Numerical simulation of distributed snow processes in complex terrain utilizing triangulated irregular networks (TINs)

NASA Astrophysics Data System (ADS)

Rinehart, A. J.; Vivoni, E. R.

2005-12-01

Snow processes play a significant role in the hydrologic cycle of mountainous and high-latitude catchments in the western United States. Snowmelt runoff contributes to a large percentage of stream runoff while snow covered regions remain highly localized to small portions of the catchment area. The appropriate representation of snow dynamics at a given range of spatial and temporal scales is critical for adequately predicting runoff responses in snowmelt-dominated watersheds. In particular, the accurate depiction of snow cover patterns is important as a range of topographic, land-use and geographic parameters create zones of preferential snow accumulation or ablation that significantly affect the timing of a region's snow melt and the persistence of a snow pack. In this study, we present the development and testing of a distributed snow model designed for simulations over complex terrain. The snow model is developed within the context of the TIN-based Real-time Integrated Basin Simulator (tRIBS), a fully-distributed watershed model capable of continuous simulations of coupled hydrological processes, including unsaturated-saturated zone dynamics, land-atmosphere interactions and runoff generation via multiple mechanisms. The use of triangulated irregular networks as a domain discretization allows tRIBS to accurately represent topography with a reduced number of computational nodes, as compared to traditional grid-based models. This representation is developed using a Delauney optimization criterion that causes areas of topographic homogeneity to be represented at larger spatial scales than the original grid, while more heterogeneous areas are represented at higher resolutions. We utilize the TIN-based terrain representation to simulate microscale (10-m to 100-m) snow pack dynamics over a catchment. The model includes processes such as the snow pack energy balance, wind and bulk redistribution, and snow interception by vegetation. For this study, we present tests from a distributed one-layer energy balance model as applied to a northern New Mexico hillslope in a ponderosa pine forest using both synthetic and real meteorological forcing. We also provide tests of the model's capability to represent spatial patterns within a small watershed in the Jemez Mountain region. Finally, we discuss the interaction of the tested snow process module with existing components in the watershed model and additional applications and capabilities under development.

Location accuracy evaluation of lightning location systems using natural lightning flashes recorded by a network of high-speed cameras

NASA Astrophysics Data System (ADS)

Alves, J.; Saraiva, A. C. V.; Campos, L. Z. D. S.; Pinto, O., Jr.; Antunes, L.

2014-12-01

This work presents a method for the evaluation of location accuracy of all Lightning Location System (LLS) in operation in southeastern Brazil, using natural cloud-to-ground (CG) lightning flashes. This can be done through a multiple high-speed cameras network (RAMMER network) installed in the Paraiba Valley region - SP - Brazil. The RAMMER network (Automated Multi-camera Network for Monitoring and Study of Lightning) is composed by four high-speed cameras operating at 2,500 frames per second. Three stationary black-and-white (B&W) cameras were situated in the cities of São José dos Campos and Caçapava. A fourth color camera was mobile (installed in a car), but operated in a fixed location during the observation period, within the city of São José dos Campos. The average distance among cameras was 13 kilometers. Each RAMMER sensor position was determined so that the network can observe the same lightning flash from different angles and all recorded videos were GPS (Global Position System) time stamped, allowing comparisons of events between cameras and the LLS. The RAMMER sensor is basically composed by a computer, a Phantom high-speed camera version 9.1 and a GPS unit. The lightning cases analyzed in the present work were observed by at least two cameras, their position was visually triangulated and the results compared with BrasilDAT network, during the summer seasons of 2011/2012 and 2012/2013. The visual triangulation method is presented in details. The calibration procedure showed an accuracy of 9 meters between the accurate GPS position of the object triangulated and the result from the visual triangulation method. Lightning return stroke positions, estimated with the visual triangulation method, were compared with LLS locations. Differences between solutions were not greater than 1.8 km.

Complex network view of evolving manifolds

NASA Astrophysics Data System (ADS)

da Silva, Diamantino C.; Bianconi, Ginestra; da Costa, Rui A.; Dorogovtsev, Sergey N.; Mendes, José F. F.

2018-03-01

We study complex networks formed by triangulations and higher-dimensional simplicial complexes representing closed evolving manifolds. In particular, for triangulations, the set of possible transformations of these networks is restricted by the condition that at each step, all the faces must be triangles. Stochastic application of these operations leads to random networks with different architectures. We perform extensive numerical simulations and explore the geometries of growing and equilibrium complex networks generated by these transformations and their local structural properties. This characterization includes the Hausdorff and spectral dimensions of the resulting networks, their degree distributions, and various structural correlations. Our results reveal a rich zoo of architectures and geometries of these networks, some of which appear to be small worlds while others are finite dimensional with Hausdorff dimension equal or higher than the original dimensionality of their simplices. The range of spectral dimensions of the evolving triangulations turns out to be from about 1.4 to infinity. Our models include simplicial complexes representing manifolds with evolving topologies, for example, an h -holed torus with a progressively growing number of holes. This evolving graph demonstrates features of a small-world network and has a particularly heavy-tailed degree distribution.

Detecting TLEs using a massive all-sky camera network

NASA Astrophysics Data System (ADS)

Garnung, M. B.; Celestin, S. J.

2017-12-01

Transient Luminous Events (TLEs) are large-scale optical events occurring in the upper-atmosphere from the top of thunderclouds up to the ionosphere. TLEs may have important effects in local, regional, and global scales, and many features of TLEs are not fully understood yet [e.g, Pasko, JGR, 115, A00E35, 2010]. Moreover, meteor events have been suggested to play a role in sprite initiation by producing ionospheric irregularities [e.g, Qin et al., Nat. Commun., 5, 3740, 2014]. The French Fireball Recovery and InterPlanetary Observation Network (FRIPON, https://www.fripon.org/?lang=en), is a national all-sky 30 fps camera network designed to continuously detect meteor events. We seek to make use of this network to observe TLEs over unprecedented space and time scales ( 1000×1000 km with continuous acquisition). To do so, we had to significantly modify FRIPON's triggering software Freeture (https://github.com/fripon/freeture) while leaving the meteor detection capability uncompromised. FRIPON has a great potential in the study of TLEs. Not only could it produce new results about spatial and time distributions of TLEs over a very large area, it could also be used to validate and complement observations from future space missions such as ASIM (ESA) and TARANIS (CNES). In this work, we present an original image processing algorithm that can detect sprites using all-sky cameras while strongly limiting the frequency of false positives and our ongoing work on sprite triangulation using the FRIPON network.

Real-world hydrologic assessment of a fully-distributed hydrological model in a parallel computing environment

NASA Astrophysics Data System (ADS)

Vivoni, Enrique R.; Mascaro, Giuseppe; Mniszewski, Susan; Fasel, Patricia; Springer, Everett P.; Ivanov, Valeriy Y.; Bras, Rafael L.

2011-10-01

SummaryA major challenge in the use of fully-distributed hydrologic models has been the lack of computational capabilities for high-resolution, long-term simulations in large river basins. In this study, we present the parallel model implementation and real-world hydrologic assessment of the Triangulated Irregular Network (TIN)-based Real-time Integrated Basin Simulator (tRIBS). Our parallelization approach is based on the decomposition of a complex watershed using the channel network as a directed graph. The resulting sub-basin partitioning divides effort among processors and handles hydrologic exchanges across boundaries. Through numerical experiments in a set of nested basins, we quantify parallel performance relative to serial runs for a range of processors, simulation complexities and lengths, and sub-basin partitioning methods, while accounting for inter-run variability on a parallel computing system. In contrast to serial simulations, the parallel model speed-up depends on the variability of hydrologic processes. Load balancing significantly improves parallel speed-up with proportionally faster runs as simulation complexity (domain resolution and channel network extent) increases. The best strategy for large river basins is to combine a balanced partitioning with an extended channel network, with potential savings through a lower TIN resolution. Based on these advances, a wider range of applications for fully-distributed hydrologic models are now possible. This is illustrated through a set of ensemble forecasts that account for precipitation uncertainty derived from a statistical downscaling model.

Estimating network parameters from combined dynamics of firing rate and irregularity of single neurons.

PubMed

Hamaguchi, Kosuke; Riehle, Alexa; Brunel, Nicolas

2011-01-01

High firing irregularity is a hallmark of cortical neurons in vivo, and modeling studies suggest a balance of excitation and inhibition is necessary to explain this high irregularity. Such a balance must be generated, at least partly, from local interconnected networks of excitatory and inhibitory neurons, but the details of the local network structure are largely unknown. The dynamics of the neural activity depends on the local network structure; this in turn suggests the possibility of estimating network structure from the dynamics of the firing statistics. Here we report a new method to estimate properties of the local cortical network from the instantaneous firing rate and irregularity (CV(2)) under the assumption that recorded neurons are a part of a randomly connected sparse network. The firing irregularity, measured in monkey motor cortex, exhibits two features; many neurons show relatively stable firing irregularity in time and across different task conditions; the time-averaged CV(2) is widely distributed from quasi-regular to irregular (CV(2) = 0.3-1.0). For each recorded neuron, we estimate the three parameters of a local network [balance of local excitation-inhibition, number of recurrent connections per neuron, and excitatory postsynaptic potential (EPSP) size] that best describe the dynamics of the measured firing rates and irregularities. Our analysis shows that optimal parameter sets form a two-dimensional manifold in the three-dimensional parameter space that is confined for most of the neurons to the inhibition-dominated region. High irregularity neurons tend to be more strongly connected to the local network, either in terms of larger EPSP and inhibitory PSP size or larger number of recurrent connections, compared with the low irregularity neurons, for a given excitatory/inhibitory balance. Incorporating either synaptic short-term depression or conductance-based synapses leads many low CV(2) neurons to move to the excitation-dominated region as well as to an increase of EPSP size.

A fast and fully automatic registration approach based on point features for multi-source remote-sensing images

NASA Astrophysics Data System (ADS)

Yu, Le; Zhang, Dengrong; Holden, Eun-Jung

2008-07-01

Automatic registration of multi-source remote-sensing images is a difficult task as it must deal with the varying illuminations and resolutions of the images, different perspectives and the local deformations within the images. This paper proposes a fully automatic and fast non-rigid image registration technique that addresses those issues. The proposed technique performs a pre-registration process that coarsely aligns the input image to the reference image by automatically detecting their matching points by using the scale invariant feature transform (SIFT) method and an affine transformation model. Once the coarse registration is completed, it performs a fine-scale registration process based on a piecewise linear transformation technique using feature points that are detected by the Harris corner detector. The registration process firstly finds in succession, tie point pairs between the input and the reference image by detecting Harris corners and applying a cross-matching strategy based on a wavelet pyramid for a fast search speed. Tie point pairs with large errors are pruned by an error-checking step. The input image is then rectified by using triangulated irregular networks (TINs) to deal with irregular local deformations caused by the fluctuation of the terrain. For each triangular facet of the TIN, affine transformations are estimated and applied for rectification. Experiments with Quickbird, SPOT5, SPOT4, TM remote-sensing images of the Hangzhou area in China demonstrate the efficiency and the accuracy of the proposed technique for multi-source remote-sensing image registration.

Possibility of using NURBS for surface plotting by survey data

NASA Astrophysics Data System (ADS)

Pravdina, E. A.; Lepikhina, O. J.

2018-05-01

Different methods of surface plotting were discussed in this article. Constructing the surface with the help of the Delaunay triangulation algorithm is described. The TIN-surfaces (triangles irregular net) method is used in the entire CAD software. This type of surfaces is plotting by results of laser scanning and stadia surveying. Possibility of using spline surfaces (NURBS) for surface plotting is studied. For a defined number of points by Mathcad software, the curvilinear function that described two-dimensional spline surfaces was calculated and plotted.

State-of-the-Art: DTM Generation Using Airborne LIDAR Data

PubMed Central

Chen, Ziyue; Gao, Bingbo; Devereux, Bernard

2017-01-01

Digital terrain model (DTM) generation is the fundamental application of airborne Lidar data. In past decades, a large body of studies has been conducted to present and experiment a variety of DTM generation methods. Although great progress has been made, DTM generation, especially DTM generation in specific terrain situations, remains challenging. This research introduces the general principles of DTM generation and reviews diverse mainstream DTM generation methods. In accordance with the filtering strategy, these methods are classified into six categories: surface-based adjustment; morphology-based filtering, triangulated irregular network (TIN)-based refinement, segmentation and classification, statistical analysis and multi-scale comparison. Typical methods for each category are briefly introduced and the merits and limitations of each category are discussed accordingly. Despite different categories of filtering strategies, these DTM generation methods present similar difficulties when implemented in sharply changing terrain, areas with dense non-ground features and complicated landscapes. This paper suggests that the fusion of multi-sources and integration of different methods can be effective ways for improving the performance of DTM generation. PMID:28098810

a Method of Generating dem from Dsm Based on Airborne Insar Data

NASA Astrophysics Data System (ADS)

Lu, W.; Zhang, J.; Xue, G.; Wang, C.

2018-04-01

Traditional methods of terrestrial survey to acquire DEM cannot meet the requirement of acquiring large quantities of data in real time, but the DSM can be quickly obtained by using the dual antenna synthetic aperture radar interferometry and the DEM generated by the DSM is more fast and accurate. Therefore it is most important to acquire DEM from DSM based on airborne InSAR data. This paper aims to the method that generate DEM from DSM accurately. Two steps in this paper are applied to acquire accurate DEM. First of all, when the DSM is generated by interferometry, unavoidable factors such as overlay and shadow will produce gross errors to affect the data accuracy, so the adaptive threshold segmentation method is adopted to remove the gross errors and the threshold is selected according to the coherence of the interferometry. Secondly DEM will be generated by the progressive triangulated irregular network densification filtering algorithm. Finally, experimental results are compared with the existing high-precision DEM results. The results show that this method can effectively filter out buildings, vegetation and other objects to obtain the high-precision DEM.

Recent Greenland Thinning from Operation IceBridge ATM and LVIS Data

NASA Astrophysics Data System (ADS)

Sutterley, T. C.; Velicogna, I.

2015-12-01

We investigate regional thinning rates in Greenland using two Operation IceBridge lidar instruments, the Airborne Topographic Mapper (ATM) and the Land, Vegetation and Ice Sensor (LVIS). IceBridge and Pre-IceBridge ATM data are available from 1993 to present and IceBridge and Pre-Icebridge LVIS data are available from 2007 to present. We compare different techniques for combining the two datasets: overlapping footprints, triangulated irregular network meshing and radial basis functions. We validate the combination for periods with near term overlap of the two instruments. By combining the two lidar datasets, we are able to investigate intra-annual, annual, interannual surface elevation change. We investigate both the high melt season of 2012 and the low melt season of 2013. In addition, the major 2015 IceBridge Arctic campaign provides new crucial data for determining seasonal ice sheet thinning rates. We compare our LVIS/ATM results with surface mass balance outputs from two regional climate models: the Regional Atmospheric Climate Model (RACMO) and the Modèle Atmosphérique Régional (MAR). We also investigate the thinning rates of major outlet glaciers.

Exact and heuristic algorithms for Space Information Flow.

PubMed

Uwitonze, Alfred; Huang, Jiaqing; Ye, Yuanqing; Cheng, Wenqing; Li, Zongpeng

2018-01-01

Space Information Flow (SIF) is a new promising research area that studies network coding in geometric space, such as Euclidean space. The design of algorithms that compute the optimal SIF solutions remains one of the key open problems in SIF. This work proposes the first exact SIF algorithm and a heuristic SIF algorithm that compute min-cost multicast network coding for N (N ≥ 3) given terminal nodes in 2-D Euclidean space. Furthermore, we find that the Butterfly network in Euclidean space is the second example besides the Pentagram network where SIF is strictly better than Euclidean Steiner minimal tree. The exact algorithm design is based on two key techniques: Delaunay triangulation and linear programming. Delaunay triangulation technique helps to find practically good candidate relay nodes, after which a min-cost multicast linear programming model is solved over the terminal nodes and the candidate relay nodes, to compute the optimal multicast network topology, including the optimal relay nodes selected by linear programming from all the candidate relay nodes and the flow rates on the connection links. The heuristic algorithm design is also based on Delaunay triangulation and linear programming techniques. The exact algorithm can achieve the optimal SIF solution with an exponential computational complexity, while the heuristic algorithm can achieve the sub-optimal SIF solution with a polynomial computational complexity. We prove the correctness of the exact SIF algorithm. The simulation results show the effectiveness of the heuristic SIF algorithm.

Using a Calculated Pulse Rate with an Artificial Neural Network to Detect Irregular Interbeats.

PubMed

Yeh, Bih-Chyun; Lin, Wen-Piao

2016-03-01

Heart rate is an important clinical measure that is often used in pathological diagnosis and prognosis. Valid detection of irregular heartbeats is crucial in the clinical practice. We propose an artificial neural network using the calculated pulse rate to detect irregular interbeats. The proposed system measures the calculated pulse rate to determine an "irregular interbeat on" or "irregular interbeat off" event. If an irregular interbeat is detected, the proposed system produces a danger warning, which is helpful for clinicians. If a non-irregular interbeat is detected, the proposed system displays the calculated pulse rate. We include a flow chart of the proposed software. In an experiment, we measure the calculated pulse rates and achieve an error percentage of < 3% in 20 participants with a wide age range. When we use the calculated pulse rates to detect irregular interbeats, we find such irregular interbeats in eight participants.

Modelling of Rainfall Induced Landslides in Puerto Rico

NASA Astrophysics Data System (ADS)

Lepore, C.; Arnone, E.; Sivandran, G.; Noto, L. V.; Bras, R. L.

2010-12-01

We performed an island-wide determination of static landslide susceptibility and hazard assessment as well as dynamic modeling of rainfall-induced shallow landslides in a particular hydrologic basin. Based on statistical analysis of past landslides, we determined that reliable prediction of the susceptibility to landslides is strongly dependent on the resolution of the digital elevation model (DEM) employed and the reliability of the rainfall data. A distributed hydrology model, Triangulated Irregular Network (TIN)-based Real-time Integrated Basin Simulator with VEGetation Generator for Interactive Evolution (tRIBS-VEGGIE), tRIBS-VEGGIE, has been implemented for the first time in a humid tropical environment like Puerto Rico and validated against in-situ measurements. A slope-failure module has been added to tRIBS-VEGGIE’s framework, after analyzing several failure criterions to identify the most suitable for our application; the module is used to predict the location and timing of landsliding events. The Mameyes basin, located in the Luquillo Experimental Forest in Puerto Rico, was selected for modeling based on the availability of soil, vegetation, topographical, meteorological and historic landslide data. Application of the model yields a temporal and spatial distribution of predicted rainfall-induced landslides.

A Coarse-to-Fine Geometric Scale-Invariant Feature Transform for Large Size High Resolution Satellite Image Registration

PubMed Central

Chang, Xueli; Du, Siliang; Li, Yingying; Fang, Shenghui

2018-01-01

Large size high resolution (HR) satellite image matching is a challenging task due to local distortion, repetitive structures, intensity changes and low efficiency. In this paper, a novel matching approach is proposed for the large size HR satellite image registration, which is based on coarse-to-fine strategy and geometric scale-invariant feature transform (SIFT). In the coarse matching step, a robust matching method scale restrict (SR) SIFT is implemented at low resolution level. The matching results provide geometric constraints which are then used to guide block division and geometric SIFT in the fine matching step. The block matching method can overcome the memory problem. In geometric SIFT, with area constraints, it is beneficial for validating the candidate matches and decreasing searching complexity. To further improve the matching efficiency, the proposed matching method is parallelized using OpenMP. Finally, the sensing image is rectified to the coordinate of reference image via Triangulated Irregular Network (TIN) transformation. Experiments are designed to test the performance of the proposed matching method. The experimental results show that the proposed method can decrease the matching time and increase the number of matching points while maintaining high registration accuracy. PMID:29702589

Irregular behavior in an excitatory-inhibitory neuronal network

NASA Astrophysics Data System (ADS)

Park, Choongseok; Terman, David

2010-06-01

Excitatory-inhibitory networks arise in many regions throughout the central nervous system and display complex spatiotemporal firing patterns. These neuronal activity patterns (of individual neurons and/or the whole network) are closely related to the functional status of the system and differ between normal and pathological states. For example, neurons within the basal ganglia, a group of subcortical nuclei that are responsible for the generation of movement, display a variety of dynamic behaviors such as correlated oscillatory activity and irregular, uncorrelated spiking. Neither the origins of these firing patterns nor the mechanisms that underlie the patterns are well understood. We consider a biophysical model of an excitatory-inhibitory network in the basal ganglia and explore how specific biophysical properties of the network contribute to the generation of irregular spiking. We use geometric dynamical systems and singular perturbation methods to systematically reduce the model to a simpler set of equations, which is suitable for analysis. The results specify the dependence on the strengths of synaptic connections and the intrinsic firing properties of the cells in the irregular regime when applied to the subthalamopallidal network of the basal ganglia.

A fuzzy pattern matching method based on graph kernel for lithography hotspot detection

NASA Astrophysics Data System (ADS)

Nitta, Izumi; Kanazawa, Yuzi; Ishida, Tsutomu; Banno, Koji

2017-03-01

In advanced technology nodes, lithography hotspot detection has become one of the most significant issues in design for manufacturability. Recently, machine learning based lithography hotspot detection has been widely investigated, but it has trade-off between detection accuracy and false alarm. To apply machine learning based technique to the physical verification phase, designers require minimizing undetected hotspots to avoid yield degradation. They also need a ranking of similar known patterns with a detected hotspot to prioritize layout pattern to be corrected. To achieve high detection accuracy and to prioritize detected hotspots, we propose a novel lithography hotspot detection method using Delaunay triangulation and graph kernel based machine learning. Delaunay triangulation extracts features of hotspot patterns where polygons locate irregularly and closely one another, and graph kernel expresses inner structure of graphs. Additionally, our method provides similarity between two patterns and creates a list of similar training patterns with a detected hotspot. Experiments results on ICCAD 2012 benchmarks show that our method achieves high accuracy with allowable range of false alarm. We also show the ranking of the similar known patterns with a detected hotspot.

Basic research and data analysis for the National Geodetic Satellite Program

NASA Technical Reports Server (NTRS)

1972-01-01

Investigations of triangulation nets and scaling are reported. Adjustment of the BC-4 worldwide geometric satellite triangulation net is described, along with procedures for correcting type II data and the contents of magnetic tapes containing data from the Pageos network. Computational steps for the further reduction of partially reduced satellite image plate coordinates are outlined. The problem of improving existing triangulation systems by means of satellite super-control points was studied. The SAO-69 geometric solution was scaled with C-band radar data, resulting in SAO and C-band adjustment compatible with one another in the Western Hemisphere. The North America solution NA-6, obtained from GEOS 1 data, was readjusted with new heights as constraints on all 30 optical stations and is referred to as the NA-8 solution.

Propagating waves can explain irregular neural dynamics.

PubMed

Keane, Adam; Gong, Pulin

2015-01-28

Cortical neurons in vivo fire quite irregularly. Previous studies about the origin of such irregular neural dynamics have given rise to two major models: a balanced excitation and inhibition model, and a model of highly synchronized synaptic inputs. To elucidate the network mechanisms underlying synchronized synaptic inputs and account for irregular neural dynamics, we investigate a spatially extended, conductance-based spiking neural network model. We show that propagating wave patterns with complex dynamics emerge from the network model. These waves sweep past neurons, to which they provide highly synchronized synaptic inputs. On the other hand, these patterns only emerge from the network with balanced excitation and inhibition; our model therefore reconciles the two major models of irregular neural dynamics. We further demonstrate that the collective dynamics of propagating wave patterns provides a mechanistic explanation for a range of irregular neural dynamics, including the variability of spike timing, slow firing rate fluctuations, and correlated membrane potential fluctuations. In addition, in our model, the distributions of synaptic conductance and membrane potential are non-Gaussian, consistent with recent experimental data obtained using whole-cell recordings. Our work therefore relates the propagating waves that have been widely observed in the brain to irregular neural dynamics. These results demonstrate that neural firing activity, although appearing highly disordered at the single-neuron level, can form dynamical coherent structures, such as propagating waves at the population level. Copyright © 2015 the authors 0270-6474/15/351591-15$15.00/0.

Source parameters for the 1952 Kern County earthquake, California: A joint inversion of leveling and triangulation observations

USGS Publications Warehouse

Bawden, G.W.

2001-01-01

Coseismic leveling and triangulation observations are used to determine the faulting geometry and slip distribution of the July 21, 1952, Mw 7.3 Kem County earthquake on the White Wolf fault. A singular value decomposition inversion is used to assess the ability of the geodetic network to resolve slip along a multisegment fault and shows that the network is sufficient to resolve slip along the surface rupture to a depth of 10 km. Below 10 km, the network can only resolve dip slip near the fault ends. The preferred source model is a two-segment right-stepping fault with a strike of 51?? and a dip of 75?? SW. The epicentral patch has deep (6-27 km) leftlateral oblique slip, while the northeastern patch has shallow (1-12.5 km) reverse slip. There is nearly uniform reverse slip (epicentral, 1.6 m; northeast, 1.9 m), with 3.6 m of left-lateral strike slip limited to the epicentral patch. The seismic moment is M0= 9.2 ?? 0.5 ?? 1019 N m (Mw= 7.2). The signal-to-noise ratio of the leveling and triangulation data is reduced by 96% and 49%, respectively. The slip distribution from the preferred model matches regional geomorphic features and may provide a driving mechanism for regional shortening across the Comanche thrust and structural continuity with the Scodie seismic lineament to the northeast.

A technique for inferring zonal irregularity drift from single-station GNSS measurements of intensity (S4) and phase (σφ) scintillations

NASA Astrophysics Data System (ADS)

Carrano, Charles S.; Groves, Keith M.; Rino, Charles L.; Doherty, Patricia H.

2016-08-01

The zonal drift of ionospheric irregularities at low latitudes is most commonly measured by cross-correlating observations of a scintillating satellite signal made with a pair of closely spaced antennas. The Air Force Research Laboratory-Scintillation Network Decision Aid (AFRL-SCINDA) network operates a small number of very high frequency (VHF) spaced-receiver systems at low latitudes for this purpose. A far greater number of Global Navigation Satellite System (GNSS) scintillation monitors are operated by the AFRL-SCINDA network (25-30) and the Low-Latitude Ionospheric Sensor Network (35-50), but the receivers are too widely separated from each other for cross-correlation techniques to be effective. In this paper, we present an alternative approach that leverages the weak scatter scintillation theory to infer the zonal irregularity drift from single-station GNSS measurements of S4, σφ, and the propagation geometry. Unlike the spaced-receiver technique, this approach requires assumptions regarding the height of the scattering layer (which introduces a bias in the drift estimates) and the spectral index of the irregularities (which affects the spread of the drift estimates about the mean). Nevertheless, theory and experiment suggest that the ratio of σφ to S4 is less sensitive to these parameters than it is to the zonal drift. We validate the technique using VHF spaced-receiver measurements of zonal irregularity drift obtained from the AFRL-SCINDA network. While the spaced-receiver technique remains the preferred way to monitor the drift when closely spaced antenna pairs are available, our technique provides a new opportunity to monitor zonal irregularity drift using regional or global networks of widely separated GNSS scintillation monitors.

Spectral Analysis for Weighted Iterated Triangulations of Graphs

NASA Astrophysics Data System (ADS)

Chen, Yufei; Dai, Meifeng; Wang, Xiaoqian; Sun, Yu; Su, Weiyi

Much information about the structural properties and dynamical aspects of a network is measured by the eigenvalues of its normalized Laplacian matrix. In this paper, we aim to present a first study on the spectra of the normalized Laplacian of weighted iterated triangulations of graphs. We analytically obtain all the eigenvalues, as well as their multiplicities from two successive generations. As an example of application of these results, we then derive closed-form expressions for their multiplicative Kirchhoff index, Kemeny’s constant and number of weighted spanning trees.

Automatic pre-processing for an object-oriented distributed hydrological model using GRASS-GIS

NASA Astrophysics Data System (ADS)

Sanzana, P.; Jankowfsky, S.; Branger, F.; Braud, I.; Vargas, X.; Hitschfeld, N.

2012-04-01

Landscapes are very heterogeneous, which impact the hydrological processes occurring in the catchments, especially in the modeling of peri-urban catchments. The Hydrological Response Units (HRUs), resulting from the intersection of different maps, such as land use, soil types and geology, and flow networks, allow the representation of these elements in an explicit way, preserving natural and artificial contours of the different layers. These HRUs are used as model mesh in some distributed object-oriented hydrological models, allowing the application of a topological oriented approach. The connectivity between polygons and polylines provides a detailed representation of the water balance and overland flow in these distributed hydrological models, based on irregular hydro-landscape units. When computing fluxes between these HRUs, the geometrical parameters, such as the distance between the centroid of gravity of the HRUs and the river network, and the length of the perimeter, can impact the realism of the calculated overland, sub-surface and groundwater fluxes. Therefore, it is necessary to process the original model mesh in order to avoid these numerical problems. We present an automatic pre-processing implemented in the open source GRASS-GIS software, for which several Python scripts or some algorithms already available were used, such as the Triangle software. First, some scripts were developed to improve the topology of the various elements, such as snapping of the river network to the closest contours. When data are derived with remote sensing, such as vegetation areas, their perimeter has lots of right angles that were smoothed. Second, the algorithms more particularly address bad-shaped elements of the model mesh such as polygons with narrow shapes, marked irregular contours and/or the centroid outside of the polygons. To identify these elements we used shape descriptors. The convexity index was considered the best descriptor to identify them with a threshold of 0.75. Segmentation procedures were implemented and applied with criteria of homogeneous slope, convexity of the elements and maximum area of the HRUs. These tasks were implemented using a triangulation approach, applying the Triangle software, in order to dissolve the polygons according to the convexity index criteria. The automatic pre-processing was applied to two peri-urban French catchment, the Mercier and Chaudanne catchments, with 7.3 km2 and 4.1 km2 respectively. We show that the optimized mesh allows a substantial improvement of the overland flow pathways, because the segmentation procedure gives a more realistic representation of the drainage network. KEYWORDS: GRASS-GIS, Hydrological Response Units, Automatic processing, Peri-urban catchments, Geometrical Algorithms

Data governance requirements for distributed clinical research networks: triangulating perspectives of diverse stakeholders

PubMed Central

Kim, Katherine K; Browe, Dennis K; Logan, Holly C; Holm, Roberta; Hack, Lori; Ohno-Machado, Lucila

2014-01-01

There is currently limited information on best practices for the development of governance requirements for distributed research networks (DRNs), an emerging model that promotes clinical data reuse and improves timeliness of comparative effectiveness research. Much of the existing information is based on a single type of stakeholder such as researchers or administrators. This paper reports on a triangulated approach to developing DRN data governance requirements based on a combination of policy analysis with experts, interviews with institutional leaders, and patient focus groups. This approach is illustrated with an example from the Scalable National Network for Effectiveness Research, which resulted in 91 requirements. These requirements were analyzed against the Fair Information Practice Principles (FIPPs) and Health Insurance Portability and Accountability Act (HIPAA) protected versus non-protected health information. The requirements addressed all FIPPs, showing how a DRN's technical infrastructure is able to fulfill HIPAA regulations, protect privacy, and provide a trustworthy platform for research. PMID:24302285

On the Longitudinal Morphology of Zonal Irregularity Drift Measured using Networks of GPS Scintillation Monitors

NASA Astrophysics Data System (ADS)

Carrano, C. S.; Groves, K. M.; Valladares, C. E.; Delay, S. H.

2014-12-01

A complete characterization of field-aligned ionospheric irregularities responsible for the scintillation of satellite signals includes not only their spectral properties (power spectral strength, spectral index, anisotropy ratio, and outer-scale) but also their horizontal drift velocity. From a system impacts perspective, the horizontal drift velocity is important in that it dictates the rate of signal fading and also, to an extent, the level of phase fluctuations encountered by the receiver. From a physics perspective, studying the longitudinal morphology of zonal irregularity may lead to an improved understanding of the F region dynamo and regional electrodynamics at low latitudes. The irregularity drift at low latitudes is predominantly zonal and is most commonly measured by cross-correlating observations of satellite signals made by a pair of closely-spaced antennas. The AFRL-SCINDA network operates a small number of VHF spaced-antenna systems at low latitude stations for this purpose. A far greater number of GPS scintillation monitors are operated by AFRL-SCINDA (25-30) and the Low Latitude Ionospheric Sensor Network (35-50), but the receivers are situated too far apart to monitor the drift using cross-correlation techniques. In this paper, we present an alternative approach that leverages the weak scatter scintillation theory (Rino, Radio Sci., 1979) to infer the zonal irregularity drift from single-station GPS measurements of S4, sigma-phi, and the propagation geometry alone. Unlike the spaced-receiver technique, this technique requires assumptions for the height of the scattering layer (which introduces a bias in the drift estimates) and the spectral index of the irregularities (which affects the spread of the drift estimates about the mean). Nevertheless, theory and experiment show that the ratio of sigma-phi to S4 is less sensitive to these parameters than it is to the zonal drift, and hence the zonal drift can be estimated with reasonable accuracy. In this talk, we first validate the technique using spaced VHF-antenna measurements of zonal irregularity drift from the AFRL-SCINDA network. Next, we discuss preliminary results from our investigation into the longitudinal morphology of zonal irregularity drift using the AFRL-SCINDA and LISN networks of GPS scintillation monitors.

Physically based modeling of rainfall-triggered landslides: a case study in the Luquillo Forest, Puerto Rico

NASA Astrophysics Data System (ADS)

Lepore, C.; Arnone, E.; Noto, L. V.; Sivandran, G.; Bras, R. L.

2013-01-01

This paper presents the development of a rainfall-triggered landslide module within a physically based spatially distributed ecohydrologic model. The model, Triangulated Irregular Networks Real-time Integrated Basin Simulator and VEGetation Generator for Interactive Evolution (tRIBS-VEGGIE), is capable of a sophisticated description of many hydrological processes; in particular, the soil moisture dynamics is resolved at a temporal and spatial resolution required to examine the triggering mechanisms of rainfall-induced landslides. The validity of the tRIBS-VEGGIE model to a tropical environment is shown with an evaluation of its performance against direct observations made within the Luquillo Forest (the study area). The newly developed landslide module builds upon the previous version of the tRIBS landslide component. This new module utilizes a numerical solution to the Richards equation to better represent the time evolution of soil moisture transport through the soil column. Moreover, the new landslide module utilizes an extended formulation of the Factor of Safety (FS) to correctly quantify the role of matric suction in slope stability and to account for unsaturated conditions in the evaluation of FS. The new modeling framework couples the capabilities of the detailed hydrologic model to describe soil moisture dynamics with the Infinite Slope model creating a powerful tool for the assessment of landslide risk.

Integration of remote sensing technique and hydrologic model for monitoring tidal flat dynamics of Juiduansha in Shanghai

NASA Astrophysics Data System (ADS)

Zheng, Zongsheng; Zhou, Yunxuan; Jiang, Xuezhong

2007-06-01

Ground survey is restricted by the difficulty of access to wide-range and dynamic salt marsh. Waterline method and hydrodynamic model were investigated to construct Digital Elevation Model (DEM) at Jiudunasha Shoals. A series of waterlines were extracted from multi-temporal remotely sensing images collected over the period of 2000-2004. The assignment of an elevation to each waterline at the satellite overpass was performed according to hydrodynamic model. The corrected waterlines labeled elevations were used to construct Triangulated Irregular Networks (TINs). Then an interpolation for each grid elevation was performed in accordance with the associated triangle. This initial DEM, produced using the corrected waterline set, was then used to refine the topography in the intertidal zone, and the model was re-run to produce improved water levels and a new DEM. This procedure was iterated by comparing modeled and actual waterlines until no further improvement occurred. Three DEMs of different intervals were built by this approach and were compared to evaluate the effect of Deep Water Channel Project (DWCP) at the north of Jiuduansha Island. Waterline method combined with numerical model, is an effective tool for constructing digital elevation model of mudflats. The result can provide invaluable information for coastal land use and engineer construction.

Individual Tree Crown Delineation Using Multi-Wavelength Titan LIDAR Data

NASA Astrophysics Data System (ADS)

Naveed, F.; Hu, B.

2017-10-01

The inability to detect the Emerald Ash Borer (EAB) at an early stage has led to the enumerable loss of different species of ash trees. Due to the increasing risk being posed by the EAB, a robust and accurate method is needed for identifying Individual Tree Crowns (ITCs) that are at a risk of being infected or are already diseased. This paper attempts to outline an ITC delineation method that employs airborne multi-spectral Light Detection and Ranging (LiDAR) to accurately delineate tree crowns. The raw LiDAR data were initially pre-processed to generate the Digital Surface Models (DSM) and Digital Elevation Models (DEM) using an iterative progressive TIN (Triangulated Irregular Network) densification method. The DSM and DEM were consequently used for Canopy Height Model (CHM) generation, from which the structural information pertaining to the size and shape of the tree crowns was obtained. The structural information along with the spectral information was used to segment ITCs using a region growing algorithm. The availability of the multi-spectral LiDAR data allows for delineation of crowns that have otherwise homogenous structural characteristics and hence cannot be isolated from the CHM alone. This study exploits the spectral data to derive initial approximations of individual tree tops and consequently grow those regions based on the spectral constraints of the individual trees.

Movement pattern recognition in basketball free-throw shooting.

PubMed

Schmidt, Andrea

2012-04-01

The purpose of the present study was to analyze the movement patterns of free-throw shooters in basketball at different skill levels. There were two points of interest. First, to explore what information can be drawn from the movement pattern and second, to examine the methodological possibilities of pattern analysis. To this end, several qualitative and quantitative methods were employed. The resulting data were converged in a triangulation. Using a special kind of ANN named Dynamically Controlled Networks (DyCoN), a 'complex feature' consisting of several isolated features (angle displacements and velocities of the articulations of the kinematic chain) was calculated. This 'complex feature' was displayed by a trajectory combining several neurons of the network, reflecting the devolution of the twelve angle measures over the time course of each shooting action. In further network analyses individual characteristics were detected, as well as movement phases. Throwing patterns were successfully classified and the stability and variability of the realized pattern were established. The movement patterns found were clearly individually shaped as well as formed by the skill level. The triangulation confirmed the individual movement organizations. Finally, a high stability of the network methods was documented. Copyright © 2012. Published by Elsevier B.V.

Efficient content-based low-altitude images correlated network and strips reconstruction

NASA Astrophysics Data System (ADS)

He, Haiqing; You, Qi; Chen, Xiaoyong

2017-01-01

The manual intervention method is widely used to reconstruct strips for further aerial triangulation in low-altitude photogrammetry. Clearly the method for fully automatic photogrammetric data processing is not an expected way. In this paper, we explore a content-based approach without manual intervention or external information for strips reconstruction. Feature descriptors in the local spatial patterns are extracted by SIFT to construct vocabulary tree, in which these features are encoded in terms of TF-IDF numerical statistical algorithm to generate new representation for each low-altitude image. Then images correlated network is reconstructed by similarity measure, image matching and geometric graph theory. Finally, strips are reconstructed automatically by tracing straight lines and growing adjacent images gradually. Experimental results show that the proposed approach is highly effective in automatically rearranging strips of lowaltitude images and can provide rough relative orientation for further aerial triangulation.

Delaunay Triangulation as a New Coverage Measurement Method in Wireless Sensor Network

PubMed Central

Chizari, Hassan; Hosseini, Majid; Poston, Timothy; Razak, Shukor Abd; Abdullah, Abdul Hanan

2011-01-01

Sensing and communication coverage are among the most important trade-offs in Wireless Sensor Network (WSN) design. A minimum bound of sensing coverage is vital in scheduling, target tracking and redeployment phases, as well as providing communication coverage. Some methods measure the coverage as a percentage value, but detailed information has been missing. Two scenarios with equal coverage percentage may not have the same Quality of Coverage (QoC). In this paper, we propose a new coverage measurement method using Delaunay Triangulation (DT). This can provide the value for all coverage measurement tools. Moreover, it categorizes sensors as ‘fat’, ‘healthy’ or ‘thin’ to show the dense, optimal and scattered areas. It can also yield the largest empty area of sensors in the field. Simulation results show that the proposed DT method can achieve accurate coverage information, and provides many tools to compare QoC between different scenarios. PMID:22163792

Data governance requirements for distributed clinical research networks: triangulating perspectives of diverse stakeholders.

PubMed

Kim, Katherine K; Browe, Dennis K; Logan, Holly C; Holm, Roberta; Hack, Lori; Ohno-Machado, Lucila

2014-01-01

There is currently limited information on best practices for the development of governance requirements for distributed research networks (DRNs), an emerging model that promotes clinical data reuse and improves timeliness of comparative effectiveness research. Much of the existing information is based on a single type of stakeholder such as researchers or administrators. This paper reports on a triangulated approach to developing DRN data governance requirements based on a combination of policy analysis with experts, interviews with institutional leaders, and patient focus groups. This approach is illustrated with an example from the Scalable National Network for Effectiveness Research, which resulted in 91 requirements. These requirements were analyzed against the Fair Information Practice Principles (FIPPs) and Health Insurance Portability and Accountability Act (HIPAA) protected versus non-protected health information. The requirements addressed all FIPPs, showing how a DRN's technical infrastructure is able to fulfill HIPAA regulations, protect privacy, and provide a trustworthy platform for research. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Irregular Collective Behavior of Heterogeneous Neural Networks

NASA Astrophysics Data System (ADS)

Luccioli, Stefano; Politi, Antonio

2010-10-01

We investigate a network of integrate-and-fire neurons characterized by a distribution of spiking frequencies. Upon increasing the coupling strength, the model exhibits a transition from an asynchronous regime to a nontrivial collective behavior. Numerical simulations of large systems indicate that, at variance with the Kuramoto model, (i) the macroscopic dynamics stays irregular and (ii) the microscopic (single-neuron) evolution is linearly stable.

Ergodic properties of spiking neuronal networks with delayed interactions

NASA Astrophysics Data System (ADS)

Palmigiano, Agostina; Wolf, Fred

The dynamical stability of neuronal networks, and the possibility of chaotic dynamics in the brain pose profound questions to the mechanisms underlying perception. Here we advance on the tractability of large neuronal networks of exactly solvable neuronal models with delayed pulse-coupled interactions. Pulse coupled delayed systems with an infinite dimensional phase space can be studied in equivalent systems of fixed and finite degrees of freedom by introducing a delayer variable for each neuron. A Jacobian of the equivalent system can be analytically obtained, and numerically evaluated. We find that depending on the action potential onset rapidness and the level of heterogeneities, the asynchronous irregular regime characteristic of balanced state networks loses stability with increasing delays to either a slow synchronous irregular or a fast synchronous irregular state. In networks of neurons with slow action potential onset, the transition to collective oscillations leads to an increase of the exponential rate of divergence of nearby trajectories and of the entropy production rate of the chaotic dynamics. The attractor dimension, instead of increasing linearly with increasing delay as reported in many other studies, decreases until eventually the network reaches full synchrony

Online Teaching in Networked Learning Communities: A Multi-Method Approach to Studying the Role of the Teacher

ERIC Educational Resources Information Center

De Laat, Maarten; Lally, Vic; Lipponen, Lasse; Simons, Robert-Jan

2007-01-01

The aim of this paper is to study the online teaching styles of two teachers who each tutor a networked learning community (NLC), within the same workshop. The study is undertaking empirical work using a multi-method approach in order to triangulate and contextualise our findings and enrich our understanding of the teacher participation in these…

Changing Mindsets: A Case Study of a Community of Practice between Charter and Traditional Public School Leaders in the School Leaders Network

ERIC Educational Resources Information Center

Ponce, Manuel N., Jr.

2013-01-01

The purpose of this study was to examine the essential elements of a community of practice intended to increase communication and collaboration between traditional public and charter school leaders. Members of the Los Angeles Cohort of the School Leaders Network participated in this study. This case study triangulated observation, interview, and…

Modelling and prediction for chaotic fir laser attractor using rational function neural network.

PubMed

Cho, S

2001-02-01

Many real-world systems such as irregular ECG signal, volatility of currency exchange rate and heated fluid reaction exhibit highly complex nonlinear characteristic known as chaos. These chaotic systems cannot be retreated satisfactorily using linear system theory due to its high dimensionality and irregularity. This research focuses on prediction and modelling of chaotic FIR (Far InfraRed) laser system for which the underlying equations are not given. This paper proposed a method for prediction and modelling a chaotic FIR laser time series using rational function neural network. Three network architectures, TDNN (Time Delayed Neural Network), RBF (radial basis function) network and the RF (rational function) network, are also presented. Comparisons between these networks performance show the improvements introduced by the RF network in terms of a decrement in network complexity and better ability of predictability.

Calculating electronic tunnel currents in networks of disordered irregularly shaped nanoparticles by mapping networks to arrays of parallel nonlinear resistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aghili Yajadda, Mir Massoud

2014-10-21

We have shown both theoretically and experimentally that tunnel currents in networks of disordered irregularly shaped nanoparticles (NPs) can be calculated by considering the networks as arrays of parallel nonlinear resistors. Each resistor is described by a one-dimensional or a two-dimensional array of equal size nanoparticles that the tunnel junction gaps between nanoparticles in each resistor is assumed to be equal. The number of tunnel junctions between two contact electrodes and the tunnel junction gaps between nanoparticles are found to be functions of Coulomb blockade energies. In addition, the tunnel barriers between nanoparticles were considered to be tilted at highmore » voltages. Furthermore, the role of thermal expansion coefficient of the tunnel junction gaps on the tunnel current is taken into account. The model calculations fit very well to the experimental data of a network of disordered gold nanoparticles, a forest of multi-wall carbon nanotubes, and a network of few-layer graphene nanoplates over a wide temperature range (5-300 K) at low and high DC bias voltages (0.001 mV–50 V). Our investigations indicate, although electron cotunneling in networks of disordered irregularly shaped NPs may occur, non-Arrhenius behavior at low temperatures cannot be described by the cotunneling model due to size distribution in the networks and irregular shape of nanoparticles. Non-Arrhenius behavior of the samples at zero bias voltage limit was attributed to the disorder in the samples. Unlike the electron cotunneling model, we found that the crossover from Arrhenius to non-Arrhenius behavior occurs at two temperatures, one at a high temperature and the other at a low temperature.« less

3rd Interplanetary Network Gamma-Ray Burst Website

NASA Astrophysics Data System (ADS)

Hurley, Kevin

1998-05-01

We announce the opening of the 3rd Interplanetary Network web site at http://ssl.berkeley.edu/ipn3/index.html This site presently has four parts: 1. A bibliography of over 3000 publications on gamma-ray bursts, 2. IPN data on all bursts triangulated up to February 1998, 3. A master list showing which spacecraft observed which bursts, 4. Preliminary IPN data on the latest bursts observed.

A Control Simulation Method of High-Speed Trains on Railway Network with Irregular Influence

NASA Astrophysics Data System (ADS)

Yang, Li-Xing; Li, Xiang; Li, Ke-Ping

2011-09-01

Based on the discrete time method, an effective movement control model is designed for a group of highspeed trains on a rail network. The purpose of the model is to investigate the specific traffic characteristics of high-speed trains under the interruption of stochastic irregular events. In the model, the high-speed rail traffic system is supposed to be equipped with the moving-block signalling system to guarantee maximum traversing capacity of the railway. To keep the safety of trains' movements, some operational strategies are proposed to control the movements of trains in the model, including traction operation, braking operation, and entering-station operation. The numerical simulations show that the designed model can well describe the movements of high-speed trains on the rail network. The research results can provide the useful information not only for investigating the propagation features of relevant delays under the irregular disturbance but also for rerouting and rescheduling trains on the rail network.

Physically based modeling of rainfall-triggered landslides: a case study in the Luquillo forest, Puerto Rico

NASA Astrophysics Data System (ADS)

Lepore, C.; Arnone, E.; Noto, L. V.; Sivandran, G.; Bras, R. L.

2013-09-01

This paper presents the development of a rainfall-triggered landslide module within an existing physically based spatially distributed ecohydrologic model. The model, tRIBS-VEGGIE (Triangulated Irregular Networks-based Real-time Integrated Basin Simulator and Vegetation Generator for Interactive Evolution), is capable of a sophisticated description of many hydrological processes; in particular, the soil moisture dynamics are resolved at a temporal and spatial resolution required to examine the triggering mechanisms of rainfall-induced landslides. The validity of the tRIBS-VEGGIE model to a tropical environment is shown with an evaluation of its performance against direct observations made within the study area of Luquillo Forest. The newly developed landslide module builds upon the previous version of the tRIBS landslide component. This new module utilizes a numerical solution to the Richards' equation (present in tRIBS-VEGGIE but not in tRIBS), which better represents the time evolution of soil moisture transport through the soil column. Moreover, the new landslide module utilizes an extended formulation of the factor of safety (FS) to correctly quantify the role of matric suction in slope stability and to account for unsaturated conditions in the evaluation of FS. The new modeling framework couples the capabilities of the detailed hydrologic model to describe soil moisture dynamics with the infinite slope model, creating a powerful tool for the assessment of rainfall-triggered landslide risk.

Accuracy Assessment of Lidar-Derived Digital Terrain Model (dtm) with Different Slope and Canopy Cover in Tropical Forest Region

NASA Astrophysics Data System (ADS)

Salleh, M. R. M.; Ismail, Z.; Rahman, M. Z. A.

2015-10-01

Airborne Light Detection and Ranging (LiDAR) technology has been widely used recent years especially in generating high accuracy of Digital Terrain Model (DTM). High density and good quality of airborne LiDAR data promises a high quality of DTM. This study focussing on the analysing the error associated with the density of vegetation cover (canopy cover) and terrain slope in a LiDAR derived-DTM value in a tropical forest environment in Bentong, State of Pahang, Malaysia. Airborne LiDAR data were collected can be consider as low density captured by Reigl system mounted on an aircraft. The ground filtering procedure use adaptive triangulation irregular network (ATIN) algorithm technique in producing ground points. Next, the ground control points (GCPs) used in generating the reference DTM and these DTM was used for slope classification and the point clouds belong to non-ground are then used in determining the relative percentage of canopy cover. The results show that terrain slope has high correlation for both study area (0.993 and 0.870) with the RMSE of the LiDAR-derived DTM. This is similar to canopy cover where high value of correlation (0.989 and 0.924) obtained. This indicates that the accuracy of airborne LiDAR-derived DTM is significantly affected by terrain slope and canopy caver of study area.

Mapping coastal morphodynamics with geospatial techniques, Cape Henry, Virginia, USA

NASA Astrophysics Data System (ADS)

Allen, Thomas R.; Oertel, George F.; Gares, Paul A.

2012-01-01

The advent and proliferation of digital terrain technologies have spawned concomitant advances in coastal geomorphology. Airborne topographic Light Detection and Ranging (LiDAR) has stimulated a renaissance in coastal mapping, and field-based mapping techniques have benefitted from improvements in real-time kinematic (RTK) Global Positioning System (GPS). Varied methodologies for mapping suggest a need to match geospatial products to geomorphic forms and processes, a task that should consider product and process ontologies from each perspective. Towards such synthesis, coastal morphodynamics on a cuspate foreland are reconstructed using spatial analysis. Sequential beach ridge and swale topography are mapped using photogrammetric spot heights and airborne LiDAR data and integrated with digital bathymetry and large-scale vector shoreline data. Isobaths from bathymetric charts were digitized to determine slope and toe depth of the modern shoreface and a reconstructed three-dimensional antecedent shoreface. Triangulated irregular networks were created for the subaerial cape and subaqueous shoreface models of the cape beach ridges and sets for volumetric analyses. Results provide estimates of relative age and progradation rate and corroborate other paleogeologic sea-level rise data from the region. Swale height elevations and other measurements quantifiable in these data provide several parameters suitable for studying coastal geomorphic evolution. Mapped paleoshorelines and volumes suggest the Virginia Beach coastal compartment is related to embryonic spit development from a late Holocene shoreline located some 5 km east of the current beach.

A Physically-based Model For Rainfall-triggered Landslides At A Regional Scale

NASA Astrophysics Data System (ADS)

Teles, V.; Capolongo, D.; Bras, R. L.

Rainfall has long been recognized as a major cause of landslides. Historical records have shown that large rainfall can generate hundreds of landslides over hundreds of square kilometers. Although a great body of work has documented the morphology and mechanics of individual slope failure, few studies have considered the process at basin and regional scale. A landslide model is integrated in the landscape evolution model CHILD and simulates rainfall-triggered events based on a geotechnical index, the factor of safety, which takes into account the slope, the soil effective cohesion and weight, the friction angle, the regolith thickness and the saturated thickness. The stat- urated thickness is represented by the wetness index developed in the TOPMODEL. The topography is represented by a Triangulated Irregular Network (TIN). The factor of safety is computed at each node of the TIN. If the factor of safety is lower than 1, a landslide is intiated at this node. The regolith is then moved downstream. We applied the model to the Fortore basin whose valley cuts the flysch terrain that constitute the framework of the so called "sub-Apennines" chain that is the most eastern part of the Southern Apennines (Italy). We will discuss its value according to its sensitivity to the used parameters and compare it to the actual data available for this basin.

A Participatory Modeling Application of a Distributed Hydrologic Model in Nuevo Leon, Mexico for the 2010 Hurricane Alex Flood Event

NASA Astrophysics Data System (ADS)

Baish, A. S.; Vivoni, E. R.; Payan, J. G.; Robles-Morua, A.; Basile, G. M.

2011-12-01

A distributed hydrologic model can help bring consensus among diverse stakeholders in regional flood planning by producing quantifiable sets of alternative futures. This value is acute in areas with high uncertainties in hydrologic conditions and sparse observations. In this study, we conduct an application of the Triangulated Irregular Network (TIN)-based Real-time Integrated Basin Simulator (tRIBS) in the Santa Catarina basin of Nuevo Leon, Mexico, where Hurricane Alex in July 2010 led to catastrophic flooding of the capital city of Monterrey. Distributed model simulations utilize best-available information on the regional topography, land cover, and soils obtained from Mexican government agencies or analysis of remotely-sensed imagery from MODIS and ASTER. Furthermore, we developed meteorological forcing for the flood event based on multiple data sources, including three local gauge networks, satellite-based estimates from TRMM and PERSIANN, and the North American Land Data Assimilation System (NLDAS). Remotely-sensed data allowed us to quantify rainfall distributions in the upland, rural portions of the Santa Catarina that are sparsely populated and ungauged. Rural areas had significant contributions to the flood event and as a result were considered by stakeholders for flood control measures, including new reservoirs and upland vegetation management. Participatory modeling workshops with the stakeholders revealed a disconnect between urban and rural populations in regard to understanding the hydrologic conditions of the flood event and the effectiveness of existing and potential flood control measures. Despite these challenges, the use of the distributed flood forecasts developed within this participatory framework facilitated building consensus among diverse stakeholders and exploring alternative futures in the basin.

The Detection of Transport Land-Use Data Using Crowdsourcing Taxi Trajectory

NASA Astrophysics Data System (ADS)

Ai, T.; Yang, W.

2016-06-01

This study tries to explore the question of transport land-use change detection by large volume of vehicle trajectory data, presenting a method based on Deluanay triangulation. The whole method includes three steps. The first one is to pre-process the vehicle trajectory data including the point anomaly removing and the conversion of trajectory point to track line. Secondly, construct Deluanay triangulation within the vehicle trajectory line to detect neighborhood relation. Considering the case that some of the trajectory segments are too long, we use a interpolation measure to add more points for the improved triangulation. Thirdly, extract the transport road by cutting short triangle edge and organizing the polygon topology. We have conducted the experiment of transport land-use change discovery using the data of taxi track in Beijing City. We extract not only the transport land-use area but also the semantic information such as the transformation speed, the traffic jam distribution, the main vehicle movement direction and others. Compared with the existed transport network data, such as OpenStreet Map, our method is proved to be quick and accurate.

Neural substrates of sublexical processing for spelling.

PubMed

DeMarco, Andrew T; Wilson, Stephen M; Rising, Kindle; Rapcsak, Steven Z; Beeson, Pélagie M

2017-01-01

We used fMRI to examine the neural substrates of sublexical phoneme-grapheme conversion during spelling in a group of healthy young adults. Participants performed a writing-to-dictation task involving irregular words (e.g., choir), plausible nonwords (e.g., kroid), and a control task of drawing familiar geometric shapes (e.g., squares). Written production of both irregular words and nonwords engaged a left-hemisphere perisylvian network associated with reading/spelling and phonological processing skills. Effects of lexicality, manifested by increased activation during nonword relative to irregular word spelling, were noted in anterior perisylvian regions (posterior inferior frontal gyrus/operculum/precentral gyrus/insula), and in left ventral occipito-temporal cortex. In addition to enhanced neural responses within domain-specific components of the language network, the increased cognitive demands associated with spelling nonwords engaged domain-general frontoparietal cortical networks involved in selective attention and executive control. These results elucidate the neural substrates of sublexical processing during written language production and complement lesion-deficit correlation studies of phonological agraphia. Copyright © 2016 Elsevier Inc. All rights reserved.

Neural Substrates of Sublexical Processing for Spelling

PubMed Central

Wilson, Stephen M.; Rising, Kindle; Rapcsak, Steven Z.; Beeson, Pélagie M.

2016-01-01

We used fMRI to examine the neural substrates of sublexical phoneme-grapheme conversion during spelling in a group of healthy young adults. Participants performed a writing-to-dictation task involving irregular words (e.g., choir), plausible nonwords (e.g., kroid), and a control task of drawing familiar geometric shapes (e.g., squares). Written production of both irregular words and nonwords engaged a left-hemisphere perisylvian network associated with reading/spelling and phonological processing skills. Effects of lexicality, manifested by increased activation during nonword relative to irregular word spelling, were noted in anterior perisylvian regions (posterior inferior frontal gyrus/operculum/precentral gyrus/insula), and in left ventral occipito-temporal cortex. In addition to enhanced neural responses within domain-specific components of the language network, the increased cognitive demands associated with spelling nonwords engaged domain-general frontoparietal cortical networks involved in selective attention and executive control. These results elucidate the neural substrates of sublexical processing during written language production and complement lesion-deficit correlation studies of phonological agraphia. PMID:27838547

The use of triangulation in qualitative research.

PubMed

Carter, Nancy; Bryant-Lukosius, Denise; DiCenso, Alba; Blythe, Jennifer; Neville, Alan J

2014-09-01

Triangulation refers to the use of multiple methods or data sources in qualitative research to develop a comprehensive understanding of phenomena (Patton, 1999). Triangulation also has been viewed as a qualitative research strategy to test validity through the convergence of information from different sources. Denzin (1978) and Patton (1999) identified four types of triangulation: (a) method triangulation, (b) investigator triangulation, (c) theory triangulation, and (d) data source triangulation. The current article will present the four types of triangulation followed by a discussion of the use of focus groups (FGs) and in-depth individual (IDI) interviews as an example of data source triangulation in qualitative inquiry.

Synthesis of irregular graphene oxide tubes using green chemistry and their potential use as reinforcement materials for biomedical applications.

PubMed

Serrano-Aroca, Ángel; Deb, Sanjukta

2017-01-01

Micrometer length tubes of graphene oxide (GO) with irregular form were synthesised following facile and green metal complexation reactions. These materials were obtained by crosslinking of GO with calcium, zinc or strontium chlorides at three different temperatures (24, 34 and 55°C) using distilled water as solvent for the compounds and following a remarkably simple and low-cost synthetic method, which employs no hazardous substances and is conducted without consumption of thermal or sonic energy. These irregular continuous GO networks showed a very particular interconnected structure by Field Emission Scanning Electron Microscopy with Energy-Disperse X-Ray Spectroscopy for elemental analysis and High-resolution Transmission Electron Microscopy with Scanning Transmission Electron Microscope Dark Field Imaging, and were analysed by Raman Spectroscopy. To demonstrate the potential use of these 3D GO networks as reinforcement materials for biomedical applications, two composites of calcium alginate with irregular tubes of GO and with single GO nanosheets were prepared with the same amount of GO and divalent atoms and analysed. Thus, the dynamic-mechanical modulus of the composites synthesised with the 3D crosslinked GO networks showed a very significant mechanical improvement due to marked microstructural changes confirmed by confocal microscopy, differential scanning calorimetry and Fourier transform infrared spectroscopy.

Synthesis of irregular graphene oxide tubes using green chemistry and their potential use as reinforcement materials for biomedical applications

PubMed Central

Deb, Sanjukta

2017-01-01

Micrometer length tubes of graphene oxide (GO) with irregular form were synthesised following facile and green metal complexation reactions. These materials were obtained by crosslinking of GO with calcium, zinc or strontium chlorides at three different temperatures (24, 34 and 55°C) using distilled water as solvent for the compounds and following a remarkably simple and low-cost synthetic method, which employs no hazardous substances and is conducted without consumption of thermal or sonic energy. These irregular continuous GO networks showed a very particular interconnected structure by Field Emission Scanning Electron Microscopy with Energy-Disperse X-Ray Spectroscopy for elemental analysis and High-resolution Transmission Electron Microscopy with Scanning Transmission Electron Microscope Dark Field Imaging, and were analysed by Raman Spectroscopy. To demonstrate the potential use of these 3D GO networks as reinforcement materials for biomedical applications, two composites of calcium alginate with irregular tubes of GO and with single GO nanosheets were prepared with the same amount of GO and divalent atoms and analysed. Thus, the dynamic-mechanical modulus of the composites synthesised with the 3D crosslinked GO networks showed a very significant mechanical improvement due to marked microstructural changes confirmed by confocal microscopy, differential scanning calorimetry and Fourier transform infrared spectroscopy. PMID:28934354

A spiking network model of cerebellar Purkinje cells and molecular layer interneurons exhibiting irregular firing

PubMed Central

Lennon, William; Hecht-Nielsen, Robert; Yamazaki, Tadashi

2014-01-01

While the anatomy of the cerebellar microcircuit is well-studied, how it implements cerebellar function is not understood. A number of models have been proposed to describe this mechanism but few emphasize the role of the vast network Purkinje cells (PKJs) form with the molecular layer interneurons (MLIs)—the stellate and basket cells. We propose a model of the MLI-PKJ network composed of simple spiking neurons incorporating the major anatomical and physiological features. In computer simulations, the model reproduces the irregular firing patterns observed in PKJs and MLIs in vitro and a shift toward faster, more regular firing patterns when inhibitory synaptic currents are blocked. In the model, the time between PKJ spikes is shown to be proportional to the amount of feedforward inhibition from an MLI on average. The two key elements of the model are: (1) spontaneously active PKJs and MLIs due to an endogenous depolarizing current, and (2) adherence to known anatomical connectivity along a parasagittal strip of cerebellar cortex. We propose this model to extend previous spiking network models of the cerebellum and for further computational investigation into the role of irregular firing and MLIs in cerebellar learning and function. PMID:25520646

Hydro-geomorphic perturbations on the soil-atmosphere CO2 exchange: How (un)certain are our balances?

NASA Astrophysics Data System (ADS)

Dialynas, Yannis G.; Bras, Rafael L.; deB. Richter, Daniel

2017-02-01

Attempts to estimate the influence of erosion on the carbon (C) cycle are limited by difficulties in accounting for the fate of mobilized organic material and for the uncertainty associated with land management practices. This study proposes a method to quantify the uncertainty introduced by the influence of land management on soil organic C (SOC) generation and decomposition at eroding soils. The framework is implemented in tRIBS-ECO (Triangulated Irregular Network-based Real-time Integrated Basin Simulator-Erosion and Carbon Oxidation). tRIBS-ECO is a spatially and depth-explicit model of C dynamics coupled with a process-based hydro-geomorphic model. We assess the impact of soil erosion on the net soil-atmosphere CO2 exchange at the Calhoun Critical Zone Observatory, one of the most severely agriculturally eroded regions in the U.S. Measurements of SOC storage are used from different catena positions. We demonstrate that the spatiotemporal variations of land management practices introduce significant uncertainty in estimates of the erosion-induced CO2 exchange with the atmosphere. Observations and simulations suggest that a substantial portion of eroded organic material is buried in alluvial sediments at the study site. According to results, recent reforestation led to a partial decline in soil and SOC erosion rates. It is suggested that the representation of the fine spatiotemporal variability of the dynamics of eroded C is important in the computation of C budgets in regional and global scales.

Topographic lidar survey of the Chandeleur Islands, Louisiana, February 6, 2012

USGS Publications Warehouse

Guy, Kristy K.; Plant, Nathaniel G.; Bonisteel-Cormier, Jamie M.

2014-01-01

This Data Series Report contains lidar elevation data collected February 6, 2012, for Chandeleur Islands, Louisiana. Point cloud data in lidar data exchange format (LAS) and bare earth digital elevation models (DEMs) in ERDAS Imagine raster format (IMG) are available as downloadable files. The point cloud data—data points described in three dimensions—were processed to extract bare earth data; therefore, the point cloud data are organized into the following classes: 1– and 17–unclassified, 2–ground, 9–water, and 10–breakline proximity. Digital Aerial Solutions, LLC, (DAS) was contracted by the U.S. Geological Survey (USGS) to collect and process these data. The lidar data were acquired at a horizontal spacing (or nominal pulse spacing) of 0.5 meters (m) or less. The USGS conducted two ground surveys in small areas on the Chandeleur Islands on February 5, 2012. DAS calculated a root mean square error (RMSEz) of 0.034 m by comparing the USGS ground survey point data to triangulated irregular network (TIN) models built from the lidar elevation data. This lidar survey was conducted to document the topography and topographic change of the Chandeleur Islands. The survey supports detailed studies of Louisiana, Mississippi and Alabama barrier islands that resolve annual and episodic changes in beaches, berms and dunes associated with processes driven by storms, sea-level rise, and even human restoration activities. These lidar data are available to Federal, State and local governments, emergency-response officials, resource managers, and the general public.

Erosion and Channel Incision Analysis with High-Resolution Lidar

NASA Astrophysics Data System (ADS)

Potapenko, J.; Bookhagen, B.

2013-12-01

High-resolution LiDAR (LIght Detection And Ranging) provides a new generation of sub-meter topographic data that is still to be fully exploited by the Earth science communities. We make use of multi-temporal airborne and terrestrial lidar scans in the south-central California and Santa Barbara area. Specifically, we have investigated the Mission Canyon and Channel Islands regions from 2009-2011 to study changes in erosion and channel incision on the landscape. In addition to gridding the lidar data into digital elevation models (DEMs), we also make use of raw lidar point clouds and triangulated irregular networks (TINs) for detailed analysis of heterogeneously spaced topographic data. Using recent advancements in lidar point cloud processing from information technology disciplines, we have employed novel lidar point cloud processing and feature detection algorithms to automate the detection of deeply incised channels and gullies, vegetation, and other derived metrics (e.g. estimates of eroded volume). Our analysis compares topographically-derived erosion volumes to field-derived cosmogenic radionuclide age and in-situ sediment-flux measurements. First results indicate that gully erosion accounts for up to 60% of the sediment volume removed from the Mission Canyon region. Furthermore, we observe that gully erosion and upstream arroyo propagation accelerated after fires, especially in regions where vegetation was heavily burned. The use of high-resolution lidar point cloud data for topographic analysis is still a novel method that needs more precedent and we hope to provide a cogent example of this approach with our research.

A morphologically preserved multi-resolution TIN surface modeling and visualization method for virtual globes

NASA Astrophysics Data System (ADS)

Zheng, Xianwei; Xiong, Hanjiang; Gong, Jianya; Yue, Linwei

2017-07-01

Virtual globes play an important role in representing three-dimensional models of the Earth. To extend the functioning of a virtual globe beyond that of a "geobrowser", the accuracy of the geospatial data in the processing and representation should be of special concern for the scientific analysis and evaluation. In this study, we propose a method for the processing of large-scale terrain data for virtual globe visualization and analysis. The proposed method aims to construct a morphologically preserved multi-resolution triangulated irregular network (TIN) pyramid for virtual globes to accurately represent the landscape surface and simultaneously satisfy the demands of applications at different scales. By introducing cartographic principles, the TIN model in each layer is controlled with a data quality standard to formulize its level of detail generation. A point-additive algorithm is used to iteratively construct the multi-resolution TIN pyramid. The extracted landscape features are also incorporated to constrain the TIN structure, thus preserving the basic morphological shapes of the terrain surface at different levels. During the iterative construction process, the TIN in each layer is seamlessly partitioned based on a virtual node structure, and tiled with a global quadtree structure. Finally, an adaptive tessellation approach is adopted to eliminate terrain cracks in the real-time out-of-core spherical terrain rendering. The experiments undertaken in this study confirmed that the proposed method performs well in multi-resolution terrain representation, and produces high-quality underlying data that satisfy the demands of scientific analysis and evaluation.

Long-Term Memory Stabilized by Noise-Induced Rehearsal

PubMed Central

Wei, Yi

2014-01-01

Cortical networks can maintain memories for decades despite the short lifetime of synaptic strengths. Can a neural network store long-lasting memories in unstable synapses? Here, we study the effects of ongoing spike-timing-dependent plasticity (STDP) on the stability of memory patterns stored in synapses of an attractor neural network. We show that certain classes of STDP rules can stabilize all stored memory patterns despite a short lifetime of synapses. In our model, unstructured neural noise, after passing through the recurrent network connections, carries the imprint of all memory patterns in temporal correlations. STDP, combined with these correlations, leads to reinforcement of all stored patterns, even those that are never explicitly visited. Our findings may provide the functional reason for irregular spiking displayed by cortical neurons and justify models of system memory consolidation. Therefore, we propose that irregular neural activity is the feature that helps cortical networks maintain stable connections. PMID:25411507

Enhancing the Classification Accuracy of IP Geolocation

DTIC Science & Technology

2013-10-01

accurately identify the geographic location of Internet devices has signficant implications for online- advertisers, application developers , network...Real Media, Comedy Central, Netflix and Spotify) and target advertising (e.g., Google). More re- cently, IP geolocation techniques have been deployed...distance to delay function and how they triangulate the position of the target. Statistical Geolocation [14] develops a joint probability density

Plasma Irregularities on the Leading and Trailing Edges of Polar Cap Patches

NASA Astrophysics Data System (ADS)

Lamarche, L. J.; Varney, R. H.; Gillies, R.; Chartier, A.; Mitchell, C. N.

2017-12-01

Plasma irregularities in the polar cap have often been attributed to the gradient drift instability (GDI). Traditional fluid theories of GDI predicts irregularity growth only on the trailing edge of polar patches, where the plasma density gradient is parallel to the plasma drift velocity, however many observations show irregularities also form on the leading edge of patches. We consider decameter-scale irregularities detected by polar-latitude SuperDARN (Super Dual Auroral Radar Network) radars with any relationship between the background density gradients and drift velocity. Global electron density from the Multi-Instrument Data Analysis System (MIDAS), a GPS tomography routine, is used to provide context for where irregularities are observed relative to polar patches and finer-scale background density gradients are found from 3D imaging from both the North and Canada faces of the Resolute Bay Incoherent Scatter Radars (RISR-N and RISR-C) jointly. Shear-based instabilities are considered as mechanisms by which plasma irregularities could form on the leading edge of patches. Theoretical predictions of instability growth from both GDI and shear instabilities are compared with irregularity observations for the October 13, 2016 storm.

Dynamics of self-sustained asynchronous-irregular activity in random networks of spiking neurons with strong synapses

PubMed Central

Kriener, Birgit; Enger, Håkon; Tetzlaff, Tom; Plesser, Hans E.; Gewaltig, Marc-Oliver; Einevoll, Gaute T.

2014-01-01

Random networks of integrate-and-fire neurons with strong current-based synapses can, unlike previously believed, assume stable states of sustained asynchronous and irregular firing, even without external random background or pacemaker neurons. We analyze the mechanisms underlying the emergence, lifetime and irregularity of such self-sustained activity states. We first demonstrate how the competition between the mean and the variance of the synaptic input leads to a non-monotonic firing-rate transfer in the network. Thus, by increasing the synaptic coupling strength, the system can become bistable: In addition to the quiescent state, a second stable fixed-point at moderate firing rates can emerge by a saddle-node bifurcation. Inherently generated fluctuations of the population firing rate around this non-trivial fixed-point can trigger transitions into the quiescent state. Hence, the trade-off between the magnitude of the population-rate fluctuations and the size of the basin of attraction of the non-trivial rate fixed-point determines the onset and the lifetime of self-sustained activity states. During self-sustained activity, individual neuronal activity is moreover highly irregular, switching between long periods of low firing rate to short burst-like states. We show that this is an effect of the strong synaptic weights and the finite time constant of synaptic and neuronal integration, and can actually serve to stabilize the self-sustained state. PMID:25400575

Dynamics of self-sustained asynchronous-irregular activity in random networks of spiking neurons with strong synapses.

PubMed

Kriener, Birgit; Enger, Håkon; Tetzlaff, Tom; Plesser, Hans E; Gewaltig, Marc-Oliver; Einevoll, Gaute T

2014-01-01

Random networks of integrate-and-fire neurons with strong current-based synapses can, unlike previously believed, assume stable states of sustained asynchronous and irregular firing, even without external random background or pacemaker neurons. We analyze the mechanisms underlying the emergence, lifetime and irregularity of such self-sustained activity states. We first demonstrate how the competition between the mean and the variance of the synaptic input leads to a non-monotonic firing-rate transfer in the network. Thus, by increasing the synaptic coupling strength, the system can become bistable: In addition to the quiescent state, a second stable fixed-point at moderate firing rates can emerge by a saddle-node bifurcation. Inherently generated fluctuations of the population firing rate around this non-trivial fixed-point can trigger transitions into the quiescent state. Hence, the trade-off between the magnitude of the population-rate fluctuations and the size of the basin of attraction of the non-trivial rate fixed-point determines the onset and the lifetime of self-sustained activity states. During self-sustained activity, individual neuronal activity is moreover highly irregular, switching between long periods of low firing rate to short burst-like states. We show that this is an effect of the strong synaptic weights and the finite time constant of synaptic and neuronal integration, and can actually serve to stabilize the self-sustained state.

Designing Next Generation Massively Multithreaded Architectures for Irregular Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tumeo, Antonino; Secchi, Simone; Villa, Oreste

Irregular applications, such as data mining or graph-based computations, show unpredictable memory/network access patterns and control structures. Massively multi-threaded architectures with large node count, like the Cray XMT, have been shown to address their requirements better than commodity clusters. In this paper we present the approaches that we are currently pursuing to design future generations of these architectures. First, we introduce the Cray XMT and compare it to other multithreaded architectures. We then propose an evolution of the architecture, integrating multiple cores per node and next generation network interconnect. We advocate the use of hardware support for remote memory referencemore » aggregation to optimize network utilization. For this evaluation we developed a highly parallel, custom simulation infrastructure for multi-threaded systems. Our simulator executes unmodified XMT binaries with very large datasets, capturing effects due to contention and hot-spotting, while predicting execution times with greater than 90% accuracy. We also discuss the FPGA prototyping approach that we are employing to study efficient support for irregular applications in next generation manycore processors.« less

The Interplanetary Network Supplement to the Fermi GBM Catalog - An AO-2 and AO-3 Guest Investigator Project

NASA Technical Reports Server (NTRS)

Hurley, K.; Briggs, M.; Connaughton, V.; Meegan, C.; von Kienlin, A.; Rau, A.; Zhang, X.; Golenetskii, S.; Aptekar, R.; Mazets, E.;

Long-term versus short-term deformation of the meizoseismal area of the 2008 Achaia-Elia (MW 6.4) earthquake in NW Peloponnese, Greece: Evidence from historical triangulation and morphotectonic data

NASA Astrophysics Data System (ADS)

Stiros, Stathis; Moschas, Fanis; Feng, Lujia; Newman, Andrew

2013-04-01

The deformation of the meizoseismal area of the 2008 Achaia-Elia (MW 6.4) earthquake in NW Peloponnese, of the first significant strike slip earthquake in continental Greece, was examined in two time scales; of 102 years, based on the analysis of high-accuracy historical triangulation data describing shear, and of 105-106 years, based on the analysis of the hydrographic network of the area for signs of streams offset by faulting. Our study revealed pre-seismic accumulation of shear strain of the order of 0.2 μrad/year in the study area, consistent with recent GPS evidence, but no signs of significant strike slip-induced offsets in the hydrographic network. These results confirm the hypothesis that the 2008 fault, which did not reached the surface and was not associated with significant seismic ground deformation, probably because of a surface flysch layer filtering high-strain events, was associated with an immature or a dormant, recently activated fault. This fault, about 150 km long and discordant to the morphotectonic trends of the area, seems first, to contain segments which have progressively reactivated in a specific direction in the last 20 years, reminiscent of the North Anatolian Fault, and second, to limit an 150 km wide (recent?) shear zone in the internal part of the arc, in a region mostly dominated by thrust faulting and strong destructive earthquakes. Deformation of the first main strike slip fault in continental Greece analyzed. Triangulation data show preseismic shear, hydrographic net no previous faulting. Surface shear deformation only in low strain rates. Immature or reactivated dormant strike slip fault, with gradual oriented rupturing. Interplay between shear and thrusting along the arc.

A control network of Triton

NASA Astrophysics Data System (ADS)

Davies, Merton E.; Rogers, Patricia G.; Colvin, Tim R.

1991-08-01

A control network for Triton has been computed using a bundle-type analytical triangulation program. The network contains 105 points that were measured on 57 Voyager-2 pictures. The adjustment contained 1010 observation equations and 382 normal equations and resulted in a standard measurement error of 13.36 microns. The coordinates of the control points, the camera orientation angles at the times when the pictures were taken, and Triton's mean radius were determined. A separate statistical analysis confirmed Triton's radius to be 1352.6 + or - 2.4 km. Attempts to tie the control network around the satellite were unsuccessful because discontinuities exist in high-resolution coverage between 66 deg and 289 deg longitude, north of 38 deg latitude, and south of 78 deg latitude.

The development of a hydrologic-hydraulic representation of an urbanscape: the case study of Nashville, Tennessee

NASA Astrophysics Data System (ADS)

Sedlar, F.; Ivanov, V. Y.; Shao, J.; Narayan, U.; Nardi, F.; Adams, T. E.; Merwade, V.; Wright, D. B.; Kim, J.; Fatichi, S.; Rakhmatulina, E.

2013-12-01

Incorporating elevation data into coupled hydraulic and hydrologic models with the use of triangulated irregular networks (TINs) provides a detailed and highly customizable representation of the original domain. Until recently the resolution of such digital elevation models was 1 or 1/3 arc second (10-30 meters). Aided by the use of LiDAR, digital elevation models are now available at the 1/9 arc second resolution (1-3 meters). With elevation data at this level of resolution watershed details that are overlooked at a 10-30 meter resolution can now be resolved and incorporated into the TIN. For urban flood modeling this implies that street level features can be resolved. However to provide a useful picture of the flooding as a whole, this data would need to be integrated across a citywide scale. To prove the feasibility, process, and capabilities of generating such a detailed and large scale TIN, we present a case study of Nashville, TN, USA, during the May 1-2, 2010 flooding, a 1,000 year storm event. With the use of ArcGIS, HEC-RAS, Triangle, and additionally developed processing methodologies, an approach is developed to generate a hydrologically relevant and detailed TIN of the entire urbanscape of Nashville. This TIN incorporates three separate aspects; the watershed, the floodplain, and the city. The watershed component contains the elevation data for the delineated watershed, roughly 1,000 km2 at 1-3 meter resolution. The floodplain encompasses over 300 channel cross sections of the Cumberland River and a delineated floodplain. The city element comprises over 500,000 buildings and all major roadways within the watershed. Once generated, the resulting triangulation of the TIN is optimized with the Triangle software for input to the coupled hydraulic and hydrological model, tRIBS-OFM. Hydrologically relevant areas such as the floodplain are densified and constraints are set on the minimum triangle area for the entire TIN. Upon running the coupled hydraulic and hydrological model with the appropriate forcings, the spatial dynamics of the flooding will then be resolved at a street level across the entire city. The analysis capabilities afforded at this resolution and across such a large area will facilitate urban flood predictions coupled with hydrologic forecasts as well as a better understanding of the spatial dynamics of urban flooding.

The InterPlanetary Network Supplement to the Second Fermi GBM Catalog of Cosmic Gamma-Ray Bursts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurley, K.; Aptekar, R. L.; Golenetskii, S. V.

InterPlanetary Network (IPN) data are presented for the gamma-ray bursts in the second Fermi Gamma-Ray Burst Monitor (GBM) catalog. Of the 462 bursts in that catalog between 2010 July 12 and 2012 July 11, 428, or 93%, were observed by at least 1 other instrument in the 9-spacecraft IPN. Of the 428, the localizations of 165 could be improved by triangulation. For these bursts, triangulation gives one or more annuli whose half-widths vary between about 2.′3° and 16°, depending on the peak flux, fluence, time history, arrival direction, and the distance between the spacecraft. We compare the IPN localizations withmore » the GBM 1 σ , 2 σ , and 3 σ error contours and find good agreement between them. The IPN 3 σ error boxes have areas between about 8 square arcminutes and 380 square degrees, and are an average of 2500 times smaller than the corresponding GBM 3 σ localizations. We identify four bursts in the IPN/GBM sample whose origins were given as “uncertain,” but may in fact be cosmic. This leads to an estimate of over 99% completeness for the GBM catalog.« less

A constrained Delaunay discretization method for adaptively meshing highly discontinuous geological media

NASA Astrophysics Data System (ADS)

Wang, Yang; Ma, Guowei; Ren, Feng; Li, Tuo

2017-12-01

A constrained Delaunay discretization method is developed to generate high-quality doubly adaptive meshes of highly discontinuous geological media. Complex features such as three-dimensional discrete fracture networks (DFNs), tunnels, shafts, slopes, boreholes, water curtains, and drainage systems are taken into account in the mesh generation. The constrained Delaunay triangulation method is used to create adaptive triangular elements on planar fractures. Persson's algorithm (Persson, 2005), based on an analogy between triangular elements and spring networks, is enriched to automatically discretize a planar fracture into mesh points with varying density and smooth-quality gradient. The triangulated planar fractures are treated as planar straight-line graphs (PSLGs) to construct piecewise-linear complex (PLC) for constrained Delaunay tetrahedralization. This guarantees the doubly adaptive characteristic of the resulted mesh: the mesh is adaptive not only along fractures but also in space. The quality of elements is compared with the results from an existing method. It is verified that the present method can generate smoother elements and a better distribution of element aspect ratios. Two numerical simulations are implemented to demonstrate that the present method can be applied to various simulations of complex geological media that contain a large number of discontinuities.

Complex Quantum Network Manifolds in Dimension d > 2 are Scale-Free

NASA Astrophysics Data System (ADS)

Bianconi, Ginestra; Rahmede, Christoph

2015-09-01

In quantum gravity, several approaches have been proposed until now for the quantum description of discrete geometries. These theoretical frameworks include loop quantum gravity, causal dynamical triangulations, causal sets, quantum graphity, and energetic spin networks. Most of these approaches describe discrete spaces as homogeneous network manifolds. Here we define Complex Quantum Network Manifolds (CQNM) describing the evolution of quantum network states, and constructed from growing simplicial complexes of dimension . We show that in d = 2 CQNM are homogeneous networks while for d > 2 they are scale-free i.e. they are characterized by large inhomogeneities of degrees like most complex networks. From the self-organized evolution of CQNM quantum statistics emerge spontaneously. Here we define the generalized degrees associated with the -faces of the -dimensional CQNMs, and we show that the statistics of these generalized degrees can either follow Fermi-Dirac, Boltzmann or Bose-Einstein distributions depending on the dimension of the -faces.

A balanced memory network.

PubMed

Roudi, Yasser; Latham, Peter E

2007-09-01

A fundamental problem in neuroscience is understanding how working memory--the ability to store information at intermediate timescales, like tens of seconds--is implemented in realistic neuronal networks. The most likely candidate mechanism is the attractor network, and a great deal of effort has gone toward investigating it theoretically. Yet, despite almost a quarter century of intense work, attractor networks are not fully understood. In particular, there are still two unanswered questions. First, how is it that attractor networks exhibit irregular firing, as is observed experimentally during working memory tasks? And second, how many memories can be stored under biologically realistic conditions? Here we answer both questions by studying an attractor neural network in which inhibition and excitation balance each other. Using mean-field analysis, we derive a three-variable description of attractor networks. From this description it follows that irregular firing can exist only if the number of neurons involved in a memory is large. The same mean-field analysis also shows that the number of memories that can be stored in a network scales with the number of excitatory connections, a result that has been suggested for simple models but never shown for realistic ones. Both of these predictions are verified using simulations with large networks of spiking neurons.

Distributed Wavelet Transform for Irregular Sensor Network Grids

DTIC Science & Technology

2005-01-01

implement it in a multi-hop, wireless sensor network ; and illustrate with several simulations. The new transform performs on par with conventional wavelet methods in a head-to-head comparison on a regular grid of sensor nodes.

Mapping to Irregular Torus Topologies and Other Techniques for Petascale Biomolecular Simulation

PubMed Central

Phillips, James C.; Sun, Yanhua; Jain, Nikhil; Bohm, Eric J.; Kalé, Laxmikant V.

2014-01-01

Currently deployed petascale supercomputers typically use toroidal network topologies in three or more dimensions. While these networks perform well for topology-agnostic codes on a few thousand nodes, leadership machines with 20,000 nodes require topology awareness to avoid network contention for communication-intensive codes. Topology adaptation is complicated by irregular node allocation shapes and holes due to dedicated input/output nodes or hardware failure. In the context of the popular molecular dynamics program NAMD, we present methods for mapping a periodic 3-D grid of fixed-size spatial decomposition domains to 3-D Cray Gemini and 5-D IBM Blue Gene/Q toroidal networks to enable hundred-million atom full machine simulations, and to similarly partition node allocations into compact domains for smaller simulations using multiple-copy algorithms. Additional enabling techniques are discussed and performance is reported for NCSA Blue Waters, ORNL Titan, ANL Mira, TACC Stampede, and NERSC Edison. PMID:25594075

A Triangulation Methodology in Research on Social Cultures.

ERIC Educational Resources Information Center

Owens, Robert G.; And Others

The purpose of this research was to develop, test, and demonstrate a systematic methodology of triangulation. Triangulation is a technique used to establish credibility of data gathered in qualitative ways. Triangulated conclusions are more stable than any of the individual vantage points from which they were triangulated. Using a previous study…

Long-term memory stabilized by noise-induced rehearsal.

PubMed

Wei, Yi; Koulakov, Alexei A

2014-11-19

Cortical networks can maintain memories for decades despite the short lifetime of synaptic strengths. Can a neural network store long-lasting memories in unstable synapses? Here, we study the effects of ongoing spike-timing-dependent plasticity (STDP) on the stability of memory patterns stored in synapses of an attractor neural network. We show that certain classes of STDP rules can stabilize all stored memory patterns despite a short lifetime of synapses. In our model, unstructured neural noise, after passing through the recurrent network connections, carries the imprint of all memory patterns in temporal correlations. STDP, combined with these correlations, leads to reinforcement of all stored patterns, even those that are never explicitly visited. Our findings may provide the functional reason for irregular spiking displayed by cortical neurons and justify models of system memory consolidation. Therefore, we propose that irregular neural activity is the feature that helps cortical networks maintain stable connections. Copyright © 2014 the authors 0270-6474/14/3415804-12$15.00/0.

Distributed Hydrologic Modeling of Semiarid Basins in Arizona: A Platform for Land Cover and Climate Change Assessments

NASA Astrophysics Data System (ADS)

Hawkins, G. A.; Vivoni, E. R.

2011-12-01

Watershed management is challenged by rising concerns over climate change and its potential to interact with land cover alterations to impact regional water supplies and hydrologic processes. The inability to conduct experimental manipulations that address climate and land cover change at watershed scales limits the capacity of water managers to make decisions to protect future supplies. As a result, spatially-explicit, physically-based models possess value for predicting the possible consequences on watershed hydrology. In this study, we apply a distributed watershed model, the Triangulated Irregular Network (TIN)-based Real-time Integrated Basin Simulator (tRIBS), to the Beaver Creek basin in Arizona. This sub-basin of the Verde River is representative of the regional topography, land cover, soils distribution and availability of hydrologic data in forested regions of northern Arizona. As such, it can serve as a demonstration study in the broader region to illustrate the utility of distributed models for change assessment studies. Through a model application to summertime conditions, we compare the hydrologic response from three sources of meteorological input: (1) an available network of ground-based stations, (2) weather radar rainfall estimates, and (3) the North American Land Data Assimilation System (NLDAS). Comparisons focus on analysis of spatiotemporal distributions of precipitation, soil moisture, runoff generation, evapotranspiration and recharge from the root zone at high resolution for an assessment of sustainable water supplies for agricultural and domestic purposes. We also present a preliminary analysis of the impact of vegetation change arising from historical treatments in the Beaver Creek to inform the hydrologic consequences in the form of soil moisture and evapotranspiration patterns with differing degrees of proposed forest thinning. Our results are discussed in the context of improved hydrologic predictions for sustainability and decision-making under the uncertainties induced by combined climate and land cover change.

Parallelization of a Fully-Distributed Hydrologic Model using Sub-basin Partitioning

NASA Astrophysics Data System (ADS)

Vivoni, E. R.; Mniszewski, S.; Fasel, P.; Springer, E.; Ivanov, V. Y.; Bras, R. L.

2005-12-01

A primary obstacle towards advances in watershed simulations has been the limited computational capacity available to most models. The growing trend of model complexity, data availability and physical representation has not been matched by adequate developments in computational efficiency. This situation has created a serious bottleneck which limits existing distributed hydrologic models to small domains and short simulations. In this study, we present novel developments in the parallelization of a fully-distributed hydrologic model. Our work is based on the TIN-based Real-time Integrated Basin Simulator (tRIBS), which provides continuous hydrologic simulation using a multiple resolution representation of complex terrain based on a triangulated irregular network (TIN). While the use of TINs reduces computational demand, the sequential version of the model is currently limited over large basins (>10,000 km2) and long simulation periods (>1 year). To address this, a parallel MPI-based version of the tRIBS model has been implemented and tested using high performance computing resources at Los Alamos National Laboratory. Our approach utilizes domain decomposition based on sub-basin partitioning of the watershed. A stream reach graph based on the channel network structure is used to guide the sub-basin partitioning. Individual sub-basins or sub-graphs of sub-basins are assigned to separate processors to carry out internal hydrologic computations (e.g. rainfall-runoff transformation). Routed streamflow from each sub-basin forms the major hydrologic data exchange along the stream reach graph. Individual sub-basins also share subsurface hydrologic fluxes across adjacent boundaries. We demonstrate how the sub-basin partitioning provides computational feasibility and efficiency for a set of test watersheds in northeastern Oklahoma. We compare the performance of the sequential and parallelized versions to highlight the efficiency gained as the number of processors increases. We also discuss how the coupled use of TINs and parallel processing can lead to feasible long-term simulations in regional watersheds while preserving basin properties at high-resolution.

The finite body triangulation: algorithms, subgraphs, homogeneity estimation and application.

PubMed

Carson, Cantwell G; Levine, Jonathan S

2016-09-01

The concept of a finite body Dirichlet tessellation has been extended to that of a finite body Delaunay 'triangulation' to provide a more meaningful description of the spatial distribution of nonspherical secondary phase bodies in 2- and 3-dimensional images. A finite body triangulation (FBT) consists of a network of minimum edge-to-edge distances between adjacent objects in a microstructure. From this is also obtained the characteristic object chords formed by the intersection of the object boundary with the finite body tessellation. These two sets of distances form the basis of a parsimonious homogeneity estimation. The characteristics of the spatial distribution are then evaluated with respect to the distances between objects and the distances within them. Quantitative analysis shows that more physically representative distributions can be obtained by selecting subgraphs, such as the relative neighbourhood graph and the minimum spanning tree, from the finite body tessellation. To demonstrate their potential, we apply these methods to 3-dimensional X-ray computed tomographic images of foamed cement and their 2-dimensional cross sections. The Python computer code used to estimate the FBT is made available. Other applications for the algorithm - such as porous media transport and crack-tip propagation - are also discussed. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

Reconfigurable optical interconnections via dynamic computer-generated holograms

NASA Technical Reports Server (NTRS)

Liu, Hua-Kuang (Inventor); Zhou, Shaomin (Inventor)

1994-01-01

A system is proposed for optically providing one-to-many irregular interconnections, and strength-adjustable many-to-many irregular interconnections which may be provided with strengths (weights) w(sub ij) using multiple laser beams which address multiple holograms and means for combining the beams modified by the holograms to form multiple interconnections, such as a cross-bar switching network. The optical means for interconnection is based on entering a series of complex computer-generated holograms on an electrically addressed spatial light modulator for real-time reconfigurations, thus providing flexibility for interconnection networks for largescale practical use. By employing multiple sources and holograms, the number of interconnection patterns achieved is increased greatly.

On the Non-Uniqueness of Sediment Yield

NASA Astrophysics Data System (ADS)

Kim, J.; Ivanov, V. Y.; Fatichi, S.

2014-12-01

There has been ample experimental evidence that soil erosion does not necessarily occur at the same rate, given the same amount of rainfall or runoff. Such a non-unique phenomenon has been often referred to in literature as due to 'natural variability'. Our recent study hypothesized that uncertainties in the distribution and properties of a sediment layer can be a potential clue to one of the reasons of the non-unique sediment yield. Specifically, numerical experimentation with a sophisticated two-dimensional model showed that a deposited layer plays two conflicting roles: it can both increase and decrease soil erosion, given the same magnitude of runoff. The difference in erodibilities of the "original, intact soil layer" and the "deposited, loose soil layer" and the composition of soil particles in the underlying layers give rise to the non-uniqueness of the amount of eroded materials. In continuing efforts, we attempt to investigate this phenomenon using a comprehensive the Universal Soil Loss Erosion (USLE) database, that contains data on paired hillslopes that show a high degree of non-uniqueness in the response, even though the hillslopes exhibit the same topography, soil type, rainfall and meteorological forcings, and landuse. An underlying hypothesis of this study is that uncertainties in the distribution of soil substrate prior to a rainfall event lead to low predictability skill, i.e., a stochastically-varying outcome. A large number of simulation cases demonstrating the proposed hypothesis are conducted using a coupled numerical model, tRIBS-VEGGIE-FEaST (Triangulated irregular network - based Real time Integrated Basin Simulator- VEGetation Generator for Interactive Evolution -Flow Erosion and Sediment Transport).

Research on optimal DEM cell size for 3D visualization of loess terraces

NASA Astrophysics Data System (ADS)

Zhao, Weidong; Tang, Guo'an; Ji, Bin; Ma, Lei

2009-10-01

In order to represent the complex artificial terrains like loess terraces in Shanxi Province in northwest China, a new 3D visual method namely Terraces Elevation Incremental Visual Method (TEIVM) is put forth by the authors. 406 elevation points and 14 enclosed constrained lines are sampled according to the TIN-based Sampling Method (TSM) and DEM Elevation Points and Lines Classification (DEPLC). The elevation points and constrained lines are used to construct Constrained Delaunay Triangulated Irregular Networks (CD-TINs) of the loess terraces. In order to visualize the loess terraces well by use of optimal combination of cell size and Elevation Increment Value (EIV), the CD-TINs is converted to Grid-based DEM (G-DEM) by use of different combination of cell size and EIV with linear interpolating method called Bilinear Interpolation Method (BIM). Our case study shows that the new visual method can visualize the loess terraces steps very well when the combination of cell size and EIV is reasonable. The optimal combination is that the cell size is 1 m and the EIV is 6 m. Results of case study also show that the cell size should be at least smaller than half of both the terraces average width and the average vertical offset of terraces steps for representing the planar shapes of the terraces surfaces and steps well, while the EIV also should be larger than 4.6 times of the terraces average height. The TEIVM and results above is of great significance to the highly refined visualization of artificial terrains like loess terraces.

GIS data models for coal geology

DOE Office of Scientific and Technical Information (OSTI.GOV)

McColloch, G.H. Jr.; Timberlake, K.J.; Oldham, A.V.

A variety of spatial data models can be applied to different aspects of coal geology. The simple vector data models found in various Computer Aided Drafting (CAD) programs are sometimes used for routine mapping and some simple analyses. However, more sophisticated applications that maintain the topological relationships between cartographic elements enhance analytical potential. Also, vector data models are best for producing various types of high quality, conventional maps. The raster data model is generally considered best for representing data that varies continuously over a geographic area, such as the thickness of a coal bed. Information is lost when contour linesmore » are threaded through raster grids for display, so volumes and tonnages are more accurately determined by working directly with raster data. Raster models are especially well suited to computationally simple surface-to-surface analysis, or overlay functions. Another data model, triangulated irregular networks (TINs) are superior at portraying visible surfaces because many TIN programs support break fines. Break lines locate sharp breaks in slope such as those generated by bodies of water or ridge crests. TINs also {open_quotes}honor{close_quotes} data points so that a surface generated from a set of points will be forced to pass through those points. TINs or grids generated from TINs, are particularly good at determining the intersections of surfaces such as coal seam outcrops and geologic unit boundaries. No single technique works best for all coal-related applications. The ability to use a variety of data models, and transform from one model to another is essential for obtaining optimum results in a timely manner.« less

A Vectorial Model to Compute Terrain Parameters, Local and Remote Sheltering, Scattering and Albedo using TIN Domains for Hydrologic Modeling.

NASA Astrophysics Data System (ADS)

Moreno, H. A.; Ogden, F. L.; Steinke, R. C.; Alvarez, L. V.

2015-12-01

Triangulated Irregular Networks (TINs) are increasingly popular for terrain representation in high performance surface and hydrologic modeling by their skill to capture significant changes in surface forms such as topographical summits, slope breaks, ridges, valley floors, pits and cols. This work presents a methodology for estimating slope, aspect and the components of the incoming solar radiation by using a vectorial approach within a topocentric coordinate system by establishing geometric relations between groups of TIN elements and the sun position. A normal vector to the surface of each TIN element describes slope and aspect while spherical trigonometry allows computing a unit vector defining the position of the sun at each hour and DOY. Thus, a dot product determines the radiation flux at each TIN element. Remote shading is computed by scanning the projection of groups of TIN elements in the direction of the closest perpendicular plane to the sun vector. Sky view fractions are computed by a simplified scanning algorithm in prescribed directions and are useful to determine diffuse radiation. Finally, remote radiation scattering is computed from the sky view factor complementary functions for prescribed albedo values of the surrounding terrain only for significant angles above the horizon. This methodology represents an improvement on the current algorithms to compute terrain and radiation parameters on TINs in an efficient manner. All terrain features (e.g. slope, aspect, sky view factors and remote sheltering) can be pre-computed and stored for easy access for a subsequent ground surface or hydrologic simulation.

Application Possibility of Smartphone as Payload for Photogrammetric Uav System

NASA Astrophysics Data System (ADS)

Yun, M. H.; Kim, J.; Seo, D.; Lee, J.; Choi, C.

2012-07-01

Smartphone can not only be operated under 3G network environment anytime and anyplace but also cost less than the existing photogrammetric UAV since it provides high-resolution image, 3D location and attitude data on a real-time basis from a variety of built-in sensors. This study is aimed to assess the possibility of smartphone as a payload for photogrammetric UAV system. Prior to such assessment, a smartphone-based photogrammetric UAV system application was developed, through which real-time image, location and attitude data was obtained using smartphone under both static and dynamic conditions. Subsequently the accuracy assessment on the location and attitude data obtained and sent by this system was conducted. The smartphone images were converted into ortho-images through image triangulation. The image triangulation was conducted in accordance with presence or absence of consideration of the interior orientation (IO) parameters determined by camera calibration. In case IO parameters were taken into account in the static experiment, the results from triangulation for any smartphone type were within 1.5 pixel (RMSE), which was improved at least by 35% compared to when IO parameters were not taken into account. On the contrary, the improvement effect of considering IO parameters on accuracy in triangulation for smartphone images in dynamic experiment was not significant compared to the static experiment. It was due to the significant impact of vibration and sudden attitude change of UAV on the actuator for automatic focus control within the camera built in smartphone under the dynamic condition. This cause appears to have a negative impact on the image-based DEM generation. Considering these study findings, it is suggested that smartphone is very feasible as a payload for UAV system. It is also expected that smartphone may be loaded onto existing UAV playing direct or indirect roles significantly.

The Civil Side of Irregular Warfare

DTIC Science & Technology

2014-05-22

Burj al -Shimali.52 While Musa al Sadr is not the founder of Hezbollah, his work resulted in the network of connections and the recasting of Shia...Center AMAL afwaj al -muqawama al -lubnaniya (Lebanese Resistance Regiments) = amal (Hope) CA Civil Affairs CAO Civil Affairs Operations CGSC US Army...HAMAS Harakat al -Muqawama al -Islamiyya (the Islamic Resistance Movement) IDF Israel Defense Forces IGO Intergovernmental Organization IW Irregular

Network model of chemical-sensing system inspired by mouse taste buds.

PubMed

Tateno, Katsumi; Igarashi, Jun; Ohtubo, Yoshitaka; Nakada, Kazuki; Miki, Tsutomu; Yoshii, Kiyonori

2011-07-01

Taste buds endure extreme changes in temperature, pH, osmolarity, so on. Even though taste bud cells are replaced in a short span, they contribute to consistent taste reception. Each taste bud consists of about 50 cells whose networks are assumed to process taste information, at least preliminarily. In this article, we describe a neural network model inspired by the taste bud cells of mice. It consists of two layers. In the first layer, the chemical stimulus is transduced into an irregular spike train. The synchronization of the output impulses is induced by the irregular spike train at the second layer. These results show that the intensity of the chemical stimulus is encoded as the degree of the synchronization of output impulses. The present algorithms for signal processing result in a robust chemical-sensing system.

A Balanced Memory Network

PubMed Central

Roudi, Yasser; Latham, Peter E

2007-01-01

A fundamental problem in neuroscience is understanding how working memory—the ability to store information at intermediate timescales, like tens of seconds—is implemented in realistic neuronal networks. The most likely candidate mechanism is the attractor network, and a great deal of effort has gone toward investigating it theoretically. Yet, despite almost a quarter century of intense work, attractor networks are not fully understood. In particular, there are still two unanswered questions. First, how is it that attractor networks exhibit irregular firing, as is observed experimentally during working memory tasks? And second, how many memories can be stored under biologically realistic conditions? Here we answer both questions by studying an attractor neural network in which inhibition and excitation balance each other. Using mean-field analysis, we derive a three-variable description of attractor networks. From this description it follows that irregular firing can exist only if the number of neurons involved in a memory is large. The same mean-field analysis also shows that the number of memories that can be stored in a network scales with the number of excitatory connections, a result that has been suggested for simple models but never shown for realistic ones. Both of these predictions are verified using simulations with large networks of spiking neurons. PMID:17845070

Inverse gravity modeling for depth varying density structures through genetic algorithm, triangulated facet representation, and switching routines

NASA Astrophysics Data System (ADS)

King, Thomas Steven

A hybrid gravity modeling method is developed to investigate the structure of sedimentary mass bodies. The method incorporates as constraints surficial basement/sediment contacts and topography of a mass target with a quadratically varying density distribution. The inverse modeling utilizes a genetic algorithm (GA) to scan a wide range of the solution space to determine initial models and the Marquardt-Levenberg (ML) nonlinear inversion to determine final models that meet pre-assigned misfit criteria, thus providing an estimate of model variability and uncertainty. The surface modeling technique modifies Delaunay triangulation by allowing individual facets to be manually constructed and non-convex boundaries to be incorporated into the triangulation scheme. The sedimentary body is represented by a set of uneven prisms and edge elements, comprised of tetrahedrons, capped by polyhedrons. Each underlying prism and edge element's top surface is located by determining its point of tangency with the overlying terrain. The remaining overlying mass is gravitationally evaluated and subtracted from the observation points. Inversion then proceeds in the usual sense, but on an irregular tiered surface with each element's density defined relative to their top surface. Efficiency is particularly important due to the large number of facets evaluated for surface representations and the many repeated element evaluations of the stochastic GA. The gravitation of prisms, triangular faceted polygons, and tetrahedrons can be formulated in different ways, either mathematically or by physical approximations, each having distinct characteristics, such as evaluation time, accuracy over various spatial ranges, and computational singularities. A decision tree or switching routine is constructed for each element by combining these characteristics into a single cohesive package that optimizes the computation for accuracy and speed while avoiding singularities. The GA incorporates a subspace technique and parameter dependency to maintain model smoothness during development, thus minimizing creating nonphysical models. The stochastic GA explores the solution space, producing a broad range of unbiased initial models, while the ML inversion is deterministic and thus quickly converges to the final model. The combination allows many solution models to be determined from the same observed data.

Estimating dynamic permeability in fractal pore network saturated by Maxwellian fluid

NASA Astrophysics Data System (ADS)

Sun, W.

2017-12-01

The frequency dependent flow of fluid in porous media is an important issue in geophysical prospecting. Oscillating flow in pipe leads to frequency dependent dynamic permeability and has been studied in pore network containing Newtonian fluid. But there is little work on oscillating complex fluid in pipe network, especially in irregular network. Here we formulated frequency dependent permeability for Maxwellian fluid and estimated the permeability in three-dimensional fractal network model. We consider an infinitely long cylindrical pipe with rigid solid wall. The pipe is filled with Maxwellian fluids. Based on the mass conservation equation, the equilibrium equation of force and Maxwell constitutive relationship, we formulated the flux by integration of axial velocity component over the pipe's cross section. Then we extend single pipe formulation to a 3D irregular network. Flux balance condition yields a set of linear equations whose unknowns are the fluid pressure at each node. By evaluating the total flow flux through the network, the dynamic permeability can be calculated.We investigated the dynamic permeability of brine and CPyCl/NaSal in a 3D porous sample with a cubic side length 1 cm. The pore network is created by a Voronoi cell filling method. The porosity, i.e., volume ratio between pore/pipe network and the overall cubic, is set as 0.1. The irregular pore network has a fractal structure. The dimension d of the pore network is defined by the relation between node number M within a sphere and the radius r of the sphere,M=rd.The results show that both brine and Maxwellian fluid's permeability maintain a stable value at low frequency, then decreases with fluctuating peaks. The dynamic permeability in pore networks saturated by Maxwellian fluid (CPyCl/NaSal (60 mM)) show larger peaks during the decline process at high frequency, which represents the typical resonance behavior. Dynamic permeability shows clear dependence on the dimension of the fractal network. Small-scale network has higher dimension than large-scale networks. The reason is that in larger networks pore and inter-pore connections are so dense that the probability P(r) to have a neighboring pore at distance r decays faster. The proposed model may be used to explain velocity dispersion in unconventional reservoir rocks observed in laboratory.

Construction of a stochastic model of track geometry irregularities and validation through experimental measurements of dynamic loading

NASA Astrophysics Data System (ADS)

Panunzio, Alfonso M.; Puel, G.; Cottereau, R.; Simon, S.; Quost, X.

2017-03-01

This paper describes the construction of a stochastic model of urban railway track geometry irregularities, based on experimental data. The considered irregularities are track gauge, superelevation, horizontal and vertical curvatures. They are modelled as random fields whose statistical properties are extracted from a large set of on-track measurements of the geometry of an urban railway network. About 300-1000 terms are used in the Karhunen-Loève/Polynomial Chaos expansions to represent the random fields with appropriate accuracy. The construction of the random fields is then validated by comparing on-track measurements of the contact forces and numerical dynamics simulations for different operational conditions (train velocity and car load) and horizontal layouts (alignment, curve). The dynamics simulations are performed both with and without randomly generated geometrical irregularities for the track. The power spectrum densities obtained from the dynamics simulations with the model of geometrical irregularities compare extremely well with those obtained from the experimental contact forces. Without irregularities, the spectrum is 10-50 dB too low.

The Development of the Puerto Rico Lightning Detection Network for Meteorological Research

NASA Technical Reports Server (NTRS)

Legault, Marc D.; Miranda, Carmelo; Medin, J.; Ojeda, L. J.; Blakeslee, Richard J.

2011-01-01

A land-based Puerto Rico Lightning Detection Network (PR-LDN) dedicated to the academic research of meteorological phenomena has being developed. Five Boltek StormTracker PCI-Receivers with LTS-2 Timestamp Cards with GPS and lightning detectors were integrated to Pentium III PC-workstations running the CentOS linux operating system. The Boltek detector linux driver was compiled under CentOS, modified, and thoroughly tested. These PC-workstations with integrated lightning detectors were installed at five of the University of Puerto Rico (UPR) campuses distributed around the island of PR. The PC-workstations are left on permanently in order to monitor lightning activity at all times. Each is networked to their campus network-backbone permitting quasi-instantaneous data transfer to a central server at the UPR-Bayam n campus. Information generated by each lightning detector is managed by a C-program developed by us called the LDN-client. The LDN-client maintains an open connection to the central server operating the LDN-server program where data is sent real-time for analysis and archival. The LDN-client also manages the storing of data on the PC-workstation hard disk. The LDN-server software (also an in-house effort) analyses the data from each client and performs event triangulations. Time-of-arrival (TOA) and related hybrid algorithms, lightning-type and event discriminating routines are also implemented in the LDN-server software. We also have developed software to visually monitor lightning events in real-time from all clients and the triangulated events. We are currently monitoring and studying the spatial, temporal, and type distribution of lightning strikes associated with electrical storms and tropical cyclones in the vicinity of Puerto Rico.

A new approach for categorizing pig lying behaviour based on a Delaunay triangulation method.

PubMed

Nasirahmadi, A; Hensel, O; Edwards, S A; Sturm, B

2017-01-01

Machine vision-based monitoring of pig lying behaviour is a fast and non-intrusive approach that could be used to improve animal health and welfare. Four pens with 22 pigs in each were selected at a commercial pig farm and monitored for 15 days using top view cameras. Three thermal categories were selected relative to room setpoint temperature. An image processing technique based on Delaunay triangulation (DT) was utilized. Different lying patterns (close, normal and far) were defined regarding the perimeter of each DT triangle and the percentages of each lying pattern were obtained in each thermal category. A method using a multilayer perceptron (MLP) neural network, to automatically classify group lying behaviour of pigs into three thermal categories, was developed and tested for its feasibility. The DT features (mean value of perimeters, maximum and minimum length of sides of triangles) were calculated as inputs for the MLP classifier. The network was trained, validated and tested and the results revealed that MLP could classify lying features into the three thermal categories with high overall accuracy (95.6%). The technique indicates that a combination of image processing, MLP classification and mathematical modelling can be used as a precise method for quantifying pig lying behaviour in welfare investigations.

Reconfigurable Optical Interconnections Via Dynamic Computer-Generated Holograms

NASA Technical Reports Server (NTRS)

Liu, Hua-Kuang (Inventor); Zhou, Shao-Min (Inventor)

1996-01-01

A system is presented for optically providing one-to-many irregular interconnections, and strength-adjustable many-to-many irregular interconnections which may be provided with strengths (weights) w(sub ij) using multiple laser beams which address multiple holograms and means for combining the beams modified by the holograms to form multiple interconnections, such as a cross-bar switching network. The optical means for interconnection is based on entering a series of complex computer-generated holograms on an electrically addressed spatial light modulator for real-time reconfigurations, thus providing flexibility for interconnection networks for large-scale practical use. By employing multiple sources and holograms, the number of interconnection patterns achieved is increased greatly.

Recurrent Neural Network Applications for Astronomical Time Series

NASA Astrophysics Data System (ADS)

Protopapas, Pavlos

2017-06-01

The benefits of good predictive models in astronomy lie in early event prediction systems and effective resource allocation. Current time series methods applicable to regular time series have not evolved to generalize for irregular time series. In this talk, I will describe two Recurrent Neural Network methods, Long Short-Term Memory (LSTM) and Echo State Networks (ESNs) for predicting irregular time series. Feature engineering along with a non-linear modeling proved to be an effective predictor. For noisy time series, the prediction is improved by training the network on error realizations using the error estimates from astronomical light curves. In addition to this, we propose a new neural network architecture to remove correlation from the residuals in order to improve prediction and compensate for the noisy data. Finally, I show how to set hyperparameters for a stable and performant solution correctly. In this work, we circumvent this obstacle by optimizing ESN hyperparameters using Bayesian optimization with Gaussian Process priors. This automates the tuning procedure, enabling users to employ the power of RNN without needing an in-depth understanding of the tuning procedure.

Incremental triangulation by way of edge swapping and local optimization

NASA Technical Reports Server (NTRS)

Wiltberger, N. Lyn

1994-01-01

This document is intended to serve as an installation, usage, and basic theory guide for the two dimensional triangulation software 'HARLEY' written for the Silicon Graphics IRIS workstation. This code consists of an incremental triangulation algorithm based on point insertion and local edge swapping. Using this basic strategy, several types of triangulations can be produced depending on user selected options. For example, local edge swapping criteria can be chosen which minimizes the maximum interior angle (a MinMax triangulation) or which maximizes the minimum interior angle (a MaxMin or Delaunay triangulation). It should be noted that the MinMax triangulation is generally only locally optical (not globally optimal) in this measure. The MaxMin triangulation, however, is both locally and globally optical. In addition, Steiner triangulations can be constructed by inserting new sites at triangle circumcenters followed by edge swapping based on the MaxMin criteria. Incremental insertion of sites also provides flexibility in choosing cell refinement criteria. A dynamic heap structure has been implemented in the code so that once a refinement measure is specified (i.e., maximum aspect ratio or some measure of a solution gradient for the solution adaptive grid generation) the cell with the largest value of this measure is continually removed from the top of the heap and refined. The heap refinement strategy allows the user to specify either the number of cells desired or refine the mesh until all cell refinement measures satisfy a user specified tolerance level. Since the dynamic heap structure is constantly updated, the algorithm always refines the particular cell in the mesh with the largest refinement criteria value. The code allows the user to: triangulate a cloud of prespecified points (sites), triangulate a set of prespecified interior points constrained by prespecified boundary curve(s), Steiner triangulate the interior/exterior of prespecified boundary curve(s), refine existing triangulations based on solution error measures, and partition meshes based on the Cuthill-McKee, spectral, and coordinate bisection strategies.

Methodological triangulation in a study of social support for siblings of children with cancer.

PubMed

Murray, J S

1999-10-01

Triangulation is an approach to research that is becoming increasingly popular among nurse researchers. Five types of triangulation are used in nursing research: data, methodological, theoretical, researcher, and analytical triangulation. Methodological triangulation is an attempt to improve validity by combining various techniques in one study. In this article, an example of quantitative and qualitative triangulation is discussed to illustrate the procedures used and the results achieved. The secondary data used as an example are from a previous study that was conducted by the researcher and investigated nursing interventions used by pediatric oncology nurses to provide social support to siblings of children with cancer. Results show that methodological triangulation was beneficial in this study for three reasons. First, the careful comparison of quantitative and qualitative data added support for the social support variables under investigation. Second, the comparison showed more in-depth dimensions about pediatric oncology nurses providing social support to siblings of children with cancer. Finally, the use of methodological triangulation provided insight into revisions for the quantitative instrument.

A FAST ITERATIVE METHOD FOR SOLVING THE EIKONAL EQUATION ON TRIANGULATED SURFACES*

PubMed Central

Fu, Zhisong; Jeong, Won-Ki; Pan, Yongsheng; Kirby, Robert M.; Whitaker, Ross T.

2012-01-01

This paper presents an efficient, fine-grained parallel algorithm for solving the Eikonal equation on triangular meshes. The Eikonal equation, and the broader class of Hamilton–Jacobi equations to which it belongs, have a wide range of applications from geometric optics and seismology to biological modeling and analysis of geometry and images. The ability to solve such equations accurately and efficiently provides new capabilities for exploring and visualizing parameter spaces and for solving inverse problems that rely on such equations in the forward model. Efficient solvers on state-of-the-art, parallel architectures require new algorithms that are not, in many cases, optimal, but are better suited to synchronous updates of the solution. In previous work [W. K. Jeong and R. T. Whitaker, SIAM J. Sci. Comput., 30 (2008), pp. 2512–2534], the authors proposed the fast iterative method (FIM) to efficiently solve the Eikonal equation on regular grids. In this paper we extend the fast iterative method to solve Eikonal equations efficiently on triangulated domains on the CPU and on parallel architectures, including graphics processors. We propose a new local update scheme that provides solutions of first-order accuracy for both architectures. We also propose a novel triangle-based update scheme and its corresponding data structure for efficient irregular data mapping to parallel single-instruction multiple-data (SIMD) processors. We provide detailed descriptions of the implementations on a single CPU, a multicore CPU with shared memory, and SIMD architectures with comparative results against state-of-the-art Eikonal solvers. PMID:22641200

A fast high-precision six-degree-of-freedom relative position sensor

NASA Astrophysics Data System (ADS)

Hughes, Gary B.; Macasaet, Van P.; Griswold, Janelle; Sison, Claudia A.; Lubin, Philip; Meinhold, Peter; Suen, Jonathan; Brashears, Travis; Zhang, Qicheng; Madajian, Jonathan

2016-03-01

Lasers are commonly used in high-precision measurement and profiling systems. Some laser measurement systems are based on interferometry principles, and others are based on active triangulation, depending on requirements of the application. This paper describes an active triangulation laser measurement system for a specific application wherein the relative position of two fixed, rigid mechanical components is to be measured dynamically with high precision in six degrees of freedom (DOF). Potential applications include optical systems with feedback to control for mechanical vibration, such as target acquisition devices with multiple focal planes. The method uses an array of several laser emitters mounted on one component. The lasers are directed at a reflective surface on the second component. The reflective surface consists of a piecewise-planar pattern such as a pyramid, or more generally a curved reflective surface such as a hyperbolic paraboloid. The reflected spots are sensed at 2-dimensional photodiode arrays on the emitter component. Changes in the relative position of the emitter component and reflective surface will shift the location of the reflected spots within photodiode arrays. Relative motion in any degree of freedom produces independent shifts in the reflected spot locations, allowing full six-DOF relative position determination between the two component positions. Response time of the sensor is limited by the read-out rate of the photodiode arrays. Algorithms are given for position determination with limits on uncertainty and sensitivity, based on laser and spot-sensor characteristics, and assuming regular surfaces. Additional uncertainty analysis is achievable for surface irregularities based on calibration data.

Complex Quantum Network Manifolds in Dimension d > 2 are Scale-Free

PubMed Central

Bianconi, Ginestra; Rahmede, Christoph

2015-01-01

In quantum gravity, several approaches have been proposed until now for the quantum description of discrete geometries. These theoretical frameworks include loop quantum gravity, causal dynamical triangulations, causal sets, quantum graphity, and energetic spin networks. Most of these approaches describe discrete spaces as homogeneous network manifolds. Here we define Complex Quantum Network Manifolds (CQNM) describing the evolution of quantum network states, and constructed from growing simplicial complexes of dimension . We show that in d = 2 CQNM are homogeneous networks while for d > 2 they are scale-free i.e. they are characterized by large inhomogeneities of degrees like most complex networks. From the self-organized evolution of CQNM quantum statistics emerge spontaneously. Here we define the generalized degrees associated with the -faces of the -dimensional CQNMs, and we show that the statistics of these generalized degrees can either follow Fermi-Dirac, Boltzmann or Bose-Einstein distributions depending on the dimension of the -faces. PMID:26356079

Complex Quantum Network Manifolds in Dimension d > 2 are Scale-Free.

PubMed

Bianconi, Ginestra; Rahmede, Christoph

2015-09-10

In quantum gravity, several approaches have been proposed until now for the quantum description of discrete geometries. These theoretical frameworks include loop quantum gravity, causal dynamical triangulations, causal sets, quantum graphity, and energetic spin networks. Most of these approaches describe discrete spaces as homogeneous network manifolds. Here we define Complex Quantum Network Manifolds (CQNM) describing the evolution of quantum network states, and constructed from growing simplicial complexes of dimension d. We show that in d = 2 CQNM are homogeneous networks while for d > 2 they are scale-free i.e. they are characterized by large inhomogeneities of degrees like most complex networks. From the self-organized evolution of CQNM quantum statistics emerge spontaneously. Here we define the generalized degrees associated with the δ-faces of the d-dimensional CQNMs, and we show that the statistics of these generalized degrees can either follow Fermi-Dirac, Boltzmann or Bose-Einstein distributions depending on the dimension of the δ-faces.

Morpho-physiological Characteristics of Dorsal Subicular Network in Mice after Pilocarpine Induced Status Epilepticus

PubMed Central

He, De Fu; Ma, Dong Liang; Tang, Yong Cheng; Engel, Jerome; Bragin, Anatol; Tang, Feng Ru

2010-01-01

The goal of this study was to examine morpho-physiological changes in the dorsal subiculum network in the mouse model of temporal lobe epilepsy using extracellular recording, juxtacellular and immunofluorescence double labeling, and anterograde tracing methods. A significant loss of total dorsal subicular neurons, particularly calbindin, parvalbumin (PV), and immunopositive interneurons, was found at 2 months after pilocarpine-induced status epilepticus (SE). However, the sprouting of axons from lateral entorhinal cortex (LEnt) was observed to contact with surviving subicular neurons. These neurons had two predominant discharge patterns: bursting and fast irregular discharges. The bursting neurons were mainly pyramidal cells, and their dendritic spine density and bursting discharge rates were increased significantly in SE mice compared to the control group. Fast irregular discharge neurons were PV-immunopositive interneurons, and had less dendritic spines in SE mice when compared to control mice. When LEnt was stimulated, bursting and fast irregular discharge neurons had much shorter latency and stronger excitatory response in SE mice compared to the control group. Our results illustrate that morpho-physiological changes in the dorsal subiculum could be part of a multilevel pathological network that occurs simultaneously in many brain areas to contribute to the generation of epileptiform activity. PMID:19298597

Synaptic Plasticity Enables Adaptive Self-Tuning Critical Networks

PubMed Central

Stepp, Nigel; Plenz, Dietmar; Srinivasa, Narayan

2015-01-01

During rest, the mammalian cortex displays spontaneous neural activity. Spiking of single neurons during rest has been described as irregular and asynchronous. In contrast, recent in vivo and in vitro population measures of spontaneous activity, using the LFP, EEG, MEG or fMRI suggest that the default state of the cortex is critical, manifested by spontaneous, scale-invariant, cascades of activity known as neuronal avalanches. Criticality keeps a network poised for optimal information processing, but this view seems to be difficult to reconcile with apparently irregular single neuron spiking. Here, we simulate a 10,000 neuron, deterministic, plastic network of spiking neurons. We show that a combination of short- and long-term synaptic plasticity enables these networks to exhibit criticality in the face of intrinsic, i.e. self-sustained, asynchronous spiking. Brief external perturbations lead to adaptive, long-term modification of intrinsic network connectivity through long-term excitatory plasticity, whereas long-term inhibitory plasticity enables rapid self-tuning of the network back to a critical state. The critical state is characterized by a branching parameter oscillating around unity, a critical exponent close to -3/2 and a long tail distribution of a self-similarity parameter between 0.5 and 1. PMID:25590427

On the spatial distribution of decameter‒scale subauroral ionospheric irregularities observed by SuperDARN radars

NASA Astrophysics Data System (ADS)

Larquier, S.; Ponomarenko, P.; Ribeiro, A. J.; Ruohoniemi, J. M.; Baker, J. B. H.; Sterne, K. T.; Lester, M.

2013-08-01

The midlatitude Super Dual Auroral Radar Network (SuperDARN) radars regularly observe nighttime low‒velocity Sub‒Auroral Ionospheric Scatter (SAIS) from decameter‒scale ionospheric density irregularities during quiet geomagnetic conditions. To establish the origin of the density irregularities responsible for low‒velocity SAIS, it is necessary to distinguish between the effects of high frequency (HF) propagation and irregularity occurrence itself on the observed backscatter distribution. We compare range, azimuth, and elevation data from the Blackstone SuperDARN radar with modeling results from ray tracing coupled with the International Reference Ionosphere assuming a uniform irregularity distribution. The observed and modeled distributions are shown to be very similar. The spatial distribution of backscattering is consistent with the requirement that HF rays propagate nearly perpendicular to the geomagnetic field lines (aspect angle ≤1°). For the first time, the irregularities responsible for low‒velocity SAIS are determined to extend between 200 and 300 km altitude, validating previous assumptions that low‒velocity SAIS is an F‒region phenomenon. We find that the limited spatial extent of this category of ionospheric backscatter within SuperDARN radars' fields‒of‒view is a consequence of HF propagation effects and the finite vertical extent of the scattering irregularities. We conclude that the density irregularities responsible for low‒velocity SAIS are widely distributed horizontally within the midlatitude ionosphere but are confined to the bottom‒side F‒region.

Adolescent Triangulation into Parental Conflicts: Longitudinal Implications for Appraisals and Adolescent-Parent Relations

ERIC Educational Resources Information Center

Fosco, Gregory M.; Grych, John H.

2010-01-01

Although triangulation into parental conflict is a risk factor for child and adolescent maladjustment, little is known about how triangulation affects adolescents' functioning or the factors that lead children to be drawn into parental disagreements. This prospective study examined the relations between triangulation, appraisals of conflict, and…

Defining Tolerance: Impacts of Delay and Disruption when Managing Challenged Networks

NASA Technical Reports Server (NTRS)

Birrane, Edward J. III; Burleigh, Scott C.; Cerf, Vint

2011-01-01

Challenged networks exhibit irregularities in their communication performance stemming from node mobility, power constraints, and impacts from the operating environment. These irregularities manifest as high signal propagation delay and frequent link disruption. Understanding those limits of link disruption and propagation delay beyond which core networking features fail is an ongoing area of research. Various wireless networking communities propose tools and techniques that address these phenomena. Emerging standardization activities within the Internet Research Task Force (IRTF) and the Consultative Committee for Space Data Systems (CCSDS) look to build upon both this experience and scalability analysis. Successful research in this area is predicated upon identifying enablers for common communication functions (notably node discovery, duplex communication, state caching, and link negotiation) and how increased disruptions and delays affect their feasibility within the network. Networks that make fewer assumptions relating to these enablers provide more universal service. Specifically, reliance on node discovery and link negotiation results in network-specific operational concepts rather than scalable technical solutions. Fundamental to this debate are the definitions, assumptions, operational concepts, and anticipated scaling of these networks. This paper presents the commonalities and differences between delay and disruption tolerance, including support protocols and critical enablers. We present where and how these tolerances differ. We propose a set of use cases that must be accommodated by any standardized delay-tolerant network and discuss the implication of these on existing tool development.

Reflections on a Strategic Vision for Computer Network Operations

DTIC Science & Technology

2010-05-25

either a traditional or an irregular war. It cannot include the disarmament or destruction of enemy forces or the occupation of its geographic territory...Washington, DC: Chairman of the Joint Chiefs of Staff, 15 August 2007), GL-7. 34 Mr. John Mense , Basic Computer Network Operations Planners Course

Plasma Irregularity Production in the Polar Cap F-Region Ionosphere

NASA Astrophysics Data System (ADS)

Lamarche, Leslie

Plasma in the Earth's ionosphere is highly irregular on scales ranging between a few centimeters and hundreds of kilometers. Small-scale irregularities or plasma waves can scatter radio waves resulting in a loss of signal for navigation and communication networks. The polar region is particularly susceptible to strong disturbances due to its direct connection with the Sun's magnetic field and energetic particles. In this thesis, factors that contribute to the production of decameter-scale plasma irregularities in the polar F region ionosphere are investigated. Both global and local control of irregularity production are studied, i.e. we consider global solar control through solar illumination and solar wind as well as much more local control by plasma density gradients and convection electric field. In the first experimental study, solar control of irregularity production is investigated using the Super Dual Auroral Radar Network (SuperDARN) radar at McMurdo, Antarctica. The occurrence trends for irregularities are analyzed statistically and a model is developed that describes the location of radar echoes within the radar's field-of-view. The trends are explained through variations in background plasma density with solar illumination affecting radar beam propagation. However, it is found that the irregularity occurrence during the night is higher than expected from ray tracing simulations based on a standard ionospheric density model. The high occurrence at night implies an additional source of plasma density and it is proposed that large-scale density enhancements called polar patches may be the source of this density. Additionally, occurrence maximizes around the terminator due to different competing irregularity production processes that favor a more or less sunlit ionosphere. The second study is concerned with modeling irregularity characteristics near a large-scale density gradient reversal, such as those expected near polar patches, with a particular focus on the asymmetry of the irregularity growth rate across the gradient reversal. Directional dependencies on the plasma density gradient, plasma drift, and wavevector are analyzed in the context of the recently developed general fluid theory of the gradient-drift instability. In the ionospheric F region, the strongest asymmetry is found when an elongated structure is oriented along the radar's boresight and moving perpendicular to its direction of elongation. These results have important implications for finding optimal configurations for oblique-scanning ionospheric radars such as SuperDARN to observe gradient reversals. To test the predictions of the developed model and the general theory of the gradient-drift instability, an experimental investigation is presented focusing on decameter-scale irregularities near a polar patch and the previously uninvestigated directional dependence of irregularity characteristics. Backscatter power and occurrence of irregularities are analyzed using measurements from the SuperDARN radar at Rankin Inlet, Canada, while background density gradients and convection electric fields are found from the north face of the Resolute Bay Incoherent Scatter Radar. It is shown that irregularity occurrence tends to follow the expected trends better than irregularity power, suggesting that while the gradient-drift instability may be a dominant process in generating small-scale irregularities, other mechanisms such as a shear-driven instability or nonlinear process may exert greater control over their intensity. It is concluded from this body of work that the production of small-scale plasma irregularities in the polar F-region ionosphere is controlled both by global factors such as solar illumination as well as local plasma density gradients and electric fields. In general, linear gradient-drift instability theory describes small-scale irregularity production well, particularly for low-amplitude perturbations. The production of irregularities is complex, and while ground-based radars are invaluable tools to study the ionosphere, care must be taken to interpret results correctly.

A range-based predictive localization algorithm for WSID networks

NASA Astrophysics Data System (ADS)

Liu, Yuan; Chen, Junjie; Li, Gang

2017-11-01

Most studies on localization algorithms are conducted on the sensor networks with densely distributed nodes. However, the non-localizable problems are prone to occur in the network with sparsely distributed sensor nodes. To solve this problem, a range-based predictive localization algorithm (RPLA) is proposed in this paper for the wireless sensor networks syncretizing the RFID (WSID) networks. The Gaussian mixture model is established to predict the trajectory of a mobile target. Then, the received signal strength indication is used to reduce the residence area of the target location based on the approximate point-in-triangulation test algorithm. In addition, collaborative localization schemes are introduced to locate the target in the non-localizable situations. Simulation results verify that the RPLA achieves accurate localization for the network with sparsely distributed sensor nodes. The localization accuracy of the RPLA is 48.7% higher than that of the APIT algorithm, 16.8% higher than that of the single Gaussian model-based algorithm and 10.5% higher than that of the Kalman filtering-based algorithm.

Holocene monsoon variability as resolved in small complex networks from palaeodata

NASA Astrophysics Data System (ADS)

Rehfeld, K.; Marwan, N.; Breitenbach, S.; Kurths, J.

2012-04-01

To understand the impacts of Holocene precipitation and/or temperature changes in the spatially extensive and complex region of Asia, it is promising to combine the information from palaeo archives, such as e.g. stalagmites, tree rings and marine sediment records from India and China. To this end, complex networks present a powerful and increasingly popular tool for the description and analysis of interactions within complex spatially extended systems in the geosciences and therefore appear to be predestined for this task. Such a network is typically constructed by thresholding a similarity matrix which in turn is based on a set of time series representing the (Earth) system dynamics at different locations. Looking into the pre-instrumental past, information about the system's processes and thus its state is available only through the reconstructed time series which -- most often -- are irregularly sampled in time and space. Interpolation techniques are often used for signal reconstruction, but they introduce additional errors, especially when records have large gaps. We have recently developed and extensively tested methods to quantify linear (Pearson correlation) and non-linear (mutual information) similarity in presence of heterogeneous and irregular sampling. To illustrate our approach we derive small networks from significantly correlated, linked, time series which are supposed to capture the underlying Asian Monsoon dynamics. We assess and discuss whether and where links and directionalities in these networks from irregularly sampled time series can be soundly detected. Finally, we investigate the role of the Northern Hemispheric temperature with respect to the correlation patterns and find that those derived from warm phases (e.g. Medieval Warm Period) are significantly different from patterns found in cold phases (e.g. Little Ice Age).

Images of Bottomside Irregularities Observed at Topside Altitudes

NASA Technical Reports Server (NTRS)

Burke, William J.; Gentile, Louise C.; Shomo, Shannon R.; Roddy, Patrick A.; Pfaff, Robert F.

2012-01-01

We analyzed plasma and field measurements acquired by the Communication/ Navigation Outage Forecasting System (C/NOFS) satellite during an eight-hour period on 13-14 January 2010 when strong to moderate 250 MHz scintillation activity was observed at nearby Scintillation Network Decision Aid (SCINDA) ground stations. C/NOFS consistently detected relatively small-scale density and electric field irregularities embedded within large-scale (approx 100 km) structures at topside altitudes. Significant spectral power measured at the Fresnel (approx 1 km) scale size suggests that C/NOFS was magnetically conjugate to bottomside irregularities similar to those directly responsible for the observed scintillations. Simultaneous ion drift and plasma density measurements indicate three distinct types of large-scale irregularities: (1) upward moving depletions, (2) downward moving depletions, and (3) upward moving density enhancements. The first type has the characteristics of equatorial plasma bubbles; the second and third do not. The data suggest that both downward moving depletions and upward moving density enhancements and the embedded small-scale irregularities may be regarded as Alfvenic images of bottomside irregularities. This interpretation is consistent with predictions of previously reported theoretical modeling and with satellite observations of upward-directed Poynting flux in the low-latitude ionosphere.

Exploring Manycore Multinode Systems for Irregular Applications with FPGA Prototyping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ceriani, Marco; Palermo, Gianluca; Secchi, Simone

We present a prototype of a multi-core architecture implemented on FPGA, designed to enable efficient execution of irregular applications on distributed shared memory machines, while maintaining high performance on regular workloads. The architecture is composed of off-the-shelf soft-core cores, local interconnection and memory interface, integrated with custom components that optimize it for irregular applications. It relies on three key elements: a global address space, multithreading, and fine-grained synchronization. Global addresses are scrambled to reduce the formation of network hot-spots, while the latency of the transactions is covered by integrating an hardware scheduler within the custom load/store buffers to take advantagemore » from the availability of multiple executions threads, increasing the efficiency in a transparent way to the application. We evaluated a dual node system irregular kernels showing scalability in the number of cores and threads.« less

Complex quantum network geometries: Evolution and phase transitions

NASA Astrophysics Data System (ADS)

Bianconi, Ginestra; Rahmede, Christoph; Wu, Zhihao

2015-08-01

Networks are topological and geometric structures used to describe systems as different as the Internet, the brain, or the quantum structure of space-time. Here we define complex quantum network geometries, describing the underlying structure of growing simplicial 2-complexes, i.e., simplicial complexes formed by triangles. These networks are geometric networks with energies of the links that grow according to a nonequilibrium dynamics. The evolution in time of the geometric networks is a classical evolution describing a given path of a path integral defining the evolution of quantum network states. The quantum network states are characterized by quantum occupation numbers that can be mapped, respectively, to the nodes, links, and triangles incident to each link of the network. We call the geometric networks describing the evolution of quantum network states the quantum geometric networks. The quantum geometric networks have many properties common to complex networks, including small-world property, high clustering coefficient, high modularity, and scale-free degree distribution. Moreover, they can be distinguished between the Fermi-Dirac network and the Bose-Einstein network obeying, respectively, the Fermi-Dirac and Bose-Einstein statistics. We show that these networks can undergo structural phase transitions where the geometrical properties of the networks change drastically. Finally, we comment on the relation between quantum complex network geometries, spin networks, and triangulations.

Complex quantum network geometries: Evolution and phase transitions.

PubMed

Bianconi, Ginestra; Rahmede, Christoph; Wu, Zhihao

2015-08-01

Networks are topological and geometric structures used to describe systems as different as the Internet, the brain, or the quantum structure of space-time. Here we define complex quantum network geometries, describing the underlying structure of growing simplicial 2-complexes, i.e., simplicial complexes formed by triangles. These networks are geometric networks with energies of the links that grow according to a nonequilibrium dynamics. The evolution in time of the geometric networks is a classical evolution describing a given path of a path integral defining the evolution of quantum network states. The quantum network states are characterized by quantum occupation numbers that can be mapped, respectively, to the nodes, links, and triangles incident to each link of the network. We call the geometric networks describing the evolution of quantum network states the quantum geometric networks. The quantum geometric networks have many properties common to complex networks, including small-world property, high clustering coefficient, high modularity, and scale-free degree distribution. Moreover, they can be distinguished between the Fermi-Dirac network and the Bose-Einstein network obeying, respectively, the Fermi-Dirac and Bose-Einstein statistics. We show that these networks can undergo structural phase transitions where the geometrical properties of the networks change drastically. Finally, we comment on the relation between quantum complex network geometries, spin networks, and triangulations.

New Media: The Key to Influence in Irregular Warfare

DTIC Science & Technology

2013-05-20

Pew-Internet-Social-Networking-full-detail.aspx. 13 May 2013. 5 Most Global Internet Users Turn to the Web for Emails (85%) and Social Networking Sites (62...sent from within Libya on various social networking sites after his friends within Libya had recorded them on his cell phone. 33 When cell...to the Web for Emails (85%) and Social Networking Sites (62%), New York, http://www.ipsos-na.com/news- polls/pressrelease.aspx?id=5564. May 4, 2013

The relevance of network micro-structure for neural dynamics.

PubMed

Pernice, Volker; Deger, Moritz; Cardanobile, Stefano; Rotter, Stefan

2013-01-01

The activity of cortical neurons is determined by the input they receive from presynaptic neurons. Many previous studies have investigated how specific aspects of the statistics of the input affect the spike trains of single neurons and neurons in recurrent networks. However, typically very simple random network models are considered in such studies. Here we use a recently developed algorithm to construct networks based on a quasi-fractal probability measure which are much more variable than commonly used network models, and which therefore promise to sample the space of recurrent networks in a more exhaustive fashion than previously possible. We use the generated graphs as the underlying network topology in simulations of networks of integrate-and-fire neurons in an asynchronous and irregular state. Based on an extensive dataset of networks and neuronal simulations we assess statistical relations between features of the network structure and the spiking activity. Our results highlight the strong influence that some details of the network structure have on the activity dynamics of both single neurons and populations, even if some global network parameters are kept fixed. We observe specific and consistent relations between activity characteristics like spike-train irregularity or correlations and network properties, for example the distributions of the numbers of in- and outgoing connections or clustering. Exploiting these relations, we demonstrate that it is possible to estimate structural characteristics of the network from activity data. We also assess higher order correlations of spiking activity in the various networks considered here, and find that their occurrence strongly depends on the network structure. These results provide directions for further theoretical studies on recurrent networks, as well as new ways to interpret spike train recordings from neural circuits.

Modeling the distributed effects of forest thinning on the long-term water balance and streamflow extremes for a semi-arid basin in the southwestern US

NASA Astrophysics Data System (ADS)

Moreno, Hernan A.; Gupta, Hoshin V.; White, Dave D.; Sampson, David A.

2016-03-01

To achieve water resource sustainability in the water-limited southwestern US, it is critical to understand the potential effects of proposed forest thinning on the hydrology of semi-arid basins, where disturbances to headwater catchments can cause significant changes in the local water balance components and basinwise streamflows. In Arizona, the Four Forest Restoration Initiative (4FRI) is being developed with the goal of restoring 2.4 million acres of ponderosa pine along the Mogollon Rim. Using the physically based, spatially distributed triangulated irregular network (TIN)-based Real-time Integrated Basin Simulator (tRIBS) model, we examine the potential impacts of the 4FRI on the hydrology of Tonto Creek, a basin in the Verde-Tonto-Salt (VTS) system, which provides much of the water supply for the Phoenix metropolitan area. Long-term (20-year) simulations indicate that forest removal can trigger significant shifts in the spatiotemporal patterns of various hydrological components, causing increases in net radiation, surface temperature, wind speed, soil evaporation, groundwater recharge and runoff, at the expense of reductions in interception and shading, transpiration, vadose zone moisture and snow water equivalent, with south-facing slopes being more susceptible to enhanced atmospheric losses. The net effect will likely be increases in mean and maximum streamflow, particularly during El Niño events and the winter months, and chiefly for those scenarios in which soil hydraulic conductivity has been significantly reduced due to thinning operations. In this particular climate, forest thinning can lead to net loss of surface water storage by vegetation and snowpack, increasing the vulnerability of ecosystems and populations to larger and more frequent hydrologic extreme conditions on these semi-arid systems.

Bathymetry of Ashokan, Cannonsville, Neversink, Pepacton, Rondout, and Schoharie Reservoirs, New York, 2013–15

USGS Publications Warehouse

Nystrom, Elizabeth A.

2018-02-01

Drinking water for New York City is supplied from several large reservoirs, including a system of reservoirs west of the Hudson River. To provide updated reservoir capacity tables and bathymetry maps of the City’s six West of Hudson reservoirs, bathymetric surveys were conducted by the U.S. Geological Survey from 2013 to 2015. Depths were surveyed with a single-beam echo sounder and real-time kinematic global positioning system along planned transects at predetermined intervals for each reservoir. A separate quality assurance dataset of echo sounder points was collected along transects at oblique angles to the main transects for accuracy assessment. Field-survey data were combined with water surface elevations in a geographic information system to create three-dimensional surfaces in the form of triangulated irregular networks (TINs) representing the elevations of the reservoir geomorphology. The TINs were linearly enforced to better represent geomorphic features within the reservoirs. The linearly enforced TINs were then used to create raster surfaces and 2-foot-interval contour maps of the reservoirs. Elevation-area-capacity tables were calculated at 0.01-foot intervals. The results of the surveys show that the total capacity of the West of Hudson reservoirs has decreased by 11.5 billion gallons (Ggal), or 2.3 percent, since construction, and the useable capacity (the volume above the minimum operating level required to deliver full flow for drinking water supply) has decreased by 7.9 Ggal (1.7 percent). The available capacity (the volume between the spillway elevation and the lowest intake or sill elevation used for drinking water supply) decreased by 9.6 Ggal (2.0 percent), and dead storage (the volume below the lowest intake or sill elevation) decreased by 1.9 Ggal (11.6 percent).

Digital floodplain mapping and an analysis of errors involved

USGS Publications Warehouse

Hamblen, C.S.; Soong, D.T.; Cai, X.

2007-01-01

Mapping floodplain boundaries using geographical information system (GIS) and digital elevation models (DEMs) was completed in a recent study. However convenient this method may appear at first, the resulting maps potentially can have unaccounted errors. Mapping the floodplain using GIS is faster than mapping manually, and digital mapping is expected to be more common in the future. When mapping is done manually, the experience and judgment of the engineer or geographer completing the mapping and the contour resolution of the surface topography are critical in determining the flood-plain and floodway boundaries between cross sections. When mapping is done digitally, discrepancies can result from the use of the computing algorithm and digital topographic datasets. Understanding the possible sources of error and how the error accumulates through these processes is necessary for the validation of automated digital mapping. This study will evaluate the procedure of floodplain mapping using GIS and a 3 m by 3 m resolution DEM with a focus on the accumulated errors involved in the process. Within the GIS environment of this mapping method, the procedural steps of most interest, initially, include: (1) the accurate spatial representation of the stream centerline and cross sections, (2) properly using a triangulated irregular network (TIN) model for the flood elevations of the studied cross sections, the interpolated elevations between them and the extrapolated flood elevations beyond the cross sections, and (3) the comparison of the flood elevation TIN with the ground elevation DEM, from which the appropriate inundation boundaries are delineated. The study area involved is of relatively low topographic relief; thereby, making it representative of common suburban development and a prime setting for the need of accurately mapped floodplains. This paper emphasizes the impacts of integrating supplemental digital terrain data between cross sections on floodplain delineation. ?? 2007 ASCE.

Bathymetric survey of Carroll Creek Tributary to Lake Tuscaloosa, Tuscaloosa County, Alabama, 2010

USGS Publications Warehouse

Lee, K.G.; Kimbrow, D.R.

2011-01-01

The U.S. Geological Survey, in cooperation with the City of Tuscaloosa, conducted a bathymetric survey of Carroll Creek, on May 12-13, 2010. Carroll Creek is one of the major tributaries to Lake Tuscaloosa and contributes about 6 percent of the surface drainage area. A 3.5-mile reach of Carroll Creek was surveyed to prepare a current bathymetric map, determine storage capacities at specified water-surface elevations, and compare current conditions to historical cross sections. Bathymetric data were collected using a high-resolution interferometric mapping system consisting of a phase-differencing bathymetric sonar, navigation and motion-sensing system, and a data acquisition computer. To assess the accuracy of the interferometric mapping system and document depths in shallow areas of the study reach, an electronic total station was used to survey 22 cross sections spaced 50 feet apart. The data were combined and processed and a Triangulated Irregular Network (TIN) and contour map were generated. Cross sections were extracted from the TIN and compared with historical cross sections. Between 2004 and 2010, the area (cross section 1) at the confluence of Carroll Creek and the main run of LakeTuscaloosa showed little to no change in capacity area. Another area (cross section 2) showed a maximum change in elevation of 4 feet and an average change of 3 feet. At the water-surface elevation of 224 feet (National Geodetic Vertical Datum of 1929), the cross-sectional area has changed by 260 square feet for a total loss of 28 percent of cross-sectional storage area. The loss of area may be attributed to sedimentation in Carroll Creek and (or) the difference in accuracy between the two surveys.

Digital Elevation Models of the Pre-Eruption 2000 Crater and 2004-07 Dome-Building Eruption at Mount St. Helens, Washington, USA

USGS Publications Warehouse

Messerich, J.A.; Schilling, S.P.; Thompson, R.A.

2008-01-01

Presented in this report are 27 digital elevation model (DEM) datasets for the crater area of Mount St. Helens. These datasets include pre-eruption baseline data collected in 2000, incremental model subsets collected during the 2004-07 dome building eruption, and associated shaded-relief image datasets. Each dataset was collected photogrammetrically with digital softcopy methods employing a combination of manual collection and iterative compilation of x,y,z coordinate triplets utilizing autocorrelation techniques. DEM data points collected using autocorrelation methods were rigorously edited in stereo and manually corrected to ensure conformity with the ground surface. Data were first collected as a triangulated irregular network (TIN) then interpolated to a grid format. DEM data are based on aerotriangulated photogrammetric solutions for aerial photograph strips flown at a nominal scale of 1:12,000 using a combination of surveyed ground control and photograph-identified control points. The 2000 DEM is based on aerotriangulation of four strips totaling 31 photographs. Subsequent DEMs collected during the course of the eruption are based on aerotriangulation of single aerial photograph strips consisting of between three and seven 1:12,000-scale photographs (two to six stereo pairs). Most datasets were based on three or four stereo pairs. Photogrammetric errors associated with each dataset are presented along with ground control used in the photogrammetric aerotriangulation. The temporal increase in area of deformation in the crater as a result of dome growth, deformation, and translation of glacial ice resulted in continual adoption of new ground control points and abandonment of others during the course of the eruption. Additionally, seasonal snow cover precluded the consistent use of some ground control points.

Modeling erosion and sedimentation coupled with hydrological and overland flow processes at the watershed scale

NASA Astrophysics Data System (ADS)

Kim, Jongho; Ivanov, Valeriy Y.; Katopodes, Nikolaos D.

2013-09-01

A novel two-dimensional, physically based model of soil erosion and sediment transport coupled to models of hydrological and overland flow processes has been developed. The Hairsine-Rose formulation of erosion and deposition processes is used to account for size-selective sediment transport and differentiate bed material into original and deposited soil layers. The formulation is integrated within the framework of the hydrologic and hydrodynamic model tRIBS-OFM, Triangulated irregular network-based, Real-time Integrated Basin Simulator-Overland Flow Model. The integrated model explicitly couples the hydrodynamic formulation with the advection-dominated transport equations for sediment of multiple particle sizes. To solve the system of equations including both the Saint-Venant and the Hairsine-Rose equations, the finite volume method is employed based on Roe's approximate Riemann solver on an unstructured grid. The formulation yields space-time dynamics of flow, erosion, and sediment transport at fine scale. The integrated model has been successfully verified with analytical solutions and empirical data for two benchmark cases. Sensitivity tests to grid resolution and the number of used particle sizes have been carried out. The model has been validated at the catchment scale for the Lucky Hills watershed located in southeastern Arizona, USA, using 10 events for which catchment-scale streamflow and sediment yield data were available. Since the model is based on physical laws and explicitly uses multiple types of watershed information, satisfactory results were obtained. The spatial output has been analyzed and the driving role of topography in erosion processes has been discussed. It is expected that the integrated formulation of the model has the promise to reduce uncertainties associated with typical parameterizations of flow and erosion processes. A potential for more credible modeling of earth-surface processes is thus anticipated.

Automatic drawing for traffic marking with MMS LIDAR intensity

NASA Astrophysics Data System (ADS)

Takahashi, G.; Takeda, H.; Shimano, Y.

2014-05-01

Upgrading the database of CYBER JAPAN has been strategically promoted because the "Basic Act on Promotion of Utilization of Geographical Information", was enacted in May 2007. In particular, there is a high demand for road information that comprises a framework in this database. Therefore, road inventory mapping work has to be accurate and eliminate variation caused by individual human operators. Further, the large number of traffic markings that are periodically maintained and possibly changed require an efficient method for updating spatial data. Currently, we apply manual photogrammetry drawing for mapping traffic markings. However, this method is not sufficiently efficient in terms of the required productivity, and data variation can arise from individual operators. In contrast, Mobile Mapping Systems (MMS) and high-density Laser Imaging Detection and Ranging (LIDAR) scanners are rapidly gaining popularity. The aim in this study is to build an efficient method for automatically drawing traffic markings using MMS LIDAR data. The key idea in this method is extracting lines using a Hough transform strategically focused on changes in local reflection intensity along scan lines. However, also note that this method processes every traffic marking. In this paper, we discuss a highly accurate and non-human-operator-dependent method that applies the following steps: (1) Binarizing LIDAR points by intensity and extracting higher intensity points; (2) Generating a Triangulated Irregular Network (TIN) from higher intensity points; (3) Deleting arcs by length and generating outline polygons on the TIN; (4) Generating buffers from the outline polygons; (5) Extracting points from the buffers using the original LIDAR points; (6) Extracting local-intensity-changing points along scan lines using the extracted points; (7) Extracting lines from intensity-changing points through a Hough transform; and (8) Connecting lines to generate automated traffic marking mapping data.

Root niche separation can explain avoidance of seasonal drought stress and vulnerability of overstory trees to extended drought in a mature Amazonian forest

NASA Astrophysics Data System (ADS)

Ivanov, Valeriy Y.; Hutyra, Lucy R.; Wofsy, Steven C.; Munger, J. William; Saleska, Scott R.; de Oliveira, Raimundo C., Jr.; de Camargo, Plínio B.

2012-12-01

Large areas of Amazonian evergreen forest experience seasonal droughts extending for three or more months, yet show maximum rates of photosynthesis and evapotranspiration during dry intervals. This apparent resilience is belied by disproportionate mortality of the large trees in manipulations that reduce wet season rainfall, occurring after 2-3 years of treatment. The goal of this study is to characterize the mechanisms that produce these contrasting ecosystem responses. A mechanistic model is developed based on the ecohydrological framework of TIN (Triangulated Irregular Network)-based Real Time Integrated Basin Simulator + Vegetation Generator for Interactive Evolution (tRIBS+VEGGIE). The model is used to test the roles of deep roots and soil capillary flux to provide water to the forest during the dry season. Also examined is the importance of "root niche separation," in which roots of overstory trees extend to depth, where during the dry season they use water stored from wet season precipitation, while roots of understory trees are concentrated in shallow layers that access dry season precipitation directly. Observational data from the Tapajós National Forest, Brazil, were used as meteorological forcing and provided comprehensive observational constraints on the model. Results strongly suggest that deep roots with root niche separation adaptations explain both the observed resilience during seasonal drought and the vulnerability of canopy-dominant trees to extended deficits of wet season rainfall. These mechanisms appear to provide an adaptive strategy that enhances productivity of the largest trees in the face of their disproportionate heat loads and water demand in the dry season. A sensitivity analysis exploring how wet season rainfall affects the stability of the rainforest system is presented.

Prediction of River Flooding using Geospatial and Statistical Analysis in New York, USA and Kent, UK

NASA Astrophysics Data System (ADS)

Marsellos, A.; Tsakiri, K.; Smith, M.

2014-12-01

Flooding in the rivers normally occurs during periods of excessive precipitation (i.e. New York, USA; Kent, UK) or ice jams during the winter period (New York, USA). For the prediction and mapping of the river flooding, it is necessary to evaluate the spatial distribution of the water (volume) in the river as well as study the interaction between the climatic and hydrological variables. Two study areas have been analyzed; one in Mohawk River, New York and one in Kent, United Kingdom (UK). A high resolution Digital Elevation Model (DEM) of the Mohawk River, New York has been used for a GIS flooding simulation to determine the maximum elevation value of the water that cannot continue to be restricted in the trunk stream and as a result flooding in the river may be triggered. The Flooding Trigger Level (FTL) is determined by incremental volumetric and surface calculations from Triangulated Irregular Network (TIN) with the use of GIS software and LiDAR data. The prediction of flooding in the river can also be improved by the statistical analysis of the hydrological and climatic variables in Mohawk River and Kent, UK. A methodology of time series analysis has been applied for the decomposition of the hydrological (water flow and ground water data) and climatic data in both locations. The KZ (Kolmogorov-Zurbenko) filter is used for the decomposition of the time series into the long, seasonal, and short term components. The explanation of the long term component of the water flow using the climatic variables has been improved up to 90% for both locations. Similar analysis has been performed for the prediction of the seasonal and short term component. This methodology can be applied for flooding of the rivers in multiple sites.

Transformation of Context-dependent Sensory Dynamics into Motor Behavior

PubMed Central

Latorre, Roberto; Levi, Rafael; Varona, Pablo

2013-01-01

The intrinsic dynamics of sensory networks play an important role in the sensory-motor transformation. In this paper we use conductance based models and electrophysiological recordings to address the study of the dual role of a sensory network to organize two behavioral context-dependent motor programs in the mollusk Clione limacina. We show that: (i) a winner take-all dynamics in the gravimetric sensory network model drives the typical repetitive rhythm in the wing central pattern generator (CPG) during routine swimming; (ii) the winnerless competition dynamics of the same sensory network organizes the irregular pattern observed in the wing CPG during hunting behavior. Our model also shows that although the timing of the activity is irregular, the sequence of the switching among the sensory cells is preserved whenever the same set of neurons are activated in a given time window. These activation phase locks in the sensory signals are transformed into specific events in the motor activity. The activation phase locks can play an important role in motor coordination driven by the intrinsic dynamics of a multifunctional sensory organ. PMID:23459114

Investigation of the role of plasma wave cascading processes in the formation of midlatitude irregularities utilizing GPS and radar observations

NASA Astrophysics Data System (ADS)

Eltrass, A.; Scales, W. A.; Erickson, P. J.; Ruohoniemi, J. M.; Baker, J. B. H.

2016-06-01

Recent studies reveal that midlatitude ionospheric irregularities are less understood due to lack of models and observations that can explain the characteristics of the observed wave structures. In this paper, the cascading processes of both the temperature gradient instability (TGI) and the gradient drift instability (GDI) are investigated as the cause of these irregularities. Based on observations obtained during a coordinated experiment between the Millstone Hill incoherent scatter radar and the Blackstone Super Dual Auroral Radar Network radar, a time series for the growth rate of both TGI and GDI is calculated for observations in the subauroral ionosphere under both quiet and disturbed geomagnetic conditions. Recorded GPS scintillation data are analyzed to monitor the amplitude scintillations and to obtain the spectral characteristics of irregularities producing ionospheric scintillations. Spatial power spectra of the density fluctuations associated with the TGI from nonlinear plasma simulations are compared with both the GPS scintillation spectral characteristics and previous in situ satellite spectral measurements. The spectral comparisons suggest that initially, TGI or/and GDI irregularities are generated at large-scale size (kilometer scale), and the dissipation of the energy associated with these irregularities occurs by generating smaller and smaller (decameter scale) irregularities. The alignment between experimental, theoretical, and computational results of this study suggests that in spite of expectations from linear growth rate calculations, cascading processes involving TGI and GDI are likely responsible for the midlatitude ionospheric irregularities associated with GPS scintillations during disturbed times.

Research on Visualization of Ground Laser Radar Data Based on Osg

NASA Astrophysics Data System (ADS)

Huang, H.; Hu, C.; Zhang, F.; Xue, H.

2018-04-01

Three-dimensional (3D) laser scanning is a new advanced technology integrating light, machine, electricity, and computer technologies. It can conduct 3D scanning to the whole shape and form of space objects with high precision. With this technology, you can directly collect the point cloud data of a ground object and create the structure of it for rendering. People use excellent 3D rendering engine to optimize and display the 3D model in order to meet the higher requirements of real time realism rendering and the complexity of the scene. OpenSceneGraph (OSG) is an open source 3D graphics engine. Compared with the current mainstream 3D rendering engine, OSG is practical, economical, and easy to expand. Therefore, OSG is widely used in the fields of virtual simulation, virtual reality, science and engineering visualization. In this paper, a dynamic and interactive ground LiDAR data visualization platform is constructed based on the OSG and the cross-platform C++ application development framework Qt. In view of the point cloud data of .txt format and the triangulation network data file of .obj format, the functions of 3D laser point cloud and triangulation network data display are realized. It is proved by experiments that the platform is of strong practical value as it is easy to operate and provides good interaction.

SuperDARN HF Scattering and Propagation in the Presence of Polar Patches Imaged Using RISR

NASA Astrophysics Data System (ADS)

Gillies, R. G.; Perry, G. W.; Varney, R. H.; Gillies, D. M.; Donovan, E.

2017-12-01

The global array of High Frequency (HF) Super Dual Auroral Radar Network (SuperDARN) radars continuously monitors ionospheric convection in the middle-to-high latitude region. The radars measure coherent backscatter from decameter scale field-aligned irregularities. One of the main generation mechanisms for these field-aligned irregularities is the gradient drift instability (GDI). The edges of ionospheric density structures, such as polar cap patches, provide ideal locations for GDI growth. The geometry required for GDI growth results in irregularities forming on the trailing edge of polar patches. However, irregularities generated by the non-linear evolution of the GDI can become prevalent throughout the patch within minutes. Modelling the irregularity growth and measurements of backscatter within patches have both confirmed this. One aspect that has often been overlooked in studies of coherent backscatter within patches is the effect of HF propagation on echo location. This study examines HF echo locations in the vicinity of patches that were imaged using the Resolute Bay Incoherent Scatter Radars (RISR). The effect of both vertical and lateral refraction of the HF wave on echo location is examined.

Application of 3D triangulations of airborne laser scanning data to estimate boreal forest leaf area index

NASA Astrophysics Data System (ADS)

Majasalmi, Titta; Korhonen, Lauri; Korpela, Ilkka; Vauhkonen, Jari

2017-07-01

We propose 3D triangulations of airborne Laser Scanning (ALS) point clouds as a new approach to derive 3D canopy structures and to estimate forest canopy effective LAI (LAIe). Computational geometry and topological connectivity were employed to filter the triangulations to yield a quasi-optimal relationship with the field measured LAIe. The optimal filtering parameters were predicted based on ALS height metrics, emulating the production of maps of LAIe and canopy volume for large areas. The LAIe from triangulations was validated with field measured LAIe and compared with a reference LAIe calculated from ALS data using logarithmic model based on Beer's law. Canopy transmittance was estimated using All Echo Cover Index (ACI), and the mean projection of unit foliage area (β) was obtained using no-intercept regression with field measured LAIe. We investigated the influence species and season on the triangulated LAIe and demonstrated the relationship between triangulated LAIe and canopy volume. Our data is from 115 forest plots located at the southern boreal forest area in Finland and for each plot three different ALS datasets were available to apply the triangulations. The triangulation approach was found applicable for both leaf-on and leaf-off datasets after initial calibration. Results showed the Root Mean Square Errors (RMSEs) between LAIe from triangulations and field measured values agreed the most using the highest pulse density data (RMSE = 0.63, the coefficient of determination (R2) = 0.53). Yet, the LAIe calculated using ACI-index agreed better with the field measured LAIe (RMSE = 0.53 and R2 = 0.70). The best models to predict the optimal alpha value contained the ACI-index, which indicates that within-crown transmittance is accounted by the triangulation approach. The cover indices may be recommended for retrieving LAIe only, but for applications which require more sophisticated information on canopy shape and volume, such as radiative transfer models, the triangulation approach may be preferred.

A Real-Time Monitoring System of Industry Carbon Monoxide Based on Wireless Sensor Networks.

PubMed

Yang, Jiachen; Zhou, Jianxiong; Lv, Zhihan; Wei, Wei; Song, Houbing

2015-11-20

Carbon monoxide (CO) burns or explodes at over-standard concentration. Hence, in this paper, a Wifi-based, real-time monitoring of a CO system is proposed for application in the construction industry, in which a sensor measuring node is designed by low-frequency modulation method to acquire CO concentration reliably, and a digital filtering method is adopted for noise filtering. According to the triangulation, the Wifi network is constructed to transmit information and determine the position of nodes. The measured data are displayed on a computer or smart phone by a graphical interface. The experiment shows that the monitoring system obtains excellent accuracy and stability in long-term continuous monitoring.

Delaunay Refinement Mesh Generation

DTIC Science & Technology

1997-05-18

edge is locally Delaunay; thus, by Lemma 3, every edge is Delaunay. Theorem 5 Let V be a set of three or more vertices in the plane that are not all...this document. Delaunay triangulations are valuable in part because they have the following optimality properties. Theorem 6 Among all triangulations of...no locally Delaunay edges. By Theorem 5, a triangulation with no locally Delaunay edges is the Delaunay triangulation. The property of max-min

High-resolution seismic data regularization and wavefield separation

NASA Astrophysics Data System (ADS)

Cao, Aimin; Stump, Brian; DeShon, Heather

2018-04-01

We present a new algorithm, non-equispaced fast antileakage Fourier transform (NFALFT), for irregularly sampled seismic data regularization. Synthetic tests from 1-D to 5-D show that the algorithm may efficiently remove leaked energy in the frequency wavenumber domain, and its corresponding regularization process is accurate and fast. Taking advantage of the NFALFT algorithm, we suggest a new method (wavefield separation) for the detection of the Earth's inner core shear wave with irregularly distributed seismic arrays or networks. All interfering seismic phases that propagate along the minor arc are removed from the time window around the PKJKP arrival. The NFALFT algorithm is developed for seismic data, but may also be used for other irregularly sampled temporal or spatial data processing.

The relationships between stressful life events during childhood and differentiation of self and intergenerational triangulation in adulthood.

PubMed

Peleg, Ora

2014-12-01

This study examined the relationships between stressful life events in childhood and differentiation of self and intergenerational triangulation in adulthood. The sample included 217 students (173 females and 44 males) from a college in northern Israel. Participants completed the Hebrew versions of Life Events Checklist (LEC), Differentiation of Self Inventory-Revised (DSI-R) and intergenerational triangulation (INTRI). The main findings were that levels of stressful life events during childhood and adolescence among both genders were positively correlated with the levels of fusion with others and intergenerational triangulation. The levels of positive life events were negatively related to levels of emotional reactivity, emotional cut-off and intergenerational triangulation. Levels of stressful life events in females were positively correlated with emotional reactivity. Intergenerational triangulation was correlated with emotional reactivity, emotional cut-off, fusion with others and I-position. Findings suggest that families that experience higher levels of stressful life events may be at risk for higher levels of intergenerational triangulation and lower levels of differentiation of self. © 2014 International Union of Psychological Science.

Efficient Usage of Dense GNSS Networks in Central Europe for the Visualization and Investigation of Ionospheric TEC Variations

PubMed Central

Zanimonskiy, Yevgen M.; Yampolski, Yuri M.; Figurski, Mariusz

2017-01-01

The technique of the orthogonal projection of ionosphere electronic content variations for mapping total electron content (TEC) allows us to visualize ionospheric irregularities. For the reconstruction of global ionospheric characteristics, numerous global navigation satellite system (GNSS) receivers located in different regions of the Earth are used as sensors. We used dense GNSS networks in central Europe to detect and investigate a special type of plasma inhomogeneities, called travelling ionospheric disturbances (TID). Such use of GNSS sensors allows us to reconstruct the main TID parameters, such as spatial dimensions, velocities, and directions of their movement. The paper gives examples of the restoration of dynamic characteristics of ionospheric irregularities for quiet and disturbed geophysical conditions. Special attention is paid to the dynamics of ionospheric disturbances stimulated by the magnetic storms of two St. Patrick’s Days (17 March 2013 and 2015). Additional opportunities for the remote sensing of the ionosphere with the use of dense regional networks of GNSS receiving sensors have been noted too. PMID:28994718

Efficient Usage of Dense GNSS Networks in Central Europe for the Visualization and Investigation of Ionospheric TEC Variations.

PubMed

Nykiel, Grzegorz; Zanimonskiy, Yevgen M; Yampolski, Yuri M; Figurski, Mariusz

2017-10-10

The technique of the orthogonal projection of ionosphere electronic content variations for mapping total electron content (TEC) allows us to visualize ionospheric irregularities. For the reconstruction of global ionospheric characteristics, numerous global navigation satellite system (GNSS) receivers located in different regions of the Earth are used as sensors. We used dense GNSS networks in central Europe to detect and investigate a special type of plasma inhomogeneities, called travelling ionospheric disturbances (TID). Such use of GNSS sensors allows us to reconstruct the main TID parameters, such as spatial dimensions, velocities, and directions of their movement. The paper gives examples of the restoration of dynamic characteristics of ionospheric irregularities for quiet and disturbed geophysical conditions. Special attention is paid to the dynamics of ionospheric disturbances stimulated by the magnetic storms of two St. Patrick's Days (17 March 2013 and 2015). Additional opportunities for the remote sensing of the ionosphere with the use of dense regional networks of GNSS receiving sensors have been noted too.

Crystal surface analysis using matrix textural features classified by a probabilistic neural network

NASA Astrophysics Data System (ADS)

Sawyer, Curry R.; Quach, Viet; Nason, Donald; van den Berg, Lodewijk

1991-12-01

A system is under development in which surface quality of a growing bulk mercuric iodide crystal is monitored by video camera at regular intervals for early detection of growth irregularities. Mercuric iodide single crystals are employed in radiation detectors. A microcomputer system is used for image capture and processing. The digitized image is divided into multiple overlapping sub-images and features are extracted from each sub-image based on statistical measures of the gray tone distribution, according to the method of Haralick. Twenty parameters are derived from each sub-image and presented to a probabilistic neural network (PNN) for classification. This number of parameters was found to be optimal for the system. The PNN is a hierarchical, feed-forward network that can be rapidly reconfigured as additional training data become available. Training data is gathered by reviewing digital images of many crystals during their growth cycle and compiling two sets of images, those with and without irregularities.

Birth of an Abstraction: A Dynamical Systems Account of the Discovery of an Elsewhere Principle in a Category Learning Task

ERIC Educational Resources Information Center

Tabor, Whitney; Cho, Pyeong W.; Dankowicz, Harry

2013-01-01

Human participants and recurrent ("connectionist") neural networks were both trained on a categorization system abstractly similar to natural language systems involving irregular ("strong") classes and a default class. Both the humans and the networks exhibited staged learning and a generalization pattern reminiscent of the…

Forecasting the Appearance and Evolution of Ionospheric Irregularities and Structures: Their Effects on AF Systems

DTIC Science & Technology

2015-08-21

building (right) hosting the electronic unit, USB power sully and the wireless network . Figure 48. Ionosonde Field Site at Maseno, Kenya Figure 49... wireless 3G network . Continuous access to the system requires regular purchasing of data bundles. Web data repository Boston College has also...support of ionospheric instruments that have been deployed around the world in support of the SCINDA and LISN Networks . 15. SUBJECT TERMS Total

Effect of Downscaled Forcings and Soil Texture Properties on Hyperresolution Hydrologic Simulations in a Regional Basin in Northwest Mexico

NASA Astrophysics Data System (ADS)

Ko, A.; Mascaro, G.; Vivoni, E. R.

2017-12-01

Hyper-resolution (< 1 km) hydrological modeling is expected to support a range of studies related to the terrestrial water cycle. A critical need for increasing the utility of hyper-resolution modeling is the availability of meteorological forcings and land surface characteristics at high spatial resolution. Unfortunately, in many areas these datasets are only available at coarse (> 10 km) scales. In this study, we address some of the challenges by applying a parallel version of the Triangulated Irregular Network (TIN)-based Real Time Integrated Basin Simulator (tRIBS) to the Rio Sonora Basin (RSB) in northwest Mexico. The RSB is a large, semiarid watershed ( 21,000 km2) characterized by complex topography and a strong seasonality in vegetation conditions, due to the North American monsoon. We conducted simulations at an average spatial resolution of 88 m over a decadal (2004-2013) period using spatially-distributed forcings from remotely-sensed and reanalysis products. Meteorological forcings were derived from the North American Land Data Assimilation System (NLDAS) at the original resolution of 12 km and were downscaled at 1 km with techniques accounting for terrain effects. Two grids of soil properties were created from different sources, including: (i) CONABIO (Comisión Nacional para el Conocimiento y Uso de la Biodiversidad) at 6 km resolution; and (ii) ISRIC (International Soil Reference Information Centre) at 250 m. Time-varying vegetation parameters were derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) composite products. The model was first calibrated and validated through distributed soil moisture data from a network of 20 soil moisture stations during the monsoon season. Next, hydrologic simulations were conducted with five different combinations of coarse and downscaled forcings and soil properties. Outputs in the different configurations were then compared with independent observations of soil moisture, and with estimates of land surface temperature (1 km, daily) and evapotranspiration (1 km, monthly) from MODIS. This study is expected to support the community involved in hyper-resolution hydrologic modeling by identifying the crucial factors that, if available at higher resolution, lead to the largest improvement of the simulation prognostic capability.

Methodological triangulation: an approach to understanding data.

PubMed

Bekhet, Abir K; Zauszniewski, Jaclene A

2012-01-01

To describe the use of methodological triangulation in a study of how people who had moved to retirement communities were adjusting. Methodological triangulation involves using more than one kind of method to study a phenomenon. It has been found to be beneficial in providing confirmation of findings, more comprehensive data, increased validity and enhanced understanding of studied phenomena. While many researchers have used this well-established technique, there are few published examples of its use. The authors used methodological triangulation in their study of people who had moved to retirement communities in Ohio, US. A blended qualitative and quantitative approach was used. The collected qualitative data complemented and clarified the quantitative findings by helping to identify common themes. Qualitative data also helped in understanding interventions for promoting 'pulling' factors and for overcoming 'pushing' factors of participants. The authors used focused research questions to reflect the research's purpose and four evaluative criteria--'truth value', 'applicability', 'consistency' and 'neutrality'--to ensure rigour. This paper provides an example of how methodological triangulation can be used in nursing research. It identifies challenges associated with methodological triangulation, recommends strategies for overcoming them, provides a rationale for using triangulation and explains how to maintain rigour. Methodological triangulation can be used to enhance the analysis and the interpretation of findings. As data are drawn from multiple sources, it broadens the researcher's insight into the different issues underlying the phenomena being studied.

An overview of the stereo correlation and triangulation formulations used in DICe.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turner, Daniel Z.

This document provides a detailed overview of the stereo correlation algorithm and triangulation formulation used in the Digital Image Correlation Engine (DICe) to triangulate three dimensional motion in space given the image coordinates and camera calibration parameters.

Powering the Network: The Forgotten Infrastructure.

ERIC Educational Resources Information Center

Learn, Larry L., Ed.

1995-01-01

Discusses systems that power the telecommunications infrastructure. Highlights include power for central telephone company offices; private branch exchange systems; power interruptions and power irregularities; uninterruptible power systems; problems in the systems; and photovoltaic systems. (LRW)

A canonical neural mechanism for behavioral variability

NASA Astrophysics Data System (ADS)

Darshan, Ran; Wood, William E.; Peters, Susan; Leblois, Arthur; Hansel, David

2017-05-01

The ability to generate variable movements is essential for learning and adjusting complex behaviours. This variability has been linked to the temporal irregularity of neuronal activity in the central nervous system. However, how neuronal irregularity actually translates into behavioural variability is unclear. Here we combine modelling, electrophysiological and behavioural studies to address this issue. We demonstrate that a model circuit comprising topographically organized and strongly recurrent neural networks can autonomously generate irregular motor behaviours. Simultaneous recordings of neurons in singing finches reveal that neural correlations increase across the circuit driving song variability, in agreement with the model predictions. Analysing behavioural data, we find remarkable similarities in the babbling statistics of 5-6-month-old human infants and juveniles from three songbird species and show that our model naturally accounts for these `universal' statistics.

The Occurrence of Small-scale Irregularities in the Mid-latitude Ionosphere from SuperDARN HF Radar Observations

NASA Astrophysics Data System (ADS)

Ruohoniemi, J. M.; Baker, J. B.; Maimaiti, M.; Oksavik, K.; Erickson, P. J.; Scales, W.; Eltrass, A.

2017-12-01

The mid-latitude radars of the SuperDARN network routinely observe backscatter from nighttime decameter-scale F region irregularities at latitudes well equatorward of the auroral boundary. This Sub-Auroral Ionospheric Scatter (SAIS) is strongly distinguished from auroral and SAPS backscatter by low Doppler velocities ( tens m/s) and stable, long-lived ( hours) occurrence in discrete events that are extended in both latitude and longitude. Statistical and event studies of SAIS with the SuperDARN radars indicate that the subauroral F region ionosphere is replete with irregularities during events, at least poleward of the 50° Λ horizon of the North American mid-latitude radars, and that radar observation of SAIS backscatter is then primarily limited by the magnetic aspect condition. Joint experiments with incoherent scatter radar have furnished sets of plasma measurements suitable for testing theories of plasma instability. Modeling work stimulated by the observations has explored the temperature-gradient instability (TGI) and the gradient drift instability (GDI) as possible sources of the irregularities. In this talk we review the findings on the occurrence of the SAIS category of mid-latitude F region irregularities, summarize the results of the modeling work, and discuss future research directions.

Topologically invariant macroscopic statistics in balanced networks of conductance-based integrate-and-fire neurons.

PubMed

Yger, Pierre; El Boustani, Sami; Destexhe, Alain; Frégnac, Yves

2011-10-01

The relationship between the dynamics of neural networks and their patterns of connectivity is far from clear, despite its importance for understanding functional properties. Here, we have studied sparsely-connected networks of conductance-based integrate-and-fire (IF) neurons with balanced excitatory and inhibitory connections and with finite axonal propagation speed. We focused on the genesis of states with highly irregular spiking activity and synchronous firing patterns at low rates, called slow Synchronous Irregular (SI) states. In such balanced networks, we examined the "macroscopic" properties of the spiking activity, such as ensemble correlations and mean firing rates, for different intracortical connectivity profiles ranging from randomly connected networks to networks with Gaussian-distributed local connectivity. We systematically computed the distance-dependent correlations at the extracellular (spiking) and intracellular (membrane potential) levels between randomly assigned pairs of neurons. The main finding is that such properties, when they are averaged at a macroscopic scale, are invariant with respect to the different connectivity patterns, provided the excitatory-inhibitory balance is the same. In particular, the same correlation structure holds for different connectivity profiles. In addition, we examined the response of such networks to external input, and found that the correlation landscape can be modulated by the mean level of synchrony imposed by the external drive. This modulation was found again to be independent of the external connectivity profile. We conclude that first and second-order "mean-field" statistics of such networks do not depend on the details of the connectivity at a microscopic scale. This study is an encouraging step toward a mean-field description of topological neuronal networks.

Mixed Methods, Triangulation, and Causal Explanation

ERIC Educational Resources Information Center

Howe, Kenneth R.

2012-01-01

This article distinguishes a disjunctive conception of mixed methods/triangulation, which brings different methods to bear on different questions, from a conjunctive conception, which brings different methods to bear on the same question. It then examines a more inclusive, holistic conception of mixed methods/triangulation that accommodates…

GPS and GLONASS 1 Hz phase rate observations to study high latitudes ionospheric irregularities

NASA Astrophysics Data System (ADS)

Ghoddousi-Fard, R.; Prikryl, P.; Jacobsen, K. S.; Lahaye, F.

2016-12-01

It has been shown that dual frequency 1 Hz GPS phase rate observations can serve as a promising proxy for phase scintillation over high latitudes (see e.g. Ghoddousi-Fard et al., 2013, 2015). However signals from other GNSS constellations including GLONASS have been available and widely used for positioning applications. Usage of additional GNSS constellations should allow improved sampling of the ionosphere, a critical advantage to study small scale ionospheric irregularities over high latitudes. Migration of global GPS networks to multi-GNSS are now underway such as International GNSS Service (IGS) Multi-GNSS Experiment (MGEX) and other national, public and private sector networks. In this presentation, GPS and GLONASS observations from high latitude MGEX stations as well as a dense regional network over Norway are used to map high latitude ionospheric irregularities by means of standard deviation of phase rate variations. Occurrence of GPS phase irregularities as a function of magnetic latitude and local time are compared with those from both GPS and GLONASS. By including 1 Hz GLONASS measurements at about 185 stations over Norway during geomagnetic storm of March 17-18, 2015, this study complements a recently submitted paper that examined the GPS phase scintillation occurrence in the context of solar wind coupling to the magnetosphere-ionosphere system and auroral electrojet currents (Prikryl et al., 2016). Ghoddousi-Fard et al. (2013). GPS phase difference variation statistics: A comparison between phase scintillation index and proxy indices. Adv. Space Res., 52, 1397-1405, doi: 10.1016/j.asr.2013.06.035. Ghoddousi-Fard et al. (2015). Analysis of GPS phase rate variations in response to geomagnetic field perturbations over the Canadian auroral region. Adv. Space Res., 55, 1372-1381, doi: 10.1016/j.asr.2014.12.021. Prikryl et al. (2016). GPS phase scintillation at high latitudes during the geomagnetic storm of March 17-18, 2015, submitted to J. Geophys. Res. ESS contribution number: 20160112

A comparison of TEC fluctuations and scintillations at Ascension Island

NASA Astrophysics Data System (ADS)

Basu, S.; Groves, K. M.; Quinn, J. M.; Doherty, P.

1999-11-01

With increasing reliance on space-based platforms for global navigation and communication, concerns about the impact of ionospheric scintillation on these systems have become a high priority. Recently, the Air Force Research Laboratory (AFRL) performed amplitude scintillation measurements of L1 (1.575 MHz) signals from GPS satellites at Ascension Island (14.45° W, 7.95° S; magnetic latitude 16° S) during February-April, 1998, to compare amplitude scintillations with fluctuations of the total electron content (TEC). Ascension Island is located in the South Atlantic under the southern crest of the equatorial anomaly of F2 ionization where scintillations will be much enhanced during the upcoming solar maximum period. Ascension Island is included in the global network of the International GPS Service (IGS) and the GPS receivers in this network report the carrier to noise (C/N) ratio, the dual frequency carrier phase and pseudorange data at 30-s intervals. Such data with a sampling interval of 30 s were analyzed to determine TEC, the rate of change of TEC (ROT) and also ROTI, defined as the standard deviation of ROT. The spatial scale of ROTI, sampled at 30 s interval, will correspond to 6 km when the vector sum of the ionospheric projection of the satellite velocity and the irregularity drift orthogonal to the propagation path is of the order of 100 m/s. On the other hand, the scale-length of the amplitude scintillation index corresponds to the Fresnel dimension which is about 400 m for the GPS L1 frequency and an ionospheric height of 400 km. It is shown that, in view of the co-existence of large and small scale irregularities in equatorial irregularity structures, during the early evening hours, and small magnitude of irregularity drifts, ROTI measurements can be used to predict the presence of scintillation causing irregularities. The quantitative relationship between ROTI and S4, however, varies considerably due to variations of the ionospheric projection of the satellite velocity and the ionospheric irregularity drift. During the post-midnight period, due to the decay of small scale irregularities leading to a steepening of irregularity power spectrum, ROTI, on occasions, may not be associated with detectable levels of scintillation. In view of the power law type of irregularity power spectrum, ROTI will, in general, be larger than S4 and the ratio, ROTI/S4, in the present dataset is found to vary between 2 and 10. At high latitudes, where the ionospheric motion, driven by large electric fields of magnetospheric origin, is much enhanced during magnetically active periods, ROTI/S4 may be considerably larger than that in the equatorial region.

Triangulation 2.0

ERIC Educational Resources Information Center

Denzin, Norman K.

2012-01-01

The author's thesis is simple and direct. Those in the mixed methods qualitative inquiry community need a new story line, one that does not confuse pragmatism for triangulation, and triangulation for mixed methods research (MMR). A different third way is required, one that inspires generative politics and dialogic democracy and helps shape…

Onomatopoeia characters extraction from comic images using constrained Delaunay triangulation

NASA Astrophysics Data System (ADS)

Liu, Xiangping; Shoji, Kenji; Mori, Hiroshi; Toyama, Fubito

2014-02-01

A method for extracting onomatopoeia characters from comic images was developed based on stroke width feature of characters, since they nearly have a constant stroke width in a number of cases. An image was segmented with a constrained Delaunay triangulation. Connected component grouping was performed based on the triangles generated by the constrained Delaunay triangulation. Stroke width calculation of the connected components was conducted based on the altitude of the triangles generated with the constrained Delaunay triangulation. The experimental results proved the effectiveness of the proposed method.

Prediction of heart abnormality using MLP network

NASA Astrophysics Data System (ADS)

Hashim, Fakroul Ridzuan; Januar, Yulni; Mat, Muhammad Hadzren; Rizman, Zairi Ismael; Awang, Mat Kamil

2018-02-01

Heart abnormality does not choose gender, age and races when it strikes. With no warning signs or symptoms, it can result to a sudden death of the patient. Generally, heart's irregular electrical activity is defined as heart abnormality. Via implementation of Multilayer Perceptron (MLP) network, this paper tries to develop a program that allows the detection of heart abnormality activity. Utilizing several training algorithms with Purelin activation function, an amount of heartbeat signals received through the electrocardiogram (ECG) will be employed to condition the MLP network.

Predawn plasma bubble cluster observed in Southeast Asia

NASA Astrophysics Data System (ADS)

Watthanasangmechai, Kornyanat; Yamamoto, Mamoru; Saito, Akinori; Tsunoda, Roland; Yokoyama, Tatsuhiro; Supnithi, Pornchai; Ishii, Mamoru; Yatini, Clara

2016-06-01

Predawn plasma bubble was detected as deep plasma depletion by GNU Radio Beacon Receiver (GRBR) network and in situ measurement onboard Defense Meteorological Satellite Program F15 (DMSPF15) satellite and was confirmed by sparse GPS network in Southeast Asia. In addition to the deep depletion, the GPS network revealed the coexisting submesoscale irregularities. A deep depletion is regarded as a primary bubble. Submesoscale irregularities are regarded as secondary bubbles. Primary bubble and secondary bubbles appeared together as a cluster with zonal wavelength of 50 km. An altitude of secondary bubbles happened to be lower than that of the primary bubble in the same cluster. The observed pattern of plasma bubble cluster is consistent with the simulation result of the recent high-resolution bubble (HIRB) model. This event is only a single event out of 76 satellite passes at nighttime during 3-25 March 2012 that significantly shows plasma depletion at plasma bubble wall. The inside structure of the primary bubble was clearly revealed from the in situ density data of DMSPF15 satellite and the ground-based GRBR total electron content.

Ionospheric irregularities and acoustic/gravity wave activity above low-latitude thunderstorms

DOE PAGES

Lay, Erin H.

2017-12-18

Ionospheric irregularities due to plasma bubbles, scintillation, and acoustic/gravity waves are studied in the low-latitude ionosphere in relation to thunderstorm activity. Ionospheric total electron content (TEC) measurements from the Low Latitude Ionospheric Sensor Network (LISN) and lightning measurements from the World-Wide Lightning Location Network (WWLLN) are compared during two summer months and two winter months in 2013. Large amplitude fluctuations in TEC are found to have a strongly-peaked diurnal pattern in the late evening and nighttime summer ionosphere. The maximum magnitude and coverage area of these fluctuations increases as thunderstorm area increases. Summertime mid-amplitude fluctuations do not exhibit the samemore » diurnal variation, but do increase in magnitude and coverage area as thunderstorm area increases. Wintertime ionospheric fluctuations do not appear to be related to thunderstorm activity. Lastly, these findings show that thunderstorms have an observable effect on magnitude and coverage area of ionospheric fluctuations.« less

Sparse matrix-vector multiplication on network-on-chip

NASA Astrophysics Data System (ADS)

Sun, C.-C.; Götze, J.; Jheng, H.-Y.; Ruan, S.-J.

2010-12-01

In this paper, we present an idea for performing matrix-vector multiplication by using Network-on-Chip (NoC) architecture. In traditional IC design on-chip communications have been designed with dedicated point-to-point interconnections. Therefore, regular local data transfer is the major concept of many parallel implementations. However, when dealing with the parallel implementation of sparse matrix-vector multiplication (SMVM), which is the main step of all iterative algorithms for solving systems of linear equation, the required data transfers depend on the sparsity structure of the matrix and can be extremely irregular. Using the NoC architecture makes it possible to deal with arbitrary structure of the data transfers; i.e. with the irregular structure of the sparse matrices. So far, we have already implemented the proposed SMVM-NoC architecture with the size 4×4 and 5×5 in IEEE 754 single float point precision using FPGA.

Ionospheric irregularities and acoustic/gravity wave activity above low-latitude thunderstorms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lay, Erin H.

Ionospheric irregularities due to plasma bubbles, scintillation, and acoustic/gravity waves are studied in the low-latitude ionosphere in relation to thunderstorm activity. Ionospheric total electron content (TEC) measurements from the Low Latitude Ionospheric Sensor Network (LISN) and lightning measurements from the World-Wide Lightning Location Network (WWLLN) are compared during two summer months and two winter months in 2013. Large amplitude fluctuations in TEC are found to have a strongly-peaked diurnal pattern in the late evening and nighttime summer ionosphere. The maximum magnitude and coverage area of these fluctuations increases as thunderstorm area increases. Summertime mid-amplitude fluctuations do not exhibit the samemore » diurnal variation, but do increase in magnitude and coverage area as thunderstorm area increases. Wintertime ionospheric fluctuations do not appear to be related to thunderstorm activity. Lastly, these findings show that thunderstorms have an observable effect on magnitude and coverage area of ionospheric fluctuations.« less

Ionospheric Irregularities and Acoustic/Gravity Wave Activity Above Low-Latitude Thunderstorms

NASA Astrophysics Data System (ADS)

Lay, Erin H.

2018-01-01

Ionospheric irregularities due to plasma bubbles, scintillation, and acoustic/gravity waves are studied in the low-latitude ionosphere in relation to thunderstorm activity. Ionospheric total electron content (TEC) measurements from the Low Latitude Ionospheric Sensor Network and lightning measurements from the World-Wide Lightning Location Network are compared during two summer months and two winter months in 2013. Large amplitude fluctuations in TEC are found to have a strongly peaked diurnal pattern in the late evening and nighttime summer ionosphere. The maximum magnitude and coverage area of these fluctuations increases as thunderstorm area increases. Summertime midamplitude fluctuations do not exhibit the same diurnal variation but do increase in magnitude and coverage area as thunderstorm area increases. Wintertime ionospheric fluctuations do not appear to be related to thunderstorm activity. These findings show that thunderstorms have an observable effect on magnitude and coverage area of ionospheric fluctuations.

Triangulation, Respondent Validation, and Democratic Participation in Mixed Methods Research

ERIC Educational Resources Information Center

Torrance, Harry

2012-01-01

Over the past 10 years or so the "Field" of "Mixed Methods Research" (MMR) has increasingly been exerting itself as something separate, novel, and significant, with some advocates claiming paradigmatic status. Triangulation is an important component of mixed methods designs. Triangulation has its origins in attempts to validate research findings…

Triangulation Processes Experienced by Children in Contemporary China

ERIC Educational Resources Information Center

Wang, Meiping; Liu, Siwei; Belsky, Jay

2017-01-01

Most family-system research on triangulation processes has been undertaken in the West, with little known about this family dynamic in the East. The present cross-sectional study analysed 1,073 Chinese 3rd-12th-graders' self-reported exposure to three kinds of triangulation--cross-generation coalition, scapegoating, and parentification--in…

Profiles of Cognitive Appraisals and Triangulation into Interparental Conflict: Implications for Adolescent Adjustment

PubMed Central

Fosco, Gregory M.; Bray, Bethany C.

2016-01-01

Youth appraisals and triangulation into conflicts are key mechanisms by which interparental conflict places youth at risk for psychological maladjustment. Although evidence suggests that there are multiple mechanisms at work (e.g., Fosco & Feinberg, 2015; Grych, Harold, & Miles, 2003), this body of work has relied on variable-centered analyses that are limited to the unique contributions of each process to the variance in outcomes. In reality, it is possible that different combinations of these risk mechanisms may account for multifinality in risk outcomes. Using latent profile analysis (LPA) we examined profiles of threat appraisals, self-blaming attributions, and triangulation in relation to internalizing and externalizing problems in a sample of 285, ethnically diverse high school students. The current analyses revealed five distinct profiles of appraisals and triangulation, including an overall low-risk group and a global high-risk group, in which all three processes were below average or above average, respectively. Additional profiles included combinations of threat and blame, threat and triangulation, and blame and triangulation. Links between these profiles and emotional distress, problem behavior, and academic outcomes are discussed. PMID:26963695

SATSIN System Manual

DOE Office of Scientific and Technical Information (OSTI.GOV)

Livingston, R.C.

1995-01-01

This report outlines the design, functions and operation of the HAARP Diagnostic Satellite Scintillation (SATSIN) system that will be used to characterize the structure and dynamics of F region ionospheric irregularities created during HF heating. When in routine operation, the SATSIN system will be located so that the propagation path from satellite radio beacons passes through the heated volume created by HAARP. The signal, altered in phase and amplitude by the irregularities, is received by the SATSIN array of eight antennas and is processed to extract the spatial and temporal characteristics of the scintillation. From this information, the strength, shapemore » and motion of the in situ irregularities generated by HAARP can be implied. The hardware and software components of the system are reviewed, and the installation and operation in conjunction with the HAARP network are outlined.« less

A canonical neural mechanism for behavioral variability

PubMed Central

Darshan, Ran; Wood, William E.; Peters, Susan; Leblois, Arthur; Hansel, David

2017-01-01

The ability to generate variable movements is essential for learning and adjusting complex behaviours. This variability has been linked to the temporal irregularity of neuronal activity in the central nervous system. However, how neuronal irregularity actually translates into behavioural variability is unclear. Here we combine modelling, electrophysiological and behavioural studies to address this issue. We demonstrate that a model circuit comprising topographically organized and strongly recurrent neural networks can autonomously generate irregular motor behaviours. Simultaneous recordings of neurons in singing finches reveal that neural correlations increase across the circuit driving song variability, in agreement with the model predictions. Analysing behavioural data, we find remarkable similarities in the babbling statistics of 5–6-month-old human infants and juveniles from three songbird species and show that our model naturally accounts for these ‘universal' statistics. PMID:28530225

GPS TEC Fluctuations in the Low and High Latitudes During the 2015 St. Patrick`s Day Storm

NASA Astrophysics Data System (ADS)

Chung, Jong-Kyun; Hong, Junseok; Yoo, Sung-Moon; Kim, Jeong-Han; Jee, Geonhwa; Hegai, Valery V.

2017-12-01

As a part of collaborative efforts to understand ionospheric irregularities, the Korea ionospheric scintillation sites (KISS) network has been built based on global positioning system (GPS) receivers with sampling rates higher than 1 Hz. We produce the rate of TEC index (ROTI) to represent GPS TEC fluctuations related to ionospheric irregularities. In the KISS network, two ground-based GPS sites at Kiruna (marker: KIRN; geographic: 67.9° N, 21.4° E; geomagnetic: 65.2° N) and Chuuk (marker: CHUK; geographic: 7.5° N, 151.9° E; geomagnetic: 0.4° N) were selected to evaluate the ROTI value for ionospheric irregularities during the occurrence of the 2015 St. Patrick’s Day storm. The KIRN ROTI values in the aurora region appear to be generally much higher than the CHUK ROTI values in the EIA region. The CHUK ROTI values increased to 0.5 TECU/min around UT=13:00 (LT=23:00) on March 16 in the quiet geomagnetic condition. On March 17, 2015, CHUK ROTI values more than 1.0 TECU/min were measured between UT=9:00 and 12:00 (LT=19:00 and 22:00) during the first main phase of the St. Patrick’s Day storm. This may be due to ionospheric irregularities by increased pre-reversal enhancement (PRE) after sunset during the geomagnetic storm. Post-midnight, the CHUK ROTI showed two peaks of 0.5 TECU/min and 0.3 TECU/min near UT=15:00 (LT=01:00) and UT=18:00 (LT=04:00) at the second main phase. The KIRN site showed significant peaks of ROTI around geomagnetic latitude=63.3° N and MLT=15:40 on the same day. These can be explained by enhanced ionospheric irregularities in the auroral oval at the maximum of AE index

SDH-NET: a South-North-South collaboration to build sustainable research capacities on social determinants of health in low- and middle-income countries.

PubMed

Cash-Gibson, Lucinda; Guerra, German; Salgado-de-Snyder, V Nelly

2015-10-22

It is desirable that health researchers have the ability to conduct research on health equity and contribute to the development of their national health system and policymaking processes. However, in low- and middle-income countries (LMICs), there is a limited capacity to conduct this type of research due to reasons mostly associated with the status of national (health) research systems. Building sustainable research capacity in LMICs through the triangulation of South-North-South (S-N-S) collaborative networks seems to be an effective way to maximize limited national resources to strengthen these capacities. This article describes how a collaborative project (SDH-Net), funded by the European Commission, has successfully designed a study protocol and a S-N-S collaborative network to effectively support research capacity building in LMICs, specifically in the area of social determinants of health (SDH); this project seeks to elaborate on the vital role of global collaborative networks in strengthening this practice. The implementation of SDH-Net comprised diverse activities developed in three phases. Phase 1: national level mapping exercises were conducted to assess the needs for SDH capacity building or strengthening in local research systems. Four strategic areas were defined, namely research implementation and system performance, social appropriation of knowledge, institutional and national research infrastructure, and research skills and training/networks. Phase 2: development of tools to address the identified capacity building needs, as well as knowledge management and network strengthening activities. Phase 3: identifying lessons learned in terms of research ethics, and how policies can support the capacity building process in SDH research. The implementation of the protocol has led the network to design innovative tools for strengthening SDH research capacities, under a successful S-N-S collaboration that included national mapping reports, a global open-access learning platform with tools and resources, ethical guidelines for research, policy recommendations, and academic contributions to the global SDH discourse. The effective triangulation of S-N-S partnerships can be of high value in building sustainable research capacity in LMICs. If designed appropriately, these multicultural, multi-institutional, and multidisciplinary collaborations can enable southern and northern academics to contextualize global research according to their national realities.

Large N Limits in Tensor Models: Towards More Universality Classes of Colored Triangulations in Dimension d≥2

NASA Astrophysics Data System (ADS)

Bonzom, Valentin

2016-07-01

We review an approach which aims at studying discrete (pseudo-)manifolds in dimension d≥ 2 and called random tensor models. More specifically, we insist on generalizing the two-dimensional notion of p-angulations to higher dimensions. To do so, we consider families of triangulations built out of simplices with colored faces. Those simplices can be glued to form new building blocks, called bubbles which are pseudo-manifolds with boundaries. Bubbles can in turn be glued together to form triangulations. The main challenge is to classify the triangulations built from a given set of bubbles with respect to their numbers of bubbles and simplices of codimension two. While the colored triangulations which maximize the number of simplices of codimension two at fixed number of simplices are series-parallel objects called melonic triangulations, this is not always true anymore when restricting attention to colored triangulations built from specific bubbles. This opens up the possibility of new universality classes of colored triangulations. We present three existing strategies to find those universality classes. The first two strategies consist in building new bubbles from old ones for which the problem can be solved. The third strategy is a bijection between those colored triangulations and stuffed, edge-colored maps, which are some sort of hypermaps whose hyperedges are replaced with edge-colored maps. We then show that the present approach can lead to enumeration results and identification of universality classes, by working out the example of quartic tensor models. They feature a tree-like phase, a planar phase similar to two-dimensional quantum gravity and a phase transition between them which is interpreted as a proliferation of baby universes. While this work is written in the context of random tensors, it is almost exclusively of combinatorial nature and we hope it is accessible to interested readers who are not familiar with random matrices, tensors and quantum field theory.

Characterization of the low latitude plasma density irregularities observed using C/NOFS and SCINDA data

NASA Astrophysics Data System (ADS)

Andima, Geoffrey; Amabayo, Emirant B.; Jurua, Edward; Cilliers, Pierre J.

2018-01-01

Complex electrodynamic processes over the low latitude region often result in post sunset plasma density irregularities which degrade satellite communication and navigation. In order to forecast the density irregularities, their occurrence time, duration and location need to be quantified. Data from the Communication/Navigation Outage Forecasting System (C/NOFS) satellite was used to characterize the low latitude ion density irregularities from 2011 to 2013. This was supported by ground based data from the SCIntillation Network Decision Aid (SCINDA) receivers at Makerere (Geographic coordinate 32.6°E, 0.3°N, and dip latitude -9.3°N) and Nairobi (Geographic coordinate 36.8°E, -1.3°N, and dip latitude -10.8°N). The results show that irregularities in ion density have a daily pattern with peaks from 20:00 to 24:00 Local Time (LT). Scintillation activity at L band and VHF over East Africa peaked in 2011 and 2012 from 20:00 to 24:00 LT, though in many cases scintillation at VHF persisted longer than that at L band. A longitudinal pattern in ion density irregularity occurrence was observed with peaks over 135-180°E and 270-300°E. The likelihood of ion density irregularity occurrence decreased with increasing altitude. Analysis of C/NOFS zonal ion drift velocities showed that the largest nighttime and daytime drifts were in 270-300°E and 300-330°E longitude regions respectively. Zonal irregularity drift velocities over East Africa were for the first time estimated from L-band scintillation indices. The results show that the velocity of plasma density irregularities in 2011 and 2012 varied daily, and hourly in the range of 50-150 m s-1. The zonal drift velocity estimates from the L-band scintillation indices had good positive correlation with the zonal drift velocities derived from VHF receivers by the spaced receiver technique.

Characterizing the 10 November 2004 storm-time middle-latitude plasma bubble event in Southeast Asia using multi-instrument observations

NASA Astrophysics Data System (ADS)

Li, Guozhu; Ning, Baiqi; Zhao, Biqiang; Liu, Libo; Wan, Weixing; Ding, Feng; Xu, J. S.; Liu, J. Y.; Yumoto, K.

2009-07-01

The development and dynamics of ionospheric plasma bubble (PB) irregularity during the super storm of 7-11 November 2004 are investigated using the data from a multi-instrument network operated in Southeast Asia. Analysis of fluctuations in Global Positioning System total electron content (GPS TEC), ionosonde, GPS scintillation, and in situ satellite density data indicates a series of intense PB-associated irregularities at equatorial, low, and middle latitudes in the Japanese longitude on 10 November. However, in the Chinese sector, the scintillations and PB irregularities are confined within the range of 20-50°N in geographic latitude and 110-125°E in geographic longitude. The absence of equatorial PB irregularities in this sector shows a major difference from that in the close-by longitude Japanese sector. In the Southern Hemisphere Australian sector, the irregularities occurrence is present as a symmetrical distribution at conjugate latitudes. Combined analysis of the data from Osan and Wuhan ionosondes illustrates that the middle-latitude spread F irregularities initially develop at the lower part of the F region and then distribute in the whole F region. This initiation of spread F at lower altitudes indicates that the middle-latitude PB-associated irregularities are locally generated. These results together with the irregularities occurrence sequence from higher to lower latitudes, and the onset time delay of several hours implies that the presence of PB-associated irregularities within a latitude range of 20-50°N in the Chinese sector cannot be attributed to the effects of prompt penetration electric fields (PPEFs), although the equatorial PBs in the close-by longitude are seen to be associated with PPEFs. The possible mechanism is the F region plasma instabilities triggered by wave structures, which act as an external driving force and seed active plasma dynamics and instability growth at middle latitude.

Tle Triangulation Campaign by Japanese High School Students as a Space Educational Project of the Ssh Consortium Kochi

NASA Astrophysics Data System (ADS)

Yamamoto, Masa-Yuki; Okamoto, Sumito; Miyoshi, Terunori; Takamura, Yuzaburo; Aoshima, Akira; Hinokuchi, Jin

As one of the space educational projects in Japan, a triangulation observation project of TLE (Transient Luminous Events: sprites, elves, blue-jets, etc.) has been carried out since 2006 in collaboration between 29 Super Science High-schools (SSH) and Kochi University of Technol-ogy (KUT). Following with previous success of sprite observations by "Astro High-school" since 2004, the SSH consortium Kochi was established as a national space educational project sup-ported by Japan Science and Technology Agency (JST). High-sensitivity CCD camera (Watec, Neptune-100) with 6 mm F/1.4 C-mount lens (Fujinon) and motion-detective software (UFO-Capture, SonotaCo) were given to each participating team in order to monitor Northern night sky of Japan with almost full-coverage. During each school year (from April to March in Japan) since 2006, thousands of TLE images were taken by many student teams, with considerably large numbers of successful triangulations, i.e., (School year, Numbers of TLE observations, Numbers of triangulations) are (2006, 43, 3), (2007, 441, 95), (2008, 734, 115), and (2009, 337, 78). Note that, school year in Japan begins on April 1 and ends on March 31. The observation campaign began in December 2006, numbers are as of Feb. 28, 2010. Recently, some high schools started wide field observations using multiple cameras, and others started VLF observations using handmade loop antennae and amplifiers. Infomation exchange among the SSH consortium Kochi is frequently communicated with scientific discussion via KUT's mailing lists. Also, interactions with amateur observers in Japan are made through an internet forum of "SonotaCo Network Japan" (http://sonotaco.jp). Not only as an educational project but also as a scientific one, the project is also in success. In February 2008, simultaneous observations of Elves were obtained, in November 2009 a Giant "Graft-shaped" Sprites driven by Jets was clearly imaged with VLF signals. Most recently, ob-servations of Elves and sprite halos with stripes like wave structures on airglow were successfully imaged in January 2010. In this talk, four years activities of the SSH consortium Kochi will be presented by participating high-school students and teachers with their own impressions.

Identification of Abnormal System Noise Temperature Patterns in Deep Space Network Antennas Using Neural Network Trained Fuzzy Logic

NASA Technical Reports Server (NTRS)

Lu, Thomas; Pham, Timothy; Liao, Jason

2011-01-01

This paper presents the development of a fuzzy logic function trained by an artificial neural network to classify the system noise temperature (SNT) of antennas in the NASA Deep Space Network (DSN). The SNT data were classified into normal, marginal, and abnormal classes. The irregular SNT pattern was further correlated with link margin and weather data. A reasonably good correlation is detected among high SNT, low link margin and the effect of bad weather; however we also saw some unexpected non-correlations which merit further study in the future.

Atmospheric pressure, density, temperature and wind variations between 50 and 200 km

NASA Technical Reports Server (NTRS)

Justus, C. G.; Woodrum, A.

1972-01-01

Data on atmospheric pressure, density, temperature and winds between 50 and 200 km were collected from sources including Meteorological Rocket Network data, ROBIN falling sphere data, grenade release and pitot tube data, meteor winds, chemical release winds, satellite data, and others. These data were analyzed by a daily difference method and results on the distribution statistics, magnitude, and spatial structure of the irregular atmospheric variations are presented. Time structures of the irregular variations were determined by the analysis of residuals from harmonic analysis of time series data. The observed height variations of irregular winds and densities are found to be in accord with a theoretical relation between these two quantities. The latitude variations (at 50 - 60 km height) show an increasing trend with latitude. A possible explanation of the unusually large irregular wind magnitudes of the White Sands MRN data is given in terms of mountain wave generation by the Sierra Nevada range about 1000 km west of White Sands. An analytical method is developed which, based on an analogy of the irregular motion field with axisymmetric turbulence, allows measured or model correlation or structure functions to be used to evaluate the effective frequency spectra of scalar and vector quantities of a spacecraft moving at any speed and at any trajectory elevation angle.

Automatic Generation of CFD-Ready Surface Triangulations from CAD Geometry

NASA Technical Reports Server (NTRS)

Aftosmis, M. J.; Delanaye, M.; Haimes, R.; Nixon, David (Technical Monitor)

1998-01-01

This paper presents an approach for the generation of closed manifold surface triangulations from CAD geometry. CAD parts and assemblies are used in their native format, without translation, and a part's native geometry engine is accessed through a modeler-independent application programming interface (API). In seeking a robust and fully automated procedure, the algorithm is based on a new physical space manifold triangulation technique which was developed to avoid robustness issues associated with poorly conditioned mappings. In addition, this approach avoids the usual ambiguities associated with floating-point predicate evaluation on constructed coordinate geometry in a mapped space, The technique is incremental, so that each new site improves the triangulation by some well defined quality measure. Sites are inserted using a variety of priority queues to ensure that new insertions will address the worst triangles first, As a result of this strategy, the algorithm will return its 'best' mesh for a given (prespecified) number of sites. Alternatively, the algorithm may be allowed to terminate naturally after achieving a prespecified measure of mesh quality. The resulting triangulations are 'CFD-ready' in that: (1) Edges match the underlying part model to within a specified tolerance. (2) Triangles on disjoint surfaces in close proximity have matching length-scales. (3) The algorithm produces a triangulation such that no angle is less than a given angle bound, alpha, or greater than Pi - 2alpha This result also sets bounds on the maximum vertex degree, triangle aspect-ratio and maximum stretching rate for the triangulation. In addition to tile output triangulations for a variety of CAD parts, tile discussion presents related theoretical results which assert the existence of such all angle bound, and demonstrate that maximum bounds of between 25 deg and 30 deg may be achieved in practice.

From Fob to Noc: A Pathway to a Cyber Career for Combat Veterans

DTIC Science & Technology

2014-06-01

Assurance Certifications GS general schedule HSAC Homeland Security Advisory Council IDS intrusion detection system IP internet protocol IPS...NIPRNET non-secure internet protocol router network NIST National Institute for Standards and Technology NOC network operations center NSA National...twice a day on an irregular schedule or during contact with the enemy to keep any observing enemy wary of the force protection 13 condition at any

Fin whale tracks recorded by a seismic network on the Juan de Fuca Ridge, Northeast Pacific Ocean.

PubMed

Soule, Dax C; Wilcock, William S D

2013-03-01

Fin whale calls recorded from 2003 to 2004 by a seafloor seismic network on the Endeavour segment of the Juan de Fuca Ridge were analyzed to determine tracks and calling patterns. Over 150 tracks were obtained with a total duration of ~800 h and swimming speeds from 1 to 12 km/h. The dominant inter-pulse interval (IPI) is 24 s and the IPI patterns define 4 categories: a 25 s single IPI and 24/30 s dual IPI produced by single calling whales, a 24/13 s dual IPI interpreted as two calling whales, and an irregular IPI interpreted as groups of calling whales. There are also tracks in which the IPI switches between categories. Call rates vary seasonally with all the tracks between August and April. From August to October tracks are dominated by the irregular IPI and are predominantly headed to the northwest, suggesting that a portion of the fin whale population does not migrate south in the fall. The other IPI categories occur primarily from November to March. These tracks have slower swimming speeds, tend to meander, and are predominantly to the south. The distribution of fin whales around the network is non-random with more calls near the network and to the east and north.

First results of registering ionospheric disturbances obtained with SibNet network of GNSS receivers in active space experiments

NASA Astrophysics Data System (ADS)

Ishin, Artem; Perevalova, Natalia; Voeykov, Sergey; Khakhinov, Vitaliy

2017-12-01

Global and regional networks of GNSS receivers have been successfully used for geophysical research for many years; the number of continuous GNSS stations in the world is steadily growing. The article presents the first results of the use of a new regional network of GNSS stations (SibNet) in active space experiments. The Institute of Solar-Terrestrial Physics of Siberian Branch of Russian Academy of Sciences (ISTP SB RAS) has established this network in the South Baikal region. We describe in detail SibNet, characteristics of receivers in use, parameters of antennas and methods of their installation. We also present the general structure of observation site and the plot of coverage of the receiver operating zone at 50-55° latitudes by radio paths. It is shown that the selected location of receivers allows us to detect ionospheric irregularities of various scales. The purpose of the active space experiments was to reveal and record parameters of the ionospheric irregu larities caused by effects from jet streams of Progress cargo spacecraft. The mapping technique enabled us to identify weak, vertically localized ionospheric irregularities and associate them with the Progress spacecraft engine impact. Thus, it has been shown that SibNet deployed in the Southern Baikal region is an effective instrument for monitoring ionospheric conditions.

DCS-Neural-Network Program for Aircraft Control and Testing

NASA Technical Reports Server (NTRS)

Jorgensen, Charles C.

2006-01-01

A computer program implements a dynamic-cell-structure (DCS) artificial neural network that can perform such tasks as learning selected aerodynamic characteristics of an airplane from wind-tunnel test data and computing real-time stability and control derivatives of the airplane for use in feedback linearized control. A DCS neural network is one of several types of neural networks that can incorporate additional nodes in order to rapidly learn increasingly complex relationships between inputs and outputs. In the DCS neural network implemented by the present program, the insertion of nodes is based on accumulated error. A competitive Hebbian learning rule (a supervised-learning rule in which connection weights are adjusted to minimize differences between actual and desired outputs for training examples) is used. A Kohonen-style learning rule (derived from a relatively simple training algorithm, implements a Delaunay triangulation layout of neurons) is used to adjust node positions during training. Neighborhood topology determines which nodes are used to estimate new values. The network learns, starting with two nodes, and adds new nodes sequentially in locations chosen to maximize reductions in global error. At any given time during learning, the error becomes homogeneously distributed over all nodes.

The Application of a Multiphase Triangulation Approach to Mixed Methods: The Research of an Aspiring School Principal Development Program

ERIC Educational Resources Information Center

Youngs, Howard; Piggot-Irvine, Eileen

2012-01-01

Mixed methods research has emerged as a credible alternative to unitary research approaches. The authors show how a combination of a triangulation convergence model with a triangulation multilevel model was used to research an aspiring school principal development pilot program. The multilevel model is used to show the national and regional levels…

An advancing front Delaunay triangulation algorithm designed for robustness

NASA Technical Reports Server (NTRS)

Mavriplis, D. J.

1992-01-01

A new algorithm is described for generating an unstructured mesh about an arbitrary two-dimensional configuration. Mesh points are generated automatically by the algorithm in a manner which ensures a smooth variation of elements, and the resulting triangulation constitutes the Delaunay triangulation of these points. The algorithm combines the mathematical elegance and efficiency of Delaunay triangulation algorithms with the desirable point placement features, boundary integrity, and robustness traditionally associated with advancing-front-type mesh generation strategies. The method offers increased robustness over previous algorithms in that it cannot fail regardless of the initial boundary point distribution and the prescribed cell size distribution throughout the flow-field.

Self-sustained asynchronous irregular states and Up-Down states in thalamic, cortical and thalamocortical networks of nonlinear integrate-and-fire neurons.

PubMed

Destexhe, Alain

2009-12-01

Randomly-connected networks of integrate-and-fire (IF) neurons are known to display asynchronous irregular (AI) activity states, which resemble the discharge activity recorded in the cerebral cortex of awake animals. However, it is not clear whether such activity states are specific to simple IF models, or if they also exist in networks where neurons are endowed with complex intrinsic properties similar to electrophysiological measurements. Here, we investigate the occurrence of AI states in networks of nonlinear IF neurons, such as the adaptive exponential IF (Brette-Gerstner-Izhikevich) model. This model can display intrinsic properties such as low-threshold spike (LTS), regular spiking (RS) or fast-spiking (FS). We successively investigate the oscillatory and AI dynamics of thalamic, cortical and thalamocortical networks using such models. AI states can be found in each case, sometimes with surprisingly small network size of the order of a few tens of neurons. We show that the presence of LTS neurons in cortex or in thalamus, explains the robust emergence of AI states for relatively small network sizes. Finally, we investigate the role of spike-frequency adaptation (SFA). In cortical networks with strong SFA in RS cells, the AI state is transient, but when SFA is reduced, AI states can be self-sustained for long times. In thalamocortical networks, AI states are found when the cortex is itself in an AI state, but with strong SFA, the thalamocortical network displays Up and Down state transitions, similar to intracellular recordings during slow-wave sleep or anesthesia. Self-sustained Up and Down states could also be generated by two-layer cortical networks with LTS cells. These models suggest that intrinsic properties such as adaptation and low-threshold bursting activity are crucial for the genesis and control of AI states in thalamocortical networks.

Tansig activation function (of MLP network) for cardiac abnormality detection

NASA Astrophysics Data System (ADS)

Adnan, Ja'afar; Daud, Nik Ghazali Nik; Ishak, Mohd Taufiq; Rizman, Zairi Ismael; Rahman, Muhammad Izzuddin Abd

2018-02-01

Heart abnormality often occurs regardless of gender, age and races. This problem sometimes does not show any symptoms and it can cause a sudden death to the patient. In general, heart abnormality is the irregular electrical activity of the heart. This paper attempts to develop a program that can detect heart abnormality activity through implementation of Multilayer Perceptron (MLP) network. A certain amount of data of the heartbeat signals from the electrocardiogram (ECG) will be used in this project to train the MLP network by using several training algorithms with Tansig activation function.

Constructing Precisely Computing Networks with Biophysical Spiking Neurons.

PubMed

Schwemmer, Michael A; Fairhall, Adrienne L; Denéve, Sophie; Shea-Brown, Eric T

2015-07-15

While spike timing has been shown to carry detailed stimulus information at the sensory periphery, its possible role in network computation is less clear. Most models of computation by neural networks are based on population firing rates. In equivalent spiking implementations, firing is assumed to be random such that averaging across populations of neurons recovers the rate-based approach. Recently, however, Denéve and colleagues have suggested that the spiking behavior of neurons may be fundamental to how neuronal networks compute, with precise spike timing determined by each neuron's contribution to producing the desired output (Boerlin and Denéve, 2011; Boerlin et al., 2013). By postulating that each neuron fires to reduce the error in the network's output, it was demonstrated that linear computations can be performed by networks of integrate-and-fire neurons that communicate through instantaneous synapses. This left open, however, the possibility that realistic networks, with conductance-based neurons with subthreshold nonlinearity and the slower timescales of biophysical synapses, may not fit into this framework. Here, we show how the spike-based approach can be extended to biophysically plausible networks. We then show that our network reproduces a number of key features of cortical networks including irregular and Poisson-like spike times and a tight balance between excitation and inhibition. Lastly, we discuss how the behavior of our model scales with network size or with the number of neurons "recorded" from a larger computing network. These results significantly increase the biological plausibility of the spike-based approach to network computation. We derive a network of neurons with standard spike-generating currents and synapses with realistic timescales that computes based upon the principle that the precise timing of each spike is important for the computation. We then show that our network reproduces a number of key features of cortical networks including irregular, Poisson-like spike times, and a tight balance between excitation and inhibition. These results significantly increase the biological plausibility of the spike-based approach to network computation, and uncover how several components of biological networks may work together to efficiently carry out computation. Copyright © 2015 the authors 0270-6474/15/3510112-23$15.00/0.

Image matching for digital close-range stereo photogrammetry based on constraints of Delaunay triangulated network and epipolar-line

NASA Astrophysics Data System (ADS)

Zhang, K.; Sheng, Y. H.; Li, Y. Q.; Han, B.; Liang, Ch.; Sha, W.

2006-10-01

In the field of digital photogrammetry and computer vision, the determination of conjugate points in a stereo image pair, referred to as "image matching," is the critical step to realize automatic surveying and recognition. Traditional matching methods encounter some problems in the digital close-range stereo photogrammetry, because the change of gray-scale or texture is not obvious in the close-range stereo images. The main shortcoming of traditional matching methods is that geometric information of matching points is not fully used, which will lead to wrong matching results in regions with poor texture. To fully use the geometry and gray-scale information, a new stereo image matching algorithm is proposed in this paper considering the characteristics of digital close-range photogrammetry. Compared with the traditional matching method, the new algorithm has three improvements on image matching. Firstly, shape factor, fuzzy maths and gray-scale projection are introduced into the design of synthetical matching measure. Secondly, the topology connecting relations of matching points in Delaunay triangulated network and epipolar-line are used to decide matching order and narrow the searching scope of conjugate point of the matching point. Lastly, the theory of parameter adjustment with constraint is introduced into least square image matching to carry out subpixel level matching under epipolar-line constraint. The new algorithm is applied to actual stereo images of a building taken by digital close-range photogrammetric system. The experimental result shows that the algorithm has a higher matching speed and matching accuracy than pyramid image matching algorithm based on gray-scale correlation.

Adapting a Planetary Science Observational Facility for Space Situational Awareness

NASA Astrophysics Data System (ADS)

Bland, P.; DFN Team

2016-09-01

The Desert Fireball Network (DFN) is designed to track meteoroids entering the atmosphere, determine pre-entry orbits (their origin in the solar system), and pinpoint fall positions for recovery by field teams. Fireball observatories are sited at remote dark-sky sites across Australia - logistics for power, sensor platforms, and data connection are in place. Each observatory is a fully autonomous unit, taking 36MP all-sky images (with fisheye lenses) throughout the night, capable of operating for 12 months in a harsh environment, and storing all imagery collected over that period. They are intelligent imaging systems, using neural network algorithms to recognize and report fireball events. An automated data reduction pipeline delivers orbital data and meteorite fall positions. Currently the DFN stands at 50 observing stations covering 2.5 million km2. A sub-set of the existing stations will be upgraded with a parallel camera package using 50mm prime lenses. Paired stations will allow triangulation. The high resolution array would deliver a Gpixel tiled image of the visible sky every 10 sec, at 20 arcsec resolution, with a limiting magnitude of 13 in a 10 sec snapshot. There are benefits in transient astronomy (optical flashes associated with gamma-ray bursts; flares from sources that generate ultra-high energy cosmic rays), and space situational awareness. The hardware upgrade would extend the resolution of the DFN into the V=11-12 magnitude range for objects in LEO, allowing us to observe significant activity during the terminator period. The result would be a wide field array, capable of triangulation, with a 3500km baseline enabling a larger terminator observing window.

Geomorphic Mapping and Paleoterrain Generation for use in Modeling Holocene (8,000 1,500 yr) Agropastoral Landuse and Landscape Interactions in Southeast Spain

NASA Astrophysics Data System (ADS)

Arrowsmith, J. R.; Dimaggio, E. N.; Barton, C. M.; Sarjoughian, H. S.; Fall, P.; Falconer, S. E.; Ullah, I. I.

2006-12-01

Dramatic changes in land use were associated with the rise of agriculture in the mid Holocene. Both the surface properties and the drainage networks were changed. Along with the direct modifications to surface properties (vegetation change, sediment liberation, and compaction) and drainage network alteration (terracing, canals), up and downstream responses in the watersheds communicated these changes throughout the landscape. The magnitude, rate, and feedbacks with the growing human populations are critical questions in our effort to assess human-landscape interactions. Our interdisciplinary team has focused on two field sites around the Mediterranean for model development and testing. We are combining high resolution process- based models of landscape change implemented within the GRASS GIS with agent based models of agropastoral behavior and driven by high resolution climate and vegetation models. In the Spanish field area (Penaguila Valley, 38.41 N 0.23 W), we have produced detailed (1:10,000) geomorphic maps which we combine with high resolution Digital Elevation Models (DEMs) on which we can run the surface process models to assess the portions of the landscape that are most sensitive to the postulated agropastoral landuse changes. To support this modeling we have produced the 1 m DEMs from softcopy photogrammetry. This DEM has greatly improved our overall spatial resolution to permit more accurate terrace correlations and improved quantitative assessment of morphologic processes (e.g. channel erosion, slope stability). In stereo, we have mapped overall landscape morphology that emphasizes areas of active erosion and alluvial terrace surfaces. Alluvial terraces are crucial to this research because they record periods of past stable topography and those of mid Holocene age were settled and farmed. We have correlated mapped terraces across the landscape using elevation and morphological distinctions. Using ArcGIS, we interpolated surfaces across equivalent terraces using triangulated irregular networks (TINs) allowing reconstruction of multiple regional landscapes to establish a chronosequence of absolute landscape change. This mapping and reconstruction will be field checked and numerical age constraints applied. Interestingly, our tentative age assessment of the lowest broad surface indicates that it was occupied about 5 ka, and now has been incised by 20 m. Archeological sites have been cut by the incision. This change from a broad low relief alluvial surface to one cut by narrow channels may have been an important change for the local populations and caused them to change their behaviors, even though it may have been initially triggered by distributed landscape change in the watershed, due to agropastoral activities.

Changes in functional connectivity within the fronto-temporal brain network induced by regular and irregular Russian verb production

PubMed Central

Kireev, Maxim; Slioussar, Natalia; Korotkov, Alexander D.; Chernigovskaya, Tatiana V.; Medvedev, Svyatoslav V.

2015-01-01

Functional connectivity between brain areas involved in the processing of complex language forms remains largely unexplored. Contributing to the debate about neural mechanisms underlying regular and irregular inflectional morphology processing in the mental lexicon, we conducted an fMRI experiment in which participants generated forms from different types of Russian verbs and nouns as well as from nonce stimuli. The data were subjected to a whole brain voxel-wise analysis of context dependent changes in functional connectivity [the so-called psychophysiological interaction (PPI) analysis]. Unlike previously reported subtractive results that reveal functional segregation between brain areas, PPI provides complementary information showing how these areas are functionally integrated in a particular task. To date, PPI evidence on inflectional morphology has been scarce and only available for inflectionally impoverished English verbs in a same-different judgment task. Using PPI here in conjunction with a production task in an inflectionally rich language, we found that functional connectivity between the left inferior frontal gyrus (LIFG) and bilateral superior temporal gyri (STG) was significantly greater for regular real verbs than for irregular ones. Furthermore, we observed a significant positive covariance between the number of mistakes in irregular real verb trials and the increase in functional connectivity between the LIFG and the right anterior cingulate cortex in these trails, as compared to regular ones. Our results therefore allow for dissociation between regularity and processing difficulty effects. These results, on the one hand, shed new light on the functional interplay within the LIFG-bilateral STG language-related network and, on the other hand, call for partial reconsideration of some of the previous findings while stressing the role of functional temporo-frontal connectivity in complex morphological processes. PMID:25741262

Disturbance dynamo effects over low-latitude F region: A study by network of VHF spaced receivers

NASA Astrophysics Data System (ADS)

Kakad, B.; Surve, G.; Tiwari, P.; Yadav, V.; Bhattacharyya, A.

2017-05-01

Generation of equatorial spread F (ESF) irregularities resulting from magnetic disturbance is known for past few decades. However, better prediction models for this phenomenon are still lacking. Magnetic storms also affects the F region plasma drifts. In this work we examined variability in (i) occurrence of such freshly generated ESF and (ii) low-latitude F region zonal plasma drifts over Indian longitude. For this purpose simultaneous observations of amplitude scintillations on 251 MHz signal, recorded by a network of spaced receivers located at low-latitude stations, are utilized. Observational stations are situated such that it longitudinally (latitudinally) covers an area of 5.6° (13°). Here effect of disturbance dynamo (DD) electric field at low-latitude F region and its variability are studied for three magnetic storms occurring in 2011. These magnetic storms are having nearly similar type characteristics except their start time. We find that as time difference (i.e., ΔT) between local sunset and start of magnetic activity decreases, the DD effects seen at low-latitude F region zonal irregularity drift around midnight becomes stronger. For a given magnetic storm the DD effect on F region zonal irregularity drifts is found to be only marginally stronger at dip equator in comparison to off-equatorial stations. Although effect of DD on F region zonal irregularity drifts are felt simultaneously, generation of fresh ESF is variable within a smaller longitudinal belt of 5.6°. It is attributed to the presence of LSWS at the bottomside of F region, as initiation of ESF is highly likely (unlikely) in the vicinity of crest (trough) of such LSWS.

Scaling Irregular Applications through Data Aggregation and Software Multithreading

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morari, Alessandro; Tumeo, Antonino; Chavarría-Miranda, Daniel

Bioinformatics, data analytics, semantic databases, knowledge discovery are emerging high performance application areas that exploit dynamic, linked data structures such as graphs, unbalanced trees or unstructured grids. These data structures usually are very large, requiring significantly more memory than available on single shared memory systems. Additionally, these data structures are difficult to partition on distributed memory systems. They also present poor spatial and temporal locality, thus generating unpredictable memory and network accesses. The Partitioned Global Address Space (PGAS) programming model seems suitable for these applications, because it allows using a shared memory abstraction across distributed-memory clusters. However, current PGAS languagesmore » and libraries are built to target regular remote data accesses and block transfers. Furthermore, they usually rely on the Single Program Multiple Data (SPMD) parallel control model, which is not well suited to the fine grained, dynamic and unbalanced parallelism of irregular applications. In this paper we present {\\bf GMT} (Global Memory and Threading library), a custom runtime library that enables efficient execution of irregular applications on commodity clusters. GMT integrates a PGAS data substrate with simple fork/join parallelism and provides automatic load balancing on a per node basis. It implements multi-level aggregation and lightweight multithreading to maximize memory and network bandwidth with fine-grained data accesses and tolerate long data access latencies. A key innovation in the GMT runtime is its thread specialization (workers, helpers and communication threads) that realize the overall functionality. We compare our approach with other PGAS models, such as UPC running using GASNet, and hand-optimized MPI code on a set of typical large-scale irregular applications, demonstrating speedups of an order of magnitude.« less

Aerial multi-camera systems: Accuracy and block triangulation issues

NASA Astrophysics Data System (ADS)

Rupnik, Ewelina; Nex, Francesco; Toschi, Isabella; Remondino, Fabio

2015-03-01

Oblique photography has reached its maturity and has now been adopted for several applications. The number and variety of multi-camera oblique platforms available on the market is continuously growing. So far, few attempts have been made to study the influence of the additional cameras on the behaviour of the image block and comprehensive revisions to existing flight patterns are yet to be formulated. This paper looks into the precision and accuracy of 3D points triangulated from diverse multi-camera oblique platforms. Its coverage is divided into simulated and real case studies. Within the simulations, different imaging platform parameters and flight patterns are varied, reflecting both current market offerings and common flight practices. Attention is paid to the aspect of completeness in terms of dense matching algorithms and 3D city modelling - the most promising application of such systems. The experimental part demonstrates the behaviour of two oblique imaging platforms in real-world conditions. A number of Ground Control Point (GCP) configurations are adopted in order to point out the sensitivity of tested imaging networks and arising block deformations. To stress the contribution of slanted views, all scenarios are compared against a scenario in which exclusively nadir images are used for evaluation.

Complete graph model for community detection

NASA Astrophysics Data System (ADS)

Sun, Peng Gang; Sun, Xiya

2017-04-01

Community detection brings plenty of considerable problems, which has attracted more attention for many years. This paper develops a new framework, which tries to measure the interior and the exterior of a community based on a same metric, complete graph model. In particular, the exterior is modeled as a complete bipartite. We partition a network into subnetworks by maximizing the difference between the interior and the exterior of the subnetworks. In addition, we compare our approach with some state of the art methods on computer-generated networks based on the LFR benchmark as well as real-world networks. The experimental results indicate that our approach obtains better results for community detection, is capable of splitting irregular networks and achieves perfect results on the karate network and the dolphin network.

dfnWorks: A discrete fracture network framework for modeling subsurface flow and transport

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hyman, Jeffrey D.; Karra, Satish; Makedonska, Nataliia

DFNWORKS is a parallelized computational suite to generate three-dimensional discrete fracture networks (DFN) and simulate flow and transport. Developed at Los Alamos National Laboratory over the past five years, it has been used to study flow and transport in fractured media at scales ranging from millimeters to kilometers. The networks are created and meshed using DFNGEN, which combines FRAM (the feature rejection algorithm for meshing) methodology to stochastically generate three-dimensional DFNs with the LaGriT meshing toolbox to create a high-quality computational mesh representation. The representation produces a conforming Delaunay triangulation suitable for high performance computing finite volume solvers in anmore » intrinsically parallel fashion. Flow through the network is simulated in dfnFlow, which utilizes the massively parallel subsurface flow and reactive transport finite volume code PFLOTRAN. A Lagrangian approach to simulating transport through the DFN is adopted within DFNTRANS to determine pathlines and solute transport through the DFN. Example applications of this suite in the areas of nuclear waste repository science, hydraulic fracturing and CO 2 sequestration are also included.« less

dfnWorks: A discrete fracture network framework for modeling subsurface flow and transport

DOE PAGES

Hyman, Jeffrey D.; Karra, Satish; Makedonska, Nataliia; ...

2015-11-01

DFNWORKS is a parallelized computational suite to generate three-dimensional discrete fracture networks (DFN) and simulate flow and transport. Developed at Los Alamos National Laboratory over the past five years, it has been used to study flow and transport in fractured media at scales ranging from millimeters to kilometers. The networks are created and meshed using DFNGEN, which combines FRAM (the feature rejection algorithm for meshing) methodology to stochastically generate three-dimensional DFNs with the LaGriT meshing toolbox to create a high-quality computational mesh representation. The representation produces a conforming Delaunay triangulation suitable for high performance computing finite volume solvers in anmore » intrinsically parallel fashion. Flow through the network is simulated in dfnFlow, which utilizes the massively parallel subsurface flow and reactive transport finite volume code PFLOTRAN. A Lagrangian approach to simulating transport through the DFN is adopted within DFNTRANS to determine pathlines and solute transport through the DFN. Example applications of this suite in the areas of nuclear waste repository science, hydraulic fracturing and CO 2 sequestration are also included.« less

Conditional bistability, a generic cellular mnemonic mechanism for robust and flexible working memory computations.

PubMed

Rodriguez, Guillaume; Sarazin, Matthieu; Clemente, Alexandra; Holden, Stephanie; Paz, Jeanne T; Delord, Bruno

2018-04-30

Persistent neural activity, the substrate of working memory, is thought to emerge from synaptic reverberation within recurrent networks. However, reverberation models do not robustly explain fundamental dynamics of persistent activity, including high-spiking irregularity, large intertrial variability, and state transitions. While cellular bistability may contribute to persistent activity, its rigidity appears incompatible with persistent activity labile characteristics. Here, we unravel in a cellular model a form of spike-mediated conditional bistability that is robust, generic and provides a rich repertoire of mnemonic computations. Under asynchronous synaptic inputs of the awakened state, conditional bistability generates spiking/bursting episodes, accounting for the irregularity, variability and state transitions characterizing persistent activity. This mechanism has likely been overlooked because of the sub-threshold input it requires and we predict how to assess it experimentally. Our results suggest a reexamination of the role of intrinsic properties in the collective network dynamics responsible for flexible working memory. SIGNIFICANCE STATEMENT This study unravels a novel form of intrinsic neuronal property, i.e. conditional bistability. We show that, thanks of its conditional character, conditional bistability favors the emergence of flexible and robust forms of persistent activity in PFC neural networks, in opposition to previously studied classical forms of absolute bistability. Specifically, we demonstrate for the first time that conditional bistability 1) is a generic biophysical spike-dependent mechanism of layer V pyramidal neurons in the PFC and that 2) it accounts for essential neurodynamical features for the organisation and flexibility of PFC persistent activity (the large irregularity and intertrial variability of the discharge and its organization under discrete stable states), which remain unexplained in a robust fashion by current models. Copyright © 2018 the authors.

Detection on vehicle vibration induced by the engine shaking based on the laser triangulation

NASA Astrophysics Data System (ADS)

Chen, Wenxue; Yang, Biwu; Ni, Zhibin; Hu, Xinhan; Han, Tieqiang; Hu, Yaocheng; Zhang, Wu; Wang, Yunfeng

2017-10-01

The magnitude of engine shaking is chosen to evaluate the vehicle performance. The engine shaking is evaluated by the vehicle vibration. Based on the laser triangulation, the vehicle vibration is measured by detecting the distance variation between the bodywork and road surface. The results represent the magnitude of engine shaking. The principle and configuration of the laser triangulation is also introduced in this paper.

Yet another method for triangulation and contouring for automated cartography

NASA Technical Reports Server (NTRS)

De Floriani, L.; Falcidieno, B.; Nasy, G.; Pienovi, C.

1982-01-01

An algorithm is presented for hierarchical subdivision of a set of three-dimensional surface observations. The data structure used for obtaining the desired triangulation is also singularly appropriate for extracting contours. Some examples are presented, and the results obtained are compared with those given by Delaunay triangulation. The data points selected by the algorithm provide a better approximation to the desired surface than do randomly selected points.

On triangulations of the plane by pencils of conics. II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lazareva, V B; Shelekhov, A M

2013-06-30

The present work continues our previous paper in which all possible triangulations of the plane using three pencils of circles were listed. In the present article we find all projectively distinct triangulations of the plane by pencils of conics that are obtained by projecting regular three-webs, cut out on a nondegenerate cubic surface by three pencils of planes, whose axes lie on this surface. Bibliography: 6 titles.

Characteristics of community savings groups in rural Eastern Uganda: opportunities for improving access to maternal health services.

PubMed

Mutebi, Aloysius; Muhumuza Kananura, Rornald; Ekirapa-Kiracho, Elizabeth; Bua, John; Namusoke Kiwanuka, Suzanne; Nammazi, Getrude; Paina, Ligia; Tetui, Moses

2017-08-01

Rural populations in Uganda have limited access to formal financial Institutions, but a growing majority belong to saving groups. These saving groups could have the potential to improve household income and access to health services. To understand organizational characteristics, benefits and challenges, of savings groups in rural Uganda. This was a cross-sectional descriptive study that employed both quantitative and qualitative data collection techniques. Data on the characteristics of community-based savings groups (CBSGs) were collected from 247 CBSG leaders in the districts of Kamuli, Kibukuand Pallisa using self-administered open-ended questionnaires. To triangulate the findings, we conducted in-depth interviews with seven CBSG leaders. Descriptive quantitative and content analysis for qualitative data was undertaken respectively. Almost a quarter of the savings groups had 5-14 members and slightly more than half of the saving groups had 15-30 members. Ninety-three percent of the CBSGs indicated electing their management committees democratically to select the group leaders and held meetings at least once a week. Eighty-nine percent of the CBSGs had used metallic boxes to keep their money, while 10% of the CBSGs kept their money using mobile money and banks,respectively. The main reasons for the formation of CBSGs were to increase household income, developing the community and saving for emergencies. The most common challenges associated with CBSG management included high illiteracy (35%) among the leaders,irregular attendance of meetings (22%), and lack of training on management and leadership(19%). The qualitative findings agreed with the quantitative findings and served to triangulate the main results. Saving groups in Uganda have the basic required structures; however, challenges exist in relation to training and management of the groups and their assets. The government and development partners should work together to provide technical support to the groups.

Characteristics of community savings groups in rural Eastern Uganda: opportunities for improving access to maternal health services

PubMed Central

Mutebi, Aloysius; Muhumuza Kananura, Rornald; Ekirapa-Kiracho, Elizabeth; Bua, John; Namusoke Kiwanuka, Suzanne; Nammazi, Gertrude; Paina, Ligia; Tetui, Moses

2017-01-01

ABSTRACT Background: Rural populations in Uganda have limited access to formal financial Institutions, but a growing majority belong to saving groups. These saving groups could have the potential to improve household income and access to health services. Objective: To understand organizational characteristics, benefits and challenges, of savings groups in rural Uganda. Methods: This was a cross-sectional descriptive study that employed both quantitative and qualitative data collection techniques. Data on the characteristics of community-based savings groups (CBSGs) were collected from 247 CBSG leaders in the districts of Kamuli, Kibukuand Pallisa using self-administered open-ended questionnaires. To triangulate the findings, we conducted in-depth interviews with seven CBSG leaders. Descriptive quantitative and content analysis for qualitative data was undertaken respectively. Results: Almost a quarter of the savings groups had 5–14 members and slightly more than half of the saving groups had 15–30 members. Ninety-three percent of the CBSGs indicated electing their management committees democratically to select the group leaders and held meetings at least once a week. Eighty-nine percent of the CBSGs had used metallic boxes to keep their money, while 10% of the CBSGs kept their money using mobile money and banks,respectively. The main reasons for the formation of CBSGs were to increase household income, developing the community and saving for emergencies. The most common challenges associated with CBSG management included high illiteracy (35%) among the leaders,irregular attendance of meetings (22%), and lack of training on management and leadership(19%). The qualitative findings agreed with the quantitative findings and served to triangulate the main results. Conclusions: Saving groups in Uganda have the basic required structures; however, challenges exist in relation to training and management of the groups and their assets. The government and development partners should work together to provide technical support to the groups. PMID:28856988

Optimization of deformation monitoring networks using finite element strain analysis

NASA Astrophysics Data System (ADS)

Alizadeh-Khameneh, M. Amin; Eshagh, Mehdi; Jensen, Anna B. O.

2018-04-01

An optimal design of a geodetic network can fulfill the requested precision and reliability of the network, and decrease the expenses of its execution by removing unnecessary observations. The role of an optimal design is highlighted in deformation monitoring network due to the repeatability of these networks. The core design problem is how to define precision and reliability criteria. This paper proposes a solution, where the precision criterion is defined based on the precision of deformation parameters, i. e. precision of strain and differential rotations. A strain analysis can be performed to obtain some information about the possible deformation of a deformable object. In this study, we split an area into a number of three-dimensional finite elements with the help of the Delaunay triangulation and performed the strain analysis on each element. According to the obtained precision of deformation parameters in each element, the precision criterion of displacement detection at each network point is then determined. The developed criterion is implemented to optimize the observations from the Global Positioning System (GPS) in Skåne monitoring network in Sweden. The network was established in 1989 and straddled the Tornquist zone, which is one of the most active faults in southern Sweden. The numerical results show that 17 out of all 21 possible GPS baseline observations are sufficient to detect minimum 3 mm displacement at each network point.

Accuracy analysis for triangulation and tracking based on time-multiplexed structured light.

PubMed

Wagner, Benjamin; Stüber, Patrick; Wissel, Tobias; Bruder, Ralf; Schweikard, Achim; Ernst, Floris

2014-08-01

The authors' research group is currently developing a new optical head tracking system for intracranial radiosurgery. This tracking system utilizes infrared laser light to measure features of the soft tissue on the patient's forehead. These features are intended to offer highly accurate registration with respect to the rigid skull structure by means of compensating for the soft tissue. In this context, the system also has to be able to quickly generate accurate reconstructions of the skin surface. For this purpose, the authors have developed a laser scanning device which uses time-multiplexed structured light to triangulate surface points. The accuracy of the authors' laser scanning device is analyzed and compared for different triangulation methods. These methods are given by the Linear-Eigen method and a nonlinear least squares method. Since Microsoft's Kinect camera represents an alternative for fast surface reconstruction, the authors' results are also compared to the triangulation accuracy of the Kinect device. Moreover, the authors' laser scanning device was used for tracking of a rigid object to determine how this process is influenced by the remaining triangulation errors. For this experiment, the scanning device was mounted to the end-effector of a robot to be able to calculate a ground truth for the tracking. The analysis of the triangulation accuracy of the authors' laser scanning device revealed a root mean square (RMS) error of 0.16 mm. In comparison, the analysis of the triangulation accuracy of the Kinect device revealed a RMS error of 0.89 mm. It turned out that the remaining triangulation errors only cause small inaccuracies for the tracking of a rigid object. Here, the tracking accuracy was given by a RMS translational error of 0.33 mm and a RMS rotational error of 0.12°. This paper shows that time-multiplexed structured light can be used to generate highly accurate reconstructions of surfaces. Furthermore, the reconstructed point sets can be used for high-accuracy tracking of objects, meeting the strict requirements of intracranial radiosurgery.

Networking among young global health researchers through an intensive training approach: a mixed methods exploratory study.

PubMed

Lenters, Lindsey M; Cole, Donald C; Godoy-Ruiz, Paula

2014-01-25

Networks are increasingly regarded as essential in health research aimed at influencing practice and policies. Less research has focused on the role networking can play in researchers' careers and its broader impacts on capacity strengthening in health research. We used the Canadian Coalition for Global Health Research (CCGHR) annual Summer Institute for New Global Health Researchers (SIs) as an opportunity to explore networking among new global health researchers. A mixed-methods exploratory study was conducted among SI alumni and facilitators who had participated in at least one SI between 2004 and 2010. Alumni and facilitators completed an online short questionnaire, and a subset participated in an in-depth interview. Thematic analysis of the qualitative data was triangulated with quantitative results and CCGHR reports on SIs. Synthesis occurred through the development of a process model relevant to networking through the SIs. Through networking at the SIs, participants experienced decreased isolation and strengthened working relationships. Participants accessed new knowledge, opportunities, and resources through networking during the SI. Post-SI, participants reported ongoing contact and collaboration, although most participants desired more opportunities for interaction. They made suggestions for structural supports to networking among new global health researchers. Networking at the SI contributed positively to opportunities for individuals, and contributed to the formation of a network of global health researchers. Intentional inclusion of networking in health research capacity strengthening initiatives, with supportive resources and infrastructure could create dynamic, sustainable networks accessible to global health researchers around the world.

The 1982 control network of Mars

NASA Technical Reports Server (NTRS)

Davies, M. E.; Katayama, F. Y.

1983-01-01

Attention is given to a planet-wide control network of Mars that was computed in September 1982 using a large single-block analytical triangulation with 47,524 measurements of 6853 control points on 1054 Mariner 9 and 757 Viking pictures. In all, 19,139 normal equations were solved, with a resulting standard error of measurement of 18.06 microns. The control points identified by name and letter designation are given, as are the aerographic coordinates of the control points. In addition, the coordinates of the Viking I lander site are given: latitude, 22.480 deg; longitude, 47.962 deg (radius, 3389.32 km). This study expands and updates the previously published network (1978). It is noted that the computation differs in many respects from standard aerial mapping photogrammetric practice. In comparison with aerial mapping photography, the television formats are small and the focal lengths are long; stereo coverage is rare, the scale of the pictures varies greatly, and the residual camera distortions are large.

Stimulus features underlying reduced tremor suppression with temporally patterned deep brain stimulation

PubMed Central

Birdno, Merrill J.; Kuncel, Alexis M.; Dorval, Alan D.; Turner, Dennis A.; Gross, Robert E.

2012-01-01

Deep brain stimulation (DBS) provides dramatic tremor relief when delivered at high-stimulation frequencies (more than ∼100 Hz), but its mechanisms of action are not well-understood. Previous studies indicate that high-frequency stimulation is less effective when the stimulation train is temporally irregular. The purpose of this study was to determine the specific characteristics of temporally irregular stimulus trains that reduce their effectiveness: long pauses, bursts, or irregularity per se. We isolated these characteristics in stimulus trains and conducted intraoperative measurements of postural tremor in eight volunteers. Tremor varied significantly across stimulus conditions (P < 0.015), and stimulus trains with pauses were significantly less effective than stimulus trains without (P < 0.002). There were no significant differences in tremor between trains with or without bursts or between trains that were irregular or periodic. Thus the decreased effectiveness of temporally irregular DBS trains is due to long pauses in the stimulus trains, not the degree of temporal irregularity alone. We also conducted computer simulations of neuronal responses to the experimental stimulus trains using a biophysical model of the thalamic network. Trains that suppressed tremor in volunteers also suppressed fluctuations in thalamic transmembrane potential at the frequency associated with cerebellar burst-driver inputs. Clinical and computational findings indicate that DBS suppresses tremor by masking burst-driver inputs to the thalamus and that pauses in stimulation prevent such masking. Although stimulation of other anatomic targets may provide tremor suppression, we propose that the most relevant neuronal targets for effective tremor suppression are the afferent cerebellar fibers that terminate in the thalamus. PMID:21994263

On the non-uniqueness of sediment yield

NASA Astrophysics Data System (ADS)

Kim, J.; Ivanov, V. Y.; Katopodes, N.

2012-12-01

Estimation of sediment yield at the catchment scale plays an important role for optimal design of hydraulic structures, such as bridges, culverts, reservoirs, and detention basins, as well as making informed decisions in environmental management. Many experimental studies focused on obtaining flow and sediment data in search of unique relationships between runoff (specifically, volume and peak) and sediment characteristics. These relationships were employed to predict sediment yield from flow information. However, despite the same flow volume, the actual sediment yield produced by river basins can vary significantly depending on several conditions: (i) the catchment size, (ii) land use, topography, and soil type, (iii) climatic variations or characteristics , and (iv) initial conditions of soil moisture and soil surface . Additionally, shield formation by relatively larger particles can be one of the possible controllers of erosion and net sediment transport. Smaller particles have low settling velocities and tend to move far from their original position of detachment. Conversely, larger particles can settle quickly near their original locations. Eventually, such particles can form a shield on soil bed and protect underlying soil from rainfall detachment and runoff entrainment. The shield formation and temporal development can be influenced by rainfall intensity, frequency, and volume. Rainfall influences the generation of runoff leading to different conditions of flow depth and velocity that can perturb intact soil into a loose condition. In this study, we numerically investigate the effects of precipitation patterns on the generation of sediment yield. In particular, we address reasons of non-uniqueness of basin sediment yield for the same runoff volume as well as causes of unsteady phenomena in erosion processes under steady state flow conditions. For numerical simulations, the two-dimensional Hairsine-Rose model coupled with a fully distributed hydrology and hydraulics model (tRIBS-OFM: Triangulated irregular network - based Real time Integrated Basin Simulator-Overland Flow Model) is used.

A probabilistic approach for shallow rainfall-triggered landslide modeling at basin scale. A case study in the Luquillo Forest, Puerto Rico

NASA Astrophysics Data System (ADS)

Dialynas, Y. G.; Arnone, E.; Noto, L. V.; Bras, R. L.

2013-12-01

Slope stability depends on geotechnical and hydrological factors that exhibit wide natural spatial variability, yet sufficient measurements of the related parameters are rarely available over entire study areas. The uncertainty associated with the inability to fully characterize hydrologic behavior has an impact on any attempt to model landslide hazards. This work suggests a way to systematically account for this uncertainty in coupled distributed hydrological-stability models for shallow landslide hazard assessment. A probabilistic approach for the prediction of rainfall-triggered landslide occurrence at basin scale was implemented in an existing distributed eco-hydrological and landslide model, tRIBS-VEGGIE -landslide (Triangulated Irregular Network (TIN)-based Real-time Integrated Basin Simulator - VEGetation Generator for Interactive Evolution). More precisely, we upgraded tRIBS-VEGGIE- landslide to assess the likelihood of shallow landslides by accounting for uncertainty related to geotechnical and hydrological factors that directly affect slope stability. Natural variability of geotechnical soil characteristics was considered by randomizing soil cohesion and friction angle. Hydrological uncertainty related to the estimation of matric suction was taken into account by considering soil retention parameters as correlated random variables. The probability of failure is estimated through an assumed theoretical Factor of Safety (FS) distribution, conditioned on soil moisture content. At each cell, the temporally variant FS statistics are approximated by the First Order Second Moment (FOSM) method, as a function of parameters statistical properties. The model was applied on the Rio Mameyes Basin, located in the Luquillo Experimental Forest in Puerto Rico, where previous landslide analyses have been carried out. At each time step, model outputs include the probability of landslide occurrence across the basin, and the most probable depth of failure at each soil column. The use of the proposed probabilistic approach for shallow landslide prediction is able to reveal and quantify landslide risk at slopes assessed as stable by simpler deterministic methods.

Hydrologic Drivers of Soil Organic Carbon Erosion and Burial: Insights from a Spatially-explicit Model of a Degraded Landscape at the Calhoun Critical Zone Observatory

NASA Astrophysics Data System (ADS)

Dialynas, Y. G.; Bras, R. L.; Richter, D. D., Jr.

2017-12-01

Soil erosion and burial of organic material may constitute a substantial sink of atmospheric CO2. Attempts to quantify impacts of soil erosion on the soil-atmosphere C exchange are limited by difficulties in accounting for the fate of eroded soil organic carbon (SOC), a key factor in estimating of the net effect of erosion on the C cycle. Processes that transport SOC are still inadequately represented in terrestrial carbon (C) cycle models. This study investigates hydrologic controls on SOC redistribution across the landscape focusing on dynamic feedbacks between watershed hydrology, soil erosional processes, and SOC burial. We use tRIBS-ECO (Triangulated Irregular Network-based Real-time Integrated Basin Simulator-Erosion and Carbon Oxidation), a spatially-explicit model of SOC dynamics coupled with a physically-based hydro-geomorphic model. tRIBS-ECO systematically accounts for the fate of eroded SOC across the watershed: Rainsplash erosion and sheet erosion redistribute SOC from upland sites to depositional environments, altering depth-dependent soil biogeochemical properties in diverse soil profiles. Eroded organic material is transferred with sediment and can be partially oxidized upon transport, or preserved from decomposition by burial. The model was applied in the Calhoun Critical Zone Observatory (CZO), a site that is recovering from some of the most serious agricultural erosion in North America. Soil biogeochemical characteristics at multiple soil horizons were used to initialize the model and test performance. Remotely sensed soil moisture data (NASA SMAP) were used for model calibration. Results show significant rates of hydrologically-induced burial of SOC at the Calhoun CZO. We find that organic material at upland eroding soil profiles is largely mobilized by rainsplash erosion. Sheet erosion mainly drives C transport in lower elevation clayey soils. While SOC erosion and deposition rates declined with recent reforestation at the study site, the erosional potential of the degraded landscape remains significant.

A Multi-Scale Integrated Approach to Representing Watershed Systems: Significance and Challenges

NASA Astrophysics Data System (ADS)

Kim, J.; Ivanov, V. Y.; Katopodes, N.

2013-12-01

A range of processes associated with supplying services and goods to human society originate at the watershed level. Predicting watershed response to forcing conditions has been of high interest to many practical societal problems, however, remains challenging due to two significant properties of the watershed systems, i.e., connectivity and non-linearity. Connectivity implies that disturbances arising at any larger scale will necessarily propagate and affect local-scale processes; their local effects consequently influence other processes, and often convey nonlinear relationships. Physically-based, process-scale modeling is needed to approach the understanding and proper assessment of non-linear effects between the watershed processes. We have developed an integrated model simulating hydrological processes, flow dynamics, erosion and sediment transport, tRIBS-OFM-HRM (Triangulated irregular network - based Real time Integrated Basin Simulator-Overland Flow Model-Hairsine and Rose Model). This coupled model offers the advantage of exploring the hydrological effects of watershed physical factors such as topography, vegetation, and soil, as well as their feedback mechanisms. Several examples investigating the effects of vegetation on flow movement, the role of soil's substrate on sediment dynamics, and the driving role of topography on morphological processes are illustrated. We show how this comprehensive modeling tool can help understand interconnections and nonlinearities of the physical system, e.g., how vegetation affects hydraulic resistance depending on slope, vegetation cover fraction, discharge, and bed roughness condition; how the soil's substrate condition impacts erosion processes with an non-unique characteristic at the scale of a zero-order catchment; and how topographic changes affect spatial variations of morphologic variables. Due to feedback and compensatory nature of mechanisms operating in different watershed compartments, our conclusion is that a key to representing watershed systems lies in an integrated, interdisciplinary approach, whereby a physically-based model is used for assessments/evaluations associated with future changes in landuse, climate, and ecosystems.

Rapid intraplate strain accumulation in the New Madrid seismic zone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, L.; Zoback, M.D.; Segall, P.

1992-09-01

Remeasurement of a triangulation network in the southern part of the New Madrid seismic zone with the Global Positioning System has revealed rapid crustal strain accumulation since the 1950s. This area experienced three large (moment magnitudes greater than 8) earthquakes in 1811 to 1812. The orientation and sense of shear is consistent with right-lateral strike slip motion along a northeast-trending fault zone (as indicated by current seismicity). Detection of crustal strain accumulation may be a useful discriminant for identifying areas where potentially damaging intraplate earthquakes may occur despite the absence of large earthquakes during historic time. 34 refs.

Optimal design approach for heating irregular-shaped objects in three-dimensional radiant furnaces using a hybrid genetic algorithm-artificial neural network method

NASA Astrophysics Data System (ADS)

Darvishvand, Leila; Kamkari, Babak; Kowsary, Farshad

2018-03-01

In this article, a new hybrid method based on the combination of the genetic algorithm (GA) and artificial neural network (ANN) is developed to optimize the design of three-dimensional (3-D) radiant furnaces. A 3-D irregular shape design body (DB) heated inside a 3-D radiant furnace is considered as a case study. The uniform thermal conditions on the DB surfaces are obtained by minimizing an objective function. An ANN is developed to predict the objective function value which is trained through the data produced by applying the Monte Carlo method. The trained ANN is used in conjunction with the GA to find the optimal design variables. The results show that the computational time using the GA-ANN approach is significantly less than that of the conventional method. It is concluded that the integration of the ANN with GA is an efficient technique for optimization of the radiant furnaces.

A Detailed Evaluation of a Laser Triangulation Ranging System for Mobile Robots

DTIC Science & Technology

1983-08-01

System Accuracy Factors ..................10 2.1.2 Detector "Cone of Vision" Problem ..................... 10 2. 1.3 Laser Triangulation Justification... product of these advances. Since 1968, when the effort began under a NASA grant, the project has undergone many changes both in the design goals and in...MD Vision System Accuracy Factors The accuracy of the data obtained by triangulation system depends on essentially three independent factors . They

Thickness and topographic inspection of RPG contact lenses by optical triangulation

NASA Astrophysics Data System (ADS)

Costa, Manuel F. M.

2001-06-01

Optical triangulation as a non-destructive test method extensively proved its usefulness on the dimensional and topographic inspection of a large range of objects and surfaces. In this communication the issue of microtopographic and thickness inspection of hard contact lenses (RPG) is addressed. The use of optical triangulation is discussed based on the results of the application of our MICROTOP.03.MFC microtopographer to this kind of tasks will be presented.

Potential benefits and harms of a peer support social network service on the internet for people with depressive tendencies: qualitative content analysis and social network analysis.

PubMed

Takahashi, Yoshimitsu; Uchida, Chiyoko; Miyaki, Koichi; Sakai, Michi; Shimbo, Takuro; Nakayama, Takeo

2009-07-23

Internet peer support groups for depression are becoming popular and could be affected by an increasing number of social network services (SNSs). However, little is known about participant characteristics, social relationships in SNSs, and the reasons for usage. In addition, the effects of SNS participation on people with depression are rather unknown. The aim was to explore the potential benefits and harms of an SNS for depression based on a concurrent triangulation design of mixed methods strategy, including qualitative content analysis and social network analysis. A cross-sectional Internet survey of participants, which involved the collection of SNS log files and a questionnaire, was conducted in an SNS for people with self-reported depressive tendencies in Japan in 2007. Quantitative data, which included user demographics, depressive state, and assessment of the SNS (positive vs not positive), were statistically analyzed. Descriptive contents of responses to open-ended questions concerning advantages and disadvantages of SNS participation were analyzed using the inductive approach of qualitative content analysis. Contents were organized into codes, concepts, categories, and a storyline based on the grounded theory approach. Social relationships, derived from data of "friends," were analyzed using social network analysis, in which network measures and the extent of interpersonal association were calculated based on the social network theory. Each analysis and integration of results were performed through a concurrent triangulation design of mixed methods strategy. There were 105 participants. Median age was 36 years, and 51% (36/71) were male. There were 37 valid respondents; their number of friends and frequency of accessing the SNS were significantly higher than for invalid/nonrespondents (P = .008 and P = .003). Among respondents, 90% (28/31) were mildly, moderately, or severely depressed. Assessment of the SNS was performed by determining the access frequency of the SNS and the number of friends. Qualitative content analysis indicated that user-selectable peer support could be passive, active, and/or interactive based on anonymity or ease of use, and there was the potential harm of a downward depressive spiral triggered by aggravated psychological burden. Social network analysis revealed that users communicated one-on-one with each other or in small groups (five people or less). A downward depressive spiral was related to friends who were moderately or severely depressed and friends with negative assessment of the SNS. An SNS for people with depressive tendencies provides various opportunities to obtain support that meets users' needs. To avoid a downward depressive spiral, we recommend that participants do not use SNSs when they feel that the SNS is not user-selectable, when they get egocentric comments, when friends have a negative assessment of the SNS, or when they have additional psychological burden.

Network-induced oscillatory behavior in material flow networks and irregular business cycles

NASA Astrophysics Data System (ADS)

Helbing, Dirk; Lämmer, Stefen; Witt, Ulrich; Brenner, Thomas

2004-11-01

Network theory is rapidly changing our understanding of complex systems, but the relevance of topological features for the dynamic behavior of metabolic networks, food webs, production systems, information networks, or cascade failures of power grids remains to be explored. Based on a simple model of supply networks, we offer an interpretation of instabilities and oscillations observed in biological, ecological, economic, and engineering systems. We find that most supply networks display damped oscillations, even when their units—and linear chains of these units—behave in a nonoscillatory way. Moreover, networks of damped oscillators tend to produce growing oscillations. This surprising behavior offers, for example, a different interpretation of business cycles and of oscillating or pulsating processes. The network structure of material flows itself turns out to be a source of instability, and cyclical variations are an inherent feature of decentralized adjustments.

Connectivity Restoration in Wireless Sensor Networks via Space Network Coding.

PubMed

Uwitonze, Alfred; Huang, Jiaqing; Ye, Yuanqing; Cheng, Wenqing

2017-04-20

The problem of finding the number and optimal positions of relay nodes for restoring the network connectivity in partitioned Wireless Sensor Networks (WSNs) is Non-deterministic Polynomial-time hard (NP-hard) and thus heuristic methods are preferred to solve it. This paper proposes a novel polynomial time heuristic algorithm, namely, Relay Placement using Space Network Coding (RPSNC), to solve this problem, where Space Network Coding, also called Space Information Flow (SIF), is a new research paradigm that studies network coding in Euclidean space, in which extra relay nodes can be introduced to reduce the cost of communication. Unlike contemporary schemes that are often based on Minimum Spanning Tree (MST), Euclidean Steiner Minimal Tree (ESMT) or a combination of MST with ESMT, RPSNC is a new min-cost multicast space network coding approach that combines Delaunay triangulation and non-uniform partitioning techniques for generating a number of candidate relay nodes, and then linear programming is applied for choosing the optimal relay nodes and computing their connection links with terminals. Subsequently, an equilibrium method is used to refine the locations of the optimal relay nodes, by moving them to balanced positions. RPSNC can adapt to any density distribution of relay nodes and terminals, as well as any density distribution of terminals. The performance and complexity of RPSNC are analyzed and its performance is validated through simulation experiments.

On the Use of CAD-Native Predicates and Geometry in Surface Meshing

NASA Technical Reports Server (NTRS)

Aftosmis, M. J.

1999-01-01

Several paradigms for accessing CAD geometry during surface meshing for CFD are discussed. File translation, inconsistent geometry engines and non-native point construction are all identified as sources of non-robustness. The paper argues in favor of accessing CAD parts and assemblies in their native format, without translation, and for the use of CAD-native predicates and constructors in surface mesh generation. The discussion also emphasizes the importance of examining the computational requirements for exact evaluation of triangulation predicates during surface meshing. The native approach is demonstrated through an algorithm for the generation of closed manifold surface triangulations from CAD geometry. CAD parts and assemblies are used in their native format, and a part's native geometry engine is accessed through a modeler-independent application programming interface (API). In seeking a robust and fully automated procedure, the algorithm is based on a new physical space manifold triangulation technique specially developed to avoid robustness issues associated with poorly conditioned mappings. In addition, this approach avoids the usual ambiguities associated with floating-point predicate evaluation on constructed coordinate geometry in a mapped space. The technique is incremental, so that each new site improves the triangulation by some well defined quality measure. The algorithm terminates after achieving a prespecified measure of mesh quality and produces a triangulation such that no angle is less than a given angle bound, a or greater than pi - 2alpha. This result also sets bounds on the maximum vertex degree, triangle aspect-ratio and maximum stretching rate for the triangulation. In addition to the output triangulations for a variety of CAD parts, the discussion presents related theoretical results which assert the existence of such an angle bound, and demonstrate that maximum bounds of between 25 deg and 30 deg may be achieved in practice.

A computational geometry approach to pore network construction for granular packings

NASA Astrophysics Data System (ADS)

van der Linden, Joost H.; Sufian, Adnan; Narsilio, Guillermo A.; Russell, Adrian R.; Tordesillas, Antoinette

2018-03-01

Pore network construction provides the ability to characterize and study the pore space of inhomogeneous and geometrically complex granular media in a range of scientific and engineering applications. Various approaches to the construction have been proposed, however subtle implementational details are frequently omitted, open access to source code is limited, and few studies compare multiple algorithms in the context of a specific application. This study presents, in detail, a new pore network construction algorithm, and provides a comprehensive comparison with two other, well-established Delaunay triangulation-based pore network construction methods. Source code is provided to encourage further development. The proposed algorithm avoids the expensive non-linear optimization procedure in existing Delaunay approaches, and is robust in the presence of polydispersity. Algorithms are compared in terms of structural, geometrical and advanced connectivity parameters, focusing on the application of fluid flow characteristics. Sensitivity of the various networks to permeability is assessed through network (Stokes) simulations and finite-element (Navier-Stokes) simulations. Results highlight strong dependencies of pore volume, pore connectivity, throat geometry and fluid conductance on the degree of tetrahedra merging and the specific characteristics of the throats targeted by the merging algorithm. The paper concludes with practical recommendations on the applicability of the three investigated algorithms.

Peer-to-peer model for the area coverage and cooperative control of mobile sensor networks

NASA Astrophysics Data System (ADS)

Tan, Jindong; Xi, Ning

2004-09-01

This paper presents a novel model and distributed algorithms for the cooperation and redeployment of mobile sensor networks. A mobile sensor network composes of a collection of wireless connected mobile robots equipped with a variety of sensors. In such a sensor network, each mobile node has sensing, computation, communication, and locomotion capabilities. The locomotion ability enhances the autonomous deployment of the system. The system can be rapidly deployed to hostile environment, inaccessible terrains or disaster relief operations. The mobile sensor network is essentially a cooperative multiple robot system. This paper first presents a peer-to-peer model to define the relationship between neighboring communicating robots. Delaunay Triangulation and Voronoi diagrams are used to define the geometrical relationship between sensor nodes. This distributed model allows formal analysis for the fusion of spatio-temporal sensory information of the network. Based on the distributed model, this paper discusses a fault tolerant algorithm for autonomous self-deployment of the mobile robots. The algorithm considers the environment constraints, the presence of obstacles and the nonholonomic constraints of the robots. The distributed algorithm enables the system to reconfigure itself such that the area covered by the system can be enlarged. Simulation results have shown the effectiveness of the distributed model and deployment algorithms.

Drifting States and Synchronization Induced Chaos in Autonomous Networks of Excitable Neurons.

PubMed

Echeveste, Rodrigo; Gros, Claudius

2016-01-01

The study of balanced networks of excitatory and inhibitory neurons has led to several open questions. On the one hand it is yet unclear whether the asynchronous state observed in the brain is autonomously generated, or if it results from the interplay between external drivings and internal dynamics. It is also not known, which kind of network variabilities will lead to irregular spiking and which to synchronous firing states. Here we show how isolated networks of purely excitatory neurons generically show asynchronous firing whenever a minimal level of structural variability is present together with a refractory period. Our autonomous networks are composed of excitable units, in the form of leaky integrators spiking only in response to driving currents, remaining otherwise quiet. For a non-uniform network, composed exclusively of excitatory neurons, we find a rich repertoire of self-induced dynamical states. We show in particular that asynchronous drifting states may be stabilized in purely excitatory networks whenever a refractory period is present. Other states found are either fully synchronized or mixed, containing both drifting and synchronized components. The individual neurons considered are excitable and hence do not dispose of intrinsic natural firing frequencies. An effective network-wide distribution of natural frequencies is however generated autonomously through self-consistent feedback loops. The asynchronous drifting state is, additionally, amenable to an analytic solution. We find two types of asynchronous activity, with the individual neurons spiking regularly in the pure drifting state, albeit with a continuous distribution of firing frequencies. The activity of the drifting component, however, becomes irregular in the mixed state, due to the periodic driving of the synchronized component. We propose a new tool for the study of chaos in spiking neural networks, which consists of an analysis of the time series of pairs of consecutive interspike intervals. In this space, we show that a strange attractor with a fractal dimension of about 1.8 is formed in the mentioned mixed state.

Drifting States and Synchronization Induced Chaos in Autonomous Networks of Excitable Neurons

PubMed Central

Echeveste, Rodrigo; Gros, Claudius

2016-01-01

The study of balanced networks of excitatory and inhibitory neurons has led to several open questions. On the one hand it is yet unclear whether the asynchronous state observed in the brain is autonomously generated, or if it results from the interplay between external drivings and internal dynamics. It is also not known, which kind of network variabilities will lead to irregular spiking and which to synchronous firing states. Here we show how isolated networks of purely excitatory neurons generically show asynchronous firing whenever a minimal level of structural variability is present together with a refractory period. Our autonomous networks are composed of excitable units, in the form of leaky integrators spiking only in response to driving currents, remaining otherwise quiet. For a non-uniform network, composed exclusively of excitatory neurons, we find a rich repertoire of self-induced dynamical states. We show in particular that asynchronous drifting states may be stabilized in purely excitatory networks whenever a refractory period is present. Other states found are either fully synchronized or mixed, containing both drifting and synchronized components. The individual neurons considered are excitable and hence do not dispose of intrinsic natural firing frequencies. An effective network-wide distribution of natural frequencies is however generated autonomously through self-consistent feedback loops. The asynchronous drifting state is, additionally, amenable to an analytic solution. We find two types of asynchronous activity, with the individual neurons spiking regularly in the pure drifting state, albeit with a continuous distribution of firing frequencies. The activity of the drifting component, however, becomes irregular in the mixed state, due to the periodic driving of the synchronized component. We propose a new tool for the study of chaos in spiking neural networks, which consists of an analysis of the time series of pairs of consecutive interspike intervals. In this space, we show that a strange attractor with a fractal dimension of about 1.8 is formed in the mentioned mixed state. PMID:27708572

Family processes that shape the impact of interparental conflict on adolescents.

PubMed

Grych, John H; Raynor, Sarah R; Fosco, Gregory M

2004-01-01

This study draws on the family systems concepts of triangulation and wholism to investigate how interparental conflict may affect adolescents' psychological adjustment. An ethnically and socioeconomically diverse sample (N = 388) of 14- to 18-year-olds completed measures of interparental conflict, family relationships, internalizing problems, and externalizing problems. We found that triangulation into parental disagreements mediated the association between parental conflict and both internalizing and externalizing problems. Adolescents exposed to more frequent, intense, and poorly resolved conflict were more likely to feel triangulated, but this association was moderated by the nature of the alliances they had with their parents. Specifically, at low levels of interparental conflict, adolescents who had substantially stronger alliances with one parent than the other reported greater triangulation than those with more balanced alliances. At high levels of conflict, these groups reported similar degrees of triangulation. We also found that supportive parent-child relationships reduced adolescents' appraisals of threat and self-blame for interparental conflict, while more empathic relationships with siblings increased these appraisals. Finally, close relationships with fathers acted as a protective factor that reduced symptoms of maladjustment.

Three-dimensional unstructured grid generation via incremental insertion and local optimization

NASA Technical Reports Server (NTRS)

Barth, Timothy J.; Wiltberger, N. Lyn; Gandhi, Amar S.

1992-01-01

Algorithms for the generation of 3D unstructured surface and volume grids are discussed. These algorithms are based on incremental insertion and local optimization. The present algorithms are very general and permit local grid optimization based on various measures of grid quality. This is very important; unlike the 2D Delaunay triangulation, the 3D Delaunay triangulation appears not to have a lexicographic characterization of angularity. (The Delaunay triangulation is known to minimize that maximum containment sphere, but unfortunately this is not true lexicographically). Consequently, Delaunay triangulations in three-space can result in poorly shaped tetrahedral elements. Using the present algorithms, 3D meshes can be constructed which optimize a certain angle measure, albeit locally. We also discuss the combinatorial aspects of the algorithm as well as implementational details.

Cardiac abnormality prediction using HMLP network

NASA Astrophysics Data System (ADS)

Adnan, Ja'afar; Ahmad, K. A.; Mat, Muhamad Hadzren; Rizman, Zairi Ismael; Ahmad, Shahril

2018-02-01

Cardiac abnormality often occurs regardless of gender, age and races but depends on the lifestyle. This problem sometimes does not show any symptoms and usually detected once it already critical which lead to a sudden death to the patient. Basically, cardiac abnormality is the irregular electrical signal that generate by the pacemaker of the heart. This paper attempts to develop a program that can detect cardiac abnormality activity through implementation of Hybrid Multilayer Perceptron (HMLP) network. A certain amount of data of the heartbeat signals from the electrocardiogram (ECG) will be used in this project to train the MLP and HMLP network by using Modified Recursive Prediction Error (MRPE) algorithm and to test the network performance.

Evaluation of statistical methods for quantifying fractal scaling in water-quality time series with irregular sampling

NASA Astrophysics Data System (ADS)

Zhang, Qian; Harman, Ciaran J.; Kirchner, James W.

2018-02-01

River water-quality time series often exhibit fractal scaling, which here refers to autocorrelation that decays as a power law over some range of scales. Fractal scaling presents challenges to the identification of deterministic trends because (1) fractal scaling has the potential to lead to false inference about the statistical significance of trends and (2) the abundance of irregularly spaced data in water-quality monitoring networks complicates efforts to quantify fractal scaling. Traditional methods for estimating fractal scaling - in the form of spectral slope (β) or other equivalent scaling parameters (e.g., Hurst exponent) - are generally inapplicable to irregularly sampled data. Here we consider two types of estimation approaches for irregularly sampled data and evaluate their performance using synthetic time series. These time series were generated such that (1) they exhibit a wide range of prescribed fractal scaling behaviors, ranging from white noise (β = 0) to Brown noise (β = 2) and (2) their sampling gap intervals mimic the sampling irregularity (as quantified by both the skewness and mean of gap-interval lengths) in real water-quality data. The results suggest that none of the existing methods fully account for the effects of sampling irregularity on β estimation. First, the results illustrate the danger of using interpolation for gap filling when examining autocorrelation, as the interpolation methods consistently underestimate or overestimate β under a wide range of prescribed β values and gap distributions. Second, the widely used Lomb-Scargle spectral method also consistently underestimates β. A previously published modified form, using only the lowest 5 % of the frequencies for spectral slope estimation, has very poor precision, although the overall bias is small. Third, a recent wavelet-based method, coupled with an aliasing filter, generally has the smallest bias and root-mean-squared error among all methods for a wide range of prescribed β values and gap distributions. The aliasing method, however, does not itself account for sampling irregularity, and this introduces some bias in the result. Nonetheless, the wavelet method is recommended for estimating β in irregular time series until improved methods are developed. Finally, all methods' performances depend strongly on the sampling irregularity, highlighting that the accuracy and precision of each method are data specific. Accurately quantifying the strength of fractal scaling in irregular water-quality time series remains an unresolved challenge for the hydrologic community and for other disciplines that must grapple with irregular sampling.

Measuring Ionospheric Irregularities Globally by the Rate of TEC Index and GNSS Networks

NASA Technical Reports Server (NTRS)

Pi, Xiaoqing

2012-01-01

Outline of presentation: Why do we use the rate of TEC index (ROTI) instead of the standard s4 and sigma-phi indices? What are the differences between S4, sigma-phi and ROTI? Examples of ROTI measurements and Development status and plan.

Very long transients, irregular firing, and chaotic dynamics in networks of randomly connected inhibitory integrate-and-fire neurons.

PubMed

Zillmer, Rüdiger; Brunel, Nicolas; Hansel, David

2009-03-01

We present results of an extensive numerical study of the dynamics of networks of integrate-and-fire neurons connected randomly through inhibitory interactions. We first consider delayed interactions with infinitely fast rise and decay. Depending on the parameters, the network displays transients which are short or exponentially long in the network size. At the end of these transients, the dynamics settle on a periodic attractor. If the number of connections per neuron is large ( approximately 1000) , this attractor is a cluster state with a short period. In contrast, if the number of connections per neuron is small ( approximately 100) , the attractor has complex dynamics and very long period. During the long transients the neurons fire in a highly irregular manner. They can be viewed as quasistationary states in which, depending on the coupling strength, the pattern of activity is asynchronous or displays population oscillations. In the first case, the average firing rates and the variability of the single-neuron activity are well described by a mean-field theory valid in the thermodynamic limit. Bifurcations of the long transient dynamics from asynchronous to synchronous activity are also well predicted by this theory. The transient dynamics display features reminiscent of stable chaos. In particular, despite being linearly stable, the trajectories of the transient dynamics are destabilized by finite perturbations as small as O(1/N) . We further show that stable chaos is also observed for postsynaptic currents with finite decay time. However, we report in this type of network that chaotic dynamics characterized by positive Lyapunov exponents can also be observed. We show in fact that chaos occurs when the decay time of the synaptic currents is long compared to the synaptic delay, provided that the network is sufficiently large.

Irregular employment amongst migrants in Spanish cities.

PubMed

Sole, C; Ribas, N; Bergalli, V; Parella, S

1998-04-01

This article presents the irregular employment situation of non-European union immigrants in Spanish cities. Foreign labor is remarkable for its heterogeneity in terms of country of origin, demographic characteristics, and the different ways in which immigrants have entered the job market. Legal immigrants tend to concentrate in five different branches of activity, such as domestic service (mostly women), hotel and restaurant industry, agriculture, building and retail trade. Migrants who work in agriculture suffer the worst labor conditions than all other migrants. However, all migrants experience difficulty in obtaining residency and labor permits. Four integration strategies among Moroccan immigrants in Catalonia are discussed and can be viewed as support networks of the immigrants.

Performance effects of irregular communications patterns on massively parallel multiprocessors

NASA Technical Reports Server (NTRS)

Saltz, Joel; Petiton, Serge; Berryman, Harry; Rifkin, Adam

1991-01-01

A detailed study of the performance effects of irregular communications patterns on the CM-2 was conducted. The communications capabilities of the CM-2 were characterized under a variety of controlled conditions. In the process of carrying out the performance evaluation, extensive use was made of a parameterized synthetic mesh. In addition, timings with unstructured meshes generated for aerodynamic codes and a set of sparse matrices with banded patterns on non-zeroes were performed. This benchmarking suite stresses the communications capabilities of the CM-2 in a range of different ways. Benchmark results demonstrate that it is possible to make effective use of much of the massive concurrency available in the communications network.

Analysis of the acoustic spectral signature of prosthetic heart valves in patients experiencing atrial fibrillation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scott, D.D.; Jones, H.E.

1994-05-06

Prosthetic heart valves have increased the life span of many patients with life threatening heart conditions. These valves have proven extremely reliable adding years to what would have been weeks to a patient`s life. Prosthetic valves, like the heart however, can suffer from this constant work load. A small number of valves have experienced structural fractures of the outlet strut due to fatigue. To study this problem a non-intrusive method to classify valves has been developed. By extracting from an acoustic signal the opening sounds which directly contain information from the outlet strut and then developing features which are suppliedmore » to an adaptive classification scheme (neural network) the condition of the valve can be determined. The opening sound extraction process has proved to be a classification problem itself. Due to the uniqueness of each heart and the occasional irregularity of the acoustic pattern it is often questionable as to the integrity of a given signal (beat), especially one occurring during an irregular beat pattern. A common cause of these irregular patterns is a condition known as atrial fibrillation, a prevalent arrhythmia among patients with prosthetic hear valves. Atrial fibrillation is suspected when the ECG shows no obvious P-waves. The atria do not contract and relax correctly to help contribute to ventricular filling during a normal cardiac cycle. Sometimes this leads to irregular patterns in the acoustic data. This study compares normal beat patterns to irregular patterns of the same heart. By analyzing the spectral content of the beats it can be determined whether or not these irregular patterns can contribute to the classification of a heart valve or if they should be avoided. The results have shown that the opening sounds which occur during irregular beat patterns contain the same spectral information as the opening which occur during a normal beat pattern of the same heart and these beats can be used for classification.« less

From time-series to complex networks: Application to the cerebrovascular flow patterns in atrial fibrillation

NASA Astrophysics Data System (ADS)

Scarsoglio, Stefania; Cazzato, Fabio; Ridolfi, Luca

2017-09-01

A network-based approach is presented to investigate the cerebrovascular flow patterns during atrial fibrillation (AF) with respect to normal sinus rhythm (NSR). AF, the most common cardiac arrhythmia with faster and irregular beating, has been recently and independently associated with the increased risk of dementia. However, the underlying hemodynamic mechanisms relating the two pathologies remain mainly undetermined so far; thus, the contribution of modeling and refined statistical tools is valuable. Pressure and flow rate temporal series in NSR and AF are here evaluated along representative cerebral sites (from carotid arteries to capillary brain circulation), exploiting reliable artificially built signals recently obtained from an in silico approach. The complex network analysis evidences, in a synthetic and original way, a dramatic signal variation towards the distal/capillary cerebral regions during AF, which has no counterpart in NSR conditions. At the large artery level, networks obtained from both AF and NSR hemodynamic signals exhibit elongated and chained features, which are typical of pseudo-periodic series. These aspects are almost completely lost towards the microcirculation during AF, where the networks are topologically more circular and present random-like characteristics. As a consequence, all the physiological phenomena at the microcerebral level ruled by periodicity—such as regular perfusion, mean pressure per beat, and average nutrient supply at the cellular level—can be strongly compromised, since the AF hemodynamic signals assume irregular behaviour and random-like features. Through a powerful approach which is complementary to the classical statistical tools, the present findings further strengthen the potential link between AF hemodynamic and cognitive decline.

Enhanced three-dimensional stochastic adjustment for combined volcano geodetic networks

NASA Astrophysics Data System (ADS)

Del Potro, R.; Muller, C.

2009-12-01

Volcano geodesy is unquestionably a necessary technique in studies of physical volcanology and for eruption early warning systems. However, as every volcano geodesist knows, obtaining measurements of the required resolution using traditional campaigns and techniques is time consuming and requires a large manpower. Moreover, most volcano geodetic networks worldwide use a combination of data from traditional techniques; levelling, electronic distance measurements (EDM), triangulation and Global Navigation Satellite Systems (GNSS) but, in most cases, these data are surveyed, analysed and adjusted independently. This then leaves it to the authors’ criteria to decide which technique renders the most realistic results in each case. Herein we present a way of solving the problem of inter-methodology data integration in a cost-effective manner following a methodology were all the geodetic data of a redundant, combined network (e.g. surveyed by GNSS, levelling, distance, angular data, INSAR, extensometers, etc.) is adjusted stochastically within a single three-dimensional referential frame. The adjustment methodology is based on the least mean square method and links the data with its geometrical component providing combined, precise, three-dimensional, displacement vectors, relative to external reference points as well as stochastically-quantified, benchmark-specific, uncertainty ellipsoids. Three steps in the adjustment allow identifying, and hence dismissing, flagrant measurement errors (antenna height, atmospheric effects, etc.), checking the consistency of external reference points and a final adjustment of the data. Moreover, since the statistical indicators can be obtained from expected uncertainties in the measurements of the different geodetic techniques used (i.e. independent of the measured data), it is possible to run a priori simulations of a geodetic network in order to constrain its resolution, and reduce logistics, before the network is even built. In this work we present a first effort to apply this technique to a new volcano geodetic network on Arenal volcano in Costa Rica, using triangulation, EDM and GNSS data from four campaigns. An a priori simulation, later confirmed by field measurements, of the movement detection capacity of different benchmarks within the network, shows how the network design is optimised to detect smaller displacement at the points where these are expected. Data from the four campaigns also proves the repeatability and consistency of the statistical indicators. A preliminary interpretation of the geodetic data relative to Arenal’s volcanic activity could indicate a correlation between displacement velocity and direction with the location and thickness of the recent lava flow field. This then suggests that a deflation caused by the weight of the lava field could be obscuring the effects of possible deep magmatic sources. Although this study is specific to Arenal volcano and its regional tectonic setting, we suggest that the cost-effective, high-quality results we present, prove the methodology’s potential to be incorporated into the design and analysis of volcano geodetic networks worldwide.

Networking among young global health researchers through an intensive training approach: a mixed methods exploratory study

PubMed Central

2014-01-01

Background Networks are increasingly regarded as essential in health research aimed at influencing practice and policies. Less research has focused on the role networking can play in researchers’ careers and its broader impacts on capacity strengthening in health research. We used the Canadian Coalition for Global Health Research (CCGHR) annual Summer Institute for New Global Health Researchers (SIs) as an opportunity to explore networking among new global health researchers. Methods A mixed-methods exploratory study was conducted among SI alumni and facilitators who had participated in at least one SI between 2004 and 2010. Alumni and facilitators completed an online short questionnaire, and a subset participated in an in-depth interview. Thematic analysis of the qualitative data was triangulated with quantitative results and CCGHR reports on SIs. Synthesis occurred through the development of a process model relevant to networking through the SIs. Results Through networking at the SIs, participants experienced decreased isolation and strengthened working relationships. Participants accessed new knowledge, opportunities, and resources through networking during the SI. Post-SI, participants reported ongoing contact and collaboration, although most participants desired more opportunities for interaction. They made suggestions for structural supports to networking among new global health researchers. Conclusions Networking at the SI contributed positively to opportunities for individuals, and contributed to the formation of a network of global health researchers. Intentional inclusion of networking in health research capacity strengthening initiatives, with supportive resources and infrastructure could create dynamic, sustainable networks accessible to global health researchers around the world. PMID:24460819

Interplay of intrinsic and synaptic conductances in the generation of high-frequency oscillations in interneuronal networks with irregular spiking.

PubMed

Baroni, Fabiano; Burkitt, Anthony N; Grayden, David B

2014-05-01

High-frequency oscillations (above 30 Hz) have been observed in sensory and higher-order brain areas, and are believed to constitute a general hallmark of functional neuronal activation. Fast inhibition in interneuronal networks has been suggested as a general mechanism for the generation of high-frequency oscillations. Certain classes of interneurons exhibit subthreshold oscillations, but the effect of this intrinsic neuronal property on the population rhythm is not completely understood. We study the influence of intrinsic damped subthreshold oscillations in the emergence of collective high-frequency oscillations, and elucidate the dynamical mechanisms that underlie this phenomenon. We simulate neuronal networks composed of either Integrate-and-Fire (IF) or Generalized Integrate-and-Fire (GIF) neurons. The IF model displays purely passive subthreshold dynamics, while the GIF model exhibits subthreshold damped oscillations. Individual neurons receive inhibitory synaptic currents mediated by spiking activity in their neighbors as well as noisy synaptic bombardment, and fire irregularly at a lower rate than population frequency. We identify three factors that affect the influence of single-neuron properties on synchronization mediated by inhibition: i) the firing rate response to the noisy background input, ii) the membrane potential distribution, and iii) the shape of Inhibitory Post-Synaptic Potentials (IPSPs). For hyperpolarizing inhibition, the GIF IPSP profile (factor iii)) exhibits post-inhibitory rebound, which induces a coherent spike-mediated depolarization across cells that greatly facilitates synchronous oscillations. This effect dominates the network dynamics, hence GIF networks display stronger oscillations than IF networks. However, the restorative current in the GIF neuron lowers firing rates and narrows the membrane potential distribution (factors i) and ii), respectively), which tend to decrease synchrony. If inhibition is shunting instead of hyperpolarizing, post-inhibitory rebound is not elicited and factors i) and ii) dominate, yielding lower synchrony in GIF networks than in IF networks.

Interplay of Intrinsic and Synaptic Conductances in the Generation of High-Frequency Oscillations in Interneuronal Networks with Irregular Spiking

PubMed Central

Baroni, Fabiano; Burkitt, Anthony N.; Grayden, David B.

2014-01-01

High-frequency oscillations (above 30 Hz) have been observed in sensory and higher-order brain areas, and are believed to constitute a general hallmark of functional neuronal activation. Fast inhibition in interneuronal networks has been suggested as a general mechanism for the generation of high-frequency oscillations. Certain classes of interneurons exhibit subthreshold oscillations, but the effect of this intrinsic neuronal property on the population rhythm is not completely understood. We study the influence of intrinsic damped subthreshold oscillations in the emergence of collective high-frequency oscillations, and elucidate the dynamical mechanisms that underlie this phenomenon. We simulate neuronal networks composed of either Integrate-and-Fire (IF) or Generalized Integrate-and-Fire (GIF) neurons. The IF model displays purely passive subthreshold dynamics, while the GIF model exhibits subthreshold damped oscillations. Individual neurons receive inhibitory synaptic currents mediated by spiking activity in their neighbors as well as noisy synaptic bombardment, and fire irregularly at a lower rate than population frequency. We identify three factors that affect the influence of single-neuron properties on synchronization mediated by inhibition: i) the firing rate response to the noisy background input, ii) the membrane potential distribution, and iii) the shape of Inhibitory Post-Synaptic Potentials (IPSPs). For hyperpolarizing inhibition, the GIF IPSP profile (factor iii)) exhibits post-inhibitory rebound, which induces a coherent spike-mediated depolarization across cells that greatly facilitates synchronous oscillations. This effect dominates the network dynamics, hence GIF networks display stronger oscillations than IF networks. However, the restorative current in the GIF neuron lowers firing rates and narrows the membrane potential distribution (factors i) and ii), respectively), which tend to decrease synchrony. If inhibition is shunting instead of hyperpolarizing, post-inhibitory rebound is not elicited and factors i) and ii) dominate, yielding lower synchrony in GIF networks than in IF networks. PMID:24784237

Bias Reduction and Filter Convergence for Long Range Stereo

NASA Technical Reports Server (NTRS)

Sibley, Gabe; Matthies, Larry; Sukhatme, Gaurav

2005-01-01

We are concerned here with improving long range stereo by filtering image sequences. Traditionally, measurement errors from stereo camera systems have been approximated as 3-D Gaussians, where the mean is derived by triangulation and the covariance by linearized error propagation. However, there are two problems that arise when filtering such 3-D measurements. First, stereo triangulation suffers from a range dependent statistical bias; when filtering this leads to over-estimating the true range. Second, filtering 3-D measurements derived via linearized error propagation leads to apparent filter divergence; the estimator is biased to under-estimate range. To address the first issue, we examine the statistical behavior of stereo triangulation and show how to remove the bias by series expansion. The solution to the second problem is to filter with image coordinates as measurements instead of triangulated 3-D coordinates.

Triangulation and the importance of establishing valid methods for food safety culture evaluation.

PubMed

Jespersen, Lone; Wallace, Carol A

2017-10-01

The research evaluates maturity of food safety culture in five multi-national food companies using method triangulation, specifically self-assessment scale, performance documents, and semi-structured interviews. Weaknesses associated with each individual method are known but there are few studies in food safety where a method triangulation approach is used for both data collection and data analysis. Significantly, this research shows that individual results taken in isolation can lead to wrong conclusions, resulting in potentially failing tactics and wasted investments. However, by applying method triangulation and reviewing results from a range of culture measurement tools it is possible to better direct investments and interventions. The findings add to the food safety culture paradigm beyond a single evaluation of food safety culture using generic culture surveys. Copyright © 2017. Published by Elsevier Ltd.

Branches of Triangulated Origami Near the Unfolded State

NASA Astrophysics Data System (ADS)

Chen, Bryan Gin-ge; Santangelo, Christian D.

2018-01-01

Origami structures are characterized by a network of folds and vertices joining unbendable plates. For applications to mechanical design and self-folding structures, it is essential to understand the interplay between the set of folds in the unfolded origami and the possible 3D folded configurations. When deforming a structure that has been folded, one can often linearize the geometric constraints, but the degeneracy of the unfolded state makes a linear approach impossible there. We derive a theory for the second-order infinitesimal rigidity of an initially unfolded triangulated origami structure and use it to study the set of nearly unfolded configurations of origami with four boundary vertices. We find that locally, this set consists of a number of distinct "branches" which intersect at the unfolded state, and that the number of these branches is exponential in the number of vertices. We find numerical and analytical evidence that suggests that the branches are characterized by choosing each internal vertex to either "pop up" or "pop down." The large number of pathways along which one can fold an initially unfolded origami structure strongly indicates that a generic structure is likely to become trapped in a "misfolded" state. Thus, new techniques for creating self-folding origami are likely necessary; controlling the popping state of the vertices may be one possibility.

LISN: A distributed observatory to image and study ionospheric irregularities

NASA Astrophysics Data System (ADS)

Sheehan, R.; Valladares, C. E.

2013-05-01

During nighttime the low-latitude ionosphere commonly develops plasma irregularities and density structures able to disrupt radio wave signals. This interference produces an adverse impact on satellite communication and navigation signals. For example, EM signals originated from satellites can suffer fading as deep as 20 dB even at UHF frequencies. In addition, civil aviation is increasingly dependent upon Global Navigation Satellite Systems and disruption of the navigation capability from ionospheric irregularities poses a clear threat to passengers and crews. To monitor and specify the conditions of the ionosphere over South America, the Low-latitude Ionospheric Sensor Network (LISN) was established as a permanent array of scientific instruments that operate continuously and transmit their observables to a central server in a real-time basis. Presently, the LISN observatory includes 3 different types of instruments: (1) 47 GPS receivers, (2) 5 flux-gate magnetometers and (3) 2 Vertical Incidence Pulsed Ionospheric Radar (VIPIR) ionosondes. In addition to providing a nowcast of the disturbed state of the ionosphere over South America, LISN permits detailed studies of the initiation and development of plasma irregularities. By using data assimilation and tomography techniques, LISN provides continuous estimates of several important geophysical parameters that are indispensable to a program aimed at forecasting the plasma electrodynamics and the formation of density structures in the low-latitude ionosphere.

Path integral measure and triangulation independence in discrete gravity

NASA Astrophysics Data System (ADS)

Dittrich, Bianca; Steinhaus, Sebastian

2012-02-01

A path integral measure for gravity should also preserve the fundamental symmetry of general relativity, which is diffeomorphism symmetry. In previous work, we argued that a successful implementation of this symmetry into discrete quantum gravity models would imply discretization independence. We therefore consider the requirement of triangulation independence for the measure in (linearized) Regge calculus, which is a discrete model for quantum gravity, appearing in the semi-classical limit of spin foam models. To this end we develop a technique to evaluate the linearized Regge action associated to Pachner moves in 3D and 4D and show that it has a simple, factorized structure. We succeed in finding a local measure for 3D (linearized) Regge calculus that leads to triangulation independence. This measure factor coincides with the asymptotics of the Ponzano Regge Model, a 3D spin foam model for gravity. We furthermore discuss to which extent one can find a triangulation independent measure for 4D Regge calculus and how such a measure would be related to a quantum model for 4D flat space. To this end, we also determine the dependence of classical Regge calculus on the choice of triangulation in 3D and 4D.

Development of high resolution target monitor.

DOT National Transportation Integrated Search

2008-01-01

The proposed High-resolution Target Movement Monitor uses triangulation theory but in a unique way. Unlike the commercially available triangulation systems which use sensing diodes to perceive reflected laser signatures and are limited to very short ...

Learning-based computing techniques in geoid modeling for precise height transformation

NASA Astrophysics Data System (ADS)

Erol, B.; Erol, S.

2013-03-01

Precise determination of local geoid is of particular importance for establishing height control in geodetic GNSS applications, since the classical leveling technique is too laborious. A geoid model can be accurately obtained employing properly distributed benchmarks having GNSS and leveling observations using an appropriate computing algorithm. Besides the classical multivariable polynomial regression equations (MPRE), this study attempts an evaluation of learning based computing algorithms: artificial neural networks (ANNs), adaptive network-based fuzzy inference system (ANFIS) and especially the wavelet neural networks (WNNs) approach in geoid surface approximation. These algorithms were developed parallel to advances in computer technologies and recently have been used for solving complex nonlinear problems of many applications. However, they are rather new in dealing with precise modeling problem of the Earth gravity field. In the scope of the study, these methods were applied to Istanbul GPS Triangulation Network data. The performances of the methods were assessed considering the validation results of the geoid models at the observation points. In conclusion the ANFIS and WNN revealed higher prediction accuracies compared to ANN and MPRE methods. Beside the prediction capabilities, these methods were also compared and discussed from the practical point of view in conclusions.

Distributed Memory Compiler Methods for Irregular Problems - Data Copy Reuse and Runtime Partitioning

DTIC Science & Technology

1991-09-01

addition, support for Saltz was provided by NSF from NSF Grant ASC-8819374. i 1, introduction Over the past fewyers, ,we have devoped -methods needed to... network . In Third Conf. on Hypercube Concurrent Computers and Applications, pages 241-27278, 1988. [17] G. Fox, S. Hiranandani, K. Kennedy, C. Koelbel

Seeing in three dimensions: correlation and triangulation of Mars Exploration Rover imagery

NASA Technical Reports Server (NTRS)

Deen, Robert; Lorre, Jean

2005-01-01

This paper describes in detail the middle parts of the ground-based terrain derivation process: correlation, which finds matching points in the stereo pair, and triangulation, which converts those points to XYZ coordinates.

Triangulation Error Analysis for the Barium Ion Cloud Experiment. M.S. Thesis - North Carolina State Univ.

NASA Technical Reports Server (NTRS)

Long, S. A. T.

1973-01-01

The triangulation method developed specifically for the Barium Ion Cloud Project is discussed. Expression for the four displacement errors, the three slope errors, and the curvature error in the triangulation solution due to a probable error in the lines-of-sight from the observation stations to points on the cloud are derived. The triangulation method is then used to determine the effect of the following on these different errors in the solution: the number and location of the stations, the observation duration, east-west cloud drift, the number of input data points, and the addition of extra cameras to one of the stations. The pointing displacement errors, and the pointing slope errors are compared. The displacement errors in the solution due to a probable error in the position of a moving station plus the weighting factors for the data from the moving station are also determined.

The Family System and Depressive Symptoms during the College Years: Triangulation, Parental Differential Treatment, and Sibling Warmth as Predictors.

PubMed

Ponappa, Sujata; Bartle-Haring, Suzanne; Holowacz, Eugene; Ferriby, Megan

2017-01-01

Guided by Bowen theory, we investigated the relationships between parent-child triangulation, parental differential treatment (PDT), sibling warmth, and individual depressive symptoms in a sample of 77 sibling dyads, aged 18-25 years, recruited through undergraduate classes at a U.S. public University. Results of the actor-partner interdependence models suggested that being triangulated into parental conflict was positively related to both siblings' perception of PDT; however, as one sibling felt triangulated, the other perceived reduced levels of PDT. For both siblings, the perception of higher levels of PDT was related to decreased sibling warmth and higher sibling warmth was associated with fewer depressive symptoms. The implications of these findings for research and the treatment of depression in the college-aged population are discussed. © 2016 American Association for Marriage and Family Therapy.

Numerical Schemes for the Hamilton-Jacobi and Level Set Equations on Triangulated Domains

NASA Technical Reports Server (NTRS)

Barth, Timothy J.; Sethian, James A.

1997-01-01

Borrowing from techniques developed for conservation law equations, numerical schemes which discretize the Hamilton-Jacobi (H-J), level set, and Eikonal equations on triangulated domains are presented. The first scheme is a provably monotone discretization for certain forms of the H-J equations. Unfortunately, the basic scheme lacks proper Lipschitz continuity of the numerical Hamiltonian. By employing a virtual edge flipping technique, Lipschitz continuity of the numerical flux is restored on acute triangulations. Next, schemes are introduced and developed based on the weaker concept of positive coefficient approximations for homogeneous Hamiltonians. These schemes possess a discrete maximum principle on arbitrary triangulations and naturally exhibit proper Lipschitz continuity of the numerical Hamiltonian. Finally, a class of Petrov-Galerkin approximations are considered. These schemes are stabilized via a least-squares bilinear form. The Petrov-Galerkin schemes do not possess a discrete maximum principle but generalize to high order accuracy.

Fast algorithms of constrained Delaunay triangulation and skeletonization for band images

NASA Astrophysics Data System (ADS)

Zeng, Wei; Yang, ChengLei; Meng, XiangXu; Yang, YiJun; Yang, XiuKun

2004-09-01

For the boundary polygons of band-images, a fast constrained Delaunay triangulation algorithm is presented and based on it an efficient skeletonization algorithm is designed. In the process of triangulation the characters of uniform grid structure and the band-polygons are utilized to improve the speed of computing the third vertex for one edge within its local ranges when forming a Delaunay triangle. The final skeleton of the band-image is derived after reducing each triangle to local skeleton lines according to its topology. The algorithm with a simple data structure is easy to understand and implement. Moreover, it can deal with multiply connected polygons on the fly. Experiments show that there is a nearly linear dependence between triangulation time and size of band-polygons randomly generated. Correspondingly, the skeletonization algorithm is also an improvement over the previously known results in terms of time. Some practical examples are given in the paper.

Grey signal processing and data reconstruction in the non-diffracting beam triangulation measurement system

NASA Astrophysics Data System (ADS)

Meng, Hao; Wang, Zhongyu; Fu, Jihua

2008-12-01

The non-diffracting beam triangulation measurement system possesses the advantages of longer measurement range, higher theoretical measurement accuracy and higher resolution over the traditional laser triangulation measurement system. Unfortunately the measurement accuracy of the system is greatly degraded due to the speckle noise, the CCD photoelectric noise and the background light noise in practical applications. Hence, some effective signal processing methods must be applied to improve the measurement accuracy. In this paper a novel effective method for removing the noises in the non-diffracting beam triangulation measurement system is proposed. In the method the grey system theory is used to process and reconstruct the measurement signal. Through implementing the grey dynamic filtering based on the dynamic GM(1,1), the noises can be effectively removed from the primary measurement data and the measurement accuracy of the system can be improved as a result.

Realist explanatory theory building method for social epidemiology: a protocol for a mixed method multilevel study of neighbourhood context and postnatal depression.

PubMed

Eastwood, John G; Jalaludin, Bin B; Kemp, Lynn A

2014-01-01

A recent criticism of social epidemiological studies, and multi-level studies in particular has been a paucity of theory. We will present here the protocol for a study that aims to build a theory of the social epidemiology of maternal depression. We use a critical realist approach which is trans-disciplinary, encompassing both quantitative and qualitative traditions, and that assumes both ontological and hierarchical stratification of reality. We describe a critical realist Explanatory Theory Building Method comprising of an: 1) emergent phase, 2) construction phase, and 3) confirmatory phase. A concurrent triangulated mixed method multilevel cross-sectional study design is described. The Emergent Phase uses: interviews, focus groups, exploratory data analysis, exploratory factor analysis, regression, and multilevel Bayesian spatial data analysis to detect and describe phenomena. Abductive and retroductive reasoning will be applied to: categorical principal component analysis, exploratory factor analysis, regression, coding of concepts and categories, constant comparative analysis, drawing of conceptual networks, and situational analysis to generate theoretical concepts. The Theory Construction Phase will include: 1) defining stratified levels; 2) analytic resolution; 3) abductive reasoning; 4) comparative analysis (triangulation); 5) retroduction; 6) postulate and proposition development; 7) comparison and assessment of theories; and 8) conceptual frameworks and model development. The strength of the critical realist methodology described is the extent to which this paradigm is able to support the epistemological, ontological, axiological, methodological and rhetorical positions of both quantitative and qualitative research in the field of social epidemiology. The extensive multilevel Bayesian studies, intensive qualitative studies, latent variable theory, abductive triangulation, and Inference to Best Explanation provide a strong foundation for Theory Construction. The study will contribute to defining the role that realism and mixed methods can play in explaining the social determinants and developmental origins of health and disease.

Feasibility of employing a smartphone as the payload in a photogrammetric UAV system

NASA Astrophysics Data System (ADS)

Kim, Jinsoo; Lee, Seongkyu; Ahn, Hoyong; Seo, Dongju; Park, Soyoung; Choi, Chuluong

2013-05-01

Smartphones can be operated in a 3G network environment at any time or location, and they also cost less than existing photogrammetric UAV systems, providing high-resolution images and 3D location and attitude data from a variety of built-in sensors. This study aims to assess the feasibility of using a smartphone as the payload for a photogrammetric UAV system. To carry out the assessment, a smartphone-based photogrammetric UAV system was developed and utilized to obtain image, location, and attitude data under both static and dynamic conditions. The accuracy of the location and attitude data obtained and sent by this system was then evaluated. The smartphone images were converted into ortho-images via image triangulation, which was carried out both with and without consideration of the interior orientation (IO) parameters determined by camera calibration. In the static experiment, when the IO parameters were taken into account, the triangulation results were less than 1.28 pixels (RMSE) for all smartphone types, an improvement of at least 47% compared with the case when IO parameters were not taken into account. In the dynamic experiment, on the other hand, the accuracy of smartphone image triangulation was not significantly improved by considering IO parameters. This was because the electronic rolling shutter within the complementary metal-oxide semiconductor (CMOS) sensor built into the smartphone and the actuator for the voice coil motor (VCM)-type auto-focusing affected by the vibration and the speed of the UAV, which is likely to have a negative effect on image-based digital elevation model (DEM) generation. However, considering that these results were obtained using a single smartphone, this suggests that a smartphone is not only feasible as the payload for a photogrammetric UAV system but it may also play a useful role when installed in existing UAV systems.

Networks for image acquisition, processing and display

NASA Technical Reports Server (NTRS)

Ahumada, Albert J., Jr.

1990-01-01

The human visual system comprises layers of networks which sample, process, and code images. Understanding these networks is a valuable means of understanding human vision and of designing autonomous vision systems based on network processing. Ames Research Center has an ongoing program to develop computational models of such networks. The models predict human performance in detection of targets and in discrimination of displayed information. In addition, the models are artificial vision systems sharing properties with biological vision that has been tuned by evolution for high performance. Properties include variable density sampling, noise immunity, multi-resolution coding, and fault-tolerance. The research stresses analysis of noise in visual networks, including sampling, photon, and processing unit noises. Specific accomplishments include: models of sampling array growth with variable density and irregularity comparable to that of the retinal cone mosaic; noise models of networks with signal-dependent and independent noise; models of network connection development for preserving spatial registration and interpolation; multi-resolution encoding models based on hexagonal arrays (HOP transform); and mathematical procedures for simplifying analysis of large networks.

Using GPS TEC measurements to probe ionospheric spatial spectra at mid-latitudes

NASA Astrophysics Data System (ADS)

Lay, E. H.; Parker, P. A.; Light, M. E.; Carrano, C. S.; Debchoudhury, S.; Haaser, R. A.

2017-12-01

The physics of how random ionospheric structure causes signal degradation is well understood as weak forward scattering through an effective diffraction grating created by plasma irregularities in the ionosphere. However, the spatial scale spectrum of those irregularities required for input into scintillation models and models of traveling ionospheric disturbances is poorly characterized, particularly at the kilometer to tens of kilometer scale lengths important for very-high-frequency (VHF) scintillation prediction. Furthermore, the majority of characterization studies have been performed in low-latitude or high-latitude regions where geomagnetic activity dominates the physical processes. At mid-latitudes, tropospheric and geomagnetic phenomena compete in disturbing the ionosphere, and it is not well understood how these multiple sources affect the drivers that influence the spatial spectrum. In this study, we are interested in mid-latitude electron density irregularities on the order of 10s of kilometers that would affect VHF signals. Data from the GPS networks Japan GEONET and the Plate Boundary Observatory (PBO, UNAVCO) in the western United States were analyzed for this study. Japan GEONET is a dense network of GPS receivers (station spacing of tens of km), with fairly evenly spaced positions over all of Japan. The PBO, on the other hand, has several pockets of extremely dense coverage (station spacing within a few km), but is less dense on average. We analyze a day with a large solar storm (2015/03/17, St. Patrick's Day Storm) to allow high scintillation potential at mid-latitudes, a day with low geomagnetic activity and low thunderstorm activity (2016/01/31), and a day with low geomagnetic activity and high thunderstorm activity (2015/08/02). We then perform two-dimensional spatial analyses on the TEC data from these two networks on scale lengths of 20 to 200 km to infer the spatial scale spectra.

Electrophysiological evidence of sublexical phonological access in character processing by L2 Chinese learners of L1 alphabetic scripts.

PubMed

Yum, Yen Na; Law, Sam-Po; Mo, Kwan Nok; Lau, Dustin; Su, I-Fan; Shum, Mark S K

2016-04-01

While Chinese character reading relies more on addressed phonology relative to alphabetic scripts, skilled Chinese readers also access sublexical phonological units during recognition of phonograms. However, sublexical orthography-to-phonology mapping has not been found among beginning second language (L2) Chinese learners. This study investigated character reading in more advanced Chinese learners whose native writing system is alphabetic. Phonological regularity and consistency were examined in behavioral responses and event-related potentials (ERPs) in lexical decision and delayed naming tasks. Participants were 18 native English speakers who acquired written Chinese after age 5 years and reached grade 4 Chinese reading level. Behaviorally, regular characters were named more accurately than irregular characters, but consistency had no effect. Similar to native Chinese readers, regularity effects emerged early with regular characters eliciting a greater N170 than irregular characters. Regular characters also elicited greater frontal P200 and smaller N400 than irregular characters in phonograms of low consistency. Additionally, regular-consistent characters and irregular-inconsistent characters had more negative amplitudes than irregular-consistent characters in the N400 and LPC time windows. The overall pattern of brain activities revealed distinct regularity and consistency effects in both tasks. Although orthographic neighbors are activated in character processing of L2 Chinese readers, the timing of their impact seems delayed compared with native Chinese readers. The time courses of regularity and consistency effects across ERP components suggest both assimilation and accommodation of the reading network in learning to read a typologically distinct second orthographic system.

Dynamic model of time-dependent complex networks.

PubMed

Hill, Scott A; Braha, Dan

2010-10-01

The characterization of the "most connected" nodes in static or slowly evolving complex networks has helped in understanding and predicting the behavior of social, biological, and technological networked systems, including their robustness against failures, vulnerability to deliberate attacks, and diffusion properties. However, recent empirical research of large dynamic networks (characterized by irregular connections that evolve rapidly) has demonstrated that there is little continuity in degree centrality of nodes over time, even when their degree distributions follow a power law. This unexpected dynamic centrality suggests that the connections in these systems are not driven by preferential attachment or other known mechanisms. We present an approach to explain real-world dynamic networks and qualitatively reproduce these dynamic centrality phenomena. This approach is based on a dynamic preferential attachment mechanism, which exhibits a sharp transition from a base pure random walk scheme.

Occultation and Triangulation Camera (OcTriCam) Cubesat

NASA Astrophysics Data System (ADS)

Batchelor, D. A.

2018-02-01

A camera at Earth-Moon L2 would provide a 240,000 km triangulation baseline to augment near-Earth object observations with Earth-based telescopes such as Pan-STARRS, and planetary occultation research to refine ephemerides and probe ring systems.

A tour about existence and uniqueness of dg enhancements and lifts

NASA Astrophysics Data System (ADS)

Canonaco, Alberto; Stellari, Paolo

2017-12-01

This paper surveys the recent advances concerning the relations between triangulated (or derived) categories and their dg enhancements. We explain when some interesting triangulated categories arising in algebraic geometry have a unique dg enhancement. This is the case, for example, for the unbounded derived category of quasi-coherent sheaves on an algebraic stack or for its full triangulated subcategory of perfect complexes. Moreover we give an account of the recent results about the possibility to lift exact functors between the bounded derived categories of coherent sheaves on smooth schemes to dg (quasi-)functors.

Numerical Schemes for the Hamilton-Jacobi and Level Set Equations on Triangulated Domains

NASA Technical Reports Server (NTRS)

Barth, Timothy J.; Sethian, James A.

2006-01-01

Borrowing from techniques developed for conservation law equations, we have developed both monotone and higher order accurate numerical schemes which discretize the Hamilton-Jacobi and level set equations on triangulated domains. The use of unstructured meshes containing triangles (2D) and tetrahedra (3D) easily accommodates mesh adaptation to resolve disparate level set feature scales with a minimal number of solution unknowns. The minisymposium talk will discuss these algorithmic developments and present sample calculations using our adaptive triangulation algorithm applied to various moving interface problems such as etching, deposition, and curvature flow.

Assessment of four midcarpal radiologic determinations.

PubMed

Cho, Mickey S; Battista, Vincent; Dubin, Norman H; Pirela-Cruz, Miguel

2006-03-01

Several radiologic measurement methods have been described for determining static carpal alignment of the wrist. These include the scapholunate, radiolunate, and capitolunate angles. The triangulation method is an alternative radiologic measurement which we believe is easier to use and more reproducible and reliable than the above mentioned methods. The purpose of this study is to assess the intraobserver reproducibility and interobserver reliability of the triangulation method, scapholunate, radiolunate, and capitolunate angles. Twenty orthopaedic residents and staff at varying levels of training made four radiologic measurements including the scapholunate, radiolunate and capitolunate angles as well as the triangulation method on five different lateral, digitized radiographs of the wrist and forearm in neutral radioulnar deviation. Thirty days after the initial measurements, the participants repeated the four radiologic measurements using the same radiographs. The triangulation method had the best intra-and-interobserver agreement of the four methods tested. This agreement was significantly better than the capitolunate and radiolunate angles. The scapholunate angle had the next best intraobserver reproducibility and interobserver reliability. The triangulation method has the best overall observer agreement when compared to the scapholunate, radiolunate, and capitolunate angles in determining static midcarpal alignment. No comment can be made on the validity of the measurements since there is no radiographic gold standard in determining static carpal alignment.

A neural-network-based model for the dynamic simulation of the tire/suspension system while traversing road irregularities.

PubMed

Guarneri, Paolo; Rocca, Gianpiero; Gobbi, Massimiliano

2008-09-01

This paper deals with the simulation of the tire/suspension dynamics by using recurrent neural networks (RNNs). RNNs are derived from the multilayer feedforward neural networks, by adding feedback connections between output and input layers. The optimal network architecture derives from a parametric analysis based on the optimal tradeoff between network accuracy and size. The neural network can be trained with experimental data obtained in the laboratory from simulated road profiles (cleats). The results obtained from the neural network demonstrate good agreement with the experimental results over a wide range of operation conditions. The NN model can be effectively applied as a part of vehicle system model to accurately predict elastic bushings and tire dynamics behavior. Although the neural network model, as a black-box model, does not provide a good insight of the physical behavior of the tire/suspension system, it is a useful tool for assessing vehicle ride and noise, vibration, harshness (NVH) performance due to its good computational efficiency and accuracy.

irGPU.proton.Net: Irregular strong charge interaction networks of protonatable groups in protein molecules--a GPU solver using the fast multipole method and statistical thermodynamics.

PubMed

Kantardjiev, Alexander A

2015-04-05

A cluster of strongly interacting ionization groups in protein molecules with irregular ionization behavior is suggestive for specific structure-function relationship. However, their computational treatment is unconventional (e.g., lack of convergence in naive self-consistent iterative algorithm). The stringent evaluation requires evaluation of Boltzmann averaged statistical mechanics sums and electrostatic energy estimation for each microstate. irGPU: Irregular strong interactions in proteins--a GPU solver is novel solution to a versatile problem in protein biophysics--atypical protonation behavior of coupled groups. The computational severity of the problem is alleviated by parallelization (via GPU kernels) which is applied for the electrostatic interaction evaluation (including explicit electrostatics via the fast multipole method) as well as statistical mechanics sums (partition function) estimation. Special attention is given to the ease of the service and encapsulation of theoretical details without sacrificing rigor of computational procedures. irGPU is not just a solution-in-principle but a promising practical application with potential to entice community into deeper understanding of principles governing biomolecule mechanisms. © 2015 Wiley Periodicals, Inc.

A survey of plasma irregularities as seen by the midlatitude Blackstone SuperDARN radar

NASA Astrophysics Data System (ADS)

Ribeiro, A. J.; Ruohoniemi, J. M.; Baker, J. B. H.; Clausen, L. B. N.; Greenwald, R. A.; Lester, M.

2012-02-01

The Super Dual Auroral Radar Network (SuperDARN) is a chain of HF radars that monitor plasma dynamics in the ionosphere. In recent years, SuperDARN has expanded to midlatitudes in order to provide enhanced coverage during geomagnetically active periods. A new type of backscatter from F region plasma irregularities with low Doppler velocity has been frequently observed on the nightside during quiescent conditions. Using three years of data from the Blackstone, VA radar, we have implemented a method for extracting this new type of backscatter from routine observations. We have statistically characterized the occurrence properties of the Sub Auroral Ionospheric Scatter (SAIS) events, including the latitudinal relationships to the equatorward edge of the auroral oval and the ionospheric projection of the plasmapause. We find that the backscatter is confined to local night, occurs on ≈70% of nights, is fixed in geomagnetic latitude, and is equatorward of both the auroral region and the plasmapause boundary. We conclude that SAIS irregularities are observed within a range of latitudes that is conjugate to the inner magnetosphere (plasmasphere).

Regularity and/or Consistency in the Production of the Past Participle?

ERIC Educational Resources Information Center

Colombo, Lucia; Laudanna, Alessandro; De Martino, Maria; Brivio, Cristina

2004-01-01

In the present study we have investigated the acquisition of the past participle of Italian verbs of the second (including mostly irregular verbs) and third (including mostly regular verbs) conjugations in school age children, and with simulations with an artificial neural network. We aimed to verify the extent to which children are sensitive to…

Error-correcting codes on scale-free networks

NASA Astrophysics Data System (ADS)

Kim, Jung-Hoon; Ko, Young-Jo

2004-06-01

We investigate the potential of scale-free networks as error-correcting codes. We find that irregular low-density parity-check codes with the highest performance known to date have degree distributions well fitted by a power-law function p (k) ˜ k-γ with γ close to 2, which suggests that codes built on scale-free networks with appropriate power exponents can be good error-correcting codes, with a performance possibly approaching the Shannon limit. We demonstrate for an erasure channel that codes with a power-law degree distribution of the form p (k) = C (k+α)-γ , with k⩾2 and suitable selection of the parameters α and γ , indeed have very good error-correction capabilities.

Coseismic slip distribution of the 1923 Kanto earthquake, Japan

USGS Publications Warehouse

Pollitz, F.F.; Nyst, M.; Nishimura, T.; Thatcher, W.

2005-01-01

The slip distribution associated with the 1923 M = 7.9 Kanto, Japan, earthquake is reexamined in light of new data and modeling. We utilize a combination of first-order triangulation, second-order triangulation, and leveling data in order to constrain the coseismic deformation. The second-order triangulation data, which have not been utilized in previous studies of 1923 coseismic deformation, are associated with only slightly smaller errors than the first-order triangulation data and expand the available triangulation data set by about a factor of 10. Interpretation of these data in terms of uniform-slip models in a companion study by Nyst et al. shows that a model involving uniform coseismic slip on two distinct rupture planes explains the data very well and matches or exceeds the fit obtained by previous studies, even one which involved distributed slip. Using the geometry of the Nyst et al. two-plane slip model, we perform inversions of the same geodetic data set for distributed slip. Our preferred model of distributed slip on the Philippine Sea plate interface has a moment magnitude of 7.86. We find slip maxima of ???8-9 m beneath Odawara and ???7-8 m beneath the Miura peninsula, with a roughly 2:1 ratio of strike-slip to dip-slip motion, in agreement with a previous study. However, the Miura slip maximum is imaged as a more broadly extended feature in our study, with the high-slip region continuing from the Miura peninsula to the southern Boso peninsula region. The second-order triangulation data provide good evidence for ???3 m right-lateral strike slip on a 35-km-long splay structure occupying the volume between the upper surface of the descending Philippine Sea plate and the southern Boso peninsula. Copyright 2005 by the American Geophysical Union.

Irregular synchronous activity in stochastically-coupled networks of integrate-and-fire neurons.

PubMed

Lin, J K; Pawelzik, K; Ernst, U; Sejnowski, T J

1998-08-01

We investigate the spatial and temporal aspects of firing patterns in a network of integrate-and-fire neurons arranged in a one-dimensional ring topology. The coupling is stochastic and shaped like a Mexican hat with local excitation and lateral inhibition. With perfect precision in the couplings, the attractors of activity in the network occur at every position in the ring. Inhomogeneities in the coupling break the translational invariance of localized attractors and lead to synchronization within highly active as well as weakly active clusters. The interspike interval variability is high, consistent with recent observations of spike time distributions in visual cortex. The robustness of our results is demonstrated with more realistic simulations on a network of McGregor neurons which model conductance changes and after-hyperpolarization potassium currents.

Percolation in three-dimensional fracture networks for arbitrary size and shape distributions

NASA Astrophysics Data System (ADS)

Thovert, J.-F.; Mourzenko, V. V.; Adler, P. M.

2017-04-01

The percolation threshold of fracture networks is investigated by extensive direct numerical simulations. The fractures are randomly located and oriented in three-dimensional space. A very wide range of regular, irregular, and random fracture shapes is considered, in monodisperse or polydisperse networks containing fractures with different shapes and/or sizes. The results are rationalized in terms of a dimensionless density. A simple model involving a new shape factor is proposed, which accounts very efficiently for the influence of the fracture shape. It applies with very good accuracy in monodisperse or moderately polydisperse networks, and provides a good first estimation in other situations. A polydispersity index is shown to control the need for a correction, and the corrective term is modelled for the investigated size distributions.

First evidence of anisotropy of GPS phase slips caused by the mid-latitude field-aligned ionospheric irregularities

NASA Astrophysics Data System (ADS)

Afraimovich, E. L.; Ishin, A. B.; Tinin, M. V.; Yasyukevich, Yu. V.; Jin, S. G.

2011-05-01

The mid-latitude field-aligned irregularity (FAI) along the magnetic field line is a common phenomenon in the ionosphere. However, few data reveal the field-aligned ionospheric irregularities. They are insufficient to identify FAIs effects so far, particularly effect on global positioning system (GPS) signals. In this paper, the mid-latitude FAIs by line-of-sight angular scanning relative to the local magnetic field vector are investigated using the denser GPS network observations in Japan. It has been the first found that total GPS L2 phase slips over Japan, during the recovery phase of the 12 Feb 2000 geomagnetic storm were caused by GPS signal scattering on FAIs both for the lines-of-sight aligned to the magnetic field line (the field of aligned scattering, FALS) and across the magnetic field line (the field of across scattering, FACS). The FALS results are also in a good agreement with the data of the magnetic field orientation control of GPS occultation observations of equatorial scintillation during thorough low earth orbit (LEO) satellites measurements, e.g. Challenging Minisatellite Payload (CHAMP) and Satellite de Aplicaciones Cientificas-C (SAC-C). The role of large-angle scattering almost along the normal to the magnetic field line in GPS scintillation is determined by attenuation of the irregularity anisotropy factor as compared with the other factors.

Fractal analysis of scatter imaging signatures to distinguish breast pathologies

NASA Astrophysics Data System (ADS)

Eguizabal, Alma; Laughney, Ashley M.; Krishnaswamy, Venkataramanan; Wells, Wendy A.; Paulsen, Keith D.; Pogue, Brian W.; López-Higuera, José M.; Conde, Olga M.

2013-02-01

Fractal analysis combined with a label-free scattering technique is proposed for describing the pathological architecture of tumors. Clinicians and pathologists are conventionally trained to classify abnormal features such as structural irregularities or high indices of mitosis. The potential of fractal analysis lies in the fact of being a morphometric measure of the irregular structures providing a measure of the object's complexity and self-similarity. As cancer is characterized by disorder and irregularity in tissues, this measure could be related to tumor growth. Fractal analysis has been probed in the understanding of the tumor vasculature network. This work addresses the feasibility of applying fractal analysis to the scattering power map (as a physical modeling) and principal components (as a statistical modeling) provided by a localized reflectance spectroscopic system. Disorder, irregularity and cell size variation in tissue samples is translated into the scattering power and principal components magnitude and its fractal dimension is correlated with the pathologist assessment of the samples. The fractal dimension is computed applying the box-counting technique. Results show that fractal analysis of ex-vivo fresh tissue samples exhibits separated ranges of fractal dimension that could help classifier combining the fractal results with other morphological features. This contrast trend would help in the discrimination of tissues in the intraoperative context and may serve as a useful adjunct to surgeons.

Ionospheric Irregularities Characterization by Ground and Space-based GPS Observations

NASA Astrophysics Data System (ADS)

Zakharenkova, I.; Cherniak, I.; Krankowski, A.

2017-12-01

We present new results on detection and investigation of the topside ionospheric irregularities using GPS measurements from Precise Orbit Determination (POD) GPS antenna onboard Low Earth Orbit satellites. Our investigation is based on the recent ESA's Swarm mission launched on 22 November 2013 and consisted of three identical satellites, two of them fly in a tandem at an orbit altitude of 460 km while the third satellite - at an orbit altitude of 510 km. Each satellite is equipped with a zenith-looking antenna and 8-channel dual-frequency GPS receiver that delivered 1 Hz data for POD purposes, as well as Langmuir Probe instrument for in situ electron density. Additionally, we have analyzed GPS measurements onboard GRACE and TerraSAR-X satellite, which have rather similar to Swarm orbit altitude of 500 km. GPS measurements onboard MetOP-A and MetOP-B satellites (altitude of 840 km) can complement these observations in order to estimate an altitudinal extent of the ionospheric irregularities penetrating to higher altitudes. We demonstrate that space-based GPS observations can be effectively used for monitoring of the topside ionospheric irregularities occurrence in both high-latitude and equatorial regions and may essentially contribute to the multi-instrumental analysis of the ground-based and in situ data. Climatological characteristics of the equatorial ionospheric irregularities occurrence probability are derived from POD GPS measurements for all longitudinal sectors for the years 2013-2016. Several examples of strong geomagnetic storms, including the 2015 St. Patrick's Day storm, were analyzed to demonstrate differences between the climatlogical characteristics in space-based GPS data and storm-induced equatorial irregularities observations (postsunset suppression, night/morning-time occurrence). To support our observations and conclusions, we involve into our analysis in situ plasma density provided by Swarm constellation, GRACE KBR, DMSP satellites, as well as ground-based GNSS and digisonde networks. New International GNSS Service (IGS) product - the Northern Hemisphere GPS-based ROTI (rate of the TEC index) maps - was analyzed to determine similarities and differences in ionospheric irregularities signatures in the ground and space-based GPS observations.

Resolving the Quantitative-Qualitative Dilemma: A Critical Realist Approach

ERIC Educational Resources Information Center

Scott, David

2007-01-01

The philosophical issues underpinning the quantitative-qualitative divide in educational research are examined. Three types of argument which support a resolution are considered: pragmatism, false duality and warranty through triangulation. In addition a number of proposed strategies--alignment, sequencing, translation and triangulation--are…

Adjustment technique without explicit formation of normal equations /conjugate gradient method/

NASA Technical Reports Server (NTRS)

Saxena, N. K.

1974-01-01

For a simultaneous adjustment of a large geodetic triangulation system, a semiiterative technique is modified and used successfully. In this semiiterative technique, known as the conjugate gradient (CG) method, original observation equations are used, and thus the explicit formation of normal equations is avoided, 'huge' computer storage space being saved in the case of triangulation systems. This method is suitable even for very poorly conditioned systems where solution is obtained only after more iterations. A detailed study of the CG method for its application to large geodetic triangulation systems was done that also considered constraint equations with observation equations. It was programmed and tested on systems as small as two unknowns and three equations up to those as large as 804 unknowns and 1397 equations. When real data (573 unknowns, 965 equations) from a 1858-km-long triangulation system were used, a solution vector accurate to four decimal places was obtained in 2.96 min after 1171 iterations (i.e., 2.0 times the number of unknowns).

Spectrum of the Laplace-Beltrami operator and the phase structure of causal dynamical triangulations

NASA Astrophysics Data System (ADS)

Clemente, Giuseppe; D'Elia, Massimo

2018-06-01

We propose a new method to characterize the different phases observed in the nonperturbative numerical approach to quantum gravity known as causal dynamical triangulations. The method is based on the analysis of the eigenvalues and the eigenvectors of the Laplace-Beltrami operator computed on the triangulations: it generalizes previous works based on the analysis of diffusive processes and proves capable of providing more detailed information on the geometric properties of the triangulations. In particular, we apply the method to the analysis of spatial slices, showing that the different phases can be characterized by a new order parameter related to the presence or absence of a gap in the spectrum of the Laplace-Beltrami operator, and deriving an effective dimensionality of the slices at the different scales. We also propose quantities derived from the spectrum that could be used to monitor the running to the continuum limit around a suitable critical point in the phase diagram, if any is found.

Low and Mid-Latitude Ionospheric Irregularities Studies Using TEC and Radio Scintillation Data from the CITRIS Radio Beacon Receiver in Low-Earth-Orbit

NASA Astrophysics Data System (ADS)

Siefring, C. L.; Bernhardt, P. A.; Huba, J.; Krall, J.; Roddy, P. A.

2009-12-01

Unique data on ionospheric plasma irregularities from the Naval Research Laboratory (NRL) CITRIS (Scintillation and TEC Receiver in Space) instrument will be presented. CITRIS is a multi-band receiver that recorded TEC (Total Electron Content) and radio scintillations from Low-Earth Orbit (LEO) on STPSat1. The 555+/5 km altitude 35° inclination orbit covers low and mid-latitudes. The measurements require propagation from a transmitter to a receiver through the F-region plasma. CITRIS used both 1) satellite beacons in LEO, such as the NRL CERTO (Coherent Electromagnetic Radio TOmography) beacons and 2) the global network of ground-based DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) beacons. The TEC measurements allow for tracking of ionospheric disturbances and irregularities while the measurements of scintillations can simultaneously characterize their effects. CITRIS was operated in a complementary fashion with the C/NOFS (Communication/Navigations Outages Forecasting System) satellite during most of its first year of operations. C/NOFS carries a three-frequency 150/400/1067 MHz CERTO beacon and is dedicated to the study of Spread-F. In the case of Spread-F, ionospheric irregularities start with large scale size density gradients (100s of km) and cascade through complex processes to short scale sizes (10s of meters). It is typically the 100m-1km scale features that harm communication and navigation systems through scintillations. A multi-sensor approach is needed to completely understand this complex system, such as, the combination of CITRIS remote radio sensing and C/NOFS in-situ data. Several types of irregularities have been studied including Spread-F and the newly discovered dawn-side depletions. Comparisons with the physics based SAMI3 model are being performed to help our understanding of the morphology of the irregularities.

Modular networks with delayed coupling: Synchronization and frequency control

NASA Astrophysics Data System (ADS)

Maslennikov, Oleg V.; Nekorkin, Vladimir I.

2014-07-01

We study the collective dynamics of modular networks consisting of map-based neurons which generate irregular spike sequences. Three types of intramodule topology are considered: a random Erdös-Rényi network, a small-world Watts-Strogatz network, and a scale-free Barabási-Albert network. The interaction between the neurons of different modules is organized by relatively sparse connections with time delay. For all the types of the network topology considered, we found that with increasing delay two regimes of module synchronization alternate with each other: inphase and antiphase. At the same time, the average rate of collective oscillations decreases within each of the time-delay intervals corresponding to a particular synchronization regime. A dual role of the time delay is thus established: controlling a synchronization mode and degree and controlling an average network frequency. Furthermore, we investigate the influence on the modular synchronization by other parameters: the strength of intermodule coupling and the individual firing rate.

Quantifying climatic controls on river network topology across scales

NASA Astrophysics Data System (ADS)

Ranjbar Moshfeghi, S.; Hooshyar, M.; Wang, D.; Singh, A.

2017-12-01

Branching structure of river networks is an important topologic and geomorphologic feature that depends on several factors (e.g. climate, tectonic). However, mechanisms that cause these drainage patterns in river networks are poorly understood. In this study, we investigate the effects of varying climatic forcing on river network topology and geomorphology. For this, we select 20 catchments across the United States with different long-term climatic conditions quantified by climate aridity index (AI), defined here as the ratio of mean annual potential evaporation (Ep) to precipitation (P), capturing variation in runoff and vegetation cover. The river networks of these catchments are extracted, using a curvature-based method, from high-resolution (1 m) digital elevation models and several metrics such as drainage density, branching angle, and width functions are computed. We also use a multiscale-entropy-based approach to quantify the topologic irregularity and structural richness of these river networks. Our results reveal systematic impacts of climate forcing on the structure of river networks.

The 3-D unstructured mesh generation using local transformations

NASA Technical Reports Server (NTRS)

Barth, Timothy J.

1993-01-01

The topics are presented in viewgraph form and include the following: 3D combinatorial edge swapping; 3D incremental triangulation via local transformations; a new approach to multigrid for unstructured meshes; surface mesh generation using local transforms; volume triangulations; viscous mesh generation; and future directions.

Triangulation in aetiological epidemiology

PubMed Central

Lawlor, Debbie A; Tilling, Kate; Davey Smith, George

2016-01-01

Abstract Triangulation is the practice of obtaining more reliable answers to research questions through integrating results from several different approaches, where each approach has different key sources of potential bias that are unrelated to each other. With respect to causal questions in aetiological epidemiology, if the results of different approaches all point to the same conclusion, this strengthens confidence in the finding. This is particularly the case when the key sources of bias of some of the approaches would predict that findings would point in opposite directions if they were due to such biases. Where there are inconsistencies, understanding the key sources of bias of each approach can help to identify what further research is required to address the causal question. The aim of this paper is to illustrate how triangulation might be used to improve causal inference in aetiological epidemiology. We propose a minimum set of criteria for use in triangulation in aetiological epidemiology, summarize the key sources of bias of several approaches and describe how these might be integrated within a triangulation framework. We emphasize the importance of being explicit about the expected direction of bias within each approach, whenever this is possible, and seeking to identify approaches that would be expected to bias the true causal effect in different directions. We also note the importance, when comparing results, of taking account of differences in the duration and timing of exposures. We provide three examples to illustrate these points. PMID:28108528

A Coral Reef Algorithm Based on Learning Automata for the Coverage Control Problem of Heterogeneous Directional Sensor Networks

PubMed Central

Li, Ming; Miao, Chunyan; Leung, Cyril

2015-01-01

Coverage control is one of the most fundamental issues in directional sensor networks. In this paper, the coverage optimization problem in a directional sensor network is formulated as a multi-objective optimization problem. It takes into account the coverage rate of the network, the number of working sensor nodes and the connectivity of the network. The coverage problem considered in this paper is characterized by the geographical irregularity of the sensed events and heterogeneity of the sensor nodes in terms of sensing radius, field of angle and communication radius. To solve this multi-objective problem, we introduce a learning automata-based coral reef algorithm for adaptive parameter selection and use a novel Tchebycheff decomposition method to decompose the multi-objective problem into a single-objective problem. Simulation results show the consistent superiority of the proposed algorithm over alternative approaches. PMID:26690162

A Coral Reef Algorithm Based on Learning Automata for the Coverage Control Problem of Heterogeneous Directional Sensor Networks.

PubMed

Li, Ming; Miao, Chunyan; Leung, Cyril

2015-12-04

Coverage control is one of the most fundamental issues in directional sensor networks. In this paper, the coverage optimization problem in a directional sensor network is formulated as a multi-objective optimization problem. It takes into account the coverage rate of the network, the number of working sensor nodes and the connectivity of the network. The coverage problem considered in this paper is characterized by the geographical irregularity of the sensed events and heterogeneity of the sensor nodes in terms of sensing radius, field of angle and communication radius. To solve this multi-objective problem, we introduce a learning automata-based coral reef algorithm for adaptive parameter selection and use a novel Tchebycheff decomposition method to decompose the multi-objective problem into a single-objective problem. Simulation results show the consistent superiority of the proposed algorithm over alternative approaches.

A modeling approach on why simple central pattern generators are built of irregular neurons.

PubMed

Reyes, Marcelo Bussotti; Carelli, Pedro Valadão; Sartorelli, José Carlos; Pinto, Reynaldo Daniel

2015-01-01

The crustacean pyloric Central Pattern Generator (CPG) is a nervous circuit that endogenously provides periodic motor patterns. Even after about 40 years of intensive studies, the rhythm genesis is still not rigorously understood in this CPG, mainly because it is made of neurons with irregular intrinsic activity. Using mathematical models we addressed the question of using a network of irregularly behaving elements to generate periodic oscillations, and we show some advantages of using non-periodic neurons with intrinsic behavior in the transition from bursting to tonic spiking (as found in biological pyloric CPGs) as building components. We studied two- and three-neuron model CPGs built either with Hindmarsh-Rose or with conductance-based Hodgkin-Huxley-like model neurons. By changing a model's parameter we could span the neuron's intrinsic dynamical behavior from slow periodic bursting to fast tonic spiking, passing through a transition where irregular bursting was observed. Two-neuron CPG, half center oscillator (HCO), was obtained for each intrinsic behavior of the neurons by coupling them with mutual symmetric synaptic inhibition. Most of these HCOs presented regular antiphasic bursting activity and the changes of the bursting frequencies was studied as a function of the inhibitory synaptic strength. Among all HCOs, those made of intrinsic irregular neurons presented a wider burst frequency range while keeping a reliable regular oscillatory (bursting) behavior. HCOs of periodic neurons tended to be either hard to change their behavior with synaptic strength variations (slow periodic burster neurons) or unable to perform a physiologically meaningful rhythm (fast tonic spiking neurons). Moreover, 3-neuron CPGs with connectivity and output similar to those of the pyloric CPG presented the same results.

Multi-static networked 3D ladar for surveillance and access control

NASA Astrophysics Data System (ADS)

Wang, Y.; Ogirala, S. S. R.; Hu, B.; Le, Han Q.

2007-04-01

A theoretical design and simulation of a 3D ladar system concept for surveillance, intrusion detection, and access control is described. It is a non-conventional system architecture that consists of: i) multi-static configuration with an arbitrarily scalable number of transmitters (Tx's) and receivers (Rx's) that form an optical wireless code-division-multiple-access (CDMA) network, and ii) flexible system architecture with modular plug-and-play components that can be deployed for any facility with arbitrary topology. Affordability is a driving consideration; and a key feature for low cost is an asymmetric use of many inexpensive Rx's in conjunction with fewer Tx's, which are generally more expensive. The Rx's are spatially distributed close to the surveyed area for large coverage, and capable of receiving signals from multiple Tx's with moderate laser power. The system produces sensing information that scales as NxM, where N, M are the number of Tx's and Rx's, as opposed to linear scaling ~N in non-network system. Also, for target positioning, besides laser pointing direction and time-of-flight, the algorithm includes multiple point-of-view image fusion and triangulation for enhanced accuracy, which is not applicable to non-networked monostatic ladars. Simulation and scaled model experiments on some aspects of this concept are discussed.

Using the IMS infrasound network for the identification of mountain-associated waves and gravity waves hotspots

NASA Astrophysics Data System (ADS)

Hupe, Patrick; Ceranna, Lars; Pilger, Christoph; Le Pichon, Alexis

2017-04-01

The infrasound network of the International Monitoring System (IMS) has been established for monitoring the atmosphere to detect violations of the Comprehensive nuclear-Test-Ban Treaty (CTBT). The IMS comprises 49 certified infrasound stations which are globally distributed. Each station provides data for up to 16 years. Due to the uniform distribution of the stations, the IMS infrasound network can be used to derive global information on atmospheric dynamics' features. This study focuses on mountain-associated waves (MAWs), i.e. acoustic waves in the frequency range between approximately 0.01 Hz and 0.05 Hz. MAWs can be detected in infrasound data by applying the Progressive Multi-Channel Correlation (PMCC) algorithm. As a result of triangulation, global hotspots of MAWs can be identified. Previous studies on gravity waves indicate that global hotspots of gravity waves are similar to those found for MAWs by using the PMCC algorithm. The objective of our study is an enhanced understanding of the excitation sources and of possible interactions between MAWs and gravity waves. Therefore, spatial and temporal correlation analyses will be performed. As a preceding step, we will present (seasonal) hotspots of MAWs as well as hotspots of gravity waves derived by the IMS infrasound network.

Laser Altimeter for Flight Simulator

NASA Technical Reports Server (NTRS)

Webster, L. D.

1986-01-01

Height of flight-simulator probe above model of terrain measured by automatic laser triangulation system. Airplane simulated by probe that moves over model of terrain. Altitude of airplane scaled from height of probe above model. Height measured by triangulation of laser beam aimed at intersection of model surface with plumb line of probe.

Communication Intervention in an Organization: Measuring the Results through a Triangulation Approach.

ERIC Educational Resources Information Center

Zamanou, Sonia; Glaser, Susan R.

A study examined organizational culture change to determine the effectiveness of a communication based intervention program to increase productivity and motivation. The cultural change was measured through a triangulation approach combining questionnaires, interview data and direct observation. Pre- and post-intervention data were obtained in the…

The Movement of Conflict in Organizations: The Joint Dynamics of Splitting and Triangulation.

ERIC Educational Resources Information Center

Smith, Kenwyn K.

1989-01-01

Based on a long-term public school system study, the paper examines the sociopsychological process through which conflicts move around in organizations and are transported from one place to another. The conceptualization draws on "triangulation" from social psychology and family therapy and "splitting," developed in…

Triangulation and Mixed Methods Designs: Data Integration with New Research Technologies

ERIC Educational Resources Information Center

Fielding, Nigel G.

2012-01-01

Data integration is a crucial element in mixed methods analysis and conceptualization. It has three principal purposes: illustration, convergent validation (triangulation), and the development of analytic density or "richness." This article discusses such applications in relation to new technologies for social research, looking at three…

Manhunting: Counter-Network Organization for Irregular Warfare

DTIC Science & Technology

2009-09-01

received his B.A. in International Relations from the University of Kansas in 1985 and M.S. in Computer Applications Management from Lesley University...collection management , and targeting.b. Operational level processes begin with intelligence on the adversary capabilities with granular focus to mitigate... managers work with analysts, targeting experts, decision makers, planners, and operations personnel, guiding multidisciplinary intelligence collection to

Predicting healthcare trajectories from medical records: A deep learning approach.

PubMed

Pham, Trang; Tran, Truyen; Phung, Dinh; Venkatesh, Svetha

2017-05-01

Personalized predictive medicine necessitates the modeling of patient illness and care processes, which inherently have long-term temporal dependencies. Healthcare observations, stored in electronic medical records are episodic and irregular in time. We introduce DeepCare, an end-to-end deep dynamic neural network that reads medical records, stores previous illness history, infers current illness states and predicts future medical outcomes. At the data level, DeepCare represents care episodes as vectors and models patient health state trajectories by the memory of historical records. Built on Long Short-Term Memory (LSTM), DeepCare introduces methods to handle irregularly timed events by moderating the forgetting and consolidation of memory. DeepCare also explicitly models medical interventions that change the course of illness and shape future medical risk. Moving up to the health state level, historical and present health states are then aggregated through multiscale temporal pooling, before passing through a neural network that estimates future outcomes. We demonstrate the efficacy of DeepCare for disease progression modeling, intervention recommendation, and future risk prediction. On two important cohorts with heavy social and economic burden - diabetes and mental health - the results show improved prediction accuracy. Copyright © 2017 Elsevier Inc. All rights reserved.

Earth's gravity field to the eighteenth degree and geocentric coordinates for 104 stations from satellite and terrestrial data

NASA Technical Reports Server (NTRS)

Gaposchkin, E. M.

1973-01-01

Geodetic parameters describing the earth's gravity field and the positions of satellite-tracking stations in a geocentric reference frame were computed. These parameters were estimated by means of a combination of five different types of data: routine and simultaneous satellite observations, observations of deep-space probes, measurements of terrestrial gravity, and surface-triangulation data. The combination gives better parameters than does any subset of data types. The dynamic solution used precision-reduced Baker-Nunn observations and laser range data of 25 satellites. Data from the 49-station National Oceanic and Atmospheric Administration BC-4 network, the 19-station Smithsonian Astrophysical Observatory Baker-Nunn network, and independent camera stations were employed in the geometrical solution. Data from the tracking of deep-space probes were converted to relative longitudes and distances to the earth's axis of rotation of the tracking stations. Surface-gravity data in the form of 550-km squares were derived from 19,328 1 deg X 1 deg mean gravity anomalies.

Sub-pixel accuracy thickness calculation of poultry fillets from scattered laser profiles

NASA Astrophysics Data System (ADS)

Jing, Hansong; Chen, Xin; Tao, Yang; Zhu, Bin; Jin, Fenghua

2005-11-01

A laser range imaging system based on the triangulation method was designed and implemented for online high-resolution thickness calculation of poultry fillets. A laser pattern was projected onto the surface of the chicken fillet for calculation of the thickness of the meat. Because chicken fillets are relatively loosely-structured material, a laser light easily penetrates the meat, and scattering occurs both at and under the surface. When laser light is scattered under the surface it is reflected back and further blurs the laser line sharpness. To accurately calculate the thickness of the object, the light transportation has to be considered. In the system, the Bidirectional Reflectance Distribution Function (BSSRDF) was used to model the light transportation and the light pattern reflected into the cameras. BSSRDF gives the reflectance of a target as a function of illumination geometry and viewing geometry. Based on this function, an empirical method has been developed and it has been proven that this method can be used to accurately calculate the thickness of the object from a scattered laser profile. The laser range system is designed as a sub-system that complements the X-ray bone inspection system for non-invasive detection of hazardous materials in boneless poultry meat with irregular thickness.

Robotic tool positioning process using a multi-line off-axis laser triangulation sensor

NASA Astrophysics Data System (ADS)

Pinto, T. C.; Matos, G.

2018-03-01

Proper positioning of a friction stir welding head for pin insertion, driven by a closed chain robot, is important to ensure quality repair of cracks. A multi-line off-axis laser triangulation sensor was designed to be integrated to the robot, allowing relative measurements of the surface to be repaired. This work describes the sensor characteristics, its evaluation and the measurement process for tool positioning to a surface point of interest. The developed process uses a point of interest image and a measured point cloud to define the translation and rotation for tool positioning. Sensor evaluation and tests are described. Keywords: laser triangulation, 3D measurement, tool positioning, robotics.

Low-Cost Photogrammetric Technique Used to Measure Dome Growth at Mount St. Helens Volcano, 2007-2007

NASA Astrophysics Data System (ADS)

Diefenbach, A. K.; Crider, J. G.; Schilling, S. P.; Dzurisin, D.

2007-12-01

We describe a low-cost application of digital photogrammetry using commercial grade software, an off-the-shelf digital camera, a laptop computer and oblique photographs to reconstruct volcanic dome morphology during the on-going eruption at Mount St. Helens, Washington. Renewed activity at Mount St. Helens provides a rare opportunity to devise and test new methods for better understanding and predicting volcanic events, because the new method can be validated against other observations on this well-instrumented volcano. Uncalibrated, oblique aerial photographs (snap shots) taken from a helicopter are the raw data. Twelve sets of overlapping digital images of the dome taken during 2004-2007 were used to produce digital elevation models (DEMs) from which dome height, eruption volume and extrusion rate can be derived. Analyses of the digital images were carried out using PhotoModeler software, which produces three dimensional coordinates of points identified in multiple photos. The steps involved include: (1) calibrating the digital camera using this software package, (2) establishing control points derived from existing DEMs, (3) identifying tie points located in each photo of any given model date, and (4) identifying points in pairs of photos to build a three dimensional model of the evolving dome at each photo date. Text files of three-dimensional points encompassing the dome at each date were imported into ArcGIS and three-dimensional models (triangulated irregular network or TINs) were generated. TINs were then converted to 2 m raster DEMs. The evolving morphology of the growing dome was modeled by comparison of successive DEMs. The volume of extruded lava visible in each DEM was calculated using the 1986 pre-eruption crater floor topography as a basal surface. Results were validated by comparing volume measurements derived from traditional aerophotogrammetric surveys run by the USGS Cascades Volcano Observatory. Our new "quick and cheap" technique yields estimates of eruptive volume consistently within 5% of the volumes estimated with traditional surveys. The end result of this project is a new technique that provides an inexpensive, rapid assessment tool for tracking lava dome growth or other topographic changes at restless volcanoes.

Evaluating Team Project-Work Using Triangulation: Lessons from Communities in Northern Ghana

ERIC Educational Resources Information Center

Clark, Gordon; Jasaw, Godfred Seidu

2014-01-01

This paper uses triangulation to assess key aspects of a team-based, participatory action research programme for undergraduates in rural communities across northern Ghana. The perceptions of the programme and its effects on the students, staff and host communities are compared, showing areas of agreement and disagreement. The successes of the…

The Triangulation Interview Form: A Possible Criterion for Field-Based Objectives.

ERIC Educational Resources Information Center

Licata, Joseph W.; Norman, Reuben L.

1979-01-01

To test the general reliability and validity of the Triangulation Interview Form (TIF), 52 observers viewed a videotape simulation of an interview situation. Agreement among observers for each of 16 TIF questions ranged from 85 to 98 percent. Observers significantly discriminated between eight behaviors judged complete and eight behaviors judged…

The Use of Triangulation Methods in Qualitative Educational Research

ERIC Educational Resources Information Center

Oliver-Hoyo, Maria; Allen, DeeDee

2006-01-01

Triangulation involves the careful reviewing of data collected through different methods in order to achieve a more accurate and valid estimate of qualitative results for a particular construct. This paper describes how we used three qualitative methods of data collection to study attitudes of students toward graphing, hands-on activities, and…

Assessing the Potential Use of Eye-Tracking Triangulation for Evaluating the Usability of an Online Diabetes Exercise System.

PubMed

Schaarup, Clara; Hartvigsen, Gunnar; Larsen, Lars Bo; Tan, Zheng-Hua; Årsand, Eirik; Hejlesen, Ole Kristian

2015-01-01

The Online Diabetes Exercise System was developed to motivate people with Type 2 diabetes to do a 25 minutes low-volume high-intensity interval training program. In a previous multi-method evaluation of the system, several usability issues were identified and corrected. Despite the thorough testing, it was unclear whether all usability problems had been identified using the multi-method evaluation. Our hypothesis was that adding the eye-tracking triangulation to the multi-method evaluation would increase the accuracy and completeness when testing the usability of the system. The study design was an Eye-tracking Triangulation; conventional eye-tracking with predefined tasks followed by The Post-Experience Eye-Tracked Protocol (PEEP). Six Areas of Interests were the basis for the PEEP-session. The eye-tracking triangulation gave objective and subjective results, which are believed to be highly relevant for designing, implementing, evaluating and optimizing systems in the field of health informatics. Future work should include testing the method on a larger and more representative group of users and apply the method on different system types.

Constrained CVT meshes and a comparison of triangular mesh generators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Hoa; Burkardt, John; Gunzburger, Max

2009-01-01

Mesh generation in regions in Euclidean space is a central task in computational science, and especially for commonly used numerical methods for the solution of partial differential equations, e.g., finite element and finite volume methods. We focus on the uniform Delaunay triangulation of planar regions and, in particular, on how one selects the positions of the vertices of the triangulation. We discuss a recently developed method, based on the centroidal Voronoi tessellation (CVT) concept, for effecting such triangulations and present two algorithms, including one new one, for CVT-based grid generation. We also compare several methods, including CVT-based methods, for triangulatingmore » planar domains. To this end, we define several quantitative measures of the quality of uniform grids. We then generate triangulations of several planar regions, including some having complexities that are representative of what one may encounter in practice. We subject the resulting grids to visual and quantitative comparisons and conclude that all the methods considered produce high-quality uniform grids and that the CVT-based grids are at least as good as any of the others.« less

Passive range estimation using dual baseline triangulation

NASA Astrophysics Data System (ADS)

Pieper, Ronald J.; Cooper, Alfred W.; Pelegris, G.

1996-03-01

Modern combat systems based on active radar sensing suffer disadvantages against low-flying targets in cluttered backgrounds. Use of passive infrared sensors with these systems, either in cooperation or as an alternative, shows potential for improving target detection and declaration range for targets crossing the horizon. Realization of this potential requires fusion of target position data from dissimilar sensors, or passive sensor measurement of target range. The availability of passive sensors that can supply both range and bearing data on such targets would significantly extend the robustness of an integrated ship self-defense system. This paper considers a new method of range determination with passive sensors based on the principle of triangulation, extending the principle to two orthogonal baselines. The performance of single or double baseline triangulation depends on sensor bearing precision and direction to target. An expression for maximum triangulation range at a required accuracy is derived as a function of polar angle relative to the center of the dual-baseline system. Limitations in the dual- baseline model due to the geometrically assessed horizon are also considered.

Monitoring of manufacturing processes in the automotive industry using indoor location system

NASA Astrophysics Data System (ADS)

Ionescu, LM; Belu, N.; Rachieru, N.; Mazăre, AG; Anghel, D.-C.

2016-08-01

This paper presents a method for locating the operators, equipment and parts using radio communications systems. Specifically there will be radio transceiver arranged in a network of active and passive radio receivers placed on personnel, equipment or parts. Based on a radio triangulation method, it is determined the location of the all resources and parts involved in manufacturing process. The transceivers communicate with each other via “routers” - also components of the network. Such a structure may extend over large distances even in indoor spaces where there are obstacles (walls between rooms). The location is done by determining the power of transmission signal for at least three end points. The receiver position is then transmitted over the network through routers, to a central server where all positions of the resources are centralized. Our solution is a non-invasive and low cost method for determining resource position in the factory. The system can be used for both resource planning production for current process more efficient and for further analysis of the movement of resources during previous processes with possible adjustments to the workspace and re-planning of resources for future processes.

[From normative aspects to the reality of the Unified Health System: revealing barriers that curtail access to the health care network].

PubMed

Sousa, Fabiana de Oliveira Silva; de Medeiros, Kátia Rejane; Gurgel Júnior, Garibaldi Dantas; de Albuquerque, Paulette Cavalcanti

2014-04-01

This article analyzes the conditions of comprehensive access to health care in Recife in the state of Pernambuco based on the trajectory experienced by users from primary health services through to specialist care. Quantitative and qualitative approaches were combined with triangulation of methods as the research technique. Systemic Arterial Hypertension was chosen as a core condition, as it is an ailment that requires attention at various levels of the city's health network. The research revealed various barriers of access in primary health care becoming more accentuated at other levels of care resulting in delays in timely care and consequently prolonging the suffering of the population. Structural problems such as a shortage of medical professionals in primary care, insufficient access to specialized consultations and exams, together with the inherent dynamics of the health services, are real obstacles that the user faces in the quest for continuous and comprehensive care in the Unified Health System (SUS). In addition to broadening and enhancing the availability of services, especially complementary exams, it is necessary to ensure communication between the departments of the SUS, in order to consolidate an articulated network, thereby improving health care.

Overview of acoustic measurements in South-East of France in 2012 during severe weather

NASA Astrophysics Data System (ADS)

Farges, Thomas; Blanc, Elisabeh; Le Pichon, Alexis; Defer, Eric; Fullekrug, Martin; Soula, Serge; van der Velde, Oscar

2013-04-01

CEA (Commissariat à l'Energie Atomique et aux Energies Alternatives) installed two acoustic networks in South-East of France. The first one was located in Observatoire Haute Provence in the framework of the ARISE European design project (arise-project.eu). It was composed of 4 microbarometers set in an equilateral triangle. The other network was located close to Uzès in the frame of the HyMeX (www.hymex.org) Special Operational Period from August 27th to November 16th. It was composed of 4 microbarometers and 4 microphones. From August to November 2012, several thunderstorms occurred close to these stations. The global thunder spectrum from 0.01 Hz to 250 Hz is studied using the microbarometer and microphone recordings. A very large thunderstorm, in August 30th-31st, produced more than 100 sprites over the south-western part of the Mediterranean Sea. Ten of them were dancing sprites. This kind of sprites can produce infrasound. This experiment offers a unique to triangulate sprites with infrasound measurements. Lastly, a tornado occurred in October 14th. This event will be analyzed with the data of both networks.

Development of a program for tele-rehabilitation of COPD patients across sectors: co-innovation in a network

PubMed Central

Dinesen, Birthe; Seeman, Janne; Gustafsson, Jeppe

2011-01-01

Introduction The aim of the Telekat project is to prevent re-admissions of patients with chronic obstructive pulmonary disease (COPD) by developing a preventive program of tele-rehabilitation across sectors for COPD patients. The development of the program is based on a co-innovation process between COPD patients, relatives, healthcare professionals and representatives from private firms and universities. This paper discusses the obstacles that arise in the co-innovation process of developing an integrated technique for tele-rehabilitation of COPD patients. Theory Network and innovation theory. Methods The case study was applied. A triangulation of data collection techniques was used: documents, observations (123 hours), qualitative interviews (n=32) and action research. Findings Obstacles were identified in the network context; these obstacles included the mindset of the healthcare professionals, inter-professionals relations, views of technology as a tool and competing visions for the goals of tele-rehabilitation. Conclusion We have identified obstacles that emerge in the co-innovation process when developing a programme for tele-rehabilitation of COPD patients in an inter-organizational context. Action research has been carried out and can have helped to facilitate the co-innovation process. PMID:21637709

Toward link predictability of complex networks

PubMed Central

Lü, Linyuan; Pan, Liming; Zhou, Tao; Zhang, Yi-Cheng; Stanley, H. Eugene

2015-01-01

The organization of real networks usually embodies both regularities and irregularities, and, in principle, the former can be modeled. The extent to which the formation of a network can be explained coincides with our ability to predict missing links. To understand network organization, we should be able to estimate link predictability. We assume that the regularity of a network is reflected in the consistency of structural features before and after a random removal of a small set of links. Based on the perturbation of the adjacency matrix, we propose a universal structural consistency index that is free of prior knowledge of network organization. Extensive experiments on disparate real-world networks demonstrate that (i) structural consistency is a good estimation of link predictability and (ii) a derivative algorithm outperforms state-of-the-art link prediction methods in both accuracy and robustness. This analysis has further applications in evaluating link prediction algorithms and monitoring sudden changes in evolving network mechanisms. It will provide unique fundamental insights into the above-mentioned academic research fields, and will foster the development of advanced information filtering technologies of interest to information technology practitioners. PMID:25659742

Triangulation in aetiological epidemiology.

PubMed

Lawlor, Debbie A; Tilling, Kate; Davey Smith, George

2016-12-01

Triangulation is the practice of obtaining more reliable answers to research questions through integrating results from several different approaches, where each approach has different key sources of potential bias that are unrelated to each other. With respect to causal questions in aetiological epidemiology, if the results of different approaches all point to the same conclusion, this strengthens confidence in the finding. This is particularly the case when the key sources of bias of some of the approaches would predict that findings would point in opposite directions if they were due to such biases. Where there are inconsistencies, understanding the key sources of bias of each approach can help to identify what further research is required to address the causal question. The aim of this paper is to illustrate how triangulation might be used to improve causal inference in aetiological epidemiology. We propose a minimum set of criteria for use in triangulation in aetiological epidemiology, summarize the key sources of bias of several approaches and describe how these might be integrated within a triangulation framework. We emphasize the importance of being explicit about the expected direction of bias within each approach, whenever this is possible, and seeking to identify approaches that would be expected to bias the true causal effect in different directions. We also note the importance, when comparing results, of taking account of differences in the duration and timing of exposures. We provide three examples to illustrate these points. © The Author 2017. Published by Oxford University Press on behalf of the International Epidemiological Association.

A Qualitative Study to Examine Feasibility and Design of an Online Social Networking Intervention to Increase Physical Activity in Teenage Girls.

PubMed

Van Kessel, Gisela; Kavanagh, Madeleine; Maher, Carol

2016-01-01

Online social networks present wide-reaching and flexible platforms through which to deliver health interventions to targeted populations. This study used a social marketing approach to explore teenage girls' perceptions of physical activity and the potential use of online social networks to receive a physical activity intervention. Six focus groups were conducted with 19 Australian teenage girls (ages 13 to 18 years) with varying levels of physical activity and socioeconomic status. A semi-structured format was used, with groups discussion transcribed verbatim. Content analysis identified emergent themes, with triangulation and memos used to ensure accuracy. Physical activity was most appealing when it emphasised sport, exercise and fitness, along with opportunities for socialisation with friends and self-improvement. Participants were receptive to delivery of a physical activity intervention via online social networks, with Facebook the most widely reported site. Participants commonly accessed online social networks via mobile devices and particularly smartphones. Undesirable features included promotion of physical activity in terms of walking; use of cartoon imagery; use of humour; and promotion of the intervention via schools, each of which were considered "uncool". Participants noted that their parents were likely to be supportive of them using an online social networking physical activity intervention, particularly if not promoted as a weight loss intervention. This study identified key features likely to increase the feasibility and retention of an online social networking physical activity intervention for teenage girls. Guidelines for the design of interventions for teenage girls are provided for future applications.

A Qualitative Study to Examine Feasibility and Design of an Online Social Networking Intervention to Increase Physical Activity in Teenage Girls

PubMed Central

Van Kessel, Gisela; Kavanagh, Madeleine; Maher, Carol

2016-01-01

Background Online social networks present wide-reaching and flexible platforms through which to deliver health interventions to targeted populations. This study used a social marketing approach to explore teenage girls’ perceptions of physical activity and the potential use of online social networks to receive a physical activity intervention. Methods Six focus groups were conducted with 19 Australian teenage girls (ages 13 to 18 years) with varying levels of physical activity and socioeconomic status. A semi-structured format was used, with groups discussion transcribed verbatim. Content analysis identified emergent themes, with triangulation and memos used to ensure accuracy. Results Physical activity was most appealing when it emphasised sport, exercise and fitness, along with opportunities for socialisation with friends and self-improvement. Participants were receptive to delivery of a physical activity intervention via online social networks, with Facebook the most widely reported site. Participants commonly accessed online social networks via mobile devices and particularly smartphones. Undesirable features included promotion of physical activity in terms of walking; use of cartoon imagery; use of humour; and promotion of the intervention via schools, each of which were considered “uncool”. Participants noted that their parents were likely to be supportive of them using an online social networking physical activity intervention, particularly if not promoted as a weight loss intervention. Conclusion This study identified key features likely to increase the feasibility and retention of an online social networking physical activity intervention for teenage girls. Guidelines for the design of interventions for teenage girls are provided for future applications. PMID:26934191

Robustness of external/internal correlation models for real-time tumor tracking to breathing motion variations

NASA Astrophysics Data System (ADS)

Seregni, M.; Cerveri, P.; Riboldi, M.; Pella, A.; Baroni, G.

2012-11-01

In radiotherapy, organ motion mitigation by means of dynamic tumor tracking requires continuous information about the internal tumor position, which can be estimated relying on external/internal correlation models as a function of external surface surrogates. In this work, we propose a validation of a time-independent artificial neural networks-based tumor tracking method in the presence of changes in the breathing pattern, evaluating the performance on two datasets. First, simulated breathing motion traces were specifically generated to include gradually increasing respiratory irregularities. Then, seven publically available human liver motion traces were analyzed for the assessment of tracking accuracy, whose sensitivity with respect to the structural parameters of the model was also investigated. Results on simulated data showed that the proposed method was not affected by hysteretic target trajectories and it was able to cope with different respiratory irregularities, such as baseline drift and internal/external phase shift. The analysis of the liver motion traces reported an average RMS error equal to 1.10 mm, with five out of seven cases below 1 mm. In conclusion, this validation study proved that the proposed method is able to deal with respiratory irregularities both in controlled and real conditions.

Dynamic Reorganization of the Cytoskeleton during Apoptosis: The Two Coffins Hypothesis.

PubMed

Povea-Cabello, Suleva; Oropesa-Ávila, Manuel; de la Cruz-Ojeda, Patricia; Villanueva-Paz, Marina; de la Mata, Mario; Suárez-Rivero, Juan Miguel; Álvarez-Córdoba, Mónica; Villalón-García, Irene; Cotán, David; Ybot-González, Patricia; Sánchez-Alcázar, José A

2017-11-11

During apoptosis, cells undergo characteristic morphological changes in which the cytoskeleton plays an active role. The cytoskeleton rearrangements have been mainly attributed to actinomyosin ring contraction, while microtubule and intermediate filaments are depolymerized at early stages of apoptosis. However, recent results have shown that microtubules are reorganized during the execution phase of apoptosis forming an apoptotic microtubule network (AMN). Evidence suggests that AMN is required to maintain plasma membrane integrity and cell morphology during the execution phase of apoptosis. The new "two coffins" hypothesis proposes that both AMN and apoptotic cells can adopt two morphological patterns, round or irregular, which result from different cytoskeleton kinetic reorganization during the execution phase of apoptosis induced by genotoxic agents. In addition, round and irregular-shaped apoptosis showed different biological properties with respect to AMN maintenance, plasma membrane integrity and phagocyte responses. These findings suggest that knowing the type of apoptosis may be important to predict how fast apoptotic cells undergo secondary necrosis and the subsequent immune response. From a pathological point of view, round-shaped apoptosis can be seen as a physiological and controlled type of apoptosis, while irregular-shaped apoptosis can be considered as a pathological type of cell death closer to necrosis.

Dynamic Reorganization of the Cytoskeleton during Apoptosis: The Two Coffins Hypothesis

PubMed Central

Povea-Cabello, Suleva; Oropesa-Ávila, Manuel; de la Cruz-Ojeda, Patricia; Villanueva-Paz, Marina; de la Mata, Mario; Álvarez-Córdoba, Mónica; Villalón-García, Irene; Cotán, David; Ybot-González, Patricia

2017-01-01

During apoptosis, cells undergo characteristic morphological changes in which the cytoskeleton plays an active role. The cytoskeleton rearrangements have been mainly attributed to actinomyosin ring contraction, while microtubule and intermediate filaments are depolymerized at early stages of apoptosis. However, recent results have shown that microtubules are reorganized during the execution phase of apoptosis forming an apoptotic microtubule network (AMN). Evidence suggests that AMN is required to maintain plasma membrane integrity and cell morphology during the execution phase of apoptosis. The new “two coffins” hypothesis proposes that both AMN and apoptotic cells can adopt two morphological patterns, round or irregular, which result from different cytoskeleton kinetic reorganization during the execution phase of apoptosis induced by genotoxic agents. In addition, round and irregular-shaped apoptosis showed different biological properties with respect to AMN maintenance, plasma membrane integrity and phagocyte responses. These findings suggest that knowing the type of apoptosis may be important to predict how fast apoptotic cells undergo secondary necrosis and the subsequent immune response. From a pathological point of view, round-shaped apoptosis can be seen as a physiological and controlled type of apoptosis, while irregular-shaped apoptosis can be considered as a pathological type of cell death closer to necrosis. PMID:29137119

REM sleep respiratory behaviours mental content in narcoleptic lucid dreamers.

PubMed

Oudiette, Delphine; Dodet, Pauline; Ledard, Nahema; Artru, Emilie; Rachidi, Inès; Similowski, Thomas; Arnulf, Isabelle

2018-02-08

Breathing is irregular during rapid eye-movement (REM) sleep, whereas it is stable during non-REM sleep. Why this is so remains a mystery. We propose that irregular breathing has a cortical origin and reflects the mental content of dreams, which often accompany REM sleep. We tested 21 patients with narcolepsy who had the exceptional ability to lucid dream in REM sleep, a condition in which one is conscious of dreaming during the dream and can signal lucidity with an ocular code. Sleep and respiration were monitored during multiple naps. Participants were instructed to modify their dream scenario so that it involved vocalizations or an apnoea, -two behaviours that require a cortical control of ventilation when executed during wakefulness. Most participants (86%) were able to signal lucidity in at least one nap. In 50% of the lucid naps, we found a clear congruence between the dream report (e.g., diving under water) and the observed respiratory behaviour (e.g., central apnoea) and, in several cases, a preparatory breath before the respiratory behaviour. This suggests that the cortico-subcortical networks involved in voluntary respiratory movements are preserved during REM sleep and that breathing irregularities during this stage have a cortical/subcortical origin that reflects dream content.

Dual-band beacon experiment over Southeast Asia for ionospheric irregularity analysis

NASA Astrophysics Data System (ADS)

Watthanasangmechai, K.; Yamamoto, M.; Saito, A.; Saito, S.; Maruyama, T.; Tsugawa, T.; Nishioka, M.

2013-12-01

An experiment of dual-band beacon over Southeast Asia was started in March 2012 in order to capture and analyze ionospheric irregularities in equatorial region. Five GNU Radio Beacon Receivers (GRBRs) were aligned along 100 degree geographic longitude. The distances between the stations reach more than 500 km. The field of view of this observational network covers +/- 20 degree geomagnetic latitude including the geomagnetic equator. To capture ionospheric irregularities, the absolute TEC estimation technique was developed. The two-station method (Leitinger et al., 1975) is generally accepted as a suitable method to estimate TEC offsets of dual-band beacon experiment. However, the distances between the stations directly affect on the robustness of the technique. In Southeast Asia, the observational network is too sparse to attain a benefit of the classic two-station method. Moreover, the least-squares approch used in the two-station method tries too much to adjust the small scales of the TEC distribution which are the local minima. We thus propose a new technique to estimate the TEC offsets with the supporting data from absolute GPS-TEC from local GPS receivers and the ionospheric height from local ionosondes. The key of the proposed technique is to utilize the brute-force technique with weighting function to find the TEC offset set that yields a global minimum of RMSE in whole parameter space. The weight is not necessary when the TEC distribution is smooth, while it significantly improves the TEC estimation during the ESF events. As a result, the latitudinal TEC shows double-hump distribution because of the Equatorial Ionization Anomaly (EIA). In additions, the 100km-scale fluctuations from an Equatorial Spread F (ESF) are captured at night time in equinox seasons. The plausible linkage of the meridional wind with triggering of ESF is under invatigating and will be presented. The proposed method is successful to estimate the latitudinal TEC distribution from dual-band frequency beacon data for the sparse observational network in Southeast Asia which may be useful for other equatorial sectors like Affrican region as well.

Monitoring of ionospheric irregularities with multi-GNSS observations: a new ionosphere activity index and product services

NASA Astrophysics Data System (ADS)

Wang, Ningbo; Li, Zishen; Yuan, Yunbin; Yuan, Hong

2017-04-01

Key words: Ionospheric irregularity, Rate of TEC (ROT), Rate of ROT index (RROT), GPS and GLONASS The ionospheric irregularities have a strong impact on many applications of Global Navigation Satellite Systems (GNSS) and other space-based radio systems. The rate of ionospheric total electron content (TEC) change index (ROTI, TECu/min), defined as the standard deviation of rate of TEC change (ROT) within a short time (e.g. 5 minutes), has been developed to describe the ionospheric irregularities and associated scintillations. However, ROT parameter may still contain the trend term of ionospheric TEC in spite of small-scale fluctuations. On the basis of single-differenced ROT (dROT) values, we develop a new ionosphere activity index, rate of ROT change index (RROT, TECu/min), to characterize the irregularity degree of the ionosphere. To illustrate the use of the index, we investigated the consistency between ROTI and RROT indexes, through the analysis of GPS data and S4 observations collected at two high-latitude stations of the northern hemisphere. It is confirmed that the correlation coefficients between RROT and S4 are higher than those between ROTI and S4 for the test period, meaning that the proposed RROT index is applicable to monitor the ionospheric irregularities and associated scintillations. RROT index can be easily calculated from dual-frequency GNSS signals (like GPS L1 and L2 carrier phase measurements). On the basis of GPS and GLONASS data provided by the IGS, ARGN, EPN and USCORS tracking networks (more than 1500 stations per day), absolute ROT (AROT), gradient of TEC index (GOTI), ROTI and RROT maps are generated to reflect the ionospheric irregularity activities. These maps are provided in an IONEX-like format on a global scale with a temporal resolution of 15 minutes and a spatial resolution of 5 and 2.5 degrees in longitude and latitude, respectively, and the maps with high spatial resolution (2x2 degrees) are also generated for European, Australia and North American regions. The product files are produced on a daily basis with a latency of 3 days. Users now can access these products from the ftp archive of the Chinese Academy of Sciences (CAS, ftp://ftp.gipp.org.cn/product/). These maps can be used for ionospheric weather services, ionospheric irregularity modeling and foresting, as well as other GNSS applications. Although they are provided in a post-processing mode at present, it is expected that the near real-time services will be available since the availability of real-time data streams from the IGS.

RIACS

NASA Technical Reports Server (NTRS)

Oliger, Joseph

1997-01-01

Topics considered include: high-performance computing; cognitive and perceptual prostheses (computational aids designed to leverage human abilities); autonomous systems. Also included: development of a 3D unstructured grid code based on a finite volume formulation and applied to the Navier-stokes equations; Cartesian grid methods for complex geometry; multigrid methods for solving elliptic problems on unstructured grids; algebraic non-overlapping domain decomposition methods for compressible fluid flow problems on unstructured meshes; numerical methods for the compressible navier-stokes equations with application to aerodynamic flows; research in aerodynamic shape optimization; S-HARP: a parallel dynamic spectral partitioner; numerical schemes for the Hamilton-Jacobi and level set equations on triangulated domains; application of high-order shock capturing schemes to direct simulation of turbulence; multicast technology; network testbeds; supercomputer consolidation project.

Feminist Approaches to Triangulation: Uncovering Subjugated Knowledge and Fostering Social Change in Mixed Methods Research

ERIC Educational Resources Information Center

Hesse-Biber, Sharlene

2012-01-01

This article explores the deployment of triangulation in the service of uncovering subjugated knowledge and promoting social change for women and other oppressed groups. Feminist approaches to mixed methods praxis create a tight link between the research problem and the research design. An analysis of selected case studies of feminist praxis…

A Triangulation Method for Identifying Hydrostratigraphic Locations of Well Screens

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whiteside, T. S.

2015-01-31

A method to identify the hydrostratigraphic location of well screens was developed using triangulation with known locations. This method was applied to all of the monitor wells being used to develop the new GSA groundwater model. Results from this method are closely aligned with those from an alternate method which uses a mesh surface.

The Marginalized "Model" Minority: An Empirical Examination of the Racial Triangulation of Asian Americans

ERIC Educational Resources Information Center

Xu, Jun; Lee, Jennifer C.

2013-01-01

In this article, we propose a shift in race research from a one-dimensional hierarchical approach to a multidimensional system of racial stratification. Building upon Claire Kim's (1999) racial triangulation theory, we examine how the American public rates Asians relative to blacks and whites along two dimensions of racial stratification: racial…

Multi-Sensor Triangulation of Multi-Source Spatial Data

NASA Technical Reports Server (NTRS)

Habib, Ayman; Kim, Chang-Jae; Bang, Ki-In

2007-01-01

The introduced methodologies are successful in: a) Ising LIDAR features for photogrammetric geo-refererncing; b) Delivering a geo-referenced imagery of the same quality as point-based geo-referencing procedures; c) Taking advantage of the synergistic characteristics of spatial data acquisition systems. The triangulation output can be used for the generation of 3-D perspective views.

Making the Most of Obesity Research: Developing Research and Policy Objectives through Evidence Triangulation

ERIC Educational Resources Information Center

Oliver, Kathryn; Aicken, Catherine; Arai, Lisa

2013-01-01

Drawing lessons from research can help policy makers make better decisions. If a large and methodologically varied body of research exists, as with childhood obesity, this is challenging. We present new research and policy objectives for child obesity developed by triangulating user involvement data with a mapping study of interventions aimed at…

A Mixed Methods Approach to Understanding School Counseling Program Evaluation: High School Counselors' Methods and Perceptions

ERIC Educational Resources Information Center

Aucoin, Jennifer Mangrum

2013-01-01

The purpose of this mixed methods concurrent triangulation study was to examine the program evaluation practices of high school counselors. A total of 294 high school counselors in Texas were assessed using a mixed methods concurrent triangulation design. A researcher-developed survey, the School Counseling Program Evaluation Questionnaire…

An Array of Qualitative Data Analysis Tools: A Call for Data Analysis Triangulation

ERIC Educational Resources Information Center

Leech, Nancy L.; Onwuegbuzie, Anthony J.

2007-01-01

One of the most important steps in the qualitative research process is analysis of data. The purpose of this article is to provide elements for understanding multiple types of qualitative data analysis techniques available and the importance of utilizing more than one type of analysis, thus utilizing data analysis triangulation, in order to…

Hand-held triangulation laser profilometer with audio output for blind people Profilométre laser à triangulation tenu en main avec sortie sonare pour non-voyants

NASA Astrophysics Data System (ADS)

Farcy, R.; Damaschini, R.

1998-06-01

We describe a device currently under industrial development which will give to the blind a means of three-dimensional space perception. It consists of a 350 g hand-held triangulating laser telemeter including electronic parts and batteries, with auditory feedback either inside the apparatus or close to the ear. The microprocessor unit converts in real time the distance measured by the telemeter into a musical note. Scanning the space with an adequate movement of the hand produces musical lines corresponding to the profiles of the environment. We discuss the optical configuration of the system relative to our first year of clinical experimentation.

Discovery and problem solving: Triangulation as a weak heuristic

NASA Technical Reports Server (NTRS)

Rochowiak, Daniel

1987-01-01

Recently the artificial intelligence community has turned its attention to the process of discovery and found that the history of science is a fertile source for what Darden has called compiled hindsight. Such hindsight generates weak heuristics for discovery that do not guarantee that discoveries will be made but do have proven worth in leading to discoveries. Triangulation is one such heuristic that is grounded in historical hindsight. This heuristic is explored within the general framework of the BACON, GLAUBER, STAHL, DALTON, and SUTTON programs. In triangulation different bases of information are compared in an effort to identify gaps between the bases. Thus, assuming that the bases of information are relevantly related, the gaps that are identified should be good locations for discovery and robust analysis.

Paleoclimate networks: a concept meeting central challenges in the reconstruction of paleoclimate dynamics

NASA Astrophysics Data System (ADS)

Rehfeld, Kira; Goswami, Bedartha; Marwan, Norbert; Breitenbach, Sebastian; Kurths, Jürgen

2013-04-01

Statistical analysis of dependencies amongst paleoclimate data helps to infer on the climatic processes they reflect. Three key challenges have to be addressed, however: the datasets are heterogeneous in time (i) and space (ii), and furthermore time itself is a variable that needs to be reconstructed, which (iii) introduces additional uncertainties. To address these issues in a flexible way we developed the paleoclimate network framework, inspired by the increasing application of complex networks in climate research. Nodes in the paleoclimate network represent a paleoclimate archive, and an associated time series. Links between these nodes are assigned, if these time series are significantly similar. Therefore, the base of the paleoclimate network is formed by linear and nonlinear estimators for Pearson correlation, mutual information and event synchronization, which quantify similarity from irregularly sampled time series. Age uncertainties are propagated into the final network analysis using time series ensembles which reflect the uncertainty. We discuss how spatial heterogeneity influences the results obtained from network measures, and demonstrate the power of the approach by inferring teleconnection variability of the Asian summer monsoon for the past 1000 years.

Balanced excitation and inhibition are required for high-capacity, noise-robust neuronal selectivity

PubMed Central

Abbott, L. F.; Sompolinsky, Haim

2017-01-01

Neurons and networks in the cerebral cortex must operate reliably despite multiple sources of noise. To evaluate the impact of both input and output noise, we determine the robustness of single-neuron stimulus selective responses, as well as the robustness of attractor states of networks of neurons performing memory tasks. We find that robustness to output noise requires synaptic connections to be in a balanced regime in which excitation and inhibition are strong and largely cancel each other. We evaluate the conditions required for this regime to exist and determine the properties of networks operating within it. A plausible synaptic plasticity rule for learning that balances weight configurations is presented. Our theory predicts an optimal ratio of the number of excitatory and inhibitory synapses for maximizing the encoding capacity of balanced networks for given statistics of afferent activations. Previous work has shown that balanced networks amplify spatiotemporal variability and account for observed asynchronous irregular states. Here we present a distinct type of balanced network that amplifies small changes in the impinging signals and emerges automatically from learning to perform neuronal and network functions robustly. PMID:29042519

Fast global oscillations in networks of integrate-and-fire neurons with low firing rates.

PubMed

Brunel, N; Hakim, V

1999-10-01

We study analytically the dynamics of a network of sparsely connected inhibitory integrate-and-fire neurons in a regime where individual neurons emit spikes irregularly and at a low rate. In the limit when the number of neurons --> infinity, the network exhibits a sharp transition between a stationary and an oscillatory global activity regime where neurons are weakly synchronized. The activity becomes oscillatory when the inhibitory feedback is strong enough. The period of the global oscillation is found to be mainly controlled by synaptic times but depends also on the characteristics of the external input. In large but finite networks, the analysis shows that global oscillations of finite coherence time generically exist both above and below the critical inhibition threshold. Their characteristics are determined as functions of systems parameters in these two different regions. The results are found to be in good agreement with numerical simulations.

Multirate control with incomplete information over Profibus-DP network

NASA Astrophysics Data System (ADS)

Salt, J.; Casanova, V.; Cuenca, A.; Pizá, R.

2014-07-01

When a process field bus-decentralized peripherals (Profibus-DP) network is used in an industrial environment, a deterministic behaviour is usually claimed. However, due to some concerns such as bandwidth limitations, lack of synchronisation among different clocks and existence of time-varying delays, a more complex problem must be faced. This problem implies the transmission of irregular and, even, random sequences of incomplete information. The main consequence of this issue is the appearance of different sampling periods at different network devices. In this paper, this aspect is checked by means of a detailed Profibus-DP timescale study. In addition, in order to deal with the different periods, a delay-dependent dual-rate proportional-integral-derivative control is introduced. Stability for the proposed control system is analysed in terms of linear matrix inequalities.

Structural methodologies for auditing SNOMED.

PubMed

Wang, Yue; Halper, Michael; Min, Hua; Perl, Yehoshua; Chen, Yan; Spackman, Kent A

2007-10-01

SNOMED is one of the leading health care terminologies being used worldwide. As such, quality assurance is an important part of its maintenance cycle. Methodologies for auditing SNOMED based on structural aspects of its organization are presented. In particular, automated techniques for partitioning SNOMED into smaller groups of concepts based primarily on relationships patterns are defined. Two abstraction networks, the area taxonomy and p-area taxonomy, are derived from the partitions. The high-level views afforded by these abstraction networks form the basis for systematic auditing. The networks tend to highlight errors that manifest themselves as irregularities at the abstract level. They also support group-based auditing, where sets of purportedly similar concepts are focused on for review. The auditing methodologies are demonstrated on one of SNOMED's top-level hierarchies. Errors discovered during the auditing process are reported.

Improved laser-based triangulation sensor with enhanced range and resolution through adaptive optics-based active beam control.

PubMed

Reza, Syed Azer; Khwaja, Tariq Shamim; Mazhar, Mohsin Ali; Niazi, Haris Khan; Nawab, Rahma

2017-07-20

Various existing target ranging techniques are limited in terms of the dynamic range of operation and measurement resolution. These limitations arise as a result of a particular measurement methodology, the finite processing capability of the hardware components deployed within the sensor module, and the medium through which the target is viewed. Generally, improving the sensor range adversely affects its resolution and vice versa. Often, a distance sensor is designed for an optimal range/resolution setting depending on its intended application. Optical triangulation is broadly classified as a spatial-signal-processing-based ranging technique and measures target distance from the location of the reflected spot on a position sensitive detector (PSD). In most triangulation sensors that use lasers as a light source, beam divergence-which severely affects sensor measurement range-is often ignored in calculations. In this paper, we first discuss in detail the limitations to ranging imposed by beam divergence, which, in effect, sets the sensor dynamic range. Next, we show how the resolution of laser-based triangulation sensors is limited by the interpixel pitch of a finite-sized PSD. In this paper, through the use of tunable focus lenses (TFLs), we propose a novel design of a triangulation-based optical rangefinder that improves both the sensor resolution and its dynamic range through adaptive electronic control of beam propagation parameters. We present the theory and operation of the proposed sensor and clearly demonstrate a range and resolution improvement with the use of TFLs. Experimental results in support of our claims are shown to be in strong agreement with theory.

Public health triangulation: approach and application to synthesizing data to understand national and local HIV epidemics.

PubMed

Rutherford, George W; McFarland, William; Spindler, Hilary; White, Karen; Patel, Sadhna V; Aberle-Grasse, John; Sabin, Keith; Smith, Nathan; Taché, Stephanie; Calleja-Garcia, Jesus M; Stoneburner, Rand L

2010-07-29

Public health triangulation is a process for reviewing, synthesising and interpreting secondary data from multiple sources that bear on the same question to make public health decisions. It can be used to understand the dynamics of HIV transmission and to measure the impact of public health programs. While traditional intervention research and meta-analysis would be ideal sources of information for public health decision making, they are infrequently available, and often decisions can be based only on surveillance and survey data. The process involves examination of a wide variety of data sources and both biological, behavioral and program data and seeks input from stakeholders to formulate meaningful public health questions. Finally and most importantly, it uses the results to inform public health decision-making. There are 12 discrete steps in the triangulation process, which included identification and assessment of key questions, identification of data sources, refining questions, gathering data and reports, assessing the quality of those data and reports, formulating hypotheses to explain trends in the data, corroborating or refining working hypotheses, drawing conclusions, communicating results and recommendations and taking public health action. Triangulation can be limited by the quality of the original data, the potentials for ecological fallacy and "data dredging" and reproducibility of results. Nonetheless, we believe that public health triangulation allows for the interpretation of data sets that cannot be analyzed using meta-analysis and can be a helpful adjunct to surveillance, to formal public health intervention research and to monitoring and evaluation, which in turn lead to improved national strategic planning and resource allocation.

L1 Use in EFL Classes with English-Only Policy: Insights from Triangulated Data

ERIC Educational Resources Information Center

Sa'd, Seyyed Hatam Tamimi; Qadermazi, Zohre

2015-01-01

This study examines the role of the use of the L1 in EFL classes from the perspective of EFL learners. The triangulated data were collected using class observations, focus group semi-structured interviews and the learners' written reports of their perceptions and attitudes in a purpose-designed questionnaire. The participants consisted of sixty…

Academic Rigour, Managerial Relevance and Triangulation of Research Methods: A Perspective of Expectations Fulfilment in Postgraduate Education

ERIC Educational Resources Information Center

Hui, Loi Teck; Fatt, Quek Kia

2008-01-01

Developing high-quality human capital and advancing existing knowledge stocks are crucial for the competitive advantage of a nation. The authors argue that offering postgraduate programmes that give great emphasis to academic rigour, managerial relevance and the triangulation of research methods is vital if these ends are to be achieved. They…

Interprofessional collaboration from nurses and physicians – A triangulation of quantitative and qualitative data

PubMed

Schärli, Marianne; Müller, Rita; Martin, Jacqueline S; Spichiger, Elisabeth; Spirig, Rebecca

2017-01-01

Background: Interprofessional collaboration between nurses and physicians is a recurrent challenge in daily clinical practice. To ameliorate the situation, quantitative or qualitative studies are conducted. However, the results of these studies have often been limited by the methods chosen. Aim: To describe the synthesis of interprofessional collaboration from the nursing perspective by triangulating quantitative and qualitative data. Method: Data triangulation was performed as a sub-project of the interprofessional Sinergia DRG Research program. Initially, quantitative and qualitative data were analyzed separately in a mixed methods design. By means of triangulation a „meta-matrix“ resulted in a four-step process. Results: The „meta-matrix“ displays all relevant quantitative and qualitative results as well as their interrelations on one page. Relevance, influencing factors as well as consequences of interprofessional collaboration for patients, relatives and systems become visible. Conclusion: For the first time, the interprofessional collaboration from the nursing perspective at five Swiss hospitals is shown in a „meta-matrix“. The consequences of insufficient collaboration between nurses and physicians are considerable. This is why it’s necessary to invest in interprofessional concepts. In the „meta-matrix“ the factors which influence the interprofessional collaboration positively or negatively are visible.

Graph Frequency Analysis of Brain Signals

PubMed Central

Huang, Weiyu; Goldsberry, Leah; Wymbs, Nicholas F.; Grafton, Scott T.; Bassett, Danielle S.; Ribeiro, Alejandro

2016-01-01

This paper presents methods to analyze functional brain networks and signals from graph spectral perspectives. The notion of frequency and filters traditionally defined for signals supported on regular domains such as discrete time and image grids has been recently generalized to irregular graph domains, and defines brain graph frequencies associated with different levels of spatial smoothness across the brain regions. Brain network frequency also enables the decomposition of brain signals into pieces corresponding to smooth or rapid variations. We relate graph frequency with principal component analysis when the networks of interest denote functional connectivity. The methods are utilized to analyze brain networks and signals as subjects master a simple motor skill. We observe that brain signals corresponding to different graph frequencies exhibit different levels of adaptability throughout learning. Further, we notice a strong association between graph spectral properties of brain networks and the level of exposure to tasks performed, and recognize the most contributing and important frequency signatures at different levels of task familiarity. PMID:28439325

De novo design of protein homo-oligomers with modular hydrogen bond network-mediated specificity

PubMed Central

Boyken, Scott E.; Chen, Zibo; Groves, Benjamin; Langan, Robert A.; Oberdorfer, Gustav; Ford, Alex; Gilmore, Jason; Xu, Chunfu; DiMaio, Frank; Pereira, Jose Henrique; Sankaran, Banumathi; Seelig, Georg; Zwart, Peter H.; Baker, David

2017-01-01

In nature, structural specificity in DNA and proteins is encoded quite differently: in DNA, specificity arises from modular hydrogen bonds in the core of the double helix, whereas in proteins, specificity arises largely from buried hydrophobic packing complemented by irregular peripheral polar interactions. Here we describe a general approach for designing a wide range of protein homo-oligomers with specificity determined by modular arrays of central hydrogen bond networks. We use the approach to design dimers, trimers, and tetramers consisting of two concentric rings of helices, including previously not seen triangular, square, and supercoiled topologies. X-ray crystallography confirms that the structures overall, and the hydrogen bond networks in particular, are nearly identical to the design models, and the networks confer interaction specificity in vivo. The ability to design extensive hydrogen bond networks with atomic accuracy is a milestone for protein design and enables the programming of protein interaction specificity for a broad range of synthetic biology applications. PMID:27151862

Information in a Network of Neuronal Cells: Effect of Cell Density and Short-Term Depression

PubMed Central

Onesto, Valentina; Cosentino, Carlo; Di Fabrizio, Enzo; Cesarelli, Mario; Amato, Francesco; Gentile, Francesco

2016-01-01

Neurons are specialized, electrically excitable cells which use electrical to chemical signals to transmit and elaborate information. Understanding how the cooperation of a great many of neurons in a grid may modify and perhaps improve the information quality, in contrast to few neurons in isolation, is critical for the rational design of cell-materials interfaces for applications in regenerative medicine, tissue engineering, and personalized lab-on-a-chips. In the present paper, we couple an integrate-and-fire model with information theory variables to analyse the extent of information in a network of nerve cells. We provide an estimate of the information in the network in bits as a function of cell density and short-term depression time. In the model, neurons are connected through a Delaunay triangulation of not-intersecting edges; in doing so, the number of connecting synapses per neuron is approximately constant to reproduce the early time of network development in planar neural cell cultures. In simulations where the number of nodes is varied, we observe an optimal value of cell density for which information in the grid is maximized. In simulations in which the posttransmission latency time is varied, we observe that information increases as the latency time decreases and, for specific configurations of the grid, it is largely enhanced in a resonance effect. PMID:27403421

Fighting Networks: The Defining Challenge of Irregular Warfare

DTIC Science & Technology

2011-06-01

Terror on the Internet, describes the collection of this information as “data mining ,” and describes extensive research, information sharing using...suicide bombings. The first, a dramatically increased use of mines and IEDs, reflects both their ability to emplace such explosive devices stealthfully, as...well as the Russian reliance on more static positions supported by road arteries. The ‘ mine warfare’ employed by the Chechen fighters presented

Navy Irregular Warfare and Counterterrorism Operations: Background and Issues for Congress

DTIC Science & Technology

2016-05-27

ordnance disposal (counter- IED), combat construction engineering , cargo handling, combat logistics, maritime security, detainee operations, customs...Rutherford, “Navy’s Maritime Domain Awareness System ‘Up And Running’,” Defense Daily, September 4, 2008; and Dan Taylor , “New Network Allows Navy To...with twin diesel engines and water jets. It has a range of 600 nautical miles. 34 Other Organizational Initiatives Other Navy initiatives in recent

Leveraging U.S. Geo-Strategic Positional Advantage to Prevail in a Mercantile World

DTIC Science & Technology

2013-02-14

Underwater Acoustic Sensor Networks,” gravimetric analysis, as discussed in the American Scientist article , “Detecting Irregular Gravity,” and...Technology. Atlanta, GA: 21 January 2005. http://www.ece.gatech.edu/research/labs/bwn/surveys/underwater.pdf. American Scientist article . “Detecting... culture , and civil law and order. The challenge of implementing these adjustments, combined with other internal challenges, will relegate India to

The Israeli Approach to Irregular Warfare and Implications for the United States

DTIC Science & Technology

2007-02-01

JSOU Senior Fellow Alvaro de Souza Pinheiro Major General, Brazilian Army, Ret. JSOU Associate Fellow Kenneth H. Poole Colonel, U.S. Air Force, Ret...Educational Leadership JSOU Dean of Academics J. Paul de B. Taillon Ph.D., International Affairs Royal Military College of Canada and JSOU Associate...J. Paul de B. Taillon Operationalizing COIN, September 2005, Joseph D. Celeski Theoretical Perspectives of Terrorist Enemies as Networks, October

An Integrative Structural Health Monitoring System for the Local/Global Responses of a Large-Scale Irregular Building under Construction

PubMed Central

Park, Hyo Seon; Shin, Yunah; Choi, Se Woon; Kim, Yousok

2013-01-01

In this study, a practical and integrative SHM system was developed and applied to a large-scale irregular building under construction, where many challenging issues exist. In the proposed sensor network, customized energy-efficient wireless sensing units (sensor nodes, repeater nodes, and master nodes) were employed and comprehensive communications from the sensor node to the remote monitoring server were conducted through wireless communications. The long-term (13-month) monitoring results recorded from a large number of sensors (75 vibrating wire strain gauges, 10 inclinometers, and three laser displacement sensors) indicated that the construction event exhibiting the largest influence on structural behavior was the removal of bents that were temporarily installed to support the free end of the cantilevered members during their construction. The safety of each member could be confirmed based on the quantitative evaluation of each response. Furthermore, it was also confirmed that the relation between these responses (i.e., deflection, strain, and inclination) can provide information about the global behavior of structures induced from specific events. Analysis of the measurement results demonstrates the proposed sensor network system is capable of automatic and real-time monitoring and can be applied and utilized for both the safety evaluation and precise implementation of buildings under construction. PMID:23860317

Pragmatic estimation of a spatio-temporal air quality model with irregular monitoring data

NASA Astrophysics Data System (ADS)

Sampson, Paul D.; Szpiro, Adam A.; Sheppard, Lianne; Lindström, Johan; Kaufman, Joel D.

2011-11-01

Statistical analyses of health effects of air pollution have increasingly used GIS-based covariates for prediction of ambient air quality in "land use" regression models. More recently these spatial regression models have accounted for spatial correlation structure in combining monitoring data with land use covariates. We present a flexible spatio-temporal modeling framework and pragmatic, multi-step estimation procedure that accommodates essentially arbitrary patterns of missing data with respect to an ideally complete space by time matrix of observations on a network of monitoring sites. The methodology incorporates a model for smooth temporal trends with coefficients varying in space according to Partial Least Squares regressions on a large set of geographic covariates and nonstationary modeling of spatio-temporal residuals from these regressions. This work was developed to provide spatial point predictions of PM 2.5 concentrations for the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air) using irregular monitoring data derived from the AQS regulatory monitoring network and supplemental short-time scale monitoring campaigns conducted to better predict intra-urban variation in air quality. We demonstrate the interpretation and accuracy of this methodology in modeling data from 2000 through 2006 in six U.S. metropolitan areas and establish a basis for likelihood-based estimation.

Sporadic frame dropping impact on quality perception

NASA Astrophysics Data System (ADS)

Pastrana-Vidal, Ricardo R.; Gicquel, Jean Charles; Colomes, Catherine; Cherifi, Hocine

2004-06-01

Over the past few years there has been an increasing interest in real time video services over packet networks. When considering quality, it is essential to quantify user perception of the received sequence. Severe motion discontinuities are one of the most common degradations in video streaming. The end-user perceives a jerky motion when the discontinuities are uniformly distributed over time and an instantaneous fluidity break is perceived when the motion loss is isolated or irregularly distributed. Bit rate adaptation techniques, transmission errors in the packet networks or restitution strategy could be the origin of this perceived jerkiness. In this paper we present a psychovisual experiment performed to quantify the effect of sporadically dropped pictures on the overall perceived quality. First, the perceptual detection thresholds of generated temporal discontinuities were measured. Then, the quality function was estimated in relation to a single frame dropping for different durations. Finally, a set of tests was performed to quantify the effect of several impairments distributed over time. We have found that the detection thresholds are content, duration and motion dependent. The assessment results show how quality is impaired by a single burst of dropped frames in a 10 sec sequence. The effect of several bursts of discarded frames, irregularly distributed over the time is also discussed.

Quality Tetrahedral Mesh Smoothing via Boundary-Optimized Delaunay Triangulation

PubMed Central

Gao, Zhanheng; Yu, Zeyun; Holst, Michael

2012-01-01

Despite its great success in improving the quality of a tetrahedral mesh, the original optimal Delaunay triangulation (ODT) is designed to move only inner vertices and thus cannot handle input meshes containing “bad” triangles on boundaries. In the current work, we present an integrated approach called boundary-optimized Delaunay triangulation (B-ODT) to smooth (improve) a tetrahedral mesh. In our method, both inner and boundary vertices are repositioned by analytically minimizing the error between a paraboloid function and its piecewise linear interpolation over the neighborhood of each vertex. In addition to the guaranteed volume-preserving property, the proposed algorithm can be readily adapted to preserve sharp features in the original mesh. A number of experiments are included to demonstrate the performance of our method. PMID:23144522

Ichnology of an upper carboniferous fluvio-estuarine paleovalley: The tonganoxie sandstone, buildex quarry, eastern Kansas, USA

USGS Publications Warehouse

Buatois, L.A.; Mangano, M.G.; Maples, C.G.; Lanier, Wendy E.

1998-01-01

Tidal rhythmites of the Tonganoxie Sandstone Member (Stranger Formation, Douglas Group) at Buildex Quarry, eastern Kansas, contain a relatively diverse ichnofauna. The assemblage includes arthropod locomotion (Dendroidichnites irregulare, Diplichnites gouldi type A and B, Diplopodichnus biformis, Kouphichnium isp., Mirandaichnium famatinense, and Stiaria intermedia), resting (Tonganoxichnus buildexensis) and feeding traces (Stiallia pilosa, Tonganoxichnus ottawensis); grazing traces (Gordia indianaensis, Helminthoidichnites tenuis, Helminthopsis hieroglyphica); feeding structures (Circulichnis montanus, Treptichnus bifurcus, Treptichnus pollardi, irregular networks), fish traces (Undichna britannica, Undichna simplicitas), tetrapod trackways, and root traces. The taxonomy of some of these ichnotaxa is briefly reviewed and emended diagnoses for Gordia indianaensis and Helminthoidichnites tenuis are proposed. Additionally, the combined name Dendroidichnites irregulare is proposed for nested chevron trackways. Traces previously regarded as produced by isopods are reinterpreted as myriapod trackways (D. gouldi type B). Trackways formerly interpreted as limulid crawling and swimming traces are assigned herein to Kouphichnium isp and Dendroidichnites irregulare, respectively. Taphonomic analysis suggests that most grazing and feeding traces were formed before the arthropod trackways and resting traces. Grazing/feeding traces were formed in a soft, probably submerged substrate. Conversely, the majority of trackways and resting traces probably were produced subaerially in a firmer, dewatered and desiccated sediment. The Buildex Quarry ichnofauna records the activity of a terrestrial and freshwater biota. The presence of this assemblage in tidal rhythmites is consistent with deposition on tidal flats in the most proximal zone of the inner estuary, between the maximum landward limit of tidal currents and the salinity limit further towards the sea.

Social and Emotional Learning Competencies and Cross-Thematic Curriculum-Related Skills of Greek Students: A Multifactorial and Triangulation Analysis

ERIC Educational Resources Information Center

Tsolou, Olympia; Margaritis, Vasileios

2013-01-01

The cross-thematic curriculum (CTC) for school education has recently been implemented so that the quality of the Greek educational system is improved. This study aimed at assessing social and emotional learning competencies and CTC-related skills of 541 Greek students aged 11-13. Data triangulation was also used for validating these findings,…

Keys to Successful Implementation and Sustainment of Managed Maintenance for Healthcare Facilities

DTIC Science & Technology

2004-03-23

second they involve studying those phenomena in all their complexity (Leedy and Ormrod, 2001). According to Denzin and Lincoln (1994), qualitative...people being studied (Leedy and Ormrod, 2001). Research Design Methodological Triangulation Denzin and Lincoln (1994) suggest because different...the setting. This dual view is refereed to as methodological triangulation ( Denzin and Lincoln , 1994). A research design develops a logical plan for

Using the virtual brain to reveal the role of oscillations and plasticity in shaping brain's dynamical landscape.

PubMed

Roy, Dipanjan; Sigala, Rodrigo; Breakspear, Michael; McIntosh, Anthony Randal; Jirsa, Viktor K; Deco, Gustavo; Ritter, Petra

2014-12-01

Spontaneous brain activity, that is, activity in the absence of controlled stimulus input or an explicit active task, is topologically organized in multiple functional networks (FNs) maintaining a high degree of coherence. These "resting state networks" are constrained by the underlying anatomical connectivity between brain areas. They are also influenced by the history of task-related activation. The precise rules that link plastic changes and ongoing dynamics of resting-state functional connectivity (rs-FC) remain unclear. Using the framework of the open source neuroinformatics platform "The Virtual Brain," we identify potential computational mechanisms that alter the dynamical landscape, leading to reconfigurations of FNs. Using a spiking neuron model, we first demonstrate that network activity in the absence of plasticity is characterized by irregular oscillations between low-amplitude asynchronous states and high-amplitude synchronous states. We then demonstrate the capability of spike-timing-dependent plasticity (STDP) combined with intrinsic alpha (8-12 Hz) oscillations to efficiently influence learning. Further, we show how alpha-state-dependent STDP alters the local area dynamics from an irregular to a highly periodic alpha-like state. This is an important finding, as the cortical input from the thalamus is at the rate of alpha. We demonstrate how resulting rhythmic cortical output in this frequency range acts as a neuronal tuner and, hence, leads to synchronization or de-synchronization between brain areas. Finally, we demonstrate that locally restricted structural connectivity changes influence local as well as global dynamics and lead to altered rs-FC.

Distribution of Orientation Selectivity in Recurrent Networks of Spiking Neurons with Different Random Topologies

PubMed Central

Sadeh, Sadra; Rotter, Stefan

2014-01-01

Neurons in the primary visual cortex are more or less selective for the orientation of a light bar used for stimulation. A broad distribution of individual grades of orientation selectivity has in fact been reported in all species. A possible reason for emergence of broad distributions is the recurrent network within which the stimulus is being processed. Here we compute the distribution of orientation selectivity in randomly connected model networks that are equipped with different spatial patterns of connectivity. We show that, for a wide variety of connectivity patterns, a linear theory based on firing rates accurately approximates the outcome of direct numerical simulations of networks of spiking neurons. Distance dependent connectivity in networks with a more biologically realistic structure does not compromise our linear analysis, as long as the linearized dynamics, and hence the uniform asynchronous irregular activity state, remain stable. We conclude that linear mechanisms of stimulus processing are indeed responsible for the emergence of orientation selectivity and its distribution in recurrent networks with functionally heterogeneous synaptic connectivity. PMID:25469704

Application of small-size antennas for estimation of angles of arrival of HF signals scattered by ionospheric irregularities

NASA Astrophysics Data System (ADS)

Guo, Qiang; Galushko, Volodymyr G.; Zalizovski, Andriy V.; Kashcheyev, Sergiy B.; Zheng, Yu

2018-05-01

A modification of the Doppler Interferometry Technique is suggested to enable estimating angles of arrival of comparatively broadband HF signals scattered by random irregularities of the ionospheric plasma with the use of small-size weakly directional antennas. The technique is based on the measurements of cross-spectra phases of the probe radiation recorded at least in three spatially separated points. The developed algorithm has been used to investigate the angular and frequency-time characteristics of HF signals propagating at frequencies above the maximum usable one (MUF) for the direct radio path Moscow-Kharkiv. The received signal spectra show presence of three families of spatial components attributed, respectively, to scattering by plasma irregularities near the middle point of the radio path, ground backscatter signals and scattering of the sounding signals by the intense plasma turbulence associated with auroral activations. It has been shown that the regions responsible for the formation of the third family components are located well inside the auroral oval. The drift velocity and direction of the auroral ionosphere plasma have been determined. The obtained estimates are consistent with the classical conception of the ionospheric plasma convection at high latitudes and do not contradict the results of investigations of the auroral ionosphere dynamics using the SuperDARN network.

The Holst spin foam model via cubulations

NASA Astrophysics Data System (ADS)

Baratin, Aristide; Flori, Cecilia; Thiemann, Thomas

2012-10-01

Spin foam models are an attempt at a covariant or path integral formulation of canonical loop quantum gravity. The construction of such models usually relies on the Plebanski formulation of general relativity as a constrained BF theory and is based on the discretization of the action on a simplicial triangulation, which may be viewed as an ultraviolet regulator. The triangulation dependence can be removed by means of group field theory techniques, which allows one to sum over all triangulations. The main tasks for these models are the correct quantum implementation of the Plebanski constraints, the existence of a semiclassical sector implementing additional ‘Regge-like’ constraints arising from simplicial triangulations and the definition of the physical inner product of loop quantum gravity via group field theory. Here we propose a new approach to tackle these issues stemming directly from the Holst action for general relativity, which is also a proper starting point for canonical loop quantum gravity. The discretization is performed by means of a ‘cubulation’ of the manifold rather than a triangulation. We give a direct interpretation of the resulting spin foam model as a generating functional for the n-point functions on the physical Hilbert space at finite regulator. This paper focuses on ideas and tasks to be performed before the model can be taken seriously. However, our analysis reveals some interesting features of this model: firstly, the structure of its amplitudes differs from the standard spin foam models. Secondly, the tetrad n-point functions admit a ‘Wick-like’ structure. Thirdly, the restriction to simple representations does not automatically occur—unless one makes use of the time gauge, just as in the classical theory.

Do academic knowledge brokers exist? Using social network analysis to explore academic research-to-policy networks from six schools of public health in Kenya

PubMed Central

Jessani, Nasreen S; Boulay, Marc G; Bennett, Sara C

2016-01-01

The potential for academic research institutions to facilitate knowledge exchange and influence evidence-informed decision-making has been gaining ground. Schools of public health (SPHs) may play a key knowledge brokering role—serving as agencies of and for development. Understanding academic-policymaker networks can facilitate the enhancement of links between policymakers and academic faculty at SPHs, as well as assist in identifying academic knowledge brokers (KBs). Using a census approach, we administered a sociometric survey to academic faculty across six SPHs in Kenya to construct academic-policymaker networks. We identified academic KBs using social network analysis (SNA) in a two-step approach: First, we ranked individuals based on (1) number of policymakers in their network; (2) number of academic peers who report seeking them out for advice on knowledge translation and (3) their network position as ‘inter-group connectors’. Second, we triangulated the three scores and re-ranked individuals. Academic faculty scoring within the top decile across all three measures were classified as KBs. Results indicate that each SPH commands a variety of unique as well as overlapping relationships with national ministries in Kenya. Of 124 full-time faculty, we identified 7 KBs in 4 of the 6 SPHs. Those scoring high on the first measure were not necessarily the same individuals scoring high on the second. KBs were also situated in a wide range along the ‘connector/betweenness’ measure. We propose that a composite score rather than traditional ‘betweenness centrality’, provides an alternative means of identifying KBs within these networks. In conclusion, SNA is a valuable tool for identifying academic-policymaker networks in Kenya. More efforts to conduct similar network studies would permit SPH leadership to identify existing linkages between faculty and policymakers, shared linkages with other SPHs and gaps so as to contribute to evidence-informed health policies. PMID:26537610

Towards a phase diagram for spin foams

NASA Astrophysics Data System (ADS)

Delcamp, Clement; Dittrich, Bianca

2017-11-01

One of the most pressing issues for loop quantum gravity and spin foams is the construction of the continuum limit. In this paper, we propose a systematic coarse-graining scheme for three-dimensional lattice gauge models including spin foams. This scheme is based on the concept of decorated tensor networks, which have been introduced recently. Here we develop an algorithm applicable to gauge theories with non-Abelian groups, which for the first time allows for the application of tensor network coarse-graining techniques to proper spin foams. The procedure deals efficiently with the large redundancy of degrees of freedom resulting from gauge invariance. The algorithm is applied to 3D spin foams defined on a cubical lattice which, in contrast to a proper triangulation, allows for non-trivial simplicity constraints. This mimics the construction of spin foams for 4D gravity. For lattice gauge models based on a finite group we use the algorithm to obtain phase diagrams, encoding the continuum limit of a wide range of these models. We find phase transitions for various families of models carrying non-trivial simplicity constraints.

Plate motions and deformations from geologic and geodetic data

NASA Technical Reports Server (NTRS)

Jordan, Thomas H.

1989-01-01

The very long baseline interferometry (VLBI) measurements made in the western U.S. since 1979 provide discrete samples of the temporal and spatial deformation field. The interpretation of the VLBI derived rates of deformation requires an examination of geologic information and more densely sampled ground based geodetic data. Triangulation and trilateration data measured on two regional networks, one in the central Mojave Desert and one in the Coast Ranges east of the San Andreas fault, were processed. At the spatial scales spanned by these local geodetic networks, auxiliary geologic and geophysical data were utilized to examine the relation between measured incremental strain and the accommodation of strain seen in local geologic structures, strain release in earthquakes, and principal stress directions inferred from in situ measurements. VLBI data was also processed from stations distributed across the Pacific-North America plate boundary zone in the western U.S. The VLBI data were used to constrain the integrated rate of deformation across portions of the continental plate boundary in California and to provide a tectonic framework to interpret regional geodetic and geologic studies.

Emergent Oscillations in Networks of Stochastic Spiking Neurons

PubMed Central

van Drongelen, Wim; Cowan, Jack D.

2011-01-01

Networks of neurons produce diverse patterns of oscillations, arising from the network's global properties, the propensity of individual neurons to oscillate, or a mixture of the two. Here we describe noisy limit cycles and quasi-cycles, two related mechanisms underlying emergent oscillations in neuronal networks whose individual components, stochastic spiking neurons, do not themselves oscillate. Both mechanisms are shown to produce gamma band oscillations at the population level while individual neurons fire at a rate much lower than the population frequency. Spike trains in a network undergoing noisy limit cycles display a preferred period which is not found in the case of quasi-cycles, due to the even faster decay of phase information in quasi-cycles. These oscillations persist in sparsely connected networks, and variation of the network's connectivity results in variation of the oscillation frequency. A network of such neurons behaves as a stochastic perturbation of the deterministic Wilson-Cowan equations, and the network undergoes noisy limit cycles or quasi-cycles depending on whether these have limit cycles or a weakly stable focus. These mechanisms provide a new perspective on the emergence of rhythmic firing in neural networks, showing the coexistence of population-level oscillations with very irregular individual spike trains in a simple and general framework. PMID:21573105

The success of the Uttarakhand Cluster: a case study of organisational change towards disability inclusive development.

PubMed

Grills, Nathan; Varghese, Jubin; Hughes, Nicole; Jolly, Tamara; Kumar, Robert

2016-08-02

Persons with disability are often marginalised and excluded from international development efforts. This case study reviews the success of Uttarakhand Cluster of development NGOs in changing organisational behaviour towards being disability inclusive in their development (DID) activities. A triangulation of qualitative research methods was used, including key informant interviews, focus group discussions and review of textual data. The results synthesise data into Kotter's framework for organisational change, explaining the different stages of change experienced by the Cluster as it moved towards DID. Development of a disability mission, sharing of capacity and resources, and presence of disability champions were key in the organisations' transition towards DID. This case study demonstrates that the Cluster, a low - cost network, was able to drive organisational change and promote DID.

Derivation of formulas for root-mean-square errors in location, orientation, and shape in triangulation solution of an elongated object in space

NASA Technical Reports Server (NTRS)

Long, S. A. T.

1974-01-01

Formulas are derived for the root-mean-square (rms) displacement, slope, and curvature errors in an azimuth-elevation image trace of an elongated object in space, as functions of the number and spacing of the input data points and the rms elevation error in the individual input data points from a single observation station. Also, formulas are derived for the total rms displacement, slope, and curvature error vectors in the triangulation solution of an elongated object in space due to the rms displacement, slope, and curvature errors, respectively, in the azimuth-elevation image traces from different observation stations. The total rms displacement, slope, and curvature error vectors provide useful measure numbers for determining the relative merits of two or more different triangulation procedures applicable to elongated objects in space.

Automated detection and localization of bowhead whale sounds in the presence of seismic airgun surveys.

PubMed

Thode, Aaron M; Kim, Katherine H; Blackwell, Susanna B; Greene, Charles R; Nations, Christopher S; McDonald, Trent L; Macrander, A Michael

2012-05-01

An automated procedure has been developed for detecting and localizing frequency-modulated bowhead whale sounds in the presence of seismic airgun surveys. The procedure was applied to four years of data, collected from over 30 directional autonomous recording packages deployed over a 280 km span of continental shelf in the Alaskan Beaufort Sea. The procedure has six sequential stages that begin by extracting 25-element feature vectors from spectrograms of potential call candidates. Two cascaded neural networks then classify some feature vectors as bowhead calls, and the procedure then matches calls between recorders to triangulate locations. To train the networks, manual analysts flagged 219 471 bowhead call examples from 2008 and 2009. Manual analyses were also used to identify 1.17 million transient signals that were not whale calls. The network output thresholds were adjusted to reject 20% of whale calls in the training data. Validation runs using 2007 and 2010 data found that the procedure missed 30%-40% of manually detected calls. Furthermore, 20%-40% of the sounds flagged as calls are not present in the manual analyses; however, these extra detections incorporate legitimate whale calls overlooked by human analysts. Both manual and automated methods produce similar spatial and temporal call distributions.

Unconventional Counterinsurgency: Leveraging Traditional Social Networks and Irregular Forces in Remote and Ungoverned Areas

DTIC Science & Technology

2010-05-13

Identity: Why We Are Losing Our Wars”, Michael Vlahos argues that today’s wars with non-state enemies are “above all, wars of identity.”29 Moreover, he...together these manuals powerfully reinforce Michael Vlahos ’ imperative to reshape the population and enemy narrative by co-opting identity.34...29 Michael Vlahos , "Fighting Identity: Why We Are Losing Our Wars," Military Review (United States

Accuracy of an acoustic location system for monitoring the position of duetting songbirds in tropical forest

PubMed Central

Mennill, Daniel J.; Burt, John M.; Fristrup, Kurt M.; Vehrencamp, Sandra L.

2008-01-01

A field test was conducted on the accuracy of an eight-microphone acoustic location system designed to triangulate the position of duetting rufous-and-white wrens (Thryothorus rufalbus) in Costa Rica’s humid evergreen forest. Eight microphones were set up in the breeding territories of twenty pairs of wrens, with an average inter-microphone distance of 75.2±2.6 m. The array of microphones was used to record antiphonal duets broadcast through stereo loudspeakers. The positions of the loudspeakers were then estimated by evaluating the delay with which the eight microphones recorded the broadcast sounds. Position estimates were compared to coordinates surveyed with a global-positioning system (GPS). The acoustic location system estimated the position of loudspeakers with an error of 2.82±0.26 m and calculated the distance between the “male” and “female” loudspeakers with an error of 2.12±0.42 m. Given the large range of distances between duetting birds, this relatively low level of error demonstrates that the acoustic location system is a useful tool for studying avian duets. Location error was influenced partly by the difficulties inherent in collecting high accuracy GPS coordinates of microphone positions underneath a lush tropical canopy, and partly by the complicating influence of irregular topography and thick vegetation on sound transmission. PMID:16708941

Evidence for asymptotic safety from lattice quantum gravity.

PubMed

Laiho, J; Coumbe, D

2011-10-14

We calculate the spectral dimension for nonperturbative quantum gravity defined via Euclidean dynamical triangulations. We find that it runs from a value of ∼3/2 at short distance to ∼4 at large distance scales, similar to results from causal dynamical triangulations. We argue that the short-distance value of 3/2 for the spectral dimension may resolve the tension between asymptotic safety and the holographic principle.

Triangulation of written assessments from patients, teachers and students: useful for students and teachers?

PubMed

Gran, Sarah Frandsen; Braend, Anja Maria; Lindbaek, Morten

2010-01-01

Many medical students in general practice clerkships experience lack of observation-based feedback. The StudentPEP project combined written feedback from patients, observing teachers and students. This study analyzes the perceived usefulness of triangulated written feedback. A total of 71 general practitioners and 79 medical students at the University of Oslo completed project evaluation forms after a 6-week clerkship. A principal component analysis was performed to find structures within the questionnaire. Regression analysis was performed regarding students' answers to whether StudentPEP was worthwhile. Free-text answers were analyzed qualitatively. Student and teacher responses were mixed within six subscales, with highest agreement on 'Teachers oral and written feedback' and 'Attitude to patient evaluation'. Fifty-four per cent of the students agreed that the triangulation gave concrete feedback on their weaknesses, and 59% valued the teachers' feedback provided. Two statements regarding the teacher's attitudes towards StudentPEP were significantly associated with the student's perception of worthwhileness. Qualitative analysis showed that patient evaluations were encouraging or distrusted. Some students thought that StudentPEP ensured observation and feedback. The patient evaluations increased the students' awareness of the patient perspective. A majority of the students considered the triangulated written feedback beneficial, although time-consuming. The teacher's attitudes strongly influenced how the students perceived the usefulness of StudentPEP.

Shared decision-making in medical encounters regarding breast cancer treatment: the contribution of methodological triangulation.

PubMed

Durif-Bruckert, C; Roux, P; Morelle, M; Mignotte, H; Faure, C; Moumjid-Ferdjaoui, N

2015-07-01

The aim of this study on shared decision-making in the doctor-patient encounter about surgical treatment for early-stage breast cancer, conducted in a regional cancer centre in France, was to further the understanding of patient perceptions on shared decision-making. The study used methodological triangulation to collect data (both quantitative and qualitative) about patient preferences in the context of a clinical consultation in which surgeons followed a shared decision-making protocol. Data were analysed from a multi-disciplinary research perspective (social psychology and health economics). The triangulated data collection methods were questionnaires (n = 132), longitudinal interviews (n = 47) and observations of consultations (n = 26). Methodological triangulation revealed levels of divergence and complementarity between qualitative and quantitative results that suggest new perspectives on the three inter-related notions of decision-making, participation and information. Patients' responses revealed important differences between shared decision-making and participation per se. The authors note that subjecting patients to a normative behavioural model of shared decision-making in an era when paradigms of medical authority are shifting may undermine the patient's quest for what he or she believes is a more important right: a guarantee of the best care available. © 2014 John Wiley & Sons Ltd.

Recursive inverse factorization.

PubMed

Rubensson, Emanuel H; Bock, Nicolas; Holmström, Erik; Niklasson, Anders M N

2008-03-14

A recursive algorithm for the inverse factorization S(-1)=ZZ(*) of Hermitian positive definite matrices S is proposed. The inverse factorization is based on iterative refinement [A.M.N. Niklasson, Phys. Rev. B 70, 193102 (2004)] combined with a recursive decomposition of S. As the computational kernel is matrix-matrix multiplication, the algorithm can be parallelized and the computational effort increases linearly with system size for systems with sufficiently sparse matrices. Recent advances in network theory are used to find appropriate recursive decompositions. We show that optimization of the so-called network modularity results in an improved partitioning compared to other approaches. In particular, when the recursive inverse factorization is applied to overlap matrices of irregularly structured three-dimensional molecules.

Scaling Properties of Dimensionality Reduction for Neural Populations and Network Models

PubMed Central

Cowley, Benjamin R.; Doiron, Brent; Kohn, Adam

2016-01-01

Recent studies have applied dimensionality reduction methods to understand how the multi-dimensional structure of neural population activity gives rise to brain function. It is unclear, however, how the results obtained from dimensionality reduction generalize to recordings with larger numbers of neurons and trials or how these results relate to the underlying network structure. We address these questions by applying factor analysis to recordings in the visual cortex of non-human primates and to spiking network models that self-generate irregular activity through a balance of excitation and inhibition. We compared the scaling trends of two key outputs of dimensionality reduction—shared dimensionality and percent shared variance—with neuron and trial count. We found that the scaling properties of networks with non-clustered and clustered connectivity differed, and that the in vivo recordings were more consistent with the clustered network. Furthermore, recordings from tens of neurons were sufficient to identify the dominant modes of shared variability that generalize to larger portions of the network. These findings can help guide the interpretation of dimensionality reduction outputs in regimes of limited neuron and trial sampling and help relate these outputs to the underlying network structure. PMID:27926936

Parallel Processing and Scientific Applications

DTIC Science & Technology

1992-11-30

Lattice QCD Calculations on the Connection Machine), SIAM News 24, 1 (May 1991) 5. C. F. Baillie and D. A. Johnston, Crumpling Dynamically Triangulated...hypercubic lattice ; in the second, the surface is randomly triangulated once at the beginning of the simulation; and in the third the random...Sharpe, QCD with Dynamical Wilson Fermions 1I, Phys. Rev. D44, 3272 (1991), 8. R. Gupta and C. F. Baillie, Critical Behavior of the 2D XY Model, Phys

Three-dimensional unstructured grid refinement and optimization using edge-swapping

NASA Technical Reports Server (NTRS)

Gandhi, Amar; Barth, Timothy

1993-01-01

This paper presents a three-dimensional (3-D) 'edge-swapping method based on local transformations. This method extends Lawson's edge-swapping algorithm into 3-D. The 3-D edge-swapping algorithm is employed for the purpose of refining and optimizing unstructured meshes according to arbitrary mesh-quality measures. Several criteria including Delaunay triangulations are examined. Extensions from two to three dimensions of several known properties of Delaunay triangulations are also discussed.

Personal authentication using hand vein triangulation and knuckle shape.

PubMed

Kumar, Ajay; Prathyusha, K Venkata

2009-09-01

This paper presents a new approach to authenticate individuals using triangulation of hand vein images and simultaneous extraction of knuckle shape information. The proposed method is fully automated and employs palm dorsal hand vein images acquired from the low-cost, near infrared, contactless imaging. The knuckle tips are used as key points for the image normalization and extraction of region of interest. The matching scores are generated in two parallel stages: (i) hierarchical matching score from the four topologies of triangulation in the binarized vein structures and (ii) from the geometrical features consisting of knuckle point perimeter distances in the acquired images. The weighted score level combination from these two matching scores are used to authenticate the individuals. The achieved experimental results from the proposed system using contactless palm dorsal-hand vein images are promising (equal error rate of 1.14%) and suggest more user friendly alternative for user identification.

Application of Stereo Vision to the Reconnection Scaling Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klarenbeek, Johnny; Sears, Jason A.; Gao, Kevin W.

The measurement and simulation of the three-dimensional structure of magnetic reconnection in astrophysical and lab plasmas is a challenging problem. At Los Alamos National Laboratory we use the Reconnection Scaling Experiment (RSX) to model 3D magnetohydrodynamic (MHD) relaxation of plasma filled tubes. These magnetic flux tubes are called flux ropes. In RSX, the 3D structure of the flux ropes is explored with insertable probes. Stereo triangulation can be used to compute the 3D position of a probe from point correspondences in images from two calibrated cameras. While common applications of stereo triangulation include 3D scene reconstruction and robotics navigation, wemore » will investigate the novel application of stereo triangulation in plasma physics to aid reconstruction of 3D data for RSX plasmas. Several challenges will be explored and addressed, such as minimizing 3D reconstruction errors in stereo camera systems and dealing with point correspondence problems.« less

Interactive Display of Surfaces Using Subdivision Surfaces and Wavelets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duchaineau, M A; Bertram, M; Porumbescu, S

2001-10-03

Complex surfaces and solids are produced by large-scale modeling and simulation activities in a variety of disciplines. Productive interaction with these simulations requires that these surfaces or solids be viewable at interactive rates--yet many of these surfaced solids can contain hundreds of millions of polygondpolyhedra. Interactive display of these objects requires compression techniques to minimize storage, and fast view-dependent triangulation techniques to drive the graphics hardware. In this paper, we review recent advances in subdivision-surface wavelet compression and optimization that can be used to provide a framework for both compression and triangulation. These techniques can be used to produce suitablemore » approximations of complex surfaces of arbitrary topology, and can be used to determine suitable triangulations for display. The techniques can be used in a variety of applications in computer graphics, computer animation and visualization.« less

Mechanism of cross-sectoral coordination between nature protection and forestry in the Natura 2000 formulation process in Slovakia.

PubMed

Sarvašová, Zuzana; Sálka, Jaroslav; Dobšinská, Zuzana

2013-09-01

Nature protection as a policy sector is not isolated and is directly or indirectly influenced by many other sectors (e.g. forestry, water management, rural development, energy, etc.). These policy sectors are neither completely segmented nor unaffected by the decisions taken in other policy sectors. Policy formulation in nature protection is therefore also influenced by different sectors. For that reason it is inevitable to stress the need for inter-sectoral coordination to assure their policy coherence. The aim of this article is to describe the mechanism and modes of cross-sectoral coordination and to analyze the relevant actors and their interaction, using the case of the Natura 2000 formulation process in Slovakia. The European Union (EU) set up an ecological network of special protected areas, known as Natura 2000 to ensure biodiversity by conserving natural habitats and wild fauna and flora in the territory of the Member States. An optimized nature protection must therefore carefully consider existing limits and crossdisciplinary relationships at the EU, national and regional levels. The relations between forestry and biodiversity protection are analyzed using the advocacy coalition framework (ACF). The ACF is used for analyzing how two coalitions, in this case ecological and forest owners' coalitions, advocate or pursue their beliefs from the nature protection and forestry policy field. The whole process is illustrated at the regional scale on the case study of Natura 2000 sites formulation in the Slovak Republic. For better reliability and validity of research, a combination of various empiric research methods was used, supported by existing theories. So called triangulation of sociological research or triangulation of methods consists of mutual results testing of individual methodological steps through identifying corresponding political-science theories, assessing their formal points using primary and secondary document analysis and assessing their informal points with standardized interviews with experts. We can conclude that adequate cross-sectoral coordination represented by new modes is missing and the formulation of the Natura 2000 network in Slovakia shows deficits resulting from different policy beliefs concerning nature protection and forestry coalition. Copyright © 2012 Elsevier Ltd. All rights reserved.

Determining Position Inside Non-industrial Buildings Using Ultrasound Transducers

PubMed Central

Escudero, Francesc; Margalef, Jordi; Luengo, Sonia; Alsina, Maria; Ribes, Josep M.; Pérez, Juan

2007-01-01

The position determination inside a building where no GPS signal is being received can be ascertained using laser transmitters in industrial situations where there are no people or using triangulation of the signal strength, normally electro-magnetic signals, if the required accuracy is more than a metre. Our solution is aimed at situations where people are present and where the required accuracy is less than 30 cm, such as in shopping precincts or supermarkets. To achieve this, a network of ultrasonic transmitters is fitted into the ceiling which receives a synchronised time signal. Each transmitter has a unique identifier code and emits its code with a delay with respect to the common time signal which is proportional to its code number with an ASK modulation over the ultrasonic band centred on 40 KHz. The receivers circulating beneath the transmitters receive the codes of those within their detection range, translate the time delays into distances and then obtain their position by triangulation since the receivers know the position of every transmitter. Since the receivers are not synchronised with the common time signal or the actual speed of the sound, whose value varies appreciably with temperature, relative humidity and atmospheric pressure, a consecutive approximation algorithm has been introduced. This is based on the fact that the Z coordinator of the receiver is known and constant and thus it is possible, with only three different identifiers received, to deduce the phase of the common time signal and estimate the speed of the sound with a fourth identifier. PMID:28903247

Oscillations emerging from noise-driven steady state in networks with electrical synapses and subthreshold resonance

PubMed Central

Tchumatchenko, Tatjana; Clopath, Claudia

2014-01-01

Oscillations play a critical role in cognitive phenomena and have been observed in many brain regions. Experimental evidence indicates that classes of neurons exhibit properties that could promote oscillations, such as subthreshold resonance and electrical gap junctions. Typically, these two properties are studied separately but it is not clear which is the dominant determinant of global network rhythms. Our aim is to provide an analytical understanding of how these two effects destabilize the fluctuation-driven state, in which neurons fire irregularly, and lead to an emergence of global synchronous oscillations. Here we show how the oscillation frequency is shaped by single neuron resonance, electrical and chemical synapses.The presence of both gap junctions and subthreshold resonance are necessary for the emergence of oscillations. Our results are in agreement with several experimental observations such as network responses to oscillatory inputs and offer a much-needed conceptual link connecting a collection of disparate effects observed in networks. PMID:25405458

How noise affects the synchronization properties of recurrent networks of inhibitory neurons.

PubMed

Brunel, Nicolas; Hansel, David

2006-05-01

GABAergic interneurons play a major role in the emergence of various types of synchronous oscillatory patterns of activity in the central nervous system. Motivated by these experimental facts, modeling studies have investigated mechanisms for the emergence of coherent activity in networks of inhibitory neurons. However, most of these studies have focused either when the noise in the network is absent or weak or in the opposite situation when it is strong. Hence, a full picture of how noise affects the dynamics of such systems is still lacking. The aim of this letter is to provide a more comprehensive understanding of the mechanisms by which the asynchronous states in large, fully connected networks of inhibitory neurons are destabilized as a function of the noise level. Three types of single neuron models are considered: the leaky integrate-and-fire (LIF) model, the exponential integrate-and-fire (EIF), model and conductance-based models involving sodium and potassium Hodgkin-Huxley (HH) currents. We show that in all models, the instabilities of the asynchronous state can be classified in two classes. The first one consists of clustering instabilities, which exist in a restricted range of noise. These instabilities lead to synchronous patterns in which the population of neurons is broken into clusters of synchronously firing neurons. The irregularity of the firing patterns of the neurons is weak. The second class of instabilities, termed oscillatory firing rate instabilities, exists at any value of noise. They lead to cluster state at low noise. As the noise is increased, the instability occurs at larger coupling, and the pattern of firing that emerges becomes more irregular. In the regime of high noise and strong coupling, these instabilities lead to stochastic oscillations in which neurons fire in an approximately Poisson way with a common instantaneous probability of firing that oscillates in time.

Understanding the Longitudinal Variability of Equatorial Electrodynamics using integrated Ground- and Space-based Observations

NASA Astrophysics Data System (ADS)

Yizengaw, E.; Moldwin, M.; Zesta, E.

2015-12-01

The currently funded African Meridian B-Field Education and Research (AMBER) magnetometer array comprises more than thirteen magnetometers stationed globally in the vicinity of geomagnetic equator. One of the main objectives of AMBER network is to understand the longitudinal variability of equatorial electrodynamics as function of local time, magnetic activity, and season. While providing complete meridian observation in the region and filling the largest land-based gap in global magnetometer coverage, the AMBER array addresses two fundamental areas of space physics: first, the processes governing electrodynamics of the equatorial ionosphere as a function of latitude (or L-shell), local time, longitude, magnetic activity, and season, and second, ULF pulsation strength at low/mid-latitude regions and its connection with equatorial electrojet and density fluctuation. The global AMBER network can also be used to augment observations from space-based instruments, such us the triplet SWARM mission and the upcoming ICON missions. Thus, in coordination with space-based and other ground-based observations, the AMBER magnetometer network provides a great opportunity to understand the electrodynamics that governs equatorial ionosphere motions. In this paper we present the longitudinal variability of the equatorial electrodynamics using the combination of instruments onboard SWARM and C/NOFS satellites and ground-based AMBER network. Both ground- and pace-based observations show stronger dayside and evening sector equatorial electrodynamics in the American and Asian sectors compared to the African sector. On the other hand, the African sector is home to stronger and year-round ionospheric bubbles/irregularities compared to the American and Asian sectors. This raises the question if the evening sector equatorial electrodynamics (vertical drift), which is believed to be the main cause for the enhancement of Rayleigh-Taylor (RT) instability growth rate, is stronger in the American sector and weaker in the African sector - why are the occurrence and amplitude of equatorial irregularities stronger in the African sector?

Identifying major depressive disorder using Hurst exponent of resting-state brain networks.

PubMed

Wei, Maobin; Qin, Jiaolong; Yan, Rui; Li, Haoran; Yao, Zhijian; Lu, Qing

2013-12-30

Resting-state functional magnetic resonance imaging (fMRI) studies of major depressive disorder (MDD) have revealed abnormalities of functional connectivity within or among the resting-state networks. They provide valuable insight into the pathological mechanisms of depression. However, few reports were involved in the "long-term memory" of fMRI signals. This study was to investigate the "long-term memory" of resting-state networks by calculating their Hurst exponents for identifying depressed patients from healthy controls. Resting-state networks were extracted from fMRI data of 20 MDD and 20 matched healthy control subjects. The Hurst exponent of each network was estimated by Range Scale analysis for further discriminant analysis. 95% of depressed patients and 85% of healthy controls were correctly classified by Support Vector Machine with an accuracy of 90%. The right fronto-parietal and default mode network constructed a deficit network (lower memory and more irregularity in MDD), while the left fronto-parietal, ventromedial prefrontal and salience network belonged to an excess network (longer memory in MDD), suggesting these dysfunctional networks may be related to a portion of the complex of emotional and cognitive disturbances. The abnormal "long-term memory" of resting-state networks associated with depression may provide a new possibility towards the exploration of the pathophysiological mechanisms of MDD. © 2013 Elsevier Ireland Ltd. All rights reserved.

Pore network extraction from pore space images of various porous media systems

NASA Astrophysics Data System (ADS)

Yi, Zhixing; Lin, Mian; Jiang, Wenbin; Zhang, Zhaobin; Li, Haishan; Gao, Jian

2017-04-01

Pore network extraction, which is defined as the transformation from irregular pore space to a simplified network in the form of pores connected by throats, is significant to microstructure analysis and network modeling. A physically realistic pore network is not only a representation of the pore space in the sense of topology and morphology, but also a good tool for predicting transport properties accurately. We present a method to extract pore network by employing the centrally located medial axis to guide the construction of maximal-balls-like skeleton where the pores and throats are defined and parameterized. To validate our method, various rock samples including sand pack, sandstones, and carbonates were used to extract pore networks. The pore structures were compared quantitatively with the structures extracted by medial axis method or maximal ball method. The predicted absolute permeability and formation factor were verified against the theoretical solutions obtained by lattice Boltzmann method and finite volume method, respectively. The two-phase flow was simulated through the networks extracted from homogeneous sandstones, and the generated relative permeability curves were compared with the data obtained from experimental method and other numerical models. The results show that the accuracy of our network is higher than that of other networks for predicting transport properties, so the presented method is more reliable for extracting physically realistic pore network.

Bistability and up/down state alternations in inhibition-dominated randomly connected networks of LIF neurons.

PubMed

Tartaglia, Elisa M; Brunel, Nicolas

2017-09-20

Electrophysiological recordings in cortex in vivo have revealed a rich variety of dynamical regimes ranging from irregular asynchronous states to a diversity of synchronized states, depending on species, anesthesia, and external stimulation. The average population firing rate in these states is typically low. We study analytically and numerically a network of sparsely connected excitatory and inhibitory integrate-and-fire neurons in the inhibition-dominated, low firing rate regime. For sufficiently high values of the external input, the network exhibits an asynchronous low firing frequency state (L). Depending on synaptic time constants, we show that two scenarios may occur when external inputs are decreased: (1) the L state can destabilize through a Hopf bifucation as the external input is decreased, leading to synchronized oscillations spanning d δ to β frequencies; (2) the network can reach a bistable region, between the low firing frequency network state (L) and a quiescent one (Q). Adding an adaptation current to excitatory neurons leads to spontaneous alternations between L and Q states, similar to experimental observations on UP and DOWN states alternations.

Molecular dynamics study on the evolution of interfacial dislocation network and mechanical properties of Ni-based single crystal superalloys

NASA Astrophysics Data System (ADS)

Li, Nan-Lin; Wu, Wen-Ping; Nie, Kai

2018-05-01

The evolution of misfit dislocation network at γ /γ‧ phase interface and tensile mechanical properties of Ni-based single crystal superalloys at various temperatures and strain rates are studied by using molecular dynamics (MD) simulations. From the simulations, it is found that with the increase of loading, the dislocation network effectively inhibits dislocations emitted in the γ matrix cutting into the γ‧ phase and absorbs the matrix dislocations to strengthen itself which increases the stability of structure. Under the influence of the temperature, the initial mosaic structure of dislocation network gradually becomes irregular, and the initial misfit stress and the elastic modulus slowly decline as temperature increasing. On the other hand, with the increase of the strain rate, it almost has no effect on the elastic modulus and the way of evolution of dislocation network, but contributes to the increases of the yield stress and tensile strength. Moreover, tension-compression asymmetry of Ni-based single crystal superalloys is also presented based on MD simulations.

Attacking Transnational Organized Criminal Networks: Applying Principles of Irregular Warfare to an Emerging Salient Threat

DTIC Science & Technology

2014-12-04

of anonymity. 6 The environmental frame of this monograph expands on the Title 10 and NDAA authorities that frame DoD counterdrug support to...36 United Nations Office on Drugs and Crime, The Globalization of Crime, 131. Smuggling of environmental resources constitutes a growing illicit...initial context for an examination of the DoD CD mission. In 1986, in response to increased trafficking of Colombian cocaine into the United States

Finite element generation of arbitrary 3-D fracture networks for flow analysis in complicated discrete fracture networks

NASA Astrophysics Data System (ADS)

Zhang, Qi-Hua

2015-10-01

Finite element generation of complicated fracture networks is the core issue and source of technical difficulty in three-dimensional (3-D) discrete fracture network (DFN) flow models. Due to the randomness and uncertainty in the configuration of a DFN, the intersection lines (traces) are arbitrarily distributed in each face (fracture and other surfaces). Hence, subdivision of the fractures is an issue relating to subdivision of two-dimensional (2-D) domains with arbitrarily-distributed constraints. When the DFN configuration is very complicated, the well-known approaches (e.g. Voronoi Delaunay-based methods and advancing-front techniques) cannot operate properly. This paper proposes an algorithm to implement end-to-end connection between traces to subdivide 2-D domains into closed loops. The compositions of the vertices in the common edges between adjacent loops (which may belong to a single fracture or two connected fractures) are thus ensured to be topologically identical. The paper then proposes an approach for triangulating arbitrary loops which does not add any nodes to ensure consistency of the meshes at the common edges. In addition, several techniques relating to tolerance control and improving code robustness are discussed. Finally, the equivalent permeability of the rock mass is calculated for some very complicated DFNs (the DFN may contain 1272 fractures, 633 connected fractures, and 16,270 closed loops). The results are compared with other approaches to demonstrate the veracity and efficiency of the approach proposed in this paper.

Death and rebirth of neural activity in sparse inhibitory networks

NASA Astrophysics Data System (ADS)

Angulo-Garcia, David; Luccioli, Stefano; Olmi, Simona; Torcini, Alessandro

2017-05-01

Inhibition is a key aspect of neural dynamics playing a fundamental role for the emergence of neural rhythms and the implementation of various information coding strategies. Inhibitory populations are present in several brain structures, and the comprehension of their dynamics is strategical for the understanding of neural processing. In this paper, we clarify the mechanisms underlying a general phenomenon present in pulse-coupled heterogeneous inhibitory networks: inhibition can induce not only suppression of neural activity, as expected, but can also promote neural re-activation. In particular, for globally coupled systems, the number of firing neurons monotonically reduces upon increasing the strength of inhibition (neuronal death). However, the random pruning of connections is able to reverse the action of inhibition, i.e. in a random sparse network a sufficiently strong synaptic strength can surprisingly promote, rather than depress, the activity of neurons (neuronal rebirth). Thus, the number of firing neurons reaches a minimum value at some intermediate synaptic strength. We show that this minimum signals a transition from a regime dominated by neurons with a higher firing activity to a phase where all neurons are effectively sub-threshold and their irregular firing is driven by current fluctuations. We explain the origin of the transition by deriving a mean field formulation of the problem able to provide the fraction of active neurons as well as the first two moments of their firing statistics. The introduction of a synaptic time scale does not modify the main aspects of the reported phenomenon. However, for sufficiently slow synapses the transition becomes dramatic, and the system passes from a perfectly regular evolution to irregular bursting dynamics. In this latter regime the model provides predictions consistent with experimental findings for a specific class of neurons, namely the medium spiny neurons in the striatum.

Comparisons of COSMIC and C/NOFS GPS Occultation Ionospheric Scintillation Measurements with Ground-based Radar and VHF Measurements

NASA Astrophysics Data System (ADS)

Ruggiero, F. H.; Groves, K. M.; Straus, P. R.; Caton, R. G.; Starks, M. J.; Tanyi, K. L.; Verlinden, M.

2009-12-01

Ionospheric irregularities are known to cause scintillation of trans-ionospheric radio signals and can affect space-based UHF/VHF communications, causing outages, and degrading GPS accuracy and precision. Current capability for characterizing and predicting ionospheric scintillation utilizes a network of ground-based receivers to detect scintillation and then extrapolate for short-term forecasts. Practical limits on deploying the ground receivers limits the accuracy and spatial coverage one can achieve with this approach. A more global approach is to use a set of space-based satellites equipped with GPS receivers, such as the COSMIC satellite constellation, to measure scintillations observed during so-called occultations with GPS satellites. In this paper the signal-to-noise values of GPS L1 signals received on the COSMIC and C/NOFS satellites for the portions of the occultations that are not affected by the terrestrial atmosphere are examined to help identify areas of ionospheric scintillation. Three years of S4 scintillation index values from COSMIC occultations are compared with near-zenith ground-based VHF S4 scintillation measurements from the AFRL SCIntillation Network Decision Aid (SCINDA) network stations. The data are correlated to ascertain the viability of using space-based scintillation measurements to characterize and predict scintillation to ground-based receivers. Several days of COSMIC and C/NOFS data are compared with each other and the ALTAIR radar located on Kwajalein Atoll, Marshall Islands to examine how occultation geometry affects observed scintillation and also to verify techniques that provide an upper bound on the spatial location of the ionospheric irregularities contributing to scintillations observed in the occultations.

An Energy-Efficient Underground Localization System Based on Heterogeneous Wireless Networks

PubMed Central

Yuan, Yazhou; Chen, Cailian; Guan, Xinping; Yang, Qiuling

2015-01-01

A precision positioning system with energy efficiency is of great necessity for guaranteeing personnel safety in underground mines. The location information of the miners' should be transmitted to the control center timely and reliably; therefore, a heterogeneous network with the backbone based on high speed Industrial Ethernet is deployed. Since the mobile wireless nodes are working in an irregular tunnel, a specific wireless propagation model cannot fit all situations. In this paper, an underground localization system is designed to enable the adaptation to kinds of harsh tunnel environments, but also to reduce the energy consumption and thus prolong the lifetime of the network. Three key techniques are developed and implemented to improve the system performance, including a step counting algorithm with accelerometers, a power control algorithm and an adaptive packets scheduling scheme. The simulation study and experimental results show the effectiveness of the proposed algorithms and the implementation. PMID:26016918

PageRank versatility analysis of multilayer modality-based network for exploring the evolution of oil-water slug flow.

PubMed

Gao, Zhong-Ke; Dang, Wei-Dong; Li, Shan; Yang, Yu-Xuan; Wang, Hong-Tao; Sheng, Jing-Ran; Wang, Xiao-Fan

2017-07-14

Numerous irregular flow structures exist in the complicated multiphase flow and result in lots of disparate spatial dynamical flow behaviors. The vertical oil-water slug flow continually attracts plenty of research interests on account of its significant importance. Based on the spatial transient flow information acquired through our designed double-layer distributed-sector conductance sensor, we construct multilayer modality-based network to encode the intricate spatial flow behavior. Particularly, we calculate the PageRank versatility and multilayer weighted clustering coefficient to quantitatively explore the inferred multilayer modality-based networks. Our analysis allows characterizing the complicated evolution of oil-water slug flow, from the opening formation of oil slugs, to the succedent inter-collision and coalescence among oil slugs, and then to the dispersed oil bubbles. These properties render our developed method particularly powerful for mining the essential flow features from the multilayer sensor measurements.

Hindrances to precise recovery of cellular forces in fibrous biopolymer networks.

PubMed

Zhang, Yunsong; Feng, Jingchen; Heizler, Shay I; Levine, Herbert

2018-01-11

How cells move through the three-dimensional extracellular matrix (ECM) is of increasing interest in attempts to understand important biological processes such as cancer metastasis. Just as in motion on flat surfaces, it is expected that experimental measurements of cell-generated forces will provide valuable information for uncovering the mechanisms of cell migration. However, the recovery of forces in fibrous biopolymer networks may suffer from large errors. Here, within the framework of lattice-based models, we explore possible issues in force recovery by solving the inverse problem: how can one determine the forces cells exert to their surroundings from the deformation of the ECM? Our results indicate that irregular cell traction patterns, the uncertainty of local fiber stiffness, the non-affine nature of ECM deformations and inadequate knowledge of network topology will all prevent the precise force determination. At the end, we discuss possible ways of overcoming these difficulties.

Artificial Intelligence Procedures for Tree Taper Estimation within a Complex Vegetation Mosaic in Brazil

PubMed Central

Nunes, Matheus Henrique

2016-01-01

Tree stem form in native tropical forests is very irregular, posing a challenge to establishing taper equations that can accurately predict the diameter at any height along the stem and subsequently merchantable volume. Artificial intelligence approaches can be useful techniques in minimizing estimation errors within complex variations of vegetation. We evaluated the performance of Random Forest® regression tree and Artificial Neural Network procedures in modelling stem taper. Diameters and volume outside bark were compared to a traditional taper-based equation across a tropical Brazilian savanna, a seasonal semi-deciduous forest and a rainforest. Neural network models were found to be more accurate than the traditional taper equation. Random forest showed trends in the residuals from the diameter prediction and provided the least precise and accurate estimations for all forest types. This study provides insights into the superiority of a neural network, which provided advantages regarding the handling of local effects. PMID:27187074

Software Architecture of Sensor Data Distribution In Planetary Exploration

NASA Technical Reports Server (NTRS)

Lee, Charles; Alena, Richard; Stone, Thom; Ossenfort, John; Walker, Ed; Notario, Hugo

2006-01-01

Data from mobile and stationary sensors will be vital in planetary surface exploration. The distribution and collection of sensor data in an ad-hoc wireless network presents a challenge. Irregular terrain, mobile nodes, new associations with access points and repeaters with stronger signals as the network reconfigures to adapt to new conditions, signal fade and hardware failures can cause: a) Data errors; b) Out of sequence packets; c) Duplicate packets; and d) Drop out periods (when node is not connected). To mitigate the effects of these impairments, a robust and reliable software architecture must be implemented. This architecture must also be tolerant of communications outages. This paper describes such a robust and reliable software infrastructure that meets the challenges of a distributed ad hoc network in a difficult environment and presents the results of actual field experiments testing the principles and actual code developed.

Artificial Intelligence Procedures for Tree Taper Estimation within a Complex Vegetation Mosaic in Brazil.

PubMed

Nunes, Matheus Henrique; Görgens, Eric Bastos

2016-01-01

Tree stem form in native tropical forests is very irregular, posing a challenge to establishing taper equations that can accurately predict the diameter at any height along the stem and subsequently merchantable volume. Artificial intelligence approaches can be useful techniques in minimizing estimation errors within complex variations of vegetation. We evaluated the performance of Random Forest® regression tree and Artificial Neural Network procedures in modelling stem taper. Diameters and volume outside bark were compared to a traditional taper-based equation across a tropical Brazilian savanna, a seasonal semi-deciduous forest and a rainforest. Neural network models were found to be more accurate than the traditional taper equation. Random forest showed trends in the residuals from the diameter prediction and provided the least precise and accurate estimations for all forest types. This study provides insights into the superiority of a neural network, which provided advantages regarding the handling of local effects.

Hindrances to precise recovery of cellular forces in fibrous biopolymer networks

NASA Astrophysics Data System (ADS)

Zhang, Yunsong; Feng, Jingchen; Heizler, Shay I.; Levine, Herbert

2018-03-01

How cells move through the three-dimensional extracellular matrix (ECM) is of increasing interest in attempts to understand important biological processes such as cancer metastasis. Just as in motion on flat surfaces, it is expected that experimental measurements of cell-generated forces will provide valuable information for uncovering the mechanisms of cell migration. However, the recovery of forces in fibrous biopolymer networks may suffer from large errors. Here, within the framework of lattice-based models, we explore possible issues in force recovery by solving the inverse problem: how can one determine the forces cells exert to their surroundings from the deformation of the ECM? Our results indicate that irregular cell traction patterns, the uncertainty of local fiber stiffness, the non-affine nature of ECM deformations and inadequate knowledge of network topology will all prevent the precise force determination. At the end, we discuss possible ways of overcoming these difficulties.

Angles-Only Navigation: Position and Velocity Solution from Absolute Triangulation

DTIC Science & Technology

2011-01-01

geocentric position vectors. Using two vectors derived from each such observation (see next section), a solution for a portion of the boat’s track was...t)x0 describes the curvature of the path in the direction x 0, which, for a geocentric coordinate system and /(t) < 0, will be toward the center of...finite distances, with geocentric coordinates known to a meter or better (readily available on the Internet) a straightfor- ward triangulation method

Radio triangulation - mapping the 3D position of the solar radio emission

NASA Astrophysics Data System (ADS)

Magdalenic, Jasmina

2016-04-01

Understanding the relative position of the sources of the radio emission and the associated solar eruptive phenomena (CME and the associated shock wave) has always been a challenge. While ground-based radio interferometer observations provide us with the 2D position information for the radio emission originating from the low corona (up to 2.5 Ro), this is not the case for the radio emission originating at larger heights. The radio triangulation measurements (also referred to as direction-finding or goniopolarimetric measurements) from two or more widely separated spacecraft can provide information on the 3D positions of the sources of the radio emission. This type of interplanetary radio observations are currently performed by STEREO WAVES and WIND WAVES instruments, providing a unique possibility for up to three simultaneous radio triangulations (using up to three different pairs of spacecraft). The recent results of the radio triangulation studies bring new insight into the causal relationship of the solar radio emission and CMEs. In this presentation I will discuss some of the most intriguing results on the source positions of: a) type III radio bursts indicating propagation of the fast electrons accelerated along the open field lines, b) type II radio bursts indicating interaction of the CME-driven shocks and other coronal structures e.g. streamers and c) type IV-like radio bursts possibly associated with CME-CME interaction.

Concurrent enterprise: a conceptual framework for enterprise supply-chain network activities

NASA Astrophysics Data System (ADS)

Addo-Tenkorang, Richard; Helo, Petri T.; Kantola, Jussi

2017-04-01

Supply-chain management (SCM) in manufacturing industries has evolved significantly over the years. Recently, a lot more relevant research has picked up on the development of integrated solutions. Thus, seeking a collaborative optimisation of geographical, just-in-time (JIT), quality (customer demand/satisfaction) and return-on-investment (profits), aspects of organisational management and planning through 'best practice' business-process management - concepts and application; employing system tools such as certain applications/aspects of enterprise resource planning (ERP) - SCM systems information technology (IT) enablers to enhance enterprise integrated product development/concurrent engineering principles. This article assumed three main organisation theory applications in positioning its assumptions. Thus, proposing a feasible industry-specific framework not currently included within the SCOR model's level four (4) implementation level, as well as other existing SCM integration reference models such as in the MIT process handbook's - Process Interchange Format (PIF), the TOVE project, etc. which could also be replicated in other SCs. However, the wider focus of this paper's contribution will be concentrated on a complimentary proposed framework to the SCC's SCOR reference model. Quantitative empirical closed-ended questionnaires in addition to the main data collected from a qualitative empirical real-life industrial-based pilot case study were used: To propose a conceptual concurrent enterprise framework for SCM network activities. This research adopts a design structure matrix simulation approach analysis to propose an optimal enterprise SCM-networked value-adding, customised master data-management platform/portal for efficient SCM network information exchange and an effective supply-chain (SC) network systems-design teams' structure. Furthermore, social network theory analysis will be employed in a triangulation approach with statistical correlation analysis to assess the scale/level of frequency, importance, level of collaborative-ness, mutual trust as well as roles and responsibility among the enterprise SCM network for systems product development (PD) design teams' technical communication network as well as extensive literature reviews.

Networks of conforming or nonconforming individuals tend to reach satisfactory decisions.

PubMed

Ramazi, Pouria; Riehl, James; Cao, Ming

2016-11-15

Binary decisions of agents coupled in networks can often be classified into two types: "coordination," where an agent takes an action if enough neighbors are using that action, as in the spread of social norms, innovations, and viral epidemics, and "anticoordination," where too many neighbors taking a particular action causes an agent to take the opposite action, as in traffic congestion, crowd dispersion, and division of labor. Both of these cases can be modeled using linear-threshold-based dynamics, and a fundamental question is whether the individuals in such networks are likely to reach decisions with which they are satisfied. We show that, in the coordination case, and perhaps more surprisingly, also in the anticoordination case, the agents will indeed always tend to reach satisfactory decisions, that is, the network will almost surely reach an equilibrium state. This holds for every network topology and every distribution of thresholds, for both asynchronous and partially synchronous decision-making updates. These results reveal that irregular network topology, population heterogeneity, and partial synchrony are not sufficient to cause cycles or nonconvergence in linear-threshold dynamics; rather, other factors such as imitation or the coexistence of coordinating and anticoordinating agents must play a role.

Coupled flow and deformations in granular systems beyond the pendular regime

NASA Astrophysics Data System (ADS)

Yuan, Chao; Chareyre, Bruno; Darve, Felix

2017-06-01

A pore-scale numerical model is proposed for simulating the quasi-static primary drainage and the hydro-mechanical couplings in multiphase granular systems. The solid skeleton is idealized to a dense random packing of polydisperse spheres by DEM. The fluids (nonwetting and wetting phases) space is decomposed to a network of tetrahedral pores based on the Regular Triangulation method. The local drainage rules and invasion logic are defined. The fluid forces acting on solid grains are formulated. The model can simulate the hydraulic evolution from a fully saturated state to a low level of saturation but beyond the pendular regime. The features of wetting phase entrapments and capillary fingering can also be reproduced. Finally, a primary drainage test is performed on a 40,000 spheres of sample. The water retention curve is obtained. The solid skeleton first shrinks then swells.

Geodetic measurement of deformation east of the San Andreas Fault in Central California

NASA Technical Reports Server (NTRS)

Sauber, Jeanne; Solomon, Sean C.; Lisowski, Michael

1988-01-01

The shear strain rates in the Diablo Range of California have been calculated, and the slip rate along the Calaveras and Paicines faults in Central California have been estimated, on the basis of triangulation and trilateration data from two geodetic networks located between the western edge of the Great Valley and the San Andreas Fault. The orientation of the principal compressive strain predicted from the azimuth of the major structures in the region is N 25 deg E, leading to an average shear strain value that corresponds to a relative shortening rate of 4.5 + or - 2.4 mm/yr. It is inferred that the measured strain is due to compression across the fold of this area. The hypothesized uniform, fault-normal compression within the Coast Ranges is not supported by these results.

Improved heuristics for early melanoma detection using multimode hyperspectral dermoscopy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Vasefi, Fartash; MacKinnon, Nicholas B.; Booth, Nicholas; Farkas, Daniel L.

2017-02-01

Purpose: To determine the performance of a multimode dermoscopy system (SkinSpect) designed to quantify and 3-D map in vivo melanin and hemoglobin concentrations in skin and its melanoma scoring system, and compare the results accuracy with SIAscopy, and histopathology. Methods: A multimode imaging dermoscope is presented that combines polarization, fluorescence and hyperspectral imaging to accurately map the distribution of skin melanin, collagen and hemoglobin in pigmented lesions. We combine two depth-sensitive techniques: polarization, and hyperspectral imaging, to determine the spatial distribution of melanin and hemoglobin oxygenation in a skin lesion. By quantifying melanin absorption in pigmented areas, we can also more accurately estimate fluorescence emission distribution mainly from skin collagen. Results and discussion: We compared in vivo features of melanocytic lesions (N = 10) extracted by non-invasive SkinSpect and SIMSYS-MoleMate SIAscope, and correlate them to pathology report. Melanin distribution at different depths as well as hemodynamics including abnormal vascularity we detected will be discussed. We will adapt SkinSpect scoring with ABCDE (asymmetry , border, color, diameter, evolution) and seven point dermatologic checklist including: (1) atypical pigment network, (2) blue-whitish veil, (3) atypical vascular pattern, (4) irregular streaks, (5) irregular pigmentation, (6) irregular dots and globules, (7) regression structures estimated by dermatologist. Conclusion: Distinctive, diagnostic features seen by SkinSpect in melanoma vs. normal pigmented lesions will be compared by SIAscopy and results from histopathology.

Detection of Atrial Fibrillation Using Artifical Neural Network with Power Spectrum Density of RR Interval of Electrocardiogram

NASA Astrophysics Data System (ADS)

Afdala, Adfal; Nuryani, Nuryani; Satrio Nugroho, Anto

2017-01-01

Atrial fibrillation (AF) is a disorder of the heart with fairly high mortality in adults. AF is a common heart arrythmia which is characterized by a missing or irregular contraction of atria. Therefore, finding a method to detect atrial fibrillation is necessary. In this article a system to detect atrial fibrillation has been proposed. Detection system utilized backpropagation artifical neural network. Data input in this method includes power spectrum density of R-peaks interval of electrocardiogram which is selected by wrapping method. This research uses parameter learning rate, momentum, epoch and hidden layer. System produces good performance with accuracy, sensitivity, and specificity of 83.55%, 86.72 % and 81.47 %, respectively.

On the space and time evolution of regular or irregular human heart or brain signals

NASA Astrophysics Data System (ADS)

Tuncay, Ç.

2009-01-01

A coupled map is suggested to investigate various spatial or temporal designs in biology: several cells (or tissues) in an organ are considered as connected to each other in terms of some molecular diffusions or electrical potential differences and so on. The biological systems (groups of cells) start from various initial conditions for spatial designs (or initial signals for temporal designs) and they evolve in time in terms of the mentioned interactions (connections) besides some individual feedings. The basic aim of the present contribution is to mimic various empirical data for the heart (in normal, quasi-stable, unstable and post operative physiological conditions) or brain (regular or irregular; for epilepsy) signals. The mentioned empirical data are borrowed from various works in the literature which are cited. The suggested model (to be used besides or instead of the artificial network models) involves simple mathematics and the related software is easy. The results may be considered as in good agreement with the mentioned real signals.

Qualitative to quantitative: linked trajectory of method triangulation in a study on HIV/AIDS in Goa, India.

PubMed

Bailey, Ajay; Hutter, Inge

2008-10-01

With 3.1 million people estimated to be living with HIV/AIDS in India and 39.5 million people globally, the epidemic has posed academics the challenge of identifying behaviours and their underlying beliefs in the effort to reduce the risk of HIV transmission. The Health Belief Model (HBM) is frequently used to identify risk behaviours and adherence behaviour in the field of HIV/AIDS. Risk behaviour studies that apply HBM have been largely quantitative and use of qualitative methodology is rare. The marriage of qualitative and quantitative methods has never been easy. The challenge is in triangulating the methods. Method triangulation has been largely used to combine insights from the qualitative and quantitative methods but not to link both the methods. In this paper we suggest a linked trajectory of method triangulation (LTMT). The linked trajectory aims to first gather individual level information through in-depth interviews and then to present the information as vignettes in focus group discussions. We thus validate information obtained from in-depth interviews and gather emic concepts that arise from the interaction. We thus capture both the interpretation and the interaction angles of the qualitative method. Further, using the qualitative information gained, a survey is designed. In doing so, the survey questions are grounded and contextualized. We employed this linked trajectory of method triangulation in a study on the risk assessment of HIV/AIDS among migrant and mobile men. Fieldwork was carried out in Goa, India. Data come from two waves of studies, first an explorative qualitative study (2003), second a larger study (2004-2005), including in-depth interviews (25), focus group discussions (21) and a survey (n=1259). By employing the qualitative to quantitative LTMT we can not only contextualize the existing concepts of the HBM, but also validate new concepts and identify new risk groups.

Water volume and sediment volume and density in Lake Linganore between Boyers Mill Road Bridge and Bens Branch, Frederick County, Maryland, 2012

USGS Publications Warehouse

Sekellick, Andrew J.; Banks, William S.L.; Myers, Michael K.

2013-01-01

To assist in understanding sediment loadings and the management of water resources, a bathymetric survey was conducted in the part of Lake Linganore between Boyers Mill Road Bridge and Bens Branch in Frederick County, Maryland. The bathymetric survey was performed in January 2012 by the U.S. Geological Survey, in cooperation with the City of Frederick and Frederick County. A separate, but related, field effort to collect 18 sediment cores was conducted in March and April 2012. Depth and location data from the bathymetric survey and location data for the sediment cores were compiled and edited by using geographic information system (GIS) software. A three-dimensional triangulated irregular network (TIN) model of the lake bottom was created to calculate the volume of stored water in the reservoir. Large-scale topographic maps of the valley prior to inundation in 1972 were provided by the Frederick County Division of Utilities and Solid Waste Management and digitized for comparison with current (2012) conditions in order to calculate sediment volume. Cartographic representations of both water depth and sediment accumulation were produced, along with an accuracy assessment for the resulting bathymetric model. Vertical accuracies at the 95-percent confidence level for the collected data, the bathymetric surface model, and the bathymetric contour map were calculated to be 0.64 feet (ft), 1.77 ft, and 2.30 ft, respectively. A dry bulk sediment density was calculated for each of the 18 sediment cores collected during March and April 2012, and used to determine accumulated sediment mass. Water-storage capacity in the study area is 110 acre-feet (acre-ft) at a full-pool elevation 308 ft above the National Geodetic Vertical Datum of 1929, whereas total sediment volume in the study area is 202 acre-ft. These totals indicate a loss of about 65 percent of the original water-storage capacity in the 40 years since dam construction. This corresponds to an average rate of sediment accumulation of 5.1 acre-ft per year since Linganore Creek was impounded. Sediment thicknesses ranged from 0 to 16.7 ft. Sediment densities ranged from 0.38 to 1.08 grams per cubic centimeter, and generally decreased in the downstream direction. The total accumulated-sediment mass was 156,000 metric tons between 1972 and 2012.

Water volume and sediment accumulation in Lake Linganore, Frederick County, Maryland, 2009

USGS Publications Warehouse

Sekellick, Andrew J.; Banks, S.L.

2010-01-01

To assist in understanding sediment and phosphorus loadings and the management of water resources, a bathymetric survey was conducted at Lake Linganore in Frederick County, Maryland in June 2009 by the U.S. Geological Survey, in cooperation with the City of Frederick and Frederick County, Maryland. Position data and water-depth data were collected using a survey grade echo sounder and a differentially corrected global positioning system. Data were compiled and edited using geographic information system software. A three-dimensional triangulated irregular network model of the lake bottom was created to calculate the volume of stored water in the reservoir. Large-scale topographic maps of the valley prior to inundation in 1972 were provided by the City of Frederick and digitized. The two surfaces were compared and a sediment volume was calculated. Cartographic representations of both water depth and sediment accumulation were produced along with an area/capacity table. An accuracy assessment was completed on the resulting bathymetric model. Vertical accuracy at the 95-percent confidence level for the collected data, the bathymetric surface model, and the bathymetric contour map was calculated to be 0.95 feet, 1.53 feet, and 3.63 feet, respectively. The water storage volume of Lake Linganore was calculated to be 1,860 acre-feet at full pool elevation. Water volume in the reservoir has decreased by 350 acre-feet (about 16 percent) in the 37 years since the dam was constructed. The total calculated volume of sediment deposited in the lake since 1972 is 313 acre-feet. This represents an average rate of sediment accumulation of 8.5 acre-feet per year since Linganore Creek was impounded. A sectional analysis of sediment distribution indicates that the most upstream third of Lake Linganore contains the largest volume of sediment whereas the section closest to the dam contains the largest amount of water. In comparison to other Maryland Piedmont reservoirs, Lake Linganore was found to have one of the lowest sedimentation rates at 0.26 cubic yards per year per acre of drainage area. Sedimentation rates in other comparable Maryland reservoirs were Prettyboy Reservoir (filling at a rate of 2.26 cubic yards per year per acre), Loch Raven Reservoir (filling at a rate of 0.88 cubic yards per year per acre) and Piney Run Reservoir (filling at a negligible rate).

Rockfall hazard assessment of nearly vertical rhyolite tuff cliff faces by using terrestrial laser scanner, UAV and FEM analyses

NASA Astrophysics Data System (ADS)

Török, Ákos; Barsi, Árpád; Görög, Péter; Lovas, Tamás; Bögöly, Gyula; Czinder, Balázs; Vásárhelyi, Balázs; Molnár, Bence; József Somogyi, Árpád

2017-04-01

Nearly vertical rhyolite tuff cliff faces are located in NE-Hungary representing rock fall hazard in the touristic region of Sirok. Larger blocks of the cliff have fallen in recent years menacing tourists and human lives. The rhyolite tuff, that forms the Castle Hill was formed during Miocene volcanism and comprises of brecciated lapilli tuffs and tuffs with intercalating ignimbritic horizons. The paper focuses on the 3D mapping of cliff faces and modeling of rock fall hazard. The topography and 3D model of the cliff was obtained by using GNSS supported terrestrial laser scanner and UAV. With imaging techniques of UAV a Triangulated Irregular Network (TIN) model was developed that contained triangles with 5-10 cm side lengths. GNSS supported terrestrial laser scanning allowed the observation with a resolution 1-5 cm of point spacing. The point clouds were further processed and with the combination of laser scanner and UAV data a 3D model of the studied cliff faces were obtained. Geological parameters for rock fall analyses included both field observations and laboratory tests. The lithotypes were identified on the field and were sampled for rock mechanical laboratory analyses. Joint- and fault system was mapped and visualized by using Rocscience Dip. EN test methods were used to obtain the density properties of various lithotypes of rhyolite tuff. Other standardized EN tests included ultrasonic pulse velocity, water absorption, indirect tensile strength (Brasilian), uniaxial compressive strength and modulus of elasticity of air dry and of water saturated samples. GSI values were denoted based on filed observations and rock mass properties. The stability analyses of cliff faces were made by using 2D FEM software (Phase 2). Cross sections were evaluated and global factor of safety was also calculated. The modeled displacements were in the order of few centimeters; however several locations were pinpointed where wedge failure and planar slip surfaces were identified as major cliff stability hazards. These were associated with the major joint systems dissecting cliff faces. This research have proved that the combined methods of field surveying, imaging techniques, data processing and FEM modelling with rock mechanical laboratory analyses allowed the identification of major rock fall hazards even at areas which are difficult to access.

GIS-based analysis and modelling with empirical and remotely-sensed data on coastline advance and retreat

NASA Astrophysics Data System (ADS)

Ahmad, Sajid Rashid

With the understanding that far more research remains to be done on the development and use of innovative and functional geospatial techniques and procedures to investigate coastline changes this thesis focussed on the integration of remote sensing, geographical information systems (GIS) and modelling techniques to provide meaningful insights on the spatial and temporal dynamics of coastline changes. One of the unique strengths of this research was the parameterization of the GIS with long-term empirical and remote sensing data. Annual empirical data from 1941--2007 were analyzed by the GIS, and then modelled with statistical techniques. Data were also extracted from Landsat TM and ETM+ images. The band ratio method was used to extract the coastlines. Topographic maps were also used to extract digital map data. All data incorporated into ArcGIS 9.2 were analyzed with various modules, including Spatial Analyst, 3D Analyst, and Triangulated Irregular Networks. The Digital Shoreline Analysis System was used to analyze and predict rates of coastline change. GIS results showed the spatial locations along the coast that will either advance or retreat over time. The linear regression results highlighted temporal changes which are likely to occur along the coastline. Box-Jenkins modelling procedures were utilized to determine statistical models which best described the time series (1941--2007) of coastline change data. After several iterations and goodness-of-fit tests, second-order spatial cyclic autoregressive models, first-order autoregressive models and autoregressive moving average models were identified as being appropriate for describing the deterministic and random processes operating in Guyana's coastal system. The models highlighted not only cyclical patterns in advance and retreat of the coastline, but also the existence of short and long-term memory processes. Long-term memory processes could be associated with mudshoal propagation and stabilization while short-term memory processes were indicative of transitory hydrodynamic and other processes. An innovative framework for a spatio-temporal information-based system (STIBS) was developed. STIBS incorporated diverse datasets within a GIS, dynamic computer-based simulation models, and a spatial information query and graphical subsystem. Tests of the STIBS proved that it could be used to simulate and visualize temporal variability in shifting morphological states of the coastline.

A note on statistical analysis of shape through triangulation of landmarks

PubMed Central

Rao, C. Radhakrishna

2000-01-01

In an earlier paper, the author jointly with S. Suryawanshi proposed statistical analysis of shape through triangulation of landmarks on objects. It was observed that the angles of the triangles are invariant to scaling, location, and rotation of objects. No distinction was made between an object and its reflection. The present paper provides the methodology of shape discrimination when reflection is also taken into account and makes suggestions for modifications to be made when some of the landmarks are collinear. PMID:10737780

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Qishi; Berry, M. L..; Grieme, M.

We propose a localization-based radiation source detection (RSD) algorithm using the Ratio of Squared Distance (ROSD) method. Compared with the triangulation-based method, the advantages of this ROSD method are multi-fold: i) source location estimates based on four detectors improve their accuracy, ii) ROSD provides closed-form source location estimates and thus eliminates the imaginary-roots issue, and iii) ROSD produces a unique source location estimate as opposed to two real roots (if any) in triangulation, and obviates the need to identify real phantom roots during clustering.

Lithification of vitric- and clastic-matrix breccias - SEM petrography

NASA Technical Reports Server (NTRS)

Phinney, W. C.; Mckay, D. S.; Warner, J. L.; Simonds, C. H.

1976-01-01

A scanning electron microscope was used in a petrographic investigation of the matrix textures of 41 lunar breccias ranging from very friable soil clods through coherent microbreccias and tough vitric breccias to tough, fine-grained crystalline breccias. It was found that as their coherence increases, the matrices display a gradual increase in the content of glass from 1 or 2% as filaments less than 1 micron across through 5-50% as irregularly shaped patches up to 200 microns across to over 50% as continuous networks.

On k-ary n-cubes: Theory and applications

NASA Technical Reports Server (NTRS)

Mao, Weizhen; Nicol, David M.

1994-01-01

Many parallel processing networks can be viewed as graphs called k-ary n-cubes, whose special cases include rings, hypercubes and toruses. In this paper, combinatorial properties of k-ary n-cubes are explored. In particular, the problem of characterizing the subgraph of a given number of nodes with the maximum edge count is studied. These theoretical results are then used to compute a lower bounding function in branch-and-bound partitioning algorithms and to establish the optimality of some irregular partitions.

Structural Health Monitoring and Impact Detection Using Neural Networks for Damage Characterization

NASA Technical Reports Server (NTRS)

Ross, Richard W.

2006-01-01

Detection of damage due to foreign object impact is an important factor in the development of new aerospace vehicles. Acoustic waves generated on impact can be detected using a set of piezoelectric transducers, and the location of impact can be determined by triangulation based on the differences in the arrival time of the waves at each of the sensors. These sensors generate electrical signals in response to mechanical motion resulting from the impact as well as from natural vibrations. Due to electrical noise and mechanical vibration, accurately determining these time differentials can be challenging, and even small measurement inaccuracies can lead to significant errors in the computed damage location. Wavelet transforms are used to analyze the signals at multiple levels of detail, allowing the signals resulting from the impact to be isolated from ambient electromechanical noise. Data extracted from these transformed signals are input to an artificial neural network to aid in identifying the moment of impact from the transformed signals. By distinguishing which of the signal components are resultant from the impact and which are characteristic of noise and normal aerodynamic loads, the time differentials as well as the location of damage can be accurately assessed. The combination of wavelet transformations and neural network processing results in an efficient and accurate approach for passive in-flight detection of foreign object damage.

Status of the Desert Fireball Network

NASA Astrophysics Data System (ADS)

Devillepoix, H. A. R.; Bland, P. A.; Towner, M. C.; Cupák, M.; Sansom, E. K.; Jansen-Sturgeon, T.; Howie, R. M.; Paxman, J.; Hartig, B. A. D.

2016-01-01

A meteorite fall precisely observed from multiple locations allows us to track the object back to the region of the Solar System it came from, and sometimes link it with a parent body, providing context information that helps trace the history of the Solar System. The Desert Fireball Network (DFN) is built in arid areas of Australia: its observatories get favorable observing conditions, and meteorite recovery is eased thanks to the mostly featureless terrain. After the successful recovery of two meteorites with 4 film cameras, the DFN has now switched to a digital network, operating 51 cameras, covering 2.5 million km2 of double station triangulable area. Mostly made of off-the-shelf components, the new observatories are cost effective while maintaining high imaging performance. To process the data (~70TB/month), a significant effort has been put to writing an automated reduction pipeline so that all events are reduced with little human intervention. Innovative techniques have been implemented for this purpose: machine learning algorithms for event detection, blind astrometric calibration, and particle filter simulations to estimate both physical properties and state vector of the meteoroid. On 31 December 2015, the first meteorite from the digital systems was recovered: Murrili (the 1.68 kg H5 ordinary chondrite was observed to fall on 27 November 2015). Another 11 events have been flagged as potential meteorites droppers, and are to be searched in the coming months.

Depth measurements of drilled holes in bone by laser triangulation for the field of oral implantology

NASA Astrophysics Data System (ADS)

Quest, D.; Gayer, C.; Hering, P.

2012-01-01

Laser osteotomy is one possible method of preparing beds for dental implants in the human jaw. A major problem in using this contactless treatment modality is the lack of haptic feedback to control the depth while drilling the implant bed. A contactless measurement system called laser triangulation is presented as a new procedure to overcome this problem. Together with a tomographic picture the actual position of the laser ablation in the bone can be calculated. Furthermore, the laser response is sufficiently fast as to pose little risk to surrounding sensitive areas such as nerves and blood vessels. In the jaw two different bone structures exist, namely the cancellous bone and the compact bone. Samples of both bone structures were examined with test drillings performed either by laser osteotomy or by a conventional rotating drilling tool. The depth of these holes was measured using laser triangulation. The results and the setup are reported in this study.

Lattice gas simulations of dynamical geometry in two dimensions.

PubMed

Klales, Anna; Cianci, Donato; Needell, Zachary; Meyer, David A; Love, Peter J

2010-10-01

We present a hydrodynamic lattice gas model for two-dimensional flows on curved surfaces with dynamical geometry. This model is an extension to two dimensions of the dynamical geometry lattice gas model previously studied in one dimension. We expand upon a variation of the two-dimensional flat space Frisch-Hasslacher-Pomeau (FHP) model created by Frisch [Phys. Rev. Lett. 56, 1505 (1986)] and independently by Wolfram, and modified by Boghosian [Philos. Trans. R. Soc. London, Ser. A 360, 333 (2002)]. We define a hydrodynamic lattice gas model on an arbitrary triangulation whose flat space limit is the FHP model. Rules that change the geometry are constructed using the Pachner moves, which alter the triangulation but not the topology. We present results on the growth of the number of triangles as a function of time. Simulations show that the number of triangles grows with time as t(1/3), in agreement with a mean-field prediction. We also present preliminary results on the distribution of curvature for a typical triangulation in these simulations.

Coherent Structure Detection using Persistent Homology and other Topological Tools

NASA Astrophysics Data System (ADS)

Smith, Spencer; Roberts, Eric; Sindi, Suzanne; Mitchell, Kevin

2017-11-01

For non-autonomous, aperiodic fluid flows, coherent structures help organize the dynamics, much as invariant manifolds and periodic orbits do for autonomous or periodic systems. The prevalence of such flows in nature and industry has motivated many successful techniques for defining and detecting coherent structures. However, often these approaches require very fine trajectory data to reconstruct velocity fields and compute Cauchy-Green-tensor-related quantities. We use topological techniques to help detect coherent trajectory sets in relatively sparse 2D advection problems. More specifically, we have developed a homotopy-based algorithm, the ensemble-based topological entropy calculation (E-tec), which assigns to each edge in an initial triangulation of advected points a topologically forced lower bound on its future stretching rate. The triangulation and its weighted edges allow us to analyze flows using persistent homology. This topological data analysis tool detects clusters and loops in the triangulation that are robust in the presence of noise and in this case correspond to coherent trajectory sets.

An artificial neural network architecture for non-parametric visual odometry in wireless capsule endoscopy

NASA Astrophysics Data System (ADS)

Dimas, George; Iakovidis, Dimitris K.; Karargyris, Alexandros; Ciuti, Gastone; Koulaouzidis, Anastasios

2017-09-01

Wireless capsule endoscopy is a non-invasive screening procedure of the gastrointestinal (GI) tract performed with an ingestible capsule endoscope (CE) of the size of a large vitamin pill. Such endoscopes are equipped with a usually low-frame-rate color camera which enables the visualization of the GI lumen and the detection of pathologies. The localization of the commercially available CEs is performed in the 3D abdominal space using radio-frequency (RF) triangulation from external sensor arrays, in combination with transit time estimation. State-of-the-art approaches, such as magnetic localization, which have been experimentally proved more accurate than the RF approach, are still at an early stage. Recently, we have demonstrated that CE localization is feasible using solely visual cues and geometric models. However, such approaches depend on camera parameters, many of which are unknown. In this paper the authors propose a novel non-parametric visual odometry (VO) approach to CE localization based on a feed-forward neural network architecture. The effectiveness of this approach in comparison to state-of-the-art geometric VO approaches is validated using a robotic-assisted in vitro experimental setup.

Primary health care and the coordination of care in health regions: managers' and users' perspective.

PubMed

Bousquat, Aylene; Giovanella, Ligia; Campos, Estela Márcia Saraiva; Almeida, Patty Fidelis de; Martins, Cleide Lavieri; Mota, Paulo Henrique Dos Santos; Mendonça, Maria Helena Magalhães de; Medina, Maria Guadalupe; Viana, Ana Luiza d'Ávila; Fausto, Márcia Cristina Rodrigues; Paula, Daniel Baffini de

2017-04-01

This paper aims to analyze the healthcare coordination by Primary Health Care (PHC), with the backdrop of building a Health Care Network (RAS) in a region in the state of São Paulo, Brazil. We conducted a case study with qualitative and quantitative approaches, proceeding to the triangulation of data between the perception of managers and experience of users. We drew analysis realms and variables from the three pillars of healthcare coordination - informational, clinical and administrative/organizational. Stroke was the tracer event chosen and therapeutic itineraries were conducted with users and questionnaires applied to the managers. The central feature of the construction of the Health Care Network in the studied area is the prominence of a philanthropic organization. The results suggest fragility of PHC in healthcare coordination in all analyzed realms. Furthermore, we identified a public-private mix, in addition to services contracted from the Unified Health System (SUS), with out-of-pocket payments for specialist consultation, tests and rehabilitation. Much in the same way that there is no RAS without a robust PHC capable of coordinating care, PHC is unable to play its role without a solid regional arrangement and a virtuous articulation between the three federative levels.

Geodetic measurement of deformation in California. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Sauber, Jeanne Marie

1988-01-01

The very long baseline interferometry (VLBI) measurements made in the western U.S. since 1979 as part of the NASA Crustal Dynamics Project provide discrete samples of the temporal and spatial deformation field. The interpretation of the VLBI-derived rates of deformation requires an examination of geologic information and more densely sampled ground-based geodetic data. In the first two of three related studies embodying this thesis triangulation and trilateration data measured on two regional networks are processed, one in the central Mojave Desert and one in the Coast Ranges east of the San Andreas fault. At the spatial scales spanned by these local geodetic networks, auxiliary geologic and geophysical data have been utilized to examine the relation between measured incremental strain and the accommodation of strain seen in local geological structures, strain release in earthquakes, and principal stress directions inferred from in situ measurements. In the third study, VLBI data from stations distributed across the Pacific - North American plate boundary zone in the western United States are processed. The VLBI data have been used to constrain the integrated rate of deformation across portions of the continental plate boundary in California and to provide a tectonic framework to interpret regional geodetic and geologic studies.

Geodetic measurement of deformation in California. Ph.D. Thesis - Massachusetts Inst. of Technology

NASA Technical Reports Server (NTRS)

Sauber, Jeanne

1989-01-01

The very long baseline interferometry (VLBI) measurements made in the western U.S. since 1979 as part of the NASA Crustal Dynamics Project provide discrete samples of the temporal and spatial deformation field. The interpretation of the VLBI-derived rates of deformation requires an examination of geologic information and more densely sampled ground-based geodetic data. In the first two of three related studies, triangulation and trilateration data measured on two regional networks, one in the central Mojave Desert and one in the Coast Ranges east of the San Andreas fault, have been processed. At the spatial scales spanned by these local geodetic networks, auxiliary geologic and geophysical data have been utilized to examine the relation between measured incremental strain and the accommodation of strain seen in local geological structures, strain release in earthquakes, and principal stress directions inferred from in situ measurements. In a third study, the geocentric position vectors from a set of 77 VLBI experiments beginning in October 1982 have been used to estimate the tangential rate of change of station positions in the western U.S. in a North-America-Fixed reference frame.

Performance Of The IEEE 802.15.4 Protocol As The Marker Of Augmented Reality In Museum

NASA Astrophysics Data System (ADS)

Kurniawan Saputro, Adi; Sumpeno, Surya; Hariadi, Mochamad

2018-04-01

Museum is a place to keep the historic objects and historical education center to introduce the nation’s culture. Utilizing technology in a museum to become a smart city is a challenge. Internet of thing (IOT) is a technological advance in Information and communication (ICT) that can be applied in the museum The current ICT development is not only a transmission medium, but Augmented Reality technology is also being developed. Currently, Augmented Reality technology creates virtual objects into the real world using markers or images. In this study, researcher used signals to make virtual objects appear in the real world using the IEEE 802.14.5 protocol replacing the Augmented Reality marker. RSSI and triangulation are used as a substitute microlocation for AR objects. The result is the performance of Wireless Sensor Network could be used for data transmission in the museum. LOS research at a distance of 15 meters with 1000 ms delay found 1.4% error rate and NLOS with 2.3% error rate. So it can be concluded that utilization technology (IOT) using signal wireless sensor network as a replace for marker augmented reality can be used in museum

Knowledge exchange in the UK CLAHRCs.

PubMed

Racko, Girts

2018-04-09

Purpose The purpose of this paper is to examine how knowledge exchange between academics and clinicians in Collaborations for Leadership in Applied Health Research and Care (CLAHRCs) is influenced by their social position based on their symbolic and social capitals, that is, their personal professional status and connections to high-status professional peers, knowledge brokers, and unfamiliar professional peers. Design/methodology/approach Using an online survey, the author triangulates the cross-sectional measurement of the effects of academic and clinicians' social position in the initial and later phases of CLAHRCs with the longitudinal measurement of these effects over a two-year period. Findings First, academics and clinicians with a higher personal professional status are more likely to develop joint networks and decision making both in the early and later phases of a CLAHRC. Second, academics and clinicians who are more connected to higher status occupational peers are more likely to develop joint networks in the early phase of a knowledge exchange partnership but are less likely to become engaged in joint networks over time. Third, involvement of knowledge brokers in the networks of academics and clinicians is likely to facilitate their inter-professional networking only in the later partnership phase. Practical implications Academics and clinicians' capitals have a distinctive influence on knowledge exchange in the early and later phases of CLAHRCs and on a change in knowledge exchange over a two-year period. Originality/value Prior research on CLAHRCs has examined how knowledge exchange between academics and clinicians can be encouraged by the creation of shared governance mechanisms. The author advances this research by highlighting the role of their social position in facilitating knowledge exchange.

Fireballs in the Sky

NASA Astrophysics Data System (ADS)

Day, B. H.; Bland, P.

2016-12-01

Fireballs in the Sky is an innovative Australian citizen science program that connects the public with the research of the Desert Fireball Network (DFN). This research aims to understand the early workings of the solar system, and Fireballs in the Sky invites people around the world to learn about this science, contributing fireball sightings via a user-friendly app. To date, more than 23,000 people have downloaded the app world-wide and participated in planetary science. The Fireballs in the Sky app allows users to get involved with the Desert Fireball Network research, supplementing DFN observations and providing enhanced coverage by reporting their own meteor sightings to DFN scientists. Fireballs in the Sky reports are used to track the trajectories of meteors - from their orbit in space to where they might have landed on Earth. Led by Phil Bland at Curtin University in Australia, the Desert Fireball Network (DFN) uses automated observatories across Australia to triangulate trajectories of meteorites entering the atmosphere, determine pre-entry orbits, and pinpoint their fall positions. Each observatory is an autonomous intelligent imaging system, taking 1000×36Megapixel all-sky images throughout the night, using neural network algorithms to recognize events. They are capable of operating for 12 months in a harsh environment, and store all imagery collected. We developed a completely automated software pipeline for data reduction, and built a supercomputer database for storage, allowing us to process our entire archive. The DFN currently stands at 50 stations distributed across the Australian continent, covering an area of 2.5 million km^2. Working with DFN's partners at NASA's Solar System Exploration Research Virtual Institute, the team is expanding the network beyond Australia to locations around the world. Fireballs in the Sky allows a growing public base to learn about and participate in this exciting research.

A Program to Improve the Triangulated Surface Mesh Quality Along Aircraft Component Intersections

NASA Technical Reports Server (NTRS)

Cliff, Susan E.

2005-01-01

A computer program has been developed for improving the quality of unstructured triangulated surface meshes in the vicinity of component intersections. The method relies solely on point removal and edge swapping for improving the triangulations. It can be applied to any lifting surface component such as a wing, canard or horizontal tail component intersected with a fuselage, or it can be applied to a pylon that is intersected with a wing, fuselage or nacelle. The lifting surfaces or pylon are assumed to be aligned in the axial direction with closed trailing edges. The method currently maintains salient edges only at leading and trailing edges of the wing or pylon component. This method should work well for any shape of fuselage that is free of salient edges at the intersection. The method has been successfully demonstrated on a total of 125 different test cases that include both blunt and sharp wing leading edges. The code is targeted for use in the automated environment of numerical optimization where geometric perturbations to individual components can be critical to the aerodynamic performance of a vehicle. Histograms of triangle aspect ratios are reported to assess the quality of the triangles attached to the intersection curves before and after application of the program. Large improvements to the quality of the triangulations were obtained for the 125 test cases; the quality was sufficient for use with an automated tetrahedral mesh generation program that is used as part of an aerodynamic shape optimization method.

Triangulated Proxy Reporting: a technique for improving how communication partners come to know people with severe cognitive impairment.

PubMed

Lyons, Gordon; De Bortoli, Tania; Arthur-Kelly, Michael

2017-09-01

This paper explains and demonstrates the pilot application of Triangulated Proxy Reporting (TPR); a practical technique for enhancing communication around people who have severe cognitive impairment (SCI). An introduction explains SCI and how this impacts on communication; and consequently on quality of care and quality of life. This is followed by an explanation of TPR and its origins in triangulation research techniques. An illustrative vignette explicates its utility and value in a group home for a resident with profound multiple disabilities. The Discussion and Conclusion sections propose the wider application of TPR for different cohorts of people with SCIs, their communication partners and service providers. TPR presents as a practical technique for enhancing communication interactions with people who have SCI. The paper demonstrates the potential of the technique for improving engagement amongst those with profound multiple disabilities, severe acquired brain injury and advanced dementia and their partners in and across different care settings. Implications for Rehabilitation Triangulated Proxy Reporting (TPR) shows potential to improve communications between people with severe cognitive impairments and their communication partners. TPR can lead to improved quality of care and quality of life for people with profound multiple disabilities, very advanced dementia and severe acquired brain injury, who otherwise are very difficult to support. TPR is a relatively simple and inexpensive technique that service providers can incorporate into practice to improving communications between clients with severe cognitive impairments, their carers and other support professionals.

Reconstructing the Sky Location of Gravitational-Wave Detected Compact Binary Systems: Methodology for Testing and Comparison

NASA Technical Reports Server (NTRS)

Sidney, T.; Aylott, B.; Christensen, N.; Farr, B.; Farr, W.; Feroz, F.; Gair, J.; Grover, K.; Graff, P.; Hanna, C.;

Reconstructing the sky location of gravitational-wave detected compact binary systems: Methodology for testing and comparison

NASA Astrophysics Data System (ADS)

Sidery, T.; Aylott, B.; Christensen, N.; Farr, B.; Farr, W.; Feroz, F.; Gair, J.; Grover, K.; Graff, P.; Hanna, C.; Kalogera, V.; Mandel, I.; O'Shaughnessy, R.; Pitkin, M.; Price, L.; Raymond, V.; Röver, C.; Singer, L.; van der Sluys, M.; Smith, R. J. E.; Vecchio, A.; Veitch, J.; Vitale, S.

2014-04-01

The problem of reconstructing the sky position of compact binary coalescences detected via gravitational waves is a central one for future observations with the ground-based network of gravitational-wave laser interferometers, such as Advanced LIGO and Advanced Virgo. Different techniques for sky localization have been independently developed. They can be divided in two broad categories: fully coherent Bayesian techniques, which are high latency and aimed at in-depth studies of all the parameters of a source, including sky position, and "triangulation-based" techniques, which exploit the data products from the search stage of the analysis to provide an almost real-time approximation of the posterior probability density function of the sky location of a detection candidate. These techniques have previously been applied to data collected during the last science runs of gravitational-wave detectors operating in the so-called initial configuration. Here, we develop and analyze methods for assessing the self consistency of parameter estimation methods and carrying out fair comparisons between different algorithms, addressing issues of efficiency and optimality. These methods are general, and can be applied to parameter estimation problems other than sky localization. We apply these methods to two existing sky localization techniques representing the two above-mentioned categories, using a set of simulated inspiral-only signals from compact binary systems with a total mass of ≤20M⊙ and nonspinning components. We compare the relative advantages and costs of the two techniques and show that sky location uncertainties are on average a factor ≈20 smaller for fully coherent techniques than for the specific variant of the triangulation-based technique used during the last science runs, at the expense of a factor ≈1000 longer processing time.

The application of GPS precise point positioning technology in aerial triangulation

NASA Astrophysics Data System (ADS)

Yuan, Xiuxiao; Fu, Jianhong; Sun, Hongxing; Toth, Charles

In traditional GPS-supported aerotriangulation, differential GPS (DGPS) positioning technology is used to determine the 3-dimensional coordinates of the perspective centers at exposure time with an accuracy of centimeter to decimeter level. This method can significantly reduce the number of ground control points (GCPs). However, the establishment of GPS reference stations for DGPS positioning is not only labor-intensive and costly, but also increases the implementation difficulty of aerial photography. This paper proposes aerial triangulation supported with GPS precise point positioning (PPP) as a way to avoid the use of the GPS reference stations and simplify the work of aerial photography. Firstly, we present the algorithm for GPS PPP in aerial triangulation applications. Secondly, the error law of the coordinate of perspective centers determined using GPS PPP is analyzed. Thirdly, based on GPS PPP and aerial triangulation software self-developed by the authors, four sets of actual aerial images taken from surveying and mapping projects, different in both terrain and photographic scale, are given as experimental models. The four sets of actual data were taken over a flat region at a scale of 1:2500, a mountainous region at a scale of 1:3000, a high mountainous region at a scale of 1:32000 and an upland region at a scale of 1:60000 respectively. In these experiments, the GPS PPP results were compared with results obtained through DGPS positioning and traditional bundle block adjustment. In this way, the empirical positioning accuracy of GPS PPP in aerial triangulation can be estimated. Finally, the results of bundle block adjustment with airborne GPS controls from GPS PPP are analyzed in detail. The empirical results show that GPS PPP applied in aerial triangulation has a systematic error of half-meter level and a stochastic error within a few decimeters. However, if a suitable adjustment solution is adopted, the systematic error can be eliminated in GPS-supported bundle block adjustment. When four full GCPs are emplaced in the corners of the adjustment block, then the systematic error is compensated using a set of independent unknown parameters for each strip, the final result of the bundle block adjustment with airborne GPS controls from PPP is the same as that of bundle block adjustment with airborne GPS controls from DGPS. Although the accuracy of the former is a little lower than that of traditional bundle block adjustment with dense GCPs, it can still satisfy the accuracy requirement of photogrammetric point determination for topographic mapping at many scales.

Observations of Global and Regional Ionospheric Irregularities and Scintillation Using GNSS Tracking Networks

NASA Technical Reports Server (NTRS)

Pi, Xiaoqing; Mannucci, Anthony J.; Valant-Spaight, Bonnie; Bar-Sever, Yoaz; Romans, Larry J.; Skone, Susan; Sparks, Lawrence; Hall, G. Martin

2013-01-01

The rate of TEC index (ROTI) is a measurement that characterizes ionospheric irregularities. It can be obtained from standard GNSS dual-frequency phase data collected using a geodetic type of GNSS receiver. By processing GPS data from ground-based networks of International GNSS Service and Continuously Operating Reference Station (CORS), ROTI maps have been produced to observe global and regional scintillation activities. A major mid-latitude scintillation event in the contiguous United States is reported here that was captured in ROTI maps produced using CORS GPS data collected during a space weather storm. The analyses conducted in this work and previously by another group indicate that ROTI is a good occurrence indicator of both amplitude and phase scintillations of GPS L-band signals, even though the magnitudes of ROTI, S4, and sigma(sub phi) can be different. For example, our analysis indicates that prominent ROTI and the L1 phase scintillation (sigma(sub phi)) are well correlated temporally in the polar region while L1 amplitude scintillation rarely occurs. The differences are partially attributed to physics processes in different latitude regions, such as high-speed plasma convection in the polar region that can suppress the amplitude scintillation. An analysis of the impact of ionospheric scintillation on precise positioning, which requires use of dual-frequency phase data, is also conducted. The results indicate that significant (more than an order of magnitude) positioning errors can occur under phase scintillation conditions.

GDTN: Genome-Based Delay Tolerant Network Formation in Heterogeneous 5G Using Inter-UA Collaboration.

PubMed

You, Ilsun; Sharma, Vishal; Atiquzzaman, Mohammed; Choo, Kim-Kwang Raymond

2016-01-01

With a more Internet-savvy and sophisticated user base, there are more demands for interactive applications and services. However, it is a challenge for existing radio access networks (e.g. 3G and 4G) to cope with the increasingly demanding requirements such as higher data rates and wider coverage area. One potential solution is the inter-collaborative deployment of multiple radio devices in a 5G setting designed to meet exacting user demands, and facilitate the high data rate requirements in the underlying networks. These heterogeneous 5G networks can readily resolve the data rate and coverage challenges. Networks established using the hybridization of existing networks have diverse military and civilian applications. However, there are inherent limitations in such networks such as irregular breakdown, node failures, and halts during speed transmissions. In recent years, there have been attempts to integrate heterogeneous 5G networks with existing ad hoc networks to provide a robust solution for delay-tolerant transmissions in the form of packet switched networks. However, continuous connectivity is still required in these networks, in order to efficiently regulate the flow to allow the formation of a robust network. Therefore, in this paper, we present a novel network formation consisting of nodes from different network maneuvered by Unmanned Aircraft (UA). The proposed model utilizes the features of a biological aspect of genomes and forms a delay tolerant network with existing network models. This allows us to provide continuous and robust connectivity. We then demonstrate that the proposed network model has an efficient data delivery, lower overheads and lesser delays with high convergence rate in comparison to existing approaches, based on evaluations in both real-time testbed and simulation environment.

GDTN: Genome-Based Delay Tolerant Network Formation in Heterogeneous 5G Using Inter-UA Collaboration

PubMed Central

2016-01-01

With a more Internet-savvy and sophisticated user base, there are more demands for interactive applications and services. However, it is a challenge for existing radio access networks (e.g. 3G and 4G) to cope with the increasingly demanding requirements such as higher data rates and wider coverage area. One potential solution is the inter-collaborative deployment of multiple radio devices in a 5G setting designed to meet exacting user demands, and facilitate the high data rate requirements in the underlying networks. These heterogeneous 5G networks can readily resolve the data rate and coverage challenges. Networks established using the hybridization of existing networks have diverse military and civilian applications. However, there are inherent limitations in such networks such as irregular breakdown, node failures, and halts during speed transmissions. In recent years, there have been attempts to integrate heterogeneous 5G networks with existing ad hoc networks to provide a robust solution for delay-tolerant transmissions in the form of packet switched networks. However, continuous connectivity is still required in these networks, in order to efficiently regulate the flow to allow the formation of a robust network. Therefore, in this paper, we present a novel network formation consisting of nodes from different network maneuvered by Unmanned Aircraft (UA). The proposed model utilizes the features of a biological aspect of genomes and forms a delay tolerant network with existing network models. This allows us to provide continuous and robust connectivity. We then demonstrate that the proposed network model has an efficient data delivery, lower overheads and lesser delays with high convergence rate in comparison to existing approaches, based on evaluations in both real-time testbed and simulation environment. PMID:27973618

Birth of an abstraction: a dynamical systems account of the discovery of an elsewhere principle in a category learning task.

PubMed

Tabor, Whitney; Cho, Pyeong W; Dankowicz, Harry

2013-01-01

Human participants and recurrent ("connectionist") neural networks were both trained on a categorization system abstractly similar to natural language systems involving irregular ("strong") classes and a default class. Both the humans and the networks exhibited staged learning and a generalization pattern reminiscent of the Elsewhere Condition (Kiparsky, 1973). Previous connectionist accounts of related phenomena have often been vague about the nature of the networks' encoding systems. We analyzed our network using dynamical systems theory, revealing topological and geometric properties that can be directly compared with the mechanisms of non-connectionist, rule-based accounts. The results reveal that the networks "contain" structures related to mechanisms posited by rule-based models, partly vindicating the insights of these models. On the other hand, they support the one mechanism (OM), as opposed to the more than one mechanism (MOM), view of symbolic abstraction by showing how the appearance of MOM behavior can arise emergently from one underlying set of principles. The key new contribution of this study is to show that dynamical systems theory can allow us to explicitly characterize the relationship between the two perspectives in implemented models. © 2013 Cognitive Science Society, Inc.

A Recurrent Network Model of Somatosensory Parametric Working Memory in the Prefrontal Cortex

PubMed Central

Miller, Paul; Brody, Carlos D; Romo, Ranulfo; Wang, Xiao-Jing

2015-01-01

A parametric working memory network stores the information of an analog stimulus in the form of persistent neural activity that is monotonically tuned to the stimulus. The family of persistent firing patterns with a continuous range of firing rates must all be realizable under exactly the same external conditions (during the delay when the transient stimulus is withdrawn). How this can be accomplished by neural mechanisms remains an unresolved question. Here we present a recurrent cortical network model of irregularly spiking neurons that was designed to simulate a somatosensory working memory experiment with behaving monkeys. Our model reproduces the observed positively and negatively monotonic persistent activity, and heterogeneous tuning curves of memory activity. We show that fine-tuning mathematically corresponds to a precise alignment of cusps in the bifurcation diagram of the network. Moreover, we show that the fine-tuned network can integrate stimulus inputs over several seconds. Assuming that such time integration occurs in neural populations downstream from a tonically persistent neural population, our model is able to account for the slow ramping-up and ramping-down behaviors of neurons observed in prefrontal cortex. PMID:14576212

Optimizing a neural network for detection of moving vehicles in video

NASA Astrophysics Data System (ADS)

Fischer, Noëlle M.; Kruithof, Maarten C.; Bouma, Henri

2017-10-01

In the field of security and defense, it is extremely important to reliably detect moving objects, such as cars, ships, drones and missiles. Detection and analysis of moving objects in cameras near borders could be helpful to reduce illicit trading, drug trafficking, irregular border crossing, trafficking in human beings and smuggling. Many recent benchmarks have shown that convolutional neural networks are performing well in the detection of objects in images. Most deep-learning research effort focuses on classification or detection on single images. However, the detection of dynamic changes (e.g., moving objects, actions and events) in streaming video is extremely relevant for surveillance and forensic applications. In this paper, we combine an end-to-end feedforward neural network for static detection with a recurrent Long Short-Term Memory (LSTM) network for multi-frame analysis. We present a practical guide with special attention to the selection of the optimizer and batch size. The end-to-end network is able to localize and recognize the vehicles in video from traffic cameras. We show an efficient way to collect relevant in-domain data for training with minimal manual labor. Our results show that the combination with LSTM improves performance for the detection of moving vehicles.

Cardiac Arrhythmia Classification by Multi-Layer Perceptron and Convolution Neural Networks.

PubMed

Savalia, Shalin; Emamian, Vahid

2018-05-04

The electrocardiogram (ECG) plays an imperative role in the medical field, as it records heart signal over time and is used to discover numerous cardiovascular diseases. If a documented ECG signal has a certain irregularity in its predefined features, this is called arrhythmia, the types of which include tachycardia, bradycardia, supraventricular arrhythmias, and ventricular, etc. This has encouraged us to do research that consists of distinguishing between several arrhythmias by using deep neural network algorithms such as multi-layer perceptron (MLP) and convolution neural network (CNN). The TensorFlow library that was established by Google for deep learning and machine learning is used in python to acquire the algorithms proposed here. The ECG databases accessible at PhysioBank.com and kaggle.com were used for training, testing, and validation of the MLP and CNN algorithms. The proposed algorithm consists of four hidden layers with weights, biases in MLP, and four-layer convolution neural networks which map ECG samples to the different classes of arrhythmia. The accuracy of the algorithm surpasses the performance of the current algorithms that have been developed by other cardiologists in both sensitivity and precision.

Chaos and Correlated Avalanches in Excitatory Neural Networks with Synaptic Plasticity

NASA Astrophysics Data System (ADS)

Pittorino, Fabrizio; Ibáñez-Berganza, Miguel; di Volo, Matteo; Vezzani, Alessandro; Burioni, Raffaella

2017-03-01

A collective chaotic phase with power law scaling of activity events is observed in a disordered mean field network of purely excitatory leaky integrate-and-fire neurons with short-term synaptic plasticity. The dynamical phase diagram exhibits two transitions from quasisynchronous and asynchronous regimes to the nontrivial, collective, bursty regime with avalanches. In the homogeneous case without disorder, the system synchronizes and the bursty behavior is reflected into a period doubling transition to chaos for a two dimensional discrete map. Numerical simulations show that the bursty chaotic phase with avalanches exhibits a spontaneous emergence of persistent time correlations and enhanced Kolmogorov complexity. Our analysis reveals a mechanism for the generation of irregular avalanches that emerges from the combination of disorder and deterministic underlying chaotic dynamics.

Coverage Dependent Assembly of Anthraquinone on Au(111)

NASA Astrophysics Data System (ADS)

Conrad, Brad; Deloach, Andrew; Einstein, Theodore; Dougherty, Daniel

A study of adsorbate-adsorbate and surface state mediated interactions of anthraquinone (AnQ) on Au(111) is presented. We utilize scanning tunneling microscopy (STM) to characterize the coverage dependence of AnQ structure formation. Ordered structures are observed up to a single monolayer (ML) and are found to be strongly dependent on molecular surface density. While the complete ML forms a well-ordered close-packed layer, for a narrow range of sub-ML coverages irregular close-packed islands are observed to coexist with a disordered pore network linking neighboring islands. This network displays a characteristic pore size and at lower coverages, the soliton walls of the herringbone reconstruction are shown to promote formation of distinct pore nanostructures. We will discuss these nanostructure formations in the context of surface mediated and more direct adsorbate interactions.

Commutative semigroups of real and complex matrices. [with use of the jordan form

NASA Technical Reports Server (NTRS)

Brown, D. R.

1974-01-01

The computation of divergence is studied. Covariance matrices to be analyzed admit a common diagonalization, or even triangulation. Sufficient conditions are given for such phenomena to take place, the arguments cover both real and complex matrices, and are not restricted to Hermotian or other special forms. Specifically, it is shown to be sufficient that the matrices in question commute in order to admit a common triangulation. Several results hold in the case that the matrices in question form a closed and bounded set, rather than only in the finite case.

Error in telemetry studies: Effects of animal movement on triangulation

USGS Publications Warehouse

Schmutz, Joel A.; White, Gary C.

1990-01-01

We used Monte Carlo simulations to investigate the effects of animal movement on error of estimated animal locations derived from radio-telemetry triangulation of sequentially obtained bearings. Simulated movements of 0-534 m resulted in up to 10-fold increases in average location error but <10% decreases in location precision when observer-to-animal distances were <1,000 m. Location error and precision were minimally affected by censorship of poor locations with Chi-square goodness-of-fit tests. Location error caused by animal movement can only be eliminated by taking simultaneous bearings.

Mapping Gnss Restricted Environments with a Drone Tandem and Indirect Position Control

NASA Astrophysics Data System (ADS)

Cledat, E.; Cucci, D. A.

2017-08-01

The problem of autonomously mapping highly cluttered environments, such as urban and natural canyons, is intractable with the current UAV technology. The reason lies in the absence or unreliability of GNSS signals due to partial sky occlusion or multi-path effects. High quality carrier-phase observations are also required in efficient mapping paradigms, such as Assisted Aerial Triangulation, to achieve high ground accuracy without the need of dense networks of ground control points. In this work we consider a drone tandem in which the first drone flies outside the canyon, where GNSS constellation is ideal, visually tracks the second drone and provides an indirect position control for it. This enables both autonomous guidance and accurate mapping of GNSS restricted environments without the need of ground control points. We address the technical feasibility of this concept considering preliminary real-world experiments in comparable conditions and we perform a mapping accuracy prediction based on a simulation scenario.

KSC-2009-3126

NASA Image and Video Library

2009-05-11

CAPE CANAVERAL, Fla. – This photo shows one of two lightning strikes that occurred on May 11 around 11 p.m. within a third of a mile of space shuttle Endeavour on Launch Pad 39B at NASA's Kennedy Space Center in Florida. Engineers and safety personnel evaluated data and performed a walkdown of the pad and determined there is no damage to the vehicle or the pad. The images are from Kennedy's Operational Television cameras which can be used to triangulate the location of lightning strikes. Other detection systems include the Cloud-To-Ground Lightning Surveillance System, Strikenet/National Lightning Detection Network, Lightning Induced Voltage Instrumentation System and the Catenary Wire Lightning Instrumentation System. Endeavour is standing by on the pad, prepared for liftoff in the unlikely event that a rescue mission is necessary during space shuttle Atlantis' STS-125 mission to service NASA's Hubble Space Telescope. Photo credit: NASA

KSC-2009-3125

NASA Image and Video Library

2009-05-11

CAPE CANAVERAL, Fla. – This photo shows one of two lightning strikes that occurred on May 11 around 11 p.m. within a third of a mile of space shuttle Endeavour on Launch Pad 39B at NASA's Kennedy Space Center in Florida. Engineers and safety personnel evaluated data and performed a walkdown of the pad and determined there is no damage to the vehicle or the pad. The images are from Kennedy's Operational Television cameras which can be used to triangulate the location of lightning strikes. Other detection systems include the Cloud-To-Ground Lightning Surveillance System, Strikenet/National Lightning Detection Network, Lightning Induced Voltage Instrumentation System and the Catenary Wire Lightning Instrumentation System. Endeavour is standing by on the pad, prepared for liftoff in the unlikely event that a rescue mission is necessary during space shuttle Atlantis' STS-125 mission to service NASA's Hubble Space Telescope. Photo credit: NASA

KSC-2009-3127

NASA Image and Video Library

2009-05-11

CAPE CANAVERAL, Fla. – This photo taken from Launch Pad 39A at NASA's Kennedy Space Center in Florida shows one of two lightning strikes that occurred on May 11 around 11 p.m. within a third of a mile of space shuttle Endeavour on Launch Pad 39B. Engineers and safety personnel evaluated data and performed a walkdown of the pad and determined there is no damage to the vehicle or the pad. The images are from Kennedy's Operational Television cameras which can be used to triangulate the location of lightning strikes. Other detection systems include the Cloud-To-Ground Lightning Surveillance System, Strikenet/National Lightning Detection Network, Lightning Induced Voltage Instrumentation System and the Catenary Wire Lightning Instrumentation System. Endeavour is standing by on the pad, prepared for liftoff in the unlikely event that a rescue mission is necessary during space shuttle Atlantis' STS-125 mission to service NASA's Hubble Space Telescope. Photo credit: NASA

An approach to computing direction relations between separated object groups

NASA Astrophysics Data System (ADS)

Yan, H.; Wang, Z.; Li, J.

2013-06-01

Direction relations between object groups play an important role in qualitative spatial reasoning, spatial computation and spatial recognition. However, none of existing models can be used to compute direction relations between object groups. To fill this gap, an approach to computing direction relations between separated object groups is proposed in this paper, which is theoretically based on Gestalt principles and the idea of multi-directions. The approach firstly triangulates the two object groups; and then it constructs the Voronoi Diagram between the two groups using the triangular network; after this, the normal of each Vornoi edge is calculated, and the quantitative expression of the direction relations is constructed; finally, the quantitative direction relations are transformed into qualitative ones. The psychological experiments show that the proposed approach can obtain direction relations both between two single objects and between two object groups, and the results are correct from the point of view of spatial cognition.

An approach to computing direction relations between separated object groups

NASA Astrophysics Data System (ADS)

Yan, H.; Wang, Z.; Li, J.

2013-09-01

Direction relations between object groups play an important role in qualitative spatial reasoning, spatial computation and spatial recognition. However, none of existing models can be used to compute direction relations between object groups. To fill this gap, an approach to computing direction relations between separated object groups is proposed in this paper, which is theoretically based on gestalt principles and the idea of multi-directions. The approach firstly triangulates the two object groups, and then it constructs the Voronoi diagram between the two groups using the triangular network. After this, the normal of each Voronoi edge is calculated, and the quantitative expression of the direction relations is constructed. Finally, the quantitative direction relations are transformed into qualitative ones. The psychological experiments show that the proposed approach can obtain direction relations both between two single objects and between two object groups, and the results are correct from the point of view of spatial cognition.

A Comprehensive Model for Real Gas Transport in Shale Formations with Complex Non-planar Fracture Networks

PubMed Central

Yang, Ruiyue; Huang, Zhongwei; Yu, Wei; Li, Gensheng; Ren, Wenxi; Zuo, Lihua; Tan, Xiaosi; Sepehrnoori, Kamy; Tian, Shouceng; Sheng, Mao

2016-01-01

A complex fracture network is generally generated during the hydraulic fracturing treatment in shale gas reservoirs. Numerous efforts have been made to model the flow behavior of such fracture networks. However, it is still challenging to predict the impacts of various gas transport mechanisms on well performance with arbitrary fracture geometry in a computationally efficient manner. We develop a robust and comprehensive model for real gas transport in shales with complex non-planar fracture network. Contributions of gas transport mechanisms and fracture complexity to well productivity and rate transient behavior are systematically analyzed. The major findings are: simple planar fracture can overestimate gas production than non-planar fracture due to less fracture interference. A “hump” that occurs in the transition period and formation linear flow with a slope less than 1/2 can infer the appearance of natural fractures. The sharpness of the “hump” can indicate the complexity and irregularity of the fracture networks. Gas flow mechanisms can extend the transition flow period. The gas desorption could make the “hump” more profound. The Knudsen diffusion and slippage effect play a dominant role in the later production time. Maximizing the fracture complexity through generating large connected networks is an effective way to increase shale gas production. PMID:27819349

A Comprehensive Model for Real Gas Transport in Shale Formations with Complex Non-planar Fracture Networks.

PubMed

Yang, Ruiyue; Huang, Zhongwei; Yu, Wei; Li, Gensheng; Ren, Wenxi; Zuo, Lihua; Tan, Xiaosi; Sepehrnoori, Kamy; Tian, Shouceng; Sheng, Mao

2016-11-07

A complex fracture network is generally generated during the hydraulic fracturing treatment in shale gas reservoirs. Numerous efforts have been made to model the flow behavior of such fracture networks. However, it is still challenging to predict the impacts of various gas transport mechanisms on well performance with arbitrary fracture geometry in a computationally efficient manner. We develop a robust and comprehensive model for real gas transport in shales with complex non-planar fracture network. Contributions of gas transport mechanisms and fracture complexity to well productivity and rate transient behavior are systematically analyzed. The major findings are: simple planar fracture can overestimate gas production than non-planar fracture due to less fracture interference. A "hump" that occurs in the transition period and formation linear flow with a slope less than 1/2 can infer the appearance of natural fractures. The sharpness of the "hump" can indicate the complexity and irregularity of the fracture networks. Gas flow mechanisms can extend the transition flow period. The gas desorption could make the "hump" more profound. The Knudsen diffusion and slippage effect play a dominant role in the later production time. Maximizing the fracture complexity through generating large connected networks is an effective way to increase shale gas production.

optGpSampler: an improved tool for uniformly sampling the solution-space of genome-scale metabolic networks.

PubMed

Megchelenbrink, Wout; Huynen, Martijn; Marchiori, Elena

2014-01-01

Constraint-based models of metabolic networks are typically underdetermined, because they contain more reactions than metabolites. Therefore the solutions to this system do not consist of unique flux rates for each reaction, but rather a space of possible flux rates. By uniformly sampling this space, an estimated probability distribution for each reaction's flux in the network can be obtained. However, sampling a high dimensional network is time-consuming. Furthermore, the constraints imposed on the network give rise to an irregularly shaped solution space. Therefore more tailored, efficient sampling methods are needed. We propose an efficient sampling algorithm (called optGpSampler), which implements the Artificial Centering Hit-and-Run algorithm in a different manner than the sampling algorithm implemented in the COBRA Toolbox for metabolic network analysis, here called gpSampler. Results of extensive experiments on different genome-scale metabolic networks show that optGpSampler is up to 40 times faster than gpSampler. Application of existing convergence diagnostics on small network reconstructions indicate that optGpSampler converges roughly ten times faster than gpSampler towards similar sampling distributions. For networks of higher dimension (i.e. containing more than 500 reactions), we observed significantly better convergence of optGpSampler and a large deviation between the samples generated by the two algorithms. optGpSampler for Matlab and Python is available for non-commercial use at: http://cs.ru.nl/~wmegchel/optGpSampler/.

Using synchrotron X-ray microtomography to characterize the pore network of reservoir rocks: A case study on carbonates

NASA Astrophysics Data System (ADS)

Arzilli, F.; Cilona, A.; Mancini, L.; Tondi, E.

2016-09-01

In this work we propose a new methodology to calculate pore connectivity in granular rocks. This method is useful to characterize the pore networks of natural and laboratory compaction bands (CBs), and compare them with the host rock pore network. Data were collected using the synchrotron X-ray microtomography technique and quantitative analyses were carried out using the Pore3D software library. The porosity was calculated from segmented tridimensional images of deformed and pristine rocks. A process of skeletonization of the pore space was used to obtain the number of connected pores within the rock volume. By analyzing the skeletons the differences between natural and laboratory CBs were highlighted. The natural CB has a lower porosity than to the laboratory one. In natural CBs, the grain contacts appear welded, whereas laboratory CBs show irregular pore shape. Moreover, we assessed for the first time how pore connectivity evolves as a function of deformation, documenting the mechanism responsible for pore connectivity drop within the CBs.

Prolongation of SMAP to Spatiotemporally Seamless Coverage of Continental U.S. Using a Deep Learning Neural Network

NASA Astrophysics Data System (ADS)

Fang, Kuai; Shen, Chaopeng; Kifer, Daniel; Yang, Xiao

2017-11-01

The Soil Moisture Active Passive (SMAP) mission has delivered valuable sensing of surface soil moisture since 2015. However, it has a short time span and irregular revisit schedules. Utilizing a state-of-the-art time series deep learning neural network, Long Short-Term Memory (LSTM), we created a system that predicts SMAP level-3 moisture product with atmospheric forcings, model-simulated moisture, and static physiographic attributes as inputs. The system removes most of the bias with model simulations and improves predicted moisture climatology, achieving small test root-mean-square errors (<0.035) and high-correlation coefficients >0.87 for over 75% of Continental United States, including the forested southeast. As the first application of LSTM in hydrology, we show the proposed network avoids overfitting and is robust for both temporal and spatial extrapolation tests. LSTM generalizes well across regions with distinct climates and environmental settings. With high fidelity to SMAP, LSTM shows great potential for hindcasting, data assimilation, and weather forecasting.

Statistical modeling of the Internet traffic dynamics: To which extent do we need long-term correlations?

NASA Astrophysics Data System (ADS)

Markelov, Oleg; Nguyen Duc, Viet; Bogachev, Mikhail

2017-11-01

Recently we have suggested a universal superstatistical model of user access patterns and aggregated network traffic. The model takes into account the irregular character of end user access patterns on the web via the non-exponential distributions of the local access rates, but neglects the long-term correlations between these rates. While the model is accurate for quasi-stationary traffic records, its performance under highly variable and especially non-stationary access dynamics remains questionable. In this paper, using an example of the traffic patterns from a highly loaded network cluster hosting the website of the 1998 FIFA World Cup, we suggest a generalization of the previously suggested superstatistical model by introducing long-term correlations between access rates. Using queueing system simulations, we show explicitly that this generalization is essential for modeling network nodes with highly non-stationary access patterns, where neglecting long-term correlations leads to the underestimation of the empirical average sojourn time by several decades under high throughput utilization.

Parametric Loop Division for 3D Localization in Wireless Sensor Networks

PubMed Central

Ahmad, Tanveer

2017-01-01

Localization in Wireless Sensor Networks (WSNs) has been an active topic for more than two decades. A variety of algorithms were proposed to improve the localization accuracy. However, they are either limited to two-dimensional (2D) space, or require specific sensor deployment for proper operations. In this paper, we proposed a three-dimensional (3D) localization scheme for WSNs based on the well-known parametric Loop division (PLD) algorithm. The proposed scheme localizes a sensor node in a region bounded by a network of anchor nodes. By iteratively shrinking that region towards its center point, the proposed scheme provides better localization accuracy as compared to existing schemes. Furthermore, it is cost-effective and independent of environmental irregularity. We provide an analytical framework for the proposed scheme and find its lower bound accuracy. Simulation results shows that the proposed algorithm provides an average localization accuracy of 0.89 m with a standard deviation of 1.2 m. PMID:28737714

Gap junction plasticity as a mechanism to regulate network-wide oscillations

PubMed Central

Nicola, Wilten; Clopath, Claudia

2018-01-01

Cortical oscillations are thought to be involved in many cognitive functions and processes. Several mechanisms have been proposed to regulate oscillations. One prominent but understudied mechanism is gap junction coupling. Gap junctions are ubiquitous in cortex between GABAergic interneurons. Moreover, recent experiments indicate their strength can be modified in an activity-dependent manner, similar to chemical synapses. We hypothesized that activity-dependent gap junction plasticity acts as a mechanism to regulate oscillations in the cortex. We developed a computational model of gap junction plasticity in a recurrent cortical network based on recent experimental findings. We showed that gap junction plasticity can serve as a homeostatic mechanism for oscillations by maintaining a tight balance between two network states: asynchronous irregular activity and synchronized oscillations. This homeostatic mechanism allows for robust communication between neuronal assemblies through two different mechanisms: transient oscillations and frequency modulation. This implies a direct functional role for gap junction plasticity in information transmission in cortex. PMID:29529034

An Adaptive Memory Interface Controller for Improving Bandwidth Utilization of Hybrid and Reconfigurable Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Castellana, Vito G.; Tumeo, Antonino; Ferrandi, Fabrizio

Emerging applications such as data mining, bioinformatics, knowledge discovery, social network analysis are irregular. They use data structures based on pointers or linked lists, such as graphs, unbalanced trees or unstructures grids, which generates unpredictable memory accesses. These data structures usually are large, but difficult to partition. These applications mostly are memory bandwidth bounded and have high synchronization intensity. However, they also have large amounts of inherent dynamic parallelism, because they potentially perform a task for each one of the element they are exploring. Several efforts are looking at accelerating these applications on hybrid architectures, which integrate general purpose processorsmore » with reconfigurable devices. Some solutions, which demonstrated significant speedups, include custom-hand tuned accelerators or even full processor architectures on the reconfigurable logic. In this paper we present an approach for the automatic synthesis of accelerators from C, targeted at irregular applications. In contrast to typical High Level Synthesis paradigms, which construct a centralized Finite State Machine, our approach generates dynamically scheduled hardware components. While parallelism exploitation in typical HLS-generated accelerators is usually bound within a single execution flow, our solution allows concurrently running multiple execution flow, thus also exploiting the coarser grain task parallelism of irregular applications. Our approach supports multiple, multi-ported and distributed memories, and atomic memory operations. Its main objective is parallelizing as many memory operations as possible, independently from their execution time, to maximize the memory bandwidth utilization. This significantly differs from current HLS flows, which usually consider a single memory port and require precise scheduling of memory operations. A key innovation of our approach is the generation of a memory interface controller, which dynamically maps concurrent memory accesses to multiple ports. We present a case study on a typical irregular kernel, Graph Breadth First search (BFS), exploring different tradeoffs in terms of parallelism and number of memories.« less

Stereo-tomography in triangulated models

NASA Astrophysics Data System (ADS)

Yang, Kai; Shao, Wei-Dong; Xing, Feng-yuan; Xiong, Kai

2018-04-01

Stereo-tomography is a distinctive tomographic method. It is capable of estimating the scatterer position, the local dip of scatterer and the background velocity simultaneously. Building a geologically consistent velocity model is always appealing for applied and earthquake seismologists. Differing from the previous work to incorporate various regularization techniques into the cost function of stereo-tomography, we think extending stereo-tomography to the triangulated model will be the most straightforward way to achieve this goal. In this paper, we provided all the Fréchet derivatives of stereo-tomographic data components with respect to model components for slowness-squared triangulated model (or sloth model) in 2D Cartesian coordinate based on the ray perturbation theory for interfaces. A sloth model representation means a sparser model representation when compared with conventional B-spline model representation. A sparser model representation leads to a smaller scale of stereo-tomographic (Fréchet) matrix, a higher-accuracy solution when solving linear equations, a faster convergence rate and a lower requirement for quantity of data space. Moreover, a quantitative representation of interface strengthens the relationships among different model components, which makes the cross regularizations among these model components, such as node coordinates, scatterer coordinates and scattering angles, etc., more straightforward and easier to be implemented. The sensitivity analysis, the model resolution matrix analysis and a series of synthetic data examples demonstrate the correctness of the Fréchet derivatives, the applicability of the regularization terms and the robustness of the stereo-tomography in triangulated model. It provides a solid theoretical foundation for the real applications in the future.

The on-orbit calibration of geometric parameters of the Tian-Hui 1 (TH-1) satellite

NASA Astrophysics Data System (ADS)

Wang, Jianrong; Wang, Renxiang; Hu, Xin; Su, Zhongbo

2017-02-01

The on-orbit calibration of geometric parameters is a key step in improving the location accuracy of satellite images without using Ground Control Points (GCPs). Most methods of on-orbit calibration are based on the self-calibration using additional parameters. When using additional parameters, different number of additional parameters may lead to different results. The triangulation bundle adjustment is another way to calibrate the geometric parameters of camera, which can describe the changes in each geometric parameter. When triangulation bundle adjustment method is applied to calibrate geometric parameters, a prerequisite is that the strip model can avoid systematic deformation caused by the rate of attitude changes. Concerning the stereo camera, the influence of the intersection angle should be considered during calibration. The Equivalent Frame Photo (EFP) bundle adjustment based on the Line-Matrix CCD (LMCCD) image can solve the systematic distortion of the strip model, and obtain high accuracy location without using GCPs. In this paper, the triangulation bundle adjustment is used to calibrate the geometric parameters of TH-1 satellite cameras based on LMCCD image. During the bundle adjustment, the three-line array cameras are reconstructed by adopting the principle of inverse triangulation. Finally, the geometric accuracy is validated before and after on-orbit calibration using 5 testing fields. After on-orbit calibration, the 3D geometric accuracy is improved to 11.8 m from 170 m. The results show that the location accuracy of TH-1 without using GCPs is significantly improved using the on-orbit calibration of the geometric parameters.

Measuring teamwork in primary care: Triangulation of qualitative and quantitative data.

PubMed

Brown, Judith Belle; Ryan, Bridget L; Thorpe, Cathy; Markle, Emma K R; Hutchison, Brian; Glazier, Richard H

2015-09-01

This article describes the triangulation of qualitative dimensions, reflecting high functioning teams, with the results of standardized teamwork measures. The study used a mixed methods design using qualitative and quantitative approaches to assess teamwork in 19 Family Health Teams in Ontario, Canada. This article describes dimensions from the qualitative phase using grounded theory to explore the issues and challenges to teamwork. Two quantitative measures were used in the study, the Team Climate Inventory (TCI) and the Providing Effective Resources and Knowledge (PERK) scale. For the triangulation analysis, the mean scores of these measures were compared with the qualitatively derived ratings for the dimensions. The final sample for the qualitative component was 107 participants. The qualitative analysis identified 9 dimensions related to high team functioning such as common philosophy, scope of practice, conflict resolution, change management, leadership, and team evolution. From these dimensions, teams were categorized numerically as high, moderate, or low functioning. Three hundred seventeen team members completed the survey measures. Mean site scores for the TCI and PERK were 3.87 and 3.88, respectively (of 5). The TCI was associated will all dimensions except for team location, space allocation, and executive director leadership. The PERK was associated with all dimensions except team location. Data triangulation provided qualitative and quantitative evidence of what constitutes teamwork. Leadership was pivotal in forging a common philosophy and encouraging team collaboration. Teams used conflict resolution strategies and adapted to the changes they encountered. These dimensions advanced the team's evolution toward a high functioning team. (c) 2015 APA, all rights reserved).

Sol-gel optics for biomeasurements

NASA Astrophysics Data System (ADS)

Lechna-Marczynska, Monika I.; Podbielska, Halina; Ulatowska-Jarza, Agnieszka; Holowacz, Iwona; Andrzejewski, Damian

2001-10-01

Sol-gel technique is a method for producing of glass-like materials without involving a melting process. Organic compounds such as alcoholates of silicon, sodium or calcium can be used. The irregular non-crystalline network forms a gel structure where the metallic atoms are bonded to oxygen atoms. Low-temperature treatment turns this gel into an inorganic glass-like structure. There are numbers of applications of these materials that can be produced in various forms and shapes. Here, silica based sol-gel bulks and thin films optodes for biomedical applications will be presented.

Emergence of Slow Collective Oscillations in Neural Networks with Spike-Timing Dependent Plasticity

NASA Astrophysics Data System (ADS)

Mikkelsen, Kaare; Imparato, Alberto; Torcini, Alessandro

2013-05-01

The collective dynamics of excitatory pulse coupled neurons with spike-timing dependent plasticity is studied. The introduction of spike-timing dependent plasticity induces persistent irregular oscillations between strongly and weakly synchronized states, reminiscent of brain activity during slow-wave sleep. We explain the oscillations by a mechanism, the Sisyphus Effect, caused by a continuous feedback between the synaptic adjustments and the coherence in the neural firing. Due to this effect, the synaptic weights have oscillating equilibrium values, and this prevents the system from relaxing into a stationary macroscopic state.

The small world of osteocytes: connectomics of the lacuno-canalicular network in bone

NASA Astrophysics Data System (ADS)

Kollmannsberger, Philip; Kerschnitzki, Michael; Repp, Felix; Wagermaier, Wolfgang; Weinkamer, Richard; Fratzl, Peter

2017-07-01

Osteocytes and their cell processes reside in a large, interconnected network of voids pervading the mineralized bone matrix of most vertebrates. This osteocyte lacuno-canalicular network (OLCN) is believed to play important roles in mechanosensing, mineral homeostasis, and for the mechanical properties of bone. While the extracellular matrix structure of bone is extensively studied on ultrastructural and macroscopic scales, there is a lack of quantitative knowledge on how the cellular network is organized. Using a recently introduced imaging and quantification approach, we analyze the OLCN in different bone types from mouse and sheep that exhibit different degrees of structural organization not only of the cell network but also of the fibrous matrix deposited by the cells. We define a number of robust, quantitative measures that are derived from the theory of complex networks. These measures enable us to gain insights into how efficient the network is organized with regard to intercellular transport and communication. Our analysis shows that the cell network in regularly organized, slow-growing bone tissue from sheep is less connected, but more efficiently organized compared to irregular and fast-growing bone tissue from mice. On the level of statistical topological properties (edges per node, edge length and degree distribution), both network types are indistinguishable, highlighting that despite pronounced differences at the tissue level, the topological architecture of the osteocyte canalicular network at the subcellular level may be independent of species and bone type. Our results suggest a universal mechanism underlying the self-organization of individual cells into a large, interconnected network during bone formation and mineralization.

The effect of road network patterns on pedestrian safety: A zone-based Bayesian spatial modeling approach.

PubMed

Guo, Qiang; Xu, Pengpeng; Pei, Xin; Wong, S C; Yao, Danya

2017-02-01

Pedestrian safety is increasingly recognized as a major public health concern. Extensive safety studies have been conducted to examine the influence of multiple variables on the occurrence of pedestrian-vehicle crashes. However, the explicit relationship between pedestrian safety and road network characteristics remains unknown. This study particularly focused on the role of different road network patterns on the occurrence of crashes involving pedestrians. A global integration index via space syntax was introduced to quantify the topological structures of road networks. The Bayesian Poisson-lognormal (PLN) models with conditional autoregressive (CAR) prior were then developed via three different proximity structures: contiguity, geometry-centroid distance, and road network connectivity. The models were also compared with the PLN counterpart without spatial correlation effects. The analysis was based on a comprehensive crash dataset from 131 selected traffic analysis zones in Hong Kong. The results indicated that higher global integration was associated with more pedestrian-vehicle crashes; the irregular pattern network was proved to be safest in terms of pedestrian crash occurrences, whereas the grid pattern was the least safe; the CAR model with a neighborhood structure based on road network connectivity was found to outperform in model goodness-of-fit, implying the importance of accurately accounting for spatial correlation when modeling spatially aggregated crash data. Copyright © 2016 Elsevier Ltd. All rights reserved.

Variational electric fields at low latitudes and their relation to spread F and plasma irregularities

NASA Technical Reports Server (NTRS)

Holtet, J. A.; Maynard, N. C.; Heppner, J. P.

1976-01-01

Recordings from OGO 6 show that electric field irregularities are frequently present between + or - 35 deg geomagnetic latitude in the 2000 - 0600 local time sector. The signatures are very clear, and are easily distinguished from the normal AC background noise, and whistler and emission activity. The spectral appearance of the fields makes it meaningful to distinguish between 3 different types of irregularities: strong irregularities, weak irregularities, and weak irregularities with a rising spectrum. Strong irregularities seem most likely to occur in regions where gradients in ionization are present. Changes in plasma composition, resulting in an increase in the mean ion mass, are also often observed in the irregularity regions. Comparison with ground based ionosondes indicates a connection between strong irregularities and low latitude spread F. A good correlation is also present between strong fields and small scale fluctuations in ionization, delta N/N 1 percent. From the data it appears as if a gradient driven instability is the most likely source of the strong irregularities.

Triangulation-based 3D surveying borescope

NASA Astrophysics Data System (ADS)

Pulwer, S.; Steglich, P.; Villringer, C.; Bauer, J.; Burger, M.; Franz, M.; Grieshober, K.; Wirth, F.; Blondeau, J.; Rautenberg, J.; Mouti, S.; Schrader, S.

2016-04-01

In this work, a measurement concept based on triangulation was developed for borescopic 3D-surveying of surface defects. The integration of such measurement system into a borescope environment requires excellent space utilization. The triangulation angle, the projected pattern, the numerical apertures of the optical system, and the viewing angle were calculated using partial coherence imaging and geometric optical raytracing methods. Additionally, optical aberrations and defocus were considered by the integration of Zernike polynomial coefficients. The measurement system is able to measure objects with a size of 50 μm in all dimensions with an accuracy of +/- 5 μm. To manage the issue of a low depth of field while using an optical high resolution system, a wavelength dependent aperture was integrated. Thereby, we are able to control depth of field and resolution of the optical system and can use the borescope in measurement mode with high resolution and low depth of field or in inspection mode with low resolution and higher depth of field. First measurements of a demonstrator system are in good agreement with our simulations.

Irregular Applications: Architectures & Algorithms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feo, John T.; Villa, Oreste; Tumeo, Antonino

Irregular applications are characterized by irregular data structures, control and communication patterns. Novel irregular high performance applications which deal with large data sets and require have recently appeared. Unfortunately, current high performance systems and software infrastructures executes irregular algorithms poorly. Only coordinated efforts by end user, area specialists and computer scientists that consider both the architecture and the software stack may be able to provide solutions to the challenges of modern irregular applications.

Exploring Solar System Origins With The Desert Fireball Network

NASA Astrophysics Data System (ADS)

Day, B. H.; Bland, P.

2016-12-01

Fireball camera networks are designed to recover meteorites with orbits. A geological context is a prerequisite for understanding terrestrial rocks. An improved dynamical context would benefit our understanding of extraterrestrial geology. A dozen projects - professional and amateur - have pursued this goal over the years. The effort has yielded 10 meteorites with orbits. Why so few? All these projects were in the temperate zone of the northern hemisphere: areas where meteorite recovery is marginal. Deserts are one of the few places on Earth where field searches for meteorites can be mounted with a realistic chance of success. This was the driver behind the Desert Fireball Network. The Desert Fireball Network (DFN) uses automated observatories across Australia to triangulate trajectories of meteorites entering the atmosphere, determine pre-entry orbits, and pinpoint their fall positions. Each observatory is an autonomous intelligent imaging system, taking 1000×36Megapixel all-sky images throughout the night, using neural network algorithms to recognise events. They are capable of operating for 12 months in a harsh environment, and store all imagery collected. We developed a completely automated software pipeline for data reduction, and built a supercomputer database for storage, allowing us to process our entire archive. We successfully recovered a meteorite from Lake Eyre on 31st December 2015, using this pipeline. By February 2016 we had reduced our complete fireball dataset, deriving precise orbits for >350 events: a dataset that provides a unique window on the dynamics of material in the inner solar system. The DFN currently stands at 50 stations distributed across the Australian continent, covering an area of 2.5 million km2. The fireball and meteorite orbital data that it can provide will deliver a new dynamical window on the inner solar system, and new insights into solar system origins. Working with DFN's partners at NASA's Solar System Exploration Research Virtual Institute, the team is now working to expand the network beyond Australia to locations around the world.

Fractal interrelationships in field and seismic data. Quarterly report, September 21 - December 31, 1995

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilson, T.H.; Dominic, J.; Halverson, J.

1995-12-31

Under task 1 contour irregularities traced over both study areas in the previous quarter were scanned into the computer and digitized at a 30 meter interval. Patters mapped in both the Granny Creek and Middle Mountain field areas are presented in Figures 1 and 2 respectively. One of the hypotheses of this research project is that contour irregularities must be controlled by a combination of sedimentation features, lithologic variation, and local structure and fracture distribution. The most promising result obtained thus far in this study are those reported under Tasks 4 and 5, seismic analysis. If further tests continue tomore » support the observation that increased fractal dimension reflects the presence of detached structure, the analytical techniques employed here may be of use in the routine evaluation of seismic data to locate subtle traps. The observations may allow one to predict the variation of fractal dimension within a subsurface fracture network based on seismic observation of resolvable structural parameters. Such predictions would provide a working hypothesis, which could be modified within the context of available subsurface data.« less

Graph Partitioning for Parallel Applications in Heterogeneous Grid Environments

NASA Technical Reports Server (NTRS)

Bisws, Rupak; Kumar, Shailendra; Das, Sajal K.; Biegel, Bryan (Technical Monitor)

2002-01-01

The problem of partitioning irregular graphs and meshes for parallel computations on homogeneous systems has been extensively studied. However, these partitioning schemes fail when the target system architecture exhibits heterogeneity in resource characteristics. With the emergence of technologies such as the Grid, it is imperative to study the partitioning problem taking into consideration the differing capabilities of such distributed heterogeneous systems. In our model, the heterogeneous system consists of processors with varying processing power and an underlying non-uniform communication network. We present in this paper a novel multilevel partitioning scheme for irregular graphs and meshes, that takes into account issues pertinent to Grid computing environments. Our partitioning algorithm, called MiniMax, generates and maps partitions onto a heterogeneous system with the objective of minimizing the maximum execution time of the parallel distributed application. For experimental performance study, we have considered both a realistic mesh problem from NASA as well as synthetic workloads. Simulation results demonstrate that MiniMax generates high quality partitions for various classes of applications targeted for parallel execution in a distributed heterogeneous environment.

Wide-field microscopy using microcamera arrays

NASA Astrophysics Data System (ADS)

Marks, Daniel L.; Youn, Seo Ho; Son, Hui S.; Kim, Jungsang; Brady, David J.

2013-02-01

A microcamera is a relay lens paired with image sensors. Microcameras are grouped into arrays to relay overlapping views of a single large surface to the sensors to form a continuous synthetic image. The imaged surface may be curved or irregular as each camera may independently be dynamically focused to a different depth. Microcamera arrays are akin to microprocessors in supercomputers in that both join individual processors by an optoelectronic routing fabric to increase capacity and performance. A microcamera may image ten or more megapixels and grouped into an array of several hundred, as has already been demonstrated by the DARPA AWARE Wide-Field program with multiscale gigapixel photography. We adapt gigapixel microcamera array architectures to wide-field microscopy of irregularly shaped surfaces to greatly increase area imaging over 1000 square millimeters at resolutions of 3 microns or better in a single snapshot. The system includes a novel relay design, a sensor electronics package, and a FPGA-based networking fabric. Biomedical applications of this include screening for skin lesions, wide-field and resolution-agile microsurgical imaging, and microscopic cytometry of millions of cells performed in situ.

Reversed flow events in the cusp ionosphere detected by SuperDARN HF radars

NASA Astrophysics Data System (ADS)

Oksavik, K.; Moen, J. I.; Rekaa, E. H.; Carlson, H. C.; Lester, M.

2011-12-01

We present several examples of reversed flow events (RFEs) from the cusp ionosphere. RFEs are 100-200 km wide flow channels opposing the background plasma convection. RFEs were discovered a few years ago by the incoherent scatter European Incoherent Scatter Svalbard Radar. In this paper we show that coherent scatter Super Dual Auroral Radar Network (SuperDARN) HF radars can also see RFEs. We report a close relationship between RFEs and the development of HF backscatter power and spectral width. Wide spectra were seen near the edges of the RFEs (i.e., associated with the flow shear), and there was a significant increase in SuperDARN HF backscatter power when the RFE expanded. This increase in power is much faster than anticipated from the gradient drift instability alone, supporting the hypothesis that RFE flow shears foster rapid growth of Kelvin-Helmholtz instabilities. That decameter-scale irregularities form so rapidly should be an important guide to the development of instability theory for cascade of plasma irregularities from larger to smaller scale sizes.

Effects of irregularity anisotropy on Faraday polarization fluctuations

NASA Technical Reports Server (NTRS)

Lee, M. C.; Nghiem, S. V.; Yoo, C.

1989-01-01

The previous model (Lee et al., 1982) of the Faraday polarization fluctuations (FPF) is extended after taking into account the anisotropic nature of the commonly observed, rodlike and sheetlike ionospheric irregularities. Striking effects of irregularity anisotropy are found in the longitudinal radio propagation. However, if the wave propagation angle is not small (say, greater than 5 deg), the effects of irregularity anisotropy on FPF introduced by rodlike irregularities weaken significantly, while those caused by sheetlike irregularities remain prominent. Therefore, under the same ionospheric propagation conditions, sheetlike ionospheric irregularities are more effective than rodlike ionospheric irregularities in causing the FPF of radio waves. It is expected that intense FPF of VHF radio signals can be observed not only near the equatorial anomaly but also in the auroral region.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rebay, S.

This work is devoted to the description of an efficient unstructured mesh generation method entirely based on the Delaunay triangulation. The distinctive characteristic of the proposed method is that point positions and connections are computed simultaneously. This result is achieved by taking advantage of the sequential way in which the Bowyer-Watson algorithm computes the Delaunay triangulation. Two methods are proposed which have great geometrical flexibility, in that they allow us to treat domains of arbitrary shape and topology and to generate arbitrarily nonuniform meshes. The methods are computationally efficient and are applicable both in two and three dimensions. 11 refs.,more » 20 figs., 1 tab.« less

A linear photodiode array employed in a short range laser triangulation obstacle avoidance sensor. M.S. Thesis; [Martian roving vehicle sensor

NASA Technical Reports Server (NTRS)

Odenthal, J. P.

1980-01-01

An opto-electronic receiver incorporating a multi-element linear photodiode array as a component of a laser-triangulation rangefinder was developed as an obstacle avoidance sensor for a Martian roving vehicle. The detector can resolve the angle of laser return in 1.5 deg increments within a field of view of 30 deg and a range of five meters. A second receiver with a 1024 elements over 60 deg and a 3 meter range is also documented. Design criteria, circuit operation, schematics, experimental results and calibration procedures are discussed.

First Instances of Generalized Expo-Rational Finite Elements on Triangulations

NASA Astrophysics Data System (ADS)

Dechevsky, Lubomir T.; Zanaty, Peter; Laksa˚, Arne; Bang, Børre

2011-12-01

In this communication we consider a construction of simplicial finite elements on triangulated two-dimensional polygonal domains. This construction is, in some sense, dual to the construction of generalized expo-rational B-splines (GERBS). The main result is in the obtaining of new polynomial simplicial patches of the first several lowest possible total polynomial degrees which exhibit Hermite interpolatory properties. The derivation of these results is based on the theory of piecewise polynomial GERBS called Euler Beta-function B-splines. We also provide 3-dimensional visualization of the graphs of the new polynomial simplicial patches and their control polygons.

Laser triangulation method for measuring the size of parking claw

NASA Astrophysics Data System (ADS)

Liu, Bo; Zhang, Ming; Pang, Ying

2017-10-01

With the development of science and technology and the maturity of measurement technology, the 3D profile measurement technology has been developed rapidly. Three dimensional measurement technology is widely used in mold manufacturing, industrial inspection, automatic processing and manufacturing, etc. There are many kinds of situations in scientific research and industrial production. It is necessary to transform the original mechanical parts into the 3D data model on the computer quickly and accurately. At present, many methods have been developed to measure the contour size, laser triangulation is one of the most widely used methods.

Markerless positional verification using template matching and triangulation of kV images acquired during irradiation for lung tumors treated in breath-hold

NASA Astrophysics Data System (ADS)

Hazelaar, Colien; Dahele, Max; Mostafavi, Hassan; van der Weide, Lineke; Slotman, Ben; Verbakel, Wilko

2018-06-01

Lung tumors treated in breath-hold are subject to inter- and intra-breath-hold variations, which makes tumor position monitoring during each breath-hold important. A markerless technique is desirable, but limited tumor visibility on kV images makes this challenging. We evaluated if template matching  +  triangulation of kV projection images acquired during breath-hold stereotactic treatments could determine 3D tumor position. Band-pass filtering and/or digital tomosynthesis (DTS) were used as image pre-filtering/enhancement techniques. On-board kV images continuously acquired during volumetric modulated arc irradiation of (i) a 3D-printed anthropomorphic thorax phantom with three lung tumors (n  =  6 stationary datasets, n  =  2 gradually moving), and (ii) four patients (13 datasets) were analyzed. 2D reference templates (filtered DRRs) were created from planning CT data. Normalized cross-correlation was used for 2D matching between templates and pre-filtered/enhanced kV images. For 3D verification, each registration was triangulated with multiple previous registrations. Generally applicable image processing/algorithm settings for lung tumors in breath-hold were identified. For the stationary phantom, the interquartile range of the 3D position vector was on average 0.25 mm for 12° DTS  +  band-pass filtering (average detected positions in 2D  =  99.7%, 3D  =  96.1%, and 3D excluding first 12° due to triangulation angle  =  99.9%) compared to 0.81 mm for band-pass filtering only (55.8/52.9/55.0%). For the moving phantom, RMS errors for the lateral/longitudinal/vertical direction after 12° DTS  +  band-pass filtering were 1.5/0.4/1.1 mm and 2.2/0.3/3.2 mm. For the clinical data, 2D position was determined for at least 93% of each dataset and 3D position excluding first 12° for at least 82% of each dataset using 12° DTS  +  band-pass filtering. Template matching  +  triangulation using DTS  +  band-pass filtered images could accurately determine the position of stationary lung tumors. However, triangulation was less accurate/reliable for targets with continuous, gradual displacement in the lateral and vertical directions. This technique is therefore currently most suited to detect/monitor offsets occurring between initial setup and the start of treatment, inter-breath-hold variations, and tumors with predominantly longitudinal motion.

Repair of Irregularly Irregular Astigmatism by Transepithelial Phototherapeutic Keratectomy.

PubMed

Guglielmetti, Stefano; Kirton, Amy; Reinstein, Dan Z; Carp, Glenn I; Archer, Timothy J

2017-10-01

To evaluate the outcome of transepithelial phototherapeutic keratectomy (PTK) in the management of irregularly irregular astigmatism. This was a case series of two patients who underwent transepithelial PTK for irregularly irregular astigmatism. In the first case, the patient complained of diplopia due to corneal scarring caused by a metallic foreign body injury. The topography demonstrated irregularly irregular astigmatism with significant asymmetry in the inferotemporal to superonasal axis. In the second case, the patient complained of blurred vision and ghosting caused by significant central epithelial ingrowth through a buttonhole LASIK flap, which was causing a localized irregularity on topography. Due to the localized nature of the irregularities, a transepithelial PTK treatment was preferred to custom ablation given the degree of epithelial masking present. Transepithelial PTK was performed in both cases using the Schwind Amaris 500E excimer laser (Schwind eye-tech-solutions, Kleinostheim, Germany) and an 8-mm optical zone. The ablation depth was planned to reach the depth of the epithelium using a stepwise protocol, reviewing the pattern of the remaining epithelium and regularity of the stromal surface between each ablation. A marked improvement in the regularity of the topography was achieved in both cases, with only regular astigmatism remaining. Both patients reported a subjective improvement in quality of vision and the corrected distance visual acuity improved by one and two lines, respectively. Transepithelial PTK was effective in treating these cases of localized irregularly irregular astigmatism, achieving both objective and subjective improvement in vision. Compensatory epithelial remodeling over the irregularities enabled the transepithelial PTK approach to target the stromal surface irregularities. [J Refract Surg. 2017;33(10):714-719.]. Copyright 2017, SLACK Incorporated.

Emergence of Leadership in Communication

PubMed Central

Allahverdyan, Armen E.; Galstyan, Aram

2016-01-01

We study a neuro-inspired model that mimics a discussion (or information dissemination) process in a network of agents. During their interaction, agents redistribute activity and network weights, resulting in emergence of leader(s). The model is able to reproduce the basic scenarios of leadership known in nature and society: laissez-faire (irregular activity, weak leadership, sizable inter-follower interaction, autonomous sub-leaders); participative or democratic (strong leadership, but with feedback from followers); and autocratic (no feedback, one-way influence). Several pertinent aspects of these scenarios are found as well—e.g., hidden leadership (a hidden clique of agents driving the official autocratic leader), and successive leadership (two leaders influence followers by turns). We study how these scenarios emerge from inter-agent dynamics and how they depend on behavior rules of agents—in particular, on their inertia against state changes. PMID:27532484

Emergence of Leadership in Communication.

PubMed

Allahverdyan, Armen E; Galstyan, Aram

2016-01-01

We study a neuro-inspired model that mimics a discussion (or information dissemination) process in a network of agents. During their interaction, agents redistribute activity and network weights, resulting in emergence of leader(s). The model is able to reproduce the basic scenarios of leadership known in nature and society: laissez-faire (irregular activity, weak leadership, sizable inter-follower interaction, autonomous sub-leaders); participative or democratic (strong leadership, but with feedback from followers); and autocratic (no feedback, one-way influence). Several pertinent aspects of these scenarios are found as well-e.g., hidden leadership (a hidden clique of agents driving the official autocratic leader), and successive leadership (two leaders influence followers by turns). We study how these scenarios emerge from inter-agent dynamics and how they depend on behavior rules of agents-in particular, on their inertia against state changes.

Discontinuities concentrate mobile predators: Quantifying organism-environment interactions at a seascape scale

USGS Publications Warehouse

Kennedy, Christina G.; Mather, Martha E.; Smith, Joseph M.; Finn, John T.; Deegan, Linda A.

2016-01-01

Understanding environmental drivers of spatial patterns is an enduring ecological problem that is critical for effective biological conservation. Discontinuities (ecologically meaningful habitat breaks), both naturally occurring (e.g., river confluence, forest edge, drop-off) and anthropogenic (e.g., dams, roads), can influence the distribution of highly mobile organisms that have land- or seascape scale ranges. A geomorphic discontinuity framework, expanded to include ecological patterns, provides a way to incorporate important but irregularly distributed physical features into organism–environment relationships. Here, we test if migratory striped bass (Morone saxatilis) are consistently concentrated by spatial discontinuities and why. We quantified the distribution of 50 acoustically tagged striped bass at 40 sites within Plum Island Estuary, Massachusetts during four-monthly surveys relative to four physical discontinuities (sandbar, confluence, channel network, drop-off), one continuous physical feature (depth variation), and a geographic location variable (region). Despite moving throughout the estuary, striped bass were consistently clustered in the middle geographic region at sites with high sandbar area, close to channel networks, adjacent to complex confluences, with intermediate levels of bottom unevenness, and medium sized drop-offs. In addition, the highest striped bass concentrations occurred at sites with the greatest additive physical heterogeneity (i.e., where multiple discontinuities co-occurred). The need to incorporate irregularly distributed features in organism–environment relationships will increase as high-quality telemetry and GIS data accumulate for mobile organisms. The spatially explicit approach we used to address this challenge can aid both researchers who seek to understand the impact of predators on ecosystems and resource managers who require new approaches for biological conservation.

Fast and Accurate Simulation of the Cray XMT Multithreaded Supercomputer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Villa, Oreste; Tumeo, Antonino; Secchi, Simone

Irregular applications, such as data mining and analysis or graph-based computations, show unpredictable memory/network access patterns and control structures. Highly multithreaded architectures with large processor counts, like the Cray MTA-1, MTA-2 and XMT, appear to address their requirements better than commodity clusters. However, the research on highly multithreaded systems is currently limited by the lack of adequate architectural simulation infrastructures due to issues such as size of the machines, memory footprint, simulation speed, accuracy and customization. At the same time, Shared-memory MultiProcessors (SMPs) with multi-core processors have become an attractive platform to simulate large scale machines. In this paper, wemore » introduce a cycle-level simulator of the highly multithreaded Cray XMT supercomputer. The simulator runs unmodified XMT applications. We discuss how we tackled the challenges posed by its development, detailing the techniques introduced to make the simulation as fast as possible while maintaining a high accuracy. By mapping XMT processors (ThreadStorm with 128 hardware threads) to host computing cores, the simulation speed remains constant as the number of simulated processors increases, up to the number of available host cores. The simulator supports zero-overhead switching among different accuracy levels at run-time and includes a network model that takes into account contention. On a modern 48-core SMP host, our infrastructure simulates a large set of irregular applications 500 to 2000 times slower than real time when compared to a 128-processor XMT, while remaining within 10\\% of accuracy. Emulation is only from 25 to 200 times slower than real time.« less

Star Formation in Irregular Galaxies.

ERIC Educational Resources Information Center

Hunter, Deidre; Wolff, Sidney

1985-01-01

Examines mechanisms of how stars are formed in irregular galaxies. Formation in giant irregular galaxies, formation in dwarf irregular galaxies, and comparisons with larger star-forming regions found in spiral galaxies are considered separately. (JN)

Enhancing Breast Cancer Recurrence Algorithms Through Selective Use of Medical Record Data.

PubMed

Kroenke, Candyce H; Chubak, Jessica; Johnson, Lisa; Castillo, Adrienne; Weltzien, Erin; Caan, Bette J

2016-03-01

The utility of data-based algorithms in research has been questioned because of errors in identification of cancer recurrences. We adapted previously published breast cancer recurrence algorithms, selectively using medical record (MR) data to improve classification. We evaluated second breast cancer event (SBCE) and recurrence-specific algorithms previously published by Chubak and colleagues in 1535 women from the Life After Cancer Epidemiology (LACE) and 225 women from the Women's Health Initiative cohorts and compared classification statistics to published values. We also sought to improve classification with minimal MR examination. We selected pairs of algorithms-one with high sensitivity/high positive predictive value (PPV) and another with high specificity/high PPV-using MR information to resolve discrepancies between algorithms, properly classifying events based on review; we called this "triangulation." Finally, in LACE, we compared associations between breast cancer survival risk factors and recurrence using MR data, single Chubak algorithms, and triangulation. The SBCE algorithms performed well in identifying SBCE and recurrences. Recurrence-specific algorithms performed more poorly than published except for the high-specificity/high-PPV algorithm, which performed well. The triangulation method (sensitivity = 81.3%, specificity = 99.7%, PPV = 98.1%, NPV = 96.5%) improved recurrence classification over two single algorithms (sensitivity = 57.1%, specificity = 95.5%, PPV = 71.3%, NPV = 91.9%; and sensitivity = 74.6%, specificity = 97.3%, PPV = 84.7%, NPV = 95.1%), with 10.6% MR review. Triangulation performed well in survival risk factor analyses vs analyses using MR-identified recurrences. Use of multiple recurrence algorithms in administrative data, in combination with selective examination of MR data, may improve recurrence data quality and reduce research costs. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Enhancing Breast Cancer Recurrence Algorithms Through Selective Use of Medical Record Data

PubMed Central

Chubak, Jessica; Johnson, Lisa; Castillo, Adrienne; Weltzien, Erin; Caan, Bette J.

2016-01-01

Abstract Background: The utility of data-based algorithms in research has been questioned because of errors in identification of cancer recurrences. We adapted previously published breast cancer recurrence algorithms, selectively using medical record (MR) data to improve classification. Methods: We evaluated second breast cancer event (SBCE) and recurrence-specific algorithms previously published by Chubak and colleagues in 1535 women from the Life After Cancer Epidemiology (LACE) and 225 women from the Women’s Health Initiative cohorts and compared classification statistics to published values. We also sought to improve classification with minimal MR examination. We selected pairs of algorithms—one with high sensitivity/high positive predictive value (PPV) and another with high specificity/high PPV—using MR information to resolve discrepancies between algorithms, properly classifying events based on review; we called this “triangulation.” Finally, in LACE, we compared associations between breast cancer survival risk factors and recurrence using MR data, single Chubak algorithms, and triangulation. Results: The SBCE algorithms performed well in identifying SBCE and recurrences. Recurrence-specific algorithms performed more poorly than published except for the high-specificity/high-PPV algorithm, which performed well. The triangulation method (sensitivity = 81.3%, specificity = 99.7%, PPV = 98.1%, NPV = 96.5%) improved recurrence classification over two single algorithms (sensitivity = 57.1%, specificity = 95.5%, PPV = 71.3%, NPV = 91.9%; and sensitivity = 74.6%, specificity = 97.3%, PPV = 84.7%, NPV = 95.1%), with 10.6% MR review. Triangulation performed well in survival risk factor analyses vs analyses using MR-identified recurrences. Conclusions: Use of multiple recurrence algorithms in administrative data, in combination with selective examination of MR data, may improve recurrence data quality and reduce research costs. PMID:26582243

E-I balance emerges naturally from continuous Hebbian learning in autonomous neural networks.

PubMed

Trapp, Philip; Echeveste, Rodrigo; Gros, Claudius

2018-06-12

Spontaneous brain activity is characterized in part by a balanced asynchronous chaotic state. Cortical recordings show that excitatory (E) and inhibitory (I) drivings in the E-I balanced state are substantially larger than the overall input. We show that such a state arises naturally in fully adapting networks which are deterministic, autonomously active and not subject to stochastic external or internal drivings. Temporary imbalances between excitatory and inhibitory inputs lead to large but short-lived activity bursts that stabilize irregular dynamics. We simulate autonomous networks of rate-encoding neurons for which all synaptic weights are plastic and subject to a Hebbian plasticity rule, the flux rule, that can be derived from the stationarity principle of statistical learning. Moreover, the average firing rate is regulated individually via a standard homeostatic adaption of the bias of each neuron's input-output non-linear function. Additionally, networks with and without short-term plasticity are considered. E-I balance may arise only when the mean excitatory and inhibitory weights are themselves balanced, modulo the overall activity level. We show that synaptic weight balance, which has been considered hitherto as given, naturally arises in autonomous neural networks when the here considered self-limiting Hebbian synaptic plasticity rule is continuously active.

Cortical Dynamics in Presence of Assemblies of Densely Connected Weight-Hub Neurons

PubMed Central

Setareh, Hesam; Deger, Moritz; Petersen, Carl C. H.; Gerstner, Wulfram

2017-01-01

Experimental measurements of pairwise connection probability of pyramidal neurons together with the distribution of synaptic weights have been used to construct randomly connected model networks. However, several experimental studies suggest that both wiring and synaptic weight structure between neurons show statistics that differ from random networks. Here we study a network containing a subset of neurons which we call weight-hub neurons, that are characterized by strong inward synapses. We propose a connectivity structure for excitatory neurons that contain assemblies of densely connected weight-hub neurons, while the pairwise connection probability and synaptic weight distribution remain consistent with experimental data. Simulations of such a network with generalized integrate-and-fire neurons display regular and irregular slow oscillations akin to experimentally observed up/down state transitions in the activity of cortical neurons with a broad distribution of pairwise spike correlations. Moreover, stimulation of a model network in the presence or absence of assembly structure exhibits responses similar to light-evoked responses of cortical layers in optogenetically modified animals. We conclude that a high connection probability into and within assemblies of excitatory weight-hub neurons, as it likely is present in some but not all cortical layers, changes the dynamics of a layer of cortical microcircuitry significantly. PMID:28690508

Distributed Bandpass Filtering and Signal Demodulation in Cortical Network Models

NASA Astrophysics Data System (ADS)

McDonnell, Mark D.

Experimental recordings of cortical activity often exhibit narrowband oscillations, at various center frequencies ranging in the order of 1-200 Hz. Many neuronal mechanisms are known to give rise to oscillations, but here we focus on a population effect known as sparsely synchronised oscillations. In this effect, individual neurons in a cortical network fire irregularly at slow average spike rates (1-10 Hz), but the population spike rate oscillates at gamma frequencies (greater than 40 Hz) in response to spike bombardment from the thalamus. These cortical networks form recurrent (feedback) synapses. Here we describe a model of sparsely synchronized population oscillations using the language of feedback control engineering, where we treat spiking as noisy feedback. We show, using a biologically realistic model of synaptic current that includes a delayed response to inputs, that the collective behavior of the neurons in the network is like a distributed bandpass filter acting on the network inputs. Consequently, the population response has the character of narrowband random noise, and therefore has an envelope and instantaneous frequency with lowpass characteristics. Given that there exist biologically plausible neuronal mechanisms for demodulating the envelope and instantaneous frequency, we suggest there is potential for similar effects to be exploited in nanoscale electronics implementations of engineered communications receivers.

Characterization of the fibrillar layer at the epithelial-mesenchymal junction in tooth germs.

PubMed

Sawada, T; Inoue, S

1994-12-01

A characteristic layer containing numerous fibrils is associated with the basement membrane of the inner enamel epithelium during the early stages of odontogenesis. However, its nature is not well understood. In this study, the layer was examined with high-resolution electron microscopy and immuno-histochemical staining. Tooth germs of monkeys (Macaca fuscata) were studied and each fibril in the layer was found to be a tubular structure, 8-9 nm in width, resembling a "basotubule", the tubular structure previously observed in various basement membranes. The space between the fibrils was filled with a network formed by irregular anastomosing strands with an average thickness of 4 nm; these strands resembled the "cords" forming the network in the lamina densa of basement membranes. After immunoperoxidase staining, fine threads immunoreactive for laminin staining were seen winding along the strands of the network, and 1.5-nm wide filaments, immunoreactive for type IV collagen, took the form of a network arrangement. The 5-nm-wide ribbon-like structures associated with the strands were identified as heparan sulfate proteoglycan by immunostaining. These results are similar to those obtained for the cord network of the lamina densa. The "fibrillar layer" therefore represents a highly specialized lamina fibroreticularis of the basement membrane of the inner enamel epithelium, and rich in basotubules.

Jordan recurrent neural network versus IHACRES in modelling daily streamflows

NASA Astrophysics Data System (ADS)

Carcano, Elena Carla; Bartolini, Paolo; Muselli, Marco; Piroddi, Luigi

2008-12-01

SummaryA study of possible scenarios for modelling streamflow data from daily time series, using artificial neural networks (ANNs), is presented. Particular emphasis is devoted to the reconstruction of drought periods where water resource management and control are most critical. This paper considers two connectionist models: a feedforward multilayer perceptron (MLP) and a Jordan recurrent neural network (JNN), comparing network performance on real world data from two small catchments (192 and 69 km 2 in size) with irregular and torrential regimes. Several network configurations are tested to ensure a good combination of input features (rainfall and previous streamflow data) that capture the variability of the physical processes at work. Tapped delayed line (TDL) and memory effect techniques are introduced to recognize and reproduce temporal dependence. Results show a poor agreement when using TDL only, but a remarkable improvement can be obtained with JNN and its memory effect procedures, which are able to reproduce the system memory over a catchment in a more effective way. Furthermore, the IHACRES conceptual model, which relies on both rainfall and temperature input data, is introduced for comparative study. The results suggest that when good input data is unavailable, metric models perform better than conceptual ones and, in general, it is difficult to justify substantial conceptualization of complex processes.

Neural networks for the generation of sea bed models using airborne lidar bathymetry data

NASA Astrophysics Data System (ADS)

Kogut, Tomasz; Niemeyer, Joachim; Bujakiewicz, Aleksandra

2016-06-01

Various sectors of the economy such as transport and renewable energy have shown great interest in sea bed models. The required measurements are usually carried out by ship-based echo sounding, but this method is quite expensive. A relatively new alternative is data obtained by airborne lidar bathymetry. This study investigates the accuracy of these data, which was obtained in the context of the project `Investigation on the use of airborne laser bathymetry in hydrographic surveying'. A comparison to multi-beam echo sounding data shows only small differences in the depths values of the data sets. The IHO requirements of the total horizontal and vertical uncertainty for laser data are met. The second goal of this paper is to compare three spatial interpolation methods, namely Inverse Distance Weighting (IDW), Delaunay Triangulation (TIN), and supervised Artificial Neural Networks (ANN), for the generation of sea bed models. The focus of our investigation is on the amount of required sampling points. This is analyzed by manually reducing the data sets. We found that the three techniques have a similar performance almost independently of the amount of sampling data in our test area. However, ANN are more stable when using a very small subset of points.