The inverse shortest paths problem with upper bounds on shortest paths costs.
Toint, Philippe
The inverse shortest paths problem with upper bounds on shortest paths costs. by D. Burton 1 W of the inverse shortest paths problem with upper bounds on shortest path costs, and prove that obtaining, Belgium Keywords : computational complexity, shortest paths, inverse problems, traffic modelling. #12; 1
ERIC Educational Resources Information Center
Shore, M. L.
1980-01-01
There are many uses for the shortest path algorithm presented which are limited only by our ability to recognize when a problem may be converted into the shortest path in a graph representation. (Author/TG)
Shortest Path Problems with Resource Constraints
Stefan Irnich; Guy Desaulniers
In most vehicle routing and crew scheduling applications solved by column generation, the subproblem corresponds to a shortest\\u000a path problem with resource constraints (SPPRC) or one of its variants.\\u000a \\u000a This chapter proposes a classification and a generic formulation for the SPPRCs, briefly discusses complex modeling issues\\u000a involving resources, and presents the most commonly used SPPRC solution methods. First and foremost,
Shortest-path problems Proofs Weight of path p = v0 v1 vk
California at Davis, University of
Shortest-path problems Proofs Weight of path p = v0 v1 · · · vk: w(p) = k i=1 w(vi-1, vi) Shortest-path weight u ; v (u, v) = min{w(p) : u p ; v} if there exists a path u ; v otherwise Shortest-path u ; v any path p such that w(p) = (u, v) #12;Shortest-paths properties Triangular inequality
Analysis of Algorithms Problem Set no. 3 --Dynamic All-Pairs Shortest Paths
Zwick, Uri
Analysis of Algorithms Problem Set no. 3 -- Dynamic All-Pairs Shortest Paths Given: December 15, 2010 Exercise 3.1 Describe a simple dynamic all-pairs shortest path algorithm that can handle decreas a weighted n-vertex graph with unique shortest paths in which there are (n3) locally shortest paths. (b) Show
THE K SHORTEST PATHS PROBLEM Ernesto de Queir' os Vieira Martins
Pascoal, Marta Margarida Braz
THE K SHORTEST PATHS PROBLEM Ernesto de Queir' os Vieira Martins Marta Margarida Braz Pascoal Jos Coimbra PORTUGAL June 1998 Abstract: The shortest path problem is a classical network programming problem that has been extensively studied. The problem of determining not only the shortest path, but also listing
An improved Physarum polycephalum algorithm for the shortest path problem.
Zhang, Xiaoge; Wang, Qing; Adamatzky, Andrew; Chan, Felix T S; Mahadevan, Sankaran; Deng, Yong
2014-01-01
Shortest path is among classical problems of computer science. The problems are solved by hundreds of algorithms, silicon computing architectures and novel substrate, unconventional, computing devices. Acellular slime mould P. polycephalum is originally famous as a computing biological substrate due to its alleged ability to approximate shortest path from its inoculation site to a source of nutrients. Several algorithms were designed based on properties of the slime mould. Many of the Physarum-inspired algorithms suffer from a low converge speed. To accelerate the search of a solution and reduce a number of iterations we combined an original model of Physarum-inspired path solver with a new a parameter, called energy. We undertook a series of computational experiments on approximating shortest paths in networks with different topologies, and number of nodes varying from 15 to 2000. We found that the improved Physarum algorithm matches well with existing Physarum-inspired approaches yet outperforms them in number of iterations executed and a total running time. We also compare our algorithm with other existing algorithms, including the ant colony optimization algorithm and Dijkstra algorithm. PMID:24982960
THE K SHORTEST LOOPLESS PATHS PROBLEM Ernesto de Queir' os Vieira Martins
Pascoal, Marta Margarida Braz
THE K SHORTEST LOOPLESS PATHS PROBLEM Ernesto de Queir' os Vieira Martins Marta Margarida Braz loopless paths problem. It is shown that in general this problem does not satisfy the optimality principle and as a consequence only methods based on the computation of a super set of the set of the K shortest loopless paths
Randomized shortest-path problems: two related models.
Saerens, Marco; Achbany, Youssef; Fouss, Franois; Yen, Luh
2009-08-01
This letter addresses the problem of designing the transition probabilities of a finite Markov chain (the policy) in order to minimize the expected cost for reaching a destination node from a source node while maintaining a fixed level of entropy spread throughout the network (the exploration). It is motivated by the following scenario. Suppose you have to route agents through a network in some optimal way, for instance, by minimizing the total travel cost-nothing particular up to now-you could use a standard shortest-path algorithm. Suppose, however, that you want to avoid pure deterministic routing policies in order, for instance, to allow some continual exploration of the network, avoid congestion, or avoid complete predictability of your routing strategy. In other words, you want to introduce some randomness or unpredictability in the routing policy (i.e., the routing policy is randomized). This problem, which will be called the randomized shortest-path problem (RSP), is investigated in this work. The global level of randomness of the routing policy is quantified by the expected Shannon entropy spread throughout the network and is provided a priori by the designer. Then, necessary conditions to compute the optimal randomized policy-minimizing the expected routing cost-are derived. Iterating these necessary conditions, reminiscent of Bellman's value iteration equations, allows computing an optimal policy, that is, a set of transition probabilities in each node. Interestingly and surprisingly enough, this first model, while formulated in a totally different framework, is equivalent to Akamatsu's model ( 1996 ), appearing in transportation science, for a special choice of the entropy constraint. We therefore revisit Akamatsu's model by recasting it into a sum-over-paths statistical physics formalism allowing easy derivation of all the quantities of interest in an elegant, unified way. For instance, it is shown that the unique optimal policy can be obtained by solving a simple linear system of equations. This second model is therefore more convincing because of its computational efficiency and soundness. Finally, simulation results obtained on simple, illustrative examples show that the models behave as expected. PMID:19323635
On the Complexity of Shortest Path Problems on Discounted Cost Graphs
Alur, Rajeev
it contains. In a generalized version of the shortest- path problem, each edge is labeled with a cost as wellOn the Complexity of Shortest Path Problems on Discounted Cost Graphs Rajeev Alur, Sampath Kannan, Kevin Tian, and Yifei Yuan University of Pennsylvania, Philadelphia, PA, US Abstract. Discounted Cost
Self-organization and solution of shortest-path optimization problems with memristive networks.
Pershin, Yuriy V; Di Ventra, Massimiliano
2013-07-01
We show that memristive networks, namely networks of resistors with memory, can efficiently solve shortest-path optimization problems. Indeed, the presence of memory (time nonlocality) promotes self organization of the network into the shortest possible path(s). We introduce a network entropy function to characterize the self-organized evolution, show the solution of the shortest-path problem and demonstrate the healing property of the solution path. Finally, we provide an algorithm to solve the traveling salesman problem. Similar considerations apply to networks of memcapacitors and meminductors, and networks with memory in various dimensions. PMID:23944581
Label-setting algorithms for a polynomial bi-objective multimodal shortest path problem
Paris-Sud XI, Universit de
Label-setting algorithms for a polynomial bi-objective multimodal shortest path problem Fallou the multimodality of urban transportation networks for com- puting the itinerary of an individual passenger techniques are discussed. keywords: bi-objective viable shortest paths, multimodal transportation, finite
The role of convexity for solving some shortest path problems in plane without triangulation
NASA Astrophysics Data System (ADS)
An, Phan Thanh; Hai, Nguyen Ngoc; Hoai, Tran Van
2013-09-01
Solving shortest path problems inside simple polygons is a very classical problem in motion planning. To date, it has usually relied on triangulation of the polygons. The question: "Can one devise a simple O(n) time algorithm for computing the shortest path between two points in a simple polygon (with n vertices), without resorting to a (complicated) linear-time triangulation algorithm?" raised by J. S. B. Mitchell in Handbook of Computational Geometry (J. Sack and J. Urrutia, eds., Elsevier Science B.V., 2000), is still open. The aim of this paper is to show that convexity contributes to the design of efficient algorithms for solving some versions of shortest path problems (namely, computing the convex hull of a finite set of points and convex rope on rays in 2D, computing approximate shortest path between two points inside a simple polygon) without triangulation on the entire polygons. New algorithms are implemented in C and numerical examples are presented.
Aloul, Fadi
efficient implementa- tions of Dijkstra's algorithm exist and can handle large net- works in short runtimesAbstract--Today, most routing problems are solved using Dijkstra's shortest path algorithm. Many Dijkstra's algorithm. Such conditions can include forcing the path to go through a specific node, forcing
Finding the k Shortest Paths David Eppstein
Eppstein, David
constraints beyond having a small length, but those other constraints may be ill-defined or hard to optimize-known shortest path problem, in which not one but several short paths must be produced. The k shortest paths problem, for a given k and a given source-destination pair in a digraph, is to list the k paths
A Bio-Inspired Method for the Constrained Shortest Path Problem
Wang, Hongping; Lu, Xi; Wang, Qing
2014-01-01
The constrained shortest path (CSP) problem has been widely used in transportation optimization, crew scheduling, network routing and so on. It is an open issue since it is a NP-hard problem. In this paper, we propose an innovative method which is based on the internal mechanism of the adaptive amoeba algorithm. The proposed method is divided into two parts. In the first part, we employ the original amoeba algorithm to solve the shortest path problem in directed networks. In the second part, we combine the Physarum algorithm with a bio-inspired rule to deal with the CSP. Finally, by comparing the results with other method using an examples in DCLC problem, we demonstrate the accuracy of the proposed method. PMID:24959603
The d-edge shortest-path problem for a Monge graph
Bein, W.W. [New Mexico Univ., Albuquerque, NM (United States). Dept. of Computer Science; Larmore, L.L. [California Univ., Riverside, CA (United States). Dept. of Computer Science; Park, J.K. [Sandia National Labs.,Albuquerque, NM (United States)
1992-07-14
A complete edge-weighted directed graph on vertices 1,2,...,n that assigns cost c(i,j) to the edge (i,j) is called Monge if its edge costs form a Monge array, i.e., for all i < k and j < l, c[i, j]+c[k,l]{le} < c[i,l]+c[k,j]. One reason Monge graphs are interesting is that shortest paths can be computed quite quickly in such graphs. In particular, Wilber showed that the shortest path from vertex 1 to vertex n of a Monge graph can be computed in O(n) time, and Aggarwal, Klawe, Moran, Shor, and Wilber showed that the shortest d-edge 1-to-n path (i.e., the shortest path among all 1-to-n paths with exactly d edges) can be computed in O(dn) time. This paper`s contribution is a new algorithm for the latter problem. Assuming 0 {le} c[i,j] {le} U and c[i,j + 1] + c[i + 1,j] {minus} c[i,j] {minus} c[i + 1, j + 1] {ge} L > 0 for all i and j, our algorithm runs in O(n(1 + 1g(U/L))) time. Thus, when d {much_gt} 1 + 1g(U/L), our algorithm represents a significant improvement over Aggarwal et al.`s O(dn)-time algorithm. We also present several applications of our algorithm; they include length-limited Huffman coding, finding the maximum-perimeter d-gon inscribed in a given convex n-gon, and a digital-signal-compression problem.
Yang, Shengxiang
Genetic Algorithms with Elitism-based Immigrants for Dynamic Shortest Path Problem in Mobile Ad Hoc) in MANETs. In this paper, we propose to use elitism-based immigrants GA (EIGA) to solve the dynamic SP
Shortest Paths, Network Design and Associated Polyhedra
Magnanti, Thomas L.
We study a specialized version of network design problems that arise in telecommunication, transportation and other industries. The problem, a generalization of the shortest path problem, is defined on an undirected network ...
Physarum can compute shortest paths.
Bonifaci, Vincenzo; Mehlhorn, Kurt; Varma, Girish
2012-09-21
Physarum polycephalum is a slime mold that is apparently able to solve shortest path problems. A mathematical model has been proposed by Tero et al. (Journal of Theoretical Biology, 244, 2007, pp. 553-564) to describe the feedback mechanism used by the slime mold to adapt its tubular channels while foraging two food sources s(0) and s(1). We prove that, under this model, the mass of the mold will eventually converge to the shortest s(0)-s(1) path of the network that the mold lies on, independently of the structure of the network or of the initial mass distribution. This matches the experimental observations by Tero et al. and can be seen as an example of a "natural algorithm", that is, an algorithm developed by evolution over millions of years. PMID:22732274
Optimal Distributed All Pairs Shortest Paths
Optimal Distributed All Pairs Shortest Paths ETH Zurich Distributed Computing Group Stephan = Number of hops of shortest path #12;Diameter of a network Distance between two nodes = Number of hops of shortest path #12;Diameter of a network Distance between two nodes = Number of hops of shortest path
Genetic Algorithm for Solving Fuzzy Shortest Path Problem in a Network with mixed fuzzy arc lengths
NASA Astrophysics Data System (ADS)
Mahdavi, Iraj; Tajdin, Ali; Hassanzadeh, Reza; Mahdavi-Amiri, Nezam; Shafieian, Hosna
2011-06-01
We are concerned with the design of a model and an algorithm for computing a shortest path in a network having various types of fuzzy arc lengths. First, we develop a new technique for the addition of various fuzzy numbers in a path using ? -cuts by proposing a linear least squares model to obtain membership functions for the considered additions. Then, using a recently proposed distance function for comparison of fuzzy numbers. we propose a new approach to solve the fuzzy APSPP using of genetic algorithm. Examples are worked out to illustrate the applicability of the proposed model.
A Simpler Algorithm for the All Pairs Shortest Path Problem with O(n 2logn) Expected Time
NASA Astrophysics Data System (ADS)
Takaoka, Tadao; Hashim, Mashitoh
The best known expected time for the all pairs shortest path problem on a directed graph with non-negative edge costs is O(n 2logn) by Moffat and Takaoka. Let the solution set be the set of vertices to which the given algorithm has established shortest paths. The Moffat-Takaoka algorithm maintains complexities before and after the critical point in balance, which is the moment when the size of the solution set is n - n/logn. In this paper, we remove the concept of critical point and the data structure, called a batch list, whereby we make the algorithm simpler and seamless, resulting in a simpler analysis and speed-up.
Evans, Will
16th Canadian Conference on Computational Geometry, 2004 Optimistic Shortest Paths on Uncertain shortest path on an un- certain terrain is NP-hard using a reduction similar to Canny and Reif's reduction of 3SAT to 3D Euclidean shortest path. !#"%$&'() Shortest path problems are a well-studied class
Physarum Can Compute Shortest Paths
Bonifaci, Vincenzo; Varma, Girish
2011-01-01
A mathematical model has been proposed by biologists to describe the feedback mechanism used by the Physarum Polycephalum slime mold to adapt its tubular channels while foraging two food sources $s_0$ and $s_1$. We give a proof of the fact that, under this model, the mass of the mold will eventually converge to the shortest $s_0$-$s_1$ path of the network that the mold lies on, independently of the structure of the network or of the initial mass distribution. This matches the experimental observations by the biologists and can be seen as an example of a "natural algorithm", that is, an algorithm developed by evolution over millions of years.
Shortest path algorithm based on city emergency system
Gui-Qin Dou; Yan-Song Zhu; Yu-Min Han
2011-01-01
It requires that the savers get to the spot with the quickest speed when the accidents take place in the City Emergency System, therefore the Shortest Path problem is one of the pivotal technology to satisfy the system. This paper put forward a real-time and effective algorithm realization of Shortest Path, according to the characteristics of City Emergency System, taking
Improved Hardness of Approximation for Stackelberg Shortest-Path Pricing
Khanna, Sanjeev
Improved Hardness of Approximation for Stackelberg Shortest-Path Pricing Patrick Briest1, , Parinya blaekh@cs.mcgill.ca 5 College of Computing, Georgia Tech, Atlanta, GA, USA danupon@cc.gatech.edu Abstract. We consider the Stackelberg shortest-path pricing problem, which is defined as follows. Given a graph
Shortest path and Schramm-Loewner Evolution
Pos, N.; Schrenk, K. J.; Arajo, N. A. M.; Herrmann, H. J.
2014-01-01
We numerically show that the statistical properties of the shortest path on critical percolation clusters are consistent with the ones predicted for Schramm-Loewner evolution (SLE) curves for ? = 1.04 0.02. The shortest path results from a global optimization process. To identify it, one needs to explore an entire area. Establishing a relation with SLE permits to generate curves statistically equivalent to the shortest path from a Brownian motion. We numerically analyze the winding angle, the left passage probability, and the driving function of the shortest path and compare them to the distributions predicted for SLE curves with the same fractal dimension. The consistency with SLE opens the possibility of using a solid theoretical framework to describe the shortest path and it raises relevant questions regarding conformal invariance and domain Markov properties, which we also discuss. PMID:24975019
Distributional properties of stochastic shortest paths for smuggled nuclear material
Cuellar, Leticia [Los Alamos National Laboratory; Pan, Feng [Los Alamos National Laboratory; Roach, Fred [Los Alamos National Laboratory; Saeger, Kevin J [Los Alamos National Laboratory
2011-01-05
The shortest path problem on a network with fixed weights is a well studied problem with applications to many diverse areas such as transportation and telecommunications. We are particularly interested in the scenario where a nuclear material smuggler tries to succesfully reach herlhis target by identifying the most likely path to the target. The identification of the path relies on reliabilities (weights) associated with each link and node in a multi-modal transportation network. In order to account for the adversary's uncertainty and to perform sensitivity analysis we introduce random reliabilities. We perform some controlled experiments on the grid and present the distributional properties of the resulting stochastic shortest paths.
The Multiple Choice Elementary Constrained Shortest Path Problem Karen Smilowitz Guangming Zhang
Smilowitz, Karen
-and-price approaches for variations of the vehicle routing problem in which the nodes to be visited are chosen among incorporate these methods into a branch-and-price approach to solve a variation of the vehicle routing problem-and-price method for a variation of the vehicle routing problem, known as the Multi-Resource Routing Problem (MRRP
Approximate Euclidean Shortest Paths amid Convex Obstacles Pankaj K. Agarwal R. Sharathkumar Hai Yu
Agarwal, Pankaj K.
Approximate Euclidean Shortest Paths amid Convex Obstacles Pankaj K. Agarwal R. Sharathkumar Hai Yu and data structures for the approximate Euclidean shortest path problem amid a set P of k convex obstacles for computing the exact Euclidean shortest path between two points amid polygonal obstacles. In three dimensions
Shortest Path Edit Distance for Enhancing UMLS Integration and Audit
Rudniy, Alex; Geller, James; Song, Min
2010-01-01
Expansion of the UMLS is an important long-term research project. This paper proposes Shortest Path Edit Distance (SPED) as an algorithm for improving existing source-integration and auditing techniques. We use SPED as a string similarity measure for UMLS terms that are known to be synonyms because they are assigned to the same concept. We compare SPED with several other well known string matching algorithms using two UMLS samples as test bed. One of those samples is SNOMED-based. SPED transforms the task of calculating edit distance among two strings into a problem of finding a shortest path from a source to a destination in a node and link graph. In the algorithm, the two strings are used to construct the graph. The Pulling algorithm is applied to find a shortest path, which determines the string similarity value. SPED was superior for one of the data sets, with a precision of 0.6. PMID:21347068
Detecting duplicate biological entities using Shortest Path Edit Distance.
Rudniy, Alex; Song, Min; Geller, James
2010-01-01
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
An Implementation of Chen & Han's Shortest Paths Algorithm
O'Rourke, Joseph
An Implementation of Chen & Han's Shortest Paths Algorithm Biliana Kaneva Joseph O'Rourke \\Lambda Abstract In 1990 Chen and Han proposed a quadratic algorithm for finding the shortest paths from one source In 1990 Chen and Han proposed a quadratic algorithm for finding the shortest paths from one source point
Curvature-Constrained Shortest Paths in a Convex Polygon (Extended Abstract)
Agarwal, Pankaj K.
and shed some light on curvature-constrained shortest paths amid obstacles. Center for Geometric Computing-planning problem, a central problem in robotics, involves planning a collision-free path for a robot moving amid
Shortest path optimization under limited information
Dahleh, Munther A.
The problem of finding an optimal path in an uncertain graph arises in numerous applications, including network routing, path-planning for vehicles, and the control of finite-state systems. While techniques in robust and ...
A bidirectional/multi-queue algorithm for the bi-objective multimodal viable shortest path
Paris-Sud XI, Universit de
A bidirectional/multi-queue algorithm for the bi-objective multimodal viable shortest path problem fgueye@mobigis.fr, artigues@laas.fr, huguet@laas.fr Abstract Taking into account the multimodality-objective viable shortest path, multi-modal transportation, multi-queue label setting algorithms, deterministic
Shortest paths synthesis for a car-like robot
P. Soueres; J.-P. Laumond
1996-01-01
This paper deals with the complete characterization of the shortest paths for a car-like robot. Previous works have shown that the search for a shortest path may be limited to a simple family of trajectories. Our work completes this study by providing a way to select inside this family an optimal path to link any two configurations. We combine the
Minimizing Average Shortest Path Distances via Shortcut Edge Addition
Meyerson, Adam W.
Minimizing Average Shortest Path Distances via Shortcut Edge Addition Adam Meyerson and Brian typically use mesh networks since regular topologies are easier to manufacture. However, many pairs of nodes k shortcut edges (of length 0) whose addition minimizes the weighted average shortest path
Two betweenness centrality measures based on Randomized Shortest Paths
Kivimki, Ilkka; Saramki, Jari; Saerens, Marco
2015-01-01
This paper introduces two new closely related betweenness centrality measures based on the Randomized Shortest Paths (RSP) framework, which fill a gap between traditional network centrality measures based on shortest paths and more recent methods considering random walks or current flows. The framework defines Boltzmann probability distributions over paths of the network which focus on the shortest paths, but also take into account longer paths depending on an inverse temperature parameter. RSP's have previously proven to be useful in defining distance measures on networks. In this work we study their utility in quantifying the importance of the nodes of a network. The proposed RSP betweenness centralities combine, in an optimal way, the ideas of using the shortest and purely random paths for analysing the roles of network nodes, avoiding issues involving these two paradigms. We present the derivations of these measures and how they can be computed in an efficient way. In addition, we show with real world exa...
Using shortest path to discover criminal community
Magalingam, Pritheega; Rao, Asha
2015-01-01
Extracting communities using existing community detection algorithms yields dense sub-networks that are difficult to analyse. Extracting a smaller sample that embodies the relationships of a list of suspects is an important part of the beginning of an investigation. In this paper, we present the efficacy of our shortest paths network search algorithm (SPNSA) that begins with an "algorithm feed", a small subset of nodes of particular interest, and builds an investigative sub-network. The algorithm feed may consist of known criminals or suspects, or persons of influence. This sets our approach apart from existing community detection algorithms. We apply the SPNSA on the Enron Dataset of e-mail communications starting with those convicted of money laundering in relation to the collapse of Enron as the algorithm feed. The algorithm produces sparse and small sub-networks that could feasibly identify a list of persons and relationships to be further investigated. In contrast, we show that identifying sub-networks o...
Corridor location: the multi-gateway shortest path model
NASA Astrophysics Data System (ADS)
Scaparra, Maria P.; Church, Richard L.; Medrano, F. Antonio
2014-07-01
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.
ON THE ACCELERATION OF SHORTEST PATH CALCULATIONS IN TRANSPORTATION NETWORKS
BAKER, ZACHARY K.; GOKHALE, MAYA B.
2007-01-08
Shortest path algorithms are a key element of many graph problems. They are used in such applications as online direction finding and navigation, as well as modeling of traffic for large scale simulations of major metropolitan areas. As the shortest path algorithms are an execution bottleneck, it is beneficial to move their execution to parallel hardware such as Field-Programmable Gate Arrays (FPGAs). Hardware implementation is accomplished through the use of a small A core replicated on the order of 20 times on an FPGA device. The objective is to maximize the use of on-board random-access memory bandwidth through the use of multi-threaded latency tolerance. Each shortest path core is responsible for one shortest path calculation, and when it is finished it outputs its result and requests the next source from a queue. One of the innovations of this approach is the use of a small bubble sort core to produce the extract-min function. While bubble sort is not usually considered an appropriate algorithm for any non-trivial usage, it is appropriate in this case as it can produce a single minimum out of the list in O(n) cycles, whwere n is the number of elements in the vertext list. The cost of this min operation does not impact the running time of the architecture, because the queue depth for fetching the next set of edges from memory is roughly equivalent to the number of cores in the system. Additionally, this work provides a collection of simulation results that model the behavior of the node queue in hardware. The results show that a hardware queue, implementing a small bubble-type minimum function, need only be on the order of 16 elements to provide both correct and optimal paths. Because the graph database size is measured in the hundreds of megabytes, the Cray SRAM memory is insufficient. In addition to the A* cores, they have developed a memory management system allowing round-robin servicing of the nodes as well as virtual memory managed over the Hypertransport bus. With support for a DRAM graph store with SRAM-based caching on the FPGA, the system provides a speedup of roughly 8.9x over the CPU-based implementation.
Multiple-Source Shortest Paths in Embedded Graphs Sergio Cabello
Erickson, Jeff
Multiple-Source Shortest Paths in Embedded Graphs Sergio Cabello Erin W. Chambers Jeff Erickson of Mathematics, FMF, University of Ljubljana, Slovenia, sergio. cabello@fmf.uni-lj.si. Research partially
Shortest Path Games: Computational Complexity of Solution Concepts
Amsterdam, University of
Shortest Path Games: Computational Complexity of Solution Concepts MSc Thesis (Afstudeerscriptie 9 2.1 Coalitional Games . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2 Concepts for Coalitional Games . . . . . . . . . . . . . . . . . . . . . . . 12 2.3.1 Power Indices
Shortest node-disjoint paths on random graphs
NASA Astrophysics Data System (ADS)
De Bacco, C.; Franz, S.; Saad, D.; Yeung, C. H.
2014-07-01
A localized method to distribute paths on random graphs is devised, aimed at finding the shortest paths between given source/destination pairs while avoiding path overlaps at nodes. We propose a method based on message-passing techniques to process global information and distribute paths optimally. Statistical properties such as scaling with system size and number of paths, average path-length and the transition to the frustrated regime are analysed. The performance of the suggested algorithm is evaluated through a comparison against a greedy algorithm.
Expected Shortest Paths for Landmark-Based Robot Navigation
Scharstein, Daniel
Expected Shortest Paths for Landmark-Based Robot Navigation Amy J. Briggs1 , Carrick Detweiler1 of planning reliable landmark- based robot navigation strategies in the presence of significant sensor uncertainty. The navigation environments are modeled with directed weighted graphs in which edges can
FINDING THE SHORTEST PATH FOR QUALITY ASSURANCE OF ELECTRIC COMPONENTS
Masaru Kageura; CANON IN; Kenji Shimada
This paper presents a computational method for calculating the shortest path along the surface of a product assembly between two components. The goal of this method is to check whether or not there is sufficient distance between two electrical components to prevent the occurrence of a spark between them. Our approach is an approximating method using a discrete weighted graph.
Efficient Shortest Paths on Massive Social Graphs (Invited Paper)
Almeroth, Kevin C.
extended to locate (near-) shortest paths between node pairs. After a one- time preprocessing cost, Rigel node distance queries on the original graph. Our initial system, Orion, was a centralized system in practice. First, Orion's initial graph embedding process is centralized and computationally expensive
Shortest Paths in Distance-Regular Graphs Enrique Bendito, Angeles Carmona and Andres M. Encinas
Bendito, Enrique
Shortest Paths in Distance-Regular Graphs Enrique Bendito, Angeles Carmona and Andres M. Encinas and Shortest Paths Angeles Carmona: e-mail:carmona@etseccpb.upc.es 2 #12;Abstract We aim here at introducing
Shortest Path Planning for a Tethered Robot or an Anchored Cable
Xavier, P.G.
1999-02-22
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.
THE SHORTEST PATH AMID 3-D POLYHEDRAL OBSTACLES SHUI-NEE CHOW, JUN LU, HAO-MIN ZHOU
Ferguson, Thomas S.
, namely it consists of straight line segments connected by junctions on the edges of the polyhedral in the presence of obstacles is one of the fundamental problems in path planning and robotics. The problem can be described as follows: given a finite number of obstacles in R2 or R3, what is the shortest path connecting
von Thienen, Wolfhard; Metzler, Dirk; Witte, Volker
2015-05-01
The emergence of self-organizing behavior in ants has been modeled in various theoretical approaches in the past decades. One model explains experimental observations in which Argentine ants (Linepithema humile) selected the shorter of two alternative paths from their nest to a food source (shortest path experiments). This model serves as an important example for the emergence of collective behavior and self-organization in biological systems. In addition, it inspired the development of computer algorithms for optimization problems called ant colony optimization (ACO). In the model, a choice function describing how ants react to different pheromone concentrations is fundamental. However, the parameters of the choice function were not deduced experimentally but freely adapted so that the model fitted the observations of the shortest path experiments. Thus, important knowledge was lacking about crucial model assumptions. A recent study on the Argentine ant provided this information by measuring the response of the ants to varying pheromone concentrations. In said study, the above mentioned choice function was fitted to the experimental data and its parameters were deduced. In addition, a psychometric function was fitted to the data and its parameters deduced. Based on these findings, it is possible to test the shortest path model by applying realistic parameter values. Here we present the results of such tests using Monte Carlo simulations of shortest path experiments with Argentine ants. We compare the choice function and the psychometric function, both with parameter values deduced from the above-mentioned experiments. Our results show that by applying the psychometric function, the shortest path experiments can be explained satisfactorily by the model. The study represents the first example of how psychophysical theory can be used to understand and model collective foraging behavior of ants based on trail pheromones. These findings may be important for other models of pheromone guided ant behavior and might inspire improved ACO algorithms. PMID:25769943
J. Sussmann; Guoqing Tang
1991-01-01
We illustrate the use of the techniques of modern geometric optimal control theory by studying the shortest paths for a model of a car that can move forwards and backwards. This problem was discussed in recent work by Reeds and Shepp who showed, by special methods, (a) that shortest path motion could always be achieved by means of trajectories of
Route Dynamics for Shortest Path First Routing in Mobile Ad Hoc Networks
Bhatti, Saleem N.
dynamics of Shortest-Path First (SPF) routing in mobile ad hoc networks (MANETs). In particular, we find Path First (SPF) algorithm as in Optimised Link State Routing Protocol (OLSR) [1]. Moreover, fast]. In this paper we investigate the route dynamics of Shortest- Path First (SPF) routing protocols in MANETs
Damage detection via shortest-path network sampling
NASA Astrophysics Data System (ADS)
Ciulla, Fabio; Perra, Nicola; Baronchelli, Andrea; Vespignani, Alessandro
2014-05-01
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.
Watershed cuts: thinnings, shortest path forests, and topological watersheds.
Cousty, Jean; Bertrand, Gilles; Najman, Laurent; Couprie, Michel
2010-05-01
We recently introduced watershed cuts, a notion of watershed in edge-weighted graphs. In this paper, our main contribution is a thinning paradigm from which we derive three algorithmic watershed cut strategies: The first one is well suited to parallel implementations, the second one leads to a flexible linear-time sequential implementation, whereas the third one links the watershed cuts and the popular flooding algorithms. We state that watershed cuts preserve a notion of contrast, called connection value, on which several morphological region merging methods are (implicitly) based. We also establish the links and differences between watershed cuts, minimum spanning forests, shortest path forests, and topological watersheds. Finally, we present illustrations of the proposed framework to the segmentation of artwork surfaces and diffusion tensor images. PMID:20299715
Accepted Manuscript Shortest path in a multiply-connected domain having curved
Ramanathan, M.
Accepted Manuscript Shortest path in a multiply-connected domain having curved boundaries S this article as: Bharath Ram S, Ramanathan M. Shortest path in a multiply-connected domain having curved manuscript that has been accepted for publication. As a service to our customers we are providing this early
Shortest Paths in Time-Dependent FIFO Networks Using Edge Load Forecasts
Dehene, Frank
Shortest Paths in Time-Dependent FIFO Networks Using Edge Load Forecasts Frank Dehne School shortest paths in time- dependent networks with edge load forecasts where the be- havior of each edge in a pre- dictable manner and are given as edge load forecasts. For example, in many road networks
Formal language constrained path problems
Barrett, C.; Jacob, R.; Marathe, M.
1997-07-08
In many path finding problems arising in practice, certain patterns of edge/vertex labels in the labeled graph being traversed are allowed/preferred, while others are disallowed. Motivated by such applications as intermodal transportation planning, the authors investigate the complexity of finding feasible paths in a labeled network, where the mode choice for each traveler is specified by a formal language. The main contributions of this paper include the following: (1) the authors show that the problem of finding a shortest path between a source and destination for a traveler whose mode choice is specified as a context free language is solvable efficiently in polynomial time, when the mode choice is specified as a regular language they provide algorithms with improved space and time bounds; (2) in contrast, they show that the problem of finding simple paths between a source and a given destination is NP-hard, even when restricted to very simple regular expressions and/or very simple graphs; (3) for the class of treewidth bounded graphs, they show that (i) the problem of finding a regular language constrained simple path between source and a destination is solvable in polynomial time and (ii) the extension to finding context free language constrained simple paths is NP-complete. Several extensions of these results are presented in the context of finding shortest paths with additional constraints. These results significantly extend the results in [MW95]. As a corollary of the results, they obtain a polynomial time algorithm for the BEST k-SIMILAR PATH problem studied in [SJB97]. The previous best algorithm was given by [SJB97] and takes exponential time in the worst case.
Bi-Qing Li; Tao Huang; Lei Liu; Yu-Dong Cai; Kuo-Chen Chou
2012-01-01
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
FORMAL-LANGUAGE-CONSTRAINED PATH PROBLEMS CHRIS BARRETT, RIKO JACOB, AND MADHAV MARATHE
FORMAL-LANGUAGE-CONSTRAINED PATH PROBLEMS CHRIS BARRETT, RIKO JACOB, AND MADHAV MARATHE SIAM J , the formal-language-constrained shortest/simple path problem con- sists of finding a shortest (simple) path p by concatenating the -labels of the edges along the path p. The main contributions of this paper include
Larsen, Kristian; Faulkner, Guy E.?J.; Stone, Michelle R.
2013-01-01
Objectives. School route measurement often involves estimating the shortest network path. We challenged the relatively uncritical adoption of this method in school travel research and tested the route discordance hypothesis that several types of difference exist between shortest network paths and reported school routes. Methods. We constructed the mapped and shortest path through network routes for a sample of 759 children aged 9 to 13 years in grades 5 and 6 (boys?=?45%, girls?=?54%, unreported gender?=?1%), in Toronto, Ontario, Canada. We used Wilcoxon signed-rank tests to compare reported with shortest-path route measures including distance, route directness, intersection crossings, and route overlap. Measurement difference was explored by mode and location. Results. We found statistical evidence of route discordance for walkers and children who were driven and detected it more often for inner suburban cases. Evidence of route discordance varied by mode and school location. Conclusions. We found statistically significant differences for route structure and built environment variables measured along reported and geographic information systemsbased shortest-path school routes. Uncertainty produced by the shortest-path approach challenges its conceptual and empirical validity in school travel research. PMID:23865648
The Stable Paths Problem and Interdomain Routing Timothy G. Griffin F. Bruce Shepherd Gordon Wilfong
Wilfong, Gordon
The Stable Paths Problem and Interdomain Routing Timothy G. Griffin F. Bruce Shepherd Gordon essentially im plement distributed algorithms for solving the Shortest Paths Problem. The Border Gateway is not solving a shortest paths problem since any interdomain protocol is required to allow policybased metrics
Maximum Entropy Models of Shortest Path and Outbreak Distributions in Networks
Bauckhage, Christian; Hadiji, Fabian
2015-01-01
Properties of networks are often characterized in terms of features such as node degree distributions, average path lengths, diameters, or clustering coefficients. Here, we study shortest path length distributions. On the one hand, average as well as maximum distances can be determined therefrom; on the other hand, they are closely related to the dynamics of network spreading processes. Because of the combinatorial nature of networks, we apply maximum entropy arguments to derive a general, physically plausible model. In particular, we establish the generalized Gamma distribution as a continuous characterization of shortest path length histograms of networks or arbitrary topology. Experimental evaluations corroborate our theoretical results.
Lecture notes for "Analysis of Algorithms": Dynamic All-Pairs Shortest Paths
Zwick, Uri
Lecture notes for "Analysis of Algorithms": Dynamic All-Pairs Shortest Paths Lecturer: Uri Zwick December 2010 Function apsp(G = (V, E, c)) t 0 foreach u V do E[u] [u] path(u) d[u, u] 0 p[u, u] [u] foreach u = v V do P[u, v] heap() insert-edges(E) build-paths() Function insert-edges(Eins) foreach e
Effective usage of shortest paths promotes transportation efficiency on scale-free networks
NASA Astrophysics Data System (ADS)
Du, Wen-Bo; Wu, Zhi-Xi; Cai, Kai-Quan
2013-09-01
With rapid economic and social development, the problem of traffic congestion is getting more and more serious. Accordingly, network traffic models have attracted extensive attention. In this paper, we introduce a shortest-remaining-path-first queuing strategy into a network traffic model on Barabsi-Albert scale-free networks under efficient routing protocol, where one packets delivery priority is related to its current distance to the destination. Compared with the traditional first-in-first-out queuing strategy, although the network capacity has no evident changes, some other indexes reflecting transportation efficiency are significantly improved in the congestion state. Extensive simulation results and discussions are carried out to explain the phenomena. Our work may be helpful for the designing of optimal networked-traffic systems.
A Continuous-State Version of Discrete Randomized Shortest-Paths, with Application to Path Planning
Del Moral , Pierre
a weighted directed graph G, the RSP considers the policy that minimizes the expected cost (exploitation] is a well-known problem in the robotics community, described by [26] as "checking the consequences entropy [23]. The introduced path randomization allows balancing the load (number of packages) per path
The approach for shortest paths in fire succor based on component GIS technology
NASA Astrophysics Data System (ADS)
Han, Jie; Zhao, Yong; Dai, K. W.
2007-06-01
Fire safety is an important issue for the national economy and people's living. Efficiency and exactness of fire department succor directly relate to safety of peoples' lives and property. Many disadvantages of the traditional fire system have been emerged in practical applications. The preparation of pumpers is guided by wireless communication or wire communication, so its real-time and accurate performances are much poorer. The information about the reported fire, such as the position, disaster and map, et al., for alarm and command was processed by persons, which slows the reaction speed and delays the combat opportunity. In order to solve these disadvantages, it has an important role to construct a modern fire command center based on high technology. The construction of modern fire command center can realize the modernization and automation of fire command and management. It will play a great role in protecting safety of peoples' lives and property. The center can enhance battle ability and can reduce the direct and indirect loss of fire damage at most. With the development of science technology, Geographic Information System (GIS) has becoming a new information industry for hardware production, software development, data collection, space analysis and counseling. With the popularization of computers and the development of GIS, GIS has gained increasing broad applications for its strong functionality. Network analysis is one of the most important functions of GIS, and the most elementary and pivotal issue of network analysis is the calculation of shortest paths. The shortest paths are mostly applied to some emergent systems such as 119 fire alarms. These systems mainly require that the computation time of the optimal path should be 1-3 seconds. And during traveling, the next running path of the vehicles should be calculated in time. So the implement of the shortest paths must have a high efficiency. In this paper, the component GIS technology was applied to collect and record the data information (such as, the situation of this disaster, map and road status et al) of the reported fire firstly. The ant colony optimization was used to calculate the shortest path of fire succor secondly. The optimization results were sent to the pumpers, which can let pumpers choose the shortest paths intelligently and come to fire position with least time. The programming method for shortest paths is proposed in section 3. There are three parts in this section. The elementary framework of the proposed programming method is presented in part one. The systematic framework of GIS component is described in part two. The ant colony optimization employed is presented in part three. In section 4, a simple application instance was presented to demonstrate the proposed programming method. There are three parts in this section. The distributed Web application based on component GIS was described in part one. The optimization results without traffic constraint were presented in part two. The optimization results with traffic constraint were presented in part three. The contributions of this paper can be summarized as follows. (1) It proposed an effective approach for shortest paths in fire succor based on component GIS technology. This proposed approach can achieve the real-time decisions of shortest paths for fire succor. (2) It applied the ant colony optimization to implement the shortest path decision. The traffic information was considered in the shortest path decision using ant colony optimization. The final application instance suggests that the proposed approach is feasible, correct and valid.
State-based accelerations and bidirectional search for bi-objective multimodal shortest paths
Paris-Sud XI, Universit de
State-based accelerations and bidirectional search for bi-objective multimodal shortest paths artigues@laas.fr, huguet@laas.fr Abstract Taking into account the multimodality of urban transportation-dependent context, is not a challenge anymore for labeling algorithms [6, 7, 19]. The case of multimodal passenger
Routing and Protection in GMPLS Networks: From Shortest Paths to Optimized Designs*
Elwalid, Anwar
Abstract-- Shortest path algorithms such as SPF and CSPF are widely used in online traffic engineering indicate that DBR outperforms SPF and CSPF under a wide range of operating con- ditions, and is robust- tion, protection, SPF, CSPF, DBR. I. INTRODUCTION A. Background and Motivation Service Providers
A Shortest Path Dependency Kernel for Relation Extraction Razvan C. Bunescu and Raymond J. Mooney
Bunescu, Razvan C.
of automatically derived syn- tactic information can lead to significant improve- ments in extraction accuracyA Shortest Path Dependency Kernel for Relation Extraction Razvan C. Bunescu and Raymond J. Mooney razvan,mooney@cs.utexas.edu Abstract We present a novel approach to relation extraction, based
Should QoS routing algorithms prefer shortest paths? Karol Kowalik and Martin Collier
Collier, Martin
Should QoS routing algorithms prefer shortest paths? Karol Kowalik and Martin Collier Research is the task of Quality of Service (QoS) routing. This paper considers link-state routing, and the choice of cost metric used to implement QoS routing. There are two schools of thought regarding the choice
Performance of Shortest Path Routing under Various Link Cost Metrics for non-GEO Satellite Systems
Papapetrou, Evaggelos
. Specially in new generation satellite systems which employ Inter-Satellite Links (ISLs) [1,2] is foundPerformance of Shortest Path Routing under Various Link Cost Metrics for non-GEO Satellite Systems for non- GEO satellite systems. The Modified Dijkstra algorithm is used for different link cost functions
He, Yunyue; Liu, Zhong; Shi, Jianmai; Wang, Yishan; Zhang, Jiaming; Liu, Jinyuan
2015-01-01
Emergency evacuation aims to transport people from dangerous places to safe shelters as quickly as possible. Police play an important role in the evacuation process, as they can handle traffic accidents immediately and help people move smoothly on roads. This paper investigates an evacuation routing problem that involves police resource allocation. We propose a novel k-th-shortest-path-based technique that uses explicit congestion control to optimize evacuation routing and police resource allocation. A nonlinear mixed-integer programming model is presented to formulate the problem. The models objective is to minimize the overall evacuation clearance time. Two algorithms are given to solve the problem. The first one linearizes the original model and solves the linearized problem with CPLEX. The second one is a heuristic algorithm that uses a police resource utilization efficiency index to directly solve the original model. This police resource utilization efficiency index significantly aids in the evaluation of road links from an evacuation throughput perspective. The proposed algorithms are tested with a number of examples based on real data from cities of different sizes. The computational results show that the police resource utilization efficiency index is very helpful in finding near-optimal solutions. Additionally, comparing the performance of the heuristic algorithm and the linearization method by using randomly generated examples indicates that the efficiency of the heuristic algorithm is superior. PMID:26226109
He, Yunyue; Liu, Zhong; Shi, Jianmai; Wang, Yishan; Zhang, Jiaming; Liu, Jinyuan
2015-01-01
Emergency evacuation aims to transport people from dangerous places to safe shelters as quickly as possible. Police play an important role in the evacuation process, as they can handle traffic accidents immediately and help people move smoothly on roads. This paper investigates an evacuation routing problem that involves police resource allocation. We propose a novel k-th-shortest-path-based technique that uses explicit congestion control to optimize evacuation routing and police resource allocation. A nonlinear mixed-integer programming model is presented to formulate the problem. The model's objective is to minimize the overall evacuation clearance time. Two algorithms are given to solve the problem. The first one linearizes the original model and solves the linearized problem with CPLEX. The second one is a heuristic algorithm that uses a police resource utilization efficiency index to directly solve the original model. This police resource utilization efficiency index significantly aids in the evaluation of road links from an evacuation throughput perspective. The proposed algorithms are tested with a number of examples based on real data from cities of different sizes. The computational results show that the police resource utilization efficiency index is very helpful in finding near-optimal solutions. Additionally, comparing the performance of the heuristic algorithm and the linearization method by using randomly generated examples indicates that the efficiency of the heuristic algorithm is superior. PMID:26226109
Do People Use the Shortest Path? An Empirical Test of Wardrops First Principle
Zhu, Shanjiang; Levinson, David
2015-01-01
Most recent route choice models, following either the random utility maximization or rule-based paradigm, require explicit enumeration of feasible routes. The quality of model estimation and prediction is sensitive to the appropriateness of the consideration set. However, few empirical studies of revealed route characteristics have been reported in the literature. This study evaluates the widely applied shortest path assumption by evaluating routes followed by residents of the MinneapolisSt. Paul metropolitan area. Accurate Global Positioning System (GPS) and Geographic Information System (GIS) data were employed to reveal routes people used over an eight to thirteen week period. Most people did not choose the shortest path. Using three weeks of that data, we find that current route choice set generation algorithms do not reveal the majority of paths that individuals took. Findings from this study may guide future efforts in building better route choice models. PMID:26267756
Improved Approximation Results on the Shortest Common Supersequence Problem
NASA Astrophysics Data System (ADS)
Gotthilf, Zvi; Lewenstein, Moshe
The problem of finding the Shortest Common Supersequence (SCS) of an arbitrary number of input strings is a well-studied problem. Given a set L of k strings, s 1, s 2, ..., s k , over an alphabet ?, we say that their SCS is the shortest string that contains each of the input strings as a subsequence. The problem is known to be NP-hard [8] even over binary alphabet [12]. In this paper we focus on approximating two NP-hard variants of the SCS problem. For the first variant, where all input strings are of length 2, we present a 2 - frac {2}{1 + log{n}log{log{n}}} approximation algorithm, where |?| = n. This result immediately improves the 2 - frac {4}{n+1} approximation algorithm presented in [17]. Moreover, we present a 7/6 (? 1.166bar{6}) approximation algorithm for the restricted variant (but still NP-hard) where all input strings are of length 2 and every character in ? has at most 3 occurrences in L.
Shepherd, Bruce
The Stable Paths Problem and Interdomain Routing Timothy G. Griffin and F. Bruce Shepherd distributed algorithms for solving the Shortest Paths Problem. The Border Gateway Protocol (BGP) is currently the only interdomain routing proto col deployed in the Internet. BGP is not solving a shortest paths
Cognitive Shortest Path Tree Restoration (CSPTR) for MANET Using Cost-Sensitivity Analysis
NASA Astrophysics Data System (ADS)
Chen, Huan; Cheng, Bo-Chao; Tseng, Po-Kai
With quick topology changes due to mobile node movement or signal fading in MANET environments, conventional routing restoration processes are costly to implement and may incur high flooding of network traffic overhead and long routing path latency. Adopting the traditional shortest path tree (SPT) recomputation and restoration schemes used in Internet routing protocols will not work effectively for MANET. An object of the next generation SPT restoration system is to provide a cost-effective solution using an adaptive learning control system, wherein the SPT restoration engine is able to skip over the heavy SPT computation. We proposed a novel SPT restoration scheme, called Cognitive Shortest Path Tree Restoration (CSPTR). CSPTR is designed based on the Network Simplex Method (NSM) and Sensitivity Analysis (SA) techniques to provide a comprehensive and low-cost link failure healing process. NSM is used to derive the shortest paths for each node, while the use of SA can greatly reduce the effort of unnecessary recomputation of the SPT when network topology changes. In practice, a SA range table is used to enable the learning capability of CSPTR. The performance of computing and communication overheads are compared with other two well-known schemes, such as Dijstra's algorithm and incremental OSPF. Results show that CSPTR can greatly eliminate unnecessary SPT recomputation and reduce large amounts of the flooding overheads.
Ultrafast Shortest-Path Queries with Linear-Time Preprocessing
Matijevic, Domagoj
]. The asymptotic running time of Dijkstra's algorithm is O(m + n log m), where n is the number of nodes, and m in exactly that problem. Note that 1 #12;Figure 1: Transit nodes (red/bold dots) for a part of a city (center, dark) when travelling far (outside the light-gray area). road networks are particular in at least two
Scaling of average receiving time and average weighted shortest path on weighted Koch networks
NASA Astrophysics Data System (ADS)
Dai, Meifeng; Chen, Dandan; Dong, Yujuan; Liu, Jie
2012-12-01
In this paper we present weighted Koch networks based on classic Koch networks. A new method is used to determine the average receiving time (ART), whose key step is to write the sum of mean first-passage times (MFPTs) for all nodes to absorption at the trap located at a hub node as a recursive relation. We show that the ART exhibits a sublinear or linear dependence on network order. Thus, the weighted Koch networks are more efficient than classic Koch networks in receiving information. Moreover, average weighted shortest path (AWSP) is calculated. In the infinite network order limit, the AWSP depends on the scaling factor. The weighted Koch network grows unbounded but with the logarithm of the network size, while the weighted shortest paths stay bounded.
Multiple Source Shortest Paths in a Genus g Graph Sergio Cabello
Erickson, Jeff
Multiple Source Shortest Paths in a Genus g Graph Sergio Cabello Erin W. Chambers Abstract We give of Mathematics, IMFM, and Department of Mathematics, FMF, University of Ljubljana, Slovenia, sergio.cabello- Peled [5], O(g3/2 n3/2 log n) by Cabello and Mohar [1], and O(gO(g) n log n) by Kutz [10]. Our approach
Exact Algorithms for the Canadian Traveller Problem on Paths and Trees
Karger, David
2008-01-28
The Canadian Traveller problem is a stochastic shortest paths problem in which one learns the cost of an edge only when arriving at one of its endpoints. The goal is to find an adaptive policy (adjusting as one learns more ...
NASA Astrophysics Data System (ADS)
Schafer, Sebastian; Singh, Vikas; Hoffmann, Kenneth R.; Nol, Peter B.; Xu, Jinhui
2007-03-01
Endovascular interventional procedures are being used more frequently in cardiovascular surgery. Unfortunately, procedural failure, e.g., vessel dissection, may occur and is often related to improper guidewire and/or device selection. To support the surgeon's decision process and because of the importance of the guidewire in positioning devices, we propose a method to determine the guidewire path prior to insertion using a model of its elastic potential energy coupled with a representative graph construction. The 3D vessel centerline and sizes are determined for a specified vessel. Points in planes perpendicular to the vessel centerline are generated. For each pair of consecutive planes, a vector set is generated which joins all points in these planes. We construct a graph representing these vector sets as nodes. The nodes representing adjacent vector sets are joined by edges with weights calculated as a function of the angle between the corresponding vectors (nodes). The optimal path through this weighted directed graph is then determined using shortest path algorithms, such as topological sort based shortest path algorithm or Dijkstra's algorithm. Volumetric data of an internal carotid artery phantom ( 3.5mm) were acquired. Several independent guidewire ( 0.4mm) placements were performed, and the 3D paths were determined using rotational angiography. The average RMS distance between the actual and the average simulated guidewire path was 0.7mm; the computation time to determine the path was 3 seconds. The ability to predict the guidewire path inside vessels may facilitate calculation of vessel-branch access and force estimation on devices and the vessel wall.
Analytical results for the distribution of shortest path lengths in random networks
NASA Astrophysics Data System (ADS)
Katzav, Eytan; Nitzan, Mor; ben-Avraham, Daniel; Krapivsky, P. L.; Khn, Reimer; Ross, Nathan; Biham, Ofer
2015-07-01
We present two complementary analytical approaches for calculating the distribution of shortest path lengths in Erd?s-Rnyi networks, based on recursion equations for the shells around a reference node and for the paths originating from it. The results are in agreement with numerical simulations for a broad range of network sizes and connectivities. The average and standard deviation of the distribution are also obtained. In the case in which the mean degree scales as N? with the network size, the distribution becomes extremely narrow in the asymptotic limit, namely almost all pairs of nodes are equidistant, at distance d=\\lfloor1/?\\rfloor from each other. The distribution of shortest path lengths between nodes of degree m and the rest of the network is calculated. Its average is shown to be a monotonically decreasing function of m, providing an interesting relation between a local property and a global property of the network. The methodology presented here can be applied to more general classes of networks.
Faster Shortest Path Algorithm for H-Minor Free Graphs with Negative Edge Weights
Wulff-Nilsen, Christian
2010-01-01
Let $H$ be a fixed graph and let $G$ be an $H$-minor free $n$-vertex graph with integer edge weights and no negative weight cycles reachable from a given vertex $s$. We present an algorithm that computes a shortest path tree in $G$ rooted at $s$ in $\\tilde{O}(n^{4/3}\\log L)$ time, where $L$ is the absolute value of the smallest edge weight. The previous best bound was $\\tilde{O}(n^{\\sqrt{11.5}-2}\\log L) = O(n^{1.392}\\log L)$. Our running time matches an earlier bound for planar graphs by Henzinger et al.
Freight Network Modeling System. Volume IV. Shortest-Path Analysis and Display user's guide
Not Available
1985-04-01
The Freight Network Modeling System (FNEM) is a general and flexible modeling system designed to have wide applicability to a variety of freight transportation analyses. The system consists of compatible network data bases, data management software, models of freight transportation, report generators, and graphics output. In many studies, a model as comprehensive as FNEM is not required. The second model, Shortest-Path Analysis and Display (SPAD), is a simpler model that optimizes routings of single shipments. The routing criteria that can be used are numerous - including minimizing cost, minimizing delay, minimizing population exposure (useful when considering shipments of hazardous materials), and minimizing accident risk. In addition to the above criteria, the routes can also be restricted to those with clearance for oversized loads or with sufficient load capabilities. SPAD can be used interactively and the routes can be displayed graphically. This volume contains a user's guide for SPAD including preprocessor programs and SPAD execution. 7 figs., 19 tabs.
Tubule detection in testis images using boundary weighting and circular shortest path.
Zhang, Chao; Sun, Changming; Davey, Rhonda; Su, Ran; Bischof, Leanne; Vallotton, Pascal; Lovell, David; Hope, Shelly; Lehnert, Sigrid; Pham, Tuan D
2013-01-01
In studies of germ cell transplantation, measureing tubule diameters and counting cells from different populations using antibodies as markers are very important. Manual measurement of tubule sizes and cell counts is a tedious and sanity grinding work. In this paper, we propose a new boundary weighting based tubule detection method. We first enhance the linear features of the input image and detect the approximate centers of tubules. Next, a boundary weighting transform is applied to the polar transformed image of each tubule region and a circular shortest path is used for the boundary detection. Then, ellipse fitting is carried out for tubule selection and measurement. The algorithm has been tested on a dataset consisting of 20 images, each having about 20 tubules. Experiments show that the detection results of our algorithm are very close to the results obtained manually. PMID:24110438
Almeroth, Kevin C.
Orion: Shortest Path Estimation for Large Social Graphs Xiaohan Zhao, Alessandra Sala, Christo allowing constant time node distance computation. We describe Orion, a pro- totype graph coordinate system, and explore critical de- cisions in its design. Finally, we evaluate the accuracy of Orion's node distance
NASA Astrophysics Data System (ADS)
Megherbi, Dalila B.; Teirelbar, A.; Boulenouar, A. J.
2001-09-01
Autonomous agent path planning is a main problem in the fields of machine learning and artificial intelligence. Reactive execution is often used in order to provide best decision for the agent's reactions. Although this problem is important in the stationary environment, most interesting environments are time varying. This paper is based on our previous work focusing on combining the potential field model with reinforcement learning to solve the stationary path problem. In this work we deal with the case of dynamic environment. In the dynamic environment, the motion of the obstacles provides for different problems and challenges, which our proposed algorithm in this paper encounters and addresses.
Kchichian, Razmig; Valette, Sbastien; Desvignes, Michel; Prost, Rmy
2013-11-01
We derive shortest-path constraints from graph models of structure adjacency relations and introduce them in a joint centroidal Voronoi image clustering and Graph Cut multiobject semiautomatic segmentation framework. The vicinity prior model thus defined is a piecewise-constant model incurring multiple levels of penalization capturing the spatial configuration of structures in multiobject segmentation. Qualitative and quantitative analyses and comparison with a Potts prior-based approach and our previous contribution on synthetic, simulated, and real medical images show that the vicinity prior allows for the correct segmentation of distinct structures having identical intensity profiles and improves the precision of segmentation boundary placement while being fairly robust to clustering resolution. The clustering approach we take to simplify images prior to segmentation strikes a good balance between boundary adaptivity and cluster compactness criteria furthermore allowing to control the trade-off. Compared with a direct application of segmentation on voxels, the clustering step improves the overall runtime and memory footprint of the segmentation process up to an order of magnitude without compromising the quality of the result. PMID:23807445
NASA Astrophysics Data System (ADS)
Wu, Zikai; Hou, Baoyu; Zhang, Hongjuan; Jin, Feng
2014-04-01
Deterministic network models have been attractive media for discussing dynamical processes' dependence on network structural features. On the other hand, the heterogeneity of weights affect dynamical processes taking place on networks. In this paper, we present a family of weighted expanded Koch networks based on Koch networks. They originate from a r-polygon, and each node of current generation produces mr-polygons including the node and whose weighted edges are scaled by factor w in subsequent evolutionary step. We derive closed-form expressions for average weighted shortest path length (AWSP). In large network, AWSP stays bounded with network order growing (0 < w < 1). Then, we focus on a special random walks and trapping issue on the networks. In more detail, we calculate exactly the average receiving time (ART). ART exhibits a sub-linear dependence on network order (0 < w < 1), which implies that nontrivial weighted expanded Koch networks are more efficient than un-weighted expanded Koch networks in receiving information. Besides, efficiency of receiving information at hub nodes is also dependent on parameters m and r. These findings may pave the way for controlling information transportation on general weighted networks.
Wu, Jie
. The work of J. Wu was supported in part by U.S. NSF Grant CCR 9900646 and Grant ANI 0073736. Responsible, Philadelphia, PA 19104 USA (e-mail: LSheng@mcs.drexel.edu). J. Wu is with the Department of Computer Science) is Not Optimal for a General N N Torus Li Sheng and Jie Wu, Senior Member, IEEE Abstract--A shortest-path routing
NASA Astrophysics Data System (ADS)
Huang, Guo-Jiao; Bai, Chao-Ying; Greenhalgh, Stewart
2013-09-01
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.
NASA Astrophysics Data System (ADS)
Blezek, Daniel J.; Robb, Richard A.
1999-05-01
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.
Metropolis Algorithm for solving Shortest Lattice Vector Problem(SVP)
Biswas, Somenath
spanning from robotics to computational number theory, viz., polynomial factorization. At the same time problem for a long time. A breakthrough result by Ajtai[4] in 1998 finally showed that SVP is NP-hard under randomized reductions. Another breakthrough by Micciancio [5]in 2001 showed that SVP is hard
The Shortest Path to Happiness: Recommending Beautiful, Quiet, and Happy Routes in the City
Quercia, Daniele; Aiello, Luca Maria
2014-01-01
When providing directions to a place, web and mobile mapping services are all able to suggest the shortest route. The goal of this work is to automatically suggest routes that are not only short but also emotionally pleasant. To quantify the extent to which urban locations are pleasant, we use data from a crowd-sourcing platform that shows two street scenes in London (out of hundreds), and a user votes on which one looks more beautiful, quiet, and happy. We consider votes from more than 3.3K individuals and translate them into quantitative measures of location perceptions. We arrange those locations into a graph upon which we learn pleasant routes. Based on a quantitative validation, we find that, compared to the shortest routes, the recommended ones add just a few extra walking minutes and are indeed perceived to be more beautiful, quiet, and happy. To test the generality of our approach, we consider Flickr metadata of more than 3.7M pictures in London and 1.3M in Boston, compute proxies for the crowdsourced...
A Computational Study Identifies HIV Progression-Related Genes Using mRMR and Shortest Path Tracing
Liu, Lei
2013-01-01
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
A computational study identifies HIV progression-related genes using mRMR and shortest path tracing.
Ma, Chengcheng; Dong, Xiao; Li, Rudong; Liu, Lei
2013-01-01
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
Patrikalakis, Nicholas M.
Journal of Mechanical Design, ASME Transactions, Vol. 118 No. 4, pages 499-508, 1996. Computation of Shortest Paths on Free-Form Parametric Surfaces Takashi Maekawa Massachusetts Institute of Technology, computation of medial axis transforms of trimmed surface patches, terrain navigation and NC machining
Spreading and shortest paths in systems with sparse long-range connections
Cristian F. Moukarzel
1999-01-01
Spreading according to simple rules (e.g. of fire or diseases), and\\u000ashortest-path distances are studied on d-dimensional systems with a small\\u000adensity p per site of long-range connections (``Small-World'' lattices). The\\u000avolume V(t) covered by the spreading quantity on an infinite system is exactly\\u000acalculated in all dimensions. We find that V(t) grows initially as t^d\\/d for\\u000at<< t^* =
Stochastic Shortest Path MDPs with Dead Ends Andrey Kolobov Mausam Daniel S. Weld
Mausam
.g., sending a rover on Mars). Even though MDP algo- rithms are used for solving problems with dead with in many real-world planning problems, be it sending a rover on Mars or navigating a robot in a building for them. The first class we present, SSPADE, is a small extension of SSP that has well-defined easily
Computing Single Source Shortest Paths using Single-Objective Fitness Functions
Doerr, Benjamin
such as vehicle routing [8] and routing problems in networks [6, 10] have been tackled. Therefore, it seems- est in recent years. One approach to analyze evolutionary Work supported by the Collaborative Research
The terminal area automated path generation problem
NASA Technical Reports Server (NTRS)
Hsin, C.-C.
1977-01-01
The automated terminal area path generation problem in the advanced Air Traffic Control System (ATC), has been studied. Definitions, input, output and the interrelationships with other ATC functions have been discussed. Alternatives in modeling the problem have been identified. Problem formulations and solution techniques are presented. In particular, the solution of a minimum effort path stretching problem (path generation on a given schedule) has been carried out using the Newton-Raphson trajectory optimization method. Discussions are presented on the effect of different delivery time, aircraft entry position, initial guess on the boundary conditions, etc. Recommendations are made on real-world implementations.
All-Pairs Almost Shortest Paths Ausarbeitung des Vortrags von Martin Holzer
Brandes, Ulrik
Grafen. Wird nun die Bedingung der Exaktheit dieser Distanzen etwas aufgeweicht und ein einseiti- ger und das APASP-Problem f¨ur einen Grafen mit einem ein- seitigen additiven Fehler von maximal k l-Emulator zu einem ungewichteten Grafen einen gewichteten Grafen mit derselben Knotenmenge so, dass die Distanz
Fekete, Sándor P.
Networks S´andor Fekete Tom Kamphans Michael Stelzer Abstract A problem studied in Systems Biology is how do not properly reflect biochemical facts. An approach to overcome this issue is to use edge labels@freenet.de Helmholtz Centre for Infection Research (HZI), Systems Biology, 38124 Braunschweig, Germany Figure 1
All-Pairs Shortest Paths for Unweighted Undirected Graphs in o(mn) Time
Chan, Timothy M.
n) if m > n log n log log log n O(mn log log n= log n) if m > n log log n O(n 2 log 2 log n= log n) if m #20; n log log n: These represent the best time bounds known for the problem for all m #28; n 1 in the general case with real-valued weights (the #12;rst subcubic time bound was O(n 3 (log log n= log n) 1
Replacement Paths via Fast Matrix Multiplication Oren Weimann
Yuster, Raphael
Replacement Paths via Fast Matrix Multiplication Oren Weimann Department of Computer Science be a directed edge-weighted graph and let P be a shortest path from s to t in G. The replacement paths problem asks to compute, for every edge e on P, the shortest s-to-t path that avoids e. Apart from
An Alternate Path To Stoichiometric Problem Solving.
ERIC Educational Resources Information Center
Schmidt, Hans-Jurgen
1997-01-01
Discusses an alternate path to teaching introductory stoichiometry based on research findings. The recommendation is to use problems that can be solved easily by rapid mental calculation as well as by pure logic. (AIM)
Micciancio, Daniele
vector problem. Nearest vector problem. Minimum distance problem. 1 PROBLEM DEFINITION A point lattice. Definition 1 (Shortest Vector Problem, SVP # ). Given a lattice L(B), find a nonzero lattice vector Bx (where x # Z n \\ {0}) such that #Bx# # # #By# for any y # Z n \\ {0}. Definition 2 (Closest Vector Problem
Spreading paths in partially observed social networks
NASA Astrophysics Data System (ADS)
Onnela, Jukka-Pekka; Christakis, Nicholas A.
2012-03-01
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 static, structurally realistic social networks as platforms 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.
Approximability of 3-and 4-hop bounded disjoint paths problems
Nabben, Reinhard
Approximability of 3- and 4-hop bounded disjoint paths problems Andreas Bley1 and Jose Neto2 1 TU & Management SudParis, CNRS UMR 5157, 9 rue Charles Fourier, F-91011 Evry, France Abstract A path is said to be -bounded if it contains at most edges. We consider two types of -bounded disjoint paths problems
A NEW IMPLEMENTATION OF YEN'S RANKING LOOPLESS PATHS ALGORITHM 1
Pascoal, Marta Margarida Braz
A NEW IMPLEMENTATION OF YEN'S RANKING LOOPLESS PATHS ALGORITHM 1 Ernesto de Queir' os Vieira algorithm for ranking the K shortest loopless paths between a pair of nodes in a network. In this paper to conclude. Keywords: network, path, loopless path, paths ranking. 1 Introduction The problem of determining
Jiang, Hai, 1979-
2004-01-01
This thesis aims at the development of faster Dynamic Traffic Assignment (DTA) models to meet the computational efficiency required by real world applications. A DTA model can be decomposed into several sub-models, of which ...
Scalability of Parallel Algorithms for the AllPairs Shortest Path Problem \\Lambda
Kumar, Vipin
version of this paper appeared in the proceedings of the 1990 International Conference on Parallel Computer Science Department University of Minnesota Minneapolis, MN 55455 Internet: kumar@cs.umn.edu Vineet. \\Lambda This work was partially supported by Army Research Office grant # 28408MASDI to the University
Approximation Algorithms for Disjoint Paths Problems Jon Michael Kleinberg
Kleinberg, Jon
a number of related algorithms by this approach, including a routing algorithm for the mesh that is optimalApproximation Algorithms for Disjoint Paths Problems by Jon Michael Kleinberg S.M., Electrical Students #12; 2 #12; Approximation Algorithms for Disjoint Paths Problems by Jon Michael Kleinberg
MinimumCost Spanning Tree PathFinding Problem
Maggs, Bruce M.
MinimumCost Spanning Tree as a PathFinding Problem Bruce M. Maggs Serge A. Plotkin Laboratorycost spanning tree is a special case of the closed semiring pathfinding problem. This observation gives us a nonrecursive algorithm for finding minimum cost spanning trees on meshconnected computers that has
Energy-Aware Two Link-Disjoint Paths Routing Gongqi Lin, Sieteng Soh, Mihai Lazarescu
Chin, Kwan-Wu
. To address this problem, we present a fast heuristic, called TLDP by Shortest Path First (TLDP-SPF simulation results show that TLDP-SPF can reduce network energy usage, on average, by more than 20%, even for MLU below 50%. As compared to using Shortest Path routing, while reducing energy by about 20%, TLDP-SPF
Shortest route algorithm with movement prohibitions
Said M. Easa
1985-01-01
This paper presents an algorithm with movement prohibitions which eliminates some problems encountered in network representation used for traffic assignment models, and further allows the representation of the network to be simplified. The paper first presents an appraisal of some proposed methods and reviews the basic concept of existing shortest-route algorithms. The problem of obtaining shortest routes in networks with
Adleman[1] 1994 DNA Hamiltonian Path Problem , DNA
1. Adleman[1] 1994 DNA Hamiltonian Path Problem , DNA DNA [2]. DNA DNA , . , , 2 , DNA 4 . DNA 4 A(Adenine), C(Cytosine), G(Guanine), T(Thymine) 2 4 . , . 1 mole 6x10 23 DNA DNA . , . DNA NP-complete [1, 2], [2
An Application of Calculus: Optimum Parabolic Path Problem
ERIC Educational Resources Information Center
Atasever, Merve; Pakdemirli, Mehmet; Yurtsever, Hasan Ali
2009-01-01
A practical and technological application of calculus problem is posed to motivate freshman students or junior high school students. A variable coefficient of friction is used in modelling air friction. The case in which the coefficient of friction is a decreasing function of altitude is considered. The optimum parabolic path for a flying object
Shortest Non-trivial Cycles in Directed Surface Graphs Jeff Erickson
Erickson, Jeff
the observation by Cabello and Mohar [12] that the shortest non-trivial cycle crosses any shortest path at most condition [44] and Cabello and Mo- har's crossing condition [12] are consequences of the following easy
Searching in an Unknown Environment: An Optimal Randomized Algorithm for the Cow-Path Problem
Tate, Steve
Searching in an Unknown Environment: An Optimal Randomized Algorithm for the Cow-Path Problem Ming in mind, the abstract problem known as the w-lane cow-path problem was designed. There are known optimal deterministic algorithms for the cow-path problem, and we give the first randomized algorithm in this paper. We
Quasiexactly solvable problems in the path-integral formalism
NASA Astrophysics Data System (ADS)
Lucht, M. W.; Jarvis, P. D.
1993-02-01
Quasiexactly solvable problems are treated via the path-integral approach. The generalized Duru-Kleinert formalism involving a combination of a point-canonical transformation and a new-time transformation is applied to power-law and Morse-like quasiexactly solvable problems, and it is shown that these can be grouped into two families. A truncated kernel hypothesis is advanced, whereby the exactly solvable parts of the kernels of each problem within a given family can be transformed into one another. As an application, the ground-state energy eigenvalue and wave function of the N=0 generalized harmonic oscillator are derived from those of the N=0 generalized Coulomb problem.
Zhao, Gongyun
Underlying Paths in Interior Point Methods for the Monotone Semidefinite Linear Complementarity call such curves off-central paths. We study off-central paths for the monotone semidefinite linear complementarity problem (SDLCP). We show that each off-central path is a well-defined analytic curve
Felner, Ariel
2004-01-01
tile puzzle and Rubik's Cube (Korf, 1999) are examples of the c fl2004 AI Access Foundation. All rights unknown territory. We introduce the PhysicalA* algorithm (PHA*) for solving this problem. PHA* expands. However, due to the physical nature of the problem, the complexity of the algorithm is measured
A general approximation technique for constrained forest problems
Michel X. Goemans; David P. Williamson
1992-01-01
We present a general approximation technique for a large class of graph problems. Our technique mostly applies to problems of covering, at minimum cost, the vertices of a graph with trees, cycles or paths satisfying certain requirements. In particular, many basic combinatorial optimization problems fit in this framework, including the shortest path, minimum spanning tree, minimum-weight perfect matching, traveling salesman
NASA Astrophysics Data System (ADS)
Shakeri, Nadim; Jalili, Saeed; Ahmadi, Vahid; Rasoulzadeh Zali, Aref; Goliaei, Sama
2015-01-01
The problem of finding the Hamiltonian path in a graph, or deciding whether a graph has a Hamiltonian path or not, is an NP-complete problem. No exact solution has been found yet, to solve this problem using polynomial amount of time and space. In this paper, we propose a two dimensional (2-D) optical architecture based on optical electronic devices such as micro ring resonators, optical circulators and MEMS based mirror (MEMS-M) to solve the Hamiltonian Path Problem, for undirected graphs in linear time. It uses a heuristic algorithm and employs n+1 different wavelengths of a light ray, to check whether a Hamiltonian path exists or not on a graph with n vertices. Then if a Hamiltonian path exists, it reports the path. The device complexity of the proposed architecture is O(n2).
Path-integral--Riemann-space approach to the electromagnetic wedge diffraction problem
Ziolkowski, R.W.
1986-09-01
A path integral constructed over a particular Riemann space is developed and applied to two-dimensional wedge problems. This path-integral--Riemann-space (PIRS) approach recovers the exact solutions of the heat conduction and the corresponding electromagnetic wedge problems. A high-frequency asymptotic evaluation of the PIRS electromagnetic wedge solution returns the standard geometrical theory of diffraction (GTD) results. Ramifications of this approach and its relationships with known path-integral methods are examined.
Seedlings in the Theory of Shortest Paths
Steele, J. Michael
(x) is the density of the absolutely continuous part of the distribution of the Xi. This result has proved fruitful is the existence of measure preserving transformations from [0, 1] onto [0, 1]d that are Lipschitz of order 1/d
Seedlings in the Theory of Shortest Paths
Grimmett, Geoffrey
of the distribution of the X i . This result has proved fruitful in most of the ways that are open to a mathematical preserving transformations from [0, 1] onto [0, 1] d that are Lipschitz of order 1/d. A basic objective
An analysis of the elastic net approach to the travelling salesman problem
Richard Durbin; R. Szeliski; A. Yuille
1989-01-01
This paper analyzes the elastic net approach (Durbin and Willshaw 1987) to the traveling salesman problem of finding the shortest path through a set of cities. The elastic net approach jointly minimizes the length of an arbitrary path in the plane and the distance between the path points and the cities. The tradeoff between these two requirements is controlled by
Complementarity Problems in GAMS and the PATH Solver
Michael C. Ferris; Todd S. Munson
1998-01-01
A fundamental mathematical problem is to find a solution to a square system of nonlinear equations. There are many methods to approach this problem, the most famous of which is Newton's method. In this paper, we describe a generalization of this problem, the comple- mentarity problem. We show how such problems are modeled within the GAMS modeling language and provide
Shape Analysis as a Generalized Path Problem Thomas Reps
Reps, Thomas W.
, Madison, WI 53706. Telephone: (608) 262-1204. Electronic mail: reps@cs.wisc.edu. tions of selection to connect two vertices only if the con- catenation of the labels on the edges of the path is a word on the run- ning time of an algorithm for shape analysis. It also per- mits us to obtain a demand algorithm
Two-Point Boundary Value Problems for Curves: The Case of Minimum Free Energy Paths
Skeel, Robert
Two-Point Boundary Value Problems for Curves: The Case of Minimum Free Energy Paths corrected.S.A. Abstract The calculation of a minimum free energy path can be considered as a two-point boundary value box solvers. The second paragraph of Section 1 is corrected. Because free energy is defined in terms
Multiple Manifold Clustering Using Curvature Constrained Path
Babaeian, Amir; Bayestehtashk, Alireza; Bandarabadi, Mojtaba
2015-01-01
The problem of multiple surface clustering is a challenging task, particularly when the surfaces intersect. Available methods such as Isomap fail to capture the true shape of the surface near by the intersection and result in incorrect clustering. The Isomap algorithm uses shortest path between points. The main draw back of the shortest path algorithm is due to the lack of curvature constrained where causes to have a path between points on different surfaces. In this paper we tackle this problem by imposing a curvature constraint to the shortest path algorithm used in Isomap. The algorithm chooses several landmark nodes at random and then checks whether there is a curvature constrained path between each landmark node and every other node in the neighborhood graph. We build a binary feature vector for each point where each entry represents the connectivity of that point to a particular landmark. Then the binary feature vectors could be used as a input of conventional clustering algorithm such as hierarchical clustering. We apply our method to simulated and some real datasets and show, it performs comparably to the best methods such as K-manifold and spectral multi-manifold clustering. PMID:26375819
Fusion proteins as alternate crystallization paths to difficult structure problems
NASA Technical Reports Server (NTRS)
Carter, Daniel C.; Rueker, Florian; Ho, Joseph X.; Lim, Kap; Keeling, Kim; Gilliland, Gary; Ji, Xinhua
1994-01-01
The three-dimensional structure of a peptide fusion product with glutathione transferase from Schistosoma japonicum (SjGST) has been solved by crystallographic methods to 2.5 A resolution. Peptides or proteins can be fused to SjGST and expressed in a plasmid for rapid synthesis in Escherichia coli. Fusion proteins created by this commercial method can be purified rapidly by chromatography on immobilized glutathione. The potential utility of using SjGST fusion proteins as alternate paths to the crystallization and structure determination of proteins is demonstrated.
Algorithms for an Unmanned Vehicle Path Planning Problem
Qin, Jianglei
2013-06-25
of targets to satisfy the quota requirement on the total prize collected in the tour. In the budget problem, the vehicle has to comply with a constraint of the distance traveled by the UV. We solve both these problems using a practical heuristic called...
International Association for Cryptologic Research (IACR)
On the quaternion -isogeny path problem David Kohel, Kristin Lauter, Christophe Petit , Jean quaternion algebra over Q of prime discriminant p, and a small prime. We describe a probabilistic algorithm in expected polynomial time. This breaks the underlying problem for a quaternion analog of the Charles
Proof of a Lattice Paths Conjecture Connected to the Tennis Ball Problem
Niederhausen, Heinrich
Proof of a Lattice Paths Conjecture Connected to the Tennis Ball Problem Joshua Fallon a Shanzhen Abstract The authors give a history of the so-called tennis ball problem, and discuss its relation when the number of balls removed each turn is exactly half the number inserted. Key words: Tennis Ball
A General Approximation Technique for Constrained Forest Problems
Michel X. Goemans; David P. Williamson
1995-01-01
Abstract.,We present,a general approximation technique for a large class of graph problems.,Our technique mostly applies to problems of covering, at minimum cost, the vertices ofa graph with trees, cycles, or paths satisfying certain requirements. In particular, many basic combinatorial optimization problems fit in this framework, including the shortest path, minimum-cost spanning tree, minimum-weight perfect matching, traveling salesman, and Steiner tree,problems.
The three-body problem in the path integral formalism
NASA Astrophysics Data System (ADS)
Chouchaoui, A.
2004-08-01
The propagator related to the Calogero potential is calculated in the phase space by way of Feynman formalism. The energy spectrum is determined along with the corresponding wave functions. In case some constraints are introduced, the problem may be reduced to the one corresponding to a particle constrained to move into a sector of opening angle ?. It is shown as well that complicated potentials, may be transformed to allow the calculation of the energy spectrum via the Kleinert method.
Application of the CIRSSE cooperating robot path planner to the NASA Langley truss assembly problem
NASA Technical Reports Server (NTRS)
Weaver, Jonathan M.; Derby, Stephen J.
1993-01-01
A method for autonomously planning collision free paths for two cooperating robots in a static environment was developed at the Center for Intelligent Robotic Systems for Space Exploration (CIRSSE). The method utilizes a divide-and-conquer type of heuristic and involves non-exhaustive mapping of configuration space. While there is no guarantee of finding a solution, the planner was successfully applied to a variety of problems including two cooperating 9 degrees of freedom (dof) robots. Although developed primarily for cooperating robots the method is also applicable to single robot path planning problems. A single 6 dof version of the planner was implemented for the truss assembly east, at NASA Langley's Automated Structural Assembly Lab (ASAL). The results indicate that the planner could be very useful in addressing the ASAL path planning problem and that further work along these lines is warranted.
Shortest billiard trajectories Daniel Bezdek Karoly Bezdek
de Leon, Alex R.
Shortest billiard trajectories D´aniel Bezdek K´aroly Bezdek October 23, 2008 Abstract shortest generalized billiard trajectory moreover, any of its shortest generalized billiard trajectories of its generating disks are at most r. We prove that any of the shortest generalized billiard
NASA Astrophysics Data System (ADS)
Zamirian, M.; Kamyad, A. V.; Farahi, M. H.
2009-09-01
In this Letter a new approach for solving optimal path planning problems for a single rigid and free moving object in a two and three dimensional space in the presence of stationary or moving obstacles is presented. In this approach the path planning problems have some incompatible objectives such as the length of path that must be minimized, the distance between the path and obstacles that must be maximized and etc., then a multi-objective dynamic optimization problem (MODOP) is achieved. Considering the imprecise nature of decision maker's (DM) judgment, these multiple objectives are viewed as fuzzy variables. By determining intervals for the values of these fuzzy variables, flexible monotonic decreasing or increasing membership functions are determined as the degrees of satisfaction of these fuzzy variables on their intervals. Then, the optimal path planning policy is searched by maximizing the aggregated fuzzy decision values, resulting in a fuzzy multi-objective dynamic optimization problem (FMODOP). Using a suitable t-norm, the FMODOP is converted into a non-linear dynamic optimization problem (NLDOP). By using parametrization method and some calculations, the NLDOP is converted into the sequence of conventional non-linear programming problems (NLPP). It is proved that the solution of this sequence of the NLPPs tends to a Pareto optimal solution which, among other Pareto optimal solutions, has the best satisfaction of DM for the MODOP. Finally, the above procedure as a novel algorithm integrating parametrization method and fuzzy aggregation to solve the MODOP is proposed. Efficiency of our approach is confirmed by some numerical examples.
Search Path Mapping: A Versatile Approach for Visualizing Problem-Solving Behavior.
ERIC Educational Resources Information Center
Stevens, Ronald H.
1991-01-01
Computer-based problem-solving examinations in immunology generate graphic representations of students' search paths, allowing evaluation of how organized and focused their knowledge is, how well their organization relates to critical concepts in immunology, where major misconceptions exist, and whether proper knowledge links exist between content
Approximation Algorithms and Heuristics for a 2-depot, Heterogeneous Hamiltonian Path Problem
Doshi, Riddhi Rajeev
2011-10-21
Various civil and military applications of UAVs, or ground robots, require a set of vehicles to monitor a group of targets. Routing problems naturally arise in this setting where the operators of the vehicles have to plan the paths suitably in order...
High-order path-integral Monte Carlo methods for solving quantum dot problems
NASA Astrophysics Data System (ADS)
Chin, Siu A.
2015-03-01
The conventional second-order path-integral Monte Carlo method is plagued with the sign problem in solving many-fermion systems. This is due to the large number of antisymmetric free-fermion propagators that are needed to extract the ground state wave function at large imaginary time. In this work we show that optimized fourth-order path-integral Monte Carlo methods, which use no more than five free-fermion propagators, can yield accurate quantum dot energies for up to 20 polarized electrons with the use of the Hamiltonian energy estimator.
Modeling "wiggling" as a multi-path interference problem in AMCW ToF imaging.
Feigin, Micha; Whyte, Refael; Bhandari, Ayush; Dorington, Adrian; Raskar, Ramesh
2015-07-27
Amplitude modulated continuous wave time-of-flight range cameras suffer from an inherent depth measurement error due to aliasing of the emitted signal vs reference signal correlation function. This is due to higher harmonics present in both signals which are not accounted for in the model or measurements. This "wiggling" error is generally corrected by employing a correction function based on frequency and depth dependent calibration data. This problem is shown to be equivalent to a multi-path interference problem. Casting the problem into the multi-path interference domain and utilizing multiple modulation frequencies provides tools for dealing with the depth error without calibration in a frequency independent way. PMID:26367583
Discrete Optimization An exact algorithm for a single-vehicle routing problem
Potvin, Jean-Yves
Discrete Optimization An exact algorithm for a single-vehicle routing problem with time windows from benchmark instances of the classical vehicle routing problem with time windows. 2006 Elsevier B; Elementary shortest paths 1. Introduction In this work, we consider a variant of the vehicle routing problem
A methodology for predicting minimum travel paths using real-time traffic network data
Liu, Chang
1991-01-01
the shortest path between any two nodes. This is the path with minimum total link length. The links can be either directional or nondirectional. Mathematically, this problem can be defined as follows: if node V, and V, are the source and 11 destination... directional links. The TRANSYT computer program developed by Robertson in 19& can determine optimum cycle length, phase splits, and offsets that minimize a performance index which is a linear combination of stops and delays. The TRANSYT program can predict...
Zhu, Xiaoyan
2007-04-25
is acyclic, only one resource constraint is involved, and all resource requirements and costs are positive (Dumitrescu and Boland (2003)). Hassin (1992) showed that SRCSP is polynomial solvable if arc costs or arc resource requirements are bounded. Dror... (1988a) presented a primal-dual reoptimization approach for SPPTW and Desrochers (1988) generalized it to solve SPPRW. Dumitrescu and Boland (2003) investigated variants of the label-setting algorithm of Desrochers and Soumis (1988b) for both SRCSP...
Shortest recurrence periods of novae
Kato, Mariko [Department of Astronomy, Keio University, Hiyoshi, Yokohama 223-8521 (Japan); Saio, Hideyuki [Astronomical Institute, Graduate School of Science, Tohoku University, Sendai 980-8578 (Japan); Hachisu, Izumi [Department of Earth Science and Astronomy, College of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902 (Japan); Nomoto, Ken'ichi, E-mail: mariko@educ.cc.keio.ac.jp [Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan)
2014-10-01
Stimulated by the recent discovery of the 1 yr recurrence period nova M31N 2008-12a, we examined the shortest recurrence periods of hydrogen shell flashes on mass-accreting white dwarfs (WDs). We discuss the mechanism that yields a finite minimum recurrence period for a given WD mass. Calculating the unstable flashes for various WD masses and mass accretion rates, we identified a shortest recurrence period of about two months for a non-rotating 1.38 M {sub ?} WD with a mass accretion rate of 3.6 10{sup 7} M {sub ?} yr{sup 1}. A 1 yr recurrence period is realized for very massive (? 1.3 M {sub ?}) WDs with very high accretion rates (? 1.5 10{sup 7} M {sub ?} yr{sup 1}). We revised our stability limit of hydrogen shell burning, which will be useful for binary evolution calculations toward Type Ia supernovae.
High-order Path Integral Monte Carlo methods for solving strongly correlated fermion problems
NASA Astrophysics Data System (ADS)
Chin, Siu A.
2015-03-01
In solving for the ground state of a strongly correlated many-fermion system, the conventional second-order Path Integral Monte Carlo method is plagued with the sign problem. This is due to the large number of anti-symmetric free fermion propagators that are needed to extract the square of the ground state wave function at large imaginary time. In this work, I show that optimized fourth-order Path Integral Monte Carlo methods, which uses no more than 5 free-fermion propagators, in conjunction with the use of the Hamiltonian energy estimator, can yield accurate ground state energies for quantum dots with up to 20 polarized electrons. The correlations are directly built-in and no explicit wave functions are needed. This work is supported by the Qatar National Research Fund NPRP GRANT #5-674-1-114.
Gambardella, Luca Maria
. This elementary behavior of real ants can be used to explain how they can find the shortest path that reconnects the obstacle shape and ants distributed behavior: Although all ants move at approximately the same speedDorigo and Gambardella - Ant colonies for the traveling salesman problem 1 Ant colonies
Path planning strategies for autonomous ground vehicles
NASA Astrophysics Data System (ADS)
Gifford, Kevin Kent
Several key issues involved with the planning and executing of optimally generated paths for autonomous vehicles are addressed. Two new path planning algorithms are developed, and examined, which effectively minimize replanning as unmapped hazards are encountered. The individual algorithms are compared via extensive simulation. The search strategy results are implemented and tested using the University of Colorado's autonomous vehicle test-bed, RoboCar, and results show the advantages of solving the single-destination all-paths problem for autonomous vehicle path planning. Both path planners implement a graph search methodology incorporating dynamic programming that solves the single-destination shortest-paths problem. Algorithm 1, termed DP for dynamic programming, searches a state space where each state represents a potential vehicle location in a breadth-first fashion expanding from the goal to all potential start locations in the state space. Algorithm 2, termed DP*, couples the heuristic search power of the well-known A* search procedure (Nilsson-80) with the dynamic programming principle applied to graph searching to efficiently make use of overlapping subproblems. DP* is the primary research contribution of the work contained within this thesis. The advantage of solving the single-destination shortest-paths problem is that the entire terrain map is solved in terms of reaching a specified goal. Therefore, if the robot is diverted from the pre-planned path, an alternative path is already computed. The search algorithms are extended to include a probabilistic approach using empirical loss functions to incorporate terrain map uncertainties into the path considering terrain planning process. The results show the importance of considering terrain uncertainty. If the map representation ignores uncertainty by marking any area with less than perfect confidence as unpassable or assigns it the worst case rating, then the paths are longer than intuitively necessary. A hierarchical software control architecture is introduced that uses as the main guidance function an arbitration-based scheme which is able to efficiently and robustly integrate disparate sensor data. The flexibility provided by such an architecture allows for very easy integration of any type of environmental sensing device into the path planning algorithm.
Solution to the variation problem for information path functional of a controlled random process
NASA Astrophysics Data System (ADS)
Lerner, Vladimir S.
2007-10-01
The paper introduces a new approach to dynamic modeling, using the variation principle, applied to a functional on trajectories of a controlled random process, and its connection to the process' information functional. In [V.S. Lerner, Dynamic approximation of a random information functional, J. Math. Anal. Appl. 327 (1) (2007) 494-514, available online 5-24-06], we presented the information path functional with the Lagrangian, determined by the parameters of a controlled stochastic equation. In this paper, the solution to the path functional's variation problem provides both a dynamic model of a random process and the model's optimal control, which allows us to build a two-level information model with a random process at the microlevel and a dynamic process at the macrolevel. A wide class of random objects, modeled by the Markov diffusion process and a common structure of the process' information functional, leads to a universal information structure of the dynamic model, which is specified and identified on a particular object with the applied optimal control functions. The developed mathematical formalism, based on classical methods, is aimed toward the solution of problems identification, combined with an optimal control synthesis, which is practically implemented and also demonstrated in the paper's example.
Zhao, Gongyun
Asymptotic Behavior of HKM Paths in Interior Point Methods for Monotone Semidefinite Linear (ODEs). Thus, it is natural to define the underlying paths of the IPM as the solutions of the system of ODEs. In [9], these off- central paths are shown to be well-defined analytic curves and any
Hammock-on-Ears Decomposition: A Technique for the E cient Parallel Solution of Shortest
Waldmann, Uwe
Hammock-on-Ears Decomposition: A Technique for the E cient Parallel Solution of Shortest Paths the sequential hammock decomposition technique intro- duced by G. Frederickson and the parallel ear decomposition technique, thus we call it the hammock-on-ears decomposition. We mention that hammock-on-ears decomposi
Methodology for Augmenting Existing Paths with Additional Parallel Transects
Wilson, John E.
2013-09-30
Visual Sample Plan (VSP) is sample planning software that is used, among other purposes, to plan transect sampling paths to detect areas that were potentially used for munition training. This module was developed for application on a large site where existing roads and trails were to be used as primary sampling paths. Gap areas between these primary paths needed to found and covered with parallel transect paths. These gap areas represent areas on the site that are more than a specified distance from a primary path. These added parallel paths needed to optionally be connected together into a single paththe shortest path possible. The paths also needed to optionally be attached to existing primary paths, again with the shortest possible path. Finally, the process must be repeatable and predictable so that the same inputs (primary paths, specified distance, and path options) will result in the same set of new paths every time. This methodology was developed to meet those specifications.
Shortest Path Computation with No Information Leakage Kyriakos Mouratidis
Yiu, Man Lung
reveal personal information, such as social habits, health condition, shop- ping preferences, lifestyle systems and the diffusion of smart-phones has led to an expanding market of location-based services (LBSs nature of the queries may disclose per- sonal information (such as health status, shopping habits
Densities of shortest path lengths in spatial stochastic networks
Schmidt, Volker
for the probability density of this distribution which is based on functionals of the so-called typical serving zone processes, we derive a representation formula for the density of C # which is based on some functional for the typical serving zone which are used in a numerical study in order to estimate the density and moments
Parameter Shortest Path Algorithms with an Application to Cyclic Staffing
Karp, Richard M.
Let G = (V,E) be a digraph with n vertices including a special vertex s. Let E' C E be a designated subset of edges. For each e E E there is an associated real number fl(e). Furthermore, let 1 if e E E' f2(e): 0 if e E-E' ...
DT-MRI Fiber Tracking: A Shortest Paths Approach
Andrew Zalesky
2008-01-01
We derive a new fiber tracking algorithm for DT- MRI that parts with the locally 'greedy' paradigm intrinsic to conventional tracking algorithms. We demonstrate the ability to precisely reconstruct a diverse range of fiber trajectori es in authentic and computer-generated DT-MRI data, for which well- known conventional tracking algorithms are shown to fail. Our approach is to pose fiber tracking
Scalable Shortest Paths Browsing on Land Surface Songhua Xing
Shahabi, Cyrus
popularity of online Earth visualization tools and geo-realistic games and the availability of high, where N is the size of the terrain. With this method, the time and space requirements for an exhaustive leading to the growing popularity of online Earth visualization platforms (e.g., Google EarthTM) and geo
Modeling wildfire propagation with Delaunay triangulation and shortest path algorithms
Smith, J. MacGregor
) reported in excess of 459 thousand fires on 9.6 million hectares of land. The cost of fire extinction U.S. dollars were spent daily on fire extinction during 2000-2004; 108 firefighters lost their lives analytical models of fire behavior/propagation are required to assess potential risk to human lives, property
Dynamic Approximate AllPairs Shortest Paths in Undirected Graphs
Zwick, Uri
/#, such estimated distances are exact.) # School of Computer Science, Tel Aviv University, Tel Aviv 69978, Israel. E(mn) and it answers each distance query in O(1) worstcase time. The algorithm uses ? O(n 2 ) space. A running time weighted undirected graphs: 1. For any fixed # > 0, a decremental algorithm with an expected total running
Exact Path-Integral Solution of the Dirac-Coulomb Problem
NASA Astrophysics Data System (ADS)
Kayed, M. A.; Inomata, A.
1984-07-01
An exact path-integral solution of the Dirac equation with a Coulomb potential is found. The energy-dependent Green's function of the second-order Dirac-Coulomb equation, expressed as a polar-coordinate path integral, is reduced to the exactly solvable path integral for an isotropic harmonic oscillator by a coordinate transformation combined with a local time rescaling. The Green's function of the linear Dirac equation is evaluated with the help of the Biedenharn transformation. The energy spectrum for the bound states is also obtained.
On Dirac-Coulomb problem in (2+1) dimensional space-time and path integral quantization
Haouat, S. [L.P.Th, Departement de physique, Universite de Jijel, BP 98, Ouled Aissa, Jijel 18000 (Algeria); Chetouani, L. [Departement de Physique, Faculte de Sciences, Universite Mentouri, Route Ain El-Bey, Constantine 25000 (Algeria)
2012-06-15
The problem of Dirac particle interacting with Coulomb potential in (2+1) dimensions is formulated in the framework of super-symmetric path integrals where the spin degrees of freedom are described by odd Grassmannian variables. The relative propagator is expressed through Cartesian coordinates in a Hamiltonian form by the use of an adequate transformation. The passage to the polar coordinates permitted us to calculate the fixed energy Green's function and to extract bound states and associating wave functions.
On Dirac-Coulomb problem in (2+1) dimensional space-time and path integral quantization
NASA Astrophysics Data System (ADS)
Haouat, S.; Chetouani, L.
2012-06-01
The problem of Dirac particle interacting with Coulomb potential in (2+1) dimensions is formulated in the framework of super-symmetric path integrals where the spin degrees of freedom are described by odd Grassmannian variables. The relative propagator is expressed through Cartesian coordinates in a Hamiltonian form by the use of an adequate transformation. The passage to the polar coordinates permitted us to calculate the fixed energy Green's function and to extract bound states and associating wave functions.
An Efficient Graph Cut Algorithm for Computer Vision Problems
Chetan Arora; Subhashis Banerjee; Prem Kalra; S. N. Maheshwari
2010-01-01
\\u000a Graph cuts has emerged as a preferred method to solve a class of energy minimization problems in computer vision. It has been\\u000a shown that graph cut algorithms designed keeping the structure of vision based flow graphs in mind are more efficient than\\u000a known strongly polynomial time max-flow algorithms based on preflow push or shortest augmenting path paradigms [1]. We present
NASA Astrophysics Data System (ADS)
Castro, Alex Lcio; Koiller, Jair
2013-01-01
Andrei Andreyevich Markov proposed in 1889 the problem (solved by Dubins in 1957) of finding the twice continuously differentiable (arc length parameterized) curve with bounded curvature, of minimum length, connecting two unit vectors at two arbitrary points in the plane. In this note we consider the following variant, which we call the dynamic Markov-Dubins problem (dM-D): to find the time-optimal C 2 trajectory connecting two velocity vectors having possibly different norms. The control is given by a force whose norm is bounded. The acceleration may have a tangential component, and corners are allowed, provided the velocity vanishes there. We show that for almost all the two vectors boundary value conditions, the optimization problem has a smooth solution. We suggest some research directions for the dM-D problem on Riemannian manifolds, in particular we would like to know what happens if the underlying geodesic problem is completely integrable. Path planning in robotics and aviation should be the usual applications, and we suggest a pursuit problem in biolocomotion. Finally, we suggest a somewhat unexpected application to "dynamic imaging science". Short time processes (in medicine and biology, in environment sciences, geophysics, even social sciences?) can be thought as tangent vectors. The time needed to connect two processes via a dynamic Markov-Dubins problem provides a notion of distance. Statistical methods could then be employed for classification purposes using a training set.
Pebbles in Motion Polynomial Algorithms for Multi-Agent Path Planning Problems
Vetter, Thomas
) is a common problem in robotics and memory management. Pebbles in Motion is an implementation of a problem by Kornhauser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.2.1 Introductory Overview Arms and Handles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 4.2.3 Moving Pebbles
Searching in an unknown environment: an optimal randomized algorithm for the cow-path problem
Ming-Yang Kao; John H. Reif; Stephen R. Tate
1993-01-01
Searching for a goal is a central and extensively studied problem in computer science. Inclassical searching problems, the cost of a search function is simply the number of queries madeto an oracle that knows the position of the goal. In many robotics problems, as well as inproblems from other areas, we want to charge a cost proportional to the distance
Algorithms for Three Versions of the Shortest Common Superstring
Lonardi, Stefano
| + . . . + |sk| = n. Output: the shortest word s containing each si as a factor. Example: s1 = abaab, s2 = baba. Output: the shortest word s containing each si as a factor. Example: s1 = abaab, s2 = baba, s3 = aabbb, s. Output: the shortest word s containing each si as a factor. Example: s1 = abaab, s2 = baba, s3 = aabbb, s
Efficient Algorithms for Shortest Partial Seeds in Words
Lonardi, Stefano
Efficient Algorithms for Shortest Partial Seeds in Words Tomasz Kociumaka1 , Solon P. Pissis2. Wale Efficient Algorithms for Shortest Partial Seeds in Words 2/16 #12;Periodicity and quasiperiodicity. Radoszewski, W. Rytter, T. Wale Efficient Algorithms for Shortest Partial Seeds in Words 2/16 #12;Periodicity
ERIC Educational Resources Information Center
Brody, Gene H.; Kim, Sooyeon; Murry, Velma McBride; Brown, Anita C.
2004-01-01
A 4-wave longitudinal design was used to examine protective links from child competence to behavioral problems in first- (M=10.97 years) and second- (M=8.27 years) born rural African American children. At 1-year intervals, teachers assessed child behavioral problems, mothers reported their psychological functioning, and both mothers and children
Show me the (shortest) way to go home Foams, soap films and minimization
Cox, Simon
Simon Cox Show me the (shortest) way to go home Foams, soap films and minimization #12;The force two possible (non-trivial) soap film combinations that touch all edges: Wire Frames foams not be straight. Wire Frames foams@aber.ac.uk #12;Soap films solve the Steiner problem: Given n cities on a plain
Finding shortest and closest vectors in a lattice of Voronoi's first kind
Finding shortest and closest vectors in a lattice of Voronoi's first kind Robby McKilliam Alex;Lattices Lattices of Voronoi's first kind Graphs, cuts, and minimum cuts A series of relevant vectors What will show that the problem is relatively easy to solve for lattices of Voronoi's first kind. 8 / 46 #12;The
Information Spread of Emergency Events: Path Searching on Social Networks
Hu, Hongzhi; Wu, Tunan
2014-01-01
Emergency has attracted global attentions of government and the public, and it will easily trigger a series of serious social problems if it is not supervised effectively in the dissemination process. In the Internet world, people communicate with each other and form various virtual communities based on social networks, which lead to a complex and fast information spread pattern of emergency events. This paper collects Internet data based on data acquisition and topic detection technology, analyzes the process of information spread on social networks, describes the diffusions and impacts of that information from the perspective of random graph, and finally seeks the key paths through an improved IBF algorithm. Application cases have shown that this algorithm can search the shortest spread paths efficiently, which may help us to guide and control the information dissemination of emergency events on early warning. PMID:24600323
Paths to literacy and numeracy problems: evidence from two British birth cohorts
Richards, M; Power, C; Sacker, A
2012-01-01
Objective To test a life course model linking circumstances of origin to self-reported literacy and numeracy problems in midlife, and to investigate the effects in this model of changing social circumstances in two post-war cohorts. Methods Based on data from men and women in the British 1946 and 1958 birth cohorts, we used the relative index of inequality and logistical regression to test associations between fathers occupation, childhood cognition, educational attainment, own occupation in the 3rd decade, and a binary variable representing self-reported literacy and numeracy problems in the 4th decade. Results There was a lower frequency of literacy and numeracy problems in the 1958 cohort compared to the 1946 cohort. In both cohorts there were associations between fathers occupation and childhood cognition, educational attainment and own occupation, a pattern that was mirrored by the associations between childhood cognition, educational attainment and own occupation to adult literacy and numeracy problems. Positive associations between childhood cognition and educational attainment, and between educational attainment and own occupation, were stronger in the 1946 cohort than in the 1958 cohort. However, inverse associations between educational attainment and literacy and numeracy problems were stronger in the 1958 cohort, possibly reflecting the expansion of secondary education in the intervening years. Conclusions Literacy and numeracy problems have a robust structure of life course associations, although the changing pattern of these associations may reflect important social structural changes from the early post war years to the early 1960s in the UK. PMID:18718979
Path Model of the Processes Influencing Drinking-Related Problems among College Students.
ERIC Educational Resources Information Center
Fenzel, L. Mickey; Patel, Shreya
This study tested a causal model of the prediction of the rate of occurrence of social and academic problems that results from college students' drinking. The model posited two pathways, one examining self-worth perceptions and symptoms of depression as mediators and one examining binge-drinking frequency as a mediator. Predictors included:
Status Problem and Expectations of Competence: A Challenging Path for Teachers
ERIC Educational Resources Information Center
Pescarmona, Isabella
2015-01-01
Complex Instruction (CI) is a cooperative learning approach, which aims at improving the equal status interaction among students working in groups who may be at different academic and social levels. Based on an ethnographic research, the article examines how a group of Italian primary school teachers understand the status problem and how the
Mahajan, Meena
Longest Paths in Planar DAGs in Unambiguous Log-Space Nutan Limaye, Meena Mahajan, Prajakta,meena,prajakta}@imsc.res.in November 13, 2009 Abstract We present a transformation from longest paths to shortest paths in sub in the same class of graphs. As a corollary, we obtain our main result: Longest Paths in planar DAGs is in UL
Evading the sign problem in the mean-field approximation through Lefschetz-thimble path integral
NASA Astrophysics Data System (ADS)
Tanizaki, Yuya; Nishimura, Hiromichi; Kashiwa, Kouji
2015-05-01
The fermion sign problem appearing in the mean-field approximation is considered, and the systematic computational scheme of the free energy is devised by using the Lefschetz-thimble method. We show that the Lefschetz-thimble method respects the reflection symmetry, which makes physical quantities manifestly real at any order of approximations using complex saddle points. The formula is demonstrated through the Airy integral as an example, and its application to the Polyakov-loop effective model of dense QCD is discussed in detail.
From Parent to Child to Parent: Paths In and Out of Problem Behavior
Bradley, Robert H.; Corwyn, Robert
2014-01-01
This study used data from the NICHD Study of Early Child Care and Youth Development to examine relations between parenting, self-control and externalizing behavior from early childhood to mid-adolescence (N=956; 49.9% male). Results indicated that maternal sensitivity, parental harshness and productive activity are related to externalizing problems but that patterns of relations change from early childhood to middle childhood to adolescence, with evidence suggesting that externalizing behavior influences parenting more than the reverse from middle childhood onward. Self-control measured during early adolescence partially mediated relations between maternal sensitivity and adolescent-reported externalizing behavior. Parental monitoring during adolescence was also related to externalizing behavior at age 15. Monitoring partially mediated the relation between externalizing behavior in early adolescence and externalizing at age 15. PMID:23135289
NASA Astrophysics Data System (ADS)
Peng, Jinmin; Yan, He; Li, Taifu
2005-12-01
The focus of this study is path selection for manufacturing processing, such as finding the shortest processing path, in an application of such a printed circuit board in the electronic industry. This paper models this kind of processing path optimization problem by application of a GA algorithm. First, the related problem of math modeling is discussed, such as coding methods, selection of fitness functions, and choice of genetic operators such as a selection operator, crossover operator, reverse operator, mutation operator and related parameters. All of these are used to build a solving model. Then related factor of genetic optimization algorithm such as initial generation, fitness evaluation, computing steps and so on was designed. The results of simulation and comparisons with practical application show that GA is feasible and valid.
GRECS: Graph Encryption for Approximate Shortest Distance Queries
International Association for Cryptologic Research (IACR)
GRECS: Graph Encryption for Approximate Shortest Distance Queries Xianrui Meng1 , Seny Kamara2 Research 3 Department of Computer Science, Ben-Gurion University Abstract We propose graph encryption schemes that efficiently support approximate shortest distance queries on large-scale encrypted graphs
Finding the Minimum-Cost Path Without Cutting Corners
van Vliet, Lucas J.
, and Lucas J. van Vliet Quantitative Imaging Group, Delft University of Technology, The Netherlands L tracks are examples of string-like (network) structures, whose minimum-cost path is cutting through suggests that the path with the shortest arrival time will in general be longer than the Euclidean distance
Fast marching methods for the continuous traveling salesman problem
Andrews, J.; Sethian, J.A.
2008-12-01
We consider a problem in which we are given a domain, a cost function which depends on position at each point in the domain, and a subset of points ('cities') in the domain. The goal is to determine the cheapest closed path that visits each city in the domain once. This can be thought of as a version of the Traveling Salesman Problem, in which an underlying known metric determines the cost of moving through each point of the domain, but in which the actual shortest path between cities is unknown at the outset. We describe algorithms for both a heuristic and an optimal solution to this problem. The order of the heuristic algorithm is at worst case M * N logN, where M is the number of cities, and N the size of the computational mesh used to approximate the solutions to the shortest paths problems. The average runtime of the heuristic algorithm is linear in the number of cities and O(N log N) in the size N of the mesh.
Optimal paths for a car that goes both forwards and backwards
J. A. Reeds; L. A. Shepp
1990-01-01
The path taken by a car with a given minimum turning radius has a lower bound on its radius of curvature at each point, but the path has cusps if the car shifts into or out of reverse gear. What is the shortest such path a car can travel between two points if its starting and ending directions are specified?
Parallel Shortest Lattice Vector Enumeration on Graphics Cards
International Association for Cryptologic Research (IACR)
Parallel Shortest Lattice Vector Enumeration on Graphics Cards Jens Hermans 1 , Michael Schneider2/SCD-COSIC and IBBT {Jens.Hermans,Frederik.Vercauteren,Bart.Preneel}@esat.kuleuven.be 2 Technische Universit
A new efficient optimal path planner for mobile robot based on Invasive Weed Optimization algorithm
NASA Astrophysics Data System (ADS)
Mohanty, Prases K.; Parhi, Dayal R.
2014-12-01
Planning of the shortest/optimal route is essential for efficient operation of autonomous mobile robot or vehicle. In this paper Invasive Weed Optimization (IWO), a new meta-heuristic algorithm, has been implemented for solving the path planning problem of mobile robot in partially or totally unknown environments. This meta-heuristic optimization is based on the colonizing property of weeds. First we have framed an objective function that satisfied the conditions of obstacle avoidance and target seeking behavior of robot in partially or completely unknown environments. Depending upon the value of objective function of each weed in colony, the robot avoids obstacles and proceeds towards destination. The optimal trajectory is generated with this navigational algorithm when robot reaches its destination. The effectiveness, feasibility, and robustness of the proposed algorithm has been demonstrated through series of simulation and experimental results. Finally, it has been found that the developed path planning algorithm can be effectively applied to any kinds of complex situation.
Path finding by tube morphogenesis in an amoeboid organism.
Nakagaki, T; Yamada, H; Tth, A
2001-08-30
We have studied how the plasmodium of Physarum polycephalum, a large amoeboid cell, is able to track the shortest path between two selected points in a labyrinth. When nutrients are supplied at these points to a sheet-like plasmodium extended fully in a maze, the organism forms a single tube which connects the two sites via the shortest route. During the path finding, plasmodial parts in dead ends of the maze shrink and finally the tube with the minimum-length is selected from the existing possibilities. A simple cellular mechanism based on interacting cellular rhythms may describe the experimental observations. PMID:11527578
Computing the Length of the Shortest Telomere in the Nucleus
NASA Astrophysics Data System (ADS)
Dao Duc, K.; Holcman, D.
2013-11-01
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.
Approximating geometric bottleneck shortest Prosenjit Bose
Zeh, Norbert
, and all of whose edges have length at most |pq|. A preliminary version of this paper appeared(L) , then (L) (p, q) = .) In this paper, we will consider the following three query problems. 1 and an airplane that can fly a distance of L kilometres without 2 #12;refueling, and have to compute
MINIMUM WEIGHT PATHS TIMEDEPENDENT NETWORKS
Orda, Ariel
MINIMUM WEIGHT PATHS in TIMEDEPENDENT NETWORKS Ariel Orda Raphael Rom Department of Electrical) ABSTRACT We investigate the minimum weight path problem in networks whose link weights and link delays are both functions of time. We demonstrate that in general there exist cases in which no finite path
Tunable path centrality: Quantifying the importance of paths in networks
NASA Astrophysics Data System (ADS)
Pu, Cun-Lai; Cui, Wei; Yang, Jian
2014-07-01
Centrality is a fundamental measure in network analysis. Specifically, centrality of a path describes the importance of the path with respect to the remaining part of the network. In this paper, we propose a tunable path centrality (TPC) measure, which quantifies the centrality of a path by integrating the path degree (PD) (number of neighbors of the path) and the path bridge (PB) (number of bridges in the path) with a control parameter ?. Considering the complexity of large-scale and dynamical topologies of many real-world networks, both PD and PB are computed with only the local topological structure of a path. We demonstrate the distribution of the three path centralities (TPC, PD and PB) in computer-generated networks and real-world networks. Furthermore, we apply the three path centralities to the network fragility problem, and exploit the distribution of the optimal control parameter ? through simulation and analysis. Finally, the simulation results show that generally TPC is more efficient than PD and PB in the network fragility problem. These path centralities are also applicable in many other network problems including spread, control, prediction and so on.
Solving nonlinear multicommodity flow problems with the analytic center cutting plane method
Goffin, J.L.; Gondzio, J.; Sarkissian, R.; Vial, J.P.
1994-12-31
A talk deals with nonlinear multicommodity flow problems with convex costs. A decomposition method is proposed to solve them. The approach applies a potential reduction algorithm to (approximately) solve the master problem and a column generation technique defining a sequence of primal linear programming problems. Each subproblem consists in finding a minimum cost flow between an origin and a destination node on an uncapacited network. It is thus formulated as a shortest path problem and it is solved with the Dijkstra`s d-heap algorithm. An experimental implementation is described that takes full advantage of the supersparsity of the network in the linear algebra operations. Computational results show high efficiency of the approach on (known from the literature) nondifferentiable problems, real-life large scale France Telecom problem and other large scale randomly generated problems (sized up to 1000 arcs and 4000 commodities).
ERIC Educational Resources Information Center
Wilson, Helen W.; Widom, Cathy Spatz
2010-01-01
Behaviors beginning in childhood or adolescence may mediate the relationship between childhood maltreatment and involvement in prostitution. This paper examines 5 potential mediators: early sexual initiation, running away, juvenile crime, school problems, and early drug use. Using a prospective cohort design, abused and neglected children (ages
NASA Astrophysics Data System (ADS)
Law, Richard; Waters, Dave; Morgan, Sven; Stahr, Don; Francsis, Matthew; Ashley, Kyle; Kronenberg, Andreas; Thomas, Jay; Mazza, Sarah; Heaverlo, Nicholas
2013-04-01
The quartz c-axis fabric opening-angle thermometer proposed by Kruhl (1998) offers a potential analytical technique for estimating deformation temperatures in rocks deformed by crystal plastic flow. However, in addition to deformation temperature, opening-angle is also sensitive to other variables such as strain rate, degree of hydrolytic weakening, and 3D strain type. Unless the influence of these individual variables can be quantified, use of fabric opening-angle as a deformation thermometer remains problematic and controversial. Over the last decade close correlations between: a) deformation temperatures indicated by fabric opening-angles and, b) temperatures of metamorphism indicated by trace element and mineral phase equilibria analyses, have been reported from a range of different tectonic settings, thereby arguably giving support to the use of opening-angles as a deformation thermometer. However, it needs to be demonstrated that the similar temperatures estimated by the different methods are related to the same geologic event, and therefore occupy at least a similar position on the PTt path - something that is in practice difficult to achieve for an individual rock sample. In cases where temperatures indicated by opening angles and mineral assemblages are markedly different, these differences could, for example, be explained by penetrative deformation and mineral growth/diffusion occurring at different times. Alternatively, when apparent deformation temperatures based on quartz fabrics are significantly greater than temperatures indicated by synchronous metamorphic mineral assemblages, this might be due to extreme hydrolytic weakening of quartz. We illustrate this talk on the pros and cons of using fabric opening-angles as a deformation thermometer with examples from: a) Aureoles of forcibly emplaced plutons in the White-Inyo Range of eastern California where crystal-plastic deformation and recrystallization was short-lived and synchronous with contact metamorphism. b) Footwall to the South Tibetan Detachment in the Mount Everest area where deformation is demonstrably related to the exhumation stage of a petrologically well-constrained PT path. c) Hanging wall to the Main Central Thrust in the Sutlej Valley of NW India where deformation temperatures inferred from fabric opening angles are closely similar to temperatures of metamorphism indicated by garnet-biotite and oxygen isotope-based thermometry. d) Moine, Ben Hope and Naver thrust sheets of NW Scotland where structurally upwards-increasing deformation temperatures are compared with temperatures indicated by garnet-biotite thermometry. e) Mylonitic quartzites in footwall to Moine thrust at the Stack of Glencoul where hydrolytic weakening may have played an important role in deformation/recrystallization and associated fabric development. f) Thrust sheets in the Appalachians of Vermont that display a complex PTt history due to thrust sheet loading. Kruhl, J.H. 1998. Reply: Prism- and basal-plane parallel subgrain boundaries in quartz: a microstructural geothermobarometer. Journal of Metamorphic Geology, 16, 142-146.
Pair correlations in classical crystals: The shortest-graph method
NASA Astrophysics Data System (ADS)
Yurchenko, Stanislav O.; Kryuchkov, Nikita P.; Ivlev, Alexei V.
2015-07-01
The shortest-graph method is applied to calculate the pair correlation functions of crystals. The method is based on the representation of individual correlation peaks by the Gaussian functions, summed along the shortest graph connecting the two given points. The analytical expressions for the Gaussian parameters are derived for two- and three-dimensional crystals. The obtained results are compared with the pair correlation functions deduced from the molecular dynamics simulations of Yukawa, inverse-power law, Weeks-Chandler-Andersen, and Lennard-Jones crystals. By calculating the Helmholtz free energy, it is shown that the method is particularly accurate for soft interparticle interactions and for low temperatures, i.e., when the anharmonicity effects are insignificant. The accuracy of the method is further demonstrated by deriving the solid-solid transition line for Yukawa crystals, and the compressibility for inverse-power law crystals.
Pair correlations in classical crystals: The shortest-graph method.
Yurchenko, Stanislav O; Kryuchkov, Nikita P; Ivlev, Alexei V
2015-07-21
The shortest-graph method is applied to calculate the pair correlation functions of crystals. The method is based on the representation of individual correlation peaks by the Gaussian functions, summed along the shortest graph connecting the two given points. The analytical expressions for the Gaussian parameters are derived for two- and three-dimensional crystals. The obtained results are compared with the pair correlation functions deduced from the molecular dynamics simulations of Yukawa, inverse-power law, Weeks-Chandler-Andersen, and Lennard-Jones crystals. By calculating the Helmholtz free energy, it is shown that the method is particularly accurate for soft interparticle interactions and for low temperatures, i.e., when the anharmonicity effects are insignificant. The accuracy of the method is further demonstrated by deriving the solid-solid transition line for Yukawa crystals, and the compressibility for inverse-power law crystals. PMID:26203035
Mobile transporter path planning
NASA Technical Reports Server (NTRS)
Baffes, Paul; Wang, Lui
1990-01-01
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.
Inter-Domain Redundancy Path Computation Methods Based on PCE
NASA Astrophysics Data System (ADS)
Hayashi, Rie; Oki, Eiji; Shiomoto, Kohei
This paper evaluates three inter-domain redundancy path computation methods based on PCE (Path Computation Element). Some inter-domain paths carry traffic that must be assured of high quality and high reliability transfer such as telephony over IP and premium virtual private networks (VPNs). It is, therefore, important to set inter-domain redundancy paths, i. e. primary and secondary paths. The first scheme utilizes an existing protocol and the basic PCE implementation. It does not need any extension or modification. In the second scheme, PCEs make a virtual shortest path tree (VSPT) considering the candidates of primary paths that have corresponding secondary paths. The goal is to reduce blocking probability; corresponding secondary paths may be found more often after a primary path is decided; no protocol extension is necessary. In the third scheme, PCEs make a VSPT considering all candidates of primary and secondary paths. Blocking probability is further decreased since all possible candidates are located, and the sum of primary and secondary path cost is reduced by choosing the pair with minimum cost among all path pairs. Numerical evaluations show that the second and third schemes offer only a few percent reduction in blocking probability and path pair total cost, while the overheads imposed by protocol revision and increase of the amount of calculation and information to be exchanged are large. This suggests that the first scheme, the most basic and simple one, is the best choice.
Finding Shortest Paths on Surfaces by Fast Global Approximation and Precise Local Refinement
Kimmel, Ron
. The 3D curve shortening flow is transformed into an equivalent 2D one that is implemented using an arbi trary initial curve ending at two given surface points via geodesic curvature shortening flow numerical solutions of differential equations by numerical integration [2], and are com putationally
A Parametric Copula Approach for Modelling Shortest-Path Trees in Telecommunication Networks
Schmidt, Volker
estimation in telecommunication networks, it is desir- able to gain knowledge about distributional properties derive a joint bivariate distribution for the lengths of these branches by means of copula functions, i copula, parametric marginal distribution, stochastic ge- ometry, network planning, Palm calculus
A Dynamic Programming Approach to Identifying the Shortest Path in Virtual Learning Environments
ERIC Educational Resources Information Center
Fazlollahtabar, Hamed
2008-01-01
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
Shortest Path versus Multi-Hub Routing in Networks with Uncertain Demand
Shepherd, Bruce
-to- point peak demands. Second, design the network to support all hose matrices (all matrices not exceeding patterns is available. We introduce a capped hose model to explore a range of traffic scenarios, which includes the above two as special cases. It is known that optimal network designs for the hose model
Collier, Martin
applications such as e- commerce, multimedia, distributed data analysis and advanced collaborative environments by the Internet, a route from source to destination for such a flow may not be available which is comprised routing algorithms, the most reliable shortest path (MR-S) algorithm and the shortest most reliable
NSDL National Science Digital Library
Perry Samson
This website catalogs all the tornado paths in the United States since 1950. The tornado path data is overlaid onto a Google Maps base for easy browsing and manipulation of the map view. Clicking on individual tornados provides the user with information such as its Fujita rating, the amount of damage caused by the tornado, the size of the path that the tornado made, and the length of time the tornado was on the ground.
Disjoint paths in tournaments Maria Chudnovsky1
Scott, Alexander Alexander
Disjoint paths in tournaments Maria Chudnovsky1 Columbia University, New York, NY 10027, USA Alex) (1 i k) of a digraph G, how can we test whether there exist k vertex-disjoint directed paths from G. The k vertex-disjoint paths problem is to determine whether there exist vertex-disjoint paths P1
Pedestrian traffic: on the quickest path
NASA Astrophysics Data System (ADS)
Kretz, Tobias
2009-03-01
When a large group of pedestrians moves around a corner, most pedestrians do not follow the shortest path, which is to stay as close as possible to the inner wall, but try to minimize the travel time. For this they accept to move on a longer path with some distance to the corner, to avoid large densities and by this succeed in maintaining a comparatively high speed. In many models of pedestrian dynamics the basic rule of motion is often either 'move as far as possible toward the destination' orreformulated'of all coordinates accessible in this time step move to the one with the smallest distance to the destination'. On top of this rule modifications are placed to make the motion more realistic. These modifications usually focus on local behavior and neglect long-ranged effects. Compared to real pedestrians this leads to agents in a simulation valuing the shortest path a lot better than the quickest. So, in a situation such as the movement of a large crowd around a corner, one needs an additional element in a model of pedestrian dynamics that makes the agents deviate from the rule of the shortest path. In this work it is shown how this can be achieved by using a flood fill dynamic potential field method, where during the filling process the value of a field cell is not increased by 1, but by a larger value, if it is occupied by an agent. This idea may be an obvious one: however, the tricky partand therefore in a strict sense the contribution of this workis (a) to minimize unrealistic artifacts, as naive flood fill metrics deviate considerably from the Euclidean metric and in this respect yield large errors, (b) do this with limited computational effort and (c) keep agents' movement at very low densities unaltered.
Theraulaz, Guy
2006-01-01
the foraging behavior of ants moving in an artificial network of tunnels in which several interconnected paths and those of the experiments, showing that simple behavioral rules can lead ants to find the shortest paths; Trail; Collective behavior 1. Introduction In a lot of ant species foragers do not exploit food sources
Solving Hard Lattice Problems and the Security of Lattice-Based Cryptosystems
International Association for Cryptologic Research (IACR)
Solving Hard Lattice Problems and the Security of Lattice-Based Cryptosystems Thijs Laarhoven Joop: Solving the Approximate Shortest Vector Problem, Section 5: Solving the Exact Shortest Vector Problem techniques for solving these problems are the so-called lattice basis Department of Mathematics and Computer
Challenging of path planning algorithms for autonomous robot in known environment
NASA Astrophysics Data System (ADS)
Farah, R. N.; Irwan, N.; Zuraida, Raja Lailatul; Shaharum, Umairah; Hanafi@Omar, Hafiz Mohd
2014-06-01
Most of the mobile robot path planning is estimated to reach its predetermined aim through the shortest path and avoiding the obstacles. This paper is a survey on path planning algorithms of various current research and existing system of Unmanned Ground Vehicles (UGV) where their challenging issues to be intelligent autonomous robot. The focuses are some short reviews on individual papers for UGV in the known environment. Methods and algorithms in path planning for the autonomous robot had been discussed. From the reviews, we obtained that the algorithms proposed are appropriate for some cases such as single or multiple obstacles, static or movement obstacle and optimal shortest path. This paper also describes some pros and cons for every reviewed paper toward algorithms improvement for further work.
Parsimonious path openings and closings.
Morard, Vincent; Dokladal, Petr; Decenciere, Etienne
2014-04-01
Path openings and closings are morphological tools used to preserve long, thin, and tortuous structures in gray level images. They explore all paths from a defined class, and filter them with a length criterion. However, most paths are redundant, making the process generally slow. Parsimonious path openings and closings are introduced in this paper to solve this problem. These operators only consider a subset of the paths considered by classical path openings, thus achieving a substantial speed-up, while obtaining similar results. In addition, a recently introduced 1D opening algorithm is applied along each selected path. Its complexity is linear with respect to the number of pixels, independent of the size of the opening. Furthermore, it is fast for any input data accuracy (integer or floating point) and works in stream. Parsimonious path openings are also extended to incomplete paths, i.e., paths containing gaps. Noise-corrupted paths can thus be processed with the same approach and complexity. These parsimonious operators achieve a several orders of magnitude speed-up. Examples are shown for incomplete path openings, where computing times are brought from minutes to tens of milliseconds, while obtaining similar results. PMID:24569442
Dispersion of nonlinear group velocity determines shortest envelope solitons
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
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.
Complexity analysis of pipeline mapping problems in distributed heterogeneous networks
Lin, Ying; Wu, Qishi; Zhu, Mengxia; Rao, Nageswara S
2009-04-01
Largescale scientific applications require using various system resources to execute complex computing pipelines in distributed networks to support collaborative research. System resources are typically shared in the Internet or over dedicated connections based on their location, availability, capability, and capacity. Optimizing the network performance of computing pipelines in such distributed environments is critical to the success of these applications. We consider two types of largescale distributed applications: (1) interactive applications where a single dataset is sequentially processed along a pipeline; and (2) streaming applications where a series of datasets continuously flow through a pipeline. The computing pipelines of these applications consist of a number of modules executed in a linear order in network environments with heterogeneous resources under different constraints. Our goal is to find an efficient mapping scheme that allocates the modules of a pipeline to network nodes for minimum endtoend delay or maximum frame rate. We formulate the pipeline mappings in distributed environments as optimization problems and categorize them into six classes with different optimization goals and mapping constraints: (1) Minimum Endtoend Delay with No Node Reuse (MEDNNR), (2) Minimum Endtoend Delay with Contiguous Node Reuse (MEDCNR), (3) Minimum Endtoend Delay with Arbitrary Node Reuse (MEDANR), (4) Maximum Frame Rate with No Node Reuse or Share (MFRNNRS), (5) Maximum Frame Rate with Contiguous Node Reuse and Share (MFRCNRS), and (6) Maximum Frame Rate with Arbitrary Node Reuse and Share (MFRANRS). Here, 'contiguous node reuse' means that multiple contiguous modules along the pipeline may run on the same node and 'arbitrary node reuse' imposes no restriction on node reuse. Note that in interactive applications, a node can be reused but its resource is not shared. We prove that MEDANR is polynomially solvable and the rest are NP-complete. MEDANR, where either contiguous or noncontiguous modules in the pipeline can be mapped onto the same node, is essentially the Maximum n-hop Shortest Path problem, and can be solved using a dynamic programming method. In MEDNNR and MFRNNRS, any network node can be used only once, which requires selecting the same number of nodes for onetoone onto mapping. We show its NP-completeness by reducing from the Hamiltonian Path problem. Node reuse is allowed in MEDCNR, MFRCNRS and MFRANRS, which are similar to the Maximum n-hop Shortest Path problem that considers resource sharing. We prove their NP-completeness by reducing from the Disjoint-Connecting-Path Problem and Widest path with the Linear Capacity Constraints problem, respectively.
Visualization of Ant Pheromone Based Path Following
Sutherland, Benjamin T.
2010-07-14
This thesis develops a simulation and visualization of a path finding algorithm based on ant pheromone paths created in 3D space. The simulation is useful as a demonstration of a heuristic approach to NP-complete problems ...
Model Checking Almost All Paths Can Be Less Expensive than Checking All Paths
Varacca, Daniele - Laboratoire Preuves, Programmes et Systèmes, Université Paris 7
Model Checking Almost All Paths Can Be Less Expensive than Checking All Paths Matthias Schmalz 1 model checking problems: checking whether a linear-time formula is satised by all paths (which we call universal model checking) and checking whether a formula is satised by almost all paths (which we call fair
Bicriteria network design problems
Marathe, M.V.; Ravi, R.; Sundaram, R.; Ravi, S.S.; Rosenkrantz, D.J.; Hunt, H.B. III
1994-12-31
We study several bicriteria network design problems phrased as follows: given an undirected graph and two minimization objectives with a budget specified on one objective, find a subgraph satisfying certain connectivity requirements that minimizes the second objective subject to the budget on the first. Define an ({alpha}, {beta})-approximation algorithm as a polynomial-time algorithm that produces a solution in which the first objective value is at most {alpha} times the budget, and the second objective value is at most {alpha} times the minimum cost of a network obeying the budget oil the first objective. We, present the first approximation algorithms for bicriteria problems obtained by combining classical minimization objectives such as the total edge cost of the network, the diameter of the network and a weighted generalization of the maximum degree of any node in the network. We first develop some formalism related to bicriteria problems that leads to a clean way to state bicriteria approximation results. Secondly, when the two objectives are similar but only differ based on the cost function under which they are computed we present a general parametric search technique that yields approximation algorithms by reducing the problem to one of minimizing a single objective of the same type. Thirdly, we present an O(log n, log n)-approximation algorithm for finding a diameter-constrained minimum cost spanning tree of an undirected graph on n nodes generalizing the notion of shallow, light trees and light approximate shortest-path trees that have been studied before. Finally, for the class of treewidth-bounded graphs, we provide pseudopolynomial-time algorithms for a number of bicriteria problems using dynamic programming. These pseudopolynomial-time algorithms can be converted to fully polynomial-time approximation schemes using a scaling technique.
Path Integral Methods Nancy Makri
Makri, Nancy
attractions can be summarized as follows: the path integral formulation offers an ideal way of obtaining approach to many-body problems; and it leads to powerful influence functional meth- ods for studying this expression with the same weight. In the classical limit 0 small variations of a path generally result
Pascal Frossard; Juan Carlos de Martin; M. Reha Civanlar
Today's packet networks including the Internet offer an intrinsic diversity for media distribution in terms of available network paths and servers or information sources. Novel communication infrastructures such as ad hoc or wireless mesh networks use network diversity to extend their reach at low cost. Diversity can bring interesting benefits in supporting resource greedy applications such as media streaming services,
Survivable paths in multilayer networks
Parandehgheibi, Marzieh
We consider the problem of protection in multilayer networks. In single-layer networks, a pair of disjoint paths can be used to provide protection for a source-destination pair. However, this approach cannot be directly ...
Survivable paths in multilayer networks
Parandehgheibi, Marzieh
2012-01-01
We consider the problem of protection in multilayer networks. In single-layer net- works, a pair of disjoint paths can be used to provide protection for a source-destination pair. However, this approach cannot be directly ...
Pokemon Cards and the Shortest Common Superstring Mark Stamp Austin E Stamp
Stamp, Mark
Pokemon Cards and the Shortest Common Superstring Mark Stamp Austin E Stamp June 12, 2003 Abstract Evidence is presented that certain sequences of Pokemon cards are determined by selecting consecutive (SCS), i.e., the shortest string that contains each of the Pokemon card sequences as a consecutive
A Genetic Algorithm for Searching Shortest Lattice Vector of SVP Challenge
International Association for Cryptologic Research (IACR)
A Genetic Algorithm for Searching Shortest Lattice Vector of SVP Challenge Dan Ding1 , Guizhen Zhu2, China P. R. Abstract. In this paper, we propose a genetic algorithm for solving the shortest vector pruning. The experimental results show that the genetic algorithm runs rather good on the SVP challenge
Path planning using a tangent graph for mobile robots among polygonal and curved obstacles
Liu, Yun-Hui; Arimoto, Suguru (Univ. of Tokyo (Japan))
1992-08-01
This article proposes a tangent graph for path planning of mobile robots among obstacles with a general boundary. The tangent graph is defined on the basis of the locally shortest path. It has the same data structure as the visibility graph, but its nodes represent common tangent points on obstacle boundaries, and its edges correspond to collision-free common tangents between the boundaries and convex boundary segments between the tangent points. The tangent graph requires O(K[sup 2]) memory, where K denotes the total number of convex segments of the obstacle boundaries. The tangent graph includes all locally shortest paths and is capable of coping with path planning not only among polygonal obstacles but also among curved obstacles.
Minimum Wheel-Rotation Paths for Differential-Drive Mobile Hamidreza Chitsaz
LaValle, Steven M.
Minimum Wheel-Rotation Paths for Differential-Drive Mobile Robots Hamidreza Chitsaz , Steven M. La. To obtain a well-defined notion of shortest, the total amount of wheel rotation is optimized. Using-Shepp car is equal to minimum wheel-rotation for the differential drive, and minimum time curves
An Explicit Characterization of Minimum Wheel-Rotation Paths for Differential-Drives
LaValle, Steven M.
An Explicit Characterization of Minimum Wheel-Rotation Paths for Differential-Drives Hamidreza. A well-defined notion of shortest is obtained by optimizing the total amount of wheel rotation. This paper extends our previous characterization of the minimum wheel-rotation trajectories that are maximal
Sullivan, Blair D; Seymour, Dr. Paul Douglas
2010-01-01
Say a digraph is k-free if it has no directed cycles of length at most k, for k {element_of} Z{sup +}. Thomasse conjectured that the number of induced 3-vertex directed paths in a simple 2-free digraph on n vertices is at most (n-1)n(n+1)/15. We present an unpublished result of Bondy proving there are at most 2n{sup 3}/25 such paths, and prove that for the class of circular interval digraphs, an upper bound of n{sup 3}/16 holds. We also study the problem of bounding the number of (non-induced) 4-vertex paths in 3-free digraphs. We show an upper bound of 4n{sup 4}/75 using Bondy's result for Thomasse's conjecture.
Minimum-Risk Path Finding by an Adaptive Amoebal Network
NASA Astrophysics Data System (ADS)
Nakagaki, Toshiyuki; Iima, Makoto; Ueda, Tetsuo; Nishiura, Yasumasa; Saigusa, Tetsu; Tero, Atsushi; Kobayashi, Ryo; Showalter, Kenneth
2007-08-01
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.
Preferential Path Profiling: Compactly Numbering Interesting Paths
Chilimbi, Trishul
Preferential Path Profiling: Compactly Numbering Interesting Paths Kapil Vaswani Indian Institute@microsoft.com Trishul M. Chilimbi Microsoft Research trishulc@microsoft.com Abstract Path profiles provide a more preferential path profiling (PPP), that reduces the overhead of path profiling. PPP leverages the observation
An InternationalJournal Available online at www.sciencedirectcom computers&
Fan, Yueyue
in networks with correlated link service levels. The motivation for this research is that natural disasters of multiple criteria [1-4]. The shortest path problem and k-shortest paths problems are the most intensively
NSDL National Science Digital Library
Cynthia Ann Radle (McCullough High School REV)
1995-06-30
Students follow several pathways using anatomical directions on a simulated "body" produced from a copy of a school building's fire evacuation plan. The main hallways are designated as major blood vessels and the various areas of the school, the head, chest, abdomen, etc. Students complete several pathways using anatomical terms as directions. For example, one of my paths begins, "Ex- ot-, ad- superior, ecto- derm-, peri-frontal, circum- rhino-, " which loosely means, exit the ear, go to the superior region, outside the skin, around the frontal region, around the nose. At the end of each path I leave a clue that lets me know the students actually made it. The combined clues form a sentence.
The shortest modulation period Blazhko RR Lyrae star: SS Cnc
J. Jurcsik; B. Szeidl; . Sdor; I. Dkny; Zs. Hurta; K. Posztobnyi; K. Vida; M. Vradi; A. Szing
2006-03-20
Extended BV(RI)c CCD observations of SS Cnc, a short period RRab star are presented. Nearly 1400 data points in each band have been obtained spanning over 79 days during the spring of 2005. The star exhibits light curve modulation, the so called Blazhko effect with small amplitude (B maximum brightness varies 0.1 mag) and with the shortest modulation period (5.309 d) ever observed. In the Fourier spectrum of the V light curve the pulsation frequency components are detected up to the 24th harmonic order, and modulation side lobe frequencies with significantly asymmetric amplitudes are seen up to the 15th and 9th orders for the lower and higher frequency components, respectively. Detailed comparison of the modulation behavior of SS Cnc and RR Gem, the two recently discovered small amplitude, short modulation period Blazhko stars is presented. The modulation frequency (f_m) appears in the Fourier spectrum of both stars with similar amplitude. We also demonstrate that the modulation frequencies have basically different properties as the pulsation and modulation side lobe frequencies have, indicating that the physics behind these frequency components are not the same. The discovery of small amplitude modulations of RRab stars cautions that the large photometric surveys (MACHO, OGLE) may seriously underestimate the number of modulated RR Lyrae stars.
Identification of Biochemical Network Modules Based on Shortest Retroactive Distances
Sridharan, Gautham Vivek; Hassoun, Soha; Lee, Kyongbum
2011-01-01
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
Path Integrals for Photonic Crystals
Dimant, Yair
2009-01-01
We develop a path integrals approach for analyzing stationary light propagation appropriate for photonic crystals. The hermitian form of the stationary Maxwell equations is transformed into a quantum mechanical problem of a spin 1 particle with spin-orbit coupling and position dependent mass. After appropriate ordering several path integral representations of a solution are constructed. One leaves the propagation of polarization degrees of freedom in an operator form integrated over paths in coordinate space. The use of spin 1 coherent states allows to represent this part as a path integral over such states. Finally a path integral in transversal momentum space with explicit transversality enforced at every time slice is also given. As an example the geometrical optics limit is discussed and the ray equation is recovered together with the Rytov rotation of the polarization vector.
Constrained motion control on a hemispherical surface: path planning.
Berman, Sigal; Liebermann, Dario G; McIntyre, Joseph
2014-03-01
Surface-constrained motion, i.e., motion constraint by a rigid surface, is commonly found in daily activities. The current work investigates the choice of hand paths constrained to a concave hemispherical surface. To gain insight regarding paths and their relationship with task dynamics, we simulated various control policies. The simulations demonstrated that following a geodesic path (the shortest path between 2 points on a sphere) is advantageous not only in terms of path length but also in terms of motor planning and sensitivity to motor command errors. These stem from the fact that the applied forces lie in a single plane (that of the geodesic path). To test whether human subjects indeed follow the geodesic, and to see how such motion compares to other paths, we recorded movements in a virtual haptic-visual environment from 11 healthy subjects. The task comprised point-to-point motion between targets at two elevations (30 and 60). Three typical choices of paths were observed from a frontal plane projection of the paths: circular arcs, straight lines, and arcs close to the geodesic path for each elevation. Based on the measured hand paths, we applied k-means blind separation to divide the subjects into three groups and compared performance indicators. The analysis confirmed that subjects who followed paths closest to the geodesic produced faster and smoother movements compared with the others. The "better" performance reflects the dynamical advantages of following the geodesic path and may also reflect invariant features of control policies used to produce such a surface-constrained motion. PMID:24259548
Time optimal paths for high speed maneuvering
Reister, D.B.; Lenhart, S.M.
1993-01-01
Recent theoretical results have completely solved the problem of determining the minimum length path for a vehicle with a minimum turning radius moving from an initial configuration to a final configuration. Time optimal paths for a constant speed vehicle are a subset of the minimum length paths. This paper uses the Pontryagin maximum principle to find time optimal paths for a constant speed vehicle. The time optimal paths consist of sequences of axes of circles and straight lines. The maximum principle introduces concepts (dual variables, bang-bang solutions, singular solutions, and transversality conditions) that provide important insight into the nature of the time optimal paths. We explore the properties of the optimal paths and present some experimental results for a mobile robot following an optimal path.
Searching Paths of Constant Bandwidth Bernd Borchert and Klaus Reinhardt
Borchert, Bernd
Searching Paths of Constant Bandwidth Bernd Borchert and Klaus Reinhardt Universitat T. As a generalization of paths, the notion of paths of band- width w is introduced. We show that, for constant w 1, the corre- sponding search problem for such a path of length k in a given graph is NP-complete and fixed
Road Network Reconstruction for Organizing Paths Daniel Chen
Sun, Jian
Road Network Reconstruction for Organizing Paths Daniel Chen Leonidas J. Guibas John Hershberger Jian Sun Abstract We consider the problem of reconstructing a road net- work from a collection of path to allow efficient path sim- ilarity queries against new query paths on the same road network
Road Network Reconstruction for Organizing Paths Daniel Chen
Guibas, Leonidas J.
Road Network Reconstruction for Organizing Paths Daniel Chen Leonidas J. Guibas John Hershberger Jian Sun Abstract We consider the problem of reconstructing a road net- work from a collection of path efficient path similarity queries against new query paths on the same road network. This is a timely prob
A hybrid genetic algorithm for the weight setting problem in OSPF\\/ISIS routing
Luciana S. Buriol; Mauricio G. C. Resende; Celso C. Ribeiro; Mikkel Thorup
2005-01-01
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
21. Solve the initial value problem y ~ y' 2y : 0,y(0) = or, y'(0) = 2. .... coef?cients, thereby resolving a question that had been open since the sixteenth century His reatest ..... Equation (9) is known as Euler's formula and is an extremely important ..... Plot the nonhomogeneous term and the solution as functions of time.
Path Planner With Vision Capability
NASA Astrophysics Data System (ADS)
Distante, Arcangelo; Attolico, Giovanni; Radicci, Maria G.; Stella, Ettore
1990-03-01
In this paper we are going to describe an ongoing research project intended to integrate a full vision system in a flexible robot programming environment. The use of the vision system sensors, allows the robot to derive a description of the work cell. This description is used for the collision avoidance problem of robot manipulators. The work cell in assembly context can include moving objects. Without any previous knowledge of the work space, the vision system thus immediately determines the work cell map in its entirely. Successively this map is used as input for the path planner process to find the collision-free path. During the assembly robot operation, the vision system is activated to reflect any changes in the robot environment. In this way the path planner works recursively, updating the collision free path until the goal is reached.
Analog and digital FPGA implementation of BRIN for optimization problems.
Ng, H S; Lam, K P
2003-01-01
The binary relation inference network (BRIN) shows promise in obtaining the global optimal solution for optimization problem, which is time independent of the problem size. However, the realization of this method is dependent on the implementation platforms. We studied analog and digital FPGA implementation platforms. Analog implementation of BRIN for two different directed graph problems is studied. As transitive closure problems can transform to a special case of shortest path problems or a special case of maximum spanning tree problems, two different forms of BRIN are discussed. Their circuits using common analog integrated circuits are investigated. The BRIN solution for critical path problems is expressed and is implemented using the separated building block circuit and the combined building block circuit. As these circuits are different, the response time of these networks will be different. The advancement of field programmable gate arrays (FPGAs) in recent years, allowing millions of gates on a single chip and accompanying with high-level design tools, has allowed the implementation of very complex networks. With this exemption on manual circuit construction and availability of efficient design platform, the BRIN architecture could be built in a much more efficient way. Problems on bandwidth are removed by taking all previous external connections to the inside of the chip. By transforming BRIN to FPGA (Xilinx XC4010XL and XCV800 Virtex), we implement a synchronous network with computations in a finite number of steps. Two case studies are presented, with correct results verified from simulation implementation. Resource consumption on FPGAs is studied showing that Virtex devices are more suitable for the expansion of network in future developments. PMID:18244587
PATHS groundwater hydrologic model
Nelson, R.W.; Schur, J.A.
1980-04-01
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.
ERIC Educational Resources Information Center
Beebe, Mona
A study examined the reading problems of adults in Newfoundland (Canada) with low reading ability. It explored the genesis of these problems through a retrospective analysis of their lives as school children; and determined the relationship between literacy development and personal background factors, school factors, physiological factors, and
NSDL National Science Digital Library
2011-01-01
This article, written for middle grades students, relates the history of the famous Konigsberg Bridge problem and introduces the idea of networks and paths that do not retrace themselves. The article concludes with a path the student must work out.
Route choices of transport bicyclists: a comparison of actually used and shortest routes
2014-01-01
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
A Random Sampling Scheme for Path Planning
Latombe, Jean-Claude
precludes any useful application. This negative result has led some researchers to seek heuristic algorithms path planners have been proposed during the last few years. Their at tractiveness stems from for future research. 1 Introduction Robot path planning has been proven a hard problem [40]. There is strong
PARALLEL EVOLUTIONARY ALGORITHMS FOR UAV PATH PLANNING
PARALLEL EVOLUTIONARY ALGORITHMS FOR UAV PATH PLANNING Dong Jia Post-Doctoral Research Associate vehicles (UAVs). Premature convergence prevents evolutionary-based algorithms from reaching global optimal. To overcome this problem, this paper presents a framework of parallel evolutionary algorithms for UAV path
Kochanska, Grazyna; Brock, Rebecca L.; Chen, Kuan-Hua; Aksan, Nazan; Anderson, Steven W.
2014-01-01
Electrodermal hyporeactivity (or low skin conductance level, SCL) has been long established as a correlate of and diathesis for antisocial behavior, aggression, disregard for rules of conduct and feelings of others, and generally, externalizing behavior problems in children and adults. Much less is known, however, about how individual differences in childrens SCL and qualities of their early experiences in relationships with parents interact to produce antisocial outcomes. In a community sample of 102 families (51 girls), we examined childrens SCL, assessed in standard laboratory tasks at age 8 (N=81), as a moderator of the links between parentchild socialization history and childrens externalizing behavior problems at ages 8 and 10, reported by mothers and fathers in well-established instruments and by children in clinical interviews. Mother- and father-child socialization history was assessed in frequent, intensive observations. Parentchild mutually responsive orientation (MRO) was observed from infancy to age 10, parental power assertion was observed from 15 months to age 6 , and children reported their attachment security in interviews at age 8 and 10. For children with lower SCL, variations in mothers power assertion and father-child MRO were associated with parent-rated externalizing problems. The former interaction was consistent with diathesis-stress, and the latter with differential susceptibility. For children with higher SCL, there were no links between socialization history and externalizing problems. PMID:25218772
Buldyrev, Sergey
away. For example, in oil recovery the rst passage time from the injection well to a production well:1300:005 2 and dmin 1:13070:0004 3 . There has been an extensive theoretical and computer work done
Almeroth, Kevin C.
between node pairs. After a one- time preprocessing cost, Rigel answers node-distance queries in 10's, Orion, was a centralized system that approximated node distances by mapping nodes to the Euclidean coordinate system [4]. It has several limitations in practice. First, Orion's initial graph embedding process
Elsayed, Khaled Fouad
in MPLS Networks Khaled M. F. Elsayed, Senior Member, IEEE Department of Electronics and Communications for routing of MPLS bandwidth-guaranteed tunnels in general topology networks. The HCASP algorithm tries of bandwidth-guaranteed tunnels in MPLS networks are the minimum interference routing algorithm (MIRA
Kuperstein, Inna; Grieco, Luca; Cohen, David P A; Thieffry, Denis; Zinovyev, Andrei; Barillot, Emmanuel
2015-03-01
Several decades of molecular biology research have delivered a wealth of detailed descriptions of molecular interactions in normal and tumour cells. This knowledge has been functionally organised and assembled into dedicated biological pathway resources that serve as an invaluable tool, not only for structuring the information about molecular interactions but also for making it available for biological, clinical and computational studies. With the advent of high-throughput molecular profiling of tumours, close to complete molecular catalogues of mutations, gene expression and epigenetic modifications are available and require adequate interpretation. Taking into account the information about biological signalling machinery in cells may help to better interpret molecular profiles of tumours. Making sense out of these descriptions requires biological pathway resources for functional interpretation of the data. In this review, we describe the available biological pathway resources, their characteristics in terms of construction mode, focus, aims and paradigms of biological knowledge representation. We present a new resource that is focused on cancer-related signalling, the Atlas of Cancer Signalling Networks. We briefly discuss current approaches for data integration, visualisation and analysis, using biological networks, such as pathway scoring, guilt-by-association and network propagation. Finally, we illustrate with several examples the added value of data interpretation in the context of biological networks and demonstrate that it may help in analysis of high-throughput data like mutation, gene expression or small interfering RNA screening and can guide in patients stratification. Finally, we discuss perspectives for improving precision medicine using biological network resources and tools. Taking into account the information about biological signalling machinery in cells may help to better interpret molecular patterns of tumours and enable to put precision oncology into general clinical practice. PMID:25688112
Zhang, Hongwei
" with intermediate speed, and "super-containment wave" with the highest speed. The containment wave contains a different propagation speed, i.e., "stabilization wave" with the lowest speed, "containment wave the mistakenly initiated stabilization wave, the super-containment wave contains the mistakenly initiated
All-Pairs Shortest Paths with Real Weights in O(n 3 = log n) Time Timothy M. Chan
Chan, Timothy M.
is attainable: he gave an algorithm with an impressive-looking time bound of O(n 3 (log log n= log n) 1 log log n= log n) and O(n 3 = p log n) respectively. Just last year, several interesting, independent developments have occurred: #12;rst Han [12] announced an improved O(n 3 (log log n= log n) 5=7 )-time
Roughan, Matthew
in providing realistic network scenarios for other researchers. The Rocketfuel project attempted this process to assess the quality of the weight inference. We used this to test Rocketfuel's algo- rithm, and our tests in properties of large networks (or graphs). The Rocketfuel project [1, 2] suggested techniques for "reverse
A method for finding the statically sensitized critical path in VLSI circuits
Sen, Anindita
1995-01-01
The longest sensitizable paths of a circuit are referred to as the critical paths of the circuit. Finding all the critical paths in a circuit is called the critical path problem. There are various methods at present to find the critical path of a...
Research on Taxiway Path Optimization Based on Conflict Detection
Zhou, Hang; Jiang, Xinxin
2015-01-01
Taxiway path planning is one of the effective measures to make full use of the airport resources, and the optimized paths can ensure the safety of the aircraft during the sliding process. In this paper, the taxiway path planning based on conflict detection is considered. Specific steps are shown as follows: firstly, make an improvement on A * algorithm, the conflict detection strategy is added to search for the shortest and safe path in the static taxiway network. Then, according to the sliding speed of aircraft, a time table for each node is determined and the safety interval is treated as the constraint to judge whether there is a conflict or not. The intelligent initial path planning model is established based on the results. Finally, make an example in an airport simulation environment, detect and relieve the conflict to ensure the safety. The results indicate that the model established in this paper is effective and feasible. Meanwhile, make comparison with the improved A*algorithm and other intelligent algorithms, conclude that the improved A*algorithm has great advantages. It could not only optimize taxiway path, but also ensure the safety of the sliding process and improve the operational efficiency. PMID:26226485
Research on Taxiway Path Optimization Based on Conflict Detection.
Zhou, Hang; Jiang, Xinxin
2015-01-01
Taxiway path planning is one of the effective measures to make full use of the airport resources, and the optimized paths can ensure the safety of the aircraft during the sliding process. In this paper, the taxiway path planning based on conflict detection is considered. Specific steps are shown as follows: firstly, make an improvement on A * algorithm, the conflict detection strategy is added to search for the shortest and safe path in the static taxiway network. Then, according to the sliding speed of aircraft, a time table for each node is determined and the safety interval is treated as the constraint to judge whether there is a conflict or not. The intelligent initial path planning model is established based on the results. Finally, make an example in an airport simulation environment, detect and relieve the conflict to ensure the safety. The results indicate that the model established in this paper is effective and feasible. Meanwhile, make comparison with the improved A*algorithm and other intelligent algorithms, conclude that the improved A*algorithm has great advantages. It could not only optimize taxiway path, but also ensure the safety of the sliding process and improve the operational efficiency. PMID:26226485
NASA Technical Reports Server (NTRS)
Smedes, H. W.; Hulstrom, R. L.; Ranson, K. J.
1975-01-01
The results of LANDSAT and Skylab research programs on the effects of the atmosphere on computer mapping of terrain include: (1) the concept of a ground truth map needs to be drastically revised; (2) the concept of training areas and test areas is not as simple as generally thought because of the problem of pixels that represent a mixture of terrain classes; (3) this mixture problem needs to be more widely recognized and dealt with by techniques of calculating spectral signatures of mixed classes, or by other methods; (4) atmospheric effects should be considered in computer mapping of terrain and in monitoring changes; and (5) terrain features may be used as calibration panels on the ground, from which atmospheric conditions can be determined and monitored. Results are presented of a test area in mountainous terrain of south-central Colorado for which an initial classification was made using simulated mixture-class spectral signatures and actual LANDSAT-1-MSS data.
THE LENGTH OF THE SHORTEST CLOSED GEODESIC ON A 2 -DIMENSIONAL SPHERE
Nabutovsky, Alexander
by C. Croke [2] and Maeda [4]. 1. Introduction The connection between the length of a shortest closed connected manifold are the results of Croke [2] and Maeda [4]. Croke proved that if a Riemannian manifold M; 9d . The last in- equality was later improved by Maeda who demonstrated that l(M) #20; 5d if M is di
On the Evaluation of Shortest Journeys in Dynamic Networks Afonso Ferreira
Bermond, Jean-Claude
On the Evaluation of Shortest Journeys in Dynamic Networks Afonso Ferreira CNRS - MASCOTTE Project Department of Computer Science, University of Sao Paulo, Brazil {gold,jm}@ime.usp.br Abstract The assessment industry and are widely available in our every day life. A promising type of these networks is the Mobile
Finding Shortest Non-Trivial Cycles in Directed Graphs on Surfaces
Colin de Verdire, ric
Finding Shortest Non-Trivial Cycles in Directed Graphs on Surfaces Sergio Cabello Department of Mathematics, IMFM Department of Mathematics, FMF University of Ljubljana, Slovenia sergio.cabello or hard copies of all or part of this work for personal or classroom use is granted without fee provided
NASA Technical Reports Server (NTRS)
Zuk, J.
1976-01-01
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.
Thermoalgebras and path integral
Khanna, F.C. [Theoretical Physics Institute, University of Alberta, Edmonton, AB T6G 2J1 (Canada); TRIUMF, Vancouver, BC, V6T 2A3 (Canada)], E-mail: khanna@phys.ualberta.ca; Malbouisson, A.P.C. [Centro Brasileiro de Pesquisas Fisicas/MCT, 22290-180 Rio de Janeiro, RJ (Brazil)], E-mail: adolfo@cbpf.br; Malbouisson, J.M.C. [Instituto de Fisicas, Universidade Federal da Bahia, 40210-340 Salvador, BA (Brazil)], E-mail: jmalboui@ufba.br; Santana, A.E. [Instituto de Fisicas, Universidade de Brasilia, 70910-900 Brasilia, DF (Brazil)], E-mail: asantana@fis.unb.br
2009-09-15
Using a representation for Lie groups closely associated with thermal problems, we derive the algebraic rules of the real-time formalism for thermal quantum field theories, the so-called thermo-field dynamics (TFD), including the tilde conjugation rules for interacting fields. These thermo-group representations provide a unified view of different approaches for finite-temperature quantum fields in terms of a symmetry group. On these grounds, a path integral formalism is constructed, using Bogoliubov transformations, for bosons, fermions and non-abelian gauge fields. The generalization of the results for quantum fields in (S{sup 1}){sup d}xR{sup D-d} topology is addressed.
Dynamic programming and minimum risk paths Paolo Serafini
Serafini, Paolo
Dynamic programming and minimum risk paths by Paolo Serafini University of Udine, Department Abstract: This paper addresses the problem of computing minimum risk paths by taking as objective be considered an extension of usual dynamic programming models: path costs are recursively computed via
Counting Lattice Paths with Privileged Access using Sheer Sequences
Niederhausen, Heinrich
Counting Lattice Paths with Privileged Access using She¤er Sequences Katherine Humphreys 160 Abstract A lattice path has privileged access to the line y = a (x `) ; a; ` 2 N1 be reached by steps from P . If P is empty, then the lattice paths are bounded by a line; a classical problem
An Effective Framework for Path Planning amidst Movable Obstacles
Utrecht, Universiteit
Technical Report UU-CS-2006-035 www.cs.uu.nl ISSN: 0924-3275 #12;An Effective Framework for Path PlanningAn Effective Framework for Path Planning amidst Movable Obstacles Dennis Nieuwenhuisen A. Frank van framework for solving path planning problems among movable obstacles. Heuristics are presented to provide
Robot Path Planning in Uncertain Environments: A Language-Measure-
Ray, Asok
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
Numerical evaluation of Feynman path integrals
NASA Astrophysics Data System (ADS)
Baird, William Hugh
1999-11-01
The notion of path integration developed by Feynman, while an incredibly successful method of solving quantum mechanical problems, leads to frequently intractable integrations over an infinite number of paths. Two methods now exist which sidestep this difficulty by defining "densities" of actions which give the relative number of paths found at different values of the action. These densities are sampled by computer generation of paths and the propagators are found to a high degree of accuracy for the case of a particle on the infinite half line and in a finite square well in one dimension. The problem of propagation within a two dimensional radial well is also addressed as the precursor to the problem of a particle in a stadium (quantum billiard).
Breakdown of the Coherent State Path Integral: Two Simple Examples
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
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.
NASA Technical Reports Server (NTRS)
Janich, Karl W.
2005-01-01
The At-Least version of the Generalized Minimum Spanning Tree Problem (L-GMST) is a problem in which the optimal solution connects all defined clusters of nodes in a given network at a minimum cost. The L-GMST is NPHard; therefore, metaheuristic algorithms have been used to find reasonable solutions to the problem as opposed to computationally feasible exact algorithms, which many believe do not exist for such a problem. One such metaheuristic uses a swarm-intelligent Ant Colony System (ACS) algorithm, in which agents converge on a solution through the weighing of local heuristics, such as the shortest available path and the number of agents that recently used a given path. However, in a network using a solution derived from the ACS algorithm, some nodes may move around to different clusters and cause small changes in the network makeup. Rerunning the algorithm from the start would be somewhat inefficient due to the significance of the changes, so a genetic algorithm based on the top few solutions found in the ACS algorithm is proposed to quickly and efficiently adapt the network to these small changes.
ERIC Educational Resources Information Center
Guven, Bulent
2008-01-01
As any ordinary person knows, the shortest distance between two points is a straight line. What, then, is the shortest distance between three points? Four points? The study reported in this article deals with the observed actions of Turkish student mathematics teachers as they were working with minimal network problems. Having analysed the
Walden's Paths - Ensemble Edition
NSDL National Science Digital Library
2011-01-04
Walden?s Paths enables users of digital document collections (e.g. the Web) to exploit these documents by reusing them for previously unintended audiences in an academic setting. Authors of paths (usually educators) overlay a linear, directed meta-structure over the Web documents and recontextualize these by adding explanatory text to achieve their curricular goals. Paths do not modifythe structure or content of the Web resources that they include. The creation of a path over pre-organized content (e.g. books, Web pages) to reorganize and associate related information serves to facilitate easy retrieval and communication. Walden?s Paths displays the information that the path points to in conjunction with the textual annotations added by the author of the path.
Cooperative optimal path planning for herding problems
Lu, Zhenyu
2009-05-15
of as a shepherd and the evader as a member of a ock. A. System Model x r Pursuer ? Evader y [0,0] ? Fig. 1. System Model for 1P1E Figure 1 gives us a representation of the two agents. The pursuer is generally located at [xp,yp] and the evader... is generally located at [xe,ye]. Beginning at the 5 initial positions, [xp0,yp0] for the pursuer and [xe0,ye0] for the evader, the pursuer should optimally drive the evader to a certain location or region. For the 1P1E scenario, this is the [0,0] position...
NASA Technical Reports Server (NTRS)
Barker, L. Keith
1998-01-01
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.
Christian Fleischhack
2015-03-21
The symmetries of paths in a manifold $M$ are classified with respect to a given pointwise proper action of a Lie group $G$ on $M$. Here, paths are embeddings of a compact interval into $M$. There are at least two types of symmetries: Firstly, paths that are parts of an integral curve of a fundamental vector field on $M$ (continuous symmetry). Secondly, paths that can be decomposed into finitely many pieces, each of which is the translate of some free segment, where possibly the translate is cut at the two ends of the paths (discrete symmetry). Here, a free segment is a path $e$ whose $G$-translates either equal $e$ or intersect it in at most finitely many points. Note that all the statements above are understood up to the parametrization of the paths. We will show, for the category of analytic manifolds, that each path is of exactly one of either types. For the proof, we use that the overlap of a path $\\gamma$ with one of its translates is encoded uniquely in a mapping between subsets of $\\dom\\gamma$. Running over all translates, these mappings form the so-called reparametrization set to $\\gamma$. It will turn out that, up to conjugation with a diffeomorphism, any such set is given by the action of a Lie subgroup of $O(2)$ on $S^1$, restricted in domain and range to some compact interval on $S^1$. Now, the infinite subgroups correspond to the continuous symmetry above, finite ones to the discrete symmetry.
Path Integrals and Hamiltonians
NASA Astrophysics Data System (ADS)
Baaquie, Belal E.
2014-03-01
1. Synopsis; Part I. Fundamental Principles: 2. The mathematical structure of quantum mechanics; 3. Operators; 4. The Feynman path integral; 5. Hamiltonian mechanics; 6. Path integral quantization; Part II. Stochastic Processes: 7. Stochastic systems; Part III. Discrete Degrees of Freedom: 8. Ising model; 9. Ising model: magnetic field; 10. Fermions; Part IV. Quadratic Path Integrals: 11. Simple harmonic oscillators; 12. Gaussian path integrals; Part V. Action with Acceleration: 13. Acceleration Lagrangian; 14. Pseudo-Hermitian Euclidean Hamiltonian; 15. Non-Hermitian Hamiltonian: Jordan blocks; 16. The quartic potential: instantons; 17. Compact degrees of freedom; Index.
A Path Algorithm for Constrained Estimation
Zhou, Hua; Lange, Kenneth
2013-01-01
Many least-square problems involve affine equality and inequality constraints. Although there are a variety of methods for solving such problems, most statisticians find constrained estimation challenging. The current article proposes a new path-following algorithm for quadratic programming that replaces hard constraints by what are called exact penalties. Similar penalties arise in l1 regularization in model selection. In the regularization setting, penalties encapsulate prior knowledge, and penalized parameter estimates represent a trade-off between the observed data and the prior knowledge. Classical penalty methods of optimization, such as the quadratic penalty method, solve a sequence of unconstrained problems that put greater and greater stress on meeting the constraints. In the limit as the penalty constant tends to ?, one recovers the constrained solution. In the exact penalty method, squared penalties!are replaced by absolute value penalties, and the solution is recovered for a finite value of the penalty constant. The exact path-following method starts at the unconstrained solution and follows the solution path as the penalty constant increases. In the process, the solution path hits, slides along, and exits from the various constraints. Path following in Lasso penalized regression, in contrast, starts with a large value of the penalty constant and works its way downward. In both settings, inspection of the entire solution path is revealing. Just as with the Lasso and generalized Lasso, it is possible to plot the effective degrees of freedom along the solution path. For a strictly convex quadratic program, the exact penalty algorithm can be framed entirely in terms of the sweep operator of regression analysis. A few well-chosen examples illustrate the mechanics and potential of path following. This article has supplementary materials available online. PMID:24039382
From Path Graphs to Directed Path Graphs Steven Chaplick1
Felsner, Stefan
From Path Graphs to Directed Path Graphs Steven Chaplick1 , Marisa Gutierrez2 , Benjamin L´ev^eque3 time algorithm to greedily orient the edges of a path graph model to obtain a directed path graph model. This algorithm has several interesting conse- quences concerning the relationship between path graphs
NSDL National Science Digital Library
Australian National University
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.
Calix[4]pyrroles with Shortest Possible Strap: Exclusively Selective toward Fluoride Ion.
Samanta, Ritwik; Kumar, B Sathish; Panda, Pradeepta K
2015-09-01
Four new calix[4]pyrroles with the shortest possible strap so far through ortho-linking of the aromatic unit have been synthesized, including a naphthalene-derived fluorescent receptor. They show exclusive selectivity toward the fluoride ion as confirmed by (1)H NMR, isothermal titration calorimetry, and fluorescence spectroscopic study. Anion affinity could also be modulated further via functionalization at the strap. Computational analysis displays calix[4]pyrroles binding to fluoride ion in a very unusual 1,3-alternate conformation where the anion resides on the opposite side of the strap. PMID:26313641
The School Bus Problem on Trees Adrian Bock1
Knemann, Jochen
The School Bus Problem on Trees Adrian Bock1 , Elyot Grant2 , Jochen Konemann2 , and Laura Sanit`a1 1 EPFL, Lausanne, Switzerland 2 University of Waterloo, Canada Abstract. The School Bus Problem to a school such that for each child, the distance travelled on the bus does not exceed the shortest distance
Breast Contour Detection with Stable Paths
NASA Astrophysics Data System (ADS)
Cardoso, Jaime S.; Sousa, Ricardo; Teixeira, Lus F.; Cardoso, M. J.
Breast cancer conservative treatment (BCCT), due to its proven oncological safety, is considered, when feasible, the gold standard of breast cancer treatment. However, aesthetic results are heterogeneous and difficult to evaluate in a standardized way, due to the lack of reproducibility of the subjective methods usually applied. The objective assessment methods, considered in the past as being less capable of evaluating all aspects of BCCT, are nowadays being preferred to overcome the drawbacks of the subjective evaluation. A computer-aided medical system was recently developed to objectively and automatically evaluate the aesthetic result of BCCT. In this system, the detection of the breast contour on the patient's digital photograph is a necessary step to extract the features subsequently used in the evaluation process. In this paper an algorithm based on the shortest path on a graph is proposed to detect automatically the breast contour. The proposed method extends an existing semi-automatic algorithm for the same purpose. A comprehensive comparison with manually-drawn contours reveals the strength of the proposed method.
Spin up in RX J0806+15 - the shortest period binary
Hakala, P; Wu, K; Hjalmarsdotter, L; Jrvinen, S; Jrvinen, A; Cropper, M; Hakala, Pasi; Ramsay, Gavin; Wu, Kinwah; Hjalmarsdotter, Linnea; Jarvinen, Silva; Jarvinen, Arto; Cropper, Mark
2003-01-01
RX J0806+15 has recently been identified as the binary system with the shortest known orbital period. We present a series of observations of RX J0806+15 including new optical observations taken one month apart. Using these observations and archival data we find that the period of this system is decreasing over time. Our measurements imply f_dot = 6.11x10^-16 Hz/s, which is in agreement with a rate expected from the gravitational radiation for two white dwarfs orbiting at a given period. However, a smaller value of f_dot = 3.14x10^-16 Hz/s cannot be ruled out. Our result supports the idea that the 321.5 s period is the orbital period and that the system is the shortest period binary known so far and that it is one of the strongest sources of constant gravitational radiation in the sky. Furthermore, the decrease of the period strongly favours the unipolar inductor (or electric star) model rather than the accretion models.
Spin up in RX J0806+15 - the shortest period binary
Pasi Hakala; Gavin Ramsay; Kinwah Wu; Linnea Hjalmarsdotter; Silva Jarvinen; Arto Jarvinen; Mark Cropper
2003-05-15
RX J0806+15 has recently been identified as the binary system with the shortest known orbital period. We present a series of observations of RX J0806+15 including new optical observations taken one month apart. Using these observations and archival data we find that the period of this system is decreasing over time. Our measurements imply f_dot = 6.11x10^-16 Hz/s, which is in agreement with a rate expected from the gravitational radiation for two white dwarfs orbiting at a given period. However, a smaller value of f_dot = 3.14x10^-16 Hz/s cannot be ruled out. Our result supports the idea that the 321.5 s period is the orbital period and that the system is the shortest period binary known so far and that it is one of the strongest sources of constant gravitational radiation in the sky. Furthermore, the decrease of the period strongly favours the unipolar inductor (or electric star) model rather than the accretion models.
Local path configuration method considering global path optimality in multilayer networks
NASA Astrophysics Data System (ADS)
Takehara, Takayoshi; Tode, Hideki; Murakami, Koso
2005-10-01
Recently, further high-speed and larger capacity communication is requested in the IP network. And multilayer network that constructs the IP network on an optical network such as IP over WDM is focused on. Under such a network environment, the multipath routing for setting two or more paths between a starting and ending nodes in each network is researched. The multipaths are taken advantage of load balance and path recovery and damaged traffic is switched to other paths at the starting node if a failure happens on a path. However, the traditional routing often finds multipaths overlapping on some links and nodes because of its low "disjoint property". Hence, path recovery is difficult because the multipaths may be interrupted at the same time. In order to resolve the problem in multilayer network, we propose the local path configuration method considering global path optimality. Concretely, we propose a network architecture where networks are connected by multiple edge nodes and multipath routing method with new link cost and parallel calculation of multipaths. As a result, the multipaths are prevented from overlapping and the disjointed multipaths enable efficient path recovery in case of a failure. Moreover, we verify the effectiveness of the disjoint property.
Path Following with an Optimal Forward Velocity for a Mobile Robot
Zell, Andreas
trailer vehicle. Path following controllers for aircraft and marine ve- hicles were reported in (Al environments. Given linearized error dynamic equations, model predictive control (MPC) is employed to produce, obstacle avoidance, path following, model predictive control. 1. INTRODUCTION Fundamental problems
Wei, Quantum Jichi
2015-01-01
Path-planning has many applications, ranging from self-driving cars to flying drones, and to our daily commute to work. Path-planning for autonomous underwater vehicles presents an interesting problem: the ocean flow is ...
A Simulation Method for Calculating the Path Travel Time in Dynamic Transportation Network
Lin, G.C.
The calculation of path travel times is an essential component for the dynamic traffic assignment and equilibrium problems. This paper presents a simulation method for calculating actual path travel times for the traffic ...
ERIC Educational Resources Information Center
Stegemoller, William; Stegemoller, Rebecca
2004-01-01
The path taken and the turns made as a turtle traces a polygon are examined to discover an important theorem in geometry. A unique tool, the Angle Adder, is implemented in the investigation. (Contains 9 figures.)
Tortuous path chemical preconcentrator
Manginell, Ronald P. (Albuquerque, NM); Lewis, Patrick R. (Albuquerque, NM); Adkins, Douglas R. (Albuquerque, NM); Wheeler, David R. (Albuquerque, NM); Simonson, Robert J. (Cedar Crest, NM)
2010-09-21
A non-planar, tortuous path chemical preconcentrator has a high internal surface area having a heatable sorptive coating that can be used to selectively collect and concentrate one or more chemical species of interest from a fluid stream that can be rapidly released as a concentrated plug into an analytical or microanalytical chain for separation and detection. The non-planar chemical preconcentrator comprises a sorptive support structure having a tortuous flow path. The tortuosity provides repeated twists, turns, and bends to the flow, thereby increasing the interfacial contact between sample fluid stream and the sorptive material. The tortuous path also provides more opportunities for desorption and readsorption of volatile species. Further, the thermal efficiency of the tortuous path chemical preconcentrator is comparable or superior to the prior non-planar chemical preconcentrator. Finally, the tortuosity can be varied in different directions to optimize flow rates during the adsorption and desorption phases of operation of the preconcentrator.
NSDL National Science Digital Library
In this lesson, younger students will be introduced to the various orbital paths that are used for satellites. Using a globe and a satellite model or a large picture of Earth, the teacher will introduce three types of orbital paths (polar, elliptical, and geosynchronous). The students should be able to define 'satellite', define the three types of orbits, describe how satellites orbit the Earth, and understand how they are slowed down by drag from the atmosphere.
Applications of Path Compression on Balanced Trees
Robert Endre Tarjan
1979-01-01
Several fast algorithms are presented for computing functions defined on paths in trees under various assumpuons. The algorithms are based on tree mampulatton methods first used to efficiently represent equivalence relations. The algorithms have O((m + n)a(m + n, n)) running tunes, where m and n are measures of the problem size and a Is a functional reverse of Ackermann's
Path Integration in Desert Ants, Cataglyphis fortis
Martin Muller; Rudiger Wehner
1988-01-01
Foraging desert ants, Cataglyphis fortis, continually keep track of their own positions relative to home--i.e., integrate their tortuous outbound routes and return home along straight (inbound) routes. By experimentally manipulating the ants' outbound trajectories we show that the ants solve this path integration problem not by performing a true vector summation (as a human navigator does) but by employing a
A 2D analytical cylindrical gate tunnel FET (CG-TFET) model: impact of shortest tunneling distance
NASA Astrophysics Data System (ADS)
Dash, S.; Mishra, G. P.
2015-09-01
A 2D analytical tunnel field-effect transistor (FET) potential model with cylindrical gate (CG-TFET) based on the solution of Laplaces equation is proposed. The band-to-band tunneling (BTBT) current is derived by the help of lateral electric field and the shortest tunneling distance. However, the analysis is extended to obtain the subthreshold swing (SS) and transfer characteristics of the device. The dependency of drain current, SS and transconductance on gate voltage and shortest tunneling distance is discussed. Also, the effect of scaling the gate oxide thickness and the cylindrical body diameter on the electrical parameters of the device is analyzed.
Multi-Level Indoor Path Planning Method
NASA Astrophysics Data System (ADS)
Xiong, Q.; Zhu, Q.; Zlatanova, S.; Du, Z.; Zhang, Y.; Zeng, L.
2015-05-01
Indoor navigation is increasingly widespread in complex indoor environments, and indoor path planning is the most important part of indoor navigation. Path planning generally refers to finding the most suitable path connecting two locations, while avoiding collision with obstacles. However, it is a fundamental problem, especially for 3D complex building model. A common way to solve the issue in some applications has been approached in a number of relevant literature, which primarily operates on 2D drawings or building layouts, possibly with few attached attributes for obstacles. Although several digital building models in the format of 3D CAD have been used for path planning, they usually contain only geometric information while losing abundant semantic information of building components (e.g. types and attributes of building components and their simple relationships). Therefore, it becomes important to develop a reliable method that can enhance application of path planning by combining both geometric and semantic information of building components. This paper introduces a method that support 3D indoor path planning with semantic information.
Flux Control in Networks of Diffusion Paths
A. I. Zhmoginov and N. J. Fisch
2009-07-08
A class of optimization problems in networks of intersecting diffusion domains of a special form of thin paths has been considered. The system of equations describing stationary solutions is equivalent to an electrical circuit built of intersecting conductors. The solution of an optimization problem has been obtained and extended to the analogous electrical circuit. The interest in this network arises from, among other applications, an application to wave-particle diffusion through resonant interactions in plasma.
Monochromatic paths and path squares in infinite graphs
Mildenberger, Heike
Monochromatic paths and path squares in infinite graphs Lajos Soukup Alfréd Rényi Institute disjoint monochromatic paths with different colours which cover all vertices of K. #12;The beginning complete graph K is coloured with r colors. Then there are r disjoint monochromatic paths with different
On the Optimal Path Length for Tor Kevin Bauer1
Borisov, Nikita
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
UNIVERSAL GRAPHS WITH A FORBIDDEN SUBGRAPH: BLOCK PATH SOLIDITY
Cherlin, Gregory
UNIVERSAL GRAPHS WITH A FORBIDDEN SUBGRAPH: BLOCK PATH SOLIDITY GREGORY CHERLIN DEPARTMENT for which there is a count- able universal C-free graph, and whose tree of blocks is a path. Then the blocks. Publication 1033. #12;2 G. CHERLIN AND S. SHELAH Introduction The main theorem. The general problem
Cost effective path to DEMO University of Washington
1 Cost effective path to DEMO By Tom Jarboe University of Washington To Fusion Power Associates December 14, 2011 #12;2 Outline Maximizing the development-cost benefit from ITER knowledge Getting on cost effective path Requirements of smaller scale experiment Cost problems are helped
Path Planning in Practice; Lazy Evaluation on a Multiresolution Grid
LaValle, Steven M.
, especially when collision checking is computationally ex pensive. Single queries are handled quickly since no pre processing is required. 1 Introduction Path planning for robots has received much atten tion over the last decades. The general problem is to find collisionfree paths for a robot
Toward Efficient Trajectory Planning: The Path-Velocity Decomposition
Kamal Kant; Steven W. Zucker
1986-01-01
We present a novel approach to solving the trajectory plan ning problem (TPP) in time-varying environments. The es sence of our approach lies in a heuristic but natural decom position of TPP into two subproblems: (1) planning a path to avoid collision with static obstacles and (2) planning the velocity along the path to avoid collision with moving obsta cles.
A Decentralized Model for Virtual Path Capacity Allocation
Konstantopoulos, Takis
in an ATM network. function, and investigated the equilibrium point and converging algorithms. In [41 A Decentralized Model for Virtual Path Capacity Allocation SEUNG H. RHEE and TAKIS,takis @alea.ece.utexas.edu Abstract--We investigate the problem of Virtual Path (VP) capacity al- location
Minimal entropy probability paths between genome families.
Ahlbrandt, Calvin; Benson, Gary; Casey, William
2004-05-01
We develop a metric for probability distributions with applications to biological sequence analysis. Our distance metric is obtained by minimizing a functional defined on the class of paths over probability measures on N categories. The underlying mathematical theory is connected to a constrained problem in the calculus of variations. The solution presented is a numerical solution, which approximates the true solution in a set of cases called rich paths where none of the components of the path is zero. The functional to be minimized is motivated by entropy considerations, reflecting the idea that nature might efficiently carry out mutations of genome sequences in such a way that the increase in entropy involved in transformation is as small as possible. We characterize sequences by frequency profiles or probability vectors, in the case of DNA where N is 4 and the components of the probability vector are the frequency of occurrence of each of the bases A, C, G and T. Given two probability vectors a and b, we define a distance function based as the infimum of path integrals of the entropy function H( p) over all admissible paths p(t), 0 < or = t< or =1, with p(t) a probability vector such that p(0)=a and p(1)=b. If the probability paths p(t) are parameterized as y(s) in terms of arc length s and the optimal path is smooth with arc length L, then smooth and "rich" optimal probability paths may be numerically estimated by a hybrid method of iterating Newton's method on solutions of a two point boundary value problem, with unknown distance L between the abscissas, for the Euler-Lagrange equations resulting from a multiplier rule for the constrained optimization problem together with linear regression to improve the arc length estimate L. Matlab code for these numerical methods is provided which works only for "rich" optimal probability vectors. These methods motivate a definition of an elementary distance function which is easier and faster to calculate, works on non-rich vectors, does not involve variational theory and does not involve differential equations, but is a better approximation of the minimal entropy path distance than the distance //b-a//(2). We compute minimal entropy distance matrices for examples of DNA myostatin genes and amino-acid sequences across several species. Output tree dendograms for our minimal entropy metric are compared with dendograms based on BLAST and BLAST identity scores. PMID:15133624
Atmospheric Science Data Center
2014-12-08
... is natural to name each of these different trajectories or paths. For MISR, the path is the generic name (actually the numeric label) of ... that are close to each other in longitude will be covered by paths with similar numbers. The path number is also included in the file name ...
X-ray counterpart of the shortest activity cycle found to date
NASA Astrophysics Data System (ADS)
Sanz-Forcada, Jorge
2011-10-01
Activity cycles are commonly found among late type stars through the chromospheric Ca II emission. Their coronal counterpart, remains elusive in most cases, despite of the clear cycle observed in the solar corona, spanning as much as 1.7 dex in Lx. The recent discovery of a Ca II cycle in HR 810 of just 1.6 yr, the shortest to date, offers a unique opportunity to test the existence of an X-ray counterpart of the cycle within two XMM-Newton observing periods. The star offers two more interesting properties: it represents a young (500 Myr) solar analog, and a 1.9 Mj planet orbits the star at 0.9 a.u. We started our search for the cycle of HR 810 in AO 10 and we intend to make 5 new snapshots during XMM-Newton AO 11, for a total of 25 ks, to complete the coverage of the cycle.
Breakdown of the coherent state path integral: two simple examples.
Wilson, Justin H; Galitski, Victor
2011-03-18
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. PMID:21469843
A load-balance path selection algorithm in automatically swiched optical network (ASON)
NASA Astrophysics Data System (ADS)
Gao, Fei; Lu, Yueming; Ji, Yuefeng
2007-11-01
In this paper, a novel load-balance algorithm is proposed to provide an approach to optimized path selection in automatically swiched optical network (ASON). By using this algorithm, improved survivability and low congestion can be achieved. The static nature of current routing algorithms, such as OSPF or IS-IS, has made the situation worse since the traffic is concentrated on the "least-cost" paths which causes the congestion for some links while leaving other links lightly loaded. So, the key is to select suitable paths to balance the network load to optimize network resource utilization and traffic performance. We present a method to provide the capability to control traffic engineering so that the carriers can define their own strategies for optimizations and apply them to path selection for dynamic load balancing. With considering load distribution and topology information, capacity utilization factor is introduced into Dijkstra (shortest path selection) for path selection to achieve balancing traffic over network. Routing simulations have been done over mesh networks to compare the two different algorithms. With the simulation results, a conclusion can be made on the performance of different algorithms.
Path planning for everday robotics with SANDROS
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
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.
Quantum Extremism: Effective Potential and Extremal Paths
E. N. Argyres; M. T. M. van Kessel; R. H. P. Kleiss
2009-07-07
The reality and convexity of the effective potential in quantum field theories has been studied extensively in the context of Euclidean space-time. It has been shown that canonical and path-integral approaches may yield different results, thus resolving the `convexity problem'. We discuss the transferral of these treatments to Minkowskian space-time, which also necessitates a careful discussion of precisely which field configurations give the dominant contributions to the path integral. In particular, we study the effective potential for the N=1 linear sigma model.
Asymptotically optimal path planning and surface reconstruction for inspection
Papadopoulos, Georgios
2014-01-01
Motivated by inspection applications for marine structures, this thesis develops algorithms to enable their autonomous inspection. Two essential parts of the inspection problem are (1) path planning and (2) surface ...
Path planning of Autonomous Underwater Vehicles for adaptive sampling
Yilmaz, Namik Kemal, 1975-
2006-01-01
This thesis develops new methods for path planning of Autonomous Underwater Vehicles for adaptive sampling. The problem is approached in an optimization framework and two methods are developed to solve it based on Mixed ...
Human-Automation Path Planning Optimization and Decision Support
Cummings, M.L.
2011-01-01
Path planning is a problem encountered in multiple domains, including unmanned vehicle control, air traffic control, and future exploration missions to the Moon and Mars. Due to the voluminous and complex nature of the ...
Stochastic Evolutionary Algorithms for Planning Robot Paths
NASA Technical Reports Server (NTRS)
Fink, Wolfgang; Aghazarian, Hrand; Huntsberger, Terrance; Terrile, Richard
2006-01-01
A computer program implements stochastic evolutionary algorithms for planning and optimizing collision-free paths for robots and their jointed limbs. Stochastic evolutionary algorithms can be made to produce acceptably close approximations to exact, optimal solutions for path-planning problems while often demanding much less computation than do exhaustive-search and deterministic inverse-kinematics algorithms that have been used previously for this purpose. Hence, the present software is better suited for application aboard robots having limited computing capabilities (see figure). The stochastic aspect lies in the use of simulated annealing to (1) prevent trapping of an optimization algorithm in local minima of an energy-like error measure by which the fitness of a trial solution is evaluated while (2) ensuring that the entire multidimensional configuration and parameter space of the path-planning problem is sampled efficiently with respect to both robot joint angles and computation time. Simulated annealing is an established technique for avoiding local minima in multidimensional optimization problems, but has not, until now, been applied to planning collision-free robot paths by use of low-power computers.
arXiv:1005.1035v1[math.PR]6May2010 DIFFUSION LIMITS FOR SHORTEST REMAINING
Puha, Amber
, that is, the job with the shortest remaining processing time. More Research supported in part by NSF Remaining Processing Time (SRPT) policy, preemptive priority is given to the job that can be completed first.i.d. service times, and let I(t) index those jobs that are in the queue at time t. For i I(t), let wi
Min-cuts and Shortest Cycles in Planar Graphs in O(n log log n) Time
\\L\\kacki, Jakub
2011-01-01
We present a deterministic O(n log log n) time algorithm for finding shortest cycles and minimum cuts in planar graphs. The algorithm improves the previously known fastest algorithm by Italiano et al. in STOC'11 by a factor of log n. This speedup is obtained through the use of dense distance graphs combined with a divide-and-conquer approach.
Qian, Weixian; Zhou, Xiaojun; Lu, Yingcheng; Xu, Jiang
2015-09-15
Both the Jones and Mueller matrices encounter difficulties when physically modeling mixed materials or rough surfaces due to the complexity of light-matter interactions. To address these issues, we derived a matrix called the paths correlation matrix (PCM), which is a probabilistic mixture of Jones matrices of every light propagation path. Because PCM is related to actual light propagation paths, it is well suited for physical modeling. Experiments were performed, and the reflection PCM of a mixture of polypropylene and graphite was measured. The PCM of the mixed sample was accurately decomposed into pure polypropylene's single reflection, pure graphite's single reflection, and depolarization caused by multiple reflections, which is consistent with the theoretical derivation. Reflection parameters of rough surface can be calculated from PCM decomposition, and the results fit well with the theoretical calculations provided by the Fresnel equations. These theoretical and experimental analyses verify that PCM is an efficient way to physically model light-matter interactions. PMID:26371930
Path integral control and state-dependent feedback.
Thijssen, Sep; Kappen, H J
2015-03-01
In this paper we address the problem of computing state-dependent feedback controls for path integral control problems. To this end we generalize the path integral control formula and utilize this to construct parametrized state-dependent feedback controllers. In addition, we show a relation between control and importance sampling: Better control, in terms of control cost, yields more efficient importance sampling, in terms of effective sample size. The optimal control provides a zero-variance estimate. PMID:25871051
Sven Koenig; Maxim Likhachev; David Furcy
2004-01-01
Heuristic search methods promise to find shortest paths for path-planning problems faster than uninformed search methods. Incremental search methods, on the other hand, promise to find shortest paths for series of similar path-planning problems faster than is possible by solving each path-planning problem from scratch. In this article, we develop Lifelong Planning A* (LPA*), an incremental version of A* that
Space operations center communications path obscuration
NASA Astrophysics Data System (ADS)
Carl, J. R.; Lu, B. P.
Computer assisted techniques were developed to determine the obscuration of a communications path caused by the physical objects that comprise the Space Operations Center (SOC). Of particular interest in this paper is the obscuration of the line-of-sight path from an antenna, mounted somewhere on or in the vicinity of the SOC, to a geosynchronous satellite, such as a Telemetry Data Relay Satellite. The dynamic geometry of this type of problem makes it difficult to visualize, in a complete manner, without the aid of a computer. Blockage is shown graphically by computer-generated displays, and the percentage of time that the path is blocked is calculated. Graphics permit a ready comparison of one antenna location to another.
Automatically Detecting Equivalent Mutants and Infeasible Paths A. Je erson O utt
Offutt, Jeff
Automatically Detecting Equivalent Mutants and Infeasible Paths A. Je erson O utt ISSE Department is a partial solution to the problem of automatically detecting equivalent mutant programs. Equivalent mutants equivalent mutants is a speci c instance of a more general problem, commonly called the feasible path problem
ERIC Educational Resources Information Center
McGarvey, Lynn M.; Sterenberg, Gladys Y.; Long, Julie S.
2013-01-01
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
DNA Computing Hamiltonian path
Hagiya, Masami
2014 DNA DNA #12;DNA Computing Feynman Adleman DNASIMD ... DNADNA #12;DNA DNA DNA #12;2000 2005 2010 1995 Hamiltonian path DNA tweezers DNA tile DNA origami DNA box Sierpinski DNA tile self assembly DNA logic gates Whiplash PCR DNA automaton DNA spider MAYA
ERIC Educational Resources Information Center
Coleman, Toni
2012-01-01
A growing number of institutions are being more deliberate about bringing in fundraisers who fit the culture of the development department and about assessing skills and providing training that fill specific needs. Development shops are paying more attention to cultivating their staffs, staying attuned to employees' needs and creating career paths
NSDL National Science Digital Library
CareerPath offers a searchable index of employment ads from six major newspapers: The Boston Globe, Chicago Tribune, Los Angeles Times, The New York Times, The San Jose Mercury News, and The Washington Post. The total ads available on October 21 was 21,442. The site is attractive and easy to use.
ERIC Educational Resources Information Center
Grimm, Karen
1999-01-01
Describes "Off the Beaten Path", a program that takes at-risk students out of the traditional classroom and puts them into a camping atmosphere in order to increase academic achievement, improve self-esteem, and promote better social skills. (WRM)
ERIC Educational Resources Information Center
Rodia, Becky
2004-01-01
This article profiles Diane Stanley, an author and illustrator of children's books. Although she was studying to be a medical illustrator in graduate school, Stanley's path changed when she got married and had children. As she was raising her children, she became increasingly enamored of the colorful children's books she would check out of the
NASA Technical Reports Server (NTRS)
Bill, R. C.; Johnson, R. D. (inventors)
1979-01-01
A gas path seal suitable for use with a turbine engine or compressor is described. A shroud wearable or abradable by the abrasion of the rotor blades of the turbine or compressor shrouds the rotor bades. A compliant backing surrounds the shroud. The backing is a yieldingly deformable porous material covered with a thin ductile layer. A mounting fixture surrounds the backing.
2013-03-05
where j a differential 1-form on some vector space V and t/Xt is a path in V not necessarily of .... Let C be the algebra of bounded continuous functions from R to R and ... Let OC g be the subspace of elements XAOC such that. jjXjjg : sup t;
Path analysis in genetic epidemiology: a critique.
Karlin, S; Cameron, E C; Chakraborty, R
1983-01-01
Path analysis, a form of general linear structural equation models, is used in studies of human genetics data to discern genetic, environmental, and cultural factors contributing to familial resemblance. It postulates a set of linear and additive parametric relationships between phenotypes and genetic and cultural variables and then essentially uses the assumption of multivariate normality to estimate and perform tests of hypothesis on parameters. Such an approach has been advocated for the analysis of genetic epidemiological data by D. C. Rao, N. Morton, C. R. Cloninger, L. J. Eaves, and W. E. Nance, among others. This paper reviews and evaluates the formulations, assumptions, methodological procedures, interpretations, and applications of path analysis. To give perspective, we begin with a discussion of path analysis as it occurs in the form of general linear causal models in several disciplines of the social sciences. Several specific path analysis models applied to lipoprotein concentrations, IQ, and twin data are then reviewed to keep the presentation self-contained. The bulk of the critical discussion that follows is directed toward the following four facets of path analysis: (1) coherence of model specification and applicability to data; (2) plausibility of modeling assumptions; (3) interpretability and utility of the model; and (4) validity of statistical and computational procedures. In the concluding section, a brief discussion of the problem of appropriate model selection is presented, followed by a number of suggestions of essentially model-free alternative methods of use in the treatment of complex structured data such as occurs in genetic epidemiology. PMID:6349335
Interpretation of pressure-temperature-time paths
England, P.C.
1985-01-01
Pressure-temperature-time (PTt) paths inferred from mineral assemblages or compositions in metamorphic rocks are used to place constraints on metamorphic processes on several different scales. The purpose of this paper is to indicate the kind of questions that may be answered, and those that cannot, by interpretation of PTt data. The intensity of regional metamorphism depends both on the intensity of available heat sources and the length of time available for thermal relaxation; consequently the addition of reliable dates to a PT path is a crucial element in containing thermal history. For example, the question as to whether or not Archaean continental thermal regimes were similar to today's cannot be answered without PTt paths dated to a precision of better than 30 Myr. As there is always local perturbation due to tectonic, igneous or other fluid activity it is essential to obtain widespread PTt data before making estimates of thermal budgets for regional metamorphism. However, on the smaller scale, PTt paths may be used to infer tectonic style where structural data are ambiguous or lacking. Particular attention is paid to the problems of inferring extensional events from the PTt paths recorded by rocks from regional metamorphic belts.
PathFinder: a negotiation-based performance-driven router for FPGAs
Larry McMurchie; Carl Ebeling
1995-01-01
Routing FPGAs is a challenging problem because of the relative scarcity of routing resources, both wires and connection points. This can lead either to slow implementations caused by long wiring paths that avoid congestion or a failure to route all signals. This paper presents PathFinder, a router that balances the goals of performance and routability. PathFinder uses an iterative algorithm
Node-capacitated packing of A-paths How to make a polynomial algorithm strongly polynomial?
Pap, Gyula
Node-capacitated packing of A-paths -- How to make a polynomial algorithm strongly polynomial, January, 2008 Gyula Pap Node-capacitated packing of A-paths #12;Polynomial Time Algorithm (P) INPUT: n Node-capacitated packing of A-paths #12;Some famous sp algorithms Assume our problem given as an LP
Planning Paths of Complete Coverage of an Unstructured Environment by a Mobile Robot
Planning Paths of Complete Coverage of an Unstructured Environment by a Mobile Robot A. Zelinsky 1 of the focus of the research effort in path planning for mobile robots has centred on the problem of finding a path from a start location to a goal location, while minimising one or more parameters such as length
An E#ective Framework for Path Planning amidst Movable Obstacles
Utrecht, Universiteit
Technical Report UUCS2006035 www.cs.uu.nl ISSN: 09243275 #12; An E#ective Framework for Path PlanningAn E#ective Framework for Path Planning amidst Movable Obstacles Dennis Nieuwenhuisen A. Frank van framework for solving path planning problems among movable obstacles. Heuristics are presented to provide e
Elegantly colored paths and cycles in edge colored random graphs Lisa Espig
Frieze, Alan
problem. We generate random edges and randomly color them black or white. A path/cycle is said to zebraic assume that the edges of a graph G have been colored black or white. A path or cycle will be called of rainbow paths and cycles that have been well-studied. Rainbow Hamilton cycles in edge colored complete
A topological approach of path planning for autonomous robot navigation in dynamic environments
Aswin Thomas Abraham; Shuzhi Sam Ge; Pey Yuen Tao
2009-01-01
This paper proposes a novel approach, Simultaneous Path Planning and Topological Mapping (SP2ATM), to address the problem of path planning by registering the topology of the perceived dynamic environment as opposed to the conventional grid representation. The local topology is encoded, concurrent and incremental with path planning, by extracting only the admissible free space. The resulting Admissible Space Topological Map
PoiRoot: Investigating the Root Cause of Interdomain Path Changes
Anderson, Richard
Keywords Path Changes, Root Cause Analysis, Measurement, Monitoring, BGP 1. INTRODUCTION Internet pathsPoiRoot: Investigating the Root Cause of Interdomain Path Changes Umar Javed University changes, the general problem of identifying the root cause remains unsolved. In this work, we design
Benefit of adaptive FEC in shared backup path protected elastic optical network.
Guo, Hong; Dai, Hua; Wang, Chao; Li, Yongcheng; Bose, Sanjay K; Shen, Gangxiang
2015-07-27
We apply an adaptive forward error correction (FEC) allocation strategy to an Elastic Optical Network (EON) operated with shared backup path protection (SBPP). To maximize the protected network capacity that can be carried, an Integer Linear Programing (ILP) model and a spectrum window plane (SWP)-based heuristic algorithm are developed. Simulation results show that the FEC coding overhead required by the adaptive FEC scheme is significantly lower than that needed by a fixed FEC allocation strategy resulting in higher network capacity for the adaptive strategy. The adaptive FEC allocation strategy can also significantly outperform the fixed FEC allocation strategy both in terms of the spare capacity redundancy and the average FEC coding overhead needed per optical channel. The proposed heuristic algorithm is efficient and not only performs closer to the ILP model but also does much better than the shortest-path algorithm. PMID:26367673
Fast quantum algorithms for traversing paths of eigenstates
S. Boixo; E. Knill; R. D. Somma
2010-05-17
Consider a path of non-degenerate eigenstates of unitary operators or Hamiltonians with minimum eigenvalue gap G. The eigenpath traversal problem is to transform one or more copies of the initial to the final eigenstate. Solutions to this problem have applications ranging from quantum physics simulation to optimization. For Hamiltonians, the conventional way of doing this is by applying the adiabatic theorem. We give ``digital'' methods for performing the transformation that require no assumption on path continuity or differentiability other than the absence of large jumps. Given sufficient information about eigenvalues and overlaps between states on the path, the transformation can be accomplished with complexity O(L/G log(L/e)), where L is the angular length of the path and e is a specified bound on the error of the output state. We show that the required information can be obtained in a first set of transformations, whose complexity per state transformed has an additional factor that depends logarithmically on a maximum angular velocity along the path. This velocity is averaged over constant angular distances and does not require continuity. Our methods have substantially better behavior than conventional adiabatic algorithms, with fewer conditions on the path. They also improve on the previously best digital methods and demonstrate that path length and the gap are the primary parameters that determine the complexity of state transformation along a path.
IP-oriented control of unidirectional-path-switched-ring-based transport networks
NASA Astrophysics Data System (ADS)
Sharma, Vishal; Das, Abhimanyu; Chen, Charles
2003-03-01
An important requirement in the IP-based control of time-division multiplexing (TDM) optical transport networks is to utilize the in-built protection capabilities of synchronous optical network (SONET) unidirectional path-switched rings (UPSRs) and to automate the UPSR-protected path setup in mixed mesh-ring networks. This requires modifications to existing IP signaling and routing protocols and new processing rules at the network nodes. Here we leverage IP routing and signaling and multiprotocol label switching (MPLS) fast-reroute techniques for accurately advertising UPSR ring topologies to remote nodes and dynamically establishing UPSR-protected paths across a transport network. Our proposal also makes a NUT1-like (nonpreemptible unprotected traffic) feature possible in UPSRs, which allows for efficient utilization of UPSR protection bandwidth. We achieve this by encoding UPSR-specific information in the open shortest-path-first (OSPF) link state advertisements and in signaling messages of the Resource Reservation Protocol (RSVP) with TE extensions. In addition, we modify the signaling and routing state machines at the nodes to interpret and process this information to perform UPSR topology discovery and path computation. The uniqueness of our proposals is that the algorithms and the rules specified here allow for existing IP-based protocols [such as those within the generalized MPLS (GMPLS) framework, which currently applies to mesh networks] to be efficiently adapted for this context while still achieving our objective of exploiting UPSR-protection capabilities.
Geoffrey F. Chew
2008-02-21
Arrowed-time divergence-free rules or cosmological quantum dynamics are formulated through stepped Feynman paths across macroscopic slices of Milne spacetime. Slice boundaries house totally-relativistic rays representing elementary entities--preons. Total relativity and the associated preon Fock space, despite distinction from special relativity (which lacks time arrow), are based on the Lorentz group. Each path is a set of cubic vertices connected by straight, directed and stepped arcs that carry inertial, electromagnetic and gravitational action. The action of an arc step comprises increments each bounded by Planck's constant. Action from extremely-distant sources is determined by universe mean energy density. Identifying the arc-step energy that determines inertial action with that determining gravitational action establishes both arc-step length and universe density. Special relativity is accurate for physics at laboratory spacetime scales far below that of Hubble and far above that of Planck.
Louis Fishman
2006-01-01
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
Studness, C.M.
1995-05-01
The financial community`s focus on utility competition has been riveted on the proceedings now in progress at state regulatory commissions. The fear that something immediately damaging will come out of these proceedings seems to have diminished in recent months, and the stock market has reacted favorably. However, regulatory developments are only one of four paths leading to competition; the others are the marketplace, the legislatures, and the courts. Each could play a critical role in the emergence of competition.
An analogue approach to the travelling salesman problem using an elastic net method
Richard Durbin; David Willshaw
1987-01-01
The travelling salesman problem1 is a classical problem in the field of combinatorial optimization, concerned with efficient methods for maximizing or minimizing a function of many independent variables. Given the positions of N cities, which in the simplest case lie in the plane, what is the shortest closed tour in which each city can be visited once? We describe how
Efficient Dissection of Composite Problems, with Applications to Cryptanalysis, Knapsacks, and
International Association for Cryptologic Research (IACR)
, to solve hard knapsack problems, and to find the shortest solution to a generalized version of Rubik's cube with a new type of algorithm called dissection, which has much better time/memory tradeoffs than previously known algorithms. A typical ex- ample is the problem of finding the key of multiple encryption schemes
Path Flow Estimation Using Time Varying Coefficient State Space Model
NASA Astrophysics Data System (ADS)
Jou, Yow-Jen; Lan, Chien-Lun
2009-08-01
The dynamic path flow information is very crucial in the field of transportation operation and management, i.e., dynamic traffic assignment, scheduling plan, and signal timing. Time-dependent path information, which is important in many aspects, is nearly impossible to be obtained. Consequently, researchers have been seeking estimation methods for deriving valuable path flow information from less expensive traffic data, primarily link traffic counts of surveillance systems. This investigation considers a path flow estimation problem involving the time varying coefficient state space model, Gibbs sampler, and Kalman filter. Numerical examples with part of a real network of the Taipei Mass Rapid Transit with real O-D matrices is demonstrated to address the accuracy of proposed model. Results of this study show that this time-varying coefficient state space model is very effective in the estimation of path flow compared to time-invariant model.
Computational path planner for product assembly in complex environments
NASA Astrophysics Data System (ADS)
Shang, Wei; Liu, Jianhua; Ning, Ruxin; Liu, Mi
2013-03-01
Assembly path planning is a crucial problem in assembly related design and manufacturing processes. Sampling based motion planning algorithms are used for computational assembly path planning. However, the performance of such algorithms may degrade much in environments with complex product structure, narrow passages or other challenging scenarios. A computational path planner for automatic assembly path planning in complex 3D environments is presented. The global planning process is divided into three phases based on the environment and specific algorithms are proposed and utilized in each phase to solve the challenging issues. A novel ray test based stochastic collision detection method is proposed to evaluate the intersection between two polyhedral objects. This method avoids fake collisions in conventional methods and degrades the geometric constraint when a part has to be removed with surface contact with other parts. A refined history based rapidly-exploring random tree (RRT) algorithm which bias the growth of the tree based on its planning history is proposed and employed in the planning phase where the path is simple but the space is highly constrained. A novel adaptive RRT algorithm is developed for the path planning problem with challenging scenarios and uncertain environment. With extending values assigned on each tree node and extending schemes applied, the tree can adapts its growth to explore complex environments more efficiently. Experiments on the key algorithms are carried out and comparisons are made between the conventional path planning algorithms and the presented ones. The comparing results show that based on the proposed algorithms, the path planner can compute assembly path in challenging complex environments more efficiently and with higher success. This research provides the references to the study of computational assembly path planning under complex environments.
NASA Technical Reports Server (NTRS)
Prabhakaran, Nagarajan; Rishe, Naphtali; Athauda, Rukshan
1997-01-01
The South East coastal region experiences hurricane threat for almost six months in every year. To improve the accuracy of hurricane forecasts, meteorologists would need the storm paths of both the present and the past. A hurricane path can be established if we could identify the correct position of the storm at different times right from its birth to the end. We propose a method based on both spatial and temporal image correlations to locate the position of a storm from satellite images. During the hurricane season, the satellite images of the Atlantic ocean near the equator are examined for the hurricane presence. This is accomplished in two steps. In the first step, only segments with more than a particular value of cloud cover are selected for analysis. Next, we apply image processing algorithms to test the presence of a hurricane eye in the segment. If the eye is found, the coordinate of the eye is recorded along with the time stamp of the segment. If the eye is not found, we examine adjacent segments for the existence of hurricane eye. It is probable that more than one hurricane eye could be found from different segments of the same period. Hence, the above process is repeated till the entire potential area for hurricane birth is exhausted. The subsequent/previous position of each hurricane eye will be searched in the appropriate adjacent segments of the next/previous period to mark the hurricane path. The temporal coherence and spatial coherence of the images are taken into account by our scheme in determining the segments and the associated periods required for analysis.
Quad-rotor flight path energy optimization
NASA Astrophysics Data System (ADS)
Kemper, Edward
Quad-Rotor unmanned areal vehicles (UAVs) have been a popular area of research and development in the last decade, especially with the advent of affordable microcontrollers like the MSP 430 and the Raspberry Pi. Path-Energy Optimization is an area that is well developed for linear systems. In this thesis, this idea of path-energy optimization is extended to the nonlinear model of the Quad-rotor UAV. The classical optimization technique is adapted to the nonlinear model that is derived for the problem at hand, coming up with a set of partial differential equations and boundary value conditions to solve these equations. Then, different techniques to implement energy optimization algorithms are tested using simulations in Python. First, a purely nonlinear approach is used. This method is shown to be computationally intensive, with no practical solution available in a reasonable amount of time. Second, heuristic techniques to minimize the energy of the flight path are tested, using Ziegler-Nichols' proportional integral derivative (PID) controller tuning technique. Finally, a brute force look-up table based PID controller is used. Simulation results of the heuristic method show that both reliable control of the system and path-energy optimization are achieved in a reasonable amount of time.
Covariant path integrals on hyperbolic surfaces
NASA Astrophysics Data System (ADS)
Schaefer, Joe
1997-11-01
DeWitt's covariant formulation of path integration [B. De Witt, "Dynamical theory in curved spaces. I. A review of the classical and quantum action principles," Rev. Mod. Phys. 29, 377-397 (1957)] has two practical advantages over the traditional methods of "lattice approximations;" there is no ordering problem, and classical symmetries are manifestly preserved at the quantum level. Applying the spectral theorem for unbounded self-adjoint operators, we provide a rigorous proof of the convergence of certain path integrals on Riemann surfaces of constant curvature -1. The Pauli-DeWitt curvature correction term arises, as in DeWitt's work. Introducing a Fuchsian group ? of the first kind, and a continuous, bounded, ?-automorphic potential V, we obtain a Feynman-Kac formula for the automorphic Schrdinger equation on the Riemann surface ?H. We analyze the Wick rotation and prove the strong convergence of the so-called Feynman maps [K. D. Elworthy, Path Integration on Manifolds, Mathematical Aspects of Superspace, edited by Seifert, Clarke, and Rosenblum (Reidel, Boston, 1983), pp. 47-90] on a dense set of states. Finally, we give a new proof of some results in C. Grosche and F. Steiner, "The path integral on the Poincare upper half plane and for Liouville quantum mechanics," Phys. Lett. A 123, 319-328 (1987).
Encoding folding paths of RNA switches
Xayaphoummine, A.; Viasnoff, V.; Harlepp, S.; Isambert, H.
2007-01-01
RNA co-transcriptional folding has long been suspected to play an active role in helping proper native folding of ribozymes and structured regulatory motifs in mRNA untranslated regions (UTRs). Yet, the underlying mechanisms and coding requirements for efficient co-transcriptional folding remain unclear. Traditional approaches have intrinsic limitations to dissect RNA folding paths, as they rely on sequence mutations or circular permutations that typically perturb both RNA folding paths and equilibrium structures. Here, we show that exploiting sequence symmetries instead of mutations can circumvent this problem by essentially decoupling folding paths from equilibrium structures of designed RNA sequences. Using bistable RNA switches with symmetrical helices conserved under sequence reversal, we demonstrate experimentally that native and transiently formed helices can guide efficient co-transcriptional folding into either long-lived structure of these RNA switches. Their folding path is controlled by the order of helix nucleations and subsequent exchanges during transcription, and may also be redirected by transient antisense interactions. Hence, transient intra- and inter-molecular base pair interactions can effectively regulate the folding of nascent RNA molecules into different native structures, provided limited coding requirements, as discussed from an information theory perspective. This constitutive coupling between RNA synthesis and RNA folding regulation may have enabled the early emergence of autonomous RNA-based regulation networks. PMID:17178750
NASA Technical Reports Server (NTRS)
Mehhtz, Peter
2005-01-01
JPF is an explicit state software model checker for Java bytecode. Today, JPF is a swiss army knife for all sort of runtime based verification purposes. This basically means JPF is a Java virtual machine that executes your program not just once (like a normal VM), but theoretically in all possible ways, checking for property violations like deadlocks or unhandled exceptions along all potential execution paths. If it finds an error, JPF reports the whole execution that leads to it. Unlike a normal debugger, JPF keeps track of every step how it got to the defect.
Bleakley, Hoyt; Lin, Jeffrey
2012-05-01
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
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.
Bleakley, Hoyt; Lin, Jeffrey
2012-01-01
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
Reaction Path Optimization with Holonomic Constraints and Kinetic Energy Potentials
Brokaw, Jason B.; Haas, Kevin R.; Chu, Jhih-wei
2009-08-11
Two methods are developed to enhance the stability, efficiency, and robustness of reaction path optimization using a chain of replicas. First, distances between replicas are kept equal during path optimization via holonomic constraints. Finding a reaction path is, thus, transformed into a constrained optimization problem. This approach avoids force projections for finding minimum energy paths (MEPs), and fast-converging schemes such as quasi-Newton methods can be readily applied. Second, we define a new objective function - the total Hamiltonian - for reaction path optimization, by combining the kinetic energy potential of each replica with its potential energy function. Minimizing the total Hamiltonian of a chain determines a minimum Hamiltonian path (MHP). If the distances between replicas are kept equal and a consistent force constant is used, then the kinetic energy potentials of all replicas have the same value. The MHP in this case is the most probable isokinetic path. Our results indicate that low-temperature kinetic energy potentials (<5 K) can be used to prevent the development of kinks during path optimization and can significantly reduce the required steps of minimization by 2-3 times without causing noticeable differences between a MHP and MEP. These methods are applied to three test cases, the C?eq-to-Cax isomerization of an alanine dipeptide, the ?C?- to-C? transition of an ?-D-glucopyranose, and the helix-to-sheet transition of a GNNQQNY heptapeptide. By applying the methods developed in this work, convergence of reaction path optimization can be achieved for these complex transitions, involving full atomic details and a large number of replicas (>100). For the case of helix-to-sheet transition, we identify pathways whose energy barriers are consistent with experimental measurements. Further, we develop a method based on the work energy theorem to quantify the accuracy of reaction paths and to determine whether the atoms used to define a path are enough to provide quantitative estimation of energy barriers.
AH Cam: A metal-rich RR Lyrae star with the shortest known Blazhko period
NASA Technical Reports Server (NTRS)
Smith, Horace A.; Matthews, Jaymie M.; Lee, Kevin M.; Williams, Jeffrey; Silbermann, N. A.; Bolte, Michael
1994-01-01
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.
Shortest Loops are Pacemakers in Random Networks of Electrically Coupled Axons
Vladimirov, Nikita; Tu, Yuhai; Traub, Roger D.
2012-01-01
High-frequency oscillations (HFOs) are an important part of brain activity in health and disease. However, their origins remain obscure and controversial. One possible mechanism depends on the presence of sparsely distributed gap junctions that electrically couple the axons of principal cells. A plexus of electrically coupled axons is modeled as a random network with bi-directional connections between its nodes. Under certain conditions the network can demonstrate one of two types of oscillatory activity. Type I oscillations (100200?Hz) are predicted to be caused by spontaneously spiking axons in a network with strong (high conductance) gap junctions. Type II oscillations (200300?Hz) require no spontaneous spiking and relatively weak (low-conductance) gap junctions, across which spike propagation failures occur. The type II oscillations are reentrant and self-sustained. Here we examine what determines the frequency of type II oscillations. Using simulations we show that the distribution of loop lengths is the key factor for determining frequency in type II network oscillations. We first analyze spike failure between two electrically coupled cells using a model of anatomically reconstructed CA1 pyramidal neuron. Then network oscillations are studied by a cellular automaton model with random network connectivity, in which we control loop statistics. We show that oscillation periods can be predicted from the networks loop statistics. The shortest loop, around which a spike can travel, is the most likely pacemaker candidate. The principle of one loop as a pacemaker is remarkable, because random networks contain a large number of loops juxtaposed and superimposed, and their number rapidly grows with network size. This principle allows us to predict the frequency of oscillations from network connectivity and visa versa. We finally propose that type I oscillations may correspond to ripples, while type II oscillations correspond to so-called fast ripples. PMID:22514532
Iwamoto, Takahiro; Slanina, Zdenek; Mizorogi, Naomi; Guo, Jingdong; Akasaka, Takeshi; Nagase, Shigeru; Takaya, Hikaru; Yasuda, Nobuhiro; Kato, Tatsuhisa; Yamago, Shigeru
2014-10-27
[11]Cycloparaphenylene ([11]CPP) selectively encapsulates La@C82 to form the shortest possible metallofullerene-carbon nanotube (CNT) peapod, La@C82 ?[11]CPP, in solution and in the solid state. Complexation in solution was affected by the polarity of the solvent and was 16?times stronger in the polar solvent nitrobenzene than in the nonpolar solvent 1,2-dichlorobenzene. Electrochemical analysis revealed that the redox potentials of La@C82 were negatively shifted upon complexation from free La@C82 . Furthermore, the shifts in the redox potentials increased with polarity of the solvent. These results are consistent with formation of a polar complex, (La@C82 )(?-) ?[11]CPP(?+) , by partial electron transfer from [11]CPP to La@C82 . This is the first observation of such an electronic interaction between a fullerene pea and CPP pod. Theoretical calculations also supported partial charge transfer (0.07) from [11]CPP to La@C82 . The structure of the complex was unambiguously determined by X-ray crystallographic analysis, which showed the La atom inside the C82 near the periphery of the [11]CPP. The dipole moment of La@C82 was projected toward the CPP pea, nearly perpendicular to the CPP axis. The position of the La atom and the direction of the dipole moment in La@C82 ?[11]CPP were significantly different from those observed in La@C82 ?CNT, thus indicating a difference in orientation of the fullerene peas between fullerene-CPP and fullerene-CNT peapods. These results highlight the importance of pea-pea interactions in determining the orientation of the metallofullerene in metallofullerene-CNT peapods. PMID:25224281
Counting Depth Zero Patterns in Ballot Paths
Niederhausen, Heinrich
Counting Depth Zero Patterns in Ballot Paths Heinrich Niederhausen and Shaun Sullivan Florida it to the enu- meration of certain lattice paths. The lattice paths we consider are ballot paths. A ballot path is a path that stays weakly above the diagonal y = x, starts at the origin, and takes steps from the set f
Deciding a Class of Path Formulas for ConflictFree Petri Nets \\Lambda
Wang, Bow-Yaw
Deciding a Class of Path Formulas for ConflictFree Petri Nets \\Lambda HsuChun Yen y BowYaw Wang results for problems concerning conflictfree Petri nets. To do so, we first define a class of formulas for paths in Petri nets. We then show that answering the satisfiability problem for conflict free Petri
Automatically Detecting Equivalent Mutants and Infeasible Paths \\Lambda A. Jefferson Offutt
Offutt, Jeff
Automatically Detecting Equivalent Mutants and Infeasible Paths \\Lambda A. Jefferson Offutt ISSE is a partial solution to the problem of automatically detecting equivalent mutant programs. Equivalent mutants equivalent mutants is a specific instance of a more general problem, commonly called the feasible path
A hybrid genetic algorithm for rescue path planning in uncertain adversarial environment
Jean Berger; Khaled Jabeur; Abdeslem Boukhtouta; Adel Guitouni; Ahmed Ghanmi
2010-01-01
Efficient vehicle path planning in hostile environment to carry out rescue or tactical logistic missions remains very challenging. Most approaches reported so far relies on key assumptions and heuristic procedures to reduce problem complexity. In this paper, a new model and a hybrid genetic algorithm are proposed to solve the rescue path planning problem for a single vehicle navigating in
Hardwick, R D
1989-01-01
The design and implementation of an Intrusion Path Analysis (IPA) function came about as a result of the upgrades to the security systems at the Savannah River Site (SRS), near Aiken, South Carolina. The stated requirements for IPA were broad, leaving opportunity for creative freedom during design and development. The essential elements were that it: be based on alarm and sensor state data; consider insider as well as outsider threats; be flexible and easily enabled or disabled; not be processor intensive; and provide information to the operator in the event the analysis reveals possible path openings. The final design resulted from many and varied conceptual inputs, and will be implemented in selected test areas at SRS. It fulfils the requirements and: allows selective inclusion of sensors in the analysis; permits the formation of concentric rings of protection around assets; permits the defining of the number of rings which must be breached before issuing an alert; evaluates current sensor states as well as a recent, configurable history of sensor states; considers the sensors' physical location, with respect to the concentric rings; and enables changes for maintenance without software recompilation. 3 figs.
NASA Technical Reports Server (NTRS)
2008-01-01
[figure removed for brevity, see original site] Click on the image for movie of Phoenix's Path to Mars
This artist's animation shows the route NASA's Phoenix Mars Lander took to get from Earth to Mars. The spacecraft's path is shown in yellow, and the orbits of Mars and Earth are shown in red and blue, respectively.
Phoenix was launched from Cape Canaveral Air Force Station, Fla., on Aug. 4, 2007, when Earth and Mars were 195 million kilometers (121 million miles) apart. It will have traveled a total of 679 million kilometers (422 million miles) when it is scheduled to reach Mars on May 25, 2008. At that time, Earth and Mars will be farther apart, at 276 million kilometers (171 million miles).
The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver
Path integrals on curved manifolds
NASA Astrophysics Data System (ADS)
Grosche, C.; Steiner, F.
1987-12-01
A general framework for treating path integrals on curved manifolds is presented. We also show how to perform general coordinate and space-time transformations in path integrals. The main result is that one has to subtract a quantum correction ?V h 2 from the classical Lagrangian ?, i.e. the correct effective Lagrangian to be used in the path integral is ?eff = ?- ?V. A general prescription for calculating the quantum correction ? V is given. It is based on a canonical approach using Weyl-ordering and the Hamiltonian path integral defined by the midpoint prescription. The general framework is illustrated by several examples: The d-dimensional rotator, i.e. the motion on the sphere S d-1, the path integral in d-dimensional polar coordinates, the exact treatment of the hydrogen atom in R 2 and R 3 by performing a Kustaanheimo-Stiefel transformation, the Langer transformation and the path integral for the Morse potential.
Iterative path attacks on networks
NASA Astrophysics Data System (ADS)
Pu, Cunlai; Li, Siyuan; Michaelson, Andrew; Yang, Jian
2015-08-01
We investigate a path-attack process on model networks and real-world networks. Based on the local topological structure of a path, we propose an attack centrality measure with a control parameter ? for quantifying the influence of a path. In the path-attack process, we iteratively remove the path with the largest attack centrality from a network. Results demonstrate that, for a specific network, there is an optimal ? which results in maximum attack efficiency. The denser and more homogeneous the networks, the more robust the networks are against iterative path attacks. Our work helps to explain the vulnerability of networks and provides some clues about the protection and design of real complex systems.
Integrated Flight Path Planning System and Flight Control System for Unmanned Helicopters
Jan, Shau Shiun; Lin, Yu Hsiang
2011-01-01
This paper focuses on the design of an integrated navigation and guidance system for unmanned helicopters. The integrated navigation system comprises two systems: the Flight Path Planning System (FPPS) and the Flight Control System (FCS). The FPPS finds the shortest flight path by the A-Star (A*) algorithm in an adaptive manner for different flight conditions, and the FPPS can add a forbidden zone to stop the unmanned helicopter from crossing over into dangerous areas. In this paper, the FPPS computation time is reduced by the multi-resolution scheme, and the flight path quality is improved by the path smoothing methods. Meanwhile, the FCS includes the fuzzy inference systems (FISs) based on the fuzzy logic. By using expert knowledge and experience to train the FIS, the controller can operate the unmanned helicopter without dynamic models. The integrated system of the FPPS and the FCS is aimed at providing navigation and guidance to the mission destination and it is implemented by coupling the flight simulation software, X-Plane, and the computing software, MATLAB. Simulations are performed and shown in real time three-dimensional animations. Finally, the integrated system is demonstrated to work successfully in controlling the unmanned helicopter to operate in various terrains of a digital elevation model (DEM). PMID:22164029
Hippocampal place cells connected by Hebbian synapses can solve spatial problems.
Muller, R U; Stead, M
1996-01-01
We propose that a cognitive map can be stored in the synapses between the pyramidal cells of CA3 in the form of the pattern of synaptic strengths connecting them. The model requires only that there are place cells in CA3 and that the connections between them are modifiable in a Hebbian manner. Given these suppositions, the synaptic strengths must evolve to represent the distance between firing centers of synaptically connected place cells. We argue that this arrangement of synaptic weights embodies all the formal properties of a map. We demonstrate that the information stored in such a structure is sufficient to solve several classic spatial problems including finding shortest paths, and negotiating detours. It is clear that much of the physiology and anatomy necessary to more precisely characterize the model is not known at this time. Nevertheless the model is robust under a variety of cell and connection densities. It also performs well under several different functions relating distance to synaptic strength. What is most remarkable in the model is that it is a logical consequence of the several key anatomical and physiological properties of the CA3 region of rats. Whether this information is used by the rat is difficult to assess at this time. Regardless of the outcome of this question, the model has promising applications to the field of robot navigation. PMID:9034857
Interactive cutting path analysis programs
NASA Technical Reports Server (NTRS)
Weiner, J. M.; Williams, D. S.; Colley, S. R.
1975-01-01
The operation of numerically controlled machine tools is interactively simulated. Four programs were developed to graphically display the cutting paths for a Monarch lathe, Cintimatic mill, Strippit sheet metal punch, and the wiring path for a Standard wire wrap machine. These programs are run on a IMLAC PDS-ID graphic display system under the DOS-3 disk operating system. The cutting path analysis programs accept input via both paper tape and disk file.
Handbook of Feynman Path Integrals
NASA Astrophysics Data System (ADS)
Grosche, Christian, Steiner, Frank
The Handbook of Feynman Path Integrals appears just fifty years after Richard Feynman published his pioneering paper in 1948 entitled "Space-Time Approach to Non-Relativistic Quantum Mechanics", in which he introduced his new formulation of quantum mechanics in terms of path integrals. The book presents for the first time a comprehensive table of Feynman path integrals together with an extensive list of references; it will serve the reader as a thorough introduction to the theory of path integrals. As a reference book, it is unique in its scope and will be essential for many physicists, chemists and mathematicians working in different areas of research.
Path Integration in Conical Space
Akira Inomata; Georg Junker
2011-11-24
Quantum mechanics in conical space is studied by the path integral method. It is shown that the curvature effect gives rise to an effective potential in the radial path integral. It is further shown that the radial path integral in conical space can be reduced to a form identical with that in flat space when the discrete angular momentum of each partial wave is replaced by a specific non-integral angular momentum. The effective potential is found proportional to the squared mean curvature of the conical surface embedded in Euclidean space. The path integral calculation is compatible with the Schr\\"odinger equation modified with the Gaussian and the mean curvature.
MultiPath TCP -Architecture MultiPath TCP -Receive-Buffer
Bonaventure, Olivier
MultiPath TCP - Architecture MultiPath TCP - Receive-Buffer MultiPath TCP - Congestion Control MultiPath TCP - Live-Demo MultiPath TCP: From Theory to Practice Sebastien Barre Christoph Paasch - Olivier Bonaventure MultiPath TCP: From Theory to Practice 1 / 17 #12;MultiPath TCP - Architecture Multi
NASA Technical Reports Server (NTRS)
Horton, Kent; Huffman, Mitch; Eppic, Brian; White, Harrison
2005-01-01
Path Loss Measurements were obtained on three (3) GPS equipped 757 aircraft. Systems measured were Marker Beacon, LOC, VOR, VHF (3), Glide Slope, ATC (2), DME (2), TCAS, and GPS. This data will provide the basis for assessing the EMI (Electromagnetic Interference) safety margins of comm/nav (communication and navigation) systems to portable electronic device emissions. These Portable Electronic Devices (PEDs) include all devices operated in or around the aircraft by crews, passengers, servicing personnel, as well as the general public in the airport terminals. EMI assessment capability is an important step in determining if one system-wide PED EMI policy is appropriate. This data may also be used comparatively with theoretical analysis and computer modeling data sponsored by NASA Langley Research Center and others.
Restoration by Path Concatenation: Fast Recovery of MPLS Paths
Bremler-Barr, Anat
Restoration by Path Concatenation: Fast Recovery of MPLS Paths Yehuda Afek Anat Bremler techniques in MPLS (multiprotocol label switching), to achieve powerful schemes for restoration in MPLS based networks. We thus transform MPLS into a flexible and robust method for forward ing packets
Restoration by Path Concatenation: Fast Recovery of MPLS Paths
Kaplan, Haim
Restoration by Path Concatenation: Fast Recovery of MPLS Paths Yehuda Afek Anat Bremler-Barr Haim techniques in MPLS (multi-protocol label switching), to achieve powerful schemes for restoration in MPLS based networks. We thus transform MPLS into a flexible and robust method for forward- ing packets
Finding Good Paths: Applications of Least Cost Caloric Path Computations
Wood, Zo J.
for crowds and individuals. 1 Introduction Humans have been traveling by foot for thousands of years and the task of finding good foot-paths to travel from point A to point B is something we all think about with disabilities, an individual planning out his or her path in a freeform race or even in arche- ology, to model
Decision paths in complex tasks
NASA Technical Reports Server (NTRS)
Galanter, Eugene
1991-01-01
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.
ERIC Educational Resources Information Center
Conway, Robert, Ed.; Izard, John, Ed.
Twelve papers produced at an annual convention were selected for inclusion in this work on behavior management and behavior change in Australian children and youth with emotional and/or behavior problems. The papers are: (1) Developing Personal Strengths, Choosing More Effective Behaviours: Control Theory, Reality Therapy and Quality Management
Approximating the Generalized Minimum Manhattan Network Problem
Kobourov, Stephen G.
Approximating the Generalized Minimum Manhattan Network Problem Aparna Das1 , Krzysztof Fleszar2urzburg, Germany Abstract. We consider the generalized minimum Manhattan network problem (GMMN). The input-length rectilinear network that connects every pair in R by a Manhattan path, that is, a path of axis-parallel line
Ji, Chuanyi
Abstract--We investigate network management information for light-path assessment to dynamically. INTRODUCTION Dynamically assessing the quality of light-paths is important to many applications in wavelength the light-path assessment as a decision problem, and define the performance as the probability
Optimal Path to a Laser Fusion Energy Power Plant
NASA Astrophysics Data System (ADS)
Bodner, Stephen
2013-10-01
There was a decision in the mid 1990s to attempt ignition using indirect-drive targets. It is now obvious that this decision was unjustified. The target design was too geometrically complex, too inefficient, and too far above plasma instability thresholds. By that same time, the mid 1990s, there had also been major advances in the direct-drive target concept. It also was not yet ready for a major test. Now, finally, because of significant advances in target designs, laser-target experiments, and laser development, the direct-drive fusion concept is ready for significant enhancements in funding, on the path to commercial fusion energy. There are two laser contenders. A KrF laser is attractive because of its shortest wavelength, broad bandwidth, and superb beam uniformity. A frequency-converted DPSSL has the disadvantage of inherently narrow bandwidth and longer wavelength, but by combining many beams in parallel one might be able to produce at the target the equivalent of an ultra-broad bandwidth. One or both of these lasers may also meet all of the engineering and economic requirements for a reactor. It is time to further develop and evaluate these two lasers as rep-rate systems, in preparation for a future high-gain fusion test.
Reasoning with Temporal Logic on Truncated Paths
Francalanza, Adrian
Reasoning with Temporal Logic on Truncated Paths Cindy Eisner1 Dana Fisman1,2 John Havlicek3 Yoad of reasoning with linear temporal logic on truncated paths. A truncated path is a path which is finite, but not necessarily maximal. Truncated paths arise naturally in several areas, among which are incomplete verification
Topological quantization by controlled paths: application to Cooper pairs pumps
Raphal Leone; Laurent Lvy
2007-11-05
When physical systems are tunable by three classical parameters, level degeneracies may occur at isolated points in parameter space. A topological singularity in the phase of the degenerate eigenvectors exists at these points. When a path encloses such point, the accumulated geometrical phase is sensitive to its presence. Furthermore, surfaces in parameter space enclosing such point can be used to characterize the eigenvector singularities through their Chern indices, which are integers. They can be used to quantize a physical quantity of interest. This quantity changes continuously during an adiabatic evolution along a path in parameter space. Quantization requires to turn this path into a surface with a well defined Chern index. We analyze the conditions necessary to a {\\em Topological Quantization by Controlled Paths}. It is applied to Cooper pair pumps. For more general problems, a set of four criteria are proposed to check if topological quantization is possible.
Topological quantization by controlled paths: application to Cooper pairs pumps
Leone, Raphal
2007-01-01
When physical systems are tunable by three classical parameters, level degeneracies may occur at isolated points in parameter space. A topological singularity in the phase of the degenerate eigenvectors exists at these points. When a path encloses such point, the accumulated geometrical phase is sensitive to its presence. Furthermore, surfaces in parameter space enclosing such point can be used to characterize the eigenvector singularities through their Chern indices, which are integers. They can be used to quantize a physical quantity of interest. This quantity changes continuously during an adiabatic evolution along a path in parameter space. Quantization requires to turn this path into a surface with a well defined Chern index. We analyze the conditions necessary to a {\\em Topological Quantization by Controlled Paths}. It is applied to Cooper pair pumps. For more general problems, a set of four criteria are proposed to check if topological quantization is possible.
Topological quantization by controlled paths: Application to Cooper pairs pumps
NASA Astrophysics Data System (ADS)
Leone, Raphael; Lvy, Laurent
2008-02-01
When physical systems are tunable by three classical parameters, level degeneracies may occur at isolated points in parameter space. A topological singularity in the phase of the degenerate eigenvectors exists at these points. When a path encloses such point, the accumulated geometrical phase is sensitive to its presence. Furthermore, surfaces in parameter space enclosing such point can be used to characterize the eigenvector singularities through their Chern indices, which are integers. They can be used to quantize a physical quantity of interest. This quantity changes continuously during an adiabatic evolution along a path in parameter space. Quantization requires to turn this path into a surface with a well defined Chern index. We analyze the conditions necessary to a topological quantization by controlled paths. It is applied to Cooper pair pumps. For more general problems, a set of four criteria is proposed to check if topological quantization is possible.
PCB Drill Path Optimization by Combinatorial Cuckoo Search Algorithm
Lim, Wei Chen Esmonde; Kanagaraj, G.; Ponnambalam, S. G.
2014-01-01
Optimization of drill path can lead to significant reduction in machining time which directly improves productivity of manufacturing systems. In a batch production of a large number of items to be drilled such as printed circuit boards (PCB), the travel time of the drilling device is a significant portion of the overall manufacturing process. To increase PCB manufacturing productivity and to reduce production costs, a good option is to minimize the drill path route using an optimization algorithm. This paper reports a combinatorial cuckoo search algorithm for solving drill path optimization problem. The performance of the proposed algorithm is tested and verified with three case studies from the literature. The computational experience conducted in this research indicates that the proposed algorithm is capable of efficiently finding the optimal path for PCB holes drilling process. PMID:24707198
PCB drill path optimization by combinatorial cuckoo search algorithm.
Lim, Wei Chen Esmonde; Kanagaraj, G; Ponnambalam, S G
2014-01-01
Optimization of drill path can lead to significant reduction in machining time which directly improves productivity of manufacturing systems. In a batch production of a large number of items to be drilled such as printed circuit boards (PCB), the travel time of the drilling device is a significant portion of the overall manufacturing process. To increase PCB manufacturing productivity and to reduce production costs, a good option is to minimize the drill path route using an optimization algorithm. This paper reports a combinatorial cuckoo search algorithm for solving drill path optimization problem. The performance of the proposed algorithm is tested and verified with three case studies from the literature. The computational experience conducted in this research indicates that the proposed algorithm is capable of efficiently finding the optimal path for PCB holes drilling process. PMID:24707198
Mobile transporter path planning using a genetic algorithm approach
NASA Technical Reports Server (NTRS)
Baffes, Paul; Wang, Lui
1988-01-01
The use of an optimization technique known as a genetic algorithm for solving the mobile transporter path planning problem is investigated. The mobile transporter is a traveling robotic vehicle proposed for the Space Station which must be able to reach any point of the structure autonomously. Specific elements of the genetic algorithm are explored in both a theoretical and experimental sense. Recent developments in genetic algorithm theory are shown to be particularly effective in a path planning problem domain, though problem areas can be cited which require more research. However, trajectory planning problems are common in space systems and the genetic algorithm provides an attractive alternative to the classical techniques used to solve these problems.
Reconfigurable data path processor
NASA Technical Reports Server (NTRS)
Donohoe, Gregory (Inventor)
2005-01-01
A reconfigurable data path processor comprises a plurality of independent processing elements. Each of the processing elements advantageously comprising an identical architecture. Each processing element comprises a plurality of data processing means for generating a potential output. Each processor is also capable of through-putting an input as a potential output with little or no processing. Each processing element comprises a conditional multiplexer having a first conditional multiplexer input, a second conditional multiplexer input and a conditional multiplexer output. A first potential output value is transmitted to the first conditional multiplexer input, and a second potential output value is transmitted to the second conditional multiplexer output. The conditional multiplexer couples either the first conditional multiplexer input or the second conditional multiplexer input to the conditional multiplexer output, according to an output control command. The output control command is generated by processing a set of arithmetic status-bits through a logical mask. The conditional multiplexer output is coupled to a first processing element output. A first set of arithmetic bits are generated according to the processing of the first processable value. A second set of arithmetic bits may be generated from a second processing operation. The selection of the arithmetic status-bits is performed by an arithmetic-status bit multiplexer selects the desired set of arithmetic status bits from among the first and second set of arithmetic status bits. The conditional multiplexer evaluates the select arithmetic status bits according to logical mask defining an algorithm for evaluating the arithmetic status bits.
A Bat Algorithm with Mutation for UCAV Path Planning
Wang, Gaige; Guo, Lihong; Duan, Hong; Liu, Luo; Wang, Heqi
2012-01-01
Path planning for uninhabited combat air vehicle (UCAV) is a complicated high dimension optimization problem, which mainly centralizes on optimizing the flight route considering the different kinds of constrains under complicated battle field environments. Original bat algorithm (BA) is used to solve the UCAV path planning problem. Furthermore, a new bat algorithm with mutation (BAM) is proposed to solve the UCAV path planning problem, and a modification is applied to mutate between bats during the process of the new solutions updating. Then, the UCAV can find the safe path by connecting the chosen nodes of the coordinates while avoiding the threat areas and costing minimum fuel. This new approach can accelerate the global convergence speed while preserving the strong robustness of the basic BA. The realization procedure for original BA and this improved metaheuristic approach BAM is also presented. To prove the performance of this proposed metaheuristic method, BAM is compared with BA and other population-based optimization methods, such as ACO, BBO, DE, ES, GA, PBIL, PSO, and SGA. The experiment shows that the proposed approach is more effective and feasible in UCAV path planning than the other models. PMID:23365518
A bat algorithm with mutation for UCAV path planning.
Wang, Gaige; Guo, Lihong; Duan, Hong; Liu, Luo; Wang, Heqi
2012-01-01
Path planning for uninhabited combat air vehicle (UCAV) is a complicated high dimension optimization problem, which mainly centralizes on optimizing the flight route considering the different kinds of constrains under complicated battle field environments. Original bat algorithm (BA) is used to solve the UCAV path planning problem. Furthermore, a new bat algorithm with mutation (BAM) is proposed to solve the UCAV path planning problem, and a modification is applied to mutate between bats during the process of the new solutions updating. Then, the UCAV can find the safe path by connecting the chosen nodes of the coordinates while avoiding the threat areas and costing minimum fuel. This new approach can accelerate the global convergence speed while preserving the strong robustness of the basic BA. The realization procedure for original BA and this improved metaheuristic approach BAM is also presented. To prove the performance of this proposed metaheuristic method, BAM is compared with BA and other population-based optimization methods, such as ACO, BBO, DE, ES, GA, PBIL, PSO, and SGA. The experiment shows that the proposed approach is more effective and feasible in UCAV path planning than the other models. PMID:23365518
K. J. Kyriakopoulos; G. N. Saridis
1988-01-01
A simple method of trajectory generation of robot manipulators is presented. It is based on an optimal control problem formulation. The jerk, the third derivative of position, of the desired trajectory, adversely affect the efficiency of the control algorithms and therefore should be minimized. assuming joint position, velocity and acceleration to be constrained, a cost criterion containing jerk is considered.
NASA Astrophysics Data System (ADS)
Sasada, Mahito; Uemura, Makoto; Arai, Akira; Fukazawa, Yasushi; Kawabata, Koji S.; Ohsugi, Takashi; Yamashita, Takuya; Isogai, Mizuki; Sato, Shuji; Kino, Masaru
2008-12-01
We present the results of near-infrared and optical observations of the BL Lac object S5 0716 + 714, carried out with the KANATA telescope. S5 0716 + 714 has both a long-term, high-amplitude variability and a short-term variability within one night. The shortest variability (microvariability) time-scale is important for understanding the geometry of jets and the magnetic field, because it provides a possible minimum size of variation sources. Here, we report on the detection of 15-min variability in S5 0716 + 714, which is one of the shortest time scales in optical and near-infrared variations observed in blazars. The detected microvariation had an amplitude of 0.061 0.005mag in the V band and a blue color of ? (V - J) = - 02025 0.011. Furthermore, we successfully detected an unprecedented, short time-scale polarimetric variation, which correlated with the brightness change. We revealed that the microvariation had a specific polarization component. The polarization degree of the variation component was higher than that of the total flux. These results suggest that the microvariability originated from a small and local region where the magnetic field was aligned.
Pon, Allison; Jewison, Timothy; Su, Yilu; Liang, Yongjie; Knox, Craig; Maciejewski, Adam; Wilson, Michael; Wishart, David S
2015-07-01
PathWhiz (http://smpdb.ca/pathwhiz) is a web server designed to create colourful, visually pleasing and biologically accurate pathway diagrams that are both machine-readable and interactive. As a web server, PathWhiz is accessible from almost any place and compatible with essentially any operating system. It also houses a public library of pathways and pathway components that can be easily viewed and expanded upon by its users. PathWhiz allows users to readily generate biologically complex pathways by using a specially designed drawing palette to quickly render metabolites (including automated structure generation), proteins (including quaternary structures, covalent modifications and cofactors), nucleic acids, membranes, subcellular structures, cells, tissues and organs. Both small-molecule and protein/gene pathways can be constructed by combining multiple pathway processes such as reactions, interactions, binding events and transport activities. PathWhiz's pathway replication and propagation functions allow for existing pathways to be used to create new pathways or for existing pathways to be automatically propagated across species. PathWhiz pathways can be saved in BioPAX, SBGN-ML and SBML data exchange formats, as well as PNG, PWML, HTML image map or SVG images that can be viewed offline or explored using PathWhiz's interactive viewer. PathWhiz has been used to generate over 700 pathway diagrams for a number of popular databases including HMDB, DrugBank and SMPDB. PMID:25934797
Practical and conceptual path sampling issues
NASA Astrophysics Data System (ADS)
Bolhuis, P. G.; Dellago, C.
2015-06-01
In the past 15 years transition path sampling (TPS) has evolved from its basic algorithm to an entire collection of methods and a framework for investigating rare events in complex systems. The methodology is applicable to a wide variety of systems and processes, ranging from transitions in small clusters or molecules to chemical reactions, phase transitions, and conformational changes in biomolecules. The basic idea of TPS is to harvest dynamical unbiased trajectories that connect a reactant with a product, by a Markov Chain Monte Carlo procedure called shooting. This simple importance sampling yields the rate constants, the free energy surface, insight in the mechanism of the rare event of interest, and by using the concept of the committor, also access to the reaction coordinate. In the last decade extensions to TPS have been developed, notably the transition interface sampling (TIS) methods, and its generalization multiple state TIS. Combination with advanced sampling methods such as replica exchange and the Wang-Landau algorithm, among others, improves sampling efficiency. Notwithstanding the success of TPS, there are issues left to discuss, and, despite the method's apparent simplicity, many pitfalls to avoid. This paper discusses several of these issues and pitfalls: the choice of stable states and interface order parameters, the problem of positioning the TPS windows and TIS interfaces, the matter of convergence of the path ensemble, the matter of kinetic traps, and the question whether TPS is able to investigate and sample Markov state models. We also review the reweighting technique used to join path ensembles. Finally we discuss the use of the sampled path ensemble to obtain reaction coordinates.
NASA Technical Reports Server (NTRS)
Chandler, J. A.
1983-01-01
Long helical vent path cools and releases hot pyrotechnical gas that exits along its spiraling threads. Current design uses 1/4-28 threads with outer diameter of stud reduced by 0.025 in. (0.62 mm). To open or close gassampler bottle, pyrotechnic charges on either one side or other of valve cylinder are actuated. Gases vented slowly over long path are cool enough to present no ignition hazard. Vent used to meter flow in refrigeration, pneumaticcontrol, and fluid-control systems by appropriately adjusting size and length of vent path.
NASA Astrophysics Data System (ADS)
Matvienko, G. G.; Oshlakov, V. K.; Stepanov, A. N.; Sukhanov, A. Ya
2015-02-01
We consider the algorithms that implement a broadband ('multiwave') radiative transfer with allowance for multiple (aerosol) scattering and absorption by main atmospheric gases. In the spectral range of 0.6 1 ?m, a closed numerical simulation of modifications of the supercontinuum component of a probing femtosecond pulse is performed. In the framework of the algorithms for solving the inverse atmospheric-optics problems with the help of a genetic algorithm, we give an interpretation of the experimental backscattered spectrum of the supercontinuum. An adequate reconstruction of the distribution mode for the particles of artificial aerosol with the narrow-modal distributions in a size range of 0.5 2 mm and a step of 0.5 mm is obtained.
Path Planning Algorithms for Autonomous Border Patrol Vehicles
NASA Astrophysics Data System (ADS)
Lau, George Tin Lam
This thesis presents an online path planning algorithm developed for unmanned vehicles in charge of autonomous border patrol. In this Pursuit-Evasion game, the unmanned vehicle is required to capture multiple trespassers on its own before any of them reach a target safe house where they are safe from capture. The problem formulation is based on Isaacs' Target Guarding problem, but extended to the case of multiple evaders. The proposed path planning method is based on Rapidly-exploring random trees (RRT) and is capable of producing trajectories within several seconds to capture 2 or 3 evaders. Simulations are carried out to demonstrate that the resulting trajectories approach the optimal solution produced by a nonlinear programming-based numerical optimal control solver. Experiments are also conducted on unmanned ground vehicles to show the feasibility of implementing the proposed online path planning algorithm on physical applications.
FINDING TWO DISJOINT PATHS IN A NETWORK WITH NORMALIZED -MIN-SUM OBJECTIVE FUNCTION
Lu, Enyue "Annie"
FINDING TWO DISJOINT PATHS IN A NETWORK WITH NORMALIZED -MIN-SUM OBJECTIVE FUNCTION Bing Yang consider the problem of finding two disjoint paths (0) and (21 from & to ' such that 3547698@'BACD(E)F$HGPIQ3D47698@'BACD(!1R$ with 3D47698@'BACD(E)F$TS 354R698U'BAV5(%W@$ is minimized. The paths may be node
On the scalability of network management information for inter-domain light-path assessment
Guanglei Liu; Chuanyi Ji; Vincent W. S. Chan
2005-01-01
We investigate the necessary amount of network management information for light-path assessment to dynamically set up end-to-end light-paths across administrative domains in optical networks. Our focus is on the scalability of partial management information. We pose light-path assessment as a decision problem, and define the performance as the Bayes probability of an erroneous decision. We then characterize the scalability of
Energy aware path planning in complex four dimensional environments
NASA Astrophysics Data System (ADS)
Chakrabarty, Anjan
This dissertation addresses the problem of energy-aware path planning for small autonomous vehicles. While small autonomous vehicles can perform missions that are too risky (or infeasible) for larger vehicles, the missions are limited by the amount of energy that can be carried on board the vehicle. Path planning techniques that either minimize energy consumption or exploit energy available in the environment can thus increase range and endurance. Path planning is complicated by significant spatial (and potentially temporal) variations in the environment. While the main focus is on autonomous aircraft, this research also addresses autonomous ground vehicles. Range and endurance of small unmanned aerial vehicles (UAVs) can be greatly improved by utilizing energy from the atmosphere. Wind can be exploited to minimize energy consumption of a small UAV. But wind, like any other atmospheric component , is a space and time varying phenomenon. To effectively use wind for long range missions, both exploration and exploitation of wind is critical. This research presents a kinematics based tree algorithm which efficiently handles the four dimensional (three spatial and time) path planning problem. The Kinematic Tree algorithm provides a sequence of waypoints, airspeeds, heading and bank angle commands for each segment of the path. The planner is shown to be resolution complete and computationally efficient. Global optimality of the cost function cannot be claimed, as energy is gained from the atmosphere, making the cost function inadmissible. However the Kinematic Tree is shown to be optimal up to resolution if the cost function is admissible. Simulation results show the efficacy of this planning method for a glider in complex real wind data. Simulation results verify that the planner is able to extract energy from the atmosphere enabling long range missions. The Kinematic Tree planning framework, developed to minimize energy consumption of UAVs, is applied for path planning in ground robots. In traditional path planning problem the focus is on obstacle avoidance and navigation. The optimal Kinematic Tree algorithm named Kinematic Tree* is shown to find optimal paths to reach the destination while avoiding obstacles. A more challenging path planning scenario arises for planning in complex terrain. This research shows how the Kinematic Tree* algorithm can be extended to find minimum energy paths for a ground vehicle in difficult mountainous terrain.
An Introduction to Path Analysis
ERIC Educational Resources Information Center
Wolfe, Lee M.
1977-01-01
The analytical procedure of path analysis is described in terms of its use in nonexperimental settings in the social sciences. The description assumes a moderate statistical background on the part of the reader. (JKS)
COMPUTER SCIENCE: MISCONCEPTIONS, CAREER PATHS
Hristidis, Vagelis
COMPUTER SCIENCE: MISCONCEPTIONS, CAREER PATHS AND RESEARCH CHALLENGES School of Computing Undergraduate Student) #12;Computer Science Misconceptions Intro to Computer Science - Florida International University 2 Some preconceived ideas & stereotypes about Computer Science (CS) are quite common
Yong Seung Cho; Soon-Tae Hong
2007-06-01
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.
The optimal flight path for airborne gravimetry
NASA Astrophysics Data System (ADS)
Bos, M. S.; Bastos, L.; Deurloo, R. A.
2007-12-01
The most important cost driver for any airborne gravimetry campaing is the flight time. Therefore, it is important to investigate the possiblies of designing a flight path that will minimize the needed time while at the same time ensuring that the research objectives are met. In our case, the objective is to derive the local geoid from observed gravity values. Unfortunately, only observations along the flight path can be made, leaving areas between the flight lines uncovered. When one tries to fit a surface function (such as spherical harmonics or a set of sines and cosines) to the observations, this function tends to produce spurious oscillations in these particular areas. The advantage of fitting spherical harmonics to gravity data is that once the Stokes coefficients are known, the geoid can be computed directly. To avoid the oscillation problem, one normally uses another approach called Least-Squares Collocation (LSC) to predict the most probable gravity values in the unobserved areas. Afterwards, the gravity values are converted into geoid undulations by applying the Stokes integral. A possible problem with this approach is that the spatial covariance function used could be incorrect for the surveyed area, producing an incorrect geoid. In practise, the accuracy of the obtained geoid is estimated by comparing the result at points where GPS and levelling values are available. Another validation approach is to use different programs to compute the geoid with the same observations and see if their results correspond. For both approaches (fitting of spatial functions to observations and the LSC/Stokes method) we will present a full propagation of errors that will help to predict the accuracy of the geoid before the observations have been made. Taking the Azores as a test case, we will use the instrumental noise observed during the AGMASCO campaign and state the required spacing between the flight paths.
The Path Less Travelled: Overcoming Tor's Bottlenecks with Traffic Splitting
Goldberg, Ian
The Path Less Travelled: Overcoming Tor's Bottlenecks with Traffic Splitting Mashael AlSabah, Kevin of Computer Science University of Waterloo Abstract. Tor is the most popular low-latency anonymity network, Tor has a variety of performance problems that result in poor quality of service, a strong
A Multi-Path Strategy for Hierarchical Ensemble Classification
Coenen, Frans
is investigated based on the idea of using Classification Association Rule Miners at individual nodesA Multi-Path Strategy for Hierarchical Ensemble Classification Esra'a Alshdaifat, Frans Coenen,coenen,dures}@liv.ac.uk. Abstract. A solution to the multi-class classification problem is pro- posed founded on the concept
Path-Sensitive Resource Analysis Compliant with Assertions
Jaffar, Joxan
Path-Sensitive Resource Analysis Compliant with Assertions Duc-Hiep Chu National University@comp.nus.edu.sg Abstract We consider the problem of bounding the worst-case resource us- age of programs, where assertions that under these conditions, enforcing assertions produces unsound results. The fundamental reason
Best Mitigation Paths To Effectively Reduce Earth's Orbital Debris
NASA Technical Reports Server (NTRS)
Wiegman, Bruce M.
2009-01-01
This slide presentation reviews some ways to reduce the problem posed by debris in orbit around the Earth. It reviews the orbital debris environment, the near-term needs to minimize the Kessler syndrome, also known as collisional cascading, a survey of active orbital debris mitigation strategies, the best paths to actively remove orbital debris, and technologies that are required for active debris mitigation.
Path Planning in Dynamic Environments Roman Smierzchalski1
Michalewicz, Zbigniew
planning problem for mobile robots is typically formulated as follows: given a robot and a description on dealing with uncertainties when the robot traverses the environment. On-line planning is also referred is typically formulated as follows [19]: given a robot and a description of an environment, plan a path
Time-Optimal Control of Robotic Manipulators Along Specified Paths
J. E. Bobrow; S. Dubowsky; J. S. Gibson
1985-01-01
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
PATH FOLLOWING CONTROL FOR A MOBILE ROBOT PUSHING A BALL
Zell, Andreas
with some flexible manipulators, the robot could grip the object, pick it up and place it at the idealPATH FOLLOWING CONTROL FOR A MOBILE ROBOT PUSHING A BALL Xiang Li, Andreas Zell Wilhelm}@informatik.uni-tuebingen.de Abstract: This paper focuses on the control problem of a mobile robot pushing a ball. In order to drive
Chain Based Path Formation in Swarms of Robots
Libre de Bruxelles, Universit
Chain Based Path Formation in Swarms of Robots Shervin Nouyan and Marco Dorigo IRIDIA, Co analyse a previously introduced swarm intel- ligence control mechanism used for solving problems of robot related to dynamic environments and multiple robots. In swarm robotics, the goal is to emphasize
ANALYTICAL SYNTHESIS LEAST CURVATURE PATHS FOR UNDERWATER APPLICATIONS
Zimmer, Uwe
holonomic vehicles concerned with generation algorithms. problem smooth least curvature 3D planning is addressed a variational approach general 3D EulerPoisson equation derived. solution calculated as the projection general as proportional elastic ergy of curve. Due to sought plane path sometimes called least energy curve literature
Seismic refraction analysis: the path forward
Haines, Seth S.; Zelt, Colin; Doll, William
2012-01-01
Seismic Refraction Methods: Unleashing the Potential and Understanding the Limitations; Tucson, Arizona, 29 March 2012 A workshop focused on seismic refraction methods took place on 29 May 2012, associated with the 2012 Symposium on the Application of Geophysics to Engineering and Environmental Problems. This workshop was convened to assess the current state of the science and discuss paths forward, with a primary focus on near-surface problems but with an eye on all applications. The agenda included talks on these topics from a number of experts interspersed with discussion and a dedicated discussion period to finish the day. Discussion proved lively at times, and workshop participants delved into many topics central to seismic refraction work.
Kitching, T D
2015-01-01
Here we present a Bayesian formalism for the goodness-of-fit that is the evidence for a fixed functional form over the evidence for all functions that are a general perturbation about this form. This is done under the assumption that the statistical properties of the data can be modelled by a multivariate Gaussian distribution. We use this to show how one can optimise an experiment to find evidence for a fixed function over perturbations about this function. We apply this formalism to an illustrative problem of measuring perturbations in the dark energy equation of state about a cosmological constant.
NASA Astrophysics Data System (ADS)
Kitching, T. D.; Taylor, A. N.
2015-09-01
Here we present a Bayesian formalism for the goodness of fit that is the evidence for a fixed functional form over the evidence for all functions that are a general perturbation about this form. This is done under the assumption that the statistical properties of the data can be modelled by a multivariate Gaussian distribution. We use this to show how one can optimize an experiment to find evidence for a fixed function over perturbations about this function. We apply this formalism to an illustrative problem of measuring perturbations in the dark energy equation of state about a cosmological constant.
Maximum distributions of bridges of noncolliding Brownian paths
NASA Astrophysics Data System (ADS)
Kobayashi, Naoki; Izumi, Minami; Katori, Makoto
2008-11-01
One-dimensional Brownian motion starting from the origin at time t=0 , conditioned to return to the origin at time t=1 and to stay positive during time interval 0
A Theory of Refractive and Specular 3D Shape by Light-Path Triangulation
Toronto, University of
A Theory of Refractive and Specular 3D Shape by Light-Path Triangulation KIRIAKOS N. KUTULAKOS-shaped specular scene (refractive or mirror-like) from one or more viewpoints. By reducing shape recovery to the problem of reconstructing individual 3D light paths that cross the image plane, we obtain three key
Coordinated Path Planning for Multiple Robots Petr Svestka, Mark H. Overmars
Utrecht, Universiteit
more than 3 robots. The approach is a flexible one,Coordinated Path Planning for Multiple Robots Petr Ÿ Svestka, Mark H. Overmars Department@cs.ruu.nl, markov@cs.ruu.nl Abstract We present a new approach to the multirobot path planning problem, where
Bloom Filter-based XML Packets Filtering for Millions of Path Queries
Xueqing Gong; Ying Yan; Weining Qian; Aoying Zhou
2005-01-01
The filtering of XML data is the basis of many complex applications. Lots of algorithms have been proposed to solve this problem(2, 3, 5, 6, 7, 8, 9, 11, 12, 13, 18). One important challenge is that the number of path queries is huge. It is necessary to take an efficient data structure rep- resenting path queries. Another challenge is
Lookahead Pathology in Real-Time Path-Finding Mitja Lustrek (mitja.lustrek@ijs.si)
Lu?trek, Mitja
Lookahead Pathology in Real-Time Path-Finding Mitja Lustrek (mitja.lustrek@ijs.si) Jozef Stefan to produce better actions Sometimes the opposite is true: pathology Setting Path-finding in grid world of pathology: number of lookahead depths where error is larger than at the previous depth 1,000 problems (map
Lookahead Pathology in Real-Time Path-Finding Vadim Bulitko (bulitko@ualberta.ca)
Lu?trek, Mitja
Lookahead Pathology in Real-Time Path-Finding Vadim Bulitko (bulitko@ualberta.ca) University to produce better actions Sometimes the opposite is true: pathology Setting Path-finding in grid world of pathology: number of lookahead depths where error is larger than at the previous depth 1,000 problems (map
Paths for Z_k parafermionic models
P. Jacob; P. Mathieu
2007-07-03
We present a simple bijection between restricted (Bressoud) lattice paths and RSOS paths in regime II. Both types of paths describe states in Z_k parafermionic irreducible modules. The bijection implies a direct correspondence between a RSOS path and a parafermionic state in a quasi-particle basis.
Reactive Path Deformation for Nonholonomic Mobile Robots
Lamiraux, Florent
. A collision-free initial path being given for a robot, obstacles detected while following this path can make, [21] proposed a method that enables him to deform on line the path to be fol- lowed by the robot1 Reactive Path Deformation for Nonholonomic Mobile Robots F. Lamiraux, D. Bonnafous, and O
Arithmetic area for m planar Brownian paths
Jean Desbois; Stephane Ouvry
2012-02-04
We pursue the analysis made in [1] on the arithmetic area enclosed by m closed Brownian paths. We pay a particular attention to the random variable S{n1,n2, ...,n} (m) which is the arithmetic area of the set of points, also called winding sectors, enclosed n1 times by path 1, n2 times by path 2, ...,nm times by path m. Various results are obtained in the asymptotic limit m->infinity. A key observation is that, since the paths are independent, one can use in the m paths case the SLE information, valid in the 1-path case, on the 0-winding sectors arithmetic area.
Path Integral Invariance under Point Canonical Transformations
Jordan, A; Jordan, Andres; Libedinsky, Matias
1997-01-01
It is often stated in the literature on path integrals that naive changes of coordinates might in general give inequivalent theories. The discrepancy is presumably connected to subtleties in the discretization, to the stochastic nature of quantum paths, or to operator order ambiguities in the canonical quantization. Here we argue that in order to define a path integral one needs not only a Lagrangian but also a set of paths that join succesive points in the discretized paths. If the set of paths is maintained when performing a point canonical transformation the path integral does not change. We explicitly show this with the calculation of the free particle kernel in polar coordinates.
Path-integral derivation of the nonrelativistic scale anomaly
NASA Astrophysics Data System (ADS)
Lin, Chris L.; Ordez, Carlos R.
2015-04-01
In this paper we calculate the scale anomaly for a quantum field theoretic 2D-nonrelativistic Bose gas with contact interactions using Fujikawa's method, both in vacuum and in many-body systems. The use of path integrals for these problems is novel and motivated by a recently developed path-integral framework for addressing questions about scaling in these systems. A natural class of regulators is found that produces the correct value of the anomaly traditionally calculated via other methods, e.g., diagrammatically via the ? function.
Relationship between total quality management, critical paths, and outcomes management.
Lynn, P A
1996-09-01
Total quality management (TQM), clinical paths, and outcomes management are high-profile strategies in today's health care environment. Each strategy is distinct, yet there are interrelationships among them. TQM supports a customer-focused organizational culture, providing tools and techniques to identify and solve problems. Clinical paths are tools for enhancing patient care coordination and for identifying system-wide and patient population specific issues. Outcomes management is an integrated system for measuring the results in patient populations over time. There is a recent shift in outcomes measurement towards expanding both the nature of the outcomes examined and the timeframes in which they are studied. PMID:8920370
Solving the Curriculum Sequencing Problem with DNA Computing Approach
ERIC Educational Resources Information Center
Debbah, Amina; Ben Ali, Yamina Mohamed
2014-01-01
In the e-learning systems, a learning path is known as a sequence of learning materials linked to each others to help learners achieving their learning goals. As it is impossible to have the same learning path that suits different learners, the Curriculum Sequencing problem (CS) consists of the generation of a personalized learning path for each
UAV PATH FOLLOWING FOR CONSTANT LINE-OF-SIGHT Rolf Rysdyk,
UAV PATH FOLLOWING FOR CONSTANT LINE-OF-SIGHT Rolf Rysdyk, University of Washington, Seattle, WA to a method to model `helmsman behavior'. The UAV control problem typically involves: air- speed, aerodynamic
Kulling, Karl Christian
2009-01-01
This thesis presents new algorithms for path planning in a communications constrained environment for teams of unmanned vehicles. This problem involves a lead vehicle that must gather information from a set of locations ...
Light transport on path-space manifolds
NASA Astrophysics Data System (ADS)
Jakob, Wenzel Alban
The pervasive use of computer-generated graphics in our society has led to strict demands on their visual realism. Generally, users of rendering software want their images to look, in various ways, "real", which has been a key driving force towards methods that are based on the physics of light transport. Until recently, industrial practice has relied on a different set of methods that had comparatively little rigorous grounding in physics---but within the last decade, advances in rendering methods and computing power have come together to create a sudden and dramatic shift, in which physics-based methods that were formerly thought impractical have become the standard tool. As a consequence, considerable attention is now devoted towards making these methods as robust as possible. In this context, robustness refers to an algorithm's ability to process arbitrary input without large increases of the rendering time or degradation of the output image. One particularly challenging aspect of robustness entails simulating the precise interaction of light with all the materials that comprise the input scene. This dissertation focuses on one specific group of materials that has fundamentally been the most important source of difficulties in this process. Specular materials, such as glass windows, mirrors or smooth coatings (e.g. on finished wood), account for a significant percentage of the objects that surround us every day. It is perhaps surprising, then, that it is not well-understood how they can be accommodated within the theoretical framework that underlies some of the most sophisticated rendering methods available today. Many of these methods operate using a theoretical framework known as path space integration. But this framework makes no provisions for specular materials: to date, it is not clear how to write down a path space integral involving something as simple as a piece of glass. Although implementations can in practice still render these materials by side-stepping limitations of the theory, they often suffer from unusably slow convergence; improvements to this situation have been hampered by the lack of a thorough theoretical understanding. We address these problems by developing a new theory of path-space light transport which, for the first time, cleanly incorporates specular scattering into the standard framework. Most of the results obtained in the analysis of the ideally smooth case can also be generalized to rendering of glossy materials and volumetric scattering so that this dissertation also provides a powerful new set of tools for dealing with them. The basis of our approach is that each specular material interaction locally collapses the dimension of the space of light paths so that all relevant paths lie on a submanifold of path space. We analyze the high-dimensional differential geometry of this submanifold and use the resulting information to construct an algorithm that is able to "walk" around on it using a simple and efficient equation-solving iteration. This manifold walking algorithm then constitutes the key operation of a new type of Markov Chain Monte Carlo (MCMC) rendering method that computes lighting through very general families of paths that can involve arbitrary combinations of specular, near-specular, glossy, and diffuse surface interactions as well as isotropic or highly anisotropic volume scattering. We demonstrate our implementation on a range of challenging scenes and evaluate it against previous methods.
Orthogonal Scan Paths for Data Path Logic Robert B. Norwood* and Edward J. McCluskey
Stanford University
Orthogonal Scan Paths for Data Path Logic Robert B. Norwood* and Edward J. McCluskey Center Abstract We have implemented a synthesis-for-test algorithm to implement orthogonal scan paths in data path logic. Orthogonal scan paths [Avra 92] facilitate the sharing of the functional and the test logic
Improving accuracy and precision in estimating fractal dimension of animal movement paths.
Nams, Vilis O
2006-01-01
It is difficult to watch wild animals while they move, so often biologists analyse characteristics of animal movement paths. One common path characteristic used is tortuousity, measured using the fractal dimension (D). The typical method for estimating fractal D, the divider method, is biased and imprecise. The bias occurs because the path length is truncated. I present a method for minimising the truncation error. The imprecision occurs because sometimes the divider steps land inside the bends of curves, and sometimes they miss the curves. I present three methods for minimising this variation and test the methods with simulated correlated random walks. The traditional divider method significantly overestimates fractal D when paths are short and the range of spatial scales is narrow. The best method to overcome these problems consists of walking the dividers forwards and backwards along the path, and then estimating the path length remaining at the end of the last divider step. PMID:16823606
Path planning for mobile robots based on visibility graphs and A* algorithm
NASA Astrophysics Data System (ADS)
Contreras, Juan D.; Martnez S., Fernando; Martnez S., Fredy H.
2015-07-01
One of most worked issues in the last years in robotics has been the study of strategies to path planning for mobile robots in static and observable conditions. This is an open problem without pre-defined rules (non-heuristic), which needs to measure the state of the environment, finds useful information, and uses an algorithm to select the best path. This paper proposes a simple and efficient geometric path planning strategy supported in digital image processing. The image of the environment is processed in order to identify obstacles, and thus the free space for navigation. Then, using visibility graphs, the possible navigation paths guided by the vertices of obstacles are produced. Finally the A* algorithm is used to find a best possible path. The alternative proposed is evaluated by simulation on a large set of test environments, showing in all cases its ability to find a free collision plausible path.
Aircraft Engine Gas Path Diagnostic Methods: Public Benchmarking Results
NASA Technical Reports Server (NTRS)
Simon, Donald L.; Borguet, Sebastien; Leonard, Olivier; Zhang, Xiaodong (Frank)
2013-01-01
Recent technology reviews have identified the need for objective assessments of aircraft engine health management (EHM) technologies. To help address this issue, a gas path diagnostic benchmark problem has been created and made publicly available. This software tool, referred to as the Propulsion Diagnostic Method Evaluation Strategy (ProDiMES), has been constructed based on feedback provided by the aircraft EHM community. It provides a standard benchmark problem enabling users to develop, evaluate and compare diagnostic methods. This paper will present an overview of ProDiMES along with a description of four gas path diagnostic methods developed and applied to the problem. These methods, which include analytical and empirical diagnostic techniques, will be described and associated blind-test-case metric results will be presented and compared. Lessons learned along with recommendations for improving the public benchmarking processes will also be presented and discussed.
Benchmarking Gas Path Diagnostic Methods: A Public Approach
NASA Technical Reports Server (NTRS)
Simon, Donald L.; Bird, Jeff; Davison, Craig; Volponi, Al; Iverson, R. Eugene
2008-01-01
Recent technology reviews have identified the need for objective assessments of engine health management (EHM) technology. The need is two-fold: technology developers require relevant data and problems to design and validate new algorithms and techniques while engine system integrators and operators need practical tools to direct development and then evaluate the effectiveness of proposed solutions. This paper presents a publicly available gas path diagnostic benchmark problem that has been developed by the Propulsion and Power Systems Panel of The Technical Cooperation Program (TTCP) to help address these needs. The problem is coded in MATLAB (The MathWorks, Inc.) and coupled with a non-linear turbofan engine simulation to produce "snap-shot" measurements, with relevant noise levels, as if collected from a fleet of engines over their lifetime of use. Each engine within the fleet will experience unique operating and deterioration profiles, and may encounter randomly occurring relevant gas path faults including sensor, actuator and component faults. The challenge to the EHM community is to develop gas path diagnostic algorithms to reliably perform fault detection and isolation. An example solution to the benchmark problem is provided along with associated evaluation metrics. A plan is presented to disseminate this benchmark problem to the engine health management technical community and invite technology solutions.
Three-dimension path planning for UCAV using hybrid meta-heuristic ACO-DE algorithm
Haibin Duan; Yaxiang Yu; Xiangyin Zhang; Shan Shao
2010-01-01
Three-dimension path planning of uninhabited combat air vehicle (UCAV) is a complicated optimal problem, which mainly focuses on optimizing the flight route considering the different types of constrains under complicated combating environments. A new hybrid meta-heuristic ant colony optimization (ACO) and differential evolution (DE) algorithm is proposed to solve the UCAV three-dimension path planning problem. DE is applied to optimize
Distortion-oriented welding path optimization based on elastic net method and genetic algorithm
H. Yang; H. Shao
2009-01-01
The optimization of welding path is one of the most combinatorial problems in robotic welding. This paper is focused on the optimization for both productivity and quality in robotic welding. The productivity related scheduling problem is similar to the well-known traveling salesman problem (TSP). An optimization strategy for TSP based on the elastic net method (ENM) and artificial neural network
Hierarchical path planning and control of a small fixed-wing UAV: Theory and experimental validation
NASA Astrophysics Data System (ADS)
Jung, Dongwon
2007-12-01
Recently there has been a tremendous growth of research emphasizing control of unmanned aerial vehicles (UAVs) either in isolation or in teams. As a matter of fact, UAVs increasingly find their way into military and law enforcement applications (e.g., reconnaissance, remote delivery of urgent equipment/material, resource assessment, environmental monitoring, battlefield monitoring, ordnance delivery, etc.). This trend will continue in the future, as UAVs are poised to replace the human-in-the-loop during dangerous missions. Civilian applications of UAVs are also envisioned such as crop dusting, geological surveying, search and rescue operations, etc. In this thesis we propose a new online multiresolution path planning algorithm for a small UAV with limited on-board computational resources. The proposed approach assumes that the UAV has detailed information of the environment and the obstacles only in its vicinity. Information about far-away obstacles is also available, albeit less accurately. The proposed algorithm uses the fast lifting wavelet transform (FLWT) to get a multiresolution cell decomposition of the environment, whose dimension is commensurate to the on-board computational resources. A topological graph representation of the multiresolution cell decomposition is constructed efficiently, directly from the approximation and detail wavelet coefficients. Dynamic path planning is sequentially executed for an optimal path using the A* algorithm over the resulting graph. The proposed path planning algorithm is implemented on-line on a small autopilot. Comparisons with the standard D*-lite algorithm are also presented. We also investigate the problem of generating a smooth, planar reference path from a discrete optimal path. Upon the optimal path being represented as a sequence of cells in square geometry, we derive a smooth B-spline path that is constrained inside a channel that is induced by the geometry of the cells. To this end, a constrained optimization problem is formulated by setting up geometric linear constraints as well as boundary conditions. Subsequently, we construct B-spline path templates by solving a set of distinct optimization problems. For application in UAV motion planning, the path templates are incorporated to replace parts of the entire path by the smooth B-spline paths. Each path segment is stitched together while preserving continuity to obtain a final smooth reference path to be used for path following control. The path following control for a small fixed-wing UAV to track the prescribed smooth reference path is also addressed. Assuming the UAV is equipped with an autopilot for low level control, we adopt a kinematic error model with respect to the moving Serret-Frenet frame attached to a path for tracking controller design. A kinematic path following control law that commands heading rate is presented. Backstepping is applied to derive the roll angle command by taking into account the approximate closed-loop roll dynamics. A parameter adaptation technique is employed to account for the inaccurate time constant of the closed-loop roll dynamics during actual implementation. Finally, we implement the proposed hierarchical path control of a small UAV on the actual hardware platform, which is based on an 1/5 scale R/C model airframe (Decathlon) and the autopilot hardware and software. Based on the hardware-in-the-loop (HIL) simulation environment, the proposed hierarchical path control algorithm has been validated through on-line, real-time implementation on a small micro-controller. By a seamless integration of the control algorithms for path planning, path smoothing, and path following, it has been demonstrated that the UAV equipped with a small autopilot having limited computational resources manages to accomplish the path control objective to reach the goal while avoiding obstacles with minimal human intervention.
Multiple paths in complex tasks
NASA Technical Reports Server (NTRS)
Galanter, Eugene; Wiegand, Thomas; Mark, Gloria
1987-01-01
The relationship between utility judgments of subtask paths and the utility of the task as a whole was examined. The convergent validation procedure is based on the assumption that measurements of the same quantity done with different methods should covary. The utility measures of the subtasks were obtained during the performance of an aircraft flight controller navigation task. Analyses helped decide among various models of subtask utility combination, whether the utility ratings of subtask paths predict the whole tasks utility rating, and indirectly, whether judgmental models need to include the equivalent of cognitive noise.
Transport path optimization algorithm based on fuzzy integrated weights
NASA Astrophysics Data System (ADS)
Hou, Yuan-Da; Xu, Xiao-Hao
2014-11-01
Natural disasters cause significant damage to roads, making route selection a complicated logistical problem. To overcome this complexity, we present a method of using a trapezoidal fuzzy number to select the optimal transport path. Using the given trapezoidal fuzzy edge coefficients, we calculate a fuzzy integrated matrix, and incorporate the fuzzy multi-weights into fuzzy integrated weights. The optimal path is determined by taking two sets of vertices and transforming undiscovered vertices into discoverable ones. Our experimental results show that the model is highly accurate, and requires only a few measurement data to confirm the optimal path. The model provides an effective, feasible, and convenient method to obtain weights for different road sections, and can be applied to road planning in intelligent transportation systems.
The career path choices of veterinary radiologists.
Jelinski, Murray D; Silver, Tawni I
2015-01-01
Concerns of a shortage of board certified specialists willing to work in academia have shadowed the medical and veterinary communities for decades. As a result, a number of studies have been conducted to determine how to foster, attract, and retain specialists in academia. More recently, there has been a growing perception that it is difficult for academic institutions to hire board certified veterinary radiologists. The objective of this study was to describe the career paths (academia vs. private sector) of veterinary radiologists and to determine what factors influenced their career path decisions. A mixed mode cross-sectional survey was used to survey ACVR radiologists and residents-in-training, 48% (255/529) of which responded. There was a near unidirectional movement of radiologists from academia to the private sector: 45.7% (59/129) of the respondents who began their careers in academia had switched to the private sector while only 8% (7/88) had left the private sector for academia. If a shortage of academic radiologists exists, then perhaps the issue should be framed as a problem with retention vs. recruitment. The most influential factors in the decision to leave academia were remuneration (wages and benefits), lack of interest/enjoyment in research, geographical location, and family considerations. It is salient that average salaries increased by twofold after leaving academia for the private sector. PMID:24920350
Perceived Shrinkage of Motion Paths
ERIC Educational Resources Information Center
Sinico, Michele; Parovel, Giulia; Casco, Clara; Anstis, Stuart
2009-01-01
We show that human observers strongly underestimate a linear or circular trajectory that a luminous spot follows in the dark. At slow speeds, observers are relatively accurate, but, as the speed increases, the size of the path is progressively underestimated, by up to 35%. The underestimation imposes little memory load and does not require
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...
Horbez, Camille
2012-01-01
We prove that a collection of paths defined in the sphere model of outer space using a surgery process are uniform quasi-geodesics, provided they remain in some thick part of outer space. To do so, we relate the Lipschitz metric on outer space to a notion of intersection numbers.
Immigration: Rubio's path to presidency?
Fernandez, Eduardo
Immigration: Rubio's path to presidency? In media blitz retorting conservative critics, he aims Writer Of the four Democratic and four Republican senators who wrote the immigration reform proposal now, both in Congress and nationwide, need more convincing on immigration reform than Democrats. And Rubio
E J Janse van Rensburg; T Prellberg; A Rechnitzer
2007-06-28
Directed paths have been used extensively in the scientific literature as a model of a linear polymer. Such paths models in particular the conformational entropy of a linear polymer and the effects it has on the free energy. These directed models are simplified versions of the self-avoiding walk, but they do nevertheless give insight into the phase behaviour of a polymer, and also serve as a tool to study the effects of conformational degrees of freedom in the behaviour of a linear polymer. In this paper we examine a directed path model of a linear polymer in a confining geometry (a wedge). The main focus of our attention is $c_n$, the number of directed lattice paths of length $n$ steps which takes steps in the North-East and South-East directions and which is confined to the wedge $Y=\\pm X/p$, where $p$ is an integer. In this paper we examine the case $p=2$ in detail, and we determine the generating function using the iterated kernel method. We also examine the asymtotics of $c_n$. In particular, we show that $$ c_n = [0.67874...]\\times 2^{n-1}(1+(-1)^n) + O((4/3^{3/4})^{n+o(n)}) + o((4/3^{3/4})^n) $$ where we can determine the constant $0.67874...$ to arbitrary accuracy with little effort.
van Rensburg, E J J; Rechnitzer, A
2007-01-01
Directed paths have been used extensively in the scientific literature as a model of a linear polymer. Such paths models in particular the conformational entropy of a linear polymer and the effects it has on the free energy. These directed models are simplified versions of the self-avoiding walk, but they do nevertheless give insight into the phase behaviour of a polymer, and also serve as a tool to study the effects of conformational degrees of freedom in the behaviour of a linear polymer. In this paper we examine a directed path model of a linear polymer in a confining geometry (a wedge). The main focus of our attention is $c_n$, the number of directed lattice paths of length $n$ steps which takes steps in the North-East and South-East directions and which is confined to the wedge $Y=\\pm X/p$, where $p$ is an integer. In this paper we examine the case $p=2$ in detail, and we determine the generating function using the iterated kernel method. We also examine the asymtotics of $c_n$. In particular, we show th...
NASA Astrophysics Data System (ADS)
Apostolopoulos, John G.
2000-12-01
Video communication over lossy packet networks such as the Internet is hampered by limited bandwidth and packet loss. This paper presents a system for providing reliable video communication over these networks, where the system is composed of two subsystems: (1) multiple state video encoder/decoder and (2) a path diversity transmission system. Multiple state video coding combats the problem of error propagation at the decoder by coding the video into multiple independently decodable streams, each with its own prediction process and state. If one stream is lost the other streams can still be decoded to produce usable video, and furthermore, the correctly received streams provide bidirectional (previous and future) information that enables improved state recovery for the corrupted stream. This video coder is a form of multiple description coding (MDC), and its novelty lies in its use of information from the multiple streams to perform state recovery at the decoder. The path diversity transmission system explicitly sends different subsets of packets over different paths, as opposed to the default scenarios where the packets proceed along a single path, thereby enabling the end- to-end video application to effectively see an average path behavior. We refer to this as path diversity. Generally, seeing this average path behavior provides better performance than seeing the behavior of any individual random path. For example, the probability that all of the multiple paths are simultaneously congested is much less than the probability that a single path is congested. The resulting path diversity provides the multiple state video decoder with an appropriate virtual channel to assist in recovering from lost packets, and can also simplify system design, e.g. FEC design. We propose two architectures for achieving path diversity, and examine the effectiveness of path diversity in communicating video over a lossy packet network.
Sampling-based algorithms for optimal path planning problems
Karaman, Sertac
2012-01-01
Sampling-based motion planning received increasing attention during the last decade. In particular, some of the leading paradigms, such the Probabilistic RoadMap (PRM) and the Rapidly-exploring Random Tree (RRT) algorithms, ...
How to (path-) integrate by differentiating
NASA Astrophysics Data System (ADS)
Kempf, Achim; Jackson, David M.; Morales, Alejandro H.
2015-07-01
Path integrals are at the heart of quantum field theory. In spite of their covariance and seeming simplicity, they are hard to define and evaluate. In contrast, functional differentiation, as it is used, for example, in variational problems, is relatively straightforward. This has motivated the development of new techniques that allow one to express functional integration in terms of functional differentiation. In fact, the new techniques allow one to express integrals in general through differentiation. These techniques therefore add to the general toolbox for integration and for integral transforms such as the Fourier and Laplace transforms. Here, we review some of these results, we give simpler proofs and we add new results, for example, on expressing the Laplace transform and its inverse in terms of derivatives, results that may be of use in quantum field theory, e.g., in the context of heat traces.
Magnetohydrodynamics Using Path or Stream Functions
NASA Astrophysics Data System (ADS)
Naor, Yossi; Keshet, Uri
2015-09-01
Magnetization in highly conductive plasmas is ubiquitous to astronomical systems. Flows in such media can be described by three path functions {{{? }}}? , or, for a steady flow, by two stream functions {? }? and an additional field such as mass density ?, velocity v, or travel time {{? }}t. While typical analyses of a frozen magnetic field {\\boldsymbol{B}} are problem-specific and involve nonlocal gradients of the fluid element position {\\boldsymbol{x}}(t), we derive the general, local (in ? or ? space) solution {\\boldsymbol{B}}={(\\partial {\\boldsymbol{x}}/\\partial {{{? }}}? )}t{\\tilde{B}}? ? /\\tilde{? }, where Lagrangian constants denoted by a tilde are directly fixed at a boundary hypersurface \\tilde{H} on which {\\boldsymbol{B}} is known. For a steady flow, \\tilde{? }{\\boldsymbol{B}}/? ={(\\partial {\\boldsymbol{x}}/\\partial {? }? )}{{? }t}{\\tilde{B}}? +{\\boldsymbol{v}}{\\tilde{B}}3/\\tilde{v}; here the electric field {\\boldsymbol{E}}? ({\\tilde{B}}2{\\boldsymbol{\
Aircraft flight path angle display system
NASA Technical Reports Server (NTRS)
Lambregts, Antonius A. (Inventor)
1991-01-01
A display system for use in an aircraft control wheel steering system provides the pilot with a single, quickened flight path angle display to overcome poor handling qualities due to intrinsic flight path angle response lags, while avoiding multiple information display symbology. The control law for the flight path angle control system is designed such that the aircraft's actual flight path angle response lags the pilot's commanded flight path angle by a constant time lag .tau., independent of flight conditions. The synthesized display signal is produced as a predetermined function of the aircraft's actual flight path angle, the time lag .tau. and command inputs from the pilot's column.
Green, Jeremy Donald
1998-01-01
in complicated environments which require backtracking or directed search for a valid path. The specific safe travel requirements of the prototype AUV allow reduction of the path planning problem for the AUV to that of path planning for a point robot. An octree...
Robust Path Planning and Feedback Design Under Stochastic Uncertainty
NASA Technical Reports Server (NTRS)
Blackmore, Lars
2008-01-01
Autonomous vehicles require optimal path planning algorithms to achieve mission goals while avoiding obstacles and being robust to uncertainties. The uncertainties arise from exogenous disturbances, modeling errors, and sensor noise, which can be characterized via stochastic models. Previous work defined a notion of robustness in a stochastic setting by using the concept of chance constraints. This requires that mission constraint violation can occur with a probability less than a prescribed value.In this paper we describe a novel method for optimal chance constrained path planning with feedback design. The approach optimizes both the reference trajectory to be followed and the feedback controller used to reject uncertainty. Our method extends recent results in constrained control synthesis based on convex optimization to solve control problems with nonconvex constraints. This extension is essential for path planning problems, which inherently have nonconvex obstacle avoidance constraints. Unlike previous approaches to chance constrained path planning, the new approach optimizes the feedback gain as wellas the reference trajectory.The key idea is to couple a fast, nonconvex solver that does not take into account uncertainty, with existing robust approaches that apply only to convex feasible regions. By alternating between robust and nonrobust solutions, the new algorithm guarantees convergence to a global optimum. We apply the new method to an unmanned aircraft and show simulation results that demonstrate the efficacy of the approach.
Enzymatic reaction paths as determined by transition path sampling
NASA Astrophysics Data System (ADS)
Masterson, Jean Emily
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.
Extracting contours of oval-shaped objects by Hough transform and minimal path algorithms
NASA Astrophysics Data System (ADS)
Tleis, Mohamed; Verbeek, Fons J.
2014-04-01
Circular and oval-like objects are very common in cell and micro biology. These objects need to be analyzed, and to that end, digitized images from the microscope are used so as to come to an automated analysis pipeline. It is essential to detect all the objects in an image as well as to extract the exact contour of each individual object. In this manner it becomes possible to perform measurements on these objects, i.e. shape and texture features. Our measurement objective is achieved by probing contour detection through dynamic programming. In this paper we describe a method that uses Hough transform and two minimal path algorithms to detect contours of (ovoid-like) objects. These algorithms are based on an existing grey-weighted distance transform and a new algorithm to extract the circular shortest path in an image. The methods are tested on an artificial dataset of a 1000 images, with an F1-score of 0.972. In a case study with yeast cells, contours from our methods were compared with another solution using Pratt's figure of merit. Results indicate that our methods were more precise based on a comparison with a ground-truth dataset. As far as yeast cells are concerned, the segmentation and measurement results enable, in future work, to retrieve information from different developmental stages of the cell using complex features.
Succinct Indices for Path Minimum, with Applications to Path Reporting
Chan, Timothy M.
in O((m, n)) time, and occupies O(m) bits of space in addition to the space required for the input tree weights are within a query range. We achieve three different time/space tradeoffs for path reporting by designing (a) an O(n)-word structure with O(lg n + occ lg n) query time, where occ is the number of nodes
Cottage View Ct. Pedestrian/Bike Path
Kostic, Milivoje M.
51N Buses Only Miles Cottage View Ct. Pedestrian/Bike Path Commuter Students ( white circled lots Resources Barsema Hall NIU Convocation Center To NIU Broadcast Center via Bike Path NIU Center for the Study
Electron Inelastic-Mean-Free-Path Database
National Institute of Standards and Technology Data Gateway
SRD 71 NIST Electron Inelastic-Mean-Free-Path Database (PC database, no charge) This database provides values of electron inelastic mean free paths (IMFPs) for use in quantitative surface analyses by AES and XPS.
Model for Delay Faults Based upon Paths
Gordon L. Smith
1985-01-01
Delay testing of combinational logic in a clocked environment is analyzed. A model based upon paths is introduced for delay faults. Any path with a total delay exceeding the clock interval is called a \\
Working on interesting problems
NASA Astrophysics Data System (ADS)
Smith, Arfon M.
2015-01-01
BSc Chemistry, The University of Sheffield 2001... PhD Astrochemistry, The University of Nottingham 2006... Scientist at GitHub Inc. 2013.From the outside, the path an individual has taken from academia to industry is not an obvious one. In this session I'll (try and) explain how an interest in software, engineering and chasing interesting problems makes internet startup in San Francisco a great home.
Path perception during rotation: influence of instructions, depth range, and dot density
NASA Technical Reports Server (NTRS)
Li, Li; Warren, William H Jr
2004-01-01
How do observers perceive their direction of self-motion when traveling on a straight path while their eyes are rotating? Our previous findings suggest that information from retinal flow and extra-retinal information about eye movements are each sufficient to solve this problem for both perception and active control of self-motion [Vision Res. 40 (2000) 3873; Psych. Sci. 13 (2002) 485]. In this paper, using displays depicting translation with simulated eye rotation, we investigated how task variables such as instructions, depth range, and dot density influenced the visual system's reliance on retinal vs. extra-retinal information for path perception during rotation. We found that path errors were small when observers expected to travel on a straight path or with neutral instructions, but errors increased markedly when observers expected to travel on a curved path. Increasing depth range or dot density did not improve path judgments. We conclude that the expectation of the shape of an upcoming path can influence the interpretation of the ambiguous retinal flow. A large depth range and dense motion parallax are not essential for accurate path perception during rotation, but reference objects and a large field of view appear to improve path judgments.
Wada, Taeko; Koyama, Daisuke; Kikuchi, Jiro; Honda, Hiroaki; Furukawa, Yusuke
2015-06-11
Recent investigations indicate that epigenetic regulators act at the initial step of myeloid leukemogenesis by forming preleukemic hematopoietic stem cells (HSCs), which possess the increased self-renewal potential but retain multidifferentiation ability, and synergize with genetic abnormalities in later stages to develop full-blown acute myeloid leukemias. However, it is still unknown whether this theory is applicable to other malignancies. In this study, we demonstrate that lysine-specific demethylase 1 (LSD1) overexpression is a founder abnormality for the development of T-cell lymphoblastic leukemia/lymphoma (T-LBL) using LSD1 transgenic mice. LSD1 expression is tightly regulated via alternative splicing and transcriptional repression in HSCs and is altered in most leukemias, especially T-LBL. Overexpression of the shortest isoform of LSD1, which is specifically repressed in quiescent HSCs and demethylates histone H3K9 more efficiently than other isoforms, increases self-renewal potential via upregulation of the HoxA family but retains multidifferentiation ability with a skewed differentiation to T-cell lineages at transcriptome levels in HSCs. Transgenic mice overexpressing LSD1 in HSCs did not show obvious abnormalities but developed T-LBL at very high frequency after ?-irradiation. LSD1 overexpression appears to be the first hit in T-cell leukemogenesis and provides an insight into novel strategies for early diagnosis and effective treatment of the disease. PMID:25904247
Qian, S.-B.; Zhang, J.; Wang, J.-J.; Zhu, L.-Y.; Liu, L.; Zhao, E. G.; Li, L.-J.; He, J.-J., E-mail: qsb@ynao.ac.cn [Yunnan Observatories, Chinese Academy of Sciences (CAS), P.O. Box 110, 650011 Kunming (China)
2013-08-15
We discovered that the O-C curve of V753 Mon shows an upward parabolic change while undergoing a cyclic variation with a period of 13.5 yr. The upward parabolic change reveals a long-term period increase at a rate of P-dot = +7.8 x 10{sup -8} days yr{sup -1}. Photometric solutions determined using the Wilson-Devinney method confirm that V753 Mon is a semi-detached binary system where the slightly less massive, hotter component star is transferring mass to the more massive one. This is in agreement with the long-term increase of the orbital period. The increase of the orbital period, the mass ratio very close to unity, and the semi-detached configuration with a less massive lobe-filling component all suggest that V753 Mon is on a key evolutionary stage just after the evolutionary stage with the shortest period during mass transfer. The results in this paper will shed light on the formation of massive contact binaries and the evolution of binary stars. The cyclic oscillation in the O-C diagram indicates that V753 Mon may be a triple system containing an extremely cool stellar companion that may play an important role for the formation and evolution in the binary system.
Reynolds, Andy M; Dutta, Tushar K; Curtis, Rosane H C; Powers, Stephen J; Gaur, Hari S; Kerry, Brian R
2011-04-01
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
Reichard, M; Polacik, M; Sedlcek, O
2009-01-01
Intensive collection in southern Mozambique across and outside the potential range of Nothobranchius furzeri, the species with the shortest recorded life span among vertebrates used as a model in ageing research, revealed that, contrary to previous data, it is a widespread species. It occurs in small freshwater pools south of the Save River and north of the Incomati River, including basins of the Limpopo, Changane, Chefu, Mazimechopes and Vaneteze Rivers. During collection in February 2008 (the second part of the rainy season), populations were strongly female biased (mean, 28% of males across 19 populations), and there was a spatial pattern in female bias among metapopulations. Populations varied in the proportion of male colour morphs. Fourteen populations were composed exclusively of the red male phenotype, three populations of the yellow male phenotype and 12 populations were mixed. Overall, the red phenotype was more common, but there was strong geographical variation in morph proportion, with yellow males more abundant at the periphery and red male dominance in the centre of the range of N. furzeri in the Limpopo basin. Nothobranchius furzeri was sympatric with Nothobranchius orthonotus (35% of investigated pools) and Nothobranchius rachovii (27% of sites). Analysis of habitat use of N. furzeri is presented; N. furzeri was associated with pools containing a soft muddy substratum and turbid water. PMID:20735533
Measuring Continuous-Path Accuracies of Robots
NASA Technical Reports Server (NTRS)
Allison, T. A.; Arnold, G. A.
1986-01-01
Sensors yield data on deviation from predetermined path and speed. Accuracy and repeatability of continuous-path robot motion measured with new method. Determines ability of robot to maintain tool orientation. Used with any type of manipulator arm and with separate, coordinated part positioner. Noncontacting eddy-current sensors measure distance from tool to aluminum path plate as robot end effector moves tool at prescribed distance from plate. Flat, sloped, curved, and other shapes used for path plate.
Geodesics on path spaces and double category
Saikat Chatterjee
2015-09-16
Let $M$ be a Riemannian manifold and ${\\mathcal P}M$ be the space of all smooth paths on $M$. We describe geodesics on path space ${\\mathcal P}M$. Normal neighbourhood structure on ${\\mathcal P}M$ has been discussed. We identify paths on $M$ under "back-track" equivalence. Under this identification we show that if $M$ is complete, then geodesics on path space yield a double category.We gave a physical interpretation of this double category.
Path entanglement of surface plasmons
NASA Astrophysics Data System (ADS)
Fakonas, James S.; Mitskovets, Anna; Atwater, Harry A.
2015-02-01
Metals can sustain traveling electromagnetic waves at their surfaces supported by the collective oscillations of their free electrons in unison. Remarkably, classical electromagnetism captures the essential physics of these surface plasma waves using simple models with only macroscopic features, accounting for microscopic electronelectron and electronphonon interactions with a single, semi-empirical damping parameter. Nevertheless, in quantum theory these microscopic interactions could be important, as any substantial environmental interactions could decohere quantum superpositions of surface plasmons, the quanta of these waves. Here we report a measurement of path entanglement between surface plasmons with 95% contrast, confirming that a path-entangled state can indeed survive without measurable decoherence. Our measurement suggests that elastic scattering mechanisms of the type that might cause pure dephasing in plasmonic systems must be weak enough not to significantly perturb the state of the metal under the experimental conditions we investigated.
Spacetime path formalism: localized states
Ed Seidewitz
2010-11-14
This note is an addendum to quant-ph/0507115. In that paper, I present a formalism for relativistic quantum mechanics in which the spacetime paths of particles are considered fundamental, reproducing the standard results of the traditional formulation of relativistic quantum mechanics and quantum field theory. Now, it is well known that there are issues with the ability to localize the position of particles in the usual formulation of relativistic quantum mechanics. The present note shows how, in the spacetime path formalism, the natural representation of on-shell 3-momentum states is effectively a Foldy-Wouthuysen transformation of the traditional representation, addressing the localization issues of position states and, further, providing a straightforward non-relativistic limit.
Path integral Monte Carlo and the electron gas
NASA Astrophysics Data System (ADS)
Brown, Ethan W.
Path integral Monte Carlo is a proven method for accurately simulating quantum mechanical systems at finite-temperature. By stochastically sampling Feynman's path integral representation of the quantum many-body density matrix, path integral Monte Carlo includes non-perturbative effects like thermal fluctuations and particle correlations in a natural way. Over the past 30 years, path integral Monte Carlo has been successfully employed to study the low density electron gas, high-pressure hydrogen, and superfluid helium. For systems where the role of Fermi statistics is important, however, traditional path integral Monte Carlo simulations have an exponentially decreasing efficiency with decreased temperature and increased system size. In this thesis, we work towards improving this efficiency, both through approximate and exact methods, as specifically applied to the homogeneous electron gas. We begin with a brief overview of the current state of atomic simulations at finite-temperature before we delve into a pedagogical review of the path integral Monte Carlo method. We then spend some time discussing the one major issue preventing exact simulation of Fermi systems, the sign problem. Afterwards, we introduce a way to circumvent the sign problem in PIMC simulations through a fixed-node constraint. We then apply this method to the homogeneous electron gas at a large swatch of densities and temperatures in order to map out the warm-dense matter regime. The electron gas can be a representative model for a host of real systems, from simple medals to stellar interiors. However, its most common use is as input into density functional theory. To this end, we aim to build an accurate representation of the electron gas from the ground state to the classical limit and examine its use in finite-temperature density functional formulations. The latter half of this thesis focuses on possible routes beyond the fixed-node approximation. As a first step, we utilize the variational principle inherent in the path integral Monte Carlo method to optimize the nodal surface. By using a ansatz resembling a free particle density matrix, we make a unique connection between a nodal effective mass and the traditional effective mass of many-body quantum theory. We then propose and test several alternate nodal ansatzes and apply them to single atomic systems. Finally, we propose a method to tackle the sign problem head on, by leveraging the relatively simple structure of permutation space. Using this method, we find we can perform exact simulations this of the electron gas and 3He that were previously impossible.
Squeezed states and path integrals
NASA Technical Reports Server (NTRS)
Daubechies, Ingrid; Klauder, John R.
1992-01-01
The continuous-time regularization scheme for defining phase-space path integrals is briefly reviewed as a method to define a quantization procedure that is completely covariant under all smooth canonical coordinate transformations. As an illustration of this method, a limited set of transformations is discussed that have an image in the set of the usual squeezed states. It is noteworthy that even this limited set of transformations offers new possibilities for stationary phase approximations to quantum mechanical propagators.
Free Space Path Loss of UWB Communications
Pichaya Supanakoon; Sathit Aroonpraparat; Sathaporn Promwong; Jun-ichi Takada
Although the Friis' formula is widely used to calculate the free space path loss of narrowband communications, it is considered only single frequency. Therefore, it should be extended to calculate the free space path loss of ultra wideband (UWB) communications by considering the frequency bandwidth. In this paper, the free space path loss of UWB communications is studies. The Friis'
The area determined by underdiagonal lattice paths
Merlini, Donatella
The area determined by underdiagonal lattice paths Donatella Merlini, Renzo Sprugnoli, M. Cecilia of underdiagonal lattice paths and the main diagonal. This area is important because it is connected to the number of inversions in permutations and to the internal path length in various types of trees. We obtain
Powers of Hamiltonian Paths in Interval Graphs
Isaak, Garth
Powers of Hamiltonian Paths in Interval Graphs Garth Isaak* DEPARTMENT OF MATHEMATICS LEHIGH of a Hamiltonian path are sufficient for the class of interval graphs. The proof is based on showing that a greedy algorithm tests for the existence of Hamiltonian path powers in interval graphs. We will also discuss covers
Realistic Human Walking Paths David C. Brogan
Brogan, David
Realistic Human Walking Paths David C. Brogan Department of Computer Science University of Virginia are influenced by kinematic and dynami- cal constraints. A realistic model of human walking paths is an important model of path planning that extends previous models through its significant use of pedestrian
Chip layout optimization using critical path weighting
A. E. Dunlop; V. D. Agrawal; D. N. Deutsch; M. F. Jukl; P. Kozak; M. Wiesel
1984-01-01
A chip layout procedure for optimizing the performance of critical timing paths in a synchronous digital circuit is presented. The procedure uses the path analysis data produced by a static timing analysis program to generate weights for critical nets on clock and data paths. These weights are then used to bias automatic placement and routing in the layout program. This
Evaluation of the Learning Path Specification
ERIC Educational Resources Information Center
Janssen, Jose; Berlanga, Adriana J.; Koper, Rob
2011-01-01
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,
Adaptive Path Planner for Highly Dynamic Environments
Baltes, Jacky
://www.citr.auckland.ac.nz/~jacky Abstract. This paper describes adaptive path planning, a novel ap- proach to path planning for car a collision free path through a set of obstacles from an initial to a goal position. A simple example through objects moving. In fact, RoboCup features an active opponent that tries #12;2 to prevent a robot
Path optimization for oil probe
NASA Astrophysics Data System (ADS)
Smith, O'Neil; Rahmes, Mark; Blue, Mark; Peter, Adrian
2014-05-01
We discuss a robust method for optimal oil probe path planning inspired by medical imaging. Horizontal wells require three-dimensional steering made possible by the rotary steerable capabilities of the system, which allows the hole to intersect multiple target shale gas zones. Horizontal "legs" can be over a mile long; the longer the exposure length, the more oil and natural gas is drained and the faster it can flow. More oil and natural gas can be produced with fewer wells and less surface disturbance. Horizontal drilling can help producers tap oil and natural gas deposits under surface areas where a vertical well cannot be drilled, such as under developed or environmentally sensitive areas. Drilling creates well paths which have multiple twists and turns to try to hit multiple accumulations from a single well location. Our algorithm can be used to augment current state of the art methods. Our goal is to obtain a 3D path with nodes describing the optimal route to the destination. This algorithm works with BIG data and saves cost in planning for probe insertion. Our solution may be able to help increase the energy extracted vs. input energy.
Path integral solution for an angle-dependent anharmonic oscillator
S. Haouat
2012-04-04
We have given a straightforward method to solve the problem of noncentral anharmonic oscillator in three dimensions. The relative propagator is presented by means of path integrals in spherical coordinates. By making an adequate change of time we were able to separate the angular motion from the radial one. The relative propagator is then exactly calculated. The energy spectrum and the corresponding wave functions are obtained.
A path integral approach to data assimilation in stochastic nonlinear systems
NASA Astrophysics Data System (ADS)
Quinn, John C.
In this dissertation the problem of data assimilation in stochastic nonlinear systems is formulated using path integrals. Each path represents a time evolution of the model states, and the time independent model parameters. In the path integral, every possible path is integrated over with each path weighted by P(X?Y) ? exp[--A 0(X,Y)], where A0(X,Y ) is the action, which quantifies how likely it is that the given path X was actually realized in the experiment which produced the observed time series Y. The goal of data assimilation is to combine information from a measurement time series with a dynamical model to make statistical estimates or predictions of model states and parameters. Both the measurements and the dynamical model may be noisy, and this fact is incorporated by using a probabilistic formulation for P(X?Y), the posterior path distribution conditioned on the observed time series. With an expression for P(X?Y) it is possible to express expectation values, conditioned upon the observations, of any function of the path as a path integral over all possible paths. The path integrals can then be numerically approximated using a Markov chain Monte Carlo method such as the Metropolis method. This method is discussed and applied to two example systems: the Colpitts oscillator circuit, and the Lorenz 96 toy atmosphere model. By studying the characteristics of the action as a function of the path, properties of the data assimilation problem can be deduced. For instance, if the surface in path space defined by the action is rough with many local minima with similar values of action, then the data assimilation problem is not well-defined. If more observations are made which rule out regions of path space that were previously likely, then the surface may become smoother with a single minimum. By examining the shape of the action, the question of how many measurements are needed to fully reconstruct the model state can be answered. It is also important to examine the shape of the action in the vicinity of the global minimum to find the level of uncertainty in state and parameter estimates. These ideas are illustrated with the Lorenz 96 system as an example.
Limited-path-length entanglement percolation in quantum complex networks
Cuquet, Marti; Calsamiglia, John
2011-03-15
We study entanglement distribution in quantum complex networks where nodes are connected by bipartite entangled states. These networks are characterized by a complex structure, which dramatically affects how information is transmitted through them. For pure quantum state links, quantum networks exhibit a remarkable feature absent in classical networks: it is possible to effectively rewire the network by performing local operations on the nodes. We propose a family of such quantum operations that decrease the entanglement percolation threshold of the network and increase the size of the giant connected component. We provide analytic results for complex networks with an arbitrary (uncorrelated) degree distribution. These results are in good agreement with numerical simulations, which also show enhancement in correlated and real-world networks. The proposed quantum preprocessing strategies are not robust in the presence of noise. However, even when the links consist of (noisy) mixed-state links, one can send quantum information through a connecting path with a fidelity that decreases with the path length. In this noisy scenario, complex networks offer a clear advantage over regular lattices, namely, the fact that two arbitrary nodes can be connected through a relatively small number of steps, known as the small-world effect. We calculate the probability that two arbitrary nodes in the network can successfully communicate with a fidelity above a given threshold. This amounts to working out the classical problem of percolation with a limited path length. We find that this probability can be significant even for paths limited to few connections and that the results for standard (unlimited) percolation are soon recovered if the path length exceeds by a finite amount the average path length, which in complex networks generally scales logarithmically with the size of the network.
Path-following control of wheeled planetary exploration robots moving on deformable rough terrain.
Ding, Liang; Gao, Hai-bo; Deng, Zong-quan; Li, Zhijun; Xia, Ke-rui; Duan, Guang-ren
2014-01-01
The control of planetary rovers, which are high performance mobile robots that move on deformable rough terrain, is a challenging problem. Taking lateral skid into account, this paper presents a rough terrain model and nonholonomic kinematics model for planetary rovers. An approach is proposed in which the reference path is generated according to the planned path by combining look-ahead distance and path updating distance on the basis of the carrot following method. A path-following strategy for wheeled planetary exploration robots incorporating slip compensation is designed. Simulation results of a four-wheeled robot on deformable rough terrain verify that it can be controlled to follow a planned path with good precision, despite the fact that the wheels will obviously skid and slip. PMID:24790582
Paths to adolescent parenthood: implications for prevention.
Flick, L H
1986-01-01
Adolescent pregnancy and parenthood are increasingly common today and pose many problems for both the individual persons involved and society as a whole. For programs to address these issues successfully, factors associated with unintended pregnancy and resulting parenthood must first be identified and understood. This paper is a review of current research on the factors associated with the four steps leading to an adolescent becoming a parent. Being an adolescent parent requires taking a particular path at four crossroads: becoming sexually active, not using or incorrectly using contraceptives, carrying rather than aborting a pregnancy, and parenting rather than placing a child for adoption. Much research in the last 15 years has explored adolescent childbearing, but many studies only compared adolescent parents to nonparents to reach conclusions about differences in these groups. This review focuses on recent studies that explore the four processes, or crossroads, separately and it excludes studies that generalize and overlap these processes. Factors that influence adolescent behavior at multiple points on the path to parenthood indicate areas particularly relevant for preventive intervention. For instance, boyfriends exert influence at all four crossroads. Sexual activity and contraceptive use increase with longevity of relationships, yet closer relationships are less often associated with raising a child. Better general communication skills, and particularly an increased ability to discuss sexuality, increases use of contraceptives, and low educational and occupational aspirations appear to influence each successive turn toward parenthood. This summary of current research serves to highlight those individual, family, dyadic, and social factors that exert great impact on adolescent parenthood by influencing young people at each of the four crossroads. These factors suggest potentially effective points for intervention to reduce the incidence of adolescent parenthood. However, poverty, unemployment, and racism also play central roles in early intercourse and childbearing, and any attempt at fundamental change must take these forces into account. PMID:3083468
Transition paths of Met-enkephalin from Markov state modeling of a molecular dynamics trajectory.
Banerjee, Rahul; Cukier, Robert I
2014-03-20
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