For comprehensive and current results, perform a real-time search at Science.gov.

1

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

2

Intra-domain traffic engineering with shortest path routing protocols

Throughout the last decade, extensive deployment of popular intra-domain routing protocols such as open shortest path first\\u000a and intermediate system–intermediate 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

Aysegül Altin; Bernard Fortz; Mikkel Thorup

2009-01-01

3

Engineering Shortest Path Algorithms Camil Demetrescu1

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

4

Highway Hierarchies Hasten Exact Shortest Path Queries

\\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

5

A shortest path representation for video summarisation

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

6

Robust constrained shortest path problems under budgeted ...

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

7

Shorter Path Constraints for the Resource Constrained Shortest Path Problem

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

8

Shortest paths synthesis for a car-like robot

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

P. Soueres; J.-P. Laumond

1996-01-01

9

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

10

Distributional properties of stochastic shortest paths for smuggled nuclear material

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

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

2011-01-05

11

Detecting duplicate biological entities using Shortest Path Edit Distance.

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

12

Quantum algorithms for shortest paths problems in structured instances

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

13

Interval order representation via shortest paths Garth Isaak

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

14

Minimizing communication in all-pairs shortest paths Edgar Solomonik

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 BuluÃ§ Lawrence

California at Berkeley, University of

15

Experimental analysis of dynamic all pairs shortest path algorithms

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

16

Efficient Algorithms for Shortest Paths in Sparse Networks

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

17

Fully Dynamic Algorithms for Maintaining Shortest Paths Trees

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

18

Finding Shortest Path for Developed Cognitive Map Using Medial Axis

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

Farhan, Hazim A; Al-Ghazi, Suhaib I

2011-01-01

19

An Improved Physarum polycephalum Algorithm for the Shortest Path Problem

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

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

2014-01-01

20

Multiple Object Tracking Using the Shortest Path Faster Association Algorithm

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

Liu, Heping; Liu, Huaping; Yang, Bin

2014-01-01

21

Fully Dynamic All Pairs Shortest Paths with Real Edge Weights

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

22

A new approach to dynamic all pairs shortest paths

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

23

A new approach to dynamic all pairs shortest paths

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 Õ(n2) amortized time per update and unit worst-case time per distance query, where n

Camil Demetrescu; Giuseppe F. Italiano

2003-01-01

24

ON THE ACCELERATION OF SHORTEST PATH CALCULATIONS IN TRANSPORTATION NETWORKS

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

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

2007-01-08

25

A Graph Search Heuristic for Shortest Distance Paths

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

Chow, E

2005-03-24

26

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

27

A Bio-Inspired Method for the Constrained Shortest Path Problem

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

Wang, Hongping; Lu, Xi; Wang, Qing

2014-01-01

28

The robust shortest path problem with interval data via Benders decomposition

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

29

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

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

30

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

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

31

Damage detection via shortest-path network sampling.

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

32

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

33

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

34

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

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

35

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

}@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

36

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

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 congesÂ tion. On real and synthetic networks we demonstrate experimentally

Roughan, Matthew

37

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

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

38

We provide an improved FPTAS for multiobjective shortest paths—a fundamental (NP-hard) problem in multiobjective optimization—along\\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

We provide an improved FPTAS for multiobjective shortest paths—a fundamental (NP-hard) problem in multiobjective optimization—along 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

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

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

Gambardella, Luca Maria

41

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

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

42

Trans-dichotomous Algorithms for Minimum Spanning Trees and Shortest Paths

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

Michael L. Fredman; Dan E. Willard

1990-01-01

43

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

, 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

44

Snell's law and light traveling along the shortest path

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

Carlos Lara

2006-01-01

45

Discrete Approximation to Continuous Anisotropic Shortest-Path Problem

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

Hespanha, JoÃ£o Pedro

46

Shortest Path Planning for a Tethered Robot or an Anchored Cable

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

47

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

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

48

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

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

49

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

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

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

2002-01-01

50

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

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

51

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

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

52

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

53

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

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

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

1992-07-14

54

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

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

55

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

56

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

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

57

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

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

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

1989-04-01

58

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

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

Zhang, Junying; Zhao, Xiaoxue; He, Xiaotao

2014-08-01

59

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

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

60

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

61

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

62

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

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

63

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

64

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

65

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

66

NASA Astrophysics Data System (ADS)

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

Kröger, Martin

2005-06-01

67

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

68

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

69

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

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

70

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

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

71

Computing shortest heterochromatic monotone routes

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;

José Miguel Díaz-báñez; G. Hernández; D. Oliveros; A. Ramírez-vigueras; Joan Antoni Sellarès; Jorge Urrutia; Inmaculada Ventura

2008-01-01

72

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

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

73

Understanding and applying open-path optical sensing data

NASA Astrophysics Data System (ADS)

During the last 10 years, open-path air monitors have evolved to yield reliable and effective measurements of single and multiple compounds on a real-time basis. To many individuals within the optical remote sensing community, the attributes of open-path and its the potential uses seem unlimited. Then why has the market has been stagnant for the last few years? The reason may center on how open-path information is applied and how well the end user understands that information. We constantly try to compare open-path data to risk/health or safety levels that are based for use at a single point and for a specific averaging period often far longer than a typical open-path data point. Often this approach is perceived as putting a square peg in a round hole. This perception may be well founded, as open-path data at times may need to go through extensive data manipulation and assumptions before it can be applied. This paper will review pervious open-path monitoring programs and their success in applying the data collected. We will also look at how open-path data is being currently used, some previous pitfalls in data use, alternate methods of data interpretation, and how open-path data can be best practically applied to fit current needs.

Virag, Peter; Kricks, Robert J.

1999-02-01

74

All pairs almost shortest paths

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

75

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 205–214, 2012.

2014-09-19

76

Semiring Frameworks and Algorithms for Shortest-Distance Problems

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

77

OPEN PATH AMBIENT MEASUREMENTS OF POLLUTANTS WITH A DOAS SYSTEM

A differential optical absorption spectrometer (DOAS) has been in operation since August 1991 at the U.S. EPA in RTP, NC. he analyzer unit is located in an environmentally-controlled shelter in the EPA parking lot. our separate open optical paths have been established, ranging fr...

78

Shortest trajectory planning of wheeled mobile robots with constraints

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

79

NASA Astrophysics Data System (ADS)

Methane () fluxes observed with the eddy-covariance technique using an open-path analyzer and a closed-path analyzer in a rice paddy field were evaluated with an emphasis on the flux correction methodology. A comparison of the fluxes obtained by the analyzers revealed that both the open-path and closed-path techniques were reliable, provided that appropriate corrections were applied. For the open-path approach, the influence of fluctuations in air density and the line shape variation in laser absorption spectroscopy (hereafter, spectroscopic effect) was significant, and the relative importance of these corrections would increase when observing small fluxes. A new procedure proposed by Li-Cor Inc. enabled us to accurately adjust for these effects. The high-frequency loss of the open-path analyzer was relatively large (11 % of the uncorrected covariance) at an observation height of 2.5 m above the canopy owing to its longer physical path length, and this correction should be carefully applied before correcting for the influence of fluctuations in air density and the spectroscopic effect. Uncorrected fluxes observed with the closed-path analyzer were substantially underestimated (37 %) due to high-frequency loss because an undersized pump was used in the observation. Both the bandpass and transfer function approaches successfully corrected this flux loss. Careful determination of the bandpass frequency range or the transfer function and the cospectral model is required for the accurate calculation of fluxes with the closed-path technique.

Iwata, Hiroki; Kosugi, Yoshiko; Ono, Keisuke; Mano, Masayoshi; Sakabe, Ayaka; Miyata, Akira; Takahashi, Kenshi

2014-04-01

80

New open-path remote optical sensing method to estimate methane emission from soil

Technology Transfer Automated Retrieval System (TEKTRAN)

The U.S. EPA recently developed an open-path remote sensing method to identify hot spots and estimate fugitive gas emissions from closed landfills. The method measures several path-integrated concentrations (PICs) of gases using open-path optical instruments. These PICs are then processed using a co...

81

Completely automated open-path FT-IR spectrometry.

Atmospheric analysis by open-path Fourier-transform infrared (OP/FT-IR) spectrometry has been possible for over two decades but has not been widely used because of the limitations of the software of commercial instruments. In this paper, we describe the current state-of-the-art of the hardware and software that constitutes a contemporary OP/FT-IR spectrometer. We then describe advances that have been made in our laboratory that have enabled many of the limitations of this type of instrument to be overcome. These include not having to acquire a single-beam background spectrum that compensates for absorption features in the spectra of atmospheric water vapor and carbon dioxide. Instead, an easily measured "short path-length" background spectrum is used for calculation of each absorbance spectrum that is measured over a long path-length. To accomplish this goal, the algorithm used to calculate the concentrations of trace atmospheric molecules was changed from classical least-squares regression (CLS) to partial least-squares regression (PLS). For calibration, OP/FT-IR spectra are measured in pristine air over a wide variety of path-lengths, temperatures, and humidities, ratioed against a short-path background, and converted to absorbance; the reference spectrum of each analyte is then multiplied by randomly selected coefficients and added to these background spectra. Automatic baseline correction for small molecules with resolved rotational fine structure, such as ammonia and methane, is effected using wavelet transforms. A novel method of correcting for the effect of the nonlinear response of mercury cadmium telluride detectors is also incorporated. Finally, target factor analysis may be used to detect the onset of a given pollutant when its concentration exceeds a certain threshold. In this way, the concentration of atmospheric species has been obtained from OP/FT-IR spectra measured at intervals of 1 min over a period of many hours with no operator intervention. PMID:18946664

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

2009-01-01

82

An Open-path Laser Transmissometer for Atmospheric Extinction Measurements

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

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

2011-10-20

83

TATP stand-off detection with open path: FTIR techniques

NASA Astrophysics Data System (ADS)

TATP is a very easy to synthesize [9], sensitive, high explosive [10] and high volatile explosive [1, 3, 7] with great absorption in the IR Spectra [4, 5, 6]. In this project we detect TATP gas traces with open path FTIR - techniques. The first project phase was to construct and build a heatable multi-reflection cell with adjustable optical path length and a heatable intake to evaporate solid TATP samples. In this cell reference TATP - spectra were collected under controlled conditions with a Bruker FTIR system (Typ OPAG 33). The next step was to find out how the TATP gas will be diluted in the ambient air and validate some physical properties which are described inconsistently in literature e.g. evaporation rates. We constructed a special double - T shaped chamber with stabile air conditions. In this chamber the dispersion kinetics of the TATP vapour could be tested. It turned out that the TATP vapours has the tendency to drop down. Therefore the highest TATP - concentrations were measured below the TATP sample. During the investigation for this study it turned out, that some materials scrub the TATP- vapour out of the air, e.g. Metals, fabric, leather. In the second phase of the project successful open path FTIR- measurements were taken in ambient air and will be continued with different system configurations of the OPAG 33 to lower the detection limits. Also successful measurements were taken in indoor ambient air with a Hyper spectral camera (passive FTIR with array sensor) to detect TATP in solid and gaseous phase. This technique allows detecting TATP and identifying the TATP source. The poster shows some selected results of the continued research.

Fischer, C.; Pohl, T.; Weber, K.; Vogel, A.; van Haren, G.; Schweikert, W.

2012-10-01

84

COMPARISON OF FLUX MEASUREMENTS WITH OPEN-AND CLOSED-PATH GAS ANALYZERS ABOVE AN AGRICULTURAL

COMPARISON OF FLUX MEASUREMENTS WITH OPEN- AND CLOSED-PATH GAS ANALYZERS ABOVE AN AGRICULTURAL 16 March, 1993) Abstract. Comparison was made of the flux measurements of a closed-path CO2/H20), the measurement can be made using the eddy correlation technique with a velocity sensor and an adjacent open

Lee, Xuhui

85

Interval Order Representation via Shortest Paths

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

86

Water Vapor, Cloud Liquid Water Paths, and Rain Rates over the Northern High Latitude Open Seas

Water Vapor, Cloud Liquid Water Paths, and Rain Rates over the Northern High Latitude Open Seas-based Instrumentation: May 1-8 time series 35 GHz cloud radar ice cloud properties depolarization lidar-determined liquid cloud base Microwave radiometer-derived liquid water paths Near-surface T ~ -30 C, inversion

Zuidema, Paquita

87

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.

88

Industrial applications of open-path Fourier transform infrared spectrometry

NASA Astrophysics Data System (ADS)

A commercially available fieldable Fourier transform infrared (FT-IR) spectrometer has been evaluated for monitoring volatile organic compounds (VOCs) in and around incineration equipment for VOC emissions. During this data collection a 20 X 20 inch polished stainless steel plate was used as the reflection surface, to evaluate the use of less expansive optics for industrial applications. Research has also progressed on developing a method to produce an I0 spectrum utilizing a short path length.

Spartz, Martin L.; Eldridge, Jess S.; Hipple, Gary D.; Reagen, William K.; Stock, Jeffrey W.

1994-01-01

89

Restoration by Path Concatenation: Fast Recovery of MPLS Paths

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

90

Restoration by Path Concatenation: Fast Recovery of MPLS Paths

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

91

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

92

PARTICULATE MATTER MEASUREMENTS USING OPEN-PATH FOURIER TRANSFORM INFRARED SPECTROSCOPY

Open-path Fourier transform infrared (OP-FT1R) spectroscopy is an accepted technology for measuring gaseous air contaminants. OP-FT1R absorbance spectra acquired during changing aerosols conditions reveal related changes in very broad baseline features. Usually, this shearing of ...

93

Methane emission rates from a herd of grazing dairy cows were determined from concentration measurements with four open-path lasers positioned around the fenced grazing area. The emission rates were calculated with the aid of a backward-Lagrangian stochastic model (BLS). After discarding data with insufficient laser light levels (due to technical issues discussed in the paper) and periods of light winds,

Johannes Laubach; Francis M. Kelliher

2005-01-01

94

OPEN-PATH FTIR MEASUREMENTS OF NOX AND OTHER DIESEL EMISSIONS

The paper gives results of a demonstration of the feasibility of using an open-path Fourier transform infrared (OP-FTIR) monitoring technique to address the across-road characterization of diesel vehicle emissions of criteria pollutants and hazardous air pollutants. Four sets of ...

95

NASA Astrophysics Data System (ADS)

A multiwavelength technique for open-path spectrophotometric measurements of the concentrations of the principal constituents of the atmosphere is presented. It uses a standard least squares procedure to minimize deviations of the calculated optical thickness of the working path from the measured value. The novel feature of this technique is that the effects of various sources of error on the computational results are interpreted as the difference in spectra of the probe radiation propagating along the working path and a comparison path. This difference yields a systematic error that is independent of the actual concentrations. The advantage of the multiwavelength technique is that an increased number of measurement wavelengths significantly reduces the effect of the various sources of error on the results.

Liudchik, A. M.

2012-07-01

96

Novel In-situ Calibrations for Open-path Ammonia Sensing

NASA Astrophysics Data System (ADS)

As a major gas phase precursor of fine particulate matter, ammonia plays an important role in the nitrogen cycle. However, its concentration is rather poorly quantified due to various measurement challenges. Open-path detection addresses the sampling issue caused by surface affinity of ammonia and greatly simplifies the sensor design. We have developed an open-path ammonia sensor using a quantum cascade (QC) laser at 9.06 ?m. The sensor has been deployed in 2010 CALNEX campaign in Bakersfield, CA and locally in Princeton in July 2011. The sensor achieved a field detection limit of 1 ppbv ammonia at 1 Hz. Open-path measurements avoid the common sampling problems and biases for ammonia, but ultimately one needs to enclose the open-path system for calibration. To this end, an off-line spectroscopic method to calibrate the ammonia signal was successfully used in CALNEX using ethylene, a stable, relatively inert gas. Ethylene occurs at ambient pptv atmospheric mixing ratios and does thus not cause interference at ambient conditions. However, at much higher concentrations used to calibrate, ethylene exhibits a significant absorption feature that is just offset spectrally from the ammonia absorption feature but comparable in size and thus can serve as a reference absorption signal for ammonia. The open-path QC ammonia measurements intercompared well with ion chromatography measurements in the 5-35 ppbv range. Line shape parameters of both ammonia and ethylene were measured experimentally to confirm the spectroscopic reference calibration technique, and the results were within 10% of HITRAN values over a range of 265-300 K and 10-1000 hPa. Wavelength modulation spectroscopy (WMS) is used in the sensor to enhance the sensitivity as a baseline-free sensing technique. A numerical model was developed to simulate and validate the WMS signals with the experimental spectroscopic data. Model simulations indicate that the 2f WMS signal magnitude for ammonia is largely invariant to pressure and temperature changes. A 2.5 cm reduced pressure in-line ethylene calibration cell was simulated by the WMS model with the goal of in-situ, continuous calibrations for our open-path system. The simulation indicates that ambient ammonia spectra have little interference (<1% over 0-100 ppbv NH3) on the ethylene 2f reference signal when a novel dual modulation is performed. This in-line ethylene calibration technique enables open-path and continuous calibration methods for atmospheric ammonia, and experimental and field results will be demonstrated.

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

2011-12-01

97

Spreading paths in partially observed social networks

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

98

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

99

Open-path sensor for atmospheric methane based on chirped laser dispersion spectroscopy

NASA Astrophysics Data System (ADS)

The design and characterization of a near-IR Chirped Laser Dispersion Spectroscopy (CLaDS) sensor for atmospheric methane detection are reported. The near-IR CLaDS system exhibits the benefits of the prior mid-IR CLaDS systems implemented for open-path sensing while taking advantage of the robust fiber-optic components available in the near-IR. System noise, long-term stability, and comparison with existing technology for methane detection are presented.

Nikodem, Michal; Plant, Genevieve; Sonnenfroh, David; Wysocki, Gerard

2014-10-01

100

Open-path, quantum cascade-laser-based sensor for high-resolution atmospheric ammonia measurements

NASA Astrophysics Data System (ADS)

We demonstrate a compact, open-path, quantum cascade-laser-based atmospheric ammonia sensor operating at 9.06 ?m for high-sensitivity, high temporal resolution, ground-based measurements. Atmospheric ammonia (NH3) is a gas-phase precursor to fine particulate matter, with implications for air quality and climate change. Currently, NH3 sensing challenges have led to a lack of widespread in situ measurements. Our open-path sensor configuration minimizes sampling artifacts associated with NH3 surface adsorption onto inlet tubing and reduced pressure sampling cells, as well as condensed-phase partitioning ambiguities. Multi-harmonic wavelength modulation spectroscopy allows for selective and sensitive detection of atmospheric pressure-broadened absorption features. An in-line ethylene reference cell provides real-time calibration (±20% accuracy) and normalization for instrument drift under rapidly changing field conditions. The sensor has a sensitivity and noise-equivalent limit (1?) of 0.15 ppbv NH3 at 10 Hz, a mass of ~ 5 kg and consumes ~ 50 W of electrical power. The total uncertainty in NH3 measurements is 0.20 ppbv NH3 ± 10%, based on a spectroscopic calibration method. Field performance of this open-path NH3 sensor is demonstrated, with 10 Hz time resolution and a large dynamic response for in situ NH3 measurements. This sensor provides the capabilities for improved in situ gas-phase NH3 sensing relevant for emission source characterization and flux measurements.

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

2014-01-01

101

Open-path, quantum cascade laser-based sensor for high resolution atmospheric ammonia measurements

NASA Astrophysics Data System (ADS)

We demonstrate a compact, open-path, quantum cascade laser-based atmospheric ammonia sensor operating at 9.06 ?m for high sensitivity, high temporal resolution, ground-based measurements. Atmospheric ammonia (NH3) is a gas-phase precursor to fine particulate matter, with implications for air quality and climate change. Currently, NH3 sensing challenges have led to a lack of widespread in-situ measurements. Our open-path sensor configuration avoids sampling artifacts associated with NH3 surface adsorption onto inlet tubing and reduced pressure sampling cells, as well as condensed-phase partitioning ambiguities. Multi-harmonic wavelength modulation spectroscopy allows for selective and sensitive detection of atmospheric-pressure broadened absorption features. An in-line ethylene reference cell provides real-time calibration (±20% accuracy) and normalization for instrument drift under rapidly changing field conditions. The sensor has a sensitivity and minimum detection limit of 0.15 ppbv NH3 at 10 Hz, a mass of ~ 5 kg and consumes ~ 50 W of electrical power. In-situ field performance of this open-path NH3 sensor is demonstrated, with 10 Hz time resolution and a large dynamic response for in-situ NH3 measurements. This sensor provides the capabilities for improved in-situ gas phase NH3 sensing relevant for emission source characterization and flux measurements.

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

2013-07-01

102

Field experiments were carried out in the vicinity of anisolated building using open-path and point monitoring airpollution detectors to measure concentrations of a tracer gasreleased from a source located either on the building or at thedownwind face of the building. Experiments were conducted underneutral or slightly unstable weather conditions. Either threeor five fast-response point monitors were located along thebeam path

I. Mavroidis; R. F. Griffiths

2002-01-01

103

Open-path Fourier transform infrared (OP/FTIR) spectrometry was used to measure the concentrations of ammonia, methane, and other atmospheric gasses around an integrated industrial swine production facility in eastern North Carolina. Several single-path measurements were made ove...

104

Cost-based Filtering for Shorter Path Constraints

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

105

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

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

2011-01-01

106

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

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

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

1995-12-31

107

Improved Eddy Flux Measurements by Open-Path Gas Analyzer and Sonic Anemometer Co-Location

NASA Astrophysics Data System (ADS)

A novel instrument design combines the sensing paths of an open-path gas analyzer and a 3-D sonic anemometer and integrates the sensors in a single aerodynamic body. Common electronics provide fast-response, synchronized measurements of wind vector, sonic temperature, CO2 and H2O densities, and atmospheric pressure. An instantaneous CO2 mixing ratio, relative to dry air, is computed in real time. The synergy of combined sensors offers an alternative to the traditional density-based flux calculation method historically used for standalone open-path analyzers. A simple method is described for a direct, in-situ, mixing-ratio-based flux calculation. The method consists of: (i) correcting sonically derived air temperature for humidity effects using instantaneous water vapor density and atmospheric pressure measurements, (ii) computing water vapor pressure based on water-vapor density and humidity-corrected sonic temperature, (iii) computing fast-response CO2 mixing ratio based on CO2 density, sonic temperature, water vapor, and atmospheric pressures, and (iv) computing CO2 flux from the covariance of the vertical wind speed and the CO2 mixing ratio. Since CO2 mixing ratio is a conserved quantity, the proposed method simplifies the calculations and eliminates the need for corrections in post-processing by accounting for temperature, water-vapor, and pressure-fluctuation effects on the CO2 density. A field experiment was conducted using the integrated sensor to verify performance of the mixing-ratio method and to quantify the differences with density-derived CO2 flux corrected for sensible and latent-heat fluxes. The pressure term of the density corrections was also included in the comparison. Results suggest that the integrated sensor with co-located sonic and gas sensing paths and the mixing-ratio-based method minimize or eliminate the following uncertainties in the measured CO2 flux: (i) correcting for frequency-response losses due to spatial separation of measured quantities, (ii) correcting sonically-derived, sensible-heat flux for humidity, (iii) correcting latent-heat flux for sensible-heat flux and water-vapor self-dilution, (iv) correcting CO2 flux for sensible- and latent-heat fluxes, (v) correcting CO2 flux for pressure-induced density fluctuations.

Bogoev, Ivan

2014-05-01

108

Open Path Tracer Measurements of Methane Emissions from Free Ranging Cattle

NASA Astrophysics Data System (ADS)

This paper addresses the need for more accurate and representative measurements of methane emissions from cattle in their natural environments. Improved measurements are or will be required to quantify methane emissions for national greenhouse gas budgets and future carbon trading schemes, and to assess the effectiveness of proposed mitigation strategies. We describe measurements of methane emissions from free- ranging cattle grazing in their natural outdoor environments in Australia and New Zealand. We employ a novel tracer method in which nitrous oxide is released at a known rate from fenceline tubing or canisters attached to individual cows, and the mixing ratios of methane, nitrous oxide and carbon dioxide are measured continuously and simultaneously downwind by open path FTIR spectroscopy. Correlations between methane, nitrous oxide and carbon dioxide can be used to infer the herd-average methane flux directly. Measurements will be compared with the more conventional SF6 ruminal tracer technique.

Griffith, D. W.; Tonini, M.; Bryant, G. R.; Eckard, R.; Grainger, C.; McGinn, S. M.

2006-12-01

109

NASA Astrophysics Data System (ADS)

It is widely known that methane, together with carbon dioxide, is one of the most effective greenhouse gases contributing to climate global change. According to EMEP/CORINAIR Emission Inventory Guidebook1, around 25% of global CH4 emissions originate from animal husbandry, especially from enteric fermentation. However, uncertainties in the CH4 emission factors provided by EMEP/CORINAIR are around 30%. For this reason, works addressed to calculate emissions experimentally are so important to improve the estimations of emissions due to livestock and to calculate emission factors not included in this inventory. FTIR spectroscopy has been frequently used in different methodologies to measure emission rates in many environmental problems. Some of these methods are based on dispersion modelling techniques, wind data, micrometeorological measurements or the release of a tracer gas. In this work, a new method for calculating emission rates from livestock buildings applying Open-Path FTIR spectroscopy is proposed. This method is inspired by the accumulation chamber method used for CO2 flux measurements in volcanic areas or CH4 flux in wetlands and aquatic ecosystems. The process is the following: livestock is outside the building, which is ventilated in order to reduce concentrations to ambient level. Once the livestock has been put inside, the building is completely closed and the concentrations of gases emitted by livestock begin to increase. The Open-Path system measures the concentration evolution of gases such as CO2, CH4, NH3 and H2O. The slope of the concentration evolution function, dC/dt, at initial time is directly proportional to the flux of the corresponding gas. This method has been applied in a cow shed in the surroundings of La Laguna, Tenerife Island, Spain). As expected, evolutions of gas concentrations reveal that the livestock building behaves like an accumulation chamber. Preliminary results show that the CH4 emission factor is lower than the proposed by the Emission Inventory.

Briz, Susana; Barrancos, José; Nolasco, Dácil; Melián, Gladys; Padrón, Eleazar; Pérez, Nemesio

2009-09-01

110

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

111

Scalable Shortest Paths Browsing on Land Surface Songhua Xing

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

112

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

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

113

Fast shortest path distance estimation in large networks

@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

114

Fast shortest path distance estimation in large networks

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

115

OBSTACLE-AVOIDING SIMILARITY METRICS AND SHORTEST PATH PROBLEMS

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

116

Integer programming formulations for the elementary shortest path ...

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

117

Shortest Path Computation with No Information Leakage Kyriakos Mouratidis

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

118

Methodology for Augmenting Existing Paths with Additional Parallel Transects

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

Wilson, John E.

2013-09-30

119

NASA Astrophysics Data System (ADS)

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

Wang, Wei; Liu, Wenqing; Zhang, Tianshu

2012-12-01

120

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

Sheng Wu

2012-10-02

121

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

122

NASA Astrophysics Data System (ADS)

Eddy flux is computed using a covariance between fast changes in gas density and vertical wind speed. The measured changes in gas density happen due to gas flux itself, thermal expansion and contraction of the sampled gas, water vapor dilution, and pressure-related expansions and contractions. These are standard processes described by the Ideal Gas Law and by the Law of Partial Pressures, and are often called density effects. The gas flux is usually corrected for such density effects using Webb-Pearman-Leuning terms (WPL). When gas density is measured by laser spectroscopy, there are also spectroscopic effects affecting measured gas density depending on fluctuations in temperature, water vapor and pressure, in addition to the density effects. The spectroscopic effects are related to changes in the shape of the absorption line due to changes in gas temperature, pressure and the presence of water vapor. These effects are specific for each specific absorption line, and the measurement technique. The majority of density effects and spectroscopic effects are reduced or eliminated in the closed-path analyzers, when: (a) intake tube is very long, (b) gas sample is dried, and (c) pressure fluctuations are very small. However, the use of long intake tubes and drying of the air sample also lead to a significant increase in power demand, and to increased uncertainties due to excess attenuation of the fluctuations of the gas in the drier. Not drying the air sample leads to a need for applying a density correction for dilution, and spectroscopic corrections for gas absorption due to fast fluctuations in water vapor pressure. For both of these corrections water vapor should be measured accurately at high-speed inside the closed-path device, which increases measurements costs. In addition, current fast closed-path analyzers based on laser spectroscopy have to operate under significantly reduced pressures, and require powerful pumps and grid power (400-1500 Watts). Power demands may be why these instruments are often deployed at locations with infrastructure and grid power, and not where the gas is produced. Open-path gas analyzers can require very low-power (e.g., 5-10 Watts), permitting solar-powered deployments, cost-effectively permitting an addition of a single new gas measurement to the present array of CO2 and H2O measurements, and avoiding attenuation of gas fluctuations in the intake tube. These features enable long-term deployments of permanent, portable or mobile open-path flux stations at remote locations with high production of the gas of interest. However, in open-path analyzers, density and spectroscopic effects cannot be neglected. Here we propose a new way to account for spectroscopic effects due to fast fluctuations in air temperature, water vapor and pressure in the same manner as Webb et al. (1980) proposed a way of accounting for respective density effects. Since both density effects and spectroscopic effects are known from Gas Laws and HITRAN, respectively, they can be incorporated into the WPL correction. We use an example of a fast open-path CH4 gas analyzer, the LI-7700, yet the proposed approach would also apply to any closed-path design where fluctuations in temperature, water vapor and pressure are not fully eliminated.

Burba, George; McDermitt, Dayle; Anderson, Tyler; Komissarov, Anatoly

2013-04-01

123

Path optimization using sub-Riemannian manifolds with applications to astrodynamics

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

124

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

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.

125

in the open and distance from cover to numbers of domestic cats as well as to presence of raptors and coyotes in Palomino Park, a xeric park with low shrub density, cats, and no coyotes exhibited the greatest predator, both availability of cover (shrubs Â Fig. 4) and predator presence (cats/coyotes Â Fig. 5

Hall, Sharon J.

126

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

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

127

Extracting optimal paths from roadmaps for motion planning

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

128

Open-path Atmospheric N2O, CO, and NH3 Measurements Using Quantum Cascade Laser Spectroscopy

NASA Astrophysics Data System (ADS)

We develop a compact, mid-infrared quantum cascade (QC) laser based sensor to perform high precision measurements of N2O and CO simultaneously. Since CO is a good tracer of anthropogenic emissions, simultaneous measurements of CO and N2O allow us to correlate the sources of N2O emissions. The thermoelectrically (TE) cooled, and continuous wave QC laser enables room-temperature and unattended operation. The laser is scanned over the absorption features of N2O and CO near 4.54 ?m by laser current modulation. A novel cylindrical multi-pass optical cell terminated at the (N/2)th spot is used to simplify the optical configuration by separating the laser and TE cooled detector. Our systems are open-path and non-cryogenic, which avoids vacuum pump and liquid nitrogen. This configuration enables a future design of a non-intrusive, compact (shoe box size), and low-power (10W) sensor. Wavelength modulation spectroscopy (WMS) is used to enhance measurement sensitivity. Higher-harmonic detection (4f and 6f) is performed to improve the resolution between the nearly overlapping N2O and CO lines. Relevant atmospheric N2O and CO concentration is measured, with a detection limit of 0.3 ppbv for N2O and 2 ppbv for CO for 1 s averaging in terms of noise. We also develop an open-path high sensitivity atmospheric ammonia (NH3) sensor using a very similar instrument design. A 9.06 ?m QC laser is used to probe absorption features of NH3. Open-path detection of NH3 is even more beneficial due to the surface absorption effect of NH3 and its tendency to readily partition into condensed phases. The NH3 sensor was deployed at the CALNEX 2010 field campaign. The entire system was stable throughout the campaign and acquired data with 10 s time resolution under adverse ambient temperatures and dusty conditions. The measurements were in general agreement with other NH3 and trace gases sensors. Both the N2O/CO and NH3 sensors will be deployed in a local eddy-covariance station to examine long term stability and detection limit in the field. Future sensor applications include characterizing urban and agricultural N2O and NH3 emission sources and quantifying their respective fluxes.

Sun, K.; Khan, A.; Miller, D. J.; Rafferty, K.; Schreiber, J.; Puzio, C.; Portenti, M.; Silver, J.; Zondlo, M. A.

2010-12-01

129

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

130

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

Tomasko, M.S.

1995-12-31

131

A ray-tracing analysis of cat's-eye retroreflectors for use in active open-path Fourier-transform-infrared (OP/FT-IR) spectrometry and the results of testing f/0.5 and f/1.75 cat's-eye retroreflectors built in our laboratory with a commercial active OP/FT-IR spectrometer are presented. The ray-tracing model is based on the optical characteristics of a commercial single-telescope monostatic OP/FT-IR spectrometer and explores trends in cat's-eye behavior in practical but rigorous field conditions encountered during transportable outdoor use. All mirrors modeled are paraboloids for which the focal ratios of the primary mirror are f/0.5, f/1.75, and f/3. The effect of the focal ratio of the primary mirror, the focal length of the secondary mirror, and the off-axis alignment of the primary and the secondary mirror have been evaluated as a function of path length, including variable input-beam divergence, between the spectrometer and the cat's-eye. The paraboloidal mirrors comprising the primary and secondary of the cat's-eye retroreflectors tested were made in our laboratory by spin casting liquid epoxy-graphite composite mixtures followed by in situ polymerization with no postpolishing. PMID:12396182

Richardson, Robert L; Griffiths, Peter R

2002-10-20

132

NASA Astrophysics Data System (ADS)

In trials of a mass balance method for measuring methane (CH 4) emissions, sonic anemometers and an open-path laser were used to measure the transport of CH 4 released from a ground-level source across a downwind face 50 m long and 6 m high. Release rates matched emissions expected from dairy herds of 2 to 40 cows. The long laser path permitted inferences from measurements in only two planes, one upwind and one downwind, while the fast-response instruments allowed calculation of instantaneous horizontal fluxes rather than fluxes calculated from mean wind speeds and mean concentrations. The detection limit of the lasers was 0.02 ppmv, with the separation between the transmitters and reflectors being about 50 m. The main conclusions from the 23 trials were: (1) Emissions calculated from mean wind speeds and concentrations overestimated the true emissions calculated from instantaneous measurements by 5%. (2) Because of small changes in methane concentration, the minimum sample size in animal trials would be 10 dairy cows, producing about 40 mg CH 4 s -1. (3) For release rates greater than 40 mg CH 4 s -1 and with sufficient replication, the technique could detect a change in production rate of 9% ( P<=0.05). (4) Attention to perceived weaknesses in the present technique should help towards detecting changes of 5%.

Desjardins, R. L.; Denmead, O. T.; Harper, L.; McBain, M.; Massé, D.; Kaharabata, S.

133

ERIC Educational Resources Information Center

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

Kelly, Hope

2014-01-01

134

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

in complex 3D environments Â· probability of radar acquisition depends on UAVs attitude Â· "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, JoÃ£o Pedro

135

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

136

The paper describes a methodology developed to estimate emissions factors for a variety of different area sources in a rapid, accurate, and cost effective manner. he methodology involves using an open-path Fourier transform infrared (FTIR) spectrometer to measure concentrations o...

137

NASA Astrophysics Data System (ADS)

The path-averaging, multi-component Fourier Transform Infrared (FTIR) absorption spectrometry at an open path of 100 m length is applied for the up-scaling of greenhouse gas (GHG) flux measurements from soil surfaces. For the detection of the emissions of N2O and further GHG from arable field soils a measuring tunnel for controlled enrichment of released gases was installed at the soil surface covering an area of 495 or 306 m2. The concentrations of GHG were measured by FTIR across the whole measuring tunnel. The precision of the FTIR system is discussed to detect the concentration increases during a time period of up to two hours. During a 2-years-time frame the N2O fluxes between the soil and the atmosphere at the agricultural field varied between 1.0 and 21 ?g N2O-N m-2 h-1. A non-intrusive emission and flux measurement method at a scale from 100 m up to 27.000 m2 on the basis of the fluxgradient method (0.50 and 2.70 m height above surface) was developed and tested by means of FTIR (N2O and further GHG concentrations) and area averaging meteorological measurements (determination of horizontal winds and friction velocity using acoustic tomography). To detect the concentration gradient between the two heights the precision of the FTIR system is discussed. Two campaigns in October 2007 and June 2008 were performed with this new methodology when wind speeds were low. The measurement errors are discussed and the results compared with the measurement tunnel results that were higher by up to 25 %.

Schäfer, Klaus; Jahn, Carsten; Wiwiorra, Michael; Schleichardt, Anja; Emeis, Stefan; Raabe, Armin; Böttcher, Jürgen; Landmeyer, Nils-Demian; Bonecke, Christoph; Deurer, Marcus; von der Heide, Carolin; Weymann, Daniel

2009-09-01

138

Opening paths to novel analgesics: the role of potassium channels in chronic pain.

Chronic pain is associated with abnormal excitability of the somatosensory system and remains poorly treated in the clinic. Potassium (K?) channels are crucial determinants of neuronal activity throughout the nervous system. Opening of these channels facilitates a hyperpolarizing K? efflux across the plasma membrane that counteracts inward ion conductance and therefore limits neuronal excitability. Accumulating research has highlighted a prominent involvement of K? channels in nociceptive processing, particularly in determining peripheral hyperexcitability. We review salient findings from expression, pharmacological, and genetic studies that have untangled a hitherto undervalued contribution of K? channels in maladaptive pain signaling. These emerging data provide a framework to explain enigmatic pain syndromes and to design novel pharmacological treatments for these debilitating states. PMID:24461875

Tsantoulas, Christoforos; McMahon, Stephen B

2014-03-01

139

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

140

Parallel transport of long mean-free-path plasma along an open magnetic field line is characterized by strong temperature anisotropy, which is driven by two effects. The first is magnetic moment conservation in a non-uniform magnetic field, which can transfer energy between parallel and perpendicular degrees of freedom. The second is decompressional cooling of the parallel temperature due to parallel flow acceleration by conventional presheath electric field which is associated with the sheath condition near the wall surface where the open magnetic field line intercepts the discharge chamber. To the leading order in gyroradius to system gradient length scale expansion, the parallel transport can be understood via the Chew-Goldbeger-Low (CGL) model which retains two components of the parallel heat flux, i.e., q{sub n} associated with the parallel thermal energy and q{sub s} related to perpendicular thermal energy. It is shown that in addition to the effect of magnetic field strength (B) modulation, the two components (q{sub n} and q{sub s}) of the parallel heat flux play decisive roles in the parallel variation of the plasma profile, which includes the plasma density (n), parallel flow (u), parallel and perpendicular temperatures (T{sub Parallel-To} and T{sub Up-Tack }), and the ambipolar potential ({phi}). Both their profile (q{sub n}/B and q{sub s}/B{sup 2}) and the upstream values of the ratio of the conductive and convective thermal flux (q{sub n}/nuT{sub Parallel-To} and q{sub s}/nuT{sub Up-Tack }) provide the controlling physics, in addition to B modulation. The physics described by the CGL model are contrasted with those of the double-adiabatic laws and further elucidated by comparison with the first-principles kinetic simulation for a specific but representative flux expander case.

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

2012-08-15

141

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

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

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

2014-01-01

142

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

143

How can epilepsy gene hunting lead to better care for patients with epilepsy? Lessons may be learned from the progress made by identifying the mutated genes that cause Benign Familial Neonatal Convulsions (BFNC). In 1998, a decade of clinical and laboratory-based genetics work resulted in the cloning of the KCNQ2 potassium channel gene at the BFNC locus on chromosome 20. Subsequently, computer "mining" of public DNA databases allowed the rapid identification of three more brain KCNQ genes. Mutations in each of these additional genes were implicated as causes of human hereditary diseases: epilepsy (KCNQ3), deafness (KCNQ4), and, possibly, retinal degeneration (KCNQ5). Physiologists discovered that the KCNQ genes encoded subunits of the "M-channel," a type of potassium channel known to control repetitive neuronal discharges. Finally, pharmacologists discovered that retigabine, a novel anticonvulsant with a broad but distinctive efficacy profile in animal studies, was a potent KCNQ channel opener. These studies suggest that KCNQ channels may be an important new class of targets for anticonvulsant therapies. The efficacy of retigabine is currently being tested in multicenter clinical trials; identification of its molecular targets will allow it to be more efficiently exploited as a "lead compound." Cloned human KCNQ channels can now be expressed in cultured cells for "high-throughput" screening of drug candidates. Ongoing studies of the KCNQ channels in humans and animal models will refine our understanding of how M-channels control excitability at the cellular, network, and behavioral levels, and may reveal additional targets for therapeutic manipulation. PMID:11887968

Cooper, E C

2001-01-01

144

Formal language constrained path problems

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

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

1997-07-08

145

Optimal paths for a car that goes both forwards and backwards

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

J. A. Reeds; L. A. Shepp

1990-01-01

146

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

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

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

2012-06-15

147

NASA Astrophysics Data System (ADS)

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

Sung, Lung-Yu; Lu, Chia-Jung

2014-09-01

148

Although most coke oven research is focused on the emission of polycyclic aromatic hydrocarbons, well-known carcinogens, little has been done on the emission of volatile organic compounds, some of which are also thought to be hazardous to workers and the environment. To profile coke oven gas (COG) emissions, we set up an open-path Fourier transform infrared (OP-FTIR) system on top of a battery of coke ovens at a steel mill located in Southern Taiwan and monitored average emissions in a coke processing area for 16.5 hr. Nine COGs were identified, including ammonia, CO, methane, ethane, ethylene, acetylene, propylene, cyclohexane, and O-xylene. Time series plots indicated that the type of pollutants differed over time, suggesting that different emission sources (e.g., coke pushing, quench tower, etc.) were involved at different times over the study period. This observation was confirmed by the low cross-correlation coefficients of the COGs. It was also found that, with the help of meteorological analysis, the data collected by the OP-FTIR system could be analyzed effectively to characterize differences in the location of sources. Although the traditional single-point samplings of emissions involves sampling various sources in a coke processing area at several different times and is a credible profiling of emissions, our findings strongly suggest that they are not nearly as efficient or as cost-effective as the continuous line average method used in this study. This method would make it easier and cheaper for engineers and health risk assessors to identify and to control fugitive volatile organic compound emissions and to improve environmental health. PMID:17458466

Lin, Chitsan; Liou, Naiwei; Chang, Pao-Erh; Yang, Jen-Chin; Sun, Endy

2007-04-01

149

We report trace-gas emission factors from three pine-understory prescribed fires in South Carolina, U.S. measured during the fall of 2011. The fires were an attempt to simulate high-intensity burns and the fuels included mature pine stands not frequently subjected to prescribed fire that were lit following a sustained period of drought. In this work we focus on the emission factor measurements made using a fixed open-path gas analyzer Fourier transform infrared (FTIR) system. We compare these emission factors with those measured using a roving, point sampling, land-based FTIR and an airborne FTIR that were deployed on the same fires. We also compare to emission factors measured by a similar open-path FTIR system deployed on savanna fires in Africa. The data suggest that the method in which the smoke is sampled can strongly influence the relative abundance of the emissions that are observed. The airborne FTIR probed the bulk of the emissions, which were lofted in the convection column and the downwind chemistry while the roving ground-based point sampling FTIR measured the contribution of individual residual smoldering combustion fuel elements scattered throughout the burn site. The open-path FTIR provided a fixed path-integrated sample of emissions produced directly upwind mixed with emissions that were redirected by wind gusts, or right after ignition and before the adjacent plume achieved significant vertical development. It typically probed two distinct combustion regimes, “flaming-like” (immediately after adjacent ignition) and “smoldering-like”, denoted “early” and “late”, respectively. The calculated emission factors from open-path measurements were closer to the airborne than to the point measurements, but this could vary depending on the calculation method or from fire to fire given the changing MCE and dynamics over the duration of a typical burn. The emission factors for species whose emissions are not highly fuel dependent (e.g. CH4 and CH3OH) from all three systems can be plotted versus modified combustion efficiency and fit to a single consistent trend suggesting that differences between the systems for these species may be mainly due to the unique mix of flaming and smoldering that each system sampled. For other more fuel dependent species, the different fuels sampled also likely contributed to platform differences in emission factors. The path-integrated sample of the ground-level smoke layer adjacent to the fire provided by the open-path measurements is important for estimating fire-line exposure to smoke for wildland fire personnel. We provide a table of estimated fire-line exposures for numerous known air toxics based on synthesizing results from several studies. Our data suggest that peak exposures are more likely to challenge permissible exposure limits for wildland fire personnel than shift-average exposures.

Akagi, Sheryl; Burling, Ian R.; Mendoza, Albert; Johnson, Timothy J.; Cameron, Melanie; Griffith, David WT; Paton-Walsh, C.; Weise, David; Reardon, James; Yokelson, Robert J.

2014-01-08

150

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

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

2013-03-01

151

Short paths in expander graphs

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

152

relationship between sediment transport capacity and detach- ment developed for the USDA Water Erosion1479 Path sampling method for modeling overland water flow, sediment transport, and short term-scale/multi-process treatments. It has been used to develop simulation tools for overland shallow water flow and for sed- iment

Thaxton, Christopher S.

153

A path sampling method is proposed for solving the continuity equations describing mass flows over complex landscape surfaces. The modeled quantities are represented by an ensemble of sampling points which are evolved according to the corresponding Green function. The method enables incorporation of multi-scale\\/multi-process treatments. It has been used to develop simulation tools for overland shallow water flow and for

Helena Mitasova; Jaroslav Hofierka

154

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

155

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.

156

Internet Traffic Engineering by Optimizing OSPF Weights

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

Bernard Fortz; Mikkel Thorup

2000-01-01

157

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

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.

158

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

159

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

160

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. Â· dynamic creation to be acquired. Therefore, multiagent-based simulation (MABS) can be used to procure well-founded assess- ments

161

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

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

162

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

) 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

163

An exact algorithm for the capacitated shortest spanning arborescence

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

164

NASA Astrophysics Data System (ADS)

Measurements of land-surface emission rates of greenhouse and other gases at large spatial scales (10 000 m2) are needed to assess the spatial distribution of emissions. This can be more readily done using spatial-integrating micro-meteorological methods than the widely-utilized small chamber measurements. Several micro-meteorological flux-gradient methods utilizing a non-intrusive path-averaging measurement method were evaluated for determining land-surface emission rates of trace gases under stable boundary layers. Successful application of a flux-gradient method requires confidence in the gradients of trace gas concentration and wind and in the applicability of boundary-layer turbulence theory. While there is relatively high confidence in flux measurements made under unstable atmospheres with mean winds greater than 1 m s-1, there is greater uncertainty in flux measurements made under free convective or stable conditions. The study involved quality-assured determinations of fluxes under low wind, stable or night-time atmospheric conditions when the continuous "steady-state" turbulence of the surface boundary layer breaks down and the layer has intermittent turbulence. Results indicate that the Monin-Obukhov similarity theory (MOST) flux-gradient methods that assume a log-linear profile of the wind speed and concentration gradient incorrectly determine vertical profiles and thus fluxes in the stable boundary layer.

Schäfer, K.; Grant, R. H.; Emeis, S.; Raabe, A.; von der Heide, C.; Schmid, H. P.

2012-02-01

165

NASA Astrophysics Data System (ADS)

Ground-based optical remote sensing has become an essential technology for quantifying pollutant or greenhouese gas (GHG) emissions from point or area sources and for the validation of airborne or satellite remote sensing data. Extensive studies have shown the capability of both ground and airborne surveys in meeting the necessary requirements for large-scale monitoring programs of atmospheric gas variations, e.g. in urban environments or regions with variable land use intensity. Open path instruments (such as infrared or laser spectrometer) that can rapidly scan in ambient air over significant distances are especially useful tools when it comes to detecting any GHG concentration variations (e.g. carbon dioxide CO2, nitrous oxide N2O, methane CH4) that are above normal background levels. Fourier-transform infrared spectroscopy is proven to be a powerful and non-invasive technique that can be used for online monitoring of fugitive emissions for industrial, environmental and health applications. We applied ground-based OP-FTIR spectroscopy as part of a hierarchical monitoring concept to investigate path-averaged atmospheric composition on a large scale, in terms of identifying areas with higher emission rates that subsequently require further detailed meso-scale investigations. A mobile passive and a bistatic active OP-FTIR spectrometer system (Bruker) were installed and a survey of column abundances of CO2 and several other trace gases was performed, allowing a maximum spatial coverage area of several square km to be mapped. In this presentation, we show results of a feasibility study investigating various scenarios (such as a Central European urban region, an agricultural landscape and a natural CO2 degassing area). The data were analysed and compared with accompanying in-situ geophysical, soil gas and micro-meteorological investigation results. Here, we present the significant spatial and temporal variability of CO2 emissions related to local anomalies, temporal events, and / or any correlations with rapidly changing environmental conditions.

Schuetze, C.; Sauer, U.; Dietrich, P.

2013-12-01

166

NASA Astrophysics Data System (ADS)

Measurements of land-surface emission rates of greenhouse and other gases at large spatial scales (10 000 m2) are needed to assess the spatial distribution of emissions. This can be readily done using spatial-integrating micro-meteorological methods like flux-gradient methods which were evaluated for determining land-surface emission rates of trace gases under stable boundary layers. Non-intrusive path-integrating measurements are utilized. Successful application of a flux-gradient method requires confidence in the gradients of trace gas concentration and wind, and in the applicability of boundary-layer turbulence theory; consequently the procedures to qualify measurements that can be used to determine the flux is critical. While there is relatively high confidence in flux measurements made under unstable atmospheres with mean winds greater than 1 m s-1, there is greater uncertainty in flux measurements made under free convective or stable conditions. The study of N2O emissions of flat grassland and NH3 emissions from a cattle lagoon involves quality-assured determinations of fluxes under low wind, stable or night-time atmospheric conditions when the continuous "steady-state" turbulence of the surface boundary layer breaks down and the layer has intermittent turbulence. Results indicate that following the Monin-Obukhov similarity theory (MOST) flux-gradient methods that assume a log-linear profile of the wind speed and concentration gradient incorrectly determine vertical profiles and thus flux in the stable boundary layer. An alternative approach is considered on the basis of turbulent diffusivity, i.e. the measured friction velocity as well as height gradients of horizontal wind speeds and concentrations without MOST correction for stability. It is shown that this is the most accurate of the flux-gradient methods under stable conditions.

Schäfer, K.; Grant, R. H.; Emeis, S.; Raabe, A.; von der Heide, C.; Schmid, H. P.

2012-07-01

167

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

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

Banerjee, Rahul; Cukier, Robert I

2014-03-20

168

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

169

Dispersion of nonlinear group velocity determines shortest envelope solitons

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

170

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

171

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

172

Langevin equation path integral ground state.

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

173

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

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.

174

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

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

Salim Hima; Yasmina Bestaoui

175

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

176

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

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

Fitelson, Branden

177

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

178

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

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

Stamp, Mark

179

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

180

NASA Astrophysics Data System (ADS)

Atmospheric ammonia (NH3) is an important fine aerosol gas-phase precursor, with implications for regional air quality and climate change. Atmospheric methane (CH4) is an important greenhouse gas, with high uncertainties in the partitioning of various emission sources. Ammonia and methane agricultural emissions are highly variable in space and time and are highly uncertain, with a lack of widespread, in-situ measurements. We characterize the spatial variability of dairy livestock emissions by performing high resolution (5 Hz), in-situ, on-road mobile measurements of NH3, CH4, CO2, N2O, CO and H2O simultaneously with open-path sensors mounted on a passenger vehicle. This suite of multiple trace gas measurements allows for emission ratio calculations and separation of agricultural, petrochemical and combustion emission signatures. Mobile measurements were performed in the Tulare County dairy farm region (~120 dairy farms sampled downwind) in the Central Valley, California during NASA DISCOVER-AQ in winter 2013. We calculate the ?NH3/?CH4 and ?NH3/?CO2 emission ratios for each dairy farm sampled downwind. Emission plumes from individual farms are isolated based on known dairy farm locations and high resolution (1 km) surface wind field simulations. Background concentrations are subtracted to calculate the emission ratios. We find high spatial variability of ammonia and methane concentrations, with localized maximums of >1 ppmv NH3 downwind of individual dairy farms. The spatial extent of individual farm emission plumes are evaluated for NH3, CH4 and CO2, which all show well-defined enhancements localized to the dairy farms near the roadside (typical sampling proximity of ? 50 m). The NH3 concentrations are correlated with the distance from each dairy farm. The observed median concentration within 100 m downwind of the dairy farms is 63 ppbv NH3, with the 95th percentile at 417 ppbv NH3 and decreases to background conditions at ~500 m distance downwind. The diurnal variability of NH3 and CH4 background concentrations at the same locations sampled on multiple days is also evaluated; including a case study of a strong morning temperature inversion. Finally, we find the NH3/CH4 ratios at the sub-farm scale vary by at least a factor of two due to spatially heterogeneous farming practices. These results highlight the need for widespread, in-situ spatial and temporal sampling of agricultural regions to further characterize these heterogeneous emissions. Future analyses will inform emission inventories and regional air quality modeling efforts.

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

2013-12-01

181

Analyzing methods for path mining with applications in metabolomics.

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

182

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

183

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

184

Identification of Biochemical Network Modules Based on Shortest Retroactive Distances

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

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

2011-01-01

185

The shortest modulation period Blazhko RR Lyrae star: SS Cnc

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

J. Jurcsik; B. Szeidl; Á. Sódor; I. Dékány; Zs. Hurta; K. Posztobányi; K. Vida; M. Váradi; A. Szing

2006-03-20

186

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

187

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

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

2014-01-01

188

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

189

Non-classical paths in interference experiments

In a double slit interference experiment, the wave function at the screen with both slits open is not exactly equal to the sum of the wave functions with the slits individually open one at a time. The three scenarios represent three different boundary conditions and as such, the superposition principle should not be applicable. However, most well known text books in quantum mechanics implicitly and/or explicitly use this assumption 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

190

One-dimensional nanomaterials have short Li(+) diffusion paths and promising structural stability, which results in a long cycle life during Li(+) insertion and extraction processes in lithium rechargeable batteries. In this study, we fabricated one-dimensional spinel Li4Ti5O12 (LTO) nanofibers using an electrospinning technique and studied the Zr(4+) doping effect on the lattice, electronic structure, and resultant electrochemical properties of Li-ion batteries (LIBs). Accommodating a small fraction of Zr(4+) ions in the Ti(4+) sites of the LTO structure gave rise to enhanced LIB performance, which was due to structural distortion through an increase in the average lattice constant and thereby enlarged Li(+) diffusion paths rather than changes to the electronic structure. Insulating ZrO2 nanoparticles present between the LTO grains due to the low Zr(4+) solubility had a negative effect on the Li(+) extraction capacity, however. These results could provide key design elements for LTO anodes based on atomic level insights that can pave the way to an optimal protocol to achieve particular functionalities. PMID:24700792

Kim, Jae-Geun; Park, Min-Sik; Hwang, Soo Min; Heo, Yoon-Uk; Liao, Ting; Sun, Ziqi; Park, Jong Hwan; Kim, Ki Jae; Jeong, Goojin; Kim, Young-Jun; Kim, Jung Ho; Dou, Shi Xue

2014-05-01

191

Path Coupling and Aggregate Path Coupling

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

192

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

193

NASA Astrophysics Data System (ADS)

For up-scaling the emissions of N2O, CO2 and CH4 (GHG) from arable field soils a measuring tunnel for controlled enrichment of released gases was installed at the soil surface covering an area of 495 or 306 m2. The concentrations of GHG and humidity were measured by the path-averaging, multi-component Fourier Transform Infrared (FTIR) absorption spectrometry at an open path of 100 m length across the whole measuring tunnel. During a 2-years-time frame the N2O fluxes between the soil and the atmosphere at the agricultural field varied between 1.0 and 21 µg N2O-N m-2 h-1. These results were compared with N2O emission rates that were simultaneously measured with a conventional closed chamber technique. The resulting N2O fluxes between the soil and the atmosphere of both methods had the same order of magnitude. However, we found an extreme spatial variability of N2O fluxes at the scale of the closed chambers. The hypothesis that an enlargement of the measured soil surface area is an appropriate measure to avoid the problems of up-scaling results of small scale chamber measurements was confirmed by the results obtained with the measuring tunnel. Currently, a non-intrusive emission and flux measurement method at a scale from 100 m up to. 27.000 m2 on the basis of the flux-gradient method (0.50 and 2.70 m height above surface) is developed and tested by means of open-path multi-component measurement methods (FTIR, GHG) and area averaging meteorological measurements (determination of horizontal winds, friction velocity using acoustic tomography). Two campaigns in October 2007 and June 2008 were performed with this new methodology when wind speeds were low. Due to the very low wind speeds and insufficient turbulence for the application of the usual flux-gradient method a new concept introducing the viscosity instead of stability corrections was developed. It requires a direct measurement of the friction velocity and the vertical gradient of the horizontal wind speeds by ultra-sonic anemometers. The mean results of this measurement method during both campaigns and the measuring tunnel results differ by about 25 % to the mean measuring tunnel results. The calculated single values on the basis of 10-minutes-mean data varied from 2 up to 42 µg N2O-N m-2 h-1.

Schäfer, K.; Jahn, C.; Emeis, S.; Wiwiorra, M.; von der Heide, C.; Böttcher, J.; Deurer, M.; Weymann, D.; Schleichardt, A.; Raabe, A.

2009-09-01

194

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

195

Information Spread of Emergency Events: Path Searching on Social Networks

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

Hu, Hongzhi; Wu, Tunan

2014-01-01

196

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

197

Walden's Paths - Ensemble Edition

NSDL National Science Digital Library

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

2011-01-04

198

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.

199

Path entanglement of continuous-variable quantum microwaves.

Path entanglement constitutes an essential resource in quantum information and communication protocols. Here, we demonstrate frequency-degenerate entanglement between continuous-variable quantum microwaves propagating along two spatially separated paths. We combine a squeezed and a vacuum state using a microwave beam splitter. Via correlation measurements, we detect and quantify the path entanglement contained in the beam splitter output state. Our experiments open the avenue to quantum teleportation, quantum communication, or quantum radar with continuous variables at microwave frequencies. PMID:23368439

Menzel, E P; Di Candia, R; Deppe, F; Eder, P; Zhong, L; Ihmig, M; Haeberlein, M; Baust, A; Hoffmann, E; Ballester, D; Inomata, K; Yamamoto, T; Nakamura, Y; Solano, E; Marx, A; Gross, R

2012-12-21

200

On the Optimal Path Length for Tor Kevin Bauer1

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

201

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

Reidl-Leuthner, Christoph; Lendl, Bernhard

2013-12-01

202

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

203

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

204

NASA Astrophysics Data System (ADS)

Melt inclusions indicate that the basaltic-hawaiitic magmas from Mt Etna (Sicily) contained up to 2.3 wt% H 2O dissolved in the melt, prior to eruption. The effect of H 2O degassing during magma ascent has been experimentally constrained between 1135 and 1009°C, for P H 2O = P total varying from 800 to 270 bars. The starting material was a primitive hawaiitic lava sample (MgO = 7.1 wt%) representative of the less evolved lava emitted at Mt Etna. Experiments were conducted in TZM pressure vessels, with Ag 70Pd 30 capsules in order to minimize the FeO loss. At temperatures of 1135-1090°C, P H 2O = 800 bars, with NiNiO and FMQ buffers, olivine (Fo 83-80) is the liquidus phase in equilibrium with a residual hawaiitic melt (Mg# 0.60-0.57; CaO/Al 2O 3 = 0.82). Salitic pyroxene begins to crystallize at 1075°C, plagioclase at 1025°C and at 1009°C, the magma is 33.5% crystallized with olivine, Ca-rich pyroxene, and plagioclase (16:60:24). At P H 2O = 270 bars, FMQ buffer, olivine (Fo 79.3-80) and salitic pyroxene are the main liquidus phases between 1100 and 1090°C. They are in equilibrium with hawaiitic melts (Mg# 0.51; CaO/Al 2O 3 = 0.73). At 1070°C, the experimental charges are highly crystallized (?51.5%) with olivine (Fo 70), salite, and plagioclase (An 78.4-76.3) in 14:44:42 relative proportions. Increasing the water content of hawaiitic-basaltic magmas expands the stability field of the olivine (relative to the other phases), lowers the crystallization temperatures of pyroxene and plagioclase, and results in the development of a more An-rich plagioclase. When compared to the natural samples, these results support a model of early and moderate crystallization of olivine from Etnean primitive hawaiitic magmas, containing close to 2.5 wt% H 2O, with NNO oxygen buffering conditions, at low pressure (P H 2O =P total). We propose a model of crystallization driven by decompression and water degassing during the emplacement of magma in the volcanic pile itself and possibly concomitant with the opening of fractures.

Métrich, Nicole; Rutherford, Malcolm J.

1998-04-01

205

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

206

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.

207

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

208

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

209

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

210

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

211

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

212

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.

213

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

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

214

OPEN PATH OPTICAL SENSING OF PARTICULATE MATTER

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

215

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

216

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

217

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

218

DNA Computing Hamiltonian path

2014 DNA DNA #12;DNA Computing Â· Feynman Â· Adleman Â· DNASIMD Â· ... Â· Â· Â· Â· Â· DNADNA #12;DNA Â· DNA Â· Â· Â· Â· DNA Â· Â· #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

219

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

220

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

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

221

Modeling DNA Dynamics by Path Integrals

NASA Astrophysics Data System (ADS)

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

Zoli, Marco

2013-02-01

222

SOCIAL PATH FOLLOWING Carmine Oliva

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

223

Triggered plasma opening switch

A triggerable opening switch for a very high voltage and current pulse includes a transmission line extending from a source to a load and having an intermediate switch section including a plasma for conducting electrons between transmission line conductors and a magnetic field for breaking the plasma conduction path and magnetically insulating the electrons when it is desired to open the switch.

Mendel, Clifford W. (Albuquerque, NM)

1988-01-01

224

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

225

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

226

PATHS groundwater hydrologic model

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

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

1980-04-01

227

Path Integrals in Quantum Mechanics

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

228

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

229

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

230

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

231

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

232

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 â 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

233

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

234

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

235

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

236

New Paths in Early Literacy Teaching and Learning.

ERIC Educational Resources Information Center

Offers ideas for opening up new paths in literacy teaching in early childhood settings. Focuses on the role of phonics in everyday classroom instruction, working with dyslexic children, home reading programs, special concerns about boys' literacy, the impact of inequities in social status in the classroom on children's literacy opportunities, and…

Peterson, Shelley

2003-01-01

237

Time-Optimal Control of Robotic Manipulators Along Specified Paths

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

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

1985-01-01

238

Unique Quantum Paths by Continuous Diagonalization of the Density Operator

In this short note we show that for a Markovian open quantum system it is always possible to construct a unique set of perfectly consistent Schmidt paths, supporting quasi-classicality. Our Schmidt process, elaborated several years ago, is the $\\Delta t\\to 0$ limit of the Schmidt chain constructed very recently by Paz and Zurek.

Lajos Diosi

1993-05-01

239

Unique quantum paths by continuous diagonalization of the density operator

In this short note we show that for a Markovian open quantum system it is always possible to construct a unique set of perfectly consistent Schmidt paths, supporting quasi-classicality. Our Schmidt process, elaborated several years ago, is the Deltat-->0 limit of the Schmidt chain constructed very recently by Paz and Zurek.

Lajos Diósi

1994-01-01

240

Multiflow and disjoint paths of minimum total cost

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

241

PathVisio-Faceted Search: an exploration tool for multi-dimensional navigation of large pathways

Purpose: The PathVisio-Faceted Search plugin helps users explore and understand complex pathways by overlaying experimental data and data from webservices, such as Ensembl BioMart, onto diagrams drawn using formalized notations in PathVisio. The plugin then provides a filtering mechanism, known as a faceted search, to find and highlight diagram nodes (e.g. genes and proteins) of interest based on imported data. The tool additionally provides a flexible scripting mechanism to handle complex queries. Availability: The PathVisio-Faceted Search plugin is compatible with PathVisio 3.0 and above. PathVisio is compatible with Windows, Mac OS X and Linux. The plugin, documentation, example diagrams and Groovy scripts are available at http://PathVisio.org/wiki/PathVisioFacetedSearchHelp. The plugin is free, open-source and licensed by the Apache 2.0 License. Contact: augustin@mail.nih.gov or jakeyfried@gmail.com PMID:23547033

Fried, Jake Y.; Luna, Augustin

2013-01-01

242

.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

243

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

244

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

245

SDSS J0926+3624: the shortest period eclipsing binary star

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

246

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

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

Jan, Shau Shiun; Lin, Yu Hsiang

2011-01-01

247

Outdoor visual path following experiments

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; François Chaumette

2007-01-01

248

Path integrals as discrete sums

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

249

Data Generation for Path Testing

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

250

Robust optimization of OSPF\\/ISIS weights

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

Bernard Fortz; Mikkel Thorup

2003-01-01

251

Initial Studies Toward Real-Time Transmission Path Rating

Demand continues to increase while transmission line construction is being constrained by multiple factors— economic, environmental, and political. Effective and efficient utilization of transmission lines is thus of great importance in an open access environment. Large blocks of power are transferred from areas with inexpensive generation to heavy load demand areas or areas with high generation costs. This results in some transmission paths being loaded closer to their path ratings, which limits further power transfer between areas. Traditionally, rating of important paths was determined off line by assuming the worst-case study scenario; once determined, it could be used for years. With increasing uncertainty arising from rapid growth of renewable energy and smart technologies, path rating studies are needed in near-real time to account for the latest system status and support a reliable and economic power grid. This paper adopts a simplified procedure based on standards of the North American Electric Reliability Corporation (NERC) to determine total transfer capability (TTC) or transfer limit for the purpose of demonstrating the benefits and necessity of real-time path rating. Initial studies are conducted to compute TTC of a two-area test system and a 39-bus test system. Results indicate that path rating can be significantly affected by loading conditions, generator schedules, system topology and other factors.

Singh, Ruchi; Diao, Ruisheng; Cai, Niannian; Huang, Zhenyu; Tuck, Brian; Guo, Xinxin

2012-07-26

252

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

253

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

254

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

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

255

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

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

256

Heuristically optimal path scanning for high-speed multiphoton circuit imaging

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

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

2011-01-01

257

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

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

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

2011-09-01

258

Partnership for Advancing Technologies in Housing (PATH)

... 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 ...

259

COMPUTER SCIENCE: MISCONCEPTIONS, CAREER PATHS

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

Hristidis, Vagelis

260

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

261

Collaborative Authoring of Walden's Paths

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

262

Scattering theory with path integrals

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

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

2014-03-15

263

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

264

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

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

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

2003-01-01

265

On hallucinated garden paths UC San Diego

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

266

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

267

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

268

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

269

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

270

Path integrals for potential scattering

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

271

Career Paths in Environmental Sciences

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

272

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

273

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

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

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

2013-08-01

274

Path-Based Failure and Evolution Management

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

275

Model for Delay Faults Based upon Paths

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

Gordon L. Smith

1985-01-01

276

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

277

The diagnostic path, a useful visualisation tool in virtual microscopy

Background The Virtual Microscopy based on completely digitalised histological slide. Concerning this digitalisation many new features in mircoscopy can be processed by the computer. New applications are possible or old, well known techniques of image analyses can be adapted for routine use. Aims A so called diagnostic path observes in the way of a professional sees through a histological virtual slide combined with the text information of the dictation process. This feature can be used for image retrieval, quality assurance or for educational purpose. Materials and methods The diagnostic path implements a metadata structure of image information. It stores and processes the different images seen by a pathologist during his "slide viewing" and the obtained image sequence ("observation path"). Contemporary, the structural details of the pathology reports were analysed. The results were transferred into an XML structure. Based on this structure, a report editor and a search function were implemented. The report editor compiles the "diagnostic path", which is the connection from the image viewing sequence ("observation path") and the oral report sequence of the findings ("dictation path"). The time set ups of speech and image viewing serve for the link between the two sequences. The search tool uses the obtained diagnostic path. It allows the user to search for particular histological hallmarks in pathology reports and in the corresponding images. Results The new algorithm was tested on 50 pathology reports and 74 attached histological images. The creation of a new individual diagnostic path is automatically performed during the routine diagnostic process. The test prototype experienced an insignificant prolongation of the diagnosis procedure (oral case description and stated diagnosis by the pathologist) and a fast and reliable retrieval, especially useful for continuous education and quality control of case description and diagnostic work. Discussion The Digital Virtual Microscope has been designed to handle 1000 images per day in the daily routine work of a pathology institution. It implies the necessity of an automatic mechanism of image meta dating. The non – deterministic correlation between the oral statements (case report) and image information content guides the image meta dating. The presented software opens up new possibilities for a content oriented search in a virtual slide, and can successfully support medical education and diagnostic quality assurance. PMID:17092352

Schrader, Thomas; Niepage, Sonja; Leuthold, Thomas; Saeger, Kai; Schluns, Karsten; Hufnagl, Peter; Kayser, Klaus; Dietel, Manfred

2006-01-01

278

Path entanglement of surface plasmons

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

279

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

280

Multiple paths to encephalization and technical civilizations.

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

281

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

282

Accelerating cleanup: Paths to closure

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

Edwards, C.

1998-06-30

283

Multiphoton Path Entanglement by Nonlocal Bunching

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

284

Multilinear decomposition of human walking paths

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

285

SOME PROPERTIES OF PATH MEASURES CHRISTIAN LEONARD

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 LÂ´EONARD Abstract. We call any measure on a path space

Paris-Sud XI, UniversitÃ© de

286

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

287

Quantifying the Causes of Path Inflation

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

Neil Spring; Ratul Mahajan; Thomas Anderson

2003-01-01

288

Test data generation and feasible path analysis

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

289

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

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

290

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

291

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

292

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

293

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

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

294

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

295

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

296

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

297

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

298

An advanced open path atmospheric pollution monitor for large areas

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

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

1996-12-31

299

ERIC Educational Resources Information Center

Visitors to the FDR Memorial in Washington, D.C., enter the area through ceremonial openings: from the pathway around the reflecting pond of the Jefferson Memorial, or across a small shaded plaza reached from a roadway parallel to the Potomac River. The FDR Memorial itself cannot be seen at the start of either of these paths. It is out there…

Adelman, Clifford

2005-01-01

300

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

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

301

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

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

302

Keeping All Students on the Learning Path Judy Mousley, PhD

open-ended inquiry-based lessons have starting points and target learning objectives where the aimKeeping All Students on the Learning Path Judy Mousley, PhD Deakin University Geelong Australia components, "differentiated learning trajectories". INTRODUCTION An underpinning principle of Vygotsky

Spagnolo, Filippo

303

Technology Transfer Automated Retrieval System (TEKTRAN)

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

304

Optimum gradient of mountain paths.

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

305

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

306

Critical Path-Based Thread Placement for NUMA Systems

Multicore multiprocessors use Non Uniform Memory Architecture (NUMA) to improve their scalability. However,NUMA introduces performance penalties due to remote memory accesses. Without efficiently managing data layout and thread mapping to cores, scientific applications, even if they are optimized for NUMA, may suffer performance loss. In this paper, we present an algorithm that optimizes the placement of OpenMP threads on NUMA processors. By collecting information from hardware counters and defining new metrics to capture the effects of thread placement, the algorithm reduces NUMA performance penalty by minimizing the critical path of OpenMP parallel regions and by avoiding local memory resource contention. We evaluate our algorithm with NPB benchmarks and achieve performance improvement between 8.13% and 25.68%, compared to the OS default scheduling.

Su, Chun-Yi [Virginia Polytechnic Institute and State University (Virginia Tech); Li, Dong [ORNL; Nikolopoulos, Dimitrios [FORTH-ICS; Grove, Matthew [Virginia Polytechnic Institute and State University (Virginia Tech); Cameron, Kirk W. [Virginia Polytechnic Institute and State University (Virginia Tech); de Supinski, Bronis R. [Lawrence Livermore National Laboratory (LLNL)

2012-01-01

307

Paths - What Are They and Who Makes Them?

NSDL National Science Digital Library

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

308

Sequential Path Entanglement for Quantum Metrology

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

309

Steam Path Audits on Industrial Steam Turbines

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.

310

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

311

Multiphoton Path Entanglement by Nonlocal Bunching

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

312

Multiphoton path entanglement by nonlocal bunching.

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

313

Walden's Paths quiz: system design and implementation

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

314

Microwave propagation over mountain-diffraction paths

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

315

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

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

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

2012-11-01

316

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

317

The Logic behind Feynman's Paths

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

Edgardo T. Garcia Alvarez

2010-11-22

318

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

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

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

2014-03-10

319

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

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 SystÃ¨mes, UniversitÃ© Paris 7

320

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

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

321

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

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

322

Energetic Path Finding Across Massive Terrain Data

Energetic Path Finding Across Massive Terrain Data Andrew Tsui and ZoÂ¨e Wood California Polytechnic of this work include: Â 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, ZoÃ« J.

323

Career path of a corruption entrepreneur

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

324

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

325

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

326

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

327

Finding Regular Simple Paths in Graph Databases

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

Alberto O. Mendelzon; Peter T. Wood

1989-01-01

328

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

329

Katrina'sPath Lake Pontchartrain

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

330

Converging towards the optimal path to extinction

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

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

2011-01-01

331

A clinical path for adult diabetes.

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

332

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

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

333

Bergman Kernel from Path Integral

NASA Astrophysics Data System (ADS)

We rederive the expansion of the Bergman kernel on Kähler 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 Kähler 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

334

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

335

Path Integral for Inflationary Perturbations

The quantum theory of cosmological perturbations in single field inflation is formulated in terms of a path integral. Starting from a canonical formulation, we show how the free propagators can be obtained from the well known gauge-invariant quadratic action for scalar and tensor perturbations, and determine the interactions to arbitrary order. This approach does not require the explicit solution of the energy and momentum constraints, a novel feature which simplifies the determination of the interaction vertices. The constraints and the necessary imposition of gauge conditions is reflected in the appearance of various commuting and 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

336

Path integral for inflationary perturbations

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

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

2010-07-15

337

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

338

As a window into the subject, we recount some of the his- tory (and geography) of two mature, challenging, partially open, partially closed problems in the theory of rewriting (numbers 13 and 21 from the original RTA List of Open Problems). One problem deals with (criteria for left-linear) confluence and the other with termination (of one linear or string rule),

Nachum Dershowitz

2005-01-01

339

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

340

The behavioural final common path.

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

341

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

342

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

343

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

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 SierpiÂ´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

344

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

345

Building a path in cell biology

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

346

Multi-objective stochastic path planning

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

347

A path-following algorithm for missiles

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

348

Path integral approach on Schrodinger's cat

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

Zinkoo Yun

2013-10-30

349

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.

350

Non-sensory inputs to angular path integration

Non-sensory (cognitive) inputs can play a powerful role in monitoring one’s self-motion. Previously, we showed that access to spatial memory dramatically increases response precision in an angular self-motion updating task [1]. Here, we examined whether spatial memory also enhances a particular type of self-motion updating – angular path integration. “Angular path integration” refers to the ability to maintain an estimate of self-location after a rotational displacement by integrating internally-generated (idiothetic) self-motion signals over time. It was hypothesized that remembered spatial frameworks derived from vision and spatial language should facilitate angular path integration by decreasing the uncertainty of self-location estimates. To test this we implemented a whole-body rotation paradigm with passive, non-visual body rotations (ranging 40°–140°) administered about the yaw axis. Prior to the rotations, visual previews (Experiment 1) and verbal descriptions (Experiment 2) of the surrounding environment were given to participants. Perceived angular displacement was assessed by open-loop pointing to the origin (0°). We found that within-subject response precision significantly increased when participants were provided a spatial context prior to whole-body rotations. The present study goes beyond our previous findings by first establishing that memory of the environment enhances the processing of idiothetic self-motion signals. Moreover, we show that knowledge of one’s immediate environment, whether gained from direct visual perception or from indirect experience (i.e., spatial language), facilitates the integration of incoming self-motion signals. PMID:20448337

Arthur, Joeanna C.; Philbeck, John W.; Chichka, David

2010-01-01

351

Quantum cosmology based on discrete Feynman paths

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

352

Tracking the energy flow along the reaction path

We report a comprehensive study of the quantum-state correlation property of product pairs from reactions of chlorine atoms with both the ground-state and the CH stretch-excited CHD3. In light of available ab initio theoretical results, this set of experimental data provides a conceptual framework to visualize the energy-flow pattern along the reaction path, to classify the activity of different vibrational modes in a reactive encounter, to gain deeper insight into the concept of vibrational adiabaticity, and to elucidate the intermode coupling in the transition-state region. This exploratory approach not only opens up an avenue to understand polyatomic reaction dynamics, even for motions at the molecular level in the fleeting transition-state region, but it also leads to a generalization of Polanyi's rules to reactions involving a polyatomic molecule. PMID:18664573

Yan, Shannon; Wu, Yen-Tien; Liu, Kopin

2008-01-01

353

Path-memory induced quantization of classical orbits

A droplet bouncing on a liquid bath can self-propel due to its interaction with the waves it generates. The resulting “walker” is a dynamical association where, at a macroscopic scale, a particle (the droplet) is driven by a pilot-wave field. A specificity of this system is that the wave field itself results from the superposition of the waves generated at the points of space recently visited by the particle. It thus contains a memory of the past trajectory of the particle. Here, we investigate the response of this object to forces orthogonal to its motion. We find that the resulting closed orbits present a spontaneous quantization. This is observed only when the memory of the system is long enough for the particle to interact with the wave sources distributed along the whole orbit. An additional force then limits the possible orbits to a discrete set. The wave-sustained path memory is thus demonstrated to generate a quantization of angular momentum. Because a quantum-like uncertainty was also observed recently in these systems, the nonlocality generated by path memory opens new perspectives.

Fort, Emmanuel; Eddi, Antonin; Boudaoud, Arezki; Moukhtar, Julien; Couder, Yves

2010-01-01

354

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

355

A path-integral Langevin equation treatment of low-temperature doped helium clusters

NASA Astrophysics Data System (ADS)

We present an implementation of path integral molecular dynamics for sampling low temperature properties of doped helium clusters using Langevin dynamics. The robustness of the path integral Langevin equation and white-noise Langevin equation [M. Ceriotti, M. Parrinello, T. E. Markland, and D. E. Manolopoulos, J. Chem. Phys. 133, 124104 (2010)], 10.1063/1.3489925 sampling methods are considered for those weakly bound systems with comparison to path integral Monte Carlo (PIMC) in terms of efficiency and accuracy. Using these techniques, convergence studies are performed to confirm the systematic error reduction introduced by increasing the number of discretization steps of the path integral. We comment on the structural and energetic evolution of HeN-CO2 clusters from N = 1 to 20. To quantify the importance of both rotations and exchange in our simulations, we present a chemical potential and calculated band origin shifts as a function of cluster size utilizing PIMC sampling that includes these effects. This work also serves to showcase the implementation of path integral simulation techniques within the molecular modelling toolkit [K. Hinsen, J. Comp. Chem. 21, 79 (2000)], 10.1002/(SICI)1096-987X(20000130)21:2<79::AID-JCC1>3.0.CO;2-B, an open-source molecular simulation package.

Ing, Christopher; Hinsen, Konrad; Yang, Jing; Zeng, Toby; Li, Hui; Roy, Pierre-Nicholas

2012-06-01

356

ERIC Educational Resources Information Center

This book contains 11 papers on creativity, spirituality, and transcendence as paths to integrity and wisdom in the mature self. The book begins with the paper "Introduction--Creativity in Adulthood: Personal Maturity and Openness to Extraordinary Sources of Inspiration" (Susanne R. Cook-Greuter, Melvin E. Miller). The next four papers, which…

Miller, Melvin E., Ed.; Cook-Greuter, Susanne R., Ed.

357

The non-Markovian stochastic Schrödinger equation for open systems

We present the non-Markovian generalisation of the widely used stochastic Schrödinger equation. Our result allows one to describe open quantum systems in terms of stochastic state vectors rather than density operators, without Markov approximation. Moreover, it unifies two recent independent attempts towards a stochastic description of non-Markovian open systems, based on path integrals on the one hand and coherent states

Lajos Diósi; Walter T. Strunz

1997-01-01

358

The non-Markovian stochastic Schrodinger equation for open systems

We present the non-Markovian generalization of the widely used stochastic Schrodinger equation. Our result allows to describe open quantum systems in terms of stochastic state vectors rather than density operators, without Markov approximation. Moreover, it unifies two recent independent attempts towards a stochastic description of non-Markovian open systems, based on path integrals on the one hand and coherent states on

Lajos Diosi; Walter T. Strunz

359

An Adaptive Path Planning Algorithm for Cooperating Unmanned Air Vehicles

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

360

Adaptive path planning algorithm for cooperating unmanned air vehicles

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

361

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

362

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.

363

Model Discrepancy in the Saturated Path Hydrology Model: Initial Analysis

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

364

Achieving Path Diversity over the Internet using MDS Codes

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

365

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

366

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

367

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

368

14 CFR 171.265 - Glide path performance requirements.

Code of Federal Regulations, 2012 CFR

2012-01-01

369

The non-Markovian stochastic Schrodinger equation for open systems

We present the non-Markovian generalization of the widely used stochastic Schrodinger equation. Our result allows to describe open quantum systems in terms of stochastic state vectors rather than density operators, without approximation. Moreover, it unifies two recent independent attempts towards a stochastic description of non-Markovian open systems, based on path integrals on the one hand and coherent states on the other. The latter approach utilizes the analytical properties of coherent states and enables a microscopic interpretation of the stochastic states. The alternative first approach is based on the general description of open systems using path integrals as originated by Feynman and Vernon.

Lajos Diosi; Walter T. Strunz

1997-06-22

370

The non-Markovian stochastic Schrödinger equation for open systems

We present the non-Markovian generalization of the widely used stochastic Schrodinger equation. Our result allows to describe open quantum systems in terms of stochastic state vectors rather than density operators, without approximation. Moreover, it unifies two recent independent attempts towards a stochastic description of non-Markovian open systems, based on path integrals on the one hand and coherent states on the other. The latter approach utilizes the analytical properties of coherent states and enables a microscopic interpretation of the stochastic states. The alternative first approach is based on the general description of open systems using path integrals as originated by Feynman and Vernon.

Diósi, L; Diosi, Lajos; Strunz, Walter T.

1997-01-01

371

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

372

Chocked flows in open capillary channels

Capillary systems provide a passive means to control fluids and are widely used for space craft fuel management. In the present study the forced liquid flow through an open capillary channel under low gravity conditions is investigated. Due to convective and viscous momentum transport the pressure along the flow path decreases and causes the free surface to bend inwards the

Joerg Klatte; U. Rosendahl; D. Haake; A. Grah; M. Dreyer

2007-01-01

373

Scientific Utopia: I. Opening Scientific Communication

Existing norms for scientific communication are rooted in anachronistic practices of bygone eras making them needlessly inefficient. We outline a path that moves away from the existing model of scientific communication to improve the efficiency in meeting the purpose of public science—knowledge accumulation. We call for six changes: (a) full embrace of digital communication; (b) open access to all published

Brian A. Nosek; Yoav Bar-Anan

2012-01-01

374

A taxonomy of integral reaction path analysis

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

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

2004-12-23

375

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

376

SILK: Scout Paths in the Linux Kernel

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

377

Tornado intensity estimated from damage path dimensions.

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

378

Tornado Intensity Estimated from Damage Path Dimensions

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

379

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

380

Path Factorization Approach to Stochastic Simulations

NASA Astrophysics Data System (ADS)

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

Athènes, Manuel; Bulatov, Vasily V.

2014-12-01

381

Priming on the path of least resistance

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

382

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

383

Path planning for everday robotics with SANDROS

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

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

1997-02-01

384

ERIC Educational Resources Information Center

Conceived by the British Labor Government in the 1960's the Open University was viewed as a way to extend higher education to Britain's working class, but enrollment figures in classes that represent traditional academic disciplines show that the student population is predominantly middle class. Bringing education into the home presents numerous…

Tunstall, Jeremy, Ed.

385

Path Integration in Desert Ants, Cataglyphis fortis

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

386

LONG PATH LASER OZONE MONITOR EVALUATION

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

387

Fusion Development Path Panel Preliminary Report

Fusion Development Path Panel Preliminary Report Summary for NRC BPAC Panel (Focus on MFE of a demonstration power plant in approximately 35 years. The plan should recognize the capabilities of all fusion facilities around the world, and include both magnetic fusion energy (MFE) and inertial fusion energy (IFE

388

Path integral Monte Carlo applied to vortices

The thermodynamic properties of the vortex lattice in a high-Tc superconductor can be understood by considering a system of bosons in two dimensions. In this picture, the imaginary time world-line of the boson corresponds to the vortex. The vortex lattice melting transition maps to melting the Bose Wigner crystal by means of increasing hbar. We use Path Integral Monte Carlo

Henrik Nordborg; Gianni Blatter

1996-01-01

389

Folded-path optical analysis gas cell

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

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

1995-01-01

390

The Erratic Path of Hungarian Higher Education

ERIC Educational Resources Information Center

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

Marcus, Jon

2014-01-01

391

Motion on Cycloid Paths: A Project

ERIC Educational Resources Information Center

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

Gluck, P.

2010-01-01

392

Virtual path bandwidth allocation in multiuser networks

We consider a multiuser network that is shared by noncooperative users. Each user sets up virtual paths that optimize its own selfish performance measure. This measure accounts for the guaranteed call level quality of service, as well as for the cost incurred for reserving the resource. The interaction among the user strategies is formalized as a noncooperative game. We show

Aurel A. Lazar; Ariel Orda; Dimitrios E. Pendarakis

1997-01-01

393

2006 Spring Issue Page The Critical Path

2006 Spring Issue Page The Critical Path Kevin McCarthy's (Code 450) 64 Days with FEMA Watching the Fed- eral Emergency Management Agency (FEMA) requested vol- unteers from other federal agencies list a day or two later. After volunteering, I did not hear from FEMA until I received an email on Sept

Christian, Eric

394

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

395

Planning Flight Paths of Autonomous Aerobots

NASA Technical Reports Server (NTRS)

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

Kulczycki, Eric; Elfes, Alberto; Sharma, Shivanjli

2009-01-01

396

Ambivalent Journey: Teacher Career Paths in Oman

ERIC Educational Resources Information Center

This study investigated the career paths of 625 university graduates who prepared to be secondary school teachers in Oman, their assessment of their current work situation, and the extent to which their initial commitment to teaching was related to their subsequent career satisfaction and intention to remain in teaching. While nearly all graduates…

Chapman, David W.; Al-Barwani, Thuwayba; Al Mawali, Fathiya; Green, Elizabeth

2012-01-01

397

ELLIPTIC ENUMERATION OF NONINTERSECTING LATTICE PATHS

ELLIPTIC ENUMERATION OF NONINTERSECTING LATTICE PATHS MICHAEL SCHLOSSER Abstract. We enumerate degenerate cases including Jackson's 8 #7 and Dougall's 7 F6 summation. By considering nonintersecting and Probabilistic Number Theory''). 1 #12; 2 MICHAEL SCHLOSSER We need the following theorem which is a special case

Schlosser, Michael

398

ELLIPTIC ENUMERATION OF NONINTERSECTING LATTICE PATHS

ELLIPTIC ENUMERATION OF NONINTERSECTING LATTICE PATHS MICHAEL SCHLOSSER Abstract. We enumerate degenerate cases including Jackson's 87 and Dougall's 7F6 summation. By considering nonintersecting lattice Combinatorics and Probabilistic Number Theory"). 1 #12;2 MICHAEL SCHLOSSER We need the following theorem which

Schlosser, Michael

399

Path detection and the uncertainty principle

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

Pippa Storey; Sze Tan; Matthew Collett; Daniel Walls

1994-01-01

400

Path Integral Method for DNA Denaturation

The statistical physics of homogeneous DNA is investigated by the imaginary time path integral formalism. The base pair stretchings are described by an ensemble of paths selected through a macroscopic constraint, the fulfillement of the second law of thermodynamics. The number of paths contributing to the partition function strongly increases around and above a specific temperature $T^*_c$ whereas the fraction of unbound base pairs grows continuosly around and above $T^*_c$. The latter is identified with the denaturation temperature. Thus, the separation of the two complementary strands appears as a highly cooperative phenomenon displaying a smooth crossover versus $T$. The thermodynamical properties have been computed in a large temperature range by varying the size of the path ensemble at the lower bound of the range. No significant physical dependence on the system size has been envisaged. The entropy grows continuosly versus $T$ while the specific heat displays a remarkable peak at $T^*_c$. The location of the peak versus $T$ varies with the stiffness of the anharmonic stacking interaction along the strand. The presented results suggest that denaturation in homogeneous DNA has the features of a second order phase transition. The method accounts for the cooperative behavior of a very large number of degrees of freedom while the computation time is kept within a reasonable limit.

Marco Zoli

2009-03-26

401

Efficient Data Mining for Path Traversal Patterns

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

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

1998-01-01

402

Folded-path optical analysis gas cell

A folded-path gas cell employs an elliptical concave mirror in confronting relationship to two substantially spherical concave mirrors. At least one of the spherical mirrors, and usually both, are formed with an added cylindrical component to increase orthogonal foci coincidence and thereby to increase the radiation energy throughput characteristic of the cell. 10 figs.

Carangelo, R.M.; Wright, D.D.

1995-08-08

403

Asymmetrical Path Interference Test of Light

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

Mei Xiaochun

2006-03-05

404

Adaptable Path Planning in Regionalized Environments

Adaptable Path Planning in Regionalized Environments Kai-Florian Richter Transregional Collaborative Research Center SFB/TR 8 Spatial Cognition UniversitÂ¨at Bremen, Germany richter@sfbtr8.uni planning and execution of the wayfinding task--at least on the large-scale, environmental level [3, 4

Bremen, UniversitÃ¤t

405

Soft energy path works for Hawaii

Constrained by small land mass, total dependence on imported oil, and a high cost of living, Hawaii has adopted soft energy paths. Geothermal energy, ocean energy, wind energy, solar energy, and biomass energy play dominant parts. The volcanic origin of the islands makes it unlikely that any oil or natural gas will ever be found there. The volcanic nature of

Crull

2009-01-01

406

Learning to improve path planning performance

In robotics, path planning refers to finding a short. collision-free path from an initial robot configuration to a desired configuratioin. It has to be fast to support real-time task-level robot programming. Unfortunately, current planning techniques are still too slow to be effective, as they often require several minutes, if not hours of computation. To remedy this situation, we present and analyze a learning algorithm that uses past experience to increase future performance. The algorithm relies on an existing path planner to provide solutions to difficult tasks. From these solutions, an evolving sparse network of useful robot configurations is learned to support faster planning. More generally, the algorithm provides a speedup-learning framework in which a slow but capable planner may be improved both cost-wise and capability-wise by a faster but less capable planner coupled with experience. The basic algorithm is suitable for stationary environments, and can be extended to accommodate changing environments with on-demand experience repair and object-attached experience abstraction. To analyze the algorithm, we characterize the situations in which the adaptive planner is useful, provide quantitative bounds to predict its behavior, and confirm our theoretical results with experiments in path planning of manipulators. Our algorithm and analysis are sufficiently, general that they may also be applied to other planning domains in which experience is useful.

Chen, Pang C.

1995-04-01

407

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

408

Current SPE Hydrodynamic Modeling and Path Forward

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

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

2012-08-14

409

The Path to Disaster The Deepwater Horizon

21/08/2013 1 The Path to Disaster The Deepwater Horizon BP's disaster in the Gulf of Mexico was not disconnected Â· The escaping gas ignited Â· 11 dead Â· The drilling rig Deepwater Horizon sank after 2 days #12 Â· They drilled on to get below the pay-zone Â· An initial plan was produced on April 12th Â· Feedback

Pym, David J.

410

Using path analysis to measure natural selection

We expand current methods for calculating selection coefficients using path analysis and demonstrate how to analyse nonlinear selection. While this incorporation is a straightforward extension of current procedures, the rules for combining these traits to calculate selection coefficients can be complex. We demonstrate our method with an analysis of selection in an experimental population of Arabidopsis thaliana consisting of 289

Scheiner; H. S. CALLAHAN

2000-01-01

411

Path Planning Algorithms for Multiple Heterogeneous Vehicles

: : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 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

412

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

413

Applications of Path Compression on Balanced Trees

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

414

SNMP-based Layer3 Path Discovery

This paper presents a process for discovering the layer-3 path between two endpoints in a computernetwork using information available through SNMP in commonly used MIB objects. The pathinformation is useful for analyzing computer networks (e.g., as needed for Avaya Inc.\\

David T. Stott

2002-01-01

415

The holomorphic anomaly for open string moduli

NASA Astrophysics Data System (ADS)

We complete the holomorphic anomaly equations for topological strings with their dependence on open moduli. We obtain the complete system by standard path integral arguments generalizing the analysis of BCOV (Commun. Math. Phys. 165 (1994) 311) to strings with boundaries. We study both the anti-holomorphic dependence on open moduli and on closed moduli in presence of Wilson lines. By providing the compactification à la Deligne-Mumford of the moduli space of Riemann surfaces with boundaries, we show that the open holomorphic anomaly equations are structured on the (real codimension one) boundary components of this space.

Bonelli, Giulio; Tanzini, Alessandro

2007-10-01

416

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

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

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

2005-01-01

417

Photon path length retrieval from GOSAT observations

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

418

Path Finding on High-Dimensional Free Energy Landscapes

NASA Astrophysics Data System (ADS)

We present a method for determining the average transition path and the free energy along this path in the space of selected collective variables. The formalism is based upon a history-dependent bias along a flexible path variable within the metadynamics framework but with a trivial scaling of the cost with the number of collective variables. Controlling the sampling of the orthogonal modes recovers the average path and the minimum free energy path as the limiting cases. The method is applied to resolve the path and the free energy of a conformational transition in alanine dipeptide.

Díaz Leines, Grisell; Ensing, Bernd

2012-07-01

419

Rapid Yield and Depth Estimation from Global Calibrated Paths

NASA Astrophysics Data System (ADS)

Comprehensive test ban monitoring in terms of location has progressed significantly in recent years. However, the estimation of low yields remains a particular challenge because only limited number of teleseismic and local stations record the events. As the North Korean (NK) Explosion demonstrated, we can probably expect to have a small set of teleseismic data, some set of in-country (closed and open) regional data to estimate yield. The mb estimate from only a few station typically has large errors if calibration of mantle attenuation (t*) is not taken into account. Since stacking helps bring signals out of the noise, it becomes useful to conduct comparable analyses on neighboring events. If these auxiliary events have accurate moments, we have a means of directly estimating yields for an unknown test. The method starts with a detailed waveform inversion of natural earthquakes (M4-5) near the test site recorded by local or regional broadband stations with the Cut and Paste method which leads to accurate estimates of moment and focal mechanism. With the source parameters well known, we obtain amplitude path corrections by matching observed and synthetic teleseismic waveforms. Or alternatively, we can choose station specific t* to make the synthetic amplitude agree with the observations. We modeled three events with magnitude between M4-M5 in Korea Peninsular, and find t* of ~0.5s works for most stations for events in Korea Peninsular. We use this method of path calibration to estimate the 2006 NK Explosion at 1-2 kt using the Amchitka scaling laws and the yield estimate of the 2009 NK explosion will also be reported.

Ni, S.; Chu, R.; Helmberger, D. V.

2009-12-01

420

Path planning and Ground Control Station simulator for UAV

NASA Astrophysics Data System (ADS)

In this paper we present a Universal and Interoperable Ground Control Station (UIGCS) simulator for fixed and rotary wing Unmanned Aerial Vehicles (UAVs), and all types of payloads. One of the major constraints is to operate and manage multiple legacy and future UAVs, taking into account the compliance with NATO Combined/Joint Services Operational Environment (STANAG 4586). Another purpose of the station is to assign the UAV a certain degree of autonomy, via autonomous planification/replanification strategies. The paper is organized as follows. In Section 2, we describe the non-linear models of the fixed and rotary wing UAVs that we use in the simulator. In Section 3, we describe the simulator architecture, which is based upon interacting modules programmed independently. This simulator is linked with an open source flight simulator, to simulate the video flow and the moving target in 3D. To conclude this part, we tackle briefly the problem of the Matlab/Simulink software connection (used to model the UAV's dynamic) with the simulation of the virtual environment. Section 5 deals with the control module of a flight path of the UAV. The control system is divided into four distinct hierarchical layers: flight path, navigation controller, autopilot and flight control surfaces controller. In the Section 6, we focus on the trajectory planification/replanification question for fixed wing UAV. Indeed, one of the goals of this work is to increase the autonomy of the UAV. We propose two types of algorithms, based upon 1) the methods of the tangent and 2) an original Lyapunov-type method. These algorithms allow either to join a fixed pattern or to track a moving target. Finally, Section 7 presents simulation results obtained on our simulator, concerning a rather complicated scenario of mission.

Ajami, A.; Balmat, J.; Gauthier, J.-P.; Maillot, T.

421

NASA Astrophysics Data System (ADS)

The reaction path potential (RPP) follows the ideas from the reaction path Hamiltonian of Miller, Handy and Adams for gas phase reactions but is designed specifically for large systems described with QM/MM methods. RPP is an analytical energy expression of the combined QM/MM potential energy along the minimum energy path (J. Chem. Phys. 121, 89, 2004). An expansion around the minimum energy path is made in both the nuclear and the electronic degrees of freedom for the QM subsystem, while the interaction between the QM and MM subsystems is described as the interaction of the MM charges with polarizable QM charges. The input data for constructing the reaction path potential are energies, frequencies and electron density response properties of the QM subsystem. RPP provides a potential energy surface for rigorous statistical mechanics and mixed quantum/classical reaction dynamics calculations of complex systems, as will be shown for several enzymes. Recent further development in determining QM/MM free energy reaction paths will also be presented.

Yang, Weitao

2006-03-01

422

76 FR 17064 - Shared Use Path Accessibility Guidelines

Federal Register 2010, 2011, 2012, 2013, 2014

...blended transitions, landings, and gutter areas within the shared use path. Grade...the curb at right angles or meets the gutter grade break at right angles. Running...blended transitions, landings, and gutter areas within the shared use path....

2011-03-28

423

14 CFR 171.267 - Glide path automatic monitor system.

Code of Federal Regulations, 2010 CFR

...DEPARTMENT OF TRANSPORTATION (CONTINUED) NAVIGATIONAL FACILITIES NON-FEDERAL NAVIGATION FACILITIES Interim Standard Microwave Landing System (ISMLS) § 171.267 Glide path automatic monitor system. (a) The ISMLS glide path...

2010-01-01

424

14 CFR 171.267 - Glide path automatic monitor system.

Code of Federal Regulations, 2014 CFR

... § 171.267 Glide path automatic monitor system. (a) The ISMLS glide path equipment must provide an automatic monitor system that transmits a warning to designated local and remote control points when any of the...

2014-01-01

425

FOLLOWING CARBON'S EVOLUTIONARY PATH: FROM NUCLEOSYNTHESIS TO THE SOLAR SYSTEM

FOLLOWING CARBON'S EVOLUTIONARY PATH: FROM NUCLEOSYNTHESIS TO THE SOLAR SYSTEM by Stefanie Nicole by Stefanie Nicole Milam entitled Following Carbon's Evolutionary Path: From Nucleosynthesis to the Solar of Doctor of Philosophy _______________________________________________________________________ Date

426

Inquiry-based learning templates for creating online educational paths

the appropriate websites are collected for inclusion in a path, the path author still faces the challenge of determining how to organize and present the This thesis follows the style of the Journal of the ACM...

Davis, Sarah Alice

2006-10-30

427

Mission Geography: Paths (title provided or enhanced by cataloger)

NSDL National Science Digital Library

Mission Geography uses existing NASA data and images where possible to engage students in active, hands-on inquiry, modeling the scientific method and developing students' understanding of environment-society relations and Earth science. This module looks at many different kinds of paths and considers why paths are where they are and how they look from space. People and animals make paths that take into account the terrain and other features of the landscape. Rivers, lava, smoke, and other natural phenomena follow paths. The module contains four investigations in which students interpret paths in their immediate environment, use literature to investigate paths, inspect unusual paths, and use satellite images to view paths of natural disasters. Each investigation is complete with overview, a list of materials and supplies, content preview, classroom procedures, worksheets, background, and evaluation.

428

Sensitivity of ray paths to initial condition

Using a parabolic equation, we consider ray propagation in a waveguide with the sound speed profile that corresponds to the dynamics of a nonlinear oscillator. An analytical consideration of the dependence of the travel time on the initial conditions is presented. Using an exactly solvable model and the path integral representation of the travel time, we explain the step-like behavior of the travel time (T) as a function of the starting momentum (p_0) (related to the starting ray grazing angle (\\chi_0) by (p_0=\\tan\\chi_0)). A periodic perturbation of the waveguide along the range leads to wave and ray chaos. We explain an inhomogeneity of distribution of the chaotic ray travel times, which has obvious maxima. These maxima lead to the clustering of rays and each maximum relates to a ray identifier, {\\em i.e.} to the number of ray semi--cycles along the ray path.

A. Iomin; G. M. Zaslavsky

2007-06-03

429

Mining Preferred Traversal Paths with HITS

NASA Astrophysics Data System (ADS)

Web usage mining can discover useful information hidden in web logs data. However, many previous algorithms do not consider the structure of web pages, but regard all web pages with the same importance. This paper utilizes HITS values and PNT preferences as measures to mine users' preferred traversal paths. Wë structure mining uses HITS (hypertext induced topic selection) to rank web pages. PNT (preferred navigation tree) is an algorithm that finds users' preferred navigation paths. This paper introduces the Preferred Navigation Tree with HITS (PNTH) algorithm, which is an extension of PNT. This algorithm uses the concept of PNT and takes into account the relationships among web pages using HITS algorithm. This algorithm is suitable for E-commerce applications such as improving web site design and web server performance.

Yeh, Jieh-Shan; Lin, Ying-Lin; Chen, Yu-Cheng

430

Adaptive path planning for flexible manufacturing

Path planning needs to be fast to facilitate real-time robot programming. Unfortunately, current planning techniques are still too slow to be effective, as they often require several minutes, if not hours of computation. To overcome this difficulty, we present an adaptive algorithm that uses past experience to speed up future performance. It is a learning algorithm suitable for automating flexible manufacturing in incrementally-changing environments. The algorithm allows the robot to adapt to its environment by having two experience manipulation schemes: For minor environmental change, we use an object-attached experience abstraction scheme to increase the flexibility of the learned experience; for major environmental change, we use an on-demand experience repair scheme to retain those experiences that remain valid and useful. Using this algorithm, we can effectively reduce the overall robot planning time by re-using the computation result for one task to plan a path for another.

Chen, Pang C.

1994-08-01

431

Breakdown of the Coherent State Path Integral: Two Simple Examples

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

432

Path Diversity over the Internet: Performance Analysis and Rate Allocation

Abstract 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 endto-end reliability. Internet paths are modeled as erasure Gilbert-Elliot channels [1], [2]. First, it is shown that over any erasure channel, Maximum Distance

Shervan Fashandi; Shahab Oveis Gharan; Amir K. Khandani

2007-01-01

433

A long path, low temperature cell.

Design and performance are given of a multiple traversal low temperature absorption cell that operates routinely at a path length of 230 m. The system is comprised of an f/30-aperture White cell surrounded by an aluminum Dewar. The cell has been used in the temperature range 300-77 K and may be pressurized to 3 atm. Vacuum feedthrough adjustments are employed in order to correct for defocusing of the mirrors during the cooling process. PMID:20068970

Blickensderfer, R P; Ewing, G E; Leonard, R

1968-11-01

434

Variational Methods for Path Integral Scattering

In this master thesis, a new approximation scheme to non-relativistic potential scattering is developed and discussed. The starting points are two exact path integral representations of the T-matrix, which permit the application of the Feynman-Jensen variational method. A simple Ansatz for the trial action is made, and, in both cases, the variational procedure singles out a particular one-particle classical equation

Julien Carron; Roland Rosenfelder; PSI Villigen; Jurg Fr; ETH Zurich

2009-01-01

435

Variational Methods for Path Integral Scattering

In this master thesis, a new approximation scheme to non-relativistic potential scattering is developed and discussed. The starting points are two exact path integral representa- tions of the T-matrix, which permit the application of the Feynman-Jensen variational method. A simple Ansatz for the trial action is made, and, in both cases, the varia- tional procedure singles out a particular one-particle

Roland Rosenfelder; PSI Villigen; Jurg Frohlich; ETH Zurich

436

Feyman path integrals in real time

The numerical calculation of Feynman path integrals (F.P.I.) can be performed in real time, i.e. without continuing to imaginary time, at least for quantum mechanical systems with a small number of degrees of freedom. The algorithm stems from the phase space formulation of the F.P.I. and makes intensive use of the Fast Fourier transform to achieve the required efficiency. Scope

Enrico Onofri; Gian Pietro Tecchiolli

1988-01-01

437

Do-It-Yourself Critical Path Method.

ERIC Educational Resources Information Center

This report describes the critical path method (CPM), a system for planning and scheduling work to get the best time-cost combination for any particular job. With the use of diagrams, the report describes how CPM works on a step-by-step basis. CPM uses a network to show which parts of a job must be done and how they would eventually fit together…

Morris, Edward P., Jr.

438

Local path control for an autonomous vehicle

A control system for an autonomous robot cart designed to operate in well-structured environments such as offices and factories is described. The onboard navigation system comprises a reference-state generator, an error-feedback controller, and cart-location sensing using odometry. There is a convenient separation between the path guidance and control logic. Under normal operating conditions, the controller ensures that the errors between

Winston L. Nelson; Ingeniar J. Cox

1988-01-01

439

Bagging for Path-Based Clustering

Abstract—A resampling,scheme,for clustering with similarity to bootstrap aggregation,(bagging) is presented. Bagging is used to improve,the quality of path- based clustering, a data clustering method that can extract elongated structures from data in a noise robust way. The results of an agglomerative,optimization method,are influenced by small fluctuations of the input data. To increase the reliability of clustering solutions, a stochastic resampling

Bernd Fischer; Joachim M. Buhmann

2003-01-01

440

Free Energy Changes, Fluctuations, and Path Probabilities

We illustrate some of the static and dynamic relations discovered by Cohen, Crooks, Evans, Jarzynski, Kirkwood, Morriss, Searles, and Zwanzig. These relations link nonequilibrium processes to equilibrium isothermal free energy changes and to dynamical path probabilities. We include ideas suggested by Dellago, Geissler, Oberhofer, and Schoell-Paschinger. Our treatment is intended to be pedagogical, for use in an updated version of our book: Time Reversibility, Computer Simulation, and Chaos. Comments are very welcome.

William G. Hoover; Carol G. Hoover

2011-04-20

441

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

442

Toroidal path filter for orbital conjunction screening

NASA Astrophysics Data System (ADS)

For satellite conjunction prediction containing many objects, timely processing can be a concern. Various filters are used to identify orbiting pairs that cannot come close enough over a prescribed time period to be considered hazardous. Such pairings can then be eliminated from further computation to quicken the overall processing time. One such filter is the orbit path filter (also known as the geometric pre-filter), designed to eliminate pairs of objects based on characteristics of orbital motion. The goal of this filter is to eliminate pairings where the distance (geometry) between their orbits remains above some user-defined threshold, irrespective of the actual locations of the satellites along their paths. Rather than using a single distance bound, this work presents a toroid approach, providing a measure of versatility by allowing the user to specify different in-plane and out-of-plane bounds for the path filter. The primary orbit is used to define a focus-centered elliptical ring torus with user-defined thresholds. An assessment is then made to determine if the secondary orbit can touch or penetrate this torus. The method detailed here can be used on coplanar, as well as non-coplanar, orbits.

Alfano, Salvatore

2012-07-01

443

PaTH: towards a learning health system in the Mid-Atlantic region.

The PaTH (University of Pittsburgh/UPMC, Penn State College of Medicine, Temple University Hospital, and Johns Hopkins University) clinical data research network initiative is a collaborative effort among four academic health centers in the Mid-Atlantic region. PaTH will provide robust infrastructure to conduct research, explore clinical outcomes, link with biospecimens, and improve methods for sharing and analyzing data across our diverse populations. Our disease foci are idiopathic pulmonary fibrosis, atrial fibrillation, and obesity. The four network sites have extensive experience in using data from electronic health records and have devised robust methods for patient outreach and recruitment. The network will adopt best practices by using the open-source data-sharing tool, Informatics for Integrating Biology and the Bedside (i2b2), at each site to enhance data sharing using centrally defined common data elements, and will use the Shared Health Research Information Network (SHRINE) for distributed queries across the network. PMID:24821745

Amin, Waqas; Tsui, Fuchiang Rich; Borromeo, Charles; Chuang, Cynthia H; Espino, Jeremy U; Ford, Daniel; Hwang, Wenke; Kapoor, Wishwa; Lehmann, Harold; Martich, G Daniel; Morton, Sally; Paranjape, Anuradha; Shirey, William; Sorensen, Aaron; Becich, Michael J; Hess, Rachel

2014-01-01

444

PaTH: towards a learning health system in the Mid-Atlantic region

The PaTH (University of Pittsburgh/UPMC, Penn State College of Medicine, Temple University Hospital, and Johns Hopkins University) clinical data research network initiative is a collaborative effort among four academic health centers in the Mid-Atlantic region. PaTH will provide robust infrastructure to conduct research, explore clinical outcomes, link with biospecimens, and improve methods for sharing and analyzing data across our diverse populations. Our disease foci are idiopathic pulmonary fibrosis, atrial fibrillation, and obesity. The four network sites have extensive experience in using data from electronic health records and have devised robust methods for patient outreach and recruitment. The network will adopt best practices by using the open-source data-sharing tool, Informatics for Integrating Biology and the Bedside (i2b2), at each site to enhance data sharing using centrally defined common data elements, and will use the Shared Health Research Information Network (SHRINE) for distributed queries across the network. PMID:24821745

Amin, Waqas; Tsui, Fuchiang (Rich); Borromeo, Charles; Chuang, Cynthia H; Espino, Jeremy U; Ford, Daniel; Hwang, Wenke; Kapoor, Wishwa; Lehmann, Harold; Martich, G Daniel; Morton, Sally; Paranjape, Anuradha; Shirey, William; Sorensen, Aaron; Becich, Michael J; Hess, Rachel

2014-01-01

445

Multiple Damage Progression Paths in Model-based Prognostics

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

446

ENERGETIC PATH FINDING ACROSS MASSIVE TERRAIN DATA Presented to

ENERGETIC PATH FINDING ACROSS MASSIVE TERRAIN DATA A Thesis Presented to the Faculty of California;COMMITTEE MEMBERSHIP TITLE: Energetic Path Finding Across Massive Terrain Data AUTHOR: Andrew Tsui DATE: Chris Buckalew, Ph.D. iii #12;Abstract Energetic Path Finding Across Massive Terrain Data Andrew Tsui

Wood, ZoÃ« J.

447

Systematic Upscaling for Feynman Path Integrals A Progress Report

Systematic Upscaling for Feynman Path Integrals A Progress Report Mark Zlochin and Achi Brandt The Weizmann Institute of Science, Rehovot 76100, Israel November 24, 2005 1 Path Integrals 1.1 The basic setup The path integral approach was introduced by Feynman in his seminal paper (Feynman, 1948). It provides

448

A GA path planner based on domain knowledge for AUV

Autonomous underwater vehicle (AUV) is extensively used for marine engineering, oceanography research and some other civil area. Path planning is a necessary and fundamental technology for AUV autonomy, its goal is to search an optimized path according to some optimization criteria in a certain environment and makes AUV fulfill its mission objectives along the collision-free path. Based on the theory

WANG Hong-jianl; Bian Xin-qian; ZHAO Jiel; Ding Fu-guang; Xia Guo-qing

2004-01-01

449

Vector Field Path Following for Miniature Air Vehicles

In this paper, a method for accurate path following for miniature air vehicles is developed. The method is based on the notion of vector fields, which are used to generate desired course inputs to inner-loop attitude control laws. Vector field path following control laws are developed for straight-line paths and circular arcs and orbits. Lyapunov stability arguments are used to

Derek R. Nelson; D. Blake Barber; Timothy W. Mclain; Randal W. Beard

2007-01-01

450

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

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

451

Integrated Path Planning and ynamic Steering Control for Autonomous Vehicles

A method is presented for combining two previously proposed algorithms for path-planning and dynamic steering control into a computationally feasible scheme for real-time feedback control of autonomous vehicles in uncertain environments. In the proposed approach to vehicle guidance and control, Path Relaxation is used to compute critical points along a globally desirable path using a priori information and sensor data'.

Bruce P. I. Krogh; Charles E. Thorpe

1986-01-01

452

Integrated path planning and dynamic steering control for autonomous vehicles

A method is presented for combining two previously proposed algorithms for path-planning and dynamic steering control into a computationally feasible scheme for real-time feedback control of autonomous vehicles in uncertain environments. In the proposed approach to vehicle guidance and control, Path Relaxation is used to compute critical points along a globally desirable path using a priori information and sensor data.

B. Krogh; C. Thorpe

1986-01-01

453

Stable periodic billiard paths in obtuse isosceles triangles

Stable periodic billiard paths in obtuse isosceles triangles W. Patrick Hooper March 27, 2006 Can you place a small billiard ball on a frictionless triangular pool table and hit it so that it comes dynamics s of a periodic billiard path is the bi-infinite sequence of edges the billiard path hits, which

Hooper, Patrick

454

Stable periodic billiard paths in obtuse isosceles triangles

Stable periodic billiard paths in obtuse isosceles triangles W. Patrick Hooper March 27, 2006 Can you place a small billiard ball on a frictionless triangular pool table and hit it so that it comes dynamics s # of a periodic billiard path # is the biÂinfinite sequence of edges the billiard path hits

Hooper, Patrick

455

Unstructured path problems and the making of semirings

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

456

Multiple-Goals Path Planning for Coordinate Measuring Machines

Path planning is a crucial step in automatic programming of coor- dinate measuring machines (CMMs). The goal is to generate an efficient and collision-free path for the CMM to inspect a collec- tion of points. Previous research concentrates on path plan ning be- tween two points, or sequencing the points without regard to obsta- cles and collisions. In this paper

Steven N. Spitz; Aristides A. G. Requicha

2000-01-01

457

Spare Capacity Assignment in Telecom Networks using Path Restoration*

Spare Capacity Assignment in Telecom Networks using Path Restoration* Jeyakesavan Veerasamy and S.C.Sha h Alcatel Network Systems, 1225 N. Alma Road Richardson, TX 75081 Abstract Path restoration scheme to achieve a desired level of protection against link failures. Path restoration planning cor- responds

Venkatesan, S.

458

Preferential flow paths: biological ‘hot spots’ in soils

Preferential flow of water in soils is a common phenomenon. Our objective was to investigate whether preferential flow paths have higher microbial biomass and different microbial community structures than the rest of the soil. We stained the preferential flow paths in a forest soil with a food dye and sampled soil material from preferential flow paths and from the soil

M. Bundt; F. Widmer; M. Pesaro; J. Zeyer; P. Blaser

2001-01-01

459

NC machine tool path generation from CSG part

NC machine tool path generation from CSG part representations James E Bobrow Recent improvements for machine tool path generation. Current machining algorithms require that any port geometric information of numerically controlled (NC) machine tool paths. In this paper, we discuss the widely used APT 1

Bobrow, James E.

460

A Note On Minimum Path Bases Petra M. Gleissa

A Note On Minimum Path Bases Petra M. Gleissa , Josef Leydoldb , Peter F. Stadlera,c a Institute that there exist two vertices x and y in C, not necessarily distinct, and two paths D1 and #12;Minimum Path Bases of Graphs 3 D2 from u to x and from v to y, respectively, such that D1

Stadler, Peter F.

461

EQUILIBRIUM PATHS OF MECHANICAL SYSTEMS WITH UNILATERAL CONSTRAINTS

EQUILIBRIUM PATHS OF MECHANICAL SYSTEMS WITH UNILATERAL CONSTRAINTS PART II: DEPLOYABLE REFLECTOR M, by imple- menting the theory for tracing the equilibrium path of a mechanical system with unilateral had not been previously explained, is the existence of a corner limit point on the equilibrium path

Pellegrino, Sergio

462

Module for Business, Management, and Technology Career Path.

ERIC Educational Resources Information Center

Designed for use with secondary students who have explored career paths and wish to pursue a career in business, management, and technology (BM&T), this module focuses on providing work-based learning experiences. Introductory materials include the following: career paths rationale and philosophy, benefits of using career paths, information on…

Broeker, Arlene M.

463

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

464

Controlling unboundedness in the gravitational path integral

NASA Astrophysics Data System (ADS)

New results are presented on the Euclidean path-integral formulation for the partition function and density of states pertinent to spherically symmetric black-hole systems in thermodynamic equilibrium. We extend the path-integral construction of Halliwell and Louko which has already been used by one of us (Louko and Whiting), and investigate further a lack of uniqueness in our previous formulation of the microcanonical density of states and in the canonical partition function. In that work, the method chosen for removing the ambiguity resulted in two specific path-integral contours having finite extent. Physically motivated criteria exercised a dominant influence on that choice, as did the need to overcome the unboundedness from below of the gravitational action. The new results presented here satisfy the same physical criteria, but differ in ways which are physically significant. The unboundedness is not now eliminated directly but, for positive temperatures only, it is dealt with by what may be viewed as the introduction of an effective measure, which nevertheless may be of exponential order. Having chosen to investigate alternative contours which, in fact, have infinite extent, we find that imposing the Wheeler-DeWitt equation automatically selects out particular finite end points for the contours, at which the singularity in the action is canceled. A further important outcome of this work is the emergence of a variational principle for the black hole entropy, which has already proved useful at the level of a zero-loop approximation to the coupling of a shell of quantum matter in equilibrium around a Schwarzschild black hole (Horwitz and Whiting). In the course of enquiring into the nature of the variables in which the path integral is constructed and evaluated, we were able to see how to give a unifying description of several previous results in the literature. A concise review of these separate approaches forms an integral part of our new synthesis, relating their various underlying ideas on Hamilton-Jacobi theory and Hamiltonian reduction in the context of path integration. The new insight we gain finally helps motivate the choice of the integration variables, identification of which has played an important role in our whole analysis.

Melmed, Jeffrey; Whiting, Bernard F.

1994-01-01

465

This paper investigates active and passive short-wave infrared (SWIR) imaging for slant paths close to ground. The main sensor, a gated SWIR camera, was collecting both passive and active images along a 2 km long path over an airfield and also from our rooftop laboratory looking over open fields. For some investigations we also used a gated system working in the near-infrared region and thermal as well as color CCD cameras. The sensor was elevated by a lift in steps from 1.6-13.5 m or placed in a rooftop laboratory 13 m above ground. Targets were resolution charts and man targets. The turbulence was measured along the path with anemometers and scintillometers. The image performance was evaluated by measurement of the image blur and also by performing observer perception tests. The results reveal a strong dependence on the sensor height especially during daytime. PMID:23852188

Steinvall, Ove; Elmqvist, Magnus; Chevalier, Tomas; Gustafsson, Ove

2013-07-10

466

Adjustments of Speed and Path when Avoiding Collisions with Another Pedestrian

When walking in open space, collision avoidance with other pedestrians is a process that successfully takes place many times. To pass another pedestrian (an interferer) walking direction, walking speed or both can be adjusted. Currently, the literature is not yet conclusive of how humans adjust these two parameters in the presence of an interferer. This impedes the development of models predicting general obstacle avoidance strategies in humans’ walking behavior. The aim of this study was to investigate the adjustments of path and speed when a pedestrian is crossing a non-reactive human interferer at different angles and speeds, and to compare the results to general model predictions. To do so, we designed an experiment where a pedestrian walked a 12 m distance to reach a goal position. The task was designed in such a way that collision with an interferer would always occur if the pedestrian would not apply a correction of movement path or speed. Results revealed a strong dependence of path and speed adjustments on crossing angle and walking speed, suggesting local planning of the collision avoidance strategy. Crossing at acute angles (i.e. 45° and 90°) seems to require more complex collision avoidance strategies involving both path and speed adjustments than crossing at obtuse angles, where only path adjustments were observed. Overall, the results were incompatible with predictions from existing models of locomotor collision avoidance. The observed initiations of both adjustments suggest a collision avoidance strategy that is temporally controlled. The present study provides a comprehensive picture of human collision avoidance strategies in walking, which can be used to evaluate and adjust existing pedestrian dynamics models, or serve as an empirical basis to develop new models. PMID:24586895

Huber, Markus; Su, Yi-Huang; Krüger, Melanie; Faschian, Katrin; Glasauer, Stefan; Hermsdörfer, Joachim

2014-01-01

467

On the Feynman Path Integral for Nonrelativistic Quantum Electrodynamics

NASA Astrophysics Data System (ADS)

The Feynman path integral for regularized nonrelativistic quantum electrodynamics is studied rigorously. We begin with the Lagrangian function of the corresponding classical mechanics and construct the Feynman path integral. In the present paper, the electromagnetic potentials are assumed to be periodic with respect to a large box and quantized through their Fourier coefficients with large wave numbers cut off. Firstly, the Feynman path integral with respect to paths on the space of particles and vector potentials is defined rigorously by means of broken line paths under the constraints. Secondly, the Feynman path integral with respect to paths on the space of particles and electromagnetic potentials is also defined rigorously by means of broken line paths and piecewise constant paths without the constraints. This Feynman path integral is stated heuristically in Feynman and Hibbs' book. Thirdly, the vacuum and the state of photons of given momenta and polarizations are expressed concretely as functions of variables consisting of the Fourier coefficients of vector potentials. It is also proved rigorously in terms of distribution theory that the Coulomb potentials between charged particles naturally appear in the above Feynman path integral approach. This shows that the photons give rise to the Coulomb force.

Ichinose, Wataru

468

Improved initial guess for minimum energy path calculations

A method is presented for generating a good initial guess of a transition path between given initial and final states of a system without evaluation of the energy. An objective function surface is constructed using an interpolation of pairwise distances at each discretization point along the path and the nudged elastic band method then used to find an optimal path on this image dependent pair potential (IDPP) surface. This provides an initial path for the more computationally intensive calculations of a minimum energy path on an energy surface obtained, for example, by ab initio or density functional theory. The optimal path on the IDPP surface is significantly closer to a minimum energy path than a linear interpolation of the Cartesian coordinates and, therefore, reduces the number of iterations needed to reach convergence and averts divergence in the electronic structure calculations when atoms are brought too close to each other in the initial path. The method is illustrated with three examples: (1) rotation of a methyl group in an ethane molecule, (2) an exchange of atoms in an island on a crystal surface, and (3) an exchange of two Si-atoms in amorphous silicon. In all three cases, the computational effort in finding the minimum energy path with DFT was reduced by a factor ranging from 50% to an order of magnitude by using an IDPP path as the initial path. The time required for parallel computations was reduced even more because of load imbalance when linear interpolation of Cartesian coordinates was used.

Smidstrup, Søren [QuantumWise A/S, Lersø Parkallé 107, DK-2100 Copenhagen (Denmark); Science Institute and Faculty of Physical Sciences, University of Iceland VR-III, 107 Reykjavík (Iceland); Pedersen, Andreas [Science Institute and Faculty of Physical Sciences, University of Iceland VR-III, 107 Reykjavík (Iceland); Integrated Systems Laboratory, ETH Zurich, 8092 Zurich (Switzerland); Stokbro, Kurt [QuantumWise A/S, Lersø Parkallé 107, DK-2100 Copenhagen (Denmark); Jónsson, Hannes, E-mail: hj@hi.is [Science Institute and Faculty of Physical Sciences, University of Iceland VR-III, 107 Reykjavík (Iceland); Department of Applied Physics, Aalto University, Espoo, FI-00076 (Finland)

2014-06-07

469

Vulnerability of complex networks under path-based attacks

NASA Astrophysics Data System (ADS)

We investigate vulnerability of complex networks including model networks and real-world networks subject to path-based attacks. Specifically, we remove approximately the longest simple path from a network iteratively until there are no paths left in the network. We propose two algorithms, the random augmenting approach (RPA) and the Hamilton-path based approach (HPA), for finding the approximately longest simple path in a network. Results demonstrate that steps of longest-path attacks increase with network density linearly for random networks, while exponentially increasing for scale-free networks. The more homogeneous the degree distribution is, the more fragile the network, which is different from the previous results of node or edge attacks. HPA is generally more efficient than RPA in the longest-path attacks of complex networks. These findings further help us understand the vulnerability of complex systems, better protect complex systems, and design more tolerant complex systems.

Pu, Cun-Lai; Cui, Wei

2015-02-01

470

Simulated final approach path captures using the microwave landing system

NASA Technical Reports Server (NTRS)

Computer simulation results are presented for intercepting final approach paths using various Microwave Landing System (MLS) path capture concepts. This study, conducted under the Advanced Transport Operating System (ATOPS) program, simulated these captures using the MD-80 aircraft as the study model. Several different capture concepts were investigated. Systems that could be retrofitted into existing aircraft with minimum hardware and software changes were considered. An enhanced ILS look-alike capture provided improved tracking performance over conventional ILS without using a full-up path computer. The other concepts used waypoint databases and path computers to provide smart captures. These captures included lateral path intercepts as well as vertical path control. Winds, turbulence, and MLS noise were included in the simulation. In all cases, acceptable tracking errors were obtained during transition to the final approach path.

Feather, J. B.

1988-01-01

471

Global Freshwater Resources: Soft-Path Solutions for the 21st Century

NASA Astrophysics Data System (ADS)

Twentieth-century water policies relied on the construction of massive infrastructure in the form of dams, aqueducts, pipelines, and complex centralized treatment plants to meet human demands. These facilities brought tremendous benefits to billions of people, but they also had serious and often unanticipated social, economical, and ecological costs. Many unsolved water problems remain, and past approaches no longer seem sufficient. A transition is under way to a |P`soft path|P' that complements centralized physical infrastructure with lower cost community-scale systems, decentralized and open decision-making, water markets and equitable pricing, application of efficient technology, and environmental protection.

Gleick, Peter H.

2003-11-01

472

Auditory Perception of Motor Vehicle Travel Paths

Objective These experiments address concerns that motor vehicles in electric engine mode are so quiet that they pose a risk to pedestrians, especially those with visual impairments. Background The “quiet car” issue has focused on hybrid and electric vehicles, although it also applies to internal combustion engine vehicles. Previous research has focused on detectability of vehicles, mostly in quiet settings. Instead, we focused on the functional ability to perceive vehicle motion paths. Method Participants judged whether simulated vehicles were traveling straight or turning, with emphasis on the impact of background traffic sound. Results In quiet, listeners made the straight-or-turn judgment soon enough in the vehicle’s path to be useful for deciding whether to start crossing the street. This judgment is based largely on sound level cues rather than the spatial direction of the vehicle. With even moderate background traffic sound, the ability to tell straight from turn paths is severely compromised. The signal-to-noise ratio needed for the straight-or-turn judgment is much higher than that needed to detect a vehicle. Conclusion Although a requirement for a minimum vehicle sound level might enhance detection of vehicles in quiet settings, it is unlikely that this requirement would contribute to pedestrian awareness of vehicle movements in typical traffic settings with many vehicles present. Application The findings are relevant to deliberations by government agencies and automobile manufacturers about standards for minimum automobile sounds and, more generally, for solutions to pedestrians’ needs for information about traffic, especially for pedestrians with sensory impairments. PMID:22768645

Ashmead, Daniel H.; Grantham, D. Wesley; Maloff, Erin S.; Hornsby, Benjamin; Nakamura, Takabun; Davis, Timothy J.; Pampel, Faith; Rushing, Erin G.

2012-01-01

473

Automated generation of weld path trajectories.

AUTOmated GENeration of Control Programs for Robotic Welding of Ship Structure (AUTOGEN) is software that automates the planning and compiling of control programs for robotic welding of ship structure. The software works by evaluating computer representations of the ship design and the manufacturing plan. Based on this evaluation, AUTOGEN internally identifies and appropriately characterizes each weld. Then it constructs the robot motions necessary to accomplish the welds and determines for each the correct assignment of process control values. AUTOGEN generates these robot control programs completely without manual intervention or edits except to correct wrong or missing input data. Most ship structure assemblies are unique or at best manufactured only a few times. Accordingly, the high cost inherent in all previous methods of preparing complex control programs has made robot welding of ship structures economically unattractive to the U.S. shipbuilding industry. AUTOGEN eliminates the cost of creating robot control programs. With programming costs eliminated, capitalization of robots to weld ship structures becomes economically viable. Robot welding of ship structures will result in reduced ship costs, uniform product quality, and enhanced worker safety. Sandia National Laboratories and Northrop Grumman Ship Systems worked with the National Shipbuilding Research Program to develop a means of automated path and process generation for robotic welding. This effort resulted in the AUTOGEN program, which has successfully demonstrated automated path generation and robot control. Although the current implementation of AUTOGEN is optimized for welding applications, the path and process planning capability has applicability to a number of industrial applications, including painting, riveting, and adhesive delivery.

Sizemore, John M. (Northrop Grumman Ship Systems); Hinman-Sweeney, Elaine Marie; Ames, Arlo Leroy

2003-06-01

474

Path integral quantization of generalized quantum electrodynamics

In this paper, a complete covariant quantization of generalized electrodynamics is shown through the path integral approach. To this goal, we first studied the Hamiltonian structure of the system following Dirac's methodology and, then, we followed the Faddeev-Senjanovic procedure to obtain the transition amplitude. The complete propagators (Schwinger-Dyson-Fradkin equations) of the correct gauge fixation and the generalized Ward-Fradkin-Takahashi identities are also obtained. Afterwards, an explicit calculation of one-loop approximations of all Green's functions and a discussion about the obtained results are presented.

Bufalo, R.; Pimentel, B. M.; Zambrano, G. E. R. [Instituto de Fisica Teorica (IFT), UNESP-Sao Paulo State University, Rua Doutor Bento Teobaldo Ferraz 271, Bloco II, Barra Funda CEP 01140-070, Sao Paulo, Sao Paulo (Brazil); Departamento de Fisica, Universidad de Narino, Calle 18 Cuadra 50, San Juan de Pasto, Narino (Colombia)

2011-02-15

475

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

476

The Path to Magnetic Fusion Energy

When the possibility of fusion as an energy source for electricity generation was realized in the 1950s, understanding of the plasma state was primitive. The fusion goal has been paced by, and has stimulated, the development of plasma physics. Our understanding of complex, nonlinear processes in plasmas is now mature. We can routinely produce and manipulate 100 million degree plasmas with remarkable finesse, and we can identify a path to commercial fusion power. The international experiment, ITER, will create a burning (self-sustained) plasma and produce 500 MW of thermal fusion power. This talk will summarize the progress in fusion research to date, and the remaining steps to fusion power.

Prager, Stewart (PPPL) [PPPL

2011-05-04

477

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

478

Technology Transfer Automated Retrieval System (TEKTRAN)

Vegetative treatment systems (VTSs) are one type of control structure that has shown potential to control runoff from open feedlots. To achieve maximum performance, sheet-flow over the width of the vegetative treatment area (VTA) is required. Tools, such as maps of flow paths through the VTA, are ne...

479

Time optimal paths and acceleration lines of robotic manipulators

NASA Technical Reports Server (NTRS)

The concept of acceleration lines and their correlation with time-optimal paths of robotic manipulators is presented. The acceleration lines represent the directions of maximum tip acceleration from a point in the manipulator work-space, starting at a zero velocity. These lines can suggest the number and shapes of time-optimal paths for a class of manipulators. It is shown that nonsingular time-optimal paths are tangent to one of the acceleration lines near the end-points. A procedure for obtaining near-optimal paths, utilizing the acceleration lines, is developed. These paths are obtained by connecting the end-points with B splines tangent to the acceleration lines. The near-minimum paths are shown to yield better traveling times than the straight-line path between the same end-points. The near-minimum paths can be used as initial conditions in existing optimization methods to speed-up convergence and computation time. This method can be used for online robot path planning and for interactive designs of robotic-cell layouts. Examples of time-optimal paths of a two-link manipulator, obtained by other optimization procedures and their acceleration lines, are shown.

Shiller, Zvi; Dubowsky, Steven

1987-01-01

480

The authors describe an implementation of a path planner suitable for an autonomous underwater vehicle (AUV). The path planning unit is capable of maintaining a quadtree database of depth information, obstacles, and exclusion zones: verifying a previously planned path; generating a new path between successive goal points; and generating a path to the nearest point of a safe region. If

K. P. Carroll; S. R. McClaran; E. L. Nelson; D. M. Barnett; D. K. Friesen; G. N. William

1992-01-01

481

Vibration Analysis of a Split Path Gearbox

NASA Technical Reports Server (NTRS)

Split path gearboxes can be attractive alternatives to the common planetary designs for rotorcraft, but because they have seen little use, they are relatively high risk designs. To help reduce the risk of fielding a rotorcraft with a split path gearbox, the vibration and dynamic characteristics of such a gearbox were studied. A mathematical model was developed by using the Lagrangian method, and it was applied to study the effect of three design variables on the natural frequencies and vibration energy of the gearbox. The first design variable, shaft angle, had little influence on the natural frequencies. The second variable, mesh phasing, had a strong effect on the levels of vibration energy, with phase angles of 0 deg and 180 deg producing low vibration levels. The third design variable, the stiffness of the shafts connecting the spur gears to the helical pinions, strongly influenced the natural frequencies of some of the vibration modes, including two of the dominant modes. We found that, to achieve the lowest level of vibration energy, the natural frequencies of these two dominant modes should be less than those of the main excitation sources.

Krantz, Timothy L.; Rashidi, Majid

1995-01-01

482

Adaptive robot path planning in changing environments

Path planning needs to be fast to facilitate real-time robot programming. Unfortunately, current planning techniques are still too slow to be effective, as they often require several minutes, if not hours of computation. To overcome this difficulty, we present an adaptive algorithm that uses past experience to speed up future performance. It is a learning algorithm suitable for incrementally-changing environments such as those encountered in manufacturing of evolving products and waste-site remediation. The algorithm allows the robot to adapt to its environment by having two experience manipulation schemes: For minor environmental change, we use an object-attached experience abstraction scheme to increase the flexibility of the learned experience; for major environmental change, we use an on-demand experience repair scheme to retain those experiences that remain valid and useful. Using this algorithm, we can effectively reduce the overall robot planning time by re-using the computation result for one task to plan a path for another.

Chen, P.C.

1994-08-01

483

Efficiently finding the minimum free energy path from steepest descent path

NASA Astrophysics Data System (ADS)

Minimum Free Energy Path (MFEP) is very important in computational biology and chemistry. The barrier in the path is related to the reaction rate, and the start-to-end difference gives the relative stability between reactant and product. All these information is significant to experiment and practical application. But finding MFEP is not an easy job. Lots of degrees of freedom make the computation very complicated and time consuming. In this paper, we use the Steepest Descent Path (SDP) to accelerate the sampling of MFEP. The SHAKE algorithm and the Lagrangian multipliers are used to control the optimization of both SDP and MFEP. These strategies are simple and effective. For the former, it is more interesting. Because as we known, SHAKE algorithm was designed to handle the constraints in molecular dynamics in the past, has never been used in geometry optimization. Final applications on ALA dipeptide and 10-ALA peptide show that this combined optimization method works well. Use the information in SDP, the initial path could reach the more optimal MFEP. So more accurate free energies could be obtained and the amount of computation time could be saved.

Chen, Changjun; Huang, Yanzhao; Ji, Xiaofeng; Xiao, Yi

2013-04-01

484

Looping probabilities of elastic chains: A path integral approach

NASA Astrophysics Data System (ADS)

We consider an elastic chain at thermodynamic equilibrium with a heat bath, and derive an approximation to the probability density function, or pdf, governing the relative location and orientation of the two ends of the chain. Our motivation is to exploit continuum mechanics models for the computation of DNA looping probabilities, but here we focus on explaining the novel analytical aspects in the derivation of our approximation formula. Accordingly, and for simplicity, the current presentation is limited to the illustrative case of planar configurations. A path integral formalism is adopted, and, in the standard way, the first approximation to the looping pdf is obtained from a minimal energy configuration satisfying prescribed end conditions. Then we compute an additional factor in the pdf which encompasses the contributions of quadratic fluctuations about the minimum energy configuration along with a simultaneous evaluation of the partition function. The original aspects of our analysis are twofold. First, the quadratic Lagrangian describing the fluctuations has cross-terms that are linear in first derivatives. This, seemingly small, deviation from the structure of standard path integral examples complicates the necessary analysis significantly. Nevertheless, after a nonlinear change of variable of Riccati type, we show that the correction factor to the pdf can still be evaluated in terms of the solution to an initial value problem for the linear system of Jacobi ordinary differential equations associated with the second variation. The second novel aspect of our analysis is that we show that the Hamiltonian form of these linear Jacobi equations still provides the appropriate correction term in the inextensible, unshearable limit that is commonly adopted in polymer physics models of, e.g. DNA. Prior analyses of the inextensible case have had to introduce nonlinear and nonlocal integral constraints to express conditions on the relative displacement of the end points. Our approximation formula for the looping pdf is of quite general applicability as, in contrast to most prior approaches, no assumption is made of either uniformity of the elastic chain, nor of a straight intrinsic shape. If the chain is uniform the Jacobi system evaluated at certain minimum energy configurations has constant coefficients. In such cases our approximate pdf can be evaluated in an entirely explicit, closed form. We illustrate our analysis with a planar example of this type and compute an approximate probability of cyclization, i.e., of forming a closed loop, from a uniform elastic chain whose intrinsic shape is an open circular arc.

Cotta-Ramusino, Ludovica; Maddocks, John H.

2010-11-01

485

ERIC Educational Resources Information Center

The Internet lets us share perfect copies of our work with a worldwide audience at virtually no cost. We take advantage of this revolutionary opportunity when we make our work "open access": digital, online, free of charge, and free of most copyright and licensing restrictions. Open access is made possible by the Internet and copyright-holder…

Suber, Peter

2012-01-01

486

Spurred by the publication of Massachusetts Institute of Technology OpenCourseWare in 2002, the open educational resources (OER) movement, which has rapidly expanded and captured the imagination and energy of millions of creators and users throughout the world, now faces many opportunities and substantial challenges as it moves to become an integral part of the world's educational environment. The confluence of

Marshall S. Smith

2009-01-01