Science.gov

Sample records for failure-independent path protection

  1. Efficient capacity sharing for path protection in meshed optical networks

    NASA Astrophysics Data System (ADS)

    Dziong, Zbigniew; Nagarajan, Ramesh

    2004-03-01

    Efficient resource management in meshed optical networks is critical for supporting differentiated services, such as network restoration, in a cost-competitive manner. We propose and study several alternatives for dynamic and distributed selection of primary and protection paths. The focus is on algorithms where the bandwidth can be shared efficiently among protection paths, although other alternatives are considered as well. The routing algorithm and link cost function are based on a Markov decision-process framework. In particular, we use this framework to justify the link cost structure for primary and shared bandwidth. We also propose and study several options for describing the link state, which in turn determines the link cost, with the objective of minimizing the amount of data to be advertised without sacrificing performance. The proposed solutions can be implemented without changing the existing set of protocols. The numerical results show performance and cost savings for the different algorithm options.

  2. Four-path multiple ∞-shaped fiber protection mechanism for cable television networks

    NASA Astrophysics Data System (ADS)

    Shih, Fu-Hung; Lai, Jiunn-Ru; Chen, Wen-Ping; Wang, Luke K.

    2015-03-01

    Traditional cable television (CATV) network configuration is mainly a branch topology. When fibers break, there are always disconnections of CATV and Internet access. Meanwhile, network service providers usually cannot be instantly informed of network breakage; network problems are noticed only after the users call for services. Network breakage location detection and repair are, in general, costly and time-consuming. This paper proposes a new framework to protect CATV fiber optic networks, where a HUB with multiple optical protection switching (OPS) is constructed between the head end and the fiber nodes. The first layer ranging from the head end to the HUB forms a 1+1 protection path ring structure. The second layer ranging from the HUB to the fiber nodes forms multiple 1+1 protection path ring structures. The framework can form a four fiber optic path protection architecture with multiple ∞-shapes between the head end and the fiber nodes. When the CATV network system experiences a malfunction, such as fiber optic cable breakage or poor signal quality, OPS can immediately switch the fiber transmission path in order to maintain uninterrupted CATV network traffic. After simulation tests on fiber path switching time automatic protection switching, frame loss, packet jitter, latency, bit errors, and system traffic flow monitoring by manually switching OPS and pulling broken fiber optic cable, results show that the fiber path protection switching mechanism can react immediately, and test data results show that network traffic is unaffected, so the proposed framework can effectively enhance the survivability and quality of service of CATV network systems.

  3. Power-aware provisioning strategy with shared path protection in optical WDM networks

    NASA Astrophysics Data System (ADS)

    Bao, Ning-Hai; Li, Le-Min; Yu, Hong-Fang; Zhang, Zhi-Zhong; Luo, Hong-Bin

    2012-03-01

    As the Internet continues to grow, the power consumption of telecommunication networks is rising at a considerable speed, which seriously increases the operational expenditure and greenhouse gas emission. Since optical Wavelength Division Multiplexing (WDM) networks are currently the most promising network infrastructures, power saving issue on these networks has received more attention in recent years. In traditional optical WDM networks, a large amount of power is drained by the redundant idle resources and reserved backup resources although these powered on resources do not carry traffic in most of the time. In order to reduce the network power consumption, turning off the corresponding network components or switching them to a low-power, standby state (or called sleep mode) is a promising greening approach. In this paper, we study the power-aware provisioning strategies and propose a sleep mode based Power-Aware Shared Path Protection (PASPP) heuristic algorithm to achieve the power efficiency of optical WDM networks. By jointly utilizing link-cost and fiber-cost in path routing, resource assignment, and resource release, PASPP makes working paths and backup paths converge on different fibers as much as possible, and switch idle and backup components to sleep mode to realize power saving. Simulation results show that our PASPP can obtain notable power saving and achieve satisfactory tradeoff between power efficiency and blocking probability with respect to Power-Unaware Shared Path Protection (PUSPP).

  4. A Multi-Backup Path Protection scheme for survivability in Elastic Optical Networks

    NASA Astrophysics Data System (ADS)

    Yadav, Dharmendra Singh; Chakraborty, Abhishek; Manoj, B. S.

    2016-07-01

    Two important challenges in designing a survivable optical network are minimizing backup spectrum allocation and ensuring spectrum assignment constraints. Allocating backup spectrum is one important approach for survivable optical network design. Connection requests which are rejected due to the unavailability of a single backup path can be survived using multiple backup routes. Multiple backup routes not only increase connection acceptance rate, but also improve backup resource sharing. In this paper, we present a strategy for survivability which optimizes primary and backup spectrum allocations and multiple backup route assignments for surviving a connection request. In our strategy, named as Backup Spectrum Reservation with MultiPath Protection (BSR-MPP), multiple backup routes are searched over advance reserved backup resources when an optical connection is concerned. Simulation results show that confinement of backup resources result in higher resource sharing and assignment of multiple backup lightpaths. It can also be observed that BSR-MPP has lower Bandwidth Blocking Probability and higher spectrum efficiency as compared to conventional Shared Path Protection (SPP) and MultiPath Protection (MPP) strategies.

  5. Exposure Path Perceptions and Protective Actions in Biological Water Contamination Emergencies

    PubMed Central

    Lindell, Michael K; Mumpower, Jeryl L; Huang, Shih-Kai; Wu, Hao-Che; Samuelson, Charles D

    2015-01-01

    This study extends the Protective Action Decision Model, developed to address disaster warning responses in the context of natural hazards, to “boil water” advisories. The study examined 110 Boston residents’ and 203 Texas students’ expectations of getting sick through different exposure paths for contact with contaminated water. In addition, the study assessed respondents’ actual implementation (for residents) or behavioral expectations (for students) of three different protective actions – bottled water, boiled water, and personally chlorinated water – as well as their demographic characteristics and previous experience with water contamination. The results indicate that people distinguish among the exposure paths, but the differences are small (one-third to one-half of the response scale). Nonetheless, the perceived risk from the exposure paths helps to explain why people are expected to consume (or actually consumed) bottled water rather than boiled or personally chlorinated water. Overall, these results indicate that local authorities should take care to communicate the relative risks of different exposure paths and should expect that people will respond to a boil water order primarily by consuming bottled water. Thus, they should make special efforts to increase supplies of bottled water in their communities during water contamination emergencies. PMID:26609238

  6. Exposure Path Perceptions and Protective Actions in Biological Water Contamination Emergencies.

    PubMed

    Lindell, Michael K; Mumpower, Jeryl L; Huang, Shih-Kai; Wu, Hao-Che; Samuelson, Charles D

    2015-01-01

    This study extends the Protective Action Decision Model, developed to address disaster warning responses in the context of natural hazards, to "boil water" advisories. The study examined 110 Boston residents' and 203 Texas students' expectations of getting sick through different exposure paths for contact with contaminated water. In addition, the study assessed respondents' actual implementation (for residents) or behavioral expectations (for students) of three different protective actions - bottled water, boiled water, and personally chlorinated water - as well as their demographic characteristics and previous experience with water contamination. The results indicate that people distinguish among the exposure paths, but the differences are small (one-third to one-half of the response scale). Nonetheless, the perceived risk from the exposure paths helps to explain why people are expected to consume (or actually consumed) bottled water rather than boiled or personally chlorinated water. Overall, these results indicate that local authorities should take care to communicate the relative risks of different exposure paths and should expect that people will respond to a boil water order primarily by consuming bottled water. Thus, they should make special efforts to increase supplies of bottled water in their communities during water contamination emergencies. PMID:26609238

  7. A Path to Planetary Protection Requirements for Human Exploration: A Literary Analysis and Systems Engineering Approach

    NASA Astrophysics Data System (ADS)

    Johnson, James; Conley, Catharine; Siegel, Bette

    As systems, technologies, and plans for the human exploration of Mars and other destinations beyond low Earth orbit begin to coalesce, it is imperative that frequent and early consideration is given to how planetary protection practices and policy will be upheld. While the development of formal planetary protection requirements for future human space systems and operations may still be a few years from fruition, guidance to appropriately influence mission and system design will be needed soon to avoid costly design and operational changes. The path to constructing such requirements is a journey that espouses key systems engineering practices of understanding shared goals, objectives and concerns, identifying key stakeholders, and iterating a draft requirement set to gain community consensus. This paper traces through each of these practices, beginning with a literary analysis of nearly three decades of publications addressing planetary protection concerns with respect to human exploration. Key goals, objectives and concerns, particularly with respect to notional requirements, required studies and research, and technology development needs have been compiled and categorized to provide a current ‘state of knowledge’. This information, combined with the identification of key stakeholders in upholding planetary protection concerns for human missions, has yielded a draft requirement set that might feed future iteration among space system designers, exploration scientists, and the mission operations community. Combining the information collected with a proposed forward path will hopefully yield a mutually agreeable set of timely, verifiable, and practical requirements for human space exploration that will uphold international commitment to planetary protection. Keywords: planetary protection, human spaceflight requirements, human space exploration, human space operations, systems engineering, literature analysis

  8. Atomic Layer Deposited Corrosion Protection: A Path to Stable and Efficient Photoelectrochemical Cells.

    PubMed

    Scheuermann, Andrew G; McIntyre, Paul C

    2016-07-21

    A fundamental challenge in developing photoelectrochemical cells for the renewable production of solar chemicals and fuels is the simultaneous requirement of efficient light absorption and robust stability under corrosive conditions. Schemes for corrosion protection of semiconductor photoelectrodes such as silicon using deposited layers were proposed and attempted for several decades, but increased operational lifetimes were either insufficient or the resulting penalties for device efficiency were prohibitive. In recent years, advances in atomic layer deposition (ALD) of thin coatings have made novel materials engineering possible, leading to substantial and simultaneous improvements in stability and efficiency of photoelectrochemical cells. The self-limiting, layer-by-layer growth of ALD makes thin films with low pinhole densities possible and may also provide a path to defect control that can generalize this protection technology to a large set of materials necessary to fully realize photoelectrochemical cell technology for artificial photosynthesis. PMID:27359352

  9. Connection Availability Analysis of Shared Backup Path-Protected Mesh Networks

    NASA Astrophysics Data System (ADS)

    Zhou, Ling; Held, Marcel; Sennhauser, Urs

    2007-05-01

    Dual-span failures dominate the system unavailability in a mesh-restorable network with full restorability to single-span failures. Traditional availability analysis based on reliability block diagrams is not suitable for survivable networks with shared spare capacity. Therefore, a new concept is proposed to facilitate the calculations of connection availability. A U.S. network consisting of 19 nodes and 28 spans yielding 171 bidirectional connections is investigated. We find that networks with shared backup path protection can have average connection unavailabilities of the same order of magnitude as those with dedicated automatic protection switching, however, with a much better capacity efficiency. The proposed method can exactly calculate the unavailability of a specific connection with known restoration details or the average connection performance without any restoration details by presuming the dual-span failures to be the only failure mode and an arbitrary allocation rule of spare capacity.

  10. PHOTO: An Efficient Shared-Path-Protection Strategy Based on Connection-Holding-Time Awareness

    NASA Astrophysics Data System (ADS)

    Tornatore, Massimo; Ou, Canhui Sam; Zhang, Jing; Pattavina, Achille; Mukherjee, Biswanath

    2005-10-01

    Recent trends in bandwidth markets show that customers are tending to ask providers for a large bandwidth but for a limited amount of time to support new short-term bandwidth-hungry applications. In order to meet these new requirements, progress in network technologies (fast and reconfigurable switching equipment) and protocols [such as generalized multiprotocol label switching (GMPLS) and automatically switched optical network (ASON)] is paving the road towards flexible optical transport networks in which leasable circuits could be set up and released on a short-term basis. As a result, for dynamic traffic, the holding time of connection requests can be known in advance. The authors propose to exploit knowledge of connection holding time to design an efficient algorithm, called PHOTO, for the dynamic provisioning of shared-path-protected connections in optical mesh networks. The core idea of the proposal consists of exploiting the knowledge of the holding time of connection requests to minimize resource overbuild (RO) due to backup capacity and hence achieve resource-usage efficiency. For a typical US nationwide network, savings on RO of up to 10% were obtained for practical scenarios compared to a holding-time-unaware, but otherwise shared-path-efficient, approach.

  11. Shared end-to-content backup path protection in k-node (edge) content connected elastic optical datacenter networks.

    PubMed

    Li, Xin; Huang, Shanguo; Yin, Shan; Guo, Bingli; Zhao, Yongli; Zhang, Jie; Zhang, Min; Gu, Wanyi

    2016-05-01

    To quantitatively measure content connectivity and provide protection for different kinds of content, the concept of k-node (edge) content connectivity is proposed recently. Based on k-node (edge) content connectivity, k-node (edge) content connected elastic optical datacenter network (KC-EODN) is proposed to design disaster-resilient and spectrum-efficient optical datacenter networks. In KC-EODN, k independent end-to-content paths are established for each request. However, it will consume too much resource to assign dedicated spectrum for each end-to-content path. Spectrum sharing among multiple end-to-content paths of different requests can greatly improve resource efficiency. In this paper, a novel perfect matching based sharing principle among multiple end-to-content paths of different requests is proposed. Based on the new proposed sharing principle, we present the shared end-to-content backup path protection (SEBPP) scheme for KC-EODN. Integer linear program (ILP) model and heuristic algorithms are designed for SEBPP scheme with the objective of minimizing the total of working and backup spectrum resources. Numerical results show that the proposed SEBPP scheme can greatly reduce spectrum consumption while ensuring the survivability against natural disaster and multi-failures. PMID:27137559

  12. Wavelength and opto-electro-opto sharing and optimization in wavelength division multiplexing mesh networks with path protection

    NASA Astrophysics Data System (ADS)

    Wang, Kefei; Hamza, Haitham S.; Deogun, Jitender S.

    2006-03-01

    Given a physical network topology and a traffic demand, the problem of designing a survivable network with path protection is to select primary and backup paths based on resource optimization. A common approach to minimize resources is sharing. This problem has been investigated with the goal of optimizing the number of channels (i.e., wavelengths) needed for backup paths by imposing capacity sharing. However, because of the need and the cost for other devices, such as opto-electro-opto (OEO) regenerators, network provisioning should also take into consideration such resources in the optimization process. We address the problem of routing and wavelength assignment (RWA) for survivable networks with the objective of simultaneously optimizing wavelength links and OEOs. An integer linear program solution, a tabu search heuristic, and a genetic algorithm are proposed, and their performance is experimentally evaluated through extensive simulation. Our simulation results confirm an average of 30% reduction in the number of OEOs compared to that required with the well known shared-path protection scheme.

  13. Path Finder

    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).

  14. Shortest Paths.

    ERIC Educational Resources Information Center

    Shore, M. L.

    1980-01-01

    There are many uses for the shortest path algorithm presented which are limited only by our ability to recognize when a problem may be converted into the shortest path in a graph representation. (Author/TG)

  15. Path ANalysis

    SciTech Connect

    Snell, Mark K.

    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 during 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.

  16. Path ANalysis

    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

  17. Path Pascal

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  18. Level of Cognitive Performance as a Correlate and Predictor of Health Behaviors that Protect against Cognitive Decline in Late Life: The Path through Life Study

    ERIC Educational Resources Information Center

    Anstey, Kaarin J.; Low, Lee-Fay; Christensen, Helen; Sachdev, Perminder

    2009-01-01

    There is a lack of information on how cognitive ability relates to both health behaviors and change in health behaviors over time. This study examined verbal ability and processing speed as predictors of health behaviors in the PATH Through Life Study that includes cohorts aged in their 20s, 40s and 60s. Higher cognitive scores were associated…

  19. Transfer of ultraviolet photon energy into fluorescent light in the visible path represents a new and efficient protection mechanism of sunscreens.

    PubMed

    Vergou, Theognosia; Patzelt, Alexa; Richter, Heike; Schanzer, Sabine; Zastrow, Leonhard; Golz, Karin; Doucet, Olivier; Antoniou, Christina; Sterry, Wolfram; Lademann, Juergen

    2011-10-01

    The development of sunscreens with high sun protection factor (SPF) values but low filter concentrations is the ultimate goal. The purpose of the present study was to investigate why a sunscreen spray and cream with different concentrations of the same UV-filters provided the same SPF. Therefore, the homogeneity of the distribution of both sunscreens was investigated by laser scanning microscopy (LSM) and tape stripping (TS). Additionally, the energy transfer mechanisms of the sunscreens on the skin were analyzed. The TS and LSM showed a better homogeneity of the distribution of the spray. With Wood's light, a total absorption of the irradiation was detected in the spray area. In contrast, after cream treatment, an intensive fluorescent signal was observed. It was demonstrated that this fluorescent signal was caused by nonthermal energy transferred from the UV-filters to one compound of the cream releasing its excitation energy by fluorescence. This nonthermal energy transfer seemed to be the reason for the high efficiency of the cream, which is subjected to thermal relaxation. The transfer of UV photon energy into fluorescent light represents a new approach to increase the efficiency of sunscreens and could form the basis for a new generation of sunscreens. PMID:22029345

  20. Transfer of ultraviolet photon energy into fluorescent light in the visible path represents a new and efficient protection mechanism of sunscreens

    NASA Astrophysics Data System (ADS)

    Vergou, Theognosia; Patzelt, Alexa; Richter, Heike; Schanzer, Sabine; Zastrow, Leonhard; Golz, Karin; Doucet, Olivier; Antoniou, Christina; Sterry, Wolfram; Lademann, Juergen

    2011-10-01

    The development of sunscreens with high sun protection factor (SPF) values but low filter concentrations is the ultimate goal. The purpose of the present study was to investigate why a sunscreen spray and cream with different concentrations of the same UV-filters provided the same SPF. Therefore, the homogeneity of the distribution of both sunscreens was investigated by laser scanning microscopy (LSM) and tape stripping (TS). Additionally, the energy transfer mechanisms of the sunscreens on the skin were analyzed. The TS and LSM showed a better homogeneity of the distribution of the spray. With Wood's light, a total absorption of the irradiation was detected in the spray area. In contrast, after cream treatment, an intensive fluorescent signal was observed. It was demonstrated that this fluorescent signal was caused by nonthermal energy transferred from the UV-filters to one compound of the cream releasing its excitation energy by fluorescence. This nonthermal energy transfer seemed to be the reason for the high efficiency of the cream, which is subjected to thermal relaxation. The transfer of UV photon energy into fluorescent light represents a new approach to increase the efficiency of sunscreens and could form the basis for a new generation of sunscreens.

  1. Path Separability of Graphs

    NASA Astrophysics Data System (ADS)

    Diot, Emilie; Gavoille, Cyril

    In this paper we investigate the structural properties of k-path separable graphs, that are the graphs that can be separated by a set of k shortest paths. We identify several graph families having such path separability, and we show that this property is closed under minor taking. In particular we establish a list of forbidden minors for 1-path separable graphs.

  2. The absolute path command

    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

  3. The absolute path command

    SciTech Connect

    Moody, A.

    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 can provide the absolute path to a relative directory from the current working directory.

  4. The universal path integral

    NASA Astrophysics Data System (ADS)

    Lloyd, Seth; Dreyer, Olaf

    2016-02-01

    Path integrals calculate probabilities by summing over classical configurations of variables such as fields, assigning each configuration a phase equal to the action of that configuration. This paper defines a universal path integral, which sums over all computable structures. This path integral contains as sub-integrals all possible computable path integrals, including those of field theory, the standard model of elementary particles, discrete models of quantum gravity, string theory, etc. The universal path integral possesses a well-defined measure that guarantees its finiteness. The probabilities for events corresponding to sub-integrals can be calculated using the method of decoherent histories. The universal path integral supports a quantum theory of the universe in which the world that we see around us arises out of the interference between all computable structures.

  5. LONG PATH LASER OZONE MONITOR EVALUATION

    EPA Science Inventory

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

  6. A Path to Discovery

    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.)

  7. Tortuous path chemical preconcentrator

    DOEpatents

    Manginell, Ronald P.; Lewis, Patrick R.; Adkins, Douglas R.; Wheeler, David R.; Simonson, Robert J.

    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.

  8. Sampling diffusive transition paths

    SciTech Connect

    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.

  9. Sampling diffusive transition paths.

    PubMed

    Miller, Thomas F; Predescu, Cristian

    2007-04-14

    The authors 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 the sampling of infinitesimal Brownian increments of the path, as well as a different type of stiffness associated with the sampling of the coarse features of long paths. The fine-feature sampling stiffness is eliminated with the use of the fast sampling algorithm, 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. The authors use the algorithm to sample the transition path ensemble for the structural interconversion of the 38-atom Lennard-Jones cluster at low temperature. PMID:17444696

  10. Paths correlation matrix.

    PubMed

    Qian, Weixian; Zhou, Xiaojun; Lu, Yingcheng; Xu, Jiang

    2015-09-15

    Both the Jones and Mueller matrices encounter difficulties when physically modeling mixed materials or rough surfaces due to the complexity of light-matter interactions. To address these issues, we derived a matrix called the paths correlation matrix (PCM), which is a probabilistic mixture of Jones matrices of every light propagation path. Because PCM is related to actual light propagation paths, it is well suited for physical modeling. Experiments were performed, and the reflection PCM of a mixture of polypropylene and graphite was measured. The PCM of the mixed sample was accurately decomposed into pure polypropylene's single reflection, pure graphite's single reflection, and depolarization caused by multiple reflections, which is consistent with the theoretical derivation. Reflection parameters of rough surface can be calculated from PCM decomposition, and the results fit well with the theoretical calculations provided by the Fresnel equations. These theoretical and experimental analyses verify that PCM is an efficient way to physically model light-matter interactions. PMID:26371930

  11. 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.

  12. Coherence-path duality relations for N paths

    NASA Astrophysics Data System (ADS)

    Hillery, Mark; Bagan, Emilio; Bergou, Janos; Cottrell, Seth

    2016-05-01

    For an interferometer with two paths, there is a relation between the information about which path the particle took and the visibility of the interference pattern at the output. The more path information we have, the smaller the visibility, and vice versa. We generalize this relation to a multi-path interferometer, and we substitute two recently defined measures of quantum coherence for the visibility, which results in two duality relations. The path information is provided by attaching a detector to each path. In the first relation, which uses an l1 measure of coherence, the path information is obtained by applying the minimum-error state discrimination procedure to the detector states. In the second, which employs an entropic measure of coherence, the path information is the mutual information between the detector states and the result of measuring them. Both approaches are quantitative versions of complementarity for N-path interferometers. Support provided by the John Templeton Foundation.

  13. Following the Path

    ERIC Educational Resources Information Center

    Rodia, Becky

    2004-01-01

    This article profiles Diane Stanley, an author and illustrator of children's books. Although she was studying to be a medical illustrator in graduate school, Stanley's path changed when she got married and had children. As she was raising her children, she became increasingly enamored of the colorful children's books she would check out of the…

  14. An Unplanned Path

    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…

  15. Nonadiabatic transition path sampling

    NASA Astrophysics Data System (ADS)

    Sherman, M. C.; Corcelli, S. A.

    2016-07-01

    Fewest-switches surface hopping (FSSH) is combined with transition path sampling (TPS) to produce a new method called nonadiabatic path sampling (NAPS). The NAPS method is validated on a model electron transfer system coupled to a Langevin bath. Numerically exact rate constants are computed using the reactive flux (RF) method over a broad range of solvent frictions that span from the energy diffusion (low friction) regime to the spatial diffusion (high friction) regime. The NAPS method is shown to quantitatively reproduce the RF benchmark rate constants over the full range of solvent friction. Integrating FSSH within the TPS framework expands the applicability of both approaches and creates a new method that will be helpful in determining detailed mechanisms for nonadiabatic reactions in the condensed-phase.

  16. Nonadiabatic transition path sampling.

    PubMed

    Sherman, M C; Corcelli, S A

    2016-07-21

    Fewest-switches surface hopping (FSSH) is combined with transition path sampling (TPS) to produce a new method called nonadiabatic path sampling (NAPS). The NAPS method is validated on a model electron transfer system coupled to a Langevin bath. Numerically exact rate constants are computed using the reactive flux (RF) method over a broad range of solvent frictions that span from the energy diffusion (low friction) regime to the spatial diffusion (high friction) regime. The NAPS method is shown to quantitatively reproduce the RF benchmark rate constants over the full range of solvent friction. Integrating FSSH within the TPS framework expands the applicability of both approaches and creates a new method that will be helpful in determining detailed mechanisms for nonadiabatic reactions in the condensed-phase. PMID:27448877

  17. Four paths of competition

    SciTech Connect

    Studness, C.M.

    1995-05-01

    The financial community`s focus on utility competition has been riveted on the proceedings now in progress at state regulatory commissions. The fear that something immediately damaging will come out of these proceedings seems to have diminished in recent months, and the stock market has reacted favorably. However, regulatory developments are only one of four paths leading to competition; the others are the marketplace, the legislatures, and the courts. Each could play a critical role in the emergence of competition.

  18. PATHS groundwater hydrologic model

    SciTech Connect

    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.

  19. Spirit's Path to Bonneville

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Scientists created this overlay map by laying navigation and panoramic camera images taken from the surface of Mars on top of one of Spirit's descent images taken as the spacecraft descended to the martian surface. The map was created to help track the path that Spirit has traveled through sol 44 and to put into perspective the distance left to travel before reaching the edge of the large crater nicknamed 'Bonneville.'

    The area boxed in yellow contains the ground images that have been matched to and layered on top of the descent image. The yellow line shows the path that Spirit has traveled and the red dashed line shows the intended path for future sols. The blue circles highlight hollowed areas on the surface, such as Sleepy Hollow, near the lander, and Laguna Hollow, the sol 45 drive destination. Scientists use these hollowed areas - which can be seen in both the ground images and the descent image - to correctly match up the overlay.

    Field geologists on Earth create maps like this to assist them in tracking their observations.

  20. Critical Path Web Site

    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

  1. Critical Path Web Site

    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

  2. Thermoalgebras and path integral

    NASA Astrophysics Data System (ADS)

    Khanna, F. C.; Malbouisson, A. P. C.; Malbouisson, J. M. C.; Santana, A. E.

    2009-09-01

    Using a representation for Lie groups closely associated with thermal problems, we derive the algebraic rules of the real-time formalism for thermal quantum field theories, the so-called thermo-field dynamics (TFD), including the tilde conjugation rules for interacting fields. These thermo-group representations provide a unified view of different approaches for finite-temperature quantum fields in terms of a symmetry group. On these grounds, a path integral formalism is constructed, using Bogoliubov transformations, for bosons, fermions and non-abelian gauge fields. The generalization of the results for quantum fields in (S1)d×R topology is addressed.

  3. Path Integrals and Supersolids

    NASA Astrophysics Data System (ADS)

    Ceperley, D. M.

    2008-11-01

    Recent experiments by Kim and Chan on solid 4He have been interpreted as discovery of a supersolid phase of matter. Arguments based on wavefunctions have shown that such a phase exists, but do not necessarily apply to solid 4He. Imaginary time path integrals, implemented using Monte Carlo methods, provide a definitive answer; a clean system of solid 4He should be a normal quantum solid, not one with superfluid properties. The Kim-Chan phenomena must be due to defects introduced when the solid is formed.

  4. JAVA PathFinder

    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.

  5. Portage and Path Dependence*

    PubMed Central

    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

  6. Portage and Path Dependence.

    PubMed

    Bleakley, Hoyt; Lin, Jeffrey

    2012-05-01

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

  7. Internet's critical path horizon

    NASA Astrophysics Data System (ADS)

    Valverde, S.; Solé, R. V.

    2004-03-01

    Internet is known to display a highly heterogeneous structure and complex fluctuations in its traffic dynamics. Congestion seems to be an inevitable result of user's behavior coupled to the network dynamics and it effects should be minimized by choosing appropriate routing strategies. But what are the requirements of routing depth in order to optimize the traffic flow? In this paper we analyse the behavior of Internet traffic with a topologically realistic spatial structure as described in a previous study [S.-H. Yook et al., Proc. Natl Acad. Sci. USA 99, 13382 (2002)]. The model involves self-regulation of packet generation and different levels of routing depth. It is shown that it reproduces the relevant key, statistical features of Internet's traffic. Moreover, we also report the existence of a critical path horizon defining a transition from low-efficient traffic to highly efficient flow. This transition is actually a direct consequence of the web's small world architecture exploited by the routing algorithm. Once routing tables reach the network diameter, the traffic experiences a sudden transition from a low-efficient to a highly-efficient behavior. It is conjectured that routing policies might have spontaneously reached such a compromise in a distributed manner. Internet would thus be operating close to such critical path horizon.

  8. 757 Path Loss Measurements

    NASA Technical Reports Server (NTRS)

    Horton, Kent; Huffman, Mitch; Eppic, Brian; White, Harrison

    2005-01-01

    Path Loss Measurements were obtained on three (3) GPS equipped 757 aircraft. Systems measured were Marker Beacon, LOC, VOR, VHF (3), Glide Slope, ATC (2), DME (2), TCAS, and GPS. This data will provide the basis for assessing the EMI (Electromagnetic Interference) safety margins of comm/nav (communication and navigation) systems to portable electronic device emissions. These Portable Electronic Devices (PEDs) include all devices operated in or around the aircraft by crews, passengers, servicing personnel, as well as the general public in the airport terminals. EMI assessment capability is an important step in determining if one system-wide PED EMI policy is appropriate. This data may also be used comparatively with theoretical analysis and computer modeling data sponsored by NASA Langley Research Center and others.

  9. Fundamental changes to EPA's research enterprise: the path forward.

    PubMed

    Anastas, Paul T

    2012-01-17

    Environmental protection in the United States has reached a critical juncture. It has become clear that to address the complex and interrelated environmental challenges we face, we must augment our traditional approaches. The scientific community must build upon its deep understanding of risk assessment, risk management, and reductionism with tools, technologies, insights and approaches to pursue sustainability. The U.S. Environmental Protection Agency (EPA) has recognized this need for systemic change by implementing a new research paradigm called "The Path Forward." This paper outlines the principles of the Path Forward and the actions taken since 2010 to align EPA's research efforts with the goal of sustainability. PMID:22216884

  10. Choosing a Carreer Path

    EPA Science Inventory

    Having graduated with a PhD in wetland ecology and recently completed a post-doctorate fellowship with Mary E. Kentula at the US Environmental Protection Agency, I have a lot of practical advice for undergraduates who are interested in pursuing a career in aquatic sciences. The g...

  11. Interactive cutting path analysis programs

    NASA Technical Reports Server (NTRS)

    Weiner, J. M.; Williams, D. S.; Colley, S. R.

    1975-01-01

    The operation of numerically controlled machine tools is interactively simulated. Four programs were developed to graphically display the cutting paths for a Monarch lathe, Cintimatic mill, Strippit sheet metal punch, and the wiring path for a Standard wire wrap machine. These programs are run on a IMLAC PDS-ID graphic display system under the DOS-3 disk operating system. The cutting path analysis programs accept input via both paper tape and disk file.

  12. Multi-Criteria Path Finding

    NASA Astrophysics Data System (ADS)

    Mohammadi, E.; Hunter, A.

    2012-07-01

    Path finding solutions are becoming a major part of many GIS applications including location based services and web-based GIS services. Most traditional path finding solutions are based on shortest path algorithms that tend to minimize the cost of travel from one point to another. These algorithms make use of some cost criteria that is usually an attribute of the edges in the graph network. Providing one shortest path limits user's flexibility when choosing a possible route, especially when more than one parameter is utilized to calculate cost (e.g., when length, number of traffic lights, and number of turns are used to calculate network cost.) K shortest path solutions tend to overcome this problem by providing second, third, and Kth shortest paths. These algorithms are efficient as long as the graphs edge weight does not change dynamically and no other parameters affect edge weights. In this paper we try to go beyond finding shortest paths based on some cost value, and provide all possible paths disregarding any parameter that may affect total cost. After finding all possible paths, we can rank the results by any parameter or combination of parameters, without a substantial increase in time complexity.

  13. 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.

  14. The Environmental Protection Agency's Safety Standards for Disposal of Spent Nuclear Fuel: Potential Path Forward in Response to the Report of the Blue Ribbon Commission on America's Nuclear Future - 13388

    SciTech Connect

    Forinash, Betsy; Schultheisz, Daniel; Peake, Tom

    2013-07-01

    Following the decision to withdraw the Yucca Mountain license application, the Department of Energy created a Blue Ribbon Commission (BRC) on America's Nuclear Future, tasked with recommending a national strategy to manage the back end of the nuclear fuel cycle. The BRC issued its final report in January 2012, with recommendations covering transportation, storage and disposal of spent nuclear fuel (SNF); potential reprocessing; and supporting institutional measures. The BRC recommendations on disposal of SNF and high-level waste (HLW) are relevant to the U.S. Environmental Protection Agency (EPA), which shares regulatory responsibility with the Nuclear Regulatory Commission (NRC): EPA issues 'generally applicable' performance standards for disposal repositories, which are then implemented in licensing. For disposal, the BRC endorses developing one or more geological repositories, with siting based on an approach that is adaptive, staged and consent-based. The BRC recommends that EPA and NRC work cooperatively to issue generic disposal standards-applying equally to all sites-early in any siting process. EPA previously issued generic disposal standards that apply to all sites other than Yucca Mountain. However, the BRC concluded that the existing regulations should be revisited and revised. The BRC proposes a number of general principles to guide the development of future regulations. EPA continues to review the BRC report and to assess the implications for Agency action, including potential regulatory issues and considerations if EPA develops new or revised generic disposal standards. This review also involves preparatory activities to define potential process and public engagement approaches. (authors)

  15. Path Integral Simulations of Graphene

    NASA Astrophysics Data System (ADS)

    Yousif, Hosam

    2007-10-01

    Some properties of graphene are explored using a path integral approach. The path integral method allows us to simulate relatively large systems using monte carlo techniques and extract thermodynamic quantities. We simulate the effects of screening a large external charge potential, as well as conductivity and charge distributions in graphene sheets.

  16. Collabortive Authoring of Walden's Paths

    SciTech Connect

    Li, Yuanling; Bogen II, Paul Logasa; Pogue, Daniel; Furuta, Richard Keith; Shipman, Frank Major

    2012-01-01

    This paper presents a prototype of an authoring tool to allow users to collaboratively build, annotate, manage, share and reuse collections of distributed resources from the World Wide Web. This extends on the Walden’s Path project’s work to help educators bring resources found on the World Wide Web into a linear contextualized structure. The introduction of collaborative authoring feature fosters collaborative learning activities through social interaction among participants, where participants can coauthor paths in groups. Besides, the prototype supports path sharing, branching and reusing; specifically, individual participant can contribute to the group with private collections of knowledge resources; paths completed by group can be shared among group members, such that participants can tailor, extend, reorder and/or replace nodes to have sub versions of shared paths for different information needs.

  17. Pathways with PathWhiz.

    PubMed

    Pon, Allison; Jewison, Timothy; Su, Yilu; Liang, Yongjie; Knox, Craig; Maciejewski, Adam; Wilson, Michael; Wishart, David S

    2015-07-01

    PathWhiz (http://smpdb.ca/pathwhiz) is a web server designed to create colourful, visually pleasing and biologically accurate pathway diagrams that are both machine-readable and interactive. As a web server, PathWhiz is accessible from almost any place and compatible with essentially any operating system. It also houses a public library of pathways and pathway components that can be easily viewed and expanded upon by its users. PathWhiz allows users to readily generate biologically complex pathways by using a specially designed drawing palette to quickly render metabolites (including automated structure generation), proteins (including quaternary structures, covalent modifications and cofactors), nucleic acids, membranes, subcellular structures, cells, tissues and organs. Both small-molecule and protein/gene pathways can be constructed by combining multiple pathway processes such as reactions, interactions, binding events and transport activities. PathWhiz's pathway replication and propagation functions allow for existing pathways to be used to create new pathways or for existing pathways to be automatically propagated across species. PathWhiz pathways can be saved in BioPAX, SBGN-ML and SBML data exchange formats, as well as PNG, PWML, HTML image map or SVG images that can be viewed offline or explored using PathWhiz's interactive viewer. PathWhiz has been used to generate over 700 pathway diagrams for a number of popular databases including HMDB, DrugBank and SMPDB. PMID:25934797

  18. Pathways with PathWhiz

    PubMed Central

    Pon, Allison; Jewison, Timothy; Su, Yilu; Liang, Yongjie; Knox, Craig; Maciejewski, Adam; Wilson, Michael; Wishart, David S.

    2015-01-01

    PathWhiz (http://smpdb.ca/pathwhiz) is a web server designed to create colourful, visually pleasing and biologically accurate pathway diagrams that are both machine-readable and interactive. As a web server, PathWhiz is accessible from almost any place and compatible with essentially any operating system. It also houses a public library of pathways and pathway components that can be easily viewed and expanded upon by its users. PathWhiz allows users to readily generate biologically complex pathways by using a specially designed drawing palette to quickly render metabolites (including automated structure generation), proteins (including quaternary structures, covalent modifications and cofactors), nucleic acids, membranes, subcellular structures, cells, tissues and organs. Both small-molecule and protein/gene pathways can be constructed by combining multiple pathway processes such as reactions, interactions, binding events and transport activities. PathWhiz's pathway replication and propagation functions allow for existing pathways to be used to create new pathways or for existing pathways to be automatically propagated across species. PathWhiz pathways can be saved in BioPAX, SBGN-ML and SBML data exchange formats, as well as PNG, PWML, HTML image map or SVG images that can be viewed offline or explored using PathWhiz's interactive viewer. PathWhiz has been used to generate over 700 pathway diagrams for a number of popular databases including HMDB, DrugBank and SMPDB. PMID:25934797

  19. 14 CFR 23.57 - Takeoff path.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Takeoff path. 23.57 Section 23.57... path. For each commuter category airplane, the takeoff path is as follows: (a) The takeoff path extends... completed; and (1) The takeoff path must be based on the procedures prescribed in § 23.45; (2) The...

  20. 14 CFR 23.57 - Takeoff path.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Takeoff path. 23.57 Section 23.57... path. For each commuter category airplane, the takeoff path is as follows: (a) The takeoff path extends... completed; and (1) The takeoff path must be based on the procedures prescribed in § 23.45; (2) The...

  1. Tapped-Hole Vent Path

    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.

  2. Path Integrals on Ultrametric Spaces.

    NASA Astrophysics Data System (ADS)

    Blair, Alan

    A framework for the study of path integrals on adelic spaces is developed, and it is shown that a family of path space measures on the localizations of an algebraic number field may, under certain conditions, be combined to form a global path space measure on its adele ring. An operator on the field of p-adic numbers analogous to the harmonic oscillator operator is then analyzed, and used to construct an Ornstein-Uhlenbeck type process on the adele ring of the rationals. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-5668; Fax 617-253-1690.).

  3. Scattering theory with path integrals

    SciTech Connect

    Rosenfelder, R.

    2014-03-15

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

  4. Final Rulison Path Forward

    SciTech Connect

    2010-06-01

    commission. This report outlines DOE's recommendation that gas developers adopt a conservative, staged drilling approach allowing gas reserves near the Rulison site to be recovered in a manner that minimizes the likelihood of encountering contamination. This staged approach calls for collecting data from wells outside the half-mile zone before drilling closer, and then drilling within the half-mile zone in a sequential manner, first at low contamination probability locations and then moving inward. DOE's recommended approach for drilling in this area will protect public safety while allowing collection of additional data to confirm that contamination is contained within the 40-acre institutional control boundary.

  5. Shortest Paths between Shortest Paths and Independent Sets

    NASA Astrophysics Data System (ADS)

    Kamiński, Marcin; Medvedev, Paul; Milanič, Martin

    We study problems of reconfiguration of shortest paths in graphs. We prove that the shortest reconfiguration sequence can be exponential in the size of the graph and that it is NP-hard to compute the shortest reconfiguration sequence even when we know that the sequence has polynomial length. Moreover, we also study reconfiguration of independent sets in three different models and analyze relationships between these models, observing that shortest path reconfiguration is a special case of independent set reconfiguration in perfect graphs, under any of the three models. Finally, we give polynomial results for restricted classes of graphs (even-hole-free and P 4-free graphs).

  6. Helicobacter pylori vaccination: Is there a path to protection?

    PubMed Central

    Anderl, Florian; Gerhard, Markus

    2014-01-01

    Helicobacter pylori (H. pylori) is a pathogenic, extracellular bacterium that colonizes the stomach in approximately 50% of the world population. It strongly interacts with the gastric epithelium and mostly causes asymptomatic gastritis. The colonization of H. pylori leads to ulcer development in around 20% of infected patients and may progress to gastric cancer or mucosa-associated lymphoid tissue lymphoma in 1%. Thus, H. pylori is the major cause of gastric cancer worldwide. It has been classified as a class I carcinogen by the World Health Organization. Since its discovery in the early eighties by Warren and Marshall, research has been focused on the investigation of H. pylori biology, host-pathogen interaction, prevention and treatment. Although H. pylori induces a strong humoral and local cellular immune response, the pathogen is not cleared and establishes a chronic infection after encounters in childhood. The ability to colonize the stomach is mediated by several virulence factors that change the host environment, promote adhesion to the epithelium, influence the gastric inflammation and induce immune evasion. H. pylori can be eradicated by antibiotic treatment in combination with a proton-pump inhibitor, but efficacy is decreasing. Current therapies are expensive, have side effects and contribute to increasing antibiotic resistance, underlining the need for novel therapeutics. PMID:25232229

  7. Path coloring on the Mesh

    SciTech Connect

    Rabani, Y.

    1996-12-31

    In the minimum path coloring problem, we are given a list of pairs of vertices of a graph. We are asked to connect each pair by a colored path. Paths of the same color must be edge disjoint. Our objective is to minimize the number of colors used. This problem was raised by Aggarwal et al and Raghavan and Upfal as a model for routing in all-optical networks. It is also related to questions in circuit routing. In this paper, we improve the O (ln N) approximation result of Kleinberg and Tardos for path coloring on the N x N mesh. We give an O(1) approximation algorithm to the number of colors needed, and a poly(ln ln N) approximation algorithm to the choice of paths and colors. To the best of our knowledge, these are the first sub-logarithmic bounds for any network other than trees, rings, or trees of rings. Our results are based on developing new techniques for randomized rounding. These techniques iteratively improve a fractional solution until it approaches integrality. They are motivated by the method used by Leighton, Maggs, and Rao for packet routing.

  8. Gas-path seal technology

    NASA Technical Reports Server (NTRS)

    Zuk, J.

    1976-01-01

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

  9. Balanced Paths in Colored Graphs

    NASA Astrophysics Data System (ADS)

    Bianco, Alessandro; Faella, Marco; Mogavero, Fabio; Murano, Aniello

    We consider finite graphs whose edges are labeled with elements, called colors, taken from a fixed finite alphabet. We study the problem of determining whether there is an infinite path where either (i) all colors occur with the same asymptotic frequency, or (ii) there is a constant which bounds the difference between the occurrences of any two colors for all prefixes of the path. These two notions can be viewed as refinements of the classical notion of fair path, whose simplest form checks whether all colors occur infinitely often. Our notions provide stronger criteria, particularly suitable for scheduling applications based on a coarse-grained model of the jobs involved. We show that both problems are solvable in polynomial time, by reducing them to the feasibility of a linear program.

  10. 14 CFR 25.111 - Takeoff path.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Takeoff path. 25.111 Section 25.111... STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Performance § 25.111 Takeoff path. (a) The takeoff path... and VFTO is reached, whichever point is higher. In addition— (1) The takeoff path must be based on...

  11. 14 CFR 25.111 - Takeoff path.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Takeoff path. 25.111 Section 25.111... STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Performance § 25.111 Takeoff path. (a) The takeoff path... and VFTO is reached, whichever point is higher. In addition— (1) The takeoff path must be based on...

  12. 14 CFR 25.111 - Takeoff path.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Takeoff path. 25.111 Section 25.111... STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Performance § 25.111 Takeoff path. (a) The takeoff path... and VFTO is reached, whichever point is higher. In addition— (1) The takeoff path must be based on...

  13. 14 CFR 25.111 - Takeoff path.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Takeoff path. 25.111 Section 25.111... STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Performance § 25.111 Takeoff path. (a) The takeoff path... and VFTO is reached, whichever point is higher. In addition— (1) The takeoff path must be based on...

  14. 14 CFR 23.57 - Takeoff path.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Takeoff path. 23.57 Section 23.57... path. For normal, utility, and acrobatic category multiengine jets of more than 6,000 pounds maximum weight and commuter category airplanes, the takeoff path is as follows: (a) The takeoff path extends...

  15. 14 CFR 23.57 - Takeoff path.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Takeoff path. 23.57 Section 23.57... path. For normal, utility, and acrobatic category multiengine jets of more than 6,000 pounds maximum weight and commuter category airplanes, the takeoff path is as follows: (a) The takeoff path extends...

  16. 14 CFR 23.57 - Takeoff path.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Takeoff path. 23.57 Section 23.57... path. Link to an amendment published at 76 FR 75753, December 2, 2011. For each commuter category airplane, the takeoff path is as follows: (a) The takeoff path extends from a standing start to a point...

  17. 14 CFR 25.111 - Takeoff path.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Takeoff path. 25.111 Section 25.111... STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Performance § 25.111 Takeoff path. (a) The takeoff path... and VFTO is reached, whichever point is higher. In addition— (1) The takeoff path must be based on...

  18. Optical Path, Phase, and Interference

    NASA Astrophysics Data System (ADS)

    Newburgh, Ronald

    2005-11-01

    A powerful tool in wave optics is the concept of optical path length, a notion usually introduced with Fermat's principle.1-3 The analysis of Fermat's principle requires the application of the calculus of variations and the concept of an extremum, ideas too advanced for beginning students. However, the concept has proven its usefulness in the analysis4 of interference experiments such as those of Michelson and Fabry-Perot. In this paper we shall show how optical path length can aid in the analysis of a modified two-slit Young experiment.

  19. Speckle imaging over horizontal paths

    NASA Astrophysics Data System (ADS)

    Carrano, Carmen J.

    2002-09-01

    Atmospheric aberrations reduce the resolution and contrast in surveillance images recorded over horizontal or slant paths. This paper describes our recent horizontal and slant-path imaging experiments of extended scenes as well as the results obtained using speckle imaging. The experiments were performed with an 8-inch diameter telescope placed on either a rooftop or hillside and cover ranges of interest from 0.5 km up to 10 km. The scenery includes resolution targets, people, vehicles, and other structures. The improvement in image quality using speckle imaging is dramatic in many cases, and depends significantly upon the atmospheric conditions. We quantify resolution improvement through modulation transfer function measurement comparisons.

  20. Speckle Imaging Over Horizontal Paths

    SciTech Connect

    Carrano, C J

    2002-05-21

    Atmospheric aberrations reduce the resolution and contrast in surveillance images recorded over horizontal or slant paths. This paper describes our recent horizontal and slant path imaging experiments of extended scenes as well as the results obtained using speckle imaging. The experiments were performed with an 8-inch diameter telescope placed on either a rooftop or hillside and cover ranges of interest from 0.5 km up to 10 km. The scenery includes resolution targets, people, vehicles, and other structures. The improvement in image quality using speckle imaging is dramatic in many cases, and depends significantly upon the atmospheric conditions. We quantify resolution improvement through modulation transfer function measurement comparisons.

  1. 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.

  2. Career Paths in Environmental Sciences

    EPA Science Inventory

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

  3. Choosing the Path with Honor.

    ERIC Educational Resources Information Center

    Arredondo, Michael

    2002-01-01

    The author describes the difficulties of achieving his life-long dream of going to an Ivy League college, and how his Shawnee grandfather advised him to acquire the white man's skills and bring them back to his people. He advises young Native Americans to choose the more difficult, yet honorable path of serving their own people. (TD)

  4. 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…

  5. 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…

  6. 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…

  7. 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

  8. 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.

  9. Physarum can compute shortest paths.

    PubMed

    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

  10. 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.

  11. Path optimization for oil probe

    NASA Astrophysics Data System (ADS)

    Smith, O'Neil; Rahmes, Mark; Blue, Mark; Peter, Adrian

    2014-05-01

    We discuss a robust method for optimal oil probe path planning inspired by medical imaging. Horizontal wells require three-dimensional steering made possible by the rotary steerable capabilities of the system, which allows the hole to intersect multiple target shale gas zones. Horizontal "legs" can be over a mile long; the longer the exposure length, the more oil and natural gas is drained and the faster it can flow. More oil and natural gas can be produced with fewer wells and less surface disturbance. Horizontal drilling can help producers tap oil and natural gas deposits under surface areas where a vertical well cannot be drilled, such as under developed or environmentally sensitive areas. Drilling creates well paths which have multiple twists and turns to try to hit multiple accumulations from a single well location. Our algorithm can be used to augment current state of the art methods. Our goal is to obtain a 3D path with nodes describing the optimal route to the destination. This algorithm works with BIG data and saves cost in planning for probe insertion. Our solution may be able to help increase the energy extracted vs. input energy.

  12. Accelerating cleanup: Paths to closure

    SciTech Connect

    Edwards, C.

    1998-06-30

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

  13. 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.

  14. Copper foil provides uniform heat sink path

    NASA Technical Reports Server (NTRS)

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

    1966-01-01

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

  15. Time optimal paths for high speed maneuvering

    SciTech Connect

    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.

  16. 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.

  17. 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,…

  18. Performance Analysis of Path Planning Modeling

    NASA Astrophysics Data System (ADS)

    Wang, Zhirui; Li, Shuanghong; Zhang, Ying; Du, Qiaoling

    Ant colony system (ACS) algorithm was applied to the path planning for the robot. In the same working environment, path planning based on MAKLINK graph theory and Voronoi diagram were simulated and compared. MAKLINK graph theory is appropriate to apply to precise searching in small-scale district, and Voronoi diagram is suitable for fast path planning in a large area.

  19. IP-oriented control of unidirectional-path-switched-ring-based transport networks

    NASA Astrophysics Data System (ADS)

    Sharma, Vishal; Das, Abhimanyu; Chen, Charles

    2003-03-01

    An important requirement in the IP-based control of time-division multiplexing (TDM) optical transport networks is to utilize the in-built protection capabilities of synchronous optical network (SONET) unidirectional path-switched rings (UPSRs) and to automate the UPSR-protected path setup in mixed mesh-ring networks. This requires modifications to existing IP signaling and routing protocols and new processing rules at the network nodes. Here we leverage IP routing and signaling and multiprotocol label switching (MPLS) fast-reroute techniques for accurately advertising UPSR ring topologies to remote nodes and dynamically establishing UPSR-protected paths across a transport network. Our proposal also makes a NUT1-like (nonpreemptible unprotected traffic) feature possible in UPSRs, which allows for efficient utilization of UPSR protection bandwidth. We achieve this by encoding UPSR-specific information in the open shortest-path-first (OSPF) link state advertisements and in signaling messages of the Resource Reservation Protocol (RSVP) with TE extensions. In addition, we modify the signaling and routing state machines at the nodes to interpret and process this information to perform UPSR topology discovery and path computation. The uniqueness of our proposals is that the algorithms and the rules specified here allow for existing IP-based protocols [such as those within the generalized MPLS (GMPLS) framework, which currently applies to mesh networks] to be efficiently adapted for this context while still achieving our objective of exploiting UPSR-protection capabilities.

  20. Characterizing the Evolutionary Path(s) to Early Homo

    PubMed Central

    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

  1. 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

  2. Link prediction based on path entropy

    NASA Astrophysics Data System (ADS)

    Xu, Zhongqi; Pu, Cunlai; Yang, Jian

    2016-08-01

    Information theory has been taken as a prospective tool for quantifying the complexity of complex networks. In this paper, first we study the information entropy or uncertainty of a path using the information theory. After that, 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 of link predictors.

  3. Relations between Coherence and Path Information.

    PubMed

    Bagan, Emilio; Bergou, János A; Cottrell, Seth S; Hillery, Mark

    2016-04-22

    We find two relations between coherence and path information in a multipath 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. PMID:27152780

  4. Optical path control in the MAM testbed

    NASA Technical Reports Server (NTRS)

    Regehr, M. W.; Hines, B.; Holmes, B.

    2003-01-01

    Future space-based optical interferometers will require control of the optical path delay to accomplish some or all of the three objectives: balancing the optical path in the two arms to within a tolerance corresponding to the coherence length of the star light being observed, modulating the optical path in order to observe the phase of the star light interference fringe, and modulating the path length in order to reduce the effect of cyclic errors in the laser metrology system used to measure the optical path length in the two arms of the interferometer.

  5. Relations between Coherence and Path Information

    NASA Astrophysics Data System (ADS)

    Bagan, Emilio; Bergou, János A.; Cottrell, Seth S.; Hillery, Mark

    2016-04-01

    We find two relations between coherence and path information in a multipath 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 l1 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.

  6. 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.

  7. 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.

  8. Staff detection with stable paths.

    PubMed

    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

  9. Space Shuttle Solid Rocket Nozzle Joint 2 Gas Path Study

    NASA Technical Reports Server (NTRS)

    Lui, R. C.; Hyer, R. L.

    1999-01-01

    Each Space Shuttle solid rocket nozzle contains five joints. By design, each nozzle joint utilizes room-temperature vulcanized (RTV) rubber as a thermal barrier to protect the nozzle metal parts and O-rings from heat degradation due to motor combustion gas. Typically, combustion gas does not penetrate through the RTV in nozzle Joints. However, Joint currently experiences gas penetration through the RTV over 90 percent of the time. The occurrence of Joint gas paths is a very complex phenomenon with several known contributors such as the unique geometry of the joint, motor pressure, nozzle vectoring, manufacturing induced RTV voids. RTV material capability, and joint skip (relative radial displacement of joint components). The occurrence of Joint gas paths appears to be a combination of these causes. To better understand the causes of gas paths in Joint, the circumferential locations of gas paths in the RTV were identified and correlated with nozzle vectoring, RTV closeour locations (where the RTV backfill is completed), and X-ray low-density. anomaly (LDA) indications. Results that no specific cause was determined.

  10. MANAGING HANFORD'S LEGACY NO-PATH-FORWARD WASTES TO DISPOSITION

    SciTech Connect

    WEST LD

    2011-01-13

    The U.S. Department of Energy (DOE) Richland Operations Office (RL) has adopted the 2015 Vision for Cleanup of the Hanford Site. This vision will protect the Columbia River, reduce the Site footprint, and reduce Site mortgage costs. The CH2M HILL Plateau Remediation Company's (CHPRC) Waste and Fuels Management Project (W&FMP) and their partners support this mission by providing centralized waste management services for the Hanford Site waste generating organizations. At the time of the CHPRC contract award (August 2008) slightly more than 9,000 m{sup 3} of waste was defined as 'no-path-forward waste.' The majority of these wastes are suspect transuranic mixed (TRUM) wastes which are currently stored in the low-level Burial Grounds (LLBG), or stored above ground in the Central Waste Complex (CWC). A portion of the waste will be generated during ongoing and future site cleanup activities. The DOE-RL and CHPRC have collaborated to identify and deliver safe, cost-effective disposition paths for 90% ({approx}8,000 m{sup 3}) of these problematic wastes. These paths include accelerated disposition through expanded use of offsite treatment capabilities. Disposal paths were selected that minimize the need to develop new technologies, minimize the need for new, on-site capabilities, and accelerate shipments of transuranic (TRU) waste to the Waste Isolation Pilot Plant (WIPP) in Carlsbad, New Mexico.

  11. Reconsidering employer-sponsored health care: four paths to long-term strategic change.

    PubMed

    Winkler, Jim

    2013-01-01

    With Supreme Court and election uncertainty now resolved over the Patient Protection and Affordable Care Act (ACA), employers are recognizing the need for immediate action and reassessing the role they play in promoting and insuring the health of their population. Centered on a consistent need to have a workforce that is healthy, present and high-performing, employers face four possible strategic paths. This article discusses those paths along with their attendant risks and opportunities. PMID:23943950

  12. 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.

  13. Mechanics of the crack path formation

    NASA Technical Reports Server (NTRS)

    Rubinstein, Asher A.

    1991-01-01

    A detailed analysis of experimentally obtained curvilinear crack path trajectories formed in a heterogeneous stress field is presented. Experimental crack path trajectories were used as data for the numerical simulations, recreating the actual stress field governing the development of the crack path. Thus, the current theories of crack curving and kinking could be examined by comparing them with the actual stress field parameters as they develop along the experimentally observed crack path. The experimental curvilinear crack path trajectories were formed in the tensile specimens with a hole positioned in the vicinity of a potential crack path. The numerical simulation, based on the solution of equivalent boundary value problems with the possible perturbations of the crack path, is presented.

  14. 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.

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

    PubMed Central

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

    2012-01-01

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

  16. NGNP Program 2013 Status and Path Forward

    SciTech Connect

    Hans Gougar

    2014-03-01

    High temperature gas-cooled reactor (HTGR) technology can play an important role in the energy future of the United States by extending the use of nuclear energy for non-electricity energy production missions, as well as continuing to provide a considerable base load electric power generation capability. Extending nuclear energy into the industrial and transportation sectors through the coproduction of process heat and electricity provides safe, reliable energy for these sectors in an environmentally responsible manner. The modular HTGR provides a substantial improvement in nuclear plant safety for the protection of the public and the environment, and supports collocation of the HTGRhigh temperature gas-cooled reactor with major industrial facilities. Under U.S. Department of Energy direction since 2006, the Next Generation Nuclear Plant Project at Idaho National Laboratory has been working toward commercializing the HTGR technology. However, a recent decision by the Secretary of Energy to reduce the scope of the Next Generation Nuclear Plant Project to a research and development program, considerable realignment has taken place. This report: (1) summarizes the accomplishments of the Next Generation Nuclear Plant Program from FY2011 through FY2013; (2) lays out the path forward necessary to achieve the ultimate objective of commercializing HTGR technology; and (3) discusses ongoing technical, licensing, and evaluation activities under the realigned Next Generation Nuclear Plant program considered important to preserve the significant investment made by the government to-date and to maintain some progress in meeting the objectives of the Energy Policy Act of 2005 (EPAct2005).

  17. Integrated assignment and path planning

    NASA Astrophysics Data System (ADS)

    Murphey, Robert A.

    2005-11-01

    A surge of interest in unmanned systems has exposed many new and challenging research problems across many fields of engineering and mathematics. These systems have the potential of transforming our society by replacing dangerous and dirty jobs with networks of moving machines. This vision is fundamentally separate from the modern view of robotics in that sophisticated behavior is realizable not by increasing individual vehicle complexity, but instead through collaborative teaming that relies on collective perception, abstraction, decision making, and manipulation. Obvious examples where collective robotics will make an impact include planetary exploration, space structure assembly, remote and undersea mining, hazardous material handling and clean-up, and search and rescue. Nonetheless, the phenomenon driving this technology trend is the increasing reliance of the US military on unmanned vehicles, specifically, aircraft. Only a few years ago, following years of resistance to the use of unmanned systems, the military and civilian leadership in the United States reversed itself and have recently demonstrated surprisingly broad acceptance of increasingly pervasive use of unmanned platforms in defense surveillance, and even attack. However, as rapidly as unmanned systems have gained acceptance, the defense research community has discovered the technical pitfalls that lie ahead, especially for operating collective groups of unmanned platforms. A great deal of talent and energy has been devoted to solving these technical problems, which tend to fall into two categories: resource allocation of vehicles to objectives, and path planning of vehicle trajectories. An extensive amount of research has been conducted in each direction, yet, surprisingly, very little work has considered the integrated problem of assignment and path planning. This dissertation presents a framework for studying integrated assignment and path planning and then moves on to suggest an exact

  18. The path to adaptive microsystems

    NASA Astrophysics Data System (ADS)

    Zolper, John C.; Biercuk, Michael J.

    2006-05-01

    Scaling trends in microsystems are discussed frequently in the technical community, providing a short-term perspective on the future of integrated microsystems. This paper looks beyond the leading edge of technological development, focusing on new microsystem design paradigms that move far beyond today's systems based on static components. We introduce the concept of Adaptive Microsystems and outline a path to realizing these systems-on-a-chip. The role of DARPA in advancing future components and systems research is discussed, and specific DARPA efforts enabling and producing adaptive microsystems are presented. In particular, we discuss efforts underway in the DARPA Microsystems Technology Office (MTO) including programs in novel circuit architectures (3DIC), adaptive imaging and sensing (AFPA, VISA, MONTAGE, A-to-I) and reconfigurable RF/Microwave devices (SMART, TFAST, IRFFE).

  19. The Logic Behind Feynman's Paths

    NASA Astrophysics Data System (ADS)

    García Álvarez, Edgardo T.

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

  20. 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.

  1. Extracting Critical Path Graphs from MPI Applications

    SciTech Connect

    Schulz, M

    2005-07-27

    The critical path is one of the fundamental runtime characteristics of a parallel program. It identifies the longest execution sequence without wait delays. In other words, the critical path is the global execution path that inflicts wait operations on other nodes without itself being stalled. Hence, it dictates the overall runtime and knowing it is important to understand an application's runtime and message behavior and to target optimizations. We have developed a toolset that identifies the critical path of MPI applications, extracts it, and then produces a graphical representation of the corresponding program execution graph to visualize it. To implement this, we intercept all MPI library calls, use the information to build the relevant subset of the execution graph, and then extract the critical path from there. We have applied our technique to several scientific benchmarks and successfully produced critical path diagrams for applications running on up to 128 processors.

  2. A note on the path interval distance.

    PubMed

    Coons, Jane Ivy; Rusinko, Joseph

    2016-06-01

    The path interval distance accounts for global congruence between locally incongruent trees. We show that the path interval distance provides a lower bound for the nearest neighbor interchange distance. In contrast to the Robinson-Foulds distance, random pairs of trees are unlikely to be maximally distant from one another under the path interval distance. These features indicate that the path interval distance should play a role in phylogenomics where the comparison of trees on a fixed set of taxa is becoming increasingly important. PMID:27040521

  3. Geodesics on path spaces and double category

    NASA Astrophysics Data System (ADS)

    Chatterjee, Saikat

    2016-09-01

    Let M be a Riemannian manifold and 𝒫M be the space of all smooth paths on M. We describe geodesics on path space 𝒫M. Normal neighborhoods on 𝒫M have been discussed. We identify paths on M under “back-track” equivalence. Under this identification, we show that if M is complete, then geodesics on the path space yield a double category. This double category has a natural interpretation in terms of the worldsheets generated by freely moving (without any external force) strings.

  4. Sun protection

    MedlinePlus

    ... age spots are caused by exposure to the sun. The two types of sun rays that can injure the skin are ultraviolet ... changes is to protect your skin from the sun. This includes using sunscreen and other protective measures. ...

  5. 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.

  6. Path integral for inflationary perturbations

    NASA Astrophysics Data System (ADS)

    Prokopec, Tomislav; Rigopoulos, Gerasimos

    2010-07-01

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

  7. 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.

  8. 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.

  9. Evaluation of Calcine Disposition Path Forward

    SciTech Connect

    Birrer, S.A.; Heiser, M.B.

    2003-02-26

    This document describes an evaluation of the baseline and two alternative disposition paths for the final disposition of the calcine wastes stored at the Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory. The pathways are evaluated against a prescribed set of criteria and a recommendation is made for the path forward.

  10. Evaluation of Calcine Disposition - Path Forward

    SciTech Connect

    Steve Birrer

    2003-02-01

    This document describes an evaluation of the baseline and two alternative disposition paths for the final disposition of the calcine wastes stored at the Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory. The pathways are evaluated against a prescribed set of criteria and a recommendation is made for the path forward.

  11. The path dependence of deformation texture development

    SciTech Connect

    Takeshita, T.; Kocks, U.F.; Wenk, H.R.

    1987-01-01

    It is demonstrated for the case of three different strain paths, all of which end up with the same, elongated specimen shape, that the texture developed during straining is path dependent. This is true both for experiments on aluminum polycrystals and for simulations using the LApp code.

  12. The Path of Carbon in Photosynthesis VI.

    DOE R&D Accomplishments Database

    Calvin, M.

    1949-06-30

    This paper is a compilation of the essential results of our experimental work in the determination of the path of carbon in photosynthesis. There are discussions of the dark fixation of photosynthesis and methods of separation and identification including paper chromatography and radioautography. The definition of the path of carbon in photosynthesis by the distribution of radioactivity within the compounds is described.

  13. Career Path Guide for Adult Career Choices.

    ERIC Educational Resources Information Center

    Case, Clydia

    Intended for adults who are considering career choices or changes, this booklet provides opportunities for self-study and reflection in six career paths. The booklet begins with tips for long-term career survival and myths and realities of career planning. After a brief career survey, readers are introduced to six career paths: arts and…

  14. Adaptively Ubiquitous Learning in Campus Math Path

    ERIC Educational Resources Information Center

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

    2012-01-01

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

  15. A Random Walk on a Circular Path

    ERIC Educational Resources Information Center

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

    2005-01-01

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

  16. 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.

  17. Excitation of nucleobases from a computational perspective I: reaction paths.

    PubMed

    Giussani, Angelo; Segarra-Martí, Javier; Roca-Sanjuán, Daniel; Merchán, Manuela

    2015-01-01

    The main intrinsic photochemical events in nucleobases can be described on theoretical grounds within the realm of non-adiabatic computational photochemistry. From a static standpoint, the photochemical reaction path approach (PRPA), through the computation of the respective minimum energy path (MEP), can be regarded as the most suitable strategy in order to explore the electronically excited isolated nucleobases. Unfortunately, the PRPA does not appear widely in the studies reported in the last decade. The main ultrafast decay observed experimentally for the gas-phase excited nucleobases is related to the computed barrierless MEPs from the bright excited state connecting the initial Franck-Condon region and a conical intersection involving the ground state. At the highest level of theory currently available (CASPT2//CASPT2), the lowest excited (1)(ππ*) hypersurface for cytosine has a shallow minimum along the MEP deactivation pathway. In any case, the internal conversion processes in all the natural nucleobases are attained by means of interstate crossings, a self-protection mechanism that prevents the occurrence of photoinduced damage of nucleobases by ultraviolet radiation. Many alternative and secondary paths have been proposed in the literature, which ultimately provide a rich and constructive interplay between experimentally and theoretically oriented research. PMID:24264958

  18. Shortest path and Schramm-Loewner Evolution

    PubMed Central

    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 κ = 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

  19. Universal Geometric Path to a Robust Majorana Magic Gate

    NASA Astrophysics Data System (ADS)

    Karzig, Torsten; Oreg, Yuval; Refael, Gil; Freedman, Michael H.

    2016-07-01

    A universal quantum computer requires a full set of basic quantum gates. With Majorana bound states one can form all necessary quantum gates in a topologically protected way, bar one. In this paper, we present a scheme that achieves the missing, so-called, π /8 magic phase gate without the need of fine-tuning for distinct physical realizations. The scheme is based on the manipulation of geometric phases described by a universal protocol and converges exponentially with the number of steps in the geometric path. Furthermore, our magic gate proposal relies on the most basic hardware previously suggested for topologically protected gates, and can be extended to an any-phase gate, where π /8 is substituted by any α .

  20. Evolution paths for advanced automation

    NASA Technical Reports Server (NTRS)

    Healey, Kathleen J.

    1990-01-01

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

  1. The behavioural final common path.

    PubMed

    McFarland, D J; Sibly, R M

    1975-05-15

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

  2. The Path of Human Evolution

    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.

  3. Methodology for Augmenting Existing Paths with Additional Parallel Transects

    SciTech Connect

    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.

  4. 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.

  5. Automated flight path planning for virtual endoscopy.

    PubMed

    Paik, D S; Beaulieu, C F; Jeffrey, R B; Rubin, G D; Napel, S

    1998-05-01

    In this paper, a novel technique for rapid and automatic computation of flight paths for guiding virtual endoscopic exploration of three-dimensional medical images is described. While manually planning flight paths is a tedious and time consuming task, our algorithm is automated and fast. Our method for positioning the virtual camera is based on the medial axis transform but is much more computationally efficient. By iteratively correcting a path toward the medial axis, the necessity of evaluating simple point criteria during morphological thinning is eliminated. The virtual camera is also oriented in a stable viewing direction, avoiding sudden twists and turns. We tested our algorithm on volumetric data sets of eight colons, one aorta and one bronchial tree. The algorithm computed the flight paths in several minutes per volume on an inexpensive workstation with minimal computation time added for multiple paths through branching structures (10%-13% per extra path). The results of our algorithm are smooth, centralized paths that aid in the task of navigation in virtual endoscopic exploration of three-dimensional medical images. PMID:9608471

  6. 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.

  7. Insider protection

    SciTech Connect

    Waddoups, I.G.

    1993-07-01

    The government community is broadly addressing the insider threat. The first section of this paper defines protection approaches and the latter sections present various applicable technology developments. The bulk of the paper discusses technology developments applied to (1) personnel and material tracking and inventory, (2) classified document protection, and (3) protecting security systems. The personnel and material tracking system uses a PC based-host to (1) collect information from proximity tags and material movement sensors, (2) apply rules to this input to assure that the ongoing activity meets the site selectable rules and, (3) forward the results to either an automated inventory system or an alarm system. The document protection system uses a PC network to efficiently and securely control classified material which is stored on write-once-read-mostly optical media. The protection of sensor to multiplexer communications in a security system is emphasized in the discussion of protecting security systems.

  8. Steering Chiral Swimmers along Noisy Helical Paths

    NASA Astrophysics Data System (ADS)

    Friedrich, Benjamin M.; Jülicher, Frank

    2009-08-01

    Chemotaxis along helical paths towards a target releasing a chemoattractant is found in sperm cells and many microorganisms. We discuss the stochastic differential geometry of the noisy helical swimming path of a chiral swimmer. A chiral swimmer equipped with a simple feedback system can navigate in a concentration gradient of chemoattractant. We derive an effective equation for the alignment of helical paths with a concentration gradient which is related to the alignment of a dipole in an external field and discuss the chemotaxis index.

  9. 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.

  10. 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.

  11. ADÈLIC Path Space Integrals

    NASA Astrophysics Data System (ADS)

    Blair, Alan D.

    A framework for the study of path integrals on adèlic spaces is developed, and it is shown that a family of path space measures on the localizations of an algebraic number field may, under certain conditions, be combined to form a global path space measure on its adèle ring. An operator on the field of p-adic numbers analogous to the harmonic oscillator operator is then analyzed, and used to construct an Ornstein-Uhlenbeck type process on the adèle ring of the rationals.

  12. 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

  13. IRIS Optical Instrument and Light Paths

    NASA Video Gallery

    The optical portion of the instrument and the light paths from the primary and secondary mirror of the telescope assembly into the spectrograph. The spectrograph then breaks the light into 2 Near U...

  14. Exploring Zika's Path Through the Placenta

    MedlinePlus

    ... https://medlineplus.gov/news/fullstory_159075.html Exploring Zika's Path Through the Placenta Researchers find the virus ... research seems to shed light on how the Zika virus infects, but doesn't kill, placenta cells. ...

  15. Exploring Zika's Path Through the Placenta

    MedlinePlus

    ... nih.gov/medlineplus/news/fullstory_159075.html Exploring Zika's Path Through the Placenta Researchers find the virus ... research seems to shed light on how the Zika virus infects, but doesn't kill, placenta cells. ...

  16. Orbital Path of the International Space Station

    NASA Video Gallery

    Astronauts Don Pettit, Andre Kuipers and Dan Burbank explain the orbital path of the International Space Station. Earth video credit: Image Science and Analysis Laboratory, NASA's Johnson Space Cen...

  17. Animation: Path of 2010 Solar Eclipse

    NASA Video Gallery

    On Sunday, 2010 July 11, a total eclipse of the Sun is visible from within a narrow corridor that traverses Earth's southern hemisphere. The path of the Moon's umbral shadow crosses the South Pacif...

  18. Local-time representation of path integrals

    NASA Astrophysics Data System (ADS)

    Jizba, Petr; Zatloukal, Václav

    2015-12-01

    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.

  19. 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.

  20. Nonclassical Paths in Quantum Interference Experiments

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  1. 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)

  2. Numerical evaluation of Feynman path integrals

    NASA Astrophysics Data System (ADS)

    Baird, William Hugh

    1999-11-01

    The notion of path integration developed by Feynman, while an incredibly successful method of solving quantum mechanical problems, leads to frequently intractable integrations over an infinite number of paths. Two methods now exist which sidestep this difficulty by defining "densities" of actions which give the relative number of paths found at different values of the action. These densities are sampled by computer generation of paths and the propagators are found to a high degree of accuracy for the case of a particle on the infinite half line and in a finite square well in one dimension. The problem of propagation within a two dimensional radial well is also addressed as the precursor to the problem of a particle in a stadium (quantum billiard).

  3. Create three distinct career paths for innovators.

    PubMed

    O'Connor, Gina Colarelli; Corbett, Andrew; Pierantozzi, Ron

    2009-12-01

    Large companies say they Create Three Distinct want to be Career Paths for Innovators innovative, but they fundamentally mismanage their talent. Expecting innovators to grow along with their projects-from discovery to incubation to acceleration--sets them up to fail. Most people excel at one of the phases, not all three. By allowing innovation employees to develop career paths suited to their strengths, companies will create a sustainable innovation function. PMID:19968059

  4. Path optimization with limited sensing ability

    NASA Astrophysics Data System (ADS)

    Kang, Sung Ha; Kim, Seong Jun; Zhou, Haomin

    2015-10-01

    We propose a computational strategy to find the optimal path for a mobile sensor with limited coverage to traverse a cluttered region. The goal is to find one of the shortest feasible paths to achieve the complete scan of the environment. We pose the problem in the level set framework, and first consider a related question of placing multiple stationary sensors to obtain the full surveillance of the environment. By connecting the stationary locations using the nearest neighbor strategy, we form the initial guess for the path planning problem of the mobile sensor. Then the path is optimized by reducing its length, via solving a system of ordinary differential equations (ODEs), while maintaining the complete scan of the environment. Furthermore, we use intermittent diffusion, which converts the ODEs into stochastic differential equations (SDEs), to find an optimal path whose length is globally minimal. To improve the computation efficiency, we introduce two techniques, one to remove redundant connecting points to reduce the dimension of the system, and the other to deal with the entangled path so the solution can escape the local traps. Numerical examples are shown to illustrate the effectiveness of the proposed method.

  5. Path optimization with limited sensing ability

    SciTech Connect

    Kang, Sung Ha Kim, Seong Jun Zhou, Haomin

    2015-10-15

    We propose a computational strategy to find the optimal path for a mobile sensor with limited coverage to traverse a cluttered region. The goal is to find one of the shortest feasible paths to achieve the complete scan of the environment. We pose the problem in the level set framework, and first consider a related question of placing multiple stationary sensors to obtain the full surveillance of the environment. By connecting the stationary locations using the nearest neighbor strategy, we form the initial guess for the path planning problem of the mobile sensor. Then the path is optimized by reducing its length, via solving a system of ordinary differential equations (ODEs), while maintaining the complete scan of the environment. Furthermore, we use intermittent diffusion, which converts the ODEs into stochastic differential equations (SDEs), to find an optimal path whose length is globally minimal. To improve the computation efficiency, we introduce two techniques, one to remove redundant connecting points to reduce the dimension of the system, and the other to deal with the entangled path so the solution can escape the local traps. Numerical examples are shown to illustrate the effectiveness of the proposed method.

  6. 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.

  7. Equivalence of trans paths in ion channels

    NASA Astrophysics Data System (ADS)

    Alvarez, Juan; Hajek, Bruce

    2006-04-01

    We explore stochastic models for the study of ion transport in biological cells. Analysis of these models explains and explores an interesting feature of ion transport observed by biophysicists. Namely, the average time it takes ions to cross certain ion channels is the same in either direction, even if there is an electric potential difference across the channels. It is shown for simple single ion models that the distribution of a path (i.e., the history of location versus time) of an ion crossing the channel in one direction has the same distribution as the time-reversed path of an ion crossing the channel in the reverse direction. Therefore, not only is the mean duration of these paths equal, but other measures, such as the variance of passage time or the mean time a path spends within a specified section of the channel, are also the same for both directions of traversal. The feature is also explored for channels with interacting ions. If a system of interacting ions is in reversible equilibrium (net flux is zero), then the equivalence of the left-to-right trans paths with the time-reversed right-to-left trans paths still holds. However, if the system is in equilibrium, but not reversible equilibrium, then such equivalence need not hold.

  8. Infiltration Flow Path Distributions in Unsaturated Rocks

    NASA Astrophysics Data System (ADS)

    Tokunaga, T. K.; Olson, K. R.; Wan, J.

    2004-12-01

    Spatial distributions of infiltration flow paths through rock formations are complex networks that determine flow velocities, control rates of natural geochemical reactions in the subsurface, as well as rates of contaminant transport to underlying groundwater. Despite these important consequences, distributions of infiltration paths and locally fast seepage rates through rocks are not well understood. Laboratory-based studies on fractured rocks cannot easily be conducted on systems large enough to include sufficient fracture network complexity, so that inferences of field-scale flux distributions cannot be reliably made. Field-based studies to date have permitted quantification of only a small fraction of the flow distribution, typically while imposing extremely high fluxes, and therefore have not allowed comprehensive delineation of flow distributions expected under natural recharge. Based on hydraulic scaling considerations, we hypothesize that unsaturated flow path distributions in rock deposits will be similar to those occurring in fractured rock formations under low overall infiltration rates. Talus rock deposits and mine waste rock piles control flow and transport into their respective underlying groundwaters. All of these reasons motivated infiltration experiments in rock packs. Experiments have been conducted on 4 different rock types and system scales ranging from 1 to 46 rock layers. Our experiments showed that infiltration through rocks conforms to no previously reported behavior in soils, and that flow paths do not progressively converge into fewer and fewer flow paths. Instead, a fundamentally different hydraulic structure develops, having an exponential (geometric) flux distribution, with the characteristic scale determined by the characteristic rock size. Although the phenomena are very different, the evolution of flow path distributions and local seepage rate distributions is predictable based on a statistical mechanical model for energy

  9. Memory protection

    NASA Technical Reports Server (NTRS)

    Denning, Peter J.

    1988-01-01

    Accidental overwriting of files or of memory regions belonging to other programs, browsing of personal files by superusers, Trojan horses, and viruses are examples of breakdowns in workstations and personal computers that would be significantly reduced by memory protection. Memory protection is the capability of an operating system and supporting hardware to delimit segments of memory, to control whether segments can be read from or written into, and to confine accesses of a program to its segments alone. The absence of memory protection in many operating systems today is the result of a bias toward a narrow definition of performance as maximum instruction-execution rate. A broader definition, including the time to get the job done, makes clear that cost of recovery from memory interference errors reduces expected performance. The mechanisms of memory protection are well understood, powerful, efficient, and elegant. They add to performance in the broad sense without reducing instruction execution rate.

  10. Protective Eyewear

    MedlinePlus

    ... Whether you’re on the basketball court, in chemistry class, or sitting by the pool, wearing protective ... remember to wear safety goggles. Using chemicals in chemistry class? Look like a real scientist by wearing ...

  11. Corrosion protection

    DOEpatents

    Brown, Donald W.; Wagh, Arun S.

    2003-05-27

    There has been invented a chemically bonded phosphate corrosion protection material and process for application of the corrosion protection material for corrosion prevention. A slurry of iron oxide and phosphoric acid is used to contact a warm surface of iron, steel or other metal to be treated. In the presence of ferrous ions from the iron, steel or other metal, the slurry reacts to form iron phosphates which form grains chemically bonded onto the surface of the steel.

  12. Minimal entropy probability paths between genome families.

    PubMed

    Ahlbrandt, Calvin; Benson, Gary; Casey, William

    2004-05-01

    We develop a metric for probability distributions with applications to biological sequence analysis. Our distance metric is obtained by minimizing a functional defined on the class of paths over probability measures on N categories. The underlying mathematical theory is connected to a constrained problem in the calculus of variations. The solution presented is a numerical solution, which approximates the true solution in a set of cases called rich paths where none of the components of the path is zero. The functional to be minimized is motivated by entropy considerations, reflecting the idea that nature might efficiently carry out mutations of genome sequences in such a way that the increase in entropy involved in transformation is as small as possible. We characterize sequences by frequency profiles or probability vectors, in the case of DNA where N is 4 and the components of the probability vector are the frequency of occurrence of each of the bases A, C, G and T. Given two probability vectors a and b, we define a distance function based as the infimum of path integrals of the entropy function H( p) over all admissible paths p(t), 0 < or = t< or =1, with p(t) a probability vector such that p(0)=a and p(1)=b. If the probability paths p(t) are parameterized as y(s) in terms of arc length s and the optimal path is smooth with arc length L, then smooth and "rich" optimal probability paths may be numerically estimated by a hybrid method of iterating Newton's method on solutions of a two point boundary value problem, with unknown distance L between the abscissas, for the Euler-Lagrange equations resulting from a multiplier rule for the constrained optimization problem together with linear regression to improve the arc length estimate L. Matlab code for these numerical methods is provided which works only for "rich" optimal probability vectors. These methods motivate a definition of an elementary distance function which is easier and faster to calculate, works on non

  13. Biochemical analysis of plant protection afforded by a nonpathogenic endophytic mutant of Colletotrichum magna

    SciTech Connect

    Redman, R.S.; Rodriguez, R.J. Univ. of Washington, Seattle, WA . Dept. of Botany); Clifton, D.R.; Morrel, J.; Brown, G. ); Freeman, S. . Dept. of Plant Pathology)

    1999-02-01

    A nonpathogenic mutant of Colletotrichum magna (path-1) was previously shown to protect watermelon (Citrullus lanatus) and cucumber (Cucumis sativus) seedlings from anthracnose disease elicited by wild-type C. magna. Disease protection was observed in stems of path-1-colonized cucurbits but not in cotyledons, indicating that path-1 conferred tissue-specific and/or localized protection. Plant biochemical indicators of a localized and systemic (peroxidase, phenylalanine ammonia-lyase, lignin, and salicylic acid) plant-defense response were investigated in anthracnose-resistant and-susceptible cultivars of cucurbit seedlings exposed to four treatments: (1) water (control), (2) path-1 conidia, (3) wild-type conidia, and (4) challenge conditions (inoculation into path-1 conidia for 48 h and then exposure to wild-type conidia). Collectively, these analyses indicated that disease protection in path-1-colonized plants was correlated with the ability of these plants to mount a defense response more rapidly and to equal or greater levels than plants exposed to wild-type C. magna alone. Watermelon plants colonized with path-1 were also protected against disease caused by Colletotrichum orbiculare and Fusarium oxysporum. A model based on the kinetics of plant-defense activation is presented to explain the mechanism of path-1-conferred disease protection.

  14. Biochemical Analysis of Plant Protection Afforded by a Nonpathogenic Endophytic Mutant of Colletotrichum magna1

    PubMed Central

    Redman, Regina S.; Freeman, Stanley; Clifton, David R.; Morrel, Jed; Brown, Gayle; Rodriguez, Rusty J.

    1999-01-01

    A nonpathogenic mutant of Colletotrichum magna (path-1) was previously shown to protect watermelon (Citrullus lanatus) and cucumber (Cucumis sativus) seedlings from anthracnose disease elicited by wild-type C. magna. Disease protection was observed in stems of path-1-colonized cucurbits but not in cotyledons, indicating that path-1 conferred tissue-specific and/or localized protection. Plant biochemical indicators of a localized and systemic (peroxidase, phenylalanine ammonia-lyase, lignin, and salicylic acid) “plant-defense” response were investigated in anthracnose-resistant and -susceptible cultivars of cucurbit seedlings exposed to four treatments: (1) water (control), (2) path-1 conidia, (3) wild-type conidia, and (4) challenge conditions (inoculation into path-1 conidia for 48 h and then exposure to wild-type conidia). Collectively, these analyses indicated that disease protection in path-1-colonized plants was correlated with the ability of these plants to mount a defense response more rapidly and to equal or greater levels than plants exposed to wild-type C. magna alone. Watermelon plants colonized with path-1 were also protected against disease caused by Colletotrichum orbiculare and Fusarium oxysporum. A model based on the kinetics of plant-defense activation is presented to explain the mechanism of path-1-conferred disease protection. PMID:9952476

  15. Biochemical analysis of plant protection afforded by a nonpathogenic endophytic mutant of Colletotrichum magna

    USGS Publications Warehouse

    Redman, R.S.; Freeman, S.; Clifton, D.R.; Morrel, J.; Brown, G.; Rodriguez, R.J.

    1999-01-01

    A nonpathogenic mutant of Colletotrichum magna (path-1) was previously shown to protect watermelon (Citrullus lanatus) and cucumber (Cucumis sativus) seedlings from anthracnose disease elicited by wild-type C. magna. Disease protection was observed in stems of path-1-colonized cucurbits but not in cotyledons, indicating that path-1 conferred tissue-specific and/or localized protection. Plant biochemical indicators of a localized and systemic (peroxidase, phenylalanine ammonia-lyase, lignin, and salicylic acid) 'plant-defense' response were investigated in anthracnose-resistant and -susceptible cultivars of cucurbit seedlings exposed to four treatments: (1) water (control), (2) path-1 conidia, (3) wild-type conidia, and (4) challenge conditions (inoculation into path-1 conidia for 48 h and then exposure to wild-type conidia). Collectively, these analyses indicated that disease protection in path-1 colonized plants was correlated with the ability of these plants to mount a defense response more rapidly and to equal or greater levels than plants exposed to wild-type C. magna alone. Watermelon plants colonized with path-1 were also protected against disease caused by Colletotrichum orbiculare and Fusarium oxysporum. A model based on the kinetics of plant-defense activation is presented to explain the mechanism of path-1-conferred disease protection.

  16. DNA computing the Hamiltonian path problem.

    PubMed

    Lee, C M; Kim, S W; Kim, S M; Sohn, U

    1999-10-31

    The directed Hamiltonian path (DHP) problem is one of the hard computational problems for which there is no practical algorithm on a conventional computer available. Many problems, including the traveling sales person problem and the longest path problem, can be translated into the DHP problem, which implies that an algorithm for DHP can also solve all the translated problems. To study the robustness of the laboratory protocol of the pioneering DNA computing for the DHP problem performed by Leonard Adleman (1994), we investigated how the graph size, multiplicity of the Hamiltonian paths, and the size of oligonucleotides that encode the vertices would affect the laboratory procedures. We applied Adleman's protocol with 18-mer oligonucleotide per node to a graph with 8 vertices and 14 edges containing two Hamiltonian paths (Adleman used 20-mer oligonucleotides for a graph with 7 nodes, 14 edges and one Hamiltonian path). We found that depending on the graph characteristics such as the number of short cycles, the oligonucleotide size, and the hybridization conditions that used to encode the graph, the protocol should be executed with different parameters from Adleman's. PMID:10597033

  17. Multiple Manifold Clustering Using Curvature Constrained Path

    PubMed Central

    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

  18. Unbiased sampling of lattice Hamilton path ensembles

    NASA Astrophysics Data System (ADS)

    Mansfield, Marc L.

    2006-10-01

    Hamilton paths, or Hamiltonian paths, are walks on a lattice which visit each site exactly once. They have been proposed as models of globular proteins and of compact polymers. A previously published algorithm [Mansfield, Macromolecules 27, 5924 (1994)] for sampling Hamilton paths on simple square and simple cubic lattices is tested for bias and for efficiency. Because the algorithm is a Metropolis Monte Carlo technique obviously satisfying detailed balance, we need only demonstrate ergodicity to ensure unbiased sampling. Two different tests for ergodicity (exact enumeration on small lattices, nonexhaustive enumeration on larger lattices) demonstrate ergodicity unequivocally for small lattices and provide strong support for ergodicity on larger lattices. Two other sampling algorithms [Ramakrishnan et al., J. Chem. Phys. 103, 7592 (1995); Lua et al., Polymer 45, 717 (2004)] are both known to produce biases on both 2×2×2 and 3×3×3 lattices, but it is shown here that the current algorithm gives unbiased sampling on these same lattices. Successive Hamilton paths are strongly correlated, so that many iterations are required between statistically independent samples. Rules for estimating the number of iterations needed to dissipate these correlations are given. However, the iteration time is so fast that the efficiency is still very good except on extremely large lattices. For example, even on lattices of total size 10×10×10 we are able to generate tens of thousands of uncorrelated Hamilton paths per hour of CPU time.

  19. Path analysis in genetic epidemiology: a critique.

    PubMed Central

    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

  20. Quantum state of wormholes and path integral

    SciTech Connect

    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.

  1. A taxonomy of integral reaction path analysis

    SciTech Connect

    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.

  2. 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.

  3. Paths to Licensure: Things Physicists Should Know

    NASA Astrophysics Data System (ADS)

    Stewart, Gay; Stewart, John

    2016-03-01

    The path to licensure can be quite complicated, and can thwart a physics department's efforts to produce more and better prepared high school physics teachers. Each state has different pathways to licensure. Acronyms like CAEP and SPA are not within the normal physicist's vocabulary. Some understanding of this topic can allow physics faculty advisers to help our students so that fewer are derailed on their path to the classroom, or take a path that will leave them less well prepared if they do find themselves there. Examples of different approaches that work within state licensure systems from two different states will be presented. Physics teacher preparation efforts in both Arkansas and West Virginia have been supported in part by the Physics Teacher Education Coalition (PhysTEC).

  4. Self-calibrating common-path interferometry.

    PubMed

    Porras-Aguilar, Rosario; Falaggis, Konstantinos; Ramirez-San-Juan, Julio C; Ramos-Garcia, Ruben

    2015-02-01

    A quantitative phase measuring technique is presented that estimates the object phase from a series of phase shifted interferograms that are obtained in a common-path configuration with unknown phase shifts. The derived random phase shifting algorithm for common-path interferometers is based on the Generalized Phase Contrast theory [pl. Opt.40(2), 268 (2001)10.1063/1.1404846], which accounts for the particular image formation and includes effects that are not present in two-beam interferometry. It is shown experimentally that this technique can be used within common-path configurations employing nonlinear liquid crystal materials as self-induced phase filters for quantitative phase imaging without the need of phase shift calibrations. The advantages of such liquid crystal elements compared to spatial light modulator based solutions are given by the cost-effectiveness, self-alignment, and the generation of diminutive dimensions of the phase filter size, giving unique performance advantages. PMID:25836191

  5. Graphene coatings: An efficient protection from oxidation

    NASA Astrophysics Data System (ADS)

    Topsakal, Mehmet; Sahin, Hasan; Ciraci, Salim

    2012-02-01

    We demonstrate that graphene coating can provide an efficient protection from oxidation by posing a high energy barrier to the path of oxygen atom, which could have penetrated from the top of graphene to the reactive surface underneath. Graphene bilayer, which blocks the diffusion of oxygen with a relatively higher energy barrier provides even better protection from oxidation. While an oxygen molecule is weakly bound to bare graphene surface and hence becomes rather inactive, it can easily dissociates into two oxygen atoms adsorbed to low coordinated carbon atoms at the edges of a vacancy. For these oxygen atoms the oxidation barrier is reduced and hence the protection from oxidation provided by graphene coatings is weakened. Our predictions obtained from the state of the art first-principles calculations of electronic structure, phonon density of states and reaction path will unravel how a graphene can be used as a corrosion resistant coating and guide further studies aiming at developing more efficient nanocoating materials.

  6. 14 CFR 171.267 - Glide path automatic monitor system.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 3 2014-01-01 2014-01-01 false Glide path automatic monitor system. 171... Landing System (ISMLS) § 171.267 Glide path automatic monitor system. (a) The ISMLS glide path equipment... control points when any of the following occurs: (1) A shift of the mean ISMLS glide path angle...

  7. 14 CFR 23.61 - Takeoff flight path.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Takeoff flight path. 23.61 Section 23.61... flight path. For each commuter category airplane, the takeoff flight path must be determined as follows: (a) The takeoff flight path begins 35 feet above the takeoff surface at the end of the...

  8. 14 CFR 23.61 - Takeoff flight path.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Takeoff flight path. 23.61 Section 23.61... flight path. For each commuter category airplane, the takeoff flight path must be determined as follows: (a) The takeoff flight path begins 35 feet above the takeoff surface at the end of the...

  9. 14 CFR 171.267 - Glide path automatic monitor system.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Glide path automatic monitor system. 171... Landing System (ISMLS) § 171.267 Glide path automatic monitor system. (a) The ISMLS glide path equipment... control points when any of the following occurs: (1) A shift of the mean ISMLS glide path angle...

  10. 14 CFR 171.267 - Glide path automatic monitor system.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Glide path automatic monitor system. 171... Landing System (ISMLS) § 171.267 Glide path automatic monitor system. (a) The ISMLS glide path equipment... control points when any of the following occurs: (1) A shift of the mean ISMLS glide path angle...

  11. 14 CFR 171.267 - Glide path automatic monitor system.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 3 2013-01-01 2013-01-01 false Glide path automatic monitor system. 171... Landing System (ISMLS) § 171.267 Glide path automatic monitor system. (a) The ISMLS glide path equipment... control points when any of the following occurs: (1) A shift of the mean ISMLS glide path angle...

  12. 14 CFR 23.61 - Takeoff flight path.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Takeoff flight path. 23.61 Section 23.61... flight path. Link to an amendment published at 76 FR 75753, December 2, 2011. For each commuter category airplane, the takeoff flight path must be determined as follows: (a) The takeoff flight path begins 35...

  13. 14 CFR 171.267 - Glide path automatic monitor system.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 3 2011-01-01 2011-01-01 false Glide path automatic monitor system. 171... Landing System (ISMLS) § 171.267 Glide path automatic monitor system. (a) The ISMLS glide path equipment... control points when any of the following occurs: (1) A shift of the mean ISMLS glide path angle...

  14. An Adaptive Path Planning Algorithm for Cooperating Unmanned Air Vehicles

    SciTech Connect

    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.

  15. Adaptive path planning algorithm for cooperating unmanned air vehicles

    SciTech Connect

    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.

  16. Path Analysis: A Link between Family Theory and Reseach.

    ERIC Educational Resources Information Center

    Rank, Mark R.; Sabatelli, Ronald M.

    This paper discusses path analysis and the applicability of this methodology to the field of family studies. The statistical assumptions made in path analysis are presented along with a description of the two types of models within path analysis, i.e., recursive and non-recursive. Methods of calculating in the path model and the advantages of…

  17. Tornado intensity estimated from damage path dimensions.

    PubMed

    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

  18. Tornado Intensity Estimated from Damage Path Dimensions

    PubMed Central

    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

  19. Which coordinate system for modelling path integration?

    PubMed

    Vickerstaff, Robert J; Cheung, Allen

    2010-03-21

    Path integration is a navigation strategy widely observed in nature where an animal maintains a running estimate, called the home vector, of its location during an excursion. Evidence suggests it is both ancient and ubiquitous in nature, and has been studied for over a century. In that time, canonical and neural network models have flourished, based on a wide range of assumptions, justifications and supporting data. Despite the importance of the phenomenon, consensus and unifying principles appear lacking. A fundamental issue is the neural representation of space needed for biological path integration. This paper presents a scheme to classify path integration systems on the basis of the way the home vector records and updates the spatial relationship between the animal and its home location. Four extended classes of coordinate systems are used to unify and review both canonical and neural network models of path integration, from the arthropod and mammalian literature. This scheme demonstrates analytical equivalence between models which may otherwise appear unrelated, and distinguishes between models which may superficially appear similar. A thorough analysis is carried out of the equational forms of important facets of path integration including updating, steering, searching and systematic errors, using each of the four coordinate systems. The type of available directional cue, namely allothetic or idiothetic, is also considered. It is shown that on balance, the class of home vectors which includes the geocentric Cartesian coordinate system, appears to be the most robust for biological systems. A key conclusion is that deducing computational structure from behavioural data alone will be difficult or impossible, at least in the absence of an analysis of random errors. Consequently it is likely that further theoretical insights into path integration will require an in-depth study of the effect of noise on the four classes of home vectors. PMID:19962387

  20. Overload protection circuit for output driver

    DOEpatents

    Stewart, Roger G.

    1982-05-11

    A protection circuit for preventing excessive power dissipation in an output transistor whose conduction path is connected between a power terminal and an output terminal. The protection circuit includes means for sensing the application of a turn on signal to the output transistor and the voltage at the output terminal. When the turn on signal is maintained for a period of time greater than a given period without the voltage at the output terminal reaching a predetermined value, the protection circuit decreases the turn on signal to, and the current conduction through, the output transistor.

  1. Path planning for everday robotics with SANDROS

    SciTech Connect

    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.

  2. Optical tomography with discretized path integral.

    PubMed

    Yuan, Bingzhi; Tamaki, Toru; Kushida, Takahiro; Mukaigawa, Yasuhiro; Kubo, Hiroyuki; Raytchev, Bisser; Kaneda, Kazufumi

    2015-07-01

    We present a framework for optical tomography based on a path integral. Instead of directly solving the radiative transport equations, which have been widely used in optical tomography, we use a path integral that has been developed for rendering participating media based on the volume rendering equation in computer graphics. For a discretized two-dimensional layered grid, we develop an algorithm to estimate the extinction coefficients of each voxel with an interior point method. Numerical simulation results are shown to demonstrate that the proposed method works well. PMID:26839903

  3. 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.

  4. Practical path planning among movable obstacles

    SciTech Connect

    Chen, Pang C.; Hwang, Yong K.

    1990-09-05

    Path planning among movable obstacles is a practical problem that is in need of a solution. In this paper an efficient heuristic algorithm that uses a generate-and-test paradigm: a good'' candidate path is hypothesized by a global planner and subsequently verified by a local planner. In the process of formalizing the problem, we also present a technique for modeling object interactions through contact. Our algorithm has been tested on a variety of examples, and was able to generate solutions within 10 seconds. 5 figs., 27 refs.

  5. 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.

  6. 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

  7. Lightning Protection

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Kit-built airplanes are more affordable because they are assembled by the owner and do not require Federal Aviation Administration (FAA) certification. The Glasair III, is an advanced technology homebuilt, constructed of a fiberglass and graphite fiber composite material, and equipped with digital instruments. Both technologies make the airplane more susceptible to lightning effects. When Glasair manufacturer, Stoddard-Hamilton, decided that lightning protection would enable more extensive instrument flight and make the plane more marketable, they proposed a joint development program to NASA Langley Research Center (LAR). Under a Small Business Innovation Research (SBIR) contract, Langley contractors designed and tested a lightning protection system, and the Glasair III-LP became the first kit-built composite aircraft to be lightning tested and protection-verified under FAA guidelines for general aviation aircraft.

  8. Lightning Protection

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Lightning Technologies, Inc., Pittsfield, MA, - a spinoff company founded by president J. Anderson Plumer, a former NASA contractor employee who developed his expertise with General Electric Company's High Voltage Laboratory - was a key player in Langley Research Center's Storm Hazards Research Program. Lightning Technologies used its NASA acquired experience to develop protective measures for electronic systems and composite structures on aircraft, both of which are particularly susceptible to lightning damage. The company also provides protection design and verification testing services for complete aircraft systems or individual components. Most aircraft component manufacturers are among Lightning Technologies' clients.

  9. Noise Protection

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Environmental Health Systems puts forth an increasing effort in the U.S. to develop ways of controlling noise, particularly in industrial environments due to Federal and State laws, labor union insistence and new findings relative to noise pollution impact on human health. NASA's Apollo guidance control system aided in the development of a noise protection product, SMART. The basis of all SMART products is SMART compound a liquid plastic mixture with exceptional energy/sound absorbing qualities. The basic compound was later refined for noise protection use.

  10. Corrosion protected reversing heat exchanger

    SciTech Connect

    Zawierucha, R.

    1984-09-25

    A reversing heat exchanger of the plate and fin type having multiple aluminum parting sheets in a stacked arrangement with corrugated fins separating the sheets to form multiple flow paths, means for closing the ends of the sheets, an input manifold arrangement of headers for the warm end of of the exchanger and an output manifold arrangement for the cold end of the exchanger with the input air feed stream header and the waste gas exhaust header having an alloy of zinc and aluminum coated on the inside surface for providing corrosion protection to the stack.

  11. Finding the optimal-path maps for path planning across weighted regions

    SciTech Connect

    Rowe, N.C.; Alexander, R.S.

    2000-02-01

    Optimal-path maps tell robots or people the best way to reach a goal point from anywhere in a known terrain area, eliminating most of the need to plan during travel. The authors address the construction of optimal-path maps for two-dimensional polygonal weighted-region terrain, terrain partitioned into polygonal areas such that the cost per unit of distance traveled is homogeneous and isotropic within each area. This is useful for overland route planning across varied ground surfaces and vegetation. The authors propose a new algorithm that recursively partitions terrain into regions of similar optimal-path behavior, and defines corresponding path subspaces for these regions. This process constructs a piecewise-smooth function of terrain position whose gradient direction is everywhere the optimal-path direction, permitting quick path finding. The algorithm used is more complicated than the current path-caching and wavefront-propagation algorithms, but it gives more accurate maps requiring less space to represent. Experiments with an implementation confirm the practicality of the authors' algorithm.

  12. Folded-path optical analysis gas cell

    DOEpatents

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

    1995-08-08

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

  13. Ambivalent Journey: Teacher Career Paths in Oman

    ERIC Educational Resources Information Center

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

    2012-01-01

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

  14. A Critical Path Analysis of Scientific Productivity.

    ERIC Educational Resources Information Center

    Loehle, Craig

    1994-01-01

    This article presents a queuing model simulation of scientific productivity utilizing critical path analysis. Creativity is found to have a large positive effect, a negative effect, or no effect on productivity, depending on the stage of the problem-solving process to which it is applied and the nature of the bottlenecks inherent to the specific…

  15. 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.

  16. Administrator Career Paths and Decision Processes

    ERIC Educational Resources Information Center

    Farley-Ripple, Elizabeth N.; Raffel, Jeffrey A.; Welch, Jennie Christine

    2012-01-01

    Purpose: The purpose of this paper is to present qualitative evidence on the processes and forces that shape school administrator career paths. Design/methodology/approach: An embedded case study approach is used to understand more than 100 administrator career transitions within the Delaware education system. Semi-structured interview data were…

  17. Learning to improve path planning performance

    SciTech Connect

    Chen, Pang C.

    1995-04-01

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

  18. Visualizing Transmedia Networks: Links, Paths and Peripheries

    ERIC Educational Resources Information Center

    Ruppel, Marc Nathaniel

    2012-01-01

    'Visualizing Transmedia Networks: Links, Paths and Peripheries' examines the increasingly complex rhetorical intersections between narrative and media ("old" and "new") in the creation of transmedia fictions, loosely defined as multisensory and multimodal stories told extensively across a diverse media set. In order…

  19. Gender Differences in Career Paths in Banking.

    ERIC Educational Resources Information Center

    Morgan, Sandra; And Others

    1993-01-01

    Analyzed career paths of middle managers in bank. Study of matched pairs found that men (n=25) advanced faster and reached middle management through fewer promotions and positions than did women (n=25). Men had significantly more work experience outside of banking. In banking careers, men held more jobs in lending, whereas women occupied more…

  20. 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.

  1. 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.

  2. Folded-path optical analysis gas cell

    DOEpatents

    Carangelo, Robert M.; Wright, David D.

    1995-01-01

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

  3. Path integral method for DNA denaturation

    NASA Astrophysics Data System (ADS)

    Zoli, Marco

    2009-04-01

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

  4. Local-time representation of path integrals.

    PubMed

    Jizba, Petr; Zatloukal, Václav

    2015-12-01

    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. PMID:26764662

  5. Motion on Cycloid Paths: A Project

    ERIC Educational Resources Information Center

    Gluck, P.

    2010-01-01

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

  6. Explore the Many Paths to Leadership

    ERIC Educational Resources Information Center

    Crow, Tracy

    2015-01-01

    The road to leadership is not necessarily one that educators plan carefully with a series of logical steps. Certainly some educators start as teachers and then systematically work through a traditional hierarchy on their way to the superintendency. No matter their role or their path, education leaders demand more from themselves and others and…

  7. An Introduction to Career Path Employability Profiles.

    ERIC Educational Resources Information Center

    Alvir, Howard P.

    An employability profile specifies employment opportunities for which an individual is qualified. A career path is the term applied to an employability profile that combines both the career ladder aspect of advancement and the career lattice element of wide selection. After a descriptive analysis of typical employability profiles, this document…

  8. Extremal paths on a random Cayley tree

    NASA Astrophysics Data System (ADS)

    Majumdar, Satya N.; Krapivsky, P. L.

    2000-12-01

    We investigate the statistics of extremal path(s) (both the shortest and the longest) from the root to the bottom of a Cayley tree. The lengths of the edges are assumed to be independent identically distributed random variables drawn from a distribution ρ(l). Besides, the number of branches from any node is also random. Exact results are derived for arbitrary distribution ρ(l). In particular, for the binary \\{0,1\\} distribution ρ(l)=pδl,1+(1-p)δl,0, we show that as p increases, the minimal length undergoes an unbinding transition from a ``localized'' phase to a ``moving'' phase at the critical value, p=pc=1-b-1, where b is the average branch number of the tree. As the height n of the tree increases, the minimal length saturates to a finite constant in the localized phase (ppc) where the velocity vmin(p) is determined via a front selection mechanism. At p=pc, the minimal length grows with n in an extremely slow double-logarithmic fashion. The length of the maximal path, on the other hand, increases linearly as vmax(p)n for all p. The maximal and minimal velocities satisfy a general duality relation, vmin(p)+vmax(1-p)=1, which is also valid for directed paths on finite-dimensional lattices.

  9. Path to Scholarships: "Making Dreams Come True."

    ERIC Educational Resources Information Center

    McBride, June

    This easy-to-read book with worksheets and instructional guides details a simple organizational portfolio method that has been used for over 6 years to obtain over one-half million dollars in scholarships for migrant students. Following an introduction, chapter 2, "Path of Hard Work," discusses scholarship qualifications such as a 3.0 grade point…

  10. Planning Flight Paths of Autonomous Aerobots

    NASA Technical Reports Server (NTRS)

    Kulczycki, Eric; Elfes, Alberto; Sharma, Shivanjli

    2009-01-01

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

  11. 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.

  12. The Erratic Path of Hungarian Higher Education

    ERIC Educational Resources Information Center

    Marcus, Jon

    2014-01-01

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

  13. Current SPE Hydrodynamic Modeling and Path Forward

    SciTech Connect

    Knight, Earl E.; Rougier, Esteban

    2012-08-14

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

  14. Behavioral Path Analysis and Environmental Evaluation.

    ERIC Educational Resources Information Center

    Wise, James A.; Kahle, Ellen

    Behavioral Path Analysis is both a theory and a methodology for studying person-environment interactions. It is designed to be applicable to the evaluation of both environments in use and proposed designed environments. This paper presents the basics of the theory, and some examples of recent applications that have guided its development. The…

  15. Career Paths for Managers in the Arts

    ERIC Educational Resources Information Center

    Inglis, Loretta; Cray, David

    2012-01-01

    In this article we examine the career paths of top-level managers in the arts. By analysing the training and work history of 23 managers in a variety of arts organisations we evaluate the utility of several existing theories for understanding careers that are characterised by low levels of initial knowledge, the absence of a clear method of entry…

  16. Judgments of Path, Not Heading, Guide Locomotion

    ERIC Educational Resources Information Center

    Wilkie, Richard M.; Wann, John P.

    2006-01-01

    To steer a course through the world, people are almost entirely dependent on visual information, of which a key component is optic flow. In many models of locomotion, heading is described as the fundamental control variable; however, it has also been shown that fixating points along or near one's future path could be the basis of an efficient…

  17. Protective Clothing

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Beta Glass material, originating from the Apollo program is supplied to Fyrepel by Owens-Corning and incorporated into Fyrepel's Fyretex and Beta-Mex aluminized fabrics. Fabrics are used in fire entry suits, several other types of protective suits for wear in hot industrial environments and such accessory items as heat-reflecting curtains for industrial applications.

  18. Protect thyself

    SciTech Connect

    Sullivan, A.M.

    1982-06-01

    The article considers items of personal protection for miners: Self-rescuers, respirators, hard hats and cap lamps. A table provides a comparison between five types of self-contained self-rescuer. Details are also given of hard hat cap lamp and respirator manufacturers.

  19. Protecting Privacy.

    ERIC Educational Resources Information Center

    Coyle, Karen

    2001-01-01

    Discusses privacy issues related to use of the Internet. Topics include data gathering functions that are built into applications of the World Wide Web; cookies that identify Web site visitors; personal identity information; libraries and privacy, including the need for privacy policies; protecting your privacy; and developing privacy literacy.…

  20. Measuring Phonon Mean Free Path Distributions by Probing Quasiballistic Phonon Transport in Grating Nanostructures

    NASA Astrophysics Data System (ADS)

    Zeng, Lingping; Collins, Kimberlee C.; Hu, Yongjie; Luckyanova, Maria N.; Maznev, Alexei A.; Huberman, Samuel; Chiloyan, Vazrik; Zhou, Jiawei; Huang, Xiaopeng; Nelson, Keith A.; Chen, Gang

    2015-11-01

    Heat conduction in semiconductors and dielectrics depends upon their phonon mean free paths that describe the average travelling distance between two consecutive phonon scattering events. Nondiffusive phonon transport is being exploited to extract phonon mean free path distributions. Here, we describe an implementation of a nanoscale thermal conductivity spectroscopy technique that allows for the study of mean free path distributions in optically absorbing materials with relatively simple fabrication and a straightforward analysis scheme. We pattern 1D metallic grating of various line widths but fixed gap size on sample surfaces. The metal lines serve as both heaters and thermometers in time-domain thermoreflectance measurements and simultaneously act as wire-grid polarizers that protect the underlying substrate from direct optical excitation and heating. We demonstrate the viability of this technique by studying length-dependent thermal conductivities of silicon at various temperatures. The thermal conductivities measured with different metal line widths are analyzed using suppression functions calculated from the Boltzmann transport equation to extract the phonon mean free path distributions with no calibration required. This table-top ultrafast thermal transport spectroscopy technique enables the study of mean free path spectra in a wide range of technologically important materials.

  1. Measuring Phonon Mean Free Path Distributions by Probing Quasiballistic Phonon Transport in Grating Nanostructures.

    PubMed

    Zeng, Lingping; Collins, Kimberlee C; Hu, Yongjie; Luckyanova, Maria N; Maznev, Alexei A; Huberman, Samuel; Chiloyan, Vazrik; Zhou, Jiawei; Huang, Xiaopeng; Nelson, Keith A; Chen, Gang

    2015-01-01

    Heat conduction in semiconductors and dielectrics depends upon their phonon mean free paths that describe the average travelling distance between two consecutive phonon scattering events. Nondiffusive phonon transport is being exploited to extract phonon mean free path distributions. Here, we describe an implementation of a nanoscale thermal conductivity spectroscopy technique that allows for the study of mean free path distributions in optically absorbing materials with relatively simple fabrication and a straightforward analysis scheme. We pattern 1D metallic grating of various line widths but fixed gap size on sample surfaces. The metal lines serve as both heaters and thermometers in time-domain thermoreflectance measurements and simultaneously act as wire-grid polarizers that protect the underlying substrate from direct optical excitation and heating. We demonstrate the viability of this technique by studying length-dependent thermal conductivities of silicon at various temperatures. The thermal conductivities measured with different metal line widths are analyzed using suppression functions calculated from the Boltzmann transport equation to extract the phonon mean free path distributions with no calibration required. This table-top ultrafast thermal transport spectroscopy technique enables the study of mean free path spectra in a wide range of technologically important materials. PMID:26612032

  2. TUMOR CONTAMINATION IN THE BIOPSY PATH OF PRIMARY MALIGNANT BONE TUMORS

    PubMed Central

    Oliveira, Marcelo Parente; Lima, Pablo Moura de Andrade; de Mello, Roberto José Vieira

    2015-01-01

    Objective: To study factors possibly associated with tumor contamination in the biopsy path of primary malignant bone tumors. Method: Thirty-five patients who underwent surgical treatment with diagnoses of osteosarcoma, Ewing's tumor and chondrosarcoma were studied retrospectively. The sample was analyzed to characterize the biopsy technique used, histological type of the tumor, neoadjuvant chemotherapy used, local recurrences and tumor contamination in the biopsy path. Results: Among the 35 patients studied, four cases of contamination occurred (11.43%): one from osteosarcoma, two from Ewing's tumor and one from chondrosarcoma. There was no association between the type of tumor and presence of tumor contamination in the biopsy path (p = 0.65). There was also no association between the presence of tumor contamination and the biopsy technique (p = 0.06). On the other hand, there were associations between the presence of tumor contamination and local recurrence (p = 0.01) and between tumor contamination and absence of neoadjuvant chemotherapy (p = 0.02). Conclusion: Tumor contamination in the biopsy path of primary malignant bone tumors was associated with local recurrence. On the other hand, the histological type of the tumor and the type of biopsy did not have an influence on tumor contamination. Neoadjuvant chemotherapy had a protective effect against this complication. Despite these findings, tumor contamination is a complication that should always be taken into consideration, and removal of the biopsy path is recommended in tumor resection surgery. PMID:27047877

  3. Measuring phonon mean free path distributions by probing quasiballistic phonon transport in grating nanostructures

    DOE PAGESBeta

    Zeng, Lingping; Collins, Kimberlee C.; Hu, Yongjie; Luckyanova, Maria N.; Maznev, Alexei A.; Huberman, Samuel; Chiloyan, Vazrik; Zhou, Jiawei; Huang, Xiaopeng; Nelson, Keith A.; et al

    2015-11-27

    Heat conduction in semiconductors and dielectrics depends upon their phonon mean free paths that describe the average travelling distance between two consecutive phonon scattering events. Nondiffusive phonon transport is being exploited to extract phonon mean free path distributions. Here, we describe an implementation of a nanoscale thermal conductivity spectroscopy technique that allows for the study of mean free path distributions in optically absorbing materials with relatively simple fabrication and a straightforward analysis scheme. We pattern 1D metallic grating of various line widths but fixed gap size on sample surfaces. The metal lines serve as both heaters and thermometers in time-domainmore » thermoreflectance measurements and simultaneously act as wiregrid polarizers that protect the underlying substrate from direct optical excitation and heating. We demonstrate the viability of this technique by studying length-dependent thermal conductivities of silicon at various temperatures. The thermal conductivities measured with different metal line widths are analyzed using suppression functions calculated from the Boltzmann transport equation to extract the phonon mean free path distributions with no calibration required. Furthermore, this table-top ultrafast thermal transport spectroscopy technique enables the study of mean free path spectra in a wide range of technologically important materials.« less

  4. Measuring Phonon Mean Free Path Distributions by Probing Quasiballistic Phonon Transport in Grating Nanostructures

    PubMed Central

    Zeng, Lingping; Collins, Kimberlee C.; Hu, Yongjie; Luckyanova, Maria N.; Maznev, Alexei A.; Huberman, Samuel; Chiloyan, Vazrik; Zhou, Jiawei; Huang, Xiaopeng; Nelson, Keith A.; Chen, Gang

    2015-01-01

    Heat conduction in semiconductors and dielectrics depends upon their phonon mean free paths that describe the average travelling distance between two consecutive phonon scattering events. Nondiffusive phonon transport is being exploited to extract phonon mean free path distributions. Here, we describe an implementation of a nanoscale thermal conductivity spectroscopy technique that allows for the study of mean free path distributions in optically absorbing materials with relatively simple fabrication and a straightforward analysis scheme. We pattern 1D metallic grating of various line widths but fixed gap size on sample surfaces. The metal lines serve as both heaters and thermometers in time-domain thermoreflectance measurements and simultaneously act as wire-grid polarizers that protect the underlying substrate from direct optical excitation and heating. We demonstrate the viability of this technique by studying length-dependent thermal conductivities of silicon at various temperatures. The thermal conductivities measured with different metal line widths are analyzed using suppression functions calculated from the Boltzmann transport equation to extract the phonon mean free path distributions with no calibration required. This table-top ultrafast thermal transport spectroscopy technique enables the study of mean free path spectra in a wide range of technologically important materials. PMID:26612032

  5. Measuring phonon mean free path distributions by probing quasiballistic phonon transport in grating nanostructures

    SciTech Connect

    Zeng, Lingping; Collins, Kimberlee C.; Hu, Yongjie; Luckyanova, Maria N.; Maznev, Alexei A.; Huberman, Samuel; Chiloyan, Vazrik; Zhou, Jiawei; Huang, Xiaopeng; Nelson, Keith A.; Chen, Gang

    2015-11-27

    Heat conduction in semiconductors and dielectrics depends upon their phonon mean free paths that describe the average travelling distance between two consecutive phonon scattering events. Nondiffusive phonon transport is being exploited to extract phonon mean free path distributions. Here, we describe an implementation of a nanoscale thermal conductivity spectroscopy technique that allows for the study of mean free path distributions in optically absorbing materials with relatively simple fabrication and a straightforward analysis scheme. We pattern 1D metallic grating of various line widths but fixed gap size on sample surfaces. The metal lines serve as both heaters and thermometers in time-domain thermoreflectance measurements and simultaneously act as wiregrid polarizers that protect the underlying substrate from direct optical excitation and heating. We demonstrate the viability of this technique by studying length-dependent thermal conductivities of silicon at various temperatures. The thermal conductivities measured with different metal line widths are analyzed using suppression functions calculated from the Boltzmann transport equation to extract the phonon mean free path distributions with no calibration required. Furthermore, this table-top ultrafast thermal transport spectroscopy technique enables the study of mean free path spectra in a wide range of technologically important materials.

  6. Three-Dimensional Path Planning and Guidance of Leg Vascular Based on Improved Ant Colony Algorithm in Augmented Reality.

    PubMed

    Gao, Ming-ke; Chen, Yi-min; Liu, Quan; Huang, Chen; Li, Ze-yu; Zhang, Dian-hua

    2015-11-01

    Preoperative path planning plays a critical role in vascular access surgery. Vascular access surgery has superior difficulties and requires long training periods as well as precise operation. Yet doctors are on different leves, thus bulky size of blood vessels is usually chosen to undergo surgery and other possible optimal path is not considered. Moreover, patients and surgeons will suffer from X-ray radiation during the surgical procedure. The study proposed an improved ant colony algorithm to plan a vascular optimal three-dimensional path with overall consideration of factors such as catheter diameter, vascular length, diameter as well as the curvature and torsion. To protect the doctor and patient from exposing to X-ray long-term, the paper adopted augmented reality technology to register the reconstructed vascular model and physical model meanwhile, locate catheter by the electromagnetic tracking system and used Head Mounted Display to show the planning path in real time and monitor catheter push procedure. The experiment manifests reasonableness of preoperative path planning and proves the reliability of the algorithm. The augmented reality experiment real time and accurately displays the vascular phantom model, planning path and the catheter trajectory and proves the feasibility of this method. The paper presented a useful and feasible surgical scheme which was based on the improved ant colony algorithm to plan vascular three-dimensional path in augmented reality. The study possessed practical guiding significance in preoperative path planning, intraoperative catheter guiding and surgical training, which provided a theoretical method of path planning for vascular access surgery. It was a safe and reliable path planning approach and possessed practical reference value. PMID:26319273

  7. Global path planning of mobile robots using a memetic algorithm

    NASA Astrophysics Data System (ADS)

    Zhu, Zexuan; Wang, Fangxiao; He, Shan; Sun, Yiwen

    2015-08-01

    In this paper, a memetic algorithm for global path planning (MAGPP) of mobile robots is proposed. MAGPP is a synergy of genetic algorithm (GA) based global path planning and a local path refinement. Particularly, candidate path solutions are represented as GA individuals and evolved with evolutionary operators. In each GA generation, the local path refinement is applied to the GA individuals to rectify and improve the paths encoded. MAGPP is characterised by a flexible path encoding scheme, which is introduced to encode the obstacles bypassed by a path. Both path length and smoothness are considered as fitness evaluation criteria. MAGPP is tested on simulated maps and compared with other counterpart algorithms. The experimental results demonstrate the efficiency of MAGPP and it is shown to obtain better solutions than the other compared algorithms.

  8. 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.

  9. Protective Coating

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Inorganic Coatings, Inc.'s K-Zinc 531 protective coating is water-based non-toxic, non-flammable and has no organic emissions. High ratio silicate formula bonds to steel, and in 30 minutes, creates a very hard ceramic finish with superior adhesion and abrasion resistance. Improved technology allows application over a minimal commercial sandblast, fast drying in high humidity conditions and compatibility with both solvent and water-based topcoats. Coating is easy to apply and provides long term protection with a single application. Zinc rich coating with water-based potassium silicate binder offers cost advantages in materials, labor hours per application, and fewer applications over a given time span.

  10. Arena geometry and path shape: when rats travel in straight or in circuitous paths?

    PubMed

    Yaski, Osnat; Portugali, Juval; Eilam, David

    2011-12-01

    We show here that the global geometry of the environment affects the shape of the paths of travel in rats. To examine this, individual rats were introduced into an unfamiliar arena. One group of rats (n=8) was tested in a square arena (2 m × 2 m), and the other group (n=8) in a round arena (2 m diameter). Testing was in a total darkness, since in the absence of visual information the geometry is not perceived immediately and the extraction of environment shape is slower. We found that while the level of the rats' activity did not seem to differ between both arenas, path shape differed significantly. When traveling along the perimeter, path shape basically followed the arena walls, with perimeter paths curving along the walls of the round arena, while being straight along the walls of the square arena. A similar impact of arena geometry was observed for travel away from the arena walls. Indeed, when the rats abandoned the arena walls to crosscut through the center of the arena, their center paths were circuitous in the round arena and relatively straight in the square arena. We suggest that the shapes of these paths are exploited for the same spatial task: returning back to a familiar location in the unsighted environment. PMID:21840341

  11. Paths in the minimally weighted path model are incompatible with Schramm-Loewner evolution

    NASA Astrophysics Data System (ADS)

    Norrenbrock, C.; Melchert, O.; Hartmann, A. K.

    2013-03-01

    We study numerically the geometrical properties of minimally weighted paths that appear in the minimally weighted path (MWP) model on two-dimensional lattices assuming a combination of periodic and free boundary conditions (BCs). Each realization of the disorder consists of a random fraction (1-ρ) of bonds with unit strength and a fraction ρ of bond strengths drawn from a Gaussian distribution with zero mean and unit width. For each such sample, a path is forced to span the lattice along the direction with the free BCs. The path and a set of negatively weighted loops form a ground state. A ground state on such a lattice can be determined performing a nontrivial transformation of the original graph and applying sophisticated matching algorithms. Here we examine whether the geometrical properties of the paths are in accordance with the predictions of the Schramm-Loewner evolution (SLE). Measuring the fractal dimension, considering the winding angle statistics, and reviewing Schramm's left passage formula indicate that the paths cannot be described in terms of SLE.

  12. A whole-path importance-sampling scheme for Feynman path integral calculations of absolute partition functions and free energies.

    PubMed

    Mielke, Steven L; Truhlar, Donald G

    2016-01-21

    Using Feynman path integrals, a molecular partition function can be written as a double integral with the inner integral involving all closed paths centered at a given molecular configuration, and the outer integral involving all possible molecular configurations. In previous work employing Monte Carlo methods to evaluate such partition functions, we presented schemes for importance sampling and stratification in the molecular configurations that constitute the path centroids, but we relied on free-particle paths for sampling the path integrals. At low temperatures, the path sampling is expensive because the paths can travel far from the centroid configuration. We now present a scheme for importance sampling of whole Feynman paths based on harmonic information from an instantaneous normal mode calculation at the centroid configuration, which we refer to as harmonically guided whole-path importance sampling (WPIS). We obtain paths conforming to our chosen importance function by rejection sampling from a distribution of free-particle paths. Sample calculations on CH4 demonstrate that at a temperature of 200 K, about 99.9% of the free-particle paths can be rejected without integration, and at 300 K, about 98% can be rejected. We also show that it is typically possible to reduce the overhead associated with the WPIS scheme by sampling the paths using a significantly lower-order path discretization than that which is needed to converge the partition function. PMID:26801023

  13. A whole-path importance-sampling scheme for Feynman path integral calculations of absolute partition functions and free energies

    NASA Astrophysics Data System (ADS)

    Mielke, Steven L.; Truhlar, Donald G.

    2016-01-01

    Using Feynman path integrals, a molecular partition function can be written as a double integral with the inner integral involving all closed paths centered at a given molecular configuration, and the outer integral involving all possible molecular configurations. In previous work employing Monte Carlo methods to evaluate such partition functions, we presented schemes for importance sampling and stratification in the molecular configurations that constitute the path centroids, but we relied on free-particle paths for sampling the path integrals. At low temperatures, the path sampling is expensive because the paths can travel far from the centroid configuration. We now present a scheme for importance sampling of whole Feynman paths based on harmonic information from an instantaneous normal mode calculation at the centroid configuration, which we refer to as harmonically guided whole-path importance sampling (WPIS). We obtain paths conforming to our chosen importance function by rejection sampling from a distribution of free-particle paths. Sample calculations on CH4 demonstrate that at a temperature of 200 K, about 99.9% of the free-particle paths can be rejected without integration, and at 300 K, about 98% can be rejected. We also show that it is typically possible to reduce the overhead associated with the WPIS scheme by sampling the paths using a significantly lower-order path discretization than that which is needed to converge the partition function.

  14. Adaptive path planning for flexible manufacturing

    SciTech Connect

    Chen, Pang C.

    1994-08-01

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

  15. Degenerate optimal paths in thermally isolated systems

    NASA Astrophysics Data System (ADS)

    Acconcia, Thiago V.; Bonança, Marcus V. S.

    2015-04-01

    We present an analysis of the work performed on a system of interest that is kept thermally isolated during the switching of a control parameter. We show that there exists, for a certain class of systems, a finite-time family of switching protocols for which the work is equal to the quasistatic value. These optimal paths are obtained within linear response for systems initially prepared in a canonical distribution. According to our approach, such protocols are composed of a linear part plus a function which is odd with respect to time reversal. For systems with one degree of freedom, we claim that these optimal paths may also lead to the conservation of the corresponding adiabatic invariant. This points to an interesting connection between work and the conservation of the volume enclosed by the energy shell. To illustrate our findings, we solve analytically the harmonic oscillator and present numerical results for certain anharmonic examples.

  16. Hamiltonian formalism and path entropy maximization

    NASA Astrophysics Data System (ADS)

    Davis, Sergio; González, Diego

    2015-10-01

    Maximization of the path information entropy is a clear prescription for constructing models in non-equilibrium statistical mechanics. Here it is shown that, following this prescription under the assumption of arbitrary instantaneous constraints on position and velocity, a Lagrangian emerges which determines the most probable trajectory. Deviations from the probability maximum can be consistently described as slices in time by a Hamiltonian, according to a nonlinear Langevin equation and its associated Fokker-Planck equation. The connections unveiled between the maximization of path entropy and the Langevin/Fokker-Planck equations imply that missing information about the phase space coordinate never decreases in time, a purely information-theoretical version of the second law of thermodynamics. All of these results are independent of any physical assumptions, and thus valid for any generalized coordinate as a function of time, or any other parameter. This reinforces the view that the second law is a fundamental property of plausible inference.

  17. A path model of aircraft noise annoyance

    NASA Astrophysics Data System (ADS)

    Taylor, S. M.

    1984-09-01

    This paper describes the development and testing of a path model of aircraft noise annoyance by using noise and social survey data collected in the vicinity of Toronto International Airport. Path analysis is used to estimate the direct and indirect effects of seventeen independent variables on individual annoyance. The results show that the strongest direct effects are for speech interference, attitudes toward aircraft operations, sleep interruption and personal sensitivity to noise. The strongest indirect effects are for aircraft Leq(24) and sensitivity. Overall the model explains 41 percent of the variation in the annoyance reported by the 673 survey respondents. The findings both support and extend existing statements in the literature on the antecedents of annoyance.

  18. Path integral learning of multidimensional movement trajectories

    NASA Astrophysics Data System (ADS)

    André, João; Santos, Cristina; Costa, Lino

    2013-10-01

    This paper explores the use of Path Integral Methods, particularly several variants of the recent Path Integral Policy Improvement (PI2) algorithm in multidimensional movement parametrized policy learning. We rely on Dynamic Movement Primitives (DMPs) to codify discrete and rhythmic trajectories, and apply the PI2-CMA and PIBB methods in the learning of optimal policy parameters, according to different cost functions that inherently encode movement objectives. Additionally we merge both of these variants and propose the PIBB-CMA algorithm, comparing all of them with the vanilla version of PI2. From the obtained results we conclude that PIBB-CMA surpasses all other methods in terms of convergence speed and iterative final cost, which leads to an increased interest in its application to more complex robotic problems.

  19. Manipulator path planning in 3-dimensional space

    NASA Astrophysics Data System (ADS)

    Pavlov, Dmitry A.

    2006-04-01

    Present paper is aimed to work out efficient algorithm of multi-chain manipulator path planning in 3D space with static polygonal obstacles. The resulting solution is based on navigational maps approach. Using this approach, manipulator features are considered as intellectual agent, and reachability information is stored in compact form. This enables fast adaptation to arbitrary parameters of manipulator and workspace. The paper describes two algorithms: (i) a local walkthrough with obstacle avoidance, and (ii) incremental navigational map building, performed at running stage. Both algorithms take an extensive use of the specific features of the task. Working simultaneously, they allow real-time manipulator path planning, as well as self-learning in idle mode. Algorithms are implemented as a demonstration program.

  20. Broadband Phase Spectroscopy over Turbulent Air Paths

    NASA Astrophysics Data System (ADS)

    Giorgetta, Fabrizio R.; Rieker, Gregory B.; Baumann, Esther; Swann, William C.; Sinclair, Laura C.; Kofler, Jon; Coddington, Ian; Newbury, Nathan R.

    2015-09-01

    Broadband atmospheric phase spectra are acquired with a phase-sensitive dual-frequency-comb spectrometer by implementing adaptive compensation for the strong decoherence from atmospheric turbulence. The compensation is possible due to the pistonlike behavior of turbulence across a single spatial-mode path combined with the intrinsic frequency stability and high sampling speed associated with dual-comb spectroscopy. The atmospheric phase spectrum is measured across 2 km of air at each of the 70 000 comb teeth spanning 233 cm-1 across hundreds of near-infrared rovibrational resonances of CO2 , CH4 , and H2O with submilliradian uncertainty, corresponding to a 10-13 refractive index sensitivity. Trace gas concentrations extracted directly from the phase spectrum reach 0.7 ppm uncertainty, demonstrated here for CO2 . While conventional broadband spectroscopy only measures intensity absorption, this approach enables measurement of the full complex susceptibility even in practical open path sensing.

  1. Laser-reactive protection of spacecraft from fine debris

    SciTech Connect

    Kuznetsov, L I; Savichev, V Yu; Tikhonov, N N

    1998-04-30

    An analysis is made of the optimal conditions for laser irradiation and of typical paths of man-made debris in laser-reactive protection of spacecraft. Protection is provided by the recoil momentum resulting from laser evaporation of the surface layers of a debris particle, which can change its path, thus avoiding an collision with a spacecraft. Estimates are obtained of changes in the paths of particles with a characteristic size 1 cm when they are irradiated by radiation from a laser located on the protected spacecraft moving along one of the circular orbits at altitudes of 200, 400, or 700 km above the Earth's surface. (laser applications and other topics in quantum electronics)

  2. Evolutionary software for autonomous path planning

    SciTech Connect

    Couture, S; Hage, M

    1999-02-10

    This research project demonstrated the effectiveness of using evolutionary software techniques in the development of path-planning algorithms and control programs for mobile vehicles in radioactive environments. The goal was to take maximum advantage of the programmer's intelligence by tasking the programmer with encoding the measures of success for a path-planning algorithm, rather than developing the path-planning algorithms themselves. Evolutionary software development techniques could then be used to develop algorithms most suitable to the particular environments of interest. The measures of path-planning success were encoded in the form of a fitness function for an evolutionary software development engine. The task for the evolutionary software development engine was to evaluate the performance of individual algorithms, select the best performers for the population based on the fitness function, and breed them to evolve the next generation of algorithms. The process continued for a set number of generations or until the algorithm converged to an optimal solution. The task environment was the navigation of a rover from an initial location to a goal, then to a processing point, in an environment containing physical and radioactive obstacles. Genetic algorithms were developed for a variety of environmental configurations. Algorithms were simple and non-robust strings of behaviors, but they could be evolved to be nearly optimal for a given environment. In addition, a genetic program was evolved in the form of a control algorithm that operates at every motion of the robot. Programs were more complex than algorithms and less optimal in a given environment. However, after training in a variety of different environments, they were more robust and could perform acceptably in environments they were not trained in. This paper describes the evolutionary software development engine and the performance of algorithms and programs evolved by it for the chosen task.

  3. Quantitative Molecular Thermochemistry Based on Path Integrals

    SciTech Connect

    Glaesemann, K R; Fried, L E

    2005-03-14

    The calculation of thermochemical data requires accurate molecular energies and heat capacities. Traditional methods rely upon the standard harmonic normal mode analysis to calculate the vibrational and rotational contributions. We utilize path integral Monte Carlo (PIMC) for going beyond the harmonic analysis, to calculate the vibrational and rotational contributions to ab initio energies. This is an application and extension of a method previously developed in our group.

  4. Vertical flight path steering system for aircraft

    NASA Technical Reports Server (NTRS)

    Lambregts, Antonius A. (Inventor)

    1983-01-01

    Disclosed is a vertical flight path angle steering system for aircraft, utilizing a digital flight control computer which processes pilot control inputs and aircraft response parameters into suitable elevator commands and control information for display to the pilot on a cathode ray tube. The system yields desirable airplane control handling qualities and responses as well as improvements in pilot workload and safety during airplane operation in the terminal area and under windshear conditions.

  5. Fractional Levy motion through path integrals

    SciTech Connect

    Calvo, Ivan; Sanchez, Raul; Carreras, Benjamin A

    2009-01-01

    Fractional Levy motion (fLm) is the natural generalization of fractional Brownian motion in the context of self-similar stochastic processes and stable probability distributions. In this paper we give an explicit derivation of the propagator of fLm by using path integral methods. The propagators of Brownian motion and fractional Brownian motion are recovered as particular cases. The fractional diffusion equation corresponding to fLm is also obtained.

  6. Do-It-Yourself Critical Path Method.

    ERIC Educational Resources Information Center

    Morris, Edward P., Jr.

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

  7. Flux Control in Networks of Diffusion Paths

    SciTech Connect

    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.

  8. Adaptive path planning: Algorithm and analysis

    SciTech Connect

    Chen, Pang C.

    1995-03-01

    To address the need for a fast path planner, we present a learning algorithm that improves path planning by using past experience to enhance future performance. The algorithm relies on an existing path planner to provide solutions difficult tasks. From these solutions, an evolving sparse work of useful robot configurations is learned to support faster planning. More generally, the algorithm provides a framework in which a slow but effective planner may be improved both cost-wise and capability-wise by a faster but less effective planner coupled with experience. We analyze algorithm by formalizing the concept of improvability and deriving conditions under which a planner can be improved within the framework. The analysis is based on two stochastic models, one pessimistic (on task complexity), the other randomized (on experience utility). Using these models, we derive quantitative bounds to predict the learning behavior. We use these estimation tools to characterize the situations in which the algorithm is useful and to provide bounds on the training time. In particular, we show how to predict the maximum achievable speedup. Additionally, our analysis techniques are elementary and should be useful for studying other types of probabilistic learning as well.

  9. Optimum flight paths of turbojet aircraft

    NASA Technical Reports Server (NTRS)

    Miele, Angelo

    1955-01-01

    The climb of turbojet aircraft is analyzed and discussed including the accelerations. Three particular flight performances are examined: minimum time of climb, climb with minimum fuel consumption, and steepest climb. The theoretical results obtained from a previous study are put in a form that is suitable for application on the following simplifying assumptions: the Mach number is considered an independent variable instead of the velocity; the variations of the airplane mass due to fuel consumption are disregarded; the airplane polar is assumed to be parabolic; the path curvatures and the squares of the path angles are disregarded in the projection of the equation of motion on the normal to the path; lastly, an ideal turbojet with performance independent of the velocity is involved. The optimum Mach number for each flight condition is obtained from the solution of a sixth order equation in which the coefficients are functions of two fundamental parameters: the ratio of minimum drag in level flight to the thrust and the Mach number which represents the flight at constant altitude and maximum lift-drag ratio.

  10. Path Models of Vocal Emotion Communication.

    PubMed

    Bänziger, Tanja; Hosoya, Georg; Scherer, Klaus R

    2015-01-01

    We propose to use a comprehensive path model of vocal emotion communication, encompassing encoding, transmission, and decoding processes, to empirically model data sets on emotion expression and recognition. The utility of the approach is demonstrated for two data sets from two different cultures and languages, based on corpora of vocal emotion enactment by professional actors and emotion inference by naïve listeners. Lens model equations, hierarchical regression, and multivariate path analysis are used to compare the relative contributions of objectively measured acoustic cues in the enacted expressions and subjective voice cues as perceived by listeners to the variance in emotion inference from vocal expressions for four emotion families (fear, anger, happiness, and sadness). While the results confirm the central role of arousal in vocal emotion communication, the utility of applying an extended path modeling framework is demonstrated by the identification of unique combinations of distal cues and proximal percepts carrying information about specific emotion families, independent of arousal. The statistical models generated show that more sophisticated acoustic parameters need to be developed to explain the distal underpinnings of subjective voice quality percepts that account for much of the variance in emotion inference, in particular voice instability and roughness. The general approach advocated here, as well as the specific results, open up new research strategies for work in psychology (specifically emotion and social perception research) and engineering and computer science (specifically research and development in the domain of affective computing, particularly on automatic emotion detection and synthetic emotion expression in avatars). PMID:26325076

  11. Four vortices on doubly periodic paths

    NASA Astrophysics Data System (ADS)

    Rott, Nicholas

    1994-02-01

    Plane vortex configurations in ideal flow are considered for which the total ``mass'' of the vortex strengths, their ``moments,'' and their ``polar moments of inertia'' all vanish. These properties are conserved for all times. The simplest nontrivial realization of such a configuration requires four vortices. For this case, which belongs to the more extended family of four-vortex problems that are known to be integrable [Phys. Fluids 31, 2796 (1989); Phys. Fluids A 2, 1477 (1990)], some simple closed-form results are given. The analysis shows that the paths are periodic in a ``configuration plane'' moving with the vortices as well as in the absolute fluid plane. A ``winding number'' is determined from the analysis, which gives the ratio of the two periods. Patterns of the vortex paths are determined by a program based on the step-by-step integration of the equations of motion, which is—beyond a certain level of the analysis—still the more practical method of solution. Results showing the typical behavior of the motion paths for different winding numbers are presented.

  12. Automatic tool path generation for finish machining

    SciTech Connect

    Kwok, Kwan S.; Loucks, C.S.; Driessen, B.J.

    1997-03-01

    A system for automatic tool path generation was developed at Sandia National Laboratories for finish machining operations. The system consists of a commercially available 5-axis milling machine controlled by Sandia developed software. This system was used to remove overspray on cast turbine blades. A laser-based, structured-light sensor, mounted on a tool holder, is used to collect 3D data points around the surface of the turbine blade. Using the digitized model of the blade, a tool path is generated which will drive a 0.375 inch diameter CBN grinding pin around the tip of the blade. A fuzzified digital filter was developed to properly eliminate false sensor readings caused by burrs, holes and overspray. The digital filter was found to successfully generate the correct tool path for a blade with intentionally scanned holes and defects. The fuzzified filter improved the computation efficiency by a factor of 25. For application to general parts, an adaptive scanning algorithm was developed and presented with simulation results. A right pyramid and an ellipsoid were scanned successfully with the adaptive algorithm.

  13. Path Models of Vocal Emotion Communication

    PubMed Central

    Bänziger, Tanja; Hosoya, Georg; Scherer, Klaus R.

    2015-01-01

    We propose to use a comprehensive path model of vocal emotion communication, encompassing encoding, transmission, and decoding processes, to empirically model data sets on emotion expression and recognition. The utility of the approach is demonstrated for two data sets from two different cultures and languages, based on corpora of vocal emotion enactment by professional actors and emotion inference by naïve listeners. Lens model equations, hierarchical regression, and multivariate path analysis are used to compare the relative contributions of objectively measured acoustic cues in the enacted expressions and subjective voice cues as perceived by listeners to the variance in emotion inference from vocal expressions for four emotion families (fear, anger, happiness, and sadness). While the results confirm the central role of arousal in vocal emotion communication, the utility of applying an extended path modeling framework is demonstrated by the identification of unique combinations of distal cues and proximal percepts carrying information about specific emotion families, independent of arousal. The statistical models generated show that more sophisticated acoustic parameters need to be developed to explain the distal underpinnings of subjective voice quality percepts that account for much of the variance in emotion inference, in particular voice instability and roughness. The general approach advocated here, as well as the specific results, open up new research strategies for work in psychology (specifically emotion and social perception research) and engineering and computer science (specifically research and development in the domain of affective computing, particularly on automatic emotion detection and synthetic emotion expression in avatars). PMID:26325076

  14. Protective Coatings

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Ameron International Protective Coatings Group developed a special coating for NASA that would withstand the high temperatures generated by the Space Shuttle rocket engines. The coating remains intact for at least 10 minutes, and insulates the launch pad so that it does not exceed 150 degrees and buckle. The NASA formulation was from Ameron's Engineered Siloxane (PSX) chemistry, which employs an inorganic silicon-oxygen structure which the company states is stronger and more reliable than organic polymers. Some of Ameron's PSX product line is based on the NASA technology, used for everything from industrial equipment to bridges.

  15. Protecting Antarctica

    NASA Astrophysics Data System (ADS)

    Carlowicz, Michael

    House Science Committee Chairman Robert Walker (R-Pa.) has introduced a bill into Congress to give the United States the legislative authority to implement the 1991 Environmental Protocol to the Antarctic Treaty. That protocol established rules and principles to shield the Antarctic environment from human spoilage—placing limits on the discharge of pollutants, protecting plant and animal life, and requiring environmental impact assessments before new activities and programs are launched. The protocol also forbids prospecting or developing of mineral resources except for scientific research.

  16. 1. AERIAL VIEW OF THE PATH TRANSIT SYSTEM BRIDGE, LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. AERIAL VIEW OF THE PATH TRANSIT SYSTEM BRIDGE, LOOKING NORTHEAST. THE CONRAIL BRIDGE (HAER No. NJ-43) AND THE NEWARK TURNPIKE ARE VISIBLE IN THE BACKGROUND - Path Transit System Bridge, Spanning Hackensack River, Kearny, Hudson County, NJ

  17. A Note on the Stochastic Nature of Feynman Quantum Paths

    NASA Astrophysics Data System (ADS)

    L. Botelho, Luiz C.

    2016-06-01

    We propose a Fresnel stochastic white noise framework to analyze the stochastic nature of the Feynman paths entering on the Feynman Path Integral expression for the Feynman Propagator of a particle quantum mechanically moving under a time-independent potential.

  18. Light transport on path-space manifolds

    NASA Astrophysics Data System (ADS)

    Jakob, Wenzel Alban

    The pervasive use of computer-generated graphics in our society has led to strict demands on their visual realism. Generally, users of rendering software want their images to look, in various ways, "real", which has been a key driving force towards methods that are based on the physics of light transport. Until recently, industrial practice has relied on a different set of methods that had comparatively little rigorous grounding in physics---but within the last decade, advances in rendering methods and computing power have come together to create a sudden and dramatic shift, in which physics-based methods that were formerly thought impractical have become the standard tool. As a consequence, considerable attention is now devoted towards making these methods as robust as possible. In this context, robustness refers to an algorithm's ability to process arbitrary input without large increases of the rendering time or degradation of the output image. One particularly challenging aspect of robustness entails simulating the precise interaction of light with all the materials that comprise the input scene. This dissertation focuses on one specific group of materials that has fundamentally been the most important source of difficulties in this process. Specular materials, such as glass windows, mirrors or smooth coatings (e.g. on finished wood), account for a significant percentage of the objects that surround us every day. It is perhaps surprising, then, that it is not well-understood how they can be accommodated within the theoretical framework that underlies some of the most sophisticated rendering methods available today. Many of these methods operate using a theoretical framework known as path space integration. But this framework makes no provisions for specular materials: to date, it is not clear how to write down a path space integral involving something as simple as a piece of glass. Although implementations can in practice still render these materials by side

  19. Characterizing Reactive Flow Paths in Fractured Cement

    NASA Astrophysics Data System (ADS)

    Wenning, Q. C.; Huerta, N. J.; Hesse, M. A.; Bryant, S. L.

    2011-12-01

    Geologic carbon sequestration can be a viable method for reducing anthropogenic CO2 flux into the atmosphere. However, the technology must be economically feasible and pose acceptable risk to stakeholders. One key risk is CO2 leakage out of the storage reservoir. Potential driving forces for leakage are the overpressure due to CO2 injection and the buoyancy of free phase CO2. Potential hazards of leakage are contamination of Underground Sources of Drinking Water or the atmosphere and would be deemed an unacceptable risk. Wells potentially provide a fast path for leakage from the reservoir. While the well's cement casing is reactive with CO2 and CO2-saturated brine, the low cement matrix permeability and slow diffusion rate make it unlikely that CO2 will escape through a properly constructed wellbore. However, highly permeable fractures with micrometer scale apertures can occur in cement casings. Reactions that occur in the flow in these fractures can either be self-limiting or self-enhancing. Therefore, understanding the reactive flow is critical to understanding of leakage evolution through these fractures. The goal of our work is to characterize the modification of the flow paths in the fracture due to reaction with acidic brine. With this aim we have characterized both the initial flow path of un-reactive flow and the final flow path after introduction of low-pH acid along the same fracture. Class H cement cores 3-6 cm in length and 2.5 cm diameter are created and a single natural and unique fracture is produced in each core using the Brazilian method. Our experimental fluid is injected at a constant rate into the cement core housed in a Hassler Cell under confining pressure. A solution of red dye and deionized water is pumped through the fracture to stain the un-reactive flow paths. Deionized water is then pumped through the core to limit diffusion of the dye into non-flowing portions of the fracture. After staining the initial flow path, low pH water due to

  20. Path probability of stochastic motion: A functional approach

    NASA Astrophysics Data System (ADS)

    Hattori, Masayuki; Abe, Sumiyoshi

    2016-06-01

    The path probability of a particle undergoing stochastic motion is studied by the use of functional technique, and the general formula is derived for the path probability distribution functional. The probability of finding paths inside a tube/band, the center of which is stipulated by a given path, is analytically evaluated in a way analogous to continuous measurements in quantum mechanics. Then, the formalism developed here is applied to the stochastic dynamics of stock price in finance.

  1. Lightning protection system for a wind turbine

    DOEpatents

    Costin, Daniel P.; Petter, Jeffrey K.

    2008-05-27

    In a wind turbine (104, 500, 704) having a plurality of blades (132, 404, 516, 744) and a blade rotor hub (120, 712), a lightning protection system (100, 504, 700) for conducting lightning strikes to any one of the blades and the region surrounding the blade hub along a path around the blade hub and critical components of the wind turbine, such as the generator (112, 716), gearbox (708) and main turbine bearings (176, 724).

  2. Module for Business, Management, and Technology Career Path.

    ERIC Educational Resources Information Center

    Broeker, Arlene M.

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

  3. A Navigation Path Planning Assistant for Web-Based Learning.

    ERIC Educational Resources Information Center

    Suzuki, Ryoichi; Hasegawa, Shinobu; Kashihara, Akihiro; Toyoda, Jun'ichi

    This paper addresses how to help learners navigate in existing Web-based learning resources. In order to resolve this issue, a learner-centered navigation path-planning model is proposed. The main objective is to provide learners with a path planning space in which they can see through hyperspace to plan a navigation path. This paper describes an…

  4. 14 CFR 25.123 - En route flight paths.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false En route flight paths. 25.123 Section 25... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Performance § 25.123 En route flight paths. (a) For the en route configuration, the flight paths prescribed in paragraph (b) and (c) of this section...

  5. 28 CFR 36.403 - Alterations: Path of travel.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 28 Judicial Administration 1 2014-07-01 2014-07-01 false Alterations: Path of travel. 36.403... Alterations: Path of travel. (a) General. (1) An alteration that affects or could affect the usability of or... the maximum extent feasible, the path of travel to the altered area and the restrooms, telephones,...

  6. 14 CFR 25.115 - Takeoff flight path.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Takeoff flight path. 25.115 Section 25.115... STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Performance § 25.115 Takeoff flight path. (a) The takeoff flight path shall be considered to begin 35 feet above the takeoff surface at the end of the...

  7. 14 CFR 25.123 - En route flight paths.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false En route flight paths. 25.123 Section 25... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Performance § 25.123 En route flight paths. (a) For the en route configuration, the flight paths prescribed in paragraph (b) and (c) of this section...

  8. 14 CFR 29.59 - Takeoff path: Category A.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Takeoff path: Category A. 29.59 Section 29... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight Performance § 29.59 Takeoff path: Category A. (a) The takeoff path extends from the point of commencement of the takeoff procedure to a point at...

  9. 14 CFR 23.61 - Takeoff flight path.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Takeoff flight path. 23.61 Section 23.61... flight path. For normal, utility, and acrobatic category multiengine jets of more than 6,000 pounds maximum weight and commuter category airplanes, the takeoff flight path must be determined as follows:...

  10. 14 CFR 25.123 - En route flight paths.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false En route flight paths. 25.123 Section 25... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Performance § 25.123 En route flight paths. (a) For the en route configuration, the flight paths prescribed in paragraph (b) and (c) of this section...

  11. 14 CFR 25.115 - Takeoff flight path.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Takeoff flight path. 25.115 Section 25.115... STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Performance § 25.115 Takeoff flight path. (a) The takeoff flight path shall be considered to begin 35 feet above the takeoff surface at the end of the...

  12. 14 CFR 29.59 - Takeoff path: Category A.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Takeoff path: Category A. 29.59 Section 29... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight Performance § 29.59 Takeoff path: Category A. (a) The takeoff path extends from the point of commencement of the takeoff procedure to a point at...

  13. 14 CFR 25.115 - Takeoff flight path.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Takeoff flight path. 25.115 Section 25.115... STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Performance § 25.115 Takeoff flight path. (a) The takeoff flight path shall be considered to begin 35 feet above the takeoff surface at the end of the...

  14. 14 CFR 29.59 - Takeoff path: Category A.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Takeoff path: Category A. 29.59 Section 29... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight Performance § 29.59 Takeoff path: Category A. (a) The takeoff path extends from the point of commencement of the takeoff procedure to a point at...

  15. 14 CFR 29.59 - Takeoff path: Category A.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Takeoff path: Category A. 29.59 Section 29... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight Performance § 29.59 Takeoff path: Category A. (a) The takeoff path extends from the point of commencement of the takeoff procedure to a point at...

  16. 14 CFR 25.123 - En route flight paths.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false En route flight paths. 25.123 Section 25... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Performance § 25.123 En route flight paths. (a) For the en route configuration, the flight paths prescribed in paragraph (b) and (c) of this section...

  17. 14 CFR 25.123 - En route flight paths.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false En route flight paths. 25.123 Section 25... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Performance § 25.123 En route flight paths. (a) For the en route configuration, the flight paths prescribed in paragraph (b) and (c) of this section...

  18. 75 FR 51750 - Accessibility Guidelines for Shared Use Paths

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-23

    ... TRANSPORTATION BARRIERS COMPLIANCE BOARD Accessibility Guidelines for Shared Use Paths AGENCY: Architectural and... plans to develop new accessibility guidelines specific to shared use paths (SUPs) designed for use by... shared use paths, and those with expertise in this area to provide information to assist the Access...

  19. 14 CFR 25.115 - Takeoff flight path.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Takeoff flight path. 25.115 Section 25.115... STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Performance § 25.115 Takeoff flight path. (a) The takeoff flight path shall be considered to begin 35 feet above the takeoff surface at the end of the...

  20. 14 CFR 29.59 - Takeoff path: Category A.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Takeoff path: Category A. 29.59 Section 29... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight Performance § 29.59 Takeoff path: Category A. (a) The takeoff path extends from the point of commencement of the takeoff procedure to a point at...

  1. 14 CFR 171.265 - Glide path performance requirements.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Glide path performance requirements. 171... Landing System (ISMLS) § 171.265 Glide path performance requirements. This section prescribes the performance requirements for glide path equipment components of the ISMLS. These requirements are based on...

  2. 28 CFR 36.403 - Alterations: Path of travel.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 28 Judicial Administration 1 2011-07-01 2011-07-01 false Alterations: Path of travel. 36.403... Alterations: Path of travel. (a) General. (1) An alteration that affects or could affect the usability of or... the maximum extent feasible, the path of travel to the altered area and the restrooms, telephones,...

  3. 28 CFR 36.403 - Alterations: Path of travel.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 28 Judicial Administration 1 2010-07-01 2010-07-01 false Alterations: Path of travel. 36.403... Alterations: Path of travel. (a) General. An alteration that affects or could affect the usability of or... the maximum extent feasible, the path of travel to the altered area and the restrooms, telephones,...

  4. 28 CFR 36.403 - Alterations: Path of travel.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 28 Judicial Administration 1 2012-07-01 2012-07-01 false Alterations: Path of travel. 36.403... Alterations: Path of travel. (a) General. (1) An alteration that affects or could affect the usability of or... the maximum extent feasible, the path of travel to the altered area and the restrooms, telephones,...

  5. 14 CFR 25.115 - Takeoff flight path.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Takeoff flight path. 25.115 Section 25.115... STANDARDS: TRANSPORT CATEGORY AIRPLANES Flight Performance § 25.115 Takeoff flight path. (a) The takeoff flight path shall be considered to begin 35 feet above the takeoff surface at the end of the...

  6. 14 CFR 23.61 - Takeoff flight path.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Takeoff flight path. 23.61 Section 23.61... flight path. For normal, utility, and acrobatic category multiengine jets of more than 6,000 pounds maximum weight and commuter category airplanes, the takeoff flight path must be determined as follows:...

  7. 28 CFR 36.403 - Alterations: Path of travel.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 28 Judicial Administration 1 2013-07-01 2013-07-01 false Alterations: Path of travel. 36.403... Alterations: Path of travel. (a) General. (1) An alteration that affects or could affect the usability of or... the maximum extent feasible, the path of travel to the altered area and the restrooms, telephones,...

  8. Study on the reversibility of the diffraction light path

    NASA Astrophysics Data System (ADS)

    Zhang, Weiping; Wan, Lingyu; Liu, Yun; Dong, Jianjie; Shen, Xiaoming

    2009-08-01

    of grating. First, we studied the reversibility of optical path of grating illuminated by monochromatic light, and then illuminated by polychromatic light. We found that the optical path of diffraction of grating has partial reversibility. Using the partial reversibility of optical path of diffraction of grating, we analyzed the spectral combination characteristic of grating and the bi-grating diffraction imaging effect.

  9. Time optimal paths for a constant speed unicycle

    SciTech Connect

    Reister, D.B.

    1991-01-01

    This paper uses the Pontryagin maximum principle to find time optimal paths for a constant speed unicycle. The time optimal paths consist of sequences of arcs of circles and straight lines. The maximum principle introduced concepts (dual variables, bang-bang solutions, singular solutions, and transversality conditions) that provide important insight into the nature of the time optimal paths. 10 refs., 6 figs.

  10. Perspectives on an alternative career path in regulatory science.

    PubMed

    Fields, F Owen

    2013-07-01

    Perspectives are provided on an alternative career path in regulatory science for those currently involved in basic biology research. This path is compared and contrasted with basic research, and factors to be examined if one is considering such a path are discussed. PMID:23846346

  11. Perspectives on an alternative career path in regulatory science

    PubMed Central

    Fields, F. Owen

    2013-01-01

    Perspectives are provided on an alternative career path in regulatory science for those currently involved in basic biology research. This path is compared and contrasted with basic research, and factors to be examined if one is considering such a path are discussed. PMID:23846346

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

    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.

  13. Protective Coatings

    NASA Technical Reports Server (NTRS)

    1980-01-01

    General Magnaplate Corporation's pharmaceutical machine is used in the industry for high speed pressing of pills and capsules. Machine is automatic system for molding glycerine suppositories. These machines are typical of many types of drug production and packaging equipment whose metal parts are treated with space spinoff coatings that promote general machine efficiency and contribute to compliance with stringent federal sanitation codes for pharmaceutical manufacture. Collectively known as "synergistic" coatings, these dry lubricants are bonded to a variety of metals to form an extremely hard slippery surface with long lasting self lubrication. The coatings offer multiple advantages; they cannot chip, peel or be rubbed off. They protect machine parts from corrosion and wear longer, lowering maintenance cost and reduce undesired heat caused by power-robbing friction.

  14. Automated generation of weld path trajectories.

    SciTech Connect

    Sizemore, John M.; Hinman-Sweeney, Elaine Marie; Ames, Arlo Leroy

    2003-06-01

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

  15. Auditory Perception of Motor Vehicle Travel Paths

    PubMed Central

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

    2012-01-01

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

  16. QED spectra in the path integral formalism

    NASA Astrophysics Data System (ADS)

    Simonov, Yu. A.

    2014-07-01

    Relativistic Hamiltonians, derived from the path integrals, are known to provide a simple and useful formalism for hadron spectroscopy in QCD. The accuracy of this approach is tested using the QED systems, and the calculated spectrum is shown to reproduce exactly that of the Dirac hydrogen atom, while the Breit-Fermi nonrelativistic expansion is obtained using Foldy-Wouthuizen transformation. The calculated positronium spectrum, including spin-dependent terms, coincides with the standard QED perturbation theory to the considered order O(α4).

  17. Technical Development Path for Foil Gas Bearings

    NASA Technical Reports Server (NTRS)

    DellaCorte, Christopher

    2008-01-01

    Foil gas bearings are in widespread commercial use in air cycle machines, turbocompressors and microturbine generators and are emerging in more challenging applications such as turbochargers, auxiliary power units and propulsion gas turbines. Though not well known, foil bearing technology is well over fifty years old. Recent technological developments indicate that their full potential has yet to be realized. This paper investigates the key technological developments that have characterized foil bearing advances. It is expected that a better understanding of foil gas bearing development path will aid in future development and progress towards more advanced applications.

  18. The Path to Magnetic Fusion Energy

    SciTech Connect

    Prager, Stewart

    2011-05-04

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

  19. Summation Paths in Clenshaw-Curtis Quadrature

    NASA Astrophysics Data System (ADS)

    Adam, S.; Adam, Gh.

    2016-02-01

    Two topics concerning the use of Clenshaw-Curtis quadrature within the Bayesian automatic adaptive quadrature approach to the numerical solution of Riemann integrals are considered. First, it is found that the efficient floating point computation of the coefficients of the Chebyshev series expansion of the integrand is to be done within a mathematical structure consisting of the union of coefficient families ordered into complete binary trees. Second, the scrutiny of the decay rates of the involved even and odd rank Chebyshev expansion coefficients with the increase of their rank labels enables the definition of Bayesian decision paths for the advancement to the numerical output.

  20. UV laser long-path absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Dorn, Hans-Peter; Brauers, Theo; Neuroth, Rudolf

    1994-01-01

    Long path Differential Optical Absorption Spectroscopy (DOAS) using a picosecond UV laser as a light source was developed in our institute. Tropospheric OH radicals are measured by their rotational absorption lines around 308 nm. The spectra are obtained using a high resolution spectrograph. The detection system has been improved over the formerly used optomechanical scanning device by application of a photodiode array which increased the observed spectral range by a factor of 6 and which utilizes the light much more effectively leading to a considerable reduction of the measurement time. This technique provides direct measurements of OH because the signal is given by the product of the absorption coefficient and the OH concentration along the light path according to Lambert-Beers law. No calibration is needed. Since the integrated absorption coefficient is well known the accuracy of the measurement essentially depends on the extent to which the OH absorption pattern can be detected in the spectra. No interference by self generated OH radicals in the detection lightpath has been observed. The large bandwidth (greater than 0.15 nm) and the high spectral resolution (1.5 pm) allows absolute determination of interferences by other trace gas absorptions. The measurement error is directly accessible from the absorption-signal to baseline-noise ratio in the spectra. The applicability of the method strongly depends on visibility. Elevated concentrations of aerosols lead to considerable attenuation of the laser light which reduces the S/N-ratio. In the moderately polluted air of Julich, where we performed a number of OH measurement spectra. In addition absorption features of unidentified species were frequently detected. A quantitative deconvolution even of the known species is not easy to achieve and can leave residual structures in the spectra. Thus interferences usually increase the noise and deteriorate the OH detection sensitivity. Using diode arrays for sensitive

  1. Path integral quantization of generalized quantum electrodynamics

    SciTech Connect

    Bufalo, R.; Pimentel, B. M.; Zambrano, G. E. R.

    2011-02-15

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

  2. Life Paths into Effective Environmental Action.

    ERIC Educational Resources Information Center

    Chawla, Louise

    1999-01-01

    Explores interviews with environmentalists in Kentucky (n=30) and Norway (n=26) who represented a broad range of issues from wilderness protection to urban planning to determine the sources of their environmental commitment. (Author/CCM)

  3. On the Feynman Path Integral for Nonrelativistic Quantum Electrodynamics

    NASA Astrophysics Data System (ADS)

    Ichinose, Wataru

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

  4. Improved initial guess for minimum energy path calculations.

    PubMed

    Smidstrup, Søren; Pedersen, Andreas; Stokbro, Kurt; Jónsson, Hannes

    2014-06-01

    A method is presented for generating a good initial guess of a transition path between given initial and final states of a system without evaluation of the energy. An objective function surface is constructed using an interpolation of pairwise distances at each discretization point along the path and the nudged elastic band method then used to find an optimal path on this image dependent pair potential (IDPP) surface. This provides an initial path for the more computationally intensive calculations of a minimum energy path on an energy surface obtained, for example, by ab initio or density functional theory. The optimal path on the IDPP surface is significantly closer to a minimum energy path than a linear interpolation of the Cartesian coordinates and, therefore, reduces the number of iterations needed to reach convergence and averts divergence in the electronic structure calculations when atoms are brought too close to each other in the initial path. The method is illustrated with three examples: (1) rotation of a methyl group in an ethane molecule, (2) an exchange of atoms in an island on a crystal surface, and (3) an exchange of two Si-atoms in amorphous silicon. In all three cases, the computational effort in finding the minimum energy path with DFT was reduced by a factor ranging from 50% to an order of magnitude by using an IDPP path as the initial path. The time required for parallel computations was reduced even more because of load imbalance when linear interpolation of Cartesian coordinates was used. PMID:24907989

  5. Improved initial guess for minimum energy path calculations

    SciTech Connect

    Smidstrup, Søren; Pedersen, Andreas; Stokbro, Kurt

    2014-06-07

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

  6. The mean shape of transition and first-passage paths

    NASA Astrophysics Data System (ADS)

    Kim, Won Kyu; Netz, Roland R.

    2015-12-01

    Based on the one-dimensional Fokker-Planck equation in an arbitrary free energy landscape including a general inhomogeneous diffusivity profile, we analytically calculate the mean shape of transition paths and first-passage paths, where the shape of a path is defined as the kinetic profile in the plane spanned by the mean time and the position. The transition path ensemble is the collection of all paths that do not revisit the start position xA and that terminate when first reaching the final position xB. In contrast, a first-passage path can revisit its start position xA before it terminates at xB. Our theoretical framework employs the forward and backward Fokker-Planck equations as well as first-passage, passage, last-passage, and transition-path time distributions, for which we derive the defining integral equations. We show that the mean shape of transition paths, in other words the mean time at which the transition path ensemble visits an intermediate position x, is equivalent to the mean first-passage time of reaching the position xA when starting from x without ever visiting xB. The mean shape of first-passage paths is related to the mean shape of transition paths by a constant time shift. Since for a large barrier height U, the mean first-passage time scales exponentially in U, while the mean transition path time scales linearly inversely in U, the time shift between first-passage and transition path shapes is substantial. We present explicit examples of transition path shapes for linear and harmonic potentials and illustrate our findings by trajectories obtained from Brownian dynamics simulations.

  7. The mean shape of transition and first-passage paths.

    PubMed

    Kim, Won Kyu; Netz, Roland R

    2015-12-14

    Based on the one-dimensional Fokker-Planck equation in an arbitrary free energy landscape including a general inhomogeneous diffusivity profile, we analytically calculate the mean shape of transition paths and first-passage paths, where the shape of a path is defined as the kinetic profile in the plane spanned by the mean time and the position. The transition path ensemble is the collection of all paths that do not revisit the start position x(A) and that terminate when first reaching the final position x(B). In contrast, a first-passage path can revisit its start position x(A) before it terminates at x(B). Our theoretical framework employs the forward and backward Fokker-Planck equations as well as first-passage, passage, last-passage, and transition-path time distributions, for which we derive the defining integral equations. We show that the mean shape of transition paths, in other words the mean time at which the transition path ensemble visits an intermediate position x, is equivalent to the mean first-passage time of reaching the position x(A) when starting from x without ever visiting x(B). The mean shape of first-passage paths is related to the mean shape of transition paths by a constant time shift. Since for a large barrier height U, the mean first-passage time scales exponentially in U, while the mean transition path time scales linearly inversely in U, the time shift between first-passage and transition path shapes is substantial. We present explicit examples of transition path shapes for linear and harmonic potentials and illustrate our findings by trajectories obtained from Brownian dynamics simulations. PMID:26671359

  8. Adaptive robot path planning in changing environments

    SciTech Connect

    Chen, P.C.

    1994-08-01

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

  9. Adaptive path planning: Algorithm and analysis

    SciTech Connect

    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.

  10. Journeys in science: glycobiology and other paths.

    PubMed

    Dwek, Raymond A

    2014-01-01

    My scientific journeys began at Oxford nearly 50 years ago. My paths have taken me from magnetic resonance through enzyme systems to antibodies, which led directly to glycobiology. Oxford University's first industrial grant helped the development of the technology for isolating and sequencing oligosaccharides from glycoproteins. This technology was disseminated through a spin-off company, Oxford GlycoSystems, and by the establishment of the Glycobiology Institute. The technology gave rise to the concept of glycoforms, which allow diversification of a protein's properties. Iminosugars, which are glucosidase inhibitors, can interfere with the initial steps of glycan processing on proteins and inhibit three-dimensional folding of glycoproteins. Glucosidase targets for therapy include viral envelope glycoproteins. Clinical trials of an iminosugar as an antiviral for dengue virus are under way. Another iminosugar activity, inhibition of glycolipid synthesis, resulted in a drug for Gaucher disease, which was approved worldwide in 2002. The success of the company and the institute allowed me to undertake several initiatives, in the United Kingdom and abroad, that might help the paths of future generations of scientists. PMID:24437663

  11. Dynamical anisotropy of the optical propagation paths

    NASA Astrophysics Data System (ADS)

    Arsenyan, Tatiana I.; Pisklin, Maksim V.; Suhareva, Natalia A.; Zotov, Aleksey M.

    2015-11-01

    Dynamics of laser beam intensity profile spatial modulations over a model tropospheric path with the controlled meteorological parameters was studied. Influence of the underlying surface temperature as well as the side wind load were considered. The increase of dynamic anisotropic disturbances saturation with the path length was observed. Spatio-temporal correlation characteristics of the directivity pattern in the signal beam registration plane were obtained. Proposed method of the experimental samples analysis on the base of chronogram with the following definition of the dynamic structure tensors array allows to estimate local and averaged projections of the flow velocities over the chosen spatio-temporal region and to restore their geometry in the zone of intersection with the signal beam. Additional characteristics suggested for the diagonalized local structure tensors such as local energy capacity and local structuredness are informative for the estimation of the inhomogeneities spatial dimensions, time of access through the section considered, the dynamics of energetic jets. The concepts of rotational and translational dynamic anisotropy are introduced to discriminate the types of the changes of the local ellipsoids axes orientation as well as their values. Rotational anisotropy shows itself in the changes of the local ellipsoids orientation, thus characterizing the illumination variation over the beam cross-section. Translational anisotropy describes the difference between the axes values for local ellipsoids.

  12. Gibbon travel paths are goal oriented.

    PubMed

    Asensio, Norberto; Brockelman, Warren Y; Malaivijitnond, Suchinda; Reichard, Ulrich H

    2011-05-01

    Remembering locations of food resources is critical for animal survival. Gibbons are territorial primates which regularly travel through small and stable home ranges in search of preferred, limited and patchily distributed resources (primarily ripe fruit). They are predicted to profit from an ability to memorize the spatial characteristics of their home range and may increase their foraging efficiency by using a 'cognitive map' either with Euclidean or with topological properties. We collected ranging and feeding data from 11 gibbon groups (Hylobates lar) to test their navigation skills and to better understand gibbons' 'spatial intelligence'. We calculated the locations at which significant travel direction changes occurred using the change-point direction test and found that these locations primarily coincided with preferred fruit sources. Within the limits of biologically realistic visibility distances observed, gibbon travel paths were more efficient in detecting known preferred food sources than a heuristic travel model based on straight travel paths in random directions. Because consecutive travel change-points were far from the gibbons' sight, planned movement between preferred food sources was the most parsimonious explanation for the observed travel patterns. Gibbon travel appears to connect preferred food sources as expected under the assumption of a good mental representation of the most relevant sources in a large-scale space. PMID:21221693

  13. Robotic Online Path Planning on Point Cloud.

    PubMed

    Liu, Ming

    2016-05-01

    This paper deals with the path-planning problem for mobile wheeled- or tracked-robot which drive in 2.5-D environments, where the traversable surface is usually considered as a 2-D-manifold embedded in a 3-D ambient space. Specially, we aim at solving the 2.5-D navigation problem using raw point cloud as input. The proposed method is independent of traditional surface parametrization or reconstruction methods, such as a meshing process, which generally has high-computational complexity. Instead, we utilize the output of 3-D tensor voting framework on the raw point clouds. The computation of tensor voting is accelerated by optimized implementation on graphics computation unit. Based on the tensor voting results, a novel local Riemannian metric is defined using the saliency components, which helps the modeling of the latent traversable surface. Using the proposed metric, we prove that the geodesic in the 3-D tensor space leads to rational path-planning results by experiments. Compared to traditional methods, the results reveal the advantages of the proposed method in terms of smoothing the robot maneuver while considering the minimum travel distance. PMID:26011876

  14. Vibration Analysis of a Split Path Gearbox

    NASA Technical Reports Server (NTRS)

    Krantz, Timothy L.; Rashidi, Majid

    1995-01-01

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

  15. Flexible integration of path-planning capabilities

    NASA Astrophysics Data System (ADS)

    Stobie, Iain C.; Tambe, Milind; Rosenbloom, Paul S.

    1993-05-01

    Robots pursuing complex goals must plan paths according to several criteria of quality, including shortness, safety, speed and planning time. Many sources and kinds of knowledge, such as maps, procedures and perception, may be available or required. Both the quality criteria and sources of knowledge may vary widely over time, and in general they will interact. One approach to address this problem is to express all criteria and goals numerically in a single weighted graph, and then to search this graph to determine a path. Since this is problematic with symbolic or uncertain data and interacting criteria, we propose that what is needed instead is an integration of many kinds of planning capabilities. We describe a hybrid approach to integration, based on experiments with building simulated mobile robots using Soar, an integrated problem-solving and learning system. For flexibility, we have implemented a combination of internal planning, reactive capabilities and specialized tools. We illustrate how these components can complement each other's limitations and produce plans which integrate geometric and task knowledge.

  16. The career path choices of veterinary radiologists.

    PubMed

    Jelinski, Murray D; Silver, Tawni I

    2015-01-01

    Concerns of a shortage of board certified specialists willing to work in academia have shadowed the medical and veterinary communities for decades. As a result, a number of studies have been conducted to determine how to foster, attract, and retain specialists in academia. More recently, there has been a growing perception that it is difficult for academic institutions to hire board certified veterinary radiologists. The objective of this study was to describe the career paths (academia vs. private sector) of veterinary radiologists and to determine what factors influenced their career path decisions. A mixed mode cross-sectional survey was used to survey ACVR radiologists and residents-in-training, 48% (255/529) of which responded. There was a near unidirectional movement of radiologists from academia to the private sector: 45.7% (59/129) of the respondents who began their careers in academia had switched to the private sector while only 8% (7/88) had left the private sector for academia. If a shortage of academic radiologists exists, then perhaps the issue should be framed as a problem with retention vs. recruitment. The most influential factors in the decision to leave academia were remuneration (wages and benefits), lack of interest/enjoyment in research, geographical location, and family considerations. It is salient that average salaries increased by twofold after leaving academia for the private sector. PMID:24920350

  17. Path Integral Monte Carlo Methods for Fermions

    NASA Astrophysics Data System (ADS)

    Ethan, Ethan; Dubois, Jonathan; Ceperley, David

    2014-03-01

    In general, Quantum Monte Carlo methods suffer from a sign problem when simulating fermionic systems. This causes the efficiency of a simulation to decrease exponentially with the number of particles and inverse temperature. To circumvent this issue, a nodal constraint is often implemented, restricting the Monte Carlo procedure from sampling paths that cause the many-body density matrix to change sign. Unfortunately, this high-dimensional nodal surface is not a priori known unless the system is exactly solvable, resulting in uncontrolled errors. We will discuss two possible routes to extend the applicability of finite-temperatue path integral Monte Carlo. First we extend the regime where signful simulations are possible through a novel permutation sampling scheme. Afterwards, we discuss a method to variationally improve the nodal surface by minimizing a free energy during simulation. Applications of these methods will include both free and interacting electron gases, concluding with discussion concerning extension to inhomogeneous systems. Support from DOE DE-FG52-09NA29456, DE-AC52-07NA27344, LLNL LDRD 10- ERD-058, and the Lawrence Scholar program.

  18. 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

  19. Efficiently finding the minimum free energy path from steepest descent path.

    PubMed

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

    2013-04-28

    Minimum Free Energy Path (MFEP) is very important in computational biology and chemistry. The barrier in the path is related to the reaction rate, and the start-to-end difference gives the relative stability between reactant and product. All these information is significant to experiment and practical application. But finding MFEP is not an easy job. Lots of degrees of freedom make the computation very complicated and time consuming. In this paper, we use the Steepest Descent Path (SDP) to accelerate the sampling of MFEP. The SHAKE algorithm and the Lagrangian multipliers are used to control the optimization of both SDP and MFEP. These strategies are simple and effective. For the former, it is more interesting. Because as we known, SHAKE algorithm was designed to handle the constraints in molecular dynamics in the past, has never been used in geometry optimization. Final applications on ALA dipeptide and 10-ALA peptide show that this combined optimization method works well. Use the information in SDP, the initial path could reach the more optimal MFEP. So more accurate free energies could be obtained and the amount of computation time could be saved. PMID:23635126

  20. The procedure 'OPRE' for the optimization of a transmission network satisfying a fixed protection level

    NASA Astrophysics Data System (ADS)

    Mocci, U.; Ravaioli, G.

    1981-05-01

    A transmission network can be protected either by routing traffic along disjoint paths or by rerouting interrupted capacities through a standby network. A procedure to find the minimum total cost combination of the protective measures under the constraint of a fixed protection level is described. The protection level is defined as the maximum permissible reduction of capacity for any given failure condition. The results of the application of the optimization procedure to a test network are reported.

  1. Vulnerabilities, Influences and Interaction Paths: Failure Data for Integrated System Risk Analysis

    NASA Technical Reports Server (NTRS)

    Malin, Jane T.; Fleming, Land

    2006-01-01

    We describe graph-based analysis methods for identifying and analyzing cross-subsystem interaction risks from subsystem connectivity information. By discovering external and remote influences that would be otherwise unexpected, these methods can support better communication among subsystem designers at points of potential conflict and to support design of more dependable and diagnosable systems. These methods identify hazard causes that can impact vulnerable functions or entities if propagated across interaction paths from the hazard source to the vulnerable target. The analysis can also assess combined impacts of And-Or trees of disabling influences. The analysis can use ratings of hazards and vulnerabilities to calculate cumulative measures of the severity and importance. Identification of cross-subsystem hazard-vulnerability pairs and propagation paths across subsystems will increase coverage of hazard and risk analysis and can indicate risk control and protection strategies.

  2. Following control for a UUV using temporary path generation guidance

    NASA Astrophysics Data System (ADS)

    Yan, Zheping; Chi, Dongnan; Zhou, Jiajia; Zhao, Yufei

    2012-06-01

    A path following control algorithm for an unmanned underwater vehicle (UUV) using temporary path generation guidance was proposed in this paper. Owing to different initial states of the vehicle, such as position and orientation, the path following control in the horizontal plane may yield a poor performance. To deal with the negative effect induced by initial states, a temporary path generation was presented based on the relationship between the original reference path and the vehicle's initial states. With different relative positions between the vehicle and reference path, including out of straight lines, as well as inside and outside a circle, the related temporary paths guiding the vehicle to the reference path were able to be generated in real time. The vehicle was guided to steer along the temporary path until it reached the tangent point at the reference path, where the controller was designed using the input-output feedback linearization method. Simulation results demonstrated that the proposed algorithm is effective under the three different situations mentioned above.

  3. Evolutionary development of path planning algorithms

    SciTech Connect

    Hage, M

    1998-09-01

    This paper describes the use of evolutionary software techniques for developing both genetic algorithms and genetic programs. Genetic algorithms are evolved to solve a specific problem within a fixed and known environment. While genetic algorithms can evolve to become very optimized for their task, they often are very specialized and perform poorly if the environment changes. Genetic programs are evolved through simultaneous training in a variety of environments to develop a more general controller behavior that operates in unknown environments. Performance of genetic programs is less optimal than a specially bred algorithm for an individual environment, but the controller performs acceptably under a wider variety of circumstances. The example problem addressed in this paper is evolutionary development of algorithms and programs for path planning in nuclear environments, such as Chernobyl.

  4. The paths of gravity in galileon cosmology

    SciTech Connect

    Appleby, Stephen; Linder, Eric V. E-mail: evlinder@lbl.gov

    2012-03-01

    Galileon gravity offers a robust gravitational theory for explaining cosmic acceleration, having a rich phenomenology of testable behaviors. We explore three classes of Galileon models — standard uncoupled, and linearly or derivatively coupled to matter — investigating the expansion history with particular attention to early time and late time attractors, as well as the linear perturbations. From the relativistic and nonrelativistic Poisson equations we calculate the generalizations of the gravitational strength (Newton's constant), deriving its early and late time behavior. By scanning through the parameters we derive distributions of the gravitational strength at various epochs and trace the paths of gravity in its evolution. Using ghost-free and stability criteria we restrict the allowed parameter space, finding in particular that the linear and derivative coupled models are severely constrained by classical instabilities in the early universe.

  5. How to (path-) integrate by differentiating

    NASA Astrophysics Data System (ADS)

    Kempf, Achim; Jackson, David M.; Morales, Alejandro H.

    2015-07-01

    Path integrals are at the heart of quantum field theory. In spite of their covariance and seeming simplicity, they are hard to define and evaluate. In contrast, functional differentiation, as it is used, for example, in variational problems, is relatively straightforward. This has motivated the development of new techniques that allow one to express functional integration in terms of functional differentiation. In fact, the new techniques allow one to express integrals in general through differentiation. These techniques therefore add to the general toolbox for integration and for integral transforms such as the Fourier and Laplace transforms. Here, we review some of these results, we give simpler proofs and we add new results, for example, on expressing the Laplace transform and its inverse in terms of derivatives, results that may be of use in quantum field theory, e.g., in the context of heat traces.

  6. (Quickly) Testing the Tester via Path Coverage

    NASA Technical Reports Server (NTRS)

    Groce, Alex

    2009-01-01

    The configuration complexity and code size of an automated testing framework may grow to a point that the tester itself becomes a significant software artifact, prone to poor configuration and implementation errors. Unfortunately, testing the tester by using old versions of the software under test (SUT) may be impractical or impossible: test framework changes may have been motivated by interface changes in the tested system, or fault detection may become too expensive in terms of computing time to justify running until errors are detected on older versions of the software. We propose the use of path coverage measures as a "quick and dirty" method for detecting many faults in complex test frameworks. We also note the possibility of using techniques developed to diversify state-space searches in model checking to diversify test focus, and an associated classification of tester changes into focus-changing and non-focus-changing modifications.

  7. Differential fertility in Bangladesh: a path analysis.

    PubMed

    Ahmed, B

    1981-01-01

    Previous studies of fertility in Bangladesh have mostly used crosstabular and multivariate analyses revealing the direct effect of selected socioeconomic and background variables. The indirect effects are relatively unknown. Analysis of data from the 1975-1976 Bangladesh Fertility Survey seeks to identify variables that significantly affect the cumulative fertility of both urban and rural women and to construct causal models to clarify the complex set of relationships. Path analysis is used on 8 variables: fertility index (number of children ever born to ever married women aged 9-49, age of wife (respondent), age at marriage, religion, childhood background of wife and husband, and educational attainment of both wife and husband. Data obtained from a sample of 4875 rural and 1403 urban women are used. Causal ordering of the variables began with the 4 exogenous variables: age, religion, and childhood backgrounds of the wife and husband. Education of husband and wife are placed next in sequence, followed by age at marriage and the fertility index. Path coefficients are estimated by applying ordinary least squares regression to the equations. "Children ever born" is regressed on all other variables for urban and rural areas. The 2 sets of coefficients are not equivalent and urban and rural data are analyzed separately. 13 paths are significant in the urban model and 11 in the rural model. The coefficients are small suggesting that other variables not included in the study effect fertility. In the urban model, 5 variables were found to have a statistically significant effect on fertility: age, religion, education for both husband and wife, and age at marriage. The indirect effect of religion operating through a network of compound paths suggests that Muslim affiliation tends to depress wife's and husband's education and age at marriage. Holding other variables constant, Muslim women tend to have more children than non-Muslim women. Wife's age at marriage negatively

  8. Complexified Path Integrals, Exact Saddles, and Supersymmetry.

    PubMed

    Behtash, Alireza; Dunne, Gerald V; Schäfer, Thomas; Sulejmanpasic, Tin; Ünsal, Mithat

    2016-01-01

    In the context of two illustrative examples from supersymmetric quantum mechanics we show that the semiclassical analysis of the path integral requires complexification of the configuration space and action, and the inclusion of complex saddle points, even when the parameters in the action are real. We find new exact complex saddles, and show that without their contribution the semiclassical expansion is in conflict with basic properties such as the positive semidefiniteness of the spectrum, as well as constraints of supersymmetry. Generic saddles are not only complex, but also possibly multivalued and even singular. This is in contrast to instanton solutions, which are real, smooth, and single valued. The multivaluedness of the action can be interpreted as a hidden topological angle, quantized in units of π in supersymmetric theories. The general ideas also apply to nonsupersymmetric theories. PMID:26799010

  9. Nanotechnology - A path forward for developing nations

    NASA Astrophysics Data System (ADS)

    Shah, S. Ismat; Powers, Thomas M.

    2015-10-01

    One of the major issues with technology in general, and nanotechnology in particular, is that it could exacerbate the divide between developed and developing nations. If the benefits of the research do not flow beyond the national and geographical borders of the traditional major bastions of R&D, these benefits will not be equally and globally available. The consequence is that the technological divide becomes wider at the expense of mutual reliance. As much as developed nations need to rethink the strategy and the policy to bring nanotechnology products to market with the goal of global prosperity, developing nations cannot afford to simply wait for the lead from the developed nations. In the spirit of collaboration and collegiality, we describe issues with the current practices in nanotechnology R&D in the developing world and suggest a path for nanotechnology research in energy, water and the environment that developing nations could follow in order to become contributors rather than simply consumers.

  10. Measuring Oscillating Walking Paths with a LIDAR

    PubMed Central

    Teixidó, Mercè; Pallejà, Tomàs; Tresanchez, Marcel; Nogués, Miquel; Palacín, Jordi

    2011-01-01

    This work describes the analysis of different walking paths registered using a Light Detection And Ranging (LIDAR) laser range sensor in order to measure oscillating trajectories during unsupervised walking. The estimate of the gait and trajectory parameters were obtained with a terrestrial LIDAR placed 100 mm above the ground with the scanning plane parallel to the floor to measure the trajectory of the legs without attaching any markers or modifying the floor. Three different large walking experiments were performed to test the proposed measurement system with straight and oscillating trajectories. The main advantages of the proposed system are the possibility to measure several steps and obtain average gait parameters and the minimum infrastructure required. This measurement system enables the development of new ambulatory applications based on the analysis of the gait and the trajectory during a walk. PMID:22163891

  11. Small Aircraft RF Interference Path Loss Measurements

    NASA Technical Reports Server (NTRS)

    Nguyen, Truong X.; Koppen, Sandra V.; Ely, Jay J.; Szatkowski, George N.; Mielnik, John J.; Salud, Maria Theresa P.

    2007-01-01

    Interference to aircraft radio receivers is an increasing concern as more portable electronic devices are allowed onboard. Interference signals are attenuated as they propagate from inside the cabin to aircraft radio antennas mounted on the outside of the aircraft. The attenuation level is referred to as the interference path loss (IPL) value. Significant published IPL data exists for transport and regional category airplanes. This report fills a void by providing data for small business/corporate and general aviation aircraft. In this effort, IPL measurements are performed on ten small aircraft of different designs and manufacturers. Multiple radio systems are addressed. Along with the typical worst-case coupling values, statistical distributions are also reported that could lead to more meaningful interference risk assessment.

  12. Small Aircraft RF Interference Path Loss

    NASA Technical Reports Server (NTRS)

    Nguyen, Truong X.; Koppen, Sandra V.; Ely, Jay J.; Szatkowski, George N.; Mielnik, John J.; Salud, Maria Theresa P.

    2007-01-01

    Interference to aircraft radio receivers is an increasing concern as more portable electronic devices are allowed onboard. Interference signals are attenuated as they propagate from inside the cabin to aircraft radio antennas mounted on the outside of the aircraft. The attenuation level is referred to as the interference path loss (IPL) value. Significant published IPL data exists for transport and regional category airplanes. This report fills a void by providing data for small business/corporate and general aviation aircraft. In this effort, IPL measurements are performed on ten small aircraft of different designs and manufacturers. Multiple radio systems are addressed. Along with the typical worst-case coupling values, statistical distributions are also reported that could lead to better interference risk assessment.

  13. Hot gas path component cooling system

    DOEpatents

    Lacy, Benjamin Paul; Bunker, Ronald Scott; Itzel, Gary Michael

    2014-02-18

    A cooling system for a hot gas path component is disclosed. The cooling system may include a component layer and a cover layer. The component layer may include a first inner surface and a second outer surface. The second outer surface may define a plurality of channels. The component layer may further define a plurality of passages extending generally between the first inner surface and the second outer surface. Each of the plurality of channels may be fluidly connected to at least one of the plurality of passages. The cover layer may be situated adjacent the second outer surface of the component layer. The plurality of passages may be configured to flow a cooling medium to the plurality of channels and provide impingement cooling to the cover layer. The plurality of channels may be configured to flow cooling medium therethrough, cooling the cover layer.

  14. A Development Path for the Stabilized Spheromak

    SciTech Connect

    Fowler, T K

    2007-07-13

    In Refs. [1] - [3], I suggest a concerted computational effort to study profile control of spheromaks, in anticipation that it is timely to incorporate the q < 1 regime of RFP's and spheromaks into an integrated advanced toroidal confinement program, together with improvements in tokamaks and stellarators now being pursued. For profile control of spheromaks by neutral beam injection, with care to avoid super-Alfvenic beam instability the main issue is excitation of tearing modes that can be studied using the NIMROD code already calibrated to MST and SSPX. In this note, I show that profile control on spheromaks could be demonstrated in a device the size of SSPX, leading ultimately to a very compact ignition facility, and possibly modular fusion reactors with a shorter development path.

  15. Statechart Analysis with Symbolic PathFinder

    NASA Technical Reports Server (NTRS)

    Pasareanu, Corina S.

    2012-01-01

    We report here on our on-going work that addresses the automated analysis and test case generation for software systems modeled using multiple Statechart formalisms. The work is motivated by large programs such as NASA Exploration, that involve multiple systems that interact via safety-critical protocols and are designed with different Statechart variants. To verify these safety-critical systems, we have developed Polyglot, a framework for modeling and analysis of model-based software written using different Statechart formalisms. Polyglot uses a common intermediate representation with customizable Statechart semantics and leverages the analysis and test generation capabilities of the Symbolic PathFinder tool. Polyglot is used as follows: First, the structure of the Statechart model (expressed in Matlab Stateflow or Rational Rhapsody) is translated into a common intermediate representation (IR). The IR is then translated into Java code that represents the structure of the model. The semantics are provided as "pluggable" modules.

  16. MYC on the Path to Cancer

    PubMed Central

    Dang, Chi V.

    2012-01-01

    The MYC oncogene contributes to the genesis of many human cancers. Recent insights into its expression and function have led to new cancer therapeutic opportunities. MYC’s activation by bromodomain proteins could be inhibited by drug-like molecules, resulting in tumor inhibition in vivo. Tumor growth can also be curbed by pharmacologically uncoupling bioenergetic pathways involving glucose or glutamine metabolism from Myc-induced cellular biomass accumulation. Other approaches to halt Myc on the path to cancer involve targeting Myc-Max dimerization or Myc-induced microRNA expression. Here the richness of our understanding of MYC is reviewed, highlighting new biological insights and opportunities for cancer therapies. PMID:22464321

  17. Seismic refraction analysis: the path forward

    USGS Publications Warehouse

    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.

  18. Ceramic high pressure gas path seal

    NASA Technical Reports Server (NTRS)

    Liotta, G. C.

    1987-01-01

    Stage 1 ceramic shrouds (high pressure turbine gas path seal) were developed for the GE T700 turbine helicopter engine under the Army/NASA Contract NAS3-23174. This contract successfully proved the viability and benefits of a Stage 1 ceramic shroud for production application. Stage 1 ceramic shrouds were proven by extensive component and engine testing. This Stage 1 ceramic shroud, plasma sprayed ceramic (ZrOs-BY2O3) and bond coating (NiCrAlY) onto a cast metal backing, offers significant engine performance improvement. Due to the ceramic coating, the amount of cooling air required is reduced 20% resulting in a 0.5% increase in horsepower and a 0.3% decrease in specific fuel consumption. This is accomplished with a component which is lower in cost than the current production shroud. Stage 1 ceramic shrouds will be introduced into field service in late 1987.

  19. Path selection in the growth of rivers

    PubMed Central

    Cohen, Yossi; Devauchelle, Olivier; Seybold, Hansjörg F.; Yi, Robert S.; Szymczak, Piotr; Rothman, Daniel H.

    2015-01-01

    River networks exhibit a complex ramified structure that has inspired decades of studies. However, an understanding of the propagation of a single stream remains elusive. Here we invoke a criterion for path selection from fracture mechanics and apply it to the growth of streams in a diffusion field. We show that, as it cuts through the landscape, a stream maintains a symmetric groundwater flow around its tip. The local flow conditions therefore determine the growth of the drainage network. We use this principle to reconstruct the history of a network and to find a growth law associated with it. Our results show that the deterministic growth of a single channel based on its local environment can be used to characterize the structure of river networks. PMID:26578756

  20. Paths to adolescent parenthood: implications for prevention.

    PubMed Central

    Flick, L H

    1986-01-01

    Adolescent pregnancy and parenthood are increasingly common today and pose many problems for both the individual persons involved and society as a whole. For programs to address these issues successfully, factors associated with unintended pregnancy and resulting parenthood must first be identified and understood. This paper is a review of current research on the factors associated with the four steps leading to an adolescent becoming a parent. Being an adolescent parent requires taking a particular path at four crossroads: becoming sexually active, not using or incorrectly using contraceptives, carrying rather than aborting a pregnancy, and parenting rather than placing a child for adoption. Much research in the last 15 years has explored adolescent childbearing, but many studies only compared adolescent parents to nonparents to reach conclusions about differences in these groups. This review focuses on recent studies that explore the four processes, or crossroads, separately and it excludes studies that generalize and overlap these processes. Factors that influence adolescent behavior at multiple points on the path to parenthood indicate areas particularly relevant for preventive intervention. For instance, boyfriends exert influence at all four crossroads. Sexual activity and contraceptive use increase with longevity of relationships, yet closer relationships are less often associated with raising a child. Better general communication skills, and particularly an increased ability to discuss sexuality, increases use of contraceptives, and low educational and occupational aspirations appear to influence each successive turn toward parenthood. This summary of current research serves to highlight those individual, family, dyadic, and social factors that exert great impact on adolescent parenthood by influencing young people at each of the four crossroads. These factors suggest potentially effective points for intervention to reduce the incidence of adolescent

  1. Guidewire path determination for intravascular applications.

    PubMed

    Cardoso, Fernando M; Furuie, Sergio S

    2016-01-01

    Vascular diseases are among the major causes of death in developed countries and the treatment of those pathologies may require endovascular interventions, in which the physician utilizes guidewires and catheters through the vascular system to reach the injured vessel region. Several computational studies related to endovascular procedures are in constant development. Thus, predicting the guidewire path may be of great value for both physicians and researchers. However, attaining good accuracy and precision is still an important issue. We propose a method to simulate and predict the guidewire and catheter path inside a blood vessel based on equilibrium of a new set of forces, which leads, iteratively, to the minimum energy configuration. This technique was validated with phantoms using a ∅0.33 mm stainless steel guidewire and compared to other relevant methods in the literature. This method presented RMS error 0.30 mm and 0.97 mm, which represents less than 2% and 20% of the lumen diameter of the phantom, in 2D and 3D cases, respectively. The proposed technique presented better results than other methods from the literature, which were included in this work for comparison. Moreover, the algorithm presented low variation (σ=0:03 mm) due to the variation of the input parameters. Therefore, even for a wide range of different parameters configuration, similar results are presented for the proposed approach, which is an important feature and makes this technique easier to work with. Since this method is based on basic physics, it is simple, intuitive, easy to learn and easy to adapt. PMID:26176911

  2. Cathodic protection of prestressed concrete cylinder pipe utilizing zinc anodes

    SciTech Connect

    Benedict, R.L.; Ott, J.G. II; Marshall, D.H.; White, D.

    1997-05-01

    Prestressed concrete cylinder pipe in two pipelines experienced corrosion failure within the first 10 years of service. Mechanical damages developed a migration path for chlorides in the soil to reach the prestress wire. A safe, reliable cathodic protection (CP) system was required to keep the lines viable for their design life. A sacrificial zinc anode CP system was developed.

  3. On the protection of "protected areas".

    PubMed

    Joppa, Lucas N; Loarie, Scott R; Pimm, Stuart L

    2008-05-01

    Tropical moist forests contain the majority of terrestrial species. Human actions destroy between 1 and 2 million km(2) of such forests per decade, with concomitant carbon release into the atmosphere. Within these forests, protected areas are the principle defense against forest loss and species extinctions. Four regions-the Amazon, Congo, South American Atlantic Coast, and West Africa-once constituted about half the world's tropical moist forest. We measure forest cover at progressively larger distances inside and outside of protected areas within these four regions, using datasets on protected areas and land-cover. We find important geographical differences. In the Amazon and Congo, protected areas are generally large and retain high levels of forest cover, as do their surroundings. These areas are protected de facto by being inaccessible and will likely remain protected if they continue to be so. Deciding whether they are also protected de jure-that is, whether effective laws also protect them-is statistically difficult, for there are few controls. In contrast, protected areas in the Atlantic Coast forest and West Africa show sharp boundaries in forest cover at their edges. This effective protection of forest cover is partially offset by their very small size: little area is deep inside protected area boundaries. Lands outside protected areas in the Atlantic Coast forest are unusually fragmented. Finally, we ask whether global databases on protected areas are biased toward highly protected areas and ignore "paper parks." Analysis of a Brazilian database does not support this presumption. PMID:18451028

  4. MACHINE PROTECTION FOR HIGH AVERAGE CURRENT LINACS

    SciTech Connect

    Jordan, Kevin; Allison, Trent; Evans, Richard; Coleman, James; Grippo, Albert

    2003-05-01

    A fully integrated Machine Protection System (MPS) is critical to efficient commissioning and safe operation of all high current accelerators. The Jefferson Lab FEL [1,2] has multiple electron beam paths and many different types of diagnostic insertion devices. The MPS [3] needs to monitor both the status of these devices and the magnet settings which define the beam path. The matrix of these devices and beam paths are programmed into gate arrays, the output of the matrix is an allowable maximum average power limit. This power limit is enforced by the drive laser for the photocathode gun. The Beam Loss Monitors (BLMs), RF status, and laser safety system status are also inputs to the control matrix. There are 8 Machine Modes (electron path) and 8 Beam Modes (average power limits) that define the safe operating limits for the FEL. Combinations outside of this matrix are unsafe and the beam is inhibited. The power limits range from no beam to 2 megawatts of electron beam power.

  5. Improved genetic algorithm for fast path planning of USV

    NASA Astrophysics Data System (ADS)

    Cao, Lu

    2015-12-01

    Due to the complex constraints, more uncertain factors and critical real-time demand of path planning for USV(Unmanned Surface Vehicle), an approach of fast path planning based on voronoi diagram and improved Genetic Algorithm is proposed, which makes use of the principle of hierarchical path planning. First the voronoi diagram is utilized to generate the initial paths and then the optimal path is searched by using the improved Genetic Algorithm, which use multiprocessors parallel computing techniques to improve the traditional genetic algorithm. Simulation results verify that the optimal time is greatly reduced and path planning based on voronoi diagram and the improved Genetic Algorithm is more favorable in the real-time operation.

  6. Building a cognitive map by assembling multiple path integration systems.

    PubMed

    Wang, Ranxiao Frances

    2016-06-01

    Path integration and cognitive mapping are two of the most important mechanisms for navigation. Path integration is a primitive navigation system which computes a homing vector based on an animal's self-motion estimation, while cognitive map is an advanced spatial representation containing richer spatial information about the environment that is persistent and can be used to guide flexible navigation to multiple locations. Most theories of navigation conceptualize them as two distinctive, independent mechanisms, although the path integration system may provide useful information for the integration of cognitive maps. This paper demonstrates a fundamentally different scenario, where a cognitive map is constructed in three simple steps by assembling multiple path integrators and extending their basic features. The fact that a collection of path integration systems can be turned into a cognitive map suggests the possibility that cognitive maps may have evolved directly from the path integration system. PMID:26442503

  7. Method of path coefficients: a trademark of Sewall Wright.

    PubMed

    Li, C C

    1991-02-01

    This address is a tribute to a pioneer of population genetics, including human population genetics. The unique methodology employed by Sewall Wright in many genetic problems is the method of path coefficients. This essay traces the historical landmarks in the development of the path method and then shows how some of the conventional statistical results can be converted into expressions involving path coefficients. The construction of a path diagram to represent such statistical results is explained in terms of examples. In the last section an example of applying the path method to the problem of genetic linkage in a random mating population is given. I hope that, despite the ending of the Sewall Wright era, the path method will continue to serve the scientific world. PMID:2004740

  8. 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.

  9. Multiobjective Evolutionary Path Planning via Sugeno-Based Tournament Selection

    NASA Technical Reports Server (NTRS)

    Dozier, Gerry; McCullough, Shaun; Homaifar, Abdollah; Esterline, Albert

    1998-01-01

    This paper introduces a new tournament selection algorithm that can be used for evolutionary path planning systems. The fuzzy (Sugeno) tournament selection algorithm (STSA) described in this paper selects candidate paths (CPs) to be parents and undergo reproduction based on: (1) path feasibility, (2) the euclidean distance of a path from the origin to its destination, and (3) the average change in the slope of a path. In this paper, we provide a detailed description of the fuzzy inference system used in the STSA as well as some examples of its usefulness. We then use 12 instances of our STSA to rank a population of CPs based on the above criteria. We also show how the STSA can obviate the need for the development of an explicit (lexicographic multiobjective) evaluation function and use it to develop multiobjective motion paths.

  10. Planning 3-D collision-free paths using spheres

    NASA Technical Reports Server (NTRS)

    Bonner, Susan; Kelley, Robert B.

    1989-01-01

    A scheme for the representation of objects, the Successive Spherical Approximation (SSA), facilitates the rapid planning of collision-free paths in a 3-D, dynamic environment. The hierarchical nature of the SSA allows collision-free paths to be determined efficiently while still providing for the exact representation of dynamic objects. The concept of a freespace cell is introduced to allow human 3-D conceptual knowledge to be used in facilitating satisfying choices for paths. Collisions can be detected at a rate better than 1 second per environment object per path. This speed enables the path planning process to apply a hierarchy of rules to create a heuristically satisfying collision-free path.

  11. A path-tracking criterion for an LHD articulated vehicle

    SciTech Connect

    Altafini, C.

    1999-05-01

    A path-tracking criterion for the so-called LHD (load-haul-dump) truck used in underground mining is proposed in this paper. It exploits the particular configuration of this vehicle, composed of two units connected by an actuated articulation. The task is to follow the path represented by the middle of the tunnel, maintaining the whole vehicle at a reduced distance from the path itself, to decrease the risk of crashes against the walls of the tunnel. This is accomplished via feedback through the synthesis of an appropriate path-tracking criterion. The criterion is based on monitoring the distances of the midpoints of both axles of the vehicle from their orthogonal projections on the path, using two different moving frames simultaneously. Local asymptotic stability to paths of constant curvature is achieved by means of linear-state feedback.

  12. Survival paths for reaction dynamics in fluctuating environments

    NASA Astrophysics Data System (ADS)

    Wang, Jin; Wolynes, Peter

    1994-03-01

    We study rate processes in general Gaussian fluctuating environments using a path integral formalism. We derive a variational equation for the dominant survival path when the fluctuations relax exponentially or according to a stretched exponential law. In the case of a slowly varying barrier, the equilibrium regression approximation which is used by Frauenfelder and coworkers emerges. In this approximation, the survival path follows the ordinary law of relaxation to equilibrium. If the rate coefficients vary rapidly with environmental variables, however, the dominant survival paths exhibit more complex behaviour. Many phenomena analogous to geometrical optics occur. These include reflection off of rapid variations in rate constant, as well as refraction, giving paths very different from the equilibrium relaxation properties. A model with a piece-wise linear rate exhibits the basic phenomena, and the survival path equation is exactly solved for the general stretched exponential relaxing environment.

  13. An ordinary differential equation based solution path algorithm.

    PubMed

    Wu, Yichao

    2011-01-01

    Efron, Hastie, Johnstone and Tibshirani (2004) proposed Least Angle Regression (LAR), a solution path algorithm for the least squares regression. They pointed out that a slight modification of the LAR gives the LASSO (Tibshirani, 1996) solution path. However it is largely unknown how to extend this solution path algorithm to models beyond the least squares regression. In this work, we propose an extension of the LAR for generalized linear models and the quasi-likelihood model by showing that the corresponding solution path is piecewise given by solutions of ordinary differential equation systems. Our contribution is twofold. First, we provide a theoretical understanding on how the corresponding solution path propagates. Second, we propose an ordinary differential equation based algorithm to obtain the whole solution path. PMID:21532936

  14. Path sampling with stochastic dynamics: Some new algorithms

    SciTech Connect

    Stoltz, Gabriel . E-mail: stoltz@cermics.enpc.fr

    2007-07-01

    We propose here some new sampling algorithms for path sampling in the case when stochastic dynamics are used. In particular, we present a new proposal function for equilibrium sampling of paths with a Monte-Carlo dynamics (the so-called 'brownian tube' proposal). This proposal is based on the continuity of the dynamics with respect to the random forcing, and generalizes all previous approaches when stochastic dynamics are used. The efficiency of this proposal is demonstrated using some measure of decorrelation in path space. We also discuss a switching strategy that allows to transform ensemble of paths at a finite rate while remaining at equilibrium, in contrast with the usual Jarzynski like switching. This switching is very interesting to sample constrained paths starting from unconstrained paths, or to perform simulated annealing in a rigorous way.

  15. 47 CFR 101.143 - Minimum path length requirements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Minimum path length requirements. 101.143... SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path length requirements. (a) The...) Minimum path length (km) Below 1,850 N/A 1,850 to 7,125 17 10,550 to 13,250 5 Above 17,700 N/A (b)...

  16. Polymer quantum mechanics some examples using path integrals

    SciTech Connect

    Parra, Lorena; Vergara, J. David

    2014-01-14

    In this work we analyze several physical systems in the context of polymer quantum mechanics using path integrals. First we introduce the group averaging method to quantize constrained systems with path integrals and later we use this procedure to compute the effective actions for the polymer non-relativistic particle and the polymer harmonic oscillator. We analyze the measure of the path integral and we describe the semiclassical dynamics of the systems.

  17. 47 CFR 101.143 - Minimum path length requirements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Minimum path length requirements. 101.143... SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path length requirements. (a) The...) Minimum path length (km) Below 1,850 N/A 1,850 to 7,125 17 10,550 to 13,250 5 Above 17,700 N/A (b)...

  18. 47 CFR 101.143 - Minimum path length requirements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Minimum path length requirements. 101.143... SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path length requirements. (a) The...) Minimum path length (km) Below 1,850 N/A 1,850 to 7,125 17 10,550 to 13,250 5 Above 17,700 N/A (b)...

  19. Beam-path conditioning for high-power laser systems

    SciTech Connect

    Stephens, T.; Johnson, D.; Languirand, M.

    1990-01-01

    Heating of mirrors and windows by high-power radiation from a laser transmitter produces turbulent density gradients in the gas near the optical surfaces. If the gradients are left uncontrolled, the resulting phase errors reduce the intensity on the target and degrade the signal returned to a receiver. Beam path conditioning maximizes the efficiency of the optical system by alleviating thermal turbulence within the beam path. Keywords: High power radiation, Beam path, Optical surface, Laser beams, Reprints. (JHD)

  20. A fast spectrum dual path flow cermet reactor

    SciTech Connect

    Anghaie, S.; Feller, G.J. ); Peery, S.D.; Parsley, R.C. )

    1993-01-15

    A cermet fueled, dual path fast reactor for space nuclear propulsion applications is conceptually designed. The reactor utilizes an outer annulus core and an inner cylindrical core with radial and axial reflector. The dual path flow minimizes the impact of power peaking near the radial reflector. Basic neutronics and core design aspects of the reactor are discussed. The dual path reactor is integrated into a 25000 lbf thrust nuclear rocket.

  1. Path entanglement of continuous-variable quantum microwaves.

    PubMed

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

    2012-12-21

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

  2. View of exterior circumferential path at northeast side of building ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of exterior circumferential path at northeast side of building beneath trellis, looking southeast - National Zoological Park, Bird House, 3001 Connecticut Avenue NW, Washington, District of Columbia, DC

  3. Graph Coarsening for Path Finding in Cybersecurity Graphs

    SciTech Connect

    Hogan, Emilie A.; Johnson, John R.; Halappanavar, Mahantesh

    2013-01-01

    n the pass-the-hash attack, hackers repeatedly steal password hashes and move through a computer network with the goal of reaching a computer with high level administrative privileges. In this paper we apply graph coarsening in network graphs for the purpose of detecting hackers using this attack or assessing the risk level of the network's current state. We repeatedly take graph minors, which preserve the existence of paths in the graph, and take powers of the adjacency matrix to count the paths. This allows us to detect the existence of paths as well as find paths that have high risk of being used by adversaries.

  4. Two-path plasmonic interferometer with integrated detector

    DOEpatents

    Dyer, Gregory Conrad; Shaner, Eric A.; Aizin, Gregory

    2016-03-29

    An electrically tunable terahertz two-path plasmonic interferometer with an integrated detection element can down convert a terahertz field to a rectified DC signal. The integrated detector utilizes a resonant plasmonic homodyne mixing mechanism that measures the component of the plasma waves in-phase with an excitation field that functions as the local oscillator in the mixer. The plasmonic interferometer comprises two independently tuned electrical paths. The plasmonic interferometer enables a spectrometer-on-a-chip where the tuning of electrical path length plays an analogous role to that of physical path length in macroscopic Fourier transform interferometers.

  5. Diagnosis of multilayer clouds using photon path length distributions

    NASA Astrophysics Data System (ADS)

    Li, Siwei; Min, Qilong

    2010-10-01

    Photon path length distribution is sensitive to 3-D cloud structures. A detection method for multilayer clouds has been developed, by utilizing the information of photon path length distribution. The photon path length method estimates photon path length information from the low level, single-layer cloud structure that can be accurately observed by a millimeter-wave cloud radar (MMCR) combined with a micropulse lidar (MPL). As multiple scattering within the cloud layers and between layers would substantially enhance the photon path length, the multilayer clouds can be diagnosed by evaluating the estimated photon path information against observed photon path length information from a co-located rotating shadowband spectrometer (RSS). The measurements of MMCR-MPL and RSS at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site have been processed for the year 2000. Cases studies illustrate the consistency between MMCR-MPL detection and the photon path length method under most conditions. However, the photon path length method detected some multilayer clouds that were classified by the MMCR-MPL as single-layer clouds. From 1 year statistics at the ARM SGP site, about 27.7% of single-layer clouds detected by the MMCR-MPL with solar zenith angle less than 70° and optical depth greater than 10 could be multilayer clouds. It suggests that a substantial portion of single-layer clouds detected by the MMCR-MPL could also be influenced by some "missed" clouds or by the 3-D effects of clouds.

  6. Definition of average path and relativity parameter computation in CASA

    NASA Astrophysics Data System (ADS)

    Wu, Dawei; Huang, Yan; Chen, Xiaohua; Yu, Chang

    2001-09-01

    System CASA (computer-assisted semen analysis) is a medical applicable system which gets the sperm motility and its parameters using image processing method. But there is no any authoritative administration or academic organization gives a set of criterion for CASA now result in lowering the effective compare of work between the labs or researchers. The average path and parameters relative to it as average path velocity, amplitude of lateral head displacement and beat cross frequency are often unable to compare between systems because of different algorithm. The paper presents a new algorithm that could define the average path uniquely and compute those 3 parameters above quickly and handy from any real path.

  7. PathCase-SB architecture and database design

    PubMed Central

    2011-01-01

    Background Integration of metabolic pathways resources and regulatory metabolic network models, and deploying new tools on the integrated platform can help perform more effective and more efficient systems biology research on understanding the regulation in metabolic networks. Therefore, the tasks of (a) integrating under a single database environment regulatory metabolic networks and existing models, and (b) building tools to help with modeling and analysis are desirable and intellectually challenging computational tasks. Description PathCase Systems Biology (PathCase-SB) is built and released. The PathCase-SB database provides data and API for multiple user interfaces and software tools. The current PathCase-SB system provides a database-enabled framework and web-based computational tools towards facilitating the development of kinetic models for biological systems. PathCase-SB aims to integrate data of selected biological data sources on the web (currently, BioModels database and KEGG), and to provide more powerful and/or new capabilities via the new web-based integrative framework. This paper describes architecture and database design issues encountered in PathCase-SB's design and implementation, and presents the current design of PathCase-SB's architecture and database. Conclusions PathCase-SB architecture and database provide a highly extensible and scalable environment with easy and fast (real-time) access to the data in the database. PathCase-SB itself is already being used by researchers across the world. PMID:22070889

  8. Distributional properties of stochastic shortest paths for smuggled nuclear material

    SciTech Connect

    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.

  9. Path collapse in Feynman formula. Stable path integral formula from local time reparametrization invariant amplitude

    NASA Astrophysics Data System (ADS)

    Kleinert, H.

    1989-06-01

    The Feynman formula, which expresses the time displacement amplitude > x b | exp (-t Ȟ) | x a< in terms of a path integral Π 1N (∫ dn) Π 1N+1 ( {∫ dp n}/{2π}) exp{Σ 1N [ ip n(x n-x n-1) - ɛH (p n, x n)]} with large N, does not exist for systems with Coulomb {-1}/{r} potential and gives incorrect threshold behaviours near centrifugal {1}/{r 2} or angular {1}/{sin2θ } barriers. We discuss the physical origin of this failure and propose an alternative well-defined path integral formula based on a family of amplitudes that is invariant under arbitrary local time reparametrizations. The time slicing with finite N breaks this invariance. For appropriate choices of the reparametrization function the fluctuations are stabilized and the new formula is applicable to all the above systems.

  10. Assessing Perceptions AbouT Hazardous Substances (PATHS): The PATHS questionnaire

    PubMed Central

    Amlôt, Richard; Page, Lisa; Pearce, Julia; Wessely, Simon

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Gleick, Peter H.

    2003-11-01

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

  12. Occupant Protection Project

    NASA Technical Reports Server (NTRS)

    Bopp, Genie; Somers, Jeff; Granderson, Brad; Gernhardt, Mike; Currie, Nancy; Lawrence, Chuck

    2010-01-01

    Topics include occupant protection overview with a focus on crew protection during dynamic phases of flight; occupant protection collaboration; modeling occupant protection; occupant protection considerations; project approach encompassing analysis tools, injury criteria, and testing program development; injury criteria update methodology, unique effects of pressure suits and other factors; and a summary.

  13. Hanford spent nuclear fuel project recommended path forward, volume III: Alternatives and path forward evaluation supporting documentation

    SciTech Connect

    Fulton, J.C.

    1994-10-01

    Volume I of the Hanford Spent Nuclear Fuel Project - Recommended Path Forward constitutes an aggressive series of projects to construct and operate systems and facilities to safely retrieve, package, transport, process, and store K Basins fuel and sludge. Volume II provided a comparative evaluation of four Alternatives for the Path Forward and an evaluation for the Recommended Path Forward. Although Volume II contained extensive appendices, six supporting documents have been compiled in Volume III to provide additional background for Volume II.

  14. Flow paths inside a hillslope (Invited)

    NASA Astrophysics Data System (ADS)

    Dietrich, W. E.; Rempe, D. M.; Oshun, J.; Salve, R.

    2013-12-01

    Although limited direct measurements exist, soil-mantled hillslopes appear to be commonly underlain by weathered fractured bedrock of enhanced porosity and permeability compared to deeper, fresh bedrock. This conductive zone, inside the hillslope, may vary systematically with topography, becoming thicker towards the hillslope divide in many cases. Geomorphic evolution gives rise to a structured heterogeneity that strongly influences flow paths, moisture availability, solute loading, and erosion processes. Systematic changes in permeability, porosity, and structure occur between the soil and the weathered bedrock zone, but the soil- bedrock boundary may be insignificant hydrologically: all infiltrating water can pass into the bedrock. In this deeper zone, observations are difficult, but field data suggest strongly structured flow paths matter. Here we describe measurements at a heavily instrumented, forested ~30 degree hillslope (Rivendell) in the Angelo Coast Range Reserve along the Eel River in northern California. The site is underlain by vertically dipping mudstone (with a sandstone layer forming a local ridge) with a weathering front into it that varies from 4 m thick near the channel to 24 m at the divide. A thin (<50 cm) gravelly soil caps the weathered rock zone, and at the interface is a variably thick saprolite. This saprolite, which has soil-like texture but retains a relict rock structure, may play an important role in establishing a relatively rapid deep delivery of storm precipitation. Even the first light rains of the wet season (13 mm in 4.5 hours -2009, 19 mm in 13 hours-2010) penetrate past the soil and into the saprolite in a few locations. The first major storm (134 mm in 43 hours-2009; 220 mm in 41 hours in 2010) penetrates rapidly through the soil and more slowly through the saprolite, but before the wetting front reaches about 1 m below the surface, the groundwater at depths of 18 m below the surface responds. The storm in 2010 caused the

  15. Pattern formation, logistics, and maximum path probability

    NASA Astrophysics Data System (ADS)

    Kirkaldy, J. S.

    1985-05-01

    The concept of pattern formation, which to current researchers is a synonym for self-organization, carries the connotation of deductive logic together with the process of spontaneous inference. Defining a pattern as an equivalence relation on a set of thermodynamic objects, we establish that a large class of irreversible pattern-forming systems, evolving along idealized quasisteady paths, approaches the stable steady state as a mapping upon the formal deductive imperatives of a propositional function calculus. In the preamble the classical reversible thermodynamics of composite systems is analyzed as an externally manipulated system of space partitioning and classification based on ideal enclosures and diaphragms. The diaphragms have discrete classification capabilities which are designated in relation to conserved quantities by descriptors such as impervious, diathermal, and adiabatic. Differentiability in the continuum thermodynamic calculus is invoked as equivalent to analyticity and consistency in the underlying class or sentential calculus. The seat of inference, however, rests with the thermodynamicist. In the transition to an irreversible pattern-forming system the defined nature of the composite reservoirs remains, but a given diaphragm is replaced by a pattern-forming system which by its nature is a spontaneously evolving volume partitioner and classifier of invariants. The seat of volition or inference for the classification system is thus transferred from the experimenter or theoretician to the diaphragm, and with it the full deductive facility. The equivalence relations or partitions associated with the emerging patterns may thus be associated with theorems of the natural pattern-forming calculus. The entropy function, together with its derivatives, is the vehicle which relates the logistics of reservoirs and diaphragms to the analog logistics of the continuum. Maximum path probability or second-order differentiability of the entropy in isolation are

  16. Leak Path Development in CO2 Wells

    NASA Astrophysics Data System (ADS)

    Torsater, M.; Todorovic, J.; Opedal, N.; Lavrov, A.

    2014-12-01

    Wells have in numerous scientific works been denoted the "weak link" of safe and cost-efficient CO2 Capture and Storage (CCS). Whether they are active or abandoned, all wells are man-made intrusions into the storage reservoir with sealing abilities depending on degradable materials like steel and cement. If dense CO2 is allowed to expand (e.g. due to leakage) it will cool down its surroundings and cause strong thermal and mechanical loading on the wellbore. In addition, CO2 reacts chemically with rock, cement and steel. To ensure long-term underground containment, it is therefore necessary to study how, why, where and when leakage occurs along CO2wells. If cement bonding to rock or casing is poor, leak paths can form already during drilling and completion of the well. In the present work, we have mapped the bonding quality of cement-rock and cement-steel interfaces - and measured their resistance towards CO2 flow. This involved a large experimental matrix including different rocks, steels, cement types and well fluids. The bonding qualities were measured on composite cores using micro computed tomography (µ-CT), and CO2 was flooded through the samples to determine leakage rates. These were further compared to numerical simulations of leakage through the digitalized µ-CT core data, and CO2chemical interactions with the materials were mapped using electron microscopy. We also present a new laboratory set-up for measuring how well integrity is affected by downhole temperature variations - and we showcase some initial results. Our work concludes that leak path development in CO2 wells depends critically on the drilling fluids and presflushes/spacers chosen already during drilling and completion of a well. Fluid films residing on rock and casing surfaces strongly degrade the quality of cement bonding. The operation of the well is also important, as even slight thermal cycling (between 10°C and 95°C on casing) leads to significant de-bonding of the annular cement.

  17. COMMUNITY BASED ENVIRONMENTAL PROTECTION

    EPA Science Inventory

    Community Based Environmental Protection intends to make environmental protection spring from the needs and values of the community of interest. Real community involvement in protecting the environment requires a process in which the environmental needs of communities and ecosyst...

  18. Crystal Diagnostics MultiPath System™.

    PubMed

    Stumpf, Curtis H; Zhao, Weidong; Bullard, Brian; Ammons, Christine; Devlin, Karl I; Niehaus, Gary D

    2014-01-01

    The Crystal Diagnostics MultiPath System™ provides rapid detection of Escherichia coli O157 in fresh raw ground beef, raw beeftrim, and spinach. The Crystal Diagnostics system combines patented Liquid Crystal technology with antibody-coated paramagnetic microspheres to selectively capture and detect E. coli O157 in food matrixes. This is the only liquid crystal-based biosensor commercially available for the detection of pathogens. The Crystal Diagnostics system expeditiously provides the sensitivity and accuracy of the U.S. Department of Agriculture Food Safety Inspection Service (USDA-FSIS) and the U.S. Food and Drug Administration Bacteriological Analytical Manual (FDA-BAM) methods for detecting as low as one CFU of E. coli O157 per 375 g of raw ground beef and raw beef trim, or 200 g of raw spinach. An internal inclusivity validation demonstrated detection of all 50 tested strains of . coli O157. The internal and independent laboratory tests demonstrate that the method is rapid and sensitive for detecting of E. coli O157 in fresh raw ground beef, beef trim, and spinach. PMID:25632437

  19. 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 {{{Λ }}}α , or, for a steady flow, by two stream functions {λ }κ and an additional field such as mass density ρ, velocity v, or travel time {{Δ }}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 Λ or λ space) solution {\\boldsymbol{B}}={(\\partial {\\boldsymbol{x}}/\\partial {{{Λ }}}α )}t{\\tilde{B}}α ρ /\\tilde{ρ }, 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{ρ }{\\boldsymbol{B}}/ρ ={(\\partial {\\boldsymbol{x}}/\\partial {λ }κ )}{{Δ }t}{\\tilde{B}}κ +{\\boldsymbol{v}}{\\tilde{B}}3/\\tilde{v}; here the electric field {\\boldsymbol{E}}∼ ({\\tilde{B}}2{\\boldsymbol{\

  20. Helical path separation for guided wave tomography

    SciTech Connect

    Huthwaite, P.; Seher, M.

    2015-03-31

    The pipe wall loss caused by corrosion can be quantified across an area by transmitting guided Lamb waves through the region and measuring the resulting signals. Typically the dispersive relationship for these waves, resulting in the wave velocity being a function of thickness, is exploited which enables the wall thickness to be determined from a velocity reconstruction. The accuracy and quality of this reconstruction is commonly limited by the angle of view available from the transducer arrays. These arrays are often attached as a pair of ring arrays either side of the inspected region, and due to the cyclic nature of the pipe, waves are able to travel in an inifinite number of helical paths between any two transducers. The first arrivals can be separated relatively easily by time gating, but by using just these components the angle of view is strongly restricted. To improve the viewing angle, it is necessary to separate the wavepackets. This paper provides an outline of a separation approach: initially the waves are backpropagated to their source to align the different signals, then a filtering technique is applied to select the desired components. The technique is applied to experimental data and demonstrated to robustly separate the signals.

  1. Adaptive path planning in changing environments

    SciTech Connect

    Chen, Pang C.

    1993-10-01

    Path planning needs to be fast to facilitate real-time robot programming. Unfortunately, current planning techniques are still too slow to be effective, as they often require several minutes, if not hours of computation. To overcome this difficulty, we present an adaptive algorithm that uses previous experience to speed up future performance. It is a learning algorithm suitable for incrementally-changing environments such as those encountered in manufacturing of evolving products and waste-site remediation. The algorithm extends our previous work for stationary environments in two directions: For minor environmental change, an object-attached experience abstraction scheme is introduced to increase the flexibility of the learned experience; for major environmental change, an on-demand experience repair scheme is also introduced to retain those experiences that remain valid and useful. In addition to presenting this algorithm, we identify three other variants with different repair strategies. To compare these algorithms, we develop an analytic model to compare the costs and benefits of the corresponding repair processes. Using this model, we formalize the concept of incremental change, and prove the optimality of our proposed algorithm under such change. Empirically, we also characterize the performance curve of each variant, confirm our theoretical optimality results, and demonstrate the practicality of our algorithm.

  2. 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.

  3. Automatic tracking of neuro vascular tree paths

    NASA Astrophysics Data System (ADS)

    Suryanarayanan, S.; Gopinath, A.; Mallya, Y.; Shriram, K. S.; Joshi, M.

    2006-03-01

    3-D analysis of blood vessels from volumetric CT and MR datasets has many applications ranging from examination of pathologies such as aneurysm and calcification to measurement of cross-sections for therapy planning. Segmentation of the vascular structures followed by tracking is an important processing step towards automating the 3-D vessel analysis workflow. This paper demonstrates a fast and automated algorithm for tracking the major arterial structures that have been previously segmented. Our algorithm uses anatomical knowledge to identify the start and end points in the vessel structure that allows automation. Voxel coding scheme is used to code every voxel in the vessel based on its geodesic distance from the start point. A shortest path based iterative region growing is used to extract the vessel tracks that are subsequently smoothed using an active contour method. The algorithm also has the ability to automatically detect bifurcation points of major arteries. Results are shown for tracking the major arteries such as the common carotid, internal carotid, vertebrals, and arteries coming off the Circle of Willis across multiple cases with various data related and pathological challenges from 7 CTA cases and 2 MR Time of Flight (TOF) cases.

  4. No oculomotor plant, no final common path.

    PubMed

    Miller, Joel

    2003-12-01

    The assumption that there is an oculomotor plant, a fixed relationship between motoneuron firing rate and eye position, is disproved by brainstem recording studies showing that this relationship depends on which supernuclear subsystem determines firing rate. But it remains possible that there is a final common path (FCP), a fixed relationship between firing rate and muscle force. But then, brainstem recording studies predict that lateral rectus (LR) forces (and probably medial rectus (MR) forces, as well) will be higher in converged than in unconverged gaze for a given eye position. We recently measured these forces and found that they are slightly lower in convergence, disproving the FCP hypothesis. Thus, even the relationship between motoneuron firing rate and muscle force is under supernuclear control. What peripheral oculomotor articulations could vary the relationship of firing rate to muscle force?: (1) Actively movable EOM pulleys could alter oculorotary muscle force for a given oculorotory innervation by altering muscle lengths. (2) 'Outer' motoneurons may function as gamma efferents in conjunction with palisade endings and non-twitch global EOM fibers. (3) Complex nonlinear interactions likely arise among both parallel and serially connected muscle fibers. PMID:14730457

  5. 'Accelerated aging': a primrose path to insight?

    PubMed

    Miller, Richard A

    2004-04-01

    Organism envy afflicts most researchers who work on aging in mice; how frustrating it is to see the worm and fly biologists nail down milestone after milestone, citation after citation! Surely genetic trickery can produce mice that age in a comparable jiffy? Alas, our near-total ignorance of what times the aging process makes it hard to guess what genes to tweak, if indeed aging can be mimicked a presto. Building a case that a given short-lived mutant ages quickly is a steep and thorny path, requiring more than just plucking a symptom here and there from a list of things that sometimes go wrong in old people or old mice. The hallmark of aging is that a lot goes wrong more or less at the same time, in 2-year-old mice, 10-year-old dogs and 70-year-old people. Finding ways to damage one or two systems in a 6-week or 6-month-old mouse is not too hard to do, but the implications of such studies for improved understanding of aging per se are at best indirect and at worst imaginary and distracting. PMID:15038817

  6. Path-integral simulation of solids.

    PubMed

    Herrero, C P; Ramírez, R

    2014-06-11

    The path-integral formulation of the statistical mechanics of quantum many-body systems is described, with the purpose of introducing practical techniques for the simulation of solids. Monte Carlo and molecular dynamics methods for distinguishable quantum particles are presented, with particular attention to the isothermal-isobaric ensemble. Applications of these computational techniques to different types of solids are reviewed, including noble-gas solids (helium and heavier elements), group-IV materials (diamond and elemental semiconductors), and molecular solids (with emphasis on hydrogen and ice). Structural, vibrational, and thermodynamic properties of these materials are discussed. Applications also include point defects in solids (structure and diffusion), as well as nuclear quantum effects in solid surfaces and adsorbates. Different phenomena are discussed, as solid-to-solid and orientational phase transitions, rates of quantum processes, classical-to-quantum crossover, and various finite-temperature anharmonic effects (thermal expansion, isotopic effects, electron-phonon interactions). Nuclear quantum effects are most remarkable in the presence of light atoms, so that especial emphasis is laid on solids containing hydrogen as a constituent element or as an impurity. PMID:24810944

  7. Religion and spirituality along the suicidal path.

    PubMed

    Colucci, Erminia; Martin, Graham

    2008-04-01

    The inner experience of spiritual and religious feelings is an integral part of the everyday lives of many individuals. For over 100 years the role of religion as a deterrent to suicidal behavior has been studied in various disciplines. We attempt to systematize the existing literature investigating the relationship between religion/spirituality and suicide in this paper. After an overview of the attitudes of the dominant religions (e.g., Catholicism, Islam, and Buddhism) toward suicide, the three main theories that have speculated regarding the link between religion and suicide are presented: "integration theory" (Durkheim, 1897/1997), "religious commitment theory" (Stack, 1983a; Stark, 1983), and "network theory" (Pescosolido & Georgianna, 1989). Subsequent to this theoretical introduction, we report on studies on religion/spirituality keeping the suicidal path as a reference: from suicidal ideation to nonlethal suicidal behavior to lethal suicidal behavior. Studies presenting indications of religious beliefs as a possible risk factor for suicidal behavior are also presented. The last section reviews possible intervention strategies for suicidal patients and suicide survivors. Indications for future research, such as more studies on nonreligious forms of spirituality and the use of qualitative methodology to achieve a better and deeper understanding of the spiritual dimension of suicidal behavior and treatment, are offered. PMID:18444780

  8. Hidden Topological Angles in Path Integrals

    NASA Astrophysics Data System (ADS)

    Behtash, Alireza; Sulejmanpasic, Tin; Schäfer, Thomas; Ünsal, Mithat

    2015-07-01

    We demonstrate the existence of hidden topological angles (HTAs) in a large class of quantum field theories and quantum mechanical systems. HTAs are distinct from theta parameters in the Lagrangian. They arise as invariant angles associated with saddle points of the complexified path integral and their descent manifolds (Lefschetz thimbles). Physical effects of HTAs become most transparent upon analytic continuation in nf to a noninteger number of flavors, reducing in the integer nf limit to a Z2 valued phase difference between dominant saddles. In N =1 super Yang-Mills theory we demonstrate the microscopic mechanism for the vanishing of the gluon condensate. The same effect leads to an anomalously small condensate in a QCD-like S U (N ) gauge theory with fermions in the two-index representation. The basic phenomenon is that, contrary to folklore, the gluon condensate can receive both positive and negative contributions in a semiclassical expansion. In quantum mechanics, a HTA leads to a difference in semiclassical expansion of integer and half-integer spin particles.

  9. Mining Relational Paths in Integrated Biomedical Data

    PubMed Central

    He, Bing; Tang, Jie; Ding, Ying; Wang, Huijun; Sun, Yuyin; Shin, Jae Hong; Chen, Bin; Moorthy, Ganesh; Qiu, Judy; Desai, Pankaj; Wild, David J.

    2011-01-01

    Much life science and biology research requires an understanding of complex relationships between biological entities (genes, compounds, pathways, diseases, and so on). There is a wealth of data on such relationships in publicly available datasets and publications, but these sources are overlapped and distributed so that finding pertinent relational data is increasingly difficult. Whilst most public datasets have associated tools for searching, there is a lack of searching methods that can cross data sources and that in particular search not only based on the biological entities themselves but also on the relationships between them. In this paper, we demonstrate how graph-theoretic algorithms for mining relational paths can be used together with a previous integrative data resource we developed called Chem2Bio2RDF to extract new biological insights about the relationships between such entities. In particular, we use these methods to investigate the genetic basis of side-effects of thiazolinedione drugs, and in particular make a hypothesis for the recently discovered cardiac side-effects of Rosiglitazone (Avandia) and a prediction for Pioglitazone which is backed up by recent clinical studies. PMID:22162991

  10. Resonant Doppler imaging with common path OCT

    NASA Astrophysics Data System (ADS)

    Koch, Edmund; Hammer, Daniel; Wang, Siqian; Cuevas, Maximiliano; Walther, Julia

    2009-07-01

    Resonant Doppler flow imaging based on optical coherence tomography (OCT) is a recently developed imaging modality that provides, besides the structural information, dynamic blood flow information. We show that this method can be applied to a common path OCT system by mounting the mirror in the reference arm on a small piezo actor leading to a simpler and more stable system design. Besides the known 3 state cycle, we describe other cycles with any number of states leading to higher measurement speed or larger velocity range. The hysteresis of the piezo actor is compensated by applying an optimized electrical signal. Two different approaches, one using a Levenberg-Marquardt optimization, the other using the Prandtl-Ishlinskii model for compensation of hysteresis, are applied to generate the optimized control signal. Besides providing an analytical formula for the calculation of the axial velocity for cycles having certain spacings in the reference velocity, we describe deviations from the signal degradation caused by the transversal part of the motion causing errors in the velocity estimation. The performance of the system with two and three states is first evaluated with a mirror on a loud speaker. Measurements with a flow phantom consisting of 1 % Intralipid dilution flowing through small diameter capillaries show the suitability of the system and the expected deviations at high velocities.

  11. Hidden Topological Angles in Path Integrals.

    PubMed

    Behtash, Alireza; Sulejmanpasic, Tin; Schäfer, Thomas; Ünsal, Mithat

    2015-07-24

    We demonstrate the existence of hidden topological angles (HTAs) in a large class of quantum field theories and quantum mechanical systems. HTAs are distinct from theta parameters in the Lagrangian. They arise as invariant angles associated with saddle points of the complexified path integral and their descent manifolds (Lefschetz thimbles). Physical effects of HTAs become most transparent upon analytic continuation in n_{f} to a noninteger number of flavors, reducing in the integer n_{f} limit to a Z_{2} valued phase difference between dominant saddles. In N=1 super Yang-Mills theory we demonstrate the microscopic mechanism for the vanishing of the gluon condensate. The same effect leads to an anomalously small condensate in a QCD-like SU(N) gauge theory with fermions in the two-index representation. The basic phenomenon is that, contrary to folklore, the gluon condensate can receive both positive and negative contributions in a semiclassical expansion. In quantum mechanics, a HTA leads to a difference in semiclassical expansion of integer and half-integer spin particles. PMID:26252675

  12. Luigi Galvani's path to animal electricity.

    PubMed

    Piccolino, Marco

    2006-01-01

    In spite of the historical importance of the research that, in the second half of the 18th century, led Luigi Galvani (1737-1798) to lay down the foundation of modern electrophysiology, his scientific personality is largely misrepresented in science history and in popular imagery. He is still considered as a pioneer that by chance incurred some surprising experimental observations and was incapable of pursuing his research in a coherent way. In contrast with these views, Galvani was a high-standard scientist who succeeded, with the strength of experimental science, in demonstrating, in animals, electricity in a condition of disequilibrium between the interior and the exterior of excitable fibres. This electricity, called 'animal electricity', was deemed responsible for nerve conduction. By studying the scientific endeavours of Galvani, through his published and unpublished material, and by situating them in the historical context of the physiology of the Enlightenment, this paper attempts to trace the elusive and complex path that led Galvani to his extraordinary discovery. PMID:16731488

  13. Gender differences in career paths in psychiatry.

    PubMed

    Krener, P

    1994-03-01

    Although psychiatry has one of the highest proportions of women entering its residency programs, women have not assumed a proportionate amount of academic or research leadership positions in the field. This literature review identifies three general groups of models that explain disparities between men's and women's careers, but these do not fully account for observed differences in psychiatric practice and academic progression of women in psychiatry. Gender differences in career paths in psychiatry are not only affected by individual traits and choices, but also by economic factors. Theories based on organizational discrimination, and systems and market factors are also reviewed. No single explanatory model accounts for disparities between the careers of men and those of women. Because psychiatric practice patterns may be broadly distributed across labor sectors, more diverse career patterns are possible in psychiatry than in more constrained and traditional fields. Research on gender differences in psychiatry careers must consider not only the individual work style and choice, but also the position of individuals within the organization and the position of those organizations across the labor market. PMID:24435498

  14. Breast Contour Detection with Stable Paths

    NASA Astrophysics Data System (ADS)

    Cardoso, Jaime S.; Sousa, Ricardo; Teixeira, Luís F.; Cardoso, M. J.

    Breast cancer conservative treatment (BCCT), due to its proven oncological safety, is considered, when feasible, the gold standard of breast cancer treatment. However, aesthetic results are heterogeneous and difficult to evaluate in a standardized way, due to the lack of reproducibility of the subjective methods usually applied. The objective assessment methods, considered in the past as being less capable of evaluating all aspects of BCCT, are nowadays being preferred to overcome the drawbacks of the subjective evaluation. A computer-aided medical system was recently developed to objectively and automatically evaluate the aesthetic result of BCCT. In this system, the detection of the breast contour on the patient's digital photograph is a necessary step to extract the features subsequently used in the evaluation process. In this paper an algorithm based on the shortest path on a graph is proposed to detect automatically the breast contour. The proposed method extends an existing semi-automatic algorithm for the same purpose. A comprehensive comparison with manually-drawn contours reveals the strength of the proposed method.

  15. A Path to Collaborative Strategic Learning

    SciTech Connect

    Nancy M. Carlson

    2003-10-01

    Collaborative learning is critical for the future of any organization and must align with the strategic organizational processes that result in products valued by others. To discover these processes, proposal preparation is explored using topic-oriented ethnography, grounded theory, and an innovative addition to qualitative interviewing, called metainquiry. Using interview data from editors, graphic artists, text processors, scientists, engineers, and technical managers, substantive theory emerges. The research discovers the five essential processes of owning, visioning, reviewing, producing, and contributing needed for organizational strategic learning to occur. The dimensions of these processes are made explicit and can be used to gauge the health of any organization. The substantive theory also provides insight into the ability of collaborative learning to evolve, flourish, and adapt to the strategic advantage of the organization. Lastly, actionable goals with ten essential elements emerge that link owning, visioning, reviewing, producing, and contributing as a path for all organizations to follow to promote collaborative learning communities and enhance their competitive advantage.

  16. Gap Filling as Exact Path Length Problem.

    PubMed

    Salmela, Leena; Sahlin, Kristoffer; Mäkinen, Veli; Tomescu, Alexandru I

    2016-05-01

    One of the last steps in a genome assembly project is filling the gaps between consecutive contigs in the scaffolds. This problem can be naturally stated as finding an s-t path in a directed graph whose sum of arc costs belongs to a given range (the estimate on the gap length). Here s and t are any two contigs flanking a gap. This problem is known to be NP-hard in general. Here we derive a simpler dynamic programming solution than already known, pseudo-polynomial in the maximum value of the input range. We implemented various practical optimizations to it, and compared our exact gap-filling solution experimentally to popular gap-filling tools. Summing over all the bacterial assemblies considered in our experiments, we can in total fill 76% more gaps than the best previous tool, and the gaps filled by our method span 136% more sequence. Furthermore, the error level of the newly introduced sequence is comparable to that of the previous tools. The experiments also show that our exact approach does not easily scale to larger genomes, where the problem is in general difficult for all tools. PMID:26959081

  17. Preoperative transcutaneous electrical nerve stimulation for localizing superficial nerve paths.

    PubMed

    Natori, Yuhei; Yoshizawa, Hidekazu; Mizuno, Hiroshi; Hayashi, Ayato

    2015-12-01

    During surgery, peripheral nerves are often seen to follow unpredictable paths because of previous surgeries and/or compression caused by a tumor. Iatrogenic nerve injury is a serious complication that must be avoided, and preoperative evaluation of nerve paths is important for preventing it. In this study, transcutaneous electrical nerve stimulation (TENS) was used for an in-depth analysis of peripheral nerve paths. This study included 27 patients who underwent the TENS procedure to evaluate the peripheral nerve path (17 males and 10 females; mean age: 59.9 years, range: 18-83 years) of each patient preoperatively. An electrode pen coupled to an electrical nerve stimulator was used for superficial nerve mapping. The TENS procedure was performed on patients' major peripheral nerves that passed close to the surgical field of tumor resection or trauma surgery, and intraoperative damage to those nerves was apprehensive. The paths of the target nerve were detected in most patients preoperatively. The nerve paths of 26 patients were precisely under the markings drawn preoperatively. The nerve path of one patient substantially differed from the preoperative markings with numbness at the surgical region. During surgery, the nerve paths could be accurately mapped preoperatively using the TENS procedure as confirmed by direct visualization of the nerve. This stimulation device is easy to use and offers highly accurate mapping of nerves for surgical planning without major complications. The authors conclude that TENS is a useful tool for noninvasive nerve localization and makes tumor resection a safe and smooth procedure. PMID:26420473

  18. Paths of Target Seeking Missiles in Two Dimensions

    NASA Technical Reports Server (NTRS)

    Watkins, Charles E.

    1946-01-01

    Parameters that enter into equation of trajectory of a missile are discussed. Investigation is made of normal pursuit, of constant, proportional, and line--of-sight methods of navigation employing target seeker, and of deriving corresponding pursuit paths. Pursuit paths obtained under similar conditions for different methods are compared. Proportional navigation is concluded to be best method for using target seeker installed in missile.

  19. Controlling the path of discretized light in waveguide lattices

    SciTech Connect

    Longhi, Stefano

    2011-01-15

    A general method for flexible control of the path of discretized light beams in homogeneous waveguide lattices, based on longitudinal modulation of the coupling constant, is theoretically proposed. As compared to beam steering and refraction achievable in graded-index waveguide arrays, the proposed approach enables the synthesis of rather arbitrary target paths.

  20. Implementation of the PATHS Curriculum in an Urban Elementary School

    ERIC Educational Resources Information Center

    Seifer, Ronald; Gouley, Kathleen; Miller, Alison L.; Zakriski, Audrey

    2004-01-01

    We examined the effectiveness of the PATHS curriculum in a magnet elementary school serving a distressed urban area. Aspects of social-emotional competence were examined for second graders who had, and had not, received the PATHS intervention. The intervention groups differed, with the control group having lower social-emotional competence than…

  1. Infant Categorization of Path Relations during Dynamic Events

    ERIC Educational Resources Information Center

    Pruden, Shannon M.; Roseberry, Sarah; Goksun, Tilbe; Hirsh-Pasek, Kathy; Golinkoff, Roberta M.

    2013-01-01

    Fundamental to amassing a lexicon of relational terms (i.e., verbs, prepositions) is the ability to abstract and categorize spatial relations such as a figure (e.g., "boy") moving along a path (e.g., "around" the barn). Three studies examine how infants learn to categorize path over changes in "manner," or how an action is performed (e.g., running…

  2. 4. AERIAL 'BARREL' SHOT OF THE PATH TRANSIT SYSTEM BRIDGE, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. AERIAL 'BARREL' SHOT OF THE PATH TRANSIT SYSTEM BRIDGE, LOOKING SOUTHEAST TOWARDS JERSEY CITY. TO THE RIGHT ARE THE NEWARK TURNPIKE AND THE CONRAIL BRIDGE (HAER No. NJ-43). THE PULASKI SKYWAY (HAER No. NJ-34) IS IN THE BACKGROUND TO THE RIGHT - Path Transit System Bridge, Spanning Hackensack River, Kearny, Hudson County, NJ

  3. 6. AERIAL VIEW OF THE PATH TRANSIT SYSTEM BRIDGE LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. AERIAL VIEW OF THE PATH TRANSIT SYSTEM BRIDGE LOOKING SOUTHEAST. TO THE RIGHT ARE THE NEWARK TURNPIKE AND THE CONRAIL BRIDGE (HAER No. NJ-43). THE PULASKI SKYWAY (HAER No. NJ-34) IS IN THE BACKGROUND - Path Transit System Bridge, Spanning Hackensack River, Kearny, Hudson County, NJ

  4. Computing the optimal path in stochastic dynamical systems.

    PubMed

    Bauver, Martha; Forgoston, Eric; Billings, Lora

    2016-08-01

    In stochastic systems, one is often interested in finding the optimal path that maximizes the probability of escape from a metastable state or of switching between metastable states. Even for simple systems, it may be impossible to find an analytic form of the optimal path, and in high-dimensional systems, this is almost always the case. In this article, we formulate a constructive methodology that is used to compute the optimal path numerically. The method utilizes finite-time Lyapunov exponents, statistical selection criteria, and a Newton-based iterative minimizing scheme. The method is applied to four examples. The first example is a two-dimensional system that describes a single population with internal noise. This model has an analytical solution for the optimal path. The numerical solution found using our computational method agrees well with the analytical result. The second example is a more complicated four-dimensional system where our numerical method must be used to find the optimal path. The third example, although a seemingly simple two-dimensional system, demonstrates the success of our method in finding the optimal path where other numerical methods are known to fail. In the fourth example, the optimal path lies in six-dimensional space and demonstrates the power of our method in computing paths in higher-dimensional spaces. PMID:27586597

  5. 52. May 1985. LOOKING SOUTH DOWN BRIDLE PATH TOWARD CARRIAGE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    52. May 1985. LOOKING SOUTH DOWN BRIDLE PATH TOWARD CARRIAGE HOUSE IN SPRING (Bridle path forms part of eastern boundary of formal garden plan) - Borough House, West Side State Route 261, about .1 mile south side of junction with old Garners Ferry Road, Stateburg, Sumter County, SC

  6. 5. AERIAL VIEW OF THE PATH TRANSIT SYSTEM BRIDGE LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. AERIAL VIEW OF THE PATH TRANSIT SYSTEM BRIDGE LOOKING SOUTHEAST. TO THE RIGHT ARE THE NEWARK TURNPIKE AND THE CONRAIL BRIDGE (HAER No. NJ-43). THE PULASKI SKYWAY (HAER No. NJ-34) IS IN THE BACKGROUND - Path Transit System Bridge, Spanning Hackensack River, Kearny, Hudson County, NJ

  7. Experimental Study of Split-Path Transmission Load Sharing

    NASA Technical Reports Server (NTRS)

    Krantz, Timothy L.; Delgado, Irebert R.

    1996-01-01

    Split-path transmissions are promising, attractive alternatives to the common planetary transmissions for helicopters. The split-path design offers two parallel paths for transmitting torque from the engine to the rotor. Ideally, the transmitted torque is shared equally between the two load paths; however, because of manufacturing tolerances, the design must be sized to allow for other than equal load sharing. To study the effect of tolerances, experiments were conducted using the NASA split-path test gearbox. Two gearboxes, nominally identical except for manufacturing tolerances, were tested. The clocking angle was considered to be a design parameter and used to adjust the load sharing of an otherwise fixed design. The torque carried in each path was measured for a matrix of input torques and clocking angles. The data were used to determine the optimal value and a tolerance for the clocking angles such that the most heavily loaded split path carried no greater than 53 percent of an input shaft torque of 367 N-m. The range of clocking angles satisfying this condition was -0.0012 +/- 0.0007 rad for box 1 and -0.0023 +/- 0.0009 rad for box 2. This study indicates that split-path gearboxes can be used successfully in rotorcraft and can be manufactured with existing technology.

  8. An Empirical Comparison of Two Path Coefficient Estimates.

    ERIC Educational Resources Information Center

    Tam, Peter T. K.; And Others

    Since the development of causal path analysis by Wright, both the standardized and unstandardized procedures in path coefficient estimates have been advocated in the related literature, but the superiority of one technique over the other has not been demonstrated empirically or mathematically. In this study, the sampling properties of both…

  9. Germany's ECEC Workforce: A Difficult Path to Professionalisation

    ERIC Educational Resources Information Center

    Rauschenbach, Thomas; Riedel, Birgit

    2016-01-01

    In a European comparison, the childcare profession in Germany has taken a distinct path of development which is closely interwoven with the history of early childhood education and care (ECEC) in general. Institutional choices critical to this path are the assignment of childcare as part of social welfare, the pursuit of a maternalist tradition in…

  10. A middle path for electricity options and sustainable development

    SciTech Connect

    Mills, J.I.; Herring, J.S.

    1994-12-31

    In a landmark article in Foreign Affairs in October 1976, Amory Lovins presented his vision of two vastly different and seemingly irreconcilable paths that energy provision might take into the future. One path was a ``hard`` path, characterized by extensive development of large, capital-intensive centralized electrical generating facilities and their peripherals, designed with little consideration given to the matching of these facilities to the requirements of the end-use needs. The second, ``soft`` path was characterized by energy technologies that are diverse, operate on renewable energy flows, are relatively simple, less capital-intensive, and matched in scale and energy quality to end-use needs. One of the most controversial arguments in the Lovins` paper was that the ``hard`` and ``soft`` paths are culturally and institutionally antagonistic. In retrospect, it seems this argument was self-fulfilling, for the history of the energy debate throughout the developed world since the appearance of the Lovins` article has been marked by an either-or antagonism that has left little room for serious discussion of a ``middle-path.`` In this paper, we argue that ``middle-path,`` paved with elements of both the soft and hard, is especially suited for developing countries, since they do not now carry the burden of an existing and extensive ``hard path`` energy infrastructure.

  11. Computing the optimal path in stochastic dynamical systems

    NASA Astrophysics Data System (ADS)

    Bauver, Martha; Forgoston, Eric; Billings, Lora

    2016-08-01

    In stochastic systems, one is often interested in finding the optimal path that maximizes the probability of escape from a metastable state or of switching between metastable states. Even for simple systems, it may be impossible to find an analytic form of the optimal path, and in high-dimensional systems, this is almost always the case. In this article, we formulate a constructive methodology that is used to compute the optimal path numerically. The method utilizes finite-time Lyapunov exponents, statistical selection criteria, and a Newton-based iterative minimizing scheme. The method is applied to four examples. The first example is a two-dimensional system that describes a single population with internal noise. This model has an analytical solution for the optimal path. The numerical solution found using our computational method agrees well with the analytical result. The second example is a more complicated four-dimensional system where our numerical method must be used to find the optimal path. The third example, although a seemingly simple two-dimensional system, demonstrates the success of our method in finding the optimal path where other numerical methods are known to fail. In the fourth example, the optimal path lies in six-dimensional space and demonstrates the power of our method in computing paths in higher-dimensional spaces.

  12. NO2 measurements in Hong Kong using LED based long path differential optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Chan, K. L.; Pöhler, D.; Kuhlmann, G.; Hartl, A.; Platt, U.; Wenig, M. O.

    2012-05-01

    In this study we present the first long term measurements of atmospheric nitrogen dioxide (NO2) using a LED based Long Path Differential Optical Absorption Spectroscopy (LP-DOAS) instrument. This instrument is measuring continuously in Hong Kong since December 2009, first in a setup with a 550 m absorption path and then with a 3820 m path at about 30 m to 50 m above street level. The instrument is using a high power blue light LED with peak intensity at 450 nm coupled into the telescope using a Y-fibre bundle. The LP-DOAS instrument measures NO2 levels in the Kowloon Tong and Mongkok district of Hong Kong and we compare the measurement results to mixing ratios reported by monitoring stations operated by the Hong Kong Environmental Protection Department in that area. Hourly averages of coinciding measurements are in reasonable agreement (R = 0.74). Furthermore, we used the long-term data set to validate the Ozone Monitoring Instrument (OMI) NO2 data product. Monthly averaged LP-DOAS and OMI measurements correlate well (R = 0.84) when comparing the data for the OMI overpass time. We analyzed weekly patterns in both data sets and found that the LP-DOAS detects a clear weekly cycle with a reduction on weekends during rush hour peaks, whereas OMI is not able to observe this weekly cycle due to its fix overpass time (13:30-14:30 LT - local time).

  13. Proton and electron mean free paths: The Palmer consensus revisited

    NASA Technical Reports Server (NTRS)

    Bieber, John W.; Matthaeus, William H.; Smith, Charles W.; Wanner, Wolfgang; Kallenrode, May-Britt; Wibberenz, Gerd

    1994-01-01

    We present experimental and theoretical evidence suggesting that the mean free path of cosmic-ray electrons and protons may be fundamentally different at low to intermediate (less than 50 MV) rigidities. The experimental evidence is from Helios observations of solar energetic particles, which show that the mean free path of 1.4 MV electrons is often similar to that of 187 MV protons, even though proton mean free paths continue to decrease comparatively rapidly with decreasing rigidty down to the lowest channels (about 100 MV) observed. The theoretical evidence is from computations of particle scattering in dynamical magnetic turbulence, which predict that electrons will have a larger mean free path than protons of the same rigidity. In the light of these new results, 'consensus' ideas about cosmic-ray mean free paths may require drastic revision.

  14. Yang-Mills Theory and Fermionic Path Integrals

    NASA Astrophysics Data System (ADS)

    Fujikawa, Kazuo

    The Yang-Mills gauge field theory, which was proposed 60 years ago, is extremely successful in describing the basic interactions of fundamental particles. The Yang-Mills theory in the course of its developments also stimulated many important field theoretical machinery. In my talk I discuss the path integral techniques, in particular, the fermionic path integrals which were developed together with the successful applications of quantized Yang-Mills field theory. I start with the Faddeev-Popov path integral formula with emphasis on the treatment of fermionic ghosts as an application of Grassmann numbers. I then discuss the ordinary fermionic path integrals and the general treatment of quantum anomalies. The contents of this talk are mostly pedagogical except for a recent analysis of path integral bosonization.

  15. Yang-Mills theory and fermionic path integrals

    NASA Astrophysics Data System (ADS)

    Fujikawa, Kazuo

    2016-01-01

    The Yang-Mills gauge field theory, which was proposed 60 years ago, is extremely successful in describing the basic interactions of fundamental particles. The Yang-Mills theory in the course of its developments also stimulated many important field theoretical machinery. In this brief review I discuss the path integral techniques, in particular, the fermionic path integrals which were developed together with the successful applications of quantized Yang-Mills field theory. I start with the Faddeev-Popov path integral formula with emphasis on the treatment of fermionic ghosts as an application of Grassmann numbers. I then discuss the ordinary fermionic path integrals and the general treatment of quantum anomalies. The contents of this review are mostly pedagogical except for a recent analysis of path integral bosonization.

  16. Multi optical path generator for fiber optic strain sensors multiplexing

    NASA Astrophysics Data System (ADS)

    Luo, Hao; Yuan, Yonggui; Yuan, Libo

    2015-07-01

    A multi optical path generator based on a tunable long Fabry-Perot optical fiber cavity is proposed and demonstrated. It would be used in an optical fiber sensing system which could multiplex a number of fiber sensors with different gauge lengths. Using this optical path generator, we can get a sequence of light beams with different optical paths, which will be coupled to the fiber sensor array in the sensing system. The multi optical path lengths generated by the device are analyzed and discussed. And the relative intensity of the corresponding light beam is calculated. The multiplexing capability caused by the optical path generator is discussed and the experimental results are confirmed this. The system can be used in strain or deformation sensing for smart structure health monitoring.

  17. Infants' ability to associate motion paths with object kinds.

    PubMed

    Baker, Rachel K; Pettigrew, Tamara L; Poulin-Dubois, Diane

    2014-02-01

    The goal of the present research was to examine whether infants associate different paths of motion with animate beings and inanimate objects. An infant-controlled habituation procedure was used to examine 10-20-month-old infants' ability to associate a non-linear motion path (jumping) with animals and a linear (rebounding) motion path with vehicles (Experiment 1) and furniture (Experiment 2). During the habituation phase, infants saw a dog jumping over a barrier and either a vehicle or a piece of furniture rebounding off the barrier. In the test phase, infants looked longer when another inanimate object jumped rather than rebounded, but showed no such differential looking in the case of another animate object. The ability to restrict the animate motion path of jumping to animate beings was present by 10 months of age. The present findings support the hypothesis that motion path is associated with the animate-inanimate distinction early in infancy. PMID:24486789

  18. Hamiltonian Paths Through Two- and Three-Dimensional Grids

    PubMed Central

    Mitchell, William F.

    2005-01-01

    This paper addresses the existence of Hamiltonian paths and cycles in two-dimensional grids consisting of triangles or quadrilaterals, and three-dimensional grids consisting of tetrahedra or hexahedra. The paths and cycles may be constrained to pass from one element to the next through an edge, through a vertex, or be unconstrained and pass through either. It was previously known that an unconstrained Hamiltonian path exists in a triangular grid under very mild conditions, and that there are triangular grids for which there is no through-edge Hamiltonian path. In this paper we prove that a through-vertex Hamiltonian cycle exists in any triangular or tetrahedral grid under very mild conditions, and that there exist quadrilateral and hexahedral grids for which no unconstrained Hamiltonian path exists. The existence proofs are constructive, and lead to an efficient algorithm for finding a through-vertex Hamiltonian cycle.

  19. Tikhonov regularization-based operational transfer path analysis

    NASA Astrophysics Data System (ADS)

    Cheng, Wei; Lu, Yingying; Zhang, Zhousuo

    2016-06-01

    To overcome ill-posed problems in operational transfer path analysis (OTPA), and improve the stability of solutions, this paper proposes a novel OTPA based on Tikhonov regularization, which considers both fitting degrees and stability of solutions. Firstly, fundamental theory of Tikhonov regularization-based OTPA is presented, and comparative studies are provided to validate the effectiveness on ill-posed problems. Secondly, transfer path analysis and source contribution evaluations for numerical cases studies on spherical radiating acoustical sources are comparatively studied. Finally, transfer path analysis and source contribution evaluations for experimental case studies on a test bed with thin shell structures are provided. This study provides more accurate transfer path analysis for mechanical systems, which can benefit for vibration reduction by structural path optimization. Furthermore, with accurate evaluation of source contributions, vibration monitoring and control by active controlling vibration sources can be effectively carried out.

  20. Optical path switching based differential absorption radiometry for substance detection

    NASA Technical Reports Server (NTRS)

    Sachse, Glen W. (Inventor)

    2003-01-01

    An optical path switch divides sample path radiation into a time series of alternating first polarized components and second polarized components. The first polarized components are transmitted along a first optical path and the second polarized components along a second optical path. A first gasless optical filter train filters the first polarized components to isolate at least a first wavelength band thereby generating first filtered radiation. A second gasless optical filter train filters the second polarized components to isolate at least a second wavelength band thereby generating second filtered radiation. A beam combiner combines the first and second filtered radiation to form a combined beam of radiation. A detector is disposed to monitor magnitude of at least a portion of the combined beam alternately at the first wavelength band and the second wavelength band as an indication of the concentration of the substance in the sample path.

  1. Optical path switching based differential absorption radiometry for substance detection

    NASA Technical Reports Server (NTRS)

    Sachse, Glen W. (Inventor)

    2005-01-01

    An optical path switch divides sample path radiation into a time series of alternating first polarized components and second polarized components. The first polarized components are transmitted along a first optical path and the second polarized components along a second optical path. A first gasless optical filter train filters the first polarized components to isolate at least a first wavelength band thereby generating first filtered radiation. A second gasless optical filter train filters the second polarized components to isolate at least a second wavelength band thereby generating second filtered radiation. A beam combiner combines the first and second filtered radiation to form a combined beam of radiation. A detector is disposed to monitor magnitude of at least a portion of the combined beam alternately at the first wavelength band and the second wavelength band as an indication of the concentration of the substance in the sample path.

  2. Teleconnection Paths via Climate Network Direct Link Detection

    NASA Astrophysics Data System (ADS)

    Zhou, Dong; Gozolchiani, Avi; Ashkenazy, Yosef; Havlin, Shlomo

    2015-12-01

    Teleconnections describe remote connections (typically thousands of kilometers) of the climate system. These are of great importance in climate dynamics as they reflect the transportation of energy and climate change on global scales (like the El Niño phenomenon). Yet, the path of influence propagation between such remote regions, and weighting associated with different paths, are only partially known. Here we propose a systematic climate network approach to find and quantify the optimal paths between remotely distant interacting locations. Specifically, we separate the correlations between two grid points into direct and indirect components, where the optimal path is found based on a minimal total cost function of the direct links. We demonstrate our method using near surface air temperature reanalysis data, on identifying cross-latitude teleconnections and their corresponding optimal paths. The proposed method may be used to quantify and improve our understanding regarding the emergence of climate patterns on global scales.

  3. Collision avoidance of two moving objects using the anticipated path

    NASA Astrophysics Data System (ADS)

    Rhee, Seung Hak; Ahmad, Muhammad Bilal; Park, Seung-Jin; Beak, Kyoung-Ju; Park, Jong An

    2004-03-01

    Collision avoidance is one of the most important problems in autonomous vehicles, ship navigation, and robot manipulators, etc. Image processing technique could be applied for solving the collision avoidance of moving objects. The collision could be avoided if the direction of the moving object could be accurately anticipated. The problem is how to anticipate the expected path of the moving object, so that the other moving objects in the expected path should be detected and avoided for collision avoidance. Collisions could be avoided by searching the obstacles and moving objects in the expected path, but the moving objects, which would come inside the expected path, should also be detected for fully collision avoidance. In this paper, the expected path of the moving object is determined from the previous history of the moving object using the statistical measurements.

  4. EuPathDB: a portal to eukaryotic pathogen databases.

    PubMed

    Aurrecoechea, Cristina; Brestelli, John; Brunk, Brian P; Fischer, Steve; Gajria, Bindu; Gao, Xin; Gingle, Alan; Grant, Greg; Harb, Omar S; Heiges, Mark; Innamorato, Frank; Iodice, John; Kissinger, Jessica C; Kraemer, Eileen T; Li, Wei; Miller, John A; Nayak, Vishal; Pennington, Cary; Pinney, Deborah F; Roos, David S; Ross, Chris; Srinivasamoorthy, Ganesh; Stoeckert, Christian J; Thibodeau, Ryan; Treatman, Charles; Wang, Haiming

    2010-01-01

    EuPathDB (http://EuPathDB.org; formerly ApiDB) is an integrated database covering the eukaryotic pathogens of the genera Cryptosporidium, Giardia, Leishmania, Neospora, Plasmodium, Toxoplasma, Trichomonas and Trypanosoma. While each of these groups is supported by a taxon-specific database built upon the same infrastructure, the EuPathDB portal offers an entry point to all these resources, and the opportunity to leverage orthology for searches across genera. The most recent release of EuPathDB includes updates and changes affecting data content, infrastructure and the user interface, improving data access and enhancing the user experience. EuPathDB currently supports more than 80 searches and the recently-implemented 'search strategy' system enables users to construct complex multi-step searches via a graphical interface. Search results are dynamically displayed as the strategy is constructed or modified, and can be downloaded, saved, revised, or shared with other database users. PMID:19914931

  5. Path planning and the topology of configuration space

    SciTech Connect

    Maciejewski, A.A.; Fox, J.J.

    1993-08-01

    This work considers the path planning problem for planar revolute manipulators operating in a workspace of polygonal obstacles. This problem is solved by determining the topological characteristics of obstacles in configuration space, thereby determining where feasible paths can be found. A collision-free path is then calculated by using the mathematical description of the boundaries of only those configuration space obstacles with which collisions are possible. The key to this technique is a simple test for determining whether two disjoint obstacles are connected in configuration space. This test allows the path planner to restrict its calculations to regions in which collision-free paths are guaranteed a priori, thus avoiding unnecessary computations and resulting in an efficient implementations. Typical timing results for environments consisting of four polyhedral obstacles comprised of a total of 27 vertices are on the order of 22 ms on a SPARC-IPC workstation.

  6. 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.

  7. Teleconnection Paths via Climate Network Direct Link Detection.

    PubMed

    Zhou, Dong; Gozolchiani, Avi; Ashkenazy, Yosef; Havlin, Shlomo

    2015-12-31

    Teleconnections describe remote connections (typically thousands of kilometers) of the climate system. These are of great importance in climate dynamics as they reflect the transportation of energy and climate change on global scales (like the El Niño phenomenon). Yet, the path of influence propagation between such remote regions, and weighting associated with different paths, are only partially known. Here we propose a systematic climate network approach to find and quantify the optimal paths between remotely distant interacting locations. Specifically, we separate the correlations between two grid points into direct and indirect components, where the optimal path is found based on a minimal total cost function of the direct links. We demonstrate our method using near surface air temperature reanalysis data, on identifying cross-latitude teleconnections and their corresponding optimal paths. The proposed method may be used to quantify and improve our understanding regarding the emergence of climate patterns on global scales. PMID:26765033

  8. PathVisio 3: An Extendable Pathway Analysis Toolbox

    PubMed Central

    Kutmon, Martina; van Iersel, Martijn P.; Bohler, Anwesha; Kelder, Thomas; Nunes, Nuno; Pico, Alexander R.; Evelo, Chris T.

    2015-01-01

    PathVisio is a commonly used pathway editor, visualization and analysis software. Biological pathways have been used by biologists for many years to describe the detailed steps in biological processes. Those powerful, visual representations help researchers to better understand, share and discuss knowledge. Since the first publication of PathVisio in 2008, the original paper was cited more than 170 times and PathVisio was used in many different biological studies. As an online editor PathVisio is also integrated in the community curated pathway database WikiPathways. Here we present the third version of PathVisio with the newest additions and improvements of the application. The core features of PathVisio are pathway drawing, advanced data visualization and pathway statistics. Additionally, PathVisio 3 introduces a new powerful extension systems that allows other developers to contribute additional functionality in form of plugins without changing the core application. PathVisio can be downloaded from http://www.pathvisio.org and in 2014 PathVisio 3 has been downloaded over 5,500 times. There are already more than 15 plugins available in the central plugin repository. PathVisio is a freely available, open-source tool published under the Apache 2.0 license (http://www.apache.org/licenses/LICENSE-2.0). It is implemented in Java and thus runs on all major operating systems. The code repository is available at http://svn.bigcat.unimaas.nl/pathvisio. The support mailing list for users is available on https://groups.google.com/forum/#!forum/wikipathways-discuss and for developers on https://groups.google.com/forum/#!forum/wikipathways-devel. PMID:25706687

  9. Path Following in the Exact Penalty Method of Convex Programming

    PubMed Central

    Zhou, Hua; Lange, Kenneth

    2015-01-01

    Classical penalty methods solve a sequence of unconstrained problems that put greater and greater stress on meeting the constraints. In the limit as the penalty constant tends to ∞, one recovers the constrained solution. In the exact penalty method, squared penalties are replaced by absolute value penalties, and the solution is recovered for a finite value of the penalty constant. In practice, the kinks in the penalty and the unknown magnitude of the penalty constant prevent wide application of the exact penalty method in nonlinear programming. In this article, we examine a strategy of path following consistent with the exact penalty method. Instead of performing optimization at a single penalty constant, we trace the solution as a continuous function of the penalty constant. Thus, path following starts at the unconstrained solution and follows the solution path as the penalty constant increases. In the process, the solution path hits, slides along, and exits from the various constraints. For quadratic programming, the solution path is piecewise linear and takes large jumps from constraint to constraint. For a general convex program, the solution path is piecewise smooth, and path following operates by numerically solving an ordinary differential equation segment by segment. Our diverse applications to a) projection onto a convex set, b) nonnegative least squares, c) quadratically constrained quadratic programming, d) geometric programming, and e) semidefinite programming illustrate the mechanics and potential of path following. The final detour to image denoising demonstrates the relevance of path following to regularized estimation in inverse problems. In regularized estimation, one follows the solution path as the penalty constant decreases from a large value. PMID:26366044

  10. Fermion path integrals and topological phases

    NASA Astrophysics Data System (ADS)

    Witten, Edward

    2016-07-01

    Symmetry-protected topological (SPT) phases of matter have been interpreted in terms of anomalies, and it has been expected that a similar picture should hold for SPT phases with fermions. Here a description is given in detail of what this picture means for phases of quantum matter that can be understood via band theory and free fermions. The main examples considered are time-reversal invariant topological insulators and superconductors in two or three space dimensions. Along the way, the precise meaning of the statement that in the bulk of a 3D topological insulator, the electromagnetic θ angle is equal to π , is clarified.

  11. Path of Carbon in Photosynthesis III.

    DOE R&D Accomplishments Database

    Benson, A. A.; Calvin, M.

    1948-06-01

    Although the overall reaction of photosynthesis can be specified with some degree of certainty (CO{sub 2} + H{sub 2}O + light {yields} sugars + possibly other reduced substances), the intermediates through which the carbon passes during the course of this reduction have, until now, been largely a matter of conjecture. The availability of isotopic carbon, that is, a method of labeling the carbon dioxide, provides the possibility of some very direct experiments designed to recognize these intermediates and, perhaps, help to understand the complex sequence and interplay of reactions which must constitute the photochemical process itself. The general design of such experiments is an obvious one, namely the exposure of the green plant to radioactive carbon dioxide and light under a variety of conditions and for continually decreasing lengths of time, followed by the identification of the compounds into which the radioactive carbon is incorporated under each condition and time period. From such data it is clear that in principle, at least, it should be possible to establish the sequence of compounds in time through which the carbon passes on its path from carbon dioxide to the final products. In the course of shortening the photosynthetic times, one times, one ultimately arrives at the condition of exposing the plants to the radioactive carbon dioxide with a zero illumination time, that is, in the dark. Actually, in the work the systematic order of events was reversed, and they have begun by studying first the dark fixation and then the shorter photosynthetic times. The results of the beginnings of this sort of a systematic investigation are given in Table I which includes three sets of experiments, namely a dark fixation experiment and two photosynthetic experiments, one of 30 seconds duration and the other of 60 seconds duration.

  12. Path forward for dosimetry cross sections

    SciTech Connect

    Griffin, P.J.; Peters, C.D.

    2011-07-01

    In the 1980's the dosimetry community embraced the need for a high fidelity quantification of uncertainty in nuclear data used for dosimetry applications. This led to the adoption of energy-dependent covariance matrices as the accepted manner of quantifying the uncertainty data. The trend for the dosimetry community to require high fidelity treatment of uncertainty estimates has continued to the current time where requirements on nuclear data are codified in standards such as ASTM E 1018. This paper surveys the current state of the dosimetry cross sections and investigates the quality of the current dosimetry cross section evaluations by examining calculated-to-experimental ratios in neutron benchmark fields. In recent years more nuclear-related technical areas are placing an emphasis on uncertainty quantification. With the availability of model-based cross sections and covariance matrices produced by nuclear data codes, some nuclear-related communities are considering the role these covariance matrices should play. While funding within the dosimetry community for cross section evaluations has been very meager, other areas, such as the solar-related astrophysics community and the US Nuclear Criticality Safety Program, have been supporting research in the area of neutron cross sections. The Cross Section Evaluation Working Group (CSEWG) is responsible for the creation and maintenance of the ENDF/B library which has been the mainstay for the reactor dosimetry community. Given the new trends in cross section evaluations, this paper explores the path forward for the US nuclear reactor dosimetry community and its use of the ENDF/B cross-sections. The major concern is maintenance of the sufficiency and accuracy of the uncertainty estimate when used for dosimetry applications. The two major areas of deficiency in the proposed ENDF/B approach are: 1) the use of unrelated covariance matrices in ENDF/B evaluations and 2) the lack of 'due consideration' of experimental data

  13. A flow path model for regional water distribution optimization

    NASA Astrophysics Data System (ADS)

    Cheng, Wei-Chen; Hsu, Nien-Sheng; Cheng, Wen-Ming; Yeh, William W.-G.

    2009-09-01

    We develop a flow path model for the optimization of a regional water distribution system. The model simultaneously describes a water distribution system in two parts: (1) the water delivery relationship between suppliers and receivers and (2) the physical water delivery network. In the first part, the model considers waters from different suppliers as multiple commodities. This helps the model clearly describe water deliveries by identifying the relationship between suppliers and receivers. The physical part characterizes a physical water distribution network by all possible flow paths. The flow path model can be used to optimize not only the suppliers to each receiver but also their associated flow paths for supplying water. This characteristic leads to the optimum solution that contains the optimal scheduling results and detailed information concerning water distribution in the physical system. That is, the water rights owner, water quantity, water location, and associated flow path of each delivery action are represented explicitly in the results rather than merely as an optimized total flow quantity in each arc of a distribution network. We first verify the proposed methodology on a hypothetical water distribution system. Then we apply the methodology to the water distribution system associated with the Tou-Qian River basin in northern Taiwan. The results show that the flow path model can be used to optimize the quantity of each water delivery, the associated flow path, and the water trade and transfer strategy.

  14. Voronoi-based extraction and visualization of molecular paths.

    PubMed

    Lindow, Norbert; Baum, Daniel; Hege, Hans-Christian

    2011-12-01

    Visual analysis is widely used to study the behavior of molecules. Of particular interest are the analysis of molecular interactions and the investigation of binding sites. For large molecules, however, it is difficult to detect possible binding sites and paths leading to these sites by pure visual inspection. In this paper, we present new methods for the computation and visualization of potential molecular paths. Using a novel filtering method, we extract the significant paths from the Voronoi diagram of spheres. For the interactive visualization of molecules and their paths, we present several methods using deferred shading and other state-of-the-art techniques. To allow for a fast overview of reachable regions of the molecule, we illuminate the molecular surface using a large number of light sources placed on the extracted paths. We also provide a method to compute the extension surface of selected paths and visualize it using the skin surface. Furthermore, we use the extension surface to clip the molecule to allow easy visual tracking of even deeply buried paths. The methods are applied to several proteins to demonstrate their usefulness. PMID:22034320

  15. Heuristic optimization of the scanning path of particle therapy beams

    SciTech Connect

    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.

  16. Seeking the Path to Metadata Nirvana

    NASA Astrophysics Data System (ADS)

    Graybeal, J.

    2008-12-01

    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.

  17. 45 Km Horizontal Path Optical Link Experiment

    NASA Technical Reports Server (NTRS)

    Biswas, A.; Ceniceros, J.; Novak, M.; Jeganathan, M.; Portillo, A.; Erickson, D.; Depew, J.; Sanii, B.; Lesh, J. R.

    2000-01-01

    Mountain-top to mountain-top optical link experiments have been initiated at JPL, in order to perform a systems level evaluation of optical communications. Progress made so far is reported. ne NASA, JPL developed optical communications demonstrator (OCD) is used to transmit a laser signal from Strawberry Peak (SP), located in the San Bernadino mountains of California. This laser beam is received by a 0.6 m aperture telescope at JPL's Table Mountain Facility (TMF), located in Wrightwood, California. The optical link is bi-directional with the TMF telescope transmitting a continuous 4-wave (cw) 780 run beacon and the OCD sending back a 840 nm, 100 - 500 Mbps pseudo noise (PN) modulated, laser beam. The optical link path is at an average altitude of 2 km above sea level, covers a range of 46.8 km and provides an atmospheric channel equivalent to approx. 4 air masses. Average received power measured at either end fall well within the uncertainties predicted by link analysis. The reduction in normalized intensity variance (sigma(sup 2, sub I)) for the 4-beam beacon, compared to each individual beam, at SP, was from approx. 0.68 to 0.22. With some allowance for intra-beam mis-alignment, this is consistent with incoherent averaging. The sigma(sup2, sub I) measured at TMF approx. 0.43 +/- 0.22 exceeded the expected aperture averaged value of less than 0.1, probably because of beam wander. The focused spot sizes of approx. 162 +/- 6 microns at the TMF Coude and approx. 64 +/- 3 microns on the OCD compare to the predicted size range of 52 - 172 microns and 57 - 93 microns, respectively. This is consistent with 4 - 5 arcsec of atmospheric "seeing". The preliminary evaluation of OCD's fine tracking indicates that the uncompensated tracking error is approx. 3.3 micro rad compared to approx. 1.7 micro rad observed in the laboratory. Fine tracking performance was intermittent, primarily due to beacon fades on the OCD tracking sensor. The best bit error rates observed while

  18. Spin in the worldline path integral in 2 + 1 dimensions

    SciTech Connect

    Fosco, C.D.; Sanchez-Guillen, J.; Vazquez, R.A.

    2008-02-15

    We present a constructive derivation of a worldline path integral for the effective action and the propagator of a Dirac field in 2 + 1 dimensions, in terms of spacetime and SU(2) paths. After studying some general properties of this representation, we show that the auxiliary gauge-group variable can be integrated, deriving a worldline action depending only on x({tau}), the spacetime paths. We then show that the functional integral automatically imposes the constraint x{sup .2}({tau})=1, while there is a spin action, which agrees with the one one should expect for a spin-1/2 field.

  19. Light-like Wilson line in QCD without path ordering

    NASA Astrophysics Data System (ADS)

    Nayak, Gouranga C.

    2016-07-01

    Unlike the Wilson line in QED the Wilson line in QCD contains path ordering. In this paper we get rid of the path ordering in the light-like Wilson line in QCD by simplifying all the infinite number of noncommuting terms in the SU(3) pure gauge. We prove that the light-like Wilson line in QCD naturally emerges when path integral formulation of QCD is used to prove factorization of soft and collinear divergences at all order in coupling constant in QCD processes at high energy colliders.

  20. Path Planning for Semi-automated Simulated Robotic Neurosurgery

    PubMed Central

    Hu, Danying; Gong, Yuanzheng; Hannaford, Blake; Seibel, Eric J.

    2015-01-01

    This paper considers the semi-automated robotic surgical procedure for removing the brain tumor margins, where the manual operation is a tedious and time-consuming task for surgeons. We present robust path planning methods for robotic ablation of tumor residues in various shapes, which are represented in point-clouds instead of analytical geometry. Along with the path plans, corresponding metrics are also delivered to the surgeon for selecting the optimal candidate in the automated robotic ablation. The selected path plan is then executed and tested on RAVEN™ II surgical robot platform as part of the semi-automated robotic brain tumor ablation surgery in a simulated tissue phantom. PMID:26705501

  1. Applying Source and Path Corrections to Improve Discrimination in China,

    SciTech Connect

    Hartse, H. E.; Taylor, S. R.; Phillips, W. S.; Randall, G. E.

    1997-01-01

    Monitoring the Comprehensive Test Ban Treaty (CTBT) to magnitude levels below 4.0 will require use of regional seismic data recorded at distances of less than 2000 km. To improve regional discriminant performance we tested three different methods of correcting for path effects, and the third method includes a correction for source-scaling. We used regional recordings of broadband from stations in and near China. Our first method removes trends between phase ratios and physical parameters associated with each event-station path. This approach requires knowledge of the physical parameters along an event-station path, such as topography, basin thickness, and crustal thickness. Our second approach is somewhat more empirical. We examine spatial distributions of phase amplitudes after subtracting event magnitude and correcting for path distance. For a given station, phase, and frequency band, we grid and then smooth the magnitude-corrected and distance-corrected amplitudes to create a map representing a correction surface. We reference these maps to correct phase amplitudes prior to forming discrimination ratios. Our third approach is the most complicated, but also the most rigorous. For a given station and phase, we invert the spectra of a number of well-recorded earthquakes for source and path parameters. We then use the values obtained from the inversion to correct phase amplitudes for the effects of source size, distance, and attenuation. Finally,the amplitude residuals are gridded and smoothed to create a correction surface representing secondary path effects. We find that simple ratio- parameter corrections can improve discrimination performance along some paths (such as Kazakh Test Site (KTS) to WMQ), but for other paths (such as Lop Nor to AAK) the corrections are not beneficial. Our second method, the empirical path correction surfaces, improves discrimination performance for Lop Nor to AAK paths. Our third method, combined source and path corrections, has only

  2. Generating penetration path hypotheses for decision support in multiple trauma.

    PubMed Central

    Ogunyemi, O.; Kaye, J.; Webber, B.; Clarke, J. R.

    1995-01-01

    We present a 3D graphical system that allows users to visualize different penetration path hypotheses for (multiple) gunshot or stab wounds, using a 3D graphical model of a human body with appropriate anatomical structures. The system also identifies the anatomical structures associated with each hypothesis. The various penetration path hypotheses follow from a combinatorial analysis of the set of surface wounds. The affected structures are determined by performing a detailed interpenetration analysis between 3D models of a penetration path and each anatomical structure within the body. Images Figure 2 Figure 3 PMID:8563315

  3. Path Integrals and Exotic Options:. Methods and Numerical Results

    NASA Astrophysics Data System (ADS)

    Bormetti, G.; Montagna, G.; Moreni, N.; Nicrosini, O.

    2005-09-01

    In the framework of Black-Scholes-Merton model of financial derivatives, a path integral approach to option pricing is presented. A general formula to price path dependent options on multidimensional and correlated underlying assets is obtained and implemented by means of various flexible and efficient algorithms. As an example, we detail the case of Asian call options. The numerical results are compared with those obtained with other procedures used in quantitative finance and found to be in good agreement. In particular, when pricing at the money (ATM) and out of the money (OTM) options, path integral exhibits competitive performances.

  4. Selecta from a Life-Long Obsession with Path Integrals

    SciTech Connect

    Klauder, John R.

    2008-06-18

    The definition and interpretation of canonical, phase space path integrals has evolved over many years to achieve a form that now admits a correct and rigorous formulation, which is also covariant under canonical coordinate transformations. Such formulations involve coherent state representations, which, in their modern version, were originally introduced as an alternative tool to construct phase space path integrals. Moreover, coherent state representations lead to physical interpretations that are more natural than those afforded by more traditional representations. Suitable continuous time regularization procedures lead to a covariant phase space path integral formulation that greatly clarifies the vague phrase that canonical quantization requires Cartesian coordinates.

  5. Oblique along path toward structures at rear of parcel. Original ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Oblique along path toward structures at rear of parcel. Original skinny mosaic path along edge of structures was altered (delineation can be seen in concrete) path was widened with a newer mosaic to make access to the site safer. Structures (from right) edge of Round House (with "Spring Garden"), Pencil house, Shell House, School House, wood lattice is attached to chain-link fence along north (rear) property line. These structures were all damaged by the 1994 Northridge earthquake. Camera facing northeast. - Grandma Prisbrey's Bottle Village, 4595 Cochran Street, Simi Valley, Ventura County, CA

  6. ZLN005 protects cardiomyocytes against high glucose-induced cytotoxicity by promoting SIRT1 expression and autophagy.

    PubMed

    Li, Wenju; Li, Xiaoli; Wang, Bin; Chen, Yan; Xiao, Aiping; Zeng, Di; Ou, Dongbo; Yan, Song; Li, Wei; Zheng, Qiangsun

    2016-07-01

    Diabetic cardiomyopathy increases the risk for the development of heart failure independent of coronary artery disease and hypertension. Either type 1 or type 2 diabetes is often accompanied by varying degrees of hyperglycemia, which has been proven to induce myocardial apoptosis in animal models. Recently, a novel small molecule, ZLN005, has been reported to show antidiabetic efficacy in a mouse model, possibly by induction of PGC-1α expression. In this study, we investigated whether ZLN005 protects cardiomyocytes against high glucose-induced cytotoxicity and the mechanisms involved. Neonatal mouse cardiomyocytes were incubated with media containing 5.5 or 33mM glucose for 24h in the presence or absence of ZLN005. ZLN005 treatment led to ameliorated cardiomyocyte oxidative injury, enhanced cell viability, and reduced apoptosis in the high glucose environment. Western blot analysis revealed that high glucose suppressed cardiomyocyte autophagy, whereas ZLN005 increased the expression of autophagy marker proteins ATG5, beclin1, and LC3 II/LC3 I; this increase was accompanied by increased expression of SIRT1. Furthermore, EX527, a SIRT1-specific inhibitor, weakened the protective effects of ZLN005 on cardiomyocytes subjected to high glucose. Taken together, these results suggest that ZLN005 suppresses high glucose-induced cardiomyocyte injury by promoting SIRT1 expression and autophagy. PMID:27208585

  7. Dissemination of veterinary antibiotics and corresponding resistance genes from a concentrated swine feedlot along the waste treatment paths.

    PubMed

    Wang, Jian; Ben, Weiwei; Yang, Min; Zhang, Yu; Qiang, Zhimin

    2016-01-01

    Swine feedlots are an important pollution source of antibiotics and antibiotic resistance genes (ARGs) to the environment. This study investigated the dissemination of two classes of commonly-used veterinary antibiotics, namely, tetracyclines (TCs) and sulfonamides (SAs), and their corresponding ARGs along the waste treatment paths from a concentrated swine feedlot located in Beijing, China. The highest total TC and total SA concentrations detected were 166.7mgkg(-1) and 64.5μgkg(-1) in swine manure as well as 388.7 and 7.56μgL(-1) in swine wastewater, respectively. Fourteen tetracycline resistance genes (TRGs) encoding ribosomal protection proteins (RPP), efflux proteins (EFP) and enzymatic inactivation proteins, three sulfonamide resistance genes (SRGs), and two integrase genes were detected along the waste treatment paths with detection frequencies of 33.3-75.0%. The relative abundances of target ARGs ranged from 2.74×10(-6) to 1.19. The antibiotics and ARGs generally declined along both waste treatment paths, but their degree of reduction was more significant along the manure treatment path. The RPP TRGs dominated in the upstream samples and then decreased continuously along both waste treatment paths, whilst the EFP TRGs and SRGs maintained relatively stable. Strong correlations between antibiotic concentrations and ARGs were observed among both manure and wastewater samples. In addition, seasonal temperature, and integrase genes, moisture content and nutrient level of tested samples could all impact the relative abundances of ARGs along the swine waste treatment paths. This study helps understand the evolution and spread of ARGs from swine feedlots to the environment as well as assess the environmental risk arising from swine waste treatment. PMID:27128716

  8. Kinetic paths, time scale, and underlying landscapes: A path integral framework to study global natures of nonequilibrium systems and networks

    NASA Astrophysics Data System (ADS)

    Wang, Jin; Zhang, Kun; Wang, Erkwang

    2010-09-01

    We developed a general framework to quantify three key ingredients for dynamics of nonequilibrium systems through path integrals in length space. First, we identify dominant kinetic paths as the ones with optimal weights, leading to effective reduction of dimensionality or degrees of freedom from exponential to polynomial so large systems can be treated. Second, we uncover the underlying nonequilibrium potential landscapes from the explorations of the state space through kinetic paths. We apply our framework to a specific example of nonequilibrium network system: lambda phage genetic switch. Two distinct basins of attractions emerge. The dominant kinetic paths from one basin to another are irreversible and do not follow the usual steepest descent or gradient path along the landscape. It reflects the fact that the dynamics of nonequilibrium systems is not just determined by potential gradient but also the residual curl flux force, suggesting experiments to test theoretical predictions. Third, we have calculated dynamic transition time scales from one basin to another critical for stability of the system through instantons. Theoretical predictions are in good agreements with wild type and mutant experiments. We further uncover the correlations between the kinetic transition time scales and the underlying landscape topography: the barrier heights along the dominant paths. We found that both the dominant paths and the landscape are relatively robust against the influences of external environmental perturbations and the system tends to dissipate less with less fluctuations. Our general framework can be applied to other nonequilibrium systems.

  9. Dynamic protected lightpath provisioning in mesh WDM networks

    NASA Astrophysics Data System (ADS)

    Zhu, Guolong; Zeng, Qingji; Xu, Tian; Ye, Tong; Yang, Junjie

    2005-03-01

    This paper investigates the problem of dynamic protected lightpath services provisioning in optical mesh networks employing wavelength division multiplexing (WDM). A variety of schemes for dynamic protected services provisioning have been proposed, supporting a range of tradeoffs among restoration speed, capacity efficiency, and scalability. In this paper, we propose a novel scheme, called p-cycles-based maximum protected working capacity envelope (PC-MPWCE), which can offer an attractive combination of features: ring-like speed, mesh-like capacity efficiency, and good scalability. To evaluate the performance of PC-MPWCE, we compare it via simulation with 1+1 automatic protection switching (APS) and two well-known shared backup path protection (SBPP) on NSFNET. Our simulation results show that PC-MPWCE can achieve much better blocking performance than 1+1 APS, and perform the similar blocking performance and capacity efficiency as SBPP.

  10. 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.

  11. Diffractive paths for weak localization in quantum billiards

    NASA Astrophysics Data System (ADS)

    Březinová, Iva; Stampfer, Christoph; Wirtz, Ludger; Rotter, Stefan; Burgdörfer, Joachim

    2008-04-01

    We study the weak-localization effect in quantum transport through a clean ballistic cavity with regular classical dynamics. We address the question which paths account for the suppression of conductance through a system where disorder and chaos are absent. By exploiting both quantum and semiclassical methods, we unambiguously identify paths that are diffractively backscattered into the cavity (when approaching the lead mouths from the cavity interior) to play a key role. Diffractive scattering couples transmitted and reflected paths and is thus essential to reproduce the weak-localization peak in reflection and the corresponding antipeak in transmission. A comparison of semiclassical calculations featuring these diffractive paths yields good agreement with full quantum calculations and experimental data. Our theory provides system-specific predictions for the quantum regime of few open lead modes and can be expected to be relevant also for mixed as well as chaotic systems.

  12. Cool & Dry: Dual-Path Approach for a Florida School.

    ERIC Educational Resources Information Center

    Khattar, Mukesh; Shirey, Don, III; Raustad, Richard

    2003-01-01

    Describes how the Brevard County School District in Florida teamed with companies EPRI and Florida Power and Light to implement a dual-path, low temperature air-distribution system used in conjunction with thermal energy storage. (EV)

  13. A self-interfering clock as a "which path" witness.

    PubMed

    Margalit, Yair; Zhou, Zhifan; Machluf, Shimon; Rohrlich, Daniel; Japha, Yonathan; Folman, Ron

    2015-09-11

    In Einstein's general theory of relativity, time depends locally on gravity; in standard quantum theory, time is global-all clocks "tick" uniformly. We demonstrate a new tool for investigating time in the overlap of these two theories: a self-interfering clock, comprising two atomic spin states. We prepare the clock in a spatial superposition of quantum wave packets, which evolve coherently along two paths into a stable interference pattern. If we make the clock wave packets "tick" at different rates, to simulate a gravitational time lag, the clock time along each path yields "which path" information, degrading the pattern's visibility. In contrast, in standard interferometry, time cannot yield "which path" information. This proof-of-principle experiment may have implications for the study of time and general relativity and their impact on fundamental effects such as decoherence and the emergence of a classical world. PMID:26249229

  14. 24. VIEW IN THE HOLLOW ALONG THE PATH, LOOKING SOUTHEAST. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    24. VIEW IN THE HOLLOW ALONG THE PATH, LOOKING SOUTHEAST. (NOTE: HISTORIC FLOWERING DOGWOOD AND MAXIMUM RHODODENDRON IN RIGHT FOREGROUND; EPIMEDIUM, FERNS, AND IRIS IN CENTER BED). - Fairsted, 99 Warren Street, Brookline, Norfolk County, MA

  15. View of exterior circumferential path at northwest side of building, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of exterior circumferential path at northwest side of building, looking east toward building entrance - National Zoological Park, Bird House, 3001 Connecticut Avenue NW, Washington, District of Columbia, DC

  16. Nonlinear Dimensionality Reduction via Path-Based Isometric Mapping.

    PubMed

    Najafi, Amir; Joudaki, Amir; Fatemizadeh, Emad

    2016-07-01

    Nonlinear dimensionality reduction methods have demonstrated top-notch performance in many pattern recognition and image classification tasks. Despite their popularity, they suffer from highly expensive time and memory requirements, which render them inapplicable to large-scale datasets. To leverage such cases we propose a new method called "Path-Based Isomap". Similar to Isomap, we exploit geodesic paths to find the low-dimensional embedding. However, instead of preserving pairwise geodesic distances, the low-dimensional embedding is computed via a path-mapping algorithm. Due to the much fewer number of paths compared to number of data points, a significant improvement in time and memory complexity with a comparable performance is achieved. The method demonstrates state-of-the-art performance on well-known synthetic and real-world datasets, as well as in the presence of noise. PMID:26452249

  17. Critical Path Modeling: University Planning in an Urban Context.

    ERIC Educational Resources Information Center

    Vasse, William W.; And Others

    1983-01-01

    The experiences of the University of Michigan in developing its Flint campus since the mid-1970s and the use of the Critical Path Method are described. The usefulness of the method during several phases of development is highlighted. (MSE)

  18. Safe Maritime Autonomous Path Planning in a High Sea State

    NASA Technical Reports Server (NTRS)

    Ono, Masahiro; Quadrelli, Marco; Huntsberger, Terrance L.

    2014-01-01

    This paper presents a path planning method for sea surface vehicles that prevents capsizing and bow-diving in a high sea-state. A key idea is to use response amplitude operators (RAOs) or, in control terminology, the transfer functions from a sea state to a vessel's motion, in order to find a set of speeds and headings that results in excessive pitch and roll oscillations. This information is translated to arithmetic constraints on the ship's velocity, which are passed to a model predictive control (MPC)-based path planner to find a safe and optimal path that achieves specified goals. An obstacle avoidance capability is also added to the path planner. The proposed method is demonstrated by simulations.

  19. 4. STREAMSIDE PATH, SOUTH OF STREAM, LOOKING WEST AT MIDDLE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. STREAM-SIDE PATH, SOUTH OF STREAM, LOOKING WEST AT MIDDLE FALLS OF THE THREE BRIDGE FALLS NEAR JUNCTION WITH FORSYTHIA WALK 1988 - Dumbarton Oaks Park, Thirty-second & R Streets Northwest, Washington, District of Columbia, DC

  20. 8. STREAMSIDE PATH NEAR MIDDLE OF THREE SISTERS FALLS, LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. STREAM-SIDE PATH NEAR MIDDLE OF THREE SISTERS FALLS, LOOKING WEST Photocopy of photograph, 1930s National Park Service, National Capital Region files - Dumbarton Oaks Park, Thirty-second & R Streets Northwest, Washington, District of Columbia, DC

  1. GENERAL VIEW LOOKING NORTH TOWARDS THE OUTBUILDINGS. PATH IN FOREGROUND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    GENERAL VIEW LOOKING NORTH TOWARDS THE OUTBUILDINGS. PATH IN FOREGROUND EXTENDS NORTHWESTERLY FROM THE SCHUYLKILL RIVER TO THE HOUSE - John Bartram House & Garden, 54th Street & Lindbergh Boulevard, Philadelphia, Philadelphia County, PA

  2. 58. HAIWEE POWER PLANT LOOKING NORTH ALONG PATH OF AQUEDUCT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    58. HAIWEE POWER PLANT LOOKING NORTH ALONG PATH OF AQUEDUCT - Los Angeles Aqueduct, From Lee Vining Intake (Mammoth Lakes) to Van Norman Reservoir Complex (San Fernando Valley), Los Angeles, Los Angeles County, CA

  3. Overview in two parts: Right view showing orchard path on ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Overview in two parts: Right view showing orchard path on left eucalyptus windbreak bordering knoll on right. Camera facing 278" west. - Goerlitz House, 9893 Highland Avenue, Rancho Cucamonga, San Bernardino County, CA

  4. 25. SAME AREA, FROM LEFT TO RIGHT: PATH, BEACH DRIVE, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    25. SAME AREA, FROM LEFT TO RIGHT: PATH, BEACH DRIVE, AND PARK ROAD ATOP ROCK FACE. NOTE STONE INFILL MIMICKING NATURAL STONE OUTCROPPING. VIEW N. - Rock Creek Park Road System, Washington, District of Columbia, DC

  5. 2. DETAIL OF CONVEYOR BELT PATH AND CATWALK, NORTHEAST VIEW. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. DETAIL OF CONVEYOR BELT PATH AND CATWALK, NORTHEAST VIEW. - Vanadium Corporation of America (VCA) Naturita Mill, Grinding Rod Mill, 3 miles Northwest of Naturita, between Highway 141 & San Miguel River, Naturita, Montrose County, CO

  6. VIEW ALONG PATH EXTENDING NORTHWESTERLY FROM THE SCHUYLKILL RIVER TO ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW ALONG PATH EXTENDING NORTHWESTERLY FROM THE SCHUYLKILL RIVER TO THE HOUSE. (DUPLICATE OF HALS NO. PA-1-15) - John Bartram House & Garden, 54th Street & Lindbergh Boulevard, Philadelphia, Philadelphia County, PA

  7. Alarm guided critical function and success path monitoring

    DOEpatents

    Scarola, Kenneth; Jamison, David S.; Manazir, Richard M.; Rescorl, Robert L.; Harmon, Daryl L.

    1994-01-01

    The use of alarm indication on the overview (IPSO) display to initiate diagnosis of challenges to critical functions or unavailability of success paths, and further alarm-based guidance toward ultimate diagnosis.

  8. Evolution-based path planning and management for autonomous vehicles

    NASA Astrophysics Data System (ADS)

    Capozzi, Brian Joseph

    2001-07-01

    This dissertation describes an approach to adaptive path planning based on the problem solving capabilities witnessed in nature---namely the influence of natural selection in uncovering solutions to the characteristics of the environment. The competition for survival forces organisms to either respond to changes or risk being evolved out of the population. We demonstrate the applicability of this process to the problem of finding paths for an autonomous vehicle through a number of different static and dynamic environments. In doing so, we develop a number of different ways in which these paths can be modeled for the purposes of evolution. Through analysis and experimentation, we develop and reinforce a set of principles and conditions which must hold for the search process to be successful. Having demonstrated the viability of evolution as a guide for path planning, we discuss implications for on-line, real-time planning for autonomous vehicles.

  9. Single molecule fluorescence experiments determine protein folding transition path times

    PubMed Central

    Chung, Hoi Sung; McHale, Kevin; Louis, John M.; Eaton, William A.

    2013-01-01

    The transition path is the tiny fraction of an equilibrium molecular trajectory when a transition occurs by crossing the free-energy barrier between two states. It is a single-molecule property that contains all the mechanistic information on how a process occurs. As a step toward observing transition paths in protein folding we determined the average transition-path time for a fast- and a slow-folding protein from a photon-by-photon analysis of fluorescence trajectories in single-molecule Förster-resonance-energy-transfer experiments. While the folding rate coefficients differ by a factor of 10,000, the transition-path times differ by less than a factor of 5, showing that a fast-and a slow-folding protein take almost the same time to fold when folding actually happens. A very simple model based on energy landscape theory can explain this result. PMID:22363011

  10. Global path following control for underactuated stratospheric airship

    NASA Astrophysics Data System (ADS)

    Zheng, Zewei; Wu, Zhe

    2013-10-01

    This paper develops a nonlinear path following control method that drives an underactuated stratospheric airship onto a predefined planar path with a given speed profile. The dynamic model of the airship used for controller design is first introduced with kinematics and dynamics equations. In order to render good pilot behavior for the control action, a guidance controller by referring to the guidance-based path following principle is derived. Then the controller is extended to cope with the airship attitude and velocity by resorting to the backstepping and Lyapunov-based techniques. The designed control system finally possesses a cascaded structure which consists of guidance loop, attitude control loop and velocity control loop. Stability analysis shows that the controlled closed-loop system is globally asymptotically stable, and the sway velocity which cannot be directly controlled is bounded. Simulation results for the airship following typical paths are illustrated to verify effectiveness of the proposed approach.

  11. Assessment of weighted-least-squares-based gas path analysis

    NASA Astrophysics Data System (ADS)

    Doel, D. L.

    1994-04-01

    Manufacturers of gas turbines have searched for three decades for a reliable way to use gas path measurements to determine the health of jet engine components. They have been hindered in this pursuit by the quality of the measurements used to carry out the analysis. Engine manufacturers have chosen weighted-least-squares techniques to reduce the inaccuracy caused by sensor error. While these algorithms are clearly an improvement over the previous generation of gas path analysis programs, they still fail in many situations. This paper describes some of the failures and explores their relationship to the underlying analysis technique. It also describes difficulties in implementing a gas path analysis program. The paper concludes with an appraisal of weighted-least-squares-based gas path analysis.

  12. Maximal Sensitive Dependence and the Optimal Path to Epidemic Extinction

    PubMed Central

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

    2010-01-01

    Extinction of an epidemic or a species is a rare event that occurs due to a large, rare stochastic fluctuation. Although the extinction process is dynamically unstable, it follows an optimal path that maximizes the probability of extinction. We show that the optimal path is also directly related to the finite-time Lyapunov exponents of the underlying dynamical system in that the optimal path displays maximum sensitivity to initial conditions. We consider several stochastic epidemic models, and examine the extinction process in a dynamical systems framework. Using the dynamics of the finite-time Lyapunov exponents as a constructive tool, we demonstrate that the dynamical systems viewpoint of extinction evolves naturally toward the optimal path. PMID:20352495

  13. THREEQUARTER VIEW FROM PEDESTRIAN PATH LEVEL, LOOKING SOUTHEAST, SHOWING BALUSTRADE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    THREE-QUARTER VIEW FROM PEDESTRIAN PATH LEVEL, LOOKING SOUTHEAST, SHOWING BALUSTRADE AND WEST ELEVATION OF BRIDGE. - Central Park Bridges, Gothic Arch, Spanning bridlepath south of tennis courts at northwest edge of Reservoir, Central Park, New York County, NY

  14. 3. Threequarter view from pedestrian path level, looking southeast, showing ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. Three-quarter view from pedestrian path level, looking southeast, showing balustrade and west elevation of bridge - Central Park Bridges, Gothic Arch, Spanning bridlepath south of tennis courts at northwest edge of Reservoir, Central Park, New York County, NY

  15. 47 CFR 101.143 - Minimum path length requirements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path length requirements. (a) The... carrier fixed point-to-point microwave services must equal or exceed the value set forth in the...

  16. 47 CFR 101.143 - Minimum path length requirements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.143 Minimum path length requirements. (a) The... carrier fixed point-to-point microwave services must equal or exceed the value set forth in the...

  17. Bifurcation of transition paths induced by coupled bistable systems.

    PubMed

    Tian, Chengzhe; Mitarai, Namiko

    2016-06-01

    We discuss the transition paths in a coupled bistable system consisting of interacting multiple identical bistable motifs. We propose a simple model of coupled bistable gene circuits as an example and show that its transition paths are bifurcating. We then derive a criterion to predict the bifurcation of transition paths in a generalized coupled bistable system. We confirm the validity of the theory for the example system by numerical simulation. We also demonstrate in the example system that, if the steady states of individual gene circuits are not changed by the coupling, the bifurcation pattern is not dependent on the number of gene circuits. We further show that the transition rate exponentially decreases with the number of gene circuits when the transition path does not bifurcate, while a bifurcation facilitates the transition by lowering the quasi-potential energy barrier. PMID:27276971

  18. PCB Drill Path Optimization by Combinatorial Cuckoo Search Algorithm

    PubMed Central

    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

  19. Analyzing methods for path mining with applications in metabolomics.

    PubMed

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

    2014-01-25

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

  20. 7. ORIGINAL SOUTH SIDE, EAST PART, ALSO SHOWING PATH FROM ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. ORIGINAL SOUTH SIDE, EAST PART, ALSO SHOWING PATH FROM EAST FRONT LEADING TO CENTRAL CAMPUS. - U.S. Geological Survey, Rock Magnetics Laboratory, 345 Middlefield Road, Menlo Park, San Mateo County, CA