path-integrated measurements. The measurements ran continuously from June - November 2014. We introduce the open path FTS measurement system and present an analysis of the results, including assessment of precision, accuracy relative to co-incident in situ measurements, reliability, and avenues for further improvements and extensions. Short term precision of the open path measurement of CO2 was better than 1 ppm for 5 minute averages and thus sufficient for studies in urban and other non-background environments. Measurement bias relative to calibrated in situ measurements was stable across the measurement period. The system operated reliably with data losses mainly due only to weather events such as rain and fog preventing transmission of the IR beam. In principle the system can be improved to provide longer pathlengths and higher precision.
Restoration by Path Concatenation: Fast Recovery of MPLS Paths
Bremler-Barr, Anat
Restoration by Path Concatenation: Fast Recovery of MPLS Paths Yehuda Afek Anat Bremler,natali,haimkg@math.tau.ac.il, fedith,mischug@research.att.com Abstract A new general theory about restoration of network paths is first introduced. The theory pertains to restoration of shortest paths in a network following failure, e.g., we
Restoration by Path Concatenation: Fast Recovery of MPLS Paths
Kaplan, Haim
Restoration by Path Concatenation: Fast Recovery of MPLS Paths Yehuda Afek Anat Bremler-Barr Haim,natali,haimk}@math.tau.ac.il, {edith,mischu}@research.att.com Abstract A new general theory about restoration of network paths is first introduced. The theory pertains to restoration of shortest paths in a network following failure, e.g., we
OLiMPS: OpenFlow Link-layer MultiPath Switching
Newman, Harvey B [California Institute of Technology; Barczyk, Artur [California Institute of Technology; Bredel, Michael [California Institute of Technology
2014-11-17
The OLiMPS project’s goal was the development of an OpenFlow controller application allowing load balancing over multiple switched paths across a complex network topology. The second goal was to integrate the controller with Dynamic Circuit Network systems such as ESnet’s OSCARS. Both goals were achieved successfully, as laid out in this report.
PARTICULATE MATTER MEASUREMENTS USING OPEN-PATH FOURIER TRANSFORM INFRARED SPECTROSCOPY
Open-path Fourier transform infrared (OP-FT1R) spectroscopy is an accepted technology for measuring gaseous air contaminants. OP-FT1R absorbance spectra acquired during changing aerosols conditions reveal related changes in very broad baseline features. Usually, this shearing of ...
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 ...
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...
Open path FTIR detection of threat chemicals in air and on surfaces
John R. Castro-Suarez; Leonardo C. Pacheco-Londoño; William Ortiz-Rivera; Miguel Vélez-Reyes; Max Diem; Samuel P. Hernandez-Rivera
2011-01-01
A remote infrared spectroscopy (RIRS) detection system was assembled using a mid infrared (MIR) Fourier Transform interferometer useful in open-path (OP) mode, a reflective infrared telescope and a cryocooled wide band, MCT detector. The system was used for passive mode IR thermal emission measurements and was also coupled to another Newtonian telescope in conjunction with a globar source for active
OPEN-PATH FTIR MEASUREMENTS OF NOX AND OTHER DIESEL EMISSIONS
The paper gives results of a demonstration of the feasibility of using an open-path Fourier transform infrared (OP-FTIR) monitoring technique to address the across-road characterization of diesel vehicle emissions of criteria pollutants and hazardous air pollutants. Four sets of ...
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...
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...
Application of FTIR spectroscopy to open-path measurements at industrial sites in Germany
NASA Astrophysics Data System (ADS)
Lamp, Torsten; Weber, Konradin; Weidemann, Johannes; van Haren, Guenther
1995-05-01
Emissions of air pollutants from industrial sources are of major public concern in Germany. Remarkable efforts have been made to control and reduce there emissions. A strong reduction of these so-called classical air pollutants like e.g. SO2 out of channeled industrial sources could be recorded throughout the last years. However, at some industrial sites there are still several measurement problems that cannot always be solved appropriately by conventional measurement systems. For example, screening of fugitive emissions or sudden releases out of leakages is difficult to monitor correctly by conventional point sensors. In these cases the open-path FTIR method can show up with several advantages because of its measurement principle. In this paper, different open-path measurements at industrial sites are presented, including measurements of sudden releases of ammonia and measurements at and above an olefin production plant.
An open path, fast response infrared absorption gas analyzer for H2O and CO2
David L. Auble; Tilden P. Meyers
1992-01-01
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
Open-path sensor for atmospheric methane based on chirped laser dispersion spectroscopy
NASA Astrophysics Data System (ADS)
Nikodem, Michal; Plant, Genevieve; Sonnenfroh, David; Wysocki, Gerard
2015-04-01
The design and characterization of a near-IR Chirped Laser Dispersion Spectroscopy (CLaDS) sensor for atmospheric methane detection are reported. The near-IR CLaDS system exhibits the benefits of the prior mid-IR CLaDS systems implemented for open-path sensing while taking advantage of the robust fiber-optic components available in the near-IR. System noise, long-term stability, and comparison with existing technology for methane detection are presented.
Laser-Induced Breakdown Spectroscopy in open-path configuration for the analysis of distant objects
B. Sallé; P. Mauchien; S. Maurice
2007-01-01
A review of recent results on stand-off Laser-Induced Breakdown Spectroscopy (LIBS) analysis and applications is presented. Stand-off LIBS was suggested for elemental analysis of materials located in environments where any physical access was not possible but optical access could be envisaged. This review only refers to the use of the open-path LIBS configuration in which the laser beam and the
Feasibility study of detection of hazardous airborne pollutants using passive open-path FTIR
NASA Astrophysics Data System (ADS)
Segal-Rosenheimer, M.; Dubowski, Y.; Jahn, C.; Schäfer, K.; Gerl, G.; Linker, R.
2010-04-01
In recent years open-path FTIR systems (active and passive) have demonstrated great potential and success for monitoring air pollution, industrial stack emissions, and trace gas constituents in the atmosphere. However, most of the studies were focused mainly on monitoring gaseous species and very few studies have investigated the feasibility of detecting bio-aerosols and dust by passive open-path FTIR measurements. The goal of the present study was to test the feasibility of detecting a cloud of toxic aerosols by a passive mode open-path FTIR. More specifically, we are focusing on the detection of toxic organophosphorous nerve agents for which we use Tri-2-ethyl-hexyl-phosphate as a model compound. We have determined the compounds' optical properties, which were needed for the radiative calculations, using a procedure developed in our laboratory. In addition, measurements of the aerosol size distribution in an airborne cloud were performed, which provided the additional input required for the radiative transfer model. This allowed simulation of the radiance signal that would be measured by the FTIR instrument and hence estimation of the detection limit of such a cloud. Preliminary outdoor measurements have demonstrated the possibility of detecting such a cloud using two detection methods. However, even in a simple case consisting of the detection of a pure airborne cloud, detection is not straightforward and reliable identification of the compound would require more advanced methods than simple correlation with spectral library.
Long-range open-path greenhouse gas monitoring using mid-infrared laser dispersion spectroscopy
NASA Astrophysics Data System (ADS)
Daghestani, Nart; Brownsword, Richard; Weidmann, Damien
2015-04-01
Accurate and sensitive methods of monitoring greenhouse gas (GHG) emission over large areas has become a pressing need to deliver improved estimates of both human-made and natural GHG budgets. These needs relate to a variety of sectors including environmental monitoring, energy, oil and gas industry, waste management, biogenic emission characterization, and leak detection. To address the needs, long-distance open-path laser spectroscopy methods offer significant advantages in terms of temporal resolution, sensitivity, compactness and cost effectiveness. Path-integrated mixing ratio measurements stemming from long open-path laser spectrometers can provide emission mapping when combined with meteorological data and/or through tomographic approaches. Laser absorption spectroscopy is the predominant method of detecting gasses over long integrated path lengths. The development of dispersion spectrometers measuring tiny refractive index changes, rather than optical power transmission, may offer a set of specific advantages1. These include greater immunity to laser power fluctuations, greater dynamic range due to the linearity of dispersion, and ideally a zero baseline signal easing quantitative retrievals of path integrated mixing ratios. Chirped laser dispersion spectrometers (CLaDS) developed for the monitoring of atmospheric methane and carbon dioxide will be presented. Using quantum cascade laser as the source, a minimalistic and compact system operating at 7.8 ?m has been developed and demonstrated for the monitoring of atmospheric methane over a 90 meter open path2. Through full instrument modelling and error propagation analysis, precision of 3 ppm.m.Hz-0.5 has been established (one sigma precision for atmospheric methane normalized over a 1 m path and 1 s measurement duration). The system was fully functional in the rain, sleet, and moderate fog. The physical model and system concept of CLaDS can be adapted to any greenhouse gas species. Currently we are developing an in-lab instrument that can measure carbon dioxide using a quantum cascade laser operating in the 4 ?m range. In this case, the dynamic range benefit of CLaDS is used to provide high precision even when peak absorbance in the CO2 spectrum gets greater than 2. Development for this deployable CO2 measurement system is still at an early stage. So far laboratory gas cell experiments have demonstrated a 9.3 ppm.m.Hz-0.5 for CO2 monitoring. This corresponds to about 0.02% relative precision in measuring CO2 atmospheric background over a 100 m open-path in one second. 1 G. Wysocki and D. Weidmann, "Molecular dispersion spectroscopy for chemical sensing using chirped mid-infrared quantum cascade laser," Opt. Express 18(25), 26123-26140 (2010). 2 N.S. Daghestani, R. Brownsword, D. Weidmann, 'Analysis and demonstration of atmospheric methane monitoring by mid-infrared open-path chirped dispersion spectroscopy' Opt. Express 22(25), A1731-A1743 (2014).
Apparent downward CO 2 flux observed with open-path eddy covariance over a non-vegetated surface
K. Ono; A. Miyata; T. Yamada
2008-01-01
Summary The open-path eddy covariance (EC) method often shows unlikely downward CO2 fluxes in late winter and early spring over drained paddy fields with few active plants. To understand why, we carried out\\u000a intensive measurements in a bare paddy field from 9 to 11 April 2003, simultaneously using open- and closed-path EC methods;\\u000a aerodynamic and dynamic closed-chamber methods were also used.
Detto, M.; Verfaillie, J.; Anderson, F.; Xu, L.; Baldocchi, D.
2011-01-01
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.
Inline multi-harmonic calibration method for open-path atmospheric ammonia measurements
NASA Astrophysics Data System (ADS)
Sun, Kang; Tao, Lei; Miller, David J.; Khan, M. Amir; Zondlo, Mark A.
2013-02-01
We demonstrate a real-time inline calibration method for an open-path ammonia sensor using a quantum cascade laser (QCL) at 9.06 ?m. Ethylene (C2H4) has an absorption feature partially offset from the ammonia absorption feature, and the ethylene signal serves as a reference signal for ammonia concentration in real time. Spectroscopic parameters of ammonia and ethylene are measured and compared with the HITRAN database to ensure the accuracy of the calibration. Multiple harmonic wavelength modulation spectroscopy (WMS) signals are used to separate the ambient ammonia and reference ethylene absorption signals. The ammonia signal is detected with the second harmonic (2f), while it is calibrated simultaneously with a high-harmonic (6-12f) signal of ethylene. The interference of ambient ammonia absorption on the ethylene reference signal is shown to be negligible when using ultra high-harmonics (?6f). This in situ calibration method yields a field precision of 3 % and accuracy of 20 % for open-path atmospheric ammonia measurements.
Improved Eddy Flux Measurements by Open-Path Gas Analyzer and Sonic Anemometer Co-Location
NASA Astrophysics Data System (ADS)
Bogoev, Ivan
2014-05-01
A novel instrument design combines the sensing paths of an open-path gas analyzer and a 3-D sonic anemometer and integrates the sensors in a single aerodynamic body. Common electronics provide fast-response, synchronized measurements of wind vector, sonic temperature, CO2 and H2O densities, and atmospheric pressure. An instantaneous CO2 mixing ratio, relative to dry air, is computed in real time. The synergy of combined sensors offers an alternative to the traditional density-based flux calculation method historically used for standalone open-path analyzers. A simple method is described for a direct, in-situ, mixing-ratio-based flux calculation. The method consists of: (i) correcting sonically derived air temperature for humidity effects using instantaneous water vapor density and atmospheric pressure measurements, (ii) computing water vapor pressure based on water-vapor density and humidity-corrected sonic temperature, (iii) computing fast-response CO2 mixing ratio based on CO2 density, sonic temperature, water vapor, and atmospheric pressures, and (iv) computing CO2 flux from the covariance of the vertical wind speed and the CO2 mixing ratio. Since CO2 mixing ratio is a conserved quantity, the proposed method simplifies the calculations and eliminates the need for corrections in post-processing by accounting for temperature, water-vapor, and pressure-fluctuation effects on the CO2 density. A field experiment was conducted using the integrated sensor to verify performance of the mixing-ratio method and to quantify the differences with density-derived CO2 flux corrected for sensible and latent-heat fluxes. The pressure term of the density corrections was also included in the comparison. Results suggest that the integrated sensor with co-located sonic and gas sensing paths and the mixing-ratio-based method minimize or eliminate the following uncertainties in the measured CO2 flux: (i) correcting for frequency-response losses due to spatial separation of measured quantities, (ii) correcting sonically-derived, sensible-heat flux for humidity, (iii) correcting latent-heat flux for sensible-heat flux and water-vapor self-dilution, (iv) correcting CO2 flux for sensible- and latent-heat fluxes, (v) correcting CO2 flux for pressure-induced density fluctuations.
Pokemon Cards and the Shortest Common Superstring
Mark Stamp; Austin E Stamp
2003-01-01
Evidence is presented that certain sequences of Pokemon cards are determined by selecting consecutive elements from a longer sequence. We then consider the problem of recovering the shortest common superstring (SCS), i.e., the shortest string that contains each of the Pokemon card sequences as a consecutive substring. The SCS problem arises in many applications, most notably in DNA sequencing.
Tool Path Design of Incremental Open-Die Disk Forging Using Physical Modeling
NASA Astrophysics Data System (ADS)
Lee, Sung-Uk; Yang, Dong-Yol
A small-batch product of large-sized parts is usually manufactured using incremental open-die forging. In order to control the overall change in the shape of a part, it is essential to be able to predict the shape changes that occur during each step. This paper addresses shape changes of a material according to the forging path. Rapid prediction of metal flows for continuing incremental deformation using theoretical methods is difficult. Accordingly, instead of a theoretical approach, an experiment that tests the tendency of the metal flow for development of forming processes is required. For the sake of convenience, simulative experiments are carried out using plasticine at room temperature. In present study, the tool movement is dominant parameters to with respect to changing the shape of the workpiece.
NASA Technical Reports Server (NTRS)
Anderson, Stuart M.; Zahniser, Mark S.
1991-01-01
Biogenic emissions from and dry deposition to terrestrial surfaces are important processes determining the trace gas composition of the atmosphere. An instrument has been developed 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 and short base pathlength 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.
Multi-objective stochastic path planning
Dasgupta, Sumantra
2009-05-15
of multiple objectives and stochastic edge parameters. 2. Identify candidate constraints where clustering based multi-level programming can be applied to eliminate infeasible edges. 3. Provide an exact O (V.E) algorithm for building redundant shortest paths. 4...
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 ...
Multiple paths extraction in images using a constrained expanded trellis.
Sun, Changming; Appleton, Ben
2005-12-01
Single shortest path extraction algorithms have been used in a number of areas such as network flow and image analysis. In image analysis, shortest path techniques can be used for object boundary detection, crack detection, or stereo disparity estimation. Sometimes one needs to find multiple paths as opposed to a single path in a network or an image where the paths must satisfy certain constraints. In this paper, we propose a new algorithm to extract multiple paths simultaneously within an image using a constrained expanded trellis (CET) for feature extraction and object segmentation. We also give a number of application examples for our multiple paths extraction algorithm. PMID:16355660
Visibility-Polygon Search and Euclidean Shortest Paths
Takao Asano; Tetsuo Asano; Leonidas J. Guibas; John Hershberger; Hiroshi Imai
1985-01-01
Consider a collection of disjoint polygons in the plane containing a total of n edges. We show how to build, in O(n2) time and space, a data structure from which in O(n) time we can compute the visibility polygon of a given point with respect to the polygon collection. As an application of this structure, the visibility graph of the
Shortest Path Discovery Problems: A Framework, Algorithms and Experimental Results
Szepesvari, Csaba
with execution like in real-time search, etc. Recently there has been a growing interest in incremental search assumptions made on the underlying search graph one gets fundamentally different problem types: the graph may of estimates of the cost- to-go function like in heuristic search, or the search might be interleaved
Solution Methods for the Multi-trip Elementary Shortest Path ...
2011-03-15
algorithm-specific details of the computational experiments and presents computational results ... Figure 1 displays a visualization of a pricing problem and its solution. ...... European Journal of Operational Research, 100:180–191, 1997.
Watershed Cuts: Thinnings, Shortest Path Forests, and Topological Watersheds
Jean Cousty; Gilles Bertrand; Laurent Najman; Michel Couprie
2010-01-01
We recently introduced watershed cuts, a notion of watershed in edge-weighted graphs. In this paper, our main contribution is a thinning paradigm from which we derive three algorithmic watershed cut strategies: The first one is well suited to parallel implementations, the second one leads to a flexible linear-time sequential implementation, whereas the third one links the watershed cuts and the
Mapping Atmospheric Ammonia Emissions Using a Mobile Quantum Cascade Laser-based Open-path Sensor
NASA Astrophysics Data System (ADS)
Sun, K.; Tao, L.; Miller, D. J.; Khan, M. A.; Zondlo, M. A.
2012-12-01
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.
NASA Astrophysics Data System (ADS)
Steill, J. D.; Hager, J. S.; Compton, R. N.
2005-12-01
Air quality issues in the Knoxville and East Tennessee region are of great concern, particularly as regards the nearby Great Smoky Mountains National Park. Integration of a Bomem DA8 FT-IR spectrometer with rooftop sun-tracking optics and an open-path system provides a unique opportunity to analyze the local atmospheric chemical composition. Many trace atmospheric constituents are open to this analysis, such as O3, CO, CH4, and N2O. Boundary layer concentrations as well as total column abundances and vertical concentration profiles are derived. Vertical concentration profiles are determined by fitting solar absorbance lines with the SFIT2 algorithm. Improved fitting of solar spectra has been demonstrated by incorporating the tropospheric concentrations as determined by open-path measurements. In addition to providing a means to improve the analysis of solar spectra, the open-path data is useful for elucidation of diurnal trends in the trace gas concentrations. Anthropogenic influences are of special interest, and seasonal and daily trends in amounts of tropospheric pollutants such as ozone correlate with other sources such as the EPA. Although obviously limited by weather considerations, the technique is suited to the regional climate and a body of data of more than two years extent is available for analysis.
NASA Astrophysics Data System (ADS)
Wang, Wei; Liu, Wenqing; Zhang, Tianshu
2012-12-01
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.
Chitsan Lin; Naiwei Liou; Pao-Erh Chang; Jen-Chin Yang; Endy Sun
2007-01-01
Although most coke oven research is focused on the emission of polycyclic aromatic hydrocarbons, well-known carcinogens, little has been done on the emission of volatile organic compounds, some of which are also thought to be hazardous to workers and the environment. To profile coke oven gas (COG) emissions, we set up an open-path Fourier transform infrared (OP-FTIR) system on top
Hashmonay, R A; Natschke, D F; Wagoner, K; Harris, D B; Thompson, E L; Yost, M G
2001-06-01
This paper describes results from the first field experiment designed to evaluate 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) technique and computed tomography (CT) technique. In this study, an open-path Fourier transform infrared (OP-FTIR) instrument sampled path-integrated concentrations along five radial beam paths in a vertical plane downwind from the source. A meteorological station collected measurements of wind direction and wind speed. Nitrous oxide (N2O) was released from a controlled area source simulator. The innovative CT technique, which applies the smooth basis function minimization method to the beam data in conjunction with measured wind data, was used to estimate the total flux from the simulated area source. The new approach estimates consistently underestimated the true emission rates in unstable atmospheric conditions and agreed with the true emission rate in neutral atmospheric conditions. This approach is applicable to many types of industrial areas or volume sources, given the use of an adequate PI-ORS system. PMID:11414037
NASA Astrophysics Data System (ADS)
Wu, J. B.; Zhou, X. Y.; Wang, A. Z.; Yuan, F. H.
2015-05-01
Eddy covariance using infrared gas analyses has been a useful tool for gas exchange measurements between soil, vegetation and atmosphere. So far, comparisons between the open- and closed-path eddy covariance (CP) system have been extensively made on CO2 flux estimations, while lacking in the comparison of water vapor flux estimations. In this study, the specific performance of water vapor flux measurements of an open-path eddy covariance (OP) system was compared against a CP system over a tall temperate forest in Northeast China. The results show that the fluxes from the OP system (LEop) were generally greater than the (LEcp though the two systems shared one sonic anemometer. The tube delay of closed-path analyser depended on relative humidity, and the fixed median time lag contributed to a significant underestimation of (LEcp between the forest and atmosphere, while slight systematic overestimation was also found for covariance maximization method with single broad time lag search window. After the optimized time lag compensation was made, the average difference between the 30 min (LEop and (LEcp was generally within 6%. Integrated over the annual cycle, the CP system yielded a 5.1% underestimation of forest evapotranspiration as compared to the OP system measurements (493 vs. 469 mm yr-1). This study indicates the importance to estimate the sampling tube delay accurately for water vapor flux calculations with closed-path analysers, and it also suggests that when discuss the energy balance closure problem in flux sites with closed-path eddy covariance systems, it has to be aware that some of the imbalance is possibly caused by the systematic underestimation of water vapor fluxes.
Path optimization using sub-Riemannian manifolds with applications to astrodynamics
Whiting, James K. (James Kalani), 1980-
2011-01-01
Differential geometry provides mechanisms for finding shortest paths in metric spaces. This work describes a procedure for creating a metric space from a path optimization problem description so that the formalism of ...
NASA Astrophysics Data System (ADS)
Steill, J. D.; Hager, J. S.; Compton, R. N.
2006-05-01
Air quality issues in the Knoxville and East Tennessee region are of great concern, particularly as regards the nearby Great Smoky Mountains National Park. Infrared absorption spectroscopy of the atmosphere provides a unique opportunity to analyze the local chemical composition, since many trace atmospheric constituents are open to this analysis, such as O3, CO, CH4, and N2O. Integration of a Bomem DA8 FT-IR spectrometer with rooftop sun-tracking optics and an open-path system provide solar-sourced and boundary- layer atmospheric infrared spectra of these and other relevant atmospheric components. Boundary layer concentrations as well as total column abundances and vertical concentration profiles are derived. Vertical concentration profiles are determined by fitting solar-sourced absorbance lines with the SFIT2 algorithm. Improved fitting of solar spectra has been demonstrated by incorporating the tropospheric concentrations as determined by open-path measurements. A record of solar-sourced atmospheric spectra of greater than two years duration is under analysis to characterize experimental error and thus the limit of precision in the concentration determinations. Initial efforts using atmospheric O2 as a calibration indicate the solar- sourced spectra may not yet meet the precision required for accurate atmospheric CO2 quantification by such efforts as the OCO and NDSC. However, this variability is also indicative of local concentration fluxes pertinent to the regional atmospheric chemistry. In addition to providing a means to improve the analysis of solar spectra, the open-path data is useful for elucidation of seasonal and diurnal trends in the local trace gas concentrations.
Efficient Algorithms for Shortest Partial Seeds in Words
Lonardi, Stefano
Efficient Algorithms for Shortest Partial Seeds in Words Tomasz Kociumaka1 , Solon P. Pissis2 Algorithms for Shortest Partial Seeds in Words 1/16 #12;Periodicity and quasiperiodicity Periodicity. Wale Efficient Algorithms for Shortest Partial Seeds in Words 2/16 #12;Periodicity and quasiperiodicity
NASA Astrophysics Data System (ADS)
Childers, J. W.; Thompson, E. L.; Harris, D. B.; Kirchgessner, D. A.; Clayton, M.; Natschke, D. F.; Phillips, W. J.
Open-path Fourier transform infrared (OP/FTIR) spectrometry was used to measure the concentrations of ammonia, methane, and other atmospheric gases around an integrated industrial swine production facility in eastern North Carolina. Several single-path measurements were made over an 8-day period from 11 to 22 January 1999. Nine different monitoring paths were configured to determine the concentration ranges of ammonia and methane throughout this facility, with an emphasis on isolating the emissions from the farrowing/nursery barns, the finishing barns, and the waste lagoon. A series of sequential measurements was made on 13 January 1999, to estimate the target gas concentrations downwind from each of these sources and at an upwind background site under similar meteorological conditions. The path-averaged concentration (mean±standard deviation) of ammonia during these measurements was below the estimated method detection limit of 0.003 ppm at the background site, 0.328±0.044 ppm between the farrowing/nursery and finishing barns, 2.063±0.140 ppm perpendicular to the airflow from the exhaust fans of the finishing barns, 0.488±0.110 ppm along the western berm of the lagoon, and 0.722±0.659 ppm along the eastern berm of the lagoon. The mean-path-averaged concentration of methane during this same time period was 1.89±0.03 ppm at the background site, 2.58±0.11 ppm between the farrowing/nursery and finishing barns, 2.70±0.05 ppm perpendicular to the airflow from the exhaust fans of the finishing barns, 2.27±0.06 ppm along the western berm of the lagoon, and 11.02±9.69 ppm along the eastern berm of the lagoon as the prevailing westerly winds died down. The concentration measurements made along different monitoring paths during this study indicate that the confinement barns can be a significant source of ammonia, while the lagoon is a major source of methane. Attempts to apply tracer-based dispersion modeling techniques to the single-path OP/FTIR data to estimate emission rates of ammonia and methane from the different sources present at this facility were met with limited success.
Einfield, W. [Sandia National Labs., Albuquerque, NM (United States). Environmental Characterization and Monitoring Dept.
1997-05-01
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.
NASA Astrophysics Data System (ADS)
David, P. A.; Pauls, R. E.; Baughman, Ernie H.
1995-05-01
A field study was performed to evaluate the strengths and limitations of open-path FTIR for the measurement of volatile organic compounds within operating process units. The infrared measurement pathlengths of 100 to 300 meters traversed pipe alleys and pump rows within the units. Three different gas chromatographic-based measurements were made in parallel with the infrared measurements. This was done to provide a verification on the accuracy of the infrared measurements and to provide a cross comparison among the various gas chromatographic (GC) measurements. Measurements at plants found extremely low (sub-ppm) concentrations of organic compounds within the units tested. FTIR results were generally lower than those observed by the three GC methods. Open-path FTIR measurements appear to suffer from a number of limitations at this time including problems with background correction, high detection limits and the impact of meteorological conditions. Further refinements in the technology are required before it can provide high accuracy/precision measurements. At present, best applications might be for leak monitoring and alarming.
Application of the open path FTIR with COL1SB to measurements of ozone and VOCs in the urban area
NASA Astrophysics Data System (ADS)
Hong, Dae Woong; Heo, Gwi Suk; Han, Jin Seok; Cho, Seog Yeon
The COnstrained L1-norm minimization with the Synthetic Background generation method (COL1SB) is newly developed open-path FTIR analysis software, designed to efficiently handle chemical interferences and to systematically generate background spectra. The performance of COL1SB was evaluated mainly against artificially generated field spectra. The present paper aims at application of COL1SB to ambient monitoring. In order to satisfy low detection limit requirements of ambient monitoring, COL1SB was further improved to accurately determine path averaged water vapor pressures, to dynamically select appropriate spectral bands, and to use site specific background spectra. The modified COL1SB was applied to measure ozone, ammonia, methane, carbon monoxide, and 26 VOC species in the park located at the urban area from 12:00 a.m., 25 May to 12:00 a.m., 26 May 2000. The open-path FTIR measurements for ozone, water vapor, alkane concentrations compared very well with those by sampling methods both in magnitudes and in diurnal variations. Furthermore, the detection rates of VOCs were considerably enhanced such that the detection rates based on the correlation coefficients appeared to be above 50% for 12 species out of 16 representative chemical species. Especially ethylene and isoprene, chemically reactive olefins, had high detection rates exceeding 80% despite of their low concentrations. These detection rates by COL1SB are 2-5 times higher than those derived by the conventional CLS method in the previous work (SPIE Conference on Environmental Monitoring and Remediation Technologies SPIE (1998) 3534, 140).
NASA Astrophysics Data System (ADS)
Wada, Ryuichi; Beames, Joseph M.; Orr-Ewing, Andrew J.
2009-06-01
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.
NASA Astrophysics Data System (ADS)
Reidl-Leuthner, Christoph; Ofner, Johannes; Tomischko, Wolfgang; Lohninger, Hans; Lendl, Bernhard
2015-07-01
Within this work we present the application of a new, portable open-path measurement system for the simultaneous determination of NO and NO2 in the atmosphere. The system is based on two pulsed distributed feedback mid-IR quantum cascade laser and a fast thermo-electrically cooled mercury-cadmium-telluride detector. Limits of detection (LoD) below 1 ?gm-3 are achieved for both analytes during one minute measurement time and using an optical path-length of up to 428 m. An accuracy below 10 ngm-3 and a precision below 0.76 ?gm-3 could be calculated based on minute mean values for 100 m path-length. Reducing the measurement time to one second LoDs of approximately 7 ?gm-3 are obtained. During the 300 ns laser pulses micro-spectra for NO and NO2, each of typically 1.2 cm-1 width and a spectral resolution of 0.02 cm-1, are recorded and evaluated. The chosen rotation-vibrational doublets are located at approximately 1900 cm-1 for NO and 1630 cm-1 for NO2. The obtained results show good correlation to the reference method based on chemiluminescence. A particular advantage of the new method is that it provides real time information on the existing NO/NO2 ratio in the measured air. This in turn allows distinguishing between the different emission sources and is demonstrated here by data obtained from different vehicles passing close to the measurement path. These events temporally increased the NO and NO2 concentrations at characteristic ratios from the background values.
Many-body Propagator Theory with Three-Body Interactions: a Path to Exotic Open Shell Isotopes
NASA Astrophysics Data System (ADS)
Barbieri, C.
2014-08-01
Ab-initio predictions of nuclei with masses up to A~100 or more are 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.
Path Planning Algorithm for Vehicles Based on Time-dependent Optimization Criterion
Qing Li; Sijiang Xie; Xinhai Tong; Guangjun Liu
2007-01-01
A specialized genetic algorithm is proposed in this paper for path planning of vehicles based on time-dependent optimization criterion. A variable signal encoding scheme is adopted to represent the path and a particular fitness function is investigated for time-dependent shortest path planning. Domain heuristic knowledge based crossover, mutation and deletion operators are also specifically designed to fit the vehicle path
Daghestani, Nart S; Brownsword, Richard; Weidmann, Damien
2014-12-15
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
NASA Astrophysics Data System (ADS)
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
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
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...
Isaac T. Bertschi; Robert J. Yokelson; Darold E. Ward; Ted J. Christian; Wei Min Hao
2003-01-01
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
George M. Russwurm; Bill Phillips
1999-01-01
The response of a Fourier-transform infrared (FTIR) instrument to changes in absorbance is inherently nonlinear for a number of reasons. One is that the interferogram acquired by the FTIR is truncated and then apodized before further processing of the data is accomplished. A commonly used apodization function in open-path FTIR research is triangular apodization, and all the research presented here
NASA Astrophysics Data System (ADS)
Michel, A. P.; Liu, P. Q.; Yeung, J. K.; Zhang, Y.; Baeck, M. L.; Pan, X.; Dong, H.; Wang, Z.; Smith, J. A.; Gmachl, C. F.
2009-05-01
The 2008 Olympic Games focused attention on the air quality of Beijing, China and served as an important test-bed for developing, deploying, and testing new technologies for analysis of air quality and regional climate in urban environments. Poor air quality in urban locations has a significant detrimental effect on the health of residents while also impacting both regional and global climate change. As a result, there exists a great need for highly sensitive trace gas sensors for studying the atmosphere of the urban environment. Open-path remote sensors are of particular interest as they can obtain data on spatial scales similar to those used in regional climate models. Quantum cascade lasers (QCLs) can be designed for operation in the mid-infrared (mid-IR) with a central wavelength anywhere between 3 to 24 ?m and made tunable over a wavelength interval of over 0.1 ?m. The Quantum Cascade Laser Open-Path System (QCLOPS) is a mid-infrared laser absorption spectrometer that uses a tunable, thermoelectrically cooled, pulsed Daylight Solutions Inc. QCL for measurement of trace gases. The system is aimed at applications with path lengths ranging from approximately 0.1 to 1.0 km. The system is designed to continuously monitor multiple trace gases [water vapor (H2O), ozone (O3), ammonia (NH3), and carbon dioxide (CO2)] in the lower atmosphere. A field campaign from July to September 2008 in Beijing used QCLOPS to study trace gas concentrations before, during, and after the Olympic Games in an effort to capture changes induced by emissions reduction methods. QCLOPS was deployed at the Institute of Atmospheric Physics - Chinese Academy of Sciences on the roof of a two-story building, at an approximate distance of 2 miles from the Olympic National Stadium ("The Bird's Nest.") QCLOPS operated with an open-path round trip distance of approximately 75 m. The system ran with minimal human interference, twenty-four hours per day for the full campaign period. In order to collect data over numerous absorption peaks belonging to the target gases of H2O, NH3, O3, and CO2, measurements were made at 317 different wavelengths within the full tuning range of the laser (1020 - 1070 cm-1). We present the design of this novel sensor which was successfully built, deployed, and operated with minimal operator intervention for the three month field campaign period. Furthermore, we present the results of the field campaign and the capabilities of the QCLOPS system to measure fluctuations of the trace gases at parts-per-billion levels. The time series data illustrate the changing levels of the trace gases over the campaign period. In addition, data from commercial sensors simultaneously deployed at the field site are presented as a validation of the capabilities of the QCLOPS system. This work was supported by MIRTHE (NSF-ERC #EEC-0540832).
Algorithms for the Shortest and Closest Lattice Vector Problems
Hanrot, Guillaume
Algorithms for the Shortest and Closest Lattice Vector Problems Guillaume Hanrot and Xavier Pujol of the art solvers of the Shortest and Closest Lattice Vector Problems in the Euclidean norm. We recall the three main families of algorithms for these problems, namely the algo- rithm by Micciancio and Voulgaris
Minimal Realizations of Linear Systems: The "Shortest Basis" Approach
Forney, G. David, Jr.
Given a discrete-time linear system C, a shortest basis for C is a set of linearly independent generators for C with the least possible lengths. A basis B is a shortest basis if and only if it has the predictable span ...
[Study on the measurement of ambient ammonia in urban area based on open-path DOAS technique].
Wang, Jie; Xie, Pin-hua; Qin, Min; Ling, Liu-yi; Ye, Cong-lei; Liu, Jian-guo; Liu, Wen-qing
2012-02-01
As a key role in the acid-deposition and the generation of secondary particle matter (PM), measurement of the concentration of atmospheric ammonia in urban area has been attracting the scientists' interests nowadays. After studying the special absorption features of ammonia in short UV wavelength range, detailed concernful issues were put forward in the present paper. The decision of using xenon lamp as the light source was made after the evaluation of measurement of light spectroscopy. Retrieval wavelength band for NH3 was fixed from 204 to 214 nm and optimal method of deducting other interferential gases was also shown. A home-made open-path DOAS (OP-DOAS) system was set up for the measurement of the concentration of atmospheric NH3. The detection limit of such system was calculated with the typical noise level as low as 0.33 microg x m(-3) with the optical path 228 m. Through field experiment in Guangzhou city, such a system can be competent for the online and high time-resolution monitoring of the concentration of atmospheric ammonia. With a significant diurnal variation, the atmospheric ammonia changed from 0.83 to 3.11 microg x m(-3) with the mean value 1.59 microg x m(-3). The representative character of the diurnal variation is that the concentration of NH3 peaks during night while drops to bottom in the daytime. After the error analysis procedure, typical measurement accuracy of such OP-DOAS system was within 10%. PMID:22512193
Encoding user motion preferences in harmonic function path planning
Giles D'silva; Manfred Huber
2009-01-01
Humans have unique motion preferences when pursuing a given task. These motion preferences could be expressed as moving in a straight line, following the wall, avoiding sharp turns, avoiding damp surfaces or choosing the shortest path. While it would be very useful for a range of applications to allow robot systems or artificial agents to generate paths with similar specific
NASA Astrophysics Data System (ADS)
Buchholz, B.; Afchine, A.; Ebert, V.
2014-05-01
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.
NASA Astrophysics Data System (ADS)
He, Ying; Zhang, Yujun; Liu, Wenqing; Kan, Ruifeng; Xia, Hui
2009-07-01
Gaseous ammonia is the most abundant alkaline trace gas in the atmosphere. As ammonia plays an important role in acid deposition and aerosol formation, it influences the regional air quality and atmospheric visibility. TDLAS (Tunable Diode Laser Absorption Spectroscopy)is a method to obtain the spectroscopy of single molecule absorption line in the characteristic absorption spectrum region as the characteristic of the distributed feed back (DFB) diode laser with narrow linewidth and tunability, which makes it possible to detect trace-gas qualitatively or quantificationally. The NH3 in-situ monitoring instrument based on TDLAS and long open path technology have been developed combining with wavelength modulation and harmonic detection techniques to obtain the necessary detection sensitivity. This instrument has been used to measure atmospheric NH3 concentration at an urban site near Beijing National Stadium from July to October in 2008, especially in the period of Beijing Olympics and Paralympics. The continuously monitoring results show that the atmospheric NH3 concentration variation has an obvious diurnal periodicity in the urban of Beijing. First of all, the general diurnal variation rule is the concentration decreased to the minimum in the daytime, and then increased to the maximum at night. Moreover, the NH3 peak concentration decreased obviously at the beginning of the Beijing Olympics then it kept descending during the Paralympics. The obtained maximum of NH3 is between 20.31?g/m3? 48.54?g/m3 with the daily average concentration between 12.6?g/m3?27.5?g/m3. During these three months, Air Quality Assurance Scheme for the Olympics (AQASO) was implemented through the joint actions of Beijing Municipal Government and the five neighboring provinces/municipalities in north China. The measures such as auto restriction and plant ejection-decreasing are carried out in Beijing. In conclusion, the open-path TDLAS instrument is suitable for atmospheric trace gases detection on-line with its high resolution, high sensitivity, rapid response time without gas sampling. Also correlation studies have verified the positive effects of measures taken for improving the air quality including restricting ammonia formation.
Opening paths to novel analgesics: the role of potassium channels in chronic pain
Tsantoulas, Christoforos; McMahon, Stephen B.
2014-01-01
Chronic pain is associated with abnormal excitability of the somatosensory system and remains poorly treated in the clinic. Potassium (K+) channels are crucial determinants of neuronal activity throughout the nervous system. Opening of these channels facilitates a hyperpolarizing K+ efflux across the plasma membrane that counteracts inward ion conductance and therefore limits neuronal excitability. Accumulating research has highlighted a prominent involvement of K+ channels in nociceptive processing, particularly in determining peripheral hyperexcitability. We review salient findings from expression, pharmacological, and genetic studies that have untangled a hitherto undervalued contribution of K+ channels in maladaptive pain signaling. These emerging data provide a framework to explain enigmatic pain syndromes and to design novel pharmacological treatments for these debilitating states. PMID:24461875
NASA Astrophysics Data System (ADS)
Yokelson, Robert J.; Susott, Ronald; Ward, Darold E.; Reardon, James; Griffith, David W. T.
1997-08-01
Biomass samples from a diverse range of ecosystems were burned in the Intermountain Fire Sciences Laboratory open combustion facility. Midinfrared spectra of the nascent emissions were acquired at several heights above the fires with a Fourier transform infrared spectrometer (FTIR) coupled to an open multipass cell. In this report, the results from smoldering combustion during 24 fires are presented including production of carbon dioxide, carbon monoxide, methane, ethene, ethyne, propene, formaldehyde, 2-hydroxyethanal, methanol, phenol, acetic acid, formic acid, ammonia, hydrogen cyanide, and carbonyl sulfide. These were the dominant products observed, and many have significant influence on atmospheric chemistry at the local, regional, and global scale. Included in these results are the first optical, in situ measurements of smoke composition from fires in grasses, hardwoods, and organic soils. About one half of the detected organic emissions arose from fuel pyrolysis which produces white smoke rich in oxygenated organic compounds. These compounds deserve more attention in the assessment of fire impacts on the atmosphere. The compound 2-hydroxyethanal is a significant component of the smoke, and it is reported here for the first time as a product of fires. Most of the observed alkane and ammonia production accompanied visible glowing combustion. NH3 is normally the major nitrogen-containing emission detected from smoldering combustion of biomass, but from some smoldering organic soils, HCN was dominant. Tar condensed on cool surfaces below the fires accounting for ˜1% of the biomass burned, but it was enriched in N by a factor of 6-7 over the parent material, and its possible role in postfire nutrient cycling should be further investigated.
NASA Astrophysics Data System (ADS)
Guo, Zehua; Tang, Xian-Zhu
2012-08-01
Parallel transport of long mean-free-path plasma along an open magnetic field line is characterized by strong temperature anisotropy, which is driven by two effects. The first is magnetic moment conservation in a non-uniform magnetic field, which can transfer energy between parallel and perpendicular degrees of freedom. The second is decompressional cooling of the parallel temperature due to parallel flow acceleration by conventional presheath electric field which is associated with the sheath condition near the wall surface where the open magnetic field line intercepts the discharge chamber. To the leading order in gyroradius to system gradient length scale expansion, the parallel transport can be understood via the Chew-Goldbeger-Low (CGL) model which retains two components of the parallel heat flux, i.e., qn associated with the parallel thermal energy and qs related to perpendicular thermal energy. It is shown that in addition to the effect of magnetic field strength (B) modulation, the two components (qn and qs) of the parallel heat flux play decisive roles in the parallel variation of the plasma profile, which includes the plasma density (n), parallel flow (u), parallel and perpendicular temperatures (T? and T?), and the ambipolar potential (?). Both their profile (qn/B and qs/B2) and the upstream values of the ratio of the conductive and convective thermal flux (qn/nuT? and qs/nuT?) provide the controlling physics, in addition to B modulation. The physics described by the CGL model are contrasted with those of the double-adiabatic laws and further elucidated by comparison with the first-principles kinetic simulation for a specific but representative flux expander case.
Guo Zehua; Tang Xianzhu [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2012-08-15
Parallel transport of long mean-free-path plasma along an open magnetic field line is characterized by strong temperature anisotropy, which is driven by two effects. The first is magnetic moment conservation in a non-uniform magnetic field, which can transfer energy between parallel and perpendicular degrees of freedom. The second is decompressional cooling of the parallel temperature due to parallel flow acceleration by conventional presheath electric field which is associated with the sheath condition near the wall surface where the open magnetic field line intercepts the discharge chamber. To the leading order in gyroradius to system gradient length scale expansion, the parallel transport can be understood via the Chew-Goldbeger-Low (CGL) model which retains two components of the parallel heat flux, i.e., q{sub n} associated with the parallel thermal energy and q{sub s} related to perpendicular thermal energy. It is shown that in addition to the effect of magnetic field strength (B) modulation, the two components (q{sub n} and q{sub s}) of the parallel heat flux play decisive roles in the parallel variation of the plasma profile, which includes the plasma density (n), parallel flow (u), parallel and perpendicular temperatures (T{sub Parallel-To} and T{sub Up-Tack }), and the ambipolar potential ({phi}). Both their profile (q{sub n}/B and q{sub s}/B{sup 2}) and the upstream values of the ratio of the conductive and convective thermal flux (q{sub n}/nuT{sub Parallel-To} and q{sub s}/nuT{sub Up-Tack }) provide the controlling physics, in addition to B modulation. The physics described by the CGL model are contrasted with those of the double-adiabatic laws and further elucidated by comparison with the first-principles kinetic simulation for a specific but representative flux expander case.
Sung, Lung-Yu; Shie, Ruei-Hou; Lu, Chia-Jung
2014-01-30
A new approach employing two pollution rose plots to locate the sources of multiple hazardous gas emissions was proposed and tested in an industrial area. The data used for constructing the pollution rose plots were obtained from two side-by-side measurements of open-path Fourier Transform Infrared (OP-FTIR) spectrometers during one week of continuous analysis on the rooftop of a semiconductor plant. Hazardous gases such as CF4, C2F6, CH3OH, NH3, NO2, and SF6 were found and quantified at the ppb level by both OP-FTIR measurement sites. The data of the top 20% highest concentrations and associated wind directions were used to construct the pollution rose plots. Pollution source probability contours for each compound were constructed using the probability-product of directional probability from two pollution rose plots. Hot spots for SF6, CF4, NO2, and C2F6 pointed to the stack area of the plant, but the sources of CH3OH and NH3 were found outside of this plant. The influences of parameters for this approach such as the variation in wind direction, lower limit concentration threshold and the nearby buildings were discussed. PMID:24333712
NASA Astrophysics Data System (ADS)
Wu, Chang-Fu; Wu, Tzong-gang; Hashmonay, Ram A.; Chang, Shih-Ying; Wu, Yu-Syuan; Chao, Chun-Ping; Hsu, Cheng-Ping; Chase, Michael J.; Kagann, Robert H.
2014-01-01
Fugitive emission of air pollutants is conventionally estimated based on standard emission factors. The Vertical Radial Plume Mapping (VRPM) technique, as described in the US EPA OTM-10, is designed to measure emission flux by directly monitoring the concentration of the plume crossing a vertical plane downwind of the site of interest. This paper describes the evaluation results of implementing VRPM in a complex industrial setting (a petrochemical tank farm). The vertical plane was constructed from five retroreflectors and an open-path Fourier transform infrared spectrometer. The VRPM configuration was approximately 189.2 m in width × 30.7 m in height. In the accompanying tracer gas experiment, the bias of the VRPM estimate was less than 2% and its 95% confidence interval contained the true release rate. Emission estimates of the target VOCs (benzene, m-xylene, o-xylene, p-xylene, and toluene) ranged from 0.86 to 2.18 g s-1 during the 14-day field campaign, while estimates based on the standard emission factors were one order of magnitude lower, possibly leading to an underestimation of the impact of these fugitive emissions on air quality and human health. It was also demonstrated that a simplified 3-beam geometry (i.e., without one dimensional scanning lines) resulted in higher uncertainties in the emission estimates.
A methodology for predicting minimum travel paths using real-time traffic network data
Liu, Chang
1991-01-01
, existing traffic simulation and optimization models have been reviewed, and appropriate models have been chosen to predict link travel time and fuel consumption. Link-node types of mathematical networks have been established, and minimum travel distance... Integration of ATMS with ADIS Traffic Data Fusion For Link Time Prediction . . NETWORK ANALYSIS Shortest Path Problem Shortest Path with Fixed-Charges Problem . . STUDY DESIGN REVIEW OF EXISTING TRAFFIC MODELS PASSER II-87 PASSER III-88 TRANSYT-7F...
Historical Traffic-Tolerant Paths in Road Networks Pui Hang Li Man Lung Yiu
Yiu, Man Lung
paths that mini- mize the aggregate (historical) travel time. Unlike the shortest path problem, the TTP problem has a combinatorial search space that renders the optimal solution expensive to compute. We demonstrate the effectiveness of TTP paths and the efficiency of our proposed algorithms. Categories
A Specific Genetic Algorithm for Optimum Path Planning in Intelligent Transportation System
Qing Li; Guangjun Liu; Wei Zhang; Cailu Zhao; Yixin Yin; Zhiliang Wang
2006-01-01
A specific genetic algorithm is proposed in this paper for optimum path planning. Operations such as encoding, crossover and mutation are tailored to fit optimum path planning. Simulation results show that the specific genetic algorithm has advantages such as rapid calculation speed and high probability of optimal solution. It is a new approach for solving shortest path problems in practical
Optimal paths for a car that goes both forwards and backwards
J. A. Reeds; L. A. Shepp
1990-01-01
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?
Finding a least hop(s) path subject to multiple additive constraints Gang Cheng, Nirwan Ansari*
Ansari, Nirwan
Finding a least hop(s) path subject to multiple additive constraints Gang Cheng, Nirwan Ansari referred to as the least hop(s) multiple additively constrained path (LHMACP) selection, which is NP of computing All Hops k-shortest Paths (AHKP) between a source and a destination. Through extensive analysis
Wen-Shing Chang; Shiao-Shing Chen; Jung-Hua Chang; Chih-Hui Tang; Tzi-Chin Chang
2009-01-01
In this article, a case study was conducted to correlate the odor index and possible pollutants from a pharmaceutical plant based on the odor threshold and Open Path Fourier Transform Infrared (OP-FTIR) technique to model the results using American Meteorological Society\\/Environmental Protection Agency Regulatory Dispersion Model (AERMOD). Although nine different pollutants were obtained from OP-FTIR, the contribution to the detected
Formal language constrained path problems
Barrett, C.; Jacob, R.; Marathe, M.
1997-07-08
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.
Inquiry-based learning templates for creating online educational paths
Davis, Sarah Alice
2006-10-30
(with annotation enlarged)............................................. 49 9 Second Stop in Density Path (with annotation enlarged) ........................................ 49 10 Third Stop in Density Path..........................................................................................50 11 Fourth Stop in Density Path..................................................................................... 50 12 Last Stop in Density Path (with annotation enlarged)............................................. 50 13 Opening...
On path selection for traffic with bandwidth guarantees
Qingming Ma; Peter Steenkiste
1997-01-01
Transmission of multimedia streams imposes a minimum-band width requirementon the path being used to ensure end-to-end Qual ity-of- Service (QoS) guarantees. While any shortest-path algorit hm can be used to select a feasible path, additional constraints th at limit resource consumption and balance the network load are neede d to achieve efficient resource utilization. We present a syst ematic evaluation
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...
Lin, Chitsan; Liou, Naiwei; Chang, Pao-Erh; Yang, Jen-Chin; Sun, Endy
2007-04-01
Although most coke oven research is focused on the emission of polycyclic aromatic hydrocarbons, well-known carcinogens, little has been done on the emission of volatile organic compounds, some of which are also thought to be hazardous to workers and the environment. To profile coke oven gas (COG) emissions, we set up an open-path Fourier transform infrared (OP-FTIR) system on top of a battery of coke ovens at a steel mill located in Southern Taiwan and monitored average emissions in a coke processing area for 16.5 hr. Nine COGs were identified, including ammonia, CO, methane, ethane, ethylene, acetylene, propylene, cyclohexane, and O-xylene. Time series plots indicated that the type of pollutants differed over time, suggesting that different emission sources (e.g., coke pushing, quench tower, etc.) were involved at different times over the study period. This observation was confirmed by the low cross-correlation coefficients of the COGs. It was also found that, with the help of meteorological analysis, the data collected by the OP-FTIR system could be analyzed effectively to characterize differences in the location of sources. Although the traditional single-point samplings of emissions involves sampling various sources in a coke processing area at several different times and is a credible profiling of emissions, our findings strongly suggest that they are not nearly as efficient or as cost-effective as the continuous line average method used in this study. This method would make it easier and cheaper for engineers and health risk assessors to identify and to control fugitive volatile organic compound emissions and to improve environmental health. PMID:17458466
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...
NASA Astrophysics Data System (ADS)
Tao, L.; Sun, K.; Pan, D.; Golston, L.; Stanton, L. G.; Ham, J. M.; Shonkwiler, K. B.; Nash, C.; Zondlo, M. A.
2014-12-01
Ammonia (NH3) is the dominant alkaline species in the atmosphere and an important compound in the global nitrogen cycle. There is a large uncertainty in NH3 emission inventory from agriculture, which is the largest source of NH3, including livestock farming and fertilizer applications. In recent years, a quantum cascade laser (QCL)-based open-path sensor has been developed to provide high-resolution, fast-response and high-sensitivity NH3 measurements. It has a detection limit of 150 pptv with a sample rate up to 20 Hz. This sensor has been integrated into a mobile platform mounted on the roof of a car to perform measurement of multiple trace gases. We have also used the sensor for eddy covariance (EC) flux measurements. The mobile sensing method provides high spatial resolution and fast mapping of measured gases. Meanwhile, the EC flux method offers accurate flux measurements and resolves the diurnal variability of NH3emissions. During the DISCOVER-AQ and FRAPPÉ field campaigns in 2014, this mobile platform was used to study NH3 emissions from cattle feedlot near Fort Morgan, Colorado. This specific feedlot was mapped multiple times in different days to study the variability of its plume characteristics. At the same time, we set up another open-path NH3 sensor with LICOR open-path sensors to perform EC flux measurements of NH3, CH4 and CO2 simultaneously in the same cattle feedlot as shown in Fig. 1. NH3/CH4 emission flux ratio show a strong temperature dependence from EC flux measurements. The median value of measured NH3 and CH4 emission flux ratio is 0.60 ppmv/ppmv. In contrast, the median value of ?NH3/?CH4 ratios measured from mobile platform is 0.53 ppmv/ppmv for the same farm. The combination of mobile mapping and EC flux measurements with the same open-path sensors greatly improves understanding of NH3 emissions both spatially and temporally.
Tao, Lei; Sun, Kang; Khan, M Amir; Miller, David J; Zondlo, Mark A
2012-12-17
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
CS 105: Algorithms (Grad) Solving Shortest Superstring via Set Cover
Chakrabarti, Amit
CS 105: Algorithms (Grad) Solving Shortest Superstring via Set Cover Khanh Do Ba Feb 24, 2005 1 Recap: Minimum Set Cover Recall the (Weighted) Set Cover problem, defined as follows. Set Cover Problem. First, the algorithm is as follows. Algorithm 1: GreedySetCover(X, F) C - 1 U - X2 while U = do3 Find
Energy-efficient Paths in Radio Networks Rene Beier1
Matijevic, Domagoj
Introduction The shortest-path problem is one of the fundamental problems which has been studied for a long, Cp is a node-dependent offset cost and |pq| denotes the Euclidean distance between p and q. For every in wireless networking. In recent years wireless network technology has gained tremendous importance
Traffic engineering approach to path selection in optical burst switching networks
NASA Astrophysics Data System (ADS)
Teng, Jing; Rouskas, George N.
2005-11-01
It is usually assumed that optical burst switching (OBS) networks use the shortest path routing along with next-hop burst forwarding. The shortest path routing minimizes delay and optimizes utilization of resources, however, it often causes certain links to become congested while others remain underutilized. In a bufferless OBS network in which burst drop probability is the primary metric of interest, the existence of a few highly congested links could lead to unacceptable performance for the entire network. We take a traffic engineering approach to path selection in OBS networks with the objective of balancing the traffic across the network links to reduce congestion and to improve overall performance. We present an approximate integer linear optimization problem as well as a simple integer relaxation heuristic to solve the problem efficiently for large networks. Numerical results demonstrate that our approach is effective in reducing the network-wide burst drop probability, in many cases significantly, over the shortest path routing.
Minimum Wheel-Rotation Paths for Differential-Drive Mobile Hamidreza Chitsaz
LaValle, Steven M.
, with the goal of classifying solutions in the spirit of Dubins curves and Reeds-Shepp curves for car-like robotsMinimum Wheel-Rotation Paths for Differential-Drive Mobile Robots Hamidreza Chitsaz , Steven M. LaValle, Devin J. Balkcom, and Matthew T. Mason August 7, 2007 Abstract The shortest paths for a mobile robot
A Proficient Path Selection for Wireless Ad Hoc Routing Protocol
A. N. Al-Khwildi; H. S. Al-Raweshidy
2006-01-01
Usually, routing protocols which are based on link-state information such as (OSPF, OLSR, and FSR) compute the shortest routes to each reachable destination using a path-selection algorithm like Dijkstra's algorithm or the Bellman-Ford algorithm. However, in an on-demand link-state routing protocol, there is no need to know the path to every other node. Accordingly, when a node chooses a next
Near-infrared open-path measurement of CO_{2} concentration in the urban atmosphere.
Saito, Hayato; Manago, Naohiro; Kuriyama, Kenji; Kuze, Hiroaki
2015-06-01
Average concentration of carbon dioxide (CO_{2}) has been measured over a path length of 5.1 km in the lower troposphere by the method of differential optical absorption spectroscopy (DOAS) using a near-infrared light source based on amplified spontaneous emission. The analysis of CO_{2} absorption intensity around 1575 nm observed during 10 days over the Chiba city area has revealed that the CO_{2} concentration varied in the range of around 360-450 ppmv, with presumable influence of air mass advection from nearby industrial facilities. In addition, a good correlation has been found in relative humidity values between the DOAS and meteorological station data. As a whole, the present result indicates the usefulness of such a DOAS approach for measuring the concentration of CO_{2} averaged over an optical path of a few kilometers in the lower troposphere. PMID:26030559
Internet Traffic Engineering by Optimizing OSPF Weights
Bernard Fortz; Mikkel Thorup
2000-01-01
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
NASA Astrophysics Data System (ADS)
Paton-Walsh, C.; Smith, T. E. L.; Young, E. L.; Griffith, D. W. T.; Guérette, É.-A.
2014-02-01
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.
NASA Astrophysics Data System (ADS)
Kühnreich, B.; Wagner, S.; Habig, J. C.; Möhler, O.; Saathoff, H.; Ebert, V.
2015-04-01
An advanced in situ diode laser hygrometer for simultaneous, sampling-free detection of interstitial H2 16O and H2 18O vapor was developed and tested in the aerosol interaction and dynamics in atmosphere (AIDA) cloud chamber during dynamic cloud formation processes. The spectrometer to measure isotope-resolved water vapor concentrations comprises two rapidly time-multiplexed DFB lasers near 1.4 and 2.7 µm and an open-path White cell with 227-m absorption path length and 4-m mirror separation. A dynamic water concentration range from 2.6 ppb to 87 ppm for H2 16O and 87 ppt to 3.6 ppm for H2 18O could be achieved and was used to enable a fast and direct detection of dynamic isotope ratio changes during ice cloud formation in the AIDA chamber at temperatures between 190 and 230 K. Relative changes in the H2 18O/H2 16O isotope ratio of 1 % could be detected and resolved with a signal-to-noise ratio of 7. This converts to an isotope ratio resolution limit of 0.15 % at 1-s time resolution.
NASA Astrophysics Data System (ADS)
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
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.
All-Pairs Almost Shortest Paths Ausarbeitung des Vortrags von Martin Holzer
Brandes, Ulrik
Grafen. Wird nun die Bedingung der Exaktheit dieser Distanzen etwas aufgeweicht und ein einseiti- ger und das APASP-Problem fÂ¨ur einen Grafen mit einem ein- seitigen additiven Fehler von maximal k l-Emulator zu einem ungewichteten Grafen einen gewichteten Grafen mit derselben Knotenmenge so, dass die Distanz
Multi-population Genetic Algorithms with Immigrants Scheme for Dynamic Shortest Path
Yang, Shengxiang
.g., artificial neural networks, genetic algo- rithms (GAs), particle swarm optimization, etc. However intelligence techniques, e.g., artificial neural networks (ANNs) [2], genetic algorithms (GAs) [3, they will be effective in fixed infrastructure wireless or wired networks. But, they exhibit unacceptably high com
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
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
Geometric SpeedUp Techniques for Finding Shortest Paths in Large Sparse Graphs
Dorothea Wagner; Thomas Willhalm
2003-01-01
In this paper, we consider Dijkstra's algorithm for the single source single target shortestpaths problem in large sparse graphs. The goal is to reduce the response time for onlinequeries by using precomputed information. For the result of the preprocessing, we admit atmost linear space. We assume that a layout of the graph is given. From this layout, in thepreprocessing, we
All-Pairs Shortest Paths for Unweighted Undirected Graphs in o(mn) Time
Chan, Timothy M.
well-known examples of log-factor speedup was Arlazarov et al.'s (a.k.a. the \\four-Russians") algorithm with n vertices and m edges. We present new algorithms with the following running times: 8 log n) if m > n log n log log log n O(mn log log n= log n) if m > n log log n O(n 2 log 2 log n= log n
On designing a shortest-path-based cache replacement in a transcoding proxy
Hao-ping Hung; Ming-syan Chen
2009-01-01
The technology advance in network has accelerated the development of multimedia applications over the wired and wireless communication.\\u000a To alleviate network congestion and to reduce latency and workload on multimedia servers, the concept of multimedia proxy\\u000a has been proposed to cache popular contents. Caching the data objects can relieve the bandwidth demand on the external network,\\u000a and reduce the average
The Multiple Choice Elementary Constrained Shortest Path Problem Karen Smilowitz Guangming Zhang
Hazen, Gordon
to solve the Vehicle Routing Problem (VRP) and variations of the VRP, including the Pickup and Delivery®ort required to solve the linear relaxation of the VRP at the nodes of the branch-and-price tree by considering
The Multiple Choice Elementary Constrained Shortest Path Problem Karen Smilowitz Guangming Zhang
Smilowitz, Karen
Problem (VRP) and variations of the VRP, including the Pickup and Delivery Problem; see, for example the linear relaxation of the VRP at the nodes of the branch-and-price tree by considering a reduced subset
NASA Astrophysics Data System (ADS)
Rajagopalan, Srinivasan; Robb, Richard
2006-03-01
The degree of match between the delineation result produced by a segmentation technique and the ground truth can be assessed using robust "presence-absence" resemblance measures. Previously, we had investigated and introduced an exhaustive list of similarity indices for assessing multiple segmentation techniques. However, these measures are highly sensitive to even minor boundary perturbations which imminently manifest in the segmentations of random biphasic spaces reminiscent of the stochastic pore-solid distributions in the tissue engineering scaffolds. This paper investigates the ideas adapted from ecology to emphasize global resemblances and ignore minor local dissimilarities. It uses concepts from graph theory to perform controlled local mutations in order to maximize the similarities. The effect of this adjustment is investigated on a comprehensive list (forty nine) of similarity indices sensitive to the over- and under- estimation errors associated with image delineation tasks.
Shortest Average Routing Path-Based d-hop Clustering in wireless sensor networks
Ailian Jiangl; Weili Wu; Keming Xie; Donghyun Kirn; Wei Wang
2010-01-01
In the paper, we propose a new d-hop Clustering method for a clustering-based multi-hop routing scheme in large-scale wireless sensor network. d-hop clustering means that each cluster contains all nodes that are at distance at most d-hops from the clusterhead, so that the number of clusters can be getting smaller to make it possible to guarantee the combined system performances
The All-Pair Shortest-Path Problem in Shared-Memory Heterogeneous Systems
Llanos, Diego R.
-Arranz, Yuri Torres, Diego R. Llanos, Ph.D., and Arturo Gonzalez-Escribano, Ph.D. Departamento de Inform, ed.). By Hector Ortega-Arranz, Yuri Torres, Diego R. Llanos and Arturo Gonzalez-Escribano Copyright c
Weifeng Huang; Anan Osothsilp; Farzad Pourboghrat
2010-01-01
In this paper, a vision-based obstacle avoiding path generation problem is considered for autonomous mobile robots under a top-view workspace. The collision-free path planning problem is converted to a convex optimization problem that can be solved numerically using linear matrix inequalities (LMI). A new optimal (shortest) path cost formulation is given for LMI optimization using a novel Line of Sight
NSDL National Science Digital Library
Perry Samson
This website catalogs all the tornado paths in the United States since 1950. The tornado path data is overlaid onto a Google Maps base for easy browsing and manipulation of the map view. Clicking on individual tornados provides the user with information such as its Fujita rating, the amount of damage caused by the tornado, the size of the path that the tornado made, and the length of time the tornado was on the ground.
Examination of the long-path open-air FTIR technique for air monitoring in the state of Kentucky
NASA Astrophysics Data System (ADS)
Chakraborty, Dilip K.
1995-05-01
The Kentucky Department for Environmental Protection has been developing on-site monitoring capability for the measurement of air pollutants. The department has purchased a mobile laboratory equipped with a GC/MS for point monitoring and a long-path Fourier transform infrared (FT-IR) remote sensor unit for monitoring air pollutants at different locations in the State. Prior to deploying the FT-IR instrument in the field, the instrument has been evaluated for precision and accuracy with 15 certified gases (CO, NO, NH3, COS, CS2, SO2, (CH3)2S, acetone, benzene, CH3OH, CH4, CCl4, CCl3H, C2H5OH, and H2S) against the vendor provided calibration spectra by using a 15 cm quality control internal cell. Results of this study are presented. Some other studies include the cases of strong spectral overlaps and structured spectral features. Results of some short-term field study at Calvert City, Western Kentucky are also presented.
NASA Astrophysics Data System (ADS)
Jarboe, Thomas; Marklin, George; Nelson, Brian; Sutherland, Derek; HIT Team Team
2013-10-01
A proof of principle experiment to study closed-flux energy confinement of a spheromak sustained by imposed dynamo current drive is described. A two-fluid validated NIMROD code has simulated closed-flux sustainment on a stable spheromak using imposed dynamo current drive (IDCD), demonstrating that dynamo current drive is compatible with closed flux. (submitted for publication and see adjacent poster.(spsap)) HIT-SI, a = 0.25 m, has achieved 90 kA of toroidal current, current gains of nearly 4, and operation from 5.5 kHz to 68 kHz, demonstrating the robustness of the method.(spsap) Finally, a reactor design study using fusion technology developed for ITER and modern nuclear technology shows a design that is economically superior to coal.(spsap) The spheromak reactor and development path are about a factor of 10 less expensive than that of the tokamak/stellarator. These exciting results justify a proof of principle (PoP) confinement experiment of a spheromak sustained by IDCD. Such an experiment (R = 1.5 m, a = 1 m, Itor = 3 . 2 MA, n = 4e19/m3, T = 3 keV) is described in detail.
NASA Astrophysics Data System (ADS)
Bogoev, Ivan; Helbig, Manuel; Sonnentag, Oliver
2015-04-01
A growing number of studies report systematic differences in CO2 flux estimates obtained with the two main types of gas analyzers: compared to eddy-covariance systems based on closed-path (CP) gas analyzers, systems with open-path (OP) gas analyzers systematically overestimate CO2 uptake during daytime periods with high positive sensible heat fluxes, while patterns for differences in nighttime CO2 exchange are less obvious. These biases have been shown to correlate with the sign and the magnitude of the sensible heat flux and to introduce large uncertainties when calculating annual CO2 budgets. In general, CP and OP gas analyzers commonly used to measure the CO2 density in the atmosphere operate on the principle of infrared light absorption approximated by Beer-Lambert's law. Non-dispersive interference-based optical filter elements are used to select spectral bands with strong attenuation of light transmission, characteristic to the gas of interest. The intensity of the light passing through the optical sensing path depends primarily on the amount of absorber gas in the measurement volume. Besides the density of the gas, barometric pressure and air temperature are additional factors affecting the strength and the half-width of the absorption lines. These so-called spectroscopic effects are accounted for by measuring barometric pressure and air temperature in the sensing path and scaling the light-intensity measurements before applying the calibration equation. This approach works well for CP gas analyzers with an intake tube that acts as a low-pass filter on fast air-temperature fluctuations. Low-frequency response temperature sensors in the measurement cell are therefore sufficient to account for spectroscopic temperature effects. In contrast, OP gas analyzers are exposed to high-frequency air-temperature fluctuations associated with the atmospheric surface-layer turbulent heat exchange. If not corrected adequately, these fast air-temperature variations can cause systematic errors in the CO2 density measurements. Under conditions of high positive or negative sensible heat flux, air-temperature fluctuations are correlated with fluctuations of the vertical wind component and can lead to significant biases in the CO2 flux estimates. This study demonstrates that sonically derived fast-response air temperature in the optical sensing path of an OP gas analyzer can replace the slow-response measurements from the temperature sensor as a scaling parameter in the calibration model to correct for these air temperature-induced spectroscopic effects. Our approach is evaluated by comparison between different OP and CP gas analyzer-based eddy-covariance systems in ecosystems with low CO2 uptake under a range of sensible heat flux regimes and varying meteorological parameters. We show that ignoring high-frequency spectroscopic effects can lead to false interpretations of net ecosystem CO2 exchange for specific site and environmental conditions.
Metabolic PathFinding: inferring relevant pathways in biochemical networks.
Croes, Didier; Couche, Fabian; Wodak, Shoshana J; van Helden, Jacques
2005-07-01
Our knowledge of metabolism can be represented as a network comprising several thousands of nodes (compounds and reactions). Several groups applied graph theory to analyse the topological properties of this network and to infer metabolic pathways by path finding. This is, however, not straightforward, with a major problem caused by traversing irrelevant shortcuts through highly connected nodes, which correspond to pool metabolites and co-factors (e.g. H2O, NADP and H+). In this study, we present a web server implementing two simple approaches, which circumvent this problem, thereby improving the relevance of the inferred pathways. In the simplest approach, the shortest path is computed, while filtering out the selection of highly connected compounds. In the second approach, the shortest path is computed on the weighted metabolic graph where each compound is assigned a weight equal to its connectivity in the network. This approach significantly increases the accuracy of the inferred pathways, enabling the correct inference of relatively long pathways (e.g. with as many as eight intermediate reactions). Available options include the calculation of the k-shortest paths between two specified seed nodes (either compounds or reactions). Multiple requests can be submitted in a queue. Results are returned by email, in textual as well as graphical formats (available in http://www.scmbb.ulb.ac.be/pathfinding/). PMID:15980483
NASA Astrophysics Data System (ADS)
Goode, Jon G.; Yokelson, Robert J.; Susott, Ronald A.; Ward, Darold E.
1999-09-01
The trace gas emissions from six biomass fires, including three grass fires, were measured using a Fourier transform infrared (FTIR) spectrometer coupled to an open-path, multipass cell (OP-FTIR). The quantified emissions consisted of carbon dioxide, nitric oxide, water vapor, carbon monoxide, methane, ammonia, ethylene, acetylene, isobutene, methanol, acetic acid, formic acid, formaldehyde, and hydroxyacetaldehyde. By including grass fires in this study we have now measured smoke composition from fires in each major vegetation class. The emission ratios of the oxygenated compounds, formaldehyde, methanol, and acetic acid, were 1-2% of CO in the grass fires, similar to our other laboratory and field measurements but significantly higher than in some other studies. These oxygenated compounds are important, as they affect O3 and HOx chemistry in both biomass fire plumes and the free troposphere. The OP-FTIR data and the simultaneously collected canister data indicated that the dominant C4 emission was isobutene (C4H8) and not 1-butene. The rate constant for the reaction of isobutene with the OH radical is 60% larger than that of 1-butene. We estimate that 67±9% of the fuel nitrogen was volatilized with the major nitrogen emissions, ammonia, and nitric oxide, accounting for 22±8%.
Path to Market for Compact Modular Fusion Power Cores
Path to Market for Compact Modular Fusion Power Cores S. Woodruff, J. K. Baerny, N. Mattor, J. E distant' Solution: making fusion systems compact and modular opens path to market #12;12/13/11 3 Outline fusion systems compact and modular opens path to market #12;12/13/11 4 CT Lead CT Lead ICC special
UAV Intelligent Path Planning for Wilderness Search and Rescue Computer Science Department
Goodrich, Michael A.
UAV 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 of the limited UAV flying time. I. INTRODUCTION The use of mini-UAVs (Unmanned Aerial Vehicles) in Wilderness
An efficient dynamic system for real-time robot-path planning
Allan R. Willms; Simon X. Yang
2006-01-01
This paper presents a simple yet efficient dynamic-programming (DP) shortest path algorithm for real-time collision-free robot-path planning applicable to situations in which targets and barriers are permitted to move. The algorithm works in real time and requires no prior knowledge of target or barrier movements. In the case that the barriers are stationary, this paper proves that this algorithm always
A disjoint path selection scheme with shared risk link groups in GMPLS networks
Eiji Oki; Nobuaki Matsuura; Kohei Shiomoto; Naoaki Yamanaka
2002-01-01
This letter proposes a disjoint path selection scheme for generalized multi-protocol label switching (GMPLS) networks with shared risk link group (SRLG) constraints. It is called the weighted-SRLG (WSRLG) scheme. It treats the number of SRLG members related to a link as part of the link cost when the k-shortest path algorithm is executed. In WSRLG, a link that has many
The shortest modulation period Blazhko RR Lyrae star: SS Cnc
J. Jurcsik; B. Szeidl; Á. Sódor; I. Dékány; Zs. Hurta; K. Posztobányi; K. Vida; M. Váradi; A. Szing
2006-03-20
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.
NASA Astrophysics Data System (ADS)
Helbig, Manuel; Humphreys, Elyn; Bogoev, Ivan; Quinton, William L.; Wischnweski, Karoline; Sonnentag, Oliver
2015-04-01
Long-term measurements of net ecosystem exchange of CO2 (NEE) are conducted across a global network of flux tower sites. These sites are characterised by varying climatic and vegetation conditions, but also differ in the type of CO2/H2O gas analyser used to obtain NEE. Several studies have observed a systematic bias in measured NEE when comparing open-path (OP) and closed-path (CP) sensors with consistently more negative daytime NEE measurements when using OP sensors, both during the growing and non-growing season. A surface heating correction has been proposed in the literature, but seems not to be universally applicable. Systematic biases in NEE measurements are particularly problematic for synthesis papers and inter-comparison studies between sites where the 'true' NEE is small compared to the potential instrument bias. For example, NEE estimates for boreal forest sites derived from OP sensors show large, ecologically unreasonable winter CO2 uptake. To better understand the causes and the magnitude of this potential bias, we conducted a sensor inter-comparison study at the Mer Bleue peatland near Ottawa, ON, Canada. An eddy covariance system with a CP (LI7000 & GILL R3-50) and an OP sensor (EC150 & CSAT3A) was used. Measurements were made between September 2012 and January 2013 and covered late summer, fall, and winter conditions. Flux calculations were made as consistently as possible to minimise differences due to differing processing procedures (e.g. spectral corrections). The latent (LE, slope of orthogonal linear regression of LEOP on LECP: 1.02 ± 0.01 & intercept: -0.2 ± 0.6 W m-2 and sensible heat fluxes (H, slope of HCSAT3A on HGILL: 0.96 ± 0.01 & intercept: 0.1 ± 0.03 W m-2) did not show any significant bias. However, a significant bias was apparent in the NEE measurements (slope of NEEOP on NEECP: 1.36 ± 0.02 & intercept: -0.1 ± 0.05). The differences between NEEOP and NEECP were linearly related to the magnitude of HCSAT3A with a slope of -0.02 ± 0.001 ?mol CO2 m-2 s-1 and an intercept of -0.1 ± 0.03 ?mol CO2 m-2 s-1 (R2 = 0.82, p = 0.001) indicating a consistent overestimation of CO2 uptake during the day and an overestimation of ecosystem respiration during the night. Air temperatures did not have a significant effect on NEE differences. Winter NEE measurements at two boreal forest, one boreal wetland, and one tundra site show similar relationships with H further supporting the findings of this study. In contrast to OP sensors, CP sensors are less affected by high frequency air temperature fluctuations and do not require a correction for air density fluctuations to obtain NEE. Our results point toward a consistent bias in NEEOP that is likely related to the magnitude of H, the main input to the WPL term. The additional findings from five contrasting ecosystems suggest that the bias in NEEOP depends on the site-specific H regime, questioning the accuracy of comparison studies across contrasting ecosystems. Since the absolute magnitude of the bias seems to be directly related to the magnitude of H rather than to the magnitude of NEE, the relative error is likely larger for sites with small NEE. These findings are therefore particularly important for NEE studies at high latitude sites.
NSDL National Science Digital Library
Cynthia Ann Radle (McCullough High School REV)
1995-06-30
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.
Trajectory Generation and Path Planning for Autonomous Aerobots
NASA Technical Reports Server (NTRS)
Sharma, Shivanjli; Kulczycki, Eric A.; Elfes, Alberto
2007-01-01
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.
Finding the dominant energy transmission paths in statistical energy analysis
NASA Astrophysics Data System (ADS)
Guasch, Oriol; Aragonès, Àngels
2011-05-01
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.
NASA Astrophysics Data System (ADS)
Miller, D. J.; Sun, K.; Tao, L.; Zondlo, M. A.
2013-12-01
Atmospheric ammonia (NH3) is an important fine aerosol gas-phase precursor, with implications for regional air quality and climate change. Atmospheric methane (CH4) is an important greenhouse gas, with high uncertainties in the partitioning of various emission sources. Ammonia and methane agricultural emissions are highly variable in space and time and are highly uncertain, with a lack of widespread, in-situ measurements. We characterize the spatial variability of dairy livestock emissions by performing high resolution (5 Hz), in-situ, on-road mobile measurements of NH3, CH4, CO2, N2O, CO and H2O simultaneously with open-path sensors mounted on a passenger vehicle. This suite of multiple trace gas measurements allows for emission ratio calculations and separation of agricultural, petrochemical and combustion emission signatures. Mobile measurements were performed in the Tulare County dairy farm region (~120 dairy farms sampled downwind) in the Central Valley, California during NASA DISCOVER-AQ in winter 2013. We calculate the ?NH3/?CH4 and ?NH3/?CO2 emission ratios for each dairy farm sampled downwind. Emission plumes from individual farms are isolated based on known dairy farm locations and high resolution (1 km) surface wind field simulations. Background concentrations are subtracted to calculate the emission ratios. We find high spatial variability of ammonia and methane concentrations, with localized maximums of >1 ppmv NH3 downwind of individual dairy farms. The spatial extent of individual farm emission plumes are evaluated for NH3, CH4 and CO2, which all show well-defined enhancements localized to the dairy farms near the roadside (typical sampling proximity of ? 50 m). The NH3 concentrations are correlated with the distance from each dairy farm. The observed median concentration within 100 m downwind of the dairy farms is 63 ppbv NH3, with the 95th percentile at 417 ppbv NH3 and decreases to background conditions at ~500 m distance downwind. The diurnal variability of NH3 and CH4 background concentrations at the same locations sampled on multiple days is also evaluated; including a case study of a strong morning temperature inversion. Finally, we find the NH3/CH4 ratios at the sub-farm scale vary by at least a factor of two due to spatially heterogeneous farming practices. These results highlight the need for widespread, in-situ spatial and temporal sampling of agricultural regions to further characterize these heterogeneous emissions. Future analyses will inform emission inventories and regional air quality modeling efforts.
Calculating Least Risk Paths in 3d Indoor Space
NASA Astrophysics Data System (ADS)
Vanclooster, A.; De Maeyer, Ph.; Fack, V.; Van de Weghe, N.
2013-08-01
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.
Ohya, Akihisa
Transform [2][3] (Fig.1) Fig.1 Obstacle plot 2.2 Fig.2 ( ) (Fig.2) #12;Fig.2 Obstacle judgment 2.3 Distance Transform 0 (Fig.3) ( ) 4 1 (Fig.3) Fig.3 Distance Transform 4 +1 1 ( +5) (Fig.4) Fig.3 Path generation (the same weight) Fig.4 Path generation (different weights) 2.4 (Fig.5) Fig.5 #12;Fig.5 Shortest path
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
Rida T. Farouki; Jairam Manjunathaiah; Guo-Feng Yuan
1999-01-01
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
Chen Xin; Xiucheng Guo; Dongtao Fan
2011-01-01
Aviation safety is the base for the operation of air transportation system. It plays a significant role in maneuvering accidents quickly and efficiently. In this paper, the network of airport on the airside was analyzed from the aspect of aviation safety; then a nodes-arcs relation database was built to describe the airside network topology and the Dijkstra algorithm was employed
Jzau-sheng Lin; Mingshou Liu; Nen-fu Huang
2000-01-01
Many network services, such as video conferencing and video on demand, have popularly used the multimedia communications. The attached hosts\\/routers are required to transmit data as multicasting in most multimedia applications. In order to provide an efficient data routing, routers must provide multicast capability. In this paper, a new cooling schedule in Hopfield neural network with annealing strategy is proposed
NASA Astrophysics Data System (ADS)
Kim, Ki-Hyun; Kim, Min-Young
A field-based intercomparison study was conducted to evaluate the performance of a line-integrating monitoring technique (a commercial differential optical absorption spectroscopy, DOAS, system by Opsis AB, Sweden) in concert with a conventional in situ monitoring technique (MACSAM-2 (or MS2) system, Japan). In the course of our study, the mixing ratios of three trace gases including SO 2, NO 2, and O 3 were measured routinely from the Ban Po district of Seoul during a 13 month period (June 1999-August 2000). The data obtained from two different systems were used to evaluate various aspects of DOAS performance. The differences in the observed mixing ratios between two techniques, if assessed in terms of the percent difference (PD) values between different data sets, were in general rather compatible not only among different species but also as a function of varying time scale. The differences in the measured mixing ratio between the two systems were also examined statistically using linear regression analysis. Results of the regression analysis indicated the existence of significant correlations among all trace gases monitored, confirming the strong compatibility between the two systems. The effects of meteorological factors on the DOAS performance were also examined through investigation of the mixing ratio differences between two systems and the concurrently determined environmental parameters. According to our analysis, it is concluded that the level of agreement between the two systems can be affected by the variations in the spatial mixing conditions. Although some uncertainties remain to be resolved, our preliminary attempts to evaluate an open path monitoring technique clearly demonstrated that consideration of meteorological conditions may be required to properly assess the DOAS performance due to its capacity to cover spatial scale over the open path length.
Li-Pei Wong; Malcolm Yoke Hean Low; Chin Soon Chong
2011-01-01
Identifying the shortest Hamiltonian circuit is a task which appears in various types of industrial and logistics applications. It is a NP-hard problem (1). This paper intends to find the shortest Hamiltonian circuit of the selected 68 towns\\/cities in Penang state, Malaysia using the generic Bee Colony Optimization (BCO) framework (2). The proposed BCO framework realizes computationally the foraging process
Development of a potential field estimator for a path-planning application using neural networks
Smith, Darin William
1997-01-01
. . . . . . . . . . . b. Attractive and Repulsive Potentials B. Operational Space Approach . 1. Shortest Path Computation . a. Graph Theory b. Methodology for the SSRMS Problem . BACK-PROPAGATION ARTIFICIAL NEURAL NETWORK THEORY A. IvIotivation . 1. Fuzzy Logic 2... advantages and disadvantages with respe&t to the others. 1. Fuzzy Logic The particular problem being studied is known as a classilication problem. Harral has developed an aircraft situation recognizer using fuzzy logi&:l5). The situation rccognizer...
Non-classical paths in interference experiments
Rahul Sawant; Joseph Samuel; Aninda Sinha; Supurna Sinha; Urbasi Sinha
2014-08-09
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 which is only approximately true. In our present study, we have used the Feynman path integral formalism to quantify contributions from non-classical paths in quantum interference experiments which provide a measurable deviation from a naive application of the superposition principle. A direct experimental demonstration for the existence of these non-classical paths is hard. We find that contributions from such paths can be significant and we propose simple three-slit interference experiments to directly confirm their existence.
CS 105: Algorithms (Grad) Set Cover and Application to Shortest Superstring
Chakrabarti, Amit
CS 105: Algorithms (Grad) Set Cover and Application to Shortest Superstring Valika K. Wan & Khanh Do Ba Feb 21-24, 2005 1 Approximating Set Cover 1.1 Definition An Instance (X, F) of the set-covering a minimum size subset C F whose members cover all of X. X = SC S (1) The cost of the set-covering
On the ideal of the shortest vectors in the Leech lattice and other lattices
Martin, Bill
On the ideal of the shortest vectors in the Leech lattice and other lattices William J. Martin, E7, E8, 24 (the Leech lattice) and determine for each: (i) the smallest degree of a non to cometric association schemes. 1 Introduction The Leech lattice 24 is well-studied in several mathematical
Zone-Based Shortest Positioning Time First Scheduling for MEMS-Based Storage Devices
Miller, Ethan L.
Zone-Based Shortest Positioning Time First Scheduling for MEMS-Based Storage Devices Bo Hong, Scott. MEMS-based storage devices use orthog- onal magnetic or physical recording techniques and thou- sands of simultaneously active MEMS-based read-write tips to provide high-density low-latency non-volatile storage
Finding a Shortest Diagonal of a Simple Polygon in Linear John Hershberger
Âknown, for instance, that a closest pair among n points in the plane can be found in O(n log n) time for finding a closest pair of vertices in a simple polygon---observe that a shortest diagonal is defined by a closest pair of vertices satisfying an additional visibility constraint. 1 #12; 1 Introduction Closest
Information spread of emergency events: path searching on social networks.
Dai, Weihui; Hu, Hongzhi; Wu, Tunan; Dai, Yonghui
2014-01-01
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
Traveling salesman path problems
Lam, Fumei
2005-01-01
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 ...
S. A. Bortoff; E. Hartford
2000-01-01
In this paper, a two step path-planning algorithm for UAVs is proposed. The algorithm generates a stealthy path through a set of enemy radar sites of known location, and provides an intuitive way to trade-off stealth versus path length. In the first step, a suboptimal rough-cut path is generated through the radar sites by constructing and searching a graph based
Hard paths, soft paths or no paths? Cross-cultural perceptions of water solutions
Hall, Sharon J.
Hard paths, soft paths or no paths? Cross-cultural perceptions of water solutions Drew Blasco1 to the availability of clean, safe water. In this study we examined cross cultural preferences for soft path vs. hard conceptualize water solutions (hard paths, soft paths, no paths) cross-culturally? 2) What role does development
On the near-optimality of the shortest-latency-time-first drum scheduling discipline
Harold S. Stone; Samuel H. Fuller
1973-01-01
For computer systems in which it is practical to determine the instantaneous drum position, a popular discipline for determining the sequence in which the records are to be accessed is the so-called shortest-latency-time-first, SLTF, discipline. When a collection of varying-length records is to be accessed from specified drum positions, it is known that the SLTF discipline does not necessarily minimize
Shortest-route formulation of mixed-model assembly line balancing problem
Erdal Erel; Hadi Gökçen
1999-01-01
A shortest-route formulation of the mixed-model assembly line balancing problem is presented. Common tasks across models are assumed to exist and these tasks are performed in the same stations. The formulation is based on an algorithm which solves the single-model version of the problem. The mixed-model system is transformed into a single-model system with a combined precedence diagram. The model
Twins: The Two Shortest Period Non-Interacting Double Degenerate White Dwarf Stars
F. Mullally; Carles Badenes; Susan E. Thompson; Robert Lupton
2009-01-01
We report on the detection of the two shortest period non-interacting white dwarf binary systems. These systems, SDSS J143633.29+501026.8 and SDSS J105353.89+520031.0, were identified by searching for radial velocity variations in the individual exposures that make up the published spectra from the Sloan Digital Sky Survey. We followed up these systems with time series spectroscopy to measure the period and
Ciardo, Gianfranco
Ciardo Department of Computer Science College of William and Mary Williamsburg, VA 23187-8795, USA {gli, ciardo}@cs.wm.edu Abstract In distributed or multi-processor systems, the join the shortest queue (JSQ
Twins: The Two Shortest Period Non-Interacting Double Degenerate White Dwarf Stars
F. Mullally; Carles Badenes; Susan E. Thompson; Robert Lupton
2009-01-01
We report on the detection of the two shortest period non-interacting white\\u000adwarf binary systems. These systems, SDSS J143633.29+501026.8 and SDSS\\u000aJ105353.89+520031.0, were identified by searching for radial velocity\\u000avariations in the individual exposures that make up the published spectra from\\u000athe Sloan Digital Sky Survey. We followed up these systems with time series\\u000aspectroscopy to measure the period and
NASA Astrophysics Data System (ADS)
Gelfand, I.; Cui, M.; Tao, L.; Sun, K.; Tang, J.; Zondlo, M. A.; Robertson, G. P.
2012-12-01
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.
Automatic tracking of neuro vascular tree paths
NASA Astrophysics Data System (ADS)
Suryanarayanan, S.; Gopinath, A.; Mallya, Y.; Shriram, K. S.; Joshi, M.
2006-03-01
3-D analysis of blood vessels from volumetric CT and MR datasets has many applications ranging from examination of pathologies such as aneurysm and calcification to measurement of cross-sections for therapy planning. Segmentation of the vascular structures followed by tracking is an important processing step towards automating the 3-D vessel analysis workflow. This paper demonstrates a fast and automated algorithm for tracking the major arterial structures that have been previously segmented. Our algorithm uses anatomical knowledge to identify the start and end points in the vessel structure that allows automation. Voxel coding scheme is used to code every voxel in the vessel based on its geodesic distance from the start point. A shortest path based iterative region growing is used to extract the vessel tracks that are subsequently smoothed using an active contour method. The algorithm also has the ability to automatically detect bifurcation points of major arteries. Results are shown for tracking the major arteries such as the common carotid, internal carotid, vertebrals, and arteries coming off the Circle of Willis across multiple cases with various data related and pathological challenges from 7 CTA cases and 2 MR Time of Flight (TOF) cases.
GED Revision Opens Path to Higher Ed.
ERIC Educational Resources Information Center
Gewertz, Catherine
2011-01-01
The General Educational Development program, or GED, is undergoing the biggest revamping in its 69-year history, driven by mounting recognition that young adults' future success depends on getting more than a high-school-level education. Potent forces have converged to stoke the GED's redesign. A labor market that increasingly seeks some…
Tortuous path chemical 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
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.
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.
Twins: The Two Shortest Period Non-Interacting Double Degenerate White Dwarf Stars
NASA Astrophysics Data System (ADS)
Mullally, F.; Badenes, Carles; Thompson, Susan E.; Lupton, Robert
2009-12-01
We report on the detection of the two shortest period non-interacting white dwarf binary systems. These systems, SDSS J143633.29+501026.8 and SDSS J105353.89+520031.0, were identified by searching for radial velocity variations in the individual exposures that make up the published spectra from the Sloan Digital Sky Survey. We followed up these systems with time series spectroscopy to measure the period and mass ratios of these systems. Although we only place a lower bound on the companion masses, we argue that they must also be white dwarf stars. With periods of approximately 1 hr, we estimate that the systems will merge in less than 100 Myr, but the merger product will likely not be massive enough to result in a Type 1a supernova.
Twins: The Two Shortest Period Non-Interacting Double Degenerate White Dwarf Stars
Mullally, F; Thompson, Susan E; Lupton, Robert
2009-01-01
We report on the detection of the two shortest period non-interacting white dwarf binary systems. These systems, SDSS J143633.29+501026.8 and SDSS J105353.89+520031.0, were identified by searching for radial velocity variations in the individual exposures that make up the published spectra from the Sloan Digital Sky Survey. We followed up these systems with time series spectroscopy to measure the period and mass ratios of these systems. Although we only place a lower bound on the companion masses, we argue that they must also be white dwarf stars. With periods of approximately 1 hour, we estimate that the systems will merge in less than 100 Myr, but the merger product will likely not be massive enough to result in a Type 1a supernova.
TWINS: THE TWO SHORTEST PERIOD NON-INTERACTING DOUBLE DEGENERATE WHITE DWARF STARS
Mullally, F.; Badenes, Carles; Lupton, Robert [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Thompson, Susan E., E-mail: fergal@astro.princeton.ed [Department of Physics and Astronomy, University of Delaware, 217 Sharp Lab, Newark, DE 19716 (United States)
2009-12-10
We report on the detection of the two shortest period non-interacting white dwarf binary systems. These systems, SDSS J143633.29+501026.8 and SDSS J105353.89+520031.0, were identified by searching for radial velocity variations in the individual exposures that make up the published spectra from the Sloan Digital Sky Survey. We followed up these systems with time series spectroscopy to measure the period and mass ratios of these systems. Although we only place a lower bound on the companion masses, we argue that they must also be white dwarf stars. With periods of approximately 1 hr, we estimate that the systems will merge in less than 100 Myr, but the merger product will likely not be massive enough to result in a Type 1a supernova.
From (2,3)-Motzkin Paths to Schröder Paths
NASA Astrophysics Data System (ADS)
Yan, Sherry H. F.
2007-08-01
In this paper, we provide a bijection between the set of restricted (2,3)-Motzkin paths of length n and the set of Schroder paths of semilength n. Furthermore, we give a one-to-one correspondence between the set of (2,3)-Motzkin paths of length n and the set of little Schroder paths of semilength n+1. By applying the bijections, we get the enumerations of Schroder paths according to the statistics "number of udd's" and "number of hd's".
Triggered plasma opening switch
Mendel, Clifford W. (Albuquerque, NM)
1988-01-01
A triggerable opening switch for a very high voltage and current pulse includes a transmission line extending from a source to a load and having an intermediate switch section including a plasma for conducting electrons between transmission line conductors and a magnetic field for breaking the plasma conduction path and magnetically insulating the electrons when it is desired to open the switch.
Sullivan, Blair D [ORNL; Seymour, Dr. Paul Douglas [Princeton University
2010-01-01
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.
Pedestrian paths: why path-dependence theory leaves health policy analysis lost in space.
Brown, Lawrence D
2010-08-01
Path dependence, a model first advanced to explain puzzles in the diffusion of technology, has lately won allegiance among analysts of the politics of public policy, including health care policy. Though the central premise of the model--that past events and decisions shape options for innovation in the present and future--is indisputable (indeed path dependence is, so to speak, too shallow to be false), the approach, at least as applied to health policy, suffers from ambiguities that undercut its claims to illuminate policy projects such as managed care, on which this article focuses. Because path dependence adds little more than marginal value to familiar images of the politics of policy--incrementalism, for one--analysts might do well to put it on the back burner and pursue instead "thick descriptions" that help them to distinguish different degrees of openness to exogenous change among diverse policy arenas. PMID:21057101
ERIC Educational Resources Information Center
Coleman, Toni
2012-01-01
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…
Jeffrey Michael Hebert
2001-01-01
This dissertation explores optimal path planning for air vehicles. An air vehicle exposed to illumination by a tracking radar is considered and the problem of determining an optimal planar trajectory connecting two prespecified points is addressed. An analytic solution yielding the trajectory minimizing the received radar energy reflected from the target is derived using the Calculus of Variations. Additionally, the
Danil Sokolov; Ivan Poliakov; Alexandre Yakovlev
2007-01-01
A token-based model for asynchronous data path is formally defined and three token game semantics, spread token, antitoken and counterflow, are introduced. These semantics are studied and their advantages and drawbacks are highlighted. For analysis and comparison a software tool is developed which integrates these models into a consistent framework. The models are verified by mapping them into Petri nets
DNA Computing Hamiltonian path
Hagiya, Masami
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
A new efficient optimal path planner for mobile robot based on Invasive Weed Optimization algorithm
NASA Astrophysics Data System (ADS)
Mohanty, Prases K.; Parhi, Dayal R.
2014-12-01
Planning of the shortest/optimal route is essential for efficient operation of autonomous mobile robot or vehicle. In this paper Invasive Weed Optimization (IWO), a new meta-heuristic algorithm, has been implemented for solving the path planning problem of mobile robot in partially or totally unknown environments. This meta-heuristic optimization is based on the colonizing property of weeds. First we have framed an objective function that satisfied the conditions of obstacle avoidance and target seeking behavior of robot in partially or completely unknown environments. Depending upon the value of objective function of each weed in colony, the robot avoids obstacles and proceeds towards destination. The optimal trajectory is generated with this navigational algorithm when robot reaches its destination. The effectiveness, feasibility, and robustness of the proposed algorithm has been demonstrated through series of simulation and experimental results. Finally, it has been found that the developed path planning algorithm can be effectively applied to any kinds of complex situation.
Incremental Multi-Scale Search Algorithm for Dynamic Path Planning With Low Worst-Case Complexity.
Lu, Yibiao; Huo, Xiaoming; Arslan, Oktay; Tsiotras, Panagiotis
2011-06-16
Path-planning (equivalently, path-finding) problems are fundamental in many applications, such as transportation, VLSI design, robot navigation, and many more. In this paper, we consider dynamic shortest path-planning problems on a graph with a single endpoint pair and with potentially changing edge weights over time. Several algorithms exist in the literature that solve this problem, notably among them the Lifelong Planning A(?) (LPA(?)) algorithm. The LPA(?) algorithm is an incremental search algorithm that replans the path when there are changes in the environment. In numerical experiments, however, it was observed that the performance of LPA(?) is sensitive in the number of vertex expansions required to update the graph when an edge weight value changes or when a vertex is added or deleted. Although, in most cases, the classical LPA(?) requires a relatively small number of updates, in some other cases the amount of work required by the LPA(?) to find the optimal path can be overwhelming. To address this issue, in this paper, we propose an extension of the baseline LPA(?) algorithm, by making efficient use of a multiscale representation of the environment. This multiscale representation allows one to quickly localize the changed edges, and subsequently update the priority queue efficiently. This incremental multiscale LPA(?) ( m-LPA(?) for short) algorithm leads to an improvement both in terms of robustness and computational complexity-in the worst case-when compared to the classical LPA(?). Numerical experiments validate the aforementioned claims. PMID:21690015
Atmospheric Science Data Center
2014-12-08
... every 233 revolutions around the Earth, it is natural to name each of these different trajectories or paths. For MISR, the path is the generic name (actually the numeric label) of all orbits that observe the same areas ...
Bike path Schools Bike friendly
Crews, Stephen
Bike path Schools Parks Greenways Bike lane Bike friendly Bike path on sidewalk (uphill only a left turn, merge with motor vehicle traffic well in advance of the intersection. When bicycle paths stopping distance in inclement weather. Use a backpack or bike bag to carry items. Reasons to Bike
Autonomous ground vehicle path tracking
Jeff Wit; Carl D. Crane III; David G. Armstrong II
2004-01-01
Autonomous ground vehicle navigation requires the integration of many technologies such as path planning, position and orientation sensing, vehicle control, and obstacle avoidance. The work presented here focuses on the control of a nonholonomic ground vehicle as it tracks a given path. A new path tracking technique called ''vector pursuit'' is presented. This new technique is based on the theory
A CONTINUATION METHOD FOR NONHOLONOMIC PATH-FINDING
, a trajectory of that goes from p to q. If we let U denote the space of admissible open-loop controls de#12.e. the map that assigns, to each control 2 U, the terminal point ;p(b) of the trajectory ;p : [a;b] ! M. If the starting trajectory 0 corresponds to an open-loop control 0, then q0 is equal to Ep(0). Since the path
Iwamoto, Takahiro; Slanina, Zdenek; Mizorogi, Naomi; Guo, Jingdong; Akasaka, Takeshi; Nagase, Shigeru; Takaya, Hikaru; Yasuda, Nobuhiro; Kato, Tatsuhisa; Yamago, Shigeru
2014-10-27
[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
NLTT 5306: the shortest period detached white dwarf+brown dwarf binary
NASA Astrophysics Data System (ADS)
Steele, P. R.; Saglia, R. P.; Burleigh, M. R.; Marsh, T. R.; Gänsicke, B. T.; Lawrie, K.; Cappetta, M.; Girven, J.; Napiwotzki, R.
2013-03-01
We have spectroscopically confirmed a brown dwarf mass companion to the hydrogen atmosphere white dwarf NLTT 5306. The white dwarf's atmospheric parameters were measured using the Sloan Digital Sky Survey and X-shooter spectroscopy as Teff = 7756 ± 35 K and log(g) = 7.68 ± 0.08, giving a mass for the primary of MWD = 0.44 ± 0.04 M? at a distance of 71 ± 4 pc with a cooling age of 710 ± 50 Myr. The existence of the brown dwarf secondary was confirmed through the near-infrared arm of the X-shooter data and a spectral type of dL4-dL7 was estimated using standard spectral indices. Combined radial velocity measurements from the Sloan Digital Sky Survey, X-shooter and the Hobby-Eberly Telescope's High Resolution Spectrograph of the white dwarf give a minimum mass of 56 ± 3 MJup for the secondary, confirming the substellar nature. The period of the binary was measured as 101.88 ± 0.02 min using both the radial velocity data and i'-band variability detected with the Isaac Newton Telescope. This variability indicates `day' side heating of the brown dwarf companion. We also observe H? emission in our higher resolution data in phase with the white dwarf radial velocity, indicating that this system is in a low level of accretion, most likely via a stellar wind. This system represents the shortest period white dwarf+brown dwarf binary and the secondary has survived a stage of common envelope evolution, much like its longer period counterpart, WD 0137-349. Both systems likely represent bona fide progenitors of cataclysmic variables with a low-mass white dwarf and a brown dwarf donor.
Accretion disc mapping of the shortest period eclipsing binary SDSS J0926+36
NASA Astrophysics Data System (ADS)
Schlindwein, W.; Baptista, R.
2014-10-01
AM CVn stars are ultracompact binaries (P_{orb}< 65 min) where a hydrogen-deficient low-mass, degenerate donor star overfills its Roche lobe and transfers matter to a companion white dwarf via an accretion disc. SDSS J0926+36 is currently the only eclipsing AM CVn star and also the shortest period eclipsing binary known. Its light curve displays deep (˜ 2 mag) eclipses every 28.3 min, which last for ˜ 2 min, as well as ˜ 2 mag amplitude outbursts every ˜ 100-200 d. Superhumps were seen in its quiescent light curve in some occasions, probably as a reminiscence of a (in some cases undetected) previous outburst. Its eclipsing nature allows a unique opportunity to disentangle the emission from several different light sources, and to map the surface brightness distribution of its hydrogen-deficient accretion disc with the aid of maximum entropy eclipse mapping techniques. Here we report the eclipse mapping analysis of optical light curves of SDSS J0926+36, collected with the 2.4 m Liverpool Robotic Telescope, covering 20 orbits of the binary over 5 nights of observations between 2012 February and March. The object was in quiescence at all runs. Our data show no evidence of superhumps nor of orbital modulation due to anisotropic emission from a bright spot at disc rim. Accordingly, the average out-of-eclipse flux level is consistent with that of the superhump-subtracted previous light curves. We combined all runs to obtain an orbital light curve of improved S/N. The corresponding eclipse map shows a compact source at disc centre (T_{b}simeq 17000 K), a faint, cool accretion disc (˜ 4000 K) plus enhanced emission along the gas stream (˜ 6000 K) beyond the impact point at the outer disc rim, suggesting the occurrence of gas stream overflow at that epoch.
PathVisio 3: an extendable pathway analysis toolbox.
Kutmon, Martina; van Iersel, Martijn P; Bohler, Anwesha; Kelder, Thomas; Nunes, Nuno; Pico, Alexander R; Evelo, Chris T
2015-02-01
PathVisio is a commonly used pathway editor, visualization and analysis software. Biological pathways have been used by biologists for many years to describe the detailed steps in biological processes. Those powerful, visual representations help researchers to better understand, share and discuss knowledge. Since the first publication of PathVisio in 2008, the original paper was cited more than 170 times and PathVisio was used in many different biological studies. As an online editor PathVisio is also integrated in the community curated pathway database WikiPathways. Here we present the third version of PathVisio with the newest additions and improvements of the application. The core features of PathVisio are pathway drawing, advanced data visualization and pathway statistics. Additionally, PathVisio 3 introduces a new powerful extension systems that allows other developers to contribute additional functionality in form of plugins without changing the core application. PathVisio can be downloaded from http://www.pathvisio.org and in 2014 PathVisio 3 has been downloaded over 5,500 times. There are already more than 15 plugins available in the central plugin repository. PathVisio is a freely available, open-source tool published under the Apache 2.0 license (http://www.apache.org/licenses/LICENSE-2.0). It is implemented in Java and thus runs on all major operating systems. The code repository is available at http://svn.bigcat.unimaas.nl/pathvisio. The support mailing list for users is available on https://groups.google.com/forum/#!forum/wikipathways-discuss and for developers on https://groups.google.com/forum/#!forum/wikipathways-devel. PMID:25706687
The Longest Path Problem Is Polynomial on Interval Graphs
NASA Astrophysics Data System (ADS)
Ioannidou, Kyriaki; Mertzios, George B.; Nikolopoulos, Stavros D.
The longest path problem is the problem of finding a path of maximum length in a graph. Polynomial solutions for this problem are known only for small classes of graphs, while it is NP-hard on general graphs, as it is a generalization of the Hamiltonian path problem. Motivated by the work of Uehara and Uno in [20], where they left the longest path problem open for the class of interval graphs, in this paper we show that the problem can be solved in polynomial time on interval graphs. The proposed algorithm runs in O(n 4) time, where n is the number of vertices of the input graph, and bases on a dynamic programming approach.
Stay on marked paths to avoid poison ivy. Watch young children carefully around river and creeks.
Shyy, Wei
Caution · Stay on marked paths to avoid poison ivy. · Watch young children carefully around river or outdoor cooking are not permitted. Poison Ivy Hours · Trails and gardens open 8 am to dusk. · Conservatory
Felner, Ariel
2004-01-01
Journal of Artificial Intelligence Research 21 (2004) 631Â670 Submitted 9/03; published 6/04 PHA unknown territory. We introduce the PhysicalÂA* algorithm (PHA*) for solving this problem. PHA* expands by the traveling effort of the moving agent and not by the number of generated nodes, as in standard A*. PHA
NASA Technical Reports Server (NTRS)
Mehhtz, Peter
2005-01-01
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.
Thermoalgebras and path integral
NASA Astrophysics Data System (ADS)
Khanna, F. C.; Malbouisson, A. P. C.; Malbouisson, J. M. C.; Santana, A. E.
2009-09-01
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 (S1)d×R topology is addressed.
pathChirp: Efficient Available Bandwidth Estimation for Network Paths
Cottrell, Les
2003-04-30
This paper presents pathChirp, a new active probing tool for estimating the available bandwidth on a communication network path. Based on the concept of ''self-induced congestion,'' pathChirp features an exponential flight pattern of probes we call a chirp. Packet chips offer several significant advantages over current probing schemes based on packet pairs or packet trains. By rapidly increasing the probing rate within each chirp, pathChirp obtains a rich set of information from which to dynamically estimate the available bandwidth. Since it uses only packet interarrival times for estimation, pathChirp does not require synchronous nor highly stable clocks at the sender and receiver. We test pathChirp with simulations and Internet experiments and find that it provides good estimates of the available bandwidth while using only a fraction of the number of probe bytes that current state-of-the-art techniques use.
Crack path prediction near an elliptical inclusion
NASA Astrophysics Data System (ADS)
Patton, E. M.; Santare, M. H.
1993-01-01
A technique is presented which will predict the path of a naturally growing crack where the stress field can be modeled as two-dimensional. The Green function for an arbitrarily oriented edge dislocation interacting with a rigid inclusion (or void) is used in an integral formulation of the elasticity problem. The technique uses a boundary integral approach to solve for the dislocation density along an arbitrarily shaped crack interacting with a rigid elliptical inclusion or void. The crack path is parameterized as a cubic spline, and a first order perturbation solution is employed to account for the generally curvilinear nature of the crack. The singular integrals are solved using a numerical technique which describes the distribution of dislocations along the crack as a piecewise quadratic polynomial to transform the integral equations into algebraic equations well suited to a matrix-type solution. Results of each step of the analysis have been verified with previously published results, and with experimental results of a crack propagating near an open circular hole. New results are also presented as paths of cracks interacting with inclusions of differing ellipticity ratios and at different orientations with respect to the initial crack.
NASA Astrophysics Data System (ADS)
Hebert, Jeffrey Michael
This dissertation explores optimal path planning for air vehicles. An air vehicle exposed to illumination by a tracking radar is considered and the problem of determining an optimal planar trajectory connecting two prespecified points is addressed. An analytic solution yielding the trajectory minimizing the received radar energy reflected from the target is derived using the Calculus of Variations. Additionally, the related problem of an air vehicle tracked by a passive sensor is also solved. Using the insights gained from the single air vehicle radar exposure minimization problem, a hierarchical cooperative control law is formulated to determine the optimal trajectories that minimize the cumulative exposure of multiple air vehicles during a rendezvous maneuver. The problem of one air vehicle minimizing exposure to multiple radars is also addressed using a variational approach, as well as a sub-optimal minmax argument. Local and global optimality issues are explored. A novel decision criterion is developed determining the geometric conditions dictating when it is preferable to go between or around two radars. Lastly, an optimal minimum time control law is obtained for the target identification and classification mission of an autonomous air vehicle. This work demonstrates that an awareness of the consequences of embracing sub-optimal and non-globally optimal solutions for optimization problems, such as air vehicle path planning, is essential.
Internet's critical path horizon
NASA Astrophysics Data System (ADS)
Valverde, S.; Solé, R. V.
2004-03-01
Internet is known to display a highly heterogeneous structure and complex fluctuations in its traffic dynamics. Congestion seems to be an inevitable result of user's behavior coupled to the network dynamics and it effects should be minimized by choosing appropriate routing strategies. But what are the requirements of routing depth in order to optimize the traffic flow? In this paper we analyse the behavior of Internet traffic with a topologically realistic spatial structure as described in a previous study [S.-H. Yook et al., Proc. Natl Acad. Sci. USA 99, 13382 (2002)]. The model involves self-regulation of packet generation and different levels of routing depth. It is shown that it reproduces the relevant key, statistical features of Internet's traffic. Moreover, we also report the existence of a critical path horizon defining a transition from low-efficient traffic to highly efficient flow. This transition is actually a direct consequence of the web's small world architecture exploited by the routing algorithm. Once routing tables reach the network diameter, the traffic experiences a sudden transition from a low-efficient to a highly-efficient behavior. It is conjectured that routing policies might have spontaneously reached such a compromise in a distributed manner. Internet would thus be operating close to such critical path horizon.
Integrated Flight Path Planning System and Flight Control System for Unmanned Helicopters
Jan, Shau Shiun; Lin, Yu Hsiang
2011-01-01
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
Integrated flight path planning system and flight control system for unmanned helicopters.
Jan, Shau Shiun; Lin, Yu Hsiang
2011-01-01
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
ERIC Educational Resources Information Center
Smutny, Joan Franklin
2011-01-01
While resources for the gifted are not abundant, many schools do offer classes, programs, services, and/or clubs that broaden student learning beyond the curriculum. What can educators do to expand the horizons of gifted children--to open their minds to new worlds of knowledge and understanding? Programs for gifted students, particularly those…
Collaborative Authoring of Walden's Paths
Li, Yuanling
2012-10-19
COLLABORATIVE AUTHORING OF WALDEN’S PATHS A Thesis by YUANLING LI Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE... August 2012 Major Subject: Computer Science Collaborative Authoring of Walden’s Paths Copyright 2012 Yuanling Li COLLABORATIVE AUTHORING OF WALDEN’S PATHS A Thesis by YUANLING LI...
Interactive cutting path analysis programs
NASA Technical Reports Server (NTRS)
Weiner, J. M.; Williams, D. S.; Colley, S. R.
1975-01-01
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.
Path planning for virtual bronchoscopy.
Negahdar, Mohamadreza; Ahmadian, Alireza; Navab, Nassir; Firouznia, Kavous
2006-01-01
We have developed an automated path planning method, which enables virtual bronchoscopic 3D multidetector computed tomography (MDCT) image analysis and follow on image-guided bronchoscopy. The method fundamentals are novel combination of distance transformation and snake-based models. The computation time of our algorithm is faster than similar works and there were no missing or false branches in the final path of airways. The planned path is suitable for quantitative airway analysis and smooth virtual navigation. PMID:17946384
Handbook of Feynman Path Integrals
NASA Astrophysics Data System (ADS)
Grosche, Christian, Steiner, Frank
The Handbook of Feynman Path Integrals appears just fifty years after Richard Feynman published his pioneering paper in 1948 entitled "Space-Time Approach to Non-Relativistic Quantum Mechanics", in which he introduced his new formulation of quantum mechanics in terms of path integrals. The book presents for the first time a comprehensive table of Feynman path integrals together with an extensive list of references; it will serve the reader as a thorough introduction to the theory of path integrals. As a reference book, it is unique in its scope and will be essential for many physicists, chemists and mathematicians working in different areas of research.
NASA Technical Reports Server (NTRS)
Horton, Kent; Huffman, Mitch; Eppic, Brian; White, Harrison
2005-01-01
Path Loss Measurements were obtained on three (3) GPS equipped 757 aircraft. Systems measured were Marker Beacon, LOC, VOR, VHF (3), Glide Slope, ATC (2), DME (2), TCAS, and GPS. This data will provide the basis for assessing the EMI (Electromagnetic Interference) safety margins of comm/nav (communication and navigation) systems to portable electronic device emissions. These Portable Electronic Devices (PEDs) include all devices operated in or around the aircraft by crews, passengers, servicing personnel, as well as the general public in the airport terminals. EMI assessment capability is an important step in determining if one system-wide PED EMI policy is appropriate. This data may also be used comparatively with theoretical analysis and computer modeling data sponsored by NASA Langley Research Center and others.
Path integral solution for a particle confined in a region
NASA Astrophysics Data System (ADS)
Chetouani, L.; Chouchaoui, A.; Hammann, T. F.
1990-04-01
The propagator relative to a particle constrained to move in a finite region of space is calculated in the framework of path integrals. This region of the three-dimensional space is delimited through a sector of opening angle ?, and also through the action of two attractive harmonic potentials, one being central and located in the 0xy plan, and the other directed along the z axis, with respective pulsations ? and ?0. It is shown that for ?=?/2 and ? the propagator is the sum of propagators evaluated on classical paths. The important case of the edge (?=2?) is considered.
XCB, the last of the shortest single axioms for the classical equivalential calculus.
Wos, L.; Ulrich, D.; Fitelson, B.; Mathematics and Computer Science; Purdue Univ.; San Jose State Univ.
2003-01-01
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.
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...
Path detection in video surveillance
Dimitrios Makris; Tim Ellis
2002-01-01
This paper addresses the problem of automatically extracting frequently used pedestrian pathways from video sequences of natural outdoor scenes. Path models are learnt from the accumulation of trajectory data over long time periods, and can be used to augment the classification of subseq uent track data. In particular, labelled paths provide an efficient means for compressing the trajectory data for
Using Runtime Paths for Macroanalysis
Mike Y. Chen; Emre Kiciman; Anthony Accardi; Armando Fox; Eric A. Brewer
2003-01-01
We introduce macroanalysis, an approach used to infer the high-level properties of dynamic, distributed systems, and an indispensable tool when faced with tasks where lo- cal context and individual component details are insuffi- cient. We present a new methodology, runtime path anal- ysis, where paths are traced through software components and then aggregated to understand global system behav- ior via
Path Analysis: A Brief Introduction.
ERIC Educational Resources Information Center
Carducci, Bernardo J.
Path analysis is presented as a technique that can be used to test on a priori model based on a theoretical conceptualization involving a network of selected variables. This being an introductory source, no previous knowledge of path analysis is assumed, although some understanding of the fundamentals of multiple regression analysis might be…
Optimal Path to a Laser Fusion Energy Power Plant
NASA Astrophysics Data System (ADS)
Bodner, Stephen
2013-10-01
There was a decision in the mid 1990s to attempt ignition using indirect-drive targets. It is now obvious that this decision was unjustified. The target design was too geometrically complex, too inefficient, and too far above plasma instability thresholds. By that same time, the mid 1990s, there had also been major advances in the direct-drive target concept. It also was not yet ready for a major test. Now, finally, because of significant advances in target designs, laser-target experiments, and laser development, the direct-drive fusion concept is ready for significant enhancements in funding, on the path to commercial fusion energy. There are two laser contenders. A KrF laser is attractive because of its shortest wavelength, broad bandwidth, and superb beam uniformity. A frequency-converted DPSSL has the disadvantage of inherently narrow bandwidth and longer wavelength, but by combining many beams in parallel one might be able to produce at the target the equivalent of an ultra-broad bandwidth. One or both of these lasers may also meet all of the engineering and economic requirements for a reactor. It is time to further develop and evaluate these two lasers as rep-rate systems, in preparation for a future high-gain fusion test.
Hard paths, soft paths or no paths? Cross-cultural perceptions of water solutions
NASA Astrophysics Data System (ADS)
Wutich, A.; White, A. C.; Roberts, C. M.; White, D. D.; Larson, K. L.; Brewis, A.
2013-06-01
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.
Hard paths, soft paths or no paths? Cross-cultural perceptions of water solutions
NASA Astrophysics Data System (ADS)
Wutich, A.; White, A. C.; White, D. D.; Larson, K. L.; Brewis, A.; Roberts, C.
2014-01-01
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.
Reasoning with Temporal Logic on Truncated Paths
Francalanza, Adrian
Reasoning with Temporal Logic on Truncated Paths Cindy Eisner1 Dana Fisman1,2 John Havlicek3 Yoad of reasoning with linear temporal logic on truncated paths. A truncated path is a path which is finite for reasoning about truncated paths, and analyze its characteristics. 1 Introduction Traditional ltl semantics
Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Path Testing
Mousavi, Mohammad
Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Path Testing Mohammad Mousavi Eindhoven University of Technology, The Netherlands Software Testing, 2012 Mousavi: Path Testing #12;Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Outline Structural
Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Path Testing
Mousavi, Mohammad
Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Path Testing Mohammad Mousavi Eindhoven University of Technology, The Netherlands Software Testing, 2013 Mousavi: Path Testing #12;Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Outline Structural
British Pathe Newsreels Online
NSDL National Science Digital Library
2002-01-01
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.
Reconfigurable data path processor
NASA Technical Reports Server (NTRS)
Donohoe, Gregory (Inventor)
2005-01-01
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.
Pon, Allison; Jewison, Timothy; Su, Yilu; Liang, Yongjie; Knox, Craig; Maciejewski, Adam; Wilson, Michael; Wishart, David S.
2015-01-01
PathWhiz (http://smpdb.ca/pathwhiz) is a web server designed to create colourful, visually pleasing and biologically accurate pathway diagrams that are both machine-readable and interactive. As a web server, PathWhiz is accessible from almost any place and compatible with essentially any operating system. It also houses a public library of pathways and pathway components that can be easily viewed and expanded upon by its users. PathWhiz allows users to readily generate biologically complex pathways by using a specially designed drawing palette to quickly render metabolites (including automated structure generation), proteins (including quaternary structures, covalent modifications and cofactors), nucleic acids, membranes, subcellular structures, cells, tissues and organs. Both small-molecule and protein/gene pathways can be constructed by combining multiple pathway processes such as reactions, interactions, binding events and transport activities. PathWhiz's pathway replication and propagation functions allow for existing pathways to be used to create new pathways or for existing pathways to be automatically propagated across species. PathWhiz pathways can be saved in BioPAX, SBGN-ML and SBML data exchange formats, as well as PNG, PWML, HTML image map or SVG images that can be viewed offline or explored using PathWhiz's interactive viewer. PathWhiz has been used to generate over 700 pathway diagrams for a number of popular databases including HMDB, DrugBank and SMPDB. PMID:25934797
jCompoundMapper: An open source Java library and command-line tool for chemical fingerprints
2011-01-01
Background The decomposition of a chemical graph is a convenient approach to encode information of the corresponding organic compound. While several commercial toolkits exist to encode molecules as so-called fingerprints, only a few open source implementations are available. The aim of this work is to introduce a library for exactly defined molecular decompositions, with a strong focus on the application of these features in machine learning and data mining. It provides several options such as search depth, distance cut-offs, atom- and pharmacophore typing. Furthermore, it provides the functionality to combine, to compare, or to export the fingerprints into several formats. Results We provide a Java 1.6 library for the decomposition of chemical graphs based on the open source Chemistry Development Kit toolkit. We reimplemented popular fingerprinting algorithms such as depth-first search fingerprints, extended connectivity fingerprints, autocorrelation fingerprints (e.g. CATS2D), radial fingerprints (e.g. Molprint2D), geometrical Molprint, atom pairs, and pharmacophore fingerprints. We also implemented custom fingerprints such as the all-shortest path fingerprint that only includes the subset of shortest paths from the full set of paths of the depth-first search fingerprint. As an application of jCompoundMapper, we provide a command-line executable binary. We measured the conversion speed and number of features for each encoding and described the composition of the features in detail. The quality of the encodings was tested using the default parametrizations in combination with a support vector machine on the Sutherland QSAR data sets. Additionally, we benchmarked the fingerprint encodings on the large-scale Ames toxicity benchmark using a large-scale linear support vector machine. The results were promising and could often compete with literature results. On the large Ames benchmark, for example, we obtained an AUC ROC performance of 0.87 with a reimplementation of the extended connectivity fingerprint. This result is comparable to the performance achieved by a non-linear support vector machine using state-of-the-art descriptors. On the Sutherland QSAR data set, the best fingerprint encodings showed a comparable or better performance on 5 of the 8 benchmarks when compared against the results of the best descriptors published in the paper of Sutherland et al. Conclusions jCompoundMapper is a library for chemical graph fingerprints with several tweaking possibilities and exporting options for open source data mining toolkits. The quality of the data mining results, the conversion speed, the LPGL software license, the command-line interface, and the exporters should be useful for many applications in cheminformatics like benchmarks against literature methods, comparison of data mining algorithms, similarity searching, and similarity-based data mining. PMID:21219648
Learning for informative path planning
Park, Sooho, S.M. Massachusetts Institute of Technology
2008-01-01
Through the combined use of regression techniques, we will learn models of the uncertainty propagation efficiently and accurately to replace computationally intensive Monte- Carlo simulations in informative path planning. ...
COMPUTER SCIENCE: MISCONCEPTIONS, CAREER PATHS
Hristidis, Vagelis
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
An introduction to critical paths.
Coffey, Richard J; Richards, Janet S; Remmert, Carl S; LeRoy, Sarah S; Schoville, Rhonda R; Baldwin, Phyllis J
2005-01-01
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
Scattering theory with path integrals
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
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.
Uwe Brandenburger; Theo Brauers; Hans-Peter Dorn; Martin Hausmann; Dieter H. Ehhalt
1998-01-01
Absolutely calibrated in-situ measurements of tropospheric hydroxyl radicals, formaldehyde, sulfur dioxide, and naphthalene (C10H8) were performed by long-path laser absorption spectroscopy during the field campaign POPCORN. The absorption light path was folded into an open optical multiple reflection cell with a mirror separation of 38.5 m. Using a light path length of 1848 m and an integration time of 200
Quantum Mechanics: Sum Over Paths
NSDL National Science Digital Library
Taylor, Edwin F.
Created by Edwin F. Taylor a former professor at the Department of Physics at the Massachusetts Institute of Technology, this material describes methods of presenting quantum mechanics using the path-integral formulation. Included are links to a paper and presentation outlining the method, software to simulate the path integrals, and student workbook materials. This course has been used for introducing quantum physics to high school teachers.
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
Characterizing Reactive Flow Paths in Fractured Cement
NASA Astrophysics Data System (ADS)
Wenning, Q. C.; Huerta, N. J.; Hesse, M. A.; Bryant, S. L.
2011-12-01
Geologic carbon sequestration can be a viable method for reducing anthropogenic CO2 flux into the atmosphere. However, the technology must be economically feasible and pose acceptable risk to stakeholders. One key risk is CO2 leakage out of the storage reservoir. Potential driving forces for leakage are the overpressure due to CO2 injection and the buoyancy of free phase CO2. Potential hazards of leakage are contamination of Underground Sources of Drinking Water or the atmosphere and would be deemed an unacceptable risk. Wells potentially provide a fast path for leakage from the reservoir. While the well's cement casing is reactive with CO2 and CO2-saturated brine, the low cement matrix permeability and slow diffusion rate make it unlikely that CO2 will escape through a properly constructed wellbore. However, highly permeable fractures with micrometer scale apertures can occur in cement casings. Reactions that occur in the flow in these fractures can either be self-limiting or self-enhancing. Therefore, understanding the reactive flow is critical to understanding of leakage evolution through these fractures. The goal of our work is to characterize the modification of the flow paths in the fracture due to reaction with acidic brine. With this aim we have characterized both the initial flow path of un-reactive flow and the final flow path after introduction of low-pH acid along the same fracture. Class H cement cores 3-6 cm in length and 2.5 cm diameter are created and a single natural and unique fracture is produced in each core using the Brazilian method. Our experimental fluid is injected at a constant rate into the cement core housed in a Hassler Cell under confining pressure. A solution of red dye and deionized water is pumped through the fracture to stain the un-reactive flow paths. Deionized water is then pumped through the core to limit diffusion of the dye into non-flowing portions of the fracture. After staining the initial flow path, low pH water due to hydrochloric acid (HCL), is pumped through the core at the same rate as the dye. The low pH water is used as a proxy for acidic CO2-saturated brine. Both staining from the un-reactive dye and acid produce visible permanent color alterations on the cement fracture plane. Results show that nearly the entire fracture width is stained by the red dye, with only a few asperities un-dyed. However the low pH HCl forms restricted reacted channels that are a subset of the area open to un-reactive flow, occupying only 10-50% of the entire fracture width. Low pH HCl is believed to be the driving force for the reaction that causes channeling. As acid flows through the fracture, calcium is stripped from the low pH high velocity flow front and precipitates along of the edges of the channel where pH is higher due to the lower flow velocities outside the channel. It is hypothesized that this mineral precipitation restricts the flow into localized channels within the plane of fractures having apertures of tens of micrometers. Reactions restrict the flow path to a smaller fraction of the surface, which may be an indication of self-limiting behavior.
Parikh, Kush Jay
2013-01-01
follow. The driver only sends information and never receivesclient receives information from the driver (not necessarydriver is omitted in this experiment) .23 4.2 (b) The neighbor topology (direction of arrow represents the path of information
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 · Garden-path sentence a consequence of incrementality recent examples don't match this definition · Tabor et al. (2004): garden-paths on continuous substrings
Cooperative organic mine avoidance path planning
Christopher B. McCubbin; Christine D. Piatko; Adam V. Peterson; Creighton R. Donnald; David Cohen
2005-01-01
The JHU\\/APL Path Planning team has developed path planning techniques to look for paths that balance the utility and risk associated with different routes through a minefield. Extending on previous years' efforts, we investigated real-world Naval mine avoidance requirements and developed a tactical decision aid (TDA) that satisfies those requirements. APL has developed new mine path planning techniques using graph
Graphs and Paths Page 1 Introduction
Allan, Vicki H.
? For example: I want to travel every bike path in Logan (assuming they had any ) but I don't want to everGraphs and Paths Page 1 Chapter 9 Graphs Introduction What are some characteristics of a binary travel on the same path twice. Can I begin at my home, visit every path, and then return? The data
Complexity of path discovery game problems
Hiroaki Tohyama; Akeo Adachi
2000-01-01
In this paper path discovery games are introduced, and complexity of the game problems is studied. It is shown that the path discovery game problem played on directed graphs is PSPACE-complete, and the path discovery game problem played on undirected graphs is in the class SSPACE(nlogn). Moreover, it is shown that the acyclic path discovery game problems played on directed
Robust Flight Path Determination for Mars Precision Landing Using Genetic Algorithms
NASA Technical Reports Server (NTRS)
Bayard, David S.; Kohen, Hamid
1997-01-01
This paper documents the application of genetic algorithms (GAs) to the problem of robust flight path determination for Mars precision landing. The robust flight path problem is defined here as the determination of the flight path which delivers a low-lift open-loop controlled vehicle to its desired final landing location while minimizing the effect of perturbations due to uncertainty in the atmospheric model and entry conditions. The genetic algorithm was capable of finding solutions which reduced the landing error from 111 km RMS radial (open-loop optimal) to 43 km RMS radial (optimized with respect to perturbations) using 200 hours of computation on an Ultra-SPARC workstation. Further reduction in the landing error is possible by going to closed-loop control which can utilize the GA optimized paths as nominal trajectories for linearization.
Evaluation of steam path audits
Caudill, M.B. [Tri-State Generation and Transmission Association, Inc., Montrose, CO (United States); Griebenow, R.D. [SAIC, Huntersville, NC (United States)
1995-06-01
Tri-State Generation and Transmission association is the operating agent for the 1350 megawatt Craig Generating Station, located in northwestern Colorado. Tri-State has recently incorporated turbine steam path audits into their aggressive performance improvement program. The intent of the audits are to quantify and attain the most cost effective increase in turbine performance as a result of a major outage. Valuable information about performance losses in the turbine has been obtained from steam path audits conducted on the three Craig Units. However, accurate audit results often depend on the quality of measurements and the experience of the auditor. Without a second method to verify the results of a steam path audit, repairs might be performed on a non-cost effective basis, or significant performance degradations might be overlooked. In addition, an inaccurate audit may lead to erroneous expectations for performance improvements resulting from the maintenance performed during the outage.
Phase Diagram of Optimal Paths
Alex Hansen; Janos Kertesz
2004-02-17
We show that choosing appropriate distributions of the randomness, the search for optimal paths links diverse problems of disordered media like directed percolation, invasion percolation, directed and non-directed spanning polymers. We also introduce a simple and efficient algorithm, which solves the d-dimensional model numerically in order N^(1+d_f/d) steps where d_f is the fractal dimension of the path. Using extensive simulations in two dimensions we identify the phase boundaries of the directed polymer universality class. A new strong-disorder phase occurs where the optimum paths are self-affine with parameter-dependent scaling exponents. Furthermore, the phase diagram contains directed and non-directed percolation as well as the directed random walk models at specific points and lines.
Multiple paths in complex tasks
NASA Technical Reports Server (NTRS)
Galanter, Eugene; Wiegand, Thomas; Mark, Gloria
1987-01-01
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.
Critical Path-Based Thread Placement for NUMA Systems
Su, C Y; Li, D; Nikolopoulos, D S; Grove, M; Cameron, K; de Supinski, B R
2011-11-01
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.
The path integral model of D-pairing for HTSC, heavy fermion superconductors, and superfluids
Brusov, P.N.; Brusova, N.P. [Physical Research Inst., Rostov-on-Don (Russian Federation)
1996-05-01
A model of d-pairing for superconducting and superfluid Fermi-systems has been formulated within the path integration technique. By path integration over {open_quote}fast{close_quotes} and {open_quotes}slow{close_quotes} Fermi-fields, the action functional (which determines all properties of model system) has been obtained. This functional could be used for the determination of different superconducting (superfluid) states, for calculation of the transition temperatures for these states, and for the calculation of the collective mode spectrum for HTSC, as well as for heavy fermion superconductors.
Alternative Nuclear Paths To 2050
Ivan Vera; Evelyne Bertel; Geoffrey Stevens
he circumstances surrounding nuclear power worldwide and the importance that may be given to issues affecting its future development point toward very different alternative paths over the next 50 years. Economic deregulation, lack of competitiveness in some countries, negative public perception and concerns about waste issues suggest that nuclear power might decrease progressively with a potential phase-out of the technology
Gilbert, Matthew
NPRE at Illinois Three Paths Students choose from three concentrations: · Plasma and Fusion · Power,312,815 Research Facilities · Beckman Institute (beckman.illinois.edu) · Center for Plasma-Material Interactions (cpmi.illinois.edu) · Institute for Genomic Biology (igb.illinois.edu) · Micro and Nanotechnology
Moldovan employment relations: “path dependency”?
Claudio Morrison; Richard Croucher
2010-01-01
Purpose – The paper aims to examine the theory that trade unions' functions in a transitional economy are characterised by “path dependency”. Design\\/methodology\\/approach – The research is based on case studies of employment relations in enterprises operating in Moldova. The approach is realist (critical materialism). An ethnographic approach is taken to analysing social relations in three locally and foreign-owned companies
Noncommutative Geometry and Path Integrals
Mikhail Kapranov
2006-01-01
\\u000a We argue that there should exist a “noncommutative Fourier transform” which should identify functions of noncommutative variables\\u000a (say, of matrices of indeterminate size) and ordinary functions or measures on the space of paths. Some examples are considered.
WHEELCHAIR NEGOTIABLE PATHS ACCESSIBLE ENTRANCE
Huang, Jianyu
NEGOTIABLE PATHS ACCESSIBLE ENTRANCE ACCESSIBLE PARKING SPACE ELEVATOR ACCESS KEY PPUBLIC PARKING BUS STOP ENTRANCE ACCESSIBLE PARKING SPACE ELEVATOR ACCESS KEY PPUBLIC PARKING BUS STOP (EAGLE ESCORT) BLUE LIGHT SPACE ELEVATOR ACCESS KEY PPUBLIC PARKING BUS STOP (EAGLE ESCORT) BLUE LIGHT EMERGENCY PHONE #12
Magnetic Refocussing of Electron Paths
W. E. Stephens
1934-01-01
A general method of magnetic direction refocussing, i.e., the refocussing of slightly divergent electron paths in a uniform magnetic field, has been found, of which the familiar 180° refocussing is a particular case. If we use a wedge-shaped magnetic field, whose lines of force are perpendicular to the plane of motion of an electron beam, the field being produced by
Acyclic orientations with path constraints
Rosa M. V. Figueiredo; Valmir C. Barbosa; Nelson Maculan; Cid C. Souza
2005-01-01
Many well-known combinatorial optimization problems can be stated over the set of acyclic orientations of an undirected graph. For example, acyclic orientations with certain diameter constraints are closely related to the optimal solutions of the vertex coloring and frequency assignment problems. In this paper we introduce a linear programming formulation of acyclic orientations with path constraints, and discuss its use
SSME propellant path leak detection
NASA Technical Reports Server (NTRS)
Crawford, Roger; Shohadaee, Ahmad Ali
1989-01-01
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.
Wada, Taeko; Koyama, Daisuke; Kikuchi, Jiro; Honda, Hiroaki; Furukawa, Yusuke
2015-06-11
Recent investigations indicate that epigenetic regulators act at the initial step of myeloid leukemogenesis by forming preleukemic hematopoietic stem cells (HSCs), which possess the increased self-renewal potential but retain multidifferentiation ability, and synergize with genetic abnormalities in later stages to develop full-blown acute myeloid leukemias. However, it is still unknown whether this theory is applicable to other malignancies. In this study, we demonstrate that lysine-specific demethylase 1 (LSD1) overexpression is a founder abnormality for the development of T-cell lymphoblastic leukemia/lymphoma (T-LBL) using LSD1 transgenic mice. LSD1 expression is tightly regulated via alternative splicing and transcriptional repression in HSCs and is altered in most leukemias, especially T-LBL. Overexpression of the shortest isoform of LSD1, which is specifically repressed in quiescent HSCs and demethylates histone H3K9 more efficiently than other isoforms, increases self-renewal potential via upregulation of the HoxA family but retains multidifferentiation ability with a skewed differentiation to T-cell lineages at transcriptome levels in HSCs. Transgenic mice overexpressing LSD1 in HSCs did not show obvious abnormalities but developed T-LBL at very high frequency after ?-irradiation. LSD1 overexpression appears to be the first hit in T-cell leukemogenesis and provides an insight into novel strategies for early diagnosis and effective treatment of the disease. PMID:25904247
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
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
Residues crucial for maintaining short paths in network communication mediate signaling in proteins.
del Sol, Antonio; Fujihashi, Hirotomo; Amoros, Dolors; Nussinov, Ruth
2006-01-01
Here, we represent protein structures as residue interacting networks, which are assumed to involve a permanent flow of information between amino acids. By removal of nodes from the protein network, we identify fold centrally conserved residues, which are crucial for sustaining the shortest pathways and thus play key roles in long-range interactions. Analysis of seven protein families (myoglobins, G-protein-coupled receptors, the trypsin class of serine proteases, hemoglobins, oligosaccharide phosphorylases, nuclear receptor ligand-binding domains and retroviral proteases) confirms that experimentally many of these residues are important for allosteric communication. The agreement between the centrally conserved residues, which are key in preserving short path lengths, and residues experimentally suggested to mediate signaling further illustrates that topology plays an important role in network communication. Protein folds have evolved under constraints imposed by function. To maintain function, protein structures need to be robust to mutational events. On the other hand, robustness is accompanied by an extreme sensitivity at some crucial sites. Thus, here we propose that centrally conserved residues, whose removal increases the characteristic path length in protein networks, may relate to the system fragility. PMID:16738564
Routing Optimization in Optical Burst Switching Networks: a Multi-path Routing Approach
NASA Astrophysics Data System (ADS)
Klinkowski, Miros?aw; Marciniak, Marian; Pióro, Micha?
This chapter concerns routing optimization in optical burst switching (OBS) networks. OBS is a photonic network technology aiming at efficient transport of IP traffic. OBS architectures are in general bufferless and therefore sensitive to burst congestion. An overall burst loss probability (BLP) which adequately represents the congestion state of the entire network is the primary metric of interest in an OBS network. The network congestion can be reduced by using proper routing. We consider multi-path source routing and aim at optimal distribution of traffic over the network. In this context, we study three network loss models, a well-known loss model of an OBS network and two original approximate models. Since the objective function of each model is nonlinear, either linear programming formulations with piecewise linear approximations of this function or nonlinear optimization gradient methods can be used. The presented solution is based on nonlinear optimization; for this purpose we provide the formulas for calculation of partial derivatives. The main goal of this chapter is to show that the use of approximate models allows us to speed up significantly the optimization procedure without losing much accuracy. Moreover we show that our method effectively distributes the traffic over the network, and the overall BLP can be reduced compared with both shortest path routing and alternative routing.
Model for Delay Faults Based upon Paths
Gordon L. Smith
1985-01-01
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 \\
Path-Based Failure and Evolution Management
Mike Y. Chen; Anthony Accardi; Emre Kiciman; David A. Patterson; Armando Fox; Eric A. Brewer
2004-01-01
We present a new approach to managing failures and evolution in large, complex distributed systems using runtime paths. We use the paths that requests follow as they move through the system as our core abstraction, and our \\
Time optimal paths for high speed maneuvering
Reister, D.B.; Lenhart, S.M.
1993-01-01
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.
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.
Configuration Path Integral Monte Carlo
NASA Astrophysics Data System (ADS)
Bonitz, Michael; Schoof, Tim; Groth, Simon; Filinov, Alexei; Hochstuhl, David
2011-10-01
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). 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., fails due to the fermion sign problem. This work is supported by the Deutsche Forschungsgemeinschaft.
Path Planning for Autonomous Underwater Vehicles
Clément Pêtrès; Yan Pailhas; Pedro Patrón; Yvan R. Petillot; Jonathan Evans
2007-01-01
Efficient path planning algorithms are a crucial issue for modern autonomous underwater vehicles. Classical path planning algorithms in artificial intelligence are not designed to deal with wide continuous environments prone to currents. We present a novel Fast Marching based approach to address the following issues. First, we develop an algorithm we call FM* to efficiently extract a continuous path from
Quantifying the Causes of Path Inflation
Neil Spring; Ratul Mahajan; Thomas Anderson
2003-01-01
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
Disjoint Paths in Densely Embedded Graphs
Jon M. Kleinberg; Eva Tardoss
1995-01-01
We consider the following maximum disjoint paths problem (mdpp). We are given a large network, and pairs of nodes that wish to communicate over paths through the network — the goal is to simultaneously connect as many of these pairs as possible in such a way that no two communication paths share an edge in the network. This classical problem
Continuous Path Planning with Multiple Constraints
Mitchell, Ian
paths for unmanned aerial vehicles through enviroments with varying levels of threat. Paths an algorithm which generates paths whose costs lie on the Pareto optimal surface for each possible destina destination can be rapidly evaluated. To handle constraints, we sample the Pareto optimal surface looking
Path and Trajectory Diversity Theory and Algorithms
Branicky, Michael S.
Path and Trajectory Diversity Theory and Algorithms Ross A. Knepper International Conference. Kuffner #12;R.A. Knepper Path and Trajectory Diversity 2 Applications [Knepper and Mason, ISER, 2008][Lau and Trajectory Diversity 3 Not all path sets are created equal Introduction Conclusion
Scripted documents: a hypermedia path mechanism
Polle T. ZelIweger
1989-01-01
The concept of a path, or ordered traversal of some links in a hypertext, has been a part of the hypertext notion from its early formation. Although paths can help to solve two major problems with hypertext systems, namely user disorientation and high cognitive overhead for users, their value has not been recognized. Paths can also provide the backbone for
Code of Federal Regulations, 2011 CFR
2011-01-01
...surface to the end of the takeoff path. (d) The takeoff path must be determined by a continuous demonstrated takeoff or by synthesis from segments. If the takeoff path is determined by the segmental method— (1) The segments must be clearly...
Removing False Paths from Combinational Modules 1
Yuji Kukimoto; Robert K. Brayton
The existence of false paths complicates the task of accurate tim- ing analysis significantly. A technique to remove false paths from a combinational circuit without degrading its performance h as a prac- tical value since topological timing analysis is then good e nough to estimate the performance of false-path-free circuits accu rately. One can think of the KMS algorithm (1)
Chip layout optimization using critical path weighting
A. E. Dunlop; V. D. Agrawal; D. N. Deutsch; M. F. Jukl; P. Kozak; M. Wiesel
1984-01-01
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
Chip layout optimization using critical path weighting
A. E. Dunlop; V. D. Agrawal; D. N. Deutsch; M. F. Jukl; P. Kazak
1988-01-01
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
Squeezed states and path integrals
NASA Technical Reports Server (NTRS)
Daubechies, Ingrid; Klauder, John R.
1992-01-01
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.
Lévy flights over quantum paths
NASA Astrophysics Data System (ADS)
Laskin, Nick
2007-02-01
An impact of integration over the paths of the Lévy flights on the quantum mechanical kernel has been studied. Analytical expression for a free particle kernel has been obtained in terms of the Fox H-function. A new equation for the kernel of a particle in the box has been found. New general results include the well known quantum formulae for a free particle kernel and particle in box kernel.
Acyclic Orientations with Path Constraints
Rosa M. V. Figueiredo; Valmir C. Barbosa; Nelson Maculan; Cid C. de Souza
2008-01-01
Many well-known combinatorial optimization problems can be stated over the\\u000aset of acyclic orientations of an undirected graph. For example, acyclic\\u000aorientations with certain diameter constraints are closely related to the\\u000aoptimal solutions of the vertex coloring and frequency assignment problems. In\\u000athis paper we introduce a linear programming formulation of acyclic\\u000aorientations with path constraints, and discuss its use
A. Farrel
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.,
Hironaka, Mantaro; Tojo, Sumio; Nomakuchi, Shintaro; Filippi, Lisa; Hariyama, Takahiko
2007-06-01
Females of the subsocial shield bug, Parastrachia japonensis (Parastrachiidae), are central-place foragers, collecting drupes for their young from nearby host trees by walking along the forest floor both during the day and at night. Because burrows are often some distance from the drupe-shedding tree, the bugs must repeatedly leave their burrows, search for drupes, and return to the burrows. After a bug leaves its burrow, it searches arduously until it encounters a drupe. When a drupe is obtained, the bug always takes the shortest route back to its burrow. It has been clarified that this bug utilizes path integration during diurnal provisioning excursions. In this paper, we examined nocturnal behavior and some parameters of the path integration utilized by P. japonensis. There were no observable differences between day and night in the patterns of foraging and direct-homing behavior. When the bug was displaced to another position during the day or night, it always walked straight toward the fictive burrow, the site where the burrow should be if it had been displaced along with the bug, and then displayed searching behavior in the vicinity of the fictive burrow. The distance of the straight run corresponded accurately with a straight line between the burrow and the place where the bug obtained the drupe. These results indicate that P. japonensis orients toward the burrow using path integration both during diurnal and nocturnal provisioning behavior. PMID:17867854
Middle Path Coarse Grain Parallelization
Kasahara, Hironori
Backend OpenMP Fortran OpenMP Backend MPI Fortran MPI Backend ½ ÇË Ê BPA RB SB Program Near fine grain layer 3rd layer Near fine grain parallelism in loop body BPA RB SB BPA RB SB BPA RB SB BPA RB SB BPA RB SB BPA RB SB ¾ ¾º½º½ È Ç Á Ê Ë Ê ¾ Data Dependency Extended Contorol Dependency Conditional Branch
THE SHORTEST PERIOD sdB PLUS WHITE DWARF BINARY CD-30 11223 (GALEX J1411-3053)
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
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.
Random paths and current fluctuations in nonequilibrium statistical mechanics
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
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.
Arithmetic area for m planar Brownian paths
NASA Astrophysics Data System (ADS)
Desbois, Jean; Ouvry, Stéphane
2012-05-01
We pursue the analysis made in Desbois and Ouvry (2011 J. Stat. Mech. P05024) on the arithmetic area enclosed by m closed Brownian paths. We pay particular attention to the random variable Sn1, n2,..., nm(m), which is the arithmetic area of the set of points, also called winding sectors, enclosed n1 times by path 1, n2 times by path 2,..., and nm times by path m. Various results are obtained in the asymptotic limit m\\to \\infty . A key observation is that, since the paths are independent, one can use in the m-path case the SLE information, valid in the one-path case, on the zero-winding sectors arithmetic area.
Mechanics of the crack path formation
NASA Technical Reports Server (NTRS)
Rubinstein, Asher A.
1991-01-01
A detailed analysis of experimentally obtained curvilinear crack path trajectories formed in a heterogeneous stress field is presented. Experimental crack path trajectories were used as data for the numerical simulations, recreating the actual stress field governing the development of the crack path. Thus, the current theories of crack curving and kinking could be examined by comparing them with the actual stress field parameters as they develop along the experimentally observed crack path. The experimental curvilinear crack path trajectories were formed in the tensile specimens with a hole positioned in the vicinity of a potential crack path. The numerical simulation, based on the solution of equivalent boundary value problems with the possible perturbations of the crack path, is presented.
Mechanics of the crack path formation
NASA Technical Reports Server (NTRS)
Rubinstein, Asher A.
1989-01-01
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.
Clearing the Path: Metaphors to Live by in Yup'ik Eskimo Oral Tradition.
ERIC Educational Resources Information Center
Fienup-Riordan, Ann
1994-01-01
Analyzes two Yup'ik tales depicting the cyclic relationships between humans and animals and between the living and the dead. Emphasizes the importance in the Yup'ik world view of boundaries and passages. Suggests that human actions, rules, and ceremonies create boundaries or may close or open paths between people, as well as between human/animal…
ECO order theory I. Lattices of lattice paths \\Lambda Luca Ferrari y Renzo Pinzani z
Zeilberger, Doron
ECO order theory I. Lattices of lattice paths \\Lambda Luca Ferrari y Renzo Pinzani z Abstract We. The last section is devoted to the presentation of a couple of open problems. Keywords ECO method called ECO method, which has proved fruitful in many prob lems of enumeration. A rough description
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...
GPS moving performance on open sky and forested paths
Luis Yoichi Morales Saiki; Takashi Tsubouchi
2007-01-01
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,
Theoretical determination of conformational paths in citrate synthase.
Ech-Cherif el-Kettani, M A; Durup, J
1992-05-01
Two methods are developed for the theoretical determination of a conformational path between two well-documented forms, a closed form and the open form [Remington et al. (1982) J. Mol. Biol. 158, 111-152] of pig heart citrate synthase, a dimeric enzyme of 2 x 437 residues. The first method uses the minimization of the sum of the potential energies at a set of equidistant points, according to Elber and Karplus [(1987) Chem. Phys. Lett. 139, 375-380]. The initialization of the algorithm is modified to account for large-angle rotations of many groups by performing the interpolations in the space of internal polar coordinates of a set of generalized Jacobi vectors earlier introduced by Durup [(1991) J. Phys. Chem. 95, 1817-1829] and by carefully testing all choices of directions of rotation for determining the initialized midpoint between the known forms. The path includes intermediate points, created by successive splittings of each interval into two equal parts, with a partial energy minimization performed after each splitting. The minimization encounters the well-known local-minima problem, which here is handled by low-temperature molecular dynamics annealing. It is shown that the best ratio of potential energy decrease to rms deviation is achieved by running the dynamics at 50 K, as compared to 100 K and above. The main character of the path obtained is the occurrence of strong to-and-fro variations of some dihedral angles at specific stages along the path. The second method, which we name directed dynamics, uses only low-temperature molecular dynamics simulations by starting trajectories from each of the two known forms with initial velocities directed toward the other one. The procedure is iterated by restarting trajectory pairs after the points of closest approach of the preceding pair. The two half-paths thus built eventually meet after 70 iterations. This method provides a second path with strong similarities, as well as some differences, with respect to the path obtained by the first method. PMID:1515547
N. Gobinath; J. Cecil; A. Trivedi
2006-01-01
This paper outlines the design of an information based manufacturing framework for micro devices assembly (MDA). The focus of discussion is on the virtual reality based assembly environment along with the use of path planning components. The virtual environment is implemented using C++ and Open Inventor. Two path planning software modules have also been implemented to demonstrate the overall approach.
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.
Communication path for extreme environments
NASA Technical Reports Server (NTRS)
Jorgensen, Charles C. (Inventor); Betts, Bradley J. (Inventor)
2010-01-01
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.
Multiple order common path spectrometer
NASA Technical Reports Server (NTRS)
Newbury, Amy B. (Inventor)
2010-01-01
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.
Critical Path-Based Thread Placement for NUMA Systems
Su, Chun-Yi [Virginia Polytechnic Institute and State University (Virginia Tech); Li, Dong [ORNL; Nikolopoulos, Dimitrios [FORTH-ICS; Grove, Matthew [Virginia Polytechnic Institute and State University (Virginia Tech); Cameron, Kirk W. [Virginia Polytechnic Institute and State University (Virginia Tech); de Supinski, Bronis R. [Lawrence Livermore National Laboratory (LLNL)
2012-01-01
Multicore multiprocessors use 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 an algorithm that optimizes the placement of OpenMP threads on NUMA processors. By collecting information from hardware counters and defining new metrics to capture the effects of thread placement, the algorithm reduces NUMA performance penalty by minimizing the critical path of OpenMP parallel regions and by avoiding local memory resource contention. We evaluate our algorithm with NPB benchmarks and achieve performance improvement between 8.13% and 25.68%, compared to the OS default scheduling.
NASA Astrophysics Data System (ADS)
Bishop, Kevin P.; Constable, Steve; Faruk, Nabil F.; Roy, Pierre-Nicholas
2015-06-01
In this work, we provide an interface developed to link the Molecular Modelling toolkit (MMTK) with OpenMM in order to take advantage of the fast evaluation techniques of OpenMM. This interface allows MMTK scripts using the Langevin dynamics integrator, for both classical and path integral simulations, to be executed on a variety of hardware including graphical processing units via OpenMM. The interface has been developed using Python and Cython to take advantage of the high level abstraction thanks to the MMTK and OpenMM software packages. We have tested the interface on a number of systems to observe which systems benefit most from the acceleration libraries of OpenMM.
NASA Astrophysics Data System (ADS)
Janssen, Hans-Karl; Stenull, Olaf
2012-01-01
Long linear polymers in strongly disordered media are well described by self-avoiding walks (SAWs) on percolation clusters and a lot can be learned about the statistics of these polymers by studying the length distribution of SAWs on percolation clusters. This distribution encompasses 2 distinct averages, viz., the average over the conformations of the underlying cluster and the SAW conformations. For the latter average, there are two basic options, one being static and one being kinetic. It is well known for static averaging that if the disorder of the underlying medium is weak, this disorder is redundant in the sense the renormalization group; i.e., differences to the ordered case appear merely in nonuniversal quantities. Using dynamical field theory, we show that the same holds true for kinetic averaging. Our main focus, however, lies on strong disorder, i.e., the medium being close to the percolation point, where disorder is relevant. Employing a field theory for the nonlinear random resistor network in conjunction with a real-world interpretation of the corresponding Feynman diagrams, we calculate the scaling exponents for the shortest, the longest, and the mean or average SAW to 2-loop order. In addition, we calculate to 2-loop order the entire family of multifractal exponents that governs the moments of the the statistical weights of the elementary constituents (bonds or sites of the underlying fractal cluster) contributing to the SAWs. Our RG analysis reveals that kinetic averaging leads to renormalizability whereas static averaging does not, and hence, we argue that the latter does not lead to a well-defined scaling limit. We discuss the possible implications of this finding for experiments and numerical simulations which have produced widespread results for the exponent of the average SAW. To corroborate our results, we also study the well-known Meir-Harris model for SAWs on percolation clusters. We demonstrate that the Meir-Harris model leads back up to 2-loop order to the renormalizable real-world formulation with kinetic averaging if the replica limit is consistently performed at the first possible instant in the course of the calculation.
Generating transition paths by Langevin bridges
NASA Astrophysics Data System (ADS)
Orland, Henri
2011-05-01
We propose a novel stochastic method to generate paths conditioned to start in an initial state and end in a given final state during a certain time tf. These paths are weighted with a probability given by the overdamped Langevin dynamics. We show that these paths can be exactly generated by a non-local stochastic differential equation. In the limit of short times, we show that this complicated non-solvable equation can be simplified into an approximate local stochastic differential equation. For longer times, the paths generated by this approximate equation do not satisfy the correct statistics, but this can be corrected by an adequate reweighting of the trajectories. In all cases, the paths are statistically independent and provide a representative sample of transition paths. The method is illustrated on the one-dimensional quartic oscillator.
Duality of Quantum Coherence and Path Distinguishability
Manabendra Nath Bera; Tabish Qureshi; Mohd Asad Siddiqui; Arun Kumar Pati
2015-03-10
We derive a generalized wave-particle duality relation for arbitrary dimensional multi-path quantum interference phenomena. Beyond the traditional signature of the wave nature of a quantum system, i.e., the fringe visibility, we introduce a novel quantifier as the normalized quantum coherence, recently defined in the frame-work of quantum information theory. To witness the particle nature, we quantify the path distinguishability or the which-path information based on unambiguous quantum state discrimination. Then, the Bohr complementarity principle, for multi-path quantum interference, can be stated as a duality relation between the quantum coherence and the path distinguishability. For two-path interference, the quantum coherence is identical to the interference fringe visibility, and the relation reduces to the well-know complementarity relation. The new duality relation continues to hold in the case where mixedness is introduced due to possible decoherence effects.
SeeingWithOPenCV FindingFacesin lmages
Oh, Paul
severalscales. The classifierusesdata storedin an XMLfileto decidehow to classify each image location.The OPenCVClassifier,Anyhow?"explains want it to use.The one l'll be usingiscalledhaarcascade-frontal face-default.xml.In OPenCV version1Pn'icv-noor]is the Path to your OpenCVinstallation.For example,if you'reonWindowsXP FIGURE1.Facedetectionwith OpenCV
Continuous-curvature paths for autonomous vehicles
Winston Nelson
1989-01-01
The paths followed by autonomously guided vehicles (AGVs) are generally made up of line and circular-arc segments. For most AGVs, the steering functions required to keep the position and heading of the cart continuously aligned with such paths have discontinuities at the line-arc-line transitions points, because the curvature of the path is discontinuous at these points. For applications where continuous-curvature
Steam Path Audits on Industrial Steam Turbines
Mitchell, D. R.
steam Path Audits on Industrial steam Turbines DOUGLAS R. MITCHELL. ENGINEER. ENCOTECH, INC., SCHENECTADY, NEW YORK ABSTRACT The electric utility industry has benefitted from steam path audits on steam turbines for several years. Benefits... include the ability to identify areas of performance degradation during a turbine outage. Repair priorities can then be set in accordance with quantitative results from the steam path audit. As a result of optimized repair decisions, turbine...
Revealing Genuine Optical-Path Entanglement
NASA Astrophysics Data System (ADS)
Monteiro, F.; Vivoli, V. Caprara; Guerreiro, T.; Martin, A.; Bancal, J.-D.; Zbinden, H.; Thew, R. T.; Sangouard, N.
2015-05-01
How can one detect entanglement between multiple optical paths sharing a single photon? We address this question by proposing a scalable protocol, which only uses local measurements where single photon detection is combined with small displacement operations. The resulting entanglement witness does not require postselection, nor assumptions about the photon number in each path. Furthermore, it guarantees that entanglement lies in a subspace with at most one photon per optical path and reveals genuinely multipartite entanglement. We demonstrate its scalability and resistance to loss by performing various experiments with two and three optical paths. We anticipate applications of our results for quantum network certification.
The critical path system. The road toward an efficient OR.
Grudich, G
1991-03-01
Since January 1990, surgeons have been able to make their incision within 15 minutes of the scheduled time. Total joint procedures, craniotomies, open heart surgery, and thoracic surgeries have had incision times within 15 minutes of the critical path timetable. Daily analysis of activity is done by reviewing the time study. The monthly delay report is becoming a quality assurance monitor for the hospital. Reports are sent to nurse managers, the director of surgical services, and the vice president of nursing. Daily review of the time study points out trends that can be addressed before they become a major problem. For example, in one month a surgical group had three delays. An informal meeting was held with the SDS nurse manager and the surgeon. The SDS manager and I met with the business manager of the group and the problem was resolved. In another example, a surgeon established a trend of consistently being late for cases. After a brief hallway chat, the problem was identified and an agreement reached that his time would be moved to 8 AM induction time. The last example concerns equipment failures. In one month, we had 20 delays due to equipment failures. By the next month, we had reduced equipment failures to 10, and by the end of the following month, we had three delays due to equipment failure. This was achieved through accurate documentation of the failures and frequent follow-up calls until the equipment was repaired. Surgeons and anesthesiologists still complain about delays, but not as often. Using the critical path concept has improved our efficiency and our image. This is only one facet of achieving timeliness in the OR. The teamwork between the OR nursing staff, surgical nursing staff, anesthesia staff, and the surgeons makes this program successful. Daily maintenance of the path with timely follow-up keeps the path working. PMID:2031583
Free path lengths in quasicrystals
Jens Marklof; Andreas Strömbergsson
2013-04-07
Previous studies of kinetic transport in the Lorentz gas have been limited to cases where the scatterers are distributed at random (e.g. at the points of a spatial Poisson process) or at the vertices of a Euclidean lattice. In the present paper we investigate quasicrystalline scatterer configurations, which are non-periodic, yet strongly correlated. A famous example is the vertex set of the Penrose tiling. Our main result proves the existence of a limit distribution of the free path length, which answers a question of Wennberg. The limit distribution is characterised by a certain random variable on the space of higher dimensional lattices, and is distinctly different from the exponential distribution observed for random scatterer configurations. The key ingredients in the proofs are equidistribution theorems on homogeneous spaces, which follow from Ratner's measure classification.
The Logic behind Feynman's Paths
Edgardo T. Garcia Alvarez
2010-11-22
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.
Choosing Your Geosciences Career Path
NASA Astrophysics Data System (ADS)
Paluszkiewicz, T.
2002-12-01
There are many possibilities for rewarding careers in the geosciences including positions in academia, government, industry, and other parts of the private sector. How do you choose the right path to meet your goals and needs and find the right career? What are the tradeoffs and strategic moves that you should make at different stages in your career? Some of the pros and cons between soft-money research, government research, and management and industry positions are discussed from a personal perspective. In addition this presentation will provide some perspective on different career choices as seen by program managers in funding agencies. The competing priorities between work life and private life are discussed with the some thoughts on compromising between "having it all" and finding what works for you.
The path to adaptive microsystems
NASA Astrophysics Data System (ADS)
Zolper, John C.; Biercuk, Michael J.
2006-05-01
Scaling trends in microsystems are discussed frequently in the technical community, providing a short-term perspective on the future of integrated microsystems. This paper looks beyond the leading edge of technological development, focusing on new microsystem design paradigms that move far beyond today's systems based on static components. We introduce the concept of Adaptive Microsystems and outline a path to realizing these systems-on-a-chip. The role of DARPA in advancing future components and systems research is discussed, and specific DARPA efforts enabling and producing adaptive microsystems are presented. In particular, we discuss efforts underway in the DARPA Microsystems Technology Office (MTO) including programs in novel circuit architectures (3DIC), adaptive imaging and sensing (AFPA, VISA, MONTAGE, A-to-I) and reconfigurable RF/Microwave devices (SMART, TFAST, IRFFE).
Path integral for Koenigs spaces
Grosche, C., E-mail: Christian.Grosche@desy.d [II Institut fuer Theoretische Physik Universitaet Hamburg (Germany)
2008-05-15
I discuss a path-integral approach for the quantum motion on two-dimensional spaces according to Koenigs, for short 'Koenigs spaces'. Their construction is simple: one takes a Hamiltonian from a two-dimensional flat space and divides it by a two-dimensional superintegrable potential. These superintegrable potentials are the isotropic singular oscillator, the Holt potential, and the Coulomb potential. In all cases, a nontrivial space of nonconstant curvature is generated. We can study free motion and the motion with an additional superintegrable potential. For possible bound-state solutions, we find in all three cases an equation of the eighth order in the energy E. The special cases of the Darboux spaces are easily recovered by choosing the parameters accordingly.
Flexible-Path Human Exploration
NASA Technical Reports Server (NTRS)
Sherwood, B.; Adler, M.; Alkalai, L.; Burdick, G.; Coulter, D.; Jordan, F.; Naderi, F.; Graham, L.; Landis, R.; Drake, B.; Hoffman, S.; Grunsfeld, J.; Seery, B. D.
2010-01-01
In the fourth quarter of 2009 an in-house, multi-center NASA study team briefly examined "Flexible Path" concepts to begin understanding characteristics, content, and roles of potential missions consistent with the strategy proposed by the Augustine Committee. We present an overview of the study findings. Three illustrative human/robotic mission concepts not requiring planet surface operations are described: assembly of very large in-space telescopes in cis-lunar space; exploration of near Earth objects (NEOs); exploration of Mars' moon Phobos. For each, a representative mission is described, technology and science objectives are outlined, and a basic mission operations concept is quantified. A fourth type of mission, using the lunar surface as preparation for Mars, is also described. Each mission's "capability legacy" is summarized. All four illustrative missions could achieve NASA's stated human space exploration objectives and advance human space flight toward Mars surface exploration. Telescope assembly missions would require the fewest new system developments. NEO missions would offer a wide range of deep-space trip times between several months and two years. Phobos exploration would retire several Marsclass risks, leaving another large remainder set (associated with entry, descent, surface operations, and ascent) for retirement by subsequent missions. And extended lunar surface operations would build confidence for Mars surface missions by addressing a complementary set of risks. Six enabling developments (robotic precursors, ISS exploration testbed, heavy-lift launch, deep-space-capable crew capsule, deep-space habitat, and reusable in-space propulsion stage) would apply across multiple program sequence options, and thus could be started even without committing to a specific mission sequence now. Flexible Path appears to be a viable strategy, with meaningful and worthy mission content.
Relationship between phase path and effective path for oblique ionospheric propagation
P. J. D. Gething
1965-01-01
The effects of earth curvature were neglected by Appleton in deriving the well-known relationship between phase path P and effective path P' for oblique propagation of a signal of frequency . It is shown that this equation is still rigorously satisfied when earth curvature is taken into account. An expression for phase path, correct to first order curvature terms, is
PathExpander: Architectural Support for Increasing the Path Coverage of Dynamic Bug Detection #
Zhou, Yuanyuan
PathExpander: Architectural Support for Increasing the Path Coverage of Dynamic Bug Detection,pinzhou,liuwei,yyzhou,torrellas}@cs.uiuc.edu Abstract Dynamic software bug detection tools are commonly used be cause they leverage runtime information. However, they suffer from a fundamental limitation, the Path Coverage Problem: they detect bugs
PathExpander: Architectural Support for Increasing the Path Coverage of Dynamic Bug Detection
Torrellas, Josep
PathExpander: Architectural Support for Increasing the Path Coverage of Dynamic Bug Detection Shan,pinzhou,liuwei,yyzhou,torrellas}@cs.uiuc.edu Abstract Dynamic software bug detection tools are commonly used be- cause they leverage run-time information. However, they suffer from a fundamental limitation, the Path Coverage Problem: they detect bugs
A Molecular Dynamics Study of the Ligand Release Path in Yeast Cytosine Deaminase
Yao, Lishan; Yan, Honggao; Cukier, Robert I.
2007-01-01
Yeast cytosine deaminase, a zinc metalloenzyme, catalyzes the deamination of cytosine to uracil. Experimental and computational evidence indicates that the rate-limiting step is product release, instead of the chemical reaction step. In this work, we use molecular dynamics to suggest ligand exit paths. Simulation at 300 K shows that the active site is well protected by the C-terminal helix (residues 150–158) and F-114 loop (residues 111–117) and that on the molecular dynamics timescale water does not flow in or out of the active site. In contrast, simulation at 320 K shows a significant increase in flexibility of the C-terminal helix and F-114 loop. The motions of these two regions at 320 K open the active site and permit water molecules to diffuse into and out of the active site through two paths with one much more favored than the other. Cytosine is pushed out of the active site by a restraint method in two directions specified by these two paths. In path 1 the required motion of the protein is local—involving only the C-terminal helix and F-114 loop—and two residues, F-114 and I-156, are identified that have to be moved away to let cytosine out; whereas in path 2, the protein has to rearrange itself much more extensively, and the changes are also much larger compared to the path 1 simulation. PMID:17218460
Path Matching in Compressed Control Flow Traces
Gupta, Rajiv
Path Matching in Compressed Control Flow Traces Youtao Zhang Rajiv Gupta Dept. of Computer Science in compressed form generated using SEQUITUR. The occurrence of an intraprocedural path in the WPP cannot with large amounts of data are often stored in compressed form and one of the commonly used compression
Visualization of Ant Pheromone Based Path Following
Sutherland, Benjamin T.
2010-07-14
This thesis develops a simulation and visualization of a path finding algorithm based on ant pheromone paths created in 3D space. The simulation is useful as a demonstration of a heuristic approach to NP-complete problems and as an educational tool...
't Hooft's quantum determinism -- path integral viewpoint
Massimo Blasone; Petr Jizba; Hagen Kleinert
2005-04-07
We present a path integral formulation of 't Hooft's derivation of quantum from classical physics. Our approach is based on two concepts: Faddeev-Jackiw's treatment of constrained systems and Gozzi's path integral formulation of classical mechanics. This treatment is compared with our earlier one [quant-ph/0409021] based on Dirac-Bergmann's method.
PATH PLANNING BY MULTIHEURISTIC SEARCH VIA SUBGOALS
Pekka Isto
1996-01-01
An efficient path planning algorithm for general 6 degrees of freedom robots is presented in the paper. The path planner is based on multiheuristic A * search algorithm with dynamic subgoal generation for rapid escaping from deep local-minimum wells. The algorithm has been implemented as an extension to a robot off-line programming and simulation system for testing. The presented test
Cooperative organic mine avoidance path planning
NASA Astrophysics Data System (ADS)
McCubbin, Christopher B.; Piatko, Christine D.; Peterson, Adam V.; Donnald, Creighton R.; Cohen, David
2005-06-01
The JHU/APL Path Planning team has developed path planning techniques to look for paths that balance the utility and risk associated with different routes through a minefield. Extending on previous years' efforts, we investigated real-world Naval mine avoidance requirements and developed a tactical decision aid (TDA) that satisfies those requirements. APL has developed new mine path planning techniques using graph based and genetic algorithms which quickly produce near-minimum risk paths for complicated fitness functions incorporating risk, path length, ship kinematics, and naval doctrine. The TDA user interface, a Java Swing application that obtains data via Corba interfaces to path planning databases, allows the operator to explore a fusion of historic and in situ mine field data, control the path planner, and display the planning results. To provide a context for the minefield data, the user interface also renders data from the Digital Nautical Chart database, a database created by the National Geospatial-Intelligence Agency containing charts of the world's ports and coastal regions. This TDA has been developed in conjunction with the COMID (Cooperative Organic Mine Defense) system. This paper presents a description of the algorithms, architecture, and application produced.
Multi-Path Time Protocols Alexander Shpiner
Segall, Adrian
IP networks. Keywords: multiple paths, slave diversity, IEEE 1588, PTP, NTP, time protocol, clock are the Network Time Protocol (NTP) [1], and the Precision Time Protocol (PTP) [2]. In both protocols the master transport types. Our Multi-path Time Protocol approach is an extension to the PTP and NTP protocols
Multiresolution Path Planning Via Sector Decompositions
Tsiotras, Panagiotis
Multiresolution Path Planning Via Sector Decompositions Compatible to On-Board Sensor Data that includes actual path length along with a risk-induced metric. We use a multi-resolution cell decomposition or popup threats. Several multi-resolution or hierarchical algorithms have been proposed in the literature
A Random Walk on a Circular Path
ERIC Educational Resources Information Center
Ching, W.-K.; Lee, M. S.
2005-01-01
This short note introduces an interesting random walk on a circular path with cards of numbers. By using high school probability theory, it is proved that under some assumptions on the number of cards, the probability that a walker will return to a fixed position will tend to one as the length of the circular path tends to infinity.
Fast path planning in virtual colonoscopy.
Lee, Jeongjin; Kim, Gyehyun; Lee, Ho; Shin, Byeong-Seok; Shin, Yeong Gil
2008-09-01
We propose a fast path planning algorithm using multi-resolution path tree propagation and farthest visible point. Initial path points are robustly generated by propagating the path tree, and all internal voxels locally most distant from the colon boundary are connected. The multi-resolution scheme is adopted to increase computational efficiency. Control points representing the navigational path are successively selected from the initial path points by using the farthest visible point. The position of the initial path point in a down-sampled volume is accurately adjusted in the original volume. Using the farthest visible point, the number of control points is adaptively changed according to the curvature of the colon shape so that more control points are assigned to highly curved regions. Furthermore, a smoothing step is unnecessary since our method generates a set of control points to be interpolated with the cubic spline interpolation. We applied our method to 10 computed tomography datasets. Experimental results showed that the path was generated much faster than using conventional methods without sacrificing accuracy, and clinical efficiency. The average processing time was approximately 1s when down-sampling by a factor of 2, 3, or 4. We concluded that our method is useful in diagnosing colon cancer using virtual colonoscopy. PMID:18707681
Using Runtime Paths for Macro Analysis
Mike Chen; Emre Kiciman; Anthony Accardi; Armando Fox; Eric Brewer
2002-01-01
We introduce macro analysis, an approach used to infer the high-level properties of dynamic, distributed systems , and an indispensable tool when faced with tasks where lo- cal context and individual component details are insuffi- cient. We present a new methodology,runtime path analysis, where paths are traced through software components and then aggregated to understand global system behavior via statistical
Career Path Guide for Adult Career Choices.
ERIC Educational Resources Information Center
Case, Clydia
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…
Fatigue failure paths for offshore platform inspection
Demir I. Karsan; Ashok Kumar
1990-01-01
A closed- form, reliability-based procedure is developed to identify fatigue failure paths of offshore structures and assess the notional probability of system failure through these paths. The procedure utilizes the Miners rule node fatigue failure reliability model developed by Wirsching. Effects of load redistribution following the fatigue failure of a node on the time to failure of remaining unfailed nodes
NASA Astrophysics Data System (ADS)
Pahlavani, Parham; Delavar, Mahmoud R.; Frank, Andrew U.
2012-08-01
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.
Precision Cleaning - Path to Premier
NASA Technical Reports Server (NTRS)
Mackler, Scott E.
2008-01-01
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.
NSDL National Science Digital Library
Math Forum
2000-01-01
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.
Nonholonomic catheter path reconstruction using electromagnetic tracking
NASA Astrophysics Data System (ADS)
Lugez, Elodie; Sadjadi, Hossein; Akl, Selim G.; Fichtinger, Gabor
2015-03-01
Catheter path reconstruction is a necessary step in many clinical procedures, such as cardiovascular interventions and high-dose-rate brachytherapy. To overcome limitations of standard imaging modalities, electromagnetic tracking has been employed to reconstruct catheter paths. However, tracking errors pose a challenge in accurate path reconstructions. We address this challenge by means of a filtering technique incorporating the electromagnetic measurements with the nonholonomic motion constraints of the sensor inside a catheter. The nonholonomic motion model of the sensor within the catheter and the electromagnetic measurement data were integrated using an extended Kalman filter. The performance of our proposed approach was experimentally evaluated using the Ascension's 3D Guidance trakStar electromagnetic tracker. Sensor measurements were recorded during insertions of an electromagnetic sensor (model 55) along ten predefined ground truth paths. Our method was implemented in MATLAB and applied to the measurement data. Our reconstruction results were compared to raw measurements as well as filtered measurements provided by the manufacturer. The mean of the root-mean-square (RMS) errors along the ten paths was 3.7 mm for the raw measurements, and 3.3 mm with manufacturer's filters. Our approach effectively reduced the mean RMS error to 2.7 mm. Compared to other filtering methods, our approach successfully improved the path reconstruction accuracy by exploiting the sensor's nonholonomic motion constraints in its formulation. Our approach seems promising for a variety of clinical procedures involving reconstruction of a catheter path.
Functional equivalence and spatial path memory.
Lyon, Don R; Gunzelmann, Glenn M
2011-11-01
Loomis, Klatzky, Avraamides, Lippa and Golledge ( 2007 ) suggest that, when it comes to spatial information, verbal description and perceptual experience are nearly functionally equivalent with respect to the cognitive representations they produce. We tested this idea for the case of spatial memory for complex paths. Paths consisted entirely of unit-length segments followed by 90-degree turns, thus assuring that a path could be described with equal precision using either an egocentric verbal description or a virtual self-motion experience. The verbal description was analogous to driving directions (e.g., turn left and go one block, then turn right, etc.) except in three dimensions (allowing rotation followed by up or down movement). Virtual self-motion was depicted as first-person travel through a 3D grid of featureless corridors. Comparison of these two conditions produced a result that may be surprising to some, but nevertheless appears to support the notion of functional equivalence: Virtual self-motion does not produce better path memory than verbal description, when care is taken to present equally precise path information. This result holds for even very complex paths and despite evidence from proximity-based interference that the memory representation of the path is spatial. PMID:22044400
14 CFR 29.59 - Takeoff path: Category A.
Code of Federal Regulations, 2010 CFR
2010-01-01
...2010-01-01 false Takeoff path: Category A. 29.59 Section 29.59 ...AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight Performance § 29.59 Takeoff path: Category A. (a) The takeoff path...
14 CFR 29.59 - Takeoff path: Category A.
Code of Federal Regulations, 2011 CFR
2011-01-01
...2011-01-01 false Takeoff path: Category A. 29.59 Section 29.59 ...AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight Performance § 29.59 Takeoff path: Category A. (a) The takeoff path...
Path Selection Methods for Localized Quality of Service Routing
Yuan, Xin
performance, local- ized QoS routing must effectively select the predetermined set of candi- date paths was used to select candi- date paths. This paper fills in the gap by studying path selec- tion schemes
Unusual bond paths in organolithium compounds
Bachrach, S.M.; Ritchie, J.P.
1986-01-01
We have applied the topological method to a number of organolithium compounds. The wavefunctions were determined with GAUSSIAN-82 using 3-21G basis set and fully optimized geometries. Gradient paths were obtained using the RHODER package and critical points were located using EXTREME. These results indicate the unusual nature of organolithium compounds. The strange bond paths arise mainly from the ionic nature of the C-Li interaction. We suggest that the term ''bond path'' may best be suited for covalent bonds. 4 figs., 1 tab.
Scientific Utopia: I. Opening Scientific Communication
Brian A. Nosek; Yoav Bar-Anan
2012-01-01
Existing norms for scientific communication are rooted in anachronistic practices of bygone eras making them needlessly inefficient. We outline a path that moves away from the existing model of scientific communication to improve the efficiency in meeting the purpose of public science—knowledge accumulation. We call for six changes: (a) full embrace of digital communication; (b) open access to all published
NASA Astrophysics Data System (ADS)
Wang, Po-Jen; Keyawa, Nicholas R.; Euler, Craig
2012-01-01
In order to achieve highly accurate motion control and path planning for a mobile robot, an obstacle avoidance algorithm that provided a desired instantaneous turning radius and velocity was generated. This type of obstacle avoidance algorithm, which has been implemented in California State University Northridge's Intelligent Ground Vehicle (IGV), is known as Radial Polar Histogram (RPH). The RPH algorithm utilizes raw data in the form of a polar histogram that is read from a Laser Range Finder (LRF) and a camera. A desired open block is determined from the raw data utilizing a navigational heading and an elliptical approximation. The left and right most radii are determined from the calculated edges of the open block and provide the range of possible radial paths the IGV can travel through. In addition, the calculated obstacle edge positions allow the IGV to recognize complex obstacle arrangements and to slow down accordingly. A radial path optimization function calculates the best radial path between the left and right most radii and is sent to motion control for speed determination. Overall, the RPH algorithm allows the IGV to autonomously travel at average speeds of 3mph while avoiding all obstacles, with a processing time of approximately 10ms.
Riemann Curvature Tensor and Closed Geodesic Paths
ERIC Educational Resources Information Center
Morganstern, Ralph E.
1977-01-01
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)
Steam Path Audits on Industrial Steam Turbines
Mitchell, D. R.
1992-01-01
The electric utility industry has benefitted from steam path audits on steam turbines for several years. Benefits include the ability to identify areas of performance degradation during a turbine outage. Repair priorities can then be set...
Locating ''sneak paths'' in electrical circuitry
NASA Technical Reports Server (NTRS)
Dannback, T. M.
1968-01-01
Use of a matrix system wherein circuit pin connections are assigned arbitrary designators and these used in formation of the matrix is illustrated. The matrix is a format that shows the current paths.
Building a path in cell biology
Cheeseman, Iain McPherson
Setting up a new lab is an exciting but challenging prospect. We discuss our experiences in finding a path to tackle some of the key current questions in cell biology and the hurdles that we have encountered along the way.
Identifying decohering paths in closed quantum systems
NASA Technical Reports Server (NTRS)
Albrecht, Andreas
1990-01-01
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.
Walden's Paths quiz: system design and implementation
Arora, Avital Jayant
2002-01-01
This thesis describes the motivation for online testing, compares the effectiveness of online tests versus conventional tests and outlines the features of online-testing mechanisms. It details the features and implementation of the Walden's Paths...
Code of Federal Regulations, 2011 CFR
2011-01-01
...by a continuous demonstrated takeoff. (e) The takeoff path to 35 feet above the takeoff surface must be determined by synthesis from segments; and (1) The segments must be clearly defined and must be related to distinct changes in...
Code of Federal Regulations, 2010 CFR
2010-01-01
...by a continuous demonstrated takeoff. (e) The takeoff path to 35 feet above the takeoff surface must be determined by synthesis from segments; and (1) The segments must be clearly defined and must be related to distinct changes in...
Predicting missing links via effective paths
NASA Astrophysics Data System (ADS)
Zhu, Xuzhen; Tian, Hui; Cai, Shimin
2014-11-01
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.
ERIC Educational Resources Information Center
Tunstall, Jeremy, Ed.
Conceived by the British Labor Government in the 1960's the Open University was viewed as a way to extend higher education to Britain's working class, but enrollment figures in classes that represent traditional academic disciplines show that the student population is predominantly middle class. Bringing education into the home presents numerous…
Path-memory induced quantization of classical orbits
Fort, Emmanuel; Eddi, Antonin; Boudaoud, Arezki; Moukhtar, Julien; Couder, Yves
2010-01-01
A droplet bouncing on a liquid bath can self-propel due to its interaction with the waves it generates. The resulting “walker” is a dynamical association where, at a macroscopic scale, a particle (the droplet) is driven by a pilot-wave field. A specificity of this system is that the wave field itself results from the superposition of the waves generated at the points of space recently visited by the particle. It thus contains a memory of the past trajectory of the particle. Here, we investigate the response of this object to forces orthogonal to its motion. We find that the resulting closed orbits present a spontaneous quantization. This is observed only when the memory of the system is long enough for the particle to interact with the wave sources distributed along the whole orbit. An additional force then limits the possible orbits to a discrete set. The wave-sustained path memory is thus demonstrated to generate a quantization of angular momentum. Because a quantum-like uncertainty was also observed recently in these systems, the nonlocality generated by path memory opens new perspectives.
The calculation of ionospheric ray paths
Koehler, Buford Ray
1967-01-01
Parabolic ionospheric layer of electrons, altitude versus electron density Page 1- 2 Sample ray paths with constant angle of propagation and increasing frequency, parabolic ionosphere of electrons assumed, earth's magnetic field neglected 1- 3 Sample... 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...
Optimization of Loading Paths for Tube Hydroforming
Suwat Jirathearanat; Taylan Altan
2004-01-01
An iterative FE simulation approach enhanced with numerical optimization schemes has been implemented for determination of optimum loading paths for tube hydroforming (THF) processes. A general optimization code, PAM-OPT, has been applied to optimize several THF processes simulated by PAM-STAMP. This paper discusses formulations of optimization of loading paths for various THF processes including a Y-shape and a complex structural
New England Forests: The Path to Sustainability
Wolfe, Patrick J.
New England Forests: The Path to Sustainability A R E P O R T B Y N E W E N G L A N D F O R E S T R Y F O U N D A T I O N #12;#12;New England Forests: The Path to Sustainability Forests define New tree in a town or state park? Forests are part of New Englanders' daily lives. Nearly all of us rely
Louisa Pavey; Paul Sparks
2009-01-01
Autonomy, often associated with an open and reflective evaluation of experience, is sometimes confused with reactance, which\\u000a indicates resistance to persuasion attempts. Two studies examined a path model in which autonomy and reactance predicted motivation\\u000a following the provision of anonymous or source-identified health-risk information, via the mediation of perceived threat to decision-making freedom and of perceived informational\\u000a value. Study 1
ERIC Educational Resources Information Center
Miller, Melvin E., Ed.; Cook-Greuter, Susanne R., Ed.
This book contains 11 papers on creativity, spirituality, and transcendence as paths to integrity and wisdom in the mature self. The book begins with the paper "Introduction--Creativity in Adulthood: Personal Maturity and Openness to Extraordinary Sources of Inspiration" (Susanne R. Cook-Greuter, Melvin E. Miller). The next four papers, which…
Equivalence of trans paths in ion channels
NASA Astrophysics Data System (ADS)
Alvarez, Juan; Hajek, Bruce
2006-04-01
We explore stochastic models for the study of ion transport in biological cells. Analysis of these models explains and explores an interesting feature of ion transport observed by biophysicists. Namely, the average time it takes ions to cross certain ion channels is the same in either direction, even if there is an electric potential difference across the channels. It is shown for simple single ion models that the distribution of a path (i.e., the history of location versus time) of an ion crossing the channel in one direction has the same distribution as the time-reversed path of an ion crossing the channel in the reverse direction. Therefore, not only is the mean duration of these paths equal, but other measures, such as the variance of passage time or the mean time a path spends within a specified section of the channel, are also the same for both directions of traversal. The feature is also explored for channels with interacting ions. If a system of interacting ions is in reversible equilibrium (net flux is zero), then the equivalence of the left-to-right trans paths with the time-reversed right-to-left trans paths still holds. However, if the system is in equilibrium, but not reversible equilibrium, then such equivalence need not hold.
Quantum cosmology based on discrete Feynman paths
Chew, Geoffrey F.
2002-10-10
Although the rules for interpreting local quantum theory imply discretization of process, Lorentz covariance is usually regarded as precluding time quantization. Nevertheless a time-discretized quantum representation of redshifting spatially-homogeneous universe may be based on discrete-step Feynman paths carrying causal Lorentz-invariant action--paths that not only propagate the wave function but provide a phenomenologically-promising elementary-particle Hilbert-space basis. In a model under development, local path steps are at Planck scale while, at a much larger ''wave-function scale'', global steps separate successive wave-functions. Wave-function spacetime is but a tiny fraction of path spacetime. Electromagnetic and gravitational actions are ''at a distance'' in Wheeler-Feynman sense while strong (color) and weak (isospin) actions, as well as action of particle motion, are ''local'' in a sense paralleling the action of local field theory. ''Nonmaterial'' path segments and ''trivial events'' collaborate to define energy and gravity. Photons coupled to conserved electric charge enjoy privileged model status among elementary fermions and vector bosons. Although real path parameters provide no immediate meaning for ''measurement'', the phase of the complex wave function allows significance for ''information'' accumulated through ''gentle'' electromagnetic events involving charged matter and ''soft'' photons. Through its soft-photon content the wave function is an ''information reservoir''.
Multi-Level Indoor Path Planning Method
NASA Astrophysics Data System (ADS)
Xiong, Q.; Zhu, Q.; Zlatanova, S.; Du, Z.; Zhang, Y.; Zeng, L.
2015-05-01
Indoor navigation is increasingly widespread in complex indoor environments, and indoor path planning is the most important part of indoor navigation. Path planning generally refers to finding the most suitable path connecting two locations, while avoiding collision with obstacles. However, it is a fundamental problem, especially for 3D complex building model. A common way to solve the issue in some applications has been approached in a number of relevant literature, which primarily operates on 2D drawings or building layouts, possibly with few attached attributes for obstacles. Although several digital building models in the format of 3D CAD have been used for path planning, they usually contain only geometric information while losing abundant semantic information of building components (e.g. types and attributes of building components and their simple relationships). Therefore, it becomes important to develop a reliable method that can enhance application of path planning by combining both geometric and semantic information of building components. This paper introduces a method that support 3D indoor path planning with semantic information.
Development Paths in Archaeological Surveying
NASA Astrophysics Data System (ADS)
Tabbagh, A.
2005-05-01
Geophysical surveys of archaeological sites began in 1938, when an electrical survey was performed at the historical site of Williamsburg (Virginia, USA). Its full development, however, has been achieved by several European teams, which have continuously worked on it since the fifties. Geophysical survey is one step of archaeological site reconnaissance, which comprises many other non-invasive techniques such as document studies, field walking, air photo interpretation...Nevertheless solely geophysical techniques allow a direct exploration of the underground itself over a significant depth of investigation. Several physical properties can be measured to detect and map archaeological features and/or remains but electrical resistivity and magnetisation has been commonly used for fifty years and dielectric permittivity more recently. The major path of the technical evolution was to increase both the speed of the survey and the size of the area by using short measurement duration (less than 0.1 s) and to incorporate mechanical systems that allow the continuous pulling of the sensors on the field. Magnetic measurements are thus achieved either by fluxgate or optically pumped sensors, while electrical measurements are achieved by mobile multi-pole systems simultaneously over two or three different depths. In such surveys the mesh grid is 1 x 1 m or 0.5 x 0.5 m. Another aim is to limit the size of the surveyed area but to increase the geometrical resolution by using ground penetrating radars (GPR) with a very fine mesh (0.2 x 0.2 m) and by processing the data by `time slices' which allow to follow precisely the extension in depth of the different features. In addition for magnetic features, the simultaneous inversion of magnetic field and susceptibility (and soon viscosity) measurements using linear filtering allows the differentiation among the types of magnetization and allows for an improved determination of the depths of magnetic property contrasts. By considering the geological context, global magnetic susceptibility values in the field is also an indication of possible settlement and of the type of land use in the past.
Towards an Error Model for OpenMP
Wong, M; Klemm, M; Duran, A; Mattson, T; Haab, G; de Supinski, B R; Churbanov, A
2010-03-22
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.
A CP-LP approach to network management in OSPF routing
Mats Petter Pettersson; Radoslaw Szymanek; Krzysztof Kuchcinski
2007-01-01
In this paper, we consider a routing problem related to the widely used Open Shortest Path First (OSPF) proto- col, which is considered a challenge within the Constraint Programming (CP) community. We address the special ver- sion of OSPF which requires unique and symmetrical paths. To solve this problem, we propose a novel hybrid approach which combines CP and Linear
Approximate path seeking for statistical iterative reconstruction
NASA Astrophysics Data System (ADS)
Wu, Meng; Yang, Qiao; Maier, Andreas; Fahrig, Rebecca
2015-03-01
Statistical iterative reconstruction (IR) techniques have demonstrated many advantages in X-ray CT reconstruction. The statistical iterative reconstruction approach is often modeled as an optimization problem including a data fitting function and a penalty function. The tuning parameter values that regulate the strength of the penalty function are critical for achieving good reconstruction results. However, appropriate tuning parameter values that are suitable for the scan protocols and imaging tasks are often difficult to choose. In this work, we propose a path seeking algorithm that is capable of generating a series of IR images with different strengths of the penalty function. The path seeking algorithm uses the ratio of the gradients of the data fitting function and the penalty function to select pixels for small fixed size updates. We describe the path seeking algorithm for penalized weighted least squares (PWLS) with a Huber penalty function in both the directions of increasing and decreasing tuning parameter value. Simulations using the XCAT phantom show the proposed method produces path images that are very similar to the IR images that are computed via direct optimization. The root-mean- squared-error of one path image generated by the proposed method relative to full iterative reconstruction is about 6 HU for the entire image and 10 HU for a small region. Different path seeking directions, increment sizes and updating percentages of the path seeking algorithm are compared in simulations. The proposed method may reduce the dependence on selection of good tuning parameter values by instead generating multiple IR images, without significantly increasing the computational load.
Minefield path planning: architecture and algorithms obeying kinematic constraints
Christopher B. McCubbin; Christine D. Piatko; Steven J. Marshall
2004-01-01
We have been developing path planning techniques to look for paths that balance the utility and risk associated with different routes through a minefield. Such methods will allow a battlegroup commander to evaluate alternative route options while searching for low risk paths. Extending on previous years' efforts, we have implemented a generalized path planning framework to allow rapid evaluation and
Path Analysis: A Link between Family Theory and Reseach.
ERIC Educational Resources Information Center
Rank, Mark R.; Sabatelli, Ronald M.
This paper discusses path analysis and the applicability of this methodology to the field of family studies. The statistical assumptions made in path analysis are presented along with a description of the two types of models within path analysis, i.e., recursive and non-recursive. Methods of calculating in the path model and the advantages of…
An Overview of Autonomous Mobile Robot Path Planning Algorithms
N. Sariff; N. Buniyamin
2006-01-01
Determination of a collision free path for a robot between start and goal positions through obstacles cluttered in a workspace is central to the design of an autonomous robot path planning. This paper presents an overview of autonomous mobile robot path planning focusing on algorithms that produce an optimal path for a robot to navigate in an environment. To complete
Best-path planning for public transportation systems
Chao-Lin Liu
2002-01-01
The author examines methods for a special class of path planning problems in which the routes are constrained. General search algorithms assume that we can move around in the traffic network freely, so they extend the partial paths from the very last location to each of its neighbors to form more partial paths. The best partial paths are then selected
Advanced path interpolation in high performance motion control systems
Dongjun Zhang; Zexiang Li; Shuang Cong; Hong Wu
2010-01-01
In the path following motion control system, the reference tool path of the machine tool is geometric curves predetermined by applications. The reference motion command for servo control system is generated based on the geometric tool path and the feedrate. The command generation module is called path interpolation. It is a classical problem in the motion control system. However, a
Diagnosis for Covariance Structure Models by Analyzing the Path
ERIC Educational Resources Information Center
Yuan, Ke-Hai; Kouros, Chrystyna D.; Kelley, Ken
2008-01-01
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…
A Comparison of Two Path Planners for Planetary Rovers
NASA Technical Reports Server (NTRS)
Tarokh, M.; Shiller, Z.; Hayati, S.
1999-01-01
The paper presents two path planners suitable for planetary rovers. The first is based on fuzzy description of the terrain, and genetic algorithm to find a traversable path in a rugged terrain. The second planner uses a global optimization method with a cost function that is the path distance divided by the velocity limit obtained from the consideration of the rover static and dynamic stability. A description of both methods is provided, and the results of paths produced are given which show the effectiveness of the path planners in finding near optimal paths. The features of the methods and their suitability and application for rover path planning are compared
Minimal entropy probability paths between genome families.
Ahlbrandt, Calvin; Benson, Gary; Casey, William
2004-05-01
We develop a metric for probability distributions with applications to biological sequence analysis. Our distance metric is obtained by minimizing a functional defined on the class of paths over probability measures on N categories. The underlying mathematical theory is connected to a constrained problem in the calculus of variations. The solution presented is a numerical solution, which approximates the true solution in a set of cases called rich paths where none of the components of the path is zero. The functional to be minimized is motivated by entropy considerations, reflecting the idea that nature might efficiently carry out mutations of genome sequences in such a way that the increase in entropy involved in transformation is as small as possible. We characterize sequences by frequency profiles or probability vectors, in the case of DNA where N is 4 and the components of the probability vector are the frequency of occurrence of each of the bases A, C, G and T. Given two probability vectors a and b, we define a distance function based as the infimum of path integrals of the entropy function H( p) over all admissible paths p(t), 0 < or = t< or =1, with p(t) a probability vector such that p(0)=a and p(1)=b. If the probability paths p(t) are parameterized as y(s) in terms of arc length s and the optimal path is smooth with arc length L, then smooth and "rich" optimal probability paths may be numerically estimated by a hybrid method of iterating Newton's method on solutions of a two point boundary value problem, with unknown distance L between the abscissas, for the Euler-Lagrange equations resulting from a multiplier rule for the constrained optimization problem together with linear regression to improve the arc length estimate L. Matlab code for these numerical methods is provided which works only for "rich" optimal probability vectors. These methods motivate a definition of an elementary distance function which is easier and faster to calculate, works on non-rich vectors, does not involve variational theory and does not involve differential equations, but is a better approximation of the minimal entropy path distance than the distance //b-a//(2). We compute minimal entropy distance matrices for examples of DNA myostatin genes and amino-acid sequences across several species. Output tree dendograms for our minimal entropy metric are compared with dendograms based on BLAST and BLAST identity scores. PMID:15133624
The formal path integral and quantum mechanics
Johnson-Freyd, Theo [Department of Mathematics, University of California - Berkeley, 970 Evans Hall, Berkeley, California 94720 (United States)
2010-11-15
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.
Paris-Sud XI, Université de
- 1 - Orphan innovation, or when path-creation goes stale: a design framework to characterize path,version1-12Jun2012 #12;- 2 - Orphan innovation, or when path-creation goes stale: a design framework to characterize path-dependence in realtime How can we identify whether innovation processes in an organization
Achieving fast and bandwidth-efficient shared-path protection
Yizhi Xiong; Dahai Xu; Chunming Qiao
2003-01-01
Dynamic provisioning of restorable bandwidth guaranteed paths is a challenge in the design of broad-band transport networks, especially next-generation optical networks. A common approach is called (failure-independent) path protection, whereby for every mission-critical active path to be established, a link (or node) disjoint backup path (BP) is also established. To optimize network resource utilization, shared path protection should be adopted,
Information Flow Analysis via Path Condition Refinement
NASA Astrophysics Data System (ADS)
Taghdiri, Mana; Snelting, Gregor; Sinz, Carsten
We present a new approach to information flow control (IFC), which exploits counterexample-guided abstraction refinement (CEGAR) technology. The CEGAR process is built on top of our existing IFC analysis in which illegal flows are characterized using program dependence graphs (PDG) and path conditions (as described in [12]). Although path conditions provide an already precise abstraction that can be used to generate witnesses to the illegal flow, they may still cause false alarms. Our CEGAR process recognizes false witnesses by executing them and monitoring their executions, and eliminates them by automatically refining path conditions in an iterative way as needed. The paper sketches the foundations of CEGAR and PDG-based IFC, and describes the approach in detail. An example shows how the approach finds illegal flow, and demonstrates how CEGAR eliminates false alarms.
A taxonomy of integral reaction path analysis
Grcar, Joseph F.; Day, Marcus S.; Bell, John B.
2004-12-23
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.
Quickest Paths for Different Network Router Mechanisms
Rao, N.S.V.; Grimmell, W.C.; Radhakrishnan, S.; Bang, Y.C.
2000-06-01
The quickest path problem deals with the transmission of a message of size {sigma} from a source to a destination with the minimum end-to-end delay over a network with bandwidth and delay constraints on the links. The authors consider four basic modes and two variations for the message delivery at the nodes reflecting the mechanisms such as circuit switching, Internet protocol, and their combinations. For each of the first three modes, they present O(m{sup 2} + mn log n) time algorithm to compute the quickest path for a given message size {sigma}. For the last mode, the quickest path can be computed in O(m + n log n) time.
Line transect sampling from a curving path.
Hiby, L; Krishna, M B
2001-09-01
Cutting straight line transects through dense forest is time consuming and expensive when large areas need to be surveyed for rare or highly clustered species. We argue that existing paths or game trails may be suitable as transects for line transect sampling even though they will not, in general, run straight. Formulas and software currently used to estimate local density using perpendicular distance data can be used with closest approach distances measured from curving transects. Suitable paths or trails are those for which the minimum radius of curvature is rarely less than the width of the shoulder in the detection probability function. The use of existing paths carries the risk of bias resulting from unrepresentative sampling of available habitats, and this must be weighed against the increase in coverage available. PMID:11550921
Tornado intensity estimated from damage path dimensions.
Elsner, James B; Jagger, Thomas H; Elsner, Ian J
2014-01-01
The Newcastle/Moore and El Reno tornadoes of May 2013 are recent reminders of the destructive power of tornadoes. A direct estimate of a tornado's power is difficult and dangerous to get. An indirect estimate on a categorical scale is available from a post-storm survery of the damage. Wind speed bounds are attached to the scale, but the scale is not adequate for analyzing trends in tornado intensity separate from trends in tornado frequency. Here tornado intensity on a continuum is estimated from damage path length and width, which are measured on continuous scales and correlated to the EF rating. The wind speeds on the EF scale are treated as interval censored data and regressed onto the path dimensions and fatalities. The regression model indicates a 25% increase in expected intensity over a threshold intensity of 29 m s(-1) for a 100 km increase in path length and a 17% increase in expected intensity for a one km increase in path width. The model shows a 43% increase in the expected intensity when fatalities are observed controlling for path dimensions. The estimated wind speeds correlate at a level of .77 (.34, .93) [95% confidence interval] with a small sample of wind speeds estimated independently from a doppler radar calibration. The estimated wind speeds allow analyses to be done on the tornado database that are not possible with the categorical scale. The modeled intensities can be used in climatology and in environmental and engineering applications. Research is needed to understand the upward trends in path length and width. PMID:25229242
Exploiting Deterministic TPG for Path Delay Testing
Xiaowei Li; Paul Y. S. Cheung
2000-01-01
Detection of path delay faults requires two-pattern tests. BIST technique provides a low-cost test solution. This paper proposes\\u000a an approach to designing a cost-effective deterministic test pattern generator (TPG) for path delay testing. Given a set of\\u000a pre-generated test-pairs with pre-determined fault coverage, a deterministic TPG is synthesized to apply the given test-pair\\u000a set in a limited test time. To
Multi-objective stochastic path planning
Dasgupta, Sumantra
2009-05-15
[6, 7]. Genetic Algorithms have been applied to generate the non-dominated Pareto optimal set in multi- criteria path planning [8]. Potential and value-function approaches have been reported for multi-criteria path planning in [9, 10]. C... per grid, source node, s and destination node, d. The first parameter is the average height (normalized) of the grid and the second parameter is the type of vegetation in the terrain. To be navigable, the average normalized height is set to 3...
Connections on decorated path space bundles
Saikat Chatterjee; Amitabha Lahiri; Ambar N. Sengupta
2015-02-11
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.
Gas path sealing in turbine engines
NASA Technical Reports Server (NTRS)
Ludwig, L. P.
1978-01-01
Survey of gas path seals is presented with particular attention given to sealing clearance effects on engine component efficiency. The effects on compressor pressure ratio and stall margin are pointed out. Various case-rotor relative displacements, which affect gas path seal clearances, are identified. Forces produced by nonuniform sealing clearances and their effect on rotor stability are discussed qualitatively, and recent work on turbine-blade-tip sealing for high temperatures is described. The need for active clearance control and for engine structural analysis is discussed. The functions of the internal-flow system and its seals are reviewed.
Gas path sealing in turbine engines
NASA Technical Reports Server (NTRS)
Ludwig, L. P.
1978-01-01
Gas path seals are discussed with emphasis on sealing clearance effects on engine component efficiency, compressor pressure ratio, and stall margin. Various case-rotor relative displacements, which affect gas path seal clearances, are identified. Forces produced by nonuniform sealing clearances and their effect on rotor stability are examined qualitatively, and recent work on turbine-blade-tip sealing for high temperatures is described. The need for active clearance control and for engine structural analysis is discussed. The functions of the internal-flow system and its seals are reviewed.
Path Factorization Approach to Stochastic Simulations
NASA Astrophysics Data System (ADS)
Athènes, Manuel; Bulatov, Vasily V.
2014-12-01
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.
Path factorization approach to stochastic simulations.
Athènes, Manuel; Bulatov, Vasily V
2014-12-01
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. PMID:25526107
Jue, Jason P.
Abstract-- Path protection requires finding a working path and a protection path that are link disjoint. In this paper, we consider the dynamic lightpath protection problem in WDM mesh networks under-disjoint lightpaths on a single wavelength; however, such algorithms fail if the working and protection lightpaths
Jue, Jason P.
Abstract-- Path protection requires finding a working path and a protection path that are link disjoint. In this paper, we consider the dynamic lightpath protection problem in WDM mesh networks where-- Optical network, lightpath protection, shared risk link group, risk disjoint, integer linear program (ILP
self-avoiding path dSG self-avoiding path
Hattori, Tetsuya
0: SAP on dSG (Self-Avoiding Path) w : Z+ G L(w) = inf{i | w(j) = w(i), j i} W0 = {w : Z+ G, 6, Â· Â· Â· dSG, d = 2, 3, SAP SAP path dSG SAP SAP #12;( ) (i) (path ) ( ) (ii) (iii) dSG SAP (re- cursion) #12;recursion SAP (A) SAP Â· d = 2: I2 = {(1), (2)} {Ov1} ( ) {Ov1v2} ( ) Â· I3 = {(1), (2), (3
Visualizing Transmedia Networks: Links, Paths and Peripheries
ERIC Educational Resources Information Center
Ruppel, Marc Nathaniel
2012-01-01
'Visualizing Transmedia Networks: Links, Paths and Peripheries' examines the increasingly complex rhetorical intersections between narrative and media ("old" and "new") in the creation of transmedia fictions, loosely defined as multisensory and multimodal stories told extensively across a diverse media set. In order…
COUNTING NONINTERSECTING LATTICE PATHS WITH TURNS
Krattenthaler, Christian
COUNTING NONINTERSECTING LATTICE PATHS WITH TURNS C. Krattenthaler Institut fÂ¨ur Mathematik der points and a given total number of North-East turns. These formulas are important for the computation with given starting and end points and a given total number of turns in certain regions. If one forgets about
2005 Spring Quarter Page The Critical Path
Christian, Eric
2005 Spring Quarter Page The Critical Path GOES-N About to Launch GOES-R Coming Down the Line February 6, 1975. SMS-C heralded the GOES era when it was named GOES-A. (GOES Continued on page 6) GOES-N/GOES-R
Fusion Development Path Panel Preliminary Report
Fusion Development Path Panel Preliminary Report Summary for NRC BPAC Panel (Focus on MFE of a demonstration power plant in approximately 35 years. The plan should recognize the capabilities of all fusion facilities around the world, and include both magnetic fusion energy (MFE) and inertial fusion energy (IFE
Building a path in cell biology
Voeltz, Gia; Cheeseman, Iain
2012-01-01
Setting up a new lab is an exciting but challenging prospect. We discuss our experiences in finding a path to tackle some of the key current questions in cell biology and the hurdles that we have encountered along the way. PMID:23112222
Path Integration in Desert Ants, Cataglyphis fortis
Martin Muller; Rudiger Wehner
1988-01-01
Foraging desert ants, Cataglyphis fortis, continually keep track of their own positions relative to home--i.e., integrate their tortuous outbound routes and return home along straight (inbound) routes. By experimentally manipulating the ants' outbound trajectories we show that the ants solve this path integration problem not by performing a true vector summation (as a human navigator does) but by employing a
The Many Paths of Hypervalent Iodine Reactions
Stoltz, Brian M.
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
Biometric Secret Path for Mobile User Authentication
Boyer, Edmond
is organized as follows. Section 2 is dedicated to the state of the art on biometric authentication on mobile. STATE OF THE ART In the literature, biometric based mobile authentication is an emerging issueBiometric Secret Path for Mobile User Authentication: A Preliminary Study Michael Beton National
Applications of Path Compression on Balanced Trees
Robert Endre Tarjan
1979-01-01
Several fast algorithms are presented for computing functions defined on paths in trees under various assumpuons. The algorithms are based on tree mampulatton methods first used to efficiently represent equivalence relations. The algorithms have O((m + n)a(m + n, n)) running tunes, where m and n are measures of the problem size and a Is a functional reverse of Ackermann's
Folded-path optical analysis gas cell
Carangelo, Robert M. (Glastonbury, CT); Wright, David D. (Vershire, VT)
1995-01-01
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.
Folded-path optical analysis gas cell
Carangelo, R.M.; Wright, D.D.
1995-08-08
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 foci coincidence and thereby to increase the radiation energy throughput characteristic of the cell. 10 figs.
Fractional quantum mechanics and Lévy path integrals
NASA Astrophysics Data System (ADS)
Laskin, Nikolai
2000-04-01
A new extension of a fractality concept in quantum physics has been developed. The path integrals over the Lévy paths are defined and fractional quantum and statistical mechanics have been developed via new fractional path integrals approach. A fractional generalization of the Schrödinger equation has been found. The new relation between the energy and the momentum of non-relativistic fractional quantum-mechanical particle has been established. We have derived a free particle quantum-mechanical kernel using Fox's H-function. The equation for the fractional plane wave function has been obtained. As a physical application of the developed fQM we have proposed a new fractional approach to the QCD problem of quarkonium. A fractional generalization of the motion equation for the density matrix has been found. The density matrix of a free particle has been expressed in term of the Fox's H-function. We also discuss the relationships between fractional and the well-known Feynman path integral approaches to quantum and statistical mechanics.
Judgments of Path, Not Heading, Guide Locomotion
Richard M. Wilkie; John P. Wann
2006-01-01
To steer a course through the world, people are almost entirely dependent on visual information, of which a key component is optic flow. In many models of locomotion, heading is described as the fundamental control variable; however, it has also been shown that fixating points along or near one's future path could be the basis of an efficient control solution.
Four Paths that Led to Careers.
ERIC Educational Resources Information Center
Witherspoon, W. Roger
1989-01-01
Traces the alternative career paths that four minority individuals followed to professional journalism. Includes a potential doctoral candidate in 17th century poetry, a future aeronautical engineer, a jazz musician, and possible pharmacist. Contends that minorities must often approach the profession through alternative routes in order to succeed.…
Quad-rotor flight path energy optimization
NASA Astrophysics Data System (ADS)
Kemper, Edward
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.
Stochastic Evolutionary Algorithms for Planning Robot Paths
NASA Technical Reports Server (NTRS)
Fink, Wolfgang; Aghazarian, Hrand; Huntsberger, Terrance; Terrile, Richard
2006-01-01
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.
Planning Flight Paths of Autonomous Aerobots
NASA Technical Reports Server (NTRS)
Kulczycki, Eric; Elfes, Alberto; Sharma, Shivanjli
2009-01-01
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.
Crack path prediction near an elliptical inclusion
E. M. Patton; M. H. Santare
1993-01-01
A technique is presented which will predict the path of a naturally growing crack where the stress field can be modeled as two-dimensional. The Green function for an arbitrarily oriented edge dislocation interacting with a rigid inclusion (or void) is used in an integral formulation of the elasticity problem. The technique uses a boundary integral approach to solve for the
Volcanic eruption induced WWVB transmission path interruption
H. A. Buckmaster; C. H. Hansen
1985-01-01
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
Motion on Cycloid Paths: A Project
ERIC Educational Resources Information Center
Gluck, P.
2010-01-01
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…
New formulas for tropospheric scatter path loss
Steen A. Parl
1979-01-01
The predicted performance of tropospheric scatter transmission is investigated in terms of spectrum slope, refractive index variance, and scale of turbulence. The common volume integral is evaluated to yield a useful expression for path loss in terms of these parameters. Formulas for the coupling loss in the asymptotic case of very wide and very narrow antenna beams are derived. Approximate
Current SPE Hydrodynamic Modeling and Path Forward
Knight, Earl E. [Los Alamos National Laboratory; Rougier, Esteban [Los Alamos National Laboratory
2012-08-14
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.
PATH. Gamma Dose Calculations and Shielding Analysis
Su, S.D.; Baylor, K.J.; Engholm, B.A. [CEGA Corporation, San Diego, CA (United States)
1988-02-01
PATH is a highly flexible shielding code utilizing the common point-kernel integration technique primarily for treating gamma radiation from reactors, radioactive components and from complex piping systems. Major features of the code include complex geometry capability, various source options, extensive data library, simple but flexible input and well-organized output format.
Analysis on free Riemannian path spaces
Shizan Fang; Feng-Yu Wang
2005-01-01
The gradient operator is defined on the free path space with reference measure P?, the law of the Brownian motion on the base manifold with initial distribution ?, where ? has strictly positive density w.r.t. the volume measure. The formula of integration by parts is established for the underlying directional derivatives, which implies the closability of the gradient operator so
Minimum padding to satisfy short path constraints
Narendra V. Shenoy; Robert K. Brayton; Alberto L. Sangiovanni-Vincentelli
1993-01-01
Combinational circuits are ojlen embedded in synchronous designs with rnernory elements at the input and output ports. A performance metric for a circuit is the cycle time of the clock signal. Correct circuit operatwn requires that all paths have a delay that lies between an upper bound and a lower bound. Traditional approaches in delay optimizatwn for combinational circuits [9,
Arto Annila
2011-01-01
The variational principle in its original form á la Maupertuis is used to delineate paths of light through varying energy densities and to associate shifts in frequency and changes in momentum. The gravitational bending and Doppler shift are in this way found as mere manifestations of least-time energy dispersal. In particular, the general principle of least action due to Maupertuis
employment opportunities in exciting career paths
Barthelat, Francois
IN FOOD SCIENCE McGillMcGillMcGILL UNIVERSITY Photos: © USDA. Used with permission Design © 2006/03 HCR) 398-7977 e-mail: foodscience@mcgill.ca We are also on the web: www.mcgill.ca/foodscience/ McGill Food in exciting career paths Food Science Cerificate for BSc graduates Food Science Cerificate for BSc graduates