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1

Robust constrained shortest path problems under budgeted ...  

E-print Network

2Department of Mechanical, Energy and Management Engineering, University of ... We study the robust constrained shortest path problem under resource uncertainty. ... can readily extend the algorithms presented in this paper to problems that ... such properties are related to the computational complexity and probabilistic...

2014-09-12

2

Shorter Path Constraints for the Resource Constrained Shortest Path Problem  

Microsoft Academic Search

Recently, new cost-based filtering algorithms for shorter-path con- straints have been developed. However, so far only the theoretical properties of shorter-path constraint filtering have been studied. We provide the first extensive experimental evaluation of the new algorithms in the context of the resource con- strained shortest path problem. We show how reasoning about path-substructures in combination with CP-based Lagrangian relaxation

Thorsten Gellermann; Meinolf Sellmann; Robert Wright

2005-01-01

3

An Improved Physarum polycephalum Algorithm for the Shortest Path Problem  

PubMed Central

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

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

2014-01-01

4

An Effective Evolutionary Approach for Bicriteria Shortest Path Routing Problems  

NASA Astrophysics Data System (ADS)

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

Lin, Lin; Gen, Mitsuo

5

Quantum algorithms for shortest paths problems in structured instances  

E-print Network

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.

Aran Nayebi; Virginia Vassilevska Williams

2014-10-23

6

The robust shortest path problem with interval data via Benders decomposition  

Microsoft Academic Search

Many real problems can be modelled as robust shortest path problems on digraphs with interval costs, where intervals represent uncertainty about real costs and a robust path is not too far from the shortest path for each possible configuration of the arc costs. In this paper we discuss the application of a Benders decomposition approach to this problem. Computational results

Roberto Montemanni; Luca Maria Gambardella

2005-01-01

7

A branch and bound algorithm for the robust shortest path problem with interval data  

Microsoft Academic Search

Many real problems in transportation and telecommunications can be modelled in mathematical terms as shortest path problems on in- terval digraphs, where an interval of costs is associated with each arc. Intervals represent uncertainty, typical of real situations, about the exact values of costs. In this context, a robust shortest path is a path which is ideally not too far

R. Montemanni; L. M. Gambardella; A. E. Rizzoli; A. V. Donati

2002-01-01

8

A branch and bound algorithm for the robust shortest path problem with interval data  

Microsoft Academic Search

Many real problems in transportation and telecommunications can be modelled in mathematical terms as shortest path problems on interval digraphs, where an interval cost is associated with each arc. Intervals represent uncertainty, typical of real situations, about the exact values of costs. A robust shortest path is a path which is not too far from the best one, whatever the

Roberto Montemanni; Luca Maria Gambardella; Alberto V. Donati

2004-01-01

9

A Benders decomposition approach for the robust shortest path problem with interval data  

E-print Network

}@idsia.ch Abstract Many real problems can be modelled as robust shortest path problems on digraphs with interval terms, a network is usually represented as a weighted digraph, where arcs are associated], a book entirely devoted to robust discrete optimization. A robust deviation shortest path from

Gambardella, Luca Maria

10

Discrete Approximation to Continuous Anisotropic Shortest-Path Problem  

E-print Network

-path (CSP) problem in 3D. · Incorporates ellipsoid model of radar cross sections of UAVs. Carlyle, Royset-Risk Path Planning for Groups of UAVs James Riehl João Hespanha INFORMS Meeting November 6, 2007 #12;start + #12;Minimum-Risk Path Planning for Groups of UAVs ( , )x v xi xf · Heterogeneous group of M UAVs · K

Hespanha, João Pedro

11

An exact algorithm for the robust shortest path problem with interval data  

E-print Network

terms as shortest path problems on weighted digraphs, where a fixed cost is associated with each arc´nski [10]), is the one we adopt. This criterion is discussed in Kouvelis and Yu [6], a book entirely

Gambardella, Luca Maria

12

An algorithm for the relative robust shortest path problem with interval data  

Microsoft Academic Search

Many real transport and telecommunications problems can be rep- resented in mathematical terms as shortest path problems on weighted digraphs, where a fixed cost is associated with each arc. Sometimes the level of abstraction induced by this model is too high, and consequently more complex representations of reality have to be considered. In this paper the interval data model, where

R. Montemanni; L. M. Gambardella

2002-01-01

13

FAST NUMERICAL METHODS BASED ON SDES FOR SEVERAL PROBLEMS RELATED TO THE SHORTEST PATH  

E-print Network

or disappearing at arbitrary times. The methods are based on solving finite dimensional stochastic differential into a finite dimensional problem of finding points on the boundaries to connect those line segments and arcs, JUN LU, HAO-MIN ZHOU Figure 1. Structure of a shortest path set, namely a finite dimensional set K

Soatto, Stefano

14

A Bio-Inspired Method for the Constrained Shortest Path Problem  

PubMed Central

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

Wang, Hongping; Lu, Xi; Wang, Qing

2014-01-01

15

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

SciTech Connect

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

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

1992-07-14

16

Exploring the runtime of an evolutionary algorithm for the multi-objective shortest path problem.  

PubMed

We present a natural vector-valued fitness function f for the multi-objective shortest path problem, which is a fundamental multi-objective combinatorial optimization problem known to be NP-hard. Thereafter, we conduct a rigorous runtime analysis of a simple evolutionary algorithm (EA) optimizing f. Interestingly, this simple general algorithm is a fully polynomial-time randomized approximation scheme (FPRAS) for the problem under consideration, which exemplifies how EAs are able to find good approximate solutions for hard problems. Furthermore, we present lower bounds for the worst-case optimization time. PMID:20560760

Horoba, Christian

2010-01-01

17

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

SciTech Connect

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

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

1989-04-01

18

A comparison of two new exact algorithms for the robust shortest path problem  

Microsoft Academic Search

Real road networks can be modelled in mathematical terms as interval digraphs, where an interval of travel times (costs) is associated with each arc. Intervals represent uncer- tainty, typical of real situations, about exact travel times. A robust shortest path is a path which is not too far from the shortest one, whatever the exact values of arc costs are.

Roberto Montemanni; Luca Maria; Gambardella Alberto Donati

2004-01-01

19

Enhanced Genetic Algorithm approach for Solving Dynamic Shortest Path Routing Problems using Immigrants and Memory Schemes  

E-print Network

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...

Nair, T R Gopalakrishnan; Yashoda, M B

2011-01-01

20

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

PubMed

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

Zhang, Junying; Zhao, Xiaoxue; He, Xiaotao

2014-08-01

21

A fuzzy shortest path with the highest reliability  

NASA Astrophysics Data System (ADS)

This paper concentrates on a shortest path problem on a network where arc lengths (costs) are not deterministic numbers, but imprecise ones. Here, costs of the shortest path problem are fuzzy intervals with increasing membership functions, whereas the membership function of the total cost of the shortest path is a fuzzy interval with a decreasing linear membership function. By the max-min criterion suggested in [R.E. Bellman, L.A. Zade, Decision-making in a fuzzy environment, Management Science 17B (1970) 141-164], the fuzzy shortest path problem can be treated as a mixed integer nonlinear programming problem. We show that this problem can be simplified into a bi-level programming problem that is very solvable. Here, we propose an efficient algorithm, based on the parametric shortest path problem for solving the bi-level programming problem. An illustrative example is given to demonstrate our proposed algorithm.

Keshavarz, Esmaile; Khorram, Esmaile

2009-08-01

22

A branch and bound algorithm for the robust shortest path problem with interval data  

E-print Network

problems on interval digraphs, where intervals represent uncertainty about real costs and a robust path, a road network is usually represented as a weighted digraph, where each arc is asso- ciated with a road to a destination node on a network. Also in this case, where the network is usually modelled as a weighted digraph

Gambardella, Luca Maria

23

Engineering Shortest Path Algorithms Camil Demetrescu1  

E-print Network

Engineering Shortest Path Algorithms Camil Demetrescu1 and Giuseppe F. Italiano2 1 Dipartimento di: italiano@disp.uniroma2.it, URL: http://www.disp.uniroma2.it/users/italiano/ Abstract. In this paper, we

Demetrescu, Camil

24

Highway Hierarchies Hasten Exact Shortest Path Queries  

Microsoft Academic Search

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

Peter Sanders; Dominik Schultes

2005-01-01

25

Distributional properties of stochastic shortest paths for smuggled nuclear material  

SciTech Connect

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

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

2011-01-05

26

Semiring Frameworks and Algorithms for Shortest-Distance Problems  

Microsoft Academic Search

We dene general algebraic frameworks for shortest-distance problems based on the structure of semirings. We give a generic algorithm for nding single-source shortest distances in a weighted directed graph when the weights satisfy the conditions of our general semiring framework. The same algorithm can be used to solve ecien tly clas- sical shortest paths problems or to nd the k-shortest

Mehryar Mohri

2002-01-01

27

A shortest path representation for video summarisation  

Microsoft Academic Search

A novel approach is presented to select multiple key frames within an isolated video shot where there is cam- era motion causing significant scene change. This is achieved by determining the dominant motion between frame pairs whose similarities are represented using a di- rected weighted graph. The shortest path in the graph, found using the search algorithm, designates the key

Sarah V. Porter; Majid Mirmehdi; Barry T. Thomas

2003-01-01

28

Detecting duplicate biological entities using Shortest Path Edit Distance.  

PubMed

Duplicate entity detection in biological data is an important research task. In this paper, we propose a novel and context-sensitive Shortest Path Edit Distance (SPED) extending and supplementing our previous work on Markov Random Field-based Edit Distance (MRFED). SPED transforms the edit distance computational problem to the calculation of the shortest path among two selected vertices of a graph. We produce several modifications of SPED by applying Levenshtein, arithmetic mean, histogram difference and TFIDF techniques to solve subtasks. We compare SPED performance to other well-known distance algorithms for biological entity matching. The experimental results show that SPED produces competitive outcomes. PMID:20815139

Rudniy, Alex; Song, Min; Geller, James

2010-01-01

29

Experimental analysis of dynamic all pairs shortest path algorithms  

Microsoft Academic Search

We present the results of an extensive computational study on dynamic algorithms for all pairs shortest path problems. We describe our implementations of the recent dynamic algorithms of King [18] and of Demetrescu and Italiano [7], and compare them to the dynamic algorithm of Ramalingam and Reps [25] and to static algorithms on random, real-world and hard instances. Our experimental

Camil Demetrescu; Stefano Emiliozzi; Giuseppe F. Italiano

2004-01-01

30

Efficient Algorithms for Shortest Paths in Sparse Networks  

Microsoft Academic Search

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

Donald B. Johnson

1977-01-01

31

Shortest Paths, Soap Films, and Minimal Surfaces  

NSDL National Science Digital Library

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

Dorff, Michael

2012-10-10

32

Multiple Object Tracking Using the Shortest Path Faster Association Algorithm  

PubMed Central

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

Liu, Heping; Liu, Huaping; Yang, Bin

2014-01-01

33

MIKKEL THORUP & MATTHEW ROUGHAN 1 Avoiding Ties in Shortest Path First Routing  

E-print Network

MIKKEL THORUP & MATTHEW ROUGHAN 1 Avoiding Ties in Shortest Path First Routing Mikkel Thorup,roughan)@research.att.com Abstract---First we discuss problems associated with ties and flow splitting with shortest path first ties and yet minimize conges­ tion. On real and synthetic networks we demonstrate experimentally

Roughan, Matthew

34

MIKKEL THORUP & MATTHEW ROUGHAN 1 Avoiding Ties in Shortest Path First Routing  

E-print Network

MIKKEL THORUP & MATTHEW ROUGHAN 1 Avoiding Ties in Shortest Path First Routing Mikkel Thorup,roughan)@research.att.com Abstract--First we discuss problems associated with ties and flow splitting with shortest path first ties and yet minimize conges- tion. On real and synthetic networks we demonstrate experimentally

Roughan, Matthew

35

Shortest paths synthesis for a car-like robot  

Microsoft Academic Search

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

P. Soueres; J.-P. Laumond

1996-01-01

36

A new approach to dynamic all pairs shortest paths  

Microsoft Academic Search

We study novel combinatorial properties of graphs that allow us to devise a completely new approach to dynamic all pairs shortest paths problems. Our approach yields a fully dynamic algorithm for general directed graphs with non-negative real-valued edge weights that supports any sequence of operations in O(n2log3n) amortized time per update and unit worst-case time per distance query, where n

Camil Demetrescu; Giuseppe F. Italiano

2004-01-01

37

A new approach to dynamic all pairs shortest paths  

Microsoft Academic Search

We study novel combinatorial properties of graphs that allow us to devise a completely new approach to dynamic all pairs shortest paths problems. Our approach yields a fully dynamic algorithm for general directed graphs with non-negative real-valued edge weights that supports any sequence of operations in (n2) amortized time per update and unit worst-case time per distance query, where n

Camil Demetrescu; Giuseppe F. Italiano

2003-01-01

38

Multiobjective Optimization: Improved FPTAS for Shortest Paths and Non-Linear Objectives with Applications  

Microsoft Academic Search

We provide an improved FPTAS for multiobjective shortest pathsa fundamental (NP-hard) problem in multiobjective optimizationalong\\u000a with a new generic method for obtaining FPTAS to any multiobjective optimization problem with non-linear objectives. We show how these results can be used to obtain better approximate solutions to three related problems, multiobjective\\u000a constrained [optimal] path and non-additive shortest path, that have important applications

George Tsaggouris; Christos D. Zaroliagis

2009-01-01

39

Multiobjective Optimization: Improved FPTAS for Shortest Paths and Non-linear Objectives with Applications  

Microsoft Academic Search

We provide an improved FPTAS for multiobjective shortest pathsa fundamental (NP-hard) problem in multiobjective optimizationalong with a new generic method for obtaining FPTAS to any multiobjective optimization problem with non-linear objectives. We show how these results can be used to obtain better approximate solutions to three related problems, multiobjective constrained (optimal) path and non-additive shortest path, that have important applications

George Tsaggouris; Christos D. Zaroliagis

2006-01-01

40

Corridor location: the multi-gateway shortest path model  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

41

ON THE ACCELERATION OF SHORTEST PATH CALCULATIONS IN TRANSPORTATION NETWORKS  

SciTech Connect

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

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

2007-01-08

42

Intra-domain traffic engineering with shortest path routing protocols  

Microsoft Academic Search

Throughout the last decade, extensive deployment of popular intra-domain routing protocols such as open shortest path first\\u000a and intermediate systemintermediate system, has drawn an ever increasing attention to Internet traffic engineering. This\\u000a paper reviews optimization techniques that have been deployed for managing intra-domain routing in networks operated with\\u000a shortest path routing protocols, and the state-of-the-art research that has been carried

Aysegl Altin; Bernard Fortz; Mikkel Thorup

2009-01-01

43

Trans-dichotomous Algorithms for Minimum Spanning Trees and Shortest Paths  

Microsoft Academic Search

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

Michael L. Fredman; Dan E. Willard

1990-01-01

44

An exact algorithm for computing the shortest path touring n circles in 2D  

Microsoft Academic Search

This paper introduces the problem of computing the shortest Euclidean path touring n disjoint circles in 2D. The problem is a generalization of Travelling Salesman Problem (TSP) in Euclidean 2D space and is not a purely combinatorial problem. Based on the author's previous work, this paper proposes an exact algorithm to solve the studied problem. The proposed algorithm can be

Chang-Chien Chou

2010-01-01

45

Interval order representation via shortest paths Garth Isaak  

E-print Network

results for potentials in digraphs. This viewpoint yields short proofs of the representation theorems the reals may be required. For more on this see Fish- burn's book [4]. For this paper we will stick to potentials, shortest paths and negative cycles in digraphs. We will assume that all orders considered

Isaak, Garth

46

Minimizing communication in all-pairs shortest paths Edgar Solomonik  

E-print Network

Minimizing communication in all-pairs shortest paths Edgar Solomonik Aydin Buluc James Demmel Electrical Engineering and Computer Sciences University of California at Berkeley Technical Report No. UCB Solomonik Univ. of California, Berkeley Department of EECS solomon@eecs.berkeley.edu Aydin Buluç Lawrence

California at Berkeley, University of

47

Fully Dynamic Algorithms for Maintaining Shortest Paths Trees  

Microsoft Academic Search

We propose fully dynamic algorithms for maintaining the distances and the shortest paths from a single source in either a directed or an undirected graph with positive real edge weights, handling insertions, deletions, and weight updates of edges. The algorithms require linear space and optimal query time. The cost of the update operations depends on the class of the considered

Daniele Frigioni; Alberto Marchetti-spaccamela; Umberto Nanni

2000-01-01

48

Finding Shortest Path for Developed Cognitive Map Using Medial Axis  

E-print Network

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

Farhan, Hazim A; Al-Ghazi, Suhaib I

2011-01-01

49

Shortest Path Planning for a Tethered Robot or an Anchored Cable  

SciTech Connect

We consider the problem of planning shortest paths for a tethered robot with a finite length tether in a 2D environment with polygonal obstacles. We present an algorithm that runs in time O((k{sub 1} + 1){sup 2}n{sup 4}) and finds the shortest path or correctly determines that none exists that obeys the constraints; here n is the number obstacle vertices, and k{sub 1} is the number loops in the initial configuration of the tether. The robot may cross its tether but nothing can cross obstacles, which cause the tether to bend. The algorithm applies as well for planning a shortest path for the free end of an anchored cable.

Xavier, P.G.

1999-02-22

50

Fully Dynamic All Pairs Shortest Paths with Real Edge Weights  

Microsoft Academic Search

We present the first fully dynamic algorithm for maintaining all pairs shortest paths in directed graphs with real-valued edge weights. Given a dynamic directed graph G such that each edge can assume at most S different real values, we show how to support updates in O(n2.5 ? S log3 n) amor- tized time and queries in optimal worst-case time. This

Camil Demetrescu; Giuseppe F. Italiano

2001-01-01

51

A Graph Search Heuristic for Shortest Distance Paths  

SciTech Connect

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

Chow, E

2005-03-24

52

Snell's law and light traveling along the shortest path  

Microsoft Academic Search

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

Carlos Lara

2006-01-01

53

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

Microsoft Academic Search

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

J. Sussmann; Guoqing Tang

1991-01-01

54

Damage detection via shortest-path network sampling.  

PubMed

Large networked systems are constantly exposed to local damages and failures that can alter their functionality. The knowledge of the structure of these systems is, however, often derived through sampling strategies whose effectiveness at damage detection has not been thoroughly investigated so far. Here, we study the performance of shortest-path sampling for damage detection in large-scale networks. We define appropriate metrics to characterize the sampling process before and after the damage, providing statistical estimates for the status of nodes (damaged, not damaged). The proposed methodology is flexible and allows tuning the trade-off between the accuracy of the damage detection and the number of probes used to sample the network. We test and measure the efficiency of our approach considering both synthetic and real networks data. Remarkably, in all of the systems studied, the number of correctly identified damaged nodes exceeds the number of false positives, allowing us to uncover the damage precisely. PMID:25353853

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

2014-05-01

55

Damage detection via shortest-path network sampling  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

56

Formal language constrained path problems  

SciTech Connect

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

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

1997-07-08

57

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

E-print Network

.4 TSA for repeatedly solving RCSP......................................................................42 5.5 Summary.............................................................................................................43 VI LABEL...-SETTING ALGORITHM ...........................................................................44 VII COMPUTATIONAL EVALUATION OF TSA......................................................47 7.1 Test problems and computational platform...

Zhu, Xiaoyan

2007-04-25

58

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

Microsoft Academic Search

One of the most important and challenging problems in biomedicine and genomics is how to identify the disease genes. In this study, we developed a computational method to identify colorectal cancer-related genes based on (i) the gene expression profiles, and (ii) the shortest path analysis of functional protein association networks. The former has been used to select differentially expressed genes

Bi-Qing Li; Tao Huang; Lei Liu; Yu-Dong Cai; Kuo-Chen Chou

2012-01-01

59

Computing shortest heterochromatic monotone routes  

Microsoft Academic Search

Abstract. Given a set of n points on the plane colored with k n colors, the Trip Planning Problem asks for the shortest path visiting the k colors. It is a well-known NP-hard problem. We show that under some natural constraints on the path, the problem can be solved in polynomial time. Keywords: Routing; Heterochromatic Monotone Route; Shortest Path;

Jos Miguel Daz-bez; G. Hernndez; D. Oliveros; A. Ramrez-vigueras; Joan Antoni Sellars; Jorge Urrutia; Inmaculada Ventura

2008-01-01

60

A NEW APPROACH IN SYSTEM RELIABILITY EVALUATION, SHORTEST PATH OF E-NETWORKS  

Microsoft Academic Search

By applying shortest path analysis in stochastic networks, we introduce a new approach to obtain the reliability function of time-dependent systems. We assume that not all elements of the system are set to function from the beginning. Upon the failure of each element of the active path in the reliability graph, the system switches to the next path. Then, the

A. AZARON; M. MODARRES

61

A FAST ALGORITHM FOR FINDING THE SHORTEST PATH BY SOLVING INITIAL VALUE ODE'S  

E-print Network

, such as the combinatorial methods or partial differential equation methods, our algorithm seems to be faster and easier methods are based on the theory of differential equations. For instance, in the planar path evolution differential equations under random perturbations. The idea is based on the fact that every shortest path

Soatto, Stefano

62

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

Microsoft Academic Search

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

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

2002-01-01

63

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

E-print Network

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

Imai, Hiroshi

64

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

PubMed Central

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

Li, Longxiang; Gong, Jianhua; Zhou, Jieping

2014-01-01

65

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

NASA Astrophysics Data System (ADS)

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

Krger, Martin

2005-06-01

66

Finding splitting lines for touching cell nuclei with a shortest path algorithm.  

PubMed

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

Bai, Xiangzhi; Wang, Peng; Sun, Changming; Zhang, Yu; Zhou, Fugen; Meng, Cai

2014-10-22

67

A critical exponent for shortest-path scaling in continuum percolation  

NASA Astrophysics Data System (ADS)

We carry out Monte Carlo experiments to study the scaling behavior of shortest path lengths in continuum percolation. These studies suggest that the critical exponent governing this scaling is the same for both continuum and lattice percolation. We use splitting, a technique that has not yet been fully exploited in the physics literature, to increase the speed of our simulations. This technique can also be applied to other models where clusters are grown sequentially.

Brereton, Tim; Hirsch, Christian; Schmidt, Volker; Kroese, Dirk

2014-12-01

68

Faster exponential time algorithms for the shortest vector problem Daniele Micciancio Panagiotis Voulgaris  

E-print Network

algorithmic applications (see survey papers [14, 6, 21]), and the problem underlying many cryptographic for the cryptographic function. In this paper we present and analyze new algorithms to find the shortest vectorFaster exponential time algorithms for the shortest vector problem Daniele Micciancio Panagiotis

Wang, Deli

69

Shortest-path fractal dimension for percolation in two and three dimensions.  

PubMed

We carry out a high-precision Monte Carlo study of the shortest-path fractal dimension d(min) for percolation in two and three dimensions, using the Leath-Alexandrowicz method which grows a cluster from an active seed site. A variety of quantities are sampled as a function of the chemical distance, including the number of activated sites, a measure of the radius, and the survival probability. By finite-size scaling, we determine d(min)=1.13077(2) and 1.3756(6) in two and three dimensions, respectively. The result in two dimensions rules out the recently conjectured value d(min)=217/192 [Deng et al., Phys. Rev. E 81, 020102(R) (2010)]. PMID:23367887

Zhou, Zongzheng; Yang, Ji; Deng, Youjin; Ziff, Robert M

2012-12-01

70

Identifying Gastric Cancer Related Genes Using the Shortest Path Algorithm and Protein-Protein Interaction Network  

PubMed Central

Gastric cancer, as one of the leading causes of cancer related deaths worldwide, causes about 800,000 deaths per year. Up to now, the mechanism underlying this disease is still not totally uncovered. Identification of related genes of this disease is an important step which can help to understand the mechanism underlying this disease, thereby designing effective treatments. In this study, some novel gastric cancer related genes were discovered based on the knowledge of known gastric cancer related ones. These genes were searched by applying the shortest path algorithm in protein-protein interaction network. The analysis results suggest that some of them are indeed involved in the biological process of gastric cancer, which indicates that they are the actual gastric cancer related genes with high probability. It is hopeful that the findings in this study may help promote the study of this disease and the methods can provide new insights to study various diseases. PMID:24729971

Shi, Ying; Li, Li-Peng; Ren, Hui

2014-01-01

71

A Shortest Path Representation for Video Summarisation S.V. Porter, M. Mirmehdi and B.T. Thomas  

E-print Network

A Shortest Path Representation for Video Summarisation S.V. Porter, M. Mirmehdi and B.T. Thomas information from the video and enable content-based video browsing. 2 Video Summarisation Different approaches to video summarisation often de- pend on the purpose of the abstract. Lienhart et al. [8] concentrate

Mirmehdi, Majid

72

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

73

OBSTACLE-AVOIDING SIMILARITY METRICS AND SHORTEST PATH PROBLEMS  

E-print Network

Foundation grant NSF CAREER CCF-0643597 and the 2009 University of Texas at San Antonio Presidential with guidelines which permit the inclusion as part of the Doctoral Dissertation the text of an original paper

Texas at San Antonio, University of

74

Constraint-Based Local Search for Constrained Optimum Paths Problems  

NASA Astrophysics Data System (ADS)

Constrained Optimum Path (COP) problems arise in many real-life applications and are ubiquitous in communication networks. They have been traditionally approached by dedicated algorithms, which are often hard to extend with side constraints and to apply widely. This paper proposes a constraint-based local search (CBLS) framework for COP applications, bringing the compositionality, reuse, and extensibility at the core of CBLS and CP systems. The modeling contribution is the ability to express compositional models for various COP applications at a high level of abstraction, while cleanly separating the model and the search procedure. The main technical contribution is a connected neighborhood based on rooted spanning trees to find high-quality solutions to COP problems. The framework, implemented in COMET, is applied to Resource Constrained Shortest Path (RCSP) problems (with and without side constraints) and to the edge-disjoint paths problem (EDP). Computational results show the potential significance of the approach.

Pham, Quang Dung; Deville, Yves; van Hentenryck, Pascal

75

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

76

Center line algorithm for virtual endoscopy based on chamfer distance transform and Dijkstra's single-source shortest-path algorithm  

NASA Astrophysics Data System (ADS)

Successful applications of virtual endoscopy often require the generation of centerlines as flight paths for fly-through examinations of anatomic structures. Criteria for design of effective centerline algorithms should include the following: (1) tracking of the most medial path possible, (2) robustness to segmentation errors, (3) computational efficiency, and (4) minimum of user interaction. To satisfy these design goals, we have developed a centerline generation algorithm based on the chamfer distance transform and Dijkstra's single-source shortest path algorithm. The distance transformation is applied to a segmented volume to determine the distance from each object voxel to the nearest background voxel -- a 'medialness' measure for each voxel. From a user specified source voxel, the distance and path from each object voxel to the source voxel is determined using Dijkstra's single-source shortest path algorithm, with the 'medialness' measure used as the weighting or distance factor between voxels. After execution of the algorithm is complete, paths from all voxels in the object to the source can be easily computed, a feature that is useful for all implementations of virtual endoscopy, but particularly for virtual bronchoscopy, which involves branching. The algorithm runs in O[2n(1 + f)] time, where n is the number of voxels in the volume, and f is the ratio of object voxels to total voxels in the volume. The algorithm is efficient, requiring approximately 90 seconds for a 60 megabyte dataset containing a segmented colon, and is robust to noise, segmentation errors, and start/end voxel selection. The only user interaction required is choosing the starting and ending voxels for the path. We report on objective and subjective evaluations of the algorithm when applied to several mathematical phantoms, the Visible Human Male Dataset and patient exams.

Blezek, Daniel J.; Robb, Richard A.

1999-05-01

77

Longest Path Problems on Ptolemaic Graphs  

NASA Astrophysics Data System (ADS)

Longest path problem is a problem for finding a longest path in a given graph. While the graph classes in which the Hamiltonian path problem can be solved efficiently are widely investigated, there are few known graph classes such that the longest path problem can be solved efficiently. Polynomial time algorithms for finding a longest cycle and a longest path in a Ptolemaic graph are proposed. Ptolemaic graphs are the graphs that satisfy the Ptolemy inequality, and they are the intersection of chordal graphs and distance-hereditary graphs. The algorithms use the dynamic programming technique on a laminar structure of cliques, which is a recent characterization of Ptolemaic graphs.

Takahara, Yoshihiro; Teramoto, Sachio; Uehara, Ryuhei

78

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

PubMed Central

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

Liu, Lei

2013-01-01

79

Cost-based Filtering for Shorter Path Constraints  

Microsoft Academic Search

Many real world problems, e.g. personnel scheduling and transporta- tion planning, can be modeled naturally as Constrained Shortest Path Problems (CSPPs), i.e., as Shortest Path Problems with additional constraints. A well studied problem in this class is the Resource Constrained Shortest Path Problem. Reduction techniques are vital ingredients of solvers for the CSPP, that is frequently NP-hard, depending on the

Meinolf Sellmann; Thorsten Gellermann; Robert Wright

2007-01-01

80

Percolation threshold, Fisher exponent, and shortest path exponent for four and five dimensions.  

PubMed

We develop a method of constructing percolation clusters that allows us to build very large clusters using very little computer memory by limiting the maximum number of sites for which we maintain state information to a number of the order of the number of sites in the largest chemical shell of the cluster being created. The memory required to grow a cluster of mass s is of the order of s(straight theta) bytes where straight theta ranges from 0.4 for two-dimensional (2D) lattices to 0.5 for six (or higher)-dimensional lattices. We use this method to estimate d(min), the exponent relating the minimum path l to the Euclidean distance r, for 4D and 5D hypercubic lattices. Analyzing both site and bond percolation, we find d(min)=1.607+/-0.005 (4D) and d(min)=1.812+/-0.006 (5D). In order to determine d(min) to high precision, and without bias, it was necessary to first find precise values for the percolation threshold, p(c): p(c)=0.196889+/-0.000003 (4D) and p(c)=0.14081+/-0.00001 (5D) for site and p(c)=0.160130+/-0.000003 (4D) and p(c)=0.118174+/-0.000004 (5D) for bond percolation. We also calculate the Fisher exponent tau determined in the course of calculating the values of p(c): tau=2.313+/-0.003 (4D) and tau=2.412+/-0.004 (5D). PMID:11497659

Paul, G; Ziff, R M; Stanley, H E

2001-08-01

81

Spreading paths in partially observed social networks  

PubMed Central

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

Onnela, Jukka-Pekka; Christakis, Nicholas A.

2012-01-01

82

Unstructured path problems and the making of semirings  

Microsoft Academic Search

The solution of the algebraic path problem, for instance with the algorithm by Floyd and Warshall, is part of the classical repertoire on algorithms. This solution presupposes that path costs are computed in a closed semiring or a similar algebraic structure. The associativity and distributivity laws in such algebraic structures exclude many possible path costs. In the seventies, several authors

T. Lengauer; D. Theune

83

Thick Non-Crossing Paths and Minimum-Cost Flows in Polygonal Domains  

E-print Network

Math and Statistics Stony Brook University jsbm@ams.stonybrook.edu Valentin Polishchuk Helsinki Institute for Information Technology valentin@compgeom.com ABSTRACT We study the problem of finding shortest of points (s, t), find a shortest s-t path avoiding the obstacles. The non-crossing paths problem

Mitchell, Joseph S.B.

84

Path optimization using sub-Riemannian manifolds with applications to astrodynamics  

E-print Network

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 ...

Whiting, James K. (James Kalani), 1980-

2011-01-01

85

The Minimum Equivalent DNF Problem and Shortest Implicants Christopher Umans \\Lambda  

E-print Network

that the Minimum Equivalent DNF problem is \\Sigma p 2 ­complete, resolving a conjecture due to Stockmeyer in the polynomial hierarchy. In his well­ know polynomial hierarchy paper [12], Stockmeyer conjec­ tured occurrences of literals? In this paper we prove Stockmeyer's conjecture. Our proof involves a variant

Umans, Chris

86

All pairs almost shortest paths  

SciTech Connect

Let G = (V, E) be an unweighted undirected graph on n vertices. A simple argument shows that computing all distances in G with an additive one-sided error of at most is as hard as Boolean matrix multiplication. Building on recent work of Aingworth, Chekuri and Motwani, we describe an O(min n{sup 3/2}m{sup 1/2}, n{sup 7/3}) time algorithm APASP{sub 2} for computing all distances in G with an additive one-sided error of at most 2. The algorithm APASP{sub 2} is simple, easy to implement, and faster than the fastest known matrix multiplication algorithm. Furthermore, for every even k > 2, we describe an O(min n{sup 2} 2/k +2 m 2/2+k, n{sup 2+} 2/3k-2) time algorithm APASP{sub {infinity}} for computing all distances in G with an additive one-sided error of at most k. We also give an O(n 2) time algorithm APASP{sub {infinity}}. for producing stretch 3 estimated distances in an unweighted and undirected graph on n vertices. No constant stretch factor was previously achieved in O(n{sup 2}) time. We say that a weighted graph F = (V,E`) k-emulates an unweighted graph G = (V,E) if for every u, v {element_of} V we have {delta}{sub G} (u, {nu}) {le} {delta}{sub F} (u, {nu}) {le} {delta}{sub G} (u, {nu}) + k. We show that every unweighted graph on n vertices has a 2-emulator with O(n{sup 3/2}) edges and a 4-emulator with O(n{sup 4/3}) edges. These results are asymptotically tight. Finally, we show that any weighted undirected graph on n vertices has a 3-spanner with O(n{sup 1/2}) edges and that such a 3-spanner can be built in O(mn{sup 1/2}) time. We also describe an O(n (m{sup 2/3} + n)) time algorithm for estimating all distances in a weighted undirected graph on n vertices with a stretch factor of at most 3.

Dor, D.; Halperin, S.; Zwick, U. [Tel Aviv Univ. (Israel)

1996-12-31

87

On the Shortest Path Game  

E-print Network

Sep 19, 2014 ... ?Andreas Darmann was supported by the Austrian Science Fund (FWF): [P .... der the additional restriction that the degree of every vertex is bounded by a ...... on Logic in Computer Science, LICS 2012, pages 205214, 2012.

2014-09-19

88

Cooperative optimal path planning for herding problems  

E-print Network

of herding as another part of the performance index. The performance index J can be expressed in this form: J = w1 ?tf +w2 ? Z tf 0 (_x2p + _y2p)dt (2.3) In the above expression, w1 and w2 are the weights for time optimal and efiort optimal respectively... (t0 = 0) are randomly cho- sen: [xe(t0);ye(t0)] = [3;4] , [xp(t0);yp(t0)] = [4;4:6]. The flnal constraint at tf is [xe(tf);ye(tf)] = [0;0]. C. Dynamic Programming (SNOPT) Once the 1P1E herding problem is formulated as an optimal control problem...

Lu, Zhenyu

2009-05-15

89

An Application of Calculus: Optimum Parabolic Path Problem  

ERIC Educational Resources Information Center

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

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

2009-01-01

90

Adleman[1] 1994 DNA Hamiltonian Path Problem , DNA  

E-print Network

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

91

Shortest trajectory planning of wheeled mobile robots with constraints  

Microsoft Academic Search

In this paper, we suggest a shortest trajectory planning algorithm for wheeled mobile robots with constraints; bounded curvature paths and moving forward only motion of robots; for example, aerial vehicles or moving forward car-like mobile robots. The main purpose of the paper is to find the optimal shortest path between a starting point and a goal point with constraints. Based

Joe W. Yeol; Y. S. Ryu; M. A. Montalvo

2005-01-01

92

Algorithms for an Unmanned Vehicle Path Planning Problem  

E-print Network

ALGORITHMS FOR AN UNMANNED VEHICLE PATH PLANNING PROBLEM A Thesis by JIANGLEI QIN 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... Chair of Committee, Sivakumar Rathinam Committee Members, Darbha Swaroop Bruce Wang Head of Department, Andreas A. Polycarpou August 2013 Major Subject: Mechanical Engineering Copyright 2013 Jianglei Qin ii ABSTRACT Unmanned...

Qin, Jianglei

2013-06-25

93

Prizing on Paths: A PTAS for the Highway Problem  

E-print Network

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

Grandoni, Fabrizio

2010-01-01

94

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

95

A general approximation technique for constrained forest problems  

Microsoft Academic Search

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

Michel X. Goemans; David P. Williamson

1992-01-01

96

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

97

Local Pruning for Information Dissemination in Dynamic Networks for Solving the Idempotent Semiring Algebraic Path Problem  

E-print Network

Local Pruning for Information Dissemination in Dynamic Networks for Solving the Idempotent Semiring routing in dynamic data networks, to solve the Semiring Algebraic Path Problem (SAPP) for dynamic graphs as instances of the Semiring Algebraic Path Problems (SAPPs) on graphs [19]. These include well known graph

Baras, John S.

98

Path integral and variation method in the band tail problem  

NASA Astrophysics Data System (ADS)

A one-dimensional random system represented by a tridiagonal random matrix with diagonal elements distributed independently in Gaussian fashion as proposed by Bulatov and Birman [Phys. Rev. B 54 (1996) 16 305] for the calculation of the density of states in the band tails is formulated in terms of Feynman path integrals. It is shown that in the asymptotic limits both the prefactor and the exponent give the correct energy dependence for the density of states. A precise comparison of the random matrix theory and the path integral approach is given.

Sa-yakanit, V.

1998-03-01

99

Interval Order Representation via Shortest Paths  

Microsoft Academic Search

Our goal in this paper is to illustrate how the representation theorems for finite interval orders and semiorders can be seen\\u000a as special instances of existence results for potentials in digraphs. This viewpoint yields short proofs of the representation\\u000a theorems and provides a framework for certain types of additional constraints on the intervals. We also use it to obtain a

Garth Isaak

100

Multicommodity flow problems with a bounded number of paths: A flow deviation approach  

Microsoft Academic Search

Abstract We propose a modified version of the Flow Deviation method of Fratta, Gerla and Kleinrock to solve multicommodity,problems,with minimal,congestion and a bounded,number,of active paths. We discuss the approximation,of the min-max objective function by a separable convex potential function and give a mixed-integer non linear model for the constrained routing problem. A heuristic control of the path generation is then

Christophe Duhamel; Philippe Mahey

2007-01-01

101

Fusion proteins as alternate crystallization paths to difficult structure problems  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

102

PATH  

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.

103

Constrained Graph Optimization: Interdiction and Preservation Problems  

SciTech Connect

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

Schild, Aaron V [Los Alamos National Laboratory

2012-07-30

104

Approximability of Dense and Sparse Instances of Minimum 2-Connectivity, TSP and Path Problems  

E-print Network

Approximability of Dense and Sparse Instances of Minimum 2-Connectivity, TSP and Path Problems B#19 in Arora et al. [3]. We characterize the approximability of all these problems by proving tight upper that were left open from the approximability point of view, in the paper of Arora et al. [3] (see also [13

Krysta, Piotr

105

Approximability of Dense and Sparse Instances of Minimum 2-Connectivity, TSP and Path Problems  

E-print Network

Approximability of Dense and Sparse Instances of Minimum 2-Connectivity, TSP and Path Problems B#19 in Arora et al. [3]. We characterize the approximability of all these problems by proving tight upper the approximability point of view, in the pa- per of Arora et al. [3] (see also [14]). In this paper Arora et al. show

Karpinski, Marek

106

Near-Optimal Hardness Results and Approximation Algorithms for Edge-Disjoint Paths and Related Problems  

E-print Network

-disjoint paths, hardness of approximation, multicommodity ow, network routing, unsplittable ow, vertex for the directed graph case; we omit de#12;ning their standard restrictions to the undirected case. Multicommodity Flow Problems: In multicommodity problems, we are given a directed graph G = (V; A) and a set T of k

Shepherd, Bruce

107

A General Approximation Technique for Constrained Forest Problems  

Microsoft Academic Search

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

Michel X. Goemans; David P. Williamson

1995-01-01

108

A novel algorithm for solving optimal path planning problems based on parametrization method and fuzzy aggregation  

NASA Astrophysics Data System (ADS)

In this Letter a new approach for solving optimal path planning problems for a single rigid and free moving object in a two and three dimensional space in the presence of stationary or moving obstacles is presented. In this approach the path planning problems have some incompatible objectives such as the length of path that must be minimized, the distance between the path and obstacles that must be maximized and etc., then a multi-objective dynamic optimization problem (MODOP) is achieved. Considering the imprecise nature of decision maker's (DM) judgment, these multiple objectives are viewed as fuzzy variables. By determining intervals for the values of these fuzzy variables, flexible monotonic decreasing or increasing membership functions are determined as the degrees of satisfaction of these fuzzy variables on their intervals. Then, the optimal path planning policy is searched by maximizing the aggregated fuzzy decision values, resulting in a fuzzy multi-objective dynamic optimization problem (FMODOP). Using a suitable t-norm, the FMODOP is converted into a non-linear dynamic optimization problem (NLDOP). By using parametrization method and some calculations, the NLDOP is converted into the sequence of conventional non-linear programming problems (NLPP). It is proved that the solution of this sequence of the NLPPs tends to a Pareto optimal solution which, among other Pareto optimal solutions, has the best satisfaction of DM for the MODOP. Finally, the above procedure as a novel algorithm integrating parametrization method and fuzzy aggregation to solve the MODOP is proposed. Efficiency of our approach is confirmed by some numerical examples.

Zamirian, M.; Kamyad, A. V.; Farahi, M. H.

2009-09-01

109

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

ERIC Educational Resources Information Center

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

Stevens, Ronald H.

1991-01-01

110

A Path-following Method for Solving BMI Problems in Arash Hassibi1  

E-print Network

A Path-following Method for Solving BMI Problems in Control Arash Hassibi1 Jonathan How Stephen (BMI) prob- lems in control. The method is to linearize the BMI using a first order perturbation (BMI), linear matrix in- equality (LMI), semidefinite programming (SDP), robust control, low

111

A path-following method for solving BMI problems in control  

Microsoft Academic Search

We present a path-following (homotopy) method for (locally) solving bilinear matrix inequality (BMI) problems in control. The method is to linearize the BMI using a first order perturbation approximation, and then iteratively compute a perturbation that slightly improves the controller performance by solving a semidefinite program. This process is repeated until the desired performance is achieved, or the performance cannot

Arash Hassibi; Stephen Boyd

1999-01-01

112

Restoration by Path Concatenation: Fast Recovery of MPLS Paths  

E-print Network

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

Kaplan, Haim

113

Restoration by Path Concatenation: Fast Recovery of MPLS Paths  

E-print Network

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

Bremler-Barr, Anat

114

Home-delivered Problem Adaptation Therapy (PATH) for Depressed, Cognitively Impaired, Disabled Elders: A Preliminary Study  

PubMed Central

Objectives This preliminary study examines the efficacy of 12-week home-delivered Problem Adaptation Therapy (PATH) vs. home-delivered Supportive Therapy (ST) in reducing depression and disability in 30 depressed, cognitively impaired, disabled older adults. Design A 12-week randomized clinical trial. Research assistants were unaware of the participants' randomization status. Assessments were conducted at baseline, 6 and 12 weeks. Setting Weill Cornell - Advanced Center for Interventions and Services Research (ACISR). Participants Thirty elders with major depression, cognitive impairment, and disability were recruited through advertisement and the Home-Delivered Meals Program of the Westchester County Department of Senior Programs and Services. Intervention PATH is a home-delivered intervention designed to reduce depression and disability in depressed, cognitively impaired, disabled elders. PATH is based on Problem Solving Therapy (PST) and integrates environmental adaptation and caregiver participation. PATH is consistent with Lawton's ecological model of adaptive functioning in aging. Measurements Depression and disability were measured with Hamilton Depression Rating Scale 24 items and Sheehan Disability Scale, respectively. Client Satisfaction Questionnaire was used to assess patient satisfaction with treatment. Results Mixed-effects model analyses revealed that PATH was more efficacious than ST in reducing depression and disability at 12 weeks. Participants in both treatment groups were satisfied with treatment. Conclusions This preliminary study suggests that PATH is well accepted and efficacious in depressed elders with major depression, cognitive impairment, and disability. Because this population may not adequately respond to antidepressant medication treatment, PATH may provide relief to many patients who would otherwise remain depressed and suffer. PMID:20808092

Kiosses, Dimitris N.; Arean, Patricia A.; Teri, Linda; Alexopoulos, George S.

2010-01-01

115

Nonequilibrium problems in quantum field theory and Schwinger`s closed time path formalism  

SciTech Connect

We review the closed time path formalism of Schwinger using a path integral approach. We apply this formalism to the study of pair production from strong external fields as well as the time evolution of a nonequilibrium chiral phase transition. In 1961 in his classic paper ``Brownian Motion of a Quantum Particle,`` Schwinger solved the formidable technical problem of how to use the action principle to study initial value problems. Previously, the action principle was formulated to study only transition matrix elements from an earlier time to a later time. The elegant solution of this problem was the invention of the closed time path (CTP) formalism. This formalism was first used to study field theory problems by Mahanthappa and Bakshi. With the advent of supercomputers, it has now become possible to use this formalism to numerically solve important field theory questions which are presented as initial value problems. Two of these problems we shall review here. They are (1) The time evolution of the quark- gluon plasma. (2) Dynamical evolution of a non-equilibrium chiral phase transition following a relativistic heavy ion collision.

Cooper, F.

1995-05-01

116

Short paths in expander graphs  

SciTech Connect

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

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

1996-12-31

117

Hard water problems and soft water paths: The "supply versus demand" conundrum  

NASA Astrophysics Data System (ADS)

Water problems are complex, interdisciplinary, and have profound effects on human and ecosystem health and well-being. And they are classic "hard" problems. Good science is necessary to solve these problems, but it is rarely sufficient. One of these hard problems is that of "perception" and "frame" - traditional water planners and managers frame freshwater as a "supply" problem, i.e., how can we access and deliver sufficient quantities of water of suitable quality, to satisfy perceived demand. In recent years, however, as water scarcity in different regions has increased due to growing populations and expanding economies, "peak water" limits (including peak renewable, non-renewable, and ecological limits) have started to constrain development of traditional "supply" options (Figure 1). That has led to new thinking about the other side of the equation: what is meant by water "demand" and can demand management tools and approaches offer a way to solve water problems. The "soft path for water" addresses this issue of water demand directly, but implementing demand-side solutions faces serious barriers. This talk will expound on the soft path approach and its potential to overcome some of the gridlock and stagnation in current water policy debates, with examples from both developed and developing countries, and different economic sectors.umulative global reservoir storage (major reservoirs) from 1900 to 2010, showing leveling off of traditional supply expansion. Data from the GRanD database.

Gleick, P. H.

2012-12-01

118

Faster and Simpler Algorithms for Multicommodity Flow and Other Fractional Packing Problems  

Microsoft Academic Search

This paper considers the problem of designing fast, approx- imate, combinatorial algorithms for multicommodity flows and other fractional packing problems. We provide a dif- ferent approach to these problems which yields faster and much simpler algorithms. Our approach also allows us to substitute shortest path computations for min-cost flow computations in computing maximum concurrent flow and min-cost multicommodity flow; this

Naveen Garg; Jochen Knemann

1998-01-01

119

Role of Self-Efficacy and Self-Concept Beliefs in Mathematical Problem Solving: A Path Analysis  

Microsoft Academic Search

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

Frank Pajares; M. David Miller

1994-01-01

120

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

Microsoft Academic Search

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

Frank Pajares; M. David Miller

1994-01-01

121

The Aquarium Keeper's Problem* Jurek Czyzowiczt Peter Egyed$ Hazel EvereW  

E-print Network

Chapter 51 The Aquarium Keeper's Problem* Jurek Czyzowiczt Peter Egyed$ Hazel EvereW David (Aquarium Z{eeper's Tour). For convex polygons, we present a linear-time algorithm which uses the reflection for the shortest closed path inside a simple polygon (Aquarium Keeper's Tour) which visits every edge at least once

Urrutia, Jorge

122

Scalable Shortest Paths Browsing on Land Surface Songhua Xing  

E-print Network

University of Southern California Los Angeles, CA 90089-0781 sxing@usc.edu Cyrus Shahabi Computer Science Department University of Southern California Los Angeles, CA 90089-0781 shahabi@usc.edu ABSTRACT The growing.g., earthquakes in mountainous regions), military operations, environment protection, tourism applications

Shahabi, Cyrus

123

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

E-print Network

Previous Work. Because ... The most common resources considered are such things as vehicle capacity, time windows, and maximum ... Outline. One typical setting in which an algorithm for the ESPPRC is required is the solution of the capac-.

2011-03-15

124

Fast shortest path distance estimation in large networks  

E-print Network

@cs.bu.edu Francesco Bonchi Yahoo! Research, Barcelona bonchi@yahoo-inc.com Carlos Castillo Yahoo! Research, Barcelona chato@yahoo-inc.com Aristides Gionis Yahoo! Research, Barcelona gionis@yahoo-inc.com ABSTRACT We study while the first author was vis- iting Yahoo! Research Barcelona, under the Yahoo! intern- ship program

125

Fast shortest path distance estimation in large networks  

E-print Network

@cs.bu.edu Francesco Bonchi Yahoo! Research, Barcelona bonchi@yahoo­inc.com Carlos Castillo Yahoo! Research, Barcelona chato@yahoo­inc.com Aristides Gionis Yahoo! Research, Barcelona gionis@yahoo­inc.com ABSTRACT We study was done while the first author was vis­ iting Yahoo! Research Barcelona, under the Yahoo! intern­ ship

126

Integer programming formulations for the elementary shortest path ...  

E-print Network

In order to compare MCF and GCS, we need to project out also the q-variables of the MCF formulation. ..... imum throughput network routing subject to fair flow allocation,. ISCO, Lecture Notes in Computer Science, vol. 8596, Springer, 2014,.

2014-09-26

127

Shortest Path Computation with No Information Leakage Kyriakos Mouratidis  

E-print Network

systems and the diffusion of smart-phones has led to an expanding market of location-based services (LBSs example of a leading mobile device company, which had been tracking the locations of its clients without S that includes s and a number of fake source locations. Similarly, it sends to the LBS a set of candidate

Yiu, Man Lung

128

Methodology for Augmenting Existing Paths with Additional Parallel Transects  

SciTech Connect

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

Wilson, John E.

2013-09-30

129

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

SciTech Connect

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

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

2012-06-15

130

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

NASA Astrophysics Data System (ADS)

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

Haouat, S.; Chetouani, L.

2012-06-01

131

Searching in an unknown environment: an optimal randomized algorithm for the cow-path problem  

Microsoft Academic Search

Searching for a goal is a central and extensively studied problem in computer science. Inclassical searching problems, the cost of a search function is simply the number of queries madeto an oracle that knows the position of the goal. In many robotics problems, as well as inproblems from other areas, we want to charge a cost proportional to the distance

Ming-Yang Kao; John H. Reif; Stephen R. Tate

1993-01-01

132

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

Microsoft Academic Search

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

Rainer E. Burkard; Jakob Krarup

1998-01-01

133

The longest shortest piercing. B. Kawohl & V. Kurta.  

E-print Network

The longest shortest piercing. B. Kawohl & V. Kurta. December 8, 2010 Abstract: We generalize shortest piercing. Mathematics Subject Classification (2010). 52A40 Keywords. starshaped rearrangement, geometric inequality, bisector, piercing 1 Motivation and Result Let be a measurable (possibly unbounded

Kawohl, Bernd

134

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

Microsoft Academic Search

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

Christos G. Panayiotou; Christos G. Cassandras

1999-01-01

135

Extracting optimal paths from roadmaps for motion planning  

Microsoft Academic Search

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

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

2003-01-01

136

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

PubMed Central

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

2014-01-01

137

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

PubMed

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

Wilson, Helen W; Widom, Cathy Spatz

2010-01-01

138

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

PubMed Central

Behaviors beginning in childhood or adolescence may mediate the relationship between childhood maltreatment and involvement in prostitution. This paper examines five potential mediators: early sexual initiation, running away, juvenile crime, school problems, and early drug use. Using a prospective cohort design, abused and neglected children (ages 011) with cases processed during 19671971 were matched with non-abused, non-neglected children and followed into young adulthood. Data are from in-person interviews at approximate age 29 and arrest records through 1994. Structural Equation Modeling tested path models. Results indicated that victims of child abuse and neglect were at increased risk for all problem behaviors, except drug use. In the full model, only early sexual initiation remained significant as a mediator in the pathway from child abuse and neglect to prostitution. Findings were generally consistent for physical and sexual abuse and neglect. These findings suggest that interventions to reduce problem behaviors among maltreated children may also reduce their risk for prostitution later in life. PMID:20186260

Wilson, Helen W.; Widom, Cathy Spatz

2009-01-01

139

Information Spread of Emergency Events: Path Searching on Social Networks  

PubMed Central

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

Hu, Hongzhi; Wu, Tunan

2014-01-01

140

Discrete Approximations to Continuous Shortest-Path: Application to Minimum-Risk Path Planning for  

E-print Network

in complex 3D environments · probability of radar acquisition depends on UAVs attitude · "safe-space" is very probability of UAV being acquired by radar on an elementary time interval dt: acquisition density function engagement zone engagement zone changes significantly with the attitude of the UAV with respect to the radar

Hespanha, João Pedro

141

Random generation of structured linear optimization problems  

SciTech Connect

We describe the on-going development of a random generator for linear optimization problems (LPs) founded on the concept of block structure. The general LP: minimize z = cx subject to Ax = b, x {ge} 0 can take a variety of special forms determined (primarily) by predefined structures on the matrix A of constraint coefficients. The authors have developed several random problem generators which provide instances of LPs having such structure; in particular (i) general (non-structured) problems, (ii) generalized upper bound (GUB) constraints, (iii) minimum cost network flow problems, (iv) transportation and assignment problems, (v) shortest path problems, (vi) generalized network flow problems, and (vii) multicommodity network flow problems. This paper discusses the general philosophy behind the construction of these generators. In addition, the task of combining the generators into a single generator -- in which the matrix A can contain various blocks, each of a prescribed structure from those mentioned above -- is described.

Arthur, J.; Frendewey, J. Jr.

1994-12-31

142

A GRASP with path-relinking heuristic for the survivable IP/MPLS-over-WSON multi-layer network optimization problem  

E-print Network

adaptive search procedure (GRASP) Path-relinking (PR) Biased random-key genetic algorithm (BRKGA) a b s t r (MPLS)-over- wavelength switched optical network (WSON) multi-layer network optimization problem (SIMNO time, ensuring the highest availability of services and minimizing the capital expenditures (CAPEX

Politècnica de Catalunya, Universitat

143

Optimal paths for a car that goes both forwards and backwards  

Microsoft Academic Search

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

J. A. Reeds; L. A. Shepp

1990-01-01

144

Faster and Simpler Algorithms for Multicommodity Flow and other Fractional Packing Problems  

Microsoft Academic Search

Abstract This paper considers the problem of designing fast, approximate, combinatorial algorithms for multicommodity flows and other fractional packing problems. We provide a different approach,to these problems,which yields faster and much,simpler algorithms. Our approach,also allows us to substitute shortest path computations,for min-cost flow computations,in computing,maximum,concurrent flow and min-cost multicommodity,flow; this yields much,faster algorithms when the number,of commodities,is large.

N. Garg

1997-01-01

145

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

NASA Astrophysics Data System (ADS)

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

Mohanty, Prases K.; Parhi, Dayal R.

2014-12-01

146

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

NASA Astrophysics Data System (ADS)

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

Mohanty, Prases K.; Parhi, Dayal R.

2014-08-01

147

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

E-print Network

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

Alexander Biryukov; Mark Shleenkov

2014-07-15

148

Time calibration of a PT-path from the Western Tauern Window, Eastern Alps: the problem of closure temperatures  

Microsoft Academic Search

New Hornblende K-Ar and 39Ar-40Ar and mica Rb-Sr and K-Ar ages are used to place specific timemarks on a well-constrained pressure-temperature path for the late Alpine metamorphism in the Western Tauern Window. After identification of excess 40Ar, the closure behavior of Ar in hornblende is compared with that of Sr and Ar in phengite and biotite. Samples were collected in

F. Blanckenburg; I. M. Villa; H. Baur; G. Morteani; R. H. Steiger

1989-01-01

149

Computing the Length of the Shortest Telomere in the Nucleus  

NASA Astrophysics Data System (ADS)

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

Dao Duc, K.; Holcman, D.

2013-11-01

150

Path Integrals in Quantum Mechanics  

Microsoft Academic Search

Jean Zinn-Justin's textbook Path Integrals in Quantum Mechanics aims to familiarize the reader with the path integral as a calculational tool in quantum mechanics and field theory. The emphasis is on quantum statistical mechanics, starting with the partition function Tr exp(-? H) and proceeding through the diffusion equation to barrier penetration problems and their semiclassical limit. The 'real time' path

J Louko

2005-01-01

151

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

ERIC Educational Resources Information Center

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

Wilson, Helen W.; Widom, Cathy Spatz

2010-01-01

152

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

153

Fracturing the optimal paths.  

PubMed

Optimal paths play a fundamental role in numerous physical applications ranging from random polymers to brittle fracture, from the flow through porous media to information propagation. Here for the first time we explore the path that is activated once this optimal path fails and what happens when this new path also fails and so on, until the system is completely disconnected. In fact many applications can also be found for this novel fracture problem. In the limit of strong disorder, our results show that all the cracks are located on a single self-similar connected line of fractal dimension D(b) approximately = 1.22. For weak disorder, the number of cracks spreads all over the entire network before global connectivity is lost. Strikingly, the disconnecting path (backbone) is, however, completely independent on the disorder. PMID:20366106

Andrade, J S; Oliveira, E A; Moreira, A A; Herrmann, H J

2009-11-27

154

A new approach to the maximum flow problem  

Microsoft Academic Search

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

Andrew V. Goldberg; Robert Endre Tarjan

1986-01-01

155

Mobile transporter path planning  

NASA Technical Reports Server (NTRS)

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

Baffes, Paul; Wang, Lui

1990-01-01

156

Solving nonlinear multicommodity flow problems with the analytic center cutting plane method  

SciTech Connect

A talk deals with nonlinear multicommodity flow problems with convex costs. A decomposition method is proposed to solve them. The approach applies a potential reduction algorithm to (approximately) solve the master problem and a column generation technique defining a sequence of primal linear programming problems. Each subproblem consists in finding a minimum cost flow between an origin and a destination node on an uncapacited network. It is thus formulated as a shortest path problem and it is solved with the Dijkstra`s d-heap algorithm. An experimental implementation is described that takes full advantage of the supersparsity of the network in the linear algebra operations. Computational results show high efficiency of the approach on (known from the literature) nondifferentiable problems, real-life large scale France Telecom problem and other large scale randomly generated problems (sized up to 1000 arcs and 4000 commodities).

Goffin, J.L.; Gondzio, J.; Sarkissian, R.; Vial, J.P.

1994-12-31

157

Tornado Paths  

NSDL National Science Digital Library

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

Samson, Perry; Michigan, University O.

158

Do People Use the Shortest Path? Empirical Test of Wardrop's First  

E-print Network

maximization #12;Motivation: I-35W Bridge Collapse MnPASS Program #12;Data Collection #12;Traffic-35W Mississippi River Bridge Collapse, Transportation Research Part A: Policy and Practice, 44DOT, Metropolitan Consortium BRIDGE: Behavioral Response to the I-35W Disruption: Gauging Equilibration (National

Levinson, David M.

159

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

ERIC Educational Resources Information Center

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

Fazlollahtabar, Hamed

2008-01-01

160

Genetic regulatory networks established by shortest path algorithm and conditional probabilities for ovarian carcinoma microarray data  

Microsoft Academic Search

In the cancer research recently, it still doesn't have a definitive conclusion for the regulatory mechanisms of tumorigenesis and metastasis. But different genes have different biological functions, and these functions with interactions between genes play an important key in gene regulatory networks. Microarray is a tool most commonly used in the disease research, and scientists usually use that the feature

Meng-Hsiun Tsai; Hsiao-Han Ko; Sheng-Chuan Chiu

2010-01-01

161

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

E-print Network

mobility concepts has come in sharp focus. Applying new traffic concepts to the real world can be veryStreetMap database yielding simulation re- sults based on real-world transportation data. · dynamic creation to be acquired. Therefore, multiagent-based simulation (MABS) can be used to procure well-founded assess- ments

162

Approximating shortest paths in arrangements of lines Prosenjit Bose William Evans David Kirkpatrick  

E-print Network

1: (a) An arrangement of lines with cell Cell(st) in bold, (b) cross lines with critical lines arrangement: the arrangement A without the cross lines and including all lines that contain s or t. A cell is an endpoint of a cell edge; it is an upper cell vertex if it is above the line st and is a lower cell vertex

Bose, Prosenjit

163

Approximating shortest paths in arrangements of lines Prosenjit Bose William Evans David Kirkpatrick  

E-print Network

) An arrangement of lines, (b) cross lines with critical lines ` + and ` \\Gamma , and (c) cell Cell(st). Definition vertex is an endpoint of a cell edge; it is an upper cell vertex if it is above the line st and is a lower cell vertex if it is below the line st; vertices s and t are both upper and lower cell vertices

Evans, Will

164

An exact algorithm for the capacitated shortest spanning arborescence  

Microsoft Academic Search

We are given a complete and loop-free digraphG=(V, A), whereV={1,...,n} is the vertex set,A={(i, j) :i, j ?V} the arc set, andr ?V is a distinguishedroot vertex. For each arc (i, j) ?A, letcij be the associatedcost, and for each vertexi, letqi?0 be the associateddemand (withqr=0). Moreover, a nonnegativebranch capacity, Q, is defined.A Capacitated Shortest Spanning Arborescence rooted at r

Paolo Toth; Daniele Vigo

1995-01-01

165

Convergent Duality for the Traveling Salesman Problem  

E-print Network

A constructive method is presented for optimizing exactly the Traveling Salesman Problem as a sequence of shortest route problems. The method combines group theoretic and Lagrangean relaxation constructions. Key Words: ...

Shapiro, Jeremy F., 1939-

166

Representing the nominal path for an interior libration point orbit in the Sun-Earth+Moon elliptic restricted three-body problem  

NASA Astrophysics Data System (ADS)

Bounded nominal paths can be constructed in the vicinity of the interior equilibrium point (sometimes called a libration or Lagrange point) for the Sun-Earth+Moon Elliptic Restricted Three-Body Problem. Numerical integration is used to generate the periodic or quasi-periodic reference trajectories in this effort. The output of the routine will be numerical values for each of the six states (three position and three velocity) at each of the integration time steps. Linearization of both the equations of motion and of the equations representing the tracking solution assumes access to a continuous representation of the spacecraft's orbit. Follow-on research that investigates tracking errors or station-keeping costs may also need a continuous (and smooth) representation of the six states or, at least, may need access to an interpolation routine. Consequently, this work explores the generation of curves through the numerical data representing the libration point orbits in the Sun-Earth+Moon ER3BP; these orbits are computed in the vicinity of the interior libration point between the Sun and the Earth+Moon barycenter.

Gordon, Steven C.

1991-09-01

167

Path Pascal  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

168

Trees, paths and avalanches on random networks  

NASA Astrophysics Data System (ADS)

The investigation of equilibrium and non-equilibrium processes in disordered systems and particularly the relation between them is a complex problem that deserves attention. We concentrate on analyzing several relations of this type and appropriate numerical solutions. Invasion percolation (IP) model was motivated by the problem of fluid displacement in disordered media but in principle it could be applied to any invasion process which evolves along the minimum resistance path. Finding the invasion paths is a global optimization problem where the front advances by occupying the least resistant bond. Once the invasion is finished, the union of all the invasion paths on the lattice forms a minimum energy spanning tree (MST). We show that the geometry of a MST on random graphs is universal. Due to this geometric universality, we are able to characterize the energy of this optimal tree for any type of disorder using a scaling distribution found using uniform disorder. Therefore we expect the hopping transport in random media to have universal behavior. Kinetic interfaces is an important branch of statistical mechanics, fueled by application such as fluid-fluid displacement, imbibition in porous media, flame fronts, tumors, etc. These processes can be unified via Kardar-Parisi-Zhang (KPZ) equation, which is mapped exactly to an equilibrium problem (DPRM). We are able to characterize both using Dijkstra's algorithm, which is known to generate shortest path tree in a random network. We found that while obtaining the polymers the algorithm develops a KPZ type interface. We have extracted the interface exponents for both 2d square lattice and 3 d cubic lattice, being in agreement with previously recorded results for KPZ. The IP and KPZ classes are known to be very different: while the first one generates a distinct self-similar (fractal) interface, the second one has a self-similar invasion front. Though they are different we are able to construct a generalized algorithm that interpolates between these two universality classes. We discuss the relationship with the IP, the directed polymer in a random media; and the implications for the broader issue of universality in disordered systems. Random Field Ising Model (RFIM) is one of the most important models of phase transitions in disordered systems. We present exact results for the critical behavior of the RFIM on complete graphs and trees, both at equilibrium and away from equilibrium, i.e., models for hysteresis and Barkhausen noise. We show that for stretched exponential and powerlaw distributions of random fields the behavior on complete graphs is non-universal, while the behavior on Cayley trees is universal even in the limit of large coordination. Until recently, the evolution of WWW, Internet, etc., was thought to be highly complex. The model proposed by Barabasi and Albert shows that such networks can be modeled with the help of "preferential attachment", i.e. a highly connected vertex has a higher chance to get further links compared with a weakly connected vertex. We find that the random network constructed from a self-organized critical mechanism, (IP), falls in the same class without imposing any "preferential" growth rule. The network obtained has a connectivity exponent gamma ? 2.45, close to the WWW outgoing-links exponent.

Dobrin, Radu

169

Media Streaming With Network Diversity Research indicates opportunities for improving media quality, in networks like the Internet with multiple paths, but also poses new coding, scheduling, routing, and path-computation problems  

Microsoft Academic Search

Today's packet networks including the Internet offer an intrinsic diversity for media distribution in terms of available network paths and servers or information sources. Novel communication infrastructures such as ad hoc or wireless mesh networks use network diversity to extend their reach at low cost. Diversity can bring interesting benefits in supporting resource greedy applications such as media streaming services,

Pascal Frossard; Juan Carlos de Martin; M. Reha Civanlar

170

Data Generation for Path Testing  

Microsoft Academic Search

We present two stochastic search algorithms for generating test cases that execute specified paths in a program. The two algorithms are: a simulated annealing algorithm (SA), and a genetic algorithm (GA). These algorithms are based on an optimization formulation of the path testing problem which include both integer- and real-value test cases. We empirically compare the SA and GA algorithms

Nashat Mansour; Miran Salame

2004-01-01

171

Dispersion of nonlinear group velocity determines shortest envelope solitons  

SciTech Connect

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

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

2011-10-15

172

The Travelling Salesman Problem  

NSDL National Science Digital Library

The Traveling Salesman Problem is one of the most intensively studied problems in computational mathematics. These pages are devoted to the history, applications, and current research of this challenge of finding the shortest route visiting each member of a collection of locations and returning to your starting point.

Cook, William

173

Complexity analysis of pipeline mapping problems in distributed heterogeneous networks  

SciTech Connect

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

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

2009-04-01

174

Bicriteria network design problems  

SciTech Connect

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

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

1994-12-31

175

Multi-objective stochastic path planning  

E-print Network

The present research formulates the path planning as an optimization problem with multiple objectives and stochastic edge parameters. The first section introduces different variants of the PP problem and discusses existing solutions to the problem...

Dasgupta, Sumantra

2009-05-15

176

Test data generation and feasible path analysis  

Microsoft Academic Search

This paper describes techniques used by Test Specifica- tion and Determination Tool (TSDT), an experimental prototype for analysis and testing of critical applica- tions written in Ada. Two problems dominate structural testing of programs: exponential explosion in the num- ber of execution paths and feasible path determination, A path is feasible if there exists some input that will cause the

Robert Jasper; Mike Brennan; Keith E. Williamson; Bill Currier; David Zimmerman

1994-01-01

177

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

E-print Network

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

Goodrich, Michael A.

178

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

Microsoft Academic Search

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

Salim Hima; Yasmina Bestaoui

179

Term Paths  

NSDL National Science Digital Library

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

Cynthia Ann Radle (McCullough High School REV)

1995-06-30

180

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

E-print Network

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

Fitelson, Branden

181

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

E-print Network

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

Stamp, Mark

182

Minimum-Risk Path Finding by an Adaptive Amoebal Network  

NASA Astrophysics Data System (ADS)

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

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

2007-08-01

183

Analyzing methods for path mining with applications in metabolomics.  

PubMed

Metabolomics is one of the key approaches of systems biology that consists of studying biochemical networks having a set of metabolites, enzymes, reactions and their interactions. As biological networks are very complex in nature, proper techniques and models need to be chosen for their better understanding and interpretation. One of the useful strategies in this regard is using path mining strategies and graph-theoretical approaches that help in building hypothetical models and perform quantitative analysis. Furthermore, they also contribute to analyzing topological parameters in metabolome networks. Path mining techniques can be based on grammars, keys, patterns and indexing. Moreover, they can also be used for modeling metabolome networks, finding structural similarities between metabolites, in-silico metabolic engineering, shortest path estimation and for various graph-based analysis. In this manuscript, we have highlighted some core and applied areas of path-mining for modeling and analysis of metabolic networks. PMID:24230973

Tagore, Somnath; Chowdhury, Nirmalya; De, Rajat K

2014-01-25

184

Trajectory Generation and Path Planning for Autonomous Aerobots  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

185

Finding Regular Simple Paths in Graph Databases  

Microsoft Academic Search

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

Alberto O. Mendelzon; Peter T. Wood

1989-01-01

186

Identification of Biochemical Network Modules Based on Shortest Retroactive Distances  

PubMed Central

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

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

2011-01-01

187

The shortest modulation period Blazhko RR Lyrae star: SS Cnc  

E-print Network

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

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

2006-03-20

188

PATHS groundwater hydrologic model  

SciTech Connect

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

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

1980-04-01

189

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

Microsoft Academic Search

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

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

2005-01-01

190

Lagrangian relaxation method for testing the infeasibility of certain VLSI routing problems. II. Efficient reduction of planar networks for solving certain combinatorial problems  

SciTech Connect

An important VLSI technique that recognizes the infeasibility of routing two-terminal nets in graphs is presented. The method is based on a novel Lagrangian relaxation of the general vertex disjoint paths problem. Positive empirical results obtained from difficult problems found in both the literature and in industry strongly support the usefulness of this method. An O(absolute value of V/sup 2/) time, O(absolute value of V) space algorithm that reduces a two terminal, undirected, planar graph to a single edge is presented. The algorithm employs series and parallel reductions and delta-wave transformations. These reductions and transformations are known to preserve optimality for the shortest path and maximum flow measures, yielding O(absolute value of V/sup 2/) time algorithms for both these problems on two terminal, undirected, planar networks. Important applications to the multicommodity flows problem and the two-terminal network reliability problem are also presented. Empirical evidence indicates that the O(absolute value V/sup 2/) worst case time bound might be improved as near linear time behavior has always been observed.

Feo, T.A.

1985-01-01

191

The Knigsberg Bridge Problem  

NSDL National Science Digital Library

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

2011-01-01

192

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

PubMed Central

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

2014-01-01

193

Uncharted Paths*  

PubMed Central

Wide variation between hospitals in the quality of critical care lead to many potentially avoidable deaths. Regionalization of critical care is a possible solution; regionalization has been implemented for trauma and neonatal intensive care, and it is under active discussion for medical and cardiac critical care. However, regionalization is only one possible approach to reorganizing critical care services. This commentary introduces the technique of network analysis as a framework for the following: (1) understanding how critically ill patients move between hospitals, (2) defining the roles hospitals play in regional care delivery, and (3) suggesting systematic improvements that may benefit population health. We examined transfers of critically ill Medicare patients in Connecticut in 2005 as a model system. We found that patients are systematically transferred to more capable hospitals. However, we find the standard distinction of hospitals into either secondary hospitals or tertiary hospitals poorly explains observed transfer patterns; instead, hospitals show a continuum of roles. We further examine the implications of the network pattern in a simulation of quarantine of a hospital to incoming transfers, as occurred during the severe acute respiratory syndrome epidemic. Network perspectives offer new ways to study systems to care for critically ill patients and provide additional tools for addressing pragmatic problems in triage and bed management, regionalization, quality improvement, and disaster preparedness. PMID:19265091

Iwashyna, Theodore J.; Christie, Jason D.; Kahn, Jeremy M.; Asch, David A.

2009-01-01

194

Path Coupling and Aggregate Path Coupling  

E-print Network

In this survey paper, we describe and characterize an extension to the classical path coupling method applied statistical mechanical models, referred to as aggregate path coupling. In conjunction with large deviations estimates, we use this aggregate path coupling method to prove rapid mixing of Glauber dynamics for a large class of statistical mechanical models, including models that exhibit discontinuous phase transitions which have traditionally been more difficult to analyze rigorously. The parameter region for rapid mixing for the generalized Curie-Weiss-Potts model is derived as a new application of the aggregate path coupling method.

Kovchegov, Yevgeniy

2015-01-01

195

Application research of ground shortest path based on GIS in the Emergency Rescue Information Management System for airport airside  

Microsoft Academic Search

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

Chen Xin; Xiucheng Guo; Dongtao Fan

2011-01-01

196

Gas-path seal technology  

NASA Technical Reports Server (NTRS)

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

Zuk, J.

1976-01-01

197

Monte-Carlo Fork Search for Cooperative Path-Finding  

E-print Network

), a new algorithm that solves Cooperative Path-Finding (CPF) problems with simultaneity. The background in the built tree. This idea fits CPF problems in which the branching factor is too large for MCTS or A agents. 1 Introduction Cooperative pathfinding (CPF) addresses the problem of finding paths for a set

Bouzy, Bruno

198

Multiple Damage Progression Paths in Model-based Prognostics  

E-print Network

Multiple Damage Progression Paths in Model-based Prognostics Matthew Daigle University, each resulting in their own damage progression path, overlapping to contribute to the overall, in which the problem of charac- terizing multiple damage progression paths is cast as a joint state

Daigle, Matthew

199

Robot Path Planning in Uncertain Environments: A Language-Measure-  

E-print Network

Robot Path Planning in Uncertain Environments: A Language-Measure- Theoretic Approach Devesh K. Jha the problem of goal-directed robot path planning in the presence of uncertainties that are induced by bounded, probabilistic finite state automata 1 Motivation and Introduction In general, path planning of robots (e

Ray, Asok

200

An evolutionary approach for the selective pickup and delivery problem  

Microsoft Academic Search

The pickup and delivery problem addresses the real-world issues in logistic industry and establishes an important category of vehicle routing problems. The problem is to find the shortest route to collect and distribute objects under the assumption that the total supply and the total demand are in equilibrium. This study formulates a new problem, called the selective pickup and delivery

Xin-Lan Liao; Chuan-Kang Ting

2010-01-01

201

A global path planning approach for redundant manipulators  

NASA Technical Reports Server (NTRS)

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

Seereeram, Sanjeev; Wen, J.

1993-01-01

202

Path planning for UAVs  

Microsoft Academic Search

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

S. A. Bortoff; E. Hartford

2000-01-01

203

Breakdown of the Coherent State Path Integral: Two Simple Examples  

SciTech Connect

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

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

2011-03-18

204

Walden's Paths - Ensemble Edition  

NSDL National Science Digital Library

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

2011-01-04

205

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

NASA Technical Reports Server (NTRS)

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

Janich, Karl W.

2005-01-01

206

A path-following algorithm for missiles  

Microsoft Academic Search

The missile path-following problem has not been studied particularly as much as other vehicles. This fact is the source of our motivation behind this work. In this paper, a path-following algorithm, which is specifically designed for missiles but can be applied to other vehicles as well, is proposed. Presented algorithm is composed of a feedback and feed-forward control rule. Feedback

Gorkem Secer

2012-01-01

207

The shortest-graph method for calculation of the pair-correlation function in crystalline systems  

NASA Astrophysics Data System (ADS)

A new method for approximate calculation of the pair correlation function g(r) is proposed for crystalline systems of identical particles with isotropic interactions. The main idea of the method is to account for the relative delocalization of each node in g(r) by using only the shortest lattice graph between the given points, thus neglecting smaller contributions from other (non-shortest) graphs. By employing the Lennard-Jones and Yukawa crystalline systems as representative examples, it is shown that the proposed approach yields very good agreement with the results of molecular dynamics simulations up to the melting line. The approach can be useful in approximating the structure of simple crystals (in particular, of crystalline colloids and plasma crystals), and can also be generalized for systems with anisotropic interactions.

Yurchenko, Stanislav O.

2014-04-01

208

An attempt of microwave CT system which discriminates the transmission path by means of time domain measurement.  

PubMed

A microwave-based computed tomography system was developed based on a method that uses time domain measurement to determine the shortest path of propagation components between two antennas. The method calculates shortest path of propagation components by examining mixer output DC components, delivering similar precision as chirp-pulse microwave computed tomography. Because post-mixer signal processing need only concerns DC currents, the effects of overshoot characteristics of baseband filters and the like are removed, simplifying measurement. System circuit composition is also simplified, lowering system costs. This paper provides a theoretical framework for the method, an S-parameter verification of the theory, and an experimental verification using a basic hardware construction. Results showed a restored image from the measurement data, indicating the utility of the method for microwave imaging. PMID:22255201

Tamura, Mutsumi; Ogawa, Takahiro; Miyakawa, Michio

2011-01-01

209

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

NASA Technical Reports Server (NTRS)

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

Barker, L. Keith

1998-01-01

210

Advanced Physics: Path Integral  

NSDL National Science Digital Library

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

Christian, Wolfgang; Belloni, Mario

2006-01-19

211

The SunPath  

NSDL National Science Digital Library

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

University, Australian N.

212

On brittle fracture paths  

Microsoft Academic Search

Two classes of fracture are defined: I fracture path completely predictable, and II fracture path predictable only after initial random propagation. Class I fractures occur when there is a line of principal stress passing through the tip of the initiating notch or slit across which the stress is a maximum away from the tip. All Class II fractures

B. Cotterell

1965-01-01

213

Path integration in insects.  

PubMed

The most notable advance in our knowledge of path integration in insects is a new understanding of how the honeybee measures the distance that it travels during its foraging trips. Data from two groups show that the bee's odometer records distance in terms of the net amount of image motion over the retina that is accumulated during a flight. Progress has also been made in clarifying the relation between path integration and other navigational strategies. On unfamiliar ground, path integration is the only available means of navigation. In familiar surroundings, however, guidance by landmarks may override guidance by path integration. Path integration then becomes a back-up strategy that is used primarily when landmarks fail. PMID:11240286

Collett, T S; Collett, M

2000-12-01

214

Homotopy and Path Integrals  

E-print Network

This is an introductory review of the connection between homotopy theory and path integrals, mainly focus on works done by Schulman [23] that he compared path integral on SO(3) and its universal covering space SU(2), DeWitt and Laidlaw [15] that they proved the theorem to the case of path integrals on the multiply-connected topological spaces. Also, we discuss the application of the theorem in Aharonov-Bohm effect given by [20,24]. An informal introduction to homotopy theory is provided for readers who are not familiar with the theory.

Fumika Suzuki

2011-08-31

215

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

E-print Network

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

Lin, G.C.

216

Follow the Paths  

NSDL National Science Digital Library

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

217

Twins: The Two Shortest Period Non-Interacting Double Degenerate White Dwarf Stars  

Microsoft Academic Search

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

F. Mullally; Carles Badenes; Susan E. Thompson; Robert Lupton

2009-01-01

218

Path Integration in Desert Ants, Cataglyphis fortis  

Microsoft Academic Search

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

Martin Muller; Rudiger Wehner

1988-01-01

219

A modified reconfigurable data path processor  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

220

Path Planning Algorithms for Multiple Heterogeneous Vehicles  

E-print Network

: : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 30 viii LIST OF FIGURES FIGURE Page 1 Example solution of PCATSP : : : : : : : : : : : : : : : : : : : : : : 12 2 Example solutions of Hamiltonian path problem : : : : : : : : : : : : 15 3 Edge subset in an infeasible solution... : : : : : : : : : : : : : : : : : : 17 4 "W" set in an infeasible solution : : : : : : : : : : : : : : : : : : : : 17 5 Edges dictating the "W" cut : : : : : : : : : : : : : : : : : : : : : : 18 6 LP feasible solution : : : : : : : : : : : : : : : : : : : : : : : : : : : 20 7 Remove...

Oberlin, Paul V.

2010-01-16

221

Applications of Path Compression on Balanced Trees  

Microsoft Academic Search

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

Robert Endre Tarjan

1979-01-01

222

On the Optimal Path Length for Tor Kevin Bauer1  

E-print Network

On the Optimal Path Length for Tor Kevin Bauer1 , Joshua Juen2 , Nikita Borisov2 , Dirk Grunwald1 that optimally balances security and performance is an open problem. Tor's design decision to build paths frequently involve achieving a correct balance between security and performance. For example, Tor does

Borisov, Nikita

223

Link prediction and path analysis using Markov chains  

Microsoft Academic Search

The enormous growth in the number of documents in the World Wide Web increases the need for improved link navigation and path analysis models. Link prediction and path analysis are important problems with a wide range of applications ranging from personalization to Web server request prediction. The sheer size of the World Wide Web coupled with the variation in users'

Ramesh R. Sarukkai

2000-01-01

224

Algorithms for Computing QoS Paths with Restoration  

E-print Network

1 Algorithms for Computing QoS Paths with Restoration Yigal Bejerano, Yuri Breitbart, Member, IEEE and the restoration topology should be a major consideration of the routing process. We undertake a comprehensive study of problems related to finding suitable restoration topologies for QoS paths. We consider both

Sprintson, Alexander

225

Toward Efficient Trajectory Planning: The Path-Velocity Decomposition  

Microsoft Academic Search

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

Kamal Kant; Steven W. Zucker

1986-01-01

226

Mission Path Following for an Autonomous Unmanned Airship  

Microsoft Academic Search

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

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

2000-01-01

227

VISCOSITY SOLUTIONS OF FULLY NONLINEAR ELLIPTIC PATH DEPENDENT PDES  

E-print Network

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

Paris-Sud XI, Université de

228

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

NASA Astrophysics Data System (ADS)

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

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

1987-11-01

229

Simple Wriggling is Hard unless You Are a Fat Hippo  

E-print Network

Simple Wriggling is Hard unless You Are a Fat Hippo Irina Kostitsyna Valentin Polishchuk Abstract to the problem is to inflate the obstacles by half the path width, and search for the shortest s-t path amidst the inflated obstacles [9]. The found path, when inflated, is the shortest thick s-t path. It went almost

230

Path planning for everday robotics with SANDROS  

SciTech Connect

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

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

1997-02-01

231

Stochastic Evolutionary Algorithms for Planning Robot Paths  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

232

Asymptotically optimal path planning and surface reconstruction for inspection  

E-print Network

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

Papadopoulos, Georgios

2014-01-01

233

An Unplanned Path  

ERIC Educational Resources Information Center

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

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

2013-01-01

234

DNA Computing Hamiltonian path  

E-print Network

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

Hagiya, Masami

235

Path to the Profession  

ERIC Educational Resources Information Center

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

Coleman, Toni

2012-01-01

236

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

ERIC Educational Resources Information Center

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

Guerrieri, Bruno

237

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

Microsoft Academic Search

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

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

2001-01-01

238

TWINS: THE TWO SHORTEST PERIOD NON-INTERACTING DOUBLE DEGENERATE WHITE DWARF STARS  

SciTech Connect

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.

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

239

Path-Planning with Obstacle-Avoiding Minimum Curvature Variation B-splines  

Microsoft Academic Search

Abstract We study the general problem of computing an obstacle-avoiding path that, for a prescribed weight, minimizes the weighted sum of a smoothness measure and a safety measure of the path. We consider planar curvaturecontinuous paths, that are functions on an interval of a room axis, for a point-size vehicle amidst obstacles. The obstacles are two disjoint continuous functions on

Tomas Berglund

240

Edge-Disjoint Paths in Planar Graphs with Constant Congestion Chandra Chekuri  

E-print Network

the number of demands that can be connected (routed) by edge-disjoint paths. The natural multicommodity flow, and Multicommodity Flow In this paper we study the edge-disjoint path problem (EDP) in undirected graphs. We (multicommodity flow) or we may require that the whole demand be routed on a single path (unsplittable flow

Shepherd, Bruce

241

SOCIAL PATH FOLLOWING Carmine Oliva  

E-print Network

of path following; each agent is now able to avoid static and dynamic obstacles along its path, to predict a specific profile for each agent, our system can also show how different stereotypes of people act in those

Karlsson, Brynjar

242

Helmholtz Path Integrals  

NASA Astrophysics Data System (ADS)

The multidimensional, scalar Helmholtz equation of mathematical physics is addressed. Rather than pursuing traditional approaches for the representation and computation of the fundamental solution, path integral representations, originating in quantum physics, are considered. Constructions focusing on the global, two-way nature of the Helmholtz equation, such as the Feynman/Fradkin, Feynman/Garrod, and Feynman/DeWitt-Morette representations, are reviewed, in addition to the complementary phase space constructions based on the exact, well-posed, one-way reformulation of the Helmholtz equation. Exact, Feynman/Kac, stochastic representations are also briefly addressed. These complementary path integral approaches provide an effective means of highlighting the underlying physics in the solution representation, and, subsequently, exploiting this more transparent structure in natural computational algorithms.

Fishman, Louis

2006-05-01

243

Lander flight path analysis  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

244

ON THE INTEGRALITY OF THE UNCAPACITATED FACILITY ...  

E-print Network

Key words and phrases. uncapacitated facility location problem, odd cycle ...... and extend the labels adding each time a path to the graph Gl. The two ..... In order to reduce this to a shortest path problem several graph transformation are.

245

Algorithms and Sensors for Small Robot Path Following  

NASA Technical Reports Server (NTRS)

Tracked mobile robots in the 20 kg size class are under development for applications in urban reconnaissance. For efficient deployment, it is desirable for teams of robots to be able to automatically execute path following behaviors, with one or more followers tracking the path taken by a leader. The key challenges to enabling such a capability are (l) to develop sensor packages for such small robots that can accurately determine the path of the leader and (2) to develop path following algorithms for the subsequent robots. To date, we have integrated gyros, accelerometers, compass/inclinometers, odometry, and differential GPS into an effective sensing package. This paper describes the sensor package, sensor processing algorithm, and path tracking algorithm we have developed for the leader/follower problem in small robots and shows the result of performance characterization of the system. We also document pragmatic lessons learned about design, construction, and electromagnetic interference issues particular to the performance of state sensors on small robots.

Hogg, Robert W.; Rankin, Arturo L.; Roumeliotis, Stergios I.; McHenry, Michael C.; Helmick, Daniel M.; Bergh, Charles F.; Matthies, Larry

2002-01-01

246

Parallel Traveling Salesman Problem  

NSDL National Science Digital Library

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

Joiner, David; Hassinger, Jonathan

247

Pick-a-Path  

NSDL National Science Digital Library

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

2012-01-01

248

The California PATH Database  

NSDL National Science Digital Library

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

1997-01-01

249

Portage and Path Dependence*  

PubMed Central

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

Bleakley, Hoyt; Lin, Jeffrey

2012-01-01

250

JAVA PathFinder  

NASA Technical Reports Server (NTRS)

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

Mehhtz, Peter

2005-01-01

251

Quad-rotor flight path energy optimization  

NASA Astrophysics Data System (ADS)

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

Kemper, Edward

252

Theory Comput Syst DOI 10.1007/s00224-007-9096-4  

E-print Network

for Shortest Paths and Non-Linear Objectives with Applications George Tsaggouris · Christos Zaroliagis for obtaining FPTAS to any multiobjective optimization problem with non-linear objectives. We show how · FPTAS · Non-linear objectives · Multiple constrained (optimal) path · Non-additive shortest path · Qos

Zaroliagis, Christos D.

253

Nonlinear regularization path for quadratic loss support vector machines.  

PubMed

Regularization path algorithms have been proposed to deal with model selection problem in several machine learning approaches. These algorithms allow computation of the entire path of solutions for every value of regularization parameter using the fact that their solution paths have piecewise linear form. In this paper, we extend the applicability of regularization path algorithm to a class of learning machines that have quadratic loss and quadratic penalty term. This class contains several important learning machines such as squared hinge loss support vector machine (SVM) and modified Huber loss SVM. We first show that the solution paths of this class of learning machines have piecewise nonlinear form, and piecewise segments between two breakpoints are characterized by a class of rational functions. Then we develop an algorithm that can efficiently follow the piecewise nonlinear path by solving these rational equations. To solve these rational equations, we use rational approximation technique with quadratic convergence rate, and thus, our algorithm can follow the nonlinear path much more precisely than existing approaches such as predictor-corrector type nonlinear-path approximation. We show the algorithm performance on some artificial and real data sets. PMID:21880570

Karasuyama, Masayuki; Takeuchi, Ichiro

2011-10-01

254

Crossing-Optimal Acyclic Hamiltonian Path Completion and Its Application to Upward Topological Book Embeddings  

Microsoft Academic Search

Given an embedded planar acyclic digraph G, we define the problem of acyclic hamiltonian path completion with crossing minimization (Acyclic-HPCCM) to be the problem of determining a hamiltonian path completion set of edges such that, when these edges are embedded on G, they create the smallest possible number of edge crossings and turn G to an acyclic hamiltonian digraph. Our

Tamara Mchedlidze; Antonios Symvonis

2009-01-01

255

Multiflow and disjoint paths of minimum total cost  

SciTech Connect

We discuss some earlier and recent results in the field of combinatorial network flow theory, considering problems on minimum cost maximum value multiflows (multicommodity flows), minimum cost maximum cardinality sets of edge-disjoint or openly disjoint paths, and related problems. Multiflows (multicommodity flows), minimum cost maximum cardinality sets of edge-disjoint or openly disjoint paths, and related problems. Throughout we deal with the undirected case. We exactly characterize the set of commodity graphs H for which, given an arbitrary network with nonnegative integer-valued capacities and costs, there exists an optimal multiflow f such that the denominator of each component of the vector f is bounded by a constant depending only on H. Moreover, for these H`s there are purely combinatorial polynomial time algorithms for finding such optimal solutions. Another, more complicated, problem is: given a graph G, a subset T of its vertices and a nonnegative function of cost on its edges, find a maximum cardinality set of pairwise edge-disjoint T-paths (i.e., paths in G connecting arbitrary pairs in T) such that the sum of costs of edges occurring in these paths is as small as possible. We give a minimax relation for this problem and develop a strongly polynomial algorithm to solve it. In fact, the former result generalizes the minimax relation involving the maximum number of edge-disjoint T-paths that has been established by Mader and, independently, Lomonosov. As a consequence, one can derive a description of the dominant polyhedron for the set of T,d-joins (a generalization of T-joins) and the dominant polyhedron for the set of so-called multi-joins of a graph. Finally, we present a minimax relation that concerns minimum cost maximum cardinality sets of pairwise openly disjoint T-paths, thus extending another result of Mader. The proof gives rise to a strongly polynomial solution algorithm.

Karzanov, A.

1994-12-31

256

Student Behaviour Outcomes: Choosing Appropriate Paths. Selected Papers from the National Conference on Behaviour Management and Behaviour Change of Children and Youth with Emotional and/or Behaviour Problems (7th, Newcastle, New South Wales, Australia, 1995).  

ERIC Educational Resources Information Center

Twelve papers produced at an annual convention were selected for inclusion in this work on behavior management and behavior change in Australian children and youth with emotional and/or behavior problems. The papers are: (1) Developing Personal Strengths, Choosing More Effective Behaviours: Control Theory, Reality Therapy and Quality Management

Conway, Robert, Ed.; Izard, John, Ed.

257

Decision paths in complex tasks  

NASA Technical Reports Server (NTRS)

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

Galanter, Eugene

1991-01-01

258

A path planning method for human tracking agents using variable-term prediction based on dynamic k-nearest neighbor algorithm  

Microsoft Academic Search

This paper deals with a multi-agent path plan- ning problem for tracking humans in order to obtain detail information such like human behavior and characteristics. To achieve this, paths of agents are planned based on similarity between the predicted positions of humans and agents' field of views, and the path length in the path planning is determined according to the

Noriko Takemura; Yutaka Nakamura; Hiroshi Ishiguro

2011-01-01

259

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

NASA Astrophysics Data System (ADS)

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

Schlindwein, W.; Baptista, R.

2014-10-01

260

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

261

SDSS J0926+3624: the shortest period eclipsing binary star  

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

262

CS130N Problem set 4: BST and height balancing February 19, 2001  

E-print Network

such that the black heights of the resulting Red-Black trees are 2, 3 and 4. 5. Suppose that root of a Red-Black tree is red. If we make it black, does the tree remain a Red-Black tree? 6. Show that the longest simple path from a node x in a Red-Black tree to a descendant leaf has length at most twice that of the shortest

Banerjee, Subhashis

263

The flow-refueling location problem for alternative-fuel vehicles  

Microsoft Academic Search

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

Michael Kuby; Seow Lim

2005-01-01

264

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

PubMed Central

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

Jan, Shau Shiun; Lin, Yu Hsiang

2011-01-01

265

Outdoor visual path following experiments  

Microsoft Academic Search

In this paper the performance of a topological- metric visual path following framework is investigated in different environments. The framework relies on a monocular camera as the only sensing modality. The path is represented as a series of reference images such that each neighboring pair contains a number of common landmarks. Local 3D geometries are reconstructed between the neighboring reference

Albert Diosi; Anthony Remazeilles; Sinisa Segvic; Franois Chaumette

2007-01-01

266

Path integrals as discrete sums  

SciTech Connect

We present a new formulation of Feynman's path integral, based on Voronin's theorems on the universality of the Riemann zeta function. The result is a discrete sum over paths,'' each given by a zeta function. A new measure which leads to the correct quantum mechanics is explicitly given.

Bitar, K.; Khuri, N.N.; Ren, H.C. (Supercomputer Computations Research Institute, Florida State University, Tallahasee, Florida (USA) Department of Physics, The Rockefeller University, New York, New York (USA))

1991-08-12

267

Genetic-algorithm-based path optimization methodology for spatial decision  

NASA Astrophysics Data System (ADS)

In this paper, we proposed a method based on GA to solve the path-optimization problem. Unlike the traditional methods, it considers many other factors besides the road length including the task assignment and its balance, which are beyond the capability of path analysis and make this problem a Combinatorial Optimization problem. It can't be solved by a traditional graph-based algorithm. This paper proposes a new algorithm that integrates the Graph Algorithm and Genetic Algorithm together to solve this problem. The traditional Graph-Algorithm is responsible for preprocessing data and GA is responsible for the global optimization. The goal is to find the best combination of paths to meet the requirement of time, cost and the reasonable task assignment. The prototype of this problem is named the TSP (Traveling Salesman Problem) problem and known as NP-Hard Problem. However, we demonstrate how these problems are resolved by the GA without complicated programming, the result proves it's effective. The technique presented in this paper is helpful to those GIS developer working on an intelligent system to provide more effective decision-making.

Yu, Liang; Bian, Fuling

2006-10-01

268

DOI: 10.1007/s10288-005-0066-x 4OR 3: 315328 (2005)  

E-print Network

be modelled as robust shortest path problems on digraphs with interval costs, where intervals represent network is usually represented as a weighted digraph, where each arc is associated with a road and costs modelled as a weighted digraph and costs are associated with transmission delays, a shortest path problem

Gambardella, Luca Maria

269

Reconfigurable data path processor  

NASA Technical Reports Server (NTRS)

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

Donohoe, Gregory (Inventor)

2005-01-01

270

British Pathe Newsreels Online  

NSDL National Science Digital Library

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

2002-01-01

271

PCB drill path optimization by combinatorial cuckoo search algorithm.  

PubMed

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

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

2014-01-01

272

PCB Drill Path Optimization by Combinatorial Cuckoo Search Algorithm  

PubMed Central

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

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

2014-01-01

273

An expert path through a thermo maze  

NSDL National Science Digital Library

Several studies in recent years have demonstrated that upper-division students struggle with partial derivatives and the complicated chain rules ubiquitous in thermodynamics. We asked several experts (primarily faculty who teach thermodynamics) to solve a challenging and novel thermodynamics problem in order to understand how they navigate through this maze. What we found was a tremendous variety in solution strategies and sense-making tools, both within and between individuals. This case study focuses on one particular expert: his solution paths, use of sense-making tools, and comparison of different approaches.

Kustusch, Mary B.; Roundy, David J.; Dray, Tevian; Manogue, Corinne

2014-02-01

274

Predicting link directions using local directed path  

NASA Astrophysics Data System (ADS)

Link prediction in directed network is attracting growing interest among many network scientists. Compared with predicting the existence of a link, determining its direction is more complicated. In this paper, we propose an efficient solution named Local Directed Path to predict link direction. By adding an extra ground node to the network, we solve the information loss problem in sparse network, which makes our method effective and robust. As a quasi-local method, our method can deal with large-scale networks in a reasonable time. Empirical analysis on real networks shows that our method can correctly predict link directions, which outperforms some local and global methods.

Wang, Xiaojie; Zhang, Xue; Zhao, Chengli; Xie, Zheng; Zhang, Shengjun; Yi, Dongyun

2015-02-01

275

Scanning path optimization for ultrasound surgery  

NASA Astrophysics Data System (ADS)

One of the problems in ultrasound surgery is the long treatment times when large tumour volumes are sonicated. Large tumours are usually treated by scanning the tumour volume using a sequence of individual focus points. During the scanning, it is possible that surrounding healthy tissue suffers from undesired temperature rise. The selection of the scanning path so that the tumour volume is treated as fast as possible while temperature rise in healthy tissue is minimized would increase the efficiency of ultrasound surgery. The main purpose of this paper is to develop a computationally efficient method which optimizes the scanning path. The optimization algorithm is based on the minimum time formulation of the optimal control theory. The developed algorithm uses quadratic cost criteria to obtain the desired thermal dose in the tumour region. The derived method is evaluated with numerical simulations in 3D which are applied to ultrasound surgery of the breast in simplified geometry. Results from the simulations show that the treatment time as well as the total applied energy can be decreased from 16% to 43% as compared to standard sonication. The robustness of the optimized scanning path is studied by varying the perfusion and absorption in the tumour region.

Malinen, Matti; Huttunen, Tomi; Kaipio, Jari P.; Hynynen, Kullervo

2005-08-01

276

One-dimensional Gromov minimal filling problem  

NASA Astrophysics Data System (ADS)

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

Ivanov, Alexandr O.; Tuzhilin, Alexey A.

2012-05-01

277

One-dimensional Gromov minimal filling problem  

SciTech Connect

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

Ivanov, Alexandr O; Tuzhilin, Alexey A

2012-05-31

278

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

E-print Network

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

Mousavi, Mohammad

279

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

E-print Network

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

Mousavi, Mohammad

280

Heuristically optimal path scanning for high-speed multiphoton circuit imaging  

PubMed Central

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

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

2011-01-01

281

Heuristically optimal path scanning for high-speed multiphoton circuit imaging.  

PubMed

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

Sadovsky, Alexander J; Kruskal, Peter B; Kimmel, Joseph M; Ostmeyer, Jared; Neubauer, Florian B; MacLean, Jason N

2011-09-01

282

A Bat Algorithm with Mutation for UCAV Path Planning  

PubMed Central

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

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

2012-01-01

283

A bat algorithm with mutation for UCAV path planning.  

PubMed

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

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

2012-01-01

284

Restricted Delivery Problems on a Network Esther M. Arkin y , Refael Hassin z and Limor Klein x  

E-print Network

Restricted Delivery Problems on a Network Esther M. Arkin y , Refael Hassin z and Limor Klein x December 17, 1996 Abstract We consider a delivery problem on a network one is given a network in which asks for a shortest delivery route of all products from their origin to their destination. Here we

Arkin, Estie

285

Length-constrained Path-matchings in Graphs M. Ghodsi , M.T. Hajiaghayi y , M. Mahdian y , and V.S. Mirrokni y  

E-print Network

-matching in G covering S is a collection C of paths in G, such that every vertex of S is an endpoint of exactly-disjoint, or edge-disjoint, if the collection of paths has this property. The path-matching problem is to #12;nd (if by the paths, and the weight of the paths in weighted graphs can also be considered (see Cohen et al. [1

Hajiaghayi, Mohammad

286

Partnership for Advancing Technologies in Housing (PATH)  

NSF Publications Database

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

287

COMPUTER SCIENCE: MISCONCEPTIONS, CAREER PATHS  

E-print Network

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

Hristidis, Vagelis

288

Morse theory in path space  

E-print Network

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

Yong Seung Cho; Soon-Tae Hong

2007-06-01

289

Collaborative Authoring of Walden's Paths  

E-print Network

of educators, the authoring tool allows educators to collaboratively build a Walden's Path by filtering and organizing web pages into an ordered linear structure for the common information needs, which can be extended, tailored and modified into a derivative...

Li, Yuanling

2012-10-19

290

Scattering theory with path integrals  

SciTech Connect

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

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

2014-03-15

291

Quantum Mechanics: Sum Over Paths  

NSDL National Science Digital Library

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.

Taylor, Edwin F.

2009-05-26

292

Supercomputer Architectures: The Path to Tera/PetaFLOPS  

E-print Network

Supercomputer Architectures: The Path to Tera/PetaFLOPS Stephen Jenks Electrical Engineering Lab 4 Outline Why Supercomputing Matters Current Top Systems Future Architectures Asymmetric Systems Lab 5 Why Supercomputing? Some Problems Larger Than Single Computer Can Process Memory Space (>> 4

Shinozuka, Masanobu

293

Path Integral Monte-Carlo Calculations for Relativistic Oscillator  

E-print Network

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

Alexandr Ivanov; Oleg Pavlovsky

2014-11-11

294

Irrelevant Vertices for the Planar Disjoint Paths Problema Isolde Adlerb  

E-print Network

properties of planar graphs. Keywords: Graph Minors, Treewidth, Disjoint Paths Problem a Emails: Isolde Adler, National and Kapodistrian University of Athens, Athens, Greece. j AlGCo project-team, CNRS, LIRMM, France. 1 Tight Bounds for Linkages in Planar Graphs. 38th International Colloquium on Automata, Languages

Dimitrios, Thilikos

295

Time-Optimal Control of Robotic Manipulators Along Specified Paths  

Microsoft Academic Search

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

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

1985-01-01

296

Mobile robot path tracking using a robust PID controller  

Microsoft Academic Search

This paper presents a simple and effective solution for the path tracking problem of a mobile robot using a PID controller. The proposed method uses a simple linearized model of the mobile robot composed of an integrator and a delay. The synthesis procedure is simple and allows the PID controller to be tuned considering the nominal performance and the robustness

Julio E. Normey-Rico; Ismael Alcal; Juan Gmez-Ortega; Eduardo F. Camacho

2001-01-01

297

Optimal capacity placement for path restoration in mesh survivable networks  

Microsoft Academic Search

The total capacity required by a transport network to satisfy demand and protect it from failures contributes significantly to its cost. Previously the spare capacity of a network with a given set of working span sizes has been optimized to facilitate span restoration. Path restorable networks can, however, be even more efficient by defining the restoration problem from an end

R. R. Iraschko; M. H. MacGregor; W. D. Grover

1996-01-01

298

Regularization Paths for Generalized Linear Models via Coordinate Descent  

Microsoft Academic Search

We develop fast algorithms for estimation of generalized linear mod- els with convex penalties. The models include linear regression, two- class logistic regression, and multinomial regression problems while the penalties include '1 (the lasso), '2 (ridge regression) and mixtures of the two (the elastic net). The algorithms use cyclical coordinate de- scent, computed along a regularization path. The methods can

Jerome Friedman; Trevor Hastie; Rob Tibshirani

2008-01-01

299

Cooperative path planning and navigation based on distributed sensing  

Microsoft Academic Search

In this paper, path planning for robots of distributed autonomous robotic system (DARS) in unknown or partially known environment is described based on the distributed sensing. We believe that the basic problem of optimality for motion planning and replanning in unknown or partially known environment is related to the environmental information sensed by robot. Particularly the key to enhance the

Anhui CAI; Toshio FUKUDA; Fumihito ARAI; Hidenori ISHIHARA

1996-01-01

300

Bounding the Number of Light Paths for Robust LSP Routing  

Microsoft Academic Search

Summary form only given. We consider a routing problem where we want to minimize the maximal relative congestion on the arcs of the network with a bounded number of paths. This problem is relevant in the context of MPLS core networks where one looks for a compromise between higher QoS and fewer splitting of the point-to-point connections. We consider modelling

P. Makey; J. Truffot

2006-01-01

301

Cooperative path planning for multiple UAVs in dynamic and uncertain environments  

Microsoft Academic Search

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

John S. Bellingham; Michael Tillerson; Mehdi Alighanbari

2002-01-01

302

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

E-print Network

mobile robots, path planning techniques have to simul- taneously solve two complementary tasks. On one systems. The existing methods for solving the problem of motion planning for multiple robots canAn Experimental Comparison of Path Planning Techniques for Teams of Mobile Robots Maren Bennewitz

Teschner, Matthias

303

Lookahead Pathology in Real-Time Path-Finding Vadim Bulitko (bulitko@ualberta.ca)  

E-print Network

Lookahead Pathology in Real-Time Path-Finding Vadim Bulitko (bulitko@ualberta.ca) University to produce better actions · Sometimes the opposite is true: pathology Setting · Path-finding in grid world of pathology: number of lookahead depths where error is larger than at the previous depth · 1,000 problems (map

Lu?trek, Mitja

304

Lookahead Pathology in Real-Time Path-Finding Mitja Lustrek (mitja.lustrek@ijs.si)  

E-print Network

Lookahead Pathology in Real-Time Path-Finding Mitja Lustrek (mitja.lustrek@ijs.si) Jozef Stefan to produce better actions · Sometimes the opposite is true: pathology Setting · Path-finding in grid world of pathology: number of lookahead depths where error is larger than at the previous depth · 1,000 problems (map

Lu?trek, Mitja

305

Artificial potential field based path planning for mobile robots using a virtual obstacle concept  

Microsoft Academic Search

The artificial potential field (APF) based path planning methods have a local minimum problem, which can trap mobile robots before reaching it's goal. In this study, a new concept using a virtual obstacle is proposed to escape local minimums occurred in local path planning. A virtual obstacle is located around local minimums to repel a mobile robot from local minimums.

Min Cheol Lee; Min Gyu Park

2003-01-01

306

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

E-print Network

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

307

INVESTIGATION OF THE PERFORMANCE OF EP-BAVP (EVOLUTIONARY PROGRAMMING FOR VIRTUAL PATH  

E-print Network

INVESTIGATION OF THE PERFORMANCE OF EP-BAVP (EVOLUTIONARY PROGRAMMING FOR VIRTUAL PATH BANDWIDTH investigate the usefulness of an evolutionary programming (EP) optimization algorithm for tackling the problem of Bandwidth Allocation for Virtual Paths (EP-BAVP). Results for two network topologies obtained with EP

Pitsillides, Andreas

308

Covert path planning in unknown environments with known or suspected sentry location  

Microsoft Academic Search

This paper describes an approach for solving a visibility-based covert path planning problem. It is an extension to our research on covert robotics which aims to create robots with the ability to achieve different covert navigation missions. A promising method is presented that allows a mobile robot in a complex, initially unknown environment to discover a path to a nominated

Mohamed Marzouqi; Ray A. Jarvis

2005-01-01

309

On hallucinated garden paths UC San Diego  

E-print Network

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

310

Path Integral Analysis of Arrival Times with a Complex Potential  

E-print Network

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

J. J. Halliwell

2008-01-28

311

Relationship between total quality management, critical paths, and outcomes management.  

PubMed

Total quality management (TQM), clinical paths, and outcomes management are high-profile strategies in today's health care environment. Each strategy is distinct, yet there are interrelationships among them. TQM supports a customer-focused organizational culture, providing tools and techniques to identify and solve problems. Clinical paths are tools for enhancing patient care coordination and for identifying system-wide and patient population specific issues. Outcomes management is an integrated system for measuring the results in patient populations over time. There is a recent shift in outcomes measurement towards expanding both the nature of the outcomes examined and the timeframes in which they are studied. PMID:8920370

Lynn, P A

1996-09-01

312

Journal of Computer and System Sciences 60, 1 12 (2000) On the Inapproximability of Disjoint Paths  

E-print Network

polylog n ], the integer multicommodity flow problem in directed graphs cannot be approximated within directed?undirected vertex?edge-disjoint paths, integer multicommodity flow, and minimum Steiner forest

Wang, Lusheng

313

Solving the Curriculum Sequencing Problem with DNA Computing Approach  

ERIC Educational Resources Information Center

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

Debbah, Amina; Ben Ali, Yamina Mohamed

2014-01-01

314

Multiple paths in complex tasks  

NASA Technical Reports Server (NTRS)

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

Galanter, Eugene; Wiegand, Thomas; Mark, Gloria

1987-01-01

315

Aircraft Engine Gas Path Diagnostic Methods: Public Benchmarking Results  

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

316

Tool Path Planning for 5Axis Flank Milling Based on Dynamic Programming Techniques  

Microsoft Academic Search

This paper proposes a novel computation method for tool path planning in 5-axis flank milling of ruled surfaces. This method\\u000a converts the path planning (a geometry problem) into a curve matching task (a mathematical programming problem). Discrete\\u000a dynamic programming techniques are applied to obtain the optimal matching with machining error as the objective function.\\u000a Each matching line corresponds to a

Ping-han Wu; Yu-wei Li; Chih-hsing Chu

2008-01-01

317

Hierarchical path planning and control of a small fixed-wing UAV: Theory and experimental validation  

NASA Astrophysics Data System (ADS)

Recently there has been a tremendous growth of research emphasizing control of unmanned aerial vehicles (UAVs) either in isolation or in teams. As a matter of fact, UAVs increasingly find their way into military and law enforcement applications (e.g., reconnaissance, remote delivery of urgent equipment/material, resource assessment, environmental monitoring, battlefield monitoring, ordnance delivery, etc.). This trend will continue in the future, as UAVs are poised to replace the human-in-the-loop during dangerous missions. Civilian applications of UAVs are also envisioned such as crop dusting, geological surveying, search and rescue operations, etc. In this thesis we propose a new online multiresolution path planning algorithm for a small UAV with limited on-board computational resources. The proposed approach assumes that the UAV has detailed information of the environment and the obstacles only in its vicinity. Information about far-away obstacles is also available, albeit less accurately. The proposed algorithm uses the fast lifting wavelet transform (FLWT) to get a multiresolution cell decomposition of the environment, whose dimension is commensurate to the on-board computational resources. A topological graph representation of the multiresolution cell decomposition is constructed efficiently, directly from the approximation and detail wavelet coefficients. Dynamic path planning is sequentially executed for an optimal path using the A* algorithm over the resulting graph. The proposed path planning algorithm is implemented on-line on a small autopilot. Comparisons with the standard D*-lite algorithm are also presented. We also investigate the problem of generating a smooth, planar reference path from a discrete optimal path. Upon the optimal path being represented as a sequence of cells in square geometry, we derive a smooth B-spline path that is constrained inside a channel that is induced by the geometry of the cells. To this end, a constrained optimization problem is formulated by setting up geometric linear constraints as well as boundary conditions. Subsequently, we construct B-spline path templates by solving a set of distinct optimization problems. For application in UAV motion planning, the path templates are incorporated to replace parts of the entire path by the smooth B-spline paths. Each path segment is stitched together while preserving continuity to obtain a final smooth reference path to be used for path following control. The path following control for a small fixed-wing UAV to track the prescribed smooth reference path is also addressed. Assuming the UAV is equipped with an autopilot for low level control, we adopt a kinematic error model with respect to the moving Serret-Frenet frame attached to a path for tracking controller design. A kinematic path following control law that commands heading rate is presented. Backstepping is applied to derive the roll angle command by taking into account the approximate closed-loop roll dynamics. A parameter adaptation technique is employed to account for the inaccurate time constant of the closed-loop roll dynamics during actual implementation. Finally, we implement the proposed hierarchical path control of a small UAV on the actual hardware platform, which is based on an 1/5 scale R/C model airframe (Decathlon) and the autopilot hardware and software. Based on the hardware-in-the-loop (HIL) simulation environment, the proposed hierarchical path control algorithm has been validated through on-line, real-time implementation on a small micro-controller. By a seamless integration of the control algorithms for path planning, path smoothing, and path following, it has been demonstrated that the UAV equipped with a small autopilot having limited computational resources manages to accomplish the path control objective to reach the goal while avoiding obstacles with minimal human intervention.

Jung, Dongwon

2007-12-01

318

Transport path optimization algorithm based on fuzzy integrated weights  

NASA Astrophysics Data System (ADS)

Natural disasters cause significant damage to roads, making route selection a complicated logistical problem. To overcome this complexity, we present a method of using a trapezoidal fuzzy number to select the optimal transport path. Using the given trapezoidal fuzzy edge coefficients, we calculate a fuzzy integrated matrix, and incorporate the fuzzy multi-weights into fuzzy integrated weights. The optimal path is determined by taking two sets of vertices and transforming undiscovered vertices into discoverable ones. Our experimental results show that the model is highly accurate, and requires only a few measurement data to confirm the optimal path. The model provides an effective, feasible, and convenient method to obtain weights for different road sections, and can be applied to road planning in intelligent transportation systems.

Hou, Yuan-Da; Xu, Xiao-Hao

2014-11-01

319

Solving the broken link problem in Walden's Paths  

E-print Network

they experimented with include TF3DF2, TF4DF1 and TFIDF4DF1. For example, TFIDF4DF1 represents a signature consisting of 4 keywords selected making use of their TFIDFs and 1 keyword selected on the basis of its DF. These keywords were used... was created. This file contains a list of previously occurred phrases with their IDFs. Hence once a phrase has been isolated as a keyphrase and its IDF has been calculated, it is stored in the phraselist file for more efficient lookup...

Dalal, Zubin Jamshed

2004-09-30

320

Path-integral seismic imaging  

Microsoft Academic Search

A new type of seismic imaging, based on Feynman path integrals for waveform mod- elling, is capable of producing accurate subsurface images without any need for a reference velocity model. Instead of the usual optimization for traveltime curves with maximal signal semblance, a weighted summation over all representative curves avoids the need for velocity analysis, with its common difficulties of

E. Landa; S. Fomel; T. J. Moser

2006-01-01

321

Path integrals for potential scattering  

Microsoft Academic Search

Two path integral representations for the T matrix in nonrelativistic potential scattering are derived and proved to produce the complete Born series when expanded to all orders. They are obtained with the help of ``phantom'' degrees of freedom which take away explicit phases that diverge for asymptotic times. In addition, energy conservation is enforced by imposing a Faddeev-Popov-like constraint in

R. Rosenfelder

2009-01-01

322

Career Paths in Environmental Sciences  

EPA Science Inventory

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

323

Enzymatic reaction paths as determined by transition path sampling  

NASA Astrophysics Data System (ADS)

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

Masterson, Jean Emily

324

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

PubMed

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

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

2013-08-01

325

Path-average kernels for long wavelength traveltime tomography  

NASA Astrophysics Data System (ADS)

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

Mosca, I.; Trampert, J.

2009-05-01

326

Robust Path Planning and Feedback Design Under Stochastic Uncertainty  

NASA Technical Reports Server (NTRS)

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

Blackmore, Lars

2008-01-01

327

Path-Based Failure and Evolution Management  

Microsoft Academic Search

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 \\

Mike Y. Chen; Anthony Accardi; Emre Kiciman; David A. Patterson; Armando Fox; Eric A. Brewer

2004-01-01

328

Model for Delay Faults Based upon Paths  

Microsoft Academic Search

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

Gordon L. Smith

1985-01-01

329

Copper foil provides uniform heat sink path  

NASA Technical Reports Server (NTRS)

Thermal path prevents voids and discontinuities which make heat sinks in electronic equipment inefficient. The thermal path combines the high thermal conductivity of copper with the resiliency of silicone rubber.

Phillips, I. E., Jr.; Schreihans, F. A.

1966-01-01

330

On the Hardness of Subset Sum Problem from Different Intervals  

NASA Astrophysics Data System (ADS)

The subset sum problem, which is often called as the knapsack problem, is known as an NP-hard problem, and there are several cryptosystems based on the problem. Assuming an oracle for shortest vector problem of lattice, the low-density attack algorithm by Lagarias and Odlyzko and its variants solve the subset sum problem efficiently, when the density of the given problem is smaller than some threshold. When we define the density in the context of knapsack-type cryptosystems, weights are usually assumed to be chosen uniformly at random from the same interval. In this paper, we focus on general subset sum problems, where this assumption may not hold. We assume that weights are chosen from different intervals, and make analysis of the effect on the success probability of above algorithms both theoretically and experimentally. Possible application of our result in the context of knapsack cryptosystems is the security analysis when we reduce the data size of public keys.

Kogure, Jun; Kunihiro, Noboru; Yamamoto, Hirosuke

331

Path entanglement of surface plasmons  

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

332

Multiple Paths to Encephalization and Technical Civilizations  

NASA Astrophysics Data System (ADS)

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

Schwartzman, David; Middendorf, George

2011-12-01

333

Multiple paths to encephalization and technical civilizations.  

PubMed

We propose consideration of at least two possible evolutionary paths for the emergence of intelligent life with the potential for technical civilization. The first is the path via encephalization of homeothermic animals; the second is the path to swarm intelligence of so-called superorganisms, in particular the social insects. The path to each appears to be facilitated by environmental change: homeothermic animals by decreased climatic temperature and for swarm intelligence by increased oxygen levels. PMID:22139517

Schwartzman, David; Middendorf, George

2011-12-01

334

Working on interesting problems  

NASA Astrophysics Data System (ADS)

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

Smith, Arfon M.

2015-01-01

335

Integer Muticommodity Flow Problems  

Microsoft Academic Search

We present a column generation model and solution approach for large integer multicommodity flow problems. We solve the model using branch-and-bound, with bounds provided by linear programs at each node of the branch-and-bound tree. Since the model contains one variable for each origin-destination path, for every commodity, the linear programming relaxation is solved using column generation, i.e., implicit pricing of

Cynthia Barnhart; Christopher Ao Hane; Pamela H. Vance

1996-01-01

336

Obstacle Bypassing in Optimal Ship Routing Using Simulated Annealing  

SciTech Connect

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

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

2008-11-06

337

Squeezed states and path integrals  

NASA Technical Reports Server (NTRS)

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

Daubechies, Ingrid; Klauder, John R.

1992-01-01

338

Accelerating cleanup: Paths to closure  

SciTech Connect

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

Edwards, C.

1998-06-30

339

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

NASA Technical Reports Server (NTRS)

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

Li, Li; Warren, William H Jr

2004-01-01

340

Multiphoton Path Entanglement by Nonlocal Bunching  

Microsoft Academic Search

Multiphoton path entanglement is created without applying postselection, by manipulating the state of stimulated parametric down-conversion. A specific measurement on one of the two output spatial modes leads to the nonlocal bunching of the photons of the other mode, forming the desired multiphoton path entangled state. We present experimental results for the case of a heralded two-photon path entangled state

H. S. Eisenberg; J. F. Hodelin; G. Khoury; D. Bouwmeester

2005-01-01

341

Multilinear decomposition of human walking paths  

Microsoft Academic Search

In a previous work, the authors have shown how the Principal Components Analysis (PCA) of a set of human walking paths provides sufficient information to derive a linear human-like path generator based on examples. The present work aims to provide an analysis of human walking paths from the perspective of multilinear algebra, using the n-mode Singular Value Decomposition (SVD). This

Christian A. Ramirez; M. Castela?n; G. Arechavaleta

2010-01-01

342

SOME PROPERTIES OF PATH MEASURES CHRISTIAN LEONARD  

E-print Network

an unbounded measure. Indeed, its reversing measure is Lebesgue measure (or any of its positive multiple x Rn . Obviously, this path measure has the same unbounded mass as Lebesgue measure.SOME PROPERTIES OF PATH MEASURES CHRISTIAN L´EONARD Abstract. We call any measure on a path space

Paris-Sud XI, Université de

343

Evaluation of the Learning Path Specification  

ERIC Educational Resources Information Center

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

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

2011-01-01

344

Quantifying the Causes of Path Inflation  

Microsoft Academic Search

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

Neil Spring; Ratul Mahajan; Thomas Anderson

2003-01-01

345

A Discrete History of the Lorentzian Path Integral  

Microsoft Academic Search

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

Renate Loll

2003-01-01

346

Hypertext Paths and the World-Wide Web: Experiences with Walden's Paths  

Microsoft Academic Search

Walden's Paths applies the concept of hypertextual paths to the World-Wide Web. Walden's Paths is being developed for use in the K-12 school environment. The heterogene- ity of the Web coupled with the desirability of supporting the teacher-student relationship make this an interesting and challenging project. We describe the Walden's Paths imple- mentation, discuss ...

Richard Furuta; Frank M. Shipman III; Catherine C. Marshall; Donald Brenner; Hao-wei Hsieh

1997-01-01

347

Challenge in Flow Path Delineation and Modification: SECUREarth Initiative  

NASA Astrophysics Data System (ADS)

After decades of studies, our knowledge about subsurface flow paths has large uncertainty and our capability to enhance or reduce formation permeability is inefficient and rudimentary. This is the case for fossil energy production, in environment remediation, in greenhouse gas sequestration, in nuclear waste disposal, in geothermal heat extraction, and in groundwater management. Fluid imaging, in addition to rock structure imaging, is needed to enhance petroleum extraction, to isolate contaminant plumes, and to prevent leakage from storage reservoirs. Flow focusing from surface to depth must be quantified to determine the flow path magnitude and spacing in order to determine the degrees of dissolution and transport of emplaced wastes. These diverse problems have common goals: either to isolate or to enhance subsurface fluid movement. It is crucial to identify the common features from different problems and refocus our efforts to delineate and then to manipulate flow paths. Geochemical engineering and geomicrobiological engineering need to combine laboratory studies, field experiments, and modeling approaches to verify and validate our understanding and to design solutions. An initiative SECUREarth is being developed to rally the scientists and engineers from national laboratories, universities, and industry to address key critical bottlenecks that prevent significant progress in solving common subsurface issues. SECUREarth is aimed to develop cross-cutting, multi-disciplinary approaches for solving urgent energy and environment problems in the earth, in order to achieve quantum leaps and breakthroughs in earth science and technology.

Bodvarsson, G. S.; Majer, E. L.; Wang, J. S.; Colwell, F.; Redden, G.

2005-12-01

348

Pareto-path multitask multiple kernel learning.  

PubMed

A traditional and intuitively appealing Multitask Multiple Kernel Learning (MT-MKL) method is to optimize the sum (thus, the average) of objective functions with (partially) shared kernel function, which allows information sharing among the tasks. We point out that the obtained solution corresponds to a single point on the Pareto Front (PF) of a multiobjective optimization problem, which considers the concurrent optimization of all task objectives involved in the Multitask Learning (MTL) problem. Motivated by this last observation and arguing that the former approach is heuristic, we propose a novel support vector machine MT-MKL framework that considers an implicitly defined set of conic combinations of task objectives. We show that solving our framework produces solutions along a path on the aforementioned PF and that it subsumes the optimization of the average of objective functions as a special case. Using the algorithms we derived, we demonstrate through a series of experimental results that the framework is capable of achieving a better classification performance, when compared with other similar MTL approaches. PMID:25532155

Li, Cong; Georgiopoulos, Michael; Anagnostopoulos, Georgios C

2015-01-01

349

Timeless path integral for relativistic quantum mechanics  

NASA Astrophysics Data System (ADS)

Starting from the canonical formalism of relativistic (timeless) quantum mechanics, the formulation of a timeless path integral is rigorously derived. The transition amplitude is reformulated as the sum, or functional integral, over all possible paths in the constraint surface specified by the (relativistic) Hamiltonian constraint, and each path contributes with a phase identical to the classical action divided by ?. The timeless path integral manifests the timeless feature as it is completely independent of the parametrization for paths. For the special case that the Hamiltonian constraint is a quadratic polynomial in momenta, the transition amplitude admits the timeless Feynman's path integral over the (relativistic) configuration space. Meanwhile, the difference between relativistic quantum mechanics and conventional nonrelativistic (with time) quantum mechanics is elaborated on in light of the timeless path integral.

Chiou, Dah-Wei

2013-06-01

350

Continuous Path Tracking Control by Considering Voltage Saturation and Current Saturation for AC Servo Motor  

NASA Astrophysics Data System (ADS)

Continuous path tracking control is an important technology for the position control system such as factory automation field. Particulaly, large torque is required for continuous path tracking control at its start position and its goal position. Each AC servo motor of continuous path tracking control have limitation of current and voltage. Therefore, in controlling a multi-degree-of-freedom continuous path tracking control system, even if only the motor torque of one axis has the current limitation, the actual position response is not often equal to the desired trajectory reference. In order to overcome these problems, this paper proposes a new continuous path tracking control algorithm by considering both the saturation of voltage and current. The proposed method assures the coordinated motion by considering the saturation of voltage and current. The effectiveness of the proposed method is confirmed by the experimental results in this paper.

Sazawa, Masaki; Ohishi, Kiyoshi; Katsura, Seiichiro

351

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

NASA Technical Reports Server (NTRS)

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

Goldhirsh, J.

1978-01-01

352

Path Integration: Effect of Curved Path Complexity and Sensory System on Blindfolded Walking  

PubMed Central

Path integration refers to the ability to integrate continuous information of the direction and distance travelled by the system relative to the origin. Previous studies have investigated path integration through blindfolded walking along simple paths such as straight line and triangles. However, limited knowledge exists regarding the role of path complexity in path integration. Moreover, little is known about how information from different sensory input systems (like vision and proprioception) contributes to accurate path integration. The purpose of the current study was to investigate how sensory information and curved path complexity affect path integration. Forty blindfolded participants had to accurately reproduce a curved path and return to the origin. They were divided into four groups that differed in the curved path, circle (simple) or figure-eight (complex), and received either visual (previously seen) or proprioceptive (previously guided) information about the path before they reproduced it. The dependent variables used were average trajectory error, walking speed, and distance travelled. The results indicated that (a) both groups that walked on a circular path and both groups that received visual information produced greater accuracy in reproducing the path. Moreover, the performance of the group that received proprioceptive information and later walked on a figure-eight path was less accurate than their corresponding circular group. The groups that had the visual information also walked faster compared to the group that had proprioceptive information. Results of the current study highlight the roles of different sensory inputs while performing blindfolded walking for path integration. PMID:22840893

Koutakis, Panagiotis; Mukherjee, Mukul; Vallabhajosula, Srikant; Blanke, Daniel J.; Stergiou, Nicholas

2012-01-01

353

Regularization Paths for Generalized Linear Models via Coordinate Descent  

PubMed Central

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

Friedman, Jerome; Hastie, Trevor; Tibshirani, Rob

2010-01-01

354

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

PubMed

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

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

2011-04-01

355

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

PubMed Central

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

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

2011-01-01

356

Multiple order common path spectrometer  

NASA Technical Reports Server (NTRS)

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

Newbury, Amy B. (Inventor)

2010-01-01

357

Intellimotion: California PATH's Quarterly Newsletter  

NSDL National Science Digital Library

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

1998-01-01

358

Average Photon Path-Length in Isotropically Scattering Finite Atmospheres  

NASA Astrophysics Data System (ADS)

The determination of the average path-length of photons in a finite isotropically scattering plane-parallel homogeneous atmosphere is discussed. To solve this problem we have used the kernel approximation method which easily allows us to find the derivatives of the intensity with respect to optical depth, optical thickness and albedo of single scattering. In order to check the results we have used another approach by exploiting the set of integrodifferential equations of Chandrasekhar for theX- andY-functions. This approach allows us to find the average path length only at the boundaries of the atmosphere but on the other hand it gives also the dispersion of the path-length distribution function, thus generating the input parameters for determining the approximate path-length distribution function. It occurred that the set so obtained is stable and the results are highly accurate. As a by-product we obtain the first two derivatives of theX- andY-functions with respect to the albedo of single scattering and optical thickness, and the mixed derivative.

Viik, Tnu

1995-03-01

359

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

E-print Network

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

Luiz. C. L. Botelho

2009-02-23

360

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

E-print Network

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

Jepson, Allan D.

361

Flight path optimization passing through waypoints for autonomous flight control systems  

Microsoft Academic Search

Trajectory optimization is performed to generate a flight path passing specified waypoints. To deal with the unspecified time of passing through a waypoint, an auxiliary variable is introduced. Normalization of the time variable by the auxiliary variable transforms the waypoint optimization problem into the conventional optimization problem. The condition for passing through the waypoints can be relaxed, so that the

Gwanyoung Moon; Youdan Kim

2005-01-01

362

Mobile Manipulation: Collision-Free Path Modi cation and Motion Coordination  

E-print Network

to achieve real-time perfor- mance addresses the problem of planning for two cooperating robot arms [11 to higher- dimensional problems cannot preserve the real-time performance of these methods. In this paper weMobile Manipulation: Collision-Free Path Modi#12;cation and Motion Coordination Oliver Brock

Pratt, Vaughan

363

Robust Flight Path Determination for Mars Precision Landing Using Genetic Algorithms  

NASA Technical Reports Server (NTRS)

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

Bayard, David S.; Kohen, Hamid

1997-01-01

364

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

PubMed Central

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

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

2010-01-01

365

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

PubMed

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

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

2012-01-01

366

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

PubMed Central

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

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

2012-01-01

367

Optimum gradient of mountain paths.  

PubMed

By combining the experiment results of R. Margaria (Atti Accad. Naz. Lincei Memorie 7: 299-368, 1938), regarding the metabolic cost of gradient locomotion, together with recent insights on gait biomechanics, a prediction about the most economical gradient of mountain paths (approximately 25%) is obtained and interpreted. The pendulum-like mechanism of walking produces a waste of mechanical work against gravity within the gradient range of up to 15% (the overall efficiency is dominated by the low transmission efficiency), whereas for steeper values only the muscular efficiency is responsible for the (slight) metabolic change (per meter of vertical displacement) with respect to gradient. The speeds at the optimum gradient turned out to be approximately 0.65 m/s (+0.16 m/s vertical) and 1.50 m/s (-0.36 m/s vertical), for uphill and downhill walking, respectively, and the ascensional energy expenditure was 0.4 and 2.0 ml O2.kg body mass-1.vertical m-1 climbed or descended. When the metabolic power becomes a burden, as in high-altitude mountaineering, the optimum gradient should be reduced. A sample of real mountain path gradients, experimentally measured, mimics the obtained predictions. PMID:8594031

Minetti, A E

1995-11-01

368

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

PubMed

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

Banerjee, Rahul; Cukier, Robert I

2014-03-20

369

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

SciTech Connect

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

Kidd, M.E.C.

1996-07-01

370

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

SciTech Connect

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

Kidd, M.E.C.

1997-02-01

371

Substation automation problems and possibilities  

SciTech Connect

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

Smith, H.L.

1996-10-01

372

The shortest wavelength far-infrared laser line from CW CO2 laser pumped CH3OH and M-independent Stark splitting of laser lines  

Microsoft Academic Search

Methyl alcohol (CH3OH) molecules pumped with the 9R(16) CW CO2 laser line generate two new far-infrared laser lines at wavelengths of 33.4 and 36.4 mu m. The 33.4 mu m line has the shortest wavelength among the sub-mm lines reported so far from CH3OH and its isotopic species pumped with CW CO2 laser lines. Stark splitting is observed on the

N. Sokabe; T. Miyatake; Y. Nishi; A. Murai

1983-01-01

373

Real-Time Edge Follow: A Real-Time Path Search Approach  

Microsoft Academic Search

Real-time path search is the problem of searching a path from a starting point to a goal point in real-time. In dynamic and partially observable environments, agents need to observe the environment to track changes, explore to learn unknowns, and search suitable routes to reach the goal rapidly. These tasks fre- quently require real-time search. In this paper, we address

Cagatay Undeger; Faruk Polat

2007-01-01

374

Planning Smooth and Obstacle-Avoiding B-Spline Paths for Autonomous Mining Vehicles  

Microsoft Academic Search

We study the problem of automatic generation of smooth and obstacle-avoiding planar paths for efficient guidance of autonomous mining vehicles. Fast traversal of a path is of special interest. We consider fourwheel four-gear articulated vehicles and assume that we have an a priori knowledge of the mine wall environment in the form of polygonal chains. Computing quartic uniform B-spline curves,

Tomas Berglund; Andrej Brodnik; Hkan Jonsson; Mats Staffanson; Inge Sderkvist

2010-01-01

375

Collision-Free Path Planning for Mobile Robots Using Chaotic Particle Swarm Optimization  

Microsoft Academic Search

\\u000a Path planning for mobile robots is an important topic in modern robotics studies. This paper proposes a new approach to collision-free\\u000a path planning problem for mobile robots using the particle swarm optimization combined with chaos iterations. The particle\\u000a swarm optimization algorithm is run to get the global best particle as the candidate solution, and then local chaotic search\\u000a iterations are

Qiang Zhao; Shaoze Yan

2005-01-01

376

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

Microsoft Academic Search

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

David E. Kaufman; Robert L. Smith

1993-01-01

377

Open-Ended Math Problems  

NSDL National Science Digital Library

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

Math Forum

2000-01-01

378

Sequential Path Entanglement for Quantum Metrology  

PubMed Central

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

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

2013-01-01

379

Steam Path Audits on Industrial Steam Turbines  

E-print Network

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...

Mitchell, D. R.

380

Multiphoton Path Entanglement by Nonlocal Bunching  

NASA Astrophysics Data System (ADS)

Multiphoton path entanglement is created without applying postselection, by manipulating the state of stimulated parametric down-conversion. A specific measurement on one of the two output spatial modes leads to the nonlocal bunching of the photons of the other mode, forming the desired multiphoton path entangled state. We present experimental results for the case of a heralded two-photon path entangled state and show how to extend this scheme to higher photon numbers.

Eisenberg, H. S.; Hodelin, J. F.; Khoury, G.; Bouwmeester, D.

2005-03-01

381

Multiphoton Path Entanglement by Nonlocal Bunching  

Microsoft Academic Search

Multiphoton path entanglement is created without applying post-selection, by\\u000amanipulating the state of stimulated parametric down-conversion. A specific\\u000ameasurement on one of the two output spatial modes leads to the non-local\\u000abunching of the photons of the other mode, forming the desired multiphoton path\\u000aentangled state. We present experimental results for the case of a heralded\\u000atwo-photon path entangled state

H. S. Eisenberg; J. F. Hodelin; G. Khoury; D. Bouwmeester

2005-01-01

382

Multiphoton path entanglement by nonlocal bunching.  

PubMed

Multiphoton path entanglement is created without applying postselection, by manipulating the state of stimulated parametric down-conversion. A specific measurement on one of the two output spatial modes leads to the nonlocal bunching of the photons of the other mode, forming the desired multiphoton path entangled state. We present experimental results for the case of a heralded two-photon path entangled state and show how to extend this scheme to higher photon numbers. PMID:15783951

Eisenberg, H S; Hodelin, J F; Khoury, G; Bouwmeester, D

2005-03-11

383

Walden's Paths quiz: system design and implementation  

E-print Network

assessment io guide instruction, to provide fccdback to students, and to plan for further development ol the path or the Web pages included in the path. Cox and Junkin [13] discuss how instructors can use the results of an automatically evaluated test... Walden's Paths Quiz: System Design and Implementation. (December 2002) Avital Jayant Arora, B. E. , Universiiy of Bombay Chair of Advisory Committee: Dr. Richard Furuta Thts thesis describes the motivation for onlme testing, compares the effectiveness...

Arora, Avital Jayant

2012-06-07

384

Microwave propagation over mountain-diffraction paths  

Microsoft Academic Search

An experimental study was undertaken to obtain a more complete picture of wide-band transmission via microwave propagation over mountain-diffraction paths. Such paths are characterized by obstacles of irregular shape, and pathlength very large compared to wavelength. Swept-frequency transmission was used to provide a record of signal-level variations with time and frequency on two different paths. Other observations included polarization dependence,

A. Carlson

1966-01-01

385

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

SciTech Connect

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

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

2012-11-01

386

Linear Polymers in Disordered Media - the shortest, the longest and the mean(est) SAW on percolation clusters  

E-print Network

Long linear polymers in strongly disordered media are well described by self-avoiding walks (SAWs) on percolation clusters. The length-distribution of these SAWs encompasses to distinct averages, viz. the averages over cluster- and 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, differences to the ordered case appear merely in non-universal quantities. Using dynamical field theory, we show that the same holds true for kinetic averaging. For strong disorder, i.e., the medium being close to the percolation point, we employ a field theory for the nonlinear random resistor network in conjunction with a real-world interpretation of Feynman diagrams, and 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 wide-spread 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 this model leads back 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 of the calculation.

Hans-Karl Janssen; Olaf Stenull

2011-11-22

387

Langevin equation path integral ground state.  

PubMed

We propose a Langevin equation path integral ground state (LePIGS) approach for the calculation of ground state (zero temperature) properties of molecular systems. The approach is based on a modification of the finite temperature path integral Langevin equation (PILE) method (J. Chem. Phys. 2010, 133, 124104) to the case of open Feynman paths. Such open paths are necessary for a ground state formulation. We illustrate the applicability of the method using model systems and the weakly bound water-parahydrogen dimer. We show that the method can lead to converged zero point energies and structural properties. PMID:23738885

Constable, Steve; Schmidt, Matthew; Ing, Christopher; Zeng, Tao; Roy, Pierre-Nicholas

2013-08-15

388

The Logic behind Feynman's Paths  

E-print Network

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

Edgardo T. Garcia Alvarez

2010-11-22

389

Graphs and Matroids Weighted in a Bounded Incline Algebra  

PubMed Central

Firstly, for a graph weighted in a bounded incline algebra (or called a dioid), a longest path problem (LPP, for short) is presented, which can be considered the uniform approach to the famous shortest path problem, the widest path problem, and the most reliable path problem. The solutions for LPP and related algorithms are given. Secondly, for a matroid weighted in a linear matroid, the maximum independent set problem is studied. PMID:25126607

Lu, Ling-Xia; Zhang, Bei

2014-01-01

390

On Models of Nonlinear Evolution Paths in Adiabatic Quantum Algorithms  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

391

Path-based rules in object-oriented programming  

SciTech Connect

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

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

1996-12-31

392

Path planning for robotic truss assembly  

NASA Astrophysics Data System (ADS)

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

Sanderson, Arthur C.

1993-09-01

393

Model Checking Almost All Paths Can Be Less Expensive than Checking All Paths  

E-print Network

Model Checking Almost All Paths Can Be Less Expensive than Checking All Paths Matthias Schmalz 1 and nite-state systems, the two notions of smallness coincide. More importantly, they coincide 1 Matthias.Schmalz

Varacca, Daniele - Laboratoire Preuves, Programmes et Systèmes, Université Paris 7

394

Seeking the Path to Metadata Nirvana  

NASA Astrophysics Data System (ADS)

Scientists have always found reusing other scientists' data challenging. Computers did not fundamentally change the problem, but enabled more and larger instances of it. In fact, by removing human mediation and time delays from the data sharing process, computers emphasize the contextual information that must be exchanged in order to exchange and reuse data. This requirement for contextual information has two faces: "interoperability" when talking about systems, and "the metadata problem" when talking about data. As much as any single organization, the Marine Metadata Interoperability (MMI) project has been tagged with the mission "Solve the metadata problem." Of course, if that goal is achieved, then sustained, interoperable data systems for interdisciplinary observing networks can be easily built -- pesky metadata differences, like which protocol to use for data exchange, or what the data actually measures, will be a thing of the past. Alas, as you might imagine, there will always be complexities and incompatibilities that are not addressed, and data systems that are not interoperable, even within a science discipline. So should we throw up our hands and surrender to the inevitable? Not at all. Rather, we try to minimize metadata problems as much as we can. In this we increasingly progress, despite natural forces that pull in the other direction. Computer systems let us work with more complexity, build community knowledge and collaborations, and preserve and publish our progress and (dis-)agreements. Funding organizations, science communities, and technologists see the importance interoperable systems and metadata, and direct resources toward them. With the new approaches and resources, projects like IPY and MMI can simultaneously define, display, and promote effective strategies for sustainable, interoperable data systems. This presentation will outline the role metadata plays in durable interoperable data systems, for better or worse. It will describe times when "just choosing a standard" can work, and when it probably won't work. And it will point out signs that suggest a metadata storm is coming to your community project, and how you might avoid it. From these lessons we will seek a path to producing interoperable, interdisciplinary, metadata-enlightened environment observing systems.

Graybeal, J.

2008-12-01

395

Balance Problems  

MedlinePLUS

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

396

Resynthesis of Combinational Circuts for Path Count Reduction and for Path Delay Fault Testability  

Microsoft Academic Search

Path delay fault model is the most suitable model for detecting distributed manufacturing defects that can cause delay faults. However, the number of paths in a modern design can be extremely large and the path delay testability of many practical designs could be very low. In this paper we show how to resynthesize a combinational circuit in order to reduce

Angela Krstic; Kwang-Ting Cheng

1996-01-01

397

Backup Path Re-optimizations for Shared Path Protection in Multi-domain Networks  

Microsoft Academic Search

Within the context of dynamic routing models for shared path protection in multi-domain networks, we propose a backup path re-optimization phase with possible rerouting of the existing backup paths in order to increase the bandwidth sharing among them while minimizing the network backup cost. The re- optimization phase is activated periodically or when routing a new connection fails because of

B. Jaumard; T. Dieu Linh Truong

2006-01-01

398

Problems pilots face involving wind shear  

NASA Technical Reports Server (NTRS)

Educating pilots and the aviation industry about wind shears presents a major problem associated with this meteorological phenomenon. The pilot's second most pressing problem is the need for a language to discuss wind shear encounters with other pilots so that the reaction of the aircraft to the wind shear encounter can be accurately described. Another problem is the flight director which gives a centered pitch command for a given angular displacement from the glide slope. It was suggested that they should instead be called flight path command and should not center unless the aircraft is actually correcting to the flight path.

Melvin, W. W.

1977-01-01

399

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

400

Energetic Path Finding Across Massive Terrain Data  

E-print Network

Energetic Path Finding Across Massive Terrain Data Andrew Tsui and Zo¨e Wood California Polytechnic of this work include: ­ Tools for managing and performing energetic analysis on massive out-of- core datasets builds on two previous projects involving human centered paths across terrain data, Energetic Analyst [5

Wood, Zoë J.

401

Career path of a corruption entrepreneur  

Microsoft Academic Search

The study of criminal career paths is necessary to understand the methods of success employed by high-performing criminals. The aim of this article is to focus on the career path of Jack Herbert who set up and maintained extensive corruption networks between organised crime groups and police in the Australian state of Queensland. This study builds on Morselli's work on

Mark Lauchs; Zoe Staines

2012-01-01

402

A Random Walk on a Circular Path  

ERIC Educational Resources Information Center

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

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

2005-01-01

403

Cooperative organic mine avoidance path planning  

NASA Astrophysics Data System (ADS)

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.

McCubbin, Christopher B.; Piatko, Christine D.; Peterson, Adam V.; Donnald, Creighton R.; Cohen, David

2005-06-01

404

Asymmetric fluctuation relaxation paths in FPU models  

NASA Astrophysics Data System (ADS)

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

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

2006-06-01

405

Adaptively Ubiquitous Learning in Campus Math Path  

ERIC Educational Resources Information Center

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

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

2012-01-01

406

Katrina'sPath Lake Pontchartrain  

E-print Network

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

407

Converging towards the optimal path to extinction  

PubMed Central

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

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

2011-01-01

408

A clinical path for adult diabetes.  

PubMed

The use of clinical paths for patient care management was explored by this development team as a mechanism to provide consistent, high-quality care to hospitalized patients in high-volume, high-risk diagnostic categories. Reviewing the historical aspects and importance of clinical paths helped expand the team's perspective to incorporate pre- and posthospitalization phases of patient care into the clinical path being developed. A multidisciplinary team of physicians, nurses, health educators, and dietitians from both inpatient and outpatient departments of Kaiser-Santa Teresa Medical Center in San Jose, California, devised and implemented an Adult Diabetes Mellitus care path. Staff education preceded the implementation of the care paths. Measurements of quality indicators showed improvements in patient satisfaction, patient education, patient knowledge, and nutrition assessments. PMID:9416030

Courtney, L; Gordon, M; Romer, L

1997-01-01

409

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

E-print Network

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

410

Forbidden vertices  

E-print Network

An explicit description of a polytope P ? Rn is a system Ax ? b defining P. ...... Office of Scientific Research (Grant #FA9550-12-1-0154) and by Deutsche ... application to the shortest path problem, Management Science 18 (1972), 401

2014-03-01

411

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

ERIC Educational Resources Information Center

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

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

2011-01-01

412

Path integral measure, constraints and ghosts for massive gravitons with a cosmological constant  

SciTech Connect

For massive gravity in a de Sitter background one encounters problems of stability when the curvature is larger than the graviton mass. I analyze this situation from the path integral point of view and show that it is related to the conformal factor problem of Euclidean quantum (massless) gravity. When a constraint for massive gravity is incorporated and the proper treatment of the path integral measure is taken into account one finds that, for particular choices of the DeWitt metric on the space of metrics (in fact, the same choices as in the massless case), one obtains the opposite bound on the graviton mass.

Metaxas, Dimitrios [Department of Physics, National Technical University of Athens, Zografou Campus, 15780 Athens (Greece)

2009-12-15

413

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

NASA Astrophysics Data System (ADS)

The supersymetric path integrals in solving the problem of relativistic spinning particle interacting with pseudoscalar potentials is examined. The relative propagator is presented by means of path integral, where the spin degrees of freedom are described by odd Grassmannian variables and the gauge invariant part of the effective action has a form similar to the standard pseudoclassical action given by Berezin and Marinov. After integrating over fermionic variables (Grassmannian variables), the problem is reduced to a nonrelativistic one with an effective supersymetric potential. Some explicit examples are considered, where we have extracted the energy spectrum of the electron and the wave functions.

Haouat, S.; Chetouani, L.

2007-06-01

414

Ranking paths in statistical energy analysis models with non-deterministic loss factors  

NASA Astrophysics Data System (ADS)

Finding the contributions of transmission paths in statistical energy analysis (SEA) models has become an established valuable tool to detect and remedy vibro-acoustic problems. Paths are identified in SEA according to Craik's definition and recently, very efficient methods have been derived to rank them in the framework of graph theory. However, up to date classification schemes have only considered the mean values of loss factors for path comparison, their variance being ignored. This can result in significant errors in the final results. In this work it is proposed to address this problem by defining stochastic biparametric SEA graphs whose edges are assigned both, mean and variance values. Paths between subsystems are then compared according to a proposed cost function that accounts for the stochastic nature of loss factors. For an efficacious ranking of paths, the stochastic SEA graph is converted to an extended deterministic SEA graph where fast classification deterministic algorithms can be applied. The importance of nonneglecting the influence of the variance in path ranking is illustrated by means of some academic numerical examples.

Aragons, ngels; Guasch, Oriol

2015-02-01

415

Bergman Kernel from Path Integral  

NASA Astrophysics Data System (ADS)

We rederive the expansion of the Bergman kernel on Khler manifolds developed by Tian, Yau, Zelditch, Lu and Catlin, using path integral and perturbation theory, and generalize it to supersymmetric quantum mechanics. One physics interpretation of this result is as an expansion of the projector of wave functions on the lowest Landau level, in the special case that the magnetic field is proportional to the Khler form. This is relevant for the quantum Hall effect in curved space, and for its higher dimensional generalizations. Other applications include the theory of coherent states, the study of balanced metrics, noncommutative field theory, and a conjecture on metrics in black hole backgrounds discussed in [24]. We give a short overview of these various topics. From a conceptual point of view, this expansion is noteworthy as it is a geometric expansion, somewhat similar to the DeWitt-Seeley-Gilkey et al short time expansion for the heat kernel, but in this case describing the long time limit, without depending on supersymmetry.

Douglas, Michael R.; Klevtsov, Semyon

2010-01-01

416

Biological path to nanoelectronics devices  

NASA Astrophysics Data System (ADS)

The biology and semiconductor technology have progressed independently. There was a large distance between them and a substantial interdisciplinary research area was left untouched. Recently, this situation is changing. Some researchers are stimulating semiconductor technology to introduce bio-molecules into the nano-fabrication process. We proposed a new process for fabricating functional nano-structure on a solid surface using protein supramolecules, which is named "Bio Nano Process" (BNP). We employed a cage-shaped protein, apoferritin and synthesized several kinds of nanoparticles (NP) in the apoferritin cavity. A two-dimensional array of them was made on the silicon wafer and this array was heat treated or UV/ozone treated. These processes produced a two-dimensional inorganic NP array on the silicon surface. The size of NP is small enough as quantum dots and the floating nanodots memory using this NP array is now under development. We also proposed another process using the obtained nanodot array as the nanometric etching mask. This was realized by the neutral beam etching and 7nm Si nano columns with high aspect ratio were fabricated. These experimental results demonstrated that the BNP can fabricate the inorganic nanostructure using protein supramolecules and the BNP opened up a biological path to nanoelectronics devices.

Yamashita, Ichiro

2005-02-01

417

Path integral for inflationary perturbations  

NASA Astrophysics Data System (ADS)

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

Prokopec, Tomislav; Rigopoulos, Gerasimos

2010-07-01

418

Path Integral for Inflationary Perturbations  

E-print Network

The quantum theory of cosmological perturbations in single field inflation is formulated in terms of a path integral. Starting from a canonical formulation, we show how the free propagators can be obtained from the well known gauge-invariant quadratic action for scalar and tensor perturbations, and determine the interactions to arbitrary order. This approach does not require the explicit solution of the energy and momentum constraints, a novel feature which simplifies the determination of the interaction vertices. The constraints and the necessary imposition of gauge conditions is reflected in the appearance of various commuting and anti-commuting auxiliary fields in the action. These auxiliary fields are not propagating physical degrees of freedom but need to be included in internal lines and loops in a diagrammatic expansion. To illustrate the formalism we discuss the tree-level 3-point and 4-point functions of the inflaton perturbations, reproducing the results already obtained by the methods used in the current literature. Loop calculations are left for future work.

Tomislav Prokopec; Gerasimos Rigopoulos

2010-12-11

419

Path integral for inflationary perturbations  

SciTech Connect

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

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

2010-07-15

420

The reaction path intrinsic reaction coordinate method and the Hamilton-Jacobi theory.  

PubMed

The definition and location of an intrinsic reaction coordinate path is of crucial importance in many areas of theoretical chemistry. Differential equations used to define the path hitherto are complemented in this study with a variational principle of Fermat type, as Fukui [Int. J. Quantum Chem., Quantum Chem. Symp. 15, 633 (1981)] reported in a more general form some time ago. This definition is more suitable for problems where initial and final points are given. The variational definition can naturally be recast into a Hamilton-Jacobi equation. The character of the variational solution is studied via the Weierstrass necessary and sufficient conditions. The characterization of the local minima character of the intrinsic reaction coordinate is proved. Such result leads to a numerical algorithm to find intrinsic reaction coordinate paths based on the successive minimizations of the Weierstrass E-function evaluated on a guess curve connecting the initial and final points of the desired path. PMID:16008428

Crehuet, Ramon; Bofill, Josep Maria

2005-06-15

421

Direct path planning in image plane and tracking for visual servoing  

NASA Astrophysics Data System (ADS)

The image-based visual servoing would lead to image singularities that might cause control instabilities, and there exit other constraints such as the object should remain in the camera field of view and avoid obstacles. This problem can be solved by coupling path planning and image-based control. The trajectory is planned directly in the image space in our strategy to avoid the 3D estimation of the object, which is required in the motion space based path planning method. In the presented method, the initial path is given using the artificial potential field method without considering the constraints and then genetic algorithm based method is used to check and modify the initial path. This method can achieve satisfactory task while decrease the computation. The proposed method is used to align the micro peg and hole, and the simulation results show that the object can reach its desired position accurately without violation these constrains.

Wang, Junping; Liu, An; Cho, Hyungsuck

2007-10-01

422

Robot path planning using a genetic algorithm  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

423

The behavioural final common path.  

PubMed

In this paper it is argued that any model of the motivational (i.e. reversible) processes governing the behaviour of an animal can be represented by means of isoclines in a multidimensional 'causal-factor space'. The argument is axiomatic, based upon the two prime assumptions: that (1) it is always possible to classify the behavioural repertoire of a species in such a way that the classes are mutually exclusive in the sense that the members of different classes cannot occur simultaneously, and (2) these incompatible actions are uniquely determined by a particular set of causal factors. The isoclines join all points in the space which present a given 'degree of competitiveness' of a particular 'candidate' for overt behavioural expression. The competition between candidates is an inevitable consequence of the fact that animals cannot 'do more than one thing at a time', and is envisaged as taking place in the behavioural final common path. An empirical method of determining the motivational state (i.e. point in causal-factor space) is outlined. This is a 'relative' method, independent of the arbitrary calibration of the axes of the causal-factor space. It is shown that an arbitrary scale of measurement along any two axes of the causal-factor space is all that is necessary for empirical determination of the shape of a motivational isocline. Experiments in which this method has been applied to the measurement of hunger and thirst in doves are outlined, and the results are discussed in terms of their implications for motivation theory in general. PMID:239416

McFarland, D J; Sibly, R M

1975-05-15

424

Evolution paths for advanced automation  

NASA Technical Reports Server (NTRS)

As Space Station Freedom (SSF) evolves, increased automation and autonomy will be required to meet Space Station Freedom Program (SSFP) objectives. As a precursor to the use of advanced automation within the SSFP, especially if it is to be used on SSF (e.g., to automate the operation of the flight systems), the underlying technologies will need to be elevated to a high level of readiness to ensure safe and effective operations. Ground facilities supporting the development of these flight systems -- from research and development laboratories through formal hardware and software development environments -- will be responsible for achieving these levels of technology readiness. These facilities will need to evolve support the general evolution of the SSFP. This evolution will include support for increasing the use of advanced automation. The SSF Advanced Development Program has funded a study to define evolution paths for advanced automaton within the SSFP's ground-based facilities which will enable, promote, and accelerate the appropriate use of advanced automation on-board SSF. The current capability of the test beds and facilities, such as the Software Support Environment, with regard to advanced automation, has been assessed and their desired evolutionary capabilities have been defined. Plans and guidelines for achieving this necessary capability have been constructed. The approach taken has combined indepth interviews of test beds personnel at all SSF Work Package centers with awareness of relevant state-of-the-art technology and technology insertion methodologies. Key recommendations from the study include advocating a NASA-wide task force for advanced automation, and the creation of software prototype transition environments to facilitate the incorporation of advanced automation in the SSFP.

Healey, Kathleen J.

1990-01-01

425

Multiple time scale numerical methods for the inverted pendulum problem  

E-print Network

Multiple time scale numerical methods for the inverted pendulum problem Richard Sharp1, Yen (HMM) [1]. We apply the methods to compute the averaged path of the inverted pendulum under a highly and thus compute the average path of the inverted pendulum. 1 Introduction The focus of this paper

Tsai, Yen-Hsi Richard

426

MULTIPLE TIME SCALE NUMERICAL METHODS FOR THE INVERTED PENDULUM PROBLEM  

E-print Network

MULTIPLE TIME SCALE NUMERICAL METHODS FOR THE INVERTED PENDULUM PROBLEM RICHARD SHARP, YEN-HSI TSAI multiscale methods (HMM) [1]. We apply the methods to compute the averaged path of the inverted pendulum approximate the averaged equation and thus compute the average path of the inverted pendulum. 1. INTRODUCTION

Soatto, Stefano

427

Handbook for the estimation of microwave propagation effects: Link calculations for earth-space paths (path loss and noise estimation)  

NASA Technical Reports Server (NTRS)

A single model for a standard of comparison for other models when dealing with rain attenuation problems in system design and experimentation is proposed. Refinements to the Global Rain Production Model are incorporated. Path loss and noise estimation procedures as the basic input to systems design for earth-to-space microwave links operating at frequencies from 1 to 300 GHz are provided. Topics covered include gaseous absorption, attenuation by rain, ionospheric and tropospheric scintillation, low elevation angle effects, radome attenuation, diversity schemes, link calculation, and receiver noise emission by atmospheric gases, rain, and antenna contributions.

Crane, R. K.; Blood, D. W.

1979-01-01

428

QoS routing via multiple paths using bandwidth reservation  

SciTech Connect

The authors address the problem of computing a multipath, consisting of possibly overlapping paths, to transmit data from the source node s to the destination node d over a computer network while ensuring deterministic bounds on end-to-end delay or delivery rate. They consider two generic routing problems within the framework wherein bandwidth can be reserved, and guaranteed, once reserved, on various links of the communication network. The first problem requires that a message of finite length be transmitted from s to d within {tau} units of time. The second problem requires that a sequential message of r units be transmitted at a rate of {eta} such that maximum time difference between two units that are received out of order is no more than q. They propose a polynomial-time algorithm to the first problem based on an adaptation of the classical Ford-Fulkerson`s method. They present simulation results to illustrate the applicability of the proposed algorithm. They show the second problem to be NP-complete and propose a polynomial-time approximate solution.

Rao, N.S.V.; Batsell, S.G.

1997-11-01

429

QoS routing via multiple paths using bandwidth reservation  

SciTech Connect

The authors address the problem of computing a multipath, consisting of possibly overlapping paths, to transmit data from the source node s to the destination node d over a computer network while ensuring deterministic bounds on end-to-end delay or delivery rate.They consider two generic routing problems within the framework wherein bandwidth can be reserved, and guaranteed, once reserved, on various links of the communication network. The first problem requires that a message of finite length be transmitted from s to d within {tau} units of time. The second problem requires that a sequential message of r units be transmitted at a rate of {eta} such that maximum time difference between two units that are received out of order is no more than q. They propose a polynomial-time algorithm to the first problem based on an adaptation of the classical Ford-Fulkerson`s method. They present simulation results to illustrate the applicability of the proposed algorithm. They show the second problem to be NP-complete, and propose a polynomial-time approximately solution.

Rao, N.S.V.; Batsell, S.G.

1998-01-01

430

d self-avoiding path (canonical surface) (fixed point)  

E-print Network

d self-avoiding path 2004 2 1 1 path (canonical surface) (fixed point) canonical surface [1, ] self-avoiding path Self-avoiding path d pre-gasket self-avoiding path d pre-gasket Sierpi´nski gasket d pre-gasket self-avoiding path 1 E-mail: hattori@math.nagoya-u.ac.jp 1 #12;d pre-gasket d pre-gasket 1 2 self

Hattori, Tetsuya

431

Problem Solving  

NSDL National Science Digital Library

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

K-12 Outreach,

432

Calibration of neural networks using genetic algorithms, with application to optimal path planning  

NASA Technical Reports Server (NTRS)

Genetic algorithms (GA) are used to search the synaptic weight space of artificial neural systems (ANS) for weight vectors that optimize some network performance function. GAs do not suffer from some of the architectural constraints involved with other techniques and it is straightforward to incorporate terms into the performance function concerning the metastructure of the ANS. Hence GAs offer a remarkably general approach to calibrating ANS. GAs are applied to the problem of calibrating an ANS that finds optimal paths over a given surface. This problem involves training an ANS on a relatively small set of paths and then examining whether the calibrated ANS is able to find good paths between arbitrary start and end points on the surface.

Smith, Terence R.; Pitney, Gilbert A.; Greenwood, Daniel

1987-01-01

433

DNA Computing for Complex Scheduling Problem  

Microsoft Academic Search

\\u000a Interest in DNA computing has increased overwhelmly since Adleman successfully demonstrated its capability to solve Hamiltonian\\u000a Path Problem (HPP). Many research results of similar combinatorial problems which are mainly in the realm of computer science\\u000a and mathematics have been presented. In this paper, implementation ideas and methods to solve an engineering related combinatorial\\u000a problem using this DNA computing approach is

Mohd Saufee Muhammad; Zuwairie Ibrahim; Satomi Ueda; Osamu Ono; Marzuki Khalid

2005-01-01

434

Identifying decohering paths in closed quantum systems  

NASA Technical Reports Server (NTRS)

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

Albrecht, Andreas

1990-01-01

435

How Do Paths Look From Different Perspectives?  

NSDL National Science Digital Library

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

436

Nonclassical Paths in Quantum Interference Experiments  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

437

Non-classical paths in interference experiments  

E-print Network

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.

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

2014-08-09

438

Building a path in cell biology  

E-print Network

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.

Cheeseman, Iain McPherson

439

A Generalized Sylvester Problem and a Generalized Fermat-Torricelli Problem: Existence and Uniqueness of Optimal Solutions  

E-print Network

In this paper, we introduce and study the following problem and its further generalizations: given two finite collections of sets in a normed space, find a ball whose center lies in a given constraint set with the smallest radius that encloses all the sets in the first collection and intersects all the sets in the second one. This problem can be considered as a generalized version of the Sylvester smallest enclosing circle problem introduced in the 19th century by Sylvester which asks for the circle of smallest radius enclosing a given set of finite points in the plane. We also consider a generalized version of the Fermat-Torricelli problem: given two finite collections of sets in a normed space, find a point in a given constraint set that minimizes the sum of the farthest distances to the sets in the first collection and shortest distances (distances) to the sets in the second collection.

Nam, Nguyen Mau

2012-01-01

440

Path integral approach on Schrodinger's cat  

E-print Network

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

Zinkoo Yun

2013-10-30

441

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

NSDL National Science Digital Library

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

442

Quantum cosmology based on discrete Feynman paths  

SciTech Connect

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''.

Chew, Geoffrey F.

2002-10-10

443

Multiple Damage Progression Paths in Model-Based Prognostics  

NASA Technical Reports Server (NTRS)

Model-based prognostics approaches employ domain knowledge about a system, its components, and how they fail through the use of physics-based models. Component wear is driven by several different degradation phenomena, each resulting in their own damage progression path, overlapping to contribute to the overall degradation of the component. We develop a model-based prognostics methodology using particle filters, in which the problem of characterizing multiple damage progression paths is cast as a joint state-parameter estimation problem. The estimate is represented as a probability distribution, allowing the prediction of end of life and remaining useful life within a probabilistic framework that supports uncertainty management. We also develop a novel variance control mechanism that maintains an uncertainty bound around the hidden parameters to limit the amount of estimation uncertainty and, consequently, reduce prediction uncertainty. We construct a detailed physics-based model of a centrifugal pump, to which we apply our model-based prognostics algorithms. We illustrate the operation of the prognostic solution with a number of simulation-based experiments and demonstrate the performance of the chosen approach when multiple damage mechanisms are active

Daigle, Matthew; Goebel, Kai Frank

2011-01-01

444

Spatially robust vehicle path tracking using normal error feedback  

NASA Astrophysics Data System (ADS)

The problem of path tracking is critical to autonomous vehicle navigation. This problem has been approached using multiple feedback sensors that measure both the vehicle heading and position and also using cable guided systems measuring lateral error. This paper describes a path tracking controller that uses only the vehicle position as the single feedback value while providing a spatially similar response to disturbances independent of vehicle velocity. The results obtained on vehicles using this tracking controller are comparable to those obtained with systems measuring both vehicle position and heading. The controller has the additional benefits of being simple to implement, dealing effectively and predictably with system non-linearities, and providing a good measure of insensitivity to system variations. The controller described in this paper was developed for a two hundred horsepower farm tractor with Ackerman steering and has since been successfully used on a smaller tractor. The paper includes the derivation of the vehicle model, the development of the controller, and a discussion of system stability.

Cripps, Donald L.

2001-09-01

445

A Constrained Path Quantum Monte Carlo study of magnetism in the disordered 2D Hubbard model  

Microsoft Academic Search

The ground state Constrained Path Quantum Monte Carlo (CPQMC) (S. Zhang, J. Carlson, and J.E. Gubernatis, Phys. Rev. B) 55 7464 (1997) method has been used successfully to study correlated fermi systems where other Monte Carlo methods have failed because of a decay in signal to noise, the signature of a Monte Carlo sign problem. The method has been applied

Matthew Enjalran; Frederic Hebert; George Batrouni; Richard T. Scalettar; Shiwei Zhang; M. H. Kalos

2000-01-01

446

OPTIMAL VIABLE PATH SEARCH FOR A CHEESE RIPENING PROCESS USING A MULTI-OBJECTIVE EA  

E-print Network

OPTIMAL VIABLE PATH SEARCH FOR A CHEESE RIPENING PROCESS USING A MULTI-OBJECTIVE EA Salma Mesmoudi-food process modeling, cheese ripening. Abstract: Viability theory is a very attractive theoretical approach address here is a real size problem from dairy industry, the modeling of a Camembert cheese ripening

Boyer, Edmond

447

Path Following Control for an Eel-like Robot Lionel Lapierre  

E-print Network

Path Following Control for an Eel-like Robot Lionel Lapierre LIRMM Montpellier, France Email investigate the problem of controlling the motion of an eel like-robot. Recent work has shown promising results to illustrate the performances of our solution. II. SYSTEM MODELING We model the eel-like robot

Paris-Sud XI, Université de

448

Finding Solvable Priority Schemes for Decoupled Path Planning Techniques for Teams of Mobile Robots  

E-print Network

in mobile robotics. As mentioned by Latombe [11], the capability of effectively planning its motions." In this paper we consider the problem of motion planning for multiple mobile robots. The goal is to computeFinding Solvable Priority Schemes for Decoupled Path Planning Techniques for Teams of Mobile Robots

Teschner, Matthias

449

Optimal Scheduling of Two Communication Flows on Multiple Disjoint Packet-Type Aware Paths  

Microsoft Academic Search

Abstract Communication flows in distributed systems often present a poor performance, because they are unawareof each other and end up competing for the same bottleneck resources. A solution to this problem consists of scheduling the communication flows in order to optimize some performance metric. In this paper we study the scheduling of two communication flows over multiple disjoint paths, such

Mugurel Ionut Andreica; Nicolae Tapus

2008-01-01

450

Telomeres and telomerase: the path from maize, Tetrahymena and yeast to human  

E-print Network

Telomeres and telomerase: the path from maize, Tetrahymena and yeast to human cancer and aging Elizabeth H Blackburn, Carol W Greider & Jack W Szostak The telomere problem Scientific discoveries are each- mosome to the end of another [intact chromo- some]"1.In1938,Mullernamedthenaturalends of chromosomes`telomeres

Heller, Eric

451

Clearing the Path tor All of Us Where Trains Once Ran.  

ERIC Educational Resources Information Center

Describes the concept behind the rail-to-trails movement; the history, process and problems of converting abandoned railroad beds to bike and walking paths. Introduces the concept and trend of ergo, or linear parks, corridors, and greenways to meet the increasing need for public access to land for recreational purposes. (MCO)

Mills, Judy

1990-01-01

452

Wind-Energy based Path Planning For Electric Unmanned Aerial Vehicles Using Markov Decision Processes  

E-print Network

Wind-Energy based Path Planning For Electric Unmanned Aerial Vehicles Using Markov Decision wind-energy is one possible way to ex- tend flight duration for Unmanned Arial Vehicles. Wind-energy sources of wind energy available to exploit for this problem [5]: 1) Vertical air motion, such as thermal

Smith, Ryan N.

453

The Satisfiability-IndicatingMulti-Index Organization for Maintaining Materialized Path Query OODB Views  

Microsoft Academic Search

Materialized database views allow applications to benefitfrom the powerful flexibility of views while minimizing the performance penalties traditionally associated with views. However, the need to maintain materialized views in the face of updates limits the variety of queries that can be used to definethem. In this paper we address the problem of incrementally maintaining OODB views formed using path queries.

Harumi A. Kuno; Elke A. Rundensteiner

1996-01-01

454

Probabilistic Path Planning for Multiple Robots with Subdimensional Glenn Wagner, Minsu Kang, Howie Choset  

E-print Network

) and Probabilistic Roadmaps (PRMs) are powerful path planning algorithms for high dimensional systems, but even PRMs can solve problems involving 32 robots and 128 total degrees of freedom in less than 10 minutes. We also demonstrate that enhancing RRTs and PRMs with subdimensional expansion can decrease the time

Choset, Howie

455

Heterogeneous Multi-Agent Architecture for ATM Virtual Path Network Resource Configuration  

Microsoft Academic Search

This paper illustrates a new approach to the problem of making a logical network resource configuration, adapt to customer utilisation. This is to be achieved through the use of distributed multi-agent based control techniques. The agents have goals derived from different quality metrics, which the network has to provide. In ATM networks a well designed Virtual Path Connection (VPC) overlay

Alex L. Hayzelden; John Bigham

1998-01-01

456

Evolvable Neuronal Paths: A Novel Basis for Information and Search in the Brain  

PubMed Central

We propose a previously unrecognized kind of informational entity in the brain that is capable of acting as the basis for unlimited hereditary variation in neuronal networks. This unit is a path of activity through a network of neurons, analogous to a path taken through a hidden Markov model. To prove in principle the capabilities of this new kind of informational substrate, we show how a population of paths can be used as the hereditary material for a neuronally implemented genetic algorithm, (the swiss-army knife of black-box optimization techniques) which we have proposed elsewhere could operate at somatic timescales in the brain. We compare this to the same genetic algorithm that uses a standard genetic informational substrate, i.e. non-overlapping discrete genotypes, on a range of optimization problems. A path evolution algorithm (PEA) is defined as any algorithm that implements natural selection of paths in a network substrate. A PEA is a previously unrecognized type of natural selection that is well suited for implementation by biological neuronal networks with structural plasticity. The important similarities and differences between a standard genetic algorithm and a PEA are considered. Whilst most experiments are conducted on an abstract network model, at the conclusion of the paper a slightly more realistic neuronal implementation of a PEA is outlined based on Izhikevich spiking neurons. Finally, experimental predictions are made for the identification of such informational paths in the brain. PMID:21887266

Fernando, Chrisantha; Vasas, Vera; Szathmry, Ers; Husbands, Phil

2011-01-01

457

Feynman-Kac path integral calculation of the ground state energy of atoms  

SciTech Connect

In a paper written in 1950, the mathematician, Marc Kac, established a rigorous basis for the Feynman path-integral formulation of quantum mechanics. The original Feynman path integral lacks mathematical rigor in the definition of [open quotes]summing over all paths[close quotes], which are infinite in number (a theorem by Cameron states that a finite, real or complex, Lebesgue measure of the path defined by Feynman does not exist). The difficulty of using Feynman's method in a computation is supported by the observation that an accurate path integral solution of the hydrogen groundstate was only recently computed (in 1984). Since its introduction in 1950, the Feynman-Kac path integral (FKPI) has received limited attention despite its simplicity and power in solving quantum many-body problems. This work demonstrates that the FKPI method can be used to find the ground state and excited states of small atomic systems to within experimental accuracy, and is ideally suited for the new massively parallel computer architectures, such as Thinking Machines CM-5, the INTEL Paragon, et al., or can be effectively used in a cluster of loosely-coupled workstations. It also demonstrates a simple procedure for incorporating into the FKPI computational method restrictions on the many-body wavefunction imposed by permutation symmetries of identical particles.

Orr, D.E.

1992-01-01

458

Improved methods for path integral Monte Carlo integration in fermionic systems  

NASA Astrophysics Data System (ADS)

We generalize the discretized Feynman path integral expansion by replacing the path through pure states with a path through idempotent density matrices. The transformed expression converges to the ordinary path integral, but is computationally more flexible than the ordinary form. By introducing a particular choice of these idempotent density matrices, based on rotational averaging around the two-particle center of mass, we greatly reduce the sign problem for systems of two fermions in three dimensions. In the ordinary path integral Monte Carlo approach, low temperature simulation of fermions is inefficient as the integral decays exponentially faster than the integrand (and its variance) as the temperature decreases. The new rotationally averaged algorithm dramatically retards this relative decay. Fermionic simulations of the model system of Kestner and Sinanoglu, and of the harmonic oscillator, demonstrate this improvement, as integrals calculated at temperatures much lower than the singlet-triplet splitting display negligible decay of the desired averages relative to the partition function of the modified path ensemble.

Newman, William H.; Kuki, Atsuo

1992-01-01

459

Evolvable neuronal paths: a novel basis for information and search in the brain.  

PubMed

We propose a previously unrecognized kind of informational entity in the brain that is capable of acting as the basis for unlimited hereditary variation in neuronal networks. This unit is a path of activity through a network of neurons, analogous to a path taken through a hidden Markov model. To prove in principle the capabilities of this new kind of informational substrate, we show how a population of paths can be used as the hereditary material for a neuronally implemented genetic algorithm, (the swiss-army knife of black-box optimization techniques) which we have proposed elsewhere could operate at somatic timescales in the brain. We compare this to the same genetic algorithm that uses a standard 'genetic' informational substrate, i.e. non-overlapping discrete genotypes, on a range of optimization problems. A path evolution algorithm (PEA) is defined as any algorithm that implements natural selection of paths in a network substrate. A PEA is a previously unrecognized type of natural selection that is well suited for implementation by biological neuronal networks with structural plasticity. The important similarities and differences between a standard genetic algorithm and a PEA are considered. Whilst most experiments are conducted on an abstract network model, at the conclusion of the paper a slightly more realistic neuronal implementation of a PEA is outlined based on Izhikevich spiking neurons. Finally, experimental predictions are made for the identification of such informational paths in the brain. PMID:21887266

Fernando, Chrisantha; Vasas, Vera; Szathmry, Ers; Husbands, Phil

2011-01-01

460

Improving the Quality of Non-Holonomic Motion by Hybridizing C-PRM Paths  

E-print Network

Sampling-based motion planners are an effective means for generating collision-free motion paths. However, the quality of these motion paths, with respect to different quality measures such as path length, clearance, smoothness or energy, is often notoriously low. This problem is accentuated in the case of non-holonomic sampling-based motion planning, in which the space of feasible motion trajectories is restricted. In this study, we combine the C-PRM algorithm by Song and Amato with our recently introduced path-hybridization approach, for creating high quality non-holonomic motion paths, with combinations of several different quality measures such as path length, smoothness or clearance, as well as the number of reverse car motions. Our implementation includes a variety of code optimizations that result in nearly real-time performance, and which we believe can be extended with further optimizations to a real-time tool for the planning of high-quality car-like motion.

Berger, Itamar; Zohar, Gal; Raveh, Barak; Halperin, Dan

2010-01-01

461

A Parallel Reduction of Hamiltonian Cycle to Hamiltonian Path in Tournaments  

Microsoft Academic Search

We propose a parallel algorithm which reduces the problem of computing Hamiltonian cycles in tournaments to the problem of computing Hamiltonian paths. The running time of our algorithm is O(log n) using O(n\\u000a2\\/log n) processors on a CRCW PRAM, and O(log n log log n) on an EREW PRAM using O(n\\u000a2\\/log n log log n) processors. As a

Evripidis Bampis; Mohamed El Haddad; Yannis Manoussakis; Miklos Santha

1993-01-01

462

On the complexity of column generation in survivable network design with path-based survivability mechanisms  

Microsoft Academic Search

Abstract This survey concerns optimization problems arising in the design of survivable communica- tion networks. It turns out that such problems can be modeled,in a natural way as non-compact linear programming,formulations based on multicommodity,fl ow network models. These non- compact formulations involve an exponential number of path flow variables, and therefore require column,generation to be solved to optimality. We consider

SEBASTIAN ORLOWSKI

463

The use of 3-D sensing techniques for on-line collision-free path planning  

NASA Technical Reports Server (NTRS)

The state of the art in collision prevention for manipulators with revolute joints, showing that it is a particularly computationally hard problem, is discussed. Based on the analogy with other hard or undecidable problems such as theorem proving, an extensible multi-resolution architecture for path planning, based on a collection of weak methods is proposed. Finally, the role that sensors can play for an on-line use of sensor data is examined.

Hayward, V.; Aubry, S.; Jasiukajc, Z.

1987-01-01

464

IEEE/ACM TRANSACTIONS ON NETWORKING, VOL. 13, NO. 4, AUGUST 2005 717 Conditions That Impact the Complexity  

E-print Network

-constrained path, QoS routing, phase transition. I. INTRODUCTION THERE is an increasing demand for using real-time--Finding a path in a network based on multiple con- straints (the MCP problem) is often considered an integral. The routing algorithm uses this information to compute shortest paths. Best-effort routing performs

Van Mieghem, Piet

465

A Path-Independent Forming Limit Criterion for Stamping Simulations  

SciTech Connect

Forming Limit Diagram (FLD) has been proved to be a powerful tool for assessing necking failures in sheet metal forming analysis for majority of stamping operations over the last three decades. However, experimental evidence and theoretical analysis suggest that its applications are limited to linear or almost linear strain paths during its deformation history. Abrupt changes or even gradual deviations from linear strain-paths will shift forming limit curves from their original values, a situation that occurs in vast majority of sequential stamping operations such as where the drawing process is followed by flanging and re-strike processes. Various forming limit models have been put forward recently to provide remedies for the problem, noticeably stress-based and strain gradient-based forming limit criteria. This study presents an alternative path-independent forming limit criterion. Instead of traditional Forming Limit Diagrams (FLD) which are constructed in terms of major - minor principal strains throughout deformation history, the new criterion defines a critical effective strain {epsilon}-bar* as the limit strain for necking, and it is shown that {epsilon}-bar* can be expressed as a function of current strain rate state and material work hardening properties, without the need of explicitly considering strain-path effects. It is given by {epsilon}-bar* = f({beta}, k, n) where {beta} = (d{epsilon}{sub 2}/d{epsilon}{sub 1}) at current deformation state, and k and n are material strain hardening parameters if a power law is assumed. The analysis is built upon previous work by Storen and Rice [1975] and Zhu et al [2002] with the incorporation of anisotropic yield models such as Hill'48 for quadratic orthotropic yield and Hill'79 for non-quadratic orthotropic yield. Effects of anisotropic parameters such as R-values and exponent n-values on necking are investigated in detail for a variety of strain paths. Results predicted according to current analysis are compared against experimental data gathered from literature and good agreements are achieved. This provides a powerful validation for this approach.The new criterion retains all the advantages of the traditional FLDs since it's still constructed in the strain space. Its relationship with stress-based forming limit criteria is discussed. It is believed that the approach is especially suitable for production stamping CAE analysis since the strain rate state at any material point during forming deformation is readily available from FEA simulations. It can be easily embedded in forming simulation software or alternatively deployed as a post-processing function for forming simulations.

Zhu Xinhai [Livermore Software Technology Co., Livermore, CA 94550 (United States); Chappuis, Laurent; Xia, Z. Cedric [Ford Motor Company, Dearborn, MI 48121 (United States)

2005-08-05

466

Aircraft Routing -A Global Optimization Problem Michael C Bartholomew-Biggs  

E-print Network

Aircraft Routing - A Global Optimization Problem Michael C Bartholomew-Biggs matqmb@herts.ac.uk University of Hertfordshire, England This paper deals with the problem of calculating aircraft flight paths

Neumaier, Arnold

467

A multilevel blocking approach to the sign problem in real-time quantum Monte Carlo simulations  

Microsoft Academic Search

We propose a novel approach toward the general solution of the sign problem in real-time path-integral simulations. Using a recursive multilevel blocking strategy, this method circumvents the sign problem by synthesizing the phase cancellations arising from interfering quantum paths on multiple timescales. A number of numerical examples with one or a few explicit degrees of freedom illustrate the usefulness of

C. H. Mak; R. Egger

1999-01-01

468

A Hybrid Genetic Algorithm for the Point to Multipoint Routing Problem with  

E-print Network

A Hybrid Genetic Algorithm for the Point to Multipoint Routing Problem with Single Split Paths Words: Genetic Algorithm, Steiner Trees, Point to Multipoint Routing, Telecommunications Network to Multipoint Routing Problem with Single Split Paths. Our hybrid algorithm uses a genetic algorithm

Wainwright, Roger L.

469

Analysis of the contact graph routing algorithm: Bounding interplanetary paths  

NASA Astrophysics Data System (ADS)

Interplanetary communication networks comprise orbiters, deep-space relays, and stations on planetary surfaces. These networks must overcome node mobility, constrained resources, and significant propagation delays. Opportunities for wireless contact rely on calculating transmit and receive opportunities, but the Euclidean-distance diameter of these networks (measured in light-seconds and light-minutes) precludes node discovery and contact negotiation. Propagation delay may be larger than the line-of-sight contact between nodes. For example, Mars and Earth orbiters may be separated by up to 20.8 min of signal propagation time. Such spacecraft may never share line-of-sight, but may uni-directionally communicate if one orbiter knows the other's future position. The Contact Graph Routing (CGR) approach is a family of algorithms presented to solve the messaging problem of interplanetary communications. These algorithms exploit networks where nodes exhibit deterministic mobility. For CGR, mobility and bandwidth information is pre-configured throughout the network allowing nodes to construct transmit opportunities. Once constructed, routing algorithms operate on this contact graph to build an efficient path through the network. The interpretation of the contact graph, and the construction of a bounded approximate path, is critically important for adoption in operational systems. Brute force approaches, while effective in small networks, are computationally expensive and will not scale. Methods of inferring cycles or other librations within the graph are difficult to detect and will guide the practical implementation of any routing algorithm. This paper presents a mathematical analysis of a multi-destination contact graph algorithm (MD-CGR), demonstrates that it is NP-complete, and proposes realistic constraints that make the problem solvable in polynomial time, as is the case with the originally proposed CGR algorithm. An analysis of path construction to complement hop-by-hop forwarding is presented as the CGR-EB algorithm. Future work is proposed to handle the presence of dynamic changes to the network, as produced by congestion, link disruption, and errors in the contact graph. We conclude that pre-computation, and thus CGR style algorithms, is the only efficient method of routing in a multi-node, multi-path interplanetary network and that algorithmic analysis is the key to its implementation in operational systems.

Birrane, Edward; Burleigh, Scott; Kasch, Niels

2012-06-01

470

An Adaptive Path Planning Algorithm for Cooperating Unmanned Air Vehicles  

SciTech Connect

An adaptive path planning algorithm is presented for cooperating Unmanned Air Vehicles (UAVs) that are used to deploy and operate land-based sensor networks. The algorithm employs a global cost function to generate paths for the UAVs, and adapts the paths to exceptions that might occur. Examples are provided of the paths and adaptation.

Cunningham, C.T.; Roberts, R.S.

2000-09-12

471

Adaptive path planning algorithm for cooperating unmanned air vehicles  

SciTech Connect

An adaptive path planning algorithm is presented for cooperating Unmanned Air Vehicles (UAVs) that are used to deploy and operate land-based sensor networks. The algorithm employs a global cost function to generate paths for the UAVs, and adapts the paths to exceptions that might occur. Examples are provided of the paths and adaptation.

Cunningham, C T; Roberts, R S

2001-02-08

472

Diagnosis for Covariance Structure Models by Analyzing the Path  

ERIC Educational Resources Information Center

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

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

2008-01-01

473

The Use of Path Analysis in Program Evaluation. No. 12.  

ERIC Educational Resources Information Center

Path analysis, a technique related to multiple regression analysis is used for ascribing causal relationships among variables. Path analysis involves the construction of explicitly formulated causal models and makes the reasoning explicit in the form of path diagrams and structural equations. Regression analysis is then used to construct path

Smith, Nick L.; Murray, Stephen L.

474

Model Discrepancy in the Saturated Path Hydrology Model: Initial Analysis  

E-print Network

Model Discrepancy in the Saturated Path Hydrology Model: Initial Analysis Tom Fricker University discrepancy in the Saturated Path Hydrology Model (logSPM, Kuczera et al., 2006). The purpose). 1 #12;3 The Saturated Path Hydrology Model We consider the Saturated Path Hydrology Model (log

Oakley, Jeremy

475

Achieving Path Diversity over the Internet using MDS Codes  

Microsoft Academic Search

Path diversity works by setting up multiple parallel connections between the end points using the topological path redundancy of the network. In this paper, Forward Error Correction (FEC) is applied across multiple independent paths to enhance the end- to-end reliability. Internet paths are modeled as erasure Gilbert-Elliot channels (1), (2). First, it is shown that over any erasure channel, Maximum

Shervan Fashandi; Shahab Oveis Gharan; Amir K. Khandani

476

14 CFR 171.265 - Glide path performance requirements.  

Code of Federal Regulations, 2010 CFR

...tone predominating below the path and the 90 Hz tone predominating above the path to at least...angular displacement above and below the glide path of... (o) The DDM below the ISMLS glide path...less than 0.30? above the...

2010-01-01

477

14 CFR 171.265 - Glide path performance requirements.  

Code of Federal Regulations, 2013 CFR

...tone predominating below the path and the 90 Hz tone predominating above the path to at least...angular displacement above and below the glide path of... (o) The DDM below the ISMLS glide path...less than 0.30? above the...

2013-01-01

478

14 CFR 171.265 - Glide path performance requirements.  

Code of Federal Regulations, 2011 CFR

...tone predominating below the path and the 90 Hz tone predominating above the path to at least...angular displacement above and below the glide path of... (o) The DDM below the ISMLS glide path...less than 0.30? above the...

2011-01-01

479

14 CFR 171.265 - Glide path performance requirements.  

Code of Federal Regulations, 2012 CFR

...tone predominating below the path and the 90 Hz tone predominating above the path to at least...angular displacement above and below the glide path of... (o) The DDM below the ISMLS glide path...less than 0.30? above the...

2012-01-01

480

On the efficacy of spatial sampling using manual scanning paths to determine the spatial average sound pressure level in rooms.  

PubMed

In architectural acoustics, noise control and environmental noise, there are often steady-state signals for which it is necessary to measure the spatial average, sound pressure level inside rooms. This requires using fixed microphone positions, mechanical scanning devices, or manual scanning. In comparison with mechanical scanning devices, the human body allows manual scanning to trace out complex geometrical paths in three-dimensional space. To determine the efficacy of manual scanning paths in terms of an equivalent number of uncorrelated samples, an analytical approach is solved numerically. The benchmark used to assess these paths is a minimum of five uncorrelated fixed microphone positions at frequencies above 200 Hz. For paths involving an operator walking across the room, potential problems exist with walking noise and non-uniform scanning speeds. Hence, paths are considered based on a fixed standing position or rotation of the body about a fixed point. In empty rooms, it is shown that a circle, helix, or cylindrical-type path satisfy the benchmark requirement with the latter two paths being highly efficient at generating large number of uncorrelated samples. In furnished rooms where there is limited space for the operator to move, an efficient path comprises three semicircles with 45-60 separations. PMID:21568406

Hopkins, Carl

2011-05-01

481

A Comparison of Two Path Planners for Planetary Rovers  

NASA Technical Reports Server (NTRS)

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

Tarokh, M.; Shiller, Z.; Hayati, S.

1999-01-01

482

Erection problems  

MedlinePLUS

... heart problems, or low testosterone A device you wear at night to check for normal nighttime erections Ultrasound of your penis to check for blood flow problems Rigidity monitoring to test how strong your erection is Psychological tests to ...

483

Walking Problems  

MedlinePLUS

... your legs or feet Movement disorders such as Parkinson's disease Diseases such as arthritis or multiple sclerosis Vision or balance problems Treatment of walking problems depends on the cause. Physical ...

484

Path Planning Using a Hybrid Evolutionary Algorithm Based on Tree Structure Encoding  

PubMed Central

A hybrid evolutionary algorithm using scalable encoding method for path planning is proposed in this paper. The scalable representation is based on binary tree structure encoding. To solve the problem of hybrid genetic algorithm and particle swarm optimization, the dummy node is added into the binary trees to deal with the different lengths of representations. The experimental results show that the proposed hybrid method demonstrates using fewer turning points than traditional evolutionary algorithms to generate shorter collision-free paths for mobile robot navigation. PMID:24971389

Wang, Siao-En; Guo, Jian-Horn

2014-01-01

485

Path planning using a hybrid evolutionary algorithm based on tree structure encoding.  

PubMed

A hybrid evolutionary algorithm using scalable encoding method for path planning is proposed in this paper. The scalable representation is based on binary tree structure encoding. To solve the problem of hybrid genetic algorithm and particle swarm optimization, the "dummy node" is added into the binary trees to deal with the different lengths of representations. The experimental results show that the proposed hybrid method demonstrates using fewer turning points than traditional evolutionary algorithms to generate shorter collision-free paths for mobile robot navigation. PMID:24971389

Ju, Ming-Yi; Wang, Siao-En; Guo, Jian-Horn

2014-01-01

486

On the complexity of Minimum Path Cover with Subpath Constraints for multi-assembly  

PubMed Central

Background Multi-assembly problems have gathered much attention in the last years, as Next-Generation Sequencing technologies have started being applied to mixed settings, such as reads from the transcriptome (RNA-Seq), or from viral quasi-species. One classical model that has resurfaced in many multi-assembly methods (e.g. in Cufflinks, ShoRAH, BRANCH, CLASS) is the Minimum Path Cover (MPC) Problem, which asks for the minimum number of directed paths that cover all the nodes of a directed acyclic graph. The MPC Problem is highly popular because the acyclicity of the graph ensures its polynomial-time solvability. Results In this paper, we consider two generalizations of it dealing with integrating constraints arising from long reads or paired-end reads; these extensions have also been considered by two recent methods, but not fully solved. More specifically, we study the two problems where also a set of subpaths, or pairs of subpaths, of the graph have to be entirely covered by some path in the MPC. We show that in the case of long reads (subpaths), the generalized problem can be solved in polynomial-time by a reduction to the classical MPC Problem. We also consider the weighted case, and show that it can be solved in polynomial-time by a reduction to a min-cost circulation problem. As a side result, we also improve the time complexity of the classical minimum weight MPC Problem. In the case of paired-end reads (pairs of subpaths), the generalized problem becomes NP-hard, but we show that it is fixed-parameter tractable (FPT) in the total number of constraints. This computational dichotomy between long reads and paired-end reads is also a general insight into multi-assembly problems. PMID:25252805

2014-01-01

487

Classic Problems  

NSDL National Science Digital Library

Classic problems from the Ask Dr. Math FAQ (Frequently Asked Questions) files, including: age word problems, birthday probability, boy or girl?, camel and bananas, coin problems, doubling pennies, grazing animals, liars and truthtellers, the missing dollar, Monty Hall (three doors), three houses three utilities, the Tower of Hanoi, two trains, two trains and a fly, and working together.

Forum, Math; Math Forum; Ask Dr. Math FAQ

2002-01-01

488

A taxonomy of integral reaction path analysis  

SciTech Connect

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

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

2004-12-23

489

Fermionic path integrals and local anomalies  

NASA Astrophysics Data System (ADS)

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

Roepstorff, G.

2003-05-01

490

SILK: Scout Paths in the Linux Kernel  

E-print Network

SILK stands for Scout In the Linux Kernel, and is a port of the Scout operating system to run as a Linux kernel module. SILK forms a replacement networking subsystem for standard Linux 2.4 kernels. Linux applications create and use Scout paths via the Linux socket interface with virtually no modifications to the applications themselves. SILK provides Linux applications with the benefits of Scout paths, including early packet demultiplexing, per-flow accounting of resources, and explicit scheduling of network processing. SILK also introduces the concept of an extended path to provide a framework for application QoS. We demonstrate the utility of SILK by showing how it can provide QoS for the Apache Web server.

Andy Bavier; Thiemo Voigt; Mike Wawrzoniak; Larry Peterson; Per Gunningberg

2002-01-01

491

STAR UNFOLDING OF A POLYTOPE WITH APPLICATIONS  

Microsoft Academic Search

We introduce the notion of a star unfolding of the surface P of a three-dimensional convex polytope with n vertices, and use it to solve several problems related to shortest paths on P. The rst algorithm computes the edge sequences traversed by shortest paths on P in time O(n6(n)logn), where (n) is an extremely slowly growing function. A much simpler

PANKAJ K. AGARWALy; CATHERINE A. SCHEVON

492

Tornado intensity estimated from damage path dimensions.  

PubMed

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

Elsner, James B; Jagger, Thomas H; Elsner, Ian J

2014-01-01

493

Tornado Intensity Estimated from Damage Path Dimensions  

PubMed Central

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

Elsner, James B.; Jagger, Thomas H.; Elsner, Ian J.

2014-01-01

494

Gas path sealing in turbine engines  

NASA Technical Reports Server (NTRS)

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.

Ludwig, L. P.

1978-01-01

495

Path Factorization Approach to Stochastic Simulations  

NASA Astrophysics Data System (ADS)

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

Athnes, Manuel; Bulatov, Vasily V.

2014-12-01

496

Priming on the path of least resistance  

E-print Network

PRIMING ON THE PATH OF LEAST RESISTANCE A Thesis by ERIC MICHAEL WRUCK 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 2001 Major... Subject: Psychology PRIMING ON THE PATH OF LEAST RESISTANCE A Thesis by ERIC MICHAEL WRUCK Submitted to Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Approved as to style and content by...

Wruck, Eric Michael

2001-01-01

497

Gas Path Sealing in Turbine Engines  

NASA Technical Reports Server (NTRS)

A 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 temperature 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.

Ludwig, L. P.

1978-01-01

498

Quantum Calisthenics: Gaussians, The Path Integral and Guided Numerical Approximations  

SciTech Connect

It is apparent to anyone who thinks about it that, to a large degree, the basic concepts of Newtonian physics are quite intuitive, but quantum mechanics is not. My purpose in this talk is to introduce you to a new, much more intuitive way to understand how quantum mechanics works. I begin with an incredibly easy way to derive the time evolution of a Gaussian wave-packet for the case free and harmonic motion without any need to know the eigenstates of the Hamiltonian. This discussion is completely analytic and I will later use it to relate the solution for the behavior of the Gaussian packet to the Feynman path-integral and stationary phase approximation. It will be clear that using the information about the evolution of the Gaussian in this way goes far beyond what the stationary phase approximation tells us. Next, I introduce the concept of the bucket brigade approach to dealing with problems that cannot be handled totally analytically. This approach combines the intuition obtained in the initial discussion, as well as the intuition obtained from the path-integral, with simple numerical tools. My goal is to show that, for any specific process, there is a simple Hilbert space interpretation of the stationary phase approximation. I will then argue that, from the point of view of numerical approximations, the trajectory obtained from my generalization of the stationary phase approximation specifies that subspace of the full Hilbert space that is needed to compute the time evolution of the particular state under the full Hamiltonian. The prescription I will give is totally non-perturbative and we will see, by the grace of Maple animations computed for the case of the anharmonic oscillator Hamiltonian, that this approach allows surprisingly accurate computations to be performed with very little work. I think of this approach to the path-integral as defining what I call a guided numerical approximation scheme. After the discussion of the anharmonic oscillator I will turn to tunneling problems and show that the instanton can also be though of in the same way. I will do this for the classic problem of a double well potential in the extreme limit when the splitting between the two lowest levels is extremely small and the tunneling rate from one well to another is also very small.

Weinstein, Marvin; /SLAC

2009-02-12

499

An algorithm to find minimum free-energy paths using umbrella integration  

NASA Astrophysics Data System (ADS)

The calculation of free-energy barriers by umbrella sampling and many other methods is hampered by the necessity for an a priori choice of the reaction coordinate along which to sample. We avoid this problem by providing a method to search for saddle points on the free-energy surface in many coordinates. The necessary gradients and Hessians of the free energy are obtained by multidimensional umbrella integration. We construct the minimum free-energy path by following the gradient down to minima on the free-energy surface. The change of free energy along the path is obtained by integrating out all coordinates orthogonal to the path. While we expect the method to be applicable to large systems, we test it on the alanine dipeptide in vacuum. The minima, transition states, and free-energy barriers agree well with those obtained previously with other methods.

Bohner, Matthias U.; Kstner, Johannes

2012-07-01

500

A 2D chaotic path planning for mobile robots accomplishing boundary surveillance missions in adversarial conditions  

NASA Astrophysics Data System (ADS)

The path-planning algorithm represents a crucial issue for every autonomous mobile robot. In normal circumstances a patrol robot will compute an optimal path to ensure its task accomplishment, but in adversarial conditions the problem is getting more complicated. Here, the robots trajectory needs to be altered into a misleading and unpredictable path to cope with potential opponents. Chaotic systems provide the needed framework for obtaining unpredictable motion in all of the three basic robot surveillance missions: area, points of interests and boundary monitoring. Proficient approaches have been provided for the first two surveillance tasks, but for boundary patrol missions no method has been reported yet. This paper addresses the mentioned research gap by proposing an efficient method, based on chaotic dynamic of the Hnon system, to ensure unpredictable boundary patrol on any shape of chosen closed contour.

Curiac, Daniel-Ioan; Volosencu, Constantin

2014-10-01