Neural Networks for Dynamic Shortest Path Routing Problems - A Survey
Nallusamy, R
2009-01-01
This paper reviews the overview of the dynamic shortest path routing problem and the various neural networks to solve it. Different shortest path optimization problems can be solved by using various neural networks algorithms. The routing in packet switched multi-hop networks can be described as a classical combinatorial optimization problem i.e. a shortest path routing problem in graphs. The survey shows that the neural networks are the best candidates for the optimization of dynamic shortest path routing problems due to their fastness in computation comparing to other softcomputing and metaheuristics algorithms
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
An Improved Physarum polycephalum Algorithm for the Shortest Path Problem
Wang, Qing; Adamatzky, Andrew; Chan, Felix T. S.; Mahadevan, Sankaran
2014-01-01
Shortest path is among classical problems of computer science. The problems are solved by hundreds of algorithms, silicon computing architectures and novel substrate, unconventional, computing devices. Acellular slime mould P. polycephalum is originally famous as a computing biological substrate due to its alleged ability to approximate shortest path from its inoculation site to a source of nutrients. Several algorithms were designed based on properties of the slime mould. Many of the Physarum-inspired algorithms suffer from a low converge speed. To accelerate the search of a solution and reduce a number of iterations we combined an original model of Physarum-inspired path solver with a new a parameter, called energy. We undertook a series of computational experiments on approximating shortest paths in networks with different topologies, and number of nodes varying from 15 to 2000. We found that the improved Physarum algorithm matches well with existing Physarum-inspired approaches yet outperforms them in number of iterations executed and a total running time. We also compare our algorithm with other existing algorithms, including the ant colony optimization algorithm and Dijkstra algorithm. PMID:24982960
An improved bio-inspired algorithm for the directed shortest path problem.
Zhang, Xiaoge; Zhang, Yajuan; Deng, Yong
2014-01-01
Because most networks are intrinsically directed, the directed shortest path problem has been one of the fundamental issues in network optimization. In this paper, a novel algorithm for finding the shortest path in directed networks is proposed. It extends a bio-inspired path finding model of Physarum polycephalum, which is designed only for undirected networks, by adopting analog circuit analysis. Illustrative examples are given to show the effectiveness of the proposed algorithm in finding the directed shortest path. PMID:25405318
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.
Discrete Approximation to Continuous Anisotropic Shortest-Path Problem
Hespanha, Joăo Pedro
-Risk Path Planning for Groups of UAVs James Riehl Joăo Hespanha INFORMS Meeting November 6, 2007 #12;start [ ]: ( ( ), ( )) T J x t v t dt = #12;Related Work Rowe and Ross, 1990. · Ground vehicles moving on hilly terrain + #12;Minimum-Risk Path Planning for Groups of UAVs ( , )x v xi xf · Heterogeneous group of M UAVs · K
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
Parallel shortest augmenting path algorithm for the assignment problem. Technical report
Balas, E.; Miller, D.; Pekny, J.; Toth, P.
1989-04-01
We describe a parallel version of the shortest augmenting path algorithm for the assignment problem. While generating the initial dual solution and partial assignment in parallel does not require substantive changes in the sequential algorithm, using several augmenting paths in parallel does require a new dual variable recalculation method. The parallel algorithm was tested on a 14-processor Butterfly Plus computer, on problems with up to 900 million variables. The speedup obtained increases with problem size. The algorithm was also embedded into a parallel branch and bound procedure for the traveling salesman problem on a directed graph, which was tested on the Butterfly Plus on problems involving up to 7,500 cities. To our knowledge, these are the largest assignment problems and traveling salesman problems solved so far.
Nair, T R Gopalakrishnan; Yashoda, M B
2011-01-01
In Internet Routing, the static shortest path (SP) problem has been addressed using well known intelligent optimization techniques like artificial neural networks, genetic algorithms (GAs) and particle swarm optimization. Advancement in wireless communication lead more and more mobile wireless networks, such as mobile networks [mobile ad hoc networks (MANETs)] and wireless sensor networks. Dynamic nature of the network is the main characteristic of MANET. Therefore, the SP routing problem in MANET turns into dynamic optimization problem (DOP). Here the nodes ae made aware of the environmental condition, thereby making it intelligent, which goes as the input for GA. The implementation then uses GAs with immigrants and memory schemes to solve the dynamic SP routing problem (DSPRP) in MANETS. In our paper, once the network topology changes, the optimal solutions in the new environment can be searched using the new immigrants or the useful information stored in the memory. Results shows GA with new immigrants sho...
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
A minimum resource neural network framework for solving multiconstraint shortest path problems.
Zhang, Junying; Zhao, Xiaoxue; He, Xiaotao
2014-08-01
Characterized by using minimum hard (structural) and soft (computational) resources, a novel parameter-free minimal resource neural network (MRNN) framework is proposed for solving a wide range of single-source shortest path (SP) problems for various graph types. The problems are the k-shortest time path problems with any combination of three constraints: time, hop, and label constraints, and the graphs can be directed, undirected, or bidirected with symmetric and/or asymmetric traversal time, which can be real and time dependent. Isomorphic to the graph where the SP is to be sought, the network is activated by generating autowave at source neuron and the autowave travels automatically along the paths with the speed of a hop in an iteration. Properties of the network are studied, algorithms are presented, and computation complexity is analyzed. The framework guarantees globally optimal solutions of a series of problems during the iteration process of the network, which provides insight into why even the SP is still too long to be satisfied. The network facilitates very large scale integrated circuit implementation and adapt to very large scale problems due to its massively parallel processing and minimum resource utilization. When implemented in a sequentially processing computer, experiments on synthetic graphs, road maps of cities of the USA, and vehicle routing with time windows indicate that the MRNN is especially efficient for large scale sparse graphs and even dense graphs with some constraints, e.g., the CPU time taken and the iteration number used for the road maps of cities of the USA is even less than ? 2% and 0.5% that of the Dijkstra's algorithm. PMID:25050952
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.
NASA Astrophysics Data System (ADS)
Yu, Feng; Li, Yanjun; Wu, Tie-Jun
2010-02-01
A large number of networks in the real world have a scale-free structure, and the parameters of the networks change stochastically with time. Searching for the shortest paths in a scale-free dynamic and stochastic network is not only necessary for the estimation of the statistical characteristics such as the average shortest path length of the network, but also challenges the traditional concepts related to the “shortest path” of a network and the design of path searching strategies. In this paper, the concept of shortest path is defined on the basis of a scale-free dynamic and stochastic network model, and a temporal ant colony optimization (TACO) algorithm is proposed for searching for the shortest paths in the network. The convergence and the setup for some important parameters of the TACO algorithm are discussed through theoretical analysis and computer simulations, validating the effectiveness of the proposed algorithm.
Locally Constrained Shortest Paths and an Application in Mission Planning
Kunkle, Tom
Locally Constrained Shortest Paths and an Application in Mission Planning Greg Angelides MIT on a feasible path. This problem has applications in robotics and optimal mission planning. We propose planning. 4. RESULTS AND CONTRIBUTIONS A dynamic programming heuristic Dijkstra's classical shortest path
A fuzzy shortest path with the highest reliability
NASA Astrophysics Data System (ADS)
Keshavarz, Esmaile; Khorram, Esmaile
2009-08-01
This paper concentrates on a shortest path problem on a network where arc lengths (costs) are not deterministic numbers, but imprecise ones. Here, costs of the shortest path problem are fuzzy intervals with increasing membership functions, whereas the membership function of the total cost of the shortest path is a fuzzy interval with a decreasing linear membership function. By the max-min criterion suggested in [R.E. Bellman, L.A. Zade, Decision-making in a fuzzy environment, Management Science 17B (1970) 141-164], the fuzzy shortest path problem can be treated as a mixed integer nonlinear programming problem. We show that this problem can be simplified into a bi-level programming problem that is very solvable. Here, we propose an efficient algorithm, based on the parametric shortest path problem for solving the bi-level programming problem. An illustrative example is given to demonstrate our proposed algorithm.
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 and Schramm-Loewner Evolution
Posé, N.; Schrenk, K. J.; Araújo, N. A. M.; Herrmann, H. J.
2014-01-01
We numerically show that the statistical properties of the shortest path on critical percolation clusters are consistent with the ones predicted for Schramm-Loewner evolution (SLE) curves for ? = 1.04 ± 0.02. The shortest path results from a global optimization process. To identify it, one needs to explore an entire area. Establishing a relation with SLE permits to generate curves statistically equivalent to the shortest path from a Brownian motion. We numerically analyze the winding angle, the left passage probability, and the driving function of the shortest path and compare them to the distributions predicted for SLE curves with the same fractal dimension. The consistency with SLE opens the possibility of using a solid theoretical framework to describe the shortest path and it raises relevant questions regarding conformal invariance and domain Markov properties, which we also discuss. PMID:24975019
Shortest path and Schramm-Loewner Evolution
NASA Astrophysics Data System (ADS)
Posé, N.; Schrenk, K. J.; Araújo, N. A. M.; Herrmann, H. J.
2014-06-01
We numerically show that the statistical properties of the shortest path on critical percolation clusters are consistent with the ones predicted for Schramm-Loewner evolution (SLE) curves for ? = 1.04 +/- 0.02. The shortest path results from a global optimization process. To identify it, one needs to explore an entire area. Establishing a relation with SLE permits to generate curves statistically equivalent to the shortest path from a Brownian motion. We numerically analyze the winding angle, the left passage probability, and the driving function of the shortest path and compare them to the distributions predicted for SLE curves with the same fractal dimension. The consistency with SLE opens the possibility of using a solid theoretical framework to describe the shortest path and it raises relevant questions regarding conformal invariance and domain Markov properties, which we also discuss.
Kahng, Andrew B.
problem is called the Minimum Rectilinear Steiner Arborescence MRSA problem. Given a set of terminals N. It can be shown that an MSPSA of GHN;N;r is an MRSA of N. Exact methods for the MRSA problem can in the RSA DP algorithm by Leung and Cong 18 . Nastansky et al. 20 formulated the MRSA problem and its D
Distributional properties of stochastic shortest paths for smuggled nuclear material
Cuellar, Leticia; Pan, Feng; Roach, Fred; Saeger, Kevin J
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.
Kahng, Andrew B.
]. The rectilinear version of the MSPSA problem is called the Minimum Rectilinear Steiner Arborescence (MRSA) problem(N) ) be the induced Hanan grid graph [10] of N . It can be shown that an MSPSA of (G H(N) ; N; r) is an MRSA of N . Exact methods for the MRSA problem can be classified into (1) dynamic programming, (2) integer
Kahng, Andrew B.
the Minimum Rectilinear Steiner Arborescence (MRSA) problem. Given a set of terminals N (including the root r be shown that an MSPSA of (GH(N) ; N; r) is an MRSA of N . Exact methods for the MRSA problem can in the RSA/DP algorithm by Leung and Cong [18]. Nastansky et al. [20] formulated the MRSA problem (and its D
Tsiotras, Panagiotis
to Kinodynamic Path Planning Raghvendra V. Cowlagi and Panagiotis Tsiotras Abstract-- A new algorithm of the path to the current node. The algorithm is applied to solve path planning problems with curvature constraints. I. INTRODUCTION The problem of planning a path for an autonomous vehicle in a given environment
A Continuous-State Version of Discrete Randomized Shortest-Paths, with Application to Path Planning
Del Moral , Pierre
A Continuous-State Version of Discrete Randomized Shortest-Paths, with Application to Path Planning are of capital importance in a variety of problems, from robot path planning, to maze solving. Path planning [16 RSP is investigated and applied to path planning. By defining a grid where each node has four
An Improved Algorithm in Shortest Path Planning for a Tethered , Peter Brass
Goldman, William
An Improved Algorithm in Shortest Path Planning for a Tethered Robot Ning Xu , Peter Brass , Ivo power supply and stable communication through the tether. Following [1], the shortest path planning consider two different models of the short- est path planning problem. In the first model, the tether
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...
Discrete Approximations to Continuous Shortest-Path: Application to Minimum-Risk Path Planning for
Hespanha, Joăo Pedro
1 Discrete Approximations to Continuous Shortest-Path: Application to Minimum-Risk Path Planning Barbara Research supported by DARPA/IXO MICA program Outline 1. Motivation--minimum-risk path planning 2. Discretization approach to shortest-path 3. Sampling methods 4. Back to minimum-risk path planning... #12
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.
Adaptive pyramidal clustering for shortest path determination
NASA Astrophysics Data System (ADS)
Olson, Keith; Speigle, Scott A.
1996-05-01
This paper will present a unique concept implemented in a software design that determines near optimal paths between hundreds of randomly connected nodes of interest in a faster time than current near optimal path determining algorithms. The adaptive pyramidal clustering (APC) approach to determining near optimal paths between numerous nodes uses an adaptive neural network along with classical heuristic search techniques. This combination is represented by a nearest neighbor clustering up function (performed by the neural network) and a trickle down pruning function (performed by the heuristic search). The function of the adaptive neural network is a significant reason why the APC algorithm is superior to several well known approaches. The APC algorithm has already been applied to autonomous route planning for unmanned ground vehicles. The intersections represent navigational waypoints that can be selected as source and destination locations. The APC algorithm then determines a near optimal path to navigate between the selected waypoints.
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
Modeling wildfire propagation with Delaunay triangulation and shortest path algorithms
Smith, J. MacGregor
Modeling wildfire propagation with Delaunay triangulation and shortest path algorithms Alexander In this paper, a methodology for modeling surface wildfire propagation through a complex landscape is presented, wildfire modeling 1 Introduction During the years 2000-2004, the National Interagency Fire Center (NIFC
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.
Fuel-Optimal Centralized Coordination of Truck Platooning Based on Shortest Paths
Dimarogonas, Dimos
Fuel-Optimal Centralized Coordination of Truck Platooning Based on Shortest Paths Sebastian van de fuel consumption of trucks. Vehicles that drive at close inter- vehicle distance assisted by automatic the formation and the breakup of platoons in a fuel-optimal way. We formulate an optimization problem which
Hespanha, Joăo Pedro
, in fact, the most basic problem in Calculus of Variations (cf., e.g., [7]). Assuming for simplicity that R defenses, e.g., Surface-to-Air Missiles (SAMs). The computation of shortest-paths has a long history and is
The Union of Shortest Path Trees of Functional Brain Networks.
Meier, Jil; Tewarie, Prejaas; Van Mieghem, Piet
2015-11-01
Communication between brain regions is still insufficiently understood. Applying concepts from network science has shown to be successful in gaining insight in the functioning of the brain. Recent work has implicated that especially shortest paths in the structural brain network seem to play a major role in the communication within the brain. So far, for the functional brain network, only the average length of the shortest paths has been analyzed. In this article, we propose to construct the union of shortest path trees (USPT) as a new topology for the functional brain network. The minimum spanning tree, which has been successful in a lot of recent studies to comprise important features of the functional brain network, is always included in the USPT. After interpreting the link weights of the functional brain network as communication probabilities, the USPT of this network can be uniquely defined. Using data from magnetoencephalography, we applied the USPT as a method to find differences in the network topology of multiple sclerosis patients and healthy controls. The new concept of the USPT of the functional brain network also allows interesting interpretations and may represent the highways of the brain. PMID:26027712
A Graph Search Heuristic for Shortest Distance Paths
Chow, E
2005-03-24
This paper presents a heuristic for guiding A* search for finding the shortest distance path between two vertices in a connected, undirected, and explicitly stored graph. The heuristic requires a small amount of data to be stored at each vertex. The heuristic has application to quickly detecting relationships between two vertices in a large information or knowledge network. We compare the performance of this heuristic with breadth-first search on graphs with various topological properties. The results show that one or more orders of magnitude improvement in the number of vertices expanded is possible for large graphs, including Poisson random graphs.
A new approach to shortest paths on networks based on the quantum bosonic mechanism
NASA Astrophysics Data System (ADS)
Jiang, Xin; Wang, Hailong; Tang, Shaoting; Ma, Lili; Zhang, Zhanli; Zheng, Zhiming
2011-01-01
This paper presents quantum bosonic shortest path searching (QBSPS), a natural, practical and highly heuristic physical algorithm for reasoning about the recognition of network structure via quantum dynamics. QBSPS is based on an Anderson-like itinerant bosonic system in which a boson's Green function is used as a navigation pointer for one to accurately approach the terminals. QBSPS is demonstrated by rigorous mathematical and physical proofs and plenty of simulations, showing how it can be used as a greedy routing to seek the shortest path between different locations. In methodology, it is an interesting and new algorithm rooted in the quantum mechanism other than combinatorics. In practice, for the all-pairs shortest-path problem in a random scale-free network with N vertices, QBSPS runs in O(?(N) ln ln N) time. In application, we suggest that the corresponding experimental realizations are feasible by considering path searching in quantum optical communication networks; in this situation, the method performs a pure local search on networks without requiring the global structure that is necessary for current graph algorithms.
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.
Dynamic behavior of shortest path routing algorithms for communication networks
NASA Astrophysics Data System (ADS)
Bertsekas, D. P.
1980-06-01
Several proposed routing algorithms for store and forward communication networks, including one currently in operation in the ARPANET, route messages along shortest paths computed by using some set of link lengths. When these lengths depend on current traffic conditions as they must in an adaptive algorithm, dynamic behavior questions such as stability convergence, and speed of convergence are of interest. This paper is the first attempt to analyze systematically these issues. It is shown that minimum queuing delay path algorithms tend to exhibit violent oscillatory behavior in the absence of a damping mechanism. The oscillations can be damped by means of several types of schemes, two of which are analyzed in this paper. In the first scheme a constant bias is added to the queuing delay thereby providing a preference towards paths with a small number of links. In the second scheme the effects of several past routings are averaged as, for example, when the link lengths are computed and communicated asynchronously throughout the network.
Makarychev, Konstantin
or involve a compromise, performing more opera- tions than the best sequential algorithm for the same problem. In this paper we introduce a compromise-free algorithm for the single-source shortest path problem on road linear-time traversal of the graph. This indicates that any significant practical improvements
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.
Color texture classification using shortest paths in graphs.
de Mesquita Sa Junior, Jarbas Joaci; Cortez, Paulo Cesar; Backes, Andre Ricardo
2014-09-01
Color textures are among the most important visual attributes in image analysis. This paper presents a novel method to analyze color textures by modeling a color image as a graph in two different and complementary manners (each color channel separately and the three color channels altogether) and by obtaining statistical moments from the shortest paths between specific vertices of this graph. Such an approach allows to create a set of feature vectors, which were extracted from VisTex, USPTex, and TC00013 color texture databases. The best classification results were 99.07%, 96.85%, and 91.54% (LDA with leave-one-out), 87.62%, 66.71%, and 88.06% (1NN with holdout), and 98.62%, 96.16%, and 91.34% (LDA with holdout) of success rate (percentage of samples correctly classified) for these three databases, respectively. These results prove that the proposed approach is a powerful tool for color texture analysis to be explored. PMID:24988594
Shortest paths and load scaling in scale-free trees
NASA Astrophysics Data System (ADS)
Bollobás, Béla; Riordan, Oliver
2004-03-01
Szabó, Alava, and Kertész [Phys. Rev. E 66, 026101 (2002)] considered two questions about the scale-free random tree given by the m=1 case of the Barabási-Albert (BA) model (identical with a random tree model introduced by Szyma?ski in 1987): what is the distribution of the node to node distances, and what is the distribution of node loads, where the load on a node is the number of shortest paths passing through it? They gave heuristic answers to these questions using a “mean-field” approximation, replacing the random tree by a certain fixed tree with carefully chosen branching ratios. By making use of our earlier results on scale-free random graphs, we shall analyze the random tree rigorously, obtaining and proving very precise answers to these questions. We shall show that, after dividing by N (the number of nodes), the load distribution converges to an integer distribution X with Pr(X=c)=2/[(2c+1)(2c+3)], c=0,1,2,…, confirming the asymptotic power law with exponent -2 predicted by Szabó, Alava, and Kertész. For the distribution of node-node distances, we show asymptotic normality, and give a precise form for the (far from normal) large deviation law. We note that the mean-field methods used by Szabó, Alava, and Kertész give very good results for this model.
On the Comparison-Addition Complexity of All-Pairs Shortest Paths ?
Cafarella, Michael J.
programs. We present, in the same vein, an APSP algorithm that makes O(mn log #11;(m; n)) comparisons refer the reader to Zwick's survey [Z01] for a summary of other shortest path algorithms. It is still
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.
Spreading and shortest paths in systems with sparse long-range connections
Cristian F. Moukarzel
1999-05-21
Spreading according to simple rules (e.g. of fire or diseases), and shortest-path distances are studied on d-dimensional systems with a small density p per site of long-range connections (``Small-World'' lattices). The volume V(t) covered by the spreading quantity on an infinite system is exactly calculated in all dimensions. We find that V(t) grows initially as t^d/d for t>t^*$, generalizing a previous result in one dimension. Using the properties of V(t), the average shortest-path distance \\ell(r) can be calculated as a function of Euclidean distance r. It is found that \\ell(r) = r for rr_c. The characteristic length r_c, which governs the behavior of shortest-path lengths, diverges with system size for all p>0. Therefore the mean separation s \\sim p^{-1/d} between shortcut-ends is not a relevant internal length-scale for shortest-path lengths. We notice however that the globally averaged shortest-path length, divided by L, is a function of L/s only.
A single source k-shortest paths algorithm to infer regulatory pathways in a gene network
Shih, Yu-Keng; Parthasarathy, Srinivasan
2012-01-01
Motivation: Inferring the underlying regulatory pathways within a gene interaction network is a fundamental problem in Systems Biology to help understand the complex interactions and the regulation and flow of information within a system-of-interest. Given a weighted gene network and a gene in this network, the goal of an inference algorithm is to identify the potential regulatory pathways passing through this gene. Results: In a departure from previous approaches that largely rely on the random walk model, we propose a novel single-source k-shortest paths based algorithm to address this inference problem. An important element of our approach is to explicitly account for and enhance the diversity of paths discovered by our algorithm. The intuition here is that diversity in paths can help enrich different functions and thereby better position one to understand the underlying system-of-interest. Results on the yeast gene network demonstrate the utility of the proposed approach over extant state-of-the-art inference algorithms. Beyond utility, our algorithm achieves a significant speedup over these baselines. Availability: All data and codes are freely available upon request. Contact: srini@cse.ohio-state.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:22689778
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.
LIDS REPORT 2875 1 Stochastic Shortest Path Games and Q-Learning
Yu, Huizhen Janey
stochastic dynamic games (or Markov games) that have a cost-free termination state. Our main focusLIDS REPORT 2875 1 Stochastic Shortest Path Games and Q-Learning Huizhen Yu Abstract We consider a class of two-player zero-sum stochastic games with finite state and compact control spaces, which we
Shortest Path Stochastic Control for Hybrid Electric Vehicles , J.W. Grizzle2
Grizzle, Jessy W.
1 of 28 Shortest Path Stochastic Control for Hybrid Electric Vehicles Ed Tate1 , J.W. Grizzle2 , Huei Peng3 Abstract: When a Hybrid Electric Vehicle (HEV) is certified for emissions and fuel economy this is the Hybrid Electric Vehicle (HEV) which consists of an electric powertrain coupled to a conventional
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
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 Wardrop’s 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 Minneapolis—St. 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
Do people use the shortest path? An empirical test of Wardrop's 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 Minneapolis-St. 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
Fast shortest path distance estimation in large networks
, they require as much as 250 times less space than the current approach in the literature which considers on a daily basis. For graphs of this size even the algorithmic problems that are seemingly simple become including among many others protein interaction networks in biology and route computation in transportation
Modeling the average shortest-path length in growth of word-adjacency networks
NASA Astrophysics Data System (ADS)
Kulig, Andrzej; Dro?d?, Stanis?aw; Kwapie?, Jaros?aw; O?wiČ©cimka, Pawe?
2015-03-01
We investigate properties of evolving linguistic networks defined by the word-adjacency relation. Such networks belong to the category of networks with accelerated growth but their shortest-path length appears to reveal the network size dependence of different functional form than the ones known so far. We thus compare the networks created from literary texts with their artificial substitutes based on different variants of the Dorogovtsev-Mendes model and observe that none of them is able to properly simulate the novel asymptotics of the shortest-path length. Then, we identify the local chainlike linear growth induced by grammar and style as a missing element in this model and extend it by incorporating such effects. It is in this way that a satisfactory agreement with the empirical result is obtained.
Shortest Path Induced Vertex Ordering and its Application to Multi-agent Formation Path Planning
Yu, Jingjin
2012-01-01
For the task of moving a group of indistinguishable agents on a connected graph with unit edge length into an arbitrary goal formation, it was shown previously that distance optimal paths can be planned to complete with a tight convergence time guarantee. In this study, we show that the problem formulation in fact induces a more fundamental structure on the underlying graph network, which directly leads to an algorithm with similar performance characteristics. We then generalize the results to graphs with integer edge lengths and capacities.
Improved Nguyen-Vidick Heuristic Sieve Algorithm for Shortest Vector Problem
International Association for Cryptologic Research (IACR)
Improved Nguyen-Vidick Heuristic Sieve Algorithm for Shortest Vector Problem Xiaoyun Wang1 of the Nguyen-Vidick heuristic sieve algorithm for shortest vector problem in general lattices, which time, sieve, heuristic, sphere covering 1 Introduction The n-dimensional lattice is generated by the basis B
Hardness of Approximating the Shortest Vector Problem in High L p Norms
Khot, Subhash
Hardness of Approximating the Shortest Vector Problem in High L p Norms Subhash Khot email : khot integers p #21; p(#15;), it is NPÂhard to approximate the Shortest Vector Problem in L p norm within factor hardness shown by Micciancio [27]. 1 #12; 1 Introduction An nÂdimensional lattice L is a set of vectors f P
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
Identification of Novel Thyroid Cancer-Related Genes and Chemicals Using Shortest Path Algorithm
Zhang, Peiwei; Li, Li-Peng; He, Yi-Chun; Gao, Ru-jian; Gao, Yu-Fei
2015-01-01
Thyroid cancer is a typical endocrine malignancy. In the past three decades, the continued growth of its incidence has made it urgent to design effective treatments to treat this disease. To this end, it is necessary to uncover the mechanism underlying this disease. Identification of thyroid cancer-related genes and chemicals is helpful to understand the mechanism of thyroid cancer. In this study, we generalized some previous methods to discover both disease genes and chemicals. The method was based on shortest path algorithm and applied to discover novel thyroid cancer-related genes and chemicals. The analysis of the final obtained genes and chemicals suggests that some of them are crucial to the formation and development of thyroid cancer. It is indicated that the proposed method is effective for the discovery of novel disease genes and chemicals. PMID:25874234
Liu, Lei; Cai, Yu-Dong; Chou, Kuo-Chen
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 as disease genes for quite a long time, while the latter has been widely used to study the mechanism of diseases. With the existing protein-protein interaction data from STRING (Search Tool for the Retrieval of Interacting Genes), a weighted functional protein association network was constructed. By means of the mRMR (Maximum Relevance Minimum Redundancy) approach, six genes were identified that can distinguish the colorectal tumors and normal adjacent colonic tissues from their gene expression profiles. Meanwhile, according to the shortest path approach, we further found an additional 35 genes, of which some have been reported to be relevant to colorectal cancer and some are very likely to be relevant to it. Interestingly, the genes we identified from both the gene expression profiles and the functional protein association network have more cancer genes than the genes identified from the gene expression profiles alone. Besides, these genes also had greater functional similarity with the reported colorectal cancer genes than the genes identified from the gene expression profiles alone. All these indicate that our method as presented in this paper is quite promising. The method may become a useful tool, or at least plays a complementary role to the existing method, for identifying colorectal cancer genes. It has not escaped our notice that the method can be applied to identify the genes of other diseases as well. PMID:22496748
Solving the Shortest Vector Problem in Lattices Faster Using Quantum Search
Thijs Laarhoven; Michele Mosca; Joop van de Pol
2013-01-25
By applying Grover's quantum search algorithm to the lattice algorithms of Micciancio and Voulgaris, Nguyen and Vidick, Wang et al., and Pujol and Stehl\\'{e}, we obtain improved asymptotic quantum results for solving the shortest vector problem. With quantum computers we can provably find a shortest vector in time $2^{1.799n + o(n)}$, improving upon the classical time complexity of $2^{2.465n + o(n)}$ of Pujol and Stehl\\'{e} and the $2^{2n + o(n)}$ of Micciancio and Voulgaris, while heuristically we expect to find a shortest vector in time $2^{0.312n + o(n)}$, improving upon the classical time complexity of $2^{0.384n + o(n)}$ of Wang et al. These quantum complexities will be an important guide for the selection of parameters for post-quantum cryptosystems based on the hardness of the shortest vector problem.
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...
NASA Astrophysics Data System (ADS)
Forkert, Nils Daniel; Schmidt-Richberg, Alexander; Säring, Dennis; Illies, Till; Fiehler, Jens; Handels, Heinz
2010-03-01
Exact segmentations of the cerebrovascular system are the basis for several medical applications, like preoperation planning, postoperative monitoring and medical research. Several automatic methods for the extraction of the vascular system have been proposed. These automatic approaches suffer from several problems. One of the major problems are interruptions in the vascular segmentation, especially in case of small vessels represented by low intensities. These breaks are problematic for the outcome of several applications e.g. FEM-simulations and quantitative vessel analysis. In this paper we propose an automatic post-processing method to connect broken vessel segmentations. The approach proposed consists of four steps. Based on an existing vessel segmentation the 3D-skeleton is computed first and used to detect the dead ends of the segmentation. In a following step possible connections between these dead ends are computed using a graph based approach based on the vesselness parameter image. After a consistency check is performed, the detected paths are used to obtain the final segmentation using a level set approach. The method proposed was validated using a synthetic dataset as well as two clinical datasets. The evaluation of the results yielded by the method proposed based on two Time-of-Flight MRA datasets showed that in mean 45 connections between dead ends per dataset were found. A quantitative comparison with semi-automatic segmentations by medical experts using the Dice coefficient revealed that a mean improvement of 0.0229 per dataset was achieved. In summary the approach presented can considerably improve the accuracy of vascular segmentations needed for following analysis steps.
Yuan, Fei; Zhang, Yu-Hang; Wan, Sibao; Wang, ShaoPeng; Kong, Xiang-Yin
2015-01-01
Pancreatic cancer (PC) is a highly malignant tumor derived from pancreas tissue and is one of the leading causes of death from cancer. Its molecular mechanism has been partially revealed by validating its oncogenes and tumor suppressor genes; however, the available data remain insufficient for medical workers to design effective treatments. Large-scale identification of PC-related genes can promote studies on PC. In this study, we propose a computational method for mining new candidate PC-related genes. A large network was constructed using protein-protein interaction information, and a shortest path approach was applied to mine new candidate genes based on validated PC-related genes. In addition, a permutation test was adopted to further select key candidate genes. Finally, for all discovered candidate genes, the likelihood that the genes are novel PC-related genes is discussed based on their currently known functions. PMID:26613085
Yuan, Fei; Zhou, You; Wang, Meng; Yang, Jing; Wu, Kai; Lu, Changhong; Kong, Xiangyin; Cai, Yu-Dong
2015-01-01
Prostate cancer is a type of cancer that occurs in the male prostate, a gland in the male reproductive system. Because prostate cancer cells may spread to other parts of the body and can influence human reproduction, understanding the mechanisms underlying this disease is critical for designing effective treatments. The identification of as many genes and chemicals related to prostate cancer as possible will enhance our understanding of this disease. In this study, we proposed a computational method to identify new candidate genes and chemicals based on currently known genes and chemicals related to prostate cancer by applying a shortest path approach in a hybrid network. The hybrid network was constructed according to information concerning chemical-chemical interactions, chemical-protein interactions, and protein-protein interactions. Many of the obtained genes and chemicals are associated with prostate cancer. PMID:26504486
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.
A Parametric Copula Approach for Modelling Shortest-Path Trees in Telecommunication Networks
Schmidt, Volker
.neuhaeuser,christian.hirsch,volker.schmidt}@uni-ulm.de http://www.uni-ulm.de/mawi/mawi-stochastik 2 Orange Labs, 38-40 rue du General Leclerc, 92794 Issy engineers are mainly interested in minimising the total length of the telecommunication network in a city companies such as Orange Labs can draw conclusions about ca- pacity problems and cost estimation
Shortest Paths Dijkstra's algorithm
Sedgewick, Robert
numbers Â· not necessarily distances Â· need not satisfy the triangle inequality Â· Ex: airline fares [stay. Bellman (1958). Dynamic programming. Moore (1959). Routing long-distance telephone calls for Bell Labs
Path querying system on mobile devices
NASA Astrophysics Data System (ADS)
Lin, Xing; Wang, Yifei; Tian, Yuan; Wu, Lun
2006-01-01
Traditional approaches to path querying problems are not efficient and convenient under most circumstances. A more convenient and reliable approach to this problem has to be found. This paper is devoted to a path querying solution on mobile devices. By using an improved Dijkstra's shortest path algorithm and a natural language translating module, this system can help people find the shortest path between two places through their cell phones or other mobile devices. The chosen path is prompted in text of natural language, as well as a map picture. This system would be useful in solving best path querying problems and have potential to be a profitable business system.
Sreenan, Cormac J.
. These networks are subject to failures: the wireless devices are often unre- liable, they have limited battery placement Vertex-disjoint paths a b s t r a c t Wireless sensor networks (WSNs) are prone to failures. To be robust to failures, the net- work topology should provide alternative routes to the sinks so when
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 ...
Relative Improvement by Alternative Solutions for Classes of Simple Shortest Path Problems
with Uncertain Data -- Part I: Strings of Pearls Gn with Unbiased Perturbations l l l l l l l l s s s s s s s 3 3 of this section we introduce the considered model in detail: the graph model (string of pearls Gn) and an unbiased.1 The Model We consider the following graph model: Definition 1.1 (string of pearls Gn) Consider a weighted
Relative Improvement by Alternative Solutions for Classes of Simple Shortest Path Problems
with Uncertain Data -- Part II: Strings of Pearls Gn,r with Biased Perturbations l l l l l l l l the considered models in detail: the graph model (string of pearls Gn,r) and two different biased perturbation. We finish with conclusions in Section 5. 1.1 The Models Definition 1.1 (string of pearls Gn
Path optimization using sub-Riemannian manifolds with applications to astrodynamics
Whiting, James K. (James Kalani), 1980-
2011-01-01
Differential geometry provides mechanisms for finding shortest paths in metric spaces. This work describes a procedure for creating a metric space from a path optimization problem description so that the formalism of ...
Cooperative optimal path planning for herding problems
Lu, Zhenyu
2009-05-15
] method has been widely used in military applications such as aerial intercept guided missile systems [7]. In most of the pursuit evasion models considered to date, the pursuer?s aim is to intercept or hunt the evader. Very natural and interesting...) try to control the motion of another group (the ock). It mainly focuses on group behavior instead of the optimal path for the ock to travel to the goal. The journal model is IEEE Transactions on Automatic Control. 2 Multiple robot systems have been a...
The optimal path-matching problem
Cunningham, W.H.; Geelen, J.F.
1996-12-31
We describe a common generalization of the weighted matching problem and the weighted matroid intersection problem. In this context we present results implying the polynomial-time solvability of the two problems. We also use our results to give the first strongly polynomial separation algorithm for the convex hull of matchable sets of a graph, and the first polynomial-time algorithm to compute the rank of a certain matrix of indeterminates. Our algorithmic results are based on polyhedral characterizations, and on the equivalence of separation and optimization.
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…
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
Tsiotras, Panagiotis
A Hierarchical On-Line Path Planning Scheme using Wavelets Panagiotis Tsiotras and Efstathios Bakolas Abstract-- We present an algorithm for solving the shortest (collision-free) path planning problem representation of W or a discrete one. In this work we propose an algorithm which solves the path planning
Worst-Case Analysis of Network Design Problem Heuristics
Wong, Richard T.
The Optimal Network problem (as defined by Scott [16]) consists of selecting a subset of arcs that minimizes the sum of the shortest paths between all nodes subject to a budget constraint. This paper considers the worst-case ...
Link prediction based on path entropy
Xu, Zhongqi; Yang, Jian
2015-01-01
Information theory has been taken as a prospective tool for quantifying the complexity of complex networks. In this paper, we first study the information entropy or uncertainty of a path using the information theory. Then we apply the path entropy to the link prediction problem in real-world networks. Specifically, we propose a new similarity index, namely Path Entropy (PE) index, which considers the information entropies of shortest paths between node pairs with penalization to long paths. Empirical experiments demonstrate that PE index outperforms the mainstream link predictors.
Algorithms for an Unmanned Vehicle Path Planning Problem
Qin, Jianglei
2013-06-25
Unmanned Vehicles (UVs) have been significantly utilized in military and civil applications over the last decade. Path-planning of UVs plays an important role in effectively using the available resources such as the UVs and sensors as efficiently...
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
The Edge-Disjoint Path Problem on Random Graphs by Message-Passing.
Altarelli, Fabrizio; Braunstein, Alfredo; Dall'Asta, Luca; De Bacco, Caterina; Franz, Silvio
2015-01-01
We present a message-passing algorithm to solve a series of edge-disjoint path problems on graphs based on the zero-temperature cavity equations. Edge-disjoint paths problems are important in the general context of routing, that can be defined by incorporating under a unique framework both traffic optimization and total path length minimization. The computation of the cavity equations can be performed efficiently by exploiting a mapping of a generalized edge-disjoint path problem on a star graph onto a weighted maximum matching problem. We perform extensive numerical simulations on random graphs of various types to test the performance both in terms of path length minimization and maximization of the number of accommodated paths. In addition, we test the performance on benchmark instances on various graphs by comparison with state-of-the-art algorithms and results found in the literature. Our message-passing algorithm always outperforms the others in terms of the number of accommodated paths when considering non trivial instances (otherwise it gives the same trivial results). Remarkably, the largest improvement in performance with respect to the other methods employed is found in the case of benchmarks with meshes, where the validity hypothesis behind message-passing is expected to worsen. In these cases, even though the exact message-passing equations do not converge, by introducing a reinforcement parameter to force convergence towards a sub optimal solution, we were able to always outperform the other algorithms with a peak of 27% performance improvement in terms of accommodated paths. On random graphs, we numerically observe two separated regimes: one in which all paths can be accommodated and one in which this is not possible. We also investigate the behavior of both the number of paths to be accommodated and their minimum total length. PMID:26710102
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.
Constrained Graph Optimization: Interdiction and Preservation Problems
Schild, Aaron V
2012-07-30
The maximum flow, shortest path, and maximum matching problems are a set of basic graph problems that are critical in theoretical computer science and applications. Constrained graph optimization, a variation of these basic graph problems involving modification of the underlying graph, is equally important but sometimes significantly harder. In particular, one can explore these optimization problems with additional cost constraints. In the preservation case, the optimizer has a budget to preserve vertices or edges of a graph, preventing them from being deleted. The optimizer wants to find the best set of preserved edges/vertices in which the cost constraints are satisfied and the basic graph problems are optimized. For example, in shortest path preservation, the optimizer wants to find a set of edges/vertices within which the shortest path between two predetermined points is smallest. In interdiction problems, one deletes vertices or edges from the graph with a particular cost in order to impede the basic graph problems as much as possible (for example, delete edges/vertices to maximize the shortest path between two predetermined vertices). Applications of preservation problems include optimal road maintenance, power grid maintenance, and job scheduling, while interdiction problems are related to drug trafficking prevention, network stability assessment, and counterterrorism. Computational hardness results are presented, along with heuristic methods for approximating solutions to the matching interdiction problem. Also, efficient algorithms are presented for special cases of graphs, including on planar graphs. The graphs in many of the listed applications are planar, so these algorithms have important practical implications.
Solving the broken link problem in Walden's Paths
Dalal, Zubin Jamshed
2004-09-30
With the extent of the web expanding at an increasing rate, the problems caused by broken links are reaching epidemic proportions. Studies have indicated that a substantial number of links on the Internet are broken. User ...
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.
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...
A Path-following Method for Solving BMI Problems in Arash Hassibi1
A Path-following Method for Solving BMI Problems in Control Arash Hassibi1 Jonathan How Stephen (BMI) prob- lems in control. The method is to linearize the BMI using a first order perturbation (BMI), linear matrix in- equality (LMI), semidefinite programming (SDP), robust control, low
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…
Zhao, Gongyun
Problem Chee-Khian Sim Gongyun Zhao May 22, 2006 Abstract An interior point method (IPM) defines a search to interior point methods (IPMs). Since then, people have realized that an IPM is actually a homotopy methodUnderlying Paths in Interior Point Methods for the Monotone Semidefinite Linear Complementarity
Nonequilibrium problems in Quantum Field Theory and Schwinger's closed time path formalism
NASA Astrophysics Data System (ADS)
Cooper, Fred
1995-04-01
We review the closed time path formalism of Schwinger using a path integral approach. We apply this formalism to the study of pair production from strong external fields as well as the time evolution of a nonequilibrium chiral phase transition. In 1961 in his classic paper 'Brownian Motion of a Quantum Particle,' Schwinger solved the formidable technical problem of how to use the action principle to study initial value problems. Previously, the action principle was formulated to study only transition matrix elements from an earlier time to a later time. The elegant solution of this problem was the invention of the closed time path (CTP) formalism. This formalism was first used to study field theory problems by Mahanthappa and Bakshi. With the advent of supercomputers, it has now become possible to use this formalism to numerically solve important field theory questions which are presented as initial value problems. Two of these problems we shall review here. They are: (1) The time evolution of the quark-gluon plasma; and (2) Dynamical evolution of a non-equilibrium chiral phase transition following a relativistic heavy ion collision.
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.
Zhu, Xiaoyan
2007-04-25
I would like to express my sincere gratitude to my advisor Dr. Wilbert E. Wilhelm, Department of Industrial Engineering, Texas A&M University, for his continuous guidance and many educational contributions. Throughout my Ph.D. program, I have... learned so many aspects of life from him. Without his guidence and encouragement I could not have finished my Ph.D. studies smoothly. Dr. Wilhelm has co-authored papers that are in review and I am very grateful for his significent contributions...
Orbital Systolic Algorithms and Array Processors for Solution of the Algebraic Path Problem
NASA Astrophysics Data System (ADS)
Sedukhin, Stanislav G.; Miyazaki, Toshiaki; Kuroda, Kenichi
The algebraic path problem (APP) is a general framework which unifies several solution procedures for a number of well-known matrix and graph problems. In this paper, we present a new 3-dimensional (3-D) orbital algebraic path algorithm and corresponding 2-D toroidal array processors which solve the n × n APP in the theoretically minimal number of 3n time-steps. The coordinated time-space scheduling of the computing and data movement in this 3-D algorithm is based on the modular function which preserves the main technological advantages of systolic processing: simplicity, regularity, locality of communications, pipelining, etc. Our design of the 2-D systolic array processors is based on a classical 3-D?2-D space transformation. We have also shown how a data manipulation (copying and alignment) can be effectively implemented in these array processors in a massively-parallel fashion by using a matrix-matrix multiply-add operation.
Hard water problems and soft water paths: The "supply versus demand" conundrum
NASA Astrophysics Data System (ADS)
Gleick, P. H.
2012-12-01
Water problems are complex, interdisciplinary, and have profound effects on human and ecosystem health and well-being. And they are classic "hard" problems. Good science is necessary to solve these problems, but it is rarely sufficient. One of these hard problems is that of "perception" and "frame" - traditional water planners and managers frame freshwater as a "supply" problem, i.e., how can we access and deliver sufficient quantities of water of suitable quality, to satisfy perceived demand. In recent years, however, as water scarcity in different regions has increased due to growing populations and expanding economies, "peak water" limits (including peak renewable, non-renewable, and ecological limits) have started to constrain development of traditional "supply" options (Figure 1). That has led to new thinking about the other side of the equation: what is meant by water "demand" and can demand management tools and approaches offer a way to solve water problems. The "soft path for water" addresses this issue of water demand directly, but implementing demand-side solutions faces serious barriers. This talk will expound on the soft path approach and its potential to overcome some of the gridlock and stagnation in current water policy debates, with examples from both developed and developing countries, and different economic sectors.umulative global reservoir storage (major reservoirs) from 1900 to 2010, showing leveling off of traditional supply expansion. Data from the GRanD database.
Mapping Student Search Paths Through Immunology Problems by Computer Based Testing
Stevens, Ronald H.; Kwak, Anthony R.; McCoy, J. Michael
1990-01-01
The development and use of uncued computer based testing in Immunology has encouraged second year UCLA medical students to become more independent, active learners and problem solvers. We have used the Windows-based IMMEX software this year to show that these problem solving exercises are a valid form of testing and that student performance did not correlate with computer anxiety or performance on objective examinations. More importantly, we have developed a graphical display of the student's solution path through the problems which allows a visualization of the problem solving processes associated with successful or unsuccessful solutions. This approach provides an analysis of the student's reasoning about complex concepts in immunology and will make it possible in the future to specifically and personally address each student's educational needs.
Shortest recurrence periods of novae
Kato, Mariko; Saio, Hideyuki; Hachisu, Izumi; Nomoto, Ken'ichi
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.
All-Optical Monitoring Path Computation Using Lower Bounds of Required Number of Paths
NASA Astrophysics Data System (ADS)
Ogino, Nagao; Nakamura, Hajime
To reduce the cost of fault management in all-optical networks, it is a promising approach to detect the degradation of optical signal quality solely at the terminal points of all-optical monitoring paths. The all-optical monitoring paths must be routed so that all single-link failures can be localized using route information of monitoring paths where signal quality degradation is detected. However, route computation for the all-optical monitoring paths that satisfy the above condition is time consuming. This paper proposes a procedure for deriving the lower bounds of the required number of monitoring paths to localize all single-link failures, and proposes an efficient monitoring path computation method based on the derived lower bounds. The proposed method repeats the route computation for the monitoring paths until feasible routes can be found, while the assumed number of monitoring paths increases, starting from the lower bounds. With the proposed method, the minimum number of monitoring paths with the overall shortest routes can be obtained quickly by solving several small-scale integer linear programming problems when the possible terminal nodes of monitoring paths are arbitrarily given. Thus, the proposed method can minimize the required number of monitors for detecting the degradation of signal quality and the total overhead traffic volume transferred through the monitoring paths.
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.
Robot path planning with distance-safety criterion
NASA Technical Reports Server (NTRS)
Suh, Suk-Hwan; Shin, Kang G.
1987-01-01
A method for determining an optimal path with a weighted distance-safety criterion is developed. The goal is to strike a compromise between the shortest path and the centerline path, which is safer. The method is composed of three parts: (i) construction of a region map by dividing the workspace, (ii) interregion optimization to determine the entry and departure points of the path in each region, and (iii) intraregion optimization for determining the (optimal) path segment within each region. The region map is generated by using an approximate Voronoi diagram, and region optimization is achieved using variational dynamic programming. Although developed for 2-D problems, the method can be easily extended to a class of 3-D problems. Numerical examples are presented to demonstrate the method.
Approximating Cycles in a Shortest Basis of the First Homology Group from Point Data
Sun, Jian
Approximating Cycles in a Shortest Basis of the First Homology Group from Point Data Tamal K. Dey the rank of the homology groups from point data, but there is no result on approximating the shortest basis its point data is a funda- mental problem arising in many scientific studies and engineering
Roman, Gabriela D; Ensor, Rosie; Hughes, Claire
2016-02-01
This study investigated the mediation role played by children's executive function in the relationship between exposure to mild maternal depressive symptoms and problem behaviors. At ages 2, 3, and 6years, 143 children completed executive function tasks and a verbal ability test. Mothers completed the Beck Depression Inventory at each time-point, and teachers completed the Strengths and Difficulties Questionnaire at child age 6. Longitudinal autoregressive mediation models showed a mediation effect that was significant and quite specific; executive function (and not verbal ability) at age 3 mediated the path between mothers' depressive symptoms (but not general social disadvantage) at the first time-point and children's externalizing and internalizing problems at age 6. Improving children's executive functioning might protect them against the adverse effects of exposure to maternal depressive symptoms. PMID:26550956
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.
Path Planning with obstacle avoidance
NASA Technical Reports Server (NTRS)
Krause, Donald M.
1987-01-01
The research report here summarizes a solution for two dimensional Path Planning with obstacle avoidance in a workspace with stationary obstacles. The solution finds the shortest path for the end effector of a manipulator arm. The program uses an overhead image of the robot work space and the starting and ending positions of the manipulator arm end effector to generate a search graph which is used to find the shortest path through the work area. The solution was originally implemented in VAX Pascal, but was later converted to VAX C.
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
Kiosses, Dimitris N.; Ravdin, Lisa D.; Gross, James J; Raue, Patrick; Kotbi, Nabil; Alexopoulos, George S.
2015-01-01
Importance Problem Adaptation Therapy (PATH) is a treatment for older adults with major depression, cognitive impairment (from mild cognitive deficits to moderate dementia) and disability. Antidepressants have limited efficacy in this population and psychosocial interventions are inadequately investigated. Objective To test the efficacy of 12-week PATH vs. Supportive Therapy for Cognitively Impaired patients (ST-CI) in reducing depression and disability in 74 older adults with major depression, cognitive impairment and disability. Design Randomized Controlled Trial from April 1, 2006 until September 31, 2011. Setting Weill-Cornell Institute of Geriatric Psychiatry; interventions were administered at participants’ homes. Participants Seventy-four older participants (age?65 years) with major depression and cognitive impairment up to the level of moderate dementia were recruited through collaborating community agencies of Weill-Cornell Institute of Geriatric Psychiatry and were randomly assigned to 12 weekly sessions of PATH or ST-CI (14.8% attrition rate). Interventions Home-delivered PATH vs. home-delivered ST-CI. PATH integrates a problem solving approach with compensatory strategies, environmental adaptations, and caregiver participation to improve patients’ emotion regulation. ST-CI focuses on expression of affect, understanding and empathy. Main Outcome Measures Mixed-effects models for longitudinal data compared the efficacy of PATH to that of ST-CI in reducing depression (MADRS) and disability (WHODAS-II) over 12 weeks of treatment. Results PATH participants had significantly greater reduction in depression (treatment X time: F[1,179]=8.03, p=0.0051; Cohen’s D at 12 weeks: 0.60) and disability (treatment X time: F[1,169]=14.86, p=0.0002; Cohen’s D at 12 weeks: 0.67) than ST-CI participants over the 12-week period (primary outcomes). Further, PATH participants had significantly greater depression remission rates than ST-CI participants (37.84% vs. 13.51%; Chi-square: 5.74, df=1, p=0.0174; Number Needed to Treat (NNT)=4.11) (secondary outcome). Exploratory analysis showed that PATH led to greater reduction in depression than ST-CI even in the subgroup of participants with drug treatment resistant depression (F[1,72.7]=6.01, p=0.0166; Cohen’s d: week 12: 0.95). Conclusions and Relevance PATH was more efficacious than ST-CI in reducing depression and disability. PATH may provide relief to a large group of depressed, cognitively impaired older adults with few treatment options. PMID:25372657
Vervet monkeys use paths consistent with context-specific spatial movement heuristics.
Teichroeb, Julie A
2015-10-01
Animal foraging routes are analogous to the computationally demanding "traveling salesman problem" (TSP), where individuals must find the shortest path among several locations before returning to the start. Humans approximate solutions to TSPs using simple heuristics or "rules of thumb," but our knowledge of how other animals solve multidestination routing problems is incomplete. Most nonhuman primate species have shown limited ability to route plan. However, captive vervets were shown to solve a TSP for six sites. These results were consistent with either planning three steps ahead or a risk-avoidance strategy. I investigated how wild vervet monkeys (Chlorocebus pygerythrus) solved a path problem with six, equally rewarding food sites; where site arrangement allowed assessment of whether vervets found the shortest route and/or used paths consistent with one of three simple heuristics to navigate. Single vervets took the shortest possible path in fewer than half of the trials, usually in ways consistent with the most efficient heuristic (the convex hull). When in competition, vervets' paths were consistent with different, more efficient heuristics dependent on their dominance rank (a cluster strategy for dominants and the nearest neighbor rule for subordinates). These results suggest that, like humans, vervets may solve multidestination routing problems by applying simple, adaptive, context-specific "rules of thumb." The heuristics that were consistent with vervet paths in this study are the same as some of those asserted to be used by humans. These spatial movement strategies may have common evolutionary roots and be part of a universal mental navigational toolkit. Alternatively, they may have emerged through convergent evolution as the optimal way to solve multidestination routing problems. PMID:26668734
Shortest Path Computation with No Information Leakage Kyriakos Mouratidis
Yiu, Man Lung
Systems Singapore Management University kyriakos@smu.edu.sg Man Lung Yiu Department of Computing Hong Kong PIR techniques, which we treat as black-box building blocks. Experiments on real, large-scale road
Fast shortest path distance estimation in large networks
, they require as much as 250 times less space than the current approach in the literature which considers, or instant messaging systems nowadays count hundreds of millions of users that are active on a daily basis others protein interaction networks in biology and route computation in transportation. Recently, new
Optimal Distributed All Pairs Shortest Paths and Applications
) time. 1 #12;1 Introduction In networks, basically two types of routing algorithms are known: distance the information about the network graph is collected, and then optimal routes between all nodes are computed, using an efficient centralized algorithm. Distance-vector routing protocols on the other hand represent
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 path—the shortest path possible. The paths also needed to optionally be attached to existing primary paths, again with the shortest possible path. Finally, the process must be repeatable and predictable so that the same inputs (primary paths, specified distance, and path options) will result in the same set of new paths every time. This methodology was developed to meet those specifications.
Dorfer, Matthias; Kazmar, Tomáš; Šmíd, Mat?j; Sing, Sanchit; Kneißl, Julia; Keller, Simone; Debeir, Olivier; Luber, Birgit; Mattes, Julian
2016-01-01
In this paper we address the problem of recovering spatio-temporal trajectories of cancer cells in phase contrast video-microscopy where the user provides the paths on which the cells are moving. The paths are purely spatial, without temporal information. To recover the temporal information associated to a given path we propose an approach based on automatic cell detection and on a graph-based shortest path search. The nodes in the graph consist of the projections of the cell detections onto the geometrical cell path. The edges relate nodes which correspond to different frames of the sequence and potentially to the same cell and trajectory. In this directed graph we search for the shortest path and use it to define a temporal parametrization of the corresponding geometrical cell path. An evaluation based on 286 paths of 7 phase contrast microscopy videos shows that our algorithm allows to recover 92% of trajectory points with respect to the associated ground truth. We compare our method with a state-of-the-art algorithm for semi-automated cell tracking in phase contrast microscopy which requires interactively placed starting points for the cells to track. The comparison shows that supporting geometrical paths in combination with our algorithm allow us to obtain more reliable cell trajectories. PMID:25987193
On Dirac-Coulomb problem in (2+1) dimensional space-time and path integral quantization
Haouat, S.; Chetouani, L.
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.
Zhao, Gongyun
method (IPM) defines a search direction at each interior point of the feasible region. These search is introduced by Sonnevend [10] in 1985 to interior point method (IPM). Since then, people realize that IPMAsymptotic Behavior of HKM Paths in Interior Point Methods for Monotone Semidefinite Linear
Obstacle-Aware Longest-Path Routing with Constraint Programming and Parallel MILP
NASA Astrophysics Data System (ADS)
Tseng, I.-Lun; Chen, Huan-Wen; Kao, Yung-Wei; Lee, Che-I.
2011-08-01
Longest-path routing problems, which can arise in the design of high-performance printed circuit boards (PCBs), have been proven to be NP-hard. In this article, we propose a constraint programming (CP) formulation and a mixed integer linear programming (MILP) formulation to gridded longest-path routing problems; each of which may contain obstacles. After a longest-path routing problem has been transformed into a CP problem, a CP solver can be used to find optimal solutions. On the other hand, parallel MILP solvers can be used to find optimal solutions after the longest-path routing problem has been transformed into an MILP problem. Also, suboptimal solutions can be generated in exchange for reduced execution time. The proposed formulation methods can also be used to solve shortest-path routing problems. Experimental results show that more than 3,700x speed-up can be achieved by using a parallel MILP solver with 16 threads in solving formulated longest-path routing problems. The execution time can be further reduced if a computer containing more processer cores is available.
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…
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
A Well-Balanced Path-Integral f-Wave Method for Hyperbolic Problems with Source Terms
2014-01-01
Systems of hyperbolic partial differential equations with source terms (balance laws) arise in many applications where it is important to compute accurate time-dependent solutions modeling small perturbations of equilibrium solutions in which the source terms balance the hyperbolic part. The f-wave version of the wave-propagation algorithm is one approach, but requires the use of a particular averaged value of the source terms at each cell interface in order to be “well balanced” and exactly maintain steady states. A general approach to choosing this average is developed using the theory of path conservative methods. A scalar advection equation with a decay or growth term is introduced as a model problem for numerical experiments. PMID:24563581
Wilson, Helen W.; Widom, Cathy Spatz
2009-01-01
Behaviors beginning in childhood or adolescence may mediate the relationship between childhood maltreatment and involvement in prostitution. This paper examines five potential mediators: early sexual initiation, running away, juvenile crime, school problems, and early drug use. Using a prospective cohort design, abused and neglected children (ages 0–11) with cases processed during 1967–1971 were matched with non-abused, non-neglected children and followed into young adulthood. Data are from in-person interviews at approximate age 29 and arrest records through 1994. Structural Equation Modeling tested path models. Results indicated that victims of child abuse and neglect were at increased risk for all problem behaviors, except drug use. In the full model, only early sexual initiation remained significant as a mediator in the pathway from child abuse and neglect to prostitution. Findings were generally consistent for physical and sexual abuse and neglect. These findings suggest that interventions to reduce problem behaviors among maltreated children may also reduce their risk for prostitution later in life. PMID:20186260
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
Minimal Realizations of Linear Systems: The "Shortest Basis" Approach
Forney, G. David, Jr.
Given a discrete-time linear system C, a shortest basis for C is a set of linearly independent generators for C with the least possible lengths. A basis B is a shortest basis if and only if it has the predictable span ...
DNA computing, computation complexity and problem of biological evolution rate.
Melkikh, Alexey V
2008-12-01
An analogy between the evolution of organisms and some complex computational problems (cryptosystem cracking, determination of the shortest path in a graph) is considered. It is shown that in the absence of a priori information about possible species of organisms such a problem is complex (is rated in the class NP) and cannot be solved in a polynomial number of steps. This conclusion suggests the need for re-examination of evolution mechanisms. Ideas of a deterministic approach to the evolution are discussed. PMID:18787960
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.
Carrell, Jim
MATH 317 SUPPLEMENTARY PROBLEM SET I 1) Find the velocity, speed and acceleration at time t of the particle whose position is r(t). Describe the path of the particle. a) r(t) = a cos t^i + a sin t ^ + ct ^k is in the air, it experiences a downward (vertical) gravitational acceleration of 9.8 m/s2 and an eastward
From Planning to Searching for the Shortest Plan
Kreinovich, Vladik
with applying A bN=2c ; if this algorithm A bN=2c finds a plan, we then try A bN=4c , otherwise, we apply A b3NFrom Planning to Searching for the Shortest Plan: An Optimal Transition R. Trejo, J. Galloway C frtrejo,vladikg@cs.utep.edu Abstract If we want to find the shortest plan, then usually, we try plans
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.
Brachistochrones are the shortest Franois Rouvire
Vallette, Bruno
in the eighteenth century by Euler and Lagrange, Bernoulli's problem gave rise to the calculus of variations. More by more elementary tools (i.e. without any knowledge of the calculus of variations) a class of problems details on this fascinating chapter in the history of mathematical analysis can be found in Nahin [3
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.
EXTENDING THE PATH-PLANNING Robotics Institute
EXTENDING THE PATH-PLANNING HORIZON Bart Nabbe Robotics Institute Carnegie Mellon University to plan inefficient paths that trace obstacle boundaries. To alleviate this problem, We present an op . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3. Path Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Proposed
Energy Science and Technology Software Center (ESTSC)
2014-01-07
PathFinder is a graph search program, traversing a directed cyclic graph to find pathways between labeled nodes. Searches for paths through ordered sequences of labels are termed signatures. Determining the presence of signatures within one or more graphs is the primary function of Path Finder. Path Finder can work in either batch mode or interactively with an analyst. Results are limited to Path Finder whether or not a given signature is present in the graph(s).
Genome comparison without alignment using shortest unique substrings
Haubold, Bernhard; Pierstorff, Nora; Möller, Friedrich; Wiehe, Thomas
2005-01-01
Background Sequence comparison by alignment is a fundamental tool of molecular biology. In this paper we show how a number of sequence comparison tasks, including the detection of unique genomic regions, can be accomplished efficiently without an alignment step. Our procedure for nucleotide sequence comparison is based on shortest unique substrings. These are substrings which occur only once within the sequence or set of sequences analysed and which cannot be further reduced in length without losing the property of uniqueness. Such substrings can be detected using generalized suffix trees. Results We find that the shortest unique substrings in Caenorhabditis elegans, human and mouse are no longer than 11 bp in the autosomes of these organisms. In mouse and human these unique substrings are significantly clustered in upstream regions of known genes. Moreover, the probability of finding such short unique substrings in the genomes of human or mouse by chance is extremely small. We derive an analytical expression for the null distribution of shortest unique substrings, given the GC-content of the query sequences. Furthermore, we apply our method to rapidly detect unique genomic regions in the genome of Staphylococcus aureus strain MSSA476 compared to four other staphylococcal genomes. Conclusion We combine a method to rapidly search for shortest unique substrings in DNA sequences and a derivation of their null distribution. We show that unique regions in an arbitrary sample of genomes can be efficiently detected with this method. The corresponding programs shustring (SHortest Unique subSTRING) and shulen are written in C and available at . PMID:15910684
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.
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.
On Distributed Time-Dependent Shortest Paths over Duty-Cycled Wireless Sensor Networks
Ravindran, Binoy
for all nodes. The performance of our solution is evaluated under diverse network configurations, a node periodically switches between active and sleep state. The period for one active/sleep switching, even though the physical propagation condition does not change with time. This raises a non
, Germany 2Center for Infrastructure, Sustainable Transportation and Urban Planning, Indian Institute. The multiagent model is generic in the sense that different public and individual transport agents. While planning, the agents consider both public and individual transportation options. · enhanced
Applied Probability Trust (12 May 2009) SCALING LIMITS FOR SHORTEST PATH LENGTHS ALONG
Schmidt, Volker
OF STATIONARY TESSELLATIONS FLORIAN VOSS, Ulm University CATHERINE GLOAGUEN, Orange Labs VOLKER SCHMIDT, Ulm: Orange Labs, 38-40, rue du GÂ´enÂ´eral Leclerc, 92794 Issy-les-Moulineaux, France 1 #12;2 F. Voss, C.g. an inner-city street system. Thus, we study a class of stochastic network models which has been introduced
Geometric Shortest Paths and Network Optimization Joseph S.B. Mitchell \\Lambda
Mitchell, Joseph S.B.
complex geometry? single shot vs. repetitive mode queries: Do we want to build an effective data structure9504192, and by grants from Boeing Computer Services, Bridgeport Machines, Hughes Aircraft, and Sun extensive lists of results on parallel algorithms in geometry. We will freely use the ``bigOh'' notation
Should QoS routing algorithms prefer shortest paths? Karol Kowalik and Martin Collier
Collier, Martin
-- Multimedia traffic and real-time e-commerce appli- cations can experience quality degradation in traditional resources for future connections. Others advocate load balancing mechanisms so as to increase overall for the traffic flows and so is not suitable for use by multimedia or real-time e-commerce applications
Ohya, Akihisa
, , ( ) Obstacle Avoidance Algorithm for Mobile Robot Running on the Planned Path Gao Cheng algorithm by the information obtained with the SOKUIKI sensor for mobile robot running on the planned path Shortest path generation proach to Planning, Sensing and Navigation for Mo- bile Robots ,1993 Preprints
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.
Energy Science and Technology Software Center (ESTSC)
2007-07-14
The PANL software determines path through an Adversary Sequence Diagram (ASD) with minimum Probability of Interruption, P(I), given the ASD information and data about site detection, delay, and response force times. To accomplish this, the software generates each path through the ASD, then applies the Estimate of Adversary Sequence Interruption (EASI) methodology for calculating P(I) to each path, and keeps track of the path with the lowest P(I). Primary use is for training purposes duringmore »courses on physical security design. During such courses PANL will be used to demonstrate to students how more complex software codes are used by the US Department of Energy to determine the most-vulnerable paths and, where security needs improvement, how such codes can help determine physical security upgrades.« less
Continuous Path Planning with Multiple Constraints
Mitchell, Ian
Continuous Path Planning with Multiple Constraints Ian M. Mitchell and Shankar Sastry Department examine the problem of planning a path through a low di- mensional continuous state space subject to upper Few problems are as well studied as the path planning or routing prob- lem; it appears in engineering
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.
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.
Path planning under spatial uncertainty.
Wiener, Jan M; Lafon, Matthieu; Berthoz, Alain
2008-04-01
In this article, we present experiments studying path planning under spatial uncertainties. In the main experiment, the participants' task was to navigate the shortest possible path to find an object hidden in one of four places and to bring it to the final destination. The probability of finding the object (probability matrix) was different for each of the four places and varied between conditions. Givensuch uncertainties about the object's location, planning a single path is not sufficient. Participants had to generate multiple consecutive plans (metaplans)--for example: If the object is found in A, proceed to the destination; if the object is not found, proceed to B; and so on. The optimal solution depends on the specific probability matrix. In each condition, participants learned a different probability matrix and were then asked to report the optimal metaplan. Results demonstrate effective integration of the probabilistic information about the object's location during planning. We present a hierarchical planning scheme that could account for participants' behavior, as well as for systematic errors and differences between conditions. PMID:18491490
Sampling diffusive transition paths
F. Miller III, Thomas; Predescu, Cristian
2006-10-12
We address the problem of sampling double-ended diffusive paths. The ensemble of paths is expressed using a symmetric version of the Onsager-Machlup formula, which only requires evaluation of the force field and which, upon direct time discretization, gives rise to a symmetric integrator that is accurate to second order. Efficiently sampling this ensemble requires avoiding the well-known stiffness problem associated with sampling infinitesimal Brownian increments of the path, as well as a different type of stiffness associated with sampling the coarse features of long paths. The fine-features sampling stiffness is eliminated with the use of the fast sampling algorithm (FSA), and the coarse-feature sampling stiffness is avoided by introducing the sliding and sampling (S&S) algorithm. A key feature of the S&S algorithm is that it enables massively parallel computers to sample diffusive trajectories that are long in time. We use the algorithm to sample the transition path ensemble for the structural interconversion of the 38-atom Lennard-Jones cluster at low temperature.
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
Pokemon Cards and the Shortest Common Superstring Mark Stamp Austin E Stamp
Stamp, Mark
PokÂ´emon Cards and the Shortest Common Superstring Mark Stamp Austin E Stamp June 12, 2003 Abstract Evidence is presented that certain sequences of PokÂ´emon cards are determined by selecting consecutive (SCS), i.e., the shortest string that contains each of the PokÂ´emon card sequences as a consecutive
Time Constrained Randomized Path Planning Using Spatial Networks Christopher Lum*
Lum, Christopher
Time Constrained Randomized Path Planning Using Spatial Networks Christopher Lum* Department time planning of optimal paths remains an open problem in many applications of autonomous systems an open problem. The path planning problem is often addressed as a non- holonomic planning problem
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.
White Matter Tract Analysis in 454 Adults using Maximum Density Paths
Thompson, Paul
fuzzy clustering [18], normalized cuts [5], k-means [15], spectral clustering [16], Dirichlet, tractography, MRI, brain, clustering, atlas, Dijk- stra, shortest path, geodesic distance, Hough, connectivity to be clustered for analysis. A wealth of clustering methods have been applied to tractography results including
Notes on Feynman path integral-like methods of quantization on Riemannian manifolds
Yoshihisa Miyanishi
2015-12-20
We propose an alternative method for Feynman path integrals on compact Riemannian manifolds. Our method employs action integrals along the shortest paths. In the case of rank 1 locally symmetric Riemannian manifolds, we prove the strong convergence of time slicing products of oscillatory integrals for low energy functions. Moreover, the strong limit includes Dewitt curvature $R/6$, where $R$ denotes the scalar curvature of a Riemannian manifold.
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.
The shortest modulation period Blazhko RR Lyrae star: SS Cnc
J. Jurcsik; B. Szeidl; Á. Sódor; I. Dékány; Zs. Hurta; K. Posztobányi; K. Vida; M. Váradi; A. Szing
2006-03-20
Extended BV(RI)c CCD observations of SS Cnc, a short period RRab star are presented. Nearly 1400 data points in each band have been obtained spanning over 79 days during the spring of 2005. The star exhibits light curve modulation, the so called Blazhko effect with small amplitude (B maximum brightness varies 0.1 mag) and with the shortest modulation period (5.309 d) ever observed. In the Fourier spectrum of the V light curve the pulsation frequency components are detected up to the 24th harmonic order, and modulation side lobe frequencies with significantly asymmetric amplitudes are seen up to the 15th and 9th orders for the lower and higher frequency components, respectively. Detailed comparison of the modulation behavior of SS Cnc and RR Gem, the two recently discovered small amplitude, short modulation period Blazhko stars is presented. The modulation frequency (f_m) appears in the Fourier spectrum of both stars with similar amplitude. We also demonstrate that the modulation frequencies have basically different properties as the pulsation and modulation side lobe frequencies have, indicating that the physics behind these frequency components are not the same. The discovery of small amplitude modulations of RRab stars cautions that the large photometric surveys (MACHO, OGLE) may seriously underestimate the number of modulated RR Lyrae stars.
Trajectory Generation and Path Planning for Autonomous Aerobots
NASA Technical Reports Server (NTRS)
Sharma, Shivanjli; Kulczycki, Eric A.; Elfes, Alberto
2007-01-01
This paper presents global path planning algorithms for the Titan aerobot based on user defined waypoints in 2D and 3D space. The algorithms were implemented using information obtained through a planner user interface. The trajectory planning algorithms were designed to accurately represent the aerobot's characteristics, such as minimum turning radius. Additionally, trajectory planning techniques were implemented to allow for surveying of a planar area based solely on camera fields of view, airship altitude, and the location of the planar area's perimeter. The developed paths allow for planar navigation and three-dimensional path planning. These calculated trajectories are optimized to produce the shortest possible path while still remaining within realistic bounds of airship dynamics.
A novel approach of global path planning for UGV
NASA Astrophysics Data System (ADS)
Choe, TokSon; Park, YongWoon; Kim, Jun; Kang, Sin Cheon; Jee, Tae Young; Ryu, Chul-Hyung
2006-05-01
Global path planning (GPP) is the generation of an optimal trajectory to efficiently move from one position to specified target position with known environment. Most of GPP methodologies offer an optimal 2D-shortest path without considering vehicle parameters on the plain environments. However, it is motivated to consider 3D terrain and vehicle parameters to enhance traversability on the rough terrain. In this paper, we propose a novel approach of GPP method for unmanned ground vehicles (UGVs) by applying distance transform (3D to 2D) based on the slope of terrain. In addition, the generated path is modified by smoothing process based on the local path planning method which considers vehicle stability on the specified candidate curve and speed. The proposed methodology is tested by simulations and shows enhanced performance.
Calculating Least Risk Paths in 3d Indoor Space
NASA Astrophysics Data System (ADS)
Vanclooster, A.; De Maeyer, Ph.; Fack, V.; Van de Weghe, N.
2013-08-01
Over the last couple of years, research on indoor environments has gained a fresh impetus; more specifically applications that support navigation and wayfinding have become one of the booming industries. Indoor navigation research currently covers the technological aspect of indoor positioning and the modelling of indoor space. The algorithmic development to support navigation has so far been left mostly untouched, as most applications mainly rely on adapting Dijkstra's shortest path algorithm to an indoor network. However, alternative algorithms for outdoor navigation have been proposed adding a more cognitive notion to the calculated paths and as such adhering to the natural wayfinding behaviour (e.g. simplest paths, least risk paths). These algorithms are currently restricted to outdoor applications. The need for indoor cognitive algorithms is highlighted by a more challenged navigation and orientation due to the specific indoor structure (e.g. fragmentation, less visibility, confined areas…). As such, the clarity and easiness of route instructions is of paramount importance when distributing indoor routes. A shortest or fastest path indoors not necessarily aligns with the cognitive mapping of the building. Therefore, the aim of this research is to extend those richer cognitive algorithms to three-dimensional indoor environments. More specifically for this paper, we will focus on the application of the least risk path algorithm of Grum (2005) to an indoor space. The algorithm as proposed by Grum (2005) is duplicated and tested in a complex multi-storey building. The results of several least risk path calculations are compared to the shortest paths in indoor environments in terms of total length, improvement in route description complexity and number of turns. Several scenarios are tested in this comparison: paths covering a single floor, paths crossing several building wings and/or floors. Adjustments to the algorithm are proposed to be more aligned to the specific structure of indoor environments (e.g. no turn restrictions, restricted usage of rooms, vertical movement) and common wayfinding strategies indoors. In a later stage, other cognitive algorithms will be implemented and tested in both an indoor and combined indoor-outdoor setting, in an effort to improve the overall user experience during navigation in indoor environments.
NASA Technical Reports Server (NTRS)
Mcroberts, Malcolm
1990-01-01
Viewgraphs on path planning control are presented. Topics covered include: model based path planning; sensor based path planning; hybrid path planning; proximity sensor array; and applications for fuzzy logic.
Modeling Strategic Optimization Criteria in Spatial Combinatorial Optimization Problems.
Perelman, Brandon; Mueller, Shane
2015-09-01
In many real-world route planning and search tasks, humans must solve a combinatorial optimization problem that holds many similarities to the Euclidean Traveling Salesman Problem (TSP). The problem spaces used in real-world tasks differ most starkly from traditional TSP in terms of optimization criteria - Whereas the traditional TSP asks participants to connect all of the nodes to produce the solution that minimizes overall path length, real-world search tasks are often conducted with the goal of minimizing the duration of time required to find the target (i.e., the average distance between nodes). Traditional modeling approaches to TSP assume that humans solve these problems using intrinsic characteristics of the brain and perceptual system (e.g., hierarchical structure in the visual system). A consequence of these approaches is that they are not robust to strategic changes in the aforementioned optimization criteria during path planning. To investigate performance in these tasks, 28 participants solved 18 randomly-presented computer-based combinatorial optimization problems with two sets of task instructions, one designed to encourage shortest-path solutions and the other to encourage solutions that minimized the estimated time to find a target hidden among the nodes (i.e., locations). The node distributions were designed to discriminate between these two strategies. In nearly every case, participants were capable of strategically adapting optimization criteria based on instruction alone. These results indicate the importance of modeling cognition in behaviors that are traditionally thought to be driven automatically by perceptual processes. In addition, we discuss computational models that we have developed to produce optimization criteria-specific solutions to these combinatorial optimization problems using a strategic optimization parameter to guide solutions using a single underlying mechanism. Such models have applications in approximating human behavior in real-world tasks. Meeting abstract presented at VSS 2015. PMID:26326160
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.
Analyzing the applicability of the least risk path algorithm in indoor space
NASA Astrophysics Data System (ADS)
Vanclooster, A.; Viaene, P.; Van de Weghe, N.; Fack, V.; De Maeyer, Ph.
2013-11-01
Over the last couple of years, applications that support navigation and wayfinding in indoor environments have become one of the booming industries. However, the algorithmic support for indoor navigation has so far been left mostly untouched, as most applications mainly rely on adapting Dijkstra's shortest path algorithm to an indoor network. In outdoor space, several alternative algorithms have been proposed adding a more cognitive notion to the calculated paths and as such adhering to the natural wayfinding behavior (e.g. simplest paths, least risk paths). The need for indoor cognitive algorithms is highlighted by a more challenged navigation and orientation due to the specific indoor structure (e.g. fragmentation, less visibility, confined areas…). Therefore, the aim of this research is to extend those richer cognitive algorithms to three-dimensional indoor environments. More specifically for this paper, we will focus on the application of the least risk path algorithm of Grum (2005) to an indoor space. The algorithm as proposed by Grum (2005) is duplicated and tested in a complex multi-story building. Several analyses compare shortest and least risk paths in indoor and in outdoor space. The results of these analyses indicate that the current outdoor least risk path algorithm does not calculate less risky paths compared to its shortest paths. In some cases, worse routes have been suggested. Adjustments to the original algorithm are proposed to be more aligned to the specific structure of indoor environments. In a later stage, other cognitive algorithms will be implemented and tested in both an indoor and combined indoor-outdoor setting, in an effort to improve the overall user experience during navigation in indoor environments.
Processor Would Find Best Paths On Map
NASA Technical Reports Server (NTRS)
Eberhardt, Silvio P.
1990-01-01
Proposed very-large-scale integrated (VLSI) circuit image-data processor finds path of least cost from specified origin to any destination on map. Cost of traversal assigned to each picture element of map. Path of least cost from originating picture element to every other picture element computed as path that preserves as much as possible of signal transmitted by originating picture element. Dedicated microprocessor at each picture element stores cost of traversal and performs its share of computations of paths of least cost. Least-cost-path problem occurs in research, military maneuvers, and in planning routes of vehicles.
Multiresolution Path Planning with Wavelets: A Local Replanning Approach
Tsiotras, Panagiotis
Multiresolution Path Planning with Wavelets: A Local Replanning Approach Raghvendra V. Cowlagi and Panagiotis Tsiotras Abstract-- A path planning algorithm based on multireso- lution cell decomposition approaches transform the path planning problem into a graph search problem. In particular, cell decomposition
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.
Mechanics of the crack path formation
NASA Technical Reports Server (NTRS)
Rubinstein, Asher A.
1989-01-01
A detailed analysis of experimentally obtained curvilinear crack path trajectories formed in a heterogeneous stress field is presented. Experimental crack path trajectories were used as data for numerical simulations, recreating the actual stress field governing the development of the crack path. Thus, the current theories of crack curving and kinking could be examined by comparing them with the actual stress field parameters as they develop along the experimentally observed crack path. The experimental curvilinear crack path trajectories were formed in the tensile specimens with a hole positioned in the vicinity of a potential crack path. The numerical simulation, based on the solution of equivalent boundary value problems with the possible perturbations of the crack path, is presented here.
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 children’s 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 children’s SCL, assessed in standard laboratory tasks at age 8 (N=81), as a moderator of the links between parent–child socialization history and children’s 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. Parent–child 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
of Physics, Bar-Ilan University, Ramat Gan, Israel 3 BP Exploration Operating Company Ltd., Sunbury away. For example, in oil recovery the rst passage time from the injection well to a production well
M*: A Complete Multirobot Path Planning Algorithm with Performance Glenn Wagner, Howie Choset
Choset, Howie
M*: A Complete Multirobot Path Planning Algorithm with Performance Bounds Glenn Wagner, Howie Choset Abstract-- Multirobot path planning is difficult because the full configuration space a high dimensional configuration space is the fundamental problem of multirobot path planning. Multirobot
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
Zone-Based Shortest Positioning Time First Scheduling for MEMS-Based Storage Devices
California at Santa Cruz, University of
Zone-Based Shortest Positioning Time First Scheduling for MEMS-Based Storage Devices Bo Hong, Scott. MEMS-based storage devices use orthog- onal magnetic or physical recording techniques and thou- sands of simultaneously active MEMS-based read-write tips to provide high-density low-latency non-volatile storage
Vanquishing the XCB Question: The Methodological Discovery of the Last Shortest Single Axiom for the
Fitelson, Branden
1. History, Signi cance, and Terminology With the use of an e ective methodology, we answer the nalVanquishing the XCB Question: The Methodological Discovery of the Last Shortest Single Axiom. With the inclusion of an e ective methodology, this article answers in detail a question that, for a quarter
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 of path, energy consumption or journey time. A path of complete coverage is a planned path in which
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 Astrophysics Data System (ADS)
Chin, Siu A.
2014-03-01
The sign-problem in PIMC simulations of non-relativistic fermions increases in serverity with the number of fermions and the number of beads (or time-slices) of the simulation. A large of number of beads is usually needed, because the conventional primitive propagator is only second-order and the usual thermodynamic energy-estimator converges very slowly from below with the total imaginary time. The Hamiltonian energy-estimator, while more complicated to evaluate, is a variational upper-bound and converges much faster with the total imaginary time, thereby requiring fewer beads. This work shows that when the Hamiltonian estimator is used in conjunction with fourth-order propagators with optimizable parameters, the ground state energies of 2D parabolic quantum-dots with approximately 10 completely polarized electrons can be obtain with ONLY 3-5 beads, before the onset of severe sign problems. This work was made possible by NPRP GRANT #5-674-1-114 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the author.
Path Coupling and Aggregate Path Coupling
Yevgeniy Kovchegov; Peter T. Otto
2015-01-13
In this survey paper, we describe and characterize an extension to the classical path coupling method applied statistical mechanical models, referred to as aggregate path coupling. In conjunction with large deviations estimates, we use this aggregate path coupling method to prove rapid mixing of Glauber dynamics for a large class of statistical mechanical models, including models that exhibit discontinuous phase transitions which have traditionally been more difficult to analyze rigorously. The parameter region for rapid mixing for the generalized Curie-Weiss-Potts model is derived as a new application of the aggregate path coupling method.
Path Coupling and Aggregate Path Coupling
Kovchegov, Yevgeniy
2015-01-01
In this survey paper, we describe and characterize an extension to the classical path coupling method applied statistical mechanical models, referred to as aggregate path coupling. In conjunction with large deviations estimates, we use this aggregate path coupling method to prove rapid mixing of Glauber dynamics for a large class of statistical mechanical models, including models that exhibit discontinuous phase transitions which have traditionally been more difficult to analyze rigorously. The parameter region for rapid mixing for the generalized Curie-Weiss-Potts model is derived as a new application of the aggregate path coupling method.
Optimizing Schedules for Prioritized Path Planning of MultiRobot Systems
Burgard, Wolfram
Optimizing Schedules for Prioritized Path Planning of MultiRobot Systems Maren Bennewitz y Wolfram prioritized and decoupled path planning techniques and even for large teams of robots. 1 Introduction Path for multiple mobile robots. This problem is significantly harder than the path planning problem for single
Energy Science and Technology Software Center (ESTSC)
2012-05-11
The ap command traveres all symlinks in a given file, directory, or executable name to identify the final absolute path. It can print just the final path, each intermediate link along with the symlink chan, and the permissions and ownership of each directory component in the final path. It has functionality similar to "which", except that it shows the final path instead of the first path. It is also similar to "pwd", but it canmore »provide the absolute path to a relative directory from the current working directory.« less
Surface-adaptive and Collision-avoiding Path Planning
Morik, Katharina
Surface-adaptive and Collision-avoiding Path Planning for Five-axis Milling Peter Bollweg, Dino-adaptive and Collision-avoiding Path Planning for Five-axis Milling Peter Bollweg, Dino Hasanbegovic, Heinrich M. 808/2006 January 2006 #12;Abstract Automatic path planning for 5-axis-milling is a difficult problem
A Path Planning Method Using Cubic Spiral with Curvature Constraint
Chen, Sheng-Wei
A Path Planning Method Using Cubic Spiral with Curvature Constraint Tzu-Chen Liang and Jing-Sin Liu@iis.sinica.edu.tw and liu@iis.sinica.edu.tw Abstract. This paper addresses a new path planning method, whose objective constraints like wall-collision avoidance. This will also be discussed. I. Introduction Path planning problem
Multi-Vehicle Path Planning in Dynamically Changing Environments
Pappas, George J.
Multi-Vehicle Path Planning in Dynamically Changing Environments Ali Ahmadzadeh1, Nader Motee2, Ali Jadbabaie1 and George Pappas1 Abstract-- In this paper, we propose a path planning method for nonholonomic this idea, we formulate an arbitrarily fine relaxation of the path planning problem as a nonconvex
Constraint Manifold Subsearch for Multirobot Path Planning with Cooperative Tasks
Choset, Howie
Constraint Manifold Subsearch for Multirobot Path Planning with Cooperative Tasks Glenn Wagner, Jae Il Kim, Konrad Urban, Howie Choset Abstract-- The cooperative path planning problem seeks. This paper describes a new approach to cooperative path planning called Constraint Manifold Subsearch (CMS
Safe Receding Horizon Path Planning for Autonomous Vehicles
Safe Receding Horizon Path Planning for Autonomous Vehicles Tom Schouwenaars Eric Feron Jonathan a recently developed approach to optimal path planning of autonomous vehicles to account for safety. Recent environments. A significant portion of the autonomy consists of path planning capabilities: the problem
Constraintbased Optimization of Priority Schemes for Decoupled Path Planning Techniques
Burgard, Wolfram
Constraintbased Optimization of Priority Schemes for Decoupled Path Planning Techniques Maren and in the ability to find valid plans. 1 Introduction Path planning is one of the fundamental problems in mobile in planning paths for multiple robots operating in a single, shared environment, where physical limitations
An Effective Framework for Path Planning amidst Movable Obstacles
Utrecht, Universiteit
An Effective Framework for Path Planning amidst Movable Obstacles Dennis Nieuwenhuisen A. Frank van Technical Report UU-CS-2006-035 www.cs.uu.nl ISSN: 0924-3275 #12;An Effective Framework for Path Planning framework for solving path planning problems among movable obstacles. Heuristics are presented to provide
Discrete Optimal View Path Planning Sebastian Haner and Anders Heyden
Lunds Universitet
Discrete Optimal View Path Planning Sebastian Haner and Anders Heyden Centre for Mathematical Sciences, Lund University, Lund, Sweden {haner,heyden}@maths.lth.se Keywords: Path Planning, Next Best View: This paper presents a discrete model of a sensor path planning problem, with a long-term planning horizon
A global path planning approach for redundant manipulators
NASA Technical Reports Server (NTRS)
Seereeram, Sanjeev; Wen, J.
1993-01-01
A new approach for global path planning of redundant manipulators is proposed. It poses the path planning problem as a finite time nonlinear control problem. The solution is found by a Newton-Raphson type algorithm. This technique is capable of handling various goal task descriptions as well as incorporating both joint and task space constraints. The algorithm has shown promising preliminary results in planning joint path sequences for 3R and 4R planar robots to meet Cartesian tip tracking and goal endpoint planning. It is robust with respect to local path planning problems such as singularity considerations and local minimum problems. Repetitive joint path solutions for cyclic end-effector tasks are also generated. Eventual goals of this work include implementation on full spatial robots, as well as provision of an interface for supervisory input to aid in path planning for more complex problems.
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.
Hot Big Planets Kepler Survey: Measuring the Repopulation Rate of the Shortest-Period Planets
Taylor, Stuart F
2013-01-01
By surveying new fields for the shortest-period "big" planets, the Kepler spacecraft could provide the statistics to more clearly measure the occurrence distributions of giant and medium planets. This would allow separate determinations for giant and medium planets of the relationship between the inward rate of tidal migration of planets and the strength of the stellar tidal dissipation (as expressed by the tidal quality factor Q). We propose a "Hot Big Planets Survey" to find new big planets to better determine the planet occurrence distribution at the shortest period. We call planets that Kepler will be able to find as "big", for the purpose of comparing the distribution of giant and medium planets (above and below 8 earth radii). The distribution of planets from one field has been interpreted to show that the shortest period giant planets are at the end of an ongoing flow of high eccentricity migration, likely from scattering from further out. The numbers of planets at these short periods is still small, l...
Path Planning for Elastic Plates Under Manipulation Constraints Florent Lamiraux Lydia E. Kavraki
Lamiraux, Florent
Path Planning for Elastic Plates Under Manipulation Constraints Florent Lamiraux Lydia E. Kavraki This paper addresses the problem of path planning for a thin elastic metal plate under fairly general Introduction The Problem The problem of planning a collision free path for a rigid robot has been extensively
Path layout on tree networks: Bounds in different label switching models
Epstein, Leah
Path layout on tree networks: Bounds in different label switching models Anat Bremler-Barr Leah Epstein Abstract Path Layout is a fundamental graph problem in label switching protocols. This problem protocol standardized recently by the IETF. Path layout is essentially the problem of reducing the size
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…
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.
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.
A Variational Approach to Path Planning in Three Dimensions Using Level Set Methods
Ferguson, Thomas S.
A Variational Approach to Path Planning in Three Dimensions Using Level Set Methods Thomas Cecil], proposing a variational approach to a path planning problem in three dimensions using a level set framework extends results seen in [4] to path planning in three dimensions. Path planning in an obstacle
An Experimental Comparison of Path Planning Techniques for Teams of Mobile Robots
Teschner, Matthias
An Experimental Comparison of Path Planning Techniques for Teams of Mobile Robots Maren Bennewitz,burgardˇ @informatik.uni-freiburg.de Abstract. This paper considers the problem of path planning for teams of mobile. The second approach is an ˘¤Ł -based path planning technique which computes the paths for the individual
A Variational Approach to Search and Path Planning Using Level Set Methods
Ferguson, Thomas S.
A Variational Approach to Search and Path Planning Using Level Set Methods Thomas Cecil ICES, UT September 30, 2004 Abstract In this paper we propose a variational approach to a path planning problem in 2 constraints has multiple applications. From path planning for autonomous vehicles [23], to computing tool path
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 Chinese Postman Problem in Regular Graphs of Suil O # , Douglas B. West +
West, Douglas B.
The Chinese Postman Problem in Regular Graphs of Odd Degree Suil O # , Douglas B. West + March 13, 2013 Abstract The Chinese Postman Problem in a multigraph is the problem of finding a shortest closed The Chinese Postman Problem was introduced in the early 1960s by the Chinese mathemati cian Guan Meigu
Efficient Path Planning for Mobile Robots in Environments with Deformable Objects
Teschner, Matthias
Efficient Path Planning for Mobile Robots in Environments with Deformable Objects Barbara Frank, we consider the problem of path planning in environments with non-rigid obstacles such as curtains planning is one of the fundamental problems in robotics, and the ability to plan collision-free paths
Path optimization with limited sensing ability Sung Ha Kanga,1
Ferguson, Thomas S.
-known watchman route problem [6], which shares the same goal except observers in the watchman route problem have. 1 #12;The watchman route problem, and the more general path planning problems have been studied of research may be found in [5, 9, 15, 20, 23, 25, 26, 38], including a survey [24] that provides many more
Discrete convexity : retractions, morphisms and the partition problem
Duchet, Pierre
a pour nombre de Helly h , pour nombre de Radon p 2 et a un k Ă¨me nombre de partition (gĂ©odĂ©sique) au is geodetically convex if it contains the vertices of any shortest path joining two of its elements). For instance) a finite connected graph whose (geodetic) convexity has Helly number h, Radon number p 2 and a k
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.
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 ...
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 Laplace’s 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.
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.
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.)
ERIC Educational Resources Information Center
Spanier, Graham B.; Glick, Paul C.
1980-01-01
Presents a demographic analysis of the paths to remarriage--the extent and timing of remarriage, social factors associated with remarriage, and the impact of the event which preceded remarriage (divorce or widowhood). (Author)
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.
Finding Good Paths: Applications of Least Cost Caloric Path Computations
Wood, Zoë J.
Google Earth API to explore the use of least cost caloric path computations to create an interactive path for the creation of crowd path computations that consider the terrain as one factor in agent path computations. The second application builds on the popular Google Earth API to provide a tool for users to compute
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.
TWINS: THE TWO SHORTEST PERIOD NON-INTERACTING DOUBLE DEGENERATE WHITE DWARF STARS
Mullally, F.; Badenes, Carles; Lupton, Robert; Thompson, Susan E.
2009-12-10
We report on the detection of the two shortest period non-interacting white dwarf binary systems. These systems, SDSS J143633.29+501026.8 and SDSS J105353.89+520031.0, were identified by searching for radial velocity variations in the individual exposures that make up the published spectra from the Sloan Digital Sky Survey. We followed up these systems with time series spectroscopy to measure the period and mass ratios of these systems. Although we only place a lower bound on the companion masses, we argue that they must also be white dwarf stars. With periods of approximately 1 hr, we estimate that the systems will merge in less than 100 Myr, but the merger product will likely not be massive enough to result in a Type 1a supernova.
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
DIGITAL SEARCH TREES AGAIN REVISITED: THE INTERNAL PATH LENGTH PERSPECTIVE
Prodinger, Helmut
DIGITAL SEARCH TREES AGAIN REVISITED: THE INTERNAL PATH LENGTH for the inte* *rnal path length in a symmetric digital search tree. The problem was open up to no* *w. We prove that for the binary digital search tree the variance is asymptotica* *lly equal
Use of a Colony of Cooperating Agents and MAPLE To Solve the Traveling Salesman Problem.
ERIC Educational Resources Information Center
Guerrieri, Bruno
This paper reviews an approach for finding optimal solutions to the traveling salesman problem, a well-known problem in combinational optimization, and describes implementing the approach using the MAPLE computer algebra system. The method employed in this approach to the problem is similar to the way ant colonies manage to establish shortest…
Autonomous Ground Vehicle Path Tracking
Florida, University of
Autonomous Ground Vehicle Path Tracking Jeff Wit Wintec, Inc. 104 Research Road, Building 9738 vehicle navigation requires the integration of many technologies such as path planning, position of a nonholonomic ground vehicle as it tracks a given path. A new path tracking technique called ``vector pursuit
Path planning for everday robotics with SANDROS
Watterberg, P.; Xavier, P.; Hwang, Y.
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.
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 ...
Minimum energy path planning for ad hoc networks
Chen, Danjie
2005-01-01
We introduce the problem of finding a path for a mobile node traveling from a source to a destination while communicating with at least one node from a set of stationary nodes in such a way that minimizes the transmission ...
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 ...
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 ...
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.
Kambhampati, Subbarao
is discussed. I. INTRODUCTION THE PROBLEM of automatic collision-free path planning is central to mobile robot applications. Path planning for mobile robots is inmanyways different from the more familiarcase of path occlusionand reduction in the field of view. Conventional path-planning algorithms can be divided broadly
Path matching and graph matching in biological networks.
Yang, Qingwu; Sze, Sing-Hoi
2007-01-01
We develop algorithms for the following path matching and graph matching problems: (i) given a query path p and a graph G, find a path p' that is most similar to p in G; (ii) given a query graph G (0) and a graph G, find a graph G (0)' that is most similar to G (0) in G. In these problems, p and G (0) represent a given substructure of interest to a biologist, and G represents a large network in which the biologist desires to find a related substructure. These algorithms allow the study of common substructures in biological networks in order to understand how these networks evolve both within and between organisms. We reduce the path matching problem to finding a longest weighted path in a directed acyclic graph and show that the problem of finding top k suboptimal paths can be solved in polynomial time. This is in contrast with most previous approaches that used exponential time algorithms to find simple paths which are practical only when the paths are short. We reduce the graph matching problem to finding highest scoring subgraphs in a graph and give an exact algorithm to solve the problem when the query graph G (0) is of moderate size. This eliminates the need for less accurate heuristic or randomized algorithms. We show that our algorithms are able to extract biologically meaningful pathways from protein interaction networks in the DIP database and metabolic networks in the KEGG database. Software programs implementing these techniques (PathMatch and GraphMatch) are available at http://faculty.cs.tamu.edu/shsze/pathmatch and http://faculty.cs.tamu.edu/shsze/graphmatch. PMID:17381346
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…
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
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.
Approximate path seeking for statistical iterative reconstruction
NASA Astrophysics Data System (ADS)
Wu, Meng; Yang, Qiao; Maier, Andreas; Fahrig, Rebecca
2015-03-01
Statistical iterative reconstruction (IR) techniques have demonstrated many advantages in X-ray CT reconstruction. The statistical iterative reconstruction approach is often modeled as an optimization problem including a data fitting function and a penalty function. The tuning parameter values that regulate the strength of the penalty function are critical for achieving good reconstruction results. However, appropriate tuning parameter values that are suitable for the scan protocols and imaging tasks are often difficult to choose. In this work, we propose a path seeking algorithm that is capable of generating a series of IR images with different strengths of the penalty function. The path seeking algorithm uses the ratio of the gradients of the data fitting function and the penalty function to select pixels for small fixed size updates. We describe the path seeking algorithm for penalized weighted least squares (PWLS) with a Huber penalty function in both the directions of increasing and decreasing tuning parameter value. Simulations using the XCAT phantom show the proposed method produces path images that are very similar to the IR images that are computed via direct optimization. The root-mean- squared-error of one path image generated by the proposed method relative to full iterative reconstruction is about 6 HU for the entire image and 10 HU for a small region. Different path seeking directions, increment sizes and updating percentages of the path seeking algorithm are compared in simulations. The proposed method may reduce the dependence on selection of good tuning parameter values by instead generating multiple IR images, without significantly increasing the computational load.
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
Distributed Path Planning for Mobile Robots using a Swarm of Interacting Reinforcement Learners
Massachusetts at Amherst, University of
Distributed Path Planning for Mobile Robots using a Swarm of Interacting Reinforcement Learners Amherst, MA, United States vigorito@cs.umass.edu ABSTRACT Path planning for mobile robots in stochastic. While many approaches to solving this problem put the computational burden of path planning on the robot
Path Planning using a Dynamic Vehicle Model Romain Pepy, Alain Lambert and Hugues Mounier
Choset, Howie
Path Planning using a Dynamic Vehicle Model Romain Pepy, Alain Lambert and Hugues Mounier Institut {pepy, lambert, mounier} @ief. u-psud.fr Abstract This paper addresses the problem of path plan- nrng can significantly deviate from the planned trajectory. Consequently, the planned path becomes unusable
An E#ective Framework for Path Planning amidst Movable Obstacles
Utrecht, Universiteit
An E#ective Framework for Path Planning amidst Movable Obstacles Dennis Nieuwenhuisen A. Frank van Technical Report UUCS2006035 www.cs.uu.nl ISSN: 09243275 #12; An E#ective Framework for Path Planning framework for solving path planning problems among movable obstacles. Heuristics are presented to provide e
Constraint-based Optimization of Priority Schemes for Decoupled Path Planning Techniques
Teschner, Matthias
Constraint-based Optimization of Priority Schemes for Decoupled Path Planning Techniques Maren and in the ability to find valid plans. 1 Introduction Path planning is one of the fundamental problems in mobile in planning paths for multiple robots operating in a single, shared environment, where physical limitations
An Experimental Comparison of Path Planning Techniques for Teams of Mobile Robots
Burgard, Wolfram
An Experimental Comparison of Path Planning Techniques for Teams of Mobile Robots Maren Bennewitz,burgardg@informatik.unifreiburg.de Abstract. This paper considers the problem of path planning for teams of mobile robots. It investigates two planning technique which computes the paths for the individual robots in the con figuration time
Randomized Path Planning on Manifolds based on Higher-Dimensional Continuation
Porta, Josep M.
Randomized Path Planning on Manifolds based on Higher-Dimensional Continuation Josep M. Porta, L Abstract Despite the significant advances in path planning methods, highly constrained problems are still space manifold. In this paper, we present a new path planning algorithm specially tailored for highly
The Path of a Pseudo-Triangulation Oswin Aichholzer Bettina Speckmann Ileana Streinu
The Path of a Pseudo-Triangulation Oswin Aichholzer Bettina Speckmann Ileana Streinu Abstract We define the path of a pseudo-triangulation, a data structure generalizing the path of a triangulation.e. decompos- able) problems on pseudo-triangulations. We illustrate this method by presenting a novel
Path integral quantization of parametrized field theory
NASA Astrophysics Data System (ADS)
Varadarajan, Madhavan
2004-10-01
Free scalar field theory on a flat spacetime can be cast into a generally covariant form known as parametrized field theory in which the action is a functional of the scalar field as well as the embedding variables which describe arbitrary, in general curved, foliations of the flat spacetime. We construct the path integral quantization of parametrized field theory in order to analyze issues at the interface of quantum field theory and general covariance in a path integral context. We show that the measure in the Lorentzian path integral is nontrivial and is the analog of the Fradkin-Vilkovisky measure for quantum gravity. We construct Euclidean functional integrals in the generally covariant setting of parametrized field theory using key ideas of Schleich and show that our constructions imply the existence of nonstandard “Wick rotations” of the standard free scalar field two-point function. We develop a framework to study the problem of time through computations of scalar field two-point functions. We illustrate our ideas through explicit computation for a time independent (1+1)-dimensional foliation. Although the problem of time seems to be absent in this simple example, the general case is still open. We discuss our results in the contexts of the path integral formulation of quantum gravity and the canonical quantization of parametrized field theory.
Swift J1753.5-0127: The Black Hole Candidate with the shortest orbital period
C. Zurita; M. Durant; M. A. P. Torres; T. Shahbaz; J. Casares; D. Steeghs
2008-03-17
We present time-resolved photometry of the optical counterpart to the black hole candidate Swift J1753.5-0127, which has remained in the low/hard X-ray state and bright at optical/IR wavelengths since its discovery in 2005. At the time of our observations Swift J1753.5-0127 does not show a decay trend but remains stable at R=16.45 with a night to night variability of ~0.05 mag. The R-band light curves, taken from 2007 June 3 to August 31, are not sinusoidal, but exhibit a complex morphology with remarkable changes in shape and amplitude. The best period determination is 3.2443+-0.0010 hours. This photometric period is likely a superhump period, slightly larger than the orbital period. Therefore, Swift J1753.5-0127 is the black hole candidate with the shortest orbital period observed to date. Our estimation of the distance is comparable to values previously published and likely places Swift J1753.5-0127 in the Galactic halo.
Resonating-Valence-Bond Physics Is Not Always Governed by the Shortest Tunneling Loops.
Ralko, Arnaud; Rousochatzakis, Ioannis
2015-10-16
It is well known that the low-energy sector of quantum spin liquids and other magnetically disordered systems is governed by short-ranged resonating-valence bonds. Here we show that the standard minimal truncation to the nearest-neighbor valence-bond basis fails completely even for systems where it should work the most, according to received wisdom. This paradigm shift is demonstrated for the quantum spin-1/2 square kagome, where strong geometric frustration, similar to the kagome, prevents magnetic ordering down to zero temperature. The shortest tunneling events bear the strongest longer-range singlet fluctuations, leading to amplitudes that do not drop exponentially with the length of the loop L, and to an unexpected loop-six valence-bond crystal, which is otherwise very high in energy at the minimal truncation level. The low-energy effective description gives in addition a clear example of correlated loop processes that depend not only on the type of the loop but also on its lattice embedding, a direct manifestation of the long-range nature of the virtual singlets. PMID:26550898
Resonating-Valence-Bond Physics Is Not Always Governed by the Shortest Tunneling Loops
NASA Astrophysics Data System (ADS)
Ralko, Arnaud; Rousochatzakis, Ioannis
2015-10-01
It is well known that the low-energy sector of quantum spin liquids and other magnetically disordered systems is governed by short-ranged resonating-valence bonds. Here we show that the standard minimal truncation to the nearest-neighbor valence-bond basis fails completely even for systems where it should work the most, according to received wisdom. This paradigm shift is demonstrated for the quantum spin-1 /2 square kagome, where strong geometric frustration, similar to the kagome, prevents magnetic ordering down to zero temperature. The shortest tunneling events bear the strongest longer-range singlet fluctuations, leading to amplitudes that do not drop exponentially with the length of the loop L , and to an unexpected loop-six valence-bond crystal, which is otherwise very high in energy at the minimal truncation level. The low-energy effective description gives in addition a clear example of correlated loop processes that depend not only on the type of the loop but also on its lattice embedding, a direct manifestation of the long-range nature of the virtual singlets.
Chew, Geoffrey F
2008-01-01
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.
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.
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.
Algorithms and Sensors for Small Robot Path Following
NASA Technical Reports Server (NTRS)
Hogg, Robert W.; Rankin, Arturo L.; Roumeliotis, Stergios I.; McHenry, Michael C.; Helmick, Daniel M.; Bergh, Charles F.; Matthies, Larry
2002-01-01
Tracked mobile robots in the 20 kg size class are under development for applications in urban reconnaissance. For efficient deployment, it is desirable for teams of robots to be able to automatically execute path following behaviors, with one or more followers tracking the path taken by a leader. The key challenges to enabling such a capability are (l) to develop sensor packages for such small robots that can accurately determine the path of the leader and (2) to develop path following algorithms for the subsequent robots. To date, we have integrated gyros, accelerometers, compass/inclinometers, odometry, and differential GPS into an effective sensing package. This paper describes the sensor package, sensor processing algorithm, and path tracking algorithm we have developed for the leader/follower problem in small robots and shows the result of performance characterization of the system. We also document pragmatic lessons learned about design, construction, and electromagnetic interference issues particular to the performance of state sensors on small robots.
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.
NASA Technical Reports Server (NTRS)
Robinson, Judith L.; Charles, John B.; Rummel, John A. (Technical Monitor)
2000-01-01
Approximately three years ago, the Agency's lead center for the human elements of spaceflight (the Johnson Space Center), along with the National Biomedical Research Institute (NSBRI) (which has the lead role in developing countermeasures) initiated an activity to identify the most critical risks confronting extended human spaceflight. Two salient factors influenced this activity: first, what information is needed to enable a "go/no go" decision to embark on extended human spaceflight missions; and second, what knowledge and capabilities are needed to address known and potential health, safety and performance risks associated with such missions. A unique approach was used to first define and assess those risks, and then to prioritize them. This activity was called the Critical Path Roadmap (CPR) and it represents an opportunity to develop and implement a focused and evolving program of research and technology designed from a "risk reduction" perspective to prevent or minimize the risks to humans exposed to the space environment. The Critical Path Roadmap provides the foundation needed to ensure that human spaceflight, now and in the future, is as safe, productive and healthy as possible (within the constraints imposed on any particular mission) regardless of mission duration or destination. As a tool, the Critical Path Roadmap enables the decisionmaker to select from among the demonstrated or potential risks those that are to be mitigated, and the completeness of that mitigation. The primary audience for the CPR Web Site is the members of the scientific community who are interested in the research and technology efforts required for ensuring safe and productive human spaceflight. They may already be informed about the various space life sciences research programs or they may be newcomers. Providing the CPR content to potential investigators increases the probability of their delivering effective risk mitigations. Others who will use the CPR Web Site and its content include program managers and administrators who track the program and are involved in decisions regarding resource allocation and program evaluation.
NASA Technical Reports Server (NTRS)
Robinson, Judith L.; Charles, John B.; Rummel, John A. (Technical Monitor)
2000-01-01
Approximately three years ago, the Agency's lead center for the human elements of spaceflight (the Johnson Space Center), along with the National Biomedical Research Institute (NSBRI) (which has the lead role in developing countermeasures) initiated an activity to identify the most critical risks confronting extended human spaceflight. Two salient factors influenced this activity: first, what information is needed to enable a "go/no go" decision to embark on extended human spaceflight missions; and second, what knowledge and capabilities are needed to address known and potential health, safety and performance risks associated with such missions. A unique approach was used to first define and assess those risks, and then to prioritize them. This activity was called the Critical Path Roadmap (CPR) and it represents an opportunity to develop and implement a focused and evolving program of research and technology designed from a "risk reduction" perspective to prevent or minimize the risks to humans exposed to the space environment. The Critical Path Roadmap provides the foundation needed to ensure that human spaceflight, now and in the future, is as safe, productive and healthy as possible (within the constraints imposed on any particular mission) regardless of mission duration or destination. As a tool, the Critical Path Roadmap enables the decision maker to select from among the demonstrated or potential risks those that are to be mitigated, and the completeness of that mitigation. The primary audience for the CPR Web Site is the members of the scientific community who are interested in the research and technology efforts required for ensuring safe and productive human spaceflight. They may already be informed about the various space life sciences research programs or they may be newcomers. Providing the CPR content to potential investigators increases the probability of their delivering effective risk mitigations. Others who will use the CPR Web Site and its content include program managers and administrators who track the program and are involved in decisions regarding resource allocation and program evaluation.
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
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.
Damage detection using frequency shift path
NASA Astrophysics Data System (ADS)
Wang, Longqi; Lie, Seng Tjhen; Zhang, Yao
2016-01-01
This paper introduces a novel concept called FREquency Shift (FRESH) path to describe the dynamic behavior of structures with auxiliary mass. FRESH path combines the effects of frequency shifting and amplitude changing into one space curve, providing a tool for analyzing structure health status and properties. A damage index called FRESH curvature is then proposed to detect local stiffness reduction. FRESH curvature can be easily adapted for a particular problem since the sensitivity of the index can be adjusted by changing auxiliary mass or excitation power. An algorithm is proposed to adjust automatically the contribution from frequency and amplitude in the method. Because the extraction of FRESH path requires highly accurate frequency and amplitude estimators; therefore, a procedure based on discrete time Fourier transform is introduced to extract accurate frequency and amplitude with the time complexity of O (n log n), which is verified by simulation signals. Moreover, numerical examples with different damage sizes, severities and damping are presented to demonstrate the validity of the proposed damage index. In addition, applications of FRESH path on two steel beams with different damages are presented and the results show that the proposed method is valid and computational efficient.
Star-Paths, Stones and Horizon Astronomy
NASA Astrophysics Data System (ADS)
Brady, Bernadette
2015-05-01
Archaeoastronomers tend to approach ancient monuments focusing on the landscape and the horizon calendar events of sun and moon and, due to problems with precession, generally ignore the movement of the stars. However, locating the position of solar calendar points on the horizon can have other uses apart from calendar and/or cosmological purposes. This paper firstly suggests that the stars do not need to be ignored. By considering the evidence of the Phaenomena, a sky poem by Aratus of Soli, a third century BC Greek poet, and his use of second millennium BC star lore fragments, this paper argues that the stars were a part of the knowledge of horizon astronomy. Aratus' poem implied that the horizon astronomy of the late Neolithic and Bronze Age periods included knowledge of star-paths or 'linear constellations' that were defined by particular horizon calendar events and other azimuths. Knowledge of such star-paths would have enabled navigation and orientation, and by using permanent markers, constructed or natural, to define these paths, they were immune to precession as the stones could redefine a star-path for a future generation. Finally the paper presents other possible intentions behind the diverse orientation of passage tombs and some megalithic sites.
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.
Two arm robot path planning in a static environment using polytopes and string stretching. Thesis
NASA Technical Reports Server (NTRS)
Schima, Francis J., III
1990-01-01
The two arm robot path planning problem has been analyzed and reduced into components to be simplified. This thesis examines one component in which two Puma-560 robot arms are simultaneously holding a single object. The problem is to find a path between two points around obstacles which is relatively fast and minimizes the distance. The thesis involves creating a structure on which to form an advanced path planning algorithm which could ideally find the optimum path. An actual path planning method is implemented which is simple though effective in most common situations. Given the limits of computer technology, a 'good' path is currently found. Objects in the workspace are modeled with polytopes. These are used because they can be used for rapid collision detection and still provide a representation which is adequate for path planning.
A Flight Examination of Operating Problems of V/STOL Aircraft in STOL-Type Landing and Approach
NASA Technical Reports Server (NTRS)
Innis, Robert C.; Quigley, Hervey C.
1961-01-01
A flight investigation has been conducted using a large twin-engine cargo aircraft to isolate the problems associated with operating propeller-driven aircraft in the STOL speed range where appreciable engine power is used to augment aerodynamic lift. The problems considered would also be representative of those of a large overloaded VTOL aircraft operating in an STOL manner with comparable thrust-to-weight ratios. The study showed that operation at low approach speeds was compromised by the necessity of maintaining high thrust to generate high lift and yet achieving the low lift-drag ratios needed for steep descents. The useable range of airspeed and flight path angle was limited by the pilot's demand for a positive climb margin at the approach speed, a suitable stall margin, and a control and/or performance margin for one engine inoperative. The optimum approach angle over an obstacle was found to be a compromise between obtaining the shortest air distance and the lowest touchdown velocity. In order to realize the greatest low-speed potential from STOL designs, the stability and control characteristics must be satisfactory.
MAXI J1659-152: the shortest orbital period black-hole transient in outburst
NASA Astrophysics Data System (ADS)
Kuulkers, E.; Kouveliotou, C.; Belloni, T.; Cadolle Bel, M.; Chenevez, J.; Díaz Trigo, M.; Homan, J.; Ibarra, A.; Kennea, J. A.; Muńoz-Darias, T.; Ness, J.-U.; Parmar, A. N.; Pollock, A. M. T.; van den Heuvel, E. P. J.; van der Horst, A. J.
2013-04-01
MAXI J1659-152 is a bright X-ray transient black-hole candidate binary system discovered in September 2010. We report here on MAXI, RXTE, Swift, and XMM-Newton observations during its 2010/2011 outburst. We find that during the first one and a half week of the outburst the X-ray light curves display drops in intensity at regular intervals, which we interpret as absorption dips. About three weeks into the outbursts, again drops in intensity are seen. These dips have, however, a spectral behaviour opposite to that of the absorption dips, and are related to fast spectral state changes (hence referred to as transition dips). The absorption dips recur with a period of 2.414 ± 0.005 h, which we interpret as the orbital period of the system. This implies that MAXI J1659-152 is the shortest period black-hole candidate binary known to date. The inclination of the accretion disk with respect to the line of sight is estimated to be 65-80°. We propose the companion to the black-hole candidate to be close to an M5 dwarf star, with a mass and radius of about 0.15-0.25 M? and 0.2-0.25 R?, respectively. We derive that the companion had an initial mass of about 1.5 M?, which evolved to its current mass in about 5-6 billion years. The system is rather compact (orbital separation of ?1.33 R?), and is located at a distance of 8.6 ± 3.7 kpc, with a height above the Galactic plane of 2.4 ± 1.0 kpc. The characteristics of short orbital period and high Galactic scale height are shared with two other transient black-hole candidate X-ray binaries, i.e., XTE J1118+480 and Swift J1735.5-0127. We suggest that all three are kicked out of the Galactic plane into the halo, rather than being formed in a globular cluster. Table 1 is available in electronic form at http://www.aanda.org
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.
One-dimensional Gromov minimal filling problem
Ivanov, Alexandr O; Tuzhilin, Alexey A
2012-05-31
The paper is devoted to a new branch in the theory of one-dimensional variational problems with branching extremals, the investigation of one-dimensional minimal fillings introduced by the authors. On the one hand, this problem is a one-dimensional version of a generalization of Gromov's minimal fillings problem to the case of stratified manifolds. On the other hand, this problem is interesting in itself and also can be considered as a generalization of another classical problem, the Steiner problem on the construction of a shortest network connecting a given set of terminals. Besides the statement of the problem, we discuss several properties of the minimal fillings and state several conjectures. Bibliography: 38 titles.
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.
Restricted Delivery Problems on a Network Esther M. Arkin y , Refael Hassin z and Limor Klein x
Arkin, Estie
Restricted Delivery Problems on a Network Esther M. Arkin y , Refael Hassin z and Limor Klein x December 17, 1996 Abstract We consider a delivery problem on a network one is given a network in which asks for a shortest delivery route of all products from their origin to their destination. Here we
Solving closest vector instances using an approximate shortest independent vectors oracle
International Association for Cryptologic Research (IACR)
mathematical objects that have been used to efficiently solve many important problems in computer science, most Laboratory of Information Security, Institute of Information Engineering, Chinese Academy of Sciences, this paper studies the algorithms for approximate closest vector problem (CVP) by using an approximate
Hard paths, soft paths or no paths? Cross-cultural perceptions of water solutions
NASA Astrophysics Data System (ADS)
Wutich, A.; White, A. C.; White, D. D.; Larson, K. L.; Brewis, A.; Roberts, C.
2014-01-01
In this study, we examine how development status and water scarcity shape people's perceptions of "hard path" and "soft path" water solutions. Based on ethnographic research conducted in four semi-rural/peri-urban sites (in Bolivia, Fiji, New Zealand, and the US), we use content analysis to conduct statistical and thematic comparisons of interview data. Our results indicate clear differences associated with development status and, to a lesser extent, water scarcity. People in the two less developed sites were more likely to suggest hard path solutions, less likely to suggest soft path solutions, and more likely to see no path to solutions than people in the more developed sites. Thematically, people in the two less developed sites envisioned solutions that involve small-scale water infrastructure and decentralized, community-based solutions, while people in the more developed sites envisioned solutions that involve large-scale infrastructure and centralized, regulatory water solutions. People in the two water-scarce sites were less likely to suggest soft path solutions and more likely to see no path to solutions (but no more likely to suggest hard path solutions) than people in the water-rich sites. Thematically, people in the two water-rich sites seemed to perceive a wider array of unrealized potential soft path solutions than those in the water-scarce sites. On balance, our findings are encouraging in that they indicate that people are receptive to soft path solutions in a range of sites, even those with limited financial or water resources. Our research points to the need for more studies that investigate the social feasibility of soft path water solutions, particularly in sites with significant financial and natural resource constraints.
Hard paths, soft paths or no paths? Cross-cultural perceptions of water solutions
NASA Astrophysics Data System (ADS)
Wutich, A.; White, A. C.; Roberts, C. M.; White, D. D.; Larson, K. L.; Brewis, A.
2013-06-01
In this study, we examine how development status and water scarcity shape people's perceptions of "hard path" and "soft path" water solutions. Based on ethnographic research conducted in four semi-rural/peri-urban sites (in Bolivia, Fiji, New Zealand, and the US), we use content analysis to conduct statistical and thematic comparisons of interview data. Our results indicate clear differences based on development status and, to a lesser extent, water scarcity. People in less developed sites were more likely to suggest hard path solutions, less likely to suggest soft path solutions, and more likely to see no path to solutions than people in more developed sites. Thematically, people in less developed sites envisioned solutions that involve small-scale water infrastructure and decentralized, community based solutions, while people in more developed sites envisioned solutions that involve large-scale infrastructure and centralized, regulatory water solutions. People in water-scarce sites were less likely to suggest soft path solutions and more likely to see no path to solutions (but no more likely to suggest hard path solutions) than people in water-rich sites. Thematically, people in water-rich sites seemed to perceive a wider array of unrealized potential soft path solutions than those in water-scarce sites. On balance, our findings are encouraging in that they indicate that people are receptive to soft path solutions in a range of sites, even those with limited financial or water resources. Our research points to the need for more studies that investigate the social feasibility of soft path water solutions, particularly in sites with significant financial and natural resource constraints.
Dudek, Gregory
Socially-Driven Collective Path Planning for Robot Missions Juan Camilo Gamboa Higuera, Anqi Xu,anqixu,florian,dudek}@cim.mcgill.ca Abstract--We address the problem of path planning for robot missions based on waypoints suggested. We then propose an approximative path planning algorithm with parameterized control over the degree
Agarwal, Pankaj K.
Nonholonomic Path Planning for Pushing a Disk Among Obstacles Pankaj K. Agarwal Jean-Claude Latombe y Rajeev Motwani z Prabhakar Raghavan x Abstract We consider the path-planning problem for a robot the path-planning prob- lem for a robot pushing an object on a plane cluttered with obstacles, under quasi
Pappas, George J.
A Duality Approach to Path Planning for Multiple Robots Nader Motee1, Ali Jadbabaie2, and George Pappas2 Abstract-- In this paper, we propose an optimization-based framework for path planning) and collision avoidance. First, we formulate a relaxation of the path planning problem using polygonal
IEEE TRANSACTIONS ON ROBOTICS, VOL. 26, NO. 4, AUGUST 2010 635 Sampling-Based Path Planning on
Cortés, Juan
IEEE TRANSACTIONS ON ROBOTICS, VOL. 26, NO. 4, AUGUST 2010 635 Sampling-Based Path Planning have been developed in field robotics for outdoor navigation, where the goal is to find optimal paths.g., real-time problems [7], [10] or statisti- cal learning of feasible paths [8]) in the context of 2-D
Heuristically optimal path scanning for high-speed multiphoton circuit imaging.
Sadovsky, Alexander J; Kruskal, Peter B; Kimmel, Joseph M; Ostmeyer, Jared; Neubauer, Florian B; MacLean, Jason N
2011-09-01
Population dynamics of patterned neuronal firing are fundamental to information processing in the brain. Multiphoton microscopy in combination with calcium indicator dyes allows circuit dynamics to be imaged with single-neuron resolution. However, the temporal resolution of fluorescent measures is constrained by the imaging frequency imposed by standard raster scanning techniques. As a result, traditional raster scans limit the ability to detect the relative timing of action potentials in the imaged neuronal population. To maximize the speed of fluorescence measures from large populations of neurons using a standard multiphoton laser scanning microscope (MPLSM) setup, we have developed heuristically optimal path scanning (HOPS). HOPS optimizes the laser travel path length, and thus the temporal resolution of neuronal fluorescent measures, using standard galvanometer scan mirrors. Minimizing the scan path alone is insufficient for prolonged high-speed imaging of neuronal populations. Path stability and the signal-to-noise ratio become increasingly important factors as scan rates increase. HOPS addresses this by characterizing the scan mirror galvanometers to achieve prolonged path stability. In addition, the neuronal dwell time is optimized to sharpen the detection of action potentials while maximizing scan rate. The combination of shortest path calculation and minimization of mirror positioning time allows us to optically monitor a population of neurons in a field of view at high rates with single-spike resolution, ? 125 Hz for 50 neurons and ? 8.5 Hz for 1,000 neurons. Our approach introduces an accessible method for rapid imaging of large neuronal populations using traditional MPLSMs, facilitating new insights into neuronal circuit dynamics. PMID:21715667
Schiefer, H. Peters, S.; Plasswilm, L.; Ingulfsen, N.; Kluckert, J.
2015-03-15
Purpose: For stereotactic radiosurgery, the AAPM Report No. 54 [AAPM Task Group 42 (AAPM, 1995)] requires the overall stability of the isocenter (couch, gantry, and collimator) to be within a 1 mm radius. In reality, a rotating system has no rigid axis and thus no isocenter point which is fixed in space. As a consequence, the isocenter concept is reviewed here. It is the aim to develop a measurement method following the revised definitions. Methods: The mechanical isocenter is defined here by the point which rotates on the shortest path in the room coordinate system. The path is labeled as “isocenter path.” Its center of gravity is assumed to be the mechanical isocenter. Following this definition, an image-based and radiation-free measurement method was developed. Multiple marker pairs in a plane perpendicular to the assumed gantry rotation axis of a linear accelerator are imaged with a smartphone application from several rotation angles. Each marker pair represents an independent measuring system. The room coordinates of the isocenter path and the mechanical isocenter are calculated based on the marker coordinates. The presented measurement method is by this means strictly focused on the mechanical isocenter. Results: The measurement result is available virtually immediately following completion of measurement. When 12 independent measurement systems are evaluated, the standard deviations of the isocenter path points and mechanical isocenter coordinates are 0.02 and 0.002 mm, respectively. Conclusions: The measurement is highly accurate, time efficient, and simple to adapt. It is therefore suitable for regular checks of the mechanical isocenter characteristics of the gantry and collimator rotation axis. When the isocenter path is reproducible and its extent is in the range of the needed geometrical accuracy, it should be taken into account in the planning process. This is especially true for stereotactic treatments and radiosurgery.
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.
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.
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.
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
Pappas, George J.
Elastic Multi-Particle Systems for Bounded-Curvature Path Planning Ali Ahmadzadeh, Ali Jadbabaie, George J. Pappas and Vijay Kumar Abstract-- This paper investigates a path planning algorithm for Dubins The bounded-curvature path-planning problem, a central problem in robotics, involves planning a collision
Graviton-graviton scattering and path integral
NASA Astrophysics Data System (ADS)
Li, Rong
One of the exciting developments to emerge from the work in recent years on string duality is the conjecture proposed by Banks, Fischler, Shenker and Susskind (BFSS) that in the infinite momentum frame, String theory (M theory) is described by a large N matrix model. In addition, the finite N matrix model has been conjectured to describe M-theory on a compact light-like circle. Although there are still many open questions in the Matrix model formulation of M-theory, numerous pieces of evidence give one reason to believe that finite N matrix theory describes the discrete light-cone quantization (DLCQ) of M-theory with eleven dimensional DLCQ supergravity as its low energy limit. One of the important Pieces of support for the original Matrix model conjecture was that it successfully reproduced graviton- graviton scattering in eleven dimensional supergravity. In this thesis, we verify the duality of Matrix model and eleven dimensional supergravity on multigraviton scattering amplitude by a path integral approach. This systematic path integral approach to compute the S-Matrix resolves the ordering problem for applying the second order Born approximation to the velocity dependent one- loop effective potential of the Matrix model. By applying the rules derived from the path integral approach, the exact agreement between the Matrix model and the eleven dimensional supergravity on the scattering amplitude of six gravitons-three incoming and three outgoing, is verified.
Faster sieving for shortest lattice vectors using spherical locality-sensitive hashing
International Association for Cryptologic Research (IACR)
], and efficient crypto- graphic primitives like NTRU [20] and LWE [40]. An important problem in the study], and a recent method based on discrete Gaussian sampling [1]. Enumeration has a low space complexity, but a time
Heuristic optimization of the scanning path of particle therapy beams
Pardo, J.; Donetti, M.; Bourhaleb, F.; Ansarinejad, A.; Attili, A.; Cirio, R.; Garella, M. A.; Giordanengo, S.; Givehchi, N.; La Rosa, A.; Marchetto, F.; Monaco, V.; Pecka, A.; Peroni, C.; Russo, G.; Sacchi, R.
2009-06-15
Quasidiscrete scanning is a delivery strategy for proton and ion beam therapy in which the beam is turned off when a slice is finished and a new energy must be set but not during the scanning between consecutive spots. Different scanning paths lead to different dose distributions due to the contribution of the unintended transit dose between spots. In this work an algorithm to optimize the scanning path for quasidiscrete scanned beams is presented. The classical simulated annealing algorithm is used. It is a heuristic algorithm frequently used in combinatorial optimization problems, which allows us to obtain nearly optimal solutions in acceptable running times. A study focused on the best choice of operational parameters on which the algorithm performance depends is presented. The convergence properties of the algorithm have been further improved by using the next-neighbor algorithm to generate the starting paths. Scanning paths for two clinical treatments have been optimized. The optimized paths are found to be shorter than the back-and-forth, top-to-bottom (zigzag) paths generally provided by the treatment planning systems. The gamma method has been applied to quantify the improvement achieved on the dose distribution. Results show a reduction of the transit dose when the optimized paths are used. The benefit is clear especially when the fluence per spot is low, as in the case of repainting. The minimization of the transit dose can potentially allow the use of higher beam intensities, thus decreasing the treatment time. The algorithm implemented for this work can optimize efficiently the scanning path of quasidiscrete scanned particle beams. Optimized scanning paths decrease the transit dose and lead to better dose distributions.
Practical and conceptual path sampling issues
NASA Astrophysics Data System (ADS)
Bolhuis, P. G.; Dellago, C.
2015-09-01
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.
Subdimensional Expansion for Multirobot Path Glenn Wagner
Choset, Howie
Subdimensional Expansion for Multirobot Path Planning Glenn Wagner , Howie Choset Robotics 4, 2015 #12;Subdimensional Expansion for Multirobot Path Planning Glenn Wagner , Howie Choset framework for multirobot path plan- ning called subdimensional expansion, which initially plans for each
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.
Geraerts, R.J.
immersion in digital games. 1.1 Related Work The general path planning problem in homogeneous virtual- ulations and gaming applications. Keywords: path planning, autonomous agents, heterogeneous vir- tual
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.
Commercializing Biorefineries The Path Forward
Commercializing Biorefineries The Path Forward Bioenergy ExCo 59 Workshop Golden, CO Lawrence J Agricultural lands · Corn stover, wheat straw, soybean residue, manure, switchgrass, poplar/willow energy crops
Collaborative Authoring of Walden's Paths
Li, Yuanling
2012-10-19
The World Wide Web contains rich collections of digital materials that can be used in education and learning settings. The collaborative authoring prototype of Walden's Paths targets two groups of users: educators and learners. From the perspective...
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.
COMPUTER SCIENCE: MISCONCEPTIONS, CAREER PATHS
Hristidis, Vagelis
COMPUTER SCIENCE: MISCONCEPTIONS, CAREER PATHS AND RESEARCH CHALLENGES School of Computing Undergraduate Student) #12;Computer Science Misconceptions Intro to Computer Science - Florida International University 2 Some preconceived ideas & stereotypes about Computer Science (CS) are quite common
An introduction to critical paths.
Coffey, Richard J; Richards, Janet S; Remmert, Carl S; LeRoy, Sarah S; Schoville, Rhonda R; Baldwin, Phyllis J
2005-01-01
A critical path defines the optimal sequencing and timing of interventions by physicians, nurses, and other staff for a particular diagnosis or procedure. Critical paths are developed through collaborative efforts of physicians, nurses, pharmacists, and others to improve the quality and value of patient care. They are designed to minimize delays and resource utilization and to maximize quality of care. Critical paths have been shown to reduce variation in the care provided, facilitate expected outcomes, reduce delays, reduce length of stay, and improve cost-effectiveness. The approach and goals of critical paths are consistent with those of total quality management (TQM) and can be an important part of an organization's TQM process. PMID:15739581
Scattering Theory with Path Integrals
R. Rosenfelder
2013-02-25
Starting from well-known expressions for the $T$-matrix and its derivative in standard nonrelativistic potential scattering I rederive recent path-integral formulations due to Efimov and Barbashov et al. Some new relations follow immediately.
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.
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.
Adaptive path planning: Algorithm and analysis
Chen, Pang C.
1993-03-01
Path planning has to be fast to support real-time robot programming. Unfortunately, current planning techniques are still too slow to be effective, as they often require several minutes, if not hours of computation. To alleviate this problem, we present a learning algorithm that uses past experience to enhance future performance. The algorithm relies on an existing path planner to provide solutions to difficult tasks. From these solutions, an evolving sparse network of useful subgoals is learned to support faster planning. The algorithm is suitable for both stationary and incrementally-changing environments. To analyze our algorithm, we use a previously developed stochastic model that quantifies experience utility. Using this model, we characterize the situations in which the adaptive planner is useful, and provide quantitative bounds to predict its behavior. The results are demonstrated with problems in manipulator planning. Our algorithm and analysis are sufficiently general that they may also be applied to task planning or other planning domains in which experience is useful.
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
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
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.
Geodesics Between 3D Closed Curves Using Path-Straightening
Srivastava, Anuj
. Since most objects of interest are 3D objects, and 3D observations of objects using laser scans image understanding problems, a more general issue is to study and compare shapes of objects in 3DGeodesics Between 3D Closed Curves Using Path-Straightening Eric Klassen1 and Anuj Srivastava2 1
DIGITAL SEARCH TREES AGAIN REVISITED: THE INTERNAL PATH LENGTH PERSPECTIVE
Prodinger, Helmut
DIGITAL SEARCH TREES AGAIN REVISITED: THE INTERNAL PATH LENGTH PERSPECTIVE Peter Kirschenhofery digital search tree. The problem was open up to now. We prove that for the binary digital search tree indicator how well the digital trees are balanced. We shall show that the digital search tree is the best
Road Network Reconstruction for Organizing Paths Daniel Chen
Sun, Jian
of an underlying road network may not be available. Our method of finding shared structure begins by considering to imple- ment a simple data structure for partial matching of paths. Road network reconstruction problem, since road networks contain many challenging non-manifold structures such as cross- ings. Chazal
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
Hespanha, Joăo Pedro
Coordinated path-following of multiple underactuated autonomous vehicles with bidirectional autonomous vehicles along given spatial paths, while holding a desired inter-vehicle formation pattern in the problem of coordi- nated motion control of multiple autonomous vehicles. The types of applications
10 Metric Path Planning Chapter objectives
Sukthankar, Gita Reese
10 Metric Path Planning Chapter objectives: Define Cspace, path relaxation, digitization bias, and create a graph suitable for path planning. Apply the A* search algorithm to a graph to find the optimal between continuous and event-driven replanning. 10.1 Objectives and Overview Metric path planning
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…
NASA Astrophysics Data System (ADS)
Tuszynski, Jack A.; Woolf, Nancy
This chapter provides an introduction to the rest of the book, which has a multidisciplinary approach to the physics of consciousness. We summarize the various contributions and present our own point of view, which is that there are some deficiencies in defining higher-order consciousness in strict terms of classic physics. We favor a proposal that considers some aspects of quantum-mechanical operations among molecules involved with neurotransmission and mechanical transport of synaptic proteins. In our view, the wiring of the brain is not as complex, and certainly not as integrated, as commonly assumed. Instead, the wiring pattern redundantly obeys a few general principles focused on high resolution rather than crossmodal integration. Basing cognitive functions, such as higher-order consciousness, solely on electrophysiological responses in neural networks thus wired may not suffice. On the other hand, coherent quantum computing, executed by tubulins, the protein subunits of microtubules, may exert en masse influences over the transport of many receptor and scaffolding proteins to various activated synapses, thereby accounting for the unity of conscious experience. We discuss the potential problems of quantum computing, such as decoherence, and also present counterarguments, as well as recent empirical results consistent with the notion that quantum computing in the interiors of neurons, in particular, within the interiors of dendrites may indeed be possible.
Asymptotically-optimal path planning for manipulation using incremental sampling-based algorithms
Perez, Alejandro Tomas
A desirable property of path planning for robotic manipulation is the ability to identify solutions in a sufficiently short amount of time to be usable. This is particularly challenging for the manipulation problem due to ...
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 ...
Classification of world sheet instantons and the path integral measure in string theories
NASA Astrophysics Data System (ADS)
Hong Gao, Yi; Li, Miao
1987-10-01
A classification of world sheet instantons propagating in some internal spaces is presented. The associated path integral measure problem or ?-angles, as discussed by Wen and Witten, and by Li, is addressed.
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
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.
Path queries for Web data Path queries for Web data
databases, ubiquitous in transactional applications, websites etc. follow the relational model, representing data with a fixed structure. The recent spread of graph-structured data such as linked open data the structure of graph data. Unlike basic SQL queries over relational data, path queries allow to express
Path-dependent entropy production
NASA Astrophysics Data System (ADS)
Kwon, Chulan
2015-09-01
A rigorous derivation of nonequilibrium entropy production via the path-integral formalism is presented. Entropy production is defined as the entropy change piled in a heat reservoir as a result of a nonequilibrium thermodynamic process. It is a central quantity by which various forms of the fluctuation theorem are obtained. The two kinds of the stochastic dynamics are investigated: the Langevin dynamics for an even-parity state and the Brownian motion of a single particle. Mathematical ambiguities in deriving the functional form of the entropy production, which depends on path in state space, are clarified by using a rigorous quantum mechanical approach.
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.
Path planning for mobile robots based on visibility graphs and A* algorithm
NASA Astrophysics Data System (ADS)
Contreras, Juan D.; Martínez S., Fernando; Martínez 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.
Using a reflection model for modeling the dynamic feedback path of digital hearing aids.
Ma, Guilin; Gran, Fredrik; Jacobsen, Finn; Agerkvist, Finn
2010-03-01
Feedback whistling is one of the severe problems with hearing aids, especially in dynamic situations when the users hug, pick up a telephone, etc. This paper investigates the properties of the dynamic feedback paths of digital hearing aids and proposes a model based on a reflection assumption. The model is compared with two existing models: a direct model and an initialization model, using the measured dynamic feedback paths. The comparison shows that the proposed approach is able to model the dynamic feedback paths more efficiently and accurately in terms of mean-square error and maximum stable gain. The method is also extended to dual-microphone hearing aids to assess the possibility of relating the two dynamic feedback paths through the reflection model. However, it is found that in a complicated acoustic environment, the relation between the two feedback paths can be very intricate and difficult to exploit to yield better modeling of the dynamic feedback paths. PMID:20329846
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, ...
Engineering Diagnostic Links Problem Topic Link Path Comments
Rowell, Eric C.
of Lines Linear Eq & Ineq. In 2 Variables http://webalg.math.tamu.edu/linear-and- inequal/slines0201.pdf http://webalg.math.tamu.edu/linear-and- inequal/slines0301.pdf http://webalg.math.tamu.edu/functions/sfunctions0501.pdf 4a5 Closest match 3 Operations with Rational Expressions http://webalg.math
Path-Integral Approach to Problems in Quantum Optics
Hillery, M.; Zubairy, M. Suhail
1982-01-01
, 1982; Rusting, 1998; Rusting, 1999). Thus, if a negativity bias is present it could affect accurate recall of facial expressions seen in the past. This has important implications, as a negative recall bias could perpetuate a negative mood state...
Conditions for transmission path analysis in energy distribution models
NASA Astrophysics Data System (ADS)
Aragončs, Ŕngels; Guasch, Oriol
2016-02-01
In this work, we explore under which conditions transmission path analysis (TPA) developed for statistical energy analysis (SEA) can be applied to the less restrictive energy distribution (ED) models. It is shown that TPA can be extended without problems to proper-SEA systems whereas the situation is not so clear for quasi-SEA systems. In the general case, it has been found that a TPA can always be performed on an ED model if its inverse influence energy coefficient (EIC) matrix turns to have negative off-diagonal entries. If this condition is satisfied, it can be shown that the inverse EIC matrix automatically becomes an M-matrix. An ED graph can then be defined for it and use can be made of graph theory ranking path algorithms, previously developed for SEA systems, to classify dominant paths in ED models. A small mechanical system consisting of connected plates has been used to illustrate some of the exposed theoretical results.
SSME propellant path leak detection
NASA Technical Reports Server (NTRS)
Crawford, Roger; Shohadaee, Ahmad Ali
1989-01-01
The complicated high-pressure cycle of the space shuttle main engine (SSME) propellant path provides many opportunities for external propellant path leaks while the engine is running. This mode of engine failure may be detected and analyzed with sufficient speed to save critical engine test hardware from destruction. The leaks indicate hardware failures which will damage or destroy an engine if undetected; therefore, detection of both cryogenic and hot gas leaks is the objective of this investigation. The primary objective of this phase of the investigation is the experimental validation of techniques for detecting and analyzing propellant path external leaks which have a high probability of occurring on the SSME. The selection of candidate detection methods requires a good analytic model for leak plumes which would develop from external leaks and an understanding of radiation transfer through the leak plume. One advanced propellant path leak detection technique is obtained by using state-of-the-art technology infrared (IR) thermal imaging systems combined with computer, digital image processing, and expert systems for the engine protection. The feasibility of IR leak plume detection is evaluated on subscale simulated laboratory plumes to determine sensitivity, signal to noise, and general suitability for the application.
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…
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
Employer Resource Manual. Project Path.
ERIC Educational Resources Information Center
Kane, Karen R.; Del George, Eve
Project Path at Illinois' College of DuPage was established to provide pre-employment training and career counseling for disabled students. To encourage the integration of qualified individuals with disabilities into the workplace, the project compiled this resource manual for area businesses, providing tips for interacting with disabled people…
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...
Career Paths of Academic Deans.
ERIC Educational Resources Information Center
Wolverton, Mimi; Gonzales, Mary Jo
This paper examines various career paths leading to deanship and considers the implications of the findings for women and minorities who aspire to this position. The paper is part of a larger study of academic deanship conducted by the Center for Academic Leadership at Washington State University between October 1996 and January 1997. Data for the…
Obstacle Bypassing in Optimal Ship Routing Using Simulated Annealing
Kosmas, O. T.; Vlachos, D. S.; Simos, T. E.
2008-11-06
In this paper we are going to discuss a variation on the problem of finding the shortest path between two points in optimal ship routing problems consisting of obstacles that are not allowed to be crossed by the path. Our main goal are going to be the construction of an appropriate algorithm, based in an earlier work by computing the shortest path between two points in the plane that avoids a set of polygonal obstacles.
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{\
Relations between coherence and path information
Emilio Bagan; Janos A. Bergou; Seth S. Cottrell; Mark Hillery
2015-12-10
We find two relations between coherence and path-information in a multi-path interferometer. The first builds on earlier results for the two-path interferometer, which used minimum-error state discrimination between detector states to provide the path information. For visibility, which was used in the two-path case, we substitute a recently defined $l_{1}$ measure of quantum coherence. The second is an entropic relation in which the path information is characterized by the mutual information between the detector states and the outcome of the measurement performed on them, and the coherence measure is one based on relative entropy.
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.
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.
Reynolds, Andy M.; Dutta, Tushar K.; Curtis, Rosane H. C.; Powers, Stephen J.; Gaur, Hari S.; Kerry, Brian R.
2011-01-01
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
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.
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.
Nir, Talia M; Villalon-Reina, Julio E; Prasad, Gautam; Jahanshad, Neda; Joshi, Shantanu H; Toga, Arthur W; Bernstein, Matt A; Jack, Clifford R; Weiner, Michael W; Thompson, Paul M
2015-01-01
Characterizing brain changes in Alzheimer's disease (AD) is important for patient prognosis and for assessing brain deterioration in clinical trials. In this diffusion weighted imaging study, we used a new fiber-tract modeling method to investigate white matter integrity in 50 elderly controls (CTL), 113 people with mild cognitive impairment, and 37 AD patients. After clustering tractography using a region-of-interest atlas, we used a shortest path graph search through each bundle's fiber density map to derive maximum density paths (MDPs), which we registered across subjects. We calculated the fractional anisotropy (FA) and mean diffusivity (MD) along all MDPs and found significant MD and FA differences between AD patients and CTL subjects, as well as MD differences between CTL and late mild cognitive impairment subjects. MD and FA were also associated with widely used clinical scores. As an MDP is a compact low-dimensional representation of white matter organization, we tested the utility of diffusion tensor imaging measures along these MDPs as features for support vector machine based classification of AD. PMID:25444597
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.
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.
Multiple Paths to Encephalization and Technical Civilizations
NASA Astrophysics Data System (ADS)
Schwartzman, David; Middendorf, George
2011-12-01
We propose consideration of at least two possible evolutionary paths for the emergence of intelligent life with the potential for technical civilization. The first is the path via encephalization of homeothermic animals; the second is the path to swarm intelligence of so-called superorganisms, in particular the social insects. The path to each appears to be facilitated by environmental change: homeothermic animals by decreased climatic temperature and for swarm intelligence by increased oxygen levels.
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.
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.
Least expected time paths in stochastic, time-varying transportation networks
Miller-Hooks, E.D.; Mahmassani, H.S.
1999-06-01
The authors consider stochastic, time-varying transportation networks, where the arc weights (arc travel times) are random variables with probability distribution functions that vary with time. Efficient procedures are widely available for determining least time paths in deterministic networks. In stochastic but time-invariant networks, least expected time paths can be determined by setting each random arc weight to its expected value and solving an equivalent deterministic problem. This paper addresses the problem of determining least expected time paths in stochastic, time-varying networks. Two procedures are presented. The first procedure determines the a priori least expected time paths from all origins to a single destination for each departure time in the peak period. The second procedure determines lower bounds on the expected times of these a priori least expected time paths. This procedure determines an exact solution for the problem where the driver is permitted to react to revealed travel times on traveled links en route, i.e. in a time-adaptive route choice framework. Modifications to each of these procedures for determining least expected cost (where cost is not necessarily travel time) paths and lower bounds on the expected costs of these paths are given. Extensive numerical tests are conducted to illustrate the algorithms` computational performance as well as the properties of the solution.
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,…
Analogical Path Planning Saul Simhon, Gregory Dudek
Dudek, Gregory
Analogical Path Planning Saul Simhon, Gregory Dudek Centre for Intelligent Machines Mc for path planning that considers trajectories constrained by both the environment and an ensemble of the path, and planning in the presence of such constraints in often difficult (an automobile
Clearance Based Path Optimization for Motion Planning
Utrecht, Universiteit
Clearance Based Path Optimization for Motion Planning Roland Geraerts Mark Overmars institute;Clearance Based Path Optimization for Motion Planning Roland Geraerts Mark Overmars Institute of Information to generate paths of a much higher quality than previous approaches. 1 Introduction Motion planning can
Clearance Based Path Optimization for Motion Planning
Utrecht, Universiteit
Clearance Based Path Optimization for Motion Planning Roland Geraerts Mark Overmars institute; Clearance Based Path Optimization for Motion Planning Roland Geraerts Mark Overmars Institute of Information to generate paths of a much higher quality than previous approaches. 1 Introduction Motion planning can
Multiresolution Path Planning Via Sector Decompositions
Tsiotras, Panagiotis
Multiresolution Path Planning Via Sector Decompositions Compatible to On-Board Sensor Data Efstathios Bakolas and Panagiotis Tsiotras In this paper we present a hybrid local-global path planning-free manner. The path planning algorithm is based on information gathered on-line by the available on
CALIFORNIA PATH PROGRAM INSTITUTE OF TRANSPORTATION STUDIES
Agogino, Alice M.
CALIFORNIA PATH PROGRAM INSTITUTE OF TRANSPORTATION STUDIES UNIVERFITY OF CALIFORNIA, BERKELEY Agogino, Kai Goebel SatnamAlag University of California,Berkeley CaliforniaPATH Research Report UCB-ITS-PRR-97-31 This work was performed as part of the CaliforniaPATH Program of the University of California
Universal Path Spaces W. A. Bogley
Universal Path Spaces W. A. Bogley Oregon State University A. J. Sieradski University of Oregon Abstract This paper examines a theory of universal path spaces that properly includes the covering space is a wild metric 2-complex, the universal path space is simply connected if and only if the fundamental
NASA Technical Reports Server (NTRS)
Goldhirsh, J.
1978-01-01
Yearly, monthly, and time of day fade statistics are presented and characterized. A 19.04 GHz yearly fade distribution, corresponding to a second COMSTAR beacon frequency, is predicted using the concept of effective path length, disdrometer, and rain rate results. The yearly attenuation and rain rate distributions follow with good approximation log normal variations for most fade and rain rate levels. Attenuations were exceeded for the longest and shortest periods of times for all fades in August and February, respectively. The eight hour time period showing the maximum and minimum number of minutes over the year for which fades exceeded 12 db were approximately between 1600 to 2400, and 0400 to 1200 hours, respectively. In employing the predictive method for obtaining the 19.04 GHz fade distribution, it is demonstrated theoretically that the ratio of attenuations at two frequencies is minimally dependent of raindrop size distribution providing these frequencies are not widely separated.
Multi-agent Path Planning and Network Flow
Yu, Jingjin
2012-01-01
This paper connects multi-agent path planning on graphs (roadmaps) to network flow problems, showing that the former can be reduced to the latter, therefore enabling the application of combinatorial network flow algorithms, as well as general linear program techniques, to multi-agent path planning problems on graphs. Exploiting this connection, we show that when the goals are permutation invariant, the problem always has a feasible solution path set with a longest finish time of no more than $n + V - 1$ steps, in which $n$ is the number of agents and $V$ is the number of vertices of the underlying graph. We then give a complete algorithm that finds such a solution in $O(nVE)$ time, with $E$ being the number of edges of the graph. Taking a further step, we study time and distance optimality of the feasible solutions, show that they have a pairwise Pareto optimal structure, and again provide efficient algorithms for optimizing each of these practical objectives.
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.
THE SHORTEST PERIOD sdB PLUS WHITE DWARF BINARY CD-30 11223 (GALEX J1411-3053)
Vennes, S.; Kawka, A.; Nemeth, P.; O'Toole, S. J.; Burton, D.
2012-11-01
We report on the discovery of the shortest period binary comprising a hot subdwarf star (CD-30 11223, GALEX J1411-3053) and a massive unseen companion. Photometric data from the All Sky Automated Survey show ellipsoidal variations of the hot subdwarf primary and spectroscopic series revealed an orbital period of 70.5 minutes. The large velocity amplitude suggests the presence of a massive white dwarf in the system (M{sub 2}/M{sub Sun} {approx}> 0.77) assuming a canonical mass for the hot subdwarf (0.48 M{sub Sun }), although a white dwarf mass as low as 0.75 M{sub Sun} is allowable by postulating a subdwarf mass as low as 0.44 M{sub Sun }. The amplitude of ellipsoidal variations and a high rotation velocity imposed a high-inclination to the system (i {approx}> 68 Degree-Sign ) and, possibly, observable secondary transits (i {approx}> 74 Degree-Sign ). At the lowest permissible inclination and assuming a subdwarf mass of {approx}0.48 M{sub Sun }, the total mass of the system reaches the Chandrasekhar mass limit at 1.35 M{sub Sun} and would exceed it for a subdwarf mass above 0.48 M{sub Sun }. The system should be considered, like its sibling KPD 1930+2752, a candidate progenitor for a Type Ia supernova. The system should become semi-detached and initiate mass transfer within Almost-Equal-To 30 Myr.
Sky Segmentation by Fusing Clustering with Neural Ali Pour Yazdanpanah1
Bebis, George
and path planning for autonomous air and ground vehicles. In this paper, we present a method their missions are route planning, and path finding. The first step in route planning and path finding problem where a shortest path is found extending from the left most column to the right most column
NASA Astrophysics Data System (ADS)
Sazawa, Masaki; Ohishi, Kiyoshi; Katsura, Seiichiro
Continuous path tracking control is an important technology for the position control system such as factory automation field. Particulaly, large torque is required for continuous path tracking control at its start position and its goal position. Each AC servo motor of continuous path tracking control have limitation of current and voltage. Therefore, in controlling a multi-degree-of-freedom continuous path tracking control system, even if only the motor torque of one axis has the current limitation, the actual position response is not often equal to the desired trajectory reference. In order to overcome these problems, this paper proposes a new continuous path tracking control algorithm by considering both the saturation of voltage and current. The proposed method assures the coordinated motion by considering the saturation of voltage and current. The effectiveness of the proposed method is confirmed by the experimental results in this paper.
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
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
Arithmetic area for m planar Brownian paths
NASA Astrophysics Data System (ADS)
Desbois, Jean; Ouvry, Stéphane
2012-05-01
We pursue the analysis made in Desbois and Ouvry (2011 J. Stat. Mech. P05024) on the arithmetic area enclosed by m closed Brownian paths. We pay particular attention to the random variable Sn1, n2,..., nm(m), which is the arithmetic area of the set of points, also called winding sectors, enclosed n1 times by path 1, n2 times by path 2,..., and nm times by path m. Various results are obtained in the asymptotic limit m\\to \\infty . A key observation is that, since the paths are independent, one can use in the m-path case the SLE information, valid in the one-path case, on the zero-winding sectors arithmetic area.
Characterizing the Evolutionary Path(s) to Early Homo
Schroeder, Lauren; Roseman, Charles C.; Cheverud, James M.; Ackermann, Rebecca R.
2014-01-01
Numerous studies suggest that the transition from Australopithecus to Homo was characterized by evolutionary innovation, resulting in the emergence and coexistence of a diversity of forms. However, the evolutionary processes necessary to drive such a transition have not been examined. Here, we apply statistical tests developed from quantitative evolutionary theory to assess whether morphological differences among late australopith and early Homo species in Africa have been shaped by natural selection. Where selection is demonstrated, we identify aspects of morphology that were most likely under selective pressure, and determine the nature (type, rate) of that selection. Results demonstrate that selection must be invoked to explain an Au. africanus—Au. sediba—Homo transition, while transitions from late australopiths to various early Homo species that exclude Au. sediba can be achieved through drift alone. Rate tests indicate that selection is largely directional, acting to rapidly differentiate these taxa. Reconstructions of patterns of directional selection needed to drive the Au. africanus—Au. sediba—Homo transition suggest that selection would have affected all regions of the skull. These results may indicate that an evolutionary path to Homo without Au. sediba is the simpler path and/or provide evidence that this pathway involved more reliance on cultural adaptations to cope with environmental change. PMID:25470780
Attention trees and semantic paths
NASA Astrophysics Data System (ADS)
Giusti, Christian; Pieroni, Goffredo G.; Pieroni, Laura
2007-02-01
In the last few decades several techniques for image content extraction, often based on segmentation, have been proposed. It has been suggested that under the assumption of very general image content, segmentation becomes unstable and classification becomes unreliable. According to recent psychological theories, certain image regions attract the attention of human observers more than others and, generally, the image main meaning appears concentrated in those regions. Initially, regions attracting our attention are perceived as a whole and hypotheses on their content are formulated; successively the components of those regions are carefully analyzed and a more precise interpretation is reached. It is interesting to observe that an image decomposition process performed according to these psychological visual attention theories might present advantages with respect to a traditional segmentation approach. In this paper we propose an automatic procedure generating image decomposition based on the detection of visual attention regions. A new clustering algorithm taking advantage of the Delaunay- Voronoi diagrams for achieving the decomposition target is proposed. By applying that algorithm recursively, starting from the whole image, a transformation of the image into a tree of related meaningful regions is obtained (Attention Tree). Successively, a semantic interpretation of the leaf nodes is carried out by using a structure of Neural Networks (Neural Tree) assisted by a knowledge base (Ontology Net). Starting from leaf nodes, paths toward the root node across the Attention Tree are attempted. The task of the path consists in relating the semantics of each child-parent node pair and, consequently, in merging the corresponding image regions. The relationship detected in this way between two tree nodes generates, as a result, the extension of the interpreted image area through each step of the path. The construction of several Attention Trees has been performed and partial results will be shown.
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
Multiple order common path spectrometer
NASA Technical Reports Server (NTRS)
Newbury, Amy B. (Inventor)
2010-01-01
The present invention relates to a dispersive spectrometer. The spectrometer allows detection of multiple orders of light on a single focal plane array by splitting the orders spatially using a dichroic assembly. A conventional dispersion mechanism such as a defraction grating disperses the light spectrally. As a result, multiple wavelength orders can be imaged on a single focal plane array of limited spectral extent, doubling (or more) the number of spectral channels as compared to a conventional spectrometer. In addition, this is achieved in a common path device.
Staff detection with stable paths.
Dos Santos Cardoso, Jaime; Capela, Artur; Rebelo, Ana; Guedes, Carlos; Pinto da Costa, Joaquim
2009-06-01
The preservation of musical works produced in the past requires their digitalization and transformation into a machine-readable format. The processing of handwritten musical scores by computers remains far from ideal. One of the fundamental stages to carry out this task is the staff line detection. We investigate a general-purpose, knowledge-free method for the automatic detection of music staff lines based on a stable path approach. Lines affected by curvature, discontinuities, and inclination are robustly detected. Experimental results show that the proposed technique consistently outperforms well-established algorithms. PMID:19372615
Communication path for extreme environments
NASA Technical Reports Server (NTRS)
Jorgensen, Charles C. (Inventor); Betts, Bradley J. (Inventor)
2010-01-01
Methods and systems for using one or more radio frequency identification devices (RFIDs), or other suitable signal transmitters and/or receivers, to provide a sensor information communication path, to provide location and/or spatial orientation information for an emergency service worker (ESW), to provide an ESW escape route, to indicate a direction from an ESW to an ES appliance, to provide updated information on a region or structure that presents an extreme environment (fire, hazardous fluid leak, underwater, nuclear, etc.) in which an ESW works, and to provide accumulated thermal load or thermal breakdown information on one or more locations in the region.
Multi-Vehicle Path Planning for Non-Line of Sight Communication Tom Schouwenaars, Eric Feron. This coordination problem can be formulated as a connectivity-constrained multi-vehicle path planning prob- lem and the ground station is always main- tained. The corresponding coordinated multi-vehicle trajectory
Luiz. C. L. Botelho
2012-07-02
By means of the Minlos Theorem on support of cylindrical measures on vectorial topological spaces, we present several results on the rigorous definitions of Euclidean path integrals and applications to some problems on non-linear diffusion, nonlinear wave propagations and covariant Polyakov"s path Integrals yielding news results on the subject as well.
Robust Flight Path Determination for Mars Precision Landing Using Genetic Algorithms
NASA Technical Reports Server (NTRS)
Bayard, David S.; Kohen, Hamid
1997-01-01
This paper documents the application of genetic algorithms (GAs) to the problem of robust flight path determination for Mars precision landing. The robust flight path problem is defined here as the determination of the flight path which delivers a low-lift open-loop controlled vehicle to its desired final landing location while minimizing the effect of perturbations due to uncertainty in the atmospheric model and entry conditions. The genetic algorithm was capable of finding solutions which reduced the landing error from 111 km RMS radial (open-loop optimal) to 43 km RMS radial (optimized with respect to perturbations) using 200 hours of computation on an Ultra-SPARC workstation. Further reduction in the landing error is possible by going to closed-loop control which can utilize the GA optimized paths as nominal trajectories for linearization.
A Hybrid Metaheuristic DE/CS Algorithm for UCAV Three-Dimension Path Planning
Wang, Gaige; Guo, Lihong; Duan, Hong; Wang, Heqi; Liu, Luo; Shao, Mingzhen
2012-01-01
Three-dimension path planning for uninhabited combat air vehicle (UCAV) is a complicated high-dimension optimization problem, which primarily centralizes on optimizing the flight route considering the different kinds of constrains under complicated battle field environments. A new hybrid metaheuristic differential evolution (DE) and cuckoo search (CS) algorithm is proposed to solve the UCAV three-dimension path planning problem. DE is applied to optimize the process of selecting cuckoos of the improved CS model during the process of cuckoo updating in nest. The cuckoos can act as an agent in searching the optimal UCAV path. And then, the UCAV can find the safe path by connecting the chosen nodes of the coordinates while avoiding the threat areas and costing minimum fuel. This new approach can accelerate the global convergence speed while preserving the strong robustness of the basic CS. The realization procedure for this hybrid metaheuristic approach DE/CS is also presented. In order to make the optimized UCAV path more feasible, the B-Spline curve is adopted for smoothing the path. To prove the performance of this proposed hybrid metaheuristic method, it is compared with basic CS algorithm. The experiment shows that the proposed approach is more effective and feasible in UCAV three-dimension path planning than the basic CS model. PMID:23193383
Kidd, M.E.C.
1997-02-01
The goal of our work is to provide a high level of confidence that critical software driven event sequences are maintained in the face of hardware failures, malevolent attacks and harsh or unstable operating environments. This will be accomplished by providing dynamic fault management measures directly to the software developer and to their varied development environments. The methodology employed here is inspired by previous work in path expressions. This paper discusses the perceived problems, a brief overview of path expressions, the proposed methods, and a discussion of the differences between the proposed methods and traditional path expression usage and implementation.
Ensuring critical event sequences in high integrity software by applying path expressions
Kidd, M.E.C.
1996-07-01
The goal of this work is to extend the use of existing path expression theory and methodologies to ensure that critical software event sequences are maintained even in the face of malevolent attacks and harsh or unstable operating environments. This will be accomplished by providing dynamic fault management measures directly to the software developer and to their varied development environments. This paper discusses the perceived problems, a brief overview of path expressions, and the author`s proposed extension areas. The authors discuss how the traditional path expression usage and implementation differs from the intended usage and implementation.
SSME propellant path leak detection
NASA Technical Reports Server (NTRS)
Crawford, Roger; Shohadaee, Ahmad Ali; Powers, W. T.
1995-01-01
The primary objective of this phase of the investigation is the experimental validation of techniques for detecting and analyzing propellant path external leaks which have a high probability of occurring on the SSME. The selection of candidate detection methods requires a good analytic model for leak plumes which would develop from external leaks and an understanding of radiation transfer through the leak plume. One advanced propellant path leak detection technique is obtained by using state-of-art technology of infrared (IR) thermal imaging systems combined with computer, digital image processing and expert systems for the engine protection. The feasibility of the IR leak plume detection will be evaluated on subscale simulated laboratory plumes to determine sensitivity, signal to noise, and general suitability for the application. The theoretical analysis was undertaken with the objective of developing and testing simple, easy-to-use models to predict the amount of radiation coming from a radiation source, background plate (BP), which can be absorbed, emitted and scattered by the gas leaks.
... often, it could be a sign of a balance problem. Balance problems can make you feel unsteady or as ... fall-related injuries, such as hip fracture. Some balance problems are due to problems in the inner ...
Janssen, Hans-Karl; Stenull, Olaf
2012-01-01
Long linear polymers in strongly disordered media are well described by self-avoiding walks (SAWs) on percolation clusters and a lot can be learned about the statistics of these polymers by studying the length distribution of SAWs on percolation clusters. This distribution encompasses 2 distinct averages, viz., the average over the conformations of the underlying cluster and the SAW conformations. For the latter average, there are two basic options, one being static and one being kinetic. It is well known for static averaging that if the disorder of the underlying medium is weak, this disorder is redundant in the sense the renormalization group; i.e., differences to the ordered case appear merely in nonuniversal quantities. Using dynamical field theory, we show that the same holds true for kinetic averaging. Our main focus, however, lies on strong disorder, i.e., the medium being close to the percolation point, where disorder is relevant. Employing a field theory for the nonlinear random resistor network in conjunction with a real-world interpretation of the corresponding Feynman diagrams, we calculate the scaling exponents for the shortest, the longest, and the mean or average SAW to 2-loop order. In addition, we calculate to 2-loop order the entire family of multifractal exponents that governs the moments of the the statistical weights of the elementary constituents (bonds or sites of the underlying fractal cluster) contributing to the SAWs. Our RG analysis reveals that kinetic averaging leads to renormalizability whereas static averaging does not, and hence, we argue that the latter does not lead to a well-defined scaling limit. We discuss the possible implications of this finding for experiments and numerical simulations which have produced widespread results for the exponent of the average SAW. To corroborate our results, we also study the well-known Meir-Harris model for SAWs on percolation clusters. We demonstrate that the Meir-Harris model leads back up to 2-loop order to the renormalizable real-world formulation with kinetic averaging if the replica limit is consistently performed at the first possible instant in the course of the calculation. PMID:22400528
Modeling growth paths of interacting crack pairs in elastic media.
Ghelichi, Ramin; Kamrin, Ken
2015-10-28
The problem of predicting the growth of a system of cracks, each crack influencing the growth of the others, arises in multiple fields. We develop an analytical framework toward this aim, which we apply to the 'En-Passant' family of crack growth problems, in which a pair of initially parallel, offset cracks propagate nontrivially toward each other under far-field opening stress. We utilize boundary integral and perturbation methods of linear elasticity, linear elastic fracture mechanics, and common crack opening criteria to calculate the first analytical model for curved En-Passant crack paths. The integral system is reduced under a hierarchy of approximations, producing three methods of increasing simplicity for computing crack paths. The last such method is a major highlight of this work, using an asymptotic matching argument to predict crack paths based on superposition of simple, single-crack fields. Within the corresponding limits of the three methods, all three are shown to agree with each other. We provide comparisons to exact results and existing experimental data to verify certain approximation steps. PMID:26330342
Modeling Growth Paths of Interacting Crack Pairs in Elastic Media
Ramin Ghelichi; Ken Kamrin
2015-08-14
The problem of predicting the growth of a system of cracks, each crack influencing the growth of the others, arises in multiple fields. We develop an analytical framework toward this aim, which we apply to the `En-Passant' family of crack growth problems, in which a pair of initially parallel, offset cracks propagate nontrivially toward each other under far-field opening stress. We utilize boundary integral and perturbation methods of linear elasticity, Linear Elastic Fracture Mechanics, and common crack opening criteria to calculate the first analytical model for curved En-Passant crack paths. The integral system is reduced under a hierarchy of approximations, producing three methods of increasing simplicity for computing crack paths. The last such method is a major highlight of this work, using an asymptotic matching argument to predict crack paths based on superposition of simple, single-crack fields. Within the corresponding limits of the three methods, all three are shown to agree with each other. We provide comparisons to exact results and existing experimental data to verify certain approximation steps.
Path integral measure factorization in path integrals for diffusion of Yang--Mills fields
S. N. Storchak
2007-11-19
Factorization of the (formal) path integral measure in a Wiener path integrals for Yang--Mills diffusion is studied. Using the nonlinear filtering stochastic differential equation, we perform the transformation of the path integral defined on a total space of the Yang--Mills principal fiber bundle and come to the reduced path integral on a Coulomb gauge surface. Integral relation between the path integral representing the "quantum" evolution given on the original manifold of Yang--Mills fields and the path integral on the reduced manifold defined by the Coulomb gauge is obtained.
Sequential Path Entanglement for Quantum Metrology
Jin, Xian-Min; Peng, Cheng-Zhi; Deng, Youjin; Barbieri, Marco; Nunn, Joshua; Walmsley, Ian A.
2013-01-01
Path entanglement is a key resource for quantum metrology. Using path-entangled states, the standard quantum limit can be beaten, and the Heisenberg limit can be achieved. However, the preparation and detection of such states scales unfavourably with the number of photons. Here we introduce sequential path entanglement, in which photons are distributed across distinct time bins with arbitrary separation, as a resource for quantum metrology. We demonstrate a scheme for converting polarization Greenberger-Horne-Zeilinger entanglement into sequential path entanglement. We observe the same enhanced phase resolution expected for conventional path entanglement, independent of the delay between consecutive photons. Sequential path entanglement can be prepared comparably easily from polarization entanglement, can be detected without using photon-number-resolving detectors, and enables novel applications.
Schoenmakers, John
is in Lyons' rough path sense [LQ02, LCL07, FV10b]. This requires smoothness/boundedness conditions with an exploding number of new applications (including non-linear SPDE theory, robustness of the filtering problem
. Email: boros@rutcor.rutgers.edu bRUTCOR, Rutgers University, 640 Bartholomew Road, Piscataway NJ 08854 for Shortest-Path Network Interdiction Problems Endre Boros Konrad Borys Khaled Elbassioni Vladimir Gurvich
Path-based rules in object-oriented programming
Crawford, J.M.; Dvorak, D.; Litman, D.; Mishra, A.; Patel-Schneider, P.F.
1996-12-31
Object-oriented programming has recently emerged as one of the most important programming paradigms. While object-oriented programming clearly owes an intellectual debt to AI, it appears to be displacing some AI techniques, such as rule-based programming, from the marketplace. This need not be so as path-based rules-forward-chaining production rules that are restricted to follow pointers between objects-fit into the object-oriented paradigm in a clean and elegant way. The combination of path-based rules and object-oriented programming should be useful in AI applications, and in the more general problem of transferring AI techniques to the larger computer science community.
A Discrete History of the Lorentzian Path Integral
NASA Astrophysics Data System (ADS)
Loll, Renate
In these lecture notes, I describe the motivation behind a recent formulation of a non-perturbative gravitational path integral for Lorentzian (instead of the usual Euclidean) space-times, and give a pedagogical introduction to its main features. At the regularized, discrete level this approach solves the problems of (i) having a well-defined Wick rotation, (ii) possessing a coordinate-invariant cutoff, and (iii) leading to convergent sums over geometries. Although little is known as yet about the existence and nature of an underlying continuum theory of quantum gravity in four dimensions, there are already a number of beautiful results in d=2 and d=3 where continuum limits have been found. They include an explicit example of the inequivalence of the Euclidean and Lorentzian path integrals, a non-perturbative mechanism for the cancellation of the conformal factor, and the discovery that causality can act as an effective regulator of quantum geometry.
A path-oriented matrix-based knowledge representation system
NASA Technical Reports Server (NTRS)
Feyock, Stefan; Karamouzis, Stamos T.
1993-01-01
Experience has shown that designing a good representation is often the key to turning hard problems into simple ones. Most AI (Artificial Intelligence) search/representation techniques are oriented toward an infinite domain of objects and arbitrary relations among them. In reality much of what needs to be represented in AI can be expressed using a finite domain and unary or binary predicates. Well-known vector- and matrix-based representations can efficiently represent finite domains and unary/binary predicates, and allow effective extraction of path information by generalized transitive closure/path matrix computations. In order to avoid space limitations a set of abstract sparse matrix data types was developed along with a set of operations on them. This representation forms the basis of an intelligent information system for representing and manipulating relational data.
Path integral for Koenigs spaces
Grosche, C.
2008-05-15
I discuss a path-integral approach for the quantum motion on two-dimensional spaces according to Koenigs, for short 'Koenigs spaces'. Their construction is simple: one takes a Hamiltonian from a two-dimensional flat space and divides it by a two-dimensional superintegrable potential. These superintegrable potentials are the isotropic singular oscillator, the Holt potential, and the Coulomb potential. In all cases, a nontrivial space of nonconstant curvature is generated. We can study free motion and the motion with an additional superintegrable potential. For possible bound-state solutions, we find in all three cases an equation of the eighth order in the energy E. The special cases of the Darboux spaces are easily recovered by choosing the parameters accordingly.
Fragmentation paths in dynamical models
M. Colonna; A. Ono; J. Rizzo
2010-11-05
We undertake a quantitative comparison of multi-fragmentation reactions, as modeled by two different approaches: the Antisymmetrized Molecular Dynamics (AMD) and the momentum-dependent stochastic mean-field (SMF) model. Fragment observables and pre-equilibrium (nucleon and light cluster) emission are analyzed, in connection to the underlying compression-expansion dynamics in each model. Considering reactions between neutron-rich systems, observables related to the isotopic properties of emitted particles and fragments are also discussed, as a function of the parametrization employed for the isovector part of the nuclear interaction. We find that the reaction path, particularly the mechanism of fragmentation, is different in the two models and reflects on some properties of the reaction products, including their isospin content. This should be taken into account in the study of the density dependence of the symmetry energy from such collisions.
Fragmentation paths in dynamical models
Colonna, M.; Rizzo, J.; Ono, A.
2010-11-15
We undertake a quantitative comparison of multifragmentation reactions, as modeled by two different approaches: the antisymmetrized molecular dynamics (AMD) and the momentum-dependent stochastic mean-field (SMF) model. Fragment observables and pre-equilibrium (nucleon and light cluster) emission are analyzed, in connection with the underlying compression-expansion dynamics in each model. Considering reactions between neutron-rich systems, observables related to the isotopic properties of emitted particles and fragments are also discussed, as a function of the parametrization employed for the isovector part of the nuclear interaction. We find that the reaction path, particularly the mechanism of fragmentation, is different in the two models and reflects on some properties of the reaction products, including their isospin content. This should be taken into account in the study of the density dependence of the symmetry energy from such collisions.
Flexible-Path Human Exploration
NASA Technical Reports Server (NTRS)
Sherwood, B.; Adler, M.; Alkalai, L.; Burdick, G.; Coulter, D.; Jordan, F.; Naderi, F.; Graham, L.; Landis, R.; Drake, B.; Hoffman, S.; Grunsfeld, J.; Seery, B. D.
2010-01-01
In the fourth quarter of 2009 an in-house, multi-center NASA study team briefly examined "Flexible Path" concepts to begin understanding characteristics, content, and roles of potential missions consistent with the strategy proposed by the Augustine Committee. We present an overview of the study findings. Three illustrative human/robotic mission concepts not requiring planet surface operations are described: assembly of very large in-space telescopes in cis-lunar space; exploration of near Earth objects (NEOs); exploration of Mars' moon Phobos. For each, a representative mission is described, technology and science objectives are outlined, and a basic mission operations concept is quantified. A fourth type of mission, using the lunar surface as preparation for Mars, is also described. Each mission's "capability legacy" is summarized. All four illustrative missions could achieve NASA's stated human space exploration objectives and advance human space flight toward Mars surface exploration. Telescope assembly missions would require the fewest new system developments. NEO missions would offer a wide range of deep-space trip times between several months and two years. Phobos exploration would retire several Marsclass risks, leaving another large remainder set (associated with entry, descent, surface operations, and ascent) for retirement by subsequent missions. And extended lunar surface operations would build confidence for Mars surface missions by addressing a complementary set of risks. Six enabling developments (robotic precursors, ISS exploration testbed, heavy-lift launch, deep-space-capable crew capsule, deep-space habitat, and reusable in-space propulsion stage) would apply across multiple program sequence options, and thus could be started even without committing to a specific mission sequence now. Flexible Path appears to be a viable strategy, with meaningful and worthy mission content.
Path planning for robotic truss assembly
NASA Technical Reports Server (NTRS)
Sanderson, Arthur C.
1993-01-01
A new Potential Fields approach to the robotic path planning problem is proposed and implemented. Our approach, which is based on one originally proposed by Munger, computes an incremental joint vector based upon attraction to a goal and repulsion from obstacles. By repetitively adding and computing these 'steps', it is hoped (but not guaranteed) that the robot will reach its goal. An attractive force exerted by the goal is found by solving for the the minimum norm solution to the linear Jacobian equation. A repulsive force between obstacles and the robot's links is used to avoid collisions. Its magnitude is inversely proportional to the distance. Together, these forces make the goal the global minimum potential point, but local minima can stop the robot from ever reaching that point. Our approach improves on a basic, potential field paradigm developed by Munger by using an active, adaptive field - what we will call a 'flexible' potential field. Active fields are stronger when objects move towards one another and weaker when they move apart. An adaptive field's strength is individually tailored to be just strong enough to avoid any collision. In addition to the local planner, a global planning algorithm helps the planner to avoid local field minima by providing subgoals. These subgoals are based on the obstacles which caused the local planner to fail. A best-first search algorithm A* is used for graph search.
Vacuum stress and closed paths in rectangles, pistons and pistols
NASA Astrophysics Data System (ADS)
Fulling, S. A.; Kaplan, L.; Kirsten, K.; Liu, Z. H.; Milton, K. A.
2009-04-01
Rectangular cavities are solvable models that nevertheless touch on many of the controversial or mysterious aspects of the vacuum energy of quantum fields. This paper is a thorough study of the two-dimensional scalar field in a rectangle by the method of images, or closed classical (or optical) paths, which is exact in this case. For each point r and each specularly reflecting path beginning and ending at r, we provide formulae for all components of the stress tensor T??(r), for all values of the curvature coupling constant ? and all values of an ultraviolet cutoff parameter. Arbitrary combinations of Dirichlet and Neumann conditions on the four sides can be treated. The total energy is also investigated, path by path. These results are used in an attempt to clarify the physical reality of the repulsive (outward) force on the sides of the box predicted by calculations that neglect both boundary divergences and the exterior of the box. Previous authors have studied 'piston' geometries that avoid these problems and have found the force to be attractive. We consider a 'pistol' geometry that comes closer to the original problem of a box with a movable lid. We find again an attractive force, although its origin and detailed behavior are somewhat different from the piston case. However, the pistol (and the piston) model can be criticized for extending idealized boundary conditions into short distances where they are physically implausible. Therefore, it is of interest to see whether leaving the ultraviolet cutoff finite yields results that are more plausible. We then find that the force depends strongly on a geometrical parameter; it can be made repulsive, but only by forcing that parameter into the regime where the model is least convincing physically.
Seeking the Path to Metadata Nirvana
NASA Astrophysics Data System (ADS)
Graybeal, J.
2008-12-01
Scientists have always found reusing other scientists' data challenging. Computers did not fundamentally change the problem, but enabled more and larger instances of it. In fact, by removing human mediation and time delays from the data sharing process, computers emphasize the contextual information that must be exchanged in order to exchange and reuse data. This requirement for contextual information has two faces: "interoperability" when talking about systems, and "the metadata problem" when talking about data. As much as any single organization, the Marine Metadata Interoperability (MMI) project has been tagged with the mission "Solve the metadata problem." Of course, if that goal is achieved, then sustained, interoperable data systems for interdisciplinary observing networks can be easily built -- pesky metadata differences, like which protocol to use for data exchange, or what the data actually measures, will be a thing of the past. Alas, as you might imagine, there will always be complexities and incompatibilities that are not addressed, and data systems that are not interoperable, even within a science discipline. So should we throw up our hands and surrender to the inevitable? Not at all. Rather, we try to minimize metadata problems as much as we can. In this we increasingly progress, despite natural forces that pull in the other direction. Computer systems let us work with more complexity, build community knowledge and collaborations, and preserve and publish our progress and (dis-)agreements. Funding organizations, science communities, and technologists see the importance interoperable systems and metadata, and direct resources toward them. With the new approaches and resources, projects like IPY and MMI can simultaneously define, display, and promote effective strategies for sustainable, interoperable data systems. This presentation will outline the role metadata plays in durable interoperable data systems, for better or worse. It will describe times when "just choosing a standard" can work, and when it probably won't work. And it will point out signs that suggest a metadata storm is coming to your community project, and how you might avoid it. From these lessons we will seek a path to producing interoperable, interdisciplinary, metadata-enlightened environment observing systems.
A global approach to kinematic path planning to robots with holonomic and nonholonomic constraints
NASA Technical Reports Server (NTRS)
Divelbiss, Adam; Seereeram, Sanjeev; Wen, John T.
1993-01-01
Robots in applications may be subject to holonomic or nonholonomic constraints. Examples of holonomic constraints include a manipulator constrained through the contact with the environment, e.g., inserting a part, turning a crank, etc., and multiple manipulators constrained through a common payload. Examples of nonholonomic constraints include no-slip constraints on mobile robot wheels, local normal rotation constraints for soft finger and rolling contacts in grasping, and conservation of angular momentum of in-orbit space robots. The above examples all involve equality constraints; in applications, there are usually additional inequality constraints such as robot joint limits, self collision and environment collision avoidance constraints, steering angle constraints in mobile robots, etc. The problem of finding a kinematically feasible path that satisfies a given set of holonomic and nonholonomic constraints, of both equality and inequality types is addressed. The path planning problem is first posed as a finite time nonlinear control problem. This problem is subsequently transformed to a static root finding problem in an augmented space which can then be iteratively solved. The algorithm has shown promising results in planning feasible paths for redundant arms satisfying Cartesian path following and goal endpoint specifications, and mobile vehicles with multiple trailers. In contrast to local approaches, this algorithm is less prone to problems such as singularities and local minima.
: A Holistic Path Join Algorithm for Path Query with Not-predicates on XML Data
Ling, Tok Wang
-to-leaf paths in tree-structured XML documents that satisfy certain selection predicates is the basis of complex XML query processing. Such selection predicates are called path queries (i.e., twig queries without applications. As an example of a path query with a not-predicate, consider the XPath query: //supplier
Transition Path Theory E. Vanden-Eijnden
Van Den Eijnden, Eric
Transition Path Theory E. Vanden-Eijnden Courant Institute of Mathematical Sciences, New York University New York, NY 10012 eve2cims.nyu.edu Eric Vanden-Eijnden E. Vanden-Eijnden: Transition Path Theory of the Current and Transition Tubes . . . . . . . . . . . . . . . . . . . . . . 451 5 Comparison with Transition
Cooperative organic mine avoidance path planning
NASA Astrophysics Data System (ADS)
McCubbin, Christopher B.; Piatko, Christine D.; Peterson, Adam V.; Donnald, Creighton R.; Cohen, David
2005-06-01
The JHU/APL Path Planning team has developed path planning techniques to look for paths that balance the utility and risk associated with different routes through a minefield. Extending on previous years' efforts, we investigated real-world Naval mine avoidance requirements and developed a tactical decision aid (TDA) that satisfies those requirements. APL has developed new mine path planning techniques using graph based and genetic algorithms which quickly produce near-minimum risk paths for complicated fitness functions incorporating risk, path length, ship kinematics, and naval doctrine. The TDA user interface, a Java Swing application that obtains data via Corba interfaces to path planning databases, allows the operator to explore a fusion of historic and in situ mine field data, control the path planner, and display the planning results. To provide a context for the minefield data, the user interface also renders data from the Digital Nautical Chart database, a database created by the National Geospatial-Intelligence Agency containing charts of the world's ports and coastal regions. This TDA has been developed in conjunction with the COMID (Cooperative Organic Mine Defense) system. This paper presents a description of the algorithms, architecture, and application produced.
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 natural human behavior than previous models. 1. Introduction Realistic walking animations are required
Optimal Path Synthesis for Automated Guided Vehicles
Vuik, Kees
Optimal Path Synthesis for Automated Guided Vehicles Preliminary Research Reijer Idema 2005 TU;Optimal Path Synthesis for Automated Guided Vehicles Preliminary Research Author: Reijer Idema Supervisors. FROG is a manufacturer of Automated Guided Vehicles. They have de- veloped a multitude of vehicles
FESAC Development Path Meeting Draft Agenda
FESAC Development Path Meeting Draft Agenda October 28, 2002 9:00 - 9:35: 1) Structural Materials Development for MFE and IFE - Steve Zinkle What options could be possible for a 35-year Demo? ODS steels Development Path - Mohamed Abdou / Mike Ulrickson Speak about what a blanket is. Range of blanket options
Path integral measure, constraints and ghosts for massive gravitons with a cosmological constant
Metaxas, Dimitrios
2009-12-15
For massive gravity in a de Sitter background one encounters problems of stability when the curvature is larger than the graviton mass. I analyze this situation from the path integral point of view and show that it is related to the conformal factor problem of Euclidean quantum (massless) gravity. When a constraint for massive gravity is incorporated and the proper treatment of the path integral measure is taken into account one finds that, for particular choices of the DeWitt metric on the space of metrics (in fact, the same choices as in the massless case), one obtains the opposite bound on the graviton mass.
The formal path integral and quantum mechanics
Johnson-Freyd, Theo
2010-01-01
Given an arbitrary Lagrangian function on \\RR^d and a choice of classical path, one can try to define Feynman's path integral supported near the classical path as a formal power series parameterized by "Feynman diagrams," although these diagrams may diverge. We compute this expansion and show that it is (formally, if there are ultraviolet divergences) invariant under volume-preserving changes of coordinates. We prove that if the ultraviolet divergences cancel at each order, then our formal path integral satisfies a "Fubini theorem" expressing the standard composition law for the time evolution operator in quantum mechanics. Moreover, we show that when the Lagrangian is inhomogeneous-quadratic in velocity such that its homogeneous-quadratic part is given by a matrix with constant determinant, then the divergences cancel at each order. Thus, by "cutting and pasting" and choosing volume-compatible local coordinates, our construction defines a Feynman-diagrammatic "formal path integral" for the nonrelativistic qu...
On Path Decomposition Conjecture of Tibor Gallai
Dhananjay P. Mehendale
2011-06-02
We settle the Path Decomposition Conjecture (P.D.C.) due to Tibor Gallai for minimally connected graphs, i.e. trees. We use this validity for trees and settle the P. D. C. using induction on the number of edges for all connected graphs. We then obtain a new bound for the number of paths in a path cover in terms of the number of edges using idea of associating a tree with a connected graph. We then make use of a spanning tree in the given connected graph and its associated basic path cover to settle the conjecture of Tibor Gallai in an alternative way. Finally, we show the existence of Hamiltonian path cover satisfying Gallai bound for complete graphs of even order and discuss some of its possible ramifications.
... version of this page please turn Javascript on. Balance Problems About Balance Problems Have you ever felt dizzy, lightheaded, or ... dizziness problem during the past year. Why Good Balance is Important Having good balance means being able ...
González, Jorge E.; Romero, Ivonne; Gregoire, Eric; Martin, Cécile; Lamadrid, Ana I.; Voisin, Philippe; Barquinero, Joan-Francesc; GarcÍa, Omar
2014-01-01
The combination of automatic image acquisition and automatic image analysis of premature chromosome condensation (PCC) spreads was tested as a rapid biodosimeter protocol. Human peripheral lymphocytes were irradiated with 60Co gamma rays in a single dose of between 1 and 20 Gy, stimulated with phytohaemaglutinin and incubated for 48 h, division blocked with Colcemid, and PCC-induced by Calyculin A. Images of chromosome spreads were captured and analysed automatically by combining the Metafer 4 and CellProfiler platforms. Automatic measurement of chromosome lengths allows the calculation of the length ratio (LR) of the longest and the shortest piece that can be used for dose estimation since this ratio is correlated with ionizing radiation dose. The LR of the longest and the shortest chromosome pieces showed the best goodness-of-fit to a linear model in the dose interval tested. The application of the automatic analysis increases the potential use of the PCC method for triage in the event of massive radiation causalities. PMID:24789085
Precision Cleaning - Path to Premier
NASA Technical Reports Server (NTRS)
Mackler, Scott E.
2008-01-01
ITT Space Systems Division s new Precision Cleaning facility provides critical cleaning and packaging of aerospace flight hardware and optical payloads to meet customer performance requirements. The Precision Cleaning Path to Premier Project was a 2007 capital project and is a key element in the approved Premier Resource Management - Integrated Supply Chain Footprint Optimization Project. Formerly precision cleaning was located offsite in a leased building. A new facility equipped with modern precision cleaning equipment including advanced process analytical technology and improved capabilities was designed and built after outsourcing solutions were investigated and found lacking in ability to meet quality specifications and schedule needs. SSD cleans parts that can range in size from a single threaded fastener all the way up to large composite structures. Materials that can be processed include optics, composites, metals and various high performance coatings. We are required to provide verification to our customers that we have met their particulate and molecular cleanliness requirements and we have that analytical capability in this new facility. The new facility footprint is approximately half the size of the former leased operation and provides double the amount of throughput. Process improvements and new cleaning equipment are projected to increase 1st pass yield from 78% to 98% avoiding $300K+/yr in rework costs. Cost avoidance of $350K/yr will result from elimination of rent, IT services, transportation, and decreased utility costs. Savings due to reduced staff expected to net $4-500K/yr.
Gerbertian paths for the Jubilee
NASA Astrophysics Data System (ADS)
Sigismondi, Costantino
2015-04-01
Gerbert before becoming Pope Sylvester II came several times in Rome, as reported in his Letters and in the biography of Richerus. Eight places in Rome can be connected with Gerbertian memories. 1. The Cathedral of St. John in the Lateran where the gravestone of his tumb is still preserved near the Holy Door; 2. the “Basilica Hierusalem” (Santa Croce) where Gerbert had the stroke on May 3rd 1003 which lead him to death on May 12th; 3. the Aventine hill, with the church of the Knights of Malta in the place where the palace of the Ottonian Emperors was located; 4. the church of St. Bartholomew in the Tiber Island built in 997 under Otto III; 5. the Obelisk of Augustus in Montecitorio to remember the relationship between Gerbert, Astronomy and numbers which led the birth of the legends on Gerbert magician; 6. St. Mary Major end of the procession of August 15, 1000; 7. St. Paul outside the walls with the iconography of the Popes and 8. St. Peter's tumb end of all Romaei pilgrimages. This Gerbertian path in Rome suggests one way to accomplish the pilgrimage suggested by Pope Francis in the Bulla Misericordiae Vultus (14) of indiction of the new Jubilee.
MAS 05 Informative Path Planning MAS 05.1 Overview
Soatto, Stefano
MAS 05 Informative Path Planning MAS 05.1 Overview My goal is to create path planning algorithms that robots provide, it is necessary to come up with a path planning algorithm that can choose paths which gather the most useful information. Over the past year, I have focused primarily on path planning
The reaction path intrinsic reaction coordinate method and the Hamilton-Jacobi theory.
Crehuet, Ramon; Bofill, Josep Maria
2005-06-15
The definition and location of an intrinsic reaction coordinate path is of crucial importance in many areas of theoretical chemistry. Differential equations used to define the path hitherto are complemented in this study with a variational principle of Fermat type, as Fukui [Int. J. Quantum Chem., Quantum Chem. Symp. 15, 633 (1981)] reported in a more general form some time ago. This definition is more suitable for problems where initial and final points are given. The variational definition can naturally be recast into a Hamilton-Jacobi equation. The character of the variational solution is studied via the Weierstrass necessary and sufficient conditions. The characterization of the local minima character of the intrinsic reaction coordinate is proved. Such result leads to a numerical algorithm to find intrinsic reaction coordinate paths based on the successive minimizations of the Weierstrass E-function evaluated on a guess curve connecting the initial and final points of the desired path. PMID:16008428
Optimal impulsive time-fixed orbital rendezvous and interception with path constraints
NASA Technical Reports Server (NTRS)
Taur, D.-R.; Prussing, J. E.; Coverstone-Carroll, V.
1990-01-01
Minimum-fuel, impulsive, time-fixed solutions are obtained for the problem of orbital rendezvous and interception with interior path constraints. Transfers between coplanar circular orbits in an inverse-square gravitational field are considered, subject to a circular path constraint representing a minimum or maximum permissible orbital radius. Primer vector theory is extended to incorporate path constraints. The optimal number of impulses, their times and positions, and the presence of initial or final coasting arcs are determined. The existence of constraint boundary arcs and boundary points is investigated as well as the optimality of a class of singular arc solutions. To illustrate the complexities introduced by path constraints, an analysis is made of optimal rendezvous in field-free space subject to a minimum radius constraint.
MULTIPLE TIME SCALE NUMERICAL METHODS FOR THE INVERTED PENDULUM PROBLEM
Ferguson, Thomas S.
MULTIPLE TIME SCALE NUMERICAL METHODS FOR THE INVERTED PENDULUM PROBLEM RICHARD SHARP, YEN-HSI TSAI multiscale methods (HMM) [1]. We apply the methods to compute the averaged path of the inverted pendulum approximate the averaged equation and thus compute the average path of the inverted pendulum. 1. INTRODUCTION
Multiple time scale numerical methods for the inverted pendulum problem
Tsai, Yen-Hsi Richard
Multiple time scale numerical methods for the inverted pendulum problem Richard Sharp1, Yen (HMM) [1]. We apply the methods to compute the averaged path of the inverted pendulum under a highly and thus compute the average path of the inverted pendulum. 1 Introduction The focus of this paper
Smart random walkers: the cost of knowing the path.
Perotti, Juan I; Billoni, Orlando V
2012-07-01
In this work we study the problem of targeting signals in networks using entropy information measurements to quantify the cost of targeting. We introduce a penalization rule that imposes a restriction on the long paths and therefore focuses the signal to the target. By this scheme we go continuously from fully random walkers to walkers biased to the target. We found that the optimal degree of penalization is mainly determined by the topology of the network. By analyzing several examples, we have found that a small amount of penalization reduces considerably the typical walk length, and from this we conclude that a network can be efficiently navigated with restricted information. PMID:23005381
Biclique-colouring powers of paths and powers of cycles
Filho, Hélio B Macędo; Machado, Raphael C S; de Figueiredo, Celina M H
2012-01-01
Biclique-colouring is a colouring of the vertices of a graph in such a way that no maximal complete bipartite subgraph with at least one edge is monochromatic. We show that it is co$\\mathcal{NP}$-complete to check if a colouring of vertices is a valid biclique-colouring, a result that justifies the search for structured classes where the biclique-colouring problem could be efficiently solved. We consider biclique-colouring restricted to powers of paths and powers of cycles. We determine the biclique-chromatic number of powers of paths and powers of cycles. The biclique-chromatic number of a power of a path $P_{n}^{k}$ is $\\max(2k + 2 - n, 2)$ if $n \\geq k + 1$ and exactly $n$ otherwise. The biclique-chromatic number of a power of a cycle $C_n^k$ is at most 3 if $n \\geq 2k + 2$ and exactly $n$ otherwise; we additionally determine the powers of cycles that are 2-biclique-colourable. All the proofs are algorithmic and we provide polynomial-time biclique-colouring algorithms for graphs in the investigated classes...
Planning Paths Through Singularities in the Center of Mass Space
NASA Technical Reports Server (NTRS)
Doggett, William R.; Messner, William C.; Juang, Jer-Nan
1998-01-01
The center of mass space is a convenient space for planning motions that minimize reaction forces at the robot's base or optimize the stability of a mechanism. A unique problem associated with path planning in the center of mass space is the potential existence of multiple center of mass images for a single Cartesian obstacle, since a single center of mass location can correspond to multiple robot joint configurations. The existence of multiple images results in a need to either maintain multiple center of mass obstacle maps or to update obstacle locations when the robot passes through a singularity, such as when it moves from an elbow-up to an elbow-down configuration. To illustrate the concepts presented in this paper, a path is planned for an example task requiring motion through multiple center of mass space maps. The object of the path planning algorithm is to locate the bang- bang acceleration profile that minimizes the robot's base reactions in the presence of a single Cartesian obstacle. To simplify the presentation, only non-redundant robots are considered and joint non-linearities are neglected.
Scheduling And Path Planning Of Multiple Robots In A Factory
NASA Astrophysics Data System (ADS)
Meng, Alexander C.; Choong, Yong F.; Sullivan, Michael
1989-03-01
This paper describes the work in progress for scheduling and planning paths for map-guided robots (AGVs) maneuvering in a dynamic factory floor environment. A schedule of a group of robots consists of a set of paths to be traversed and the start, stop and wait time at each point of a single robot's path segment. The optimal schedule will minimize the finish time of all the robots's tasks. We will show that the optimal routing problem for multiple robots is computationally intractable (NP-Complete). Our methodology is to generate reasonably good schedules in time by combining techniques from two different disciplines. We use a time map management system from artificial intelligence (AI) research to generate an initial schedule quickly, then we pass the initial schedule to an iterative refinement loop (or local search) to gradually improve it locally using an optimization process from operations research (OR). We will briefly recount the basic principles for map-guided autonomous navigation, which has been published in [Meng88b].
Min-Max Problems on Factor-Graphs We study the min-max problem in factor graphs,
Toronto, University of
assignment problem (Gross 1959). Edmonds & Fulkerson (1970) introduce a bottleneck framework with a duality a and b Â minimum of the maximum weight in a cut Â and min-max path between a and bÂ minimum of maximum weight in a path (Fulkerson 1966). Hoch
Emilio Bagan; Janos A. Bergou; Mark Hillery
2015-09-15
We find a relation between coherence and path-information in a multi-path interferometer. This work builds on earlier results for the two-path interferometer, which used minimum-error state discrimination between detector states to provide the path information. For visibility, which was used in the two-path case, we substitute a recently defined measure of quantum coherence.
Robot path planning using a genetic algorithm
NASA Technical Reports Server (NTRS)
Cleghorn, Timothy F.; Baffes, Paul T.; Wang, Liu
1988-01-01
Robot path planning can refer either to a mobile vehicle such as a Mars Rover, or to an end effector on an arm moving through a cluttered workspace. In both instances there may exist many solutions, some of which are better than others, either in terms of distance traversed, energy expended, or joint angle or reach capabilities. A path planning program has been developed based upon a genetic algorithm. This program assumes global knowledge of the terrain or workspace, and provides a family of good paths between the initial and final points. Initially, a set of valid random paths are constructed. Successive generations of valid paths are obtained using one of several possible reproduction strategies similar to those found in biological communities. A fitness function is defined to describe the goodness of the path, in this case including length, slope, and obstacle avoidance considerations. It was found that with some reproduction strategies, the average value of the fitness function improved for successive generations, and that by saving the best paths of each generation, one could quite rapidly obtain a collection of good candidate solutions.
Nonholonomic catheter path reconstruction using electromagnetic tracking
NASA Astrophysics Data System (ADS)
Lugez, Elodie; Sadjadi, Hossein; Akl, Selim G.; Fichtinger, Gabor
2015-03-01
Catheter path reconstruction is a necessary step in many clinical procedures, such as cardiovascular interventions and high-dose-rate brachytherapy. To overcome limitations of standard imaging modalities, electromagnetic tracking has been employed to reconstruct catheter paths. However, tracking errors pose a challenge in accurate path reconstructions. We address this challenge by means of a filtering technique incorporating the electromagnetic measurements with the nonholonomic motion constraints of the sensor inside a catheter. The nonholonomic motion model of the sensor within the catheter and the electromagnetic measurement data were integrated using an extended Kalman filter. The performance of our proposed approach was experimentally evaluated using the Ascension's 3D Guidance trakStar electromagnetic tracker. Sensor measurements were recorded during insertions of an electromagnetic sensor (model 55) along ten predefined ground truth paths. Our method was implemented in MATLAB and applied to the measurement data. Our reconstruction results were compared to raw measurements as well as filtered measurements provided by the manufacturer. The mean of the root-mean-square (RMS) errors along the ten paths was 3.7 mm for the raw measurements, and 3.3 mm with manufacturer's filters. Our approach effectively reduced the mean RMS error to 2.7 mm. Compared to other filtering methods, our approach successfully improved the path reconstruction accuracy by exploiting the sensor's nonholonomic motion constraints in its formulation. Our approach seems promising for a variety of clinical procedures involving reconstruction of a catheter path.
Baras, John S.
the topology control problem of selective link-state broadcast as a graph pruning problem with restricted local the Stable Path Topology Control algorithm, to compute this local policy that yields a pruned graph. Using. This problem is referred to as the broadcast storm problem [2]. We adopt a graph pruning approach to reduce
Dissociable cognitive mechanisms underlying human path integration.
Wiener, Jan M; Berthoz, Alain; Wolbers, Thomas
2011-01-01
Path integration is a fundamental mechanism of spatial navigation. In non-human species, it is assumed to be an online process in which a homing vector is updated continuously during an outward journey. In contrast, human path integration has been conceptualized as a configural process in which travelers store working memory representations of path segments, with the computation of a homing vector only occurring when required. To resolve this apparent discrepancy, we tested whether humans can employ different path integration strategies in the same task. Using a triangle completion paradigm, participants were instructed either to continuously update the start position during locomotion (continuous strategy) or to remember the shape of the outbound path and to calculate home vectors on basis of this representation (configural strategy). While overall homing accuracy was superior in the configural condition, participants were quicker to respond during continuous updating, strongly suggesting that homing vectors were computed online. Corroborating these findings, we observed reliable differences in head orientation during the outbound path: when participants applied the continuous updating strategy, the head deviated significantly from straight ahead in direction of the start place, which can be interpreted as a continuous motor expression of the homing vector. Head orientation-a novel online measure for path integration-can thus inform about the underlying updating mechanism already during locomotion. In addition to demonstrating that humans can employ different cognitive strategies during path integration, our two-systems view helps to resolve recent controversies regarding the role of the medial temporal lobe in human path integration. PMID:20972774
QoS routing via multiple paths using bandwidth reservation
Rao, N.S.V.; Batsell, S.G.
1998-01-01
The authors address the problem of computing a multipath, consisting of possibly overlapping paths, to transmit data from the source node s to the destination node d over a computer network while ensuring deterministic bounds on end-to-end delay or delivery rate.They consider two generic routing problems within the framework wherein bandwidth can be reserved, and guaranteed, once reserved, on various links of the communication network. The first problem requires that a message of finite length be transmitted from s to d within {tau} units of time. The second problem requires that a sequential message of r units be transmitted at a rate of {eta} such that maximum time difference between two units that are received out of order is no more than q. They propose a polynomial-time algorithm to the first problem based on an adaptation of the classical Ford-Fulkerson`s method. They present simulation results to illustrate the applicability of the proposed algorithm. They show the second problem to be NP-complete, and propose a polynomial-time approximately solution.
QoS routing via multiple paths using bandwidth reservation
Rao, N.S.V.; Batsell, S.G.
1997-11-01
The authors address the problem of computing a multipath, consisting of possibly overlapping paths, to transmit data from the source node s to the destination node d over a computer network while ensuring deterministic bounds on end-to-end delay or delivery rate. They consider two generic routing problems within the framework wherein bandwidth can be reserved, and guaranteed, once reserved, on various links of the communication network. The first problem requires that a message of finite length be transmitted from s to d within {tau} units of time. The second problem requires that a sequential message of r units be transmitted at a rate of {eta} such that maximum time difference between two units that are received out of order is no more than q. They propose a polynomial-time algorithm to the first problem based on an adaptation of the classical Ford-Fulkerson`s method. They present simulation results to illustrate the applicability of the proposed algorithm. They show the second problem to be NP-complete and propose a polynomial-time approximate solution.
NASA Astrophysics Data System (ADS)
Feibel, C. S.
2004-12-01
A complex series of evolutionary steps, contingent upon a dynamic environmental context and a long biological heritage, have led to the ascent of Homo sapiens as a dominant component of the modern biosphere. In a field where missing links still abound and new discoveries regularly overturn theoretical paradigms, our understanding of the path of human evolution has made tremendous advances in recent years. Two major trends characterize the development of the hominin clade subsequent to its origins with the advent of upright bipedalism in the Late Miocene of Africa. One is a diversification into two prominent morphological branches, each with a series of 'twigs' representing evolutionary experimentation at the species or subspecies level. The second important trend, which in its earliest manifestations cannot clearly be ascribed to one or the other branch, is the behavioral complexity of an increasing reliance on technology to expand upon limited inherent morphological specializations and to buffer the organism from its environment. This technological dependence is directly associated with the expansion of hominin range outside Africa by the genus Homo, and is accelerated in the sole extant form Homo sapiens through the last 100 Ka. There are interesting correlates between the evolutionary and behavioral patterns seen in the hominin clade and environmental dynamics of the Neogene. In particular, the tempo of morphological and behavioral innovation may be tracking major events in Neogene climatic development as well as reflecting intervals of variability or stability. Major improvements in analytical techniques, coupled with important new collections and a growing body of contextual data are now making possible the integration of global, regional and local environmental archives with an improved biological understanding of the hominin clade to address questions of coincidence and causality.
Path planning using optically computed potential fields
NASA Technical Reports Server (NTRS)
Reid, Max B.
1993-01-01
An algorithm for the optical computation of potential field maps suitable for mobile robot navigation is described and experimentally produced maps and paths are presented. The parallel analog optical computation employs a two-dimensional spatial light modulator on which an image of the potential field map is generated. Optically calculated fields contain no local minima, tend to produce paths centered in gaps between obstacles, and produce paths which give preference to wide gaps. Calculation of 128 x 128 pixel fields at a few hertz are possible with current technology, and calculation time vs. map size scales favorably in comparison to digital electronic computation.
Crack-path effect on material toughness
NASA Technical Reports Server (NTRS)
Rubinstein, Asher A.
1990-01-01
The main features of a toughening mechanism associated with a curvilinear crack path are examined using a model consisting of a macrocrack in a brittle solid with a curvilinear segment at the crack tip. A numerical procedure for finite and semiinfinite cracks is formulated and evaluated using an example which has an exact solution (a finite crack in the form of a circular arc in a uniform stress field). It is shown that, for a relatively small amplitude of crack path oscillations, the toughening ratio can be taken equal to the ratio of the corresponding crack path lengths.
EFFICIENT STRUCTURE AND MOTION: PATH PLANNING, UNCERTAINTY AND SPARSITY
Lunds Universitet
EFFICIENT STRUCTURE AND MOTION: PATH PLANNING, UNCERTAINTY AND SPARSITY SEBASTIAN HANER Faculty", Workshop on Mobile Vision, San Francisco, 2010. · S. Haner and A. Heyden, "Optimal View Path Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 B Optimal View Path Planning for Visual SLAM 31 1 Introduction
MOBILE ROBOTS PATH PLANNING OPTIMIZATION IN STATIC AND DYNAMIC ENVIRONMENTS
Areibi, Shawki M
MOBILE ROBOTS PATH PLANNING OPTIMIZATION IN STATIC AND DYNAMIC ENVIRONMENTS A Thesis Presented PATH PLANNING OPTIMIZATION IN STATIC AND DYNAMIC ENVIRONMENTS Ahmed Elshamli University of Guelph, 2004 Advisor: Professor: Hussein A. Abdullah Professor: Shawki Areibi Path planning for mobile robots
Multiresolution Hierarchical Path-Planning for Small UAVs Panagiotis Tsiotras
Tsiotras, Panagiotis
Multiresolution Hierarchical Path-Planning for Small UAVs Panagiotis Tsiotras School of Aerospace-- In this paper we review some recent results on a new multiresolution hierarchical path planning algorithm, wavelet decomposition, path planning, collision avoidance, adjacency matrix, UAVs I. INTRODUCTION
Calibration of neural networks using genetic algorithms, with application to optimal path planning
NASA Technical Reports Server (NTRS)
Smith, Terence R.; Pitney, Gilbert A.; Greenwood, Daniel
1987-01-01
Genetic algorithms (GA) are used to search the synaptic weight space of artificial neural systems (ANS) for weight vectors that optimize some network performance function. GAs do not suffer from some of the architectural constraints involved with other techniques and it is straightforward to incorporate terms into the performance function concerning the metastructure of the ANS. Hence GAs offer a remarkably general approach to calibrating ANS. GAs are applied to the problem of calibrating an ANS that finds optimal paths over a given surface. This problem involves training an ANS on a relatively small set of paths and then examining whether the calibrated ANS is able to find good paths between arbitrary start and end points on the surface.
conference on inverse problems in honor of gunther uhlmann
2012-06-20
Jun 18, 2012 ... Abstract: We study semiclassical measures of distorted plane waves functions on ... problems that caused me to cross paths with Gunther Uhlmann. ..... Riemannian manifolds of bounded sectional curvature and diameter.
Problem drinkers and their problems
Buchan, I. C.; Buckley, E. G.; Deacon, G. L. S.; Irvine, R.; Ryan, M. P.
1981-01-01
From general practice records of 9,763 patients, 106 problem drinkers were compared with a control group. The drinkers had a substantially higher number of problems and they consulted their doctor and attended casualty departments frequently. Social and marital problems were especially prevalent in the families of problem drinkers. PMID:7277292
47 CFR 22.515 - Permissible communications paths.
Code of Federal Regulations, 2010 CFR
2010-10-01
...false Permissible communications paths. 22.515...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...CARRIER SERVICES PUBLIC MOBILE SERVICES ...515 Permissible communications paths....
Identifying decohering paths in closed quantum systems
NASA Technical Reports Server (NTRS)
Albrecht, Andreas
1990-01-01
A specific proposal is discussed for how to identify decohering paths in a wavefunction of the universe. The emphasis is on determining the correlations among subsystems and then considering how these correlations evolve. The proposal is similar to earlier ideas of Schroedinger and of Zeh, but in other ways it is closer to the decoherence functional of Griffiths, Omnes, and Gell-Mann and Hartle. There are interesting differences with each of these which are discussed. Once a given coarse-graining is chosen, the candidate paths are fixed in this scheme, and a single well defined number measures the degree of decoherence for each path. The normal probability sum rules are exactly obeyed (instantaneously) by these paths regardless of the level of decoherence. Also briefly discussed is how one might quantify some other aspects of classicality. The important role that concrete calculations play in testing this and other proposals is stressed.
Building a path in cell biology
Cheeseman, Iain McPherson
Setting up a new lab is an exciting but challenging prospect. We discuss our experiences in finding a path to tackle some of the key current questions in cell biology and the hurdles that we have encountered along the way.
Walden's Paths quiz: system design and implementation
Arora, Avital Jayant
2002-01-01
This thesis describes the motivation for online testing, compares the effectiveness of online tests versus conventional tests and outlines the features of online-testing mechanisms. It details the features and implementation of the Walden's Paths...
A chemist building paths to cell biology.
Weibel, Douglas B
2013-11-01
Galileo is reported to have stated, "Measure what is measurable and make measurable what is not so." My group's trajectory in cell biology has closely followed this philosophy, although it took some searching to find this path. PMID:24174456
MODELING DENDRITIC SHAPES Using Path Planning
Mould, David
MODELING DENDRITIC SHAPES Using Path Planning Ling Xu, David Mould Department of Computer Science, University of Saskatchewan, Saskatoon, Canada lix272@mail.usask.ca, mould@cs.usask.ca Keywords: dendrites
Path integral distance for data interpretation
Volchenkov, D
2015-01-01
The process of data interpretation is always based on the implicit introduction of equivalence relations on the set of walks over the database. Every equivalence relation on the set of walks specifies a Markov chain describing the transitions of a discrete time random walk. In order to geometrize and interpret the data, we propose the new distance between data units defined as a "Feynman path integral", in which all possible paths between any two nodes in a graph model of the data are taken into account, although some paths are more preferable than others. Such a path integral distance approach to the analysis of databases has proven its efficiency and success, especially on multivariate strongly correlated data where other methods fail to detect structural components (urban planning, historical language phylogenies, music, street fashion traits analysis, etc. ). We believe that it would become an invaluable tool for the intelligent complexity reduction and big data interpretation.
Regularization Path Algorithms for Detecting Gene Interactions
Hastie, Trevor
of indicators can be selected simultaneously. Here we introduce another version of group-Lars. In addi- tion, we models. We regard this strategy of using path algorithms as a compromise between our two earlier studies
Riemann Curvature Tensor and Closed Geodesic Paths
ERIC Educational Resources Information Center
Morganstern, Ralph E.
1977-01-01
Demonstrates erroneous results obtained if change in a vector under parallel transport about a closed path in Riemannian spacetime is made in a complete circuit rather than just half a circuit. (Author/SL)
Duality of quantum coherence and path distinguishability
NASA Astrophysics Data System (ADS)
Bera, Manabendra Nath; Qureshi, Tabish; Siddiqui, Mohd Asad; Pati, Arun Kumar
2015-07-01
We derive a generalized wave-particle duality relation for arbitrary multipath quantum interference phenomena. Beyond the conventional notion of the wave nature of a quantum system, i.e., the interference fringe visibility, we introduce a quantifier as the normalized quantum coherence, recently defined in the framework of quantum information theory. To witness the particle nature, we quantify the path distinguishability or the which-path information based on unambiguous quantum state discrimination. Then, the Bohr complementarity principle for multipath quantum interference can be stated as a duality relation between the quantum coherence and the path distinguishability. For two-path interference, the quantum coherence is identical to the interference fringe visibility, and the relation reduces to the well-known complementarity relation. The duality relation continues to hold in the case where mixedness is introduced due to possible decoherence effects.
Local-time representation of path integrals
Petr Jizba; Vaclav Zatloukal
2015-06-02
We derive a local-time path-integral representation for a generic one-dimensional time-independent system. In particular, we show how to rephrase the matrix elements of the Bloch density matrix as a path integral over x-dependent local-time profiles. The latter quantify the time that the sample paths x(t) in the Feynman path integral spend in the vicinity of an arbitrary point x. Generalization of the local-time representation that includes arbitrary functionals of the local time is also provided. We argue that the results obtained represent a powerful alternative to the traditional Feynman-Kac formula, particularly in the high and low temperature regimes. To illustrate this point, we apply our local-time representation to analyze the asymptotic behavior of the Bloch density matrix at low temperatures. Further salient issues, such as connections with the Sturm-Liouville theory and the Rayleigh-Ritz variational principle are also discussed.
When Does Changing Representation Improve Problem-Solving Performance?
NASA Technical Reports Server (NTRS)
Holte, Robert; Zimmer, Robert; MacDonald, Alan
1992-01-01
The aim of changing representation is the improvement of problem-solving efficiency. For the most widely studied family of methods of change of representation it is shown that the value of a single parameter, called the expulsion factor, is critical in determining (1) whether the change of representation will improve or degrade problem-solving efficiency and (2) whether the solutions produced using the change of representation will or will not be exponentially longer than the shortest solution. A method of computing the expansion factor for a given change of representation is sketched in general and described in detail for homomorphic changes of representation. The results are illustrated with homomorphic decompositions of the Towers of Hanoi problem.
Performance analysis of CCSDS path service
NASA Technical Reports Server (NTRS)
Johnson, Marjory J.
1989-01-01
A communications service, called Path Service, is currently being developed by the Consultative Committee for Space Data Systems (CCSDS) to provide a mechanism for the efficient transmission of telemetry data from space to ground for complex space missions of the future. This is an important service, due to the large volumes of telemetry data that will be generated during these missions. A preliminary analysis of performance of Path Service is presented with respect to protocol-processing requirements and channel utilization.
Multiple path transport in quantum networks
Cohen, Doron
] GA, DC, Multiple path transport (JPA 2013) [2] DD, DC, Double path crossing (JPA 2013) [3] http://www.bgu.ac [Kubo, Thouless, Avron, Berry]: dQ = G du ; I = G u G(u) = 2Im u =0 Splitting ratio picture [MC,IS,DC crosses an half-filled energy band For a Fermi sea occupation we have to sum the currents of all
Visualization of Ant Pheromone Based Path Following
Sutherland, Benjamin T.
2010-07-14
OF ANT PHEROMONE BASED PATH FOLOWING A Thesis by Benjamin Sutherland Submited to the O?ce of Graduate Studies of Texas A&M University in partial fulfilment of the requirements for the degre of MASTER OF SCIENCE December... 2009 Major Subject: Visualization Sciences VISUALIZATION OF ANT PHEROMONE BASED PATH FOLOWING A Thesis by Benjamin Sutherland Submited to the O?ce of Graduate Studies of Texas A&M University in partial fulfilment...
Thermodynamic Metrics and Optimal Paths
Sivak, David; Crooks, Gavin
2012-05-08
A fundamental problem in modern thermodynamics is how a molecular-scale machine performs useful work, while operating away from thermal equilibrium without excessive dissipation. To this end, we derive a friction tensor that induces a Riemannian manifold on the space of thermodynamic states. Within the linear-response regime, this metric structure controls the dissipation of finite-time transformations, and bestows optimal protocols with many useful properties. We discuss the connection to the existing thermodynamic length formalism, and demonstrate the utility of this metric by solving for optimal control parameter protocols in a simple nonequilibrium model.
Multiple Damage Progression Paths in Model-Based Prognostics
NASA Technical Reports Server (NTRS)
Daigle, Matthew; Goebel, Kai Frank
2011-01-01
Model-based prognostics approaches employ domain knowledge about a system, its components, and how they fail through the use of physics-based models. Component wear is driven by several different degradation phenomena, each resulting in their own damage progression path, overlapping to contribute to the overall degradation of the component. We develop a model-based prognostics methodology using particle filters, in which the problem of characterizing multiple damage progression paths is cast as a joint state-parameter estimation problem. The estimate is represented as a probability distribution, allowing the prediction of end of life and remaining useful life within a probabilistic framework that supports uncertainty management. We also develop a novel variance control mechanism that maintains an uncertainty bound around the hidden parameters to limit the amount of estimation uncertainty and, consequently, reduce prediction uncertainty. We construct a detailed physics-based model of a centrifugal pump, to which we apply our model-based prognostics algorithms. We illustrate the operation of the prognostic solution with a number of simulation-based experiments and demonstrate the performance of the chosen approach when multiple damage mechanisms are active
Quantum cosmology based on discrete Feynman paths
Chew, Geoffrey F.
2002-10-10
Although the rules for interpreting local quantum theory imply discretization of process, Lorentz covariance is usually regarded as precluding time quantization. Nevertheless a time-discretized quantum representation of redshifting spatially-homogeneous universe may be based on discrete-step Feynman paths carrying causal Lorentz-invariant action--paths that not only propagate the wave function but provide a phenomenologically-promising elementary-particle Hilbert-space basis. In a model under development, local path steps are at Planck scale while, at a much larger ''wave-function scale'', global steps separate successive wave-functions. Wave-function spacetime is but a tiny fraction of path spacetime. Electromagnetic and gravitational actions are ''at a distance'' in Wheeler-Feynman sense while strong (color) and weak (isospin) actions, as well as action of particle motion, are ''local'' in a sense paralleling the action of local field theory. ''Nonmaterial'' path segments and ''trivial events'' collaborate to define energy and gravity. Photons coupled to conserved electric charge enjoy privileged model status among elementary fermions and vector bosons. Although real path parameters provide no immediate meaning for ''measurement'', the phase of the complex wave function allows significance for ''information'' accumulated through ''gentle'' electromagnetic events involving charged matter and ''soft'' photons. Through its soft-photon content the wave function is an ''information reservoir''.
Approximation Algorithms for Disjoint st-Paths with Minimum Activation Cost
Erlebach, Thomas
Approximation Algorithms for Disjoint st-Paths with Minimum Activation Cost Hasna Mohsen Alqahtani.erlebach}@leicester.ac.uk Abstract. In network activation problems we are given a directed or undirected graph G = (V, E) with a family {fuv (xu, xv) : (u, v) E} of monotone non-decreasing activation functions from D2 to {0, 1
Clearing the Path tor All of Us Where Trains Once Ran.
ERIC Educational Resources Information Center
Mills, Judy
1990-01-01
Describes the concept behind the rail-to-trails movement; the history, process and problems of converting abandoned railroad beds to bike and walking paths. Introduces the concept and trend of ergo, or linear parks, corridors, and greenways to meet the increasing need for public access to land for recreational purposes. (MCO)
Errata to the Werts-Linn Comments on Boyle's "Path Analysis and Ordinal Data."
ERIC Educational Resources Information Center
Werts, Charles E.; Linn, Robert L.
The Werts-Linn procedure for dealing with categorical errors of measurement in "Comments on Boyle's 'Path Analysis and Ordinal Data'" in The American Journal of Sociology, volume 76, number 6, May 1971, is shown to be inappropriate to the problem of ordered categories. (For related document, see TM 002 301.) (DB)
Bimodality and transient trimodality for Brownian particles in shear flows: A path-integral approach
Wio, H.S.; Zanette, D.H. )
1993-01-01
The problem of Brownian motion in shear flows is analyzed using a path-integral approach and a piecewise-linearized velocity profile. In this way, the complete two-dimensional conditional probability distribution is found and the unimodal-bimodal transition in the longitudinal distribution is consistently described. A remarkable aspect is the appearance of a transient trimodal regime.
LMPS: Localized Multi-Path Selection for QoS Routing in VoIP Networks
Elsayed, Khaled Fouad
S state using locally collected information based on flow blocking statistics, and perform flow routing to avoid the overloaded links to minimize the overall blocking ratio in the network. We demonstrate through information. Another well-known problem is path oscil- lations which may occur when a node discovers
Zhou, Xuesong
1 Designing Heterogeneous Sensor Networks for Estimating and Predicting Path Travel Time Dynamics on the end-to-end travel time prediction problem, this paper proposes an information- theoretic sensor in the travel time estimation/prediction process, such as the uncertainty associated with prior travel time
Dong Jianping
2013-01-14
The solution to the fractional Schr\\"odinger equation with infinite square well is obtained in this paper, by use of the L\\'evy path integral approach. We obtain the even and odd parity wave functions of this problem, which are in accordance with those given by Laskin in [Chaos 10 (2000), 780--790].
An Evaluation of the Preschool PATHS Curriculum on the Development of Preschool Children
ERIC Educational Resources Information Center
Hughes, Cerian; Cline, Tony
2015-01-01
This study evaluated the efficacy of preschool Promoting Alternative Thinking Strategies (PATHS), an early years curriculum designed to improve children's social and emotional competence, and reduce problem behaviour. Fifty-seven children aged three to four years took part in the study over one academic year. The control group (Group 1)…
TrueErase: Full-storage-data-path Per-file Secure Deletion
Wang, Andy
In reality Actual data remains 3 #12;The Problem Decommissioned storage devices leak sensitive informationTrueErase: Full-storage-data-path Per-file Secure Deletion Sarah Diesburg Christopher Meyers Mark Important for expired data, statute of limitations, etc. Existing solutions tend to be Limited
Jamming-Aware Traffic Allocation for Multiple-Path Routing Using Portfolio Selection
Poovendran, Radha
1 Jamming-Aware Traffic Allocation for Multiple-Path Routing Using Portfolio Selection Patrick, we consider the problem of jamming-aware source routing in which the source node performs traffic allocation based on empirical jamming statistics at individual network nodes. We formulate this traffic
Supervised Feature Selection in Graphs with Path Coding Penalties and Network Flows
McAuliffe, Jon
on Optimization for Machine Learning (OPT 2011) at the Neural Information Processing System (NIPS) conference estimation problems have been the topic of much research in statistical machine learning and signalSupervised Feature Selection in Graphs with Path Coding Penalties and Network Flows Julien Mairal
SMOOTH AND TIME-OPTIMAL TRAJECTORY PLANNING FOR INDUSTRIAL MANIPULATORS ALONG SPECIFIED PATHS
Constantinescu, Daniela
DSC-17A-2 SMOOTH AND TIME-OPTIMAL TRAJECTORY PLANNING FOR INDUSTRIAL MANIPULATORS ALONG SPECIFIED@mech.ubc.ca ABSTRACT This paper presents a method for determining smooth and time-optimal path-constrained trajectories to parameterize the state space trajectory. The optimization problem is solved using the exible tolerance method
Aircraft Routing -A Global Optimization Problem Michael C Bartholomew-Biggs
Neumaier, Arnold
Aircraft Routing - A Global Optimization Problem Michael C Bartholomew-Biggs matqmb@herts.ac.uk University of Hertfordshire, England This paper deals with the problem of calculating aircraft flight paths
... get around, and exercise. Having a problem with walking can make daily life more difficult. The pattern ... an abnormal gait and lead to problems with walking. These include: Injuries, diseases, or abnormal development of ...
... asthma, arthritis or heart failure Medicines and certain foods or drinks back to top Why Is It Important to Get Help? Poor sleep can slow your loved one’s recovery. Sleep problems can lead to depression, memory problems ...
... may include: Taking your blood pressure Examining your penis and rectum to check for problems Your doctor ... check for normal nighttime erections Ultrasound of your penis to check for blood flow problems Rigidity monitoring ...
... ankles and toes. Other types of arthritis include gout or pseudogout. Sometimes, there is a mechanical problem ... for more information on osteoarthritis, rheumatoid arthritis and gout. How Common are Joint Problems? Osteoarthritis, which affects ...
A Hybrid Genetic Algorithm for the Point to Multipoint Routing Problem with
Wainwright, Roger L.
A Hybrid Genetic Algorithm for the Point to Multipoint Routing Problem with Single Split Paths Words: Genetic Algorithm, Steiner Trees, Point to Multipoint Routing, Telecommunications Network to Multipoint Routing Problem with Single Split Paths. Our hybrid algorithm uses a genetic algorithm
The use of 3-D sensing techniques for on-line collision-free path planning
NASA Technical Reports Server (NTRS)
Hayward, V.; Aubry, S.; Jasiukajc, Z.
1987-01-01
The state of the art in collision prevention for manipulators with revolute joints, showing that it is a particularly computationally hard problem, is discussed. Based on the analogy with other hard or undecidable problems such as theorem proving, an extensible multi-resolution architecture for path planning, based on a collection of weak methods is proposed. Finally, the role that sensors can play for an on-line use of sensor data is examined.
How one British National Health Service Trust follows the path to continuous quality improvement.
O'Sullivan, K E
1999-01-01
Most hospitals in the United Kingdom are not convinced that total quality management (TQM) is a feasible or appropriate method for dealing with National Health Service (NHS) problems. However, continuous quality improvement (CQI), with its emphasis on quality outcomes, is being adopted with great enthusiasm at most NHS sites. This article describes how Brighton Health Care NHS Trust in the south of England follows the CQI path and discusses some of its achievements and the problems encountered along the way. PMID:10351216
A path planning algorithm for lane-following-based autonomous mobile robot navigation
NASA Astrophysics Data System (ADS)
Aljeroudi, Yazan; Paulik, Mark; Krishnan, Mohan; Luo, Chaomin
2010-01-01
In this paper we address the problem of autonomous robot navigation in a "roadway" type environment, where the robot has to drive forward on a defined path that could be impeded by the presence of obstacles. The specific context is the Autonomous Challenge of the Intelligent Ground Vehicle Competition (www.igvc.org). The task of the path planner is to ensure that the robot follows the path without turning back, as can happen in switchbacks, and/or leaving the course, as can happen in dashed or single lane line situations. A multi-behavior path planning algorithm is proposed. The first behavior determines a goal using a center of gravity (CoG) computation from the results of image processing techniques designed to extract lane lines. The second behavior is based on developing a sense of the current "general direction" of the contours of the course. This is gauged based on the immediate path history of the robot. An adaptive-weight-based fusion of the two behaviors is used to generate the best overall direction. This multi-behavior path planning strategy has been evaluated successfully in a Player/Stage simulation environment and subsequently implemented in the 2009 IGVC. The details of our experience will be presented at the conference.
ERIC Educational Resources Information Center
Hale, Norman; Lindelow, John
Chapter 12 in a volume on school leadership, this chapter cites the work of several authorities concerning problem-solving or decision-making techniques based on the belief that group problem-solving effort is preferable to individual effort. The first technique, force-field analysis, is described as a means of dissecting complex problems into…
NASA Astrophysics Data System (ADS)
Boz, Utku; Basdogan, Ipek
2015-12-01
Structural vibrations is a major cause for noise problems, discomfort and mechanical failures in aerospace, automotive and marine systems, which are mainly composed of plate-like structures. In order to reduce structural vibrations on these structures, active vibration control (AVC) is an effective approach. Adaptive filtering methodologies are preferred in AVC due to their ability to adjust themselves for varying dynamics of the structure during the operation. The filtered-X LMS (FXLMS) algorithm is a simple adaptive filtering algorithm widely implemented in active control applications. Proper implementation of FXLMS requires availability of a reference signal to mimic the disturbance and model of the dynamics between the control actuator and the error sensor, namely the secondary path. However, the controller output could interfere with the reference signal and the secondary path dynamics may change during the operation. This interference problem can be resolved by using an infinite impulse response (IIR) filter which considers feedback of the one or more previous control signals to the controller output and the changing secondary path dynamics can be updated using an online modeling technique. In this paper, IIR filtering based filtered-U LMS (FULMS) controller is combined with online secondary path modeling algorithm to suppress the vibrations of a plate-like structure. The results are validated through numerical and experimental studies. The results show that the FULMS with online secondary path modeling approach has more vibration rejection capabilities with higher convergence rate than the FXLMS counterpart.
Cell Representations of the Configuration Space for Planning Optimal Paths
Cell Representations of the Configuration Space for Planning Optimal Paths Ajay Kannan Advisor that is useful for planning optimal paths. Each cell in the decomposition is path subconvex (defined by Balkcom be leveraged for other tasks, such as obtaining diverse sets of paths around obstacles, creating motion plans
Adaptive path planning algorithm for cooperating unmanned air vehicles
Cunningham, C T; Roberts, R S
2001-02-08
An adaptive path planning algorithm is presented for cooperating Unmanned Air Vehicles (UAVs) that are used to deploy and operate land-based sensor networks. The algorithm employs a global cost function to generate paths for the UAVs, and adapts the paths to exceptions that might occur. Examples are provided of the paths and adaptation.
An Adaptive Path Planning Algorithm for Cooperating Unmanned Air Vehicles
Cunningham, C.T.; Roberts, R.S.
2000-09-12
An adaptive path planning algorithm is presented for cooperating Unmanned Air Vehicles (UAVs) that are used to deploy and operate land-based sensor networks. The algorithm employs a global cost function to generate paths for the UAVs, and adapts the paths to exceptions that might occur. Examples are provided of the paths and adaptation.
Diagnosis for Covariance Structure Models by Analyzing the Path
ERIC Educational Resources Information Center
Yuan, Ke-Hai; Kouros, Chrystyna D.; Kelley, Ken
2008-01-01
When a covariance structure model is misspecified, parameter estimates will be affected. It is important to know which estimates are systematically affected and which are not. The approach of analyzing the path is both intuitive and informative for such a purpose. Different from path analysis, analyzing the path uses path tracing and elementary…
The formal path integral and quantum mechanics
Theo Johnson-Freyd
2010-09-05
Given an arbitrary Lagrangian function on \\RR^d and a choice of classical path, one can try to define Feynman's path integral supported near the classical path as a formal power series parameterized by "Feynman diagrams," although these diagrams may diverge. We compute this expansion and show that it is (formally, if there are ultraviolet divergences) invariant under volume-preserving changes of coordinates. We prove that if the ultraviolet divergences cancel at each order, then our formal path integral satisfies a "Fubini theorem" expressing the standard composition law for the time evolution operator in quantum mechanics. Moreover, we show that when the Lagrangian is inhomogeneous-quadratic in velocity such that its homogeneous-quadratic part is given by a matrix with constant determinant, then the divergences cancel at each order. Thus, by "cutting and pasting" and choosing volume-compatible local coordinates, our construction defines a Feynman-diagrammatic "formal path integral" for the nonrelativistic quantum mechanics of a charged particle moving in a Riemannian manifold with an external electromagnetic field.
The formal path integral and quantum mechanics
Johnson-Freyd, Theo
2010-11-15
Given an arbitrary Lagrangian function on R{sup d} and a choice of classical path, one can try to define Feynman's path integral supported near the classical path as a formal power series parameterized by 'Feynman diagrams', although these diagrams may diverge. We compute this expansion and show that it is (formally, if there are ultraviolet divergences) invariant under volume-preserving changes of coordinates. We prove that if the ultraviolet divergences cancel at each order, then our formal path integral satisfies a 'Fubini theorem' expressing the standard composition law for the time evolution operator in quantum mechanics. Moreover, we show that when the Lagrangian is inhomogeneous quadratic in velocity such that its homogeneous-quadratic part is given by a matrix with constant determinant, then the divergences cancel at each order. Thus, by 'cutting and pasting' and choosing volume-compatible local coordinates, our construction defines a Feynman-diagrammatic 'formal path integral' for the nonrelativistic quantum mechanics of a charged particle moving in a Riemannian manifold with an external electromagnetic field.
Accurate free energy calculation along optimized paths.
Chen, Changjun; Xiao, Yi
2010-05-01
The path-based methods of free energy calculation, such as thermodynamic integration and free energy perturbation, are simple in theory, but difficult in practice because in most cases smooth paths do not exist, especially for large molecules. In this article, we present a novel method to build the transition path of a peptide. We use harmonic potentials to restrain its nonhydrogen atom dihedrals in the initial state and set the equilibrium angles of the potentials as those in the final state. Through a series of steps of geometrical optimization, we can construct a smooth and short path from the initial state to the final state. This path can be used to calculate free energy difference. To validate this method, we apply it to a small 10-ALA peptide and find that the calculated free energy changes in helix-helix and helix-hairpin transitions are both self-convergent and cross-convergent. We also calculate the free energy differences between different stable states of beta-hairpin trpzip2, and the results show that this method is more efficient than the conventional molecular dynamics method in accurate free energy calculation. PMID:19859916
A Comparison of Two Path Planners for Planetary Rovers
NASA Technical Reports Server (NTRS)
Tarokh, M.; Shiller, Z.; Hayati, S.
1999-01-01
The paper presents two path planners suitable for planetary rovers. The first is based on fuzzy description of the terrain, and genetic algorithm to find a traversable path in a rugged terrain. The second planner uses a global optimization method with a cost function that is the path distance divided by the velocity limit obtained from the consideration of the rover static and dynamic stability. A description of both methods is provided, and the results of paths produced are given which show the effectiveness of the path planners in finding near optimal paths. The features of the methods and their suitability and application for rover path planning are compared
On the complexity of Minimum Path Cover with Subpath Constraints for multi-assembly
2014-01-01
Background Multi-assembly problems have gathered much attention in the last years, as Next-Generation Sequencing technologies have started being applied to mixed settings, such as reads from the transcriptome (RNA-Seq), or from viral quasi-species. One classical model that has resurfaced in many multi-assembly methods (e.g. in Cufflinks, ShoRAH, BRANCH, CLASS) is the Minimum Path Cover (MPC) Problem, which asks for the minimum number of directed paths that cover all the nodes of a directed acyclic graph. The MPC Problem is highly popular because the acyclicity of the graph ensures its polynomial-time solvability. Results In this paper, we consider two generalizations of it dealing with integrating constraints arising from long reads or paired-end reads; these extensions have also been considered by two recent methods, but not fully solved. More specifically, we study the two problems where also a set of subpaths, or pairs of subpaths, of the graph have to be entirely covered by some path in the MPC. We show that in the case of long reads (subpaths), the generalized problem can be solved in polynomial-time by a reduction to the classical MPC Problem. We also consider the weighted case, and show that it can be solved in polynomial-time by a reduction to a min-cost circulation problem. As a side result, we also improve the time complexity of the classical minimum weight MPC Problem. In the case of paired-end reads (pairs of subpaths), the generalized problem becomes NP-hard, but we show that it is fixed-parameter tractable (FPT) in the total number of constraints. This computational dichotomy between long reads and paired-end reads is also a general insight into multi-assembly problems. PMID:25252805
Path-Integral Derivation of the Non-relativistic Scale Anomaly
Chris L. Lin; Carlos. R. Ordonez
2015-04-21
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 beta function.
Combinatorics of lattice paths with and without spikes
NASA Astrophysics Data System (ADS)
González-Arroyo, A.
2000-02-01
We derive a series of results on random walks on a d -dimensional hypercubic lattice (lattice paths). We introduce the notions of terse and simple paths corresponding to the path having no backtracking parts (spikes). These paths label equivalence classes which allow a rearrangement of the sum over paths. The basic combinatorial quantities of this construction are given. These formulae are useful when performing strong-coupling (hopping parameter) expansions of lattice models. Some applications are described.
A taxonomy of integral reaction path analysis
Grcar, Joseph F.; Day, Marcus S.; Bell, John B.
2004-12-23
W. C. Gardiner observed that achieving understanding through combustion modeling is limited by the ability to recognize the implications of what has been computed and to draw conclusions about the elementary steps underlying the reaction mechanism. This difficulty can be overcome in part by making better use of reaction path analysis in the context of multidimensional flame simulations. Following a survey of current practice, an integral reaction flux is formulated in terms of conserved scalars that can be calculated in a fully automated way. Conditional analyses are then introduced, and a taxonomy for bidirectional path analysis is explored. Many examples illustrate the resulting path analysis and uncover some new results about nonpremixed methane-air laminar jets.
Heterodyne interferometer with unequal path lengths
Kumar, Deepak; Bellan, Paul M.
2006-08-15
Laser interferometry is an extensively used diagnostic for plasma experiments. Existing plasma interferometers are designed on the presumption that the scene and reference beam path lengths have to be equal, a requirement that is costly in both the number of optical components and the alignment complexity. It is shown here that having equal path lengths is not necessary, instead, what is required is that the path length difference be an even multiple of the laser cavity length. This assertion has been verified in a heterodyne laser interferometer that measures typical line-average densities of {approx}10{sup 21}/m{sup 2} with an error of {approx}10{sup 19}/m{sup 2}.
Molecular path control in zeolite membranes
Dubbeldam, D.; Beerdsen, E.; Calero, S.; Smit, B.
2005-01-01
We report molecular simulations of diffusion in confinement showing a phenomenon that we denote as molecular path control (MPC); depending on loading, molecules follow a preferred pathway. MPC raises the important question to which extent the loading may affect the molecular trajectories in nanoporous materials. Through MPC one is able to manually adjust the ratio of the diffusivities through different types of pores, and as an application one can direct the flow of diffusing particles in membranes forward or sideward by simply adjusting the pressure, without the need for mechanical parts like valves. We show that the key ingredient of MPC is the anisotropic nature of the nanoporous material that results in a complex interplay between different diffusion paths as a function of loading. These paths may be controlled by changing the loading, either through a change in pressure or temperature. PMID:16109769
Fermionic path integrals and local anomalies
NASA Astrophysics Data System (ADS)
Roepstorff, G.
2003-05-01
No doubt, the subject of path integrals proved to be an immensely fruitful human, i.e. Feynman's idea. No wonder it is more timely than ever. Some even claim that it is the most daring, innovative and revolutionary idea since the days of Heisenberg and Bohr. It is thus likely to generate enthusiasm, if not addiction among physicists who seek simplicity together with perfection. Professor Devreese's long-lasting interest in, if not passion on the subject stems from his firm conviction that, beyond being the tool of choice, path integration provides the key to all quantum phenomena, be it in solid state, atomic, molecular or particle physics as evidenced by the impressive list of publications at the address http://lib.ua.ac.be/AB/a867.html. In this note, I review a pitfall of fermionic path integrals and a way to get around it in situations relevant to the Standard Model of particle physics.
Quantum state of wormholes and path integral
Garay, L.J. )
1991-08-15
The quantum state of a wormhole can be represented by a path integral over all asymptotically Euclidean four-geometries and all matter fields which have prescribed values, the arguments of the wave function, on a three-surface {ital S} which divides the spacetime manifold into two disconnected parts. The ground-state wave function is picked out by requiring that there be no matter excitations in the asymptotic region. Once the path integrals over the lapse and shift functions are evaluated, the requirement that the spacetime be asymptotically Euclidean can be accomplished by fixing the asymptotic gravitational momentum in the remaining path integral. It is claimed that no wave function exists which corresponds to asymptotic field configurations such that the effective gravitational constant is negative in the asymptotic region. The wormhole wave functions are worked out in minisuperspace models with massless minimal and conformal scalar fields.
Differentiable-path integrals in quantum mechanics
NASA Astrophysics Data System (ADS)
Koch, Benjamin; Reyes, Ignacio
2015-06-01
A method is presented which restricts the space of paths entering the path integral of quantum mechanics to subspaces of C?, by only allowing paths which possess at least ? derivatives. The method introduces two external parameters, and induces the appearance of a particular time scale ?D such that for time intervals longer than ?D the model behaves as usual quantum mechanics. However, for time scales smaller than ?D, modifications to standard formulation of quantum theory occur. This restriction renders convergent some quantities which are usually divergent in the time-continuum limit ? ? 0. We illustrate the model by computing several meaningful physical quantities such as the mean square velocity
Tornado intensity estimated from damage path dimensions.
Elsner, James B; Jagger, Thomas H; Elsner, Ian J
2014-01-01
The Newcastle/Moore and El Reno tornadoes of May 2013 are recent reminders of the destructive power of tornadoes. A direct estimate of a tornado's power is difficult and dangerous to get. An indirect estimate on a categorical scale is available from a post-storm survery of the damage. Wind speed bounds are attached to the scale, but the scale is not adequate for analyzing trends in tornado intensity separate from trends in tornado frequency. Here tornado intensity on a continuum is estimated from damage path length and width, which are measured on continuous scales and correlated to the EF rating. The wind speeds on the EF scale are treated as interval censored data and regressed onto the path dimensions and fatalities. The regression model indicates a 25% increase in expected intensity over a threshold intensity of 29 m s(-1) for a 100 km increase in path length and a 17% increase in expected intensity for a one km increase in path width. The model shows a 43% increase in the expected intensity when fatalities are observed controlling for path dimensions. The estimated wind speeds correlate at a level of .77 (.34, .93) [95% confidence interval] with a small sample of wind speeds estimated independently from a doppler radar calibration. The estimated wind speeds allow analyses to be done on the tornado database that are not possible with the categorical scale. The modeled intensities can be used in climatology and in environmental and engineering applications. Research is needed to understand the upward trends in path length and width. PMID:25229242
Tornado Intensity Estimated from Damage Path Dimensions
Elsner, James B.; Jagger, Thomas H.; Elsner, Ian J.
2014-01-01
The Newcastle/Moore and El Reno tornadoes of May 2013 are recent reminders of the destructive power of tornadoes. A direct estimate of a tornado's power is difficult and dangerous to get. An indirect estimate on a categorical scale is available from a post-storm survery of the damage. Wind speed bounds are attached to the scale, but the scale is not adequate for analyzing trends in tornado intensity separate from trends in tornado frequency. Here tornado intensity on a continuum is estimated from damage path length and width, which are measured on continuous scales and correlated to the EF rating. The wind speeds on the EF scale are treated as interval censored data and regressed onto the path dimensions and fatalities. The regression model indicates a 25% increase in expected intensity over a threshold intensity of 29 m s?1 for a 100 km increase in path length and a 17% increase in expected intensity for a one km increase in path width. The model shows a 43% increase in the expected intensity when fatalities are observed controlling for path dimensions. The estimated wind speeds correlate at a level of .77 (.34, .93) [95% confidence interval] with a small sample of wind speeds estimated independently from a doppler radar calibration. The estimated wind speeds allow analyses to be done on the tornado database that are not possible with the categorical scale. The modeled intensities can be used in climatology and in environmental and engineering applications. Research is needed to understand the upward trends in path length and width. PMID:25229242
Approximate resolution of hard numbering problems
Bailleux, O.; Chabrier, J.J.
1996-12-31
We present a new method for estimating the number of solutions of constraint satisfaction problems. We use a stochastic forward checking algorithm for drawing a sample of paths from a search tree. With this sample, we compute two values related to the number of solutions of a CSP instance. First, an unbiased estimate, second, a lower bound with an arbitrary low error probability. We will describe applications to the Boolean Satisfiability problem and the Queens problem. We shall give some experimental results for these problems.
Multi-instantons and exact results IV: Path integral formalism
Jentschura, Ulrich D.; Zinn-Justin, Jean
2011-08-15
Highlights: > O(N) anharmonic oscillators are considered in the path integral formalism. > Higher-order corrections to instantons are obtained using Feynman diagram calculations. > Generalized Bender-Wu formulas are confirmed. > The O(N) functional determinant describing the zero modes leads to higher-order terms. > Surprising cancellations are observed for the sextic oscillator. - Abstract: This is the fourth paper in a series devoted to the large-order properties of anharmonic oscillators. We attempt to draw a connection of anharmonic oscillators to field theory, by investigating the partition function in the path integral representation around both the Gaussian saddle point, which determines the perturbative expansion of the eigenvalues, as well as the nontrivial instanton saddle point. The value of the classical action at the saddle point is the instanton action which determines the large-order properties of perturbation theory by a dispersion relation. In order to treat the perturbations about the instanton, one has to take into account the continuous symmetries broken by the instanton solution because they lead to zero-modes of the fluctuation operator of the instanton configuration. The problem is solved by changing variables in the path integral, taking the instanton parameters as integration variables (collective coordinates). The functional determinant (Faddeev-Popov determinant) of the change of variables implies nontrivial modifications of the one-loop and higher-loop corrections about the instanton configuration. These are evaluated and compared to exact WKB calculations. A specific cancellation mechanism for the first perturbation about the instanton, which has been conjectured for the sextic oscillator based on a nonperturbative generalized Bohr-Sommerfeld quantization condition, is verified by an analytic Feynman diagram calculation.
Gas Path Sealing in Turbine Engines
NASA Technical Reports Server (NTRS)
Ludwig, L. P.
1978-01-01
A survey of gas path seals is presented with particular attention given to sealing clearance effects on engine component efficiency. The effects on compressor pressure ratio and stall margin are pointed out. Various case-rotor relative displacements, which affect gas path seal clearances, are identified. Forces produced by nonuniform sealing clearances and their effect on rotor stability are discussed qualitatively, and recent work on turbine-blade-tip sealing for high temperature is described. The need for active clearance control and for engine structural analysis is discussed. The functions of the internal-flow system and its seals are reviewed.
Connections on decorated path space bundles
Saikat Chatterjee; Amitabha Lahiri; Ambar N. Sengupta
2015-02-11
For a principal bundle $P\\to M$ equipped with a connection ${\\bar A}$, we study an infinite dimensional bundle ${\\mathcal P}^{\\rm dec}_{\\bar A}P$ over the space of paths on $M$, with the points of ${\\mathcal P}^{\\rm dec}_{\\bar A}P$ being horizontal paths on $P$ decorated with elements of a second structure group. We construct parallel transport processes on such bundles and study holonomy bundles in this setting. We explain the relationship with categorical geometry and explore the notion of categorical connections on categorical principal bundles in a concrete differential geometric way.
Mars PathFinder Rover Traverse Image
NASA Technical Reports Server (NTRS)
1998-01-01
This figure contains an azimuth-elevation projection of the 'Gallery Panorama.' The original Simple Cylindrical mosaic has been reprojected to the inside of a sphere so that lines of constant azimuth radiate from the center and lines of constant elevation are concentric circles. This projection preserves the resolution of the original panorama. Overlaid onto the projected Martian surface is a delineation of the Sojourner rover traverse path during the 83 Sols (Martian days) of Pathfinder surface operations. The rover path was reproduced using IMP camera 'end of day' and 'Rover movie' image sequences and rover vehicle telemetry data as references.